Passive optical elements and systems, i.e. elements and systems which are not based on the optical properties of the material used being altered by the application of an external field.

In particular:

Whereas G02B relates to passive optics, "active" optics, i.e. where the optical properties of the material used in the optical device are altered by the application of an external field, e.g. electro-optical devices, magneto-optical devices, LCDs, is covered by G02F.

In this subclass, classification of additional information is mandatory,

For example, a document describing the detailed structure of a wire-grid polarizer should be classified with G02B 5/3058 INV – invention-information aspect of a wire-grid polarizer.

Instead a document describing a display system making explicit use of a wire-grid polarizer, without providing structural details of the polarizer itself, should be classified with G02B 5/3058 ADD – as to the additional-information aspect of a wire-grid polarizer.

Optical elements characterised by the material of which they are made.

Simple or compound lenses including arrays.

Optical elements other than lenses, e.g. prisms, diffusers, mirrors, diffraction gratings, filters, polarisers,light absorbing elements, diaphragms, surface plasmon devices or birefringent or phase retarding elements

Filters for plasma panel displays are classified under H01J and in H01J 2217/49292. A further classification in G02B 5/20 is optional.

Optical elements being prisms

Optical elements being mirrors

Filters in which the spectral filtering is performed by a conductive grid or mesh. The background is that for microwave optics, there has long existed a technique in which a conductive periodic pattern (a so-called "frequency selective surface" or FSS) is used to select a particular set of frequencies. For microwaves they are found in the subgroup H01Q 15/0006. In recent years this technique has been extended to IR and even visible wavelengths. It is these types of filters (and only these) which should go into G02B 5/204. Basically they look something like this:

G02B 5/204 is not to be used for classifying normal spectral filters which just happen to have some additional conducting elements for other purposes not to do with spectral selection. In particular it is not for filters having a conductive EM shielding layer or a conductive louvre light blocking grid attached. For such arrangements, the following places may be appropriate:

Light guides per se, coupling light guides and mechanical protection of light guides.

The term "light" as used in G02B 6/00 refers to visible, infrared and ultraviolet light only.

The group covers the optical and mechanical aspects of light guides and light guide coupling, including the coupling of light into, out of and between light guides, as well as positioning, holding and protecting the light guides. This includes optical cables and arrangements for handling optical cables. The group covers the manufacture of some light guides, in particular optical waveguides of the integrated circuit kind.

Light guides per se, coupling light guides and mechanical protection of light guides.

The term "light" as used in G02B 6/00 refers to visible, infrared and ultraviolet light only.

The group covers the optical and mechanical aspects of light guides and light guide coupling, including the coupling of light into, out of and between light guides, as well as positioning, holding and protecting the light guides. This includes optical cables and arrangements for handling optical cables. The group covers the manufacture of some light guides, in particular optical waveguides of the integrated circuit kind.

The group covers light guides for illumination.

"Active" optics, i.e. where the optical property of the light guide or of an optical element coupled to the light guide is altered by the application of an external field are classified in G02F. Backlights characterised by the light guides for liquid crystal display panels are classified in G02B 6/0001 - G02B 6/0096.

Light amplifying light guides are classified in H01S.

Systems for communication are classified in H04, in particular optical transmission systems in general are classified in H04B 10/00, optical multiplex systems are classified in H04J 14/00, H04J 14/05 and H04J 14/07 and optical switching systems are classified in H04Q 11/0001. Network and system aspects are classified in H04 and not in G02B 6/00. Light guide arrangements as components, modules or subsystems of communication systems are classified in G02B 6/00: "in the box" aspects are classified in G02B 6/00. For example modules based on light guides for coupling, splitting, mixing, switching and dispersion compensation are classified in G02B 6/00.

Light guides occur in many areas of technology. To avoid unnecessary double classification, the implementation of light guides in optical systems and instruments for which specific entries exist elsewhere (for example in surgical instruments or for chemical sensing) are not generally given a secondary class in G02B 6/00. This applies particularly to systems and instruments where light guide use is well established. The brief mention of a light guide does not in itself justify classifying in G02B 6/00. Exceptionally, where an optical aspect of the light guide coupling of general interest is disclosed, such a secondary class may be given. A class in G02B 6/00 is always given where a passive light guide per se has been specially adapted.

The primary protective coating immediately surrounding the cladding of an optical fibre is considered to be a component of an optical fibre and is thus classified in the G02B 6/02 subgroup. Further layers around the optical fibre are considered to form optical cables and are thus classified in G02B 6/44 and subgroups. This definition is also used to decide on the subgroup to be used for classifying a coupling. For example a clamp for an optical fibre is classified in G02B 6/36 whereas a clamp for an optical cable is classified in G02B 6/4471.

The following arrangement is observed for the coupling aspects of the various types of light guides:

Polarisation aspects

The following arrangement is observed in relation to polarisation aspects of light guides and light guide couplings

Wavelength selective aspects

The following arrangement is observed in relation to wavelength aspects of light guides and light guide couplings

Indexing Codes are used in some subgroups related particularly to coupling aspects to indicate additional details not available for the particular type of light guide, for example G02B 6/293 - G02B 6/29398 are assigned to waveguides of the integrated circuit kind with wavelength selective elements in addition to G02B 6/12007.

The Indexing Codes corresponding to G02B 6/0001 - G02B 6/001 and G02B 6/0096 are in F21V 2200/00.

Indexing Codes with additional detail compared to the subgroups exist in various parts of G02B 6/00, including G02B 6/032, G02B 6/02123, G02B 6/2804, G02B 6/36, G02B 6/4292 and G02B 6/4296.

G02B 2006/0098 is assigned to light guides for scanning in addition to the appropriate invention group which depends on the type of light guide.

An Indexing Code is occasionally given as a tag to the implementation of light guides in optical systems which are not covered by G02B 6/00 for assisting awareness of the existence of the related subclasses.

Aspects of the light guides for illumination per se as well as light coupling aspects.

G02B 6/0016

Illustrative example of the subject matter classified in this group:

Grooves in the light input face of light guide 100. (Source US2004/0207775 A1).

G02B 6/0018

Illustrative example of the subject matter classified in this group:

Redirecting reflective surfaces 13. (Source EP1113218 A1).

G02B 6/002

Illustrative example of the subject matter classified in this group:

Input face 2 shaped as a lens surface. (Source WO 2004/104476).

G02B 6/0021

Illustrative example of the subject matter classified in this group:

Recesses 9 in the light guide housing the light sources 8. (Source EP1666936 A1).

G02B 6/0025

Illustrative example of the subject matter classified in this group:

Prismatic sheets 56a, 56b between light source 52 and light guide 34. (Source US2003/0117793 A1).

G02B 6/0026

Illustrative example of the subject matter classified in this group:

Interference reflector 30 as wavelength selective element between light source 20 and light guide 12. (Source US2006/0002678 A1).

G02B 6/0028

Illustrative example of the subject matter classified in this group:

Intermediate light guides (optical fibers 121, 122, 123) for coupling into light guide plate 13. (source US2006/0007702 A1).

Intermediate light guide rod 2 with sideways coupling into light guide 1. (Source EP 1139015 A1).

G02B 6/003

Illustrative example of the subject matter classified in this group:

Intermediate lens 105, also used for lens sheets. (Source EP 1574780 A1)

G02B 6/0031

Illustrative example of the subject matter classified in this group:

Reflector 5. (Source WO2004/109380).

G02B 6/0036

Illustrative example of the subject matter classified in this group:

Protrusions 20 arranged in a 2D-array (applied for both regular and irregular arrays). (Source US2003/0156403 A1).

G02B 6/0038

Illustrative example of the subject matter classified in this group:

Grooves 11. (Source EP 939273 A1)

G02B 6/0041

Illustrative example of the subject matter classified in this group:

Scattering particles 29, 30 in the bulk. (Source WO2005/024478).

G02B 6/0043

Illustrative example of the subject matter classified in this group:

Scattering dots 31 on the surface of the light guide 20. (Source US 2004/0228109 A1).

G02B 6/0046

Illustrative example of the subject matter classified in this group:

Variation of the thickness of light guide plates. (Source WO2005/080863).

G02B 6/0048

Illustrative example of the subject matter classified in this group:

Stepped variation of the thickness of light guide plates. (source US2005/0248959 A1).

G02B 6/005

The mere indication that a diffusion film, a prism film or a reflecting film is present does not justify classifying in G02B 6/005 and its subclasses. At least some details of these elements have to be given in the document.

G02B 6/0051

Illustrative example of the subject matter classified in this group:

Diffusion film 14. (Source EP 1677047 A1).

G02B 6/0053

Illustrative example of the subject matter classified in this group:

Prism film 11. (Source WO2005/026793).

G02B 6/0055

Illustrative example of the subject matter classified in this group:

Reflection sheet 5. (Source US 6,486,931 B1).

G02B 6/0056

Illustrative example of the subject matter classified in this group:

(Source EP 0597261 A1).

G02B 6/006

Illustrative example of the subject matter classified in this group:

Variations purposely generating inhomogeneous light output, e.g. to display indicia or text. (Source US 5,846,070).

G02B 6/0061

Illustrative example of the subject matter classified in this group:

Variations (dot size) to compensate non-uniformities of light propagating in the light guide, so as to achieve homogeneous output intensity. (Source US2004/0136173 A1).

G02B 6/0063

Illustrative example of the subject matter classified in this group:

Light exits through top and bottom surfaces. (Source DE102004038344 A1).

G02B 6/0065

Manufacturing and material aspects of light guides having one of the features classified in G02B 6/0033 and G02B 6/0013 and lower.

Note: when classifying in this group, classification must also be made in one or more of the groups of G02B 6/0013 or G02B 6/0033 for the related device aspects

Illustrative example of the subject matter classified in this group:

The invention relates to the manufacturing apparatus for surface light source apparatus 10 and includes a pattern design system for designing the light guide pattern portions 15. (Source US 2003/0210539 A1).

G02B 6/0068

Illustrative example of the subject matter classified in this group:

Plural light sources 22. (Source US 2006/0245210 A1).

G02B 6/007

Illustrative example of the subject matter classified in this group:

Lamp 11. (Source GB 2180051 A).

G02B 6/0071

Illustrative example of the subject matter classified in this group:

Lamp tubes 212 and 222. (Source US 2003/0198038 A1).

G02B 6/0073

The mere indication that an LED is used does not justify classifying in this group.

Illustrative example of the subject matter classified in this group:

Translucent concave end face 3a has the same curvature as a translucent convex face 6 of the LED lamp 2 (Source EP 1434277 A1).

G02B 6/0076

Illustrative example of the subject matter classified in this group:

Stacked light guide plates 11 and 13. (Source US 2006/0164862 A1).

G02B 6/0078

Illustrative example of the subject matter classified in this group:

(Source DE 102004046256).

G02B 6/008

Illustrative example of the subject matter classified in this group:

Sections 7b and 7c of adjacent light guides overlap. (Source EP 2241800 A1).

G02B 6/0083

Illustrative example of the subject matter classified in this group:

Chips 62, Wiring elements 66. (Source US 2010/0246209 A1).

G02B 6/0085

Illustrative example of the subject matter classified in this group:

Heat sink 224. (Source US2010/0027293 A1).

G02B 6/0088

Illustrative example of the subject matter classified in this group:

Fixing projections 110, 210 in the housing and support grooves 130, 230 in the light guide for fixing the light guide in the housing. (Source EP 2259104 A2).

G02B 6/009

Illustrative example of the subject matter classified in this group:

Guiding structure 300 and securing device 202 for fixing the light source in the housing. (Source US2009/0290381 A1).

G02B 6/0091

Illustrative example of the subject matter classified in this group:

This group is used for devices holding the light source(s) and being directly attached to the light guide, like clamp 8 containing light emitter 9 and being attached to light guide plate 1. (Source US 2007/0285944 A1).

G02B 6/0093

Illustrative example of the subject matter classified in this group:

Protective cover 28. (Source EP 1283391 A2).

G02B 6/0095

Illustrative example of the subject matter classified in this group:

Shelves 32 formed as light guide panels. (Source US 2004/0264161 A1).

Bath tub with light guide 11 and light source 16. (Source WO 02/100230).

G02B 6/0001 and subgroups include backlights comprising light guides for liquid crystal display panels. Other aspects (other than the light guide) of liquid crystal display backlights are classified in G02F 1/1336. Direct backlights not including a light guide are classified in G02F 1/133602

Light guides in the form of long rods for illumination are classified in G02B 6/0005 and subgroups. The Indexing Codes corresponding to G02B 6/0001 - G02B 6/001 and G02B 6/0096 are in F21V 2200/00.

Optical and mechanical properties of optical fibres per se as well as optical fibres with an integral optical element, such as a Bragg grating.

G02B 6/02004

What is considered large or small usually depends on the type of fibre. For example an area of 50 square microns can be considered large for a dispersion compensating fibre (then G02B 6/02009 and G02B 6/02261 should be given) but not large for a non-zero dispersion shifted fibre (i.e. not classified in G02B 6/02004).

G02B 6/02033

Graded multimode plastic optical fibres are classified in G02B 6/02038 not G02B 6/0288. Fibres compensating modal dispersion are usually classified in G02B 6/0288 or G02B 6/02038 as they typically involve a graded index multimode fibre. 1 mm core graded POF is classified in G02B 6/02038.

G02B 6/02214

G02B 6/02214 is for dispersion tailoring only at wavelengths other than around the 1550nm window (e.g. for 850 nm, 1300 nm). G02B 6/02223 is for dispersion tailoring at 1550nm and another wavelength, e.g. 1300 nm, in the same optical fibre.

Illustrative example of the subject matter classified in this group:

G02B 6/02233

The preceding image includes references to G02B 6/02214, G02B 6/02219, G02B 6/02276, G02B 6/02223, G02B 6/02266, G02B 6/02276, G02B 6/02252.

Illustrative example of the subject matter classified in this group:

G02B 6/02242

Illustrative example of the subject matter classified in this group:

G02B 6/02247

Illustrative example of the subject matter classified in this group:

G02B 6/028

Graded multimode plastic optical fibres are classified in G02B 6/02038 not G02B 6/0288. Fibres compensating modal dispersion are usually classified in G02B 6/0288 or G02B 6/02038 as they typically involve a graded index multimode fibre. 1 mm core graded POF is classified in G02B 6/02038.

G02B 6/0285

Illustrative example of the subject matter classified in this group:

With reference to the notes to G02B 6/03616, graded inner clad 2 is not considered a layer in the sense of G02B 6/03616. Hence these examples are not for G02B 6/03633.

G02B 6/036

Some documents define the central core as the segment from the centre to where the refractive index delta is zero (e.g. US6421490 defines "the radius from the waveguide centerline to the location of the last refractive index point is the outer radius of the core segment."). The definition in the G02B 6/03616 notes takes precedence.

The outer cladding is also considered a layer. If the coating affects the guiding due to its refractive index then it is also considered a cladding layer. Care must be taken not to count beyond the external clad e.g. the following example has 2 clad layers, the top figure can be misleading.

When the profile shows many alternating refractive index layers possibly G02B 6/023 will be relevant.

G02B 6/036

Illustrative example of the subject matter classified in this group:

Radial asymmetry concept not reflected in lower subgroups.

G02B 6/03605

Illustrative example of the subject matter classified in this group:

G02B 6/03611

Illustrative example of the subject matter classified in this group:

G02B 6/03611 as additional information is used for some documents where the profile has a centreline depression as a result of the manufacturing procedure but there is no purposeful effect on the guiding properties or dispersion properties.

This is however not classified in G02B 6/03611 Since the centreline dip does not affect the optical fibre properties and it is not discussed in the document in detail.

G02B 6/03627

Illustrative example of the subject matter classified in this group:

e.g. W profile

Layers 2 (- relative to central core of width a) and 7 (+ relative to 2).

G02B 6/03633

Illustrative example of the subject matter classified in this group:

Two layers 2 and 5 around central core segment 1. Layer 2 is a layer in the sense of the G02B 6/03616 definitions, and thus G02B 6/0285 is not appropriate.

Central core segment between -a and a, first layer (ring) between a and b, second layer (ring) between b and d.

G02B 6/03638

Illustrative example of the subject matter classified in this group:

G02B 6/03644

Illustrative example of the subject matter classified in this group:

e.g. WT profile

Layer 1 -, layer 2 +, layer 3 -.

Central core segment 41 (design), 60 (measurement) with three surrounding layers arranged - + -.

G02B 6/0365

Illustrative example of the subject matter classified in this group:

- (21) - (22) + (23).

G02B 6/03655

Illustrative example of the subject matter classified in this group:

G02B 6/03661

Illustrative example of the subject matter classified in this group:

G02B 6/03666

Illustrative example of the subject matter classified in this group:

G02B 6/03672

Illustrative example of the subject matter classified in this group:

G02B 6/03677

Illustrative example of the subject matter classified in this group:

- (74) + (76) + (78) - (79).

G02B 6/03683

Illustrative example of the subject matter classified in this group:

- (21) - (22) + (40) + (41).

G02B 6/03688

Illustrative example of the subject matter classified in this group:

74-80= 5 layers.

6 layers.

G02B 6/03694

Illustrative example of the subject matter classified in this group:

Layers 122 and 123 have the same refractive index but different loss properties.

The Ge and Ge+Al l have the same refractive index but different acoustic properties.

Layers 15 and 16 have the same refractive index but are formed by different methods so that layer 15 has lower losses but takes longer to form.

Indexing Codes

Fluid core or claddings are classified in G02B 6/032 and G02B 2006/0325. No corresponding group exists for Indexing Code G02B 2006/0325.

All embodiments of patent documents are classified. This is of particular relevance for classifying multilayered optical fibre refractive index profiles in G02B 6/036 - G02B 6/03694.

Waveguides which are not of the integrated circuit kind, are not optical fibres and are not used for illumination are classified in the subgroups G02B 6/10 - G02B 6/107. There are three exceptions: the subgroups G02B 6/102 and G02B 6/105 include both optical fibres and waveguides of the integrated circuit kind, and G02B 6/107 includes all sub-wavelength diameter waveguides.

Light guiding paths in an integrated circuit, particularly waveguides formed in a planar substrate, including single paths as well as multiple paths which interact with each other with or without optical elements in or between the light guiding paths. This subgroup further covers methods of producing the waveguides.

Wavelength selective arrangements are classified in G02B 6/12007 with the corresponding Indexing Code symbols G02B 6/293 - G02B 6/29398 assigned. For example a planar waveguide arrangement of ring resonators for wavelength selection is classified in G02B 6/12007 and G02B 6/29338.

The coupling of light within planar waveguide substrates is classified in G02B 6/12 and subgroups. Coupling light into or out of an integrated circuit having light guiding paths is classified in the appropriate one of G02B 6/26, G02B 6/30 - G02B 6/305, G02B 6/34, G02B 6/3596, G02B 6/42 and G02B 6/43.

Indexing Codes

G02B 2006/12085 - G02B 2006/12092, G02B 2006/12111 and G02B 2006/12035 are inactive, i.e. they contain some documents but are not used for classification of new documents.

Some of the remaining Indexing Codes correspond to groups as shown in the table below.

The Indexing Codes G02B 2006/12095 - G02B 2006/12104, G02B 2006/12109, G02B 2006/12114 - G02B 2006/12128, G02B 2006/12135 - G02B 2006/12161, G02B 2006/12169, G02B 2006/12173, G02B 2006/12192 and G02B 2006/12197 are used for additional details not listed in the G02B 6/12 subgroups, for example a bent planar waveguide is classified in group G02B 6/125 and with Indexing Code G02B 2006/12119.

The status of the use of the Indexing Codes G02B 2006/12083 - G02B 2006/12197 is shown in the table below:

Mechanical coupling aspects of optical elements other than the light guides is classified in the subgroup relating to the optical coupling. For example the mechanical coupling of a fixed reflective bulk diffraction grating between optical fibres is classified in G02B 6/2931, and mechanical means for holding a lens between an optical fibre and an opto-electronic element are classified in G02B 6/4204.

The mechanical coupling of light guides is classified in G02B 6/36-G02B 6/406 and/or G02B 6/42-G02B 6/43. When the mechanical coupling is for a particular type of optical coupling between light guides then the appropriate one of G02B 6/26-G02B 6/3596 is also given. For example a lens coupling together light guides which are mechanically coupled on a substrate is classified in G02B 6/36 - G02B 6/3696 and G02B 6/32.

The optical coupling of light into, out of or between light guides.

G02B 6/29302

Illustrative example of the subject matter classified in this group:

(Source US6208442).

NOTE US6804057 not for G02B 6/29302 as wavelength selection based on etalons not wavelength dependent polarisation effect

G02B 6/29304

See additional explanation in the special rules section for more details relating to separation between G02B 6/29305 and G02B 6/29316 (concerning diffractive elements attached to optical fibres)

G02B 6/29305

Free space means not confined, not necessarily that there is no material

Bulk grating 25. (Source WO0137021).

G02B 6/29307

Illustrative example of the subject matter classified in this group:

Transparent block formed of 26', 28 and 22. (Source WO9931532).

G02B 6/29308

Illustrative example of the subject matter classified in this group:

Curved bulk grating 47. (Sources US2002181856 for fig. 11, US4784935 for fig.8).

G02B 6/2931

Illustrative example of the subject matter classified in this group:

(Source WO0137021).

G02B 6/29311

Illustrative example of the subject matter classified in this group:

Transmissive grating 9. (Source WO0029888).

G02B 6/29313

Illustrative example of the subject matter classified in this group:

Adjustable support 14 for positioning optical fibres 5 to 8. (Source US5305402).

G02B 6/29314

Illustrative example of the subject matter classified in this group:

Screw 17 for moving grating 9. (Source US4763969).

G02B 6/29316

includes gratings in contact with the light guide causing diffraction in the light guide, e.g. in contact with the side of a polished fibre (i.e. no free space, no intermediate element other than coupling medium, closely linked to diffractive elements integrated in the light guide) i.e. beam interacting with the diffractive element confined in at least one dimension transverse to propagation. EP1574883 fig. 1 has collimator between fibre and diffractive film thus is not for group G02B 6/29317 (Indexing Code G02B 6/29317 is appropriate). US4148556 fig. 3 is for group G02B 6/29322 as grating is butt coupled.

G02B 6/29317

Illustrative example of the subject matter classified in this group:

Optical fibre 71 with grating 72. (Source US6334014).

G02B 6/29319

Illustrative example of the subject matter classified in this group:

Cascade of optical fibre gratings 325. (Source EP1024378).

G02B 6/2932

Illustrative example of the subject matter classified in this group:

Directional router 18 (circulator) and optical fibre grating cascade 12, 14. (Source EP857988).

G02B 6/29322

Illustrative example of the subject matter classified in this group:

Tunable optical fibre gratings 104 to 109. (Source EP95385).

Tunable Bragg gratings (indicated by electrodes). (Source US6097861).

G02B 6/29323

Illustrative example of the subject matter classified in this group:

Light coupled via grating 12 through bottom (lateral) surface of light guide 10. (Source US6016375).

G02B 6/29325

Illustrative example of the subject matter classified in this group:

Slab light guide 50. (Source WO9211517).

G02B 6/29326

Illustrative example of the subject matter classified in this group:

Curved grating 22 on plate light guide 20. (Source US4784935).

G02B 6/29332

Illustrative example of the subject matter classified in this group:

Evanescent coupling in tapered portion 3. (Source EP416537).

G02B 6/29334

Illustrative example of the subject matter classified in this group:

Grating 130 in evanescent coupling region. (Source US20020028040).

G02B 6/29335

Emphasis is on evanescent coupling from a waveguide mode to a resonant mode of a closed loop resonator but see US4720160 fig. 1 where loop resonators are not used. NB in a Sagnac, light only circulates once before interfering thus G02B 6/29347

NOTE: see additional explanation in the special rules section below for more details relating to separation between G02B 6/29335 and G02B 6/29356 or G02B 6/29358 (evanescent and non-evanescent coupling of resonators)

G02B 6/29337

Illustrative example of the subject matter classified in this group:

Linear resonator between 5 and 8 coupled via evanescent coupling at region 6. (Source US4859017).

G02B 6/29338

Illustrative example of the subject matter classified in this group:

Ring resonator 1404. (Source US6718086).

G02B 6/2934

Illustrative example of the subject matter classified in this group:

Evanescent coupling to a loop cavity 14a. (Source US4720160).

G02B 6/29341

Whispering gallery mode (WGM) resonance corresponds to light that is trapped in circular orbits just within the surface of the structure. The modes are most strongly coupled along the equatorial plane and they can be thought to propagate along a zig-zag paths around the sphere.

Microsphere 120 supports WGM resonance. (Source US6389197).

(Source US2005128566).

G02B 6/29343

Illustrative example of the subject matter classified in this group:

Cascade of loop resonators 1004, 1008, 1016, 1018,1020, 1022. (Source US6643421).

G02B 6/29344

At wavelength L1 shown in FIG. 1a, the dual-mode section W2 is n beatlengths long and the filter (fig. 5) passes radiation. At wavelength L2 shown in FIG. 1b, the dual-mode W2 section is n-1/2 beatlengths long and so radiation is not coupled from the dual-mode filter to the output single-mode filter (W3). (Source US5796891).

G02B 6/29347

Emphasis is on interference between split beams at least one of which travels a loop delay distance

Loops 27 and 37 apply two different delays to beams along optical paths, so that the beams are interfered to form respective output beams corresponding to odd and even communication channels. (Source US2003234935).

G02B 6/29349

Illustrative example of the subject matter classified in this group:

US6252716

(Source US6252716).

G02B 6/2935

Illustrative example of the subject matter classified in this group:

(Source EP1293814).

G02B 6/29353

Illustrative example of the subject matter classified in this group:

Ring resonator 310 coupled to arm 322 of Mach-Zehnder Interferometer. (Source US6834141).

Gratings 212 & 214 in arms 208 & 201 of Mach-Zehnder Interferometer. (Source US2006002653).

G02B 6/29355

Illustrative example of the subject matter classified in this group:

Cascade of Mach-Zehnder Interferometers 13a-13d. (Source WO2005071453).

G02B 6/29356

Illustrative example of the subject matter classified in this group:

End coupling into cavities formed by reflective gratings 209, 210. (Source EP1024378).

NOTE: see additional explanation in the special rules section for more details relating to separation between G02B 6/29335 and G02B 6/29356 or G02B 6/29358 (evanescent and non-evanescent coupling of resonators)

G02B 6/29358

Interferometer 1. (Source EP1703307).

NOTE: see additional explanation in the special rules section for more details relating to separation between G02B 6/29335 and G02B 6/29356 or G02B 6/29358 (evanescent and non-evanescent coupling of resonators)

G02B 6/29359

Cavity outside light guide, does not include intermediate elements between fibre end face and filter.

Cavity 26 between mirrors 30 & 32 on ends of light guides 38 & 40. (Source US5202939).

G02B 6/29362

Illustrative example of the subject matter classified in this group:

Cascade of filters 131, 132, 133. (Source US2008112668).

Cascade of filters 73 & 75. (Source WO2006080249).

G02B 6/29364

Illustrative example of the subject matter classified in this group:

Cascade of filtering operations on single filter 24 by light guide 12. (Source WO03021319).

G02B 6/29365

Illustrative example of the subject matter classified in this group:

Zigzag path between filter film 7 and reflector film 8. (Source GB2304204).

G02B 6/29367

Illustrative example of the subject matter classified in this group:

Zigzag path in solid block formed of components 74,78,81 and single solid block 2 (Sources WO2006080249 for fig. 30, GB2304204 for fig. 1).

G02B 6/29368

No coupling optics (such as a lens) between fibre and filter

(Source Yokosuka et al. Proc. 40th Electronic components and technology conference, May 20-23, 1990, p. 865, XP144764).

G02B 6/2937

Illustrative example of the subject matter classified in this group:

(Source US2004042719)

(Source US2003025967)

G02B 6/29373

Illustrative example of the subject matter classified in this group:

Dispersive prism 3. (Source JP55057804).

G02B 6/29376

Illustrative example of the subject matter classified in this group:

Light guides 103, 105, 107 and 109 with different dispersion. (Source EP0684709).

G02B 6/2938

Illustrative example of the subject matter classified in this group:

Input signal A demultiplexed into different wavelength signals. (Source US6643421).

G02B 6/29383

Illustrative example of the subject matter classified in this group:

Signal added at F-A and dropped at F-D. (Source US6718086).

G02B 6/29386

Illustrative example of the subject matter classified in this group:

Input signal 1610 de-interleaved into odd and even channels 1620, 1630. (Source EP1293814).

G02B 6/287 is not used for classification. G02B 6/255, G02B 6/2835, G02B 6/2856 and G02B 6/29331 are used instead.

The following arrangement is observed in relation to optical fibre couplers:

Prisms or gratings coupled to light guides for purposes other than wavelength selection are classified in G02B 6/34.

Systems for wavelength division multiplexing based on optical fibres are classified in H04J 14/02, H04J 14/03, H04J 14/0305 and H04J 14/0307. Reference is made to the section "Relationship between large subject-matter areas" under G02B 6/00.

Planar waveguides

Couplings between separate planar waveguide substrates, e.g. using intermediate bulk optics, are classified in G02B 6/26. Planar waveguide couplings are also classified in G02B 6/30-G02B 6/305, G02B 6/34, G02B 6/3596, G02B 6/42 and G02B 6/43.

G02B 6/262-G02B 6/29398, G02B 6/32-G02B 6/327 are restricted to light guides of the optical fibre type.

The coupling of light within planar waveguide substrates is classified in G02B 6/12 and subgroups. For example optical fibre couplers are classified in G02B 6/2804 whereas planar waveguide couplers are classified in G02B 6/125. The one exception is G02B 6/3596.

In G02B 6/35 and subgroups a single subgroup is assigned (the most relevant) with further aspects classified in the Indexing Code.

Indexing Codes

No groups correspond to Indexing Codes G02B 2006/2839 and G02B 2006/2865.

Separation between G02B 6/29305 and G02B 6/29316

G02B 6/29305 is for bulk diffraction elements (gratings) with free space between the light guide and grating. This means that before interacting with the grating the light beams are not guided in the light guide for a certain distance (or vice-versa).

G02B 6/29316 is for light guides comprising the grating. This means there is no free space between the light guide and the grating and the light beams are guided in the light guide onto the grating (or vice-versa).

Examples.

G02B 6/29311

Diffractive film DF is on a collimator C. (Source EP1574883).

G02B 6/29322

Butt coupled grating 50, no free space to light guide 42. (Source US4148556).

G02B 6/29317

No free space between grating and fiber. (Source Sorin et al. in Journal of Lightwave Technology, Vol. LT-3, Oct 1985, p. 1041, XP1652325).

Separation between G02B 6/29346 and G02B 6/29335

Parallel plate resonators can be in either G02B 6/29358 or G02B 6/29335 - the correct group depends on how the resonator is coupled to the light guide.

Where light is coupled into the resonator from the light guide by evanescence G02B 6/29335 is appropriate (i.e. the evanescent field of the light guided in the light guide overlaps with the resonant mode of the resonator). This is usually the case with lateral coupling, but not always.

Examples

US20070104421 in G02B 6/29358

Parallel plate resonators formed by resonator members 18, 19, 28 and 29 external to light guides 13, 23 and light coupled between resonators and light guides by deflector means 16 and 26. (Source US20070104421).

G02B 6/29337

Linear resonator between 5 and 8 coupled via evanescent coupling at region 6. (Source US4859017).

Devices of the type shown in fig. 1-3 below with evanescent coupling to a linear cavity between mirrors 24 & 26 are classified in G02B 6/29337, of the type shown in fig. 4 below with evanescent coupling to a loop cavity 14a are classified in G02B 6/2934

(Source US4720160).

Devices of the type shown in fig. 6B with evanescent coupling to a cascade of loop resonators 180 are classified in G02B 6/29343. Devices of the type shown in fig. 7A & 9C below with end coupling into cavities formed by reflective gratings (i.e. without evanescent coupling into a resonator cavity) are classified in G02B 6/29356.

(Source EP1024378).

The mechanical coupling of optical fibres, e.g. mechanical means for holding optical fibres on a substrate, and mechanical means such as connectors for the interconnection of optical fibres.

G02B 6/3608

Illustrative example of the subject matter classified in this group:

(Source US2003/0179980).

G02B 6/3612

Illustrative example of the subject matter classified in this group:

(Source EP 1 182 483).

G02B 6/3616

Illustrative example of the subject matter classified in this group:

(Source US2006/0251374).

G02B 6/3624

Illustrative example of the subject matter classified in this group:

(Source US 4,799,755).

G02B 6/3628

Illustrative example of the subject matter classified in this group:

Optical fibre (16). (Source WO03/021312).

G02B 6/364

Illustrative example of the subject matter classified in this group:

(Source US 2004/0086255).

G02B 6/3652

Illustrative example of the subject matter classified in this group:

(Source US2001/0042756).

G02B 6/3656

Illustrative example of the subject matter classified in this group:

(Source WO01/37005).

G02B 6/366

Illustrative example of the subject matter classified in this group:

(Source US2004/0208422).

G02B 6/3668

Illustrative example of the subject matter classified in this group:

(Source US2003/0031436). (also classified in G02B 6/3676).

G02B 6/3672

Illustrative example of the subject matter classified in this group:

(Source US2003/0215206).

G02B 6/3676

Illustrative example of the subject matter classified in this group:

(Source WO03/007036).

G02B 6/368

Illustrative example of the subject matter classified in this group:

(Source GB2331161).

The mechanical coupling between optical fibres or of optical fibres with opto-electronic elements is classified in the appropriate groups of G02B 6/38 - G02B 6/3897 and G02B 6/42-G02B 6/43 and additionally in Indexing Codes G02B 6/3608-G02B 6/3696, especially when the latter are more detailed. Light guides coupled together as a splice by mechanical holding means, i.e. mechanical splices, are classified in G02B 6/3801.

The mechanical coupling of optical fibre cables and the storage of optical fibres is classified in G02B 6/4401 and subgroups.

In G02B 6/3608-G02B 6/3696 as far as possible only one subgroup is assigned with further aspects classified in Indexing Codes G02B 6/3608-G02B 6/3696.

A demountable optical fibre connector is often classified in several of the G02B 6/3807 - G02B 6/3897 subgroups and/or Indexing Codes G02B 6/3807-G02B 6/3897 to reflect the various aspects of the connector. This is especially important to allow retrieval of mechanical configurations which are not easily searchable using words.

Optical fibre connector accessories and tools, e.g. for assembling, insertion or extraction of connectors not provided for elsewhere are classified in G02B 6/3807. The testing of optical fibre connectors is classified in G01M 11/00 and subgroups. Devices for cleaning optical fibre connectors are classified in G02B 6/3807 and circulated to B08B 1/00.

G02B 6/40-G02B 6/403 relate to optical fibre bundles in the sense of G02B 6/04.

Planar Waveguides

The mechanical coupling of planar waveguides is classified in the appropriate one of G02B 6/12-G02B 6/12033, G02B 6/30-G02B 6/305, G02B 6/42 and G02B 6/43.

Demountable optical fibre connectors presenting a protuding free optical fibre end

Illustrative example of subject matter classified in this group:

(Sources: US5,694,506, FR2818839)

Demountable optical fibre connectors having ferrules.

Illustrative example of subject-matter classified in this group:

Ferrules 11a, 11b. (Source: JPS5674211)

Details of the ferrule, mounting of prepared optical fibre in the ferrule.

Mounting of the assembled fibre and ferrule into the connector body and details of the connector body.

Optical coupling aspects of light guides for illumination are classified in G02B 6/0001 - G02B 6/0096. The coupling of non coherent light, including lamps, into optical fibres for purposes other than illumination is classified in G02B 6/4298.

Electric, thermal and mechanical aspects of packages not covered by G02B 6/4202 - G02B 6/4298 are classified in G02B 6/4201. G02B 6/4201 - G02B 6/4215 also include documents where the light guide is implicit.

The coupling of light guides with opto-electronic elements using a wavelength selective or polarisation selective and adjusting optical element are classified in G02B 6/4215 or G02B 6/4246 and the relevant G02B 6/27 - G02B 6/2793 and/or G02B 6/293 - G02B 6/29398, since the latter are more detailed.

Mechanical coupling aspects of optical fibre arrangements classified in G02B 6/42 - G02B 6/43 are additionally classified in G02B 6/36 - G02B 6/3696 especially when the latter are more detailed.

Connector aspects of disconnectable light guide arrangements classified in G02B 6/4292 are also classified in G02B 6/3807 - G02B 6/3897 and/or G02B 6/3807 - G02B 6/3897.

Planar Waveguides

Planar waveguides coupled with optoelectronic elements are classified in G02B 6/42 with G02B 6/4201 - G02B 6/4296 assigned for the details (e.g. G02B 6/42 and G02B 6/4214), however monolithic configurations, i.e. where the planar waveguide and optoelectronic element are grown on the same substrate are classified in G02B 6/12004.

Indexing Codes

G02B 6/4292 has the additional Indexing Code G02B 2006/4297 for protection means, e.g. using shutters to avoid inadvertent exposure

G02B 6/4439 - G02B 6/44785 are also used for classifying auxiliary devices with uncabled optical fibres. For example the storage of optical fibres in spools is classified in G02B 6/4457.

Optical cable installations in buildings, for example over multiple floors, are classified in G02B 6/475.

Mountings, adjusting means, including means for effecting focusing and zooming, and light-tight connections for optical elements like lenses, prisms or mirrors or the like.

The following simplified arrangements are to be observed in relation to mechanical aspects of focusing and zooming (G02B 7/04):

The following IPC subclasses are not used for classification: G02B 7/185 - G02B 7/198 (subject-matter covered by G02B 7/182 and other subgroups of G02B 7/182).

Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -. The plus (+) symbol represents a positive lens, and the minus (-) symbol represents a negative lens

Optical objectives specially designed for specific purposes.

Concerning the subgroup G02B 13/001 (miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras), symbols from G02B 13/0015 and G02B 13/0055 will usually be assigned. In G02B 13/002, one compound lens counts as one lens. The symbol G02B 13/006 indicates the presence of a compound element. The following figures illustrate typical examples of the subject-matter found in the indicated subdivisions:

With the exception of G02B 13/06, optical objectives having reflecting surfaces are not classified under G02B 13/00, but under G02B 17/00.

Unless specified in the title of the subgroups, this group and its subgroups do not cover objectives comprising reflecting surfaces, which are covered by G02B 17/06, G02B 17/08 and their subgroups

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

(note: second group G02B 13/007)

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

(as a tag, double classification with the group for the respective element)

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

(lenses 310 are deformed by exerting radial force on the lens bodies; other variable elements, diaphragm, LC-elements, etc.)

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Details covered by G02B 15/00 are to be classified there as well.

Objectives designed to cover a very wide field of view not achievable by standard lens systems.

For example:

G02B 13/06 is also used to classify catadioptric optical systems providing a 360°overage

Rectilinear,e.g. non-distorting, wide angle objective are classified in G02B 13/04

Refractive optical objectives with means for varying the magnification, e.g. zoom lenses;

optical aspects thereof.

The range G02B 15/142 - G02B 15/1465 covers zoom objectives characterised by the number of groups and the corresponding refractive power sign sequence of the groups.

The refractive power of a group is the combined refractive power of the lenses constituting the group.

Groups are counted as consecutive sets of one or more lenses that remain fixed or move in unison, e.g., distances between lenses are constant within a group whereas distances between groups are variable during zooming.

Lens groups having two or more separate subgroups with a variable spacing are to be counted as multiple groups.

The symbols have the following systematic structure:

"A" is the number of groups

"B" defines the sign of the first group: 1 if the refractive power of the group is positive and 5 if negative

"CD" is a two-digit number with an eventual leading zero defining the remaining refractive power sequence on the basis of a decimal conversion of the plus (1) or minus (0) binary sequence of the positive groups, e.g. the sum of the values of the remaining positive groups, plus one (1):

The first group has always the value of one (1) regardless of the sign of the first group, e.g. one (1) is added to the total, to avoid trailing zeros.

The sign of the first group is coded in position B.

Examples:

A = 4 groups

B = 5 (1^st negative)

CD = 1*1+2*1+4*1+8*0 = 07

G02B 15/144507 { arranged - + + - }

A = 5 groups

B = 1 (1^st positive)

CD = 1*1+2*1+4*1+8*0+16*1 = 23

G02B 15/145123 { arranged + + + - + }

Systems with reflecting surfaces, with or without refracting elements, e.g. catoptric systems, catadioptric systems

G02B 17/00, as the main group, is only for reflecting systems which do not fit into any of the sub-groups.

Example: a polar to rectangular coordinates converter:

G02B 17/00 in general should be seen as an optical design group.

The division with G02B 17/08 (catadioptric systems) is strict, the presence of any refracting element having power or asphere to correct the aberrations of the system qualifies the combination as catadioptric.

Solid systems (where the air is replaced by glass) are also catadioptric, even with zero power air interfaces.

Some application specific mirror systems relating to G02B are covered by groups outside this main group. However details might be classified in G02B 17/00. Examples are:

Arrays of reflective systems. This is essentially to mirror systems what lens arrays are for lenses. The class can be combined with other G02B 17/02, G02B 17/04, G02B 17/06, G02B 17/08 classes describing the optical design.

Systems comprising multiple reflections between at least two reflecting surfaces, e.g. cells, resonators. This subgroup covers both catadioptric and catoptric systems, as the number of documents is too small to justify a division between G02B 17/06 and G02B 17/08.

Systems in which the light is reflected on a plurality of parallel laminas (venetian blind lens, louvre mirror, TIR - total internal reflection lens). This subgroup covers both catadioptric and catoptric systems, as the number of documents is too small to justify a division between G02B 17/06 and G02B 17/08. Fresnel mirrors are in G02B 5/09.

Reflective systems specially adapted to form relays or chainable optical systems. Mainly unit magnification systems like Dyson optics or Offner relays.

Sequences of flat reflective (zero power) surfaces made of mirrors and prisms.

Essentially sequences of flat mirrors to extend a path length, e.g. in a flatbed scanner.

For extending an optical path length, e.g. delay lines

Image erecting and reversing systems, beam redirecting.

Static systems for changing the direction of a beam or pivoting an image

Prism sequences as far as the reflecting surfaces have no power. Powered prisms generally go in the catadioptric class G02B 17/08 (unless an image erecting effect is produced).

Image erecting and reversing systems, including classical erecting prisms. Similar to G02B 17/026, but with prisms only. Some overlap with G02B 5/04 and G02B 27/14.

The class might also be given for solid catadioptric systems that integrate an erecting function.

Systems comprising mirrors only.

combinations of a single curved mirror (on or off axis) with any number of plane mirrors go into the group G02B 17/06. Single segmented mirrors are classified in G02B 5/09. Synthetic aperture systems G02B 27/58)

The subgroups G02B 17/0605, G02B 17/0626 and G02B 17/0647 relate to systems having 2 mirrors, 3 mirrors and more than 3 mirrors respectively, and are strictly imaging groups, including linear field imaging systems (scanner optics).

The structure of these groups, by way of example for G02B 17/0605 is the following:

The general rule is to count the number of optical surfaces relevant for the optical design process:

On axis systems, without a central aperture.

On axis systems, with at least one central aperture.

Off-axis, unobscured, optical systems, the mirrors having a common optical axis.

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

mirror 2 is actually two mirrors 1 and 3.

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative examples of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Non imaging systems.

Devices that are not emitter or receiver specific.

The group has been subdivided to cover systems disclosed as being used to illuminate a detector, or used in close conjunction with a light source (e.g. for LED illumination). Often the emitter/detector is an integral part of the device. Reflecting pipes are in G02B 27/0994 or G02B 6/00.

Example: a non-imaging system in the form of a rotating optical joint

G02B 17/0673 ..for light condensing (emitters)

G02B 17/0678 ... in a 360° plane or hemisphere

G02B 17/0684 ...for light collecting (receivers)

G02B 17/0689 ...in a 360° plane or hemisphere

Zoom mirror systems, but also multiple focus or multiple magnification systems, and systems having both large and small FOVs.

Catadioptric systems

This group is subdivided according to the same scheme as the systems of G02B 17/06.

In addition, subgroups have been added to cover the structure or function of the refractive element.

G02B 17/0852: Field Corrector

Systems where a set of field lenses correct the aberrations of the mirrors.

The field corrector definition should be taken broadly to include systems where all lenses are located between the focal plane and the first mirror (starting from the FP).

Systems with field flattener lenses and pupil correctors get also this class when the design of the field corrector is detailed or discussed.

G02B 17/0884: Pupil Corrector

The pupil corrector having spherical surfaces, e.g. Maksutov or Houghton telescopes

G02B 17/0888: Pupil Corrector

The pupil corrector having an aspheric surface, e.g. Schmidt camera

G02B 17/0856 : Mangin mirror, i.e. a lens with a mirrored surface

G02B 17/086: Solid Catadioptric, e.g. comprising solid blocks

G02B 17/0864: Non imaging catadioptric

The G02B 17/0864 subgroup is subdivided according to the same scheme as the systems of G02B 17/0668.

G02B 17/0892: Specially adapted for UV (includes lithography objectives even without an explicit UV reference)

G02B 17/0896: With means for varying the magnification or providing a plurality of image planes from a single pupil (same rules as for G02B 17/0694)

The following table gives examples of patent documents classified in the subgroups of G02B 17/06 or G02B 17/08:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Illustrative example of subject matter classified in this group:

Optical condensers, light collectors and similar non-imaging optics.

Concerning optical arrangements for illumination from LEDs, the practice is to classify in G02B 19/0061 (or G02B 19/0066 for LED arrays) and in one or more other classes under G02B 19/00 according to the optical means employed. In particular:

In the above examples, the classification G02B 19/0071 is additionally given in the case of adaptation to illuminate a complete hemisphere or a plane extending 360° around the source. For example, the following arrangement would be classified in G02B 19/0061, G02B 19/0028 and G02B 19/0071:

Optical microscopes including conventional microscopes, as well as laser scanning microscopes, confocal microscopes, fluorescence microscopes, video microscopes or optical aspects of surgical microscopes.

Non-confocal fluorescence microscopes, including visible and infrared ones, are classified in G02B 21/16

Eyepieces (e.g. for microscopes or telescopes); Magnifying glasses

Optical devices or arrangements using movable or deformable optical elements for controlling the intensity, colour, phase, polarisation or direction of light, e.g. switching, gating, modulating

Optical devices or arrangements the optical operation of which involves changing the optical properties of the material used by an applied field or force G02F 1/00

Systems providing spectral filtering by an adjustable, e.g. variable spacing, optical cavity.

Adjustable Fabry-Perot devices in spectroscopy applications, e.g. as monochromators or for spectral analysis are classified in G01J 3/26. A further classification in G02B 26/001 is optional.

All documents describing rotating particle displays ("gyricons" etc.) are to be classified in G02B 26/026, for example:

However, electrophoretic displays (involving particles moving linearly under the influence of an electric field) are classified in G02F 1/167.

Control of the intensity of light based on variable absorption of orientable dipolar particles is classified in G02F 1/172.

G02B 26/0833 is directed to optical MEMS per se with a high emphasis on the optical properties of the devices and their interaction with other optical elements in the apparatus.

Other optical systems, for example, head-up displays, head-mounted displays, beam-shaping systems, beam-splitting or combining systems, systems for producing stereoscopic or three-dimensional effects, polarising systems, diffraction systems.

Further details of other subgroups of G02B 27/00, like G02B 27/10 through G02B 27/44, see the definition of G02B 27/01.

The following IPC group is not used for classification: G02B 27/18, see the relevant subclasses according to the projector type. The subclass G02B 27/20 is, however, used for laser pointers or the like.

Devices for superimposing a synthetic image on a background scene by projection of a synthetic image on a background scene on a partially transparent surface:

Examples of subject matter covered are:

Projection of flight or drive data on the windscreen of a plane or of a car (see for example US2011298693 paragraphs [0022],[0023], figure 1).

Vizor of pilots helmet with a partially transparent surface ("helmet mounted displays")

Further details covered by G02B 27/01 and not provided for in any of its subgroups is provided for in the subgroups of Indexing Codes G02B 27/01 and below. Classification is obligatory.

Further details of other subgroups of G02B 27/00

G02B 27/10: Beam splitting or combining systems

The scheme comprises subgroups covering specific structural technical solutions ("means") and a parallel set of subgroups covering the purposes of the devices, independently of the specific type of beamsplitter used.

The subgroup G02B 27/10 is intended for beamsplitting/combining systems which cannot be given any lower means subgroup in the scheme. In general, documents should be assigned at least one means subgroup and at least one purpose subgroup.

Purpose Subgroups: Examples

G02B 27/1006 for splitting or combining different wavelengths

For wavelength specific documents which are not covered by any lower entry.

All color imaging related documents are in the color sensing subgroup (G02B 27/1013) or in one of the color reproducing subgroups (G02B 27/102 and subgroups). These subgroups are not limited to RGB devices and cover also non visible or pseudocolor devices as long as the final image is intended for the human viewer.

G02B 27/1013

For color or multispectral image sensors, e.g. splitting an image into monochromatic image components on respective sensors.

The devices must be imaging devices, including line scanning. Other spectral sensing devices belong to G02B 27/1006.

G02B 27/102

For generating a color image from monochromatic image signal sources.

Essentially covers color generating systems not specifically designed for a particular type of SLM, e.g. illumination systems combining multiple light sources

G02B 27/1026

For use with reflective spatial light modulators

WO0038432

US2001000973

G02B 27/1033

Having a single light modulator for all colour channels

G02B 27/104

For use with scanning systems

Beams splitter/combiner arrangement for color scanning display arrangements

G02B 27/1046

For use with transmissive spatial light modulators

The "classic" 3 LCD projector;

G02B 27/1053

Using a single light modulator for all colour channels

for example time sequential led sources used with a single SLM, US2006196944

could be extended to light pipes: EP1003064

G02B 27/106

For splitting or combining a plurality of identical beams or images, e.g. image replication.

Quite a few documents deal with obtaining multiple identical copies of a beam. The numbers of beam should be four or more, color aspects are not relevant for this class.

US2006082890: construction laser

DE3502382: Laser beam replication.

G02B 27/1073

Characterized by manufacturing or alignment methods, e.g. assembly of cross dichroic cubes.

US5455678

EP0947869

The subgroup is also relevant for mechanical aspects and devices where the alignment of the beams requires a particular construction (equivalent to G02B 7/00 for beamsplitters).

G02B 27/1066

For enhancing image performance, e.g. resolution, pixel numbers, dual magnifications or dynamic range, by tiling, slicing or overlapping fields of view. Covers sensing or imaging devices where fields are either

Resolution should be taken in a broad sense, including high dynamic range systems.

GB2222892: high resolution CRT with a low resolution LCD

WO2008129552: "foveal" devices, narrow HD field with a large low resolution field

WO98/10402: mosaic displays

CA1073715: Slicing/dividing an image

G02B 27/108

For sampling a portion of a beam or combining a small beam in a larger one, e.g. wherein the area ratio or power ratio of the divided beams significantly differs from unity, without spectral selectivity. Sampling devices for high power laser, laser beam insertion.

US4746205

GB2027222

Means Subgroups: Examples

The decisive criterion is the physical principle leading to the splitting or combining, and not other aspects of the device. For example a cube beamsplitting prism operates by reflecting (part of) the beam, and hence operates by reflection, even though it also has refracting surfaces. Following the optical path, the relevant surface marks the boundary between the single beam and the multiple beams.

IPC classes G02B 27/12 and G02B 27/14 refer to "refraction only" or "reflection only" but some devices use both reflecting and refracting beamsplitting structure, e.g. US6400512 :

Applying strictly the IPC wording of the headers G02B 27/12 or G02B 27/14, such documents would not have their details classified in these subgroups. For the purpose of CPC classification, the limitation "only" should be disregarded. The above document would therefore be classified in G02B 27/12 (or a subgroup thereof) and G02B 27/14 (or a subgroup thereof).

G02B 27/1086

Operating by diffraction only

Polychromatic diffractive combiners may be additionally classified in G02B 27/1013 or G02B 27/102.

US2006109876

G02B 27/1093

For use with monochromatic radiation only, e.g. devices for splitting a single laser source

Since diffractive elements are intrinsically wavelength dependent, purely monochromatic devices represent special applications. G02B 27/1086 and G02B 27/1093 cover passive diffractive devices only

G02B 27/12

Operating by refraction only.

This subgroup comprises inter alia systems using birefringent materials for standard beamsplitting applications, for example not polarization relevant (polarization beamsplitters G02B 27/283).

G02B 27/123

The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power.

FR2889746: beam splitting takes place at 110a,110b

In G02B 27/123 the optical path should be branched. Fly eye beam shaping devices belong to G02B 27/0961, lens arrays per se in G02B 3/0006.

G02B 27/126

The splitting element being a prism or prismatic array, including systems based on total internal reflection.

The class covers both refracting deviating prisms, including spectral deviation and systems where the splitting/combining is achieved by total internal reflection without reflecting coatings:

US2005174658

G02B 27/14

Operating by reflection only

For example a non conventional reflective beamsplitter as in US6266359:

G02B 27/141

Using dichroic mirrors

For simple dichroic mirror arrangements transmitting a wavelength band and reflecting the other. G02B 27/1006 covers color splitting in general, and RGB image analysis or synthesis is covered by G02B 27/1013 or G02B 27/102 and lower.

G02B 27/142

Coating structure, e.g. thin films multilayers.

When the focus is the structure of the beam splitter coatings (thicknesses, materials, refractive indexes) including single thin metallic layers.

JP58208701: a polarisation independent multilayer semi-transparent coating.

G02B 27/143

Macroscopically faceted or segmented reflective surfaces

The segmentation here is macroscopic, compare with G02B 27/147.

G02B 27/144

Using partially transparent surfaces without spectral selectivity (G02B 27/147 takes precedence) for conventional half-mirrors.

US5198930:

G02B 27/145

Having sequential partially reflecting surfaces

GB2153546

G02B 27/146

With a tree or branched structure

EP1626585

G02B 27/147

Using averaging effects by spatially variable reflectivity on a microscopic level, e.g. polka dots, chequered or discontinuous patterns, or rapidly moving surfaces (G02B 27/1086 takes precedence).

US4941012

The subgroup also covers time averaging systems such as chopper mirrors rotating at high speed to emulate a beamsplitter.

JP52011894:

G02B 27/149

Devices incorporating crossed beamsplitting surfaces, e.g. cross-dichroic cubes or X-cubes. Not limited to three channels

G02B 27/148

Including stacked surfaces having at least one double-pass partially reflecting surface

A special type but common type of beamsplitter where at least the front surface is crossed twice. Common for RGB angular separation, the last surface can be fully reflective.

US2009251783

G02B 27/16

Used as aids for focusing

Covers split prisms historically used to focus an image in reflex cameras and has almost no activity.

G02B 30/00

There are two groups for autostereoscopic systems (i.e. systems in which left and right images projected to the left and right eyes of an observer who is not required to view the images through special glasses optical systems placed adjacent to the eyes:

Autostereoscopic systems which comprise lenticular arrays or parallax barriers are classified in G02B 30/27.

Autostereoscopic displays which do not comprise lenticular arrays or parallax barriers, for example systems in which the left and right images are projected directly into the left and right eyes of the observer, are classified in G02B 30/26. An example of such a display is shown in the figure below

G02B 30/50

Concerns volumetric displays, i.e. in which an image is built up from image elements distributed over a three-dimensional volume. An example is US2007/0242324, in which visible fluorescence is excited at the crossing points of two scanned invisible lasers:

There are three subgroups:

G02B 30/52

The image being built up using a stack of two dimensional planes, e.g. US 2002/0130820:

G02B 30/54

The volume being generated by a moving (vibrating or rotating) surface, e.g. US6115006:

G02B 30/56

Projecting an aerial or floating image, typical examples of which would be WO02/061492:

or WO95/19584

G02B 27/42: Diffraction optics

G02B 27/42 deals with systems comprising a DOE (diffractive optical element) having a significant interaction with another component of the optical system. If the document also discloses significant details about the diffractive element as such, it should be additionally classified in G02B 5/18. This subgroup contains documents in which the diffractive effect results from a purposeful design of a DOE. It does NOT include documents in which light is merely diffracted by an aperture, an edge or a particle. G02B 27/4266 is an exception to this rule. G02B 27/42 is essentially structured into two major groups:

.. imaging systems (G02B 27/4205 and lower)

.. non-imaging systems (G02B 27/4233 and lower).

Besides this major differentiation, there are three further divisions:

.. physical properties of the DOE:

polarization G02B 27/4261,

thermal G02B 27/4283,

spectral G02B 27/4288, G02B 27/4294

.. sequential DOEs G02B 27/4272 and G02B 27/4277

.. theory, models G02B 27/4266

In deciding whether a system is an imaging system or a non-imaging system, concepts such as image resolution or extended objects/images are strong hints towards imaging systems. On-axis point-like objects/images are pointers to non-imaging systems. It is important to note that G02B 27/4205 (and lower) and G02B 27/4233 (and lower) relate to the specific role played by the DOE in the system: a DOE within an imaging system, but merely deviating light for illumination purposes in a subsystem of the imaging system, is classified in G02B 27/4233 (or lower).

Specific rules

G02B 27/4233 (and lower) should preferably not contain documents which have a more specific class e.g. G02B 6/00 (optical fibers, waveguides), H01S (laser pulse compression), G01J (spectroscopy).

G02B 27/4238 should contain no document from the field of optical pick-up devices (these documents should be classified in G11B 7/1353).

G02B 27/425 should preferably contain no document about mask illumination in a lithographic apparatus (these documents should be classified in G03F 7/70158). This should not be confused with a DOE projecting an image of the mask onto a wafer, which is classified in G02B 27/4222).

G02B 27/4272 and G02B 27/4277 relate to plural diffractive elements positioned sequentially along the optical path means that the distance between sequential diffractive elements is large enough to ensure that each period of the subsequent grating receives diffracted light from several periods of the previous grating, i.e. far-field diffraction. For instance, DOEs which, at least in certain portions of the DOE are in direct contact or multilayered DOEs are normally not plural diffractive elements in the sense of G02B 27/4272 and G02B 27/4277.

When allocating G02B 27/42, consider also the relevance of the following classes in G02B relating to diffraction or gratings:

G02B 1/005 (photonic crystals)

G02B 1/118 (moth-eye anti-reflection structures)

G02B 5/0252 (diffusers using holographic or diffractive means)

G02B 5/18 (diffraction gratings per se)

G02B 5/203 (filters using holographic or diffractive means)

G02B 5/32 (holographic optical elements)

G02B 26/0808 (controlling direction of light)

G02B 26/106 (scanners using movable diffraction gratings)

G02B 27/0944 (beam shaping using diffractive optical elements)

G02B 27/1086 (beam splitting and combining by diffraction)

G02B 27/46 (spatial filters)

G02B 27/58 (superresolution, apodization)

G02B 27/60 (systems using moiré fringes)

Exemplary drawings for G02B 27/42

Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect (G02B 27/60 takes precedence)