Patent Publication Number: US-2020304695-A1

Title: Terahertz wave camera and detection module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of International Patent Application No. PCT/JP2018/044828, filed Dec. 6, 2018, which claims the benefit of Japanese Patent Application No. 2017-239114, filed Dec. 13, 2017 and Japanese Patent Application No. 2018-193166, filed Oct. 12, 2018, all of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a terahertz wave camera, a detection module, and the like that are information acquisition devices using a terahertz wave. More specifically, the present invention relates to a technique for suppressing influence on a function of acquiring information on an electromagnetic wave having a wavelength different from a terahertz wave. 
     Description of the Related Art 
     A terahertz wave is a radio wave typically having a signal of any frequency band out of a range from 0.2 THz to 30 THz. In the frequency band, there is much characteristic absorption caused by the structure or the state of various substances such as a biomolecule or a resin. Because of having a larger wavelength than visible light or infrared light, a terahertz wave is less likely to be affected by scattering and has high transmittance for many substances. On the other hand, a terahertz wave has a shorter wavelength than a millimeter wave that is also a radio wave. Thus, in a radio wave camera using a terahertz wave (also referred to as a terahertz wave camera), an image having high resolution can be expected compared to an image generated from a millimeter wave. By making use of these characteristics, application to safe imaging techniques instead of X-rays is expected. For example, application to security check in public places and a surveillance technique has been considered. 
     In radio wave cameras, there are a passive type that selects and detects a desired radio wave out of an electromagnetic wave (radio wave and light) generated from a subject due to heat radiation and an active type that irradiates a subject with a desired radio wave and detects a reflected radio wave. Since the radio wave generated from a subject due to heat radiation is very weak, many passive type radio wave cameras realize selection of a radio wave and reduction of noise of a system by using a high frequency circuit such as a mixer. Since a high frequency circuit technique driven in a terahertz wave band is under development, an active type terahertz wave camera is often considered in order to ensure a required SN ratio. 
     In both types of terahertz wave cameras, a signal of a terahertz wave is weak and fast. Thus, a technique for avoiding an increase in noise due to a parasitic component of a circuit and deterioration of the frequency characteristic by integrating an element that detects a signal and a peripheral circuit (also referred to as readout circuit) that reads out a signal is disclosed (see Japanese Patent Application Laid-Open No. 2014-175819,  FIG. 1A ,  FIG. 1B ,  FIG. 6 ,  FIG. 7 , and the like). 
     A peripheral circuit integrated in an element that detects a terahertz wave and reads out a signal related to a terahertz wave is often formed of a silicon-based semiconductor circuit (for example, CMOS) having high spectral sensitivity to visible light and infrared light. Here, since a signal related to a terahertz wave is weak, it is desirable that a terahertz wave camera use a lens with an F value as low as possible and collect a terahertz wave to an element that detects a terahertz wave. At this time, when visible light or infrared light is emitted to a peripheral circuit, unnecessary charges are generated by influence of a photoelectric effect inside the circuit due to the visible light or the infrared light. Such unnecessary charges may cause noise, and the SN ratio may decrease. 
     SUMMARY OF THE INVENTION 
     In view of the problems described above, a terahertz wave camera according to one aspect of the present disclosure is a terahertz wave camera that detects a terahertz wave from a measurement target and acquires information on the measurement target, and the terahertz wave camera includes: a sensor unit in which a plurality of detection elements having spectral sensitivity to the terahertz wave are arranged; a readout circuit unit that reads out signals from the detection elements; a first light-shielding portion that reduces disturbance light to which the readout circuit unit has spectral sensitivity; and an optical unit that guides a terahertz wave from the measurement target to the sensor unit. 
     According to another aspect of the present disclosure, provided is a detection module used for a terahertz wave camera that detects a terahertz wave from a measurement target and acquires information on the measurement target, and the detection module includes: a sensor substrate; a plurality of detection elements provided on a first primary face of the sensor substrate and having spectral sensitivity to the terahertz wave; a first light-shielding portion that reduces disturbance light other than the terahertz wave and is arranged in a different level from the detection elements in sectional view of the sensor substrate; a readout circuit substrate provided so as to face a second primary face of the sensor substrate; and a readout circuit unit that is provided on the readout circuit substrate, has spectral sensitivity to the disturbance light, and reads out signals from the detection elements. 
     Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a diagram illustrating a configuration of a terahertz wave camera of a first embodiment. 
         FIG. 1B  is a plan view and a sectional view of a detection module of the first embodiment. 
         FIG. 2  is a sectional view illustrating an example of the structure that scatters disturbance light of a second light-shielding portion. 
         FIG. 3  is a sectional view illustrating another example of the structure that scatters disturbance light of the second light-shielding portion. 
         FIG. 4A  is a sectional view illustrating an example of an arrangement of a first light-shielding portion and a second light-shielding portion of a second embodiment. 
         FIG. 4B  is a sectional view illustrating an example of an arrangement of the first light-shielding portion and the second light-shielding portion of the second embodiment. 
         FIG. 5  is a diagram illustrating a configuration of a terahertz wave camera of a third embodiment. 
         FIG. 6  is a diagram illustrating a configuration of a terahertz wave camera of a fourth embodiment. 
         FIG. 7  is a diagram illustrating a plan view and a sectional view of another arrangement example of a detection module of the first embodiment. 
         FIG. 8A  is a plan view of an arrangement example of a detection module of a sixth embodiment. 
         FIG. 8B  is a sectional view of an arrangement example of the detection module of the sixth embodiment. 
         FIG. 9A  is a plan view of another arrangement example of the detection module of the sixth embodiment. 
         FIG. 9B  is a sectional view of another arrangement example of the detection module of the sixth embodiment. 
         FIG. 10A  is a plan view of an element of the first embodiment. 
         FIG. 10B  is a sectional view of the element of the first embodiment. 
         FIG. 10C  is a sectional view of the element of the first embodiment. 
         FIG. 11A  is a plan view of a configuration example of the detection module of the sixth embodiment. 
         FIG. 11B  is a sectional view of a configuration example of the detection module of the sixth embodiment. 
         FIG. 12A  is a plan view of an arrangement example of the detection module of the sixth embodiment. 
         FIG. 12B  is a sectional view of an arrangement example of the detection module of the sixth embodiment. 
         FIG. 12C  is a sectional view of an arrangement example of the detection module of the sixth embodiment. 
         FIG. 13  is a sectional view of a part of the detection module of the sixth embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     A typical silicon-based general-purpose circuit used as a readout circuit unit of a terahertz wave sensor unit has spectral sensitivity to disturbance light such as visible light. Further, in a high frequency circuit for a millimeter wave, a terahertz wave, or the like, in particular, influence of a parasitic component caused by laying a wiring around is not negligible. It is therefore desirable that a peripheral circuit, which is a readout circuit unit, be arranged as close as possible to a sensor unit. From this point of view, a terahertz wave camera that acquires information on a measurement target has a sensor unit having spectral sensitivity to a terahertz wave, a readout circuit unit, and a light-shielding portion that reduces undesirable disturbance light. In the present specification, “reduce light” and “block light” may mean reducing the amount or intensity of disturbance light toward the readout circuit unit. The readout circuit unit is preferably arranged close to the sensor unit. Herein, whether it is “close to” or not is determined by considering whether or not a parasitic component caused by laying a wiring around in the readout circuit unit prevents establishment of a performance condition required by a device including the sensor unit and the readout circuit unit. Whether it is “disturbance light” or not is determined by whether or not the wavelength range is in a wavelength range of spectral sensitivity of the readout circuit unit, and there may be some deviation or the like. Hereinafter, while embodiments and examples will be described, the present invention is not limited thereto, and various modifications or changes are possible within the scope not departing from the spirit of the present invention to realize a configuration that can solve the above problems. 
     According to study by the present inventors, it has been found that, since a signal of a terahertz wave is weak, influence of noise due to unnecessary charges is not a negligible problem in structuring a terahertz wave camera. As described above, for a peripheral circuit integrated near the detection element of a terahertz wave, suppression of influence of noise due to unnecessary charges caused by visible light or infrared light is a problem specific to a terahertz wave camera using a detection element and a peripheral circuit for a terahertz wave that have different spectral sensitivity. 
     According to one aspect of the present invention, a configuration that reduces light of an undesirable electromagnetic wave (disturbance light such as visible light or infrared light) that may reach a circuit unit used for reading out a signal of an element that detects a terahertz wave can be employed. 
     First Embodiment 
     A first embodiment of the present invention will be described with reference to the drawings.  FIG. 1A  and  FIG. 1B  are schematic configuration diagrams of a terahertz wave camera of the present embodiment.  FIG. 1A  is a diagram illustrating a configuration of a terahertz wave camera  100 , and  FIG. 1B  is a plan view and a sectional view of a detection module including a configuration around a sensor unit  101  of the terahertz wave camera  100 . 
     The terahertz wave camera  100  of  FIG. 1A  has at least a first light-shielding portion  103 , the sensor unit  101 , and a readout circuit unit  102 . Such components are accommodated in a camera casing  105 . The terahertz wave camera  100  detects and images a terahertz wave  108  from a subject  107 . An imaged terahertz wave image is displayed on a monitor  106 , if necessary. The terahertz wave  108  from the subject  107  is a terahertz wave generated by the subject  107  due to heat radiation or a terahertz wave emitted from an external lighting and then reflected by the subject  107 . A terahertz wave is a radio wave and preferably has a signal in any frequency band out of a range from 0.2 THz to 30 THz. 
     The first light-shielding portion  103  blocks disturbance light  111  and guides the terahertz wave  108  to the sensor unit  101 . In principle, although the first light-shielding portion  103  can be divided into a light-shielding portion having a function of blocking light and an optical unit having a function of image capturing, when the first light-shielding portion  103  has both functions of blocking light and image capturing, the number of components forming the terahertz wave camera  100  can be reduced. The disturbance light  111  is visible light or infrared light generated from a disturbance light source  110  and is an electromagnetic wave other than a terahertz wave. The disturbance light source  110  is a lighting apparatus, natural light, a heat source, or the like. The first light-shielding portion  103  has optical power to capture an image of the terahertz wave  108  onto the sensor unit  101  and is a convex lens, for example. The first light-shielding portion  103  is formed of a member that transmits the terahertz wave  108 . 
     While the first light-shielding portion  103  is formed of one lens in  FIG. 1A , the first light-shielding portion  103  may be formed of a plurality of lenses. Further, it is desirable that the first light-shielding portion  103  is a member that absorbs and scatters the disturbance light  111  in order to block the disturbance light  111 . For example, as a material of a member that blocks the disturbance light  111  and transmits the terahertz wave  108 , materials such as high density polyethylene (HDPE), Teflon (registered trademark) (trade name: PolyTetraFluoroethylene, PTFE), high resistance silicon, or the like having transmittance to a terahertz wave higher than transmittance to disturbance light can be applied. With a use of such a material, the first light-shielding portion  103  that transmits the terahertz wave  108  and absorbs the disturbance light  111  can be formed. Further, with the structure such as a porous structure that scatters the disturbance light  111  being contained in the member, the first light-shielding portion  103  that transmits the terahertz wave  108  and scatters the disturbance light  111  can be formed. 
     A lens may collect not only the terahertz wave  108  but also the disturbance light  111 . As with the present embodiment, however, the first light-shielding portion  103  having a function of a lens blocks the disturbance light  111  by the configuration as described above. Thus, since it is possible to suppress the disturbance light  111  from being collected to a peripheral circuit, generation of unnecessary charges, which is caused by influence of a photoelectric effect inside a circuit due to the disturbance light  111 , can be suppressed. As a result, an advantage of reduction of noise can be obtained, the SN ratio of the terahertz wave camera  100  can be improved. 
     A support portion that supports the first light-shielding portion  103  in the camera casing  105  is formed of a material that transmits at least the terahertz wave  108 , or the center part of the support portion is opened. Further, another part of the camera casing  105  is preferably formed of a material that transmits neither the disturbance light  111  nor the terahertz wave  108  and is formed of a material that does not transmits at least the disturbance light  111 . 
     The sensor unit  101  has a plurality of elements (pixels)  191  arranged two-dimensionally in a matrix, and the element  191  has spectral sensitivity to the terahertz wave  108 . The sensor unit  101  is formed in a sensor substrate  194 . To have spectral sensitivity to the terahertz wave  108 , the elements  191  of the sensor unit  101  have the structure in which a detection element such as a Schottky barrier diode (SBD) made of a compound semiconductor or a semiconductor and an antenna are integrated, for example. Further, the detection element of the element  191  may be a rectifying detection element such as a self-switching diode or a metal-insulator-metal (MIM) diode, a transistor such as a field effect transistor (FET) or a high electron mobility transistor (HEMT), or a detection element using a quantum well. In a terahertz wave camera, the element  191  corresponds to a pixel. 
     As the elements  191  of the sensor unit  101 , the following can be used.  FIG. 10A ,  FIG. 10B , and  FIG. 10C  are diagrams illustrating configuration examples of the element  191 .  FIG. 10A  is a plan view of the element  191 , and  FIG. 10B  and  FIG. 10C  are sectional views of the element  191  of  FIG. 10A .  FIG. 10C  further illustrates the element  191  as a modified example. 
     In  FIG. 10A , the element  191  may have a sensor substrate  194  in which a recess (concave part)  1001  is formed, an antenna  1003 , and a detection element  1004 . On the sensor substrate  194 , the recesses  1001  are formed on an element  191  basis, and the recess  1001  forms a circle in plan view. The recess  1001  is formed of an inner wall part that reflects a received electromagnetic wave. The inner wall part may be formed of a side wall, a bottom part, or the like of the recess  1001 . On the bottom part of the recess  1001 , support portions  1005  and  1005 ′ are provided in a protruding manner. Each of the support portions  1005  and  1005 ′ has a cylindrical shape, and the height of the support portion  1005 ′ is smaller than the height of the support portion  1005 . The detection element  1004  is provided on the top face of the support portion  1005 ′. The antenna  1003  that receives an electromagnetic wave is fixed on the support portions  1005  and  1005 ′. The antenna  1003  has an annular shape in plan view and is formed of metal portions  1003   a  and  1003   b . The length of the metal portion  1003   a  is larger than the length of the metal portion  1003   b . One ends of respective metal portions  1003   a  and  1003   b  are connected to the detection element  1004 , and an air gap having a predetermined width is formed between the other ends of respective metal portions  1003   a  and  1003   b . Herein, the metal portions  1003   a  and  1003   b  each have a portion provided on an opening of the recess  1001  and a portion connected to the detection element  1004  arranged on the support portion  1005 ′ that is provided on the sensor substrate  194 . 
     As illustrated in  FIG. 10A  and  FIG. 10B , the support portion  1005  also supports the antenna  1003 . The inner wall of the recess  1001  that reflects an electromagnetic wave reflects an electromagnetic wave by using a difference in the refractive index of the interface between the sensor substrate  194  and the recess  1001 . As illustrated in  FIG. 10B , a metal layer  1006  may be provided on the bottom face of the recess  1001  as the structure that reflects an electromagnetic wave. Further, as illustrated in  FIG. 10C , the metal layer  1006  may be provided on a back face of the sensor substrate  194 . When a distance W between the antenna  1003  and the side wall of the recess  1001  changes, a radiation pattern of an electromagnetic wave of the element  191  changes. It is therefore preferable that the distance W have a sufficient length so that the radiation pattern is not disturbed. Preferably, the distance W is 0.1λ or longer with respect to a wavelength λ that is an effective electromagnetic wave. Further, the radiation direction of an electromagnetic wave changes in accordance with a distance D of the metal layer  1006  to the front face of the sensor substrate  194 . Specifically, the radiation direction of an electromagnetic wave is determined to be concentrated above the antenna  1003  or concentrated inside the sensor substrate  194  in accordance with the distance D. In the present embodiment, the metal layer  1006  is arranged at a position at which the radiation pattern is concentrated above the sensor substrate  194 . Preferably, the distance D is 0.25λ with respect to the wavelength λ that is an effective electromagnetic wave. 
     For example, when an electromagnetic wave of 0.5 THz is used, the radius of the antenna  1003  is 65 μm. At this time, when the antenna  1003  and the recess  1001  are filled with air, the distance W is 60 μm. When the element  191  has the sectional structure illustrated in  FIG. 10B , and the sensor substrate  194  is formed of silicon, the distance D is 60 μm. 
     Note that, while the support portion  1005  of  FIG. 10A  and  FIG. 10B  has a cylindrical shape, the shape is not limited thereto. For example, the support portion  1005  may have a prism shape or may have a trapezoid shape. Further, a space surrounded by the recess  1001  may be filled with not only air but also a material having a refractive index that is different from a refractive index of air. For example, the space of the recess  1001  may be filled with benzocyclobutene (BCB) that is a resin material. 
     The metal layer  1006  formed on the sensor substrate  194  can also serve as a light-shielding portion for visible light and infrared light that are disturbance light. In other words, the sensor substrate  194  has a light-shielding portion that reflects disturbance light to a different level from the detection element  1004 . Note that a light-shielding portion having a dielectric multilayer film structure that reflects disturbance light may be provided to a part other than the metal layer  1006  or may be formed partially or entirely for a level on which the light-shielding portion is arranged. With such a configuration, the disturbance light that would otherwise reach a readout circuit unit described later can be blocked. 
     Turning back to  FIG. 1A , the sensor unit  101  may be configured such that a plurality of pixels each having a detection element that detects an electromagnetic wave from a subject and a plurality of switches used for reading out signals from the pixels may be arranged, respectively. Here, the sensor unit  101  has a generation unit that generates a signal of a predetermined cycle, and the pixel is connected to a transmission line used for supplying a signal of a predetermined cycle to the pixel and a scan line used for reading out a signal from the pixel via a switch. Further, the pixel has a frequency conversion element that performs a frequency conversion on a detection signal of the detection element by using a signal of a predetermined cycle. 
     The readout circuit unit  102  is a circuit that reads out a signal related to the terahertz wave  108  from the element  191 . The readout circuit unit  102  includes an amplifier circuit, a filter circuit, a switch circuit, a power source circuit, or the like, and a general-purpose semiconductor circuit technique such as a CMOS circuit technique can be applied thereto, for example. Since a semiconductor used for such a circuit has high spectral sensitivity to a wavelength range of visible light or infrared light, the disturbance light  111  causes noise due to unnecessary charges of the circuit. Therefore, to remove a cause of the noise, the first light-shielding portion  103 , a second light-shielding portion  104  described later, and the like are provided. As illustrated in  FIG. 1B , the readout circuit unit  102  is formed on a readout circuit substrate  195 . The readout circuit unit  102  and the sensor unit  101  are integrally formed. In the present example, the readout circuit substrate  195  and the sensor substrate  194  are coupled and integrated. To integrate the readout circuit substrate  195  and the sensor substrate  194 , the readout circuit substrate  195  and the sensor substrate  194  may be provided on the front face and the back face of a common substrate, respectively. 
       FIG. 1B  illustrates a plan view of a sensor unit and a readout circuit unit and a sectional view taken along a dashed line  1 B- 1 B′ and is a diagram illustrating an arrangement example of the sensor unit  101  and the readout circuit unit  102 . As illustrated in  FIG. 1B , the sensor unit  101  and the readout circuit unit  102  are stacked and connected to each other via a through electrode  193  provided in the sensor substrate  194 . The sensor unit  101  is provided on a first primary face of the sensor substrate  194 , and the readout circuit substrate  195  is opposed thereto and provided on a second primary face of the sensor substrate  194 . In more detail, the sensor substrate  194  having the sensor unit  101  and the readout circuit substrate  195  having the readout circuit unit  102  are arranged to be attached to each other along an optical axis  109  of the terahertz wave camera  100 . The readout circuit substrate  195  is arranged to be opposed to the first light-shielding portion  103  with the sensor substrate  194  being interposed therebetween. 
     According to such arrangement, since at least a part of the readout circuit unit  102  is shielded by the sensor unit  101 , a circuit exposure portion of the readout circuit unit  102  decreases. Thus, since a region in which the disturbance light  111  reaches the readout circuit unit  102  decreases, the influence of noise due to unnecessary charges of the circuit is reduced, and the noise characteristic is improved. As a result, the SN ratio of the terahertz wave camera  100  is improved. 
     The arrangement of the sensor unit  101  and the readout circuit unit  102  is not limited to the form of being attached as described above.  FIG. 7  illustrates a plan view of a detection module including a sensor unit and a readout circuit unit as a modified example and a sectional view taken along a dashed line  7 - 7 ′. As illustrated in  FIG. 7 , the sensor unit  101  and the readout circuit units  102  may be integrally arranged on the same face on the first light-shielding portion  103  side of a module substrate  896 . Here, the readout circuit units  102  are arranged in two regions that are different from each other near a region of the sensor unit  101 . For example, the readout circuit units  102  may be arranged so as to interpose the sensor unit  101  in plan view. The readout circuit units  102  in the two regions are electrically connected to each other by a wiring or the like formed on the top face or in the inner region of the module substrate  896 . 
     The sensor unit  101  has spectral sensitivity to the terahertz wave  108 , and the readout circuit unit  102  has spectral sensitivity to the disturbance light (visible light and infrared light)  111  and is integrally arranged with the sensor unit  101 . The first light-shielding portion  103  shields the sensor unit  101  and the readout circuit units  102  from the disturbance light  111 . Further, the first light-shielding portion  103  captures an image of the terahertz wave  108  onto the sensor unit  101 . Since the first light-shielding portion  103  blocks visible light or infrared light that would otherwise reach the readout circuit units  102 , the noise due to the unnecessary charges of the readout circuit units  102  is suppressed. 
     In the present embodiment, while the first light-shielding portion  103  is intended for blocking the disturbance light  111 , the disturbance light  111  from a part other than the first light-shielding portion  103  may invade the inside of the terahertz wave camera  100 . Accordingly, as illustrated in  FIG. 1A , a second light-shielding portion  104  that transmits the terahertz wave  108  may be provided in the terahertz wave camera  100 . The second light-shielding portion  104  is arranged along the optical axis  109  of the terahertz wave camera  100  in the same manner as the first light-shielding portion  103 . In  FIG. 1A , the second light-shielding portion  104  is arranged between the first light-shielding portion  103  and the sensor unit  101  along the optical axis  109  of the terahertz wave camera  100 . According to such an arrangement, since the second light-shielding portion  104  is inserted between the first light-shielding portion  103  and the sensor unit  101 , it is not required to change the size of an optical system of the terahertz wave camera  100 . However, the arrangement of the second light-shielding portion  104  is not limited thereto, and the second light-shielding portion  104  may be arranged at a position opposed to the sensor unit  101  via the first light-shielding portion  103 , for example. In such a case, since the second light-shielding portion  104  is arranged at the end (left end in  FIG. 1A ) of the terahertz wave camera  100 , it is possible to easily replace the second light-shielding portion  104  without disassembling the terahertz wave camera  100 . 
     In  FIG. 1A , the second light-shielding portion  104  is arranged in the camera casing  105  so as to be inclined with respect to the optical axis  109 . That is, the axis perpendicular to the surface of the second light-shielding portion  104  is not parallel to the optical axis  109 . By arranging the second light-shielding portion  104  so as to be inclined with respect to the optical axis  109 , for example, it is possible to prevent the disturbance light  111  reflected on the surface of the sensor unit  101  or the readout circuit unit  102  from being reflected at the surface of the second light-shielding portion  104 , traveling along the same light path, and re-entering the readout circuit unit  102 . According to such arrangement, since the disturbance light  111  that re-enters the readout circuit unit  102  can be suppressed, noise due to unnecessary charges of the readout circuit unit  102  can be more suppressed. 
     The second light-shielding portion  104  blocks the disturbance light  111  by absorbing or scattering the disturbance light  111  or the like in the same manner as the first light-shielding portion  103 . The second light-shielding portion  104  in  FIG. 1A  has the structure that scatters the disturbance light  111 , and an example of outputting scattering light  112  is illustrated. 
       FIG. 2  is a diagram illustrating an example of the structure that scatters the disturbance light  111  in the second light-shielding portion  104 , which illustrates a sectional view of a part of the second light-shielding portion  104 . The second light-shielding portion  104  has a member  213  in which a plurality of air hole parts  214  are formed. The scattering structure of the second light-shielding portion  104  corresponds to the air hole parts  214  provided in the member  213 . The material of the member  213  is a material that has transmittance to the terahertz wave  108 . The disturbance light  111  is absorbed at the member  213 , is scattered at the interface between an air hole of the air hole part  214  and the member  213 , and becomes the scattering light  112 . Such a scattering phenomenon is caused by geometrical optic scattering and the Mie scattering. Thus, the size of the air hole part  214  is required to be substantially the same as or larger than the wavelength of the disturbance light  111 . Further, the structure of the air hole part  214  is required to have transmittance to the terahertz wave  108 . Thus, the size of the air hole part  214  is required to be substantially the same as or smaller than the wavelength of the terahertz wave  108 . Alternatively, the distance between adjacent air hole parts  214  is required to be substantially the same as or smaller than the wavelength of the terahertz wave  108 . Specifically, it is desirable that the size of the air hole part  214  be 1/10×λ 1  or smaller with respect to a wavelength λ 1  of the terahertz wave  108 . Alternatively, it is desirable that the distance between the adjacent air hole parts  214  be 1/10×λ 1  or smaller with respect to a wavelength λ 1  of the terahertz wave  108 . Further, it is desirable that the size of the air hole part  214  be λ 2  or larger with respect to a wavelength λ 2  of the disturbance light  111 . As the second light-shielding portion  104 , styrene foam, polyethylene foam, or the like having a controlled size of the air hole part  214  can be used. 
       FIG. 3  illustrates an example of another structure that scatters the disturbance light  111  in the second light-shielding portion  104 , which illustrates a sectional view of a part of the second light-shielding portion  104 . The second light-shielding portion  104  has a member  313  in which an unevenness portion  315  is formed on the surface. The scattering structure of the second light-shielding portion  104  is the unevenness portion  315  provided on the surface of the member  313 . The member  313  is a material having transmittance to the terahertz wave  108 . The disturbance light  111  is absorbed in the member  313  and scattered at the interface between the unevenness portion  315  and the atmosphere (for example, air) surrounding the second light-shielding portion  104 . Such a scattering phenomenon is caused by geometrical optic scattering and the Mie scattering. Thus, the size (the depth, the width, or the like of the unevenness) of the unevenness portion  315  is required to be substantially the same as or larger than the wavelength of the disturbance light  111 . Further, to suppress scattering of the terahertz wave  108  due to the unevenness portion  315 , the size of the unevenness portion  315  is required to be substantially the same as or smaller than the wavelength of the terahertz wave  108 . Specifically, it is desirable that the size of the unevenness portion  315  be 1/10×λ 1  or smaller with respect to a wavelength λ 1  of the terahertz wave  108 . Further, it is desirable that the size of the unevenness portion  315  be λ 2  or larger with respect to a wavelength λ 2  of the disturbance light  111 . As the second light-shielding portion  104 , polyethylene whose surface is processed to be a sand surface, a quartz substrate, or the like can be used, for example. 
     As set forth, in the present embodiment, a configuration that blocks the disturbance light  111  is provided to a configuration in which the sensor unit  101  and the readout circuit unit  102  having different spectral sensitivity are integrated. According to such a configuration, the sensor unit  101  having spectral sensitivity to the terahertz wave  108  and the readout circuit unit  102  having spectral sensitivity to the disturbance light (visible light and infrared light)  111  and arranged integrally with the sensor unit  101  are shielded from the disturbance light  111  by the first light-shielding portion  103  and the second light-shielding portion  104 . Further, the first light-shielding portion  103  captures an image of the terahertz wave  108  onto the sensor unit  101 . Since the first light-shielding portion  103  and the second light-shielding portion  104  blocks, in two steps, visible light and infrared light that would otherwise reach the readout circuit unit  102 , noise due to unnecessary charges of the readout circuit unit  102  is further suppressed. Thus, noise in the terahertz wave camera  100  is reduced, and the SN ratio of the terahertz wave camera  100  is further improved. 
     In particular, as illustrated in  FIG. 2  and  FIG. 3 , when the second light-shielding portion  104  has the structure that scatters the disturbance light  111 , the disturbance light  111  is diffused by scattering. Thus, since the light amount of the disturbance light  111  reaching the readout circuit unit  102  is reduced, noise in the terahertz wave camera  100  is further reduced, and the SN ratio of the terahertz wave camera  100  is improved. Note that the structure that scatters disturbance light may be provided to the first light-shielding portion. That is, the structure that scatters disturbance light can be provided at least one of the first light-shielding portion and the second light-shielding portion. 
     Example 1 
     Specific examples of materials of each member, numerical values, and the like of the terahertz wave camera of the first embodiment will be described with reference to the drawings. The present invention is not limited to the following examples. The terahertz wave camera of the present example is the active type terahertz wave camera that irradiates a subject with a terahertz wave. 
     The frequency of the terahertz wave  108  of  FIG. 1A  ranges from 0.43 THz to 0.5 THz. The terahertz wave  108  is a reflected wave that is emitted from a terahertz wave source (not illustrated) to the subject  107  and reflected by the subject  107 . The terahertz wave source is a flat light source in which a plurality of terahertz wave sources are arranged in a matrix. In more detail, the terahertz wave source is an element in which a resonance tunnel diode (RTD) and a patch antenna, which is a resonator, are integrated, and the output of the terahertz wave source is slightly lower than 0.1 mW. In the present example, the terahertz wave source is a flat light source in which 25 elements of terahertz wave sources are arranged. The number of arranged terahertz wave sources is not limited thereto. Further, the configuration of the terahertz wave source is not limited to the above, and a known terahertz wave source can be used. The disturbance light source  110  is indoor lighting or natural light. 
     The first light-shielding portion  103  is also a non-sphere biconvex lens, and the material thereof is high density polyethylene (HDPE). The first light-shielding portion  103  blocks the disturbance light  111  that is visible light and transmits the terahertz wave  108 . The focal distance and the working distance of the first light-shielding portion  103  are 100 mm and 400 mm, respectively. Further, the magnification of the first light-shielding portion  103  is 0.33, and this causes an image of the subject  107  to be captured on the sensor unit  101 . 
     The second light-shielding portion  104  is a polystyrene board having a thickness of 5 mm, and the size of the air hole part  214  is approximately 100 μm. Further, the distance between adjacent air hole parts  214  is approximately 20 μm. As illustrated in  FIG. 1A , the second light-shielding portion  104  is installed diagonally with respect to the optical axis  109  of the camera  100 . The second light-shielding portion  104  further blocks the disturbance light  111  leaked from the first light-shielding portion  103 . 
     The element  191  of the sensor unit  101  is a Schottky barrier diode (SBD) on which antennae are integrated. Each antenna is a loop antenna, and the resonance frequency of the antenna has been adjusted to the frequency of a terahertz wave generated from the RTD described above. The element  191  is a photoelectric conversion element that converts a signal of the terahertz wave  108  into an electrical signal. The sensor unit  101  includes, for example, 4096 elements  191  arranged in a matrix, and the size of the sensor unit  101  is approximately 32 mm×32 mm. With such a configuration, the sensor unit  101  has spectral sensitivity to a terahertz wave. 
     The readout circuit unit  102  is a line readout circuit and has a switch circuit and a shift register circuit that select a position of a line, a bias circuit that determines an operation point of the element  191  of the sensor unit  101 , a circuit that converts the output of the element  191  into a charge signal, and the like. These circuits are formed on a silicon-based semiconductor substrate and thus have a high spectral sensitivity to visible light and infrared light. 
     As illustrated in  FIG. 1B , the sensor substrate  194  and the readout circuit substrate  195  are attached to each other and arranged along the optical axis  109  of the terahertz wave camera  100 . Since the sensor substrate  194  and the readout circuit substrate  195  are configured by being attached to each other, a part of the disturbance light  111  is blocked by the sensor unit  101 , and the intensity of the disturbance light  111  entering the readout circuit unit  102  decreases. 
     The output terminal of the readout circuit unit  102  is connected to an amplifier circuit, a filter circuit, a correlated double sampling (CDS) circuit, or the like (which are not illustrated), and a signal associated with the terahertz wave  108  is adjusted and processed. These circuits may be included in the readout circuit unit  102 . The terahertz wave camera  100  sequentially selects rows of the sensor unit  101  by using a shift register circuit, acquires signals of the elements  191  included in the rows, and thereby acquires an intensity distribution of a signal associated with the terahertz wave  108 . The terahertz wave camera  100  then constructs an intensity distribution image of the terahertz wave  108  (also referred to as a terahertz wave image) by referencing the selected positions of the rows of the sensor unit  101  and arranging signals in the intensity distribution. In constructing the terahertz wave image, the terahertz wave camera  100  may perform image processing such as averaging of terahertz wave images, removal of an unnecessary fixed pattern, or image adjustment such as γ correction. In the present embodiment, image processing of averaging and removal of a fixed pattern are performed. In particular, in the present example, for the purpose of handling a signal after the decimal point in performing image processing, the terahertz wave camera  100  shifts digital data associated with an intensity signal of the terahertz wave  108  by four bits. In other words, the intensity signal of the terahertz wave is multiplied by 16. In the present example, a terahertz wave image is displayed on the monitor  106  and thereby presented to a user. 
     Noise of the terahertz wave camera  100  under the environment in the absence of the subject  107  was measured by setting the framerate to 40 frames per second (FPS) and utilizing a recursive filter with 512 frames as an averaging process of terahertz wave images. Since the subject  107  is absent, the terahertz wave  108  from the subject  107  is also absent, and the signal detected by the terahertz wave camera  100  is mainly the disturbance light  111 . Noise of the terahertz wave camera  100  in the absence of the second light-shielding portion  104  is 8.9 least significant bit (LSB). Compared to this, noise of the terahertz wave camera  100  with arrangement of the second light-shielding portion  104  is 8.1 LSB, and it was confirmed that noise originating in the disturbance light  111  can be reduced by around 10 percent. Under the environment in the presence of the subject  107 , since the disturbance light  111  is reflected by the subject  107 , and the amount of light entering the terahertz wave camera  100  increases, such a noise reduction effect is more significant. 
     Second Embodiment 
     A second embodiment of the present invention will be described with reference to the drawings. The present embodiment is a modified example regarding the arrangement of the first light-shielding portion  103  and the second light-shielding portion  104 . Configurations different from the first embodiment will be mainly described, and description of the part common to the description provided so far will be omitted or simplified. 
       FIG. 4A  and  FIG. 4B  are diagrams illustrating the configuration of the first light-shielding portion  103  and the second light-shielding portion  104  of the present embodiment and illustrate sectional views of the first light-shielding portion  103  and the second light-shielding portion  104 . In  FIG. 4A , one of the primary surfaces of the first light-shielding portion  103  is curved in a convex shape. The other primary surface of the first light-shielding portion  103  is formed flat and attached to the second light-shielding portion  104 . That is, the first light-shielding portion  103  and the second light-shielding portion  104  are integrally formed. At this time, it is desirable that the second light-shielding portion  104  be formed of the scattering structure so as not to deteriorate an image capturing characteristic to the terahertz wave  108  of the first light-shielding portion  103 . For example, when the air hole part  214  described in the first embodiment is applied as the scattering structure, the average refractive index to the terahertz wave  108  of the second light-shielding portion  104  is closer to that of the atmosphere. Thus, deterioration of the image capturing characteristic of the first light-shielding portion  103  due to the second light-shielding portion  104  can be suppressed. 
     Further,  FIG. 4B  represents a modified example of the first light-shielding portion  103 . An unevenness portion  415  is formed on the other primary surface of the first light-shielding portion  103 . That is, the unevenness portion  415  that functions as the second light-shielding portion  104  is integrally formed in a part of the first light-shielding portion  103 . As described in the first embodiment, when the size of the unevenness portion  415  is less than or equal to 1/10×λ 1  with respect to the wavelength λ 1  of the terahertz wave  108 , it becomes difficult to detect the structure of the unevenness portion  415  by the terahertz wave  108 . Thus, since the unevenness portion  415 , which is the second light-shielding portion  104 , is considered as an even surface to the terahertz wave  108 , deterioration of the image capturing characteristic of the first light-shielding portion  103  due to the second light-shielding portion  104  can be suppressed. 
     According to the configuration of the present embodiment, since the second light-shielding portion  104  is formed integrally with the first light-shielding portion  103 , the holding mechanism of the second light-shielding portion  104  can be eliminated. This enables a reduction in size of the terahertz wave camera  100 . Further, the same advantageous effects as those obtained by the first embodiment can be obtained. 
     Third Embodiment 
     A third embodiment of the present invention will be described with reference to the drawings. The present embodiment is a modified example of the camera casing  105 . Configurations different from the embodiments described above will be mainly described, and description of the common part common will be omitted or simplified. 
       FIG. 5  is a sectional view illustrating the configuration of a terahertz wave camera  500  of the present embodiment. A difference from the configuration of the terahertz wave camera  100  of the embodiments described above is that the camera casing  105  has a third light-shielding portion  520 . In more detail, the camera casing  105  has the third light-shielding portion  520  that blocks the disturbance light  111  on the inner wall of the camera casing  105 . A flocking sheet that serves as an absorption structure or a sand surface structure that is an unevenness portion that serves as the scattering structure is formed in the third light-shielding portion  520 . 
     According to the configuration of the present embodiment, since the disturbance light  111  reflected at the inner wall of the camera casing  105  can be absorbed or scattered, reflection of unnecessary disturbance light  111  inside the camera casing  105  can be suppressed. Thus, since the light amount of the disturbance light  111  reaching the readout circuit unit  102  is reduced, noise of the terahertz wave camera  500  is further reduced, and the SN ratio of the terahertz wave camera  500  is improved. 
     Fourth Embodiment 
     A fourth embodiment of the present invention will be described with reference to the drawings. The present embodiment is a modified example of the second light-shielding portion  104 . Configurations different from the embodiments described above will be mainly described, and description of the common part will be omitted or simplified.  FIG. 6  is a diagram illustrating the configuration of a terahertz wave camera  600  of the present embodiment. A difference from the configuration of the terahertz wave camera  100  or  500  of the embodiment described above is in the arrangement of the second light-shielding portion  104 . The second light-shielding portion  104  is arranged in contact with at least the first light-shielding portion  103  (or the support portion of the first light-shielding portion) and the exposed circuit portion of the readout circuit unit  102 . Further, the second light-shielding portion  104  is filled between the first light-shielding portion  103  and the readout circuit unit  102 . That is, the second light-shielding portion  104  is filled in a space surrounded by the first light-shielding portion  103 , the camera casing  105 , and the readout circuit unit  102 . 
     As described in the second embodiment, it is desirable that the second light-shielding portion  104  have a scattering structure so as not to deteriorate the image capturing characteristic to the terahertz wave  108  of the first light-shielding portion  103 . For example, when the air hole part  214  described in the first embodiment is applied as the scattering structure, the average refractive index to the terahertz wave  108  of the second light-shielding portion  104  becomes closer to the refractive index of the atmosphere. Thus, deterioration of an image capturing characteristic of the first light-shielding portion  103  due to the second light-shielding portion  104  can be suppressed. 
     According to such a configuration, since the space interposed between the first light-shielding portion  103  and the readout circuit unit  102  is filled with the second light-shielding portion  104 , the light-shielding region to the disturbance light  111  increases. Thus, since the light amount of the disturbance light  111  reaching the readout circuit unit  102  decreases, noise of the terahertz wave camera  600  is further reduced, and the SN ratio of the terahertz wave camera  600  is improved. 
     Fifth Embodiment 
     A fifth embodiment of the present invention will be described with reference to the drawings. The present embodiment is a modified example of the second light-shielding portion  104 . Configurations different from the embodiment described above will be mainly described, and description of the common part will be simplified or omitted. 
     The terahertz wave  108  attenuates due to water vapor contained in the atmosphere, and the signal intensity thereof decreases. Accordingly, in the present embodiment, at least a part of the circumference or the surface of the second light-shielding portion  104  is sealed by a member transparent to the terahertz wave  108 , and the internal air hole part  214  sealed by the transparent member is replaced with a drying gas. The transparent member may be, for example, a film (a polyolefin film or a polyethylene film) that exhibits a low loss to the terahertz wave  108 . In detail, the transparent member is formed in contact with at least a portion where a propagation path along which the terahertz wave  108  reaches the sensor unit  101  intersects the boundary of the outermost portion of the second light-shielding portion  104 , and a drying gas is enclosed. The boundary of a portion not intersecting the propagation path of the terahertz wave  108  may be replaced with a non-transparent member. In the configuration of  FIG. 6 , the transparent member may be provided at least at the boundary between the first light-shielding portion  103  and the second light-shielding portion  104  or the boundary between the sensor unit  101  and the second light-shielding portion  104 . In the configuration of  FIG. 1A , the transparent member may be provided at the boundary between an air layer inside the camera casing  105  and the second light-shielding portion  104 . 
     According to the present embodiment, the propagation path of the terahertz wave  108  inside the terahertz wave camera  600  is filled with a drying gas, and attenuation of the terahertz wave  108  due to the atmosphere can be suppressed. Thus, since the light amount of the disturbance light  111  reaching the readout circuit unit  102  decreases and attenuation of the terahertz wave  108  is suppressed, each SN ratio of the terahertz wave cameras  100  and  600  is improved. 
     Sixth Embodiment 
     A sixth embodiment of the present invention will be described with reference to the drawings. The present embodiment is a modified example of the second light-shielding portion  104 . Configurations different from the embodiment described above will be mainly described, and description of the common part will be omitted or simplified. The present embodiment can be regarded as a detection module used for a terahertz wave camera that detects a terahertz wave from a measurement target and acquires information on the measurement target. 
       FIG. 13  is a sectional view of a part of the detection module in the present embodiment. In  FIG. 13 , a detection module  1300  has elements arranged in a matrix as described in  FIG. 10A  to  FIG. 10C . Each of these elements has at least the detection element  1004  that has spectral sensitivity to a terahertz wave and detects the terahertz wave and the antenna  1003  used for receiving a terahertz wave. These elements are formed on the sensor substrate  194 . That is, the readout circuit unit  102  is formed on the readout circuit substrate  195 , and the sensor substrate  194  is provided on the readout circuit unit  102  via a first light-shielding portion  1301 . That is, the sensor substrate  194  and the readout circuit substrate  195  are joined so as to face each other and interpose the readout circuit unit  102 . The first light-shielding portion  1301  that reflects disturbance light is formed on the underside of the sensor substrate  194  in the same manner as the element configuration of  FIG. 10A  to  FIG. 10C . The first light-shielding portion  1301  is arranged in a different level from the detection element  1004 . 
     The first light-shielding portion  1301  is formed of a metal layer, for example, and concentrates a terahertz wave above the sensor substrate  194 . The metal layer reflects external incident disturbance light and prevents the disturbance light from reaching the readout circuit unit  102  provided below the sensor substrate  194 . In such a way, the metal layer functions as a light-shielding portion. The first light-shielding portion  1301  is not limited to a metal layer but may be formed of a dielectric multilayer film. 
     Various modified examples of the detection module in the present embodiment will be described below.  FIG. 8A  and  FIG. 8B  illustrate a plan view and a sectional view taken along a dashed line  8 A- 8 A′ of a detection module as a modified example of the present embodiment. A difference from the arrangement of the second light-shielding portion  104  in the embodiments described above is that the second light-shielding portion  104  is arranged in at least an exposed circuit portion of the readout circuit unit  102  and is not arranged on the surface of the sensor unit  101  that detects the terahertz wave  108 . 
     In  FIG. 8A  and  FIG. 8B , the sensor substrate  194  having the sensor unit  101  and the readout circuit substrate  195  having the readout circuit unit  102  are attached to each other. The external shape of the sensor substrate  194  is smaller than the external shape of the readout circuit substrate  195 , and the readout circuit substrate  195  around the sensor substrate  194  is exposed in plan view. The second light-shielding portion  104  is arranged to cover the exposed circuit portion of the readout circuit unit  102  along the outer circumference of the sensor unit  101 . The second light-shielding portion  104  is preferably arranged in contact with the side wall portion  196  of the sensor unit  101  so as to cover the exposed circuit portion of the readout circuit unit  102 . Herein, the exposed circuit portion is a portion which is not covered with the sensor substrate  194  out of the readout circuit unit  102 . Further, in sectional view, the second light-shielding portion  104  is thicker (higher) than the sensor substrate  194 . It is therefore possible to shield the sensor substrate  194  from diagonal disturbance light. 
       FIG. 11A  and  FIG. 11B  illustrate a plan view and a sectional view taken along a dashed line  11 A- 11 A′ of a detection module as a modified example. As illustrated in  FIG. 11B , the reflective portion  197  that reflects disturbance light is formed on the top face of the second light-shielding portion  104 . The reflective portion  197  may be formed using a metal layer or a dielectric multilayer film layer that reflects disturbance light. Further, when the reflective portion  197  is formed of a metal layer, the metal layer may also function as a heatsink that dissipates heat generated by the readout circuit unit  102 . With such a configuration, it is possible to reduce disturbance light reaching the exposed circuit portion of the readout circuit unit  102 . 
       FIG. 12A ,  FIG. 12B , and  FIG. 12C  illustrate a plan view and sectional views taken along a dashed line  12 A- 12 A′ of a detection module as yet another modified example. The disturbance light reaching the center part of the readout circuit unit  102  is blocked to some degrees by the sensor unit  101  and the sensor substrate  194 . Thus, the sensor unit  101  and the sensor substrate  194  may serve as the second light-shielding portion. For example, in the detection module of  FIG. 12A  and  FIG. 12B , the external shape of the readout circuit substrate  195  is substantially the same as the external shape of the sensor substrate  194 . With the external shape of the readout circuit substrate  195  being substantially the same as that of the sensor substrate  194 , the whole readout circuit unit  102  arranged in the readout circuit substrate  195  can be reliably covered with the sensor substrate  194 . In other words, the exposed circuit portion of the readout circuit unit  102  can be reliably eliminated. Thus, disturbance light that would otherwise reach the readout circuit unit  102  is blocked by the sensor unit  101  or the sensor substrate  194 . 
     In  FIG. 12A  to  FIG. 12C , the whole top face of the readout circuit unit  102  is covered with the sensor substrate  194 , and the readout circuit unit  102  is not exposed. It is therefore desirable that the readout circuit unit  102  and an external circuit be connected by a through electrode  1201  penetrating through the readout circuit substrate  195 . 
       FIG. 12C  illustrates a sectional view of a detection module that is a modified example of the detection module illustrated in  FIG. 12A  and  FIG. 12B . A difference from the configuration of  FIG. 12B  will be mainly described below. The external shape of the readout circuit substrate  195  is smaller than the external shape of the sensor substrate  194  in plan view. That is, the readout circuit substrate  195  does not protrude from the sensor substrate  194  in plan view. Further, compared to the detection module of  FIG. 12B , the readout circuit substrate  195  is formed thinner. When the thickness of the readout circuit substrate  195  is thinner than that of the sensor substrate  194 , if the peripheral edge of the sensor substrate  194  protrudes in the horizontal direction, the readout circuit substrate  195  would be damaged due to external force applied to the peripheral edge. To prevent the damage, a substrate support portion  1202  is provided to the peripheral edge of the sensor substrate  194 , the peripheral edge of the sensor substrate  194  is supported by the substrate support portion  1202 . 
     In the configuration illustrated in  FIG. 12A ,  FIG. 12B , and  FIG. 12C , since the readout circuit unit  102  is covered with the sensor substrate  194 , disturbance light to the readout circuit unit  102  is reduced by the sensor unit  101  or the sensor substrate  194 . Further, since the second light-shielding portion  104  can be omitted, this facilitates a reduction in size of the device while suppressing influence of disturbance light. Furthermore, the external shape of the readout circuit substrate  195  is the same as or smaller than the external shape of the sensor substrate  194 , and thereby the disturbance light reaching the readout circuit unit  102  on the readout circuit substrate  195  can be reliably reduced. Thus, since influence of noise due to unnecessary charges caused by disturbance light is suppressed in the readout circuit unit  102 , the SN ratio of the terahertz wave camera  100  is improved. 
       FIG. 9A  and  FIG. 9B  illustrate a plan view and a sectional view taken along a dashed line  9 A- 9 A′ of a modified example of the detection module illustrated in  FIG. 8A  and  FIG. 8B . The sensor unit  101  and the readout circuit unit  102  are formed integrally with the common module substrate  896 . The second light-shielding portion  104  is arranged so as to cover the readout circuit unit  102  along the outer circumference of the sensor unit  101 . In this example, the exposed circuit portion is the readout circuit unit  102 . In the present embodiment, the second light-shielding portion  104  is arranged in the whole outer circumference of the sensor unit  101  but may be arranged in a part thereof. For example, the second light-shielding portion  104  may be arranged selectively only in a portion where the readout circuit unit  102  is exposed to the outside. 
     According to the configuration of the present embodiment, since the second light-shielding portion  104  is arranged integrally with an exposed circuit portion of the readout circuit unit  102 , a holding mechanism of the second light-shielding portion  104  can be eliminated. This enables a reduction in the size of the terahertz wave camera  100 . 
     Further, the detection module of the present embodiment can reduce disturbance light reaching the readout circuit unit by using the sensor substrate having the first light-shielding portion or otherwise the sensor substrate and the second light-shielding portion. Thus, since influence of noise due to unnecessary charges caused by disturbance light is suppressed in the readout circuit unit, the SN ratio of the detection module is improved. In particular, with the external shape of the readout circuit substrate being the same as or smaller than the external shape of the sensor substrate, the exposed portion of the readout circuit unit can be eliminated, and therefore the disturbance light reaching the readout circuit unit on the readout circuit substrate can be reliably reduced. Further, since the present detection module is configured to be less likely to be affected by disturbance light, a casing used for light-shielding can be simplified. Furthermore, because of the configuration that is less likely to be affected by disturbance light, there is flexibility in installation of the detection module within the device, and this allows for easier handling of the detection module. 
     The present invention is not limited to the embodiments described above, and various changes and modifications are possible without departing from the spirit and the scope of the present invention. Therefore, the following claims are attached in order to make the scope of the present invention public. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.