JPS61102893A - Projecting type display device - Google Patents

Abstract

PURPOSE:To obtain a compact projector free of image distortion and color aberration and capable of adjusting the size of the picture and white balance by providing plural transmitting liquid crystals that polarize the incident colored lights and the polarizing plates that transmit the polarized colored lights. CONSTITUTION:In the vicinity of liquid crystals 11, 15, and 18, detector elements 39-41 made of photoelectric elements are provided. These detector elements 39-41 detect the colored lights that passed through crystals 11, 15, and 18, and its detection signals are inputted to a white balance adjuster 36. The detector elements 39-41 are disposed so as to detect the colored lights that penetrate the areas other than the usual picture areas of the liquid crystals 11, 15, and 18. Thus, plural cathode rays are not used and the liquid crystal matrix is not deflected by a high voltage like CTR, therefore, the peripheral circuitries are minimized to provided a compact device.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a projection display device that projects television images and the like onto a screen.

Conventional technology A color image projector that projects television images onto a screen uses three cathode ray tubes that each project R, G, and B images, and projects and synthesizes the images from each cathode ray tube onto the screen. By doing this, a color image is obtained.

Problems to be Solved by the Invention Since the conventional color projector is configured as described above, it has the following drawbacks.

(1) The device becomes large.

(2) There are many external peripheral circuits such as high-voltage deflection circuits.

(3) Image distortion, color shift, etc. are likely to occur, and adjustments such as registration alignment are difficult.

(4) The size of the screen displayed on the screen is determined to be a fixed size.

(5) The screen is dark.

Means to solve problems In this example, we use dichroic light from white light.

The three color lights of R, G, and B whose polarization axes are aligned are separated through a mirror, polarizing filter, etc.
, the B signal is transmitted through three transmissive liquid crystals configured in a liquid crystal matrix that is polarized according to the B signal, and the transmitted light from each liquid crystal is combined and projected onto a screen through a lens. I try to do that.

Effect: With the above configuration, it is possible to obtain a compact color projector that is free from image distortion, color shift, etc. and whose screen size is adjustable.

Embodiment In FIG. 1, the light source 1 is, for example, a xenon lamp, a fluorescent lamp, a halogen lamp, etc. of about 150 W.

Note that it is also possible to use sunlight as the light source 1. This light source 1 is driven by a drive source 2 and emits white light. The light source 1 is housed in a container 3 made of a cold mirror whose inner surface is a curved reflecting mirror. The light rays from the light source 1 are reflected by the cold mirror of the container 3, thereby removing heat rays and concentrating visible light.

The concentrated visible light is radiated to the outside from the opening of the container 3. Next, the heat rays are removed again by passing through a cold filter 4, and then converted into parallel rays by a collimating lens 5. This parallel light beam is incident on the cold mirror 6, the remaining heat beams are transmitted, and only the visible light is reflected. The heat rays transmitted through the cold mirror 6 are
As will be described later, this is used to correct uneven brightness on the screen.

The parallel visible light reflected by the cold mirror 6 then passes through a polarizing beam splinter 7, so that its polarization axis is aligned with, for example, the X axis. Polarized beam splinter 7
The visible light whose polarization axis is the Y axis reflected by the polarization axis is converted into the X axis by a polarization axis conversion device 8, which will be described later.

The X-axis visible light transmitted through the polarizing beam splitter 7 is then applied to a dichroic mirror 9.

As will be described later, the X-axis visible light converted by the polarization axis conversion device 8 is applied to the dichroic mirror 9 together with the X-axis visible light transmitted through the polarization beam splinter 7. The energy of light is about 10
0% can be used.

The dichroic mirror 9 used has a characteristic of reflecting blue light and transmitting yellow light. The X-axis blue light reflected by the dichroic ink mirror 9 is reflected by the mirror 10, and then the liquid crystal 11 is controlled by a B signal applied from a control circuit 25, which will be described later.
By transmitting the light, polarization modulation is applied. The liquid crystal 11 is a known TFT type liquid crystal, which is provided with transparent electrodes for controlling the polarization axis and a matrix-structured drive circuit for driving the transparent electrodes, corresponding to 300 x 250 pixels, for example. It is being Therefore, by applying a voltage corresponding to the B signal to the transparent electrode of each pixel, the polarization axis of the incident light is controlled. In this case, when the maximum voltage is applied to the transparent electrode, if the incident light is on the X-axis, the output light will also be on the X-axis. In addition, when the transparent electrode is voltage-free, when the incident light is on the X axis, the output light is such that the polarization axis of the incident light is 90°.
It is switched and converted to the Y axis. Therefore, by controlling the voltage applied to the transparent electrode according to the B signal,
The amount of the X-axis (or Y-axis) component of the output light can be controlled, and polarization modulation can be applied according to the B signal. This polarization-modulated blue light is incident on the dichroic mirror 12.

On the other hand, the yellow light transmitted through the dichroic mirror 9 is incident on the dichroic mirror 13.

The dichroic mirror 13 used has a characteristic of transmitting green light and reflecting red light. The reflected red light is reflected by the mirror 14 and transmitted through the liquid crystal 15. This liquid crystal 15 is configured in a TFT type like the liquid crystal 11, and R is applied from a control circuit 25.
Polarization modulation is applied to the incident red light by controlling the signal. This polarization-modulated red light is incident on the dichroic mirror 16.

On the other hand, the green light transmitted through the dichroic mirror 13 is reflected by the mirror 17 and then enters the TFT liquid crystal 18 which is controlled by the G signal applied from the control circuit 25, thereby undergoing polarization modulation. This polarization-modulated green light is incident on the dichroic mirror 16. This dichroic mirror 16 has the same characteristics as the dichroic mirror 13 described above. Therefore, the green light from the liquid crystal 18 is transmitted, and the red light from the liquid crystal 15 is reflected, so that the output light becomes yellow light. This yellow light is the dichroic mirror 1
2. This dichroic ink mirror 12 has the same characteristics as the dichroic mirror 9. Therefore, while transmitting the yellow light, the blue light from the liquid crystal 11 is reflected, and as output light, composite light of blue light, red light, and green light, each of which has been polarized, is obtained. By transmitting this combined light through the polarizing plate 19, for example, combined light on the X axis is extracted.

This X-axis combined light forms a color image.

For example, regarding blue light, if the X-axis blue light incident on a certain pixel on the liquid crystal 11 is bright and the level of the B signal is high, then all or most of it will be reflected by this liquid crystal. 11 will pass through. This X
Since the blue light on the axis passes through the polarizing plate 19 that transmits the X-axis forward, the blue light passing through the polarizing plate 19 becomes brighter for the above-mentioned pixels. When the pixel is dark, the level of the B signal is low, so the liquid crystal 11 converts all or most of the incident blue light on the X axis to the Y axis. This Y-axis blue light is blocked by the polarizing plate 19 that passes through the X-axis, so the blue light transmitted to that pixel becomes dark. The same effect as described above is performed for red light and green light, and as a result, a color image is obtained from the polarizing plate 19. This color image is projected onto a screen 21 through a zoom lens 20. Therefore, focus adjustment can be performed using the focus adjustment ring 22 of the zoom lens 20, and the image size on the screen 21 can be easily changed to an arbitrary size using the zoom adjustment ring 23.

Next, the configuration and operation of the control circuit 25 will be explained.

A combo shift video signal is input to the input terminal 26. This composite video signal is applied to a Y/C processing circuit 27 to obtain R, G, and B color signals, and is also applied to a sync separation circuit 28 to generate horizontal and vertical sync signals H.
1■ is obtained. This synchronizing signal H1■ drives the clock generator 29. This clock generator 29 outputs a predetermined timing pulse p and supplies it to a predetermined circuit.

The above R, G, and B color signals are provided by an AC drive amplifier 30.
．． 31. After being amplified by 32, the sample and hold circuit 3
3.34.35, sample and hold is performed based on the timing pulse.

The sampled and held R, G, B signals are applied to liquid crystals 11, 15, 18 controlled by timing pulses p to polarization modulate the colored light incident on each liquid crystal.

The sample hold and polarization modulation operations described above are performed, for example, as follows.

1 for a screen with 300 x 250 pixels arranged
The scanning lines of the book are divided into 25 groups of 12 each, and the color signals are sequentially sampled and launched for each group.
This sampled color signal is applied to the transparent electrode of each pixel on the liquid crystal. By repeating this 25 times, one scanning line is completed. By sequentially performing the same operation for all scanning lines based on vertical timing pulses,
One field screen is completed. In addition, liquid crystal 11.15.
18 is AC driven in a known manner by AC drive amplifiers 30, 31, and 32. Further, the optical path lengths of blue, red, and green light from the dichroic mirror 9 to the polarizing plate 19 are formed to be equal.

Next, brightness unevenness correction will be explained.

As mentioned above, the light source 1 is housed in a container 3 made of a cold mirror, but if the mirror surface of this container is uneven, the visible light collimated by the collimating lens 5 will be uneven.
This appears as uneven brightness on the screen.

In order to correct this brightness unevenness, in this embodiment, parallel heat rays transmitted through the cold filter 6 are used. This heat ray is incident on the brightness unevenness detector 36. The detector 36 is constructed such that a plurality of photoelectric elements are arranged in correspondence with the pixels of the image, and these photoelectric elements are scanned by a cross pulse in accordance with the scanning of the screen. As the photoelectric element, a known one such as a phototransistor or a solid-state image sensor such as a CCD is used. The photoelectric elements may be provided in the same number as the pixels so as to correspond to all the pixels on the screen, or the screen may be divided into squares and one photoelectric element may be arranged in each square.

Luminance signals corresponding to luminance unevenness, which are sequentially extracted from these photoelectric elements as the screen is scanned, are passed through an amplifier 37 to control the gains of AC drive amplifiers 30, 31 and 32. This corrects uneven brightness on the screen.

Next, the white balance adjustment circuit 38 will be explained.

As mentioned above, halogen lamps, xenon lamps, fluorescent lights, sunlight, etc. are used as light a1, but they have different spectra, and the spectra change depending on the drive voltage and drive current, so the white balance of the screen will collapse.

In order to automatically adjust the white balance, in this embodiment, detection elements 39, 40, 41 consisting of photoelectric elements are provided in the vicinity of each liquid crystal 11, 15, 18. By .41, LCD 11.15
．． 18 is detected, and the detected signal is applied to a white balance adjustment circuit 38.

The detection elements 39, 40, 41 are connected to each liquid crystal 11, 15, .
They are arranged to detect colored light that passes through areas outside the 18 effective screen areas. FIG. 2 shows an example of the arrangement of the detection element 39, taking the liquid crystal 11 as an example, and the detection element 39 is arranged at a position facing an area outside the effective screen area 11a on the liquid crystal 11.

FIG. 3 shows a first embodiment of the white balance adjustment circuit 38.

This circuit uses green light as a reference and adjusts other blue light and red light. For this purpose, the detection signal obtained from the green light detection element 41 is applied to a comparator 42.43 and compared with the detection signal from the detection element 39.40.

The AC drive amplifier 30 is controlled by the comparison output obtained from the comparator 42, and the AC drive amplifier 31 is controlled by the comparison output obtained from the comparator 43, whereby white balance is automatically adjusted.

FIG. 4 shows a second embodiment of the white balance adjustment circuit.

The pedestal level of the B signal obtained from the AC drive amplifier 32 is detected by the pedestal level detection circuit 44, and this detected voltage is applied between the detection transparent electrodes 45 and 46 provided outside the screen area of the liquid crystal 11. Apply polarization modulation to blue light. This polarization-modulated blue light is passed through a polarizing plate 47 that passes through the X-axis, and this X-axis blue light, that is, blue light corresponding to the pedestal level of the B signal, is applied to the detection element 39. A detection signal from the detection element 39 is applied to a comparator 48 .

On the other hand, the pedestal level of the G signal obtained from the AC drive amplifier 30 is detected by the pedestal level detection circuit 49, and this detected voltage is applied between the detection transparent electrodes 50 and 51 provided outside the screen area of the liquid crystal 18. Apply polarization modulation to the green light on the axis. This polarization-modulated green light is passed through a polarizing plate 52 that passes through the X-axis, and the X-axis green light, that is, the green light corresponding to the pedestal level of the G signal is applied to the detection element 41. Adding the detection signal of the detection element 41 to the comparator 48,
It is compared with the detection signal of the detection element 39 described above.

The AC drive amplifier 32 is controlled by the comparison output. The pedestal level of the R signal (not shown) is also detected, and this detected level is applied to the detection transparent electrode of the liquid crystal 15 to apply polarization modulation to the red light. Furthermore, it passes through a polarizing plate to obtain red color on the X axis, which is detected by the detection element 40. This detection signal and the detection signal of the detection element 41 are compared by a separately provided comparator, and the AC drive amplifier 31 is controlled by the comparison output. According to the above, white balance adjustment is performed by controlling the pedestal levels of the B signal and the R signal using the pedestal level of the G signal as a reference.

Next, the polarization axis conversion device 8 will be explained.

In FIG. 1, the polarization axis conversion device 8 includes a mirror 55 and a T
FT type liquid crystal 56.

The mirror 55 receives the Y reflected by the polarization beam splinter 7.
It is arranged to reflect parallel visible light along the axis and make it incident on the liquid crystal 56. Therefore, the Y-axis incident visible light is transmitted through the liquid crystal 56 and converted to the X-axis. If this X-axis visible light is applied to the dichroic mirror 9 along with the X-axis visible light that has passed through the polarizing beam splitter 7 as described above, approximately 100% of the light energy can be used, and the screen can be It can be made brighter.

In addition, as another embodiment, the Y-axis visible light reflected by the mirror 55 is applied as it is to the microink mirror 9, and the X-axis visible light transmitted through the polarizing beam splinter 7 is transmitted through the liquid crystal to be reflected on the Y-axis. It may be added to the dichroic mirror 9 by converting it into . In that case, a polarizing plate 19 that transmits Y-axis visible light is used.

Next, the polarization axis conversion device 8 and the polarization beam splitter 7
A negative/positive conversion device using this will be explained with reference to FIG.

In the figure, the liquid crystal 55 constituting the polarization axis conversion device 8
Transparent electrodes 57 and 58 are provided on both sides. In addition, on the transmission side of the polarized beam splitter, there is a liquid crystal 59.
Transparent electrodes 60.6 are provided on both sides of the liquid crystal 59.
1 is provided.

The light transmitted through the two liquid crystals 56 and 59 is focused by a lens 62, collimated by a lens 63, and applied to the dichroic mirror 9. Also the length in Figure 5! 1
, β2 are selected to be n, :f2=1:2.

In the above configuration, when a voltage is applied to the transparent electrodes 57, 58 and no voltage is applied to the transparent electrodes 60, 61, the liquid crystal 56
The Y-axis light incident on the liquid crystal 59 is transmitted as is, and the X-axis light incident on the liquid crystal 59 is converted into Y-axis light. Therefore, since Y-axis light is incident on the dichroic mirror, the color image finally taken out from the polarizing plate 19 becomes a negative image.

Also, in the opposite way to the above, if voltage is applied to the transparent electrodes 60, 61 and no voltage is applied to the transparent electrodes 57, 58, X-axis light is extracted from both liquid crystals 56, 59.
Finally, a positive image is obtained.

According to the above, two sets of transparent electrodes 57.58 and 60.61
By controlling one of them to be ON and the other to be OFF, negative/positive conversion can be easily performed.

The negative/positive conversion device described above is not limited to the image projector shown in FIG. 1, but can be applied to other image display devices and imaging devices. When applied to an imaging device, the light from the subject may be applied to the funorm surface or the photocathode via the negative/positive conversion device.

In addition, as another method of performing negative/positive conversion in FIG. 1, the polarizing plate 19 may be replaced with one that passes the Y axis, or a liquid crystal provided with transparent electrodes may be provided instead of the polarizing plate 19. good.

Effects of the Invention Since multiple cathode rays are not used as in the past, and the liquid crystal matrix does not use high voltage deflection like a cathode ray tube, the number of peripheral external circuits can be reduced, and the device can therefore be made smaller. can do. Since each color light is combined and then projected onto a screen through a lens, image distortion and color shift occur, and adjustments can be made easily. Screen size can be easily changed by using a zoom lens. With less light loss, you can get a brighter screen. Negative/positive conversion can be easily performed with a single switch.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram including circuit blocks showing an embodiment of the present invention, FIG. 2 is a schematic plan view of a liquid crystal, and FIG. 3 is a block diagram showing a first embodiment of a white balance adjustment circuit. Figure 4 is a block diagram showing the second embodiment, and Figure 5 is a block diagram showing the second embodiment.
1 is a schematic diagram showing an embodiment of a positive conversion device; FIG. In addition, in the symbols used in the drawings, 1----1~-1・-・−・・・・Light source 5−・−・
−・−１−−−・−・・Collimating lens 7・・−・
−・・−・−・・・・・・・Polarized beam Subrinok 9
, 13.12.16-・Dikroi Tsukumira 11.
15.18 - Liquid crystal 19 --- Polarizing plate 25 --- Control circuit.

Claims (1)

[Claims] means for obtaining parallel rays; means for aligning the polarization axes of the parallel rays in a certain direction; means for separating the parallel rays with the aligned polarization axes into a plurality of colored lights; and each of the separated colored lights is incident on the parallel rays. A drive circuit arranged in a matrix is provided for each pixel, and by controlling this drive circuit with a color signal corresponding to each color light, polarization modulation is applied to the incident color light. A projection display device comprising a plurality of transmissive liquid crystals and a polarizing plate that passes the polarized light of each color.