Refractive index measuring device, refractive index measuring equipment and refractive index measuring method

Abstract

The invention provides a refractive index measuring device, measuring equipment and a measuring method. The measuring device comprises a light source, a linear wave zone plate and an imaging sensor. Measurement light emitted by the light source penetrates through the linear wave zone plate and then is refracted by the sample to form a diffraction pattern containing a plurality of linear light spots on the imaging sensor. A diffraction pattern corresponding to a reference sample and a diffraction pattern corresponding to a to-be-tested sample are respectively obtained by using the measuring device, and the refractive index of the to-be-tested sample can be determined according to the two diffraction patterns and the refractive index of the reference sample. The measuring device, the measuring equipment and the measuring method provided by the invention have the advantages of high precision of a refractive index measuring result and wide measuring range, can be widely applied to the measurement of liquid refractive index and solid refractive index, and is particularly suitable for the field of HPCL (High Performance Liquid Chromatography).

Description

Technical Field

[0001] The present application relates to the field of optics, and in particular, to a refractive index measuring device, a measuring equipment and a measuring method. Background Art

[0002] Critical angle measurement method, phase change measurement method, interference fringe difference method and light diffraction method can all be used to measure the refractive index of materials. These measurement methods often require more stringent conditions to obtain high-precision measurement results, which to a certain extent limits the application of test devices using these test methods in gradient chromatography.

[0003] How to improve the measurement accuracy of refractive index is a question worth considering. Summary of the invention

[0004] The present application provides a refractive index measuring device, measuring equipment and measuring method. After the measuring light is diffracted by the linear wave zone plate, a diffraction pattern containing multiple linear light spots can be formed on the imaging sensor. The refractive index of the sample to be measured by using the diffraction pattern has a higher accuracy. The refractive index measuring device provided in the embodiment of the present application can be applied to the refractive index measurement in the field of HPLC.

[0005] In a first aspect, a refractive index measuring device is provided, which comprises: a light source for emitting measuring light, a zone plate comprising a plurality of mutually parallel prisms, and an imaging sensor for receiving measuring light passing through the zone plate, a reference sample and / or a reference sample.

[0006] In a possible implementation, the refractive index measuring device includes a reference sample, and the refractive index of the reference sample is known.

[0007] In combination with the first aspect, in certain implementations of the first aspect, the diffraction pattern formed by the measuring light on the imaging sensor includes a plurality of linear light spots.

[0008] In combination with the first aspect, in some implementations of the first aspect, the measuring device further includes a measuring chamber, the measuring chamber is used to accommodate a reference sample and / or a sample to be measured, and the measuring chamber is located on a side of the zone plate away from the light source.

[0009] A zone plate can also be called a Fresnel zone plate, and the multiple parallel prisms contained in the zone plate can also be called a narrow band. A Fresnel zone plate containing multiple parallel prisms can also be called a linear Fresnel zone plate. When the measurement light is incident on the prisms of the zone plate, diffraction can occur, and it is easier to form a diffraction pattern containing a linear spot.

[0010] The measuring chamber can be used to accommodate both the reference sample and the sample to be measured, or can be used to accommodate only one of the reference sample and the sample to be measured. It should be understood that the reference sample refers to a sample with a known refractive index.

[0011] Compared with a general diffraction grating, the diffraction pattern formed by diffraction using a zone plate can form linear diffraction fringes, and the diffraction fringes are clearer, and the position information of the diffraction fringes is easier to determine. Since the accuracy (or error) of the difference between the refractive index of the sample to be measured and the refractive index of the reference sample is positively correlated with the measurement accuracy (or error) of the position information of the diffraction fringes, the refractive index of the sample to be measured by the refractive index measurement device provided by the present application is more accurate.

[0012] In combination with the first aspect, in certain implementations of the first aspect, the device also includes a mobile platform, which is located on a side of the measuring cabin away from the wave zone plate, and the imaging sensor is located on the mobile platform, and the imaging sensor can move on the mobile platform along the optical axis direction of the wave zone plate.

[0013] In some examples, the imaging sensor may be a camera or imaging device including a CCD or CMOS.

[0014] Compared to the refractive index measuring device with a fixed position of the imaging sensor, the imaging sensor of the refractive index measuring device provided by the present technical solution can be moved along the optical axis direction of the wave zone plate on a mobile platform. Regardless of the size of the deflection angle of the measuring light caused by the sample to be tested (i.e., regardless of the size of the refractive index of the sample to be tested), the measuring light passing through the sample to be tested can be received as much as possible by moving the imaging sensor, thereby determining the refractive index of the sample to be tested. The refractive index measuring device provided by the present technical solution can measure a wider range of refractive indices. To a certain extent, the refractive index measuring device provided by the present technical solution has a higher accuracy in the refractive index measurement results near the measurement boundary value.

[0015] In combination with the first aspect, in some implementations of the first aspect, the device further includes a first reflector, a second reflector, a beam splitter, and a moving platform, the moving platform is located on a side of the measuring cabin away from the zone plate, the first reflector is located on the moving platform, and the first reflector can move on the moving platform along the optical axis direction of the zone plate; the optical axis of the second reflector is inclined with respect to the optical axis of the zone plate;

[0016] The light source and the imaging sensor are respectively located on both sides of the beam splitter; the measuring light is incident on the first reflector along a first optical path, and the measuring light is incident on the imaging sensor along a second optical path after being reflected by the first reflector;

[0017] The first optical path passes through the beam splitter, the second reflector, the zone plate and the measuring chamber in sequence, and the second optical path passes through the measuring chamber, the zone plate, the second reflector and the second beam splitter in sequence.

[0018] In the present technical solution, the optical path of the measuring light is changed by using the first reflector and the second reflector, so that the measuring light can pass through the reference sample and / or the sample to be measured twice, that is, the measuring light can be deflected twice during one measurement process. Compared with the method of measuring the refractive index of the sample to be measured by only one deflection, the method of two deflection measurements is conducive to reducing the relative error caused by factors such as measurement errors, and is conducive to improving the accuracy of the measurement results of the refractive index measuring device. On the other hand, by using a reflector to adjust the propagation path of the measuring light, it is conducive to improving the utilization rate of the internal space of the refractive index measuring device to a certain extent and reducing the volume of the refractive index measuring device.

[0019] In combination with the first aspect, in certain implementations of the first aspect, the device also includes a second reflector, which is arranged close to the wave zone plate, and the measuring light is incident on the imaging sensor along a third optical path, wherein the third optical path passes through: the second reflector, the wave zone plate and the measuring cabin in sequence.

[0020] In the technical solution, the second reflector is used to change the optical path of the measuring light, which is beneficial to adjust the spatial layout of different devices in the measuring device, reduce the volume of the measuring device, and improve the space utilization rate of the measuring device.

[0021] In combination with the first aspect, in some implementations of the first aspect, the second reflector is a collimating reflector.

[0022] In some possible implementations, the collimating reflector may be an adjustable parabolic mirror.

[0023] In this technical solution, a collimating reflector is used on the propagation path of the measuring light to convert the originally divergent measuring light into mutually parallel light beams as much as possible. When the parallel light beam is incident on the wave zone plate and diffracted, the resulting derivative pattern is clearer. The implementation of this technical solution is conducive to improving the accuracy of the refractive index measurement results and reducing the measurement error.

[0024] In combination with the first aspect, in certain implementations of the first aspect, the measuring chamber includes a first containing chamber and a second containing chamber, and the first containing chamber and the second containing chamber are used to contain the reference sample and / or the sample to be measured.

[0025] In some examples, the measuring chamber is in the shape of a quadrangular prism, the first containing chamber and the second containing chamber are in the shape of triangular prisms of equal volumes, and the first containing chamber and the second containing chamber are isolated from each other.

[0026] In the present technical solution, the measurement chamber is provided with two containing chambers, that is, the reference sample and the sample to be measured can be contained at the same time, which is beneficial to reduce the measurement error caused by the contamination of the sample by the measurement environment and is beneficial to improve the accuracy of the refractive index measurement result.

[0027] In combination with the first aspect, in certain implementations of the first aspect, the measuring chamber is used to accommodate the sample to be tested, the reference sample is in the shape of a plate, and the reference sample is located between the wave zone plate and the measuring chamber; or, the measuring chamber is used to accommodate the reference sample, the sample to be tested is in the shape of a plate, and the sample to be tested is located between the wave zone plate and the measuring chamber.

[0028] In the present technical solution, a plate-shaped reference sample is used to replace the reference sample contained in the measurement chamber, which is beneficial to simplifying the structure of the measurement chamber, simplifying the operation process of the refractive index measurement, and to a certain extent, also beneficial to improving the accuracy of the refractive index measurement results.

[0029] In combination with the first aspect, in some implementations of the first aspect, the measuring light is coherent light, and a wavelength of the measuring light is within a threshold range.

[0030] In a possible implementation, the measuring light is monochromatic coherent light.

[0031] In the present technical solution, by controlling the wavelength and propagation angle of the measuring light, it is beneficial to improve the clarity of the diffraction pattern formed after the measuring light is diffracted by the wave zone plate, and it is beneficial to improve the accuracy of the refractive index measurement result.

[0032] In combination with the first aspect, in some implementations of the first aspect, the device further includes a polarizer, which is disposed close to the light source.

[0033] The main vibration direction of the measuring light passing through the polarizer is consistent with the polarization direction of the polarizer.

[0034] In the present technical solution, a polarizing plate is used to modulate the polarization direction of the measuring light so that the polarization direction of the measuring light is as consistent as possible. In this way, the diffraction pattern formed after the measuring light is incident on the wave zone plate and diffracted is clearer, and the refractive index measured by the measuring device is more accurate.

[0035] In combination with the first aspect, in some implementations of the first aspect, the device further includes a driving control unit, which is used to drive the mobile platform.

[0036] In a possible implementation, the driving control unit may drive the mobile platform by means of magnetic force, electric force, etc. For example, the driving control unit may be a stepping motor. The higher the control accuracy of the driving control unit, the easier it is to control the moving distance of the mobile platform, and accordingly, the higher the accuracy of the refractive index measurement result of the measuring device.

[0037] The relevant explanations and beneficial effects of the following technical solutions can refer to the relevant descriptions in the first aspect, and for the sake of brevity, they are not repeated below.

[0038] In a second aspect, a measuring device is provided, which includes a processing device and a refractive index measuring device in the first aspect and any possible implementation thereof, wherein the processing device is used to determine the refractive index of a sample to be measured based on the measuring device.

[0039] In one possible implementation, the processing device includes a distance measuring unit and a monitoring and analysis unit, wherein the distance measuring unit is used to determine the movement distance of the imaging sensor along the optical axis, and the monitoring and analysis unit is used to determine the deflection distance of the light in the pattern based on the diffraction pattern acquired by the measuring device.

[0040] In a third aspect, a method for measuring a refractive index is provided, the method comprising: obtaining a first diffraction pattern corresponding to a reference sample, the first diffraction pattern comprising a first group of linear fringes, the first group of linear fringes comprising first fringes; obtaining a second diffraction pattern corresponding to a sample to be measured, the second diffraction pattern comprising a second group of linear fringes, the second group of linear fringes comprising second fringes; determining the refractive index of the sample to be measured according to the first diffraction pattern, the second diffraction pattern and the refractive index of the reference sample;

[0041] The first stripe corresponds to the second stripe, and the measurement accuracy of the refractive index of the reference sample is positively correlated with the measurement accuracy of the distance between the first stripe and the second stripe.

[0042] Since linear fringes are more likely to obtain more accurate results in determining positions and measuring distances, the present technical solution determines the refractive index of the sample to be measured by using the linear fringes in the diffraction pattern corresponding to the reference sample and the linear fringes in the diffraction pattern corresponding to the sample to be measured, which is conducive to improving the accuracy of the refractive index measurement results. On the other hand, using the present technical solution, the accuracy of the refractive index measurement results is positively correlated with the measurement accuracy of the displacement change value between the linear fringes. In order to further improve the accuracy of the refractive index measurement results and reduce errors, it can be achieved by improving the measurement accuracy of the displacement change value between the linear fringes, for example, a higher-precision distance measurement device can be used.

[0043] In combination with the third aspect, in certain implementations of the third aspect, a first diffraction pattern is obtained after the diffracted light passes through a reference sample, where the diffracted light is formed by the measuring light diffracted by a zone plate; and a second diffraction pattern is obtained after the diffracted light passes through the sample to be measured and the reference sample.

[0044] In combination with the third aspect, in certain implementations of the third aspect, the first diffraction pattern is acquired at a first position in the optical axis direction of the zone plate; and the second diffraction pattern is acquired at a second position in the optical axis direction of the zone plate.

[0045] In a possible implementation manner, the first position and the second position are different.

[0046] In combination with the third aspect, in certain implementations of the third aspect, the refractive index of the sample to be measured is determined based on the first distance, the second distance and the refractive index of the reference sample; the first distance is the distance between the positions of the imaging sensor when acquiring the first diffraction pattern and the second diffraction pattern, and the second distance is the distance between the projections of the first stripe and the second stripe on the imaging sensor.

[0047] In combination with the third aspect, in some implementations of the third aspect, the imaging sensor includes a charge coupled device (CCD).

[0048] In combination with the third aspect, in certain implementations of the third aspect, the second distance is determined based on the distance between a first pixel and a second pixel on the imaging sensor, the first pixel being used to indicate the position of the first stripe, and the second pixel being used to indicate the position of the second stripe.

[0049] In conjunction with the third aspect, in certain implementations of the third aspect, the refractive index of the sample to be tested is determined according to the following formula:

[0050]

[0051]

[0052] Wherein, Δx is the second distance, α is the incident angle of the measuring light on the measuring chamber, d is the wall thickness of the measuring chamber, n is the ratio of the refractive index of the sample to be tested to the refractive index of the reference sample, Δz is the first distance, and the measuring chamber is used to accommodate the reference sample and / or the sample to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic diagram of the measurement principle of a refractive index provided in an embodiment of the present application.

[0054] Figure 2 It is a schematic diagram of a refractive index measuring device provided in an embodiment of the present application.

[0055] Figure 3 It is a schematic diagram of the structure of a zone plate provided in an embodiment of the present application.

[0056] Figure 4 It is a schematic diagram of the effect of a zone plate provided in an embodiment of the present application on incident light.

[0057] Figure 5 It is a structural schematic diagram of a measurement cabin provided in an embodiment of the present application.

[0058] Figure 6 It is a schematic diagram of a refractive index measurement method provided in an embodiment of the present application.

[0059] Figure 7 It is a schematic diagram of another refractive index measuring device provided in an embodiment of the present application.

[0060] Figure 8 This is a schematic diagram of another refractive index measuring device provided in an embodiment of the present application.

[0061] Fig. 9 This is a schematic diagram of another refractive index measuring device provided in an embodiment of the present application.

[0062] Fig.10 It is a simulation schematic diagram of a refractive index measurement device provided in an embodiment of the present application.

[0063] Fig.11 yes Fig.10 Simulation results of the refractive index measurement device shown.

[0064] Fig.12 It is a diffraction pattern obtained by using the refractive index measuring device provided in the embodiment of the present application.

[0065] Fig.13 This is another diffraction pattern obtained using the refractive index measuring device provided in an embodiment of the present application.

[0066] Fig.14 It is a schematic diagram of the distribution of multiple wavebands on the waveband plate provided in an embodiment of the present application.

[0067] Fig.15 This is another diffraction pattern obtained by using the refractive index measurement device provided in an embodiment of the present application and a schematic diagram of the light intensity distribution in the pattern.

[0068] Fig.16 This is another diffraction pattern obtained by using the refractive index measurement device provided in an embodiment of the present application and a schematic diagram of the light intensity distribution in the pattern.

[0069] Fig.17 It is a schematic diagram of another diffraction pattern and the frequency distribution of light in the pattern obtained by using the refractive index measuring device provided in an embodiment of the present application.

[0070] Fig.18 It is a schematic diagram of another diffraction pattern and the frequency distribution of light in the pattern obtained by using the refractive index measuring device provided in an embodiment of the present application.

[0071] Fig.19 It is a schematic diagram of the principle of a site displacement calculation method provided in an embodiment of the present application.

[0072] Fig. 20 It is a schematic diagram of the relationship between the stripe displacement and the displacement of the mobile platform provided in the embodiment of the present application.

[0073] Fig.21 It is a schematic diagram of the relationship between the standard refractive index and the measured refractive index of the sample to be tested provided in the embodiment of the present application. DETAILED DESCRIPTION

[0074] Embodiments of the present application are described in detail below, and examples of the embodiments of the present application are shown in the accompanying drawings. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0075] Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by persons having ordinary skills in the technical field to which this application belongs. In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application.

[0076] Before introducing the embodiments of the present application, some professional terms that may be used in the following embodiments are first explained.

[0077] Zone plate, usually, refers to an optical element composed of alternating transparent and opaque rings, which can be used to block odd or even bands in the Fresnel half-wave band. Linear Fresnel zone plate (LFZP), also known as linear zone plate, is a deformation of Fresnel zone plate, which cuts the rings into linear stripes.

[0078] The zone plate is a special aperture. The concentric rings on it correspond to the Fresnel half-wave zone, which allows all odd (or even) wave bands to pass through while blocking even (or odd) wave bands. The complex amplitudes generated by each passing light wave band will be superimposed in phase at a certain observation point on the axis, thereby greatly increasing the complex amplitude and light intensity at that point. Because its focusing effect is similar to that of a lens and satisfies the relationship between object distance, image distance and focal length, it is also called Fresnel lens.

[0079] Coherent light is a light wave that can produce stable and clear interference patterns. Monochromatic light field is coherent light in the strict sense.

[0080] A charge coupled device (CCD) is a type of sensor used in digital cameras. It is a chip with extremely tiny photosensitive units and registers on its surface.

[0081] Complementary metal oxide semiconductor (CMOS) is an image sensor used in digital cameras.

[0082] Figure 1 The schematic diagram of the principle of measuring the refractive index by the deflection method is provided as an example. The incident light is emitted from the light source 110 and enters the chamber 120 containing the sample to be tested and the reference sample at an incident angle α, and after being refracted by the sample to be tested and the reference sample, it is emitted from the other side away from the light source 110 at an exit angle α. The light is then emitted and finally captured by the imaging sensor 130 .

[0083] The chamber 120 may contain a reference sample and a sample to be tested, wherein the refractive index of the reference sample is n, and the refractive index of the sample to be tested is n+Δn. Figure 1 As shown, the chamber 120 may be in the shape of a quadrangular prism, and the internal space of the chamber 120 may be divided into two sub-chambers, such as a first sub-chamber 120a and a second sub-chamber 120b. The two sub-chambers may both be in the shape of a triangular prism. The two sub-chambers may be used to accommodate a reference sample and a sample to be tested, respectively.

[0084] The light source 110 , the chamber 120 , and the imaging sensor 130 may be arranged alternately in sequence in the first direction, wherein a distance between the imaging sensor 130 and the light emitting surface of the chamber 120 in the first direction may be Z.

[0085] At one stage of the refractive index measurement process, the same reference sample is contained in both sub-chambers of the chamber 120. In this case, the zeroth incident point of the incident light after being refracted by the sample in the chamber 120 and incident on the imaging sensor 130 is S 0 .

[0086] In another stage of the refractive index measurement process, the two sub-chambers in the chamber 120 contain the reference sample and the sample to be measured respectively. In this case, the first incident point of the incident light on the imaging sensor 130 after being refracted by the sample in the chamber 120 is S 1 .

[0087] The zero-incident point S 0 and the first incident point S 1 The spacing in the second direction is Δx, and the second direction is perpendicular to the first direction.

[0088] The difference between the refractive index of the sample to be tested (n+△n) and the refractive index of the reference sample (n) is △n and the incident angle α of the incident light and the exit angle The following relationship is roughly satisfied:

[0089]

[0090] The angle of incidence of incident light 101 It can be approximately determined by the distance △x between the two incident points in the second direction and the distance Z between the imaging sensor 130 and the exit surface in the first direction. Then, the difference between the refractive index (n+△n) of the sample to be tested and the refractive index (n) of the reference sample is △n, which can be expressed as:

[0091]

[0092] According to the above formula, the measurement range of the refractive index of the sample to be measured is constrained by three variables: △x, Z and α. For a certain refractive index measuring device, the size of the imaging sensor 130 and the distance between the imaging sensor 130 and the exit surface are generally determined. The value of the spacing △x of different incident points on the imaging sensor 130 in the second direction is less than the maximum size of the imaging sensor 130 in the second direction, and is therefore also limited.

[0093] On the other hand, the incident point onto the imaging sensor 130 often does not appear in the form of a point, but is more likely to be a light spot or an aperture, etc. Therefore, the measurement error of the spacing △x between different incident points in the second direction may be large. Accordingly, the measurement accuracy of the refractive index of the sample to be measured obtained by this method will also be limited.

[0094] In order to improve the measurement accuracy and measurement range of a refractive index measuring device, the present application provides a refractive index measuring device, which can be applied to liquid chromatography, and is particularly suitable for refractive index measurement in high performance liquid chromatography (HPLC).

[0095] like Figure 2 As shown, the refractive index measuring device 200 provided in the embodiment of the present application may include a light source 210 , a zone plate 220 , a measuring cabin 230 , an imaging sensor 240 and a moving platform 250 .

[0096] The light source 210, the zone plate 220, the measurement cabin 230, the imaging sensor 240 and the linear motion platform 250 can be arranged along the axial direction ( Figure 2 OO' direction) are arranged in sequence.

[0097] The light source 210 is used to provide measurement light. In some examples, the light source 210 can emit a coherent light beam, that is, the measurement light incident on the zone plate 220 is a coherent light beam.

[0098] In some examples, the light source 210 may be a helium-neon (He-Ne) laser light source, and accordingly, the light emitted by the light source 210 is monochromatic light or single-frequency light. The wavelength range of the monochromatic light or single-frequency light is relatively narrow, for example, the difference between the longest wavelength and the shortest wavelength of the monochromatic light is less than 10 -12 m.

[0099] The measurement light may be diffracted when passing through the zone plate 220 to form multiple diffracted light beams, which may be incident on the measurement chamber 230. During the measurement process, the diffracted light may pass through the reference sample and / or the sample to be measured placed in the measurement chamber 230, and converge on the imaging sensor 240. Here, the reference sample may also be referred to as a standard sample, which refers to a sample with a known refractive index. The following examples are described with reference samples. The sample to be measured refers to a sample whose refractive index is to be measured.

[0100] The imaging sensor 240 can be mounted on the mobile platform 250 and move closer to or farther from the measuring chamber 230 along a certain track. Since different samples to be tested have different refractive indices, the degree of deflection of the measuring light after passing through the samples to be tested is different, and the position incident on the imaging sensor 240 may be different. For example, for the measuring light with a large degree of deflection, the position of its incidence on the imaging sensor 240 may be located at the edge area of ​​the imaging sensor, or even cannot be captured by the imaging sensor 240. For the measuring light with a small degree of deflection, the position of its incidence on the imaging sensor 240 may be located at the center area of ​​the imaging sensor. The imaging sensor 240 mounted on the mobile platform 250 can move according to a preset track, which is conducive to capturing the measuring light after being refracted by samples with different refractive indices.

[0101] On the one hand, the provision of the movable imaging sensor 240 can improve the measurement range of the refractive index measuring device 200 provided in the embodiment of the present application to a certain extent. On the other hand, the distance that the imaging sensor 240 moves on the mobile platform 250 can be quantitatively measured, and the higher the measurement accuracy of the moving distance of the imaging sensor 240, the higher the measurement accuracy of the refractive index measuring device 200, which is conducive to improving the measurement accuracy of the refractive index measuring device 200 provided in the embodiment of the present application.

[0102] Figure 3 A schematic structural diagram of a zone plate 220 provided in an embodiment of the present application is exemplarily shown, wherein: Figure 3 (a) is a front view of the zone plate 220. Figure 3 (b) is a left view of the zone plate 220. The zone plate 220 may also be referred to as a linear Fresnel zone plate 220, a cylinder Fresnel lens 220, or a Fresnel lens 220. The zone plate 220 may be composed of a plurality of Fresnel zones (or zones) parallel to each other, each zone being in a narrow strip shape (narrow band shape), and each zone may also be referred to as an aperture (aperture or slit). Figure 3 The medium wave band 221 is an example. Figure 3 Each wave band can be regarded as a long triangular prism.

[0103] In some examples, the zone plate 220 may include 200, 300, 400, 500 or more bands. In some scenarios, the total number of bands contained in the zone plate 220 may also be represented by the number of bands contained in the unit width of the zone plate 220, for example, 20 / cm, 30 / cm, 50 / cm, 70 / cm, 80 / cm or 100 / cm, etc.

[0104] The zone plate 220 may be made of a transparent material, such as polymethyl methacrylate (PMMA). The zone plate 220 may have a certain refractive index, such as 1.49, 1.52, or 1.60.

[0105] The thickness of the zone plate 220 is H, the length is L, and the width is W. The lengths of the multiple zones 221 included in the zone plate 220 may be the same as the length of the zone plate 220, which is L. The widths of different zones may be different, and the multiple zones are arranged in sequence along the width direction of the zone plate 220. In some examples, the width of the zone located in the middle area of ​​the zone plate 220 is larger, and the width of the zone located in the edge area is smaller. Exemplarily, among the multiple zones included in the zone plate 220, the width of the zone gradually decreases from the middle area to the edge area of ​​the zone plate 220.

[0106] One of the two opposite sides of the zone plate 220 in the thickness direction can be regarded as a plane (eg Figure 3 The right side of (a) in Figure 1), and the other side can be considered as a convex surface (such as Figure 3 In some examples, light is incident from the convex side of the zone plate 220 and is emitted from the flat side of the zone plate 220 after being diffracted by a plurality of zones on the zone plate 220 .

[0107] Figure 4 Schematic diagram of the optical path of parallel light after incident on the surface of the zone plate 220. For ease of description, it is defined here that the width direction of the zone plate 220 is the x-axis direction, the optical axis direction of the zone plate 220 or the thickness direction of the zone plate 220 is the z-axis direction, and the length direction of the zone plate 220 is the y-axis direction.

[0108] The parallel light beam is incident from the convex side of the zone plate 220, and after being diffracted by multiple zones in the zone plate 220, it is emitted from the plane side of the zone plate 220 and is reflected at the main focus Z of the zone plate 220. 0 The light rays incident from different wavelength bands are emitted from the wavelength zone plate 220 and propagate to the focal point Z. 0 Assume that the distance between the i-th (i is an integer greater than or equal to 1) wave zone and the optical axis of the wave zone plate 220 is x. i After the incident light enters the i-th wave zone, it is emitted from the wave zone plate 220 and propagates to the focal point Z 0 The optical path is Si, and Si satisfies the following relationship:

[0109] S i =Z 0 +iλ (3)

[0110]

[0111] The two equations can be combined to determine the vertical distance between each band in the zone plate 200 and the optical axis and the wavelength λ and the focal length Z of the zone plate 200: 0 The following relationship is roughly satisfied:

[0112]

[0113] Among them, Z 0 is the focal length of the zone plate 200, λ is the wavelength of the light, x i is the distance of the ith waveband to the optical axis.

[0114] According to the above formula, the optical path difference generated at the focus by the diffracted light of two adjacent bands on the same side of the optical axis of the zone plate 220 is λ. In other words, when the measuring light is coherent light, the diffracted light of two adjacent bands will generate a phase difference of π at the focus of the zone 220. In other words, after the measuring light is diffracted by the linear Fresnel zone plate 220 (zone plate 220), a diffraction pattern (thin line) of alternating light and dark can be formed on the focal plane.

[0115] Unlike a lens with a converging effect, the measuring light can form multiple converging fine lines instead of converging into a light spot after being diffracted by the zone plate 220 and incident on the imaging sensor 240. The distance between the light and dark fine lines is easier to determine, so the use of the zone plate 220 is conducive to improving the accuracy of the refractive index measurement results.

[0116] It should be noted that the measurement light emitted by the zone plate can not only converge on the focal plane where the main focus is located, but also Figure 4 The secondary focus shown (such as It is understandable that the convergence effect of the diffracted light on different focal planes is different, that is, the light intensity of the diffraction patterns formed on different focal planes is different.

[0117] Different zone plates 220 have different diffraction effects for different wavelengths. In some examples, the zone plate 220 can diffract light waves with a wavelength range of 400 nm to 1100 nm.

[0118] Figure 5 The structure of a measuring chamber 230 provided in an embodiment of the present application is shown. The measuring chamber 230 can be used to accommodate a sample to be tested and / or a reference sample. The measuring chamber 230 can also be referred to as a sample chamber 230. The measuring chamber 230 can be made of a material with a certain degree of transparency, such as transparent glass. In order to improve the corrosion resistance of the measuring chamber 230 to the sample, the measuring chamber 230 can also be made of a transparent material with a certain degree of corrosion resistance.

[0119] In some examples, the measurement chamber 230 may include a first storage chamber 231 and a second storage chamber 232, and the first storage chamber 231 and the second storage chamber 232 may both be triangular prism-shaped. The volume of the first storage chamber 231 and the volume of the second storage chamber 232 may be equal, or in other words, the first storage chamber 231 and the second storage chamber 232 may contain samples of equal volume.

[0120] In some examples, the measurement chamber 230 is a quadrangular prism, the first accommodating chamber 231 and the second accommodating chamber 232 are both triangular prisms, and the volumes of the first accommodating chamber 231 and the second accommodating chamber 232 are both half of the volume of the measurement chamber 230 .

[0121] The first storage chamber 231 and the second storage chamber 232 may each be provided with one or more sample entrances and exits. Figure 5 As shown, the first containing chamber 231 may be provided with a first sample inlet 231a and a first sample outlet 232b, and the second containing chamber 232 may be provided with a second sample inlet 232a and a second sample outlet 232b.

[0122] In some examples, the reference sample and the sample to be tested may both be liquid, or the reference sample may be liquid and the sample to be tested may be solid, or the reference sample may be solid and the sample to be tested may be liquid, or both the reference sample and the sample to be tested may be solid.

[0123] The outer shell of the measurement cabin 230 may have a certain degree of transparency, so that the measurement light can be incident from the external space of the measurement cabin 230 into the measurement cabin 230 and then be emitted after passing through the measurement cabin 230 .

[0124] In some examples, the measurement chamber 230 may be used only to accommodate the sample to be measured, and the reference sample may be placed outside the measurement chamber 230. Figure 7 Related description.

[0125] The refractive index measuring device 200 may further include a drive control unit 260, which may be used to drive the mobile platform 250 to move linearly along a preset track. For example, under the driving action of the drive control unit 260, the mobile platform 250 may move linearly along the optical axis of the zone plate 220.

[0126] The refractive index measuring device 200 may further include a distance measuring unit 270, which may be used to record and determine different positions of the mobile platform 250 at different times during the refractive index measurement process, thereby determining the moving distance of the mobile platform 250, or determining the distance between the mobile platform 250 and the initial position.

[0127] The moving distance of the mobile platform 250 can have a high precision, which is conducive to improving the accuracy of the measurement result of the refractive index measuring device. The driving control unit 260 can drive the mobile platform 250 in a variety of different ways, such as magnetic drive, electric drive, etc. In some examples, the mobile platform 250 can be a high-precision (for example, the position resolution can be much less than 1 nanometer) linear mobile platform, and the driving control unit 260 can be a stepping motor, etc.

[0128] In some examples, when the imaging sensor 240 located on the mobile platform cannot receive the measuring light, the driving control unit 260 can drive the mobile platform 250 to move along the direction of the optical axis toward or away from the measuring cabin 230 until the imaging sensor 240 can capture the measuring light.

[0129] In some examples, when the linear light spot displayed on the imaging sensor 240 is blurry, the driving control unit 260 can drive the mobile platform 250 to move along the direction of the optical axis toward or away from the measuring cabin 230 until the pattern displayed on the imaging sensor 240 is clear.

[0130] The imaging sensor 240 can be used to capture the measurement light passing through the measurement chamber 230, or in other words, the imaging sensor 240 can be used to present the straight line stripes formed by the measurement light after passing through the sample to be measured and / or the reference sample. The imaging sensor 240 can be installed on the moving platform 250, so that when the driving control unit 260 drives the moving platform 250, the imaging sensor 240 can move along the corresponding track. The distance measuring unit 270 can determine the moving distance of the imaging sensor 240 by determining the moving distance of the moving platform 250.

[0131] The imaging sensor 240 may be an optical sensor. In some examples, the imaging sensor 240 may be a camera or an imaging device including a CCD, or the imaging sensor 240 may be a camera or an imaging device including a CMOS.

[0132] Exemplarily, the imaging sensor 240 may be a camera including a CCD. Before the measurement process begins, the camera may be initialized, calibrated, and the field of view (FOV) of the camera may be fixed. In some examples, the sampling rate and frame (image) size of the camera may also be set, for example, the sampling frequency of the camera may be set to 38fps and the frame size may be set to 2448×2048 pixels.

[0133] In some examples, the imaging sensor 240 is mounted on the linear motion platform 250 to measure the longitudinal deflection value of the measuring light with an accuracy of 2×10 -8 m.

[0134] Since different optical sensors have a certain optical resolution, different samples to be tested have different refractive indices, and the deflection of the measuring light after passing through the samples to be tested is also different. This means that when the position of the imaging sensor 240 is fixed, some of the straight stripes generated by the measuring light corresponding to different samples to be tested may exceed the resolution of the imaging sensor 240 and cannot be captured by the imaging sensor 240.

[0135] A mobile platform 250 is set up and an imaging sensor 240 is installed on the mobile platform 250, so that the refractive index measuring device provided in the present application can capture straight lines corresponding to different samples to be measured by the mobile imaging sensor 240, thereby expanding the refractive index measurement range of the measuring device of the present application.

[0136] The refractive index measuring device 200 may further include a monitoring and analyzing unit 280, which may be used to obtain the diffraction pattern captured by the imaging sensor 240, and determine the difference in light deflection generated by the measuring light at different stages of the measuring process according to the diffraction patterns of different images. In some examples, the monitoring and analyzing unit 280 may also determine the refractive index of the sample to be measured based on the acquired data.

[0137] The following combination Figure 6 , through the actual refractive index measurement process, the refractive index measuring device 200 provided in the embodiment of the present application is further introduced.

[0138] S601, placing a reference sample in the first sub-containing chamber 231 and the second sub-containing chamber 232 to obtain a first diffraction pattern.

[0139] Taking the refractive index of the reference sample as a reference, the reference sample can be placed in both sub-chambers of the measurement chamber 230. When the measurement light is diffracted by the zone plate 220 and incident on the side of the measurement chamber 230 close to the zone plate 220, the measurement light is as follows: Figure 6 The incident angle α shown is incident into the measurement chamber 230. After passing through the reference samples loaded in the first sub-chamber 231 and the second sub-chamber 232, the measurement light is incident at an exit angle Shoot.

[0140] In some examples, the reference sample may satisfy the following condition: after passing through the measurement chamber 230, the diffracted light of the measurement light is just focused on the main focal plane of the zone plate 220. In other words, when the imaging sensor 240 is located at the focal position (z=Z 0 ), if the two sub-chambers in the measuring chamber 230 are both loaded with reference samples, the linear fringes generated by the diffraction of the measuring light can just be captured by the imaging sensor.

[0141] In order to facilitate the measurement of the difference between the refractive index of the sample to be tested and the refractive index of the reference sample, the imaging sensor 240 can save the captured diffraction pattern, which can be called a first diffraction pattern. The first diffraction pattern can be used to determine the positions of different linear stripes on the pattern.

[0142] S602, placing a sample to be tested in the first sub-containing chamber 231, placing a reference sample in the second sub-containing chamber 232, and acquiring a second diffraction pattern.

[0143] After completing the measurement operation of S601 and before proceeding to S602 , the sample in the measurement chamber 230 may be removed by multiple cleaning and drying (eg, drying with nitrogen) to reduce the influence of sample residue on the accuracy of the measurement result.

[0144] Replace the reference sample in the first accommodating chamber 231 or the second accommodating chamber 232 in the measuring chamber 230 as the sample to be measured, and repeat the operation in S601. The measuring light is emitted from the side of the measuring chamber 230 away from the zone plate 220, and the emission angle of the light is By driving the imaging sensor 240 on the moving platform 250 to move, the linear fringes generated by the diffraction of the measurement light can be converged on the imaging sensor 240 .

[0145] Similar to S601 , the photosensitive element 240 may save the captured diffraction pattern, which may be referred to as a second diffraction pattern. The diffraction pattern may be used to determine the positions of different linear stripes on the pattern.

[0146] S603 , acquiring the axial displacement of the imaging sensor 240 and the displacement of the same point (eg, the same point on the same diffraction stripe) in the first diffraction pattern and the second diffraction pattern.

[0147] The distance that the imaging sensor 240 moves along the positive direction of the optical axis can be determined as Δz by the distance measuring unit 270. The displacement of the same point can be determined according to the first diffraction pattern and the second diffraction pattern.

[0148] According to the refraction quantification (Snell's law), when the light propagates from the first propagation medium to the second propagation medium (refractive index n), the lateral deflection displacement Δx of the light can be calculated by the following formula:

[0149]

[0150] Wherein, α is the incident angle, d is the wall thickness of the measuring chamber 230, n is the ratio of the refractive index of the sample to be tested to the refractive index of the reference sample, T is the temperature, the unit is K, and n also depends on the temperature T. According to the embodiment provided by the present application, it can be assumed that the parameter NA=n*sinn=0.45 when the light is refracted between the air (NA) and the objective lens.

[0151] The longitudinal deflection Δz of the light can be calculated by the following formula:

[0152]

[0153] Wherein, d is the wall thickness of the measuring chamber 230, and n is the ratio of the refractive index of the sample to be tested to the refractive index of the reference sample.

[0154] In some examples, in order to reduce the influence of the measurement chamber 230 itself on the deflection of the measurement light, the deflection value ΔZ of the measurement light caused by the measurement chamber 230 can be measured when the measurement chamber 230 is not loaded with a reference sample or a sample to be measured (i.e., empty). 1 When a reference sample or a sample to be measured is placed in the measurement chamber 230, the longitudinal deflection value of the measured light is ΔZ 2 , then, the longitudinal deflection value Δz' of the measurement light caused by the reference sample or the sample to be measured can be calculated by the following formula:

[0155] Δz'=ΔZ 1 -ΔZ 2 (8)

[0156] In some examples, when both the reference sample and the sample to be tested are block solids, the measuring chamber 230 may not be provided in the refractive index measuring device 200. In this case, the measuring process of the refractive index of the sample to be tested is similar to the above description, and the settlement principle of the refractive index of the sample to be tested is also similar to the above description, which will not be elaborated here for the sake of brevity.

[0157] S604, determining the refractive index difference between the sample to be tested and the reference sample and the refractive index of the sample to be tested.

[0158] The refractive index difference between the sample to be tested and the reference sample can be determined based on the Δx and Δz measured above, and the refractive index of the sample to be tested can be determined based on the refractive index of the reference sample. The detailed calculation process is further described below and will not be described in detail here.

[0159] like Figure 7 Another refractive index measuring device 700 provided in an embodiment of the present application is shown. The refractive index measuring device 700 may include a light source 210 , a zone plate 220 , a reference sample 710 , a measuring chamber 720 , an imaging sensor 240 and a moving platform 250 .

[0160] The properties and structures of the light source 210, the zone plate 220, the mobile platform 250 and the imaging sensor 240 can be found in the previous text. Figure 6 For the sake of brevity, the relevant contents in are not repeated here.

[0161] In some examples, in the refractive index measuring device 700, the measuring chamber 720 may be used only to accommodate the sample to be measured, or in other words, the measuring chamber 720 is provided with only one chamber, which is used to accommodate the sample to be measured. The reference sample 710 is not placed in the measuring chamber 720, but may be replaced by one or more (e.g., three) pieces of flat glass with known refractive index. Specifically, the one or more pieces of flat glass may be vertically installed between the zone plate 220 and the measuring chamber 720.

[0162] In other examples, in the refractive index measuring device 700, the measuring chamber 720 may be used only to accommodate the reference sample, or in other words, the measuring chamber 720 is provided with only one chamber, and the chamber is used to accommodate the reference sample. The sample to be measured may not be placed in the measuring chamber 720. For example, when the sample to be measured is a block solid, the reference sample may be placed between the zone plate 220 and the measuring chamber 720.

[0163] In the process of measuring the refractive index using the refractive index measuring device 700, a measurement process can be performed when the measuring chamber 720 is empty and loaded with a sample, respectively, to obtain the diffraction linear fringes of the measuring light under the refraction of the reference sample and the diffraction linear fringes under the common refraction of the reference sample and the sample to be measured. The refractive index of the sample to be measured is determined based on the linear fringes obtained from the two measurements.

[0164] In some examples, the refractive index measuring device 700 may further include a driving unit, and the functions of the driving unit and the like are described in detail with reference to FIG. Figure 6 The relevant descriptions in the examples shown are similar and are not repeated here for the sake of brevity.

[0165] The present application also provides a measuring device, which may include Figure 7 The refractive index measuring device 700 and the processing device shown can determine the refractive index of the sample to be measured based on the information (such as diffraction pattern, etc.) obtained by the refractive index measuring device 700.

[0166] In some examples, the processing device may include the monitoring and analysis unit and the distance measurement unit shown in the aforementioned embodiments, and the monitoring and analysis unit and the distance measurement unit may refer to the relevant descriptions in the foregoing text.

[0167] Figure 7The provided refractive index measuring device 700 uses a plate-shaped reference sample to replace the reference sample contained in the measuring chamber 720, which is beneficial to simplifying the structure of the measuring chamber 720, simplifying the operation process of the refractive index measurement, and to a certain extent, also beneficial to improving the accuracy of the refractive index measurement results.

[0168] like Figure 8 The figure shows another refractive index measuring device 800 provided in an embodiment of the present application, which includes a light source 210, an objective lens 810, a polarizing filter 820, a collimating reflector 830, a zone plate 220, a measuring cabin 230, a moving platform 250 and an imaging sensor 240.

[0169] The objective lens 810 is arranged close to the light source 210, and the polarizer or polarizing filter 820 is located on the side of the objective lens 810 away from the light source 210. The collimating reflector 830 is arranged obliquely relative to the optical axis, and the collimating reflector 830 is used to guide the measuring light to the zone plate 220. The zone plate 220, the measuring cabin 230 and the imaging sensor 240 are arranged in sequence along the direction of the optical axis, and the imaging sensor 240 can be installed on the moving platform 250 and is configured to move along the direction of the optical axis.

[0170] In some examples, the refractive index measuring device 800 may further include an interference aperture 840, which is disposed near the zone plate 220 and located on a side of the zone plate 220 away from the measuring chamber 230. The measuring light is emitted from the collimating reflector 830 and then passes through the interference aperture 840 before entering the zone plate 240.

[0171] The properties and structures of the light source 210, the zone plate 220, the measurement cabin 230, the mobile platform 250 and the imaging sensor 240 can be referred to in the previous text. Figure 6 For the sake of brevity, the relevant contents in are not repeated here.

[0172] The polarizer 820 , the collimating mirror 830 , and the interference hole 840 in the refractive index measuring device 800 are described below.

[0173] When the measuring light is incident on the polarizer 820, the part of the measuring light whose vibration direction is inconsistent with the polarization direction of the polarizer 820 cannot pass through the polarizer 820. In other words, the divergent measuring light can be filtered into polarized light whose vibration direction is consistent with the polarization direction of the polarizer 820 after passing through the polarizer 820.

[0174] The collimating reflector 830 can modulate the divergent measuring light into mutually parallel light. In some examples, the collimating reflector can be an adjustable parabolic mirror. The collimating reflector 830 can be tilted relative to the optical axis of the zone plate 220. After the divergent measuring light is incident on the collimating reflector 830, it can be modulated into parallel light without spherical aberration.

[0175] The mutually parallel measurement light rays need to pass through the interference hole 840 before being incident on the wave zone plate 220 . That is to say, the measurement light rays whose propagation paths are within the aperture range of the interference hole 840 can pass through the interference hole 840 , while the measurement light rays whose propagation paths are outside the aperture range of the interference hole 840 cannot pass through the interference hole 840 .

[0176] In some examples, the refractive index measuring device 800 may further include a driving unit, and the functions of the driving unit and the like are described in detail with reference to FIG. Figure 6 The relevant descriptions in the examples shown are similar and are not repeated here for the sake of brevity.

[0177] The present application also provides a measuring device, which may include Figure 8 The refractive index measuring device 800 and the processing device shown can determine the refractive index of the sample to be measured based on the information (such as the diffraction pattern, etc.) obtained by the refractive index measuring device 800.

[0178] In some examples, the processing device may include the monitoring and analysis unit and the distance measurement unit shown in the aforementioned embodiments, and the monitoring and analysis unit and the distance measurement unit may refer to the relevant descriptions in the foregoing text.

[0179] By setting the polarizer 820, the collimating reflector 830 and the interference hole 840, the vibration direction, incident angle and propagation range of the measuring light incident on the wave zone plate 220 can be controlled. To a certain extent, the measuring light can be diffracted to form relatively clear linear stripes after passing through the wave zone plate 220, which is beneficial to improving the measurement accuracy of the distance between the stripes, thereby helping to improve the accuracy of the measurement results of the refractive index measurement device provided in the present application.

[0180] like Fig. 9 FIG. 9 is another refractive index measuring device 900 provided in an embodiment of the present application. Figure 8 The measuring device 800 shown in the figure, the refractive index measuring device 900 provided in the embodiment of the present application may further include a beam splitter and a reflector.

[0181] Specifically, the refractive index measuring device 900 may include a light source 210 , an objective lens 810 , a polarizer 820 , a beamsplitter mirror 910 , a collimating mirror 830 , a zone plate 220 , a measuring cabin 230 , a moving platform 250 , a reflector 920 , and an imaging sensor 240 .

[0182] The objective lens 810 is arranged close to the light source 210, and the polarizer or polarizing filter 820 is located on the side of the objective lens 810 away from the light source 210. The beam splitter 910 is located between the polarizer 820 and the collimating reflector 830. The collimating reflector 830 can be arranged tilted relative to the optical axis of the zone plate 220, and the collimating reflector 830 is used to guide the measuring light to the zone plate 220.

[0183] The zone plate 220 , the measurement cabin 230 , and the reflector 920 may be arranged in sequence along the direction of the optical axis. The reflector 920 may be mounted on the moving platform 250 and configured to be movable along the direction of the optical axis.

[0184] The imaging sensor 240 is disposed on the other side of the beam splitter 910 opposite to the polarizer 820. The measurement light emitted from the collimating reflector 830 and incident on the zone plate 220 can obtain a primary diffraction light after diffraction by the zone plate 220. The primary diffraction light can be incident on the reflector 920 after passing through the measuring cabin 230. The primary diffraction light can pass through the measuring cabin 230 and be incident on the zone plate 220 after being reflected by the reflector 920, and can obtain a secondary diffraction light after being diffracted by the zone plate 220. The secondary diffraction light can be captured by the imaging sensor 240 after being reflected by the collimating reflector 830 and the beam splitter 910.

[0185] The moving platform 250 may be configured to move along the axis direction so that the aforementioned first diffracted light can be converged on the reflector.

[0186] In some examples, the refractive index measuring device 900 may further include an interference hole 840, which is disposed near the zone plate 220 and located on a side of the zone plate 220 away from the measuring chamber 230. The measuring light is emitted from the collimating reflector 830 and then passes through the interference hole 840 before entering the zone plate 220.

[0187] The properties and structures of the light source 210, the zone plate 220, the measurement cabin 230, the mobile platform 250 and the imaging sensor 240 can be referred to in the previous text. Figure 6 For the sake of brevity, the relevant contents in are not repeated here.

[0188] The properties and structures of the polarizer 820, the collimating reflector 830 and the interference hole 840 can be found in the previous text. Figure 8For the sake of brevity, the relevant contents in are not repeated here.

[0189] The beam splitter 910 is disposed between the polarizer 820 and the collimating reflector 830. When the measuring light passes through the polarizer 820 and is incident on the first surface of the beam splitter 910, it can pass through the beam splitter 910 and propagate to the collimating reflector 830. When the secondary diffracted light is reflected by the collimating reflector 830 and is incident on the second surface of the beam splitter 910 (the second surface is the other surface opposite to the first surface), it can be reflected on the second surface, thereby adjusting the propagation direction, which is conducive to being captured by the imaging sensor 240.

[0190] In some examples, the refractive index measuring device 900 may further include a driving unit, and the functions of the driving unit and the like are described in detail with reference to FIG. Figure 6 The relevant descriptions in the examples shown are similar and are not repeated here for the sake of brevity.

[0191] The present application also provides a measuring device, which may include Fig. 9 The refractive index measuring device 700 and the processing device shown can determine the refractive index of the sample to be measured based on the information (such as the diffraction pattern, etc.) obtained by the refractive index measuring device 900.

[0192] In some examples, the processing device may include the monitoring and analysis unit and the distance measurement unit shown in the aforementioned embodiments, and the monitoring and analysis unit and the distance measurement unit may refer to the relevant descriptions in the foregoing text.

[0193] In the refractive index measuring device 900 provided in this embodiment, the measuring light passes through the measuring chamber 230 twice. In other words, the measuring light is deflected twice before being captured by the imaging sensor 240. Both deflections are caused by the refraction of the sample to be measured contained in the measuring chamber 230. Compared with the method of measuring the refractive index of the sample to be measured by only one deflection, the method of measuring by two deflections is conducive to reducing the relative error caused by factors such as measurement error, and is conducive to improving the accuracy of the measurement result of the refractive index measuring device 900. On the other hand, by using a reflector to adjust the propagation path of the measuring light, it is conducive to improving the utilization rate of the internal space of the refractive index measuring device 900 to a certain extent, and reducing the volume of the refractive index measuring device 900.

[0194] Taking the refractive index measuring device 200 as an example, the following can be obtained by simulation using Zemax OpticStudio: Fig.10 and Fig.11 The simulation results are shown in Figure 2. Fig.10 is an optical device corresponding to the refractive index measuring device 200 used in the simulation process, Fig.11 FIG. 2 shows a simulated diffraction pattern captured on the imaging sensor 240. Fig.11 As shown, the simulated diffraction pattern basically presents linear stripes alternating between light and dark.

[0195] Fig.12 and Fig.13 2 shows the diffraction pattern of the measurement light captured by the imaging sensor 240 during the refractive index measurement test. Fig.12 It can be regarded as the diffraction pattern of the reference sample only loaded in the measurement chamber 230. Fig.13 It can be regarded as the diffraction pattern of the reference sample and the sample to be measured being loaded into the measurement chamber 230 at the same time.

[0196] Combination Fig.12 and Fig.13 , Fig.12 The bright linear stripes in the center of the Fig.13 . Similarly, Fig.13 The screen shown does not show Fig.12 The linear stripes in the left area, and Fig.12 The linear stripes on the right side of the picture move to the left side accordingly. Fig.13 The screen shown.

[0197] In some examples, the distribution of the plurality of wave bands on the wave zone plate 220 along the x-axis direction can be roughly expressed by the following formula: Fig.14 A schematic structural diagram of the zone plate 220 under this distribution law is provided as an example.

[0198]

[0199] For the zone plate 220 with the above-mentioned zone distribution law, the function T(x 0 ), which can be obtained by convolving the aperture function of the zone plate 220. The convolution result is expanded according to the Fourier series to obtain the following formula:

[0200]

[0201] The above formula can be regarded as a series expansion of the type III sinc function of the zone plate to measure the light transmittance distribution. If the width of the zone plate 220 is small, the diffraction pattern captured by the imaging sensor 240 will be a series of peak functions, which is consistent with T(x 0 ) corresponds to the convolution result of the narrow flat-topped square pulse function. In some examples, the diffraction pattern can be adjusted to reach the peak as much as possible by customizing the size of the wave band of the wave zone plate 220, controlling the distance from the wave zone plate 220 to the imaging sensor 240, and measuring the wavelength of the light.

[0202] As described in the above experiment, the zone plate 220 is set at the position z=0 on the Z axis, and the zone plate 220 is illuminated by a parallel light beam parallel to the optical axis of the zone plate 220, and the distribution function U(x i ,Z 0 ).

[0203]

[0204] Where λ is the wavelength of the measured light and k is the wave vector of the plane wave. In the above formula, let n = 1, which can be used to explain the convergent light beam focused at the main focal length. The focus of the light is as follows Figure 4 Z 0 shown.

[0205] In addition, the light diffracted by the zone plate 220 will also converge at the secondary focus, that is, ±1, ±2…). That is to say, the zone plate 220 can be used not only to converge parallel incident light at the position of the main focus (main focal plane), but also to converge parallel incident light at the position of the secondary focus. In the above formula, not only n is 1, but also when n is 0, ±3, ±5…±(2m-1), it will contribute to the diffraction pattern of the zone plate 220.

[0206] Fig.15 (a) is the main focal plane (z=Z) where the imaging sensor 240 is placed on the zone plate 220. 0 ) is the diffraction pattern that the imaging sensor 240 can capture when the image sensor 240 is at the position of Fig.15 (b) in FIG. 5 is the relative value of the intensity of each linear stripe in the pattern.

[0207] Fig.16 (a) shows that the imaging sensor 240 is placed at the secondary focal plane (z=3Z 0 ) is the diffraction pattern that the imaging sensor 240 can capture when the image sensor 240 is at the position of Fig.16 (b) in FIG. 5 is the relative value of the intensity of each linear stripe in the pattern.

[0208] In some examples, when the initial phases of the parallel light beams incident on the zone plate 220 are the same, equation (11) can be simplified to obtain the following equation (the last term in equation (11) is the total complex field of the original object wave excluding the constant term and the exponential term, which is the ideal term of the equation):

[0209]

[0210] Among them, A and B are constant coefficients.

[0211] In some examples, the optical system provided in the refractive index measurement device provided in the present application can determine the object scanning diffraction fringe pattern by using a time-dependent Fresnel zone plate (TDFZP) equation.

[0212] by Figure 4 Taking the physical structure of the refractive index measuring device 200 shown as an example, a point light source located on the optical axis can be expanded to form a plane wave. Fig.12 or Fig.13 The pattern shown can be regarded as the diffraction pattern formed at a certain time after the scanning beam passes through the zone plate 220, for example, at t=t 0 = 0. The zone plate 220 in this case can also be called a static zone plate or a static Fresnel zone plate. If the time changes according to equation (11), a linear stripe that continuously moves toward the middle of the pattern can be obtained.

[0213] When studying the quadratic spatial dependence of the zone plate, the spatial rate of change of the zone plate phase (for example, the rate of change along the x-axis) can be calculated by the following formula:

[0214]

[0215] This is a local fringe frequency that increases linearly with the spatial coordinate. In other words, the farther the linear fringe is from the center of the region, the higher the local spatial frequency. Therefore, if Fig.17 and Fig.18 As shown, for a fixed (local) point on the imaging sensor 240, the depth information of the point can be obtained. Specifically, the depth information of the fixed point can be determined by finding the local fringe frequency of light of a given wavelength. 0 The local fringe frequency of the aforementioned fixed point also depends on the center of the region. When the zone plate is set on the optical axis, such as Fig.17 and Fig.18 As shown, the depth information of the local fringes is encoded in the linear zone plate.

[0216] Fig.17 (a) is the main focal plane (z=Z) where the imaging sensor 240 is placed on the zone plate 220. 0 ) is the diffraction pattern that the imaging sensor 240 can capture when the image sensor 240 is at the position of Fig.17 (b) in FIG. 1 is the relative value of the spatial frequency distribution of each linear stripe in the pattern.

[0217] Fig.18 (a) shows that the imaging sensor 240 is placed at the secondary focal plane (z=3Z 0) is the diffraction pattern that the imaging sensor 240 can capture when the image sensor 240 is at the position of Fig.18 (b) in the figure is the relative value of the spatial frequency distribution of each linear stripe in the pattern.

[0218] Fig.17 and Fig.18 The local spatial frequency of the zone plate 220 along the optical axis is shown. The zone plate characteristics are a function of the depth parameter. When we change the value of z, for example, z is changed from Z to 0 Adjust to 3Z 0 , the local stripes gradually become sparse from dense. This conclusion can also be obtained from equation (13).

[0219] Therefore, one or more regions can be formed on the imaging sensor 240, each of which contains lateral position information and depth information of each individual point, which comes from the local fringe frequency of the linear fringe. According to the lateral position information and depth information of the above points, the distance between the object point and the plane where the imaging sensor is located can be determined. The distance between the two is very important for the refractive index measuring device provided by the present application to determine the refractive index of the sample to be measured. Based on the above theory, the measurement of the fringe offset of the platform can be controlled by using MATLAB code.

[0220] The imaging sensor 240 can be used to receive the converged light stripes from the wave zone plate and convert the light stripes into digital signals. The refractive index measurement device provided in the present application can be used to detect the motion stripe pattern of an object and calculate the displacement of the object. Specifically, the moving object can be detected in the order of the image and processed by the optical flow method with the help of MATLB software.

[0221] In some examples, the monitoring and analyzing unit 280 may be used to monitor the change in pixel position in the moving stripes from an initial stage to a final stage, and the monitoring and analyzing unit 280 may also segment the video signal into a plurality of images (frames).

[0222] In some examples, the image size may be 2448 x 2048 pixels.

[0223] Fig.19The first image or initial position 1910, which may also be referred to as a reference position, may be used to represent a reference pixel value for comparison purposes, and the second image or target position 1920, which may also be referred to as an "input", matches the first image 1910, and includes a moving object in the second image 1920. The starting position of the light beam on the imaging sensor 240 may be considered as a zero point, and in order to measure the difference in refractive index between the sample to be tested and the reference sample, the deflection distance of the light beam at the starting position on the imaging sensor may be agreed to be zero. By comparing the first image and the second image and calculating the difference in pixel values, the distance between the pixels, the number of images included in each time period, the speed at which the object moves, and the amount of light deflection due to the difference in refractive index between the sample to be tested and the reference may be calculated, thereby obtaining the refractive index of the sample.

[0224] Fig.19 The integer pixels determined according to the conventional motion estimation method and a pixel array are also shown. The displacement vector between the first image 1910 and the second image 1920 can be obtained by processing with the optical flow method. By determining the distance between corresponding pixels in the first image 1910 and the second image 1920, the refractive index of the sample to be measured can be calculated.

[0225] The movable imaging sensor 240 can capture the target light and reference light stripes in the order of the picture, and these stripes can be used to measure the movement of the object. Specifically, the movement of the object can be measured by measuring the displacement of the light stripes on the surface of the imaging sensor 240. The displacement of the light stripes can change as the imaging sensor 240 moves. The displacement of the light stripes can be calculated using the Euclidean distance formula. Fig.19 Taking the first pixel 1911 and the second pixel 1921 in two consecutive frames of images as an example, the distance between the two pixels can be calculated by the following formula. In some examples, the first pixel 1911 and the second pixel 1921 can represent the positions of corresponding pixels on the moving object in the initial stage and the final stage, respectively.

[0226]

[0227] Among them, x i and i is the position of the pixel, the value range of i is: 0≤i≤n-1, the value range of j is: i+1≤j≤n, and n is the total number of captured images.

[0228] Fig. 20 shows the comparison between the measured displacement of the fringe and the certified displacement of the mobile platform, Fig. 20It can be seen that there is a good linear relationship between the displacement of the stripes measured by the refractive index measuring device provided in the present application and the displacement of the moving platform, and the measurement error is small.

[0229] The mobile platform 250 can be directly driven by the control driving unit 270 through magnetic force or other means, so the longitudinal displacement of the image can be easily determined by using the movable platform 150. In some examples, the refractive index measurement device provided in the present application can use a high-resolution physical instrument optical nanoencoder (PhysikIntrumente Optical nanometrology Encoder, PIOne) with a small linear error and a mobile platform 250 with high precision, and the resolution of the displacement measurement result of the linear stripes can reach 2×10 -8 m.

[0230] The displacement of the linear stripes is proportional to the position change of the light, and is therefore also proportional to the difference in refractive index. The above method for measuring the displacement of the linear stripes is conducive to improving the accuracy of the refractive index measurement result of the refractive index measurement device provided by the present application, and is conducive to expanding the refractive index measurement range of the refractive index measurement device provided by the present application.

[0231] The refractive index measuring device provided by the present application is suitable for refractive index testing of liquids and flat samples, and is particularly suitable for liquid chromatography and flat samples with a wide range of thickness and size. The device can be applied to measuring liquids with different refractive indices, and the preparation method of the sample to be tested is simple. The composition structure of the device is simple, and the measurement result of the device is high in precision and has a wide measurement range. In some examples, the refractive index measuring device provided in the embodiments of the present application can be applied to the refractive index measurement of HPLC.

[0232] Fig.21 The relationship between the measured refractive index value and the certified value obtained by testing the sample using the refractive index measuring device provided by the present application is exemplarily provided, and the sample to be tested includes but is not limited to distilled water, ethanol, fused quartz plate, BK7 borosilicate glass and sapphire window. Fig.21 It can be seen that there is a good linear relationship between the measured value and the certified value of the refractive index of the sample to be tested, and the measurement error is small.

[0233] The uncertainty of the refractive index of the sample to be measured measured by the refractive index measuring device provided by the present application is determined by the minimum change in the longitudinal displacement on the diffraction pattern, which corresponds to the change in the pixel position that can be detected by the imaging sensor. By adopting a high-precision and high-resolution mobile platform, the refractive index measured by the refractive index measuring device provided by the present application can achieve a structural accuracy of 10 -4The refractive index unit (RIU) can be measured, and the accuracy can be further improved by using a more sensitive sensor. At the same time, since the mobile platform has a long length, for samples with different refractive indices, the imaging sensor located on the mobile platform has enough displacement space to measure the longitudinal displacement on the diffraction pattern (for example, 20 mm to 150 mm), so the refractive index measurement device provided by the present application can measure the refractive index of samples in a wider range.

[0234] References to "one embodiment" or "some embodiments" etc. described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear at different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0235] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A refractive index measuring device, characterized in that: include: A light source (210), a zone plate (220) and an imaging sensor (240), The light source (210) is used to emit measurement light; The zone plate (220) comprises a plurality of mutually parallel prisms; The imaging sensor (240) is used to receive the measurement light that passes through the zone plate (220), the reference sample and / or the sample to be measured.

2. The measuring device according to claim 1, characterized in that The diffraction pattern formed by the measuring light on the imaging sensor includes a plurality of linear light spots.

3. The measuring device according to claim 1 or 2, characterized in that: The measuring device further comprises a measuring chamber (230), wherein the measuring chamber (230) is used to accommodate a reference sample and / or a sample to be measured, and the measuring chamber (230) is located on a side of the zone plate (220) away from the light source (210).

4. The measuring device according to claim 3, characterized in that The device further comprises a moving platform (250), wherein the moving platform (250) is located on a side of the measuring cabin (230) away from the wave zone plate (220), and the imaging sensor (240) is located on the moving platform (250), and the imaging sensor (240) can move on the moving platform (250) along the optical axis direction of the wave zone plate (220).

5. The measuring device according to claim 3, characterized in that The device also includes a first reflecting mirror (920), a second reflecting mirror, a beam splitter (910) and a moving platform (250). The mobile platform (250) is located on a side of the measurement cabin (230) away from the zone plate (220), the first reflector (920) is located on the mobile platform (250), and the first reflector (920) can move on the mobile platform (250) along the optical axis direction of the zone plate (220); The optical axis of the second reflector is inclined with respect to the optical axis of the zone plate (220); The light source (210) and the imaging sensor (240) are respectively located on two sides of the beam splitter (910); The measuring light is incident on the first reflector (920) along a first optical path, and after being reflected by the first reflector (920), the measuring light is incident on the imaging sensor (240) along a second optical path; The first optical path passes through the beam splitter (910), the second reflector, the zone plate (220) and the measuring chamber (230) in sequence, and the second optical path passes through the measuring chamber (230), the zone plate (220), the second reflector and the second beam splitter in sequence.

6. The measuring device according to claim 3, characterized in that The device further comprises a second reflector, the second reflector being arranged close to the zone plate (220), the measuring light being incident on the imaging sensor (240) along a third optical path, Wherein, the third optical path passes through: the second reflector, the wave zone plate (220) and the measurement cabin (230) in sequence.

7. The measuring device according to claim 5 or 6, characterized in that The second reflector is a collimating reflector (830).

8. The measuring device according to any one of claims 3 to 7, characterized in that The measuring chamber (230) comprises a first accommodating chamber (231) and a second accommodating chamber (232), wherein the first accommodating chamber (231) and the second accommodating chamber (232) are used to accommodate the reference sample and / or the sample to be measured.

9. The measuring device according to any one of claims 3 to 7, characterized in that The measuring chamber (230) is used to accommodate the sample to be measured, the reference sample is in the shape of a plate, and the reference sample is located between the zone plate (220) and the measuring chamber (230); or, The measurement chamber (230) is used to accommodate the reference sample; the sample to be measured is in the shape of a plate; and the sample to be measured is located between the zone plate (220) and the measurement chamber (230).

10. The measuring device according to any one of claims 1 to 9, characterized in that The measuring light is coherent light, and a wavelength of the measuring light is within a threshold range.

11. The measuring device according to any one of claims 1 to 10, characterized in that The device further comprises a polarizing plate (820), wherein the polarizing plate (820) is arranged close to the light source (210).

12. The measuring device according to any one of claims 1 to 11, characterized in that The device further comprises a driving control unit (260), wherein the driving control unit (260) is used to drive the moving platform (250).

13. A measuring device, characterized in that: The invention comprises a processing device and the measuring device according to any one of claims 1 to 12, wherein the processing device is used to determine the refractive index of the sample to be measured according to the measuring device.

14. A method for measuring refractive index, characterized in that: include: Acquire a first diffraction pattern corresponding to a reference sample, wherein the first diffraction pattern includes a first group of linear fringes, and the first group of linear fringes includes a first fringe; Acquire a second diffraction pattern corresponding to the sample to be tested, wherein the second diffraction pattern includes a second group of linear fringes, and the second group of linear fringes includes second fringes; Determining the refractive index of the sample to be measured according to the first diffraction pattern, the second diffraction pattern and the refractive index of the reference sample; The first stripes correspond to the second stripes, and the measurement accuracy of the refractive index of the reference sample is positively correlated with the measurement accuracy of the distance between the first stripes and the second stripes.

15. The measuring method according to claim 14, characterized in that: The step of acquiring a first diffraction pattern corresponding to a reference sample comprises: Acquiring a first diffraction pattern formed after the diffracted light passes through the reference sample, wherein the diffracted light is formed by diffracting the measuring light through the zone plate; The step of obtaining a second diffraction pattern corresponding to the sample to be tested includes: The second diffraction pattern formed after the diffracted light passes through the sample to be tested and the reference sample is acquired.

16. The measuring method according to claim 15, characterized in that: The obtaining of a first diffraction pattern corresponding to the reference sample further comprises: Acquire the first diffraction pattern at a first position in the optical axis direction of the zone plate; The step of obtaining a second diffraction pattern corresponding to the sample to be tested further includes: The second diffraction pattern is acquired at a second position in the optical axis direction of the zone plate.

17. The measuring method according to any one of claims 14 to 16, characterized in that: Determining the refractive index of the sample to be measured according to the first diffraction pattern, the second diffraction pattern and the refractive index of the reference sample comprises: Determining the refractive index of the sample to be measured according to the first distance, the second distance and the refractive index of the reference sample; The first distance is the distance between the positions of the imaging sensor when acquiring the first diffraction pattern and the second diffraction pattern, and the second distance is the distance between the projections of the first stripes and the second stripes on the imaging sensor.

18. The measuring method according to claim 17, characterized in that: The imaging sensor includes a charge coupled device (CCD).

19. The measuring method according to claim 18, characterized in that: The second distance is determined according to a distance between a first pixel point and a second pixel point on the imaging sensor, wherein the first pixel point is used to indicate a position of the first stripe, and the second pixel point is used to indicate a position of the second stripe.

20. The measuring method according to any one of claims 17 to 19, characterized in that: The refractive index of the sample to be tested is determined according to the following formula: Among them, Δx is the second distance, α is the incident angle of the measuring light on the measuring chamber, d is the wall thickness of the measuring chamber, n is the ratio of the refractive index of the sample to be tested to the refractive index of the reference sample, Δz is the first distance, and the measuring chamber is used to accommodate the reference sample and / or the sample to be tested.

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