JP3578573B2 - Automatic convergence correction device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to automatic correction of static convergence in a projection television receiver.
[0002]
[Prior art]
Projection televisions are easier to achieve with a large screen, thinner and lighter than the direct-view tube type, but the biggest issues at present are convergence, eliminating installation adjustments and improving drift. is there.
[0003]
Generally, in a projection type color television receiver in which three primary colors are emitted from individual picture tubes and enlarged and projected on a screen, a color shift occurs on the screen. Therefore, superposition of these three primary colors, that is, convergence correction is important. .
[0004]
In particular, in the case of the rear projection type, the projection distance is shortened due to the thinning of the receiver, the incident angle on the different screen for each picture tube is increased, the raster distortion is increased, and the convergence correction amount is increasing. , It is susceptible to geomagnetism and temperature drift.
[0005]
With conventional commercial projection television receivers, it is necessary to adjust the static convergence when installed.If the receiver is displaced due to changes in the orientation of the receiver, drift due to temperature, etc., the user needs to adjust the static convergence. Adjustments had to be made.
[0006]
In order to solve this problem, a method has been proposed in which a photoelectric conversion element is provided in a peripheral portion of a screen, a convergence reference pattern superimposed on a video signal is received, and convergence is corrected based on a measured shift. .
[0007]
For example, there are JP-A-63-209388, JP-A-63-224572, JP-A-63-283383, JP-A-4-282933, and JP-A-5-191817.
Hereinafter, the conventional static convergence automatic correction device for a projection type television receiver as described above will be described with reference to the drawings.
[0008]
FIG. 5 shows a configuration example of a conventional automatic static convergence correction device.
In FIG. 5, a video signal input from a terminal 11 is projected on a cathode ray tube 13 and is enlarged and projected by a lens 14 to form an image on a screen 15. The deflection circuit 20 and the deflection yoke 21 perform horizontal and vertical beam deflection.
[0009]
As shown in FIG. 6, the photoelectric conversion element 1 is disposed at the lower center of the screen 15, and the photoelectric conversion element 2 is disposed substantially at the center on the right side of the screen 15. The components of the static convergence other than the photoelectric conversion elements include the center position detection circuits 3a and 3b, the storage circuits 4a and 4b, the pattern signal generation circuit 19, and the convergence correction circuit 18.
[0010]
The operation of the static convergence automatic correction circuit thus configured will be described below.
First, a pattern serving as a reference signal is generated from the pattern signal generator 19 and input to the video circuit 12 to display the pattern at the right electrical center outside the screen 15 and at the lower electrical center.
[0011]
The center position detecting circuits 3a and 3b detect a deviation from the display position of the pattern from the center of the photoelectric conversion element. The storage circuits 4a and 4b store the amount of shift for each of R, G, and B colors. The convergence correction circuit 18 corrects static convergence so that the deviation for each color is minimized.
[0012]
[Problems to be solved by the invention]
However, the above configuration has the following problems.
(1) Narrow correction range: Considering the influence of terrestrial magnetism, aging of the structure, and drift of the CRT and the correction circuit, a thin type of 43-inch screen with a depth of 45 cm requires a wide correction range of about 20 mm. However, in order to widen the detection range of the reference pattern, conventionally, an expensive linear sensor was used or a number of spot sensors were arranged. This complicates the detection circuit.
(2) Malfunction when non-standard signal: Normal operation when a normal standard signal is used, but when the horizontal and vertical frequencies deviate from the standard for VTR playback, etc. Patterns can come into view.
(3) In some cases, the reference pattern signal of the overscan section may be seen. The overscan of the receiver is generally set within about 10%, but the deflection amplitude is changed due to a change in high voltage due to a change in luminance of the received signal. May fluctuate, and the reference pattern of the overscan portion may enter the field of view.
[0013]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an automatic convergence correction device which improves the above-mentioned problems and has a configuration as simple as possible in terms of cost.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, an automatic convergence correction apparatus according to the present invention projects a convergence correction reference pattern on an overscan portion around a screen of a screen, and detects the reference pattern by two light detecting means. Overscan detection means for detecting the overscan portion in order to correct the convergence shift in accordance with the projection position shift of the reference pattern with respect to the center of the two light detection means; and the two light detection means for determining the position of the reference pattern. screen and position control D / a converter for movement control in the center, the provided control means for controlling the deflection circuit or convergence correction circuit detection signal overscan detecting means, the deflection amount at the overscan portion of the Larger than the amount of deflection in the screen of FIG. The control means is arranged in an enlarged portion of a scan portion and controls the convergence correction amount according to the output value of the position control D / A converter for controlling the movement of the reference pattern to the center position of the two light detection means. In the automatic convergence correction device which is controlled, a position control D / A converter is provided as a PWM type D / A converter, and a PWM output output from the PWM type D / A converter is smoothed. A smoothing circuit, a comparison circuit that compares the output voltage of the smoothing circuit with a horizontal or vertical deflection current waveform or an output voltage of the smoothing circuit and a waveform proportional to the horizontal or vertical deflection current, And a waveform generation circuit for determining the generation timing of the reference pattern signal by a pulse, wherein the PWM output output from the PWM type D / A converter is Serial performs constant small to smooth the output voltage by the correction of the outline when the smoothing circuit is then that to perform a precise correction by greatly smoothed output voltage by a time constant of the smoothing circuit.
[0015]
According to the present invention, it is possible to avoid a situation in which the reference pattern of the overscan section enters the field of view even if the deflection amplitude fluctuates due to a change in high voltage due to a change in luminance of the received signal.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Convergence automatic correction apparatus according to claim 1, wherein the projected convergence correction reference pattern in overscan portion of the periphery of the screen display of the center of the two light detecting means to detect the reference pattern with two light detecting means In order to correct a convergence shift in accordance with a projection position shift of the reference pattern with respect to the scan pattern, an overscan detection means for detecting the overscan portion, and movement control of the position of the reference pattern to the center of the two light detection means A position control D / A converter; and control means for controlling a deflection circuit or a convergence correction circuit based on a detection signal of the overscan detection means. The deflection amount in the overscan portion is deflected within a screen of a screen. And the two photodetectors are expanded in the overscan portion. And the control means controls the convergence correction amount in accordance with an output value of the position control D / A converter for controlling the movement of the reference pattern to the center position of the two light detection means. In the automatic convergence correction device described above, a position control D / A converter is provided as a PWM type D / A converter, and a smoothing circuit for smoothing a PWM output output from the PWM type D / A converter. A comparison circuit for comparing the output voltage of the smoothing circuit with a horizontal or vertical deflection current waveform or a waveform proportional to the output voltage of the smoothing circuit and the horizontal or vertical deflection current, and a reference pattern based on a pulse from the comparison circuit. A waveform generation circuit for determining a signal generation timing, wherein a PWM output output from the PWM type D / A converter is first converted to a time constant of the smoothing circuit. Small and corrects the outline by smoothing the output voltage, then characterized by being configured to perform a precise correction by greatly smoothed output voltage by a time constant of the smoothing circuit.
[0017]
According to this configuration, the light detection means is arranged at a position farther from the screen (field of view) of the screen, and the reference pattern is displayed at a position far from the screen (field of view) of the screen to automatically correct the convergence. Even if the deflection amplitude fluctuates due to, for example, the reference pattern of the overscan portion does not enter the field of view.
[0019]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
5 and 6 showing the conventional example will be described with the same reference numerals.
[0020]
FIG. 1 shows an automatic convergence correction apparatus according to the present invention. Actually, three tubes for red, green and blue are necessary for the cathode ray tube 13, the lens 14, and the like, but only one is shown in FIG. Reference numeral 16 denotes an input terminal for a vertical synchronization signal, and reference numeral 17 denotes an input terminal for a horizontal synchronization signal.
[0021]
As shown in FIG. 2, the photoelectric conversion elements 1 a and 1 b are arranged at the lower center of the screen 15, and the photoelectric conversion elements 2 a and 2 b are arranged at the center on the right side of the screen 15. FIG. 3 is an enlarged view of the photoelectric conversion elements 2a and 2b for detecting the vertical position on the right side of the screen. The reference pattern 24 for position detection in the vertical direction is a horizontal line so that it does not deviate from the photoelectric conversion elements 2a and 2b even when the raster amplitude changes. Similarly, the reference pattern in the horizontal direction is a vertical line.
[0022]
The switch 5 inputs detection signals of the photoelectric conversion elements 1a, 1b, 2a, 2b, outputs a detection signal of the photoelectric conversion elements 1a, 1b when the switching state is H, and outputs a detection signal when the switching state is V. It is configured to output detection signals of the conversion elements 2a and 2b.
[0023]
The peak hold circuits 6a and 6b detect and hold the peak of the output signal of the switch 5. The AD converters 7a and 7b convert the outputs of the peak hold circuits 6a and 6b into digital signals.
[0024]
In addition to this, the present apparatus includes a CPU 8 for controlling the present apparatus, a convergence correction circuit 18, comparison circuits 9a and 9b, a non-volatile memory 10, and an on-screen position control for controlling a reference pattern to be displayed in a raster. It includes a DA converter 22a, a static convergence correction DA converter 22b for controlling the position of the entire raster, a filter 22c, and the like.
[0025]
The operation of the television receiver configured as described above will be described with reference to FIG.
This automatic convergence correction device performs the following four basic functions under the control of the CPU 8 as a control unit with the above configuration.
(1) Project a reference signal onto the screen. The reference pattern is input to the video circuit 12 from the on-screen signal generation circuit 19 under the control of the CPU 8 as an on-screen signal, and the portion of the photoelectric conversion element outside the screen. Is projected to
(2) Detecting whether or not the reference signal is at the center of the photoelectric conversion element .... The output signal of the photoelectric conversion element is peak-held by the peak hold circuits 6a and 6b via the switch 5, and is subjected to AD conversion. It is input to the CPU 8 via the devices 7a and 7b. The CPU 8 sets the switch 5 to the H side to detect the light input of the photoelectric conversion elements 1a and 1b by the reference signal in the horizontal direction, and confirms whether the reference pattern is at the center of the two photoelectric conversion elements. When the outputs of the photoelectric conversion elements 1a and 1b become the same, the CPU 8 determines that the pattern is at the center.
(3) Move the position of the on-screen signal on the raster... The horizontal movement moves the position of the on-screen signal in the on-screen position control DA converter 22a of the CPU 8 (the raster does not move). Movement in the vertical direction is performed based on the number of the raster display line of the reference pattern.
(4) Move the raster (static convergence correction): Data is sent from the CPU 8 to the DA converter 22b for static convergence correction, and the entire raster is moved by controlling the convergence coil 23.
[0026]
The CPU 8 periodically measures the position of the reference signal using the above basic functions and corrects the static convergence if there is a raster shift.
Hereinafter, the horizontal correction will be described first.
[0027]
This system requires the following two initial adjustments: "determination of correction value of DA converter" and "storage of reference position".
The correction value of the D / A converter is determined by measuring the correlation between the amount of movement of the raster by the convergence correction D / A converter 22b and the amount of movement of the reference pattern by the on-screen D / A converter 22a, and determining the reference value obtained by the on-screen D / A converter 22a. A conversion coefficient for converting a pattern shift amount into a corresponding correction amount of the convergence correction DA converter 22b is obtained.
[0028]
For the storage of the reference position, for example, a white adjustment signal of a cross is output near the center of the screen, and the static convergence correction amount is adjusted so that the red, green, and blue color shifts are visually eliminated. Next, the CPU is instructed to move the position of the reference pattern with the output of the on-screen position control DA converter 22a of the CPU 8 so that the reference pattern is located at the center of the two photoelectric conversion elements, and to the DA converter 22a at this time. Is stored in the memory 10 as a reference value.
[0029]
Under the condition that the above initial adjustment is performed, the reference pattern is moved periodically thereafter, and the value of the position control DA converter 22a that becomes the center position of the photoelectric conversion element is measured. Determines that a convergence deviation has occurred, and changes the correction amount of the static convergence to control the reference convergence so as to come to the center positions of the two photoelectric conversion elements. As a result, the position of the raster has returned to the default position. By performing this for the three primary colors of red, green and blue, the color shift can be corrected.
[0030]
In the vertical direction, the manner of moving the reference pattern is different as described above, but the other operations are the same.
The convergence correction operation is performed in a time-division manner, such as red, green, and blue in the horizontal direction, and red, green, and blue in the vertical direction, to perform one correction operation. This correction operation is performed immediately after the power is turned on and periodically thereafter to automatically correct the deviation of the static convergence.
[0031]
Since it is difficult to obtain accuracy in a single measurement of the convergence deviation, the accuracy is improved by programming the correction operation to repeat several times until the convergence is converged within a certain range. As a result, it is possible to avoid abnormalities in measured values of raster movement due to non-synchronous non-standard signals or extraneous noises such as video tape recorder playback.
[0032]
As described above, the automatic convergence correction apparatus of the present embodiment performs the correction operation in a time-division manner, so that the photoelectric conversion elements can be shared for red, green, and blue, and a simple circuit configuration can be achieved.
[0033]
However, due to the time-sharing control and the repetitive operation for improving the accuracy, the time until the correction is completed may become a problem.
In particular, as a DA converter for which the CPU 8 performs position control, a DA converter of about 12 bits is basically required for precise control, but a general PWM system with a built-in CPU is required for cost reduction. When the D / A converter 22a is used, the PWM signal is smoothed into a DC voltage for control by the filter 22c. However, since the position detection is repeated many times to improve the accuracy, the delay due to the time constant of the filter 22c is reduced. appear. In order to cover these, the present invention is configured as follows.
[0034]
The CPU 8 is configured to first perform a rough correction by decreasing the time constant of the filter 22c, and then to perform a precise correction by increasing the time constant.
In the method of projecting the reference pattern onto the overscan section as in the present invention, the overscan of a specific color in the horizontal direction is insufficient due to the projection angle.
[0035]
In the present invention, the horizontal overscan is enlarged to prevent the reference pattern from entering the field of view.
Hereinafter, a specific description will be given with reference to FIGS.
[0036]
The overscan section is detected by comparing the horizontal sawtooth HS with a constant DC level by the comparison circuit 9b in FIG. 1, and the beam deflection amount is enlarged on the right side by the convergence correction circuit 18 as shown in FIG. The convergence correction is deformed in the enlargement direction.
[0037]
FIG. 3 shows the portions of the photoelectric conversion elements 2a and 2b on the right side of the screen for detecting in the vertical direction, whereby the overscan on the right side of the screen starts from the broken line portion A (the position where the amount of deflection is the same as that in the screen). It extends to the solid line part B.
[0038]
In this way, the overscan can be enlarged without narrowing the field of view, and the photoelectric conversion element can be arranged at the back, so that the reference pattern can be prevented from being seen when the amplitude changes. If necessary, the overscan can be similarly expanded for the horizontal detection unit (the lower part of the screen).
[0039]
The overscan enlargement correction is performed by the convergence correction circuit 18, but may be performed by a deflection circuit.
In the above-described embodiment, the AD converter, the DA converter, and the on-screen signal generation circuit are configured separately from the CPU 8, but these can be configured with either the built-in CPU 8 or external elements. Although the present invention has been described with reference to the example of automatic correction of static convergence, the present invention can be applied to automatic correction of dynamic convergence.
[0040]
【The invention's effect】
As described above, according to the present invention, the overscan detection means for detecting the overscan portion is provided, and the deflection circuit or the convergence correction circuit is controlled by the detection signal of the overscan detection means, and the amount of deflection in the overscan portion is controlled. Is configured to be larger than the amount of deflection in the screen of the screen, it is resistant to amplitude fluctuations, and the configuration can be simplified to prevent the reference pattern from entering the field of view.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an automatic convergence correction device according to an embodiment of the present invention; FIG. 2 is a front view showing an arrangement relationship between a photoelectric conversion element and a screen according to the embodiment; FIG. FIG. 4 is an explanatory diagram of an overscan enlargement of the embodiment. FIG. 5 is a configuration diagram of a conventional convergence automatic correction device. FIG. 6 is a diagram of a conventional photoelectric conversion element and a screen. Front view showing arrangement relationship [Description of reference numerals]
1a, 1b, 2a, 2b Photoelectric conversion element 8 CPU [Control unit]
9b Comparison circuit 13 CRT 14 Lens 15 Screen 18 Convergence correction circuit 22a On-screen position control DA converter 22b Static convergence correction DA converter 22c Filter 23 Convergence coil 24 Reference pattern

Claims (1)

A convergence correction reference pattern is projected on an overscan portion around the screen of the screen, and this reference pattern is detected by two light detecting means, and the projection pattern of the reference pattern is shifted with respect to the center of the two light detecting means. An overscan detecting means for detecting the overscan portion, a position control D / A converter for controlling movement of the position of the reference pattern to the center of the two light detecting means, for correcting a convergence deviation; and control means for controlling the deflection circuit or convergence correction circuit detection signal overscan detecting means is provided, the deflection amount at the overscan portion enlarged than the deflection amount in the screen display of the two photodetecting Means for disposing the reference pattern on the two light In convergence automatic correction apparatus said control means is adapted to control the convergence correction amount in accordance with the output value of the position control D / A converter for movement control in the center position of the detecting means, the position control D / A converter A smoothing circuit for smoothing a PWM output output from the PWM D / A converter, and an output voltage and a horizontal or vertical deflection current of the smoothing circuit. A comparison circuit that compares a waveform or an output voltage of the smoothing circuit with a waveform proportional to a horizontal or vertical deflection current; and a waveform generation circuit that determines a generation timing of a reference pattern signal based on a pulse from the comparison circuit. The PWM output output from the PWM type D / A converter is roughly corrected by an output voltage smoothed by first reducing the time constant of the smoothing circuit. Performed, then convergence automatic correction device being characterized in that to perform a precise correction by greatly smoothed output voltage by a time constant of the smoothing circuit.

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