JP2011112585A - Optical range finder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control an optical range finder most suitably so as to satisfy a standard for laser safety. <P>SOLUTION: This optical range finder includes: an optical scanning part capable of performing optical scanning with light entering a light reflecting surface by rocking a movable part having the light reflecting surface; a scanning driving part for supplying a driving signal for rocking the movable part to the optical scanning part with a driving frequency set in accordance with a resonance frequency carried by the movable part, and rocking and driving the movable part; a light source part for projecting laser light toward the light reflecting surface; a light receiving part for receiving reflected light acquired by reflection of laser light reflected and scanned on the light reflecting surface by an object; a light source control part set so that a distance between each irradiation position of the laser light is longer than a prescribed value, for instructing a projection timing of the laser light to the light source part; a range-finding part for measuring a distance to the object based on projection and reception timing of the laser light; and a changing means for changing the set driving frequency and the projection timing in accordance with the resonance frequency. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical distance measuring apparatus that scans a pulsed laser beam in a target area and measures the distance of an object existing in the target area.

  2. Description of the Related Art Conventionally, there has been known an optical distance measuring device that measures a distance to an object that moves or passes through a target region by, for example, Lissajous scanning in a target region. This type of optical distance measuring device includes, for example, a light source unit that projects pulsed laser light, a light source control unit that commands the timing of projecting pulsed laser light, and a two-dimensional galvanometer mirror. Based on the time difference between the light projecting timing of the pulsed laser beam and the light receiving timing of the reflected light, the optical scanning unit, the scanning drive unit that drives the optical scanning unit, the light receiving unit that receives the reflected pulsed laser beam And a distance measuring unit that measures the distance to the object (see Patent Document 1).

  By the way, in the optical distance measuring device adopting this type of distance measurement by Lissajous scanning, the optical scanning drive unit drives the optical scanning unit at a driving frequency that matches the resonance frequency of each oscillation direction of the two-dimensional galvanometer mirror. ing. Here, for example, when the ambient temperature of the optical scanning unit changes or the temperature of the optical scanning unit itself changes, the resonance frequency also changes. In this state, it is known that when the optical scanning unit is driven without changing the driving frequency, the oscillation amplitude of the two-dimensional galvanometer mirror is reduced, and as a result, the scanning region of the laser beam is reduced from the target region. . As described above, when the projection control is performed without changing the timing of projecting the pulsed laser beam in a state where the scanning region is reduced, the distance between each irradiation position of the laser beam in the scanning region is narrowed, and the laser Therefore, the interlock is generally activated and the device is stopped. In addition, the optical distance measuring device in which the optical scanning unit is configured by a known one-dimensional galvanometer mirror has the same problem as described above.

  In order to solve such a problem, the optical distance measuring device generally employs drive control by a PWM (Pulse Width Modulation) method. The scanning drive unit adopting this PWM system supplies a pulse current to the optical scanning unit at a cycle corresponding to the resonance frequency, so that the oscillation amplitude of the optical scanning unit becomes constant, that is, one By changing the ratio of the time (pulse width) for supplying the pulse current in one period to one period, the reduction of the scanning area of the laser light is suppressed and controlled. In this way, for example, when the ambient temperature changes and the resonance frequency of the optical scanning unit changes, the laser light scanning region is maintained so that the laser safety interlock does not operate.

JP 2004-157796 A

  However, in the conventional optical distance measuring device of this type, for example, when the ambient temperature of the optical scanning unit or the temperature of the optical scanning unit itself changes drastically, or the characteristics greatly change due to a slight temperature change. When the scanning unit is used, the resonance frequency of the optical scanning unit may be greatly different from the driving frequency. In the drive control by the PWM method, the duty ratio is changed so that the swing amplitude becomes constant. However, if the resonance frequency is greatly different from the drive frequency as described above, the swing amplitude is changed even if the duty ratio is changed. Cannot be controlled to a certain level. In such a state, the duty ratio exceeds 50%, for example, and the amount of power supplied to the optical scanning unit becomes excessive, and a part of the supplied power is converted into heat for swing driving. No longer contributes. As a result, since the scanning area is reduced, the distance between the respective irradiation positions of the laser light in the target area is narrowed, and the interlock still operates to stop the apparatus.

  As described above, in the optical distance measuring device adopting the optical scanning distance measuring method, in the state where the driving frequency and the light emission timing are not changed in the state where the driving characteristic changes based on the temperature, only the drive control by the PWM method is used. However, there is a limit to the control range in which the optical distance measuring device can be controlled so as not to stop.

  The present invention has been made paying attention to such problems, and in an optical distance measuring device adopting a distance measuring method by Lissajous scanning, the ambient temperature of the optical scanning unit and the temperature of the optical scanning unit itself change extremely. However, an object of the present invention is to provide an optical distance measuring device that can be driven so as to satisfy the laser safety standards even if the driving characteristics of the optical scanning unit greatly change due to a slight temperature change.

  In the optical distance measuring device according to the present invention, a movable part having a light reflecting surface is formed so as to be able to swing, and the light that can be scanned within the target region by the swinging of the movable part within the target region. A scanning drive that drives the movable unit to swing by supplying a scanning unit and a drive signal for swinging the movable unit to the optical scanning unit at a drive frequency set in accordance with a resonance frequency of the movable unit. And a light source unit that projects a pulsed laser beam toward the light reflecting surface, and a laser beam that is projected from the light source unit and reflected and scanned by the light reflecting surface exists in the target region. A laser projecting from the light source unit configured to receive a reflected light reflected by an object and a distance between each irradiation position of the laser beam in the target region to be equal to or greater than a predetermined value. Light projection timing to the light source A light source control unit for instructing, a distance measuring unit for measuring a distance of the object based on a time difference between a light projection timing of the laser light by the light source control unit and a light reception timing of the reflected light by the light receiving unit, and the scan driving unit And changing means for changing the driving frequency set to 1 and the light projection timing set to the light source controller in accordance with the resonance frequency that changes according to temperature.

  According to the optical distance measuring device of the present invention, the drive frequency set in the scanning drive unit and the light projection timing set in the light source control unit are changed in accordance with the resonance frequency that changes according to the temperature. Specifically, for example, the optical distance measuring device has a timing table that associates the resonance frequency and the light projection timing for each temperature, and the changing unit switches the timing table according to the temperature. The resonance frequency measuring means for measuring the resonance frequency is provided, and the drive frequency is changed and the projection timing data is generated based on the acquired resonance frequency. The projection timing is changed according to the generated data. As a result, for example, even when the driving characteristics of the optical scanning unit greatly change due to, for example, an extreme change in the temperature around the optical scanning unit or the temperature of the optical scanning unit itself, Therefore, it is possible to provide an optical distance measuring device that can be driven while satisfying the laser safety standard.

It is a block diagram which shows schematic structure of the optical ranging apparatus by 1st Embodiment. It is a figure which shows the structure of a two-dimensional galvanometer mirror as an optical scanning part of an optical distance measuring device. It is a figure which shows the correspondence of the locus | trajectory by which Lissajous scanning was carried out, and the rocking angles x and y of a 1st direction and a 2nd direction. It is a flowchart which shows operation | movement of the optical ranging apparatus by the said 1st Embodiment. It is a block diagram which shows schematic structure of the optical ranging apparatus by 2nd Embodiment. It is a flowchart which shows operation | movement of the optical ranging apparatus by the said 2nd Embodiment. It is a partial block diagram which shows the principal part of the modification of the optical distance measuring device by the said 2nd Embodiment. It is a partial block diagram which shows the principal part of schematic structure of the optical ranging apparatus by 3rd Embodiment. It is a block diagram which shows the structural example of the optical ranging apparatus to which the drive control by a PWM system is applied. It is a flowchart which shows operation | movement of the optical ranging apparatus by the said structural example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of the optical distance measuring device according to the first embodiment of the present invention.
The optical distance measuring device 1 according to the present embodiment performs a Lissajous scan with pulsed laser light in a target area, measures a distance to an object existing in the target area (ranging), and based on the measurement result Generate and output (display) an image.

  As shown in FIG. 1, the optical distance measuring device 1 according to the present embodiment projects an electromagnetically driven optical scanning unit 2, a scanning driving unit 3 that swings and drives the optical scanning unit 2, and a pulsed laser beam. The light source unit 4 that emits light, the light receiving unit 5 that receives the reflected light of the projected laser beam, the light source control unit 6 that instructs the light source unit 4 to project the laser beam, and the object that reflects the laser beam A distance measuring section 7 for measuring the distance of the light, a changing means 8 for changing the driving timing for swinging and driving the light projection timing and the optical scanning section 2, a timing table 9 in which each resonance frequency and the light projection timing are associated, The image generation part 10 which produces | generates a distance image based on the measurement result by the distance part 7 and the display part 11 which outputs (displays) the produced | generated distance image are provided.

  The optical scanning unit 2 is formed so that a movable part having a light reflecting surface (mirror) can swing in a first direction and a second direction orthogonal to each other, and the movable part swings to reflect light. Light (pulsed laser light) incident on the surface can be Lissajous scanned in the target region. As such an optical scanning unit 2, for example, a two-dimensional scanning semiconductor galvanometer mirror (hereinafter simply referred to as “two-dimensional galvanometer mirror”) described in Japanese Patent No. 2722314 proposed by the present applicant is used. it can.

FIG. 2 shows a configuration of a two-dimensional galvanometer mirror 20 as a specific example of the optical scanning unit 2.
As shown in FIG. 2, the two-dimensional galvanometer mirror 20 is arranged on the inner side of the frame-shaped fixed portion 21 and is movable outside and supported by a pair of first torsion bars 22, 22. An inner movable part 25 that is disposed inside the outer movable part 23 and is swingably supported by a pair of second torsion bars 24, 24 that are orthogonal to the first torsion bars 22, 22. Is provided.

  A light reflecting surface (mirror) 26 is formed at the central portion of the inner movable portion 25, and a first drive coil 27 and a second drive coil 28 are formed at the peripheral portions of the outer movable portion 23 and the inner movable portion 25, respectively. Yes. An end portion of the first drive coil 27 is connected to first electrode terminals 29 and 29 formed on the fixed portion 21, and an end portion of the second drive coil 28 is a second electrode terminal 30 formed on the fixed portion 21. , 30.

  In addition, a pair of first permanent magnets 31 and 31 for applying a magnetic field to the first drive coil 27 and a pair of second permanent magnets 32 and 32 for applying a magnetic field to the second drive coil 28 are opposed to each other with the fixed portion 21 interposed therebetween. Is arranged. The fixed portion 21, the first torsion bars 22, 22, the outer movable portion 23, the second torsion bars 24, 24, and the inner movable portion 25 are integrally formed from a semiconductor substrate.

  The two-dimensional galvanometer mirror 20 is outside by a current (for example, an alternating current) flowing through the first drive coil 27 and the second drive coil 28 and a magnetic field generated by the first permanent magnets 31, 31 and the second permanent magnets 32, 32. Lorentz force acts on the movable part 23 and the inner movable part 25, and as a result, the inner movable part 25 swings in a two-dimensional direction. When the inner movable portion 25 is swung, the pulsed laser light incident on the light reflecting surface 26 is Lissajous scanned in the target region.

  Returning to FIG. 1, the scanning drive unit 3 drives the optical scanning unit 2 to swing, and is configured by, for example, a drive circuit 3 a. The drive circuit 3a includes a first drive signal (for example, alternating current) that swings the outer movable portion 23 and the inner movable portion 25 in the direction around the axis of the first torsion bars 22 and 22 (hereinafter referred to as “first direction”). Current) is supplied to the first drive coil 27 via the first electrode terminals 29 and 29 at a drive frequency set in accordance with the resonance frequency in the first direction of the outer movable portion 23, and the inner movable portion 25. In the second direction that the inner movable portion 25 has a second drive signal (for example, an alternating current) that swings the second torsion bars 24, 24 in the direction around the axis (hereinafter referred to as "second direction"). The second drive coil 28 is supplied with the drive frequency set according to the frequency via the second electrode terminals 30 and 30. For example, the drive frequencies in the first and second directions are preset in the scanning drive unit 3 in advance, and the set drive frequencies are temperatures that change during driving (for example, the periphery of the optical scanning unit). The temperature is changed by changing means described later.

  In the present embodiment, laser light that is incident on the light reflecting surface 26 by the swinging of the outer movable portion 23 and the inner movable portion 25 in the first direction due to the supply of the first drive signal will be described later in the target region. It is assumed that the pulsed laser beam that is scanned in the horizontal direction and is incident on the light reflecting surface 26 by the swing of the inner movable portion 25 in the second direction by the supply of the second drive signal is scanned in the vertical direction to be described later. .

FIG. 3 shows a locus in which the inner movable portion 25 is driven to swing in the two-dimensional direction by the scanning drive portion 3 and the laser light incident on the light reflecting surface 26 is Lissajous scanned in the target region, and the first direction and the first direction. The correspondence relationship between the swing angles x and y in two directions is shown. Here, the irradiation position of the laser beam located on the Lissajous scanning locus is determined based on the swing angles x and y at time t and the distance from the light reflecting surface 26 to the target area, for example, the horizontal direction of the target area. And the vertical position coordinates (X, Y). As for the swing angles x and y at time t, for example, it is assumed that there is no phase difference between the first drive signal and the second drive signal, and each time t is calculated from the maximum amplitude (A or B described later) in the negative direction. The case is represented by the following formulas (1) and (2).
x = A × sin (2πtf _x −π / 2) (1)
y = B × sin (2πtf _y −π / 2) (2)
However, A is the maximum amplitude in the first direction (rad), B is the maximum amplitude in the second direction (rad), _{f x} the first direction of the resonance frequency of the optical scanning unit, _{f y} the second direction of the light scanning unit The resonance frequency of each is shown.

  Returning to FIG. 1, the light source unit 4 projects a pulsed laser beam toward the light reflecting surface 26 formed on the inner movable unit 25 of the optical scanning unit 2. An optical optical system 42. The light projection timing of the laser light projected by the light source unit 4 is commanded by the light source control unit 6 described later.

  The light source 41 is a laser diode, for example, and emits pulsed laser light by emitting light in accordance with a drive signal from the light source control unit 4 described later.

  The light projecting optical system 42 makes the laser light emitted from the light source 41 preferable, and includes, for example, a collimator lens, and converts the laser light emitted from the light source 41 into parallel light. Then, the laser light projected from the light source unit 4 is reflected by the light reflecting surface 26 of the light scanning unit 2 and is subjected to Lissajous scanning in the target region.

  The light receiving unit 5 receives and detects laser light (reflected light) reflected by an object existing in the target area, which is projected from the light source unit 4 and reflected and scanned by the light reflecting surface 26. For example, a photosensor can be used. The light receiving unit 5 may receive the reflected light directly, or may receive the reflected light via the optical scanning unit 2 (light reflecting surface 26).

  The light source control unit 6 instructs the light source unit 4 to set a light projection timing so that the distance between the respective irradiation positions of the laser light in the target region is equal to or greater than a predetermined value. For example, the light projection timing is preset in the light source control unit 6 in advance so that the distance between each irradiation position of the laser light is more than a predetermined distance satisfying the laser safety standard, and is set in the light source control unit 6. The light projection timing is changed by a changing unit described later according to a temperature that changes during driving (for example, the ambient temperature of the optical scanning unit).

  The distance measuring unit 7 measures the distance of an object based on the time difference between the light projection timing of the laser light by the light source control unit 6 and the light reception timing of the reflected light by the light receiving unit 5. The light projection timing and the light reception timing of the reflected light by the light receiving unit 5 are input, and the distance to the object that reflected the laser light is measured based on the time difference (light flight time) between the two. The distance measurement by the distance measuring unit 7 is performed at each irradiation position in the target area, that is, for each projection of the laser light from the light source unit 4, and the measurement result is output to the image generation unit 10 described later. .

  The changing means 8 changes each drive frequency in the first and second directions set in the scanning drive unit 3 and the light projection timing set in the light source control unit 6 according to the temperature. It changes according to the frequency. That is, in the present embodiment, the changing unit 8 changes the driving frequency in the first direction set in the scanning driving unit 3 in accordance with the resonance frequency in the first direction that the outer movable unit 23 has, and scan driving. The driving frequency in the second direction set in the unit 3 is changed in accordance with the resonance frequency in the second direction that the inner movable unit 25 has, and at the same time, the laser beam projection timing set in the light source control unit 6 Is changed in accordance with each resonance frequency. In the present embodiment, the changing means 8 measures, for example, the ambient temperature of the outer movable portion 23 and the inner movable portion 25 that change during driving with a thermometer (not shown) and the like according to the measurement result of the ambient temperature. The drive frequencies in the first and second directions and the light projection timing are changed.

  In the present embodiment, the optical distance measuring device 1 has a timing table 9 in which each resonance frequency and projection timing are associated with each temperature, and each timing table 9 is previously stored as data in a memory or the like (not shown). Saved. The timing table 9 is used, for example, when the temperature T is T ≦ −5 ° C. (for low temperature), when −5 ° C. <T <55 ° C. (for standard temperature), or when 55 ° C ≦ T (high temperature). For use). Each timing table 9 includes each resonance frequency of the outer movable portion 23 and the inner movable portion 25 at temperatures representative of the temperature range of each timing table 9 (for example, −5 ° C., 25 ° C., and 55 ° C.), and each resonance frequency. Projection timing data corresponding to the. The projection timing data corresponding to each resonance frequency is, for example, Lissajous scanning determined based on each resonance frequency, the above-described equations (1) and (2), and the distance from the light reflecting surface 26 to the target region. It is obtained in advance so that the distance between each irradiation position of the laser beam at each time t located on the trajectory is not less than a predetermined value. As described above, the timing table 9 is provided for each temperature (for example, for each temperature range) in association with each resonance frequency and light projection timing. The timing table 9 is initially set, for example, when the temperature T is −5 ° C. <T <55 ° C.

  In the present embodiment, the changing unit 8 is configured to change the driving frequency and the light projection timing by switching the timing table 9 according to the temperature. Specifically, the changing unit 8 starts an operation of changing each drive frequency and light projection timing when the ambient temperature of the optical scanning unit 2 exceeds a predetermined temperature range set in advance. For example, in an environment where the distance measurement operation is started in a state where the ambient temperature is normal temperature (25 ° C.) and the ambient temperature changes thereafter, the changing unit 8 changes the ambient temperature of the outer movable unit 23 and the inner movable unit 25 to a thermometer or the like When the measured temperature exceeds the temperature range of −5 ° C. <T <55 ° C., the timing table 9 (the table for the time when the ambient temperature T is −5 ° C. <T <55 ° C. is initially set. ) Is switched to the timing table 9 (table for high temperature or low temperature) to which the measured temperature belongs.

  The image generation unit 10 generates a distance image for the target region based on the distance measured by the distance measurement unit 7. The distance image is generated so that, for example, an image having a different color for each distance measured at each irradiation position, that is, a three-dimensional image in which the depth distance of an object existing in the target region is reflected. The Then, the distance image generated by the image generation unit 10 is output to the display unit 11. The display unit 11 includes a display and displays the distance image output from the image generation unit 10. It is possible to recognize not only the object existing in the target area from the distance image but also the change in the position of the object, the distance to the object, the posture of the object, and the like.

  Next, the operation of the optical distance measuring device 1 having the above configuration will be described with reference to FIGS. The case where the ambient temperature of the optical scanning unit 2 at the start of the distance measuring operation is normal temperature (25 ° C.) and the ambient temperature T exceeds the predetermined temperature range (−5 ° C. <T <55 ° C.) will be described.

  First, the distance measuring operation will be described. The drive circuit 3a of the scanning drive unit 3 supplies first and second drive signals to the first and second drive coils 27 and 28, respectively, at respective drive frequencies that are initially set when the ambient temperature is 25 ° C. By doing so, the inner movable part 25 is swung in a two-dimensional direction. At the same time, the light source control unit 6 instructs the light source unit 4 to perform light projection timing that is initially set so that the distance between the laser light irradiation positions is at least a predetermined distance that satisfies the laser safety standard at an ambient temperature of 25 ° C. . The light source unit 4 projects a pulsed laser beam onto the light reflecting surface 26 of the inner movable unit 25 that swings in a two-dimensional direction at the projection timing instructed by the light control unit 6. The laser light reflected and scanned by the light reflecting surface 26 is Lissajous scanned in the target region, reflected by an object existing in the target region, and received by the light receiving unit 5. Here, the distance measuring unit 7 measures the distance of the object for each irradiation position based on the time difference between the light projecting timing and the light receiving timing of the laser beam. The measurement result is output to the image generation unit 10. The image generation unit 10 generates a distance image based on the measurement result from the distance measurement unit 7. Then, the generated distance image is displayed on the display unit 11. The distance is measured by the operation as described above. After the distance measurement is started (STEP 1), the changing unit 8 measures, for example, the ambient temperature T of the outer movable part 23 and the inner movable part 25 with a thermometer (STEP 2). . Here, when the measured temperature is within the temperature range of −5 ° C. <T <55 ° C., the distance measuring unit 7 continues the distance measuring operation as it is. When the measured temperature exceeds the temperature range of −5 ° C. <T <55 ° C. (STEP 3), the changing means 8 changes the timing table 9 to the timing table 9 (for high temperature or low temperature to which the measured temperature belongs). (STEP 4) to change the driving frequencies in the first and second directions set in the scanning drive unit 3 and the light projection timing set in the light source control unit 6 (STEP 5). Then, returning to STEP 1, the distance measuring operation is resumed at each changed drive frequency and light projection timing. Thereafter, for example, when the measurement temperature exceeds a low temperature or high temperature range (STEP 3), that is, when the temperature range is −5 ° C. <T <55 ° C., the changing means 8 has −5 ° C. <T <Switch to timing table 9 for use at <55 ° C. (STEP 4) and continue the distance measuring operation.

  As described above, in the optical distance measuring device 1 according to the present embodiment, the drive frequencies set in the scanning drive unit 3 and the light projection timing set in the light source control unit 6 change according to the temperature. A change means 8 for changing according to each resonance frequency is provided, and a timing table 9 that associates each resonance frequency with the light projection timing is provided for each temperature. For example, the changing unit 8 switches the timing table 9 according to the ambient temperature of the optical scanning unit 2 to change each driving frequency and light projection timing. Thereby, for example, even in a state where the driving characteristics of the optical scanning unit greatly change due to an extreme change in the ambient temperature of the optical scanning unit 2, a predetermined value that predetermines the distance between each irradiation position of the laser light in the target region Thus, the optical distance measuring device 1 that can be driven while satisfying the laser safety standards can be provided.

  In the above description, in order to reduce the data capacity, the timing table 9 has been described for the case of low temperature, the case of −5 ° C. <T <55 ° C., and the case of high temperature. Thus, the configuration is not limited to each of the temperature ranges divided into three, and for example, a large number may be provided for each temperature range divided in increments of 5 ° C., and the above-described −5 ° C. <T <55 ° C. One timing table 9 for time may be provided, and on the high temperature side and the low temperature side, a large number may be provided for each temperature range divided in increments of 5 ° C., for example. As described above, by providing the timing table 9 for each temperature range finely divided, each drive frequency and light projection timing can be changed more optimally. In the above description, the timing table 9 has been described as being provided for each temperature range. However, the timing table 9 may be provided for each temperature according to the measurement accuracy of the temperature measuring device, not for each temperature range. Each drive frequency and light projection timing can be changed more optimally. The changing unit 8 measures the ambient temperature of the optical scanning unit 2 and the like, and changes each drive frequency in the first and second directions and the light projection timing according to the ambient temperature. Not only the ambient temperature of the scanning unit 2 and the like, but, for example, the temperature of the optical scanning unit 2 itself is measured, and each driving frequency in the first and second directions and the light projection timing are measured according to the temperature of the optical scanning unit 2 itself. And may be changed.

Next, an optical distance measuring device according to a second embodiment of the present invention will be described.
FIG. 5 is a block diagram showing a schematic configuration of the optical distance measuring device according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the element same as 1st Embodiment of FIG. 1, description is abbreviate | omitted, and only a different part is demonstrated.

  In the present embodiment, the changing unit 8 acquires the resonance frequencies of the outer movable portion 23 and the inner movable portion 25, and changes the drive frequencies in the first and second directions according to the acquired resonance frequencies. The projection timing of the pulsed laser beam projected by the light source unit 4 is changed based on each acquired resonance frequency. Specifically, the changing unit 8 generates projection timing data based on each acquired resonance frequency, and changes the projection timing based on the generated data, and at the same time acquires each drive frequency. To match. In this way, by providing the changing means 8 with the function of generating the projection timing data, the projection timing of the laser beam can be set according to the temperature without having the projection timing data corresponding to the temperature in advance. Can be changed.

  In the present embodiment, the optical distance measuring device 1 includes a data A storage unit 12 having data A in which the temperature is associated with each resonance frequency. The data A storage unit 12 includes, for example, each temperature data representing a temperature range divided in increments of 5 ° C., and each of the first and second directions of the outer movable unit 23 and the inner movable unit at each temperature. Resonance frequency data is stored. The temperature range is not limited to 5 ° C., but may be further finely divided. By dividing the temperature range more finely, more accurate resonance frequencies can be obtained, so that each drive frequency and light projection timing can be changed more optimally.

  And in this embodiment, the change means 8 is comprised so that each resonance frequency may be acquired based on the data A and temperature of the data A storage part 12. FIG. For example, in an environment in which the distance measurement operation is started in a state where the ambient temperature of the optical scanning unit 2 is normal temperature (25 ° C.) and the ambient temperature changes thereafter, the changing unit 8 includes the ambient temperature of the outer movable unit 23 and the inner movable unit. Is measured by a thermometer or the like, and when the measured temperature exceeds a predetermined temperature range, each resonance frequency associated with the temperature representative of the temperature range to which the measured temperature belongs is acquired from the data A storage unit 12. At the same time, the changing unit 8 generates light projection timing data based on the acquired resonance frequencies. For example, a Lissajous determined by a microcomputer (not shown) provided in the changing unit 8 based on each resonance frequency acquired, the above-described equations (1) and (2), and the distance from the light reflecting surface 26 to the target region. It generates so that the distance between each irradiation position of the laser beam at each time t located on the scanning trajectory is not less than a predetermined value. In this way, for example, when the ambient temperature exceeds a predetermined temperature range determined in advance, the changing unit 8 acquires each resonance frequency according to the ambient temperature, and first and While changing each drive frequency of a 2nd direction, a light projection timing is produced | generated based on each acquired resonance frequency, and a light projection timing is changed with the produced | generated data.

  Next, the operation of the optical distance measuring device 1 having the above configuration will be described with reference to FIGS. The ambient temperature of the optical scanning unit 2 at the start of the distance measuring operation is normal temperature (25 ° C.), and then the ambient temperature T exceeds a predetermined temperature range (for example, 22.5 ° C. <T <27.5 ° C.). The case will be described. In addition, description is simplified about the same part as operation | movement of 1st Embodiment. In addition, as for each drive frequency and light projection timing, the data for the time when ambient temperature is 25 degreeC shall be initialized.

  As in the first embodiment, after the distance measurement is started (STEP 1), the changing unit 8 measures, for example, the ambient temperature of the outer movable part 23 and the inner movable part 25 using a thermometer (STEP 2). Here, when the measured temperature is within the temperature range of 22.5 ° C. <T <27.5 ° C., the distance measuring unit 7 continues the distance measuring operation as it is. When the measured temperature exceeds the temperature range of 22.5 ° C. <T <27.5 ° C. (STEP 3), for example, when the measured temperature is 27.5 ° C., the changing unit 8 determines the temperature to which the measured temperature belongs. Resonance frequencies associated with temperature data (30 ° C.) representing the range are acquired from the data A storage unit 12 (STEP 4a), and light projection timing is generated (STEP 4b) based on the acquired resonance frequencies. The changing unit 8 changes the driving frequencies in the first and second directions based on the acquired driving frequencies, and changes the light projection timing based on the generated data (STEP 5). Then, returning to STEP 1, the distance measuring operation is resumed at each changed drive frequency and light projection timing. Thereafter, when the measured temperature exceeds, for example, a temperature range (for example, 27.5 ° C. <T <32.5 ° C.) to which the temperature (30 ° C.) corresponding to each driving frequency being used belongs (STEP 3) The changing means 8 performs the operations of the above STEPs 4a and 4b and continues the distance measuring operation.

  As described above, in the optical distance measuring device 1 according to the present embodiment, the changing unit 8 acquires each resonance frequency corresponding to the temperature, and each drive in the first and second directions based on each acquired resonance frequency. Both frequency and light projection timing can be changed. In the present embodiment, the changing unit 8 can be provided with a function of generating data of light projection timing. Therefore, as compared with the first embodiment provided with the timing table 9 in which each resonance frequency and the light projection timing are associated with each other, the data capacity can be reduced because it is not necessary to provide the light projection timing data.

  In the above description, the changing unit 8 measures the ambient temperature of the optical scanning unit 2 and changes the driving frequencies in the first and second directions according to the ambient temperature. For example, the temperature of the optical scanning unit 2 itself may be measured and the driving frequencies in the first and second directions may be changed according to the temperature of the optical scanning unit 2 itself. .

  FIG. 7 is a partial block diagram illustrating a main part of a modification of the optical distance measuring device 1 according to the second embodiment. As shown in FIG. 7, in the first modification, in addition to the data A storage unit 12, a data B storage unit 13 having data B in which each resonance frequency is associated with the light projection timing is provided.

  In the data B storage unit 13, for example, the same resonance frequencies as the resonance frequencies in the first and second directions stored in the data A storage unit 12, and light projection timing data corresponding to the resonance frequencies. Is saved. The projection timing data corresponding to each resonance frequency is, for example, Lissajous scanning determined based on each resonance frequency, the above-described equations (1) and (2), and the distance from the light reflecting surface 26 to the target region. It is obtained in advance so that the distance between each irradiation position of the laser beam at each time t located on the trajectory is not less than a predetermined value.

  Moreover, in this modification, the change means 8 is comprised so that the data B in the data B storage part 13 linked | related with each acquired resonance frequency may be extracted, and a light projection timing may be changed with the extracted data. ing.

  In the case of this modification, in STEP 4b of the operation flow shown in FIG. 6, the changing means 8 extracts the data B in the data B storage unit 13, changes the light projection timing based on the extracted data (STEP 5), Other operations are the same as those described in FIG. As described above, in the present modification, the light projection timing can be changed without providing a microcomputer or the like in order to generate the light projection timing data.

Next, an optical distance measuring apparatus according to a third embodiment of the present invention will be described.
FIG. 8 is a partial block diagram showing the main part of the schematic configuration of the optical distance measuring device according to the third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the element same as 2nd Embodiment of FIG. 5, description is abbreviate | omitted, and only a different part is demonstrated.

  In the present embodiment, the optical distance measuring device 1 includes a data C storage unit 14 having data C that associates temperature with light projection timing. In the data C storage unit 14, for example, the same temperature data as the temperature representative of the temperature range divided in 5 ° C. stored in the data A storage unit 12, and light projection timing data corresponding to each temperature Is saved. The light projection timing data corresponding to each temperature is obtained in advance so that the distance between the laser light irradiation positions at each temperature is equal to or greater than a predetermined value.

  In the present embodiment, the changing unit 8 acquires each resonance frequency, changes each driving frequency of the first and second driving signals in accordance with the acquired resonance frequency, and stores data in the data C storage unit 14. Based on C and the temperature, the light projection timing is changed. For example, the changing unit 8 measures the ambient temperature of the optical scanning unit 2 as in the second embodiment, and when the measured temperature exceeds a predetermined temperature range, a temperature representative of the temperature range to which the measured temperature belongs. Each resonance frequency associated with the data is acquired from the data A storage unit 12. And in this embodiment, the change means 8 acquires the data of the light projection timing linked | related with the temperature data representing the temperature range to which measured temperature belongs from the data C storage part 14, and each drive frequency and light projection timing are obtained. change.

  In the case of this embodiment, in STEP 4b and STEP 5 of the operation flow shown in FIG. 6, the changing means 8 changes the light projection timing based on the data C in the data C storage unit 14 and the ambient temperature, and otherwise. This operation is the same as the operation described in FIG. As described above, in the present embodiment, similarly to the modification of the second embodiment, the light projection timing can be changed without providing a microcomputer or the like in order to generate light projection timing data.

  In the second and third embodiments, the optical distance measuring device 1 includes the data A storage unit 12, and, for example, based on the measurement result of the ambient temperature of the data A storage unit 12 and the optical scanning unit 2. The resonance frequencies in the first and second directions that change according to the ambient temperature are acquired. However, the acquisition of each resonance frequency is limited to the case where the resonance frequency is acquired based on the data A storage unit 12 and the measurement result of the ambient temperature. Alternatively, it may be configured to include resonance frequency measuring means (not shown) for measuring the resonance frequencies in the first and second directions of the outer movable portion 23 and the inner movable portion 25 to acquire each resonance frequency. .

  The resonance frequency measuring means includes, for example, a third and fourth coil (not shown) provided in parallel with the first and second drive coils 27 and 28, and a measuring instrument (not shown) that measures a current flowing through the third and fourth coils. And the scanning drive unit 3 is instructed to supply the pulse current to the first and second drive coils 27 and 28 once. The resonance frequency measuring means measures the counter electromotive force generated in the third and fourth coils when the outer movable portion 23 and the inner movable portion 25 are naturally oscillated by supplying a pulse current, and the measurement waveform It is preferable that the resonance frequencies in the first and second directions can be acquired by obtaining the natural vibration frequency.

  As described above, when the resonance frequency measuring means is applied to the second and third embodiments, the distance measuring operation is stopped when the ambient temperature exceeds the predetermined temperature range in STEP 3 of the operation flow shown in FIG. In STEP 4a, the changing unit 8 obtains each resonance frequency by the resonance frequency measuring unit, and the other operations are the same as those described above. As described above, in this configuration example, each resonance frequency of the movable parts 23 and 25 can be directly measured, so that a precise resonance frequency can be acquired.

  By the way, in the optical distance measuring device 1 according to all the above embodiments, when the temperature exceeds a predetermined temperature range determined in advance, the changing operation by the changing unit 8 is started, but the changing operation is started under other conditions. You may do it. Some examples will be described below.

  As shown by a dotted line in FIG. 1, when the amplitude measuring means 15 for measuring the swinging amplitude of the outer movable portion 23 and the inner movable portion 25 is provided, and the measurement result of the amplitude measuring means 15 is less than a predetermined amplitude determined in advance. Alternatively, the changing operation by the changing means 8 may be started. In this case, after the distance measurement start (STEP 1) in FIGS. 4 and 6, the amplitude measuring means 15 measures the swinging amplitude of the outer movable portion 23 and the inner movable portion 25, and in STEP 3, the measurement result is equal to or smaller than a predetermined amplitude. When it becomes, the subsequent change operation is started.

  In addition, when the ambient temperature exceeds a predetermined temperature range, or when the swinging amplitude of the outer movable portion 23 and the inner movable portion 25 is equal to or lower than a predetermined amplitude, the changing unit 8 starts the changing operation. With this configuration, the set drive frequencies in the first and second directions and the resonance frequencies in the first and second directions are set until the change operation is started even if the ambient temperature changes. There may be a gap between the two. Therefore, the swinging amplitude of the movable parts 23 and 25 may be reduced during distance measurement. Therefore, until the changing means 8 starts the changing operation, the swing amplitudes of the outer movable portion 23 and the inner movable portion 25 are controlled to be constant by drive control by a conventionally known PWM (Pulse Width Modulation) method. The change operation of the changing means 8 may be started when a predetermined condition (STEP 3a described later) is met. In this way, the swing amplitude does not decrease before the change operation of the change means 8 is started (during distance measurement). As a specific example, a case where the present invention is applied to the optical distance measuring device 1 according to the first embodiment will be described below.

  FIG. 9 is a block diagram showing another configuration example of the optical distance measuring device 1 according to the first embodiment. As shown in FIG. 9, in this configuration example, amplitude measuring means 15 for measuring the swing amplitude of the outer movable portion 23 and the inner movable portion 25 is provided, and the scanning drive section 3 receives the pulse current from the drive circuit 3a as the first. And the second drive signal, respectively, and according to the measurement result of the amplitude measuring means 15, the duty ratio of the pulse current, that is, the respective drive frequencies of the first and second drive signals set in the scanning drive unit 3. A pulse width changing unit 3b that controls the oscillation amplitude to be constant by changing the ratio of the time (pulse width) for supplying the pulse current in one cycle determined based on the period, Yes.

  In this configuration example, the drive circuit 3a supplies a pulse current to the first and second drive coils 27 and 28 at a period determined based on the set drive frequencies of the first and second drive signals. Configured. The changing means 8 is configured to start the changing operation when the duty ratio of the pulse current exceeds a predetermined ratio.

  Next, the operation of the optical distance measuring device 1 having the above configuration will be described with reference to FIGS. In addition, description is simplified about the part same as operation | movement of 1st Embodiment mentioned above.

  First, the distance measuring operation will be described. The drive circuit 3a of the scan drive unit 3 supplies a pulse current to the first and second drive coils 27 and 28 as first and second drive signals, respectively, at a period determined based on the initially set drive frequency. The inner movable part 25 is swung in a two-dimensional direction. At the same time, the pulse width changing unit 3b changes the duty ratio of the pulse current according to the measurement result of the oscillation amplitude measuring means 15 to control the oscillation amplitudes of the outer movable portion 23 and the inner movable portion 25 to be constant. As in the first embodiment described above, the distance measuring unit 7 measures the distance of the object for each irradiation position, and the display unit 11 displays the distance image. The distance is measured by the above operation. After the distance measurement is started (STEP 1a), the changing unit 8 measures the ambient temperature of the outer movable part 23 and the inner movable part 25 with a thermometer or the like at the same time, for example. And the electric energy supplied to the 2nd drive coils 27 and 28 is calculated | required based on the present duty ratio (STEP2a). Here, when the obtained power amount is within a predetermined amount, the distance measuring unit 7 continues the distance measuring operation as it is. When the duty ratio exceeds the predetermined ratio and the obtained electric power exceeds the predetermined amount (STEP 3a), the changing unit 8 obtains the timing table 9 from the thermometer as in the first embodiment. Switching to the timing table 9 of the temperature range to which the measured temperature belongs (STEP 4), the drive frequency and the light projection timing are changed (STEP 5).

  As described above, in the optical distance measuring device 1 according to the present configuration example, the swing amplitude can be controlled to be constant before the change operation of the change unit 8 is started (during distance measurement). Thus, until the duty ratio exceeds a predetermined ratio (power consumption amount is a predetermined amount), the oscillation amplitude is controlled to be constant, taking advantage of the drive control by the PWM method, and the duty ratio is set to a predetermined ratio (power consumption amount). Even if it exceeds the predetermined amount) and exceeds the control range of the PWM system, the changing operation can be started by the changing means 8 and the ranging operation can be continued. Although the above description has been given of the case where the PWM drive control is applied to the first embodiment, it can be applied to all the above embodiments.

  In the above description of all the embodiments, the optical scanning unit 2 is configured by the two-dimensional galvanometer mirror 20 and has been described in the case of performing Lissajous scanning in the target region. However, the optical scanning unit 2 is well-known although not illustrated. A one-dimensional galvanometer mirror may be used to perform one-dimensional scanning in the target region. In this case, the movable part of the optical scanning part 2 is configured to be pivotally supported by a pair of torsion bars with respect to the fixed part 21. For example, in the case of the configuration including the timing table 9 as in the first embodiment, the timing data of the timing table 9 is obtained from the swing angle of the movable portion at the time t and the light reflection surface 26. The distance between each irradiation position of the laser light at each time t located on the one-dimensional scanning locus determined based on the distance to the region is determined in advance so as to be equal to or greater than a predetermined value. Further, as in the second embodiment described above, when the changing unit 8 is configured to generate the light projection timing data based on the acquired resonance frequency, for example, it is acquired by a microcomputer or the like provided in the changing unit 8. Based on the resonance frequency, the swing angle of the movable part at time t, and the distance from the light reflection surface 26 to the target region, data of light projection timing is generated.

DESCRIPTION OF SYMBOLS 1 ... Optical distance measuring device 2 ... Optical scanning part 3 ... Scanning drive part 4 ... Light source part 5 ... Light receiving part 6 ... Light source control part 7 ... Distance measuring part 8 ... Changing means 9 ... Timing table 12 ... Data A storage part (1st 3 data storage)
13: Data B storage (first data storage)
14: Data C storage unit (second data storage unit)
15 ... Amplitude measuring means 20 ... Two-dimensional galvanometer mirror (optical scanning unit)
DESCRIPTION OF SYMBOLS 21 ... Fixed part 22 ... 1st torsion bar 23 ... Outer movable part 24 ... 2nd torsion bar 25 ... Inner movable part 26 ... Light reflection surface 3b ... Pulse width change means

Claims (13)

A movable portion having a light reflecting surface is formed so as to be swingable, and the light scanning portion capable of scanning the light incident on the light reflecting surface within the target region by swinging the movable portion;
A scanning drive unit that supplies a drive signal for swinging the movable unit to the optical scanning unit at a drive frequency set in accordance with a resonance frequency of the movable unit, and swings the movable unit;
A light source unit that projects a pulsed laser beam toward the light reflecting surface;
A light receiving unit that receives the reflected light reflected from the object that is projected from the light source unit and reflected and scanned by the light reflecting surface in the target region;
Light source control for instructing the light source unit to project the timing of the laser beam emitted by the light source unit, which is set so that the distance between the laser beam irradiation positions in the target region is equal to or greater than a predetermined value. And
A distance measuring unit that measures a distance of the object based on a time difference between a light projection timing of the laser light by the light source control unit and a light reception timing of reflected light by the light receiving unit;
Change means for changing the drive frequency set in the scanning drive unit and the light projection timing set in the light source control unit according to the resonance frequency that changes according to temperature,
An optical distance measuring device comprising: The light scanning unit performs Lissajous scanning of light incident on the light reflecting surface within a target region by swinging the movable unit formed to be swingable in a first direction and a second direction orthogonal to each other. Is possible,
The scanning drive unit includes, as the drive signal, a first drive signal for swinging the movable unit in the first direction and a second drive signal for swinging the movable unit in the second direction. The movable portion is oscillated and driven by being supplied to the optical scanning portion at a driving frequency set in accordance with the resonance frequency in the first direction and the resonance frequency in the second direction, respectively. The optical distance measuring device according to 1. The optical scanning unit
A frame-shaped fixing part;
An outer movable portion disposed inside the fixed portion and supported by a pair of first torsion bars so as to be swingable;
An inner movable part that is disposed inside the outer movable part and is swingably supported by a pair of second torsion bars whose axial directions are perpendicular to each other with the first torsion bar;
A light reflecting surface formed on the inner movable portion;
The optical distance measuring device according to claim 2, comprising: A timing table that associates the resonance frequency and the light projection timing for each temperature,
The optical distance measuring device according to claim 1, wherein the changing unit changes the driving frequency and the light projection timing by switching the timing table according to the temperature. .   The said changing means acquires the said resonant frequency, changes the said drive frequency according to the acquired resonant frequency, and changes the said light projection timing based on the acquired resonant frequency. The optical distance measuring device according to any one of?   6. The optical ranging according to claim 5, wherein the changing unit generates the light projection timing data based on the acquired resonance frequency, and changes the light projection timing based on the generated data. apparatus. A first data storage unit having data associating the resonance frequency with the light projection timing;
The light according to claim 5, wherein the changing unit extracts data in the first data storage unit associated with the acquired resonance frequency, and changes the light projection timing based on the extracted data. Distance measuring device. A second data storage unit having data associating the temperature with the light projection timing;
The changing unit acquires the resonance frequency, changes the driving frequency according to the acquired resonance frequency, and changes the light projection timing based on the data in the second data storage unit and the temperature. The optical distance measuring device according to any one of claims 1 to 3. A third data storage unit having data relating the temperature and the resonance frequency;
The optical distance measuring device according to claim 5, wherein the changing unit acquires the resonance frequency based on data in the third data storage unit and the temperature. Resonance frequency measurement means for measuring the resonance frequency of the movable part,
9. The optical distance measuring device according to claim 5, wherein the changing unit acquires the resonance frequency by the resonance frequency measuring unit.   The optical distance measuring device according to claim 1, wherein the changing unit starts the changing operation when the temperature exceeds a predetermined temperature range set in advance. Amplitude measuring means for measuring the swing amplitude of the movable part,
The optical measurement according to claim 1, wherein the changing unit starts the changing operation when a measurement result of the amplitude measuring unit becomes equal to or less than a predetermined amplitude. Distance device. Amplitude measuring means for measuring the swing amplitude of the movable part,
The scanning drive unit supplies a pulse current as the drive signal, and changes a duty ratio of the pulse current according to a measurement result of the amplitude measuring unit, thereby controlling a swing amplitude constant. With
The optical distance measuring device according to claim 1, wherein the changing unit starts the changing operation when the duty ratio exceeds a predetermined ratio.

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