# US 7,077,546 B2 · Illumination apparatus and liquid crystal projector using the illumination apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,077,546 B2 - Document ID: US7077546B2 - Status: Granted - Kind: B2 - Application number: 11/039,921 - Filed: 2005-01-24 - Published: 2005-06-16 - Granted: 2006-07-18 - Earliest claimed: 2001-04-23 - Assignees: Ricoh Company, Ltd. - Inventors: Satoshi Yamauchi; Kazuhiro Fujita; Tadashi Honda; Osamu Nagase - Web page: https://patentgrep.com/patent/US7077546B2 ## CPC - G02B 27/0927: {Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat} - G02B 19/0028: {refractive and reflective surfaces, e.g. non-imaging catadioptric systems} - G02B 19/0047: {for use with a light source (G02B19/009, G02B19/0095 take precedence; details of lighting devices in general F21V; non-semiconductor lasers having optical devices external to the laser cavity H01S3/005)} - H04N 9/3105: {for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators (simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10)} - H04N 9/315: {Modulator illumination systems (general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20)} - H04N 9/3152: {for shaping the light beam (beam shaping per se G02B27/09)} - H04N 9/3167: {for polarizing the light beam (polarizing optical systems per se G02B27/28)} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An illumination apparatus includes a reflector including a parabolic or ellipsoidal mirror, a light source arranged near a (first) focal point of the reflector, and a front mirror having a transparent window and a mirror surface symmetrical about the light axis. Luminous flux emitted from the light source is reflected from the reflector. In the case of the parabolic mirror, the front mirror has the same size as an entrance of an output light utilizing optical system, and the luminous flux exits toward the optical system as collimated light. In the case of the ellipsoidal mirror, the front mirror is arranged between two focal points of the ellipsoidal mirror, and the luminous flux is directed toward the second focal point. However, at least one part of the luminous flux is reflected from the front mirror and returned toward the first focal point. ## Claims ### Claim 1 An illumination apparatus comprising a light source, a reflector of which at least one portion is a first parabolic mirror, an output light utilizing an optical system that comprises an integrator optical system at an entrance thereof, and a front mirror with a fly-eye lens or a member corresponding thereto of the integrator optical system as one unit. ### Claim 2 (depends on 1) The illumination apparatus as claimed in claim 1, wherein the front mirror is a plane mirror. ### Claim 3 (depends on 1) The illumination apparatus as claimed in claim 1, wherein the front mirror is a second parabolic mirror having a focal point common to a focal point of the first parabolic mirror. ### Claim 4 (depends on 1) A liquid crystal projector comprising: at least one liquid crystal panel for forming an image to be projected, the illumination apparatus as claimed in claim 1 for illuminating the liquid crystal panel, and a projection lens system for projecting the image onto a screen. ### Claim 5 An illumination apparatus comprising a reflector, a light source, a front mirror provided between an exit of the reflector and the light source, and an output light utilizing an optical system comprising an integrator optical system, wherein the reflector comprises a first parabolic mirror from which collimated light covers at least an entrance of the output light utilizing the optical system and an ellipsoidal mirror that is outside the first parabolic mirror and has a focal point common to that of the first parabolic mirror, and the front mirror comprises a window transparent to the collimated light. ### Claim 6 (depends on 5) The illumination apparatus as claimed in claim 5, wherein the reflector further comprises a second parabolic mirror that has a focal point common to the focal point of the first parabolic mirror outside the ellipsoidal mirror. ### Claim 7 (depends on 6) The illumination apparatus as claimed in claim 6, wherein a straight line through the focal point and a point on the second parabolic mirror at which a distance from a center of the window is minimum intersects the first parabolic mirror outside an edge line of a hole for inserting the light source. ### Claim 8 (depends on 5) The illumination apparatus as claimed in claim 5, wherein the front mirror is held by a spring. ### Claim 9 (depends on 5) A liquid crystal projector comprising: at least one liquid crystal panel for forming an image to be projected, the illumination apparatus as claimed in claim 5 for illuminating the liquid crystal panel, and a projection lens system for projecting the image onto a screen. ### Claim 10 An illumination apparatus comprising: a light source, a reflector of which at least one portion is a parabolic mirror, and a front mirror being a plane mirror and having a window transparent to at least one portion of light generated from the light source and reflected from the reflector. ### Claim 11 (depends on 10) A liquid crystal projector comprising: at least one liquid crystal panel for forming an image to be projected, the illumination apparatus as claimed in claim 10 for illuminating the liquid crystal panel, and a projection lens system for projecting the image onto a screen. ### Claim 12 An illumination apparatus comprising: a light source, a reflector of which at least one portion is a first parabolic mirror, and a front mirror being a plane mirror provided substantially symmetrically with respect to orthogonal axes perpendicular to an optical axis of the first parabolic mirror. ### Claim 13 (depends on 12) A liquid crystal projector comprising: at least one liquid crystal panel for forming an image to be projected, the illumination apparatus as claimed in claim 12 for illuminating the liquid crystal panel, and a projection lens system for projecting the image onto a screen.