JP6709553B2 - Three-dimensional laser light scanning device - Google Patents

Description

The present invention relates to a three-dimensional laser light scanning device.

A laser distance measuring technique of irradiating a measuring object with laser light and receiving reflected light thereof to measure a distance is utilized in various fields (for example, Patent Documents 1 and 2). In particular, it has been widely used in the field of factory automation (FA), and more recently, a laser radar for collision safety avoidance of automobiles has been put into practical use, and further expansion of demand is expected.

Also, in the construction market, the spread of ICT construction (information construction) is promoted, and it becomes necessary to measure three-dimensional data before and after construction at the construction site, and there is a demand for a three-dimensional laser scanning device for construction applications. Is growing. The three-dimensional laser light scanning device is not limited to the field of civil engineering/construction/construction, but its use is wide-ranging. , Is used in various fields such as virtual reality.

A conventional three-dimensional laser light scanning device will be described below.
The three-dimensional laser light scanning device is a laser light source that outputs a beam of light, an optical unit that includes a light receiver that receives return light that is reflected back from the measurement target, and a scanning device that projects the beam of light onto the measurement target of the surrounding environment. As a mirror rotation drive mechanism that projects the beam light from the laser light source to the surrounding environment by a mirror that rotates about a horizontal axis, and a horizontal rotation that rotates the mirror rotation drive mechanism and the optical unit about a vertical axis to perform horizontal scanning. It has a rotating mechanism. Then, in the optical unit, the distance to the measurement object is calculated from the time difference and phase difference between the emitted beam light and the return light reflected from the measurement object and returned, and the distance to the measurement object and the mirror rotation A control unit for obtaining three-dimensional coordinate information of the measurement object from the rotation angle of the mirror of the drive mechanism and the rotation angle of the horizontal rotation mechanism is provided.
This control unit is provided with a control device for controlling the rotation drive of the laser light source, the light receiver, the mirror and the device together with the arithmetic device for calculating the three-dimensional coordinate information of the surrounding environment to be measured, and the calculated three-dimensional coordinate It has the function of outputting information to the outside.

Special table 2011-511280 gazette Special table 2011-522216 gazette

Such a three-dimensional laser light scanning device has the following problems.

When a three-dimensional laser light scanning device is used outdoors, external light including sunlight enters the light receiving optical system and becomes noise, so it is necessary to suppress such external light as unnecessary light as much as possible.
In order to suppress and remove unnecessary light, conventionally, a filter is used to cut off light of wavelengths other than the desired band. However, there is an optical element that uses a dielectric multilayer film as a filter that transmits light in a desired wavelength band and attenuates light outside the desired band. There is one in which the wavelength selectivity changes depending on the incident angle of. For this reason, in order to transmit light in a desired band and attenuate unnecessary light, a large filter is provided in front of the condenser lens so as to compensate wavelength selectivity, or wavelength selectivity depending on the incident angle is excluded. Therefore, once the received return light is collimated by the collimator lens, it is transmitted through the filter to attenuate the light outside the desired band, and the condenser lens collects it to guide it to the light receiving sensor. Was there.

According to such a conventional technique, it is necessary to separately provide a filter having wavelength selectivity, and when an optical system of a collimator lens-a filter-a condenser lens is provided in front of the light receiving sensor, unnecessary light is attenuated. There is a problem in that the optical system for this is expensive. Also, if a filter for cutting unnecessary light is used, even if the transmittance of the band of the desired beam light is high, the band light of the beam light used for measurement is attenuated even a little and the transmitted light is reduced. , The amount of light entering the light receiving sensor decreases. Therefore, it is necessary to make the light receiving sensor highly sensitive to compensate for the attenuation of the beam light, or to make the light source highly efficient in order to increase the amount of light entering the light receiving sensor. The light receiving side and the light source side are required to be highly efficient and expensive, which has a problem of affecting the cost.

The present invention is for solving the above-mentioned problems, and an inexpensive three-dimensional laser light scanning device is provided by using a mirror having a dielectric reflection film that reflects light in a desired band with high reflectance. The purpose is to provide.

In order to solve the above problems, the three-dimensional laser light scanning device according to the first aspect of the present invention receives a reflected light that emits a beam of light to the surrounding environment and returns, and measures the distance, horizontal angle, and vertical angle to a measurement target. A three-dimensional laser light scanning device for obtaining three-dimensional coordinates of a surrounding measurement object based on an angle, comprising a light source for generating a beam of light and a light receiver for receiving return light reflected from the measurement object and returned. An optical unit, a mirror rotation drive mechanism that rotationally drives a first mirror that reflects the beam light and the return light around a first axis, and an optical unit and a mirror rotation drive mechanism about an axis that is orthogonal to the first axis. Controls the device rotation drive mechanism that rotates, the mirror rotation drive mechanism, and the device rotation drive mechanism, and calculates the distance to the measurement object, horizontal angle, and vertical angle based on the propagation time of the emitted beam light The mirror rotation drive mechanism includes a control unit that calculates original coordinates, and a mirror rotation drive mechanism includes a cylinder provided with a first mirror at one end, a motor that drives the cylinder to rotate, and a first rotation angle detection unit that detects a rotation angle of the cylinder. The optical unit includes an encoder, a light source, a second mirror that allows the light beam from the light source to pass therethrough and reflects the return light, and a condensing optical system that condenses the return light reflected by the second mirror. And a light receiving sensor, the device rotation drive mechanism includes a second motor and a second encoder that detects a rotation angle, and the second mirror has a reflectance for the wavelength band of the light beam. and becomes higher first wavelength selective as dielectric reflecting film is formed, the second mirror has a hole leading to the first mirror by passing the light beam generated by said light source It is characterized by

The first dielectric reflecting film is preferably formed on the surface of the second mirror facing the first mirror. Further, it is preferable that an antireflection film is formed on the back surface of the second mirror facing the light source. Further, a wavelength-selective second dielectric reflection film is formed on the reflection surface of the first mirror facing the second mirror so as to increase the reflectance in the wavelength band of the light beam. It is preferable. Furthermore, it is preferable that a second antireflection film is formed on the back surface of the first mirror opposite to the reflection surface facing the second mirror.

Since only the desired wavelength band can be received with high reflectance without using a filter and no filter is used, the three-dimensional laser light scanning device can be made inexpensive and can be miniaturized.

It is a figure showing composition of a three-dimensional laser beam scanning device which is one embodiment of the present invention. It is a figure which shows the structure of the mirror used for scanning of a light beam. It is a figure which shows the example of the reflectance of the dielectric reflection film which makes 980 nm a center wavelength. It is a figure which shows the structure of the mirror which passes a light beam and guides a return light to a light receiving sensor.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a three-dimensional laser light scanning device according to an embodiment of the present invention. The three-dimensional laser light scanning device of the present embodiment receives the return light that is reflected by the beam light to the surrounding environment and reflected from the measurement object, and returns the distance to the measurement object, the horizontal angle, and the vertical angle. And is configured as a surveying device that obtains three-dimensional coordinate information of a measurement target.

This three-dimensional laser light scanning device is a three-dimensional scanning device, and a mirror rotation drive mechanism 30 for projecting a beam light in a vertical direction by rotating a mirror inclined at 45 degrees with respect to a horizontal plane, and a laser light source for emitting a beam light. The optical unit 20 includes a light receiver that receives the return light that is reflected and returned, and a device rotation mechanism that horizontally rotates the mirror rotation drive mechanism 30 and the optical unit 20. In addition, the distance to the measurement object is calculated from the time of the projected light beam and the return light reflected back from the measurement object, and the three-dimensional coordinates of the measurement object are calculated from the angle in the vertical direction and the rotation angle in the horizontal direction. It has a control unit 25 including an arithmetic unit for obtaining information. The control unit 25 also controls the device.

The configuration and operation of the device will be described below with reference to FIG.
The horizontal rotation mechanism that rotates the optical unit 20 and the mirror rotation driving mechanism 30 about the vertical axis is a spindle that is the rotation axis of the mounting table 12 on which the optical unit 20 and the mirror rotation driving mechanism 30 are mounted. It has a motor for rotating 13 and a device rotation drive mechanism 11 having a speed reduction mechanism. The spindle 13 is provided with an encoder (rotary encoder) 14 that detects the rotation angle of the spindle 13.

The optical unit 20 is provided with a laser light source 21 that emits a beam of light 41, a mirror 22, a condenser lens 23, and a light receiving sensor 24 as a light receiver that receives the return light reflected and returned from the measurement object.

The laser light source 21 has a laser diode capable of emitting a laser beam having a wavelength in the infrared band, and the laser light source 21 emits a beam light 41 generated by the laser diode. The wavelength of the light beam is in the wavelength range of about 980 nm, for example. The beam light 41 emitted from the laser light source 21 passes through the hole in the center of the mirror 22, is reflected by the mirror 33 of the mirror rotation driving mechanism 30, and is emitted as the beam light 41 to the measurement object in the surrounding environment. ..

The return light 42 reflected and returned from the measurement object is reflected by the mirror 22 in the optical unit 20, condensed by the condenser lens 23, and guided to the light receiving sensor 24. In the light receiving sensor 24, the collected return light 42 is converted into an electric signal by the light receiving sensor 24, and the signal is sent to the control unit 25.

The mirror rotation driving mechanism 30 is provided at a position facing the optical unit 20, and rotates the mirror 33 to deflect the beam light so that the beam light 41 from the laser light source 21 reaches an object to be measured in the surrounding environment. I do. Further, the return light 42 reflected and returned from the measurement object is also deflected by the mirror 33 so as to reach the light receiver of the optical unit 20.

The mirror 33 is attached to the tip of a cylinder (cylinder) 32 at an angle of 45 degrees, and the cylinder 32 is rotated around a horizontal axis by a mirror drive motor 31. An encoder (rotary encoder) 34 is attached to the cylinder 32 so that the rotation angle of the cylinder 22 can be detected. The cylinder 33 rotates around a horizontal axis at a high speed of several thousand rpm, such as 2000 rpm or 6000 rpm. By this rotation, the mirror 33 at the tip of the cylinder 32 rotates at high speed, and the beam light 41 emitted from the laser light source 21 is emitted to the surrounding environment around the horizontal axis. That is, the surrounding environment is scanned in the vertical direction. However, since the distance to the object cannot be measured below the device because the device itself becomes an obstacle, the vertical scanning space is fan-shaped.

The encoder 34 detects the rotation angle of the cylinder 32, and this data is sent to the control unit 25, so that the control unit 25 can obtain vertical scan data for the surrounding environment.

The device is provided with a device rotation drive mechanism 11 driven by a motor having a reduction gear on a base 10, and the device rotation drive mechanism 11 mounts a mounting table 12 on which an optical unit 20 and a mirror rotation drive mechanism 30 are mounted. Rotate around the vertical axis. Unlike the mirror rotation driving mechanism, the device rotation driving mechanism 11 rotates around the vertical axis, that is, in the horizontal direction at a slow rotation angle such that one rotation is in minutes. By the rotation of the device rotation driving mechanism, the device can perform not only the vertical scanning by the rotation of the mirror but also the horizontal scanning, and the vertical and horizontal three-dimensional scanning. An encoder 14 is attached to the spindle 13 of the device rotation drive mechanism 11 to detect a rotation angle of the device about a vertical axis.

The control unit 25 includes an arithmetic unit and a storage unit, and measures the time at which the beam light emitted from the laser light source 21 is reflected back from the measurement object and returned to the measurement object by the TOF method or the phase detection method. calculate. Then, based on the rotation angle around the horizontal axis from the encoder 34 and the rotation angle around the vertical axis from the encoder 14, three-dimensional coordinate information of the measurement object is obtained from the distance to the measurement object, the horizontal angle, and the vertical angle. This three-dimensional coordinate information is stored in the storage unit in the control unit 25. Further, the three-dimensional coordinate information of the measuring object can be output to an external personal computer or the like via the interface. At the same time, the control unit 25 also controls the modulated light emission of the laser light source 21, drives the device such as the mirror drive motor 31, and controls the measurement.

The configuration of the mirror 33 that rotates around the horizontal axis will be described. FIG. 2 is a schematic diagram illustrating the configuration of the mirror 33. The mirror 33 provided at the end of the cylinder 32 for scanning in the vertical direction has a dielectric multilayer film 332 formed on the surface of the glass of the main body 331 that reflects the band of the light beam 41 with high efficiency. On the other hand, a light antireflection film 333 is formed on the back surface of the main body 331.

The dielectric multilayer film 331 is formed by forming dielectric films having different refractive indexes in multiple layers, and has different reflectance and transmittance depending on the band of light.
The principle is the same as the principle of controlling the transmittance of the light band of the filter. For example, by alternately stacking high-refractive-index titanium oxide (TiO ₂ ) and low-refractive-index silicon oxide (SiO ₂ ) at λ/4 of a desired wavelength, only light having a wavelength λ at each boundary surface is formed. The dielectric layer is formed so as to interfere with each other and strengthen each other to have a high reflectance. The dielectric multilayer film is formed on the surface of the main body of the glass substrate by vapor deposition or the like.
For example, FIG. 3 shows an example of the data of the reflectance by the dielectric multilayer film when the central wavelength is 980 nm. A high reflectance can be realized in a band of approximately 900 nm to 1100 nm, and a low reflectance can be achieved in other bands, particularly in a visible light region and a band of a wavelength of 870 nm or less.

The low reflectance in the visible light range means that the light in the visible light band entering the light receiving sensor 24 is reduced, and the same effect as the sunlight cut by the filter can be obtained. As a result, the influence of sunlight can be reduced especially when surveying is performed using a three-dimensional laser light scanning device outdoors.

Further, an antireflection film is formed on the back surface 333 of the reflecting surface of the mirror 33 shown in FIG. 2 by vapor deposition or coating. This antireflection film prevents the incident light in all bands from returning to the surface 332 side of the mirror. As such an antireflection film, a material that absorbs light as a black body, such as chromium or carbon black, is applied or vapor-deposited. As a result, it is possible to prevent the light other than the desired band from being reflected on the back surface of the glass, and to minimize the light in the unnecessary band from entering the light receiving sensor.

FIG. 4 shows the configuration of the mirror 22 of the optical unit 20. The mirror 22 guides the return light 42 reflected from the object to be measured, reflected by the mirror 33 and returned to the light receiving sensor 24. The mirror 22 is provided with a hole 224 through which the light beam 41 from the laser light source 21 passes. Further, on the reflecting surface 222 facing the mirror 33, as in the case of the mirror 33, a dielectric multilayer film having a high reflectance in the band of 980 nm used for the laser oscillation wavelength is formed. Similarly, an antireflection film is formed on the back surface 223. The hole 224 allows the beam light to pass through without any attenuation.
In addition to the mirror 33, the mirror 22 is also provided with a dielectric multilayer film that reflects light in the desired band with high reflectance, so that the effect of cutting light outside the desired band is increased.
Further, the mirror 33 is provided on the end surface of the cylinder 32 at an angle of 45 degrees, so that the mirror 33 has an integral and strong structure, and there is an advantage that it does not affect the rotation of the cylinder 32 and does not deform.

As the wavelength of the light beam, an example using 980 nm has been described in the above embodiment. This is because it is infrared light, which is outside the visible light range of sunlight, and has little effect on human eyes. Further, in order to reduce the influence of sunlight and the influence on the eyes of human beings present in the surroundings, a laser light source having a longer wavelength band of 1550 nm may be used.

Further, in the above embodiment, the control unit is provided in the optical unit and is rotated in the horizontal plane by the device rotation drive mechanism.However, the control unit does not necessarily interlock with the scanning of the horizontal plane of the surrounding environment, May be separately provided and may not rotate on the base.
Further, the device rotation mechanism is configured to rotate the mounting table on which the optical unit and the mirror rotation drive mechanism are mounted, about a vertical axis. However, the mirror rotation drive mechanism and the device rotation drive mechanism are tertiary light beams to the surrounding environment. Anything that can be originally scanned may be used. For example, a mechanism for separately rotating the motor about a vertical axis by a gear mechanism may be used.

DESCRIPTION OF SYMBOLS 10 Base 11 Device rotation drive mechanism 12 Mounting stage 13 Spindle 14 Encoder 20 Optical unit 21 Laser light source 22 Mirror 23 Condensing lens 24 Light receiving sensor 25 Control unit 30 Mirror rotation drive mechanism 31 Motor 32 Cylinder 33 Mirror 34 Encoder 41 Beam light 42 Return light

Claims (5)

A three-dimensional laser light scanning device that emits a beam of light to the surrounding environment, receives reflected light that returns, and determines the three-dimensional coordinates of the surrounding measurement target based on the distance to the measurement target, horizontal angle, and vertical angle. ,
An optical unit including a light source that generates a beam of light and a light receiver that receives the return light that is reflected back from the measurement target,
A mirror rotation driving mechanism that rotationally drives a first mirror that reflects the beam light and the return light around a first axis;
A device rotation drive mechanism for rotating the optical unit and the mirror rotation drive mechanism around an axis orthogonal to the first axis;
Measurement for controlling the mirror rotation driving mechanism and the device rotation driving mechanism and calculating the three-dimensional coordinates of the measurement object by obtaining the distance to the measurement object, the horizontal angle, and the vertical angle based on the propagation time of the emitted beam light. With a control unit,
The mirror rotation drive mechanism includes a cylinder in which the first mirror is provided at one end, a motor that drives the cylinder to rotate, and a first encoder that detects a rotation angle of the cylinder.
The optical unit includes the light source, a second mirror that passes the light beam from the light source and reflects the return light, and a condensing optical system that condenses the return light reflected by the second mirror. And a light receiving sensor,
The device rotation drive mechanism includes a second motor and a second encoder that detects a rotation angle,
The second mirror is formed with a wavelength-selective first dielectric reflection film so that the reflectance for the wavelength band of the light beam is high ,
The second mirror has a hole that allows the light beam generated by the light source to pass therethrough and leads to the first mirror.
A three-dimensional laser light scanning device characterized in that The three-dimensional laser beam scanning device according to claim 1, wherein the first dielectric reflection film is formed on a surface of the second mirror facing the first mirror. The three-dimensional laser light scanning device according to claim 1 or 2, wherein a first antireflection film is formed on a back surface of the second mirror facing the light source. On the reflecting surface of the first mirror facing the second mirror, a wavelength-selective second dielectric reflecting film is formed so that the reflectance in the wavelength band of the light beam becomes high. The three-dimensional laser light scanning device according to any one of claims 1 to 3. The three-dimensional laser according to claim 4, wherein a second antireflection film is formed on a back surface of the first mirror, which is opposite to the reflection surface facing the second mirror. Optical scanning device.

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