JP2713981B2 - Focus voltage adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a focus voltage adjusting device.

(Prior Art) Adjustment of a focus voltage is an adjustment item of a cathode ray tube, and this adjustment is performed by the following methods.
First, according to a method by an operator, this displays a predetermined pattern such as a cross hatch on a cathode ray tube, and measures the widths of vertical lines and horizontal lines of the displayed pattern visually by the operator, and the width is minimized. Is set as the optimum focus voltage.

As a method of partially adjusting the optimum focus voltage by automating the adjustment without depending on the operator's visual observation, a micro-area in a cathode ray tube, for example, an imaging device set to a magnification enough to separate each phosphor is arranged in front of the cathode ray tube. In this state, the focus voltage is changed, and the peak value of the luminance in the minute area at this time is detected to set the optimum focus voltage.

(Problems to be solved by the invention) However, the above-described method of adjusting the optimum focus voltage has the following problems. First, in the method by the worker, the focus voltage adjustment varies depending on the individual difference and the degree of fatigue of the worker, and the reliability is inferior. Further, in the partially automated method, since the phosphor emits light only at discrete intervals, even if a peak value of luminance is detected in a minute area on the display surface of the cathode ray tube, an error is included. Further, since the detection is not performed over the entire display surface of the cathode ray tube, it is not possible to reliably adjust the focus to the optimum over the entire display surface of the cathode ray tube. Therefore, it is difficult to adjust the focus voltage with high accuracy and the reliability is low.

As described above, there are methods for optimally adjusting the focus voltage, but none of them can be adjusted with high accuracy, and the reliability is low.

Therefore, an object of the present invention is to provide a focus voltage adjusting device capable of adjusting a focus voltage with high accuracy so as to obtain an optimum focus.

[Constitution of the Invention] (Means for Solving the Problems) The present invention relates to a focus voltage adjusting device for adjusting a focus voltage applied to a cathode ray tube, comprising a bright portion and a dark portion on a display surface of the cathode ray tube. Pattern generation means for generating and displaying a lattice pattern, an imaging device for imaging the display surface of a cathode ray tube, image data conversion means for converting an image signal output from the imaging device into image data having a plurality of gradations, The focus voltage applied to the cathode ray tube, and the number of pixels at each pixel level of the grayscale distribution and the number of pixels at each pixel level of the reference grayscale distribution in each image data when each of these changed focus voltages is reached. And a focus voltage calculating means for calculating a focus voltage at which the sum is maximum as an optimum focus voltage. Scan is a voltage regulator.

(Operation) With the provision of such means, the pattern generation means generates and displays a grid pattern composed of bright and dark portions on the display surface of the cathode ray tube, and images the pattern with an imaging device. The output image signal is converted into image data having a plurality of gradations by image data conversion means. Then, the focus voltage applied to the cathode ray tube is changed by the optimum focus voltage calculating means, and when reaching each of the changed focus voltages, the number of pixels for each pixel level of the gray level distribution in each image data and the reference gray level distribution are calculated. The sum of the differences from the number of pixels at each pixel level is determined, and the focus voltage that maximizes the sum is determined as the optimum focus voltage.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a focus voltage adjusting device. In FIG. 1, reference numeral 1 denotes a color cathode ray tube, which is provided with a deflection yoke 2 and a magnetic field correction magnet 3. 1a is a display surface of the color cathode ray tube 1. Reference numeral 4 denotes a television circuit for driving the color cathode-ray tube 1, to which a pattern generation circuit 5 and a focus voltage adjustment circuit 6 are connected. The pattern generating circuit 5 has a function of displaying a light and dark pattern in which light and dark portions are equally distributed, for example, a lattice pattern as shown in FIG. It has a function of variably applying a focus voltage to the CRT 1.

On the other hand, an imaging device 7 is arranged at a position facing the display surface 1a of the color CRT 1. An interface circuit 8 is connected to an output terminal of the image pickup device 7, and the interface circuit 8 samples the image signal output from the image pickup device 7 into 512 × 512 pixels, and converts each of the pixels into 256 gradations. It has a function of quantizing to a gray level and storing it in the image memory 9 as image data.
Reference numeral 10 denotes a gradation distribution processing circuit, which has a window and has a function of setting this window to image data stored in the image memory 9 and obtaining a gradation distribution in the window. It is. Arithmetic control circuit
Reference numeral 11 denotes a pattern generation circuit 5, a focus adjustment circuit 6, an interface circuit 8, an image memory 9, and a density distribution processing circuit.
It has a function to control operation by sending commands to 10,
It is composed of a CPU (Central Processing Unit) and a memory. The arithmetic control circuit 11 further has the following function. That is, the gray level distribution in the image data obtained when an arbitrary focus voltage is applied is set as the reference gray level distribution, and the gray level of this reference gray level distribution and the other focus voltages (detected focus voltages) are obtained. It has a function of calculating the total sum of the difference between the gray level and the gray level of the gray level distribution in the image data to be obtained, and setting the focus voltage at which this total becomes the maximum as the optimum focus voltage. In other words, in the density distribution when the focus is optimal, as shown in FIG. 3, the ratio of the bright part to the dark part is uniform. However, when the focus voltage is lowered or raised, the number of pixels having a low gray level increases as shown in FIGS. 4 and 5, respectively. Therefore, for example, the sum of the differences (FIG. 6) between the grayscale distribution when the focus voltage is low and high and the grayscale distribution when the focus voltage is optimal is large. An output device 12 is connected to the arithmetic control circuit 11 so as to display the optimum focus voltage and each value during the processing.

Next, the operation of the apparatus configured as described above will be described with reference to the focus voltage adjustment flowchart shown in FIG. In step s1, the arithmetic control circuit 11 sets the pattern generation circuit 5
, The pattern generation circuit 5 sends information to the television circuit 4 to display a grid pattern as shown in FIG. Upon receiving this information, the television circuit 4 drives only the green electron beam to cause the color CRT 1 to display a green grid pattern.
In step s2, the arithmetic control circuit 11 sends the focus voltage Ef as shown in FIG.
When the command of “o” is transmitted, the focus voltage adjusting circuit 6 controls the television circuit 4 to control the color CRT 1.
Let Efo be the focus voltage applied to.

On the other hand, the image pickup device 7 picks up an image of the lattice pattern displayed on the display surface 1a of the color CRT 1 and outputs an image signal. In this state, when a command is sent from the arithmetic and control circuit 11 to the interface circuit 8 in step s4, the interface circuit 8 takes in the image signal from the image pickup device 7, samples it into 512 × 512 pixels, and converts each pixel into 256 pixels. The image data is quantized to a gradation level and stored in the image memory 9 as image data. However, when the image data is stored, the grayscale distribution processing circuit 10 reads out the image data stored in the image memory 9 and obtains a grayscale distribution. The obtained grayscale distribution is stored in the memory of the arithmetic and control circuit 11 together with the focus voltage Efo as a reference grayscale distribution.

Then the controller 1 proceeds to step s5 sends an instruction to the focus voltage E ₁ by increasing the focus voltage to a focus voltage adjustment circuit 6. The operation control circuit
When a command is sent from 11 again to the interface circuit 8, the interface circuit 8 takes in the image signal from the image pickup device 7, samples it into 512 × 512 pixels, and quantizes each pixel into 256 gray levels. Stored in the image memory 9 as image data. When the image data is stored, the density distribution processing circuit 10 reads out the image data stored in the image memory 9 in step s7 to obtain a density distribution. Then, thus determined gray-scale distribution is stored with the focus voltage E ₁ to the memory of the arithmetic control circuit 11.

Now, when the shading distribution of the thus when the focus voltage E ₁ is stored, the arithmetic control circuit 11 to the eighth number of pixels by each pixel level of the reference grayscale distribution as shown in FIG. In step s8 and the focus voltage E the sum M ₁ determined of the difference between the number of pixels by each pixel level of the shading distribution when the _1, stores the sum M ₁ in the memory. Then, the larger the last sum is compared with the sum M ₁ obtained this time and the sum of previously obtained in the next step s9, the optimum focusing voltage of the previous focus voltage shifts to step s10. By the way, in this case,
Since the previous total is not stored, the next step s11
The arithmetic control circuit 11 moves to sends an instruction to set up a high focus voltage in step s12 and stores the sum M ₁ in the focus voltage E ₂ to the focus voltage adjustment circuit 6.

Then, the process again proceeds to step s6, and the interface circuit 8 takes in the image signal from the imaging device 7, converts it to image data of 512 × 512 pixels and 256 gradations and stores it in the image memory 9 in the same manner as described above. Then, in step s7, the density distribution processing circuit 10 reads out the image data stored in the image memory 9 to obtain the density distribution. Incidentally, the shading distribution is stored together with the focus voltage E ₁ to the memory of the arithmetic control circuit 11. Thus, the arithmetic control circuit 11 obtains the sum M ₂ of the difference between the number of pixels by each pixel level of the shading distribution when the pixel level on the number of pixels for the focus voltage E ₂ of the reference grayscale distribution in step s8, and stores the sum M ₂ in the memory. Then, the larger the previous sum M ₁ is compared with the total M ₂ determined this time the sum M ₁ previously determined in step s9, the optimum focusing voltage of the previous focus voltage E ₁ proceeds to step s10.

Thereafter, by repeating Steps s6 to s12, the focus voltage is sequentially increased as E ₂ ... And applied to the color cathode-ray tube 1, and the sum M ₂ of the differences between each gray level distribution and the reference gray level distribution at this time. Is required. However, the sum M ₂ of the differences between the gray scale distributions of the focus voltages E ₂ … and the reference gray scale distribution is obtained, and the sum M ₆ and the sum M ₅ are obtained.
Comparing the door becomes larger in the previous sum M _5.
In this case, the arithmetic control circuit 11 proceeds from step s9 to step s1.
Turning to 0 obtaining a focus voltage E ₅ when the sum M ₅ as an optimum focus voltage.

As described above, in the above-described embodiment, the grid pattern is displayed on the display surface 1a of the cathode ray tube 1 to obtain the image data, and in this state, the focus voltage is changed to obtain the density distribution of each image data at each focus voltage. Since the sum of the difference from the reference shading distribution is obtained and the focus voltage at which the sum is the maximum is obtained as the optimum focus voltage, the imaging area of the imaging device 7 can be widened and the shading level used for detection can be reduced. A total of 256 gradations can be used. Therefore, it is possible to reliably detect the focus voltage at which the best focus is achieved. In addition, since a wide area can be imaged as described above, and the bright and dark portions use a uniform grid pattern, the size and shape of the phosphor of the color cathode-ray tube 1 are not affected at all and can be performed with high accuracy. Focus voltage can be adjusted.

The present invention is not limited to the above-described embodiment, and may be modified without departing from the gist thereof. For example,
In the above embodiment, a green electron beam is used, but this may be red or blue. However, the electron beam is usually R, G, B
Are arranged in parallel in this order, so that only green is used in the above embodiment. Further, in the above embodiment, the reference density distribution is obtained with a low focus voltage Efo, but may be obtained with a high focus voltage, or may be set by estimating an optimal focus voltage. Further, the peak value may be estimated by linearly approximating the method of obtaining the optimum focus voltage from several data of the sum of the differences of the respective grayscale distributions on the low side and the high side of the focus voltage.

Although the present embodiment has been described by taking a cathode ray tube as an example, it goes without saying that a similar effect can be obtained if a cathode ray tube having the same operating principle is used.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a focus voltage adjustment device capable of adjusting a focus voltage with high accuracy so as to achieve optimum focus.

[Brief description of the drawings]

1 to 8 are views for explaining a focus voltage adjusting device according to the present invention. FIG.
FIG. 2 is a diagram showing a grid pattern, FIGS. 3 to 5 are diagrams showing grayscale distributions of respective focus voltages, FIG. 6 is a diagram showing an example of a difference between grayscale distributions, and FIG. FIG. 8 is a diagram for explaining the operation of detecting the optimum focus voltage. 1 ... color CRT, 4 ... television circuit, 5
... Pattern generating circuit, 6 focus voltage adjusting circuit, 7 imaging device, 8 interface circuit, 9
... Image memory, 10 ... Shadow distribution processing circuit, 11 ... Operation control circuit.

Claims (1)

(57) [Claims] 1. A focus voltage adjusting device for adjusting a focus voltage applied to a cathode ray tube, a pattern generating means for generating and displaying a grid pattern composed of a bright portion and a dark portion on a display surface of the cathode ray tube; An imaging device that images a display surface of the cathode ray tube; an image data conversion unit that converts an image signal output from the imaging device into image data having a plurality of gradations; and the focus voltage applied to the cathode ray tube. And calculating the total sum of the difference between the number of pixels at each pixel level of the grayscale distribution and the number of pixels at each pixel level of the reference grayscale distribution in each of the image data when these changed focus voltages are reached. Optimum focus voltage calculating means for obtaining the focus voltage having the maximum sum as the optimum focus voltage. Focus voltage regulator that.