	US 7,541,723 B2
	Backlight having a polarization separating element
Keiji Hayashi, Kawasaki (Japan); Tetsuya Kobayashi, Kawasaki (Japan); Tetsuya Hamada, Kawasaki (Japan); Takeshi Gotoh, Kawasaki (Japan); Toshihiro Suzuki, Kawasaki (Japan); Mari Sugawara, Kawasaki (Japan); Akio Sotokawa, Kawasaki (Japan); and Seiji Hachisuka, Kawasaki (Japan)
Assigned to Sharp Kabushiki Kaisha, Osaka (Japan)
Filed on Jun. 30, 2005, as Appl. No. 11/172,468.
Application 11/172468 is a division of application No. 10/005259, filed on Dec. 04, 2001, granted, now 7,164,224.
Claims priority of application No. 2000-380205 (JP), filed on Dec. 14, 2000; application No. 2001-012333 (JP), filed on Jan. 19, 2001; application No. 2001-78546 (JP), filed on Mar. 19, 2001; and application No. 2001-146925 (JP), filed on May 16, 2001.
Prior Publication US 2005/0236948 A1, Oct. 27, 2005
Int. Cl. H01J 7/24 (2006.01)

U.S. Cl. 313—46 [359/494; 359/495; 359/497]

9 Claims

1. A backlight comprising:

a light source device;

a light guide plate receiving light from said light source device;

a polarization separating element disposed on one side of said light guide plate; and

an interference type mirror disposed on the other side of said light guide plate;

wherein said polarization separating element comprises an element which allows a first linearly polarized light having a plane of polarization including a transmission axis to transmit therethrough and a second linearly polarized light having a plane of polarization including a reflection axis to be reflected thereby;

wherein said interference type mirror comprises a multi-layered structure including a plurality of layers having birefringence, and rotates the plane of polarization of the second linearly polarized light reflected by the polarization separating element, converts the second linearly polarized light into the first linearly polarized light, and makes the first linearly polarized light incident again to the polarization separation element through the light guide plate.