JPH09171158A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type display device without color irregularity and easy to adjust a color reproducing range. SOLUTION: Half wavelength plates 10, 11, 12 are closely adhered to field lenses 9B, 9G, 9R and this device is provided with a means for rotating the field lenses. The field lenses are plano-convex lenses whose plane sides confront liquid crystal panels 16B, 16G, 16R. The single-sided faces of the half wavelength plates 10, 11, 12 are coated with adhesive and closely adhered to the plane sides of the field lenses 9B, 9G, 9R. The outer periphery of the field lens is circular or circular arc and facilitates the addition of a rotating mechanism there. By closely adhering the half wavelength plate to the field lens, surface reflection losses between the field lens and air, air and the half wavelength plate are decreased and light transmissivity is increased. A supporting mechanism for the half wavelength plates 10, 11, 12 is unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device which illuminates an image formed on a light valve with illumination light and projects it on a screen by a projection lens.

[0002]

2. Description of the Related Art In order to obtain a large-screen image, a small light valve that forms an optical image according to a video signal is irradiated with light from a light source, and the projection lens projects the optical image on a screen to enlarge it. It is known how to do it.

Recently, a projection type display device using a liquid crystal panel for a light valve (for example, Technical Report C of the Television Society).
E '89 -17, pp55 to 60) is a lamp, a condensing optical system that condenses the light emitted from the lamp, a color separation optical system composed of three dichroic mirrors, and three field lenses. It is composed of three active matrix type liquid crystal panels, three projection lenses, and a screen. Since the three projection lenses are used, the color synthesizing optical means is not required, and the projection lens can be easily widened.

Therefore, there is a feature that a compact projection display device can be constructed.

[0005]

The light from the light source is natural light, but the liquid crystal panel is used after being linearly polarized by a polarizing plate. When the angle between the liquid crystal molecule orientation on the wall surface of the liquid crystal cell of the liquid crystal panel and the p-polarization direction of the dichroic mirror is about 45 degrees, the color light of the average value component of the p-polarization component and the s-polarization component of the dichroic mirror is used. It If the difference between the wavelength of 10% transmittance and the wavelength of 90% transmittance of the spectral transmittance characteristics of the dichroic mirror is the inclination width, p-polarized light,
The inclination width of the average value component is larger than the inclination width of the spectral transmittance characteristic of the s-polarized component. If this inclination width is large, there is a problem that the unevenness of the color of the projected image becomes large due to the incident angle dependence of the spectral transmittance characteristic of the dichroic mirror and the nonuniform film thickness.

Further, when the spectral transmittance characteristics of the dichroic mirror have minute variations, the brightness and chromaticity of the projected image change.

It is an object of the present invention to solve the above problems and to provide a projection type display device in which there is no color unevenness in a projected image and the color reproduction range can be easily adjusted.

[0008]

In order to achieve the above-mentioned object, a projection display apparatus of the present invention comprises a light source and color separation for separating white light from the light source into light of blue, green and red color components. Optical means and each color light from the color separation optical means is incident 1
A field lens provided with a / 2 wavelength plate, three light valves for forming an optical image according to a video signal by receiving light emitted from the field lens, and a projection lens for projecting the optical image on a screen, A means for rotating the field lens is provided, and the brightness and chromaticity of the projected image are adjusted by rotating the field lens.

According to the present invention, by providing the means for rotating the half-wave plate with the above structure, the spectral distribution characteristics of the color light used by the liquid crystal panel can be controlled, so that the brightness and chromaticity of the projected image can be adjusted. It will be possible. Furthermore, 1 /
Since the field lens having the two-wave plate is provided, the surface reflection loss at the boundary surface is reduced and the total transmittance of the optical system is improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A projection display apparatus according to a first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a first projection type display device, which uses a liquid crystal panel as a light valve. 1 is a lamp, 2 is a parabolic mirror, 3 is a light source composed of the lamp 1 and a parabolic mirror 2, 4 is an ultraviolet / ultraviolet cut filter, 5, 6 and 7 are dichroic mirrors, 8 is a dichroic mirror 5 Color separation optical means composed of 7, 9B, 9G, 9R are field lenses, 10, 1
1, 12 are half-wave plates, 13, 15 are polarizing plates, 14 is a liquid crystal cell provided with a switching element for each picture element, 16
B, 16G and 16R are the liquid crystal cell 14 and the polarizing plates 113 and 1
Liquid crystal panel composed of 5; 17B, 17G, 17R
Is a projection lens, and 18 is a screen.

The above-mentioned constituent elements will be described below, and their mutual relation and operation will be described.

Metal halide lamp, xenon lamp,
Light emitted from a lamp 1 such as a halogen lamp is converted into substantially parallel light by a parabolic mirror 2. The substantially parallel light from the light source 3 is made incident on the color separation optical means 8 after the ultraviolet / infrared cut filter 4 prevents ultraviolet / infrared rays from passing through the front surface. The color separation optical means 8 separates the white light from the light source into blue, green, and red colored lights by the blue reflection dichroic mirror 5, the green reflection dichroic mirror 6, and the red reflection dichroic mirror 7. The blue, green, and red color lights separated by the color separation optical means 8 enter the field lenses 9B, 9G, and 9R. The field lenses 9B, 9G, 9R are liquid crystal panels 16B, 16G, 1
The projection lens 17B, 17 transmits the light transmitted through the peripheral portion of 6R.
It is a plano-convex lens for making the light incident on G and 17R and the plane side facing the liquid crystal panels 16B, 16G and 16R. Light emitted from the field lens is a half-wave plate 1
It is incident on 0, 11, and 12.

The ½ wavelength wave is generally used for inversion of circularly polarized light, elliptically polarized light, azimuth conversion of linearly polarized light, and the like. 1/2
The wave plates 10, 11 and 12 are arranged to control the spectral distribution of the linearly polarized color light used by the liquid crystal panel. 1/2
Wave plates include inorganic optical single crystal wave plates, stretched resin film wave plates, and thin film wave plates. The two neutral polarization directions of the wave plate are the neutral axes. Three half-wave plates 10, 1
It is desirable to set the wavelengths of 1 and 12 according to the wavelength of the incident color light with the main wavelengths of the chromaticity of blue, green, and red of the projected image, but to reduce the cost, all three have a wavelength of 550 nm.
You may use the 1/2 wavelength plate which set the wavelength in the vicinity. Since the production cost of the inorganic optical single crystal wave plate is high, a wave plate made of an inexpensive stretched resin film is practical.

The half-wave plate of the stretched resin film is coated with a pressure sensitive adhesive on one surface and is attached to flat glass. By providing the flat glass with a rotation mechanism, the neutral axis of the half-wave plate is rotated. Since strong light is incident on the half-wave plates 10, 11, and 12, heat causes a problem of deterioration of the resin film, so that attention must be paid to cooling.

However, when no cooling means is provided, a thin film wave plate having high heat resistance may be used. The thin-film wave plate utilizes the fact that the obliquely vapor-deposited thin film causes birefringence with respect to a light beam which is incident perpendicularly to the film surface. The retardation of the orthorhombic vapor deposition film can be arbitrarily set according to the vapor deposition time. Further, since the film is formed similarly to other optical multilayer films, it is easy to increase the area.

The light emitted from the half-wave plates 10, 11 and 12 enters three transmissive liquid crystal panels 16B, 16G and 16R arranged on the same plane. LCD panel 16
B, 16G, and 16R are configured by arranging polarizing plates 13 and 15 in parallel Nicols on both sides of a liquid crystal cell 14 of twisted nematic mode. The liquid crystal panels 16B, 16G, 16R are of the active matrix type, and an optical image is formed as a change in transmittance according to a video signal.

The optical image formed by the liquid crystal panels 16B, 16G and 16R is displayed on the screen 1 by the three projection lenses 17B, 17G and 17R whose optical axes are arranged in parallel with each other.
8 is enlarged and projected, and the blue, green, and red projection images are combined on the screen 18. The three liquid crystal panels 16B, 16G, 16R are used to combine the images formed by the three liquid crystal panels 16B, 16G, 16R on the screen 18.
The two liquid crystal panels 16B and 16R other than the central part are moved slightly on the plane position and the tilt with respect to the optical axes of the projection lenses 17B and 17R to project blue, green and red projection images on the screen 1.
8 are overlaid.

FIG. 2 shows the dichroic mirror 5, the half wavelength 10, the polarizing plates 13 and 15, and the liquid crystal cell 14 in the polarization direction. Here, the molecular orientation directions of the incident light side and the outgoing light side wall surface of the liquid crystal cell 14 are in a state of approximately 45 degrees with respect to the x direction. When the angle between the polarization axis of the polarizing plate 13 on the incident light side and the x direction is θ (acute angle), the half-wave plate has an angle of θ / 2 between the neutral axis and the polarizing axis of the polarizing plate 13. Arrange so that The ½ wavelength plate 10 changes the direction of the polarization direction so that the color light of the p polarization component, that is, the p polarization component is transmitted through the polarization plate 13 on the incident side, and makes the color light of the p polarization component incident on the liquid crystal cell 14.

Therefore, the liquid crystal panel 16B forms an optical image by utilizing the color light of the p-polarized component of the dichroic mirror. Further, since the azimuth of the polarization direction can be continuously controlled by rotating the ½ wavelength plate, the spectral distribution characteristic of the color light used by the liquid crystal panel is changed from the p-polarized component to s.
It can be controlled within the range of the polarization component.

Although the polarizing plate 13 and the half-wave plate 10 are shown separately, the polarizing plate 13 may be adhered to the half-wave plate 10 with an adhesive. In this case, the polarizing plate 13 and 1 /
The two wavelength plates 10, 11 and 12 are integrated with each other, and the polarization plate 13
The accuracy of alignment between the polarization axis of and the neutral axis of the half-wave plate 10 is improved. If a rotation mechanism is added to the ½ wavelength plate, the contrast of the projected image can be adjusted by rotating the polarizing plate 13.

Further, the surface reflection loss of light due to the difference in refractive index at the interface between the half-wave plate and air and between the air and the polarizing plate is reduced, and the light transmittance is improved.

FIG. 3 shows the spectral transmittance characteristics of the dichroic mirror 5. Here, the solid line is the p-polarized light component, the chain line is the s-polarized light component, and the broken line is the characteristic of the average value component of the p-polarized light and the s-polarized light. The inclination width Δλ, which is the difference between the wavelength at which the transmittance is 10% and the wavelength at which the transmittance is 90%, has a larger average value component Δλ ₂ than Δλ ₁ of the p-polarized component. Since the light from the light source 3 is not a perfect parallel light, the incident angle of the light incident on the dichroic mirror 5 changes depending on the location of the dichroic mirror, and the spectral transmittance characteristic shifts to the short wavelength side or the long wavelength side.

For this reason, the brightness and chromaticity of the color light emitted onto the liquid crystal panel 16B change within the plane of the liquid crystal panel 16B, resulting in color unevenness of the projected image. Similarly, when the film thickness of the dichroic mirror is not uniform, color unevenness occurs in the projected image. The larger the inclination width Δλ of the dichroic mirror 5 is, the larger the change in the brightness and chromaticity of the illumination light on the surface of the liquid crystal panel 16B is. P is set by setting the direction of the neutral axis of the half-wave plate 10.
Since the color light having the spectral characteristic of the polarization component can be controlled to pass through the polarizing plate 13, the inclination width Δλ is smaller than that of the color light having the average value component of the p-polarized light and the s-polarized light, and the color unevenness of the projected image can be reduced.

Further, by rotating the half-wave plate 10, the liquid crystal panel 16B can utilize the colored light in the range of the p-polarized component to the s-polarized component, so that the chromaticity and brightness of the projected image can be adjusted. Therefore, even if there are variations in the spectral transmittance characteristics of the dichroic mirror 5, the variations can be corrected by the ½ wavelength plate 10. With respect to the dichroic mirrors 6 and 7, the half-wave plates 11 and 12 have the same action. Since it is possible to finely adjust the brightness and chromaticity of each blue, green, and red projected image, white balance adjustment becomes easy.

Since broadband light is incident on the half-wave plates 10, 11 and 12, the tolerance of the set wavelength of the half-wave plate is very loose. Blue, green and red colored light is incident 10,1
Even if the same half-wave plate whose set wavelength is around 550 nm is used for the half-wave plates 1 and 12, the tilt width becomes slightly larger, and the brightness and chromaticity adjustment ranges change only slightly No problem.

Although the half-wave plates 10, 11 and 12 are arranged so that the color light of the p-polarized component passes through the polarizing plate 13, s
Colored light of the polarization component may be transmitted.

The projection type display device of the second embodiment will be described below with reference to the drawings. FIG. 4 shows the configuration of the projection type display device in the second embodiment. Color separation optical means 8 including a light source 3, a blue reflection tychroic mirror 5, and a green reflection dichroic mirror 6, field lenses 9B, 9G, 9R, and half-wave plates 10, 11, 1.
2. The liquid crystal panels 16B, 16G and 16R have the same structure as that shown in FIG. What is different from FIG. 1 is that the mirrors 25 and 26 are used and the color synthesizing means 24 including the dichroic mirrors 22 and 23 is arranged and one projection lens is used.

The operation of the above-described structure will be described below. After the substantially parallel light from the light source 3 is blocked by the ultraviolet / infrared cut filter 4, ultraviolet / infrared rays are not transmitted to the front surface, and then color separation is performed. It is incident on the optical means 8 '. The color separation optical means 8'separates the white light from the light source into blue, green, and red light by the blue reflection dichroic mirror 5 and the green reflection dichroic mirror 6. The blue, green, and red color lights separated by the color separation optical means 8 ′ are
After passing through the field lenses 9B, 9G and 9R, they enter the half-wave plates 10, 11 and 12. 1/2 wave plate 10,1
Reference numerals 1 and 12 control the spectral distribution of color light used by the liquid crystal panel. The liquid crystal panels 16B, 16G, 16R receive the light emitted from the half-wave plates 10, 11, 12 and form an optical image corresponding to the video signal. Liquid crystal panels 16B, 16G,
The lights emitted from 16R are combined by the color combining means 24 including a green reflecting dichroic mirror 22 and a red reflecting dichroic mirror 23, and then enlarged and projected by the projection lens 21.

As in the first embodiment, by setting the direction of the neutral axis of the half-wave plate, it is possible to control the color light having the spectral characteristic of the p-polarized component so as to pass through the polarizing plate 13. The inclination width Δλ becomes smaller than that of the color light of the average value component, and the color unevenness of the projected image can be reduced. In addition, the half-wave plate 10,
By rotating 11 and 12, the liquid crystal panel 16
B, 16G, and 16R can use the colored light in the range from the p-polarized component to the s-polarized component, so that the brightness and chromaticity of the projected image can be adjusted. In addition, the polarization plate 13 and the half-wave plate 10, 1
By integrating 1 and 12, the contrast of the projected image due to the rotation of the polarizing plate 13 can be adjusted.

The half-wave plates 10, 11, 12 may be arranged between the liquid crystal panels 16B, 16G, 16R and the color synthesizing optical means 24. The linearly polarized light emitted from the liquid crystal panel is incident on the dichroic mirrors 22 and 23 after the direction of the polarization direction is converted to the p polarization direction or the s polarization direction of the dichroic mirrors 22 and 23 by the half-wave plate.

Therefore, the half-wave plate 10, 11, 1
2 is a color separation optical means 8'and liquid crystal panels 16B, 16G,
It has the same effect as when it is arranged between 16R.

A third embodiment of the present invention will be described below with reference to the drawings. FIG. 5 shows the configuration of the projection type display device in the third embodiment of the present invention. The difference from the configuration of the projection display apparatus of the first embodiment is the field lens 9
The point is to provide means for rotating the field lenses 9B, 9G, 9R by bringing the half-wave plates 10, 11, 12 into close contact with B, 9G, 9R.

The field lenses 9B, 9G, 9R are plano-convex lenses with their flat sides facing the liquid crystal panels 16B, 16G, 16R. An adhesive is applied to one surface of each of the half-wave plates 10, 11 and 12, and they are brought into close contact with the flat surfaces of the field lenses 9B, 9G and 9R. Field lenses 9B, 9G, 9
It is closely attached to the flat side of R. Field lens 9B, 9
The outer peripheral portions of G and 9R are circular or arc-shaped to facilitate the addition of a rotating mechanism.

By closely attaching the half-wave plate to the field lens, the field lens and air, and air and 1 /
The surface reflection loss of the two-wave plate is reduced, and the light transmittance is improved. Further, the support mechanism for the half-wave plates 10, 11, and 12 is unnecessary.

Polarizing plate 13 and half-wave plate 10, 11, 1
If 2 and the field lenses 9B, 9G, and 9R are integrated, the contrast of the projected image can be adjusted by rotating the polarizing plate 13. Moreover, the surface reflection loss at the boundary surface can be reduced.

Also in the projection type display device shown in the second embodiment, the same effect can be obtained if the half-wave plate is closely attached to the field lens.

In the above embodiment, an example in which a liquid crystal panel is used for the light valve has been shown, but a light valve for forming an optical image according to a video signal as a change in birefringence and optical rotatory power such as electro-optical effect is used. Good.

[0039]

As described above, according to the present invention, since the half-wave plate is provided, the inclination width of the spectral distribution of the color light used by the liquid crystal panel can be reduced, and the spectral transmittance characteristic of the dichroic mirror can be reduced. It is possible to reduce unevenness in the color of the projected image due to the incident angle dependence of the incident light and the uneven film thickness. By providing the means for rotating the half-wave plate, the spectral distribution characteristics of the color light used by the liquid crystal panel can be adjusted, and therefore the brightness and color reproduction range of the projected image can be adjusted, which is extremely effective. is there.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a projection display device according to a first embodiment.

FIG. 2 is an explanatory view showing a state of polarization directions of a half-wave plate and a liquid crystal panel.

FIG. 3 Spectral transmittance characteristic diagram of dichroic mirror

FIG. 4 is a configuration diagram of a projection display device according to a second embodiment.

FIG. 5 is a configuration diagram of a projection display device according to a third embodiment.

[Explanation of symbols]

 1 Lamp 2 Parabolic Area 3 Light Source 4 UV / Heat Cut Filter 5, 6, 7, 22, 23 Dichroic Mirror 8, 8'Color Separation Optical Means 9B, 9G, 9R Field Lens 10, 11, 12 1/2 Wave Plate 13, 14 Polarizing plate 14 Liquid crystal cell 16B, 16G, 16R Liquid crystal panel 17B, 17G, 17R, 21 Projection lens 18 Screen 24 Color combining optical means 25, 26 Mirror

Claims (6)

[Claims] 1. A light source, and white light from the light source is blue,
Color separation optical means for separating light of green and red color components, a field lens having a half-wave plate on which each color light from the color separation optical means is incident, and light emitted from the field lens An optical image is formed according to the video signal 3
Two light valves, a projection lens for projecting the optical image on the screen, and a means for rotating the field lens, and by rotating the field lens, the brightness and chromaticity of the projected image are adjusted. Projection display device. 2. The projection display device according to claim 1, further comprising means for rotating the half-wave plate. 3. The projection display device according to claim 1, wherein the half-wave plate is made of a stretched resin film. 4. The projection display device according to claim 1, wherein the half-wave plate is made of a thin film. 5. The half-wave plate is provided with a polarizing plate.
The projection type display device according to the above. 6. The projection display device according to claim 1, wherein the field lens is a plano-convex lens, and a half-wave plate is closely attached to the plane thereof.