JPH09105902A - Projection type picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a picture frame obvious by making the four corners of a display picture bright even in the case of using the luminous flux with the maximum efficiency while converging the luminous flux of a light source to a minimum. SOLUTION: This device is a projection type picture display device in which a display element 1 whose screen is rectangle is used and the magnified picture of the picture displayed on the screen of the display element 1 through a lens 3 is obtained as a projection picture by irradiating the luminous flux from a light source having an almost circular shaped expansion from the rear side of the display element 1. The picture signal supplying circuit 10 supplying a picture signal to the display element 1 is provided with a terminal for brightness control 11B controlling the brightness of the display picture. Moreover, a compensation circuit 13 supplying a compensation signal CC for intensifying the brightness of the picture of the four corners of a rectangular display screen to the terminal for brightness control 11B of the picture signal supplying circuit 10 is provided. Then, the picture signal compensated so that the brightness of a picture to be displayed at four corners of the screen is raised is supplied to the display element 1 by the compensation circuit 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention illuminates a liquid crystal display (hereinafter, referred to as LCD) from the back side thereof and projects an image displayed on the LCD screen onto a screen through a lens to enlarge the image. The present invention relates to a projection-type image display device capable of displaying images.

[0002]

2. Description of the Related Art As shown in FIG. 5, a projection type image display device using an LCD enlarges a display image of the LCD 1 between a front surface side of the LCD 1 and a screen 2 and projects it on the screen. LCD with a lens 3 for
A light source 4 for irradiating the LCD 1 with a light flux is provided on the back side of the LCD 1.

The LCD 1 has a rectangular display screen, and although not shown, the image signal from the image signal supply circuit is displayed on the LCD.
An image is displayed on the LCD 1 by being supplied to the LCD 1 via the drive circuit.

When the LCD 1 is irradiated with the light flux from the light source 4, the image displayed on the LCD 1 is enlarged and displayed on the screen 2 by the lens 3.

The screen 2 may be a white wall, but is preferably dedicated to the projection type image display device.

The light source 4 is, for example, a lamp, and includes a light emitting element 4L and a mirror 4M having a reflecting surface having an elliptic spherical surface shape. The mirror 4M is for focusing the light from the light source 4 into a luminous flux that efficiently irradiates the LCD 1. With such a configuration, a small lamp with a small wattage can be used as the light source 4,
This type of projection-type image display device can be downsized.

[0007]

The light beam focused by the mirror 4M of the light source 4 described above becomes a light beam having a circular spread as shown in FIG. Meanwhile, LCD
The screen 1D of No. 1 has a rectangular shape as described above. Therefore, in order to make the brightness of the screen 1D of the LCD 1 uniform, as shown in FIG. 6, it is necessary to make the luminous flux LA larger in diameter than the size of the screen 1D of the LCD 1.

However, this increases the amount of wasted light flux. In FIG. 6, the light in the shaded portion is wasted.

In order to reduce the size and cost of the projection type image display device, it is important to reduce the power of the light source 4 as much as possible. On the other hand, in order to make the screen as bright as possible and make it easier to see, it is necessary to increase the light amount of the lamp as the light source. Increasing the amount of light at a constant luminous flux is equivalent to increasing the power.

Considering the above, in order to brighten the screen without increasing the power as much as possible, it is necessary to eliminate the waste of the luminous flux and improve the utilization efficiency. Therefore,
To improve the efficiency of the luminous flux emitted from the light source 4, FIG.
It is desirable to design the device so that the screen 1D of the LCD 1 is inscribed in the circular cross section of the light flux from the light source 4 as indicated by LB in FIG.

However, when the luminous flux is designed to have the maximum efficiency as shown in FIG. 7, the screen 1D of the LCD 1 is displayed.
As described above, since it has a rectangular shape, the four corners of the screen 1D surrounded by a dotted circle in FIG.
There is a problem that it becomes darker than the central part of D.

In view of the above points, it is an object of the present invention to brighten the brightness at the four corners of a rectangular screen so that the projected image can be seen easily even when the luminous efficiency is maximized.

[0013]

In order to solve the above-mentioned problems, a projection type image display device according to the present invention has a display element having a rectangular screen for displaying an image and a substantially circular shape from the back side of the display element. A light source for irradiating a light flux having a spread, a lens provided between the surface side of the display element and the screen, and an image signal supplied to the display element and a brightness for adjusting the brightness of the display image. And an image signal supply circuit having a terminal for adjusting the height, the display device is irradiated with a light beam from the light source, and an image displayed on the screen of the display device is projected on the screen through a lens to be displayed. In the projection type image display device,
The brightness adjustment terminal of the image signal supply circuit is provided with a correction circuit for supplying a correction signal for increasing the brightness of the image at the four corners of the rectangular display screen.

The display element displays an image by sequentially performing screen scanning in the horizontal and vertical directions, and the image signal supply circuit causes the horizontal scanning period and the vertical scanning. In the case where the image signal synchronized with the cycle is supplied to the display element, and the brightness of the display image is controlled according to the brightness control voltage supplied to the brightness adjusting terminal, The correction circuit includes a parabolic wave voltage generation circuit that is synchronized with the horizontal scanning period, a parabola wave voltage generation circuit that is synchronized with the vertical scanning period, and a mixing circuit that mixes the two parabolic waveform voltages. And the output voltage of the mixing circuit is supplied to the brightness adjustment terminal of the image signal supply circuit.

According to the projection type image display apparatus of the present invention having the above-mentioned structure, the correction circuit corrects the display image signal so that the brightness of the image at the four corners of the rectangular screen becomes brighter than the other areas. By doing so, even when used with the light flux from the light source narrowed down to maximize the efficiency, the brightness of the four corners of the screen can be made as bright as the others,
This makes it possible to obtain a projection image in which the image frame is made clear and which is easy to see.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a projection type image display device according to the present invention will be described below with reference to the drawings.

In this embodiment, the LCD 1, the screen 2, the lens 3, and the light source 4 have the same construction as in the conventional case, and as shown in FIG. 7, the LCD 1 having a rectangular display screen 1D is The light flux from the light source 4 is configured to be used with maximum efficiency, and the power of the light source 4 is set to be optimum.

Although not shown, the display signal from the image signal supply circuit 10 is supplied to the LCD 1 via the LCD drive circuit 5 to the LCD 1. The LCD drive circuit 5 is
Similar to the scanning of the cathode ray tube of the television receiver, while the screen of the LCD 1 is scanned in the horizontal direction, the vertical scanning for changing the horizontal scanning position in the vertical direction is performed to display the image on the LCD 1. The timing signal Tm for this scanning is also supplied from the image signal supply circuit 10.

As described above, the luminous flux from the light source 4 is LC
When D1 is illuminated, the LCD 1 is displayed on the screen 2.
The inverted image of the image displayed in 1 is enlarged by the lens 3 and displayed. Therefore, the image signal supply circuit 10 supplies the LCD drive circuit 5 with an image signal that is a correct image when projected on the screen 2, and the image is displayed on the screen 1D of the LCD 1.

In the case of this embodiment, the image signal supply circuit 10 includes an RGB decoding circuit 11, an LCD timing signal generation circuit 12, and a correction circuit 13 for correcting the brightness of the image at the four corners of the screen of the LCD 1. Prepare

The color video signal Vi is input to the image signal supply circuit 10. This input color video signal Vi
Is, for example, a video signal of a received television signal, a reproduced color video signal from a VTR, or the like.

The RGB decoding circuit 11 generates from the input video signal Vi three color signals R, G, B for forming an image to be displayed on the screen 1D of the LCD 1,
It is supplied to the LCD drive circuit 5.

The LCD timing signal generation circuit 12 separates the horizontal synchronizing signal HD and the vertical synchronizing signal VD from the input video signal Vi, and the timing signal T for scanning the screen of the LCD 1 from these synchronizing signals HD and VD.
m is generated and supplied to the LCD drive circuit 5. LCD
The drive circuit 5 scans the screen of the LCD 1 based on the timing signal Tm, and the RGB decoding circuit 11B
An image is displayed on the screen 1D of the LCD 1 by using the color signals R, G, B from the.

The RGB decoding circuit 11 also includes a brightness adjusting terminal 11B, and the brightness adjusting terminal 11B.
By changing the level of the control voltage supplied to, the DC levels of the color signals R, G, B are changed, and the brightness of the display image can be adjusted. The variable resistor 14 constitutes a manual brightness adjustment volume, and the brightness of the image can be adjusted by manual adjustment by the user.

In this embodiment, the voltage of the brightness adjusting terminal 11B of the RGB decoding circuit 11 is controlled by the correction signal CC from the correction circuit 13, and the LCD 1
Adjust the brightness of the four corners of the display screen so that it is brighter than the other areas.

In this case, the correction signal C from the correction circuit 13
As will be described later, C is a parabolic wave signal synchronized with the horizontal scanning period and the vertical scanning period of the LCD 1. Therefore, the correction circuit 13 is supplied with the horizontal synchronizing signal HD and the vertical synchronizing signal VD from the LCD timing signal generating circuit 12. The correction circuit 13 generates the correction signal CC from the horizontal synchronization signal HD and the vertical synchronization signal VD.

FIG. 2 shows an example of the configuration of the correction circuit 13, and FIGS. 3 and 4 show the output signal waveforms of the respective parts.

That is, it comprises a parabolic wave signal forming circuit 21 having a horizontal period, a parabolic wave signal forming circuit 22 having a vertical period, and a mixer circuit 23. The parabolic wave signal forming circuit 21 having a horizontal period and the parabolic wave signal forming circuit 22 having a vertical period each have a sawtooth wave generating circuit 211.
And 221 and integrating circuits 212 and 222.

The horizontal synchronizing signal HD (see FIG. 3A)
Is supplied to the sawtooth wave generation circuit 211, and a sawtooth wave signal HSA having a horizontal cycle (see FIG. 3B) is obtained from this.
The horizontal cycle sawtooth wave signal HSA is integrated by the integrating circuit 212, and from this, the horizontal cycle parabolic wave signal HP is obtained.
R (see FIG. 3C) is obtained and supplied to the mixer circuit 23.

Further, the vertical synchronizing signal VD (see FIG. 4A) is supplied to the sawtooth wave generating circuit 211, and a sawtooth wave signal VSA (see FIG. 4B) having a vertical cycle is obtained from this. The vertical cycle sawtooth wave signal VSA is integrated by the integration circuit 212, and the vertical cycle parabolic wave signal VPR is integrated.
(See FIG. 4C) is obtained and supplied to the mixer circuit 23.

In the mixer circuit 23, the parabolic wave signal HPR having a horizontal period and the parabolic wave signal VPR having a vertical period are mixed, and the mixed signal MX (FIG. 4D) is more mixed.
(See) is obtained. As shown in a partially enlarged view of FIG. 4E, the mixed signal MX is a signal in which the average level of the horizontal-period parabolic wave signal corresponds to the vertical-period parabolic wave signal. Then, the mixed signal MX is supplied to the brightness adjustment terminal 11B of the RGB decoding circuit 11 via the capacitor 15. The color signals R, G, B whose brightness has been corrected by this correction signal are supplied to the LCD 1 through the LCD drive circuit 5.

As a result, the brightness of the display image is such that the average brightness level corresponds to the control voltage corresponding to the resistance value of the variable resistor 14 adjusted by the user, but the mixed signal M
The horizontal parabolic wave signal of X makes the left and right ends of the screen in the horizontal direction brighter than the central part, and the vertical parabolic wave state signal causes
Since the upper and lower edges in the vertical direction are corrected so that they are brighter than the central portion, the corrections in both the horizontal and vertical directions are combined so that the four corners of the displayed image are brighter than the other portions. Is corrected to.

Therefore, even when the luminous flux of the light source 4 is narrowed down to the minimum and used at maximum efficiency, the four corners of the image displayed on the rectangular screen of the LCD are darker than the other portions. Since the image frame can be clarified by making the correction, the display image is easy to see.

In the above embodiment, the display element is an LCD, but by irradiating a light flux from the back side of the display element, an image is displayed on the screen through a lens provided on the front side of the display element. Any display element can be applied as long as it can project and display.

Needless to say, the light emitting element forming the light source is not limited to the lamp.

[0036]

As described above, according to the present invention, in the projection type image display device, the four corners of the projection image displayed on the screen become bright, the image frame becomes clear, and the display image becomes easy to see.

For this reason, the luminous flux of the light source is reduced to the minimum,
Even when used with maximum efficiency, the four corners of the display screen will not be darker than the other parts.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a projection type image display device according to the present invention.

FIG. 2 is a diagram showing a configuration example of a correction circuit in FIG.

FIG. 3 is a waveform diagram for explaining the correction circuit in FIG.

FIG. 4 is a waveform diagram for explaining the correction circuit of FIG.

FIG. 5 is a diagram for explaining an outline of a projection type image display device.

FIG. 6 is a diagram for explaining the relationship between the screen of the display element and the luminous flux.

FIG. 7 is a diagram for explaining the relationship between the screen of the display element and the luminous flux.

[Explanation of symbols]

 1 LCD 2 Screen 3 Lens 4 Light Source 5 LCD Drive Circuit 10 Image Signal Supply Circuit 11 RGB Decode Circuit 11B Brightness Adjustment Terminal 12 LCD Timing Signal Generation Circuit 13 Correction Circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Daiji Takahashi 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (2)

[Claims] 1. A display element having a rectangular screen shape for displaying an image, a light source for irradiating a light flux having a substantially circular spread from the back side of the display element, a front side of the display element and a screen. A lens provided between the display element and an image signal supply circuit having a brightness adjusting terminal for adjusting the brightness of the display image while supplying an image signal to the display element, and the display element from the light source. A projection-type image display device for irradiating a light flux to display an image displayed on a screen of the display element by projecting the image on the screen through a lens, wherein the brightness adjustment of the image signal supply circuit is performed. A projection type image display device, characterized in that a correction circuit for supplying a correction signal for increasing the brightness of an image at the four corners of the rectangular display screen is provided at the terminal. 2. The display element displays an image by sequentially performing screen scanning in a horizontal direction and a vertical direction, and the image signal supply circuit includes a scanning cycle in the horizontal direction and a scanning in the vertical direction. An image signal synchronized with a cycle is supplied to the display element, and the brightness of a display image is controlled according to a brightness control voltage supplied to the brightness adjustment terminal. Includes a parabolic voltage generation circuit that is synchronized with the horizontal scanning period, a parabolic voltage generation circuit that is synchronized with the vertical scanning period, and a mixer circuit that mixes the two parabolic voltages. The projection type image display device according to claim 1, wherein the output voltage of the mixing circuit is supplied to the brightness adjustment terminal of the image signal supply circuit.