JP7352495B2 - Imaging systems and imaging system application equipment - Google Patents

Description

The present invention relates to an imaging system using an image sensor and an imaging system application device.

2. Description of the Related Art Imaging systems having image sensors are installed in nuclear power plants and radiation utilization facilities in order to monitor the inside of the plants and facilities. In addition, imaging systems having image sensors are used in internal investigations for decommissioning nuclear power plants. Image sensors included in these imaging systems include image pickup tubes that are vacuum tubes, solid-state image sensors that use semiconductors, and the like.

As described in Patent Document 1, in solid-state image sensor type image sensors, the charge photoelectrically converted by the light receiving element in the pixel is usually transferred to a CMOS type amplification amplifier (complementary metal-insulator-semiconductor field effect transistor). , CMOS-FET). The amplified voltage signal is sequentially scanned and extracted by a vertical scanning circuit and a horizontal scanning circuit to obtain a voltage signal proportional to the amount of light, that is, the brightness, of each image. As a result, an image of the object (subject) is obtained.

However, it is known that CMOS amplifiers are susceptible to deterioration due to radiation exposure. One reason for this is as follows. When a MOS type FET is irradiated with radiation, electrons and holes are generated in the oxide film (insulating film) of the gate. Electrons in the oxide film have higher mobility than holes, so they escape from the oxide film, but holes have lower mobility, so they accumulate in the oxide film as positive charges. This is because the charges accumulated in the oxide film cause the threshold value of the MOS FET to fluctuate, resulting in adverse effects such as the inability to perform stable signal amplification.

In general, circuit elements used in harsh environments such as radiation environments are protected by shielding with lead or the like or moved away from radiation sources. However, image sensors, cameras, and imaging devices cannot be shielded with lead plates that do not transmit light.

On the other hand, in order to colorize a captured image, a color filter has conventionally been placed in front of an image sensor as described in Patent Document 2. However, in this case, it is known that the color filter itself deteriorates in a radiation environment, such as a decrease in light transmittance, and it has been difficult to use the color imaging device for a long time in a radiation environment.

Japanese Patent Application Publication No. 2014-39159 JP 2018-200909 Publication

As described above, conventional solid-state image sensor type image sensors usually use CMOS type amplifiers, and the CMOS type amplifiers have a problem in that their characteristics tend to deteriorate due to radiation irradiation.

To deal with this problem, attempts have been made to use vacuum tubes such as image pickup tubes, but since image pickup tubes operate by spatially scanning an electron beam, they are physically large and heavy. There is a problem.

Furthermore, when a color filter is placed in front of an image sensor as described in Patent Document 2 for colorization, it is known that the color filter itself deteriorates in a radiation environment, such as a decrease in light transmittance. However, there was a problem in that imaging devices used in radiation environments could not be used for long periods of time.

On the other hand, in applied equipment such as robot systems, there is a demand for mounting multiple image sensors, and a small and lightweight image sensor is required. Furthermore, in support of robot work, there is a demand for color images in order to more clearly capture images of objects, rather than monochrome images such as conventional CMOS radiation-resistant cameras and image pickup tubes using vacuum tubes.

The problem to be solved by the present invention is to provide a color imaging system and imaging system application equipment that has excellent environmental performance such as radiation resistance, and uses a compact and lightweight image sensor and color separation element. be.

A typical example of the invention disclosed in this application is as follows. That is, an imaging system including a sensor unit installed in a high-dose environment where radiation is irradiated , and an image processing unit installed in a low-dose environment separated from the high-dose environment by a wall , the sensor The unit includes a color separation element that extracts light of a specific wavelength, and an image sensor that photographs the light transmitted through the color separation element, and the image sensor includes a sensor element and a transmitting/receiving unit, and the sensor The element has a light receiving element and a charging transistor for each pixel, has one or more threshold value judgment circuits for determining whether the terminal voltage of the light receiving element is equal to or higher than a predetermined threshold value, and has a plurality of sub-subs corresponding to different brightness threshold values. The image processing unit is surrounded by a radiation shielding material and processes the signals of the plurality of sub-images to generate a gray scale image , and the color separation element is configured to: The sensor unit separates the incident visible light into red light, green light, and blue light, and causes the light of each color to travel in three orthogonal directions different from the incident visible light, and the sensor unit An imaging system comprising a plurality of imaging sensors that capture transmitted light, the imaging system generating a color image by synthesizing images output from each of the imaging sensors.

According to one aspect of the present invention, it is possible to provide an imaging device and an imaging system that have excellent environmental resistance and can capture colored images even under harsh environments. Problems, configurations, and effects other than those described above will be made clear by the description of the following examples.

FIG. 1 is a configuration diagram of a radiation-resistant imaging system according to a first embodiment of the present invention. 1 is a first example of a schematic diagram showing the configuration of a color separation element according to a first embodiment; FIG. FIG. 2 is a second example of a schematic diagram showing the configuration of the color separation element of the first example. FIG. 2 is a schematic diagram showing the configuration of a sensor element. FIG. 3 is a schematic diagram showing the configuration of each pixel. FIG. 2 is a circuit diagram showing a threshold value determination circuit according to the present embodiment. FIG. 3 is a circuit diagram showing another example of the threshold value determination circuit of the first embodiment. FIG. 3 is a schematic diagram showing a pixel configuration of a sensor element of a comparative example. FIG. 3 is a timing diagram schematically showing a readout sequence from pixels in a sensor element of the first embodiment. FIG. 2 is a schematic diagram showing a method of configuring a gradation image. 3 is a logic table showing processing for configuring a gradation image in the first embodiment. 10 is a circuit diagram of a circuit that implements processing for configuring the gradation image shown in FIG. 9. FIG. FIG. 3 is a schematic diagram showing a state in which image data of a sub-image according to the first embodiment is stored on a memory. 12 is a truth table for realizing the process of configuring the gradation image shown in FIG. 11. FIG. 7 is a diagram showing the configuration of a sensor element of a second example. FIG. 7 is a timing diagram schematically showing a readout sequence from pixels in a sensor element of a second example. FIG. 7 is a schematic diagram showing the relationship between the amount of light incident on the light receiving element and the terminal voltage of the third example. FIG. 7 is a schematic diagram showing the relationship between the readout sequence from each pixel and charging voltage Vb0 in the third example. FIG. 7 is a schematic diagram showing the relationship between the readout sequence from each pixel and charging voltage Vb0 in the fourth example. It is a figure showing the robot system which is an example of applied equipment of the 7th example. FIG. 7 is a schematic diagram showing the configuration of a pixel in an eighth example. FIG. 7 is a schematic diagram showing the configuration of a sensor element of an eighth example.

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following embodiments, and can be modified, for example, by combining a plurality of embodiments or without departing from the technical idea of the present invention.

In addition, in this specification, the same members are given the same reference numerals, and redundant explanations will be omitted. For convenience of illustration, the contents of the illustrations may be changed from the actual configuration without departing from the spirit of the present invention.

FIG. 1 is a configuration diagram of an imaging system 1 of this embodiment.

The imaging system 1 of this embodiment includes a sensor section 10 and an image processing section 20. As shown in the figure, the sensor section 10 and the image processing section 20 may be configured separately and connected by a cable 30 or wirelessly, but the sensor section 10 and the image processing section 20 may be configured integrally.

The sensor unit 10 includes a color separation element 14 and a plurality of image sensors 15, and the image sensor 15 includes a sensor element 13 that detects an external image, and a sensor control unit that controls processing by a circuit within the sensor element 13. 11, and a transmitting/receiving section 12 that transmits and receives signals between the sensor section 10 and the image processing section 20. The sensor control section 11 and the transmitting/receiving section 12 are functionally separated, and the sensor element 13, the sensor controlling section 11, and the transmitting/receiving section 12 may be provided on one IC chip.

The color separation element 14 is made of an inorganic material (for example, a dielectric optical element), and separates visible light into RGB (red, green, blue) having different wavelengths. As shown in the figure, light divided into each color is received by a plurality of image sensors 15, and an image containing a specific color (for example, a red light image, a black and white image, and a red image (a composite image) or a color image. Unlike conventional color separation elements using color filters made of organic materials, the color separation element 14 of this embodiment is made of inorganic materials, so it is not easily deteriorated by radiation or ultraviolet rays, and can be used in harsh environments such as radiation environments. However, it can be used stably for a long period of time.

To describe the configuration of the color separation element 14 in more detail, it is preferable to use a dielectric optical element. A dielectric optical element is made by laminating multiple layers of inorganic materials with different refractive indexes, and reflects light in a specific wavelength band according to the thickness of the laminated layers. Since the reflection wavelength band is determined by the thickness of the laminated film, no pattern is required. Since the color separation element 14 of the present invention does not contain organic matter due to such a configuration, browning caused by radiation or ultraviolet ray irradiation can be suppressed to a greater extent than conventional color filters.

It is preferable to provide three image sensors 15 corresponding to the RGB colors separated into the three primary colors of light (red, green, and blue), but the combination thereof may be changed arbitrarily. Furthermore, by using a plurality of image sensors 15, the SN ratio (signal to noise ratio) can be improved and higher quality images can be provided.

(Configuration of color separation element)
FIG. 2 is a schematic diagram showing a first configuration example of the color separation element 14.

In configuration example 1, when visible light enters the color separation element 14 from the left in the figure, the visible light is divided into red light, green light, and blue light by three dielectric mirrors 16R, 16G, and 16B that reflect each wavelength of RGB. (RGB). In this example, red light R is reflected in the positive x-axis direction, blue light B is reflected in the negative x-axis direction, and green light G is reflected in the z-axis direction. The dielectric mirrors 16R, 16G, and 16B allow γ-rays that are not reflected to travel straight, and the radiation resistance of the imaging system 1 is further improved by preventing radiation from directly entering the imaging sensor 15. Note that, in order to simplify the configuration, the dielectric mirror 16G that reflects the green light may be eliminated, and the green light G may be allowed to travel straight as shown in FIG.

The image sensor 15 receives each of the red light, green light, and blue light reflected by the color separation element 14 . In the illustrated color separation element 14, the red light R and the blue light B are reflected twice, but the green light is reflected only once, so the green image taken by the green image sensor 15 is horizontally reversed. The image will be Therefore, the green image requires electrical left-right inversion processing in the image processing section 20. More specifically, in signal processing in the image processing unit 20, which will be described later, the column numbers of pixels on the memory schematically shown in FIG. 13 are horizontally reversed only for the green image.

A detailed study of the radiation deterioration of conventional color filters revealed that color filters undergo browning, resulting in a decrease in visible light transmittance. After intensively investigating the cause of browning caused by radiation irradiation, the inventors of the present invention came to the conclusion that it is due to the decomposition of organic substances contained in color filters due to irradiation with light with high photon energy such as gamma rays. .

Generally, the bond energy between carbons that form the skeleton of organic substances is about 4 eV (electron volt) for a single bond and about 6 eV for a double bond, so light with a wavelength of 20 nm or less, that is, a photon energy of 60 eV or more, is When irradiated, the bonds are destroyed. Therefore, when an organic substance is irradiated with radiation (generally, a wavelength of 20 nm or less, that is, a photon energy of 60 eV or more), the organic substance is decomposed and browning occurs.

This kind of browning can occur even when using a color filter whose main constituent material is an inorganic material, even if there is residual organic matter from the chemicals used in the lithography process used to pattern the color filter for each color. It can occur. This is why conventional color filters deteriorate when exposed to radiation.

Based on such consideration, in the embodiment of the present invention, a color separation element 14 containing no organic matter, that is, a color separation element 14 made of an inorganic material, was adopted.

Furthermore, in order to solve the problem of residual chemicals in the patterning process of each color of the filter, it is preferable to use a color separation element that does not use a patterning process.

FIG. 3 is a schematic diagram showing a second configuration example of the color separation element 14.

In configuration example 2, the color separation element 14 uses a filter made of an inorganic material, in particular, a half mirror 17 and a color filter 18 that transmits light in a desired wavelength range.

The half mirror 17 is a mirror that reflects a certain amount of light and transmits a certain amount of light without having wavelength selectivity in the visible wavelength range.

The incident light that has passed through the lens optical system is divided by the half mirror 17 into reflected light and transmitted light. A color filter 18 is placed in the path of the reflected light, and the image sensor 15 captures an image of the light transmitted through the color filter 18.

Another image sensor 15 is arranged on the path of the transmitted light to capture an image of the transmitted light.

In this embodiment, the color filter 18 is made of an inorganic material and transmits a red region. For example, by including a metal oxide in a glass material, a filter that transmits only red wavelengths can be constructed.

In configuration example 2, it is preferable to use a half mirror 17 made of a laminated dielectric film. However, as long as it functions as a half mirror, it is not limited to a half mirror made of laminated dielectric films.

In configuration example 2, the transmitted light of the half mirror 17 includes all colors, so the acquired image is a black and white image. On the other hand, the light reflected by the half mirror 17 passes through the red color filter, resulting in a red image. By superimposing and displaying the two images, it is possible to obtain an image in which the red part of the subject is colored red in the black and white image.

In configuration example 2, since an image is obtained by combining a monochrome image and a color image of a specific color, it is possible to capture an image in which an object of a specific color is highlighted.

Further, a color image can be obtained by photographing a red image, a green image, and a blue image using a plurality of half mirrors 17 and combining these images.

Furthermore, in the configuration shown in FIG. 3A, the reflected light is reflected by the half mirror 17 an odd number of times, resulting in an image that is horizontally inverted. Therefore, the image acquired from the reflected light may be subjected to electrical left/right inversion processing in the image processing section 20 and then combined with the transmitted light. In the horizontal reversal process, as described above, in the signal processing in the image processing unit 20, it is preferable to horizontally reverse the column numbers of pixels on the memory schematically shown in FIG. 13 only for the green image.

In the configuration shown in FIG. 3(B), a reflection plate 19 is provided at the rear stage of the half mirror 17, and the reflected light is also reflected an even number of times, thereby preventing horizontal reversal. If this configuration is used, horizontal inversion image processing is not necessary, so the processing circuit of the image processing section 20 can be simplified.

(Configuration of sensor element 13)
FIG. 4 is a schematic diagram showing the configuration of the sensor element 13.

In FIG. 4, four pixels 130 are shown for ease of explanation. The actual sensor element 13 has a larger number of pixels, typically about 100 to 2000 rows and 100 to 4000 columns.

Two horizontal wires and one vertical wire are connected to each pixel.

One of the horizontal wirings is a charge scanning line 135 for charging, and has a function of charging the light receiving element 131 of the pixel 130 as described later. Another horizontal wiring is a read scanning line (Read scanning line) 136 that specifies signal read timing. The charging scan line 135 is connected to the charging address terminal (“CA” in the figure) of each pixel 130. The readout scanning line 136 is connected to the readout address terminal (“RA” in the figure) of each pixel 130. The number of charge scanning lines 135 and readout scanning lines 136 is equal to the number of rows of each pixel 130.

The charging scanning line 135 is connected to a charging scanning circuit (Charge scanning circuit) 138. The read scanning line 136 is connected to a read scanning circuit 139 (Read scanning circuit). The charging scanning circuit 138 and the reading scanning circuit 139 output appropriate voltage waveforms to scan each pixel 130. This scanning method will be explained in detail later.

The vertical wiring is a data line 137. A data line 137 is wired to each pixel 130.

The data line 137 is connected to the data output terminal (“D” in the figure) of each pixel 130. The data line 137 has a function of reading a signal detected by the light receiving element 131 in the pixel 130. The data line 137 is connected to the horizontal scanning circuit 140 and sequentially reads out signals detected by the light receiving elements 131 in each pixel 130 and transfers them to the transmitter/receiver 12 .

(Pixel configuration)
FIG. 5 is a schematic diagram showing the configuration of each pixel 130.

Each pixel 130 has a light receiving element 131, a storage capacitor 132, a charging transistor (Charge transistor) 133, and a threshold value determination circuit 134.

In the drawings representing circuit diagrams described herein, a downward-pointing white arrow indicates a connection to ground potential. Here, the ground potential means a reference potential within the sensor element 13, and does not have to match the ground potential of the signal processing section. If necessary, a bias potential may be applied to the reference potential (ground potential) within the sensor element 13 with respect to the ground potential of the signal processing section.

In this embodiment, a silicon photodiode is preferably used as the light receiving element 131, and a silicon carbide photodiode may also be used.

The storage capacitor 132 may be provided independently of the light receiving element 131, or may utilize the junction capacitance (parasitic capacitance) of the light receiving element 131.

When a photodiode is used as the light receiving element 131, the equivalent circuit of the junction capacitance of the light receiving element 131 is the same as the holding capacitor 132 in FIG. Therefore, if the junction capacitance of the light-receiving element 131 has sufficient capacity as the holding capacitor 132, instead of providing the holding capacitor 132 separately from the light-receiving element 131, the junction capacitor can have the function of the holding capacitor 132. good. In this specification, the holding capacitor 132 includes the junction capacitance (parasitic capacitance) of the light receiving element 131 as described above.

That is, in this specification, the storage capacitor 132 also includes the junction capacitance of the light receiving element 131. The effects of the present invention can also be obtained when the holding capacitor 132 is replaced by the junction capacitor of the light receiving element 131.

A method of detecting external light in each pixel 130 will be described using FIG. When an appropriate voltage is applied to the charging scanning line 135 to turn the charging transistor 133 on (ie, conductive), the light receiving element 131 and the holding capacitor 132 are charged to the charging voltage Vb0. Note that the charging transistor 133 may be a bipolar transistor or a MOSFET.

In this state, when the light receiving element 131 is not irradiated with light, the terminal voltage of the holding capacitor 132 is held. On the other hand, when the light-receiving element 131 is irradiated with light, the light-receiving element 131 becomes conductive, so that the charge of the storage capacitor 132 leaks out little by little, so that the terminal voltage of the storage capacitor 132 decreases.

(Threshold value determination circuit 134)
A terminal of the holding capacitor 132 is connected to an input terminal IN of the threshold value determination circuit 134.

The threshold determination circuit 134 outputs a signal 1 from the output terminal O when the terminal voltage of the holding capacitor 132 is smaller than a preset voltage threshold Vth, and outputs a signal 0 from the output terminal O when it is larger than the voltage threshold Vth. Output. In other words, when the brightness of the external object exceeds the predetermined brightness threshold Bth, the pixel 130 at the corresponding position has a voltage of the storage capacitor 132 that decreases due to the leakage current of the light-receiving element 131 and becomes smaller than Vth. The circuit 134 outputs 1 as an output signal. On the other hand, when the brightness of the subject is lower than the brightness threshold Bth, the voltage of the storage capacitor 132 of the pixel 130 at the corresponding position is higher than Vth, so the threshold value determination circuit 134 outputs 0 as an output signal.

Note that the output signal 1 means the signal state 1 of the logic circuit. For example, a high voltage state (High level) is a signal "1", and a low voltage state (Low level) is a signal "0". On the contrary, the Low level may be the signal "1" and the High level may be the signal "0". Alternatively, a current level or the like may be used instead of a voltage level. In this embodiment, the signal "1" corresponds to the high level of the voltage.

In this way, a signal "1" is output at the pixel 130 corresponding to a location where the luminance of the subject is equal to or higher than the luminance threshold Bth, and a signal "0" is output at a pixel 130 corresponding to a location where the luminance is equal to or lower than the luminance threshold Bth. That is, a binary image based on the brightness threshold Bth can be obtained.

Since a binary signal flows through each data line 137, the changeover switch 141 may be a logic circuit.

(Output impedance of threshold value determination circuit 134)
The threshold value determination circuit 134 has a read enable terminal RE (Read Enable). Read enable terminal RE is connected to read scan line 136. During the period in which the enabling signal is input to the read enabling terminal RE (read valid period), a signal "0" or "1" is output from the output terminal O according to the above-described operation.

During a period in which an enabling signal is not input to the read enabling terminal RE (read invalid period), the output terminal O transitions to a higher impedance state. In this way, by making the output impedance of the output terminal O high during the readout invalid period, even if a plurality of pixels 130 are connected to the data line 137, the output of the threshold value determination circuit 134 of the selected pixel 130 is It becomes possible to extract the signal.

(Example of implementation of threshold value judgment circuit 134)
FIG. 6 is a circuit diagram showing the threshold value determination circuit 134 of this embodiment.

The threshold value determination circuit 134 of this embodiment includes a transistor 1 (Tr1) that is a PNP type transistor, a transistor 2 (Tr2) that is an NPN type transistor, and a resistor (R). The input terminal of the threshold value determination circuit 134 is connected to the base of the transistor 2 (Tr2). When the input terminal of the threshold determination circuit 134 is higher than the threshold voltage Vth of the transistor 2 (Tr2), the collector of the transistor 2 (Tr2) is maintained (latched) at the power supply voltage Vcc. The collector of Tr2 becomes the output terminal of the threshold value determination circuit 134.

The threshold determination circuit 134 used in this embodiment employs a latch circuit, and the output signal maintains the High level or Low level during the period when the power supply voltage Vcc is applied. In this way, by using a latch circuit for the threshold determination circuit 134, there is an effect that malfunctions can be reduced.

When the voltage at the RE terminal in FIG. 6 is set to a low level, the two transistors Tr1 and Tr2 become non-conductive, so the output impedance of the output terminal O becomes a high impedance state.

FIG. 7 is a circuit diagram showing another example of the threshold determination circuit 134.

In the threshold determination circuit 134 shown in FIG. 7, the operations of the two transistors Tr1 and Tr2 are the same as in FIG. 6, and a third transistor, the read transistor Tr3, is added. The read transistor Tr3 is turned on only during the period when the read enable pulse is applied, and a signal voltage is output to the data line 137. During the read invalid period, the read transistor Tr3 is in the OFF state, so the output impedance of the output terminal O of the threshold value determination circuit 134 becomes higher than that of the circuit shown in FIG.

It is more desirable to further increase the output impedance of the threshold determination circuit 134 of the unselected pixel 130 when the number of scanning lines is large. The reason for this is that each data line 137 is connected to a threshold value judgment circuit 134 for the number of scanning lines, so the higher the output impedance of the threshold value judgment circuit 134 for non-selected pixels, the higher the number of scanning lines, even if the number of scanning lines is large. This is because the impedance caused by the threshold value determination circuit 134 for non-selected pixels can be maintained at a sufficiently high level.

Note that the circuits shown in FIGS. 6 and 7 are examples of the threshold value determination circuit 134, and the effects of the present invention can be obtained even if other circuits are used as long as they satisfy the characteristics of the threshold value determination circuit 134 described above. Needless to say.

(Comparison with comparative example)
Next, a comparison with a comparative example will be made. FIG. 8 is a schematic diagram showing the configuration of a pixel 530 of a sensor element of a comparative example.

FIG. 8 is an example of a CMOS sensor (complementary MOS field effect transistor type sensor), and shows a system of an imaging device for a consumer camera.

The sensor element shown in FIG. 8 includes a light receiving element 531, a storage capacitor 532, and a charging transistor (Charge transistor) FET1 connected to a charging scanning line 535. A pixel amplifier amplifies the voltage of a holding capacitor 532 provided in parallel with the light receiving element 531 charged by the charging scanning line 535, and outputs a voltage value V2 proportional to the accumulated charge of the holding capacitor 532 as an analog signal. A CMOS type FET (field effect transistor) is used for the pixel amplifier. FET2 and FET3 in FIG. 8 constitute a pixel amplifier. In this pixel amplifier, the FET 2 operates as a source follower circuit, and performs charge amplification by converting the charge applied to the gate of the FET 2 into a low impedance voltage signal.

When an appropriate voltage is applied to the readout scanning line 536 and the FET 3 is turned on, an analog signal voltage, which is an output signal of the pixel amplifier, is outputted to the data line 537, and sequentially outputted by a horizontal scanning circuit (not shown). .

In the comparative example, since a voltage signal corresponding to the brightness level of the subject is output in an analog manner, an image with gradation can be obtained.

However, the CMOS pixel amplifier used in the circuit inside the pixel in FIG. 8 has low resistance to radiation irradiation, so there is a problem that the sensor element is likely to deteriorate when used in a harsh environment such as the presence of radiation. In contrast, the present invention uses elements that are more resistant to radiation irradiation than CMOS amplifiers, and therefore has the effect of suppressing deterioration of characteristics in a radiation environment.

In particular, it is known that bipolar transistors have higher radiation resistance than CMOS FETs, as shown in FIG. 6, which is the present embodiment of the present invention, and it is more preferable to use bipolar transistors.

Further, in the above-mentioned comparative example, the changeover switch and the transmitting/receiving circuit connected to the data line 537 need to handle analog signals. In contrast, in the present invention, the signals processed by the changeover switch 141 and the transmitting/receiving circuit 142 are binary signals, so the circuit configuration is simpler than in the comparative example.

(gradation of binary image)
As described above, the image obtained by the pixel 130 of this embodiment is a binary image in which the subject is binarized using a certain brightness threshold.

A method for constructing a gradation image from a binary image will be described below. In this embodiment, binary images are acquired using a plurality of brightness threshold values Bth[n], and each is referred to as a sub-image SIm[n] (Sub-Image). Here, the subscript n is a number for distinguishing between the brightness threshold and the sub-image, and n=1, 2, . . . .

(Means for changing the brightness threshold)
A method for changing the brightness threshold Bth[n] will be described. In the present invention, it is detected whether the voltage V1 of the storage capacitor 132 exceeds a threshold value. The voltage V1 of the storage capacitor 132 is expressed by the following equation.

Here, Vb0 is the charging voltage of the light receiving element 131, ΔV is the voltage reduction amount due to the photocurrent flowing through the light receiving element 131, J is the current density of the photocurrent flowing through the light receiving element 131, S is the light receiving area of the light receiving element 131, and Δt is The exposure time of the light receiving element 131 and C are the capacitance of the storage capacitor 132. In this embodiment, a photodiode is used as the light receiving element 131.

The following method can be used to change the brightness threshold Bth of the pixel 130.
(A) Changing the exposure time Δt.
(B) Changing the area S of the light receiving element 131.
(C) Changing the charging voltage Vb0 to the light receiving element 131.

In the present invention, the luminance threshold value may be changed using any of the methods (A), (B), and (C). Furthermore, these plural methods may be combined. Furthermore, the brightness threshold value may be changed using methods other than (A) to (C).

That is, the imaging system 1 of this embodiment includes a luminance threshold value changing means. The brightness threshold changing means includes (A) changing the exposure time Δt for each sub-image, (B) having a plurality of sub-pixels with different light-receiving areas of the light-receiving element 131, and (C) charging voltage Vb0 applied to the light-receiving element 131. There are means such as changing the value every predetermined period, and furthermore, means such as combining these (A) to (C).

Further, the above-mentioned luminance threshold value changing means is typically provided in the sensor section 10. This is because it is easier to implement. However, it may be provided at a location other than the sensor section.

(Change the brightness threshold depending on the exposure time)
In this embodiment, the brightness threshold value is changed by changing the exposure time.

FIG. 9 is a timing diagram schematically showing the readout sequence from the pixel 130 in the sensor element 13 of this embodiment. In this figure, the horizontal axis indicates time, and the vertical axis indicates the scanning line position of pixel 130 within sensor element 13. The fact that the diagram representing the scanning timing is a diagonal straight line as shown in FIG. 9 indicates that each scanning line is sequentially scanned as a first scanning line, a second scanning line, and so on.

One field is the time to acquire one image, and is typically 1/30 second to 1/60 second. In this example, it was set to 1/30 second (33.3 ms). One field is divided into four subfields. One sub-image is acquired in one sub-field. Although FIG. 9 shows an example of acquiring four sub-images, it is of course possible to divide the image into more sub-fields. The nth subfield will be denoted as SF[n].

The read sequence within the subfield will be explained using the first subfield SF[1] as an example. When a charging scanning pulse is applied to the charging scanning line 135 in the first row, the light receiving element 131 in the pixel 130 in the first row is charged to the charging voltage Vb0. From this point on, charging scanning pulses are applied to the charging scanning lines 135 in the second and subsequent rows.

When a readout scan pulse is applied to the readout scan line 136 in the first row after the time Δtex has elapsed, the threshold determination circuit 134 of each pixel 130 operates, and the output signal 1 is Alternatively, 0 is output from the threshold value determination circuit 134. Thereafter, readout scanning pulses are applied to the readout scanning lines 136 in the second and subsequent rows. In this way, the time Δtex from the application of the charge scan pulse to the application of the read scan pulse corresponds to the exposure time.

In this way, the scanning of the first subfield SF[1] is completed, and the first subimage SIm[1] is obtained. Next, the charging scanning line 135 and the reading scanning line 136 are similarly scanned in the second subfield SF[2]. However, the elapsed time Δtex between the charging scan line 135 and the read scan line 136 is made longer than SF[1]. Next, the elapsed time Δtex between the charging scanning line 135 and the reading scanning line 136 is made longer than SF[2], and the charging scanning line 135 and the reading scanning line 136 are similarly set in the third subfield SF[3]. scan. Furthermore, the elapsed time Δtex between the charging scanning line 135 and the reading scanning line 136 is made longer than SF[3], and the charging scanning line 135 and the reading scanning line 136 are similarly set in the fourth subfield SF[4]. Perform scanning. In this way, sub-images are obtained by changing the exposure time Δtex for each sub-field.

As can be seen from equation (1), when the exposure time Δtex is changed, the brightness threshold corresponding to the voltage threshold of the threshold determination circuit 134 changes. In the case of the same subject, the longer the exposure time Δtex, the lower the voltage of the storage capacitor 132, so that even lower luminance (dark luminance) exceeds the voltage threshold of the threshold determination circuit 134 and provides an output signal of "1". In this way, multiple sub-images with different brightness thresholds can be obtained.

(Configuration of gradation image)
The plurality of acquired sub-images are transmitted from the sensor section 10 to the image processing section 20, as shown in FIG. In the image processing unit 20, a gradation image is constructed from a plurality of sub-images having different brightness threshold values in the following manner.

FIG. 10 is a schematic diagram showing a method of configuring a gradation image. FIG. 10 shows an example in which a four-tone image is constructed from four sub-images.

FIG. 10(A) shows four sub-images. Each sub-image is a binary image showing the image of the subject; the first is a sub-image with a brightness threshold of 8, the second is a sub-image with a brightness threshold of 4, and the third is a sub-image with a brightness threshold of 2. The fourth image is a sub-image with a brightness threshold of 1. The hatched area in the figure is the pixel area of the output signal "1".

The higher the brightness threshold, the smaller the area of the output signal "1", that is, the area exceeding the brightness threshold. Furthermore, the area of the output signal "1" in the sub-image with a low luminance threshold includes the area of the output signal "1" of the sub-image with a higher luminance threshold.

The image data of the n-th sub-image SIm[n] is assumed to be S[n]. Since the sub-image is a binary image, its image data S[n] is two-dimensional data in which each pixel 130 is assigned a signal “1” or “0”. Then, consider a case where the smaller n is, the higher the brightness threshold Bth[n] is.

FIG. 11 is a logical table showing the process of constructing a gradation image. A gradation image GS[n] is constructed from image data S[n] and S[n-1] of sub-images with adjacent luminance threshold values. A gradation luminance corresponding to the luminance threshold Bth[n] is given to the pixel 130 whose column of GS[n] is set to "1". As shown in FIG. 11, the gradation Bth[n] is given to the pixel 130 where S[n] is "1" and S[n-1] is "0". A gradation image GS[n] can be generated by such signal processing.

The logical equation for the signal processing in FIG. 11 is given by the following equation.

The signal processing in FIG. 11 can be implemented with the circuit in FIG. 12. Whether or not the pixel 130 has the n-th gradation GS[n] is determined by ANDing the signal obtained by logically inverting the sub-image data S[n-1] using an inverter and S[n]. Get results.

When this signal processing is performed for n=1 to 4, each pixel 130 is assigned a brightness gradation of 0 or one of GS[1] to GS[4], and a gradation image can be generated. In this way, signal processing between binary sub-images has the advantage that a gradation image can be generated with a simple processing circuit. Of course, the signal processing in the logic table of FIG. 11 may be performed mathematically using a computer or a CPU (central processing unit).

Another example in which a gradation image is generated from a plurality of sub-images having different threshold values will be described using FIGS. 13 and 14.

FIG. 13 is a schematic diagram showing a state in which image data S[n] of sub-image SIm[n] is stored on the memory. In the figure, (k, m) corresponds to the pixel 130 located at row k and column m. As shown in FIG. 13, a plurality of sub-images S[n] are arranged on the memory so that the pixels 130 correspond to each other, and the gradation of each pixel 130 is calculated from there by signal processing of each pixel 130.

The method for calculating the gradation image uses the truth table shown in FIG. Depending on the values of S[1] to S[4], an output GS of gradation level is obtained. In the truth table of FIG. 14, "X" indicates that it may be either "1" or "0". Further, Bth[n] in the output GS column means the brightness threshold of the sub-image S[n].

Processing based on the truth table of FIG. 14 can be easily implemented using an FPGA (Field Programmable Gate Array). Alternatively, it may be implemented by arithmetic processing by a CPU.

The gradation images for each color generated as described above are sent to the image processing section 20 provided within the image processing section. The image processing unit 20 receives three image signals of a red (R) image, a green (G) image, and a blue (B) image, synthesizes them at an appropriate ratio, and outputs a color image.

The gradation image generated as described above is displayed on the display device 21 connected to the image processing section 20. Further, the gradation image is stored in an image recording section 22 connected to the image processing section 20 as necessary. Of course, the image recording section 22 may be incorporated into the image processing section 20.

(Advantages of separating the image processing unit 20)
In this embodiment, as shown in FIG. 1, the image processing section 20 and the sensor section 10 are separated and connected by a cable 30. Such a separate configuration has the effect of improving radiation resistance.

The sensor unit 10 is installed in a high-dose radiation environment, and the image processing unit 20 is installed in a low-dose environment. In FIG. 1, the area on the left side (area A) separated by the wall 40 is a high-dose environment, and the area on the right side of the wall 40 (area B) is a low-dose environment. This is more preferable because the image processing section 20 can be configured with a normal CPU and circuit components that have low radiation resistance.

As a method of further increasing the radiation resistance of the imaging system 1 of this embodiment, as shown in FIG. 1, the image processing section 20 may be surrounded by a radiation shielding material 25 such as a lead plate. Unlike the sensor unit 10, the image processing unit 20 does not lose its function even if it is surrounded by a member that does not transmit light. By configuring the image processing section 20 and the sensor section 10 separately in this way, there is an effect that radiation resistance is further improved.

<Example 2>
An imaging system 1 according to a second embodiment of the present invention will be described using FIGS. 15 and 16.

The imaging system 1 of this embodiment uses the sensor element 13 in which sub-pixels 1300 having different light-receiving areas are provided within the pixel 130 in order to obtain sub-images with different brightness thresholds. In the second embodiment, explanations of structures having the same functions as those of the first embodiment described above will be omitted, and mainly different structures will be explained.

FIG. 15 is a diagram showing the configuration of the sensor element 13 of the imaging system 1 of this embodiment, and shows four pixels 130 in the sensor element 13. In the figure, a portion surrounded by a chain line constitutes one pixel 130. One pixel 130 is composed of four sub-pixels 1300, and the areas of the four sub-pixels 1300 are different from each other.

The configuration of each sub-pixel 1300 is the same as that in FIG. 5. However, the light-receiving area of the light-receiving element 131 of the sub-pixel 1300 differs depending on the sub-pixel 1300. As shown in Equation (1), when trying to obtain a certain predetermined voltage reduction amount ΔV, the smaller the light receiving area is, the larger the photocurrent density J is required to obtain the predetermined ΔV. Since the photocurrent density J corresponds to the brightness of the observation target, the smaller the light receiving area, the larger the brightness threshold Bth becomes. The numbers written in each pixel 130 in FIG. 15 are relative values of the brightness threshold Bth of each sub-pixel 1300. The brightness threshold changes depending on the light-receiving area of the light-receiving element 131.

Furthermore, as can be seen from FIG. 15, one pixel 130 requires two charging scanning lines 135 and two reading scanning lines 136, so the number of scanning lines is twice that of the first embodiment. In this embodiment, a configuration in which the storage capacitor 132 is provided separately from the light receiving element 131 is preferable. The reason for this is that the magnitude of the junction capacitance of the light receiving element 131 may be approximately proportional to the area of the light receiving element 131. As can be seen from equation (1), when the size C of the capacitance is proportional to the area S, the brightness threshold value remains unchanged.

As shown in FIG. 1, the method of acquiring a color image is the same as in the first embodiment by providing a color separation element 14 that separates visible light into RGB in front of the sensor element 13.

FIG. 16 is a timing diagram schematically showing the readout sequence from the pixel 130 in the sensor element 13 of this embodiment. Since the brightness threshold is changed depending on the area of the sub-pixel 1300, four sub-images with different brightness thresholds can be obtained by scanning only once in one field period. In the case of the same number of pixels, the number of scanning lines is twice that of the first embodiment, but the number of scans can be reduced because four scans per subfield become one scan.

The method of generating a gradation image from a sub-image is the same as in the first embodiment.

(Sub-pixel arrangement pattern)
Furthermore, in the configuration of the pixel 130 in FIG. 15, the direction in which the data line 137 is taken out is reversed between the sub-pixels 1300, so that the distance between the light-receiving elements 131 of the sub-pixels 1300 is shortened. For example, in the sub-pixel 1300 with a threshold of 8, the data line 137 extends to the left, and in the sub-pixel 1300 with a threshold of 2, the data line 137 extends to the right. By employing such an arrangement pattern, the light receiving elements 131 between the sub-pixels 1300 are brought close to each other.

In this way, by adopting the arrangement of the sub-pixels 1300 in which the extraction direction of the data line 137 is reversed between the sub-pixels 1300, even if the brightness change of the observation target is spatially minute, the gradation is not disturbed. This makes it difficult for moiré to occur, resulting in the effect of reducing the so-called moiré phenomenon.

<Example 3>
An imaging system 1 according to a third embodiment of the present invention will be described using FIGS. 17 and 18.

In the imaging system 1 of this embodiment, the charging voltage Vb0 of the light receiving element 131 is changed in order to acquire sub-images with different brightness threshold values. In the third embodiment, explanations of structures having the same functions as those of the above-described embodiments will be omitted, and mainly different structures will be explained.

FIG. 17 is a schematic diagram showing the relationship between the brightness, that is, the amount of light incident on the light receiving element 131, and the terminal voltage.

This figure shows the characteristics when the charging voltage Vb0 is changed to four values of Vb01 to Vb04.

As can be seen from equation (1), when the brightness is zero, ΔV=0, so the terminal voltage V1 of the holding capacitor 132 is approximately equal to the charging voltage Vb0. When light is incident and a photocurrent flows, the voltage decreases by ΔV according to equation (1), resulting in the characteristics shown in FIG. 17.

As can be seen from FIG. 17, when the charging voltage Vb0 is changed to four types of values Vb01 to Vb04, the brightness at which the terminal voltage V1 of the storage capacitor 132 becomes equal to the predetermined threshold value Vth changes. That is, the brightness threshold Bth changes. In this embodiment, this characteristic is utilized to obtain a plurality of sub-images with different brightness thresholds.

The configuration of the sensor element 13 used in this example is the same as that shown in FIG.

FIG. 18 is a schematic diagram showing the relationship between the readout sequence from each pixel 130 and the charging voltage Vb0 in this example.

One field is divided into four subfields SF[1] to SF[4]. In each subfield, charging scan pulses are sequentially scanned (timings indicated by dotted lines in the figure), and readout scan pulses are sequentially scanned after the exposure time Δtex has elapsed. The feature of this embodiment is that the charging voltage Vb0 is changed for each subfield. This makes it possible to obtain sub-images with different brightness thresholds.

The method of generating a gradation image from a sub-image is the same as in the first embodiment.

<Example 4>
An imaging system 1 according to a fourth embodiment of the present invention will be described. The present embodiment is a hybrid type that uses a plurality of methods for changing the brightness threshold value, as described in equation (1). This has the effect of making it possible to obtain an image with a higher number of gradations. In the fourth embodiment, explanations of structures having the same functions as those of the previous embodiments will be omitted, and mainly different structures will be explained.

In this embodiment, the configuration of the sensor element 13 shown in FIG. 15 is used, and the charging voltage is changed for each subfield in the scanning sequence shown in FIG. 18. As an example, if a sensor element 13 made up of four sub-pixels 1300 is used as shown in FIG. 15, a four-tone image can be obtained. Then, as shown in FIG. 18, when sub-images are obtained by changing the charging voltage Vb0 in four stages, a four-gradation image is obtained. As a result, a 4×4 16-gradation image can be generated.

<Example 5>
An imaging system 1 according to a fifth embodiment of the present invention will be described using FIG. 19. The present embodiment is a hybrid type that uses a plurality of methods for changing the brightness threshold value, as described in equation (1). In this embodiment, a change in exposure time and a change in charging voltage Vb0 are combined. In the fifth embodiment, explanations of structures having the same functions as those of the previous embodiments will be omitted, and mainly different structures will be explained.

As shown in FIG. 19, the first field includes four subfields SF[1] to SF[4] with different exposure times. Then, in the second field, images are acquired in four subfields in which the charging voltage Vb0 is changed and the exposure time is changed. In this way, eight sub-images with different brightness thresholds are obtained. An 8-gradation image can be generated from this sub-image by the method described above.

Although the description will be omitted, as a third hybrid mode, sub-pixels 1300 having different pixel areas and changes in exposure time may be combined.

<Example 6>
An imaging system 1 according to a sixth embodiment of the present invention will be described. The imaging system 1 of this embodiment can operate in two imaging modes: normal mode and high gradation mode. In the sixth embodiment, explanations of structures having the same functions as those of the previous embodiments will be omitted, and mainly different structures will be explained.

The imaging system 1 of this embodiment obtains a four-gradation image using the drive timing shown in FIG. 9 when real-time performance is required. This is called normal mode. On the other hand, if an image with higher gradation is required, a transition is made to the high gradation mode. In the high gradation mode, the drive timing shown in FIG. 19 is used. That is, one field is divided into subfields with different exposure times, and images are captured over n field periods while changing the charging voltage Vb0 for each field. Although FIG. 19 shows the case where n=2, n=8 may be used. When n=8, the time required for imaging increases eight times, but a gradation image with 4×8=32 gradations can be generated.

Note that although the case where the gradation image in the normal mode has 4 gradations is shown, this is just an example, and the normal mode may have, for example, 16 gradations.

The key point of this embodiment is that the number of sub-images used to generate a gradation image is greater in the high gradation mode than in the normal mode. Thereby, in the high gradation mode, a high gradation image can be captured.

<Example 7>
With reference to FIG. 20, a robot system will be described as an example of an imaging system application device according to a seventh embodiment of the present invention.

The application device of this example is a robot system that can be used even under harsh environments such as high-level radiation environments. In the seventh embodiment, explanations of structures having the same functions as those of the previous embodiments will be omitted, and mainly different structures will be explained.

The robot system of this embodiment includes a robot 100 and a robot control device 200. The robot 100 includes a robot stand 101 to which tires 102 are attached, an arm 110, and a sensor section 10. The arm 110 has a joint 111 and is capable of movements such as rotation and bending. Although not shown, a mechanism that allows the arm 110 to extend and contract may be provided. The sensor section 10 has the sensor structure of any of the embodiments described above.

The robot control device 200 is a control device that can operate the robot 100 by remote control. The robot control device 200 includes an image processing section 20 and a robot control section 210. The sensor section 10 and the image processing section 20 are connected by a cable 30 and send and receive signals to and from each other. The robot 100 and the robot control unit 210 are connected by a cable 31, and transmit and receive power supply and control signals for driving the robot 100. The image processing section 20 and the robot control section 210 transmit and receive signals as necessary.

In this embodiment, since the sensor unit 10 has excellent radiation resistance, the robot 100 can capture images even in a high-level radiation environment. In particular, in this embodiment, the robot 100 (sensor unit 10) is placed in area A (left side of wall 40 in FIG. 20) which is a high-level radiation environment, and placed in area B (right side of wall 40) which is a low radiation environment. An image processing section 20 is arranged. Thereby, the image processing section 20 can be operated in a low radiation environment.

Furthermore, the sensor element 13 constituting the sensor unit 10 of this embodiment is smaller and lighter in size than when a vacuum tube type image sensor such as an image pickup tube is used. Therefore, the robot 100 can be installed in a narrow place, and even if a plurality of sensor units 10 are installed in the robot 100, an increase in weight can be suppressed, and the influence on the installation place can be reduced. This makes it possible to grasp the target object 300 more accurately, and allows the robot 100 to perform sophisticated operations.

Further, in the robot system of this embodiment, it is preferable to adopt a configuration in which the high gradation mode and the normal mode can be switched, as described in the sixth embodiment, as necessary. When the robot 100 moves or when the object 300 is operated by the arm 110, the sensor unit 10 operates in the normal mode. Thereby, images of the target object 300 can be acquired at high speed, so that high-speed feedback can be provided to the robot control unit 210. On the other hand, when photographing an image of the object 300 and its surroundings for recording purposes, the sensor section 10 is operated in a high gradation mode. This makes it possible to record high-quality images with a high number of gradations.

<Example 8>
An imaging system 1 according to an eighth embodiment of the present invention will be described using FIGS. 21 and 22.

In this embodiment, the threshold value determination circuit 134 is not provided within each pixel 130, but is provided for each data line 137. In the eighth embodiment, explanations of structures having the same functions as those of the previous embodiments will be omitted, and mainly different structures will be explained.

FIG. 21 is a schematic diagram showing the configuration of the pixel 130 of the sensor element 13 of this example.

A terminal of the storage capacitor 132 is connected to a data line 137 via a read transistor 143.

FIG. 22 is a schematic diagram showing the configuration of the sensor element 13 of the imaging system 1 of this embodiment, and shows four pixels 130 in the sensor element 13, but in reality, a larger number of pixels are arranged. .

Each data line 137 is connected to an input terminal IN of the threshold value determination circuit 134. An output terminal O of the threshold value determination circuit 134 is connected to the transmitting/receiving section 12 via a changeover switch 141.

The signal readout procedure in this embodiment will be explained. In this embodiment, scanning pulses are applied at the timing shown in FIG. When a charging scanning pulse is applied to the charging scanning line 135, the charging scanning pulse is applied to the CA terminal of the pixel (FIG. 21) on the selected scanning line, and the charging transistor 133 is turned on. Thereby, the light receiving element 131 is charged to the charging voltage Vb0. Thereafter, charging transistor 133 is turned off.

After a predetermined exposure time, when a readout scan pulse is applied to the readout scan line 136, the readout transistor 143 of the selected pixel is turned on. At this time, the readout transistors 143 of pixels on unselected scanning lines are in an OFF state. Therefore, the voltage of the storage capacitor 132 of the pixel on the selected scanning line is output to the data line 137.

At this point, a read pulse is output from the read pulse generator 144 shown in FIG. 22 and input to the RE terminal of the threshold determination circuit 134. Thereby, the output terminal O of the threshold value determination circuit 134 is latched to the signal "1" or "0" based on the magnitude relationship between the voltage of the data line 137 at the time of application of the read pulse and the predetermined threshold value.

During this period, the horizontal scanning pulses sequentially output from the horizontal scanning circuit 140 operate the changeover switch 141, and the signal voltage (“1” or “0”) of each data line 137 is transferred to the transmitting/receiving section 12. Since a binary signal flows through each data line 137 after the output of the threshold determination circuit 134, the changeover switch 141 may be a logic circuit.

In this way, binary sub-image data is obtained based on the voltage of the storage capacitor 132 of each pixel. As shown in FIG. 9, by changing the exposure time for each subfield, subimages with different brightness thresholds can be obtained. The method of generating a gradation image from a plurality of sub-images is the same as described above in the first embodiment.

In FIG. 21, a MOS FET is used as the readout transistor 143, but since the FET is operated in its saturation region, even if the gate voltage threshold of the FET changes slightly, the signal output to the data line 137 will not be affected. has little impact. Therefore, radiation resistance is improved compared to the case where a CMOS type amplifier is used.

According to this embodiment, the circuit within the pixel 130 can be simplified.

In this embodiment, the brightness threshold value is changed by changing the exposure time, but a configuration in which the charging voltage is changed (FIG. 18), a configuration in which the area of the light receiving element 131 is changed (FIG. 15), and a hybrid type that combines multiple methods are also available. (FIG. 19 etc.), a configuration in which a threshold value determination circuit 134 is provided for each data line 137 can be applied.

As described above, the imaging system 1 according to the embodiment of the present invention includes a sensor unit 10 and an image processing unit 20, and the sensor unit 10 includes a color separation element 14 that extracts light of a specific wavelength, and a color separation element 14 that extracts light of a specific wavelength. The image sensor 15 has a transmitting/receiving section 12 and a sensor element 13, and the sensor element 13 has a light receiving element 131 and a charging transistor 133 connected to each pixel 130. The sensor element 13 has one or more threshold value determination circuits 134 that determine whether the terminal voltage of the light receiving element 131 is equal to or higher than a predetermined threshold value, and the sensor element 13 has a plurality of The image processing unit 20 acquires the sub-images and processes the signals of the plurality of sub-images to generate a gradation image, so it has excellent environmental resistance and can withstand harsh environments such as high-level radiation environments. It is possible to provide an imaging device that is small and lightweight, can be used even with any computer, and captures images with at least one color.

Further, in the first embodiment, the color separation element 14 separates the incident light into three colors of light, and the sensor section 10 has a plurality of image pickup units for photographing the light transmitted through the color separation element 14. The imaging system 1 has a sensor 15 and generates a color image by combining images output from each imaging sensor 15, so it has excellent environmental resistance and can withstand harsh environments such as high-level radiation environments. It is possible to provide an imaging device that can be used even under the sun, is small and lightweight, and can take color images.

Further, in the first embodiment, since the color separation element 14 is made of an inorganic material, it is possible to suppress the occurrence of browning due to radiation or ultraviolet irradiation.

Further, in the first embodiment, since the color separation element 14 is a dielectric optical element, it has high hardness and is chemically stable, so that oxidation and deterioration are unlikely to occur and it can be used for a long period of time.

Furthermore, in the first embodiment, the color separation element 14 causes the transmitted light to travel in a direction different from that of the radiation, so that the radiation does not directly enter the imaging sensor 15, and the radiation resistance of the imaging system 1 can be improved.

Furthermore, in the first embodiment, since the sensor element 13 has a threshold value determination circuit 134 for each pixel 130, it can operate reliably even with a large number of scanning lines, and it is possible to prevent level changes due to long transmission of analog signals. The impact can be suppressed.

Further, since the sensor element 13 changes the luminance threshold by changing the exposure time of the light receiving element 131 for each sub-image, there is no need to provide a sub-pixel within the pixel, and the pixel configuration can be simplified.

Furthermore, in the second embodiment, each pixel 130 of the sensor element 13 includes a plurality of sub-pixels 1300 with different light-receiving areas of the light-receiving element 131, so one image can be acquired in one scan, and one pixel can be read out. You can make the time longer.

Furthermore, in the third embodiment, since the sensor element 13 changes the charging voltage applied to the light receiving element 131 every predetermined period, there is no need to provide a sub-pixel within the pixel, and the pixel configuration can be simplified. . Furthermore, by changing the voltage for each sub-pixel acquisition period, the brightness threshold of the sub-pixel can be changed. Further, by changing the voltage every cycle for acquiring a plurality of sub-pixels, it is possible to change the luminance threshold of a plurality of sub-pixels all at once.

In another embodiment, the sensor section 10 and the image processing section 20 are spatially separated and connected by wire or wirelessly, so that the imaging device can be used even under harsh environments such as high-level radiation environments. can be provided. Furthermore, an inexpensive and high-performance semiconductor element can be used in the image processing section 20.

Furthermore, in another embodiment, the image processing section 20 is surrounded by the radiation shielding material 25, so that it is possible to provide an imaging device that can be used even under harsh environments such as high-level radiation environments. Furthermore, an inexpensive and high-performance semiconductor element can be used in the image processing section 20.

Further, in another embodiment, the threshold value determination circuit 134 includes a bipolar transistor Tr2 to which the output voltage of the light receiving element 131 is input, so that radiation resistance performance can be improved.

In another embodiment, the imaging system 1 is operable in a normal mode and a high gradation mode, and the number of sub-images acquired to generate a gradation image in the high gradation mode is the same as that in the normal mode. Since the number of sub-images is larger than the number of sub-images acquired to generate a tone image, it is possible to obtain an image with priority given to either real-time performance or high image quality, depending on the purpose of image acquisition.

Note that the present invention is not limited to the embodiments described above, and includes various modifications and equivalent configurations within the scope of the appended claims. For example, the embodiments described above have been described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Further, a part of the configuration of one embodiment may be replaced with the configuration of another embodiment. Further, the configuration of one embodiment may be added to the configuration of another embodiment. Further, other configurations may be added, deleted, or replaced with a part of the configuration of each embodiment.

Further, each of the above-mentioned configurations, functions, processing units, processing means, etc. may be realized in part or in whole by hardware, for example by designing an integrated circuit, and a processor realizes each function. It may also be realized by software by interpreting and executing a program.

Information such as programs, tables, files, etc. that realize each function can be stored in storage devices such as memory, hard disk, SSD (Solid State Drive), or recording media such as IC cards, SD cards, DVDs, and BDs. can.

Furthermore, the control lines and information lines shown are those considered necessary for explanation, and do not necessarily show all the control lines and information lines necessary for implementation. In reality, almost all configurations can be considered interconnected.

1 Imaging system 10 Sensor section 11 Sensor control section 12 Transmission/reception section 13 Sensor element 14 Color separation element 15 Image sensor 16R, 16G, 16B Dielectric mirror 17 Half mirror 18 Color filter 19 Reflection plate 20 Image processing section 21 Display device 22 Image recording Part 25 Shielding materials 30, 31 Cable 100 Robot 101 Robot stand 102 Tire 110 Arm 111 Joint 130 Pixel 131 Light receiving element 132 Holding capacitor 133 Charging transistor 134 Threshold determination circuit 135 Charging scanning line 136 Readout scanning line 137 Data line 138 Charging scanning circuit 139 Readout scanning circuit 140 Horizontal scanning circuit 143 Readout transistor 144 Readout pulse generation section 200 Robot control device 210 Robot control section 300 Object 1300 Sub-pixel

Claims (11)

An imaging system comprising: a sensor unit installed in a high-dose environment where radiation is irradiated ; and an image processing unit installed in a low-dose environment separated from the high-dose environment by a wall ,
The sensor section includes a color separation element that extracts light of a specific wavelength, and an image sensor that photographs the light that has passed through the color separation element,
The image sensor includes a sensor element and a transmitter/receiver,
The sensor element is
Each pixel has a light receiving element and a charging transistor,
comprising one or more threshold value determination circuits for determining whether the terminal voltage of the light receiving element is equal to or higher than a predetermined threshold value;
Obtain multiple sub-images corresponding to different brightness thresholds,
The image processing unit is surrounded by a radiation shielding material, and processes the signals of the plurality of sub-images to generate a gradation image ,
The color separation element separates incident visible light into red light, green light, and blue light using a dielectric mirror, and causes the light of each color to travel in three orthogonal directions unlike the incident visible light. ,
The sensor section includes a plurality of image sensors that photograph the light transmitted through the color separation element,
The imaging system is characterized in that the imaging system generates a color image by combining images output from each of the imaging sensors . The imaging system according to claim 1,
An imaging system characterized in that the sensor element has the threshold value determination circuit for each pixel. The imaging system according to claim 1,
The imaging system is characterized in that the sensor element changes the brightness threshold by changing the exposure time of the light receiving element for each sub-image. The imaging system according to claim 1,
An imaging system characterized in that each pixel of the sensor element includes a plurality of sub-pixels having different light-receiving areas of the light-receiving element. The imaging system according to claim 1,
The imaging system is characterized in that the sensor element changes a charging voltage applied to the light receiving element every predetermined period. The imaging system according to claim 1,
An imaging system characterized in that the sensor section and the image processing section are spatially separated and connected by wire or wirelessly. The imaging system according to claim 1,
The imaging system is characterized in that the threshold determination circuit includes a bipolar transistor into which the output voltage of the light receiving element is input. The imaging system according to claim 1,
Operable in normal mode and high gradation mode,
An imaging system characterized in that the number of sub-images acquired to generate the gradation image in the high gradation mode is greater than the number of sub-images acquired to generate the gradation image in the normal mode. . An imaging system application device comprising the imaging system according to any one of claims 1 to 8. The imaging system application device according to claim 9,
a radiation-resistant device section having the sensor section;
An imaging system applied device comprising: a control device having the image processing section and a device control section that controls operations of the imaging system applied device. The imaging system application device according to claim 9,
a robot equipped with the sensor section;
An imaging system application device comprising: a control device having the image processing section and a robot control section that controls the operation of the robot.

Images