Apparatus and Method for Detecting Low-Reflectivity Aspherical Lenses Based on Interferometry

Abstract

This application provides an apparatus and method for detecting low-reflectivity aspherical lenses using interferometry. The apparatus includes a semiconductor laser, a computational hologram, and a standard mirror. The output beam of the semiconductor laser has a wavelength range of 630 nm to 640 nm and an energy greater than 5 mW. The computational hologram is positioned in the optical path of the output beam of the semiconductor laser, and the standard mirror is positioned between the semiconductor laser and the computational hologram. The computational hologram includes an alignment region and a main detection region. The output beam emitted by the semiconductor laser passes through the standard mirror and reaches the computational hologram. Part of the output beam is reflected by the alignment region of the computational hologram to form a reference beam, and another part passes through the main detection region of the computational hologram and is reflected by the low-reflectivity aspherical lens to form a test beam. The reference beam and the test beam pass through the standard mirror and form interference fringes at the semiconductor laser. By using a semiconductor laser with higher energy to provide a higher power laser, the contrast of the interference fringes between the reference beam and the test beam is improved.

Description

Technical Field

[0001] This application relates to the field of optical device manufacturing, and more specifically, to an apparatus and method for detecting low-reflectivity aspherical lenses based on interferometry. Background Technology

[0002] In optical systems, lenses and mirrors mostly use planar or spherical surfaces because these simple surfaces are easy to process and inspect, enabling mass production and achieving high-precision surface shape requirements. In particular, the advent of various high-precision surface shape inspection interferometers has greatly reduced the difficulty of inspecting high-precision planar and spherical surfaces. Nevertheless, in some high-precision imaging systems, such as lithography objectives and nuclear fusion systems, using only planar and spherical mirrors is insufficient to achieve the desired imaging quality. However, the introduction of aspherical mirrors has successfully solved this problem. Furthermore, the application of aspherical surfaces increases the freedom of aspherical design, playing a crucial role in improving the imaging quality, enhancing optical performance, and reducing size and weight of optical systems. Optical systems designed using aspherical technology can eliminate spherical aberration, coma, astigmatism, and field curvature, reducing light energy loss and thus obtaining high-quality imaging and superior optical properties. However, the processing and inspection of aspherical surfaces are much more difficult than those of spherical surfaces. This is because: spherical surfaces have countless axes of symmetry, while aspherical surfaces have only one, so aspherical surfaces cannot be processed using the methods used for spherical surfaces; furthermore, the curvature radii of the various annulus zones on an aspherical surface are different, making it difficult to correct during polishing. Currently, the main methods for inspecting aspherical surfaces are the contour method and the interferometry method.

[0003] Contour measurement methods employ contact or non-contact measurement techniques to directly measure the sag of the aspherical surface. Then, using the aspherical equation, the contour line of the ideal aspherical surface is subtracted to obtain the surface profile. A typical example of a contact measuring instrument is the Form Talysurf, which uses a probe to directly contact the aspherical surface. By moving the probe laterally and recording the change in its height, the contour of the aspherical surface is obtained. This type of equipment suffers from a trade-off between measurement range and accuracy, and it is prone to scratching the measured surface. Coordinate measuring machines (CMMs) are also contact measuring instruments. By measuring spatial coordinates, they can obtain the external contour of the measured surface. A typical example is the ZEISS MICURA. This type of equipment has a large measurement range, but its measurement accuracy is relatively low, and it is prone to damaging the measured surface. Its inspection efficiency is particularly low for the inspection of medium to large diameter freeform surfaces, such as VR lenses.

[0004] Interferometry is an important method for measuring optical components. It can sample surface contours in a single measurement, and when combined with automated systems, it can significantly improve efficiency. Furthermore, it can achieve high-precision measurements without damaging the surface being measured. Commonly used interferometry methods include aberration-free methods, compensating mirror methods, computational holography methods, annular stitching methods, sub-aperture stitching methods, and long-wavelength methods.

[0005] However, for lenses with low reflectivity, such as coated lenses, the intensity difference between the reference light and the measurement light that form the interference is huge. Especially when the lens being tested is aspherical, using computational holograms will further reduce the intensity of the detection light due to diffraction efficiency, ultimately resulting in too low fringe contrast to complete image recognition and reduce detection accuracy. Summary of the Invention

[0006] This application provides an apparatus and method for detecting low-reflectivity aspherical lenses based on interferometry, which can at least partially solve the above-mentioned problems existing in the prior art.

[0007] This application provides an apparatus for detecting low-reflectivity aspherical lenses using interferometry, comprising a semiconductor laser, a computational hologram, and a standard mirror. The output beam of the semiconductor laser has a wavelength range of 630 nm to 640 nm and an energy greater than 5 mW. The computational hologram is positioned in the optical path of the output beam of the semiconductor laser, and the standard mirror is positioned between the semiconductor laser and the computational hologram. The computational hologram includes an alignment region and a main detection region. The output beam emitted by the semiconductor laser passes through the standard mirror and reaches the computational hologram. Part of the output beam is reflected by the alignment region of the computational hologram to form a reference beam, and another part of the output beam passes through the main detection region of the computational hologram and is reflected by the low-reflectivity aspherical lens to form a test beam. The reference beam and the test beam pass through the standard mirror and form interference fringes at the semiconductor laser.

[0008] In some implementations, the main detection region is located at the center of the computational hologram, and the alignment region is located around the main detection region.

[0009] In some implementations, the computational hologram further includes: a plurality of auxiliary alignment regions for assisting in the alignment of the computational hologram with the semiconductor laser, wherein the plurality of auxiliary alignment regions and the alignment regions are located together on the periphery of the main detection region.

[0010] In some implementations, the alignment region is located at the center of the computational hologram, and the main detection region is located around the alignment region.

[0011] In some implementations, the alignment region uses an amplitude-type computational hologram, while the main detection region uses a phase-type computational hologram.

[0012] In some implementations, the reflectivity of the alignment area is greater than 20%.

[0013] In some embodiments, the alignment region is a film structure made of metallic chromium and its compounds such that the reflectivity of the alignment region is greater than 20%.

[0014] In some implementations, the diffraction order of the alignment region is any one of ±1, ±3, or ±5.

[0015] In some implementations, the etching depth of the microstructure in the main detection region ranges from 300 nm to 500 nm.

[0016] In some implementations, the diffraction order of the main detection region is plus or minus 1.

[0017] In some implementations, the transmittance of the standard mirror pair in the wavelength range of 630 nm to 640 nm, including the output beam, reference beam, and test beam, is greater than or equal to 98%.

[0018] In some implementations, a high-transmittance coating is provided on the reference surface of the standard mirror so that the transmittance of the standard mirror is greater than or equal to 98%.

[0019] An exemplary embodiment of this application also provides a method for detecting low-reflectivity aspherical lenses based on interferometry, comprising: aligning a computational hologram with a semiconductor laser using an alignment region of the computational hologram; adjusting the position of the low-reflectivity aspherical lens to be detected so that the semiconductor laser, the low-reflectivity aspherical lens, and the main detection region of the computational hologram are aligned; emitting an output beam through the semiconductor laser, wherein a portion of the output beam is reflected by the alignment region of the computational hologram to form a reference beam, and another portion of the output beam passes through the main detection region of the computational hologram and is reflected by the low-reflectivity aspherical lens to form a test beam, wherein the reference beam and the test beam form interference fringes at the semiconductor laser; adjusting the position of the low-reflectivity aspherical lens so that the interference fringes are close to a zero-fringe state; and performing zero-position compensation measurement of the low-reflectivity aspherical lens by combining the wavefront aberration results of the low-reflectivity aspherical lens with the aberration adjustment.

[0020] The apparatus and method for detecting low-reflectivity aspherical lenses provided in at least one embodiment of this application improve the detection efficiency and accuracy of low-reflectivity aspherical lenses by using computational holography to achieve aberration compensation during the interferometric lens detection process and by using a high-energy semiconductor laser as the interferometer to provide a higher power laser, thereby improving the contrast of the interference fringes between the reference light and the test light.

[0021] Furthermore, the above-mentioned scheme of this application also improves the contrast of the interference fringes between the reference light and the test light by increasing the transmittance of the standard mirror reference surface and increasing the diffraction efficiency of the alignment area and the main detection area of ​​the computational hologram. Attached Figure Description

[0022] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Wherein:

[0023] Figure 1 This is a schematic diagram of a device for detecting low-reflectivity aspherical lenses based on an exemplary embodiment of this application;

[0024] Figure 2 This is a schematic diagram of a computational hologram according to the first embodiment of this application;

[0025] Figure 3 This is a schematic diagram of a computational hologram according to the second embodiment of this application;

[0026] Figure 4 This is a schematic diagram of a computational hologram according to the third embodiment of this application;

[0027] Figure 5 This is a schematic diagram of a grating model of a phase-type computational hologram according to an exemplary embodiment of this application;

[0028] Figure 6 This is a graph showing the relationship between stripe contrast and standard mirror reflectivity in an exemplary embodiment of this application.

[0029] Figure 7 This is a graph showing the relationship between stripe contrast and standard mirror reflectance in another exemplary embodiment of this application;

[0030] Figure 8 This is a graph showing the relationship between fringe contrast and calculated holographic diffraction efficiency in an exemplary embodiment of this application; and

[0031] Figure 9 This is a flowchart illustrating a method for detecting low-reflectivity aspherical lenses based on an exemplary embodiment of this application. Detailed Implementation

[0032] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of this application and are not intended to limit the scope of this application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0033] In the accompanying drawings, the thickness, dimensions, and shapes of the parts have been slightly adjusted for ease of illustration. The drawings are for illustrative purposes only and are not drawn to scale. As used herein, the terms “approximately,” “about,” and similar terms are used as expressions of approximation, not as expressions of degree, and are intended to illustrate inherent deviations in measured or calculated values ​​that will be recognized by one of ordinary skill in the art.

[0034] It should also be understood that expressions such as "comprising," "including," "having," "containing," and / or "comprising" are open-ended rather than closed-ended expressions in this specification, indicating the presence of the stated features, elements, and / or components, but not excluding the presence of one or more other features, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not just individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to examples or illustrations.

[0035] Unless otherwise specified, all terms used herein (including engineering and technical terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that, unless expressly stated herein, terms defined in common dictionaries shall be interpreted as having the meaning consistent with their meaning in the context of the prior art, and not as having an idealized or overly formalized meaning.

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] An apparatus for detecting low-reflectivity aspherical lenses based on interferometry according to an embodiment of this application includes a semiconductor laser, a computational hologram, and a standard mirror. The output beam of the semiconductor laser has a wavelength range of 630 nm to 640 nm and an energy greater than 5 mW. The computational hologram is disposed in the optical path of the output beam of the semiconductor laser and includes an alignment region and a main detection region. The alignment region is used to align the computational hologram with the semiconductor laser and reflect the beam to form a reference beam. The main detection region is used to transmit the output beam and the test beam formed after the output beam is reflected by the low-reflectivity aspherical lens. The standard mirror is disposed between the semiconductor laser and the computational hologram and is used to transmit the output beam, the reference beam, and the test beam.

[0038] In the above scheme, aberration compensation is achieved by using computational holograms during the interferometric detection of lenses. Furthermore, a semiconductor laser with higher energy is used as the interferometer, which can provide a higher power laser to improve the contrast of the interference fringes between the reference light and the test light, thereby improving the detection efficiency and accuracy of low-reflectivity aspherical lenses.

[0039] Figure 1 A schematic diagram of the structure of an apparatus 100 for detecting low-reflectivity aspherical lenses according to an exemplary embodiment of this application is shown. Figure 2 The diagram shown is a computational hologram according to the first embodiment of this application; Figure 3 This is a schematic diagram of a computational hologram according to the second embodiment of this application; Figure 4 This is a schematic diagram of a computational hologram according to the third embodiment of this application.

[0040] In such Figure 1 In the embodiment shown, the apparatus 100 for detecting low-reflectivity aspherical lenses based on interferometry includes a semiconductor laser 110, a computational hologram 120, and a standard mirror 130.

[0041] The semiconductor laser 110 outputs a beam 111 with a wavelength range of 630nm to 640nm and an energy greater than 5mW, enabling it to provide higher power laser light. Thus, when the lens under test is a low-reflectivity aspherical lens 140, the higher power laser increases the contrast of the interference fringes formed by the interference between the reference light reflected from the alignment region 121 of the computational hologram 120 and the test light reflected from the low-reflectivity aspherical lens 140 and transmitted through the main detection region 122 of the computational hologram 120. This allows for the detection of the low-reflectivity aspherical lens.

[0042] In some embodiments, a collimating element may be provided after the semiconductor laser 110 to collimate the output beam 111.

[0043] Optionally, the wavelength of the output beam 111 of the semiconductor laser 110 is 635 nm.

[0044] like Figure 1 As shown, the computational hologram 120 is placed in the optical path of the output beam 111 of the semiconductor laser 110 to achieve aberration compensation during the measurement process.

[0045] Specifically, misalignment of optical components in the optical path can introduce additional aberrations into the detection results. Therefore, in order to ensure accurate alignment between optical components during detection, corresponding alignment areas are designed on the computational hologram to achieve accurate alignment between the computational hologram and the semiconductor laser, thereby realizing aberration compensation.

[0046] like Figures 2 to 4As shown, the computational hologram 120 of this application includes an alignment region 121 and a main detection region 122. The alignment region 121 is used to align the computational hologram 120 with the semiconductor laser 110 and reflect a portion of the output beam 111 to form a reference beam. The main detection region 122 is used to transmit another portion of the output beam 111 and the test beam formed after that portion of the output beam 111 is reflected by the low-reflectivity aspherical lens 140.

[0047] In other words, such as Figure 1 As shown, the output beam 111 emitted by the semiconductor laser 110 passes through the standard mirror 130 and reaches the computational hologram 120. Part of the output beam 111 is reflected by the alignment area 121 of the computational hologram 120 to form a reference beam, and another part of the output beam 111 passes through the main detection area 122 of the computational hologram 120 and is reflected by the low-reflectivity aspherical lens 140 to form a test beam. The reference beam and the test beam pass through the standard mirror 130 and form interference fringes at the semiconductor laser 110.

[0048] In the computational hologram 120 of the first embodiment, as Figure 2 As shown, the main detection area 122 is located at the center of the computational hologram 120, and the alignment area 121 is located around the main detection area 122. It should be noted that the main detection area 122 should cover the lens being inspected according to design requirements.

[0049] In the computational hologram 120 of the second embodiment, as Figure 3 As shown, the computational hologram 120 also includes multiple auxiliary alignment regions 123 for assisting in the alignment of the computational hologram 120 with the semiconductor laser 110, for example, by transmitting a crosshair or aligning with other components. The multiple auxiliary alignment regions 123, together with the alignment region 121, are located around the main detection region 122.

[0050] In the computational hologram 120 of the third embodiment, as Figure 4 As shown, the alignment region 121 is located at the center of the computational hologram 120, and the main detection region 122 is located on the periphery of the alignment region 121.

[0051] In some embodiments, the alignment region 121 employs an amplitude-type computational hologram, and the main detection region 122 employs a phase-type computational hologram. The alignment region 121 employs a reflection-type diffraction grating, and the main detection region 122 employs a transmission-type diffraction grating.

[0052] Optionally, the alignment region 121 of the amplitude-type computational hologram and the main detection region 122 of the phase-type computational hologram can be formed simultaneously. This can reduce the complexity of the processing technology of the computational hologram 120 and avoid the overlay error introduced by processing in stages.

[0053] For example, a chromium layer can be first deposited on a clean substrate surface, followed by spin-coating a first photoresist layer onto the chromium layer. Laser direct writing technology is then used to expose and develop the first photoresist layer within the main detection area, removing it. Next, wet etching is used to remove the chromium layer within the main detection area, followed by removal of any remaining first photoresist layer. The substrate is then cleaned and dried. A second photoresist layer with a T-shaped cross-section is then spin-coated onto the substrate surface. Laser direct writing technology is used to expose the complete computational hologram pattern onto the substrate surface, followed by development, revealing a complete computational hologram micro / nano structure on the surface of the second photoresist layer. Wet etching is then used to etch the chromium layer within the alignment area, transferring the micro / nano structure of the alignment area to the chromium layer. The substrate is then placed in a shielded fixture, with the shielded area covering the alignment area and the main detection area exposed. Dry etching is then used to transfer the micro / nano structure of the second photoresist layer within the main detection area onto the substrate. Next, the tooling was removed, the second photoresist layer remaining on the substrate was removed, and then the substrate was cleaned and dried to obtain a computational hologram of amplitude / phase hybrid type.

[0054] Since higher-order diffraction light is relatively weak, this application limits the alignment region 121 of the hologram 120 to generally use 1st, 3rd, or 5th-order diffraction light to enhance diffraction efficiency.

[0055] In the above scheme, the alignment region 121 of the hologram 120 is calculated by increasing the intensity of the reflection order light through the fabrication of a high-reflectivity amplitude-type hologram. The reflectivity of the alignment region 121 should be greater than 20%.

[0056] In some embodiments, the alignment region 121 of the computational hologram 120 uses metallic chromium with a reflectivity higher than 30%, while the reflectivity of metallic chromium used in current semiconductor processes is mostly around 10%. Therefore, the metallic chromium film in the alignment region 121 of the computational hologram 120 of this application is a high-reflectivity film composed of metallic chromium and its compounds, which can enhance the reflection of energy at higher diffraction orders. Optionally, the metallic chromium compound can be, for example, an oxide of metallic chromium.

[0057] In some implementations, the main detection region 122 of the hologram 120 is typically calculated using first-order diffraction light. Figure 5 A schematic diagram of a grating model of a phase-type computational hologram according to an exemplary embodiment of this application is shown. Taking the main detection region 122 as a second-order phase-type computational hologram as an example, the theoretical diffraction efficiency of the second-order phase-type computational hologram is calculated as shown in equation (1):

[0058]

[0059] Where η is the diffraction efficiency, T is the grating period, W is the width of the etched portion of the grating, m is the diffraction order of the grating, H is the etching depth, λ is the working wavelength, n is the refractive index of the main detection region 122 of the hologram for incident light, and sinc is the singer function.

[0060] It is evident that the etching depth H is a key parameter that can affect the diffraction efficiency of a second-order phase-type computational hologram. In some embodiments, this application limits the etching depth H to a range of 300 nm to 500 nm. Further, the etching depth H is in the range of 350 nm to 450 nm.

[0061] In the above scheme, by limiting the range of etching depth as described above, the diffracted rays formed by the main detection area 122 of the calculated hologram 120 can be perpendicularly incident on each point of the low-reflectivity aspherical lens 140. Optionally, the diffraction order is 1.

[0062] In some embodiments, this application specifies that the transmittance of the standard mirror 130 for the output beam, reference beam, and test beam in the wavelength range of 630 nm to 640 nm should be greater than or equal to 98%. This is because increasing the transmittance of the reference surface of the standard mirror 130 of the semiconductor laser 110 can provide more energy to the measurement arm, thereby improving the contrast of the interference fringes of the test beam and reference beam reflected by the low-reflectivity aspherical lens 140.

[0063] In some implementations, the standard mirror 130 may be, for example, a plane standard mirror or a spherical standard mirror.

[0064] The reference surface of standard mirror 130 is coated with a high-transmittance film so that the transmittance of standard mirror 130 is greater than or equal to 98%.

[0065] It is understandable that the reference plane of the standard mirror 130 is the surface facing the calculated hologram 120. The F-number of the standard mirror 130 can be selected according to the actual situation.

[0066] The formula for calculating the contrast of interference fringes is shown in equation (2):

[0067] Contrast = 2 * ratio / (1 + ratio) 2 (2)

[0068] Where Contrast represents the fringe contrast, and ratio represents the ratio of the light intensity of the reference light to that of the test light.

[0069] Figure 6 A graph showing the relationship between stripe contrast and standard mirror reflectivity in an exemplary embodiment of this application is illustrated. Figure 6As shown, assuming the reflectivity of the low-reflectivity aspherical lens 140 is 0.8%, and the diffraction efficiency of the main detection area 122 of the hologram 120 is calculated to be 40%, when the reflectivity of the reflective surface of the standard mirror 130 of the semiconductor laser 110 changes from 4% to 1%, that is, when the transmittance of the reference surface of the standard mirror 130 of the semiconductor laser 110 changes from 96% to 99%, it can be seen that the contrast of the interference fringes between the reference light and the test light can be increased from 5.9% to 24.7%, which increases the fringes contrast by more than 4 times.

[0070] Figure 7 A graph showing the relationship between stripe contrast and standard mirror reflectance in another exemplary embodiment of this application is illustrated. Figure 7 As shown, assuming the diffraction efficiency of the main detection area 122 of the hologram 120 is 40% and the reflectivity of the low-reflectivity aspherical lens 140 is 0.8%, when the transmittance of the reference light reflecting surface of the standard lens 130 increases from 98% to 99.6% (the reflectivity changes from 0.4% to 2%), it can be seen that the corresponding fringe contrast can be improved from approximately 12.3% to 58%.

[0071] This application improves the contrast of the interference fringes between the reference light and the test light by combining the increase of the transmittance of the reference surface of the standard mirror 130, the increase of the laser energy of the semiconductor laser 110, and the use of the computational hologram 120 as a compensation element to improve the diffraction efficiency of the computational hologram 120.

[0072] Figure 8 A graph showing the relationship between fringe contrast and calculated holographic diffraction efficiency in an exemplary embodiment of this application is illustrated. Figure 8 As shown, assuming the standard mirror 130 has a reflectivity of 1% (transmittance of 99%) and the low-reflectivity aspherical mirror 140 has a reflectivity of 0.08%, when the diffraction efficiency of the main detection region 122 of the calculated hologram 120 increases from 10% to 40%, the contrast of the interference fringes between the reference light and the test light increases from 1.57% to 24.7%. Figure 8 It can be seen that as the diffraction efficiency increases, the fringe contrast is significantly improved, with a maximum increase of 15 times. It should be noted that 1.57% is the fringe contrast corresponding to the main detection region 122 of the computational hologram 120 using an amplitude-type computational hologram 120 and a diffraction efficiency of 10%, while 24.7% is the fringe contrast corresponding to the main detection region 122 of the computational hologram 120 using a phase-type computational hologram 120 and a diffraction efficiency of 40%.

[0073] Exemplary embodiments of this application also provide a method for detecting low-reflectivity aspherical lenses based on interferometry. Figure 9 A flowchart illustrating a method for detecting low-reflectivity aspherical lenses based on an exemplary embodiment of this application is shown.

[0074] like Figure 9 As shown, the method includes the following steps:

[0075] S1. Align the computational hologram with the semiconductor laser using the alignment region of the computational hologram;

[0076] S2. Adjust the position of the low-reflectivity aspherical lens to be tested so that the semiconductor laser, the low-reflectivity aspherical lens, and the main detection area of ​​the computational hologram are aligned.

[0077] S3. An output beam is emitted by a semiconductor laser. Part of the output beam is reflected by the alignment area of ​​the computational hologram to form a reference beam. The other part of the output beam passes through the main detection area of ​​the computational hologram and is reflected by a low-reflectivity aspherical lens to form a test beam. The reference beam and the test beam form interference fringes at the semiconductor laser.

[0078] S4. Adjust the position of the low-reflectivity aspherical lens to bring the interference fringes close to zero; and

[0079] S5. Based on the wave aberration results of the low-reflectivity aspherical lens, combine the aberration adjustment to accurately position the low-reflectivity aspherical lens, and perform zero-position compensation measurement of the low-reflectivity aspherical lens.

[0080] Specifically, such as Figure 9 As shown, during detection, in step S1, the computational hologram 120 is first aligned with the semiconductor laser 110 using the alignment region 121 of the computational hologram 120. For example, by adjusting the relative position (including three-dimensional translation and tilt) between the computational hologram 120 and the semiconductor laser 110, the laser emitted by the semiconductor laser 110 is reflected back into the semiconductor laser 110 after being reflected by the alignment region 121 of the computational hologram 120, forming interference fringes with the reference light of the semiconductor laser 110. The relative position between the computational hologram 120 and the semiconductor laser 110 is then adjusted until the interference fringes reach a zero-fringe state (the interference fringes are either completely black or completely white). At this point, the semiconductor laser 110 and the computational hologram 120 are precisely aligned.

[0081] After the semiconductor laser 110 and the computational hologram 120 are precisely aligned, in step S2, the position of the low-reflectivity aspherical lens 140 to be tested is adjusted. Then, in step S3, the semiconductor laser 110 emits an output beam 111. Part of the output beam 111 is reflected by the alignment area 121 of the computational hologram 120 to form a reference beam, and the other part of the output beam 111 passes through the main detection area 122 of the computational hologram 120 and is reflected by the low-reflectivity aspherical lens 140 to form a test beam. The reference beam and the test beam form interference fringes at the semiconductor laser 110. Figure 1 As shown. At this time, in step S4, the position of the low-reflectivity aspherical lens 140 is adjusted to adjust the interference fringes to the zero-fringe state. At this time, the semiconductor laser 110, the low-reflectivity aspherical lens 140 and the computational hologram 120 are precisely aligned.

[0082] After the semiconductor laser 110, the low-reflectivity aspherical lens 140, and the computational hologram 120 are precisely aligned, in step S5, the wavelet aberration of the corresponding low-reflectivity aspherical lens 140 can be measured. The precise position of the low-reflectivity aspherical lens 140 is adjusted in combination with the aberration, and the zero-position compensation measurement of the low-reflectivity aspherical lens 140 is realized. Finally, the interferometric detection result of the mirror surface shape of the low-reflectivity aspherical lens 140 is obtained.

[0083] The above description is merely an illustration of the embodiments of this application and the technical principles employed. Those skilled in the art should understand that the scope of protection involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the technical concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A device for detecting low-reflectivity aspherical lenses based on interferometry, characterized in that, include: A semiconductor laser, wherein the wavelength range of the output beam of the semiconductor laser is 630nm~640nm and the energy is greater than 5mW; A computational hologram is disposed in the optical path of the output beam of the semiconductor laser. The computational hologram includes an alignment region and a main detection region. A standard mirror is positioned between the semiconductor laser and the computational hologram. In this configuration, the output beam emitted by the semiconductor laser passes through the standard mirror and reaches the computational hologram. A portion of the output beam is reflected by the alignment region of the computational hologram to form a reference beam, while another portion passes through the main detection region of the computational hologram and is reflected by the low-reflectivity aspherical lens to form a test beam. The reference beam and the test beam pass through the standard mirror and form interference fringes at the semiconductor laser. The alignment area uses a reflective diffraction grating, and the main detection area uses a transmission diffraction grating.

2. The apparatus according to claim 1, characterized in that, The main detection area is located at the center of the computational hologram, and the alignment area is located on the periphery of the main detection area.

3. The apparatus according to claim 2, characterized in that, The computational hologram also includes: Multiple auxiliary alignment regions are used to assist in aligning the computational hologram with the semiconductor laser, and the multiple auxiliary alignment regions and the alignment region are located together on the periphery of the main detection region.

4. The apparatus according to claim 1, characterized in that, The alignment region is located at the center of the computational hologram, and the main detection region is located on the periphery of the alignment region.

5. The apparatus according to any one of claims 1-4, characterized in that, The alignment area uses an amplitude-type computational hologram, and the main detection area uses a phase-type computational hologram.

6. The apparatus according to claim 5, characterized in that, The reflectivity of the alignment area is greater than 20%.

7. The apparatus according to claim 6, characterized in that, The alignment region is a film structure made of metallic chromium and its compounds, such that the reflectivity of the alignment region is greater than 20%.

8. The apparatus according to claim 5, characterized in that, The diffraction order of the alignment region is any one of ±1, ±3, or ±5.

9. The apparatus according to claim 5, characterized in that, The etching depth of the microstructure in the main detection area ranges from 300 nm to 500 nm.

10. The apparatus according to claim 5, characterized in that, The diffraction order of the main detection region is positive and negative 1.

11. The apparatus according to any one of claims 1-4, characterized in that, The transmittance of the output beam, the reference beam, and the test beam of the standard mirror pair in the wavelength range of 630nm to 640nm is greater than or equal to 98%.

12. The apparatus according to claim 11, characterized in that, The reference surface of the standard mirror is provided with a high-transmittance coating so that the transmittance of the standard mirror is greater than or equal to 98%.

13. A method for detecting low-reflectivity aspherical lenses based on interferometry, characterized in that, include: The computational hologram is aligned with a semiconductor laser using the alignment region of the computational hologram; Adjust the position of the low-reflectivity aspherical lens to be tested so that the semiconductor laser, the low-reflectivity aspherical lens, and the main detection area of ​​the computational hologram are aligned; The semiconductor laser emits an output beam, a portion of which is reflected by the alignment region of the computational hologram to form a reference beam, and another portion of which passes through the main detection region of the computational hologram and is reflected by the low-reflectivity aspherical lens to form a test beam. The reference beam and the test beam form interference fringes at the semiconductor laser. Adjust the position of the low-reflectivity aspherical lens so that the interference fringes are close to zero fringes; as well as Based on the wave aberration results of the low-reflectivity aspherical lens, the precise position of the low-reflectivity aspherical lens is adjusted in combination with the aberration, and the zero-position compensation measurement of the low-reflectivity aspherical lens is performed.

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