JPH0113785B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electronic scanning imaging systems, and more particularly to electronic scanning imaging systems that include a one-dimensional charge-coupled device for imaging objects in relative motion at a specific relative velocity. The present invention relates to an electronic scanning imaging method that improves the signal-to-noise ratio of an imaging signal.

Conventionally, for example, in an electronic scanning imaging method in which a radiometer equipped with a radiometer light receiving section formed by a one-dimensional charge-coupled device is mounted on an artificial satellite to obtain an imaging signal for observing a predetermined ground surface, the radiation In response to the problem of improving the imaging resolution on the earth's surface required of the radiometer, there is a problem in that the weight of the radiometer increases significantly. If the dimension of one side of a pixel (hereinafter referred to as pixel dimension) corresponding to the resolution on the ground surface of the current imaging target is a, and the ground speed of the artificial satellite is V, then from the pixel through the optical system of the radiometer, The amount of light P received by the unit light receiving element of the charge-coupled device of the radiometer
is expressed as P∝a ³ /V. That is, as the resolution at the ground surface improves, the amount of light received by the charge-coupled device decreases in proportion to the cube of the pixel dimension a corresponding to the resolution. In order to improve this decrease in sensitivity related to photoelectric conversion, conventional methods have been used to increase the aperture of the optical system of the radiometer to increase the amount of light received by the charge-coupled device. Assuming that the aperture of the optical system is D, in order to keep the amount of light received by the charge-coupled device constant regardless of the resolution and maintain the photoelectric conversion sensitivity, the pixel must be adjusted in the relationship D∝a ^-3/2 . As the value of the dimension a is decreased, the value of the optical system D may be increased. Increasing the aperture of this optical system has led to the problem of significantly increasing the weight and size of the optical system and thus the weight and size of the radiometer. That is, in the conventional electronic scanning imaging method, a method of increasing the aperture of the optical system of the radiometer is used as a means to improve the decrease in photoelectric conversion sensitivity due to improvement in the imaging resolution of the imaging target. The disadvantage is that the weight and size of the radiometer is significantly increased.

An object of the present invention is to eliminate the above-mentioned drawbacks, and to form a radiometer light receiving section provided in the radiometer by a plurality of one-dimensional charge-coupled devices, to obtain a specific number of charge-coupled devices corresponding to the same imaging target segment. An object of the present invention is to provide an electronic scanning imaging method that improves the decrease in photoelectric conversion sensitivity that accompanies improvement in imaging resolution by synchronously adding the imaging signal outputs from the one-dimensional charge-coupled device.

The electronic scanning imaging system of the present invention includes a charge-coupled device as a photoelectric conversion element and images the imaging target using a radiometer light receiving section that moves at a predetermined relative speed with respect to the imaging target. A radiometer formed by n (an integer greater than 1) one-dimensional charge-coupled devices arranged at a predetermined array interval in a predetermined plane facing an object and outputting imaging signals through electronic scanning with a predetermined period. The predetermined relative speed and the predetermined arrangement interval with respect to the image pickup signal Si (i=1, 2, ..., n) output from each of the light receiving section and the one-dimensional charge-coupled device for each electron scan. (n
-i) comprising: an imaging signal delaying means for adding and outputting a delay time corresponding to T; and an imaging signal adding means for synchronously adding the imaging signals output from the imaging signal delaying means for each of the same imaging target classifications. It consists of

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a conceptual block diagram for explaining the operation of the electronic scanning imaging system of the present invention, in which the radiometer light receiving section included in the radiometer has three one-dimensional charge-coupled devices (hereinafter referred to as charge-coupled devices). This corresponds to the case of preparing. Further, FIG. 2 shows a conceptual diagram of the mutual relationship between the radiometer light receiving section and the imaging target area for explaining the operation mode of the present invention. In FIG. 2, a radiometer light receiving section 25 included in the radiometer faces the imaging target area 101 at a predetermined distance, and images the area while moving at a predetermined relative speed.
In the present description, the radiometer light receiving section 25 moves at a specific relative speed along a predetermined direction 100, and the radiometer light receiving section 25 moves at a specific relative speed along a predetermined direction 100.
Considering the case where an imaging signal related to the imaging target area 101 is acquired through the photoelectric conversion action and electronic scanning in the three charge-coupled devices 1-1 to 1-3 forming the The charge-coupled device 1- forming the radiometer light receiving section 25
1 arrives at the position corresponding to the imaging area division A, an imaging signal S ₁ (A) corresponding to the imaging area division A is output from the charge-coupled device 1-1 through electronic scanning corresponding to that point in time. . Note that in FIG. 2, w is the scanning width of the radiometer light receiving section 25 in the imaging target region 101. Furthermore, when the specific time T elapses, the charge coupled devices 1-1 and 1-
2 arrive at positions corresponding to imaging area divisions B and A, respectively. At this point, through electronic scanning, the image pickup signal S ₁ (B) corresponding to the image pickup area section B is output from the charge-coupled device 1-1, and the image pickup signal S ₂ (A) corresponding to the image pickup area section A is charged. It is output from the coupling device 1-2. Thereafter, through the same operation process, at the time of the next electron scanning period, charge coupled devices 1-1, 1-2 and 1-3 have S ₁ (C), S ₂ (B) and S ₃ (A ) is output, and at the next time point, charge coupled devices 1-1, 1-2 and 1-3 output S ₁ (D), S ₂ (C) and S ₃ (B), respectively. An imaging signal of is output. FIG. 3a shows imaging area divisions A corresponding to each charge-coupled device forming the radiometer light receiving section 25,
B, C, DEF,... are shown with the time axis set on the horizontal axis.

Corresponding to the operational mode of the present invention as described above, the conceptual block diagram of the present invention shown in FIG. 1 will be explained. The imaging signal S ₁ (A) corresponding to
A delay time corresponding to twice (2T) is given to the image signal S' 1 (A) and the signal is inputted to the image signal addition means 3 as the image signal S' ₁ (A). Further, at a time point after the specific time T has elapsed, the imaging signal S ₁ (B) corresponding to the imaging area classification B is output from the charge coupled device 1-1, and the delay circuit 2
-1, and is given a delay time corresponding to the above-mentioned 2T and input to the image signal addition means 3 as the image signal S' ₁ (B), and at the same time, the image signal S' 1 (B) is inputted to the image signal addition means 3, and at the same time
The image signal S ₂ (A) corresponding to the charge-coupled device 1-
2, is given a delay time corresponding to the specific time T via a delay circuit 2-2, and is input to the image signal addition means 3 as an image signal S' ₂ (A). Further, at a point after the elapse of the specific time T, the imaging signal S ₁ (C) corresponding to the imaging area classification C is
is outputted from the charge-coupled device 1-1, given a delay time corresponding to the above 2T via the delay circuit 2-1, and inputted to the imaging signal adding means 3 as an imaging signal S' ₁ (C). , At the same time, an imaging signal S ₂ (B) corresponding to the imaging area classification B is output from the charge coupled device 1-2, and is given a delay time corresponding to the T via the delay circuit 2-2 to become an imaging signal.
The image signal S' ₂ (B) is input to the image signal addition means 3, and the image signal S ₃ (A) corresponding to the image area classification A is output from the charge coupled device 1-3, without passing through a delay circuit. The image signal is inputted to the image signal addition means 3. Thereafter, through the same operation process, charge coupling is performed regarding the imaging signals output from the three charge coupled devices 1-1 to 1-3, corresponding to the imaging area divisions A, B, C, D, EF, . . . Device 1-1,1-
For the outputs from 2 and 1-3, respectively,
Delay times corresponding to 2T, T and 0 are given, and the image pickup signal adding means 3 performs synchronous addition. Through such operations, three charge-coupled devices 1-1~
By synchronously adding the three imaging signals, three sets of imaging signals corresponding to the same imaging area division are synchronously added. The third diagram illustrates this situation.
In Figure b, the horizontal axis represents time and the vertical axis represents time.
X ₁ , Y ₁ , X ₂ , Y ₂ , X ₃ and Z are the first
3 shows the signal reference points shown in the figure. Figure 3b
At the signal reference point at X ₁ , i.e. the output of the charge-coupled device 1-1, the imaging signal is S ₁
(A), S ₁ (B), S ₁ (C), S ₁ (D), etc. Delay circuit 2 -
At the signal reference point Y ₁ at the output of 1, S' ₁ (A), S' ₁ is given a delay time corresponding to the above 2T.
(B), S′ ₁ (C), S′ ₁ (D), etc. are the time series signals.
Furthermore, at the signal reference point X ₂ at the output of the charge-coupled device 1-2, A ₂ (A), S ₂ which has been given a time delay corresponding to the specific time T from the S ₁ (A)
(B), S ₃ (C), ... is displayed as a time series signal,
At the signal reference point Y ₂ , the time delays corresponding to T are indicated as S' ₂ (A), S' ₂ (B), S' ₂ (C), . . . . Signal reference points for charge-coupled devices 1-3
Similarly, X ₃ is also shown as S ₃ (A), S ₃ (B), S ₃ (C), ... At the signal reference point Z at the output of the image signal addition means 3 in FIG. ), ..., these added signals can clearly be expressed by the following equation.

Σ(A)=S′ ₁ (A)+S′ ₂ (A)+S ₃ (A) Σ(B)=S′ ₁ (B)+S′ ₂ (B)+S ₃ (B) Σ(C)=S ′ ₁ (C)+S′ ₂ (C)+S ₃ (C) The same applies to Σ(D), Σ(E), etc. below. That is, when three charge-coupled devices are included in the radiometer light receiving section, the imaging signal for a specific imaging area segment corresponding to one electron scan is
At a time delay corresponding to 2T, the resultant signal is added three times and outputted from the terminal 51 in FIG. Generally, when the number of charge-coupled devices is n, an imaging signal for a specific imaging area segment corresponding to one electron scan outputted from the charge-coupled device is transmitted with a time delay of (n-1)T. It is added n times and output. Now looking at the imaging signals corresponding to the specific imaging area division A, if there are n charge-coupled devices, the signal-to-noise ratio of the n imaging signals at the input stage of the imaging signal addition means 3 is
If S _A /N (voltage ratio), then the imaging signal addition means 3
The signal-to-noise ratio at the output of is expressed by the following equation.

That is, using n charge-coupled devices, n
By synchronously adding up imaging signals, the signal-to-noise ratio is improved by a factor of √ in the voltage ratio and n
Improved twice.

Next, a first embodiment of the present invention will be described with reference to FIG. The electronic scanning imaging system of the present invention shown in FIG. 5 corresponds to a case where the radiometer light receiving section includes three charge-coupled devices, each of which includes a photoelectric conversion section 4-1 to 3, a transfer gate 5-3, and a transfer gate 5-3.
charge-coupled devices 7-1 to 7-3 including shift registers 1 to 3 and shift registers 6-1 to 3; and an amplifier circuit 8-1.
-3, AD conversion circuits 9-1 to 9-3, a timing generation circuit 10, memory circuits 11-1 to 11-2, and a synchronous addition circuit 12. In the charge-coupled devices 7-1 to 3, the amount of light received by the respective photoelectric conversion units 4-1 to 3 is converted into charges,
A reset pulse input from the timing generation circuit 10 to the transfer gates 5-1 to 5-3;
Shift register 6 from timing generation circuit 10
-1 to 3, an imaging signal is output from each shift register 6-1 to 6-3 to the corresponding amplifier circuit 8-1 to 8-3 for each electronic scan. . Amplification circuit 9
- The imaging signal amplified by AD
The conversion circuits 9-1 to 9-3 perform AD conversion, and the outputs of the AD conversion circuits 9-1 and 9-2 are as follows:
The signals are input to the memory circuits 11-1 and 11-2 and stored therein, respectively, and the output of the AD conversion circuit 9-3 is directly input to the synchronous addition circuit 12. In the memory circuit 11-1, the image pickup signal is inputted from the timing generation circuit 10 by a clock pulse whose start time is controlled, so that the image signal is generated at the specific time T.
The play time is read out, and the apparent 2T
The signal is input to the synchronous addition circuit 12 with a time delay corresponding to . Similarly, in the memory circuit 11-2, the image signal is read out with a time delay corresponding to the T under the control of the clock pulse inputted from the timing generation circuit 10.
is input. That is, in the first embodiment, a memory circuit is used as the imaging signal delay means, three imaging signals corresponding to the same imaging area division are added in the synchronous addition circuit 12, and the signal-to-noise ratio is improved. A signal is output from the terminal 52.

Next, a second embodiment of the present invention will be described with reference to FIG. The electronic scanning imaging method of the present invention shown in FIG. 6 corresponds to the case where the radiometer light receiving section includes three charge-coupled devices, as in the case of the first embodiment, and the charge-coupled device 13-1 ~
3, amplifier circuits 14-1 to 3, timing generation circuit 15, AD conversion circuits 16-1 to 3, multiplexer 17, transmitting means 18, and receiving means 1
9, a demultiplexer 20, a timing circuit 21, memory circuits 22-1 and 22-2, and a synchronous addition circuit 23. Charge coupled device 13-
The operation until the imaging signals outputted from 1 to 3 for each electronic scan are AD converted in the AD conversion circuits 16-1 to 16-3 via the amplifier circuits 14-1 to 14-3, respectively, is described in the above-mentioned section. This is similar to the case of the first embodiment. The digital imaging signals output from the AD conversion circuits 16-1 to 16-3 are input to the multiplexer 17 and multiplexed, and then sent to the transmitting means 18.
will be sent to. The transmitting means 18 includes a modulator, a transmitter, an antenna, etc., and a multiplexer 1
A predetermined high frequency signal is modulated by the multiplexed imaging signal input from 7 and transmitted to the opposing receiving means 19. The receiving means 19 includes an antenna receiving demodulator and the like, receives and demodulates the high frequency signal sent from the transmitting means 18, and outputs the multiplexed imaging signal, timing signal, etc. The timing signal is input to a timing circuit 21 which generates a predetermined timing signal including clock pulses. Further, the multiplexed imaging signal is input to a demultiplexer 20, and controlled by a timing signal input from a timing circuit 21 to the demultiplexer 20, the three charge-coupled devices 13--
It is output as an imaging signal corresponding to each of 1 to 3, and input to the memory circuits 22-1, 22-2 and the synchronous addition circuit 23, respectively. The imaging signal corresponding to the charge-coupled device 13-1 is inputted to the synchronous addition circuit 23 via the memory circuit 22-1 with a time delay corresponding to the 2T, and the imaging signal corresponding to the charge-coupled device 13-2 is inputted to the synchronous addition circuit 23 with a time delay corresponding to 2T. The operation process in which the signal is input to the synchronous addition circuit 23 via the memory circuit 22-2 with a time delay corresponding to the T is also the same as in the first embodiment. That is, in the second embodiment, the transmitting means and By providing the receiving means, three imaging signals corresponding to the same imaging area division can be synchronized by the synchronous addition circuit 23.
A digital imaging signal with an improved signal-to-noise ratio can be output from the terminal 53.

Further, the graph shown in FIG. 4 shows an example of the characteristics of the light receiving sensitivity with respect to the used wavelength of the radiometer light receiving section including the charge-coupled device. As can be seen from FIG. 4, the light receiving sensitivity of the charge-coupled device differs depending on the wavelength used. When actually imaging an object using a radiometer light receiving section, due to the physical characteristics of the object, the level of light received by the radiation receiving section has a characteristic difference related to the wavelength used. Therefore, by taking advantage of this phenomenon, the wavelength range used is divided into several bands, the target is imaged in each divided band, and the imaged signals obtained in each are processed using a predetermined method. , analysis of the imaged object is often performed. In this case, as described above, when dividing the used wavelength range into several bands, it is desirable that the light receiving sensitivity of the radiometer light receiving section be at the same level for each band. For this purpose, it is important to improve the light receiving sensitivity in the wavelength ranges of 0.5 to 0.6 microns and 0.9 to 1.1 microns in FIG. 4. As a measure for this purpose, it is also possible to apply the present invention and relatively increase the number of synchronous additions to the imaging signal in the wavelength range of low light-receiving sensitivity, thereby correcting the light-receiving sensitivity characteristics shown in FIG. 4. .

As described above in detail, the present invention forms a radiometer light receiving section with a plurality of one-dimensional charge-coupled devices, and provides imaging signals output from the plurality of one-dimensional charge-coupled devices corresponding to the same imaged object. of,
By performing synchronous addition via an imaging signal delay means having a predetermined delay time characteristic based on the specific time T, there is an effect that the light receiving sensitivity in the radiometer light receiving section can be compensated for and improved.

[Brief explanation of drawings]

Fig. 1 is a conceptual block diagram of the present invention, Fig. 2 is an explanatory diagram of the mode of operation of the present invention, Fig. 3 is a diagram of the relationship between imaging area divisions and imaging signals for explaining the operation of the invention, and Fig. 4 is 5 and 6 are block diagrams of the first and second embodiments of the present invention, respectively. In the figure, 1-1 to 3, 7-1 to 3, 13-
1-3...charge coupled device, 2-1-2...delay circuit, 3...imaging signal addition means, 4-1-3...
...Photoelectric conversion unit, 5-1 to 3...Transfer gate, 6-1 to 3...Shift register, 8-1
~3,14-1~3...amplifier circuit, 9-1~3,
16-1 to 3...A-D conversion circuit, 10, 15...
...Timing generation circuit, 11-1 to 2, 22-1
~2... Memory circuit, 12, 23... Synchronous addition circuit, 17... Multiplexer, 18... Transmitting means, 19... Receiving means, 20... Demultiplexer, 21... Timing circuit, 25... Radiometer Light receiving section, 26... Imaging signal delay means, 51 to 53...
... terminal, 100 ... direction, 101 ... imaged target area, X ₁ , Y ₁ , X ₂ , Y ₂ , Z ... signal reference point,
A, B, C, D, E, F...imaging classification, S ₁ (A), S ₁
(B), S ₁ (C), S ₁ (D), S ₁ (E), S ₁ (F), S′ ₁ (A), S′ ₁ (B)
,S′ ₁
(C), S′ ₁ (D), S ₂ (A), S ₂ (B), S ₂ (C), S ₂ (D), S ₂ (E), S
′ ₂
(A), S′ ₂ (B), S′ ₂ (C), S′ ₂ (D), S ₃ (A), S ₃ (B), S ₃ (C
), S ₃
(D), Σ(A), Σ(B), Σ(C), Σ(D)...imaging signal, w...
...scan width.

Claims (1)

[Claims] 1 In an electronic scanning imaging method that includes a charge-coupled device as a photoelectric conversion element and images the imaged object using a radiometer light receiving section that moves at a predetermined relative speed with respect to the imaged object, in a predetermined plane facing the imaged object. a radiometer light-receiving section formed by n (an integer greater than 1) one-dimensional charge-coupled devices arranged at a predetermined array interval and outputting imaging signals at a predetermined cycle; With respect to the imaging signal Si (i=1, 2,...,n) outputted for each electronic scan, each sequentially (n -i) comprising an image signal delaying means for adding and outputting a delay time corresponding to T, and an image signal adding means for synchronously adding the image signals outputted from the image signal delaying means for each of the same imaging target classifications. An electronic scanning imaging method characterized by: