JP2003241144A - Color separation and synthesis optical system and projection display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color separation and synthesis optical system which is light, excellent in video quality, and lightweight and a projection display device using the same. <P>SOLUTION: The system comprises 1st and 2nd polarized light separating means 8 and 16 which are arranged in a diagonal direction, 3rd and 4th polarized light separating means 9 and 11 which are arranged in a diagonal direction crossing the diagonal direction at right angles, and wavelength selective converting means 7 and 10, and 15 and 17 which are arranged between two or more inside opposite surfaces among the light incidence side of the 1st polarized light separating means 8, the light projection side of the 2nd polarized light separating means 16, and inside opposite surfaces of the 1st to 4th polarized light separating means 8 and 9, and 11 and 16 when the 1st polarized light separating means 8 is arranged on the light incidence side and the 2nd polarized light separating means 16 is arranged on the projection side and rotate the plane of polarization of specified color light by 90°; and the 1st, 3rd, and 4th polarized light separating means 8, 9, and 11 are plate type wire grid polarized light separating plates and the 2nd polarized light separating means 16 is a polarization beam splitter. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color separation / combination optical system having a polarization beam splitter for a projection display device using a reflective spatial light modulator, and a projection display device using the same.

[0002]

2. Description of the Related Art A color projection display device has an indefinite polarization of 3 or less.
R (red), G (green), and B (blue) color lights related to the primary color light are decomposed and guided to the spatial light modulator of the corresponding color, and the color light optically modulated by the spatial light modulator according to the video signal. Are combined and projected to display a color image on the screen.

Color projection display devices are roughly classified into three types according to the type of spatial light modulator applied to them. For example, a transmissive spatial light modulator is applied, a reflective spatial light modulator is applied, and a DMD (Di
There is an application of digital Mirror Device).

The transmissive spatial light modulator and DMD can be easily miniaturized because their optical structures can be relatively simple, but it is difficult to achieve high resolution. On the other hand, the reflective spatial light modulator is advantageous in achieving high resolution, but has a difficulty in downsizing due to the complicated optical configuration.

In particular, a projection display device to which a reflective spatial light modulator is applied has a polarization beam splitter for separating the incident light illuminating the spatial light modulator and the reflected light modulated by the spatial light modulator. Need. To achieve high contrast, one spatial light modulator,
This usually complicates the optical configuration of the reflective projection display device, because more than one polarization beam splitter is operated.

A color separation / combination optical system which has solved the problem of the optical structure of such a reflection type spatial light modulator has recently been developed by Colorlink in USA.
c. ) Provided by. In addition, regarding this, the literature (Michael G. Robinson et. "High Contrast Color Splitt
ing Architecture Using Color Polarization Filter
s ", SID 00 DIGEST, 92-95 (2000).

FIG. 3 is a schematic plan view showing an optical configuration of a projection display device to which a reflective spatial light modulator provided by Colorlink Co. is applied. The color separation / combination optical system 290 (the portion surrounded by the broken line in the figure) is a cubic or prismatic first,
Second, third and fourth polarization beam splitters 102, 1
03, 104, and 105 are replaced by their polarization splitting surfaces 121, 13
1, 141 and 151 are arranged so as to intersect each other in a substantially X shape, and further, the light-transmitting surface on the incident side of the first polarization beam splitter 102 (in FIG. 3, the first polarization beam splitter (Left side surface) 102a, and the light-transmitting surface on the emission side of the fourth polarization beam splitter 105 (the right side surface of the fourth polarization beam splitter in FIG. 3) 1
Reference numeral 05c denotes first wavelength-selective polarization conversion means (hereinafter referred to as G phase plates) 106 and 107 which both have a function of rotating the polarization plane of G light by 90 °, and the first and third polarizations. R between the beam splitters 102 and 104 and between the third and fourth polarization beam splitters 104 and 105.
Second wavelength-selective polarization conversion means (hereinafter referred to as R phase plate) 10 having a function of rotating the polarization plane of light by 90 °
8 and 109 are provided.

Here, the S-polarized light and the P-polarized light are determined by the relative relationship between the plane of polarization of the linearly polarized light and the plane of polarization separation of the polarization beam splitter on which it enters, and the plane of polarization of the linearly polarized light is the polarization of the polarization beam splitter. When it is perpendicular to the plane of incidence with respect to the plane, it is called S-polarized light, and when it is parallel, it is P
It is called polarized light.

As shown in FIG.
A phase plate having the characteristics shown in is applied. In FIG. 4, cross-polarizers (Crossed Polarizers) are spectral characteristics of output light when a polarizer and an analyzer are arranged in a cross through a wavelength-selective polarization conversion means and measured,
Parallel-polarizers are spectral characteristics of output light when a polarizer and an analyzer are arranged in parallel. From the figure, the polarization plane of G light is 90 °
You can see that it is rotating.

The R phase plates 108 and 109 have the characteristics shown in FIG. In FIG. 5, the cross-polarizer and the parallel-polarizer have the same meanings as described above. From the figure, it can be seen that the polarization plane of the R light is rotated by 90 °.

Further, wavelength selective polarization conversion means (B phase plate) having a function of rotating only the polarization plane of B light by 90 °.
Can also be made. Note that these wavelength-selective polarization conversion means are described in detail in US Pat. No. 5,751,384.

In the color separation / combination optical system 290, the first polarization beam splitter 102 serves as an incident side polarization beam splitter, and the fourth polarization beam splitter 105 located diagonally to the first polarization beam splitter 102 serves as an exit side polarization beam splitter. Becomes In addition, the second and third polarization beam splitters 103, 10 arranged at the intermediate position between them.
Reference numeral 4 is a so-called main polarization beam splitter that acts to separate the incident light illuminating the reflective spatial light modulator and the reflected light modulated by the reflective spatial light modulator.

The second polarization beam splitter (main polarization beam splitter) 10 of the color separation / combination optical system 290.
A reflective spatial light modulation element 161 corresponding to G is provided on the side of the transparent surface 103c of No. 3, and a reflective spatial light modulation corresponding to R is provided on the side of the transparent surface 104b of the third polarization beam splitter (main polarization beam splitter) 104. The element 162 and the translucent surface 104
A reflective spatial light modulator 163 corresponding to B is provided on the a side,
Further, in front of the incident side of the first polarization beam splitter (incident side polarization beam splitter) 102, a light source 171 that emits indefinite polarization and the polarization splitting surface 12 of the first polarization beam splitter (incident side polarization beam splitter) 102.
A first polarizing plate 181 whose transmission axis is selected so as to transmit only linearly polarized light having S-polarized light with respect to 1 is provided, and the output side of the fourth polarization beam splitter (emission side polarization beam splitter) 105 is provided. Behind, a second polarizing plate whose transmission axis is selected so that only linearly polarized light having a P polarization relationship with the polarization splitting surface 151 of the fourth polarization beam splitter (emission side polarization beam splitter) 105 is transmitted. The projection display device 300 includes the projection lens 182 that magnifies and projects the image light 182 and the color image light.

The polarization splitting surfaces 121, 131, 141, 151 of the first, second, third, and fourth polarization beam splitters 102, 103, 104, 105 are such that their incident surfaces are common surfaces. Since the polarization planes of the linearly polarized light that determine the S-polarized light and the P-polarized light and the polarization splitting surface are the same for all polarization beam splitters, the S-polarized light and the P-polarized light will be A description of which of the polarization beam splitters is for the polarization splitting surface is omitted.

The projection display device 300 operates as follows. The indefinite polarized light emitted from the light source 171 enters the first polarizing plate 181. Then, only the S-polarized light passes through the first polarizing plate 181, and enters the G phase plate 106. Since the G phase plate 106 is a wavelength-selective polarization conversion unit (see FIG. 4) that rotates the polarization plane of only the G light by 90 °, the G light (solid line in FIG. 3) that passes through the G phase plate 106 is changed. Such S polarized light is converted into P polarized light. Further, the G phase plate 106 is
Since they do not act on R light (broken line in FIG. 3) and B light (two-dot chain line in FIG. 3), they remain S-polarized. Hereinafter, the shift of the optical path and polarization plane of each color light will be described individually.

First, the P-polarized G light (solid line) transmitted through the G phase plate 106 is transmitted straight through the polarization separation surfaces 121 and 131 of the first and second polarization beam splitters 102 and 103, and then the second light. The light is emitted from the light-transmissive surface 103c of the polarization beam splitter 103, and enters the reflection spatial light modulator 161 corresponding to G. Then, the reflection type spatial light modulator 161 receives the light modulation corresponding to the G-compatible video signal and is reflected.

The S-polarized component of the G light generated by the light modulation is reflected by the polarization separation surface 131 of the second polarization beam splitter 103, and the fourth polarization beam splitter 10 is reflected.
It is incident on 5. Then, the light is reflected by the polarization splitting surface 151 of the fourth polarization beam splitter 105, emitted from the light transmitting surface 105c of the fourth polarization beam splitter 105, and enters the G phase plate 107 arranged in the subsequent stage. The G phase plate 107 has a polarization plane related to the G light as described above.
Since it has a function to rotate by 0 °, the G light S
The polarized light is converted into P polarized light and emitted.

Next, the R light (broken line) will be described. G
The S-polarized R light transmitted through the R phase plate 106 is reflected by the polarization splitting surface 121 of the first polarization beam splitter 102 and enters the R phase plate 108. Here, the R phase plate 1
Reference numeral 08 denotes a wavelength-selective polarization conversion means for rotating the polarization plane of the R light by 90 °, so that the R light is polarization-converted from S polarization to P polarization, which is emitted and is incident on the third polarization beam splitter 104. . Further, the P-polarized R light travels straight through the polarization separation surface 141 of the third polarization beam splitter 104, exits from the light-transmissive surface 104b, and enters the R-compatible reflective spatial light modulator 162. Then, the reflection-type spatial light modulator 162 undergoes light modulation according to the R-compatible video signal and is reflected.

The S-polarized component of the R light generated by the light modulation is reflected by the polarization splitting surface 141 of the third polarization beam splitter 104 and enters the R phase plate 109. In the R phase plate 109, the S polarization component of the R light is polarized and converted into P polarization, and the fourth polarization beam splitter 105
Incident on. And the fourth polarization beam splitter 1
The light beam is transmitted straight through the polarization splitting surface 151 of 05 and is emitted from the transparent surface 105c of the fourth polarization beam splitter 105,
It is incident on the G phase plate 107 arranged in the subsequent stage. The G phase plate 107 does not act on the R light at all, and the R light is emitted as P-polarized light.

Next, the B light (two-dot chain line) will be described. The S-polarized B light transmitted through the G phase plate 106 is
It is reflected by the polarization splitting surface 121 of the polarization beam splitter 102 and enters the R phase plate 108. Here, since the R phase plate 108 acts only on the R light and does not act on the B light at all as described above, the B light is emitted as it is as S polarized light without being polarization-converted. It enters the polarization beam splitter 104.

The S-polarized B light is reflected by the polarization splitting surface 141 of the third polarization beam splitter 104 and is transmitted through the transparent surface 104.
The light is emitted from a and enters the reflective spatial light modulator 163 corresponding to B. Then, the reflection-type spatial light modulation element 163 receives the light modulation according to the video signal corresponding to B and is reflected.

The P-polarized component of the B light generated by the light modulation is transmitted straight through the polarization splitting surface 141 of the third polarization beam splitter 104 and is incident on the R phase plate 109. Since the R phase plate 109 does not act on the B light as described above, the B light is emitted as it is as P polarized light and is incident on the fourth polarization beam splitter 105. Then, the light passes through the polarization separation surface 151 of the fourth polarization beam splitter 105 and goes straight, and is emitted from the light transmission surface 105c of the fourth polarization beam splitter 105.
It is incident on the optical phase plate 107. As described above, the G phase plate 107 acts only on the G light and not on the B light, so that the B light is emitted as P-polarized light.

In this way, the polarization planes of the R light, G light, and B light are aligned with P polarization, and a color image is enlarged and displayed on the screen (not shown) via the projection lens 191. As described above, according to the projection display device 300, a relatively simple optical configuration can be achieved while operating three polarization beam splitters on one reflective spatial light modulator. It has a feature that a projection display device with high contrast can be realized.

[0024]

However, the polarization splitting surfaces 121, 131, 141, 151 used for the four polarization beam splitters 102, 103, 104, 105 are to be solved.
Is formed of an optical film, but as shown in FIG. 4, this optical film has the wavelength dependence of the transmittance with the incident angle of light as a parameter. FIG. 6 is a diagram showing the wavelength dependence of the transmittance of P-polarized light in the visible wavelength region when the incident angle β of the incident light on the transparent surface of the polarization beam splitter is used as a parameter. In FIG. 6, the incident angle β of the incident light on the transparent surface of the polarization beam splitter is as follows: a is 0 °, b is −6 °, c is −15 °, d is + 6 °, and e is + 15 °. Show. The incident angle β is an angle formed by the light incident on the polarization beam splitter with the optical axis. As shown in FIG. 6, when the incident angle β of the incident light on the transparent surface of the polarization beam splitter is within ± 6 °, the wavelength dependence of the transmittance of P-polarized light is relatively constant. When it is more than this range, it has a large wavelength dependency and the transmittance decreases.

Usually, in the undefined polarized light, the polarization splitting surface 12
1, 131, 141, 151 include principal rays incident in parallel to the optical axis and light incident at angles other than the above-mentioned predetermined angle. Therefore, the principal rays are polarized and separated into the polarization separation surfaces 121, 13.
Although light can be made incident on 1, 141, 151 in parallel with the optical axis, other light cannot be made incident in parallel with the optical axis. Therefore, as described above, when indefinite polarized light is incident on the polarization splitting surfaces 121, 131, 141, 151, those polarization splitting surfaces 121, 131, 14 are incident.
Since the transmittances at 1 and 151 differ depending on the wavelength, the color reproducibility becomes poor.

As a countermeasure against this, the polarization splitting surfaces 121 and 13
It is conceivable that the wavelength dependence of the transmittance is reduced by narrowing the incident angle of the indefinite polarized light incident on 1, 141, and 151. However, non-constant polarized light other than the narrowed down becomes external light,
Since it is not used for the projection display device, the brightness is lowered.

Further, the light emitted from the light source 171 is absorbed by the polarization beam splitters 102, 103, 104 and 105 to generate a heat distribution, and the temperature difference in the polarization beam splitters 102, 103, 104 and 105 is generated. As a result, the refractive index changes, and birefringence occurs, which deteriorates the image quality. Further, it is desired to reduce the size and weight of the projection display device. However, the polarization beam splitters 102, 103, 104, 105 are the heaviest in the projection display device, and thus need to be lightened.

Therefore, the present invention has been made in order to solve the above problems, and provides a bright color separation / synthesis optical system having good image quality and a projection display apparatus using the same. The purpose is to do.

[0029]

According to a first aspect of the present invention, there is provided a first polarization separation means and a second polarization separation means arranged in a diagonal direction, and a diagonal direction orthogonal to the diagonal direction. When the third polarized light separating means and the fourth polarized light separating means which are arranged in the first and second polarized light separating means are arranged on the light incident side and the second polarized light separating means is arranged on the outgoing side, Between the two or more inner facing surfaces of the light incident side of the polarization separating means, the light emitting side of the second polarization separating means, and the inner facing surfaces of the first to fourth polarization separating means. Placed,
And a wavelength-selective conversion means for rotating the polarization planes of the predetermined three primary color lights incident from the light incident side of the first polarization separation means by 90 °, and the first, third and fourth polarization separation means. Is a plate-shaped wire grid polarization splitting plate, and the fourth polarization splitting means is a polarization beam splitter. A second invention comprises the color separation / combination optical system according to claim 1, and a light source and an indefinite polarized light emitted from the light source on the light incident side of the first polarization separation means of the color separation / combination optical system. A first polarization means that transmits only a predetermined linearly polarized light of
A second polarizing unit that transmits only predetermined linearly polarized light and a projection lens are provided on the light emission side of the second polarized light separating unit, and the third polarizing separating unit is provided outside the third polarized light separating unit. The third spatial light modulator which optically modulates the predetermined linearly polarized light that has passed through the third polarized light separating means, and then reflects the first linearly polarized light, and the fourth polarized light separating means on the outer surface of the fourth polarized light separating means. A second spatial light modulator that optically modulates the predetermined linearly polarized light reflected by the first spatially polarized light and a second spatial light modulator that optically modulates the predetermined linearly polarized light that has passed through the fourth polarization separating means and then reflects the first linearly polarized light. A spatial light modulator of No. 3 is provided, and a projection display device is provided.

[0030]

1 is a block diagram of an embodiment of the present invention.
Will be explained. FIG. 1 is a diagram showing a color separation / combination optical system and a projection display device according to an embodiment of the present invention. The projection display device 1 according to the embodiment of the present invention includes the first to third polarization beam splitters 10 in the conventional projection display device.
Instead of 2, 103, 104, first to third wire grid polarization separation plates 8, 9, 11 are used, and the other configurations are the same.

The characteristics of the wire grid polarization separation plate used in the embodiment of the present invention are shown in FIG. Figure 2
It is a figure which shows the wavelength dependence of the transmittance | permeability of P polarization | polarized-light when the incident angle (alpha) of the incident light to a wire grid polarization splitter is made into a parameter. In FIG. 2, the incident angle α of the incident light on the wire grid polarization separation plate is 0 for a, −15 for b, and +15 for c.
Shows the case. The incident angle α is an angle formed by the light incident on the wire grid separation polarizing plate and the optical axis. As shown in FIG. 2, the wavelength dependence of the transmittance of P-polarized light is extremely small and stable in the visible wavelength range even when the incident angle is ± 15 °, which is wider than in the past. Therefore, it can be seen that a projection display device which is bright and has good color reproducibility can be obtained by using the wire grid polarization separation plate instead of the polarization beam splitter. Further, unlike the polarization beam splitter, the wire grid polarization separation plate is a single plate-shaped polarization separation plate and is therefore lightweight. Further, even when incorporated in the projection display device, it is difficult to absorb the light emitted from the light source, so that it is possible to suppress the deterioration of the image quality due to the birefringence.

The color separation / synthesis optical system and the projection display device according to the embodiments of the present invention will be described in detail below. In the projection display device 1 according to the embodiment of the present invention, a light source 2 that emits indefinite polarized light and a transmission axis selected so that the three primary color lights of only linearly polarized light having a relation of S polarized light from this indefinite polarized light are transmitted. The first polarizing plate 3 and the linearly polarized light emitted from the first polarizing plate 3 are color-separated into three primary color lights, and the color-separated three primary color lights are modulated with video signals for the respective color lights, and then again. A color separation / synthesis optical system 4 for performing color synthesis to form a color image,
A second polarizing plate 5 whose transmission axis is selected so as to transmit only linearly polarized light having a P-polarized relation in the color-synthesized color image; and a projection lens 6 which magnifies and projects the P-polarized color image. Consists of.

The color separation / combination optical system 4 has 90 degrees of polarization plane of G light among the indefinite polarization of S polarization which has passed through the first polarizing plate 3.
Of the first G phase plate 7 that has a function of rotating to P polarized light and the three primary color lights that have passed through the first G phase plate 7,
A first wire grid polarization separation plate 8 which transmits P-polarized G light and reflects other S-polarized light and is arranged at an angle of 45 ° with respect to the optical axis of G light; A second wire grid polarization separation plate 9 arranged to transmit the polarized G light, reflect the S polarized G light, and have an angle of 135 ° with respect to the optical axis of the G light; Of the other S-polarized light reflected by the wire grid polarization separating plate 8, the first R phase plate 10 having the function of rotating the polarization plane of the R light by 90 ° to become P-polarized light, and Of the R light having passed through the R phase plate 10 of No. 1 and the other light (that is, the B light), the R of P polarization
And a third wire grid polarization separation plate 11 arranged to transmit light, reflect S-polarized G light, and have an angle of 45 ° with respect to the optical axis of R light.

Further, the second wire grid polarization separation plate 9
On the transmission side of the G light, a reflection type spatial light modulator 12 corresponding to G, which optically modulates the P polarized G light according to a video signal and converts it into S polarized light, and a third wire grid polarization separation plate. 11
On the transmission side of the R light of R, a P-polarized R light is optically modulated in accordance with a video signal and converted into S polarization, which is a reflection-type spatial light modulator 13 corresponding to R, and a third wire grid polarization separation plate. 11
On the side where the B light is reflected by, the S-polarized B light is optically modulated in accordance with the image signal and converted into P-polarized light, and the corresponding reflection-type spatial light modulator 14 corresponding to B and the reflection-type spatial light modulator are provided. The second R phase plate 15 having a function of rotating the polarization plane of the S-polarized R light reflected from 13 by 90 ° to convert it to P-polarized light.

Furthermore, the S-polarized G light reflected from the second wire grid polarization separation plate 9 is reflected, and the P-polarized B light and R light transmitted through the second R phase plate 15 are transmitted. Polarization beam splitter 16 having polarization splitting surface 16a
And a second G phase plate 17 having a function of transmitting the P-polarized R light and B light as they are and rotating the polarization plane of the S-polarized G light by 90 ° to make P-polarized light.

Next, the operation will be described. Light source 2
The indefinite polarized light emitted from is incident on the first polarizing plate 3.
Then, the first polarizing plate 3 transmits the three primary color lights of only linearly polarized light having a relationship of only S-polarized light from the indefinite polarized light,
It is incident on the G phase plate 7. Since the first G phase plate 7 is a wavelength-selective polarization conversion unit that rotates the polarization plane of only G light by 90 °, the S polarization related to the G light transmitted through the first G phase plate 7 is P polarization. Is converted to. Moreover, since the first G phase plate 7 does not act on the R light and the B light at all, they remain S-polarized.

G of P polarized light transmitted through the first G phase plate 7
The light is emitted from the first and second grid wire separation polarization plates 8 and 9
Travels straight through and enters the reflective spatial light modulator 12 for G. Then, in the reflective spatial light modulator 12, the light is modulated according to the G-compatible video signal and reflected. The S-polarized component of the G light generated by the light modulation enters from the transparent surface 16b of the polarization beam splitter 16, is reflected by the polarization splitting surface 16a of the polarization beam splitter 16, and enters the second G phase plate 17. To do. As described above, the second G phase plate 17 has a polarization plane relating to the G light of 90 °.
Since it has a function of rotating, the S polarized light of the G light is converted into the P polarized light and emitted.

Next, the R light will be described. The S-polarized R light that has passed through the first G polarizing plate 7 is reflected by the first wire grid separation polarizing plate 8 and enters the first R phase plate 10. Here, the first R phase plate 10 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the R light by 90 °, so that the R light is polarized from S polarization to P change and is emitted. It is incident on the third grid wire separation polarization plate 11.
Further, the P-polarized R light is transmitted through the third grid wire separation polarization plate 11 and is incident on the R-compatible reflection type spatial light modulation element 13. Then, in the reflective spatial light modulator 13, the light is modulated according to the R-compatible video signal and reflected.

The S-polarized component of the R light generated by the light modulation is reflected by the third grid wire separation polarizing plate 13,
It is incident on the second R phase plate 15. In the second R phase plate 15, the S polarization component of the R light is polarization-converted into P polarization and enters the polarization beam splitter 16. Then, the light beam goes straight through the polarization splitting surface 16a of the polarization beam splitter 16 and enters the second G phase plate 17. The second G phase plate 17 does not act on the R light at all and outputs the R light as it is as P polarized light.

Next, the B light will be described. The S-polarized B light that has passed through the first G phase plate 7 is reflected by the first grid wire separation polarization plate 8 and enters the first R phase plate 10. Here, as described above, the first R phase plate 10 acts only on the R light and does not act on the B light at all, so that the B light is emitted as it is as S polarized light without being polarized. Then, it is incident on the third grid wire separation polarization plate 11.

The S-polarized B light is reflected by the third grid wire separating / polarizing plate 11, and is then reflected by the B-compatible reflection type spatial light modulator 14 in accordance with the B-compatible video signal. To be done.

The P-polarized component of the B light generated by the light modulation is transmitted straight through the third grid wire separating / polarizing plate 11 and is incident on the second R phase plate 15. Since the second R phase plate 15 does not act on the B light at all as described above, the B light is emitted as it is as P polarized light and enters the polarization beam splitter 16. Then, the light beam passes through the polarization splitting surface 16a of the polarization beam splitter 16 straightly, and is emitted from the light transmitting surface 16c.
It is incident on the G phase plate 17 of. Second G phase plate 17
As described above, since it acts only on the G light and does not act on the B light at all, the B light is emitted as P-polarized light as it is.

In this way, the polarization planes of the R light, G light, and B light are aligned with P polarized light, and are not shown via the second polarizing plate 5 and the projection lens 6 which transmit only the P polarized light. Enlarge the color image on the screen.

As described above, according to the embodiment of the present invention, since the wavelength dependence of the transmittance of P-polarized light is small and the plate-shaped wire grid polarization separation plates 8, 9 and 11 are used,
A color separation / synthesis optical system with good image quality is obtained because it is lightweight and does not cause birefringence due to heat distribution. In addition, the projection display device using this color separation / combination optical system can obtain an image of bright and good video quality.

[0045]

As described above, according to the present invention, the first polarized light separating means and the second polarized light separating means arranged in the diagonal direction and the diagonal direction orthogonal to the diagonal direction are arranged. A third polarized light separating means and a fourth polarized light separating means;
When the polarized light separating means is arranged on the light incident side and the second polarized light separating means is arranged on the emitting side, the light incident side of the first polarized light separating means, the light emitting side of the second polarized light separating means and the First
Through the inner facing surfaces of the fourth polarization splitting means, between the two or more inner facing surfaces, the polarized light of the predetermined three primary colors incident from the light incident side of the first polarization splitting means is polarized. Wavelength selective conversion means for rotating the wavefront by 90 °, wherein the first, third and fourth polarization separation means are plate-shaped wire grid polarization separation plates, and the fourth polarization separation means is Since it is a polarizing beam splitter, it is lightweight,
In addition, since birefringence due to heat distribution does not occur, a color separation / combination optical system with good image quality can be obtained. Further, in the projection display device using this, a bright image with good image quality can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a color separation / combination optical system and a projection display device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the wavelength dependence of the transmittance of P-polarized light when the incident angle α of incident light on the wire grid polarization separation plate is used as a parameter.

FIG. 3 is a schematic plan view showing an optical configuration of a projection display device to which a reflective spatial light modulator provided by Colorlink Co. is applied.

FIG. 4 is a spectral characteristic of a G phase plate.

FIG. 5 is a spectral characteristic of the R phase plate.

FIG. 6 is a diagram showing the wavelength dependence of the transmittance of P-polarized light in the visible wavelength region when the incident angle β of the incident light on the transparent surface of the polarization beam splitter is used as a parameter.

[Description of Reference Signs] 1 ... Projection display device, 2 ... Light source, 3 ... First polarizing plate, 4 ...
Color separation / synthesis optical system, 5 ... Second polarizing plate, 6 ... Projection lens, 7 ... First G phase plate, 8 ... First wire grid polarization separation plate (first polarization separation means), 9 ... Second wire grid polarization separation plate (third polarization separation means), 10 ... First R phase plate, 11 ... Third wire grid polarization separation plate (fourth polarization separation means), 12 ... G Reflection-type spatial light modulator, 13 ...
4 ... B reflective type spatial light modulator, 15 ... 2nd R phase plate, 16 ... Polarization beam splitter (second polarization splitting means), 16a ... Polarization splitting surface, 17 ... 2nd G phase Board

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/74 H04N 5/74 B

Claims (2)

[Claims] 1. A first polarization separation means and a second polarization separation means arranged in a diagonal direction, and a third polarization separation means and a fourth polarization separation means arranged in a diagonal direction orthogonal to the diagonal direction. When the first polarized light separating means is arranged on the light incident side and the second polarized light separating means is arranged on the outgoing side, the light separating side of the first polarized light separating means and the second polarized light separating means are arranged. The light incident side of the first polarized light separating means is disposed between two or more inner facing surfaces of the light exit side of the polarized light separating means and the inner facing surfaces of the first to fourth polarized light separating means. Wavelength selective conversion means for rotating the polarization planes of the predetermined three primary color lights incident from the side by 90 °,
The first, third, and fourth polarization separation means are plate-shaped wire grid polarization separation plates, and the fourth polarization separation means is a polarization beam splitter. Synthetic optics. 2. A color separation / combination optical system according to claim 1,
A light source and a first polarizing means for transmitting only predetermined linearly polarized light out of the indefinitely polarized light emitted from the light source are provided on the light incident side of the first polarized light separating means of the color separation / combination optical system. On the light exit side of the second polarized light separating means, a second polarizing means that transmits only predetermined linearly polarized light and a projection lens are provided, and on the outer side of the third polarized light separating means, After optically modulating the predetermined linearly polarized light that has passed through the third polarized light separating means,
A second spatial light modulator that reflects light and a second light that modulates the predetermined linearly polarized light reflected by the fourth polarized light separating means on the outer surface of the fourth polarized light separating means and then reflects the light. And a third spatial light modulator that optically modulates the predetermined linearly polarized light that has passed through the fourth polarization separation means and then reflects the third linearly polarized light. .