JP2026011085A - Light-emitting devices, measuring devices - Google Patents

Abstract

The present invention suppresses the adverse effect of noise generated by the switching operation of a switch element on a light-receiving signal output from a light-receiving element.
[Solution] The light-emitting device includes a circuit board, a light-emitting element arranged on the circuit board, a switch element arranged on the circuit board that supplies charge to the light-emitting element and causes it to emit light by changing 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 away from the circuit board.
[Selected Figure] Figure 2

Description

The technology disclosed in this specification relates to light-emitting devices and measuring devices.

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

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, causing it to emit light, by switching from an open state to a closed state. 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.

Japanese Patent Application Laid-Open No. 2021-19194 Japanese Patent Application Laid-Open No. 2022-109724

In conventional light-emitting devices, the light-receiving element and the light-emitting element are placed on a common circuit board. This 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.

This specification discloses technology that can solve the above-mentioned problems.

The technology disclosed in this specification can be realized, for example, in the following forms:

(1) The light-emitting device disclosed in this specification comprises a circuit board, a light-emitting element disposed on the circuit board, a switch element disposed on the circuit board that supplies 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. With this configuration, the light-receiving element is disposed at a position separate from the circuit board via the support member, thereby preventing noise caused by the switching operation of the switch element from adversely affecting the light-receiving signal output from the light-receiving element.

(2) In the above-described light-emitting device, the support member may have an inner wall surface that forms a storage space for storing the light-emitting element between itself and the circuit board, and the light-receiving element may be sheet-shaped and arranged along the inner wall surface of the support member. According to this configuration, the sheet-shaped light-receiving element is arranged along the inner wall surface of the support member, thereby preventing the storage space from becoming narrower due to the presence of the light-receiving element.

(3) In the above-described light-emitting device, the support member may be configured to be made of a non-conductive material. This configuration 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.

(4) In the above-described light-emitting device, the support member may be configured to be made of a light-transmitting material. This configuration can prevent the light-emitting range of the light-emitting element from being restricted by the presence of the support member.

(5) The above-described measuring device may be configured to include a light projector having the above-described light-emitting device. This configuration makes it possible to prevent noise generated by the switching operation of the switch element from adversely affecting the light-receiving signal output from the light-receiving element.

The technology disclosed in this specification can be realized in various forms, such as a light-emitting device, a light-emitting array having multiple light-emitting devices, a floodlight having multiple light-emitting devices, a measuring device, etc.

FIG. 1 is a block diagram showing a schematic configuration of a measurement device according to an embodiment. FIG. 1 is an explanatory diagram showing the internal configuration of a light-emitting device according to an embodiment. FIG. 10 is an explanatory diagram showing the internal configuration of a light emitting device according to a comparative example.

A. Embodiments:
A-1. Configuration of the measuring device 10:
This embodiment will be described with reference to FIGS. 1 to 3 . The measurement device 10 of this embodiment is a LiDAR. The measurement device 10 is mounted on, for example, a vehicle equipped with an AD (automated driving system) or an ADAS (advanced driver assistance system). The measurement 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.

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.

A-1-1. Floodlight:
The floodlight 100 includes a light source unit 110 and a control circuit board 210 .

(Light source part):
The light source unit 110 has a plurality of light-emitting devices 101 (see FIG. 2 described later). The measurement 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.

(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) of the light source unit 110, and also controls the switching of the switch elements 104 (described below) of 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.

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.

The light receiving optical system 410 is an optical system that allows 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, various lenses such as a focusing lens, various filters such as a wavelength filter, or a reflective mirror.

The light receiving unit 420 includes a light receiving element. The light receiving element is, for example, a photodiode. The light receiving unit 420 receives the reflected laser light Lre incident from the light receiving optical system 410, converts it into a light receiving signal corresponding to the intensity and light receiving timing of the reflected laser light Lre, and outputs it.

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 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, determines 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 determined TOF and the light-receiving signal received from the light-receiving unit 420.

The information processing device 500 has a processor. The processor may be, for example, a CPU (central processing unit), MPU (micro processing unit), ASIC (application specific integrated circuit), FPGA (field programmable gate array), DSP (digital signal processor), etc. The information processing device 500 is communicatively connected to the TOF measurement device 430. The information processing device 500 receives the TOF-correlated signal and the received light signal output by the TOF measurement device 430, and generates various information such as the distance to the measurement target W based on these signals. This information may be, 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 the communication interface 600 to an external device 700 that uses the information.

The external device 700 may be, for example, a device that creates an environmental map using a point cloud, or 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).

A-2. Configuration of the light-emitting device:
Next, the configuration of the light emitting device 101 will be described. The upper part of Fig. 2 shows the external configuration of the light emitting device 101 as seen from the optical axis direction of the 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 the light emitting device 101 along the optical axis direction (the up-down direction of the paper in the lower part of Fig. 2).

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.

In this embodiment, the circuit board 115 is rectangular, but it may be other shapes (e.g., circular).

The light-emitting element 102 is mounted on the circuit board 115. The light-emitting element 102 is, for example, an infrared laser light-emitting element that emits infrared light. Examples of laser light-emitting elements include laser diodes, light-emitting diodes, and surface-emitting elements (such as VCSELs (Vertical Cavity Surface Emitting Lasers)).

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) of the light-emitting element 102, or on the high-potential side (anode of the light-emitting element 102) of 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.

The lens assembly 120 is arranged to cover at least the area of the circuit board 115 where the light emitting element 102 is arranged. The lens assembly 120 is made of a material that is non-conductive and optically transparent. For example, the lens assembly 120 is made of glass, acrylic resin, or the like. The lens assembly 120 has a lens portion 124 and a fixed portion 126.

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 collimating 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.).

The fixed portion 126 is a frame-shaped portion of the circuit board 115 that surrounds the area in which the light-emitting element 102, switch element 104, and optical sensor 106 are arranged. The fixed portion 126 has a rectangular frame shape when viewed in the optical axis direction, but may have 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, switch element 104, and optical sensor 106.

The optical sensor 106 is disposed near the light-emitting element 102 and outputs a light-receiving signal via 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, for example, a carbon nanotube photodetector and an organic transistor mounted on an ultra-thin film substrate (e.g., 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").

The optical sensor 106 is arranged along the inner wall surface that forms the accommodation space 122 of the lens assembly 120. Specifically, the optical sensor 106 is arranged on the 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 arranged at a position offset from the illumination range of the light-emitting element 102. The signal line L1 connected to the optical sensor 106 passes through the interior 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 signal line L1 do not come into contact with the circuit board 115.

A-3. Effects 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 prevents noise caused by the switching operation of the switch element 104 from adversely affecting the light reception signal output from the optical sensor 106.

The upper part of Figure 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 Figure 3). The lower part of Figure 3 shows the cross-sectional configuration of the light-emitting device 101a of the comparative example, taken along the optical axis direction (the up-down direction of the paper in the lower part of Figure 3). The light-emitting device 101a of the comparative example differs from the light-emitting device 101 of this embodiment in the position of the light-receiving element, but is otherwise the same.

Here, the control circuit board 210 repeatedly controls the switching of the switch element 104 at high speed based on an extremely short-period pulse signal (e.g., a pulse width on the order of nanoseconds and a pulse period on the order of microseconds), causing the light-emitting element 102 to emit pulsed light at high speed. As shown in Figure 3, in the comparative light-emitting device 101a, the optical sensor 106a is mounted on the circuit board 115, just like the light-emitting element 102. Therefore, noise generated by the switching operation of the switch element 104 is carried over to the light-receiving signal from the optical sensor 106a, significantly disrupting the level of the light-receiving signal. As a result, it may become impossible to accurately determine whether the light-emitting element 102 is emitting light based on the light-receiving signal from the optical sensor 106a.

In contrast, in this embodiment, the optical sensor 106 is positioned away from the circuit board 115 via the lens assembly 120 (see Figure 2). Therefore, even if the control circuit board 210 repeatedly performs switching control of the switch element 104 at high speed, noise caused by the switching operation is unlikely to be detected in 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.

In this embodiment, the sheet-like optical sensor 106 is arranged along the inner wall surface of the lens assembly 120 (see Figure 2). Therefore, this embodiment can prevent the storage space 122 from becoming narrower due to the presence of the light-receiving element. Furthermore, 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 storage space 122. Therefore, this embodiment can 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.

In this embodiment, the lens assembly 120 is formed from a non-conductive material. Therefore, this embodiment more effectively prevents noise caused by the switching operation of the switch element 104 from adversely affecting the light receiving signal output from the light receiving element.

In this embodiment, the lens assembly 120 is formed from an optically transparent material. Therefore, this embodiment can prevent the light-emitting range of the light-emitting element 102 from being restricted by the presence of the lens assembly 120.

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

In the above embodiment, a FLASH-type LiDAR was used as an example of the measurement device, but this is not limited to this and may be, for example, a scanning-type LiDAR, or an optical measurement device other than LiDAR. The measurement 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 was an infrared laser light-emitting element that emits infrared light, but this is not limited to this and may be a light-emitting element that emits visible light, ultraviolet light, etc.

The support member does not have to function as a lens. 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 be configured to support the light receiving sensor at a position separated from the circuit board.

In the above embodiment, the light receiving element was a sheet-type optical sensor 106, but this is not limited to this and may also be a photodiode capable of receiving infrared light. In the above embodiment, the optical sensor 106 was arranged along the opposing inner wall surface 123, but this is not limited to this and the optical sensor 106 may be arranged, for example, along the side inner wall surface around the optical axis of the inner wall surface that forms 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 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, compared to a configuration in which the optical sensor 106 is arranged on the circuit board 115.

10: Measuring device 100: Light emitter 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 portion 126: Fixed portion 210: Control circuit board 211: Light emitter 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 (5)

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. 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. The light emitting device according to claim 1,
The light-emitting device, wherein the support member is made of a non-conductive material. 4. The light emitting device according to claim 3,
The light-emitting device, wherein the support member is made of a light-transmitting material. A measuring device equipped with a projector having the light-emitting device described in claim 1 or claim 2.