JPH08331576A - Convergence system and display device using same - Google Patents

Abstract

PURPOSE: To correct convergence shift of an entire image with high accuracy by using a photodetecting element to catch luminous intensity as a voltage. CONSTITUTION: A pattern signal generating means 12 generates a pattern signal for automatic adjustment suitable for detecting convergence by photodetectors 9a-9h by the instruction of a arithmetic processing means 13. A photodetection circuit 14 detects light made incident onto the photodetectors 9a-9h, from which a signal of a prescribed voltage level is generated, it is given to an A/D converter means 10, in which the voltage is converted into a digital signal and it is fed to the arithmetic processing means 13. According to the arithmetic processing by the arithmetic processing means 13, whether or not adjustment pattern indication is in matching is decided by the photodetectors 9a-9h. When the adjustment pattern indication is not in matching, after correction data are converted, the processing above is again repeated. Convergence shift is automatically corrected by repeating the processing till the indication of the adjustment pattern is in matching for all the photodetectors 9a-9h.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CRT display device such as a color TV, a display, a projection TV, etc., which performs convergence correction using a digital memory, and more particularly to a convergence shift for correcting the convergence shift by using a photodetector. The present invention relates to a correction system and a display device using this system.

[0002]

2. Description of the Related Art In a color projection display device using a plurality of projection tubes, the incident angles on the screen are different for each of the red, green, and blue projection tubes, so that color shift occurs on the display screen. A convergence correction device is used to accurately match this color shift at each position on the screen. An example of this correction device is a digital convergence correction device capable of highly accurate adjustment as disclosed in Japanese Patent Laid-Open No. 57-212492. However, in the above apparatus, the possibility that the convergence may shift due to geomagnetism, temperature, etc. after the convergence adjustment has not been taken into consideration. In such cases, it is necessary to make adjustments each time. Therefore, for example, JP-A-63-2
An apparatus for automatically correcting this convergence deviation has been proposed as in Japanese Patent No. 09388.

[0003]

As a method for detecting a convergence deviation, in the above-mentioned conventional example, a detection element having a position calculation function, for example, a position detector using a semiconductor position detection element is arranged in the peripheral portion of the screen, A method is used in which an adjustment pattern is displayed near the position detection element and detected. However, the position detecting element is generally expensive. On the other hand, there is a method of performing detection similar to that of a position detector by arranging a plurality of inexpensive photodetection elements adjacent to each other, for example, as disclosed in Japanese Patent Laid-Open No. 63-224572. However, the above-mentioned conventional example does not consider that it is necessary to detect the convergence deviation at a plurality of positions in order to correct the convergence deviation with high accuracy, and that many photodetector elements must be arranged. It was

An object of the present invention is to provide a convergence system which can correct the convergence deviation of the entire screen with high accuracy by using the photo-detecting elements arranged at a plurality of positions, and a display device using this system. .

[0005]

SUMMARY OF THE INVENTION The above-mentioned object is to detect the intensity of light as a voltage with a single photo-detecting element, rather than adjoining a plurality of photo-detecting elements at one location to function as a position detector. By detecting the edge of the adjustment pattern with the output voltage level, the photodetector is installed at a plurality of locations outside the display screen, and the photodetector is used to detect and correct the convergence deviation of the entire screen. To be achieved. It is also achieved by optimizing the gain of the photodetector circuit including the plurality of photodetector elements and making the output voltage levels uniform.

[0006]

The adjustment pattern and the photodetection element are detected by only one photodetection element at one place by projecting the adjustment pattern whose brightness changes stepwise and detecting the edge of the adjustment pattern by the output voltage level of the photodetection circuit. Since it can be easily detected that the two match, the configuration is simple.

Therefore, by installing the photodetection elements at a plurality of locations outside the display screen, the convergence deviation of the entire screen can be corrected accurately, and the number of photodetection elements and the number of connecting lines can be reduced to simplify the structure. It is possible to achieve both.

Further, by making the output level of each photodetector circuit uniform and adapting to the input dynamic range of the next-stage circuit such as an A / D converter, the output voltage varies depending on the conditions such as the installation position of each photodetector. It is possible to absorb the dispersion of the above and secure sufficient light detection and adjustment accuracy.

[0009]

The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a block diagram showing a first embodiment of the present invention, and is a block diagram of a color projection display apparatus using a plurality of projection tubes to which a convergence deviation correction system is applied.

In FIG. 1, reference numeral 1 is an input terminal for a synchronization signal,
Reference numeral 2 is an address generating means for generating an address signal according to the scanning position of the screen from the synchronization signal, and 3 is a memory for storing data indicating a correction amount for performing convergence correction (hereinafter referred to as correction data). Reference numeral 4 is a waveform creating means for creating a convergence correction waveform from the correction data read from the memory 3, and 5 is a convergence yoke (hereinafter, CY).
CY driving means for driving the CY), 6 for CY for generating a convergence correction magnetic field, 7 for a projection tube for displaying an image, 8
Is a screen for optically magnifying and displaying the image projected on the projection tube 7. Reference numerals 9a to 9h denote photodetection elements such as solar cells, photodiodes, and phototransistors. In the present embodiment, amorphous silicon solar cells are arranged at eight locations on the outer periphery of the screen. It should be noted that the letters a to h added after the numbers hereinafter indicate that they correspond to the respective photodetecting elements and their installation positions. 1
Reference numeral 4 denotes a photodetector circuit, which uses the photodetector elements 9a to 9h to generate a signal having a voltage level suitable for input to the next-stage circuit.
Reference numeral 10 is an analog / digital conversion means (A / D conversion means) for converting the output of the photodetection circuit 14 into a digital quantity, and 1
1 is a keyboard that gives instructions for manual convergence adjustment,
Reference numeral 12 is a pattern generation means for generating an adjustment pattern on the screen, 14 is a video circuit for amplifying the input video signal, and performing white balance adjustment, brightness adjustment, contrast adjustment, etc. 13 is an output of the A / D conversion means 10. And an arithmetic processing unit such as a microcomputer that rewrites the contents of the memory 3 according to an instruction from the keyboard 11.

First, the operation of convergence correction will be described. The address generating means 2 generates an address signal according to the screen scanning and sequentially reads the correction data of the memory 3. The waveform creating means 4 creates a convergence correction waveform corresponding to each screen position based on the read correction data. The convergence correction waveform is converted by the CY driving means 5 into a signal to be supplied to CY6 and supplied to CY6. In CY6, a correction magnetic field according to the convergence correction waveform is generated to perform the convergence correction of the display device.

Next, the operation at the time of convergence adjustment will be described.

First, when an instruction to start convergence adjustment is input using the keyboard 11, an instruction from the arithmetic processing means 13 causes an automatic adjustment pattern signal suitable for convergence detection on the photodetection elements 9a to 9h to be a pattern signal. It is generated by the generating means 12. Next, the light detection circuit 14 detects the light incident on each of the light detection elements 9a to 9h, and the A / D
After generating a signal having a substantially constant voltage level suitable for the input of the converting means 10, the A / D converting means 10 converts the signal into a digital amount and sends the result to the arithmetic processing means 13. Then, by the arithmetic processing of the arithmetic processing means 13, the photodetection elements 9a-9a.
It is determined whether the adjustment pattern displays on the light receiving unit of h match, and if the adjustment pattern displays do not match on the light receiving unit, the correction data of the light receiving unit that does not match is changed. , Repeat the above process again. It is possible to automatically correct the convergence deviation by repeating the process until the adjustment pattern displays match on all the light receiving units. Of course, it is also possible to manually perform the convergence adjustment using the keyboard 11 without using the optical sensor.

FIG. 2 is a circuit diagram showing a first configuration example of the photodetection elements 9a to 9h and the photodetection circuit 15. 900a ~
900h is a unit light detection unit, which is independently installed for each light detection element. Unit light detection units 900a to 90
Since 0h has the same internal configuration, only 900a will be described. Reference numeral 90a is a solar cell using amorphous silicon, which is one example of realizing the photodetection element 9a in FIG. Reference numeral 91a is a load resistance, and 92a is a low-pass filter (hereinafter abbreviated as LPF). The light 93a is the solar cell 90.
When incident on a, the solar cell 90a has a photovoltaic power. Figure 2
In such a usage, the solar cell has the characteristic of generating a photocurrent according to the amount of incident light. Therefore, the load resistance 91
The incident amount of light from a is taken out as a voltage signal 94a. When such a photo detection circuit is used in a projection television or the like, light is incident only for a specific time within one field due to scanning. Therefore, the output of the photodetector circuit is large during the period when light is incident, and is small during other periods, and the signal change is abrupt. Difficult to do. Therefore, the LPF 92a is used to smooth the voltage signal 94a,
The voltage signal 95a is output to realize a system that is tolerant of detection timing errors. LPF92a
The output of is converted into digital data 101 by the A / D conversion means 10 and input to the arithmetic processing means 13.
In this configuration example, the A / D conversion means 10 selectively converts one of the eight analog voltage signals 95a to 95h into a digital signal and outputs the digital signal.

Since the photodetection elements 90a to 90h have different installation conditions such as installation locations and installation angles, the amplitudes of the respective photodetection signal voltages 95a to 95h vary as they are. This is not very preferable in terms of the input dynamic range of the A / D converter in the next stage and the S / N. Therefore, each unit light detection unit 900a-
If the values of the load resistors 91a to 91h in the 900h are optimized, the eight voltage outputs 95a to 9a of the photodetector circuit 14 will be generated.
It is possible to align the amplitude of 5h to a substantially constant level suitable for the input of the A / D converter. Therefore, it is possible to perform optimum adjustment without malfunction or accuracy deterioration.

FIG. 3 is a diagram showing a first display pattern example for obtaining the maximum detection voltage. Photodetector (solar cell)
Since the output of the photodetector circuit 15 is maximized when light is applied to the entire surface of 90, a sufficiently large window pattern 200 is used. FIG. 4 shows the photodetector circuit 1 in FIG.
5 is a diagram illustrating an example of time characteristics of the output voltage of FIG. 20 in the figure
0 is a window pattern where the internal brightness is almost constant (red,
Green and blue (each single color), and 301 is the LPF 92 in FIG.
An example of the output voltage waveform 95 of In addition, the solar cell 90
Is a rectangle (or square) and is installed so that each side is horizontal or vertical. In FIG. 4, when the scanning line passes over the solar cell 90, the output voltage rises,
After that, the light is gradually attenuated by the afterglow of the phosphor of the projection tube and the action of the LPF 92. The detection timing by the arithmetic processing means 13 is ts, and the detection voltage at that time is the maximum output voltage Emax.
Set to 1. By performing this operation for each of the red, green, and blue single-color window patterns, the maximum output voltage Emax1 at the detection timing ts can be obtained for each color.

FIG. 5 is a diagram showing the relationship between the shape of the solar cell and the display pattern at the time of adjustment, and is an explanatory view for explaining an example of position detection by the solar cell 90. A window pattern 201 for position detection has the same brightness as the window pattern 200 in FIG. Further, L represents the distance of the solar cell 90 that has entered the inside of the window pattern 201 (hereinafter referred to as the light receiving distance). FIG. 6 is a diagram showing an example of the relationship between the light receiving distance L of the solar cell and the detected voltage detected by the arithmetic processing means 13. As described above, since the solar cell has the characteristic of functioning as a current source, the calculation is performed depending on the characteristics (including the shape and size) of the load resistance 91 and the solar cell 90, and the light intensity of the window pattern. Processing means 13
The detection voltage of is different. Reference numeral 302 represents a detected voltage characteristic of the arithmetic processing means 13 when the load resistance 91 is relatively large, and 303 represents a detected voltage characteristic of the arithmetic processing means 13 when the load resistance 91 is relatively small. When the solar cell 90 is entirely inside the window pattern as shown in FIG. 3, the output voltage of the solar cell 90 is the highest. Therefore, the light receiving distance when the solar cell 90 is just inside the window pattern is L
max and the detection voltages of the characteristics 302 and 303 at that time are Emax1 and Emax2. In this embodiment, the intermediate brightness is used for position detection by the solar cell 90. That is, a predetermined ratio (for example, 5) to the maximum detection voltages Emax1 and Emax2.
When the detection voltage (Eh1, Eh2) of 0%) is obtained, it is determined that the boundary (edge) of the window pattern matches the solar cell 90. The correction data may be adjusted so that the detected voltages become Eh1 and Eh2. In other words, a method of normalizing the detection voltage obtained by the arithmetic processing means 13 and detecting the edge of the window pattern by obtaining a predetermined output is adopted. Note that although FIG. 5 has been described on the assumption that the adjustment is performed in the vertical direction, the edge detection of the window pattern can be performed in the same manner in the horizontal direction. The light receiving distances when the detection voltages become Eh1 and Eh2 are Lh1 and Lh2.

FIG. 7 is a diagram showing an example of an automatic adjustment flow using each optical inspection element. ST1 is a normalization stage. The maximum detection voltage is obtained using a sufficiently large window pattern as shown in FIG. 2, and the minimum detection voltage is obtained in the state where nothing is displayed (black display) (SB1, SB2), and a predetermined ratio is obtained from these two detection data. A detection voltage (for example, a specified detection voltage that is 50% of the difference between the maximum detection voltage and the minimum detection voltage) is calculated (SB3). In the description of FIG. 6, the minimum detection voltage is neglected as 0 for the sake of simplicity, but the minimum detection voltage must be taken into consideration accurately. As a result, it is possible to avoid the influence of external light and the influence of leak current of the photodetector. ST2 is a stage of automatic adjustment. Adjustment is performed (SB4), and the detected voltage is calculated by the arithmetic processing means each time (SB5).
It is checked whether it is equal to the specified detection voltage obtained in 3 (SB6). If the difference is equal or within the allowable value, it is considered that the solar cell 90 and the edge of the window pattern match, and the adjustment is ended. If the difference is larger than the allowable value, it is considered that the solar cell 90 has not converged and the adjustment is continued. . The above process is repeated for each photodetector. Although the flow of FIG. 7 has been described for one-dimensional adjustment,
Actually, two-dimensional adjustment in the horizontal direction and the vertical direction is required. Therefore, in the adjustment step, it is necessary to perform both the horizontal adjustment and the vertical adjustment. Also, red, green, and blue 3
Similar adjustments are required for the primary colors. FIG. 8 shows a first example of an adjustment display pattern used for actual adjustment, in which eight window patterns corresponding to the photodetection elements 9a to 9h of FIG. 1 are displayed at one time. . 210a to 210h in (a) are display patterns for horizontal adjustment, and 211a to 211h in (b) are display patterns for vertical adjustment. Since the windows are sufficiently distant from each other, the adjustment pattern does not overlap the non-corresponding photodetection element. The brightness in each window is almost constant.

FIG. 9 shows a second example of the adjustment display pattern used for the actual adjustment. The adjustment display pattern corresponding to each of the photodetection elements 9a to 9h in FIG. 8 is projected separately. It has been issued. Reference numeral 212a denotes a horizontal adjustment display pattern 213a corresponding to 210a in FIG.
Shows a vertical adjustment display pattern corresponding to 211a in FIG. 8B. Adjustment display patterns 212b to 212h and 213b to 2 corresponding to other photodetection elements
13h is the same, so the illustration is omitted.

FIG. 10 is a diagram showing a second configuration example of the photodetector circuit. One unit light detection unit 90 for simplification
Although only 0a is described, the overall configuration is the same as in FIG. In the figure, 96a is an operational amplifier, and other symbols are the same as those in FIG. 2 is that the photocurrent generated in the photodetector 90a is converted into the voltage 94a by the additional resistor 91a, but the output impedance is low because the operational amplifier 96a is used, and the bias is applied to both ends of the solar cell 90a. The difference is that no voltage is applied. If the output impedance is low, it is less susceptible to noise and is also advantageous for driving the next stage circuit. Further, particularly when an amorphous silicon solar cell is used as a photodetector, there are problems such as leakage current flow and deterioration of the element. Therefore, it is not preferable to apply a bias voltage. Therefore, it is extremely effective to adopt the circuit configuration of FIG.

FIG. 11 is a diagram showing a third configuration example of the photodetector circuit. One unit light detection unit 9 for simplification
Only 00a is described, but the overall configuration is the same as in FIG. In the figure, 97a is a transistor, 98a is a diode, 99a is a bias resistor, and other symbols are the same as in FIG. FIG. 11 is a configuration example of a photodetector circuit of a type in which a bias voltage is not applied across the solar cell 90a, as in FIG. Diode 98a and bias resistor 99a
Determines the base voltage of the transistor 97a and cancels the base-emitter voltage of the transistor 97a. When the light 93a enters the solar cell 93a, a photocurrent flows to the emitter of the transistor 97a, and most of it is converted into a voltage by the load resistor 91a. The circuit of FIG. 11 has the advantages of being less expensive than the circuit of FIG. 10 and having a wide dynamic range with a single power supply.

As described above, according to the present embodiment, by using the window pattern, even if the photodetector is inexpensive and can detect only the intensity of light, which side is the output voltage deviated from? Since the direction) can be detected, an automatic adjustment system can be realized at low cost with a simple configuration even if the photodetector is used at a plurality of locations. In addition, by normalizing the output of each photodetector circuit, the edge of the window pattern and the photodetector can be consistently matched against changes in brightness, changes in the characteristics of the photodetector, and deterioration of the phosphor in the projection tube. Can be detected, so that a highly accurate system can be realized. Further, by optimizing the gain of each unit photodetection unit corresponding to each photodetection position, the A / D
Since the voltage of the optimum level can be supplied to the next-stage circuit such as the converter, highly accurate light detection and adjustment can be performed.

In FIG. 2, the photodetector uses a rectangular solar cell made of amorphous silicon. This is because it has sufficient sensitivity to the three primary colors of red, green, and blue and is suitable for this system. Any material may be used as long as it has sufficient sensitivity to the three primary colors of red, green and blue. Further, not only a solar cell but also a photodiode or a phototransistor does not cause any particular problem.

FIG. 12 is a block diagram showing the second embodiment of the present invention. Basically, it is the same as that in FIG. 1, but the brightness balance variable pattern generating means 16 is used instead of the pattern generating means 12, and the brightness for controlling the brightness for the three primary colors of red, green and blue of the video circuit 14. The difference is that the balance control means 17 is provided. The brightness balance variable pattern generation means 16 is provided with 210 when the pattern shown in FIG. 8 is generated.
A function of optimally adjusting the brightness of each of the adjustment windows a to 210h and 211a to 211h is provided. It is used instead of optimizing the gain of each unit photodetection unit of the photodetection circuit 15. Further, the brightness balance control means 17 works on the video circuit 14 at the time of automatic adjustment to control the brightness of the display patterns for adjustment of the three primary colors of red, green, and blue, so that the output of each unit light detection unit varies for each color. It is something that should not be done. 3 photo detectors, red, blue and green
Although the sensitivity differs for each primary color, the output variation of the photodetector circuit caused by the common photodetector circuit is suppressed, and A /
Since the voltage of the optimum level can be supplied to the next-stage circuit such as the D converter, highly accurate photodetection and adjustment are possible. Of course, the function of the brightness balance control means 17 can be provided in the brightness balance variable pattern generation means. Further, the gain of each unit light detection unit is optimized, the adjustment window brightness is optimized by the brightness balance variable pattern generation means 16, and the brightness balance control means 17 is provided.
The optimization of the luminance balance of the three primary colors of red, green, and blue can be used alone or in combination.

[0025]

Even if a plurality of photodetectors are arranged in the peripheral portion of the screen, each photodetector is composed of one inexpensive photodetector, so that an automatic convergence correction system can be realized with a simple structure. Further, by using a photodetector circuit having a different gain for each photodetector element, A /
Since it is possible to obtain a uniform voltage signal that matches the input dynamic range of the D converter or the like, highly accurate photodetection / adjustment is possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a first configuration example of a photodetector circuit.

FIG. 3 is a diagram showing an example of a display pattern when measuring the maximum detected voltage of a solar cell.

FIG. 4 is a diagram showing an example of time characteristics of an output voltage of a solar cell.

FIG. 5 is a diagram showing a relationship between a solar cell shape and a display pattern during adjustment.

FIG. 6 is a diagram showing an example of a relationship between a light receiving distance L of a solar cell and a detected voltage.

FIG. 7 is a diagram showing an example of an automatic adjustment flow by each light detection element.

FIG. 8 is a diagram showing a first example of an adjustment display pattern during actual adjustment.

FIG. 9 is a diagram showing a second example of a display pattern for adjustment during actual adjustment.

FIG. 10 is a circuit diagram showing a second configuration example of a photodetector circuit.

FIG. 11 is a circuit diagram showing a third configuration example of a photodetector circuit.

FIG. 12 is a configuration diagram showing a first embodiment of the present invention.

[Explanation of symbols]

2 ... Address generating means, 3 ... Frame memory, 4 ... Waveform creating means, 5 ... CY driving means, 6 ... CY, 8 ... Screen, 9a-9h ... Photodetection element, 10 ... A / D converting means,
11 ... Keyboard, 12 ... Pattern generating means, 13 ... Arithmetic processing means, 14 ... Video circuit, 15 ... Photodetection circuit, 9
0 ... Solar cell, 92 ... LPF, L ... Receiving distance, Emax ...
Maximum detection voltage

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kuninori Matsumi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi Image Information Systems Co., Ltd.

Claims (10)

[Claims] 1. Storage means for storing correction data, address generation means for reading correction data in the storage means in response to scanning, and waveform forming means for creating a convergence correction waveform from the read correction data. In a convergence system having a convergence correction means for generating a correction magnetic field according to the convergence correction waveform to perform convergence correction,
One photodetector element for each location, pattern generating means for generating an adjustment pattern around the photodetector element, and a photodetector circuit for obtaining a voltage output according to incident light using the photodetector element. And an A / D conversion means for converting the output voltage into a digital quantity, and based on the digital quantity obtained from the A / D conversion means, a coincidence between the adjustment pattern and the photo-detecting element is detected to correct the convergence deviation. Convergence system, characterized in that arithmetic processing means is provided, and the photo-detecting means is set to a different gain for each photo-detecting element. 2. The convergence system according to claim 1, wherein the gain is set such that a portion having high pattern display luminance is small and a portion having low pattern display luminance is large, and the gain is uniform. The convergence system is characterized in that the output of the photodetector circuit corresponding to each photodetector element is set to be more uniform than that in. 3. Storage means for storing correction data, address generation means for reading correction data in the storage means in response to scanning, and waveform generation means for generating a convergence correction waveform from the read correction data. In a convergence system having a convergence correction means for generating a correction magnetic field according to the convergence correction waveform to perform convergence correction,
One photodetector element for each location, pattern generating means for generating an adjustment pattern around the photodetector element, and a photodetector circuit for obtaining a voltage output according to incident light using the photodetector element. And an A / D conversion means for converting the output voltage into a digital quantity, and based on the digital quantity obtained from the A / D conversion means, a coincidence between the adjustment pattern and the photo-detecting element is detected to correct the convergence deviation. Convergence system, characterized in that an arithmetic processing means is provided, and the pattern generating means generates an adjustment pattern of different brightness for each photodetecting element. 4. The convergence system according to claim 3, wherein the pattern brightness is set so that the outputs of the photodetector circuits corresponding to the photodetector elements are more uniform than when the pattern brightness is uniform. Convergence system characterized by being performed. 5. Storage means for storing correction data, address generation means for reading correction data in the storage means in response to scanning, and waveform generation means for generating a convergence correction waveform from the read correction data. In a convergence system having a convergence correction means for generating a correction magnetic field according to the convergence correction waveform to perform convergence correction,
One photodetector element for each location, pattern generating means for generating an adjustment pattern around the photodetector element, and a photodetector circuit for obtaining a voltage output according to incident light using the photodetector element. And an A / D conversion means for converting the output voltage into a digital quantity, and based on the digital quantity obtained from the A / D conversion means, a coincidence between the adjustment pattern and the photo-detecting element is detected to correct the convergence deviation. And a pattern processing means for each of red, green and blue.
A convergence system characterized by generating a brightness adjustment pattern that differs for each primary color. 6. The convergence system according to claim 5, wherein the pattern brightness has a uniform output from the photodetection circuits corresponding to the three primary colors of red, green and blue, as compared with the case where the pattern brightness is uniform. Convergence system characterized by being set so that 7. Storage means for storing correction data, address generation means for reading correction data in the storage means in response to scanning, and waveform generation means for generating a convergence correction waveform from the read correction data. In a convergence system having a convergence correction means for generating a correction magnetic field according to the convergence correction waveform to perform convergence correction,
One photodetector element for each location, pattern generating means for generating an adjustment pattern around the photodetector element, and a photodetector circuit for obtaining a voltage output according to incident light using the photodetector element. And an A / D conversion means for converting the output voltage into a digital quantity, and based on the digital quantity obtained from the A / D conversion means, a coincidence between the adjustment pattern and the photo-detecting element is detected to correct the convergence deviation. And a brightness balance control means for controlling the brightness balance for the three primary colors of red, green and blue of the video circuit of the projection display device using the CRT using the convergence system. system. 8. The convergence system according to claim 7, wherein the luminance balance control means outputs the outputs of the photodetection circuits corresponding to the three primary colors of red, green and blue, as compared with the case where the pattern luminance is uniform. A convergence system characterized by being set to be uniform. 9. The convergence system according to claim 1, wherein the photodetection circuit is a circuit using a transistor, and the photodetection element is connected between an emitter terminal of the transistor and a first power supply. A load resistor is connected between the collector terminal of the transistor and the second power supply,
A convergence system, wherein a bias power supply or a bias circuit for supplying a predetermined bias voltage is connected to the base of the transistor, and the output voltage is taken out from the collector terminal. 10. A projection display device by a CRT using the convergence system according to claim 1.