Angle measurement device and method for microscopic angle-resolved spectroscopy system

Abstract

The present invention discloses an angle measurement device and a method for a microscopic angle-resolved spectroscopy system, comprising: a Kohler illumination module, an angle-resolved spectroscopy test module, a microscope objective, a three-dimensional translation stage, an angle displacement stage, and a micro-reflector. The position of the micro-reflector can be accurately adjusted by the three-dimensional displacement stage. When performing angle measurement, the position of the micro-reflector can be reset by the precise three-dimensional displacement stage, thereby reducing the experimental error caused by displacement. The micro-reflector is a core component for accurate angle measurement, and its miniaturized design facilitates the measurement of the angle of the Fourier surface of an objective lens with a short working distance and a large numerical aperture. The present invention provides a simple angle measurement device and a method for a microscopic angle-resolved spectroscopy system based on Kohler illumination. The device can be used as an independent module to perform accurate angle measurement on a conventional commercial angle-resolved spectrometer or an open angle-resolved system built by a laboratory.

Description

Technical Field

[0001] The invention belongs to the technical field of spectrum analysis, and in particular relates to a simple device and method suitable for accurate angle measurement of a microscopic angle-resolved spectrum system. Background Art

[0002] As the size of individual electronic devices decreases, maintaining device performance at the nanoscale faces huge challenges, and the continuation of Moore's Law is becoming increasingly difficult to achieve, which greatly limits the continued development of the traditional semiconductor microelectronics industry. For this reason, in addition to continuing to strive for innovative technologies based on the original process, people have to seek alternative development ideas. Among them, micro-photonic devices based on photons as information carriers have gradually attracted people's attention. Photonic devices have natural characteristics of low power consumption and fast speed. At present, the most important development direction for photonic devices is to use artificial microstructures to regulate light fields. People can design and prepare material microstructures according to functional requirements, produce new physical effects, and realize new functional photonic devices, especially some microcavity integrated structures, which have great advantages in regulating light fields. In academia, a series of hot research directions and cross-cutting directions in the field of optics have been developed, such as photonic crystals, metamaterials, surface plasmons, self-configured microcavities, and metasurfaces.

[0003] For these fields, traditional spectral characterization methods cannot keep up with the demand. Because of the characteristics of these microstructures, their light field control often needs to be experimentally characterized in momentum (angle) space, and traditional commercial microscopic spectroscopy methods do not have this function. Therefore, in recent years, spectral technologies with angle resolution functions have gradually developed, including macroscopic angle resolution (mechanical rotation angle) and microscopic microscopic angle resolution (through Fourier surface imaging technology). Some spectral testing technologies with such functions have been commercialized. Among them, microscopic angle-resolved spectroscopy technology has developed very rapidly. Its micron spatial resolution is a great technological innovation in the field of microstructure light field control, which meets the requirements of microstructures for spatial resolution and becomes the basic characterization technology for research in this field. Despite this, the biggest problem with microscopic angle-resolved spectroscopy systems on the market or even built in laboratories is the angle measurement problem in Fourier surface imaging technology. Through research, it was found that some of these products or self-used equipment in the research group lack the means for angle measurement, and even have a wrong understanding of the principle. For this reason, it is urgent to develop a set of standard and simple angle measurement devices and methods that can meet the system angle measurement under the user's routine daily maintenance conditions. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem that existing commercial microscopic angle-resolved spectroscopy systems or laboratory self-built angle-resolved spectroscopy systems lack effective, fast and simple implementation method of angle measurement. An angle measurement device and measurement method based on Kohler white light illumination are proposed, which can accurately measure the angle of any position point on the Fourier plane of the microscopic angle-resolved imaging system. This method is applicable to all conventional microscopic angle-resolved spectroscopy systems currently on the market, including microscope objectives with arbitrary numerical aperture and arbitrary working distance.

[0005] This method is based on the Kohler illumination technology of the conventional microscopic angle-resolved spectroscopy system and the angle-dependent Fourier surface imaging principle. The technical principles used are as follows:

[0006] like Figure 1 As shown in (a), based on the design of Kohler illumination, the real image position of the white light source falls on the Fourier plane (back focal plane) of the microscope objective. A point (point A) on the Fourier plane is selected. The light emitted from this point will form a parallel light incident at a specific angle relative to the object plane in the object area within the numerical aperture of the objective. Here we take a ray as an example. After being reflected by the mirror of the object plane, the ray is collected and focused by the objective lens to point B on the Fourier plane (back focal plane). The imaging principle can prove that whether light can converge at point B depends entirely on the position of point A and the reflection of the mirror of the object plane.

[0007] If the mirror surface at the object plane is deflected by an angle θ, such as Figure 1 As shown in (b), it can be found from the geometric ray method that the deflection of the mirror at an angle of θ will make the light emitted from point A focus at point B' after being reflected by the deflected mirror. That is, the deflection of the object side mirror at an angle of θ will move the focal point on the focal plane from point B to point B'. Assuming that point A is the most boundary point of the Fourier surface determined by the numerical aperture of the objective lens, it can be known from the above that the deflection of the mirror at an angle of θ will make no light converge within the range from point B to point B', that is, this part of the Fourier surface will not be illuminated. It can be imagined that there is a clear light-dark boundary that gradually moves from point B to the left as the angle θ increases. The angle corresponding to the range of movement of this light-dark boundary is 2θ.

[0008] Based on the angle measurement principle of the Fourier surface, the present invention provides an angle measurement device for a microscopic angle-resolved spectroscopy system based on Kohler illumination, comprising: a Kohler illumination module, an angle-resolved spectroscopy test module, a microscope lens, a three-dimensional displacement stage, an angle displacement stage, and a micro-reflector.

[0009] The angle rotation stage 2 is fixed on the three-dimensional displacement stage 1, and the micro-reflector 3 is fixed on the angle rotation stage 2; when working, the light beam emitted by the Kohler illumination module 6 is reflected by the beam splitter 5 at 45°, and then reaches the microscope objective 4 and irradiates the micro-reflector 3 vertically. After the vertical reflection of the light beam, a part of the light will pass through the beam splitter 5 to reach the plane reflector 7, and then pass through the angle-resolved imaging optical path system 8, and finally form an image on the spectrometer with a CCD array 9; under the Kohler illumination optical path configuration, the bright and dark boundary determined by the numerical aperture of the rear focal plane of the microscope objective 4 will be controlled by the rotation angle of the micro-reflector 3 on the object plane of the microscope objective 4, and the three-dimensional displacement stage 1 accurately adjusts the position of the micro-reflector 3.

[0010] The three-dimensional translation stage 1 is manually or electrically controlled, with a stepping accuracy of 1 μm and a maximum displacement distance of 5 mm in the three axes of X, Y and Z.

[0011] The angle rotation displacement stage 2 is marked with angle indications, and the total angle range reaches 35 degrees. It adopts a coaxial angle rotation design or an arc pendulum design.

[0012] The micro reflector 3 is used as a plane reflector in the Kohler illumination working mode, and is a metal reflector or any solid surface with a plane roughness of less than 5nm and a reflectivity of 10%.

[0013] The collection angle of the microscope objective lens 4 reaches 70 degrees, and the angular resolution reaches 0.2 degrees.

[0014] The angle measurement method based on the above angle measurement device is as follows:

[0015] When measuring the angle, first turn on the white light source configured in the Kohler illumination module 6, and place the micro-reflector 3 at the object focal plane of the microscope objective lens 4 through the three-dimensional translation stage 1 until a clear reflector surface can be observed through the eyepiece. When the micro-reflector 3 is placed horizontally, a reflection angle-resolved Fourier surface spectrum image under a reflection configuration is tested through an angle-resolved imaging optical path system 8 and a spectrometer 9 equipped with a planar array CCD; the pixel strip positions at the upper and lower bright and dark boundaries of the image are read and recorded through the position function of the spectrum test software, and the number of pixel strips used by the Fourier surface is calculated through the upper and lower light-dark boundary positions, and then the pixel strip position of the center is located; next, the micro-reflector 3 is rotated by the angle rotation stage 2 with 2 degrees as the rotation step unit, and the micro-reflector 3 is observed in the eyepiece to see whether it deviates, and if it deviates, it is adjusted to a clear imaging state through the three-dimensional displacement stage 1; after completion, a reflection angle-resolved Fourier surface spectrum image is repeatedly tested through the angle-resolved imaging optical path system 8 and the spectrometer 9 equipped with a planar array CCD, and the pixel strip positions at the upper and lower bright and dark boundaries after the image is rotated by a certain angle are recorded through the image software;

[0016] When measuring the angle, the rotation of the angle rotation stage 2 will inevitably cause the spatial movement of the micro-mirror 3. The micro-mirror 3 is reset by the precise three-dimensional translation stage 1 to reduce the experimental error caused by the displacement.

[0017] When performing angle measurement, the angular deflection of the micro-mirror 3 relative to the microscope objective lens 4 is controlled by adjusting the angle rotation stage, thereby realizing the movement of the bright and dark boundary of the rear focal plane of the angle-resolved image. Through the moving position of the bright and dark boundary, the specific relationship between the angle and the number of pixel stripes on the angle-resolved image is accurately obtained, thereby measuring the angle corresponding to the position of each pixel stripe in the angle-resolved image.

[0018] The beneficial effects of the present invention are as follows: the present invention provides a simple angle measurement device and method for a microscopic angle-resolved spectroscopy system based on Kohler illumination, and the device can be used as an independent module to perform accurate angle measurement on a currently conventional commercial angle-resolved spectrometer or an open angle-resolved system built by a laboratory. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Figure a is a schematic diagram of the principle of the present invention when the micro-reflection mirror is placed horizontally, and Figure b is a schematic diagram of the principle of the present invention when the micro-reflection mirror is deflected by an angle θ relative to the horizontal plane;

[0020] Figure 2 It is a schematic diagram of the structure of the hardware device of the present invention;

[0021] Figure 3 Figure a in the middle is the angular resolution image when the micro-reflector is placed horizontally, and Figure b is the angular resolution image when the micro-reflector is deflected 10 degrees relative to the horizontal plane;

[0022] Figure 4 Figure a in the middle is a diagram showing the angle data of the pixel strips used on the Fourier surface when the micro-reflector surface is placed horizontally, and Figure b is a diagram showing the angle data of the pixel strips used on the Fourier surface when the micro-reflector surface is deflected 10 degrees relative to the horizontal plane.

[0023] Figure 2 Description of the mark:

[0024] 1——Three-dimensional translation stage;

[0025] 2——angle rotation stage;

[0026] 3——Micro reflector;

[0027] 4 – Microscope objective lens;

[0028] 5 – beam splitter;

[0029] 6——Kohler Lighting;

[0030] 7 – reflector;

[0031] 8——angle-resolved imaging optical system;

[0032] 9——Spectrometer equipped with area array CCD. DETAILED DESCRIPTION

[0033] A suitable micro-reflector 3 is selected according to the objective lens parameters used in the microscopic angular resolution system. Taking an objective lens with a working distance of 1 mm and a numerical aperture of 0.8 as an example, the selected customized micro-reflector 3 is a strip structure (1 mm wide, 10 mm long, and 1 mm thick). The strip micro-reflector 3 is placed on the angle rotation stage 2 so that the central axis of the strip micro-reflector 3 in the length direction is coaxial with the central axis of the angle rotation stage 2. This can reduce the position movement of the micro-reflector under the objective lens during rotation.

[0034] Turn on the white light source configured by the Kohler illumination 6, and place the micro-reflector 3 at the object focal plane of the microscope objective 4 through the three-dimensional translation stage 1 until a clear reflector surface can be observed through the eyepiece.

[0035] When the micro-reflector 3 is placed horizontally, a reflection angle-resolved (Fourier surface) spectrum image under a reflection configuration is tested through the angle-resolved imaging optical path system 8 and the spectrometer 9 equipped with a planar array CCD. Through the position function of the spectrum test software, the pixel strip positions of the upper and lower bright and dark boundaries of the image are read and recorded, and the number of pixel strips used by the Fourier surface is calculated through the upper and lower bright and dark boundary positions, and then the pixel strip position of the center is located.

[0036] Next, the micro-mirror 3 is rotated by the angle rotation stage 2 with a rotation step unit of 2 degrees, and the micro-mirror 3 is observed in the eyepiece to see if it deviates. If it deviates, it is adjusted to a clear imaging state by the three-dimensional stage 1. After completion, a reflection angle-resolved (Fourier surface) spectral image is repeatedly tested by the angle-resolved imaging optical path system 8 and the spectrometer 9 equipped with a planar array CCD, and the pixel strip positions of the upper and lower bright and dark boundaries of the image after the image is rotated by a certain angle are recorded by the image software.

[0037] Through multiple angle measurements, it can be found that as the rotation angle of the micro-mirror increases, one bright-dark boundary on the angle-resolved image will gradually move toward the center strip position, while the other bright-dark boundary remains unchanged. Figure 3 The angular resolution images of the micro-mirror with a deflection angle of 0 and 10 degrees relative to the horizontal plane are given. It can be seen that the bright and dark boundary below moves upward obviously, while the bright and dark boundary above is basically stationary. This is consistent with the experimental results predicted by the angle measurement principle under Kohler illumination mentioned above.

[0038] Taking the maximum angle collected by the objective lens with a numerical aperture of 0.8 as ±53.13 degrees as an example, the angle rotation stage 2 can be rotated to ~26.6 degrees. After recording each rotation (1 degree, the collection angle corresponding to the Fourier plane is 2 degrees), the angle-resolved image moves the pixel stripe position where the bright and dark boundaries are located. In this way, the angle corresponding to each position on the angle-resolved image (Fourier plane) can be measured. The specific relationship is as follows Figure 4 As shown in the measured data, it can be seen that the number of pixel fringes on the Fourier imaging image is proportional to the sine value of the angle, which means that the position on the Fourier plane takes the sine of the angle as the linear axis and strictly follows the Abbe sine relationship.

[0039] The above is only a preferred example of the present invention and does not limit the scope of application of the present invention. Any modification, replacement, improvement, etc. made by using the principles, instructions and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the protection scope of the present invention.

Claims

1. An angle measuring device for a microscopic angle-resolved spectroscopy system, comprising: A three-dimensional displacement stage (1), an angle rotation displacement stage (2), a micro-reflector (3), a microscope objective lens (4), a beam splitter (5), a Kohler illumination module (6), a plane reflector (7), an angle-resolved imaging optical path system (8), and a spectrometer with an array CCD (9), characterized in that: The angle rotation displacement stage (2) is fixed on the three-dimensional displacement stage (1), and the micro-reflector (3) is fixed on the angle rotation displacement stage (2); when in operation, the light beam emitted by the Kohler illumination module (6) is reflected at 45 degrees by the beam splitter (5), and then reaches the microscope objective (4) and vertically irradiates the micro-reflector (3); after the vertical reflection of the light beam, a part of the light beam passes through the beam splitter (5) and reaches the plane reflector (7), and then passes through the angle-resolved imaging optical path system (8), and finally forms an image on the spectrometer with a CCD array (9); under the Kohler illumination optical path configuration, the bright and dark boundary determined by the numerical aperture of the rear focal plane of the microscope objective (4) is controlled by the rotation angle of the micro-reflector (3) on the object plane of the microscope objective (4), and the three-dimensional displacement stage (1) accurately adjusts the position of the micro-reflector (3).

2. The angle measuring device for a microscopic angle-resolved spectroscopy system according to claim 1, characterized in that: The three-dimensional translation stage (1) is manually or electrically controlled, with a stepping accuracy of 1 μm and a maximum displacement distance of 5 mm in the three axes of X, Y and Z.

3. The angle measuring device for a microscopic angle-resolved spectroscopy system according to claim 1, characterized in that: The angle rotation displacement stage (2) is marked with angle indications, and the total angle range reaches 35 degrees. It adopts a coaxial angle rotation design or an arc pendulum design.

4. The angle measuring device for a micro-angle-resolved spectroscopy system according to claim 1, characterized in that: The micro reflector (3) is used as a plane reflector in the Kohler illumination working mode, and is a metal reflector or any solid surface with a plane roughness of less than 5 nm and a reflectivity of 10%.

5. The angle measuring device for a micro-angle-resolved spectroscopy system according to claim 1, characterized in that: The microscope objective lens (4) has a collection angle of 70 degrees and an angular resolution of 0.2 degrees.

6. An angle measurement method based on the angle measurement device for a microscopic angle-resolved spectroscopy system according to claim 1, characterized in that Here’s how: When measuring the angle, first turn on the white light source configured in the Kohler illumination module (6), and place the micro-reflector (3) at the object focal plane of the microscope objective lens (4) through the three-dimensional displacement stage (1) until a clear reflective mirror surface can be observed through the eyepiece; when the micro-reflector (3) is placed horizontally, a reflection angle-resolved Fourier surface spectrum image under a reflection configuration is tested through an angle-resolved imaging optical path system (8) and a spectrometer (9) equipped with a planar CCD; through the position function of the spectrum test software, the pixel strip positions of the upper and lower bright and dark boundaries of the image are read and recorded, and the Fourier angle is calculated through the upper and lower bright and dark boundary positions. The number of pixel strips used by the leaf surface is determined, and the position of the pixel strip in the center is then located; next, the micro-reflector (3) is rotated by the angle rotation stage (2) with a rotation step of 2 degrees as the rotation step unit, and the micro-reflector (3) is observed in the eyepiece to see whether it deviates. If it deviates, it is adjusted to a clear imaging state by the three-dimensional stage (1); after completion, a reflection angle-resolved Fourier leaf surface spectrum image is repeatedly tested by the angle-resolved imaging optical path system (8) and the spectrometer (9) equipped with a planar array CCD, and the pixel strip positions of the upper and lower bright and dark boundaries of the image after the image is rotated by a certain angle are recorded by the image software; When measuring the angle, the rotation of the angle rotation stage (2) will inevitably cause the micro-reflector (3) to move in space. The micro-reflector (3) is reset by the precise three-dimensional displacement stage (1) to reduce the experimental error caused by the displacement. When measuring the angle, the angle of the micro-reflector (3) is controlled relative to the microscope objective lens (4) by adjusting the angle rotation displacement stage (2), thereby achieving the movement of the bright and dark boundary of the rear focal plane of the angle-resolved image. The specific relationship between the angle and the number of pixel stripes on the angle-resolved image is accurately obtained through the movement position of the bright and dark boundary, thereby measuring the angle corresponding to the position of each pixel stripe of the angle-resolved image.

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