Photodetector

Abstract

A photodetector capable of accurately and easily positioning a sample at the focal position of a predetermined measuring light beam is provided. [Solution] The light detection device 1A includes an image intensifier I, a case 2 that supports the image intensifier I, and an attachment mechanism 9 that is configured to allow a holding structure 50 for holding the case 2 to be detachably attached. The attachment mechanism 9 is arranged so that, in an attached state where the holding structure 50 is attached to the attachment mechanism 9, the holding structure 50 indicates the target position at which light incident on the image intensifier I should be focused.

Description

[Technical Field]

[0001] The present disclosure relates to a light detection device. [Background technology]

[0002] Patent Document 1 discloses an optical emission spectrometer (photodetector) that houses a photodetector element (a photomultiplier tube in Patent Document 1) having an electron-emitting portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-79905 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when a certain sample is irradiated with a predetermined measurement light to perform some measurement, the above-described photodetector can be used for the purpose of adjusting the focus (light-collecting point) of the measurement light on the sample. For example, first, while monitoring the output value of the photodetector, the photodetector is moved parallel to the traveling direction of the measurement light, and the photodetector is fixed at the position where the output value is maximized. Then, the photodetector is replaced with the sample, and the focus of the measurement light can be adjusted to the position of the sample.

[0005] However, even if the photodetector is replaced with a sample, it is not always possible to focus the measurement light on the position of the sample. In the above-mentioned positioning method, since the photodetector element of the photodetector is actually positioned at the focus of the measurement light, even if the photodetector is replaced with a sample, if the positions of the photodetector element and the sample do not match, it may not be possible to focus the measurement light on the position of the sample.

[0006] Therefore, an object of the present disclosure is to provide a light detection device that can accurately and easily position a sample at the focal position of measurement light. [Means for solving the problem]

[0007] The present disclosure includes the following photodetector devices [1] to [7].

[0008] [1] a photodetector element; a support portion that supports the light detection element; an attachment mechanism configured to detachably attach a holding structure for holding the support portion, the mounting mechanism is configured so that, when the holding structure is attached to the mounting mechanism, the holding structure indicates a target position at which light incident on the light detection element should be focused.

[0009] In the photodetector device [1] described above, a holding structure that holds the support part is detachably attached to the support part via an attachment mechanism. Furthermore, in the attached state, the holding structure is configured to indicate the target position at which light should be focused on the photodetector element supported by the support part. According to the above configuration, after positioning the photodetector device so that the focus of a predetermined measurement light is aligned with the target position in the attached state, the attachment mechanism can be removed from the holding structure without moving the position of the holding structure, thereby accurately and easily determining the position where the target position was located (i.e., the focal position of the measurement light) based on the holding structure. Therefore, according to the photodetector device described above, a sample can be accurately and easily positioned at the focal position of the measurement light.

[0010] [2] The mounting mechanism is configured to mount the holding structure including a linearly extending rod portion; The optical detection device of [1], wherein in the attached state, the center position of the rod portion when viewed from the extension direction of the rod portion is located on a plane that is perpendicular to the direction of light incidence on the optical detection element and includes the target position.

[0011] According to the configuration [2] above, the central axis of the rod portion is positioned on a plane including the target position of the light detection element, so that the target position (the focal position of the measurement light) can be grasped more accurately and easily based on the position and posture of the rod portion.

[0012] [3] The optical detection device of [1] or [2], wherein the mounting mechanism is configured to be able to change the relative positional relationship between the holding structure and the support part while maintaining the holding structure indicating the target position in the mounted state.

[0013] According to the configuration [3] above, the position of the holding structure is fixed, and while the holding structure maintains a state in which the target position can be grasped, the relative position of the support part with respect to the holding structure (for example, the attitude, angle, etc. with respect to the holding structure) can be changed, thereby improving convenience for the person carrying out the measurement.

[0014] [4] The photodetector device according to [3], further comprising a power supply circuit section fixed to the support section and supplying a voltage to be applied to the photodetector element.

[0015] According to the configuration [4] above, the power supply circuit unit is fixed to the support unit, so that a cable or the like is not required to connect the support unit (for example, a connection interface provided on the outer wall of the support unit) to an external power source for supplying voltage that is arranged outside the support unit. As a result, the support unit can be easily moved relative to the holding structure, and problems such as twisting of the cable do not occur, improving convenience for the person carrying out the measurement.

[0016] [5] The photodetector element includes an electron emitting portion that emits electrons in response to incidence of light, and the electron emitting portion is configured to field-emit the electrons in response to incidence of electromagnetic waves having a predetermined vibration direction perpendicular to the light incidence direction when viewed from the light incidence direction relative to the electron emitting portion; The optical detection device of any of [1] to [4], wherein the mounting mechanism is configured to be able to rotate the support part around an axis that is parallel to the light incident direction and passes through the electron emission part, without changing the position of the holding structure, in the mounted state.

[0017] According to the configuration [5] above, the direction (polarization characteristics) to which the electron emitter is sensitive can be changed by rotating the support part around an axis parallel to the light incident direction while maintaining the relative position of the target position of the electron emitter with respect to the holding structure. This makes it possible to appropriately and easily adjust the orientation of the support part (i.e., the polarization characteristics of the electron emitter) according to the vibration direction of the measurement light (electromagnetic wave) incident on the electron emitter while maintaining the attached state.

[0018] [6] The mounting mechanism has a first mounting portion to which the holding structure is attached and a second mounting portion fixed to the support portion, the support portion has an outer peripheral surface along a circumference having an axis passing through the electron emission portion as a center when viewed from the light incident direction, and a rail portion provided on the outer peripheral surface along the circumference, The optical detection device of [5], wherein the second mounting portion is attached to the rail portion in a manner that can be switched between a locked state in which it is fixed to the rail portion and an unlocked state in which it can move along the rail portion.

[0019] According to the configuration [6] above, the configuration [5] above can be easily and appropriately realized.

[0020] [7] The attachment mechanism is configured as a separate body from the support part, The optical detection device of any of [1] to [6], wherein the mounting state includes a first mounting state in which the holding structure is mounted to the mounting mechanism attached to a first part of the support part, and a second mounting state in which the holding structure is mounted to the mounting mechanism attached to a second part different from the first part of the support part.

[0021] According to the configuration [7] above, by switching the position (first part or second part) at which the attachment mechanism is attached to the support part, the attitude of the support part relative to the holding structure can be appropriately set depending on the application. Furthermore, whether the attachment mechanism is attached to the first part or the second part, the target position of the light detection element can be determined by the holding structure attached to the attachment mechanism. Therefore, the above configuration can effectively improve the convenience of the person performing the measurement. [Effects of the Invention]

[0022] According to the present disclosure, it is possible to provide a light detection device that can accurately and easily position a sample at the focal position of measurement light. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a perspective view of a photodetector according to the first embodiment. [Figure 2] FIG. 2 is a front view of the photodetector shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the photodetector taken along line III-III shown in FIG. [Figure 4] FIG. 4 is a rear view of the electron-emitting portion shown in FIG. [Figure 5] FIG. 5 is a diagram schematically showing (a) the first step and (b) the second step in a measurement example using the photodetector shown in FIG. [Figure 6] FIG. 6 is a diagram showing an example of the detection result corresponding to the rotation angle of the case. [Figure 7] FIG. 7 is a perspective view of the photodetector according to the second embodiment (first mounting state). [Figure 8] FIG. 8 is a cross-sectional view of the photodetector taken along line VIII-VIII shown in FIG. [Figure 9] FIG. 9 is a side view of the photodetector in the second mounting state. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and duplicated description will be omitted.

[0025] [First embodiment] As shown in FIGS. 1 to 3, the photodetector 1A according to the first embodiment includes a case 2 (support), an image intensifier I (photodetector element) and a power supply circuit 8 disposed within the case 2, and an attachment mechanism 9. The image intensifier I includes an electron emitter 3, an electron multiplier 4, a fluorescent film 5, a light entrance window 6, a light exit window 7, and a housing H that houses and secures these components. FIGS. 1 to 3 show an attachment state in which a holding structure 50 for holding the case 2 (photodetector 1A) is attached to the attachment mechanism 9. In this embodiment, the attachment mechanism 9 is connected to both the case 2 and the holding structure 50, thereby enabling the holding structure 50 to be attached to the case 2 via the attachment mechanism 9. As an example, the holding structure 50 includes a rod 51 extending linearly.

[0026] The image intensifier I is an electron tube in which an electron emitter 3, which is a photoelectric conversion unit that emits electrons in response to the incidence of light (electromagnetic waves W in this embodiment), is housed in a housing H, which is a vacuum container. The electron multiplier 4 multiplies the electrons emitted from the electron emitter 3. The fluorescent screen 5 emits fluorescence in response to the incidence of the electrons multiplied by the electron multiplier 4. The fluorescence emitted from the fluorescent screen 5 passes through a light exit window 7, and is then imaged by imaging means (e.g., a CCD camera, etc.) not shown, which is arranged behind the light exit window 7 (on the opposite side of the light exit window 7 from the side where the electron multiplier 4 is located).

[0027] The electromagnetic wave W is an electromagnetic wave (i.e., polarized light) having a predetermined vibration direction perpendicular to the propagation direction of the electromagnetic wave W. The electromagnetic wave W is, for example, an electromagnetic wave in a predetermined band included in a frequency band from millimeter waves to infrared light, and one example is a terahertz wave. Hereinafter, the direction parallel to the propagation direction of the electromagnetic wave W is referred to as the X direction, the direction perpendicular to the X direction and in which the rod portion 51 extends in the attached state is referred to as the Z direction, and the direction perpendicular to both the X direction and the Z direction is referred to as the Y direction. In addition, in the X direction, the direction from the light exit window 7 toward the light entrance window 6 is referred to as the forward direction, and the opposite direction is referred to as the rearward direction. In addition, in the attached state (FIGS. 1 to 3), the direction from the holding structure 50 toward the case 2 is referred to as the upward direction, and the opposite direction is referred to as the downward direction. That is, in this embodiment, the rod portion 51 is arranged along the vertical direction (Z direction), and the case 2 is arranged above the rod portion 51. 3, the X direction is the direction (front-to-back direction) in which the light entrance window 6, electron emission section 3, electron multiplier section 4, fluorescent film 5, and light exit window 7 are aligned. The electron emission section 3, electron multiplier section 4, and fluorescent film 5 each extend along the YZ plane, which is perpendicular to the X direction.

[0028] As an example, the case 2 is composed of an outer member 21 and an inner member 22. The outer member 21 is formed in a substantially cylindrical shape with an axis AX1 parallel to the X direction as its central axis. The outer member 21 has a front wall portion 211 located at the front, a rear wall portion 212 located at the rear, and a side wall portion 213 extending in the X direction to connect the front wall portion 211 and the rear wall portion 212. The outer member 21 is formed of a metal such as aluminum or stainless steel. As shown in FIGS. 1 and 2, the front wall portion 211 and the rear wall portion 212 are formed in a circular shape when viewed from the X direction. Furthermore, the side wall portion 213 is formed in a cylindrical shape connecting an edge portion of the front wall portion 211 and an edge portion of the rear wall portion 212. The front wall portion 211 is provided with a circular opening 211a centered on the axis AX1. The rear wall portion 212 is provided with a circular opening 212a centered on the axis AX1. The opening 211a in the front wall 211 is provided to guide the electromagnetic wave W to the light entrance window 6. The opening 212a in the rear wall 212 is provided to extract the fluorescence emitted from the light exit window 7 to the outside of the photodetector 1A. The opening 212a may be used to position (insert) the above-mentioned imaging means for imaging the fluorescence behind the light exit window 7.

[0029] When viewed from the X direction, the outer peripheral surface 213a of the side wall portion 213 of the outer member 21 extends along a circumference centered on the axis AX1. As shown in FIGS. 1 and 3, the side wall portion 213 has a rail portion 214 provided on the outer peripheral surface 213a along the circumference. When viewed from the X direction, the rail portion 214 is provided around the entire circumference of the outer peripheral surface 213a. As shown in FIG. 3, the rail portion 214 has a bottom surface portion 214a, a wide portion 214b, and a guide portion 214c. The bottom surface portion 214a is a surface that extends along the circumference centered on the axis AX1 at the innermost side of the rail portion 214 (in the direction approaching the axis AX1). The wide portion 214b is a portion that is connected to both side edges of the bottom surface portion 214a in the X direction and extends outward (in the direction away from the axis AX1). The guide portion 214c is connected to the end of the wide portion 214b opposite the bottom surface portion 214a, and is formed so that its opening width in the X direction is narrower than that of the wide portion 214b. As an example, the wide portion 214b includes a tapered portion whose width in the X direction increases as it extends outward from the bottom surface portion 214a. The guide portion 214c is formed by a pair of protrusions that extend inward in the X direction from the upper end of the wide portion 214b. Each of the pair of protrusions that make up the guide portion 214c is provided with an inner surface 214d that faces inward.

[0030] The inner member 22 is disposed inside the outer member 21. The inner member 22 has a side wall portion 221 that extends cylindrically along the inner surface of the side wall portion 213 from the rear end of the front wall portion 211 to the front end of the rear wall portion 212, and a disk-shaped front wall portion 222 that extends inward from the front end of the side wall portion 221. The inner member 22 is formed, for example, from an insulating resin material. A portion of the front wall portion 222 overlaps with the edge of the light incident surface 6a of the light incident window 6. When viewed from the X direction, the front wall portion 222 has a circular opening 222a centered on the axis AX1. The diameter of the opening 222a is shorter than the diameter of the opening 211a. In other words, the opening 222a defines an effective area into which light (electromagnetic waves W) can be incident.

[0031] The internal space surrounded by the side wall portion 221 of the inner member 22 accommodates an image intensifier I having the above-mentioned electron emission portion 3, electron multiplier portion 4, fluorescent film 5, light entrance window 6, light exit window 7 and housing H, and a power supply circuit portion 8.

[0032] The light entrance window 6 is a plate-like member made of, for example, quartz glass. The electron emitter 3 is provided in approximately the center of the surface (rear surface) of the light entrance window 6. The light exit window 7 is, for example, a fiber optic plate (FOP) in which a plurality of optical fibers are bundled. The fluorescent screen 5 is provided on the surface (front surface) of the light exit window 7. The electron multiplier 4 is provided between the electron emitter 3 and the fluorescent screen 5. The electron multiplier 4 is, for example, a microchannel plate having an approximately circular plate shape. The electron multiplier 4 multiplies the electrons emitted from the electron emitter 3 (in this embodiment, electrons field-emitted by the incidence of the electromagnetic wave W) and outputs them toward the fluorescent screen 5.

[0033] As shown in FIG. 3 , for example, the power supply circuit unit 8 is disposed inside the inner member 22 so as to surround the housing H, the light exit window 7, and the space behind it. The power supply circuit unit 8 includes a circuit that supplies (generates) voltages to be applied to components disposed within the case 2 (inner member 22). For example, a predetermined voltage is applied from the power supply circuit unit 8 to each of the electron emitter 3, the input surface 4a of the electron multiplier unit 4 on the electron emitter 3 side, the output surface 4b of the electron multiplier unit 4 on the phosphor screen 5 side, and the phosphor screen 5 via a conductive member (not shown). For example, voltages are applied from the power supply circuit unit 8 to each component so that the potential of the electron emitter 3 is −200 V, the potential of the input surface 4a of the electron multiplier unit 4 is 0 V (GND potential), the potential of the output surface 4b of the electron multiplier unit 4 is +1 kV, and the potential of the phosphor screen 5 is +6 kV.

[0034] As shown in FIG. 4, the electron emitter 3 includes a substrate 31, a metasurface 32, a pair of electrodes 33, and a metal film 34. The substrate 31 is formed in a plate shape (e.g., a rectangular plate shape) from a material that is transparent to electromagnetic waves W. The substrate 31 is made of, for example, silicon, quartz, sapphire, or zinc selenide. The metasurface 32 and the pair of electrodes 33 are formed on a surface 31a of the substrate 31. The metal film 34 is formed on the surface 31a of the substrate 31, covering the metasurface 32 and the pair of electrodes 33. The surface 31a is the surface of the substrate 31 facing the electron multiplier 4. That is, the electron emitter 3 is disposed such that the surface of the substrate 31 opposite the surface 31a faces the rear surface of the light incident window 6 (the surface opposite the light incident surface 6a). Note that in FIG. 4, the metal film 34 is indicated by a two-dot chain line.

[0035] The metasurface 32 includes multiple antenna structures 35 arranged two-dimensionally along the surface 31a. As an example, in the state shown in FIG. 1, each antenna structure 35 includes a pair of ends 35a (see FIG. 6) facing each other in the Z direction. As an example, each antenna structure 35 may be configured as a bowtie antenna as shown in FIG. 6. However, the antenna structure 35 is not limited to this example and may be configured as, for example, a dipole antenna, a split ring antenna, a double split ring antenna, or the like. In either case, each antenna structure 35 includes a pair of ends facing each other. Each such antenna structure 35 emits electrons in response to incidence of an electromagnetic wave W whose vibration direction is the Z direction. In other words, the metasurface 32 has polarization properties that emit electrons in response to incidence of an electromagnetic wave W having a predetermined vibration direction (in the example of FIG. 1, the vibration direction is parallel to the Z direction).

[0036] As shown in FIG. 4, the metasurface 32 is disposed on an axis AX1. A pair of electrodes 33 are disposed on both sides of the metasurface 32. Each electrode 33 is electrically connected to each antenna structure 35 via a wiring. The metasurface 32 is formed of a metal (e.g., gold). Each electrode 33 is formed of, for example, the same material as the metasurface 32. A metal film 34 continuously covers the metasurface 32 and the pair of electrodes 33 and is in contact with the metasurface 32 and the pair of electrodes 33. The metal film 34 is formed of a metal (e.g., an alkali metal such as cesium) having a lower work function than the material of the metasurface 32. The metal film 34 has the function of improving the sensitivity (electron emission ability) of the metasurface 32. Note that instead of the pair of electrodes 33, a frame-shaped electrode 33 may be formed on the surface 31a.

[0037] The mounting mechanism 9 is configured as a separate body from the case 2, for example. The mounting mechanism 9 has a main body 10, a tightening screw 14 (second mounting portion), and an engaging member 15 (second mounting portion). The main body 10 is disposed in a position facing the rail portion 214 of the case 2. The main body 10 is formed in a rectangular cylindrical shape by a bottom wall 11 (first mounting portion) and a top wall 12 (second mounting portion) facing each other, and a pair of side walls 13 extending in the Z direction so as to connect both side edges of the bottom wall 11 in the Y direction with both side edges of the top wall 12 in the Y direction. The top wall 12 is disposed in a position facing an outer peripheral surface 213a of a side wall 213 of the case 2, and the bottom wall 11 is disposed on the side opposite the side on which the side wall 213 is located with respect to the top wall 12.

[0038] A holding structure 50 is attached to the bottom wall 11. As an example, the bottom wall 11 is provided with a hole 11a penetrating in the Z direction. A thread groove is formed on the inner surface of the hole 11a. A threaded portion 52 protruding upward is provided in the center of the upper end surface of a rod portion 51 of the holding structure 50. The threaded portion 52 is screwed into the hole 11a from the underside of the bottom wall 11 (the side opposite the top wall 12), thereby fixing the holding structure 50 to the bottom wall 11. From this fixed state, the rod portion 51 can be turned counterclockwise to release the screwing of the threaded portion 52 into the hole 11a, thereby removing the holding structure 50 from the attachment mechanism 9 (bottom wall 11). In this way, the bottom wall 11 is configured to allow the holding structure 50 to be detachably attached.

[0039] The top wall 12 is fixed to the case 2 by being sandwiched between the head 14a of the fastening screw 14 and the outer peripheral surface 213a of the side wall 213. The top wall 12, fastening screw 14, and engaging member 15 are attached to the rail 214 in a manner that allows them to switch between a locked state in which they are fixed to the rail 214, and an unlocked state in which they are movable along the rail 214. Figure 3 shows the unlocked state.

[0040] As an example, the top wall 12 is provided with a hole 12a penetrating in the Z direction. The fastening screw 14 has a head 14a and a threaded portion 14b provided in the center of the head 14a and protruding upward. The engaging member 15 is disposed within the rail 214. The engaging member 15 has a first portion 15a and a second portion 15b disposed inward of the first portion 15a (in the direction approaching the axis AX1). The first portion 15a extends a predetermined length in the Z direction with a width sufficient to pass through the guide portion 214c. The second portion 15b is connected to the inner end of the first portion 15a and is accommodated in the wide portion 214b of the rail 214. The second portion 15b is formed wider than the first portion 15a so as not to extend beyond the guide portion 214c. The second portion 15b has an outer surface 15c facing the inner surface 214d of the guide portion 214c. When viewed from the Z direction, a hole 15d penetrating in the Z direction is provided in the center of the engaging member 15 (first portion 15a and second portion 15b). A thread groove is formed on the inner surface of the hole 15d. The threaded portion 14b of the fastening screw 14 is inserted through the hole 12a of the top wall portion 12 and the guide portion 214c and screwed into the hole 15d of the engaging member 15, thereby attaching the mounting mechanism 9 (top wall portion 12 and engaging member 15) to the case 2.

[0041] The engaging member 15 is formed in a shape and size that prevents it from rotating in the Z direction within the rail portion 214. For example, the engaging member 15 (second portion 15b) has a predetermined width in the Y direction, so that when an attempt is made to rotate the engaging member 15 in the Z direction, the second portion 15b interferes with the wide portion 214b and prevents the engaging member 15 from rotating. Therefore, the more the threaded portion 14b is tightened into the hole 15d of the engaging member 15, the deeper the threaded portion 14b enters the hole 15d, thereby reducing the distance between the engaging member 15 and the head 14a of the clamping screw 14. Meanwhile, the head 14a of the clamping screw 14 can only approach the case 2 to a position where it abuts against the top wall portion 12. Therefore, as the tightening of the clamping screw 14 is increased, the first portion 15a enters the guide portion 214c of the rail portion 214, and the outer surface 15c of the second portion 15b approaches the inner surface 214d of the guide portion 214c. By tightening the clamping screw 14 until the outer surface 15c of the second portion 15b abuts against the inner surface 214d of the guide portion 214c, the guide portion 214c is sandwiched and fixed between the second portion 15b and the top wall portion 12. In this way, the locked state described above is achieved.

[0042] On the other hand, as shown in FIG. 3, when the threaded portion 14b of the clamping screw 14 is not tightly threaded into the hole 15d of the engagement member 15 (i.e., when the clamping screw 14 is not tightly fastened), the second portion 15b (outer surface 15c) of the engagement member 15 is separated from the inner surface 214d of the guide portion 214c, and the locked state of the guide portion 214c (i.e., the state in which the guide portion 214c is sandwiched between the second portion 15b and the top wall portion 12 and cannot move) is released. This realizes the unlocked state described above. In this unlocked state (FIG. 3), the case 2 can be rotated about the axis AX1 while the positions of the attachment mechanism 9 and the holding structure 50 are fixed. That is, when the holding structure 50 is attached to the attachment mechanism 9, the attachment mechanism 9 is configured to rotate the case 2 about the axis AX1, which is parallel to the light incident direction of the electromagnetic wave W and passes through approximately the center of the electron emitter 3, without changing the position of the holding structure 50. Since each component housed within the case 2 is fixed relative to the case 2, when the case 2 rotates, each component disposed within the case 2 also rotates together with the case 2 around the axis AX1.

[0043] The mounting mechanism 9 is provided so that, in an attached state (see FIGS. 1 to 3 ) in which the holding structure 50 is attached to the mounting mechanism 9 (in this embodiment, the bottom wall portion 11), the holding structure 50 indicates a target position at which light incident on the electron emitter 3 should be focused. The target position is, for example, a position at which a signal obtained when incident light is focused at that position exhibits a predetermined extreme value. The target position is, for example, a position at which the signal intensity (amount of emitted electrons) is maximized. In this embodiment, by aligning the focal position (converging position) of the light (electromagnetic wave W) with the position at which the metasurface 32 is provided in the electron emitter 3, the amount of electron emission (in this embodiment, the number of electrons emitted by field electron emission) is maximized, and the signal intensity is maximized. Therefore, in this embodiment, the target position is the position of the metasurface 32 in the electron emitter 3 (i.e., a position along the surface 31 a of the substrate 31). The target position may also be determined based on information obtained other than the signal intensity. For example, when it is possible to obtain an imaging result (two-dimensional image) as with image intensifier I, the position where the area of ​​the focal point (part having an intensity above a certain level) shown in the two-dimensional image is smallest may be determined as the target position.

[0044] As an example, in the attached state (see FIGS. 1 to 3), the center position of the rod portion 51 when viewed from the extension direction (Z direction) of the rod portion 51 (i.e., the position through which the central axis AX2 of the rod portion 51 shown in FIG. 3 passes) is configured to be located on a plane that is perpendicular to the light incidence direction (X direction) to the electron emitter 3 and includes the target position (metasurface 32). In other words, the attachment position of the attachment mechanism 9 relative to the case 2 and the attachment position of the holding structure 50 relative to the attachment mechanism 9 are set so that the above positional relationship is established.

[0045] [Action and effect] In the photodetector 1A, a holding structure 50 that holds the case 2 is detachably attached to the case 2 via an attachment mechanism 9. Furthermore, in the attached state, the holding structure 50 is configured to indicate the target position (in this embodiment, the position of the metasurface 32 in the electron emitter 3) at which light should be focused in the image intensifier I housed in the case 2. With the above configuration, after positioning the photodetector 1A so that the focus of a predetermined measurement light (electromagnetic wave W) is aligned with the target position in the attached state, the attachment mechanism 9 can be removed from the holding structure 50 without moving the holding structure 50. This allows the position where the target position was located (i.e., the focal position of the electromagnetic wave W) to be accurately and easily determined based on the holding structure 50. Therefore, the photodetector 1A allows a sample to be accurately and easily positioned at the focal position of the measurement light.

[0046] The above effect will be described in more detail with reference to FIG. 5. First, as shown in FIG. 5(a), the positions of the case 2 and the holding structure 50, which are fixed relative to each other via the mounting mechanism 9, are adjusted (step 1) so that the focal position of the electromagnetic wave W is at the target position (the plane including the metasurface 32). For example, this adjustment can be achieved by attaching the holding structure 50 to a moving mechanism, such as a stage, that can slide parallel to the propagation direction (X direction) of the electromagnetic wave W, and moving the case 2 and the holding structure 50 together in the X direction while monitoring the output value of the photodetector 1A (here, the intensity of the fluorescence output from the light exit window 7). The position of the moving mechanism can be adjusted to the position where the output value is maximized. Alternatively, it is possible to determine whether the focal position of the electromagnetic wave W matches the target position based on the fluorescence image (beam shape and size) emitted from the light exit window 7. This adjustment process can be performed manually or automatically by a computer (a device equipped with a processor, memory, etc., and having a computing function and the function of controlling the operation of other devices such as the stage).

[0047] 5(b), while keeping the position of the holding structure 50 fixed, the holding structure 50 is removed from the attachment mechanism 9, and the position of the sample Sa to be irradiated with the electromagnetic wave W is aligned on the central axis AX2 (see FIG. 3) of the holding structure 50 (second step). By the above operations, the sample Sa can be accurately and easily positioned at the focal position of the electromagnetic wave W.

[0048] In the photodetector 1A, the mounting mechanism 9 is configured to mount a holding structure 50 including a linearly extending rod portion 51. In addition, in the mounted state (FIGS. 1 to 3), the center position of the rod portion 51 (the position through which the central axis AX2 in FIG. 3 passes) when viewed from the extension direction (Z direction) of the rod portion 51 is located on a plane perpendicular to the light incidence direction (X direction) to the electron emitter 3 and including the target position (metasurface 32). With this configuration, the central axis AX2 of the rod portion 51 is located on a plane including the target position of the electron emitter 3. Therefore, the target position (the focal position of the electromagnetic wave W) can be more accurately and easily determined based on the position and orientation of the rod portion 51. For example, as shown in FIG. 5B, by placing the sample Sa directly above the rod portion 51 along the central axis AX2, the sample Sa can be easily positioned at the focal position of the electromagnetic wave W.

[0049] In the light detection device 1A, the mounting mechanism 9 is configured to change the relative positional relationship between the holding structure 50 and the case 2 while maintaining the holding structure 50 indicating the target position in the mounted state. According to the above configuration, the position of the holding structure 50 is fixed and the target position can be grasped by the holding structure 50 while the relative position of the case 2 with respect to the holding structure 50 (e.g., the attitude, angle, etc. of the case 2 with respect to the holding structure 50) can be changed. This improves convenience for the person performing the measurement. In this embodiment, the angle of the holding structure 50 with respect to the case 2 is changeable by rotating the case 2 around the axis AX1. However, the configuration for changing the relative positional relationship between the holding structure 50 and the case 2 is not limited to the above example. For example, the position of the case 2 in the height direction (Z direction) or the width direction (Y direction) with respect to the holding structure 50 may be changeable. In such a case, the position of the holding structure 50 is fixed and the central position (i.e., the position of the axis AX1) of the electron emitter 3 (metasurface 32) can be adjusted within the YZ plane while maintaining the holding structure 50 indicating the target position, thereby improving convenience for the person performing the measurement.

[0050] As shown in FIG. 3 , the photodetector 1A includes a power supply circuit unit 8 that is fixed to the case 2 (in this embodiment, disposed within the case 2) and supplies a voltage to the image intensifier I. According to the above configuration, since the power supply circuit unit 8 is disposed within the case 2, a cable or the like is not required to connect an external power supply for supplying voltage (a high-voltage power supply corresponding to the power supply circuit unit 8) disposed outside the case 2 to the case 2 (e.g., a connection interface provided on the outer wall of the case 2). As a result, problems such as twisting of the cable do not occur when changing the relative positional relationship between the holding structure 50 and the case 2 (in this embodiment, when rotating the case 2 around the axis AX1), improving convenience for the person performing the measurement. Furthermore, because the high-voltage power cable used to transmit the high voltage generated by the external power supply is relatively thick, even if twisting does not occur, there is a risk that interference from the cable may hinder the relative movement of the case 2 with respect to the holding structure 50. According to the photodetector 1A, such problems can be avoided, thereby facilitating the relative movement of the case 2 with respect to the holding structure 50. Furthermore, the cable may be subject to relatively large vibrations and movements caused by the relative movement of the case 2 with respect to the holding structure 50, which may cause the cable to act as a noise source and adversely affect the measurement. In contrast, with the photodetector 1A, the power supply circuit unit 8 as a high-voltage generating source is fixed to the case 2 (in this embodiment, housed within the case 2) together with the components to which voltage is applied (in this embodiment, the electron emitter 3, the electron multiplier 4, the fluorescent screen 5, etc.), thereby making it possible to avoid the occurrence of the above-mentioned problems.

[0051] In the photodetector 1A, the electron emitter 3 (metasurface 32) is configured to field emit electrons (field electron emission) in response to the incidence of electromagnetic waves W having a predetermined vibration direction (a direction parallel to the YZ plane) perpendicular to the X direction when viewed from the light incident direction (X direction) on the electron emitter 3. The mounting mechanism 9 is also configured to rotate the case 2 about an axis AX1 that is parallel to the X direction and passes through the electron emitter 3 (in this embodiment, approximately the center of the electron emitter 3) without changing the position of the holding structure 50. With this configuration, the direction to which the electron emitter 3 is sensitive (polarization characteristics) can be changed by rotating the case 2 about the axis AX1 parallel to the X direction while maintaining the relative position of the target position of the electron emitter 3 with respect to the holding structure 50. This allows the orientation of the case 2 (i.e., the polarization characteristics of the electron emitter 3) to be appropriately and easily adjusted according to the vibration direction of the predetermined measurement light (electromagnetic waves W) incident on the electron emitter 3 while maintaining the mounting state.

[0052] The above effect will be described in more detail with reference to Figure 6. Figure 6 shows the output value when an electromagnetic wave W having a vibration direction parallel to the Y direction is incident on the photodetector 1A for each state when the rotation angle of the case 2 is changed. The vertical axis (relative output value) of the graph in Figure 6 represents a value normalized by converting the maximum output value to "1." The horizontal axis represents the angle by which the case 2 is rotated clockwise from the initial state (state S1) shown in Figure 1.

[0053] As described above, in this embodiment, the electron emitter 3 (metasurface 32) has polarization characteristics that are sensitive to a predetermined vibration direction (the Z direction in the state shown in FIG. 1). Therefore, when the vibration direction of the electromagnetic wave W is the Y direction, which is perpendicular to the Z direction, and the electron emitter 3 (each antenna structure 35) is sensitive in the Z direction as shown in state S1 in FIG. 6 (i.e., the state shown in FIGS. 1 to 3), the output value of the photodetector 1A (here, the intensity of the fluorescence output from the light exit window 7) is very small (close to 0). More specifically, the direction in which each antenna structure 35 is sensitive (the direction in which the pair of ends 35a face each other) is significantly offset (90 degrees offset) from the vibration direction of the electromagnetic wave W. Therefore, the amplification of the electric field in response to the incidence of the electromagnetic wave W does not occur in each antenna structure 35 (or the amplification effect is small). Therefore, the number of electrons emitted by field emission (field electron emission) is small, resulting in a very small output value.

[0054] In such a case, the photodetector 1A can easily align the orientation (polarization characteristics) of the electron emitter 3 with the vibration direction of the electromagnetic wave W. Specifically, when the vibration direction of the electromagnetic wave W is parallel to the Y direction, the mounting state of the mounting mechanism 9 relative to the case 2 is set to the unlocked state (FIG. 3) described above, and then the case 2 is rotated 90 degrees clockwise (or counterclockwise) around the axis AX1 to state S2 (or state S4) shown in FIG. 6. In state S2 or state S4, the electron emitter 3 is sensitive in the Y direction, and thus can appropriately detect the electromagnetic wave W oscillating in the Y direction. That is, because the direction in which each antenna structure 35 is sensitive coincides with the vibration direction of the electromagnetic wave W, an electric field amplification effect occurs in each antenna structure 35 in response to the incidence of the electromagnetic wave W. This increases the number of electrons emitted by field emission (field electron emission), resulting in a high output value.

[0055] If it is desired to detect electromagnetic waves W oscillating in the Z direction, the rotation angle of case 2 can be adjusted to reach state S1 or state S3 in Figure 6. State S3 is the state in which case 2 is rotated 90 degrees clockwise around axis AX1 from state S2.

[0056] In the light detecting device 1A, the mounting mechanism 9 has a first mounting portion (in this embodiment, the bottom wall portion 11) to which the holding structure 50 is attached, and a second mounting portion (in this embodiment, the top wall portion 12, the tightening screw 14, and the engaging member 15) that is fixed to the case 2. The case 2 has an outer circumferential surface 213a that follows a circumference centered on an axis AX1 that passes through the electron emitter 3 when viewed from the light incident direction (X direction), and rail portions 214 that are provided on the outer circumferential surface 213a along the circumference. The second mounting portion is attached to the rail portion 214 in a manner switchable between a locked state in which it is fixed to the rail portion 214 (in this embodiment, a state in which the guide portion 214c is clamped between the top wall portion 12 and the second portion 15b (engaging member 15) by tightening the fastening screw 14), and an unlocked state in which it is movable along the rail portion 214 (in this embodiment, a state in which the fastening screw 14 is loosened and the guide portion 214c is able to move freely with respect to the top wall portion 12 and the engaging member 15). With the above configuration, as described above, it is possible to easily and appropriately realize a configuration in which the case 2 can rotate about the axis AX1 while maintaining the attached state (i.e., a state in which the holding structure 50 is attached to the attachment mechanism 9 so that the holding structure 50 indicates the target position).

[0057] [Second embodiment] As shown in FIGS. 7 to 9 , the photodetector 1B according to the second embodiment includes a case 70 (support), an electron tube 90 (photodetector element) disposed within the case 70, and a mounting plate 80 (mounting mechanism). The case 70 is formed in a rectangular parallelepiped shape. In the photodetector 1B, the mounting plate 80 functions similarly to the mounting mechanism 9 of the first embodiment. That is, the mounting plate 80 is configured to allow a holding structure 50 to be detachably mounted thereto. Furthermore, in the mounted state in which the holding structure 50 is mounted to the case 70 via the mounting plate 80, the holding structure 50 is configured to indicate the target position of the electron tube 90. As an example, the photodetector 1B is also configured such that the central axis AX2 of the rod portion 51 of the holding structure 50 is positioned on a plane including the target position of the electron tube 90 (for example, the position of the metasurface 32 of the electron emitter 3 included in the electron tube 90).

[0058] In the light detection device 1B, the mounting state includes a first mounting state and a second mounting state. The first mounting state is a state in which the holding structure 50 is mounted to a mounting plate 80 attached to a first portion (for example, the bottom wall portion 73) of the case 70. The second mounting state is a state in which the holding structure 50 is mounted to a mounting plate 80 attached to a second portion (for example, the side wall portion 72) different from the first portion of the case 70. Figures 7 and 8 show the first mounting state. Figure 9 shows the second mounting state.

[0059] The case 70 has a front wall 71, side walls 72, and a bottom wall 73. The front wall 71 is provided with an opening 71a that functions as an entrance opening for predetermined measurement light (electromagnetic wave W). As an example, the opening 71a is formed in a substantially square shape when viewed from the light incident direction (X direction). The side wall 72 is a wall that forms the right side of the case 70 when viewed from the front (the side facing the front wall 71). The bottom wall 73 is a wall that forms the lower surface of the case 70. The side wall 72 is provided with a plurality of (four in this embodiment) holes 70a. Thread grooves are formed on the inner surfaces of the holes 70a. Although not visible in FIG. 7 , the bottom wall 73 is also provided with a plurality of (four in this embodiment) holes 70a at positions corresponding to the four through holes 80a of the mounting plate 80, similar to the side wall 72.

[0060] The case 70 houses an electron tube 90 including an electron emitter 3. As an example, the electron tube 90 is a photomultiplier tube that includes, in addition to the electron emitter 3, an electron multiplier (not shown) disposed downstream of the electron emitter 3 and an electron collector (anode, not shown) that collects electrons multiplied by the electron multiplier. The electron multiplier may be a microchannel plate similar to the electron multiplier 4 of the photodetector 1A, or may be multiple dynodes arranged in multiple stages. The electron emitter 3 included in the electron tube 90 is the same component as the electron emitter 3 included in the photodetector 1A. That is, the electron emitter 3 included in the electron tube 90 has the structure shown in FIG. 4 and includes a metasurface 32. That is, in the photodetector 1B as well, the target position of the electron emitter 3 is the position of the metasurface 32 (a planar position along the surface 31a of the substrate 31).

[0061] A power supply circuit section 8B electrically connected to the electron tube 90 via a conductive member C such as a cable is housed inside the case 70. Similar to the power supply circuit section 8 of the photodetector 1A, the power supply circuit section 8B includes a circuit that supplies voltage to each component inside the electron tube 90 (for example, the above-mentioned electron emitter 3, electron multiplier, etc.).

[0062] The mounting plate 80 is configured as a separate member from the case 70. As shown in Figures 7 and 8, the mounting plate 80 is a rectangular plate-shaped member whose length in the Y direction is longer than the bottom wall portion 73. The mounting plate 80 is configured to be detachably attached to the case 70. The mounting plate 80 has an inner surface 81 that faces the case 70 when attached to the case 70, an outer surface 82 opposite the inner surface 81, and a square annular side surface 83 that connects an edge of the inner surface 81 with an edge of the outer surface 82.

[0063] The mounting plate 80 is provided with a plurality of (four in this embodiment) through-holes 80a penetrating from the inner surface 81 to the outer surface 82. Each through-hole 80a is a through-hole for fixing the mounting plate 80 to the case 70. As an example, a portion of the through-hole 80a along the inner surface 81 is provided with an annular flange portion 80c (see FIG. 9 ) that protrudes radially inward from the through-hole 80a. The plurality of (four) holes 70a provided in the side wall portion 72 of the case 70 are positioned opposite the respective through-holes 80a when the mounting plate 80 is positioned as shown in FIG. 9 . Similarly, the plurality of (four) holes 70a provided in the bottom wall portion 73 of the case 70 are positioned opposite the respective through-holes 80a when the mounting plate 80 is positioned as shown in FIGS. 7 and 8 .

[0064] In both the first mounting state (FIGS. 7 and 8) and the second mounting state (FIG. 9), the mounting plate 80 is attached to the case 70 (bottom wall portion 73 or side wall portion 72) by inserting the threaded portion of a mounting screw (not shown) into each through hole 80a and screwing the threaded portion of the mounting screw into the hole portion 70a until the head of the mounting screw abuts the flange portion 80c.

[0065] The mounting plate 80 has a through hole 80a for mounting the mounting plate 80 to the case 70, as well as a through hole 80b for mounting the holding structure 50. As an example, a thread groove is formed on the inner surface of the through hole 80b. The threaded portion 52 of the holding structure 50 is screwed into the through hole 80b from the outer surface 82 side of the mounting plate 80, thereby fixing the holding structure 50 to the mounting plate 80. From this fixed state, the rod portion 51 can be turned counterclockwise to release the threaded portion 52 from the through hole 80b, thereby removing the holding structure 50 from the mounting plate 80. In this manner, the mounting plate 80 is configured to allow the holding structure 50 to be removably attached.

[0066] As shown in FIG. 8 , in the first mounting state, the center position of the rod portion 51 when viewed from the extension direction (Z direction) of the rod portion 51 (i.e., the position through which the central axis AX2 of the rod portion 51 passes) is configured to be located on a plane that is perpendicular to the light incident direction (X direction) to the electron emitter 3 and that includes the target position (the metasurface 32). The electron emitter 3 is disposed relatively close to the front surface of the front wall portion 71. For this reason, in the present embodiment, as an example, the mounting plate 80 has a protrusion 84 that protrudes forward from the bottom wall portion 73 so that the rod portion 51 can be mounted to the mounting plate 80 so that the central axis AX2 of the rod portion 51 passes through the target position. By providing such a protrusion 84, it is possible to easily and appropriately mount the holding structure 50 to the mounting plate 80 even when the target position of the electron emitter 3 is disposed close to the front surface of the front wall portion 71. That is, by providing the protrusion 84, a configuration is realized in which the upper end surface of the rod portion 51 does not protrude from the outer surface 82 of the mounting plate 80, and in which the through-hole 80b into which the screw portion 52 is inserted can be provided (or in which the through-hole 80b can be prevented from coming too close to the front end of the mounting plate 80). However, if the above-mentioned problems do not occur even if the protrusion 84 is not provided, the protrusion 84 does not have to be provided. Furthermore, the outer dimension of the mounting plate 80 (length in the X direction) may be the same as or shorter than that of the case 70.

[0067] As shown in Figure 9, even in the second mounting state, the position of the through hole 80b of the mounting plate 80 in the X direction is the same as in the first mounting state (Figures 7 and 8), so the position through which the central axis AX2 of the rod portion 51 passes is configured to be located on a plane including the metasurface 32 of the electron emitter 3.

[0068] According to the photodetector 1B, by switching the position at which the mounting plate 80 is attached to the case 70, the attitude of the case 70 relative to the holding structure 50 can be appropriately set depending on the application. Furthermore, regardless of whether the mounting plate 80 is attached to the first portion (for example, the bottom wall portion 73) or the second portion (for example, the side wall portion 72), the target position of the electron emitter 3 (for example, the planar position including the metasurface 32) can be grasped by the holding structure 50 attached to the mounting plate 80. Therefore, according to the photodetector 1B, the convenience of the person performing the measurement can be effectively improved.

[0069] The mounting plate 80 has a through hole 80d similar to the through hole 80b at a position that coincides with approximately the center of the case 70 in the X direction when the mounting plate 80 is attached to the bottom wall 73 or the side wall 72. When it is not necessary to specify the target position of the electron emitter 3 based on the holding structure 50, the holding structure 50 can be attached to the through hole 80d instead of the through hole 80b, thereby allowing the holding structure 50 to hold approximately the center of the case 70 in the X direction. This improves the holding stability of the case 70. In this way, the mounting mechanism (mounting plate 80) may be provided with not only a mounting portion (through hole 80b) for specifying the target position, but also a mounting portion (through hole 80d) for other uses (here, as an example, a use for improving the holding stability of the case 70 by the holding structure 50).

[0070] [Variations] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. The materials and shapes of each component are not limited to the specific materials and shapes described above, and various materials and shapes other than those described above can be used. Furthermore, some components included in the above-described embodiments may be omitted or modified as appropriate, and can be arbitrarily combined with other additional components.

[0071] For example, the electron emitter 3 does not have to include a metasurface 32. The electron emitter 3 does not have to be configured to have polarization characteristics in a predetermined vibration direction. Correspondingly, the predetermined measurement light is not limited to the electromagnetic wave W described above. Furthermore, the target position in a photodetector (e.g., the image intensifier I of the first embodiment and the electron tube 90 of the second embodiment) is determined according to the configuration of the photodetector. For example, if the electron emitter 3 included in the photodetector is a plate-shaped member (face plate) and is configured to maximize electron emission efficiency by focusing incident light on the light-incident surface of the plate-shaped member, the light-incident surface may be the target position. On the other hand, if the electron emission efficiency is maximized by focusing incident light on the surface opposite the light-incident surface of the plate-shaped member, the target position may be the surface opposite the light-incident surface. Furthermore, the photodetector may be a phototube having an electron emitter 3 as a photoelectric conversion unit but not an electron multiplier 4. Furthermore, the photodetector element is not limited to one having an electron emitter 3 which is a photoelectric conversion unit, but may also be one having a semiconductor solid-state element such as a photodiode that directly detects incident light as an electrical signal. In this case, the light incident surface of the semiconductor solid-state element is the target position. Furthermore, the support that supports the photodetector element is not limited to one that houses the photodetector element inside, as in case 2. For example, the support may be a member (e.g., a plate-like or table-like member) configured to allow the photodetector element to be placed on or to fix the photodetector element (e.g., part of the housing of the photodetector element).

[0072] Furthermore, in the first and second embodiments, the attachment mechanism (attachment mechanism 9, attachment plate 80) is configured as a separate body from the case 2, 70 (support portion), but the attachment mechanism may be formed integrally with the case that houses (supports) the light detection element. For example, a structure for attaching the holding structure 50 to a predetermined position on the outer wall of the case (attachment mechanism integrated with the case) may be provided.

[0073] Furthermore, an electron tube other than the image intensifier I (for example, the electron tube 90 of the second embodiment) may be disposed inside the case structure of the first embodiment (a structure that rotates, such as case 2). Conversely, an electron tube other than the electron tube 90 (for example, the image intensifier I of the first embodiment) may be disposed inside the case structure of the second embodiment (a structure that allows attachment mechanisms to be attached to a plurality of different locations, such as case 70). Furthermore, a configuration in which the case can be moved relative to the holding structure 50 while maintaining the attached state (a state in which the holding structure 50 indicates the target position), as in the first embodiment, and a configuration in which the holding structure 50 can be attached to a plurality of locations on the case, as in the second embodiment, may be used in combination.

[0074] Furthermore, the method by which the holding structure 50 indicates the target position is not limited to the method of positioning the central axis AX2 of the rod portion 51 on a plane passing through the target position as in this embodiment. For example, the holding structure may be configured to have a plurality of rod portions (e.g., two) and the position of the midpoint between the central axes of the two rod portions may be configured to be located on a plane passing through the target position. Thus, in the present disclosure, the aspect in which "the holding structure indicates the target position" may be any aspect in which the target position can be identified based on the position, shape, attitude, etc. of one or more members that make up the holding structure.

[0075] Furthermore, each of the configurations described in the present disclosure may be used independently. For example, in the first embodiment, the structure that allows the case 2 to rotate around the axis AX1 while the position of the holding structure 50 is fixed may be employed in a configuration in which the holding structure 50 does not indicate the target position. In this case, although the effect of being able to identify the target position using the holding structure 50 is not obtained, the effect of being able to measure the electromagnetic wave W by appropriately adjusting the angle of the case 2 while keeping the holding position of the case 2 (i.e., the position of the holding structure 50) fixed according to the vibration direction of the electromagnetic wave W is obtained. [Explanation of symbols]

[0076] 1A, 1B...photodetector, 2, 70...case (supporting portion), 3...electron emitting portion, 8, 8B...power supply circuit portion, 9...mounting mechanism, 11...bottom wall portion (first mounting portion), 12...top wall portion (second mounting portion), 14...tightening screw (second mounting portion), 15...engaging member (second mounting portion), 50...holding structure, 51...rod portion, 72...side wall portion (second portion), 73...bottom wall portion (first portion), 80...mounting plate (mounting mechanism), 90...electron tube (photodetector element), 213a...outer surface, 214...rail portion, W...electromagnetic wave (light), I...image intensifier (photodetector element), H...housing.

Claims

1. a photodetector element; a support portion that supports the light detection element; an attachment mechanism configured to detachably attach a holding structure for holding the support portion, The mounting mechanism is configured so that, when the holding structure is attached to the mounting mechanism, the holding structure indicates a target position at which light incident on the light detection element should be focused.

2. the mounting mechanism is configured to mount the holding structure including a linearly extending rod portion; 2. The light detection device according to claim 1, wherein in the attached state, a center position of the rod portion when viewed from the extension direction of the rod portion is located on a plane that is perpendicular to the direction of light incidence on the light detection element and that includes the target position.

3. 2. The light detection device according to claim 1, wherein the mounting mechanism is configured to be able to change the relative positional relationship between the holding structure and the support portion while maintaining the holding structure indicating the target position in the mounted state.

4. The photodetector device according to claim 3 , further comprising a power supply circuit section fixed to the support section and supplying a voltage to be applied to the photodetector element.

5. the photodetector element includes an electron emitting portion that emits electrons in response to incidence of light, the electron emission portion is configured to field-emit the electrons in response to incidence of an electromagnetic wave having a predetermined vibration direction perpendicular to the light incidence direction when viewed from the light incidence direction relative to the electron emission portion, The optical detection device described in any one of claims 1 to 4, wherein the mounting mechanism is configured to be able to rotate the support portion around an axis parallel to the light incident direction and passing through the electron emission portion without changing the position of the holding structure in the mounted state.

6. the attachment mechanism has a first attachment portion to which the holding structure is attached and a second attachment portion fixed to the support portion, the support portion has an outer peripheral surface along a circumference having an axis passing through the electron emission portion as a center when viewed from the light incident direction, and a rail portion provided on the outer peripheral surface along the circumference, 6. The light detection device according to claim 5, wherein the second mounting portion is attached to the rail portion in a manner switchable between a locked state in which the second mounting portion is fixed to the rail portion and an unlocked state in which the second mounting portion is movable along the rail portion.

7. The attachment mechanism is configured as a separate body from the support portion, 2. The optical detection device of claim 1, wherein the mounting states include a first mounting state in which the holding structure is mounted to the mounting mechanism attached to a first portion of the support portion, and a second mounting state in which the holding structure is mounted to the mounting mechanism attached to a second portion of the support portion that is different from the first portion.

Images