Projector, measurement device, projector control method, computer program, and computer-readable recording medium with computer program recorded thereon

Abstract

The purpose of the present invention is to change an output voltage to be supplied to a capacitor. This projector is provided with: a light-emitting element; a switch element connected in series to the light-emitting element; a capacitor connected in parallel to the light-emitting element and the switch element; a voltage output circuit for outputting an output voltage to be supplied to the capacitor; and a voltage change unit for changing the output voltage of the voltage output circuit. For example, the output voltage to be supplied to the capacitor is changed according to a change in the light emission characteristics of the light-emitting element and a change in the ambient environment of the capacitor (for example, a temperature change or the like).

Description

Light projector, measuring device, light projector control method, computer program, and computer-readable recording medium having computer program recorded thereon

[0001] The technology disclosed in this specification relates to a projector, a measurement device, a method for controlling a projector, a computer program, and a computer-readable recording medium on which the computer program is recorded.

[0002] With the advancement of autonomous driving (AD) systems and advanced driver assistance systems (ADAS), research and development of light detection and ranging (LiDAR) is underway as one of the measurement devices used to grasp the surrounding environment and estimate the vehicle's position while driving. LiDAR includes a light projector that projects laser light onto a measurement target and a light receiver that receives the light reflected from the measurement target. LiDAR measures the distance to the measurement target based on the difference between the timing at which the light projector emits the laser light and the timing at which the light receiver receives the reflected light. The light projector includes a light-emitting element, a switch element connected in series to the light-emitting element, a capacitor connected in parallel to the light-emitting element and the switch element, and a voltage output circuit that outputs an output voltage to be supplied to the capacitor (see, for example, Patent Documents 1 and 2). The capacitor is charged by the output voltage output from the voltage output circuit, and when the switch element changes from an open state to a closed state, the charge stored in the capacitor is discharged to the light-emitting element, causing the light-emitting element to emit light.

[0003] JP 2021-19194 A JP 2022-109724 A

[0004] In conventional floodlights, the output voltage from the voltage output circuit is a fixed value, and therefore, in conventional floodlights, it may not be possible to make the light-emitting element emit light at a desired light intensity due to, for example, changes in the light-emitting characteristics of the light-emitting element or changes in the ambient environment of the light-emitting element (for example, temperature changes).

[0005] This specification discloses a technique that can solve the above-mentioned problems.

[0006] The technology disclosed in this specification can be realized, for example, in the following forms.

[0007] (1) A floodlight disclosed in this specification includes a light-emitting element, a switch element connected in series to the light-emitting element, a capacitor connected in parallel to the light-emitting element and the switch element, a voltage output circuit that outputs an output voltage to be supplied to the capacitor, and a voltage change unit that changes the output voltage of the voltage output circuit. With this configuration, the output voltage to be supplied to the capacitor can be changed in response to, for example, changes in the light-emitting characteristics of the light-emitting element or changes in the ambient environment of the capacitor (for example, temperature changes).

[0008] (2) In the above-described floodlight, the voltage output circuit may include a DC-DC converter that outputs a first output voltage obtained by stepping up or stepping down an externally supplied supply voltage, and a constant-voltage DC power supply circuit that outputs a second output voltage corresponding to the first output voltage from the DC-DC converter, and the voltage change unit may change at least one of the first output voltage output by the DC-DC converter and the second output voltage output by the constant-voltage DC power supply circuit. With this configuration, the output voltage supplied to the capacitor can be changed in response to, for example, changes in the light-emitting characteristics of a light-emitting element or changes in the ambient environment of the capacitor (for example, temperature changes).

[0009] (3) The above-described floodlight may further include a temperature sensor that outputs a temperature detection signal corresponding to the temperature of the capacitor, and the voltage change unit may change the output voltage based on the temperature detection signal from the temperature sensor so as to reduce variations in the amount of charge stored in the capacitor due to temperature changes of the capacitor. With this configuration, variations in the amount of charge stored in the capacitor due to temperature changes of the capacitor are reduced, thereby reducing fluctuations in the amount of light emitted by the light-emitting element.

[0010] (4) The above-described floodlight may further include a light quantity sensor that outputs a light quantity detection signal corresponding to the light quantity of the light-emitting element, and the voltage changer may change the output voltage based on the temperature detection signal from the temperature sensor and the light quantity detection signal from the light quantity sensor so as to reduce variations in the amount of charge stored in the capacitor due to temperature changes in the capacitor. With this configuration, variations in the amount of charge stored in the capacitor due to temperature changes in the capacitor are reduced, taking into account the light quantity of the light-emitting element, thereby more effectively reducing variations in the amount of light emitted by the light-emitting element.

[0011] (5) The above-described floodlight may further include a light quantity sensor that outputs a light quantity detection signal corresponding to the light quantity of the light-emitting element, and the voltage change unit may change the output voltage based on the light quantity detection signal from the light quantity sensor so as to reduce variations in the light quantity of the light-emitting element. With this configuration, for example, the output voltage supplied to the capacitor can be changed in accordance with changes in the light-emitting characteristics of the light-emitting element.

[0012] (6) The measuring device may be configured to include the light projector. With this configuration, the output voltage supplied to the capacitor can be changed in response to, for example, changes in the light-emitting characteristics of the light-emitting element or changes in the ambient environment of the capacitor (for example, temperature changes).

[0013] The technology disclosed in this specification can be realized in various forms, such as a floodlight, a measuring device, a power supply circuit, a light emission driving device, a method for controlling a floodlight, a computer program for controlling a floodlight, and a computer-readable recording medium on which the computer program is recorded.

[0014] A block diagram showing the configuration of a measurement device according to a first embodiment. An explanatory diagram showing the configuration of a projector according to a first embodiment. A flowchart showing the flow of an output voltage change process according to the first embodiment. A graph showing the relationship between the output voltage and the feedback voltage according to the first embodiment. An explanatory diagram showing the configuration of a projector according to a second embodiment.

[0015] A. First Embodiment: A-1. Configuration of Measuring Device 10: The first embodiment will be described with reference to FIGS. 1 to 4. The measuring device 10 of this embodiment is a LiDAR. The measuring device 10 is mounted, for example, on a vehicle equipped with an AD (automated driving system) or an ADAS (advanced driver assistance system). The measuring device 10 assists in detecting objects such as people and other vehicles while the vehicle is traveling, and provides various information to other devices and users that is useful for ensuring the safety of the vehicle driver and those around the vehicle and for reducing damage to surrounding objects while the vehicle is being driven.

[0016] As shown in FIG. 1, the measuring device 10 includes a light projector 100, a light receiver 400, an information processing device 500, and a communication interface 600.

[0017] A-1-1. Projector: The projector 100 includes a light source unit 110, a control circuit board 210, and a light projection optical system 180, as shown in FIGS.

[0018] (Light Source Unit): As shown in Fig. 2, the light source unit 110 includes a light emitting element 102. The light source unit 110 may include a light emitting source having one or more light emitting elements 102 (not shown), or one or more light emitting element arrays (for example, light emitting elements 102 arranged in a line (one-dimensional) or a plane (two-dimensional)).

[0019] The light-emitting element 102 is, for example, an infrared laser light-emitting element that emits infrared light. The laser light-emitting element is, for example, a laser diode, a light-emitting diode, or a surface-emitting element (such as a VCSEL (Vertical Cavity Surface Emitting Laser)). In FIG. 2, the projector 100 has only one light-emitting element 102, but it may also have a light-emitting element group in which a plurality of light-emitting elements 102 are connected in series or in parallel.

[0020] (Control Circuit Board): The control circuit board 210 is a circuit board on which electronic components and the like for controlling the light emission of the light source unit 110 are mounted, and as shown in Fig. 2, includes a switch element 104 and a power supply circuit 101. The switch element 104 and the power supply circuit 101 constitute a light source drive circuit.

[0021] The switch element 104 is connected in series to the switch element 104. The switch element 104 is, for example, a GaN FET (high electron mobility transistor). Note that the switch element 104 may be, for example, a field effect transistor other than a GaN FET, a bipolar transistor, or an insulated gate bipolar transistor. Furthermore, the switch element 104 is arranged on the low potential side (cathode of the light emitting element 102) with respect to the light emitting element 102, but may also be arranged on the high potential side (anode of the light emitting element 102) with respect to the light emitting element 102.

[0022] The power supply circuit 101 includes a capacitor 106 and a voltage output circuit 108 .

[0023] The capacitor 106 is connected in parallel to the light-emitting element 102 and the switch element 104. Specifically, the low-potential terminal of the capacitor 106 is electrically connected to ground, and the high-potential terminal of the capacitor 106 is electrically connected to the anode of the light-emitting element 102. The capacitor 106 is, for example, a ceramic capacitor. However, the capacitor 106 may be another type of capacitor, such as an electrolytic capacitor or a film capacitor.

[0024] The voltage output circuit 108 outputs an output voltage (second output voltage Vo2) to be supplied to the capacitor 106. The voltage output circuit 108 generates the output voltage Vo2 based on the supply voltage Vdc supplied from the outside and applies it to the capacitor 106.

[0025] In this embodiment, the voltage output circuit 108 has a DC-DC converter 115 ("DC-DC" in FIG. 2) and a constant-voltage DC power supply circuit 120 ("SRC" in FIG. 2). The DC-DC converter 115 generates a first output voltage Vo1 by boosting the supply voltage Vdc and outputs the first output voltage Vo1. The constant-voltage DC power supply circuit 120 is, for example, a linear regulator (series regulator), and generates a second output voltage Vo2 by stabilizing the first output voltage Vo1 output by the DC-DC converter 115 and outputs it to the capacitor 106.

[0026] The power supply circuit 101 further has a configuration for changing the output voltage (second output voltage Vo2) output by the voltage output circuit 108. Specifically, the power supply circuit 101 has a control circuit 130 ("CRC" in FIG. 2), a first DA converter 132 ("DAC" in FIG. 2), a second DA converter 134 ("DAC" in FIG. 2), and an AD converter 136 ("ADC" in FIG. 2). The control circuit 130, the first DA converter 132, and the second DA converter 134 are examples of a voltage changing unit.

[0027] The control circuit 130 is, for example, a microcomputer, including a processor such as a central processing unit (CPU) and a storage device such as a read-only memory (ROM) and a random access memory (RAM). The storage device stores various programs and data, and is used as a work area and data storage area when executing various processes. For example, the storage device stores a computer program for changing the output voltage (second output voltage Vo2) output by the voltage output circuit 108. This computer program is provided in a state stored on a computer-readable recording medium (not shown), such as a CD-ROM, DVD-ROM, or USB memory, or is provided in a state where it can be retrieved from an external device (e.g., a cloud server) via the communication interface 600 and stored in the storage device.

[0028] The control circuit 130 is electrically connected to the output terminal of the DC-DC converter 115 via an AD converter 136, and is able to acquire the voltage value (feedback value) of the first output voltage Vo1 from the DC-DC converter 115. The control circuit 130 is electrically connected to a first feedback terminal 112 of the DC-DC converter 115 via a first DA converter 132. The first control voltage Vc1 output from the control circuit 130 is AD converted by the first DA converter 132 and input to the first feedback terminal 112.

[0029] The DC-DC converter 115 generates a first output voltage Vo1 by boosting the supply voltage Vdc by a voltage amount or a multiplication factor corresponding to the difference between the first control voltage Vc1 and the first reference voltage input to the first feedback terminal 112. Specifically, the DC-DC converter 115 performs voltage mode control (PWM) and controls the first output voltage Vo1 by determining the pulse width of the PWM signal by comparing the voltage difference with a triangular wave.

[0030] The control circuit 130 can change the voltage value of the first output voltage Vo1 of the DC-DC converter 115 by changing the voltage value of the first control voltage Vc1 that is supplied to the first feedback terminal 112. For example, the control circuit 130 supplies the first control voltage Vc1 to the first feedback terminal 112, the voltage value of which is increased or decreased relative to the voltage value of the first output voltage Vo1 that is fed back from the AD converter 136. This increases or decreases the difference between the first control voltage Vc1 and the first reference voltage in the DC-DC converter 115. Therefore, the DC-DC converter 115 generates the first output voltage Vo1 by boosting the supply voltage Vdc by a voltage amount or a multiplying factor that corresponds to the difference after the increase or decrease.

[0031] The control circuit 130 is electrically connected to the output terminal of the constant-voltage DC power supply circuit 120 via an AD converter 136, and is able to acquire the voltage value (feedback value) of the second output voltage Vo2 from the constant-voltage DC power supply circuit 120. The control circuit 130 is electrically connected to a second feedback terminal 122 of the constant-voltage DC power supply circuit 120 via a second DA converter 134. The second control voltage Vc2 output from the control circuit 130 is AD converted by the second DA converter 134 and input to the second feedback terminal 122.

[0032] The constant-voltage DC power supply circuit 120 generates a second output voltage Vo2 by stabilizing the first output voltage Vo1 so as to cancel out the difference between the second reference voltage and the second control voltage Vc2 input to the second feedback terminal 122. Specifically, the constant-voltage DC power supply circuit 120 performs voltage-mode control (PWM) and controls the second output voltage Vo2 by determining the pulse width of the PWM signal by comparing the voltage difference with a triangular wave.

[0033] The control circuit 130 can change the voltage value of the second output voltage Vo2 of the constant-voltage DC power supply circuit 120 by changing the voltage value of the second control voltage Vc2 provided to the second feedback terminal 122. For example, the control circuit 130 provides the second feedback terminal 122 with the second control voltage Vc2, which has a voltage value that is increased or decreased relative to the voltage value of the second output voltage Vo2 fed back from the AD converter 136. As a result, in the constant-voltage DC power supply circuit 120, the difference between the second control voltage Vc2 and the second reference voltage increases or decreases. Therefore, the constant-voltage DC power supply circuit 120 generates the second output voltage Vo2, which is a constant version of the first output voltage Vo1, to cancel out the difference after the increase or decrease.

[0034] The power supply circuit 101 further has a configuration for detecting changes in the light-emitting characteristics of the light-emitting element 102 and changes in the ambient environment of the capacitor 106. Specifically, the power supply circuit 101 has a temperature sensor 140 ("TS" in FIG. 2), a light-receiving sensor 150 ("PD" in FIG. 2), and an amplifier circuit 138 ("AP" in FIG. 2). The light-receiving sensor 150 is an example of a light amount sensor.

[0035] The temperature sensor 140 is disposed near the capacitor 106 and outputs a temperature detection signal St corresponding to the temperature of the temperature sensor 140. The temperature detection signal St from the temperature sensor 140 is input to the control circuit 130 via the AD converter 136. The light receiving sensor 150 is disposed in a position where it can receive light (output laser light Lout) from the light emitting element 102 and outputs a light intensity detection signal Sp corresponding to the light emission amount of the light emitting element 102. The light intensity detection signal Sp from the light receiving sensor 150 is input to the control circuit 130 via the amplifier circuit 138 and the AD converter 136. This allows the control circuit 130 to detect the temperature of the capacitor 106 and the light emission amount (light emission amount per unit time, light emission intensity) of the light emitting element 102. By amplifying the signal level of the light intensity detection signal Sp from the light receiving sensor 150 and inputting it to the control circuit 130, the control circuit 130 can accurately detect fluctuations in the light emission amount of the light emitting element 102. The light receiving sensor 150 is, for example, a photodetector or a photodiode.

[0036] (Light Projection Optical System): The light projection optical system 180 is disposed on the optical path of the output laser light Lout output from the light source unit 110. The light projection optical system 180 adjusts the light distribution of the output laser light Lout. The light projection optical system 180 may be, for example, a lens such as a collimator lens.

[0037] A-1-2. Photoreceiver, etc.: As shown in FIG.

[0038] The light receiving optical system 410 is an optical system for causing the light receiving unit 420 to receive reflected laser light Lre, which is light that is output laser light Lout reflected by the measurement target W and returned. The light receiving optical system 410 may be, for example, any of various lenses such as a condenser lens, any of various filters such as a wavelength filter, or a reflective mirror.

[0039] The light receiving unit 420 includes a light receiving element, such as a photodiode, that receives the reflected laser light Lre incident from the light receiving optical system 410, converts the reflected laser light Lre into a light receiving signal corresponding to the intensity and timing of receiving the reflected laser light Lre, and outputs the signal.

[0040] The TOF measurement device 430 includes, for example, a time measurement integrated circuit (IC) equipped with a time-to-digital converter (TDC) circuit. The TOF measurement device 430 is communicatively connected to the light-projection control device 211 and the light-receiving unit 420. The TOF measurement device 430 receives a timing signal indicating the emission timing output from the light-projection control device 211 and a light-receiving signal output from the light-receiving unit 420, and, based on these, calculates the difference between the timing at which the output laser light Lout is emitted and the timing at which the reflected laser light Lre is received, i.e., the time of flight (TOF) of the laser light. The TOF measurement device 430 outputs a signal corresponding to the calculated TOF and the light-receiving signal received from the light-receiving unit 420.

[0041] The information processing device 500 has a processor. The processor may be, for example, a central processing unit (CPU), a micro processing unit (MPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), or the like. The information processing device 500 is communicably connected to the TOF measurement device 430. The information processing device 500 receives a signal corresponding to the TOF output by the TOF measurement device 430 and a light receiving signal, and generates various information such as the distance to the measurement target W based on these signals. The information includes, for example, a histogram used in time-correlated single photon counting, the distance to each point on the measurement target W, point cloud information, and the like. The information generated by the information processing device 500 is transmitted via a communication interface 600 to an external device 700 that uses the information.

[0042] The external device 700 may be, for example, a device that creates an environmental map using a point cloud, or may be a device that performs self-location estimation (SLAM: Simultaneous Localization and Mapping) using a scan matching algorithm such as NDT (Normal Distributions Transform) or ICP (Iterative Closest Point).

[0043] A-2. Output Voltage Change Processing Next, the output voltage change processing executed by the control circuit 130 in the above-described floodlight 100 will be described with reference to Figures 3 and 4. In order to improve the measurement accuracy of the measuring device 10, it is preferable to suppress variations in the amount of light emitted by the light-emitting element 102. Therefore, the output voltage change processing in this embodiment is processing for controlling the output voltage from the voltage output circuit 108 so as to suppress variations in the amount of light emitted by the light-emitting element 102 caused by changes in the light-emitting characteristics of the light-emitting element 102 and changes in the ambient environment of the capacitor 106 (for example, temperature changes, etc.).

[0044] When the measuring device 10 receives an instruction to start measurement, the control circuit 130 detects the temperature of the capacitor 106 based on the temperature detection signal St from the temperature sensor 140 (S110).

[0045] The control circuit 130 detects the light emission amount of the light-emitting element 102 based on the light amount detection signal Sp from the light-receiving sensor 150 (S120). The control circuit 130 calculates the error between the detected light emission amount and the target light emission amount (hereinafter referred to as the "light emission amount error") (S130). The target light emission amount is a target value for the light emission amount of the light-emitting element 102 corresponding to the predetermined measurement accuracy of the measurement device 10. Note that the execution timing of the temperature detection in S110 and the light emission amount detection in S120 may be simultaneous or different. Furthermore, the execution frequencies of the temperature detection in S110 and the light emission amount detection in S120 may be the same or different. For example, if the temperature change of the capacitor 106 is relatively gradual, the execution frequency of the temperature detection in S110 may be lower than the execution frequency of the light emission amount detection in S120.

[0046] The control circuit 130 determines a set value for the first output voltage Vo1 of the DC-DC converter 115 and a set value for the second output voltage Vo2 of the constant-voltage DC power supply circuit 120, taking into account the temperature detection result of the capacitor 106 and the error in the amount of light emitted (S140). Next, the control circuit 130 inputs a first control voltage Vc1 corresponding to the determined set value of the first output voltage Vo1 to the first feedback terminal 112 of the DC-DC converter 115, and inputs a second control voltage Vc2 corresponding to the determined set value of the second output voltage Vo2 to the second feedback terminal 122 of the constant-voltage DC power supply circuit 120 (S150). Thereafter, the control circuit 130 repeatedly executes the processes from S110 to S150 at predetermined intervals until the measuring device 10 receives an instruction to end measurement.

[0047] FIG. 4 is a graph showing the correspondence relationship between the second output voltage Vo2 and the second control voltage Vc2 for the constant-voltage DC power supply circuit 120. The amount of charge stored in the capacitor 106 varies depending on the temperature characteristics of the capacitor 106. For example, when the temperature of the capacitor 106 is a first temperature, and the second output voltage Vo2 applied to the capacitor 106 from the voltage output circuit 108 is a first voltage value V1 (e.g., 40 V), the amount of charge stored in the capacitor 106 matches the target charge amount. The target charge amount is the amount of charge stored in the capacitor 106 required to cause the light-emitting element 102 to emit light at the target light emission amount. The control circuit 130 outputs the second control voltage Vc2 having a first control value V3 (e.g., 0.6 V) corresponding to the first voltage value V1 to the constant-voltage DC power supply circuit 120 (see FIG. 4).

[0048] When the temperature of capacitor 106 changes from the first temperature to the second temperature, if second output voltage Vo2 from voltage output circuit 108 remains at the first voltage value V1, the amount of charge stored in capacitor 106 deviates from the target charge amount, causing fluctuations in the amount of light emitted by light-emitting element 102. For this reason, it is preferable to suppress variations in the amount of charge stored in capacitor 106 by changing the charging voltage (second output voltage Vo2) applied to capacitor 106 to second output voltage V2 (e.g., 45 V) corresponding to the second temperature in accordance with the change in temperature of capacitor 106.

[0049] The storage device of the control circuit 130 stores correspondence data between temperatures and charging voltages. The correspondence data indicates correspondences between a plurality of temperatures and charging voltages at which the amount of charge stored in the capacitor 106 reaches a target amount of charge at each temperature. The correspondence data can be obtained, for example, through experiments or simulations using the power supply circuit 101. When the control circuit 130 detects that the temperature of the capacitor 106 is a first temperature (S110), the control circuit 130 references the correspondence data to obtain a first charging voltage corresponding to the first temperature. Next, the control circuit 130 outputs a first control voltage Vc1 to the DC-DC converter 115, which sets the first output voltage Vo1 of the DC-DC converter 115 to the first charging voltage, and outputs a second control voltage Vc2 (the second control value V4 in FIG. 4 , e.g., 0.52 V) to the constant-voltage DC power supply circuit 120, which sets the second output voltage Vo2 of the constant-voltage DC power supply circuit 120 to the first charging voltage (S140, S150). This makes it possible to suppress variations in the amount of light emitted by the light emitting element 102 due to variations in the amount of charge stored in the capacitor 106 .

[0050] If the capacitor 106 is a ceramic capacitor (especially a high dielectric constant type), the capacitance of the capacitor changes depending on the voltage due to the voltage bias effect. In this case, it is preferable that the correspondence data is set to a charging voltage that allows the amount of charge of the capacitor 106 to reach the target amount of charge at each temperature, taking into account the change in capacitance of the ceramic capacitor.

[0051] Even if variations in the amount of charge stored in capacitor 106 can be suppressed, variations in the amount of light emitted by light-emitting element 102 may occur due to changes (deterioration, etc.) in the light-emitting characteristics of light-emitting element 102. As described above, control circuit 130 detects the amount of light emitted by light-emitting element 102 (S120), calculates the error in the amount of light emitted by light-emitting element 102 (S130), and then slightly corrects and outputs first control voltage Vc1 and second control voltage Vc2 so as to offset the error in the amount of light emitted (S140, S150). This makes it possible to suppress variations in the amount of light emitted by light-emitting element 102 due to changes in the light-emitting characteristics of light-emitting element 102.

[0052] A-3. Advantages of this embodiment: As described above, the measuring device 10 of this embodiment includes a projector 100. The projector 100 includes a light-emitting element 102, a switch element 104 connected in series to the light-emitting element 102, a capacitor 106 connected in parallel to the light-emitting element 102 and the switch element 104, a voltage output circuit 108 that outputs an output voltage to be supplied to the capacitor 106, and a voltage change unit (such as a control circuit 130) that changes the output voltage of the voltage output circuit 108.

[0053] According to this embodiment, the output voltage supplied to the capacitor 106 can be changed in response to, for example, changes in the light-emitting characteristics of the light-emitting element 102 or changes in the ambient environment of the capacitor 106 (for example, temperature changes).

[0054] In this embodiment, the control circuit 130 changes both the first output voltage Vo1 output by the DC-DC converter 115 and the second output voltage Vo2 output by the constant voltage DC power supply circuit 120. This makes it possible to change the output voltage supplied to the capacitor 106 with greater precision than, for example, a configuration in which only one of the first output voltage Vo1 and the second output voltage Vo2 is changed.

[0055] In this embodiment, the control circuit 130 changes the output voltage based on the temperature detection signal St from the temperature sensor 140 so as to reduce variations in the amount of charge stored in the capacitor 106 caused by temperature changes in the capacitor 106 (see S110, S140, and S150 in FIG. 3 ). This reduces variations in the amount of charge stored in the capacitor 106 caused by temperature changes in the capacitor 106, thereby reducing fluctuations in the amount of light emitted by the light-emitting element 102.

[0056] Furthermore, in this embodiment, the control circuit 130 changes the output voltage so as to reduce variations in the amount of light emitted by the light-emitting element 102, based on the light amount detection signal Sp from the light-receiving sensor 150. This allows the output voltage to be changed in response to temperature changes to suppress variations in the amount of charge stored in the capacitor 106, while finely correcting the output voltage based on the detection result of the actual amount of light emitted by the light-emitting element 102, thereby more effectively suppressing variations in the amount of light emitted by the light-emitting element 102.

[0057] B. Second Embodiment: A second embodiment will be described with reference to Fig. 5. A floodlight 100A of this embodiment differs from the first embodiment in the configuration of the output voltage change unit. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0058] The floodlight 100A of this embodiment includes a resistance changing circuit 131. The resistance changing circuit 131 has a plurality of resistors (R1, R2, ... Rk), and is configured to change the voltage value of the control voltage Vc applied to the feedback terminal 112A of the voltage output circuit 108 by changing the electrical connection pattern of the plurality of resistors.

[0059] Specifically, the resistance change circuit 131 has a plurality of resistors and a plurality of switch elements (SW1, SW2, ... SWk). The plurality of resistors are connected in parallel with one another between the feedback terminal 112A and the ground line. A voltage dividing resistor R is electrically connected between the feedback terminal 112A and the output terminal of the voltage output circuit 108. Each of the plurality of switch elements is connected in series with a corresponding resistor.

[0060] For example, when the first switch element SW1 changes from an open state to a closed state, a current flows through the first resistor R1. As a result, the control voltage Vc applied to the feedback terminal 112A has a voltage value that corresponds to the voltage-dividing resistance value between the voltage-dividing resistor R and the first resistor R1. The resistance values ​​of the multiple resistors may be the same, or at least some of them may be different from each other.

[0061] The control circuit 130 can change the voltage value of the control voltage Vc by changing the opening and closing patterns of the multiple switch elements. According to this embodiment, the output voltage Vo supplied to the capacitor 106 can be changed in response to, for example, changes in the light-emitting characteristics of the light-emitting element 102 or changes in the ambient environment of the capacitor 106 (for example, temperature changes).

[0062] C. Modifications: The technology disclosed in this specification is not limited to the above-described embodiment, and can be modified in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0063] In each of the above embodiments, the light emitting element 102 is an infrared laser light emitting element that emits infrared light, but is not limited to this and may be a light emitting element that emits visible light, ultraviolet light, or the like.

[0064] In the first embodiment, the voltage output circuit 108 may include either the DC-DC converter 115 or the constant voltage DC power supply circuit 120. The DC-DC converter 115 may generate the first output voltage Vo1 by stepping down the supply voltage Vdc.

[0065] In the first embodiment, the control circuit 130 may change the voltage value of the first reference voltage of the DC-DC converter 115 to change the voltage value of the first output voltage Vo1 of the DC-DC converter 115. In the first embodiment, the control circuit 130 may change the voltage value of the second reference voltage of the constant-voltage DC power supply circuit 120 to change the voltage value of the second output voltage Vo2 of the constant-voltage DC power supply circuit 120.

[0066] In the first embodiment, the control circuit 130 may change either the first output voltage Vo1 output by the DC-DC converter 115 or the second output voltage Vo2 output by the constant-voltage DC power supply circuit 120. In the first embodiment, the control circuit 130 may change the output voltage of the voltage output circuit 108 based on either the detection result of the temperature of the capacitor 106 or the detection result of the light emission amount of the light-emitting element 102. Furthermore, the control circuit 130 may change the output voltage of the voltage output circuit 108 based on, for example, an external operation by a user, regardless of the measurement result of the temperature or the like.

[0067] In the first embodiment, the light receiving sensor 150 is given as an example of a light amount sensor, but the light amount sensor is not limited to this, and may be a current sensor that detects the amount of current flowing through the light emitting element 102. The amount of light emitted by the light emitting element 102 can be detected based on the detection result of the current sensor.

[0068] This international application claims priority based on Japanese Patent Application No. 2024-106515, filed on July 2, 2024, the entire contents of which are incorporated herein by reference.

[0069] The above descriptions of specific embodiments of the present invention have been presented for purposes of illustration. They are not intended to be exhaustive or to limit the invention to the precise forms described. Numerous modifications and variations will be apparent to those skilled in the art in light of the above description.

[0070] 10: Measuring device 100, 100A: Light emitter 101: Power supply circuit 102: Light emitting element 104: Switch element 106: Capacitor 108: Voltage output circuit 110: Light source unit 112: First feedback terminal 112A: Feedback terminal 115: DC-DC converter 120: Constant voltage DC power supply circuit 122: Second feedback terminal 130: Control circuit 131: Resistance changing circuit 132: First DA converter 134: Second DA converter 136: AD converter 138: Amplification circuit 140: Temperature sensor 150: Light receiving sensor 180: Light projecting optical system 210: Control circuit board 211: Light projecting control device 400: Light receiver 410: Light receiving optical system 420: Light receiving unit 430: TOF measuring device 500: Information processing device 600: Communication interface 700: External device

Claims

1. A floodlight comprising: a light-emitting element; a switch element connected in series to the light-emitting element; a capacitor connected in parallel to the light-emitting element and the switch element; a voltage output circuit that outputs an output voltage to be supplied to the capacitor; and a voltage change unit that changes the output voltage of the voltage output circuit.

2. A floodlight as claimed in claim 1, wherein the voltage output circuit comprises: a DC-DC converter that outputs a first output voltage obtained by stepping up or stepping down an externally supplied supply voltage; and a constant voltage DC power supply circuit that outputs a second output voltage corresponding to the first output voltage from the DC-DC converter, and the voltage change unit changes at least one of the first output voltage output by the DC-DC converter and the second output voltage output by the constant voltage DC power supply circuit.

3. A floodlight as claimed in claim 1 or claim 2, further comprising a temperature sensor that outputs a temperature detection signal according to the temperature of the capacitor, and the voltage change unit changes the output voltage based on the temperature detection signal from the temperature sensor so as to reduce variations in the amount of charge of the capacitor caused by temperature changes in the capacitor.

4. A light-projecting device according to claim 3, further comprising a light intensity sensor that outputs a light intensity detection signal according to the light intensity of the light-emitting element, and wherein the voltage change unit changes the output voltage based on the temperature detection signal from the temperature sensor and the light intensity detection signal from the light intensity sensor so as to reduce variations in the amount of charge in the capacitor caused by temperature changes in the capacitor.

5. A light-projecting device as claimed in claim 1 or claim 2, further comprising a light intensity sensor that outputs a light intensity detection signal according to the light intensity of the light-emitting element, and wherein the voltage change unit changes the output voltage based on the light intensity detection signal from the light intensity sensor so as to reduce variations in the light intensity of the light-emitting element.

6. A measuring device comprising the light projector according to claim 1 or 2.

7. A light emission control method for a floodlight comprising a light-emitting element, a switch element connected in series to the light-emitting element, a capacitor connected in parallel to the light-emitting element and the switch element, and a voltage output circuit that outputs an output voltage to be supplied to the capacitor, the method comprising: detecting the temperature of the capacitor; detecting the amount of light emitted by the light-emitting element; and changing the output voltage based on the detection result of the temperature of the capacitor and the detection result of the amount of light emitted by the light-emitting element so as to reduce variations in the amount of charge charged in the capacitor due to temperature changes of the capacitor.

8. A computer program for causing a computer included in a floodlight comprising a light-emitting element, a switch element connected in series to the light-emitting element, a capacitor connected in parallel to the light-emitting element and the switch element, and a voltage output circuit that outputs an output voltage to be supplied to the capacitor, to acquire the temperature of the capacitor, acquire the amount of light emitted by the light-emitting element, and change the output voltage based on the acquired results of the temperature of the capacitor and the acquired results of the amount of light emitted by the light-emitting element so as to reduce variations in the amount of charge charged in the capacitor due to changes in the temperature of the capacitor.

9. A computer-readable recording medium having recorded thereon a computer program for controlling a floodlight comprising a light-emitting element, a switch element connected in series to the light-emitting element, a capacitor connected in parallel to the light-emitting element and the switch element, and a voltage output circuit that outputs an output voltage to be supplied to the capacitor, the computer-readable recording medium having recorded thereon a computer program that causes the floodlight to acquire the temperature of the capacitor, acquire the amount of light emitted by the light-emitting element, and, based on the acquired results of the temperature of the capacitor and the acquired results of the amount of light emitted by the light-emitting element, change the output voltage so as to reduce variations in the amount of charge charged in the capacitor due to changes in the temperature of the capacitor.

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