TW479125B - Two dimensional displacement measurement method with conjugate optical paths - Google Patents

Abstract

The present invention provides a two dimensional displacement measurement method with conjugate optical paths, wherein a first incident light is generated from a light source and is incident into a diffractive unit to form at least two first diffractive lights, the first diffractive lights further forms a second incident light returned from the original optical path and incident into the diffractive unit through the functioning of the wavefront reconstruction optics. After the reflection of the second incident light by the diffractive unit, at least two secondary diffracted lights are formed, the secondary diffracted lights form at least two interference lights through the functioning of the interference optical components, process the interference lights by the general optical interference de-phasing technology, the amount of displacement in two linearly independent directions of two dimensional motion can be obtained.

Description

479125 V. Description of the invention (l) [Background of the invention] 1. Field of the invention The present invention provides a method for measuring the misalignment between the intersect gratings of optical elements. ;, With accuracy, and two-dimensional displacement measurement method of the tolerance between the optical element and N around it 2 · Send pair of measuring mode optical ruler LVDT) For low-to-medium accuracy problems, the degree of routine, and the flow of force The new method is to directly combine the relatively bright background with the two-dimensional motion displacement group in an orthogonal manner, magnetic ruler, capacitive type, laser interferometer, etc. The accuracy of the system is gradeable, and the orthogonal structure is as follows: The interferometer's beamsplitter / south precision requirements also increase the number of positive phase risks. The method of the generation is to use the problem of the two-dimensional accuracy of the measurement system. Two-dimensional measurement can be performed by two-dimensional sensors. The method is to increase the traditional measurement, linear dependence on the accuracy and the reflector architecture. This side, however, will face the practice of capacitive sensing and optical path. In education, the module and the variable-difference method are combined together. (. This method requires the level of verticality between the insurmountable measurement planes, etc., the technical cost of the user and the talents. About the two-dimensional optical rule t〇y〇 company's us 5,204,524 integrated two-dimensional measurement " This method, and the user does not need to worry about the two-axis optical ruler is the best and most typical example. Related technologies have been published by: Mitu — (1993), usid of Heidenhain Company

Page 4 479125 V. Description of the Invention (2) 5,424, 833 (1995), and US Pat. No. 5,530,543 (1 99 6). The conventional two-dimensional optical ruler, as described in the patent US 5, 204, 524, adopts a geometric three-grating structure. The displacement measurement method uses the light beam to be shielded by the grating stripes when the first grating and other components undergo relative movement. The effect will become a light signal between light and dark. The signal of an approximate sine wave can be obtained through the conversion of the photodetector. After processing by the demodulation circuit, the displacement of the relative motion can be obtained. Its resolution and accuracy are due to Many limitations of geometric optics cannot effectively improve to high precision levels. As described in US Pat. No. 5, 4 2 4, 8 3 3, a double-grating three-diffraction optical path design is adopted. The beam is diffracted by the positive and negative first-order beams diffracted by the sub-grating, and then reflected and diffracted by the main grating disk. The beam returns to the sub-grating and passes through the sub-grating to generate a diffraction. After three times of diffraction, the beam can take out three signals with a relative displacement between the two gratings and a phase difference of 120 degrees. Radiation, the use efficiency of the light source is not good, resulting in relatively higher requirements for system assembly accuracy and component production quality level. As described in the patent US 5, 530, 543, a single grating single optical path diffraction design is adopted, and the beam is diffracted by a grating disk to generate positive and negative first-order diffracted light. The interference of first-order diffraction light = generating interference fringes with τ displacement signal. The photodetector is placed directly at the intersection of the first-order diffraction light and the interference signal is measured. The system does not have the poor self-compensation function. Optical components and light have high requirements for misalignment accuracy, and it is not easy to obtain a stable wheel output signal. a's right

Page 5 479125 V. Description of the invention (3) [Objective of the invention] The main purpose of the invention is to provide a two-line optical measurement method with a common optical path. The misalignment between the diffraction gratings and the grating defects of the second and third bodies have a high tolerance. This quantity; the integrated two-dimensional measurement method 'significantly reduces the dependence of the measurement system on the operator ^', and @ is an excellent & with a high tolerance, for the accuracy of processing of various parts and assembly between components Accuracy and alignment between two components can greatly reduce its low-r manufacturing and assembly costs. In addition, the yield of the mouth is achieved to achieve the purpose of popularizing the product. The following detailed description and technical contents of the present invention are shown in the accompanying drawings [Detailed Description of the Invention] Well / 2 Figure 1 ", which is a schematic diagram of the optical path in the previous section of the present invention; it is a light source that can emit nearly the same light. It can be m-polarized light or elliptically polarized light. The light source 2 = one: after the lens 301 is formed, the-near-parallelized = V _ near the normal direction of the incident point is incident on the second Λ incident point 1011, The diffraction grating 1.1 passes through the leaves, so that the energy of the diffracted light is concentrated in the positive and negative-order. Face center: The secondary incident light 901 is two-dimensionally wound: after the grating 101 reflects 9111v azimuths, four positive-negative-order first-orders, 913, and 914 are generated, and the first-order incident light has a dimensional shift of 901, The optical grating is originally a technology that can measure the motion of the system. So we can refer to the South-style explanatory diagram. ··············································································································· ············

Page 6 479125 V. Description of the invention (4) The same first-order diffraction angle, whose components on the X-Y plane point to (丨, J), (-I 丨), (-丨, -D, (丨, -1) In four directions, when a two-dimensional relative motion on the XY plane is generated between the two-dimensional diffraction grating 101 and the light source 201, the first Doppler effect is caused by the Doppler effect. The secondary diffracted lights 9 1 1, 9 1 2, 9 1 3, 9 1 4 will respectively carry phase shift signals related to the two-dimensional motion displacement. Take two of the first diffracted lights 9 1 1 and 9 1 3. Through two sets of wavefront reconstruction optical components composed of parallelizing lenses 311, 313 and plane mirrors 401, 403, reflecting the original optical path to form a second incident light 911, and 91 3 '' incident in the The incident point of the two-dimensional diffraction grating 1 〇1 丨 〇 丨 丨. The two sets of wavefront reconstruction optical components are arranged by placing the optical axes of the parallelizing lenses 3 1 1 and 3 1 3 on the first diffracted light. On the optical paths of 9 1 1 and 9 1 3, the plane mirrors 401 and 403 are perpendicular to the optical axis and make the incident points ι 1 and the plane mirrors 4 0 1, 4 0 3 The reflection points 4 0 1 1 and 4 0 3 1 are all on the optical axis and are respectively located at the front focus and the back focus of the parallelizing lens 3 11 and 3 1 3 'This configuration method applies the principle of reconstruction optics' to make the beam at The aberrations formed during the first diffraction are self-compensated due to two Fourier transforms during the second diffraction, so that the wavefront of the second diffraction light has the same characteristics as the original incident light. Parallel wavefront, this optical design method with wavefront reconstruction characteristics can effectively improve the system's tolerance for misalignment. As shown in "Figure 2", it is a schematic diagram of the optical path in the latter stage of the present invention, and the two incident light After 911 'and 91 3' are reflected by the two-dimensional diffraction grating 1 〇1, four positive and negative first-order diffracted lights 921, 922, 923, and 924 are generated at four azimuth angles symmetrical to the plane point. Secondary diffracted light 921, 922,

Page 7 479125 V. Description of the invention (5) 9 23, 924 and the first incident light 901 are equal in angle, and their components on the XY plane point to (丨, 〇), (〇, 1), respectively. , (— 1, 〇), (〇, -1) four directions. When a two-dimensional relative motion on the XY plane occurs between the two-dimensional diffraction grating 101 and the other optical components, the second diffraction light 921, 922, 923, 924 carries a phase deviation related to the two-dimensional motion displacement amount. Shift signal, the second diffracted light 921 and 923 form reflected light beams 931 and 93 3 through the plane mirrors 411 and 413 respectively, and then the reflected light beams 931 and 9 33 are recombined with the interference signal through the polarizing beam splitter 501 Interfering light 941; the second diffracted light 92 2 and 924 form reflected light beams 932 and 9 34 through the plane mirrors 412 and 414 respectively, and then the reflected light beams 932 and 934 are recombined by the polarizing beam splitter 502. Interference light 9 4 2 with interference signal. Finally, after the interference light 9 4 1 and 9 4 2 are processed by a general optical interference phase separation technique, the displacements in two linear independent directions in the two-dimensional movement can be obtained at the same time. Taking a two-dimensional sine wave grating with a grid pitch of 4mm and a height of 0.211111 as an example, its conversion function in the XY plane direction can be approximately expressed as ... [exp (i2 7rkx) + exp (~ 12 π kx )] x [exp (i2; rky) + exp (—i2 7Γ ky)], where k is the propagation constant. When the first incident light 9 〇1 is perpendicularly incident on the two-dimensional diffraction grating 1 0 11 ′ and reflected by the two-dimensional diffraction grating 1 〇 1, the first diffracted light generated by the first incident light 9 〇 1 The points of 911, 912, 913, and 914 in the XY plane direction can be expressed as: exp (i27rk (x + y)), exp (i27rk (~ x + y)), exp (i2 7rk (-χ-y )), Exp (i2 7rk (x-y)).

479125 V. Description of the invention (6) When a two-dimensional relative movement on the X _ γ plane is generated between a prepared one-dimensional diffraction grating 1 〇1 and a light source 2 〇1, the phase shifts can be expressed as: + φχ + φγ,-d) X + (Dy, a φχ-φγ, + Φχ—Φ ”Take the first diffracted light 9 1 1, 9 1 3, respectively, and reconstruct the optical components through the corresponding wavefronts, and retrace the original optical path. After incident on the incident point 1011 of the two-dimensional diffraction grating 101 and reflected by the two-dimensional diffraction grating 101, four second-diffraction light beams 921, 9 22, 923, and 9 24 are generated.

The second diffracted lights 921 and 923 are the first diffracted lights 913 and 911, respectively, whose original components are ex 〆 2 / rk (—x—y)) and exp (l2; rk (x + y)). , Formed by the corresponding wavefront reconstruction optical component reentering the incident point 1 0 11 incident on the two-dimensional diffraction grating 1 0 1 and formed by reflection of the two-dimensional diffraction grating 丨 〇1, which respectively contain a 2 (The phase shift signals of Dy and + 2 0y are superimposed to form interference light carrying an interference signal by the action of the corresponding plane mirrors 411 and 4 1 3 'and the polarizing beam splitter 5 01. Finally, after the optical interference phase-separation technology is processed, the displacement in the γ direction in the two-dimensional motion can be interpreted. Similarly, the second diffraction light 922 and 924 can be passed through the corresponding plane mirrors 412 and 414 ′ and The function of the polarizing beam splitter 502 forms an interference light 9 4 2 carrying an interference signal of 2 Φ X, + 2 Φ X, and interprets the amount of displacement in the X direction in a two-dimensional motion.

As shown in "Fig. 3", the optical path before the alternative embodiment of the present invention is not intended. &Quot; " " " ^ The light beam emitted by the light source 201 passes through the ^ -parallelizing lens 301, and forms an almost The first parallel incident light 9 0 1 is parallelized, and then incident on the two-dimensional diffraction grating 1 0 1 at an incidence point near the normal direction of the incident point, and reflected by the two-dimensional diffraction grating 1 0 1. , Four azimuths that are point-symmetric in the plane

Page 9 479125 V. Description of the invention (7) Generate four first-order diffracted light beams 9 π, 9 1 2, 9 1 3, 9 1 4, and the first incident light 9 0 1 Have the same first-order diffraction angle between them, and their components on the XY plane point to (1,1), (-1,1), (― 丨, — 丨), and (1, -1) respectively Direction, when a two-dimensional relative motion on the XY plane occurs between the two-dimensional diffraction grating 100 and the light source 201, the first diffraction light 91 1, 912, 913 is due to the Doppler frequency shift effect. , 914 will carry phase shift signals related to two-dimensional motion displacement, respectively. The first diffracted light 9 11, 9 1 2, 9 1 3, 9 1 4 passes through four groups using the parallelizing lenses 311, 312, 313, and 314 and the flat mirror 401, 402, 4 0 3, 4 0 4 The formed wavefront reconstruction optical component reflects the original light path to form the second incident light 911, 912, 913, and 914, and is incident on the incident point 1 0 1 of the two-dimensional spring beam grating 1 0 1 1. : The configuration method of the four sets of wavefront reconstruction optical components is to set the optical axes of the parallelized trans-mirrors 311, 312, 313, and 314 on the optical paths of the first diffraction light 911, 912, 913, and 914. The plane mirrors 401, 402, 40 3, and 404 'are perpendicular to the optical axis, and the reflection points 4011 and 4021 of the plane reflection mirrors 401, 4 0 2 ^, 4 0 3, and 404 are made. , 403 1, 404 1 are all on the optical axis' and are located on the front focus point and the back focus of the parallelizing lenses 311, 312, 313, and 314, respectively. This configuration method applies the principle of reconstruction optics, so that the beam The aberrations formed during the first diffraction are self-compensated due to the two Fourier transforms during the second diffraction, so that the light wave front of the second diffraction light has the same characteristics as the original incident light. For parallel wavefronts, this optical design method with wavefront reconstruction characteristics can effectively improve the system's offset tolerance.

Page 10 479125

As shown in "Fig. 4", it is a schematic diagram of the light after the alternative embodiment of the present invention. The second incident light 911 ', 91 2, 913, and 914 are reflected by the two-dimensional diffracted light thumb 101 and are on a plane. The four azimuths with point symmetry generate four second-order diffracted light beams of the first and second order 9 2 1, 9, 2 2, 9 2 3, 9 2 4, the first diffracted lights 921, 9 22, 9 23, 924 And the first incident light 9〇] [the angles are all equal ', and their components on the XY plane point in four directions (1, 0), (〇 $, (-1, 0), (0, -1), respectively) ... '

When the two-dimensional relative motion on the sense-y plane occurs between the two-dimensional diffraction grating 101 and the other optical components, the second diffraction light 921, 922, 923, 9M is loaded with the two-dimensional motion displacement. Light interference signal. After the table, the first diffracted light 9 2 1, 9, 2 2, 9 2 3, 9 2 4 is processed by the ordinary light interference phase separation technology, and the linear independent directions in the two-dimensional movement can be obtained at the same time. The amount of displacement. Λ Taking a two-dimensional sine wave grating with a grid pitch of 4 mm and a height of 0.2 mm as an example, its transfer function in the XY plane direction can be approximately expressed as: [αρ (i2 7rkx) + exp (—i2 7rkx) ] x [exp (i2 7rky) + exp (_ · 〇7Γ ky)], where k is the propagation constant.

When the first incident light 901 is perpendicularly incident on the two-dimensional diffraction grating 101, and after 1011, it is reflected by the two-dimensional diffraction grating 101, and the generated primary diffraction light 911, The blades of 912, 913, and 914 in the XY plane direction can be expressed as: exp (i2vk (x + y)), exp (i2 ^ (— y)) exP (i27rk (—χ—y)), eXp ( i27rk (x-y)).

-When a one-dimensional relative motion on the X-Y plane occurs between the two-dimensional diffraction grating 101 and the light source 201, the phase shifts can be expressed as: + ❿X

Page 11 479125 V. Description of the invention (9) + 〇y, -Φχ + cDy,-φχ—φγ, + φχ_φγ. The first diffracted light 9 1 1, 9 1 2, 9 1 3, 9 1 4 are respectively reconstructed through the corresponding wave chirps to rebuild the optical components, and the incident light incident on the two-dimensional diffraction grating 1 0 1 is turned back along the original optical path. After the point 1 〇1 丨 is reflected by the two-dimensional diffraction grating 丨 0i, four second diffracted lights 921, 922, 923, and 924 are generated. The second diffraction light 921 is composed of the first diffraction light 912 and & 13 whose original components are exp (i2 rk (— X + yD'expl ^ Trkl: —x ~ y)). The wavefront reconstruction optical component reenters the incident point 1 〇1 1 incident on the two-dimensional diffracted light 21 0 1 and is reflected by the two-dimensional diffractive grating 1 〇1 to form a port, which contains + 2 Φ y And a phase shift signal of 2 Φ y, which can be interpreted in the displacement in the Y direction in 2D motion after being processed by the photo-drying f phase-resolving technology. 4 The second diffraction light 9 2 2 contains + 2 Φ After the phase shift Λ 'of X and a 2 φ X is processed by the optical interference phase-separation technology, the displacement in the X direction in the two-dimensional motion can be interpreted, so that the two properties in the two-dimensional motion can be obtained at the same time. Amount of displacement in independent directions. Similarly, the second diffracted light 9 2 3 and 9 2 4 can also be obtained simultaneously by two optically independent directions Υ and X in the two-dimensional motion after being processed by the optical interference phase separation technology.

479125 Brief description of the drawings 1 · Brief description of the drawings Figure 1 is a schematic diagram of the optical path in the previous stage of the present invention. Fig. 2 is a schematic diagram of the optical path at the later stage of the present invention. Figure 3 is a schematic diagram of the optical path before the alternative embodiment of the present invention. Figure 4 is a schematic diagram of the optical path after the alternative embodiment of the present invention. 2 Brief description of the drawing number. Two-dimensional diffraction grating. ... 1011 Light source ......... 2 01 Parallel lens ... 3 0 1 Flat mirror ... 401 411 Reflection point ... 4011 Polarizing Beamsplitter ... 501 First Incident Light ......... 901 First Diffraction Light ......... 911 Second Incident Light ... 9 1 Γ Second Diffractive light 9 21 Reflected light ... 931 Interfering light ......... 941 311 402 412, 40 2 1 502 312 403 413 313 404 414 314 4031, 4041 912, 913, 914, 912 ', 913', 914 '922, 923, 924 932 ^ 933 > 934 942

Page 13

Claims (1)

479125 6. Scope of patent application1. A conjugate optical path type two-dimensional displacement measurement method, the steps include: (1) generating a first incident light by a light source, and incident on a diffraction unit; (2) The first incident light is reflected by the diffractive unit to form at least two first diffracted lights; (3) the first diffracted light is returned by the original optical path through the action of the wavefront reconstruction optical component , The second incident light incident on the diffraction unit, (4) the second incident light, after being reflected by the diffraction unit, forms at least two second diffraction lights; (5) the second diffraction light , Through the action of the interference optical component, at least two interference lights are formed; (6) after the interference light is processed by the general optical interference phase-removal technology, the displacements in two linear independent directions in the two-dimensional movement can be obtained; 2 · The conjugate optical path type two-dimensional displacement measurement method described in item 1 of the scope of the patent application, wherein the light source is a light source capable of emitting nearly homogeneous light, which may be linearly polarized light, circularly polarized light, or elliptical polarized light . 3. The conjugate optical path type two-dimensional displacement measurement method as described in item 1 of the scope of patent application, wherein the first incident light is a nearly parallel beam, which can be generated by a combination of a light source and a parallel lens Or by a light source capable of generating a parallel beam. 4 · The total optical path two-dimensional displacement measurement method as described in item 1 of the patent application scope, wherein the first incident light is incident in the direction of the diffraction unit, 479125 VI. The scope of patent application is the direction normal to the incident point. 5 · The conjugate optical path type two-dimensional displacement measurement method according to item 1 of the scope of the patent application, wherein the diffraction unit may be a reflection-type diffraction unit or a transmission-type diffraction unit. 6 · The co-roller optical path type two-dimensional displacement measurement method according to item 1 of the scope of the patent application, wherein the diffraction unit may be a planar diffraction unit, a cylindrical diffraction unit, or a spherical diffraction unit. 7 · The total vehicle optical path two-dimensional displacement measurement method as described in item 1 of the scope of the patent application, wherein the diffraction unit is a component with a two-dimensional diffraction grating pattern, and the grating pattern is based on the absolute measurement mode. Designed with measurement mode or marked incremental measurement mode. 8 · The conjugate optical path type two-dimensional displacement measurement method as described in item 1 of the scope of the patent application, wherein the first diffraction light and the second diffraction light both carry a phase shift signal related to the two-dimensional motion displacement amount . 9 · According to the optical path type two-dimensional displacement measurement method described in item 1 of the scope of the patent application, the first and second diffraction lights are the first-order diffraction light. I 0 · The conjugate optical path type two-dimensional displacement measurement method as described in item 1 of the scope of the patent application, wherein the interference light contains interference signals related to two linearly independent displacements of two-dimensional motion. II · The conjugate optical path type two-dimensional displacement measurement method described in item 1 of the scope of patent application, wherein the wavefront reconstruction optical component can be a corner cube mirror (CORNER CUBE). 1 2 · The conjugate optical path type two-dimensional displacement amount as described in item 1 of the scope of patent application Page 15 VI. Method for measuring the scope of patent application, among which, "Why?" And "Yifu%" then reconstruct the optical component, which can be combined with a flat mirror 13 ^ + facet mirror and a patented lens such as a patent application The flute, s measurement method, the conjugate optical path-type two-dimensional displacement denier as described in 11, the medium-wavefront reconstruction optical component, can be the former 14 = asymptotic index lens (grinl; ns ^ with reflection 2 : Conjugate 15-kind of conjugate light described in item i of the patent scope: J ί 丰 'can be a polarizing beam splitter. U) By -light, / two # -dimensional displacement measurement method, the steps include : Diffraction unit ", generates-first-time incident light, is incident on-diffractive diffraction unit reflects I to form (2) the first incident light, and passes through the lesser two first-order diffracted lights;) the first —Second diffracted light, through the wavefront reconstruction of the optical component) f—the first incident light ', from the sand, where ... Ding ~ Jiu Xing, two less second diffracted light; $ 成 3this second diffracted light, After the general optical interference phase-resolving technique is used, two linear independent square displacements in two-dimensional motion can be obtained. The conjugate light path type two-dimensional speculative method described in item 15 of the patent scope, wherein the light source is a light source that emits nearly homogeneous light: it can be linearly polarized light, circularly polarized light, or elliptically polarized light. Λ, formed Fold back the original light path, and incident on the diffracted secondary incident light; After being reflected by the diffractive unit, the second brother of Pingwu is formed to 16 17 as conjugated optical path type as described in item 15 of the patent application Bit color Page 16 4/9125 6. Application for Patent Scope Testing Method 'It can produce cocoa if the application testing method is near as the application testing method diffraction order as the application testing method diffraction order as the application testing method part, its formula or attached as the application The test method is similar to the application test method independent of the test method 18 19 20 21 22 23 24, which consists of a light source parallel light patent model, which is the incident patent model, which is the yuan. Patent model, in which the element or sphere patent model, in which the raster image mark i was patent model, in which the bit shift patent model, in which the direction bit patent model, in which the first incident light is a nearly parallel, and a parallel lens The combination is generated by the light source of the beam. The direction of the normal line of the direction of the point where the first incident light of the common light path type two-dimensional v described in item 15 is incident on the diffraction unit. The conjugate optical path-type two-dimensional displacement i diffraction unit described in Item 15 is a reflection-type diffraction unit or a beam displacement amount of transmission j. The surface-type diffraction single circumference of the diffraction unit in Item 15 The diffraction early element of Item 15 is the first diffraction signal measured by the sample system in accordance with the absolute measurement of Item 15 of the mold. The second diffraction around the 15th place is related to the displacement of the second diffraction around the 15th place. The conjugate optical path type two-dimensional displacement described in the first diffraction is a planar diffraction unit and a unitary unit. The two-dimensional displacement tool of the two types described above is designed in the two-dimensional diffraction grating pattern using the $ measurement mode and the incremental measurement mode. The two-dimensional displacement of the light path of the vehicle is described. The displacement of the light carrier and the two-dimensional motion is described in the following. The two-dimensional displacement of the two types is two-dimensional displacement. There are two interference signals of two-dimensional motion. Two-dimensional displacement with a light path 479125