Self-focusing laser scanning projection device based on symmetrical defocus double detector
Technical field
The present invention relates to a kind of self-focusing laser scanning projection device based on symmetrical defocus double detector, in intelligence manufacture
In assembling process, the laser assisted for various parts is processed (such as composite laying, covering bore riveting, welding) and referred to
Show positioning assembling, realize that laser scan round projects by scanning galvanometer, the parts three-dimensional profile that will be driven by three-dimensional CAD digital-to-analogue
Profile laser wire frame accurate projection is shown in target processing and assembly area, belongs to advanced processing and manufacturing technology.
Background technology
Laser scanning projection's device be it is a kind of can be by parts to be processed or to be assembled, that is, workpiece to be projected
Three-dimensional profile profile by laser beam scan round project in a manner of be converted to laser wire frame and be shown in target processing and dress
With region, the region also known as projects and accepts region, so as to realize the accurate photoelectricity of various parts machinings and assembling auxiliary instruction
Instrument.
In existing laser scanning projection's device, as shown in figure 1, laser 1, focus module 2, Amici prism 3 are same successively
Axle arranges;Twin shaft scanning galvanometer 4 is set in the transmitted light light path of Amici prism 3;In the demarcation reflected light light path of Amici prism 3
Upper setting light intensity detection module 5;The light intensity electrical signal of light intensity detection module 5 is connected to the simulation of measurement control module 6
Signal input part;Computer 7 is connected with measurement control module 6 by USB port;Measure the focusing driving letter of control module 6
Number output end is connected to the accurate displacement mechanism 8 in focus module 2;The scanning drive signal output end for measuring control module 6 connects
The precision rotation angle mechanism 9 being connected in twin shaft scanning galvanometer 4.The measurement control module 6 is one piece of multifunctional data acquisition card, energy
Enough collections, storage and processing data, the processing include digital-to-analogue, analog-to-digital conversion.
Laser scanning projection's device is the focusing adjustment of scanning projection laser facula first in the course of the work.Swash
The scanning projection laser that light device 1 is emitted successively projects to projection by focus module 2, Amici prism 3 and twin shaft scanning galvanometer 4 and held
Region 10 is connect, by operating personnel's eye-observation and judges that the focus condition of the laser facula in region 10 is accepted in projection, passes through key
Accurate displacement mechanism 8 of the disk operation from measurement control module 6 into focus module 2 sends control signal, drives accurate displacement machine
Structure 8 is movable, and until the laser facula observed reaches minimum, it is accurate along focusing for optical axis direction farthest to ensure
Degree, complete the focusing adjustment of scanning projection laser facula.
It can be seen that prior art fails to be distributed come automatic feedback control using the light path of the demarcation reflected light of scanning projection laser
The focusing adjustment of scanning projection laser facula, the raising for focusing the degree of accuracy are extremely limited.
Next to that calculate the projected coordinate system (P-X of twin shaft scanning galvanometer 4PYPZP) and workpiece three-dimensional CAD digital-to-analogue to be projected
Digital-to-analogue coordinate system (O-XOYOZO) between transformational relation.
Because twin shaft scanning galvanometer 4 is precision corner device, it can not learn that the position in region 10 is accepted in projection, can not determine
Where reflect the laser wire frame 16 of parts three-dimensional profile contour feature to be projected should be scanned projection.This is just it needs to be determined that throw
Shadow accepts the position in region 10, and establishes the D coordinates value of arbitrfary point in workpiece three-dimensional CAD digital-to-analogue to be projected and swept with twin shaft
The corresponding relation of the vertical scanning mirror 12 and the scan angle angle value of horizontal scan mirror 13 in galvanometer 4 is retouched, that is, establishes twin shaft scanning
Projected coordinate system (the P-X of galvanometer 4PYPZP) with the digital-to-analogue coordinate system (O-X of workpiece three-dimensional CAD digital-to-analogue to be projectedOYOZO) between turn
Change relation.
The needs resolved according to equation with many unknowns, the scanning mark that 4 to 6 irregular distributions are chosen in region 10 is accepted in projection
Positioning is put, and each scanning calibration position is in digital-to-analogue coordinate system (O-XOYOZO) in three-dimensional coordinate be known.Each swept described
Retouch and a back-reflection cooperative target 11 is respectively arranged in calibration position, demarcated for scanning.Swept by what measurement control module 6 was sent
Drive signal is retouched by driving two precision rotation angle mechanisms 9 in twin shaft scanning galvanometer 4 to drive respectively in twin shaft scanning galvanometer 4
Vertical scanning mirror 12 and horizontal scan mirror 13, the reflective areas of scanning back-reflection cooperative target 11, one of scanning projection laser
Divide and reflected by back-reflection cooperative target 11, returned as demarcation reflected light along original optical path, light intensity is totally reflected to by Amici prism 3
Detecting module 5, converged on photodetector 15 by convergence object lens 14 in light intensity detection module 5, entered by photodetector 15
Row opto-electronic conversion obtains light intensity electric signal, and sends measurement control module 6 to.Control module 6 is measured according to light intensity value of electrical signals
And the 13 respective deflection angle of vertical scanning mirror 12 and horizontal scan mirror when obtaining the light intensity electric signal, detect a back of the body
To the light intensity peak region of the reflective areas of reflection cooperative target 11, the regional center point is exactly the scanning calibration position, thirdly
Dimensional coordinate values are corresponding with a pair of deflection angle angle value, and the high accuracy scanning for completing a center of back-reflection cooperative target 11 is fixed
Position.Said process is repeated, the reflective areas of each back-reflection cooperative target 11 is scanned one by one, obtains each group three-dimensional coordinate
Value and deflection angle angle value, it thus can accurately calculate the projected coordinate system (P-X of twin shaft scanning galvanometer 4PYPZP) and work to be projected
Digital-to-analogue coordinate system (the O-X of part three-dimensional CAD digital-to-analogueOYOZO) between transformational relation.
It can be seen that, if it is possible to strengthen the transverse resolution of the automatic search sweep of light intensity of laser scanning projection's device, it will
More accurately calculate the projected coordinate system (P-X of twin shaft scanning galvanometer 4PYPZP) with the digital-to-analogue of workpiece three-dimensional CAD digital-to-analogue to be projected
Coordinate system (O-XOYOZO) between transformational relation.
Finally, the three-dimensional profile profile for completing workpiece to be projected accepts the laser scanning projection in region 10 in projection.It will treat
Projection workpiece three-dimensional CAD digital-to-analogue is imported into measurement control module 6, position, chi in workpiece three-dimensional CAD digital-to-analogue to be projected
The contour feature information such as very little and shape, accurately deflection and the Rapid Circulation scanning of driving twin shaft scanning galvanometer 4, by three-dimensional CAD digital-to-analogue
The definition that the contour feature information such as position, size and dimension to workpiece to be projected is done, and according to described two coordinate systems
Transformational relation, during the three-dimensional profile profile of workpiece to be projected is circulated including accepting region 10 in projection exactly, form laser
Wire frame 16.
It is it can be seen that in actual applications that the parts three-dimensional profile profile laser wire frame driven by three-dimensional CAD digital-to-analogue is accurate
Projection Display is processed in target and assembly area, this quality factor for influenceing scanning projection positional accuracy are scanning projection laser
Focusing, its influence to scanning projection positional accuracy are presented with following two aspect:
First, the line width for the laser wire frame 16 that laser scanning projection goes out, i.e., be scanned projection in region 10 is accepted in projection
When, minimum dimension that laser facula can reach.Scanning projection laser line focus module 2 is in region 10 is accepted in projection along optical axis
Direction focuses that the degree of accuracy is higher, the size of laser facula with regard to smaller, the laser wire frame 16 of laser facula scan round projection
Line width is narrower, accurately secondary process and instruction can more assemble;
Second, Scan orientation precision of the twin shaft scanning galvanometer 4 to the center of back-reflection cooperative target 11.Work as laser light
Spot size is smaller, and transverse resolution of the laser facula in the automatic search sweep of progress light intensity in back-reflection cooperative target 11 is just
Stronger, twin shaft scanning galvanometer 4 can just carry out finer scanning with smaller sweep spacing, meanwhile, light intensity detection module 5
The intensity signal of the demarcation reflected lights of more scanning calibration positions can be obtained, also just can more accurately be obtained and back-reflection
A pair of deflection angle angle value corresponding to the center of cooperative target 11, and then calculate more accurately coordinate system transformational relation.
The optical maser wavelength that laser 1 in existing laser scanning projection's device is emitted is 532nm, back-reflection cooperation
The a diameter of 6mm in reflective areas of target 11, reflectorized material is glass microballoon, and optimal laser scanning projection's orientation distance is 3~5m,
5m apart from when a width of 0.5mm of laser scanning design lines, laser scanning projection's positional accuracy is defined as the half line of laser beam
Width, positional accuracy 0.25mm.
The content of the invention
It is it is an object of the present invention to true in the scanning accuracy of twin shaft scanning galvanometer 4 and the control accuracy of measurement control module 6
On the premise of fixed, the focus degree of accuracy of the scanning projection laser of the outgoing of laser 1 along optical axis direction is further improved, obtains size
Minimum laser facula, and improve the transverse resolution of the automatic search sweep of light intensity, therefore, we have invented one kind based on pair
Claim the self-focusing laser scanning projection device of defocus double detector.Because the positional accuracy of laser scanning projection is with laser half line
Width definition, therefore, the raising for focusing the degree of accuracy directly determines the raising of the positional accuracy of laser scanning projection;Due to
The transverse resolution of the automatic search sweep of light intensity is directly connected to projected coordinate system (P-XPYPZP) and digital-to-analogue coordinate system (O-
XOYOZO) transformational relation resolving accuracy, therefore, the raising of transverse resolution equally also directly determines laser scanning projection
Positional accuracy raising.
As shown in Fig. 2 its composition of the self-focusing laser scanning projection device based on symmetrical defocus double detector of the present invention
Part includes, and laser 1, twin shaft scanning galvanometer 4, measurement control module 6, computer 7, computer 7 connect with measurement control module 6
Connect;The scanning drive signal output end of measurement control module 6 is connected to the precision rotation angle mechanism 9 in twin shaft scanning galvanometer 4, described
It is one piece of multifunctional data acquisition card to measure control module 6;Characterized in that, laser 1, beam-expanding collimation microscope group 17, dynamically from
Focus module 18, polarization splitting prism 19, quarter wave plate 20 sequentially coaxially arrange;In the scanning transmission light of polarization splitting prism 19
In light path, and twin shaft scanning galvanometer 4 is set after quarter wave plate 20;In the demarcation reflected light light path of polarization splitting prism 19
Symmetrical defocus double detector light intensity detection module 21 is set;In symmetrical defocus double detector light intensity detection module 21, it is being divided
One group of convergence object lens 14, point detecting pinhole 23 and photodetector 15, point detection are respectively equipped with the transmission of prism 22, reflected light path
Between convergence object lens 14 and photodetector 15, the photosurface of two photodetectors 15 is respectively relative to each pin hole 23
14 defocus of corresponding convergence object lens+Δ Z ,-Δ Z;The respective light intensity electrical signal of two photodetectors 15 connects respectively
To two light intensity input end of analog signal of measurement control module 6;Measure the focusing driving signal output end connection of control module 6
To the accurate displacement mechanism 8 in dynamic self-focusing module 18.
If any one in two photodetectors 15 is located at rear focus, the axial intensity response curve detected
For the axial intensity response curve at rear focus, i.e. curve 0 in Fig. 3;Actually two photodetectors 15 separately detect
To axial intensity response curve to deviate at rear focus-Δ Z and deviateing the axial intensity response curve at rear focus+Δ Z,
That is curve 1 and curve 2 in Fig. 3.From the point of view of now, with zero point O, the light intensity value of curve 1 and curve 2 just corresponds to the light of curve 0
About 0.707 times of intensity values, and the light intensity for demarcating reflected light is maintained at the atomic weak magnitude of tens of micromicrowatts (pW) originally, seems this
The effect of invention is run counter to desire, however, on this condition, can by difference and plus and in a manner of be controlled, it is pre- so as to obtain
Phase effect.
The light intensity signal of curve 1 and curve 2 is subtracted each other point by point by measurement control module 6, obtains the response of difference axial intensity
Curve 3 in curve, i.e. Fig. 3, curve 3 are accurately corresponding in zero point O and the peak point P of curve 0.Slope of the curve 0 near P points connects
It is bordering on zero, that is, change of the change to the displacement of accurate displacement mechanism 8 of light intensity value is insensitive, even if controlling mould by measurement
Block 6 sends feedback control signal according to curve 0 to dynamic self-focusing module 18, controls accurate displacement mechanism 8 therein to realize and sweeps
The axial self-focusing of projection laser hot spot is retouched, rather than eye-observation manual focusing, scanning projection laser focus along optical axis direction
The degree of accuracy still is difficult to improve.Although curve 3 is zero in zero point O light intensity, curve 3 zero point O maximum slope,
That is change maximum with axial displacement light intensity herein, and it is so far visible, using curve 3 and this particular kind of relationship of curve 0, by surveying
Measure control module 6 and send feedback control signal to dynamic self-focusing module 18, control accurate displacement mechanism 8 therein to realize scanning
The axial self-focusing of projection laser hot spot, existing eye-observation manual focusing mode, and axial focusing essence can not only be substituted
Degree can be improved significantly.
Curve 1 is added point by point with the light intensity signal of curve 2 by measurement control module 6, obtains plus is responded with axial intensity
Curve 4 in curve, i.e. Fig. 3;The peak point P " of curve 4 is corresponding with the peak point P of curve 0, and the peak value of curve 4 is about curve 0
1.414 times of peak value, therefore, compared to existing simple detector laser scanning projection apparatus and method, the present invention can be to backwards
Reflection cooperative target 11 carry out high-precision transversal scanning positioning, so as to it is sensitiveer, more accurately establish projected coordinate system
(P-XPYPZP) and digital-to-analogue coordinate system (O-XOYOZO) between transformational relation.
It can be seen that differential type light intensity detection method is combined by the present invention with plus with formula light intensity detection method, takes into account raising and swash
The axial direction of optical scanning projection arrangement focuses ability and transversal scanning resolution capability.
Beam-expanding collimation microscope group 17 is set to improve the numerical aperture 3 to 5 of the focusing microscope group in dynamic self-focusing module 18
Times.According to convergence object lens imaging theory, its spot diameter d is drawn by following formula:
In formula:λ is optical maser wavelength, and nsin α are the numerical aperture of convergence microscope group.It can be seen that the numerical value of increase convergence microscope group
Aperture, the theoretical diameter of convergence hot spot can be reduced.When laser wavelength lambda is 532nm, the operating distance for converging microscope group is 4600mm
When, convergence microscope group combined focal length is about 2500mm or so, and effective aperture of the laser light incident in convergence microscope group is 12mm, can be calculated
The theoretical diameter for obtaining Airy disc is about 0.27mm, it is meant that the theory orientation degree of accuracy brings up to 0.135mm.Limited scanning projects
Laser spot size, the subsidiary effect for improving scanning projection laser facula convergence quality is scanning projection laser spot size
It is smaller, the size of the reflective areas in the back-reflection cooperative target 11 can be reduced therewith, be such as decreased to 4~5mm, this just anticipates
Taste, which, to carry out accurate laser scanning projection in more compact, narrower projection undertaking region 10, and therefore can be expanded
Open up the application field of the present invention.
Brief description of the drawings
Fig. 1 is the structural representation of existing laser scanning projection's device.
Fig. 2 is the self-focusing laser scanning projection apparatus structure schematic diagram based on symmetrical defocus double detector of the present invention.
Fig. 3 is the axle obtained using the self-focusing laser scanning projection device based on symmetrical defocus double detector of the present invention
To Intensity response curve map, vertical pivot is light intensity I, and transverse axis is axially to normalize coordinate u, in figure:
Curve 0 is the axial intensity response curve that detector is located at rear focus;
Curve 1 is the axial intensity response curve that detector is located off at rear focus-Δ Z;
Curve 2 is the axial intensity response curve that detector is located off at rear focus+Δ Z;
Curve 3 is difference axial intensity response curve;
Curve 4 is to add and axial intensity response curve.
Embodiment
As shown in Fig. 2 its composition of the self-focusing laser scanning projection device based on symmetrical defocus double detector of the present invention
Part includes, and laser 1, twin shaft scanning galvanometer 4, measurement control module 6, computer 7, computer 7 connect with measurement control module 6
Connect;The scanning drive signal output end of measurement control module 6 is connected to the precision rotation angle mechanism 9 in twin shaft scanning galvanometer 4, described
It is one piece of multifunctional data acquisition card to measure control module 6.
Laser 1, beam-expanding collimation microscope group 17, dynamic self-focusing module 18, polarization splitting prism 19, quarter wave plate 20 are successively
Arranged in co-axial alignment.
Beam-expanding collimation microscope group 17 can compress the angle of divergence for the scanning projection laser for coming from laser 1, and expand to connecing
Convergence microscope group in nearly dynamic self-focusing module 18 expires the state of pupil, increases convergence microscope group in dynamic self-focusing module 18
Numerical aperture, and then limited scanning projection laser is irradiated to the spot size on projection undertaking region 10.In beam-expanding collimation microscope group
Illumination pin hole 24 is set in 17 so that the laser that laser 1 is sent is worked in a manner of an illumination, while is eliminated veiling glare and done
Disturb, improve beam quality, further reduce spot size, obtained in region 10 is accepted in projection and more preferably converge hot spot.
In dynamic self-focusing module 18, focusing lens 25 is installed in accurate displacement mechanism 8, realizes the axial direction of scanning projection laser facula
Self-focusing.Focusing microscope group in dynamic self-focusing module 18 is retrofocus type microscope group so that laser scanning projection's orientation distance model
Enclose and reach 1~10m, still, this can cause the numerical aperture for focusing on microscope group to reduce, and about 10-3, but, due to beam-expanding collimation mirror
The presence of group 17 can be made up.
In the scanning transmission light light path of polarization splitting prism 19, and twin shaft scanning galvanometer is set after quarter wave plate 20
4.Symmetrical defocus double detector light intensity detection module 21 is set in the demarcation reflected light light path of polarization splitting prism 19.With it is inclined
Trap is set to converge object lens 26 and notch filter 27 in the opposite light path of the Amici prism 19 that shakes demarcation reflected light light path, for disappearing
Except interference of stray light.In symmetrical defocus double detector light intensity detection module 21, in the transmission, reflected light path in Amici prism 22
Respectively be equipped with one group of convergence object lens 14, point detecting pinhole 23 and photodetector 15, point detecting pinhole 23 positioned at convergence object lens 14 with
Between photodetector 15, the photosurfaces of two photodetectors 15 be respectively relative to each self-corresponding convergence object lens 14 defocus+
ΔZ、-ΔZ;The respective light intensity electrical signal of two photodetectors 15 is connected respectively to two of measurement control module 6
Light intensity input end of analog signal.The focusing driving signal output end of measurement control module 6 is connected in dynamic self-focusing module 18
Accurate displacement mechanism 8.