Camera system, control method for camera system, and program

Abstract

To provide a camera system capable of simultaneously acquiring a feature of a subject while detecting a concealed article.SOLUTION: A camera system includes: a radiation unit configured to radiate terahertz waves; a camera unit configured to acquire a first signal at a timing at which the radiation unit radiates the terahertz waves and acquiring a second signal different from the first signal at timing at which the radiation unit does not radiate the terahertz waves; and a signal processing unit configured to generate images from the first signal and second signal acquired by the camera unit. The camera unit or the signal processing unit acquires a difference between the first signal and second signal. The signal processing unit generates a first image from the difference between the first signal and second signal and generates a second image different from the first image from the second signal.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a camera system, a control method for a camera system, and a program. [Background technology]

[0002] In recent years, inspection technologies using terahertz waves have been proposed. Terahertz waves are generally defined as electromagnetic waves with frequencies between 30 GHz and 30 THz.

[0003] Patent Document 1 proposes a camera system that is arranged to form part of a surveillance system for facilities such as railways and acquires images formed with terahertz waves in order to detect dangerous objects such as knives brought onto railway vehicles. Specifically, it discloses a configuration in which an illumination unit that irradiates terahertz waves and a camera unit that detects the terahertz waves are arranged facing a subject, and the component of the terahertz waves irradiated from the illumination unit that is reflected by the subject is acquired. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-153974 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the configuration of Patent Document 1 has the following problem. Because terahertz waves have a wavelength relatively longer than the unevenness of the surface of the subject, the terahertz waves irradiated onto the surface of the subject are not scattered by the surface but are specularly reflected. In other words, the camera unit that detects the terahertz waves can only acquire the component of the terahertz waves irradiated from the illumination unit that is specularly reflected by the surface of the subject.

[0006] Therefore, although it is suitable for detecting concealed objects, it is difficult to obtain characteristics such as the outline of the object itself, such as the human body or clothing, which has low reflectivity to terahertz waves. As a result, it is difficult to obtain information on which part of the object the concealed object is hidden.

[0007] Therefore, an object of the present invention is to provide a camera system that can detect a concealed object while simultaneously acquiring the characteristics of the subject. [Means for solving the problem]

[0008] In order to achieve the above object, one aspect of the present invention provides a camera system comprising: an illumination unit that irradiates terahertz waves; a camera unit that acquires a first signal when the illumination unit is irradiating the terahertz waves and acquires a second signal different from the first signal when the illumination unit is not irradiating the terahertz waves; and a signal processing unit that generates an image from the first signal and the second signal acquired by the camera unit, wherein the camera unit or the signal processing unit acquires the difference between the first signal and the second signal, generates a first image from the difference between the first signal and the second signal, and generates a second image different from the first image from the second signal. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a camera system that can detect a concealed object while simultaneously acquiring the characteristics of the subject. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a camera system according to a first embodiment. [Figure 2] 2 is a block diagram showing the internal configuration of a camera control device of the camera system according to the first embodiment. FIG. [Figure 3] FIG. 1 is a diagram illustrating two types of terahertz waves. [Figure 4]1 is a block diagram of a terahertz wave detection sensor according to a first embodiment. [Figure 5] 2 shows a pixel circuit of the terahertz wave detection sensor according to the first embodiment. [Figure 6] 5A to 5C are diagrams illustrating variations of control signals in the first embodiment. [Figure 7] 10 shows a pixel circuit of a terahertz wave detection sensor according to a second embodiment. [Figure 8] 10 is a timing chart of the terahertz wave detection sensor according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the following embodiments. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and redundant explanations will be omitted as appropriate. In addition, some parts that are not important for the explanation will be omitted in each drawing.

[0012] <Embodiment 1> FIG. 1 is a diagram showing an example of the configuration of a camera system 100 according to this embodiment. The camera system 100 is composed of an illumination unit 110, a camera unit (imaging unit) 120, and a signal processing unit 140. The camera system 100 further includes a processor (not shown) connected to the camera system 100 via a line. The illumination unit 110 irradiates terahertz waves. The camera unit 120 detects the terahertz waves and acquires an image formed by the terahertz waves. The signal processing unit 140 generates an image from a signal due to the terahertz waves detected (acquired) by the camera unit 120.

[0013] 1, in this embodiment, the illumination unit 110 and the camera unit 120 are configured as an integrated unit. However, this is not limiting, and the illumination unit 110 and the camera unit 120 may be formed in separate housings. Furthermore, the signal processing unit 140 may be incorporated into the camera unit 120, or may be provided outside the camera unit 120.

[0014] The terahertz waves emitted from the illumination unit 110 are specularly reflected by the inspection object 150 and enter the camera unit 120. That is, the camera unit 120 can detect the terahertz waves emitted from the illumination unit 110. The inspection object 150 is usually a human, but may also be a non-human animal or a robot.

[0015] The illumination unit 110 includes a plurality of light-emitting devices (terahertz light-emitting devices) arranged in an array. The terahertz light-emitting device may include, for example, an antenna composed of a negative differential resistance element and a resonant circuit. The negative differential resistance element may be a resonant tunneling diode or the like. The illumination unit 110 may also be composed of a plurality of terahertz light-emitting devices. The light emission intensity can be increased by resonantly driving the plurality of terahertz light-emitting devices, or the entire object to be inspected can be irradiated with terahertz waves by arranging the light-emitting devices in an array.

[0016] The camera unit 120 includes a terahertz wave detection unit 130 that detects terahertz waves. The terahertz wave detection unit may be, for example, a Schottky barrier diode, a bolometer, or an MEMS resonator. However, in this embodiment, since it is necessary to detect terahertz waves (thermal radiation) emitted from the human body in addition to terahertz waves irradiated from the illumination unit 110 having a terahertz light source, it is preferable to use a detection element such as a bolometer that has a wide detectable wavelength band. A readout circuit for signals detected by the terahertz wave detection unit 130 will be described later.

[0017] The processor (not shown) is composed of at least one computer including a CPU, a memory, and other storage media, and is connected via lines to each component of the camera system 100. The processor controls each component by sending control signals to them via lines, and performs overall control of each component of the camera system 100 in accordance with a program stored in the memory.

[0018] The camera system 100 of the present invention acquires a first signal (hereinafter referred to as an S signal) when the inspection object 150 is irradiated with terahertz waves, and acquires a second signal (hereinafter referred to as an N signal) when the inspection object is not irradiated with terahertz waves. Then, a first image is generated from the difference between the S signal and the N signal, and a second image is generated from the N signal. In this embodiment, the acquisition of the S signal and the N signal is performed by the camera unit 120. Furthermore, the generation of the first image and the second image is performed by the signal processing unit 140.

[0019] Here, the first image is an image suitable for detecting a concealed object, and the second image is an image suitable for detecting features such as the contour of an object to be inspected. Therefore, by using the camera system 100 of this embodiment, it is possible to detect a concealed object while simultaneously acquiring the features of the subject. The reason for this will be explained below.

[0020] The camera system 100 is connected to a camera control device 160 shown in Fig. 2 via a general-purpose interface such as a USB (Universal Serial Bus). Fig. 2 is a block diagram illustrating an example of the internal configuration of the camera control device (information processing device) 160 of the first embodiment.

[0021] The camera control device 160 is an image processing device (information processing device) that is configured with at least one computer. The camera control device 160 has a CPU 11, a main memory device 12, an auxiliary memory device 13, an input I / F 14, and an output I / F 15. The elements of the camera control device 160 are connected to each other via a system bus 16 so that they can communicate with each other.

[0022] The CPU 11 is a central processing unit that performs overall control of the operation of the camera control device 160. The CPU 11 may also perform overall control of the camera system 100.

[0023] The main storage device 12 is a storage device (memory) such as RAM (Random Access Memory) that functions as a temporary storage location for data of the CPU 11. The auxiliary storage device 13 is a storage device (storage unit) that stores various programs, various setting data, various parameter data, etc. Examples of the auxiliary storage device 13 include a storage device such as an HDD (Hard Disk Drive), a ROM (Read Only Memory), or an SSD (Solid State Drive).

[0024] The input I / F 14 is an interface used when the camera control device 160 receives input (signals) from the camera system 100, the input device 170, etc. The output I / F 15 is an interface used when the camera control device 160 outputs information (signals) to the display device 180, etc.

[0025] The input device 170 is composed of a mouse, a keyboard, etc., and is operated by a user of the camera control device 160. The display device (display unit) 180 is a device equipped with a monitor, etc., that displays images received from the camera control device 160.

[0026] 3A and 3B are diagrams showing terahertz waves 111 that are irradiated from illumination unit 110 onto inspection object 150, specularly reflected by inspection object 150, and incident on camera unit 120, and terahertz waves 112 that are thermally radiated from inspection object 150 and incident on camera unit 120. FIG. 3A shows an example of a case where terahertz waves are irradiated onto the inspection object. FIG. 3B shows an example of a case where terahertz waves are not irradiated onto the inspection object. The thickness of the arrows in FIG. 3 indicates the intensity of the terahertz waves.

[0027] As shown in FIG. 3A, when terahertz waves are irradiated onto an object to be inspected, both terahertz waves 111 and 112 are incident on the camera unit 120. If the S signal (first signal) itself is used, the terahertz wave 111 is buried in the terahertz wave 112, making it difficult to detect the concealed object. To address this issue, conventionally, wavelength band limiting means such as an antenna is provided in the terahertz wave detection unit 130, and the wavelength of the terahertz waves detected by the terahertz wave detection unit 130 is limited to the wavelength band irradiated by the illumination unit 110. With this configuration, the camera system 100 of this embodiment can selectively detect only the terahertz wave 111.

[0028] 3(B), when the object to be inspected is not irradiated with terahertz waves, only terahertz waves 112 are incident on camera unit 120, and therefore the features of the object to be inspected can be acquired. However, when an antenna is provided in terahertz wave detection unit 130 as in the conventional case, the amount of heat radiation that can be detected by terahertz wave detection unit 130 decreases, making it difficult to detect the features of the object to be inspected.

[0029] Therefore, in this embodiment, the amount of thermal radiation that can be obtained at the timing of Fig. 3(B) is increased by not limiting the wavelength band using a wavelength band limiting means such as an antenna. Furthermore, in this embodiment, only the terahertz wave 111 is selectively detected based on the difference between the S signal obtained at the timing of Fig. 3(A) and the N signal obtained at the timing of Fig. 3(B). With this configuration, it is possible to detect the concealed object while simultaneously obtaining the features of the subject.

[0030] 4 is a block diagram of a terahertz wave detection sensor 200 that constitutes the camera unit 120 in the camera system 100 of this embodiment. The terahertz wave detection sensor 200 includes a pixel region 201, a pixel control circuit 202, a readout circuit 203, an A / D conversion circuit 204, and a timing generator (T / G) 205. The pixel control circuit 202, the readout circuit 203, the A / D conversion circuit 204, and the timing generator (T / G) 205 are provided in a peripheral circuit region that is a region other than the pixel region 201.

[0031] A pixel region 201 has one or more pixels arranged in a matrix (two-dimensionally). A pixel control circuit 202 outputs a control signal for driving each pixel arranged in the pixel region 201. A readout circuit 203 is provided with a column amplifier, a correlated double sampling (CDS) circuit, etc., and performs noise cancellation correction, signal amplification, etc. on pixel signals read out from pixels in a row selected by the pixel control circuit 202 via a signal readout line. An A / D conversion circuit 204 converts the pixel signals from the readout circuit 203, which are analog signals, into digital signals. A timing generator (T / G) 205 receives control signals such as a synchronization signal and a clock signal from an external controller (not shown), and outputs control signals for driving the pixel control circuit 202, readout circuit 203, and A / D conversion circuit 204.

[0032] 5 shows an example of a pixel circuit 301 that constitutes each pixel in the pixel region 201. The pixel circuit 301 includes a terahertz wave detection unit 302, a signal amplification unit 303, a signal accumulation unit 304, and a selection unit 305.

[0033] Terahertz wave detection unit 302 detects terahertz waves and generates a voltage signal. Fig. 5 shows an example in which a Schottky barrier diode (SBD) is used as terahertz wave detection unit 302. When the SBD receives terahertz waves, a current flows according to the intensity of the terahertz waves, and the voltage between the terminals of the diode SBD changes, allowing terahertz wave detection unit 302 to generate a voltage signal according to the intensity of the terahertz waves.

[0034] Terahertz waves are emitted from an illumination unit 110 having a terahertz light source. The on / off of the light emission of the terahertz light source is controlled by a control signal Sync. The control signal Sync is generated by a processor (not shown) or an external controller (not shown) and input to the terahertz light source. Alternatively, the control signal Sync may be generated by a timing generator (T / G) 206 of the terahertz wave detection sensor 200.

[0035] The signal amplifier 303 amplifies the voltage signal detected by the terahertz wave detector 302 and inputs it to the signal accumulation unit 304. The voltage signal detected by the terahertz wave detector 302 may be input directly to the signal accumulation unit 304, but amplifying the signal reduces the influence of noise in the circuits subsequent to the signal accumulation unit 304 and improves the S / N ratio. A grounded-gate amplifier circuit or a grounded-source amplifier circuit is preferably used for the signal amplifier 303.

[0036] 5, the output of the terahertz wave detection unit 302 is connected to the source terminal of the NMOS transistor M1, and a current source I1 is connected to the drain terminal of the NMOS transistor M1. A switch is connected between the gate terminal and drain terminal of the NMOS transistor M1. By turning on the switch to short-circuit the gate terminal and drain terminal, the gate terminal is reset to a voltage determined according to the current flowing through the NMOS transistor M1.

[0037] This reset voltage depends on the threshold voltage and drive capability of the NMOS transistor M1, and acts to cancel out variations in the NMOS transistor M1 from pixel to pixel. A bias capacitor Cb is connected to the gate terminal of the NMOS transistor M1, and acts to maintain the reset voltage when the switch is off. This circuit connection of the NMOS transistor M1 forms a grounded-gate amplifier circuit, with the source terminal of the NMOS transistor M1 as the input terminal and the drain terminal as the output terminal.

[0038] Furthermore, the source of the NMOS transistor M1 is connected to the anode of the diode SBD in the terahertz wave detection unit 302, and the current of the current source I1 is used as the drive current for the diode SBD. With this configuration, the bias current for the NMOS transistor M1 of the grounded-gate amplifier circuit and the drive current for the diode SBD are both used, and the current consumption of the pixel circuit 301 can be reduced.

[0039] The drain terminal of NMOS transistor M1 is connected to the gate terminal of NMOS transistor M2 via capacitance Cs. The source terminal of NMOS transistor M2 is connected to ground potential, and the drain terminal of NMOS transistor M2 is connected to current source I2. A switch is connected between the gate and drain terminals of NMOS transistor M2. By turning on the switch and shorting the gate and drain terminals, the gate terminal is reset to a voltage determined by the current flowing through NMOS transistor M2. This reset voltage depends on the threshold voltage and drive capability of NMOS transistor M2, and acts to cancel out variations in NMOS transistor M2 from pixel to pixel.

[0040] The circuit connection of the NMOS transistor M2 forms a common-source amplifier circuit in which the gate terminal of the NMOS transistor M2 is the input terminal and the drain terminal is the output terminal. As a result, the output from the common-gate amplifier circuit formed by the NMOS transistor M1 is inverted and amplified by the common-source amplifier circuit formed by the NMOS transistor M2.

[0041] The signal amplifier 303 is only required to be able to amplify the voltage signal from the terahertz wave detector 302, and an amplifier circuit other than the grounded gate amplifier circuit or grounded source amplifier circuit described in this embodiment can also be used.

[0042] The output of the signal amplifier 303 is input to the signal storage unit 304. A high frequency cut filter (not shown) may be disposed at the output of the signal amplifier 303 to remove noise from the signal from the signal amplifier 303. For example, a capacitor may be used as the high frequency cut filter, and is connected between the output of the signal amplifier 303 and a fixed potential. A plurality of capacitors may be switched using a selection switch to change the cutoff frequency of the filter.

[0043] The signal accumulation unit 304 is synchronized with the control signal Sync, and is configured to accumulate the output voltage signal when the terahertz light source is on and the output voltage signal when it is off. In the example of Fig. 5, the output of the signal amplification unit 303 is connected to accumulation capacitances Cc_S and Cc_N in the signal accumulation unit 304. The other ends of the accumulation capacitances Cc_S and Cc_N are connected to ground potential. The connections to the accumulation capacitances Cc_S and Cc_N are switched by switches, and are synchronized with the control signal Sync. That is, the output voltage signal when the terahertz light source is on is accumulated in the accumulation capacitance Cc_S, and the output voltage signal when the terahertz light source is off is accumulated in the accumulation capacitance Cc_N.

[0044] When a selection signal SEL is input, the selection unit 305 operates to output the voltages of the storage capacitors Cc_S and Cc_N in the signal storage unit 304 as pixel signals to a signal readout line 306. The outputs of the pixel circuits 301 in the same column arranged in the pixel region 201 are commonly connected to the signal readout line 306. The selection unit 305 sequentially selects the pixel circuits 301 row by row and outputs the pixel signals.

[0045] The signal readout line 306 is connected to the readout circuit 203. The readout circuit 203 includes an amplifier circuit Amp, an input capacitor Ci, a feedback capacitor Cfb, and two switches for each column, two for the S signal and two for the N signal. The signal readout line 306 is input to a first input terminal of the amplifier circuit Amp via the input capacitor Ci. A feedback capacitor Cfb is connected between the first input terminal and the output terminal of the amplifier circuit Amp. When the switch is turned on, the two terminals of the feedback capacitor Cfb are connected and reset. A fixed potential is input to the second input terminal of the amplifier circuit Amp. This configuration of the readout circuit 203 makes it possible to cancel noise from the pixel signal and amplify the pixel signal.

[0046] The output of the readout circuit 203 is input to an A / D conversion circuit 204, which converts the analog pixel signals from the readout circuit 203 into digital signals. An A / D conversion circuit 204 may be provided for each column, or one A / D conversion circuit 204 may be provided for all columns and A / D conversion may be performed for each column in a time-division manner.

[0047] The camera unit 120 acquires a first signal and a second signal based on a control signal Sync output in synchronization with the illumination unit 110 and the camera unit 120. The signal processing unit 140 uses the S signal and N signal read out from the terahertz wave detection sensor 200 to generate a first image for detecting a concealed object and a second image for detecting features of the inspection target.

[0048] Specifically, the signal processing unit 140 subtracts the N signal from the S signal, i.e., compares the S signal and the N signal and obtains the difference. The signal processing unit 140 then generates a first image based on the obtained difference, and generates a second image from the N signal. When generating the first image or the second image, the signal processing unit 140 may perform image correction processing to change the brightness or contrast of the image by applying a digital gain or a gamma curve to at least one of the S signal or the N signal. Alternatively, the signal processing unit 140 may perform noise reduction processing to reduce noise by applying a low-pass filter or a bilateral filter.

[0049] It is preferable that the on-time and off-time of the control signal Sync are approximately equal. However, the duty ratio of the control signal Sync (the proportion of the on-time of the terahertz light source) can be determined depending on which image quality is prioritized: the first image or the second image. If priority is given to detecting a concealed object, it is better to increase the duty ratio of the control signal Sync. If priority is given to detecting the characteristics of the object to be detected, it is better to decrease the duty ratio of the control signal Sync. If the duty ratio of the control signal Sync is not 50%, it is preferable to apply a digital gain to at least one of the S signal and the N signal when generating the first image in order to equalize the difference in signal level due to the difference in on-time and off-time. In other words, it is preferable that the signal processing unit 140 applies a digital gain to at least one of the S signal and the N signal when generating the first image, depending on the difference in on-time and off-time of the control signal.

[0050] Fig. 6 is a diagram illustrating variations of the control signal Sync. For example, when the duty ratio of the control signal Sync is 75% as shown in Fig. 6(A), the ON time of the light emission of the terahertz light source is three times the OFF time, so it is preferable to generate the first image by subtracting a signal obtained by multiplying the N signal by a gain of three times from the S signal.

[0051] 6(B), the signal processing unit 140 may change the signal to be acquired depending on the purpose by separating the period for acquiring the difference between the S signal and the N signal from the period for acquiring the N signal. For example, first, only the N signal may be acquired to detect the characteristics of the object to be detected, and then the difference between the S signal and the N signal may be acquired to intensively detect the concealed object.

[0052] Furthermore, if camera system 100 is configured to be able to be moved manually or automatically, the terahertz light source is turned off while the camera is moving in order to determine which part of the object being photographed. It is preferable to configure the terahertz light source to be rapidly switched on and off while the camera is stopped in order to detect the concealed object. Alternatively, if camera system 100 has a switch for switching between acquiring the difference between the S signal and the N signal and acquiring the N signal, it is preferable to configure the terahertz light source to be rapidly switched on and off only when the user turns on the switch.

[0053] 2, the camera system 100 may have a display device (display unit) 180 for displaying the first image and the second image generated by the signal processing unit 140. In this case, at least one of the first image and the second image generated by the signal processing unit 140 is displayed on the screen of the display device 180. The first image and the second image may be displayed separately on the screen of the display device 180, or may be displayed on the same screen so as not to overlap each other. A third image obtained by combining the first image and the second image may be displayed on the screen of the display device 180.

[0054] Combining the first image and the second image to generate the third image is performed by the signal processing unit 140. Note that the display control process of the first image, the second image, and the third image, which is the combined image, on the display device 180 may be performed by a processor (not shown) or CPU 11 of the camera system 100, in which case the processor or CPU 11 also functions as a display control unit.

[0055] When displaying the third image, which is a composite image, on the display device 180, the signal processing unit 140 may change the blending ratio depending on the region of the composite image. For example, since the output of the first image is higher than that of the second image only in the region where a concealed object is present, comparatively bright blending can simultaneously display the features of the concealed object and the object to be detected. When first acquiring only the N signal and then acquiring the difference between the S signal and the N signal, the difference between the S signal and the N signal weakened by an arbitrary ratio may be calculated. In this case, by generating the first image based on the calculated difference, it is possible to generate an image equivalent to the third image without generating the second image. In this way, rather than subtracting the N signal 100%, the N signal is weakened to, for example, 50% of its signal value before subtracting it. This prevents the signal of the terahertz wave 111 from being buried in the signal of the terahertz wave 112, reducing the visibility of the concealed object, and allows the features of the object to be inspected to be preserved. This makes it possible to skip the process of generating the second image and the third image, which is advantageous in terms of processing speed and efficiency in the signal processing unit 140.

[0056] Alternatively, the user may be able to select a blending ratio depending on the region. It is preferable to increase the blending ratio of the first image in regions where it is desired to improve the accuracy of concealed object detection, and increase the blending ratio of the second image in regions where it is desired to detect the features of the subject of inspection. In this case, it is even more preferable to change the intensity of the lighting elements depending on the region of the combined image. That is, by arranging light-emitting devices in an array to form lighting elements, and increasing the intensity of the light-emitting devices illuminating the concealed object and decreasing the intensity of the light-emitting devices illuminating areas other than the concealed object, it is possible to improve both the accuracy of concealed object detection and the accuracy of subject feature detection. The intensity of the light-emitting devices may be changed by the signal processing unit 140 or a processor (not shown), or the user may be able to change the intensity using the input device 170, etc.

[0057] When displaying the third image obtained by combining the first image and the second image on the display device 180, the signal processing unit 140 may perform image processing on the first image and the second image, and combine the third image based on the first image and the second image after the image processing. For example, in order to display the features of the detected object without reducing the visibility of the concealed object, contour extraction may be performed on the second image before combining. Contour extraction can be performed by performing image processing using a Sobel filter.

[0058] Furthermore, when the first image and the second image are displayed on the display device 180, the first image and the second image may be displayed by switching them over time. For example, the first image and the second image may be displayed in accordance with the timing at which the S signal and the N signal are acquired by the control signal Sync. Alternatively, the first image and the second image may be displayed on the display device 180 by combining them and switching them over time.

[0059] When the first image and the second image are displayed on the display device 180, at least one of the first image and the second image may be highlighted. Due to the visual characteristics of the human eye, a blinking image is more noticeable. Therefore, for example, by displaying the second image and superimposing the first image on it while blinking, it is possible to detect a hidden object while capturing its characteristics. Furthermore, at least one of the first image and the second image may be partially or entirely colored, or an arrow, a circle, a rectangular frame, or the like may be added to a portion requiring attention and displayed on the display device 180. When a third image, which is a composite image of the first and second images, is displayed, the third image may also be highlighted and displayed on the display device 180. By highlighting the image and displaying it on the display device 180 in this manner, it is possible to make it easier for the user to confirm the image.

[0060] <Embodiment 2> The camera system 100 shown in the second embodiment differs from the camera system 100 shown in the first embodiment only in the pixel circuit of the terahertz wave detection sensor 200 that constitutes the camera unit 120. Therefore, a description of the same configuration as in the first embodiment will be omitted, and the configuration according to the second embodiment will be described below.

[0061] In the camera system 100 shown in the first embodiment, the terahertz wave detection sensor 200 acquires an S signal and an N signal, and the signal processing unit 140 generates a difference between the S signal and the N signal. In contrast, in the camera system 100 shown in the second embodiment, the terahertz wave detection sensor 400 acquires both the N signal and the difference between the S signal and the N signal. Then, the signal processing unit 140 generates a first image based on the difference between the S signal and the N signal acquired by the camera unit 120, and generates a second image based on the N signal. In this way, directly acquiring the difference between the S signal and the N signal within the sensor is preferable to generating the difference between the S signal and the N signal in the signal processing unit 140, as it reduces noise.

[0062] 7 shows an example of a pixel circuit 501 constituting each pixel of the pixel region 401 of the terahertz wave detection sensor 400 of the embodiment 2. The pixel circuit 501 is composed of a terahertz wave detection unit 502, a signal amplification unit 503, a signal accumulation unit 504, and a selection unit 505. Of these, except for the signal accumulation unit 504, the configuration is the same as that of the pixel circuit 301 shown in FIG. 5, and therefore a description thereof will be omitted.

[0063] The signal accumulation unit 504 is synchronized with the control signal Sync, and accumulates the difference between the output voltage signal when the terahertz light source is on and the output voltage signal when it is off, as well as the output voltage signal when it is off. Of these, the circuit that accumulates the output voltage signal when it is off is the same as in Fig. 5, so its explanation will be omitted.

[0064] On the other hand, the circuit that accumulates the difference between the output voltage signal when the terahertz light source is on and the output voltage signal when it is off is different from that shown in Fig. 5. Specifically, a differential voltage signal is generated between the output voltage signal from signal amplifier 503 at a certain timing and the output voltage signal from signal amplifier 503 at a different timing. Then, an operation is performed to accumulate a voltage determined from this differential voltage signal, and this operation is repeated to perform an integration operation.

[0065] In the example of FIG. 7, the output of the signal amplification unit 503 is connected to one end of a clamp capacitance Cc in the signal accumulation unit 504. The other end of the clamp capacitance Cc is commonly connected to one end of a switch SWs and one end of a switch SWi. The other end of the switch SWs is connected to a fixed potential (ground potential in FIG. 7). The other end of the switch SWi is connected to one end of a storage capacitance Cc_D. The other end of the storage capacitance Co is connected to a fixed potential (ground potential in FIG. 7). One end of the switch SWrst is connected to one end of the storage capacitance Co. The other end of the switch SWrst is connected to a fixed potential (ground potential in FIG. 7). One end of the storage capacitance Cc_D is the output of the signal accumulation unit 504 and is input to the selection unit 505.

[0066] The switch SWi is controlled to turn on / off by a control signal SPCLK. The switch SWs is controlled by an inverted signal of the control signal SPCLK. In other words, when the switch SWi is on, the switch SWs is off, and conversely, when the switch SWs is on, the switch SWi is off. When the switches SWi and SWs are switched on and off, it is preferable to drive them so that there is no period when both the switches SWi and SWs are on, and so that there is a period when both are off.

[0067] The operation of the circuit that accumulates the difference between the output voltage signal when the terahertz light source is on and the output voltage signal when it is off will be described using the timing chart shown in Fig. 8. Fig. 8 is a timing chart of the terahertz wave detection sensor in embodiment 2.

[0068] The output waveform AOUT is the output voltage signal of the signal amplifier 303. The rising and falling edges of the output waveform AOUT are linked to turning on / off the light emission of the terahertz light source. When the control signal Sync is at H level, the terahertz light source emits light, so that the terahertz wave detection unit 302 detects the terahertz waves and generates a voltage signal, which is then amplified and output by the signal amplifier 303.

[0069] Therefore, when the control signal Sync becomes H level, the output waveform AOUT rises and the voltage increases to a level corresponding to the intensity of the terahertz waves. When the control signal Sync is L level, the emission of the terahertz light source is turned off, so that the terahertz wave detection unit 302 does not detect the terahertz waves, the output waveform AOUT falls, and the voltage drops to the output level at which the emission of the terahertz waves is turned off.

[0070] In this embodiment, the period when the control signal SPCLK is at L level is referred to as a first period Tp1, and the period when it is at H level is referred to as a second period Tp2. Furthermore, the timing when the first period Tp1 switches to the second period Tp2 is referred to as a first timing Tm1, and the timing when the second period Tp2 switches to the first period Tp1 is referred to as a second timing Tm2.

[0071] First, the first operation performed in the first period Tp1 will be described. During the first period Tp1, the control signal Sync is at L level, so the emission of the terahertz light source is off, and the output waveform AOUT also drops. The output waveform AOUT when the emission of the terahertz light source is off is applied to one end of the clamp capacitor Cc, and because the switch SWs is on, a fixed potential (ground potential) is applied to the other end of the clamp capacitor Cc.

[0072] At the first timing Tm1, when the control signal SPCLK switches from L level to H level, the switch SWs turns off and the switch SWi turns on, so that the other end of the clamp capacitor Cc is connected to one end of the storage capacitor Cc_D. At this time, the voltage across the clamp capacitor Cc maintains the potential difference between the voltage signal (first voltage signal) of the output waveform AOUT at the first timing Tm1 and the fixed potential (ground potential).

[0073] Next, the second operation performed during the second period Tp2 will be described. During the second period Tp2, the control signal Sync is at H level, so the terahertz light source emits light, and the output waveform AOUT increases. This output waveform AOUT is applied to one end of the clamp capacitance Cc, and the other end of the clamp capacitance Cc is connected to one end of the storage capacitance Cc_D. Therefore, the voltage increase of the output waveform AOUT also increases the voltage of the storage capacitance Cc_D. Here, the voltage increase ΔV of the output waveform AOUT is defined as ΔV. In this case, the voltage increase ΔV' of the storage capacitance Cc_D (hereinafter referred to as the storage voltage ΔV') is multiplied by the capacitance division ratio of the clamp capacitance Cc and the storage capacitance Cc_D, expressed as ΔV' = ΔV × Cc / (Cc_D + Cc), and becomes a voltage value correlated with ΔV. Here, Cc is the capacitance value of the clamp capacitance Cc, and Cc_D is the capacitance value of the storage capacitance Co.

[0074] At second timing Tm2, the control signal SPCLK switches from H level to L level, turning off the switch SWi connecting the clamp capacitor Cc and the storage capacitor Cc_D, and the voltage increase ΔV is determined. If the voltage signal of the output waveform AOUT at second timing Tm2 is the second voltage signal, the voltage increase ΔV is the differential voltage signal between the first voltage signal and the second voltage signal.

[0075] In this way, the terahertz wave detection sensor 400 constituting the camera unit 120 can obtain the difference between the second voltage signal, that is, the S signal, and the first voltage signal, that is, the N signal.

[0076] In the configuration shown in the second embodiment, the quality of the first signal can be improved because the difference between the S signal and the N signal can be directly acquired in the signal accumulation unit 504. In particular, the configuration of the second embodiment is preferable because the quality of the first signal can be improved by transferring the signal from the signal amplification unit 503 to the signal accumulation unit 504 multiple times.

[0077] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention.

[0078] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0079] The disclosure of this embodiment includes the following configuration, method, and program.

[0080] (Configuration 1) an illumination unit that irradiates terahertz waves; a camera unit that acquires a first signal when the illumination unit is irradiating the terahertz wave and acquires a second signal different from the first signal when the illumination unit is not irradiating the terahertz wave; a signal processing unit that generates an image from the first signal and the second signal acquired by the camera unit, the camera unit or the signal processing unit acquires a difference between the first signal and the second signal, The signal processing unit generates a first image from the difference between the first signal and the second signal, and generates a second image different from the first image from the second signal.

[0081] (Configuration 2) The camera system according to configuration 1, wherein the camera unit acquires the first signal and the second signal based on a control signal output in synchronization with the lighting unit and the camera unit.

[0082] (Configuration 3) 3. The camera system according to configuration 2, wherein the on time and off time of the control signal are equal.

[0083] (Configuration 4) The camera system according to any one of configurations 1 to 3, wherein the signal processing unit applies a digital gain or a gamma curve to at least one of the first signal and the second signal when generating the first image.

[0084] (Configuration 5) 5. The camera system according to any one of configurations 1 to 4, wherein the signal processing unit applies a low-pass filter or a bilateral filter to at least one of the first signal and the second signal when generating the first image.

[0085] (Configuration 6) The camera system according to any one of configurations 1 to 5, wherein the signal processing unit acquires the difference between the first signal and the second signal during a period separate from the period for acquiring the second signal.

[0086] (Configuration 7) 7. The camera system according to any one of configurations 1 to 6, wherein the signal processing unit generates a third image by combining the first image and the second image.

[0087] (Configuration 8) the illumination unit includes a plurality of light-emitting devices arranged in an array; The camera system of configuration 7, wherein the signal processing unit changes the light emission intensity of the light emitting device and the composition ratio of the first image and the second image depending on the area of the combined image.

[0088] (Configuration 9) 9. The camera system according to any one of configurations 1 to 8, further comprising a display unit that displays at least one of the first image and the second image generated by the signal processing unit.

[0089] (Configuration 10) Further, a display control unit is configured to display at least one of the first image and the second image generated by the signal processing unit on a display unit. 10. The camera system according to any one of configurations 1 to 9.

[0090] (Configuration 11) the signal processing unit generates a third image by combining the first image and the second image; 11. The camera system according to configuration 10, wherein the display control unit causes the third image to be displayed on the display unit.

[0091] (Configuration 12) 12. The camera system according to configuration 10 or 11, wherein the display control unit causes the display unit to display the first image and the second image by switching over time.

[0092] (Configuration 13) The camera system of any one of configurations 10 to 12, characterized in that when the first image and the second image are displayed on the display unit, the display control unit highlights at least one of the first image and the second image.

[0093] (Configuration 14) 1. A method for controlling a camera system, comprising: Terahertz waves are irradiated, acquiring a first signal at a timing when the terahertz wave is irradiated and acquiring a second signal different from the first signal at a timing when the terahertz wave is not irradiated; obtaining a difference between the first signal and the second signal; generating a first image from the difference between the first signal and the second signal, and generating a second image different from the first image from the second signal; 10. A camera system control method comprising:

[0094] (Configuration 15) A program for causing a computer to execute a camera system control method, Terahertz waves are irradiated, acquiring a first signal at a timing when the terahertz wave is irradiated and acquiring a second signal different from the first signal at a timing when the terahertz wave is not irradiated; obtaining a difference between the first signal and the second signal; generating a first image from the difference between the first signal and the second signal, and generating a second image different from the first image from the second signal; A program characterized by: [Explanation of symbols]

[0095] 100 Camera System 110 Lighting Department 120 Camera Department 130 Terahertz wave detection element 140 Signal Processing Unit 150 inspection targets

Claims

1. an illumination unit that irradiates terahertz waves; a camera unit that acquires a first signal when the illumination unit is irradiating the terahertz wave and acquires a second signal different from the first signal when the illumination unit is not irradiating the terahertz wave; a signal processing unit that generates an image from the first signal and the second signal acquired by the camera unit, the camera unit or the signal processing unit acquires a difference between the first signal and the second signal, The signal processing unit generates a first image from the difference between the first signal and the second signal, and generates a second image different from the first image from the second signal.

2. The camera system according to claim 1 , wherein the camera unit acquires the first signal and the second signal based on a control signal output in synchronization with the lighting unit and the camera unit.

3. 3. The camera system according to claim 2, wherein the on-time and off-time of the control signal are equal.

4. The camera system according to claim 1 , wherein the signal processing unit applies a digital gain or a gamma curve to at least one of the first signal and the second signal when generating the first image.

5. The camera system according to claim 1 , wherein the signal processing unit applies a low-pass filter or a bilateral filter to at least one of the first signal and the second signal when generating the first image.

6. The camera system according to claim 1 , wherein the signal processing unit acquires the difference between the first signal and the second signal during a period separate from the period for acquiring the second signal.

7. The camera system according to claim 1 , wherein the signal processing unit generates a third image by combining the first image and the second image.

8. the illumination unit includes a plurality of light-emitting devices arranged in an array; The camera system according to claim 7 , wherein the signal processing unit changes the light emission intensity of the light emitting device and the composition ratio of the first image and the second image depending on the area of the combined image.

9. 2. The camera system according to claim 1, further comprising a display unit that displays at least one of the first image and the second image generated by the signal processing unit.

10. a display control unit that displays at least one of the first image and the second image generated by the signal processing unit on a display unit; 2. The camera system according to claim 1.

11. the signal processing unit generates a third image by combining the first image and the second image; The camera system according to claim 10 , wherein the display control unit causes the third image to be displayed on the display unit.

12. The camera system according to claim 10 , wherein the display control unit causes the display unit to display the first image and the second image by switching over time between them.

13. The camera system according to claim 10, characterized in that the display control unit highlights at least one of the first image and the second image when displaying the first image and the second image on the display unit.

14. 1. A method for controlling a camera system, comprising: Terahertz waves are irradiated, acquiring a first signal at a timing when the terahertz wave is irradiated and acquiring a second signal different from the first signal at a timing when the terahertz wave is not irradiated; obtaining a difference between the first signal and the second signal; generating a first image from the difference between the first signal and the second signal, and generating a second image different from the first image from the second signal; 10. A camera system control method comprising:

15. A program for causing a computer to execute a camera system control method, Terahertz waves are irradiated, acquiring a first signal at a timing when the terahertz wave is irradiated and acquiring a second signal different from the first signal at a timing when the terahertz wave is not irradiated; Obtaining a difference between the first signal and the second signal; generating a first image from the difference between the first signal and the second signal, and generating a second image different from the first image from the second signal; A program characterized by:

Images