Microstructure sample inspection apparatus and method of inspection thereof

Abstract

The application discloses a microstructure sample detection device and a detection method thereof, and belongs to the technical field of microstructure sample detection. The microstructure sample detection device comprises an imaging light path, a scanning motor and a long working distance parallel light path. The imaging light path is used for placing a microstructure sample. The scanning motor is used for axially moving the sample along a direction perpendicular to the microstructure sample, so that light field scanning is performed. The long working distance parallel light path is used for projecting single parallel illumination light on the microstructure sample in a reflection or transmission mode. The parallel light path comprises a beam expander and shaper lens group, a selected area diaphragm and a relay lens group. The beam expander and shaper lens group has an incident end and an exit end. The incident end is aligned with a light source. The selected area diaphragm is aligned with the exit end. The relay lens group comprises a front lens and a rear lens arranged on the same optical axis. The front lens is aligned with a diaphragm hole of the selected area diaphragm. The rear lens is aligned with the microstructure sample. A sample surface of the microstructure sample is object image conjugate with the selected area diaphragm, and the image side is telecentric. The application solves the problem that the existing light field scanning detection method cannot accurately detect optical parameter information of a sample.

Description

Technical Field

[0001] This invention relates to the field of microstructure optical field scanning technology, specifically to a microstructure sample detection device and its detection method. Background Technology

[0002] Today, technologies used in smart cars, smartphones, and portable display devices are changing and developing at a very rapid pace, with a growing desire to cram more and better functions into increasingly smaller spaces. Despite this, in the field of optical modules, traditional geometric optics-based design schemes face numerous limitations, hindering further technological breakthroughs and applications. With the development of micro-nano photonics, it has become possible to manipulate and control light waves using subwavelength structural units. Effectively arranging these structural units allows for the integration of various complex optical functions onto a single plane; the most representative example is the metasurface, where a metasurface functioning as a lens is called a metalens. Because metalenses are based on a fundamental design, they achieve a higher degree of freedom in light field manipulation. Compared to traditional optical lenses, they offer advantages such as planarity (hundreds of nanometers to micrometers), miniaturization (tens of micrometers in diameter), freeform surfaces, and integration, making them potentially valuable in fields such as optical communication, security, autonomous driving, consumer electronics, medical devices, scientific instruments, and sensing.

[0003] Optical field scanning detection involves placing the microstructure sample (including but not limited to metalenses) under the objective lens of a microscopic imaging system, and then illuminating the sample perpendicularly with a beam of monochromatic parallel illumination light, either through transmission or reflection. First, the processing surface of the microstructure sample is aligned with the optimal focal plane of the microscope objective lens; this point is defined as the zero point of the optical field scanning. The scanning motor is then activated to scan and acquire images along a direction perpendicular to the microstructure sample, thus achieving the scanning detection of the optical field of the microstructure sample. Based on the light intensity distribution at different scanning positions, the optical field information of the microstructure sample can be calculated, thereby determining parameters such as focal length, MTF, PSF, Strell ratio, and focusing efficiency. It can also detect the frequency domain information of the microstructure sample, which is of great significance for detecting the processing performance of microstructure samples.

[0004] Existing light field scanning detection technology has the following problems:

[0005] 1. The size and shape of the illumination spot cannot be adjusted according to the actual diameter and shape of the microstructure sample.

[0006] 2. After collimation, the laser beam diffracts after passing through the aperture, resulting in a ring-shaped intensity distribution of the illumination spot on the microstructure sample surface. When the microstructure sample being tested is a metalens, since the metalens surface also contains ring-shaped microstructure information, using an illumination spot with rings can lead to inaccurate judgment of sample information, such as the determination of sample surface height and the processing condition of the sample surface microstructure. It can also interfere with the scanning light field distribution, affecting the accuracy of calculating parameters such as sample focal length, MTF (Modulation Transfer Function), PSF (Point Spread Function), Strell ratio, and focusing efficiency.

[0007] 3. When detecting small-sized microstructure samples, a parallel beam with high energy density and a narrow beam diameter is used. When the beam passes through the lens, it undergoes significant secondary reflection, which interferes with the original beam and thus affects the detection.

[0008] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, a microstructure sample detection device and its detection method are provided to solve the problems of inaccurate sample information judgment caused by the inability to adjust the shape and size of the illumination spot, secondary reflection in the optical path, and Fresnel diffraction in existing optical field scanning detection methods.

[0010] To achieve the above objectives, a microstructure sample detection device is provided, comprising:

[0011] An imaging optical path is provided, which can simultaneously or switchably image the surface or far-field information of a microstructure sample, and the imaging optical path has a stage for placing the microstructure sample.

[0012] A scanning motor is used to scan the microstructure sample with an optical field along a direction perpendicular to the microstructure sample.

[0013] A long working distance parallel optical path is used to project a single beam of parallel illumination light onto the microstructure sample by reflection or transmission. The parallel optical path includes a beam expander and shaping lens group, a selection aperture, and a relay lens group. The beam expander and shaping lens group has an entrance end and an exit end. The entrance end is aligned with the light source, and the selection aperture is aligned with the exit end. The relay lens group includes a front lens and a rear lens arranged coaxially. The front lens is aligned with the aperture of the selection aperture, and the rear lens is aligned with the microstructure sample. The sample surface of the microstructure sample and the selection aperture are object-image conjugates and the image side is telecentric.

[0014] Furthermore, it also includes a beam-changing mirror assembly for generating parallel beam spots of different sizes, the beam-changing mirror assembly being disposed between the selection aperture and the relay mirror assembly.

[0015] Furthermore, the beam-changing mirror group is a Keplerian optical path structure or a Galilean optical path structure.

[0016] Furthermore, it also includes a first clutter stop, wherein the intermediate image plane of the selected area stop is located between the beam converter group and the relay lens group, and the first clutter stop is disposed at the intermediate image plane.

[0017] Furthermore, the relay lens assembly also includes a second stray light stop, which is disposed between the front lens and the rear lens.

[0018] This invention provides a detection method for a microstructure sample detection device, comprising the following steps:

[0019] The microstructure sample to be tested is placed on the stage of the imaging optical path, and the sample surface of the microstructure sample is adjusted to the focal plane of the imaging optical path. The sample surface of the microstructure sample and the selected area aperture are conjugate to the object and image and the image side is telecentric.

[0020] The light from the light source is guided into a parallel light path, which projects a single beam of parallel illumination light onto the microstructure sample by means of reflection or transmission.

[0021] The scanning motor scans the light field distribution of the microstructure sample along a direction perpendicular to the microstructure sample to obtain the light field information of the microstructure sample;

[0022] Based on the light field information, the optical parameters of the microstructure sample are calculated.

[0023] Switch to the far-field mode of the imaging optical path to obtain the frequency domain information of the microstructure sample.

[0024] Furthermore, the optical parameter information includes focal length, modulation transfer function, point spread function, Strell ratio, and focusing efficiency.

[0025] The beneficial effects of this invention are as follows: the microstructure sample detection device of this invention has a long working distance for its parallel optical path reflecting or transmitting parallel beams. Within a long working range, the beam parallelism is high, and the edge diffraction effect is small, making it suitable for detecting microstructure samples with different focal lengths. The parallel optical path generates parallel beams of different diameters to adapt to the sizes of different microstructure samples. A relay optical path is added after the selected area aperture, ensuring that the sample surface of the microstructure sample and the selected area aperture have an object-image conjugate relationship, with the image side being telecentric. The selected area aperture uses a polygonal aperture, which can obtain a parallel beam spot with uniform intensity at the sample surface. After the laser beam passes through the selected area aperture and relay mirror group of the parallel optical path of the microstructure sample detection device of this invention, Fresnel diffraction of the parallel beam is avoided, thereby making the intensity distribution of the illumination spot hitting the microstructure sample surface uniform and improving the accuracy of frequency domain information judgment of the microstructure sample. Attached Figure Description

[0026] 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:

[0027] Figure 1 This is a schematic diagram of the microstructure sample detection device according to an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of the parallel optical path in an embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram of the beam-changing lens assembly according to an embodiment of the present invention. Detailed Implementation

[0030] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0031] 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.

[0032] Reference Figures 1 to 3 As shown, the present invention provides a microstructure sample detection device for detecting frequency domain information of microstructure samples. Specifically, in this embodiment, the microstructure sample detection device of the present invention includes: an imaging optical path 1, a sweeping motor 2, and a long working distance parallel optical path 3.

[0033] In this embodiment, the imaging optical path is a microscope. The microscope is equipped with a microscopic imaging detector, a reflected light illumination assembly, and a spatial spectrum imaging detector.

[0034] The imaging optical path 1 has a stage 12 for placing the microstructure sample 4.

[0035] The scanning motor 2 is used to perform optical field scanning on the microstructure sample 4 along a direction perpendicular to the microstructure sample 4. The scanning motor 2 is aligned with the microstructure sample 4.

[0036] Parallel optical path 3 has a long working distance. Parallel optical path 3 is used to project a single beam of parallel illumination light onto the microstructure sample 4 by reflection or transmission.

[0037] Specifically, the parallel optical path 3 includes a beam expander and shaper lens group 31, a selection aperture 32, and a relay lens group 33. The beam expander and shaper lens group 31 has an entrance end and an exit end. The entrance end is aligned with the light source. The selection aperture 32 is aligned with the exit end. The relay lens group 33 includes a front lens 331 and a rear lens 332 arranged coaxially. The front lens 331 is aligned with the aperture of the selection aperture 32. The rear lens 332 is aligned with the microstructure sample 4. The sample surface of the microstructure sample 4 is conjugate to the selection aperture 32 and the image side is telecentric.

[0038] The microstructure samples can be planar optical components such as metasurfaces, metalenses, and vortex beam sheets. The effective aperture range of the metalens samples can be from 10 μm to 10 mm, and the focal length range can be from 5 μm to 50 mm.

[0039] The beam expanding and shaping lens assembly is used to shape and expand the beam of lasers with different input forms, such as laser beam expanding and shaping of spatial light or fiber light of different wavelengths.

[0040] The beam expander and shaping lens group uses cylindrical lenses to achieve one-dimensional or two-dimensional beam shaping and expansion.

[0041] The beam expander and shaping lens group uses a collimating lens group to achieve beam collimation and beam expansion.

[0042] The beam expander and shaping lens group uses a microlens array to achieve beam shaping of special shapes.

[0043] The beam expander and shaping lens group uses a conical lens to achieve ring beam shaping.

[0044] The optical path of the beam expander and shaping lens assembly may include achromatic elements or axial adjustment elements to ensure the beam quality of different wavelengths.

[0045] The selection aperture 32 enables modulation of the size and shape of the light spot, and can use hard-edged apertures and soft-edged apertures of various shapes.

[0046] Selective apertures are used to generate parallel beam spots of different sizes to accommodate microstructure samples of varying dimensions. They include, but are not limited to, Keplerian or Galilean optical path structures, which may contain achromatic elements or axial adjustment elements to ensure beam quality at different wavelengths.

[0047] The relay lens group performs secondary imaging of the selected area aperture to form a parallel beam with a long transmission illumination working distance and to eliminate diffraction at the aperture edge.

[0048] The relay lens assembly includes, but is not limited to, a 4F optical path, and can also be other relay imaging optical paths capable of achieving image-side telecentricity. The optical path of the relay lens assembly may include achromatic elements or axial adjustment elements to ensure the beam quality at different wavelengths.

[0049] The microstructure sample detection device of this invention features a parallel optical path that transmits a parallel beam with a long working distance. Within a long working range, the beam parallelism is high, and the edge diffraction effect is small, making it suitable for microstructure samples. The parallel optical path generates parallel beams of different diameters to accommodate the sizes of different microstructure samples. A relay optical path is added after the selected area aperture, ensuring that the sample surface of the microstructure sample and the selected area aperture have an object-image conjugate relationship, with the image side telecentric. The selected area aperture uses a polygonal aperture, resulting in a uniformly intense parallel beam spot at the sample surface. After the laser beam passes through the selected area aperture and relay mirror group of the parallel optical path of this invention's microstructure sample detection device, Fresnel diffraction of the parallel beam is avoided, resulting in a uniform intensity distribution of the illumination spot on the microstructure sample surface and improving the accuracy of frequency domain information determination for the microstructure sample.

[0050] The microstructure sample detection device of the present invention also includes a beamshifter assembly 34. The beamshifter assembly 34 is used to generate parallel beam spots of different sizes. The beamshifter assembly 34 is disposed between the selection aperture 32 and the relay mirror assembly 33.

[0051] Specifically, the beam-changing lens group 34 has a Keplerian optical path structure or a Galilean optical path structure.

[0052] The microstructure sample detection device of the present invention further includes a first stray stop 35. The intermediate image plane of the selected area stop is located between the beam converter group and the relay lens group. The first stray stop is disposed at the intermediate image plane.

[0053] A first stray stop 35 is added at the middle image plane 320 of the selection area stop 32 to block the light reflected from the interface of the front lens of the relay lens group, thereby ensuring the uniformity of the detection spot illuminating the sample surface.

[0054] In cases where extremely fine parallel beams are generated, a first stray light stop is installed in front of the relay lens group to eliminate stray light and prevent significant secondary reflections from the lenses of the relay lens group.

[0055] Furthermore, in this embodiment, the relay lens group 33 also includes a second stray light stop 333. The second stray light stop 333 is disposed between the front lens 331 and the rear lens 332.

[0056] Parallel beams are achieved by switching beam-changing mirror groups. Taking a fiber laser as the light source, the fiber light is collimated by a collimating mirror group, then passes through an adjustable aperture, and finally through a relay mirror group, before being projected onto the sample as a wide parallel beam. After the switching module is inserted into the optical path, the collimated beam passes through the adjustable aperture, and then through the secondary imaging optical path formed by the switching module and the relay mirror group, projecting onto the sample as a narrow parallel beam.

[0057] Table 1 shows... Figure 2 Optical parameters of the components for the wide-beam parallel optical path shown

[0058]

[0059]

[0060] Table 2 is... Figure 3 Optical parameters of the components of the parallel optical path for the thin beam shown

[0061]

[0062] This invention provides a detection method for a microstructure sample detection device, comprising the following steps:

[0063] S1: Place the microstructure sample 4 to be tested on the stage 12 of the imaging optical path 1, and adjust the sample surface of the microstructure sample 4 to the optimal focal plane of the objective lens 11 of the imaging optical path 1, and the sample surface of the microstructure sample 4 and the selected area aperture 32 are conjugate of the object and the image and the image side is telecentric.

[0064] S2: The light from the light source is guided into the parallel light path 3, and the parallel light path 3 projects a single beam of parallel illumination light onto the microstructure sample 4 by reflection or transmission.

[0065] S3: The scanning motor 2 scans the light field of the microstructure sample 4 along a direction perpendicular to the microstructure sample 4 to obtain the light field information of the microstructure sample 4.

[0066] S4: Based on the light field information, the frequency domain information of microstructure sample 4 is calculated. The frequency domain information includes focal length, MTF, PSF, Strell ratio, and focusing efficiency.

[0067] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention 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 inventive 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 microstructure sample detection device, characterized in that, include: An imaging optical path is provided, which can simultaneously or switchably image the surface or far-field information of a microstructure sample, and the imaging optical path has a stage for placing the microstructure sample. A scanning motor is used to scan the microstructure sample with an optical field along a direction perpendicular to the microstructure sample. A long working distance parallel optical path is used to project a single beam of parallel illumination light onto the microstructure sample by reflection or transmission. The parallel optical path includes a beam expander and shaping lens group, a selection aperture, and a relay lens group. The beam expander and shaping lens group has an entrance end and an exit end. The entrance end is aligned with the light source, and the selection aperture is aligned with the exit end. The relay lens group includes a front lens and a rear lens arranged coaxially. The front lens is aligned with the aperture of the selection aperture, and the rear lens is aligned with the microstructure sample. The sample surface of the microstructure sample and the selection aperture are conjugate in object and image, and the image side is telecentric. It also includes a beam-changing lens group for generating parallel beam spots of different sizes, the beam-changing lens group being disposed between the selection aperture and the relay lens group; It also includes a first clutter stop, wherein the intermediate image plane of the selected area stop is located between the beam converter group and the relay lens group, and the first clutter stop is disposed at the intermediate image plane; The relay lens assembly also includes a second stray light stop, which is disposed between the front lens and the rear lens.

2. The microstructure sample detection device according to claim 1, characterized in that, The beam-changing mirror group is a Keplerian optical path structure or a Galilean optical path structure.

3. A detection method for a microstructure sample detection device as described in any one of claims 1 to 2, characterized in that, Includes the following steps: The microstructure sample to be tested is placed on the stage of the imaging optical path, and the sample surface of the microstructure sample is adjusted to the focal plane of the imaging optical path. The sample surface of the microstructure sample and the selected area aperture are conjugate to the object and image and the image side is telecentric. The light from the light source is guided into a parallel light path, which projects a single beam of parallel illumination light onto the microstructure sample by means of reflection or transmission. The scanning motor scans the light field distribution of the microstructure sample along a direction perpendicular to the microstructure sample to obtain the light field information of the microstructure sample; Based on the light field information, the optical parameters of the microstructure sample are calculated. Switch to the far-field mode of the imaging optical path to obtain the frequency domain information of the microstructure sample.

4. The detection method according to claim 3, characterized in that, The optical parameters include focal length, modulation transfer function, dot spread function, Strell ratio, and focusing efficiency.

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