Method and apparatus for detecting concave cylinder and cylindrical diverging lens

Abstract

A method and an apparatus for detecting a concave cylinder and a cylindrical diverging lens are disclosed. In particular, a method for non-contact interference detection of a cylindrical shape is disclosed. A cylindrical converging lens and a cylindrical diverging lens are combined with a to-be-tested concave cylinder respectively. Wavefront error data of the combination of the cylindrical diverging lens and the to-be-tested concave cylinder and wavefront error data of the combination of the cylindrical converging lens and the to-be-tested concave cylinder are obtained through interference measurement respectively. Wavefront error data of a combination of the cylindrical diverging lens and the cylindrical converging lens is then obtained through interference measurement. Shape error data of the to-be-tested concave cylinder, the cylindrical diverging lens, and the cylindrical converging lens is obtained respectively by using a difference algorithm and a wavefront recovery algorithm.

Claims

1. A method for detecting a concave cylinder and a cylindrical diverging lens, comprising: step 1): steps of collecting wavefront error data of a combination of a cylindrical diverging lens (3) and a to-be-tested concave cylinder (1): sequentially arranging an interferometer configured to provide parallel light, the cylindrical diverging lens (3) configured to modulate parallel light into a diverging cylindrical wave, and the to-be-tested concave cylinder (1) in a direction of an optical axis, wherein a center line of curvature of the to-be-tested concave cylinder (1) coincides with a virtual focal line (2) formed by parallel light passing through the cylindrical diverging 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 cylindrical diverging lens (3) and a wavefront error W.sub.1 of the to-be-tested concave cylinder (1); step 2): steps of collecting wavefront error data of a combination of a cylindrical converging lens (4) and the to-be-tested concave cylinder (1): sequentially arranging the interferometer in step 1), the cylindrical converging lens (4) configured to modulate parallel light into a cylindrical wave, and the to-be-tested concave cylinder (1) in step 1) in the direction of the optical axis, wherein the center line of curvature of the to-be-tested concave cylinder (1) coincides with a focal line (2) formed by parallel light passing through the 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 cylindrical converging lens (4) and the wavefront error W.sub.1 of the to-be-tested concave cylinder (1); step 3): steps of collecting wavefront error data of a combination of the cylindrical diverging lens (3) and the cylindrical converging lens (4): sequentially arranging the interferometer in step 1), the cylindrical diverging lens (3) in step 1), the 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 cylindrical converging lens (4) coincides with the virtual focal line of the cylindrical diverging lens (3), the cylindrical converging lens (4) is configured to remodulate diverging light into parallel light, and the standard planar reflector (5) is placed behind the 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 cylindrical diverging lens (3) and the wavefront error W.sub.4 of the 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 concave cylinder (1), the cylindrical diverging lens (3), and the 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 concave cylinder and a cylindrical diverging lens according to claim 1, wherein the cylindrical diverging lens (3) in step 3) and the cylindrical diverging 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 cylindrical converging lens (4) between the cylindrical converging lens (4) in step 3) and the cylindrical converging lens (4) in step 2) is 180 degrees, and the cylindrical converging lens (4) is located at a position where the focal line of the cylindrical converging lens (4) coincides with the virtual focal line of the cylindrical diverging lens (3).

3. The method for detecting a concave cylinder and a cylindrical diverging 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 concave cylinder and a cylindrical diverging lens according to claim 1, wherein the to-be-tested concave cylinder (1) can be replaced with the cylindrical converging lens.

5. The method for detecting a concave cylinder and a cylindrical diverging lens according to claim 1, wherein the cylindrical converging lens (4) in step 2) is fixed on a rotating platform (10), the rotating platform is fixed on a second adjusting frame (7), and the second adjusting frame (7) and the rotating platform (10) are adjusted to enable the focal line (2) formed by parallel light passing through the cylindrical converging lens (4) to coincide with the center line of curvature of the to-be-tested concave cylinder (1).

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

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

8. An apparatus for detecting a concave cylinder and a cylindrical diverging lens, comprising a horizontal substrate (11), a first adjusting frame (6), a second adjusting frame (7), and a third adjusting frame (8) that are disposed on the horizontal substrate (11), a horizontal rotating platform (10) fixed on the second adjusting frame (7), a cylindrical diverging lens (3) disposed on the first adjusting frame (6), a cylindrical converging lens (4) disposed on the rotating platform (10), and a to-be-tested concave cylinder (1) and a standard planar reflector (5) that are clamped on the second adjusting frame (7), wherein the cylindrical diverging lens (3) is optically coaxial with the cylindrical converging lens (4) and the standard planar reflector (5) to form a first combined test area (9); the cylindrical diverging lens (3) is optically coaxial with the to-be-tested concave cylinder (1) to form a second combined test area (12); and the cylindrical converging lens (4) is optically coaxial with the to-be-tested concave cylinder (1) to form a third combined test area (13), wherein the cylindrical converging lens (4) in the first combined test area (9) is placed at a rear end of the cylindrical diverging lens (3), a focal line (2) of the cylindrical converging lens (4) coincides with a virtual focal line of the cylindrical diverging lens (3), the cylindrical converging lens (4) is configured to remodulate diverging light into parallel light, and the standard planar reflector (5) is placed at a rear end of the cylindrical converging lens (4) and configured to return parallel light; the to-be-tested concave cylinder (1) in the second combined test area (12) is placed at the rear end of the cylindrical diverging lens (3), and a center line of curvature of the to-be-tested concave cylinder (1) and coincides with the virtual focal line (2) formed by parallel light passing through the cylindrical diverging lens (3); the to-be-tested concave cylinder (1) in the third combined test area (13) is placed at the rear end of the cylindrical converging lens (4), and the center line of curvature of the to-be-tested concave cylinder (1) coincides with the focal line (2) formed by parallel light passing through the cylindrical converging lens (4); and a spatial rotation angle around the focal line of the cylindrical converging lens (4) between the cylindrical converging lens (4) in the first combined test area (9) and the cylindrical converging lens (4) in the third combined test area (13) is 180 degrees, and a curvature radius R of the to-be-tested concave cylinder (1) is greater than a focal length f of the cylindrical diverging lens (3).

9. The apparatus for detecting a concave cylinder and a cylindrical diverging lens according to claim 8, 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 (9), the second combined test area (12), and the third combined test area (13).

10. The apparatus for detecting a concave cylinder and a cylindrical diverging lens according to claim 8 or 9, wherein a rear surface of the to-be-tested concave cylinder (1) is a plane, and the concave cylinder is optically coaxial with the plane.

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 cylindrical diverging lens and a cylindrical converging lens in a first combined test area;

(3) FIG. 3 is a schematic structural diagram of a combination of a cylindrical diverging lens and a to-be-tested concave cylinder in a second combined test area; and

(4) FIG. 4 a schematic structural diagram of a combination of a cylindrical converging lens and a to-be-tested concave cylinder in a third combined test area.

(5) Where: 1 denotes a to-be-tested concave cylinder; 2 denotes a focal line (virtual focal line); 3 denotes a cylindrical diverging lens configured to modulate parallel light into a diverging cylindrical wave; 4 denotes a cylindrical converging lens configured to modulate parallel light into a converging cylindrical wave; 5 denotes a standard planar reflector; 6 to 8 respectively denote a first adjusting frame, a second adjusting frame, and a third adjusting frame; 9 denotes a first combined test area; 10 denotes a rotating platform; 11 denotes a horizontal substrate; 12 denotes a second combined test area; 13 denotes a third combined test area; and 14 denotes a standard cylindrical lens.

DETAILED DESCRIPTION OF THE EMBODIMENTS

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

(7) Embodiment 1 provides a method for detecting a concave cylinder and a cylindrical diverging lens, including the following steps:

(8) Step 1) is a step of collecting wavefront error data of a combination of a cylindrical diverging lens 3 and a to-be-tested concave cylinder 1. As shown in FIG. 3, a commercial digital wavefront interferometer, the cylindrical diverging lens 3, and the to-be-tested concave 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 cylindrical diverging lens 3 is 100 mm. The cylindrical diverging lens 3 enables wavefronts of parallel light to converge into a cylindrical wave and intersect at a focal line 2. The to-be-tested concave cylinder 1 is a concave cylinder having a curvature radius of 300 mm. The position of the to-be-tested concave cylinder is adjusted to enable a center line of curvature of the to-be-tested concave 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 cylindrical diverging lens 3 and a wavefront error W.sub.1 of the to-be-tested concave cylinder 1.

(9) Step 2) is a step of collecting wavefront error data of a combination of a cylindrical converging lens 4 and the to-be-tested concave cylinder 1. As shown in FIG. 4, the cylindrical diverging lens 3 is replaced with another cylindrical converging lens 4 having a focal length of 100 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 cylindrical converging lens 4 and the wavefront error W.sub.1 of the to-be-tested concave cylinder 1.

(10) Step 3) is a step of collecting wavefront error data of a combination of the cylindrical diverging lens 3 and the cylindrical converging lens 4. As shown in FIG. 2, the interferometer in step 1), the cylindrical diverging lens 3 in step 1), the 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 cylindrical converging lens 4 coincides with a virtual focal line of the cylindrical diverging lens 3. The 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 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 cylindrical diverging lens 3 and the wavefront error W.sub.4 of the cylindrical converging lens 4.

(11) Step 4) is a step of performing data processing to acquire a shape error: shape error data of the to-be-tested concave cylinder 1, the cylindrical diverging lens 3, and the 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.

Embodiment 2

(12) To facilitate data processing, based on Embodiment 1, the cylindrical diverging lens 3 in step 3) and the cylindrical diverging lens 3 in step 1) in Embodiment 1 are located at the same position on the optical axis. A spatial rotation angle around the focal line of the cylindrical converging lens 4 between the cylindrical converging lens 4 in step 3) and the cylindrical converging lens 4 in step 2) is 180 degrees. The cylindrical converging lens 4 is located at a position where the focal line of the cylindrical converging lens 4 coincides with the virtual focal line of the cylindrical diverging 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.BW.sub.A)/2.

(13) Embodiment 3 provides a method for detecting a cylinder and a cylindrical diverging lens based on Embodiment 1. The to-be-tested concave cylinder may alternatively be a cylindrical converging lens. One cylindrical diverging lens and two cylindrical converging lenses are used to implement mutual detection. When the to-be-tested concave 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.

(14) Embodiment 4 provides an apparatus for detecting a concave cylinder and a cylindrical diverging lens. As shown in FIG. 2, the apparatus includes a horizontal substrate 11, a first adjusting frame 6, a second adjusting frame 7, and a third adjusting frame 8 that are disposed on the horizontal substrate 11, a horizontal rotating platform 10 fixed on the second adjusting frame 7, a cylindrical diverging lens 3 disposed on the first adjusting frame 6, a cylindrical converging lens 4 disposed on the rotating platform 10, and a to-be-tested concave cylinder 1 and a standard planar reflector 5 that are clamped on the second adjusting frame 7.

(15) The cylindrical diverging lens 3 is optically coaxial with the cylindrical converging lens 4 and the standard planar reflector 5 to form a first combined test area 9. The cylindrical diverging lens 3 is optically coaxial with the to-be-tested concave cylinder 1 to form a second combined test area 12. The cylindrical converging lens 4 is optically coaxial with the to-be-tested concave cylinder 1 to form a third combined test area 13.

(16) The cylindrical converging lens 4 in the first combined test area 9 is placed at a rear end of the cylindrical diverging lens 3. A focal line 2 of the cylindrical converging lens 4 coincides with a virtual focal line of the cylindrical diverging lens 3. The 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 cylindrical converging lens 4 and configured to return parallel light.

(17) The to-be-tested concave cylinder 1 in the second combined test area 12 is placed at the rear end of the cylindrical diverging lens 3. A center line of curvature of the to-be-tested concave cylinder 1 coincides with the virtual focal line 2 formed by parallel light passing through the cylindrical diverging lens 3.

(18) The to-be-tested concave cylinder 1 in the third combined test area 13 is placed at the rear end of the cylindrical converging lens 4. The center line of curvature of the to-be-tested concave cylinder 1 coincides with the focal line 2 formed by parallel light passing through the cylindrical converging lens 4.

(19) A spatial rotation angle around the focal line of the cylindrical converging lens 4 between the cylindrical converging lens 4 in the first combined test area 9 and the cylindrical converging lens 4 in the third combined test area 13 is 180 degrees.

(20) In the present invention, one cylindrical diverging lens and one cylindrical converging lens 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 diverging lens. In addition, the cylindrical diverging lens or 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.