JPH0628460B2 - Projection display device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device that projects a television image or the like on a screen and projects the image.

2. Description of the Related Art A color image projector designed to display a television image on a screen uses three cathode ray tubes for displaying R, G, and B images, respectively, and projects the images of the respective cathode ray tubes on the screen to synthesize them. By doing so, 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 a high voltage deflection circuit.

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

(4) There is uneven brightness on the screen.

(5) The size of the screen displayed on the screen is fixed to a certain size.

(6) The screen is dark.

Therefore, it is an object of the present invention to provide a projection display device that solves these drawbacks.

Means for Solving the Problems A projection display device according to the present invention comprises a light source 1 for emitting a plurality of different colored lights R, G, B, and a collimating means 5 for making the colored lights R, G, B parallel rays. , A dividing means 6 for dividing each of the plurality of color lights R, G, B formed into the parallel rays into a first and a second part, and a polarization axis of the color lights R, G, B in the first part. Constant direction (eg X-axis direction)
Of the first portion of which the polarization means 7 and 8 and the pixels arranged in a matrix are aligned, and the polarization axes are aligned in the certain direction (for example, the X-axis direction). A plurality of transmissive liquid crystals 11, 15, 18 that allow the pixels to transmit the different colored lights R, G, B while polarization-modulating them.
And a control means 25 for controlling the polarization modulation by supplying color signals corresponding to the colored lights R, G, B of the image to be displayed to the pixels, and corresponding to the image of the second portion. A brightness unevenness detecting unit 36 for detecting brightness unevenness in the cross section, and a brightness unevenness correcting unit 37 for adjusting the level of the color signal based on the detection output of the brightness unevenness detecting unit 36.
And a synthesizing means 12 for synthesizing the color lights R, G, and B that have passed through the plurality of transmissive liquid crystals 11, 15, and 18 into synthesized light.
16 and a polarizing plate 19 that transmits the combined light having a polarization axis in a specific direction (for example, the X-axis direction).

Action In the projection display device according to the present invention, the respective color lights R, G, B are polarization-modulated according to the color signal corresponding to the image to be displayed, and the polarization axes are combined in a specific direction (for example, the X-axis direction). Since only light passes through the polarizing plate 19, this polarizing plate 19
The combined light that has passed through forms a color image.

EXAMPLE In FIG. 1, as the light source 1, for example, a xenon lamp, a fluorescent lamp, a halogen lamp or the like of about 150 W is used.
Note that it is also possible to use sunlight for the light source 1. The light source 1 is driven by the drive source 2 to emit white light. The light source 1 is housed in a container 3 made of a cold mirror whose inner surface is formed as a curved reflecting mirror. The light beam from the light source 1 is reflected by the cold mirror of the container 3,
The heat rays are removed and the visible light is concentrated. The concentrated visible light is emitted to the outside from the opening of the container 3. Next, the heat rays are removed again by passing through the cold filter 4, and then converted into parallel rays by the collimating lens 5. The parallel rays are incident on the cold mirror 6 and the remaining heat rays are transmitted, and only visible rays are reflected. The heat rays that have passed through the cold mirror 6 are used for correcting unevenness in the brightness of the screen, as will be described later.

The parallel rays of visible light reflected by the cold mirror 6 are then transmitted through the deflecting beam splitter 7 so that their polarization axes are aligned with the X axis, for example. Polarizing beam splitter 7
The visible light whose polarization axis is the Y-axis reflected by is converted into the X-axis by the polarization axis conversion device 8 described later.

The X-axis visible light transmitted through the polarization beam splitter 7 is then added to the dichroic mirror 9. As will be described later, the X-axis visible light converted by the polarization axis conversion device 8 is added to the dichroic mirror 9 together with the X-axis visible light transmitted through the polarization beam splitter 7, thereby About 100% of the energy can be used.

The dichroic mirror 9 has a characteristic of reflecting blue light and transmitting yellow light. The blue light of the X axis reflected by the dichroic mirror 9 is reflected by the mirror 10 and then the liquid crystal 11 controlled by a B signal added from a control circuit 25 described later.
The polarized light is modulated by transmitting the light. This liquid crystal 11 is, for example, a known TFT type liquid crystal provided with a transparent electrode for controlling each polarization axis and a drive circuit having a matrix structure for driving the transparent electrode, corresponding to 300 × 250 pixels. Is used. Therefore, the polarization axis of the incident light is controlled by applying a voltage according to the B signal to the transparent electrode of each pixel. 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 is also on the X axis. When the transparent electrode has no voltage and the incident light is on the X axis, the output light is converted to the Y axis by switching the polarization axis of the incident light by 90 °. 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 the polarization modulation according to the B signal can be applied. The 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 has a characteristic of transmitting green light and reflecting red light. The reflected red light is reflected by the mirror 14 and passes through the liquid crystal 15. Like the liquid crystal 11, the liquid crystal 15 is of a TFT type, and is controlled by the R signal applied from the control circuit 25 so that the incident red light is polarization-modulated. 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 type liquid crystal 18 controlled by the G signal applied from the control circuit 25, whereby polarization modulation is applied. The polarization-modulated green light is incident on the dichroic mirror 16. The dichroic mirror 16 has the same characteristics as the dichroic mirror 13. Therefore, the green light from the liquid crystal 18 is transmitted and the red light from the liquid crystal 15 is reflected, and the output light thereof becomes yellow light. This yellow light is the dichroic mirror 1
It is incident on 2. The dichroic mirror 12 has the same characteristics as the dichroic mirror 9. Therefore, the yellow light is transmitted and the blue light from the liquid crystal 11 is reflected, and as the output light thereof, the combined light of the blue light, the red light and the green light, which is polarization-modulated respectively, is obtained. The combined light is transmitted through the polarizing plate 19, so that, for example, the X-axis combined light is extracted.

This X-axis synthetic light forms a color image. That is,
For example, with respect to blue light, all or most of the X-axis blue light incident on a pixel on the liquid crystal 11 is the liquid crystal 11 if the level of the B signal is high when the pixel is bright. It will be transparent. Since the blue light of the X axis passes through the polarizing plate 19 that transmits the X axis light,
The blue light transmitted through the polarizing plate 19 becomes brighter for the pixel. If the pixel is dark, the B signal level is low, so
The liquid crystal 11 converts all or most of the incident blue light of the X axis into the Y axis. Since the Y-axis blue light is blocked by the polarizing plate 19 that passes the X-axis, the blue light transmitted to the pixel becomes dark. The same operation as described above is performed for red light and green, and as a result, a color image is obtained from the polarizing plate 19. This color image is projected on the screen 21 through the zoom lens 20. Therefore, the focus adjustment ring 22 of the zoom lens 20 enables focus adjustment, and the zoom adjustment ring 23 allows
The image size on the screen 21 can be easily changed to an arbitrary size.

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

A composite video signal is input to the input terminal 26. This composite video signal is sent to the Y / C processing circuit 27.
To obtain R, G, B color signals, and
In addition to the sync separation circuit 28, horizontal and vertical sync signals H and V are obtained. The synchronization signals H and V drive the clock generator 29. The clock generator 29 outputs a predetermined quimming pulse p and supplies it to a predetermined circuit.

The R, G, and B color signals are the AC drive amplifier 30,
After being amplified by 31, 32, the sample and hold circuit 3
3, 34, and 35 sample and hold based on the timing pulse. The sample-held R, G, and B signals are applied to the liquid crystals 11, 15, and 18 controlled by the timing pulse p, and the color light incident on each liquid crystal is polarization-modulated.

The operations of the sample hold and the polarization modulation are performed as follows, for example.

1 for a screen in which 300 x 250 pixels are arranged
This scanning line is divided into 25 groups of 12 lines each, and the color signals are sequentially sampled and latched for each group,
The sampled color signal is applied to the transparent electrode of each pixel on the liquid crystal. When this is performed 25 times, one scanning line is completed. By performing the same operation sequentially for all scanning lines based on the timing pulse in the vertical direction,
The 1-field screen is completed. In addition, the liquid crystal 11, 15,
18 is AC driven by AC drive amplifiers 30, 31, and 32 as is known. Further, the optical path lengths of the blue, red, and green light beams from the dichroic mirror 9 to the polarizing plate 19 are formed to be equal.

Next, the brightness unevenness correction will be described.

As described above, the light source 1 is housed in the container 3 made of a cold mirror. If the mirror surface of the container has unevenness, the visible light collimated by the collimating lens 5 has unevenness, which causes the unevenness of the screen. It appears as uneven brightness.

In this embodiment, in order to correct this uneven brightness, the heat rays of parallel rays that have passed through the cold filter 6 are used. This heat ray is incident on the uneven brightness detector 36. The detector 36 has a plurality of photoelectric elements arranged corresponding to the pixels of the image, and is configured to scan these photoelectric elements with a clock pulse according to the scanning of the screen. As the photoelectric element, a known element such as a solid-state image sensor such as a phototransistor or CCD is used. The photoelectric elements may be provided in the same number as the pixels corresponding to all the pixels of the screen, or the screen may be divided into cells and one may be arranged in each cell.

A luminance signal corresponding to the luminance unevenness sequentially extracted from these photoelectric elements according to the scanning of the screen controls the gains of the AC drive amplifiers 30, 31, 32 through the amplifier 37. As a result, the uneven brightness of the screen is corrected.

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

As described above, a halogen lamp, a xenon lamp, a fluorescent lamp, sunlight, etc. are used as the light source 1, but they have different spectra, and the spectrum changes depending on the drive voltage and drive current. Will collapse. In order to adjust the white balance automatically, in this embodiment, each liquid crystal 11, 1
In the vicinity of 5, 18, a detection element 39 composed of a photoelectric element,
40, 41 are provided, and these detection elements 39, 40, 41 are provided.
The color light that has passed through the liquid crystals 11, 15, and 18 is detected, and the detection signal is added to the white balance adjustment circuit 38.

The detection elements 39, 40, 41 are composed of the liquid crystals 11, 15,
It is arranged so as to detect color light transmitted through a region outside the 18 effective screen regions. FIG. 2 shows an arrangement example of the detection element 39 taking the liquid crystal 11 as an example, and the detection element 39 is arranged at a position facing the area outside the effective screen area 11 a on the liquid crystal 11.

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

This circuit adjusts other blue light and red light with reference to the green light. For this reason, the detection signal obtained from the green light detecting element 41 is added to the comparators 42 and 43 so as to be compared with the detection signals from the detecting elements 39 and 40. The AC drive amplifier 32 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 the wide balance is automatically adjusted.

FIG. 4 shows a second embodiment of the white balance adjusting 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 detection voltage is applied between the detection transparent electrodes 45 and 46 provided outside the screen area of the liquid crystal 11 to detect the X-axis. Polarization modulation is applied to blue light. The polarization-modulated blue light is passed through the X-axis polarizing plate 47, and the X-axis blue light, that is, the blue light corresponding to the pedestal level of the B signal is applied to the detection element 39. The detection signal of the detection element 39 is applied to the 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 transparent electrodes 50 and 51 for detection provided outside the screen area of the liquid crystal 18, and X Polarization modulation is applied 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 this X axis green light, that is, green light corresponding to the pedestal level of the G signal, is applied to the detection element 41. The detection signal of the detection element 41 is applied to the comparator 48,
The detection signal from the detection element 39 is compared. The AC drive amplifier 32 is controlled by the comparison output. Also for the R signal (not shown), the pedestal level is detected, and this detection level is added to the detection transparent electrode of the liquid crystal 15 to perform polarization modulation on the red light. Further through the polarizing plate X
The red color of the shaft is obtained, and this is detected by the detection element 40. This detection signal and the detection signal of the detection element 41 are compared by a comparator provided separately, and the comparison output is used to output the AC drive amplifier 31.
To control. According to the above, the pedestal level of the B signal and the R signal is controlled with the pedestal level of the G signal as a reference, so that the white balance adjustment is performed.

Next, the polarization axis converter 8 will be described.

In FIG. 1, the polarization axis conversion device 8 includes a mirror 55 and a T
It is composed of an FT type liquid crystal 56. Mirror 55
Are arranged so that the Y-axis parallel visible light reflected by the polarization beam splitter 7 is reflected and made incident on the liquid crystal 56. Therefore, the incident visible light on the Y axis is converted to the X axis by passing through the liquid crystal 56. This X
The visible light on the axis is converted into the polarized beam splitter 7 as described above.
Dichroic mirror 9 with X-axis visible light transmitted through
In addition, the energy of light can be used almost 100%, and the screen can be brightened.

As another embodiment, the Y-axis visible light reflected by the mirror 55 is directly applied to the dichroic mirror 9, and the X-axis visible light transmitted through the polarization beam splitter 7 is transmitted through the liquid crystal to be converted into the Y-axis. Then, it may be added to the dichroic mirror 9. In that case, as the polarizing plate 19, one that transmits visible light on the Y axis is used.

Next, the polarization axis conversion device 8 and the polarization beam splitter 7
A negative-to-positive conversion device using the above will be described with reference to FIG.

In the figure, the liquid crystal 55 constituting the polarization axis converter 8 is shown.
Is provided with transparent electrodes 57 and 58 on both surfaces thereof. On the transmission side of the polarization beam splitter 7, the liquid crystal 5
9 is provided, and the transparent electrodes 60,
61 is provided. The light transmitted through the two liquid crystals 56 and 59 is focused by the lens 62, collimated by the lens 63, and applied to the dichroic mirror 9. The lengths l ₁ and l ₂ in FIG. 5 are selected to be l ₁ : l ₂ = 1: 2.

In the above structure, when a voltage is applied to the transparent electrodes 57 and 58 and no voltage is applied to the transparent electrodes 60 and 61, the liquid crystal 56 is formed.
The Y-axis light incident on is transmitted as it is, and the X-axis light incident on the liquid crystal 59 is converted to the Y-axis. Therefore, since the Y-axis light is incident on the dichroic mirror 9, the color image finally extracted from the polarizing plate 19 is a negative image. On the contrary, if a voltage is applied to the transparent electrodes 60 and 61 and no voltage is applied to the transparent electrodes 57 and 58, X-axis light is extracted from the two liquid crystals 56 and 59. A positive image is obtained. According to the above, 2
By controlling one of the pair of transparent electrodes 57, 58 and 60, 61 to be ON and the other to be OFF, negative / positive conversion can be easily performed.

The negative / positive conversion device described above can be applied not only to the image projector as shown in FIG. 1 but also to other image display devices and image pickup devices. When applied to an image pickup device, light from a subject may be applied to a film surface or a photoelectric surface through the negative / positive conversion device.

As another method of performing the negative / positive conversion in FIG. 1, the polarizing plate 19 may be replaced with one that allows the Y axis to pass, or the polarizing plate 19 may be replaced with a liquid crystal provided with a transparent electrode. Good.

EFFECTS OF THE INVENTION Since a plurality of cathode lines are not used as in the prior art, and the liquid crystal matrix does not perform deflection due to high voltage unlike a cathode ray tube, there are few external circuits in the periphery, and therefore the device can be made compact. can do. Since each color of light after polarization modulation is combined by combining means and projection on a screen etc. is performed after that, image distortion and color misregistration do not occur, and adjustments such as registration adjustment can be performed easily. You can

Moreover, the uneven brightness of parallel rays is detected by the uneven brightness detecting means, and based on the detection result of the uneven brightness detecting means, the uneven brightness correcting means controls the level of the color signal for controlling the polarization modulation by the pixels of the transmissive liquid crystal. Since it is adjusted with, there is no unevenness in the brightness of the screen.

Then, of the color lights divided into the first and second parts by the dividing means, the combining means combines the first portion and the luminance unevenness detecting means detects the second portion. The detection by the detection means does not hinder the display of the image.

Further, since the respective color lights after the polarization modulation are combined by the combining means, the size of the screen can be easily changed by using the zoom lens or the like in the subsequent projection on the screen or the like.

In addition, the color light emitted from the light source is collimated by the collimating means, and the polarization axes of the collimated color light are aligned in a certain direction by the polarizing means, and then polarization-modulated by the transmissive liquid crystal. With less loss, you can get a bright screen.

[Brief description of drawings]

1 is a schematic diagram including a circuit block showing an embodiment of the present invention, FIG. 2 is a schematic plan view of a liquid crystal, FIG. 3 is a block diagram showing a first embodiment of a white balance adjusting circuit, FIG. FIG. 4 is a block diagram showing the second embodiment, and FIG.
It is a schematic diagram showing an example of a positive conversion device. In the reference numerals used in the drawings, 1 ... Light source 5 ... Collimating lens 7 ... Polarizing beam splitter 9, 13, 12, 16 ... Dichroic mirror 11, 15, 18 ... Liquid crystal 19 ... Polarizing plate 25 ...... It is a control circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshifumi Okada 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) Reference JP-A-51-52233 (JP, A) JP 57-102613 (JP, A) JP 59-131278 (JP, A)

Claims (1)

[Claims] 1. A light source which emits a plurality of different colored lights, a collimating means for converting the colored lights into parallel rays, and a division for dividing each of the plurality of colored rays into the parallel rays into a first portion and a second portion. Means, a polarizing means for aligning the polarization axes of the colored light in the first portion in a certain direction, and pixels arranged in a matrix, each having a polarization axis in the certain direction. Further, a plurality of transmissive liquid crystals that allow the pixels to transmit the different colored lights different from each other in the first portion while polarization-modulating the pixels and a color signal corresponding to the colored lights in the image to be displayed are supplied to the pixels. Control means for controlling the polarization modulation, brightness unevenness detecting means for detecting brightness unevenness in the cross section of the second portion corresponding to the image, and the color signal based on the detection output of the brightness unevenness detecting means. Nore A brightness nonuniformity correction means for adjusting a bell, a combining means for combining the color lights transmitted through the plurality of transmissive liquid crystals into a combined light, and a polarizing plate for transmitting the combined light having a polarization axis in a specific direction. Projection display device.