Laser radar device

Abstract

To improve the detection accuracy of a laser radar device.SOLUTION: A laser radar device 1 includes a laser drive circuit 4 and a laser diode 5, a scanning unit 7, a control unit 14, and a motor drive circuit 8. The laser drive circuit 4 and the laser diode 5 transmit frequency-modulated laser light. The scanning unit 7 scans with the laser light. The control unit 14 receives laser light reflected by an object, for each of a plurality of partial areas obtained by dividing a laser light scanning area preset as a two-dimensional area scanned with the laser light by the scanning unit 7, and calculates the distance to the object in the partial area. The control unit 14 and the motor drive circuit 8 control the movement of the laser light so that the laser light moves while satisfying Δθ>(1.22×λ / d) within the partial area.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 describes an FMCW laser radar device that includes a transmitter that transmits, as transmitted light, laser light modulated to have an up-modulation section in which the frequency increases linearly with time and a down-modulation section in which the frequency decreases linearly with time, and a receiver that receives, as received light, reflected light that is generated when the transmitted light is reflected by an object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2017 / 0356983 Summary of the Invention [Problem to be solved by the invention]

[0004] In FMCW laser radar devices, the amplitude of the beat signal fluctuates due to speckle caused by interference of laser light due to the roughness of the surface of an object that reflects the laser light, which causes a problem of reduced detection accuracy of the laser radar device.

[0005] The present disclosure aims to improve the detection accuracy of a laser radar device. [Means for solving the problem]

[0006] One aspect of the present disclosure is a laser radar device (1) including a transmitter (4, 5), a scanner (7), a distance calculator (14, S10 to S90), and a movement controller (8, 14). The transmitter is configured to transmit frequency modulated laser light.

[0007] The scanning unit is configured to scan the laser light emitted from the transmitting unit. The distance calculation unit is configured to receive laser light transmitted from the scanning unit and reflected by an object for each of a plurality of partial areas divided from a laser light scanning area that is preset as a two-dimensional area in which the scanning unit scans the laser light, and to calculate at least the distance to the object in the partial area.

[0008] The movement control unit is configured to control the movement of the laser light so that, for each of the multiple partial regions, the laser light moves within the partial region while satisfying Δθ > (1.22 × λ / d), where Δθ is the movement angle range within the partial region, λ is the wavelength of the laser light, and d is the diameter of the laser light on the partial region.

[0009] The laser radar device of the present disclosure configured in this manner can move the irradiation position of the laser beam within one partial region, thereby averaging the effect of speckle for each of the multiple partial regions and reducing the variation in the intensity of the received laser beam, thereby improving the detection accuracy of the laser radar device of the present disclosure. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing the configuration of a laser radar device according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing the scanning direction of the laser radar device. [Figure 3] FIG. 10 is a diagram illustrating the movement of an irradiation spot. [Figure 4] FIG. 10 is a diagram showing the moving angle range of the irradiation spot. [Figure 5] 4 is a flowchart showing distance measurement processing in the first embodiment. [Figure 6] FIG. 10 is a diagram illustrating a minute section. [Figure 7] 10 is a histogram showing the distribution of received light intensity. [Figure 8]FIG. 10 is a block diagram showing the configuration of a laser radar device according to a second embodiment. [Figure 9] FIG. 10 is a diagram illustrating a control method according to a second embodiment. [Figure 10] 10A and 10B are diagrams illustrating a method for moving an irradiation spot in the second embodiment. [Figure 11] FIG. 10 is a block diagram showing the configuration of a laser radar device according to a third embodiment. [Figure 12] FIG. 10 is a diagram showing an irradiation spot that is moved in the vertical direction. [Figure 13] FIG. 10 is a diagram showing an irradiation spot that is moved simultaneously in the horizontal and vertical directions. [Figure 14] FIG. 10 is a diagram showing a plurality of irradiation spots irradiated within one partial region. [Figure 15] FIG. 10 is a diagram showing an irradiation spot that is moved to an area beyond one partial area. [Figure 16] FIG. 10 is a diagram illustrating a plurality of overlapping signal processing sections. DETAILED DESCRIPTION OF THE INVENTION

[0011] [First embodiment] A first embodiment of the present disclosure will be described below with reference to the drawings. 1, the laser radar device 1 of this embodiment employs the well-known FMCW method and includes a housing 2, an optical window 3, a laser drive circuit 4, a laser diode 5, a branching filter 6, a scanning unit 7, a motor drive circuit 8, an oscillator 9, an optical receiving unit 10, a multiplexer 11, a photodiode 12, a transimpedance amplifier (hereinafter referred to as TIA) 13, and a control unit 14. FMCW is an abbreviation for Frequency Modulated Continuous Wave.

[0012] The housing 2 is a box having an opening for passing light, and houses a laser drive circuit 4, a laser diode 5, a splitter 6, a scanning unit 7, a motor drive circuit 8, an oscillator 9, an optical receiving unit 10, a multiplexer 11, a photodiode 12, a TIA 13, and a control unit 14 inside.

[0013] The optical window 3 is made of a light-transmitting material and is disposed so as to close the opening of the housing 2. The laser driving circuit 4, in accordance with an instruction from the control unit 14, outputs to the laser diode 5 a driving signal for generating a laser beam whose frequency has been swept.

[0014] The laser diode 5 repeatedly emits frequency-swept laser light (hereinafter referred to as transmission light) based on the drive signal output from the laser drive circuit 4. Specifically, the laser diode 5 generates and emits, at a preset modulation period Tm, transmission light modulated to have an upstream modulation section in which the frequency increases linearly with time and a downstream modulation section in which the frequency decreases linearly with time.

[0015] The demultiplexer 6 is configured by, for example, a coupler where an optical waveguide branches, and receives the transmitted light irradiated from the laser diode 5. The demultiplexer 6 irradiates a part of the transmitted light input to the demultiplexer 6 onto the scanning unit 7, and irradiates the remaining part onto the multiplexer 11.

[0016] The scanning unit 7 includes, for example, a vertical scanner (not shown) and a horizontal scanner (not shown). The vertical scanner scans the laser light in the vertical direction by rotating a mirror with a driving force generated by a motor (not shown). The horizontal scanner scans the laser light in the horizontal direction by rotating a mirror with a driving force generated by a motor (not shown). The scanning unit 7 further scans the laser light scanned by the vertical scanner with the horizontal scanner, thereby irradiating the optical window 3 with the laser light while scanning it two-dimensionally.

[0017] The motor drive circuit 8 outputs a drive signal to the motor to generate a drive force for rotating the vertical scanner and horizontal scanner of the scanning unit 7 in accordance with an instruction from the control unit 14 .

[0018] The oscillator 9 is configured to incorporate, for example, a piezoelectric element, and is attached to the horizontal scanner of the scanning unit 7. The oscillator 9 vibrates in response to a drive signal output from the control unit 14, causing the horizontal scanner to vibrate in the horizontal direction.

[0019] The light receiving section 10 receives, as received light, reflected light that is generated when transmitted light is reflected by an object. The multiplexer 11 mixes the transmitted light input from the demultiplexer 6 with the received light input from the optical receiver 10 to generate a beat signal.

[0020] The photodiode 12 converts the beat signal input from the combiner 11 into a current signal and outputs it. The TIA 13 converts the current signal input from the photodiode 12 into a voltage signal and outputs it.

[0021] The control unit 14 is an electronic control device mainly composed of a microcomputer including a CPU 21, a ROM 22, a RAM 23, etc. Various functions of the microcomputer are realized by the CPU 21 executing a program stored in a non-transitory tangible recording medium. In this example, the ROM 22 corresponds to the non-transitory tangible recording medium storing the program. Furthermore, the execution of this program executes a method corresponding to the program. Note that some or all of the functions executed by the CPU 21 may be configured as hardware using one or more ICs, etc. Furthermore, the number of microcomputers constituting the control unit 14 may be one or more.

[0022] The control unit 14 includes an AD conversion circuit, a fast Fourier transform circuit, etc. The control unit 14 converts the voltage signals sequentially input from the TIA 12 into digital signals and stores the values indicated by these digital signals in time series in the RAM 23 as the amplitude of the beat signal, thereby generating beat signal waveform data indicating the change in the amplitude of the beat signal over time. The control unit 14 then performs frequency analysis on the beat signal waveform data to calculate the distance and velocity of the object. The control unit 14 also calculates the angle of the object based on the scanning direction of the transmitted light.

[0023] In the FMCW system, an upstream beat signal and a downstream beat signal are generated as beat signals. The upstream beat signal is generated by mixing the transmitted light and the received light during the period in which the radar wave is transmitted in the upstream modulation section. Similarly, the downstream beat signal is generated by mixing the transmitted light and the received light during the period in which the radar wave is transmitted in the downstream modulation section.

[0024] The relationship between the frequency fbu of the upstream beat signal and the frequency fbd of the downstream beat signal and the distance L to the object (hereinafter referred to as object distance L) and the relative velocity v (hereinafter referred to as object relative velocity v) is expressed by the following equations (1) and (2). In equations (1) and (2), c is the speed of light, Δf is the frequency fluctuation width of the transmitted light, and f0 is the center frequency of the transmitted light.

[0025]

number

[0026] Therefore, the object distance L and the object relative velocity v are calculated by equations (3) and (4).

[0027]

number

[0028] As shown in FIG. 2, the laser light scanning region SR onto which the laser radar device 1 irradiates laser light is divided into m (m is a positive integer) rectangular partial regions in the X-axis direction and n (n is a positive integer) rectangular partial regions in the Y-axis direction, with the horizontal direction being the X-axis direction and the vertical direction being the Y-axis direction.

[0029] As indicated by arrows L1 and L2, the control unit 14 controls the irradiation of laser light by the laser diode 5 and the scanning of laser light by the scanning unit 7 so that the laser irradiation position moves to an adjacent partial region in the horizontal direction each time a modulation period Tm elapses. However, when the laser light reaches the rightmost or leftmost partial region, the control unit 14 controls the scanning of the laser light so that it moves to the partial region immediately below it. In other words, the control unit 14 controls the scanning unit 7 to perform raster scanning.

[0030] Irradiation spots SP1 and SP2 in Fig. 3 indicate the shape of the laser light on the target when the laser light irradiated from the laser radar device 1 reaches the target object while the vibrator 9 is not vibrating. Partial regions PR1 and PR2 are two partial regions adjacent to each other along the horizontal direction. Irradiation spots SP1 and SP2 are formed in partial regions PR1 and PR2, respectively. If irradiation spot SP2 indicates the irradiation position at time t1, irradiation spot SP1 indicates the irradiation position at time (t1-Tm).

[0031] 3 show the shapes of laser light on a target when the laser light emitted from the laser radar device 1 reaches the target object while the vibrator 9 is vibrating. The illumination spots SP11 to SP13 are formed within a partial region PR1, and the illumination spots SP14 to SP16 are formed within a partial region PR2. That is, the vibration of the vibrator 9 causes the illumination spots to move horizontally within the partial regions.

[0032] As shown in Fig. 4, the control unit 14 vibrates the vibrator 9 between the leftmost irradiation spot SP21 and the rightmost irradiation spot SP22 in the same partial region so as to satisfy equation (5). Δθ in equation (5) is the difference between the scanning angle of the irradiation spot SP22 and the scanning angle of the irradiation spot SP21. λ is the wavelength of the laser light. d is the diameter of the irradiation spots SP21 and SP22.

[0033] Δθ>1.22×λ / d (5) Note that the received light intensity during distance measurement varies randomly depending on the illuminated location due to the speckle phenomenon. In contrast, if multiple locations are illuminated where the speckles are independent of each other, it is possible to expect received light intensity due to independent speckles at each illuminated location. Thus, the condition under which intensity fluctuations due to speckles become independent is expressed by Equation (5).

[0034] In the laser radar device 1 configured as above, the control unit 14 executes distance measurement processing. The distance measurement processing is processing that is executed every time a modulation period Tm elapses while the control unit 14 is operating.

[0035] When the distance measurement process is executed, the CPU 21 of the control unit 14 first sets the section indication value i provided in the RAM 23 to 0 in S10, as shown in FIG. Then, in S20, the CPU 21 acquires, from the RAM 23, beat signal waveform data generated in the most recent upstream modulation section (hereinafter referred to as upstream beat signal waveform data) and beat signal waveform data generated in the most recent downstream modulation section (hereinafter referred to as downstream beat signal waveform data).

[0036] 6 shows the time variation of the frequency of the transmitted light and the received light in the upstream modulation section. The line FL1 shows the time variation of the frequency of the transmitted light, and the line FL2 shows the time variation of the frequency of the received light.

[0037] 5, in S30, the CPU 21 first sets a predetermined number of divisions N of non-overlapping micro-intervals within the time ranges of the ascending beat signal waveform data and the descending beat signal waveform data, for each of the ascending beat signal waveform data and the descending beat signal waveform data. The predetermined number of divisions N is an integer equal to or greater than 2. Hereinafter, the micro-intervals of the predetermined number of divisions N will be referred to as the first micro-interval SS1, the second micro-interval SS2, ..., and the Nth micro-interval SSN in order of earliest time.

[0038] Graph G2 in FIG. 6 shows a first minute section SS1, a second minute section SS2, a third minute section SS3, and a fourth minute section SS4 that divide the beat signal waveform in the upstream modulation section. Furthermore, as shown in FIG. 5, the CPU 21 increments the section indication value i (that is, adds 1) in S40.

[0039] Then, at S50, the CPU 21 performs frequency analysis processing on each of the ascending beat signal waveform data and the descending beat signal waveform data in the i-th minute section SSi to calculate the frequency spectrum of the ascending beat signal (hereinafter referred to as the ascending frequency spectrum) and the frequency spectrum of the descending beat signal (hereinafter referred to as the descending frequency spectrum) in the i-th minute section SSi.

[0040] The frequency spectrum represents the frequencies contained in the beat signal and the amplitude at each frequency. In this embodiment, the frequency analysis process is a fast Fourier transform. Graph G3 in FIG. 6 shows a frequency spectrum calculated by performing frequency analysis processing on the upstream beat signal waveform data in the third minute section SS3 in the upstream modulation section.

[0041] 5, the CPU 21 determines in S60 whether the interval instruction value i is equal to or greater than the predetermined division number N. If the interval instruction value i is less than the predetermined division number N, the CPU 21 proceeds to S40. On the other hand, if the interval instruction value i is equal to or greater than the predetermined division number N, the CPU 21 calculates in S70 an upstream average frequency spectrum obtained by averaging the amplitudes of the upstream frequency spectra from the first minute section SS1 to the Nth minute section SSN, and a downstream average frequency spectrum obtained by averaging the amplitudes of the downstream frequency spectra from the first minute section SS1 to the Nth minute section SSN.

[0042] Then, in S80, the CPU 21 detects the frequency peak present on the uplink average frequency spectrum calculated in S70 as frequency fbu, and detects the frequency peak present on the downlink average frequency spectrum calculated in S70 as frequency fbd.

[0043] Furthermore, in S90, the CPU 21 calculates the object distance L using the frequencies fbu and fbd detected in S80, and ends the distance measurement process. 7 is a histogram showing the distribution of received light intensity when distance measurement is performed by irradiating laser light across N regions that form independent speckles. The number of regions, N, is 1, 2, 3, 4, 8, or 16.

[0044] 7 are histograms showing the distribution of received light intensity when distance measurement is performed with the laser light spanning areas of 1, 2, 3, 4, 8, and 16 locations, respectively. Histograms HG1 to HG6 are generated by generating random numbers that follow a Rayleigh distribution and averaging them N times, a process that is repeated 100,000 times.

[0045] As shown in FIG. 7, the greater the number of regions N (that is, the wider the region spanned by the laser light), the smaller the variation in the intensity of the received light. The laser radar device 1 configured in this manner includes a laser drive circuit 4, a laser diode 5, a scanning unit 7, a control unit 14, and a vibrator 9.

[0046] The laser driver circuit 4 and the laser diode 5 are configured to transmit frequency modulated laser light. The scanning unit 7 is configured to scan the laser light emitted from the laser diode 5.

[0047] The control unit 14 is configured to receive laser light transmitted from the scanning unit 7 and reflected by an object for each of a plurality of partial areas divided from the laser light scanning area SR, which is preset as a two-dimensional area in which the scanning unit 7 scans the laser light, and to calculate at least the distance to the object in the partial area.

[0048] The control unit 14 is configured to drive the oscillator 9 to control the movement of the laser light so that the laser light moves within the partial region while satisfying Δθ>(1.22×λ / d).

[0049] Such a laser radar device 1 can move the irradiation position of the laser light within one partial region, and therefore can average the influence of speckle by averaging the amplitudes of multiple frequency spectra irradiated at different positions for each of multiple partial regions, thereby reducing the variation in the intensity of the received light, thereby improving the detection accuracy of the laser radar device 1.

[0050] In the embodiment described above, the laser drive circuit 4 and the laser diode 5 correspond to a transmitter, S10 to S90 correspond to processing as a distance calculation unit, and the control unit 14 and the motor drive circuit 8 correspond to a movement control unit.

[0051] [Second embodiment] A second embodiment of the present disclosure will be described below with reference to the drawings. In the second embodiment, only the parts that are different from the first embodiment will be described. The same reference numerals will be used to designate common components.

[0052] As shown in FIG. 8, the laser radar device 1 of the second embodiment differs from the first embodiment in that the oscillator 9 is omitted. The control unit 14 then controls the scanning of the horizontal scanner by performing feedback control so that the scanning angle of the horizontal scanner oscillates around the target angle.

[0053] Graph G11 in Figure 9 shows the change in the scanning angle over time when the scanning angle of the scanner is controlled by typical PID control. As shown in graph G11, with typical PID control, the scanning angle converges to the target angle as time passes.

[0054] 9 shows the change in the scanning angle over time when the scanning angle of the scanner is controlled by the control unit 14 of the second embodiment. As shown in graph G12, in the control performed by the control unit 14 of the second embodiment, the scanning angle does not converge to the target angle but continues to oscillate with the same amplitude around the target angle.

[0055] As a result, as shown by the irradiation spots SP31 and SP32 and the arrows L11 and L12 in FIG. 10, the irradiation spots vibrate in the horizontal direction within the partial region. In the laser radar device 1 configured in this manner, the control unit 14 and the motor drive circuit 8 perform feedback control to control the scanning unit 7 so that the scan angle for each of the multiple partial regions oscillates around the target angle corresponding to the partial region, thereby moving the laser light within the partial region while satisfying Δθ>(1.22×λ / d).

[0056] Such a laser radar device 1 can move the irradiation position of the laser light within one partial region, thereby averaging the effect of speckles for each of the partial regions and reducing the variation in the intensity of the received light, thereby improving the detection accuracy of the laser radar device 1.

[0057] In the embodiment described above, the control unit 14 and the motor drive circuit 8 correspond to a movement control unit. [Third embodiment] A third embodiment of the present disclosure will be described below with reference to the drawings. In the third embodiment, differences from the first embodiment will be described. The same reference numerals will be used to designate common components.

[0058] As shown in FIG. 11, the laser radar device 1 of the third embodiment differs from the first embodiment in that the transducer 9 is omitted and an additional scanning unit 16 is added. The additional scanning unit 16 is disposed on the path of the laser light emitted from the scanning unit 7 until it reaches the optical window 3. The additional scanning unit 16 rotates a mirror using a driving force generated by a motor (not shown), thereby scanning the laser light emitted from the scanning unit 7 in the horizontal direction. The scanning angle range of the additional scanning unit 16 is much smaller than the scanning angle range of the scanning unit 7. However, the scanning angle range of the additional scanning unit 16 satisfies equation (5). In other words, the scanning angle range of the additional scanning unit 16 is set to be larger than 1.22×λ / d.

[0059] Then, the motor drive circuit 8 outputs a drive signal to the motor to generate a drive force for rotating the additional scanning unit 16 in accordance with an instruction from the control unit 14 . This allows the laser radar device 1 of the third embodiment to vibrate the irradiation spot in the horizontal direction within the partial region.

[0060] The laser radar device 1 configured in this manner includes an additional scanning unit 16 configured to further scan the laser light transmitted from the scanning unit 7. The control unit 14 and the motor drive circuit 8 drive the additional scanning unit 16 to move the laser light within the partial region while satisfying Δθ>(1.22×λ / d).

[0061] Such a laser radar device 1 can move the irradiation position of the laser light within one partial region, thereby averaging the effect of speckles for each of the partial regions and reducing the variation in the intensity of the received light, thereby improving the detection accuracy of the laser radar device 1.

[0062] In the embodiment described above, the control unit 14 and the motor drive circuit 8 correspond to a movement control unit. Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment and can be implemented in various modifications.

[0063] [Variation 1] For example, in the above embodiment, the irradiation spot is moved or vibrated horizontally within the partial region. However, the direction in which the irradiation spot is moved or vibrated is not limited to the horizontal direction, and the irradiation spot may be moved or vibrated vertically within the partial region, as shown by irradiation spots SP41 and SP42 and arrows L21 and L22 in FIG.

[0064] Furthermore, the irradiation spots may be moved or vibrated simultaneously in the horizontal and vertical directions within a partial region, as shown by irradiation spots SP51, SP52, SP53, SP54, SP55, and SP56 and arrows L31 and L32 in Fig. 13. The horizontal direction corresponds to the main scanning direction, and the vertical direction corresponds to the sub-scanning direction.

[0065] Furthermore, as shown by irradiation spots SP61, SP62, SP63, SP64, SP65, and SP66 in FIG. 14, a plurality of laser beams may be irradiated at different positions within the same partial region.

[0066] [Variation 2] In the above embodiment, the illumination spot is moved or vibrated within the same partial region. However, as shown by illumination spots SP71 and SP72 in FIG. 15 , the illumination spot may be moved or vibrated beyond one partial region. In this laser radar device 1, the control unit 14 and the motor drive circuit 8 move the laser light not only within each of the partial regions but also beyond the partial region. This allows the laser radar device 1 to increase the number of frequency spectra used to calculate the average amplitude of the frequency spectra for each of the partial regions, thereby improving the effect of averaging the effects of speckle and further reducing the variation in the intensity of the received light.

[0067] [Variation 3] In the above embodiment, the scanning of the laser light is controlled so that the laser irradiation position moves to an adjacent partial region in the horizontal direction every time the modulation period Tm elapses (i.e., the scanning unit 7 is driven intermittently). However, the control unit 14 and the motor drive circuit 8 may also move the laser light within a partial region so that Δθ > (1.22 × λ / d) is satisfied by scanning the scanning unit 7 to move the laser light between two adjacent partial regions for each of a plurality of partial regions. In other words, the scanning unit 7 may be driven constantly so that the irradiation spot moves constantly. In this case, the scanning angle of the scanning unit 7 at the modulation period Tm must be greater than 1.22 × λ / d.

[0068] Furthermore, when the scanning unit 7 is constantly driven, as shown by signal processing sections PI1, PI2, and PI3 in FIG. 16, the signal processing sections for acquiring beat signal waveform data for calculating a frequency spectrum by executing a frequency analysis process may be set to acquire beat signal waveform data corresponding to an area exceeding one partial area.

[0069] 16, the signal processing intervals PI1, PI2, and PI3 correspond to the partial regions PR1, PR2, and PR3, respectively. However, the signal processing interval PI1 includes a portion of the partial region PR2, the signal processing interval PI2 includes portions of the partial regions PR1 and PR3, and the signal processing interval PI3 includes a portion of the partial region PR2. Therefore, for example, as shown by the overlapping region OR in FIG. 16, the signal processing intervals PI2 and PI3 overlap. This allows the laser radar device 1 to increase the number of frequency spectra used to calculate the average amplitude of the frequency spectra for each of the multiple partial regions, thereby improving the effect of averaging the effects of speckle and further reducing the variation in the received light intensity.

[0070] [Variation 4] In the above embodiment, the oscillator 9 is attached to the scanning unit 7 to move or vibrate the irradiation spot within the same partial region. However, the oscillator 9 may be attached to the optical window 3 to move or vibrate the irradiation spot.

[0071] [Variation 5] In the above embodiment, the additional scanning unit 16 scans the laser beam by rotating a mirror using a driving force generated by a motor. However, the additional scanning unit 16 may scan the laser beam using a grating or a liquid crystal polarizer.

[0072] [Variation 6] In the above embodiment, the frequencies fbu and fbd are detected by dividing the beat signal waveform data into a plurality of minute intervals for each of the up-modulation section and the down-modulation section and performing frequency analysis processing on the divided beat signal waveform data. However, the frequencies fbu and fbd may also be detected by performing frequency analysis processing on the beat signal waveform data without dividing the beat signal waveform data into a plurality of minute intervals for each of the up-modulation section and the down-modulation section.

[0073] [Variation 7] In the above embodiment, the laser diode 5 emits a laser beam whose frequency is swept based on the drive signal output from the laser drive circuit 4. However, the laser beam emitted from the laser diode 5 may be input to an external modulator, so that the laser beam whose frequency is swept is emitted from the external modulator.

[0074] The controller 14 and the methods described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the controller 14 and the methods described herein may be implemented by a special-purpose computer configured with a processor comprising one or more dedicated hardware logic circuits. Alternatively, the controller 14 and the methods described herein may be implemented by one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor comprising one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory storage medium. The methods for implementing the functions of each unit included in the controller 14 do not necessarily need to include software; all of the functions may be implemented using one or more hardware components.

[0075] In the above embodiments, multiple functions of one component may be realized by multiple components, or one function of one component may be realized by multiple components. Furthermore, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Furthermore, part of the configuration of the above embodiments may be omitted. Furthermore, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0076] In addition to the above-described laser radar device 1, the present disclosure can also be realized in various forms, such as a system including the laser radar device 1 as a component, a program for causing a computer to function as the laser radar device 1, a non-transient physical recording medium such as a semiconductor memory on which this program is recorded, and a ranging method. [Explanation of symbols]

[0077] REFERENCE SIGNS LIST 1... laser radar device, 4... laser drive circuit, 5... laser diode, 7... scanning unit, 8... motor drive circuit, 14... control unit

Claims

1. a transmitter (4, 5) configured to transmit frequency-modulated laser light; a scanning unit (7) configured to scan the laser light emitted from the transmitting unit; a distance calculation unit (14, S10 to S90) configured to receive the laser light transmitted from the scanning unit and reflected by an object for each of a plurality of partial areas obtained by dividing a laser light scanning area that is preset as a two-dimensional area in which the scanning unit scans the laser light, and to calculate at least a distance to the object in the partial area; a movement control unit (8, 14) configured to control the movement of the laser light so that, for each of the plurality of partial regions, the laser light moves within the partial region while satisfying Δθ>(1.22×λ / d), where Δθ is a movement angle range within the partial region, λ is a wavelength of the laser light, and d is a diameter of the laser light on the partial region; Equipped with The movement control unit (8, 14) controls the scanning unit by performing feedback control so that the scanning angle for each of the plurality of partial regions oscillates around a target angle corresponding to the partial region, thereby moving the laser light within the partial region while satisfying Δθ > (1.22 × λ / d).

2. A laser radar device according to claim 1, the scanning unit is configured to raster scan the laser light in a main scanning direction and a sub-scanning direction, The movement control unit moves the laser light within the partial region along at least one of the main scanning direction and the sub-scanning direction.

3. 3. The laser radar device according to claim 1, The movement control unit is a laser radar device that moves the laser light not only within each of the plurality of partial regions but also beyond the partial region.

4. a transmitter (4, 5) configured to transmit frequency-modulated laser light; a scanning unit (7) configured to scan the laser light emitted from the transmitting unit; a distance calculation unit (14, S10 to S90) configured to receive the laser light transmitted from the scanning unit and reflected by an object for each of a plurality of partial areas obtained by dividing a laser light scanning area that is preset as a two-dimensional area in which the scanning unit scans the laser light, and to calculate at least a distance to the object in the partial area; a movement control unit (8, 14) configured to control the scanning unit by performing feedback control so that a scanning angle oscillates around a target angle so that the laser light moves within each of the plurality of partial regions while satisfying Δθ>(1.22×λ / d), where Δθ is a movement angle range within the partial region, λ is a wavelength of the laser light, and d is a diameter of the laser light on the partial region; A laser radar device (1) comprising:

5. A laser radar device according to claim 4, the scanning unit is configured to raster scan the laser light in a main scanning direction and a sub-scanning direction, The movement control unit moves the laser light within the partial region along at least one of the main scanning direction and the sub-scanning direction.

6. A laser radar device according to claim 4 or claim 5, The movement control unit is a laser radar device that moves the laser light not only within each of the plurality of partial regions but also beyond the partial region.

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