Method for adjusting co-axiality in diffractive lens wavefront sensing

Abstract

The application discloses a method for adjusting coaxiality in diffraction lens wavefront detection, and a detection system comprising an interferometer, a high-precision plane mirror, a measured micro-nano structure diffraction lens and a five-dimensional adjustment table. The interferometer emits a divergent light beam through a spherical lens, and the light beam passes through the measured micro-nano structure diffraction lens and is reflected by the plane mirror to the interferometer to form interference, so that the wavefront of the measured micro-nano structure diffraction lens is measured. The focal length center of the diffraction lens will appear a phenomenon of string points, and the measured diffraction lens is finally adjusted to be coaxial with the optical axis of the system through the auxiliary adjustment of the points. The application guides the adjustment of the measured diffraction lens to be coaxial with the optical path in the diffraction lens wavefront detection, and especially effectively saves time and improves detection efficiency in the long-focus optical path.

Description

Technical Field

[0001] This invention belongs to the field of wavefront detection, and specifically relates to a method for adjusting coaxiality in wavefront detection using a diffraction lens. Background Technology

[0002] In the processing and testing of diffractive lenses, wavelet aberration of the optical system is the most important characteristic indicator of the imaging quality of diffractive lenses, comprehensively reflecting the level of diffractive lens processing.

[0003] A self-collimating optical path is typically constructed using an interferometer and a high-precision standard plane mirror to detect the wavefront aberration of the measured element; this is known as the interferometric self-collimation method. When the light source (object) is located at the focal plane of the diffraction lens, the light emitted from it will become a parallel beam after passing through the lens. If a plane mirror perpendicular to the optical axis reflects this parallel beam back, the reflected light will converge again on the focal plane of the diffraction lens after passing through the lens once more. The convergence point will be at a position symmetrical to the light source with respect to the optical axis.

[0004] Two problems arise when performing wavefront testing on long-focal-length diffraction elements: First, due to the excessively long focal length, even a small angle between the diffraction lens under test and the optical axis results in a significant difference between the reflected point and the theoretical point on the focal plane. This prevents the interferometer from being inserted into the aperture during coarse alignment, making it difficult to locate the point during wavefront testing. Second, because diffraction elements have multiple orders, points from secondary orders (besides the principal order) can interfere with the testing. Therefore, it is crucial to ensure that points from other orders do not enter the interference.

[0005] This invention guides the adjustment of the diffractive lens under test to be coaxial with the optical path in wavefront detection of diffractive lenses, which effectively saves time and improves detection efficiency, especially in long focal length optical paths. Summary of the Invention

[0006] This invention guides the adjustment of the diffractive lens under test to be coaxial with the optical path in wavefront detection of diffractive lenses, which effectively saves time and improves detection efficiency, especially in long focal length optical paths.

[0007] The technical solution adopted in this invention is: a method for adjusting coaxiality in wavefront detection of a diffractive lens, implemented according to the following steps:

[0008] Step 1: Set up an interferometer and a plane mirror on a five-dimensional adjustment platform. Adjust the relative positions of the interferometer and the plane mirror so that the center of the plane wave emitted by the interferometer coincides with the center of the plane mirror, so that the light rays incident on the plane mirror return along the original path after being reflected by the plane mirror.

[0009] Step 2: Place the diffraction lens under test between the interferometer and the plane mirror, and adjust the X and Y direction translation of the diffraction lens under test so that the center of the plane wave emitted by the interferometer coincides with the center of the diffraction lens under test.

[0010] Step 3: Select a transmission standard lens and mount it onto the interferometer; the interferometer emits spherical waves.

[0011] Step 4: Coarsely adjust the focal point of the diffractive lens under test to coincide with the focal point of the interferometer;

[0012] Step five: A series of dots will appear on the focal plane of the diffractive lens being tested; for example... Figure 2 As shown, there will be a brightest point in the center, and two strings of dots will appear next to this point in two directions. In one direction, there are symmetrical strings of dots arranged on both sides, and the brightness gradually decreases. In the other direction, there are only strings of dots arranged on one side, and the brightness gradually decreases.

[0013] Step 6: By adjusting the up, down, left, and right translation of the diffraction lens being tested, first move the brightest point in the middle back to the aperture. By tilting and pitching, adjust the continuously weakening cross-points on one side to move towards the center, but do not move them into the aperture, otherwise double fringes will appear.

[0014] Step 7: With the help of these points, the diffraction lens under test is finally adjusted to be coaxial with the optical axis of the system, so that the light rays incident on the diffraction lens under test are reflected by the plane mirror and return along the original path, thus forming a self-collimating optical path, and interference fringes appear in the interferometer; Step 8: Continue to adjust the tilt and pitch of the diffraction lens under test, and the interferometer compensates for the translation in the X and Y directions until the coma term in the wavefront detection result of the interferometer is minimized, which is the wavefront detection result of the diffraction lens under test.

[0015] Furthermore, a phenomenon of dotted lines will appear on the focal plane of the diffractive lens being tested: such as... Figure 2 As shown, there will be a brightest point at the center, and two clusters of dots will appear next to this point in two directions. In one direction, there are symmetrical clusters of dots on both sides, and the brightness gradually decreases. These clusters of dots are caused by other orders of the diffraction lens, and the energy of the other orders is weaker than that of the principal order at the focal plane.

[0016] Furthermore, a phenomenon of dotted lines will appear on the focal plane of the diffractive lens being tested: such as... Figure 2 As shown, there will be a brightest point at the center, with two clusters of dots appearing around it in two directions. In another direction, there are only one cluster of dots arranged on one side, with the intensity decreasing. This unilateral clustering is due to the angle between the diffraction lens and the optical axis. Light is reflected multiple times on the surface of the diffraction lens, resulting in clusters of dots that gradually weaken at equal angles. This reflection angle is twice the angle between the diffraction lens and the optical axis. Therefore, the unilateral clustering can be used to help adjust the diffraction lens under test to be coaxial with the optical axis.

[0017] The advantages of this invention compared to the prior art are:

[0018] Two problems arise during wavefront testing of long-focal-length diffractive elements: First, due to the excessively long focal length, even a small angle between the tested diffractive lens and the optical axis results in a significant discrepancy between the reflected point and the theoretical point on the focal plane. This prevents the interferometer from being properly aligned within the aperture, making it difficult to locate the correct point during wavefront testing. Second, because diffractive elements have multiple orders, points from orders other than the principal order can interfere with the testing. Therefore, it is crucial to ensure that these other orders do not enter the interference. By adjusting these points, the tested diffractive lens is ultimately aligned coaxially with the system's optical axis. This invention guides the adjustment of the tested diffractive lens to be coaxial with the optical path during wavefront testing, effectively saving time and improving testing efficiency, especially in long-focal-length optical paths. Attached Figure Description

[0019] Figure 1 This invention relates to a diffraction lens wavefront detection system.

[0020] Figure 2 This is a theoretical simulation diagram of the serial point.

[0021] Figure 3 This is a diagram showing the points on the focal plane during the detection process. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] Diffraction lens wavefront detection system, such as Figure 1 As shown, the detection system includes an interferometer, a plane mirror, a diffractive lens under test, a five-dimensional adjustment stage, and a small hole for placing the focal plane. The interferometer emits a diverging beam through a spherical lens, which passes through the diffractive lens under test. The plane mirror reflects the beam back to the collimator to form interference, and the wavefront of the diffractive lens under test is measured.

[0024] This embodiment of a method for adjusting coaxiality in wavefront detection using a diffraction lens is implemented according to the following steps:

[0025] Step 1: Set up an interferometer and a plane mirror on a five-dimensional adjustment platform. Adjust the relative positions of the interferometer and the plane mirror so that the center of the plane wave emitted by the interferometer coincides with the center of the plane mirror, so that the light rays incident on the plane mirror return along the original path after being reflected by the plane mirror.

[0026] Step 2: Place the diffraction lens under test between the interferometer and the plane mirror, and adjust the X and Y direction translation of the diffraction lens under test so that the center of the plane wave emitted by the interferometer coincides with the center of the diffraction lens under test.

[0027] Step 3: Select a transmission standard lens and mount it onto the interferometer; the interferometer emits spherical waves.

[0028] Step 4: Coarsely adjust the focal point of the diffractive lens under test to coincide with the focal point of the interferometer;

[0029] Step five: A series of dots will appear on the focal plane of the diffractive lens being tested; for example... Figure 3 As shown, there will be a brightest point in the center, and two strings of dots will appear next to this point in two directions. In one direction, there are symmetrical strings of dots arranged on both sides, and the brightness gradually decreases. In the other direction, there are only strings of dots arranged on one side, and the brightness gradually decreases.

[0030] Step six: By adjusting the up, down, left, and right translation of the diffraction lens being tested, first move the brightest point in the center back to the small aperture where the focal plane is placed. By tilting and pitching, adjust the continuously weakening crosshairs on one side to move towards the center of the small aperture, but do not move them into the small aperture, otherwise double fringes will appear.

[0031] Step 7: With the help of these points, the diffraction lens under test is finally adjusted to be coaxial with the optical axis of the system, so that the light rays incident on the diffraction lens under test are reflected by the plane mirror and return along the original path, thus forming a self-collimating optical path, and interference fringes appear in the interferometer; Step 8: Continue to adjust the tilt and pitch of the diffraction lens under test, and the interferometer compensates for the translation in the X and Y directions until the coma term in the wavefront detection result of the interferometer is minimized, which is the wavefront detection result of the diffraction lens under test.

[0032] Figure 2 It is a theoretical simulation diagram of cross-point interference, in which cross-point interference is clearly visible.

[0033] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for adjusting coaxiality in wavefront detection of a diffractive lens, the detection system comprising an interferometer, a plane mirror, a diffractive lens under test, a five-dimensional adjustment stage, and a focal plane placement aperture, characterized in that, Includes the following steps: Step 1: Set up the interferometer and plane mirror on the five-dimensional adjustment platform, and adjust the relative positions of the interferometer and plane mirror so that the center of the plane wave emitted by the interferometer coincides with the center of the plane mirror, so that the light rays incident on the plane mirror return along the original path after being reflected by the plane mirror. Step 2: Place the diffraction lens under test between the interferometer and the plane mirror, and adjust the X and Y direction displacements of the diffraction lens under test so that the center of the plane wave emitted by the interferometer coincides with the center of the diffraction lens under test. Step 3: Select a transmission standard lens and mount it onto the interferometer so that the spherical wave emitted by the interferometer is emitted; Step 4: Coarsely adjust the focal point of the diffractive lens under test to coincide with the focal point of the interferometer; Step 5: A series of dots appear on the focal plane of the diffractive lens being tested. The specific phenomenon of the series of dots is as follows: there is a brightest point in the center, and two series of dots appear next to this point in two directions. In one direction, there are symmetrical series of dots on both sides, and the brightness gradually decreases. In the other direction, there are only one side with a series of dots that continuously decrease in brightness. Step 6: By adjusting the up, down, left, and right displacement of the diffraction lens being tested, first move the brightest point in the center back to the focal plane and place it at the small aperture. By tilting and pitching, adjust the continuously weakening cross-points on one side to move towards the center of the small aperture, but do not move them into the small aperture, otherwise interference from reflection fringes will occur. Step 7: By adjusting with the help of the series points, the diffraction lens under test is finally adjusted to be coaxial with the optical axis of the detection system, so that the light rays incident on the diffraction lens under test are reflected by the plane mirror and return along the original path, thus forming a self-collimating optical path, and interference fringes appear in the interferometer. Step 8: Continue to adjust the tilt and pitch of the diffractive lens under test, and use the interferometer to compensate for the displacement in the X and Y directions until the coma term in the wavefront detection result of the interferometer is minimized, which is the wavefront detection result of the diffractive lens under test.

2. The method for adjusting coaxiality in wavefront detection using a diffraction lens according to claim 1, characterized in that, The phenomenon of scattering points is as follows: there is a brightest point at the center, and scattering points appear in two directions next to this point. Among them, the scattering points with gradually decreasing brightness arranged symmetrically on both sides in one direction are caused by other orders of the diffraction lens. The other orders are all weaker than the energy of the principal order at the focal plane.

3. The method for adjusting coaxiality in wavefront detection using a diffraction lens according to claim 1, characterized in that, The phenomenon of scattering points is as follows: there is a brightest point at the center, and scattering points appear in two directions next to this point. The other direction has only one side of scattering points that are constantly weakening. This is because the diffraction lens has an angle with the optical axis, and the light is reflected multiple times on the surface of the diffraction lens, thus producing scattering points that are equal in angle and constantly weakening.

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