JPH05257115A - Projection type color display device - Google Patents

Abstract

PURPOSE:To enhance the color purity of three primary color light beams and to enable the formation of high-saturation projected images by providing a specific first reflection surface and a second reflection surface having nearly equal wavelength selection characteristic of the first reflection surface. CONSTITUTION:A dichroic mirror D1 reflects the blue light of a short wavelength region from the white light emitted from a light source L, separates this light to a blue optical system B and allows the transmission of the mixed green and red color of middle and long wavelength regions. The mixed green and red color light is made incident on the dichroic mirror D2 after the unnecessary wavelength components are removed by a band selection filter F1. This mirror D2 reflects the red light of the long wavelength region and separates the light to a red optical system R, thereby allowing the transmission of the green light of the middle wavelength region. The green light is made incident on a mirror M1 after the unnecessary wavelength components are removed by a band selection filter F2. This light reflects on the mirror and advances to the green optical system. On the other hand, the unnecessary wavelength component of the S polarized light component of the blue light which is the reflected light of the dichroic mirror D1 is made incident as a P polarized light component on a dichroic mirror D5 and transmits this mirror as it is. This light passes the mirror 5 and is removed from the blue primary color heading toward an image display element E1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, for example, illuminates three liquid crystal elements for image display with red, blue, and green (RGB) primary color lights to form primary color images, and displays red, blue, and green primary color images. Combined on the same optical axis, enlarged and projected on the screen, large screen,
The present invention relates to a projection type color display device that forms a highly detailed color image.

[0002]

2. Description of the Related Art As an apparatus for forming a large-screen, high-density color image, three liquid crystal elements for image display are illuminated with red, green, and blue (hereinafter referred to as RGB) primary color lights to form a primary color image. However, a liquid crystal projector that combines these primary color images on the same optical axis and enlarges and projects them on a screen has been put into practical use.

Such a liquid crystal projector is, for example, a light source common to RGB three primary color lights for generating and emitting white light, and a red primary color optical system and a green primary color by separating the RGB three primary color lights from the white light. An optical system and a band selection optical system for guiding to the blue primary color optical system, and three liquid crystal image elements for forming three primary color projected images, one for each primary color (RGB) optical system, and three primary color projected images. A synthetic optical system that synthesizes again on the same optical axis and a synthesized color projection image
And a projection optical system for projecting toward the lens, and the band selection optical system and the synthetic optical system are transmission type (reflection type) band selection elements in which a predetermined wavelength selectivity is given to the transmission rate (reflectance). Is used to selectively transmit (reflect) only a component in a specific wavelength region included in the incident light, and reflect (transmit) the rest.

Here, the band selection element includes a dichroic mirror in which two or more thin film layers are formed on one surface of a glass substrate, and a dichroic prism in which two or more thin film layers are sandwiched at a bonding interface between two glass blocks. Alternatively, a composite type dichroic prism in which two diagonal surfaces that divide a square prism into four are provided with different wavelength selectivities is used. It is said that it is preferable to combine a dichroic mirror to form a band-selecting optical system and a combining optical system because flares caused by intersections of diagonal planes of a prism deteriorate image quality.

A band selection optical system in which a dichroic mirror is combined is, for example, a first dichroic that reflects a short wavelength (B) region obliquely arranged in the optical path of white light and transmits a medium and long wavelength (GR) region. A mirror and a second dichroic mirror that reflects a long wavelength (R) region and transmits a medium and short wavelength (GB) region obliquely arranged in the optical path of the transmitted light of the first dichroic mirror. .. At this time, in the first dichroic mirror, the blue (B) primary color light is separated in the reflection direction from the obliquely incident white light, and in the second dichroic mirror, the obliquely incident green red is transmitted through the first dichroic mirror. From the (GR) mixed color light, red (R) primary color light is separated in the reflection direction, and green (G) primary color light is separated in the transmission direction (see FIG. 1).

On the other hand, in a synthetic optical system in which a dichroic mirror is combined, for example, a long wavelength (R) region obliquely arranged in the optical path of a blue (B) primary color image is reflected to reflect a medium and short wavelength (G).
B) A third dichroic mirror that transmits the region, and a fourth dichroic that reflects the medium wavelength (G) region obliquely arranged in the subsequent stage of the third dichroic mirror and transmits the long and short wavelength (RB) regions on both sides. It consists of a mirror and.
At this time, in the third dichroic mirror, the reflected red (R) primary color image is combined with the transmitted blue (B) primary color image, and in the fourth dichroic mirror, the transmitted blue (B) primary color image is transmitted.
Reflected green (G) on primary color image and red (R) primary color image
The primary color images are combined (see FIG. 1).

[0007]

Problems to be Solved by the Invention Dichroic mirror
In the band selection optical system configured by combining the above, the dichroic mirror is obliquely arranged with respect to the incident light in order to separate the optical paths of the transmitted light and the reflected light. It has a slightly different wavelength selectivity for the polarized light component and the P polarized light component, and the wavelength selectivity for the transmitted light of the S polarized light component is narrower than the wavelength selectivity for the transmitted light of the P polarized light component. The wavelength selectivity of the component for reflected light is narrower than the wavelength selectivity of the S-polarized component for reflected light.

Therefore, the S-polarized component of the blue primary color light reflected and separated by the dichroic mirror that reflects the short wavelength (B) region includes the green primary color light component of the adjacent wavelength region which is not included in the P-polarized component, The P-polarized component of the green-red mixed color light that is transmitted and separated by the dichroic mirror that reflects the wavelength (B) region includes the blue primary color light component of the adjacent wavelength region that is not included in the S-polarized component (see FIG. 2). Further, the S-polarized component of the red primary color light reflected and separated by the dichroic mirror that reflects the long wavelength (R) region includes the green primary color light component of the adjacent wavelength region that is not included in the P polarized component, and the long wavelength (R ) The P-polarized light component of the green primary-color light that is transmitted and separated by the dichroic mirror that reflects the region includes the red-primary-color light component in the adjacent wavelength region that is not included in the S-polarized light component (see FIG. 3). Thereby, for example, the green primary color light (see FIG. 1) separated by arranging the dichroic mirror reflecting the short wavelength (B) region and the dichroic mirror reflecting the long wavelength (R) region in parallel is The P-polarized light component contains the blue primary-color light component, and the S-polarized light component contains the red primary-color light component, resulting in light with low color purity. If the three primary-color lights are guided to the liquid crystal image element as they are to form a primary-color image. Due to lack of mutual hue difference between the three primary color images,
There is a problem that the color quality of the projected image deteriorates.

That is, a thin film layer having wavelength selectivity in a band selection element such as a dichroic mirror has two polarization components constituting obliquely incident light, that is, an S polarization component vibrating in parallel with the interface and a component perpendicular to the interface. It shows a slightly different wavelength selection characteristic for the P-polarized component that oscillates in the plane,
Regarding the obliquely incident light transmitted light, the P-polarized light component is transmitted over a wider band on the long wavelength side and the short wavelength side than the S-polarized light component, and the obliquely incident light reflected light is more than the P-polarized light component. The S-polarized component is reflected over a wider band on both the long wavelength side and the short wavelength side. Therefore, when white light is obliquely incident on the band selection element and the optical path is divided into three primary color lights, one S polarization component of two primary color lights in adjacent wavelength regions contains a wavelength component common to the other P polarization component. Two
The wavelength regions of the two primary color lights are cross-overed to reduce the mutual hue difference.

Further, the wavelength selectivity of the actual band selection element is not an ideal one which is suddenly inverted from 0% to 100% at a specific wavelength, but is gradually transmitted over a wavelength range of about 20 nm. The rate (reflectance) changes (see FIGS. 2 and 3)
In this wavelength region having a width of about 20 nm, one part is reflected and the rest is transmitted. Therefore, this 20nm of incident light
A component corresponding to a wavelength region having a certain width is commonly included in reflected light and transmitted light even in the case of vertically incident light, and reduces the hue difference between two primary color lights in adjacent wavelength regions. ..

Then, the light of the three primary colors including the common wavelength region and having insufficient hue differences is guided to the respective liquid crystal elements.
When one primary color image is formed, it becomes a projected image in which the three primary colors with low color purity including other primary color components are mixed, and when this is combined on the same optical axis and projected on the screen, it becomes an image lacking whitish saturation. To be observed.

According to the present invention, incident light is obliquely incident on the band selection element to separate two adjacent wavelength regions, but for each of the two separated wavelength components, the wavelength regions of the S polarization component and the P polarization component are separated. And the unnecessary wavelength components corresponding to the wavelength region in which the transmittance (reflectance) of the band selection element gradually changes are largely removed from both of the separated two wavelength components, and therefore, A band selection optical system is proposed in which the wavelength regions of the two primary color lights in the same wavelength region are independent of each other, thereby providing a projection type color display device capable of increasing the color purity of the three primary color lights and forming a highly saturated projection image. The purpose is to do.

[0013]

A projection type color apparatus according to claim 1,
The display device includes a light source that emits white light and emits it, a band selection optical system that extracts a plurality of primary color components from the emitted white light, and a primary color pattern of a projected image using each primary color component.
And a plurality of image display elements forming an image, and projecting color for synthesizing respective primary color patterns on the same optical axis for projection.
In the display device, the band selection optical system causes a first reflection surface having a predetermined wavelength selection characteristic obliquely arranged with respect to incident light and a P-polarized reflection component of the first reflection surface to be obliquely incident as an S-polarization component. And a second reflecting surface having wavelength selection characteristics substantially equal to those of the first reflecting surface arranged as described above.

A projection type color display device according to a second aspect is the projection type color display device according to the first aspect, further comprising a transmission type band selection filter arranged so that light transmitted through the first reflecting surface is vertically incident. A pair of λ / 4 plates arranged in front of and behind the filter and intersecting the directions of crystal optical axes at right angles to each other,
Is provided.

According to another aspect of the projection type color display device of the present invention, a light source for generating and emitting white light, a band selection optical system for extracting a plurality of primary color components from the emitted white light, and respective primary color components are provided. A projection type color display device having a plurality of image display elements for forming primary color patterns of a projected image by using each of the primary color patterns and projecting them on the same optical axis. The system includes a first reflection surface having a predetermined wavelength selection characteristic obliquely arranged with respect to incident light, a transmission type band selection filter arranged so that light reflected by the first reflection surface is vertically incident, and A pair of λ / 4 arranged at the front and rear of the filter and having their crystal optical axis directions combined at right angles.
And a board.

A projection-type color display device according to a fourth aspect is the projection-type color display device according to the third aspect, further comprising a transmission-type band selection filter arranged so that the light transmitted through the first reflecting surface is vertically incident. A pair of λ / 4 plates arranged in front of and behind the filter and intersecting the directions of crystal optical axes at right angles to each other,
Is provided.

[0017]

In the projection type color display device of claim 1, the characteristic that the band selection element such as a dichroic mirror exhibits different wavelength selectivity for the S-polarized component and the P-polarized component of the obliquely incident light is used in reverse. Then, the wavelength regions of the two polarization components of the separated reflected light are aligned. That is, the incident light is reflected twice using two reflecting surfaces (first and second) having substantially the same wavelength selection characteristics, and the two polarization components of the incident light are reflected as S polarization component and P Reflection as a polarization component is performed once, and a wavelength region included in the S polarization component of the reflected light on the first reflection surface but not included in the P polarization component is incident as the P polarization component. The light is allowed to pass through the reflecting surface as it is, and is eliminated from the reflected light of the second reflecting surface.

The reflected light from the second reflecting surface, which is composed of two polarization components having the same wavelength region, is guided to the image display element and projected image corresponding to transparent opacity, reflection non-reflection, polarization non-polarization, etc. of the image display element. Is converted to the primary color pattern. After that, the respective primary color patterns are combined and projected on the same optical axis.

In the projection type color display device according to the second aspect, the wavelength regions of the two polarization components of the transmitted light of the first reflecting surface are aligned. Inside out, the S-polarized component of the reflected light of the first reflecting surface includes a long wavelength region that is not included in the P-polarized component, and the P-polarized component of the transmitted light of the first reflecting surface is a wavelength region that is not included in the S-polarized component. including. The transmission-type band selection filter in which the transmitted light of the first reflecting surface is vertically incident has a wavelength selectivity capable of reflecting at least the above-mentioned wavelength region uniquely included in the P-polarized component of the transmitted light of the first reflecting surface, that is, , The wavelength selectivity is set so that the S-polarized light component transmitted through the first reflecting surface is substantially equivalent to the S-polarized component and the other wavelength regions are reflected, and the wavelength selectivity of the reflected light on the second reflecting surface overlaps or is adjacent to the wavelength region. The wavelength range, that is, the wavelength range removed as the transmitted light on the second reflecting surface is the first
It is removed from the transmitted light on the reflecting surface. Wavelength components that cannot pass through the transmission band selection filter are vertically reflected and folded back toward the back surface of the first reflecting surface.

The unnecessary wavelength component vertically reflected by the band selection filter, if left as it is, travels backward in the incident optical path to reach the light source, resulting in unnecessary heating of a halogen lamp or the like in an incandescent state. Therefore, the band selection filter
Λ / 4 of the plane of polarization of incident light in front of
/ 4 plate is arranged so that the unnecessary wavelength component of the P-polarized light component vertically reflected by the band selection filter is not re-transmitted through the first reflecting surface as the P-polarized light component and goes backward in the incident optical path. There is. That is, unnecessary wavelength components contained in the P-polarized light component of the transmitted light of the first reflecting surface are transmitted back and forth through the λ / 4 plate before and after being reflected by the band selection filter, and the total polarization plane is summed up. The light is rotated by λ / 2 and is re-incident on the first reflecting surface as an S-polarized component. The first reflecting surface reflects the unnecessary wavelength component that was initially transmitted as the P-polarized component as the S-polarized component at the time of re-incident and removes it from the incident optical path toward the light source.

On the other hand, behind the band-selecting filter, λ / 4 is formed by intersecting the crystal optical axis at a right angle with the front one.
A plate is arranged to return the rotation of the polarization plane of the transmitted light of the band selection filter to the state of the transmitted light of the first reflection surface, which is caused by the wavelength dependence of the rotation characteristic of the polarization plane using the λ / 4 plate. Removing the inconvenience.

In the projection type color display device of the third aspect, S of the reflected light of the first reflecting surface arranged obliquely with respect to the incident light.
Unwanted wavelength components contained in the polarized component are removed by using a transmission type band selection filter. The band selection filter on which the reflected light from the first reflecting surface is vertically incident exhibits equal wavelength selectivity to the two polarization components of the reflected light, and the band selecting filter has at least the reflected light on the first reflecting surface. Of the first reflection surface is set so that at least the outside of the wavelength region of the P-polarized component of the reflected light of the first reflection surface can be blocked. From the S-polarized component of the light, a component overlapping or adjacent to the wavelength region of the P-polarized component of the transmitted light of the first reflecting surface is vertically reflected, separated, and folded back toward the first reflecting surface.

Here, a wavelength selectivity narrower than the wavelength selectivity due to the reflection on the first reflection surface may be set in the band selection filter. At this time, a slightly wider wavelength region adjacent to the wavelength region of the transmitted light of the first reflecting surface is also removed from the reflected light of the first reflecting surface, including unnecessary wavelength components, and the color purity of the separated primary color light is increased. , The amount of heat flowing into the image display element in the subsequent stage is reduced.

The λ / 4 plate arranged on the first reflection surface side of the band selection filter has the unnecessary wavelength component contained in the S-polarized component reflected by the first reflection surface and incident on the band selection filter. The polarization plane is rotated back and forth for a total of λ / 2, and is re-incident on the first reflection surface as a P polarization component. The first reflection surface transmits the unnecessary wavelength component that was initially reflected as the S-polarized component as it is as the P-polarized component when re-incident, and eliminates it from the incident optical path toward the light source. On the other hand, band selection filter
The λ / 4 plate placed on the emission side of the
The rotation of the polarization plane of the transmitted light is returned to the state of the reflection light of the first reflection surface to eliminate the inconvenience caused by the wavelength dependence of the rotation characteristic of the polarization plane using the λ / 4 plate.

In the projection type color display device according to the fourth aspect, the wavelength regions of the two polarization components of the transmitted light of the first reflecting surface are aligned. The transmissive band selection filter is set with wavelength selectivity capable of reflecting unnecessary wavelength components uniquely included in the P-polarized component of the transmitted light of the first reflecting surface. Wavelength components that cannot pass through the transmission band selection filter are vertically reflected and folded back toward the back surface of the first reflecting surface.

The λ / 4 plate arranged on the side of the first reflection surface of the band selection filter rotates the polarization plane of the incident light by λ / 4 and transmits it, thereby eliminating unnecessary wavelength components contained in the P polarization component. The polarization plane is rotated back and forth for a total of λ / 2, and is re-incident on the first reflection surface as an S polarization component. The first reflection surface reflects the unnecessary wavelength component that was initially transmitted as the P-polarized component as the S-polarized component at the time of re-incident, and eliminates it from the incident optical path toward the light source. On the other hand, the λ / 4 plate arranged on the exit side of the band selection filter returns the rotation of the polarization plane of the transmitted light of the band selection filter to the state of the reflected light of the first reflection surface, and uses the λ / 4 plate. The inconvenience caused by the wavelength dependence of the rotation characteristic of the polarization plane is eliminated.

[0027]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of the projection type color display device of the first embodiment, and FIGS. 2, 3 and 4 are characteristic diagrams of the dichroic mirror in FIG. Here, a shutter-type image display element that inverts transmission / non-transmission is commonly used for both polarization components, and both the band selection optical system and the combining optical system are configured by a dichroic mirror to provide a common image. A projection type color display device is shown which separates white light emitted from a light source into RGB primary colors. 2, FIG. 3, and FIG.
(a) shows the wavelength selection characteristics by reflection, and (b) shows the wavelength selection characteristics by transmission.

In FIG. 1, the light source L is composed of a halogen lamp, a reflecting mirror, an infrared filter, a lens, etc.
The band selection optical system consists of four dichroic mirrors D1,
D2, D5, D6, 5 Mira-M1, M3, M4, M
5, M6, two band selection filters-F1, F2, four λ / 4 plates H1, H2, H3, H4, and a blue primary color optical system B and red primary color optics separated by a band selection optical system. Image display elements E1, E2, and E3 are arranged in the system R and the green primary color optical system G, respectively. Where dichroic mirror-D
5 and D6 are arranged at an angle of 45 degrees from the plane of the paper, and the Mira-M
5 and M6 are arranged to face the dichroic mirrors D5 and D6 in parallel, respectively.

The dichroic mirrors D1 and D5 are shown in FIG.
As shown in (a) and (b), the transmittance (reflectance) in the wavelength region of 470 to 490 nm for the P-polarized component of the incident light of 45 degrees.
Has wavelength selection characteristics P and S that change linearly,
490-510 nm for S-polarized component of 5 degree incident light
The wavelength selection characteristics P and S in which the transmittance (reflectance) changes linearly in the wavelength region of. Dichroic Mira-D2,
As shown in FIGS. 3 (a) and 3 (b), D6 is a wavelength selection in which the transmittance (reflectance) changes linearly in the wavelength range of 570 to 590 nm with respect to the S-polarized component of the incident light of 45 degrees. Although it has characteristics, it is 590 to 6 for the P-polarized component of incident light of 45 degrees.
It has wavelength selection characteristics in which the transmittance (reflectance) changes linearly in the wavelength region of 10 nm.

The band selection filter F1 has a wavelength selection characteristic such as the wavelength selection characteristic S shown in FIGS. 2 (a) and 2 (b) for vertically incident light, and is transmitted in the wavelength range of 490 to 510 nm. The rate (reflectance) changes linearly. The band selection filter-F2 has a wavelength selection characteristic such as the wavelength selection characteristic S shown in FIGS. 3 (a) and 3 (b) for vertically incident light.
The transmittance (reflectance) changes linearly in the wavelength range of 0 to 590 nm.

The synthesizing optical system is composed of two dichroic mirrors D3 and D4 and a mirror M2, and a projection lens K is arranged at the subsequent stage of the synthesizing optical system. The dichroic mirror-D3 is the same as the dichroic mirror-D2. On the other hand, the dichroic mirror D4 sets the wavelength selection characteristics S and P of FIGS. 4 (a) and 4 (b) for incident light of 45 degrees, and reflects the medium wavelength (G) region of 500 to 580 nm. And a short wavelength (B) region of 500 nm or less on both sides and 58
Although it transmits a long wavelength (R) region of 0 nm or more, for transmitted light, the wavelength selection characteristic S for the S polarization component is a narrower band than the wavelength selection characteristic P for the P polarization component, while for the reflected light, P The wavelength selection characteristic P for the polarization component is S
The band is narrower than the wavelength selection characteristic S for the polarization component.

A liquid crystal projector having the above structure
In the band selection optical system, the dichroic mirror-D1 reflects the blue light in the short wavelength region from the white light emitted from the light source L and separates it into the blue optical system B, and the green-red mixed light in the medium and long wavelength region is emitted. Make it transparent. Green-red mixed light is band selection filter -F
After the unnecessary wavelength component is removed by 1, it is incident on the dichroic mirror D2, the dichroic mirror D2 reflects the red light in the long wavelength region and separates it into the red optical system R, and the green light in the medium wavelength region is emitted. Make it transparent. The green light is filtered by the band selection filter F2 to remove unnecessary wavelength components, and then enters the mirror M1 to be reflected and travels to the green optical system.

On the other hand, the S-polarized component of the blue light, which is the reflected light of the dichroic mirror-D1, contains an unnecessary wavelength component corresponding to the wavelength region of 470 nm to 510 nm, and this unnecessary wavelength component is a P-polarized component. As a dichroic mirror
It is incident on D5, passes through the dichroic mirror D5 as it is according to the wavelength selection characteristic P of FIG. 2 (b), and is removed from the blue primary color light toward the image display element E1 via the mirror M5. Further, the S-polarized component of the red light which is the reflected light of the dichroic mirror-D2 includes an unnecessary wavelength component corresponding to the wavelength region of 570 nm to 610 nm, and this unnecessary wavelength component is a P-polarized component as a dichroic mirror. Incident on D6,
According to the wavelength selection characteristic P of FIG. 3 (b), it is transmitted through the dichroic mirror D6 as it is, and is removed from the red primary color light which is directed to the image display element E2 via the mirror M6.

The P-polarized light component of the green-red mixed light which is the transmitted light of the dichroic mirror D1 includes an unnecessary wavelength component W1 corresponding to the wavelength region of 470 nm to 510 nm, and the wavelength component W1 is the band selection filter- Figure 2 set to F1
It is vertically reflected according to the wavelength selection characteristic S of (a) and is removed from the optical path toward the dichroic mirror D2. The unnecessary wavelength component W1 which is incident on the band selection filter F1 and is reflected vertically is transmitted back and forth through the λ / 4 plate H1 to rotate its polarization plane by λ / 2, and then is transmitted to the dichroic mirror D1 by S.
It is re-incident as a polarized component, is reflected at a right angle according to the wavelength selection characteristic S of FIG. 2 (a), and is removed from the optical path toward the light source L. On the other hand, the green-red mixed color light that passes through the band selection filter F1 and travels toward the dichroic mirror D2 passes through the λ / 4 plate H2 and returns its polarization plane.

The P-polarized component of the green light which is the transmitted light of the dichroic mirror D2 includes an unnecessary wavelength component W2 corresponding to the wavelength region of 570 nm to 610 nm, but the wavelength component W
2 is reflected vertically according to the wavelength selection characteristic S of FIG. 3 (a) set in the band selection filter F2, and is removed from the green light toward the mirror M1. The unnecessary wavelength component W2 incident on the band selection filter -F2 and reflected vertically is λ /
4 The plate H3 is transmitted back and forth and its polarization plane is rotated by λ / 2,
It re-enters the dichroic mirror D2 as an S-polarized component, is reflected at a right angle according to the wavelength selection characteristic S of FIG. 3 (a), and is removed from the optical path toward the light source L. On the other hand, the green light passing through the band selection filter F2 and traveling toward the mirror M1 has a wavelength of λ
After passing through the / 4 plate H4, its polarization plane is restored.

The image display elements E1, E2, E3 invert the transmission / non-transmission of the pixels in response to the blue, red, and green color control signals to form blue, red, and green primary color images. Image display element E
The blue primary color image by 1 is reflected by the mirror M2 and advances to the projection lens. On the way, the red primary color image by the image display element E2 is transmitted through the dichroic mirror D3, and then the green primary color image by the image display element E3 is transmitted through the dichroic mirror D4. The primary color images are combined on the same optical axis.

By the way, a liquid crystal display element of the type in which the liquid crystal layer is sandwiched between two polarizing plates and the transmission / non-transmission is inverted by changing the orientation of the liquid crystal by a voltage signal is used as the image display elements E1 and E2.
When adopted in E3, the polarization component that cannot pass through the polarizing plate located on the incident side of the liquid crystal display element cannot participate in the primary color image and only wastefully heats the liquid crystal display element. Such a polarized component may be blocked and removed. Further, if the polarization plane of this useless polarization component is rotated by λ / 2 to convert the polarization plate located on the incident side of the liquid crystal display element into a transmission-transmissible polarization component, the light amount generated by the light source L is projected. The percentage used for images doubles.

However, when the plane of polarization of the polarization component is rotated using a transmissive optical element such as a λ / 4 plate or a λ / 2 plate, it is separated due to the wavelength dependence of the rotation characteristic of the polarization plane in the transmissive optical element. The polarization plane of each primary color light is shifted, and it is necessary to position each liquid crystal display element separately,
Among the respective primary color lights, a component that cannot be transmitted through the polarizing plate located on the incident side of the liquid crystal display element is generated to reduce the above ratio. Therefore, as a method of rotating the polarization plane irrespective of the wavelength of incident light, a method of mechanically twisting the optical path by combining reflection surfaces can be adopted.

5 and 6 are schematic views of the light source. Here, a polarization beam splitter is arranged on the exit side of the light source in FIG. 1, only one polarization component is extracted to the left, and the polarization plane of this polarization component is λ / 2 in an optical system in which a reflection surface is combined. Rotate,
It is emitted rightward in parallel with the other polarization component.

In FIG. 5, a triangular pyramidal reflector j is provided on the left side of the cubic polarization beam splitter-h on which the light source L is arranged on the upper side, and a triangular pyramidal reflector j is provided on the lower side of the polarization beam splitter-h. Are connected to the respective mirrors i. The reflector j is formed by dividing a 6-divided quadrangular pyramid obtained on each surface of a cube having the same size as the polarizing beam splitter-h into two diagonally perpendicularly divided parts on the bottom surface, and reflecting surfaces j1 and j2 on each surface other than the bottom surface. , J3 are formed and joined again at the reflection surface j2 to return to the original quadrangular pyramid, and the S-polarized component a separated at the separation surface h1 of the polarization beam splitter-h is made incident from the bottom surface. Set the optical path to the reflective surface j1, j
By mechanically twisting the combination of 2 and j3, the S-polarized component a
It is converted into the polarized component c. After that, the P-polarized component c is directly transmitted through the separation surface h1 of the polarization beam splitter-h and is emitted to the right. Mira-i is a polarization beam splitter
The P-polarized light component b transmitted through the separation surface h1 of h is reflected by the reflection surface i1 and is emitted to the right as it is as the P-polarized light component b.

In FIG. 6, a triangular pyramidal reflector k is provided on the left side of the cubic polarization beam splitter-h on which the light source L is arranged on the upper side thereof, and a triangular pyramidal reflector k is provided on the lower side of the polarization beam splitter-h. Are connected to the respective mirrors i. The reflector k is a six-divided quadrangular pyramid having a square base having a diagonal line on one side of the square surface of the polarization beam splitter-h as the base, and two pieces further divided into four by the bottom surface. -H square surfaces are made to face each other with their diagonals being valleys, and each surface other than the bonding surface with the polarizing beam splitter-h has a reflecting surface k.
1, k2, k3 are formed. The reflector k is the S-polarized component a separated by the separation surface h1 of the polarization beam splitter-h.
Is incident from the bottom surface, and its optical path is reflected on the reflecting surfaces k1, k2, k.
The combination of 3 mechanically twists to convert the S-polarized component a into the P-polarized component c. After that, the P-polarized component c passes through the separation surface h1 of the polarization beam splitter-h and is emitted rightward. The mirror i is a separation surface h of the polarization beam splitter-h.
The P-polarized light component b that has passed through 1 is reflected by the reflecting surface i1 and is emitted to the right as it is as the P-polarized light component b.

In the light source shown in FIGS. 5 and 6 having the above-described structure, the light n emitted from the light source L is polarized by the polarization beam splitter-h.
And the P-polarized component b is emitted to the right as it is as the P-polarized component b via the mirror i.
With respect to, the light is converted to the P-polarized component c using the reflectors j and k and then emitted to the right.

FIG. 7 is a schematic view of the liquid crystal projector of the second embodiment, FIG. 8 is an explanatory view of the optical path in FIG. 7, and FIG. 9 is FIG.
10 is a perspective view of an optical path of blue primary color light in FIG. 10, FIG. 10 is a perspective view of an optical path of red primary color light in FIG. 7, and FIG. 11 is a perspective view of an optical path of green primary color light in FIG. Here, each of the RGB primary color lights is separated into two polarization components and made incident on different liquid crystal display elements, and two types of images with different viewing angles are displayed on the liquid crystal display elements corresponding to the respective polarization components. When the projection image is observed by wearing the polarized glasses in which the polarization directions of the left eye and the right eye are different by 90 degrees, two types of color projection images with different viewing angles are incident on the left eye and the right eye, and the projection image is a color stereoscopic image. Can be recognized as. Further, when the same image is displayed on the liquid crystal display element corresponding to each polarization component, the brightness of the projected image is doubled even when the liquid crystal display element which can transmit only one polarization component is used.

7 and 8, a liquid crystal projector
The band selection optical system, the liquid crystal display element, and the composite optical system have a rectangular parallelepiped appearance in which unit cubes are combined in two columns, three rows, and two stages, and the white light emitted from the light source L is on the lower left front side. The combined three-primary-color image which is incident on the unit and goes toward the projection lens K is output from the unit at the far right of the upper stage. This rectangular parallelepiped optical system includes polarizing beam splitters-1, 2, 3 and dichroic mirrors in which liquid crystal display elements 10L, 11L, 12L and liquid crystal display elements 10R, 11R, 12R are joined one by one.
4, 5, 6, 7, 8 and Mira-9.

Liquid crystal display elements 10L, 11L, 12L, 1
0R, 11R, and 12R perform reflection-type polarization modulation,
For each pixel of the image display, λ / 2 polarized light and non-polarized light of the incident light can be arbitrarily set, and in the reflected light passing through the pixel set to λ / 2 polarized light, the S-polarized component becomes the P-polarized component and the P-polarized component becomes the P-polarized component. Each is converted into an S-polarized component. Liquid crystal display element 10
L, 11L, 12L and liquid crystal display elements 10R, 11R,
12R is arranged on two surfaces of the polarization beam splitters-1, 2 and 3 which sandwich the separation surfaces 1H, 2H and 3H, and P
The polarization beam splitters-1, 2 and 3 that transmit the polarization component and the S-polarization component are liquid crystal display elements 10L and 11L, respectively.
Only reflected light that has passed through the pixels set to λ / 2 polarization in L, 12L, 10R, 11R, and 12R is extracted in a direction perpendicular to the first incident light.

The S-polarized light components reflected by the separation surfaces 1H, 2H, 3H are incident on the liquid crystal display elements 10L, 11L, 12L, and only the reflected light passing through the pixels set to the λ / 2 polarization is the P-polarized light component. As a result, the light passes through the separation surfaces 1H, 2H, and 3H as they are and travels in a direction perpendicular to the first incident light. On the other hand, the liquid crystal display elements 10R, 11R, and 12R have separation surfaces 1H,
The P-polarized light component transmitted through 2H and 3H is incident, and only the reflected light passing through the pixel set to λ / 2 polarized light is reflected as the S-polarized light component on the separation surfaces 1H, 2H, and 3H and is orthogonal to the first incident light. Go in the direction.

The dichroic mirrors-4 and 5 are shown in FIG.
3, the dichroic mirrors 6 and 7 have the wavelength selection characteristics of FIG. 3, and the dichroic mirror-8 has the wavelength selection characteristics of FIG.

A liquid crystal projector having such a configuration
In the white light emitted from the light source L, in the dichroic mirror-4, the blue light is separated to the back side, in the dichroic mirror-6, the red light is separated to the upper side, and the remaining green light is directly converted to the polarization beam splitter. It is incident on 3.
On the other hand, the blue light is reflected by the dichroic mirror-5 and travels to the upper stage to enter the polarization beam splitter-1, while the red light directly travels to the upper stage and enters the polarization beam splitter-2.

The blue primary color light incident on the polarization beam splitter-1 is divided into two primary color images corresponding to the display images on the liquid crystal display elements 10L and 10R, and the red primary color light incident on the polarization beam splitter-2 is the liquid crystal. The two primary color images corresponding to the display images of the display elements 11L and 11R, and the green primary color light incident on the polarization beam splitter-3 are converted into two primary color images corresponding to the display images of the liquid crystal display elements 12L and 12R. It Then, in the dichroic mirror-7, the two blue primary color images output to the right from the polarization beam splitter-1 are two red primary color images output to the back from the polarization beam splitter-1. Are combined, and in the dichroic mirror-8, after being output from the polarization beam splitter-3 to the back side, the mirror
Two green primary color images reflected at 9 and traveling upward are combined, and a total of six primary color images are incident on the projection lens.

Next, with reference to FIGS. 9, 10, and 11, the narrowing of the band of each primary color light and the processing of unnecessary wavelength components in the liquid crystal projector of the second embodiment will be described.

In FIG. 9, dichroic mirror-4,
No. 5 has the same wavelength selection characteristic, and as in the case of the first embodiment, unnecessary wavelength components contained in the S-polarized component reflected by the dichroic mirror-4 are made incident on the dichroic mirror-5 as P-polarized component. This time, the light is transmitted, reflected by the dichroic mirror-5, and removed from the blue primary color light which is directed to the polarization beam splitter-1.

In FIG. 10, the dichroic mirror-4
The band selector 14b arranged on the back side of the transmission type is a transmissive band that exhibits the wavelength selection characteristic of transmission that the dichroic mirror-4 has with respect to the S-polarized component of the obliquely incident light of 45 degrees with respect to the vertically incident light. Selection filter-and band selection filter-
They are placed in front of and behind, and have their crystal directions shifted 90 degrees from each other.
A pair of λ / 4 plates. On the other hand, dichroic mirror-6
Is a transmission-type band selection device that exhibits the wavelength selection characteristic of reflection that the dichroic mirror 6 has for the P-polarized component of the 45 ° obliquely incident light to the vertically incident light. It includes a filter and a pair of λ / 4 plates arranged before and after the band selection filter and having crystal directions thereof shifted by 90 degrees.

In the optical system for separating the red primary color light thus constructed, first, when the red-green mixed color light transmitted through the dichroic mirror-4 is transmitted through the band selector 14b, it is included in the P polarization component. The necessary wavelength components are reflected and removed from the red-green mixed light traveling toward the dichroic mirror-6. This unnecessary wavelength component is λ / on the incident side of the band selector 14b.
The light is transmitted back and forth through the four plates, the polarization plane is rotated by λ / 2, re-incident on the dichroic mirror-4 as an S-polarized component, reflected, and removed from the optical path toward the light source. Band selector 14b
The red-green mixed light that has passed through is then transmitted to the dichroic mirror.
6, and only the component (red light) on the long wavelength region side is reflected upward and enters the band selector 14r. An unnecessary wavelength component included in the S-polarized component of the reflected light of the dichroic mirror-6, that is, the shift portion between the two wavelength selection characteristics P and S in FIG. 3A, corresponds to the P-polarized component of the transmitted light. The unnecessary wavelength component included in common is the band selector 14r.
At the same time, the polarization plane is rotated by λ / 2, re-incident on the dichroic mirror 6 as a P-polarized component, transmitted as it is, and removed from the optical path toward the light source.

In FIG. 11, the dichroic mirror-6
The band selector 14g disposed on the back side of the is a transmissive band that exhibits the wavelength selection characteristic of transmission that the dichroic mirror-6 has with respect to the S-polarized component of the obliquely incident light of 45 degrees with respect to the vertically incident light. Selection filter-and band selection filter-
They are placed in front of and behind, and have their crystal directions shifted 90 degrees from each other.
A pair of λ / 4 plates.

In the green light optical system thus constructed, unnecessary wavelength components contained in the P polarization component are reflected when the green light transmitted through the dichroic mirror-6 is transmitted through the band selector 14g. And is removed from the green light going to the polarization beam splitter-3. This unnecessary wavelength component is
It is transmitted back and forth through the λ / 4 plate on the incident side of the band selector 14g, rotates the polarization plane by λ / 2, and is re-incident on the dichroic mirror 6 as an S-polarized component, reflected and removed from the optical path toward the light source. To be done.

[0057]

According to the projection type color display device of the first aspect, the wavelength regions of the P-polarized component and the S-polarized component of the primary color light or the mixed color light reflected by the first reflecting surface are equal,
The deviation of the band selection characteristic due to the difference in the polarization component in the band selection element such as the dichroic mirror does not pose a problem. Further, in the three-dimensional optical system as shown in FIG. 6, it can be carried out only by substituting an appropriate reflecting surface after the dichroic mirror for the dichroic mirror.

According to the projection type color display device of the second aspect, since unnecessary wavelength components contained in the transmitted light of the first reflecting surface are removed, adjacent wavelength regions separated by the first reflecting surface are removed. Since the wavelength regions of the two primary color lights are independent of each other and the color purity is increased, a projection image with high saturation can be formed.

According to the projection type color display device of the third aspect, the wavelength regions of the P-polarized component and the S-polarized component are equal in the primary color light or the mixed color light reflected by the first reflecting surface,
The deviation of the band selection characteristic due to the difference in the polarization component in the band selection element such as the dichroic mirror does not pose a problem.

According to the projection type color display device of the fourth aspect, since unnecessary wavelength components contained in the transmitted light of the first reflecting surface are removed, adjacent wavelength regions separated by the first reflecting surface are removed. Since the wavelength regions of the two primary color lights are independent of each other and the color purity is increased, a projection image with high saturation can be formed.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a projection type color display device according to a first embodiment.

FIG. 2 is a diagram showing band selection characteristics of the dichroic mirror in FIG.

FIG. 3 is a diagram of band selection characteristics of another dichroic mirror in FIG.

4 is a diagram of band selection characteristics of another dichroic mirror in FIG. 1. FIG.

5 is a schematic diagram of a modified example of the light source in FIG.

FIG. 6 is a schematic view of another modification of the light source in FIG.

FIG. 7 is a schematic diagram of a liquid crystal projector according to a second embodiment.

8 is an explanatory diagram of the optical system in FIG.

9 is a perspective view of an optical system for blue primary color light in FIG.

10 is a perspective view of an optical system for red primary color light in FIG.

11 is a perspective view of an optical system for green primary color light in FIG.

[Explanation of symbols]

 B Optical system for blue primary color G Optical system for green primary color R Optical system for red primary color K Projection lens L Light source E1 Image display device D1 Dichroic mirror-D5 Dichroic mirror-M1 Mira-F1 Band selection filter-H1 λ / 4 Plate H2 λ / 4 plate

Claims (4)

[Claims] 1. A light source for generating and emitting white light, a band selection optical system for extracting a plurality of primary color components from the emitted white light, and a primary color pattern of a projected image using each primary color component. In a projection type color display device having a plurality of image display elements to be formed and synthesizing and projecting respective primary color patterns on the same optical axis, the band selection optical system is oblique to the incident light. Arranged first having a predetermined wavelength selection characteristic
A projection including: a reflecting surface; and a second reflecting surface having a wavelength selection characteristic substantially equal to that of the first reflecting surface arranged so that the P-polarized reflection component of the first reflecting surface is obliquely incident as the S-polarized component. Type color display device. 2. The projection type color display device according to claim 1, wherein a transmission type band selection filter is arranged so that the transmitted light of the first reflection surface is vertically incident, and is arranged before and after the filter. A projection type color display device, comprising: a pair of λ / 4 plates in which the directions of the crystal optical axes intersect each other at a right angle. 3. A light source for generating and emitting white light, a band selection optical system for extracting a plurality of primary color components from the emitted white light, and a primary color pattern of a projected image using each primary color component. In a projection type color display device having a plurality of image display elements to be formed and synthesizing and projecting respective primary color patterns on the same optical axis, the band selection optical system is oblique to the incident light. Arranged first having a predetermined wavelength selection characteristic
A reflective surface, a transmissive band-selecting filter arranged so that the reflected light from the first reflective surface is vertically incident, and the filter
And a pair of λ / 4 plates, which are arranged in front of and behind each other and whose crystal optical axis directions are combined at a right angle, and a projection type color display device. 4. The projection type color display device according to claim 3, wherein the transmission type band selection filter is arranged so that the light transmitted through the first reflection surface is vertically incident, and the transmission type band selection filter is arranged before and after the filter. A projection type color display device, comprising: a pair of λ / 4 plates in which the directions of the crystal optical axes intersect each other at a right angle.