Optical device

Abstract

To control the density of spots at a desired position to a desired density.SOLUTION: A rise period UA equals a prescribed first period. As illustrated by a first non-irradiation period NA1 or a second non-irradiation period NA2, a beam B is not irradiated upon a movable reflection part (120) and a vertical drive signal SA has a prescribed first slope in a portion of the prescribed first period. Furthermore, as illustrated by an irradiation period MA, the beam B is irradiated upon the movable reflection part (120) and the vertical drive signal SA has a second slope that is different from the first slope in the other portion of the prescribed first period.SELECTED DRAWING: Figure 2

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 distance-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 mentioned.

Means for Solving the Problems

[0006] The invention according to claim 1 is provided with a signal generation unit that generates a drive signal for driving a movable reflection unit that reflects a beam irradiated from a light-emitting element in a predetermined direction, wherein a predetermined first period in which the drive signal transitions from one of a maximum value and a minimum value of the drive signal to the other includes a period in which the beam is not irradiated to the movable reflection unit and the drive signal has a predetermined first slope, and a period in which the beam is irradiated to the movable reflection unit and the drive signal has a second slope different from the first slope, and is an optical device.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

[0009] (Embodiment 1) FIG. 1 is a diagram showing an optical device 10 according to Embodiment 1.

[0010] In FIG. 1, an arrow indicating the first direction X, the second direction Y, or the third direction Z indicates that the direction from the base end 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 end of the arrow is the negative direction of the direction indicated by the arrow.

[0011] The first direction X is a direction parallel to the horizontal direction. The second direction Y is orthogonal to the first direction X. The second direction Y is a direction parallel to the vertical direction. Specifically, the positive direction of the second direction Y is the direction from the lower side to the upper side of the vertical direction, and the negative direction of the second direction Y is the direction from the upper side to the lower side of the vertical direction. The third direction Z is orthogonal to both the first direction X and the second direction Y. The third direction Z is a direction parallel to the horizontal direction. Specifically, the positive direction of the third direction Z is the direction from the side where the movable reflection part 120, which will be described later, is located to the side where the virtual plane IS, which will be described later, is located, and the negative direction of the third direction Z is the direction from the side where the virtual plane IS is located to the side where the movable reflection part 120 is located.

[0012] Note that the relationships among the first direction X, the second direction Y, the third direction Z, the horizontal direction, and the vertical direction are not limited to the above-described example. Depending on the arrangement of the optical device 10 with respect to the horizontal direction and the vertical direction, the above-described relationships change. For example, the first direction X or the third direction Z may be parallel to the vertical direction.

[0013] The optical device 10 includes a light-emitting element 110, a movable reflection part 120, a light-receiving element 130, a beam splitter 140, a driving part 210, and a signal generation part 220. The driving part 210 and the signal generation part 220 shown in FIG. 1 are functional block diagrams. Therefore, the driving part 210 and the signal generation part 220 shown in FIG. 1 do not suggest the actual sizes and actual positions of the driving part 210 and the signal generation part 220.

[0014] The light-emitting element 110 is, for example, a laser diode (LD). The light-emitting element 110 is driven by the driving part 210. The driving part 210 is, for example, a laser driver. Also, the driving part 210 is controlled by a control part such as a microcomputer (not shown). The light-emitting element 110 emits a beam B at a predetermined repetition period. As shown by the broken line extending from the light-emitting element 110 toward the movable reflection part 120 via the beam splitter 140, the beam B is emitted from the light-emitting element 110, reflected by the beam splitter 140, and irradiated onto the movable reflection part 120.

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

[0016] The signal generation part 220 inputs a horizontal drive signal and a vertical drive signal SA, which will be described later with reference to FIG. 2, to the movable reflecting part 120. The signal generation part 220 is, for example, an arbitrary signal generator. In one example, the movable reflecting part 120 is driven in the horizontal direction by the horizontal drive signal. Specifically, the movable reflecting part 120 oscillates around a predetermined first rotation axis AX at the resonance frequency of the movable reflecting part 120. Also, the movable reflecting part 120 is driven in the vertical direction by the vertical drive signal SA. Specifically, the movable reflecting part 120 oscillates around a second rotation axis AY orthogonal to the first rotation axis AX at a frequency having a fundamental frequency lower than the resonance frequency of the movable reflecting part 120. However, the driving of the movable reflecting part 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 due to the oscillation of the movable reflecting part 120 around the first rotation axis AX and the oscillation of the movable reflecting part 120 around the second rotation axis AY. Thereby, the distance measurement of an object in the visual field F can be performed. The visual field F shown in FIG. 1 shows the visual field projected on the virtual plane IS. The scanning line L exists within the visual field F projected on the virtual plane IS.

[0018] After the beam B is reflected by the movable reflection unit 120, it is irradiated onto an object (not shown) located on the positive direction side of the third direction Z of the movable reflection unit 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 reflection unit 120 as received light. As indicated by the dashed line extending from the movable reflection unit 120 through the beam splitter 140 toward the light receiving element 130, the received light is reflected by the movable reflection unit 120, transmitted through the beam splitter 140, and irradiated onto the light receiving element 130. Thus, 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 upon 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 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, thereby measuring the distance to the object irradiated by the beam B.

[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 shows 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 FIG. 2 indicates the voltage value of the vertical drive signal SA. The arrow indicating the vertical axis shows that the voltage value increases from the base end on the lower side of the arrow to the tip on the upper side of the arrow. The voltage value of the vertical drive signal SA is 0 on the horizontal axis indicating time. When the movable reflecting portion 120 is irradiated with the beam B when the voltage value of the vertical drive signal SA is 0, the spot S is generated substantially at the center in the second direction Y of the visual field F. As the voltage value of the vertical drive signal SA increases, the generation position of the spot S when the movable reflecting portion 120 is irradiated with the beam B is displaced upward in the positive direction of the second direction Y of the visual field F. As the voltage value of the vertical drive signal SA decreases, the generation position of the spot S when the movable reflecting portion 120 is irradiated with the beam B is displaced downward in the negative direction of the second direction Y of the visual field F.

[0022] The vertical drive signal SA changes periodically. Each period of the vertical drive signal SA includes a falling period DA and a rising period UA. The falling period DA and the rising period UA are repeated alternately. In the falling period DA, the vertical drive signal SA transitions from the maximum value to the minimum value of the vertical drive signal SA. In the rising period UA, the vertical drive signal SA transitions from the minimum value to the maximum value of the vertical drive signal SA.

[0023] The falling period DA will be described.

[0024] Throughout the falling period DA, the drive unit 210 causes the beam B to be emitted from the light emitting element 110 at a predetermined repetition period. For this reason, a plurality of spots S are generated along the scanning line L over the entire second direction Y of the visual field F. Therefore, the falling period DA is the main ranging period in which ranging is performed in a wider range in the second direction Y of the visual field F than the ranging in the rising period UA described later.

[0025] The slope of the falling period DA is substantially constant throughout the falling period DA. Therefore, in the falling period DA, the density of the spots S in the second direction Y is substantially constant over the entire second direction Y of the visual field F.

[0026] The rising period UA will be described.

[0027] In the example shown in FIG. 2, for the sake of explanation, a virtual line LA is attached to the rising period UA. The virtual line LA is a line segment connecting the minimum value of the vertical drive signal SA at the start of the rising period UA and the maximum value of the vertical drive signal SA at the end of the rising period UA. The slope of the virtual line LA is substantially constant throughout the entire rising period UA.

[0028] The rising period UA includes a first non-irradiation period NA1, an irradiation period MA, and a second non-irradiation period NA2. The first non-irradiation period NA1, the irradiation period MA, and the second non-irradiation period NA2 are successively continuous.

[0029] In the first non-irradiation period NA1 and the second non-irradiation period NA2, the drive unit 210 stops the emission of the beam B from the movable reflection unit 120. Therefore, in the first non-irradiation period NA1 and the second non-irradiation period NA2, no spot S is generated. On the other hand, in the irradiation period MA, the drive unit 210 emits the beam B from the light emitting element 110 at a predetermined repetition period. Therefore, in the irradiation period MA, a plurality of spots S are generated along the scanning line L. Therefore, the rising period UA is a sub-distance measurement period in which distance measurement is performed in a narrower range in the second direction Y of the visual field F than the distance measurement in the falling period DA.

[0030] The irradiation period MA according to Embodiment 1 is a period in which the voltage value of the vertical drive signal SA switches from negative to positive and the surrounding periods thereof. Therefore, in the irradiation period MA, spots S are generated at the center in the second direction Y of the visual field F and the periphery thereof in the second direction Y. Therefore, compared with the case where no spot S is generated in the irradiation period MA, the density of the spots S at the center in the second direction Y of the visual field F and the periphery thereof in the second direction Y can be increased.

[0031] In Embodiment 1, the slope of the vertical drive signal SA during the irradiation period MA is different from the slopes 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 values of the slopes of the vertical drive signal SA during the first non-irradiation period NA1 and the second non-irradiation period NA2. Note that the positive and negative signs of the slope of the vertical drive signal SA are positive when the voltage value of the vertical drive signal SA increases as time elapses, and negative when the voltage value of the vertical drive signal SA decreases as time elapses.

[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 with 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 the spot S in the second direction Y generated during the irradiation period MA can be made higher.

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

[0036] Further, the rising period UA may include a period during which the slope of the vertical drive signal SA is 0 or negative. For example, during at least a part of at least one of the first non-irradiation period NA1, the irradiation period MA, and the second non-irradiation period NA2, the slope of the vertical drive signal SA may be 0 or negative. As a result, 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 may be inverted with the positive and negative signs of the slope of the vertical drive signal SA in the irradiation period MA.

[0037] Also, 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, during a part of the predetermined first period, the beam B is not irradiated to the movable reflecting portion 120 and the vertical drive signal SA has a predetermined first slope. Also, as exemplified by the irradiation period MA, during another part of the predetermined first period, the beam B is irradiated to the movable reflecting portion 120 and the vertical drive signal SA has a second slope different from the first slope. However, the falling period DA may be the predetermined first period. In this example, during a part of the falling period DA, the beam B is not irradiated to the movable reflecting portion 120 and the vertical drive signal SA has a predetermined first slope. Also, during another part of the falling period DA, the beam B is irradiated to the movable reflecting portion 120 and the vertical drive signal SA has a second slope different from the first slope. In this example, throughout the rising period UA, the beam B emitted from the light emitting element 110 at a predetermined repetition period may be irradiated to the movable reflecting portion 120.

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

[0039] Also, the irradiation of the beam B to the movable reflection unit 120 during the rising period UA is not limited to the aspect according to Embodiment 1. For example, 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, the drive unit 210 may emit the beam B from the light-emitting element 110 at a predetermined repetition period. Further, the irradiation of the beam B to the movable reflection unit 120 during the rising period UA may be performed not only during a single period of the irradiation period MA but also during a plurality of divided periods.

[0040] (Embodiment 2) FIG. 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 in the same manner as the vertical drive signal SA according to Embodiment 1. Each period of the vertical drive signal SB according to Embodiment 2 includes a falling period DB and a rising period UB. The rising period UB according to Embodiment 2 includes a first non-irradiation period NB1, an irradiation period MB, and a second non-irradiation period NB2. Also, a virtual line LB is attached to the rising period UB according to Embodiment 2 for the sake of explanation.

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

[0043] From the descriptions of Embodiment 1 and Embodiment 2, according to the setting of the irradiation period, the density of the spot S at a desired position in the second direction Y of the visual field F can be controlled to a desired density. Specifically, according to the value of the vertical drive signal during the irradiation period, the generation position of the spot S during the rising period can be controlled. For example, when the irradiation period includes a period during which the voltage value of the vertical drive signal switches from negative to positive, the spot S during the rising period is generated at the center of the second direction Y of the visual field F and its periphery. Also, when the voltage value of the vertical drive signal is positive throughout the irradiation period, the spot S during the rising period is generated above the positive direction of the second direction Y with respect to the center of the second direction Y of the visual field F. Furthermore, when the voltage value of the vertical drive signal is negative throughout the irradiation period, the spot S during the rising period is generated below the negative direction of the second direction Y with respect to the center of the second direction Y of the visual field F.

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

[0045] The vertical drive signal SB in each period in Embodiment 2 includes a positive DC component. The DC component included 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. A constant flow of positive or negative DC current through the circuit constituting the signal generation unit 220 may cause heat generation or destruction of the circuit constituting the signal generation unit 220. Therefore, it is desirable to avoid a steady flow of the DC component included in the vertical drive signal SB.

[0046] In Embodiment 2, the vertical drive signal SB in a period different from the predetermined period shown in FIG. 3 may include a negative DC component. For example, the waveform of the vertical drive signal SB in a period different from the predetermined period may be deformed from the waveform of the vertical drive signal SB in the predetermined period. Thereby, the vertical drive signal SB in a period different from the predetermined period can be made to include a negative DC component. Further, in this case, at least a part of the positive DC component in the predetermined period can be canceled by the negative DC component in a period different from the predetermined period. In this case, the absolute value of the positive DC component in the predetermined period and the absolute value of the negative DC component in a period different from the predetermined period may be equal or different. Also, the positive DC component in the predetermined period may be canceled by the negative DC component in one period different from the predetermined period, or may be canceled by the negative DC components in a plurality of periods different from the predetermined period.

[0047] (Embodiment 3) FIG. 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 in the same manner as the vertical drive signal SB according to Embodiment 2. Each period of the vertical drive signal SC according to Embodiment 3 includes a falling period DC and a rising period UC. The rising 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 successively continuous. Also, a virtual line LC is attached to the rising period UC according to Embodiment 3 for the sake of explanation.

[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 driving unit 210 stops the emission of the beam B from the movable reflection unit 120. Therefore, in 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 spot S is not generated. On the other hand, during the irradiation period MC, the driving unit 210 emits the beam B from the light emitting element 110 at a predetermined repetition period. Therefore, in the irradiation period MC, a plurality of spots S are generated along the scanning line L.

[0050] The irradiation period MC according to Embodiment 3 is a period in which the voltage value of the vertical drive signal SC is positive. Therefore, in Embodiment 3, compared with Embodiment 1, the density of the spots S above the positive direction of the second direction Y with respect to the center of the second direction Y of the visual field F can be increased.

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

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

[0053] (Embodiment 4) FIG. 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 in the same manner as the vertical drive signal SA according to Embodiment 1. Each period of the vertical drive signal SD according to Embodiment 4 includes a falling period DD and a rising period UD. The rising period UD according to Embodiment 4 includes a first non-irradiation period ND1, an irradiation period MD, and a first non-irradiation period ND2. Also, a virtual line LD is attached to the rising period UD according to Embodiment 4 for the purpose of explanation.

[0055] The falling period DD according to Embodiment 4 includes a first falling period D1, a second falling period D2, and a third falling period D3. The first falling period D1, the second falling period D2, and the third falling period D3 are successively continuous. In the first falling period D1, the voltage value of the vertical drive signal SD is positive. In the second falling period D2, the voltage value of the vertical drive signal SD switches from positive to negative. In the third falling 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 part of the descending period DD is different from the slope of the vertical drive signal SD during another part of the ascending period UD. Specifically, the absolute value of the slope of the vertical drive signal SD in the second descending period D2 is smaller than the absolute values of the slopes of the vertical drive signal SD in the first descending period D1 and the third descending period D3. Therefore, compared with the case where the slope of the vertical drive signal SD in the descending period DD is constant throughout the entire descending period DD, the density of the spots S at the center and its periphery in the second direction Y of the visual field F can be increased.

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

[0058] For example, in the 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, by driving the movable reflection unit 120 in the same manner as in the embodiment, the density of the spots S at a desired position can be controlled to a desired density.

[0059] This application claims priority based on Japanese Patent Application No. 2021-206822 filed on December 21, 2021, and incorporates the entire disclosure thereof herein.

Description of Reference Numerals

[0060] 10 Optical device 110 Light emitting element 120 Movable reflection unit 130 Light receiving element 140 Beam splitter 210 Driving unit 220 Signal generation unit AX First rotation axis AY Second rotation axis B Beam D1 First descending period D2 Second descending period D3 Third Descent Period DA Descent Period DB Descent Period DC Descent Period DD Descent Period F Field of View IS Virtual Plane L Scanning 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 Second Non-Irradiation Period NB1 First Non-Irradiation Period NB2 Second Non-Irradiation Period NC1 First Non-Irradiation Period NC2 Second Non-Irradiation Period NC3 Third Non-Irradiation Period NC4 Fourth Non-Irradiation Period ND1 First Non-Irradiation Period ND2 First Non-Irradiation Period S Spot SA Vertical Drive Signal SB Vertical Drive Signal SC Vertical Drive Signal SD Vertical Drive Signal UA Ascent Period UB Ascent Period UC Ascent Period UD Ascent Period X First Direction Y Second Direction Z Third Direction

Claims

1. a signal generating unit that generates a first drive signal for driving a movable reflecting unit that reflects a beam emitted from a light emitting element in a predetermined direction; the signal generating section further generates a second drive signal that drives the movable reflecting section in a direction perpendicular to the predetermined direction; the frequency of the first drive signal is lower than the frequency of the second drive signal; a predetermined first period during which the first drive signal transitions from one of the maximum value and the minimum value of the first drive signal to the other includes a period during which the beam is not irradiated onto the movable reflector and the first drive signal has a predetermined first slope, and a period during which the beam is irradiated onto the movable reflector and the first drive signal has a second slope different from the first slope, An optical device, wherein the positive and negative signs of the second tilt are the same as the positive and negative signs of the first tilt.

2. a signal generating unit that generates a first drive signal for driving a movable reflecting unit that reflects a beam emitted from a light emitting element in a predetermined direction; a predetermined first period during which the first drive signal transitions from one of the maximum value and the minimum value of the first drive signal to the other includes a period during which the beam is not irradiated onto the movable reflector and the first drive signal has a predetermined first slope, and a period during which the beam is irradiated onto the movable reflector and the first drive signal has a second slope different from the first slope, the absolute value of the second slope is smaller than the absolute value of the first slope, An optical device, wherein the positive and negative signs of the second tilt are the same as the positive and negative signs of the first tilt.

3. a signal generating unit that generates a first drive signal for driving a movable reflecting unit that reflects a beam emitted from a light emitting element in a predetermined direction; An optical device, wherein the length of an irradiation period in a first period in which the first drive signal transitions from one of its maximum and minimum values ​​to the other is different from the length of an irradiation period in a second period in which the first drive signal transitions from the other of its maximum and minimum values ​​to the one of its maximum and minimum values.

4. 2. The optical device according to claim 1, The optical device, wherein the absolute value of the second tilt is smaller than the absolute value of the first tilt.

5. 5. The optical device according to claim 1, 2 or 4, the first period further includes a period during which the first drive signal has a third slope different from the first slope, An optical device, wherein the first drive signal is one of positive and negative during the period in which the first drive signal has the second slope, and the first drive signal is the other of positive and negative during the period in which the first drive signal has the third slope.

6. 5. The optical device according to claim 1, 2 or 4, An optical device, wherein the first period and a second period in which the first drive signal transitions from the other of the maximum value and the minimum value of the first drive signal to the one of the maximum value and the minimum value are repeated alternately.

7. 7. The optical device according to claim 6, an optical device, wherein a slope of the first drive signal in the second period is substantially constant throughout the second period.

8. 7. The optical device according to claim 6, An optical device, wherein a slope of the first drive signal during a portion of the second period is different from a slope of the first drive signal during another portion of the second period.

9. The optical device according to any one of claims 1 to 4, An optical device, wherein the first drive signal in a predetermined period includes a positive DC component, and the first drive signal in a period different from the predetermined period includes a negative DC component.

10. The optical device according to any one of claims 1 to 4, The optical device further includes a light receiving element that receives reflected light or scattered light of the beam reflected by the movable reflecting portion.

11. 4. The optical device according to claim 3, An optical device, wherein the length of the first period is shorter than the length of the second period.

12. 12. The optical device according to claim 3, An optical device, wherein the first period includes a period during which the beam is not irradiated, and the second period does not include a period during which the beam is not irradiated.

13. 12. The optical device according to claim 3, The optical device, wherein the second period includes a period in which the first drive signal has a first slope and a period in which the first drive signal has a second slope different from the first slope.

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