Convex secondary aspheric surface shape detection device and detection method

Abstract

The invention relates to a convex secondary aspheric surface shape detection device and detection method, belongs to the technical field of optical element detection, and realizes convex secondary aspheric surface shape detection precision, the detection device comprises a light source, an optical fiber, a collimating mirror, a 1 / 2 wave plate, a polarization beam splitter, a 1 / 4 wave plate, a reference mirror, a standard mirror, a meniscus-like mirror, a pixelated polarization device, an image collector and a five-dimensional adjusting table, and the optical fiber, the collimating mirror, the 1 / 2 wave plate and the polarizing beam splitter are sequentially arranged on an emergent light path of the light source. And the meniscus-like mirror and the measured convex secondary aspheric optical element are arranged on the five-dimensional adjusting table. The detection method comprises the following steps: adjusting the five-dimensional adjusting table, rotating the 1 / 2 wave plate, acquiring an interference fringe image, processing the interference fringe image acquired by the image acquisition device, and calculating to obtain the surface shape error of the detected convex secondary aspheric optical element. The method is used for detecting the surface shape of the convex secondary aspheric surface.

Description

Technical Field

[0001] The invention belongs to the technical field of optical element detection, and in particular relates to a convex secondary aspheric surface shape detection device and a detection method. Background Art

[0002] Compared with spherical surfaces, aspherical surfaces have the advantages of high imaging quality, light weight, and reduced number of optical components in the field of optics, and are widely used in high-performance optical systems. With the improvement of optical system performance, the requirements for the surface accuracy of aspherical optical components are getting higher and higher. Aspherical surfaces cannot be directly measured by interferometers directly. They must be compensated with the help of various compensators to turn them into spherical or plane wavefronts, which interfere with the reference spherical or plane wavefronts generated inside the interferometer. The interference pattern obtained is solved by the phase demodulation algorithm to obtain the surface error of the aspherical surface. The processing inspection of aspherical surfaces has always been a difficult point in the field of aspherical surface inspection. The classic Hindle inspection method, transmission or reflection autocollimation inspection method, and computational holography are the commonly used convex aspherical surface inspection methods in optical workshops today.

[0003] Simpson et al. proposed an improved Hindle inspection method when inspecting germanium mirrors, which effectively solved the problems of adjustment, material selection and processing difficulties caused by the large aperture of the auxiliary spherical mirror in the classic Hindle inspection method. At the same time, the inspection optical path is easier to adjust than the transmission / reflection autocollimation inspection method and the computer-generated holography method. However, this improved Hindle inspection method requires the use of a meniscus lens with an aperture equivalent to that of the mirror being tested, and the meniscus mirror needs to introduce an aspherical surface or add another small lens to compensate for the introduced spherical aberration, resulting in the introduction of more error sources and limited inspection accuracy.

[0004] The Chinese invention patent with publication number CN118111355A discloses a large-aperture high-order convex aspheric surface shape detection method. The aberrations are reasonably distributed according to the optical parameters of the high-order convex aspheric surface to be measured, and the low-order aberrations and high-order aberrations are compensated respectively by Hindle Shell compensator and CGH compensator. This method requires the joint use of two compensators, which increases the difficulty of optical path adjustment and is not conducive to improving the efficiency of surface shape detection.

[0005] The Chinese invention patent with publication number CN117589082A discloses a compensator for high-precision small-aperture and small-radius-of-curvature convex aspheric surface shape detection. The compensator as a whole is a rotationally symmetrical structure along the central axis. Three single lenses are arranged in sequence along the same optical axis to form a lens group. The aperture of the compensator must be larger than the convex aspheric surface to be measured, and it is only suitable for small-aperture convex aspheric surface shape detection.

[0006] The Chinese invention patent with publication number CN112097682A discloses a convex surface shape detection method, device and system for a convex lens. A surface shape detection method for the convex surface of a convex lens is disclosed. By indirectly obtaining the convex surface shape information of the convex lens, the difficulty of convex surface shape detection of the convex lens is greatly simplified. However, it is impossible to detect a transmissive reflective convex aspheric surface. Summary of the invention

[0007] In order to achieve high-efficiency and high-precision surface shape detection accuracy for convex quadratic aspheric surfaces, the present invention proposes a convex quadratic aspheric surface shape detection device and detection method.

[0008] The technical solution adopted by the present invention to solve the technical problem is:

[0009] A convex secondary aspheric surface shape detection device comprises a light source, an optical fiber, a collimator, a 1 / 2 wave plate, a polarization beam splitter, a 1 / 4 wave plate, a reference mirror, a standard mirror, a quasi-meniscus, a pixelated polarization device, and an image collector; the optical fiber, the collimator, the 1 / 2 wave plate, the polarization beam splitter are sequentially arranged on the outgoing light path of the light source; the 1 / 4 wave plate, the quasi-meniscus, and the convex secondary aspheric optical element to be measured are arranged on the transmission light path of the polarization beam splitter, the 1 / 4 wave plate and the reference mirror are arranged on the reflection light path of the polarization beam splitter, the pixelated polarization device and the image collector are arranged on the reflection light path on the other side of the polarization beam splitter; one end of the optical fiber is connected to the light source, and the other end is connected to the collimator, and the outgoing end face of the optical fiber is located at the focal position of the collimator. The F number of the standard mirror is smaller than the F number of the convex secondary aspheric optical element to be measured, and the 1 / 2 wave plate and the 1 / 4 wave plate are respectively perpendicular to the optical axis direction.

[0010] In the above-mentioned convex quadratic aspheric surface shape detection device, the light source is a fiber laser with a single wavelength.

[0011] In the above-mentioned convex quadratic aspheric surface shape detection device, the optical fiber is a single-mode optical fiber.

[0012] In the above-mentioned convex secondary aspheric surface shape detection device, the focal length of the collimating lens is 40 mm, the exit pupil size is 10 mm, and the operating wavelength range is 0.3 μm to 1.8 μm.

[0013] In the above-mentioned convex secondary aspheric surface shape detection device, the convex surface curvature radius of the meniscus mirror is 483.43mm, the concave surface curvature radius is 432.67mm, the center thickness is 50mm, the light aperture is 400mm, and the distance from the focus of the standard mirror is 2327.5mm.

[0014] In the above-mentioned convex quadratic aspheric surface shape detection device, the convex quadratic aspheric optical element to be measured is a convex hyperbolic SiC mirror with an aperture of 320 mm and a focal ratio of F / 1.18, and is 100 mm away from the meniscus mirror.

[0015] In the above-mentioned convex quadratic aspheric surface shape detection device, the pixelated polarization devices are arranged periodically in units of 2mm×2mm squares, and the 2mm×2mm squares are linear polarization units with a phase angle difference of π / 4.

[0016] In the above-mentioned convex quadratic aspheric surface shape detection device, the peak-to-valley (PV) value of the reference mirror shape error is less than 0.1λ (λ=632.8nm), and the root mean square (RMS) value of the surface shape error is less than 0.015λ (λ=632.8nm).

[0017] The above-mentioned convex secondary aspheric surface shape detection device can also include two adjustment platforms, which are adjustable in five dimensions, one for placing a meniscus mirror and the other for placing the convex secondary aspheric optical element to be measured.

[0018] A convex quadratic aspheric surface shape detection method comprises the following steps:

[0019] Step 1: Place the meniscus mirror and the convex secondary aspheric optical element to be tested on two five-dimensional adjustment tables of the detection device respectively.

[0020] Step 2: Turn on the detection device, the light source generates a single wavelength laser light, and adjust the five-dimensional adjustment table so that the optical axis of the meniscus mirror coincides with the optical axis of the standard mirror's output light. The focal point of the standard mirror is 2327.5 mm away from the center of the convex surface of the meniscus mirror.

[0021] Step three, adjust the five-dimensional adjustment stage so that the optical axis of the convex secondary aspheric optical element to be measured coincides with the optical axis of the output light of the meniscus mirror, and the distance from the meniscus mirror is 100 mm.

[0022] Step 4: Rotate the 1 / 2 wave plate to make the interference fringes obtained on the image collector clear, that is, the contrast is optimal.

[0023] Step 5: The image collector collects the interference fringes and obtains four phase shift interference patterns I1(x, y) to I4(x, y) with a phase difference of π / 4. The phase The surface shape error Height(x,y) of the measured convex secondary aspheric optical element is further calculated as follows:

[0024]

[0025] In equations (1) and (2), (x, y) are the coordinates of the measured convex secondary aspheric optical element, and λ is the wavelength of the light source.

[0026] The beneficial effects of the present invention are:

[0027] A convex quadratic aspheric surface shape detection device realizes zero position detection of a convex quadratic aspheric surface by adding a quasi-meniscus mirror. By reasonably calculating the curvature radii of the two surfaces of the quasi-meniscus mirror and utilizing the quasi-meniscus mirror for two transmissions and one concave reflection, the introduction of an aspheric surface or another aberration compensation element is avoided, thus simplifying the surface shape detection device.

[0028] A convex quadratic aspheric surface shape detection method only requires adjusting the posture of a meniscus mirror and the convex quadratic aspheric surface to be detected, and has high detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of a detection device according to an embodiment of the present invention;

[0030] Figure 2 is a schematic diagram of a pixelated polarization device;

[0031] Figure 3 yes Figure 2 Enlarged view of point A in the middle.

[0032] Figure numerals: 1. light source; 2. optical fiber; 3. collimator; 4. 1 / 2 wave plate; 5. polarization beam splitter; 6. 1 / 4 wave plate; 7. reference mirror; 8. standard mirror; 9. meniscus mirror; 10. convex secondary aspheric optical element to be measured; 11. pixelated polarization device; 12. image collector. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Example 1

[0035] like Figure 1 As shown, the convex secondary aspheric surface shape detection device comprises a light source 1, an optical fiber 2, a collimator 3, a 1 / 2 wave plate 4, a polarization beam splitter 5, a 1 / 4 wave plate 6, a reference mirror 7, a standard mirror 8, a meniscus mirror 9, a pixelated polarization device 11, and an image collector 12. The optical fiber 2, the collimator 3, the 1 / 2 wave plate 4, and the polarization beam splitter 5 are sequentially arranged on the outgoing light path of the light source 1; the 1 / 4 wave plate 6, the standard mirror 9, and the convex secondary aspheric optical element 10 to be measured are arranged on the transmission light path of the polarization beam splitter 5, the 1 / 4 wave plate 6 and the reference mirror 7 are arranged on the reflection light path of the polarization beam splitter 5, and the pixelated polarization device and the image collector are arranged on the reflection light path on the other side of the polarization beam splitter 5; one end of the optical fiber 2 is connected to the light source 1, and the other end is connected to the collimator 3, and the outgoing end face of the optical fiber 2 is located at the focal position of the collimator 3.

[0036] Light source 1 is a fiber laser with a single wavelength. The working wavelengths of fiber 2, reference mirror 7 and image collector cover the wavelength of light source 1. The working wavelengths of collimator 3, 1 / 2 wave plate 4, polarization beam splitter 5, 1 / 4 wave plate 6, standard mirror 9 and pixelated polarizer are the wavelength of light source 1. Light source 1 is a fiber laser with a single wavelength. Fiber 2 is a single-mode fiber. The focal length of collimator 3 is 40 mm, the exit pupil size is 10 mm, the working wavelength range is 0.3 μm to 1.8 μm, the light passing diameters of 1 / 2 wave plate 4, polarization beam splitter 5, 1 / 4 wave plate 6, reference mirror 7, standard mirror 8, pixelated polarizer and image collector are all greater than 10 mm, and the F number of standard mirror 8 is less than the F number of convex secondary aspheric optical element 10 to be measured.

[0037] The convex curvature radius of the meniscus mirror 9 is 483.43mm, the concave curvature radius is 432.67mm, the center thickness is 50mm, the light aperture is 400mm, and the distance from the focus of the standard mirror is 2327.5mm.

[0038] The convex secondary aspheric optical element 10 under test is a convex hyperbolic SiC mirror with an aperture of 320 mm and a focal ratio of F / 1.18, and the distance between the convex quadratic aspheric optical element 10 and the meniscus mirror 9 is 100 mm.

[0039] The peak-to-valley (PV) value of the surface error of the reference mirror 7 is less than 0.1λ (the wavelength λ of the light source 1 is 632.8 nm), and the root mean square (RMS) value of the surface error is less than 0.015λ (λ is 632.8 nm).

[0040] The 1 / 2 wave plate 4 can be rotated at any angle perpendicular to the optical axis. The appropriate angle is selected according to the different convex secondary aspheric optical elements 10 to be measured, so that the contrast of the interference image can be obtained on the image collector for data processing. The two 1 / 4 wave plates 6 are rotated to a fixed angle perpendicular to the optical axis, so that the light beams emitted through them are left-handed circularly polarized light and right-handed circularly polarized light respectively. The pixelated polarization device is arranged in a periodic unit of 2×2 small squares, and the 2×2 small squares are linear polarization units with a phase angle difference of π / 4, such as Figure 2 shown.

[0041] The device may also include two five-dimensional adjustment platforms, one for placing the meniscus mirror 9 and the other for placing the convex secondary aspheric optical element 10 to be measured.

[0042] The surface shape detection method based on the above-mentioned convex quadratic aspheric surface shape detection device comprises the following steps:

[0043] Step 1: Place the meniscus mirror 9 and the convex secondary aspheric optical element 10 to be tested on two five-dimensional adjustment tables of the detection device respectively.

[0044] Step 2, turn on the detection device, the light source 1 generates a single wavelength laser light, and adjusts the five-dimensional adjustment table so that the optical axis of the meniscus mirror 9 coincides with the optical axis of the output light of the standard mirror 8. The focal distance of the standard mirror 8 is 2327.5 mm from the center of the convex surface of the meniscus mirror 9.

[0045] Step three, adjust the five-dimensional adjustment stage so that the optical axis of the convex secondary aspheric optical element 10 to be measured coincides with the optical axis of the emitted light of the meniscus mirror 9, and the distance from the meniscus mirror 9 is 100 mm.

[0046] Step 4: Rotate the 1 / 2 wave plate 4 to make the interference fringes obtained on the image collector clear, that is, the contrast is optimal.

[0047] Step 5: The image collector collects the interference fringes and obtains four phase shift interference patterns I1(x, y) to I4(x, y) with a phase difference of π / 4. The phase The surface shape error Height(x,y) of the measured convex secondary aspheric optical element 10 is further calculated as follows:

[0048] .

Claims

1. A convex secondary aspheric surface shape detection device, characterized in that: It comprises a light source (1), an optical fiber (2), a collimator (3), a half-wave plate (4), a polarization beam splitter (5), a quarter-wave plate (6), a reference mirror (7), a standard mirror (8), a meniscus mirror (9), a pixelated polarization device (11), an image collector (12), and a five-dimensional adjustment platform; the optical fiber (2), the collimator (3), the half-wave plate (4), and the polarization beam splitter (5) are sequentially arranged on the outgoing light path of the light source (1); The quarter wave plate (6), the standard mirror (8), and the measured convex secondary aspherical optical element (10) are located on the transmission light path of the polarization beam splitter (5); The quarter wave plate (6) and the reference mirror (7) are located on the reflected light path on one side of the polarization beam splitter (5), and the pixelated polarization device (11) and the image collector (12) are located on the reflected light path on the other side of the polarization beam splitter (5); One end of the optical fiber (2) is connected to the light source (1), and the other end is connected to the collimator (3); the emission end face of the optical fiber (2) is located at the focal position of the collimator (3); The meniscus mirror (9) and the measured convex secondary aspheric optical element (10) are respectively placed on their own five-dimensional adjustment platforms.

2. The face shape detection device according to claim 1, characterized in that: The light source (1) is a fiber laser having a single wavelength; the working wavelengths of the optical fiber (2), the reference mirror (7) and the image collector (12) cover the wavelength of the light source (1); and the working wavelengths of the collimator (3), the 1 / 2 wave plate (4), the polarization beam splitter (5), the 1 / 4 wave plate (6), the standard mirror (8) and the pixelated polarization device (11) are the wavelength of the light source (1).

3. The face shape detection device according to claim 1, characterized in that: The light transmission diameters of the 1 / 2 wave plate (4), polarization beam splitter (5), 1 / 4 wave plate (6), reference mirror (7), standard mirror (8), pixelated polarization device (11) and image collector (12) are all greater than 10 mm, and the F number of the standard mirror (8) is less than the F number of the convex secondary aspheric optical element (10) to be measured.

4. The face shape detection device according to claim 1, characterized in that: The 1 / 2 wave plate (4) can be rotated at any angle perpendicular to the optical axis, and a suitable angle is selected according to different convex secondary aspheric optical elements (10) to be measured, so that the contrast of the interference image obtained on the image collector (12) is convenient for data processing; the two 1 / 4 wave plates (6) are rotated at a fixed angle perpendicular to the optical axis, so that the light beams emitted therefrom are left-handed circularly polarized light and right-handed circularly polarized light, respectively.

5. The face shape detection device according to claim 1, characterized in that: The optical fiber (2) is a single-mode optical fiber, the focal length of the collimator (3) is 40 mm, the exit pupil size is 10 mm, and the operating wavelength range is 0.3 μm to 1.8 μm; The reference mirror (7) has a surface error peak-to-valley PV value of less than 0.1λ, and a surface error root mean square RMS value of less than 0.015λ, where λ is the wavelength of the light source (1); The convex surface curvature radius of the meniscus mirror (9) is 483.43 mm, the concave surface curvature radius is 432.67 mm, the center thickness is 50 mm, the light aperture is 400 mm, and the distance from the focus of the standard mirror (8) is 2327.5 mm; The pixelated polarization device (11) is periodically arranged with 2mm×2mm small squares as units, and the 2mm×2mm small squares are linear polarization units with a phase angle difference of π / 4.

6. The face shape detection device according to claim 5, characterized in that: The wavelength λ of the light source (1) is 632.8 nm.

7. A method for detecting a convex secondary aspheric surface shape, using the surface shape detection device according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1, placing the meniscus mirror (9) and the convex secondary aspheric optical element (10) to be measured on their respective five-dimensional adjustment platforms; Step 2, starting the light source (1), and adjusting the five-dimensional adjustment platform of the meniscus mirror (9) until the optical axis of the meniscus mirror (9) coincides with the optical axis of the output light of the standard mirror (8); Step 3, adjusting the five-dimensional adjustment platform of the convex secondary aspheric optical element (10) to be measured, until the optical axis of the convex secondary aspheric optical element (10) to be measured coincides with the optical axis of the output light of the meniscus mirror (9); Step 4, rotating the 1 / 2 wave plate (4), and the image collector (12) collects the interference fringe image; Step 5: Process the interference fringe image collected by the image collector (12) to obtain the real-time phase The surface shape error Height (x, y) of the measured convex secondary aspheric optical element (10) is calculated.

8. The face shape detection method according to claim 7, characterized in that: The step 2 further comprises: The distance from the focus of the standard mirror (8) to the center of the convex surface of the meniscus mirror (9) is 2327.5 mm.

9. The face shape detection method according to claim 7, characterized in that: The step three further comprises: The distance between the measured convex secondary aspherical optical element (10) and the meniscus mirror (9) is 100 mm.

10. The face shape detection method according to claim 7, characterized in that: The step five further comprises: By processing the collected interference fringe images, four phase-shift interference patterns I1(x, y) to I4(x, y) with a phase difference of π / 4 are obtained; Real-time phase of a measured convex secondary aspheric optical element (10) The calculation formula is as follows: In the above formula, (x, y) is the coordinate of the measured convex secondary aspheric optical element (10); The surface shape error Height(x,y) of the measured convex secondary aspheric optical element (10) is calculated as follows: In the above formula, λ is the wavelength of the light source (1).

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