JPH01129688A - Picture signal receiver - Google Patents

Abstract

PURPOSE:To prevent flickering of a video image and disturbance of it by reading a data just before the stop repetitively so as to stop the video image at the video image just before the reception of a mixed signal. CONSTITUTION:A reception level detection circuit 10 is provided to a signal reception section and when transmission signals of two stations are received in mixture, that is, a received power is lower than a received power threshold value, a squelch circuit 14 squelches a reproduced data and an extracted clock to be OFF to stop data write in a memory circuit 17 having a capacity by one frame of picture data installed at the post-stage of the squelch circuit 14. Then the data given to the memory circuit 17 is read repetitively just before the squelch circuit 14 is operated and when the received power is over the threshold value, the data inputted to the memory 17 is read at any time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an optical space system in which a single receiving station mounted on a mobile body receives the same image signal from two or more spatially separated transmitting stations. The present invention relates to an image signal receiving device in a transmission communication system.

[Conventional technology]

FIG. 3 is a diagram showing a conventional image signal receiving device l),
fn, +21 are two transmitting stations A that are spatially separated.

and transmitting station B, +31 is the transmitted image signal A of the transmitter A (1), and +41 is the transmitted image signal B of the transmitter B (2).
, +51 is the received signal regeneration circuit 9 (61 is the received signal regeneration circuit (61 is the received signal regeneration circuit (
(7) is the extracted clock which is the output signal of the received signal regeneration circuit +51, f8 is the reproduced data which is the output signal of 5I,
) is the reproduced data +61 and the extracted clock (7)
(9) is a mobile body equipped with an image signal receiving device; A is a mobile body +91
is the direction of movement. FIG. 4 is a timing chart of the reproduction data (6) and the extraction clock (71).

Next, the operation will be explained. While the received signal reproducing circuit (5 bows) and the moving body (91) are moving, the section from To to T2 in FIG. 4 receives only the transmitted signal A (31) of the transmitter A (11).

The interval from T2 to T3 is the transmission signal A f of the transmitter A(1)
31 and transmitter B (receives the mixed signal of the transmitted signal 13 of 21 and F41.

The period from T3 to T5 is the transmission signal B i of transmitter B (2)
41, and sends out the reproduced data +61 of FIG. 4 1al and the extracted clock (7) of FIG. 4 1al to the image processing system 181 in the entire interval.

[Problem that the invention seeks to solve]

Since the conventional image signal receiving apparatus is configured as described above, in the section from T2 to T3 in FIG.

In order for the receiver to receive the mixed signal, the reproduced data (6) and the extraction clock (71) sent to the image processing system 9 are disturbed as shown in Figure 4, and there is a problem that the processed image may flicker or be distorted. Ta.

This invention has been made to solve the above-mentioned problems, and aims to provide an apparatus in which flickering or disturbance does not occur in the processed video during the reception period from To to T5° in FIG. 4.

[Means for solving problems]

The image signal receiving device according to the present invention adds a reception level detection circuit to the signal receiving section, and takes advantage of the fact that the total reception power decreases when the transmission signals of two stations are mixed and received, and the reception power is When the received power falls below the threshold, the squelch circuit turns off the reproduced data and the extracted clock.
It squelches, stops writing data to a memory circuit with a capacity for one frame of image data installed after the squelch circuit, and repeatedly reads out the booter input to the memory just before the squelch circuit operates.

(If the received power exceeds a threshold value, the data input to the memory is read out at any time.

[Effect]

In this invention, even if the receiver receives the mixed signal in the interval from T2 to T3 in FIG. 4, the image stops at the image immediately before the start of receiving the mixed signal during that time, eliminating flickering and disturbance.

〔Example〕

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

In FIG. 1, (1) to (9) are the same as in FIG. aO is the threshold PO at which the reception level of the reception signal is constant.
A reception level detection circuit (11) is a reception level detection circuit that sends out a detection signal when the signal becomes lower than .
σ2 is a data frame detection circuit that outputs a pulse synchronized with one frame of image data from the reproduction data (61).

03 is a data frame synchronization signal output from the data frame detection circuit 11z, and Oa is the reproduction data (
61, The extracted clock f''ke is a squelch circuit that squelches OFF in synchronization with the data frame from the reception level drop detection signal flll and the data frame synchronization signal 0, flip-flop (14a) * logical product 0 is a reproduced data squelch output signal outputted from the squelch circuit a4, ae is an extracted clock squelch output signal outputted from the squelch circuit +14, and aD is the reproduced data output signal. The squelch output signal a is read from the above-mentioned extracted lock squelch output signal, aS is the playback data memory output read from the above-mentioned one frame memory (171), and r19 is for reading the sound output from the playback data memory. The built-in clock is a clock oscillator that generates the built-in clock.

FIG. 2 shows operating waveforms of each part in FIG. 1.

The operation will be explained below. When the mobile body (81) is moving, if the maximum value f pmax of the received signal powers A and B during the period T2 to T3 during which the mobile body (81) receives a mixed signal of the transmitted signal A(3) and the transmitted signal B f41, the mobile body receives Since the received signal power draws a curve as shown in Figure 2, the threshold value "eP"
Reception level detection circuit CIo set as o (≧Pmax)
The received level drop detection signal is as shown in (110).

In addition, the reproduced data f61 has a transmission signal A +31 of (1o
6).

When the transmission signal B T41 has a timing as shown in (104), the data is disturbed from T2 to T3 as shown in (106), and the clock is disturbed from T2 to T3 as shown in (107). In the squelch circuit +141, the data frame detection circuit riZ detects a reception level drop detection signal (11
1) Using the klJ timing signal, reproduce the playback data (6
By squelching 1 and extraction clock (71), the reproduced data squelch output signal 051 synchronized with the frame becomes (
The extracted clock squelch output signal ae synchronized with the frame is output as shown in (N6). Data input to the 1-frame memory (L71) is performed from To to T1, and then restarts from T4 to T5. During the period from T1 to T4, a certain frame that was last input to the 1-frame memory αη at time T1 is One frame memory is read out repeatedly by the built-in oscillator output (119). This situation is shown in i ([8). At this time, the output of the image processing system is the transmission signal A T31 from TO to T1.
From T1 to T4, the final frame image of T1 is fixed, and from T4 to T5, the transmitted signal B (
41 signals will be output.

〔Effect of the invention〕

As described above, according to the present invention, even if a mixed signal is received from two or more stations, signal reception for that period is stopped, and the data immediately before the stop is repeatedly read out, so that the image changes to the image immediately before the mixed signal is received. Since the screen is configured to stop at a certain point, it has the effect of eliminating flickering and disturbances in the image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image signal receiving device according to an embodiment of the present invention, FIG. 2 is an operation waveform diagram of each part of FIG. 1, and FIG.
The figure is a block diagram of a conventional image signal receiving device, and FIG. 4 is an operation waveform diagram of each part of FIG. The squelch circuit, tiη is a one-frame memory, and ■ is a clock oscillator. In FIG. 9, the same or corresponding parts are indicated by the same reference numerals.

Claims (1)

[Claims] An optical reception signal regeneration circuit that outputs reproduced data and an extracted clock in an optical space transmission communication system in which a single reception station mounted on a mobile body receives the same image signal from two or more spatially separated transmission stations. an optical reception level detection circuit that sends out a squelch signal when the optical reception level drops below a certain threshold P_o; and a data frame detection circuit that detects a data frame synchronization signal from the reproduced data output from the optical reception signal regeneration circuit. data from the extracted clock output from the optical reception signal regeneration circuit, the reproduced data, the frame synchronization signal output from the data frame detection circuit, and the reception signal squelch signal output from the optical reception level detection circuit. The reception level synchronized with the frame is the threshold P_
a squelch circuit that prohibits the transmission of reproduced data and extracted clocks when the output voltage drops below o; a memory having a capacity for one image frame and into which the reproduced data is input in accordance with the output of the squelch circuit; and an optical receiver. an oscillator that generates a read clock that writes reproduced data to the memory when the signal is cut off and repeatedly reads the stored data from the memory after the optical reception signal is cut off until the optical reception signal is input again;
An image signal receiving device comprising an image processing system that performs image processing from output data of the memory circuit.