CN1295522C

CN1295522C - High precision combined optical grating device for optical 3D measurement

Info

Publication number: CN1295522C
Application number: CNB2003101227298A
Authority: CN
Inventors: 严隽琪; 习俊通; 姜涛
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2003-12-19
Filing date: 2003-12-19
Publication date: 2007-01-17
Anticipated expiration: 2023-12-19
Also published as: CN1554925A

Abstract

The present invention relates to a high precision combined grating device for optical three-dimensional measurement. Thirteen grating pictures are etched on a quartz glass sheet for photoetching by an electron beam scanning and photoetching method. The present invention comprises a calibrating grating of a projector, an all white grating, eight Gray code gratings and four phase shift gratings, wherein the first grating in the phase shift gratings is the eighth grating in the Gray code gratings. The sizes of the gratings are same, and the stripe directions are mutual parallel. The gratings are arranged on the quartz glass sheet for photoetching, the direction of each grating is consistent with the displacement direction of a projection mechanism, and the alignment precision of grating projection is ensured. Simultaneously, the present invention can meet the optical three-dimensional measurement based on a Gray code method and a phase shift method, the measurement precision and the stability are ensured, and the present invention has important engineering use value and obvious economic benefit.

Description

Optical three-dimensional measurement is with high-accuracy combined light gate device

Technical field:

The present invention relates to a kind of grating device, particularly a kind of optical three-dimensional measurement of making based on the electron beam scanning photoetching method that comprises projector calibrating grating, Gray code grating and phase-shifted grating belongs to mechanical engineering and field of optical measuring technologies with high-accuracy combined light gate device.

Background technology:

Along with being growing more intense of globalizing market competition, reverse engineering is generally paid attention to and widespread use in industry member as the important technology of rapid product development and design innovative.Three-dimensional measurement of objects is the first step of reverse engineering, and the precision of measurement result directly has influence on the anti-quality of asking, and has a very important role.Optical three-dimensional measurement is very extensive in present application, has become the important channel of three-dimensional measurement.In optical three-dimensional measurement equipment, need at least one an optical grating projection device and an image collecting device (being generally the CCD camera).Owing to also there is not any shadow casting technique can satisfy the requirement of optical three-dimensional measurement fully at present, therefore how appropriately to solve the projection problem, be a key issue in the optical three-dimensional measurement.

At present, Chang Yong optical projection system mainly contains liquid crystal projection apparatus, lantern projection's instrument etc.Liquid crystal projection apparatus has alignment preferably by the method projection digital raster of programming, but can not projection has the striped of continuous light distribution, contrast low (about 1: 20), and largest light intensity is lower, and the depth of field is less.In the prior art, G.Wiora mentions in High resolution measurement of phase-shift amplitude andnumeric object phase calculation one literary composition that was published in Proceedings of SPIE-The International Society for OpticalEngineering the 4117th volume in 2000, lantern projection is made up of some lantern slide gratings, can obtain to surpass 1: 100 contrast and very high light intensity, because the lantern slide raster size is little, can realize the bigger depth of field; Its deficiency is to guarantee the accurate arrangement of lantern slide, and the switching between the lantern slide is by the accurate displacement mechanism realization of linear or rotation, and is very high to the requirement of displacement accuracy, therefore can not effectively guarantee the accurate alignment of grating.

Summary of the invention:

For overcoming the deficiencies in the prior art and defective, the present invention proposes a kind of high-accuracy combined light gate device of making based on the electron beam scanning photoetching method, being the method that adopts the electron beam scanning photoetching carves 13 amplitude grating figure in the minimum photoetching of expansivity on quartz glass plate, comprise 1 width of cloth projector calibrating grating, the full white raster of 1 width of cloth (largest light intensity), 8 width of cloth Gray code gratings and 4 width of cloth phase-shifted gratings wherein have a width of cloth phase-shifted grating and Gray code grating shared.The size of every amplitude grating is all the same, be arranged in photoetching in regular turn with on the quartz glass plate, the grating fringe direction is parallel to each other, and it is consistent with the projector mechanism sense of displacement, the grating alignment accuracy is fully guaranteed, can satisfy the high-contrast requirement of Gray code grating, also can guarantee the continuity of phase-shifted grating.

Distinguish presentation logic value 0,1 with black, informal voucher line in the Gray code grating during design, then 8 amplitude gratings form the Gray code of 8 bits; The coding rule that four step phase-shift methods are measured is satisfied in the design of four width of cloth phase-shifted gratings, is offset for four/one-period (90 degree) between promptly every amplitude grating successively, and wherein first amplitude grating promptly is the 8th amplitude grating of Gray code; Demarcate grating and adopt the square pattern that size is identical, be evenly distributed, be used to realize the demarcation of projector; Full white raster is used for the decoding of Gray code grating.

The method that the present invention adopts the electron beam scanning photoetching is made all gratings in the minimum photoetching of expansivity on quartz glass plate, the stripe direction of grating is parallel to each other, and it is consistent with the projector mechanism sense of displacement, reduced harsh requirement to displacement accuracy, guaranteed the alignment accuracy of optical grating projection, thereby greatly improved the quality of optical grating projection, the present invention can satisfy the optical three-dimensional measurement based on Gray code method and phase shifting method simultaneously, guarantee the precision and the stability of optical three-dimensional measurement, had important engineering practical value and remarkable economic efficiency.

Description of drawings:

Fig. 1 is the high-accuracy combined light gate device of a present invention structural representation.

Among the figure, the 1st, photoetching quartz glass plate, the 2nd, projector calibrating grating, the 3rd, full white raster, the 4th, Gray code grating, the 5th, phase-shifted grating.

Fig. 2 is a Gray code grating fringe structural representation.

Among the figure the 1st to the 8th amplitude grating dextrorotation turn 90 degrees the back corresponding to the 3rd among Fig. 1 to the 10th amplitude grating.

Fig. 3 is a phase-shifted grating striated structure synoptic diagram.

Among the figure the 1st to the 4th amplitude grating dextrorotation turn 90 degrees the back corresponding to the 10th among Fig. 1 to the 13rd amplitude grating.

Fig. 4 is a projector calibrating optical grating construction synoptic diagram.

Embodiment:

Below in conjunction with accompanying drawing concrete enforcement of the present invention is further described.

As shown in Figure 1, mainly to be the method that adopts the electron beam scanning photoetching carve 13 amplitude grating figure in the minimum photoetching of expansivity on quartz glass plate 1 to combined light gate device of the present invention in regular turn, among the figure from left to right, the 1st width of cloth is a projector calibrating grating 2, the 2nd width of cloth is full white raster 3, the the 3rd to the 10th width of cloth is that Gray code grating the 4, the 10 to the 13rd width of cloth is a phase-shifted grating 5.As shown in Figure 2, the coding of Gray code grating 4 satisfies the coding rule of Gray code, with black, informal voucher line difference presentation logic value 0,1, then 8 amplitude gratings form the Gray code of 8 bits, wherein the first amplitude grating encoded radio is 01, width of fringe is identical, since the 2nd amplitude grating, thereafter width of fringe reduces half than last amplitude grating successively, the width of grating edge striped is half of middle width of fringe, and encoded radio is respectively second 101, the three 10101, the 4th 101010101, the rest may be inferred.As shown in Figure 3, the coding of phase-shifted grating 5 satisfies the coding rule of four step phase-shift methods, wherein the 1st amplitude grating is the 8th amplitude grating of Gray code grating 4, it is four/one-period that the 2nd to the 4th amplitude grating has been offset half width of fringe than last amplitude grating successively, its encoded radio is followed successively by first 1010 ... 0101, second 1010 ... 1010, the three 0101 ... 1010, the four 0101 ... 0101.As shown in Figure 4, projector calibrating grating 2 adopts the demarcation that size is identical, square pattern that be evenly distributed realizes projector.Full white raster 3 is the decodings that are used for Gray code grating 4.

Structure according to Fig. 1-Fig. 4 designs grating device in Ledit software, every amplitude grating size of design is the same, stripe direction is parallel to each other, and it is consistent with the projector mechanism sense of displacement, the grating alignment accuracy is fully guaranteed, can satisfy the high-contrast requirement of Gray code grating 4, also can guarantee the continuity of phase-shifted grating 5.

Then, the e-file that designs is input to the control program of electron beam scanning litho machine, the method that adopts the electron beam scanning photoetching is made grating device in photoetching on quartz glass plate 1.At quartz glass plate 1 surface coverage thin film, cover one deck sense electronics luminescent material on the film again, the electron beam scanning litho machine is write grating fringe pattern among Fig. 1 on the quartz glass plate 1 by scanner, after the exposure, mask is removed with solvent in the place of face exposure, promptly obtains designed grating.

At last, the glass sheet that photoetching is good is suitably cut out, obtained grating device.

Claims

1, a kind of optical three-dimensional measurement is with high-accuracy combined light gate device, comprise projector calibrating grating (2), full white raster (3), Gray code grating (4) and phase-shifted grating (5), it is characterized in that: the method that adopts the electron beam scanning photoetching carves 13 amplitude grating figure in the minimum photoetching of expansivity on quartz glass plate (1) in regular turn in litho machine, the 1st width of cloth is projector calibrating grating (2), the 2nd width of cloth is full white raster (3), the 3rd width of cloth to the 10 width of cloth are 8 width of cloth Gray code gratings (4), the 10th width of cloth to the 13 width of cloth are 4 width of cloth phase-shifted gratings (5), wherein the 1st amplitude grating in the phase-shifted grating (5) is the 8th amplitude grating in the Gray code grating (4), every amplitude grating size is the same, stripe direction is parallel to each other, be arranged in photoetching in regular turn with on the quartz glass plate (1), the coding of Gray code grating (4) satisfies the coding rule of Gray code, with black, the informal voucher line is presentation logic value 0 respectively, 1,8 amplitude gratings form the Gray code of 8 bits, wherein the first amplitude grating encoded radio is 01, width of fringe is identical, since the 2nd amplitude grating, thereafter width of fringe reduces half than last amplitude grating successively, the width of grating edge striped is half of middle width of fringe, and encoded radio is respectively second 101, the 3rd 10101, the 4th 101010101, the rest may be inferred; The coding of phase-shifted grating (5) satisfies the coding rule of four step phase-shift methods, with the 1st amplitude grating is benchmark, the the 2nd to the 4th amplitude grating is four/one-period than half middle width of fringe of last amplitude grating skew successively, its encoded radio is followed successively by first 1010 ... 0101, second 1010 ... 1010, the 3rd 0101 ... 1010, the four 0101 ... 0101; Projector calibrating grating (2) adopts the demarcation that size is identical, square pattern that be evenly distributed realizes projector.