JPH05312955A - Imaging unit - Google Patents

Abstract

PURPOSE:To identify and remove a spot image produced by cosmic rays within a shortest time by disposing at least two layers of cosmic rays detecting cell on the rear of a light receiving face, estimating the passing position of cosmic rays on the light receiving face, and displaying an estimated passing position and an image while superposing. CONSTITUTION:Two pieces of high energy beam detecting cells 2, 3 are disposed on the rear of the light receiving face of an imaging device 1 and a two-dimensional position of detected cosmic rays is outputted to a passing position estimating unit 4. The estimating unit 4 operates passing position data of cosmic rays and outputs the data thus operated to an image processor 5. The processor 5 superposes a marker on the estimated passing position of cosmic rays, for example, based on an output from the estimating unit 4 and data provided from the imaging device 1 and displays an image on a display means 6 thus identifying a spot image produced by the cosmic rays. Each of the high energy beam detecting cells 2, 3 is constituted of a plurality of strip electrodes arranged in parallel on a semiconductor substrate, and a two-dimensional position sensitive detector is employed in each of the detecting cells 2, 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device, and as an example, when an image consisting of extremely weak light is picked up, a point due to cosmic rays (mainly muons) superimposed on a target image. The present invention is applied to an extremely weak light imaging device capable of discriminating a pseudo-image (hereinafter referred to as a point image by cosmic rays).

[0002]

2. Description of the Related Art When performing astronomical observation with an image pickup device, a CCD (charge coupled device) cooled by liquid nitrogen, for example, is used as a highly sensitive device.

When, for example, a cooled CCD is used as an image pickup device when picking up an image of extremely weak light, the CCD is sensitive to cosmic rays, and several hundred to several thousand per cosmic ray. Since the electron-hole pairs are generated, a dot-like pseudo image is generated at the position where the cosmic ray passes in the image. Especially for applications in astronomy, it is important to identify point images by cosmic rays because the point images by cosmic rays are confusing with the images of celestial bodies that are also point-like.

Since the intensity of such cosmic rays (mainly muons) on the ground is about 1 per 1 cm ² per minute, the point image due to the cosmic rays is removed when the CCD is exposed for a long time. Or it is necessary to identify, but it is difficult to remove cosmic rays with a shield.

Therefore, the following point image removal method has been conventionally adopted. That is, the point image by cosmic rays is
Since it is considered that they occur randomly in time and space, at least two images are taken for one target,
By comparing the obtained images, the point image due to cosmic rays is identified and removed from the image.

[0006]

However, as described above, one target is imaged a plurality of times and the obtained images are compared to identify and remove the point image due to cosmic rays. The method takes twice as many times as the number of times of imaging as compared with one imaging. Also in the present invention, the image after exposure is compared with the estimated passing position of cosmic rays, and it is not real-time. An object of the present invention is to solve such a problem.

[0007]

An image pickup device according to the present invention includes an image pickup means for picking up light incident on a light receiving surface from the front, and an axis arranged behind the image pickup means and intersecting the light receiving surface. High-energy-ray detecting means having a plurality of high-energy-ray detecting cells whose detection surfaces intersect with each other, and estimating the passage position of the high-energy rays incident on the light-receiving surface based on the detection positions of the plurality of high-energy ray detecting cells And an image processing means for processing an image captured by the imaging means by the output of the passing position estimation means.

[0008]

According to the image pickup device of the present invention, since at least two layers of high energy ray (cosmic ray) detection cells are arranged, it is possible to estimate the passage position of the cosmic ray on the light receiving surface of the image pickup means. You can Then, if the image obtained from the image pickup device and the passage position of the cosmic ray are overlapped and displayed on the display device, it is possible to identify that the point at the passage position of the cosmic ray is due to the cosmic ray.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an image pickup apparatus according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the basic configuration of an embodiment of the present invention.

FIG. 1A shows an example in which two high energy ray detecting cells 2 and 3 are provided behind the image pickup device 1.
FIG. 2B shows an example in which two high energy ray detection cells 2 and 3 in the shape of a rectangular tube are arranged. In addition, regarding the same figure (b), the passing position estimation device 4, the image processing device 5, and the display device 6 are shown.
Are omitted in the drawing.

The light to be observed is incident on the light receiving surface of the image pickup device 1. Two high energy ray detection cells 2 and 3 are arranged behind the image pickup device 1 at regular intervals. The high energy ray detecting cells 2 and 3 are capable of two-dimensional position detection, and the output thereof is input to the passage position estimating device 4. The passing position estimating device 4 calculates passing position data of high energy rays by the high energy ray detecting cells 2 and 3, and estimates a passing position of the high energy rays on the light receiving surface of the imaging device 1, and its output is image processing. Device 5
Given to.

The image pickup data from the image pickup device 1 is given to the image processing device 5 and is subjected to image processing by the output of the passing position estimating device 4. For example, the marker is superimposed on the passage position of the high energy ray, and the marker is sent to the display means 6 and displayed on the screen, so that the point image by the high energy ray can be recognized.

Next, a first embodiment constructed as an extremely weak light image pickup device will be described. FIG. 2 is a diagram showing the structure of the image sensor and the cosmic ray detector. CCD 10 which is an image sensor
A three-layer cosmic ray detector 11, 12, 13 is arranged behind the. CCD 10 is a heat sink 14 for cooling
The end of the heat sink 14 (not shown) is immersed in liquid nitrogen. Further, the CCD 10 and the heat sink 14 are housed in a vacuum container 16 having a window 15 through which light enters. Cosmic ray detectors 11, 12, 1
Each of 3 is an X-direction position detector 11 _X , 12 _X , 13 _X and a Y-direction position detector 11 for detecting cosmic ray passage positions in two directions orthogonal to each other on a plane parallel to the light receiving surface of the CCD 10. _It consists of _Y , 12 _Y , and 13 _Y. As a matter of course,
The cosmic ray detectors 11, 12, and 13 have the same X direction and the same Y direction.

When the cosmic rays 17 pass through the CCD 10, a large number of electron-hole pairs 21 are created at the passage positions of the cosmic rays 17 as shown in FIG. 3A, and the charges generated in the depletion layer 22 are generated. Accumulate underneath nearby electrodes 23. As a result, CC
A point image 25 of cosmic rays is superimposed on the image 24 obtained from D10 as shown in FIG. When the CCD is used in the field of astronomy, the astronomical image 26 and the cosmic ray point image 25 are confusing.

Next, the structure of the cosmic ray detector is shown in FIG.
The X direction position detector 11 _X of the cosmic ray detector 11 is a CCD
A silicon strip detector in which strip-shaped detectors (11 _{X1 to} 11 _Xn ) are arranged in the X-direction on a plane parallel to the light-receiving surface of 10. The Y-direction position detection 11 _Y is a strip-shaped detector in the Y-direction. It is a silicon strip detector in which (11 _{Y1 to} 11 _Yn ) are arranged. The width of the strip is several tens of μm and the length thereof is larger than the size of the CCD 10, and the silicon strip detectors 11 _X and 11 _Y cover the CCD 10 as a whole. When the cosmic ray 17 is incident on the cosmic ray detectors 11 _X and 11 _Y , the strip at the incident position of the cosmic ray 17 (see FIG.
Then, electron-hole pairs are generated in 11 _X3 , 11 _Y2 ).

Each strip 11 _{X1 to} 11 _Xn of the silicon strip detector 11 _X has an amplifier 31 as shown in FIG.
It is connected to the comparators 41 _{X1 to} 41 _Xn via _{X1 to} 31 _Xn . The comparators 41 _{X1 to} 41 _Xn compare the amount of charge generated in the strip with a set value, and detect that the amount of charge generated is equal to or more than the set value as a phenomenon due to cosmic rays (hereinafter referred to as “hit”). Further, the comparator 41 _X1 to 41 _Xn is connected to the position identifier 51 _X, position identifier 51 _X provides an address X1 of the hit occurred strips.

In FIG. 5, since the cosmic ray is incident on the strip 11 _{X 3} , the address X1 is "3". The position identifier 51 _X is a silicon strip detector 11 _X.
A trigger signal 61 _X indicating that a hit has been detected is generated. Other silicon strip detectors 11 _Y , 12
Similarly, _{X 1} , 12 _Y , 13 _X and 13 _Y also generate addresses Y 1, X 2, Y 2, X 3 and Y 3 and trigger signals 61 _Y , 62 _X , 62 _Y , 63 _X and 63 _Y when cosmic rays pass through.

As shown in FIG. 6, the trigger signals 61 _X ...
63 _Y is sent to the coincidence circuit 44, and the coincidence circuit 44 sets an arbitrarily set time width (for example, 100
ns), when the trigger signals are generated from all of the six position discriminators 51 _{X to} 53 _Y , that is, one cosmic ray passes through the three cosmic ray detectors 11, 12, and 13. When it is presumed that, the arithmetic unit 45 is instructed to take in the addresses X1 to Y3 indicating the passage position of the cosmic rays.

The arithmetic unit 45 obtains the stored corresponding coordinates (see FIG. 7A) from the number of the strip in which the hit of each of the silicon strip detectors 11 _{X to} 13 _Y occurs, and calculates the minimum value. Find the formula that expresses the straight line through which cosmic rays pass by the square method. That is, (x ₁ ,
_{z x1), (x 2,} z x2), the Ax and Bx of (x _3, z _x3 Equation 3 coordinates of a straight line obtained by projecting the X-Z plane), x = Ax · z + Bx ...... (1), Also, (y ₁ , z _y1 ), (y ₂ ,
From the coordinates of z _y2 ), (y ₃ , z _y3 ), the formula of a straight line projected on the YZ plane, y = Ay · z + By (2) Ay and By can be obtained.

By substituting the Z coordinate z ₀ of the light receiving surface of the CCD 10 into the equations (1) and (2), the estimated value (x ₀ , y ₀₎ of the passing position coordinate of the cosmic ray on the light receiving surface of the CCD ₁₀ is obtained. )
Can be asked. In addition, in FIGS. 7B and 7C, the strip in which the hit has occurred is similar to FIG.
_Depicted as 11 _X3 and 11 _Y2 .

Estimated values (x ₀ , y ₀ ) of all cosmic ray passing position coordinates obtained during exposure of the CCD ₁₀ .
_i (where i = 1 to N) is stored in the memory 46, while the image by the CCD 10 is stored in the video memory 48 after the exposure is completed, and the cosmic ray passes to the corresponding position in the image obtained by the display device 47. A marker indicating that this has been done is displayed (FIG. 8). The point image 25 overlapping the marker is due to cosmic rays and can be distinguished from the celestial image 26.

Next, a second embodiment will be described. Second
In this embodiment, as shown in FIG. 9, in addition to the cosmic ray detectors 11 to 13 for measuring the passage position of cosmic rays, a cosmic ray detector 70 for detecting the passage timing of cosmic rays is arranged.

That is, by providing the cosmic ray detector 70 for detecting the timing, it is not necessary to take the coincidence with the cosmic ray detectors 11, 12, 13 for estimating the passage position. The cosmic ray detector 70 includes two sets of a plastic scintillator (71a, 71b) and a photomultiplier tube (72
a, 72b). When the cosmic rays 17 pass through the plastic scintillators 71a and 71b, the plastic scintillators 71a and 71b emit light, and pulsed currents are output from the photomultiplier tubes 72a and 72b (FIG. 10). The output currents are compared with the set value by the comparators 73a and 73b, and when the current larger than the set value is output, the timing signals 74a and 74b are output.

The coincidence circuit 75 sends the trigger signal 76 to the position discriminator 8 only when the timing signals 74a and 74b are simultaneously generated within the set time width ΔT ₁ .
Feed to 1 _X to 83 _Y, reads the address of the strip hits the silicon strip detectors occurs. The position discriminator 81 _X has a memory 91 _X and has an address of ΔT ₂
When the trigger signal 76 is received during the holding period, the held address is sent to the computing unit 77. Position discriminator 8
The configuration and operation of 1 _{Y to} 83 _Y are the same as above.

In the arithmetic unit 77, as in the first embodiment,
The passing position of cosmic rays on the light receiving surface of the CCD 10 is estimated. When a plurality of addresses are sent from one position discriminator 81, a plurality of straight line expressions can be obtained, but at least 2
Select the most probable straight line by multiplication, CCD1
Estimate the passing position (x ₀ , y ₀ ) of the cosmic ray on the light receiving surface of ₀ . The obtained estimated passage position of the cosmic rays is displayed on the screen of the display device 47 as in the first embodiment.

If a copper plate is interposed between the two plastic scintillators 71a and 71b, both cosmic rays emit light but only one gamma ray emits light. Therefore, the effect of only cosmic rays can be eliminated.

[0027]

According to the extremely weak light image pickup device of the present invention, since at least two layers of high energy ray (cosmic ray) detection cells are arranged, the cosmic ray passes through the light receiving surface of the image pickup means. The position can be estimated. Then, a point noise component due to cosmic rays in the image obtained from the image sensor can be identified on the display device. Therefore, cosmic rays can be identified in real time while performing imaging.

[Brief description of drawings]

FIG. 1 is a perspective view showing a basic configuration of an image pickup apparatus of the present invention.

FIG. 2 is a diagram showing a configuration of a part of an image sensor and a cosmic ray detector in the first embodiment.

FIG. 3 is a diagram illustrating generation of dot-like pseudo images due to cosmic rays in a CCD.

FIG. 4 is a diagram showing a configuration of a cosmic ray detector (silicon strip detector).

FIG. 5 is a block diagram showing a configuration from a silicon strip detector to a position discriminator in the first embodiment.

FIG. 6 is a diagram illustrating a function of a computing unit.

FIG. 7 is a diagram illustrating a coordinate system of a cosmic ray detector.

FIG. 8 is a diagram illustrating a function of a display device.

FIG. 9 is a diagram showing a configuration of parts of an image sensor and a cosmic ray detector in a second embodiment.

FIG. 10 is a diagram showing a configuration of a circuit system according to a second embodiment.

[Explanation of symbols]

1 ... Imaging device, 2, 3 ... High energy ray detection cell,
4 ... Passage position estimation device, 5 ... Image processing device, 6 ... Display device, 10 ... CCD, 11, 12, 13 ... Cosmic ray (passage position) detector, 11 _X , 12 _X , 13 _X ... Cosmic ray passage Silicon strip detector for detecting X component of position, 11
_{X1 to} 11 _Xn ... Silicon strip detector 11 _X comprising strips, 11 _Y , 12 _Y , 13 _Y ... Silicon strip detector for detecting the Y component at the passage position of cosmic rays, 1
1 _{Y1 to} 11 _Yn ... Strips constituting the silicon strip detector 11 _Y , 14 ... Heat sink, 15 ... Incident window,
16 ... Vacuum container, 17 ... Cosmic ray, 21 ... Electron-hole pair,
22 ... Depletion layer, 23 ... Electrode, 24 ... CCD image, 25 ...
The point image by cosmic rays, 26 ... celestial image, 31 _X1 ~31 _Xn ...
Amplifier, 41 _X1 to _41n Comparator, 44 Coincidence circuit, 45 ... Arithmetic unit, 46 ... Memory, 47 ... Display device,
51 _X ... Position discriminator, 61 _X , 61 _Y , 62 _X , 6
2 _Y , 63 _X , 63 _Y ... Trigger signal, 70 ... Cosmic ray detector, 71a ..., 71b ... Plastic scintillator,
72a, 72b ... photomultiplier tube, 73a, 73b ... comparator, 74a, 74b ... timing signal, 75 ... coincidence circuit, 76 ... trigger signal, 77 ... _{calculator, 81 X, 81 Y, 83} Y ... position identifier, 91 _X ... Memory.

Claims (5)

[Claims] 1. An image pickup means for picking up light incident on a light-receiving surface from the front, and a plurality of high energies arranged behind the image-pickup means and having detection surfaces intersecting axes intersecting with the light-receiving surface. High-energy ray detection means having a ray-detection cell, passage position estimation means for estimating a passage position on the light-receiving surface of the high-energy rays incident on the basis of the detection positions of the plurality of high-energy ray detection cells, and the imaging And an image processing means for processing an image picked up by the means by the output of the passing position estimating means. 2. The plurality of high energy ray detection cells,
The image pickup device according to claim 1, wherein a plurality of strip-shaped electrodes are formed in parallel on a semiconductor substrate, and the high-energy ray detection cells are arranged such that the strip-shaped electrodes are orthogonal to each other. 3. The high-energy ray detector has a pair of electrodes arranged in two directions orthogonal to each other on a semiconductor substrate, and the charges generated by the high-energy rays are divided by the electrodes and read out. The image pickup apparatus according to claim 1, wherein the image pickup apparatus is a two-dimensional position-sensitive detector that obtains a passing position of a high-energy ray based on a ratio of the read charge amounts. 4. The image pickup device according to claim 1, further comprising a detector for measuring a passage time of the high energy ray. 5. The image pickup apparatus according to claim 1, further comprising display means for displaying the marker of the estimated passing position in an overlapped manner on the picked-up image.