JPH01288194A - Focus voltage adjusting device - Google Patents

Abstract

PURPOSE:To adjust a focus voltage with high accuracy by displaying a grating pattern on the screen of a cathode ray tube so as to obtain its picture data and using the picture data so as to obtain an optimum focus voltage. CONSTITUTION:A pattern generating circuit 5 displays a contrast pattern where a dark part and bright part are distributed equally such as a grating pattern on the screen of a cathode ray tube 1 and the pattern is picked up by an image pickup device. An interface circuit 8 fetches the picture signal from the image pickup device 7 to quantize each picture element into the contrast level of the plural gradations and stores it into a picture memory g as the picture data. A contrast distribution processing circuit 10 reads the picture data stored in the picture memory 9 to obtain the contrast distribution. An arithmetic control circuit 11 sets the contrast distribution of the picture data as a reference contrast distribution and obtains total sum of differences between the contrast level of the reference contrast distribution and the distribution contrast level of a picture data obtained at the application of other focus voltage (focus voltage to be detected) and uses the focus voltage maximizing the total sum as an optimum focus voltage.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a focus voltage adjustment device.

(Prior Art) Adjustment of focus voltage is an adjustment item for cathode ray tubes, and this adjustment is performed using the following methods. First, a worker displays a predetermined pattern such as a crosshatch on a cathode ray tube, visually measures the valley width of the vertical lines and horizontal lines of the displayed pattern, and determines the minimum width. The focus voltage at that time is set as the optimum focus voltage.

In addition, as a method of partially automatically adjusting the optimal focus voltage without visual inspection by workers, an imaging device set at a magnification sufficient to separate each phosphor from a minute region 1 in a cathode ray tube, for example, is placed in front of the cathode ray tube. In this state, the focus voltage is changed, and the peak value of brightness in the minute area at this time is detected to set the optimum focus voltage.

(Problems to be Solved by the Invention) However, the method for adjusting the optimal focus voltage as described above has the following problems. First of all, the method performed by workers has poor reliability because the focus voltage adjustment varies depending on the individual differences and fatigue level of the workers.

Furthermore, in a partially automated method, the phosphor emits light only intermittently, so even if the peak value of brightness is detected in a minute area on the display surface of the cathode ray tube, it will contain an error.

Furthermore, since 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 level 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 allow highly accurate adjustment and have low reliability.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a focus voltage adjustment device that can adjust the focus voltage with high precision so as to achieve optimal focus.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a focus voltage adjustment device for adjusting a focus voltage applied to a cathode ray tube, which generates and displays a bright and dark pattern distributed at a predetermined ratio on the display surface of the cathode ray tube. a generating means, an imaging device that captures an image of a cathode ray tube display surface, and an image data conversion device that converts an image signal output from the imaging device into image data of multiple gradations;
Optimal focus voltage calculation means that changes the focus voltage applied to the cathode ray tube and calculates the focus voltage at which the number of pixels in the bright and dark areas becomes a predetermined ratio from the gray level portion of each image data at the time of each changed focus voltage. This is a focus voltage adjustment device that attempts to achieve the above object.

(By providing such means, the pattern generating means displays a light and dark pattern distributed at a predetermined ratio on the display surface of the cathode ray tube, and this pattern is imaged by the imaging device. At this time, the image is output from the imaging device. The image signal is converted into multi-gradation image data by the image data conversion means.Then, the focus voltage applied to the cathode ray tube is changed.This means that if the focus voltage is not optimal, the pattern displayed on the cathode ray tube will appear blurry. Therefore, the present invention makes use of this fact, and when the focus voltage is in an optimal state, the ratio of the number of pixels between the bright and dark areas of the gray areas of the image signal captured by the imaging device is calculated. A focus voltage that has the same ratio of bright parts and dark parts generated by the pattern generation means is determined by the optimum focus voltage calculation means, and the focus voltage at this time is set as the optimum focus voltage.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a focus voltage adjustment device. In the figure, 1 is a color cathode ray tube, and this color cathode ray tube 1 includes a deflection yoke 2 and a magnetic field correction magnet 3.
is provided. Note that 1a is the display surface of the color cathode ray tube 1. Further, 4 is a television circuit for driving the color cathode ray tube 1, and a pattern generation circuit 5 and a focus voltage adjustment circuit 6 are connected to this television circuit 4. The pattern generation circuit 5 has a function of displaying a bright and dark pattern in which bright and dark parts are equally distributed, for example, a grid pattern as shown in FIG. 2, on the color cathode ray tube 1. It has a function of variably applying a focus voltage to the cathode ray tube 1.

On the other hand, an imaging device 7 is arranged at a position opposite to the display surface 1a of the color cathode ray tube 1. An interface circuit 8 is connected to the output terminal of the imaging device 7, and this interface circuit 8 samples the image signal output from the imaging device 7 into 512×512 pixels, and each of these pixels is divided into 256 gradation levels. It has a function of quantizing the 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 the window to the image data stored in the image memory 9 to obtain the gradation distribution within the window. It is. The arithmetic control circuit 11 includes a pattern generation circuit 5 and a focus adjustment circuit 6.
, the interface circuit 8, the image memory 9, and the gradation distribution processing circuit 10 to send commands to control their operations, and is composed of a CPU (central processing unit), memory, and the like. This arithmetic control circuit 11 further has the following functions. In other words, the gradation distribution of image data obtained when applying an arbitrary focus voltage is set as the reference gradation distribution, and the gradation level of this reference gradation distribution and other focus voltages (detected focus voltages) are set as the reference gradation distribution.
It has a function of determining the sum of the differences from the density distribution density level of the image data obtained at the time of application, and setting the focus voltage with the maximum sum as the optimum focus voltage.

In other words, when the focus is optimal, the density distribution has a uniform ratio of bright parts to dark parts, as shown in FIG. However, when the focus voltage is lowered or increased, the number of pixels with low gray levels increases as shown in FIGS. 4 and 5, respectively. Therefore, for example, the sum of the differences between the density distribution when the focus voltage is low and high and the density distribution at the optimum focus voltage (FIG. 6) becomes large. It should be noted that an output device 12 is connected to this arithmetic control circuit 11 to display the optimum focus voltage and various points in the process.

Next, the operation of the apparatus configured as described above will be explained with reference to the focus voltage adjustment flowchart shown in FIG. When the arithmetic control circuit 11 issues a command to the pattern generation circuit 5 in step s1, 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 display a green grid pattern on the color cathode ray tube 1. Further, in step s2, when a command to set the focus voltage Efo as shown in FIG. 7 is sent from the arithmetic control circuit 11 to the focus voltage adjustment circuit 6, the focus voltage adjustment circuit 6 controls the television circuit 4 to adjust the color Let Ef'o be the focus voltage applied to the cathode ray tube 1.

On the other hand, the imaging device 7 images the grid pattern displayed on the display cloth 1a of the color cathode ray tube 1 and outputs the image signal. In this state, when a command is sent from the arithmetic control circuit 11 to the interface circuit 8 in step s4, the interface circuit 8 takes in the image signal from the imaging device 7, samples it into 5L2×512 pixels, and converts each pixel into 256th floor. The image data is quantized into gray levels and stored in the image memory 9 as image data. However,
When the image data is stored, the gradation distribution processing circuit 10 reads out the image data stored in the image memory 9 and determines the gradation distribution. Note that this obtained gradation distribution is stored in the memory of the arithmetic control circuit 11 together with the focus voltage E('o) as a reference gradation distribution.

Next, proceeding to step s5, the arithmetic control circuit 1 sends a command to the focus voltage adjustment circuit 6 to increase the focus voltage to the focus voltage E1. When a command is sent from the arithmetic control circuit 11 to the interface circuit 8 again in this state, the interface circuit 8 takes in the image signal from the imaging device 7 and samples it into 512 x 512 pixels, and also converts each pixel into 256 gradations. The image data is quantized into gray levels and stored in the image memory 9 as image data. When the image data is stored, the gradation distribution processing circuit 10 reads out the image data stored in the image memory 9 in step s7 to determine the gradation distribution. The obtained density distribution is then stored in the memory of the arithmetic control circuit 11 together with the focus voltage E1.

Now, when the gradation distribution at the time of the focus voltage E1 is stored in this way, the arithmetic control circuit 11 calculates the number of pixels for each pixel level of the reference gradation distribution as shown in FIG. 8 and the focus voltage E1 in step S8. The total sum M1 of the differences between the density distribution and the number of pixels for each pixel level is calculated, and this sum M1 is stored in a memory. Then, in the next step s9, the sum obtained last time and the sum M obtained this time are compared, and if the previous sum is larger, the process moves to step slo and the previous focus voltage is set as the optimum focus voltage. By the way, in this case, the previous total is not remembered, so
Moving to the next step sll, the arithmetic control circuit 11 calculates the sum M
1 and sends a command to the focus pressure adjustment circuit 6 to increase the focus voltage using Stella's 12 and set it to focus voltage E2.

Then, the process moves to step s6 again, and the interface circuit 8 takes in the image signal from the imaging device 7, converts it into image data of 512×512 pixels and 256 gradations, and stores it in the image memory 9, as described above. Then, in step s7, the gradation distribution processing circuit 10 reads out the image data stored in the image memory 9 and obtains the gradation distribution. Note that this density distribution is stored in the memory of the arithmetic control circuit 11 together with the focus voltage E1. Therefore, in step S8, the arithmetic control circuit 11 calculates the sum M2 of the differences between the number of pixels for each pixel level of the reference gradation distribution and the number of pixels for each pixel level of the gradation distribution when the focus voltage E2 is applied. Store M2 in memory. And step s9
Compare the sum M1 obtained last time with the sum M2 obtained this time, and if the previous sum M1 is larger, step slo
Then, the previous focus voltage E is set as the optimum focus voltage.

Thereafter, by repeating steps s6 to s12, the focus voltage is increased sequentially as E2 and applied to the color cathode ray tube 1, and the sum of the differences between each density distribution and the reference density distribution at this time is N12. ... is required. However, the sum M2... of the differences between each gradation distribution of each focus voltage E2... and the reference gradation distribution is obtained, and when comparing the sum M6 and the sum M5, the previous sum M5 is larger. ing. In this case, the arithmetic control circuit 11 moves from step S9 to step slO, and determines the focus voltage E5 when the total sum is M5 as the optimum focus voltage.

In this way, in the above embodiment, a grid pattern is displayed on the display surface 1a of the cathode ray tube 1 to obtain its image data, and in this state, the focus voltage is changed to determine the density distribution of each image data at each focus voltage. The total sum of the differences from the base L$ density distribution is determined, and the focus voltage for which this sum is the maximum is determined as the optimal focus voltage, so the imaging area of the imaging device 7 can be widened and the density used for detection can be increased. The level can be set to all 256 gradations. Therefore, it is possible to reliably detect the focus voltage that provides the best focus. Furthermore, since it is possible to image a wide area as described above and uses a lattice pattern with similar bright and dark areas, high precision is achieved without being affected by the size or shape of the phosphors in the color cathode ray tube 1. Focus voltage can be adjusted.

It should be noted that the present invention is not limited to the above embodiments, and may be modified without departing from the spirit thereof. For example, although a green electron beam is used in the above embodiment, it may be red or blue. However, normally the electron beam is R, G,
Since they are arranged in parallel in the order of B, only green was used in the above embodiment. In the above embodiment, the reference density distribution is obtained using a low focus voltage Ero, but it may be obtained using a high focus voltage, or the optimum focus voltage may be estimated and set. Furthermore, the optimum method for determining the focus voltage may be such that the peak value is estimated by linear approximation from several pieces of data of the sum totals of the differences in each density distribution on the low side and high side of the focus voltage.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a focus voltage adjustment device that can adjust the focus voltage with high precision so as to achieve optimal focus.

[Brief explanation of the drawing]

1 to 8 are diagrams for explaining a focus voltage adjustment device according to the present invention, and FIG. 1 is a configuration diagram;
Fig. 2 is a diagram showing the grid pattern, Figs. 3 to 5 are diagrams showing &m light distribution of each focus voltage, Fig. 6 is a diagram showing an example of the difference in each density distribution, and Fig. 7 is a diagram showing the focus voltage. The adjustment flowchart, FIG. 8, is a diagram for explaining the operation of detecting the optimal focus voltage. DESCRIPTION OF SYMBOLS 1... Color cathode ray tube, 4... Television circuit, 5... Pattern generation circuit, 6... Focus voltage adjustment circuit, 7... Imaging device, 8... Interface circuit, 9... Image memory, 10... Grayscale distribution processing circuit, 11... Arithmetic control circuit. Applicant's agent, patent attorney Takehiko Suzue, Agricultural Disaster Representation, Volume 5, Figure 6, Comforting Story

Claims (1)

[Claims] A focus voltage adjustment device that adjusts a focus voltage applied to a cathode ray tube, comprising: a pattern generating means for generating and displaying a bright and dark pattern distributed at a predetermined ratio on the cathode ray tube display surface; an imaging device that images the cathode ray tube display surface; an image data converting means for converting an image signal output from the device into image data of multiple gradations, and a method for changing a focus voltage applied to the cathode ray tube, and from the gray level portion of each image data at each focused voltage that has been changed. 1. A focus voltage adjustment device comprising: optimal focus voltage calculation means for determining a focus voltage at which the number of pixels in bright and dark areas is at a predetermined ratio.