JPH06269013A - Automatic convergence correction device - Google Patents

Abstract

(57) [Abstract] [Purpose] Providing an automatic convergence correction device that can automatically correct the convergence and geometric distortion of a color television receiver, and make a highly accurate correction and greatly shorten the adjustment time. The purpose is to do. [Structure] Test signal generator 2 that generates test signals
And an image pickup section 12 for picking up an image of the screen 11, and a differential filter for detecting a differential signal between photoelectric conversion signals output from the image pickup section 12.
15, the output of the linear region detection unit 16 that detects the linear region of the photoelectric conversion signal from the output of the difference filter 15, the center of gravity detection unit 17 that calculates the center of gravity position of the test signal from the photoelectric conversion output signal by linear approximation, The configuration is provided with an error detection unit 18 that detects a misconvergence error value for each color from the centroid calculation signal, and a convergence correction unit 19 that corrects convergence and geometric distortion based on the output of the error detection unit 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic convergence correction device for automatically correcting the convergence of a color television receiver.

[0002]

2. Description of the Related Art Generally, a video projector for magnifying and projecting in a screen by using three projection tubes which emit three primary colors.
In the above, since the incident angle of the projection tube with respect to the screen (hereinafter referred to as the "concentration angle") is different for each projection tube, color deviation, focus deviation, deflection distortion, and luminance change occur on the screen. Since these various corrections are performed manually by visually observing an error such as color misregistration on the screen, there is a problem that adjustment time is required. Therefore, as a method with high convergence accuracy, a digital convergence apparatus disclosed in Japanese Patent Publication No. 59-8114 and a method for automatically correcting deflection distortion are disclosed in Japanese Patent Publication No. 3-38797 and Japanese Patent Publication No. 1-48553. Japanese Patent Laid-Open No. 64-54993 discloses an automatic convergence correction apparatus disclosed in Japanese Patent Laid-Open No. 64-54993 as a method of detecting and correcting convergence errors.

FIG. 8 shows a block diagram of a conventional automatic convergence correction device capable of automatic correction. In FIG.
101 is a display device for which the convergence is to be adjusted, 102
Is a signal generator for generating a signal for convergence adjustment, 103 is a signal switcher, and 104 is a display device 101.
, 105 is the calculation of the center of gravity,
Image processing apparatus for detecting misconvergence error, 10
A controller 6 controls the signal generator 102, the signal switcher 103, and the image processor 105.

The operation of the automatic convergence correction device configured as described above will be described below. First, the signal generator 102 generates a low frequency repeating pattern shown in FIG. Here, in FIG. 9, x is the horizontal direction of the screen, y
Is the vertical direction of the screen. This repetitive pattern is displayed on the display device 101 by the signal switcher 103. The displayed repetitive pattern is imaged by the image pickup device 104, and the barycentric position of the peak of each waveform is calculated by the image processing device 105. This is performed for waveforms of R (red), G (green), and B (blue) colors, and the misconvergence error is detected by detecting the difference in their barycentric position.

The calculation of the position of the center of gravity will be described in detail.
First, the signal of the repetitive pattern picked up by the image pickup unit 104 is A / D converted, and the digital data is linearly interpolated. This figure is shown in FIG. In this figure, h _i (x)
Is the repeated pattern data. Here, only one data of the repetitive pattern has been described, but the same applies to other repetitive patterns.

The position of the center of gravity is obtained by the following quadratic curve approximation. _{D = {h i (x)} - (A · x 2 + B · x + C)} 2 dx integration range of the equation is determined by the threshold h _TH. Where A · x ² + B · x + C is an approximate quadratic curve,
The coefficients are determined so as to minimize the above equation. That is,
∂D / ∂A = 0, ∂D / ∂B = 0, ∂D / ∂C = 0, and the position x ₀ of the center of gravity is x ₀ = − (B / 2A). As described above, the center of gravity position is calculated for each color of R, G, and B by performing the quadratic curve approximation for each repeated pattern, and the difference between the center of gravity positions thereof is detected. The automatic convergence correction can be performed by performing the convergence correction of the display device as the amount of the presence error.

[0007]

However, in the correction device having the conventional structure as described above, since the position of the center of gravity of the repeated pattern for convergence adjustment is calculated by the quadratic curve approximation, the image processing is performed. There is a problem in terms of processing speed and circuit scale because complicated processing is required in some parts. Further, since the convergence adjustment signal picked up by the image pickup section is made into a mountain-shaped waveform line-symmetrical signal and the center of gravity is detected by quadratic curve approximation based on this, for example, shading in a video projector or If the convergence adjustment signal picked up due to the gamma characteristic of the display device is not a mountain-waveform line-symmetrical signal, the quadratic curve approximation error becomes large, and the center of gravity detection accuracy deteriorates. .

In view of the above points, the present invention has as its object the provision of an automatic convergence correction device with high accuracy and high processing speed.

[0009]

The present invention provides a test signal in which a photoelectric conversion signal obtained by picking up an image displayed on a display screen of an image display device is linear with respect to the horizontal and vertical directions of the screen. Of the differential signal detection means for detecting the difference signal of the photoelectric conversion signals output from the image pickup means, the test signal generation means for generating Linear area detection means for detecting the linear area of the photoelectric conversion signal from the output, the output of the linear area detection means, and the center of gravity position of the test signal displayed on the image display device from the photoelectric conversion output signal by linear approximation Center of gravity detecting means for calculating, error detecting means for detecting a misconvergence error value for each color from the center of gravity calculating signal, and convergence or geometrical analysis from the output of the error detecting means. A configuration in which a correction means for correcting.

[0010]

According to the present invention, a test signal is generated in which a photoelectric conversion signal obtained by picking up an image displayed on a display screen is linear with respect to the horizontal and vertical directions of the screen, for example, a conical shape. It has a test signal generator, calculates the barycentric position of the captured test signal for convergence adjustment by linear approximation, and detects the misconvergence amount based on the calculated barycentric position. By performing the corrections for and, the automatic convergence correction can be performed with high accuracy and at high speed without being affected by the display characteristics of the receiver such as the gamma characteristics.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the basic configuration of an automatic convergence correction device according to an embodiment of the present invention.

In FIG. 1, 1 is an input terminal for a video signal,
Reference numeral 2 is a test signal generating section for generating a test signal for convergence adjustment, 3 is an input terminal for a horizontal synchronizing signal input to the test signal generating section 4, 4 is an input terminal for a vertical synchronizing signal, 5
Is a switch for switching between a video signal and a test signal, 6 is a driving unit for driving the cathode ray tube 7, 8 is a main deflection coil for scanning an electron beam, 9 is an auxiliary deflection coil for correcting convergence, and 10 is A projection lens for projecting an image displayed on the cathode ray tube 7 on the screen 11, and 12 for the screen 1
An image pickup unit for picking up an image of the test signal projected on the image pickup device 1, and an A / D converter 13 for converting the output of the image pickup unit 12 into digital data.

Reference numeral 14 is a memory such as a frame memory for accumulating the image data converted into digital data by the A / D converter 13, and 15 is each data of the image pickup data of the image pickup section 12.
A difference filter for detecting the difference between the data, 16 a linear area detection unit for detecting the linear area of the imaging data based on the output of the difference filter 15, 17 an output of the linear area detection unit 16,
A center of gravity detection unit that detects the center of gravity of the test signal projected on the screen 11 from the output of the memory 14, 18 is an error detection unit that detects a misconvergence error based on the output of the center of gravity detection unit 17, Reference numeral 19 is a convergence correction unit that drives the auxiliary deflection coil 9 and the main deflection coil 8 so that the misconvergence error detected by the error detection unit 18 becomes zero, and corrects the convergence.

First, the test signal generator 2 will be described. A detailed configuration diagram of the test signal generator 2 is shown in FIG. In FIG. 2, 20 is a memory for storing data for test signal generation, 21 is an address generator for generating an address of the memory 20 for test signal generation from the input horizontal synchronizing signal, vertical synchronizing signal, and 22 is A gamma correction unit that performs gamma correction on a test signal based on the imaged data, 2
3 is a D / A for converting the output of the memory 20 into an analog signal
It is a conversion unit.

The operation of the test signal generator 2 will be described below. First, the memory 20 for generating a test signal generates a signal that is linear with respect to the screen horizontal direction x and the screen vertical direction y as shown in FIG. Gamma correction is not performed at this stage. Here, this test signal is projected on the screen 11, and the imaging data of the projected image is:
If the drive unit of the cathode ray tube 7 does not have a gamma correction unit, the output becomes non-linear as shown in FIG. The gamma correction unit 22 uses this imaging data.
Based on the data, the test signal data is subjected to gamma correction as shown in FIG. 5 so that the photoelectric conversion output in the image pickup unit 12 becomes linear.

For example, when the photoelectric conversion output V obtained by the image pickup section 12 has a CRT gamma (γ) characteristic such as V = kT ^r (where T is a test signal input and k is a constant), The gamma correction unit performs gamma correction such as ^{Tr on} the test signal T,
Gamma correction is applied so that the resulting image data is linear. Further, when the gamma characteristic due to the saturation of the phosphor exists, gamma correction is performed so as to cancel the influence due to the saturation of the phosphor.

The photoelectric conversion output result obtained by picking up the test signal projected on the screen 11 by the image pickup section 12 by the test signal generating section 2 as described above has a linear characteristic as shown in FIG. Here, in the following description, a CCD is used as the photoelectric conversion element of the image pickup unit 12. This is because the CCD is most suitable for practical use in terms of cost and ease of handling. First, the test signal obtained by the CCD of the image pickup unit 12 is quantized and encoded by the A / D converter 13, converted into digital data, and stored in the memory 14. Based on the data of the test signal stored in the memory 14, the position of the center of gravity of the test signal is calculated by calculation.

The reason why the position of the center of gravity of the test signal is detected by calculation is that the CCD and the A / D converter 13 are used.
This is to eliminate the influence of rounding of sampling due to and improve the accuracy of the detection of the position of the center of gravity. That is, the test signal input to the drive circuit of the cathode ray tube 7 by the test signal generator 2 and projected on the screen of the projection display apparatus is a continuous analog signal in time, but the CCD
When capturing this projected image with an image sensor such as
The test signal is sampled by the pixels of the CD. There is no problem if the CCD sampling rate is sufficiently high, but when using a practical CCD with, for example, 400,000 pixels, this sampling rate has an accuracy of about one scanning line of the NTSC system. is there. If a CCD with a higher sampling accuracy is used, this accuracy will be further improved, but it is not practical to use a CCD with a very large number of pixels from the viewpoint of cost, and a general 400,000 pixel pixel is used. I have no choice but to use a CCD.

CC having such a low sampling rate
When D is used, the problem described below with reference to FIG. 6 occurs. In FIG. 6A, the solid line shows the actual test signal, and the broken line shows the signal stored by the CCD by the LPF (low-pass filter). As can be seen from FIG. 6 (a), the test pattern apex is rounded due to the low sampling rate, and when the barycentric position is obtained from the CCD output signal, the actual barycentric position is point A. However, the point A ′ is mistakenly determined to be the center of gravity of the test signal. In order to eliminate such a detection error, the center of gravity is calculated. In the calculation of the center of gravity, the linear portion excluding the rounded portion is extended, and the intersection of the extended portions is used as the center of gravity. That is, FIG. 6 is simulated on the data.
The test signal data as shown by the solid line in (a) is obtained.

The method of detecting the center of gravity will be described in detail below. Here, for detecting the position of the center of gravity, the data is divided into areas corresponding to the respective test patterns as shown in FIG.
A calculation process for detecting the position of the center of gravity is performed for each region. By thus dividing the region and performing the arithmetic processing, it is possible to perform parallel arithmetic processing such as pipeline processing. In the following description of the arithmetic processing, only one area will be described, but similar arithmetic processing will be performed for other areas.

As the first step of the arithmetic processing, an operation of detecting only the linear portion of the test signal data is performed excluding the rounding area by sampling. This is performed by converting the image data of the test signal into digital data by the A / D converter 13, passing the data through the differential filter 15, and detecting the differential signal. When the image data of the test signal shown in FIG. 6A is input to the differential filter 15,
The output data is as shown in FIG. Further, from this output data, the linear region detecting section 16 detects the difference signal of the data, that is, the periods A and B in which the inclination of the test signal is constant. Here, the period when the slope is 0 is ignored. Hereinafter, only the image data in the periods A and B are valid and the position of the center of gravity is calculated.

The position of the center of gravity is calculated by extending the linear periods A and B on the data and setting the intersection as the center of gravity of the test pattern. As shown in FIG. 6B, in the calculation of the center of gravity, the data from the apex of the linear part A is D _A , the address corresponding to D _A is n _A , the slope of the linear part A is α, and the linear part is linear. The data from the highest vertex of part B is D _B , D _B
The position x of the center of gravity can be determined by the following equation, where n _{B is} the address corresponding to and the slope of the linear portion B is β.

X = n _A + (D _B −D _A −β · (n _B −n _A )) / (α−β) Thus, by determining the center of gravity by linear extrapolation, even if the CCD sampling is rough. Even if the test pattern
The center of gravity of the engine can be detected with high accuracy.

As described above, the center of gravity obtained by the linear extrapolation operation of the data of the test pattern imaged by the image pickup unit 12 does not limit the number of pixels of the CCD of the image pickup unit 12 and is high. The center of gravity of the test pattern can be accurately determined. Also, by using linear arithmetic,
It has an advantage that the processing unit is lightly loaded and the error of the position of the center of gravity due to the calculation is small as compared with other quadratic curve approximation.

To adjust the convergence, first, the center of gravity position serving as a reference is determined. For example, the operation for calculating the center of gravity is G (green)
Of the cathode ray tube and the data at the position of the center of gravity is used as the reference data. Next, the same operation of calculating the center of gravity is performed for the other cathode ray tubes, R (red) and B (blue). Therefore, the error detector 18 determines the position of the center of gravity of these R and B and the reference G.
The error with respect to the position of the center of gravity is calculated, and this misconvergence error amount is passed to the convergence correction unit 19.

Next, the convergence correction unit 19 will be described. FIG. 7 shows a detailed configuration diagram of the convergence correction unit 19. In FIG. 7, reference numeral 30 is an address generator for generating an address signal from the horizontal sync signal and vertical sync signal, and 31 is a calculator for calculating the convergence correction data from the misconvergence information output from the error detector 18. , 32 is a memory for storing the correction data of each correction area, 33 is a data interpolating unit for performing data interpolation between the correction data, and 34 is D / for converting the correction data into an analog amount. A
Converter, 35 is an LP for smoothing the output of the D / A converter 34
It is F.

To correct the convergence, the arithmetic unit 31
Based on the misconvergence information output from the error detection unit 18, the correction data is calculated so that the misconvergence error is set to 0, and the corrected data is calculated, and the auxiliary deflection coil 9 and the main deflection It is supplied to the coil 8 and the convergence is corrected.

As described above, according to the present embodiment, the photoelectric conversion signal obtained by picking up the image displayed on the display portion of the color television receiver is linear in the horizontal and vertical directions of the screen, for example, a conical shape. A test signal generator 2 for generating a signal that generates a test signal for convergence adjustment is generated, the barycentric position of the imaged test signal is calculated by linear approximation, and the calculated barycentric position is calculated. The amount of misconvergence is detected based on this, and the correction is performed based on this, so that automatic convergence correction can be performed accurately and at high speed without being affected by the display characteristics of the image receiver such as gamma characteristics. it can.

In the present embodiment, the configuration of the convergence correction section 19 is described as a digital one, but this is a conversion using an analog correction signal.
A presence correction device may be used.

Although the test pattern displayed on the display device has a conical shape, it may have another shape such as a quadrangular pyramid. Although the number of test patterns is nine here, other numbers may be used as long as the convergence adjustment can be effectively performed.

Further, in the description of this embodiment, a two-body type video projector (projection section and screen are separated)
This is also effective for an integrated video projector in which the projection unit and screen are integrated, a multi-video projector in which multiple screens are combined by combining projectors, or a direct-view type receiver. Is. Further, in the description of the test signal generation unit of this embodiment, the gamma correction unit is also included in the test signal generation unit.
The gamma correction unit may be provided in the test signal generation unit, the image display / imaging means.

[0032]

As described above, according to the present invention, the center of gravity position of the test pattern for convergence adjustment is calculated by linear approximation, and the misconvergence amount is detected based on the calculated center of gravity position. However, by performing the correction based on this, the automatic convergence correction can be performed with high accuracy and at high speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of an automatic convergence correction device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a test signal generator of the same embodiment.

FIG. 3 is a relationship diagram for explaining the operation of the test signal generator of the same embodiment.

FIG. 4 is a waveform diagram for explaining the operation of the test signal generator of the same embodiment.

FIG. 5 is a waveform diagram for explaining the operation of the test signal generator of the same embodiment.

FIG. 6 is a waveform diagram for explaining the operation of the center-of-gravity detector of the same embodiment.

FIG. 7 is a block diagram showing a configuration of a convergence correction unit of the same embodiment.

FIG. 8 is a block diagram showing a configuration of a conventional automatic convergence correction device.

FIG. 9 is a waveform chart for explaining the operation of the device.

FIG. 10 is an enlarged view for explaining the operation of the device.

[Explanation of symbols]

 1 Input terminal for video signal 2 Test signal generating section 3 Input terminal for horizontal synchronizing signal 4 Input terminal for vertical synchronizing signal 5 Changeover switch 6 Cathode ray tube driving section 7 Cathode ray tube 8 Main deflection coil 9 Auxiliary deflection coil 10 Projection lens 11 Screen -N 12 Imaging unit 13 A / D converter 14 Memory 15 Difference filter 16 Linear region detection unit 17 Center of gravity detection unit 18 Error detection unit 19 Convergence correction unit

Claims (3)

[Claims] 1. Test signal generating means for generating a test signal in which a photoelectric conversion signal obtained by picking up an image displayed on a display screen of an image display device is linear with respect to the horizontal and vertical directions of the screen. An image pickup means for picking up a display screen of the image display device, a differential signal detection means for detecting a differential signal of a photoelectric conversion signal output from the image pickup means, and a linear area of a photoelectric conversion signal from an output of the difference signal detection means A linear area detecting means for detecting, an output of the linear area detecting means, a barycentric position detecting means for calculating a barycentric position of a test signal displayed on the image display device from the photoelectric conversion output signal by linear approximation, Error detecting means for detecting a misconvergence error value for each color from the centroid calculation signal, and correcting means for correcting convergence and geometric distortion from the output of the error detecting means. Automatic convergence correction apparatus characterized by comprising. 2. The automatic convergence correction device according to claim 1, wherein the center of gravity detection means calculates the position of the center of gravity from a linear region of the conical photoelectric conversion signal. 3. The automatic convergence correction device according to claim 1, wherein the test signal generating means obtains the gamma characteristic of the image display device from the image pickup signal of the image pickup means and performs gamma correction on the test signal.