JP3141981B2 - Optical transmission method for image signals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal light transmission system suitable for transmitting an image signal between a signal generator such as a personal computer and an image display device.

[0002]

2. Description of the Related Art In recent years, for transmitting an image signal output from a signal generator such as a personal computer to an image display device, for example, an optical transmission system as shown in FIG. 3 has been frequently used. In this optical transmission system, the image signal output from the signal generator 1 is sequentially transmitted to a metal cable 2, an E / O converter 3, an optical fiber cable 4, an O / E converter 5, and a metal cable 6 in this order. 7. On the other hand, as a conventional transmission method of an image signal, there is a transmission method having a configuration in which an image signal output from the signal generator 1 is directly transmitted to the image display device 7 via the metal cable 2 (6).

Incidentally, one of the differences between the above-described image signal transmission method using a metal cable and the optical transmission method is a large difference in the image display state when a failure occurs.
For example, the disconnection of the metal cable 2 does not cause any special problem in the image display state, but the disconnection of the optical fiber cable 4 has a disadvantage that an unnecessary noise image is displayed on the image display device 7. The reason for this is that in the optical transmission system, an image signal is not input to the O / E converter 5 due to the disconnection of the optical fiber cable 4, so that an abnormally large signal is output from the O / E converter 5 to the image display device 7. That's why.

[0003] In the case of the optical transmission system, the state of the image signal output from the O / E converter 5 and the state of the image display of the image display device 7 will be specifically described in accordance with the fault that occurs.
When a normal image signal is not output from the signal generator 1 due to an abnormality on the signal generator 1 side, the signal output from the O / E converter 5 is not normal, so that scrolling or color shift occurs on the display screen. As a result, the image display state is disturbed. Further, when the connection state between the metal cable 2 on the input side of the E / O converter 3 and the optical fiber cable 4 on the output side is abnormal, for example, when there is no synchronization signal on the synchronization signal line due to incorrect connection, the image display state is disturbed. Had occurred.

On the other hand, when the E / O converter 3 is not operating normally, no image signal is output from the O / E converter 5 or a noise voltage larger than the standard is output. An unnecessary noise image was displayed on the display device 7. When the optical fiber cable 4 is disconnected, a noise voltage higher than the standard is output from the O / E converter 5, so that an unnecessary noise image is displayed on the image display device. Therefore, when an optical image signal is not input to the O / E converter 5, a noise voltage larger than the standard is output from the O / E converter 5, so that an unnecessary noise image is always displayed on the image display device. I was

One of the causes of the display of an unnecessary noise image in the image display state is that an APD (avalanche photodiode) is generally used as a light receiving element in the O / E conversion unit. This is because the E converter is configured to perform the AGC operation by the constant current. Therefore, even when there is no light input to the light receiving element, a constant current flows through the light receiving element, and random noise is amplified by the amplifier and output from the O / E converter, so that an unnecessary noise image is displayed on the image display device. It is because it is done.

[0006]

As described above, in the conventional image signal light transmission system, the image display state of the image display device is disturbed due to the occurrence of various obstacles as described above, or unnecessary noise is generated. There was a problem that an image was displayed. Then, in the state where the optical image signal of the normal light level or the normal synchronization signal is not input to the O / E converter, the image display state is disturbed in any case. Also, in any case where a failure such as an abnormality of the signal generator or incorrect wiring or disconnection of the metal cable has occurred,
Since the output of the O / E converter becomes abnormal, the image display state is disturbed. Therefore, for example, only by means of detecting the presence or absence of a synchronization signal in the O / E converter,
It has been extremely difficult to identify the cause of the failure to eliminate disturbances in the image display state and eliminate unnecessary noise image display phenomena.

The present invention not only can detect the occurrence of these troubles with a simple configuration, but also does not output an abnormal signal from the O / E converter which causes disturbance of the image display state when a trouble occurs. Another object of the present invention is to provide an optical signal transmission method for an image signal which does not cause disturbance in an image display state or display an unnecessary noise image.

[0008]

The <br/> image signal output from the signal generator [Means for Solving the Problems An optical transmission method of an image signal for transmission to the image display device, video signals R, G, respectively for B E / O converter, optical fiber cable, amplifier with switch
Rutotomoni allowed provided the O / E conversion section having a fine output unit,
The O / E converter 9 for the video signal G on which the synchronization signal is superimposed has a synchronization signal separation unit 20 for separating the synchronization signal ,
A frequency divider 22 that pulse-shapes the synchronization signal,
Pulse counter 23 that counts all the period signals, synchronization signal
Signal interval timer 24 that detects only the sync signal only
Pulse counter 25 to count, pulse counter 2
Digital comparator 2 to which 3,25 output data is input
6. Good or bad data is saved as the synchronization signal judgment
The output of the storage element 27 and the synchronization signal interval timer 24
Synchronizing signal determination unit 21 comprising a pulse detection timer 28
The door is provided, wherein upon detecting normal sync signal by the synchronization signal determining unit 21, a switch unit 15 with the amplifier 12 of the O / E converter 9
The rewritable output video signal G from the output unit 18 so turned ON,
O / E switch portions 14 and 16 with amplifier 11 and 13 a video signal from the output portion 17, 19 and ON each R converting section 8 and 10, caused to output B, when detecting an abnormality of the synchronization signal, the amplifier 11,12,13
Is turned off, and the video signals R, G, B outputs of the output units 17, 18, 19 are set to 0 V so that an unnecessary noise image is not displayed on the image display device or the image display state is not disturbed. Controlling and transmitting the image signal.

[0009]

In the optical signal transmission system for an image signal according to the present invention, when the synchronization signal judging unit detects the normality of the synchronization signal, the video signal switching amplifier is turned on to output a normal video signal from the output unit. When an abnormality of the synchronization signal is detected, the output of each video signal is controlled to be 0 V and output from the output unit. Therefore, when a failure occurs, an unnecessary noise image is not displayed or the image display state is not disturbed. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a main part of the present invention, FIG. 2 is a block diagram showing a configuration of a main part of FIG. 1, and FIG. 3 is a block diagram showing a configuration of the present invention. In the figure, 1 is a signal generator, 2 and 6 are metal cables, 3 is an E / O converter, 4
Denotes an optical fiber cable, 5 denotes an O / E converter, and 7 denotes an image display device. 8, 11, and 17 are video signals R, respectively.
, An amplifier and an output unit having a switch unit 14 corresponding to the O / E conversion unit 9, and 12, the video signal G
, An amplifier and an output unit with an O / E conversion unit and a switch unit 15, and 10, 13 and 19 are an amplifier and an output unit with a O / E conversion unit and a switch unit 16 corresponding to the video signal B, respectively. Each is constituted by a known circuit. Reference numerals 20 and 21 denote a synchronizing signal separating unit and a synchronizing signal judging unit, each of which is a known circuit. And switch units 14, 15,
The amplifiers 11, 12, 13 with 16 are turned on, respectively, and normal video signals R,
In addition to outputting G and B respectively, when an abnormality of the synchronization signal is detected, the output of the video signals R, G and B is controlled to be 0V.

An optical transmission system of such an image signal according to the present invention will be described with reference to the drawings. When the synchronization signal is transmitted normally, the image signal output from the signal generator 1 is transmitted to the metal cable 2, the E / O converter 3, the optical fiber cable 4, the O / E converter 5, and the metal cable 6. The data is sequentially transmitted to the image display 7 through the path. In this case, the video signals R (red), B (blue), and G (green) on which the synchronizing signal is superimposed are transmitted to the O / E converter 5 via the optical fiber cable 4, and the O / E converter 5 performs the O / E conversion. The data is E-converted and transmitted to the image display 7, which will be described in more detail with reference to FIG. In the figure, a video signal G (green) output from an O / E converter 9 is supplied to an amplifier 12 with a switch 15.
, And is input to the synchronization signal separation unit 20 to separate the synchronization signal. Then, the separated synchronizing signal is input to the synchronizing signal judging unit 21. When the synchronizing signal judging unit 21 detects the normality of the synchronizing signal, the amplifiers 11, 12, and 13 with the switch units are turned on, respectively, The video signals R, G, and B are controlled to be output from the output units 17, 18, and 19, respectively.

On the other hand, if an optical image signal of a normal light level or a normal synchronizing signal is not input to the O / E converter 9 due to some kind of trouble, the synchronizing signal judging unit 21 makes the noise image unnecessary for the image display device. Is controlled so as not to be displayed or the image display state is not disturbed. That is, the synchronization signal separated by the synchronization signal separation unit 20 is input to the synchronization signal determination unit 21. The synchronization signal determination unit 21 detects an abnormality of the synchronization signal and detects each of the amplifiers with the switch units 14, 15, and 16 In addition to turning off the switches 11, 12, and 13 respectively, the output units 17, 18, and 19 are controlled so that the respective outputs become 0V. As a result, an unnecessary image signal is not transmitted to the image display device 7, and a display phenomenon of an unnecessary noise image and a disorder of an image display state, which have conventionally occurred, do not occur.

The detection of whether the synchronizing signal is normal or abnormal is performed in the synchronizing signal judging section 21 comprising a known circuit whose specific configuration is shown in FIG. 2 as follows. . First, the synchronization signal separated by the synchronization signal separation unit 20 is pulse-shaped by the frequency divider 22. Next, the pulse-shaped synchronization signal is input to a pulse counter 23 for counting all the pulses and a synchronization signal interval timer 24.
The synchronization signal interval timer 24 detects only the synchronization signal, and inputs the output of the timer 24 to a pulse counter 25 that counts only the synchronization signal. Then, the output data of the pulse counters 23 and 25 is
When the data of the counters 23 and 25 match, good data is stored in the storage element 27 as the synchronization signal determination, and when the data of the counters 23 and 25 does not match, the data is determined as the synchronization signal determination. The data is stored in the storage element 27.

The storage element 27 stores new data each time the value of the counter 25 reaches a predetermined value.
When the synchronization signal is stopped, the output of the synchronization signal interval timer 24 is input by the pulse detection timer 28 to store the storage element 2.
7 is configured to store the data of the negative as the synchronization signal determination. As described above, the two data of the pulse counters 23 and 25 are sequentially input to the digital comparator 26 every predetermined number of pulses, and the pass / fail data is stored in the storage element 27 as the synchronization signal determination.

By providing a switch 29 in the synchronizing signal judging section 21 separately from the counters 23, 25, etc., good data for judging the synchronizing signal can be stored regardless of the input to the frequency divider 22. It is also possible to save to.

[0016]

According to the optical signal transmission system for image signals according to the present invention, even if there is no input of an optical image signal of a normal light level or a normal synchronization signal to the O / E converter, simple means is used. It is possible to configure so that an abnormal signal is not output from the O / E converter to the image display device. As a result, the image display state is not affected by various failures such as an abnormality of the signal generator, erroneous wiring of the metal cable, an abnormality of the E / O converter, disconnection of the power supply, loss increase in the optical fiber cable, and disconnection state. Disturbance and unnecessary noise images are not displayed on the image display device, and it is possible to provide an optical signal transmission system of an image signal with excellent image quality. The practical effect is large.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main configuration of the present invention.

FIG. 2 is a block diagram showing a main configuration of FIG.

FIG. 3 is an explanatory diagram showing a configuration of the present invention.

[Explanation of symbols]

 Reference Signs List 1 signal generator 2, 6 metal cable 3 E / O converter 4 optical fiber cable 5 O / E converter 7 image display device 8, 9, 10 O / E converter 11, 12, 13 amplifier 14, 15, 16 Switch section 17, 18, 19 Output section 20 Synchronization signal separation section 21 Synchronization signal determination section 22 Frequency divider 23, 25 Pulse counter 24 Synchronization signal interval timer 26 Digital comparator 27 Storage element 28 Pulse detection timer 29 Switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/00 H04N 9/64 H04N 11/00

Claims (1)

(57) [Claims] 1. An optical signal transmission system for transmitting an image signal output from a signal generator to an image display device, comprising: an E / O conversion unit and an optical fiber for video signals R, G, and B, respectively. O / O with cable, amplifier with switch and output
Allowed provided the E converter Rutotomoni, a synchronous signal separator 20 for separating a synchronizing signal to the O / E converter 9 for the video signal G obtained by superimposing the synchronizing signal, divide the pulse shaping the separated synchronizing signal 22, a pulse cow that counts all pulse-shaped synchronization signals
Counter 23, a synchronizing signal interval timer 24 for detecting only the synchronizing signal, a pulse counter 25 for counting only the synchronizing signal , a digital signal to which the output data of the pulse counters 23 and 25 are inputted.
The data comparator 26 stores good or bad data as the synchronization signal judgment.
Detects the pulse to which the output of the storage element 27 and the synchronization signal interval timer 24 is input
A synchronization signal determining unit 21 consisting of the timer 28. provided, upon detecting normal sync signal by the synchronization signal determining unit 21,
O / E switch section 15 with the amplifier 12 of the converter 9 is ON The rewritable output video signal G from the output unit 18, O / E conversion section
8,10 switches 14 and 16 amp 11 and 13 a video signal from ON to output 17 and 19 respectively R of allowed output B, when detecting an abnormality of the synchronization signal, the amplifier 11, 12 and 13 OF
In the F state, the video signals R, G, and B outputs of the output units 17, 18, and 19 are set to 0 V so that an unnecessary noise image is displayed on the image display device and the image display state is not disturbed. An optical signal transmission method for transmitting an image signal.