JPS6315792B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention provides one or more cathode ray tubes for each of the three emission colors constituting a color image, and the information light of these cathode ray tubes is transmitted through a magnifying lens or It is related to a video projector that displays a color image by projecting and forming an image on a screen via a Schmitt optical system, and in particular detects the horizontal positional deviation of the image projected and formed by each cathode ray tube on the screen. , relates to a horizontal position deviation detection device for a video projector projected image.

Background Art Figures 1a and b show one of the above video projectors.
A plan view and a front view showing an example of cathode ray tubes CRT ₁ , CRT ₂ , which correspond to three emission colors of red, green, and blue.
Information light from CRT ₃ is projected onto screen S and superimposed to display a color image. Figure 2 a, b
Figure 2 shows a plan view and a front view of another example of the video projector described above, in which a plurality of (in this case two) cathode ray tubes are used for each emission color to increase the brightness, that is, a cathode ray tube corresponding to the red emission color. Tube CRT ₁ , CRT ₄ ,
Cathode ray tubes CRT ₂ , CRT ₅ , which correspond to green emission color,
Cathode ray tubes CRT ₃ and CRT ₆ that support blue emission color
and these cathode ray tubes CRT ₁ , CRT ₂ ,...,
Information light from CRT ₆ is projected onto screen S and superimposed to display a color image.

In this way, in the above video projector,
Since the information light from the cathode ray tubes of each emission color is projected onto the same screen and superimposed, the horizontal and vertical positions of the scanning lines of each color must match each other. Conventionally, for this purpose, an adjuster was provided for each cathode ray tube, and adjustments were made manually so that the scanning lines of the other cathode ray tubes matched with the scanning lines of the reference cathode ray tube. Therefore, it is time-consuming, and the adjustment status changes over time, resulting in mismatching of the scanning lines of each cathode ray, resulting in disadvantages such as deterioration of image quality.

DISCLOSURE OF THE INVENTION The present invention was proposed in view of the above-mentioned problems, and includes detecting the horizontal positional deviation of each cathode ray tube.
It is an object of the present invention to provide a horizontal position deviation detection device for a video projector projected image.

To this end, the present invention provides a position detecting pulse signal having a pulse width slightly wider than the variation range of the horizontal position of the image by each cathode ray tube, for each cathode ray tube in the horizontal direction of the scanning lines during the vertical blanking period. These pulse signals for position detection are generated in different sections that do not overlap, and are superimposed on the video signal. A light-receiving element having a vertically elongated light-receiving area is arranged to receive the optical output of the signal, and each cathode ray tube outputs a position detection output pulse signal, which is the photoelectric conversion output of these light-receiving elements, to the normal position in the horizontal direction. By determining the temporal deviation with respect to a certain point in time, the horizontal position deviation of the image projected by each cathode ray tube is detected.

According to the present invention, the detected horizontal position deviation is output to the horizontal deflection circuit of each cathode ray tube, so that the image from each cathode ray tube is automatically controlled to be positioned at a normal horizontal position. This eliminates the need for manual adjustment, eliminates mismatches in the scanning lines of each cathode ray tube due to aging, and provides images of good quality at all times.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to drawings of embodiments. FIG. 3 is a configuration diagram of an apparatus for detecting horizontal position deviation of a video projector projected image according to an embodiment of the present invention. In this embodiment _, information light is projected and imaged onto _{a screen} S using the video projector shown in FIG. This is applied to a video projector that displays images. FIG. 4 is a timing chart of signals in each part of FIG. 3. Reference numeral 1 denotes a position detection pulse signal generation circuit, which generates position detection pulse signals S _{1 and 1} for detecting horizontal positional deviations of images produced by cathode ray tubes CRT ₁ , CRT ₂ and CRT ₃ , respectively, as shown in FIG. Generates S ₂ and S ₃ . These position detection pulse signals S ₁ , S ₂ , and S ₃ are generated on arbitrary scanning lines during the vertical blanking period, and their pulse width T _W has a value slightly wider than the horizontal variation range of the image. ,
Also, the time T ₁ , T ₂ , T ₃ from the horizontal synchronization signal H _SYNC to the center of each position detection pulse signal S ₁ , S 2 , S 3 is the same as the time T 1 , T ₂ , T ₃ from the horizontal synchronization signal H SYNC to the center of each position detection pulse signal S ₁ , S ₂ , S _{3 .} are set so that they do not overlap with each other in time. The position detection pulse signal generation circuit 1 can be easily constructed using a counter circuit, a monostable multivibrator, or the like. 2 is a clock pulse generator that generates a clock pulse CLK to determine the generation timing of the position detection pulse signals S ₁ , S ₂ , and S _3. When a predetermined number of horizontal synchronization signals H _SYNC are input, the position detection pulse signal is generated. It is driven by the drive signal S ₀ output from the generation circuit 1. 3 superimposes the position detection pulse signal S ₁ on the red video signal input from the terminal t ₁ and outputs it to the cathode ray tube CRT _1.
This is a position detection pulse signal superimposition circuit that outputs a position detection pulse signal. 4 superimposes the position detection pulse signal S ₂ on the green video signal input from the terminal t ₂ , and outputs the signal to the cathode ray tube CRT _2.
This is a position detection pulse signal superimposition circuit that outputs a position detection pulse signal. 5 superimposes the position detection pulse signal S ₃ on the blue video signal input from the terminal t ₃ and outputs it to the cathode ray tube CRT _3.
This is a position detection pulse signal superimposition circuit that outputs a position detection pulse signal. PR ₁ , PR ₂ , and PR ₃ are light-receiving elements each having a vertically elongated light-receiving area that receives the optical output of the pulse signals S ₁ , S ₂ , and S ₃ for position detection, as shown in Fig. 4. Time T ₁ of pulse signals S ₁ , S ₂ , S ₃ ,
It is arranged horizontally at the lower end of the screen S corresponding to T ₂ and T ₃ . Therefore, each cathode ray tube
When the images from CRT ₁ , CRT ₂ , and CRT ₃ are normal and there is no horizontal positional deviation, the light receiving elements PR ₁ ,
Position detection pulse signals are generated from PR ₂ and PR ₃ at times T ₁ , T ₂ , and T ₃ from the horizontal synchronization signal H _SYNC , respectively.
Pulse width T _S obtained by photoelectrically converting the optical outputs of S ₁ , S ₂ , and S ₃
position detection output pulse signals S ₁ ′, S ₂ ′, and S ₃ ′ are obtained. Also, the image from the cathode ray tube CRT ₂ is shown on the left.
If the images from the cathode ray tube CRT ₃ are shifted to the right, the position detection output pulse signals S ₂ ″, S ₃ ″ of the light receiving elements PR ₂ , PR ₂ , PR ₃ will be the same as in the above normal case. Delayed by ΔT ₂ from T ₂ and T ₃ respectively,
It is output at a time advanced by ΔT ₃ . In other words, the values of ΔT ₂ and ΔT ₃ are temporal deviations indicating the degree of horizontal deviation (positional deviation) of images by the cathode ray tubes CRT ₂ and CRT ₃ . 6 is a light receiving element PR ₁ ,
This is a horizontal position deviation calculation circuit for calculating the temporal deviations ΔT ₁ , ΔT ₂ , ΔT ₃ of the output of _the position detection output pulse signals of PR ₂ and PR ₃ . FIG. 3 is a circuit diagram of an embodiment for determining the temporal deviation ΔT ₁ of the output. Counter CT receives drive signal S ₀ from position detection pulse signal generation circuit 1.
The counter CT enters the operating state at the same time that the clock pulse CLK is output, starts counting the clock pulse CLK, and continues counting until the position detection output pulse signals S ₁ ′, S ₁ ″ are given, so the count output of the counter CT is
Time from horizontal synchronization signal H _SYNC to output of position detection output pulse signals S ₁ ′, S ₁ ″ shown in Figure 4
T ₁ ′, T ₁ ″.This counter CT
The count output is converted from digital to analog by a D/A converter DAC. E _S1 is the count value of the clock pulse CLK during the time T ₁ - (T _S /2) until the position detection output pulse signals S ₁ ′, S ₁ ″ are output when the position error is zero, in digital or analog form. This is the converted voltage (constant).D/A converter
By determining the difference between the output of the DAC and the voltage E _S1 using the differential amplifier DA, the position detection output pulse signal S ₁ ',
A temporal deviation ΔT ₁ of the output of S ₁ ″ is obtained.Other temporal deviations ΔT ₂ and ΔT ₃ are obtained in exactly the same manner.

The signals of temporal deviations ΔT ₁ , ΔT ₂ , ΔT ₃ obtained by this horizontal direction position deviation calculation circuit 6 are transmitted to each cathode ray tube.
It is added to the horizontal position correction circuit attached to the horizontal deflection circuit of CRT ₁ , CRT ₂ , and CRT ₃ , and is controlled so that the horizontal position deviation becomes zero.

The position detection pulse signals S ₁ , S ₂ , and S ₃ may be superimposed on scanning lines at different vertical positions as long as they do not overlap each other in the horizontal direction. The present invention is based on the second
Needless to say, the present invention can also be applied to a video projector having a plurality of cathode ray tubes for each emission color as shown in the figure.

[Brief explanation of the drawing]

1A and 1B are a plan view and a front view showing one example of a video projector which is an object of the present invention, and FIGS. 2A and 2B are plan views showing another example of a video projector which is an object of the present invention. FIG. 3 is a configuration diagram of a horizontal position deviation detection device for a video projector projected image according to an embodiment of the present invention, and FIG. 4 is a horizontal synchronization signal, a position detection pulse signal, and a position detection output. FIG. 5 is a timing chart of the pulse signal, and is a circuit diagram of an embodiment of the horizontal position deviation calculation circuit. CRT ₁ , CRT ₂ , CRT ₃ ...Cathode ray tube, PR ₁ ,
PR ₂ , PR ₃ ... Light receiving element, 1... Pulse signal generation circuit for position detection, 2... Clock pulse generator, 3,
4, 5...Pulse signal superimposition circuit for position detection, 6...Horizontal position deviation calculation circuit.

Claims (1)

[Scope of Claims] 1. One or more cathode ray tubes are provided for each of the three emission colors constituting a color image,
In video projectors that display color images by projecting the information light from these cathode ray tubes onto a screen via a magnifying lens or Schmitt optical system and forming an image, the range of variation in the horizontal position of the image produced by each cathode ray tube is slightly larger than that of the video projector. , a position detection pulse signal generation circuit that generates a position detection pulse signal having a wide pulse width for each cathode ray tube in different non-overlapping sections in the horizontal direction of an arbitrary scanning line in the vertical blanking period. a position detection pulse signal superimposing circuit that superimposes the position detection pulse signal on the video signal; and a position detection pulse signal superimposing circuit arranged within a corresponding section of the screen of each of the position detection pulse signals, a group of light-receiving elements each having a vertically elongated light-receiving area, and outputting a position detection output pulse signal obtained by photoelectrically converting the optical output of each of the position detection pulse signals received by each of the light-receiving elements; 1. An apparatus for detecting horizontal positional deviation of images projected by a video projector, comprising: a horizontal positional deviation calculating circuit for calculating a temporal deviation with reference to when each cathode ray tube is in a normal position in the horizontal direction.