JP2018040748A - Laser range measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the efficiency of light concentration at short distances.SOLUTION: A laser range measuring device is equipped with a first light concentrating unit, a second light concentrating unit, and a measuring unit. The first light concentrating unit concentrates the first reflected light of output light emitted from a light source into a prescribed light concentrating area in a detector. The second light concentrating unit deflects the second reflected light of the output light in the direction of the detector and concentrates it into the prescribed light concentrating area. The measuring unit measures the distance to an object having reflected the output light on the basis of at least one of the first reflected light and the second reflected light detected by the detector.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser distance measuring device.

  2. Description of the Related Art Conventionally, a technique for emitting a laser beam to an object and measuring a distance to the object based on reflected light reflected by the object is known. Such a technique is also called LiDAR (Light Detection and Ranging), and a laser distance measuring device to which this technique is applied is applied to various fields.

JP-A-5-346535

  In the laser distance measuring device described above, for example, a collimating lens and a condensing lens are arranged side by side with different central axes, and laser light emitted from a light source is converted into parallel light by a collimating lens and irradiated onto an object. Here, the object is a measurement object existing around the laser distance measuring device, and includes all objects that are irradiated with the laser light emitted from the light source and reflect the laser light to the laser distance measuring device. . The laser distance measuring device detects the reflected light by condensing the reflected light reflected by the object on a photodetector with a condenser lens. Here, in the laser distance measuring device in which the collimating lens and the condensing lens are not coaxial (the collimating lens and the condensing lens are arranged side by side with different central axes), they are incident on the condensing lens. The incident angle of the reflected light changes according to the distance to the object. That is, in a laser distance measuring device in which the collimator lens and the condenser lens are not coaxial, the incident angle of the reflected light to the condenser lens decreases as the distance to the object increases, and the reflected light decreases as the distance to the object decreases. The incident angle to the condenser lens increases.

  For example, when the distance to the object is long and the incident angle of the reflected light is small, the reflected light collected by the condenser lens is favorably collected at the light collection point of the photodetector. However, if the distance to the object is close and the incident angle of the reflected light is large, the reflected light collected by the condenser lens may be off the light collecting point of the photodetector, making it difficult to detect the reflected light. It was.

  The present invention has been made in view of the above, and an object of the present invention is to provide a laser distance measuring device capable of improving the light collection efficiency at a short distance.

  In order to solve the above-described problems and achieve the object, a laser distance measuring device according to an aspect of the present invention uses a first reflected light of output light emitted from a light source to a predetermined light collection region in a detector. A first condensing part for condensing the light, a second condensing part for deflecting the second reflected light of the output light in the direction of the detector, and condensing the predetermined condensing area, A measurement unit that measures a distance to an object that reflects the output light based on at least one of the first reflected light and the second reflected light detected by a detector.

  According to one embodiment of the present invention, light collection efficiency at a short distance can be improved.

FIG. 1 is a top view and a front view showing the configuration of the laser distance measuring apparatus according to the first embodiment. FIG. 2 is a diagram illustrating a path of the second reflected light through the small-diameter condensing lens according to the first embodiment. FIG. 3A is a diagram for explaining a method for forming a small-diameter condensing lens according to the first embodiment. FIG. 3B is a diagram illustrating an example of an optical system including the small-diameter condensing lens according to the first embodiment. FIG. 3C is a diagram showing a beam profile of the small-diameter condensing lens according to the first embodiment. FIG. 4 is a block diagram illustrating an example of the configuration of the laser distance measuring apparatus according to the first embodiment. FIG. 5A is a top view showing a configuration of a general laser distance measuring device. FIG. 5B is a front view showing a configuration of a general laser distance measuring device. FIG. 5C is a diagram illustrating a result of the tracking simulation of the light beam collected from the condenser lens. FIG. 6A is a diagram illustrating an example of a measurement result obtained by a general laser distance measuring device. FIG. 6B is a diagram illustrating an example of a measurement result obtained by the laser distance measuring device according to the first embodiment. FIG. 7 is a diagram illustrating a modified example of the second light collecting unit according to the first embodiment. FIG. 8 is a diagram illustrating a modification of the second light collecting unit according to the first embodiment. FIG. 9 is a front view showing the configuration of the laser distance measuring apparatus according to the second embodiment. FIG. 10 is a block diagram illustrating an example of the configuration of the laser distance measuring apparatus according to the second embodiment.

  Hereinafter, a laser distance measuring device according to an embodiment will be described with reference to the drawings. In addition, the relationship of the dimension of each element in a drawing, the ratio of each element, etc. may differ from reality. Even between the drawings, there are cases in which portions having different dimensional relationships and ratios are included.

(First embodiment)
FIG. 1 is a top view and a front view showing the configuration of the laser distance measuring apparatus 100 according to the first embodiment. Here, in FIG. 1, a top view of the laser distance measuring device 100 is shown in the upper diagram, and a front view is shown in the lower diagram. As shown in FIG. 1, the laser distance measuring device 100 includes a light source 110a, a light emitting circuit board 110b, a collimator lens 120, a small-diameter condenser lens 130, a large-diameter condenser lens 140, a photodetector 150a, A light receiving circuit board 150b and a control circuit board 160 are provided, and each component is housed in a housing. Here, the housing that houses each component has a window that transmits light to the collimating lens 120, the small-diameter condenser lens 130, and the large-diameter condenser lens 140, and the collimator lens 120, the small-diameter condenser lens 130, and the like. The large-diameter condenser lens 140 is disposed at the position of the window.

  The laser distance measuring device 100 emits output light (for example, laser light) emitted from the light source 110a to the target space as parallel light by the collimator lens 120, and is reflected by an object (measurement target) in the target space. Is condensed on the photodetector 150a by the large-diameter condenser lens 140, thereby detecting the reflected light reflected by the object. Then, the laser distance measuring apparatus 100 measures the distance to the object based on the detected reflected light. Note that the return light from an object at a long distance is in a greatly diffused state compared to the return light from an object at a short distance, and has a Gaussian distribution with a large dispersion around the collimating lens 120. . Here, the laser distance measuring device 100 can improve the light collection efficiency at a short distance by including the small-diameter condenser lens 130 as a condenser part different from the large-diameter condenser lens 140. That is, the laser distance measuring device 100 includes a first light collecting unit (large diameter condensing lens 140) and a second light condensing unit (small diameter condensing lens 130). Is condensed on the photodetector 150a, and the second reflected light is condensed on the photodetector 150a by the small-diameter condenser lens 130. Here, the first reflected light collected by the large-diameter condenser lens 140 is reflected light by an object at a long distance, and the second reflected light condensed by the small-diameter condenser lens 130 is This is reflected light reflected by an object at a short distance. In addition, the small-diameter condensing lens 130 can collect return light from an object at a long distance. That is, the second light collecting unit can collect not only return light (second reflected light) from an object at a short distance but also return light (first reflected light) from an object at a long distance. . Details of the laser distance measuring apparatus 100 will be described below. Hereinafter, the reflected light reflected by the object and returned to the laser distance measuring apparatus 100 is also referred to as return light.

  The light source 110a is a light emitting element such as a laser diode (LD), and outputs light (laser light) to the collimator lens 120 in accordance with a drive signal from a drive circuit disposed on the light emitting circuit board 110b. Is emitted. Here, the light source 110 a is disposed on the light emitting circuit board 110 b so that the optical axis of the laser light is emitted in the horizontal direction and the optical axis is aligned with the optical axis of the parallel light emitted from the collimator lens 120. Has been.

  The light emitting circuit board 110b is provided with a driving circuit for emitting laser light from the light source 110a, and outputs a driving signal to the light source 110a in accordance with a control signal from the control circuit board 160. Here, the light emitting circuit board 110b is disposed on a base (not shown) so that the longitudinal direction is parallel to the vertical direction, and the optical axis of the laser light emitted from the light source 110a is collimated above the longitudinal direction. A light source 110a is disposed at a position aligned with the optical axis of the parallel light emitted from the lens 120.

  The collimator lens 120 is disposed in front of the laser light emission surface of the light source 110a at a position where the optical axis is aligned with the optical axis of the laser light emitted from the light source 110a, and above the small-diameter condenser lens 130 in the vertical direction. Has been placed. Here, as shown in FIG. 1, the collimating lens 120 is arranged so that the center in the horizontal direction coincides with the center of the small-diameter condenser lens 130. Further, the collimating lens 120 is disposed beside the large-diameter condenser lens 140 in the horizontal direction. The collimating lens 120 converts the laser light emitted from the light source 110a into parallel light and emits it into the target space.

  The small-diameter condenser lens 130 is disposed in front of the laser light emission surface of the light source 110a, and is disposed below the collimating lens 120 in the vertical direction. Here, as shown in FIG. 1, the small-diameter condensing lens 130 is arranged so that the center in the horizontal direction coincides with the center of the collimating lens 120. The small-diameter condenser lens 130 is disposed beside the large-diameter condenser lens 140 in the horizontal direction. Here, as shown in FIG. 1, the small-diameter condenser lens 130 is arranged such that the center in the vertical direction coincides with the center of the large-diameter condenser lens 140. The small-diameter condensing lens 130 condenses the reflected light (second reflected light) reflected by the object at a short distance out of the return light of the parallel light emitted from the collimating lens 120 on the photodetector 150a. . Here, the return light from the object at a long distance is in a greatly diffused state compared to the return light from the object at a short distance, and a Gaussian distribution having a large dispersion around the collimating lens 120 and Become. Therefore, the small-diameter condensing lens 130 can also collect the return light from an object at a long distance. That is, the second light collecting unit can collect not only return light (second reflected light) from an object at a short distance but also return light (first reflected light) from an object at a long distance. That is, the small-diameter condensing lens 130 can condense the reflected light from the object at a long distance and the reflected light from the object at a short distance on the photodetector 150a regardless of the reflected light. . Note that details of light collection on the photodetector 150a by the small-diameter condenser lens 130 will be described later.

  The large-diameter condenser lens 140 is disposed in front of the detection surface of the photodetector 150a, and is disposed beside the collimating lens 120 and the small-diameter condenser lens 130 in the horizontal direction. Here, as shown in FIG. 1, the large-diameter condenser lens 140 is arranged so that the center in the vertical direction coincides with the center of the small-diameter condenser lens 130. The large-diameter condensing lens 140 detects the reflected light (first reflected light) reflected by the object at a long distance from the return light in which the parallel light emitted by the collimating lens 120 is reflected by the object. The light is condensed with respect to the container 150a. For example, the large-diameter condenser lens 140 is a Fresnel lens, a convex lens, or the like. Here, when a Fresnel lens is used as the large-diameter condenser lens 140, the area can be increased while keeping the thickness of the large-diameter condenser lens 140 constant.

  The photodetector 150 a is arranged at a position where the center of the detection surface coincides with the optical axis of the return light from the large-diameter condenser lens 140, and the return light condensed by the small-diameter condenser lens 130 and the large-diameter condenser lens 140. Is detected. For example, the photo detector 150a is a photomultiplier tube (PMT), a photoconductive element such as CdS or PbS that utilizes a change in electrical resistance due to light irradiation, or a photovoltaic photon that utilizes a pn junction of a semiconductor. It is a diode (Photo Diode: PD). Examples of the photodiode include a PN photodiode, a PIN photodiode, and an avalanche photodiode.

  The light receiving circuit board 150b is provided with an amplifier circuit and the like, amplifies the return light detected by the photodetector 150a, and outputs the amplified light to the control circuit board 160. Here, the light receiving circuit board 150b is disposed on a base (not shown) so that the longitudinal direction thereof is parallel to the vertical direction, and the photodetector 150a is disposed at the upper end.

  The control circuit board 160 is provided with a circuit that performs overall control of the laser distance measuring apparatus 100. For example, the control circuit board 160 controls the light emitting circuit board 110b to control the emission of laser light from the light source 110a. Further, the control circuit board 160 is provided with various circuits for measuring the distance to the object reflecting the laser beam based on the return light detected by the photodetector 150a.

  For example, the control circuit board 160 is provided with a circuit for performing a distance measurement of a TOF (Time of Flight) method, a circuit for performing a distance measurement of a phase difference method, or the like. When performing the distance measurement of the TOF method, the control circuit board 160 is provided with a circuit for calculating the distance from the delay time between the signal based on the laser light and the signal based on the return light. On the other hand, when performing phase difference distance measurement, the control circuit board 160 calculates the phase difference between the signal based on the laser light and the signal based on the return light, and calculates the distance from the calculated phase difference. Is disposed.

  The configuration of the laser distance measuring device 100 has been described above. Next, details of the small-diameter condensing lens 130 will be described. As described above, the laser distance measuring apparatus 100 includes the small-diameter condenser lens 130 in addition to the large-diameter condenser lens 140 as a condenser lens that condenses the reflected light. The large-diameter condensing lens 140 condenses the first reflected light of the laser light emitted from the light source 110a on a predetermined condensing area (for example, an area including the center of the detection surface) in the photodetector 150a. . On the other hand, the small-diameter condensing lens 130 deflects the light flux in the second reflected light of the laser light emitted from the light source 110a in the direction of the photodetector 150a, and in a predetermined condensing region in the photodetector 150a. Concentrate the light.

  As described above, in a general laser distance measuring apparatus, the incident angle of the reflected light incident on the condenser lens changes according to the distance to the object that reflects the laser light, and the distance to the object is short. In some cases, it may be difficult to detect the reflected light. The same applies to the large-diameter condenser lens 140 in the laser distance measuring device 100, and the incident angle of the return light, which is the parallel light emitted from the collimator lens 120 reflected by the object, on the large-diameter condenser lens 140 is , Depending on the distance to the object. For example, when the distance to the object is far and the incident angle of the return light to the large-diameter condensing lens 140 is small, the return light collected by the large-diameter condensing lens 140 enters the condensing region of the photodetector 150a. Condenses well. On the other hand, when the distance to the object is close and the incident angle of the return light to the large-diameter condenser lens 140 is large, the return light collected by the large-diameter condenser lens 140 is from the condensing region of the photodetector 150a. The light is collected at a position that is off, making it difficult to detect return light.

  Therefore, in the laser distance measuring device 100, the small-diameter condensing lens 130 deflects the second reflected light reflected by the object from the collimating lens 120 in the direction of the light detector 150a and detects the light. Condensing efficiency at a short distance is improved by condensing the second reflected light in the condensing region of the container 150a. FIG. 2 is a diagram illustrating a path of the second reflected light through the small-diameter condenser lens 130 according to the first embodiment. Here, in FIG. 2, the top view of the laser distance measuring device 100 is shown. For example, in the laser distance measuring apparatus 100, the collimating lens 120 emits laser light emitted from the light source 110a into parallel light as parallel light. As shown in FIG. 2, the small-diameter condensing lens 130 deflects the second reflected light, which is reflected from the measurement object, in the direction of the photodetector 150a, and at the same time collects a predetermined condensing light in the photodetector 150a. Focus on the area. Here, the small-diameter condensing lens 130 condenses the second reflected light in a condensing region substantially the same as the condensing region of the first reflected light by the large-diameter condensing lens 140 in the photodetector 150a.

  For example, as shown in FIG. 2, the diameter of the large-diameter condenser lens 140 is “20 mm”, the lateral width of the small-diameter condenser lens 130 is “5 mm”, and the center of the large-diameter condenser lens 140 and the small-diameter condenser lens 130 are arranged. Each component is arranged so that the distance from the center of the lens is “14 mm” and the distance between the photodetector 150 a and the large-diameter condenser lens 140 is “30 mm”. In this case, assuming that the second reflected light to the small-diameter condenser lens 130 is parallel light, the small-diameter condenser lens 130 converts the second reflected light to “θ = 65 ° (= atan30 / 14)” at the point A. The principal ray of the second reflected light can be incident on the center of the photodetector 150a. In order to realize this refraction, the small-diameter condensing lens 130 is formed by the following method, for example.

  FIG. 3A is a diagram for explaining a method of forming the small-diameter condenser lens 130 according to the first embodiment. For example, the small-diameter condenser lens 130 is formed using a plano-convex lens as shown in FIG. 3A. For example, in the XYZ coordinate system as shown in FIG. 3A, when a plano-convex lens is arranged so that the angle formed between the second reflected light from the measurement object and the Z axis is “25 °”, The cosine in the Y direction is “0”. Further, based on the distance from the plano-convex lens to the photodetector 150a, the curvature of the plano-convex lens is optimized so that the spot size is minimized on the light receiving surface of the photodetector 150a. By using a small-diameter condensing lens designed under such conditions, the above-described refraction can be realized.

  FIG. 3B is a diagram illustrating an example of an optical system including the small-diameter condenser lens 130 according to the first embodiment. Here, FIG. 3B shows an optical system including a small-diameter condensing lens 130 designed under the above-described conditions. For example, as shown in FIG. 3B, the small-diameter condensing lens 130 is formed by cutting out a part of a plano-convex lens having a curvature radius of approximately “40 mm”. That is, a plano-convex lens having a radius of curvature of approximately “40 mm” is disposed so that the angle formed by the second reflected light from the measurement object and the Z axis is “25 °”, and the second reflected light is incident thereon. A small-diameter condenser lens 130 is obtained by cutting out only the lens. In FIG. 3B, the entire plano-convex lens is shown, but this is shown for convenience of explanation, and only the small-diameter condensing lens 130 shown in a triangular shape is actually arranged. Further, the curvature of the small-diameter condensing lens 130 is designed according to the glass material used as the material and the wavelength of the laser light to be condensed. Further, the small-diameter condensing lens 130 is cut out in a square shape in the front view of FIG. 1, but the embodiment is not limited to this, and can be cut out in an arbitrary shape.

  FIG. 3C is a diagram showing a beam profile of the small-diameter condenser lens 130 according to the first embodiment. Here, FIG. 3C shows a beam profile of the second reflected light collected by the small-diameter condenser lens 130 in the optical system shown in FIG. 3B. As shown in FIG. 3C, the beam profile of the second reflected light collected by the small-diameter condenser lens 130 has an elliptical shape and the maximum width is “400 μm or less”. That is, the second reflected light condensed on the photodetector 150a by the small-diameter condenser lens 130 is stored in “400 μm or less”. Accordingly, in the laser distance measuring device 100, the photodetector 150a having a diameter of the light receiving surface of “0.5 mm” can be employed.

  As described above, the laser distance measuring device 100 includes the small-diameter condenser lens 130 and the large-diameter condenser lens 140 for condensing the reflected light, and reflects the reflected light of the parallel light emitted from the collimator lens 120. The light is condensed on the photodetector 150 a by the small-diameter condenser lens 130 and the large-diameter condenser lens 140. Here, for example, when the parallel light emitted from the collimator lens 120 is reflected by the first object located near the laser distance measuring device 100, the second reflected light is detected by the small-diameter condenser lens 130 as a photodetector. The light is focused on 150a and the distance to the first object can be measured. On the other hand, even when the collimated light emitted from the collimating lens 120 is reflected by the second object located far from the laser distance measuring device 100, the large-diameter condenser lens 140 is first with respect to the photodetector 150a. The reflected light can be sufficiently collected, and the distance to the second object can be measured.

  In addition, the parallel light emitted from the collimator lens 120 is reflected by objects with different distances, the large-diameter condenser lens 140 collects the first reflected light, and the small-diameter condenser lens 130 collects the second reflected light. When the light detector 150a detects two reflected lights, the circuit in the control circuit board 160 measures the distance to each object based on the respective return lights.

  Next, a distance measurement process performed by the laser distance measuring apparatus 100 will be described with reference to FIG. FIG. 4 is a block diagram illustrating an example of the configuration of the laser distance measuring apparatus 100 according to the first embodiment. In FIG. 4, a case where distance measurement by the TOF method is performed will be described as an example. As shown in FIG. 4, the control circuit board 160 of the laser distance measuring apparatus 100 includes a TDC (Time to Digital Converter) circuit 161, a signal processing circuit 162, and a control circuit 163. The signal processing circuit 162 is also described as a measurement unit.

  The control circuit 163 drives the drive circuit 111b disposed on the light emitting circuit board 110b to emit laser light from the light source 110a. For example, the control circuit 163 outputs a pulse signal having an arbitrary period to the drive circuit 111b. The drive circuit 111b drives the light source 110a by generating a drive signal in synchronization with the pulse signal and outputting it to the light source 110a. The light source 110a is driven by the drive signal input from the drive circuit 111b and emits laser light in pulses. Here, the pulse signal output by the control circuit 163 is output to the TDC circuit 161 as a reference clock.

  The amplifier circuit 151b amplifies the electrical signal of the return light detected by the photodetector 150a to a level at which signal analysis is possible and outputs the amplified signal to the TDC circuit 161. The TDC circuit 161 outputs a digital signal indicating a time difference between the pulse signal input from the control circuit 163 and the electric signal input from the amplifier circuit 151 b to the signal processing circuit 162. The signal processing circuit 162 calculates the distance to the object from the time corresponding to the digital signal input from the TDC circuit 161 and the speed of light. Here, the signal processing circuit 162 can also correct the distance to the object based on the electrical signal of the return light. The return light reflected by the object and returning to the laser distance measuring apparatus 100 has a light amount that decreases according to the distance to the object, and such a decrease in the light amount may cause an error in the detection result. Therefore, the signal processing circuit 162 can also perform correction according to the amount of light based on the electrical signal of the return light.

  As described above, according to the first embodiment, the return light from an object at a short distance can be accurately collected by the small-diameter condensing lens 130, and the collection when the distance to the object is a short distance is possible. Light efficiency can be improved.

  FIG. 5A is a top view showing a configuration of a general laser distance measuring apparatus 200. FIG. 5B is a front view showing a configuration of a general laser distance measuring apparatus 200. For example, as shown in FIG. 5A, a general laser distance measuring apparatus 200 includes a light source 210a, a collimator lens 220, a condenser lens 240, and a photodetector 250a. Here, in the laser distance measuring apparatus 200, as shown in FIG. 5A, the collimating lens 220 emits the laser light emitted from the light source 210a to the target space as parallel light. In the laser distance measuring apparatus 200, the collimating lens 220 and the condenser lens 240 are arranged in parallel. Although not shown, the laser distance measuring device 200 includes a light emitting circuit board, a light receiving circuit board, and a control circuit board.

  Here, for example, when the collimating lens 220 and the condensing lens 240 are arranged in the same size as the laser distance measuring device 100 according to the first embodiment, the laser distance measuring device 200 can detect the object from a near object. It becomes difficult to detect the return light. That is, as shown in FIG. 5B, the diameter of the condenser lens 240 is “20 mm”, the diameter of the collimator lens 220 is “5 mm”, and the distance between the center of the condenser lens 240 and the center of the collimator lens 220 is “14 mm”. Each component is arranged so that When the distance from the collimating lens 220 to the object is “500 mm”, the angle formed by the optical axis of the laser beam and the optical axis of the return light from the object at a short distance is “θ = 1.6 ° (= atan14 / 500) ".

  FIG. 5C is a diagram illustrating a result of the tracking simulation of the light beam collected from the condenser lens 240. Here, in FIG. 5C, a solid line 11 represents a simulation in the case where the return light is incident perpendicularly to the condensing surface of the condensing lens 240 (incident angle θ = 0 °). In FIG. 5C, a broken line 12 represents a simulation when the return light is incident on the condensing surface of the condensing lens 240 at “incident angle θ = 1.6 °”. The simulation condition is that the condensing lens 240 is a plano-convex lens having a diameter of “20 mm”, the radius of curvature of the lens is “19.62 mm”, the lens material is “N-SF11”, the entrance pupil diameter is “15 mm”, and the laser wavelength is “905 mm”.

  As a result of the above-described simulation, as shown in FIG. 5C, the return light incident at “incident angle θ = 1.6 °” has a condensing point of “about 0.7 mm (compared with the case where the light is incident vertically). 0.6834 mm) ”. Therefore, when the diameter size of the light receiving surface of the photodetector 250a is “0.5 mm”, the incident light deviates from the light receiving surface of the photodetector 250a. That is, when the distance between the collimator lens 220 and the condenser lens 240 (center-to-center distance) is “14 mm” and the distance to the object is near “500 mm”, the laser distance measuring device 200 has insufficient return light. Measurement becomes difficult.

  Hereinafter, actual measurement results will be described with reference to FIGS. 6A and 6B. FIG. 6A is a diagram illustrating an example of a measurement result obtained by a general laser distance measuring apparatus 200. FIG. 6B is a diagram illustrating an example of a measurement result obtained by the laser distance measuring apparatus 100 according to the first embodiment. Here, in FIGS. 6A and 6B, the measurement results are shown on the vertical axis, and the actual distance is shown on the horizontal axis. 6A and 6B show a straight line L1 indicating the theoretical relationship between the measurement result and the actual distance, and curves L2 and L3 indicating the actual measurement result, respectively. 6A and 6B show measurement results measured by the TOF method.

  As shown in FIG. 6A, in the general laser distance measuring device 200, when the actual distance is shortened, the focal point of the return light from the object at a short distance deviates from the photodetector 250a. As shown in the dotted ellipse, the relationship between the measurement result and the actual distance is opposite to that in the case of a long distance. In the case of such a result, two distances correspond to the same measurement result, and the distance cannot be measured. On the other hand, in the laser distance measuring apparatus 100 according to the first embodiment, as shown in FIG. 6B, the small-diameter condenser lens 130 collects the return light on the photodetector 150a even when the distance becomes short. Therefore, as shown in the dotted ellipse in the curve L3, the measurement result corresponds to a single distance, and the distance can be measured. The deviation from the straight line L1 is corrected by the signal processing circuit 162.

  As described above, the laser distance measuring apparatus 100 according to the first embodiment can improve the light collection efficiency at a short distance, and can accurately measure the distance to an object at a short distance. it can. In addition, the first laser distance measuring device 100 can employ a small photodetector 150a having a diameter of the light receiving surface of “0.5 mm” to reduce the processing capacity and improve the processing speed. Cost can be reduced. In addition, the first laser distance measuring apparatus 100 can achieve downsizing of the entire apparatus by adopting a small photodetector 150a having a diameter of the light receiving surface of “0.5 mm”. In addition, the first laser distance measuring device 100 can be realized by adding only the small-diameter condensing lens 130, and is easy to realize.

  The laser distance measuring device 100 according to the first embodiment has been described above. In addition, embodiment mentioned above is an example to the last, and embodiment is not limited to this. For example, in the above-described embodiment, the case where the small-diameter condenser lens 130 (second condenser part) is used as a condenser part different from the large-diameter condenser lens 140 (first condenser part) has been described as an example. . However, the embodiment is not limited to this, and the second condensing unit may be realized by other configurations.

  7 and 8 are diagrams illustrating a modification of the second light collecting unit according to the first embodiment. Here, FIGS. 7 and 8 show a modified example of the second light condensing unit in the case where the second reflected light is deflected by “25 °” and condensed on the photodetector 150a. For example, as illustrated in FIG. 7, the deflection condensing unit 130a (an example of the second condensing unit) includes a prism 131a and a deflecting light condensing lens 131b. The prism 131a is disposed at the same position as the small-diameter condensing lens 130, deflects the second reflected light by “25 °”, and emits it to the deflected light condensing lens 131b. Here, the prism 131a is an isosceles prism or a wedge prism. The deflected light condensing lens 131b is disposed on the light source 110a side, and condenses the second reflected light emitted from the prism 131a on the condensing region of the photodetector 150a.

  For example, as shown in FIG. 8, the deflection condensing unit 130b (an example of the second condensing unit) includes a deflection mirror 131c and a deflection light condensing lens 131b. The deflection mirror 131c is disposed at the same position as the small-diameter condensing lens 130 and inclined by “12.5 °” with respect to the optical axis of the second reflected light, and deflects the second reflected light by “12.5 °”. Then, the light is incident on the deflected light condensing lens 131b. As a result, the second reflected light is deflected by “25 °” by the deflection mirror 131c. The deflecting light condensing lens 131b is disposed on the light source 110a side, and condenses the second reflected light from the deflecting mirror 131c on the condensing region of the photodetector 150a.

(Second Embodiment)
Next, a second embodiment will be described. Hereinafter, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof may be omitted. In the first embodiment described above, one-dimensional distance measurement (one-dimensional LiDAR) that emits laser light in one direction and measures the distance to an object that reflects the laser light has been described. In the second embodiment, a laser distance measuring apparatus that performs two-dimensional distance measurement (two-dimensional LiDAR) will be described.

  FIG. 9 is a front view showing a configuration of a laser distance measuring apparatus 100a according to the second embodiment. FIG. 10 is a block diagram showing an example of the configuration of the laser distance measuring apparatus 100a according to the second embodiment. Compared with the laser distance measuring device 100 according to the first embodiment, the laser distance measuring device 100a according to the second embodiment has a rotating portion 171, a fixed portion 172, a motor 173, and a drive circuit in the base portion 170. The difference is that 174 is provided. Hereinafter, this point will be mainly described.

  The rotating unit 171 includes a light source 110a, a light emitting circuit board 110b, a collimating lens 120, a small-diameter condenser lens 130, a large-diameter condenser lens 140, a photodetector 150a, a light-receiving circuit board 150b, and a control circuit board. 160, and is supported rotatably about the rotation axis of the motor 173.

  The fixing unit 172 includes a motor 173 and supports the entire laser distance measuring device 100a. The motor 173 rotates the rotating shaft 171 supported by the rotating shaft by rotating the rotating shaft based on the drive signal output from the drive circuit 174. The drive circuit 174 outputs a drive signal to the motor 173 based on the control signal from the control circuit 163 to drive the motor 173.

  The laser distance measuring device 100a performs two-dimensional distance measurement by performing the above-described one-dimensional distance measurement while rotating the rotating unit 171 by the motor 173. Specifically, first, the control circuit 163 drives the motor 173 at a predetermined speed by outputting a control signal to the drive circuit 174. Further, the control circuit 163 outputs a pulse signal associated with a control signal for driving the motor 173 to the drive circuit 111b. Thereby, the pulse signal for every rotation angle of the rotation part 171 and the electrical signal of return light are detectable. The drive circuit 111b generates a drive signal in synchronization with the pulse signal from the control circuit 163 and outputs the drive signal to the light source 110a, so that laser light is pulsed from the light source 110a for each rotation angle. Here, the control circuit 163 outputs a pulse signal for each rotation angle to the TDC circuit 161 as a reference clock.

  The amplifier circuit 151b amplifies the electrical signal of the return light detected by the photodetector 150a to a level at which signal analysis is possible and outputs the amplified signal to the TDC circuit 161. The TDC circuit 161 generates a digital signal indicating a time difference between the pulse signal for each rotation angle input from the control circuit 163 and the electrical signal for each rotation angle input from the amplifier circuit 151b, and generates the generated digital signal. The signal is output to the signal processing circuit 162. The signal processing circuit 162 calculates the distance to the object for each rotation angle from the time corresponding to the digital signal input from the TDC circuit 161 and the speed of light.

  As described above, according to the second embodiment, it is possible to improve the light collection efficiency when the distance to the object is a short distance even in the two-dimensional distance measurement.

(Other embodiments)
In the above-described embodiment, the case where the small-diameter condenser lens 130 and the collimator lens 120 are arranged in the vertical direction has been described as an example. However, the embodiment is not limited to this, and can be arbitrarily arranged. For example, the positional relationship between the small-diameter condensing lens 130 and the collimating lens 120 may be changed according to the shape and direction of the parallel light emitted from the collimating lens 120.

  Further, the present invention is not limited by the above embodiment. What comprised suitably combining each component mentioned above is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

DESCRIPTION OF SYMBOLS 100, 100a Laser distance measuring apparatus 110a Light source 110b Light emission circuit board 120 Collimating lens 130 Small diameter condensing lens (an example of a 2nd condensing part)
130a, 130b Deflection condensing part (an example of a second condensing part)
131a Prism 131b Deflection light condensing lens 131c Deflection mirror 140 Large diameter condensing lens 150a Photo detector 150b Light receiving circuit board 160 Control circuit board 162 Signal processing circuit (measurement unit)
170 Base 171 Rotating unit 172 Fixed unit 173 Motor 174 Drive circuit

Claims (6)

A first condensing unit that condenses the first reflected light of the output light emitted from the light source with respect to a predetermined condensing region in the detector;
A second condensing part for deflecting the second reflected light of the output light in the direction of the detector and condensing the light on the predetermined condensing region;
A measurement unit that measures a distance to an object that reflects the output light, based on at least one of the first reflected light and the second reflected light detected by the detector;
A laser distance measuring device comprising:   The second condensing unit is a lens that is arranged at an angle that deflects the second reflected light toward the detector and is formed with a curvature that condenses the second reflected light on the predetermined condensing region. The laser distance measuring device according to claim 1.   The second condensing unit includes a prism that deflects the second reflected light in the direction of the detector, and a deflected light condensing lens that condenses the second reflected light on the predetermined condensing region. The laser distance measuring device according to claim 1.   The second condensing unit includes a deflection mirror that deflects the second reflected light toward the detector, and a deflecting light condensing lens that condenses the second reflected light on the predetermined condensing region. The laser distance measuring device according to claim 1. Further comprising a collimating lens for making the output light parallel light,
5. The laser distance measuring device according to claim 1, wherein the second light collecting unit is arranged in parallel in a vertical direction or a horizontal direction with respect to the collimating lens.   The laser distance measurement according to any one of claims 1 to 5, further comprising a rotation mechanism that rotates an optical system including the first light collecting unit and the second light collecting unit with a vertical direction as a rotation axis. apparatus.