JPH10161579A - Burn-in preventive device of crt screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the burn-in of screen phosphor without causing the operator to be confused by maintaining the picture display of a CRT at a luminance level exceeding a certain value and yet causing no abrupt change of pictures. SOLUTION: The hue and luminance values converted from a RBG value by a conversion means are stored in hue memory 102 and luminance memory 103 to be used in usual picture displays. The output value of a counter 109 which measures the period before being interrupted by a key board, etc., is compared by a comparator 110 with a threshold value set by the user, and the above device outputs a screen burn-in preventing signal after a specified value is reached. On receiving this signal, a holding means 104 of a newly generated luminance value reads out the luminance value from the luminance memory to use this as an luminance value table for new display. The luminance value of the luminance table exceeding the threshold value set by the user using the comparator 106 is rewritten to the luminance value subtracted by a luminance generating means 105.

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. Therefore, in the CRT screen burn-in prevention device described in Japanese Patent Application Laid-Open No. Hei 6-324634, the hue of each currently used color of the screen display contents 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 content is displayed on a CRT for a long time, RGB values used for a look-up table of a RAMDAC defined by a user are converted into hue / luminance values. Means for converting, and hue and color converted by the means
A brightness value holding unit, a brightness value generation unit for generating a pixel having a reduced brightness value, a comparator for determining whether or not the brightness value is reduced according to a threshold value set by a user; Means for holding a brightness value generated by a brightness value generating means separately from the brightness value of the above, a selector for selecting a brightness value actually used for display from the brightness values held in the two holding means, a hue and selection Means for converting the brightness value into RGB values, a timer counter for measuring the time elapsed since an interrupt from a keyboard or the like, and whether or not to start the screen burn-in prevention operation in accordance with a threshold value defined by the user. CRT screen burn-in prevention device having a comparator for determination.

(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 in proportion to the value of the timer counter for measuring the passage of time.

(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 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 with 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

Claims (3)

[Claims] 1. 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, converts RGB values used in a look-up table of a RAMDAC defined by a user into hue / luminance values. Means for holding the hue / brightness value converted by the means, a brightness value generating means for generating a pixel having a reduced brightness value, and a brightness value decreasing according to a threshold value set by the user. A comparator for determining whether or not to perform the operation, a storage unit for the luminance value generated by the luminance value generation unit separately from the previous luminance value, and a luminance value actually used for display held by the two storage units. A selector for selecting the hue and the selected luminance value into an RGB value, and a selector for measuring a lapse of time after an interruption by a keyboard or the like. A CRT screen burn-in prevention device, comprising: a comparator for determining whether to start a screen burn-in prevention operation according to an imma counter and a threshold value defined by a user. 2. The CRT screen according to claim 1, further comprising means for performing a subtraction process on the ALU for subtracting the luminance value in proportion to a value of the timer counter for measuring the passage of time. Anti-seizure device. 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.