KR101260280B1 - Device and method for optically scanning 3 dimensional object - Google Patents

Abstract

The three-dimensional optical scanning apparatus includes a light source, an optical transmission lens for determining a divergence angle of the light emitted from the light source, a first beam splitter for separating light passed through the optical transmission lens into light for external reference and internal reference signal, A reflector that changes the path of the light transmitted from the beam splitter to the target, a reflector that rotates in a vertical or horizontal direction, determines the direction of light emission to scan the target, receives a reflected light from the target, An optical fiber for external path for receiving light focused by the optical receiver lens and delaying the optical fiber for a predetermined period of time and emitting light, And a plurality of optical fibers for generating a plurality of optical signals having different optical intensities, And a photodetector for converting the signal generated by the optical signal generator into an electrical signal.

Description

TECHNICAL FIELD [0001] The present invention relates to a three-dimensional optical scanning device,

The present invention relates to a three-dimensional optical scanning apparatus and method, and more particularly, to a three-dimensional optical scanning apparatus and method capable of precisely measuring a profile of a target by compensating a time measurement error due to a difference in light reflectance according to a measurement point of a target .

Generally, in order to measure the profile of a three-dimensional object, the distance from the three-dimensional optical scan to each point of the object must be accurately measured.

The TOF (Time Of Flighting) method, which is the principle of distance measurement of an object, is as follows. The distance measurement unit generates a periodic signal to generate a pulse signal, such as an optical signal, an electromagnetic wave signal, or an acoustic signal, which passes through a medium such as air, a copper wire, and an optical fiber in the emitter. _E ) is measured. After the transmitted signal passes through the medium and is reflected from the target, the pulse signal passes through the medium again, and the signal arrival time (t _R ) is measured at the receiving part. In other words, a signal clock having a predetermined frequency is generated to generate a measurement signal, and a signal transmitted at a time t _E after a predetermined time delay is received at a time t _R , which is reflected back to the target. Thus, the time that the distance measurement signal travels through the medium is t _R -t _E , and multiplying this by the signal transmission rate (v) of the medium is a reciprocation distance to the target. Therefore, the distance between the distance measuring device and the target is calculated as follows.

D: Distance between the distance measuring device and the target

v: pulse signal speed in medium

t _E : signal departure time

t _R : Signal arrival time

In order for the distance measuring device to accurately measure the distance to the target, the signal round-trip time (t _R -t _E ) should be measured when the velocity of the medium is constant in Equation 1.

1, a distance measuring apparatus of another type according to the related art generates a start signal in the distance calculating unit 4, converts the electric signal into an optical signal in the transmitting unit 22, A part of the optical signal is sent to the light mixer 25 and converted into an electric signal by the receiving unit 26, and the distance calculation unit 21 measures the start time t _E. The remaining optical signals are reflected by the target 24 and pass through the optical delay element 27 and the light mixer 25 before reaching the receiver 26. The receiving unit 26 converts the optical signal reflected from the target into an electric signal and outputs the electric signal to the distance calculating unit 21. The distance calculating unit 21 receives the electric signal outputted from the receiving unit 26 and calculates the target round trip time t _R ) is measured. The distance calculation unit 21 measures the distance by removing the error due to the internal optical path of the distance measuring apparatus as t _R -t _E. Here, the optical delay element 27 is delayed beyond the pulse signal width so as not to overlap the time t _E in the minimum distance measurement, and the time lag thus corrected is corrected by the distance calculation unit 21.

On the other hand, when the time-of-flight (TOF) method is employed in the 3-dimensional optical scan, the measurement error can be reduced by always constantly adjusting the amount of received light. However, unlike a general laser distance measuring device, Since it requires time, there is no time to adjust the amount of light.

Since the prior art utilized in the 3-dimensional laser light scanning using pulsed laser can not control the intensity of the received laser pulse according to the fast laser distance measurement speed, And a method of compensating the distance error according to the intensity of the pulse was used.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the prior art described above, and it is an object of the present invention to provide a method and apparatus for generating a plurality of identical signals having various amplitudes by a light- And an object of the present invention is to provide a scanning apparatus and method.

According to an aspect of the present invention, there is provided a three-dimensional optical scanning apparatus including a light source, an optical transmission lens for determining a divergence angle of light emitted from the light source, A first beam splitter for separating the light beam into an internal reference signal light and an internal reference signal light, a transmission part reflector for changing the path of light transmitted to the target from the first beam splitter, A receiving reflector for refracting the refracted light refracted by the rotating reflector, a light receiving lens for focusing the reflected light refracted by the receiving reflector, a light receiving lens for receiving the focused light from the light receiving lens, An optical fiber for an external path that emits light after delaying the laser beam emitted from the optical fiber for external path, An optical signal generator for receiving a plurality of optical signals having different optical intensities, and a photodetector for converting signals generated in the optical signal generator into electrical signals.

The optical signal generator according to an embodiment of the present invention includes a second beam splitter for separating the light emitted from the optical fiber for external path, a second beam splitter for receiving a part of the light separated by the second beam splitter, And an infinite feedback optical fiber that receives another part of the light separated by the second beam splitter and re-emits it to the second beam splitter after a predetermined time delay.

According to another aspect of the present invention, there is provided an optical scanning method including separating light emitted from a light source into light emitted to a target by a first beam splitter and light emitted to an optical fiber for an internal optical path, A step of irradiating the laser light emitted from the optical fiber for external optical path to the optical fiber for signal detection by the second beam splitter, Separating the light incident on the infinite feedback optical fiber into the optical fiber for signal detection by the second beam splitter, re-entering the optical fiber and the light re-emitted to the optical detector, The laser light emitted from the optical fiber for signal detection is converted into an electrical signal by the optical detector Selecting an electric signal within a signal intensity range that does not cause a distance measurement error among electric signals, and calculating a distance by measuring a round trip time based on the electric signal.

The time delay compensation apparatus according to an embodiment of the present invention further includes an optical fiber winding unit for winding the first optical delay element and the second optical delay element.

According to an embodiment of the present invention, since the infinite feedback optical fiber of the light amount control unit repeatedly passes the infinite feedback optical fiber of the light amount control unit to select a signal corresponding to the light intensity within a predetermined range, It is possible to compensate the time error according to the difference of reflected light intensity within a short time according to different reflectance for each point of the target regardless of the temperature change.

1 is a block diagram showing a schematic configuration of a distance measuring apparatus according to the prior art,
FIG. 2 is a diagram showing a schematic configuration of a three-dimensional optical scanning apparatus according to an embodiment of the present invention,
FIG. 3 is a partially enlarged view showing a light amount adjusting unit of a three-dimensional optical scanning apparatus according to an embodiment of the present invention,
4 is a block diagram illustrating a three-dimensional optical scanning method according to an embodiment of the present invention.
5 is a timing chart of a start signal and a stop signal of a three-dimensional optical scanning apparatus according to an embodiment of the present invention,
6 is a conceptual diagram illustrating a horizontal scan and a vertical scan of a three-dimensional optical scanning apparatus according to an embodiment of the present invention.

Hereinafter, a three-dimensional optical scanning apparatus and method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram showing a schematic configuration of a three-dimensional optical scanning apparatus according to an embodiment of the present invention.

3 is a partially enlarged view showing a light amount adjusting unit of a three-dimensional optical scanning apparatus according to an embodiment of the present invention.

As shown in FIGS. 2 and 3, the three-dimensional optical scan includes an optical transmitter, a light receiver, a light amount controller, and an optical signal generator.

The optical transmission unit includes a light source 110 that emits light such as a laser beam, an optical transmission lens 120 that determines the beam divergence angle so that the laser beam can reach the target with a small beam size, A first beam splitter 130 for separating the external laser light transmitted to the target and the internal reference signal laser light for canceling the temperature inside the laser scanning equipment and accordingly the unstable electronic signal processing time error, And a rotating reflector 150 for determining the emitting direction of the laser beam so that the emitted laser beam rotates in the vertical or horizontal direction and can scan the target and receives the laser beam reflected from the target, .

The light receiving unit includes a receiving unit reflector 210 refracting the reflected laser light refracted by the rotating reflector 150, a light receiving lens 220 focusing the reflected laser light refracted by the receiving unit reflector 210, a light receiving lens 220 And an optical fiber 230 for an external path for emitting light after delaying the optical fiber by a length corresponding to the length of the optical fiber so as not to interfere with the internal reference optical signal partially used in the laser transmitting unit.

The optical power controller includes an optical signal generator 310 for receiving the laser light emitted from the optical fiber for external path and generating a plurality of optical signals having different optical intensities, Gt; 320 < / RTI >

The photodetector 320 may use, for example, an Avalanche Photo Diode (APD).

3, the optical signal generating unit 310 includes a second beam splitter 311 for separating the laser light emitted from the optical fiber for external path 230, and a second beam splitter 311 for separating A signal detecting optical fiber 312 for receiving a part of the laser beam split by the second beam splitter 311 and emitting the part of the laser beam split by the second beam splitter 311 to the photodetector 320, And an infinite feedback optical fiber 313 which re-emits the laser beam 311.

The operation of optical scanning according to an embodiment of the present invention will be described as follows.

First, in order to measure the distance of a point of the target, the laser emitted from the light source 110 passes through the optical transmission lens 120 and proceeds in parallel. The laser beam proceeding to the parallel light by the optical transmission lens 120 is separated by the first beam splitter 130, and a part of the laser beam proceeds to the transmission mirror 140. In this case, the reflection mirror 140 of the transmitter reflects the optical axis of the optical transmission lens 120 and the optical axis of the optical reception lens 220. The parallel laser light refracted by the transmitting part reflector 140 is transmitted to the outside by the rotating reflector 150.

Meanwhile, another part of the laser beam separated by the first beam splitter 130 is incident on the photodetector 320 via the optical fiber 240 for internal optical path. The laser light having passed through the internal light path is converted into an electric signal by the photodetector 320 and is used to cancel the time error caused by the optical path inside the three-dimensional scan.

The laser light reflected from the target is again incident on the inside of the three-dimensional optical scan by the rotating mirror 150, the optical path is refracted by the receiving part reflector 210, and is incident on the light receiving lens 220. The laser light refracted by the receiving part reflector 210 is converged by the light receiving lens 220 and is incident on the optical fiber 230 for external optical path. The laser light incident on the external optical path optical fiber 230 has a length which is constant enough to avoid interference with the laser light incident on the internal optical path optical fiber 240 used for canceling the optical path error.

A process in which a plurality of optical signals are generated by the light amount controller based on the reflected light at one point of the target will be described in detail with reference to FIGS. 4 and 5. FIG.

FIG. 4 is a block diagram illustrating a three-dimensional optical scanning method according to an embodiment of the present invention, and FIG. 5 is a timing chart of a start signal and a stop signal of a three-dimensional optical scanning apparatus according to an embodiment of the present invention.

The laser beam emitted from the optical fiber for external optical path 230 is separated by the second beam splitter 311. The separation ratio may be, for example, linear light: reflected light = 50%: 50%.

A part of the separated laser beam is incident on the signal detecting optical fiber 312 and is emitted to the photodetector 320. Another part of the separated laser beam is incident on the infinite feedback optical fiber 313 and is emitted after a predetermined time delay.

The laser beam emitted from the infinite feedback optical fiber 313 is separated again by the second beam splitter 311. A part of the re-separated laser beam is incident on the signal detecting optical fiber 312 and is emitted to the photodetector 320. The other part of the re-separated laser beam is re-incident on the infinite feedback optical fiber 313, And then released.

This process is repeated a number of times, and the laser light reflected at the same point of the target is converted into a plurality of optical signals by the light amount adjusting unit 310.

The photodetector 320 receiving the laser beam emitted from the signal detection optical fiber 312 converts the laser beam into an electrical signal.

The photodetector 320 selects an electric signal within a signal intensity range that does not generate a distance measurement error among a plurality of electric signals by converting a plurality of optical signals for one point of the target into a plurality of electric signals, And the distance is calculated by measuring the round trip time.

As shown in FIG. 5, if the intensity of the laser beam emitted from the optical fiber 230 for external path is 100%, the intensity of the laser beam input to the optical detector is 50%. The intensity of the laser light input to the second photodetector is 25%, the intensity of the third laser light is 12.5%, and the intensity of the fourth laser light is 6.25%.

At this time, the measurement time can be compensated as follows.

Tm: Measurement time between start signal and stop signal

Td: Time when the laser beam passes through the infinite feedback optical fiber

n: the n-th generation optical signal

T: Round trip time to target

6 is a conceptual diagram illustrating a horizontal scan and a vertical scan of a three-dimensional optical scanning apparatus according to an embodiment of the present invention. As shown in FIG. 2 and FIG. 5, when the vertical rotation mechanism 410 is operated to measure a distance to one point of the target and then proceed to a vertical scan measuring the distance to another vertical point of the target, The rotary reflector 150 rotates to measure the distance to another vertical point of the target in this manner.

Next, in order to proceed with the horizontal scanning for measuring the distance to the other horizontal point of the target, the horizontal rotating mechanism 420 causes the three-dimensional scanning device body to rotate horizontally and the rotating mirror 150 to rotate horizontally together, The distance to the other horizontal point is measured in the same manner as described above. When the vertical scan and the horizontal scan are completed, a three-dimensional scan of the target is completed.

The present invention has been described above with reference to the preferred embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be understood from an illustrative point of view, not from a restrictive perspective. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

4: distance calculation unit 27: optical delay element
25: light mixer 26:
110: light source 120: optical transmission range
130: First beam splitter 140: Transmitter reflector
150: rotating reflector 210: receiving part reflector
220: light receiving lens 230: optical fiber for external path
240: Optical fiber for internal path 310: Optical signal generator
311: second beam splitter 312: signal detecting optical fiber
313: Infinite feedback optical fiber 320: Photodetector
410: vertical rotating mechanism 420: horizontal rotating mechanism

Claims (7)

In a three-dimensional optical scanning apparatus,
Light source;
An optical transmission lens for determining a divergence angle of the light emitted from the light source;
A first beam splitter for separating light passing through the optical transmission lens into external light and internal reference signal light transmitted to a target;
A transmitter mirror for changing a path of light transmitted from the first beam splitter to a target;
A rotating reflector that rotates in a vertical or horizontal direction and determines a direction of light emission so as to scan the target and receives light reflected from the target;
A receiving part reflector for refracting reflected light refracted by the rotating reflector;
A light receiving lens for focusing the reflected light refracted by the receiver mirror;
An optical fiber for external path for receiving light focused by the light receiving lens, delaying the light for a predetermined time and emitting light;
An optical signal generating unit receiving a laser beam emitted from the optical fiber for external path and generating a plurality of optical signals having different optical intensities; And
And a photodetector for converting the signal generated by the optical signal generator into an electrical signal. 2. The optical transmitter of claim 1, wherein the optical signal generator
A second beam splitter for separating light emitted from the optical fiber for external path;
An optical fiber for signal detection for receiving a part of the light separated by the second beam splitter and emitting it to the photodetector; And
And an infinite feedback optical fiber that receives another portion of the light separated by the second beam splitter and re-emits the light to the second beam splitter after a predetermined time delay. 3. The method according to claim 1 or 2,
A vertical rotation mechanism connected to the rotary reflector for rotating a vertical scan to measure a distance to vertical points of the target; And
Further comprising a horizontal rotation mechanism rotating the body of the 3D scanning apparatus in a horizontal direction to rotate horizontally to measure the distance to the horizontal points of the target. The method of claim 3,
Wherein the light source is an Avalanche photodiode. In the optical scanning method,
Separating the light emitted from the light source into light emitted to the target by the first beam splitter and light emitted to the optical fiber for internal optical path;
Focusing the light reflected from the target and entering the optical fiber for external optical path;
Separating the laser light emitted from the optical fiber for external optical path into the light emitted into the optical detector and the light entering into the infinite feedback optical fiber by the second beam splitter;
Separating the light incident on the infinite feedback optical fiber into light that is re-incident on the signal detecting optical fiber by the second beam splitter and re-emitted to the optical detector and light that is re-incident on the infinite feedback optical fiber;
Receiving the laser light emitted from the signal detection optical fiber and converting the laser light into an electrical signal by a photodetector;
Selecting an electric signal within a signal intensity range that does not generate a distance measurement error among the electric signals; And
And calculating a distance by measuring a round trip time based on the selected electrical signal. 6. The method of claim 5,
Wherein the step of calculating the distance is calculated by the following equation.

Tm: Measurement time between start signal and stop signal
Td: Time when the laser beam passes through the infinite feedback optical fiber
n: the n-th generation optical signal
T: Round trip time to target The method according to claim 6,
Performing a vertical scan to measure a distance to vertical points of the target by a vertical rotating mechanism connected to a rotating reflector; And
And performing a horizontal scan to measure a distance to horizontal points of the target by a horizontal rotation mechanism connected to the body of the 3D scanning apparatus.

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