CN102183214B - Method for optically detecting large-aperture aspherical mirror structure - Google Patents
Method for optically detecting large-aperture aspherical mirror structure Download PDFInfo
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- CN102183214B CN102183214B CN201110050685.7A CN201110050685A CN102183214B CN 102183214 B CN102183214 B CN 102183214B CN 201110050685 A CN201110050685 A CN 201110050685A CN 102183214 B CN102183214 B CN 102183214B
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Abstract
The invention relates to a method for optically detecting a large-aperture aspherical mirror structure. The method comprises the following steps of: displaying a structure characteristic pattern on a display screen, projecting the structure characteristic pattern on a detected mirror and reflecting the structure characteristic pattern, and shooting by a camera. By performing analysis process on a shot image, surface shape full information of the detected aspheric surface can be obtained. The large-aperture aspherical mirror has a simple structure; the method is convenient in use and high in sensitivity; no special requirement on the environment is needed; the method can be used for detecting in a workshop environment; an effective measure is provided for detection of large-aperture or relevant-large-aperture aspherical mirror; in particular, the method has wide application prospect in accurate grinding and polishing stages during manufacturing.
Description
Technical field
The present invention relates to a kind of optical detective technology, particularly a kind of detection method for heavy caliber aspherical mirror, belongs to advanced optics manufacture and detection technique field.
Background technology
So-called aspherical optical element, refers to that face shape is by the equal not identical optical element of the multinomial equation of higher degree determines, face shape is gone up each point radius.By aspheric surface for optical system, can minimizing system in the quantity of optical element maybe can improve image quality.Along with the development of optical precision processing, aspheric surface is applied in various optical systems more and more widely.The aspheric high-acruracy survey of the dark type of aspheric measurement especially heavy caliber is become to a present hot issue.Aspheric manufacture and detection technique are that the detection of two hang-ups, especially aperture aspherical of its widespread use of restriction is all the more so always for a long time.As everyone knows, aperture aspherical is the key point of the whole aspherical mirror machining efficiency of impact in the detection in fine grinding stage.
Summary of the invention
Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, a kind of method that provides structured light to detect heavy caliber aspherical mirror, has the dynamic range of measurement large, can once complete measurement of full field, simple in structure, cost is low, dirigibility high.
Technical solution of the present invention: a kind of heavy caliber aspherical mirror structured light detection method, its feature is: the measuring system of employing is comprised of video camera, display screen and computing machine; First carry out system calibrating, comprise that camera calibration, display screen are demarcated and measured lens is demarcated, obtain the spatial relation between video camera in system, display screen and measured lens three, namely the coordinate transformation relation of camera coordinate system, display screen coordinate system and three space coordinates of measured lens coordinate system; By computing machine, produced again the Eigen Structure of a fixed structure, be presented on display screen, and project to tested minute surface, after reflection by video camera record, namely video camera is observed display screen by measured lens, can photograph the Eigen Structure that shows screen display; The face shape information that the reflected image that video camera is taken has just carried measured lens, can deform and be different from the shown Eigen Structure of display screen, and deflection depends on the face shape of measured lens; According to Eigen Structure, extract image characteristic point, be attached to display screen, video camera, measured lens three's spatial relation, carry out ray tracing and determine the locus of incident ray and reflection ray, by reflection law, calculated the face shape normal direction of tested minute surface, then rebuild tested mirror shape by integration.
Can once complete measurement of full field, also can in whole of measured lens, scan measurement of full field.
Described display screen is demarcated and can directly have been measured by ruler, laser tracker instrument, also can utilize the video camera measurement of having demarcated and calculate by coordinate system transformation with the reference planes mirror of Eigen Structure.
Described measured lens is demarcated and can directly have been measured by instruments such as ruler, laser trackers, also can on measured lens, place Eigen Structure, utilizes the video camera of having demarcated to complete.
The Eigen Structure of a described fixed structure can be sine or cosine cycle striped, circle spot, closed square, gridiron pattern, rectilinear grid or cross wire.
Described extraction image characteristic point distributes mutually for extracting the position of sine or cosine cycle striped, extracts the central point of circle spot, extracts closed square, tessellated angle point, extracts the intersection point of rectilinear grid, cross wire.
The present invention has following advantage to be:
(1) the present invention has larger measurement dynamic range, can be used for fine grinding and the detection in polishing stage of the dark type manufacturing of heavy caliber.
(2) the present invention, to environment without specific (special) requirements, can detect in workshop condition.
(3) in the present invention without special optical element, cost is very cheap.
(4) system architecture that the present invention adopts is simple, and system element is placed without special requirement.
(5) detection method of the present invention has very high sensitivity.
(6) the structure pattern and the phase-shifting technique that in the present invention, adopt have quite high precision, and can effectively suppress noise and the impact of surrounding environment on testing result.
Accompanying drawing explanation
Fig. 1 is structural representation of the present invention;
Fig. 2 is measuring principle figure of the present invention;
The schematic diagram of the spatial relation method of Fig. 3 based on reference planes catoptron calibrating camera and display screen;
Fig. 4 is characteristic feature pattern shape and unique point in the present invention, and wherein Fig. 4 a is (remaining) string cycle striped just; Fig. 4 b is circle spot; Fig. 4 c is closed square; Fig. 4 d is gridiron pattern; Fig. 4 e is rectilinear grid;
Fig. 5 is that in the present invention, video camera is taken the horizontal direction bar graph distribution obtaining;
Fig. 6 is that in the present invention, video camera is taken the vertical direction bar graph distribution obtaining;
Fig. 7 is the overlapping schematic diagram of video camera incident ray in the present invention;
Fig. 8 is sweep type cross wire Eigen Structure in the present invention.
Embodiment
As shown in Figure 1, in the present invention, detection system is mainly comprised of video camera, display screen and computing machine.Show the Eigen Structure that screen display is generated by computing machine, after measured lens reflection by shot by camera.As shown in Figure 2, the image that video camera shooting obtains is sent to computing machine and processes measuring principle, by calculating, carries out ray tracing, and the gradient that obtains tested surface shape according to light reflection law distributes, and the face shape that last integration is rebuild measured lens distributes.Take below and show that screen display sine streak Eigen Structure, as example describes, has similar measuring process when showing other Eigen Structures, this example does not comprise all the elements of the present invention.
First to carrying out camera calibration.Camera marking method is a lot, as the two-step approach of Tsai and Roger proposition, the plane reference method that Zhang Zhengyou proposes etc.Wherein, the flat method standardization application of Zhang Zhengyou is comparatively extensive.This is a kind of under the nonlinear model of camera imaging, adopts the method for all inside and outside parameter of several plane template calibrating cameras.On the plane template using in the method, have a plurality of unique points, and between corresponding picture point, have a corresponding relation on unique point and its image, this is just for solving of inner parameter provides constraint condition.Video camera is the multiple image of camera plane template (more than three width) from different perspectives, first by linear solution, obtained the initial value of partial parameters, then consider radial distortion (single order and second order) and obtain external parameter linear result is carried out to the last inner parameter and the plane template mapping matrix that calculate of utilizing of nonlinear optimization based on maximum likelihood criterion.
Second step, display screen is demarcated, obtain the spatial relation of video camera and display screen, can directly measure by ruler, laser tracker instrument, also can utilize the video camera of having demarcated to calculate by coordinate system transformation with the reference planes mirror with Eigen Structure.Here with the reference planes mirror with Eigen Structure, describe, as Fig. 3.In the camera chain of having demarcated, by the coplanar characteristic point of single plane, can be determined the locus of this plane.Unique point on the reference planes mirror of taking by camera, can obtain reference planes coordinate system (X
r, Y
r, Z
r) and camera coordinate system (X
c, Y
c, Z
c) between spatial relation.By video camera, take the mirror image of reference planes mirror to display screen again, calculate camera coordinate system (X
c, Y
c, Z
c) and this imaging plane (X
s', Y
s', Z
s') spatial relation.According to mirror imaging characteristic: the mirror image becoming is the virtual image identical with original size, can obtain display screen (X
s, Y
s, Z
s) and its mirror image (X
s', Y
s', Z
s') spatial relation.In conjunction with the spatial relation between reference planes and camera coordinate system, just can be converted to display screen (X
s, Y
s, Z
s) and camera coordinate system (X
c, Y
c, Z
c) between spatial relation.
The 3rd step, measured lens is demarcated, and obtains the spatial relation of video camera and measured lens, can directly measure by instruments such as ruler, laser trackers, also can on measured lens, place Eigen Structure, utilizes the video camera of having demarcated to complete.Completion system is demarcated and is obtained after the spatial relation of video camera, display screen and three coordinate systems of measured lens, just three's unification can be arrived under same coordinate system (camera coordinate system or display screen coordinate system or measured lens coordinate system).If the model of measured lens can be expressed as: z
m=f (x
m, y
m), consider to put S (x on display screen
s, y
s, z
s) light that sends puts M (x on tested minute surface
m, y
m, z
m) after reflection, by video camera photocentre O point, incide the some P (x in camera pixel plane
p, y
p, z
p), the direction vector representation of reflection ray is: r
i=(x
m-x
s, y
m-y
s, z
m-z
s).
The 4th step, video camera is taken and is observed display screen by measured lens, and shooting obtains the sine streak figure on display screen.The face shape information that the reflected image that video camera is taken has just carried measured lens, can deform and be different from the shown Eigen Structure of display screen, deflection depends on the face shape of measured lens, be the level of shooting and the sine streak figure of vertical two vertical direction as shown in Figure 5, Figure 6, then extract and obtain PHASE DISTRIBUTION by phase shift algorithm and phase-unwrapping algorithm.According to PHASE DISTRIBUTION, can calculate the volume coordinate (x that S is ordered
s, y
s, z
s), the direction vector representation of reflection ray is: r
r=(x
p-x
m, y
p-y
m, z
p-z
m).
The 5th step, as shown in Figure 2, according to light reflection law, by incident ray direction vector r
iwith reflection ray direction vector r
rcalculate tested mirror surface-shaped normal:
The 6th step, obtains face shape gradient by tested surface shape normal line vector and distributes, then integration is rebuild face shape:
The method of being rebuild face shape by face shape gradient data integration is a lot, as free routing integral method, and cross integral method, Fourier transform integral method, Zonal Wave-front Reconstructions method etc.
When tested mirror surface-shaped is very precipitous or regional area variation is very fast, the incident ray of video camera may overlap, and as shown in Figure 7, the same point on display screen can be surveyed by different camera pixel points after measured lens reflection.At this moment, if use streak feature pattern, will produce phase ambiguity and wrapped phase can not launch, cause the locus of corresponding point on display screen can not determine.Similarly, other Eigen Structures in using Fig. 4 also have same problem.At this moment, can adopt the cross wire Eigen Structure shown in Fig. 8 to come the position of corresponding point on unique definite display screen, in whole of measured lens, scan its point of crossing of extraction, complete the measurement of whole shape.
In sum, the present invention is simple in structure, easy to use, highly sensitive, to environment without specific (special) requirements, can in workshop condition, detect, for the detection of heavy caliber, fast aspherics mirror provides a kind of effective means, especially in fine grinding and the polishing stage of manufacturing, have broad application prospects.
Non-elaborated part of the present invention belongs to techniques well known.
Claims (3)
1. a heavy caliber aspherical mirror structured light detection method, it is characterized in that: the measuring system of employing is by video camera, display screen and computing machine form, wherein video camera and display screen are placed without other specific (special) requirements, as long as video camera can be seen display screen after by measured lens, show the Eigen Structure that screen display is generated by computing machine, after measured lens reflection by shot by camera, the image that video camera shooting obtains is sent to computing machine and processes, by calculating, carry out ray tracing, the gradient that obtains tested surface shape according to light reflection law distributes, the face shape that last integration is rebuild measured lens distributes, detection method is implemented as follows:
The first step, first demarcates video camera,
Second step, display screen is demarcated, and obtains the spatial relation of video camera and display screen, has directly measured, or utilize the video camera of having demarcated to calculate by coordinate system transformation with the reference planes mirror with Eigen Structure by ruler, laser tracker instrument;
The 3rd step, measured lens is demarcated, obtain the spatial relation of video camera and measured lens, by ruler, laser tracker instrument, directly measured, or on measured lens, place Eigen Structure, and utilize the video camera of having demarcated to complete, completion system is demarcated and is obtained after the spatial relation of video camera, display screen and three coordinate systems of measured lens, just three's unification can be arrived under same coordinate system, i.e. camera coordinate system or display screen coordinate system or measured lens coordinate system;
The 4th step, video camera is taken and is observed display screen by measured lens, and shooting obtains the sine streak figure on display screen, the face shape information that the reflected image that video camera is taken has just carried measured lens, can deform and be different from the shown Eigen Structure of display screen, deflection depends on the face shape of measured lens, according to PHASE DISTRIBUTION, calculates the volume coordinate (x that S is ordered
s, y
s, z
s), the direction vector representation of reflection ray is: r
r=(x
p-x
m, y
p-y
m, z
p-z
m); (x wherein
m, y
m, z
m) represent point on tested minute surface, (x
p, y
p, z
p) representing the point in camera pixel plane, S refers to the point on display screen;
The 5th step, according to light reflection law, by incident ray direction vector r
iwith the vectorial r of the direction of reflection ray
rcalculate tested mirror surface-shaped normal:
The 6th step, obtains face shape gradient by tested mirror surface-shaped normal line vector and distributes, then integration is rebuild face shape:
2. a kind of heavy caliber aspherical mirror structured light detection method according to claim 1, is characterized in that: can once complete measurement of full field, also can in whole of measured lens, scan measurement of full field.
3. a kind of heavy caliber aspherical mirror structured light detection method according to claim 1, is characterized in that: described Eigen Structure is sine or cosine cycle striped, circle spot, closed square, gridiron pattern, rectilinear grid or cross wire.
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| CN108225737A (en) * | 2017-12-06 | 2018-06-29 | 天津大学 | A kind of novel optical lens measurement method |
| CN108286950A (en) * | 2017-12-27 | 2018-07-17 | 中国科学院长春光学精密机械与物理研究所 | A kind of online test method of reflecting mirror surface shape |
| CN108917652B (en) * | 2018-07-09 | 2020-04-10 | 中国科学院光电技术研究所 | Pose optimization method for off-axis aspheric surface of structured light detection |
| CN108917649A (en) * | 2018-07-26 | 2018-11-30 | 深圳市智能机器人研究院 | A kind of heavy caliber aspherical mirror structure light detection method |
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