JP3223534B2 - Projection display device - Google Patents

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 capable of performing enlarged projection.

[0002]

2. Description of the Related Art A projection display apparatus displays an image using a transmission type display panel, and enlarges and projects a display image of the display panel on a screen surface by a projection lens.

A transmissive display panel does not emit light by itself, but changes its light transmittance according to an external electric signal.
The image information is displayed by modulating the intensity of light from a separately provided light source, and a liquid crystal panel is a typical example.

A general transmission type liquid crystal panel is composed of a light-transmitting transparent pixel opening, a light-shielding liquid crystal driving section, a wiring section, and the like, which are formed in a plane. Since the liquid crystal driving section and the wiring section always have a certain finite size in terms of function and manufacturing process, the higher the display density of the liquid crystal panel, the higher the aperture ratio (the area ratio of the transparent pixel opening to the pixel). Decrease and the display screen darkens. Therefore, in order to improve the quality of a display image of a projection display device using a transmissive liquid crystal panel, it is necessary to improve the pixel density of the liquid crystal panel used therein and not to lower the light use efficiency. It is important to take

As one of the measures which do not lower the light utilization efficiency, a plurality of microlenses corresponding to the transparent pixel openings are formed on the surface of the transparent substrate located on the light source side among the two substrates constituting the liquid crystal panel. The light emitted from the light source is condensed on the corresponding transparent pixel opening of the liquid crystal panel by each minute lens, and the light that was conventionally blocked by the light-blocking structure is also guided to the pixel opening. A method for brightening a display screen has been developed.

[0006]

In general, when the lens diameter is the same, the shorter the focal length of the lens, the more the incident light can be narrowed down to a narrow area. On the other hand, in a lens system having a long focal length, only light close to parallel light can be sufficiently stopped down. The means for brightening the display screen using the above-described minute lens is based on the precondition that light incident on the minute lens is light having excellent parallelism. However, in actuality, the parallelism of light emitted from the light source of the projection display device is poor, and the focal length (in other words, the numerical aperture) of the microlenses is subject to various restrictions (for example, the microlenses are formed on a substrate constituting a liquid crystal panel) That the focal length of the microlens cannot be shortened due to the physical thickness of the substrate, or that the light condensed by the microlens passes through the pixel opening, Since the light is guided to the projection lens while diverging at an angle corresponding to the focal length, there is a restriction that the focal length cannot be shortened due to the restriction of the aperture diameter of the projection lens and the angle at which the light beam is included, and it is difficult to shorten the distance. As a result, as shown in FIG.
Light incident at an incident angle of 0 ° (perpendicular) with respect to 2 is condensed at substantially the center of the pixel opening 34 and passes through the opening, but on the other hand, as shown in FIG. Light incident at a large incident angle θ is condensed on the light shielding portion 33 outside the pixel opening, so that a phenomenon occurs that the light cannot pass through the pixel opening. In other words, there is a possibility that the use efficiency of light is reduced by installing the minute lens, and it is indispensable to consider the angular distribution characteristic of the light beam emitted from the light source when using the minute lens.

A metal halide lamp used as a light source of a projection display device has high luminous efficiency, is not accompanied by explosiveness, has good coloring, and can be fine-tuned in its color tone. On the other hand, since the distance between the electrodes of the lamp is long, the size of the light-emitting portion is quite large, about 5 to 8 mm, and the parallelism of the emitted light beam through the reflector is extremely poor (normally, the reflected light beam from the reflector is (It has a divergence angle of about ± 10 ° with respect to the optical axis of the lamp).

Therefore, in a projection type display device using a light source system having poor parallelism of the emitted light beam, such as a metal halide lamp, the effect of increasing the light utilization efficiency of the converging minute lens and increasing the brightness of the display screen (hereinafter referred to as "brightness"). However, there is a problem that the effect of improving the height cannot be sufficiently exhibited.

Accordingly, the present invention solves the above-mentioned problems, and an object of the present invention is to provide a light-collecting microlens even in a projection type display apparatus using a light source system having poor parallelism of emitted light beams. It is an object of the present invention to provide a projection display device using a novel optical mechanism that can sufficiently exhibit the effect of improving the brightness of the display.

[0010]

In order to solve the above-mentioned problems, a projection display device according to the present invention comprises a light source, a display panel having a plurality of pixels, and a projection for projecting light emitted from the display panel. And a lens, wherein the display panel is provided with a lens array so as to correspond to the plurality of pixels, and the display panel has a substantially central axis formed by the projection lens. And is disposed so as not to be on the optical axis of the projection lens and parallel to the optical axis of the projection lens, and the light source emits at an angle of 0 ° to the optical axis of the light source. The amount of luminous flux emitted at an angle to the optical axis of the light source is larger than the amount of luminous flux, and
The amount of luminous flux emitted at a certain angle with respect to the optical axis of the light source has a peak characteristic, and the optical axis of the light source is disposed at a predetermined angle with respect to the substantially central axis of the display panel. Wherein the predetermined angle is set such that the peak of the amount of luminous flux emitted from the light source is located in the angle range of the incident light that can be used by the minute lenses constituting the lens array. . Further, in such a projection display device, an optical axis of the projection lens is arranged on a side opposite to a side where the light source is located, with the substantially central axis of the display panel as a boundary. And Further, in the projection display device as described above, the minute lens is a cylindrical lens.

[0011]

FIG. 4 shows an angular distribution of a light beam emitted from a general light source system using a metal halide lamp.
Areas indicated by reference numerals 41, 42, and 43 in the drawing (referred to as angle areas 1, 2, and 2 ', respectively) indicate an incident angle range of a light beam that can be used by a focusing microlens to a panel. is there. From the figure, it can be seen that the peak of the amount of emitted light beam that contributes the most to the brightness (light beam incident at an angle of ± θ) is not in the angle range where the microlens can be used, and therefore, the effect of improving the brightness of the microlens cannot be sufficiently exhibited. I understand.

FIG. 5A schematically shows, by arrows, the strongest luminous flux component which is incident on the display panel 54 at an angle θ based on FIG. 4 and which contributes most to brightness (display panel). The angle of incidence on is exaggerated.) That is, the strongest light beam 53 is incident on the display panel 54 at an angle of ± θ, but these light beams cannot be used by the minute lens (the incident angle is out of the angle range that can be used by the minute lens, and It does not contribute to the improvement in brightness (obstructed by the light-shielding part). On the other hand, FIG. 5B shows a case where the optical axis 52 of the light source is inclined at an angle θ with respect to the substantially central axis 55 of the display panel, and the display panel 54 is at 0 ° and +2.
A light beam enters at an angle of θ (or −2θ). In this state, the light beam incident at 0 ° completely enters the usable angle range of the microlens, and the light beam incident at + 2θ (or -2θ) also has appropriate focusing characteristics such as the focal length of the microlens. For example, it is possible to enter the usable angle range 2 or 2 ′, and as a result, light is not blocked by the minute lens portion (including the display panel).

That is, by inclining the optical axis of the light source system with respect to the display panel, the strongest luminous flux component contributing to brightness is taken into an angle range usable by the minute lens, and the effect of improving the brightness by the minute lens is maximized. It is possible to make use of it.

In the above configuration, the light beam passing through the display panel has a large exit angle in one direction (upward in FIG. 5B), but the projection lens is placed above the panel as shown in FIG.
In addition, by arranging the display panel such that the substantially central axis of the display panel and the optical axis of the projection lens are parallel to each other, it is possible to efficiently take in the luminous flux emitted from the display panel.

By adopting the above optical configuration, the effect of improving the brightness of the light-collecting microlenses can be sufficiently exhibited even in a projection display device using a light source system having poor parallelism of the emitted light beam. I understand.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. However, the present invention is not limited to the following examples.

(Embodiment 1) FIG. 1 is a configuration diagram showing an optical system of a projection display apparatus according to an embodiment of the present invention. Here, an active matrix type liquid crystal panel was used as the display panel. In FIG. 1, light emitted from a light source 1 is condensed by a condenser lens 10 and radiated to a display panel 4 with a reduced light beam diameter. When the light beam diameter emitted from the light source is larger than the size of the display panel, the light beam diameter can be narrowed down by using a condenser lens, and the light density can be improved by adjusting to the display panel size to obtain a bright screen display. I can do it.

On the light source side of the display panel, micro lenses 5 are arranged in an array. The micro lens used here is a cylindrical lens, which has a characteristic that a light condensing action is generated only in a direction parallel to the sheet of FIG. 1 and no light condensing action is generated in a direction perpendicular to the sheet of FIG. Of course, other general circular lenses may be used. Here, the structure of the display panel is shown in FIG.

Referring to FIG. 2, the display panel includes two transparent substrates (a counter substrate 22 and a TFT substrate 26) and a liquid crystal layer 25 formed between the substrates. Further, an active switching element 24 for driving liquid crystal is formed on the TFT substrate in contact with the liquid crystal layer. On the other hand, a light shielding film for protecting the active switching element from strong light incident on the opposite substrate in contact with the liquid crystal layer. 23 is formed so as to cover the active switching element.

Here, the minute lenses 21 formed in an array form the light shielding film 23 of the display panel as described above.
It is installed for the purpose of improving the light use efficiency of the display panel by guiding the incident light, which has been blocked by the above, through the pixel opening while being condensed by the microlenses, and guiding it to the projection lens. As shown in FIG. 3, not all light incident on the microlenses is guided to the pixel apertures, but whether or not they pass through the pixel apertures depends on the condensing property of the microlenses and the angle of incidence on the display panel. Decided. In FIG.
Light 27 incident on the display panel at an angle close to perpendicular
Passes through the pixel opening facing the microlens, and the incident angle range of the incident light in this case is indicated by angle range 1 in FIG. Also, the light 28 obliquely incident on the display panel at a considerably large specific angle passes through the pixel opening located adjacent to the pixel opening facing the microlens, and the incident angle range of the incident light in this case is Is the angle range 2 or 2 'in FIG.
Indicated by

Returning to FIG. The light source system is disposed at an angle θ with respect to the substantially central axis of the display panel. Where θ
Is the incident angle of the strongest light beam shown in FIG. When the light source system is arranged to face the display panel, the angle component of the light beam incident on the display panel is as shown in FIG. 4, and the strongest light beam that contributes the most to the brightness cannot be used by the minute lens. Are arranged at an angle of θ so that the incident angle of the strongest luminous flux on the display panel is −θ → 0 °, + θ →
Since it changes to + 2θ, the amount of luminous flux available in the microlens greatly increases. That is, the angle component of the light beam incident on the display panel is relatively equivalent to that shown in FIG. As can be seen from FIG. 6, since the peaks of the light flux intensity are located in the angle ranges 1 and 2 of the incident light that can be used by the minute lens, the amount of the light flux guided to the pixel opening through the minute lens is greatly increased.

In the display panel used in the projection display device of the present invention, the light incident side (ie, the counter substrate 22)
Only the micro lens array is formed. Therefore, the light condensed by the microlenses and passing through the pixel opening is emitted from the display panel at a certain angle while diverging.
If a lens similar to that formed on the counter substrate 22 is formed on the emission side of the TFT substrate 25, the emitted light becomes substantially parallel light again and is guided to the projection lens.
Since it is difficult to make the thickness of the FT substrate as thin as the counter substrate, it is difficult to realize an optical system using such two microlens arrays as a pair. However, if the parallelism of the light from the light source is improved, the focal length of the minute lens can be increased, and the above-described optical system using the pair of lens arrays can be employed. In that case,
It is possible to further improve the efficiency of capturing light rays in the projection lens.

Therefore, while keeping the optical axis 8 of the projection lens parallel to the substantially central axis 3 of the display panel, it is shifted to the side opposite to the side where the light source system is located with the substantially central axis of the display panel as a boundary. With this arrangement, the light transmitted through the display panel can be effectively supplemented and guided to the screen 9 by utilizing the asymmetry of the light ray taking-in angle of the projection lens. In this case, the asymmetry means that the angle of incidence of the light ray is symmetrical on the optical axis of the lens, but as the distance from the optical axis increases, the angle increases on the side where the optical axis exists and decreases on the opposite side. I do. By arranging the display panel and the projection lens as described above, it is possible to guide most of the luminous flux emitted from the display panel with a certain angle while diverging to the projection lens.

With the above configuration, the image information on the display panel is enlarged and projected on the screen surface via the projection lens.

The present embodiment has been described above by taking an active matrix type liquid crystal panel having a TFT element as a display panel as an example. Other display panels, such as a simple matrix type liquid crystal panel, an electrochromic panel, a PLZT panel, etc. The optical mechanism of the present invention can also be used in the case of using.

[0026]

As described above, according to the present invention, the light beam emitted from the light source system that contributes the most to the brightness can be used with high efficiency in the minute lens. Also,
Light transmitted through the display panel and directed to the projection lens can be guided to the projection lens with high efficiency. Therefore, it is possible to realize a projection display device in which light use efficiency is extremely high and a bright display screen is obtained.

[Brief description of the drawings]

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

FIG. 2 is a configuration sectional view of a display panel used in the first embodiment.

3A and 3B are diagrams for explaining a transmission state of a light beam incident on a display panel provided with a microlens, and FIG. 3A is a diagram illustrating a case where a parallel light beam is incident on the display panel vertically;
FIG. 3B is a diagram illustrating a case where a parallel light beam enters the display panel from an oblique direction.

FIG. 4 is a diagram showing an angular distribution of a light beam emitted from a light source.

5A and 5B are diagrams schematically showing the strongest luminous flux components incident on the display panel, and FIG. 5A is a diagram showing a case where the substantially central axis of the display panel coincides with the optical axis of the light source, and FIG. The figure which shows the case where it does not correspond.

FIG. 6 is a diagram illustrating an angle distribution of a light beam incident on the display panel when the light source is installed such that the optical axis of the light source forms an angle θ with respect to a substantially central axis of the display panel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Optical axis of light source 3 Substantially center axis of display panel 4 Display panel 5 Micro lens 6 Transmitted light 7 Projection lens 8 Optical axis of projection lens 9 Screen 10 Condenser lens 21 Micro lens 22 Opposite substrate 23 Light shielding film 24 Active switching element Reference Signs List 25 liquid crystal layer 26 TFT substrate 27 vertically incident light 28 obliquely incident light 31 minute lens substrate 32 minute lens 33 light shielding unit 34 pixel opening 41 angle area 1 42 angle area 2 43 angle area 2 '51 light source 52 light source Optical axis 53 Strongest luminous flux 54 Display panel 55 Approximately central axis of display panel 56 Transmitted light

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03B 21/00 G02F 1/1335

Claims (3)

(57) [Claims] 1. A projection type display device comprising: a light source; a display panel having a plurality of pixels; and a projection lens for projecting light emitted from the display panel, wherein the display panel includes the plurality of pixels. A lens array is provided so as to have a corresponding relationship with the pixel of the display panel, and the display panel has a substantially central axis not positioned on the optical axis of the projection lens, and with respect to the optical axis of the projection lens. The light source is configured such that the light source emits a light beam that is inclined with respect to the optical axis of the light source than the light beam that emits at an angle of 0 ° with respect to the optical axis of the light source. Many, and has a characteristic that the amount of light emitted at an angle inclined by a certain angle with respect to the optical axis of the light source has a peak, and the optical axis of the light source is substantially Are arranged at a predetermined angle, and the predetermined angle Is set so that the peak of the amount of luminous flux emitted from the light source is located in the angle range of the incident light that can be used by the minute lenses constituting the lens array. 2. The projection display device according to claim 1, wherein an optical axis of the projection lens is arranged on a side opposite to a side where the light source is located with the substantially central axis of the display panel as a boundary. A projection display device characterized by being made. 3. The projection display device according to claim 1, wherein the minute lens is a cylindrical lens.