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

Abstract

To measure a distance to a measurement object while suppressing the power consumption of an excitation laser.SOLUTION: A measurement device comprises: a projector including a seed laser, a fiber, and an excitation laser; a light receiver that receives a reflected laser beam obtained by reflecting an output laser beam emitted by the projector on a measurement object and returning; and a controller. The controller executes: seed laser light emission processing of performing pulse control on the seed laser so as to output a seed laser beam at each first light emission timing; and excitation laser light emission processing of performing pulse control on the excitation laser so as to output excitation light at each second light emission timing corresponding to the first light emission timing.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a measurement device, a method for controlling a projector, a control program for a projector, and a computer-readable recording medium on which a computer program is recorded. [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 driving. 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 off the measurement target. LiDAR outputs information about the measurement target by measuring the distance to the measurement target based on the time difference between the projection timing of the projector emitting the laser light and the reception timing of the receiver receiving the reflected light. The projector includes a fiber laser (see, for example, Patent Document 1). The fiber laser includes a seed laser that emits seed laser light, an optical fiber that is doped with a rare earth element and through which the seed laser light passes, and an excitation laser that emits excitation light that excites the rare earth element of the optical fiber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 117912 Summary of the Invention [Problem to be solved by the invention]

[0004] In the projector of the conventional measuring device, the seed laser is subjected to pulse control for intermittently outputting seed laser light at a predetermined timing, while the pumping laser is subjected to DC control for continuously outputting pumping light. That is, in the conventional measuring device, the pumping laser continues to output pumping light even during a non-emission period when the seed laser light is not emitted. This causes a problem of increased power consumption of the pumping laser.

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

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

[0007] (1) A measurement device disclosed in the present specification includes a seed laser that emits seed laser light, an optical fiber doped with a rare earth element and into which the seed laser light emitted by the seed laser is input, and an excitation laser that emits excitation light that excites the rare earth element in the optical fiber, and includes a light projector that emits output laser light output from the optical fiber to the outside, a light receiver that receives reflected laser light that is reflected by a measurement target and returned from the output laser light projector, and a controller. The controller executes a seed laser emission process that pulse-controls the seed laser to output the seed laser light at each first emission timing, and an excitation laser emission process that pulse-controls the excitation laser to output the excitation light at each second emission timing corresponding to the first emission timing.

[0008] In the present measuring device, the excitation laser intermittently outputs excitation light, so that the present measuring device can measure the distance to the measurement target while suppressing the power consumption of the excitation laser, compared to a conventional measuring device in which the excitation laser continuously outputs excitation light.

[0009] (2) In the above measurement device, an emission period of the excitation light at each of the second emission timings may be longer than an emission period of the seed laser light at each of the first emission timings. According to this measurement device, it is possible to effectively excite a rare earth element in an optical fiber, as compared with a configuration in which the emission period of the excitation light at each of the second emission timings is equal to or shorter than the emission period of the seed laser light at each of the first emission timings.

[0010] (3) In the above measurement device, the start of the emission period of the seed laser light may be configured to be later than the start of the emission period of the excitation light. According to this measurement device, the seed laser light is input to an optical fiber in a highly excited state, and therefore the seed laser light can be effectively amplified, compared to a configuration in which the start of the emission period of the seed laser light is simultaneous with the start of the emission period of the excitation light.

[0011] (4) In the above measurement device, the start of the emission period of the seed laser light may be closer to the end of the emission period of the excitation light than the start of the emission period of the excitation light. According to this measurement device, the seed laser light is input to an optical fiber in a highly excited state, compared to a configuration in which the start of the emission period of the seed laser light is closer to the start of the emission period of the excitation light, so that the seed laser light can be effectively amplified.

[0012] (5) A method for controlling a light projector disclosed in this specification is a method for controlling a light projector having a seed laser that emits seed laser light, an optical fiber doped with a rare earth element and into which the seed laser light emitted by the seed laser is input, and an excitation laser that emits excitation light that excites the rare earth element in the optical fiber. The method for controlling a light projector includes a seed laser emission step of pulse-controlling the seed laser to output the seed laser light at each first emission timing, and an excitation laser emission step of pulse-controlling the excitation laser to output the excitation light at each second emission timing corresponding to the first emission timing. According to this method for controlling a light projector, it is possible to measure the distance to a measurement target while suppressing the power consumption of the excitation laser.

[0013] (6) A control program for a projector disclosed in this specification causes a computer of a projector having a seed laser that emits seed laser light, an optical fiber, and an excitation laser that emits excitation light to execute a seed laser emission process for pulse-controlling the seed laser to output the seed laser light at each first emission timing, and an excitation laser emission process for pulse-controlling the excitation laser to output the excitation light at each second emission timing corresponding to the first emission timing. According to this control program for a projector, it is possible to measure the distance to a measurement target while suppressing the power consumption of the excitation laser.

[0014] The technology disclosed in this specification can be realized in various forms, for example, in the form of a measuring device, a floodlight, a floodlight control method, a floodlight control program, a computer-readable recording medium on which the floodlight control program is recorded, etc. [Brief description of the drawings]

[0015] [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 illustrating a schematic configuration of a projector 20. [Diagram 3] Time chart showing light emission control of the projector 20 [Figure 4] 1 is a timing chart showing light emission control of a light projector 20 according to a first modified example. [Diagram 5] 13 is a timing chart showing light emission control of the light projector 20 in the second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] A. Embodiment: A-1. Configuration of the measuring device 10: 1 is a block diagram showing a schematic configuration of a measuring device 10 according to the present embodiment. The measuring device 10 is a scan-type LiDAR. The measuring device 10 measures the difference between the timing at which the light projector 20 emits the output laser light Lout and the timing at which the light receiver 30 receives the input laser light Lin (time of flight of the laser light, hereinafter referred to as "TOF" (Time of Flight)), and acquires information about the measuring object W.

[0017] 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.

[0018] The measuring device 10 includes a light projector 20, a light receiver 30, a scanner (beam deflector) 40, and a mirror 50.

[0019] The projector 20 includes a fiber laser 22 that outputs an output laser light Lout, and a light-projection control device 26 (see FIG. 2 described later). The light-projection control device 26 controls the emission of the fiber laser 22. The light-projection control device 26 also inputs a signal indicating the timing of light projection at which the fiber laser 22 emits light to a TOF measurement device 36 described later. The light-projection control device 26 periodically and repeatedly emits light from the fiber laser 22, for example, by periodically repeating the on-off control of a current flowing through the fiber laser 22 (a seed laser 110 described later). A detailed configuration of the projector 20 will be described later.

[0020] The scanner 40 has an optical scanning optical system that deflects the optical path (direction) of the output laser light Lout output by the projector 20, and scans the output laser light Lout in a predetermined direction. The scanner 40 has a polygon mirror 42 and a scanning mirror 46 as an optical scanning optical system. The polygon mirror 42 has a plurality of reflecting surfaces 44 (four in FIG. 1), and is a rotating body that is provided so as to be rotatable about a first rotation axis G1. The scanning mirror 46 is provided so as to be rotatable about a second axis G2. The output laser light Lout output by the projector 20 is reflected by a reflecting surface 48 of the scanning mirror 46, reflected by one reflecting surface 44 of the rotating polygon mirror 42, and emitted toward the measurement object W. The input laser light Lin reflected by the measurement object W is again reflected by one reflecting surface 44 of the rotating polygon mirror 42, and reflected by the reflecting surface 48 of the scanning mirror 46.

[0021] The mirror 50 reflects the input laser light Lin reflected by the reflecting surface 48 of the scanning mirror 46 and guides it to the photoreceiver 30. Specifically, the input laser light Lin reflected by the reflecting surface 48 of the scanning mirror 46 is reflected by the reflecting surface 52 of the mirror 50 and heads toward the photoreceiver 30.

[0022] The light receiver 30 includes a light receiving optical system 34, a light receiving section 32, and a TOF measurement device 36.

[0023] The light receiving optical system 34 collects the input laser light Lin to form a spot on 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, various filters such as a wavelength filter, and a reflecting mirror.

[0024] 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 input laser light Lin incident from the light receiving optical system 34 to generate a current corresponding to the intensity of the input laser light Lin (hereinafter referred to as a "light receiving current"). The light receiving unit 32 inputs to the TOF measurement device 36 a signal indicating the light receiving timing at which the light receiving elements constituting the light receiving unit 32 received the input laser light Lin, and the light receiving current generated by the light receiving elements.

[0025] The TOF measurement device 36 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 36 has, for example, a time measurement IC (Integrated Circuit) equipped with a TDC (Time to Digital Converter) circuit. The TOF measurement device 36 inputs the obtained TOF and the light reception current input from the light receiving unit 32 to the information processing unit 54.

[0026] With the above configuration, the irradiation position of the output laser light Lout on the measurement object W can be moved in a first scanning direction (e.g., vertical direction on the paper in FIG. 1) according to a change in the rotation angle (θx) accompanying the rotation of the polygon mirror 42, thereby obtaining image information of the measurement object W in the first scanning direction. Also, the irradiation position of the output laser light Lout on the measurement object W can be moved in a second scanning direction (e.g., a direction perpendicular to the first scanning direction, the depth direction on the paper in FIG. 1) according to a change in the rotation angle (θy) accompanying the rotation of the scanning mirror 46, thereby obtaining information of the measurement object W in the second scanning direction.

[0027] The measuring device 10 further includes an information processing unit 54 and a communication I / F (Interface) 56.

[0028] The information processing unit 54 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 information processing unit 54 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 36. 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 information processing unit 54 also controls the light projection control device 26 and the light receiving unit 32. The information processing unit 54 controls, for example, the light projection control device 26 and the light receiving unit 32 to control the light projection timing and the light receiving timing described above so that the processing for generating the histogram is accelerated or optimized. The information generated by the information processing unit 54 is provided (transmitted) via the communication I / F 56 to a device that uses the information (hereinafter, referred to as "various use devices 60").

[0029] 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.

[0030] A-2. Configuration of projector 20: Fig. 2 is an explanatory diagram that shows a schematic configuration of the projector 20. As shown in Fig. 2, the projector 20 includes a fiber laser 22, a light projection optical system 24, and the light projection control device 26.

[0031] The projection optical system 24 adjusts the light distribution of the output laser light Lout by, for example, applying an optical effect (such as refraction, scattering, or diffraction) to the light emitted by the fiber laser. The projection optical system 24 is configured using optical components such as various lenses, such as a collimator lens, and a reflector (mirror).

[0032] The fiber laser includes a seed laser 110, a pump laser 120, a first optical fiber F1, and a second optical fiber F2.

[0033] The seed laser 110 emits seed light La having a peak wavelength included in the near-infrared range, for example. In this embodiment, the wavelength of the seed light La is 1550 nm, but is not limited to this and may be, for example, 900 nm.

[0034] The first optical fiber F1 and the second optical fiber F2 are doped with a rare earth element, and the seed light La passes through them. The first optical fiber F1 and the second optical fiber F2 are arranged in series. The optical fibers F1 and F2 are doped with at least one of ytterbium (Yb) and erbium (Er) as a rare earth element. The length of each of the optical fibers F1 and F2 is, for example, about 5 m.

[0035] The pumping laser 120 emits pumping light Lb (for example, 940 nm) that excites the rare earth elements contained in the optical fibers F1 and F2.

[0036] More specifically, the fiber laser 22 has a first optical isolator (ISO) 130, a first wavelength division multiplexer (WDM) 140, a wavelength division multiplexer (TAP) 150, a second optical isolator 160, and a second multiplexer 170.

[0037] The seed laser 110 is optically coupled to the first multiplexer 140 via a normal optical fiber (not shown) that is not doped with a rare earth element. A first optical isolator 130 is provided between the seed laser 110 and the first multiplexer 140. The first multiplexer 140 is coupled to an input portion of a first optical fiber F1. An output portion of the first optical fiber F1 is optically coupled to a second multiplexer 170. A second optical isolator 160 is provided between the first multiplexer 140 and the second multiplexer 170. The second multiplexer 170 is coupled to an input portion of a second optical fiber F2. An output portion of the second optical fiber F2 is directed toward the light projection optical system 24.

[0038] The pumping laser 120 is optically coupled to the splitter 150 via a normal optical fiber (not shown) that is not doped with a rare earth element. The splitter 150 splits the pumping light Lb emitted by the pumping laser 120 into multiple lights. The splitter 150 is optically coupled to the first multiplexer 140 and the second multiplexer 170. The first multiplexer 140 combines the seed light La emitted by the seed laser 110 and the pumping light Lb from the splitter 150. The second multiplexer 170 combines the seed light La amplified by the first optical fiber F1 and the pumping light Lb from the splitter 150.

[0039] With this configuration, in the fiber laser 22, the rare earth elements in the first optical fiber F1 and the second optical fiber F2 are excited by the excitation light Lb emitted by the excitation laser 120. The seed light La of the seed laser 110 is incident on the first optical fiber F1 and the second optical fiber F2 in the excited state, whereby the seed light La is amplified in two stages. As a result, a high-power output laser light Lout is output via the projection optical system 24.

[0040] A-3. Light emission control of the floodlight 20: Fig. 3 is a time chart showing the light emission control of the projector 20. The upper part of Fig. 3 shows the emission pattern of the excitation light Lb of the excitation laser 120. The period of reference D2 is the emission period of the excitation light Lb, and the period between the emission periods D2 is the non-emission period D4 of the excitation light Lb. The lower part of Fig. 3 shows the emission pattern of the seed light La of the seed laser 110. The period of reference D1 is the emission period of the seed light La, and the period between the emission periods D1 is the non-emission period D3 of the seed light La.

[0041] In this embodiment, as shown in the lower part of Fig. 3, the light-projection control device 26 executes a seed laser emission process for pulse-controlling the seed laser 110 so as to output the seed light La at each first emission timing t1. Also, as shown in the upper part of Fig. 3, the light-projection control device 26 executes an excitation laser emission process for pulse-controlling the excitation laser 120 so as to output the excitation light Lb at each second emission timing t2 corresponding to the first emission timing t1.

[0042] Specifically, the light-projection control device 26 repeatedly executes a light-emitting operation of emitting the seed light La for only a first light-emitting period D1 at a time interval of a first non-light-emitting period D3. In the present embodiment, the duty ratio (D1 / (D1+D3)) of the pulse control of the seed light La is, for example, 0.01 or less, but may be 0.005 or less, or 0.02 or more. The light-projection control device 26 repeatedly executes a light-emitting operation of emitting the excitation light Lb for only a second light-emitting period D2 at a time interval of a second non-light-emitting period D4. In the present embodiment, the duty ratio (D2 / (D2+D4)) of the pulse control of the excitation light Lb may be 0.8 or more, 0.7 or more, or 0.5 or more. The duty ratio of the pulse control of the excitation light Lb may be 0.9 or less.

[0043] In this embodiment, the second emission period D2 of the excitation light Lb is longer than the first emission period D1 of the seed light La. The second emission period D2 may be, for example, 5 times or more, or 10 times or more, as compared to the first emission period D1. In addition, in this embodiment, the second emission timing t2 coincides with the first emission timing t1, and the light projection control device 26 emits the seed light La at the first emission timing t1 synchronized with the second emission timing t2 of the excitation light Lb. In this case, it is preferable that the duty ratio of the pulse control of the excitation light Lb is relatively short (for example, 0.8 or more) so that the second optical fiber F2 can maintain a sufficiently excited state when the seed light La is emitted.

[0044] A-4. Advantages of this embodiment: As described above, in this embodiment, the light projection control device 26 executes a seed laser emission process for pulse-controlling the seed laser 110 so as to output the seed light La at each first emission timing t1 (see the lower part of FIG. 3). In addition, the light projection control device 26 executes an excitation laser emission process for pulse-controlling the excitation laser 120 so as to output the excitation light Lb at each second emission timing t2 corresponding to the first emission timing t1 (see the upper part of FIG. 3). As described above, in this embodiment, the excitation laser 120 outputs the excitation light Lb intermittently. Therefore, according to this embodiment, it is possible to measure the distance to the measurement target W while suppressing the power consumption of the fiber laser 22 (excitation laser 120) compared to a configuration in which the excitation laser continuously outputs the excitation light as in a conventional measuring device.

[0045] For example, when the fiber laser 22 of this embodiment is a high-output type and the driving current of the excitation laser 120 is 10 A or more, the power consumption of the fiber laser 22 (excitation laser 120) is high and the amount of heat generated increases. In contrast, in this embodiment, the excitation laser 120 intermittently outputs the excitation light Lb. Therefore, according to this embodiment, the power consumption of the fiber laser 22 is suppressed and the amount of heat generated is suppressed, so that it is possible to suppress an increase in the size of a heat dissipation member (not shown) of the projector 20 and, ultimately, an increase in the size of the measurement device 10 (projector 20).

[0046] In this embodiment, the second emission period D2 of the excitation light Lb is longer than the first emission period D1 of the seed light La. Therefore, according to this embodiment, the rare earth element of the optical fiber can be excited more effectively than in a configuration in which the second emission period D2 of the excitation light Lb is shorter than or equal to the first emission period D1 of the seed light La.

[0047] A-5. First Modification of the Present Embodiment: Fig. 4 is a time chart showing light emission control of the projector 20 in the first modified example. The upper part of Fig. 4 shows the emission pattern of the excitation light Lb of the excitation laser 120, similar to the upper part of Fig. 3. The lower part of Fig. 4 shows the emission pattern of the seed light La of the seed laser 110.

[0048] As shown in the lower part of FIG. 4, the light projection control device 26 repeatedly executes the light emission operation of emitting the seed light La for only the first light emission period D1 at a time interval of the first non-light emission period D3, as in the above embodiment. However, in this first modified example, the start of the first light emission period D1 of the seed light La (first light emission timing t1a) is later than the start of the second light emission period D2 of the excitation light Lb (second light emission timing t2). Specifically, the first light emission timing t1a is the timing between the second light emission timing t2 and the end of the second light emission period D2. In FIG. 4, the first light emission timing t1a is the central timing between the second light emission timing t2 and the end of the second light emission period D2. According to this first modified example, the seed light La is input to an optical fiber in a highly excited state, as compared with the configuration of the above embodiment, and therefore the seed light La can be effectively amplified.

[0049] A-6. First modified example of this embodiment: Fig. 5 is a time chart showing light emission control of the projector 20 in the second modified example. The upper part of Fig. 5 shows the emission pattern of the excitation light Lb of the excitation laser 120, similar to the upper part of Fig. 3. The lower part of Fig. 5 shows the emission pattern of the seed light La of the seed laser 110.

[0050] As shown in the lower part of FIG. 5, the light projection control device 26 repeatedly executes the light emission operation of emitting the seed light La for only the first light emission period D1 at a time interval of the first non-light emission period D3, as in the above embodiment. However, in this second modified example, the start of the first light emission period D1 of the seed light La (first light emission timing t1b) is closer to the end of the second light emission period D2 than the start of the second light emission period D2 of the excitation light Lb (second light emission timing t2). Specifically, the first light emission timing t1b is a timing corresponding to the end of the second light emission period D2. In FIG. 5, the first light emission period D1 overlaps with the end of the second light emission period D2. According to this second modified example, the seed light La is input to an optical fiber in a high excitation state, compared to a configuration in which the first light emission timing t1b is closer to the second light emission timing t2, for example, so that the seed light La can be effectively amplified.

[0051] 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.

[0052] The configuration of the measuring device 10 in the above embodiment is merely an example, and various modifications are possible. For example, the projector 20 is of a scanning type equipped with the scanner 40, but is not limited to this, and may be of a flash type or the like.

[0053] In the above embodiment, the fiber laser 22 has a first optical fiber F1 and a second optical fiber F2, and is configured to amplify the seed light La in two stages, but this is not limited to this, and the fiber laser 22 may be configured to amplify the seed light La in only one stage, or may be configured to amplify the seed light La in three or more stages.

[0054] In the above embodiment, the second emission period D2 of the excitation light Lb was longer than the first emission period D1 of the seed light La, but this is not limited to this, and as long as the excited state of the optical fiber is maintained when the seed light La is emitted, the second emission period D2 of the excitation light Lb may be shorter than or equal to the first emission period D1 of the seed light La.

[0055] Regarding the relationship between the emission period of the seed light and the emission period of the excitation light, the patterns shown in the above embodiment and modified examples (see FIG. 3 to FIG. 5) are merely examples. If the emission period of the seed light and the emission period of the excitation light overlap at least partially, this corresponds to "outputting the excitation light at each second emission timing corresponding to the first emission timing". Therefore, for example, in the above embodiment, the pattern may be one in which the first emission timing t1 is earlier than the second emission timing t2 and the emission period D1 overlaps with the second emission timing t2, or the pattern may be one in which the first emission timing t1 is later than the second emission timing t2 and is closer to the second emission timing t2 than the end of the second emission period D2.

[0056] In the above embodiment, the materials used to form the components are merely examples, and the components may be formed from other materials. [Explanation of symbols]

[0057] 10: Measuring device 20: Light projector 22: Fiber laser 24: Light projecting optical system 26: Light projecting control device 30: Light receiver 32: Light receiving section 34: Light receiving optical system 36: TOF measuring device 40: Scanner 42: Polygon mirror 46: Scanning mirror 50: Mirror 54: Information processing section 60: Utilization device 110: Seed laser 120: Excitation laser 130: First optical isolator 140: First multiplexer 150: Demultiplexer 160: Second optical isolator 170: Second multiplexer F1: First optical fiber F2: Second optical fiber

Claims

1. a light projector including a seed laser that emits seed laser light, an optical fiber that is doped with a rare earth element and into which the seed laser light emitted by the seed laser is input, and a pumping laser that emits pumping light that excites the rare earth element in the optical fiber, the light projector emitting an output laser light output from the optical fiber to the outside; a light receiver that receives a reflected laser beam that is the output laser beam emitted by the light projector and reflected by a measurement target and returns to the measurement target; A measurement device comprising: The controller: a seed laser emission process for pulse-controlling the seed laser so as to output the seed laser light at each first emission timing; an excitation laser emission process for pulse-controlling the excitation laser so as to output the excitation light at each second emission timing corresponding to the first emission timing.

2. 2. The measuring device according to claim 1, an emission period of the excitation light at each of the second emission timings is longer than an emission period of the seed laser light at each of the first emission timings.

3. The measuring device according to claim 2, A measurement apparatus, wherein the start of the emission period of the seed laser light is later than the start of the emission period of the excitation light.

4. The measuring device according to claim 3, A measurement apparatus, wherein a start of an emission period of the seed laser light is closer to an end of an emission period of the excitation light than to a start of the emission period of the excitation light.

5. A method for controlling a light projector having a seed laser that emits seed laser light, an optical fiber that is doped with a rare earth element and into which the seed laser light emitted by the seed laser is input, and an excitation laser that emits excitation light that excites the rare earth element in the optical fiber, comprising: a seed laser emission step of pulse-controlling the seed laser so as to output the seed laser light at each first emission timing; an excitation laser emission step of pulse-controlling the excitation laser so as to output the excitation light at each second emission timing corresponding to the first emission timing.

6. A computer included in a projector having a seed laser that emits a seed laser beam, an optical fiber, and a pumping laser that emits a pumping light, a seed laser emission process for pulse-controlling the seed laser so as to output the seed laser light at each first emission timing; and an excitation laser emission process for pulse-controlling the excitation laser so as to output the excitation light at each second emission timing corresponding to the first emission timing.

7. A computer-readable recording medium having a computer program recorded thereon for controlling a light projector having a seed laser that emits a seed laser beam, an optical fiber, and a pumping laser that emits a pumping light, a seed laser emission process for pulse-controlling the seed laser so as to output the seed laser light at each first emission timing; and an excitation laser emission process for pulse-controlling the excitation laser so as to output the excitation light at each second emission timing corresponding to the first emission timing.

Images