JP2001324760A - Illuminating optical system for single panel type liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illuminating optical system for a single panel type liquid crystal projector capable of attaining the cost reduction. SOLUTION: The projector is provided with an illuminating light source 2, a color separating means 12 for separating a luminous flux emitted from the light source 2 into plural luminous fluxes in accordance with the wavelength, an integrator 5 constituted of 1st and 2nd lens arrays 3 and 4, a polarized light converting means 22 for making the polarizing direction of each luminous flux uniform through plural polarized light conversion elements 22R, 22G and 22B having different wavelength band where the transmittance for the S- polarized light becomes 0% in accordance with each luminous flux separated by the color separating means 12, and the single liquid crystal panel 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical system for a single-panel type liquid crystal projector which projects an image by illuminating a single-panel liquid crystal panel with a light beam of red, green and blue light by performing polarization conversion.

[0002]

2. Description of the Related Art The illumination optical system of a conventional single-panel liquid crystal projector is shown in FIG. Natural light emitted from the light source 2 is made into a parallel light beam by the parabolic mirror 2a, and is incident on an integrator 5 including first and second lens arrays 3, 4 in which a plurality of lenses 3a, 4a are arranged. The light beam incident on the first lens array 3 is transmitted to each lens 3a.
Are converged on the corresponding lenses 4a.

[0003] Behind the second lens array 4, a polarization conversion element 6 is arranged. As shown in FIG. 16, the polarization conversion element 6 includes a plurality of polarization beam splitters 7 arranged corresponding to each lens 4 a and an adjacent polarization beam splitter 7.
And a half-wave plate 8 covering one of the two.

[0004] Of the light flux incident on the polarization conversion element 6, P
The polarized light passes through the polarizing beam splitter 7. The S-polarized light is reflected by the reflection surface 7a of the polarization beam splitter 7,
The light is reflected again by the reflection surface 7a of the adjacent polarization beam splitter 7. Then, the direction of the plane of polarization is rotated by 90 ° by the 波長 wavelength plate 8 and converted into P-polarized light. This allows
All the light beams from the light source 2 can be converted into linearly polarized light that can be used by the liquid crystal panel 13, thereby improving light use efficiency.

[0005] The light beam emitted from the polarization conversion element 6 is separated into red, green and blue lights by a color separation unit 12. The color separation section 12 includes two dichroic mirrors 9 and 10 and a reflection mirror 11. Dichroic mirror 9
Has the property of reflecting red light and transmitting blue light and green light. The dichroic mirror 10 has a characteristic of reflecting green light and transmitting blue light.

Accordingly, the red light reflected by the dichroic mirror 9, the green light reflected by the dichroic mirror 10, and the blue light reflected by the reflecting mirror 11 are condensed at adjacent positions on the liquid crystal panel 13. . Thereby, the illumination optical system 1 is configured. And
Light of a predetermined pixel portion of the liquid crystal panel 13 is transmitted according to an image, and an enlarged image is projected on a screen (not shown) via a projection optical system (not shown).

Further, instead of the polarization conversion element 6, a birefringent DOE 15 as shown in FIG.
The wave plate 8 may be used in some cases. The birefringent DOE 15 is arranged in front of the integrator 5 including the first and second lens arrays 3 and 4 similar to the above, and the half-wave plate 8 is formed integrally with the second lens array 4.

The birefringent DOE 15 comprises a blazed diffraction grating 15a and a birefringent layer 15b having different refractive indices No and Ne for P-polarized light and S-polarized light. When the refractive index N of the diffraction grating 15a matches the refractive index No of one of the birefringent layers 15b, the P-polarized light incident on the birefringent DOE 15 goes straight, and the S-polarized light is diffracted at a predetermined diffraction angle θ. .

Then, the P-polarized light and the S-polarized light are converged at different positions on each lens 4 a of the second lens array 4 by the first lens array 3. By disposing the half-wave plate 8 at a part of each lens 4a where the S-polarized light is collected, the S-polarized light passing through the second lens
The light is converted into polarized light, and the polarization direction of the outgoing light is aligned with the P-polarized light.

[0010]

According to the illumination optical system 1 of the single-panel type liquid crystal projector using the above polarizing beam splitter 7, the reflecting surface 7a of the polarizing beam splitter 7 has
Since the P-polarized light of the natural light from the light source 2 is transmitted and the S-polarized light is reflected, as shown in FIG.
For each of the red, green, and blue lights of 00 nm to 700 nm, a characteristic is required in which the transmittance of P-polarized light is 100% and that of S-polarized light is 0%. In the figure, the vertical axis indicates transmittance, and the horizontal axis indicates light wavelength.

However, it is difficult to form an optical thin film such that the transmittance of light in different polarization directions is 100% and 0% in a wide wavelength range. For this reason, there is a problem that the polarization beam splitter 7 becomes expensive and the cost of the illumination optical system 1 increases.

Further, the illumination optical system 1 of the single-panel type liquid crystal projector irradiates the liquid crystal panel 13 with red, green and blue lights mixed after the color separation by the color separation unit 12, so that the dichroic mirrors 9, 10 If the color separation is not sufficient, trimming cannot be provided, and the color purity of the formed image deteriorates.

Further, in the case of the illumination optical system 1 of the single-panel type liquid crystal projector using the birefringent DOE 15, the diffraction grating 1
The optimum height H of the blaze shape 5a is expressed by the following equation (1). The diffraction angle θ is represented by the following equation (2), where D is the pitch of the blazed shape. Here, λ is a wavelength.

H = λ / | N−Ne | (1) sin θ = λ / D (2)

According to equation (1), the optimum height H of the blaze shape of the diffraction grating 15a changes with the wavelength λ. For this reason, when the design wavelength is 550 nm (green light) and the height H is formed, the difference between the optimum height for blue light and red light becomes large, the diffraction efficiency decreases, and the light from the light source 2 is reduced. There was a problem that it could not be used sufficiently.

According to the equation (2), since the diffraction angle θ changes depending on the wavelength λ, the red, green, and blue lights are not condensed at one point on each lens 4 a of the second lens array 4. There was also the problem of blurred images.

An object of the present invention is to provide an illumination optical system of a single-panel type liquid crystal projector which can reduce costs. Another object of the present invention is to provide an illumination optical system of a single-panel liquid crystal projector that can improve image quality.

[0018]

According to the first aspect of the present invention, a light source for illumination and a light beam emitted from the light source are separated into a plurality of light beams according to a wavelength. It is characterized by comprising a color separation means, a polarization conversion means for aligning the polarization direction of each light beam separated by the color separation means, and a single-panel liquid crystal panel.

According to this configuration, the light beam emitted from the light source is separated into red, green, and blue lights by the color separation means, and then, for example, the P-polarized light is directly transmitted by the polarization conversion means, and the S-polarized light is transmitted. Is converted into P-polarized light, and the polarization directions of the emitted light are aligned. The light of each color is applied to a predetermined position of the single-panel liquid crystal panel, and an image is projected.

According to a second aspect of the present invention, in the illumination optical system of the single-panel type liquid crystal projector according to the first aspect, the polarization conversion means converts the wavelength of each light beam separated by the color separation means. It is characterized by having different characteristics depending on the type.

According to this configuration, as the polarization conversion means,
For example, in the case where a polarizing beam splitter that transmits P-polarized light and reflects S-polarized light is provided, the transmittance of S-polarized light is low in the wavelength range of each light beam separated by the color separation unit. In other wavelength regions, a polarization beam splitter whose transmittance is increased is used.

When a birefringent DOE comprising a diffraction grating and a birefringent layer is used as the polarization conversion means, the blaze shape of the diffraction grating is optimally adjusted for each wavelength range of each light beam separated by the color separation means. It is formed.

According to a third aspect of the present invention, in the illumination optical system of the single-panel liquid crystal projector according to the first or second aspect, the first and second lens arrays in which a plurality of lenses are arranged are arranged. An integrator for converging each light beam separated by the color separation means to a predetermined position on the second lens array by the first lens array;
The polarization converter is provided near the second lens array.

According to a fourth aspect of the present invention, in the illumination optical system of the single-panel type liquid crystal projector according to any one of the first to third aspects, each of the light beams separated by the color separating means is provided in a predetermined manner. The present invention is characterized in that trimming means for trimming in the above wavelength range is provided.
According to this configuration, each of the light beams separated into red, green, and blue by the color separating means passes through a trimming filter or a trimming plate and is trimmed into a predetermined wavelength range.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. For convenience of description, the same parts as those in the conventional example shown in FIGS. 15 to 17 are denoted by the same reference numerals. FIG. 1 is a configuration diagram showing an illumination optical system of the single-panel type liquid crystal projector of the first embodiment.

The natural light emitted from the light source 2 is made into a parallel light beam by the parabolic mirror 2a, and the width in one direction is narrowed by the cylindrical lens 17. The light beam emitted from the cylindrical lens 17 is separated into red, green, and blue light by the color separation unit 12. The color separation section 12 includes two dichroic mirrors 9 and 10 and a reflection mirror 11.

The dichroic mirror 9 has a characteristic of reflecting red light and transmitting blue light and green light. The dichroic mirror 10 has a characteristic of reflecting green light and transmitting blue light. Therefore, the red light reflected by the dichroic mirror 9 and the dichroic mirror 10
And the blue light reflected by the reflection mirror 11 are emitted in different directions.

The luminous flux of each color emitted from the color separation section 12 is supplied to a plurality of lenses 3 similar to the conventional example shown in FIG.
a and 4a are incident on an integrator 5 composed of first and second lens arrays 3 and 4 in which are arranged. The light beam incident on the first lens array 3 is converged on the corresponding lens 4a by each lens 3a.

A polarization conversion element 21 is arranged behind the second lens array 4. 2 (a) and FIG.
As shown in the front view of (b), the polarization conversion element 21 covers a plurality of polarization beam splitters 7 arranged corresponding to each lens 4a and one of the polarization beam splitters 7 vertically adjacent in the figure. And a half-wave plate 8.

Of the light beam incident on the polarization conversion element 21,
The P-polarized light passes through the polarization beam splitter 7. The S-polarized light is reflected by the reflection surface 7a of the polarization beam splitter 7, and is reflected again by the reflection surface 7a of the adjacent polarization beam splitter 7. Then, the direction of the plane of polarization is rotated by 90 ° by the 波長 wavelength plate 8 and converted into P-polarized light. Thus, all the light beams from the light source 2 can be converted into linearly polarized light that can be used by the liquid crystal panel 13, thereby improving the light use efficiency.

Since the red light, green light and blue light enter the integrator 5 from different directions, the second lens array 4
The regions are separated for each color above, and the polarization conversion element 21
Respectively, into the regions 21R, 21G, and 21B. For this reason, FIG. 3 shows the transmittance for the S-polarized light of the reflection surface 7a of the polarizing beam splitter 7 in each of the regions 21R, 21G, and 21B so that the S-polarized light of each color in a narrow wavelength range is reflected. Has become.

The transmissivity of each reflecting surface 7a for P-polarized light is about 100% in the red, green and blue wavelength ranges. Also, in the figure, the vertical axis indicates the transmittance, and the horizontal axis indicates the wavelength of light.

The light beam emitted from the polarization conversion element 21 is
The light passes through the trimming filter 22. The trimming filter 22 is formed integrally with three filters 22R, 22G, and 22B having different characteristics as shown in FIG. In the figure, the vertical axis indicates the transmittance, and the horizontal axis indicates the wavelength of light.

The filters 22R, 22G and 22B are formed so that the wavelength ranges of transmitted light do not overlap. Since the incident light incident on the trimming filter 22 is separated by red light, green light, and blue light, the filters 22R, 22G, 2
2B can be provided.

Here, an optical thin film capable of obtaining transmitted light having high color purity can be formed more easily than an optical thin film capable of obtaining reflected light having high color purity. For this reason, even if the light is not accurately separated into each color by the reflection of the dichroic mirrors 9 and 10, the trimming filter 2
2 can improve the color purity of each light beam transmitted therethrough.

The light beam having passed through the trimming filter 22 is irradiated with red light, green light, and blue light from the superimposing lens 18 onto a predetermined position of the liquid crystal panel 13. The field lens 20 makes the principal ray of the light beam incident on the liquid crystal panel 13 parallel. Thus, the illumination optical system 1
Is configured. Then, light of a predetermined pixel portion of the liquid crystal panel 13 is transmitted according to an image, and a projection optical system (not shown)
, An enlarged image is projected on a screen (not shown).

According to the present embodiment, the reflecting surface 7a of the polarizing beam splitter 7 can narrow the wavelength range having a low transmittance (about 0%) for S-polarized light according to the luminous flux of each color. The polarization conversion element 21 can be manufactured at low cost. Therefore, the cost of the illumination optical system 1 can be reduced.

It should be noted that the transmittance for P-polarized light is high (1
(00%) The reflecting surface 7a may be formed so that the wavelength range becomes narrower according to the luminous flux of each color. Further, the reflection surface 7a is
The polarized light may be reflected and the s-polarized light may be transmitted.

Next, FIG. 5 is a configuration diagram showing an illumination optical system of a single-panel type liquid crystal projector according to a second embodiment. The same parts as those in the first embodiment of FIG. 1 are denoted by the same reference numerals.
As in the first embodiment, natural light emitted from the light source 2 is converted into a parallel light beam by the parabolic mirror 2a, and the width in one direction is reduced by the cylindrical lens 17.

The light beam emitted from the cylindrical lens 17 is separated by the color separation section 12 into red, green and blue lights. The color separation unit 12 includes two dichroic mirrors 9 and 1.
0, and a reflection mirror 11, which emits red, green, and blue lights in different directions.

Each light beam emitted from the color separation section 12 enters the polarization separation element 25. The polarization splitting element 25 has the same configuration as the birefringent DOE 15 shown in FIG.
The two birefringent DOEs 25R, 25G, 25B are integrally formed. The red light, the green light, and the blue light enter the birefringent DOEs 25R, 25G, and 25B, respectively. For example, P-polarized light goes straight and S-polarized light is diffracted. by this,
The P-polarized light and the S-polarized light are emitted differently by a diffraction angle θ in a direction perpendicular to the paper of FIG.

The light beam emitted from the polarization splitting element 25 is
The light passes through the same trimming filter 22 as in the first embodiment. Since the incident light incident on the trimming filter 22 is separated by red light, green light, and blue light, the filters 22R, 22G, 2
2B can be provided. Thereby, the color purity of each light beam that has passed through the trimming filter 22 can be improved.

The light beam having passed through the trimming filter 22 is incident on an integrator 5 composed of first and second lens arrays 3, 4 in which a plurality of lenses 3a, 4a are arranged. Each light beam is converged on the corresponding lens 4a of the second lens array 4 by each lens 3a.
As shown in (1), red light, green light, and blue light enter the regions 4R, 4G, and 4B, respectively.

The second lens array 4 has one part on one side.
The / 2 wavelength plate 8 is stuck. The P-polarized light is converged on the portion where the half-wave plate 8 is not attached, and the S-polarized light is converged by diffraction on the portion where the half-wave plate 8 is attached. Thereby, the S-polarized light is converted to the P-polarized light.

Thereafter, red light, green light, and blue light are irradiated to predetermined positions of the liquid crystal panel 13 through the field lens 20 by the superimposing lens 18. Thereby, the illumination optical system 1 is configured. Then, light of a predetermined pixel portion of the liquid crystal panel 13 is transmitted according to the image, and an enlarged image is projected on a screen (not shown) via a projection optical system (not shown). .

According to the present embodiment, similar to the first embodiment, the color separation section 12 uses a trimming filter corresponding to each light beam separated into red light, green light and blue light, so that the color purity is improved. Can be done.

Further, the birefringence DOE 2 of the polarization separation element 25
The red light, green light, and blue light separated by the color separation unit 12 are incident on 5R, 25G, and 25B, respectively. For this reason, the height H of the blaze shape (see FIG. 17) is set to a design wavelength (for example, 650 nm for red light, 550 nm for green light, and 450 nm for blue light) according to the wavelength range of each color according to the above equation (1). It is formed based on each.

Therefore, the birefringent DOE 25R, 25G, 2G
The difference between the luminous flux of each color incident on 5B and the design wavelength for each color is small, and each wavelength (for example, in the case of red light, 600 to
(700 nm) does not greatly deviate from the height based on the design wavelength (650 nm), so that the diffraction efficiency can be improved.

Further, the birefringent DOE 25R, 25G, 25
Since the luminous flux of each color incident on B has a narrow wavelength range, the variation of the diffraction angle θ is reduced as shown in the above-mentioned equation (2). Thereby, the light flux emitted from the polarization separation element 25 can be concentrated, and the image quality can be improved by suppressing blurring of the image.

Next, FIG. 7 is a configuration diagram showing an illumination optical system of a single-panel type liquid crystal projector according to the third embodiment. 1 and 5
The same parts as those in the first and second embodiments are denoted by the same reference numerals. As in the first and second embodiments, natural light emitted from the light source 2 is converted into a parallel light beam by the parabolic mirror 2a, and the width in one direction is reduced by the cylindrical lens 17.

The light beam emitted from the cylindrical lens 17 is incident on an integrator 5 composed of first and second lens arrays 3, 4 in which a plurality of lenses 3a, 4a are arranged. The light beam incident on the first lens array 3 is
a converges on the corresponding lens 4a.

The light beam emitted from the integrator 5 is
The color separation unit 12 separates the light into red, green, and blue light. The color separation section 12 includes two dichroic mirrors 9 and 10 and a reflection mirror 11.

The dichroic mirror 9 reflects red light and transmits blue light and green light. The dichroic mirror 10 reflects green light and transmits blue light. Accordingly, the red light reflected by the dichroic mirror 9, the green light reflected by the dichroic mirror 10, and the blue light reflected by the reflection mirror 11 are emitted in different directions.

The luminous flux emitted from the color separation section 12 is first,
The light passes through the same trimming filter 22 as in the second embodiment. Since the incident light incident on the trimming filter 22 is separated by red light, green light, and blue light, the filters 22R, 22G, 2
2B can be provided. Thereby, the color purity of each light beam that has passed through the trimming filter 22 can be improved.

The light beam having passed through the trimming filter 22 enters the polarization conversion element 26. The polarization conversion element 26 has a region 26 having characteristics according to red light, green light, and blue light.
R, 26G, 26B. As shown in FIG. 8, the polarization conversion element 26 is a polarization beam splitter plate 2
8, a reflection mirror 29 and a half-wave plate 8 similar to that of the first embodiment.

The same transmittance as that of the reflection surfaces 7a of the regions 21R, 21G, and 21B of the polarization beam splitter 21 of the first embodiment shown in FIG. 3 is set to the regions 26R, 26G, and 26B.
Of each of the polarization beam splitter plates 28. For this reason, in each of the regions 21R, 21G, and 21B, the red light, the green light, and the blue light are such that the P-polarized light and the S-polarized light enter the polarization beam splitter plate 28, the P-polarized light goes straight, Light is reflected.

The S-polarized light is reflected by the reflection mirror 29 and becomes 1
The direction of the plane of polarization is rotated by 90 ° by the half-wave plate 8 and converted into P-polarized light. Thereby, the light flux of each color aligned with the P-polarized light is emitted from the polarization conversion element 26. After that, the field lens 2 is
The red light, the green light, and the blue light are applied to predetermined positions of the liquid crystal panel 13 through the light emitting device 0. Thereby, the illumination optical system 1 is configured. Then, light of a predetermined pixel portion of the liquid crystal panel 13 is transmitted according to the image, and an enlarged image is projected on a screen (not shown) via a projection optical system (not shown). .

According to the present embodiment, as in the first embodiment, the polarizing beam splitter plate 28 can narrow the wavelength range having a low transmittance for S-polarized light according to the luminous flux of each color. The polarization conversion element 26 can be manufactured at low cost. Therefore, the cost of the illumination optical system 1 can be reduced.

Since the light incident on the trimming filter 22 has its area separated by red light, green light, and blue light, the filter 22 having a characteristic corresponding to each color.
R, 22G and 22B can be provided. Thereby, the color purity of each light beam that has passed through the trimming filter 22 can be improved.

Incidentally, the polarization beam splitter plate 28 may be formed in a narrow wavelength band having a high transmittance for the P-polarized light in accordance with the luminous flux of each color. Further, the polarization beam splitter plate 28 may reflect the P-polarized light and transmit the S-polarized light.

FIG. 9 is a block diagram showing an illumination optical system of a single-panel liquid crystal projector according to the fourth embodiment. The same parts as those in the first to third embodiments are denoted by the same reference numerals.
As in the first to third embodiments, natural light emitted from the light source 2 is converged by the elliptical mirror 2b and enters the rod-type integrator 30.

The rod-type integrator 30 has a polygonal cross section and is designed to cause total internal reflection. The light incident on the integrator 30 is reflected on the inner surface, and emits a light beam in a plurality of discontinuous directions according to the number of times of reflection.

The light beam emitted by the integrator 30 enters the color separation element 31. The color separation element 31 is shown in FIG.
The hologram 35a diffracts blue light as shown in FIG.
And a hologram 35b for diffracting red light are juxtaposed. Of the incident light, the blue light is the hologram 35a.
Is diffracted at the point and travels in the direction of Kb. The red light is diffracted by the hologram 35b and travels in the direction of Kr. The green light goes straight without diffraction and travels in the direction of Kg.

As a result, the incident light of the color separation element 31 is angle-separated for each color, and the light of each color is relayed via the field lens 32 by the relay lenses including the first and second relay lenses 33 and 34. Relay lens is rod 3
An image separated for each color is formed in the vicinity of the pupil of the relay lens in order to make the exit plane of 0 and the liquid crystal panel 13 conjugate. At the pupil position of the relay lens, the same polarization conversion element 21 and trimming filter 2 as in the first embodiment shown in FIG.
2 are arranged.

After the light of each color is adjusted to P-polarized light by the polarization conversion element 21, the light passes through the trimming filter 22 to improve the color purity of the light flux of each color. Then, the image is enlarged by the second relay lens 34, and red light, green light, and blue light are applied to predetermined positions of the liquid crystal panel 13 via the field lens 20. Thereby, the illumination optical system 1 is configured. Then, light of a predetermined pixel portion of the liquid crystal panel 13 is transmitted according to the image, and an enlarged image is projected on a screen (not shown) via a projection optical system (not shown).

According to the present embodiment, in the illumination optical system 1 of the single-panel type liquid crystal projector using the rod type integrator 30 and the relay lenses (33, 34), light of each color is divided in the same manner as described above. In the vicinity of the pupil of the relay lens, a polarization conversion element (21R, 21R,
1G, 21B), the polarization conversion element 2
1 can be manufactured at low cost. In addition, by providing the filters 22R, 22G, and 22B having characteristics corresponding to each color, the color purity of each light beam that has passed through the trimming filter 22 can be improved.

In this embodiment, the color separation element 31
A birefringent DOE as shown in FIG. 11 may be used. The birefringent DOE has a diffraction grating 36a having a refractive index of Na and a refractive index of N.
b birefringent layer 36b. Refractive index Na, N
Each of b has a characteristic that varies with the wavelength as shown in FIG. 12, the vertical axis indicates the refractive index and the horizontal axis indicates the wavelength.

Therefore, in the wavelength region λb of blue light, since the refractive index Na is larger than the refractive index Nb, −1st-order diffraction occurs. No diffraction occurs in the wavelength region λg of green light because the refractive index Na is substantially equal to the refractive index Nb (zero-order diffraction). In the red light wavelength region λr, the first-order diffraction occurs because the refractive index Na is smaller than the refractive index Nb.

Accordingly, of the incident light, the blue light travels in the direction of Lb by -1st order diffraction. The red light travels in the direction of Lr by first-order diffraction. Green light is not diffracted (0
The next diffraction) goes straight and proceeds in the direction of Lg. Thereby, color separation can be performed.

Next, FIG. 13 is a configuration diagram showing an illumination optical system of a single-panel type liquid crystal projector according to a fifth embodiment. First to first
The same parts as those in the fourth embodiment are denoted by the same reference numerals. Natural light emitted from the light source 2 is converged by the elliptical mirror 2b and enters a rod-type integrator 30 similar to the fourth embodiment.

The light beam emitted by the integrator 30 enters the color separation element 31. The color separation element 31 is made of the hologram shown in FIG. 10 or the birefringent DOE shown in FIG. 12, and separates incident light into red light, green light, and blue light and advances the light in different directions.

The light of each color forms an image via the field lens 32 at the pupil position of the first and second relay lenses 33 and 34. At the pupil position of the relay lens, the same polarization conversion element 21 as in the first embodiment shown in FIG. 1 and a trimming plate 37 shown in FIG. 14 are arranged.

The trimming plate 37 is provided for the first relay lens 3
3, openings 37r, 37g, and 37b are formed at respective positions where red light, green light, and blue light are collected. The left and right sides of the openings 37r, 37g, and 37b are blocked by the plate 37a. Each plate 37a is a screw 37b
The fixed position can be changed.

The light beams of each color separated by the color separation element 31 shown in FIG. 10 include light beams of adjacent colors. For example, in FIG. 10, green light including red light has a longer wavelength than the center wavelength of green light, and therefore, in FIG.
Diffracts in the direction of g '. The red light including the green light has a wavelength shorter than the center wavelength of the red light.
Proceed in the direction of r '. Therefore, by setting the plate 37a of the trimming plate 37 to an appropriate fixed position, it is possible to block light having a wavelength distant from the center wavelength of each color and improve the purity of each color.

The light of each color trimmed by the trimming plate 37 is adjusted by the polarization conversion element 21 to P-polarized light. Then, the image is enlarged by the second relay lens 34, and red light, green light, and blue light are applied to predetermined positions of the liquid crystal panel 13 via the field lens 20. Thereby, the illumination optical system 1 is configured. Then, light of a predetermined pixel portion of the liquid crystal panel 13 is transmitted according to the image, and an enlarged image is projected on a screen (not shown) via a projection optical system (not shown). In this embodiment, the same effects as in the fourth embodiment can be obtained.

[0076]

According to the first and second aspects of the present invention, the polarization directions of the light beams of the respective colors separated by the color separation means are aligned by the polarization conversion means according to the respective light beams. For this reason, when the polarization conversion means is formed by arranging a plurality of polarizing beam splitters or polarizing beam plates that transmit one of two lights having orthogonal polarization directions and reflect the other, the polarization direction of one of the two polarization directions is changed. The transmittance or reflectance for light may be set to approximately 0% in a narrow wavelength range corresponding to the luminous flux of each color. Therefore,
The polarization conversion means can be manufactured at low cost, and the cost of the illumination optical system of the single-panel liquid crystal projector can be reduced.

In the case where the polarization conversion means comprises a birefringent DOE for diffracting light in different directions depending on the polarization direction,
By setting the height H of the blaze shape different according to the wavelength range of each color, the separated luminous flux of each color has a small difference from the design wavelength for each color, and the optimal height for each wavelength is a height based on the design wavelength. Since there is no large deviation from the above, the diffraction efficiency can be improved. Further, since each of the separated light beams has a narrow wavelength range, the dispersion of the diffraction angle is reduced.
Therefore, the light beam emitted from the polarization conversion means can be concentrated, and the image quality can be improved by suppressing blurring of the image.

According to the third aspect of the present invention, the first and second
By using a lens array type integrator composed of a lens array and arranging polarization conversion means in the vicinity of the second lens array, light beams color-separated in the vicinity of the second lens array are arranged at a distance. Can easily perform polarization conversion with different characteristics for each light flux.

According to the fourth aspect of the present invention, since the trimming unit performs trimming to a predetermined wavelength range in accordance with the luminous flux of each color separated by the color separation unit, the color separation unit does not accurately separate each color. Also, the color purity of each light beam that has passed through the trimming means can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an illumination optical system of a single-panel liquid crystal projector according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a polarization conversion element of an illumination optical system of the single-panel liquid crystal projector according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating characteristics of a polarization conversion element of an illumination optical system of the single-panel liquid crystal projector according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating characteristics of a trimming filter of an illumination optical system of the single-panel liquid crystal projector according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram illustrating an illumination optical system of a single-panel liquid crystal projector according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a second lens array of an illumination optical system of a single-panel liquid crystal projector according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing an illumination optical system of a single-panel liquid crystal projector according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating a polarization conversion element of an illumination optical system of a single-panel liquid crystal projector according to a third embodiment of the present invention.

FIG. 9 is a configuration diagram illustrating an illumination optical system of a single-panel liquid crystal projector according to a fourth embodiment of the present invention.

FIG. 10 is a diagram illustrating a color separation element of an illumination optical system of a single-panel liquid crystal projector according to a fourth embodiment of the present invention.

FIG. 11 is a diagram illustrating another color separation element of an illumination optical system of a single-panel liquid crystal projector according to a fourth embodiment of the present invention.

FIG. 12 is a diagram illustrating characteristics of another color separation element of the illumination optical system of the single-panel liquid crystal projector according to the fourth embodiment of the present invention.

FIG. 13 is a configuration diagram illustrating an illumination optical system of a single-panel liquid crystal projector according to a fifth embodiment of the present invention.

FIG. 14 is a diagram illustrating a trimming plate of an illumination optical system of a single-panel liquid crystal projector according to a fifth embodiment of the present invention.

FIG. 15 is a configuration diagram showing an illumination optical system of a conventional single-panel type liquid crystal projector.

FIG. 16 is a cross-sectional view illustrating a configuration of a polarization conversion element of an illumination optical system of a conventional single-panel liquid crystal projector.

FIG. 17 is a cross-sectional view illustrating a polarization conversion method of an illumination optical system of another conventional single-panel liquid crystal projector.

FIG. 18 is a diagram illustrating characteristics of a polarization conversion element of an illumination optical system of a conventional single-panel liquid crystal projector.

[Description of Signs] 1 illumination optical system 2 light source 3 first lens array 4 second lens array 5, 30 integrator 6, 21, 26 polarization conversion element 7 polarization beam splitter 8 1/2 wavelength plate 9, 10 dichroic mirror 11 reflection Mirror 12 Color separation unit 13 Liquid crystal panel 15a, 36a Diffraction grating 15b, 36b Birefringent layer 17 Cylindrical lens 18 Superposition lens 20, 32 Field lens 22 Trimming filter 25 Polarization separation element 28 Polarization beam splitter plate 29 Reflection mirror 31 Color separation element 33 first relay lens 34 second relay lens 35a, 35b hologram 37 trimming plate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/74 H04N 9/31 C 9/31 G02F 1/1335 530 (72) Inventor Satoshi Onishi Osaka city center 2-13-13 Azuchicho, Ward F-term in Osaka International Building Minolta Co., Ltd. (reference) 2H088 EA13 EA15 HA13 HA20 HA21 HA24 HA25 HA28 MA20 2H091 FA01Z FA05Z FA10Z FA14Z FA17Z FA19Z FA26X FA26Z FA29X FA29Z FD24 LA12 MA07 EA26 EA24 EA51 5C060 BA03 BA04 BC01 DA05 GA02 GB01 GB06 HC01 HC20 HC24 HD02 JB06 5G435 BB12 BB17 CC12 DD04 DD10 FF05 GG02 LL15

Claims (4)

[Claims] A light source for illumination; a color separation unit configured to separate a light beam emitted from the light source into a plurality of light beams according to a wavelength; and a polarization unit configured to align polarization directions of the light beams separated by the color separation unit. An illumination optical system for a single-panel liquid crystal projector, comprising: a conversion unit; and a single-panel liquid crystal panel. 2. The illumination optical system according to claim 1, wherein the polarization conversion unit has different characteristics according to the wavelength of each light beam separated by the color separation unit. 3. An integrator comprising first and second lens arrays in which a plurality of lenses are arranged, and converging each light beam separated by the color separating means to a predetermined position on the second lens array by the first lens array. The illumination optical system for a single-panel liquid crystal projector according to claim 1 or 2, wherein the polarization conversion means is arranged near the second lens array. 4. The single-panel type liquid crystal projector according to claim 1, further comprising trimming means for trimming each light beam separated by said color separation means into a predetermined wavelength range. Illumination optics.