JP2007264245A - Image projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image projector which can prevent its lifetime from becoming short due to damages on the light incident side polarizer of a specific liquid crystal panel, even if the polarizing converter element has wavelength characteristics. <P>SOLUTION: Since the polarizing converter 34 has polarizing conversion efficiency that is higher in the blue or red wavelength region to operate a blue liquid crystal panel 61b or red liquid crystal panel 61r than in other visible wavelength regions; image projection is made possible for the images having brightness increased in blue or red wavelength region. Furthermore, since the light-incident side polarizer filters 62b, 62r are omitted in the blue or red liquid crystal panels 61r and 61b, it is possible to prevent the lifetime of the liquid crystal light valve from becoming short by the polarizer filters 62b, 62r damaged by comparatively strong light, i.e. blue light LB and red light LR, and to prolong the lifetime of the projector 10, as a result. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a projector that illuminates a liquid crystal panel with illumination light from a lamp light source and projects modulated light that has passed through the liquid crystal panel.

A conventional general projector includes a light source including a lamp, an illumination optical system that uniformizes and converts the light from the light source, and a color separation optical system that separates light that has passed through the illumination optical system into three colors. Three liquid crystal panels illuminated by three colors of illumination light, a cross dichroic prism that synthesizes images from these three liquid crystal panels, and a projection lens that projects a magnified image after synthesis (see Patent Document 1) . Here, a set of polarizing plates is arranged before and after each color liquid crystal panel, and the polarized light incident on the liquid crystal panel is adjusted by the set of polarizing plates,
Modulated light having a desired polarization state is extracted from the liquid crystal panel.
JP 2004-69966 A

However, in the projector as described above, a high-intensity mercury lamp is used as a light source lamp in order to improve the brightness of the image. However, after color separation, the relatively green color light is compared with other color lights. Since the light intensity is strong, it is necessary to adjust the color balance in order to use it as image light. When the amount of light is adjusted with the liquid crystal panel to adjust the color balance, the number of gradations that can be used for image modulation decreases, and the color reproducibility of the image of the projector deteriorates.

Therefore, the present invention provides a good color balance without a decrease in color reproducibility even when a light source lamp that requires color balance adjustment to form a color image by color separation and color synthesis is used. An object is to provide a simple projector.

In order to solve the above-described problems, a projector according to the present invention provides (a) light source light having spectral characteristics in which the intensity of light in the wavelength region that becomes green light is stronger than the intensity of light in the wavelength region that becomes blue light and red light. (B) a color separation optical system that separates illumination light emitted from the illumination device into a plurality of color lights, and (c) a plurality of color lights separated by the color separation optical system. A liquid crystal light valve for each color that is modulated according to image information; and (d) a light combining optical system that combines image light of each color modulated by the liquid crystal light valve. In this projector, (e) a polarizing filter on the incident side is omitted in at least one of the liquid crystal light valve that modulates red light and the liquid crystal light valve that modulates blue light, and (f) In the liquid crystal light valve that modulates the green light, an incident side polarization filter is provided. Note that the image light combined by the light combining optical system is enlarged and projected onto a screen, for example, by a projection lens.

In the projector described above, even if the light source device emits light source light having a spectral characteristic that is stronger than the intensity of light in the wavelength region of green light and red light, the red light is modulated. In at least one of the liquid crystal light valve that modulates blue light and the liquid crystal light valve that modulates blue light, the incident side polarizing filter is omitted, and in the liquid crystal light valve that modulates green light, the incident side polarizing filter is provided. Therefore, it is possible to project an image in which the light intensity of at least one of the red light and blue light is increased.
Here, the polarizing filter is composed of a polarizing film and a support layer that supports the polarizing film, and the polarizing layer transmits one polarized component of incident light and blocks the other polarized component. Even for the light of the polarization component, the transmittance is not 100%, and the amount of light is reduced. Therefore, by omitting the polarization filter on the incident side of the liquid crystal light valve that modulates at least one of red light and blue light whose intensity is relatively weak due to the spectral characteristics of the light source device, red light and blue light are omitted. The light quantity loss of at least one of the color lights can be reduced.

Further, by omitting the incident side polarizing filter of at least one of the liquid crystal light valve that modulates red light and the liquid crystal light valve that modulates blue light, the liquid crystal is compared with the case where the polarizing filter is not omitted. Polarization components other than the desired polarization component of the light incident on the light valve will also enter the liquid crystal light valve. However, the projector has a polarization conversion device, and blue light and red light have a relative luminous sensitivity. The contrast is relatively low, and the decrease in contrast is not noticeable when the incident side polarizing filter is omitted. For example, when the polarization conversion device achieves the highest polarization conversion efficiency with blue light, the color temperature of the projected image can be increased. Further, when the polarization conversion device achieves the highest polarization conversion efficiency with red light, it is possible to increase the white balance of the projected image.
Therefore, even if the light emitted from the light source device has higher intensity of green light than red light and blue light, at least one liquid crystal light valve that modulates red light and liquid crystal light valve that modulates blue light is used. By omitting the polarizing filter on the incident side of the light valve, the amount of adjustment of the color balance by the liquid crystal light valve can be reduced without conspicuous deterioration of the contrast. The color reproducibility of the image projected by the projector can be improved. Further, since the polarizing filter on the incident side of at least one of the liquid crystal light valve that modulates red light and the liquid crystal light valve that modulates blue light is omitted, the number of parts and the number of manufacturing steps of the projector can be reduced. It is also possible to reduce the price.

Further, according to a specific aspect or aspect of the present invention, in the projector, the polarization conversion device may emit green light in at least one of a wavelength region that becomes the red light and a wavelength region that becomes the blue light. The polarization conversion efficiency is higher than that in the wavelength region. Since the polarization conversion device has higher polarization conversion efficiency than the wavelength region of green light in at least one of the wavelength region of red light and the wavelength region of blue light, red light and blue light It is possible to project an image in which at least one of the luminances is increased.

According to another aspect of the present invention, in the projector described above, the polarization converter includes a polarization separation film that is inclined with respect to the optical axis and separates incident light into two polarization components by transmission and reflection, and polarization separation. A retardation plate that converts the polarization of one polarization component separated by the film into the other polarization component. Further, in this projector, by adjusting the loss upon transmission or reflection between the polarization separation film and the retardation plate, green light is emitted in at least one of the wavelength region for red light and the wavelength region for blue light. A polarization conversion efficiency that is relatively higher than the wavelength region is achieved. In this case, the polarization conversion device can be composed of a polarization separation film and a retardation plate, and efficient polarization conversion can be achieved with a desired wavelength characteristic with a simple device.

According to another aspect of the present invention, a light source device includes a mercury lamp that is a light emission source, and a concave mirror that collects light from the mercury lamp. In this case, even if the green light used as illumination light with high luminance is an optical mercury lamp whose light intensity is relatively higher than that of red light and blue light, the reduction in contrast is conspicuous as described above. Thus, the projector can project an image with good color balance.

[First Embodiment]
FIG. 1 is a conceptual diagram illustrating the configuration of the optical system of the projector according to the first embodiment of the invention.

The projector 10 is an optical device for modulating a light beam emitted from a light source according to image information to form a color optical image and enlarging and projecting the optical image on a screen. The illumination optical system 30, the color separation device 40, the light modulator 60, the cross dichroic prism 70, and the projection optical system 80 are configured. Here, the light source lamp unit 20 and the illumination optical system 30 constitute an illumination device that generates illumination light to be supplied to the color separation device 40 and the like.

The light source lamp unit 20 is a light source device that collects and emits light beams emitted from the light source lamp 21 to the surroundings and illuminates the light modulation unit 60 via the illumination optical system 30 and the like, and is a light source lamp that is a light emitting tube. 21, a concave mirror 22 that is a concave ellipse that reflects the light source light emitted from the light source lamp 21, and a concave lens 23 that collimates the light source light reflected by the concave mirror 22.
In the light source lamp unit 20, the light source light emitted from the light source lamp 21 is collimated through the concave mirror 22 and the concave lens 23 and emitted to the front side, that is, the illumination optical system 30 side.

The above-described light source lamp 21 is normally a mercury lamp in that it can emit high-luminance light. However, the light source lamp unit 20 is not limited to the mercury lamp. However, although the light emitted from the light source lamp 21 has high luminance, the light intensity of green light is higher than the light intensity of red light or blue light. Further, various concave mirrors such as a paraboloid can be used in place of the elliptical concave mirror 22 described above. When a parabolic concave mirror is used, a parallel light beam can be emitted from the light source lamp unit 20 without providing the concave lens 23 or the like after the concave mirror 22.

The illumination optical system 30 equalizes the illuminance by dividing the light beam emitted from the light source lamp unit 20 into a plurality of partial light beams and superimposing them on the target illumination area, and making it incident.
An optical system that converts illumination light into polarized light in a specific direction, and includes a first lens array 31, a second lens array 32, a polarization conversion device 34, and a superimposing lens 35.

The first lens array 31 has a function as a light beam splitting optical element that splits a light beam emitted from the light source lamp 21 into a plurality of partial light beams, and is arranged in a matrix in a plane orthogonal to the system optical axis OA. A plurality of small lenses are provided. The contour shape of each small lens is set so as to be almost similar to the shape of the image forming area of the liquid crystal panels 61b, 61g, 61r constituting the light modulation unit 60 described later. The second lens array 32 is an optical element that collects a plurality of partial light beams divided by the first lens array 31 described above, and in the same manner as the first lens array 31, a matrix is formed in a plane orthogonal to the system optical axis OA. However, since it is intended to collect light, the contour shape of each small lens accurately corresponds to the shape of the image forming area of the liquid crystal panels 61b, 61g, 61r. There is no need.

The polarization conversion device 34 is formed of a PBS array, and has a role of aligning the polarization directions of the partial light beams divided by the first lens array 31 and individually emitted from the second lens array 32 to one-way linearly polarized light.

FIG. 2 is a plan view illustrating a specific structure of the polarization conversion device 34. This polarization conversion device 34 includes prism bodies 91, 92, 93, a polarization separation film 95, a phase difference plate 96, and a reflection film 9.
7.

The prism bodies 91, 92, and 93 are all translucent members formed of glass or the like.
The central prism body 91 through which the system optical axis OA passes has a triangular prism shape whose bottom surface (surface parallel to the paper surface) is a right triangle. Further, the two prism bodies 92 and 93 provided on the left and right sides of the prism body 91 have a quadrangular prism shape whose bottom surface is a parallelogram, and are arranged symmetrically with respect to the system optical axis OA. Has been.

The polarization separation film 95 is formed between the pair of prism bodies 91 and 92 or between the pair of prism bodies 91 and 9.
3 is arranged in a state inclined by 45 ° with respect to the incident light IL, and as a polarization separation element (polarization beam splitter) made of a dielectric multilayer film, P contained in the light beam of the incident light IL
Of the polarized light beam and the S-polarized light beam, one polarized light beam is transmitted and the other polarized light beam is reflected.
Here, the polarization separation film 95 causes the P-polarized light out of the polarization components of the incident light IL incident on the polarization conversion device 34 to travel straight as the first polarization PP, and bends the S-polarization as the second polarization SS by reflection. Shall be separated by The polarization separation film 95 is formed, for example, on one inclined side surface of the prism bodies 92 and 93 by using various film forming methods including vapor deposition.

The phase difference plate 96 is provided on the exit side of the prism body 91, and converts the first polarization PP, which is P-polarized light transmitted through the polarization separation film 95, into S-polarization as a half-wave retardation plate made of a birefringent material. To do.

The reflective film 97 is disposed between the adjacent prism bodies 92 and 92 or between the prism bodies 93 and 93 so as to be inclined by 45 ° with respect to the incident light IL. That is, the reflective film 97 is disposed in parallel to face the polarization separation film 95 with the prism bodies 92 and 93 interposed therebetween. The reflection film 97 is a second reflection element reflected by the polarization separation film 95 as a reflection element made of a dielectric multilayer film.
By further reflecting the polarized light SS, the optical path is converted in the same direction as the first polarized light PP.

Although not described above, similar prism bodies 92 and 93 are continuously arranged outside the prism bodies 92 and 93 arranged on both sides of the system optical axis OA, and polarization conversion is performed. The square plate-like outer shape of the device 34 is formed. At this time, the polarization separation film 95 and the reflection film 97
Are arranged alternately between the prism bodies 92 and 93, and the phase difference plate 96 is composed of the polarization separation film 95.
Is attached to the exit surface of every other prism body 92, 93. Here, the retardation plate 96 is disposed on the optical path of the first polarization PP that passes through the polarization separation film 95, but can be disposed on the optical path of the second polarization SS that is reflected by the reflection film 97. . In this case, the reflective film 97
The second polarized light SS, which is S-polarized light reflected at, is converted to P-polarized light.

In the polarization converter 34 described above, the incident light IL incident substantially along the system optical axis OA is emitted from the opposite side of the polarization converter 34 with the polarization directions of all the polarized light beams being aligned. By using such a polarization conversion device 34, it is possible to align the light beam emitted from the light source lamp 21 with a polarized light beam in one direction, so that the utilization factor of the light source light used in the light modulation unit 60 is improved. Can do.

FIG. 3 is a graph for explaining the polarization conversion efficiency by the polarization converter 34. In this graph, the horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance. In the graph, the dotted line indicates the polarization separation film 95.
Indicates the transmittance of the second polarized light SS reflected by the reflective film 97 and emitted, and the one-dot chain line is
The transmittance of the first polarized light PP which is transmitted through the polarization separation film 95 and is emitted after being subjected to polarization conversion by the phase difference plate 96 is shown. The solid line indicates the transmittance obtained by adding both polarizations SS and PP, that is, the polarization conversion efficiency to the specific polarization by the polarization converter 34. In this example, the polarization conversion efficiency is the highest in the blue (B) color, and the polarization conversion efficiency is the lowest in the red (R) color. The polarization conversion efficiency of green (G) color is about the middle between blue and red. Thus, when the blue polarization conversion efficiency is high, even when the light source lamp 21 emits white light source light, the relative intensity of blue increases and the color temperature of the illumination light emitted from the illumination optical system 30 is reduced. Can be high.

The wavelength characteristics in the polarization conversion efficiency as described above are caused by a loss in transmission or reflection through the polarization separation film 95, the phase difference plate 96, the reflection film 97, and the like. It is greatly affected by dependencies. Here, it is conceivable to make the polarization separation characteristic of the polarization separation film 95 flat with less wavelength dependency, but the polarization separation film 95 becomes extremely expensive. For this reason, the polarization separation characteristic of the polarization separation film 95 is mainly set to a specific wavelength (in this case,
If it is adapted to blue), the polarization separation film 95 can be made inexpensive and with relatively little loss. However, for other wavelengths (in this case, green and red), a slight relative dimming occurs, but an increase in specific blue light in the illumination light increases the color temperature of the illumination light. Therefore, in an application where a high color temperature is desired, an illumination light suitable for the application can be obtained. In particular, when the light source lamp 21 is composed of a mercury lamp, the luminance of blue or the like tends to be relatively small with respect to the luminance of green, and it is desirable to improve the utilization efficiency of blue light. As a result, the color balance of the image light is improved.

In the above example, the polarization conversion efficiency of the polarization conversion device 34 is highest in blue and relatively low in other colors. However, the polarization conversion efficiency is highest in red. It is also possible to design. In this way, when red has the highest polarization conversion efficiency, it cuts green and blue, and for the mercury lamp, the white balance is improved and the polarization conversion efficiency of green and blue is further reduced. In this case, an effect as if a cinema filter was incorporated in the illumination optical system 30 can be obtained.

Returning to FIG. 1, the superimposing lens 35 condenses a plurality of partial light beams that have passed through the first lens array 31, the second lens array 32, and the polarization conversion device 34, and liquid crystal panels 61 b, 61 g, 61.
This is an optical element that is superimposed on the image forming area r. This superimposing lens 35
Are emitted to the next color separation device 40 while being made uniform. That is, the illumination light that has passed through both the lens arrays 31 and 32 and the superimposing lens 35 passes through the color separation device 40 described in detail below, and then the illumination region of the light modulator 60, that is, the liquid crystal panels 61b, 61g, and 61r for each color.
The image forming area is uniformly superimposed and illuminated.

The color separation device 40 includes first and second dichroic mirrors 41 a and 41 b and a reflection mirror 4.
2a, 42b, 42c, field lenses 43b, 43g, 43r, and relay lens 4
5 and 46. Among these, the color separation optical system including the first and second dichroic mirrors 41a and 41b uses illumination light as blue (B) light, green (G) light, and red (R).
) Separated into three luminous fluxes of light. Each dichroic mirror 41a, 41b is an optical element obtained by forming on a transparent substrate a dielectric multilayer film having a wavelength selection function of reflecting a light beam in a predetermined wavelength region and transmitting a light beam in another wavelength region. Yes, they are arranged in an inclined state with respect to the system optical axis OA. The first dichroic mirror 41a is blue / green / red (B / G
Of the three colors R), the blue light LB is reflected and the green light LG and the red light LR are transmitted. The second dichroic mirror 41b reflects the green light LG out of the incident green light LG and red light LR and transmits the red light LR. The field lenses 43b, 43g, and 43r for each color provided on the emission side of the color separation device 40 are configured so that each partial light beam emitted from the second lens array 32 and incident on the light modulation unit 60 has an appropriate degree of convergence. Is provided. The pair of relay lenses 45 and 46 are disposed on the third optical path OP3 for red which is relatively longer than the first optical path OP1 for blue and the second optical path OP2 for green. These relay lenses 45 and 46 are
By transmitting the image formed immediately before the first relay lens 45 on the incident side to the field lens 43r on the emission side as it is, a decrease in light use efficiency due to light diffusion or the like is prevented.

In the color separation device 40, the illumination light incident from the light source lamp unit 20 via the illumination optical system 30 first enters the first dichroic mirror 41a. The blue light LB reflected by the first dichroic mirror 41a is guided to the first optical path OP1, and enters the final stage field lens 43b via the reflection mirror 42a. The first dichroic mirror 41a
The green light LG that has passed through and reflected by the second dichroic mirror 41b passes through the second optical path OP2.
Is incident on the last stage field lens 43g. Further, the red light LR that has passed through the second dichroic mirror 41b is guided to the third optical path OP3, and the reflection mirrors 42b and 42c.
Then, the light enters the field lens 43r at the final stage through the relay lenses 45 and 46.

The light modulation unit 60 includes three liquid crystal panels (liquid crystal display panels) 61b, 61g, and 61r on which the three colors of illumination lights LB, LG, and LR are respectively incident. Of these, the blue liquid crystal panel 6
For 1b, the polarizing filter 62b is disposed only on the exit side, and no polarizing filter is disposed on the incident side. On the other hand, for the other color liquid crystal panels 61g and 61r, two sets of polarizing filters 62g and 62r are arranged so as to sandwich the liquid crystal panels 61g and 61r. Here, the liquid crystal panel 61b for the blue light LB and the polarizing filter 62b provided on the emission side constitute a liquid crystal light valve for two-dimensionally modulating the illumination light based on image information. The liquid crystal panel 61g for green light LG and the pair of polarizing filters 62g and 62g sandwiching the liquid crystal panel also constitute a green liquid crystal light valve, and similarly, the liquid crystal panel 61r for red light LR and a pair of polarized light. The filters 62r and 62r also constitute a liquid crystal light valve for red. Each of the liquid crystal panels 61b, 61g, 61r is a liquid crystal which is an electro-optical material sealed between a pair of transparent glass substrates. For example, each of the liquid crystal panels 61b, 61g, 61r is a polysilicon TFT as a switching element, The polarization direction of the polarized light beam incident on the light is modulated.

In the light modulation unit 60, the blue light LB guided to the first optical path OP1 enters the illumination area provided at the position of the liquid crystal panel 61b via the field lens 43b and illuminates the image forming area in the liquid crystal panel 61b. . The green light LG guided to the second optical path OP2 enters the illumination area provided at the position of the liquid crystal panel 61g via the field lens 43g and illuminates the image forming area in the liquid crystal panel 61g. The red light LR guided to the third optical path OP3 enters the illumination area provided at the position of the liquid crystal panel 61r via the first and second relay lenses 45 and 46 and the field lens 43r, and forms an image in the liquid crystal panel 61r. Illuminate the area. Each liquid crystal panel 61b,
61g and 61r are non-luminous and transmissive light modulators for changing the spatial distribution of the polarization direction of incident illumination light. The color lights LB, LG, and LR incident on the liquid crystal panels 61b, 61g, and 61r are polarized in units of pixels in accordance with drive signals or control signals input as electrical signals to the liquid crystal panels 61b, 61g, and 61r. The state is adjusted. At that time, the polarization direction of the illumination light incident on the liquid crystal panels 61g and 61r is adjusted by the polarization filters 62g and 62r, and the light is emitted from the liquid crystal panels 61b, 61g and 61r by the polarization filters 62b, 62g and 62r. Modulated light of a predetermined polarization direction is extracted from the light.

Here, the polarizing filter 62b is not provided on the incident side of the liquid crystal panel 61b as described above. When the polarization filter 62b on the incident side is removed in this way, generally, light of a polarization component other than the light of the desired polarization component is incident on the liquid crystal panel 61b, and therefore is not blocked by the polarization filter 62b when displaying a black image. It is considered that light of a polarization component, that is, polarized light having a small extinction ratio on a black screen is incident, which causes a decrease in contrast. However, blue light and red light have low specific visibility, and even if there is a slight deterioration in light modulation characteristics such as contrast with respect to these colors, it is difficult to obstruct projected image viewing. That means
For blue light, even if the polarization filter 62b on the incident side is omitted, a decrease in contrast due to the omission of the polarization filter 62b is not noticeable. On the other hand, the illuminance of the blue light LB guided to the first optical path OP1 is the green light GL and the red light LR guided to the other optical paths OP2 and OP3.
It is larger than the illuminance. This is due to the polarization conversion efficiency of the polarization conversion device 34 described with reference to FIG. 3, and is caused by the fact that the polarization conversion rate of the blue light LB is higher than that of the other green light GL and red light LR. When the blue light LB having such a large illuminance is first incident on the polarizing filter 62b in the blue light valve, the polarizing filter 62b deteriorates severely. However, in this embodiment, the incident-side polarizing filter 62b is omitted. Because
The durability of the light modulation unit 60 as a whole can be enhanced, and the life of the light modulation unit 60 and the projector 10 can be extended. Further, by omitting the incident-side polarizing filter 62b, cost reduction can be achieved by reducing the number of components.

If the incident-side polarizing filter 62b is omitted as described above, the illuminance of the blue light LB incident on the liquid crystal panel 61b slightly increases. However, the amount of removal of the polarizing filter 62b is sufficient for the incident side of the liquid crystal panel 61b. Since a large space is formed and the cooling efficiency of the liquid crystal panel 61b is increased, a phenomenon in which the deterioration rate of the liquid crystal panel 61b particularly increases was not observed. Rather, as a result of efficiently cooling the liquid crystal panel 61b, the noise of the cooling fan can be reduced, and the power consumption of the projector 10 can be reduced.

In the above example, the incident-side polarizing filter 62b is omitted in the first optical path OP1, but the incident-side polarizing filter 62r can be omitted in the red third optical path OP3. In particular, when the polarization conversion efficiency of the polarization converter 34 is highest in red instead of blue, the white balance of the projected image can be increased by omitting the incident side polarization filter 62r.

The cross dichroic prism 70 is a light combining optical system that forms a color image by combining optical images modulated for each color light emitted from the polarization filters 62b, 62g, and 62r. The cross dichroic prism 70 has a substantially square shape in plan view in which four right angle prisms are bonded together, and a pair of dielectric multilayer films 71 and 72 intersecting in an X shape are formed at the interface where the right angle prisms are bonded to each other. Is formed. One first dielectric multilayer film 71 reflects blue light, and the other second dielectric multilayer film 72 reflects red light. The cross dichroic prism 70 reflects the blue light LB from the liquid crystal panel 61b by the first dielectric multilayer film 71 and emits the green light LG from the liquid crystal panel 61g to the first and second dielectrics. Multilayer film 71
, 72, and the red light LR from the liquid crystal panel 61r is reflected by the second dielectric multilayer film 72 and emitted to the left in the traveling direction.

The image light combined by the cross dichroic prism 70 in this way is projected as a color image on a screen (not shown) at an appropriate magnification through a projection optical system 80 as a magnification projection lens.

As is clear from the above description, according to the projector 10 of the present embodiment, the polarization conversion device 34 has another wavelength in the blue or red wavelength region in which the blue liquid crystal panel 61b or the red liquid crystal panel 61r is operated. Since the polarization conversion efficiency is higher than that in the visible wavelength range, it is possible to project an image with increased luminance in the blue or red wavelength range. Further, when a high-pressure mercury lamp that emits light with high luminance but with a light intensity of green light stronger than that of red light or blue light is used for the light source lamp 21, conventionally, for example, when projecting a white screen Even so, in order to improve the color balance of the projected image, the luminance of the green light LG is reduced by the modulation of the liquid crystal panel 61g. However, according to the projector 10 of the present embodiment, the polarization conversion device 34 is provided with green light, although the number of gradations used for modulation for forming a projected image is reduced and the color reproducibility is deteriorated. The liquid crystal panel 61g is lower than the polarization conversion efficiency in the wavelength region of blue light or red light.
Is relatively blocked by the polarizing filter 62g on the incident side, the amount of gradation that can be used in the liquid crystal panel 61g for color balance adjustment can be reduced or eliminated, and modulation for forming a projected image can be achieved. It is possible to increase the number of gradations used for the color tone and improve the color reproducibility.

Here, the polarizing filter is composed of a polarizing film and a support layer that supports the polarizing film, and the polarizing layer transmits one polarized component of incident light and blocks the other polarized component. Even for the light of the polarization component, the transmittance is not 100%, and the amount of light is reduced. Therefore, a liquid crystal light valve that modulates at least one of red light and blue light whose intensity is weak due to the spectral characteristics of the light source device, that is, the light source lamp 21, is omitted, that is, the polarizing filter on the incident side of the liquid crystal panels 61r and 61b. Thus, it is possible to reduce the light amount loss of at least one of the red light LR and the blue light LB.

In addition, at least one liquid crystal light valve (that is, at least one of the liquid crystal panels 61r, 61) among the liquid crystal light valve that modulates red light and the liquid crystal light valve that modulates blue light.
By omitting the incident side polarization filter of b), the polarization components other than the desired polarization component of the light incident on the liquid crystal panels 61r and 61b are also added to the liquid crystal panels 61r and 61b as compared with the case where the polarization filter is not omitted. The projector 10 is provided with the polarization conversion device 34, and the blue light LB and the red light LR have relatively low relative visibility, and the contrast of the incident light when the incident side polarization filter is omitted. The decrease is not noticeable.

Furthermore, if the luminance can be increased in the wavelength region of the blue light LB, the color temperature of the projected image can be increased. Further, if the luminance can be increased in the wavelength region of the red light LR, the white balance of the projected image can be increased.

Therefore, even if the light emitted from the light source device, that is, the light source lamp 21, has higher intensity of green light than red light and blue light, the liquid crystal light valve that modulates red light and the liquid crystal light valve that modulates blue light By omitting the polarizing filter on the incident side of at least one liquid crystal light valve (that is, at least one of the liquid crystal panels 61r and 61b), the adjustment amount of the color balance by the liquid crystal light valve can be reduced without conspicuous deterioration in contrast. Therefore, the decrease in the number of gradations during image formation can be reduced, and the color reproducibility of the image projected by the projector can be improved. Further, the polarizing filter on the incident side of at least one of the liquid crystal light valve for modulating red light (liquid crystal panel 61r) and the liquid crystal light valve for modulating blue light (liquid crystal panel 61b) is omitted. The number of parts and the number of manufacturing steps can be reduced, and the projector 10 can be made inexpensive.

Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and can be implemented in various modes without departing from the gist thereof. Such modifications are also possible.

That is, in the above embodiment, the polarization conversion device 34 has the highest polarization conversion efficiency of either blue or red, but both the blue and red polarization conversion efficiencies can be increased. In this case, the incident side polarization filters 62b and 62r can be omitted in the first optical path OP1 for blue and the third optical path OP3 for red.

Further, in the projector 10 of the above embodiment, a mercury lamp is also used as the light source lamp 21, but the spectrum in which the intensity of light in the wavelength region that becomes green light is stronger than the intensity of light in the wavelength region that becomes blue light and red light. If the light source device emits light source light having characteristics, the same effect can be obtained by applying the configuration of the present invention.

In the projector 10 of the above embodiment, the illumination optical system 30 is replaced with the lens arrays 31 and 3.
2, the polarization conversion device 34 and the superimposing lens 35 are used. However, the lens arrays 31 and 32 can be omitted, or can be replaced with a rod integrator.

Further, the present invention can be applied to a front projection type projector that projects from the side that observes the projected image and a rear projection type projector that projects from the side opposite to the side that observes the projected image.

It is a top view for demonstrating the optical system of the projector which concerns on 1st Embodiment. It is a figure explaining the polarization converter incorporated in the projector of FIG. It is a graph explaining the polarization conversion efficiency by the polarization converter of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Projector, 20 ... Light source lamp unit, 21 ... Light source lamp, 22 ... Concave mirror, 30 ... Illumination optical system 31, 32 ... Lens array, 34 ... Polarization converter, 3
5 ... Superimposing lens, 40 ... Color separation device, 41a, 41b ... Dichroic mirror, 4
2a, 42b, 42c ... reflective mirror, 43b, 43g, 43r ... field lens,
45, 46 ... relay lens, 60 ... light modulator, 61b, 61g, 61r ... liquid crystal panel, 62b, 62g, 62r ... polarizing filter, 62g, 62r ... incident side polarizing filter, 62b, 62g, 62r ... exit side Polarization filter, 70: Cross dichroic prism, 80: Projection optical system, 91, 92, 93 ... Prism body, 95 ... Polarization separation film, 96 ... Phase difference plate, 97 ... Reflection film, LB, LG, LR ... Illumination light, OA ... System optical axis

Claims (4)

A light source device that emits light source light having spectral characteristics that are stronger than the intensity of light in the wavelength region that becomes blue light and red light, and the light source light emitted from the light source device. An illumination device having a polarization conversion device that aligns the polarization direction;
A color separation optical system that separates the illumination light emitted from the illumination device into a plurality of color lights of the blue light, the red light, and the green light;
A liquid crystal light valve for each color that modulates the plurality of color lights separated by the color separation optical system according to image information;
A projector comprising a light combining optical system for combining image light of each color modulated by the liquid crystal light valve,
In at least one liquid crystal light valve of the liquid crystal light valve that modulates the red light and the liquid crystal light valve that modulates the blue light, the incident side polarization filter is omitted,
A projector provided with an incident side polarization filter in the liquid crystal light valve for modulating the green light. The polarization conversion device is a projector having a polarization conversion efficiency higher than that of a green light wavelength region in at least one of a wavelength region of red light and a wavelength region of blue light. The polarization conversion device is arranged to be inclined with respect to the optical axis and separates incident light into two polarization components by transmission and reflection, and the polarization of one polarization component separated by the polarization separation film to the other A retardation plate for converting into a deflection component, and by adjusting loss during transmission or reflection between the polarization separation film and the retardation plate, the wavelength region for red light and the wavelength region for blue light are adjusted. 3. The projector according to claim 2, wherein a polarization conversion efficiency relatively higher than that of the green light wavelength region is achieved in at least one wavelength region. The projector according to claim 3, wherein the light source device includes a mercury lamp that is a light emitting source, and a concave mirror that collects light from the mercury lamp.

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