Deflection device, light scanning device, and optical distance measuring device

Abstract

To provide a technique for controlling a swing amplitude of a light deflection unit in a deflection device including a plurality of light receiving elements arranged in a predetermined direction, without providing a sensor for measuring the swing amplitude of the light deflection unit.SOLUTION: A deflection device 14 includes: a light projecting unit 12; a first deflection mechanism 16 that includes a deflection mirror 28a configured to deflect and reflect measurement light emitted from the light projecting unit 12 and to be swingable around a first axis P1; a light receiving unit 44 having a plurality of light receiving elements 44a arranged in a direction along the direction around the first axis P1; a second deflection mechanism 20 configured to rotationally drive the first deflection mechanism 16 and the light receiving unit 44 around a second axis P2; a reference reflection member 22 on which the measurement light emitted from the light projecting unit 12 and deflected and reflected by the deflection mirror 28a is irradiated; and a swing control unit 70 configured to control the first deflection mechanism 16 on the basis of reflected light from the reference reflection member 22 received by a part of the plurality of light receiving elements 44a of the light receiving unit 44.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a deflection device, an optical scanning device, and an optical distance measuring device. [Background technology]

[0002] Distance measuring devices that use the TOF (Time Of Flight) method to measure the distance to an object are known. Distance measuring devices that use the TOF method can measure the distance to an object by detecting the time from when a measuring light is irradiated onto the object to when the reflected light of the measuring light is received.

[0003] For example, the distance measuring device disclosed in Patent Document 1 includes a light projecting and receiving unit, a first deflection mechanism having a deflection mirror, and a second deflection mechanism that rotates and drives the first deflection mechanism. The deflection mirror deflects and reflects measurement light emitted from the light projecting and receiving unit and deflects and reflects light reflected by an object toward the light projecting and receiving unit. In this distance measuring device, the first deflection mechanism swings the deflection mirror about a first axis extending horizontally, while the second deflection mechanism rotates the first deflection mechanism about a second axis extending vertically, thereby scanning the measurement light two-dimensionally and measuring three-dimensional distances.

[0004] In the range finder described above, the oscillation amplitude of the deflection mirror may fluctuate due to various factors such as temperature fluctuations. Since fluctuations in the oscillation amplitude of the deflection mirror make it impossible to perform proper measurements, the oscillation amplitude of the deflection mirror must be maintained at a predetermined value. One possible method for maintaining the oscillation amplitude of the deflection mirror at a predetermined value is to provide a sensor that measures the oscillation amplitude of the deflection mirror and control the first deflection mechanism based on the oscillation amplitude measured by the sensor. However, this requires a sensor and a configuration for driving the sensor, which increases the manufacturing cost of the range finder.

[0005] In this regard, in the distance measuring device of Patent Document 1, a reference reflecting member for reflecting the measurement light deflected and reflected by the deflecting mirror is provided in an area of ​​a casing that houses the deflecting mirror and other components, where no optical window is formed for emitting the measurement light deflected by the deflecting mirror to external space.The oscillation amplitude of the deflecting mirror is controlled based on the reflected light from the reference reflecting member received by the light receiving unit.In this case, there is no need to provide a sensor for measuring the oscillation amplitude of the deflecting mirror, which reduces the manufacturing cost of the distance measuring device.

[0006] In order to improve the detection sensitivity of the reflected light in the above-mentioned distance measuring device, it is necessary to increase the size of the deflection mirror and increase the amount of reflected light received. However, if the size of the deflection mirror is increased, it becomes difficult to reduce the size of the distance measuring device, the swing range of the deflection mirror becomes narrow, and it also becomes difficult to increase the swing speed of the deflection mirror.

[0007] Therefore, a technology has been proposed to improve the sensitivity of a distance measuring device without increasing the size of the deflection mirror. For example, a laser distance measuring device disclosed in Patent Document 2 includes a MEMS mirror that deflects output light from a light source, a focusing lens that focuses the reflected light of the output light reflected by an object onto a detector, and a measurement unit that measures the distance to the object that reflected the output light based on the reflected light detected by the detector. The photodetector has multiple detection elements. The reflected light of the output light scanned in the vertical direction by the MEMS mirror is detected by detection elements corresponding to the vertical scanning angle. The measurement unit measures the distance to each object that reflected the reflected light based on the reflected light detected by the multiple detection elements.

[0008] Patent Document 2 describes that the above-described configuration makes it possible to realize a small-sized, highly sensitive three-dimensional LiDAR. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-109686 [Patent Document 2] Japanese Patent Application Publication No. 2018-128432 Summary of the Invention [Problem to be solved by the invention]

[0010] Patent Document 2 does not disclose a specific means for measuring the oscillation amplitude of the MEMS mirror. As mentioned above, the oscillation amplitude of the MEMS mirror can be measured by a sensor, but this requires a sensor and a configuration for driving the sensor, which increases the manufacturing cost of the device.

[0011] One possible means for measuring the oscillation amplitude of a MEMS mirror without using a sensor is to use a reference reflecting member, as disclosed in Patent Document 1. However, the means disclosed in Patent Document 1 cannot be used as is in a device that detects reflected light using multiple detection elements.

[0012] Therefore, one example of the object of the present invention is to provide a technology that can control the oscillation amplitude of an optical deflection unit in a deflection device having a plurality of light receiving elements arranged in a predetermined direction, without providing a sensor that measures the oscillation amplitude of the optical deflection unit. [Means for solving the problem]

[0013] (1) In order to achieve the above object, a deflection device in one aspect of the present invention comprises: a light-projecting unit that emits measurement light; a first deflection mechanism that includes an optical deflection unit that deflects and reflects the measurement light emitted from the light-projecting unit and has a movable unit that can swing around a first axis and a drive unit that drives the movable unit to swing; a light-receiving unit that has a plurality of light-receiving elements arranged in a predetermined direction along the direction around the first axis and receives reflected light of the measurement light reflected by an object with any of the light-receiving elements; a second deflection mechanism that drives and rotates at least the first deflection mechanism and the light-receiving unit around a second axis different from the first axis; a reference reflecting member onto which the measurement light emitted from the light-projecting unit and deflected and reflected by the optical deflection unit is irradiated; and a swing control unit that controls the drive unit based on the reflected light from the reference reflecting member that is received by some of the plurality of light-receiving elements of the light-receiving unit.

[0014] When the resonant frequency of the movable part and the member that supports it for oscillation fluctuates due to factors such as temperature fluctuations, the oscillation amplitude of the movable part fluctuates accordingly. Therefore, to maintain the predetermined oscillation amplitude, it is necessary to measure the fluctuations in oscillation amplitude and control the drive unit that drives the movable part to oscillate. If a sensor measuring the oscillation amplitude of the movable part of the first deflection mechanism is provided for this purpose, a configuration is required to extract the signal output of the sensor from the second deflection mechanism to the outside, making the device configuration complicated. In this regard, the above-mentioned deflection device receives the measurement light reflected by the reference reflecting member from the light projecting unit installed outside the rotating system, known as the second deflection mechanism, with a part of the light receiving unit. The oscillation amplitude of the movable part (optical deflection unit) can be detected and controlled based on the received reflected light. In this case, there is no need to provide a sensor to measure the oscillation amplitude of the movable part, simplifying the configuration of the deflection device.

[0015] (2) The deflection device may further include a selector that selects a light-receiving element that receives the reflected light from among the plurality of light-receiving elements of the light-receiving unit. In this case, by appropriately selecting a light-receiving element by the selector, the oscillation amplitude of the movable part can be detected and controlled with higher accuracy.

[0016] (3) In the deflection device, the selector may select one of the plurality of light-receiving elements to fix the light-receiving element of the light-receiving unit that receives the reflected light from the reference reflecting member during the period when the measurement light is irradiated onto the reference reflecting member. In this case, the oscillation amplitude of the movable part (light deflection unit) can be easily detected based on the detection result of the fixed specific light-receiving element.

[0017] (4) In the above deflection device, the selector may select two of the light-receiving elements of the light-receiving unit that receive the reflected light from the reference reflecting member, symmetrically arranged from the center of the plurality of light-receiving elements arranged in the predetermined direction, during the period when the measurement light is irradiated onto the reference reflecting member. In this case, the movable unit can be driven to oscillate with higher precision than when the oscillation amplitude of the movable unit (light deflection unit) is detected and controlled based on the detection result of one light-receiving element.

[0018] (5) The deflection device may have two light-receiving units, and the selector may select the light-receiving elements of the light-receiving units that receive the reflected light from the reference reflecting member during the period in which the measurement light is irradiated onto the reference reflecting member so as to fix one light-receiving element of one of the two light-receiving units and one light-receiving element of the other of the two light-receiving units. In this case, during distance measurement, the distance to the object can be measured with higher accuracy using the two light-receiving units. Furthermore, the movable unit (optical deflection unit) can be oscillated with higher accuracy than when the oscillation amplitude of the movable unit is detected and controlled based on the detection result of the light-receiving element of one light-receiving unit.

[0019] (6) In the above deflection device, the movable part may be swung from the original position to one side and the other side around the first axis, and during a period in which the measurement light is irradiated onto the reference reflecting member, the one light-receiving element of one of the light-receiving parts selected by the selection part may be a light-receiving element that receives reflected light based on the measurement light deflected and reflected by the optical deflector when the movable part is swung from the original position to the one side around the first axis by a predetermined angle, and the one light-receiving element of the other light-receiving part selected by the selection part during a period in which the measurement light is irradiated onto the reference reflecting member may be a light-receiving element that receives reflected light based on the measurement light deflected and reflected by the optical deflector when the movable part is swung from the original position to the other side around the first axis by the predetermined angle. In this case, the movable part (optical deflector) can be swung with higher precision.

[0020] (7) In the above deflection device, the selector may select one of the plurality of light-receiving elements that receives the light reflected by the object, based on a control signal from the swing controller, in response to a movement of the movable part of the first deflection mechanism around the first axis, during a period when the measurement light is not irradiated onto the reference reflecting member. In this case, the distance to the object can be accurately measured based on a signal from an appropriate light-receiving element that corresponds to the movement of the movable part.

[0021] (8) In the above deflection device, the first deflection mechanism may be configured to include a fixed portion supported by the second deflection mechanism so as to be rotatable around the second axis, and a beam portion that supports the movable portion on the fixed portion, and the beam portion may be driven to rotate in a twisting manner or oscillate in a bending manner by the drive unit, and function as the first axis.

[0022] A first deflection mechanism in which a movable part is supported on a fixed part via a beam part that is torsionally rotated by a drive part can be constructed to be extremely small and lightweight using, for example, MEMS (Micro Electro Mechanical Systems) technology, and can be driven to oscillate at high speed. For example, the movable part supported by the beam part can be repeatedly oscillated by utilizing the force generated by applying a voltage to a piezoelectric element or a magnetostrictive element. Another technique can be used in which a planar coil is formed on the movable part, and the Lorentz force is applied to the coil by an alternating current flowing through the coil and a magnetic field generated by a permanent magnet provided on the fixed part, thereby oscillating the movable part. Another technique can be used in which a movable part supported by a cantilever beam is flexed back and forth to oscillate. Using such techniques, a small, lightweight, and high-speed deflection device can be realized.

[0023] (9) The above-described deflection device may further include a contactless power supply unit having a power receiving unit arranged to rotate around the second axis in accordance with the rotation of the second deflection mechanism, and a power transmitting unit arranged opposite the power receiving unit on a common axis, and the contactless power supply unit may supply power from the power transmitting unit to the power receiving unit.

[0024] For example, when a current flows through a first coil serving as a transmitter arranged opposite a second coil serving as a receiver, an electromotive force is generated in the second coil by electromagnetic induction, and power can be supplied from the second coil to a drive unit of the first deflection mechanism that rotates around the second axis together with the second coil. In this case, power can be supplied from the first coil to the second coil contactlessly, eliminating the need for a slider structure with limited mechanical life. As a result, the life of the deflection device can be improved. The contactless power supply unit is not limited to the electromagnetic induction type described above, and may be, for example, based on other methods such as electric field coupling.

[0025] (10) In the above deflection device, the reference reflecting member may have a region with uniform reflectivity along the second axis, and the swing control unit may include an amplitude detection unit that detects the swing amplitude caused by the first deflection mechanism based on the light reflected by the light receiving unit from the region with uniform reflectivity of the reference reflecting member, and an amplitude control unit that controls the drive unit so that the swing amplitude detected by the amplitude detection unit becomes a predetermined swing amplitude. In this case, the swing amplitude of the movable part can be detected based on the light reflected from the region with uniform reflectivity, thereby preventing errors due to changes in the reflectivity of the reference reflecting member and enabling more accurate control of the movable part.

[0026] (11) The above deflection device may further include a synchronization control unit that adjusts the rotation period of the second deflection mechanism and / or the measurement period of the measurement light emitted from the light projector in synchronization with the oscillation period of the movable unit. If the oscillation period of the movable unit is changed to control the amplitude to a predetermined value, the measurement direction may change, making it impossible to obtain measurement values ​​corresponding to the required measurement direction. Furthermore, the number of required measurement values ​​within the oscillation period may increase or decrease. Even in such cases, if the synchronization control unit adjusts the measurement period of the measurement light and / or the rotation period of the second deflection mechanism based on a synchronization signal synchronized with the oscillation period of the movable unit, measurement values ​​corresponding to the required measurement direction may be obtained even if the oscillation period of the movable unit changes.

[0027] (12) An optical scanning device according to one aspect of the present invention includes the above-described deflection device. The above-described deflection device can be suitably used in an optical scanning device that scans image light from a projector or the like, for example.

[0028] (13) An optical distance measuring device according to one aspect of the present invention includes a deflection device and a control unit that calculates the distance to the object based on the measurement light and the reflected light. The deflection device can be suitably used, for example, in a device that measures the distance to an object using a TOF method. [Effects of the Invention]

[0029] According to the present invention, a deflection device, an optical scanning device, and an optical distance measuring device are provided that can control the oscillation amplitude of an optical deflection unit that modifies and reflects measurement light based on reflected light received by a light receiving unit having a plurality of light receiving elements arranged in a predetermined direction. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic diagram showing an optical distance measuring device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an optical distance measuring device according to one embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing the relationship between the measurement light and the deflection mirror. [Figure 4] FIG. 4 is a schematic diagram showing a light receiving lens and a light receiving section. [Figure 5] FIG. 5 is a schematic diagram showing the internal structure of the second deflection mechanism. [Figure 6] FIG. 6 is a cross-sectional view of the casing and the reference reflecting member corresponding to the AA portion of FIG. [Figure 7] FIG. 7 is a diagram showing the reference reflecting member in an expanded state. [Figure 8] FIG. 8 is a diagram showing the configuration of a part of the signal processing unit. [Figure 9] FIG. 9 is a diagram for explaining a method for detecting the amplitude of the movable part (deflection mirror) by the amplitude detection part. [Figure 10] FIG. 10 is a diagram for explaining a method for detecting the amplitude of the movable part (deflection mirror) by the amplitude detection part. DETAILED DESCRIPTION OF THE INVENTION

[0031] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A deflection device and an optical distance measuring device according to an embodiment of the present invention will be described below with reference to the drawings.

[0032] (Device configuration) 1 and 2 are schematic diagrams showing an optical distance measuring device according to one embodiment of the present invention. Note that FIG. 2 shows the optical distance measuring device 100 in a state where a first deflection mechanism 16, which will be described later, faces in the opposite direction to the optical distance measuring device 100 shown in FIG. 1. The optical distance measuring device 100 according to this embodiment is a device that measures the distance to an object using the TOF method. Specifically, the optical distance measuring device 100 projects measurement light into a space to be measured, receives light reflected by an object (hereinafter referred to as the object) in the space to be measured, and calculates the distance to the object based on the timing at which the reflected light is received.

[0033] 1 and 2, the optical distance measuring device 100 according to this embodiment includes a casing 10, a light projecting unit 12, and a deflection device 14. The light projecting unit 12 and the deflection device 14 are housed within the casing 10. In this embodiment, the casing 10 includes a cylindrical side wall 10a, a bottom plate 10b provided at one end of the side wall 10a, and a top plate 10c provided at the other end of the side wall 10a. An optical window 10d is formed in the side wall 10a to allow measurement light and reflected light to pass through.

[0034] Although not shown, the light projecting unit 12 includes a light emitting element such as a laser diode, a light source driving unit that pulse-drives the light emitting element, and a light projecting lens that shapes the measurement light (laser light) emitted from the light emitting element into a parallel beam. In this embodiment, the light emitting element of the light projecting unit 12 emits the measurement light in synchronization with a control signal output from a signal processing unit 24, which will be described later. The measurement light is pulsed light having a pulse width of, for example, several hundred picoseconds to several tens of nanoseconds.

[0035] The deflection device 14 includes a first deflection mechanism 16, a light-receiving unit 18, a second deflection mechanism 20, a reference reflecting member 22, and a signal processing unit 24. The light-projecting unit 12, the first deflection mechanism 16, and the light-receiving unit 18 are rotated around a second axis P2 by the second deflection mechanism 20. In this embodiment, the light-projecting unit 12 projects measurement light along the second axis P2 (described later). In this embodiment, the first deflection mechanism 16 is supported by the second deflection mechanism 20 so that a deflection mirror 28a (described later) is positioned on the second axis P2. Note that the first deflection mechanism 16 only needs to be supported by the second deflection mechanism 20; the deflection mirror 28a does not necessarily have to be positioned on the second axis P2. The light-receiving unit 18 is supported by the second deflection mechanism 20 at a position offset from the second axis P2. In this embodiment, the signal processing unit 24 is mainly housed in the rotating second deflection mechanism 20. The support base 47 is formed hollow and houses a part of the signal processing unit 24 therein.

[0036] As the configuration of the first deflection mechanism, a known MEMS mirror configuration can be used, so the configuration of the first deflection mechanism 16 will be briefly described below.

[0037] The first deflection mechanism 16 includes a movable part 28 having a deflection mirror 28a and a pair of beams (not shown) made of a metal material that support the movable part 28 so that the movable part 28 can swing about a first axis P1 (see FIG. 3) relative to a fixed part (not shown). The fixed part is supported by the second deflection mechanism 20. In this embodiment, the first deflection mechanism 16 repeatedly swings the movable part 28 about the first axis P1 using a piezoelectric element (or a magnetostrictive element) that serves as a drive unit provided in the fixed part. Alternatively, the first deflection mechanism 16 may be configured such that a Lorentz force generated by a magnetic circuit provided in the fixed part and a coil (not shown) provided in the movable part 28 as a drive unit repeatedly swings the movable part 28 about the first axis P1.

[0038] In this embodiment, the deflection mirror 28a included in the movable portion 28 has a configuration in which, for example, gold, aluminum, or the like is deposited on a glass substrate or a silicon substrate. In this embodiment, the deflection mirror 28a corresponds to the light deflection portion.

[0039] 3 is a schematic diagram showing the relationship between the measurement light and the deflection mirror 28a. In FIG. 3, the original position of the deflection mirror 28a is indicated by a solid line, and the position of the deflection mirror 28a after it has rotated from the original position around the first axis P1 is indicated by a dashed line. The measurement light projected from the light projector 12 onto the deflection mirror 28a and the measurement light reflected by the deflection mirror 28a in the original position are indicated by solid arrows, and the measurement light reflected by the deflection mirror 28a after it has rotated from the original position around the first axis P1 is indicated by a dashed arrow.

[0040] 3, in this embodiment, the measurement light can be deflected and scanned within a predetermined range by irradiating the deflection mirror 28a from the light projector 12 onto the deflection mirror 28a while driving the deflection mirror 28a (movable part 28) to swing about the first axis P1. For example, by swinging the deflection mirror 28a around the first axis P1 through a mechanical angle of ±7.5°, the measurement light deflected by the deflection mirror 28a can be scanned within a range of ±15° around the first axis P1.

[0041] 1, the light-receiving unit 18 includes a casing 40, a light-receiving lens 42, and a light-receiving section 44. The casing 40 is formed with an optical window (not shown) for transmitting light reflected by an object. The light-receiving lens 42 and the light-receiving section 44 are housed within the casing 40. The light-receiving lens 42 focuses the light reflected by the object toward the light-receiving section 44.

[0042] FIG. 4 is a schematic diagram showing the light-receiving lens 42 and the light-receiving unit 44. As shown in FIG. 4, in this embodiment, the light-receiving unit 44 has a plurality of light-receiving elements 44a. In the example shown in FIG. 4, the light-receiving unit 44 has 16 light-receiving elements 44a. The plurality of light-receiving elements 44a are arranged in a direction along the direction around the first axis P1 (see FIG. 1). In this embodiment, the plurality of light-receiving elements 44a are arranged in a one-dimensional direction along the direction around the first axis P1. For example, if the first axis P1 is parallel to the horizontal direction and the deflection mirror 28a scans the measurement light projected from the light-projecting unit 12 in the vertical direction, the plurality of light-receiving elements 44a are arranged in a line along the vertical direction and in a linear or arc shape when viewed from the direction along the first axis P1.

[0043] As described above, the measurement light (parallel light) projected from the light projecting unit 12 is projected onto the measurement target space at an angle (scanning angle) corresponding to the swing angle of the deflection mirror 28a. In this case, the reflected light reflected by the target object is incident on the light-receiving lens 42 at an angle corresponding to the scanning angle of the measurement light. In this embodiment, the light-receiving lens 42 and the light-receiving unit 44 are arranged so that one of the multiple light-receiving elements 44a receives the reflected light depending on the incident angle of the reflected light entering the light-receiving lens 42. In this embodiment, the reflected light (pulsed light) of the measurement light scanned in a predetermined direction by the deflection mirror 28a is incident on the multiple light-receiving elements 44a in sequence. As a result, the reflected light (pulsed light) is detected in sequence by the multiple light-receiving elements 44a. Note that the reflected light being incident on the multiple light-receiving elements 44a in sequence includes not only the case where the reflected light is incident on each light-receiving element 44a in sequence once, but also the case where the reflected light is incident on each light-receiving element 44a in sequence multiple times. For example, the reflected light may be incident on each light-receiving element 44a twice in sequence. The light-receiving unit 44 may be, for example, an APD array composed of a plurality of photodiodes. In this embodiment, a distance measurement calculation unit included in the signal processing unit 24 determines the time difference between the emission of the measurement light and the reception of the reflected light, and calculates the distance from the optical distance measuring device 100 to the object based on this time difference. In this embodiment, a selector 72 (described later) selects one of the plurality of light-receiving elements 44a in accordance with the swing angle of the movable unit 28 (deflection mirror 28a), and calculates the distance to the object based on the measurement light received by the selected light-receiving element 44a. Since a known method can be used to calculate the distance from the optical distance measuring device 100 to the object, a detailed description thereof will be omitted.

[0044] Fig. 5 is a schematic diagram showing the internal structure of the second deflection mechanism 20. As shown in Fig. 5, the second deflection mechanism 20 includes a stator 46 and a rotor 50 rotatably supported by the stator 46 via a hollow shaft 48. In this embodiment, a coil (not shown) is provided in the stator 46, and a magnet (not shown) is provided in the rotor 50, and the stator 46, shaft 48, and rotor 50 are configured as an outer rotor type motor 51.

[0045] 1, the stator 46 of the motor 51 is fixed to the casing 10 via a support base 47. Furthermore, the light projecting unit 12, the first deflection mechanism 16, and the casing 40 are fixed to the rotor 50 of the motor 51. In this embodiment, the light projecting unit 12 is fixed to the rotor 50 via a support member 13, and the first deflection mechanism 16 is fixed to the rotor 50 via a plurality of support members 17.

[0046] In this embodiment, the motor 51 is controlled by the signal processing unit 24. The motor 51 is provided with an encoder (not shown) for detecting the rotation angle of the rotor 50. A detection signal from the encoder is sent to the signal processing unit 24. The signal processing unit 24 is composed of an electronic circuit including a microcomputer and the like, and includes at least a control block for the light projecting unit 12, a control block for the first deflection mechanism 16, a control block for the light receiving unit 18, a control block for the second deflection mechanism 20, and a calculation block for performing distance measurement calculations. In this embodiment, the signal processing unit 24 corresponds to a control unit that calculates the distance to an object.

[0047] In this embodiment, by driving the motor 51, the casing 40 including the light-projecting unit 12, the first deflection mechanism 16, and the light-receiving unit 44 can be rotated about the second axis P2 relative to the casing 10. In this embodiment, the deflection mirror 28a, which is driven to swing about the first axis P1, is driven to rotate about the second axis P2 by the second deflection mechanism 20, so that the measurement light deflected and reflected by the deflection mirror 28a is scanned two-dimensionally.

[0048] 5, hollow disk-shaped support members 52, 54 that support coils 56, 58 are provided between the stator 46 and the rotor 50 in the motor 51. The support member 52 is fixed to the stator 46, and the support member 54 is fixed to the rotor 50. The coils 56, 58 are provided on the support members 52, 54 so as to face each other on a common axis. In this embodiment, the coils 56, 58 are provided so as to face each other on the second axis P2.

[0049] When the motor 51 is driven, the coil 58 rotates around the second axis P2 together with the support member 54 in conjunction with the rotation of the rotor 50. On the other hand, the coil 56 does not rotate because it is fixed to the stator 46 via the support member 52. In this embodiment, the coils 56 and 58 form an electromagnetic induction type contactless power supply unit 60. In this embodiment, the coil 56 corresponds to the power transmitting unit, and the coil 58 corresponds to the power receiving unit.

[0050] The coil 56 is electrically connected to the signal processing unit 24 (see FIG. 1) by wiring (not shown). The coil 58 is electrically connected to the signal processing unit 24 inside the second deflection mechanism 20 and to a drive unit that drives the movable unit 28 of the first deflection mechanism 16 to swing. As will be described in detail later, in the non-contact power supply unit 60 of this embodiment, an AC current of a predetermined frequency is applied to the coil 56. When an AC current is applied to the coil 56, an AC current of the predetermined frequency also flows through the coil 58, which rotates relative to the coil 56, due to electromagnetic induction. As a result, power is applied to the second deflection mechanism 20, which rotates around the second axis P2.

[0051] Although not shown, power may be supplied from the coil 58 of the non-contact power supply unit 60 to the light projector 12 and the light receiving unit 18 by, for example, wiring (contact-type transmission path). Signals may be transmitted and received between the non-contact power supply units 60 by, for example, a transmission path that combines optical fiber or an optical link with wiring using a slider or the like. In this embodiment, for example, the space inside the stator 46 and the shaft 48 can be used to provide the transmission path.

[0052] FIG. 6 is a cross-sectional view of the casing 10 and the reference reflecting member 22 corresponding to the AA portion of FIG. 2. A deflection mirror 28a is also shown in FIG. 6. As shown in FIG. 6, the reference reflecting member 22 is fixed to the inside of the casing 10. In this embodiment, the reference reflecting member 22 is disposed along the inner circumferential surface of the casing 10 when viewed in the direction along the second axis P2. The reference reflecting member 22 is disposed in an area of ​​the casing 10 where the optical window 10d is not formed. In this embodiment, a 270° range around the second axis P2 is set as the measurement area, and the optical window 10d is formed in this range. The remaining 90° range is set as the non-measurement area, and the reference reflecting member 22 is disposed in a portion of this area. The reference reflecting member 22 is disposed so as to reflect the measurement light deflected and reflected by the deflection mirror 28a. In this embodiment, the measurement light is reflected from the entire surface of the reference reflecting member 22 with equal reflectance.

[0053] Fig. 7 is a developed view of the reference reflecting member 22. In Fig. 7, the trajectory of the measurement light irradiated onto the reference reflecting member 22 when the movable part 28 (deflection mirror 28a) is oscillating at the target oscillation amplitude is indicated by a broken line. Fig. 7 also shows a plurality of light receiving elements 44a of the light receiving unit 44 to show the relationship between the irradiation position of the measurement light on the reference reflecting member 22 and the light receiving elements 44a that detect the reflected light reflected at that irradiation position. In this embodiment, the light receiving unit 44 has light receiving elements 44a for 1 to 16 channels.

[0054] 7, the length of the reference reflecting member 22 in the direction along the second axis P2 is slightly longer than the target amplitude A of the trajectory of the measurement light corresponding to the target oscillation amplitude of the deflection mirror 28a. The reference reflecting member 22 is positioned in the casing 10 so that the measurement light deflected and reflected by the deflection mirror 28a when the deflection mirror 28a is stopped is irradiated onto the center position of the reference reflecting member 22 in the direction along the second axis P2.

[0055] Fig. 8 is a diagram showing the configuration of a portion of the signal processing unit 24. As shown in Fig. 8, the signal processing unit 24 includes a swing control unit 70, a selection unit 72, and a synchronization control unit 74, which are configured by electronic circuits including a microcomputer, etc. The swing control unit 70 includes an amplitude detection unit 70a and an amplitude control unit 70b.

[0056] In this embodiment, when the light receiving unit 44 detects reflected light from the reference reflecting member 22, a detection signal is input from the light receiving unit 44 to the swing control unit 70. As will be described later, the amplitude detection unit 70a of the swing control unit 70 detects the amplitude of the movable unit 28 (deflection mirror 28a) based on the detection signal input from the light receiving unit 44. The amplitude detected by the amplitude detection unit 70a is input to the amplitude control unit 70b, and the frequency of the AC signal applied to the drive unit that drives the movable unit 28 of the first deflection mechanism 16 to swing is adjusted while maintaining it at a predetermined value so that the amplitude becomes the target swing amplitude of the movable unit 28. The control signal for the first deflection mechanism 16 output from the amplitude control unit 70b is applied to the drive unit that drives the movable unit 28 of the first deflection mechanism 16 to swing.

[0057] A method for detecting the amplitude of the movable part 28 (deflection mirror 28a) by the amplitude detection unit 70a will be described below. In this embodiment, during the period when the measurement light deflected and reflected by the deflection mirror 28a is irradiated onto the reference reflecting member 22, the selection unit 72 fixes the light receiving element 44a that receives the reflected light from the reference reflecting member 22 to one of the multiple light receiving elements 44a. The amplitude detection unit 70a includes a comparator that binarizes the reflected light from the reference reflecting member 22 received by the light receiving element 44a selected by the selection unit 72 using a predetermined threshold value. The time at which the detection signal of the comparator changes is calculated for each step of the discrete measurement number.

[0058] Fig. 9 is a diagram illustrating an example of a method for detecting the amplitude of the movable part 28 (deflection mirror 28a) by the amplitude detection unit 70a. The upper part of Fig. 9 shows a diagram in which the reference reflecting member 22 is unfolded. The upper part of Fig. 9 also shows, with a dashed line, the trajectory (amplitude A) of the measurement light irradiated onto the reference reflecting member 22 when the movable part 28 (deflection mirror 28a) is oscillating at a target oscillation amplitude, and the upper part of Fig. 9 also shows, with a dashed line, the trajectory (amplitude B) of the measurement light irradiated onto the reference reflecting member 22 when the movable part 28 (deflection mirror 28a) is oscillating at an amplitude smaller than the target oscillation amplitude. The lower part of Fig. 9 also shows the intensity of the light-receiving signal detected by the comparator of the amplitude detection unit 70a based on the reflected light received by the 12-channel light-receiving element 44a.

[0059] Ideally, it is preferable that the movable part 28 be continuously oscillated so that the amplitude of the trajectory of the measurement light irradiated on the reference reflecting member 22 becomes the target amplitude A. However, if the resonance frequency of the movable part 28 and the pair of beam parts supporting the movable part 28 changes due to fluctuations in the environmental temperature or the like, the amplitude of the measurement light deviates from the target amplitude A. When the resonance frequency becomes closer to the frequency of the control signal, the amplitude of the movable part 28 becomes larger, and when the resonance frequency becomes farther from the frequency of the control signal, the amplitude of the movable part 28 becomes smaller.

[0060] 9, when the movable part 28 is vibrating at a target oscillation amplitude (when the amplitude of the measurement light trajectory is target amplitude A), the received light intensity in a fixed channel (ch 12 in FIG. 9) is detected as two peak values ​​while the movable part 28 oscillates for one cycle. Here, if the center positions of the respective peak values ​​are defined as, for example, the center positions obtained from the respective peaks and are designated as times T11 and T12, then the difference value T13 (T12 - T11) can be set as a control target value correlated with the amplitude of the movable part 28. In addition, the center position (T14) between T11 and T12 can be detected as a control target value for the phase position of the movable part 28 (the time point at which the amplitude is maximum).

[0061] Similarly, when the movable part 28 is vibrating at an amplitude smaller than the target oscillation amplitude (when the amplitude of the measurement light trajectory is amplitude B), the times showing two peak values ​​in one oscillation cycle are detected as T21 and T22, respectively, and their difference value T23 (T22 - T21) is detected as a control value correlated with the amplitude of the movable part 28. In addition, the center position (T24) between times T21 and T22 can be detected as a control value for the phase position (time point at which the amplitude is maximum) of the movable part 28. In this way, the amplitude detection unit 70a can detect the oscillation amplitude and phase of the movable part 28 (deflection mirror 28a) using a signal based on the measurement light detected by the light-receiving element 44a selected by the selection unit 72.

[0062] When the difference value (e.g., T23 in FIG. 9) and the center position (e.g., T24 in FIG. 9) of the section detected by the amplitude detection unit 70a deviate from the target values ​​(T13 or T14), the amplitude control unit 70b variably controls the frequency while maintaining the signal applied to the driver of the first deflection mechanism 16 at a predetermined value so that the difference value and the center position become the target values. As a result, the amplitude of the movable unit 28 (deflection mirror 28a) is maintained at the predetermined target amplitude.

[0063] The amplitude control unit 70b includes a calculation circuit that calculates the deviation between the difference value detected by the amplitude detection unit 70a and a target value for the difference value, and the deviation between the center position and the target value for the center position, a feedback calculation unit exemplified by a PID calculation or the like that calculates a control value for the frequency of the applied signal based on the deviation, and a circuit that generates a control signal that adjusts the frequency of the applied signal in accordance with the control value calculated by the feedback calculation unit.

[0064] In this embodiment, for example, the amplitude detection unit 70a detects the above-mentioned difference value and center position based on the rotation speed and rotation position of the motor 51, which are based on the output of an encoder provided on the motor 51, and the amplitude control unit 70b determines the oscillation frequency and amplitude of the movable part 28 from the above-mentioned difference value and center position.

[0065] The light-receiving element 44a selected by the selector 72 during the period when the measurement light deflected and reflected by the deflection mirror 28a is irradiated onto the reference reflecting member 22 may be changed for each rotation or a predetermined number of rotations of the motor 51. Furthermore, if the difference between the oscillation amplitude of the deflection mirror 28a and the target oscillation amplitude is equal to or less than a threshold, the light-receiving element 44a that receives the measurement light when the oscillation amplitude of the deflection mirror 28a is maximized may be fixed as the light-receiving element 44a selected during the period when the measurement light deflected and reflected by the deflection mirror 28a is irradiated onto the reference reflecting member 22. In this embodiment, for example, a 1-channel or 16-channel light-receiving element 44a may be selected during the period when the measurement light deflected and reflected by the deflection mirror 28a is irradiated onto the reference reflecting member 22. In this case, for example, as shown in FIG. 10, one peak is detected during one oscillation cycle, and the time T3 of the peak interval (the time corresponding to T13 in FIG. 9) is a control value correlated with the oscillation amplitude of the movable part 28. Furthermore, the time T4 (=T14) at the center position of the peak is detected as the phase position of the movable part 28 (the time point at which the amplitude becomes maximum).

[0066] In this embodiment, the selector 72 selects one of the light receiving elements 44a as a light receiving element that receives the light reflected by the object, based on a control signal from the swing controller 70 (amplitude controller 70b), during a period when the measurement light deflected and reflected by the deflection mirror 28a is not irradiated onto the reference reflecting member 22 (a period when the measurement light is projected into the space to be measured). More specifically, the selector 72 selects one of the light receiving elements 44a in response to the movement of the movable part 28 of the first deflection mechanism 16 around the first axis P1.

[0067] In addition, in this embodiment, the synchronization control unit 74 adjusts the rotation speed and rotation phase (rotation period) of the second deflection mechanism 20 (motor 51), as well as the timing of turning on the measurement light (measurement period), so that the measurement light is emitted in a predetermined measurement direction in synchronization with the oscillation phase (oscillation period) of the movable part 28 detected by the oscillation control unit 70.

[0068] (Action and effect) In the optical distance measuring device 100 according to this embodiment, the swing control unit 70 can control the drive unit that drives the movable part 28 of the first deflection mechanism 16, based on the reflected light from the reference reflecting member 22 that is received by some of the multiple light receiving elements 44a of the light receiving unit 44. In this case, there is no need to provide a separate sensor for measuring the swing amplitude of the movable part 28 (deflection mirror 28a), so the manufacturing costs of the optical distance measuring device 100 can be reduced.

[0069] In particular, in this embodiment, the drive unit that drives the movable part 28 of the first deflection mechanism 16 can be controlled based on the reflected light from the reference reflecting member 22 that is received by the light-receiving element 44a selected by the selection unit 72. In this case, by appropriately selecting the light-receiving element 44a by the selection unit 72, the drive unit that drives the movable part 28 can be controlled with high precision.

[0070] In this embodiment, the light-receiving element 44a of the light-receiving unit 44 that receives the reflected light from the reference reflecting member 22 is fixed to one of the multiple light-receiving elements 44a during the period when the measurement light is irradiated onto the reference reflecting member 22. In this case, there is no need to perform switching control of the light-receiving element 44a during the period when the measurement light is irradiated onto the reference reflecting member 22, so the load on the selection unit 72 is reduced.

[0071] Furthermore, in this embodiment, during a period when the measurement light is not irradiated onto the reference reflecting member 22, the selector 72 selects one of the plurality of light receiving elements 44a that receive the light reflected by the object, based on a control signal from the swing controller 70, in accordance with the movement of the movable part 28 around the first axis P1. In this case, the distance to the object can be accurately measured based on the signal from the appropriate light receiving element 44a that corresponds to the movement of the movable part 28.

[0072] (Variation) In the above-described embodiment, the entire reference reflecting member 22 is configured to reflect the measurement light with the same reflectance. However, the reflectance of a portion of the reference reflecting member 22 may be lower than the reflectance of the other portions. However, it is preferable that the reference reflecting member 22 has an area with the same reflectance along the second axis P2. The light-receiving element 44a that receives the reflected light reflected by the reference reflecting member 22 during the period when the measurement light is irradiated onto the reference reflecting member 22 is preferably selected to receive the reflected light reflected by the area with the same reflectance. For example, referring to FIG. 7, when the selector 72 selects either the light-receiving elements 44a for channels 1 to 5 or the light-receiving elements 44a for channels 12 to 16 during the period when the measurement light is irradiated onto the reference reflecting member 22, the reflectance of the area of ​​the reference reflecting member 22 corresponding to the light-receiving elements 44a for channels 6 to 11 may be lower than the reflectance of the area corresponding to the light-receiving elements 44a for channels 1 to 5 and the light-receiving elements 44a for channels 12 to 16. The term "equal reflectance" does not only mean that the reflectance is completely equal, but also that the reflectance is equal to an extent that does not affect the detection accuracy of the measurement light by the light receiving element 44a.

[0073] In the above-described embodiment, one light-receiving element 44a is selected by the selector 72 during the period when the measurement light is irradiated onto the reference reflecting member 22. However, multiple light-receiving elements 44a may be selected. For example, two light-receiving elements 44a symmetrical with respect to the center position may be selected from the multiple light-receiving elements 44a arranged in a one-dimensional direction. For example, referring to FIG. 7, the 3ch light-receiving element 44a and the 14ch light-receiving element 44a may be selected. In this case, the movable unit 28 can be driven to swing with higher precision than when the movable unit 28 is controlled based on the detection result of one light-receiving element 44a.

[0074] Furthermore, in the above-described embodiment, the optical distance measuring device 100 is described as having one light receiving unit 18, but the optical distance measuring device 100 may also have multiple light receiving units 18. For example, the optical distance measuring device 100 may also have two light receiving units 18. In this case, the selector 72 may select the light reflected from the reference reflecting member 22 to be fixed to one light receiving element 44a of one of the two light receiving sections 44 of the two light receiving units 18 and one light receiving element 44a of the other light receiving section 44 during the period in which the measurement light is irradiated onto the reference reflecting member 22.

[0075] In addition, when the optical distance measuring device 100 has two light receiving sections 44 (light receiving units 18), the two light receiving sections 44 may be arranged so that, for example, one light receiving section 44 receives the reflected light of the measurement light deflected and reflected by the deflection mirror 28a when the movable section 28 oscillates from the original position to one side around the first axis P1, and the other light receiving section 44 receives the reflected light of the measurement light deflected and reflected by the deflection mirror 28a when the movable section 28 oscillates from the original position to the other side around the first axis P1. In this case, during the period when the measurement light is irradiated onto the reference reflecting member 22, one of the light-receiving elements 44a of one of the light-receiving units 44 selected by the selector 72 may be a light-receiving element 44a that receives reflected light based on the measurement light that is deflected and reflected by the deflection mirror 28a when the movable unit 28 swings a predetermined angle from the original position to one side around the first axis P1, and the other of the light-receiving elements 44a selected by the selector 72 may be a light-receiving element 44a that receives reflected light based on the measurement light that is deflected and reflected by the deflection mirror 28a when the movable unit 28 swings a predetermined angle from the original position to the other side around the first axis P1. In this case, the movable unit 28 can be driven to swing with higher precision.

[0076] In the above embodiment, the movable part 28 is supported by a pair of beams that are driven to rotate in a twisting manner by the drive part, but the movable part 28 may also be supported by a beam that is driven to swing in a bending manner by the drive part.

[0077] In the above embodiment, the deflection device according to the present invention is described as being used in the optical distance measuring device 100, but the deflection device according to the present invention may also be used in an optical scanning device that scans image light from a projector or the like, for example.

[0078] In the above embodiment, the reference reflecting member 22 is fixed inside the casing 10, but the casing 10 itself may be used as the reference reflecting member 22.

[0079] In the above-described embodiment, the light projecting unit 12 is supported by the second deflection mechanism 20 so as to rotate integrally with the first deflection mechanism 16 and the light receiving unit 18. However, the light projecting unit 12 does not have to be rotated about the second axis P2 by the second deflection mechanism 20. For example, the light projecting unit 12 may be supported by the casing 10 so as to be able to project measurement light onto the deflection mirror 28a along the second axis P2. [Explanation of symbols]

[0080] 10 Casing 12 Light projector 14 Deflection device 16 First deflection mechanism 18 Light receiving unit 20 Second deflection mechanism 22 Reference reflective member 24 Signal Processing Section 28 Moving parts 28a Deflecting mirror 44 Light receiving part 44a Photodetector 70 Swing control section 70a Amplitude detection unit 70b Amplitude control section 72 Selection section 74 Synchronization control section 100 Optical ranging device

Claims

1. a light projecting unit that emits measurement light; a first deflection mechanism including a light deflection unit that deflects and reflects the measurement light emitted from the light projecting unit, the first deflection mechanism including a movable unit that can swing around a first axis, and a drive unit that drives the movable unit to swing; a light receiving unit including a plurality of light receiving elements arranged in a predetermined direction along the direction around the first axis, the light receiving unit receiving, with any one of the light receiving elements, light reflected by an object out of the measurement light; a second deflection mechanism that rotates at least the first deflection mechanism and the light receiving unit about a second axis that is different from the first axis; a reference reflecting member onto which the measurement light emitted from the light projecting unit and deflected and reflected by the light deflecting unit is irradiated; a swing control unit that controls the drive unit based on reflected light from the reference reflecting member that is received by some of the plurality of light receiving elements of the light receiving unit; A deflection device comprising:

2. a selector for selecting a light receiving element to receive the reflected light from among the plurality of light receiving elements of the light receiving unit; 2. The deflection device according to claim 1.

3. the selection unit selects a light receiving element of the light receiving unit that receives the reflected light from the reference reflecting member so as to fix the light receiving element to one of the plurality of light receiving elements during a period in which the measurement light is irradiated onto the reference reflecting member.

3. The deflection device according to claim 2.

4. the selection unit selects, during a period in which the measurement light is irradiated onto the reference reflecting member, the light receiving elements of the light receiving unit that receive the reflected light from the reference reflecting member, so as to fix two of the plurality of light receiving elements arranged in the predetermined direction that are symmetrical with respect to a center position.

4. The deflection device according to claim 3.

5. The light receiving unit includes two light receiving units, the selection unit selects, during a period in which the measurement light is irradiated onto the reference reflecting member, the light receiving element of the light receiving unit that receives the reflected light from the reference reflecting member, so as to fix the light receiving element of one of the two light receiving units and the light receiving element of the other of the two light receiving units.

3. The deflection device according to claim 2.

6. the movable portion swings from an original position to one side and the other side around the first axis, During a period in which the measurement light is irradiated onto the reference reflecting member, the one light-receiving element of the one light-receiving unit selected by the selection unit is a light-receiving element that receives reflected light based on the measurement light that is deflected and reflected by the optical deflection unit when the movable unit swings from the original position to the one side around the first axis by a predetermined angle, During a period in which the measurement light is irradiated onto the reference reflecting member, the one light receiving element of the other light receiving unit selected by the selection unit is a light receiving element that receives reflected light based on the measurement light deflected and reflected by the light deflection unit when the movable unit swings from the original position to the other side around the first axis by the predetermined angle.

6. The deflection device according to claim 5.

7. the selection unit selects, based on a control signal from the swing control unit, one of the plurality of light-receiving elements that receives the reflected light reflected by the object, in response to a movement of the movable unit of the first deflection mechanism around the first axis, during a period when the measurement light is not irradiated onto the reference reflecting member.

3. The deflection device according to claim 2.

8. the first deflection mechanism includes a fixed portion supported by the second deflection mechanism so as to be rotatable about the second axis, and a beam portion that supports the movable portion on the fixed portion, The beam portion is driven to rotate in a torsional manner or to swing in a flexural manner by the driving portion, and functions as the first axis.

2. The deflection device according to claim 1.

9. a contactless power supply unit including a power receiving unit arranged to rotate around the second axis in accordance with the rotation of the second deflection mechanism, and a power transmitting unit arranged to face the power receiving unit on a common axis, The non-contact power supply unit supplies power from the power transmission unit to the power receiving unit.

2. The deflection device according to claim 1.

10. the reference reflecting member has a region with uniform reflectance along the second axis; The deflection device according to claim 1, wherein the swing control unit includes an amplitude detection unit that detects the swing amplitude caused by the first deflection mechanism based on the reflected light received by the light receiving unit from an area of ​​the reference reflecting member having the same reflectivity, and an amplitude control unit that controls the drive unit so that the swing amplitude detected by the amplitude detection unit becomes a predetermined swing amplitude.

11. a synchronization control unit that adjusts the rotation period of the second deflection mechanism and / or the measurement period of the measurement light emitted from the light projecting unit in synchronization with the oscillation period of the movable unit; 2. The deflection device according to claim 1.

12. An optical scanning device comprising the deflection device according to any one of claims 1 to 11.

13. 12. An optical distance measuring device comprising: a deflection device according to claim 1; and a control unit that calculates a distance to the object based on the measurement light and the reflected light.

Images