Optical devices

Abstract

The density of spots at a desired location is controlled to a desired density. [Solution] An optical device comprising a signal generating unit that generates a first drive signal for driving a movable reflector that reflects a beam irradiated from a light-emitting element in a predetermined direction, wherein in a predetermined first period during which the first drive signal transitions from one of the maximum and minimum values ​​of the first drive signal to the other, the first drive signal includes a period having a first slope and a second slope different from the first slope, and the slope in the first period does not include a positive slope, or does not include a negative slope.

Description

Technical Field

[0001] The present invention relates to an optical device.

Background Art

[0002] In recent years, various optical devices such as LiDAR (Light Detection And Ranging) have been developed. For example, as described in Patent Document 1, an optical device includes a movable reflecting portion that reflects a beam irradiated from a light-emitting element such as a laser diode (LD). A spot is generated when the beam reflected by the movable reflecting portion irradiates an object to be measured by the optical device. By swinging the movable reflecting portion around a predetermined first rotation axis, the irradiation position of the beam can be displaced in the horizontal direction. Further, by swinging the movable reflecting portion around a second rotation axis orthogonal to the first rotation axis, the irradiation position of the beam can be displaced in the vertical direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an optical device such as LiDAR, it may be required to control the density of spots at a desired position to a desired density. For example, it may be required to make the density of spots in a part of the field of view of the optical device higher than the density of spots around that part.

[0005] As an example of the problems to be solved by the present invention, controlling the density of spots at a desired position to a desired density can be cited.

Means for Solving the Problems

[0006] The invention described in claim 1 is, It includes a signal generating unit that generates a first drive signal to drive a movable reflector that reflects a beam emitted from a light-emitting element in a predetermined direction, The first drive signal includes a predetermined first period in which the first drive signal transitions from one of its maximum and minimum values ​​to the other, and a second period in which the maximum and minimum values ​​transition from the other to the other. The length of the second period is shorter than the length of the first period. The second period includes, in order, a first sub-period having a first slope, a second sub-period having a second slope, and a third sub-period having a third slope, During the first and third short periods, the beam is not irradiated onto the movable reflector, and only during the second short period, the beam is irradiated onto the movable reflector. The optical device is such that the absolute value of the second slope is smaller than the absolute value of the first slope. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows an optical device according to Embodiment 1. [Figure 2] This is a graph showing the vertical drive signal according to Embodiment 1. [Figure 3] This is a graph showing the vertical drive signal according to Embodiment 2. [Figure 4] This is a graph showing the vertical drive signal according to Embodiment 3. [Figure 5] This is a graph showing the vertical drive signal according to Embodiment 4. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted where appropriate.

[0009] (Embodiment 1) Figure 1 shows an optical device 10 according to Embodiment 1.

[0010] In Figure 1, the arrows indicating the first direction X, the second direction Y, or the third direction Z indicate that the direction from the base to the tip of the arrow is the positive direction of the direction indicated by the arrow, and the direction from the tip to the base of the arrow is the negative direction of the direction indicated by the arrow.

[0011] The first direction X is parallel to the horizontal direction. The second direction Y is perpendicular to the first direction X. The second direction Y is parallel to the vertical direction. Specifically, the positive direction of the second direction Y is the direction from the bottom to the top in the vertical direction, and the negative direction of the second direction Y is the direction from the top to the bottom in the vertical direction. The third direction Z is perpendicular to both the first direction X and the second direction Y. The third direction Z is parallel to the horizontal direction. Specifically, the positive direction of the third direction Z is the direction from the side where the movable reflective part 120 (described later) is located to the side where the virtual surface IS (described later) is located, and the negative direction of the third direction Z is the direction from the side where the virtual surface IS is located to the side where the movable reflective part 120 is located.

[0012] The relationships between the first direction X, the second direction Y, the third direction Z, the horizontal direction, and the vertical direction are not limited to the examples described above. The relationships described above change depending on the arrangement of the optical device 10 in the horizontal and vertical directions. For example, the first direction X or the third direction Z may be parallel to the vertical direction.

[0013] The optical device 10 comprises a light-emitting element 110, a movable reflector 120, a light-receiving element 130, a beam splitter 140, a drive unit 210, and a signal generating unit 220. The drive unit 210 and signal generating unit 220 shown in Figure 1 are functional block diagrams. Therefore, the drive unit 210 and signal generating unit 220 shown in Figure 1 do not indicate the actual size or actual position of the drive unit 210 and signal generating unit 220.

[0014] The light-emitting element 110 is, for example, a laser diode (LD). The light-emitting element 110 is driven by a drive unit 210. The drive unit 210 is, for example, a laser driver. The drive unit 210 is controlled by a control unit such as a microcomputer (not shown). The light-emitting element 110 emits beam B at a predetermined repetition period. As shown by the dashed line extending from the light-emitting element 110 through the beam splitter 140 toward the movable reflector 120, beam B is emitted from the light-emitting element 110, reflected by the beam splitter 140, and irradiates the movable reflector 120.

[0015] In Embodiment 1, the movable reflector 120 is a MEMS (Micro Electro Mechanical Systems) mirror. The movable reflector 120 reflects beam B toward the positive direction side of the third direction Z of the movable reflector 120. In the example shown in Figure 1, a virtual plane IS exists on the positive direction side of the third direction Z of the movable reflector 120. The virtual plane IS is provided virtually to illustrate the optical device 10 according to Embodiment 1. Therefore, the virtual plane IS does not need to exist in the actual optical device 10. The virtual plane IS is perpendicular to the third direction Z. When beam B is irradiated onto the virtual plane IS, as shown by the dashed line extending from the movable reflector 120 to the virtual plane IS in Figure 1, a spot S is generated on the virtual plane IS.

[0016] The signal generation unit 220 inputs a horizontal drive signal and a vertical drive signal SA, which will be described later using Figure 2, to the movable reflector unit 120. The signal generation unit 220 is, for example, an arbitrary signal generator. In one example, the movable reflector unit 120 is driven horizontally by the horizontal drive signal. Specifically, the movable reflector unit 120 oscillates around a predetermined first rotation axis AX at the resonant frequency of the movable reflector unit 120. The movable reflector unit 120 is also driven vertically by the vertical drive signal SA. Specifically, the movable reflector unit 120 oscillates around a second rotation axis AY, which is orthogonal to the first rotation axis AX, at a frequency having a fundamental frequency lower than the resonant frequency of the movable reflector unit 120. However, the driving of the movable reflector unit 120 is not limited to this example.

[0017] When the beam B is emitted from the light-emitting element 110 at a predetermined repetition period, a plurality of spots S are generated along the scanning line L by the rocking of the movable reflecting portion 120 around the first rotation axis AX and the rocking of the movable reflecting portion 120 around the second rotation axis AY. Thereby, the distance measurement of the object in the visual field F can be performed. The visual field F shown in FIG. 1 shows the visual field projected onto the virtual plane IS. The scanning line L exists within the visual field F projected onto the virtual plane IS.

[0018] After the beam B is reflected by the movable reflecting portion 120, it is irradiated onto an object (not shown) located on the positive side in the third direction Z of the movable reflecting portion 120. When the beam B is reflected or scattered by the object, the reflected light or scattered light of the beam B is irradiated onto the movable reflecting portion 120 as received light. As shown by the broken line extending from the movable reflecting portion 120 toward the light-receiving element 130 via the beam splitter 140, the received light is reflected by the movable reflecting portion 120, transmitted through the beam splitter 140, and irradiated onto the light-receiving element 130. Thereby, the light-receiving element 130 is receiving the received light. The light-receiving element 130 is, for example, an avalanche photodiode (APD). For example, the light-receiving element 130 is electrically connected to a light-receiving circuit (not shown). The light-receiving circuit generates a received signal by receiving the received light by the light-receiving element 130. The optical device 10 includes a computer such as a microcomputer (not shown) electrically connected to the light-receiving circuit. The computer measures the distance of the object irradiated with the beam B by measuring the time from when the beam B is emitted from the light-emitting element 110 until the received light is received by the light-receiving element 130.

[0019] FIG. 2 is a graph showing the vertical drive signal SA according to Embodiment 1.

[0020] The horizontal axis of the graph shown in FIG. 2 indicates time. The arrow indicating the horizontal axis indicates that time elapses from the base end on the left side of the arrow toward the tip on the right side of the arrow.

[0021] The vertical axis of the graph shown in Figure 2 represents the voltage value of the vertical drive signal SA. The arrows indicating the vertical axis show that the voltage value increases from the lower base end of the arrow to the upper tip of the arrow. The voltage value of the vertical drive signal SA is 0 on the horizontal axis, which represents time. When the beam B is irradiated onto the movable reflector 120 when the voltage value of the vertical drive signal SA is 0, the spot S is generated approximately in the center of the second direction Y of the field of view F. The larger the voltage value of the vertical drive signal SA, the more the generation position of the spot S when the beam B is irradiated onto the movable reflector 120 is displaced upward in the positive direction of the second direction Y of the field of view F. The smaller the voltage value of the vertical drive signal SA, the more the generation position of the spot S when the beam B is irradiated onto the movable reflector 120 is displaced downward in the negative direction of the second direction Y of the field of view F.

[0022] The vertical drive signal SA changes periodically. Each period of the vertical drive signal SA includes a descent period DA and an ascent period UA. The descent period DA and the ascent period UA alternate. During the descent period DA, the vertical drive signal SA transitions from its maximum value to its minimum value. During the ascent period UA, the vertical drive signal SA transitions from its minimum value to its maximum value.

[0023] Let's explain the downward period DA.

[0024] Throughout the entire descent period DA, the drive unit 210 emits beam B from the light-emitting element 110 at a predetermined repetition period. As a result, multiple spots S are generated along the scan line L across the entire second direction Y of the field of view F. Therefore, the descent period DA is the main ranging period in which ranging is measured over a wider area in the second direction Y of the field of view F than in the ranging period UA described later.

[0025] The slope of the descent period DA is substantially constant throughout the entire descent period DA. Therefore, during the descent period DA, the density of spot S in the second direction Y is substantially constant throughout the entire second direction Y of the field of view F.

[0026] Let's explain the upward period of UA.

[0027] In the example shown in Figure 2, a virtual line LA is added to the rise period UA for illustrative purposes. The virtual line LA is a line segment connecting the minimum value of the vertical drive signal SA at the beginning of the rise period UA and the maximum value of the vertical drive signal SA at the end of the rise period UA. The slope of the virtual line LA is substantially constant throughout the entire rise period UA.

[0028] The rise period UA includes the first non-irradiation period NA1, the irradiation period MA, and the second non-irradiation period NA2. The first non-irradiation period NA1, the irradiation period MA, and the second non-irradiation period NA2 are consecutive.

[0029] During the first non-irradiation period NA1 and the second non-irradiation period NA2, the drive unit 210 stops the emission of beam B from the movable reflector 120. Therefore, no spots S are generated during the first non-irradiation period NA1 and the second non-irradiation period NA2. In contrast, during the irradiation period MA, the drive unit 210 emits beam B from the light-emitting element 110 at a predetermined repetition period. Therefore, multiple spots S are generated along the scan line L during the irradiation period MA. Consequently, the rising period UA is a sub-distancing period in which distance measurement is performed over a narrower range in the second direction Y of the field of view F than during distance measurement in the falling period DA.

[0030] The irradiation period MA in Embodiment 1 is the period during which the voltage value of the vertical drive signal SA switches from negative to positive, and the period surrounding that period. Therefore, during the irradiation period MA, spots S are generated at the center of the second direction Y of the field of view F and at the periphery of that second direction Y. As a result, the density of spots S at the center of the second direction Y of the field of view F and at the periphery of that second direction Y can be increased compared to the case where spots S are not generated during the irradiation period MA.

[0031] In Embodiment 1, the slope of the vertical drive signal SA during the irradiation period MA is different from the slope of the vertical drive signal SA during the first non-irradiation period NA1 and the second non-irradiation period NA2. Specifically, the absolute value of the slope of the vertical drive signal SA during the irradiation period MA is smaller than the absolute value of the slope of the vertical drive signal SA during the first non-irradiation period NA1 and the second non-irradiation period NA2. The positive and negative signs of the slope of the vertical drive signal SA are determined by whether the voltage value of the vertical drive signal SA increases over time, and whether the voltage value of the vertical drive signal SA decreases over time.

[0032] In Embodiment 1, the absolute value of the slope of the vertical drive signal SA during the irradiation period MA is smaller than the absolute value of the slope of the virtual line LA. Therefore, compared to the case where the absolute value of the slope of the vertical drive signal SA during the irradiation period MA is greater than or equal to the absolute value of the slope of the virtual line LA, the density of spots S generated in the second direction Y during the irradiation period MA can be increased.

[0033] In Embodiment 1, it is preferable that the absolute value of the slope of the vertical drive signal SA during the first non-irradiation period NA1 and the second non-irradiation period NA2 be as large as possible under the constraints of the driving characteristics of the movable reflector 120. For example, the absolute value of the slope of the vertical drive signal SA during the first non-irradiation period NA1 and the second non-irradiation period NA2 may be the maximum absolute value allowed under the constraints of the driving characteristics of the movable reflector 120. In this case, compared to the case where the vertical drive signal SA transitions with the slope of the maximum absolute value over the entire range from the minimum to the maximum value, the density of spots S at the desired position can be increased with only a slight decrease in frame rate.

[0034] The waveform of the vertical drive signal SA is not limited to the waveform according to Embodiment 1.

[0035] For example, the absolute value of the slope of the vertical drive signal SA during the irradiation period MA may be greater than the absolute value of the slope of the vertical drive signal SA during the first non-irradiation period NA1 and the second non-irradiation period NA2.

[0036] Furthermore, the rise period UA may include a period in which the slope of the vertical drive signal SA is 0 or negative. For example, the slope of the vertical drive signal SA may be 0 or negative during at least one portion of the first non-irradiation period NA1, the irradiation period MA, and the second non-irradiation period NA2. This may result in, for example, the positive and negative signs of the slope of the vertical drive signal SA in at least one of the first non-irradiation period NA1, the irradiation period MA, and the second non-irradiation period NA2 being reversed from the positive and negative signs of the slope of the vertical drive signal SA in the irradiation period MA.

[0037] Furthermore, in Embodiment 1, the rising period UA is a predetermined first period. As exemplified by the first non-irradiation period NA1 or the second non-irradiation period NA2, for a portion of the predetermined first period, the beam B is not irradiated to the movable reflector 120 and the vertical drive signal SA has a predetermined first inclination. Also, as exemplified by the irradiation period MA, for another portion of the predetermined first period, the beam B is irradiated to the movable reflector 120 and the vertical drive signal SA has a second inclination different from the first inclination. However, the descending period DA may be the predetermined first period. In this example, for a portion of the descending period DA, the beam B is not irradiated to the movable reflector 120 and the vertical drive signal SA has a predetermined first inclination. Also, for another portion of the descending period DA, the beam B is irradiated to the movable reflector 120 and the vertical drive signal SA has a second inclination different from the first inclination. In this example, the beam B emitted from the light-emitting element 110 at a predetermined repetition rate may irradiate the movable reflector 120 throughout the entire rising period UA.

[0038] In Embodiment 1, the control of the waveform of a drive signal that drives the movable reflective part 120 in the vertical direction was described, as exemplified by the vertical drive signal SA. However, the waveform control according to Embodiment 1 is applicable not only to the waveform of a drive signal that drives the movable reflective part 120 in the vertical direction, but also to the waveform of a drive signal that drives the movable reflective part 120 in a predetermined direction different from the vertical direction. In this case, the waveform control according to Embodiment 1 is applicable to either or both of the waveform of the drive signal that drives the movable reflective part 120 in the vertical direction and the waveform of the drive signal that drives the movable reflective part 120 in a direction different from the vertical direction.

[0039] Furthermore, the irradiation of the movable reflector 120 with beam B during the rising period UA is not limited to the embodiment according to Embodiment 1. For example, the drive unit 210 may emit beam B from the light-emitting element 110 at a predetermined repetition cycle not only during the irradiation period MA, but also during at least one of the first non-irradiation period NA1 and the second non-irradiation period NA2. Also, the irradiation of the movable reflector 120 with beam B during the rising period UA may be performed not only during a single period of the irradiation period MA, but also during multiple divided periods.

[0040] (Embodiment 2) Figure 3 is a graph showing the vertical drive signal SB according to Embodiment 2. The vertical drive signal SB according to Embodiment 2 is the same as the vertical drive signal SA according to Embodiment 1, except for the following points.

[0041] The vertical drive signal SB according to Embodiment 2 changes periodically, similar to the vertical drive signal SA according to Embodiment 1. Each period of the vertical drive signal SB according to Embodiment 2 includes a descent period DB and an ascent period UB. The ascent period UB according to Embodiment 2 includes a first non-irradiation period NB1, an irradiation period MB, and a second non-irradiation period NB2. Furthermore, a virtual line LB is attached to the ascent period UB according to Embodiment 2 for illustrative purposes.

[0042] In Embodiment 2, the irradiation period MB is the period during which the voltage value of the vertical drive signal SB is positive. Therefore, in Embodiment 2, compared to Embodiment 1, the density of spots S above the positive direction of the second direction Y relative to the center of the second direction Y of the field of view F can be increased. The irradiation period MB may be the period during which the voltage value of the vertical drive signal SB is negative. In this case, compared to Embodiment 1, the density of spots S below the negative direction of the second direction Y relative to the center of the second direction Y of the field of view F can be increased.

[0043] As described in Embodiments 1 and 2, the density of spots S at a desired position in the second direction Y of the field of view F can be controlled to a desired density depending on the setting of the irradiation period. Specifically, the generation position of spots S during the rising period can be controlled depending on the value of the vertical drive signal during the irradiation period. For example, if the irradiation period includes a period in which the voltage value of the vertical drive signal switches from negative to positive, spots S during the rising period are generated at the center and around the second direction Y of the field of view F. Also, if the voltage value of the vertical drive signal is positive throughout the entire irradiation period, spots S during the rising period are generated above the center of the second direction Y of the field of view F in the positive direction of the second direction Y. Furthermore, if the voltage value of the vertical drive signal is negative throughout the entire irradiation period, spots S during the rising period are generated below the center of the second direction Y of the field of view F in the negative direction of the second direction Y.

[0044] Next, we will explain the DC component included in the vertical drive signal SB.

[0045] In Embodiment 2, the vertical drive signal SB in each period contains a positive DC component. The DC component in each period of the vertical drive signal SB is positive when the integral value of each period of the vertical drive signal SB is positive, and negative when the integral value of each period of the vertical drive signal SB is negative. If a positive or negative DC current flows steadily through the circuit constituting the signal generation unit 220, it may cause overheating or damage to the circuit constituting the signal generation unit 220. For this reason, it is desirable to avoid the steady flow of the DC component contained in the vertical drive signal SB.

[0046] In Embodiment 2, the vertical drive signal SB at a period different from the predetermined period shown in Figure 3 may contain a negative DC component. For example, the waveform of the vertical drive signal SB at a period different from the predetermined period may be modified from the waveform of the vertical drive signal SB at the predetermined period. This makes it possible to include a negative DC component in the vertical drive signal SB at a period different from the predetermined period. In this case, at least a portion of the positive DC component at the predetermined period can be canceled out by the negative DC component at a period different from the predetermined period. In this case, the absolute value of the positive DC component at the predetermined period and the absolute value of the negative DC component at a period different from the predetermined period may be equal or different. Furthermore, the positive DC component at the predetermined period may be canceled out by a negative DC component at one period different from the predetermined period, or by negative DC components at multiple periods different from the predetermined period.

[0047] (Embodiment 3) Figure 4 is a graph showing the vertical drive signal SC according to Embodiment 3. The vertical drive signal SC according to Embodiment 3 is the same as the vertical drive signal SB according to Embodiment 2, except for the following points.

[0048] The vertical drive signal SC according to Embodiment 3 changes periodically, similar to the vertical drive signal SB according to Embodiment 2. Each period of the vertical drive signal SC according to Embodiment 3 includes a descent period DC and an ascent period UC. The ascent period UC according to Embodiment 3 includes a first non-irradiation period NC1, a second non-irradiation period NC2, a third non-irradiation period NC3, an irradiation period MC, and a fourth non-irradiation period NC4. The first non-irradiation period NC1, the second non-irradiation period NC2, the third non-irradiation period NC3, the irradiation period MC, and the fourth non-irradiation period NC4 are sequentially continuous. Furthermore, a virtual line LC is added to the ascent period UC according to Embodiment 3 for illustrative purposes.

[0049] During the first non-irradiation period NC1, the second non-irradiation period NC2, the third non-irradiation period NC3, and the fourth non-irradiation period NC4, the drive unit 210 stops the emission of beam B from the movable reflector 120. Therefore, no spots S are generated during the first non-irradiation period NC1, the second non-irradiation period NC2, the third non-irradiation period NC3, and the fourth non-irradiation period NC4. In contrast, during the irradiation period MC, the drive unit 210 emits beam B from the light-emitting element 110 at a predetermined repetition cycle. Therefore, during the irradiation period MC, multiple spots S are generated along the scan line L.

[0050] In Embodiment 3, the irradiation period MC is the period during which the voltage value of the vertical drive signal SC is positive. Therefore, in Embodiment 3, compared to Embodiment 1, the density of spots S above the positive direction of the second direction Y relative to the center of the second direction Y of the field of view F can be increased.

[0051] In Embodiment 3, the vertical drive signal SC during the third non-irradiation period NC3 has a predetermined first slope. During the third non-irradiation period NC3, the voltage value of the vertical drive signal SC switches from negative to positive. During the irradiation period MC, the vertical drive signal SC has a second slope different from the first slope. Specifically, the absolute value of the second slope is smaller than the absolute value of the first slope. During the irradiation period MC, the voltage value of the vertical drive signal SC is positive. During the second non-irradiation period NC2, the vertical drive signal SC has a third slope different from the first slope. Specifically, the absolute value of the third slope is smaller than the absolute value of the first slope. During the second non-irradiation period NC2, the voltage value of the vertical drive signal SC is negative. Therefore, compared to the case where the vertical drive signal SC fluctuates along the line segment connecting the start of the first non-irradiation period NC1 and the start of the irradiation period MC, the positive DC component of the vertical drive signal SC can be reduced.

[0052] The irradiation of the movable reflector 120 with beam B during the rising period UC is not limited to the configuration according to Embodiment 3. For example, the drive unit 210 may emit beam B from the light-emitting element 110 at a predetermined repetition cycle not only during the irradiation period MC, but also during periods other than the irradiation period MC of the rising period UC, such as the second non-irradiation period NC2 and the third non-irradiation period NC3.

[0053] (Embodiment 4) Figure 5 is a graph showing the vertical drive signal SD according to Embodiment 4. The vertical drive signal SD according to Embodiment 4 is the same as the vertical drive signal SA according to Embodiment 1, except for the following points.

[0054] The vertical drive signal SD according to Embodiment 4 changes periodically, similar to the vertical drive signal SA according to Embodiment 1. Each period of the vertical drive signal SD according to Embodiment 4 includes a descending period DD and an ascending period UD. The ascending period UD according to Embodiment 4 includes a first non-irradiation period ND1, an irradiation period MD, and a first non-irradiation period ND2. Furthermore, a virtual line LD is attached to the ascending period UD according to Embodiment 4 for illustrative purposes.

[0055] The descent period DD according to Embodiment 4 includes a first descent period D1, a second descent period D2, and a third descent period D3. The first descent period D1, the second descent period D2, and the third descent period D3 are sequentially consecutive. During the first descent period D1, the voltage value of the vertical drive signal SD is positive. During the second descent period D2, the voltage value of the vertical drive signal SD switches from positive to negative. During the third descent period D3, the voltage value of the vertical drive signal SD is negative.

[0056] In Embodiment 4, the slope of the vertical drive signal SD during a portion of the descent period DD differs from the slope of the vertical drive signal SD during other portions of the ascent period UD. Specifically, the absolute value of the slope of the vertical drive signal SD during the second descent period D2 is smaller than the absolute value of the slope of the vertical drive signal SD during the first descent period D1 and the third descent period D3. Therefore, compared to the case where the slope of the vertical drive signal SD during the descent period DD is constant throughout the entire descent period DD, the density of the spot S at the center and around the second direction Y of the field of view F can be increased.

[0057] The embodiments of the present invention have been described above with reference to the drawings, but these are merely examples of the present invention, and various other configurations can also be adopted.

[0058] For example, in this embodiment, the beam B emitted from the light-emitting element 110 is a pulsed beam emitted at a predetermined repetition period. However, the beam B emitted from the light-emitting element 110 may be continuous light. Even when the beam B is continuous light, the density of spots S at a desired position can be controlled to a desired density by driving the movable reflector 120 in the same manner as in this embodiment.

[0059] This application claims priority based on Japanese Patent Application No. 2021-206822, filed on 21 December 2021, and incorporates all of its disclosures herein. [Explanation of symbols]

[0060] 10 Optical equipment 110 light-emitting elements 120 Movable reflector 130 Photodetector 140 Beam Splitter 210 Drive unit 220 Signal generation unit AX First rotation axis AY Second rotation axis B beam D1 1st falling period D2 Second down period D3 Third Downward Period DA decline period DB down period DC fall period DD down period F field of view IS Virtual Surface L scan line LA virtual line LB virtual line LC virtual line LD virtual line MA irradiation period MB irradiation period MC irradiation period MD irradiation period NA1 First Non-Irradiation Period NA2 2nd non-irradiation period NB1 1st non-irradiation period NB2 Second Non-Irradiation Period NC1 1st non-irradiation period NC2 2nd non-irradiation period NC3 Third Non-Irradiation Period NC4 4th non-irradiation period ND1 First Non-Irradiation Period ND2 1st non-irradiation period S Spot SA Vertical Drive Signal SB Vertical Drive Signal SC Vertical Drive Signal SD vertical drive signal UA rise period UB rise period UC rise period UD rise period X 1st direction Y Second direction Z 3rd direction

Claims

1. It includes a signal generating unit that generates a first drive signal to drive a movable reflector that reflects a beam emitted from a light-emitting element in a predetermined direction, The first drive signal includes a predetermined first period in which the first drive signal transitions from one of its maximum and minimum values ​​to the other, and a second period in which the maximum and minimum values ​​transition from the other to the other. The length of the second period is shorter than the length of the first period. The aforementioned second period includes, in order, a first sub-period having a first slope, a second sub-period having a second slope, and a third sub-period having a third slope, During the first and third short periods, the beam is not irradiated onto the movable reflector, and only during the second short period, the beam is irradiated onto the movable reflector. An optical device in which the absolute value of the second slope is smaller than the absolute value of the first slope.

2. In the optical apparatus described in claim 1, The first drive signal drives the movable reflector in the vertical direction, an optical device.

3. In the optical apparatus described in claim 1, The optical device wherein the second short period includes a period during which the voltage value of the first drive signal switches from negative to positive.

4. In the optical apparatus described in claim 3, An optical device in which the time before and after the voltage value of the first drive signal is zero is equal.

5. In the optical apparatus described in claim 1, An optical device wherein the second short period does not include the period during which the voltage value of the first drive signal switches from negative to positive, and either the first short period or the third short period includes the period during which the voltage value of the first drive signal switches from negative to positive.

6. In the optical apparatus described in claim 1, An optical device in which the length of the second short period is longer than the sum of the lengths of the first short period and the third short period.

7. In the optical apparatus described in claim 1, The signal generating unit further generates a second drive signal that drives the movable reflector in a direction perpendicular to the predetermined direction, An optical device in which the frequency of the first drive signal is lower than the frequency of the second drive signal.

8. In the optical apparatus according to any one of claims 1 to 4, An optical device further comprising a photodetector that receives reflected or scattered light of the beam reflected by the movable reflector.

9. It includes a signal generating unit that generates a first drive signal to drive a movable reflector that reflects a beam emitted from a light-emitting element in a predetermined direction, The first drive signal includes a predetermined first period during which the first drive signal transitions from one of its maximum and minimum values ​​to the other, and a predetermined second period during which the maximum and minimum values ​​transition from the other to the other. The length of the first period is shorter than the length of the second period. The first drive signal includes a first slope and a period having a second slope different from the first slope. The slope during the first period described above is either free of positive slopes or free of negative slopes. The optical device wherein the first period is the period during which a beam is irradiated from the light-emitting element.

10. The slope in the second period is the other of not including the positive slope and not including the negative slope. The optical apparatus according to claim 9.

11. It includes a signal generating unit that generates a first drive signal to drive a movable reflector that reflects a beam emitted from a light-emitting element in a predetermined direction, The first drive signal includes a predetermined first period in which the first drive signal transitions from one of its maximum and minimum values ​​to the other, and a second period in which the maximum and minimum values ​​transition from the other to the other. The length of the second period is shorter than the length of the first period. The aforementioned second period includes, in order, a first sub-period having a first slope, a second sub-period having a second slope, and a third sub-period having a third slope, During the first, second, and third short periods, the beam is irradiated onto the movable reflector. An optical device in which the absolute value of the second slope is smaller than the absolute value of the first slope.

12. In the optical apparatus according to claim 11, The optical device wherein the second short period includes a period during which the voltage value of the first drive signal switches from negative to positive.

13. In the optical apparatus according to claim 12, An optical device in which the time before and after the voltage value of the first drive signal is zero is equal.

14. In the optical apparatus according to claim 11, An optical device wherein the second short period does not include the period during which the voltage value of the first drive signal switches from negative to positive, and either the first short period or the third short period includes the period during which the voltage value of the first drive signal switches from negative to positive.

15. In the optical apparatus according to claim 11, An optical device in which the length of the second short period is longer than the sum of the lengths of the first short period and the third short period.

16. In the optical apparatus according to claim 11, The signal generating unit further generates a second drive signal that drives the movable reflector in a direction perpendicular to the predetermined direction, An optical device in which the frequency of the first drive signal is lower than the frequency of the second drive signal.

17. In the optical apparatus according to any one of claims 9 to 16, An optical device further comprising a photodetector that receives reflected or scattered light of the beam reflected by the movable reflector.

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