JPH02145082A - Still video transmitter - Google Patents

Abstract

PURPOSE:To display a signal on a CRT and to sent it by a facsimile equipment by providing two line memories, using the one for confirming a picture on the CRT and using the other for facsimile transmission and using only one AD converter so as to change over a switch. CONSTITUTION:A clamp circuit 9 clamps a video signal to a constant DC level and an A/D converter 10 of the next stage converts the signal into a digital correctly. One of outputs of the A/D converter 10 is read by a line memory 11 for a CRT. Moreover, after the result is read with a slight time delay, the original analog video signal is decoded by a D/A converter of the next stage and the output is connected to the CRT. The other output from the A/D converter 10 is written in other line memory 13 for facsimile transmission by using a clock A. Then a low frequency clock C is used and the signal is read by a D/A converter 14 for facsimile transmission in a prescribed timing and outputting to a telephone set and sent to a receiver.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an electronic camera system that displays a playback signal from a video floppy on a CRT and utilizes a telephone line, etc. This invention relates to a still video transmitter for transmitting a reproduced video signal to a telegraph machine.

[Prior Art] Traditionally, in the field of news reporting, telephone lines and the like have been used to transmit photographs to remote locations such as branch offices using transmitters and receivers.

This F! The electrotransmitter develops film taken with a silver halide camera, prints it onto photographic paper, and stretches it to create a silver halide photograph, which is then wrapped around the drum of the electrotransmitter.A similar drum is also installed on the receiving side, and these photos are connected to each other. It was designed to transmit signals electrically one by one by rotating and scanning in synchronization.

[Problem to be solved by the invention]

However, in this type of conventional electric transmission system, it takes time to check the actual picture after taking a photo, and equipment such as a darkroom is required, and the electric transmitter is large and difficult to move. Because of the difficulty, the completed photographs had to be carried all the way to a certain place where the electric transmitter was installed, and time was wasted, which was a very big problem in the field of news reporting where time was of the essence. This was developed in consideration of various problems, and it is possible to immediately check the photos taken at the scene of the interview, and immediately send the necessary screen images from the scene to a conventional receiver using a telephone line or radio. That is.

[Means to solve problems]

For this purpose, the present invention provides two line memories,
One is for checking pictures on a CRT, and the other is for electrical transmission, and only one wire is needed for inputting to these line memories.
The above objective was achieved by switching the switch with two AD converters.

[For production]

Uses only one A/D converter that consumes a lot of power,
I decided to switch to the two line memories,
Normally, line memory for CRT display is used, so there is no time axis variation, and field/frame conversion is also performed, so reproduced images can be viewed on the CRT without jitter or skew distortion.

Since the switch is changed only before the data for electronic transmission is taken in, the image signal of the CRT screen is not affected in terms of image quality.

〔Example〕

FIG. 1 shows an embodiment of the present invention.
The preamplifier 3 reproduces the RF signal, the switch 4 switches the output of the head, and the demodulation circuit 5 reproduces the video signal.

6 is a line signal exchange circuit that replaces the signal of the line currently being transmitted with a video signal as a constant level signal and shows on the CRT which line is actually being transmitted, and 7 is a T correction circuit. be.

Here, T correction will be explained with reference to the conceptual diagram shown in Figure 2. In general, normal video signals are created on the premise that they will be interpreted on a CRT, and the gradation expression on this CRT is linear (γ =1) but about r-2.2, this is corrected in advance and the signal is processed so that γ=0.45. Therefore, by passing a normal video signal through this T circuit 7, it is possible to make a small signal into a linear gradation for electrical transmission.

Switch 8 switches to the γ circuit side only when transmitting electricity. 9
is a clamp circuit that fixes the video signal to a constant DC level, and the next AD converter 10 correctly converts it into a digital signal. One of the outputs of the AD converter 10 is CR
After being read into the T line memory 11 and read out with a slight time delay, the original analog video signal is restored by the next DA converter, and this output is sent to the CRT.
connected to. Here, the clock A for reading into the AD converter 10 and the line memory 11 is created by separating the synchronization signal from the playback video signal and multiplying it by a PLL circuit (not shown), and includes the playback time axis fluctuation. On the other hand, as the clock B for reading from the line memory 11 and the clock B to the DA converter 12, a clock that is created using a crystal or the like and has no time fluctuation is used.

The other one of the outputs from the AD converter 10 is written to yet another line memory 13 for transmission using the aforementioned clock A, and in order to drop the video signal into the telephone line band, a low frequency clock C is used to write the video signal to a predetermined value. The signal is read out to the DA converter 14 for the next electric transmission at the timing of . The output from the DA converter 14 is output to a telephone line after passing through an AM or FM modulation circuit (not shown), and this signal is sent to a conventional receiver.

〔Effect of the invention〕

As described above, according to the present invention, a high-speed AD with large power consumption
Despite using only one converter,
By using two line memories and instantaneously changing a switch, it is possible to display on a CRT and also to transmit electronically. Furthermore, since a line memory for CR1 display is normally used, there is no time axis variation, and field/frame conversion is also performed, so that reproduced images without jitter or skew distortion can be clearly seen on a CRT. In addition, since the switch is changed only at the moment when data for transmission is to be taken in and the γ-converted signal is taken into the line memory for transmission, other lines are not disturbed when the transmission signal is taken in, and therefore the C
The RT screen is not disturbed, and since a transmission line is normally displayed on the CRT screen, even if the γ-converted signal is displayed on the CRT, it is instantaneous and hardly noticeable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a still video transmitter according to the present invention, and FIG. 2 is an explanatory diagram of one circuit. [Explanation of symbols of main parts] 6... Line signal conversion circuit 7... 1 circuit 8... Changeover switch 10... AD converter 11.13.・・・・・・Line memory

Claims (1)

[Claims] An AD converter that has a circuit that processes video signals and displays them on a CRT, and a circuit that outputs them to a telephone line, etc., and that selects one of these circuits, and an AD converter that converts the output signal from the switch into AD. and a still video transmitter, characterized in that it is equipped with two types of line memories, one for CRT display and one for electrical transmission, for storing the output from the AD converter.