JPH0798571A - Horizontal synchronizing frequency measuring method, crt display method, synchronizing frequency measuring device and crt display device - Google Patents

Abstract

PURPOSE:To accurately measure a horizontal synchronizing frequency independently of existence of serration. CONSTITUTION:An AND gate 13 obstructs passage of a horizontal synchronizing signal 100 during a vertical synchronizing signal 200. Output of the AND gate 13 is counted by a counter 11 over one period of the vertical synchronizing signal except this period, and a horizontal synchronizing frequency fh is calculated with the number of output, a vertical synchronizing pulse width W outputted from a vertical synchronizing pulse width calculator 17 and a vertical synchronizing frequency fv outputted from a vertical synchronizing frequency calculator 15 by a horizontal synchronizing frequency calculator 15. Therefore, since serration is outputted during a vertical synchronizing pulse, by cutting off this period and measuring a frequency, a frequency can be accurately measured independently of existence of serration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal synchronizing frequency measuring method for image signals, a CRT display displaying method, a synchronizing frequency measuring apparatus, and a CRT display apparatus,
In particular, the present invention relates to a horizontal synchronizing frequency measuring method, a CRT display displaying method, a synchronizing frequency measuring device, and a CRT display device which are suitable for measuring the horizontal synchronizing frequencies of various image signals output from a workstation or the like.

[0002]

2. Description of the Related Art In a CRT display device, in order to reproduce an image which is geometrically the same as that on the image sending side on a cathode ray tube (hereinafter referred to as CRT), a separation scan on the image sending side and an assembly scan on the image receiving side are performed. Must be an exact match. This is called synchronization. In order to achieve synchronization, a switching signal having the same frequency as the scanning frequency is created on the image transmitting side, and this signal is used to control the scanning start point of the image pickup tube and the CRT. That is, the start point of vertical and horizontal scanning of the screen to be sent on the image sending side is controlled by adding the above switching signal to the video signal. Such switching signals are referred to as a horizontal synchronizing signal and a vertical synchronizing signal, respectively (see NHK color television textbook, published by NHK Publishing Co., P.9 to P.10, and P.24 to P.25).

An image signal from a transmission source of various standards such as a workstation is correctly CR according to the standard.
In order to display at T, it is necessary to first detect the frequencies of the vertical and horizontal synchronizing signals of the image signal. FIG. 2 is a block diagram of a conventional frequency measuring circuit 1 for that purpose, which comprises a horizontal synchronizing frequency measuring counter 11, a vertical synchronizing frequency measuring counter 12, a horizontal synchronizing frequency calculator 140, and a vertical synchronizing frequency calculator 15. A method of measuring the vertical and horizontal sync frequencies will be described with reference to this drawing.

Horizontal sync signal 100 and vertical sync signal 20
0 is input together with the image signal from the transmitting side. The horizontal sync frequency measuring counter 12 is a reference clock 300 obtained from an oscillator provided in the CRT display device.
From the one rising edge of the horizontal synchronizing signal 100 to the rising edge of the next horizontal synchronizing signal 100 (or from the falling edge to the next falling edge). The count value is N
When h0 and the frequency of the reference clock 300 are M, the horizontal synchronizing frequency calculator 14 calculates the horizontal synchronizing frequency fh according to the following equation:

[Formula 1] fh = M / Nh0

The same applies to the measurement of the vertical synchronizing frequency. When the reference clock is counted by the vertical synchronizing frequency counter 12 over one cycle of the vertical synchronizing signal 200, and the count value is Nv, the vertical synchronizing frequency calculator 15 uses the following equation. Thus the vertical sync frequency fv is calculated:

[Formula 2] fv = M / Nv

In the above conventional technique, the frequency M of the reference clock is set to a frequency sufficiently higher than the horizontal synchronizing frequency fh, whereby the accuracy of measuring the horizontal synchronizing frequency can be improved.

The technique described above is a general method for measuring the frequency of the synchronizing signal. However, as it is, for example, in the case of a cassette type VTR, jitter (small fluctuation of pulse position) or pulse is added to the horizontal synchronizing signal. If a dropout or the like occurs, the obtained sync signal becomes unstable, which adversely affects the image receiving side circuit. As a conventional example for solving this, as shown in, for example, Japanese Patent Laid-Open No. 1-2232393, when the frequency of the horizontal synchronizing signal measured as described above differs from a certain frequency f0 by a certain value β or less, The frequency of the horizontal synchronizing signal is fixed to the frequency f0 for stabilization.

[0008]

As described above, the vertical and horizontal synchronizing signals are output together with the image signal from the image transmitting side in order to synchronize the image signals, but when the vertical synchronizing signal is output, The image signal corresponds to the blanking period, and there is no image signal during this period, so no horizontal synchronizing signal is required. However, a pulse called serration may be inserted in order to stabilize the horizontal synchronization on the image receiving side. This is also called a "cutting pulse", and is a small amplitude pulse having the same period as the horizontal synchronizing signal transmitted while being superimposed on the vertical synchronizing signal during the vertical synchronizing period. This serration may or may not be used depending on the model of the workstation or the like. And it's not easy to tell the presence of serrations automatically.

Therefore, in the conventional frequency measuring circuit described with reference to FIG. 2, when there is no serration, there is no horizontal synchronizing pulse while a vertical synchronizing pulse is included.
The count value of the counter 11 is smaller than that when there is serration, and there is a problem that the measured value of the horizontal synchronizing frequency differs depending on the presence or absence of serration. This problem cannot be solved even by using the technique of the above-mentioned Japanese Patent Laid-Open No. 1-223393, because the difference in the count value due to the presence or absence of serration is usually much larger than the above-mentioned constant value β. Further, since the frequency of the horizontal synchronizing signal is also measured by counting the reference clocks, it is necessary to maintain the measurement accuracy by increasing the frequency of the reference clock as the horizontal synchronizing frequency becomes higher. However, for that purpose, there is a problem that the circuit becomes complicated and the cost becomes high.

An object of the present invention is to provide a horizontal sync frequency measuring method and a CRT display displaying method which can accurately measure the horizontal sync frequency regardless of the presence or absence of serration and the level of the horizontal sync frequency and can always display an image signal well.
A synchronous frequency measuring device and a CRT display device are provided.

The above object is to provide a counting means for counting the number of horizontal synchronizing pulses included in one period of the vertical synchronizing signal, excluding the period during which the vertical synchronizing pulse is input, and the vertical synchronizing pulse. A pulse width measuring means for measuring the pulse width is provided, and the frequency of the horizontal synchronizing signal is calculated from the count value of the counting means, the measured value of the pulse width measuring means and the cycle of the vertical synchronizing signal. And a horizontal synchronizing frequency measuring means for measuring a horizontal synchronizing frequency and a vertical synchronizing frequency using the horizontal synchronizing frequency measuring method, and a horizontal synchronizing frequency measured by the means. This is accomplished by displaying the input image signal on the CRT with the vertical sync frequency.

[0012]

Since the horizontal sync pulses are not counted during the vertical sync pulse, stable horizontal sync frequency can be measured regardless of the presence or absence of serration. Moreover, since the horizontal synchronizing frequency is measured by counting the horizontal synchronizing pulses, the circuit becomes simple without the need for a high-speed reference clock as in the past. Further, if the above method is used for synchronization, the display performance of the CRT display device is improved and stabilized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an outline of a frequency measuring circuit, which is a feature of the present invention. The horizontal synchronizing frequency measuring counter 11, the vertical synchronizing frequency measuring counter 12, the horizontal synchronizing frequency calculator 14, and the vertical synchronizing frequency calculator 15 are shown. In addition, an AND gate 13, a vertical sync pulse width measurement counter 16, and a vertical sync pulse width calculator 17 are provided.

FIG. 3 is a timing chart of the input signal of the circuit of FIG. 1, and FIG. 4 is a flow chart showing the operation of the circuit. The operation of the embodiment shown in FIG. 1 will be described below with reference to these figures. First, the vertical sync signal 2
00 is input to the vertical synchronization frequency measurement counter 12 and the AND gate 13. Vertical sync frequency measurement counter 1
2 counts the reference clock 300 from the falling edge of the vertical synchronizing signal 200 to the next falling edge (step 400).
~ 402). This count value Nv is input to the vertical synchronizing frequency calculator 15, and the calculator 15 calculates the vertical synchronizing frequency fv according to (Equation 2) (step 403, where M is the frequency of the reference clock 300). This is the same operation as in the case of FIG. 2 of the conventional example.

On the other hand, the vertical sync pulse width counter 16 counts the number of reference pulses 300 during the vertical sync signal 300 is at the LOW level (retrace period) (steps 404-4).
05), the vertical synchronization pulse width calculator 1 from this count value Nw
7 calculates the pulse width W of the vertical synchronizing signal according to (Equation 3):

[Equation 3] W = Nw / M

Next, the horizontal synchronizing signal 100 is input to the AND gate 13. In the AND gate 13, the vertical synchronizing signal 200 is at the LOW level, that is, the vertical synchronizing signal 200.
When the sync pulse is input, the horizontal sync signal 100 is cut off. Therefore, the signal pulse of the horizontal sync signal 100 is blocked by the AND gate 13 even if the horizontal sync signal 100 is input while the sync pulse of the vertical sync signal 200 is being input due to the serration, and the vertical sync signal is blocked. It is output only while 200 sync pulses are not input. And the horizontal sync frequency measurement counter 11
Does not count the reference clock as in the conventional example, but counts the number of horizontal synchronizing pulses passing through the AND gate 13 over one cycle of the vertical synchronizing signal 200 (steps 407 to 409). This count value Nh is input to the horizontal synchronizing frequency calculator 14, and this value and the calculator 1
Using the 7-output pulse width W and the vertical synchronizing frequency fv obtained by the calculator 15, the horizontal synchronizing frequency fh is calculated according to (Equation 4):

## EQU4 ## fh = Nh / ((1 / fv) -W)

According to this embodiment, since the horizontal synchronizing frequency measuring counter 11 does not count while the synchronizing pulse of the vertical synchronizing signal 200 is being input, the horizontal synchronizing frequency is accurately measured regardless of the presence or absence of serration. Can be measured.
Further, the horizontal synchronizing frequency is not obtained from the number of reference clocks included in one period of the horizontal synchronizing signal as in the conventional case, but the time width ((1 / fv ) -W), the reference clock is used only for measuring the vertical synchronizing frequency and the blanking period width W, since it is obtained by counting how many horizontal synchronizing pulses are included in this, and this does not require a particularly high frequency. . Therefore, the circuit can be simplified.

FIG. 5 shows a C using the frequency measuring circuit of FIG.
FIG. 1 is a diagram showing a schematic configuration of an RT display device, showing a frequency measuring circuit 1, a preset memory 2, a horizontal deflection circuit 3, a vertical deflection circuit 4, a signal amplification circuit 5, and a multi-scan CR.
Made of T6. In the figure, the frequency measuring circuit 1 measures the horizontal synchronizing frequency fh and the vertical synchronizing frequency fv, and outputs the measurement results to the preset memory 2. The preset memory 2 has a plurality of group data # as shown in FIG.
G1, # G2, ... Are stored as preset data. Each group data is represented by group #G ₁ in FIG. 6 as a representative, horizontal and vertical synchronization frequencies fh1, fv1, and display control data related thereto, a screen width D1,
Screen height H1, horizontal screen position Px1, vertical screen position Py
1, including pincushion distortion correction value C1 and the like. If fh1 and fv1 are set as addresses, presetting of fh1 and fv1 is unnecessary. These multiple groups are the CRT
Is a multi-scan type, and the horizontal and vertical synchronizing frequencies are made variable, and the associated display control data is made corresponding to each variable. Then, the preset horizontal sync frequency that matches the horizontal and vertical sync frequencies input from the frequency measurement circuit 1, the vertical sync frequency, and related display control data are read and output to the horizontal deflection circuit 3 and the vertical deflection circuit 4. To be done. The horizontal deflection circuit 3 and the vertical deflection circuit 4 change the horizontal deflection frequency, the vertical deflection frequency, etc. in accordance with the input from the preset memory 2 and display an appropriate screen on the CRT 6. On the other hand, the video signal 400 is amplified by the video signal amplifier circuit 5, and C
Output to RT6.

As described above, regardless of the presence or absence of serration, if the horizontal synchronizing frequency and the vertical synchronizing frequency are the same, the screen display is controlled by the preset data corresponding thereto, and an appropriate screen can be displayed.

[0020]

According to the present invention, the horizontal synchronizing signal can be accurately measured and a stable image can be displayed regardless of the presence or absence of serration and without the need for a counter having a clock with a particularly high frequency. effective.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a frequency measuring circuit that is a feature of the present invention.

FIG. 2 is a diagram showing a conventional frequency measuring circuit.

FIG. 3 is a time chart showing an example of an input signal of the circuit of FIG.

FIG. 4 is a flowchart showing the operation of the circuit of FIG.

5 is a schematic view of a CRT display device including the frequency measurement circuit of FIG.

FIG. 6 is an explanatory diagram of a preset memory of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frequency measuring circuit 11 Horizontal synchronizing frequency measuring counter 12 Vertical synchronizing frequency measuring counter 13 AND gate 14 Horizontal synchronizing frequency calculator 15 Vertical synchronizing frequency calculator 16 Vertical synchronizing pulse width measuring counter 17 Vertical synchronizing pulse width calculator 100 Horizontal synchronizing signal 200 Vertical sync signal 300 Reference clock

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H04N 17/04 K (72) Inventor Kikuo Tomita 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Factory Omika Plant (72) Inventor Kenkichi Yamashita 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Omika Factory

Claims (10)

[Claims] 1. The number of horizontal synchronizing pulses included in one period of a vertical synchronizing signal is counted excluding the period in which the vertical synchronizing pulse is input, and the pulse width of the vertical synchronizing pulse is measured to determine the number. A horizontal synchronizing frequency measuring method, wherein a frequency of the horizontal synchronizing signal is calculated from a count value, the pulse width measurement value, and a cycle of the vertical synchronizing signal. 2. A CRT display display for displaying an input video signal by performing CRT display control at the frequency of the horizontal synchronizing signal calculated by the measuring method of claim 1 and the frequency of the vertical synchronizing signal calculated from the vertical synchronizing signal. Method. 3. A counting means 11 for counting the number of horizontal synchronizing pulses included in one period of the vertical synchronizing signal excluding a period in which the vertical synchronizing pulse is input, and a pulse width of the vertical synchronizing pulse. Pulse width measuring means 17 for measuring the vertical synchronizing signal, a first calculating means for calculating the vertical synchronizing frequency from the vertical synchronizing signal, a count value of the counting means, a measured value of the pulse width measuring means and the vertical synchronizing signal. And a second calculating means for calculating the frequency of the horizontal synchronizing signal from the frequency of the synchronizing frequency measuring device. 4. The counting means prevents the horizontal sync signal from passing through when the vertical sync pulse is input, and the horizontal sync pulse output from the gate means is one rising edge of the vertical sync signal. Or fall)
4. The synchronous frequency measuring device according to claim 3, comprising a first counter for counting from one to the next rising (or falling). 5. The pulse width measuring means includes a reference clock generating means, a second counter for counting the number of reference pulses output from the means from the start time to the end time of the vertical synchronizing pulse, and 4. The synchronous frequency measuring device according to claim 3, wherein the synchronous frequency measuring device comprises a first calculating means for calculating the count value of the counter output and the frequency of the reference pulse. 6. The first calculating means calculates the reference clock generating means and the number of reference clocks output from the means, from the rising edge (or the falling edge) of the vertical synchronizing signal.
To a next rising edge (or a falling edge), and a second calculating means for calculating from the count value of the counter and the frequency of the reference pulse. The synchronous frequency measuring device according to claim 3. 7. A CRT is horizontally and vertically controlled according to a horizontal synchronizing frequency and a vertical synchronizing frequency measured by using the synchronizing frequency measuring device according to claim 3, and an input image signal is C
A CRT display device adapted to display on an RT screen. 8. The synchronous frequency measuring device according to claim 2,
The horizontal and vertical sync frequencies for multi-scan and the display control data related thereto are set as one group for multi-scan, and the data of a plurality of groups are matched with the preset memory and the horizontal and vertical sync signals measured by the sync frequency measuring device. Means for reading out group data of horizontal and vertical synchronizing frequencies from a preset memory, and horizontal and vertical deflection using the horizontal and vertical synchronizing frequencies and related display control data to display an input video signal on a CRT.
A CRT display device comprising a display control means for performing on a screen. 9. The CRT display device according to claim 8, wherein the related display control data includes a screen width, a screen height, a horizontal screen position, a vertical screen position, and a pincushion distortion correction value. 10. A horizontal synchronizing frequency measuring method for measuring the frequency of a horizontal synchronizing signal at a timing not affected by the presence or absence of serration.