JP2002228809A - Color separation and composition optical system, and projection display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color separation and composition optical system which blocks rays unnecessary for projection display and which gives excellent image quality, and to provide a projection display device which uses the optical system. SOLUTION: The color separation and composition optical system 2 is equipped with four polarization beam splitters 7, 8, 9 and 11 arranged so that their polarization separation faces 71, 81, 91 and 111 are crossed in an almost X-shape, and with wavelength selective polarization converting means 12, 13, at specified positions, which rotate the polarization planes of the color light by 90 deg.. The optical system is used for the projection display device 1. The optical system has a blocking means 12 against light in the crossing part where the polarization separation faces 71, 81, 91 and 111 cross one another and in the center part surrounded by the first to fourth polarization beam splitters 7, 8, 9 and 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color separation / synthesis optical system provided with a polarizing beam splitter of a projection display device using a reflection type spatial light modulator and a projection display device using the same, and particularly to display quality. The present invention relates to a unit for preventing unnecessary light that degrades light from being projected.

[0002]

2. Description of the Related Art A color projection display device separates R (red), G (green), and B (blue) light components of three primary colors from white light and guides them to a spatial light modulator of a corresponding color. The color light modulated by the spatial light modulator according to the video signal is synthesized and projected to display a color video on a screen.

[0003] Color projection display devices are broadly classified into three types according to the type of spatial light modulation element applied thereto. For example, a transmission type spatial light modulation element is applied, a reflection type spatial light modulation element is applied, and a DMD (Dig) is used.
It is possible to apply an application (ital Mirror Device).

The transmission type spatial light modulator and DMD can be easily miniaturized because the optical configuration can be made relatively simple, but it is difficult to increase the resolution. On the other hand, the reflection type spatial light modulation element is advantageous for high resolution, but has a difficulty in downsizing because the optical configuration is complicated.

In particular, a projection display apparatus to which a reflection type spatial light modulator is applied is a polarizing beam splitter for separating incident light for irradiating the spatial light modulator and reflected light modulated by the spatial light modulator. Need. To realize high contrast, for one spatial light modulator,
This complicates the optical configuration of the reflective projection display, usually due to the use of more than one polarizing beam splitter.

A color separation / synthesis optical system which has solved the problem of the optical configuration in such a reflection type spatial light modulator has recently been developed by Colorlink in the United States.
c. ) Provided by Regarding this, a reference (Michael G. Robinson et.
ing Architecture Using Color Polarization Filter
s ", SID 00 DIGEST, 92-95 (2000).

FIG. 5 is a schematic plan view showing an optical configuration of a projection display apparatus to which a reflective spatial light modulator provided by Color Link Co., Ltd. is applied. The color separation / synthesis optical system 290 (portion surrounded by a broken line in the figure) is a cubic or prismatic first,
Second, third, and fourth polarization beam splitters 102, 1
Nos. 03, 104, and 105 are separated by their polarization separation surfaces 121, 13
1, 141, 151 are arranged so as to intersect substantially in an X-shape, and further, a light-transmitting surface on the incident side of the first polarization beam splitter 102 (in FIG. 5, the first polarization beam splitter has A function of rotating the polarization plane of the G light by 90 ° both on the left side surface) and on 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. 5). First wavelength-selective polarization conversion means (hereinafter referred to as phase plate for G) 10 having
6, 107, and between the first and third polarization beam splitters 102, 104 and between the third and fourth polarization beam splitters 104, 105, the polarization plane of the R light is 9
Second wavelength-selective polarization conversion means (hereinafter, referred to as R phase plate) 108 and 109 having a function of rotating by 0 ° 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 splitting of the polarizing beam splitter on which it is incident. S-polarized light when perpendicular to the plane of incidence relative to the plane, and P-polarized when parallel
It is called polarized light.

The above-mentioned G phase plates 106 and 107 have the structure shown in FIG.
The phase plate having the characteristics shown in FIG. In FIG. 6, crossed polarizers are spectral characteristics of output light when a polarizer and an analyzer are arranged on a cross via a wavelength-selective polarization converter 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 the 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. 7, the cross-polarizer and the parallel-polarizer have the same meaning as described above. From the figure, it can be seen that the plane of polarization of the R light is rotated by 90 °.

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

In the above color separation / synthesis 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 at a diagonal of the first polarization beam splitter 102 serves as an exit-side polarization beam splitter. Becomes Further, the second and third polarizing beam splitters 103, 10 arranged at intermediate positions thereof
Reference numeral 4 denotes a so-called main polarization beam splitter that functions to separate incident light that irradiates the reflective spatial light modulator and reflected light that has been modulated by the reflective spatial light modulator.

The second polarization beam splitter (main polarization beam splitter) 10 of the color separation / synthesis optical system 290.
3, a G-type reflective spatial light modulator 161 is provided on the light-transmitting surface 103c side, and an R-type reflective spatial light modulator is provided on the light-transmitting surface 104b side of the third polarizing beam splitter (main polarizing beam splitter) 104. The element 162 and the light transmitting surface 104
On the a side, a reflection type spatial light modulation element 163 corresponding to B is provided.
Further, a light source 171 that emits white light and a polarization separation surface 121 of the first polarization beam splitter (incident-side polarization beam splitter) 102 are provided in front of the first polarization beam splitter (incident-side polarization beam splitter) 102 on the incident side.
A first polarizing plate 181 having a transmission axis selected so as to transmit only linearly polarized light having a relationship of S-polarized light with respect to
A fourth polarization beam splitter (emission-side polarization beam splitter) 1 is provided behind the fourth polarization beam splitter (emission-side polarization beam splitter) 105 on the exit side.
The transmission axis is selected such that only the linearly polarized light having the relationship of P-polarized light is transmitted with respect to the polarization separation surface 151 of FIG.
The projection display device 300 is provided with a polarizing plate 182 and a projection lens 191 for enlarging and projecting color image light.

The first, second, third, and fourth polarization beam splitters 102, 103, 104, and 105 have their respective polarization splitting surfaces 121, 131, 141, and 151 arranged so that their incident surfaces are common. Since the relative relationship between the polarization plane of the linearly polarized light that determines the S-polarized light and the P-polarized light and the polarization splitting plane is the same for all polarization beam splitters, the S-polarized light and the P-polarized light Description of which polarization beam splitter is for the polarization splitting surface is omitted.

The projection display device 300 operates as follows. The irregularly polarized white light emitted from the light source 171 is incident on 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 means (see FIG. 6) for rotating the plane of polarization of only the G light by 90 °, the G light is transmitted through the G phase plate 106 (the solid line in FIG. 5). Such S-polarized light is converted to P-polarized light. G phase plate 1
06 is R light (broken line in FIG. 5) and B light (two-dot chain line in FIG. 5)
Do not have any effect on, they remain S-polarized. Hereinafter, the shift of the optical path and the 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 passes straight through the polarization splitting surfaces 121 and 131 of the first and second polarization beam splitters 102 and 103, and travels straight through. Out of the light transmitting surface 103c of the polarization beam splitter 103, and enter the G-type reflective spatial light modulator 161. Then, the light is reflected by the reflective spatial light modulator 161 after being subjected to light modulation according to the G-compatible video signal.

The S-polarized light component of the G light generated by the light modulation is reflected by the polarization splitting surface 131 of the second polarization beam splitter 103, and is reflected by the fourth polarization beam splitter 10.
5 is incident. Then, the light is reflected on the polarization splitting surface 151 of the fourth polarization beam splitter 105, exits from the light transmitting surface 105 c of the fourth polarization beam splitter 105, and enters the G phase plate 107 disposed at the subsequent stage. As described above, the phase plate for G 107 sets the plane of polarization of G light to 90 degrees.
Since it has a function of rotating by °, the S-polarized light of G 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 phase plate for reflection 106 is reflected by the polarization splitting surface 121 of the first polarization beam splitter 102 and enters the phase plate for R 108. Here, the phase plate for R 1
Reference numeral 08 denotes a wavelength-selective polarization conversion unit that rotates the plane of polarization of the R light by 90 °, so that the R light is polarization-converted from S-polarized light to P-polarized light, emitted, and enters the third polarization beam splitter 104. . Further, the P-polarized R light exits from the light-transmitting surface 104b that is transmitted straight through the polarization splitting surface 141 of the third polarization beam splitter 104, and enters the R-type reflective spatial light modulator 162. Then, the reflection type spatial light modulation element 162 undergoes light modulation according to the R-compatible video signal and is reflected.

The S-polarized light 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-polarized light component of the R light is polarization-converted into P-polarized light, and the fourth polarization beam splitter 105
Incident on. Then, the fourth polarization beam splitter 1
05, passes straight through the polarization splitting surface 151, exits from the light transmitting surface 105c of the fourth polarizing beam splitter 105,
The light is incident on the G phase plate 107 arranged at the subsequent stage. The G phase plate 107 has no effect on the R light, 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
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
The polarized light is emitted as it is and enters the third polarization beam splitter 104.

The S-polarized B light is reflected by the polarization splitting surface 141 of the third polarizing beam splitter 104 and is transmitted by the light transmitting surface 104.
The light exits from a and enters the reflective spatial light modulator 163 corresponding to B. Then, the light is reflected by the reflection type spatial light modulation element 162 after being subjected to light modulation according to the video signal corresponding to B.

The P-polarized light component of the B light generated by the light modulation passes straight through the polarization splitting surface 141 of the third polarization beam splitter 104 and enters the R phase plate 109. Since the R phase plate 109 does not act on the B light at all as described above, the B light is emitted as P-polarized light and enters the fourth polarization beam splitter 105. Then, the light passes straight through the polarization splitting surface 151 of the fourth polarization beam splitter 105, exits from the light transmission surface 105 c of the fourth polarization beam splitter 105, and is disposed at a subsequent stage.
Incident on the phase plate 107 for use. As described above, since the G phase plate 107 acts only on the G light and has no effect on the B light, the B light is emitted as P-polarized light.

In this manner, the planes of polarization of the R, G, and B lights are adjusted to P-polarized light, and a color image is enlarged and displayed on a 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 three polarization beam splitters act on one reflection-type spatial light modulation element. It has the feature that a projection display device with contrast can be realized.

[0024]

However, in the color separation / synthesis optical system 290, the four polarization beam splitters 102, 103, 104, and 105 have their polarization splitting surfaces 121, 131, 141, and 151 substantially X-shaped. Because they are arranged so as to intersect in a shape, as shown in FIG.
Part of the light incident on the first polarization beam splitter (incident side polarization beam splitter) 102 is converted into a fourth polarization beam splitter (emission side polarization beam splitter) 1.
05, and the unnecessary light L generates a bright portion on a screen (not shown) via the projection lens 191, thus deteriorating the image quality. This is particularly remarkable when the four polarizing beam splitters 102, 103, 104, and 105 are joined together by a joining member 110 such as a transparent adhesive.

The reflection type spatial light modulators 161, 162, 1
In the case where an integrator is provided on the light source image side or the light source side on the 63 surface, the reflective spatial light modulators 161 and
The illumination light illuminating 62, 163 forms an image of the segment of the integrator. However, in reality, there is a light beam that spreads also around the reflection type spatial light modulators 161, 162, and 163, and a part of this light beam becomes unnecessary light L and is displayed on a projected image. There is.

The reflection type spatial light modulators 161 and 16
A part of the light reflected by 2, 163 may be re-reflected on the surface of the first polarizing plate 181 disposed on the incident side, and may be projected as unnecessary light L.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and provides a color separation / synthesis optical system which is excellent in image quality by blocking unnecessary light beams for projection display and a projection display apparatus using the same. The purpose is to do.

[0028]

According to a first aspect of the present invention, there is provided a color separation / synthesis optical system according to the present invention, which comprises a cube or a prism having a polarization separation surface formed in a diagonal direction arranged in an X shape. The first to fourth polarizing beam splitters;
When the first polarizing beam splitter is disposed on the light incident side and the fourth polarizing beam splitter is disposed on the light emitting side, the first polarizing beam splitter and the fourth polarizing beam splitter are disposed diagonally. Out of the light incident side of the polarizing beam splitter, the light emitting side of the fourth polarizing beam splitter, and the inner facing surfaces of the first to fourth polarizing beam splitters orthogonal to each other. And a wavelength-selective conversion means for rotating the plane of polarization of the predetermined color light by 90 ° disposed between the first and fourth polarizations at the intersection where the polarization separation planes cross each other. At a central portion surrounded by the beam splitter, light shielding means for blocking light leaking from the first polarization beam splitter to the fourth polarization beam splitter was provided. And wherein the door.

According to a second aspect of the present invention, there is provided a cubic or prismatic first to fourth polarization beam splitters arranged so that polarization separation surfaces formed in diagonal directions have an X shape, and the first to fourth polarization beam splitters. When the polarizing beam splitter and the fourth polarizing beam splitter are arranged diagonally, and the first polarizing beam splitter is arranged on the light incident side and the fourth polarizing beam splitter is arranged on the light emitting side, the first Of the light incident side of the polarizing beam splitter, the light emitting side of the fourth polarizing beam splitter, and the inner facing surfaces orthogonal to each other of the first to fourth polarizing beam splitters, two or more of the inner facing surfaces Wavelength-selective conversion means for rotating the plane of polarization of the predetermined color light by 90 ° disposed between the first polarization beam splitter and the fourth polarization beam splitter. Chamfered corners opposite to have, and further comprising a light shielding means to the chamfer.

According to a third aspect of the present invention, there is provided a projection display apparatus including the color separation / synthesis optical system according to the first or second aspect, and a light incidence side of the first polarization beam splitter of the color separation / synthesis optical system. A light source, and a first polarizing unit that transmits only predetermined linearly polarized light among the indeterminate polarized light emitted from the light source,
On the light exit side of the fourth polarizing beam splitter, a second polarizing means and a projection lens that transmit only predetermined linearly polarized light are provided, and on the outer light transmitting surfaces of the second and third polarizing beam splitters, And a spatial light modulator.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 shows a first embodiment of the present invention.
FIG. 1 is a plan view showing a schematic configuration of a projection display device according to an embodiment. In FIG. 1, reference numeral 1 denotes a projection display device according to a first embodiment of the present invention, which includes a color separation / synthesis optical system 2, a light source 3 disposed on the light incident side of the color separation / synthesis optical system 2, and the light source 3 A first polarizing means (for example, a polarizing plate) 4 for selectively transmitting only a predetermined linearly polarized light from the indeterminately polarized white light which is the outgoing light, and a light emitting side of the color separation / synthesis optical system 2 A second polarizing means (for example, a polarizing plate) 5 for selectively transmitting only predetermined linearly polarized light and a projection lens 6.

The color separation / synthesis optical system 2 includes a cubic or prismatic first, second, third, and fourth polarization beam splitters 7, 8, 9, and 11 having polarization separation surfaces 71, 81,
91, 111 are arranged so as to intersect substantially in an X-shape, and the first to fourth polarization beam splitters are located at intersections where the polarization separation surfaces 71, 81, 91, 111 intersect each other. A light shielding means 12 is provided at a central portion surrounded by 7, 8, 9, and 11. Here, when the first polarization beam splitter 7 is selected as the incident-side polarization beam splitter, the fourth polarization beam splitter 11 at a diagonal position thereof is set as the exit-side polarization beam splitter.

Further, the color separation / synthesis optical system 2 includes a first light transmitting surface 7a on the light incident side of the first polarizing beam splitter 7 and a first light transmitting surface 11c on the light emitting side of the fourth polarizing beam splitter 11. 90 ° polarization plane of the color light (for example, G light)
Rotating first wavelength-selective polarization conversion means (eg, G
Phase plates) 12 and 13, and a gap between opposing portions of the first and third polarization beam splitters 7 and 9 and a gap between opposing portions of the third and fourth polarization beam splitters 9 and 11 are provided with a second Second wavelength-selective polarization converting means (for example, R phase plate) for rotating the polarization plane of the color light (for example, R light) by 90 °
14 is provided. Note that the above components of the color separation / synthesis optical system 2 may be integrated by joining with a transparent joining member (for example, an adhesive) 18.

The light transmitting surfaces 8c, 9a, 9 of the second and third polarizing beam splitters 8, 9 of the color separation / synthesis optical system 2 are described.
b, reflection-type spatial light modulation elements 26, 27, 28 are provided.

In the projection display device 1 according to the first embodiment of the present invention, leak light (solid line in FIG. 1) L, which is unnecessary light from the first polarizing beam splitter (incident side polarizing beam splitter) 7, is Polarization separation surfaces 71, 81, 9
1, 111 are at the intersection where they intersect each other and
Since the light is blocked by the light shielding means 12 provided at the central portion surrounded by the fourth to fourth polarization beam splitters 7, 8, 9, 11, the projection lens 6 from the fourth polarization beam splitter (output side polarization beam splitter) 11 Is not projected onto a screen (not shown) via the screen (broken line in the figure). Accordingly, the problem of the related art that a bright portion is generated in the projected image due to unnecessary light and deteriorates image quality is solved.

FIG. 2 is a plan view showing a schematic configuration of a projection display device according to a second embodiment of the present invention. 1 will be described using the same reference numerals. Here, only the parts different from those in FIG. 1 will be described. In FIG. 2, reference numeral 20 denotes a projection display device according to the second embodiment. 1 are different from the first polarization beam splitter 22 and the fourth polarization beam splitter 22, which are components of the color separation / synthesis optical system 21.
Polarization beam splitter 23 chamfers the corners 22e and 23e facing each other in a diagonal positional relationship,
The point that the light blocking means 24 is provided at the corner of the chamfer.

Further, the fourth polarizing beam splitter 2
3 is a light transmitting surface 23c on the light emission side,
The light shielding means 25 is provided in a part of the portion c near the second polarization beam splitter 8. The light shielding means 25
Is required to enhance the light-shielding effect, but in practice, a sufficient effect can be obtained with only the light-shielding means 24.

In the second embodiment of the present invention, as in the first embodiment, the first polarization beam splitter 2 is used.
Leakage light which is unnecessary light generated in step 2 (solid line in FIG. 2)
Since L is blocked by the light shielding units 24 and 25, the light is not projected from the fourth polarizing beam splitter 23 to the screen via the projection lens 6 (broken line in the figure). Therefore, also in the second embodiment of the present invention, the problem of the prior art that a bright portion due to unnecessary light is displayed in a projected image and image quality is degraded is solved.

Next, a third embodiment of the present invention will be described. FIG. 3 is a plan view showing a schematic configuration of the projection display device according to the third embodiment of the present invention. 1 will be described using the same reference numerals. Here, only the parts different from those in FIG. 1 will be described. In FIG. 3, reference numeral 30 denotes a projection display device according to a third embodiment of the present invention. The difference from FIG. 1 is that the sizes of the second and third polarization beam splitters 32 and 33, which are constituent elements of the color separation / synthesis optical system 31, are changed by applying the reflection type spatial light modulators 26, 27 and 28 to which they are applied. The size is made smaller in accordance with the size of.

The optical distance from the light source 3 to the reflective spatial light modulators 26, 27 and 28 and the optical distance from the reflective spatial light modulators 26, 27 and 28 to the projection lens 6 are substantially equal. Have been matched.

For the purpose of shortening the optical distance and preventing surface reflection in the first to fourth polarizing beam splitters 7, 32, 33, 11, coupling means (for example, a transparent glass substrate) 34, 35. Is inserted into the gap between the opposing portions of each polarizing beam splitter.
The facing portions of the first and third polarization beam splitters 7 and 33, and the third and fourth polarization beam splitters 3
The second wavelength-selective polarization conversion means 36 provided in the gap between the opposing portions 3 and 11 is shown small in FIG. 3 according to the shape of the third polarization beam splitter, but is not limited thereto. is not.

The color separation / synthesis optical system 31 further includes first to fourth polarization beam splitters 7, 3 as in FIG.
2, 33, 11 polarization splitting surfaces 71, 321, 331, 1
A light shielding means 37 is provided in a central portion surrounded by first to fourth polarization beam splitters 7, 32, 33, and 11 at an intersection where the reference numeral 11 intersects substantially in an X shape. Note that the shape of the light shielding means 37 is not limited to the shape shown in FIG.

According to the third embodiment of the present invention, similarly to FIG. 1, leak light (solid line in FIG. 3) L, which is unnecessary light, generated by the first polarizing beam splitter 7 is blocked by the light blocking means 37. Therefore, the light is not projected from the fourth polarizing beam splitter 11 to the screen via the projection lens 6 (broken line in the figure).

Therefore, also in the third embodiment of the present invention, the problem of the prior art that a bright portion is displayed in the projected image due to unnecessary light and the image quality is deteriorated is solved. Further, according to the third embodiment of the present invention, the sizes of the second and third polarizing beam splitters 32 and 33 are formed to be small corresponding to the sizes of the reflective spatial light modulators 26, 27 and 28. Therefore, there is an effect that the cost increase of the color separation / synthesis optical system and the projection display device can be suppressed.

Next, a fourth embodiment of the present invention will be described. FIG. 4 is a plan view showing a schematic configuration of a projection display device according to a fourth embodiment of the present invention. 1 and 2 will be described using the same reference numerals. Here, only the portions different from FIG. 2 will be described. In FIG. 4, reference numeral 40 denotes a projection display device according to a fourth embodiment of the present invention. 2 is different from the color separation / synthesis optical system 41 shown in FIG.
The size of the second and third polarization beam splitters 32 and 33, which are the components of the above, is reduced in accordance with the size of the reflection type spatial light modulators 26, 27 and 28 to be applied.

Further, the light source 3 transmits the reflection type spatial light modulator 2
The optical distances to 6, 27 and 28 and the optical distances from the reflection type spatial light modulators 26, 27 and 28 to the projection lens 6 are set to be substantially the same.

Further, for the purpose of shortening the optical distance and preventing surface reflection in the first to fourth polarizing beam splitters 7, 32, 33, and 23, coupling means (for example, glass substrates) 42 and 35 are provided. The polarization beam splitter is provided by being inserted into a gap between opposing portions of the polarization beam splitter. In addition,
As in the third embodiment, the shape of the second wavelength-selective polarization conversion means 36 is not limited to the shape shown in FIG.

The color separation / synthesis optical system 41 further includes a light shielding means 43 on the inner side surface of the coupling means 42. The light shielding means 43 is not an essential element,
And a fourth polarizing beam splitter 22, 32, 33,
The present invention may be applied to a case where only the light shielding means 24 provided in 23 does not sufficiently block unnecessary light. Alternatively, the first to fourth polarization beam splitters 22, 32, 33,
In the central part surrounded by the first to fourth polarization beam splitters 22, 32, 33, and 23 at the intersection where the 23 polarization separation surfaces 221, 321, 331, and 231 intersect substantially in an X shape. A plate-shaped or block-shaped light shielding means may be provided.

According to the fourth embodiment of the present invention, similarly to FIG. 2, leak light (solid line in FIG. 4) L which is unnecessary light generated by the first polarization beam splitter 22 is
And 43, there is no projection from the fourth polarizing beam splitter 23 to the screen via the projection lens 6 (broken line in the figure).

Therefore, also in the fourth embodiment of the present invention, the problem of the prior art that a bright portion due to unnecessary light is displayed in a projected image and image quality is degraded is solved. Furthermore, the fourth embodiment of the present invention is similar to the third embodiment of the present invention in that the second and third polarizing beam splitters 3 are provided.
The size of 2, 33 is changed to the reflection type spatial light modulator 26, 2
Because it is formed small corresponding to the size of 7, 28,
This has the effect of suppressing an increase in cost of the color separation / synthesis optical system and the projection display device.

[0051]

As is apparent from the above description, the present invention relates to a color separation optical system in which four polarization beam splitters are arranged so that the polarization splitting surfaces of the four polarization beam splitters intersect substantially in an X shape. A light shielding means is provided at a crossing portion where the above-mentioned polarization separation planes cross each other and is surrounded by the first to fourth polarization beam splitters, so that light is generated by the polarization beam splitter on the light incident side. It is possible to provide a projection display device excellent in image display quality, in which unnecessary leaked light is blocked by the light blocking means, and can be suppressed from being projected on the screen via the light exit side polarization beam splitter and the projection lens. it can.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a projection display device according to a first embodiment of the present invention.

FIG. 2 is a schematic plan view of a projection display device according to a second embodiment of the present invention.

FIG. 3 is a schematic plan view of a projection display device according to a third embodiment of the present invention.

FIG. 4 is a schematic plan view of a projection display device according to a third embodiment of the present invention.

FIG. 5 is a schematic plan view of a projection display device according to the related art.

FIG. 6 shows spectral characteristics of a G phase plate.

FIG. 7 shows spectral characteristics of an R phase plate.

FIG. 8 is a schematic plan view for explaining the influence of leaked unnecessary light generated by a first polarizing beam splitter on a projected image.

[Explanation of symbols]

1, 20, 30, 40 ... Projection display device, 2, 21, 3
1, 41: color separation / synthesis optical system, 3: light source, 4: first polarizing means, 5: second polarizing means, 6: projection lens, 7, 2
2, a first polarizing beam splitter (incident side polarizing beam splitter), 8, 32, a second polarizing beam splitter (main polarizing beam splitter), 9, 33, a third polarizing beam splitter (main polarizing beam splitter), 8c, 9a, 9b: light-transmitting surface, 11, 23 ... fourth polarization beam splitter (emission-side polarization beam splitter), 12, 23, 37, 43 ... light shielding means, 13, 1
4, 36 ... wavelength-selective polarization conversion means, 26, 27, 28
... Spatial light modulator, 34, 35, 42 ... Coupling means, 71, 81, 91, 111, 321, 331 ... Polarization separation surface

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03B 33/12 G03B 33/12 H04N 9/31 H04N 9/31 C F term (Reference) 2H042 CA06 CA08 CA09 CA14 CA17 2H049 BA02 BA05 BA16 BA17 BA42 BB03 BC22 2H099 AA12 BA09 CA02 CA11 DA05 5C060 BC05 DA05 HC25 JA17 JB06

Claims (3)

[Claims] A first or fourth cubic or prismatic polarization beam splitter disposed so that a polarization separation surface formed in a diagonal direction has an X-shape; and the first polarization beam splitter. When the fourth polarization beam splitter is disposed diagonally, and the first polarization beam splitter is disposed on the light incident side and the fourth polarization beam splitter is disposed on the light exit side, the first polarization beam splitter is A light incident side, a light emitting side of the fourth polarization beam splitter, and an inner facing surface of the first to fourth polarization beam splitters which are orthogonal to each other;
Wavelength-selective conversion means for rotating the polarization plane of the predetermined color light by 90 ° disposed between two or more of the inner facing surfaces, wherein the polarization separation plane is at an intersection where the polarization separation planes intersect with each other, and A light shielding unit is provided at a central portion surrounded by the first to fourth polarization beam splitters to block light leaking from the first polarization beam splitter to the fourth polarization beam splitter. Color separation / synthesis optical system. 2. A cubic or prismatic first to fourth polarization beam splitters arranged so that polarization separation surfaces formed in a diagonal direction have an X shape, and the first polarization beam splitter. When the fourth polarization beam splitter is disposed diagonally, and the first polarization beam splitter is disposed on the light incident side and the fourth polarization beam splitter is disposed on the light exit side, the first polarization beam splitter is A light incident side, a light emitting side of the fourth polarization beam splitter, and an inner facing surface of the first to fourth polarization beam splitters which are orthogonal to each other;
And a wavelength-selective conversion means for rotating the polarization plane of the predetermined color light by 90 ° disposed between two or more of the inner facing surfaces, wherein the first polarization beam splitter and the fourth polarization beam splitter are mutually separated. A color separation / synthesis optical system characterized in that opposing corners are chamfered and a light-shielding means is provided in the chamfer. 3. A color separation / combination optical system according to claim 1, wherein a light source and an irregular light emitted from the light source are provided on the light incident side of the first polarization beam splitter of the color separation / combination optical system. The first that transmits only a predetermined linearly polarized light among the polarized lights
A second polarizing means that transmits only a predetermined linearly polarized light and a projection lens on the light emission side of the fourth polarizing beam splitter; and a second polarizing means of the second and third polarizing beam splitters. A projection display device comprising a spatial light modulator on an outer light transmitting surface.