JPS62990A - Color video monitor with improved color accuracy - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates generally to high resolution and high chroma color monitors and televisions. In particular, the present invention relates to a novel system that provides highly accurate color reproduction for color monitors and televisions.

BACKGROUND OF THE INVENTION In many task scanning monitors used in military and industrial applications, it has been found useful to display monitored information as color-coded graphs and alphanumeric data on a video screen. . The ability to display color-coded data for military command and industrial control would have significant advantages, but these advantages have not been realized to date. Because of the large amount of data that must be displayed on the screen, color monitor display devices have not been able to provide sufficient resolution, color accuracy, and color purity.

Until now, in practice, the focus has been on the clarity and readability of data across one display surface, color adjustment and reproducibility, operator adaptability, shock and vibration resistance, and performance stability over time. Considering that.

Monochrome video monitors are more practical than traditional color display devices.

In order to effectively display multicolored data and graphs on a color monitor, the monitor must produce colors that can be accurately reproduced at very high true visual display resolution. The colors produced must be free of visible jitter, shift, or defocus over the entire display surface of the monitor screen, including edges and corners. Therefore, one display parameter is controlled so that the color-coded display data is most easily readable by the operator. In the past, achieving such accuracy in display parameters required frequent maintenance, sometimes under adverse operating environmental conditions.

When these characteristics are achieved, the high density display data typically found in the military command and control field can be read with great clarity and accuracy.

In this and a variety of other industrial and transportation management applications, text, complex symbols, and other detailed data should be kept to a minimum to minimize the risk of data duplication or difficulty in reading. Must.

The display quality of a monitor constructed to obtain the above characteristics is equal to or superior to that of the best monochrome monitors of comparable size, but with the added benefit of color coding. bring.

The problem that the invention seeks to solve: Military command and control systems are increasingly having to function in high-density target environments that require large amounts of data to be rapidly processed, displayed, and made decisions. There is. The display system must present data in a format that allows the operator to quickly and accurately identify and track objects of interest from a clutter of overlapping, or similar-looking objects. Moreover, such objects constantly change position, with new objects appearing frequently and randomly, usually near the edges of one display.

When display data is color-coded, it helps distinguish between data that looks similar in a high-density display and emphasizes that data, improving operator accuracy and reducing reaction time. It is shorter and less tiring. Because of these advantages, color display devices are increasingly being used in both military and civilian applications such as air traffic control systems.

SUMMARY OF THE INVENTION Prior to the present invention, many parameters describing the performance of color display devices were less satisfactory than monochrome display devices for similar applications. The present invention provides a significant improvement needed to benefit from the addition of color codes. These improvements include: 1. intelligibility, i.e., data clarity and legibility; chromaticity, i.e., color adjustment to make it most perceivable and readable to humans; and 1. color concentration, i.e., positioning of primary colors. It concerns consistency and stability of performance over time. The color monitors described generally and the color correction circuits specifically described herein meet these performance goals.

The color reproduction circuit of the present invention produces a highly intelligible display and accurately displays selected colors controlled to tight tolerances, e.g. within 10%, even in adverse environmental conditions with fluctuating temperatures. It is designed like this. Such color reproducibility is achieved regardless of the settings of the brightness and contrast controls by the operator.

From the above description, it can be seen that 1. The ease of display devices 1. The power of having a very accurate video processor circuit so that the color resolution and color accuracy are very good) - monitors are still required in this field. It is clear that there are.

It is therefore a primary object of the present invention to provide a video processor circuit for forming displays that are very easy to understand, have high color resolution and good color accuracy, and are particularly useful in military command and control and civilian business fields. The objective is to provide a color monitor with

In particular, it is an object of the present invention to provide a color monitor having a video processor circuit capable of providing highly accurate and precise color functions such that the accuracy of one color is controlled to within a tolerance of approximately 10%.

Another object of the present invention is to provide a color monitor having a video processor circuit constructed of digital and analog circuitry for accurate operation under adverse environmental conditions.

Yet another object of the present invention is to provide a color monitor having a video processor circuit that uses a 3-bit color hood to create up to eight different colors, including black, on the display.

Yet another object of the present invention is to use digital-to-analog conversion of a 3-bit input digital code to
It is an object of the present invention to provide a color monitor having a video processor circuit that sets the GB amplitude components to a desired median value.

Yet another object of the present invention is to provide a color monitor that uses a video processor circuit with three feedback loops to maintain the brightness of each primary color within 10% of its desired value throughout operating conditions.

Another object of the present invention is to include a 3-channel amplifier that includes both a final video amplifier and a CRT to perform equalization or color tracking and to stabilize the combined signal-luminance transfer characteristics against CRT and circuit drift. The present invention provides a color monitor with a video processor circuit having two feedback loops for each of the three primary color channels.

Yet another object of the present invention is to use color tracking and non-additive blending of raster background colors and data colors to maintain operator-set brightness and contrast settings. It is an object of the present invention to provide a color monitor having a video processor circuit in which colors are formed without any problem.

In summary, these and other objects of the present invention are accomplished by providing a color monitor having a video processor circuit using three feedback loops for each of the 3H color channels.

Each feedback loop includes both the final video amplifier and the CRT to perform equalization or color tracking and to stabilize the combined signal-to-luminance transfer characteristics against CRT and circuit drift. The video processor circuit includes a digital-to-analog converter for converting the 3-bit digital code into an analog signal representing the amplitude components of each RGB color. Each video processor channel circuit includes a video preamplifier and video amplifier and three feedback loops. This feedback loop stabilizes the CRT cathode by setting a blanking bias level using a sample of the CRT cathode current, one to establish white and black sample levels, and the other to stabilize the CRT cathode by setting a blanking bias level using a sample of the CRT cathode current. The goal is to achieve this goal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It should be pointed out at the outset that it will be obvious to those skilled in the art that a circuit performing the functions shown in the block diagram of FIG. To avoid obscurity, only the parts of this circuit will be described in detail.

Referring to the various drawings in which like elements are designated with the same reference numerals throughout, FIG. 1 schematically depicts a color monitor of the present invention. The color monitor receives a 36 MHz clock signal, a composite synchronization signal, and a 3-bit digital color signal through a video interface circuit 10 and a synchronization/onboard test circuit 12, respectively.

Therefore, a color monitor can reproduce eight different colors. The horizontal drive/clock signal is provided to a digital concentration signal generation circuit 14 as well as to a horizontal deflection/dynamic focusing circuit 16.

The general function of the other circuits shown in FIG. 1 is believed to be known. However, the digital convergence signal generation circuit 14 is the subject of a separate United States patent application filed concurrently with the present invention and assigned to the assignee of the present invention.

FIG. 2 shows the circuitry of the video amplifier/processor 18 of the color monitor shown in FIG. It should be understood that the color monitor shown in FIG.

Video processor circuit 18 receives three color intensity bits (two for the blue video processor) from video synchronization circuit 12.
bit) and one background bit. The received video bit information is applied to the input of a digital-to-analog converter 200, which converts these bits into an analog video signal. Adjustments are provided to control the D/A output for each input bit to control the output strength of the CRT for a given bit input. The analog video signal is preamplified by a video preamplifier 202 and output to the CRT 2 through a video output circuit 204.
2 cathode 520. video preamplifier 20
2 and video output circuit 204 function as a high gain/wide bandwidth amplifier to generate the necessary CRT drive signals.

Video processor/amplifier 18 also generates a video blanking drive signal, which is transmitted to blanking amplifier 2.
06 is output to the blanking grid 522 of the CRT 22. In addition, sample circuits 20 for white and black levels
8 and 210 and a beam sample or cathode stabilization circuit 212 are used. These circuits are shown in FIGS. 3-6 and will be discussed below.

To control the brightness and contrast of the CRT22,
The video amplifier 18 displays reference voltage information on the control panel 2.
Receive from 4. The desired contrast and brightness settings are determined by potentiometers 214 and 2 included on the control panel.
It is determined by the position of 16. Brightness potentiometer 21
The voltage output from 4 is buffered by buffer 218 and sent to white level control circuit 20. Next, this white level control circuit 208 transfers this output to the D/A converter 2.
00, where this output is used to control the amplitude of the analog voltage drawn from the binary input color bits. This output is also added to the signal from contrast controller 216 in brightness buffer 220. This output is then sent to the D/A converter 200 and when the background bit is present, the D/A converter 200
Used to control 0. The controller 214 controls the D/A converter 2 when the background bit is present.
Used to control 00.

Video processor 18 receives horizontal parabolic signals from horizontal deflection circuit 16 and also receives vertical parabolic signals from digital convergence circuit 14 .

These two signals are added in adder 228.

The amplitude of the summed parabolic signal is controlled by a potentiometer 230 connected to the output of summer 228. The output of potentiometer 230 is connected to buffer 232
and then sent to buffer 224 where it is added to the output from black level sample circuit 210. The composite signal modifies the color analog output signal in video output circuit 204 to uniformly control the brightness of the CRT.

Brightness controller 216 is used to establish a reference voltage for measuring the output of video amplifier 18 when a white sample is present as an input to D/A converter 200. When an error is measured between the luminance reference and the white sample video output pulse, the gain of D/A converter 200 is changed to control loop circuit 2, described below with respect to FIG.
08 to establish a constant white sample video output for a given brightness setting.

Similarly, in order to maintain a constant black video level output from video amplifier 18, the second
A control loop 210 is provided. This is done by measuring the video output from video output circuit 204 when no video is present. To this end, the video output from video output circuit 204 is sent as an input to black sample feedback loop circuit 210 through buffer 222 and compared with a reference value.

If an error is measured between the black reference level and the black level of the video output stage, this error is transferred to the buffer 22.
4 to the input of video output circuit 204, and thus control loop circuit 210 adjusts the 67 volt black video level output to the desired voltage level. The timing of black level control loop 210 is established by the black level sample signal received from synchronization circuit 12. Both black level samples and white level samples are formed during the horizontal blanking period.

A third feedback control loop 212 is used by video processor circuit 18.

This control loop 212, described in connection with FIGS. 5 and 6, is used to adjust the blanking voltage level of the CRT grid 522 to control beam current.

This is done by measuring or sampling the cathode current of the CRT 22 during the vertical retrace time. W
The determined current is compared with a reference value in the feedback control loop 2.12 of the cathode stabilization circuit. The difference or error is measured and input to blanking amplifier 206.

There it is amplified and used to set the blanking voltage level, ie the voltage level of grid 522. Adjustment of the blanking voltage level sets the cathode current or beam current to the desired value.

The measurement constant of the cathode beam sample current is determined by the synchronization circuit 12.
This is done using beam sample signals received from the Cathode beam sample 212, white sample 208
and the control loop or circuit for the black sample 210 is
A separate one is provided for each of the three CRT electron guns: red, green, and blue. Combining such a cathode beam stabilization system with black and white level control loops ensures accurate color display on the CRT.

This maintains the brightness of each primary color in the mixed color data within 10% of its desired value.

The three feedback loops 208, 210 and 212 included in each of the three primary color channels include the final video amplifier 18 and the CRT 22, so that the equalization of the composite signal-luminance transfer characteristics or color against CRT and circuit drift. Tracking and stabilization is achieved. Furthermore,
Color is independent of brightness and contrast adjustments made by the operator. This is accomplished through color tracking and non-additive compositing of raster background colors and data colors.

FIG. 3 shows a white level sample control loop 208 for a color monitor in accordance with the present invention.

As previously discussed, the video output is sent from video output circuit 204 to the input of buffer 222. The thus buffered video output signal, as well as the video reference pulse, is input to analog switch 300. The output signal from the analog switch is sent to one of the inputs of sample/hold circuit 302. A luminance reference signal is sent to the other input. Sample/hold circuit 302 compares the luminance reference signal to the buffered video output signal during the white sample signal time. The white sample bit and the reference bit are received from the synchronization circuit 12, and these bits are formed using a ROM from the signals sent to the synchronization circuit.

The white sample reference bit is the brightness potentiometer 214
Start measuring sample/hold values derived from the settings. The measurements of the sample/hold circuit 302 establish the brightness or amplitude of the video signal for a particular setting of the brightness controller 214. The luminance signal thus established is then:

As described above, it is sent to the D/A converter 200.

FIG. 4 shows a feedback control loop circuit 210 for black level samples. Video output circuit 204
and buffer 222 are the same elements used by white control circuit 208.

A second analog switch 400 receives the output from the buffer 222 and, during the black reference signal time, the output from the analog switch is sent to one of the inputs of the sample 7 hold circuit 402. In addition, the sample/hold circuit 40
A reference signal is sent to the other input of 2. These black reference bits and sample bits are connected to the synchronization circuit 1 in the same manner as described for the white sample bits and reference bits.
Supplied from 2.

The black reference bit sent to analog switch 400 passes the established black level voltage setting from buffer 222 to sample/hold circuit 402 . The black sample bit sent to sample/hold circuit 402 initiates measurement of the sample/hold value to maintain the established black level voltage. The black level voltage output signal from the sample/hold circuit 402 is passed through the filter 4.
04 and then input to adder 224. This adder 224 receives as an additional input the output from the brightness uniformity correction buffer 232. A bias control signal is generated at the output of adder 224 and is sent to video output circuit 204 and from there to cathode 520 of CRT 22.

FIG. 5 illustrates the cathode stabilization or beam stabilization loop control circuit 212 of the color monitor of the present invention. The CRT beam current signal is output from video output circuit 204 to current/voltage converter 500. The voltage representing the CRT beam current signal is applied to the sample/hold circuit 5.
02 and a reference signal to the other input. Two beam sample bits are input to control loop 212. One is passed through the sample/hold circuit 502 and the other is passed through the video output stage and the C
Accepts RT beam current. The output of sample/hold circuit 502 is filtered by filter 504 and sent to blanking amplifier 206 where it is used to set a blanking bias level based on the constant CRT cathode sample current.

In addition, buffers 222 and 226 provide a shift in cathode voltage to blanking amplifier 206 during the beam sample interval such that a constant level of voltage is applied to grid 522 and cathode 520 of CRT 22 during the beam sample interval. ensure that

As mentioned above, the black level voltage and blanking bias level ensure that the CRT output is a constant function of the CRT video input. The blanking signal is CRT2
2 to the corresponding color control grid 52.

FIG. 6 shows an example implementation of the cathode stabilization circuit 212 of FIG. The circuit of FIG. 6 performs beam sampling and video driving of the CRT cathode. The advantage of driving the cathode instead of the grid with the video signal is that the cathode circuit is only subjected to a low capacitive load, resulting in a wide bandwidth response.

When the video drive is in normal condition, the diode 600
and 602 are rendered conductive, forming a current path to the video drive circuit of the CRT 22.

During the beam sample interval, the first transistor 6
04 is turned on, grounding the negative side of capacitor 606. The positive side of capacitor 606 turns on diode 608, which provides the required current for the video drive circuit and provides additional current to diode 620, thereby bringing point A to the +V supply. Clamp. In such a state, the diode 602
is reverse biased and diodes 600 and 610
The voltage will be O volts. At this time, the current flowing to the cathode, ie, the beam current of the CRT, flows through resistor 612 and is then amplified by operational amplifier 614, resistor 616, and second transistor 618. A second transistor 618 level shifts the reference output voltage relative to ground. This output voltage is proportional to the cathode current.

So far, we have described a color television monitor that uses video processing circuitry to create a highly accurate color display.

Although only preferred embodiments of the invention have been particularly shown herein, in light of the above teachings, various changes may be made to the invention within the scope of the claims and without departing from the spirit and scope of the invention. It will be understood that what can be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a color monitor circuit of the present invention, FIG. 2 is a block diagram of a video amplifier circuit of the present invention, and FIG. 3 is a white level level included in the video amplifier circuit of FIG. FIG. 4 is a schematic block diagram of a black level control circuit included in the video amplifier circuit of FIG. 2; FIG. 5 is a schematic block diagram of a black level control circuit included in the video amplifier circuit of FIG. 6 is an electrical circuit diagram of the cathode stabilization circuit of FIG. 5. 10...Video interface 12...Synchronization/onboard circuit 14...Digital concentration signal generator 16...Horizontal synchronization/dynamic focusing circuit 18...Video amplifier 22...CRT 24... Display control panel 200...D/A converter 202...Video preamplifier 204...Video output 206...Blanking amplifier 208...White level sample circuit 210...Black level sample circuit 212... ...Cathode stabilization circuit 214, 216, 230...Potentiometer 218
．． 220.222.224,226°232...Buffer 228...Adder 300...Analog switch 302...Sample and hold circuit 304...Filter 400...Analog switch 402...Sample and Hold circuit 404...filter 500...current/voltage converter 502...sample/hold circuit 504...filter 520...grid 522 of CRT22...cathode 600.602, 608.610 of CRT22. 620...Diode 604...First transistor 606...Capacitor 612.616...Resistor 614...Operation amplifier 618...Second transistor Drawing drawing (no change in content) FIG, 2 FIG, 3 FIG, 4 Procedural amendment (method) % formula % 1. Indication of case 1985 Patent Application No. 84018 2. Title of invention Color video monitor with improved color accuracy 3. Relationship Applicant Name Hazeltine Corporation 4, Agent

Claims (3)

[Claims] (1) A color video monitor having a high resolution CRT display, comprising: means for processing an input video signal; means for generating a color concentrated signal; and connected to receive the color concentrated signal;
means for performing vertical deflection and convergence drive functions for said color video monitor; means connected to said vertical deflection means for performing horizontal deflection and dynamic convergence functions for said color video monitor; means connected to a CRT for receiving the color concentration signal, the vertical and horizontal deflection signals, and controlling the display on the CRT, the means for processing the input video signal including a 3-bit digital color code input; A color video monitor comprising digital-to-analog conversion means for converting the signal into a signal representing the desired amplitude components for the primary colors. 2. A color video monitor according to claim 1, wherein said means for processing an input video signal comprises a plurality of feedback loops for maintaining the luminance of each primary color within 10% of a desired value. . (3) said means for processing an input video signal is connected to receive an operator-set luminance signal and provides a white sample output signal to said digital-to-analog converting means to convert the amplitude of the input video signal; white sample level circuit means for setting a black sample level;
black sample level circuit means for supplying the cathode of the RT to maintain the black level voltage of the CRT at a desired voltage; and a black sample level circuit means connected to receive the cathode current sample of the CRT and for blanking the CRT. and cathode stabilization circuit means for providing a cathode stabilization signal to set the bias.
A color video monitor as described in section.