Abstract
A system for measuring (200) a sample (2) by deflectometry comprising: a source (10) for generating a light beam in a source plane (105); an illumination module (19) for forming an illumination beam (9) comprising: a first converging optical element (18); a first selection optical element (16) with a first aperture (160); reflective matrix optical modulation means (30) to form a pattern (7), said first aperture (160) being configured to control the angles of said illumination beam (9) on said reflective matrix optical modulation means (30); a Schlieren lens (20) for obtaining an angle-intensity encoding of said pattern (7) on the sample (2); imaging (40) and detecting means (50) for detecting an image of said sample (2).
Claims
1. A system for measuring (200) a sample (2) by deflectometry comprising: a source (10) for generating a light beam in a source plane (105); an illumination module (19) comprising: a first converging optical element (18); a first selection optical element (16) having a first aperture (160), said first selection optical element (16) being positioned between said source plane (105) and said first converging optical element (18); said illumination module (19) being configured to generate an illumination beam (9) from said light beam of said source (10); matrix optical modulation means (30) in reflection, for forming a pattern (7) from said illumination beam (9); said first aperture (160) being configured to control angles of incidence of said illumination beam (9) on said matrix optical modulation means (30) in reflection; a Schlieren lens (20); said measuring system (200) being configured such that said pattern (7) is adapted to illuminate said Schlieren lens (20) so as to obtain an angle-intensity encoding of said pattern (7) into an inspection light beam (99); imaging means (40) for forming an image of said sample (2) after interaction of said inspection light beam (99) with said sample (2), said Schlieren lens (20) being positioned between said matrix optical modulation means (30) and said imaging means (40) along an optical path of a light beam generated by said source (10) when the latter is activated; matrix detection means (50) for detecting said image of said sample (2) formed by said imaging means (40).
2. The measuring system (200) according to the preceding claim characterized in that said matrix optical modulation means (30) are positioned in a modulation plane (195) optically conjugate to said source plane (105), said illumination beam (9) being spatially limited at the level of said matrix optical modulation means (30) in reflection by at least one of the following means: a second selection optical element (12) having a second aperture (120), positioned in said source plane (105); a third selection optical element (36) having a third aperture (360), positioned in said modulation plane (195); a source (10) comprising a spatially limited light source (15), preferably said light source (15) being a light emitting diode matrix.
3. The measuring system (200) according to any one of the preceding claims characterized in that said first selection optical element (16) is positioned in an object focal plane (185) of said first converging optical element (18).
4. The measuring system (200) according to any of the preceding claims characterized in that it further comprises: a third selection optical element (36) having a third aperture (360), said third selection optical element (36) being positioned at the level of said matrix optical modulation means (30).
5. The measuring system (200) according to any of the preceding claims characterized in that: said illumination module (19) is an illumination module 4F comprising: a second converging optical element (14) positioned between said source (10) and said first selection optical element (16), and configured such that: its object focal plane coincides with said source plane (105); its image focal plane coincides with said object focal plane (185) of said first converging optical element (18) positioned between said first (18) and second (14) converging optical elements, said image plane of the illumination module (19) coincides with the image focal plane of the first converging optical element (18).
6. The measuring system (200) according to any one of the preceding claims characterized in that said matrix optical modulation means (30) are matrix phase modulation means (30).
7. The measuring system (200) according to the preceding claim characterized in that the matrix phase modulation means (30) comprise a liquid crystal on silicon matrix.
8. The measuring system (200) according to any of the preceding claims characterized in that it further comprises: beam splitting means (60) configured so as to obtain from said illumination beam (9) resulting from said illumination module (19): a first light beam (91) deflected by said beam splitter (60) along a first optical path (61) directed towards said matrix optical modulation means (30); a second light beam (92) transmitted by said beam splitter (60) along a second optical path (62) resulting from a reflection of said first light beam deflected (91) by said matrix optical modulation means (30).
9. The measuring system (200) according to the preceding claim characterized in that said first (61) and second (62) optical paths are parallel.
10. The measuring system (200) according to any one of claims 1 to 5 characterized in that it further comprises: beam splitting means (60) configured to obtain from said illumination beam (9) resulting from the illumination module (19): a first light beam (91) transmitted by said beam splitter (60) along a first optical path (61) directed towards said matrix optical modulation means (30); a second light beam (92) deflected by said beam splitter (60) along a second optical path (62) resulting from a reflection of said first light beam (91) transmitted by said matrix optical modulation means (30).
11. The measuring system (200) according to the preceding claim characterized in that said first (61) and second (62) optical paths are perpendicular.
12. The measuring system (200) according to any one of the four preceding claims in dependence on claim 6 characterized in that the beam splitting means (60) comprise a polarizing beam splitter (60), preferably a polarizing beam splitter cube (60).
13. The measuring system (200) according to the preceding claim characterized in that said illumination beam (9) resulting from said illumination module (19) is directed along an optical axis A, said polarizing beam splitter (60) is configured such that the optical axis A is perpendicular to said second optical path (62).
14. The measuring system (200) according to any one of the preceding claims characterized in that said source (10) comprises a light source (15) and a second selection means (12) having a second aperture (120) for spatially limiting a light beam resulting from said light source (15).
15. The measuring system (200) according to the preceding claim characterized in that said second selection means (12) is positioned in said source plane (105).
16. The measuring system (200) according to any of the preceding claims characterized in that said source (10) comprises a spatially limited light source (15), preferably said light source is a LED matrix.
17. The measuring system (200) according to any one of the preceding claims when dependent on claim 5 characterized in that: said light beam is spatially limited according to a spatially limited light beam surface area S.sub.10, and, said matrix optical modulation means (30) have an optical modulation surface area S.sub.30 such that: where γ is the magnification factor of the illumination module (19) according to claim 5, so that: where f.sub.1 corresponds to the focal length of the first converging optical element (18) and f.sub.2 corresponds to the focal length of the second converging optical element (14).
18. The measuring system (200) according to any one of the preceding claims characterized in that said first aperture (16) has a first aperture surface area (160) of less than 50 mm.sup.2, preferably less than 25 mm.sup.2 and even more preferably less than 10 mm.sup.2.
19. The measuring system (200) according to any one of the preceding claims characterized in that said first aperture (160) is centered on said optical axis A.
20. The measuring system (200) according to any one of the preceding claims when dependent on claim 10 characterized in that it further comprises: a non-planar mirror (70) positioned so as to reflect said second light beam (92), resulting from a reflection on said matrix phase modulation means (30), into a third light beam (93) reflected to said beam splitter (60) along a third optical path (63).
21. The measuring system (200) according to the preceding claim characterized in that the non-planar mirror is concave.
22. The measuring system (200) according to any one of claims 20 to 21 characterized in that the beam splitter (60) is a polarizing beam splitter and in that it further comprises: a quarter-wave plate positioned between said non-planar mirror (70) and said polarizing beam splitting means (60).
23. The measuring system (200) according to claims 18 and 20 characterized in that said polarizing light beam splitter (60) is configured such that said third light beam (93) reflected by said non-planar mirror (70) along said third optical path (63) is deflected by said polarizing beam splitter (60) into a fourth light beam (94) along a fourth optical path (64).
24. The measuring system (200) according to claims 18 and 20 characterized in that said polarizing light beam splitter (60) is configured such that said third light beam reflected (93) along said third optical path (63) is transmitted by said polarizing beam splitter (60) into a fourth light beam (94) along a fourth optical path (64).
25. The measuring system (200) according to any one of claims 23 to 24 characterized in that it is configured such that: said second (62) and third (63) optical paths are substantially parallel, and, said optical axis A and said fourth optical path (64) are substantially parallel.
26. The measuring system (200) according to any one of the preceding claims characterized in that said Schlieren lens (20) is positioned between said projection device (100) and said imaging means (40).
27. The measuring system (200) according to any one of the preceding claims characterized in that said Schlieren lens (20) is positioned in an optical path between said matrix phase modulation means (30) and said imaging means (40).
28. The measuring system (200) according to any one of the preceding claims characterized in that said imaging means (40) comprise: a first (20; 420) and a second (400) converging imaging optical elements configured such that an image focus of one coincides with an object focus of the other at a second convergence point located in a second focusing plane (405) positioned between said first (20; 420) and second (400) converging imaging optical elements, said imaging means (40) being adapted to form an image of said sample (2) from said inspection beam (99) having interacted with said sample (2) on said matrix detection means (50).
29. The measuring system (200) according to the preceding claim characterized in that said imaging means (40) further comprise: a fourth selection optical element (45) having a fourth aperture surrounding said second convergence point.
30. The measuring system (200) according to the preceding claim, characterized in that said fourth aperture is positioned at the level of the image focus of said first imaging optical element (20; 420) and of the object focus of said second imaging optical element (400) so as to let pass essentially the portion of the light beam propagating parallel to the optical axis A.
31. The measuring system (200) according to any one of the three preceding claims characterized in that said Schlieren lens (20) replaces said first imaging optical element (420) along an optical path of said inspection beam (99) after the latter has interacted in reflection with said sample (2).
32. The measuring system according to any one of the preceding claims characterized in that said imaging means (40) are imaging means 4F such that: said first converging optical element (20; 420) is positioned between said Schlieren lens (20) and said fourth selecting means (45), so that its object focal plane coincides with a plane of said sample (2) and, said second converging optical element (400) is positioned between said fourth selecting means (45) and said matrix detection means (50), so that its image focal plane coincides with said matrix detection means (50).
Description
BRIEF DESCRIPTION OF FIGURES
[0113] These and other aspects of the invention will be clarified in the detailed description of particular embodiments of the invention, reference being made to the drawings of the figures, in which:
[0114] FIG. 1 shows a schematic representation of the measuring system of the invention;
[0115] FIGS. 2a, 2b, 3a, 3b, 4a, 4b show embodiments of a projection device of the measuring system of the invention;
[0116] FIG. 3c shows an embodiment of the source and the illumination module;
[0117] FIG. 5 shows an embodiment of the source;
[0118] FIG. 6 shows an embodiment of the matrix optical modulation means;
[0119] FIGS. 7, 8a, 8b, 9, 10a and 10b show embodiments of the measuring system of the invention.
[0120] The drawings in the figures are not to scale. Generally, similar elements are denoted by similar references in the figures. The presence of reference numbers in the drawings shall not be considered limiting, even when such numbers are indicated in the claims.
DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION
[0121] FIG. 1 shows a schematic representation of the deflectometry measuring system 200 of the invention. The measuring system 200 comprises a projection device 100 allowing to project onto the optical element to be measured 2, a pattern whose angle of incidence of that pattern on the optical element to be measured 2 is controlled with accuracy by the projection device. The measuring system 200 further comprises imaging means 40 for forming an image of the optical element to be measured 2 on matrix detection means 50.
[0122] FIG. 2a shows a projection device 100 according to an embodiment of the invention. This projection device 100 comprises a spatially limited light source 10 along a light source surface S.sub.10. The source 10 is configured to emit a light beam in the source plane 105. According to a preferred embodiment, the source 10 is configured to emit a spatially limited light beam in the source plane 105. The projection device 100 comprises an illumination module 19 comprising a first selection means 16 having a first aperture 160 and a first converging optical element 18. According to a preferred embodiment, the first aperture 160 is positioned in the object focal plane 185 of the first converging optical element 18. The first aperture 160 and the first converging optical element are positioned so as to collect a spatially limited portion of the light beam. The spatially limited light beam after its passage through the first aperture 160 and the first converging optical element 18 is the illumination beam 9 which is directed towards a beam splitting means 60 for further direct it towards a matrix optical modulation means 30 in reflection with a direction normal to the surface of the matrix optical modulation means 30. The matrix optical modulation means 30 have an illuminated optical modulation surface S.sub.30, at least partly, by the illumination beam 9 resulting from the passage of the light beam resulting from the source 10 in the illumination module 19. The illumination beam 9 becomes the first light beam 91 along a first optical path 61 after its passage through the splitting means 60 and is reflected into a second light beam 92 by the matrix optical modulation means 30 in reflection along a direction normal thereto along a second optical path 62. The beam splitting means 60 allows at least a portion of the light beam reflected by the matrix optical modulation means 30 to be transmitted to a Schlieren lens 20. The beam reflected by the matrix optical modulation means 30 has a pattern 7 which then illuminates the Schlieren lens 20. The Schlieren lens 20, allows an inspection light beam 99 to be projected onto an optical element to be measured 2, the angle of incidence of which varies according to an offset of the pattern 7 as it illuminates the Schlieren lens 20.
[0123] FIG. 2b is an embodiment close to that of FIG. 2a. It differs, however, in that the matrix optical modulation means 30 are positioned such that when the first light beam 91 along a first optical path 61 is reflected into a second light beam 92 by the matrix optical modulation means 30 in reflection along a direction normal thereto along a second optical path 62, the light beam splitting means 60 are configured to transmit at least a portion of the first light beam 91 and to reflect at least a portion of the second light beam 92. The beam splitting means 60 allows at least a portion of the light beam reflected 92 by the matrix optical modulation means 30 to be reflected to a Schlieren lens 20. The illumination beam 9 becomes the first light beam 91 along a first optical path 61 after its transmission through the splitting means 60.
[0124] The matrix optical modulation means 30 in reflection are configured to reflect the image of the light source 10 with a pattern 7 which after passing through the Schlieren lens 20 allows to provide an inspection beam for a deflectometry measuring system 200. According to a preferred embodiment, the source 10 is configured to emit a spatially limited light beam in the source plane 105. The pattern 7 thus formed by the projection device of the invention 100 is created by the point-by-point (pixel-by-pixel) activation or non-activation of the matrix optical modulation means 30 in reflection. The activation of the matrix optical modulation means 30 in reflection, allows for example a spatial deviation, a change in phase, a change in a reflection factor etc. The modulation can thus be carried out in intensity or in phase to illuminate the Schlieren lens 20 with the pattern 7. The phase modulation requires a polarizing optical element to convert the phase modulation into an intensity modulation, which is required in the case of the application of the projection device 100 for a measurement by deflectometry. A polarizing optical element is for example a polarizer. The phase modulation results in a modulation of the polarization of the light, which is analyzed by the polarizer.
[0125] FIG. 3a shows another embodiment of the projection device 100 of the invention. The projection device 100 comprises a spatially limited light source 100 along an emission surface S.sub.10. The projection device 100 comprises an illumination module 19, which is an imaging system 4F, for forming an image of the spatially limited light source 10 in the source plane 105 on the matrix optical modulation means 30. The illumination module 19 comprises a first 18 and a second 14 converging optical elements, such as converging thin lenses or pairs of converging thin lenses. The first 18 and second 14 converging optical elements are positioned so that the image focal plane of the second optical element 14 coincides with the object focal plane of the first optical element 18. Thus, according to a preferred embodiment, by means of the illumination module 19, an image of the light source 10 is obtained on the matrix optical modulation means 30 in reflection. The projection device further comprises a first selection optical element 16 having a first aperture 160. This first aperture 160 is positioned so as to surround a convergence point 150 corresponding to the coincidence of the image focus of the second converging optical element 14 and the object focus of the first converging optical element 18. Thus, the first aperture 160 allows to control the maximum angular aperture (maximum angular distribution) (at the level of the matrix optical modulation means and not at the level of the object to be tested) of the light beam generated by the source 10 that exhibits an excessive divergence/convergence. Indeed, the light beam resulting from the source 10 is focused and only the light beams entering parallel to the optical axis of the second convergent optical element 14 pass through its image focus located on the optical axis A. The second aperture 160 therefore allows to limit the passage of the components of the light beam passing through the first converging optical element 18. Thus, it is possible to obtain a collimated illumination beam 9 whose components propagate substantially parallel to the optical axis A. The first aperture 160 is formed in the first selection optical element 16. The first aperture 160 may have a circular, elliptical or rectangular cross-sectional area, for example. The cross-sectional area of the first aperture 160 preferably has a surface area of less than 10 mm.sup.2, more preferably less than 5 mm.sup.2 and even more preferably less than 2 mm.sup.2.
[0126] The first converging optical element 18 has a focal length f.sub.1. The second converging optical element 14 has a focal length f.sub.2.
[0127] In FIG. 3a, the device 100 comprises beam splitting means 60 which allow the optical modulation means 30 to be illuminated at a selected angle. Here, the beam splitting means 60 allows to illuminate the optical modulation means 30 with the illumination beam 9 (preferably collimated) which becomes the first light beam 91 along a first optical path 61 describing an angle of 90° with respect to the matrix phase modulation means 30. A portion of the illumination beam 9 (collimated) is transmitted through the beam splitting means 60 (not shown) and a portion is reflected to the optical modulation means 30. In a preferred embodiment, a polarizer is positioned between the source 10 and the beam splitting means 60 so as to block the portion of the illumination beam 9 that would be transmitted through the splitting means 60. Thus, the beam splitting means 60 are configured so as to obtain from said illumination beam 9 (collimated), a first light beam 91 deflected by the beam splitter 60 along a first optical path 61 directed towards said matrix optical modulation means 30. The first light beam is reflected onto the matrix optical modulation means 30 into a second light beam 92. The second light beam 92 is directed towards the beam splitter 60 where it is transmitted at least partly by said beam splitter 60 along a second optical path 62.
[0128] In FIG. 3a, in the case of beam splitting means 60 which is a polarizing cube, the illumination beam 9 which becomes the first light beam 91 when deflected by the cube corresponds to a (collimated) beam polarization. The reflection of the first light beam 91 onto the matrix phase modulation means 30 allows the polarization of portions of the second light beam 92 to be selectively modified. Preferably, the matrix phase modulation means 30 allow the polarization to be selectively modified with a 90° phase shift relative to the polarization of the first light beam 91. Thus, the portions of the second light beam 92 having undergone a 90° phase shift are transmitted by the cube 60 while the portions of the second light beam 92 having not undergone a phase shift are reflected by the cube 60 (towards the source). In this way, a pattern 7 can illuminate the Schlieren lens and be projected by the projection device 100 onto the optical element to be measured 2 with an angle-intensity encoding for a measurement by deflectometry. According to a particular embodiment, it is possible to have a non-binary image by playing on the fraction of time during which the polarization is modified.
[0129] FIG. 3b shows a variant of FIG. 3a where the phase modulation means are positioned so as to be illuminated by the portion of the (collimated) beam that is transmitted by the cube 60 rather than the portion of the (collimated) beam that is reflected/deflected by the cube 60 (as in FIG. 3a). Thus, the phase modulation means allow to induce a 90° phase shift to the illumination beam 9 which becomes the first light beam 91 in a selective manner so as to form a pattern 7. Thus, the portions of the second light beam 92 having undergone this 90° phase shift are reflected by the cube 60 while the portions (not shown) having not undergone a phase shift are transmitted by the cube 60. The pattern 7 projected onto the Schlieren lens 20 by the second light beam 92 after its passage through the cube 60 (reflection) can therefore be used for a measurement by deflectometry.
[0130] FIG. 3c shows an embodiment of the illumination module according to FIGS. 3a, 3b, 4a and 4b. In this embodiment, the first 18 and second 14 converging optical elements each comprise a pair of converging lenses. This embodiment allows commercially available lens pairs to be used to achieve shorter focal lengths. For example, the lens pairs 141, 142; 181, 182 comprise two lenses 141, 142; 181, 182 of focal length 50 mm, which allow to provide first 18 and second 14 converging optical elements of focal length 25 mm. The lenses 141, 142; 181, 182 of each pair being for example 1 mm apart.
[0131] FIG. 4a shows the projection device of FIG. 3a further comprising a non-planar mirror 70 allowing to reflect the second light beam 92 to the cube 60, into a third light beam 93 along a third optical path 63. According to a preferred embodiment, a polarizer (not shown) is positioned between the first converging optical element 18 and the beam splitting means 60 so that all the intensity of the illumination light beam 9 directed towards the beam splitting means 60 is reflected to the matrix optical modulation means 30. The third light beam 93 is then reflected by the cube 60 into a fourth light beam 94 along a fourth optical path towards an optical element to be measured 2. A quarter-wave plate is positioned between the non-planar mirror 70 and the cube 60, so that the second beam 92 which is transmitted by the cube 60 and then reflected by the non-planar mirror 70 into a third beam 93 is reflected by the cube 60 into a fourth beam 94. Indeed, the passage of the second and then of the third beam 92, 93 through the quarter-wave plate allows to generate a 90° phase shift in the light beam so that its direction is deviated when it passes back into the cube 60 (with negligible losses in intensity). The pattern 7 generated by this embodiment is then directed towards the Schlieren lens 20 and projected by the projection device 100 onto the optical element to be measured 2 with an angle-intensity encoding for a measurement by deflectometry. Due to the reflection on the non-planar mirror, this embodiment allows large angles to be generated during the angle-intensity encoding by the Schlieren lens 20, which allows the measurement of optical elements to be measured 2 with small radii of curvature.
[0132] The device of FIG. 4a comprising the non-planar mirror 70 and a quarter-wave plate can be configured from the device 100 described in FIG. 3b, by changing the position of the elements relative to the cube 60. The advantage of being able to modify the position of the elements around the cube 60 allows to make the device adaptable to different applications requiring various cluttering.
[0133] The device in FIG. 4b shows a combination of FIG. 4a with the imaging module 19 of FIG. 2a.
[0134] FIG. 5 shows a spatially limited light source 10 comprising a light source 15 and a second selection optical element 12 having a second aperture 120. The second aperture 120 is formed in the second selection optical element 12. For example, the second aperture 120 has a rectangular, square, elliptical or circular cross-sectional area. The second aperture 120 has a second aperture surface area S.sub.120 that corresponds to the surface area of the recessed portion of the second selection optical element 12. The light beam resulting from the light source 15 is therefore spatially limited by the second selection optical element 12, so as to obtain a spatially limited light beam adapted to illuminate a surface according to a rectangle, an ellipse or a circle. For example, S.sub.10 is greater than S.sub.120. The second selection optical element is positioned in a source plane 105. The use of the source 10 of FIG. 5 in a projection device of FIGS. 2a, 2b, 3a, 3b, 3c, 4 allows, thanks to the positioning of the first 16 and second 12 selection optical elements with respect to the illumination module 19, to obtain a well controlled illumination of the optical modulation means 30, that is to say an illumination with a light beam whose sizes do not exceed the sizes of the active portion of the matrix optical modulation means 30 in reflection or of the useful area for defining the maximum desired angular distribution. The active portion of the matrix optical modulation means 30 in reflection is, for example, a liquid crystal matrix on a semiconductor substrate. In addition to the spatial control of the beam illuminating the matrix optical modulation means 30 in reflection, the first aperture 160 allows to control the angles of incidence of the beam on the matrix optical modulation means 30 in reflection and thus the angles after reflection.
[0135] FIG. 6 shows an embodiment of the matrix optical modulation means 30 comprising third selection means 36 having a third aperture 360. The third aperture 360 is positioned in the plane 195 of the matrix optical modulation means 30, so as to spatially limit the light beam reflected by the matrix optical modulation means 30. The matrix optical modulation means 30 of FIG. 6 may be adapted to any embodiment of the measuring system 200 of the present invention.
[0136] FIGS. 7, 8a, 8b and 9 illustrate several embodiments of the deflectometry measuring system 200 according to the invention.
[0137] FIG. 7 illustrates an embodiment of the deflectometry measuring system 200 of the invention. The measuring system 200 comprises the projection device 100, which allows to project the pattern 7 after it passes through the Schlieren lens 20 towards the optical element to be measured 2. Then, an image of the element 2 to be measured is formed on the matrix detection means 50 by the imaging means 40. The matrix optical modulation means and the matrix imaging means are synchronized so that an image is acquired for each pattern projection 7. For each successively acquired image, the pattern 7 is shifted in phase on the Schlieren lens 20 with respect to the preceding image, so as to obtain a variation of the angles of the pattern 7 on the optical element to be measured 2. The illumination module 19 corresponds to one of the illumination modules 19 shown and described in FIGS. 2a, 2b, 3a, 3b, 3c, mutatis mutandis.
[0138] The measurement rate of an optical element 2 to be measured is in part defined by the speed of the optical modulation means 30. A possible option to achieve higher speeds is to display a binary pattern 7 instead of a sinusoidal pattern 7. Indeed, the binary pattern 7 will be transformed into a sinusoidal-like pattern 7 after convolution with the response of the blocking element 45. It should be noted that this conversion is never perfect. Also, the gain in speed translates into a loss in optical performance in general and in angular resolution in particular. It is also possible to generate a non-binary image on the matrix detection means 50 with a binary pattern 7 by adjusting the time during which the pattern 7 is displayed by the matrix optical modulation means 30. This is possible provided that said time is shorter than the integration time used by the matrix detection means 50 and that the matrix detection means 50 and the matrix optical modulation means 30 are synchronized. In the absence of sample to be measured 2 in the system 200, the second focusing plane 405 is conjugate to the image plane (or modulation plane) 195 with possible positioning tolerances.
[0139] FIG. 8a shows an embodiment of the measuring system 200 comprising, in addition to the embodiment of FIG. 7, a polarizing beam splitter cube 60 positioned between the Schlieren lens 20 and the phase modulation means 30, such that the components of the second light beam 92 that have undergone a phase modulation during the reflection of the first light beam 91 on the phase modulation means 30 are transmitted by the cube 60 along the second optical path 62. It is possible to implement the embodiment of the projection device 100 of FIG. 3b in which, the beam splitter cube 60 is positioned between the illumination module 19 and the phase modulation means 30, such that the components of the second light beam 92 having undergone a phase modulation during the reflection of the first light beam 91 on the phase modulation means 30 are reflected by the cube 60 along the second optical path 62.
[0140] FIG. 8b shows an embodiment of the measuring system 200 for the measurement of optical elements 2 in reflection. The measuring system 200 comprises the projection device 100 configured to project the pattern 7 onto the optical element 2 to be measured. The projection device 100 comprises the splitter cube 60 allowing to form the pattern 7 from the reflected beam on the matrix phase modulation means 30. The pattern 7 is projected through the Schlieren lens 20 to the optical element 2 to be measured, where it is reflected back through the Schlieren lens 20 to the cube 60. The pattern 7 is then directed by the cube 60 towards the matrix detection means 50. An image of the optical element to be measured in reflection 2 is then formed on the matrix detection means 50 by the imaging means 40 using the Schlieren lens 20 in combination with a second imaging optical element 400. A quarter-wave plate not shown positioned between the optical element 2 and the polarizing cube 60 allows the reflection by the cube 60 of the light beam reflected by the optical element 2. This embodiment is particularly compact because it uses the same polarizing cube 60 for the formation of the pattern 7 in combination with the phase modulation means 60 in reflection by playing the role of an analyzer and then allowing to carry out a measurement of an element 2 in reflection by allowing with a quarter-wave plate, a measurement with a light beam perpendicular to the optical axis of the element to be measured 2.
[0141] FIG. 9 shows an embodiment of the measuring system 200 comprising the projection device 100 of FIG. 4a or 4b. Preferably, a polarizer (not shown) is positioned between the illumination module 19 and the beam splitting means 60 to prevent all the light of the illumination beam from being directly transmitted by the light beam splitting means 60. The fourth light beam 94 defining the pattern 7 passes through the Schlieren lens 20 to encode the angle of the inspection beam 99 according to the intensity of the pattern. The inspection beam is preferably projected by the projection device 100 along the fourth optical path 64 the optical element to be measured 2. An image of the optical element to be measured is formed on the matrix detection means 50 by the imaging means 40. This embodiment is particularly well adapted to measurements of optical elements 2 having a high optical power, for example greater than 20 D and even more adapted to optical powers greater than 25 D. Optical elements 2 having a high optical power are for example intraocular lenses.
[0142] FIG. 10a shows an example of the projection device 100 similar to that of FIGS. 3a and 3b but not requiring beam splitting means.
[0143] FIG. 10b shows an example of the projection device 100 similar to that of FIGS. 2a and 2b but not requiring beam splitting means. The projection devices 100 of FIGS. 10a and 10b can be used in the embodiments of the deflectometry measuring systems of FIGS. 7, 8a, 8b, 9, and in particular with that of FIG. 7.
[0144] The present invention has been described above in connection with specific embodiments, which are illustrative and should not be considered limiting. In general, the present invention is not limited to the examples illustrated and/or described above. The use of the verbs “comprise”, “include”, or any other variant, as well as their conjugations, can in no way exclude the presence of elements other than those mentioned. The use of the indefinite article “a”, “an”, or the definite article “the”, to introduce an element does not exclude the presence of a plurality of these elements. The reference numbers in the claims do not limit their scope.
[0145] In summary, the invention can also be described as follows. A system for measuring 200 a sample 2 by deflectometry, comprising: [0146] a source 10 for generating a spatially limited light beam in a source plane 105; [0147] an imaging module 19 comprising: [0148] a first converging optical element 18; [0149] a first selection optical element 16 having a first aperture 160, said first selection optical element 16 being positioned in an object focal plane 185 of said first converging optical element 18; [0150] matrix optical modulation means 30 in reflection positioned in an image plane of the imaging module 19 which is conjugate to said source plane 105, to form a pattern 7; [0151] a Schlieren lens 20;
said measuring system 200 being configured such that said pattern 7 is adapted to illuminate said Schlieren lens 20 so as to obtain an angle-intensity encoding of said pattern 7 into an inspection light beam 99; [0152] imaging means 40 for forming an image of said sample 2 after interaction of said inspection light beam 99 with said sample 2; [0153] matrix detection means 50 for detecting said image of said sample 2 formed by said imaging means 40.
[0154] In summary, the invention can also be described as follows.
A system for measuring 200 a sample 2 by deflectometry, comprising: [0155] a source 10 for generating a light beam in a source plane 105; [0156] an illumination module 19 for forming an illumination beam (9) comprising: [0157] a first converging optical element 18; [0158] a first selection optical element 16 with a first aperture 160; [0159] matrix optical modulation means 30 in reflection, to form a pattern 7, said first aperture 160 being configured to control the angles of said illumination beam 9 on said matrix optical modulation means 30 in reflection; [0160] a Schlieren lens 20 to obtain an angle-intensity encoding of said pattern 7 on the sample 2; [0161] imaging means 40 and detecting means 50 for detecting an image of said sample 2.
