Wavefront aberration sensor compatible with high precision and large dynamic range

Abstract

The application discloses a wave aberration sensor compatible with high precision and large dynamic range, and belongs to the field of optical precision measurement and detection. The wave aberration sensor comprises a projection module, an array structured light chip and a detection module. The core idea of the wave aberration sensor is that different characteristic phases are encoded in each sub-aperture based on an array structured light chip, so that a plurality of structured light spots with obvious characteristics can be generated in the focal plane, and the different sub-aperture light spots can be distinguished. Based on the array structured light chip, the wave aberration sensor can realize measurement with a larger dynamic range without sacrificing the measurement precision. The wave aberration sensor can realize measurement of various laser wavefronts and wave aberration detection of various lenses. Therefore, the wave aberration sensor has important practical value in the fields of laser processing, laser surgery, ophthalmic detection and optical imaging.

Description

Technical Field

[0001] This invention relates to a novel wavefront aberration sensor, belonging to the field of optical precision measurement, specifically a wavefront aberration sensor based on an array structured optical chip that is compatible with high precision and a large dynamic range. Background Technology

[0002] As is well known, light possesses information such as amplitude, phase, and polarization. Optical wave aberration is essentially the spatial distribution of the phase of the light field. Conventional methods for measuring optical wave aberration include reference light interferometry, shearing interferometry, and the Shak-Hartmann detection method. Traditional interferometry requires a reference wavefront and is highly demanding in terms of environmental conditions, especially vibration isolation and temperature stability, thus limiting its application. Shearing interferometry utilizes the lateral or axial offset of the light field to generate self-interference information and inversely calculate the original phase spatial distribution, thus offering better environmental adaptability, but it has certain requirements for the coherence of the light field. The Shak-Hartmann sensor uses a microlens array superimposed with a micro-aperture array to divide the measured wavefront space into many small blocks, each of which can be approximated as having a uniform phase. Therefore, by detecting the slope of each small block, the gradient of the corresponding spatial phase can be detected, and the original phase can be calculated from the gradient using an algorithm. Compared to interferometric measurement methods, the Shak-Hartmann sensor has advantages such as real-time measurement and high robustness, and has been widely used in many applications.

[0003] Traditional Shak-Hartmann sensors rely on microlens arrays for wavefront segmentation. Each sub-lens produces a solid focal spot, and the intensity distribution of these focal spots is indistinguishable from one another. Consequently, each focal spot cannot exceed the range of its sub-aperture, which is the core bottleneck limiting its dynamic range. Dynamic range characterizes the ability to measure the magnitude of a distorted wavefront. A larger dynamic range indicates a greater wavefront slope that can be detected, and a higher degree of undulation. For conventional Shak-Hartmann sensors, the dynamic range is determined by the ratio of the maximum allowable offset of the focal spot to the focal length of the microlens, which is the ratio of the sub-aperture radius to the focal length of the microlens. Furthermore, the influence of the slope on the offset is directly proportional to the focal length of the microlens. In other words, a larger focal length results in higher sensitivity to the detected slope, which also means higher accuracy. Therefore, to improve the dynamic range of traditional Shak-Hartmann sensors, a microlens array with a shorter focal length is needed. However, this inevitably reduces the accuracy of wavefront detection. Conversely, increasing the focal length of the microlens can effectively improve detection accuracy, but it will inevitably sacrifice the dynamic range of wavefront detection. Therefore, it is difficult to achieve both measurement accuracy and measurement dynamic range simultaneously with conventional Shaker-Hartmann sensors. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a wave aberration sensor based on an array structured light chip that is compatible with high precision and large dynamic range. By loading a special characteristic phase on the basis of the traditional spherical phase, a structured focal spot array with characteristic intensity distribution can be generated. Thus, the correspondence between sub-apertures and focal spots can be distinguished by using a variety of different structured focal spots, thereby effectively improving the overall dynamic range of wave aberration detection without sacrificing detection accuracy.

[0005] According to one aspect of the present invention, a wave aberration sensor compatible with high precision and large dynamic range is provided, comprising: an array structured light chip, a projection module, and a detection module;

[0006] Each sub-aperture in the array structured optical chip is loaded with a spherical phase and a corresponding characteristic phase, so that the focal spot intensity distributions of adjacent sub-apertures are different.

[0007] The projection module includes a first lens group and a second lens group, and the effective optical power of both the first lens group and the second lens group is positive.

[0008] The detection module includes at least an array photosensitive chip, a sample-and-hold circuit, and an analog-to-digital conversion circuit.

[0009] The plane where the array structured optical chip is located and the measured wavefront carrying wave aberrations form an imaging conjugate relationship with respect to the first lens group and the second lens group in the projection module.

[0010] As a further technical solution, the array structured light chip is a multi-step relief diffraction microlens array.

[0011] Furthermore, the multi-step relief diffraction microlens array can be a two-step phase element or a multi-step phase element.

[0012] As a further technical solution, the array structured light chip is a metasurface array device, and the phase loaded on the metasurface is an arrayed spherical phase superimposed with a characteristic phase.

[0013] As a further technical solution, some equiphase regions within the sub-apertures of the array structured optical chip are coated with a layer of chromium metal to achieve consistent peak intensity of different characteristic focal spots.

[0014] Preferably, the substrate material of the array structured optical chip is fused silica.

[0015] As a further technical solution, the sub-units in the array structured light chip are arranged in a hexagonal pattern. Specifically, one-third of the sub-units are loaded with spherical phase, another one-third of the sub-units are loaded with spherical phase and additional spiral phase, and the remaining one-third of the sub-units are loaded with spherical phase and additional angular partition 0 and π phase. The sub-units corresponding to the three types of structured light arrays are arranged alternately and at intervals.

[0016] As a further technical solution, the sub-units in the array structured light chip are arranged in a rectangular pattern. Specifically, half of the sub-units are loaded with a spherical phase, and the remaining half of the sub-units are loaded with a spherical phase and an additional spiral phase. The sub-units corresponding to the two types of structured light arrays are arranged alternately and at intervals.

[0017] As a further technical solution, the position of the characteristic light spot array generated by the array structured light chip on the detection surface is calculated by the geometric center of the characteristic light spot.

[0018] As a further technical solution, the first lens group and the second lens group in the projection module form a confocal system and maintain center alignment.

[0019] As a further technical solution, the first lens group and the second lens group in the projection module include at least one aspherical lens.

[0020] As a further technical solution, the plane where the detection surface of the array optical detection chip in the detection module is located is within the effective focal depth of the array structured light chip, that is, the distance between the detection surface of the area array photosensitive chip in the detection module and the array structured light chip is f±dz / 2, where f is the equivalent focal length corresponding to the spherical phase loaded on the array structured light chip, and dz is the corresponding focal depth.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) By loading a special characteristic phase on the basis of the traditional spherical phase, the present invention can generate a structured focal spot array with characteristic intensity distribution. Thus, by using a variety of different structured focal spots, the correspondence between sub-apertures and focal spots can be distinguished, effectively improving the overall dynamic range of wavefront aberration detection without sacrificing detection accuracy. In other words, it achieves a wavefront detection effect that is compatible with both high precision and large dynamic range.

[0023] (2) The present invention can effectively reduce the influence of intensity noise on focus offset.

[0024] (3) The core device of the present invention, the array structured light chip, is a surface relief structure, which is very suitable for mass replication. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram illustrating the principle of a wave aberration sensor compatible with high precision and large dynamic range, provided for an embodiment of the present invention.

[0027] Figure 2 The schematic diagram of the phase loading principle of the sub-aperture of the array structured optical chip provided in the embodiment of the present invention is as follows: the left figure shows the spiral phase loading principle and the phase distribution of the diffractive microlens after loading; the right figure shows the angular three-part 0-π phase loading principle and the phase distribution of the diffractive microlens after loading.

[0028] Figure 3 This is a schematic diagram of the phase distribution of the sub-aperture of a typical array structured optical chip and the corresponding focal spot intensity distribution, provided for an embodiment of the present invention.

[0029] Figure 4 A schematic diagram of the overall phase distribution of a typical array structured light chip provided in an embodiment of the present invention: the first row corresponds to the phase distribution and focal spot distribution of a rectangular array structured light chip with a focal length of 5.5mm; the second row corresponds to the phase distribution and focal spot distribution of a hexagonal array structured light chip with a focal length of 3.5mm.

[0030] Figure 5 A schematic diagram of the amplitude and phase modulation principle provided for an embodiment of the present invention: the left side represents amplitude modulation; the right side represents phase modulation.

[0031] Figure 6 The diagram shows the amplitude and phase modulation effect of the array structured optical chip with a rectangular arrangement provided in the embodiment of the present invention: the upper left is amplitude modulation; the upper right is phase modulation; the lower left is the intensity distribution of the corresponding focal spot array; and the lower right is a magnified view of the intensity distribution of the corresponding focal spot array.

[0032] Figure 7 The following is a schematic diagram of the wavefront aberration sensor provided in the embodiment of the present invention: the left figure shows the wavefront detection of a fiber laser; the right figure shows the surface shape detection of a spherical mirror. Detailed Implementation

[0033] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form new technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0035] This invention provides a wavefront aberration sensor based on an array structured light chip that is compatible with high precision and large dynamic range, including a projection module, an array structured light chip, and a detection module.

[0036] The main function of the projection module is to project the measured wavefront onto the array structured light chip. Its core components include a first lens group and a second lens group. Both the first and second lens groups have positive equivalent optical power, and they form a confocal system, meaning the rear focal plane of the first lens group is located at the front focal plane of the second lens group. At least one aspherical lens needs to be designed in both the first and second lens groups to effectively compensate for aberrations in the projection module.

[0037] The structured optical array (SOC) chip is the core component in this system, responsible for segmenting the wavefront and measuring the slope of each sub-region. Each sub-aperture in the SOC is loaded with a spherical phase and a corresponding characteristic phase, which includes, but is not limited to, spiral phase, angular multi-region 0, and π phase. The purpose of loading each sub-aperture with a spherical phase and a corresponding characteristic phase is to ensure that the focal spot intensity distributions of adjacent sub-apertures differ, thus allowing for clear differentiation. This phase loading method can be achieved through a multi-step relief binary optical structure or through a metasurface-encoded microstructure. This sub-aperture array can be rectangular or hexagonal. Furthermore, certain equiphase regions of the SOC are overlaid with a layer of chromium metal to ensure consistent peak intensity across different characteristic focal spots.

[0038] The detection module mainly includes a CMOS or CCD area array photodetector and supporting circuitry, including at least a sample-and-hold circuit and an analog-to-digital converter circuit.

[0039] The measured wavefront carrying wave aberrations and the plane where the array structured light chip is located form an imaging conjugate relationship with respect to the first lens group and the second lens group in the projection module.

[0040] The present invention will be further described below with reference to the accompanying drawings.

[0041] Please refer to the appendix. Figure 1 This is a schematic diagram of a wavefront aberration sensor structure based on an array structured light chip, proposed in this embodiment of the invention, that is compatible with high precision and a large dynamic range. In the figure, 100 represents the wavefront to be measured carrying wavefront aberrations; 200 represents a projection module, mainly including a first lens group 201 and a second lens group 202, wherein the back focal plane of the first lens group 201 coincides with the front focal plane of the second lens group 202. The wavefront to be measured 100 carrying wavefront aberrations is on the front focal plane of the first lens group, and its image formed by the projection module coincides with the plane where the array structured light chip 300 is located. The photosensitive surface of the array photosensitive chip in the detection module 400 is placed within the depth of focus range of the focal array formed by the array structured light chip.

[0042] Please refer to the appendix. Figure 2 The images show two typical special phases superimposed with a spherical phase to generate a two-step phase. On the left, a spiral phase is superimposed with a spherical phase, and a regular hexagonal sub-aperture is added, resulting in a two-step phase within the sub-aperture. On the right, a 6-section angular 0 and π phase is superimposed with a spherical phase, and the corresponding spherical phase in the regular hexagonal sub-aperture diagram is added, resulting in a two-step phase within the sub-aperture. In the images, the effective focal length of the added spherical phase is 5.5 mm.

[0043] Please refer to the appendix. Figure 3Several typical sub-aperture two-step phase distributions and corresponding spot intensity distributions on the focal plane are shown. The upper left corresponds to the coded phase of a conventional spherical phase; the upper right corresponds to the coded special phase of a 4-segment angular 0 and π phase; the lower left corresponds to the coded special phase of a spiral phase; and the lower right corresponds to the coded special phase of a 6-segment angular 0 and π phase. From the figure, we can clearly see that by encoding special phases, a characteristic focal spot intensity distribution can be achieved.

[0044] Please refer to the appendix. Figure 4 The figures show the intensity distribution within the focal plane of an array structured optical chip under two typical configurations. The first row shows the array structured optical chip and its corresponding focal plane intensity distribution within a rectangular configuration, with one conventional spherical phase and one spiral phase superimposed on the spherical phase. It is clear from the figure that by loading different special phases, two distinctly different focal spots can be achieved, thus doubling the dynamic range of the wavefront aberration sensor. The second row shows the array structured optical chip and its corresponding focal plane intensity distribution under a hexagonal configuration, with three different special phases superimposed on the spherical phase: spiral phase, 4-segment angular 0-π phase, and 6-segment angular 0-π phase. It is clear from the figure that by loading these special phases, three different focal spot distributions with varying intensity distributions can be achieved, thus doubling the detection dynamic range.

[0045] Please refer to the appendix. Figure 5 Furthermore, the problem of differences in peak intensity of the light spot caused by special phase loading can be addressed by, for example... Figure 5 The amplitude-phase modulation mode shown achieves a balance between the intensity distribution differences of different types of focal spots. (See attached image.) Figure 5 As shown, for microlenses corresponding to conventional solid focal spots, opaque amplitude modulation can be added to the annular region of the microlens to attenuate the intensity of the solid focal spot, ultimately achieving a balance between the intensity distribution differences of different types of focal spots. (See attached image) Figure 6 An example of an array-based structured optical chip is presented, demonstrating the balance of peak intensities of two focal spots in a rectangular arrangement achieved through amplitude-phase modulation. Numerical simulation results in the figure show that amplitude modulation effectively balances the peak intensity distribution of the two focal spots.

[0046] (I) Specific Implementation Example 1: Wavefront Detection of Fiber Laser.

[0047] The following is a specific implementation scheme for wavefront detection of a 1070nm fiber laser after collimation and beam expansion.

[0048] Please refer to the appendix. Figure 7Left image: For a 1070nm fiber laser, the collimated spot size is approximately 10mm, and the power is 50W. After sampling by a mirror with a reflectivity of approximately 5% and passing through an adjustable attenuator, the collimated laser bypasses the projection module and directly passes through the array structured light chip, ultimately achieving photoelectric conversion via the detection module. The array structured light chip corresponding to the wavefront aberration sensor is designed as shown in the attached image. Figure 4 The sensor features a hexagonal array, a focal length of 5.5mm, a sub-aperture size of 300μm, and three coded phases: helical phase, 4-segment angular 0-π phase, and 6-segment angular 0-π phase. The sensor module uses a CMOS chip with a single pixel size of 2.5×2.5μm and a pixel count of 5120×5120.

[0049] (II) Specific Implementation Example 2: Spherical Mirror Shape Detection.

[0050] The following is a specific implementation plan for the surface shape inspection of optical components, taking the surface shape inspection of optical components as an example.

[0051] Please refer to the appendix. Figure 7 The right figure shows a 635nm LED light source with a narrowband filter (center wavelength 635nm) having a full width at half maximum (FWHM) of 2nm. The light emitted from the LED is collimated and expanded, then incident on the surface of the optical component under test via a semi-reflective lens. After surface reflection, it is reflected again by the semi-reflective lens and enters the wavefront aberration sensor. The projection module in the wavefront aberration sensor can be adjusted according to the actual size of the optical component under test. For conventional optical components with a small PV (photometer area), a diffraction-type array structured light chip with only one focal spot can be used, such as a spiral phase-encoded array structured light chip. The photosensitive chip in the detection module is a CMOS chip with a single pixel size of 2.5×2.5μm and a pixel count of 5120×5120. For an optical component with a diameter of 300mm under test, the focal lengths of the first and second lens groups in the projection module of the wavefront aberration sensor are selected as 600mm and 25mm, respectively.

[0052] The specific embodiments of the wavefront aberration sensor based on array structured optical chips with high precision and large dynamic range described above should not be construed as limiting the scope of protection of this invention. It should be noted that those skilled in the art can make various non-inventive modifications and improvements to the specific implementation details and representative devices proposed in this patent without departing from the basic idea of ​​this invention, and these modifications and improvements all fall within the scope of protection of this invention.

[0053] In summary, this invention proposes a wavefront aberration sensor based on an array structured light chip that is compatible with high precision and large dynamic range. It can be widely used in various fields such as laser wavefront detection, optical lens surface shape detection, ophthalmic detection, and optical imaging lens detection.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A wavefront aberration sensor compatible with high precision and large dynamic range, characterized in that, The application relates to an array structured light chip, a projection module and a detection module. Each sub-aperture in the array structured light chip is loaded with a spherical phase and a corresponding characteristic phase, so that the focal spot intensity distribution corresponding to adjacent sub-apertures is different. The projection module comprises a first lens group and a second lens group, and the effective focal power of the first lens group and the second lens group is positive. The detection module comprises at least a surface array photosensitive chip, a sample holding circuit and an analog-digital conversion circuit. The plane where the array structured light chip is located and the measured wave surface carrying wave aberration are in imaging conjugate relationship with respect to the first lens group and the second lens group in the projection module. The array structured light chip is a multi-step surface relief diffractive microlens array.

2. The wavefront sensor according to claim 1, wherein, The array structured light chip is a metasurface array device, and the phase loaded by the metasurface is an arrayed spherical phase and a superimposed characteristic phase.

3. The wavefront sensor according to claim 1, wherein, Part of the equal phase area in part of the sub-apertures in the array structured light chip is plated with a layer of metal chromium through overlay plating, so as to realize consistent peak intensity of different characteristic focal spots.

4. The wavefront sensor according to claim 1, wherein, The sub-units in the array structured light chip are hexagonally arranged, specifically, one third of the sub-units are loaded with a spherical phase, another third of the sub-units are loaded with a spherical phase and an additional spiral phase, and the remaining third of the sub-units are loaded with a spherical phase and an additional angularly partitioned 0 and pi phase, and the sub-units corresponding to the three structured light arrays are alternately and interval arranged in turn.

5. The wavefront sensor according to claim 1, wherein, The sub-units in the array structured light chip are rectangularly arranged, specifically, one half of the sub-units are loaded with a spherical phase, and the remaining half of the sub-units are loaded with a spherical phase and an additional spiral phase, and the sub-units corresponding to the two structured light arrays are alternately and interval arranged in turn.

6. The wavefront sensor according to claim 1, wherein, The positions of the characteristic spot array generated by the array structured light chip on the detection surface are calculated through the geometric centers of the characteristic spots.

7. The wavefront sensor according to claim 1, wherein, The first lens group and the second lens group in the projection module form a confocal system and keep central alignment.

8. The wavefront sensor according to claim 1, wherein, At least one aspherical lens is contained in the first lens group and the second lens group in the projection module.

9. The wavefront sensor according to claim 1, wherein, The distance between the detection surface of the surface array photosensitive chip in the detection module and the array structured light chip is f+dz / 2, wherein f is the equivalent focal length corresponding to the spherical phase loaded by the array structured light chip, and dz is the corresponding focal depth.

10. The wavefront sensor according to claim 1, wherein, ​

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