JP3006678B2 - CRT screen burn-in prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CRT screen burn-in prevention apparatus for preventing screen burn-in caused by displaying the same contents on a CRT for a long time.

[0002]

2. Description of the Related Art Conventionally, as a measure to prevent screen burn-in that occurs when the same content is displayed on a CRT for a long time, 1) the current display content under conditions such as when an operation cannot be performed for a certain period of time. Is stored in a memory or the like, and a display indicating that the burn-in prevention function is operating is performed at random on the screen in place of the display content. 2) The display content is completely erased, and an alarm is issued. A method of notifying that the burn-in prevention function is operating is employed. However, in the method (1), the display contents other than the original display contents are displayed, and in the method (2), the display contents are completely erased, which may cause confusion for the operator. For this reason, in the CRT screen burn-in prevention device described in JP-A-6-324634, the hue of each currently used color of the display contents of the screen is displayed by software or hardware when there is no operation for a certain period of time. Is switched to a color with low luminance while maintaining the color.

[0003]

The first problem is that, in the prior art, it may be difficult for an operator to visually recognize the display content depending on the display content.

[0004] The reason is that even if the brightness of the displayed pixel is low, the brightness is unconditionally reduced.

A second problem is that when the screen burn-in prevention operation of the CRT is started, if the operator is using the screen information, the operator may be confused.

The reason for this is that when the screen burn-in prevention operation is started, a sudden change in luminance occurs particularly in a portion having a high contrast.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image display apparatus using a RAMDAC having a look-up table (LUT) while maintaining display contents in order to prevent screen burn-in of a CRT without causing confusion to an operator. Selectively lower the brightness of the pixels displayed at high brightness, and display the pixels displayed at low brightness from the beginning so that they can be easily viewed by the operator without reducing the brightness, and the operator is using the screen information An object of the present invention is to provide a display system that does not cause confusion to the operator when the screen burn-in prevention operation is started.

[0008]

The present invention employs the following means to solve the above-mentioned problems.

(1) In a screen burn-in prevention device for preventing burn-in of a screen when the same contents are displayed on a CRT for a long time, means for converting RGB values set in a look-up table of a RAMDAC into hue / luminance values. A hue / luminance memory for holding the converted hue / luminance values, a luminance threshold comparator for judging whether or not the retained luminance is equal to or higher than a user-set threshold, a keyboard, etc. A timer counter for measuring the time elapsed since the interruption by the timer, a timer counter comparator for a value of the timer counter and a counter threshold value set by a user, and a value for the timer counter calculated by the timer counter comparator. When the counter value exceeds a preset counter threshold value, the luminance value stored in the luminance memory is exceeded when the luminance threshold value is exceeded. LU, holding means for holding the subtracted luminance value of the ALU, a selector for switching the output value of the holding means for the subtracted luminance value and the output value of the luminance memory by the timer counter comparator, the hue memory and the selector C that has means for converting the output value of
RT screen burn-in prevention device.

(2) ALU for subtracting the luminance value
The CRT screen burn-in prevention device according to (1), further comprising means for performing a subtraction process of the luminance value in proportion to a value of the timer counter for measuring a time elapsed.

(3) The device for preventing CRT screen burn-in according to (2), wherein the timer counter is reset by an interruption by a next keyboard or the like.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of a system to which the present invention is applied. In FIG. 1, a CRT display control device 100 according to one embodiment of the present invention
It operates on the value of the LUT of the MDAC 200.

FIG. 2 is a block diagram showing the configuration of an embodiment of the hardware of the present invention. In FIG.
The CRT display control device 100 includes a conversion unit 101 for converting RGB values to hue / luminance values, a conversion unit 108 for converting hue / luminance values to RGB values, a hue memory 102 for holding a hue for normal display, and holding a luminance for normal display. Brightness memory 103,
A luminance value generating unit 105 for performing a subtraction process, a comparator 106 for determining whether to subtract luminance from a threshold value set by a user, and a holding unit 1 for a newly generated luminance value
04, a selector 107 for selecting a luminance value to be actually used for display, a counter 109 for measuring a time until an interrupt occurs, and whether or not to start a screen burn-in prevention operation based on an output of the counter 109 and a threshold value set by a user. It is composed of a comparator 110 for judging whether or not.

Means 1 for converting RGB values to hue / luminance values
01, L of RAMDAC set by the user
The RGB values of the UT are converted into hue / luminance values. The converted hue / luminance values are stored in the hue memory 102 and the luminance memory 103, respectively. The hue / luminance values are used for normal screen display. The counter 109 is a timer counter that measures the time elapsed until an interrupt from a keyboard or the like is input, and the counter 109 is reset by an interrupt such as a keyboard input. The output value of the counter 109 is compared with a threshold value set by the user by the comparator 110, and when the output value of the counter 109 reaches a predetermined value, a screen burn-in prevention operation signal is output. Holding means 104 for newly generated luminance value
Receives this signal, reads the luminance value from the luminance memory 103 and uses it as a new luminance value table for display. The luminance value of the luminance value table equal to or higher than the threshold value set by the user by the comparator 106 is rewritten to the luminance value subtracted by the luminance value generation means 105 as the count of the counter 109 increases.

When all of the brightness values on the brightness value table become equal to or less than the threshold value, the counter 109 stops counting up until reset by the next interrupt. When the comparator 110 is performing the screen burn-in prevention operation, the selector 107 holds the newly generated luminance value holding unit 10.
4 is selected, and the output of the luminance memory 103 is selected during the normal display operation. From the output of the selector 107 and the output of the hue memory 102, the conversion means 108 for converting the hue / luminance value to the RGB value outputs the information of the LUT of the RAMDAC 200 reflected in the change of the luminance value by the luminance value generating means 105.

As described above, when the screen burn-in prevention operation is started, the brightness value of the pixel which is selectively displayed at a high brightness and causes the burn-in is gradually changed to a low brightness, and is displayed at a low brightness. The displayed pixels are displayed so as to be easily recognized without lowering the luminance.

[0018]

As is apparent from the above description, the present invention has the following advantages.

(1) LU referred to for CRT display
At T, by selectively setting the table set with high brightness to low brightness, it is possible to always provide information to the operator while preventing burn-in of the CRT.

The reason is that a low-luminance pixel whose luminance is not to be reduced at the time of normal display is left as it is, and only a high-luminance pixel which causes burn-in is selected, and the luminance of this pixel is determined. This is because

(2) At the start of the screen burn-in prevention operation,
Since the brightness is gradually changed, the operator is not confused.

The reason is that when the operator is watching the CRT, no sharp change in luminance occurs.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a system to which the present invention is applied.

FIG. 2 is a block diagram illustrating a configuration of an embodiment of hardware of the present invention.

[Explanation of symbols]

 Reference Signs List 100 CRT display control device 101 Conversion means from RGB value to hue / luminance value 102 Hue memory 103 Luminance memory 104 Luminance value holding means 105 Luminance value generation means 106 Comparator 107 Selector 108 Conversion from hue / luminance value to RGB value Means 109 Counter 110 Comparator 200 RAMDAC

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G09G 1/00 G09G 5/00 550 G09G 5/06 G09G 5/10

Claims (3)

(57) [Claims] 1. A screen burn-in prevention device for preventing burn-in of a screen when the same content is displayed on a CRT for a long time, means for converting RGB values set in a look-up table of a RAMDAC into hue / luminance values. A hue / luminance memory for holding the converted hue / luminance values, a luminance threshold comparator for judging whether or not the stored luminance is equal to or higher than a user-set threshold, and a keyboard or the like. A timer counter that measures the time elapsed since the interrupt was received, a timer counter comparator of the timer counter value and a user-set counter threshold,
An ALU for subtracting the luminance value held in the luminance memory when the value of the timer counter exceeds the user-set counter threshold by the timer counter comparator, and subtracting the ALU; A luminance value holding unit, a selector for switching between the output value of the subtraction luminance value holding unit and the output value of the luminance memory by the timer counter comparator, and an output value of the hue memory and the selector to an RGB value. CRT screen burn-in prevention device, characterized in that it has means for converting the image. 2. The apparatus according to claim 1, further comprising means for subtracting the luminance value from the ALU for subtracting the luminance value in proportion to a value of the timer counter for measuring an elapsed time. CRT screen burn-in prevention device as described in the above. 3. The CRT screen burn-in prevention device according to claim 2, wherein the timer counter is reset by an interruption by a next keyboard or the like.