JPS6118283A - Automatic level correcting device of analog picture signal - Google Patents

Abstract

PURPOSE:To attain sufficient correction even in real time by using a data of a gray scale signal level detected when an artifitial satellite passes the zenith so as to update a data of the gray scale signal level at the preceding reception. CONSTITUTION:When the artifitial satellite starts coming to the visual field of an earth station and a radio wave is caught by an antenna 1, an input signal (b) is generated and after the signal is received and processed by a receiver 2, the result is demodulated by an AM demodulator 3, from which a base band signal (a) is obtained. The signal (a) is inputted to an A/D converter 4 and also to a synchronous detector 5, where the line synchronization is executed by using a line synchronizing signal detected by the line synchronizing signal. When the line synchronizing signal is detected, a CPU6 fetches a picture data outputted from the converter 4 based on the line synchronizing signal. Then the picture data is corrected by using a gray scale data stored in a gray scale data storage memory area 7, and the corrected picture data is stored in a picture data storage memory area 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to level correction of an image signal transmitted from an artificial satellite using an analog transmission method.

[Prior art]

The image signal obtained by the observation by the artificial satellite is the orbiting satellite N0A.
A P T (AutomaticP
1Cture Transmission) signal, it may be transmitted using an analog transmission method. When this type of transmission method is used, a grayscale signal is inserted in addition to the image signal. For example, when receiving an image by a facsimile recorder, an image as shown in Figure 1 is obtained, and the image is compared with the grayscale signal. The infrared temperature (when using an infrared screen) or albedo (when using a visible screen) was estimated. In FIG. 1, A is an image, B is a synchronous display, and C is a gray scale.

However, in the method described above, although it is possible to perform correction after image reception is completed, it is difficult to perform actual processing, and in the case of a polar orbit satellite such as N0AA, it is difficult to perform correction at the beginning of reception. Because the input signal level is small and a good signal-to-noise level ratio cannot be obtained, a good gray scale cannot be obtained, and even if real-time processing is performed, the correction will be insufficient or the Correction can only be made after a certain amount of time has elapsed, that is, until a good signal-to-noise level ratio is obtained, resulting in a problem that the acquired image area becomes smaller.

[Summary of the invention]

The present invention has been made in view of these points, and its object is to provide an analog image signal automatic level correction device that can perform sufficient correction even in real time.

In order to achieve such an object, the present invention stores the grayscale signal level of an image received when the signal-to-noise level ratio was good the last time it was received, and uses the grayscale signal level to determine the reception level. This system corrects the level of the image signal.

[Example] The present invention will be explained using FIG. 2. In Figure 2, 1
is an antenna that captures radio waves from an artificial satellite, 2 is a receiver that receives and processes signals from antenna 1, and 3 is receiver 2
4 is an analog/digital converter that converts the baseband signal a from an analog signal to a digital signal; 5 is a synchronization detector for detecting a synchronization signal; 21 means for storing data of the currently received image signal level; 22;
means for correcting the currently received image signal level data;
23 is means for storing the data of the gray scale signal level at the time of the previous reception; 24 is the means for updating the data of the gray scale signal level at the time of the previous light emitting; 25 is the data of the gray scale signal level when the artificial satellite passes the zenith. It is a means of detecting.

Next, the operation of the present invention configured as described above will be explained. When the artificial satellite begins to enter the field of view of the ground station and radio waves are received by the antenna 1, the baseband signal a1, that is, the image signal, is extracted from the AM demodulator 3 via the receiver 2.

This image signal is converted into a digital signal by an analog/digital converter 4, and becomes data at an image signal level and data at a gray scale signal level. A synchronization detector 5 detects a synchronization signal from this image signal. The means 21 takes in image signal level data (hereinafter referred to as "image data") output from the analog/digital converter 4 in response to this synchronization signal, and the means 22 takes in data at the image signal level output from the analog/digital converter 4. The image data taken into the means 21 is corrected by the grayscale signal level data (hereinafter referred to as "grayscale data") stored in the means 23 after passing through the image processing apparatus 24. When the zenith time determined by the orbit calculation is reached, the means 25 reads gray scale data from the analog/digital converter 4.

The read data is output to the means 24, and the means 24
updates the grayscale data of means 23 with this data.

Next, the present invention will be explained in detail based on examples.

FIG. 3 shows an embodiment of the analog image signal automatic level correction device according to the present invention, and FIG. 4 shows the flow of its signal processing. In FIG. 3, 6 is a CPU that performs level correction of image signals, 7 is a grayscale data storage memory area that stores grayscale signal level data, and 8 is a grayscale data storage area stored in the grayscale data storage memory area 7. An image data storage memory area stores image signal level data corrected by signal level data, 9 is a time signal generator that generates a zenith time signal, and 10 is a system bus.

Next, the operation of the analog image signal automatic level correction device configured as described above will be explained with reference to FIGS. 3 and 4.

As shown in FIG. 4, in step 11, the orbit of the satellite to be received is first calculated, and the time when the satellite passes the zenith, that is, the reception level is the highest and the best signal-to-noise level ratio is determined. Find the resulting time.

When step 11 is completed, the apparatus advances to step 12 and enters a state of waiting for an input signal. When the artificial satellite begins to enter the field of view of the ground station and radio waves containing signals such as images are captured by the antenna 1 shown in FIG. 3, an input signal is generated and the apparatus proceeds to step 13. This input signal a is received and processed by the receiver 2, and then demodulated by the AM demodulator 3 to become a baseband signal a. This baseband signal a is an image signal, and this image signal is sent to the analog/digital converter 4.
It is also input to the synchronization detector 5. Line synchronization is performed by the line synchronization signal detected from the image signal by the synchronization detector 5. If the line synchronization signal is detected in step 13, the apparatus proceeds to step 15. Based on this line synchronization signal, CPU6
In step 15, the analog/digital converter 4
In step 16, the image data is corrected using the grayscale data stored in the grayscale data storage memory area 7, and in step 17, the corrected image data is transferred to the image data storage memory area 8. Store in. Note that when the radio waves from the artificial satellite are received for the first time, the initial values are stored in the gray scale data storage memory area 7, so accurate correction is not performed. Under normal circumstances, this device will
Step 18 returns to step 13, and real-time correction of the image is repeated. When the time elapses and the zenith time calculated earlier is reached, the time signal generator 9 generates the zenith time signal, and the device proceeds from step 18 to step 19, where the CPU reads the gray scale data and stores its value. is stored in the grayscale data storage memory area 7. The apparatus then returns to step 13 and repeats the real-time image correction from step 13 to step 18. When the line synchronization signal is no longer detected in step 13, the apparatus proceeds from step 13 to step 14, and the real-time error correction of the series of image data ends.

The same procedure is followed for the second and subsequent receptions, but since the grayscale data from the previous reception is stored in the grayscale data storage memory area 7, from the second time onward, the image is stored using the actually measured grayscale data. The data will be level corrected. This level-corrected image data is stored in the image data storage memory area 8.

The image signal level and grayscale signal level of orbital satellite N0AA are determined by the modulation degree of the transmitter on board the artificial satellite, and although the modulation degree may fluctuate over the long term, short-term fluctuations do not. Since it can be ignored, the level correction is accurate.

〔Effect of the invention〕

As explained above, the present invention stores the level of the grayscale signal of the image received when the signal-to-noise level ratio was good at the time of previous reception, and uses the level of the grayscale signal to determine the level of the received image signal. Since the level is corrected, there is an effect that the image signal level can be easily corrected in real time. In particular, in equipment that receives APT signals transmitted from the polar orbit satellite N0AA and performs image processing, initial processing of received images can be performed at low cost by using CP (J) and memory necessary for image processing. This has the effect of making it possible to correct the image signal level in real time.

[Brief explanation of the drawing]

FIG. 1 is a pattern diagram for explaining a conventional analog image signal automatic level correction device, FIGS. 2 and 3 are a functional block system diagram and a block system diagram of the analog image data automatic level correction device according to the present invention, FIG. 4 is a flow diagram for explaining the operation of the device. 1...Antenna, 2...Receiver, 3...A
M demodulator, 4...Analog/digital converter, 5.
... Synchronization detector, 6 ... CPU, 7 ... Gray scale data storage memory area, 8 ... Image data storage memory area, 9 ... Time signal generator, 10.
. . . system bus, 21 . . . means for storing currently received image signal level data, 22 . . . means for correcting currently received image signal level data, 23 . . .
...Means for storing the data of the gray scale signal level at the time of the previous reception, 24..Means for updating the data of the gray scale signal level at the time of the previous reception, 25..The gray scale when the satellite passes the zenith. A means of detecting signal level data. Figure 3 Figure 4

Claims (1)

[Claims] An analog image signal automatic level correction device for correcting the level of an image signal transmitted from an artificial satellite includes means for storing data of the gray scale signal level at the time of previous reception, and means for storing data of the gray scale signal level at the time of the previous reception. means for correcting currently received image signal level data based on the data; means for detecting grayscale signal level data when the artificial satellite passes the zenith; and grayscale signal level data detected when the artificial satellite passes the zenith. An analog image signal automatic level correction device comprising means for updating the gray scale signal level data at the time of the previous reception.