JP2001142141A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projector capable of attaining the miniaturization and reduction in weight under a condition free from troubles as for optical characteristics as compared with a transmission type by using a dichroic prism capable of attaining a color separation function and a color synthesis function with scarcely any difference in strength as a color separation/color synthesis element. SOLUTION: As for the dichroic prism 1 functioning as the color separation/ color synthesis element, by devising a multi-layered film as for a red dichroic film 1r and a blue dichroic film 1b, the maximum reflectance of the polarization component of one of S-polarized light and P-polarized light is >=80% of the maximum reflectance of the other polarization component, and by using the prism 1 with the aforesaid characteristics, polarization dependency is reduced. Thus, the reflection characteristics of the polarization component at the color separating process is made equivalent to the reflection characteristics of the polarization component at color-synthesizing the light which is made incident again after being modulated by reflection type liquid crystal panels 3R, 3G and 3B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming member such as a reflection type liquid crystal panel and a projector using a dichroic prism which functions as a single element as a color separation / color synthesis element.

[0002]

2. Description of the Related Art Generally, there are various types of projectors. For example, using a reflective liquid crystal panel rather than a transmissive liquid crystal panel provides higher resolution and higher resolution.
Since high brightness can be easily achieved and a single optical element can be used as a color separating element and a color synthesizing element, it is considered to be advantageous for miniaturization, and is attracting attention.

The basic idea of a projector using such a reflection type liquid crystal panel is disclosed in, for example,
No. 249639, which discloses a color separation of light from a light source and a reflection type liquid crystal for each color using a polarizing beam splitter and a dichroic mirror as a color separation / color combining element disposed on an input / output optical path. The modulated light reflected by the panel is subjected to color synthesis, and is projected to a projection lens system to obtain a projected color image.

FIG. 24 shows a proposal example of a liquid crystal projector utilizing the basic idea using such a reflection type liquid crystal panel. This liquid crystal projector includes a light source 101
, Illumination system 102, total reflection prism 103, communication prism 104, polarization beam splitter 105, color separation / color synthesis element 106, and three reflective liquid crystal panels 107 R and 107
G, 107B, each reflective liquid crystal panel 107R, 107
A condenser lens 108 is provided for each of G and 107B. The light source 101 includes a lamp 109 and an elliptical mirror 110. The illumination system 102 includes a total reflection mirror 111 for deflecting the optical path, a collimator lens 112, and a pair of fly-eye lens plates 113, 1 constituting an integrator optical system.
14, polarization alignment prism array 115, and condenser lens 11
6 The integrator optical system is well known from Japanese Patent Application Laid-Open No. 3-111806.

[0005] The polarization beam splitter 105 is disposed on the overlapping input / output optical paths, and reflects the S-polarized component light emitted from the illumination system 102 at 90 ° toward the color separation / color combining element 106 side. is there. Color separation / color synthesis element 1
As the reference numeral 06, a dichroic prism is used. The dichroic prism 106 includes a red dichroic film 106r having a characteristic of reflecting the long wavelength region of the red light R so as to separate the long wavelength region of the red light R from the short wavelength region of the green light G; A dichroic film for blue 10 having a characteristic of reflecting the short wavelength region of blue light B so as to separate the short wavelength region of light B from the long wavelength region of green light G.
6b is arranged as a cubic or rectangular parallelepiped optical element which is arranged orthogonally. Therefore, the dichroic prism 106 includes the polarizing beam splitter 105
Red dichroic film 106 parallel to the reflective surface 105a
r and a blue dichroic film 106b orthogonal to the red dichroic film 106r. These dichroic films 106r and 106b are formed as dielectric multilayer films.

[0006] The three reflective liquid crystal panels 107R, 107
G and 107B are the dichroic film 106r for red and the dichroic film 1 for blue of the dichroic prism 106.
06b. That is, the reflection type liquid crystal panel 107R is disposed in a long-wavelength reflection direction of the red light R reflected by the red dichroic film 106r,
A reflection type liquid crystal panel 107B is disposed in a direction of reflection of a short wavelength equal to or less than the blue light B reflected by the blue dichroic film 106b, and a reflection type liquid crystal panel in a transmission direction of the red dichroic film 106r and the blue dichroic film 106b. 107G are arranged. Although not shown, these reflective liquid crystal panels 107R, 107G, and 107B form images for each color to be projected by the information display system by on / off control of each liquid crystal element.

Further, a projection lens 11 is provided on an exit optical path between the polarizing beam splitter 105 and the screen 117.
8 is provided. Here, the optical path length from the virtual light source surface by the integrator optical system to each of the reflective liquid crystal panels 107R, 107G, and 107B, and each of the reflective liquid crystal panels 107R, 107G, and 107B.
The optical path lengths from B to the projection lens 118 are all set substantially equal.

In such a configuration, a light beam from the illumination system 102 that has been adjusted to only the S-polarized component is reflected by the total reflection prism 103 and the polarization beam splitter 105 and enters the dichroic prism 106. Here, the light is split into red light R, green light G, and blue light B according to the wavelength, and the reflection type liquid crystal panels 107R and 107 respectively correspond to each other.
G, 107B. Here, each of the reflective liquid crystal panels 107R, 107G, and 107B is turned on and off in accordance with an image signal input to the liquid crystal projector by the information display system. When the liquid crystal panel is off, the S-polarized component is reflected as the S-polarized component. The S-polarized component is converted (modulated) into a P-polarized component and reflected. And these S-polarized light components or P
Each reflective liquid crystal panel 107R, 107 composed of a polarization component
The reflected lights from G and 107B are collectively combined in the dichroic prism 106 and returned to the polarization beam splitter 105. At this time, each reflective liquid crystal panel 10
Only the P-polarized light component reflected from the liquid crystal element corresponding portions turned on in 7R, 107G, and 107B passes through the polarizing beam splitter 105, and the transmitted light is enlarged and projected on the screen 117 by the projection lens system 119. Thus, an image corresponding to the image signal input to the liquid crystal projector is displayed on the screen 117 as a color image.

As described above, by using color separation and color synthesis for one dichroic prism 106, the overall configuration can be reduced in size.

[0010]

However, regarding the dichroic prism 106, both the red dichroic film 106r and the blue dichroic film 106b can efficiently reflect the P-polarized light component and the S-polarized light component to the same extent. A function of separating the light coming from the illumination system 102 into three colors of red light R, green light G, and blue light B, which cannot be formed into a film, and reflecting the separated light for each color light. When the function of synthesizing the light modulated by the panels 107R, 107G, and 107B is performed by the same dichroic prism 106, the performance is greatly improved as compared with a projector in which color separation and color synthesis are configured by different optical elements. Is bad now.

[0011] This point will be further described. First, when the polarization characteristics of a commercially available dichroic prism were examined, the results shown in FIG. 25 were obtained. That is, the reflection characteristic of the blue light B by the blue dichroic film 106b (FIG. 25A) and the reflection characteristic of the red light R by the red dichroic film 106r (FIG. 25B).
Are shown as polarization characteristics for the P-polarized light component, the S-polarized light component, and the P * S light, and it can be seen that the reflection characteristics greatly differ depending on the polarization state of the incident light.
In particular, the reflectance of the P-polarized light component is low.

FIG. 2 shows such a dichroic prism.
As shown in FIG. 6A, transmissive liquid crystal panels 121R and 121 into which light separated by another optical element is incident.
When used as a dichroic prism 122 for color synthesis for G and 121B and configured to synthesize S-polarized light components, the polarization synthesis characteristics show excellent characteristics as shown in FIG. 26 (b).

However, as shown in FIG. 27A, the reflection type liquid crystal panels 107R, 107G, 1 shown in FIG.
When the separation characteristics of the S-polarized light component and the synthesis characteristics of the P-polarized light component when used as the dichroic prism 106 for color separation and color synthesis for 07B were examined, as shown in FIG. Dichroic prism 106
In the separation / synthesis, the intensities of the red light R and the blue light B are reduced, so that a color image with an excellent color balance cannot be obtained.

Therefore, the present invention provides a color separating function for separating incident light into three color components of red light, green light and blue light, and a color combining function for combining separated light of these colors. By using a dichroic prism, which can be achieved with almost no difference in intensity, as a color separation / color combining element, a projector that can be reduced in size and weight under conditions that do not hinder the optical characteristics as compared with a transmissive type. The purpose is to provide.

Also, the present invention provides a color separation function and a color separation function by providing a filter function in which one of the P-polarized light and the S-polarized light has a certain shift with respect to the other polarized light. It is an object of the present invention to provide a projector using a dichroic prism capable of achieving a color balance and light use efficiency comparable to a case where different optical elements are provided with a combining function.

Still another object of the present invention is to provide a projector capable of preventing a keystone which may be caused by tilting.

Another object of the present invention is to provide a projector which can be made small and lightweight to reduce uneven illuminance.

In addition, another object of the present invention is to provide a projector which is small and light in weight, improves the efficiency of use of light from the light source, and can display a bright projected image.

[0019]

According to the first aspect of the present invention, there are provided three projectors for forming an image to be projected by modulating a polarization state for each of red, green and blue color regions. Image forming member, a light source for emitting light for illuminating these image forming members, a projection lens system for projecting an image formed by the image forming member on a screen, and the image forming member from the light source An incoming light path directed toward and an outgoing light path directed from the image forming member toward the projection lens system overlaps one of the P-polarized light and the S-polarized light of the light from the light source on the incoming / outgoing light path. A polarizing beam splitter that reflects and transmits the other polarized light component in a direction different by about 90 °; and a long wave of red light on an optical path between the polarizing beam splitter and the three image forming members. A red dichroic film that separates a short wavelength region from the green light and a blue dichroic film that separates a short wavelength region of the blue light and a long wavelength region than the green light, from the light source. A function of guiding light of one polarization component separated by the polarizing beam splitter among light into a red region, a green region, and a blue region and guiding the light to the corresponding image forming member; and The polarization state is modulated by the color separation / color synthesis element which also combines the function of combining the light of each area that enters again and guiding the light to the projection lens system via the polarization beam splitter, and the red The dichroic film for red light has a maximum reflectance of 80% or more of the maximum reflectance of one of the S-polarized light and the P-polarized light of the red light, and the blue dichroic film has a S-polarized light of blue light. Or a dichroic prism in which the maximum reflectance of one of the polarization components of the P-polarized light is 80% or more of the maximum reflectance of the other polarization component;
Is provided.

Accordingly, with respect to the dichroic prism as a color separation / color combining element, the dichroic film for red and the dichroic film for blue are either polarized light of either S-polarized light or P-polarized light of the corresponding color by devising the multilayer film. By using a component having the same characteristic that the maximum reflectance of the component is 80% or more of the maximum reflectance of the other polarization component, the polarization dependence is reduced, and therefore, the reflection characteristics of the polarization component when color separation is performed. For example, it is possible to make the reflection characteristics of the polarization component when the light modulated and re-entered by the reflective liquid crystal panel as an image forming member undergo color synthesis to be equal, and a single element can secure commercial value. The function as a color synthesizing element can be exhibited, and the size and weight of the entire projector can be reduced.

According to a second aspect of the present invention, there is provided a projector, comprising: three reflective image forming members for forming an image to be projected by modulating a polarization state for each of a red region, a green region, and a blue region; A light source that emits light for illuminating these image forming members, a projection lens system that projects an image formed by the image forming members on a screen, and an incident optical path from the light source to the image forming members. Reflects either one of P-polarized light or S-polarized light component of the light from the light source on an input / output optical path where an output optical path from the image forming member toward the projection lens system overlaps, and the other polarization component And a polarizing beam splitter for transmitting light in directions substantially different by 90 °.
A red dichroic film for separating a long wavelength region of red light and a shorter wavelength region than green light on an optical path between the image forming members, and a shorter wavelength region of blue light and longer than green light. A blue dichroic film for separating a wavelength region from light, and among the light from the light source, one of the polarized light components separated by the polarizing beam splitter is color-separated into a red region, a green region, and a blue region. And the function of leading to the corresponding image forming member, the polarization state is modulated by the image forming member, and the color of the light of each area that is incident again is synthesized to the projection lens system via the polarization beam splitter. 550 nm ≦ λ ≦ 700 in the red dichroic film, which is provided as a color separation / color synthesis element that also serves as a guiding function.
The wavelength at which the reflectance of P-polarized light is 50% in the wavelength region of nm is λ.
_50P, when the reflectance of S-polarized light is a _50S the wavelength at which 50% λ, 10nm ≦ | a ≦ 50nm, | λ _50P -λ _50S
And 400 nm ≦ in the dichroic film for blue.
When the wavelength at which the reflectance of P-polarized light is 50% in the wavelength range of λ ≦ 550 nm is λ _50P , and the wavelength at which the reflectance of S-polarized light is 50% is λ _50S , 10 nm ≦ | λ _50P −λ _50S | ≦ 50
and a dichroic prism having a diameter of nm.

Therefore, the dichroic prism as a color separating / color combining element basically reduces the polarization dependence of the red dichroic film and the blue dichroic film as in the first aspect of the present invention. In this case, it is desirable to match the polarization dependence, but it is not possible to match the polarization dependency in practice, so that a filter function is provided in which one polarization component is suppressed to a constant shift component with respect to the other polarization component. As a result, the color separation function and the color synthesis function can be color-combined with a color balance comparable to that in a case where a projector is configured using different optical elements, and the light use efficiency can be improved. it can.

According to a third aspect of the present invention, in the projector according to the first or second aspect, the dichroic prism is such that the red dichroic film and the blue dichroic film are arranged orthogonally and the polarizing beam splitter has The incident surface and the incident surfaces of these dichroic films are arranged so as to be substantially orthogonal to each other.

Therefore, by arranging the plane of incidence of the polarizing beam splitter and the plane of incidence of the dichroic film of the dichroic prism so as to be substantially orthogonal to each other, the tolerance of the angle of incidence can be increased and the efficiency of light utilization can be improved. In this respect, a more advantageous design becomes possible.

According to a fourth aspect of the present invention, in the projector according to the first or second aspect, the dichroic prism is such that the red dichroic film and the blue dichroic film are arranged orthogonally, and the red dichroic film is arranged. And the blue dichroic film and the blue dichroic film are arranged so that the incident light is incident with a substantially equal shift angle.

Accordingly, the image forming member is displaced in the direction perpendicular to the optical axis so that the incident light is incident on the dichroic prism with a substantially uniform shift angle with respect to the red dichroic film and the blue dichroic film. By arranging them, keystone generated on the screen can be prevented.

According to a fifth aspect of the invention, in the projector according to the first or second aspect, in the dichroic prism, the red dichroic film and the blue dichroic film are arranged orthogonally and the red dichroic film is arranged. Incident light having a predetermined incident angle of less than 45 ° is incident on one of the films and the dichroic film for blue, and predetermined incident light having an incident angle of 45 ° or more is incident on the other film. It is arranged so that incident light at an angle is incident.

Therefore, the generation of the keystone can be prevented basically in the same manner as in the invention according to the fourth aspect. In particular, the shift direction is such that the red dichroic film and the blue dichroic film of the dichroic prism cross each other. By shifting the direction of the crossing line perpendicular to the direction of the intersection line, the characteristics of the dichroic film are shifted by taking into account the tilt of the main optical axis of the illuminating light generated due to the shift. Equivalent performance can be obtained.

[0029] The invention described in claim 6 is the invention according to claims 1 to 5.
The projector according to any one of the above, further comprising an illumination system having at least a pair of fly-eye lens plates on an incident optical path from the light source to the polarization beam splitter.

Therefore, in realizing the projector according to any one of the first to fifth aspects, by providing an illumination system using a so-called integrator optical system on the incident optical path, the substantially rectangular image forming member can be provided with uneven illuminance. It is possible to illuminate in a state where the number of images is small, and it is possible to improve the quality of a projected image.

[0031] The invention according to claim 7 is the invention according to claims 1 to 5.
In the projector according to any one of the above, at least one fly-eye lens plate and a plurality of cylindrical lenses are arranged on an incident optical path from the light source to the polarization beam splitter, and the fly-eye lens plate is collected. A first lenticular disposed near the light position, and a second lenticular disposed downstream of the first lenticular and having a plurality of cylindrical lenses arranged in a direction orthogonal to the arrangement direction of the cylindrical lenses. Is provided.

Therefore, in order to realize the projector according to any one of the first to fifth aspects, by providing an illumination system using a so-called integrator optical system on the incident optical path, the substantially rectangular image forming member can be provided with uneven illuminance. It is possible to illuminate in a state where the number of images is small and to improve the quality of a projected image.

According to an eighth aspect of the present invention, in the projector according to the seventh aspect, on the optical path between the first lenticular and the second lenticular, a polarized light for aligning a random light beam into only one polarized light component. It has an alignment function element.

Accordingly, in realizing the projector according to the seventh aspect, by providing the illumination system with the polarization alignment function element, most of the light from the light source can be used for illuminating the image forming member, and the light source light use efficiency. And projection display with high luminance can be performed.

[0035]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. First, prior to the description of the projector, characteristics of the dichroic prism 1 as a color separation / color synthesis element used in the present embodiment will be described. The dichroic prism 1 of the present embodiment is also a cubic shape in which a red dichroic film 1r and a blue dichroic film 1b are arranged orthogonally as shown in FIG. Membrane 1
r, a polarization characteristic as shown in FIG. 1 is provided by devising a further multilayer structure of the blue dichroic film 1b. FIG. 1A shows the transmittance characteristic of blue light of each of the P-polarized light component and the S-polarized light component of the S-polarized light component by the blue dichroic film 1b, and shows the reflectance characteristic of the S-polarized light component showing the maximum reflectance of 100%. The maximum reflectance of the P-polarized light component is about 99%, which indicates that the reflectance is almost the same regardless of the polarized light component. FIG. 1B shows the transmittance characteristics of the blue light of each of the P-polarized light component and the S-polarized light component by the red dichroic film 1r =
It shows reflectance characteristics, and the maximum reflectance of the P-polarized component is 98% with respect to the S-polarized component showing the maximum reflectance of 100%.
It can be seen that the reflectance is almost the same regardless of the polarization component. However, according to the considerations of the present inventors, even if the maximum reflectance for the P-polarized component is not high as shown in FIG. In this case, it has been found that a maximum reflectance of 80% or more is sufficient. In any case, according to the dichroic prism 1 used in the present embodiment, the polarization dependency is reduced, and
It can be seen that sufficient separation and reflection characteristics can be exhibited for both the polarization component and the P polarization component.

With respect to the polarization characteristics of the red dichroic film 1r and the blue dichroic film 1b, ideally, the characteristics of the P-polarized light component and the S-polarized light component match each other. Although preferable for performing color synthesis, it is actually impossible to completely match the characteristics of the two. In this regard, according to the dichroic prism 1 of the present embodiment, the polarization characteristic of the blue dichroic film 1b shown in FIG.
50% reflectance of P-polarized light in the wavelength range of m ≦ λ ≦ 550 nm
Λ _50P and λ _{50S the} wavelength at which the reflectance of S-polarized light is 50%, the shift amount is about | λ _50P −λ _50S | ≒ 50 nm, and the shift amount for red shown in FIG. In the polarization characteristics of the dichroic film 1r, 550 nm ≦ λ ≦ 70
Assuming that the wavelength at which the reflectance of P-polarized light becomes 50% in the wavelength region of 0 nm is λ _50P and the wavelength at which the reflectance of S-polarized light becomes 50% is λ _50S , | λ _50P -λ _50S | ≒ about 50 nm shift In both cases, P-polarized light has a filter function with a certain shift with respect to S-polarized light, so that color separation and color synthesis are not inferior to those in the case where they are configured by separate optical elements. Color balance can be ensured. Also in this case, according to the considerations of the present inventors, with respect to the red dichroic film 1r and the blue dichroic film 1b, 10 nm ≦
It has been confirmed that there is no problem if the shift amount is within the range of | λ _50P −λ _50S | ≦ 50 nm.

Next, as shown in FIG. 2 (a), the dichroic prism 1 having such a polarization characteristic is transmitted through the transmission type liquid crystal panels 2R, 2G on which light separated by other optical elements is incident. , 2B, the polarization combining characteristics of a configuration in which the S-polarized light component is combined are examined. As shown in FIG.
Excellent polarization synthesis characteristics were confirmed.

On the other hand, as shown in FIG. 3A, a dichroic as a single element color separation / color synthesis element for the reflection type liquid crystal panels 3R, 3G, 3B as image forming members to which the present embodiment is applied. When the polarization separation / synthesis characteristics of separating the S-polarized light component and synthesizing the P-polarized light component using the prism 1 were examined, the characteristics shown in FIG. 3B were obtained. That is, FIG.
As compared with the polarization separation / synthesis characteristics shown in (1), a decrease in intensity can be avoided for the red light R and the blue light R, and although the characteristics are greatly improved, a decrease in the amount of light in the boundary wavelength region of each color is inevitable. You can see that.

Next, as shown in FIG. 4, the incident angle dependence of the dichroic prism 1 when combined with the polarization beam splitter 4 will be described. Here, the polarizing surface 4a of the polarizing beam splitter 4 and the red dichroic surface 1r are arranged in a positional relationship of being parallel. Further, regarding each of the reflective liquid crystal panels 3R, 3G, 3B,
A case where all the pixels are displayed ON = a case where the polarization state is rotated by 90 ° is (bright), and a case where all the pixels are displayed OFF = a case where the polarization state is not changed is (dark). Here, when the efficiency characteristics of the light transmitted through the polarizing beam splitter 4 and emitted when the incident angle is changed to 40 ° or 50 ° centering on 45 °, the blue light B, green light The results shown in FIGS. 5 to 7 are obtained for each of the light G and the red light R. Since each incident angle is defined as an angle with respect to the blue dichroic film 1b as shown in FIG. 4, the incident angle is expressed as "B40". According to this result, it is understood that the wavelength band, the contrast, and the brightness all greatly change depending on the incident angle.

On the other hand, as shown in FIG. 8, the polarizing beam splitter 4 and the dichroic prism 1 are arranged so that their incident surfaces are orthogonal to each other, and the incident angle is set at 45 ° around the center.
When the efficiency characteristics of the light transmitted through the polarization beam splitter 4 when the light was incident at a change of 0 ° or 50 ° were examined, the blue light B, the green light G, and the red light R were measured as shown in FIG. Or a result as shown in FIG. According to this result, it can be seen that the tolerance of the incident angle is greatly improved.

From the above, basically, it can be said that the polarizing beam splitter 4 and the dichroic prism 1 are preferably arranged in a positional relationship in which their incident surfaces are orthogonal to each other.

FIG. 12 shows a configuration example of a reflection type liquid crystal projector using a combination of the polarizing beam splitter 4 and the dichroic prism 1 having such a positional relationship. This projector is configured as a rear projector that projects the screen 5 from the back side. This projector comprises a light source 6, an illumination system 7, a total reflection prism 8, a communication prism 9, a polarizing beam splitter 4, a dichroic prism 1, and three reflective liquid crystal panels 3R, 3G,
3B and a condenser lens 10 for each of the reflective liquid crystal panels 3R, 3G, 3B. Polarizing beam splitter 4
Is located on a common incident / emission optical path through which incident light and outgoing light pass, and is a projection lens system 1 having a plurality of projection lenses 11 on an exit optical path for the dichroic prism 1.
2 are provided.

In such a configuration, only the S-polarized light component of the light from the light source 6 is reflected by the polarizing beam splitter 4 and enters the dichroic prism 1. This light is reflected or transmitted by the red dichroic film 1r and the blue dichroic film 1b according to the wavelength range, and is separated into red light R, green light G, and blue light B,
The light enters the corresponding reflective liquid crystal panels 3R, 3G, 3B. Here, each of the reflective liquid crystal panels 3R, 3G, 3B is turned on / off in accordance with an image signal input to the liquid crystal projector by the information display system. When turned off, the S-polarized component is reflected as the S-polarized component. S polarization component is P
The light is converted (modulated) into a polarized light component and reflected. Then, the reflected light from each of the reflective liquid crystal panels 3R, 3G, 3B composed of the S-polarized component or the P-polarized component is reflected or transmitted by the dichroic prism 1 for the red dichroic film 1r and the blue dichroic film 1b. As a result, they are collectively synthesized and returned to the polarization beam splitter 4 side. At this time, P reflected from the liquid crystal element corresponding portions that are turned on in each of the reflective liquid crystal panels 3R, 3G, 3B.
Since only the polarized light component passes through the polarizing beam splitter 4, this transmitted light is transmitted by the projection lens system 12 to the screen 5.
It is enlarged and projected above. Thereby, an image corresponding to the image signal input to the liquid crystal projector is projected on the screen 5 as a color image.

As described above, by using color separation and color synthesis for one dichroic prism 1, the overall configuration of the projector can be reduced in size and weight. Here, even if the dichroic prism 1 is made to have both the function of color separation and the function of color synthesis, the dichroic prism 1 has a positional relationship and a characteristic with the polarizing beam splitter 4 as shown in FIGS.
It can be seen that a color display with a color balance comparable to that of a transmissive liquid crystal projector can be realized without lowering the light use efficiency. In particular, as shown in FIG. 12, in the case of a rear projector configuration, there is no need for shifting since there is no risk of keystone generation, and the optical path from the light source 6 to the projection lens system 12 can be arranged straight. As a result, the lens diameter of the projection lens 11 can be reduced.

A second embodiment of the present invention will be described with reference to FIG. The same portions as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments). The present embodiment is applied to a front projector that projects the screen 5 from the front side, and prevents keystone at that time. That is, in the case of the front projector, the projector is placed on a desk and projected on the screen 5 whose lower side is above the desk. Therefore, if the projector is used with the configuration shown in FIG. The image is distorted and difficult to see. Therefore, by shifting the reflective liquid crystal panels 3R, 3G, 3B in the vertical direction perpendicular to the optical axis as shown by arrows in FIG. 13, an image can be projected onto the screen 5 without generating keystone. Is well known (the shift ratio on the screen 5 is 9: 1 or more). At this time, in this embodiment, the position of the total reflection prism 8 is shifted toward the light source 6 so that the shift direction of the incident light is parallel to the direction of the intersection line where the dichroic films 1r and 1b of the dichroic prism 1 intersect. The dichroic film 1r for red and the dichroic film 1 for blue through the polarizing beam splitter 4.
b are arranged so that the incident light is incident with a substantially uniform shift angle.

Thus, in addition to the effect of the configuration of FIG. 12, keystone in the case of the front projector configuration can be prevented.

A third embodiment of the present invention will be described with reference to FIG. This embodiment is also an example of application to a front projector, in which the generation of keystone is prevented. The difference from the embodiment shown in FIG. 13 is that the shift direction of the incident light is set to a direction orthogonal to the direction of the intersection line where the dichroic films 1r and 1b of the dichroic prism 1 intersect. . In this case, by shifting the characteristics of the dichroic films 1r and 1b in consideration of the inclination of the main optical axis of the illumination light generated due to the shift, the same performance as in the case where no shift is applied can be obtained. That is, depending on the direction of the shift, the incident angle of the incident light on the red dichroic film 1r is 45 °.
In contrast, the incident angle of the incident light on the blue dichroic film 1b is 45 ° or more, and the incident angle of the incident light on the red dichroic film 1r is less than 45 °, and the incident angle on the blue dichroic film 1b is smaller than 45 °. What is necessary is just to comprise so that the incident angle of incident light may each have the characteristic demonstrated by FIG. Conversely, when the incident angle of the incident light on the red dichroic film 1r is 45 ° or more and the incident angle of the incident light on the blue dichroic film 1b is less than 45 °, the incident light on the red dichroic film 1r is obtained. A configuration may be adopted in which the light incident angle is 45 ° or more and the incident angle of the incident light on the blue dichroic film 1b is less than 45 ° and the characteristic described with reference to FIG.

The configuration of the illumination system 7 including the light source 6 shown in the first to third embodiments will be described with reference to FIG. In the illumination system 7, first, the light source 6 includes a lamp 13, a rotating parabolic mirror 14 that reflects light from the lamp 13 and emits it as parallel light, and a convex lens 15 that collects parallel light. A collimating lens 16, one fly-eye lens plate 17, a first lenticular 18, and a polarization alignment
The illumination system 7 is configured by disposing the second lenticular 9, the second lenticular 20, and the condenser lens 21. Here, one fly-eye lens plate 17 and a pair of lenticulars 18 and 20 constitute an integrator optical system 22. That is, as shown in FIG. 16, the reflective liquid crystal panels 3R, 3R
A fly in which a plurality of lens elements 23 formed in a rectangular shape having a ratio of 4: 3 substantially similar to the shapes of G and 3B (generally, a rectangular shape having an aspect ratio of 4: 3) are two-dimensionally arranged. It comprises an eye lens plate 17 and a pair of lenticules 18 and 20 in which a plurality of cylindrical lenses 24 and 25 are arranged in one direction orthogonal to each other. That is, the fly-eye lens plate 17 corresponds to a first fly-eye lens of a so-called integrator optical system, and the fly-eye lens plate 17 separates each lens element from light emitted from the lamp 13 and reflected by the rotary parabolic mirror 14. A secondary light source image is divided and formed every 23 pixels. Therefore, the surface on which the secondary light source image is formed is a virtual light source surface. First lenticular 1 provided at the subsequent stage of fly-eye lens plate 17
Numeral 8 is set so that each cylindrical lens 24 is positioned for each light beam passing through each row group of each lens element 23. In the second lenticular 20 disposed immediately after the first lenticular 18, the cylindrical lens 25 corresponds to each row group of each lens element 23. That is,
The cylindrical lenses 24 and 25 are arranged in a direction orthogonal to each other, and have lens elements arranged two-dimensionally when viewed as a lenticular pair, so that a second fly-eye lens plate in a so-called integrator optical system is provided. Is equivalent to The condensing lens 21 illuminates the entire surface of the reflective liquid crystal panels 3R, 3G, 3B after the optical axis of the light beam generated by each lens element 23 of the fly-eye lens plate 17 passes through the first and second lenticulars 18, 20. The optical axis is bent so that the optical axis is bent. By illuminating the rectangular reflective liquid crystal panels 3R, 3G, and 3B with the illumination system 7 including such an integrator optical system 22, illumination without uneven illuminance can be achieved over the entire surface and a good projected color image can be obtained. be able to. The integrator optical system may be configured by a pair of fly-eye lens plates as in the case shown in FIG.

FIG. 1 shows the structure and operation of the polarization alignment function element 19 disposed between the lenticules 18 and 20.
This will be described with reference to FIG. This polarization alignment function element 19
For each light beam (P + S) having a random polarization direction incident from the light source 6 side, the light beam (P + S) is emitted in such a manner as to be aligned with only one of the P-polarized component and the S-polarized component (in the present embodiment, , S-polarized light component). Specifically, the polarization beam splitter 26 and the reflection prisms 27 and 1
A half-wave plate 28 is arranged in a stripe shape in correspondence with each cylindrical lens 24 of the first lenticular 18, and the P-polarized light component is transmitted through the polarizing beam splitter 26 to be a half-wave plate. The light is rotated by 90 ° at 28 and converted into an S-polarized light component. The S-polarized light component is reflected by the polarizing beam splitter 26 and the reflecting prism 27 as it is and emitted, so that all light is aligned with the S-polarized light component.

The light beam emitted from the lamp 13 having a random polarization direction is emitted by aligning only the S-polarized light component with the polarization alignment function element 19 in this polarization conversion process. The light beam has higher conversion efficiency. In this regard, in the present embodiment, the first lenticulars 18 are incident on the corresponding polarizing beam splitters 26 in units of rows, so that the conversion efficiency is high.

In any case, only a P-polarized component or an S-polarized component, such as a liquid crystal panel that modulates polarized light, is used.
When only the polarized light of the type can be used, the light source 6 that emits a light beam having a random polarization direction will not use about half of the light of the light source, resulting in poor use efficiency of the light from the light source. Since the alignment function element 19 is provided and emitted in a manner that only one of the polarization components is emitted, the utilization efficiency of the light source light can be increased. At this time, the first lenticular 1
Since the row of 8 and the row of the polarization alignment function element 19 are aligned and the light beam is made incident on the polarization alignment function element 19 to align the polarization directions, the efficiency of polarization conversion is improved.

Next, a description will be given of a specific example or a modified example of implementation based on the above-described embodiment.
First, FIG. 18 shows a configuration example in which the configuration shown in FIG. 12 is folded down by a cold mirror 29 for deflecting the light from the light source 6 by 90 ° in order to make the configuration shown in FIG. Show. Reference numeral 30 denotes a fan for cooling the light source 6.

FIG. 19 shows a configuration example in which the optical path length of the illumination system 7 having the configuration shown in FIG. 15 is reduced to about half by omitting the total reflection prism 8, the connecting prism 9 and the like in the configuration shown in FIG. Is shown. 31 is a lamp house. In the case of this configuration example, although some color unevenness occurs, the size of the apparatus can be significantly reduced.

FIG. 20 shows the illumination system 7 including the light source 6.
A spheroid mirror 32 is used in place of the paraboloid mirror 14, and the lamp 13 is disposed at a first focal point of the spheroid mirror 32.
An example is shown in which the illuminated surfaces of the reflective liquid crystal panels 3R, 3G, 3B come to the second focal point. According to this, the lens system optical components can be omitted particularly for the illumination system 7, and the number of components can be reduced.

FIG. 21 shows the illumination system 7 including the light source 6.
Although the rotating parabolic mirror 14 is used as the light source 6, the convex lens 1
By forming the second focal point by using the reference numeral 5 and irradiating the surfaces of the reflective liquid crystal panels 3R, 3G, and 3B to the second focal point position, an example equivalent to the configuration in FIG. 16 is obtained. Show. Compared with FIG. 16, the configuration requires only one more convex lens 15, and the number of parts can be reduced.

FIG. 22 shows an example of a more practically configured projector using the illumination system 7 having the configuration shown in FIG.
That is, the second focal point is formed by the convex lens 15 and the second focal point is formed.
The reflective liquid crystal panels 3R, 3G, and 3B are arranged so that the illuminated surfaces of the liquid crystal panels 3R, 3G, and 3B are located at the focal position. The cold mirror 29 deflects the optical axis by 90 degrees, thereby achieving compactness.

FIG. 23 is the same as the structure shown in FIG. 19 in terms of the components, but if the layout relationship is different, especially the positional relationship between the reflective liquid crystal panels 3R, 3G, 3B and the projection lens system 12 is different. It was made. That is, light from the light source 6 side passes through the polarizing beam splitter 4 and enters the dichroic prism 1 side, where
The polarization direction is modulated by R, 3G, and 3B, and the light combined by the dichroic prism 1 is converted into a polarization beam splitter 4.
And is emitted to the projection lens system 12 side. When the layout is changed in this way, the light beam to be incident on the polarization beam splitter 4 needs to be P-polarized light.
It is necessary to change the insertion position of the half-wave plate so that the polarized light is output, and it is necessary to reverse the on and off signals of the reflection type liquid crystal panels 3R, 3G, 3B. It is clear that the same effect as in the case of the above is obtained.

[0058]

According to the projector of the first aspect of the present invention, with respect to the dichroic prism as a color separation / color combining element, the red dichroic film and the blue dichroic film correspond to each other by devising a multilayer film. S
Since the maximum reflectance of one of the polarized light components of the polarized light or the P-polarized light is equivalent to or more than 80% of the maximum reflectance of the other polarized light component, the polarization dependency is reduced, It is possible to make the reflection characteristic of the polarization component at the time of color separation equal to the reflection characteristic of the polarization component at the time of color-combining the light re-entered after being modulated by, for example, a reflective liquid crystal panel as an image forming member. In addition, a function as a color separation / color synthesis element that can secure commercial value with a single element can be exhibited, and thus the size and weight of the entire projector can be reduced.

According to the projector of the second aspect of the invention, the dichroic prism as a color separation / color combining element is basically the same as in the case of the first aspect of the invention, and the red dichroic film and the blue dichroic film are used. In this case, it is desirable to match the polarization dependence, but it is not possible to actually match, so that one polarization component is constant with respect to the other polarization component. By providing a filter function that suppresses shift components, the color separation function and the color synthesis function can be color-combined with a color balance comparable to that when a projector is configured using separate optical elements. Light efficiency can be improved.

According to the third aspect of the invention, in the projector according to the first or second aspect, the incident surface of the polarizing beam splitter and the incident surface of the dichroic film of the dichroic prism are arranged so as to be substantially orthogonal. A more advantageous design becomes possible, for example, in that the tolerance of the incident angle is increased and the light use efficiency can be improved.

According to a fourth aspect of the present invention, in the projector according to the first or second aspect, the image forming member is shifted in a direction perpendicular to the optical axis, and the dichroic prism is moved with respect to the red dichroic film and the blue dichroic film. Keystone generated on the screen can be prevented by arranging the incident light so that the incident light is incident with a substantially uniform shift angle.

According to the fifth aspect of the invention, in the projector according to the first or second aspect, the generation of keystone can be basically prevented similarly to the case of the fourth aspect of the invention. Is shifted in the vertical direction with respect to the direction of the intersection line where the red dichroic film and the blue dichroic film of the dichroic prism intersect, thereby taking into account the inclination of the main optical axis of the illumination light generated due to the shift. Then, by shifting the characteristics of the dichroic film, it is possible to obtain the same performance as when no shift is applied.

According to the sixth aspect of the present invention, in order to realize the projector according to any one of the first to fifth aspects, an illumination system using a so-called integrator optical system is provided on an incident optical path, so that a substantially rectangular shape is provided. The image forming member having the shape can be illuminated with less uneven illuminance, and the quality of the projected image can be improved.

According to the seventh aspect of the present invention, in realizing the projector according to any one of the first to fifth aspects, an illumination system using a so-called integrator optical system is provided on the incident optical path, so that a substantially rectangular shape is provided. The image forming member having the shape can be illuminated with less uneven illuminance, and the quality of the projected image can be improved.

According to the invention of claim 8, in realizing the projector of claim 7, by providing the illumination system with the polarization alignment function element, most of the light from the light source is used for illumination of the image forming member. Available, increasing the efficiency of light source light use,
High brightness projection display becomes possible.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing polarization characteristics of a dichroic prism used in a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration and a polarization combining characteristic when applied to a transmission type liquid crystal panel.

FIG. 3 is an explanatory diagram showing a configuration and polarization separation / synthesis characteristics when applied to a reflection type liquid crystal panel.

FIG. 4 is a side view showing a configuration example in which a polarization beam splitter and a dichroic prism are combined and arranged so that an incident surface is parallel.

FIG. 5 is a characteristic diagram showing the angle dependence of the blue reflection.

FIG. 6 is a characteristic diagram showing the angle dependence of green transmission.

FIG. 7 is a characteristic diagram showing the angle dependence of the red reflection.

FIG. 8 is a plan view and a side view showing an example of a configuration in which a polarizing beam splitter and a dichroic prism are combined and arranged so that the incidence plane is orthogonal.

FIG. 9 is a characteristic diagram showing the angle dependence of the blue reflection.

FIG. 10 is a characteristic diagram showing the angle dependence of the green transmission.

FIG. 11 is a characteristic diagram showing the angle dependence of the red reflection.

FIG. 12 shows a configuration example of a projector according to the present embodiment, where (a) is a plan view near a dichroic prism,
(B) is an overall side view.

FIG. 13 is an overall side view illustrating a configuration example of a projector according to a second embodiment of the present invention.

14A and 14B show an overall configuration example of a projector according to a third embodiment of the present invention, wherein FIG. 14A is a plan view and FIG. 14B is a side view.

FIG. 15 is a side view showing an extracted illumination system.

FIG. 16 is a perspective view showing an integrator optical system.

FIG. 17 is a vertical sectional side view showing a configuration example of a polarization alignment function element.

FIG. 18 is a side view of a projector showing a first modification.

FIG. 19 is a side view of a projector showing a second modification.

FIG. 20 is a side view of an illumination system showing a third modification.

FIG. 21 is a side view of an illumination system showing a fourth modification.

FIG. 22 is a side view of a projector showing a fifth modification.

FIG. 23 is a side view of a projector showing a sixth modification.

FIG. 24 is a side view showing a configuration example of a conventionally proposed reflective liquid crystal projector.

FIG. 25 is a characteristic diagram showing polarization characteristics of a conventionally available dichroic prism.

FIG. 26 is an explanatory diagram showing a configuration and a polarization combining characteristic when applied to a transmission type liquid crystal panel.

FIG. 27 is an explanatory diagram showing a configuration and polarization separation / synthesis characteristics when applied to a reflective liquid crystal panel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dichroic prism 1r Red dichroic film 1b Blue dichroic 3R, 3G, 3B Reflection type image 4 Polarization beam splitter 5 Screen 6 Light source 7 Illumination system 12 Projection lens system 17 Fly-eye lens plate 18 First lenticular 19 Polarization alignment function Element 20 Second lenticular 24, 25 cylindrical lens

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Kameyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Kazuya Miyagaki 1-3-6 Nakamagome, Ota-ku, Tokyo F-term (reference) in Ricoh Co., Ltd. DA09

Claims (8)

[Claims] 1. Three reflective image forming members for forming an image to be projected by modulating a polarization state for each of a red region, a green region, and a blue region, and illuminating these image forming members. A projection lens system for projecting an image formed by the image forming member on a screen; an incident optical path from the light source to the image forming member; and a projection lens from the image forming member. Of the light from the light source on the incoming / outgoing light path where the outgoing light path toward the system overlaps.
A polarizing beam splitter that reflects one of the polarized light components and the s-polarized light component and transmits the other polarized light component in a direction different by approximately 90 °; and an optical path between the polarized light beam splitter and the three image forming members. A dichroic film for red that separates the long wavelength region of red light from the short wavelength region than green light, and a dichroic film for blue that separates the short wavelength region of blue light and the longer wavelength region than green light. With the function of guiding the light of one polarization component separated by the polarizing beam splitter among the light from the light source into a red region, a green region, and a blue region to the corresponding image forming member by color separation. The color separation / color also serves as a function of combining the lights of the respective regions, which are separated and whose polarization state is modulated by the image forming member and are incident again, and guide the light to the projection lens system via the polarizing beam splitter. The red dichroic film has a maximum reflectance of one of the S-polarized light component and the P-polarized light component of the red light of 80% or more of the maximum reflectance of the other polarized light component; The dichroic film for use comprises a dichroic prism in which the maximum reflectance of one of the S-polarized light and the P-polarized light of the blue light is 80% or more of the maximum reflectance of the other polarized light component. . 2. Three reflective image forming members for forming an image to be projected by modulating the polarization state for each of the red, green and blue color regions, and illuminating these image forming members. A projection lens system for projecting an image formed by the image forming member on a screen; an incident optical path from the light source to the image forming member; and a projection lens from the image forming member. Of the light from the light source on the incoming / outgoing light path where the outgoing light path toward the system overlaps.
A polarizing beam splitter that reflects one of the polarized light components and the s-polarized light component and transmits the other polarized light component in a direction different by approximately 90 °; and an optical path between the polarized light beam splitter and the three image forming members. A dichroic film for red that separates the long wavelength region of red light from the short wavelength region than green light, and a dichroic film for blue that separates the short wavelength region of blue light and the longer wavelength region than green light. With the function of guiding the light of one polarization component separated by the polarizing beam splitter among the light from the light source into a red region, a green region, and a blue region to the corresponding image forming member by color separation. The color separation / color also serves as a function of combining the lights of the respective regions, which are separated and whose polarization state is modulated by the image forming member and are incident again, and guide the light to the projection lens system via the polarizing beam splitter. It is arranged as a formation element, the red P-polarized light reflectance at a wavelength range of 550 nm ≦ lambda ≦ 700 nm in the dichroic film 50% and comprising a wavelength lambda _50P, the wavelength at which the reflectance of S-polarized light becomes 50% lambda _{Assuming 50S} , 10 nm ≦ | λ
_50P- λ _50S | ≦ 50 nm, and the wavelength at which the reflectance of P-polarized light is 50% in the wavelength region of 400 nm ≦ λ ≦ 550 nm in the dichroic film for blue is λ _50P , and the reflectance of S-polarized light is 50%. _Where λ _50S is the wavelength
A dichroic prism satisfying 0 nm ≦ | λ _50P −λ _50S | ≦ 50 nm. 3. The dichroic prism, wherein the red dichroic film and the blue dichroic film are arranged orthogonally, and the plane of incidence of the polarizing beam splitter and the planes of incidence of these dichroic films are substantially orthogonal to each other. 3. The device according to claim 1, wherein
The projector as described. 4. The dichroic prism, wherein the red dichroic film and the blue dichroic film are arranged orthogonally, and have a substantially uniform shift angle with respect to the red dichroic film and the blue dichroic film. The projector according to claim 1, wherein the projector is arranged so that incident light is incident on the projector. 5. The dichroic prism, wherein the dichroic film for red and the dichroic film for blue are arranged orthogonally, and the dichroic film for one of the red dichroic film and the dichroic film for blue is disposed. Is arranged such that incident light having a predetermined incident angle of less than 45 ° is incident thereon, and incident light having a predetermined incident angle of 45 ° or more is incident on the other film. The projector according to claim 1 or 2, wherein 6. An illumination system having at least a pair of fly-eye lens plates on an incident optical path from the light source to the polarization beam splitter.
6. The projector according to any one of items 5 to 5. 7. At least one fly-eye lens plate and a plurality of cylindrical lenses are arranged on an incident optical path from the light source to the polarization beam splitter, and are arranged near a condensing position of the fly-eye lens plate. An illumination system having a first lenticular provided and a second lenticular disposed downstream of the first lenticular and having a plurality of cylindrical lenses arranged in a direction orthogonal to the arrangement direction of the cylindrical lenses. The projector according to claim 1, wherein the projector is provided. 8. A polarization alignment function element for aligning a random light beam to only one polarization component on an optical path between the first lenticular and the second lenticular. Projector.