KR101640348B1 - Apparatus of high precision optical scanning - Google Patents

Apparatus of high precision optical scanning Download PDF

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KR101640348B1
KR101640348B1 KR1020150115502A KR20150115502A KR101640348B1 KR 101640348 B1 KR101640348 B1 KR 101640348B1 KR 1020150115502 A KR1020150115502 A KR 1020150115502A KR 20150115502 A KR20150115502 A KR 20150115502A KR 101640348 B1 KR101640348 B1 KR 101640348B1
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South Korea
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scan
mirror
scan mirror
signal
scanning
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KR1020150115502A
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Korean (ko)
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김태근
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세종대학교산학협력단
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G02B26/105—Scanning systems with one or more pivoting mirrors or galvano-mirrors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
    • G02B27/0031—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration for scanning purposes

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  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Optical Scanning Systems (AREA)

Abstract

The present invention relates to a high precision optical scanning apparatus. According to the present invention, the high precision optical scanning apparatus comprises: an optical coupler to receive a beam generated from a first light source to split the beam into a first beam and a second beam, and emit the first beam to a portion of a scan mirror for optically scanning a target object; a reference mirror to which the second beam split by the optical coupler is emitted; an optical detector to detect an interference signal between the first beam and the second beam reflected from the scan mirror and the reference mirror to enter the optical coupler again; a correction signal generation unit to generate a voltage signal corresponding to a time difference between a starting point of a scanning position control signal of the scan mirror and a detection time point of the interference signal; a drive signal generation unit to generate a frequency signal corresponding to the voltage signal; and an optical refractor which is positioned between a second light source to generate a scan beam for optically scanning the target object and the scan mirror, and refracts the scan beam to an angle corresponding to the frequency signal to emit the scan beam to the scan mirror. According to the high precision optical scanning apparatus, an interferometer structure is used to detect a jitter by the scan mirror with high precision at a high speed and optically change a light path according to a magnitude of the detected jitter in real time to compensate and offset a jitter problem by mechanical vibration of the scan mirror in real time during optical scanning.

Description

[0001] Apparatus of high precision optical scanning [0002]

The present invention relates to an ultra-precise optical scanning apparatus, and more particularly, to an ultra-precise optical scanning apparatus capable of compensating for jitter caused by mechanical vibration of a scan mirror.

The optical scanning system irradiates light by rotating the scan mirror to perform optical scanning. Here, the higher the size and resolution of the object to be scanned, the faster the rotation speed of the scan mirror, and it is necessary to operate at a high speed.

Generally, in the conventional optical scanning system, a jitter problem occurs due to the mechanical vibration of the scan mirror, and therefore, there is a limit in designing an accurate position and scanning.

Since the jitter is caused by the microscopic vibration of the mirror, it is impossible to accurately detect the jitter by the conventional electronic method. Even if the jitter is detected, the light path can be corrected in real time according to the jitter detected by the electronic method There was no.

The technology of the background of the present invention is disclosed in Korean Patent No. 0318736 (published on Dec. 28, 2001).

An object of the present invention is to provide an ultra-precise optical scanning apparatus capable of real-time compensation of jitter caused by a scan mirror.

The present invention relates to an optical pickup apparatus which includes a first optical pickup unit for dividing a beam generated from a first light source into a first beam and a second beam and for irradiating the divided first beam to a part of a scan mirror for performing optical scanning of an object, A photodetector for detecting an interference signal between a first beam and a second beam reflected from the scan mirror and the reference mirror and re-incident to the optical coupler, A correction signal generator for generating a voltage signal corresponding to a time difference between a start point of a scanning position control signal of the scan mirror and a detection time point of the interference signal and a drive signal generator for generating a frequency signal corresponding to the voltage signal, And a second mirror positioned between the scan mirror and a second light source for generating a scan beam for optical scanning of the object, the scan beam corresponding to the frequency signal It is provided by refraction at an angle to the optical scanning device comprising an optical refraction of irradiation to the scan mirror.

Here, the scan mirror corresponds to the horizontal scan mirror among the vertical scan mirrors that scan the object using the horizontal scan mirror irradiated with the scan beam and the scan beam reflected from the horizontal scan mirror, The signal may correspond to a horizontal scanning position control signal for controlling the horizontal scanning mirror.

The optical refractor may cancel the jitter caused by the horizontal scan mirror by refracting the angle of the scan beam irradiated to the horizontal scan mirror at an angle corresponding to the time difference.

The correction signal generator may calculate the time difference by counting the time point of detection of the interference signal from the starting point of the scanning position control signal, and generate the voltage signal proportional to the time difference.

The optical coupler may irradiate the first beam to a part of the horizontal scanning mirror, and irradiate the first beam to a part different from the part irradiated with the scan beam.

The driving signal generator may include a voltage controlled oscillator (VCO) that generates an oscillation frequency proportional to the voltage signal.

According to the ultra-precise optical scanning apparatus according to the present invention, a jitter caused by a scan mirror is detected at an extremely high speed and a very high precision using an interferometer structure, and the optical path is changed in real time according to the size of the detected jitter, It is possible to compensate for the jitter caused by the mechanical vibration of the scan mirror during the optical scanning in real time and offset it.

1 is a configuration diagram of an ultra-precise optical scanning apparatus according to an embodiment of the present invention.
2 is a view for explaining a scanning position control signal applied to the scan mirror shown in FIG.
3 is a view illustrating a light path compensated through a light refractor shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

The present invention relates to an ultra-precise optical scanning apparatus, and more particularly, to a scanning optical apparatus for scanning an object, And the jitter problem can be canceled by changing the scan beam path in real time in accordance with the detected jitter size.

1 is a configuration diagram of an ultra-precise optical scanning apparatus according to an embodiment of the present invention. The optical scanning apparatus 100 includes a first light source 110, an optical coupler 120, a reference mirror 130, a photodetector 140, a correction signal generator 150, A generating unit 160, and a light refractor 170.

The first light source 110 provides a monitoring beam to the optical coupler 120 for monitoring jitter by the scan mirror 20 in an embodiment of the present invention. This monitoring beam substantially corresponds to an element separate from the scan beam by the second light source 10 used for optical scanning of the object.

In the case of the second light source 20, a laser beam or the like is generated, and a scan beam for scanning an object is generated to directly irradiate the scan mirror 20. The monitoring beam generated by the first light source 110 is split into two beams through the interferometer, i.e., the optical coupler 120, and then irradiated onto the scan mirror 20 and the reference mirror 130, respectively. The first light source 110 is preferably a broadband light source for ultra-precision jitter detection.

The optical coupler 120 receives the beam generated from the first light source 110 and divides the beam into a first beam and a second beam. The first beam split at the optical coupler 120 is irradiated to a part of the scan mirror 20 and the second beam split at the optical coupler 120 is irradiated to the reference mirror 130. A lens or the like may be added to the front end of each mirror for the focusing efficiency of the incident light.

The scan mirror 20 is basically an element that optically scans an object using a scan beam generated from the second light source 10. The scan mirror 20 is divided into a horizontal scan mirror 21 and a vertical scan mirror 22. The horizontal scan mirror 21 is directly scanned with the scan beam and the vertical scan mirror 22 is an element that scans an object (not shown) using a scan beam reflected from the horizontal scan mirror 21.

The technique of optically scanning the object in the horizontal and vertical directions by individually controlling the rotation of the horizontal scanning mirror 21 and the vertical scanning mirror 22 is a well-known method, and a detailed description thereof will be omitted.

Referring to FIG. 1, the first beam divided by the optical coupler 120 is irradiated to a portion of the substantially horizontal scan mirror 21, specifically, a portion irradiated with the scan beam by the second light source 10 (Ex, edge or edge portion of the horizontal scanning mirror 21) is irradiated to the other portion (ex, the edge of the horizontal scanning mirror 21).

Since the irradiation positions of the first beam (monitor beam) and the scan beam to the horizontal scan mirror 21 are different from each other, even when two beams are simultaneously irradiated to the horizontal scan mirror 21, interference between beams does not occur, It is possible to monitor the size of the jitter in real time using the monitoring beam during optical scanning of the object by the scan beam and real time correction of the jitter is possible.

In an embodiment of the present invention, the optical coupler 120 provides a first beam (monitoring beam) and a second beam to the horizontal scan mirror 21 and the reference mirror 130, respectively, The size of the jitter is detected. The reason why the jitter is detected using the beam reflected from the horizontal scan mirror 21 among the scan mirrors 20 will be described in detail as follows.

The scan mirror 20 generally operates by receiving a scanning position control signal from a scan control unit (not shown). That is, the rotation of the scan mirror 20 is controlled in accordance with the scanning position control signal. Here, the scanning position control signal is divided into a horizontal scanning position control signal for controlling the horizontal scanning mirror 21 and a vertical scanning position control signal for controlling the vertical scanning mirror 22.

2 is a view for explaining a scanning position control signal applied to the scan mirror shown in FIG. Referring to FIG. 2, the horizontal scanning position control signal (solid line) is a control signal for sequentially moving the scan position in the horizontal direction (x-axis direction) by predetermined distance units, and includes a period T .

Since the vertical scanning position control signal (dotted line) is a control signal that enables the horizontal scanning operation for the next y position when the horizontal scanning operation in the x-axis direction for an arbitrary y position is completed, Lt; / RTI > Of course, the construction of such a scan control signal follows the well-known principles.

As shown in FIG. 2, the horizontal scan mirror 21 must be rotated very quickly corresponding to the period of the horizontal scanning position control signal, and jitter is caused by mechanical vibration or the like due to rapid movement. However, since the vertical scan mirror 22 moves much slower than it, it causes little jitter. Jitter may be difficult to scan at precise locations and may be a factor that reduces the accuracy and efficiency of scanning, so it needs to be corrected in real time during the optical scanning process.

The time difference? T shown in FIG. 2 corresponds to an element directly related to the jitter. In the embodiment of the present invention, the time difference element is used to compensate for the jitter in real time. This will be described in detail as follows.

First, the photodetector 140 detects an interference signal between the first beam and the second beam reflected from the scan mirror 20 and the reference mirror 130 and re-incident on the optical coupler 120. The interference signal indicates a signal observed while constructive interference occurs when the path length of the first beam re-incident on the optical coupler 120 and the path length of the second beam are equal to each other.

The optical coupler 120 splits and outputs the first beam and the second beam through the second port and the third port when the beam generated from the light source is input through the first port. The first beam and the second beam, And an interference signal between the beams can be outputted through the fourth port.

The photodetector 140 is connected to the fourth port of the optical coupler 120 to detect an interference signal. A lens or the like may be added to the front end of the photodetector 140 in order to detect an interference signal.

The interference signal is not generated at all, and occurs at the time when the reflected first beam and the reflected second beam arrive at the reference. That is, when the path length of the first beam (reference beam) reflected from the reference mirror 130 and the path length of the second beam reflected from the horizontal scan mirror 21 are the same, a constructive interference occurs and a corresponding interference signal is generated do.

Here, in the case of the embodiment of the present invention, it is assumed that the condition for not generating the jitter is that the start point of the horizontal scanning position control signal and the generation time of the interference signal have to be synchronized (synchronized). The initial setting of the actual system may be set to synchronize the two views, but a time difference may occur due to the shaking of the scan mirror during the actual operation.

The embodiment of the present invention is a method of comparing the detection point of the interference signal detected by the photodetector 140 with the start point of the horizontal scanning position control signal while the scan mirror 20 is controlled by the scanning position control signal, Check the occurrence and extent of occurrence. Of course, the large difference between the two points of comparison means that many jitter occurred.

The correction signal generator 150 calculates the time difference using the information of the scan controller (not shown) and the photodetector 140. Specifically, the correction signal generator 150 calculates the time difference between the start point of the scanning position control signal of the scan mirror 20, Calculates a time difference between detection times, and then generates a voltage signal corresponding to the time difference.

2, the correction signal generator 150 calculates a time difference? T between a start point of a horizontal scanning position control signal (a start point of one period) and a point at which the interference signal is detected and outputs the calculated time difference? T ) As a correction signal for canceling the jitter.

The correction signal generator 150 can identify the start point of each cycle configuring the corresponding control signal from the scan control signal received from the scan controller (not shown), that is, the horizontal scanning position control signal, The time difference can be obtained by a method of comparing the detection time of the obtained interference signal with the position of the starting point.

2, the time difference between the start point of the horizontal scanning position control signal of the first cycle and the detection time of the interference signal is represented by? T. It goes without saying that the time difference can be obtained by the same method in the next cycle. This time difference can be obtained by a method of counting the detection time of the interference signal from the starting point of the scanning position control signal.

If the time difference? T is equal to or greater than the predetermined error range, it is determined that the jitter compensation is necessary. If the time difference t is within the error range, it can be determined that the compensation of the jitter is unnecessary. The correction signal generator 150 generates the voltage signal v (? T) proportional to the time difference? T (v (? T)?) Since the larger the time difference? T, T).

The driving signal generating unit 160 generates a frequency signal corresponding to the voltage signal v (? T) and provides the frequency signal to the light refractor 170 as a driving signal. The driving signal generator 160 may include a voltage controlled oscillator (VCO) that generates an oscillation frequency proportional to the voltage signal v (? T). Here, the driving signal including the oscillation frequency can be defined as a time concept as shown in Equation (1) below.

Figure 112015079402316-pat00001

W v in Equation (1) means an oscillation frequency proportional to the voltage signal v (? T) (w v? V (? T)). As a result, it can be confirmed that the driving signal generator 160 generates a frequency signal proportional to the time difference? T.

The light refractor 170 is positioned between the second light source 10 and the horizontal scan mirror 21 and can be implemented as an acoustic light refractor. The optical refractor 170 refracts the scan beam generated by the second light source 10 at an angle corresponding to the frequency signal and irradiates the scan beam to the scan mirror 20.

3 is a view illustrating a light path compensated through the optical refractor shown in FIG. 3, the optical refractor 170 corrects the position of the scan beam with respect to the horizontal scan mirror 21 by adjusting the refraction angle according to the frequency signal supplied from the drive signal generator 160, Compensate for problems. Consequently, the optical refractor 170 cancels the jitter caused by the horizontal scan mirror 21 by refracting the angle of the scan beam irradiated on the horizontal scan mirror 21 at an angle corresponding to the time difference DELTA t .

Here, the greater the time difference? T, the greater the angle of refraction of the scan beam will be, and if the time difference? T is within the error range, the scan beam may be advanced without refraction as shown in FIG. Of course, in the embodiment of the present invention, it is possible to refract at a predetermined reference refraction angle if the time difference is within the error range, and to refract at an angle larger than the reference refraction angle if the time difference is more than the error range. The reference deflection angle may correspond to an angle of 0 degree or more.

In this embodiment of the present invention, the scan beam is refracted to a degree proportional to the drive signal to correct the position of the scan beam, and at the same time, the jitter is canceled. It is also possible to compensate for the jitter in real time by continuously performing this operation every period of the horizontal scanning control signal. In addition, the path of the corrected scan beam at the current point is immediately reflected at a later point in time, and can be corrected again through a time difference operation in the next period, so that the jitter can be corrected in real time And the scan beam refraction angle can also be corrected to gradually converge to a specific angle.

According to the present invention, an ultra-high precision optical scanning device detects jitter by a scan mirror using an interferometer structure at an extremely high speed and an ultra-high precision, and changes the scan beam path in real time according to the detected jitter size Accordingly, there is an advantage that the jitter problem due to the mechanical vibration of the scan mirror can be compensated and canceled in real time even during optical scanning.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

100: ultra-precise optical scanning device 110: first light source
120: Optocoupler 130: Reference mirror
140: photodetector 150: correction signal generator
160: drive signal generator 170: optical refractor

Claims (6)

An optical coupler for receiving a beam generated from the first light source and dividing the beam into a first beam and a second beam and irradiating the divided first beam to a part of the scan mirror for performing optical scanning of the object;
A reference mirror to which the second beam divided by the optical coupler is irradiated;
A photodetector for detecting an interference signal between the first beam and the second beam reflected from the scan mirror and the reference mirror and re-incident on the optical coupler;
A correction signal generation unit for generating a voltage signal proportional to a time difference between a start point of the scanning position control signal of the scan mirror and a detection time point of the interference signal;
A driving signal generator for generating a frequency signal proportional to the voltage signal; And
And a light refractor located between the second light source for generating a scan beam for optical scanning of the object and for refracting the scan beam at an angle proportional to the frequency signal and irradiating the scan mirror with the scan beam, Scanning device. The method according to claim 1,
Wherein the scan mirror comprises:
A vertical scan mirror for scanning the object using a horizontal scan mirror irradiated with the scan beam and a scan beam reflected from the horizontal scan mirror,
The scanning position control signal includes:
And a horizontal scanning position control signal for controlling the horizontal scanning mirror. The method of claim 2,
The optical refractor includes:
And refracts an angle of the scan beam irradiated to the horizontal scan mirror at an angle corresponding to the time difference to cancel a jitter caused by the horizontal scan mirror. The method of claim 2,
Wherein the correction-
Counts the time point of detection of the interference signal from a start point of the scanning position control signal to calculate the time difference, and generates the voltage signal proportional to the time difference. The method of claim 2,
The optical coupler includes:
Irradiating the first beam to a part of the horizontal scanning mirror and irradiating the first beam to a part different from a part irradiated with the scan beam. The method according to claim 1,
Wherein the drive signal generating unit comprises:
And a voltage controlled oscillator (VCO) that generates an oscillation frequency proportional to the voltage signal.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111273315A (en) * 2018-11-19 2020-06-12 百度（美国）有限责任公司 LIDAR device with polygon mirror and prism for autonomous vehicle
WO2023177847A1 (en) * 2022-03-18 2023-09-21 Calient Technologies, Inc. Optical scanning multiplexing devices and methods

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20010029299A (en) * 1999-09-30 2001-04-06 정광현 An Apparatus and a Method for Dynamic Laser Marking
JP2013140077A (en) * 2012-01-05 2013-07-18 Univ Of Tsukuba Swept source optical coherence tomograph and phase stabilization program for the same
KR20130135438A (en) * 2012-06-01 2013-12-11 한국생산기술연구원 Measuring apparatus using optical interferometer
JP2014228473A (en) * 2013-05-24 2014-12-08 国立大学法人 筑波大学 Jones matrix oct system and program for performing image processing of measurement data obtained by the oct

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20010029299A (en) * 1999-09-30 2001-04-06 정광현 An Apparatus and a Method for Dynamic Laser Marking
JP2013140077A (en) * 2012-01-05 2013-07-18 Univ Of Tsukuba Swept source optical coherence tomograph and phase stabilization program for the same
KR20130135438A (en) * 2012-06-01 2013-12-11 한국생산기술연구원 Measuring apparatus using optical interferometer
JP2014228473A (en) * 2013-05-24 2014-12-08 国立大学法人 筑波大学 Jones matrix oct system and program for performing image processing of measurement data obtained by the oct

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111273315A (en) * 2018-11-19 2020-06-12 百度（美国）有限责任公司 LIDAR device with polygon mirror and prism for autonomous vehicle
WO2023177847A1 (en) * 2022-03-18 2023-09-21 Calient Technologies, Inc. Optical scanning multiplexing devices and methods

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