Observation device

Abstract

An observation apparatus is provided that enables the observation of a distant object of interest between the observation apparatus and the object of interest. The observation apparatus (10) includes: a transmitting unit (20) having an emitted light field of view (Ss) and emitting pulsed light having a wavelength belonging to the ultraviolet region of the solar blind band into the emitted light field of view; a receiving unit (30) having a receiving light field of view (Sr) and receiving reflected light within the receiving light field of view from the reflected pulsed light due to reflection by the object of interest; and an observation data generation unit. The optical axes (AXs) of the transmitting unit and the optical axes (AXr) of the receiving unit are parallel to each other. The emitted light viewing angle (θs) defining the emitted light field of view is larger than the receiving light viewing angle (θr) defining the receiving light field of view. The emitted light field of view and the receiving light field of view at least partially overlap each other. The observation data generation unit generates LIDAR data as observation data based on a signal output from a light receiving element.

Description

Technical Field

[0001] This disclosure relates to an observation device, and more particularly to an observation device capable of observing a target object near the ground at a short distance from the observation device. Background Technology

[0002] Patent document 1 describes an observation device that performs LiDAR observations based on observation light relative to a laser emitted toward the target object.

[0003] Reference List

[0004] Patent documents

[0005] Patent Document 1: International Patent Publication No. WO2003 / 073127 Summary of the Invention

[0006] Technical issues

[0007] However, in Patent Document 1, there is a problem: since the observation is performed using a laser, it is possible to observe the target object that exists at a relatively distant location (e.g., several kilometers away), but it is not possible to observe the target object at the distant location and the target object between the observation device, for example, the target object near the ground and at a short distance from the observation device.

[0008] This disclosure is intended to solve such a problem and aims to provide an observation device capable of observing a target object near the ground and at a short distance from the observation device.

[0009] Technical solution

[0010] According to the observation apparatus of this disclosure, the observation apparatus includes: a transmitting unit configured to have an emitting light field of view and emitting pulsed light having a wavelength belonging to the ultraviolet region of the solar blind band within the emitting light field of view; a receiving unit having a receiving light field of view and receiving reflected light from the pulsed light reflected by the observed target object within the receiving light field of view; and an observation data generation unit, wherein the transmitting unit includes: a semiconductor light-emitting element configured to emit pulsed light; and an emitting optical system configured to control the pulsed light emitted by the semiconductor light-emitting element, such that the pulsed light emitted by the semiconductor light-emitting element... The pulsed light emitted by the device is emitted within the field of view of the emitted light. The receiving unit includes: a receiving optical system configured to collect reflected light in the field of view of the received light; and a light receiving element configured to receive the collected reflected light and output a signal corresponding to the received reflected light. The optical axes of the emitting unit and the receiving unit are parallel to each other. The emitting light viewing angle that defines the field of view of the emitted light is greater than the receiving light viewing angle that defines the field of view of the received light. The emitting light field of view and the receiving light field of view overlap at least partially. The observation data generation unit generates LiDAR data as observation data based on the signal output from the light receiving element.

[0011] This structure enables the observation of target objects that are near the ground and at a short distance from the observation device.

[0012] This is because the emitted light field of view is larger than the received light field of view that defines the received light field of view, and the emitted light field of view and the received light field of view overlap at least partially with each other.

[0013] In the observation device, the field of view of the emitted light can be a conical region centered on the optical axis of the emitting unit and having a diameter that increases along the optical axis of the emitting unit with increasing distance from the emitting unit. Similarly, the field of view of the received light can be a conical region centered on the optical axis of the receiving unit and having a diameter that increases along the optical axis of the receiving unit with increasing distance from the receiving unit.

[0014] Furthermore, in the observation device, the wavelengths belonging to the ultraviolet region can be selected from the wavelength range of 240 nm to 300 nm.

[0015] Furthermore, in the observation device, the pulsed light can be incoherent light.

[0016] Furthermore, in the observation device, the frequency of the pulsed light can be from 1 to 10 MHz.

[0017] Furthermore, in the observation device, the pulse width of the pulsed light can be from 1 to 10 ns.

[0018] Furthermore, in the observation device, the signal output from the light receiving element can be a pulsed electrical signal corresponding to a photon.

[0019] In addition, in the observation device, the receiving optical system can be a non-axial parabolic mirror and a retroreflector.

[0020] Furthermore, in the observation device, the non-axial parabolic mirror and the retroreflector may include a dielectric multilayer film, which reflects light on the respective mirror surface.

[0021] Furthermore, in the observation apparatus, the non-axial parabolic mirror and the retroreflector may include an anti-reflection member that absorbs light other than reflected light on the lower layer of the corresponding dielectric multilayer film or on the rear surface of the corresponding mirror.

[0022] Beneficial effects

[0023] According to this disclosure, an observation device can be provided that is capable of observing a target object near the ground and at a short distance from the observation device. Attached Figure Description

[0024] [ Figure 1 [ ] is a schematic diagram of the configuration of the observation device 10; [ Figure 2 ]yes Figure 1 A longitudinal cross-sectional view (schematic diagram) of the observation device 10 shown; [ Figure 3 [This is a graph showing the variation pattern of the field-of-view coupling ratio Crs when the emitted light viewing angle θs = 10 mrad and the received light viewing angle θr = 3 mrad.] [ Figure 4 ]yes Figure 3 Enlarged view of the section with a mid-range distance of 0 to 30 m; [ Figure 5 [This is a graph showing the variation pattern of the field-of-view coupling ratio Crs when the emitted light viewing angle is 10 mrad and the received light viewing angle is θr = 5 mrad.] [ Figure 6 ]yes Figure 5 Enlarged view of the section with a mid-range distance of 0 to 30 m; [ Figure 7 This is a conceptual diagram of the generation and processing of observational data (LiDAR data); [ Figure 8 [This is a schematic diagram of the configuration of observation device 10A;] [ Figure 9 [This is a graph showing the emission spectrum of the deep ultraviolet LED 21;] [ Figure 10 [This is a diagram showing the state in which light PL1 and PL2 (pulsed light) emitted from deep ultraviolet LED 21 (emitting surface) are also emitted in a direction tilted relative to the optical axis AXs of emitting unit 20; [ Figure 11 [This is an example of drive circuit 24;] [ Figure 12A This is an example of the emission characteristics of pulsed light; [ Figure 12B This is an example of the emission characteristics of pulsed light; [ Figure 13 [This is a graph showing the relationship between supply voltage (V) and frequency (MHz);] [ Figure 14 ] is from Figure 8 A schematic diagram of the extracted receiving unit 30; [ Figure 15 [This is a schematic diagram of the configuration of observation device 10B;] [ Figure 16 [This is a cross-sectional view of the first receiving mirror 37;] [ Figure 17 [This is a cross-sectional view of the second receiving mirror 38; and] [ Figure 18 The reflection spectrum of the reflected light from each receiving mirror is shown. Detailed Implementation

[0025] Hereinafter, the observation apparatus 10 according to the embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, corresponding components are represented by the same reference numerals, and redundant descriptions are omitted.

[0026] <Overview of Observation Device 10>

[0027] First, an overview of the observation device 10 of this embodiment will be described.

[0028] Figure 1 This is a schematic diagram of the configuration of the observation device 10.

[0029] The observation device 10 of this embodiment is a device (LiDAR device) that remotely observes the target object Ob (e.g., airborne particles such as aerosols and dust) existing at a short distance (e.g., 10m to 150m) in a non-contact manner.

[0030] like Figure 1 As shown, the observation device 10 includes a transmitting unit 20, a receiving unit 30, and a control and analysis unit 40.

[0031] Figure 2 yes Figure 1 A longitudinal cross-sectional view (schematic diagram) of the observation device 10 shown.

[0032] like Figure 2As shown, the transmitting unit 20 has an emission light field of view Ss, and emits pulsed light (hereinafter also referred to as emitted light) within the emission light field of view Ss, having a wavelength (e.g., 265 nm) belonging to the ultraviolet region of the solar blind band. On the other hand, the receiving unit 30 has a receiving light field of view Sr, receives reflected light (reflected pulse light) reflected by the observed target object Ob and returning to the received light field of view Sr within the emitted light (pulse light), and outputs a pulsed electrical signal (electrical signal of the pulse wave) corresponding to the received reflected light. The pulsed light can be spontaneously emitted light (incoherent light).

[0033] The optical axes AXs of the transmitting unit 20 and AXr of the receiving unit 30 are arranged separately from each other and parallel to each other. The distance L1 between the optical axes AXs of the transmitting unit 20 and AXr of the receiving unit 30 is, for example, 85 mm.

[0034] The emitted light field of view Ss is a conical region centered on the optical axis AXs of the emitting unit 20, and has a diameter that increases along the optical axis AXs of the emitting unit 20 with increasing distance from the emitting unit 20. The minimum diameter of the emitted light field of view Ss (in...) Figure 2 The diameter of the left end is, for example, 60 mm. The emission angle θs, which defines the emission field of view Ss, is, for example, 10 mrad (0.57°).

[0035] On the other hand, the received light field Sr is a conical region centered on the optical axis AXr of the receiving unit 30, and has a diameter that increases along the optical axis AXr of the receiving unit 30 with increasing distance from the receiving unit 30. The minimum diameter of the received light field Sr (in...) Figure 2 The diameter of the left end is, for example, 100 mm. The receiving light viewing angle θr that defines the receiving light field of view Sr is, for example, 3 mrad (0.17°) or 5 mrad (0.29°).

[0036] As mentioned above, the transmitted light angle θs is set to be greater than the received light angle θr.

[0037] Next, the overlap (superposition) of the transmitted light field of view Ss and the received light field of view Sr will be explained.

[0038] As described above, the optical axis AXs of the transmitting unit 20 and the optical axis AXr of the receiving unit 30 are set in a state that is separate from each other and parallel to each other. The transmitted light field of view Ss and the received light field of view Sr are each a conical region, and the transmitted light viewing angle θs is set to be greater than the received light viewing angle θr.

[0039] As a result, such Figure 2 As shown, the emitted light field of view Ss and the received light field of view Sir overlap to form a superimposed light field of view Sc (see...). Figure 2The shaded area HT and the superimposed light field of view Sc in each cross-sectional view will be discussed in detail below. The superimposed light field of view Sc is the overlap of the emitted light field of view Ss and the received light field of view Sr.

[0040] The ratio of the superimposed light field of view Sc to the emitted light field of view Ss can be represented by the field coupling ratio Crs. The field coupling ratio Crs is calculated by Equation 1 as described below.

[0041] Field coupling ratio Crs = Superimposed light field of view Sc / Emitted light field of view Ss ... (Equation 1)

[0042] However, the superimposed field of view Sc is the region in each cross section where the emitted field of view Ss and the received field of view Sr overlap (see [reference]). Figure 2 (Each cross-section diagram). The emitted light field of view Ss is the area of ​​the emitted light field of view Ss in each cross-section.

[0043] A large field-of-view coupling ratio Crs indicates a large amount of reflected light (reflected pulse light) reflected from the observed target object Ob and returned to the receiving light field of view Sr.

[0044] like Figure 2 As shown, the outer edge of the emitted light field of view Ss is tangent to the outer edge of the received light field of view Sr at a first position P1, which is separated from the far end position P0 of the lens tube by a first distance r1 (see along). Figure 2 (See the cross-sectional view taken from line BB in the image). Furthermore, the outer edge of the emitted light field of view Ss contacts the optical axis AXr of the receiving unit 30 at a second position P2, which is a second distance r2 separated from the distal end position P0 of the lens barrel (see the image along the line BB). Figure 2 (Cross-sectional view taken from line CC in the image). Furthermore, the outer edge of the receiving light field Sr is internally tangent to the outer edge of the emitted light field Ss at a third position P3, a third distance r3 separate from the far end position P0 of the lens barrel (see along...). Figure 2 (Cross-sectional view taken from line DD in the diagram). Furthermore, at each position beyond the third position P3, the outer edge of the receiving light field Sr is included within the outer edge of the emitting light field Ss, without contacting the outer edge of the emitting light field Ss (see along...). Figure 2 (Cross-section diagram of line EE in the diagram).

[0045] Next, we will explain the variation mode of the field coupling ratio Crs.

[0046] First, the variation mode of the field-of-view coupling ratio Crs will be explained when the transmitted light viewing angle θs = 10 mrad and the received light viewing angle θr = 3 mrad.

[0047] Figure 3This is a graph showing the variation pattern of the field-of-view coupling ratio Crs when the transmitted light viewing angle θs = 10 mrad and the received light viewing angle θr = 3 mrad. Figure 4 yes Figure 3 Enlarged view of the section from 0 m to 30 m in the middle.

[0048] like Figure 4 As shown, with the emitted light viewing angle θs = 10 mrad and the received light viewing angle θr = 3 mrad, the first position P1 is a position where the emitter unit 20 is separated from the emitter unit 20 by a first distance r1 (0.44 m) along the optical axis AXs of the emitter unit 20 (the distal end position P0 of the lens barrel). Furthermore, the second position P2 is a position where the emitter unit 20 is separated from the emitter unit 20 by a second distance r2 (5.5 m) along the optical axis AXs of the emitter unit 20 (the distal end position P0 of the lens barrel). Furthermore, the third position P3 is a position where the emitter unit 20 is separated from the emitter unit 20 by a third distance r3 (15 m) along the optical axis AXs of the emitter unit 20 (the distal end position P0 of the lens barrel). Finally, the fourth position P4 is a position that maximizes the field-of-view coupling ratio Crs and is separated from the emitter unit 20 by 11 m along the optical axis AXs of the emitter unit 20 (the distal end position P0 of the lens barrel).

[0049] The distance region from the far end position P0 of the lens barrel to the first position P1 is the distance region where the outer periphery of the emitted light field of view Ss and the outer periphery of the received light field of view Sr are separated from each other. Therefore, since no superimposed light field of view Sc is formed, the field coupling ratio Crs is zero. Next, the distance region from the first position P1 to the second position P2 is the distance region from the point where the outer periphery of the emitted light field of view Ss contacts the outer periphery of the received light field of view Sr to the optical axis AXr of the received light field of view Sr. In this region, the field coupling ratio Crs increases sharply as the superimposed light field of view Sc expands. Next, the distance region from the second position P2 to the third position P3 is the distance region where the outer periphery of the emitted light field of view Ss reaches the far outer periphery of the received light field of view Sr on the optical axis AXr of the received light field of view Sr. In this region, since the emitted light field of view Ss also expands as the superimposed light field of view Sc expands, the field coupling ratio Crs gradually increases to a maximum value and then decreases. Finally, the distance region beyond the third position P3 is the distance region encompassing the emitted light field of view Ss and the received light field of view Sr. In this region, the superimposed light field of view Sc and the received light field of view Sr are equal to each other, but due to the large expansion rate of the emitted light field of view Ss, the field coupling ratio Crs gradually decreases.

[0050] Next, we will explain the variation mode of the field-of-view coupling ratio Crs when the transmitted light angle is 10 mrad and the received light angle is θr = 5 mrad.

[0051] Figure 5This is a graph showing the variation pattern of the field-of-view coupling ratio Crs when the emitted light angle is 10 mrad and the received light angle is θr = 5 mrad. Figure 6 yes Figure 5 Enlarged view of the section with a mid-range distance of 0 m to 30 m.

[0052] like Figure 6 As shown, with the emitted light viewing angle θs = 10 mrad and the received light viewing angle θr = 5 mrad, the first position P1 is a position where the emitter unit 20 is separated from the emitter unit 20 by a first distance r1 (0.38 m) along the optical axis AXs of the emitter unit 20 (the distal end position P0 of the lens barrel). Furthermore, the second position P2 is a position where the emitter unit 20 is separated from the emitter unit 20 by a second distance r2 (5.5 m) along the optical axis AXs of the emitter unit 20 (the distal end position P0 of the lens barrel). Furthermore, the third position P3 is a position where the emitter unit 20 is separated from the emitter unit 20 by a third distance r3 (21 m) along the optical axis AXs of the emitter unit 20 (the distal end position P0 of the lens barrel). Finally, the fourth position P4 is a position that maximizes the field-of-view coupling ratio Crs and is separated from the emitter unit 20 by 16 m along the optical axis AXs of the emitter unit 20 (the distal end position P0 of the lens barrel).

[0053] The variation of the field-of-view coupling ratio Crs in each distance region from the far end position P0 to the first position P1, from the first position P1 to the second position P2, from the second position P2 to the third position P3, and beyond the third position P3, is similar to the case where the received light viewing angle θr is 3 mrad. However, since the received light viewing angle θr of the received light field of view Sr is as large as 5 mrad, the field-of-view coupling ratio Crs increases at the same observation distance.

[0054] As described above, observations can be performed starting at a distance exceeding the first position P1 (outer tangent stacking distance) from which the superimposed light field of view Sc is formed. Furthermore, it is preferable to perform observations at a distance exceeding the second position P2 (centerline contact stacking distance), where the superimposed light field of view Sc is approximately half or more of the received light field of view Sr. Moreover, considering the missing portion of the superimposed light field of view Sc and the field coupling ratio Crs, it is preferable to perform observations at a distance exceeding the third position P3 (inner tangent stacking distance), where the superimposed light field of view Sc coincides with the received light field of view Sr. It should be noted that since the transmitting unit 20 and the receiving unit 30 are separated in the observation device 10, there is no effect caused by light blocking by the transmitting unit 20 in the distance region exceeding the first position P1. Furthermore, in the observation device 10, the optical axes AXs of the transmitted light field of view Ss and AXr of the received light field of view Sr are set to be separate from each other and parallel, such that the superimposed light field of view Sc does not have a missing portion in the distance region exceeding the third position P3.

[0055] Here, regardless of the received light angle θr, the distance r2 from the far end position P0 of the lens barrel to the second position P2 depends only on the emitted light angle θs. In this case, the distance r1 from the far end position P0 of the lens barrel to the first position P1 can be shortened by increasing the received light angle θr, and the distance r3 from the far end position P0 of the lens barrel to the third position P3 can be shortened by decreasing the received light angle θr.

[0056] In the following text, the interval between the distal end position P0 of the telescope tube and the first position P1 will be referred to as the first interval. Furthermore, the interval between the first position P1 and the second position P2 will be referred to as the second interval. Additionally, the interval between the second position P2 and the third position P3 will be referred to as the third interval. The geometrical correction elements affecting the received light in these three intervals are included in the geometrical efficiency factor Y(R) of the LiDAR equations.

[0057] The LiDAR equations are typically expressed by the following formula.

[0058] [Formula 1]

[0059] Where R is the distance, P is the received light intensity, Po is the emitted light output, Y is the geometric efficiency factor, C is the device constant, β is the backscattering coefficient, and α is the dissipation coefficient (absorption + diffusion). Furthermore, P(R), Y(R), β(R), and α(R) represent the intensity, factor, and coefficient at distance R, respectively. Additionally, r is the distance traveled up to distance R. It should be noted that each coefficient depends on the material (particles floating in the air) constituting the observed object Ob. Furthermore, in the description of the three intervals, it is assumed that the observed object Ob is uniformly distributed throughout space in the depth direction from the far end of the telescope tube, to the observation limit distance (the maximum observation distance to be explained later), and in the planar directions of the emitted light field of view Ss and the received light field of view Sr. That is, the three intervals represent the internal space of the observed object Ob.

[0060] In the first interval, the emitted light field of view Ss and the received light field of view Sr do not overlap. Therefore, in the first interval, there is almost no reflected light (reflected pulse light) reflected by the observed target object Ob and returned to the received light field of view Sr. In other words, the first interval is an unobservable interval.

[0061] In the second interval, the amount of reflected light (reflected pulse light) reflected from the observed target object Ob and returned to the receiving light field of view Sr increases or decreases as the field-of-view coupling ratio Crs increases or decreases. Specifically, the change in the field-of-view coupling ratio Crs is caused by the correlation between the increase in the overlap ratio of the emitted light field of view Ss and the received light field of view Sr and the relative decrease in the superimposed light field of view Sc based on the magnification rate (view angles θs and θr) of the emitted light field of view Ss and the received light field of view Sr. Therefore, the amount of reflected light (reflected pulse light) in the second interval increases with increasing distance R, reaches a maximum, and then decreases. In other words, the second interval is the observation transition interval.

[0062] In the third interval, since the field-of-view coupling ratio Crs decreases according to the magnification of the emitted light field of view Ss and the received light field of view Sr (view angles θs and θr), the reflected light (reflected pulse light) reflected by the observed target object Ob and returned to the received light field of view Sr also decreases. In other words, the third interval is the observation stability interval.

[0063] As described above, since the emitted light field of view Ss and the received light field of view Sr overlap, reflected light (reflected pulse light) reflected by the observed target object Ob and returned to the received light field of view Sr can be received. That is, based on the field-of-view coupling ratio Crs, the received light intensity P(R) in the second and third intervals of the obtained reflected light (reflected pulse light) is corrected using the geometric efficiency factor Y(R) in Equation 1. Therefore, close-range measurements can be performed without being affected by changes in the superimposed light field of view Sc. As a result, the observed target object Ob existing at close range (beyond the first position P1) can be observed. In other words, observation data (LiDAR data) of the observed target object Ob existing at short range (beyond the first position P1) can be generated with high precision.

[0064] Specifically, the transmitted light angle θs is set to be greater than the received light angle θr (see [reference]). Figure 2 Therefore, the distance from the far end of the telescope tube, P0, to the first position, P1 (the first interval), can be shortened, and the distance from the second position, P2, to the third position, P3 (the second interval), can also be shortened. Then, the interval distance from the third position, P3, and beyond (the third interval) to the maximum observation distance (the distance defined by the pulse interval of the emitted light) can be extended. Furthermore, in the second and third intervals where observations can be performed, when the received light angle θr is large, the field-of-view coupling ratio Crs can be increased, thereby increasing the received light intensity P(R).

[0065] On the other hand, when the received optical viewing angle θr is small, the resolution of the orthogonal plane of the optical axis improves; when the received optical viewing angle θr is large, the resolution of the orthogonal plane of the optical axis deteriorates. Furthermore, when the received optical viewing angle θr is small, the third distance r3 (see...) Figure 2The third distance r3 becomes longer when the received light angle θr is large.

[0066] In summary, when observing close-range objects at high resolution, the receiving light angle θr is preferably small (e.g., 3 mrad). On the other hand, when observing the received light intensity P(R) from a distant location, the receiving light angle θr is preferably large (e.g., 5 mrad).

[0067] Furthermore, when the observed target object Ob is a non-shading body (such as aerosol, dust, fog, rain, or snow) in the form of a screen (thin in the distance direction), another observed target object in front of or behind the observed target object Ob can also be observed in the second and third intervals.

[0068] Because the receiving light field of view Sr is included in the emitted light field of view Ss outside the third position P3 (third interval), multiple observation target objects Ob partially present in the receiving light field of view Sr can be observed (measured). If the emitted light is a linear beam (e.g., a laser), LiDAR data for the observation target object Ob other than the observation target object Ob at the location where the emitted light was emitted cannot be obtained.

[0069] Next, we will explain the generation and processing of observation data (LiDAR data).

[0070] Figure 7 This is a conceptual diagram of the generation and processing of observational data (LiDAR data).

[0071] The observation data (LiDAR data) generation and processing is performed by the control and analysis unit 40. The control and analysis unit 40 may also be a dedicated device that houses the device for generating and processing the observation data of the observation device 10, which will be described later, within a housing, or it may be a composite device that includes other observation equipment such as an observation camera.

[0072] like Figure 1 As shown, the control analysis unit 40 includes an observation data generation unit 41, a coefficient analysis and processing unit 42, a characteristic evaluation and processing unit 43, and an observation data storage unit 44.

[0073] The observation data generation unit 41 uses a photon counting circuit (a circuit that performs photon counting) to divide the pulsed electrical signal output by the receiving unit 30 in response to the received reflected light (reflected light reflected by the observed target object Ob and returned to the receiving light field of view Sr (specifically, reflected pulsed light)) into each receiving cycle, and integrates the electrical signal N times to generate observation data (LiDAR data). Figure 7The bottom figure shows an example of observation data (LiDAR data). The generated observation data (LiDAR data) is stored (accumulated) in observation data storage unit 44.

[0074] exist Figure 7 In this context, the first received electrical signal to the Nth received electrical signal represent the pulse electrical signals divided for each receiving cycle. Figure 7 In the graph to the right of the first received electrical signal, each pulse represents a pulsed electrical signal output in response to the reflected light (reflected light reflected by the observed target object Ob and returned to the received light field of view Sr during the receiving period) received by the receiving unit 30 during the receiving period, upon the emission of the first pulse light (emitted light). The same applies to each pulse described in the graph to the right of the Nth received electrical signal.

[0075] Furthermore, the flight time (t) of the first received electrical signal represents the round-trip flight time (TLT) of the photons corresponding to each pulse to and from the observed target object Ob. In the graph of the Nth received electrical signal, the flight time (t) is omitted.

[0076] It should be noted that this disclosure is not limited to photon counting circuits, and any circuit can be used as long as it performs photon counting. For example, a digital oscilloscope and a PC (an information processing device such as a personal computer) can be combined.

[0077] The coefficient analysis processing unit 42 performs the following processing: calculates the spatial distribution (range direction) of the observed target object Ob based on the increase / decrease of the observation data (LiDAR data); evaluates the observation data (LiDAR data) using the LiDAR equation; and calculates the dissipation coefficient α and backscattering coefficient β specific to the observed target object Ob.

[0078] For example, when the observed target object Ob is in a uniform atmosphere in space from the far end of the telescope tube P0 to the maximum observation distance (Rmax), the received light intensity P(R) indicates a change that increases with distance (R) and geometric efficiency factor Y(R) and decays after reaching a maximum value. Furthermore, when the observed target object Ob is spatially uniform, since the distance remains constant, the dissipation coefficient α(R) and the backscattering coefficient β(R) can be α and β, respectively. Therefore, since the LiDAR equation is Ln((P(R)R) 2 Since ) / Y(R))=-2αR+ln(P0Cβ), the dissipation coefficient α can be obtained from the slope term -2αR, and the backscattering coefficient β can be obtained from the intercept term ln(P0Cβ).

[0079] The characteristic evaluation processing unit 43 performs, for example, atmospheric evaluation at a fixed point and evaluation of smoke, dust, etc.

[0080] For example, atmospheric assessment at a fixed point can be performed by periodically observing the atmosphere annually and assessing it using the backscattering coefficient β and dissipation coefficient α of the observed fine particles (e.g., aerosols) contained in the atmosphere. Furthermore, changes in atmospheric state can be assessed by comparing observations with those of a reference year. In this case, a comparison with a published standard atmosphere can be performed to estimate, for example, the types of fine particles floating in space (see, for example, the Japan LiDAR Association, 4 (2020), Kuze, measurements of light scattering by aerosols and atmospheric molecules). Assessments of fog, rain, and snow can also be performed at a fixed point in the same manner as atmospheric assessment.

[0081] Assessments of smoke and dust (such as cleanliness assessments of equipment exhaust, chimney smoke, road dust, etc.) can be performed by comparing the characteristics of the atmosphere outside the exhaust section with the characteristics of the atmosphere outside the exhaust section.

[0082] The observation data storage unit 44 is a non-volatile storage unit, such as a hard disk drive or SSD, that stores the observation data (LiDAR data) generated by the observation data generation unit 41.

[0083] Since the control analysis unit 40 (observation data generation unit 41) has the function of measuring (calculating) the flight time of the reflected light (photons) received by the receiving unit 30 to the observed target object Ob (known direct time of flight (dToF) method, photon counting, etc.), it can measure (calculate) the flight time (round-trip flight time) of the photon corresponding to each pulse to the observed target object Ob.

[0084] Observational data (LiDAR data) is generated by integrating the first received electrical signal to the Nth received electrical signal (Nth integration). Figure 7 In the graph shown at the bottom, the vertical axis represents the received light intensity and corresponds to the number of photons. The horizontal axis represents distance. This distance is obtained by converting the time of flight (t) into distance.

[0085] Next, we will explain the improvements in the close-range observation capability, miniaturization, and ease of observation of the observation device 10. It should be noted that the close-range distance described in this article is approximately a few meters to several hundred meters.

[0086] (Close-up observation)

[0087] The observation device 10 can increase the emission frequency of the emitted light (pulsed light) from the emission unit 20 from 1 MHz to approximately 10 MHz. For example, when the target object Ob is locally present within a distance of approximately 50 m to 100 m, the maximum observation distance (Rmax) can be set to 150 m. The maximum observation distance is defined by the emission period of the emitted light (pulsed light). For example, when the emission period of the emitted light (pulsed light) is 1 microsecond (μsec), the flight distance of the emitted light is 300 m. That is, the maximum observation distance (Rmax) is 150 m, which is the distance at which the previously emitted emitted light does not interfere with the next emitted light. In this case, the emission frequency is 1 MHz. Similarly, when the maximum observation distance (Rmax) is 15 m, the emission period of the emitted light (pulsed light) is 0.1 μsec, and the emission frequency is 10 MHz.

[0088] LiDAR data is generated by integrating each pulse incident on the receiving unit 30 for one unit period multiple times. Therefore, LiDAR data can be generated in a short time by increasing the emission frequency of the emitted light (pulsed light). In particular, short-time observations are important for improving spatial resolution because the apparent velocity (angle of movement per unit time) of the observed target object Ob is large at close range. For example, when the distance to the observed target object Ob is 100 m and the number of integrations for the LiDAR data is 1000, and the emission frequency is 1 MHz (emission period 1 μsec), one observation time is 1 millisecond (msec). In this case, when the observed target object Ob moves at a wind speed of 3 m / s (approximately a light breeze), the observed target object Ob moves 3 mm between the start and end of the observation. That is, the angle of movement is 0.0017°. Therefore, when the received optical viewing angle θr is 3 mrad (0.17°), the received optical viewing angle ratio (movement angle / received optical viewing angle θr) is 0.01 (1%), and when the received optical viewing angle θr is 5 mrad (0.29°), the received optical viewing angle ratio is 0.006 (0.6%). Furthermore, when the distance to the observed target object Ob is 50 m, the movement angle is 0.0034°. Therefore, when the received optical viewing angle θr is 3 mrad, the received optical viewing angle ratio is 0.02 (2%), and when the received optical viewing angle θr is 5 mrad, the received optical viewing angle ratio is 0.012 (1.2%). As described above, even when the observed target object Ob moves at close range, by increasing the transmission frequency, it is possible to observe the observed target object Ob with high precision.

[0089] Furthermore, the observation device 10 reduces the pulse width of the emitted light (pulse light) from the emitting unit 20 to approximately 1 nanosecond (nsec). For example, when the pulse width is 10 nsec, the distance resolution is 1.5 m, and when the pulse width is 1 nsec, the distance resolution is 0.15 m. As described above, by narrowing the emitted light, it is possible to observe the target object Ob with high precision in close-range measurements.

[0090] The observation device 10 sets the wavelength of the emitted light (pulsed light) from the emitting unit 20 to a solar-blind wavelength in the deep ultraviolet band that is not absorbed by the atmosphere (absorbed by oxygen and nitrogen). Here, the solar-blind wavelength in the deep ultraviolet band is the deep ultraviolet wavelength band that significantly attenuates before reaching the Earth's surface within the sunlight. Specifically, the solar-blind wavelength is a wavelength longer than the long-wavelength absorption edge of the absorption wavelengths of oxygen and nitrogen, and shorter than the long-wavelength absorption edge of the ozone layer's absorption wavelength. Specifically, the solar-blind wavelength is 230 nanometers (nm) or more and 300 nm or less. The solar-blind wavelength is preferably between 250 nm and 280 nm. Using such a wavelength band, observations can be performed using a low-output light source because there is no influence from external light and no atmospheric absorption.

[0091] Furthermore, by setting the wavelength of the emitted light (pulsed light) to a solar-blind wavelength in the deep ultraviolet band where there is no atmospheric absorption, the backscattering coefficient β and dissipation coefficient α of the fine particles contained in the observed target object Ob become greater than those in the near-ultraviolet to infrared range. Therefore, observations can be performed even if the thickness of the observed target object Ob in the distance direction is small, or even if the concentration of contained particles is low. Specifically, the dissipation coefficient α increases inversely to 1.25 times the wavelength, and becomes approximately five times by shortening the wavelength from 900 nm to 265 nm. Since the backscattering coefficient β is approximately proportional to the dissipation coefficient α, the backscattering coefficient β also becomes approximately five times. That is, highly sensitive observations can be performed even at close range (the shorter distance through which the observed target object Ob is observed). Furthermore, characteristics of the observed target object Ob (e.g., aerosols, smoke, dust, fog, rain, or snow) can be easily identified.

[0092] (Miniaturization)

[0093] The observation device 10 uses a deep ultraviolet light-emitting diode (LED) as a semiconductor light-emitting element that emits deep ultraviolet light (e.g., with a wavelength of 265 nm). The deep ultraviolet LED has a diameter of approximately 1 mm. 2 The size. Furthermore, deep ultraviolet LEDs can also miniaturize light-emitting circuits that emit light with high frequency and narrow pulse width. Additionally, they have small apertures (approximately 60 mm). The small lens can be configured with a collimated emission system with high light throughput. Therefore, the emission unit 20 can be miniaturized.

[0094] The observation device 10 uses a photomultiplier tube (PMT) of ultraviolet light corresponding to photon counting as the light receiving element. Therefore, the PMT is relatively small. Furthermore, since the emitted light from the emitting unit 20 has a solar-blind wavelength in the deep ultraviolet band and is not subject to atmospheric absorption, the main condenser of the receiving unit 30 can be a small lens or mirror (approximately 100 mm aperture). Therefore, the receiving unit 30 can be miniaturized.

[0095] (Observational convenience)

[0096] Regardless of day or night, the observation device 10 enables observations to be performed using a semiconductor light-emitting element (e.g., an LED with a wavelength of 265 nm) as the light source for the emitting unit 20, which emits ultraviolet light in the solar-blind band without atmospheric absorption. For example, observations can be performed during the day in clear weather and at night under illumination such as fluorescent or halogen lamps. Therefore, observations can be performed at regular intervals during the day and night. Furthermore, since illumination can be projected onto the observation target Ob even at night, aiming at the observation target Ob becomes easy.

[0097] <First Configuration Example of Observation Device 10>

[0098] Next, a specific first configuration example of the observation device 10 will be described. Hereinafter, the observation device 10 of the first configuration example will be referred to as observation device 10A.

[0099] Figure 8 This is a schematic diagram of the configuration of the observation device 10A.

[0100] The observation device 10A is an observation device (LiDAR device) that includes a transmitting unit 20 and a receiving unit 30 of a refractive optical system.

[0101] like Figure 8 As shown, the observation device 10A includes a transmitting unit 20, a receiving unit 30, and a control and analysis unit 40. Figure 8 (Not shown in the image). Then, the optical axis AXs of the transmitting unit 20 and the optical axis AXr of the receiving unit 30 are set to be separate from each other and parallel.

[0102] <Launch Unit 20>

[0103] The emitting unit 20 includes a semiconductor light-emitting element 21 and an emitting lens 22 (an example of an emitting optical system of this disclosure). Figure 8In the figure, reference numeral 23 indicates the emitting lens tube, and reference numeral 24 indicates the driving circuit of the semiconductor light-emitting element 21.

[0104] Semiconductor light-emitting element 21 is a semiconductor light-emitting element that has excellent response speed (e.g., can emit high-frequency and short-pulse light) and emits light (pulsed light) with wavelengths belonging to the ultraviolet region of the solar blind band, and is, for example, a deep ultraviolet LED. In the following, semiconductor light-emitting element 21 will also be referred to as deep ultraviolet LED 21.

[0105] In the following text, an example will be described using a deep ultraviolet LED with a Lambertian light distribution (distribution) having a peak wavelength (center wavelength) of 265 nm and a half-value angle of approximately 120° as a semiconductor light-emitting element 21. In the following text, the semiconductor light-emitting element 21 will also be referred to as a deep ultraviolet LED 21.

[0106] The specifications of the deep ultraviolet LED 21 are described in the table below.

[0107] [Table 1]

[0108] The deep ultraviolet LED used has a spectrum with a peak wavelength (λp) of 265 nm and a full width at half maximum (FWHM) of 12 nm. Its directional characteristics are Lambertian type with a half-value angle of 120°. Under continuous power (cw) conditions, the light output is 50 mW at an input power of 3 W, and under pulsed output conditions, the light output ranges from 1 mW to 500 mW. The responsivity is 1 ns or greater.

[0109] The deep ultraviolet LED 21 of the emitting unit 20 for the observation device 10A is encapsulated in a CAN package. The CAN package is mounted on a heat sink included in the drive circuit 24. The portion of the CAN package, except for the light emission port, is covered with a partition made of a material that absorbs stray light emitted from the deep ultraviolet LED. Besides the CAN package, the deep ultraviolet LED can be mounted on a ceramic substrate (such as alumina, silicon nitride, or aluminum nitride) having high thermal conductivity (e.g., 30 W / m·K to 200 W / m·K) and absorbing stray light. Alternatively, the deep ultraviolet LED can be mounted on a ceramic inlay-type glass epoxy substrate, wherein the ceramic is assembled within the portion where the deep ultraviolet LED is mounted. It should be noted that a heat sink is preferably provided on the rear surface side (the surface opposite to the surface where the deep ultraviolet LED is mounted) of the ceramic substrate or the ceramic inlay-type glass epoxy substrate.

[0110] The deep ultraviolet LED 21 has a 1.04 square millimeter emitting surface. The light emitted from the deep ultraviolet LED (pulsed light) is incoherent or non-coherent light (divergent light with random phase and full width at half maximum). Furthermore, the light emitted from the deep ultraviolet LED 21 (pulsed light) is isotropic light (unpolarized light).

[0111] The emitting lens 22 is, for example, a condenser lens that is rotationally symmetrical with respect to the optical axis AXs of the emitting unit 20. Furthermore, the emitting lens 22 is made of quartz glass and transmits light emitted from the deep ultraviolet LED 21. The emitting lens 22 can be made of borosilicate glass, silicate glass, amorphous fluororesin, etc., which transmit deep ultraviolet light.

[0112] The specifications of the emitting lens 22 are described in the table below.

[0113] [Table 2]

[0114] When the acquisition angle θi of the emitting lens 22 = 30° (see...) Figure 10 ) and the diameter of the emitting lens 22 = 60 mm s (see Figure 10 When the focal length f is (see) Figure 10 The value is 52 mm. This can be determined by the formula tan(θi) = ( The angle θs of the emitted light is calculated using the formula tan(θs) = (Es / 2) / f. On the other hand, when the size of the deep ultraviolet LED 21 (emitting surface) is Es = 1.04 square millimeters, the angle of view θs is approximately 10 mrad. This can be calculated using the formula tan(θs) = (Es / 2) / f.

[0115] The optical axis of the emitting lens 22 and the optical axis of the deep ultraviolet LED 21 (emitting surface) coincide (substantially coincide) with the optical axis AXs of the emitting unit 20. The optical axis of the deep ultraviolet LED 21 (emitting surface) passes through the center of the emitting surface and extends in a direction perpendicular to the emitting surface.

[0116] The focal point of the emitting lens 22 is set near the center of the deep ultraviolet LED 21 (emitting surface). Therefore, the light (pulsed light) emitted from the deep ultraviolet LED 21 is collimated by the emitting lens 22. Thus, emitted light suitable for observation at close range (e.g., 15 m to 150 m) can be obtained.

[0117] The diameter (aperture) of the emitted light beam is sufficiently larger than the target object Ob in order to stably observe (measure) the target object Ob (e.g., fine particles (aerosols) in the atmosphere). For example, the diameter of the emitted light beam (aperture) is 60 mm.

[0118] As described above, by using a condenser lens (collimating lens) as the emitting lens 22, the light (pulsed light) emitted from the deep ultraviolet LED 21 can be formed into collimated light with a diameter equal to the lens diameter (60 mm) of the emitting lens 22.

[0119] On the other hand, the deep ultraviolet LED 21 (emitting surface) is not a point light source, but has a constant size. Therefore, the light (pulsed light) emitted from the deep ultraviolet LED 21 (emitting surface) is also emitted in a direction that is tilted relative to the optical axis AXs of the emitting unit 20.

[0120] Figure 10 This diagram shows the state in which light PL1 and PL2 (pulsed light) emitted from the deep ultraviolet LED 21 (emitting surface) are also emitted in a direction that is tilted relative to the optical axis AXs of the emitting unit 20.

[0121] like Figure 10 As shown, light PL1 emitted from the center Pa of the deep ultraviolet LED 21 (emitting surface) is refracted (collimated) by the emitting lens 22 and emitted in the direction of the optical axis AXs of the emitting unit 20. On the other hand, light PL2 emitted from a position Pb offset downward from the center of the deep ultraviolet LED 21 (emitting surface) is refracted by the emitting lens 22 and emitted in a direction tilted upward at a predetermined angle relative to the optical axis AXs of the emitting unit 20. Similarly, although not shown, light emitted from a position offset upward from the center of the deep ultraviolet LED 21 (emitting surface) is refracted by the emitting lens 22 and emitted in a direction tilted downward at a predetermined angle relative to the optical axis AXs of the emitting unit 20. This also applies to light emitted from other positions of the deep ultraviolet LED 21 (emitting surface).

[0122] Therefore, the emitted light field of view Ss becomes a conical region centered on the optical axis AXs of the emitting unit 20, and has a diameter that increases along the optical axis AXs of the emitting unit 20 with increasing distance from the emitting unit 20 (the distal end position P0 of the lens barrel) (see...). Figure 2 ).

[0123] The emitted light field of view Ss (emitted light angle θs) can be adjusted by changing the focal length f. For example, with a constant acquisition angle θi, the emitted light angle θs can be made wider than before shortening the focal length f by shortening the focal length f. In this case, the lens diameter of the emitting lens 22... s decreases. Conversely, by increasing the focal length f, the emitted light angle θs can be made narrower than before the focal length f was increased. In this case, the lens diameter of the emitting lens 22... s increases. Therefore, by using a deep ultraviolet LED 21 with Lambertian orientation characteristics and an emitting lens 22, the emitted light viewing angle θs can be easily adjusted. That is, the emitted light field of view Ss can be easily made larger than the received light field of view Sr.

[0124] The emitting lens barrel 23 is made of aluminum (Al), and its inner cylindrical surface undergoes an anti-reflection treatment with a black anodized film to prevent reflection of the emitted light (stray light) from the deep ultraviolet LED 21. The emitting lens barrel 23 can be made of corrosion-resistant metal materials such as stainless steel or Invar, resin materials such as polycarbonate, acrylic, polypropylene, polyethylene, or epoxy resin, or low-thermal-expansion ceramic materials such as alumina or silica. The anti-reflection treatment can be matte black chrome plating, nickel plating, etc. Alternatively, a ceramic coating of black alumina or carbon can be used. By performing the anti-reflection treatment on the inner cylindrical surface of the emitting lens barrel 23 as described above, excessive light (stray light) other than the light directly entering the emitting lens 22 from the deep ultraviolet LED 21 can be prevented from being reflected by the inner cylindrical surface and emitted from the emitting lens 22. That is, the emitted light can be emitted at a predetermined emission light angle θs (emission light field of view Ss), and distance errors in LiDAR data can be prevented in dToF method observations. In other words, the intensity of the received light, P(R), can be observed with high precision.

[0125] The emitting lens tube 23 may include a cover on the front side of the emitting lens 22. The inner cylindrical surface of the cover also undergoes the same anti-reflective treatment as described above.

[0126] <Driver Circuit 24>

[0127] Next, the driving circuit 24 will be described.

[0128] Figure 11 This is an example of drive circuit 24. Figure 12A and Figure 12B This is an example of the emission characteristics of pulsed light. Figure 13 It is a graph showing the relationship between supply voltage (V) and frequency (MHz). Figure 11 The drive circuit 24 shown is a drive circuit that uses transistor avalanche breakdown. Figure 12A and Figure 12B In the diagram, the horizontal axis represents time (ns), and the vertical axis represents the relative value of emission intensity (AU).

[0129] The driving circuit 24 is a driving circuit for emitting pulsed light with a frequency of 1 MHz to 10 MHz and a pulse width of 1 ns to 10 ns as emitted light. The control and analysis unit 40 controls the deep ultraviolet LED 21 to emit emitted light (pulsed light) with a frequency of 1 MHz and a pulse width of 9.6 ns via the driving circuit 24.

[0130] The pulse width of the emitted light is adjusted by selecting the capacitance of capacitor C1 in the drive circuit 24. For example, by setting the capacitance of capacitor C1 to a small or large capacitance, the emitted pulse width (full width at half maximum) can be adjusted to 1.58 ns (see [link to relevant documentation]). Figure 12A ) or 3.2 ns (see Figure 12B ).

[0131] The frequency of the emitted light (emission period) can be adjusted (controlled) by fixing the value of resistor R1 in the drive circuit and selecting the voltage applied between Vcc and ground. For example, as Figure 13 As shown, by setting the applied voltage from 72 V to 92 V, the slow recharge time can be adjusted, and the emission period can be controlled from 1 MHz to 2.1 MHz. In this case, the intensity of the pulsed light can be essentially constant because the avalanche breakdown voltage of the transistor is constant. Alternatively, the frequency of the emitted light can be selected by setting the voltage between Vcc and ground to a constant and choosing the value of resistor R1.

[0132] The range resolution (spatial resolution) is determined by the pulse width of the emitted light (pulsed light). For example, when the pulse width is 1 ns, the range resolution (spatial resolution) is 0.15 m (speed of light c (m / s) · pulse width τ (s) / 2). Therefore, it is possible to observe the detailed distribution of the target object Ob (e.g., particles in space). Furthermore, when the pulse width is 10 ns, the range resolution (spatial resolution) is 1.5 m. Therefore, it is possible to observe the distribution of the target object Ob (e.g., coarse particles in space).

[0133] The observation distance (measurement distance) is determined by the frequency of the emitted light (pulse light). For example, at a frequency of 1 MHz (period of 1 μs = 1 / 1,000,000 ( / s)), the maximum observation distance is 150 m (speed of light c (m / s) · period f (s) / 2). Furthermore, at a frequency of 10 MHz, the maximum observation distance is 15 m. In other words, the observation distance (measurement distance) can be set within a range where the return light (received light) of the previously emitted light does not overlap with the emission time of the next emitted light.

[0134] Therefore, the pulse width and frequency of the emitted light can be easily adjusted by selecting capacitor C1 and resistor R1 in the drive circuit 24 and by selecting the voltage between Vcc and ground. Specifically, by preparing and selecting capacitors C1a, C1b, C1c, ... with different capacitances than capacitor C1, and resistors R1a, R1b, R1c, ... with different resistance values ​​than resistor R1, the pulse width or frequency of the emitted light can be adjusted over a wide range.

[0135] <Receiver Unit 30>

[0136] like Figure 8 and Figure 14 As shown, the receiving unit 30 includes a first receiving lens 31 (an example of a receiving optical system of this disclosure), a field aperture 32, a second receiving lens 33, a receiving filter 34, and a light receiving element 35. Figure 8 In the figure, reference numeral 36 indicates the receiving lens tube. Figure 14 From Figure 8 A schematic diagram of the extracted receiving unit 30.

[0137] The first receiving lens 31 is, for example, a condenser lens that is rotationally symmetrical with respect to the optical axis AXr of the receiving unit 30. Furthermore, similar to the emitting lens 22, the first receiving lens 31 (and the second receiving lens 33) are made of quartz glass. The first receiving lens 31 collects the reflected light PL3 ​​and PL4 (reflected pulse light) from the observed target object Ob, which is reflected back into the received light field of view Sr within the emitted light (pulse light).

[0138] First receiving lens diameter r (the aperture of the receiving lens tube 36) is larger than the diameter of the transmitting lens 22. The aperture of the transmitting lens tube 23 is adjusted to improve the uptake amount of reflected light PL3 ​​and PL4 (reflected pulse light) reflected by the observed target object Ob and returned to the receiving light field of view Sr. As a result, reflected light PL3 ​​and PL4 (reflected pulse light) present in the expected region and returned to the receiving light field of view Sr can be received.

[0139] The specifications of the first receiving lens 31 are described in the table below.

[0140] [Table 3]

[0141] The receiving light viewing angle θr was set to be narrow (3 mrad (0.173°) to 5 mrad (0.286°)) so that the expected region (a plane orthogonal to the optical axis) could be observed.

[0142] The lens diameter of the first receiving lens 31 When r = 100 mm and focal length f = 200 mm, the convergence angle θj of the first receiving lens 31 (see...) Figure 14 The angle is approximately 14 degrees. This can be seen from the equation tan(θj) = ( The calculation is done using r / 2) / f. On the other hand, the received optical angle θr (see...) Figure 14With a focal length of 3 mrad (0.173°) and a focal length of 200 mm, the field of view image size Er is approximately 0.3 square millimeters. This can be calculated using the formula tan(θr) = (Er / 2) / f.

[0143] Similar to the transmitting lens 23, the receiving lens 36 is made of aluminum and has an inner cylindrical surface that has undergone anti-reflection treatment. Therefore, it can absorb light incident on the receiving lens 31 at an angle other than the predetermined receiving light angle θr, preventing light from reaching the light receiving element 35.

[0144] The field aperture 32 is a light-blocking aperture that controls (narrows or widens) the received light field of view Sr.

[0145] By providing a field aperture 32 at the focal point (focal plane) of the first receiving lens 31, the observation range (received light field of view Sr) can be defined. For example, when observing a wide received light field of view Sr, the field aperture 32 is open, and conversely, when observing only a narrow received light field of view Sr, the field aperture 32 is narrowed. Therefore, the received light field of view Sr can be adjusted.

[0146] Furthermore, when the received light viewing angle θr is constant, the field of view of the focal plane can be reduced by shortening the focal length f of the first receiving lens 31. Conversely, the field of view of the focal plane can be increased by increasing the focal length f of the first receiving lens 31.

[0147] The second receiving lens 33 adjusts the field of view of the focal plane to the size of the light receiving surface of the light receiving element 35. It should be noted that the second receiving lens 33 can be omitted if unnecessary.

[0148] The receiving filter 34 is a bandpass filter configured to transmit only the reflected light (reflected pulse light) reflected by the observed target object Ob and returned to the receiving light field of view Sr. In the first configuration example, a bandpass filter with a full width at half maximum (FWHM) of 266 nm ± 5 nm is used. By providing the receiving filter 34, the signal-to-noise ratio (S / N ratio) of the signal (pulse electrical signal) output by the receiving unit 30 (light receiving element 35) corresponding to the reflected light (reflected pulse light) received by the receiving unit 30 is improved.

[0149] The light receiving element 35 is an ultraviolet photomultiplier tube (PMT) used for photon counting. In this first configuration example, the PMT of the light receiving element 35 includes high-voltage circuitry required for PMT operation and a preamplifier circuitry to amplify the pulsed electrical signal converted by the PMT. It should be noted that the light receiving element 35 can be any photoelectric conversion element for photon counting other than a PMT. The light receiving element 35 outputs a signal (pulsed electrical signal) corresponding to the reflected light (reflected pulsed light) received by the light receiving element 35.

[0150] The received optical field of view Sr is determined by the aperture of the first receiving lens 31. The circle obtained by adding r to the circle drawn with respect to the received light viewing angle θr centered on the optical axis AXr of the receiving unit 30. In other words, the received light viewing field Sr is a circle whose radius is the radius of the circle with the received light viewing angle θr plus the aperture of the first receiving lens 31. The sum of the radii of r.

[0151] The optical axes AXs of the transmitting unit 20 and AXr of the receiving unit 30 are arranged separately from each other and parallel to each other. The distance L1 between the optical axes AXs of the transmitting unit 20 and AXr of the receiving unit 30 (see...) Figure 8 For example, 85 mm. The distance L1 is preferably close to the aperture additional half-value distance, which is half the sum of the apertures of the emitting lens 22 of the emitting unit 20 and the receiving lens 31 of the receiving unit 30, because the superposition start distance r1 between the emitted light field of view Ss and the received light field of view Sr is shortened. Typically, the distance L1 is preferably about 1.05 to 1.1 times the aperture additional half-value distance.

[0152] Similarly, in the first configuration example, the transmitted light field of view Ss and the received light field of view Sr overlap each other (see [reference]). Figure 2 The shaded area HT and the superimposed light field Sc in each cross-sectional view.

[0153] Therefore, also in the first configuration example, since the reflected light (reflected pulse light) reflected by the observed target object Ob and returned to the receiving optical field of view Sr can be received, the observed target object Ob existing at close range (beyond the first position P1) can be observed. In other words, observation data (LiDAR data) can be generated with high precision.

[0154] <Second Configuration Example of Observation Device 10>

[0155] Next, a specific second configuration example of the observation device 10 will be described. Hereinafter, the observation device 10 in the second configuration example will be referred to as observation device 10B.

[0156] Figure 15 This is a schematic diagram of the configuration of observation device 10B.

[0157] The observation device 10B is an observation device (LiDAR device) that includes a transmitting unit 20 of a refraction system and a receiving unit 30 of a reflection system.

[0158] like Figure 15 As shown, the observation device 10B includes a transmitting unit 20, a receiving unit 30, and a control and analysis unit 40. Figure 15(Not shown in the image). Then, the optical axis AXs of the transmitting unit 20 and the optical axis AXr of the receiving unit are set to be separate from each other and parallel.

[0159] <Launch Unit 20>

[0160] The emitting unit 20 includes a semiconductor light-emitting element 21 and an emitting lens 22 (an example of an emitting optical system disclosed herein).

[0161] The transmitting unit 20 differs from the transmitting unit 20 in the first configuration example in the specifications of the transmitting lens 22. The specifications of the transmitting lens 22 are described in the table below.

[0162] [Table 4]

[0163] In other words, compared to the emitting lens 22 in the first configuration example, the emitting lens 22 has a shorter focal length and a wider emitted light viewing angle θs. As a result, even when the receiving light aperture increases, the emitted light field of view Ss can overlap with and be included in the receiving light field of view Sr at close range. Due to the use of a 1.04 square millimeter deep ultraviolet LED, the emitted light viewing angle θs is 1.489° (25.99 mrad ≈ 26 mrad). Apart from this, the emitting unit 20 is similar to the emitting unit 20 in the first configuration example.

[0164] <Receiver Unit 30>

[0165] like Figure 15 As shown, the receiving unit 30 differs from the receiving unit 30 of the first configuration example in that it provides a first receiving mirror 37 and a second receiving mirror 38 (an example of the receiving optical system of this disclosure) instead of a first receiving lens 31. Otherwise, the receiving unit 30 is similar to the receiving unit 30 of the first configuration example. It should be noted that in... Figure 15 In the figure, reference numeral 39 indicates the receiving main tube, and reference numeral 40 indicates the receiving sub-tube.

[0166] The first receiving mirror 37 is a non-axial parabolic mirror (the peripheral portion of a parabolic mirror) and has a focal point F outside the receiving main mirror tube 39. 37 .

[0167] The second receiving mirror 38 is positioned at the focal point F of the first receiving mirror 37 and the first receiving mirror 37. 37 Between. The second receiving mirror 38 is an example of the return mirror of this disclosure.

[0168] The reflected light (reflected pulse light) reflected by the observed target object Ob and returning to the received light field of view Sr is reflected by the first receiving mirror 37 and collected toward the focal point F37, further reflected by the second receiving mirror 38, and guided to the light receiving element 35. Thus, in the observation device 10B, the transmitting unit 20 and the receiving unit 30 are separated. Furthermore, the second receiving mirror 38 and the light receiving element 35 are configured to be located outside the opening of the receiving main mirror tube 39 of the receiving unit 30 (through which the received light is acquired). This prevents the received light field of view Sr from being blocked in the observation distance region beyond the first position P1.

[0169] In the second configuration example, the optical axis AXr of the receiving unit 30 (the center line of the first receiving mirror 37) and the optical axis AX of the second receiving lens 33 are... 33 The light receiving element 35 is arranged parallel to the center line of the light receiving element 35, therefore the second receiving mirror 38 is set to be inclined to the optical axis AX of the reflected light (beam) reflected from the center of the first receiving mirror 37 and the second receiving lens 33. 33 The angle θm formed is 1 / 2.

[0170] Similar to the first configuration example, the received optical viewing angle θr is 3 mrad or 5 mrad.

[0171] Figure 16 This is a cross-sectional view of the first receiving mirror 37.

[0172] The first receiving mirror 37 includes: a non-axial parabolic mirror substrate 37a having an aluminum-coated non-axial parabolic surface as its main surface; an amorphous silicon (α-Si) first antireflective film 37c (an example of an antireflective member of this disclosure) disposed on the aluminum-coated surface of the main surface 37b and absorbing light in the near-ultraviolet to visible light band; and a first dielectric multilayer film 37d disposed on the first antireflective film 37c and reflecting light with a wavelength of 265 nm (incident at 22.5°), and reflecting and collecting light incident parallel to the optical axis of the original-shaped parabolic mirror to the focal point F of the original-shaped parabolic mirror. 37 The mirror.

[0173] It should be noted that the various membranes and settings of the first receiving mirror 37 can have the same configuration as the second receiving mirror 38, which will be described later.

[0174] A non-axial parabolic mirror is a mirror in which the outer periphery of the parabolic mirror is hollowed out and its focal point (the focal point of the original shape of the mirror) is located outside the mirror.

[0175] The first antireflective film 37c is made of amorphous silicon (α-Si), titanium carbonitride (TiCN), or diamond-like carbon (DLC), and is a layer that absorbs light in the near-ultraviolet to visible light band. In the second configuration example, the first antireflective film 37c has the function of absorbing and emitting light in the near-ultraviolet to visible light band that passes through the first dielectric multilayer film 37d.

[0176] The first dielectric multilayer film 37d is a film in which thin films of silicon oxide (SiO2) and hafnium oxide (HfO2) are laminated into multiple layers. It has high reflectivity (90% or higher) relative to deep ultraviolet light at 265 nm (incident angle 22.5°) and emits light in the near ultraviolet to visible light band.

[0177] Figure 17 This is a cross-sectional view of the second receiving mirror 38.

[0178] like Figure 17 As shown, the second receiving mirror 38 includes: a flat substrate 38a (retroreflector substrate); a second dielectric multilayer film 38c that reflects light with a wavelength of 265 nm (incident at 22.5°) on the main surface 38b; and a second antireflective film 38e of graphite (carbon) (an example of an antireflective member of this disclosure) that absorbs light in the near-ultraviolet to visible light band on the sub-surface 38d (back surface) and symmetrically reflects light incident on the main surface 38b.

[0179] The second antireflective coating 38e is made of graphite, carbon, diamond-like carbon, etc., and absorbs light transmitted through the second dielectric multilayer film 38c. In other words, light used as a noise component is absorbed, except for the light intended for observation (emitted light).

[0180] The second dielectric multilayer film 38c has the same configuration as the first dielectric multilayer film 37d.

[0181] Next, the reflectivity of each receiving mirror will be explained.

[0182] Figure 18 The reflection spectrum of the reflected light from each receiving mirror is shown.

[0183] The reflectivity of incident light at a 22.5° angle was measured relative to the reflecting surfaces of the first receiving mirror 37 (a non-axial parabolic mirror) and the second receiving mirror 38 (a retroreflective mirror). Figure 13 In the diagram, the horizontal axis represents wavelength, and the vertical axis represents reflectivity (%).

[0184] exist Figure 18 In the table below, "OA_Al" represents the reflection spectrum of the first receiving mirror 37, wherein the first antireflective film 37c and the first dielectric multilayer film 37d are disposed on the main surface 37b of the non-axial parabolic mirror substrate 37a having an aluminum layer. The configuration of the first receiving mirror 37 is described in the table below.

[0185] [Table 5]

[0186] exist Figure 18 In the text, “Φ40_Black” represents the reflection spectrum of the second receiving mirror 38, wherein the second dielectric multilayer film 38c is disposed on the main surface 38b of the retroreflective mirror substrate 38a, and the second antireflective film 38e is disposed on the sub-surface 38d (back surface).

[0187] The configuration of the second receiving mirror 38 is described in the table below.

[0188] [Table 6]

[0189] exist Figure 18 In the text, “OAxΦ40” represents the product of the reflectance of the first receiving mirror 37 and the second receiving mirror 38 (total reflectance spectrum).

[0190] Next, we will explain the function, operation, and effects of the anti-reflective coating.

[0191] The reflectivity in the deep ultraviolet band, especially the product of the reflectivity at the emitted light wavelength of 265 nm, is as high as 90% or higher.

[0192] On the other hand, the reflectivity product of light in the near-ultraviolet band of 300 nm to 400 nm is reduced to 1 / 10 or less, and the reflectivity in the visible light band of 400 nm to 700 nm is reduced to 1 / 100 or less.

[0193] As described above, by providing anti-reflective coatings on the first receiving mirror 37 and the second receiving mirror 38, noise light can be removed before it reaches the light receiving element 35. This makes it possible to suppress the effects of sunlight, especially in daytime observations. The light receiving element 35 for photon counting has high receiving sensitivity. Therefore, a structure is employed that can remove light with wavelengths different from the target wavelength (265 nm) before it reaches the light receiving element 35. Thus, noise can be suppressed, and highly accurate observations can be performed.

[0194] The values ​​described in the above embodiments are examples; of course, appropriate values ​​that are different from these can also be used.

[0195] Each of the above embodiments is merely an example in all respects. For instance, the transmitting unit 20 may be an optical system of a reflective system. Furthermore, each of the transmitting unit 20 and / or the receiving unit 30 may be a hybrid optical system of a directional system and a reflective system. Moreover, although the observed target in the above embodiments is the atmosphere containing fine particles, according to this disclosure, it is possible to simultaneously observe the distance to obstacles (trees, buildings, etc.) and the atmosphere containing fine particles. That is, this disclosure should not be construed as being limited to the description of each of the above embodiments. This disclosure may be implemented in various other forms without departing from the spirit or essential features of this disclosure.

[0196] This application claims priority to Japanese Patent Application No. 2023-197526, filed on November 21, 2023, the entire contents of which are incorporated herein by reference.

[0197] Symbol list

[0198] 10, 10A, 10B: Observation devices

[0199] 20: Launching Unit

[0200] 21: Deep ultraviolet LED (semiconductor light-emitting element)

[0201] 22: Emitting lens

[0202] 23: Launch tube

[0203] 24: Drive circuit

[0204] 30: Receiving Unit

[0205] 31: Receiving lens (first receiving lens)

[0206] 32: Field of view aperture

[0207] 33: Second receiving lens

[0208] 34: Receiver Filter

[0209] 35: Optical receiving element

[0210] 36: Receiving lens tube

[0211] 37: First receiving mirror

[0212] 37a: Non-axial parabolic mirror substrate with aluminum layer

[0213] 37b: Main surface

[0214] 37c: First anti-reflective coating

[0215] 37d: First dielectric multilayer film

[0216] 38: Second receiving mirror

[0217] 38a: Retroreflector substrate

[0218] 38b: Main surface

[0219] 38c: Second dielectric multilayer film

[0220] 38d: Subsurface

[0221] 38e: Second antireflective coating

[0222] 39: Receiving the main lens tube

[0223] 40: Control Analysis Unit

[0224] 41: Observation Data Generation Unit

[0225] 42: Coefficient Analysis and Processing Unit

[0226] 43: Characteristic Evaluation Processing Unit

[0227] 44: Observation Data Storage Unit

[0228] AX 33 AXr, AXs: Optical axis

[0229] C1, C1a: Capacitors

[0230] Crs: Field Coupling Ratio

[0231] F 37 :focus

[0232] Ob: Target object being observed

[0233] P: Received light intensity

[0234] P0: Distal position of the scope tube

[0235] P1: First position

[0236] P2: Second position

[0237] P3: Third Position

[0238] P4: Fourth Position

[0239] R1, R1a: Resistors

[0240] Sc: Superimposed optical field

[0241] Sr: Receiver of optical field of view

[0242] Ss: Emitted light field of view

[0243] r1: First distance

[0244] r2: Second distance

[0245] r3: Third distance

[0246] θs: Emitted light angle

[0247] θr: Received optical angle Claims (as amended under Article 19 of the Treaty) 1. (Modified) An observation device, said observation device comprising: The emitting unit is configured to have an emitting light field of view and to emit pulsed light with a wavelength belonging to the ultraviolet region of the solar blind band into a space containing fine particles within the emitting light field of view. A receiving unit configured to have a receiving light field of view, and to receive reflected pulse light returning to the receiving light field of view from the reflected light of the pulse light reflected by the fine particles; and Observation data generation unit, in which, The transmitting unit includes: A semiconductor light-emitting element, the semiconductor light-emitting element being configured to emit the pulsed light, and An emitting optical system configured to control the pulsed light emitted by the semiconductor light-emitting element, such that the pulsed light emitted by the semiconductor light-emitting element is emitted within the field of view of the emitted light. The receiving unit includes: A receiving optical system configured to collect the reflected light within the receiving light field of view, and A light receiving element configured to receive collected reflected pulsed light and output a signal corresponding to the received reflected pulsed light. The optical axis of the transmitting unit and the optical axis of the receiving unit are parallel to each other. The emitted light field of view is defined as having an emitted light angle that is larger than the received light field of view. The emitted light field of view and the received light field of view at least partially overlap each other, and The observation data generation unit generates LiDAR data as observation data based on the signal output from the optical receiving element. 2. The observation device according to claim 1, wherein, The emitted light field of view is a conical region centered on the optical axis of the emitting unit, and has a diameter that increases along the optical axis of the emitting unit with increasing distance from the emitting unit. The received light field of view is a conical region centered on the optical axis of the receiving unit, and has a diameter that increases along the optical axis of the receiving unit with increasing distance from the receiving unit. 3. The observation device according to claim 1, wherein the wavelength belonging to the ultraviolet region is selected from the wavelength range of 240 nm to 300 nm. 4. The observation device according to claim 3, wherein the pulsed light is spontaneously emitted light, i.e., incoherent light. 5. The observation device according to claim 4, wherein the frequency of the pulsed light is 1 to 10 MHz. 6. The observation device according to claim 5, wherein the pulse width of the pulsed light is 1 to 10 ns. 7. The observation apparatus according to claim 1, wherein the signal output from the light receiving element is a pulsed electrical signal corresponding to a photon. 8. The observation device according to claim 1, wherein the receiving optical system is a non-axial parabolic mirror and a retroreflector. 9. (Modified) The observation apparatus according to claim 1, further comprising: A coefficient analysis processing unit is configured to calculate the spatial distribution of the fine particles. 10. (Modified) The observation apparatus according to claim 1, further comprising: A characteristic evaluation processing unit is configured to perform an evaluation using the backscattering coefficient and dissipation coefficient of the fine particles.

Claims

1. An observation device, the observation device comprising: The emitting unit is configured to have an emitting light field of view and to emit pulsed light with a wavelength belonging to the ultraviolet region of the solar blind band within the emitting light field of view; A receiving unit is configured to have a receiving light field of view and to receive reflected light from the pulsed light reflected by the observed target object within the receiving light field of view; as well as Observation data generation unit, in which, The transmitting unit includes: A semiconductor light-emitting element, the semiconductor light-emitting element being configured to emit the pulsed light, and An emitting optical system configured to control the pulsed light emitted by the semiconductor light-emitting element, such that the pulsed light emitted by the semiconductor light-emitting element is emitted within the field of view of the emitted light. The receiving unit includes: A receiving optical system configured to collect the reflected light within the receiving light field of view, and A light receiving element configured to receive collected reflected light and output a signal corresponding to the received reflected light. The optical axis of the transmitting unit and the optical axis of the receiving unit are parallel to each other. The emitted light field of view is defined as having an emitted light angle that is larger than the received light field of view. The emitted light field of view and the received light field of view at least partially overlap each other, and The observation data generation unit generates LiDAR data as observation data based on the signal output from the optical receiving element.

2. The observation device according to claim 1, wherein, The emitted light field of view is a conical region centered on the optical axis of the emitting unit, and has a diameter that increases along the optical axis of the emitting unit with increasing distance from the emitting unit. The received light field of view is a conical region centered on the optical axis of the receiving unit, and has a diameter that increases along the optical axis of the receiving unit with increasing distance from the receiving unit.

3. The observation device according to claim 1, wherein, The wavelengths belonging to the ultraviolet region are selected from the wavelength range of 240 nm to 300 nm.

4. The observation device according to claim 3, wherein, The pulsed light is spontaneously emitted light (incoherent light).

5. The observation device according to claim 4, wherein, The frequency of the pulsed light is 1 to 10 MHz.

6. The observation device according to claim 5, wherein, The pulse width of the pulsed light is 1 to 10 ns.

7. The observation device according to claim 1, wherein, The signal output from the optical receiving element is a pulsed electrical signal corresponding to a photon.

8. The observation device according to claim 1, wherein, The receiving optical system consists of a non-axial parabolic mirror and a retroreflector.

9. The observation device according to claim 8, wherein, The nonaxial parabolic mirror and the retroreflector both include dielectric multilayer films configured to reflect the reflected light on their respective mirror surfaces.

10. The observation device according to claim 9, wherein, The nonaxial parabolic mirror and the retroreflective mirror include antireflective members configured to absorb light other than the reflected light on the lower layer of the respective dielectric multilayer film or on the rear surface of the respective mirror.

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