# US 7,612,939 B2 · Transmissive phase plate, polarized beam splitter, and projection display > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,612,939 B2 - Document ID: US7612939B2 - Status: Granted - Kind: B2 - Application number: 11/556,406 - Filed: 2006-11-03 - Published: 2007-05-10 - Granted: 2009-11-03 - Earliest claimed: 2005-11-10 - Assignees: Fujinon Corporation - Inventors: Shigeru Kato; Takuya Komatsu; Yoshiji Kawamura - Web page: https://patentgrep.com/patent/US7612939B2 ## CPC - G02B 5/3083: {Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001)} - G02B 5/3041: {comprising multiple thin layers, e.g. multilayer stacks} - G02B 27/283: {used for beam splitting or combining} - G02B 27/286: {for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another (G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34)} - G03B 21/2073: {Polarisers in the lamp house (peculiar to electronic spatial light modulators H04N9/3197)} - 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 transmissive phase plate with a function of correcting direction of polarization of light rays in an incident divergent or convergent light flux in addition to functions as a wave plate. Conditions of polarization of incident light rays are corrected by a polarization-correcting optical multi-layer coating which is formed by alternately depositing a high refractivity layer and a low refractivity layer on curved substrative surface of a predetermined radius of curvature. The transmissive phase plate can be applied to correct conditions of polarization of incident light rays of a polarized beam splitter for the purpose of improving contrast ratio of a projection display. ## Claims ### Claim 1 A polarized beam splitter having a polarization separating coating adapted to transmit one of p- and s-polarizations and to reflect off the other polarization, said polarized beam splitter comprises: said polarized beam splitter being composed of a first substrate member, a second substrate member and a third substrate member; said first substrate member having an incident surface of light from a light source and a curved joint surface; said second substrate member having a curved joint surface to be bonded against said curved joint surface of said first substrate and a flat opposite surface; said third substrate member having a flat joint surface to be bonded against said flat opposite surface of said second substrate member; said polarization separating coating being formed on either of said joint surfaces between said second and third substrate members; a correcting optical multi-layer coating comprising a high refractive layer and a low refractive layer being formed on either of said curved joint surfaces between said first and second substrate members; said correcting optical multi-layer coating formed on one of said curved joint surfaces functioning as a wave plate; said correcting optical multi-layer coating being imparted with a function of correcting a direction of polarization of incident light rays before entering said polarization separating coating. ### Claim 2 (depends on 1) A polarized beam splitter as defined in claim 1, wherein said correcting optical multi-layer coating is formed in a radius of curvature for correcting a direction of polarization of an incident divergent or convergent light flux into agreement with a direction of polarization determined by said polarization separating coating. ### Claim 3 (depends on 1) A polarized beam splitter as defined in claim 1, wherein at least one of the curved surface is formed in a aspheric, spheric or cylindrical shape. ### Claim 4 (depends on 1) A polarized beam splitter as defined in claim 1, wherein said correcting optical multi-layer coating is adapted to function as a λ/4 wave plate. ### Claim 5 (depends on 1) A polarized beam splitter as defined in claim 1, wherein said correcting optical multi-layer coating is adapted to function as a λ/2 wave plate. ### Claim 6 (depends on 1) A polarized beam splitter as defined in claim 1, wherein said high the refractive layer of said correcting optical multi-layer coating is formed of at least one of Ta2O5, TiO2, Nb2O5 and Al2O3 and said low the refractive layer is formed of at least one of SiO2 and MgF2. ### Claim 7 (depends on 1) A projection display incorporating the polarized beam splitter of claim 1 in a light path to or from said light source and a reflective light valve for modulating and controlling polarizing direction. ### Claim 8 (depends on 7) A projection display as defined in claim 7, wherein the curved surface bearing said correcting optical multi-layer coating is formed in a radius of curvature in the range of L/2<=R<=infinity in the direction of X-axis and in the range of L/2<=R <=10L in the direction of Y-axis, where Z-axis is a direction of propagation of light rays at a central optical axis of a incident light flux on said polarized beam splitter, Y-axis is a direction in which a plane of incidence is formed by a line normal to said polarization separating coating and said direction of propagation of light rays at said central optical axis, X-axis is a direction perpendicular to said Y-axis, L is a distance between said reflective light valve and said curved surface bearing said correcting optical multi-layer coating and R is a radius of curvature of the correcting optical multi-layer coating.