Light source device and distance measuring device

Abstract

To provide a light source device and a distance measuring device capable of easily suppressing emission of undesired light in light emitted from a light emitting element.SOLUTION: A light source device includes a light emitting element capable of emitting light including laser light and steady oscillation light having a light intensity smaller than the light intensity of the laser light, a light receiving element that transmits a power supply switching signal when a part of the light is received, and a power supply control part that controls a power supply voltage applied to the light emitting element. The power supply control part controls the power supply voltage to a second power supply voltage smaller than the first power supply voltage in response to a power supply switching signal after emitting the laser beam from the light emitting element by controlling the power supply voltage to the first power supply voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light source device and a distance measuring device. [Background technology]

[0002] Conventionally, a distance measurement technique called the time-of-flight (TOF) method has been known as one of distance measurement methods for measuring the distance to an object using light. VCSELs (Vertical Cavity Surface Emitting Lasers) are sometimes used as light-emitting elements for ToF LiDAR (Light Detection And Ranging). Patent Document 1 discloses a distance measurement device using a VCSEL. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 123974 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the distance measuring device of Patent Document 1, the light emitted from the light emitting element includes light that makes little contribution to the distance measuring operation.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a light source device and a distance measuring device that can easily suppress the emission of undesired light. [Means for solving the problem]

[0006] According to one disclosure of the present specification, there is provided a light source device comprising: a light-emitting element capable of emitting light including laser light and steady-state oscillating light having a light intensity smaller than that of the laser light; a light-receiving element that transmits a power supply switching signal when it receives a portion of the light; and a power supply control unit that controls a power supply voltage to be applied to the light-emitting element, wherein the power supply control unit controls the power supply voltage to a first power supply voltage to cause the light-emitting element to emit the laser light, and then controls the power supply voltage to a second power supply voltage smaller than the first power supply voltage in accordance with the power supply switching signal. [Effects of the Invention]

[0007] According to the present invention, it is possible to realize a light source device and a distance measuring device that can easily suppress the emission of undesired light in the light emitted from the light emitting element. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram of a light source device according to a first embodiment. [Figure 2] 1 is a cross-sectional view of a light source device according to a first embodiment. [Figure 3] FIG. 2 is a circuit diagram of a power supply switching unit according to the first embodiment. [Figure 4] 3 is a diagram showing the waveform of a power supply voltage applied to the light emitting element according to the first embodiment. FIG. [Figure 5] FIG. 10 is a diagram showing the waveform of a laser pulse beam according to a comparative example. [Figure 6] FIG. 2 is a diagram showing the waveform of a laser pulse beam according to the first embodiment. [Figure 7] 4 is a diagram showing the relationship between the waveform of a laser pulse beam and a power supply voltage according to the first embodiment. FIG. [Figure 8] 4 is a time chart of the light source device according to the first embodiment. [Figure 9] FIG. 10 is a block diagram of a light source device according to a second embodiment. [Figure 10] FIG. 10 is a cross-sectional view of a light source device according to a second embodiment. [Figure 11] FIG. 10 is a circuit diagram of a power supply switching unit according to a second embodiment. [Figure 12] FIG. 10 is a diagram showing the relationship between the RC value and the power supply voltage according to the second embodiment. [Figure 13] FIG. 10 is a block diagram of a light source device according to a third embodiment. [Figure 14] FIG. 10 is a cross-sectional view of a light source device according to a third embodiment. [Figure 15] FIG. 11 is a block diagram of a delay change unit according to a third embodiment. [Figure 16] FIG. 11 is a diagram showing the relationship between the drive current, the path, and the delay time according to the third embodiment. [Figure 17] FIG. 10 is a diagram showing the waveform of a laser pulse beam according to the third embodiment. [Figure 18] FIG. 10 is a cross-sectional view of a light source device according to a fourth embodiment. [Figure 19] FIG. 10 is a diagram showing a moving body according to a fifth embodiment. [Figure 20] FIG. 13 is a block diagram of a device according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] FIG. 1 is a block diagram of a light source device 1 according to this embodiment.

[0010] 1, the light source device 1 includes a light-emitting driver 10, a light-emitting element 20, a light-receiving driver 30, a light-receiving element 40, a power supply generator 50, a power supply switching unit 60, and a controller 70. The light-emitting driver 10 and the light-receiving driver 30 are connected to the controller 70, the light-emitting element 20 is connected to the light-emitting driver 10 and the power supply switching unit 60, the light-receiving element 40 is connected to the light-receiving driver 30, and the power supply switching unit 60 is connected to the light-receiving element 40 and the power supply generator 50.

[0011] The light-emitting drive unit 10 is a driver circuit that drives the light-emitting element 20. The light-emitting drive unit 10 controls the cathode voltage of the light-emitting element 20 based on a control signal from the control unit .

[0012] The light-emitting element 20 is a light source that emits light and may be, for example, a solid-state laser or a semiconductor laser. When miniaturization and power saving of the light source device 1 are required, the light-emitting element 20 is preferably a semiconductor laser. The semiconductor laser is a laser diode having an anode and a cathode and may be an edge-emitting laser (EEL; Edge Emitting Laser) or a surface-emitting laser (SEL; Surface Emitting Laser). When two-dimensional arraying or high-speed modulation is required, the surface-emitting laser is preferably a vertical-cavity surface-emitting laser (VCSEL; Vertical Cavity Surface Emitting Laser). The laser pulse light emitted from the VCSEL includes, for example, high-peak pulse light (laser light) and steady-state oscillation light following the high-peak pulse light. In the following description, the light-emitting element 20 will be described as a VCSEL that emits laser pulse light including high-peak pulse light. The light-emitting element 20 receives power from the power supply generation unit 50 via the power supply switching unit 60 and emits laser pulse light based on a control signal from the light-emitting driver 10.

[0013] The light-receiving driving section 30 is a driver circuit that drives the light-receiving element 40. The light-receiving driving section 30 drives the light-receiving element 40 based on a control signal from the control section .

[0014] The light receiving element 40 may be, for example, a photodiode or an avalanche photodiode. The avalanche photodiode may be a SPAD (Single Photon Avalanche Diode). In this embodiment, a SPAD operating in Geiger drive is used as the light receiving element 40 in order to quickly detect weak signals at the single photon level. The light receiving element 40 is driven by a light receiving drive unit 30. When the light receiving element 40 receives a portion of the laser pulse light from the light emitting element 20, it outputs a low-level or high-level power supply switching signal to the power supply switching unit 60. A low-level power supply switching signal is a signal that turns on the power supply switching unit 60, and a high-level power supply switching signal is a signal that turns off the power supply switching unit 60.

[0015] The power supply generating unit 50 is a power supply circuit that supplies power to the light emitting element 20. The power supply generating unit 50 may be, for example, a linear regulator, a switching regulator, etc. The power supply generating unit 50 supplies power to the light emitting element 20 via a power supply switching unit 60.

[0016] The power supply switching unit 60 switches the power supply voltage applied from the power supply generating unit 50 to the anode of the light-emitting element 20 based on a power supply switching signal from the light-receiving element 40. Here, the power supply voltage is a voltage equivalent to the voltage between the anode and the cathode. When a low-level power supply switching signal is output from the light-receiving element 40, the power supply switching unit 60 electrically connects the power supply generating unit 50 and the light-emitting element 20, allowing power to be supplied from the power supply generating unit 50 to the light-emitting element 20. On the other hand, when a high-level power supply switching signal is output from the light-receiving element 40, the power supply switching unit 60 electrically disconnects the power supply generating unit 50 from the light-emitting element 20, preventing power from being supplied from the power supply generating unit 50 to the light-emitting element 20.

[0017] The control unit 70 controls the overall operation of the light source device 1. The control unit 70 may be configured with a semiconductor integrated circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The control unit 70, the light-emitting drive unit 10, the power generation unit 50, and the power switching unit 60 are an example of a power control unit that controls the power supply voltage applied to the light-emitting element 20.

[0018] Next, the structure of the light source device 1 will be described. Fig. 2 is a cross-sectional view of the light source device 1. A light-emitting drive unit 10, a light-receiving drive unit 30, a power generation unit 50, a control unit 70, and a package substrate 90 are mounted on a printed circuit board 80 of the light source device 1. A light-emitting element 20, a light-receiving element 40, a power switching unit 60, and a housing (reflective member) 91 are mounted on the package substrate 90.

[0019] A plurality of paths P1 to P7 for transmitting various signals and power sources are formed on the printed circuit board 80 and the package substrate 90. Note that the paths P1 to P7 may be composed of metal wiring, via holes, connection terminals, etc., but in Figure 2 the paths P1 to P7 are shown schematically and do not necessarily represent the positions of the metal wiring, via holes, or connection terminals.

[0020] Path P1 supplies power supply voltage from the power generation unit 50 to the power supply switching unit 60. Path P2 supplies power supply voltage from the power supply switching unit 60 to the anode of the light-emitting element 20. Path P3 transmits a light-reception start request signal from the control unit 70 to the light-receiving drive unit 30. Path P4 transmits a drive signal from the light-receiving drive unit 30 to the light-receiving element 40. Path P5 transmits an emission start request signal from the control unit 70 to the light-emitting drive unit 10. Path P6 transmits a drive signal from the light-emitting drive unit 10 to the cathode of the light-emitting element 20. Path P7 transmits a power supply switching signal from the light-receiving element 40 to the power supply switching unit 60.

[0021] Although the package substrate 90 is provided with the power supply switching unit 60 as a component separate from the light emitting element 20, the power supply switching unit 60 may be built into the light emitting element 20.

[0022] The housing 91 covers the light-emitting element 20 and the light-receiving element 40 while supporting the diffusion portion 92 and the filter 93. The housing 91 is made of a resin material or a metal material having light-blocking properties. The housing 91 has an opening 91a on the optical axis of the light-emitting element 20, and the diffusion portion 92 is provided in the opening 91a. The housing 91 has an opening 91b above the light-receiving element 40, and the filter 93 is provided in the opening 91b. The light-emitting element 20 and the light-receiving element 40 are provided in the internal space of the housing 91. Most of the laser pulse light from the light-emitting element 20 passes through the diffusion portion 92 and is emitted to the outside. A portion of the laser pulse light is reflected inside the housing 91 as reference light La without passing through the diffusion portion 92 and is incident on the light-receiving element 40. Note that a filter may be provided along the path of the reference light La, i.e., between the light-emitting element 20 and the light-receiving element 40, to attenuate heat rays (infrared rays) generated from the light-emitting element 20 and external light that has entered via the diffusion portion 92.

[0023] The diffusion section 92 diffuses light. In the emission direction of the laser pulse light emitted from the light emitting element 20, the diffusion section 92 is disposed opposite the light emitting element 20. The diffusion section 92 is configured to include a diffusion plate having an uneven structure. The uneven structure has unevenness formed with a length of approximately the wavelength of the laser pulse light. The diffusion section 92 diffuses the laser pulse light emitted from the light emitting element 20 to the outside of the light source device 1. Note that the diffusion section 92 may also have a function such as a neutral density filter that attenuates external light.

[0024] The filter 93 is disposed opposite the light receiving element 40. The filter 93 guides the laser pulse light emitted from the light emitting element 20 and reflected by the subject to the light receiving element 40, and also suppresses the intrusion of external light other than the laser pulse light. The filter 93 may be a bandpass filter that attenuates light other than the wavelength of the laser pulse light from the light emitting element 20, or a neutral density filter that attenuates external light. The filter 93 may be configured to include a resin member or a metal member that completely blocks external light.

[0025] Next, the power supply switching unit 60 will be described in detail. Fig. 3(a) is a circuit diagram of the power supply switching unit 60, in which the power supply path to the light-emitting element 20 is conductive. Fig. 3(b) is a circuit diagram of the power supply switching unit 60, in which the power supply path to the light-emitting element 20 is blocked. The power supply switching unit 60 includes a switch circuit 61 and a low-pass filter 62 .

[0026] The switch circuit 61 is composed of a transistor and interrupts or connects the power path to the light-emitting element 20 in response to a power switching signal from the light-receiving element 40. In the switch circuit 61, an input node is connected to the power generation unit 50, an output node is connected to the light-emitting element 20 via a low-pass filter 62, and a control node is connected to the light-receiving element 40. When a low-level power switching signal is input from the light-receiving element 40 to the control node, the switch circuit 61 turns on, and a high-level (e.g., 5 V) power supply voltage is supplied from the power generation unit 50 to the light-emitting element 20 (see FIG. 3(a)). Here, when a low-level (e.g., 0 V) ​​drive signal is supplied to the cathode of the light-emitting element 20, a current flows through the light-emitting element 20, and laser pulse light can be emitted from the light-emitting element 20. Driving the light-emitting element 20 while supplying a high-level power supply voltage to the anode of the light-emitting element 20 is referred to as normal voltage (first power supply voltage) drive.

[0027] As described above, when the light-emitting element 20 emits a laser pulse beam, a portion of the laser pulse beam is incident on the light-receiving element 40 as the reference beam La. As a result, the power supply switching signal from the light-receiving element 40 changes from low level to high level, and the switch circuit 61 is turned off. As a result, power is no longer supplied from the power generation unit 50 to the light-emitting element 20, and the laser oscillation of the light-emitting element 20 is stopped or suppressed (see FIG. 3(b)). Cutting off or suppressing the power supplied to the anode of the light-emitting element 20 is referred to as low-voltage (second power supply voltage) driving.

[0028] The low-pass filter 62 has a resistive element and a capacitive element, and is provided in the power supply path between the switch circuit 61 and the light-emitting element 20. In the low-pass filter 62, one end of the resistive element is connected to the output node of the switch circuit 61, and the other end of the resistive element is connected to the anode of the light-emitting element 20. A first electrode of the capacitive element is connected to the connection node between the resistive element and the light-emitting element 20, and a second electrode of the capacitive element is connected to ground. The low-pass filter 62 removes signals with frequencies exceeding a cutoff frequency determined by the resistance value of the resistive element and the capacitance of the capacitive element.

[0029] 4(a) to 4(e) show the transient response of the power supply voltage applied between the anode and cathode of the light-emitting element 20 when the switch circuit 61 transitions from on to off. Here, the waveform of the transient response represents the result of a simulation in which the light-emitting element 20 is modeled using a rate equation. The half-width of the high-peak pulsed light from the light-emitting element 20 can be, for example, 0.1 nsec or less. Here, the half-width refers to the width of the waveform at half the height of the peak value of the high-peak pulsed light. Here, the power supply voltage applied to the light-emitting element 20 is set to 5 V, and the half-width of the high-peak pulsed light is set to approximately 0.1 nsec.

[0030] FIG. 4(a) shows the transient response of the power supply voltage when the low-pass filter 62 is not provided. Here, when the switch circuit 61 transitions from on to off, an overshoot occurs, causing the power supply voltage to swing significantly in the negative voltage direction. Overshoot can be caused by power supply wiring and parasitic inductors. Overshoot can impair the function of circuit elements. The relationship between the time constant of the low-pass filter 62 and the transient response of the power supply voltage is explained below.

[0031] FIG. 4(b) shows the waveform of the transient response of the power supply voltage in the low-pass filter 62 (time constant τ=100 nsec) composed of a 100 mΩ resistor and a 1 uF capacitor. The time constant τ of the low-pass filter 62 is large compared to the half-value width of the high-peak pulsed light. Therefore, when the switch circuit 61 transitions from on to off, the power supply voltage hardly drops. As such, it takes a long time for the power supply voltage in the light-emitting element 20 to reach the off level, making it difficult to achieve high-speed operation.

[0032] FIG. 4(c) shows the transient response of the power supply voltage in a low-pass filter 62 (time constant τ = 0.05 nsec) composed of a 50 mΩ resistor and a 1 nF capacitor. In this case, the half-width of the high-peak pulsed light is approximately equal to 2τ. While there is no problem with the power supply voltage response, the capacitance of the capacitor is somewhat large. Therefore, when the switch circuit 61 transitions from on to off, the capacitor operates as a secondary power supply, causing the power supply voltage to swing in the positive direction. Since the power supply voltage when the switch circuit 61 is off is significantly smaller than the power supply voltage (5 V) when the switch circuit 61 is on, the steady-state oscillation light of the light-emitting element 20 can be suppressed. In this case, the difference between the power supply voltages when the switch circuit 61 is on and off is small, shortening the transient response time of the power supply voltage and enabling high-speed operation. The threshold power supply voltage can be determined based on the characteristics of the light-emitting element 20.

[0033] FIG. 4(d) shows the transient response of the power supply voltage in a low-pass filter 62 (time constant τ=0.001 nsec) composed of a 10 mΩ resistive element and a 0.1 nF capacitive element. In this case, the half-width of the high-peak pulsed light is approximately equal to 100 τ. The transient response of the power supply voltage is also fast, and the power supply voltage drops to 0 V when the switch circuit 61 is turned off. This is preferable for the low-pass filter according to this embodiment.

[0034] FIG. 4(e) shows the transient response of the power supply voltage in a low-pass filter 62 (time constant τ=0.05 psec) consisting of a 5 mΩ resistor and a 0.01 nF capacitor. In this case, the half-width of the high-peak pulsed light is approximately equal to 2000 τ. Because the capacitance (=0.01 nF) is small, an overshoot occurs when the switch circuit 61 transitions from on to off, causing the power supply voltage to swing in the negative direction. At this time, no laser pulse light is output from the light-emitting element 20, but a negative power supply voltage is continuously applied to the anode of the light-emitting element 20, which may require a protection circuit.

[0035] As shown in Figures 4(a) to 4(e) above, it is desirable that the resistance and capacitance values ​​of the low-pass filter 62 be appropriately set so that the low-pass filter 62 has the transient response characteristics shown in Figure 4(c) or 4(d). For example, it is desirable to set the time constant τ so that the half-width of the high-peak pulsed light is 2τ or more and 100τ or less. By providing a low-pass filter 62 with an appropriate time constant, it is possible to reduce overshoot and protect circuit elements. In addition, the slew rate of the transient response can be improved, and high-speed operation can be expected.

[0036] Next, the waveform of the laser pulse light will be described with reference to Figures 5 and 6. In Figures 5 and 6, the horizontal axis represents time, and the vertical axis represents the light intensity of the laser pulse light.

[0037] Fig. 5 shows a laser pulse light according to a comparative example. In Fig. 5, the laser pulse light is emitted only by normal voltage driving, without low voltage driving. Since the light emitting element 20 is driven only by normal voltage, the high peak pulse light L1 is followed by steady oscillating light L2. The steady oscillating light L2 has a light intensity lower than that of the high peak pulse light L1.

[0038] FIG. 6 shows a laser pulsed light according to this embodiment. In FIG. 6, the laser pulsed light is emitted under both normal voltage driving and low voltage driving. That is, immediately after high peak pulsed light L1 is emitted under normal voltage driving, the normal voltage driving is switched to low voltage driving. This can suppress the emission of steady-state oscillation light L2. The light intensity of the peak-value pulsed light L1 of the laser pulsed light according to this embodiment is the same as the light intensity of the high peak pulsed light L1 of the comparative example, but the light intensity of the steady-state oscillation light L2 in this embodiment is smaller than the light intensity of the steady-state oscillation light L2 of the comparative example. In FIG. 6, the steady-state oscillation light L2 is suppressed to the point where it is almost not output.

[0039] FIG. 7 is a diagram showing the relationship between the waveform of the laser pulse light and the power supply voltage according to this embodiment. The power supply voltage represents the voltage at the anode of the light-emitting element 20. The horizontal axis of FIG. 7 represents time, the vertical axis on the left represents the light intensity of the laser pulse light, and the vertical axis on the right represents the power supply voltage. In FIG. 7, the dotted line shows the power supply voltage applied to the light-emitting element 20 when the resistive and capacitive elements of the low-pass filter 62 are configured under the conditions shown in FIG. 4(c). In FIG. 7, the drive voltage is switched from normal voltage driving to low voltage driving in accordance with the start timing of emission of steady-state oscillating light (time 1.2 nsec). The voltage during normal voltage driving is approximately 5 V, and the voltage during low voltage driving is approximately 1.2 V. It can be seen that the emission of steady-state oscillating light is suppressed by switching to low voltage driving.

[0040] Next, a description will be given of the operation of the light source device 1. FIG.

[0041] At time t0, the control unit 70 receives a trigger signal from outside the light source device 1 and outputs a light-receiving start request signal Sg1 to the light-receiving drive unit 30. Upon receiving the light-receiving start request signal Sg1, the light-receiving drive unit 30 starts supplying power to the light-receiving element 40. At this time, in order to prevent malfunctions due to the inclusion of external noise, the light-receiving drive unit 30 outputs a light-receiving reset signal Sg3 to the light-receiving element 40, maintaining the light-receiving element 40 in a reset state. Note that the reset state period (times t0 to t1) is preferably, for example, the time (e.g., 100 msec) required for the power supply voltage supplied to the light-receiving element 40 to stabilize. However, because different light-receiving elements 40 require different types of power supply voltages, it may take some time for all power supply voltages supplied to the light-receiving element 40 to stabilize. For this reason, the reset state period is not limited to 100 msec.

[0042] Meanwhile, the control unit 70 turns on the switch circuit 61 in the power supply switching unit 60, and the power supply switching unit 60 starts to supply a high-level power supply voltage to the anode of the light-emitting element 20 (normal voltage drive). At this time, the cathode voltage of the light-emitting element 20 is maintained at a high level, no current flows through the light-emitting element 20, and the light-emitting element 20 stops laser oscillation.

[0043] At time t1, the light-receiving driver 30 supplies a light-receiving clock signal Sg2, which is the reference for operation timing, to the light-receiving element 40. The light-receiving driver 30 also transitions the light-receiving synchronization signal Sg4 from low level to high level, and starts preparations for light reception in the light-receiving element 40. During this preparation for light reception, light reception has not yet begun.

[0044] At time t2, the light-receiving driver 30 changes the light-receiving reset signal Sg3 sent to the light-receiving element 40 from high level to low level, thereby releasing the light-receiving element 40 from the reset state.

[0045] Between times t3 and t4, the light-receiving element driver 30 outputs a light-receiving element setting signal Sg5 to the light-receiving element 40. The light-receiving element setting signal Sg5 represents the operation setting of the light-receiving element 40. The light-receiving element setting signal Sg5 is written to a register by an I2C (Inter-Integrated Circuit) or a three-wire or four-wire serial communication method.

[0046] At time t5, the light-receiving driver 30 transitions the light-receiving synchronization signal Sg4 from high to low. In response to the low-level light-receiving synchronization signal Sg4, the light-receiving element 40 is set according to the light-element setting signal Sg5, and the light-receiving element 40 transitions from a light-receiving preparation state to a light-receiving state. At the same time, the control unit 70 outputs a light-emission start request signal Sg6 to the light-emission driver 10.

[0047] At time t6, the light emission drive unit 10 receives the light emission start request signal Sg6 and transitions the cathode voltage of the light emitting element 20 from high level to low level. This causes a drive current to flow through the light emitting element 20, causing laser pulse light to be emitted from the light emitting element 20. A portion of the laser pulse light emitted from the light emitting element 20 is incident on the light receiving element 40 as reference light La.

[0048] At time t7, when the light receiving element 40 detects the reference light La, the power supply switching signal Sg7 is changed from low level to high level.

[0049] At time t8, the power supply switching unit 60 switches the switch circuit 61 from on to off in response to the high-level power supply switching signal Sg7, and switches the anode voltage from high to low (low voltage drive). This cuts off the drive current for the light-emitting element 20, and stops or suppresses emission of the steady-state oscillation light L2 from the light-emitting element 20.

[0050] At time t9, the light-receiving driver 30 transitions the light-receiving synchronization signal Sg4 from high level to low level, causing the light-receiving element 40 to transition from the light-receiving state to the light-receiving preparation state. At this time, the light-receiving driver 30 outputs a light-receiving reset signal Sg3 to the light-receiving element 40 to reset the light-receiving element 40. When the light-receiving element 40 is reset, it transitions the power supply switching signal Sg7 from high level to low level.

[0051] At time t9, when the power supply switching unit 60 receives a low-level power supply switching signal Sg7 from the light receiving element 40, it transitions the anode voltage of the light emitting element 20 from low to high (normal voltage drive). At this time, the cathode voltage of the light emitting element 20 transitions from low to high, no current flows through the light emitting element 20, and the light emitting element 20 stops lasing.

[0052] The operation from time t9 to t12 is the same as the operation from time t1 to t9. Since there is a preparation period for the light receiving element 40, it is preferable to set the period of the light emission start request signal Sg6 to at least twice the period of the light reception synchronization signal Sg4.

[0053] As described above, the light source device 1 according to this embodiment controls the power supply voltage to a normal voltage, causing the light emitting element 20 to emit the high peak pulsed light L1, and then controls the power supply voltage to a low voltage lower than the normal voltage in response to the power supply switching signal Sg7. Specifically, the light-emitting drive unit 10 causes the cathode voltage of the light emitting element 20 to transition from high to low, causing the light emitting element 20 to emit the high peak pulsed light L1. Then, the power supply switching unit 60 controls the anode voltage of the light emitting element 20 to transition from high to low in response to the power supply switching signal Sg7, thereby controlling the anode voltage to a low voltage. In this way, the power supply switching unit 60 cuts off the power path to the light emitting element 20 in response to the power supply switching signal Sg7, and controls the anode voltage to a low voltage.

[0054] This makes it easier for the light source device 1 to suppress the emission of undesired light (steady-state oscillating light L2). Therefore, the light source device 1 can reduce power consumption while maintaining the output of the high peak pulsed light L1. For example, when the light source device 1 is applied to a distance measuring device, the power supply of the distance measuring device can be improved by allocating the reduced power consumption to other devices constituting the distance measuring device. Even if the steady-state oscillating light L2, which contributes little to the distance measuring operation, is suppressed, the impact on the distance measuring operation is minimal. Furthermore, the light source device 1 controls the cathode voltage when activating the light emitting element 20, and controls the anode voltage when terminating the light emission of the light emitting element 20. Therefore, the light source device 1 can emit short pulses with higher precision compared to conventional cases where only the cathode voltage is controlled.

[0055] [Second embodiment] Next, a second embodiment will be described. Fig. 9 is a block diagram of a light source device 1A according to this embodiment.

[0056] This embodiment differs from the first embodiment in that the time constant of the low-pass filter 62A is variable. Note that in this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0057] The light source device 1A has the same configuration as the light source device 1 according to the first embodiment, except for the control by the control unit 70 and the circuit configuration of the power supply switching unit 60A.

[0058] The control unit 70 is connected to the power supply switching unit 60A and outputs an RC control signal to the power supply switching unit 60A to change the time constant of the low-pass filter 62A of the power supply switching unit 60A. Note that communication between the control unit 70 and the power supply switching unit 60A can be performed using a method such as I2C or SPI (Serial Peripheral Interface).

[0059] Fig. 10 is a cross-sectional view of light source device 1A. Light source device 1A has the same configuration as light source device 1 according to the first embodiment, except that it further includes path P8 in addition to paths P1 to P7. Path P8 may be composed of metal wiring, via holes, connection terminals, etc., but path P8 is shown schematically in Fig. 10 and does not necessarily represent the positions of the metal wiring, via holes, or connection terminals. Path P8 transmits an RC control signal from control unit 70 to power supply switching unit 60A.

[0060] 11 is a circuit diagram of the power supply switching unit 60 A. The power supply switching unit 60 A includes a switch circuit 61, a low-pass filter 62 A, and a voltage detection unit 63.

[0061] The switch circuit 61 is composed of a transistor, and cuts off or connects the power path to the light-emitting element 20 in response to a power switching signal Sg7 from the light-receiving element 40. In the switch circuit 61, an input node is connected to the power generation unit 50, an output node is connected to the light-emitting element 20 via a low-pass filter 62A, and a control node is connected to the light-receiving element 40.

[0062] The low-pass filter 62A includes N resistors, N capacitors, and a switch unit 621. The switch unit 621 includes N capacitor switches, where "N" is a natural number. The N resistors are connected in series between an input node on the switch circuit side and an output node on the light-emitting element side. The first electrodes of the N capacitors are connected to (N-1) connection nodes of the N resistors and the output node, respectively. The N capacitor switches are connected between second electrodes of the N capacitors and ground, respectively. The low-pass filter 62A can control each capacitor switch to be turned on or off based on an RC control signal from the control unit 70. Turning on a capacitor switch connects the second electrode of the capacitor to ground, and turning off a capacitor switch does not connect the second electrode of the capacitor to ground. Turning on or off each capacitor switch dynamically changes the time constant of the low-pass filter 62A. The low-pass filter 62A removes signals with frequencies exceeding a cutoff frequency determined by the time constant.

[0063] The voltage detection section 63 detects the power supply voltage applied to the light emitting element 20. The voltage detection section 63 is connected to the control section 70, and outputs the detected power supply voltage to the control section 70.

[0064] FIG. 12 summarizes the results of switching the switch circuit 61 from ON to OFF for each time constant determined by the combination of the resistance and capacitance (RC value) of the low-pass filter 62A, and reading the power supply voltage at that time from the voltage detection unit 63. In FIG. 12, the setting value representing the combination of the resistance and capacitance is expressed as 3 bits ("000" to "111"). Here, when the low-pass filter 62A is set to a time constant determined by the RC value "resistance: 20 mΩ, capacitance: 120 pF" represented by the setting value "010," the power supply voltage becomes "0 V" when the switch circuit 61 is turned OFF. Therefore, it can be seen that the time constant determined by this RC value is suitable. Note that the time constant of the low-pass filter 62A is preferably set before light reception begins, for example, during the light reception preparation period from time t1 to time t5 in FIG. 8.

[0065] Due to manufacturing variations, variations in power supply voltage, changes in ambient temperature, and the like, the transient response of the power supply voltage when the switch circuit 61 is off may differ from the design value. According to this embodiment, the time constant of the low-pass filter 62A is variable, thereby suppressing the effects of such variations. This allows the light source device 1A to reduce variations in the transient response of the power supply voltage when the switch circuit 61 is off and accurately suppress steady-state oscillation light. However, compared to the light source device 1 of the first embodiment, the light source device 1A of this embodiment has a larger number of components and requires additional processing to readjust the time constant. Therefore, in an evaluation during use, if the effects of various variations, etc., are within the expected range, the light source device 1 of the first embodiment should be adopted, and if the effects of various variations, etc., are outside the expected range, the light source device 1A of the second embodiment should be adopted.

[0066] [Third embodiment] Next, a third embodiment will be described. Fig. 13 is a block diagram of a light source device 1B according to this embodiment.

[0067] The light source device 1B of this embodiment differs from the light source devices 1 and 1A of the other embodiments in that it includes a delay change unit 110 that changes the delay of the power supply switching signal Sg7 from the light receiving element 40. In this embodiment, the same components as those in the other embodiments are denoted by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0068] The light source device 1B has the same configuration as the light source device 1 according to the first embodiment, except that it is controlled by a control unit 70 and includes a delay change unit 110.

[0069] Variations in manufacturing, variations in power supply voltage, changes in ambient temperature, etc. may cause variations in the delay of the power supply switching signal Sg7 from the light receiving element 40 to the power supply switching unit 60. If variations in the delay of the power supply switching signal Sg7 occur, the timing at which the steady-state oscillating light starts to be emitted may differ from the timing at which the power supply switching unit 60 switches to a low voltage, which may result in the steady-state oscillating light L2 not being properly suppressed. Therefore, the light source device 1B includes a delay change unit 110 that changes the delay of the power supply switching signal Sg7.

[0070] Fig. 14 is a cross-sectional view of light source device 1B. Light source device 1B has the same configuration as light source device 1 according to the first embodiment, except that it further includes paths P9 and P10 in addition to paths P1 to P6, path P7 is connected to a different destination, and it also includes a delay change unit 110. The delay change unit 110 is provided on a package substrate 90. Paths P7, P9, and P10 may be composed of metal wiring, via holes, connection terminals, etc., but Fig. 14 shows these paths schematically and does not necessarily represent the positions of the metal wiring, via holes, or connection terminals.

[0071] A path P9 transmits a control signal from the control unit 70 to the delay change unit 110. A path P7 transmits a power supply switching signal Sg7 from the light receiving element 40 to the delay change unit 110. A path P10 transmits the power supply switching signal Sg7 from the delay change unit 110 to the power supply switching unit 60.

[0072] 15 is a block diagram of the delay change unit 110. The delay change unit 110 changes the delay time of the power supply switching signal Sg7 from the light receiving element 40, and includes a buffer circuit 111, paths Q1 to Q4, and a path selector (selection circuit) 112.

[0073] The delay change unit 110 can change the drive current (output impedance) and the signal path of the power supply switching signal Sg7 based on a control signal from the control unit .

[0074] The buffer circuit 111 can change the drive current, and can appropriately change it to, for example, any of the drive currents through, 4 mA, 8 mA, and 10 mA. Here, "through" means that the power supply switching signal Sg7 is output without passing through the buffer circuit 111. The output node of the buffer circuit 111 is connected to paths Q1 to Q4 via a path selection unit 112.

[0075] The paths Q1 to Q4 are metal wirings capable of transmitting the power supply switching signal Sg7. The paths Q1 to Q4 are provided between the path selection units 112, 112. The paths Q1 to Q4 are formed to have different lengths. Here, the path Q1 is formed linearly, and parts of the paths Q2 to Q4 are formed to meander, thereby forming the paths Q2 to Q4 of different lengths. The signal delay can be changed by selecting one of the paths Q1 to Q4.

[0076] The path selection unit 112 selects one of the paths Q1 to Q4 based on a control signal from the control unit 70. The path selection units 112 are provided on both sides of the paths Q1 to Q4. Each path selection unit 112 has, for example, a switch circuit. The switch circuit of one path selection unit 112 connects the buffer circuit 111 to one of the paths Q1 to Q4. The switch circuit of the other path selection unit 112 connects the power supply switching unit 60 to one of the paths Q1 to Q4. For example, when the buffer circuit 111 is connected to the path Q1 and the power supply switching unit 60 is connected to the path Q1, a power supply switching signal Sg7 is transmitted from the buffer circuit 111 to the power supply switching unit 60 via the path Q1.

[0077] The control unit 70 can send a control signal to the buffer circuit 111 to change the drive current of the delay change unit 110. The control unit 70 can also send a control signal to the path selection unit 112 to select one of the paths Q1 to Q4 and change the delay time of the power supply switching signal Sg7.

[0078] FIG. 16 is a diagram showing the relationship between the drive current, the path, and the delay time. FIG. 16 shows four types of drive current (0 mA, 4 mA, 8 mA, 10 mA) and four paths Q1 to Q4, providing 16 patterns of delay time. The 16 patterns of delay time can be calculated in advance. In FIG. 16, the setting values ​​representing the 16 patterns of delay time are expressed as 4 bits ("0000" to "1111"). For example, under the condition of a drive current of "0 mA" and path "Q1" represented by the setting value "0000," the delay time is "100 ps." Here, by specifying the setting values ​​shown in FIG. 16, the control unit 70 sets the conditions of the drive current and the path, and a suitable delay time is found from the waveform of the laser pulse light from the light-emitting element 20 under those conditions.

[0079] 17(a) to 17(d) are diagrams showing waveforms of laser pulse light according to delay times. 17(a) shows the waveform of the laser pulse light when the delay time is too long and the switching to low voltage is significantly delayed. In this case, the timing of switching to low voltage and the timing of starting the emission of the steady-state oscillation light are significantly different, resulting in a waveform in which the steady-state oscillation light cannot be suppressed.

[0080] Figure 17(b) shows the waveform of the laser pulse light when the switching to low voltage is delayed due to a slightly long delay time. In this case, the timing of switching to low voltage and the timing of starting the emission of the steady-state oscillation light are slightly different, so the waveform shows that the steady-state oscillation light is not suppressed by about half.

[0081] Figure 17(c) shows the waveform of the laser pulse light when the switching to low voltage is delayed a little due to a slightly long delay time. In this case, the timing of switching to low voltage and the timing of starting emission of the steady-state oscillation light are slightly different, so the waveform shows that the steady-state oscillation light is not suppressed to a certain extent.

[0082] 17(d) shows the waveform when the delay time is appropriate and the timing of switching to low voltage coincides with the timing of starting emission of steady-state oscillating light. In this case, the timing of switching to low voltage coincides with the timing of starting emission of steady-state oscillating light, resulting in a waveform that can suppress steady-state oscillating light.

[0083] 16, the control unit 70 specifies the set values ​​indicating the drive current and path, and finds an appropriate delay time from the waveform of the laser pulse light from the light emitting element 20 (here, the waveform of the laser pulse light in FIG. 17(d)). Then, the drive current and path corresponding to the appropriate delay time are set in advance.

[0084] As a result, even if the delay of the power supply switching signal Sg7 fluctuates due to the influence of various variations, etc., the delay change unit 110 can change the delay of the power supply switching signal Sg7 to synchronize the timing of switching to a low voltage with the timing of starting to emit steady-state oscillating light. This allows for accurate suppression of steady-state oscillating light, thereby effectively reducing power consumption. However, compared to the light source device 1 of the first embodiment, the light source device 1B of this embodiment has a larger number of components and requires additional processing to adjust the delay time. Therefore, in an evaluation during use, if the influence of various variations, etc. is within an expected range, the light source device 1 of the first embodiment can be adopted, and if the influence of various variations, etc. is outside the expected range, the light source device 1B of the third embodiment can be adopted.

[0085] [Fourth embodiment] Next, a fourth embodiment will be described below. Fig. 18 is a cross-sectional view of a light source device 1C according to this embodiment.

[0086] The light source device 1C of this embodiment differs from the light source device 1 of the first embodiment, which switches the power supply switching unit 60 after detecting the reference light La, in that it switches the power supply switching unit 60 after detecting the spontaneous emission light Lb emitted from the side of the light-emitting element 20A.

[0087] The light emitting element 20A has a first light emitting surface 20a and a second light emitting surface 20b. The first emission surface 20a is an emission surface that emits the laser pulse light toward the diffusion section 92. In other words, the first emission surface 20a is an emission surface that emits the laser pulse light in the normal direction of the printed circuit board 80.

[0088] The second exit surface 20b is an exit surface separate from the first exit surface 20a, and is an exit surface that emits a portion of the laser pulse light (spontaneous emission light Lb) toward the light receiving element 40. In other words, the second exit surface 20b is an exit surface that emits the spontaneous emission light Lb in a direction intersecting the normal direction of the printed circuit board 80.

[0089] A portion of the laser pulse light emitted from the second emission surface 20b of the light-emitting element 20A is incident on the light-receiving element 40 as spontaneously emitted light Lb. After detecting the spontaneously emitted light Lb, the light-receiving element 40 transitions the power supply switching signal Sg7 from low level to high level and outputs the high-level power supply switching signal Sg7 to the power supply switching unit 60. Note that the spontaneously emitted light Lb may leak out and be emitted even before the high-peak pulsed light is emitted. For this reason, the light source device 1C of this embodiment requires a longer delay time for the power supply switching signal Sg7 than the other embodiments.

[0090] [Fifth embodiment] Next, a moving body according to the fifth embodiment will be described with reference to Fig. 19. Fig. 19 is a diagram showing a moving body according to the fifth embodiment.

[0091] 19(a) shows an example of the configuration of a device mounted on a vehicle as an on-board camera. The device 300 has a distance measurement unit 303 that measures the distance to an object, and a collision determination unit 304 that determines whether or not there is a possibility of a collision based on the distance measured by the distance measurement unit 303. The distance measurement unit 303 is configured to include the light source device described in the first to fourth embodiments, and a distance information acquisition unit. The distance information acquisition unit acquires information about the distance to the object based on the time difference between the timing at which light is emitted from the light-emitting element and the timing at which the light-receiving element receives the light emitted from the light-emitting element and reflected by the object.

[0092] The device 300 is connected to a vehicle information acquisition device 310 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The device 300 is also connected to a control ECU 320, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the determination result of the collision determination unit 304. The device 300 is also connected to an alarm device 330 that issues an alarm to the driver based on the determination result of the collision determination unit 304. For example, if the collision determination unit 304 determines that a collision is highly likely, the control ECU 320 performs vehicle control to avoid a collision and mitigate damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 330 warns the user by sounding an alarm, displaying alarm information on a screen of a car navigation system, etc., or vibrating a seat belt or steering wheel. These devices of the device 300 function as a mobile object control unit that controls the operation of controlling the vehicle as described above.

[0093] In this embodiment, the device 300 measures the distance around the vehicle, for example, the front or rear. Fig. 19(b) shows the device when measuring the distance in front of the vehicle (distance measurement range 350). The vehicle information acquisition device 310, which serves as a distance measurement control means, sends an instruction to the device 300 or the distance measurement unit 303 to perform a distance measurement operation. This configuration can further improve the accuracy of distance measurement.

[0094] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to prevent deviation from a lane, etc. Furthermore, the present invention is not limited to vehicles such as automobiles, but can be applied to moving objects (moving devices) such as ships, aircraft, artificial satellites, industrial robots, and consumer robots. In addition, the present invention can be applied to a wide range of devices that use object recognition or biometric recognition, such as intelligent transport systems (ITS) and surveillance systems, without being limited to moving objects.

[0095] [Sixth embodiment] An apparatus according to a sixth embodiment of the present invention will be described with reference to Fig. 20. Fig. 20 is a block diagram of an apparatus EQP according to this embodiment.

[0096] The device EQP includes a light source device according to any one of the first to fourth embodiments, and a photoelectric conversion device APR that converts an optical signal emitted from a light-emitting element of the light source device and reflected by an object into an electrical signal. All or part of the photoelectric conversion device APR is a semiconductor device IC. The photoelectric conversion device APR of this example can be used, for example, as an image sensor, an AF (Auto Focus) sensor, a photometric sensor, or a distance measurement sensor. The semiconductor device IC has a pixel area PX in which pixel circuits PXC, each including a photoelectric conversion unit, are arranged in a matrix. The semiconductor device IC can have a peripheral area PR around the pixel area PX. Circuits other than the pixel circuits can be arranged in the peripheral area PR.

[0097] The photoelectric conversion device APR may have a structure (chip stacking structure) in which a first semiconductor chip provided with a plurality of photoelectric conversion units and a second semiconductor chip provided with peripheral circuits are stacked. The peripheral circuits in the second semiconductor chip may be column circuits corresponding to the pixel columns of the first semiconductor chip. The peripheral circuits in the second semiconductor chip may also be matrix circuits corresponding to the pixels or pixel blocks of the first semiconductor chip. The first and second semiconductor chips may be connected by through-silicon vias (TSVs), inter-chip wiring formed by direct bonding of a conductor such as copper, connection by microbumps between chips, connection by wire bonding, or the like.

[0098] The photoelectric conversion device APR may include, in addition to the semiconductor device IC, a package PKG that houses the semiconductor device IC. The package PKG may include a base to which the semiconductor device IC is fixed, a cover such as glass that faces the semiconductor device IC, and connecting members such as bonding wires or bumps that connect terminals provided on the base to terminals provided on the semiconductor device IC.

[0099] The equipment EQP may further include at least one of an optical device OPT, a control device CTRL, a processing device PRCS, a display device DSPL, a memory device MMRY, and a mechanical device MCHN. The optical device OPT corresponds to the photoelectric conversion device APR and is, for example, a lens, a shutter, or a mirror. The control device CTRL controls the photoelectric conversion device APR and is, for example, a semiconductor device such as an ASIC. The processing device PRCS processes signals output from the photoelectric conversion device APR and constitutes an AFE (analog front end) or a DFE (digital front end). The processing device PRCS is a semiconductor device such as a CPU (central processing unit) or an ASIC (application-specific integrated circuit). The display device DSPL is an EL display device or a liquid crystal display device that displays information (images) obtained by the photoelectric conversion device APR. The memory device MMRY is a magnetic device or a semiconductor device that stores information (images) obtained by the photoelectric conversion device APR. The memory device MMRY is a volatile memory such as an SRAM or a DRAM, or a non-volatile memory such as a flash memory or a hard disk drive. The mechanical device MCHN has a moving part or a propulsion part such as a motor or an engine. The device EQP displays the signal output from the photoelectric conversion device APR on a display device DSPL and transmits the signal to the outside using a communication device (not shown) provided in the device EQP. For this purpose, the device EQP preferably further includes a memory device MMRY and a processing device PRCS in addition to the memory circuit unit and arithmetic circuit unit provided in the photoelectric conversion device APR.

[0100] The device EQP shown in FIG. 20 can be an electronic device such as an information terminal with a photographing function (e.g., a smartphone or a wearable device) or a camera (e.g., an interchangeable lens camera, a compact camera, a video camera, or a surveillance camera). The mechanical device MCHN in the camera can drive components of the optical device OPT for zooming, focusing, and shutter operation. The device EQP can also be transportation equipment (mobile object) such as a vehicle, a ship, or an aircraft. The device EQP can also be medical equipment such as an endoscope or a CT scanner. The device EQP can also be medical equipment such as an endoscope or a CT scanner.

[0101] The mechanical device MCHN in the transportation equipment can be used as a moving device. The device EQP as a transportation equipment is suitable for transporting the photoelectric conversion device APR and for assisting and / or automating driving (piloting) using a photographing function. The processing device PRCS for assisting and / or automating driving (piloting) can perform processing to operate the mechanical device MCHN as a moving device based on information obtained by the photoelectric conversion device APR.

[0102] The photoelectric conversion device APR according to this embodiment can provide high value to its designer, manufacturer, seller, purchaser, and / or user. Therefore, if the photoelectric conversion device APR is installed in a device EQP, the value of the device EQP can also be increased. Therefore, when manufacturing and selling the device EQP, deciding to install the photoelectric conversion device APR according to this embodiment in the device EQP is advantageous in increasing the value of the device EQP.

[0103] [Modified embodiment] The present invention is not limited to the above-described embodiments and can be modified in various ways. For example, an example in which part of the configuration of one embodiment is added to another embodiment, or an example in which part of the configuration of another embodiment is replaced with another embodiment, is also an embodiment of the present invention.

[0104] In the above description, an example has been described in which the light emitted from the light emitting element 20 is a laser pulsed light including a high peak pulsed light L1 and a steady-state oscillating light L2, but the light is not limited to this and may be, for example, a laser light having a smaller peak than the high peak pulsed light L1. In this case, the light source device according to this embodiment can suppress ringing in the laser light.

[0105] Furthermore, an example has been described in which the delay change unit 110 is combined with the power supply switching unit 60 in which the time constant of the low-pass filter 62 is fixed, but this is not limited to this. For example, the delay change unit 110 may be combined with the power supply switching unit 60A in which the time constant of the low-pass filter 62A is variable.

[0106] Furthermore, although an example in which the low-pass filters 62, 62A are configured with a resistive element and a capacitive element has been described, the present invention is not limited to this, and the low-pass filters 62, 62A may be configured with, for example, a coil and a capacitive element.

[0107] The disclosure of the above embodiment includes the following configurations. (Configuration 1) a light emitting element capable of emitting light including a laser beam and a steady-state oscillating light having a light intensity lower than that of the laser beam; a light receiving element that transmits a power supply switching signal when it receives a portion of the light; a power supply control unit that controls a power supply voltage applied to the light emitting element, the power supply control unit controls the power supply voltage to a first power supply voltage to cause the light-emitting element to emit the laser light, and then controls the power supply voltage to a second power supply voltage lower than the first power supply voltage in response to the power supply switching signal. (Configuration 2) The light source device according to configuration 1, wherein the power supply control unit cuts off a power supply path to the light emitting element in response to the power supply switching signal and controls the second power supply voltage. (Configuration 3) the light-emitting element is a laser diode having an anode and a cathode, and the power supply voltage corresponds to a voltage between the anode and the cathode; The light source device according to configuration 1 or 2, characterized in that the power supply control unit emits the laser light by transitioning the voltage of the cathode from a high level to a low level, and then controls the voltage of the anode to the second power supply voltage by transitioning the voltage of the anode from a high level to a low level in response to the power supply switching signal. (Configuration 4) 4. The light source device according to any one of configurations 1 to 3, wherein the power supply control unit controls the power supply voltage to the second power supply voltage, thereby suppressing the steady-state oscillating light. (Configuration 5) The light source device according to any one of configurations 1 to 4, wherein the power supply control unit includes a switch circuit that interrupts or connects the power supply path in response to the power supply switching signal, and a low-pass filter that is provided in the power supply path between the switch circuit and the light-emitting element. (Configuration 6) the low-pass filter includes a resistive element and a capacitive element; the resistor element is connected between the switch circuit and the light-emitting element, 6. The light source device according to configuration 5, wherein a first electrode of the capacitance element is connected to a connection node between the resistance element and the light emitting element, and a second electrode of the capacitance element is connected to ground. (Configuration 7) 6. The light source device according to configuration 5, wherein the time constant of the low-pass filter is variable. (Configuration 8) The low-pass filter is N resistor elements connected in series between an input node on the switch circuit side and an output node on the light emitting element side; N capacitance elements each having a first electrode connected to (N-1) connection nodes of the N resistance elements and the output node; N capacitance switches respectively connected between the second electrodes of the N capacitance elements and ground, 8. The light source device according to configuration 7, wherein the power supply control unit is capable of controlling each of the N capacitance switches to be on or off. (Configuration 9) 9. The light source device according to any one of configurations 1 to 8, further comprising a delay change unit that changes a delay time of the power supply switching signal from the light receiving element. (Configuration 10) The light source device described in configuration 9, characterized in that the delay change unit has a plurality of paths formed with different lengths and capable of transmitting the power supply switching signal, and a selection circuit that selects one of the plurality of paths based on the timing of starting emission of the stationary oscillation light and the timing of switching to the second power supply voltage. (Configuration 11) 11. The light source device according to configuration 10, wherein the selection circuit selects the path in advance so as to match the switching timing with the emission start timing. (Configuration 12) 10. The light source device according to configuration 9, wherein the delay change section is capable of changing the output impedance of a buffer circuit that outputs the power supply switching signal. (Configuration 13) 13. The light source device according to any one of configurations 1 to 12, wherein the half width of the laser light is 0.1 nsec or less. (Configuration 14) a diffusion unit that diffuses the light emitted from the light-emitting element to the outside of the light source device, 14. The light source device according to any one of configurations 1 to 13, wherein a portion of the light does not pass through the diffusion portion and is incident on the light receiving element. (Configuration 15) 15. The light source device according to configuration 14, further comprising a reflecting member that reflects a portion of the light and guides it to the light receiving element. (Configuration 16) The light source device described in configuration 14, wherein the light-emitting element has a first exit surface that emits the light toward the diffusion section, and a second exit surface that is separate from the first exit surface and emits a portion of the light toward the light-receiving element. (Configuration 17) a light source device according to any one of configurations 1 to 16; a distance information acquisition unit that acquires information about the distance to the object based on the time difference between the timing at which light is emitted from the light-emitting element and the timing at which the light-receiving element receives the light emitted from the light-emitting element and reflected by the object. (Configuration 18) A mobile object, a distance measuring device according to configuration 17; a control unit for controlling the moving body based on information about the distance acquired by the distance measuring device. (Configuration 19) The light source device according to any one of configurations 1 to 16, a photoelectric conversion device that converts an optical signal emitted from the light emitting element and reflected by an object into an electrical signal; an optical device corresponding to the photoelectric conversion device; a control device that controls the photoelectric conversion device; a processing device that processes a signal output from the photoelectric conversion device; a display device that displays information obtained by the photoelectric conversion device; a storage device that stores information obtained by the photoelectric conversion device; and and a mechanical device that operates based on information obtained by the photoelectric conversion device. [Explanation of symbols]

[0108] 1...Light source device 10...Light emitting drive unit 20...Light emitting element 30...Light receiving drive unit 40...Photodetector 50...Power generation section 60...Power supply switching unit 61...Switch circuit 62, 62A...Low-pass filter 70...Control unit 91...Case 93...Diffusion section 110...Delay change unit 111...Buffer circuit 112...Route selection unit

Claims

1. a light emitting element capable of emitting light including a laser beam and a steady-state oscillating light having a light intensity lower than that of the laser beam; a light receiving element that transmits a power supply switching signal when it receives a portion of the light; a power supply control unit that controls a power supply voltage applied to the light-emitting element, wherein the power supply control unit controls the power supply voltage to a first power supply voltage to cause the light-emitting element to emit the laser light, and then controls the power supply voltage to a second power supply voltage that is smaller than the first power supply voltage in response to the power supply switching signal.

2. 2. The light source device according to claim 1, wherein the power supply control unit controls the power supply voltage to the second power supply voltage by cutting off a power supply path to the light emitting element in response to the power supply switching signal.

3. the light-emitting element is a laser diode having an anode and a cathode, and the power supply voltage corresponds to a voltage between the anode and the cathode; 2. The light source device according to claim 1, wherein the power supply control unit emits the laser light by transitioning the voltage of the cathode from a high level to a low level, and then controls the voltage of the anode to the second power supply voltage by transitioning the voltage of the anode from a high level to a low level in accordance with the power supply switching signal.

4. 2. The light source device according to claim 1, wherein the power supply control unit controls the power supply voltage to the second power supply voltage to suppress the steady-state oscillating light.

5. The light source device according to claim 2, wherein the power supply control unit includes a switch circuit that interrupts or connects the power supply path in response to the power supply switching signal, and a low-pass filter provided in the power supply path between the switch circuit and the light-emitting element.

6. the low-pass filter includes a resistive element and a capacitive element; the resistor element is connected between the switch circuit and the light-emitting element, 6. The light source device according to claim 5, wherein a first electrode of the capacitance element is connected to a connection node between the resistance element and the light emitting element, and a second electrode of the capacitance element is connected to ground.

7. 6. The light source device according to claim 5, wherein the time constant of the low-pass filter is variable.

8. The low-pass filter is N resistor elements connected in series between an input node on the switch circuit side and an output node on the light emitting element side; N capacitance elements each having a first electrode connected to (N-1) connection nodes of the N resistance elements and the output node; N capacitance switches respectively connected between the second electrodes of the N capacitance elements and a ground, 8. The light source device according to claim 7, wherein the power supply control unit is capable of controlling each of the N capacitance switches to be on or off.

9. The light source device according to claim 1 , further comprising a delay change unit that changes a delay time of the power supply switching signal from the light receiving element.

10. The light source device according to claim 9, characterized in that the delay change unit has a plurality of paths formed with different lengths and capable of transmitting the power supply switching signal, and a selection circuit that selects one of the plurality of paths based on the timing of starting emission of the stationary oscillation light and the timing of switching to the second power supply voltage.

11. 11. The light source device according to claim 10, wherein the selection circuit selects the path in advance so as to synchronize the switching timing with the emission start timing.

12. 10. The light source device according to claim 9, wherein the delay change unit is capable of changing an output impedance of a buffer circuit that outputs the power supply switching signal.

13. 2. The light source device according to claim 1, wherein the half width of the laser light is 0.1 nsec or less.

14. a diffusion unit that diffuses the light emitted from the light-emitting element to the outside of the light source device, 2. The light source device according to claim 1, wherein a part of the light does not pass through the diffusion portion and is incident on the light receiving element.

15. 15. The light source device according to claim 14, further comprising a reflecting member that reflects a part of the light and guides it to the light receiving element.

16. The light source device according to claim 14, wherein the light-emitting element has a first exit surface that emits the light toward the diffusion portion, and a second exit surface that is a separate exit surface from the first exit surface and emits a portion of the light toward the light-receiving element.

17. A light source device according to any one of claims 1 to 16; a distance information acquisition unit that acquires information about the distance to the object based on the time difference between the timing at which light is emitted from the light-emitting element and the timing at which the light-receiving element receives the light emitted from the light-emitting element and reflected by the object.

18. A mobile object, a distance measuring device according to claim 17; a control unit for controlling the moving body based on information about the distance acquired by the distance measuring device.

19. The light source device according to any one of claims 1 to 16, a photoelectric conversion device that converts an optical signal emitted from the light emitting element and reflected by an object into an electrical signal; an optical device corresponding to the photoelectric conversion device; a control device that controls the photoelectric conversion device; a processing device that processes a signal output from the photoelectric conversion device; a display device that displays information obtained by the photoelectric conversion device; a storage device that stores information obtained by the photoelectric conversion device; and and a mechanical device that operates based on information obtained by the photoelectric conversion device.

Images