Polarization beam splitter and projection display apparatus
First Claim
1. A polarization beam splitter comprising a first prism, a second prism, and a dielectric multilayer film which is sandwiched between said first and second prisms,said dielectric multilayer film comprising:
- first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prism and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
second alternating layers of said high refractive index layer and a low refractive index layer having a refractive index lower than the refractive index of said intermediate refractive index layer, a reference incident angle θ
0 of light which is incident on said dielectric multilayer film through said first or second prism being within a range indicated in the following expression;
space="preserve" listing-type="equation">θ
.sub.1 <
θ
.sub.0 <
θ
.sub.2 where ##EQU4## wherein nH indicates the refractive index of said high refractive index layer, nM indicates the refractive index of said intermediate refractive index layer, nL indicates the refractive index of said low refractive index layer, and n0 indicates the refractive indices of said first and second prisms.
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Abstract
A polarization beam splitter which includes a first prism, a second prism, and a dielectric multilayer film which is sandwiched between the first and second prisms is disclosed. The dielectric multilayer film comprising: a plurality of high refractive index layers having a refractive index higher than refractive indices of the first and second prisms; a plurality of intermediate refractive index layers having a refractive index lower than the refractive index of the high refractive index layers; and a plurality of low refractive index layers having a refractive index lower than the refractive index of the intermediate refractive index layers, a reference incident angle θ0 of light which is incident on the dielectric multilayer film through the first or second prism being within a range of the following expression:
θ.sub.1 <θ.sub.0 <θ.sub.2
where ##EQU1## where nH indicates the refractive index of the high refractive index layers, nM indicates the refractive index of the intermediate refractive index layers, nL indicates the refractive index of the low refractive index layers, and n0 indicates the refractive indices of the first and second prisms.
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Citations
26 Claims
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1. A polarization beam splitter comprising a first prism, a second prism, and a dielectric multilayer film which is sandwiched between said first and second prisms,
said dielectric multilayer film comprising: - first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prism and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
second alternating layers of said high refractive index layer and a low refractive index layer having a refractive index lower than the refractive index of said intermediate refractive index layer, a reference incident angle θ
0 of light which is incident on said dielectric multilayer film through said first or second prism being within a range indicated in the following expression;
space="preserve" listing-type="equation">θ
.sub.1 <
θ
.sub.0 <
θ
.sub.2where ##EQU4## wherein nH indicates the refractive index of said high refractive index layer, nM indicates the refractive index of said intermediate refractive index layer, nL indicates the refractive index of said low refractive index layer, and n0 indicates the refractive indices of said first and second prisms. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prism and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
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9. A projection display apparatus comprising:
- a light source;
a pre-polarizer which selectively allows substantially linearly polarized light of light emitted from said light source, to pass through said pre-polarizer;
a polarization beam splitter which reflects said linearly polarized light which has passed through said pre-polarizer;
a reflection-type light valve which modulates a polarization state of light reflected by said polarization beam splitter, thereby forming an optical image; and
a projection lens which projects said optical image formed by said light valve, onto a screen, whereinsaid polarization beam splitter comprising a first prism, a second prism, and a dielectric multilayer film which is sandwiched between said first and second prisms, said dielectric multilayer film comprising;
first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prisms and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
second alternating layers of said high refractive index layer and a low refractive index layer having a refractive index lower than the refractive index of said intermediate refractive index layer, a reference incident angle θ
0 of light which is incident on said dielectric multilayer film through said first or second prism being within a range indicated in the following expression;
space="preserve" listing-type="equation">θ
.sub.1 <
θ
.sub.0 θ
.sub.2where ##EQU5## where nH indicates the refractive index of said high refractive index layer, nM indicates the refractive index of said intermediate refractive index layer, nL indicates the refractive index of said low refractive index layer, and n0 indicates the refractive indices of said first and second prisms, and said polarization beam splitter changes a propagation direction of said linearly polarized light which has passed through said pre-polarizer, to direct said linearly polarized light to said light valve, selectively transmits light which has the polarization state modulated by said light valve, and which has been reflected by said light valve, and directs said selectively transmitted linearly polarized light to said projection lens. - View Dependent Claims (10, 11)
- a light source;
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12. A projection display apparatus comprising:
- a light source which radiates light including three primary color components;
a pre-polarizer which selectively allows substantially linearly polarized light of light radiated from said light source, to pass through said pre-polarizer;
color separation means for separating light output from said pre-polarization beam splitter into three primary color light beams;
three polarization beam splitters which function as polarizers and analyzers, and which respectively correspond to said three primary color light beams;
three reflection light valves which respectively modulate polarization states of light beams entering from said three polarization beam splitters, thereby forming optical images; and
three projection lenses which respectively project said optical images formed by said three light valves, onto a screen, each of said three polarization beam splitters comprising a first prism, a second prism, and a dielectric multilayer film which is sandwiched between said first and second prisms,said dielectric multilayer film comprising;
first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prisms and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
second alternating layers of said high refractive index layer and a low refractive index layer having a refractive index lower than the refractive index of said intermediate refractive index layer, a reference incident angle θ
0 of light which is incident on said dielectric multilayer film through said first or second prism being within a range indicated in the following expression;
space="preserve" listing-type="equation">θ
.sub.1 <
θ
.sub.0 <
θ
.sub.2where ##EQU6## where nH indicates the refractive index of said high refractive index layer, nM indicates the refractive index of said intermediate refractive index layer, nL indicates the refractive index of said low refractive index layer, and n0 indicates the refractive indices of said first and second prisms. - View Dependent Claims (13, 14, 15)
- a light source which radiates light including three primary color components;
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16. A method for splitting a light beam into an S-polarized light beam and a P-polarized beam comprising the steps of:
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setting a polarization beam splitter so that said light beam is incident on said polarization beam splitter at a predetermined incident angle, wherein said polarization beam splitter comprises a first prism, a second prism, and a dielectric multilayer film which is sandwiched between said first and second prisms, said dielectric multilayer film comprising;
first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prisms and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
second alternating layers of said high refractive index layer and a low refractive index layer having a refractive index lower than the refractive index of said intermediate refractive index layer, andsaid predetermined incident angle is set to be a reference incident angle θ
0 of light which is incident on said dielectric multilayer film through said first or second prism being within a range indicated by the following conditional expression;
space="preserve" listing-type="equation">θ
.sub. <
θ
.sub. <
θ
.sub. 2where ##EQU7## where nH indicates the refractive index of said high refractive index layer, nM indicates the refractive index of said intermediate refractive index, nL indicates the refractive index of said low refractive index layer, and n0 indicates the refractive indices of said first and second prisms.
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17. A polarization beam splitter comprising a first prism, a second prism, and a transparent parallel flat plate having two dielectric multilayer films formed on each surface thereof, said transparent parallel flat plate is sandwiched between said first and second prisms,
at least one of said dielectric multilayer films comprising: - first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prisms and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
second alternating layers of said high refractive index and a low refractive index layer having a refractive index lower than the refractive index of said intermediate refractive index layer, a reference incident angle θ
0 of light which is incident on said dielectric multilayer film through said first or second prism being within a range indicated in the following expression;
space="preserve" listing-type="equation">θ
.sub.1 <
θ
.sub.0 <
θ
.sub.2where ##EQU8## where nH indicates the refractive index of said high refractive index layer, nM indicates the refractive index of said intermediate refractive index layer, nL indicates the refractive index of said low refractive index layer, and n0 indicates the refractive indices of said first and second prisms. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
- first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prisms and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
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25. A projection display apparatus comprising:
- a light source;
a pre-polarizer which selectively allows substantially linearly polarized light of light emitted from said light source, to pass through said pre-polarizer;
a polarization beam splitter which reflects said linearly polarized light which has passed through said pre-polarizer;
a reflection-type light valve which modulates a polarization state of light reflected by said polarization beam splitter, thereby forming an optical image; and
a projection lens which projects said optical image formed by said light valve, onto a screen, whereinsaid polarization beam splitter comprising a first prism, a second prism, and a transparent parallel flat plate having two dielectric multilayer films formed on each surface thereof, said transparent parallel flat plate is sandwiched between said first and second prisms, at least one of said dielectric multilayer films comprising;
first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prisms and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
second alternating layers of said high refractive index layer and a low refractive index layer having a refractive index lower than the refractive index of said intermediate refractive index layer, a reference incident angle θ
0 of light which is incident on said dielectric multilayer film through said first or second prism being within a range indicated in the following expression;
space="preserve" listing-type="equation">θ
.sub.1 <
θ
.sub.0 <
θ
.sub.2where ##EQU9## where nH indicates the refractive index of said high refractive index layer, nM indicates the refractive index of said intermediate refractive index layer, nL indicates the refractive index of said low refractive index layer, and n0 indicates the refractive indices of said first and second prisms, and said polarization beam splitter changes a propagation direction of said linearly polarized light which has passed through said pre-polarizer, to direct said linearly polarized light to said light valve, selectively transmits light which has the polarization state modulated by said light valve, and which has been reflected by said light valve, and directs said selectively transmitted linearly polarized light to said projection lens.
- a light source;
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26. A projection display apparatus comprising:
- a light source which radiates light including three primary color components;
a pre-polarizer which selectively allows substantially linearly polarized light of light radiated from said light source, to pass through said pre-polarizer;
color separation means for separating light output from said pre-polarization beam splitter into three primary color light beams;
three polarization beam splitters which function as polarizers and analyzers, and which respectively correspond to said three primary color light beams;
three reflection light valves which respectively modulate polarization states of light beams entering from said three polarization beam splitters, thereby forming optical images; and
three projection lenses which respectively project said optical images formed by said three light valves, onto a screen, each of said three polarization beam splitters comprising a first prism, a second prism, and a transparent parallel flat plate having two dielectric multilayer films formed on each surface thereof, said transparent parallel flat plate is sandwiched between said first and second prisms,at least one of said dielectric multilayer films comprising;
first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prisms and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and
second alternating layers of said high refractive index layer and a low refractive index layer having a refractive index lower than the refractive index of said intermediate refractive index layer, a reference incident angle θ
0 of light which is incident on said dielectric multilayer film through said first or second prism being within a range indicated in the following expression;
space="preserve" listing-type="equation">θ
.sub.1 <
θ
.sub.0 <
θ
.sub.2where ##EQU10## where nH indicates the refractive index of said high refractive index layer, nM indicates the refractive index of said intermediate refractive index layer, nL indicates the refractive index of said low refractive index layer, and n0 indicates the refractive indices of said first and second prisms.
- a light source which radiates light including three primary color components;
Specification