Light source drive device

Abstract

To shorten the interval of a pulse output from a light source.SOLUTION: A light source drive device 20 includes a plurality of capacitative elements 22, a power supply 21 and a discharge control section 23. The plurality of capacitative elements 22 are parallel to each other and each of the capacitative elements supplies electric power to a light-emitting device 10 when discharging. The power supply 21 charges the plurality of capacitative elements 22. The discharge control section 23 individually controls the timing that the capacitative elements 22 discharge. The light-emitting device 10 is a light source, for example, in a distance measurement device.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] There are devices that use laser pulses to measure the distance from a moving body to a target object. Specifically, they output pulsed light and receive the light reflected by the object. Then, the distance from the device to the object is calculated based on the time between output and reception. To perform this type of measurement repeatedly, it is necessary to turn on and off the light emitting element.

[0003] Patent Document 1 describes a laser light generating circuit in which a capacitor is charged by magnetic energy stored in an inductor, and a laser light is generated from a laser diode by a discharge current of the capacitor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-139295 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when driving a laser diode with the discharge current of a capacitor, the interval between light pulses cannot be made shorter than the time required to charge the capacitor. However, in a device for measuring the distance from a moving body to a target object, for example, as described above, it is desirable to make the pulse interval even shorter.

[0006] One example of a problem to be solved by the present invention is to shorten the interval between pulses output from a light source. [Means for solving the problem]

[0007] The invention described in claim 1 is A plurality of capacitance elements connected in parallel to each other and each supplying power to a light emitting element when discharging; a power source for charging the plurality of capacitance elements; and a discharge control unit that individually controls the timing at which the plurality of capacitive elements discharge. [Brief description of the drawings]

[0008] [Figure 1] 2 is a diagram illustrating a functional configuration and a usage environment of the light source driving device according to the first embodiment. FIG. [Diagram 2] 1 is a block diagram showing a functional configuration of a distance measurement device according to a first embodiment. [Diagram 3] FIG. 11 is a diagram illustrating a functional configuration of a distance measurement device according to a second embodiment. [Figure 4] FIG. 13 is a diagram showing a modified example of the distance measuring device according to the second embodiment. [Diagram 5] 1 is a diagram illustrating a circuit configuration of a light source driving device and a light emitting element according to a first embodiment; [Figure 6] FIG. 2 is a diagram showing a hardware configuration of an integrated circuit. [Figure 7] 4 is an example of a timing chart of trigger signals VT1 to VTn according to the first embodiment. [Figure 8] 10 is a diagram illustrating a circuit configuration of a light source driving device and a light emitting element according to a second embodiment. FIG. [Figure 9] 11 is a diagram illustrating a circuit configuration of a light source driving device and a light emitting element according to a third embodiment. FIG. [Figure 10] 13 is an example of a timing chart of trigger signals VT1 to VT4 according to a first example of the fourth embodiment. [Figure 11] 13 is an example of a timing chart of trigger signals VT1 to VT4 according to a second example of the fourth embodiment. [Figure 12] FIG. 13 is a diagram illustrating a circuit configuration of a light source driving device and a light emitting element according to a third example of the fourth embodiment. [Figure 13]FIG. 13 is a block diagram illustrating a functional configuration of a distance measuring device according to a fifth embodiment. [Figure 14] FIG. 11 is a diagram for explaining a first processing example. [Figure 15] 1 is a diagram illustrating a functional configuration of a light source driving device that performs a first processing example. [Figure 16] 13 is a diagram illustrating a light source driving device according to a third processing example and an environment in which the light source driving device is used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are given the same reference numerals and the description will be omitted as appropriate.

[0010] In the following description, each component of the distance measurement device 1 and the light-source driving device 20 is represented as a functional block, not as a hardware configuration. The processing unit 80 and the control unit 70 of the distance measurement device 1, and the discharge control unit 23 and the acquisition unit 24 of the light-source driving device 20 are realized by any combination of hardware and software, centered on the CPU of any computer, memory, a program loaded into the memory, a storage medium such as a hard disk that stores the program, and a network connection interface. There are various variations in the realization method and device.

[0011] (First embodiment) 1 is a diagram illustrating a functional configuration and a usage environment of a light-source driving device 20 according to a first embodiment. The light-source driving device 20 according to this embodiment includes a plurality of capacitive elements 22, a power source 21, and a discharge control unit 23. The plurality of capacitive elements 22 are parallel to each other, and each of them supplies power to the light-emitting element 10 during discharging. The power source 21 charges the plurality of capacitive elements 22. The discharge control unit 23 individually controls the timing at which the plurality of capacitive elements 22 discharge. This will be described in detail below.

[0012] The light emitting element 10 is, for example, a light emitting diode, and emits light when a current flows through it. The light emitting element 10 is also a laser diode that oscillates as a laser. The light emitting element 10 emits pulsed light when a discharge current flows through the capacitance element 22. Note that, although the figure shows an example in which the light source driving device 20 includes five capacitance elements 22, the present invention is not limited to this. The light source driving device 20 may include two or more capacitance elements 22.

[0013] In the conventional case where only one capacitance element is used and charging and discharging are repeated to make the light-emitting element emit light multiple times, the light-emitting element cannot emit light again until it is sufficiently charged after discharging once. In order to shorten the charging time, the charging time constant must be set small and a power source with a large current capacity must be used, which increases costs.

[0014] In contrast, in this embodiment, the multiple capacitance elements 22 are connected in parallel with each other. Therefore, the multiple capacitance elements 22 can be charged simultaneously. The discharge control unit 23 of this embodiment controls the discharge timing of the multiple capacitance elements 22 individually, that is, independently of each other. By doing so, for example, after discharging one capacitance element 22, the other capacitance elements 22 can be discharged while being charged. In other words, regardless of the charging time of the capacitance elements 22, the multiple capacitance elements 22 can be discharged continuously, and the light-emitting element 10 can be made to emit light at short pulse intervals.

[0015] In addition, when a single capacitance element is used as in the conventional method to repeatedly charge and discharge a light-emitting element to emit light multiple times, it is necessary to control, for example, the amount of charge stored in the capacitance element in order to change the light-emitting intensity of the light-emitting element, but such control can be difficult to perform with precision, particularly when pulsed light emission is repeated at short intervals.

[0016] In contrast, in this embodiment, for example, the discharge control unit 23 discharges multiple capacitive elements 22 individually or simultaneously to cause the light-emitting element 10 to emit light, thereby easily changing the light-emitting intensity of the light-emitting element 10.

[0017] The light source driving device 20 according to this embodiment can be used in the distance measurement device 1, for example. 2 is a block diagram showing a functional configuration of the distance measurement device 1 according to the first embodiment. The distance measurement device 1 includes a light source driving device 20, a light emitting element 10, and a processing unit 80. The processing unit 80 calculates the distance to a reflecting object that reflects the light in the light emission direction by using the time from when the light emitting element 10 emits light to when it receives the reflected light of the light. The light emitting element 10 is, for example, a light source in the distance measurement device 1.

[0018] The distance measurement device 1 further includes a light receiving unit 50 that receives the reflected light. A signal indicating the discharge timing of the capacitive element 22, i.e., the light emission timing of the light emitting element 10, is input from the light source driving device 20 to the processing unit 80. The processing unit 80 then calculates the distance based on the light emission timing and the light reception timing of the light receiving unit 50.

[0019] As described above, according to this embodiment, the light source driving device 20 includes a plurality of capacitive elements 22, and the discharge control unit 23 individually controls the timing at which the plurality of capacitive elements 22 discharge. This increases the degree of freedom in controlling the interval and intensity of the pulses output from the light source.

[0020] Second Embodiment FIG. 3 is a diagram illustrating a functional configuration of the distance measurement device 1 according to the second embodiment. The distance measurement device 1 according to this embodiment is the same as the distance measurement device 1 according to the first embodiment, except that it includes a plurality of light-emitting elements 10. The distance measurement device 1 according to this embodiment includes a light source driving device 20, a plurality of light-emitting elements 10, a light receiving unit 50, and a processing unit 80. The light source driving device 20 controls the light emission of the plurality of light-emitting elements 10. The processing unit 80 calculates the distance to the reflecting object that reflected the light in the light emission direction by using the time from when the light-emitting element 10 emits light to when it receives the reflected light of the light. A signal indicating the discharge timing of the capacitive element 22, i.e., the light emission timing of the light-emitting element 10, is input from the discharge control unit 23 of the light source driving device 20 to the processing unit 80. This will be described in detail below.

[0021] The light source driving device 20 according to this embodiment has a similar configuration to the light source driving device 20 according to the first embodiment. However, the multiple capacitive elements 22 supply discharge currents to different light emitting elements 10. The light source driving device 20 drives the multiple light emitting elements 10. The light source driving device 20 includes multiple capacitive elements 22, a power source 21, and a discharge control unit 23. Each of the multiple capacitive elements 22 supplies power to one of the multiple light emitting elements 10 during discharge. For example, the first capacitive element 22a supplies power to the first light emitting element 10a, and the second capacitive element 22b supplies power to the second light emitting element 10b. Here, the second capacitive element 22b is a capacitive element 22 different from the first capacitive element 22a, and the second light emitting element 10b is a light emitting element 10 different from the first light emitting element 10a. However, the characteristics of the first capacitive element 22a and the second capacitive element 22b may be the same or different from each other. The characteristics of the first light-emitting element 10a and the characteristics of the second light-emitting element 10b may be the same or different from each other. A power source 21 charges a plurality of capacitance elements 22. A discharge control unit 23 controls the timing at which the plurality of capacitance elements 22 discharge. The light-source driving device 20 may be a physically integrated device or may be composed of a plurality of units.

[0022] FIG. 4 is a diagram showing a modified example of the distance measurement device 1 of the second embodiment. The light source driving device 20 according to this modified example is the same as the light source driving device 20 of the second embodiment except that it includes a plurality of power sources 21. The light source driving device 20 according to this embodiment includes a plurality of capacitive elements 22, a plurality of power sources 21, and a discharge control unit 23. Each of the plurality of capacitive elements 22 supplies power to one of the plurality of light emitting elements 10 during discharge. For example, the first capacitive element 22a supplies power to the first light emitting element 10a, and the second capacitive element 22b supplies power to the second light emitting element 10b. Also, each of the plurality of power sources 21 charges one of the plurality of capacitive elements 22. For example, the first power source 21a charges the first capacitive element 22a, and the second power source 21b charges the second capacitive element 22b. Here, the second power source 21b is a power source 21 different from the first power source 21a. However, the characteristics of the first power source 21a and the characteristics of the second power source 21b may be the same or different from each other. The discharge control unit 23 controls the timing at which the multiple capacitive elements 22 discharge.

[0023] 3 and 4 show an example in which the distance measurement device 1 includes two light-emitting elements 10 and the light-source driving device 20 includes two capacitive elements 22, but the present invention is not limited to this. The distance measurement device 1 may include three or more light-emitting elements 10 and the light-source driving device 20 may include three or more capacitive elements 22.

[0024] The discharge control unit 23 of this embodiment controls the discharge timing of the multiple capacitive elements 22 independently of each other. By doing so, for example, after discharging one capacitive element 22, it is possible to discharge another capacitive element 22 while charging it. In other words, regardless of the charging time of the capacitive elements 22, it is possible to continuously discharge the multiple capacitive elements 22 and make the multiple light-emitting elements 10 emit light in sequence at short pulse intervals.

[0025] In addition, in this embodiment, for example, the discharge control unit 23 discharges the multiple capacitive elements 22 individually or simultaneously to cause the light-emitting element 10 to emit light, thereby easily changing the light-emitting intensity of the light-emitting element 10.

[0026] As described above, according to this embodiment, the distance measurement device 1 includes a plurality of light-emitting elements 10, and the discharge control unit 23 individually controls the timing at which the plurality of capacitive elements 22 discharge. This increases the degree of freedom in controlling the interval and intensity of the pulses output from the light source.

[0027] Example 1 5 is a diagram illustrating a circuit configuration of a light-source driving device 20 and a light-emitting element 10 according to Example 1. The light-source driving device 20 according to this example has the configuration described in the first embodiment. The light-source driving device 20 according to this example is realized using a circuit as shown in this figure and an integrated circuit 100 described later.

[0028] The light source driving device 20 includes n (n is a natural number) capacitance elements 22 (capacitance elements C chg1 ~C chgn ) and switches M1 to M n and resistor R lim1 ~R limn and resistor R chg1 ~R chgn and diode D clp and resistor R m and the capacitance element C p and a power supply 21. chg1 ~C chgn corresponds to the plurality of capacitance elements 22, the laser diode LD corresponds to the light emitting element 10, and the voltage V h corresponds to the output voltage of the power source 21. The discharge control unit 23 controls the switches M1 to M n and an integrated circuit 100. In the figure, an example in which the light-source driving device 20 includes five capacitive elements 22 (an example in which n=5) is shown, but the present invention is not limited to this.

[0029] In the light source driving device 20, a high voltage V h is the capacitance element C chg1 ~C chgn is applied to the capacitance element C chg1 ~C chgn is charged. Then, the capacitance element C chg1 ~C chgnThe charge stored in n The discharge is instantaneously caused through the capacitance element C, and the discharge is made to flow to the laser diode LD, thereby outputting a pulsed laser beam. chg1 ~C chgn Each is charged to several tens to several hundred volts and then discharged at several tens of amperes.

[0030] Hereinafter, the capacitance element C chgk The charging and discharging of the capacitance element 22 will be described in detail below using an example of capacitance element C (k is an integer between 1 and n). Note that in the following, the first terminal and the second terminal of each element are different terminals. chgk The first terminal of the resistor R limk The first terminal of the capacitance element C chgk The second terminal of the resistor R chgk A power supply 21 is connected via a capacitance element C chgk Between the second terminal of and the ground terminal, a switch M k is connected. Switch M k The gate of the resistor R is connected to an output terminal of the control unit 230, which will be described later. limk The second terminal of the diode D clp The anode of the diode D is connected clp The cathode of is connected to the ground terminal.

[0031] Resistance R limk The cathode of the laser diode LD is connected to the second terminal of the resistor R. The anode of the laser diode LD is connected to the ground terminal. m and the capacitance element C p A laser diode LD is connected in parallel to the series connection of the above.

[0032] Here, the discharge control unit 23 includes a control unit 230 and switches M1 to M n The present invention is configured to include the following.

[0033] During charging, the power supply 21 chgk High voltage V hand the trigger signal V Tk Switch M k As a result, the capacitance element C chgk is the high voltage V h During discharge, the trigger signal V Tk Switch M k This turns on the capacitance element C chgk The electric charge stored in the capacitance element C is instantly discharged through a discharge path 202 indicated by a dashed line in the figure, and the laser diode LD emits light. Here, a high voltage generating circuit such as a charge pump can be used as the power supply 21. chg1 ~C chgn For each of the trigger signals V Tk By providing these, charging and discharging can be controlled independently.

[0034] 6 is a diagram showing a hardware configuration of the integrated circuit 100. The control unit 230 is realized using the integrated circuit 100. The integrated circuit 100 receives a trigger signal V T1 ~V Tn The output trigger signal V T1 ~V Tn are switches M1 to M n The integrated circuit 100 is, for example, a System On Chip (SoC).

[0035] The integrated circuit 100 has a bus 102, a processor 104, a memory 106, a storage device 108, an input / output interface 110, and a network interface 112. The bus 102 is a data transmission path for the processor 104, the memory 106, the storage device 108, the input / output interface 110, and the network interface 112 to transmit and receive data to and from each other. However, the method of connecting the processor 104 and the like to each other is not limited to bus connection. The processor 104 is an arithmetic processing device realized by using a microprocessor or the like. The memory 106 is a memory realized by using a RAM (Random Access Memory) or the like. The storage device 108 is a storage device realized by using a ROM (Read Only Memory), a flash memory, or the like.

[0036] The input / output interface 110 is an interface for connecting the integrated circuit 100 to peripheral devices. T1 ~V Tn are switches M1 to M n is entered into

[0037] The network interface 112 is an interface for connecting the integrated circuit 100 to a communication network. This communication network is, for example, a CAN (Controller Area Network) communication network. The method for connecting the network interface 112 to the communication network may be a wireless connection or a wired connection.

[0038] The storage device 108 stores a program module for implementing the functions of the control unit 230. The processor 104 implements the functions of the control unit 230 by reading the program module into the memory 106 and executing it.

[0039] The hardware configuration of the integrated circuit 100 is not limited to the configuration shown in Fig. 6. For example, the program module may be stored in the memory 106. In this case, the integrated circuit 100 may not include the storage device 108.

[0040] FIG. 7 shows the trigger signal V T1 ~V Tn 1 is an example of a timing chart of the above-mentioned. According to this example, the light emitting element 10 repeatedly emits light at the same interval. Information showing the timing chart can be stored in advance, for example, in the storage device 108 of the integrated circuit 100, and the discharge control unit 23 (control unit 230) can read and execute the information to output it. The trigger signal V Tk is the capacitance element C chgk This is the trigger signal for discharging the trigger signal V Tk While is at low level, switch M k is turned off, and the capacitance element C chgk is charged. The trigger signal V Tk When the level of switch M changes from low to high, k turns on, and the capacitive element C chgk is discharged.

[0041] This figure shows the capacitance element C chg1 ~C chgn In the example of this figure, the discharge control unit 23 sequentially discharges the first capacitance element 22 (for example, capacitance element C chg1 ) is discharged, and at a second timing (for example, timing t2) different from the first timing, a second capacitive element 22 (for example, capacitive element C chg2) is discharged. This allows another capacitive element 22 to be discharged without waiting for the first capacitive element 22 to be fully charged again after discharging. Furthermore, the interval between the pulsed emission of the light-emitting element 10 can be shortened. The interval between the first timing and the second timing is not particularly limited, but the light-emitting element 10 can be caused to emit pulsed light at an interval shorter than the interval at which the charging of the capacitive element 22 is completed. For example, the interval between the first timing and the second timing is shorter than at least one of the time required from the start of charging the first capacitive element 22 to the completion of charging and the time required from the start of charging the second capacitive element 22 to the completion of charging. Note that the capacitive element C chgk The time it takes from the start of charging to the completion of charging is chgk The capacitance and resistance R limk and resistor R chgk It depends on the resistance value etc.

[0042] In the example shown in the figure, the trigger signal V T1 The time from (t1) when the signal rises, that is, when the signal changes from low to high, to (k-1) × t d Trigger signal V seconds later Tk That is, the trigger signal V Tk The timing when t k is based on t1 (t1=0), t k =(k-1)×t d (k≧2). Each trigger signal V Tk is the time t pw After the trigger signal V T1 Once you stand up, d Then, the trigger signal V T1 ~V Tn rises repeatedly in sequence, and the capacitance element C chg1 ~C chgn In this way, the light emitting element 10 discharges t dIn the example shown in the figure, the interval between the first timing and the second timing is t d In addition, the trigger signal V Tk The time during which n is at a low level can be made sufficiently long. Therefore, each capacitance element 22 can be fully charged between the time when one capacitance element 22 is discharged and the time when the next capacitance element 22 is discharged. In the example shown in the figure, the time available for charging the capacitance elements 22 is n×t d It is expressed as:

[0043] However, the timing chart of the trigger signal is not limited to the above example. For example, the intervals at which the multiple capacitive elements 22 are discharged do not have to be constant.

[0044] In this embodiment, the capacitance element C chg1 ~C chgn The capacitances of the resistors R may be the same, or at least one of them may be different. lim1 ~R limn The resistance values ​​of the resistors R may be the same, or at least one of them may be different. chg1 ~R chgn The resistance values ​​may be the same as each other, or at least one of them may be different.

[0045] In addition, the capacitance element C chg1 ~C chgn A power supply 21 is provided independently for each of the capacitance elements C chg1 ~C chgn may be charged by different power sources 21.

[0046] As described above, in this embodiment as well, similarly to the first embodiment, the light source driving device 20 includes a plurality of capacitive elements 22, and the discharge control unit 23 individually controls the timing of discharging the plurality of capacitive elements 22. This increases the degree of freedom in controlling the pulses output from the light source.

[0047] In addition, the discharge control unit 23 of this embodiment discharges the first capacitance element 22 at a first timing, and discharges the second capacitance element 22, which is different from the first capacitance element 22, at a second timing different from the first timing. Therefore, the interval between pulsed light emission of the light-emitting element 10 can be shortened.

[0048] Example 2 8 is a diagram illustrating a circuit configuration of a light-source driving device 20 and a light-emitting element 10 according to Example 2. The light-source driving device 20 according to this example has the configuration described in the second embodiment. That is, the light-source driving device 20 drives a plurality of light-emitting elements 10. The light-source driving device 20 according to this example is realized using a circuit as shown in this figure and an integrated circuit 100 as described in Example 1.

[0049] The light source driving device 20 includes n (n is an integer) capacitance elements 22 (capacitance elements C chg1 ~C chgn ) and switches M1 to M n and resistor R lim1 ~R limn and resistor R chg1 ~R chgn and diode D clp1 ~D clpn and resistor R m1 ~R mn and the capacitance element C p1 ~C pn and a power supply 21. chg1 ~C chgn correspond to the plurality of capacitance elements 22, and the laser diodes LD1 to LD n corresponds to a plurality of light-emitting elements 10, and the voltage V h These correspond to the output voltages of the power source 21. The discharge control unit 23 also includes switches M1 to M n and an integrated circuit 100. In the figure, an example in which the light-source driving device 20 includes two capacitive elements 22 (an example in which n=2) is shown, but the present invention is not limited to this.

[0050] In the light source driving device 20, a high voltage V h is the capacitance element C chg1 ~Cchgn is applied to the capacitance element C chg1 ~C chgn is charged. Then, the capacitance element C chg1 ~C chgn The charge stored in n The laser diodes LD1 to LD n By passing a current through the capacitor C, a pulsed laser beam is output. chg1 ~C chgn Each is charged to several tens to several hundred volts and then discharged at several tens of amperes.

[0051] Hereinafter, the capacitance element C chgk The charging and discharging of the capacitance element 22 will be described in detail below using an example of capacitance element C (k is an integer between 1 and n). chgk The first terminal of the resistor R limk The first terminal of the capacitance element C chgk The second terminal of the resistor R chgk A power supply 21 is connected via a capacitance element C chgk Between the second terminal of and the ground terminal, a switch M k is connected. Switch M k The gate of the resistor R limk The second terminal of the diode D clpk The anode of the diode D is connected clpk The cathode of is connected to the ground terminal.

[0052] Resistance R limk The second terminal is connected to the laser diode LD k The cathode of the laser diode LD is connected to the k The anode of is connected to the ground terminal. Also, the resistor R mk and the capacitance element C pk and a laser diode LD k are connected in parallel.

[0053] During charging, the power supply 21 chgk High voltage Vh and the trigger signal V Tk Switch M k This turns off the capacitance element C chgk is the high voltage V h During discharge, the trigger signal V Tk Switch M k This turns on the capacitance element C chgk The electric charge stored in the laser diode LD is instantly discharged. k The power supply 21 may be a high voltage generating circuit such as a charge pump. chg1 ~C chgn For each of the trigger signals V Tk By providing these, charging and discharging can be controlled independently.

[0054] The trigger signal V according to this embodiment T1 ~V Tn An example of the timing chart can be shown in the same manner as in FIG.

[0055] In this embodiment, the capacitance element C chg1 ~C chgn The capacitances of the resistors R may be the same, or at least one of them may be different. lim1 ~R limn The resistance values ​​of the resistors R may be the same, or at least one of them may be different. chg1 ~R chgn The resistance values ​​of the laser diodes LD1 to LD2 may be the same, or at least one of them may be different. n Characteristics of resistance R m1 ~R mn Characteristics of the capacitance element C p1 ~C pn The characteristics may be the same or at least one may be different.

[0056] As described above, in this embodiment as well, similarly to the second embodiment, the distance measurement device 1 includes a plurality of light emitting elements 10, and the discharge control unit 23 individually controls the timing of discharging the plurality of capacitive elements 22. Therefore, it is possible to increase the degree of freedom in controlling the pulse output from the light source.

[0057] In addition, the discharge control unit 23 of this embodiment can discharge the first capacitive element 22 at a first timing to cause the first light-emitting element 10 to emit light, and can discharge the second capacitive element 22 different from the first capacitive element 22 at a second timing different from the first timing to cause the second light-emitting element 10 to emit light. Therefore, the interval between pulsed emissions outputted by the distance measurement device 1 as a whole can be shortened.

[0058] Example 3 FIG. 9 is a diagram illustrating a circuit configuration of a light-source driving device 20 and a light-emitting element 10 according to a third embodiment. The light-source driving device 20 according to this embodiment is the same as the light-source driving device 20 according to the second embodiment, except for the points described below. The light-source driving device 20 according to this embodiment has the configuration described in the modified example of the second embodiment. In other words, a plurality of combinations of one light-emitting element and its power supply circuit are configured. The light-source driving device 20 according to this embodiment is realized using a circuit as shown in this figure and an integrated circuit 100 as described in the first embodiment.

[0059] The light source driving device 20 includes n (n is a natural number) capacitance elements 22 (capacitance elements C chg1 ~C chgn ) and switches M1 to M n and resistor R lim1 ~R limn and resistor R chg1 ~R chgn and diode D clp1 ~D clpn and resistor R m1 ~R mn and the capacitance element C p1 ~C pn and a plurality of power sources 21. chg1 ~C chgn correspond to the plurality of capacitance elements 22, and the laser diodes LD1 to LDn corresponds to a plurality of light-emitting elements 10, and the voltage V h1 ~V hn correspond to the output voltages of the power supplies 21. The discharge control unit 23 also includes switches M1 to M n and an integrated circuit 100. In the figure, an example in which the light-source driving device 20 includes two capacitive elements 22 (an example in which n=2) is shown, but the present invention is not limited to this.

[0060] In the light source driving device 20, a high voltage V h1 ~V hn is the capacitance element C chg1 ~C chgn is applied to the capacitance element C chg1 ~C chgn is charged. Then, the capacitance element C chg1 ~C chgn The charge stored in n The laser diodes LD1 to LD n By passing a current through the capacitor C, a pulsed laser beam is output. chg1 ~C chgn Each is charged to several tens to several hundred volts and then discharged at several tens of amperes.

[0061] Hereinafter, the capacitance element C chgk The charging and discharging of the capacitance element 22 will be described in detail below using an example of capacitance element C (k is an integer between 1 and n). chgk The first terminal of the resistor R limk The first terminal of the capacitance element C chgk The second terminal of the resistor R chgk A power supply 21 is connected via a capacitance element C chgk Between the second terminal of and the ground terminal, a switch M k is connected. Switch M k The gate of the resistor R limk The second terminal of the diode D clpk The anode of the diode D is connected clpk The cathode of is connected to the ground terminal.

[0062] Resistance R limk The second terminal of the laser diode LD k The cathode of the laser diode LD is connected to the k The anode of is connected to the ground terminal. Also, the resistor R mk and the capacitance element C pk and a laser diode LD k are connected in parallel.

[0063] During charging, the power supply 21 chgk High voltage V hk and the trigger signal V Tk Switch M k This turns off the capacitance element C chgk is the high voltage V hk During discharge, the trigger signal V Tk Switch M k This turns on the capacitance element C chgk The electric charge stored in the laser diode LD is instantly discharged. k The power supply 21 may be a high voltage generating circuit such as a charge pump. chg1 ~C chgn For each of the trigger signals V Tk By providing these, charging and discharging can be controlled independently.

[0064] The trigger signal V according to this embodiment T1 ~V Tn An example of the timing chart can be shown in the same manner as in FIG.

[0065] In this embodiment, the high voltage V h1 ~V hn The voltage values ​​may be the same as each other, or at least one of them may be different.

[0066] As described above, in this embodiment as well, similarly to the second embodiment, the distance measurement device 1 includes a plurality of light emitting elements 10, and the discharge control unit 23 individually controls the timing of discharging the plurality of capacitive elements 22. Therefore, it is possible to increase the degree of freedom in controlling the pulse output from the light source.

[0067] In addition, the discharge control unit 23 of this embodiment can discharge the first capacitive element 22 at a first timing to cause the first light-emitting element 10 to emit light, and can discharge the second capacitive element 22 different from the first capacitive element 22 at a second timing different from the first timing to cause the second light-emitting element 10 to emit light. Therefore, the interval between pulsed emissions outputted by the distance measurement device 1 as a whole can be shortened.

[0068] Example 4 The light-source driving device 20 according to this embodiment has a similar configuration to the light-source driving device 20 according to at least one of Examples 1 to 3. In the following, a case where the light-source driving device 20 has the configuration described in Example 1 will be described.

[0069] The discharge control unit 23 of this embodiment is configured to S , and the third timing t S The fourth timing t L At each of the fourth timing t L At the third timing t S A power larger than the above is supplied to the light emitting element 10. This will be described in detail below.

[0070] The fourth timing t L At the third timing t S The configuration of this embodiment in which a power larger than the fourth timing t is supplied to the light emitting element 10 includes the following first to third examples. L At the third timing t S By supplying a power larger than the third timing t S The fourth timing t LA pulsed light having a higher intensity is output at the

[0071] FIG. 10 shows a trigger signal V T1 ~V T4 1 is an example of a timing chart of the first example. In the first example, the plurality of capacitance elements 22 includes a third capacitance element 22 and a fourth capacitance element 22 having a capacitance larger than that of the third capacitance element 22. The discharge control unit 23 then starts the discharge at the third timing t S At the fourth timing t L In the example shown in the figure, the light source driving device 20 has at least four capacitance elements 22 (capacitance element C chg1 ~C chg4 For example, a capacitance element C chg1 Capacity and C chg2 The capacitances of the capacitance elements C chg3 Capacity and C chg4 The capacitances of the capacitance elements C chg1 and the capacitance element C chg2 is the third capacitance element 22, and the capacitance element C chg3 and the capacitance element C chg4 is defined as the fourth capacitance element 22. That is, the capacitance element C chg3 The capacitance of the capacitance element C chg1 is larger than the capacity of

[0072] And the third timing t S Trigger signal V T1 or V T2 When the capacitance element C chg1 or C chg2 is discharged. Also, at the fourth timing t L Trigger signal V T3 or V T4 When the capacitance element C chg3 or C chg4 In this way, the fourth timing t L At the fourth timing t L At the third timing t SA larger current flows through the light emitting element 10 and a larger power is supplied to the light emitting element 10.

[0073] In addition, when the third timing occurs continuously, the capacitance element C chg1 and C. chg2 and are alternately discharged, and when the fourth timing occurs consecutively, the capacitance element C chg3 and C. chg4 By alternately discharging the third capacitance elements 22 and the fourth capacitance elements 22, the light-source driving device 20 can emit light at short pulse intervals. The light-source driving device 20 may include three or more third capacitance elements 22 and three or more fourth capacitance elements 22. That is, when the third timings occur consecutively and when the fourth timings occur consecutively, the light-source driving device 20 may sequentially discharge three or more capacitance elements 22.

[0074] FIG. 11 shows a trigger signal V T1 ~V T4 1 is an example of a timing chart of the discharge control unit 23 at the fourth timing t L At the third timing t S In the example shown in the figure, for example, the light source driving device 20 discharges at least four capacitive elements 22 (capacitive elements C chg1 ~C chg4 For example, at least a capacitance element C chg1 Capacity and C chg2 The capacitances of the capacitance elements C chg3 Capacity and C chg4 The capacitances of the three timings t S Then the trigger signal V T1 or V T2 When only the capacitance element C chg1 or C chg2 Only the fourth timing t L Trigger signal V T1 and V T3 When these two rise simultaneously, the capacitance element C chg1 and C. chg3 and are discharged at the same time.L Trigger signal V T2 and V T4 When these two rise simultaneously, the capacitance element C chg2 and C. chg4 In this way, the fourth timing t L The third timing t S At the fourth timing t L At the third timing t S A larger current flows through the light emitting element 10 and a larger power is supplied to the light emitting element 10.

[0075] Also in this example, when the third timings occur consecutively and when the fourth timings occur consecutively, the light emitting element 10 can be made to emit light at short pulse intervals by alternately discharging the multiple capacitive elements 22. When the third timings occur consecutively and when the fourth timings occur consecutively, the light source driving device 20 may sequentially discharge three or more capacitive elements 22. Also, the number of capacitive elements 22 to be discharged simultaneously is not particularly limited.

[0076] In the second example, the multiple capacitance elements 22 that can be discharged simultaneously, i.e., the capacitance elements C chg1 Capacity and C chg3 The capacitances of the capacitive elements 22 may be the same, or at least one of them may be different. When the capacitances of the capacitive elements 22 are different from each other, the light emission intensity of the light emitting element 10 can be changed in three stages by combining, for example, two types of capacitance. Specifically, in the example shown in this figure, the capacitive elements C chg3 Capacity and C chg4 The capacitance of the capacitance element C chg1 Capacitance and capacitance element C chg2 If the capacitance of the capacitance element C is larger than that of the capacitance element C, the output of a weak pulse light is chg1 or C chg2 At the timing when it is desired to output a pulse of light of medium intensity, only the capacitance element C chg3 or C chg4 At the timing when you want to output a strong pulse of light, you only need to discharge the capacitance element Cchg1 and C. chg3 , or the capacitance element C chg2 and C. chg4 can be combined and discharged simultaneously.

[0077] 12 is a diagram illustrating a circuit configuration of a light source driving device 20 and a light emitting element 10 according to a third example of the fourth embodiment. The circuit configuration according to the third example is similar to the circuit configuration according to the first embodiment, except that it includes a plurality of power sources 21. The trigger signal V T1 and V T2 An example of the timing chart can be expressed similarly to FIG. 10. In the third example, the plurality of capacitance elements 22 includes a third capacitance element 22 and a fourth capacitance element 22 that is charged with a voltage higher than the voltage that charges the third capacitance element 22. The discharge control unit 23 then starts the third timing t S At the fourth timing t L The fourth capacitive element 22 is discharged.

[0078] 12, the light source driving device 20 includes a plurality of power supplies 21. The output voltages of the plurality of power supplies 21 are a high voltage V h1~ V hn It is expressed as follows: Capacitive element C chgk The first terminal of the resistor R limk is connected, and the capacitance element C chgk The second terminal of the resistor R chgk The power supply 21 is connected via the high voltage V hk is applied.

[0079] In this example, the light source driving device 20 includes at least four capacitive elements 22 (capacitive elements C chg1 ~C chg4 ) and four power supplies 21. For example, a high voltage V h1 and high voltage V h2 are the same as each other, and the high voltage V h3 and high voltage V h4 are the same as each other. For example, the high voltage V h3 is the high voltage V h1 By doing so, the capacitance element C chg3and the capacitance element C chg4 is the capacitance element C chg1 and the capacitance element C chg2 At the third timing t S Trigger signal V T1 or V T2 When the capacitance element C chg1 or capacitance element C chg2 is discharged. Also, at the fourth timing t L Trigger signal V T3 or V T4 When the capacitance element C chg3 or capacitance element C chg4 In this way, the fourth timing t L And the third timing t S At the fourth timing t L At the third timing t S A larger current flows through the light emitting element 10 and a larger power is supplied to the light emitting element 10.

[0080] Also in this example, the third timing t S In the case where the fourth timing t L When the third timing occurs successively and when the fourth timing occurs successively, the light-emitting element 10 can emit light at short pulse intervals by alternately discharging the multiple capacitive elements 22. When the third timing occurs successively and when the fourth timing occurs successively, the light-source driving device 20 may sequentially discharge three or more capacitive elements 22.

[0081] The discharge control unit 23 sets the timing at which a pulsed light with a high intensity is to be output as a fourth timing t L The other timings are called the third timing t S Specifically, for example, when the light source driving device 20 is included in the distance measurement device 1, the discharge control unit 23 outputs a trigger signal at the third timing t SThe fourth timing t L This allows the output intensity of the light emitting element 10 to be increased and measurement accuracy to be improved if desired by the user.

[0082] In this embodiment, the interval between discharges of each capacitance element 22 can be set to, for example, a time period that is longer than the time required for each capacitance element 22 to be fully charged.

[0083] In the above first to third examples, the third timing t S In the case where the fourth timing t L In the example shown, the plurality of capacitance elements 22 are alternately discharged when the third timing t S In the case where the fourth timing t L In the case where the two consecutive discharges occur, the same capacitance element 22 may be continuously discharged. Even in this case, the emission intensity can be controlled in the same manner as described above.

[0084] Moreover, the same methods as those in the first to third examples may be applied to the light source driving device 20 and the light emitting element 10 of the second embodiment.

[0085] As described above, in this embodiment as well, the light source driving device 20 includes a plurality of capacitive elements 22, and the discharge control unit 23 individually controls the timing at which the plurality of capacitive elements 22 discharge. This increases the degree of freedom in controlling the pulses output from the light source.

[0086] In addition, according to this embodiment, the fourth timing t L At the third timing t S A power larger than the above is supplied to the light emitting element 10. Therefore, the intensity of the pulsed light output from the light source can be controlled.

[0087] Example 5 13 is a block diagram illustrating a functional configuration of a distance measurement device 1 according to a fifth embodiment. The distance measurement device 1 according to the present embodiment includes a light emitting element 10, a light source driving device 20, a movable reflecting unit 30, a control unit 70, a processing unit 80, and a light receiving unit 50. The distance measurement device 1 is, for example, a LIDAR (Laser Imaging Detection and Ranging) device.

[0088] The light source driving device 20 according to this embodiment has the same configuration as at least one of the light source driving devices 20 of the first embodiment, the second embodiment, and Examples 1 to 4. As described above, the light emitting element 10 is, for example, a semiconductor laser. The wavelength of the light output from the light emitting element 10 is not particularly limited, but is, for example, near-infrared light of 700 nm or more and 1050 nm or less. The movable reflecting unit 30 is configured to include, for example, a MEMS mirror and a driving circuit. The angle of the reflecting surface of the MEMS mirror is controlled by the control unit 70. The movable reflecting unit 30 reflects the light emitted from the light emitting element 10 with its reflecting surface, thereby outputting the light in a desired direction. The movable reflecting unit 30 can scan the target object two-dimensionally with light by including, for example, a two-axis driven MEMS mirror. However, the configuration of the distance measuring device 1 is not particularly limited as long as the output direction of the light in the distance measuring device 1 is variable. For example, the light emitting element 10 may be fixed to a movable stage, and the control unit 70 may control the direction of the light emitting element 10 to control the output direction of the light.

[0089] When the light source driving device 20 has the configuration described in at least one of the second embodiment, Example 2, and Example 3, the distance measurement device 1 includes a plurality of light emitting elements 10. In this case, for example, by using an optical system (not shown), the light from the plurality of light emitting elements 10 is configured to be output coaxially.

[0090] The hardware configuration of the control unit 70 and the processing unit 80 can be exemplified in the same manner as in FIG. 6. The control unit 70 and the processing unit 80 are implemented using the above-mentioned integrated circuit 100. In this embodiment, the input / output interface 110 includes the switches M1 to M of the light source driving device 20. n, a drive circuit for the movable reflector 30, and a light receiving section 50 are connected.

[0091] The storage device 108 stores program modules for implementing the functions of the control unit 70 and the processing unit 80. The processor 104 implements the functions of the control unit 70 and the processing unit 80 by reading the program modules into the memory 106 and executing them.

[0092] The light receiving section 50 includes, for example, a photodiode and a detection circuit. In the light receiving section 50, light incident on the light receiving surface of the photodiode is photoelectrically converted to generate a light receiving signal.

[0093] The processing unit 80 calculates the distance to the object that reflected the light in the light emission direction by using the time from when the light emitting element 10 emits light to when the light receiving unit 50 receives the reflected light of the light. Specifically, a trigger indicating the timing of light output is input to the processing unit 80 from the discharge control unit 23 of the light source driving device 20. The processing unit 80 also acquires a light reception signal from the light receiving unit 50. The processing unit 80 may perform processing such as noise removal on the light reception signal as necessary. The processing unit 80 calculates the time from when the light emitting element 10 emits light to when the light receiving unit 50 receives the reflected light of the light based on the trigger from the discharge control unit 23 and the light reception signal from the light receiving unit 50. Furthermore, the processing unit 80 may correct the calculated time as necessary. The processing unit 80 calculates the distance from the distance measuring device 1 to the object by multiplying the time from when the light emitting element 10 emits light to when the light receiving unit 50 receives the reflected light of the light by the speed of light and multiplying it by half. Furthermore, the processing unit 80 can generate information indicating the direction and distance of an object by acquiring information indicating the emission direction of light from the control unit 70.

[0094] For example, when the distance measurement device 1 is attached to a moving body, the distance measurement device 1 can detect the direction and distance of surrounding objects by scanning the surroundings in two dimensions while repeatedly outputting pulsed light. In this case, the basic timing at which the distance measurement device 1 should output pulses is determined in advance. Usually, the distance measurement device 1 outputs pulses at constant intervals. However, the pulse intervals may differ depending on the area of ​​the scanning range. The discharge control unit 23 according to the first embodiment, for example, determines one of such basic timings as the first timing and the other as the second timing. Moreover, the discharge control unit 23 according to the third embodiment, for example, determines one of such basic timings as the third timing t S and the other one is the fourth timing t L It is determined as follows.

[0095] When the light source driving device 20 according to this embodiment has the configuration of the third embodiment, the discharge control unit 23 S and the fourth timing t L Examples of the process for determining the above include the following first to third process examples.

[0096] FIG. 14 is a diagram for explaining a first processing example. FIG. 15 is a diagram illustrating a functional configuration of the light-source driving device 20 that performs this processing example. In the first processing example, the distance measurement device 1 is attached to a moving body 90. That is, the light-emitting element 10 and the light-source driving device 20 are attached to the moving body 90. The light-source driving device 20 further includes an acquisition unit 24 that acquires map information about the surroundings of the moving body 90. Then, the discharge control unit 23 determines a fourth timing t L This is explained in more detail below.

[0097] The moving body 90 is, for example, a vehicle. In order to allow the moving body 90 to move smoothly on a road, it is sometimes necessary to specify the position of the moving body 90 with high accuracy. One method for this purpose is to compare the position of a landmark 92 on a map with the position of the landmark 92 actually specified by the distance measuring device 1 to improve the accuracy of specifying the position of the moving body 90. In this case, if a pulse light with a higher intensity is output in a direction d2 in which the landmark 92 is thought to be located than in other directions d1, and the direction of the landmark 92 as seen from the moving body 90 and the distance between the landmark 92 and the moving body 90 are measured, the S / N ratio becomes large, and the accuracy of specifying the position of the moving body 90 can be improved. The landmark 92 is, for example, a kilometer post, a 100m post, a delineator, a traffic infrastructure facility (for example, a sign, a direction sign, a traffic signal), a utility pole, a street light, or other feature lined up on the side of the road.

[0098] In this processing example, the mobile object 90 includes an internal sensor (not shown), such as a GPS and a compass. The acquisition unit 24 acquires advance information indicating the approximate position (e.g., latitude and longitude) and orientation of the mobile object 90 from the internal sensor. The acquisition unit 24 also acquires map information of the surroundings of the position indicated by the advance information, for example, from a server of a map service, via a communication network. The map information includes information indicating the positions of the landmarks 92. Next, the acquisition unit 24 calculates the direction and distance where the landmarks 92 are expected to be located, based on the advance information and the map information.

[0099] The acquisition unit 24 is realized by the integrated circuit 100 described above. The storage device 108 stores a program module for realizing the function of the acquisition unit 24. The processor 104 reads this program module into the memory 106 and executes it to realize the function of the acquisition unit 24.

[0100] In this processing example, the distance measurement device 1 scans the periphery of the moving object 90 with pulsed light. Then, the discharge control unit 23 sets the timing of outputting the pulsed light in the direction in which the landmark 92 is expected to be located to a fourth timing t LThe other timings are called the third timing t S By doing so, the direction of the landmark 92 as seen from the moving body 90 and the distance between the landmark 92 and the moving body 90 can be measured with higher accuracy. The processing unit 80 calculates the amount of deviation between the predicted direction and distance of the landmark 92 and the direction and distance of the landmark 92 measured by the distance measuring device 1, and corrects the prior information so as to reduce the amount of deviation, thereby improving the accuracy of identifying the position of the moving body 90.

[0101] Next, a second processing example will be described. In this processing example, the acquisition unit 24 acquires weather information indicating the weather. For example, the acquisition unit 24 can acquire information indicating the weather around the position indicated by the advance information from, for example, a server of a weather information providing service via a communication network. Then, the discharge control unit 23 determines the fourth timing t L This is explained in more detail below.

[0102] The light emitted from the distance measurement device 1 may be reflected by an object and absorbed by particles such as rain or fog before being received. In such a case, the intensity of the received light may decrease, making accurate distance measurement difficult. Therefore, when the weather is rainy, foggy, snowy, etc., it is preferable to output pulsed light with high intensity to improve measurement accuracy.

[0103] For example, when the acquired weather information indicates rain, fog, or snow, the acquisition unit 24 sets all emission timings in the scan to the fourth timing t L On the other hand, when the weather information indicates clear or cloudy, all the emission timings in the scan are set to the third timing t S The acquisition unit 24 acquires weather information every time a predetermined time period elapses, and at a third timing t S Or the fourth timing t LThe discharge control unit 23 may switch the intensity of the pulsed light to three or more stages based on the degree of rain, fog, or snow indicated by the weather information. The method of switching the intensity to three or more stages is as described in the second example of the fourth embodiment, for example. The discharge control unit 23 may discharge one or more capacitive elements 22 so as to supply a larger amount of power to the light-emitting element 10 as the degree of rain, fog, or snow becomes stronger.

[0104] FIG. 16 is a diagram showing a light-source driving device 20 according to a third processing example and its usage environment. In this processing example, the distance measurement device 1 includes a monitor light-receiving unit 12 for monitoring the light emission intensity of the light-emitting element 10. The monitor light-receiving unit 12 includes, for example, a photodiode and a detection circuit. The acquisition unit 24 in this processing example acquires the detection result of the monitor light-receiving unit 12, which receives at least a portion of the light emitted from the light-emitting element 10. Then, the discharge control unit 23 determines a fourth timing t L This is explained in more detail below.

[0105] The light emission intensity of the light emitting element 10 may vary due to deterioration of the element and other factors even with the same input power. Therefore, the light emission intensity of the light emitting element 10 is monitored by the monitor light receiving unit 12, and the discharge control unit 23 determines the third timing t S and the fourth timing t L By determining the above, a desired emission intensity can be maintained.

[0106] In this processing example, the output light from the light-emitting element 10 is branched by, for example, a half mirror, and a part of the light is incident on the detection surface of the monitor light-receiving unit 12. The monitor light-receiving unit 12 generates information indicating the intensity of the incident light, which is acquired by the discharge control unit 23. The branching of the light from the light-emitting element 10 and the detection by the monitor light-receiving unit 12 may be performed constantly during normal scanning of the distance measurement device 1, or may be performed at predetermined time intervals.

[0107] For example, when the intensity of the light received by the monitor light receiving unit 12 becomes lower than a predetermined reference, the discharge control unit 23 starts the discharge at the fourth timing t L Specifically, when the detection result of the monitor light receiving unit 12 is greater than a predetermined reference value, the discharge control unit 23 sets the subsequent emission timing to a third timing t S If the detection result is smaller than a predetermined criterion, the emission timing thereafter is set as the fourth timing t L The criteria for the detection results are stored in advance in the storage device 108 or the like, and the discharge control unit 23 can read out and use the criteria.

[0108] In this processing example, the acquisition unit 24 may acquire the light detection result from the light receiving unit 50 instead of the monitor light receiving unit 12. In this case, when the light received by the distance measurement device 1 is weak and it is difficult to measure the distance, the fourth timing t L In this case, the distance measurement device 1 does not need to be provided with a separate monitor light receiving unit 12.

[0109] As described above, in this embodiment as well, the light source driving device 20 includes a plurality of capacitive elements 22, and the discharge control unit 23 individually controls the timing at which the plurality of capacitive elements 22 discharge. This increases the degree of freedom in controlling the pulses output from the light source.

[0110] Although the embodiment and examples have been described above 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. Below, examples of reference forms are given. 1. A plurality of capacitance elements connected in parallel with each other, each of which supplies power to a light-emitting element when discharging; a power source for charging the plurality of capacitance elements; a discharge control unit that individually controls the timing at which the plurality of capacitance elements discharge. 2. In the light source driving device according to 1., The discharge control unit discharges a first capacitive element at a first timing, and discharges a second capacitive element different from the first capacitive element at a second timing different from the first timing. 3. In the light source driving device according to 2., A light source driving device, wherein the interval between the first timing and the second timing is shorter than at least one of the time it takes from the start of charging the first capacitive element to the completion of charging and the time it takes from the start of charging the second capacitive element to the completion of charging. 4. In the light source driving device according to any one of 1. to 3., the discharge control unit discharges at least one of the plurality of capacitance elements at a third timing and a fourth timing different from the third timing, The light source driving device supplies, at the fourth timing, the electric power to the light emitting element that is greater than the electric power supplied at the third timing. 5. In the light source driving device according to 4., the plurality of capacitive elements include a third capacitive element and a fourth capacitive element having a capacitance larger than a capacitance of the third capacitive element; The discharge control unit discharges the third capacitive element at the third timing, and discharges the fourth capacitive element at the fourth timing. 6. In the light source driving device according to 4., the plurality of capacitance elements include a third capacitance element and a fourth capacitance element that is charged with a voltage higher than a voltage that charges the third capacitance element; The discharge control unit discharges the third capacitive element at the third timing, and discharges the fourth capacitive element at the fourth timing. 7. In the light source driving device according to 4., The light-source driving device, wherein the discharge control unit discharges a greater amount of the capacitive element at the fourth timing than at the third timing. 8. In the light source driving device according to any one of 4. to 7., the light emitting element and the light source driving device are attached to a moving body, An acquisition unit that acquires map information about the surroundings of the moving object, The discharge control unit is a light source driving device that determines the fourth timing based on the map information. 9. In the light source driving device according to any one of 4. to 7., An acquisition unit for acquiring weather information indicating weather, The discharge control unit is a light source driving device that determines the fourth timing based on the weather information. 10. In the light source driving device according to any one of 4. to 7., An acquisition unit that acquires a detection result of a light receiving unit that receives at least a part of the light emitted from the light emitting element, The discharge control unit is a light source driving device that determines the fourth timing based on the detection result. 11. The light source driving device according to 10., The discharge control unit is a light-source driving device that sets the fourth timing when the intensity of the light received by the light receiving unit becomes lower than a predetermined reference. 12. A light source driving device according to any one of 1. to 11.; The light-emitting element; A processing unit that calculates a distance to a reflecting object that reflected the light in the emission direction of the light, using the time from when the light-emitting element emits light to when the reflected light of the light is received. [Explanation of symbols]

[0111] 1 Distance measuring device 10 Light emitting element 12 Monitor receiver 20 Light source driving device 21 Power supply 22 Capacitive element 23 Discharge control unit 24 Acquisition Department 30 Movable reflector 50 Light receiving part 70 Control section 80 Processing section 90 Mobile 92 Landmarks 100 Integrated Circuits 102 Bus 104 processors 106 Memory 108 Storage Devices 110 Input / Output Interface 112 Network Interface 201 Charging Route 202 Discharge Path

Claims

[Claim 1] A plurality of capacitance elements connected in parallel to each other and each supplying power to a light emitting element when discharging; a power source for charging the plurality of capacitance elements; a discharge control unit that individually controls the timing at which the plurality of capacitance elements discharge.

Images