Wave aberration sensor compatible with high precision and large dynamic range

Abstract

The invention 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 structure optical chip and a detection module. The core idea of the wave aberration sensor disclosed by the invention is that different characteristic phases are coded in each sub-aperture on the basis of an array structure optical chip, so that various structural light spots with obvious characteristics can be generated in a focal plane of the array structure optical chip, and the light spots with different sub-apertures can be distinguished. Based on the array structure optical chip, the wave aberration sensor can realize measurement in a larger dynamic range without sacrificing the measurement precision. According to the wave aberration sensor provided by the invention, on one hand, measurement of various laser wavefronts can be realized, and on the other hand, wave aberration detection of various lenses can be realized. Therefore, the wave aberration sensor has important practical value in the fields of laser processing, laser surgery, ophthalmology detection, optical imaging and the like.

Description

Technical Field

[0001] The invention relates to a novel wave aberration sensor, belonging to the field of optical precision measurement, and specifically to a wave aberration sensor based on an array structured light chip and compatible with high precision and a large dynamic range. Background Art

[0002] As we all know, light has information such as amplitude, phase and polarization. Optical wave aberration is essentially the spatial distribution of the phase of the light field. Conventional solutions for measuring optical wave aberration include reference light interferometry, shearing interferometry, Shack-Hartmann detection, etc. Traditional interferometry measurement requires a reference wavefront and has high requirements for the environment, especially high requirements for environmental vibration isolation and temperature stability, so the application of this solution is very limited. Shearing interferometry uses the self-interference information formed by the lateral or axial offset of the light field to reversely calculate the original phase space distribution, so it has better environmental adaptability, but it has certain requirements for the coherence of the light field. The Shack-Hartmann sensor uses a microlens array superimposed with a microhole array to divide the measured wavefront space into many small blocks, and the phase of each small block can be approximately considered to be uniform. Therefore, by detecting the corresponding slope of each small block, the gradient of the corresponding spatial phase can be detected, and finally the original phase is calculated from the gradient through an algorithm. Compared with the interferometric measurement solution, the Shack-Hartmann sensor has the advantages of real-time measurement and high robustness, and has been widely used in many occasions.

[0003] The traditional Shack-Hartmann sensor realizes wavefront segmentation based on a microlens array. Each sub-lens can produce a solid focus. The focus intensity distributions produced by all sub-lenses cannot be distinguished from each other. Therefore, each focal spot cannot exceed its sub-aperture range, which is the core bottleneck of its limited dynamic range. We know that the dynamic range characterizes the ability to measure the size of the distorted wavefront. The larger the dynamic range, the larger the slope of the detected wavefront can be and the higher the fluctuation. For a conventional Shack-Hartmann sensor, its dynamic range is determined by the ratio of the maximum allowable offset of the focal spot to the focal length of the microlens, that is, the ratio of its sub-aperture radius to the focal length of the microlens. On the other hand, the degree of influence of the slope on the offset is proportional to the focal length of the microlens. In other words, the larger the focal length, the higher the detection slope sensitivity, which also means higher accuracy. Therefore, if the traditional Shack-Hartmann sensor wants to improve the dynamic range, it needs to use a microlens array with a shorter focal length, but the problem brought about by this is that the accuracy of wavefront detection is bound to decrease; on the contrary, if the focal length of the microlens is increased, the detection accuracy can be effectively improved, but the dynamic range of wavefront detection will inevitably be sacrificed. Therefore, it is difficult to achieve simultaneous compatibility of measurement accuracy and measurement dynamic range for conventional Shack-Hartmann sensors. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the present 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 a characteristic intensity distribution can be generated, so that the correspondence between the sub-aperture and the focal spot 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, there is provided a wave aberration sensor compatible with high precision and large dynamic range, comprising: an array structured light chip, a projection module and a detection module;

[0006] 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 distributions corresponding to adjacent sub-apertures are different;

[0007] The projection module comprises a first lens group and a second lens group, and the effective optical power of the first lens group and the second lens group are both positive;

[0008] The detection module at least includes an array photosensitive chip, a sampling and holding circuit, and an analog-to-digital conversion circuit;

[0009] The plane where the array structured light chip is located and the measured wavefront carrying the wave aberration form an imaging conjugate relationship with 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 surface relief diffraction type microlens array.

[0011] Furthermore, the multi-step surface relief diffraction type 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 by the metasurface is an arrayed spherical phase and a superimposed characteristic phase.

[0013] As a further technical solution, some equal-phase regions within some sub-apertures in the array structured light chip are plated with a layer of metal chromium by overlaying to achieve consistent peak intensities of different characteristic focal spots.

[0014] Preferably, the substrate material of the array structured light chip is fused quartz.

[0015] As a further technical solution, the subunits in the array structured light chip are arranged hexagonally, specifically, one-third of the subunits are loaded with a spherical phase, another one-third of the subunits are loaded with a spherical phase and an additional spiral phase, and the remaining one-third of the subunits are loaded with a spherical phase and an additional angular partition 0 and π phase, and the subunits corresponding to the three structured light arrays are arranged alternately in sequence.

[0016] As a further technical solution, the sub-units in the array structured light chip are arranged in a rectangular shape, specifically, the phase loaded on one-half of the sub-units is a spherical phase, and the phase loaded on the remaining half of the sub-units is a spherical phase and an additional spiral phase, and the sub-units corresponding to the two structured light arrays are arranged alternately in sequence.

[0017] As a further technical solution, the position of the characteristic light spot array generated by the array structured light chip corresponding to 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 light 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 present invention has the following beneficial effects:

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

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

[0024] (3) The core device array structured light chip of the present invention is a surface relief structure, which is very suitable for mass replication. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction is given below to the drawings used in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

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

[0027] Figure 2 Schematic diagram of the phase loading principle of the sub-aperture of the array structured light chip provided in an embodiment of the present invention: the left figure shows the spiral phase loading principle and the phase distribution of the diffraction microlens after loading; the right figure shows the angular three-partition 0-π phase loading principle and the phase distribution of the diffraction microlens after loading.

[0028] Figure 3 Schematic diagram of the sub-aperture phase distribution and corresponding focal spot intensity distribution of a typical array structured light chip provided in an embodiment of the present invention.

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

[0030] Figure 5 Schematic diagram of the amplitude-phase modulation principle provided for an embodiment of the present invention: the left side is amplitude modulation; the right side is phase modulation.

[0031] Figure 6 Amplitude and phase modulation effect diagram of the array structured light chip in a rectangular arrangement provided in an embodiment of the present invention: the upper left is amplitude modulation; the upper right is phase modulation; the lower left is the corresponding focal spot array intensity distribution; the lower right is a local enlarged view of the corresponding focal spot array intensity distribution.

[0032] Figure 7 Detection schematic diagram of the wavefront aberration sensor provided in an embodiment of the present invention: the left figure is the fiber laser wavefront detection; the right figure is the spherical mirror surface shape detection. DETAILED DESCRIPTION

[0033] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions, for example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to the steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical features in the various embodiments or single embodiments provided by the present invention are arbitrarily combined with each other to form a new technical solution. This combination is not restricted by the sequence of steps and / or the structural composition mode, but must be based on the ability of ordinary technicians in this field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that this combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] An embodiment of the present invention provides a wave aberration sensor based on an array structured light chip and compatible with high precision and a large dynamic range, comprising a projection module, an array structured light chip and a detection module.

[0036] The main function of the projection module is to complete the projection imaging of the measured wavefront to the array structured light chip. Its core components include the first lens group and the second lens group. Among them, the equivalent optical focal lengths of the first lens group and the second lens group are both positive, and the two lens groups form a confocal system, that is, the back focal plane of the first lens group is at the front focal plane position of the second lens group. In the first lens group and the second lens group, at least one aspherical lens needs to be designed to effectively compensate for the aberration of the projection module.

[0037] The array structured light chip is the core device in this system that plays the role of dividing the wavefront and realizing the slope measurement of each sub-region. Each sub-aperture in the array structured light chip is loaded with a spherical phase and a corresponding characteristic phase, and the corresponding characteristic phase includes but is not limited to a spiral phase, an angular multi-region 0, π phase, etc. Each sub-aperture in the array structured light chip is loaded with a spherical phase and a corresponding characteristic phase, in order to make the focal spot intensity distribution corresponding to adjacent sub-apertures different so that they can be clearly distinguished. The phase loading method can be achieved through a multi-step surface embossed binary optical structure, or through a metasurface coding microstructure. This sub-aperture array can be arranged in a rectangular shape or in a hexagonal shape. In addition, some equal-phase areas of the array structured light chip are plated with a layer of metal chromium by overlay, so as to achieve consistent peak intensity of different characteristic focal spots.

[0038] The detection module mainly includes a CMOS or CCD area array photosensitive detector and supporting circuits, including at least a sampling and holding circuit and an analog-to-digital conversion circuit.

[0039] The measured wavefront carrying the wave aberration 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 in conjunction with the accompanying drawings.

[0041] Please see attached Figure 1 , is a schematic diagram of the structure of a wavefront aberration sensor compatible with high precision and large dynamic range based on an array structured light chip proposed in an embodiment of the present invention. In the figure, 100 is a wavefront to be measured carrying wavefront aberration; 200 is a projection module, which mainly includes 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 aberration 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 focal depth range of the focal array formed by the array structured light chip.

[0042] Please see attached Figure 2 , two typical special phases are superimposed on the spherical phase to generate a two-step phase. The left side shows the superposition of the spiral phase and the spherical phase, and the addition of the regular hexagonal sub-aperture, and the final generated two-step phase in the sub-aperture. The right side shows the superposition of the 6-partition angular 0, π phase and the spherical phase, and the addition of the corresponding spherical phase in the regular hexagonal sub-aperture diagram, and the final generated two-step phase in the sub-aperture. In the figure, the effective focal length of the loaded spherical phase is 5.5mm.

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

[0044] Please see attached Figure 4 , the array structured light chip loading phase and the corresponding intensity distribution in the focal plane under two typical arrangements. The first row shows the array structured light chip in the sub-aperture of a conventional spherical phase and a spherical phase superimposed on the spiral phase under a rectangular arrangement, and the intensity distribution in the corresponding focal plane. It can be clearly seen from the figure that by loading different special phases, two significantly different focal spots can be achieved, so that this method can be used to double the dynamic range of the wave aberration sensor. The second row shows the array structured light chip and the intensity distribution in the focal plane formed by the superposition of three different special phases of the spherical phase under a hexagonal arrangement, which are spiral phase, 4-partition angular 0-π phase, and 6-partition angular 0-π phase. From the figure, we can clearly see that through this special phase loading, three different focal spot distributions with different intensity distributions can be achieved, thereby expanding the detection dynamic range to times the original.

[0045] Please see attached Figure 5 Furthermore, the problem of spot peak intensity difference due to special phase loading can be solved by Figure 5 The amplitude phase modulation pattern shown in FIG. 1 achieves a balance between the intensity distribution differences of different types of focal spots. Figure 5 As shown in FIG. 1 , for the microlens corresponding to the conventional solid light spot, an opaque amplitude modulation can be added to the annular area of ​​the microlens to achieve the intensity attenuation of the solid focus, and finally achieve the purpose of balancing the intensity distribution differences of different types of focal spots. Figure 6 An example of an array structured light chip with balanced peak intensity of two focal spots in a rectangular arrangement using amplitude phase modulation is given. From the numerical simulation results in the figure, it can be seen that the peak intensity distribution of the two focal spots can be well balanced by adding amplitude modulation.

[0046] (I) Specific embodiment 1: Fiber laser wavefront detection.

[0047] Taking the fiber laser with an operating wavelength of 1070nm as an example, a specific implementation plan for wavefront detection after the laser is collimated and expanded is proposed below.

[0048] Please see attached Figure 7Left: For a 1070nm fiber laser, the spot size after collimation is about 10mm, the power is 50W, and after sampling by a reflector with a reflectivity of about 5%, and passing through an adjustable attenuation plate, the collimated laser passes directly through the array structured light chip without passing through the projection module, and finally passes through the detection module to achieve photoelectric conversion. At this time, the array structured light chip corresponding to the wave aberration sensor is designed as shown in the attached figure. Figure 4 The hexagonal arrangement has a focal length of 5.5mm, a subaperture size of 300μm, and three encoding phases: spiral phase, 4-partition angular 0-π phase, and 6-partition angular 0-π phase. The detection module uses a CMOS chip as the photosensitive chip, with a single pixel size of 2.5×2.5μm and a pixel number of 5120×5120.

[0049] (II) Specific embodiment 2: spherical mirror surface shape detection.

[0050] Taking the purpose of optical component surface shape detection as an example, a specific implementation plan for optical component surface shape detection is proposed below.

[0051] Please see attached Figure 7 Right: The light source uses a 635nm LED light source, and a narrowband filter with a half-width at half maximum of 2nm is added (the central wavelength is 635nm). After the light emitted by the LED is collimated and expanded, it is incident on the surface of the optical component to be tested through a half-reflecting and half-mirror, and then reflected by the surface and reflected by the half-reflecting and half-mirror to enter the wave aberration sensor. Among them, the projection module in the wave aberration sensor can be adjusted according to the actual size of the optical component to be tested. For conventional optical components with small surface PV, a diffraction array structured light chip with only one focal spot can be used, such as an array structured light chip with spiral phase encoding. The detection module photosensitive chip uses a CMOS chip, with a single pixel size of 2.5×2.5μm and a pixel number of 5120×5120. For the optical component to be tested with a diameter of 300mm, the focal lengths of the first lens group and the second lens group of the projection module in the wave aberration sensor are selected as 600mm and 25mm respectively.

[0052] The above specific embodiments of the wave aberration sensor compatible with high precision and large dynamic range based on the array structured light chip cannot be understood as limiting the scope of protection of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the basic idea of ​​the present invention, they can also make several non-creative deformations and improvements to the specific implementation details and representative devices proposed in this patent, which all belong to the scope of protection of the present invention.

[0053] In summary, the present invention proposes a wavefront aberration sensor based on an array structured light chip that is compatible with high precision and a large dynamic range, which can be widely used in various fields such as laser wavefront detection, optical lens surface 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A wave aberration sensor compatible with high precision and large dynamic range, characterized in that: include: Array structured light chip, projection module and 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 distributions corresponding to adjacent sub-apertures are different; The projection module comprises a first lens group and a second lens group, and the effective optical power of the first lens group and the second lens group are both positive; The detection module at least includes an array photosensitive chip, a sampling and holding circuit, and an analog-to-digital conversion circuit; The plane where the array structured light chip is located and the measured wavefront carrying the wave aberration form an imaging conjugate relationship with the first lens group and the second lens group in the projection module.

2. A wave aberration sensor compatible with high precision and large dynamic range according to claim 1, characterized in that: The array structured light chip is a multi-step surface relief diffraction type microlens array.

3. A wave aberration sensor compatible with high precision and large dynamic range according to claim 1, characterized in that: The array structured light chip is a metasurface array device, and the phase loaded on the metasurface is an arrayed spherical phase and a superimposed characteristic phase.

4. The wavefront aberration sensor compatible with high precision and large dynamic range according to claim 1, characterized in that: A layer of metal chromium is plated on some equal phase regions within some subapertures in the array structured light chip by overlaying to achieve consistent peak intensities of different characteristic focal spots.

5. The wavefront aberration sensor compatible with high precision and large dynamic range according to claim 1, characterized in that: The subunits in the array structured light chip are arranged hexagonally, specifically, one-third of the subunits are loaded with a spherical phase, another one-third of the subunits are loaded with a spherical phase and an additional spiral phase, and the remaining one-third of the subunits are loaded with a spherical phase and additional angular partition 0 and π phases, and the subunits corresponding to the three structured light arrays are arranged alternately in sequence.

6. The wavefront aberration sensor compatible with high precision and large dynamic range according to claim 1, characterized in that: The subunits in the array structured light chip are arranged in a rectangular shape, specifically, the phase loaded on one-half of the subunits is a spherical phase, and the phase loaded on the remaining half of the subunits is a spherical phase and an additional spiral phase, and the subunits corresponding to the two structured light arrays are arranged alternately in sequence.

7. The wavefront aberration sensor compatible with high precision and large dynamic range according to claim 1, characterized in that: The position of the characteristic light spot array generated by the array structured light chip corresponding to the detection surface is calculated by the geometric center of the characteristic light spot.

8. The wavefront aberration sensor compatible with high precision and large dynamic range according to claim 1, characterized in that: The first lens group and the second lens group in the projection module form a confocal system and maintain center alignment.

9. The wavefront aberration sensor compatible with high precision and large dynamic range according to claim 1, characterized in that: The first lens group and the second lens group in the projection module at least include one aspherical lens.

10. The wavefront aberration sensor compatible with high precision and large dynamic range according to claim 1, characterized in that: 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.

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