JPH05303085A - Projection type display device - Google Patents

Abstract

(57) [Summary] [Structure] The light flux emitted from the light source lamp 20 is collimated by the parabolic reflector 21, passes through the first lens group 70, and is provided in the vicinity of the second lens group 71 with a plurality of secondary light sources. To form. Light valve 1 that modulates light with a condenser lens 41 and scattering degree
The light flux passing through 1 enters the projection lens 14 and forms an image of the secondary light source at the position of the entrance pupil. The shape of the aperture of the projection diaphragm 43 matches the image of the secondary light source. [Effect] A high-quality image with a high contrast ratio can be obtained. Further, the amount of the secondary light source used by moving the slide shutter 72 is reduced, and at the same time, the slide shutter 73 is used.
By moving the to reduce the amount of light passing through the projection diaphragm 43, the contrast ratio can be further increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display device for enlarging and displaying an image on a screen by using a liquid crystal light valve which modulates a light beam by transmission or scattering.

[0002]

2. Description of the Related Art One of the problems in a liquid crystal projector that magnifies and displays an image on a liquid crystal panel is the efficient use of light from a light source. Since the early LCD projectors used a polarization control element, half of the light from the light source was discarded, so the utilization efficiency of the light flux was very low. Recently, PDLC (Polymer Dispersed) that modulates incident light by scattering degree by dispersing liquid crystal in polymer
A new mode of light modulation material called Liquid Crystal has been developed. In this mode, since it is not necessary to polarize the light from the light source, the light beam utilization efficiency is high, and it is receiving much attention. As an optical system of a liquid crystal projector using this mode, for example, there is one shown on pages 227 to 230 of SID 90 DIGEST.

As shown in FIG. 1, the substantially parallel luminous flux emitted from the light source device 10 is modulated by the light valve 11. The transmitted light 16 transmitted through the light valve 11 is collected by the condenser lens 12.
The light that has been collected by the aperture 13 of the diaphragm 13 and has passed therethrough is imaged on the screen 15 by the projection lens 14. On the other hand, most of the scattered light 17 scattered by the light valve 11 goes out of the opening of the diaphragm 13 and therefore does not reach the screen 15. Although the internal structure of this illuminating device is not particularly described, a light source lamp 20 and a parabolic reflector 21 for converting a luminous flux emitted from the light source lamp 20 into a parallel light 22 are generally used as shown in FIG. Be done.

[0004]

However, when the light source lamp and the parabolic reflector are used as the illuminating device in the above-mentioned prior art, the opening area is large enough to pass all the light transmitted through the light valve. When the diaphragm having the above is provided, scattered light is also transmitted to some extent, and the contrast ratio of the projected image is low and the display quality is low.

Although it was possible to raise the contrast ratio to some extent by reducing the aperture area of the diaphragm, the brightness of the displayed image is considerably lowered, and even if the aperture area of the diaphragm is reduced, The contrast ratio did not increase. Further, there is a problem that the contrast ratio of the central portion of the display screen is lower than that of the peripheral portion.

Therefore, the present invention solves such a problem, and an object of the present invention is to display a uniform high-definition image with a high contrast ratio and to use a light source light with a high utilization efficiency. It is to provide a display device.

[0007]

A projection type display device according to the present invention comprises an illuminating device, a means for modulating a light beam from the illuminating device to contain image information, and a projection optical system for projecting the modulated light beam on a screen. A projection display device including a system, wherein the lighting device collects the emitted light from the light source lamp using a means having a light collecting property,
A means for forming a secondary light source and illuminating a means for including the image information by a light flux from the secondary light source, and the means for including the image information modulates an incident light flux with a scattering degree. And a light valve using a liquid crystal composite element, which is provided inside / near the projection optical system.
A secondary light source image is formed, and a projection diaphragm perpendicular to the optical axis of the projection optical system is formed at that position, and the shape of the opening of the projection diaphragm is formed in a plane including the projection diaphragm. It is characterized in that it substantially coincides with the outer frame of the shape of the image of the secondary light source.

Further, to further improve the projection type display device of the present invention, a light source diaphragm is provided in a portion of the illumination device where the secondary light source is formed, and the light source diaphragm and the projection optical system are provided. The shape of the projection diaphragm provided inside / in the vicinity of is similar.

In a preferred embodiment of the projection type display device of the present invention, the light source diaphragm in the illuminating device and the projection diaphragm in the projection optical system are provided with a mechanism whose opening area is variable, respectively. It is characterized in that the shape of the opening of is changed so as to always maintain a similar relationship.

Further, in a preferred embodiment of the projection type display device according to the present invention, the illuminating device once makes the light emitted from the light source lamp into a substantially parallel light flux by a reflecting mirror, and then uses a plurality of lenses to make a plurality of light beams. Secondary light sources are formed, and the same number of lenses are arranged at positions where the secondary light sources can be formed,
It is a lighting device that illuminates the light valve.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A projection type display device according to the present invention will be described below in detail with reference to the drawings.

Example 1 FIG. 3 shows the structure of a light source device in a projection type display device of the present invention. The light source lamp 20 is
Use a light source close to a point, such as a halogen lamp, xenon lamp, or metal halide lamp. This light source lamp 20
Since the light source is arranged at the first focus position of the ellipsoidal reflecting mirror 30, the emitted light beam 34 is reflected by the ellipsoidal reflecting mirror 30 and goes to the second focal point 36. The light flux at the position of the second focal point 36 has a certain size because the light source is not a perfect point,
It serves as a secondary light source (hereinafter referred to as a secondary light source). The light flux once focused near the second focus 36 spreads again and passes through the collimator lens 33 to become parallel light 35.

FIG. 4 is a block diagram showing the entire optical system. The parallel light flux 35 emitted from the light source device 40 described in FIG.
Are condensed such that they are efficiently collected on the projection lens 14 through the condenser lens 41 before entering the light valve 11. The light valve 11 is a system that modulates an incident light beam by transmission or scattering. A completely transmitted light beam passes through an entrance pupil in the projection lens 14, and most of the scattered light beam 17 goes out of the entrance pupil. The light flux 42 that has passed through the entrance pupil is directed to the screen.

The contrast ratio of the displayed image can be determined by the ratio of the amount of light flux passing through the entrance pupil when the light valve 11 is transmitting (ON) and the amount of light flux passing through the entrance pupil when the light valve is scattering (OFF). .. Therefore, in order to increase the contrast ratio, a diaphragm 43 (hereinafter referred to as a projection diaphragm) is arranged at the position of the entrance pupil, and the aperture area is reduced to such an extent that the amount of transmitted light when it is on does not decrease so much, and the contrast ratio Try to be high.

Although it is basically the same as the configuration of the conventional optical system, in this case, an image of the secondary light source in the light source device is formed at or near the position of the entrance pupil. The image of this secondary light source is darker in the peripheral portion than in the center, so the projection diaphragm 43
By making the shape of the opening of the circular shape a little smaller than the size of the entire image of the secondary light source, a comparatively high contrast ratio can be obtained and the brightness is not deteriorated so much.

At this time, when the light valve 11 is on, the light beam blocked by the projection diaphragm 43 cannot be effectively used, and is scattered when the light valve 11 is off, so that a part of the scattered light is blocked by the diaphragm. It will pass and reduce the contrast ratio. Therefore, in order to remove this harmful light flux, the light flux in the peripheral portion of the secondary light source may be previously cut by a diaphragm 31 (hereinafter referred to as a light source diaphragm) as shown in FIG.

If the aperture 32 of the light source diaphragm 31 is simply opened, the illuminance of the displayed image becomes uneven. Therefore, in order to scatter the light flux to some extent, the opening 32 may be provided with, for example, a plate glass having a satin-finished surface or a compound lens such as a so-called integrator. By doing so, although the display image becomes dark to some extent, the illuminance distribution can be made uniform while the contrast ratio remains constant.

As the light source diaphragm 31, a diaphragm mechanism in which the size of the opening 51 changes as shown in FIG. 5 can be used. This diaphragm mechanism is used for a general camera lens and can be mechanically operated to change the area while keeping the opening 51 substantially circular. The movable part 50 may be formed on the surface thereof so as to reflect light so as not to be thermally deformed.

At this time, the projection diaphragm 43 in the projection lens 14 in FIG. 4 is also constructed by a similar diaphragm mechanism so that it is exactly matched with the image of the secondary light source formed there.

In the structure using the diaphragm mechanism as described above, an actual device was manufactured and its characteristics were examined. The relationship between the aperture area of the diaphragm mechanism and the light flux (light flux on the screen) that passes through the projection diaphragm is shown in FIG. The amount of light passing through when the light valve is turned on gradually increases by increasing the radius of the opening of the projection diaphragm and eventually becomes saturated. On the other hand, when the light valve is off, the light is scattered light and increases monotonically. Reference numeral 60 in the figure shows a case where the diaphragm mechanisms on the light source side and the projection lens side are changed synchronously, which is smaller than the passing light amount 61 in the case where there is no diaphragm mechanism on the light source side.

From this result, the contrast ratio is calculated by the ratio of the amount of transmitted light on and off, and FIG. 6 (B). 6
2 is a case where both diaphragm mechanisms are used, and 63 is a case where only the diaphragm mechanisms in the projection lens are used. It was found that when both aperture mechanisms are used, the brightness decreases as the radius of the aperture decreases, but the contrast ratio increases. On the other hand, it was found that the contrast ratio was relatively low and saturated at a certain value only with the diaphragm mechanism on the projection lens side. In this measurement, no scattering member is arranged in the aperture of the light source diaphragm.

As described above, it is possible to increase the contrast ratio by using the two diaphragm mechanisms. For example, when the projection display device of the present invention is used in a bright place, since there is a lot of external light and brightness is prioritized over the contrast ratio,
The aperture area of the diaphragm may be made relatively large. In a dark room, the contrast ratio is more important than the brightness, so the radius of the aperture should be reduced.

(Embodiment 2) Next, the case where a plurality of secondary light sources are formed will be described.

The overall structure of the optical system is shown in FIG. The light flux emitted from the light source lamp 20 is reflected by the parabolic reflector 21 and converted into a substantially parallel light flux. As shown in FIG. 8A, the first lens group 70 is composed of a plurality of lenses cut into 13 rectangles here. The shape of each lens is similar to the shape of the light valve 11. The first lens group 70 is arranged so as to be included in the rim 80 of the parabolic reflector 21 when viewed from the side opposite to the light source.

The second lens group 71, as shown in FIG. 8 (B), is composed of 13 rectangularly cut lenses, like the first lens group. The focal length f of each lens of the first lens group 70 is equal to the distance a between the first lens group 70 and the second lens group 71, and the light flux incident on each lens of the first lens group 70 is Focus on each corresponding lens. At this time, on each lens surface of the second lens group 71,
As shown in FIG. 8B, 13 secondary light sources 81 are formed. In this figure, when the light source lamp is a cylindrical light source such as a metal halide lamp, a secondary light source 81 formed radially with respect to the center is shown.

The second lens group 71 has a focal length f '.
8B, each lens of the second lens group 71 superimposes the rectangular image of each lens of the first lens group 70 on the light valve 11 having a similar shape. Therefore,
These two lens groups act as an integrator that mixes the light fluxes reflected by the respective parts of the parabolic reflector on the light valve 11.

The condensing lens 41 has the following focal length f ″ in order to efficiently collect the incident light flux on the projection lens 14.

F ″ = bc / (b + c) where b is the distance between the second lens group 71 and the condenser lens 41, and c is the distance between the apparent entrance pupil positions of the condenser lens 41 and the projection lens 14. is there.

A projection diaphragm 43 is arranged at the position of the entrance pupil in the projection lens 14 and has a shape as shown in FIG. 9 so that the image of the secondary light source formed at that position can pass through. is doing. The opening 90 of the projection diaphragm 43 is shown in FIG.
Since it has a similar shape to the secondary light source 81 in (B), the amount of scattered light of the light valve 11 that passes through the opening 90 of the projection diaphragm 43 is suppressed to a minimum, and the contrast ratio of the projected image becomes high.

Various other configurations are possible for each lens group. When the light emitting portion of the light source lamp is relatively long in the optical axis direction, in the configuration shown in FIG. 8 (B), the secondary light source 81 becomes longer than shown in the figure, and the light flux outside each lens is lost. Will be.

Therefore, if the second lens group is constructed so as to have an optical axis symmetry as shown in FIG. 10B, the secondary light source 81 is housed in each lens and there is no loss, so that highly efficient illumination can be performed.

In FIG. 10 (B), the first lens group is also divided into nine parts because it has a nine-part structure, for example, a structure as shown in FIG. 10 (A). Each of the lenses 70a to 70i has a shape similar to that of the light valve 11, and the light flux that has passed through each lens is the corresponding lens 71a to 71 in FIG.
It is incident on i. In this case, the light beam in the shaded area 100 shown in FIG. 10A will be lost as it is. Therefore, if the light beam from the light source is reflected and returned to the light source side, the light source lamp is once constructed. It will be used effectively after returning to the light emitting part of. In FIG. 10A, although there is a gap in the upper, lower, left and right sides of the lens 70a,
It is also possible to center 0b, 70d, 70f, and 70h.

By the way, the brightness of the secondary light source 81 shown in FIG. 8B substantially corresponds to the brightness distribution of the light emitting portion of the light source lamp, and this secondary light source is not a complete image of the light emitting portion. Therefore, the peripheral portion of each secondary light source has relatively low brightness. Therefore, a portion having a certain luminance value or less may be obstructed by a mask, and the shape of the mask and the shape of the projection diaphragm 43 may be similar. By doing so, the contrast ratio of the projected image can be improved as in the case of the first embodiment.

Further, as shown in FIG. 7, by providing slide shutters 72 and 73 near the second lens group 71 and near the projection diaphragm 43, the contrast ratio of the image can be adjusted. Two slide shutters 72,
73 denotes a secondary light source on the second lens group 71 and a projection diaphragm 43.
The openings are moved so that they always have similar shapes. At this time, the following relationship is established.

[Aperture Area of Projection Aperture] × [Contrast Ratio of Image] = [Constant Value] Therefore, as described in the first embodiment, when the contrast ratio is more important than the brightness, the aperture area of the projection diaphragm 43. Should be reduced.

If the light valve 11 is composed of a liquid crystal panel with a color filter, color display is possible, but the brightness is reduced to about 1/3. Therefore, the configuration of a color projection display device using three light valves will be described next.

A schematic diagram of the structure is shown in FIG. Light source lamp 2
The light flux emitted from 0 is collimated by the parabolic reflector 21 and enters the first lens group 70. The transmitted light flux is reflected by the blue-green reflection dichroic mirror 110.
Red light is transmitted and green light and blue light are reflected. Each light beam enters the second lens group 71, and the first lens group 7
The image of each lens of 0 is formed on the light valve 11.

The red luminous flux is then reflected by the total reflection mirrors 113, 1
The light is reflected by 15, 116 and reaches the light valve 11 through the condenser lens 41. The green light is reflected by the total reflection mirror 111, then by the green reflection dichroic mirror 112, and further by the total reflection mirror 113, and reaches the corresponding light valve 11 via the condenser lens 41. The blue light is reflected by the total reflection mirror 111, transmitted through the green reflection dichroic mirror 112 and reflected by the total reflection mirror 114, and enters the light valve 11 through the condenser lens 41 like other color lights.

The three light valves 11 modulate respective color lights and include image information corresponding to each color. The cube prism 117 combines the modulated light beams, and includes a red-reflecting dielectric multilayer film and a blue-reflecting dielectric multilayer film in a cross shape.

The projection diaphragm 43 is the projection lens 14 in this case.
It is placed in front of it, not inside. Therefore, the power of the condenser lens 41 is set so that an image of the secondary light source is formed at the position of the projection diaphragm 43. Projection diaphragm 43
The light flux that has passed through passes through the projection lens 14 and forms an image on the screen.

Of course, if the slide shutter described above is arranged at the positions of the second lens group 71 and the projection diaphragm 43,
The contrast ratio of the image can be made variable.

The arrangement of each lens group can be considered in addition to this. For example, in FIG. 11, the first lens group is arranged at a certain position of the second lens group 71, and the second lens group is arranged at the position where the light flux passing through each is reflected by the total reflection mirrors 111 and 113. May be. Of course, this system can be applied to other optical systems as long as the optical system has an equal optical path length.

In the optical system described here, the cube prism is used for synthesizing the colored light. However, the dielectric multilayer film formed in the prism is p-polarized as compared with the dielectric multilayer film formed on the plate glass. And the characteristic difference with respect to s-polarized light is large. Since the light valve 11 is a light valve of a type that uses both polarizations, that is, a type that modulates light with the degree of scattering, a light loss is likely to occur if a cube prism having different polarization characteristics is used. To avoid this, a so-called three-wavelength emission type metal halide lamp may be used as the light source lamp. R for 3-wavelength emission type
Since the emission spectrum corresponding to each primary color light of GB is a narrow band, it is possible to use a portion having no difference in both polarization characteristics of the cube prism, and it is possible to effectively use all the light fluxes.

[0044]

As described above, according to the present invention, the image of the secondary light source formed in the light source device is formed near the projection lens, and the shape of the projection diaphragm is adjusted to the image of the secondary light source. This makes it possible to display a high-quality image with a high contrast ratio.

By providing a light source diaphragm in the light source device and discarding part of the secondary light source, the contrast ratio can be further increased.

Further, by providing a mechanism for varying the size of the aperture area of the light source diaphragm and the aperture area of the projection diaphragm, and changing the shape of each aperture so as to be always similar, the contrast ratio can be arbitrarily set. It is possible to realize a projection display device that can be set to.

For example, a bright image can be obtained in a relatively bright place where the brightness of the image is easier to see than the contrast ratio, while a dark place where the contrast ratio is easier to see than the brightness. In, it is possible to display an image with a high contrast ratio. Therefore, one projection display device can be used for various purposes, and the utility value is increased.

Further, specifically, a plurality of secondary light sources are formed in the light source device, and the light valve is illuminated by each secondary light source, and similarly the shape of the projection diaphragm is similar to the shape of the secondary light source. As a result, it is possible to display a very high-quality image that has a high contrast ratio and is uniform on the display surface, has an extremely uniform illuminance distribution, and has sufficiently little display color unevenness.

In this case as well, by making the use part of the secondary light source variable and changing the aperture of the projection diaphragm at the same time, it is possible to provide a convenient projection type display device with variable contrast ratio. When the contrast ratio is relatively low, the utilization efficiency of light from the light source is extremely high. By using this method, a bright projection type display device with low power consumption can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical system configuration of a conventional projection display device.

FIG. 2 is a diagram showing a configuration of a light source device in a conventional projection type liquid crystal display device.

FIG. 3 is a diagram showing a configuration of a light source device in the projection type display device of the present invention.

FIG. 4 is a diagram showing an optical system configuration of a projection display device according to the present invention.

FIG. 5 is a view showing the structure of a diaphragm mechanism used in the projection type display device of the present invention.

FIG. 6A is a diagram showing the relationship between the amount of light passing through the diaphragm and the radius of the diaphragm. FIG. 6B is a diagram showing the relationship between the contrast ratio of the projected image and the radius of the diaphragm.

FIG. 7 is a diagram showing an optical system configuration of a projection display device according to the present invention.

FIG. 8A is a diagram showing a configuration of a first lens group used in a light source device. FIG. 6B is a diagram showing the configuration of the second lens group used in the light source device.

FIG. 9 is a diagram showing the shape of a projection diaphragm used in the projection type display device of the present invention.

FIG. 10A is a diagram showing a configuration of a first lens group used in a light source device. (B) is the second used for the light source device
The figure which shows the structure of a lens group.

FIG. 11 is a diagram showing an optical system configuration of a projection display device according to the present invention.

[Explanation of symbols]

 10 Light Source Device 11 Light Valve 14 Projection Lens 15 Screen 20 Light Source Lamp 21 Parabolic Reflector 30 Elliptical Reflector 41 Condensing Lens 43 Projection Aperture 70 First Lens Group 71 Second Lens Group 72,73 Slide Shutter 117 Cube Prism

Claims (4)

[Claims] 1. A projection type display device comprising an illuminating device, means for modulating a light beam from the illuminating device to contain image information, and a projection optical system for projecting the modulated light beam on a screen. The illuminating device collects the emitted light from the light source lamp using a means having a condensing property to form one or more secondary light sources, and uses the luminous flux from the secondary light source. Illuminating the means for including the image information, wherein the means for including the image information is a light valve using a liquid crystal composite element that modulates an incident light flux by a scattering degree, and the projection optical system. An image of the secondary light source is formed inside / near the system, and a projection diaphragm perpendicular to the optical axis of the projection optical system is provided at that position, and the shape of the opening of the projection diaphragm is Of the secondary light source formed in the plane including the projection diaphragm A projection-type display device characterized in that the outer shape of the image is substantially the same. 2. A light source diaphragm is provided in a portion of the illumination device where the secondary light source is formed, and the shape of the light source diaphragm and the projection diaphragm provided inside / near the projection optical system are similar to each other. The projection type display device according to claim 1, wherein 3. The light source diaphragm in the illuminating device and the projection diaphragm in the projection optical system are provided with a mechanism whose opening area is variable so that the shapes of the respective openings are always similar to each other. The projection type display device according to claim 2, wherein the projection type display device changes. 4. The illuminating device temporarily radiates the light emitted from the light source lamp into a substantially parallel light flux by a reflecting mirror, and then forms a plurality of secondary light sources by using a plurality of lenses, and the same number of lenses. 4. The projection display device according to claim 1, wherein the projection type display device is an illumination device that is disposed at a position where the secondary light source can be provided, and illuminates the light valve.