JP7300971B2 - Optical measuring device and light source control method - Google Patents

Description

The present invention relates to an optical measuring apparatus and a light source control method for measuring the shape of an object without contact by irradiating the object with light from a light source.

2. Description of the Related Art Conventionally, there is known an optical measuring device that measures the shape of an object without contact by irradiating the object with light such as a laser beam and capturing an image of a light spot formed on the object (for example, patent Reference 1).

The optical measuring device described above uses the principle of triangulation to calculate the distance to the object to be measured based on the imaging position of the light spot in the captured image. Specifically, as shown in FIG. 8, the captured image captured by the optical measuring device forms a light intensity waveform that indicates the image brightness with respect to the pixel position. A pixel position Px corresponds to the distance to the object.
In such an optical measuring device, when the reflectance of the surface of the object increases, the amount of light received by the imaging unit increases, and the peak height of the light intensity waveform increases. Then, as shown in FIG. 9, when the amount of light received by the imaging element is saturated, it becomes difficult to specify the peak of the light intensity waveform, and as a result, the distance to the object cannot be measured accurately.

Therefore, in the optical measuring device described in Patent Document 1, the amount of light received by the imaging element is calculated based on the captured image, and the light emission intensity of the light source is feedback-controlled so that the amount of light received by the imaging element is within a predetermined range. is being done.

Japanese Patent Application Laid-Open No. 2002-139311

However, in the optical measuring device described above, even if the feedback control described in Patent Document 1 is performed, the feedback control cannot keep up with the scanning of the object, and the amount of light received by the imaging element becomes saturated. there is a possibility. In this case, since the amount of light received by the image sensor cannot be calculated accurately based on the captured image, the light emission intensity of the light source cannot be appropriately controlled, which affects measurement accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical measuring apparatus and a light source control method that can appropriately control the emission intensity of a light source when the amount of light received by an imaging device is saturated.

An optical measuring device of the present invention includes a light source, an irradiation unit that irradiates an object with light emitted from the light source, and an irradiation unit that receives the light reflected by the object and measures the distance to the object. and a photodetector having a wider dynamic range than the imaging device and receiving the light reflected by the object and outputting a photodetection signal. and light source control for calculating a target value of light emission intensity of the light source based on the output value of the light detection signal when the amount of light received by the image sensor is saturated, and controlling the light source based on the target value. and a part.

In the optical measuring device of the present invention, each of the imaging device and the photodetector is configured to receive the light reflected by the object, and when the light emission intensity of the light source increases, the light emitted from the imaging unit outputs The peak value of the image signal and the output value of the photodetection signal output from the photodetector increase linearly. Here, since the photodetector has a wider dynamic range than the image pickup device, even if the amount of light received by the image pickup device is saturated, there is no possibility that the amount of light received by the photodetector will be saturated. low. For this reason, when the amount of light received by the image sensor is saturated, the light source control unit controls the amount of light received by the image sensor to be below the saturation level based on the output value of the photodetection signal output from the photodetector. A target value, which is the value of the emission intensity, can be calculated. By controlling the light source based on the target value, the light source control section can quickly recover the image sensor from the saturated state.
Therefore, according to the optical measuring apparatus of the present invention, it is possible to appropriately control the emission intensity of the light source when the amount of light received by the imaging element is saturated, and as a result, it is possible to improve the measurement accuracy.
In the present invention, the photodetector may directly or indirectly receive the light reflected by the object.

A light source control method according to the present invention includes a light source, an irradiation unit that irradiates an object with light emitted from the light source, and an irradiation unit that receives the light reflected by the object and controls the distance to the object. and a photodetector having a dynamic range wider than that of the imaging device and receiving the light reflected by the object and outputting a photodetection signal. wherein, when the amount of light received by the imaging device is saturated, a target value of the light emission intensity of the light source based on the output value of the light detection signal and a light source control step of controlling the light source based on the target value.
According to the light source control method of the present invention, similarly to the measurement apparatus described above, when the amount of light received by the image sensor is saturated, the light emission intensity of the light source can be appropriately controlled, and as a result, the measurement accuracy can be improved. .

In the light source control method of the present invention, in a coordinate system having the light emission intensity of the light source as the X axis and the signal level of the image signal or the light detection signal as the Y axis, the peak of the image signal with respect to the change in the light emission intensity When a straight line representing a change in value is defined as an imaging sensitivity line, and a straight line representing a change in the output value of the photodetection signal with respect to a change in the emission intensity is defined as the photodetection sensitivity line, the target value calculating step includes: calculating the light detection sensitivity line for the object based on the output values of; converting the light detection sensitivity line for the object into the imaging sensitivity line for the object; and calculating, as the target value, the value of the emission intensity at which the peak value of the image signal is adjusted to a predetermined value, based on the sensitivity line.
Note that the predetermined value by which the peak value of the image signal is adjusted may be a value lower than the saturation level of the image sensor.
ADVANTAGE OF THE INVENTION According to this invention, the target value regarding the light emission intensity of a light source can be calculated appropriately.

The measurement method of the present invention further comprises an information acquisition step of acquiring correlation information including an offset and an angular difference between the imaging sensitivity line and the light detection sensitivity line, and the target value calculation step includes: Based on this, it is preferable to convert the light detection sensitivity line regarding the object into the imaging sensitivity line regarding the object.
ADVANTAGE OF THE INVENTION According to this invention, the target value regarding the light emission intensity of a light source can be calculated more appropriately.

In the measuring method of the present invention, the information acquisition step includes, for a plurality of reference objects having different reflectances, an imaging sensitivity average straight line that is an average of the imaging sensitivity straight lines related to the plurality of reference objects, and and calculating the offset and angle difference of the imaging sensitivity average straight line with respect to the light detection sensitivity average straight line as the correlation information. and preferably comprising the steps of:
Since the present invention utilizes the average data of a plurality of reference objects with different reflectances, it is possible to appropriately calculate the target value of the emission intensity of the light source for objects with various reflectances.

1 is a schematic diagram showing an optical measuring device according to an embodiment of the present invention; FIG. 5 is a graph for explaining an information acquisition step in the light source control method of the embodiment; 6 is a graph illustrating an average imaging sensitivity straight line in the information acquisition process of the embodiment; The graph which illustrates the photodetection sensitivity average straight line in the information acquisition process of the said embodiment. 4 is a flowchart for explaining the light source control method of the embodiment; 5 is a graph for explaining a target value calculation step in the light source control method of the embodiment; The figure which shows the probe head concerning the modification of the said embodiment. Graphs illustrating light intensity waveforms. 4 is a graph illustrating an example of a light intensity waveform, and is a graph for explaining a problem in the conventional technology;

An embodiment of the present invention will be described with reference to the drawings.
[Configuration of measuring device]
In FIG. 1, an optical measuring device 1 according to this embodiment is a three-dimensional measuring device that measures the shape of an object M in a non-contact manner. A mechanism 20 and a control unit 30 that measures the shape of the object M based on a signal from the probe head 10 are provided.

(probe head)
The probe head 10 includes an irradiation section 11, an imaging section 12, and a photodetector 13, as shown in FIG.
The irradiation unit 11 has a laser light source 111 that emits laser light and an irradiation optical system 112 .
The laser light source 111 includes, for example, a laser diode. The laser light source 111 emits laser light according to a control signal (a target value of laser power) input from a light source control section 35, which will be described later. That is, the laser power of the laser light source 111 is controlled by the light source controller 35 .
Note that the laser power of the laser light source 111 corresponds to the light intensity of the present invention.

The irradiation optical system 112 is an optical system that irradiates a measurement point of the object M with laser light emitted from the laser light source 111 . The irradiation optical system 112 includes, for example, a collimating lens for collimating the laser light emitted from the laser light source 111 .

The imaging unit 12 has a light receiving optical system 121 and an image sensor 122 that receives laser light via the light receiving optical system 121 .
The light receiving optical system 121 is an optical system that forms an image of the laser light reflected by the object M on the light receiving surface of the imaging device 122 . The light-receiving optical system 121 includes, for example, a condenser lens for condensing the laser beam reflected by the object M, and the like.

The imaging element 122 is an image sensor such as a CCD, for example, and has a plurality of pixels arranged along one or two directions. The imaging device 122 receives the laser light transmitted through the light receiving optical system 121 and outputs an image signal representing a light intensity waveform. The light intensity waveform is a waveform indicating image brightness with respect to pixel position, as in the prior art (see FIG. 8). The pixel position Px corresponding to the peak of the light intensity waveform of the image signal differs according to the distance to the object M.

The photodetector 13 is, for example, a photodiode, receives the laser beam (scattered light) reflected by the object M, and outputs a photodetection signal corresponding to the amount of received light. This photodetector 13 has a wider dynamic range than the imaging device 122 of the imaging unit 12 .

(moving mechanism)
The moving mechanism 20 is a mechanism for moving the probe head 10 to an arbitrary position. Further, the moving mechanism 20 is provided with a position detection sensor (not shown) for detecting the position of the probe head 10 .
A specific configuration of the moving mechanism 20 is not particularly limited, and for example, a configuration in which the probe head 10 is held at the tip of the multi-joint arm and the angle of each arm of the multi-joint arm can be changed may be employed. In this case, an angle detection sensor such as a rotary encoder is provided to detect the rotation angle of each arm. Thereby, the control unit 30 can calculate the position and orientation of the probe head 10 based on the arm length of each arm and the angle between the arms.
Further, as the moving mechanism 20, the probe head 10 may be configured to be held by a portal frame that moves in the XYZ directions. That is, the moving mechanism 20 includes a column that can move in the Y direction, a beam that is held by the column and parallel to the X direction, a slider that can move on the beam in the X direction, and a slider that moves in the Z direction. A movable head holding member may be provided, and the probe head 10 may be held by the head holding member. In such a configuration, the moving mechanism 20 includes a Y scale for detecting the position of the column in the Y direction, an X scale for detecting the position of the slider in the X direction, and a Z scale for detecting the position of the head holding member in the Z direction. configuration. Thereby, the XYZ coordinates of the probe head 10 can be detected. An angle changing portion for changing the angle of the probe head 10 may be provided in the head holding member. In this case, the posture of the probe head 10 can be detected by providing an angle detection sensor in the angle changing portion.

(control part)
The control unit 30 is configured by a computer, and includes a calculation unit 31 and a storage unit 37 . By reading and executing various programs recorded in the storage unit 37, the calculation unit 31, as shown in FIG. It functions as part 36 .

The measurement control unit 32 controls the probe head 10 and the moving mechanism 20 to sequentially irradiate a plurality of measurement points of the object M with the laser light emitted from the irradiation unit 11, and generate an image signal for each measurement point. and obtain the light detection signal.
The shape calculator 33 calculates the distance from the probe head 10 to the measurement point of the object M based on the image signal output from the imaging unit 12 . The shape calculator 33 also calculates the three-dimensional coordinates of the measurement point based on the calculated distance to the measurement point and the position and orientation of the probe head 10 . Then, the shape calculator 33 measures the surface shape of the object M by connecting the three-dimensional coordinates calculated at the plurality of measurement points on the object M. As shown in FIG.

The saturation determination unit 34 determines whether or not the amount of light received by the image sensor 122 is saturated based on the imaging signal.
The light source control unit 35 controls the laser power of the laser light source 111 by outputting a control signal (a new target value of the laser power) to the laser light source 111 when the amount of light received by the imaging device 122 is saturated. do.
The information acquisition unit 36 acquires various information necessary for control by the light source control unit 35 .
The storage unit 37 stores programs and various information for making the control unit 30 function.

[Light source control method]
A light source control method implemented in the optical measuring apparatus 1 of this embodiment will be described below.
(pretreatment)
The optical measuring apparatus 1 of this embodiment performs an information acquisition step using a plurality of reference objects having different reflectances before measuring the object M to be measured.

First, the probe head 10 irradiates the reference object with a laser beam in a state where a reference object instead of the target object M is set. The information acquisition unit 36 acquires the peak value of the image signal and the output value of the photodetection signal each time the laser power is changed by a predetermined amount, and stores them in the storage unit 37 . In this embodiment, data is acquired using a black reference object with a relatively low reflectance and a white reference object with a relatively high reflectance as the reference objects.

Next, the information acquisition unit 36 acquires data for each of the white reference and the black reference in an XY coordinate system in which the X-axis is the laser power and the Y-axis is the output level of the image signal or the photodetection signal. By plotting and drawing a linear approximation straight line, various straight lines are calculated.

Specifically, as shown in FIG. 2, an imaging sensitivity straight line Li-W, which is a linear function (straight line) representing a change in peak value of an image signal with respect to a change in laser power, is calculated for a white reference object. Further, with respect to the white reference object, a photodetection sensitivity straight line Ld-W, which is a linear function (straight line) representing the change in the output value of the photodetection signal with respect to the change in laser power, is calculated.
Similarly, as shown in FIG. 2, an imaging sensitivity straight line Li-B, which is a linear function (straight line) representing changes in the peak value of the image signal with respect to changes in laser power, is calculated for the black reference object. Further, for the black reference object, a photodetection sensitivity straight line Ld-B, which is a linear function (straight line) representing the change in the output value of the photodetection signal with respect to the change in laser power, is calculated.

Next, as shown in FIG. 2, the coordinates of the intersection point Pi where the two imaging sensitivity straight lines Li-W and Li-B intersect with each other are calculated. Further, as shown in FIG. 3, an average imaging sensitivity straight line Li-Avg, which is the average of the two imaging sensitivity straight lines Li-W and Li-B, is calculated, and this imaging sensitivity average straight line Li-Avg is set along an arbitrary axis (for example, X axis) is calculated.
Similarly, as shown in FIG. 2, the coordinates of the intersection point Pd where the two photodetection sensitivity straight lines Ld-W and Ld-B intersect are calculated. Further, as shown in FIG. 4, a photodetection sensitivity average straight line Ld-Avg, which is the average of the two photodetection sensitivity straight lines Ld-W and Ld-B, is calculated, and this photodetection sensitivity average straight line Ld-Avg is arbitrary. An angle θd to be formed with an axis (for example, the X axis) is calculated.

Next, the offset amount Δr of the imaging sensitivity average straight line Li-Avg with respect to the photodetection sensitivity average straight line Ld-Avg is obtained. In this embodiment, the offset amount Δr can be calculated as the coordinate difference (ΔX, ΔY) of the intersection point Pd with respect to the intersection point Pi.
Also, the angle difference Δθ between the average light detection sensitivity straight line Li-Avg and the average straight line of image sensing sensitivity Ld-Avg is obtained. In this embodiment, this angle difference can be calculated as the difference between the angle θd and the angle θi.

The information acquisition unit 36 stores the offset amount Δr and the angle difference Δθ calculated above in the storage unit 37 as correlation information indicating the correlation between the imaging sensitivity straight line and the light detection sensitivity straight line. Further, the intersection point Pd where the two light detection sensitivity straight lines Ld-W and Ld-B intersect is stored in the storage unit 37 as start point information of the light detection sensitivity straight line.

Here, the shape formed by the imaging sensitivity lines Li-W and Li-B for each reference object and the shape formed by the light detection sensitivity lines Ld-W and Ld-B for each reference object are similar to each other. That is, the angle θis (see FIG. 3) between the imaging sensitivity lines Li-W and Li-B for each reference object and the angle θds between the light detection sensitivity lines Ld-W and Ld-B for each reference object (see FIG. 4) are approximately equal.
For this reason, when a light detection sensitivity straight line for the object M is estimated in the measurement process described later, the light detection The sensitivity line can be transformed into an imaging sensitivity line for the object M.

(measurement processing)
The optical measuring apparatus 1 of this embodiment controls the laser power of the laser light source 111 while measuring the shape of the object M. FIG. A method of controlling the laser light source 111 during measurement of the object M will be described below with reference to the flowchart of FIG.
It is assumed that an appropriate target value for the laser power is set in the optical measuring apparatus 1 before measuring the object M. FIG.

First, the measurement control unit 32 controls the probe head 10 and the moving mechanism 20 to irradiate the measurement point of the target object M with laser light emitted from the irradiation unit 11, and obtain an image signal and a light detection signal. (step S1).
The image signal obtained in step S1 is used by the shape calculator 33 to measure the coordinates of the measurement points. Since the processing by the shape calculation unit 33 is the same as the conventional one, the details are omitted.

The saturation determination unit 34 determines whether or not the amount of light received by the imaging element 122 is saturated based on the image signal acquired by the measurement control unit 32 (step S2). A method for determining the saturation state of the image sensor 122 is not particularly limited, but determination may be made based on the waveform shape of the image signal, or determination may be made by comparing the peak value of the image signal with a threshold value.

If it is determined that the imaging device 122 is not saturated (No in step S2), the light source control according to the image signal obtained in the immediately previous step S1 ends.

If it is determined that the image sensor 122 is saturated (Yes in step S2), the light source control unit 35 outputs the output value of the photodetection signal obtained in the previous step S1 and the output value stored in the storage unit 37. The target value of the laser power is calculated based on the obtained various information (step S3).

Specifically, as shown in FIG. 6, in an XY coordinate system in which the X-axis component is the laser power and the Y-axis component is the signal level of the image signal or the photodetection signal, the currently set laser power target value A point P1 having PWs as the X coordinate and the output value V1 of the photodetection signal obtained in the previous step S1 as the Y coordinate is determined. Then, a straight line passing through this point P1 and the starting point (intersection point Pd) of the light detection sensitivity straight line is calculated as the light detection sensitivity straight line Ld-M with respect to the object M, and the slope (X Calculate the angle θd−M) with respect to the axis.

Next, the angular difference Δθ stored in the storage section 37 is added to the angle θd-M of the photodetection sensitivity line Ld-M, and the offset amount stored in the storage section 37 is added to the photodetection sensitivity line Ld-M. Move by Δr. As a result, the light detection sensitivity line Ld-M regarding the object M is converted into the imaging sensitivity line Li-M regarding the object M. FIG. Then, using the converted imaging sensitivity straight line Li-M, the laser power value at which the peak value of the image signal is a predetermined value Vt (for example, a value of 90% of the saturation level of the image signal) is set as a new target value PWt. calculate.

For reference, FIG. 6 shows a point P2 where the currently set target value PWs of the laser power is the X coordinate and the peak value (saturation level) of the image signal obtained in the previous step S1 is the Y coordinate. for showing. However, this point P2 does not correspond to the actual amount of light received by the imaging device 122, and the point P3 shown on the imaging sensitivity straight line Li-M corresponds to the actual amount of light received.

After that, the light source control unit 35 outputs the target value PWt calculated in step S3 to the laser light source 111 as a control signal. Thereby, the laser power of the laser light source 111 is controlled to the target value PWt (step S4). This completes the light source control according to the image signal obtained in the previous step S1.

The above-described flowchart of FIG. 5 is executed for each of the plurality of measurement points of the object M until the scanning of the measurement area set on the object M is completed. After the scanning of the measurement area set on the object M is completed, the shape calculator 33 measures the shape of the object M by connecting the coordinates obtained for the plurality of measurement points.

In the flowchart of FIG. 5, after step S1, the timing at which the shape calculator 33 measures the coordinates of the measurement point based on the image signal may be independent of steps S2 to S4 relating to light source control. Alternatively, the shape calculator 33 may measure the coordinates of the measurement points after it is determined in step S2 that the imaging element 122 is not saturated. Further, if it is determined in step S2 that the image sensor 122 is in a saturated state, after the laser power is controlled in step S4, step S1 is performed for the same measurement point as the previous time, and based on the obtained image signal may be used to measure the coordinates of the measurement point.

[Effect of this embodiment]
The optical measuring apparatus 1 of this embodiment is configured such that the imaging unit 12 and the photodetector 13 each receive the light reflected by the object M, and when the laser power of the laser light source 111 increases, , the peak value of the image signal output from the imaging unit 12 and the output value of the photodetection signal output from the photodetector 13 increase linearly. Here, since the photodetector 13 has a wider dynamic range than the imaging unit 12, even when the amount of received light of the imaging device 122 is saturated, the amount of received light of the photodetector 13 may be saturated. sex is low. Therefore, when the amount of light received by the image sensor 122 is saturated, the light source control unit 35 controls the amount of light received by the image sensor 122 based on the output value of the photodetection signal output from the photodetector 13 so that the amount of light received by the image sensor 122 is not saturated. A target value, which is the laser power value of , can be calculated. By controlling the laser light source 111 based on the target value, the light source control unit 35 can quickly recover the image sensor 122 from the saturated state.
Further, the light source control method in the optical measuring apparatus 1 of the present embodiment achieves the same effect by performing the target value calculation process and the light source control process described as functions of the light source control section 35 .

Further, in the present embodiment, the target value calculation step converts the light detection sensitivity line Ld-M regarding the object M into the imaging sensitivity line Li-M regarding the object M, and based on this imaging sensitivity line Li-M, the laser Calculate power. Thereby, an appropriate target value of the laser power can be calculated.

In addition, in the present embodiment, an information acquisition step is further performed to acquire correlation information including the offset and angle difference between the imaging sensitivity line and the photodetection sensitivity line. As a result, the target value calculation step can appropriately convert the photodetection sensitivity line Ld-M into the imaging sensitivity line Li-M, and as a result, the target value of the laser power can be calculated more appropriately.

In addition, in the present embodiment, since the information acquisition step uses the average data of a plurality of reference objects with different reflectances, the target value of the laser power can be set more appropriately for objects with various reflectances. can be calculated to

In the prior art such as Japanese Patent Application Laid-Open No. 2002-200311, feedback control is performed to sequentially change and converge the set value of the laser power, so the time required for light source control affects the measurement speed. On the other hand, in the present embodiment, feedback control as in the prior art need not be performed, so the time required to control the laser light source 111 can be minimized, and the influence on the measurement speed is small.

[Modification]
The present invention is not limited to the above-described embodiments, and includes modifications, improvements, and the like within the scope of achieving the object of the present invention.
For example, although the irradiation unit 11 has the laser light source 111 in the above embodiment, it may have a light source other than the laser light source 111 . In this case, the light source control section 35 may control the light emission intensity of the light source.
Moreover, in the above embodiment, the photodetector 13 is arranged so as to directly receive the light reflected by the object M, but the present invention is not limited to this. That is, another reflecting object may be interposed in the optical path between the photodetector 13 and the object M, and the photodetector 13 is arranged so as to indirectly receive the light reflected by the object M. may be
For example, in the modification shown in FIG. 7, the photodetector 13A receives the reflected light reflected by the imaging element 122 after being reflected by the object M. As shown in FIG. Such a modified example can also provide the same effects as the above-described embodiment.

The plurality of reference objects used in the information acquisition process of the embodiment are not limited to the black reference object and the white reference object, and reference objects having other reflectances may be used.

In the above embodiment, the offset amount Δr and the angle difference Δθ of the imaging sensitivity average straight line Li-Avg with respect to the photodetection sensitivity average straight line Ld-Avg are obtained as correlation information, but the present invention is not limited to this. For example, an imaging sensitivity line and a photodetection sensitivity line regarding an arbitrary reference object may be used, and the offset amount Δr and the angle difference Δθ of the photodetection sensitivity line with respect to the imaging sensitivity line may be obtained as correlation information.

In the above embodiment, the light source control unit 35 does not change the target value set for the laser power when the imaging device 122 is not saturated, but the present invention is not limited to this. For example, the light source controller 35 may feedback-control the laser power based on the image signal as in the prior art.

DESCRIPTION OF SYMBOLS 1... Optical measuring apparatus 10... Probe head 11... Irradiation part 111... Laser light source 112... Irradiation optical system 12... Imaging part 121... Light receiving optical system 122... Imaging element 13, 13A... Light detection Device 20 Moving mechanism 30 Control unit 31 Calculation unit 32 Measurement control unit 33 Shape calculation unit 34 Saturation determination unit 35 Light source control unit 36 Information acquisition unit 37 Storage Department.

Claims (5)

an irradiation unit that includes a light source and irradiates an object with light emitted from the light source;
an imaging device that receives the light reflected by the object and outputs an image signal representing a light intensity waveform corresponding to the distance to the object;
a photodetector that has a dynamic range wider than that of the imaging element and receives the light reflected by the object and outputs a photodetection signal;
a light source control unit that calculates a target value of the emission intensity of the light source based on the output value of the light detection signal when the amount of light received by the imaging device is saturated, and controls the light source based on the target value; An optical measuring device comprising: an irradiation unit that includes a light source and irradiates an object with light emitted from the light source;
an imaging device that receives the light reflected by the object and outputs an image signal representing a light intensity waveform corresponding to the distance to the object;
A light source control method performed in an optical measuring device comprising: a photodetector having a dynamic range wider than that of the imaging element and receiving the light reflected by the object and outputting a photodetection signal There is
a target value calculation step of calculating a target value of the light emission intensity of the light source based on the output value of the light detection signal when the amount of light received by the imaging device is saturated;
and a light source control step of controlling the light source based on the target value. In the light source control method according to claim 2,
In a coordinate system in which the light emission intensity of the light source is on the X axis and the signal level of the image signal or the photodetection signal is on the Y axis, a straight line representing the change in the peak value of the image signal with respect to the change in the light emission intensity is captured. When the sensitivity line is a line representing the change in the output value of the photodetection signal with respect to the change in the emission intensity, the photodetection sensitivity line is:
The target value calculation step includes:
calculating the photodetection sensitivity line for the object based on the output value of the photodetection signal;
converting the light detection sensitivity line for the object into the imaging sensitivity line for the object;
and calculating, as the target value, the value of the light emission intensity at which the peak value of the image signal is adjusted to a predetermined value, based on the imaging sensitivity line relating to the object. control method. In the light source control method according to claim 3,
Further comprising an information acquisition step of acquiring correlation information including an offset and an angular difference between the imaging sensitivity line and the light detection sensitivity line,
The light source control method, wherein the target value calculating step converts the light detection sensitivity line regarding the object into the imaging sensitivity line regarding the object based on the correlation information. In the light source control method according to claim 4,
The information acquisition step includes:
For a plurality of reference objects having reflectances different from each other, an imaging sensitivity average straight line that is the average of the imaging sensitivity straight lines for the plurality of reference objects, and light that is the average of the light detection sensitivity straight lines corresponding to the plurality of reference objects A step of obtaining a detection sensitivity average straight line, respectively;
and calculating an offset and an angular difference between the light detection sensitivity average straight line and the imaging sensitivity average straight line as the offset and the angular difference of the correlation information.

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