Laser radar device

Abstract

To provide a laser radar device capable of performing both object detection over a 360° range and measurement distance correction.SOLUTION: A rotary mirror (54) is rotatable 360° about a predetermined rotation axis. A reference object (85) is disposed between the rotary mirror and an external space, has a known reference distance as a true distance to be calculated by a distance calculation unit (80), and is changeable between a transparent state and an opaque state. The distance calculation unit calculates a correction value on the basis of a difference between the reference distance and a distance to the reference object calculated on the basis of a measurement time measured by changing the reference object into the opaque state and reflecting the laser light by the reference object, and calculates a distance to an object on the basis of the correction value and the measurement time measured in a state where the reference object is changed into the transparent state, and the laser light passes through the reference object.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a laser radar device. [Background technology]

[0002] For example, there is a laser radar device that includes a reflector that reflects laser light horizontally and is disposed on the lower open end face of a rotatably disposed cylindrical portion, and the cylindrical portion is rotated by a motor disposed above the reflector (see, for example, Patent Document 1). In the laser radar device described in Patent Document 1, even if the cylindrical portion is rotated 360° to project laser light over the entire 360° circumference, the wiring connecting the motor to the control unit and the frame supporting the cylindrical portion and reflector do not block the laser light projected toward the external space. Therefore, the laser radar device described in Patent Document 1 can scan the entire 360° circumference with laser light to detect objects. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-132534 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, it is conceivable to place a reference object in a part of the scanning range of the laser beam inside the housing of the laser radar device, and correct distance errors due to signal transmission delay, processing delay, characteristic changes due to temperature changes, aging, etc. based on the difference between the known distance to the reference object and the measured distance to the reference object. However, in a configuration that detects objects in a 360° range, such as the laser radar device described in Patent Document 1, it is not possible to place a reference object in a part of the scanning range of the laser beam inside the housing, and therefore it is not possible to correct the measured distance.

[0005] The present invention has been made to solve these problems, and its main object is to provide a laser radar device that can perform both object detection over a 360° range and measurement distance correction. [Means for solving the problem]

[0006] The first means for solving the above problem is: a light projection unit that projects laser light; a light receiving unit that receives reflected light, which is the laser light reflected by an object; a rotating mirror that is rotatable 360° around a predetermined rotation axis, that reflects the incident laser light projected by the light projecting unit toward an external space within a 360° range, and that reflects the incident reflected light so that it can be received by the light receiving unit; a distance calculation unit that calculates a distance to the object based on a measured time that is measured from when the laser light is projected by the light projecting unit to when the reflected light is received by the light receiving unit; and A laser radar device comprising: a reference object that is arranged between the rotating mirror and the external space, the reference object being a known reference distance and capable of being changed between a transparent state and an opaque state, and a true distance to be calculated by the distance calculation unit; The distance calculation unit calculates a correction value based on the difference between the distance to the reference object calculated based on the measurement time measured by changing the reference object to the opaque state and reflecting the laser light off the reference object, and calculates the distance to the object based on the measurement time measured by changing the reference object to the transparent state and allowing the laser light to pass through the reference object, and the correction value.

[0007] According to the above configuration, the light-projecting unit projects a laser beam. The rotating mirror is rotatable 360° around a predetermined rotation axis, and reflects the laser beam projected by the light-projecting unit and incident on the rotating mirror toward a 360° range of external space. This allows the laser radar device to scan a 360° range of external space with the laser beam. The rotating mirror also reflects the reflected light that is reflected by an object and incident on the rotating mirror so that it can be received by the light-receiving unit. The light-receiving unit receives the reflected light. The distance calculation unit calculates the distance to the object based on a measurement time measured from when the light-projecting unit projects the laser beam until the light-receiving unit receives the reflected light. This allows the laser radar device to detect objects within a 360° range.

[0008] Here, the reference object is positioned between the rotating mirror and the external space and can be changed between a transparent state and an opaque state. Therefore, by changing the reference object to an opaque state, the laser light can be reflected by the reference object, and the distance to the reference object can be calculated based on the measurement time. Furthermore, the true distance to be calculated by the distance calculation unit is a known reference distance. The difference between the calculated distance to the reference object and the reference distance reflects the current influence of signal transmission delay, processing delay, characteristic changes due to temperature changes, aging, etc., on the calculation of the distance to the object. Therefore, the distance calculation unit can calculate a correction value used for measuring the distance based on this difference.

[0009] On the other hand, by changing the reference object to a transparent state, the laser light can be transmitted through the reference object and projected into the external space. Therefore, even if the reference object is located between the rotating mirror and the external space, the laser radar device can perform object detection over a 360° range. Furthermore, the distance calculation unit calculates the distance to the object based on the measurement time measured while the laser light is transmitting through the reference object and the correction value. Therefore, the distance calculation unit can correct the measured distance based on the correction value, thereby accurately calculating the distance to the object. Therefore, the laser radar device can perform both object detection over a 360° range and measured distance correction.

[0010] In the second method, the distance calculation unit changes the reference object to the opaque state every time a predetermined time elapses, calculates the correction value, updates the previous correction value to the calculated correction value, and then changes the reference object to the transparent state. With this configuration, the correction value is updated every time a predetermined time elapses, so even if the error in the measured distance changes due to changes in the outside air temperature at the location where the laser radar device is installed, the correction value can be updated to an appropriate value. The distance calculation unit then changes the reference object to the transparent state after updating the correction value. Therefore, the laser radar device can continue object detection within a 360-degree range while changing the reference object to the opaque state and updating the correction value only when necessary.

[0011] In the third means, the distance calculation unit calculates the distance to the object based on the measurement time measured by passing the laser light through the reference object before changing the reference object to the opaque state and the correction value each time the predetermined time elapses, and if the calculated distance to the object is within a predetermined range, prohibits changing the reference object to the opaque state and calculating the correction value.

[0012] According to the above configuration, each time the predetermined time elapses, it is possible to determine whether the distance to an object in the direction in which the laser light that passed through the reference object before changing the reference object to the opaque state is projected (hereinafter referred to as the "reference object direction") is within a predetermined range, i.e., whether an intruder is present. If the distance to the object in the reference object direction is within the predetermined range, i.e., if it is determined that an intruder is present in the reference object direction, the distance calculation unit prohibits changing the reference object to the opaque state and calculating the correction value. Therefore, if it is determined that an intruder is present in the reference object direction, it is possible to avoid changing the reference object to the opaque state, and it is possible to continue detecting an intruder in the reference object direction.

[0013] Specifically, as in the fourth means, a configuration can be adopted in which the predetermined time is set to be longer than 20 [min] and shorter than 40 [min].

[0014] In a fifth means, the reference object has a plurality of regions that can be individually changed between the transparent state and the opaque state, and the distance calculation unit calculates the distance to the object based on the measurement time measured by passing the laser light through each region before changing each region to the opaque state and the correction value each time the predetermined time elapses, and if there is a predetermined region where the calculated distance to the object falls within a predetermined range, prohibits changing the predetermined region to the opaque state and calculating the correction value, and changes the regions of the plurality of regions other than the predetermined region to the opaque state and calculates the correction value.

[0015] According to the above configuration, the reference object has multiple regions that can be individually changed between the transparent state and the opaque state. Therefore, it is possible to change any of the multiple regions to the opaque state and calculate the correction value. If the distance to the object calculated by transmitting the laser light through each of the regions falls within a predetermined range for any of the regions, the region (predetermined region) is prohibited from being changed to the opaque state and the correction value is calculated. Therefore, when it is determined that an intruder is present in the direction of the predetermined region, it is possible to avoid changing the predetermined region to the opaque state, and it is possible to continue detecting an intruder in the direction of the predetermined region. Furthermore, the distance calculation unit changes the regions of the multiple regions other than the predetermined region to the opaque state and calculates the correction value. Therefore, it is possible to update the correction value while continuing to detect an intruder in the direction of the predetermined region.

[0016] When the laser radar device is started, current begins to flow through the circuits and electronic components that make up the laser radar device, causing the temperature inside the laser radar device to rise. This causes a change in the error in the measured distance, which may result in an inaccurate calculation of the measured distance. After a predetermined warm-up time has elapsed, the temperature rise inside the laser radar device due to the current flow almost stops.

[0017] In this regard, in the sixth aspect, when the laser radar device is started up, the distance calculation unit changes the reference object to the opaque state, calculates the correction value, and updates the previous correction value with the calculated correction value, continuing this process until a predetermined warm-up time has elapsed. With this configuration, even if the error in the measured distance changes due to a rise in temperature inside the laser radar device when the laser radar device is started up, the correction value can be updated in accordance with the change in error. Therefore, even if the temperature inside the laser radar device rises when the laser radar device is started up, the distance to the object can be accurately calculated. [Brief explanation of the drawings]

[0018] [Figure 1]FIG. 2 is a partial cross-sectional front view of the laser radar device. [Figure 2] FIG. 2 is a partial cross-sectional side view of the laser radar device of FIG. 1. [Figure 3] FIG. 2 is a partial plan view of the laser radar device of FIG. 1. [Figure 4] FIG. 2 is a partial side view showing an optical path in the laser radar device. [Figure 5] 10 is a flowchart showing a procedure for updating a distance correction value during warm-up. [Figure 6] 10 is a flowchart showing a procedure for updating a distance correction value at predetermined time intervals. [Figure 7] 10 is a flowchart showing a procedure for updating a distance correction value at predetermined time intervals in a modified example. [Figure 8] 10 is a flowchart showing another modified example of the procedure for updating the distance correction value at every predetermined time. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment embodied in a laser radar device that detects an object that has entered a monitored area will be described with reference to the drawings.

[0020] 1 and 2, the laser radar device 100 includes a laser diode 10 and a photodiode 20 that receives reflected light L3 (see FIG. 4) from a detected object, and is configured as a device that detects the distance and direction to the detected object. The laser diode 10 is an example of a light-projecting unit, and is supplied with a pulsed current from a control unit 80 to project a pulsed laser beam (laser beam L0: see FIG. 4). The photodiode 20 is an example of a light-receiving unit, and is configured to detect reflected light L3 of the laser beam reflected by the detected object when laser beam L0 is emitted from the laser diode 10, and convert the detected laser beam into an electrical signal.

[0021] A lens 30 and a mirror 35 are provided on the optical axis of the laser light L0. The lens 30 is configured as a collimating lens, and converts the laser light L0 emitted (projected) from the laser diode 10 into parallel light. In this embodiment, the laser radar device 100 is installed so that the optical axis direction of the laser light L0 is the horizontal direction X. The mirror 35 reflects the laser light L0 incident from the horizontal direction X downward (-Y) in the vertical direction Y. The reflected laser light is indicated by the symbol L1 (see FIG. 4). The laser light L1 is incident on an optical isolator 40.

[0022] The optical isolator 40 is disposed so as to be inclined at a predetermined angle (for example, 45°) with respect to the optical axis of the laser light L1, and uses the polarization characteristics of light to separate the laser light. The optical isolator 40 transmits the laser light L1 incident from the upper side (+Y) in the vertical direction, and reflects the reflected light L4 (see FIG. 4, originally reflected light L3) incident from the lower side (-Y) in the vertical direction toward the photodiode 20. A condenser lens 45 is provided between the optical isolator 40 and the photodiode 20, and the reflected light L5 (see FIG. 4, originally reflected light L3), which is a parallel light after being reflected by the optical isolator 40, is condensed by the condenser lens 45 and enters the photodiode 20.

[0023] The optical isolator 40 can be configured differently as long as it has the functions of transmitting and reflecting laser light. For example, a through-path can be formed in the reflective surface, and the laser light L1 passes through the through-path, while the reflective surface reflects the reflected light L3 toward the photodiode 20 (light receiving unit).

[0024] A rotary deflection mechanism 50 is provided on the optical axis of the laser light L1 that has passed through the optical isolator 40.

[0025] The rotary deflection mechanism 50 has a cylindrical portion 52 that is rotatable about an axis (cylinder central axis) that extends in the optical axis direction of the laser beam L1, and a reflecting mirror 54 is connected to an open end face 52a on the lower side (-Y) of the cylindrical portion 52 via a connecting member 53. The reflecting mirror 54 (rotating mirror) is positioned so as to be inclined at a predetermined angle (for example, 45°) with respect to the optical axis of the laser beam L1 that passes through the inside of the cylindrical portion 52. Note that the predetermined angle may be other angles such as 50°, 40°, etc. instead of 45°.

[0026] The rotary deflection mechanism 50 tilts the reflecting mirror 54 by 45° with respect to the optical axis of the laser light, and arranges it so that it can rotate about a cylindrical central axis (a predetermined rotation axis) extending in the optical axis direction of the laser light L1. The cylindrical portion 52 is rotatable because the cylindrical portion 52 is rotatably supported around its side by bearings 56 and 58. The reflecting mirror 54 can rotate 360°.

[0027] The laser light L1 that passes through the interior of the cylindrical portion 52 is reflected toward the horizontal direction X by the reflecting mirror 54 of the rotary deflection mechanism 50. The laser light reflected toward the horizontal direction X is indicated by the symbol L2 (see FIG. 4). The laser light L2 is sent toward external space. That is, the reflecting mirror 54 reflects the laser light L1, which is emitted by the laser diode 10 and incident on the reflecting mirror 54, toward external space within a 360° range.

[0028] Meanwhile, reflected light L3 from the detection object is reflected by reflecting mirror 54 toward the upper side (+Y) in the vertical direction Y. Reflected light L4 reflected toward the upper side (+Y) in the vertical direction Y passes through the inside of cylindrical portion 52 and enters optical isolator 40 from the lower side (-Y). Reflected light L4 is reflected by optical isolator 40, and this reflected light L5 enters photodiode 20 via condenser lens 45. In other words, reflecting mirror 54 reflects reflected light L4 that has entered reflecting mirror 54 so that it can be received by photodiode 20.

[0029] Although the reflecting mirror 54 has a flat reflecting surface, the reflecting surface may instead be concave. By using a concave surface, it is possible to guide the reflected light L3 from the detection object to the photodiode 20 without increasing the size and complexity of the device configuration.

[0030] A motor 70 for driving the rotary deflection mechanism 50 is provided near the rotary deflection mechanism 50. A gear 72 is attached to the shaft of the motor 70. A gear belt 74 is attached around the side of the cylindrical portion 52 of the rotary deflection mechanism 50. The gear 72 and the gear belt 74 mesh together, causing the cylindrical portion 52 to rotate around the central axis of the cylinder. The motor 70 is configured, for example, by a step motor. Various step motors can be used, and using one with a small angle per step enables precise rotation. Alternatively, a driving means other than a step motor may be used for the motor 70. For example, a servo motor or the like may be used. Alternatively, a motor that rotates steadily may be used, and the desired direction may be detected by emitting a pulsed laser beam in synchronization with the timing when the reflecting mirror 54 faces the direction to be measured.

[0031] As shown in FIG. 2, the laser diode 10, the photodiode 20, and the motor 70 are electrically connected to a control unit 80 by wiring 92 and are controlled by the control unit 80.

[0032] 1 to 3, the lens 30, mirror 35, optical isolator 40, condenser lens 45, bearings 56 and 58 that support the rotary deflection mechanism 50, and motor 70 are mounted on a frame 60. Reference numerals 62 and 64 in the drawings denote bearing fixing portions of the frame 60 for fixing the bearings 56 and 58.

[0033] The laser diode 10, the photodiode 20, the components mounted on the frame 60, the control unit 80, and the like are housed in a case body 90. The connecting member 53 and the reflecting mirror 54 of the rotary deflection mechanism 50 protrude from an opening in the case body 90 and are housed in a cap 94 molded from a light-transmitting resin material that transmits laser light. The cap 94 is formed, for example, in a cylindrical shape with a larger radius at the top (+Y side portion) than at the bottom (-Y side portion), and has a disk-shaped bottom at the bottom. The case body 90 and the cap 94 provide dustproofing and shock protection. The cap 94 may also be formed in a cylindrical shape with a smaller radius at the top than at the bottom, and may have a disk-shaped bottom at the bottom. If the laser light L2 is perpendicularly incident on the cap 94, the laser light L2 is likely to be reflected by the cap 94. Therefore, it is desirable that the inner surface of the cap 94 be inclined with respect to the incident direction of the laser light L2.

[0034] Next, the basic operation of the laser radar device 100 will be described. As shown in FIG. 4, in the laser radar device 100, when a pulse current is supplied from the control unit 80 to the laser diode 10, the laser diode 10 generates a pulsed laser beam (laser beam L0) at a time interval corresponding to the pulse width of the pulse current. The laser beam L0 is projected as diffused light with a certain spread angle and converted into a parallel beam by passing through the lens 30. After passing through the lens 30, the laser beam L0 is reflected by the mirror 35 downward in the vertical direction Y (-Y) as laser beam L1 and passes through the optical isolator 40. The laser beam L1 further passes through the inside of the cylindrical portion 52 of the rotary deflection mechanism 50 and is incident on the reflecting mirror 54 of the rotary deflection mechanism 50. The laser beam L1 is reflected by the reflecting mirror 54 as parallel beam, and laser beam L2 is emitted horizontally toward the external space.

[0035] When laser light is generated from laser diode 10, control unit 80 (distance calculation unit) operates motor 70 to rotate cylindrical portion 52 of rotary deflection mechanism 50 by 360°. As a result, reflecting mirror 54, which is disposed at an angle of 45° with respect to the optical axis of laser light L1, rotates 360° around the optical axis. Laser light L2, which is emitted from reflecting mirror 54 as parallel light, is irradiated horizontally and over the entire 360° circumference into the external space.

[0036] When a detection object (e.g., an intruder) is present in the external space, the laser light L2 is reflected by the detection object, and a portion of this reflected light, called reflected light L3, is incident on the reflecting mirror 54 again. The reflected light L3 is reflected by the reflecting mirror 54 upward in the vertical direction Y (+Y), passes through the interior of the cylindrical portion 52 of the rotary deflection mechanism 50 as reflected light L4, and is incident on the optical isolator 40. The reflected light L4 is reflected by the optical isolator 40, and the reflected light L5 is incident on the photodiode 20 via the condenser lens 45. The photodiode 20 outputs an electrical signal (e.g., a voltage value corresponding to the received reflected light L5) corresponding to the received reflected light L5. In this configuration, the control unit 80 can calculate the distance x1 to the detection object by measuring the time (measurement time t1) between when the laser diode 10 outputs the laser light L0 and when the photodiode 20 detects the reflected light L5. For example, the control unit 80 can calculate the distance x1 to the detected object by multiplying the measurement time t1 by the speed of light c and dividing the result by 2 (x1 = t1 × c / 2). In addition, the direction of the detected object can also be determined from the position of the reflecting mirror 54 at that time.

[0037] As shown in FIGS. 1 and 2, a light-controlling film 85 is attached to a predetermined area on the inner surface of the cap 94. That is, the light-controlling film 85 is disposed between the reflecting mirror 54 and the external space. The predetermined area is, for example, 1 / 10 to 1 / 4 of the entire circumference of the cap 94 (36° to 90° in terms of the rotation angle of the reflecting mirror 54). The light-controlling film 85 (reference object) is, for example, a liquid crystal film whose transparency can be changed. The light-controlling film 85 is opaque when no voltage is applied and can be changed to a transparent state by applying a voltage. The transparency of the light-controlling film 85 increases with increasing applied voltage, and the transparency corresponding to the applied voltage can be maintained by maintaining the applied voltage. The transparency of the light-controlling film 85, i.e., the opaque and transparent states, is controlled by the control unit 80. The wiring that applies voltage to the light-controlling film 85 is installed so as not to block the laser light L2 and reflected light L3 that pass through the cap 94.

[0038] The optical path length Ls of the laser light L0 emitted from the laser diode 10 is determined in advance and known, passing through the mirror 35, the optical isolator 40, and the reflecting mirror 54, reflected (more specifically, diffusely reflected) by the opaque light control film 85, and then passing through the reflecting mirror 54, the optical isolator 40, and the condenser lens 45 until it is received by the photodiode 20. In this case, if the control unit 80 calculates (measures) the distance x1 to the light control film 85 based on the measurement time t1, the distance equivalent to the length obtained by dividing the optical path length Ls by 2 is calculated as the distance x1 to the light control film 85.

[0039] Here, the optical path length Ls divided by 2 is defined as the reference distance x0 (x0 = Ls / 2). The distance x1 to the light-controlling film 85 calculated by the control unit 80 in the standard equilibrium state is corrected during the calculation process so that it coincides with the reference distance x0. The standard equilibrium state is a state in which the temperature inside the laser radar device 100 has reached equilibrium (saturation) after a predetermined warm-up time tw (e.g., 5 min) has elapsed since the laser radar device 100 was started, under standard conditions where the outside air temperature is standard (e.g., 25°C) and the atmospheric pressure is standard (e.g., 10^5 Pa). 10^5 represents 10 to the fifth power. The reference distance x0 is the true distance to the light-controlling film 85 that should be calculated by the control unit 80 in the standard equilibrium state, and is a known distance that can be measured or designed (set) in advance. Therefore, the distance x1 to the light-controlling film 85 measured in the standard equilibrium state is equal to the optical path length Ls divided by 2. It is also possible to use 0° C. as the standard temperature, 101325 Pa as the standard pressure, and 1 to 10 minutes as the predetermined warm-up time tw.

[0040] When calculating the distance correction value Δx (described later), in the current state of the laser radar device 100, the control unit 80 calculates the distance x1 to the light control film 85 based on the measurement time t1 measured when the light control film 85 is changed to an opaque state and the laser light L2 is reflected by the light control film 85. Specifically, the control unit 80 changes the light control film 85 to an opaque state. The control unit 80 calculates the distance x1 to the light control film 85 based on the measurement time t1 when the laser light L2 reflected by the reflecting mirror 54 is irradiated onto the light control film 85, i.e., when the rotational position of the reflecting mirror 54 is at a rotational position where the laser light L2 is irradiated onto the light control film 85. The distance x1 includes distance errors due to signal transmission delays, processing delays, characteristic changes due to temperature changes, aging, etc. The distance error increases, for example, as the internal temperature of the laser radar device 100 increases.

[0041] Next, the control unit 80 calculates a distance correction value Δx (correction value) based on the difference between the calculated distance x1 and the reference distance x0. Specifically, the control unit 80 calculates the distance correction value Δx by subtracting the distance x1 from the reference distance x0 (Δx=x0-x1). The distance correction value Δx is the difference between the true distance (reference distance x0) in the standard equilibrium state and the distance x1 including the distance error, and is a correction value for correcting the distance error.

[0042] The control unit 80 also calculates the distance x2 to the detected object based on the measurement time t1 measured when the light control film 85 is changed to a transparent state and the laser light L2 is transmitted through the light control film 85 and the distance correction value Δx. Specifically, the control unit 80 calculates the distance x1 to the detected object based on the measurement time t1. The control unit 80 calculates the distance x2 to the detected object by adding the distance correction value Δx to the calculated distance x1 (x2 = x1 + Δx). The distance x2 is the distance after the distance error has been corrected and represents the accurate distance from the laser radar device 100 to the detected object.

[0043] When the laser radar device 100 is started up, current begins to flow through the circuits and electronic components that make up the laser radar device 100, causing the temperature inside the laser radar device 100 to rise. This changes the error in the distance x1, which may make it impossible to accurately calculate the distance x2. After a predetermined warm-up time tw has elapsed, the temperature rise inside the laser radar device 100 almost stops, and the temperature inside the laser radar device 100 reaches equilibrium (saturation).

[0044] 5 is a flowchart showing the procedure for updating the distance correction value Δx during warm-up. This series of processes is executed by the control unit 80.

[0045] First, the light control film 85 is made opaque (S10). Specifically, the light control film 85 is made opaque by applying no voltage to the light control film 85.

[0046] Next, it is determined whether a predetermined warm-up time tw has elapsed since the laser radar device 100 was started (S11). If it is determined that the predetermined warm-up time tw has not elapsed (S11: NO), the distance correction value Δx is updated (S12). Specifically, when the rotational position of the reflecting mirror 54 is such that the laser light L2 is irradiated onto the light control film 85, the distance x1 to the light control film 85 is calculated based on the measurement time t1. The distance x1 is subtracted from the reference distance x0 to calculate the distance correction value Δx (Δx = x0 - x1). Then, the previous distance correction value Δx is updated to the calculated distance correction value Δx. Then, the process is executed again from S11.

[0047] On the other hand, if it is determined in the judgment of S11 that the predetermined warm-up time tw has elapsed (S11: YES), the light control film 85 is made transparent (S13). Specifically, a voltage is applied to the light control film 85 to change the light control film 85 to a transparent state. Then, this series of processes ends (END).

[0048] 5. Specifically, after the distance correction value Δx has been updated at least once, the control unit 80 adds the distance correction value Δx to the distance x1 to calculate the distance x2 to the detected object when the laser light L2 reflected by the reflecting mirror 54 is not irradiated onto the light-controlling film 85, i.e., when the rotational position of the reflecting mirror 54 is such that the laser light L2 is not irradiated onto the light-controlling film 85. That is, the control unit 80 calculates the distance x2 to the detected object based on the measurement time t1 and the distance correction value Δx. Then, if the calculated distance x1 is within a predetermined range (for example, 0 [m] to the maximum measurable distance [m]), it determines that there is an intruder (an intruder object) in the monitored area. That is, the control unit 80 performs object detection while continuously updating the distance correction value Δx from the time the laser radar device 100 is started until the warm-up time tw has elapsed. Then, the control unit 80 starts object detection in a 360° range after the series of processes in Fig. 5 is completed. Note that the control unit 80 can also refrain from performing object detection outside the range of the light control film 85 until the series of processes in Fig. 5 is completed. In other words, the control unit 80 can also postpone the start of object detection until the series of processes in Fig. 5 is completed.

[0049] 6 is a flowchart showing the procedure for updating the distance correction value Δx at every predetermined time ta. This series of processes is executed by the control unit 80 after the warm-up time tw has elapsed.

[0050] First, the light control film 85 is made transparent (S20). Specifically, a voltage is applied to the light control film 85 to change the light control film 85 into a transparent state.

[0051] Next, it is determined whether a predetermined time ta has elapsed since the distance correction value Δx was last updated (S21). The predetermined time ta is set, for example, to be longer than 20 minutes and shorter than 40 minutes, and is set to 30 minutes as an example. If it is determined that the predetermined time ta has not elapsed (S21: NO), the determination of S21 is executed again.

[0052] On the other hand, when it is determined in the determination of S21 that the predetermined time ta has elapsed (S21: YES), the light control film 85 is made opaque (S22). Specifically, the light control film 85 is made opaque by applying no voltage to the light control film 85.

[0053] Next, the distance correction value Δx is updated (S23). Specifically, when the rotational position of the reflecting mirror 54 is at a rotational position where the laser light L2 irradiates the light control film 85, the distance x1 to the light control film 85 is calculated based on the measurement time t1. Then, the distance x1 is subtracted from the reference distance x0 to calculate the distance correction value Δx (Δx = x0 - x1). After that, this series of processes ends (END).

[0054] The control unit 80 also performs object detection in parallel with the series of processes in Fig. 6. Specifically, the control unit 80 performs object detection in a 360° range in a state in which the light control film 85 has been made transparent by the process of S20 in Fig. 6. Then, the control unit 80 makes the light control film 85 opaque and updates the distance correction value Δx only when a predetermined time ta has elapsed since the previous update of the distance correction value Δx. Thereafter, the series of processes in Fig. 6 are executed again, and the light control film 85 is made transparent by the process of S20.

[0055] As described above in detail, this embodiment has the following advantages.

[0056] The laser diode 10 emits a laser beam L0. The reflecting mirror 54 is rotatable 360° around a predetermined rotation axis and reflects the laser beam L1 emitted by the laser diode 10 and incident on the reflecting mirror 54 toward the external space within a 360° range. This allows the laser radar device 100 to scan the external space within a 360° range with the laser beam L2. The reflecting mirror 54 also reflects the reflected light L3, which is reflected by the detected object and incident on the reflecting mirror 54, so that it can be received by the photodiode 20. The photodiode 20 receives the reflected light L5. The control unit 80 then calculates the distance x1 (measured distance) to the detected object based on the measurement time t1, which is measured from when the laser diode 10 emits the laser beam L0 until the photodiode 20 receives the reflected light L5. This allows the laser radar device 100 to detect objects within a 360° range.

[0057] The light-controlling film 85 is disposed between the reflecting mirror 54 and the external space and can be changed between a transparent state and an opaque state. Therefore, by changing the light-controlling film 85 to an opaque state, the light-controlling film 85 can reflect the laser light L2, and the distance x1 to the light-controlling film 85 can be calculated based on the measurement time t1. The true distance to be calculated by the control unit 80 is the known reference distance x0. The difference between the calculated distance x1 to the light-controlling film 85 and the reference distance x0 reflects the current influence of signal transmission delays, processing delays, characteristic changes due to temperature changes, aging, and the like on the calculation of the distance x1 to the light-controlling film 85. Therefore, the control unit 80 can calculate the distance correction value Δx used to correct the measured distance based on this difference.

[0058] By changing the light-controlling film 85 to a transparent state, the laser light L2 can be transmitted through the light-controlling film 85 and projected into the external space. Therefore, even if the light-controlling film 85 is positioned between the reflector 54 and the external space, the laser radar device 100 can perform object detection over a 360° range. Furthermore, the control unit 80 calculates the distance x2 to the detected object based on the measurement time t1 measured when the laser light L2 and the reflected light L3 are transmitted through the light-controlling film 85 and the distance correction value Δx. Therefore, the control unit 80 can correct the distance x1 based on the distance correction value Δx, and can accurately calculate the distance x2 to the detected object. Therefore, the laser radar device 100 can perform both object detection over a 360° range and distance correction.

[0059] The control unit 80 changes the light-controlling film 85 to an opaque state every time a predetermined time ta elapses, calculates a distance correction value Δx, updates the previous distance correction value Δx to the calculated distance correction value Δx, and then changes the light-controlling film 85 to a transparent state. With this configuration, the distance correction value Δx is updated every time the predetermined time ta elapses. Therefore, even if the error in the distance x1 changes due to changes in the outside air temperature at the location where the laser radar device 100 is installed, the distance correction value Δx can be updated to an appropriate value. The control unit 80 then changes the light-controlling film 85 to a transparent state after updating the distance correction value Δx. Therefore, the laser radar device 100 can continue detecting objects in a 360-degree range while changing the light-controlling film 85 to an opaque state only when necessary to update the distance correction value Δx.

[0060] The predetermined time ta is set, for example, to be longer than 20 minutes and shorter than 40 minutes, e.g., 30 minutes. This allows the distance correction value Δx to be updated before the error in the distance x1 changes significantly due to changes in the outside temperature at the location where the laser radar device 100 is installed. Therefore, the laser radar device 100 can accurately calculate the distance x2 to the detected object regardless of changes in the outside temperature.

[0061] When the laser radar device 100 is started up, the control unit 80 changes the light control film 85 to an opaque state, calculates the distance correction value Δx, and updates the previous distance correction value Δx to the calculated distance correction value Δx, continuing this process until a predetermined warm-up time tw has elapsed. With this configuration, even if the error in the distance x1 changes due to a rise in the temperature inside the laser radar device 100 when the laser radar device 100 is started up, the distance correction value Δx can be updated in accordance with the change in error. Therefore, even if the temperature inside the laser radar device 100 rises when the laser radar device 100 is started up, the distance x2 to the detected object can be accurately calculated.

[0062] In the laser radar device 100, a reflecting mirror 54 is disposed on the open end face 52a on the lower (-Y) side of the rotatably disposed cylindrical portion 52, and the reflecting mirror 54 is rotationally driven by a motor 70 disposed above (+Y) the reflecting mirror 54. Therefore, even if the cylindrical portion 52 is rotated 360° to emit the laser light L2 over the entire 360° circumference, the wiring 92 connecting the motor 70 to the control unit 80 and the frame 60 supporting the rotary deflection mechanism 50 do not block part of the emission range of the laser light L2. Therefore, the laser radar device 100 can perform scanning over the entire 360° circumference.

[0063] The above embodiment can be modified as follows: The same parts as those in the above embodiment are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0064] In the process shown in the flowchart of FIG. 6, by setting the predetermined time ta to a short time such as 1 to 10 minutes, the control unit 80 (distance calculation unit) can execute only the process shown in the flowchart of FIG. 6, and omit the process shown in the flowchart of FIG. 5.

[0065] If the laser radar device 100 is installed in a clean room or the like where the temperature is kept constant by air conditioning, the control unit 80 (distance calculation unit) can execute only the processing shown in the flowchart of FIG. 5 and omit the processing shown in the flowchart of FIG. 6.

[0066] As shown in Fig. 7, the processes of S21a and S24 may be added to the process shown in the flowchart of Fig. 6. That is, if it is determined in the determination of S21 that a predetermined time ta has elapsed (S21: YES), the control unit 80 (distance calculation unit) determines whether an object has been detected within the range of the light-controlling film 85 (S21a). Specifically, it determines whether the distance x2 to the detected object detected within the range irradiated by the laser light L2 that has passed through the light-controlling film 85 is within a predetermined range. If it is determined in this determination that an object has not been detected within the range of the light-controlling film 85 (S21a: NO), the light-controlling film 85 is made opaque (S22), and the distance correction value Δx is updated (S23). On the other hand, if it is determined that an object has been detected within the range of the light-controlling film 85 (S21a: YES), the light-controlling film 85 is not made opaque, and object detection continues (S24). That is, each time a predetermined time ta has elapsed (S21: YES), the control unit 80 calculates the distance x2 to the detected object based on the measurement time t1 measured by passing laser light L2 through the light-controlling film 85 before changing the light-controlling film 85 to an opaque state (S22) and the distance correction value Δx, and if the calculated distance x2 to the detected object is within a predetermined range (S21a: YES), it prohibits changing the light-controlling film 85 to an opaque state and calculating the distance correction value Δx (S22, S23).

[0067] According to the above configuration, every time a predetermined time ta has elapsed, it is possible to determine whether the distance x2 to the detection object in the direction in which the laser light L2 that passed through the light-controlling film 85 before changing the light-controlling film 85 to the opaque state is projected (hereinafter referred to as the "light-controlling film 85 direction") is within a predetermined range, i.e., whether an intruder is present. If the distance x2 to the detection object in the direction of the light-controlling film 85 is within the predetermined range, i.e., if it is determined that an intruder is present in the direction of the light-controlling film 85, the control unit 80 changes the light-controlling film 85 to the opaque state and prohibits the calculation of the distance correction value Δx. Therefore, if it is determined that an intruder is present in the direction of the light-controlling film 85, it is possible to avoid changing the light-controlling film 85 to the opaque state, and it is possible to continue detecting an intruder in the direction of the light-controlling film 85.

[0068] The light control film 85 may have a first region and a second region (multiple regions) that can be individually switched between a transparent state and an opaque state. As shown in FIG. 8, the control unit 80 calculates the distance x2 to the detected object (S21b) based on the measurement time t1 measured by transmitting the laser light L2 through each region before changing each region to an opaque state (S22A) (S21b). If there is a predetermined region (e.g., the first region) where the calculated distance x2 to the detected object falls within a predetermined range (S21b: YES), the control unit 80 prohibits changing the predetermined region to an opaque state and calculating the distance correction value Δx (S22A, S23). If no object is detected in a region other than the predetermined region (e.g., the second region) among the multiple regions (S25: NO), the control unit 80 may change the region other than the predetermined region to an opaque state and calculate the distance correction value Δx (S26, S27). Note that the process of S25 may be omitted. The first and second regions can also be interchanged.

[0069] According to the above configuration, the light control film 85 has multiple regions that can be individually switched between transparent and opaque. Therefore, the distance correction value Δx can be calculated by changing any of the multiple regions to an opaque state. The reference distance x0 to each region is the true distance to each region that the control unit 80 should calculate in a standard equilibrium state. This is a known distance that can be measured or designed (set) in advance. If the distance x2 to the detected object calculated by transmitting the laser light L2 through each region falls within a predetermined range for any region (intruder presence), the control unit 80 prohibits changing that region (predetermined region) to an opaque state and calculating the distance correction value Δx. Therefore, if it is determined that an intruder is present in the direction of the predetermined region, the control unit 80 can avoid changing the predetermined region to an opaque state and continue to detect an intruder in the direction of the predetermined region. Furthermore, the control unit 80 calculates the distance correction value Δx by changing any region other than the predetermined region to an opaque state. Therefore, the control unit 80 can update the distance correction value Δx while continuing to detect an intruder in the direction of the predetermined region.

[0070] The control unit 80 can also calculate a time correction value Δt (correction value) based on the difference between the calculated distance x1 and the reference distance x0. Specifically, the control unit 80 calculates the time correction value Δt by subtracting the measurement time t1 (t1 = 2x1 / c), which is twice the distance x1 divided by the speed of light c, from the reference time t0 (t0 = 2x0 / c), which is twice the reference distance x0 divided by the speed of light c (Δt = t0 - t1). The control unit 80 then calculates the measurement time t2, which is the time from when the laser light L0 is projected to when the reflected light L5 (L3) reflected by the detected object is received, based on the measurement time t1 measured when the light control film 85 is changed to a transparent state and the laser light L2 is transmitted through the light control film 85, and the time correction value Δt. Specifically, the control unit 80 calculates the measurement time t2 by adding the time correction value Δt to the measurement time t1 (t2 = t1 + Δt). The measurement time t2 is the measurement time after the time error due to the distance error has been corrected, and represents the measurement time corresponding to the accurate distance from the laser radar device 100 to the detected object. The control unit 80 can then calculate the distance x2 to the detected object by multiplying the measurement time t2 by the speed of light c and dividing the result by 2 (x2=t2×c / 2).

[0071] The light control film 85 (reference object) is not limited to a liquid crystal film, but can also be an organic EL film. Furthermore, electrochromic or gasochromic methods can also be used as the light control method. In short, the reference object can be anything that can be changed between a transparent state and an opaque state.

[0072] The above-described embodiments and their modifications can be combined within the scope of possible combinations. [Explanation of symbols]

[0073] 10...laser diode (light-emitting unit), 20...photodiode (light-receiving unit), 40...optical isolator, 50...rotary deflection mechanism, 54...reflector (rotating mirror), 80...control unit (distance calculation unit), 85...light-adjusting film (reference object), 100...laser radar device.

Claims

1. a light projection unit that projects laser light; a light receiving unit that receives reflected light, which is the laser light reflected by an object; a rotating mirror that is rotatable 360° around a predetermined rotation axis, that reflects the incident laser light projected by the light projecting unit toward an external space within a 360° range, and that reflects the incident reflected light so that it can be received by the light receiving unit; a distance calculation unit that calculates a distance to the object based on a measured time that is measured from when the laser light is projected by the light projecting unit to when the reflected light is received by the light receiving unit; and A laser radar device comprising: a reference object that is arranged between the rotating mirror and the external space, the reference object being a known reference distance and capable of being changed between a transparent state and an opaque state, and a true distance to be calculated by the distance calculation unit; The distance calculation unit calculates a correction value based on the difference between the distance to the reference object calculated based on the measurement time measured by changing the reference object to the opaque state and reflecting the laser light off the reference object, and calculates the distance to the object based on the measurement time measured by changing the reference object to the transparent state and allowing the laser light to pass through the reference object and the correction value.

2. 2. The laser radar device according to claim 1, wherein the distance calculation unit changes the reference object to the opaque state every time a predetermined time elapses, calculates the correction value, updates the previous correction value with the calculated correction value, and then changes the reference object to the transparent state.

3. 3. The laser radar device according to claim 2, wherein the distance calculation unit calculates the distance to the object based on the measurement time measured by transmitting the laser light through the reference object before changing the reference object to the opaque state and the correction value each time the predetermined time elapses, and prohibits changing the reference object to the opaque state and calculating the correction value if the calculated distance to the object is within a predetermined range.

4. 4. The laser radar device according to claim 3, wherein the predetermined time is set to be longer than 20 minutes and shorter than 40 minutes.

5. the reference object has a plurality of regions that can be individually changed between the transparent state and the opaque state; 3. The laser radar device according to claim 2, wherein the distance calculation unit calculates the distance to the object based on the measurement time measured by transmitting the laser light through each region before changing each region to the opaque state and the correction value each time the predetermined time elapses, and if there is a predetermined region where the calculated distance to the object falls within a predetermined range, prohibits changing the predetermined region to the opaque state and calculating the correction value, and changes the regions of the plurality of regions other than the predetermined region to the opaque state and calculates the correction value.

6. 6. The laser radar device according to claim 1, wherein, when the laser radar device is started, the distance calculation unit changes the reference object to the opaque state, calculates the correction value, and updates the previous correction value to the calculated correction value, continuing this process until a predetermined warm-up time has elapsed.

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