JP2003295317A - Projection type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To divert a projection type display device for data display use to a projection type display device for home theater use without altering the optical system extending from a light source to a projection lens. <P>SOLUTION: The projection type display device having an optical system including a light source 1, color separating means 8a and 8b which separate the light emitted by the light source into three primary color light beams of red, green, and blue, three image forming means 10R, 10G, and 10B which each form an image by modulating one corresponding primary color light beams among the three primary color light beams according to an applied video signal, a composing means 11 which composes the three images formed by the three image forming means, and a projecting means 12 which enlarges and projects the image composed by the composing means is characterized in that an optical wavelength selecting means 15 which has lower light transmissivity in a predetermined wavelength band is arranged on the light-emitting surface side of the projecting means 12. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device such as a liquid crystal projector for enlarging and projecting an image formed on a light valve such as a liquid crystal panel onto a screen.

[0002]

2. Description of the Related Art A liquid crystal projector, which is a projection type display device using a liquid crystal panel for a light valve, is mainly used as one of presentation tools, that is, as a data projector, but in recent years, home theater applications are becoming widespread. .

FIG. 9 shows the structure of an optical system of a conventional liquid crystal projector. In the figure, 1 is a lamp 2 and a reflecting mirror 3.
A light source 101, illumination light emitted from the light source 1, 4 a first multi-lens array, 5 a second multi-lens array, 7 condenser lenses 10R, 10
G and 10B are three liquid crystal light valves corresponding to the three primary colors of R, G and B, 18a, 18b, 18c and 18d are reflection mirrors, and 8a and 8b are first and second dichroic that reflect light of a specific wavelength. Mirrors, 19a, 19b are first and second relay lenses, 9R, 9G, 9B are R, G, B
Collimator lens corresponding to each color, 11 dichroic prism, 12 projection lens, 13 screen, 1
00 is a projector main body.

The reflecting surface of the reflecting mirror 3 of the light source 1 is generally a parabolic surface, and by arranging the light emission center of the lamp 2 at the focal point of the parabolic surface, the illumination light 101 having a substantially parallel luminous flux can be obtained.
The parallel luminous flux 101 has an uneven illuminance distribution in a cross section perpendicular to the traveling direction (optical path) thereof, and uneven brightness occurs in the projected image as it is. Therefore, by passing through a multi-lens array consisting of small convex lenses that are cut out so that their contours become substantially rectangular, the illuminance distribution in the cross section of the light that illuminates the liquid crystal light valve becomes substantially uniform. I have to.

That is, the illumination light 101 enters the first multi-lens array 4 and is divided into a plurality of light beams by the small convex lens. The split luminous flux is used by the second multi-lens array 5
Are incident on the corresponding small convex lenses, and are emitted as a condensed light flux by the condenser lens 7. The light beam emitted from the condenser lens 7 has its optical path bent by the reflection mirror 18a and enters the first dichroic mirror 8a. The first dichroic mirror 8a has a characteristic of transmitting the red wavelength band and reflecting the green wavelength band and the blue wavelength band. The red illumination light 101R is transmitted in the direction of the reflection mirror 18b, and the green illumination light is emitted. 101G and the blue illumination light 101B are reflected toward the second dichroic mirror 8b. The illumination light 101R transmitted through the first dichroic mirror 8a illuminates the liquid crystal panel 10R via the reflection mirror 18b and the collimator lens 9R.

Since the second dichroic mirror 8b has a characteristic of transmitting the blue wavelength band and reflecting the green wavelength band, the illumination light 101G reflected by the first dichroic mirror 8a is reflected by the second dichroic mirror 8b. The liquid crystal panel 10G is illuminated through the collimator lens 9G by bending the optical path by the optical path, and the illumination light 101B reflected by the first dichroic mirror 8a passes through the second dichroic mirror 8b and then passes through the first relay. Lens 19a, reflection mirror 18c, second relay lens 1
The liquid crystal panel 10B is illuminated via 9b, the reflection mirror 18d, and the collimator lens 9B.

The liquid crystal panels 10R, 10G and 10B respectively modulate incident light in accordance with an applied video signal to generate red,
An image of each color of green and blue is formed. The light of these images is combined by the dichroic prism 11 to become white light 102 (here, a white image is projected) again, and is enlarged and formed as a projection image on the screen 13 via the projection lens 12.

[0008]

When the liquid crystal projector having the above-mentioned configuration is used for data display, that is, when the data projector is used, high brightness is usually prioritized over color reproduction. First dichroic mirror 8 for determining the hue of each of red), G (green), and B (blue) monochromatic light
It is necessary to minimize the light loss in a and the second dichroic mirror. However, if the light loss is reduced, the amount of yellow component mixed in the illumination light 101R, 101G for illuminating the liquid crystal panels 10R, 10G increases, and becomes yellowish red light and greenish light, respectively. Therefore, in order to prevent the color reproduction level from actually being a problem when used as a data projector,
Hue correction is performed by optimizing the first dichroic mirror 8a and the second dichroic mirror 8b, or by adding a dichroic filter (not shown).

The color-correcting dichroic filter is usually formed on the collimator lenses 9R and 9G as a multi-layer coating, or in the case of a red light path, between the first dichroic mirror 8a and the liquid crystal panel 10R. Second dichroic mirror 8 for green light path
It is arranged as a 0-degree incidence filter between b and the liquid crystal panel 10G.

However, the color reproduction level is often insufficient for home theater applications only by optimizing the dichroic mirror and color correction by the dichroic filter. Therefore, in order to manufacture a liquid crystal projector as a projector for home theater use, a dichroic mirror has a dedicated specification, and a dichroic filter for color correction formed as a multilayer film coating on a collimator lens, or a dichroic mirror and a liquid crystal panel. The dichroic filter placed between and must be specially designed to have a large yellow component reduction effect. That is, in order to manufacture a liquid crystal projector for home theater by diverting a liquid crystal projector for data display, it is necessary to change the optical system.

As a method of diverting a liquid crystal projector for data display to a liquid crystal projector for home theater, the property that the transmission characteristics of dichroic parts depend on the incident angle is used, and the hue is changed by changing the incident angle of illumination light. However, there is a drawback in that an extra space is required in the optical axis direction to change the incident angle and the optical system becomes large.

Further, when the liquid crystal projector for data display is used as the liquid crystal projector for home theater, there is another problem as described below. That is, the contrast of the liquid crystal panel has wavelength dependence as shown in FIG. 10, the contrast is low in the short wavelength region (blue region), and it tends to be bluish during black display. In particular, for home theater applications where the use environment is dark, the relative luminous efficiency curve shown in FIG. 11 is from the photopic adaptation (the photopic photopic sensitivity, and light of 555 nm looks the brightest) to the photopic adaptation (the photopic ratio). The visibility is close to that of 507 nm light and the blue light with a short wavelength appears relatively bright, resulting in an image with insufficient visual contrast. .

As described above, the required performance differs between the projector for home theater and the projector for data display, and when the projector for home theater is diverted to manufacture the projector for data display, the optical performance is required. Since it is necessary to change the system, production costs and management costs are high, and when the projector for data display is used for home theater, the environment in which it is used causes a difference in the environment, so there is the problem that sufficient contrast cannot be obtained in the image. is there.

The present invention has been made in view of the above problems, and it is an object of the present invention to directly use a projector for data display without changing its optical system when manufacturing a projector for home theater. It is possible. It is another object of the present invention to enable a projector for home theater use manufactured by diverting a projector for home theater use to project an image with a sufficient contrast even in a dark environment.

[0015]

[Means for Solving the Problems] In order to achieve the above object,
According to the invention described in claim 1, a light source, a color separation means for separating light emitted from the light source into three primary color lights of red, green and blue, and the three primary colors according to an applied video signal. Three image forming means for respectively modulating one corresponding primary color light of the light to form an image, a synthesizing means for synthesizing the three images formed by the three image forming means, and a synthesizing means of the synthesizing means. In a projection display device having an optical system including a projection unit for enlarging and projecting an image, an optical wavelength selection unit having a light transmittance reduced in a specific wavelength band is arranged on the emission surface side of the projection unit. Is characterized by.

According to a second aspect of the present invention, in the first aspect of the invention, the transmittance of the optical wavelength selecting means in the yellow wavelength band is in the blue wavelength band and in the green wavelength band. It is characterized by being lower than the transmittance.

In order to achieve the above-mentioned other object, the invention according to claim 3 is applied with a light source, and color separation means for separating light emitted from the light source into three primary color lights of red, green and blue. Three image forming means for forming an image by respectively modulating one corresponding primary color light of the three primary color lights according to the video signal, and three images formed by the three image forming means are combined. In a projection display device having an optical system including a synthesizing unit and a projecting unit for enlarging and projecting an image synthesized by the synthesizing unit, the light transmittance is lowered in a specific wavelength band on the emission surface side of the projecting unit. The optical wavelength selection means and the optical color temperature correction means whose light transmittance in a predetermined wavelength band monotonously changes according to the wavelength are arranged.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the transmittance of the optical wavelength selecting means in the yellow wavelength band is in the blue wavelength band and in the green wavelength band. It is characterized by being lower than the transmittance.

According to a fifth aspect of the present invention, in the invention of the fourth aspect, the transmittance of the optical color temperature correcting means in the blue wavelength band is in the green wavelength band and the red wavelength band. Is lower than the transmittance of

The invention according to claim 6 is the invention according to claims 3 to 5.
In the invention described in any one of the above items, the color temperature of the light emitted from the optical color temperature correction means is lower than the color temperature of the light emitted from the projection means.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 shows the configuration of the optical system of the projection display apparatus according to Embodiment 1 of the present invention. In the figure, 1 is a light source composed of a lamp 2 and a reflecting mirror 3, 101 is illumination light emitted from the light source 1, 4 is a first multi-lens array, 5 is a second multi-lens array, and 7 is a condenser lens. 10R, 10G, 10B
Are three liquid crystal light valves corresponding to the three primary colors of R, G and B, 18a, 18b, 18c and 18d are reflection mirrors, 8
a and 8b are first and second dichroic mirrors that reflect light of a specific wavelength, 19a and 19b are first and second relay lenses, and 9R, 9G and 9B are collimator lenses corresponding to R, G and B colors. , 11 is a dichroic prism, 12 is a projection lens, 15 is a wavelength selection filter, 13
Is a screen, 20a is a holding member, and 100 is a projector main body. The holding member 20a is a member that connects the projection lens 12 and the wavelength selection filter 15, and preferably has a cylindrical shape, and its diameter is larger than the diameter of the lens barrel of the projection lens 12 so as not to block the projection light.

As the lamp 2 used for the light source 1, a high pressure mercury lamp having the advantages of long life and short arc length is desirable. FIG. 2 shows the spectral characteristics of a general high pressure mercury lamp. The reflecting surface of the reflecting mirror 3 is generally a parabolic surface, and by arranging the light emission center of the lamp at the focal position of the parabolic surface, the illumination light 101 having a substantially parallel luminous flux can be obtained. The operation of the optical system having the above configuration will be described below.

The illumination light 101 enters the first multi-lens array 4 and is split into a plurality of light beams by the small convex lens. The split light flux enters the corresponding small convex lens of the second multi-lens array 5 and is emitted by the condenser lens 7 as a condensed light flux. The light beam emitted from the condenser lens 7 has its optical path bent by the reflection mirror 18a and enters the first dichroic mirror 8a. First
The dichroic mirror 8a of transmits the red wavelength band,
It has a characteristic of reflecting the green wavelength band and the blue wavelength band, the red illumination light 101R is transmitted in the direction of the reflection mirror 18b, and the green illumination light 101G and the blue illumination light 10 are transmitted.
1B is reflected in the direction of the second dichroic mirror 8b. The illumination light 101R transmitted through the first dichroic mirror 8a is reflected by the reflection mirror 18b and the collimator lens 9
The liquid crystal panel 10R is illuminated via R.

Since the second dichroic mirror 8b has a characteristic of transmitting the blue wavelength band and reflecting the green wavelength band, the illumination light 101G reflected by the first dichroic mirror 8a is reflected by the second dichroic mirror 8b. The liquid crystal panel 10G is illuminated through the collimator lens 9G by bending the optical path by the optical path, and the illumination light 101B reflected by the first dichroic mirror 8a passes through the second dichroic mirror 8b and then passes through the first relay. Lens 19a, reflection mirror 18c, second relay lens 1
The liquid crystal panel 10B is illuminated via 9b, the reflection mirror 18d, and the collimator lens 9B.

The liquid crystal panels 10R, 10G, and 10B modulate the incident light in accordance with the applied video signal, and red,
An image of each color of green and blue is formed. The light in these images is
The white light 102 is again synthesized by the dichroic prism 11 (here, a white image is projected), passes through the projection lens 12, and then passes through the wavelength selection filter 15 to change the spectral characteristics of the white light. It becomes 103 and is enlarged and formed as a projection image on the screen 13.

Next, the spectral characteristics of the color separation system that affects the hue of each of R (red), G (green), and B (blue) monochromatic light will be described. FIG. 3 is a spectral transmission characteristic diagram of the first dichroic mirror 8a. Generally, the cutoff wavelength is 58.
It is set to 0 to 590 nm. FIG. 4 is a spectral transmission characteristic diagram of the second dichroic mirror 8b, and the cutoff wavelength is generally set to around 500 nm. In order to avoid a decrease in light utilization efficiency, the dichroic prism 11 of the color combining system converts green light into P-polarized light and red light and blue light into S-polarized light to be incident. Therefore, in the color combining system, the hue of each monochromatic light is changed. Is hardly affected.

Red illumination light 101 transmitted through the liquid crystal panels 10R and 10G and combined by the dichroic prism 11
The R and green illumination light 101G is affected by the characteristics of the first dichroic mirror 8a and the characteristics of a dichroic filter (not shown), and in the case of an optical system that prioritizes high brightness, the lamp shown in FIG. Since the spectrum includes a strong yellow bright line spectrum having a central wavelength around 580 nm, the red illumination light 101
The R and green illumination lights 101G are red light and green light in which a yellow component is mixed respectively.

A dichroic filter (not shown) is formed on the collimator lenses 9R and 9G as a multi-layer coating, or in the case of the red light path, between the first dichroic mirror 8a and the liquid crystal panel 10R.
In the case of the green optical path, it is arranged as a 0-degree incident filter between the second dichroic mirror 8b and the liquid crystal panel 10G.

Next, the wavelength selection filter 15 will be described. The wavelength selection filter 15 has, for example, a spectral transmission characteristic as shown in FIG. 5, and has a yellow central wavelength (so as to selectively absorb a component near the yellow central wavelength (580 nm in the example of FIG. 5). The transmittance in the vicinity of 580 nm is lower than the transmittance in the green wavelength band (500 to 560 nm) and the red wavelength band (600 to 650 nm). The white light 102 synthesized by the dichroic prism 11 becomes a light flux 103 from which unnecessary wavelength components are removed by passing through the wavelength selection filter 15,
An image projected on the screen 13 and having high color purity is displayed. The chromaticity diagram of FIG. 6 shows the color reproducibility with and without the wavelength selection filter 15. From this figure, it can be seen that the use of the wavelength selection filter 15 improves the color purity of red and green.

In order to increase the degree of improvement in color purity, it is preferable to make the transmittance near the yellow central wavelength (580 nm) as low as possible, but if it is too low, the green and red central wavelengths (550 nm, 610 nm) are preferred. Therefore, the transmittance is also lowered, and there is a problem that the brightness is drastically lowered or the white balance is largely disturbed. Therefore, it is desirable that the degree of reduction is about 30%.

As described above, according to the first embodiment, the wavelength selection filter 15 is arranged in front of the projection lens 12, which is the final stage optical component in the projector 100, to improve the color reproducibility of the projection light. By making improvements, the projection display device for data display can be used as the projection display device for home theater where good color reproducibility is required without modifying the optical system from the light source to the projection lens. .

Although the absorption type filter is used as the wavelength selection filter 15 in the first embodiment, a reflection type filter formed by a multilayer vapor deposition film may be used. However, when the return light from the wavelength selection filter 15 to the projection lens 12 affects the image quality such as contrast, an absorption type is used as the wavelength selection filter 15, and the deterioration of the filter characteristics due to light absorption is a problem. In such a case, it is desirable to use a reflection type filter as the wavelength selection filter 15 and to use it properly according to the usage conditions.

Embodiment 2. FIG. 7 shows the configuration of the optical system of the projection display apparatus according to Embodiment 2 of the present invention. In the figure, elements that are the same as or correspond to the elements shown in FIG.

In the second embodiment, the color temperature correction filter 25 is used.
Embodiment 1 in that a holding member 20b is added.
Different from The holding member 20b is a coupling means of the wavelength selection filter 15 and the color temperature correction filter 25, and its outer shape is preferably cylindrical like the holding member 20a, and the diameter of the holding lens 20b of the projection lens 12 does not block the projection light. Larger than the diameter of the lens barrel. The color temperature correction filter 25 is a filter having a spectral characteristic such that the transmittance gradually and monotonously decreases as the wavelength becomes shorter in the visible wavelength band as shown in FIG. 8, and it is in the blue wavelength band (430 to 500 nm). The transmittance is relatively lower than the transmittances in other wavelength bands.

As described in the first embodiment, the light flux 103 transmitted through the wavelength selection filter 15 has a center wavelength of 58.
The yellow spectral component around 0 nm is reduced. Therefore, the light flux 103 has a strong blue component, which has an opposite color to yellow, and tends to be white light with a high color temperature. Therefore, in the second embodiment, the wavelength selection filter 15
The light flux 103 that has passed through the
Is transmitted, the blue wavelength component, which has become relatively strong, is absorbed and its intensity is reduced. As a result, an image having the same hue as the original white image can be displayed.

According to the second embodiment, by arranging the color temperature correction filter 25 in addition to the wavelength selection filter 15 in front of the projection lens 12 which is the final stage optical component in the projector 100, white light Since the color reproducibility of the projected light is improved without changing the color temperature, the projection display device for data display can be provided with good color reproducibility and color temperature without modifying the optical system from the light source to the projection lens. It becomes easy to apply to a projection type display device for home theater where characteristics are required.

It should be noted that the color temperature correction filter 25 has a transmittance in the blue wavelength band lower than that shown in FIG. 8 to correct the color temperature overcorrectively, and the white light 102 emitted from the projection lens 12 is corrected. You may make it remove the bluish of optically. By doing so, it is possible to correct the tendency of the screen 13 to become bluish during black display due to the wavelength dependence of the contrast of the liquid crystal panel. In this case, the screen 13 has a yellowish tint when displaying white, which can be easily dealt with by electrical correction, which is not a problem. Thus, according to the second embodiment, the color temperature correction filter 25
By setting the transmittance characteristics of the color temperature correction so that the color temperature correction is overcorrected, it is possible to realize a projection display device having a good hue during black display.

Although the absorption type filter is used as the color temperature correction filter 25 in the second embodiment, a reflection type filter formed of a multilayer vapor deposition film may be used. However, when the return light from the color temperature correction filter 25 to the projection lens 12 affects the image quality such as contrast, an absorption type is used as the color temperature correction filter 25, and the filter characteristics are deteriorated due to light absorption. Is a problem, the color temperature correction filter 25
It is desirable to use a reflection type as the above and use it properly according to the usage conditions. In the second embodiment, the color temperature correction filter 25 and the wavelength selection filter 15 are also included.
Although they are individually arranged, it is also possible to use one filter having both functions.

[0039]

According to the invention described in claims 1 and 2,
By arranging a wavelength selection filter in front of the projection lens and improving the color reproducibility of the projection light, good color reproduction of a projection display device for data display applications is possible without modifying the optical system from the light source to the projection lens. The present invention can be applied to a projection display device for home theater applications that require high performance.

According to the invention described in claims 3 to 6, a color temperature correction filter is arranged in front of the projection lens in addition to the wavelength selection filter, and the color reproduction of the projection light is performed without changing the color temperature of the white light. The projection type display device for data display applications can be used for home theater applications where good color reproducibility and color temperature characteristics are required without modifying the optical system from the light source to the projection lens. It can be used for a display device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical system of a projection display device according to a first embodiment of the present invention.

FIG. 2 is a spectral characteristic diagram of a high-pressure mercury lamp used as a light source of a projection display device.

FIG. 3 is a spectral transmission characteristic diagram of a first (red transmission) dichroic mirror.

FIG. 4 is a spectral transmission characteristic diagram of a second (blue transmission) dichroic mirror.

5 is a spectral transmission characteristic diagram of a wavelength selection filter included in the projection display apparatus of FIG.

6 is a chromaticity diagram illustrating an improvement in color reproducibility of the projection display apparatus of FIG.

FIG. 7 is a configuration diagram of an optical system of the projection display apparatus according to the second embodiment of the present invention.

8 is a spectral transmission characteristic diagram of a color temperature correction filter included in the projection display apparatus of FIG.

FIG. 9 is a configuration diagram of an optical system of a conventional projection display device.

FIG. 10 is a diagram illustrating the wavelength dependence of the contrast of a liquid crystal panel.

FIG. 11 is a diagram illustrating light adaptation and dark adaptation in a relative luminous efficiency curve.

[Explanation of symbols]

1 light source, 2 reflecting mirror, 3 lamp, 4 first multi-lens array, 5 second multi-lens array,
7 Condenser lens, 8a 1st dichroic mirror, 8b 2nd dichroic mirror, 9
Collimator lens, 10R, 10G, 10B liquid crystal panel, 11 dichroic prism, 12 projection lens, 13 screen, 15 wavelength selection filter, 25 color temperature correction filter, 20a, 20b
Holding member, 100 projector.

Claims (6)

[Claims] 1. A light source and light emitted from the light source are red, green,
A color separation means for separating the three primary color lights of blue, and a corresponding one of the three primary color lights corresponding to the applied video signal.
Three image forming means for respectively modulating the three primary color lights to form an image, a synthesizing means for synthesizing the three images formed by the three image forming means, and a projection means for enlarging and projecting the image synthesized by the synthesizing means. In a projection display device having an optical system including and, an optical wavelength selection unit having a light transmittance reduced in a specific wavelength band is arranged on the emission surface side of the projection unit. apparatus. 2. The projection according to claim 1, wherein the transmittance of the optical wavelength selection unit in the yellow wavelength band is lower than the transmittance of the blue wavelength band and the transmittance of the green wavelength band. Type display device. 3. A light source and light emitted from the light source is red, green,
A color separation means for separating the three primary color lights of blue, and a corresponding one of the three primary color lights corresponding to the applied video signal.
Three image forming means for respectively modulating the three primary color lights to form an image, a synthesizing means for synthesizing the three images formed by the three image forming means, and a projection means for enlarging and projecting the image synthesized by the synthesizing means. In a projection display device having an optical system including, an optical wavelength selection unit having a light transmittance reduced in a specific wavelength band on the emission surface side of the projection unit, and a light transmission in a predetermined wavelength band. A projection display device, characterized in that an optical color temperature correction means whose ratio changes monotonously with wavelength is arranged. 4. The projection according to claim 3, wherein the transmittance of the optical wavelength selection unit in the yellow wavelength band is lower than the transmittance of the blue wavelength band and the transmittance of the green wavelength band. Type display device. 5. The optical color temperature correcting means according to claim 4, wherein the transmittance in the blue wavelength band is lower than the transmittance in the green wavelength band and the transmittance in the red wavelength band. Projection display device. 6. The color temperature of the light emitted from the optical color temperature correction means is lower than the color temperature of the light emitted from the projection means. Projection display device.