Polarization optical system and projection-type liquid-crystal display device
View Patent ↗A polarization optical system includes a first polarization plate, arranged at the light incident side of a liquid-crystal light valve, for transmitting first polarized light (s-polarized light) included in light incident on the liquid-crystal light valve from an illumination optical system and a second polarization plate, arranged at the light exit side of the liquid-crystal light valve, for transmitting second polarized light (p-polarized light), different from the first polarized light (s-polarized light), included in imaging light emitted from the liquid-crystal light valve to a projection optical system, in which the second polarization plate is configured in such a way that its light-incident face is concave toward the liquid-crystal light valve.
1. A polarization optical system comprising:
a first polarization plate, arranged at the light incident side of a liquid-crystal light valve, for transmitting first linearly-polarized light included in light incident on the liquid-crystal light valve from an illumination optical system; and
a second polarization plate, arranged at the light exit side of the liquid-crystal light valve, for transmitting second linearly-polarized light, different from the first linearly-polarized light, included in imaging light emitted from the liquid-crystal light valve to a projection optical system, the second polarization plate having a concave face facing the light exit side of the liquid-crystal light valve,
wherein the concave face of the second polarization plate is a spherical face whose radius is an optical distance from the liquid-crystal light valve to the second polarization plate.
2. The polarization optical system as recited in claim 1 , wherein the concave face of the second polarization plate is a spherical face whose radius R 1 is given by an equation:
d 1 ≦R 1 ≦d 1+( x 1/2)/tan β
where x 1 is a longitudinal length of the light exiting end of the liquid-crystal light valve, d 1 is a distance from the light exiting end of the liquid-crystal light valve to the second polarization plate, and β is an effective divergence angle from the liquid-crystal light valve.
3. The polarization optical system as recited in claim 1 , wherein the second polarization plate includes a transmission plate having the concave face and a polarization film attached to the concave face of the transmission plate.
4. The polarization optical system as recited in claim 1 , wherein the second polarization plate includes a concave lens having the concave face and a polarization film attached to the concave face of the concave lens.
5. The polarization optical system as recited in claim 1 , further comprising a polarization plate, whose incident face is flat, arranged between the liquid-crystal light valve and the second polarization plate, for transmitting the second linearly-polarized light different from the first linearly-polarized light.
6. The polarization optical system as recited in claim 1 , wherein the polarization axis of the second linearly-polarized light is shifted by 90 degrees from that of the first linearly-polarized light.
7. The polarization optical system as recited in claim 1 , further comprising an optical compensation plate, arranged between the first polarization plate and the liquid-crystal light valve, for compensating a polarized-light's phase difference generated by the liquid-crystal light valve.
8. The polarization optical system as recited in claim 1 , further comprising an optical compensation plate, arranged between the liquid-crystal light valve and the second polarization plate, for compensating a polarized-light's phase difference generated by the liquid-crystal light valve.
9. The polarization optical system as recited in claim 1 , wherein
the liquid-crystal light valve is a reflection-type liquid-crystal light valve,
the polarization optical system further comprises a reflection-type polarization plate, arranged between the first polarization plate and the reflection-type liquid-crystal light valve, for transmitting the first linearly-polarized light, and reflecting imaging light emitted from the reflection-type liquid-crystal light valve, and
the second polarization plate is arranged downstream of the reflection-type polarization plate.
10. The polarization optical system as recited in claim 9 , further comprising an optical compensation plate, between the reflection-type polarization plate and the reflection-type liquid-crystal valve, for compensating a polarized-light's phase difference generated by the reflection-type liquid-crystal light valve.
11. A projection-type liquid-crystal display device comprising:
a liquid-crystal light valve;
a light source for emitting a light beam to irradiate the liquid-crystal light valve;
an illumination optical system for irradiating the liquid-crystal light valve with the light beam emitted from the light source;
a projection optical system for projecting onto a screen imaging light exiting from the liquid-crystal light valve; and
a polarization optical system comprising:
a first polarization plate, arranged at the light incident side of a liquid-crystal light valve, for transmitting first linearly-polarized light included in light incident on the liquid-crystal light valve from an illumination optical system; and
a second polarization plate, arranged at the light exit side of the liquid-crystal light valve, for transmitting second linearly-polarized light, different from the first linearly-polarized light, included in imaging light emitted from the liquid-crystal light valve to a projection optical system, the second polarization plate having a face concave toward the light exit side of the liquid-crystal light valve,
wherein the concave face of the second polarization plate is a spherical face whose radius is an optical distance from the liquid-crystal light valve to the second polarization plate.