JPH08107536A - Projection display device - Google Patents

Abstract

(57) [Summary] [Purpose] The vertical divergence angle of each vertical part of the screen is controlled so as to correspond to the viewing angle considering the viewer distribution from each part, and the change in brightness caused by the change in divergence angle is controlled. Compensation is performed by controlling the light density on the original image forming surface side. [Structure] The pitch of the modulation pitch lenticular lens means 12 'is large at the upper end and small at the center to the lower end. Therefore, the vertical divergence angle at the upper end can be relatively increased.
At that time, the brightness of the screen at the upper end decreases. By controlling the gain of the gain control circuit 17 so as to increase corresponding to the upper end portion of the screen, it is possible to compensate for the decrease in luminance at the upper end portion. [Effect] With a minimum increase in power consumption, a bright and easy-to-see screen can be provided to viewers distributed over a wide range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-resolution projection display device capable of providing excellent image quality even when viewed from a wide viewing direction in the vertical direction.

[0002]

2. Description of the Related Art An example of the configuration of a conventional projection display device is shown in FIG. In the figure, 1 is a screen, 2 is a projection lens, 3 is an original image forming surface, 4 is an original image forming means, 5 is an output amplifier, 6 is a preamplifier, and 7 is an image signal input terminal. In a device using a CRT, 3 is C
In a device using a liquid crystal panel, which is a face plate of RT, 3 is a liquid crystal panel.

FIG. 2 shows an example of the structure of a conventional transmission screen. In the figure, 8 is a Fresnel sheet, 9 is a vertical divergence lenticular sheet, 10 is a horizontal divergence lenticular sheet, 12 is a lenticular lens surface for vertical micro light divergence with a pitch of about 80 μm, and 11 is macro light focusing with a pitch of about 100 μm. Fresnel lens surface for use, 13 is a lenticular lens surface for horizontal micro light divergence with a pitch of about 500 μm, and 14 is a black stripe surface.
An enlarged sectional view of the sheet 10 for one cycle is shown in FIG. In the figure, the traveling direction of light is indicated by a solid line with an arrow. Reference numeral 14 'is a light transmitting portion, and 14''is a black stripe portion. Usually, a light diffusing particle layer is provided on any one of the sheets 8, 9, and 10. The detailed description of FIGS. U
See SP4725134.

FIGS. 4 and 5 show horizontal directivity and vertical directivity of the screen shown in FIG. 3, respectively. Generally, relative brightness is 1/3
The above angle range is defined as the proper viewing range and is referred to as a divergence angle in the present invention. As can be seen from FIGS. 4 and 5, in the prior art, the horizontal divergence angle was a little over 90 degrees, and the vertical divergence angle was about 20 degrees, which was constant over the entire screen surface.
The gain of this screen was about 6 times.

The above characteristics are appropriate for the current television system in which the number of scanning lines per field is about 250, but they are insufficient for computer displays having 1000 or more scanning lines. . The reason is as follows.

FIG. 6 shows the vertical directivity and the suitable viewing range of the conventional screen. In the figure, reference numeral 15 is an exit side conjugate point of the Fresnel lens described above.

Each barycentric light of the light emitted from each point on the screen goes to this conjugate point 15. H is the effective height of the screen. In the figure, the solid line with an arrow indicates the traveling direction of the light beam. The area surrounded by diagonal lines is the proper viewing range.

In the case of the ordinary television system, the appropriate value of the distance from the screen to the viewer, that is, the appropriate viewing distance is 3H to 8H. The suitable viewing range in FIG. 6 is preferable because it includes exactly this suitable viewing distance.

However, in the case of a computer display having 1000 or more scanning lines, it is necessary to be able to view the screen closer to the screen. This is shown in FIG. In the figure, 16 is the distribution of the positions of the eyes of the viewer. That is, it is desirable that the shortest viewing distance is about 1H. When used for such an application, in the prior art, the strength of the vertical divergence lenticular lens 12 of FIG. 2 is uniformly strengthened, and the vertical divergence angle shown in FIG. 5 is doubled (about 40 degrees).
Had spread to. However, in that case, the screen gain is reduced to about half, and the brightness of each part of the entire screen is reduced to about half, resulting in a problem that the image contents are difficult to read. Further, if the power of the light source is doubled to compensate for the deterioration of the brightness, there is a problem that the power consumption becomes excessive and the cost is wasted for heat dissipation.

[0010]

SUMMARY OF THE INVENTION One object of the present invention is to provide a projection display device whose vertical divergence angle is modulated according to the vertical portion on the screen.

Another object of the present invention is to provide a projection display device having a function of compensating for a relatively small part of the relative change in luminance due to the modulation of the vertical divergence angle in the screen.

[0012]

In order to achieve the above object, in the first embodiment of the present invention, for vertical divergence,
A transmissive screen with a modulated pitch lenticular lens means is used.

In another embodiment of the present invention,
A light density modulating means for modulating the light density of the original image forming surface is provided.

[0014]

The function of the modulation pitch type lenticular lens is
The array pitch at the vertical portion on the screen where the widest vertical divergence angle is required is selected to be about 1.2 times or more as large as the array pitch at the position where the narrowest divergence angle can be obtained. Since the lenticular lens means has a large number of one profile shape arranged in the one-dimensional direction, its divergence angle is almost proportional to the arrangement pitch. Therefore, the vertical divergence angle can be increased to about 1.2 times or more in the vertical portion on the screen where the widest divergence angle is required.

The light density modulating means acts to improve the light density of a portion on the original image forming surface corresponding to the portion requiring the widest divergence angle. Therefore, it is possible to partially and partially compensate the deterioration of the luminance at the widest divergence angle portion.

When the original image forming surface is a CRT face plate, the optical density modulation can be achieved by controlling the intensity of the electron beam current by an electronic circuit. Specifically, the gain of the video signal amplifier circuit is controlled in synchronization with vertical scanning. When the original image forming surface is a liquid crystal panel, the modulation of the light density can be realized by two methods. The first method is gain control of the video signal as in the above. The second method is a method of optically modulating the intensity of light incident on the liquid crystal panel. Alternatively, the first and second methods may be used in combination.

[0017]

EXAMPLE FIG. 8 shows a first example of the present invention. The figure shows the portion of the screen. In the figure, except for 12 ', it is the same as FIG. Reference numeral 12 'is a modulation pitch lenticular lens means. An enlarged view of the cross section is shown in FIG. In the figure, the vertical divergence angles are indicated by v1 to v4. In the figure, v1 to v2 from the bottom of the screen to the center are about 20.
At a constant degree, v3 is about 30 degrees, and v4 at the upper end is about 40 degrees. The arrangement pitch of the lenticular lenses at the portion where the widest divergence angle is required (upper end) is selected to be about twice the arrangement pitch of the portion (lower end to center) where the narrowest divergence angle is sufficient. Practically, if this ratio is 1.2 times or more, the improvement effect becomes remarkable. Therefore, it is a requirement of this embodiment that this ratio be 1.2 times or more.

FIG. 10 shows an appropriate viewing range when the screen shown in FIG. 9 is used. In the figure, the Fresnel lens (see FIG.
The exit side conjugate point of 11) is placed at a distance 17 of 3H. Here, the chief rays from each part of the screen are concentrated. The screen is tilted forward about 10 degrees.

As shown in the figure, the vertical divergence angle is + -20 degrees at the upper end of the screen, 40 degrees in total (actually, due to the nonlinearity inherent in Snell's law, the downward divergence is more than 20 degrees. It greatly spreads), and it is about + -10 degrees from the central portion to the lower end portion of the screen, which is 20 degrees in total. Therefore, the portion surrounded by diagonal lines in the figure is the proper viewing area. As can be seen by superimposing this figure with the previously described FIG.
It matches the use of.

In FIG. 9, the modulation pitch lenticular lens means 12 'may have a convex lens shape or a concave lens shape in cross section. Further, it may have a cylindrical lens shape or a higher-order curved shape. The maximum divergence angle obtained with a cylindrical lens is about 40 degrees. If it is hyperbolic, it can be further expanded. This is the end of the description of the first embodiment.

FIG. 11 shows a first modification of the first embodiment. In FIG. 8, the modulation pitch lenticular lens means 12 'is arranged on the exit surface, but in this example it is arranged on the entrance surface side. Others are the same as FIG.

FIG. 12 shows still another modification. In the figure, the sheet 9 is omitted, and the modulation pitch lenticular lens means 12 ′ is formed on the incident surface of the Fresnel sheet 8. With this configuration, the number of screens can be reduced. However, at the upper end of the screen in FIG. 10, the tendency that the lower divergence angle becomes larger than the upper divergence angle becomes stronger (the cause is the nonlinearity of Snell's law).
Considering the above, it is recommended to apply to each special purpose.

FIG. 12 shows a modification suitable for applying the present invention to a so-called multi-scrin system in which two or more screens are vertically stacked. In the well-known multi-screen method, the conjugate point on the light emission side of the Fresnel lens 11 is usually set to the point at infinity. Further, it is desired to ensure continuity of the vertical directional characteristics at the joint between the first stage and the second stage. FIG. 13 shows a modification suitable for use in the upper side of such an application.

In the figure, the elements other than 12 "are the same as those already described. 12" is a modified modulation pitch lenticular lens means. An enlarged sectional view of the seat 9 is shown in FIG.
4 shows. In the figure, the vertical directivity angles of the emitted light are v1, v2, v
3, v4, which are increased in this order. Such a lenticular lens surface can be realized by forming substantially only one half surface of the continuous lenticular lens at a portion where the pitch is the largest, even if such a lenticular lens surface is small. The profile of the lenticular lens may have a shape that approximates a part of a cylindrical surface or an elliptical surface to a broken line. If the shape of the ellipsoidal surface has a major axis in the normal direction of the screen, and its eccentricity is set to the middle of the reciprocal of the refractive index of the medium and 1, the vertical directional characteristics will be flat and uniform. It is effective for the use that needs to be done.

In the first embodiment and the modifications described above, the modulation pitch lenticular lens means 12 'or 12 "is used.
The pitch of can be zero (that is, a simple plane) at the portion where the narrowest divergence angle is sufficient. Because, as described in the section of the prior art, sheets 8, 9, and 10 are usually used.
This is because the light diffusing particle layer is provided in either of the above, and therefore the light diffusing particle layer can impart a minimum vertical divergence angle. Alternatively, lenticular lens means having a divergence angle of about 10 degrees may be further added to the remaining surface, for example, the incident surface of the sheet 8 or the exit surface of the sheet 9 in FIG. By doing so, the steepness of the cutoff portion of the vertical directional characteristic (FIG. 5) can be reduced, and a more gentle slope characteristic can be obtained. The pitch of the vertical lenticular lens is in the range of several tens μm to about 1 mm, and can be selected sufficiently smaller than the pixel size depending on the application.

This concludes the description of the first embodiment of the present invention and its modifications.

A second embodiment is now presented, which is recommended for use with the first embodiment of the present invention.

The second embodiment relates to a light density modulating means. First, an example of using an electronic circuit is shown in FIG. In the figure, the elements other than 17, 18, and 19 are as described above.

Reference numeral 17 denotes a light density modulating means using an electronic circuit, specifically, a gain control circuit, the gain of which is controlled substantially in proportion to an input signal from the terminal 18. Reference numeral 19 is a block in which a synchronization signal separation circuit and a waveform generation circuit are combined. These operations will be described with reference to the signal waveform diagram shown in FIG. In the figure, 6'is a waveform diagram of the output of the preamplifier 6, 18 'is a waveform of the terminal 18, 17' is a waveform diagram of the output of the gain control circuit 17, 19 is a vertical scanning period, 2
0 is a vertical blanking period, and the total of these periods is 1 vertical scanning period Tv. 21 corresponds to the upper end of the screen, 22 corresponds to the center of the screen, and 23 corresponds to the lower end of the screen. This figure shows a case where the gain from the upper end to the center of the screen is increased. This is shown for the case of compensating for the characteristics of the screen described above with reference to FIGS. 8, 9, 11, and 12.

The waveform 17 'shown in FIG. 16 can relatively increase the luminance at the upper end of the screen, so that appropriate compensation suitable for the purpose can be performed.

The above is the description of the light density modulating means using the electronic circuit.

Next, an example of optical light density modulating means is shown in FIG.
Shown in Except for 24 to 28 in the figure, it is the same as that described above. 3 is a liquid crystal panel or a light valve. Reference numeral 24 is a light source, 25 is a reflecting mirror, and 26 is a light density modulating means, specifically, a glass plate whose lower half is formed into a one-dimensional meniscus lens. 27 and 28 are portions corresponding to the upper end portion and the lower end portion of the screen of the emitted light, respectively. Solid arrows are the paths of light rays. As can be seen from the figure, the light density of the portion 27 can be increased as compared with the portion 28. Increasing the thickness of the light density modulating means 26 can improve the degree of increase. Therefore, with the configuration of FIG. 17, it is possible to compensate for the decrease in gain and brightness at the upper end of the screen 1'described above.

According to the second embodiment of the present invention (FIG. 15 or FIG. 16), a decrease in screen brightness is prevented mainly by supplying extra power only to the portion corresponding to the upper end portion of the screen. be able to. Therefore, a high degree of performance can be achieved with a minimal increase in power.

Instead of adding the one-dimensional meniscus lens means 26, in FIG. 17, the light density may be modulated by making the upper light emitting area of the light source 24 larger than the lower light emitting area.

This completes the description of the second embodiment of the present invention.

[0036]

According to the present invention, it is possible to provide a vertical divergence angle that matches the distribution of the viewer depending on the vertical portion of the screen, and the minimum power consumption increases.
It is possible to prevent deterioration of screen brightness. Therefore, eye strain of the viewer can be reduced. Therefore, it has high industrial value.

[Brief description of drawings]

FIG. 1 is a configuration of a projection display device.

FIG. 2 Prior art screen means.

FIG. 3 is an operation explanatory diagram of FIG. 2;

FIG. 4 is an operation explanatory diagram of FIG. 2;

FIG. 5 is an operation explanatory diagram of FIG. 2;

FIG. 6 is a suitable viewing range of a conventional technique.

FIG. 7 shows an example of viewer distribution.

FIG. 8 is a first embodiment of the present invention.

FIG. 9 is a modulation pitch vertical lenticular lens means of the present invention.

FIG. 10 shows an example of a suitable viewing range of the present invention.

FIG. 11 is a modification of the present invention.

FIG. 12 is a modification of the present invention.

FIG. 13 is a modification of the present invention.

FIG. 14 is a modification of the present invention.

FIG. 15 is a second embodiment of the present invention.

16 is a waveform chart for explaining the operation of FIG.

FIG. 17 is a modification of the second embodiment of the present invention.

[Explanation of symbols]

1, 1 '... Screen, 2 ... Projection lens, 3 ... Original image forming surface, 4 ... Original image forming means, 5 ... Output amplifier, 6 ... Preamplifier, 7 ... Image signal input terminal, 8 ... Fresnel sheet,
9 ... Vertical divergence lenticular sheet, 10 ... Horizontal divergence lenticular sheet, 12 '... Modulation pitch lenticular lens means, 12 "... Modified modulation pitch lenticular lens means, 17 ... Gain control circuit, 26 ... 1
Dimensional meniscus lens.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Sakamoto 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Ltd. Information & Video Media Division, Hitachi, Ltd. (72) Takashi Ito 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Information & Video Media Division (72) Inventor Makoto Kamiya 216 Totsuka-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Hitachi, Ltd. Information & Video Media Division

Claims (3)

[Claims] 1. A projection display comprising original image forming surface means, projection lens means, and transmissive screen means, the screen means comprising at least a co-Fresnel lens and a horizontal lenticular lens for diverging light in the horizontal direction. , And a vertical lenticular lens for diverging light in the vertical direction. The vertical lenticular lens is formed as a modulation pitch type lenticular lens means, and the array pitch at the portion where the widest vertical divergence angle is required is the narrowest. It is selected to be 1.2 times or more of the arrangement pitch in a region where the vertical divergence angle can suffice, and further, a light density modulation means is provided, and the light density modulation means corresponds to a region where the widest vertical divergence angle is required. The projection type display having the light density of the image forming surface means relatively increased as compared with the light density of the portion corresponding to the narrowest divergence angle. B devices. 2. A projection type display device according to claim 1, wherein said light density modulating means comprises a gain control circuit for controlling the image signal amplitude. 3. A projection display device according to claim 1, wherein said light density modulating means is constituted by one-dimensional meniscus lens means.