Swing control device for optical scanning device, photoelectric sensor, and optical ranging device

Abstract

Provided is a swing control device for an optical scanning device, wherein the swing control device swings, around a swing axis, a movable member provided with a reflection mirror for scanning measurement light on the surface thereof. A monitor light receiving element, which irradiates a monitor light reflection member provided on the rear surface of the movable member with monitor light and receives the reflected monitor light, is configured with a one-dimensional image sensor disposed in a direction intersecting the swing axis. The swing control device comprises a swing control unit that controls the swing of the movable member on the basis of the swing characteristics of the movable member detected on the basis of the peak position of the monitor light detected by the one-dimensional image sensor. In the monitor light reflection member, a high reflectance region having a high reflectance and a low reflectance region having a reflectance lower than that of the high reflectance region are formed along the direction intersecting the swing axis, and the area SA of the high reflectance region is set to be smaller than the area SB of the low reflectance region.

Description

Oscillation control device, photoelectric sensor, and optical distance measuring device for an optical scanning device

[0001] The present invention relates to an oscillation control device, a photoelectric sensor, and an optical distance measuring device for an optical scanning device that reflects measurement light incident on a reflection mirror as scanning light by controlling the oscillation of a movable member having a reflection mirror around at least one oscillation axis.

[0002] Patent Document 1 discloses a micromechanical device including at least one movable part, a fixed part, and a pair of beam parts that support the movable part on the fixed part from both sides, and the movable part can oscillate around an axis with the beam part as a torsional rotation axis.

[0003] In the micromechanical device, a coil is formed on the movable part, a magnetic field forming part is provided on the fixed part, and the movable part is configured to oscillate by an electromagnetic force generated by a current flowing through the coil and a magnetic field formed by the magnetic field forming part. The beam part has a function of supporting the movable part, a function as a conductor for energizing the coil, and a function as a spring for returning the movable part to a reference position.

[0004] And, as an oscillation control device for controlling the oscillation of the movable part of the above-described micromechanical device, monitor light guided from the movable part and having an angle that changes as the movable part oscillates along an optical axis is detected from a direction deviated in the oscillation direction with respect to the oscillation center direction of the movable part. A monitor light receiving part, an amplitude detection part including an amplitude detection circuit that detects two sections, a long-period section and a short-period section, that constitute one oscillation cycle of the movable part based on the monitor light detected by the monitor light receiving part, and the long-period section detected by the amplitude detection part And an amplitude control unit that variably controls the frequency while maintaining the current value of the applied current to the coil so that the time ratio of the short-period section becomes a target value.

[0005] Japanese Patent Application Laid-Open No. 2014-95837

[0006] In the oscillation control device disclosed in Patent Document 1, an LED is used as a light source of monitor light, and a photodiode or a phototransistor is used as a monitor light receiving part.

[0007] However, elements such as LEDs and photodiodes have different offset characteristics for each component. The intensity of LED output light fluctuates with ambient temperature, and the sensitivity of photodiodes changes with ambient temperature. Therefore, a time-consuming and complicated adjustment process was required, which involved individually testing the temperature characteristics of LEDs and photodiodes for each oscillation control device and preparing correction data based on the test results.

[0008] Furthermore, because the output of the LEDs decreases over time, there was also the problem that the oscillation characteristics of the movable parts changed over the years.

[0009] In view of the above-mentioned problems, the object of the present invention is to provide an oscillation control device for an optical scanning device, a photoelectric sensor, and an optical distance measuring device that eliminate the need for complicated adjustment processes and are not affected by aging.

[0010] To achieve the above objective, the first characteristic configuration of the oscillation control device for an optical scanning device according to the present invention is an oscillation control device for an optical scanning device that controls the oscillation of a movable member having a reflective mirror on one side around at least one oscillation axis, thereby reflecting the measurement light incident on the reflective mirror as scanning light, comprising: a monitor light source that irradiates the other side of the movable member with monitor light; a monitor light reflecting member provided on the other side that reflects the monitor light; and a plurality of photoelectric conversion elements arranged along a direction intersecting the oscillation axis, wherein the measurement light reflected by the monitor light reflecting member is reflected as scanning light as the oscillation of the movable member. The device comprises a monitor light receiving element that receives monitor light, a oscillation detection unit that detects the oscillation angle of the movable member based on the position of the photoelectric conversion element that shows a peak in the monitor light received by the monitor light receiving element, and an oscillation control unit that controls the oscillation of the movable member based on the oscillation angle detected by the oscillation detection unit, wherein the monitor light reflecting member has a high-reflectance region and a low-reflectance region with a lower reflectance than the high-reflectance region formed along a direction intersecting the oscillation axis, and is set such that the area SA of the high-reflectance region is smaller than the area SB of the low-reflectance region.

[0011] Since the monitor light reflected by the monitor light reflecting member is detected by multiple photoelectric conversion elements arranged in a direction intersecting the oscillation axis, the oscillation angle of the movable member can be detected based on the position of the photoelectric conversion element that shows a peak in the monitor light. Even if the intensity of the monitor light fluctuates, it is sufficient to detect a peak at any position of the multiple photoelectric conversion elements arranged in a direction intersecting the oscillation axis, so it is not affected by variations in the elements or degradation over time. In this case, a high-reflection region and a low-reflection region are formed in the monitor light reflecting member in a direction intersecting the oscillation axis, and the area SA of the high-reflection region is set to be smaller than the area SB of the low-reflection region, so the position of the photoelectric conversion element that shows a peak can be detected with high accuracy.

[0012] The second characteristic configuration is that, in addition to the first characteristic configuration described above, the monitor light reflecting member has a length LA of the high-reflectivity region along the direction intersecting the oscillation axis that is set to be sufficiently shorter than the length LB of the low-reflectivity region along the direction intersecting the oscillation axis.

[0013] A high signal-to-noise ratio is obtained between the reflected light from the high-reflectivity region and the reflected light from the low-reflectivity region of the monitoring light, allowing for accurate detection of the position of the photoelectric conversion element showing a peak.

[0014] The third characteristic configuration is that, in addition to the first or second characteristic configuration described above, the monitor light reflecting member has the high-reflectivity region formed in the center of the other surface, and the low-reflectivity region formed around the high-reflectivity region.

[0015] Because a highly reflective region is formed in the center of the other surface, the position of the photoelectric conversion element showing the peak becomes symmetrical with respect to the oscillation axis, regardless of the oscillation direction.

[0016] The fourth characteristic configuration is that, in addition to the third characteristic configuration described above, the high-reflectivity region is formed as a band-shaped region along the oscillation axis with a width of at least the length LA, and the monitor light receiving element is composed of a one-dimensional image sensor.

[0017] When there is only one oscillation axis, a one-dimensional image sensor is preferably used as the monitor light receiving element, in which photoelectric conversion elements are arranged in a direction intersecting the oscillation axis.

[0018] The fifth characteristic configuration is that, in addition to the third characteristic configuration described above, the optical scanning device is configured to swing around two intersecting pivot axes, the high-reflectivity region is formed along each of the pivot axes as a band-shaped region with a width of at least the length LA, and the monitor light receiving element is composed of a two-dimensional image sensor.

[0019] In the case of two axes of oscillation that intersect each other, a two-dimensional image sensor is preferably used as a monitor light receiving element, in which photoelectric conversion elements are arranged in a direction intersecting the oscillation axes.

[0020] The sixth characteristic configuration is that, in addition to the first or second characteristic configuration described above, the high-reflectivity region is composed of a specular reflective member, and the low-reflectivity region is composed of a diffuse reflective member with a black surface.

[0021] By configuring the highly reflective region with a specular reflective material, the spread of light rays from the monitor light is suppressed, allowing for accurate detection of the position of the photoelectric conversion element showing a peak.

[0022] The seventh characteristic configuration is that, in addition to the first or second characteristic configuration described above, the monitor light source is composed of LED elements.

[0023] Even when using LED elements as the monitoring light source, the system is not affected by aging degradation, making it possible to realize an inexpensive oscillation control device.

[0024] The eighth characteristic configuration is that, in addition to the first or second characteristic configuration described above, the monitor light receiving element further includes a bandpass filter that transmits only light within the frequency band of the monitor light.

[0025] Even when measurement light or ambient light enters the monitor light receiving element as stray light, the bandpass filter blocks the stray light, thus preventing malfunctions caused by stray light.

[0026] The ninth characteristic configuration is that, in addition to the first or second characteristic configuration described above, the oscillation detection unit includes an oscillation state detection unit that detects the angular amplitude and phase when the movable member is oscillating, and the oscillation control unit includes a synchronization signal output unit that adjusts the measurement timing by the measurement light in synchronization with the angular amplitude and phase detected by the oscillation state detection unit.

[0027] Based on the angular amplitude and phase of the oscillation of the movable member detected by the oscillation state detection unit, and based on the synchronization signal output from the oscillation control unit, the timing of measurement using the measurement light can be accurately determined.

[0028] The tenth characteristic configuration is that, in addition to the ninth characteristic configuration described above, the oscillation state detection unit samples the output signal of each of the photoelectric conversion elements at intervals shorter than the oscillation period of the movable member, and fits a normal distribution to the output signals to identify the position of the photoelectric conversion element that shows a peak in the monitor light, and detects the angular amplitude and the phase.

[0029] Even if one of the multiple photoelectric conversion elements is affected by a disturbance, fitting a normal distribution to the output signal allows for accurate identification of the location of the photoelectric conversion element exhibiting a peak.

[0030] The eleventh characteristic configuration is that, in addition to the ninth characteristic configuration described above, the oscillation state detection unit generates an angular amplitude waveform indicating the oscillation state of the movable member based on the position of the photoelectric conversion element showing a peak in the monitor light and the timing of its reception, and detects the angular amplitude and phase of the movable member by fitting a sine function to the angular amplitude waveform.

[0031] The oscillation state detection unit can generate an angular amplitude waveform using discrete values ​​that indicate the oscillation state of the movable member, based on the position of the photoelectric conversion element showing a peak in the monitored light and the timing of its reception. Since the oscillation state of the movable member can be represented by a sine function, the angular amplitude and phase of the movable member can be accurately obtained by fitting a sine function to the angular amplitude waveform.

[0032] The characteristic configuration of the photoelectric sensor according to the present invention is that it comprises: an oscillation control device for an optical scanning device having the first or second characteristic configuration described above; the optical scanning device; a light-emitting unit that causes the measurement light to enter the optical scanning device; a light-receiving unit that receives the reflected light reflected by the object from which the scanning light was reflected; and a system control device that controls the optical scanning device, the oscillation control device, the light-emitting unit, and the light-receiving unit to evaluate the reflected light detected by the light-receiving unit.

[0033] The characteristic configuration of the optical distance measuring device according to the present invention is that it comprises: an oscillation control device for an optical scanning device having the first or second characteristic configuration described above; the optical scanning device; a light-emitting unit that emits the measurement light into the optical scanning device; a light-receiving unit that receives the reflected light reflected by the object from the scanning light; and a system control device that controls the optical scanning device, the oscillation control device, the light-emitting unit, and the light-receiving unit to calculate the distance to the object based on the measurement light and the reflected light.

[0034] As described above, the present invention makes it possible to provide an oscillation control device for an optical scanning device, a photoelectric sensor, and an optical distance measuring device that eliminate the need for complicated adjustment processes and are not affected by aging.

[0035] Figure 1 is a perspective view of an optical distance measuring device incorporating the oscillation control device of the optical scanning device of the present invention. Figure 2A is an explanatory diagram of the optical scanning device in plan view. Figure 2B is an explanatory diagram of the optical scanning device in side view. Figure 2C is an explanatory diagram of the optical scanning device in bottom view. Figure 3A is an explanatory diagram showing the output characteristics of the photoelectric conversion element and the fitting of a normal distribution. Figure 3B is an explanatory diagram of the output characteristics of the photoelectric conversion element that detects the monitor light. Figure 3C is an explanatory diagram of the output characteristics of the photoelectric conversion element that detects the monitor light. Figure 3D is an explanatory diagram of the output characteristics of the photoelectric conversion element that detects the monitor light. Figure 3E is an explanatory diagram of the output characteristics of the photoelectric conversion element that detects the monitor light. Figure 3F is an explanatory diagram of the output characteristics of the photoelectric conversion element that detects the monitor light. Figure 4 is an explanatory diagram showing the phase and angular amplitude characteristics of the monitor light obtained from the output characteristics of the photoelectric conversion element. Figure 5A is an explanatory diagram of the optical scanning device in plan view showing another embodiment. Figure 5B is an explanatory diagram of the optical scanning device in bottom view showing another embodiment.

[0036] The oscillation control device, photoelectric sensor, and optical distance measuring device of the optical scanning device according to the present invention will be described below with reference to the drawings. As shown in Figure 1, the optical distance measuring device (photoelectric sensor) 100 comprises an optical scanning device 10, an oscillation control device 20, a light-emitting unit 30 that emits measurement light into the optical scanning device 10, a light-receiving unit 40 that receives reflected light reflected by the object T from the scanning light, and a system control device 50. The system control device 50 is composed of a microcomputer equipped with an integrated circuit that controls the optical scanning device 10, the oscillation control device 20, the light-emitting unit 30, and the light-receiving unit 40 to calculate the distance to the object T based on the measurement light and reflected light.

[0037] The system control device 50 calculates the distance from the optical distance measuring device 100 to the object T based on either the TOF (Time of Flight) method or the AM (amplitude modulation) method. In this embodiment, TOF is used. The system control device 50 also functions as a photoelectric sensor when it performs a function to evaluate characteristics such as the intensity of reflected light detected by the light receiving unit 40, instead of calculating the distance to the object T.

[0038] The TOF (Time-of-Flight) method calculates the distance D from the optical distance measuring device 100 to the object T located within the monitored area based on the detection time difference Δt between the measurement light, which is a pulsed laser beam output towards the monitored area, and the reflected light from the object T relative to the measurement light. The distance D is calculated using the following formula, where C is the speed of light: D = Δt・C / 2

[0039] The AM method calculates the distance D from the optical distance measuring device 100 to the object T located within the monitored area based on the phase difference Δφ between the amplitude-modulated measurement light output towards the monitored area and the reflected light from the object T. The distance D is calculated using the following formula: D = Δφ・C / (4π・f) where C is the speed of light and f is the modulation frequency.

[0040] The light-emitting unit 30 includes a light source 31 that outputs infrared laser light as measurement light, an optical system 32 such as a collimator lens, and a reflective mirror 33 that guides the measurement light to the optical scanning device 10. The light-receiving unit 40 includes a photodiode as a light-receiving element 41, a reflective mirror 43 that reflects the light reflected from the object T via the optical scanning device 10 toward the light-receiving element 41, and an optical system 42 such as a focusing lens that focuses the reflected light toward the light-receiving element 41.

[0041] As shown in Figures 2A, 2B, and 2C, the optical scanning device 10 is fixed to the frame 11A so as to be swingable via a frame 11A, a rectangular movable member 12, and a pair of beams 11B on which a pair of opposing sides of the movable member 12 are made of a metallic elastic material. A coil made of copper foil is printed on one side of the movable member 12, and a reflective mirror 11 is placed on it. Inside the frame 11A, a pair of permanent magnets 11C are positioned opposite the other opposing side of the movable member 12.

[0042] When an alternating voltage is applied to the coil via a pair of beam sections 11B that function as electrodes, the alternating current flowing through the coil and the magnetic field formed by the permanent magnet 11C on the frame 11A create a Lorentz force that acts on the coil, causing the beam sections 11B to twist and deform, and the movable member 12 supported by the beam sections 11B to repeatedly swing.

[0043] The oscillation control device 20 applies an alternating current of a predetermined intensity at a predetermined frequency to a coil provided on the movable member 12, thereby driving the reflective mirror 11 provided on the optical scanning device 10 to oscillate around a single oscillation axis P, and reflects the measurement light incident on the reflective mirror 11 toward the space to be measured as scanning light.

[0044] The swing control device 20 includes a monitor light reflecting member 13 provided on the other surface of the movable member 12, a monitor light source 14 formed of an LED that irradiates monitor light toward the monitor light reflecting member 13, a monitor light receiving element 15 that receives the monitor light reflected from the monitor light reflecting member 13, a swing detection unit 17 that detects the swing angle of the movable member 12, and a swing control unit 18 that swing-controls the movable member 12 based on the swing angle detected by the swing detection unit 17. The swing detection unit 17 can be constituted by a microcomputer provided with an integrated circuit that executes operations necessary for detecting the swing angle of the movable member 12, and the swing control unit 18 can be constituted by a microcomputer provided with an integrated circuit that executes operations necessary for appropriately swing-controlling the movable member 12.

[0045] The monitor light receiving element 15 includes a plurality of photoelectric conversion elements arranged along a direction intersecting, preferably orthogonal to, the swing axis P, and is constituted by a one-dimensional image sensor that receives the monitor light reflected by the monitor light reflecting member 13 as the movable member 12 swings. A CMOS image sensor is preferably used as the one-dimensional image sensor. In the present embodiment, an LED element having an emission wavelength of 527 nm is used as the monitor light source 14, and a CMOS linear image sensor having a line rate of 67568 lines / S, a pixel number of 128, a pixel pitch of 63.5 μm, and a maximum sensitivity of 700 nm is used.

[0046] The swing detection unit 17 detects the swing angle of the movable member 12 based on the position of the photoelectric conversion element indicating the peak among the monitor light received by the monitor light receiving element 15.

[0047] FIG. 3A shows the output voltage characteristics of the photoelectric conversion elements constituting the monitor light receiving element 15. In a state where the movable member 12 has stopped at the neutral position, a peak of the reflected light is detected at the central portion along the arrangement direction of the photoelectric conversion elements, and the output gradually decreases at both ends. At this time, the output of each photoelectric conversion element may be affected by external disturbance noise or the like, and it may be difficult to specify the pixel indicating the accurate peak position. Therefore, as will be described later, the position of the photoelectric conversion element indicating the peak is specified by fitting a normal distribution function to the output signal.

[0048] FIGS. 3B to 3F show the change in the rocking posture of the movable member 12 and the output characteristics of the photoelectric conversion element constituting the monitor light receiving element 15 when in the rocking posture. That is, the rocking posture of the movable member 12 can be grasped based on the position where the output of the photoelectric conversion element peaks.

[0049] The sampling period of the monitor light by the monitor light receiving element 15 is set based on the rocking frequency of the movable member 12 (reflective mirror 11). For example, when the rocking frequency is 800 Hz, sampling is performed at a sampling frequency of 1.6 kHz or higher based on the sampling theorem. However, it is not necessary to measure the rocking frequency for each rocking period of the movable member 12. By sampling over a plurality of periods and adopting the average value, it is also possible to set the sampling frequency lower than the rocking frequency.

[0050] As shown in FIG. 2C, the monitor light reflecting member 13 is formed with a high reflection region Ah having a high reflectivity and a low reflection region Al having a lower reflectivity than the high reflection region Ah along the direction intersecting the rocking axis P, and the area SA of the high reflection region Ah is set to be smaller than the area SB of the low reflection region Al.

[0051] The high reflection region Ah is constituted by a specular reflection member, and the low reflection region Al is constituted by a diffuse reflection member with a black surface. By constituting the high reflection region Ah with a specular reflection member, the spread of the reflected monitor light is suppressed, and the position of the photoelectric conversion element showing the peak can be accurately detected.

[0052] The rocking angle of the movable member 12 can be detected based on the position of the photoelectric conversion element showing the peak among the monitor lights. Even when the intensity of the monitor light fluctuates, it is only necessary to detect a peak at any position of the plurality of photoelectric conversion elements arranged along the direction intersecting the rocking axis, so it is not affected by variations or aging deterioration of elements such as LEDs.

[0053] The monitor light reflecting member 13 has a high-reflection region Ah formed along the pivot axis P in the center of the other surface, and a low-reflection region Al formed around the high-reflection region Ah. Furthermore, the length LA of the high-reflection region Ah along the direction intersecting the pivot axis P is set to be sufficiently shorter than the length LB of the low-reflection region Al along the direction intersecting the pivot axis P.

[0054] In order for the output signal of the monitor light receiving element 15 to maintain a normal distribution characteristic with respect to the monitor light, the length LA of the high-reflectivity region Ah is preferably set to 1 mm or less, in which case the length LB of the low-reflectivity region Al is several tens of mm. If the length LA of the high-reflectivity region Ah exceeds 1 mm, the output signal of the monitor light receiving element 15 deviates from the normal distribution, and the peak position cannot be accurately detected.

[0055] A high signal-to-noise ratio is obtained between the reflected light from the high-reflectivity region Ah and the reflected light from the low-reflectivity region Al of the monitoring light, allowing for accurate detection of the position of the photoelectric conversion element showing a peak. Furthermore, because the high-reflectivity region Ah is formed in the center of the other surface, the position of the photoelectric conversion element showing a peak remains symmetrical with respect to the oscillation axis regardless of the oscillation direction.

[0056] The monitor light receiving element 15 is further equipped with a bandpass filter 16 that transmits only light within the frequency band of the monitor light (center wavelength 527 nm). Even when measurement light or ambient light enters the monitor light receiving element 15 as stray light, the bandpass filter 16 blocks the stray light, thus preventing malfunctions caused by stray light.

[0057] The oscillation detection unit 17 includes an oscillation state detection unit that detects the angular amplitude and phase of the movable member 12 during oscillation. The oscillation control unit 18 controls the frequency, intensity, or phase of the alternating current applied to the coil provided on the movable member 12, or a combination thereof, so that the angular amplitude and phase detected by the oscillation state detection unit are maintained at target values. The oscillation control unit 18 also includes a synchronization signal output unit that adjusts the measurement timing by the measurement light in synchronization with the angular amplitude and phase detected by the oscillation state detection unit. Based on the synchronization signal, the measurement timing by the measurement light can be accurately obtained. The system control device 50 controls the light source 31 based on the synchronization signal output from the synchronization signal output unit, thereby calculating the scanning direction of the measurement light and the distance to the target object T located in the scanning direction.

[0058] The oscillation state detection unit samples the output signal of each photoelectric conversion element at intervals shorter than the oscillation period of the movable member 12, and by fitting a normal distribution to the output signals, it identifies the position of the photoelectric conversion element showing a peak in the monitored light and detects its angular amplitude and phase. Since the formula defining the normal distribution is a nonlinear formula, the least squares method cannot be applied directly, so an algorithm called Guo's algorithm can be used as an algorithm to perform the least squares method with a normal distribution.

[0059] Figure 3A plots the sampling data for each pixel before fitting. Due to noise and other influences, the peak position cannot be accurately determined. Therefore, as shown by the thin lines in Figure 3A, fitting the sampling data allows for accurate determination of the peak position. Even if one of the multiple photoelectric conversion elements is affected by disturbances, fitting a normal distribution to the output signal allows for accurate identification of the location of the photoelectric conversion element showing the peak.

[0060] The oscillation state detection unit generates an angular amplitude waveform indicating the oscillation state of the movable member 12 based on the position of the photoelectric conversion element showing a peak in the monitored light and the timing of its reception. By fitting a sine function to the angular amplitude waveform, the unit detects the angular amplitude and phase of the movable member 12.

[0061] The oscillation state detection unit can generate an angular amplitude waveform using discrete values ​​that indicate the oscillation state of the movable member 12, based on the position of the photoelectric conversion element showing a peak in the monitored light and the timing of its reception. Since the oscillation state of the movable member 12 can be represented by a sine function, the angular amplitude and phase of the movable member 12 can be accurately obtained by fitting a sine function to the angular amplitude waveform.

[0062] From the pixel positions showing the peak output values ​​shown in Figures 3B to 3F and the data acquisition time, plotting the phase angle of the data acquisition time on the horizontal axis and the pixel positions showing the peak values ​​on the vertical axis yields the angular amplitude waveform shown by the black dots in Figure 4. Fitting a sine function to this angular amplitude waveform yields the sine waveform shown by the solid line in Figure 4. The least squares method is used for fitting, substituting the phase data and amplitude data of multiple plotted points into the sine function y = asinx + bcosx, and finding the minimum value of the sum of squared errors, which is the difference between the left and right sides, yields the fitted sine function.

[0063] In the embodiments described above, a one-dimensional optical scanning device 10 in which the movable member 12 swings around a single pivot axis P was described. However, as shown in Figure 5A, the present invention can also be applied to a two-dimensional optical scanning device 10 in which the movable member 12 swings around two pivot axes P1 and P2 that intersect (preferably orthogonal) with each other.

[0064] The movable member 12 is oscillated around the pivot axis P1 by the twisting of a pair of beams 11B relative to the frame 11A, and the frame 11A is oscillated around the pivot axis P2 by the twisting of a pair of beams 11E relative to the frame 11D. As a result of the reflective mirror 11 on the movable member 12 oscillating two-dimensionally around the pivot axes P1 and P2, the measurement light is scanned two-dimensionally in two intersecting directions.

[0065] In this case, it is preferable that the monitor light reflecting member 13 provided on the other side of the movable member 12 has a high reflectivity region Ah formed as a band-shaped region with a width of at least LA along each of the oscillating axes P1 and P2. Furthermore, it is preferable that the monitor light receiving element 15 employs a two-dimensional image sensor.

[0066] The embodiments described above illustrate examples of the oscillation control device, photoelectric sensor, and optical distance measuring device of the optical scanning device according to the present invention, and the technical scope of the present invention is not limited by this description.

[0067] 10: Optical scanning device 11: Reflective mirror 12: Movable member 13: Monitor light reflecting member 14: Monitor light source 15: Monitor light receiving element 17: Oscillation detection unit 18: Oscillation control unit 20: Oscillation control device 30: Light emitting unit 31: Light source 40: Light receiving unit 41: Light receiving element 50: System control device 100: Optical distance measuring device (photoelectric sensor)

Claims

1. An oscillation control device for an optical scanning device that causes a movable member having a reflective mirror on one side to reflect measurement light incident on the reflective mirror as scanning light by controlling the oscillation of the movable member around at least one oscillation axis, comprising: a monitor light source that irradiates the other side of the movable member with monitor light; a monitor light reflecting member provided on the other side and reflecting the monitor light; a monitor light receiving element comprising a plurality of photoelectric conversion elements arranged along a direction intersecting the oscillation axis, which receives the monitor light reflected by the monitor light reflecting member as the movable member oscillates; an oscillation detection unit that detects the oscillation angle of the movable member based on the position of the photoelectric conversion element showing a peak in the monitor light received by the monitor light receiving element; and an oscillation control unit that controls the oscillation of the movable member based on the oscillation angle detected by the oscillation detection unit. The oscillation control device for an optical scanning device, wherein the monitor light reflecting member has a high-reflectance region and a low-reflectance region with lower reflectance than the high-reflectance region formed along a direction intersecting the oscillation axis, and is set such that the area SA of the high-reflectance region is smaller than the area SB of the low-reflectance region.

2. The oscillation control device for an optical scanning apparatus according to claim 1, wherein the length LA of the high-reflectivity region of the monitor light reflecting member along the direction intersecting the oscillation axis is set to be sufficiently shorter than the length LB of the low-reflectivity region along the direction intersecting the oscillation axis.

3. The oscillation control device for an optical scanning apparatus according to claim 1 or 2, wherein the monitor light reflecting member has the high-reflectivity region formed in the center of the other surface, and the low-reflectivity region formed around the high-reflectivity region.

4. The oscillation control device for an optical scanning apparatus according to claim 3, wherein the high-reflectivity region is formed along the oscillation axis as a strip-shaped region with a width of at least the length LA, and the monitor light receiving element is composed of a one-dimensional image sensor.

5. The oscillation control device for an optical scanning device according to claim 3, wherein the optical scanning device is configured to pivot around two mutually intersecting pivot axes, the high-reflectivity region is formed along each of the pivot axes as a strip-shaped region with a width of at least the length LA, and the monitor light receiving element is configured as a two-dimensional image sensor.

6. The oscillation control device for an optical scanning apparatus according to claim 1 or 2, wherein the high-reflectivity region is composed of a specular reflective member and the low-reflectivity region is composed of a diffuse reflective member with a black surface.

7. The oscillation control device for an optical scanning device according to claim 1 or 2, wherein the monitor light source is composed of LED elements.

8. The oscillation control device for an optical scanning apparatus according to claim 1 or 2, wherein the monitor light receiving element further comprises a bandpass filter that transmits only light in the frequency band of the monitor light.

9. The oscillation control device for an optical scanning device according to claim 1 or 2, wherein the oscillation detection unit comprises an oscillation state detection unit that detects the angular amplitude and phase when the movable member is oscillating, and the oscillation control unit comprises a synchronization signal output unit that adjusts the measurement timing by the measurement light in synchronization with the angular amplitude and phase detected by the oscillation state detection unit.

10. The oscillation state detection unit samples the output signals of each of the photoelectric conversion elements at intervals shorter than the oscillation period of the movable member, and by fitting a normal distribution to the output signals, identifies the position of the photoelectric conversion element showing a peak in the monitor light, and detects the angular amplitude and the phase, as described in claim 9.

11. The oscillation state detection unit generates an angular amplitude waveform indicating the oscillation state of the movable member based on the position of the photoelectric conversion element showing a peak in the monitor light and the timing of its reception, and detects the angular amplitude and phase of the movable member by fitting a sine function to the angular amplitude waveform, as described in claim 9.

12. A photoelectric sensor comprising: an oscillation control device for an optical scanning device according to claim 1 or 2; the optical scanning device; a light-emitting unit for causing the measurement light to enter the optical scanning device; a light-receiving unit for receiving reflected light from an object after the scanning light has been reflected; and a system control device for controlling the optical scanning device, the oscillation control device, the light-emitting unit, and the light-receiving unit to evaluate the reflected light detected by the light-receiving unit.

13. An optical distance measuring device comprising: an oscillation control device for an optical scanning device according to claim 1 or 2; the optical scanning device; a light-emitting unit for injecting the measurement light into the optical scanning device; a light-receiving unit for receiving reflected light from an object after the scanning light has been reflected; and a system control device for controlling the optical scanning device, the oscillation control device, the light-emitting unit, and the light-receiving unit to calculate the distance to an object based on the measurement light and the reflected light.

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