Observation apparatus

Abstract

To provide an observation apparatus capable of observing an observation target between an observation target at a far place and the observation apparatus.SOLUTION: An observation apparatus 10 comprises: a transmission unit 20 that transmits pulsed light of a wavelength that belongs to an ultraviolet region in a solar-blind band within a transmission light field Ss; and a reception unit 30 that receives reflected light within a reception light field Sr in the reflected light of the pulsed light reflected by an observation target. A transmission light field angle θs (θsp, θSC) is larger than a reception light field angle θr, and at least portions HT of the transmission light field and the reception light field overlap with each other. When the transmission light field angle on the opposite side with respect to a virtual center axis AXc that passes through the transmission unit and is parallel to an optical axis AXr of the reception unit is defined as a transmission light far-side field angle θsp, and the transmission light field angle on the reception unit side with respect to an optical axis of the transmission unit is defined as a transmission light near-side field angle θsc, the transmission light far-side field angle is smaller than the transmission light near-side field angle.SELECTED DRAWING: Figure 19

Description

[Technical Field]

[0001] The present disclosure relates to an observation device, and more particularly to an observation device that can observe an observation target near the earth's surface and at a short distance from the observation device. [Background technology]

[0002] Patent Document 1 describes an observation device that performs lidar observation based on observation light in response to laser light emitted toward an object to be observed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2003 / 073127 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, because observation is performed using laser light, it is possible to observe objects that are located relatively far away (for example, several kilometers away), but there is a problem in that it is not possible to observe objects that are located between the distant object and the observation device, such as objects that are near the earth's surface and close to the observation device.

[0005] The present disclosure has been made to solve such problems, and aims to provide an observation device that can observe an object near the Earth's surface and at a short distance from the observation device. [Means for solving the problem]

[0006] The observation device according to the present disclosure comprises a transmitter having a transmission light field of view and transmitting pulsed light of a wavelength belonging to the ultraviolet region of the solar blind band within the transmission light field of view, a receiver having a reception light field of view and receiving reflected light of the pulsed light reflected by an observation object within the reception light field of view, and an observation data generator, wherein the transmitter comprises a semiconductor light-emitting element that emits the pulsed light, and a transmission optical system that controls the pulsed light emitted by the semiconductor light-emitting element so that the pulsed light emitted by the semiconductor light-emitting element is transmitted within the transmission light field of view, and the receiver comprises a reception optical system that collects reflected light within the reception light field of view, and receives the collected reflected light and outputs a signal according to the received reflected light. and a light receiving element configured to receive the transmitted light from the light source, the optical axis of the transmitted light constituting the transmitted light field of view intersects with the optical axis of the received light constituting the received light field of view, and the transmitted light field of view and the received light field of view at least partially overlap each other, the observation data generation unit generates LIDAR data, which is observation data, based on signals output by the light receiving element, and when an angle corresponding to the transmitted light field of view on the side opposite the receiving unit with respect to a reference axis that passes through the transmitter and is parallel to the optical axis of the receiving unit is defined as a transmitted light far-side field of view angle, and an angle corresponding to the transmitted light field of view on the receiving unit side with respect to the reference axis is defined as a transmitted light near-side field of view angle, the transmitted light far-side field of view angle<the transmitted light near-side field of view angle, and the transmitted light far-side field of view angle≧the received light field of view angle.

[0007] With this configuration, it is possible to observe objects near the earth's surface and at a short distance from the observation device.

[0008] This is because the angle is larger than the receiving light field angle that defines the receiving light field, and the transmitting light field and the receiving light field at least partially overlap each other.

[0009] In the observation device, the semiconductor light emitting element may be disposed at a position eccentric to the opposite side of the receiver from the reference axis so that the far-side field of view of the transmitted light is smaller than the near-side field of view of the transmitted light.

[0010] In the observation device, the optical axis of the transmitter and the optical axis of the receiver may intersect so that the far-side field of view angle of the transmitted light is smaller than the near-side field of view angle of the transmitted light.

[0011] The observation device may further include an optical element that controls the pulsed light emitted by the transmitter so that the far-side field of view of the transmitted light is smaller than the near-side field of view of the transmitted light.

[0012] In the observation device, the optical axis of the transmitting unit and the optical axis of the receiving unit may be parallel to each other.

[0013] In addition, in the above observation device, the transmitted light field of view may be a cone-shaped region centered on a center line that passes through the transmitter and is inclined diagonally downward toward the front at a predetermined angle with respect to the reference axis, and the diameter of the cone-shaped region increases as it moves away from the transmitter along the center line, and the received light field of view may be a cone-shaped region centered on the optical axis of the receiver and the diameter of the cone-shaped region increases as it moves away from the receiver along the optical axis of the receiver.

[0014] In the observation device, the wavelength in the ultraviolet range may be selected from a wavelength range of 240 nm to 300 nm.

[0015] In the observation device, the pulsed light may be spontaneously emitted light (incoherent light).

[0016] In the observation device, the frequency of the pulsed light may be 1 to 10 MHz.

[0017] In the observation device, the pulsed light may have a pulse width of 1 to 10 ns.

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

[0019] In the observation device, the receiving optical system may include an off-axis parabolic mirror and a folding mirror.

[0020] The off-axis parabolic mirror and the folding mirror may each have a dielectric multilayer film on a mirror surface that reflects the reflected light.

[0021] In the above observation device, the off-axis parabolic mirror and the folding mirror may have an anti-reflection member that absorbs light other than the reflected light, either below the dielectric multilayer film or on the back surface of each mirror. [Effects of the Invention]

[0022] The present disclosure makes it possible to provide an observation device that can observe an object near the earth's surface and at a short distance from the observation device. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic diagram of an observation device 10. FIG. [Figure 2] 2 is a longitudinal cross-sectional view (schematic view) of the observation device 10 shown in FIG. [Figure 3] 10 is a graph showing a pattern of change in the field of view coupling ratio Crs when the transmitted light field of view angle θs=10 mrad and the received light field of view angle θr=3 mrad. [Figure 4] FIG. 4 is an enlarged view of the area from 0 to 30 m in FIG. [Figure 5] 10 is a graph showing a pattern of change in the field of view coupling ratio Crs when the field of view of the transmitted light is 10 mrad and the field of view of the received light θr is 5 mrad. [Figure 6] FIG. 6 is an enlarged view of the area from 0 to 30 m in FIG. 5. [Figure 7] FIG. 1 is a conceptual diagram of the observation data (lidar data) generation process. [Figure 8] FIG. 1 is a schematic diagram of an observation device 10A. [Figure 9] 1 is a graph showing the emission spectrum of a deep ultraviolet LED 21. [Figure 10]10 is a diagram illustrating how light PL1 and PL2 (pulsed light) emitted from a deep-ultraviolet LED 21 (light-emitting surface) is also transmitted in a direction inclined with respect to the optical axis AXs of the transmitter 20. FIG. [Figure 11] This is an example of the drive circuit 24. [Figure 12] (a)(b) An example of the transmission characteristics of pulsed light. [Figure 13] 1 is a graph showing the relationship between supply voltage (V) and frequency (MHz). [Figure 14] FIG. 9 is a schematic diagram of the receiving unit 30 extracted from FIG. 8. [Figure 15] FIG. 1 is a schematic diagram of an observation device 10B. [Figure 16] 3 is a cross-sectional view of the first receiving mirror 37. FIG. [Figure 17] 3 is a cross-sectional view of a second receiving mirror 38. FIG. [Figure 18] The reflection spectrum of the light reflected by each receiving mirror is shown. [Figure 19] 1A is a longitudinal cross-sectional view (schematic diagram) of an observation device 10 of the first embodiment, and FIG. 1B is a longitudinal cross-sectional view (schematic diagram) of an observation device 10A of the second embodiment. [Figure 20] 10 is a longitudinal cross-sectional view (schematic diagram) of an observation device 10B of the third embodiment. [Figure 21] FIG. 10 is a longitudinal cross-sectional view (schematic diagram) of an observation device 10C of a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0024] <Embodiment 1> Hereinafter, an observation device 10 according to a first embodiment of the present disclosure will be described with reference to the accompanying drawings. Corresponding components in each drawing are given the same reference numerals, and duplicated explanations will be omitted.

[0025] <Outline of Observation Instrument 10> First, an overview of the observation device 10 of the first embodiment will be described.

[0026] FIG. 1 is a schematic diagram of the observation device 10.

[0027] The observation device 10 of the first embodiment is a device (LiDAR device) that remotely and non-contactly observes an observation object Ob (for example, airborne particles such as aerosols and dust) that exists at a short distance (for example, 10 to 150 m).

[0028] As shown in FIG. 1, the observation device 10 includes a transmitting unit 20, a receiving unit 30, and a control analysis unit 40.

[0029] FIG. 2 is a longitudinal cross-sectional view (schematic diagram) of the observation device 10 shown in FIG.

[0030] As shown in Fig. 2, the transmitter 20 has a transmission light field of view Ss and transmits pulsed light (hereinafter also referred to as transmitted light) of a wavelength (e.g., 265 nm) belonging to the ultraviolet region of the solar blind band within the transmission light field of view Ss. Meanwhile, the receiver 30 has a reception light field of view Sr and receives reflected light (reflected pulsed light) of the transmission light (pulsed light) that is reflected by an observation target Ob and returns to the reception light field of view Sr, and outputs a pulsed electrical signal (electrical signal of a pulse wave) corresponding to the received reflected light. The pulsed light may be spontaneous emission light (incoherent light).

[0031] The optical axis AXs of the transmitter 20 and the optical axis AXr of the receiver 30 are arranged parallel to and spaced apart from each other. The distance L1 between the optical axis AXs of the transmitter 20 and the optical axis AXr of the receiver 30 is, for example, 85 mm.

[0032] The transmitted light field Ss is a cone-shaped region whose center is the optical axis AXs of the transmitter 20 and whose diameter increases with increasing distance from the transmitter 20 along the optical axis AXs of the transmitter 20. The minimum diameter of the transmitted light field Ss (the diameter at the left end in FIG. 2) is, for example, 60 mm. The transmitted light field angle θs defining the transmitted light field Ss is, for example, 10 mrad (0.57°).

[0033] On the other hand, the receiving light field Sr is a cone-shaped region centered on the optical axis AXr of the receiving unit 30 and having a diameter that increases with increasing distance from the receiving unit 30 along the optical axis AXr of the receiving unit 30. The minimum diameter of the receiving light field Sr (the diameter at the left end in FIG. 2) is, for example, 100 mm. The receiving light field angle θr that defines the receiving light field Sr is, for example, 3 mrad (0.17°) or 5 mrad (0.29°).

[0034] As described above, the transmitted light viewing angle θs is set to be larger than the received light viewing angle θr.

[0035] Next, the overlapping (superimposition) of the transmission light field Ss and the reception light field Sr will be described.

[0036] As described above, the optical axis AXs of the transmitting unit 20 and the optical axis AXr of the receiving unit 30 are arranged spaced apart 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 conical areas, and the transmitted light field of view θs is set larger than the received light field of view θr.

[0037] As a result, the transmitting light field Ss and the receiving light field Sr overlap each other to form a superimposed light field Sc, as shown in Fig. 2 (see the hatched area HT in Fig. 2 and the superimposed light field Sc in each cross-sectional view). Next, the superimposed light field Sc, which is the overlap of the transmitting light field Ss and the receiving light field Sr, will be described in detail.

[0038] The ratio of the superimposed light field of view Sc to the transmitted light field of view Ss can be expressed as the field of view combination ratio Crs, which is calculated by the following formula 1.

[0039] Field of view combination ratio Crs = superimposed light field of view Sc / transmitted light field of view Ss (Equation 1) Here, the overlapping light field Sc is the area of ​​the region where the transmitted light field Ss and the received light field Sr overlap in each cross section (see each cross section in FIG. 2). The transmitted light field Ss is the area of ​​the transmitted light field Ss in each cross section.

[0040] A large field of view coupling ratio Crs indicates that there is a large amount of reflected light (reflected pulse light) that is reflected by the observation object Ob and returns to the field of view Sr of the received light.

[0041] As shown in FIG. 2, at a first position P1, which is a first distance r1 away from the lens barrel tip position P0, the outer edge of the transmitted light field Ss circumscribes the outer edge of the received light field Sr (see the cross section B-B in FIG. 2). At a second position P2, which is a second distance r2 away from the lens barrel tip position P0, the outer edge of the transmitted light field Ss tangent to the optical axis AXr of the receiver 30 (see the cross section C-C in FIG. 2). At a third position P3, which is a third distance r3 away from the lens barrel tip position P0, the outer edge of the received light field Sr is inscribed in the outer edge of the transmitted light field Ss (see the cross section D-D in FIG. 2). At positions further away from the third position P3, the outer edge of the received light field Sr is included in the outer edge of the transmitted light field Ss without tangent to it (see the cross section E-E in FIG. 2).

[0042] Next, the change pattern of the visual field combination ratio Crs will be described.

[0043] First, the change pattern of the field of view coupling ratio Crs when the transmitted light field of view angle θs=10 mrad and the received light field of view angle θr=3 mrad will be described.

[0044] 3 is a graph showing the pattern of change in the field of view coupling ratio Crs when the transmitted light field of view angle θs=10 mrad and the received light field of view angle θr=3 mrad. FIG. 4 is an enlarged view of the portion of FIG. 3 covering a distance of 0 to 30 m.

[0045] As shown in FIG. 4, when the transmitted light field angle θs=10 mrad and the received light field angle θr=3 mrad, the first position P1 is a position that is a first distance r1 (0.44 m) away from the transmitter 20 (the end of the barrel P0) along the optical axis AXs of the transmitter 20. The second position P2 is a position that is a second distance r2 (5.5 m) away from the transmitter 20 (the end of the barrel P0) along the optical axis AXs of the transmitter 20. The third position P3 is a position that is a third distance r3 (15 m) away from the transmitter 20 (the end of the barrel P0) along the optical axis AXs of the transmitter 20. The fourth position P4 is a position where the field of view combination ratio Crs is maximum, and is a position that is 11 m away from the transmitter 20 (the end of the barrel P0) along the optical axis AXs of the transmitter 20.

[0046] The distance region from the lens barrel tip position P0 to the first position P1 is a distance region where the outer periphery of the transmitted light field Ss and the outer periphery of the received light field Sr are separated. Therefore, the superimposed light field Sc is not formed, and the field combination ratio Crs is zero. Next, the distance region from the first position P1 to the second position P2 is a distance region from where the outer periphery of the transmitted light field Ss contacts the outer periphery of the received light field Sr to the optical axis AXr of the received light field Sr. During this period, the field combination ratio Crs increases sharply as the superimposed light field Sc expands. Next, the distance region from the second position P2 to the third position P3 is a distance region where the outer periphery of the transmitted light field Ss crosses the optical axis AXr of the received light field Sr and reaches the far outer periphery of the received light field Sr. During this period, the superimposed light field Sc expands while the transmitted light field Ss also expands, so the field combination ratio Crs gradually increases, reaches a maximum value, and then decreases. Finally, the distance region beyond the third position P3 is a distance region where the transmitted light field Ss encompasses the received light field Sr. During this period, the superimposed light field Sc and the received light field Sr are equal, but because the magnification ratio of the transmitted light field Ss is large, the field combination ratio Crs gradually decreases.

[0047] Next, a change pattern of the field of view coupling ratio Crs when the transmitted light field of view angle is 10 mrad and the received light field of view angle θr is 5 mrad will be described.

[0048] 5 is a graph showing the pattern of change in the field of view coupling ratio Crs when the transmitted light field of view angle is 10 mrad and the received light field of view angle θr is 5 mrad. FIG. 6 is an enlarged view of the portion of FIG. 5 covering a distance of 0 to 30 m.

[0049] As shown in FIG. 6, when the transmitted light field angle θs=10 mrad and the received light field angle θr=5 mrad, the first position P1 is a position that is a first distance r1 (0.38 m) away from the transmitter 20 (the tip of the lens barrel P0) along the optical axis AXs of the transmitter 20. The second position P2 is a position that is a second distance r2 (5.5 m) away from the transmitter 20 (the tip of the lens barrel P0) along the optical axis AXs of the transmitter 20. The third position P3 is a position that is a third distance r3 (21 m) away from the transmitter 20 (the tip of the lens barrel P0) along the optical axis AXs of the transmitter 20. The fourth position P4 is a position where the field of view combination ratio Crs is maximum, and is a position that is a first distance r1 (0.38 m) away from the transmitter 20 (the tip of the lens barrel P0) along the optical axis AXs of the transmitter 20.

[0050] The change in the field of view combination ratio Crs in each distance region from the tip position P0 of the telescope tube 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 the same as when the received light field of view angle θr is 3 mrad. However, because the received light field of view angle θr of the received light field Sr is large at 5 mrad, the field of view combination ratio Crs at the same observation distance becomes larger.

[0051] As described above, observation is possible from a distance beyond the first position P1 (the circumscribed overlap distance) where the superimposed light field Sc is formed. Furthermore, observation is preferably performed from a distance beyond the second position P2 (the centerline tangent overlap distance) where the superimposed light field Sc is approximately half or more of the received light field Sr. Furthermore, considering the loss of the superimposed light field Sc and the field combination ratio Crs, observation is preferably performed from a distance beyond the third position P3 (the inscribed overlap distance) where the superimposed light field Sc coincides with the received light field Sr. Since the transmitter 20 and receiver 30 are separated in the observation device 10, there is no influence of light blocking by the transmitter 20 in the distance region beyond the first position P1. Furthermore, since the observation device 10 has the optical axis AXs of the transmitted light field Ss and the optical axis AXr of the received light field Sr arranged parallel to each other at a distance from each other, the superimposed light field Sc is not lost in the distance region beyond the third position P3.

[0052] Here, the distance r2 from the lens barrel tip position P0 to the second position P2 depends only on the transmitted light field angle θs, regardless of the received light field angle θr. In this case, the distance r1 from the lens barrel tip position P0 to the first position P1 can be shortened by increasing the received light field angle θr, and the distance r3 from the lens barrel tip position P0 to the third position P3 can be shortened by decreasing the received light field angle θr.

[0053] Hereinafter, the section between the lens barrel tip position P0 and the first position P1 will be referred to as the first section. The section between the first position P1 and the second position P2 will be referred to as the second section. The section between the second position P2 and the third position P3 will be referred to as the third section. The geometric correction factors that affect the received light in these three sections are included in the geometric efficiency factor Y(R) of the LIDAR equation.

[0054] The lidar equation is generally expressed as:

[0055]

number

[0056] In the first section, the transmitted light field of view Ss and the received light field of view Sr do not overlap with each other. Therefore, in the first section, there is almost no reflected light (reflected pulse light) that is reflected by the observed object Ob and returns to the received light field of view Sr. In other words, the first section is an observation blind section.

[0057] In the second section, the field of view combination ratio Crs increases or decreases, and so does the reflected light (reflected pulse light) reflected by the observed object Ob and returning to the received light field of view Sr. Specifically, the change in the field of view combination ratio Crs is due to a correlation between an increase in the overlap ratio of the transmitted light field of view Ss to the received light field of view Sr and a relative decrease in the overlapped light field of view Sc according to the magnification ratio (field of view angles θs, θr) of the transmitted light field of view Ss and the received light field of view Sr. Therefore, the reflected light (reflected pulse light) in the second section increases as the distance R increases, reaches a maximum value, and then decreases. In other words, the second section is an observation transition section.

[0058] In the third section, the field of view combination ratio Crs decreases according to the magnification ratio (field of view angles θs, θr) of the transmitted light field of view Ss and the received light field of view Sr, so the reflected light (reflected pulse light) reflected by the observed object Ob and returning to the received light field of view Sr also decreases. In other words, the third section is a stable observation section.

[0059] By overlapping the transmission light field of view Ss and the reception light field of view Sr as described above, it is possible to receive reflected light (reflected pulse light) that is reflected by the observation object Ob and returns to the reception light field of view Sr. In other words, the received light intensity P(R) in the second and third sections where the reflected light (reflected pulse light) is obtained is corrected by the geometric efficiency factor Y(R) in Equation 1 based on the field of view combination ratio Crs. Therefore, short-distance measurement can be performed without being affected by changes in the overlapping light field of view Sc. This makes it possible to observe the observation object Ob located in the short distance (farther than the first position P1). In other words, it is possible to generate accurate observation data (lidar data) of the observation object Ob located in the short distance (farther than the first position P1).

[0060] In particular, the transmitted light field angle θs is set larger than the received light field angle θr (see Figure 2). This shortens the distance (first section) from the telescope tube tip position P0 to the first position P1, and also shortens the distance (second section) from the second position P2 to the third position P3. This also lengthens the section distance from the third position P3 (third section) to the maximum observation distance (the distance defined by the pulse interval of the transmitted light). Furthermore, in the observable second and third sections, if the received light field angle θr is large, the field combination ratio Crs can be increased, thereby increasing the received light intensity P(R).

[0061] On the other hand, if the viewing angle θr of the received light is small, the resolution in the plane perpendicular to the optical axis is improved, and if the viewing angle θr of the received light is large, the resolution in the plane perpendicular to the optical axis is reduced. Also, if the viewing angle θr of the received light is small, the third distance r3 (see Figure 2) is short, and if the viewing angle θr of the received light is large, the third distance r3 is long.

[0062] From the above, when observing a short distance with high resolution, it is preferable that the viewing angle θr of the received light is small (for example, 3 mrad). On the other hand, when observing the received light intensity P(R) from a long distance, it is preferable that the viewing angle θr of the received light is large (for example, 5 mrad).

[0063] Furthermore, if the observation object Ob is a non-shading object such as aerosol, dust, fog, rainfall, or snowfall that is screen-like (thin in the distance direction), other observation objects located in front of or behind the observation object Ob can also be observed in the second and third sections.

[0064] Beyond the third position P3 (third section), the received light field of view Sr is included in the transmitted light field of view Ss, so it is possible to observe (measure) multiple observation targets Ob that are partially present within the received light field of view Sr. If the transmitted light is a linear beam (e.g., laser light), lidar data cannot be obtained for observation targets Ob other than those at the position where the transmitted light is transmitted.

[0065] Next, the observation data (lidar data) generation process will be described.

[0066] FIG. 7 is a conceptual diagram of the observation data (lidar data) generation process.

[0067] The observation data (lidar data) generation process is executed by the control and analysis unit 40. The control and analysis unit 40 can be a dedicated device that houses the equipment described below that generates and processes the observation data for the observation device 10, or it can be a composite device that includes other observation equipment such as an observation camera.

[0068] As shown in FIG. 1, the control analysis unit 40 includes an observation data generation unit 41, a coefficient analysis processing unit 42, a characteristic evaluation processing unit 43, and an observation data storage unit 44.

[0069] The observation data generation unit 41 divides the pulse electrical signal output by the receiving unit 30 in response to the reflected light (reflected light (reflected pulse light; specifically, photons) that is reflected by the observation object Ob and returns to the received light field of view Sr) for each reception cycle using a photon counting circuit (a circuit that performs photon counting), and accumulates this N times to generate observation data (lidar data). The bottom graph in Figure 7 is an example of observation data (lidar data). This generated observation data (lidar data) is stored (accumulated) in the observation data storage unit 44.

[0070] In Fig. 7, the first received electrical signal to the Nth received electrical signal represent pulse electrical signals divided for each reception cycle. In Fig. 7, each pulse shown in the graph to the right of the first received electrical signal represents a pulse electrical signal output in response to reflected light (reflected light (reflected pulsed light; specifically, photons) reflected by the observation object Ob and returning to the reception light field of view Sr) received by the receiving unit 30 during the reception cycle when the first pulsed light (transmitted light) is transmitted. The same applies to each pulse shown in the graph to the right of the Nth received electrical signal.

[0071] The time of flight (t) of the first received electrical signal represents the flight time (round-trip flight time) of the photon corresponding to each pulse to the observation object Ob. The time of flight (t) is omitted in the graph of the Nth received electrical signal.

[0072] The present invention is not limited to a photon counting circuit, and any device that performs photon counting may be used. For example, a digital oscilloscope and a PC (information processing device such as a personal computer) may be combined.

[0073] The coefficient analysis processing unit 42 calculates the spatial distribution (distance direction) of the observed object Ob from the increase or decrease in the observation data (lidar data), and also performs processing to evaluate the observation data (lidar data) using the lidar equation to calculate the extinction coefficient α and backscattering coefficient β specific to the observed object Ob.

[0074] For example, if the observation object Ob is a uniform atmosphere in the space from the telescope tip position P0 to the maximum observation distance (Rmax), the received light intensity P(R) increases according to the distance (R) and the geometric efficiency factor Y(R), and then attenuates after reaching a maximum value. Also, if the observation object Ob is spatially uniform, the extinction coefficient α(R) and backscattering coefficient β(R) do not change with distance, so they can be expressed as α and β. Therefore, the lidar equation is Ln((P(R)R 2) / Y(R))=-2αR + ln(P0Cβ), so the extinction coefficient α can be found from the slope term -2αR, and the backscattering coefficient β can be found from the intercept term ln(P0Cβ).

[0075] The characteristic evaluation processing unit 43 performs, for example, fixed-point atmospheric evaluation, evaluation of smoke, dust, and the like.

[0076] For example, atmospheric assessment at fixed points can be performed by conducting regular annual observations and evaluating the backscattering coefficient β and extinction coefficient α of aerosols and other particles contained in the observed atmosphere. Furthermore, by comparing the observed values ​​with those from a base year, it is possible to evaluate changes in atmospheric conditions. In doing so, it is also possible to estimate the types of particles suspended in space by comparing them with a disclosed standard atmosphere (see, for example, Laser Radar Society of Japan, 4 (2020), Kuze, Light Scattering Measurement of Aerosols and Atmospheric Molecules). Fog, rain, and snow can also be evaluated in the same way as fixed-point atmospheric assessment.

[0077] Smoke and dust, for example, the cleanliness of equipment exhaust, exhaust smoke from chimneys, dust on the road, etc., can be evaluated by comparing the characteristics of the air outside the exhaust section with the characteristics of the air at the exhaust section.

[0078] 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.

[0079] The control analysis unit 40 (observation data generation unit 41) has a function (such as the well-known dToF (direct Time of Flight) method or photon counting) of measuring (calculating) the time of flight of the reflected light (photons) received by the receiving unit 30 to the observation object Ob, and is therefore able to measure (calculate) the time of flight (round-trip flight time) of the photons corresponding to each pulse to the observation object Ob.

[0080] Observation data (lidar data) is generated by accumulating (accumulating N times) the first to Nth received electrical signals. In the graph at the bottom of Figure 7, the vertical axis represents the received light intensity, which corresponds to the number of photons. The horizontal axis represents the distance, which is obtained by converting the time of flight (t) into distance.

[0081] Next, we will explain the improvement of short-distance observation capability, miniaturization, and observation convenience of the observation device 10. Note that the short distance mentioned here refers to a distance of about several meters to several hundred meters.

[0082] (short-range observability) The observation device 10 can increase the transmission frequency of the transmitted light (pulsed light) transmitted from the transmitter 20 from 1 megahertz (MHz) to approximately 10 MHz. For example, if the observation target Ob is locally located at 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 a distance determined by the transmission period of the transmitted light (pulsed light). For example, if the transmission period of the transmitted light (pulsed light) is 1 microsecond (μsec), the flight distance of the transmitted light is 300 m. In other words, the maximum observation distance (Rmax) is 150 m, the distance at which the previously transmitted light does not interfere with the next transmitted light. The transmission frequency in this case is 1 MHz. Similarly, if the maximum observation distance (Rmax) is 15 m, the transmission period of the transmitted light (pulsed light) is 0.1 μsec and the transmission frequency is 10 MHz.

[0083] Lidar data is generated by integrating each pulse pulse of one unit period incident on the receiver 30 multiple times. Therefore, by increasing the transmission frequency of the transmitted light (pulsed light), it is possible to generate Lidar data in a short time. In particular, because the apparent movement speed (movement angle per unit time) of a short-distance observation object Ob is large, short-time observation is essential to improving spatial resolution. For example, if the distance to the observation object Ob is 100 m and the Lidar data is integrated 1,000 times, a transmission frequency of 1 MHz (transmission period of 1 μsec) will result in a single observation time of 1 millisecond (msec). In this case, if the observation object Ob is moving at a wind speed of 3 msec (similar to a gentle breeze), it will move 3 millimeters (mm) from the start to the end of observation. In other words, the movement angle is 0.0017°. Therefore, the received light field of view angle ratio (movement angle / received light field of view angle θr) is 0.01 (1%) if the received light field of view angle θr is 3 mrad (0.17°), and 0.006 (0.6%) if it is 5 mrad (0.29°). Furthermore, when the distance to the observation target Ob is 50 m, the movement angle is 0.0034°. Therefore, the received light field of view angle ratio is 0.02 (2%) if the received light field of view angle θr is 3 mrad, and 0.012 (1.2%) if it is 5 mrad. In this way, by increasing the transmission frequency, accurate observation is possible even when the observation target Ob is moving at close range.

[0084] Furthermore, the observation device 10 narrows the pulse width of the transmitted light (pulsed light) sent from the transmitter 20 to about 1 nanosecond (nsec). For example, a pulse width of 10 nsec results in a distance resolution of 1.5 m, and a pulse width of 1 nsec results in a distance resolution of 0.15 m. By narrowing the transmitted light in this way, it becomes possible to observe the observation target Ob with high accuracy in close-range measurements.

[0085] The observation device 10 transmits light (pulsed light) from the transmitter 20 at a solar-blind wavelength in the deep-ultraviolet light band that is free from atmospheric absorption (absorption by oxygen and nitrogen). Here, the solar-blind wavelength in the deep-ultraviolet light band refers to a deep-ultraviolet wavelength band of sunlight that reaches the Earth and is significantly attenuated before reaching the Earth's surface. Specifically, the solar-blind wavelength refers to a wavelength longer than the wavelength near the long-wavelength absorption edge of oxygen and nitrogen, but shorter than the long-wavelength absorption edge of the ozone layer. Specifically, the wavelength is between 230 nanometers (nm) and 300 nm, preferably 250 nm to 280 nm. By using such a wavelength band, observations are unaffected by external light and atmospheric absorption, enabling observations with a low-power light source.

[0086] Furthermore, by setting the wavelength of the transmitted light (pulsed light) to a solar-blind wavelength in the deep ultraviolet light band, where atmospheric absorption is not present, the backscattering coefficient β and extinction coefficient α of the particles contained in the observation object Ob become larger than those for near-ultraviolet to infrared light. This enables observation even when the observation object Ob is thin in the distance direction or contains low concentrations of particles. Specifically, the extinction coefficient α increases inversely proportional to the wavelength to the 1.25th power, and shortening the wavelength from 900 nm to 265 nm increases it by approximately five times. The backscattering coefficient β is roughly proportional to the extinction coefficient α, so it also increases by approximately five times. In other words, highly sensitive observation is possible even at close distances (where the observation object Ob travels a short distance). It also makes it easier to identify the characteristics of the observation object Ob (e.g., aerosols, smoke, dust, fog, rain, and snow).

[0087] (miniaturization) The observation device 10 uses a deep ultraviolet LED (Light Emission Diode), which is a semiconductor light emitting element that emits deep ultraviolet light (for example, a wavelength of 265 nm). 2 The size is about the same. Furthermore, the deep-ultraviolet LED allows the oscillator circuit that emits high-frequency, narrow-pulse-width light to be miniaturized. Furthermore, a collimated transmission system with high luminous flux utilization can be configured using a small lens with a small aperture (diameter of about φ60 mm). Therefore, the transmitter 20 can be miniaturized.

[0088] The observation device 10 uses a photon-counting-compatible ultraviolet photomultiplier tube (PMT) as the light-receiving element. This allows the PMT to be compact. Furthermore, because the light transmitted by the transmitter 20 is in the solar-blind wavelength range of the deep ultraviolet light band, which is not absorbed by the atmosphere, the primary collector of the receiver 30 can be a small lens or reflector (diameter φ100 mm or so). This allows the receiver 30 to be made compact.

[0089] (observation convenience) The observation device 10 uses a semiconductor light-emitting element (e.g., a 265 nm LED) that emits ultraviolet light in the solar blind band that is not absorbed by the atmosphere as the light source of the transmitter 20, making it possible to observe both day and night. For example, observation is possible during the day under clear skies, and at night under lighting such as fluorescent lamps or halogen lamps. This makes it possible to observe at regular intervals throughout 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 easier.

[0090] <Configuration example 1 of observation device 10> Next, a description will be given of a specific configuration example 1 of the observation device 10. Hereinafter, the observation device 10 of configuration example 1 will be referred to as observation device 10A.

[0091] FIG. 8 is a schematic diagram of the observation device 10A.

[0092] The observation device 10A is an observation device (LiDAR device) equipped with a transmitter 20 and a receiver 30 of a refractive optical system.

[0093] As shown in Fig. 8, the observation device 10A includes a transmitter 20, a receiver 30, and a control and analysis unit 40 (omitted from Fig. 8). The optical axis AXs of the transmitter 20 and the optical axis AXr of the receiver 30 are arranged parallel to and spaced apart from each other.

[0094] <Transmitting unit 20> The transmitter 20 includes a semiconductor light-emitting element 21 and a transmitting lens 22 (an example of the transmitting optical system of the present disclosure). In Fig. 8, reference numeral 23 denotes a transmitting lens barrel, and reference numeral 24 denotes a drive circuit for the semiconductor light-emitting element 21.

[0095] The semiconductor light emitting element 21 is a semiconductor light emitting element that has an excellent response speed (for example, can emit high-frequency, short-pulse light) and emits light (pulse light) with a wavelength belonging to the ultraviolet region of the solar blind band, such as a deep ultraviolet LED. Hereinafter, it will also be referred to as a deep ultraviolet LED 21.

[0096] Hereinafter, an example will be described in which a deep-ultraviolet LED with a peak wavelength (center wavelength) of 265 nm and a Lambertian light distribution (distribution) with a half-value angle of approximately 120° is used as the semiconductor light-emitting element 21. Hereinafter, this will also be referred to as a deep-ultraviolet LED 21.

[0097] The specifications of the deep ultraviolet LED 21 are as shown in the following table.

[0098] [Table 1] The spectrum of the deep-ultraviolet LED used, which has no atmospheric absorption, has a peak wavelength (λp) of 265 nm and a full width at half maximum (FWHM) of 12 nm. The directivity is Lambertian with a half-maximum angle of 120°. The optical output is 50 mW at an input power of 3 W under continuous output (cw) conditions, and 1 mW to 500 mW under pulsed output. The response is 1 ns or more.

[0099] The deep-ultraviolet LED 21 used in the transmitter 20 of the observation device 10A is sealed in a CAN package. The CAN package is mounted on a heat sink provided in the drive circuit 24. The portion of the CAN package other than the light exit port is covered with a partition plate made of a material that absorbs stray light emitted from the deep-ultraviolet LED. In addition to the CAN package, the deep-ultraviolet LED may be mounted on a ceramic substrate such as aluminum oxide, silicon nitride, or aluminum nitride that has high thermal conductivity (e.g., 30 to 200 W / m K) and absorbs stray light. Alternatively, the deep-ultraviolet LED may be mounted on a ceramic inlay-type glass-epoxy substrate in which ceramic is embedded in the portion where the deep-ultraviolet LED is mounted. It is preferable to provide a heat sink on the back side of the ceramic substrate or ceramic inlay-type glass-epoxy substrate (the side opposite to the side on which the deep-ultraviolet LED is mounted).

[0100] The deep-ultraviolet LED 21 has a light-emitting surface of 1.04 mm square. The light (pulsed light) emitted by the deep-ultraviolet LED is incoherent light or incoherence light (random phase, wide half-width, divergent light). In addition, the light (pulsed light) emitted by the deep-ultraviolet LED 21 is isotropic light (light without polarization).

[0101] The transmitting lens 22 is, for example, a condenser lens that is rotationally symmetric with respect to the optical axis AXs of the transmitter 20. The transmitting lens 22 is made of quartz glass that transmits the light emitted from the deep-ultraviolet LED 21. The transmitting lens 22 may also be made of borosilicate glass, silicate glass, amorphous fluororesin, or the like that transmits deep-ultraviolet light.

[0102] The specifications of the transmitting lens 22 are as shown in the following table.

[0103] [Table 2] When the acceptance angle θi (see FIG. 10) of the transmitting lens 22 is 30° and the diameter φs (see FIG. 10) of the transmitting lens 22 is 60 mm, the focal length fs (see FIG. 10) is 52 mm. This can be calculated using the formula tan(θi) = (φs / 2) / fs. On the other hand, when the size Es of the deep-ultraviolet LED 21 (light-emitting surface) is 1.04 mm square, the transmitted light viewing angle θs is approximately 10 mrad. This can be calculated using the formula tanθs = (Es / 2) / f.

[0104] Optical axis AX of the transmitting lens 22 22 and the optical axis AX of the deep ultraviolet LED21 (light-emitting surface) 21 coincides (approximately coincides) with the optical axis AXs of the transmitter 20. The optical axis of the deep-ultraviolet LED 21 (light-emitting surface) passes through the center of the light-emitting surface and extends in a direction perpendicular to the light-emitting surface.

[0105] The focal point of the transmitting lens 22 is disposed near the center of the deep-ultraviolet LED 21 (light-emitting surface). Therefore, the light (pulsed light) emitted by the deep-ultraviolet LED 21 is collimated by the transmitting lens 22. This makes it possible to make the transmitted light suitable for observation at a short distance (for example, 15 m to 150 m).

[0106] The beam diameter (aperture) of the transmitted light is sufficiently larger than the observation object Ob (e.g., fine particles (aerosols) in the atmosphere) in order to stably observe (measure) the observation object Ob. For example, the beam diameter (aperture) of the transmitted light is 60 mm in diameter.

[0107] As described above, by using a condenser lens (collimator lens) as the transmitting lens 22, the light (pulsed light) emitted from the deep-ultraviolet LED 21 can be shaped into collimated light with a diameter equal to the lens diameter of the transmitting lens 22 (60 mm).

[0108] On the other hand, the deep-ultraviolet LED 21 (light-emitting surface) is not a point light source but has a certain size. Therefore, the light (pulsed light) emitted from the deep-ultraviolet LED 21 (light-emitting surface) is also transmitted in a direction inclined with respect to the optical axis AXs of the transmitter 20.

[0109] FIG. 10 is a diagram showing how the light PL1, PL2, and PL3 (pulsed light) emitted from the deep-ultraviolet LED 21 (light-emitting surface) is also transmitted in a direction inclined with respect to the optical axis AXs of the transmitter 20. In FIG.

[0110] As shown in FIG. 10, light PL1 emitted from the center Pa of the deep ultraviolet LED 21 (light emitting surface) is refracted (collimated) by the transmitting lens 22 and transmitted in the direction of the optical axis AXs of the transmitting section 20.

[0111] On the other hand, the light PL2 emitted from a position Pb that is shifted downward from the center of the deep-ultraviolet LED 21 (light-emitting surface), for example, from the bottom end of the deep-ultraviolet LED 21 (light-emitting surface) in FIG. 10, is refracted by the transmitting lens 22 and oriented along a reference axis, here, the optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22). 22 ) in a direction inclined upward at a predetermined angle relative to the reference axis. The same applies to light emitted from other positions of the deep-ultraviolet LED 21 (light-emitting surface) that are shifted downward relative to the center. Hereinafter, the light PL2 refracted by the transmitting lens 22 and transmitted in a direction inclined upward at a predetermined angle relative to the reference axis is referred to as the transmitted light far-side field of view boundary line BL SP In addition, the reference axis and the far-side field of view boundary line BL SP The angle between the two is called the far-side field of view angle θ SP It is written as follows.

[0112] Similarly, the light PL3 ​​emitted from a position Pc shifted upward relative to the center of the deep-ultraviolet LED 21 (light-emitting surface), for example, from the top end of the deep-ultraviolet LED 21 (light-emitting surface) in FIG. 10, is refracted by the transmitting lens 22 and oriented along a reference axis, here, the optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22). 22 ) in a direction tilted downward at a predetermined angle relative to the reference axis. The same applies to light emitted from other positions of the deep-ultraviolet LED 21 (light-emitting surface) that are shifted upward relative to the center. Hereinafter, the light PL3 ​​that is refracted by the transmitting lens 22 and transmitted in a direction tilted downward at a predetermined angle relative to the reference axis is referred to as the transmitted light near-side field of view boundary line BL SC In addition, the reference axis and the field of view boundary line BL SC The angle between the two is called the near-field angle θ SCIt is written as follows.

[0113] As a result, the transmitted light field Ss is a conical area centered on the optical axis AXs of the transmitter 20 and whose diameter increases as it moves away from the transmitter 20 (the tip position P0 of the telescope barrel) along the optical axis AXs of the transmitter 20 (see Figure 2).

[0114] The transmitted light field of view Ss (transmitted light field of view θs) can be adjusted by changing the focal length fs. For example, if the acceptance angle θi is constant, shortening the focal length fs can widen the transmitted light field of view θs compared to before shortening the focal length fs. In this case, the lens diameter φs of the transmitting lens 22 becomes smaller. Conversely, lengthening the focal length fs can narrow the transmitted light field of view θs compared to before lengthening the focal length fs. In this case, the lens diameter φs of the transmitting lens 22 becomes larger. In this way, the transmitted light field of view θs can be easily adjusted by using a deep-ultraviolet LED 21 and a transmitting lens 22 with Lambertian directivity characteristics. In other words, the transmitted light field of view Ss can be easily made larger than the received light field of view Sr.

[0115] The transmitting lens barrel 23 is made of aluminum (Al), and the inner cylindrical surface is treated with a black anodized aluminum coating to prevent reflection (absorption) of the light (stray light) emitted from the deep-ultraviolet LED 21. The transmitting lens barrel 23 can also be made of corrosion-resistant metal materials such as stainless steel and invar, resin materials such as polycarbonate, acrylic, polypropylene, polyethylene, and epoxy, or low-thermal expansion ceramic materials such as alumina and silica. The anti-reflection treatment can be matte black chrome plating or nickel plating. Alternatively, a black alumina or carbon ceramic coating can be used. By treating the inner cylindrical surface of the transmitting lens barrel 23 in this way, excess light (stray light) other than the light directly entering the transmitting lens 22 from the deep-ultraviolet LED 21 can be prevented from being reflected by the inner cylindrical surface and exiting the transmitting lens 22. In other words, the transmitted light can be transmitted at a predetermined transmitted light field of view θs (transmitted light field of view Ss), preventing distance errors in LIDAR data during dToF observations. In other words, it becomes possible to observe the received light intensity P(R) with high accuracy.

[0116] The transmitting lens barrel 23 may also be provided with a hood in front of the transmitting lens 22. The inner cylindrical surface of the hood is also subjected to the same anti-reflection treatment as above.

[0117] <Drive circuit 24> Next, the drive circuit 24 will be described.

[0118] Fig. 11 shows an example of the driver circuit 24, and Figs. 12(a) and 12(b) show examples of pulsed light transmission characteristics. Fig. 13 is a graph showing the relationship between supply voltage (V) and frequency (MHz). The driver circuit 24 shown in Fig. 11 is a driver circuit that utilizes the avalanche breakdown of a transistor. The horizontal axis in Figs. 12(a) and 12(b) represents time (ns), and the vertical axis represents the relative value of the light emission intensity (AU).

[0119] The driving circuit 24 is a driving circuit for realizing pulsed light having a frequency of 1 MHz to 10 MHz and a pulse width of 1 ns to 10 ns as the transmitted light. The control and analysis unit 40 controls the deep-ultraviolet LED 21 via this driving circuit 24 so as to emit transmitted light (pulsed light) having a frequency of 1 MHz and a pulse width of 9.6 ns.

[0120] The pulse width of the transmitted light is adjusted by selecting the capacitance of the capacitor C1 of the drive circuit 24. For example, by setting the capacitance of the capacitor C1 to a small or large value, the emitted pulse width (half width) can be adjusted to 1.58 ns (see FIG. 12(a)) or 3.2 ns (see FIG. 12(b)).

[0121] The frequency of the transmitted light (emission light period) can be adjusted (controlled) by fixing the value of resistor R1 in the driver circuit and selecting the voltage applied between Vcc and ground. For example, as shown in Figure 13, by setting the applied voltage to 72V to 92V, the recharge time can be adjusted and the emission light period can be controlled to 1MHz to 2.1MHz. The optical intensity of the pulsed light at this time can be kept approximately constant because the avalanche breakdown voltage of the transistor is constant. Alternatively, the frequency of the transmitted light can be selected by selecting the value of resistor R1 while keeping the voltage between Vcc and ground constant.

[0122] The distance resolution (spatial resolution) is determined by the pulse width of the transmitted light (pulsed light). For example, if the pulse width is 1 ns, the distance resolution (spatial resolution) is 0.15 m (speed of light c (m / s) · pulse width τ (s) / 2). This makes it possible to observe the detailed distribution of the object of observation Ob (for example, particles in space). Also, if the pulse width is 10 ns, the distance resolution (spatial resolution) is 1.5 m. This makes it possible to observe the distribution of the object of observation Ob (for example, particles in space).

[0123] The observation distance (measurement distance) is determined by the frequency of the transmitted light (pulsed light). For example, if the frequency is 1 MHz (period 1 μs = 1 / 1,000,000 ( / s)), the maximum observation distance is 150 m (speed of light c (m / s) × period f (s) / 2). Also, if the frequency is 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 returning light (received light) from the previously transmitted light does not overlap with the emission time of the next transmitted light.

[0124] In this way, the pulse width and frequency of the transmitted light can be easily adjusted by selecting the capacitor C1 and resistor R1 of the driver circuit 24 and the voltage between Vcc and ground. Specifically, by preparing and selecting capacitors C1a, C1b, C1c, ... with different capacitances as the capacitor C1 and resistors R1a, R1b, R1c, ... with different resistance values ​​as the resistor R1, the pulse width or frequency of the transmitted light can be adjusted over a wide range.

[0125] <Receiving unit 30> 8 and 14, the receiving unit 30 includes a first receiving lens 31 (an example of the receiving optical system of the present disclosure), a field stop 32, a second receiving lens 33, a receiving filter 34, and a light receiving element 35. In FIG. 8, reference numeral 36 indicates a receiving lens barrel. FIG. 14 is a schematic diagram of the receiving unit 30 extracted from FIG. 8.

[0126] The first receiving lens 31 is, for example, a condenser lens that is rotationally symmetric with respect to the optical axis AXr of the receiving unit 30. The first receiving lens 31 (and the second receiving lens 33) are made of quartz glass, similar to the transmitting lens 22. The first receiving lens 31 condenses reflected light PL3, PL4 (reflected pulsed light) that is reflected by the observation object Ob and returns to the receiving light field of view Sr, out of the transmitted light (pulsed light).

[0127] In order to improve the amount of captured reflected light PL3, PL4 (reflected pulsed light) that is reflected by the observation object Ob and returns to the receiving light field of view Sr, the first receiving lens diameter φr (aperture of the receiving lens barrel 36) is larger than the diameter φs of the transmitting lens 22 (aperture of the transmitting lens barrel 23). This makes it possible to receive reflected light PL3, PL4 (reflected pulsed light) that is reflected by the observation object Ob that is present in the intended area and returns to the receiving light field of view Sr.

[0128] The specifications of the first receiving lens 31 are as shown in the following table.

[0129] [Table 3] The viewing angle θr of the received light is set narrow (3 mrad (0.173°) to 5 mrad (0.286°)) so that the intended area (plane perpendicular to the optical axis) can be observed.

[0130] When the lens diameter φr of the first receiving lens 31 is 100 mm and the focal length fr is 200 mm, the convergence angle θj (see FIG. 14) of the first receiving lens 31 is approximately 14 degrees. This can be calculated using the formula tan(θj) = (φr / 2) / f. On the other hand, when the received light field of view angle θr (see FIG. 14) is 3 mrad (0.173°) and the focal length fr is 200 mm, the field of view image size Er is approximately 0.3 mm square. This can be calculated using the formula tan(θr) = (Er / 2) / f.

[0131] The receiving barrel 36 is made of aluminum, just like the transmitting barrel 23, and has an anti-reflection treatment applied to the inner cylindrical surface. This absorbs light that enters the receiving lens 31 outside the specified receiving light viewing angle θr, preventing it from reaching the light receiving element 35.

[0132] The field stop 32 is a light blocking stop that controls (narrows or widens) the received light field Sr.

[0133] The observation range (received light field Sr) can be defined by providing a field diaphragm 32 at the focal point (focal plane) of the first receiving lens 31. For example, when observing a wide received light field Sr, the field diaphragm 32 is opened, and conversely, when observing only a narrow received light field Sr, the field diaphragm 32 is closed. This allows the received light field Sr to be adjusted.

[0134] Furthermore, when the received light viewing angle θr is constant, the field of view image on the focal plane can be made smaller by shortening the focal length fr of the first receiving lens 31. Conversely, the field of view image on the focal plane can be made larger by lengthening the focal length fr of the first receiving lens 31.

[0135] The second receiving lens 33 adjusts the field of view image on the focal plane to the size of the light receiving surface of the light receiving element 35. If the second receiving lens 33 is not necessary, it may be omitted.

[0136] The receiving filter 34 is a bandpass filter configured to transmit only reflected light (reflected pulsed light) that is reflected by the observation object Ob and returns to the receiving light field of view Sr. In configuration example 1, a bandpass filter of 266 nm ± 5 nm (corresponding to the half-width of the deep-ultraviolet LED 21) is used. Providing the receiving filter 34 improves the S / N ratio of the signal (pulse electrical signal) output by the receiving unit 30 (light-receiving element 35) in accordance with the reflected light (reflected pulsed light) received by the receiving unit 30.

[0137] The light receiving element 35 is an ultraviolet photomultiplier tube (PMT) for photon counting. The PMT, which is the light receiving element 35 of Configuration Example 1, is equipped with a high-voltage circuit required for the operation of the PMT and a preamplifier circuit that amplifies the pulse electrical signal photoelectrically converted by the PMT. Note that the light receiving element 35 may be a photoelectric conversion element for photon counting other than a PMT. The light receiving element 35 outputs a signal (pulse electrical signal) corresponding to the reflected light (reflected pulse light) received by the light receiving element 35.

[0138] The received light field of view Sr is a circle obtained by adding the diameter φr of the first receiving lens 31 to a circle drawn by the received light field of view angle θr centered on the optical axis AXr of the receiving unit 30. In other words, the received light field of view Sr is a circle whose radius is the sum of the radius of the circle of the received light field of view angle θr and the radius of the diameter φr of the first receiving lens 31.

[0139] The optical axis AXs of the transmitter 20 and the optical axis AXr of the receiver 30 are arranged parallel to and spaced apart from each other. The distance L1 (see FIG. 8) between the optical axis AXs of the transmitter 20 and the optical axis AXr of the receiver 30 is, for example, 85 mm. It is preferable that the distance L1 be closer to the combined half-aperture distance, which is half the sum of the aperture of the transmitter lens 22 of the transmitter 20 and the aperture of the receiver lens 31 of the receiver 30, because this shortens the overlap start distance r1 of the transmitted light field Ss and the received light field Sr. Generally, it is preferable that the distance L1 be approximately 1.05 to 1.1 times the combined half-aperture distance.

[0140] In the first configuration example as well, the transmitting light field Ss and the receiving light field Sr overlap each other (see the hatched area HT in FIG. 2 and the overlapping light field Sc in each cross-sectional view).

[0141] As a result, even in configuration example 1, it is possible to receive reflected light (reflected pulsed light) that is reflected by the observation object Ob and returns to the reception light field of view Sr, making it possible to observe the observation object Ob that is located at a short distance (farther than the first position P1). In other words, it is possible to generate observation data (lidar data) with high accuracy.

[0142] <Configuration Example 2 of Observation Device 10> Next, a description will be given of a specific configuration example 2 of the observation device 10. Hereinafter, the observation device 10 of configuration example 2 will be referred to as observation device 10B.

[0143] FIG. 15 is a schematic diagram of the observation device 10B.

[0144] The observation device 10B is an observation device (LiDAR device) equipped with a transmission unit 20 of a refractive system and a reception unit 30 of a reflective system.

[0145] As shown in Fig. 15, the observation device 10B includes a transmitter 20, a receiver 30, and a control and analysis unit 40 (omitted from Fig. 15). The optical axis AXs of the transmitter 20 and the optical axis AXr of the receiver are arranged parallel to and spaced apart from each other.

[0146] <Transmitting unit 20> The transmitter 20 includes a semiconductor light emitting element 21 and a transmitting lens 22 (an example of a transmitting optical system of the present disclosure).

[0147] The transmitting section 20 differs from the transmitting section 20 of Configuration Example 1 in the specifications of the transmitting lens 22. The specifications of the transmitting lens 22 are as shown in the following table.

[0148] [Table 4] That is, the transmitting lens 22 has a shorter focal length and a wider transmitted light field of view θs than the transmitting lens 22 of Configuration Example 1. As a result, even if the receiving light aperture is increased, the receiving light field of view Sr can overlap and encompass the transmitted light field of view Ss at close range. Because a 1.04 mm square deep-ultraviolet LED is used, the transmitted light field of view θs is 1.489° (25.99 mrad ≒ 26 mrad). Otherwise, the transmitting unit 20 is the same as the transmitting unit 20 of Configuration Example 1.

[0149] <Receiving unit 30> 15, the receiving section 30 differs from the receiving section 30 of Configuration Example 1 in that it includes a first receiving mirror 37 and a second receiving mirror 38 (an example of the receiving optical system of the present disclosure) instead of the first receiving lens 31. Otherwise, the receiving section 30 is similar to the receiving section 30 of Configuration Example 1. In FIG. 15, reference numeral 39 denotes a main receiving barrel, and reference numeral 40 denotes a secondary receiving barrel.

[0150] The first receiving mirror 37 is an off-axis parabolic mirror (periphery of a parabolic mirror) and has a focal point F outside the main receiving mirror 39. 37 It has the following characteristics.

[0151] The second receiving mirror 38 is located at the focal point F of the first receiving mirror 37.37 The second receiving mirror 38 is an example of a folding mirror of the present disclosure.

[0152] The reflected light (reflected pulsed light) reflected by the observation object Ob and returning to the receiving light field of view Sr is reflected by the first receiving mirror 37 so as to be focused toward the focal point F37, and is further reflected by the second receiving mirror 38 and guided to the light receiving element 35. In this way, the observation device 10B separates the transmitter 20 and the receiver 30. Also, the second receiving mirror 38 and the light receiving element 35 are provided outside the opening (opening that takes in the received light) of the main receiving mirror 39 of the receiver 30. This prevents the receiving light field Sr from being blocked in the observation distance region beyond the first position P1.

[0153] 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 aligned. 33 Since the light reflected at the center of the first receiving mirror 37 (the center line of the light receiving element 35) is arranged parallel to the optical axis AX of the second receiving lens 33, the reflected light (light beam) is 33 The second receiving mirror 38 is disposed so as to be tilted by half the angle θm formed by the beam splitter 36 and the beam splitter 37.

[0154] The received light viewing angle θr is 3 mrad or 5 mrad, similar to the first configuration example.

[0155] FIG. 16 is a cross-sectional view of the first receiving mirror 37. As shown in FIG.

[0156] The first receiving mirror 37 includes an off-axis parabolic mirror substrate 37a having an aluminum-coated off-axis parabolic surface as its main surface, an amorphous silicon (α-Si) first anti-reflection film 37c (an example of an anti-reflection member of the present disclosure) that absorbs light in the near-ultraviolet to visible light band and is provided on the aluminum-coated surface of the main surface 37b, and a first dielectric multilayer film 37d that reflects light with a wavelength of 265 nm (22.5° incidence) and is provided on the first anti-reflection film 37c. The first receiving mirror 37 reflects light that is incident parallel to the optical axis of the parabolic mirror of the original shape to a focal point F of the parabolic mirror of the original shape. 37 It is a mirror that reflects and focuses light.

[0157] The various films and arrangement of the first receiving mirror 37 may be the same as those of the second receiving mirror 38, which will be described later.

[0158] An off-axis parabolic mirror is a mirror in which the outer periphery of a parabolic mirror has been hollowed out, and the focal point (the focal point of the mirror in its original shape) is located outside the mirror.

[0159] The first antireflection film 37c is made of amorphous silicon (α-Si), titanium carbon nitride (TiCN), and diamond-like carbon (DLC), and is a layer that absorbs light in the near-ultraviolet to visible light range. In configuration example 2, the first antireflection film 37c has a function of absorbing light in the near-ultraviolet to visible light range that has passed through the first dielectric multilayer film 37d.

[0160] The first dielectric multilayer film 37d is a film made by stacking thin films of silicon oxide (SiO2) and hafnium oxide (HfO2) in multiple layers, and has a high reflectivity (90% or more) for deep ultraviolet light of 265 nm (incident angle 22.5°) and transmits light in the near ultraviolet to visible light range.

[0161] FIG. 17 is a cross-sectional view of the second receiving mirror 38.

[0162] As shown in Figure 17, the second receiving mirror 38 comprises a flat substrate 38a (folding mirror substrate), a second dielectric multilayer film 38c that reflects light with a wavelength of 265 nm (22.5° incidence) on its main surface 38b, and a second antireflection film 38e (an example of an antireflection member of the present disclosure) made of graphite (carbon) that absorbs light in the near-ultraviolet to visible light band on its subsurface 38d (rear surface), and symmetrically reflects light that is incident on the main surface 38b.

[0163] The second antireflection film 38e is made of graphite, carbon, diamond-like carbon, or the like, and absorbs light that has passed through the second dielectric multilayer film 38c. In other words, it absorbs light that becomes noise components other than the light intended for observation (transmitted light).

[0164] The second dielectric multilayer film 38c has the same configuration as the first dielectric multilayer film 37d.

[0165] Next, the reflectance of each receiving mirror will be described.

[0166] FIG. 18 shows the reflection spectrum of the light reflected by each receiving mirror.

[0167] The reflectance of light incident at an angle of 22.5° was measured on the reflecting surfaces of the first receiving mirror 37 (off-axis parabolic mirror) and the second receiving mirror 38 (folding mirror). In Fig. 13, the horizontal axis represents wavelength and the vertical axis represents reflectance (%).

[0168] 18, "OA_Al" represents the reflection spectrum of the first receiving mirror 37, which has a first antireflection coating 37c and a first dielectric multilayer coating 37d provided on the main surface 37b of an off-axis parabolic mirror substrate 37a with an aluminum layer. The configuration of this first receiving mirror 37 is as shown in the following table.

[0169] [Table 5] In FIG. 18, "Φ40_Black" represents the reflection spectrum of the second receiving mirror 38 having a second dielectric multilayer film 38c provided on the main surface 38b of the folding mirror substrate 38a and a second anti-reflection film 38e provided on the secondary surface 38d (rear surface).

[0170] The configuration of the second receiving mirror 38 is as shown in the following table.

[0171] [Table 6] In FIG. 18, "OAxφ40" represents the product of the reflectance of the first receiving mirror 37 and the second receiving mirror 38 (total reflectance spectrum).

[0172] Next, the functions, actions, and effects of the anti-reflection coating will be explained.

[0173] The reflectance in the deep ultraviolet band, especially at the transmitted light wavelength of 265 nm, is high at 90% or more.

[0174] In contrast, the reflectance product of light in the near-ultraviolet band of 300 nm to 400 nm is reduced to 1 / 10 or less, and the reflectance of light in the visible light band of 400 nm to 700 nm is reduced to 1 / 100 or less.

[0175] As described above, by providing an anti-reflection coating layer on the first receiving mirror 37 and the second receiving mirror 38, it is possible to remove noise light before it reaches the light receiving element 35. This makes it possible to reduce the effects of sunlight, particularly during daytime observations. The light receiving element 35 used for photon counting has high reception sensitivity. Therefore, it is designed to be able to remove light other than the target wavelength for detection (265 nm wavelength) before it reaches the light receiving element 35. This makes it possible to reduce noise and enable highly accurate observations.

[0176] <Embodiment 2> First, the problems with the observation device 10 of the first embodiment will be described.

[0177] FIG. 19(a) is a longitudinal cross-sectional view (schematic diagram) of the observation device 10 of the first embodiment.

[0178] In the observation device 10 of the first embodiment, the optical axis AX of the deep ultraviolet LED 21 (light emitting surface) which is a semiconductor light emitting element 21 The optical axis AX of the deep ultraviolet LED 21 (light emitting surface) passes through the center of the light emitting surface and extends in a direction perpendicular to the light emitting surface (see FIG. 10). 21 and a reference axis, here the optical axis AX of the transmitting lens 22 22 (and the optical axis AXs of the transmitter 20) coincide (approximately coincide) (see FIG. 10). Therefore, as shown in FIG. 19(a), the far-side view angle θ of the transmitted light SP and the field of view angle θ near the transmitted light SC is equal to (transmitted light far side view angle θ SP = Viewing angle θ near the transmitted light SC ).

[0179] As described above, the far-side view angle θ SP = Viewing angle θ near the transmitted light SCIn this case, within the range of circumscribed distance r1 (first section A1) where the transmitted light field of view Ss and the received light field of view Sr do not overlap each other, there is almost no reflected light (reflected pulsed light) that is reflected by the observed object Ob and returns to the received light field of view Sr. As a result, the observation device 10 of the first embodiment has a problem in that it cannot observe the observed object Ob that is located at a closer distance.

[0180] Next, as a second embodiment, an observation device 10A employing a configuration example for solving the above problem will be described.

[0181] FIG. 19(b) is a longitudinal cross-sectional view (schematic diagram) of the observation device 10A of the second embodiment.

[0182] In the second embodiment, as shown in FIG. 19(b), the far-side viewing angle θ SP <Viewing angle near the transmitted light θ SC Here, the far-side viewing angle of the transmitted light θ SP is the reference axis (here, the optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22) 22 )) and the far-side field of view boundary line BL SP On the other hand, the viewing angle θ SC is the reference axis (here, the optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22) 22 )) and the field of view boundary line BL near the transmitted light SC The angle between the two.

[0183] Specifically, in the second embodiment, the far-side viewing angle θ of the transmitted light SP <Viewing angle near the transmitted light θ SC In this case, the reference axis, the optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22) is 22 ) on the opposite side of the receiving unit 30 (upper center side in FIG. 19(b)), the deep-ultraviolet LED 21 is disposed at a position offset by an optical axis distance Ad. 21 The optical axis AX of the deep-ultraviolet LED 21 after the eccentricity is offset by the optical axis distance Ad in the direction away from the receiving unit 30 with respect to the reference axis. 21The and reference axes are parallel to each other. Otherwise, the observation device 10A of the second embodiment has the same configuration as the observation device 10 of the first embodiment.

[0184] As shown in FIG. 19(b), the light PL2 emitted from a position Pb that is shifted downward from the center of the deep-ultraviolet LED 21 (light-emitting surface), for example, from the bottom end of the deep-ultraviolet LED 21 (light-emitting surface), is refracted by the transmitting lens 22 and oriented along a reference axis, here, the optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22). 22 ) The light is transmitted upwards at a far-side viewing angle θ SP The same applies to light emitted from other positions of the deep-ultraviolet LED 21 (light-emitting surface) that are shifted downward from the center.

[0185] Similarly, the light PL3 ​​emitted from a position Pc shifted upward relative to the center of the deep-ultraviolet LED 21 (light-emitting surface), for example, the uppermost end of the deep-ultraviolet LED 21 (light-emitting surface) in FIG. 19(b), is refracted by the transmitting lens 22 and directed downward relative to the reference axis, here, the optical axis AXs of the transmitter 20, at a viewing angle θ SC The same applies to light emitted from other positions of the deep-ultraviolet LED 21 (light-emitting surface) that are shifted upward relative to the center.

[0186] In this case, the optical axis AX of the deep ultraviolet LED21 21 Since the optical axis distance Ad is shifted from the reference axis in the direction away from the receiving unit 30, the far-side field of view angle θ of the transmitted light SP <Viewing angle near the transmitted light θ SC This becomes:

[0187] As a result, the transmitted light field Ss passes through the transmitter 20 and is directed obliquely downward and forward with respect to the reference axis at a predetermined angle θ c Inclined centerline AX c is the center and the center line AX c The cone-shaped region has a diameter that increases with increasing distance from the transmitter 20 along the axis.

[0188] For example, if the size of the deep-ultraviolet LED 21 (light-emitting surface) is Ld = 1.04 mm, the transmitting aperture diameter φs = 60 mm, the focal length fs = 52 mm, and the receiving light viewing angle θr = 3 mrad (0.17°) of the receiving unit 30, the condition under which the transmitted light near-side viewing angle θsc is maximized is when the transmitted light far-side viewing angle θsp is the same as the received light viewing angle θr (θsp = θr). In this case, the inter-optical axis distance Ad is 0.364 mm, and the transmitted light near-side viewing angle θsc is 17 mrad (0.974°). Therefore, the possible range of the inter-optical axis distance Ad is 0 < inter-optical axis distance Ad ≦ 0.364 mm.

[0189] <Actions and Effects of Embodiment 2> As described above, in the second embodiment, the deep ultraviolet LED 21 is disposed at a position eccentric to the optical axis distance Ad, so that the optical axis of the transmitted light (the center line AX of the transmitted light field Ss) can be adjusted while maintaining the state in which the transmitted light field Ss includes the received light field Sr beyond P3. c ) and the optical axis of the received light (center line AX of the received light field Sr r ) can be crossed.

[0190] The sum of the transmitted light far-side field of view θsp and the transmitted light near-side field of view θsc of the observation device 10A is greater than the received light total field of view (2 × received light field of view θr) (Condition 1). Also, the transmitted light far-side field of view θsp is equal to or greater than the received light field of view θr (Condition 2). Furthermore, the transmitted light near-side field of view θsc is greater than the transmitted light far-side field of view θsp (Condition 3).

[0191] As a result, compared to embodiment 1, the circumscribed distance r1 at which the transmitted light field Ss circumscribes the received light field Sr, the centerline tangent overlap distance r2 at which the transmitted light field Ss tangents the centerline of the received light field Sr, and the inscribed overlap distance r3 at which the transmitted light field Ss is inscribed and overlapped in the received light field Sr can each be shortened without changing the transmitted light total field of view angle (θsp+θsc). In other words, in embodiment 2, the near measurement distance can be shortened without sacrificing long-distance measurement capability compared to embodiment 1. It is only necessary to satisfy at least condition 2 and condition 3 out of the above conditions 1 to 3.

[0192] Furthermore, according to the second embodiment, the range of the circumscribed distance r1 (first section A1) in which the transmitting light field of view Ss and the receiving light field of view Sr do not overlap each other is shorter than in the first embodiment (see FIGS. 19(a) and 19(b)). As a result, according to the second embodiment, it is possible to observe an observation object Ob that is located at a closer distance than in the first embodiment.

[0193] <Embodiment 3> Next, as a third embodiment, an observation device 10B that employs a configuration example for solving the above problem will be described.

[0194] 20 is a longitudinal sectional view (schematic diagram) of an observation device 10B of the third embodiment. In the third embodiment, as shown in FIG. 20, the far-side view angle θ SP <Viewing angle θ near the transmitted light SC Here, the far-side viewing angle of the transmitted light θ SP is the reference axis, here, the optical axis AXs of the transmitting unit 20 before tilting as shown in FIG. 19(a) (hereinafter referred to as the imaginary center line AX SI (also referred to as "transmitted light") and the far-side field of view boundary line BL SP On the other hand, the viewing angle θ SC is the reference axis (here, the imaginary center line AX SI ) and the near field of view boundary line BL SC The angle between the two.

[0195] Specifically, in the third embodiment, the far-side viewing angle θ of the transmitted light SP <Viewing angle θ near the transmitted light SC The optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22 in the transmitting unit 20) is 22 ) is tilted relative to the optical axis AXr of the receiving unit 30, and the transmitting unit 20 and the receiving unit 30 are fixed to each other with the optical axis AXs of the transmitting unit 20 and the optical axis AXr of the receiving unit 30 intersecting. As a result, the optical axis of the transmitted light (i.e., the center line AXc of the transmitted light field Ss) and the optical axis of the received light (i.e., the center line AXr of the received light field Sr) intersect.

[0196] As a result, the transmitted light field Ss passes through the transmitter 20 and is aligned with the reference axis (here, the imaginary center line AXSI ) at a predetermined angle θ c Inclined centerline AX c is the center and the center line AX c The region has a cone shape whose diameter increases along the axis as it moves away from the transmitter 20. Other than that, the observation device 10B of the third embodiment has the same configuration as the observation device 10 of the first embodiment.

[0197] As shown in FIG. 21, in the third embodiment, the far-side viewing angle θ SP <Viewing angle near the transmitted light θ SC The optical axis AXs of the transmitter 20 (the optical axis AX of the deep ultraviolet LED 21) 21 , the optical axis AX of the transmitting lens 22 22 ) along the virtual center line AX si A predetermined angle θ cc tilted it.

[0198] For example, if the transmitting unit 20 has a transmitted light field of view θs=10 mrad and the receiving unit 30 has a received light field of view θr=3 mrad, the maximum tilt angle θcc of the transmitting unit 20 is 7 mrad, which is obtained by subtracting the transmitted light far-side field of view θsp (=θr)=3 mrad from the transmitted light field of view θs=10 mrad. The range of the tilt angle θcc of the transmitting unit 20 is 0 mrad<θcc≦7 mrad. <Actions and Effects of Embodiment 3> As described above, by tilting the optical axis AXs of the transmitting unit 20 with respect to the optical axis AXr of the receiving unit 30, in the third embodiment, as in the second embodiment, the optical axis of the transmitted light (the center line AX of the transmitted light field Ss) can be adjusted while maintaining the state in which the transmitted light field Ss includes the received light field Sr beyond P3. c ) and the optical axis of the received light (center line AX of the received light field Sr r ) can be crossed.

[0199] Therefore, similarly to the second embodiment, conditions 1 to 3 are met.

[0200] As a result, compared to embodiment 1, the circumscribed distance r1 at which the transmitted light field Ss circumscribes the received light field Sr, the centerline tangent overlap distance r2 at which the transmitted light field Ss tangents the centerline of the received light field Sr, and the inscribed overlap distance r3 at which the transmitted light field Ss is inscribed and overlapped in the received light field Sr can each be shortened without changing the transmitted light total field angle (θsp+θsc). In other words, in embodiment 3, the near measurement distance can also be shortened compared to embodiment 1 without sacrificing long-distance measurement capability. Note that it is sufficient to satisfy at least condition 2 and condition 3 of the above conditions 1 to 3.

[0201] Furthermore, according to the third embodiment, the range of the circumscribed distance r1 (first section A1) in which the transmitting light field of view Ss and the receiving light field of view Sr do not overlap each other is shorter than in the first embodiment (see FIG. 20). As a result, according to the third embodiment, it is possible to observe an observation object Ob that exists at a closer distance than in the first embodiment.

[0202] Next, the effects of the second and third embodiments will be described in comparison with the comparative example.

[0203] The comparative example is the observation device 10 of the first embodiment.

[0204] The specifications of the light emitting element used in the comparative example, such as size, are as shown in the following table.

[0205] [Table 7] The specifications of the light emitting element used in the second embodiment, such as size, are as shown in the following table.

[0206] [Table 8] The specifications of the light emitting element used in the third embodiment, such as size, are as shown in the following table.

[0207] [Table 9] When the specifications shown in Tables 7 to 9 above are used, the axis distances and the like of the comparative example and embodiments 2 and 3 are as shown in the following table.

[0208] [Table 10] Referring to Table 10, it can be seen that in embodiments 2 and 3, the circumscribed distance r1 (first section A1) at which the transmitted light field of view Ss and the received light field of view Sr do not overlap each other is shorter than in the comparative example, and that by adopting embodiments 2 and 3, it is possible to observe the object of observation Ob that is located at a closer distance than in comparative example 1.

[0209] As described above, according to the second and third embodiments, the far-side viewing angle θ of the transmitted light SP <Viewing angle θ near the transmitted light SC By setting the angle of view θ SP = Viewing angle θ near the transmitted light SC As compared with the first embodiment, the circumscribed distance r1 (first section A1) at which the transmitting light field of view Ss and the receiving light field of view Sr do not overlap each other can be shortened (see FIGS. 19(a), 19(b), etc.). As a result, according to the second and third embodiments, it is possible to observe an observation object Ob that is located at a closer distance than in the first embodiment.

[0210] Furthermore, according to embodiments 2 and 3, the overlapping range of the transmitting light field Ss and the receiving light field Sr is wider than in embodiment 1 (see the hatched area HT in Figures 19(a), 19(b) and 20), which has the advantage of increasing the measurement accuracy when measuring the same distance.

[0211] In addition, the far-side viewing angle of the transmitted light θ SP <Viewing angle θ near the transmitted light SC By using the second embodiment as the configuration for achieving this, the observation device 10A can be made smaller than when the third embodiment is used.

[0212] In addition, the far-side viewing angle of the transmitted light θ SP <Viewing angle θ near the transmitted light SCBy using the third embodiment as the configuration for achieving this, the cost of the observation device 10A can be reduced compared to when the second embodiment is used.

[0213] Next, as a modified example, an observation device 10C that employs a configuration example for solving the above problem will be described.

[0214] FIG. 21 is a longitudinal cross-sectional view (schematic diagram) of an observation device 10C of a modified example.

[0215] In the modified example, as shown in FIG. 21, the far-side viewing angle θ SP <Viewing angle near the transmitted light θ SC Here, the far-side viewing angle of the transmitted light θ SP is the reference axis (here, the optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22) 22 )) and the far-side field of view boundary line BL SP On the other hand, the viewing angle θ SC is the reference axis (here, the optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22) 22 )) and the field of view boundary line BL near the transmitted light SC The angle between the two.

[0216] Specifically, in the modified example, an optical element 50 is provided that controls the pulsed light emitted by the transmitter 20 so that the transmitted light far-side viewing angle is smaller than the transmitted light near-side viewing angle.

[0217] The optical element 50 is, for example, a prism. The prism is disposed in front of the transmitting unit 20 with its apex positioned on the side opposite the receiving unit 30. There may be one or more prisms. This causes the optical axis of the transmitted light (i.e., the center line AXc of the transmitted light field Ss) and the optical axis of the received light (i.e., the center line AXr of the received light field Sr) to intersect.

[0218] As a result, the transmitted light field Ss passes through the transmitting unit 20 and coincides with the optical axis AXs of the transmitting unit 20 (the optical axis AX of the transmitting lens 22). 22 ) at a predetermined angle θ cInclined centerline AX c is the center and the center line AX c The region has a cone shape whose diameter increases along the axis as it moves away from the transmitter 20. Other than that, the observation device 10C of the modified example has the same configuration as the observation device 10 of the first embodiment. <Actions and effects of modified versions> As described above, by adding the optical element 50 that controls the pulsed light emitted by the transmitter 20, in the modified example, as in the second and third embodiments, the optical axis of the transmitted light (the center line AX of the transmitted light field Ss) can be adjusted while maintaining the state in which the transmitted light field Ss includes the received light field Sr beyond P3. c ) and the optical axis of the received light (center line AX of the received light field Sr r ) can be crossed.

[0219] Therefore, similarly to the second embodiment, conditions 1 to 3 are met.

[0220] As a result, compared to embodiment 1, the circumscribed distance r1 at which the transmitted light field Ss circumscribes the received light field Sr, the centerline tangent overlap distance r2 at which the transmitted light field Ss tangents the centerline of the received light field Sr, and the inscribed overlap distance r3 at which the transmitted light field Ss is inscribed and overlapped in the received light field Sr can each be shortened without changing the transmitted light total field angle (θsp+θsc). In other words, compared to embodiment 1, even in this modified example, the near measurement distance can be shortened without sacrificing long-distance measurement capability. Note that it is sufficient to satisfy at least condition 2 and condition 3 of the above conditions 1 to 3.

[0221] Furthermore, according to the modified example, the range of circumscribed distance r1 (first section A1) in which the transmitting light field of view Ss and the receiving light field of view Sr do not overlap each other is shorter than in embodiment 1 (see FIG. 21). As a result, according to the modified example, it is possible to observe an observation object Ob that exists at a closer distance than in embodiment 1.

[0222] The numerical values ​​shown in the above embodiments are all examples, and it goes without saying that other appropriate numerical values ​​can be used.

[0223] The above-described embodiments are merely illustrative in all respects. For example, the transmitter 20 may be a reflective optical system. The transmitter 20 and / or the receiver 30 may each be a mixed optical system of a tropic and reflective system. While the observation target in the above-described embodiments is the air containing particulate matter, the present disclosure makes it possible to observe the distance to obstacles (trees, buildings, etc.) simultaneously with the air containing particulate matter. In other words, the present disclosure should not be construed as being limited by the description of the above-described embodiments. The present disclosure may be embodied in various other forms without departing from its spirit or essential features. [Explanation of symbols]

[0224] 10, 10A, 10B, 10C...observation equipment 20...Transmitter 21...Deep ultraviolet LED (semiconductor light emitting element) 22...Transmitting lens 23...Transmitting telescope 24...Drive circuit 30...Receiver 31... Receiving lens (first receiving lens) 32...Field stop 33...Second receiving lens 34...Receive filter 35...Photodetector 36...Receiving telescope 37…First receiving mirror 37a...Off-axis parabolic mirror substrate with aluminum layer 37b…main surface 37c...First anti-reflection film 37d...First dielectric multilayer film 38...Second receiving mirror 38a...Folding mirror substrate 38b…main surface 38c...Second dielectric multilayer film 38d...secondary side 38e…Second anti-reflection film 39... Main receiving telescope 40...Control and Analysis Department 41...Observation data generation unit 42...Coefficient analysis processing unit 43...Characteristics evaluation processing section 44...Observation data storage unit AX 33 , AXr, AXs…optical axis C1, C1a...Capacitors Crs…Visual field combination rate F 37 …focus Ob…observed object P: Received light intensity P0: Telescope tube tip position P1…1st position P2…Second position P3…3rd position P4…4th position R1, R1a...Resistors Sc...Superimposed light field Sr...receiving light field of view Ss: Transmitted light field of view r1...first distance r2…Second distance r3...Third distance θs: Transmitted light viewing angle θr: Received light viewing angle

Claims

1. a transmitter having a transmission light field of view and transmitting pulsed light having a wavelength belonging to the ultraviolet region of the solar blind band within the transmission light field of view; a receiving unit having a receiving light field of view, which receives reflected light within the receiving light field of view of the pulsed light reflected by an object to be observed; an observation data generating unit; The transmission unit a semiconductor light emitting element that emits the pulsed light; a transmission optical system that controls the pulsed light emitted by the semiconductor light emitting element so that the pulsed light emitted by the semiconductor light emitting element is transmitted within the transmission light field, The receiving unit a receiving optical system that collects reflected light within the receiving light field; a light-receiving element that receives the collected reflected light and outputs a signal corresponding to the received reflected light, an optical axis of the transmitted light constituting the transmitted light field and an optical axis of the received light constituting the received light field intersect with each other; the transmit light field and the receive light field at least partially overlap one another; the observation data generation unit generates LIDAR data, which is observation data, based on the signal output by the light receiving element; where an angle corresponding to the transmitted light field of view on the side opposite to the receiving unit with respect to a reference axis that passes through the transmitting unit and is parallel to the optical axis of the receiving unit is defined as a transmitted light far-side field of view angle, and an angle corresponding to the transmitted light field of view on the receiving unit side with respect to the reference axis is defined as a transmitted light near-side field of view angle, the transmitted light far-side field of view angle is smaller than the transmitted light near-side field of view angle, An observation device in which the far-side field of view angle of the transmitted light is equal to or greater than the field of view angle of the received light.

2. 2. The observation device according to claim 1, wherein the semiconductor light-emitting element is positioned at an eccentric position away from the reference axis toward the opposite side of the receiver so that the far-side field of view of the transmitted light is less than the near-side field of view of the transmitted light.

3. ） 2. The observation device according to claim 1, wherein the optical axis of the transmitter and the optical axis of the receiver intersect so that the far-side field of view angle of the transmitted light is smaller than the near-side field of view angle of the transmitted light.

4. 2. The observation device according to claim 1, further comprising an optical element that controls the pulsed light emitted by the transmitter so that the far-side field of view of the transmitted light is smaller than the near-side field of view of the transmitted light.

5. 5. The observation device according to claim 2, wherein the optical axis of the transmitting unit and the optical axis of the receiving unit are parallel to each other.

6. the transmission light field of view is a cone-shaped region whose center is a center line that passes through the transmitter and is inclined obliquely downward and forward at a predetermined angle with respect to the reference axis, and whose diameter increases as the distance from the transmitter along the center line increases, 2. The observation device according to claim 1, wherein the field of view of the received light is a cone-shaped area having a center on the optical axis of the receiving unit and a diameter that increases with increasing distance from the receiving unit along the optical axis of the receiving unit.

7. 2. The observation device according to claim 1, wherein the wavelength in the ultraviolet region is selected from a wavelength range of 240 nm to 300 nm.

8. 8. The observation device according to claim 7, wherein the pulsed light is spontaneously emitted light (incoherent light).

9. 9. The observation device according to claim 8, wherein the frequency of the pulsed light is 1 to 10 MHz.

10. 10. The observation device according to claim 9, wherein the pulse width of the pulsed light is 1 to 10 ns.

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

12. 2. The observation device according to claim 1, wherein the receiving optical system comprises an off-axis parabolic mirror and a folding mirror.

13. 13. The observation device according to claim 12, wherein the off-axis parabolic mirror and the folding mirror each have a dielectric multilayer film on a mirror surface that reflects the reflected light.

14. 14. The observation device according to claim 13, wherein the off-axis parabolic mirror and the folding mirror have an anti-reflection member that absorbs light other than the reflected light, either on the lower layer of the dielectric multilayer film or on the back surface of the mirror.

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