Light modulating unit and image projection apparatus

• US 20050185139A1
• Filed: 02/08/2005
• Published: 08/25/2005
• Est. Priority Date: 02/25/2004
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: Kobayashi, Susumu, Kobayashi, Hiroyoshi, Yamanaka, Kazuya
• Granted Patent: US 7,270,416 B2
• Time in Patent Office: Days
• US Class Current: 353/20
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: 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
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

A light modulating unit includes first and second light modulating sections each of which modulates an illumination light on the basis of a video signal to generate a projection light that is a linearly polarized light, a light path synthesizing section which synthesizes the projection lights generated by the first and second light modulating sections using the nature that directions of polarizations of the projection lights cross at right angles, and a beam shifting section which sets beams of the projection lights synthesized by the light path synthesizing section, in a shifted state or a non-shifted state on the basis of the directions of polarizations of the projection lights, the beam shifting section switching the shifted state and the non-shifted state synchronously with modulation timings for the first and second light modulating sections.

Claims

1. A light modulating unit which modulates an illumination light on the basis of an inputted video signal, the light modulating unit comprising:

first and second light modulating sections each of which modulates an illumination light on the basis of a video signal to generate a projection light that is a linearly polarized light;

a light path synthesizing section which synthesizes the projection lights generated by the first and second light modulating sections using the nature that directions of polarizations of the projection lights cross at right angles; and

a beam shifting section which sets beams of the projection lights synthesized by the light path synthesizing section, in a shifted state or a non-shifted state on the basis of the directions of polarizations of the projection lights, the beam shifting section switching the shifted state and the non-shifted state synchronously with modulation timings for the first and second light modulating sections.

2. The light modulating unit according to claim 1, wherein a positional relationship between the first and second light modulating sections is determined so that pixel positions of the projection lights generated by the first and second light modulating sections and synthesized by the light path synthesizing section are adjacent to each other in a predetermined direction.

3. The light modulating unit according to claim 1, wherein the beam shifting section includes a liquid crystal panel which can rotate the direction of polarization of the projection light and a birefringence plate which generates a transmission light which is offset from an extension of an incident light if the incident light has a particular direction of polarization, and

the liquid crystal panel rotates the direction of polarization of the projection light synchronously with the modulation timings for the first and second light modulating sections.

4. The light modulating unit according to claim 1, wherein the light modulating unit comprises a plurality of sets each composed of the first and second light modulating sections and the light path synthesizing section, the first and second light modulating sections in each set generating projection lights of the same color, colors of the projection lights being different between the sets,

the light modulating unit further comprises a color synthesizing prism which synthesizes the projection lights from the respective sets, and

the beam shifting section shifts the beams of the projection lights synthesized by the color synthesizing prism on the basis of the directions of polarizations of the projection lights.

5. The light modulating unit according to claim 4, wherein the number of sets is three and the colors of the projection lights in the respective sets are red, blue, and green.

6. The light modulating unit according to claim 1, wherein the light path synthesizing section is composed of a polarization beam splitter having a first to sixth planes and a polarization plane,

the first and second light modulating sections are composed of first and second light modulating devices, respectively, arranged opposite the first and second planes that are not perpendicular to the polarization plane of the polarization beam splitter, and

when the illumination light is incident on the third plane which is not perpendicular to the polarization plane and which is different from the first and second planes, the first light modulating device is illuminated by an S-polarized light component of the illumination light reflected by the polarization plane, and the second light modulating device is illuminated by a P-polarized light component of the illumination light passing through the polarization plane.

7. The light modulating unit according to claim 1, wherein each of the first and second light modulating sections includes a plurality of light modulating devices which generate projection lights having different colors and a color synthesizing prism which synthesizes the projection lights generated by the plurality of light modulating devices, and

the direction of polarization of the projection light emitted by the color synthesizing prism of the first light modulating section is orthogonal to the direction of polarization of the projection light emitted by the color synthesizing prism of the second light modulating section.

8. The light modulating unit according to claim 1, wherein one of the first and second light modulating sections has a λ

/2 plate which makes the direction of polarization of the projection light emitted by the first light modulating section orthogonal to the direction of polarization of the projection light emitted by the second light modulating section.

9. The light modulating unit according to claim 1, wherein the light path synthesizing section is composed of a polarization beam splitter, and

a projection light of a P-polarized light and a projection light of an S-polarized light are incident on the beam shifting section.

10. The light modulating unit according to claim 3, wherein if an amount of input image information contained in the video signal is larger than an amount of display image information which can be displayed by each of the first and second light modulating sections, the liquid crystal panel sequentially assumes two states in which the liquid crystal panel rotates or does not rotate the direction of polarization of the projection light through 90°

and

if the amount of input image information is smaller than the amount of display image information, the liquid crystal panel maintains one state in which the liquid crystal panel rotates the direction of polarization of the projection light through 45°

.

11. The light modulating unit according to claim 2, wherein if an amount of input image information contained in the video signal is larger than an amount of display image information which can be displayed by each of the first and second light modulating sections, the beam shifting section sequentially sets the projection lights generated by the first and second light modulating sections, in the shifted state and the non-shifted state in a direction orthogonal to the predetermined direction, and

if the amount of input image information is smaller than the amount of display image information, the beam shifting section applies a spatial low pass filter action to the projection lights generated by the first and second light modulating sections, in the direction orthogonal to the predetermined direction.

12. An image projection apparatus comprising:

the light modulating unit according to claim 1,

a light source which supplies an illumination light to the first and second light modulating sections, and

a projection optical section which projects the projection light from the beam shifting section on a screen.

13. The image projection apparatus according to claim 12, wherein the positional relationship between the first and second light modulating sections is determined so that a pixel position of the projection light generated by the first light modulating section and synthesized by the light path synthesizing section is offset from a pixel position of the projection light generated by the second light modulating section and synthesized by the light path synthesizing section by half a pixel pitch in a predetermined direction, and

the beam shifting section is configured so that a pixel position of the projection light in the shifted state is offset from a pixel position of the projection light in the non-shifted state by half a pixel pitch in a direction orthogonal to the predetermined direction.

14. The image projection apparatus according to claim 13, wherein the light path synthesizing section is composed of a polarization beam splitter, and

one of beams of the projection lights generated by the first and second light modulating sections is shifted by the beam shifting section, and the other beam is not shifted by the beam shifting section.

15. The image projection apparatus according to claim 12, further comprising an extracting section which extracts, from the video signal, a signal corresponding to a projection light for each pixel emitted by the beam shifting section, and

wherein the first and second light modulating sections modulate the illumination light on the basis of the signal extracted by the extracting section.

16. An image projection apparatus which uses the light modulating unit set forth in claim 1 to project images based on right and left eye video signals on a screen in order to allow a three-dimensional image to be observed using a pair of polarization glasses in which a direction of polarization for a right eye and a direction of polarization for a left eye cross at right angles,

wherein if one of the first and second light modulating sections modulates an illumination light on the basis of the right eye video signal, the other of the first and second light modulating sections modulates the illumination light on the basis of the left eye video signal,

the positional relationship between the first and second light modulating sections is determined so that a pixel position of the projection light generated by the first light modulating section and synthesized by the light path synthesizing section is offset from a pixel position of the projection light generated by the second light modulating section and synthesized by the light path synthesizing section by half a pixel pitch in a predetermined direction, and

the beam shifting section is configured so that a pixel position of the projection light in the shifted state is offset from a pixel position of the projection light in the non-shifted state by half a pixel pitch in a direction orthogonal to the predetermined direction.

17. The image projection apparatus according to claim 16, further comprising an extracting section which extracts, from the video signal, a signal corresponding to a projection light for each pixel emitted by the beam shifting section, and

wherein the first and second light modulating sections modulate the illumination light on the basis of the signal extracted by the extracting section.

18. A light modulating unit which modulates an illumination light on the basis of an inputted video signal, the light modulating unit comprising:

at least one light modulating section which modulates an illumination light on the basis of a video signal to generate a projection light that is a linearly polarized light; and

a beam shifting section which sets a beam of the projection light generated by the light modulating section, in a shifted state or a non-shifted state on the basis of a direction of polarization of the projection light, the beam shifting section switching the shifted state and the non-shifted state synchronously with a modulation timing for the light modulating section,

wherein if an amount of input image information contained in the video signal is larger than an amount of display image information which can be displayed by the light modulating section, the beam shifting section sequentially sets the beam of the projection light in the shifted state and the non-shifted state, and

if the amount of input image information is smaller than the amount of display image information, the beam shifting section does not sequentially set the beam of the projection light in the shifted state and the non-shifted state but fixes the beam in one state.

19. The light modulating unit according to claim 18, wherein the beam shifting section includes a liquid crystal panel which can rotate the direction of polarization of the projection light and a birefringence plate which generates a transmission light which is offset from an extension of an incident light if the incident light has a particular direction of polarization,

if the amount of input image information is larger than the amount of display image information, the liquid crystal panel sequentially assumes two states in which the liquid crystal panel rotates or does not rotate the direction of polarization of the projection light through 90°

, and

if the amount of input image information is smaller than the amount of display image information, the liquid crystal panel maintains one state in which the liquid crystal panel rotates the direction of polarization of the projection light through 45°

.

20. A light modulating unit which modulates an illumination light on the basis of an inputted video signal, the light modulating unit comprising:

first and second light modulating means each of which modulates an illumination light on the basis of a video signal to generate a projection light that is a linearly polarized light;

light path synthesizing means which synthesizes the projection lights generated by the first and second light modulating means using the nature that directions of polarizations of the projection lights cross at right angles; and

beam shifting means which sets beams of the projection lights synthesized by the light path synthesizing means, in a shifted state or a non-shifted state on the basis of the directions of polarizations of the projection lights, the beam shifting means switching the shifted state and the non-shifted state synchronously with modulation timings for the first and second light modulating means.

21. A light modulating unit which modulates an illumination light on the basis of an inputted video signal, the light modulating unit comprising:

at least one light modulating means which modulates an illumination light on the basis of a video signal to generate a projection light that is a linearly polarized light; and

beam shifting means which sets a beam of the projection light generated by the light modulating means, in a shifted state or a non-shifted state on the basis of a direction of polarization of the projection light, the beam shifting means switching the shifted state and the non-shifted state synchronously with a modulation timing for the light modulating means,

wherein if an amount of input image information contained in the video signal is larger than an amount of display image information which can be displayed by the light modulating means, the beam shifting means sequentially sets the beam of the projection light in the shifted state and the non-shifted state, and

if the amount of input image information is smaller than the amount of display image information, the beam shifting means does not sequentially set the beam of the projection light in the shifted state and the non-shifted state but fixes the beam in one state.