JPH0313589B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a brightness unevenness correction device for a cathode ray tube. In particular, when an image of a cathode ray tube is captured using a normal camera, brightness unevenness on a phosphor screen is corrected. This is a device designed to prevent harmful effects.

[Technical background of the invention and its problems] When a cathode ray tube image is photographed, shading that is not included in the actual image is recorded. This is a considerable obstacle for the.

There is no special method for reducing the uneven brightness of a cathode ray tube phosphor screen other than keeping the voltage between the cathode of the cathode ray tube and the first grid constant. However, this is based on the premise that the phosphor screen has certain characteristics, and the cause of uneven brightness may be due to the phosphor screen itself of the cathode ray tube, and the voltage between the cathode of the cathode ray tube and the first grid is The problem may not be resolved even if you keep it constant. In such cases, the cathode ray tube that causes extremely uneven brightness has no choice but to be replaced as a defective product.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a brightness unevenness correction device for a cathode ray tube that can reduce brightness unevenness on a cathode ray tube phosphor screen.

[Summary of the Invention] The present invention is to scan the cathode ray tube phosphor screen in advance by scanning it with a photoelectric converter to sample the photoelectric conversion outputs of each of a large number of locations when the entire surface is in a constant level image display state. data storage means storing each correction data for correcting brightness unevenness corresponding to each location of the cathode ray tube using the data; and a memory reading means for generating an address corresponding to the beam sweep position of the cathode ray tube, and outputting the brightness unevenness correction data from the memory reading means when the beam sweep position corresponds to each of the locations. The data is read out from the data storage means according to the address and supplied to the grid of the cathode ray tube.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which a video signal is applied to an input terminal 11, and a video amplification device 1
It is amplified by 2. The output of this video amplifying device 12 is applied to a cathode 14 of a cathode ray tube 13.
On the other hand, the video signal is also input to the synchronization separation circuit 16, and the horizontal and vertical synchronization signals separated by this circuit are supplied to the memory readout circuit 17. This memory read circuit 17 generates read address data for a memory (eg, read-only memory) 18. In this memory 18, correction data for correcting the base characteristic regarding the brightness of the cathode ray tube 13 is stored in advance as a digital amount. This correction data is read out in synchronization with the sweep of the cathode ray tube 13, converted into an analog signal by a digital-to-analog conversion circuit 19, and supplied to the first grid 15 of the cathode ray tube 13. The correction data corresponds to the amount of brightness unevenness on the phosphor screen of the cathode ray tube 13, and when the cathode ray tube 13 is in a constant brightness display state, the grid voltage is controlled so that the brightness unevenness does not occur.

As a result, when the screen of the cathode ray tube 13 is photographed with the ordinary camera 20, it is possible to obtain a photograph that is more faithful to the actual image than in the past.

FIG. 2 is a diagram showing an example of sampling points from which information on brightness unevenness on the screen is extracted. For convenience, the size of the fluorescent screen of the cathode ray tube is set to 130 mm in the horizontal direction and 130 mm in the vertical direction.
10 mm, and the interval between sampling points for brightness unevenness information extraction to be 5 mm.

According to this, the sampling point is horizontally
130/5 = 26, vertical direction 100/5 = 20, and a total of 26 x 20 = 520 points. Each sampling point is
The average luminance value of the surrounding area of ±2.5 mm is expressed as a binary digital quantity, and this is registered in the ROM, that is, the memory 18.

FIG. 3 shows the synchronization separation circuit 16 and the memory readout circuit 17, which are circuits that generate address data at the sampling points mentioned above. The horizontal synchronization signal HS separated by the synchronization separation circuit 16 is multiplied by 32 times by the 32 times multiplier circuit 31, and the 504KHz output from this circuit is input to the count input terminal of the horizontal address counter 32. Ru. This horizontal address counter 32 counts 26 sampling points in the horizontal direction. Also,
The horizontal synchronizing signal HS is frequency-divided by a 1/27 frequency dividing circuit 33, and the frequency-divided output of 583 Hz is input to the vertical address counter 34. Vertical address counter 3
4 counts the addresses of 20 sampling points in the vertical direction. Read address data for the memory 18 is created by the horizontal address counter 32 and the vertical address counter 34, and thereby the data in the memory 18 is read. The read data is applied to the grid of the cathode ray tube via the digital-to-analog conversion circuit 19 and the amplifier circuit 35.

In a monitor using a cathode ray tube that does not correct brightness unevenness, the grid electrode of the cathode ray tube is normally grounded, but in the present invention, an analog signal for correction is applied to the grid electrode. Due to the uneven brightness of the phosphor screen, this correction signal causes areas with strong brightness to
The amount of electron beams is suppressed in the direction of weakening the brightness, and conversely, the amount of electron beams is increased in the direction of increasing the brightness in areas where the brightness is weak. This maintains uniform brightness over the entire phosphor screen.

FIG. 4 shows a system for registering brightness non-uniformity correction information of a cathode ray tube in data generating means constituted by the memory 18 and the like.

In a monitor using a cathode ray tube 13, a white signal is first applied to the video signal input terminal 11 to maintain a constant display state. In this case, the screen appears uniformly white, but we have tried to make the brightness unevenness as noticeable as possible.
It is preferable to adjust the video level and contrast using the video amplification device 12. One photo sensor 41 is used to extract the brightness unevenness, and this photo sensor 41 is brought close to the screen of the cathode ray tube 13 and moved over the entire screen in the order of beam scanning. At a predetermined sampling point during the movement of the photo sensor 41, the microcomputer 43 reads data obtained by converting the photoelectric conversion output from analog to digital. Analog-to-digital conversion processing is performed by an analog-to-digital converter 42. The photo sensor 41 is
a horizontal pulse motor 45 driven by a microcomputer 43 via a drive circuit 44;
and is moved to each sampling point by a vertical pulse motor 47 driven via a drive circuit 46. After reading all the 520 points of data explained in Figure 2, the microcomputer 43
calculates the overall average value of the data.
Next, the brightness unevenness with respect to the average value is determined for each sampling point, and this is registered at a predetermined address in the memory 18 as correction data. In this case, if the brightness level of the calculated sampling point is positive, it is registered as a negative value in the memory 18, and conversely, if the brightness level is negative, it is registered as a positive value in the memory 18.

The memory in which the correction data is stored as described above can correct the brightness unevenness of the cathode ray tube mounted on the monitor as described above. As a result, the brightness unevenness of the phosphor screen is further improved compared to the conventional method, and it is possible to obtain a high-quality photograph when an image is taken with a camera.

[Effects of the Invention] As described above, according to the present invention, it is possible to correct luminance unevenness on the entire screen of a cathode ray tube according to a large number of locations.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention, FIG. 2 is a basic explanatory diagram of sampling points for correcting uneven brightness, and FIG. 3 is a circuit diagram showing an example of data generation means according to the present invention. Figure 4 is
1 is a configuration explanatory diagram showing an embodiment of an information gathering device of the present invention. 12...Video amplification device, 13...Cathode ray tube, 1
4... Cathode, 15... Grid, 16... Synchronous separation circuit, 17... Memory read circuit, 18...
Memory, 19...Digital-to-analog conversion circuit,
41...Photo sensor, 42...Analog-to-digital conversion circuit, 43...Microcomputer,
44, 46... Drive circuit, 45, 47... Pulse motor.

Claims (1)

[Scope of Claims] 1. Sampling data storage means that stores sampling data of photoelectric conversion output obtained by scanning the screen with a photoelectric converter in advance when the phosphor screen of the cathode ray tube is in an image display state at a constant level on the entire screen; , means for generating an address corresponding to a beam sweep position of the cathode ray tube according to a synchronization signal of a video signal supplied to the cathode ray tube for display; and storage of the sampling data based on a read address from the address generation means. A brightness of a cathode ray tube characterized by comprising means for reading sampling data from the means, and digital/analog conversion means for applying the sampling data read from the means to a brightness control electrode of the cathode ray tube. Unevenness correction device.