JPH06308900A - Display device - Google Patents

Abstract

PURPOSE:To obtain a high quality video without flicker by discriminating the level of frequencies, switching the scanning frequency to a high frequency if the frequency of the input signal is low and outputting video information in accordance with the frequency. CONSTITUTION:Video signals are sampled in a sampling circuit 1 and stored in a memory 2. Synchronization signals are conunted for their frequency in counters 6 and 7 and a comparator 9 compares the counted frequency with a prescribed frequency A. When the counted frequency is lower than the frequency A, a signal, which selects a circuit to scan an image with N times horizontal and vertical frequencies, is outputted to each of changeover switches 12 to 15. By the signal, a clock is selected which calls for video information from the memory 2 to a video output circuit 17 at a speed corresponding to the N times frequency and the video is displayed. When the frequency of the input signal is higher than the frequency A, the changeover switches are switched to deal with the case. By setting the value of the frequency A to a frequency value which does not generate flicker, a high quality video is always obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for receiving and displaying an input signal in a wide frequency range.

[0002]

2. Description of the Related Art As a known example close to the present invention, Japanese Patent Laid-Open No.
There is a "display control method" in Japanese Patent Laid-Open No. 8-116582. The block diagram is shown in FIG.

According to the present invention, the address supplied together with the data from the display control unit (2) to the image memory (3) is also fetched into the detection unit (4), and the detection unit (4) has fetched it previously. If the scanning area is wider than the existing address, the address is retained in the detection unit (4). Then, when the held maximum address and the address counted by the address counter (6) match, the detection unit (4) outputs a blanking signal and the counter (6) and the deflection signal counter (8) of the CRT (1). ) Is reset to shift to the next beam scanning. By adjusting the retrace line timing of the scanning beam according to the display data amount, the number of beam scannings per unit time is increased and flicker can be reduced as compared with the case of scanning between both ends of the screen. It will be possible.

[0004]

According to the conventional method, it is possible to increase the frequency of the input signal and reduce flicker. However, even if the change amount of the scanning time is at the maximum, the raster over is reduced.
There is a problem that it can be set only within the scanning period.

Therefore, in the present invention, the scanning frequency can be changed to N times the frequency of the original signal.

[0006]

[Means for Solving the Problems] A function of identifying the frequency of a synchronizing signal of an input signal, a function of comparing the frequency with a certain value A or less, and a frequency of A or less, the frequency is multiplied by N. A function to obtain a value, a function to select a deflecting device that can scan at that frequency, a function to obtain the time to read the video information stored in the memory device, and the same to correct the difference between the frequency of the input signal and the screen scanning frequency. A control device having a function of displaying video information N times, a separation device having a function of separating an input signal into a synchronization signal and a video signal, a memory device having a function of sampling a video signal and holding it as video information, A deflection device capable of scanning at a frequency of A or higher and a video device for displaying image information on the screen are provided.

Then, the input signal is separated into an image and a sync signal by a separating device, the video signal is sampled and stored in the memory device, and the control device determines the frequency of the sync signal,
When the frequency is equal to or lower than A, a signal for selecting the deflection circuit corresponding to the frequency multiplied by N is output to the deflection device, and N
The memory read time corresponding to the doubled frequency is obtained, and the video information is read from the memory device according to this time and output to the video device. At this time, the control device outputs the video information for one screen to the video device N times, then reads and outputs the video information for the next screen to correct the difference between the frequency of the input signal and the scanning frequency, and input. Even if the frequency of the signal is low, the image can be displayed at a high scanning frequency.

[0008]

According to the present invention, the high and low frequencies are automatically discriminated inside the display device, and when the frequency of the input signal is low, the scanning frequency is switched to the high frequency, and the high scanning frequency in which the video information is switched. To output and display according to
You can always get high-quality images without flicker.

[0009]

EXAMPLE The configuration is shown below.

An embodiment of the present invention will be described with reference to FIG.

The sampling circuit (1) samples a video signal and converts it into video information.

The memory (2) is composed of a writing unit and a reading unit, and stores and calls video information.

The reference clock (3) is for generating sampling and writing timing to the memory.

The N times circuit (4) is a circuit for generating a clock for calling the video information from the memory to the video output circuit at N times the writing speed when the frequency is multiplied by N times.

The address generation circuit (5) is a circuit for writing video information in the memory and for generating an address of the memory when calling from the memory.

The counter A (6) counts the horizontal synchronizing signal with a clock and converts the frequency of the synchronizing signal into digital data.

The counter B (7) counts the vertical synchronizing signal with a clock and converts the frequency into digital data.

The N times circuit (8) multiplies the frequencies of the horizontal and vertical synchronizing signals by N times.

The comparator (9) compares the frequency of the sync signal with a certain frequency A.

The MPU (10) sets the value of the frequency A,
It controls other circuits.

The counter C (11) counts the horizontal synchronizing signal multiplied by N.

(12) to (15) are switches for switching between the case where the scanning frequency is N times the input signal and the case where it is not changed.

The deflection circuit (16) scans the screen according to the input synchronizing signal.

The video output circuit (17) outputs the input video signal to the screen.

The CRT (18) displays an image.

The operation will be described below.

The video signal is sampled in the sampling circuit (1) and stored in the memory as video information.
The frequency of the synchronizing signal is counted in the counters A and B (6, 7), and its level with the frequency A, which is the comparator (9), is determined. If the frequency is low, the horizontal and vertical frequencies multiplied by N are used. A signal for selecting a circuit for scanning an image is output to each switch. As a result, the clock for calling the video information from the memory (2) to the video output circuit (17) at a speed corresponding to the frequency of N times is selected and display is possible. The address specified at the time of writing and calling the video information in the memory is generated by the address generation circuit (5). In FIG. 1, the count value of the synchronization signal is used as the memory address.

When the frequency of the input signal is higher than A, the changeover switch is changed over to respond.

[0029]

According to the present invention, it is possible to scan at a high frequency which is always higher than a certain value A, and by setting the value of A to a frequency value where flicker does not occur, the eye can always be scanned regardless of the input frequency. It is possible to obtain high-quality images with less fatigue.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional example.

[Explanation of symbols]

In FIG. 1, 1 ... Sampling circuit, 2 ... Memory, 3
... reference clock, 4 ... N multiplication circuit, 5 ... address generation circuit, 6 ... counter A, 7 ... counter B, 8 ... N multiplication circuit,
9 ... Comparator, 10 ... MPU, 11 ... Counter C, 12 to 15 ... Changeover switch, 16 ... Deflection circuit, 17 ... Video output circuit, 18 ... CRT.

Claims (1)

[Claims] 1. A separation device for separating an input signal into a video signal and a sync signal, a memory device for sampling the video signal and storing it as video information, and identifying the frequency of the sync signal. If the frequency is equal to or higher than a certain frequency A, a deflection device suitable for the frequency is selected, image information is read from the memory device in synchronization with the frequency and output to the video device, and if the frequency of the synchronizing signal is equal to or lower than the certain frequency A. , A control device that selects a deflection device corresponding to a frequency B obtained by multiplying the frequency by a certain integer N, and reads image information from the memory device so as to be synchronized with the frequency B, and outputs the video information to the video device, and scanning at a plurality of frequencies is possible. High-definition signal, which is composed of a simple deflection device and a video device that displays an image on the screen based on the input image information, to obtain a high-quality image without flicker. When receiving, select the circuit corresponding to that frequency, and when receiving a low frequency image signal that causes flicker and increases eye fatigue, scan at a frequency N times the frequency of the input signal to obtain the video information. Is read and displayed according to the scanning frequency, and the difference between the frequency of the input signal and the scanning frequency is displayed N times, and the same image is displayed and adjusted.