JPH0127622B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a simple and high-speed still image transmission device for mutually transmitting still images using a general telephone line.

A conventional still image transmission device is shown in FIG. In FIG. 1, 11 is a video camera, 12 is a compression coder/decoder, 13 is a digital memory for storing compressed information, 14 is a clock, 15 is a memory and communication control processor, 16 is a modulator, and 17 is a Demodulator 18 is a display cathode ray tube. The image read out from the camera 11 is A/D converted by a compression coder/decoder 12, and simultaneously converted by, for example, orthogonal transformation using a coder with as high a compression rate as possible, and stored in a memory 15. The digital signal read from the memory 15 passes through the digital modem 16 (for example, 4800 b/s) and reaches the called demodulator 17 via the telephone line. On the receiving side, the information is stored once in the memory 15 by the reverse process of the sending side, and is displayed on the cathode ray tube 18 while being decoded at video speed. This method is slow because it takes 60 to 80 seconds to transmit one field using a 4800 b/s modem for a black and white TV, and nearly 150 seconds for a color image.
The high-speed A/D converter, the high-speed orthogonal transform codec, and the digital modem are all expensive, so even if digital memory becomes cheaper, the entire device is expensive and it is difficult to popularize it among general users. Ta.

The object of the present invention will be described in detail below with respect to a still image transmission device which uses an analog modem and is of a transceiver type for both transmission and reception, without using these expensive devices.

Figure 2 shows an embodiment of the present invention, in which 11 is a camera, 18 is a cathode ray tube, 211 is an A/D converter, which can be as low as 1 Mb/s, and 212 is easily a D/A converter of 2.4 Mb/s. can be realized. The camera 11 is driven by the micro CPU 22, and is assumed to scan one field at a speed that is a fraction of 60 times per second, and the A/D converter is operated at a rate that is a fraction of the normal speed. 23 is the micro CPU
It is ROM. A/
The D-converted 4-bit/dot information is stored in memory 1.
It is written in 3. As a resolution of 1 field 200 x 200, 40000 x 4 = 160k bits is sufficient.
24 is an AM/PM/VSB modem, and the signal read out from the memory at a communication speed of, for example, about 6000 dots/second is D/A converted and sent to a modulator. The modulator modulates this analog signal and sends it to the telephone network control NCU2.
The signal is sent to the telephone network via the hybrid coil No. 5. The NCU 25 controls switching with the telephone (voice communication and connection control are performed by the telephone). At the beginning of transmission, a tonal combination signal is sent out as a flag for sending an image signal, and then the image signal is sent out. On the receiving side, when the NCU receives an image signal flag, the image signal is input to the modem 24 and demodulator, where it is A/D converted at a communication speed of, for example, 6000 dots/second, and written into memory at a low speed. This writing utilizes the horizontal scanning blanking time of the cathode ray tube, and at other moments the cathode ray tube always continues scanning display via the D/A converter. When one field is completed, the device automatically switches to the telephone and starts talking. The time for one field transmission is 200×200/6000≒7 seconds.

A line amplitude and delay equalizer 27 is installed on the demodulator side of the modem, and if the received image is bad, the distortion caused by the telephone line can be corrected as appropriate and the sending side can send it again.

As explained above, in the present invention, an expensive digital modem is replaced with an inexpensive analog high-speed modem, an expensive high-speed A/D converter is replaced with an inexpensive low-speed 4-bit converter, and the image memory, D By switching all the A/A, A/D converters, microcomputers, etc. for transmission and reception, it is possible to significantly reduce costs and achieve high speed.

Since the present invention uses AM/PM/VSB modems, it can transmit high-speed halftone signals, and since everything except the cathode ray tube imaging camera uses transmitting/receiving switching, it is inexpensive, and switching between the telephone and video can be done by pressing a button on the transmitting side. A convenient communication terminal can be constructed with just one piece of paper.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional still image transmission device.
FIG. 2 is a block diagram of one embodiment of the present invention. 11...Camera, 13...Digital memory, 1
8... Braun tube, 211... A/D converter, 2
12...D/A converter, 22...CPU, 23...
ROM, 24...AM/PM/VSB modem, 25...
Telephone network control NCU, 27...amplitude and delay equalizer.

Claims (1)

[Claims] 1. Digital image memory for one image, A/D converter, D/A converter, AM/PM/VSB modem, telephone network control circuit NCU, central processing unit, and imaging. It has a camera and an image display means, and the telephone network control circuit NCU switches each image from the telephone, and when transmitting, the image taken by the imaging camera is A/D converted, stored in the image memory, and then stored in the image memory. /
The image signal is sent from the AM/PM/VSB modem with A conversion, and when receiving it, the signal received by the AM/PM/VSB modem is A/D converted, stored in the image memory, and then D/A converted. A transceiver-type still image displayed on an image display means, and characterized in that the circuit means other than the imaging camera and the image display means are used in common during transmission and reception, and an ordinary telephone is used at other times. Transmission device.