JP7628462B2 - Laser measurement device and method - Google Patents

Description

The present invention relates to a time-of-flight (TOF) type laser measurement device and measurement method that determines distance by measuring the time between irradiating an object with pulsed laser light and receiving the reflected light.

In environments where fog occurs, such as harbors, rivers, forests, and indoors, the laser light can be affected by the fog, resulting in measurement errors. For this reason, laser measurement devices use near-infrared light, which has a longer wavelength than visible light and is highly transparent to fog.

In laser measurement devices, various techniques have been devised to suppress degradation of distance measurement accuracy due to the influence of fog.
For example, there is a distance measuring device that can measure distances even in a poor measurement environment (poor air transparency in the measurement environment) by selecting the wavelength of laser light according to the transparency of the air in the measurement environment, and can perform highly accurate measurements when the measurement environment is good (Patent Document 1). In this distance measuring device, when the transparency of the air in the measurement environment is poor, a long wavelength of 1064 nm, which is less likely to be scattered by dust or water vapor, is selected.

There is also a laser range finder that is equipped with a circuit that can receive multiple reflected lights of near-infrared pulsed laser light reflected by at least one object, and distinguish between fog and non-fog reflectors by changing the threshold setting of the received light intensity according to the measurement time, i.e., the distance (Patent Document 2).

JP 2008-292370 A JP 2017-032547 A

Generally, the particle size of fog droplets is on the order of several μm to several tens of μm, which is the same as or several or several tens of times larger than the wavelength of near-infrared laser light, so the distance measuring device described in Patent Document 1 above cannot completely prevent accuracy degradation caused by the effects of fog.

In addition, the laser range finder in Patent Document 2 above can receive light reflected from water droplets in the fog and light reflected from an object deep inside the fog, but depending on the concentration of water droplets in the fog, the light may not penetrate deep into the fog, or even if it does penetrate, it may deviate from the geometric propagation path due to scattering or interference, resulting in a problem of reduced accuracy in measuring the distance to the object being measured.

The object of the present invention is to provide a laser measurement device and a measurement method that do not reduce the accuracy of the measurement results even in an environment where the concentration of fog changes from place to place.

To solve the above problem, the laser measurement device of the present invention for measuring the distance to a measurement object includes a fog state detection unit that receives reflected light from a measurement object irradiated with a visible light laser and detects the intensity of the received light, and a distance measurement unit that measures the distance using reflected light from the measurement object irradiated with a near-infrared laser and determines the distance to the measurement object in a range determined to be less affected by fog based on the intensity of the received light detected by the fog state detection unit.

The measurement method of the laser measurement device of the present invention includes a fog state detection step of receiving reflected light from a measurement object irradiated with a visible light laser and detecting the intensity of the received light, a distance measurement step in parallel with the fog state detection step using reflected light from the measurement object irradiated with a near-infrared light laser, and a distance acquisition step of obtaining the distance to the measurement object by determining the distance to the measurement object measured in the distance measurement step within a range determined to be less affected by fog based on the intensity of the received light detected in the fog state detection step.

According to the present invention, in an environment where the concentration of fog changes from place to place, distance measurements to an object are performed using a laser measurement device in an area where the effect of fog on reducing distance measurement accuracy is small, so the reliability of the measurement results can be maintained.

1 is a diagram illustrating an environment in which a laser measurement apparatus according to an embodiment performs distance measurement. 10 is a diagram showing a change over time in received light intensity of a light beam of a near-infrared laser reflected by a measurement object after the light beam of the near-infrared laser is irradiated. FIG. 11 is a diagram showing the relationship between the distance and the received light intensity of reflected light from a measurement target for each fog density. FIG. 10 is a diagram illustrating a database showing the relationship between the received light intensity of reflected light and the measurement error with respect to distance. FIG. 1 is a configuration diagram of a laser measurement device according to an embodiment; FIG. 13 is a diagram showing an example of a registration/modification screen for information in a camera parameter storage unit displayed on a monitor 3. FIG. 4 is a diagram illustrating an operation flow of the laser measurement apparatus according to the embodiment. FIG. 11 is a diagram illustrating another operation flow of the laser measurement apparatus according to the embodiment.

The following describes in detail an embodiment of the present invention with reference to the drawings.

FIG. 1 is a diagram showing an environment in which a laser measurement device 100 according to an embodiment performs distance measurement.
The laser measurement device 100 of the embodiment measures distance by a TOF method by irradiating a light beam of a near-infrared laser, and also performs three-dimensional measurement by capturing an image by irradiating a slit light of a visible laser. As shown in Fig. 1, the laser measurement device 100 irradiates an irradiation range 6 with a light beam of a near-infrared laser and a slit light of a visible laser so as to scan the irradiation range 6, and measures a distance L to a measurement object 4.

When performing measurements in ports, rivers, forests, and indoors, fog 5 may occur in the irradiation range 6. The near-infrared laser light beam and the visible laser slit light emitted from the laser measurement device 100 are scattered and attenuated by the fog 5, and the scattered light is mixed with the reflected light from the measurement target 4, reducing the accuracy of the measured distance.
Near-infrared lasers are less susceptible to the effects of fog than visible lasers, but even with a near-infrared laser beam, the loss of accuracy caused by fog cannot be ignored.

FIG. 2 is a diagram showing the change over time in the intensity of the received light of the light beam of the near-infrared laser reflected by the measurement object 4 after the light beam of the near-infrared laser is irradiated.
In distance measurement using the TOF method, the time from irradiation to reception of reflected light is converted into distance to obtain the distance from the laser measurement device 100 to the measurement target 4 .

Figure 2 shows, with solid and dashed lines, the change over time after irradiation with a near-infrared laser light beam in two fog 5 states with different fog densities. The solid line shows a state in which the fog is thinner (the fog density is lower) than the dashed line.

As shown in Figure 2, the first reflected light (fog) caused by scattering in the fog 5 and the second reflected light from the measurement object 4 are observed. As shown by the dashed lines, as the fog becomes thicker (the fog density increases), the received light intensity of the first reflected light increases and the received light intensity of the second reflected light decreases.

When the fog is thin, it is possible to eliminate the first reflected light and obtain the distance from the second reflected light to the measurement target 4 by setting an appropriate threshold value for the received light intensity. However, when the fog is thick, the received light intensities of the first reflected light and the second reflected light are approximately the same, so it is not possible to eliminate the first reflected light.
If the fog becomes even thicker, it becomes impossible to receive the second reflected light from the object 4, and the distance cannot be calculated.

In addition, in Figure 2, the second reflected light is shown as a rectangle, but as the fog thickens, the reflected light is scattered and the distribution of received light intensity becomes smoother. This causes a shift in the center value of the second reflected light, shown by the dashed vertical line, which causes a shift in the detection time of the second reflected light, resulting in an error ΔL from the distance L (true value) shown by the dashed vertical line. In other words, the thicker the fog, the greater the error ΔL in the measured distance.

The laser measurement device 100 of the embodiment improves the reliability of distance measurements by determining in advance the distance error caused by fog and identifying the measurement range in which measurements can be made with a specified distance measurement accuracy.

In detail, the laser measurement device 100 determines the relationship between the received light intensity of the reflected light from the measurement target 4, distance, and measurement error for each fog density according to the typical shape (prism, cylinder, flat plate, etc.), material (iron, aluminum, concrete, etc.) and surface condition (painted, rust, etc.) of the measurement target 4, and stores this in a database (hereinafter, sometimes referred to as judgment information).

The laser measurement device 100 measures the light intensity of reflected light from the measurement target 4 and the distance by irradiating a light beam of a near-infrared laser and measuring distance using a laser beam separate from the TOF distance measurement. Then, by referring to the database, the light intensity of reflected light required to obtain distance measurement accuracy is obtained from the relationship between the light intensity of reflected light corresponding to the measured distance and the measurement error, and it is determined whether the measured light intensity of reflected light from the measurement target 4 satisfies this requirement. If the measured light intensity of reflected light from the measurement target 4 is equal to or greater than the light intensity obtained by referring to the database, it is determined that the TOF distance measurement using the near-infrared laser light beam satisfies the specified distance measurement accuracy.

The laser measurement device 100 of the embodiment measures the distance and the received light intensity of the reflected light from the measurement target 4 using a slit light of a visible light laser that is highly sensitive to fog concentration, and determines the distance measurement accuracy.

Figure 3A shows the relationship between the distance and the received light intensity of reflected light from the measurement object 4 for each fog density. Figure 3A shows the relationship between the distance to the measurement object and the received light intensity of reflected light measured at fog density A, fog density B, and fog density C (fog density A<B<C).

3A, the received light intensity of the reflected light from the measurement target 4 decreases as the distance increases (the measurement distance increases). Also, the received light intensity of the reflected light from the measurement target 4 decreases as the fog density increases.
Furthermore, due to scattering of laser light by fog, the measurement error increases (the distance measurement accuracy decreases) as the fog density increases (gets thicker).

For example, if the reflection intensity when measuring distance nL at fog density B is nQ (intersection Q) and the reflection intensity when measuring distance L at fog density C is nP (intersection P), the distance measurement accuracy of the measurement results will be better at intersection Q. Therefore, when performing a measurement that satisfies the accuracy equivalent to the measurement error at fog density C, it can be seen that the received light intensity of the reflected light when measuring distance nL should be nP or greater.

The laser measurement device 100 of the embodiment determines in advance the relationship between the distance and the received light intensity of the reflected light from the measurement target 4 for each fog concentration shown in FIG. 3A, and stores this as a database (determination information) showing the relationship between the received light intensity of the reflected light and the measurement error relative to the distance in FIG. 3B.

In detail, when the laser measurement device 100 measures the distance 3L to the measurement target 4 using a slit beam of a visible laser, it refers to the database (determination information) in FIG. 3B to obtain the fog density C (nP rows of received light intensity of reflected light) for achieving the measurement error 3CΔ corresponding to the target measurement accuracy from the measurement errors 3CΔ, 3BΔ, and 3AΔ (see the dotted arrow in the figure). Then, it extracts the received light intensity 3P of the reflected light at which the distance 3L is measured at the fog density C (see the dashed-dotted arrow in the figure). If the received light intensity of the reflected light when measuring the distance 3L to the measurement target 4 using the slit beam of a visible laser is greater than the received light intensity 3P, then it is determined that the measurement error is smaller than 3CΔ and the target measurement accuracy can be met (the measurement accuracy is high).

The database (judgment information) may be stored as a function (formula) of the received light intensity, distance, and measurement error, as long as the minimum value of the received light intensity that satisfies a specified distance measurement accuracy is determined as the allowable received light intensity for each distance to the measurement target.

Next, the configuration of the laser measurement device 100 according to the embodiment will be described with reference to FIG.
The laser measurement device 100 comprises a fog state detection unit 1 that receives reflected light from a measurement object 4 illuminated with a visible light laser and detects the received light intensity, and a distance measurement unit 2 that performs TOF distance measurement using reflected light from the measurement object 4 illuminated with a near-infrared light laser, and determines the distance to the measurement object 4 in a range determined to be less affected by fog based on the received light intensity obtained by the fog state detection unit 1.

The fog state detection unit 1 includes a line laser 11, a camera 12, a camera/laser control unit 13, a camera parameter storage unit 14, and an image recording unit 15, and constitutes a device that performs measurements using a light-cutting method with a slit light (also called a stripe light) of a visible light laser.

More specifically, the line laser 11 irradiates the measurement object 4 with a slit beam of visible laser light.
The camera 12 captures an image of the measurement target 4 illuminated with the slit light of the visible laser.
The camera and laser control unit 13 controls the irradiation timing and direction of the slit light from the line laser 11 to scan the measurement object 4 with the slit light, and controls the camera 12 to capture an image in synchronization with the irradiation of the slit light.
The image recording unit 15 stores the captured image of the measurement target 4 irradiated with the slit light of the visible laser captured by the camera 12 .

The foggy state detection unit 1 further includes a laser emission line extraction unit 16 , a camera parameter storage unit 14 , and a reflected light analysis unit 17 .
The laser bright line extraction unit 16 sequentially acquires captured images of the measurement object 4 from the image recording unit 15, extracts a laser bright line, which is an image of the slit light irradiated onto the surface of the measurement object 4, from the captured images, and determines the pixel position of the laser bright line and the received light intensity of the reflected light of the slit light.

In more detail, the laser bright line extraction unit 16 first performs distortion correction processing on the captured image acquired from the image recording unit 15 using the camera parameters (Figure 5) in the camera parameter storage unit 14. Next, binarization processing is performed according to the threshold value (laser light intensity value) of the received light intensity of the reflected light of the visible light laser set in the measurement parameters (Figure 5) in the camera parameter storage unit 14. Then, image processing for line extraction is performed to extract the laser bright line.

When the reflectance of the visible light laser differs depending on the type of measurement object 4, a threshold value for the received intensity of the reflected light according to the measurement object may be set as a camera parameter. Also, the setting of the threshold value for the received intensity of the reflected light may be changed according to the wavelength range of the visible light laser as a camera parameter.

The reflected light analysis unit 17 calculates the three-dimensional position of the laser emission line using a light cutting method from the pixel position of the laser emission line obtained by the laser emission line extraction unit 16 and the camera parameters described later, and obtains the shape of the measurement object 4 irradiated with the slit light.
The reflected light analysis unit 17 temporarily stores the determined reflection position of the laser emission line (the irradiation position of the slit light) and the received intensity of the reflected light together with the measurement time in a storage unit (not shown).

The fog state detection unit 1 is a device that measures the three-dimensional shape of the measurement object 4 based on the camera 12, similar to known distance measurement devices, and the measurement operation will not be described here.

The distance measurement unit 2 includes a laser emission unit 21, a laser reception unit 22, a distance measurement control unit 23, and a measurement data storage unit 24, and constitutes a distance measurement device that measures distance using the TOF method by irradiating a light beam of a near-infrared laser.

The laser emitter 21 is a laser light emitting element such as a semiconductor laser diode that emits a near-infrared laser beam.
The laser light receiving unit 22 is a laser light receiving element that receives the near-infrared laser light that is emitted from the laser emitting unit 21 and reflected by the measurement target 4. An avalanche photodiode or the like is used as the laser light receiving element.

The distance measurement control unit 23 controls the scanning mechanism so that the laser emitter 21 and the laser receiver 22 are oriented in a predetermined direction, and measures the time (flight time) from when the near-infrared laser is emitted until it is reflected by the measurement target 4 and returns, based on the emission timing of the laser emitter 21 and the reception timing of the laser receiver 22, to obtain the distance to the irradiation position (reflection position) of the measurement target 4. The reflection position of the measurement target 4 is calculated from the distance obtained from the irradiation direction and the flight time, with the positions of the laser emitter 21 and the laser receiver 22 as the base points.
The distance measurement control unit 23 also acquires the intensity of the received near-infrared laser light reflected by the measurement target 4 .

The measurement data storage unit 24 stores the distance to the reflection position of the measurement target 4 and the received light intensity calculated by the distance measurement control unit 23, together with the measurement time for each reflection position corresponding to the irradiation direction of the near-infrared laser.

The judgment information storage unit 26 stores a database (judgment information) that indicates the relationship between the received light intensity of the reflected light and the measurement error relative to the distance, as described in FIG. 3B.

The fog effect determination unit 25 refers to the determination information in the determination information storage unit 26 and determines whether the reflection intensity of the visible light laser at the reflection position analyzed by the reflected light analysis unit 17 is equal to or greater than the reflection intensity that satisfies the specified distance measurement accuracy. If the reflection intensity is equal to or greater than the reflection intensity that satisfies the specified distance measurement accuracy, it determines that the influence of fog is small and the distance measurement accuracy is satisfied, and obtains the distance to the reflection position of the measurement target 4 that corresponds to the reflection position analyzed by the reflected light analysis unit 17 from the measurement data storage unit 24. The distance measurement accuracy is set in the camera parameter storage unit 14, which will be described later.

The distance data storage unit 27 stores the distance measured by the near-infrared laser to the reflection position of the measurement target 4 with a predetermined distance measurement accuracy determined by the fog effect determination unit 25, together with the measurement time.
In addition, the distance data memory unit 27 may store, in correspondence with the reflection position of the measurement target 4, the distance measured by the near-infrared light laser to the reflection position and the judgment result of the distance measurement accuracy in the fog effect judgment unit 25.

The monitor 3 is a terminal unit having a display unit and an operation input unit. It allows the operator of the laser measurement device 100 to give instructions for the operation of the device and to register and modify information such as various parameters in the camera parameter storage unit 14, which will be described later.

The camera parameter storage unit 14 stores the camera parameters used for correction processing by the laser emission line extraction unit 16, the measurement parameters of the distance measurement unit 2 that determines distance by irradiating a near-infrared laser, the laser scanner parameters of the distance measurement unit 2, and the sensor geometric arrangement conditions of the distance measurement unit 2 (laser emission unit 21 and laser reception unit 22), the camera 12, and the line laser 11.

FIG. 5 is a diagram showing an example of a registration/modification screen for the information in the camera parameter storage unit 14 displayed on the monitor 3. As shown in FIG.
As camera parameters of the camera 12, the image sensor size, the number of horizontal and vertical pixels of the image sensor, and setting information of the focal length are displayed so as to be able to be registered and modified.

As measurement parameters of the distance measurement unit 2, the measurement distance measurement accuracy referenced as the target distance measurement accuracy in the fog effect determination unit 25, the measurement object showing characteristic information such as the typical shape, material, surface condition, etc. of the measurement object, the threshold value of the received light intensity of the reflected light of the visible light laser for laser emission line extraction referenced in the laser emission line extraction unit 16 (laser light intensity value), and the setting information of the distance measurement range which is the position information of the measurement object 4 where the fog state detection unit 1 and the distance measurement unit 2 perform measurements are displayed so that they can be registered and modified.

Then, the number of scans, the number of data averaging times when measuring distance, and the threshold value when evaluating the distance measurement accuracy of the average measured distance using the data standard deviation are displayed so that they can be registered and modified as laser scanner parameters for the distance measurement unit 2. The method of using this setting information will be described later.

The monitor 3 also displays a "Sensor Geometric Arrangement Condition" button that instructs transition to a screen for registering and modifying the sensor geometric arrangement conditions stored in the camera parameter storage unit 14. In more detail, the sensor geometric arrangement conditions screen is used to register and modify the relationship between the installation positions of the laser emitter 21 and the laser receiver 22 (the base point for distance measurement using the light beam of the near-infrared laser) and the installation position of the camera 12 (the base point for distance measurement using the slit light of the visible light laser).

With the above configuration, the fog state detection unit 1 and distance measurement unit 2 of the laser measurement device 100 measure distances in parallel and synchronously within a predetermined distance measurement range of the measurement target 4. Then, time information indicating the measurement time and the measurement value are recorded. When the fog influence determination unit 25 determines that the influence of fog is small and the distance measurement accuracy is satisfied, it obtains the measurement distance result where the measurement time of the distance measurement unit 2 is within a predetermined time period relative to the measurement time of the fog state detection unit 1.

If the distance measurement operation time of the distance measurement unit 2 is faster than the distance measurement operation time of the fog state detection unit 1, the distance measurement unit 2 may average multiple measurements to determine the measured distance of the reflection position and associate it with the measurement result of the fog state detection unit 1.

Specifically, the laser measurement device 100 of the embodiment is realized by an information processing device consisting of semiconductor elements such as semiconductor lasers and photodiodes, a camera, a scanning mechanism, a central processing unit (CPU), a storage device such as a random access memory (RAM), a read only memory (ROM), a hard disk drive (HDD), and a flash memory, and an input/output interface. The functional parts of the camera/laser control unit 13, the laser emission line extraction unit 16, the reflected light analysis unit 17, the distance measurement control unit 23, and the fog effect determination unit 25 are realized by the CPU executing programs stored in the storage device.

Next, the operation flow of the laser measurement device 100 of this embodiment will be explained with reference to FIG.

In step S61, the camera parameter storage unit 14 sets the measurement conditions required for the measurement process, including the camera parameters, the measurement parameters of the distance measurement unit 2, the laser scanner parameters of the distance measurement unit 2, and the sensor geometric arrangement conditions of the distance measurement unit 2 (laser emission unit 21 and laser reception unit 22), the camera 12, and the line laser 11.

In step S62, the fog state detection unit 1 irradiates the measurement target 4 with a slit light of a visible light laser and scans while capturing an image with a camera, and the distance measurement unit 2 scans the light beam of a near-infrared laser in parallel with the camera capture to measure and record the distance using the TOF method, and performs the camera capture and near-infrared laser scanning processes.

In step S63, the foggy state detection unit 1 performs a process of extracting a laser emission line from the camera image of the measurement target 4 captured by the camera in step S62.

In step S64, the fog state detection unit 1 performs a calculation process of the distance and direction (reflection position) of the laser emission line, which calculates the three-dimensional position of the laser emission line by the light section method from the pixel position of the laser emission line extracted in step S63 and the camera parameters. At this time, the received light intensity of the reflected light of the reflected light of the visible light laser is associated with the direction (reflection position) of the laser emission line.

In step S65, the distance measurement unit 2 acquires the distance measured in S62 corresponding to the orientation (reflection position) of the laser emission line calculated in step S64, and performs processing to extract the distance measured using the near-infrared light laser corresponding to the distance and orientation (reflection position) of the laser emission line.
When the same measurement target 4 is continuously measured, a moving average of the distances measured in S62 may be calculated and used as the distance measured by the near-infrared laser.

In step S66, the distance measurement unit 2 refers to a database (determination information) showing the relationship between the received intensity of reflected light of a preset visible light laser and the measurement error for distance, determines the received intensity of reflected light required to measure the distance including the desired measurement error, and determines whether the received intensity of reflected light of the laser emission line corresponding to the orientation of the near-infrared light laser when the distance extracted in step S65 was obtained is equal to or greater than the required received intensity of reflected light. If the received intensity of reflected light is equal to or greater than the required received intensity, the distance measurement unit 2 determines that the distance extracted in step S65 is in a state where the influence of fog is small and satisfies the distance measurement accuracy, thereby determining the influence of fog on the distance data.

In step S67, the distance measurement unit 2 stores the distance and the measurement time determined in step S67 to be in a state where the influence of fog is small and the distance measurement accuracy is satisfactory, as distance data, and performs a distance data storage process.
In step S67, the distance measurement unit 2 may store the distance extracted in step S65, the measurement time, and the determination result in step S66.

In step S68, if the laser measurement device 100 continues measurement (No in S68), it returns to step S62, and if it ends measurement (Yes in S68), it ends the process.

The flow diagram in Figure 6 shows the process when the foggy state detection unit 1 and the distance measurement unit 2 measure the distance in a predetermined distance measurement range of the measurement target 4 in parallel and in sync, and each performs a measurement once in the predetermined distance measurement range. Figure 7 explains the case where the distance measurement unit 2 averages multiple measurements to determine the measured distance of the reflection position and associates it with the measurement result of the foggy state detection unit 1.

Steps S61 to S68 in the flow diagram of FIG. 7 are similar to those in FIG. 6, and therefore description thereof will be omitted here.
In step S71, the distance measurement unit 2 calculates the average value of the distances measured by the multiple near-infrared lasers extracted in step S65, and performs processing for averaging the distance data.

In step S72, the distance measurement unit 2 calculates the standard deviation of the distance data and checks whether it is equal to or less than the distance measurement accuracy. More specifically, the standard deviation of the distances measured by the multiple near-infrared lasers extracted in step S65 is calculated, and it is determined whether the calculated standard deviation is equal to or less than the distance measurement accuracy. If the calculated standard deviation is equal to or less than the distance measurement accuracy, the average value of the distances calculated in step S71 is set as the distance data to be stored in step S67.
In this way, by adding the averaging process, it is possible to further suppress the deterioration of distance measurement accuracy due to the influence of fog.

The above describes a process in which the average value of distances measured using multiple near-infrared lasers determined to be less affected by fog is used as distance data, but if the difference between the distance measured using a near-infrared laser determined to be less affected by fog and the distance calculated in step S64 from the laser emission line of a visible laser at the same reflection position is equal to or less than the distance measurement accuracy, the distance measured using the near-infrared laser determined to be less affected by fog may be used as the distance data stored in step S67.

In this case, if the difference between the average value of the distances measured using multiple near-infrared lasers determined to be less affected by fog and the distance calculated in step S64 from the laser emission line of the visible laser at the same reflection position is equal to or less than the distance measurement accuracy, the distance measured using the near-infrared laser determined to be less affected by fog may be used as the distance data stored in step S67.

Furthermore, the average value of the distances measured using multiple near-infrared lasers determined to be less affected by fog and the average value of the distance obtained from the laser emission line of a visible laser at the same reflection position may be calculated, and if the difference between the two average values is equal to or less than the distance measurement accuracy, the average value of the distances measured using the near-infrared laser determined to be less affected by fog may be used as the distance data to be stored in step S67.

In the above embodiment of the laser measurement device 100, the fog state detection unit 1 and the distance measurement unit 2 operate in parallel and synchronously over a predetermined distance measurement range of the measurement target 4. However, after the fog state detection unit 1 measures the measurement target 4, the distance measurement unit 2 may measure the distance by irradiating a near-infrared laser to a range that the distance measurement unit 2 determines to be less affected by fog and to satisfy the distance measurement accuracy based on the measurement result of the fog state detection unit 1.

In addition, in the embodiment of the laser measurement device 100, the fog state detection unit 1 is configured to irradiate the measurement object 4 with a slit beam of visible laser light and receive the reflected light from the measurement object 4 to obtain the received light intensity. However, the configuration is not limited to this, and the fog state detection unit 1 may detect the fog state between the laser measurement device 100 and the measurement object 4 using another method.

For example, distance measurements are performed using a millimeter wave radar in a foggy environment, and the relationship between the reception strength of the reflected waves, distance, and measurement error is determined in advance, and stored as a database (judgment information storage unit 26) showing the relationship between the reception strength of the millimeter wave radar's reflected waves and the measurement error versus distance. The fog state detection unit 1 is then configured to irradiate the measurement object 4 with the millimeter wave radar, receive the reflected waves from the measurement object 4, and obtain the reception strength, and the fog effect judgment unit 25 judges the effect of fog based on the reception strength of the millimeter wave radar's reflected waves.

It goes without saying that the technology of the laser measurement device 100 of the embodiment can be applied to a TOF type shape measurement device that determines the three-dimensional shape by measuring the time from when a pulsed laser light is irradiated onto an object to when the reflected light is received.

The present invention is not limited to the above-described embodiment, but includes various modified examples. The above-described embodiment has been described in detail to provide an easy-to-understand explanation of the present invention, and is not necessarily limited to having all of the configurations described. In addition, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment.

REFERENCE SIGNS LIST 1 Fog state detection unit 2 Distance measurement unit 3 Monitor 4 Measurement target 11 Line laser 12 Camera 13 Camera/laser control unit 14 Camera parameter storage unit 15 Image recording unit 16 Laser emission line extraction unit 17 Reflected light analysis unit 21 Laser emission unit 22 Laser receiving unit 23 Distance measurement control unit 24 Measurement data storage unit 25 Fog effect determination unit 26 Determination information storage unit 27 Distance data storage unit 100 Laser measurement device

Claims (3)

A laser measurement device that measures a distance to a measurement object,
a fog state detection unit that detects the intensity of reflected light from a measurement target irradiated with a visible light laser;
a distance measurement unit that measures a distance based on reflected light from a measurement object irradiated with a near-infrared laser, and obtains a distance to the measurement object in a range determined to be less affected by fog based on the received light intensity detected by the fog state detection unit;
A laser measurement device comprising: 2. The laser measurement device according to claim 1,
The fog state detection unit includes:
A line laser that irradiates a slit beam of visible laser light onto a measurement target;
a laser emission line extraction unit that extracts emission line information of the slit light from a captured image of a measurement target;
a reflected light analysis unit that determines a reflection position of the slit light on a measurement target and a light intensity of the reflected light of the slit light for each reflection position from the bright line information;
The distance measurement unit is
a fog influence determination unit that determines an influence of fog when a near-infrared laser is irradiated onto a reflection position of a visible laser on a measurement target and distance measurement is performed for each reflection position based on the received light intensity;
A laser measurement device comprising: A measurement method for a laser measurement apparatus, comprising:
a fog state detection step of receiving reflected light from a measurement target irradiated with a visible light laser and detecting a received light intensity;
In parallel with the fog state detection step, a step of measuring a distance based on reflected light from a measurement object irradiated with a near-infrared laser;
a distance acquisition step of obtaining a distance to the measurement target measured in the distance measurement step, within a range determined to be less affected by fog based on the received light intensity detected in the fog state detection step; and
A measuring method comprising:

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