# US 10,375,363 B2 · Projection optical system and projector > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,375,363 B2 - Document ID: US10375363B2 - Status: Granted - Kind: B2 - Application number: 16/044,982 - Filed: 2018-07-25 - Published: 2018-11-15 - Granted: 2019-08-06 - Earliest claimed: 2014-10-31 - Assignees: Nittoh Inc. - Applicants: Nittoh Inc. - Inventors: Takahiko Matsuo - Web page: https://patentgrep.com/patent/US10375363B2 ## CPC - 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)} - G02B 13/16: for use in conjunction with image converters or intensifiers {, or for use with projectors, e.g. objectives for projection TV} - G02B 17/08: Catadioptric systems {(used in non-imaging applications G02B19/00)} - G02B 17/0852: {having a field corrector only} - G03B 21/00: Projectors or projection-type viewers; Accessories therefor (devices for changing pictures G03B23/00) - G03B 21/14: Details - G03B 21/147: {Optical correction of image distortions, e.g. keystone} - G03B 21/28: Reflectors in projection beam {(in illumination beam G03B21/2066)} - H04N 9/3141: {Constructional details thereof (details not peculiar to the presence of an electronic spatial light modulator G03B21/14)} - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D) ## Abstract A projection optical system (10) projects from a first image plane (5) on a reducing side to a second image plane (6) on an enlargement side. The projection optical system (10) includes a first optical system (11) that includes a plurality of lenses and forms a first intermediate image (51) formed inside the first optical system (11) by light incident from the reducing side into a second intermediate image (52) on the enlargement side of the first optical system (11); a second optical system (12) that includes a first reflective surface (M1) with positive refractive power which is positioned further to the enlargement side than the second intermediate image (52); and a glass block (30) that is disposed between the first optical system (11) and the first reflective surface (M1), the glass block (30) passing light rays from the first optical system (11) to the second intermediate image (52). ## Claims ### Claim 1 A projection optical system that projects from a first image plane on a reducing side to a second image plane on an enlargement side, comprising: a first optical system that includes a plurality of lenses and forms a first intermediate image formed inside the first optical system by light incident from the reducing side into a second intermediate image on the enlargement side of the first optical system; a second optical system that includes a first reflective surface with positive refractive power which is positioned further to the enlargement side than the second intermediate image; and a first glass block that is disposed between the first optical system and the first reflective surface, wherein the first glass block is located on an output side of the first optical system and passes rays from the first optical system to the second intermediate image. ### Claim 2 (depends on 1) The projection optical system according to claim 1, further comprising a second glass block that is located on an incident side of the first optical system. ### Claim 3 (depends on 1) The projection optical system according to claim 1, wherein the first glass block includes an incident surface on a first optical system side and an exit surface on a first reflective surface side, wherein the incident surface and the exit surface are parallel with each other and perpendicular to an optical axis. ### Claim 4 (depends on 1) The projection optical system according to claim 1, wherein the first glass block includes an incident surface on a first optical system side and an exit surface on a first reflective surface side, wherein the exit surface shifts to the incident surface toward an opposite side to a projection side of an optical axis. ### Claim 5 (depends on 1) The projection optical system according to claim 1, wherein the first glass block includes an incident surface on a first optical system side and an exit surface on a first reflective surface side, wherein the exit surface is inclined to the incident surface. ### Claim 6 (depends on 1) The projection optical system according to claim 1, wherein the first glass block includes: an incident surface on a first optical system side; an exit surface on a first reflective surface side; and a side surface that is between the incident surface and the exit surface and is configured to not reflect the rays from the first optical system to the second intermediate image on the side surface. ### Claim 7 (depends on 1) The projection optical system according to claim 1, wherein the first glass block includes: an incident surface on a first optical system side; an exit surface on a first reflective surface side; and a side surface that is between the incident surface and the exit surface and is configured to reflect the rays from the first optical system to the second intermediate image on the side surface. ### Claim 8 (depends on 1) The projection optical system according to claim 1, wherein the first glass block is disposed between the first optical system and the second intermediate image. ### Claim 9 (depends on 1) The projection optical system according to claim 1, wherein the first glass block includes: an incident surface on a first optical system side; an exit surface on a first reflective surface side; and a side surface that is between the incident surface and the exit surface and is at least partially inclined with respect to an optical axis between the first optical system and the first reflective surface. ### Claim 10 (depends on 9) The projection optical system according to claim 9, wherein the side surface includes a surface that is inclined so as to be substantially parallel to lower rays of projecting light that reach the second image plane from the first reflective surface. ### Claim 11 (depends on 9) The projection optical system according to claim 9, wherein the side surface includes an internally reflective surface that reflects rays that reach the first reflective surface from the first optical system. ### Claim 12 (depends on 1) The projection optical system according to claim 1, wherein a length GBL of the first glass block along an optical axis between the first optical system and the first reflective surface and a length LML along the optical axis between the first optical system and the first reflective surface satisfy a following condition 0.1