JPH0258090A - Method and device for controlling display screen position of crt display - Google Patents

Abstract

PURPOSE:To hold an invariably constant display screen position by detecting the time from a horizontal synchronizing signal to a video signal, storing the minimum time, and varying the delay time of the horizontal synchronizing signal in a horizontal position control circuit according to the stored value. CONSTITUTION:The horizontal synchronizing signal HS and video signal VS are inputted to a time measuring circuit 6 and the time between both signals HS and VS is measured. his measured time C is compared 7 with the initially set time T in a minimum time register 8 and shorter time is written in the register 8. Similarly, time C measured by the circuit 6 is compared 7 with the output minimum time D written in the register 8. Then the output minimum time D in the register 8 and the standard time A from the horizontal signal HS to the signal VS which is stored in a storage circuit 9 are inputted to a subtracter 10, which outputs the time difference (D-A). The signal value of this output (D-A) is D/A-converted 11 and sent to a horizontal position controller 3 to hold the constant display screen position even for a signal which is different in the time from the signal HS to the signal VS.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects the time from a horizontal synchronization signal to a video signal, stores the minimum time, and adjusts the delay time of the horizontal synchronization signal according to the value. The present invention relates to a method and apparatus for controlling the display screen position of a CRT display, which maintains a constant display screen position even for signals having different times from a horizontal synchronizing signal to a video signal by changing .

[Conventional technology and its issues]

FIG. 4 is a block diagram showing an example of a conventional horizontal screen position control circuit for a CRT display.

Reference numeral 1 denotes a video amplifier, which amplifies the video signal VS so that the video can be displayed at an appropriate level on the CRT display. 2 is an automatic frequency control circuit (AFC), which outputs a horizontal deflection output while comparing the manual input of the horizontal synchronizing signal Hs with the final horizontal deflection output (comparison signal) of the horizontal deflection circuit 4; This circuit outputs a continuous free-running frequency in response to a sudden change in Hs, and prevents outputting a signal that changes suddenly to the horizontal deflection circuit 4.

3 is a horizontal position control circuit which appropriately delays the output from the automatic frequency control circuit 2 and adjusts the screen position to the normal position. Reference numeral 4 denotes a horizontal deflection circuit which inputs a horizontal position control output, causes a deflection current to flow through the horizontal deflection coil 5, outputs a signal for scanning the screen, and outputs a comparison signal to the automatic frequency control circuit 2.

Figure 2 (al is a diagram explaining the timing relationship between the horizontal synchronization signal Hs and the video signal Vs, T is the horizontal period, S is the width of the horizontal synchronization signal, and B is the bank pouch (horizontal synchronization signal HsO
(time from the trailing edge to the start of the video signal Vs), ■ represents the video display time, F represents the front porch (the time from the end of the video display time to the start of the horizontal synchronization signal), and there is a relationship of T=B+V+F+S.

Conventionally, the time of the input video signal was fixed, and the delay time of the horizontal position control circuit 3 was adjusted for one type of value so that the screen was centered. If a video signal Vs with the same horizontal period T but different horizontal timings such as back porch B, video display time ■, front porch F, and horizontal synchronization signal width S is input, the screen position will shift, and if the difference is large, the screen There are issues such as getting back on track.

[Means to solve the problem]

In order to solve the above problems, the method of the present invention detects the time C from the horizontal circumference 31Jl signal Hs to the video signal Vs as shown in the first diagram, stores the minimum time, and determines the horizontal position according to the value. By changing the delay time of the horizontal synchronizing signal Hs in the control circuit 3, a constant display screen position can be maintained even for signals having different times from the horizontal synchronizing signal Hs to the video signal VS.

In order to solve the same problem, the device of the present invention has a time measuring circuit 6 that measures the time from the horizontal synchronizing signal Hs to the video signal Vs, as shown in the first diagram, and a minimum time register 8 that stores the initial setting time and the minimum time. A comparator 7 compares the output of this register 8 with the output C of the time measurement circuit 6, outputs the smaller time and writes it into the minimum time register 8, and a A memory circuit 9 in which the standard time A of
A subtracter 10 inputs the output A and the output of the minimum time register 8 and outputs the time difference D-A, and converts the digital value of the output D-A of this subtractor 810 into an analog value and sends it to the horizontal position control circuit 3. The configuration consists of a D/A converter 11 for output.

[For production]

The horizontal synchronizing signal Hs and the video signal Vs are input to a time measuring circuit 6, and the time between both signals Hs and Vs is measured. The measured time C and the initial setting time T of the minimum time register 8 are compared by the comparator 7, and the smaller time is outputted and written into the minimum time register 8. Thereafter, the minimum time written in this register 8 and the time C measured by the time measuring circuit 6 are compared by the comparator 7 and processed in the same way.

The output (minimum time) D of the minimum time register 8.

The standard time A from the horizontal synchronizing signal Hs to the video signal Vs stored in the storage circuit 9 is input to a subtracter 10, which outputs the time difference D-A.

The digital value of this output D-A is the D/A converter 11
is converted into an analog value and output to the horizontal position control circuit 3, and the delay time of the horizontal synchronization signal Hs of the horizontal position control circuit 3 is changed to convert the horizontal synchronization signal Hs to the video signal V.
It operates to maintain a constant display screen position even for signals with different times up to s.

〔Example〕

The present invention will be described in detail below based on the drawings.

FIG. 1 is a block diagram showing the configuration of an example of a device for implementing the method of the present invention, in which a video amplifier 1, an automatic frequency control circuit 2. Horizontal position control circuit 3 Horizontal deflection circuit 4. The horizontal deflection coil 5 and the CRT display perform exactly the same functions as the conventional device shown in FIG. However, the horizontal position control circuit 3 is equipped with an external control input terminal, and the delay time can be changed by external control input.

6 is the first video signal Vs from the rise of the horizontal synchronization signal Hs
This is a circuit that measures the time C until the rise of FBL for each scan. For example, when the horizontal synchronizing signal Hs and the video signal Vs shown in FIG. 2(a) are input, the time A is When input to the signal, the time of Al (>A) is measured. This circuit 6 is a flipflop circuit 6 that is set by inputting the horizontal synchronizing signal Hs and reset by inputting the video signal Vs.
a, an AND gate circuit 6b which inputs the output of this circuit 6a and a gate pulse, and a counter 6c which is set manually by the gate circuit 6b and reset by the input of the video signal Vs.

8 is a minimum time register that stores the initial setting time T and the minimum time; first, the period T (maximum time) of the horizontal synchronizing signal Hs shown in FIG. 2 (bl) is set as the initial setting time T; The minimum value of the time from the rise of Hs to the rise of the video signal Vs is held.

7 is the output of this register 8 and the output C of the time measurement circuit 6
The subtracter 7a receives the output of the register 8 and the output C of the time measurement circuit 6 as inputs, and outputs the smaller time and writes it into the minimum time register 8. It consists of a positive/negative determining circuit 7b which inputs -C and determines whether it is positive or negative, and an AND gate circuit 7c which receives the output of this circuit 7b and the output C of the time measuring circuit 6 and supplies its output to the register 8.

Reference numeral 9 denotes a memory circuit in which the standard time A from the rise of the horizontal synchronizing signal Hs to the rise of the video signal Vs is written, and in this embodiment, a read-only ROM is used.

10 is a subtracter which inputs the output (standard time) A of this memory circuit 9 and the output of the minimum time register 8 and outputs the time difference D-A, and the D/A converter 11 inputs the output (standard time) A of the memory circuit 9 and the output of the minimum time register 8 and outputs the time difference D-A.
A is converted from a digital value to an analog value, and the output thereof is inputted to the external control input terminal of the horizontal position control circuit 3 as an external control input.

The operation of the above configuration will be explained in detail.

In the device shown in FIG. 1, with the control input terminal of the horizontal position control circuit 3 disconnected, the timing input shown in FIG. A and adjust so that the screen is in the normal position.

The minimum time register 8 first sets the maximum horizontal circumference MT, and the standard time A is written in the storage circuit 9.

As shown in FIG. The time C until the rise is measured, and if the value C is the smallest among the values measured up to that point, that value is held; otherwise, that value is discarded.

The horizontal position control circuit 3 controls when the output of the D/A converter 11 is OVO, in other words, the measured time value C=A (FIG. 2(a)
reference). When the output of the minimum time register 8 is D=T (initial setting time), the output of the comparator 7 becomes DC=TA, the output of the minimum time register 8 becomes A, and the output of the subtractor 10 becomes D.
The delay time of the horizontal synchronizing signal Hs is set so that when -A=O and the output of the D/A converter 11 is OV, the screen is positioned normally.

Therefore, the output of the D/A converter 11 is the output of the subtracter 10, that is, the minimum value D(
The voltage is the difference between the minimum time value A (output of the minimum time register 8) and the standard time value A (the output of the memory circuit 9), and operates to increase the delay time in proportion to this output.

FIG. 2(a) shows the timing of the standard video signal VS. When this is input as the first scan, the CRT screen to which the device of the present invention has been added becomes as shown in FIG. 3(a). (The shaded area indicates the bright line).

Now, Fig. 2 (bl, (d), (f)) shows the horizontal synchronization signal H.
This shows an example of the timing of the video signal Vs with respect to s, and considers a case where the bright lines are input as the first scan, second scan, and third scan, respectively, and all bright lines are displayed in black from the fourth scan to the nth scan.

When the horizontal synchronizing signal Hs and the video signal Vs are manually inputted to the time measuring circuit 6 at the timing shown in FIG.
Al (T>Al), the output of the minimum time register 8 becomes A1, and the output of the subtracter 10 becomes AI-A.

The D/A converter outputs an analog output voltage corresponding to Al-A, and the horizontal position control circuit 3 manually inputs this analog output voltage to the control input terminal to appropriately delay the horizontal synchronization signal to obtain the FC signal shown in FIG. ) horizontal synchronization signal H at the timing shown.
s and the video signal Vs are operated to be equivalent to when they are input to the time measurement circuit 6.

Next, when the horizontal synchronization signal Hs and the video signal Vs are input to the time measurement circuit 6 at the timing shown in FIG. It will be done. Therefore, the output of the D/A converter 11 becomes an analog output voltage equivalent to At-A, and the delay of the horizontal synchronization signal Hs by the horizontal position control circuit 3 remains unchanged and becomes the same as the timing shown in FIG. 2(b). Equivalently, it operates as if the horizontal synchronizing signal Hs and the video signal Vs were input to the time measuring circuit 6 at the timing shown in FIG. 2(e).

Next, as the third scan, when the horizontal synchronizing signal H3 and the video signal VS are input to the time measuring circuit 6 at the timing shown in FIG. 2(f), the measured time C is A3<AI.
3 is held in the minimum time register 8, and the output of the D/A converter 11 becomes an analog output voltage equivalent to A3-A.
It operates as if the horizontal synchronization signal Hs and the video signal Vs were input to the time measuring circuit 6 at the timing shown in FIG. 2(g) due to the change in the horizontal synchronization delay time.

From the next 4th scan to the nth scan, the video signal is at black level, so the output of the D/A converter 11 is maintained at an analog output equivalent to A3A, and then again from the 1st scan to the nth scan. Even if scanning is repeated, since A3 is the minimum value, there is no change in the analog output and this value is maintained. Therefore, the timings shown in FIGS. 2(b) and 2(d) will also be scanned with a delay time of A3-A after the second scan.

FIG. 3 Fdl is a screen obtained when the first scan to the nth scan are scanned two or more times. Figure 3(C) shows the first scan and the second scan.
This is the screen immediately after scanning. Figure 3 (bl is a CRT without a normal display screen position control circuit); Figure 2 (bl, (d),
When inputting the video signal Vs at the timing of ffl,
The last bright spot of the first scan is not displayed.

Normal video signals are T, S, B, and A in FIG. 2(a).

The values of V and F are determined in advance, and the screen position of the CRT is determined according to the values. However, by adding the device of the present invention, if the values of T and ■ are equal, or the values of T are equal and the value of v is small, and the value of A is greater than A and less than or equal to T, any value of the image can be obtained. Even signals can be displayed on the CR7 screen without interruption.

The video signals in Figure 2 (bl, (d), (r) are A
This is an example where the value of is set to A3. But in this case,
In order to capture the minimum value of A in Figure 2 (a), it must be 1
In the case of a normal display, a bright spot on the leftmost side is required, but this is not a problem because the cursor display always appears on the leftmost side in the first display.

〔Effect of the invention〕

As described above, according to the present invention, the time C from the horizontal synchronizing signal H5 to the video signal Vs is detected, the minimum time is stored, and the horizontal synchronizing signal Hs in the horizontal position control circuit 3 is controlled according to the detected value. C configured to maintain a constant display screen position even for signals with different times from the horizontal synchronizing signal Hs to the video signal Vl by changing the delay time.
This is a method and device for controlling the display screen position of an RT display, and has a function of detecting the time C from the horizontal synchronization signal Hs to the video signal Vs and automatically correcting the screen position, so that the horizontal period T is the same and the back porch B video display time V,
Even if video signals Vs of different horizontal timings are inputted to the front porch F and the horizontal synchronization signal width S, the screen position does not shift and there is no fear that the screen turns back.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an example of a device for carrying out the method of the present invention, FIGS. 2(a) to (g) are diagrams for explaining its operation, and FIGS. 4 is a block diagram showing the configuration of an example of a horizontal screen position control circuit of a conventional CRT display. 1...Video amplifier, 2...Auto frequency Control circuit, 3...Horizontal position control circuit, 4...
...Horizontal deflection circuit, 5...Horizontal deflection coil,
6...Time measurement circuit, 7...Comparator,
8: Minimum time register, 9: Memory circuit, 10: Subtractor, 11: Old D/A converter. Answer 3 Drama (α) (b)

Claims (2)

[Claims] (1) In a circuit that controls the horizontal screen position of a CRT display, the time C from the horizontal synchronizing signal Hs to the video signal Vs is detected, the minimum time is memorized, and the horizontal position control circuit 3 is controlled according to the value. A display screen position control method for a CRT display configured to maintain a constant display screen position even for signals with different times from the horizontal synchronizing signal Hs to the video signal Vs by changing the delay time of the horizontal synchronizing signal Hs . (2) In a circuit that controls the horizontal screen position of a CRT display, a time measurement circuit 6 that measures the time from the horizontal synchronization signal Hs to the video signal Vs, and a minimum time register 8 that stores the initial setting time and the minimum time; A comparator 7 compares the output D of this register 8 and the output C of the time measurement circuit 6, outputs the smaller time and writes it into the minimum time register 8, and a standard from the horizontal synchronization signal Hs to the video signal Vs. A memory circuit 9 in which time A is written, a subtracter 10 that inputs the output A of this memory circuit 9 and the output D of the minimum time register 8 and outputs the time difference D-A, and the output D of this subtracter 10. - D/A converter 1 that converts the digital value of A into an analog value and outputs it to the horizontal position control circuit 3
1. A display screen position control device for a CRT display.