Measurement device and method for manufacturing measurement device

Abstract

To suppress influence of noise passing through a filter, on measurement of a measurement device.SOLUTION: A measurement device includes: a light projector having a semiconductor laser emitting laser beams; and a light receiver having a filter for transmitting laser beams in a specific passband width of laser beams output from the light projector and reflected by a measurement target and a light reception element for receiving laser beams which passed through the filter. The specific passband of the filer is a part of a defined wavelength band determined on the basis of the manufacturing variations of the semiconductor laser.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a measuring device and a method for manufacturing the measuring device. [Background technology]

[0002] With the progress of AD (Autonomous Driving) and ADAS (Advanced Driver-Assistance Systems), research and development of LiDAR (Light Detection And Ranging) is being conducted as one of the measurement devices used for grasping the surrounding environment and estimating the vehicle's self-position while the vehicle is traveling. LiDAR includes a projector that projects (irradiates) laser light onto a measurement target, and a receiver that receives the reflected light of the laser light reflected from the measurement target. LiDAR outputs information about the measurement target by measuring 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 receiver receives the reflected light (see, for example, Patent Document 1). The projector has a semiconductor laser that emits laser light. The receiver has a filter that passes laser light of a predetermined passband among the laser light output from the projector and reflected by the measurement target, and a light receiving element that receives the laser light that has passed through the filter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-105613 A Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, a specified wavelength band is indicated on the specification sheet of a semiconductor laser. The specified wavelength band is a range of variation that is assumed in advance for the wavelength of the laser light emitted by the semiconductor laser. The specified wavelength band is specified, for example, based on the manufacturing variation of the semiconductor laser. In conventional measuring devices, it is assumed that the wavelength of the laser light of the semiconductor laser varies within the specified wavelength band, and the pass band of the filter of the optical receiver is set to a band that includes the above-mentioned specified wavelength band.

[0005] However, the actual wavelength band of the laser light emitted by the semiconductor laser mounted on the measuring device is only a part of the specified wavelength band. In other words, in conventional measuring devices, the pass band of the filter is set to a bandwidth much wider than the wavelength band required for actual measurement. For this reason, the light receiving element is likely to receive not only the laser light emitted by the semiconductor laser, but also noise (external disturbance light such as sunlight that has a different wavelength from that of the semiconductor laser), which may result in a decrease in the measurement accuracy of the measuring device (for example, the measurable distance may become shorter).

[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) The measurement device disclosed in this specification is a measurement device including a projector having a semiconductor laser that emits laser light, a filter that passes a laser light in a specific pass band among the laser light output from the projector and reflected by a measurement target, and a light receiver that has a light receiving element that receives the laser light that has passed through the filter, and the specific pass band of the filter is a part of a specified wavelength band that is specified based on manufacturing variations of the semiconductor laser. According to this measurement device, the influence of noise such as sunlight is suppressed compared to a configuration in which the specific pass band of the filter is the same as the specified wavelength band, and for example, the measurable distance can be improved.

[0009] (2) In the above-mentioned measuring device, the semiconductor laser includes a first semiconductor laser and a second semiconductor laser, the filter includes a first filter that passes the laser light emitted by the first semiconductor laser and a second filter that passes the laser light emitted by the second semiconductor laser, the first semiconductor laser and the second semiconductor laser have the same specified wavelength band, and the first filter and the second filter have different specific pass bands. According to this measuring device, in the measurement based on the laser light of each of the first semiconductor laser and the second semiconductor laser, the influence of noise is suppressed, and for example, the measurable distance can be improved.

[0010] (3) In the above measurement device, the specific passband may be equal to or smaller than half of the specified wavelength band. With this measurement device, the influence of noise can be more effectively suppressed.

[0011] (4) A method for manufacturing a measuring device disclosed in this specification includes a projector having a semiconductor laser that emits laser light, a filter that passes a laser light in a specific pass band among the laser light output from the projector and reflected by a measurement target, and a receiver having a light receiving element that receives the laser light that has passed through the filter, and includes the steps of: determining to which of multiple wavelength classes a selected semiconductor laser selected from multiple semiconductor lasers belongs by dividing a specified wavelength band that is specified based on manufacturing variations of the semiconductor lasers; and arranging the filter having a specific pass band corresponding to the wavelength class to which the selected semiconductor laser belongs in the receiver. According to this manufacturing method, a measuring device in which the influence of noise is more effectively suppressed can be efficiently manufactured.

[0012] The techniques disclosed in this specification can be realized in various forms, for example, in the form of a filter selection method, a manufacturing method for a measurement device, etc. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a measurement device 10 according to an embodiment. [Diagram 2] FIG. 2 is an explanatory diagram showing a prescribed wavelength band B of the semiconductor laser 23. [Diagram 3] 1 is a flowchart showing a part of a manufacturing process of the measuring device 10. [Figure 4] An explanatory diagram showing the classification of the prescribed wavelength band B [Diagram 5] FIG. 1 is an explanatory diagram showing a specific pass band H1 for a first wavelength class f1. [Figure 6] FIG. 1 is an explanatory diagram showing a specific pass band H2 for a second wavelength class f2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A. Embodiment: A-1. Configuration of the measuring device 10: FIG. 1 is a block diagram showing a schematic configuration of a measuring device 10 in this embodiment. As shown in FIG. 1, the measuring device 10 includes a projector 20 that irradiates an emitted light L1 (e.g., a light beam (laser light)) onto a measuring object W, and a receiver 30 that receives reflected light L2 (return light) that is reflected by the measuring object W and returns from the emitted light L1, and functions as a flash LiDAR. The measuring device 10 measures the difference between the timing at which the projector 20 emits the emitted light L1 and the timing at which the receiver 30 receives the reflected light L2 (time of flight of the laser light, hereinafter referred to as "TOF" (Time of Flight)) to acquire information about the measuring object W.

[0015] The measuring device 10 is mounted on, for example, a vehicle (not shown) equipped with AD or ADAS. For example, while the vehicle is traveling, the measuring device 10 assists in the detection of objects such as people and other vehicles, 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] The light projector 20 includes a light source 22, a light projecting optical system 24, a light projecting control device 26, and a current source 28.

[0017] The light source 22 includes a light emission source having one or more semiconductor lasers (not shown), or one or more semiconductor laser arrays (e.g., semiconductor lasers arranged linearly (one-dimensionally) or planarly (two-dimensionally)). The semiconductor laser is, for example, an external cavity vertical surface emitting laser or a laser diode. In this embodiment, the light source 22 has one semiconductor laser 23.

[0018] The current source 28 supplies a current corresponding to a control signal input from the light projection control device 26 to the semiconductor laser 23 constituting the light source 22. The current source 28 supplies, for example, a periodic square wave current to the semiconductor laser 23 for turning on and off the current flowing through the semiconductor laser 23.

[0019] The light-projection control device 26 generates a control signal for the current source 28 and inputs it to the current source 28, thereby controlling the current (drive current) supplied from the current source 28 to the semiconductor laser 23. The light-projection control device 26 inputs a signal indicating the timing of light projection at which the semiconductor laser 23 emits light to the TOF measurement device 40. The light-projection control device 26 periodically and repeatedly controls the on-off of the current flowing through the semiconductor laser 23, for example, thereby causing the semiconductor laser 23 to emit light periodically and repeatedly.

[0020] The light projection optical system 24 adjusts the light distribution of the emitted light L1, for example, by applying an optical effect (such as refraction, scattering, or diffraction) to the light emitted by the light source 22. The light projection optical system 24 is configured using optical components, for example, various lenses such as a collimator lens, a reflector (mirror), and the like.

[0021] The light receiver 30 includes a light receiving section 32, a filter 33, and a light receiving optical system .

[0022] The light receiving optical system 34 collects reflected light L2, which is light emitted from the projector 20 and reflected by the measurement target W or the like and returns, onto the light receiving unit 32. The light receiving optical system 34 is configured using optical components such as various lenses, such as a collecting lens, and a reflecting mirror (mirror).

[0023] The light receiving unit 32 is a receiving light source having one or more light receiving elements (not shown), or one or more light receiving element arrays (for example, light receiving elements arranged linearly (one-dimensionally) or planarly (two-dimensionally)). The light receiving elements are, for example, photodiodes, SPADs (Single Photon Avalanche Diodes), balanced photodetectors, etc. The light receiving unit 32 photoelectrically converts the reflected light L2 incident from the light receiving optical system 34 to generate a current (hereinafter referred to as a "received light current") according to the intensity of the reflected light L2. The light receiving unit 32 inputs to the TOF measurement device 40 a signal indicating the timing (hereinafter referred to as a "received light timing") at which the light receiving elements constituting the light receiving unit 32 receive the reflected light L2, and the received light current generated by the light receiving elements.

[0024] The filter 33 is a wavelength filter that passes a laser beam having a specific pass band, for example, a bandpass filter. The specific pass band of the filter 33 will be described later. The filter 33 is disposed between the light receiving optical system 34 and the light receiving unit 32.

[0025] The measurement apparatus 10 further includes a TOF measurement device 40, a controller 42, and a communication I / F (Interface) 50.

[0026] The TOF measurement device 40 obtains the TOF based on a signal indicating the light projection timing input from the light projection control device 26 and a signal indicating the light reception timing input from the light receiving unit 32. The TOF measurement device 40 has, for example, a time measurement IC (Integrated Circuit) equipped with a TDC (Time to Digital Converter) circuit. The TOF measurement device 40 inputs the obtained TOF and the light reception current input from the light receiving unit 32 to the controller 42.

[0027] The controller 42 has a processor (such as a central processing unit (CPU), a micro processing unit (MPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), and a digital signal processor (DSP)). The controller 42 generates information used for various measurements such as detection and distance measurement of the measurement target W based on the light receiving current and TOF input from the TOF measurement device 40. The information is, for example, a histogram used in time correlated single photon counting, a distance to each point of the measurement target W, a point cloud (point cloud information), and the like. The controller 42 also controls the light projection control device 26 and the light receiving unit 32. The controller 42 controls, for example, the light projection timing and the light receiving timing so that the process for generating the histogram is accelerated or optimized by controlling the light projection control device 26 and the light receiving unit 32. The information generated by the controller 42 is provided (transmitted) via the communication I / F 50 to a device that uses the information (hereinafter, referred to as "various use devices 60").

[0028] The various utilization devices 60 perform, for example, creating an environmental map using a point cloud, self-position estimation (SLAM (Simultaneous Localization and Mapping)) using a scan matching algorithm (NDT (Normal Distributions Transform), ICP (Iterative Closest Point), etc.), and the like.

[0029] A-2. Specific passband of filter 33: A specified wavelength band B is indicated on the specification sheet of the semiconductor laser 23. The specified wavelength band B is a variation range (bandwidth) that is assumed in advance for the wavelength of the laser light (emitted light L1) emitted by the semiconductor laser 23. The specified wavelength band B is specified based on, for example, manufacturing variations of the semiconductor laser 23.

[0030] FIG. 2 is an explanatory diagram showing the prescribed wavelength band B of the semiconductor laser 23. The horizontal axis of FIG. 2 indicates the wavelength band of light, the left vertical axis indicates the laser intensity of the laser light (emitted light L1) emitted by the semiconductor laser 23, and the right vertical axis indicates the filter transmittance of the filter 33 (the same applies to FIGS. 4 to 6 described later). Graph G1 of FIG. 2 is a result of measuring the laser intensity of the laser light for a plurality of semiconductor lasers 23 (the same applies to FIGS. 4 to 6 described later). According to graph G1, the peak wavelengths at which the laser intensity peaks are different for the plurality of semiconductor lasers 23. That is, the wavelengths (peak wavelengths) of the laser light for the plurality of semiconductor lasers 23 vary. The prescribed wavelength band B is a band that includes the range of variation in the peak wavelength that is assumed in advance for the semiconductor laser 23.

[0031] Graph G2 in FIG. 2 shows the filter transmittance (the same applies to FIGS. 5 and 6 described later). Symbol H in FIG. 2 is the passband H of the filter of the comparative example. The passband H of the filter of the comparative example is set to a bandwidth including the specified wavelength band B. Therefore, the laser light emitted by all the semiconductor lasers 23 whose peak wavelengths belong to the specified wavelength band B passes through the filter of the comparative example and is received by the light receiving unit 32. However, the passband H of the filter of the comparative example is set to a wide bandwidth including the specified wavelength band B. Therefore, not only the laser light emitted by the semiconductor laser 23, but also disturbance light such as sunlight having a wavelength different from that of the semiconductor laser 23 passes through the filter of the comparative example and is received by the light receiving unit 32. As a result, there is a risk that the measurement accuracy of the measurement device 10 (for example, the measurable distance becomes shorter) will decrease.

[0032] In contrast, in the measurement device 10 of the present embodiment, the specific pass band of the filter 33 is a part of the prescribed wavelength band B. The specific pass band of the filter 33 includes the peak wavelength of the laser light emitted by the semiconductor laser 23 mounted in the measurement device 10. Moreover, the specific pass band of the filter 33 is equal to or less than half of the prescribed wavelength band B.

[0033] A-3. Manufacturing method of the measuring device 10: Fig. 3 is a flow chart showing a part of the manufacturing process of the measurement device 10, and Fig. 4 is an explanatory diagram showing the classification of the prescribed wavelength band B. As shown in Fig. 4, the prescribed wavelength band B is divided into three wavelength classes f1 to f3. The three wavelength classes f1 to f3 are wavelength bands obtained, for example, by equally dividing the prescribed wavelength band B into three.

[0034] 3, the peak wavelength of a semiconductor laser 23 selected from the plurality of semiconductor lasers 23 (hereinafter, sometimes referred to as the "selected semiconductor laser 23") is measured (S110). For example, the selected semiconductor laser 23 is caused to emit light, and the peak wavelength of the laser light emitted by the selected semiconductor laser 23 is measured by a known wavelength measuring device (such as an optical wavelength meter).

[0035] Next, it is determined which wavelength class the peak wavelength of the selected semiconductor laser 23 belongs to (S120). Based on the measurement result in S110, it is determined which of the three wavelength classes f1 to f3 the selected semiconductor laser 23 belongs to. Note that at least a part of the steps S110 and S120 may be performed manually by a person, or may be performed automatically by a machine such as a robot.

[0036] Next, a filter 33 having a specific pass band corresponding to the wavelength class to which the selected semiconductor laser 23 belongs (hereinafter, sometimes referred to as the "corresponding filter 33") is prepared (S130). FIG. 5 is an explanatory diagram showing a specific pass band H1 for a first wavelength class f1, and FIG. 6 is an explanatory diagram showing a specific pass band H2 for a second wavelength class f2. As shown in FIG. 5, when the peak wavelength of the selected semiconductor laser 23 belongs to the first wavelength class f1, the specific pass band H1 of the filter 33 is a band whose bandwidth is narrower than the specified wavelength band B and includes the first wavelength class f1. As shown in FIG. 6, when the peak wavelength of the selected semiconductor laser 23 belongs to the second wavelength class f2, the specific pass band H2 of the filter 33 is a band whose bandwidth is narrower than the specified wavelength band B and includes the second wavelength class f2.

[0037] Next, the selected semiconductor laser 23 is disposed in the projector 20, and the corresponding filter 33 is disposed in the receiver 30 (S140). Thereafter, the remaining assembly steps and the like are performed to complete the manufacture of the measuring device 10. According to this manufacturing method, it is possible to efficiently manufacture the measuring device 10 in which the influence of noise is more effectively suppressed.

[0038] A-4. Advantages of this embodiment: As described above, in the measurement device 10 of this embodiment, the specific pass band of the filter 33 is a part of the prescribed wavelength band B. The specific pass band of the filter 33 includes the peak wavelength of the laser light emitted by the semiconductor laser 23 mounted on the measurement device 10. Therefore, according to this embodiment, compared to a configuration in which the specific pass band of the filter 33 is the same as the prescribed wavelength band B, the influence of noise such as sunlight is suppressed, and the measurable distance can be improved.

[0039] In this embodiment, the specific pass band of the filter 33 is equal to or less than half the specified wavelength band B. This makes it possible to more effectively suppress the influence of noise.

[0040] 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 of the invention. For example, the following modifications are also possible.

[0041] The configurations of the measuring device 10, the light projector 20, and the light receiver 30 in the above embodiment are merely examples and can be modified in various ways. For example, in the above embodiment, the filter 33 is disposed between the light receiving optical system 34 and the light receiving unit 32, but it may be disposed in front of the light receiving optical system 34 or may be incorporated as a part of the light receiving optical system 34.

[0042] In the above embodiment, the measuring device 10 is configured to include one semiconductor laser 23 and one filter 33, but the present invention is not limited thereto, and may include a plurality of semiconductor lasers and a plurality of filters corresponding to the plurality of semiconductor lasers. For example, the projector 20 may have a first semiconductor laser and a second semiconductor laser, and the projector 20 may have a first filter that passes the laser light emitted by the first semiconductor laser and a second filter that passes the laser light emitted by the second semiconductor laser. In this case, it is preferable that the first semiconductor laser and the second semiconductor laser have the same specified wavelength band, and the first filter and the second filter have different specific pass bands. Specifically, when the peak wavelength of the first semiconductor laser belongs to the first wavelength class f1, the specific pass band of the first filter is a specific pass band H1 corresponding to the first wavelength class f1. When the peak wavelength of the second semiconductor laser belongs to the second wavelength class f2, the specific pass band of the first filter is the specific pass band H2 corresponding to the first wavelength class f2. This makes it possible to suppress the influence of noise in measurements based on the laser light of the first semiconductor laser and the second semiconductor, thereby improving the measurable distance, for example.

[0043] In the above embodiment, the specific pass band of the filter 33 is ½ or less of the prescribed wavelength band B, but is not limited thereto. For example, it may be ⅓ or less of the prescribed wavelength band B, or ⅕ or less of the prescribed wavelength band B.

[0044] In the manufacturing method of the measurement device 10 in the above embodiment, the specified wavelength band B is divided equally into three and divided into three wavelength classes f1 to f3, but the present invention is not limited to this, and the specified wavelength band B may be divided into two wavelength classes, or into four or more wavelength classes. Furthermore, the bandwidths of at least two of the multiple wavelength classes may be different from each other.

[0045] In the above embodiment, the materials used to form the various components are merely examples, and the components may be formed from other materials. [Explanation of symbols]

[0046] 10: Measuring device 20: Light projector 22: Light source 23: Semiconductor laser 24: Light projecting optical system 26: Light projecting control device 28: Current source 30: Light receiver 32: Light receiving section 33: Filter 34: Light receiving optical system 40: TOF measuring device 42: Controller 50: Communication I / F 60: Device to be used B: Specified wavelength band L1: Emitted light L2: Reflected light W: Measurement object

Claims

1. a light projector having a semiconductor laser that emits laser light; A measurement device including a filter that passes a laser beam in a specific passband among the laser beams output from the light projector and reflected by a measurement target, and a light receiver having a light receiving element that receives the laser beam that has passed through the filter, The specific passband of the filter is a part of a prescribed wavelength band that is determined based on manufacturing variations of the semiconductor laser.

2. 2. The measuring device according to claim 1, the semiconductor laser includes a first semiconductor laser and a second semiconductor laser; the filter includes a first filter that passes the laser light emitted by the first semiconductor laser and a second filter that passes the laser light emitted by the second semiconductor laser; the first semiconductor laser and the second semiconductor laser have the same specified wavelength band; The first filter and the second filter have mutually different specific passbands.

3. The measuring device according to claim 1 or 2, The specific passband is equal to or smaller than 1 / 2 of the specified wavelength band.

4. a light projector having a semiconductor laser that emits laser light; A method for manufacturing a measuring device including a filter that passes laser light in a specific passband among laser light output from the light projector and reflected by a measurement target, and a light receiver having a light receiving element that receives the laser light that has passed through the filter, determining to which of a plurality of wavelength classes a selected semiconductor laser selected from a plurality of semiconductor lasers belongs, the wavelength classes being determined by dividing a prescribed wavelength band determined based on manufacturing variations of the semiconductor lasers; placing said filter on said optical receiver, said filter having a specific passband corresponding to a wavelength class to which said selected semiconductor laser belongs; A method for manufacturing a measuring device, comprising:

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