Method and apparatus for detecting cylinder and cylindrical converging lens

Abstract

A method and an apparatus for detecting a cylinder and a cylindrical converging lens are disclosed. In particular, a method for non-contact interference detection of a cylindrical shape is disclosed. Two converging lenses which modulate parallel light into cylindrical waves are combined with a to-be-tested cylinder respectively. Wavefront error data of the combination of the converging lens and the to-be-tested cylinder and wavefront error data of the combination of the two cylindrical converging lenses are obtained. Shape error data of the to-be-tested cylinder, the two cylindrical converging lenses is obtained respectively by using a difference algorithm and a wavefront recovery algorithm. In the technical solution, a detection light path is simple, and shape detection of a cylinder with relatively high precision can be implemented without using a high-precision detection tool calibrated in advance. The technical solution is particularly suitable for cylinder processing in the field of optical processing.

Claims

1. A method for detecting a cylinder and a cylindrical converging lens, comprising: step 1): steps of collecting wavefront error data of a combination of a first cylindrical converging lens (3) and a to-be-tested cylinder (1): sequentially arranging an interferometer configured to provide parallel light, the first cylindrical converging lens (3) configured to modulate parallel light into a cylindrical wave, and the to-be-tested cylinder (1) in a direction of an optical axis, wherein a center line of curvature of the to-be-tested cylinder (1) coincides with a focal line (2) formed by parallel light passing through the first cylindrical converging lens (3); making adjustments to enable the optical elements on the optical axis to be optically coaxial; and performing measurement by using the interferometer to obtain interferogram data of a parallel-light reference wavefront and a detected wavefront W.sub.A that is returned to the interferometer, wherein the detected wavefront W.sub.A carries a wavefront error W.sub.3 of the first cylindrical converging lens (3) and a wavefront error W.sub.1 of the to-be-tested cylinder (1); step 2): steps of collecting wavefront error data of a combination of a second cylindrical converging lens (4) and the to-be-tested cylinder (1): sequentially arranging the interferometer in step 1), the second cylindrical converging lens (4) configured to modulate parallel light into a cylindrical wave, and the to-be-tested cylinder (1) in step 1) in the direction of the optical axis, wherein the center line of curvature of the to-be-tested cylinder (1) coincides with a focal line (2) formed by parallel light passing through the second cylindrical converging lens (4); making adjustments to enable the optical elements on the optical axis to be optically coaxial; and performing measurement by using the interferometer to obtain interferogram data of the parallel-light reference wavefront and a detected wavefront W.sub.B that is returned to the interferometer, wherein the detected wavefront W.sub.B carries a wavefront error W.sub.4 of the second cylindrical converging lens (4) and the wavefront error W.sub.1 of the to-be-tested cylinder (1); step 3): steps of collecting wavefront error data of a combination of the first cylindrical converging lens (3) and the second cylindrical converging lens (4): sequentially arranging the interferometer in step 1), the first cylindrical converging lens (3) in step 1), the second cylindrical converging lens (4) in step 2), and a standard planar reflector (5) in the direction of the optical axis, wherein the focal line (2) of the second cylindrical converging lens (4) coincides with the focal line of the first cylindrical converging lens (3), the second cylindrical converging lens (4) is configured to remodulate diverging light passing through the focal line (2) into parallel light, and the standard planar reflector (5) is placed behind the second cylindrical converging lens (4) and configured to return parallel light; making adjustments to enable the optical elements on the optical axis to be optically coaxial; and performing measurement by using the interferometer to obtain interferogram data of the parallel-light reference wavefront and a wavefront W.sub.C that is returned to the interferometer and carries information about the wavefront error W.sub.3 of the first cylindrical converging lens (3) and the wavefront error W.sub.4 of the second cylindrical converging lens (4); and step 4): steps of performing data processing to acquire a shape error: recovering shape error data of the to-be-tested cylinder (1), the first cylindrical converging lens (3), and the second cylindrical converging lens (4) from the wavefronts W.sub.A, W.sub.B, and W.sub.C respectively obtained in the three measurements by using a wavefront recovery algorithm and data difference algorithms.

2. The method for detecting a cylinder and a cylindrical converging lens according to claim 1, wherein the first cylindrical converging lens (3) in step 3) and the first cylindrical converging lens (3) in step 1) are located at the same position on the optical axis, a spatial rotation angle around the focal line of the second cylindrical converging lens (4) between the second cylindrical converging lens (4) in step 3) and the second cylindrical converging lens (4) in step 2) is 180 degrees, and the second cylindrical converging lens (4) is located at a position where the focal line of the second cylindrical converging lens (4) coincides with the focal line of the first cylindrical converging lens (3).

3. The method for detecting a cylinder and a cylindrical converging lens according to claim 2, wherein in step 4), the wavefront recovery algorithm is Fourier transform, multifold path integral or Zernike fitting, and the data difference algorithms are W.sub.1=(W.sub.A+W.sub.BW.sub.C)/2, W.sub.3=(W.sub.A+W.sub.CW.sub.B)/2, and W.sub.4=(W.sub.B+W.sub.CW.sub.A)/2.

4. The method for detecting a cylinder and a cylindrical converging lens according to claim 1, wherein the to-be-tested cylinder (1) is a convex cylinder or a concave cylinder or a cylindrical converging lens.

5. The method for detecting a cylinder and a cylindrical converging lens according to claim 1, wherein the second cylindrical converging lens (4) in step 2) is fixed on a rotating platform, the rotating platform is fixed on a adjusting frame, and the adjusting frame and the rotating platform are adjusted to enable the focal line (2) formed by parallel light passing through the second cylindrical converging lens (4) to coincide with the center line of curvature of the to-be-tested cylinder (1).

6. The method for detecting a cylinder and a cylindrical converging lens according to claim 5, wherein in step 3), the rotating platform fixed with the second cylindrical converging lens (4) in step 2) is rotated 180 degrees, and the focal line of the second cylindrical converging lens (4) is adjusted by using an adjusting frame to coincide with the focal line of the first cylindrical converging lens (3).

7. The method for detecting a cylinder and a cylindrical converging lens according to claim 5, wherein the first cylindrical converging lens (3) or the second cylindrical converging lens (4) may be selected from a standard cylindrical lens, a computer-generated holographic chip that converges parallel light into a cylindrical wave, and a single lens configured to modulate parallel light into a cylinder or a cylindrical converging system that comprises more lenses.

8. The method for detecting a cylinder and a cylindrical converging lens according to claim 5, wherein the first cylindrical converging lens (3) and the second cylindrical converging lens (4) are computer-generated holographic chips, and a +1 level diffracted light of the computer-generated holographic chip is selected as an interference carrier, and a slit spatial filter (7) is placed at the focal line of the +1 level diffracted light of the computer-generated holographic chip, and the position of the spatial filter (7) is adjusted so that the +1 level diffracted light of the computer-generated holographic chip passes through the slit.

9. An apparatus for detecting a cylinder and a cylindrical converging lens, comprising a horizontal substrate (14), a first adjusting frame (10), a second adjusting frame (11), and a third adjusting frame (12) that are disposed on the horizontal substrate (14), a horizontal rotating platform (13) fixed on the second adjusting frame (11), a first cylindrical converging lens (3) disposed on the first adjusting frame (10), a second cylindrical converging lens (4) disposed on the rotating platform (13), and a to-be-tested cylinder (1) and a standard planar reflector (5) that are clamped on the second adjusting frame (11), wherein the first cylindrical converging lens (3) is optically coaxial with the second cylindrical converging lens (4) and the standard planar reflector (5) to form a first combined test area (15); the first cylindrical converging lens (3) is optically coaxial with the to-be-tested cylinder (1) to form a second combined test area (16); and the second cylindrical converging lens (4) is optically coaxial with the to-be-tested cylinder (1) to form a third combined test area (17), wherein the second cylindrical converging lens (4) in the first combined test area (15) is placed at a rear end of the first cylindrical converging lens (3), a focal line (2) of the second cylindrical converging lens (4) coincides with a focal line of the first cylindrical converging lens (3), the second cylindrical converging lens (4) is configured to remodulate diverging light passing through the focal line (2) into parallel light, and the standard planar reflector (5) is placed at a rear end of the second cylindrical converging lens (4) and configured to return parallel light; the to-be-tested cylinder (1) in the second combined test area (16) is placed at the rear end of the first cylindrical converging lens (3), and a center line of curvature of the to-be-tested cylinder (1) coincides with the focal line (2) formed by parallel light passing through the first cylindrical converging lens (3); the to-be-tested cylinder (1) in the third combined test area (17) is placed at the rear end of the second cylindrical converging lens (4), and the center line of curvature of the to-be-tested cylinder (1) coincides with the focal line (2) formed by parallel light passing through the second cylindrical converging lens (4); and a spatial rotation angle around the focal line of the second cylindrical converging lens (4) between the second cylindrical converging lens (4) in the first combined test area (15) and the second cylindrical converging lens (4) in the third combined test area (17) is 180 degrees.

10. The apparatus for detecting a cylinder and a cylindrical converging lens according to claim 9, further comprising a digital wavefront interferometer configured to provide parallel light, wherein the interferometer is respectively optically coaxial with the optical elements in the first combined test area (15), the second combined test area (16), and the third combined test area (17).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a light path of detecting a cylinder by using a standard cylinder method;

(2) FIG. 2 is a schematic structural diagram of a combination of a first cylindrical converging lens 3 and a to-be-tested cylinder 1;

(3) FIG. 3 is a schematic structural diagram of a combination of a second cylindrical converging lens 4 and a to-be-tested cylinder 1; and

(4) FIG. 4 is a schematic structural diagram of a combination of a first cylindrical converging lens 3 and a second cylindrical converging lens 4;

(5) FIG. 5 is a schematic structural diagram of a combination of a cylindrical converging holographic chip and a to-be-tested cylinder 1;

(6) FIG. 6 is a schematic structural diagram of a combination of two cylindrical converging holographic chips;

(7) FIG. 7 is a schematic structural diagram of the first combined test area;

(8) FIG. 8 is a schematic structural diagram of the second combined test area;

(9) FIG. 9 is a schematic structural diagram of the third combined test area;

(10) FIG. 10 is a schematic diagram of a light path when the to-be-tested cylinder is a convex cylinder;

(11) FIG. 11 is a schematic diagram of a light path when the to-be-tested cylinder is a cylindrical converging lens;

(12) FIG. 12 is a schematic diagram of a light path when a cylinder with a large diameter is detected using a stitching method;

(13) Where: 1 denotes a to-be-tested cylinder; 2 denotes a focal line; 3 denotes a first cylindrical converging lens configured to modulate parallel light into a cylindrical wave; 4 denotes a second cylindrical converging lens configured to modulate parallel light into a cylindrical wave; 5 denotes a standard planar reflector; 6 denotes a standard cylindrical lens; 7 denotes a slit spatial filter; 8 denotes a first holographic chip configured to modulate parallel light into a cylindrical wave; 9 denotes a second holographic chip configured to modulate parallel light into a cylindrical wave; 10 to 12 respectively denote a first adjusting frame, a second adjusting frame, and a third adjusting frame; 13 denotes a rotating platform; 14 denotes a horizontal substrate; 15 denotes a first combined test area; 16 denotes a second combined test area; 17 denotes a third combined test area.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(14) The method and apparatus for detecting a cylinder and a cylindrical converging lens of the present invention are further described below with reference to the accompanying drawings and embodiments.

(15) Embodiment 1 provides a method for detecting a cylinder and a cylindrical converging lens, including the following steps:

(16) Step 1) is a step of collecting wavefront error data of a combination of a first cylindrical converging lens 3 and a to-be-tested cylinder 1. As shown in FIG. 2 and FIG. 8, a commercial digital wavefront interferometer, the first cylindrical converging lens 3, and the to-be-tested cylinder 1 are sequentially arranged in a direction of an optical axis. A 4-inch plane standard lens is selected as a standard lens of the interferometer and is configured to provide parallel light. A focal length of the first cylindrical converging lens 3 is 100 mm. The first cylindrical converging lens 3 enables wavefronts of parallel light to converge into a cylindrical wave and intersect at a focal line 2. The to-be-tested cylinder 1 is a concave cylinder having a curvature radius of 45 mm. The position of the to-be-tested cylinder is adjusted to enable a center line of curvature of the to-be-tested cylinder to coincide with the focal line 2. Make adjustments to enable the optical elements on the optical axis to be optically coaxial. Measurement is performed by using the interferometer to obtain interferogram data of a parallel-light reference wavefront and a detected wavefront W.sub.A that is returned to the interferometer. The detected wavefront W.sub.A carries a wavefront error W.sub.3 of the first cylindrical converging lens 3 and a wavefront error W.sub.1 of the to-be-tested cylinder 1.

(17) Step 2) is a step of collecting wavefront error data of a combination of a second cylindrical converging lens 4 and the to-be-tested cylinder 1. As shown in FIG. 3 and FIG. 9, the first cylindrical converging lens 3 is replaced with a second cylindrical converging lens 4 having a focal length of 150 mm, and step 1) is repeated. Measurement is performed by using the interferometer to obtain interferogram data of the parallel-light reference wavefront and a detected wavefront W.sub.B that is returned to the interferometer. The detected wavefront W.sub.B carries a wavefront error W.sub.4 of the second cylindrical converging lens 4 and the wavefront error W.sub.1 of the to-be-tested cylinder 1.

(18) Step 3) is a step of collecting wavefront error data of a combination of the first cylindrical converging lens 3 and the second cylindrical converging lens 4. As shown in FIG. 4 and FIG. 7, the interferometer in step 1), the first cylindrical converging lens 3 in step 1), the second cylindrical converging lens 4 in step 2), and a standard planar reflector 5 are sequentially arranged in the direction of the optical axis. The focal line 2 of the second cylindrical converging lens 4 coincides with a focal line of the first cylindrical converging lens 3. The second cylindrical converging lens 4 is configured to remodulate diverging light passing through the focal line 2 into parallel light. The standard planar reflector 5 is placed behind the second cylindrical converging lens 4 and configured to return parallel light. Make adjustments to enable the optical elements on the optical axis to be optically coaxial. Measurement is performed by using the interferometer to obtain interferogram data of the parallel-light reference wavefront and a wavefront W.sub.C that is returned to the interferometer and carries information about the wavefront error W.sub.3 of the first cylindrical converging lens 3 and the wavefront error W.sub.4 of the second cylindrical converging lens 4.

(19) Step 4) is a step of performing data processing to acquire a shape error: shape error data of the to-be-tested cylinder 1, the first cylindrical converging lens 3, and the second cylindrical converging lens 4 are recovered from the wavefronts W.sub.A, W.sub.B, and W.sub.C respectively obtained in the three measurements by using a wavefront recovery algorithm and data difference algorithms.

(20) Embodiment 2: To facilitate data processing, based on Embodiment 1, the first cylindrical converging lens 3 in step 3) and the first cylindrical converging lens 3 in step 1) are located at the same position on the optical axis. A spatial rotation angle around the focal line of the second cylindrical converging lens 4 between the second cylindrical converging lens 4 in step 3) and the second cylindrical converging lens 4 in step 2) is 180 degrees. The second cylindrical converging lens 4 is located at a position where the focal line of the second cylindrical converging lens 4 coincides with the focal line of the first cylindrical converging lens 3. In step 4), the wavefront recovery algorithm is Fourier transform, multifold path integral or Zernike fitting, and the data difference algorithms are W.sub.1=(W.sub.A+W.sub.BW.sub.C)/2, W.sub.3=(W.sub.A+W.sub.CW.sub.B)/2, W.sub.4=(W.sub.B+W.sub.CW.sub.A)/2.

(21) Embodiment 3 provides a method for detecting a cylinder and a cylindrical converging lens based on Embodiment 1. The first cylindrical converging lens 3 and the second cylindrical converging lens 4 in Embodiment 1 are replaced by a first computer-generated holographic chip 8 and a second computer-generated holographic chip 9, which are transmitting phase gratings, as shown in FIG. 5 and FIG. 6, and the +1 level diffracted light of the computer-generated holographic chip is selected as an interference carrier. A slit spatial filter 7 is placed at the focal line of the +1 level diffracted light of the computer-generated holographic chip, and the position of the spatial filter 7 is adjusted so that the +1 level diffracted light of the computer-generated holographic chip passes through the slit.

(22) Embodiment 4 provides a method for detecting a cylinder and a cylindrical converging lens based on Embodiment 1. The to-be-tested cylinder may alternatively be a concave cylinder, a convex cylinder or a cylindrical converging lens. As shown in FIG. 10, when the to-be-tested cylinder is a convex cylinder, a curvature radius of the convex cylinder is smaller than a focal length f of the first cylindrical converging lenses 3 or 4 which is combined with it, and the convex cylinder is placed on a front end of the focal line 2 of the cylindrical converging lens, and a center line of curvature of the convex cylinder coincides with the focal line 2 of the cylindrical converging lens; as shown in FIG. 11, the to-be-tested cylinder can be a cylindrical converging lens, and mutual direction between each other can be achieved by using three cylindrical converging lenses; as shown in FIG. 12, when the to-be-tested cylinder is a cylinder with a large diameter, several cylinders with sub-diameters are planned on the cylinder with a large diameter, each cylinder with a sub-diameter is separately measured, and eventually a data stitching algorithm is used to detect the cylinder with a large diameter.

(23) Embodiment 5 provides an apparatus for detecting a cylinder and a cylindrical converging lens. As shown in FIG. 7, the apparatus includes a horizontal substrate 14, a first adjusting frame 10, a second adjusting frame 11, and a third adjusting frame 12 that are disposed on the horizontal substrate 14, a horizontal rotating platform 13 fixed on the second adjusting frame 11, a first cylindrical converging lens 3 disposed on the first adjusting frame 10, a second cylindrical converging lens 4 disposed on the rotating platform 13, and a to-be-tested cylinder 1 and a standard planar reflector 5 that are clamped on the second adjusting frame 11.

(24) The first cylindrical converging lens 3 is optically coaxial with the second cylindrical converging lens 4 and the standard planar reflector 5 to form a first combined test area 15. The first cylindrical converging lens 3 is optically coaxial with the to-be-tested cylinder 1 to form a second combined test area 16. The second cylindrical converging lens 4 is optically coaxial with the to-be-tested cylinder 1 to form a third combined test area 17.

(25) The second cylindrical converging lens 4 in the first combined test area 15 is placed at a rear end of the first cylindrical converging lens 3. A focal line 2 of the second cylindrical converging lens 4 coincides with a focal line of the first cylindrical converging lens 3. The second cylindrical converging lens 4 is configured to remodulate diverging light passing through the focal line 2 into parallel light. The standard planar reflector 5 is placed at a rear end of the second cylindrical converging lens 4 and configured to return parallel light.

(26) The to-be-tested cylinder 1 in the second combined test area 16 is placed at the rear end of the first cylindrical converging lens 3. A center line of curvature of the to-be-tested cylinder 1 coincides with the focal line 2 formed by parallel light passing through the first cylindrical converging lens 3.

(27) The to-be-tested cylinder 1 in the third combined test area 17 is placed at the rear end of the second cylindrical converging lens 4. The center line of curvature of the to-be-tested cylinder 1 coincides with the focal line 2 formed by parallel light passing through the second cylindrical converging lens 4.

(28) A spatial rotation angle around the focal line of the second cylindrical converging lens 4 between the second cylindrical converging lens 4 in the first combined test area 15 and the second cylindrical converging lens 4 in the third combined test area 17 is 180 degrees.

(29) In the present invention, two cylindrical converging lenses are combined and mutually detected to implement high-precision measurement. The advantage is that the problem of a shape test of a detection tool used to detect a cylinder is avoided. A difference algorithm can effectively reduce a processing precision requirement of a cylindrical converging lens. In addition, the cylindrical converging lens may be selected from a group composed of a standard cylindrical lens, a computer-generated holographic chip, and a single lens configured to modulate parallel light into a cylinder or a cylindrical converging system that includes more lenses, so that the flexibility is relatively high. A cylinder with a large diameter can further be detected by using the present invention in combination with a stitching algorithm.