JPH0683405B2 - Wide area high resolution imaging method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image pickup method and an image pickup signal processing method when performing high-resolution image observation of a wide area from an artificial satellite or the like.

[Prior art] High-resolution imaging of various phenomena on the ground surface from satellites,
The importance of high-resolution observation systems transmitted to the ground is recognized, and the demand for higher resolution is increasing more and more. In recent years, CCDs (charge-coupled devices) with multiple elements have been increasingly used as light-receiving elements in high-resolution observation systems.

Fig. 12 shows a conventional general example of such an observation system. In FIG. 12, the satellite 1 has a velocity V with respect to the ground surface.
Proceed. The image 2 of the ground surface is imaged by the optical system 3 on the light receiving device 5 placed on the image plane. A photoelectric conversion element such as a CCD (charge coupled device) is used as the light receiving device 5, whereby an image signal on the ground surface is converted into an electric signal, signal-processed, and transmitted to the ground.

[Problems to be solved by the invention]

Since the number of light-receiving elements accommodated in the light-receiving device 5 is finite, when imaging with one CCD, the range in which imaging can be performed with higher resolution becomes narrower, which causes a problem. As one method of solving this, there is a method of arranging a reflecting mirror 29 in front of the optical system as shown in FIG. 13 and changing the angle to select an area for imaging. However, as the resolution increases, it is necessary to increase the aperture D of the optical system entrance portion, so that the movable reflecting mirror arranged in front of the optical system inevitably becomes large.

Arranging such a large movable optical structure in front of the optical system and operating it in outer space has problems such as accuracy of image pickup position setting, reliability, and life in addition to deterioration of resolution due to the absence of a mirror. Further, in this method, it is possible to image a specific portion, but it is impossible to image a wide area at the same time.

As another system example, there is also a method for increasing the imaging range by disposing a plurality of light receiving devices in the image plane as shown in FIG. However, in this method, as shown in the figure, due to spherical aberration of the optical system, defocus occurs at the edge part in the image formation and the resolution deteriorates, and high resolution imaging in a wide range is impossible. Is. Therefore, it is an object of the present invention to provide an image pickup system which simultaneously picks up a high resolution image of a specific portion while picking up an image of a wide range.

[Means for solving problems]

The main means taken by the present invention to solve the problems of these conventional techniques and to achieve the above object are as follows.

The imaging of the optical system is a curved surface that matches the focal plane of the optical system, and a plurality of light receiving devices are arranged along this curved surface.

Delaying the electric signal output of each of the plurality of light receiving devices in pixel units of the light receiving device, supplying this output to a gate circuit that passes or blocks it in pixel units, and add and combine these signal outputs. By this, integration between adjacent pixels in a specific portion is performed, and further sampling is performed in pixel units corresponding to the integration period.

Further, the combined and sampled signal output is supplied to a gate circuit which passes or cuts in scanning line period units, and by adding and combining these outputs, integration between adjacent scans of a specific portion is performed, and further integration is performed. Sampling is performed for each scanning line corresponding to the period.

This output signal is applied to the memory circuit, read out at equal intervals, and the output pulses are rearranged into a format suitable for transmission.

〔Example〕

The present invention will be specifically described below with reference to the drawings.

1 (a) and 1 (b) show an embodiment of a wide area high resolution imaging system according to the present invention. In the figure, 1 is an artificial satellite, 2
Is a surface image, 3 is an optical system, 4 is an image plane, 5 is a light receiving device, 6 is a signal selecting / synthesizing circuit, 7 is a signal processing circuit, 8 is a transmitter, 9 is a ground station receiver, and 10 is received signal processing. A circuit, 11 is an image processing circuit, and 12 is an image output.

As shown in the figure, the image of the surface of the earth is imaged by the optical system 3 in the artificial satellite on the light receiving device 5 arranged on the image plane 4 to be converted into an electric signal, and passes through the signal selection / synthesis circuit 6 and the signal processing circuit 7 , To the transmitter 8 and to the ground station receiver 9. The output of the ground station receiver 9 is supplied to the image processing circuit 11 via the reception signal processing circuit 10 and is output as an image output 12.

One of the features of the present invention is to arrange a plurality of detectors 5 along the curved image plane 4 as shown in the figure. A specific configuration of this portion will be described with reference to FIGS. The ideal focal plane of the optical system has a curved shape as shown in the image plane 4 in FIG. This shape can be accurately obtained from the calculation result of the aberration of the optical system. Therefore, by forming the image plane so as to match the shape of the ideal focal plane, and attaching a plurality of light receiving devices 5-1 to 5-5 along the curved image plane 4 as shown in the figure, As shown in the figure, each light receiving device can be arranged at the position of the ideal focal plane of the optical system.

Since each light receiving device is housed in the package, as shown in FIG. 3, by arranging the adjacent light receiving devices so as to be slightly displaced in the traveling direction of the satellite, it is possible to capture the adjacent surface image without a gap.

The focal plane of the optical system is generally circular as shown by the dotted line in 4 of FIG. 3, but the actual image plane shape is as shown in FIG. 4 (a). Good. The image plane 4 can be made of a metal or the like which is opaque to the incident light, and the light receiving device has a window formed on the image plane as shown in FIGS. 4 (b) and 4 (c). It can be attached inside thereof as shown in FIG. (B) or outside thereof as shown in (c). Alternatively, as shown in the sectional view of FIG. 5 (a) and the perspective view of FIG. 5 (b), the image plane 4 is formed in the shape of an optical half prism, and the light receiving device is arranged as shown in the figure. Images can be taken without gaps.

Next, a method for selecting and synthesizing signal outputs obtained from a plurality of light receiving devices arranged in this way to perform high resolution and wide area imaging will be specifically described with reference to FIG.

FIG. 6 is an example of a detailed diagram of the signal selecting / synthesizing circuit 6 in FIG. Routes 5-1 to 21-1 and 5-2 to 21- in the figure
Route 2-5-3 to 21-3 Route 5-4 to 21-4
In principle, the paths of 5 and 21-5 are the same as each other. In the figure, the electric signal outputs of the light receiving devices 5-1 to 5 are added to the front signal processing circuits 12-1 to 12-5.
The signals output from the light receiving device are amplified in the front-end signal processing circuits 12-1 to 5-5, and A / D conversion is performed to convert the signals into digital signals when the subsequent circuits are to be simplified. 13-1 to 5 and 17-1 to 5 are delay circuits, 14-1 to 5
18-1 to 18-5 are gate circuits.

An example of the operation of the circuit of FIG. 6 will be described with reference to the waveform chart of FIG. The horizontal axis in FIG. 7 is the time axis, and the vertical axis represents the pulse level. In FIG. 7, the number of elements of each light receiving device is shown as 12 in order to simplify the drawing. Further, T in the figure represents a scanning line period of one line in each light receiving element. In FIG. 7, the operation during the scanning line period (2T) for two lines is represented by the solid line, and the operation corresponding to the period before that is represented by the dotted line.

FIG. 7 shows gates 14-1, 4,5 and gate 18 in FIG.
-1,4,5 are ON, and gates 14-2 and 3 are n (T + T1) and n (T + T2), respectively, as shown in the figure.
An example in which the ON-OFF state of the gate is switched at the time of is shown.

In FIG. 6, the gate circuits 14-1 to 5 and 18-1 to 5 are
In the OFF state (high-resolution imaging mode), the outputs of the front-end signal processing circuits 12-1 to 12-5 are the same as those of the combining circuits 15 respectively.
-1 to 5 are added to the respective synthesizing circuits 19-1 to 19-5. In this case 16-1 to
Since the sampling circuits 5 and 20-1 to 5-1 sample one pixel and one line, respectively, high resolution imaging is performed in which one pixel in the light receiving device corresponds to one pixel on the ground surface.

In this example, in the waveform diagram of FIG. 7, n (T + T1) ≦ t <in the gate circuits 14-2 and 18-2 as shown in the figure.
It corresponds to the period of (n + 1) T and the period of nT≤t <n (T + T2) in the gate circuits 14-3 and 18-3, and the outputs of the sampling circuits 20-2 and 20-3 are shown in the figure during this period. As shown in, the pulse train corresponding to one pixel on the ground surface is output. Actual signal processing is often performed with digitally converted signals, but in order to make it easy to understand in FIG. 7, it is expressed in the form of an analog signal (PAM) whose amplitude changes with the input light level. There is.

Next, the operation when the gate circuits 14-1 to 5 and 18-1 to 5 are ON (wide area imaging mode) will be described. When the gate circuit 14-1 is ON, the output of the signal processing circuit 12-1 is supplied to the synthesizing circuit 15-1 by a signal delayed by one pixel and a signal not delayed by the delay circuit 13-1. Then, addition with the adjacent pixel is performed. That is, the integration operation is performed between the adjacent pixels. Therefore, since the data after the addition includes information for every two pixels, the sampling circuits 16-1 to 16-1
At 5, every other pixel, data is sampled and output.

The outputs of the sampling circuits 16-1 to 16-5 perform addition between pixels in adjacent scanning line periods, and therefore-the line delay circuit 17-
After being supplied to the circuits 1 to 5, the synthesis circuits 19-1 to 19-5 as described above.
Is added at. In this case, since the integration operation is performed between the adjacent lines, the output of the synthesis circuit is sampled every other line by the sampling circuits 20-1 to 20-5.

Therefore, the output pulse is nT ≦ t <n of 20-2OUT in FIG.
(T + T1), n (T + T2) of 20−3OUT ≦ t <(n + 1)
As shown by T and 20-1, 20-4, 20-5OUT, the sampling operation is performed every other pixel and the sampling operation is performed every other line. The amount of data to be transmitted is reduced by this sampling operation, and it is possible to capture data in a wide area corresponding to the reduced amount of data.

The outputs of the sampling circuits 20-1 to 5-5 are further supplied to the memory circuit 22 through the gate circuits 21-1 to 21-5 of the output section.
The data of -1 to the data of 20-5 are sequentially written.
When read out, it can be sent out to the ground station as a high-speed pulse train having a constant data rate as shown by 22OUT in FIG. 7 by reading out at equal intervals. The output gate circuits 21-1 to 21-5 are gate circuits for limiting the amount of output data when the amount of data to be transmitted to the ground is too large. When transmission is possible in the imaging mode, turn off the gate circuits of 21-1 and 21-4,5 to put all the outputs of the light receiving devices 5-2 and 5-3 in the high resolution imaging mode. Can be transmitted.

Next, an example of a method of performing signal processing on the receiving side on the pulse train thus transmitted will be described.

FIG. 8 is an example of a method of constructing the received signal processing circuit, and FIGS. 9 and 10 are waveform charts for explaining the operation of FIG.
The horizontal and vertical axes in FIGS. 9 and 10 are the same as those in FIG. 7 on the transmitting side, and represent the operation during the period of two lines (2T). Also, as in the explanation on the transmitting side, the waveform diagram is displayed in analog format (PAM) for easy understanding. The configuration of the pulse train at the input of the reception signal processing circuit is shown in FIG.
As indicated by IN, it has the same configuration as the output pulse train on the transmitting side in FIG.

This pulse train is first separated into pulse trains corresponding to the respective light receiving devices by the gate circuits 23-1 to 23-5. In the artificial satellite, the method of constructing the pulse train on the transmitting side is usually determined by a command from the ground station, so the order of constructing the pulse train on the receiving side is known, and as shown in FIG. By 1 to 5, it is possible to separate the pulse train corresponding to each device output. As another method for separating, when constructing a transmission pulse train, an identification code corresponding to the light receiving devices 1 to 5 is inserted into the output pulses of 20-1 to 5 and this code is detected on the receiving side. By doing so, it is possible to separate the pulse train corresponding to each device.

The pulse trains separated by the gate circuits 23-1 to 23-5 are written in the memory circuits 24-1 to 24-5, respectively. The reading operation of the memory circuit is performed in the same manner as when the pulse train on the transmitting side is configured. That is, in the memory circuits 24-1, 4 and 5, the read speed corresponds to the transmission side and is 1/1 / the speed during high-resolution imaging.
The data of the previous line is used as it is as the data of that line in the next one line after reading at one slow speed and reading one line. As shown in the figure, this operation is performed by nT ≦ t <n (T +
N (T + T2) ≦ t <(n + 1) in T1) and 24-3
The same applies to the period of T.

Next, n (T + T1) ≦ t <(n + 1) T in 24-2
In the period of nT ≦ t <n (T + T2) in 24 and 3-4, data reading is performed at a normal high speed reading speed. That is, in this case, the data of the two lines are read out as data having different information. Memory circuit
The outputs of 24-1 to 24-5 are supplied to the multiplexing circuit 28 via the delay circuits 25, 26 and 27-1 to 5 and written in the memory in the circuit. The data read from the multiplexing circuit 28 is 28OU in FIG.
As shown by T, data of 24-1 to 24-5 are sequentially read for each line corresponding to the writing speed, and the data of all lines are output in time series as shown in the figure. Therefore, the pulse density is high in the part where high-resolution imaging is performed on the transmitting side, and in the other parts, it is output in a sampled form corresponding to the period during which integration is performed.

The delay circuits 25, 26 and 27-1 to 5 of FIG. 8 are circuits for correcting the deviation of the image pickup time of each light receiving device from the arrangement on the transmitting side. The delay circuits 25 and 26 are circuits corresponding to the case where the light receiving devices on the transmission side are arranged so as to be shifted by odd numbers and even numbers as shown in FIGS. 3 and 4, and are required to correct the mutual time difference. It is intended to correct a delay time which is longer than the line. In contrast, 27-1
The delay circuits 5 to 5 are circuits for correcting a slight time difference in arrangement, and correction of a delay time as small as several pixels is performed.

An example of a simple image pattern output in this way is shown in FIG. The figure is a two-dimensional representation of a situation in which an image of a black and white grid-like inclined pattern is captured. The horizontal axis corresponds to the positions of the pixels arranged on the scanning line, and shows the state in which the artificial satellite flies in the direction of the vertical axis and imaging is performed. The scale below the horizontal axis indicates the connection point of the light receiving device. As shown in the figure, high resolution imaging is performed in a part of the second light receiving device and the third light receiving device, and the other part is 2
The state where the integration operation is performed for each pixel is shown.

In the present invention, by increasing the capacity of the memory circuit 22 of the output unit on the transmission side to several lines or more, a certain number of lines perform high resolution imaging in a wide range, and the other several lines perform wide area imaging mode. By switching and transmitting while keeping the overall data rate of several lines constant, it is also possible to perform high-resolution imaging of a specific two-dimensional area from a wide area.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform high-resolution imaging having excellent imaging characteristics for an arbitrary specific part of a wide area without using any mechanical moving mechanism, and to select an electronic mode for imaging. It is possible to image a wide range of areas by switching the areas, and it is possible to image a part of the area with high resolution and to image other areas with a different resolution. A wide range of high-performance imaging devices are provided.

[Brief description of drawings]

1 (a) and 1 (b) are block diagrams showing the outline of the wide area high resolution imaging method of the present invention, respectively, and FIG. 2 is a cross section of the optical section and the imaging section of the wide area high resolution imaging method in FIG. Figure,
FIG. 3 is a front view of the image forming unit of the wide area high resolution imaging system of FIG. 1, and FIGS. 4 (a), (b) and (c) are the image forming units of the wide area high resolution imaging system of the present invention, respectively. FIGS. 5A and 5B are a perspective view, a cross-sectional view and another cross-sectional view, and FIGS. 5A and 5B are cross-sectional views and perspective views showing another embodiment of the image forming unit of the wide area high-imaging system of the present invention, respectively. FIG. 6 is a block diagram showing a signal selection / synthesis circuit of the wide area high resolution imaging system of FIG. 1, FIG. 7 is an output waveform diagram of the signal selection / synthesis circuit of FIG. 6, and FIG. 8 is a wide area high resolution imaging of the present invention. FIG. 9 is a block diagram showing an embodiment of a reception signal processing circuit of the present invention, FIG. 9 and FIG. 10 are input waveform diagrams of the reception signal processing circuit of FIG. 8, and FIG. 11 is an acquisition by the wide area high resolution imaging method of the present invention. Image pattern example, Fig. 12 is a block diagram showing a conventional imaging method, Fig. 13 is a schematic view of a movable reflecting mirror, and Fig. 14 is a conventional diagram. 3 is a cross-sectional view of an optical unit and an image forming unit according to the imaging method of FIG. 1 ... Artificial satellite, 2 ... Surface image, 3 ... Optical system, 4 ...
... Image plane, 5 ... Light receiving device, 6 ... Signal selection / synthesis circuit, 7 ... Signal processing circuit, 8 ... Transmitter, 9 ... Ground station receiver, 10 ... Received signal processing circuit, 11 ... ... Image processing circuit, 12 ... Image output, 13-1 to 5, 17-1 to 5 ... Delay circuit, 14-1 to 5, 18-1 to 5 ... Gate circuit, 15-1 to 5,
19-1 to 5 ... Combining circuit, 16-1 to 5, 20-1 to 5 ... Sampling circuit, 21-1 to 5 ... Gate circuit, 22 ... Memory circuit, 23 ... Gate circuit, 24 ... … Memory circuits, 25,2
6 …… Delay circuit, 27 …… Delay circuit, 28 …… Multiplex circuit, 29
...... Movable reflective mirror.

Claims (1)

[Claims] 1. In an imaging system in which a light-receiving device composed of multiple light-receiving elements is arranged on an image-forming surface of an image-pickup optical system to perform photoelectric conversion, an artificial satellite station sets the image-forming surface as a focal plane of the optical system. And a plurality of light receiving devices arranged along the curved surface, and a first delay circuit for delaying the electric signal output of each of the plurality of light receiving devices in pixel units of the light receiving device. A first gate circuit that passes or blocks the output signal of the first delay circuit in pixel units; and a first combining circuit that adds and combines the output of the first gate circuit and the electrical signal. A first sampling circuit that samples the output of the first combining circuit in pixel units; a second delay circuit that delays the output sampled by the first sampling circuit in scanning line period units; 2's A second gate circuit for passing or blocking the output of the delay circuit in scanning line period units; a second combining circuit for adding and combining the outputs of the first combining circuit and the first sampling circuit; A second sampling circuit that samples the output of the second synthesizing circuit; and a memory circuit that temporarily records the output pulse train from the second sampling circuit and rearranges it at equal intervals.
And a wide-area high-resolution imaging method which performs wide-area imaging or high-resolution imaging of an arbitrary specific portion by opening / closing the second gate circuit.