Light emitting device and measuring device

Abstract

To prevent a noise caused by a switching operation of a switch element from adversely affecting a light receiving signal output from a light receiving element.SOLUTION: The light emitting device includes a circuit board, a light emitting element disposed on the circuit board, a switch element disposed on the circuit board and configured to supply electric charges to the light emitting element to cause the light emitting element to emit light by switching from an open state to a closed state, a light receiving element configured to output a light reception signal corresponding to a light emission amount of the light emitting element, and a support member configured to support the light receiving element at a position away from the circuit board.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a light emitting device and a measuring device. [Background technology]

[0002] With the advancement of autonomous driving (AD) systems and advanced driver assistance systems (ADAS), research and development of LiDAR (light detection and ranging) is underway as one of the measurement devices used to grasp the surrounding environment and estimate the vehicle's own position while driving. LiDAR includes a projector that projects laser light onto a measurement target, and a photoreceiver that receives the light reflected from the measurement target. LiDAR measures the distance to the measurement target based on the difference between the timing when the projector emits the laser light and the timing when the photoreceiver receives the reflected light. The projector has multiple light-emitting devices (see, for example, Patent Documents 1 and 2).

[0003] The light-emitting device has a circuit board, a light-emitting element arranged on the circuit board, and a switch element arranged on the circuit board. The switch element supplies an electric charge to the light-emitting element by switching from an open state to a closed state, causing the light-emitting element to emit light. The light-emitting device also has a light-receiving element. The light-receiving element outputs a light-receiving signal corresponding to the amount of light emitted by the light-emitting element. Based on the light-receiving signal from the light-receiving element, it is possible to check whether the light-emitting element is emitting light, the light-emission level, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-19194 [Patent Document 2] Japanese Patent Publication No. 2022-109724 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional light-emitting devices, the light-receiving element and the light-emitting element are arranged on a common circuit board, which means that noise generated by the switching operation of the switch element may adversely affect the light-receiving signal output from the light-receiving element.

[0006] This specification discloses a technique that can solve the above-mentioned problems. [Means for solving the problem]

[0007] The technology disclosed in this specification can be realized, for example, in the following forms.

[0008] (1) A light-emitting device disclosed in this specification includes a circuit board, a light-emitting element disposed on the circuit board, a switch element disposed on the circuit board that supplies an electric charge to the light-emitting element to emit light by switching from an open state to a closed state, a light-receiving element that outputs a light-receiving signal corresponding to the amount of light emitted by the light-emitting element, and a support member that supports the light-receiving element at a position separate from the circuit board. According to this configuration, the light-receiving element is disposed at a position separate from the circuit board via the support member, thereby preventing noise generated by the switching operation of the switch element from adversely affecting the light-receiving signal output from the light-receiving element.

[0009] (2) In the light-emitting device, the support member may have an inner wall surface that forms a storage space for storing the light-emitting element between the support member and the circuit board, and the light-receiving element may be sheet-shaped and arranged along the inner wall surface of the support member. With this configuration, the sheet-shaped light-receiving element is arranged along the inner wall surface of the support member, which can prevent the storage space from becoming narrower due to the presence of the light-receiving element.

[0010] (3) In the light-emitting device, the support member may be made of a non-conductive material, which more effectively prevents noise caused by the switching operation of the switch element from adversely affecting the light-receiving signal output from the light-receiving element.

[0011] (4) In the light-emitting device, the support member may be made of a light-transmitting material. With this configuration, it is possible to prevent the light-emitting range of the light-emitting element from being restricted by the support member.

[0012] (5) The measuring device may be configured to include a light projector having the light emitting device. With this configuration, it is possible to prevent noise caused by the switching operation of the switch element from adversely affecting the light receiving signal output from the light receiving element.

[0013] The technology disclosed in this specification can be realized in various forms, for example, a light-emitting device, a light-emitting array having a plurality of light-emitting devices, a floodlight having a plurality of light-emitting devices, a measuring device, etc. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a measurement device according to an embodiment. [Figure 2] FIG. 1 is an explanatory diagram showing the internal configuration of a light-emitting device according to an embodiment. [Figure 3] FIG. 10 is an explanatory diagram showing the internal configuration of a light emitting device according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0015] A. Implementation: A-1. Configuration of the measuring device 10: This embodiment will be described with reference to Fig. 1 to Fig. 3. The measuring device 10 of this embodiment is a LiDAR. The measuring device 10 is mounted on a vehicle equipped with, for example, an AD (automated drive) or an ADAS (advanced driver assistance system). For example, the measuring device 10 assists in detecting objects such as people and other vehicles while the vehicle is traveling, and provides various types of information to other devices and users that are useful for ensuring the safety of the driver of the vehicle 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 measurement 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. Floodlight: The floodlight 100 includes a light source unit 110 and a control circuit board 210.

[0018] (Light source part): The light source unit 110 has a plurality of light emitting devices 101 (see FIG. 2 described later). The measuring device 10 of this embodiment is a flash type LiDAR, and the light source unit 110 has a configuration in which, for example, a plurality of light emitting devices 101 are arranged linearly (one-dimensionally) or planarly (two-dimensionally). The configuration of the light emitting devices 101 will be described later.

[0019] (Control circuit board): The control circuit board 210 is a circuit board on which electronic components and the like are mounted for controlling the light emission of the light source unit 110. The control circuit board 210 controls a power supply circuit (not shown) included in the light source unit 110, and also controls the switching of the switch elements 104 (described below) included in each light-emitting device 101. In other words, the control circuit board 210 switches each switch element 104 between an open state and a closed state.

[0020] A-1-2.Receiver, etc.: As shown in FIG. 1, the light receiver 400 includes a light receiving optical system 410, a light receiving unit 420, and a TOF measurement device 430.

[0021] 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 reflecting mirror.

[0022] The light receiving unit 420 includes a light receiving element, such as a photodiode. The light receiving element 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.

[0023] The TOF measurement device 430 has, for example, a time measurement integrated circuit (IC) equipped with a TDC (time-to-digital converter) circuit. The TOF measurement device 430 is communicably 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 light 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.

[0024] 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), or a digital signal processor (DSP). The information processing device 500 is communicatively 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, etc. 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.

[0025] 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).

[0026] A-2. Light-emitting device configuration: Next, the configuration of light emitting device 101 will be described. The upper part of Fig. 2 shows the external configuration of light emitting device 101 as seen from the optical axis direction of light emitting element 102 (the front side of the paper in the upper part of Fig. 2). The lower part of Fig. 2 shows the cross-sectional configuration of light emitting device 101 along the optical axis direction (the up-down direction of the paper in the lower part of Fig. 2).

[0027] The light emitting device 101 includes a circuit board 115, a light emitting element 102, a switch element 104, a light sensor 106, and a lens assembly 120. The light sensor 106 is an example of a light receiving element, and the lens assembly 120 is an example of a support member.

[0028] In this embodiment, the circuit board 115 has a rectangular shape, but may have a shape other than a rectangle (for example, a circle).

[0029] The light emitting element 102 is mounted on a circuit board 115. 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 light emitting element (for example, a VCSEL (Vertical Cavity Surface Emitting Laser)).

[0030] The switch element 104 is mounted on the circuit board 115. The switch element 104 is connected in series to the light-emitting element 102. 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. The switch element 104 may be disposed on the low-potential side (cathode of the light-emitting element 102) with respect to the light-emitting element 102, or on the high-potential side (anode of the light-emitting element 102) with respect to the light-emitting element 102. When the switch element 104 is turned on from an open state to a closed state by switching control by the control circuit board 210, an output voltage from a power supply circuit (not shown) is applied to the light-emitting element 102, causing the light-emitting element 102 to emit light.

[0031] The lens assembly 120 is disposed on the circuit board 115 so as to cover at least the area where the light emitting element 102 is disposed. The lens assembly 120 is formed from a material that is non-conductive and optically transparent. The lens assembly 120 is formed from, for example, glass, acrylic resin, or the like. The lens assembly 120 has a lens portion 124 and a fixed portion 126.

[0032] The lens portion 124 is disposed on the optical path of the output laser light Lout (see FIG. 1) output from the light-emitting element 102. In other words, the lens portion 124 is disposed so as to face the light-emitting element 102 in the optical axis direction of the light-emitting element 102. The lens portion 124 is disposed at a position away from the light-emitting element 102 (switch element 104) in the optical axis direction. The lens portion 124 has a light-projecting optical system (lens function) and adjusts the light distribution of the output laser light Lout. The lens portion 124 (light-projecting optical system) may be, for example, a lens such as a collimator lens. Note that the shape of the lens portion 124 when viewed in the optical axis direction is circular, but it may be a shape other than circular (for example, rectangular, etc.).

[0033] The fixed portion 126 is a frame-shaped portion of the circuit board 115 that surrounds the periphery of an area in which the light-emitting element 102, the switch element 104, and the optical sensor 106 are arranged. The shape of the fixed portion 126 when viewed in the optical axis direction is a rectangular frame, but it may be a shape other than a rectangular frame (for example, a circular frame). The fixed portion 126 is arranged between the lens portion 124 and the circuit board 115 and fixes the lens portion 124 at a position separated from the circuit board 115. The upper end of the fixed portion 126 is joined to the periphery of the lower surface of the lens portion 124 around its entire periphery. With this configuration, the lens assembly 120 forms an accommodation space 122 between itself and the circuit board 115. The accommodation space 122 accommodates the light-emitting element 102, the switch element 104, and the optical sensor 106.

[0034] The optical sensor 106 is disposed near the light-emitting element 102 and outputs a light-receiving signal via a signal line L1 according to the amount of light emitted by the light-emitting element 102. The optical sensor 106 is a sheet-type optical sensor. A sheet-type optical sensor has a configuration in which, for example, a carbon nanotube photodetector and an organic transistor are mounted on an ultra-thin film substrate (for example, 5 μm or less) (see, for example, the German scientific journal "Advanced Materials" (online, Early View), titled "Ultraflexible Wireless Imager Integrated with Organic Circuits for Broadband Infrared Thermal Analysis").

[0035] The optical sensor 106 is disposed along an inner wall surface that forms the accommodation space 122 of the lens assembly 120. Specifically, the optical sensor 106 is disposed on an opposing inner wall surface 123 of the inner wall surface of the lens assembly 120 that faces the circuit board 115. When viewed in the optical axis direction, the optical sensor 106 is disposed at a position that is shifted from the irradiation range of the light-emitting element 102. A signal line L1 connected to the optical sensor 106 passes through the inside of the lens assembly 120 and is led out of the lens assembly 120, and is electrically connected to, for example, the control circuit board 210. Therefore, the optical sensor 106 and the signal line L1 do not contact the circuit board 115.

[0036] A-3. Advantages of this embodiment: According to this embodiment, the optical sensor 106 is disposed at a position separated from the circuit board 115 via the lens assembly 120 (see FIG. 2). This makes it possible to prevent noise caused by the switching operation of the switch element 104 from adversely affecting the light reception signal output from the optical sensor 106.

[0037] The upper part of Fig. 3 shows the external configuration of the light emitting device 101a of the comparative example as viewed from the optical axis direction of the light emitting element 102 (the front side of the paper in the upper part of Fig. 3). The lower part of Fig. 3 shows the cross-sectional configuration of the light emitting device 101a of the comparative example along the optical axis direction (the up-down direction of the paper in the lower part of Fig. 3). The light emitting device 101a of the comparative example is different from the light emitting device 101 of the present embodiment in the position of the light receiving element, but is otherwise the same.

[0038] Here, control circuit board 210 repeatedly executes switching control of switch element 104 at high speed based on a pulse signal with an extremely short period (e.g., a pulse width on the order of nanoseconds and a pulse period on the order of microseconds), causing light emitting element 102 to emit pulsed light at high speed. As shown in FIG. 3, in light emitting device 101a of the comparative example, optical sensor 106a is mounted on circuit board 115, just like light emitting element 102. For this reason, noise caused by the switching operation of switch element 104 is carried over to the light reception signal from optical sensor 106a, significantly disturbing the level of the light reception signal. As a result, it may become impossible to accurately determine whether light emitting element 102 is emitting light or not, based on the light reception signal from optical sensor 106a.

[0039] In contrast, in this embodiment, the optical sensor 106 is disposed at a position separated from the circuit board 115 via the lens assembly 120 (see FIG. 2). Therefore, even if the control circuit board 210 repeatedly executes switching control of the switch element 104 at high speed, noise caused by the switching operation is unlikely to be carried over to the light reception signal from the optical sensor 106a. As a result, it is possible to accurately determine whether or not the light emitting element 102 is emitting light based on the light reception signal from the optical sensor 106a.

[0040] In this embodiment, the sheet-like optical sensor 106 is arranged along the inner wall surface of the lens assembly 120 (see FIG. 2). Therefore, according to this embodiment, it is possible to prevent the accommodation space 122 from becoming narrower due to the presence of the light-receiving element. Moreover, the optical sensor 106 is arranged along the opposing inner wall surface 123. In this embodiment, the distance between the optical sensor 106 and the circuit board 115 is longer than in a configuration in which the optical sensor 106 is arranged on a side inner wall surface that forms the accommodation space 122. Therefore, according to this embodiment, it is possible to more effectively prevent noise caused by the switching operation of the switch element 104 from adversely affecting the light-receiving signal output from the optical sensor 106.

[0041] In this embodiment, the lens assembly 120 is made of a non-conductive material, which makes it possible to more effectively prevent noise caused by the switching operation of the switch element 104 from adversely affecting the light receiving signal output from the light receiving element.

[0042] In this embodiment, the lens assembly 120 is formed from an optically transparent material. Therefore, according to this embodiment, the light emitting range of the light emitting element 102 can be prevented from being restricted due to the presence of the lens assembly 120.

[0043] B. Variations: The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the spirit thereof, for example, the following modifications are also possible.

[0044] In the above embodiment, a FLASH-type LiDAR has been described as an example of the measuring device, but the present invention is not limited to this and may be, for example, a scanning-type LiDAR or an optical measuring device other than a LiDAR. The measuring device may also be configured to have one light-emitting device 101. The light-emitting device 101 may be configured to have multiple light-emitting elements 102. In the above embodiment, the light-emitting element 102 is an infrared laser light-emitting element that emits infrared light, but the present invention is not limited to this and may be a light-emitting element that emits visible light, ultraviolet light, or the like.

[0045] The support member does not have to have a lens function. The support member may be made of a material that is neither electrically conductive nor optically transparent. In short, the support member only needs to have a configuration that supports the light-receiving sensor at a position separated from the circuit board.

[0046] In the above embodiment, the light receiving element is a sheet-type optical sensor 106. However, this is not limited to this, and a photodiode capable of receiving infrared light may also be used. In the above embodiment, the optical sensor 106 is arranged along the opposing inner wall surface 123. However, this is not limited to this. For example, the optical sensor 106 may be arranged along a side inner wall surface around the optical axis among the inner wall surfaces that form the accommodation space 122 of the lens assembly 120, or may be embedded inside the lens assembly 120, at least a portion of which is optically transparent. In the above embodiment, the signal line L1 may be configured to be in contact with the circuit board 115. Even with this configuration, it is possible to suppress the adverse effect of noise caused by the switching operation of the switch element 104 on the light receiving signal output from the optical sensor 106, compared to a configuration in which the optical sensor 106 is arranged on the circuit board 115. [Explanation of symbols]

[0047] 10: Measuring device 100: Light projector 101, 101a: Light emitting device 102: Light emitting element 104: Switch element 106, 106a: Optical sensor 110: Light source unit 115: Circuit board 120: Lens assembly 122: Storage space 123: Opposing inner wall surface 124: Lens part 126: Fixed part 210: Control circuit board 211: Light projection control device 400: Light receiver 410: Light receiving optical system 420: Light receiving part 430: TOF measuring device 500: Information processing device 600: Communication interface 700: External device

Claims

1. A circuit board; a light-emitting element disposed on the circuit board; a switch element disposed on the circuit board, the switch element supplying electric charge to the light-emitting element to emit light when the switch element changes from an open state to a closed state; a light receiving element that outputs a light receiving signal corresponding to the amount of light emitted by the light emitting element; a support member that supports the light receiving element at a position spaced apart from the circuit board.

2. 2. The light emitting device according to claim 1, the support member has an inner wall surface that forms an accommodation space for accommodating the light-emitting element between the support member and the circuit board, The light-emitting device, wherein the light-receiving element is sheet-shaped and is arranged along the inner wall surface of the support member.

3. 3. The light emitting device according to claim 1, The light-emitting device, wherein the support member is made of a non-conductive material.

4. 4. The light emitting device according to claim 3, The light-emitting device, wherein the support member is made of a light-transmitting material.

5. A measuring device comprising a projector having the light emitting device according to claim 1 or 2.

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