JP2548819B2 - Image transmitter / receiver - Google Patents

Description

The present invention relates to an image transmitting / receiving apparatus for transmitting image data using a low-speed and narrow-band transmission line such as a general telephone line and a wireless communication line. .

"Prior art" Image transmission / reception devices such as videophone devices that transmit images using a low-speed, narrow-band transmission line such as a general telephone line, after low-speed conversion (modulation) of a data signal by a modem, It is sent to the transmission line.

Modulation methods include frequency shift keying (FSK), phase shift keying (PSK), and amplitude phase keying (AM-PM / QAM).

All of these are modulation / demodulation methods for the purpose of coded transmission, but in order to transmit a large amount of data such as image data, instead of allowing redundancy of data at the time of reception like amplitude / phase modulation, The method of increasing the transmission speed is adopted.

In the method using such redundancy of received data,
Regarding the relationship between the transmission data and the image information, generally, as shown in FIG. 9, pixel data of each pixel arranged in the scanning direction (horizontal direction) of the display device is sequentially transmitted as it is.

[Problems to be Solved by the Invention] In this method, since all image information is transmitted, there is a drawback that transmission time is long.

Further, in this method, one signal having transmission data corresponds to one of the image information in a 1: 1 ratio. Therefore, if the transmission signal is affected by the line conditions, for example, if noise is mixed, this noise will be a few pixels or Since it is superimposed on the information data of more pixels, the influence of noise propagates in the horizontal scanning direction as it is. As a result, the influence of the transmission signal directly affects the image, which deteriorates the image quality.

Therefore, the present invention solves such a problem and proposes an image transmitting / receiving apparatus in which both the transmission speed and the image quality are improved.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention, an image composed of pixel lines of a plurality of lines is adjacent to the image information of the odd-numbered line of the image on the transmission side. The image information of the even-numbered lines is read alternately while forming a zigzag pattern in the line direction, and is read while thinning out a predetermined number of pixels to convert the image information into one line of image information, and each pixel in the converted image information. At the receiving side, which transmits two or more predetermined cycles for one pixel according to the frequency to which information is assigned for each gradation, and the receiving side that receives this transmission signal has pixels for the remaining cycles other than those used as the original pixel information. The information is used as interpolation pixel information of pixels thinned out in the pixel row of the other line in which at least the original pixel does not exist. Is.

[Operation] On the transmitting side, the image information of the adjacent odd-numbered line and the image information of the even-numbered line are alternately read in a zigzag pattern in the line direction, and a predetermined number of pixels are read out to read one line. Convert to image information.

For example, when picking up odd-numbered pixel information on an odd line, even-numbered pixel information is picked up on an even line. Then, the image information is transmitted after data is thinned out on both the odd line and the even line.

In the modem, frequencies are assigned to each pixel information for each gradation. That is, multi-frequency modulation is performed.

Then, the assigned frequency is transmitted for one pixel information in two or more predetermined cycles, for example, two cycles.

On the receiving side, the pixel information represented by one cycle of the received signal is used as the original image information, and the pixel information represented by the remaining cycles is used at least by the original pixel. It is used as interpolation image information for one image line. Then, for example, when the transmission signal is affected by noise, the influence is dispersed to both one image scanning line and the other image scanning line read in the zigzag pattern, so that the influence on the image quality can be reduced.

As a result, in image data transmission carried out by a general telephone line, it is possible to shorten the transmission time and prevent deterioration of image quality (image quality).

[Example] Next, a case where an example of an image transmitting / receiving apparatus according to the present invention is applied to a videophone apparatus will be described in detail with reference to the drawings. For convenience of description, the image transmission / reception mode will be described first.

As shown in FIG. 5, when the horizontal scanning direction is X, the vertical scanning direction is Y, and the pixels are indicated by circles, the image information actually transmitted is the image information of the pixels indicated by the diagonal lines.

That is, for example, in the odd line, the image information of the odd-numbered pixel is picked up and transmitted, and in the even line, the image information of the even-numbered pixel is picked up and transmitted.

At that time, image information is purely picked up in the order shown by the arrow in the horizontal scanning direction. Therefore,
Image information of two lines, an odd line and an even line, is sequentially read in zigzag in the horizontal scanning direction, that is, while being alternately thinned, and converted into image information of one line.

Then, one image data is modulated by the modem 106 to a frequency corresponding to the gradation.

For example, image data is represented by 6 bits and 64 gradations,
2000-2400 as a band used for multi-frequency modulation of image data
When the frequency band of Hz is used, 1st step (1st gradation) ... 2000Hz 2nd step (2nd gradation) ... 2005Hz 3rd step (3rd gradation) ... 2010Hz Step (65th gradation) ... Allocate frequencies at equal intervals, such as 2400 Hz (see FIG. 7).

Then, one image data (one pixel) is addressed several cycles, in this example, two cycles in succession. Therefore, the transmission data indicating one image data is 2
Since it is transmitted continuously, the transmission data is, for example, as shown in FIG. 8A.

When such transmission data is transmitted, it becomes as shown in FIG. 8B, which is decoded and converted into image data having gradation.

At that time, as in the case of transmission, the odd-numbered received image data is demodulated and used as the odd-numbered image data of the odd-numbered line, and is also used as the odd-numbered image data of the even-numbered line. This is shown in FIG.

However, of the signals transmitted in two cycles, for example, when the transmission signal of the first half cycle is used as the odd-numbered image data of the odd line, the transmission signal of the latter half cycle is used as the even-numbered image data of the even line. To be done.

That is, the transmission signal of the latter half cycle is used as an interpolation signal of even lines.

Here, as shown in FIG. 8B, the period of the received data does not completely match that of the transmitted data. This is because the reception frequency of the received data fluctuates slightly due to mutual interference of the received data.

Therefore, for example, the data value A is not demodulated as the data value A in every two cycles, but is demodulated as the data value A ′ that has undergone some level fluctuation.

In other words, this data value A'is as if the data value A
A data value that can be approximated to the data value interpolated by the adjacent data value B is obtained. This data value A'is used as interpolation image data.

Therefore, when the interpolated image data is arranged two-dimensionally, it becomes as shown in FIG.

According to this, since the influence of the transmission signal is dispersed in the vertical scanning direction, the influence of noise etc. can be reduced,
The image quality is improved accordingly.

FIG. 1 is a system diagram showing an example of an image transmitting / receiving apparatus capable of realizing such transmission processing.

This example is an example of transmission using an analog line, and image data is an example of frequency division multiplexing in the band of 2000 to 2400 Hz as described above.

In the figure, 100A and 100B are transmission / reception sets as terminal devices connected to an analog line (general telephone line) 200.

 The transmission / reception set 100A is configured as follows.

103 is an image memory. A video signal from the video camera 101 is converted into a digital signal of, for example, one sample of 6 bits by the A / D converter 102 and supplied to the image memory 103, and image data for one screen is written.

The image data read from the image memory 103 is D
Monitor TV that has been converted to analog signals by the A / A converter 104 1
Supplied in 05.

Reference numeral 106 is a modem which constitutes a multi-frequency modulation / demodulation means. This modem 106 is configured, for example, as shown in FIG.

In the figure, reference numeral 106a denotes a modulation counter. 6-bit image data indicating 64 steps (gradations) is supplied from the image memory 103 to the counter 106a. The counter 106a counts down from a predetermined value corresponding to the image data. Then, the counter 106a outputs a square wave signal for two cycles having a cycle corresponding to the value (step) of the image data.

In other words, the period of the square wave corresponding to each step is given an equal time difference.

In this case, the cycle corresponding to the first step is 1/2000 Hz,
The cycle corresponding to the 64th step is set to 1/2400 Hz.

The square wave signal is converted into an analog signal by the D / A converter 106b, and this is supplied to the low pass filter 106c, and a sine wave signal corresponding to the modulation frequency is extracted and output.

Also, 106d is a waveform shaping circuit.
A transmission signal supplied from the transmitting side via the analog line 200, that is, a voice band signal is supplied to 106d.

As will be described later, this voice band signal is a sine wave signal obtained by passing the above-mentioned square wave signal through the band pass filter 107 having a pass band of 2000 to 2400 Hz.

In the waveform shaping circuit 106d, the original square wave signal is reproduced from the zero cross point of the sine wave signal.

Then, the square wave signal from the waveform shaping circuit 106d is supplied to the demodulation counter 106e. As described above, the square wave signal has a period corresponding to the value (step) of the image data.

In the demodulation counter 106e, the counting operation is performed in each one cycle period of the square wave signal, and the cycle of each one cycle of the square wave signal is calculated from the count value. And
From the demodulation counter 106e, the value of 6 corresponding to the cycle is displayed.
Bit image data is output, and this 6-bit image data is supplied to the image memory 103.

Returning to FIG. 1, the square wave signal output from the modulation counter 106a of the modem 106 is passed through the band pass filter 107 having a pass band of 2000 to 2400 Hz, and the two-wire to four-wire conversion unit 108.
Is supplied as a voice band signal (transmitted data, see FIG. 8A).

The audio signal from the handset 109 is supplied to the conversion unit 108 via a band elimination filter 110 for removing a band of 2000 to 2400 Hz.

The conversion unit 108 is configured, for example, as shown in FIG.

In the figure, reference numeral 108a denotes a synthesizing circuit.
In 108a, the voice band signal from the band pass filter 107 and the band limited voice signal from the band elimination filter 110 are combined to form a transmission signal. This transmission signal is the fourth
As shown in the drawing, the audio band signal and the audio signal are frequency division multiplexed.

The transmission signal from the combining circuit 108a is the hybrid circuit 108b.
And is supplied to the analog line 200 via the line transformer 108c.

The transmission signal supplied from the transmission side via the analog line 200 is supplied to the buffers 108d and 108e via the line transformer 108c and the hybrid circuit 108b.

Returning to FIG. 1, the transmission signal from the buffer 108d of the conversion unit 108 is supplied to a band-pass filter 107 to extract an audio band signal, and this audio band signal is supplied to a modem 106. Then, as described above, the image data is demodulated from the audio band signal and supplied to the image memory 103.

Further, the transmission signal from the buffer 108e of the conversion unit 108 is supplied to the band elimination filter 110 to extract a voice signal, and the voice signal is supplied to the handset 109.

Although the transmission / reception set 100A is configured as described above, the transmission / reception set 100B is configured similarly to the transmission / reception set 100A.

In the above configuration, an operation in the case where the transmission / reception set 100A is the transmission side and the transmission / reception set 100B is the reception side will be described.

First, the transmission operation in transmission / reception set 100A will be described.

The video signal from the video camera 101 is converted by the A / D converter 102 into 6
Image memory 10 after being converted to digital signals of bits
3 and stored in the image memory 103 for one screen, for example,
Image data of 256 × 240 dots is written.

Then, 6-bit image data of each dot is sequentially read out from the image memory 103 and supplied to the modem 106. From the modem 106, a 2-cycle square wave signal having a cycle corresponding to the value (step) of the image data. Is output.

The square wave signal output from the modem 106 is converted into a sine wave signal in a frequency band of 2000 to 2400 Hz,
Is supplied to.

The audio signal output from the handset 109 is supplied to the conversion unit 108 after the components in the frequency band of 2000 to 2400 Hz are removed by the band removal filter 110.

Then, the conversion unit 108 performs frequency division multiplexing of the audio band signal and the audio signal to form a transmission signal, and this transmission signal is supplied to the analog line 200 and transmitted and received by the transmission / reception set
Be transmitted to.

 Next, the operation of the transmission / reception set 100B will be described.

The transmission signal transmitted from the transmission / reception set 100A via the analog line 200 is supplied to the band elimination filter 110 via the conversion unit 108, and the voice signal extracted by the band elimination filter 110 is supplied to the handset 109. The sound of the sound signal is output.

In this case, the band-elimination filter 110 removes the voice band signal of 2000 to 2400 Hz, so that the handset 109 does not output an unpleasant sound due to the voice band signal.

A transmission signal transmitted from the transmission / reception set 100A via the analog line 200 is supplied to a band-pass filter 107 via a conversion unit 108, and a voice band signal extracted by the band-pass filter 107 is supplied to a modem 106. Is done.

Then, the modem 106 demodulates 6-bit image data from the audio band signal. In this case, the bandpass filter 107 removes audio signals outside the frequency band of 2000 to 2400 Hz, so that the modem 106 does not malfunction due to the audio signals.

The 6-bit image data demodulated by the modem 106 is supplied to and written in the image memory 103.

6-bit image data of each dot is sequentially read from the image memory 103, converted into an analog signal by the D / A converter 104, and then supplied to the monitor television 105 to display an image based on the image data.

According to this structure, the voice band signal obtained by multi-frequency modulating the image data and the band-controlled voice signal are frequency-division-multiplexed and transmitted, so that the image data and the voice signal can be transmitted at the same time.

Moreover, since the voice band signal is formed by multi-frequency modulation of image data, the baud rate of data transmission can be increased and the transmission time of the image can be significantly shortened.

That is, the frequency band used for the voice band signal is 2000
The baud rate when using ~ 2400Hz is as follows on average.

Baud rate = 2200 x 6 = 13200bps Therefore, if the luminance signal has 64 gradations and the still image data is 256 x 240 dots, the capacity is 256 x 240 x 8 bits, so the transmission time is 256 x 240 x. 8 ÷ 13200 = 37 seconds. In other words, compared to telewriting using FSK of 300 baud, one image can be transmitted in about 1/40 time (assuming that the image is sent even with the telewriting standard).

It should be noted that in the above-described embodiment, the image data is shown to be 6 bits, but an image having an arbitrary number of bits can be similarly configured. Further, the frequency band used for the voice band signal is 2000 to 2400 Hz, but the frequency and range are not limited to this.

Further, in the above-described embodiment, two sets of transmission / reception sets are shown. However, those in which more transmission / reception sets are provided can be similarly configured.

Further, in the above-mentioned embodiment, the transmission using the analog line is shown, but the invention can be similarly applied to a system in which the image data and the audio signal are simultaneously transmitted by another transmission medium.

For example, it can be applied to a system that handles image data and audio signals, such as an amateur band wireless communication, a home appliance and a remote control transmitter, a home security information system using a power line (100 V), and the like. it can.

[Advantages of the Invention] As described above, according to the present invention, it is possible to shorten the time required for transmission at the time of image transmission and to perform efficient image transmission while preventing image quality deterioration due to the reduction of the amount of transmitted information.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of an image transmitting / receiving apparatus according to the present invention, FIG. 2 is a system diagram of a modem, FIG. 3 is a configuration diagram of a 2-line to 4-line conversion unit, and FIG. 4 is a signal configuration diagram. 5, FIG. 5 is a diagram showing an arrangement example of transmission image data, FIG. 6 is a diagram showing an arrangement example of reception image data, FIGS. 7 and 8 are explanatory views of multi-frequency modulation, and FIG. 9 is a conventional transmission. It is a figure which shows the example of arrangement | sequence of image data. 100A, 100B …… Transmit / receive set 101 …… Video camera 102 …… A / D converter 103 …… Image memory 104 …… D / A converter 105 …… Monitor TV 106 …… Modem 107 …… Band pass filter 108… … 2-wire to 4-wire converter 109 …… Handset 110 …… Band elimination filter

Claims (1)

(57) [Claims] 1. For an image composed of a plurality of lines of pixel rows, on the transmission side, the image information of the odd-numbered line and the image information of the even-numbered line adjacent to the image are zigzag-shaped in the line direction. Alternately and while thinning out a predetermined number of pixels, the pixels are read out and converted into image information of one line, and the pixel information in the converted image information is assigned to each gradation by a frequency of 2 or more predetermined periods for one pixel. On the receiving side, which transmits the minutes and receives this transmission signal,
The remaining period of pixel information other than that used as the original pixel information in the received signal is used as the interpolated pixel information of the pixels thinned out in the pixel row of the other line in which at least the original pixel does not exist. An image transmission / reception device characterized by the above.