An auxiliary device for measuring the birefringence of a crystal
By simplifying the optical system design and optical path layout, and combining the rotating scanning total internal reflection measurement method, a crystal birefringence measurement auxiliary device suitable for field use is provided. This solves the problems of complex structure and high cost of existing devices, and achieves the effects of portability and simplified assembly and adjustment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHANGCHUN INST OF ELECTRONIC TECH
- Filing Date
- 2026-06-25
- Publication Date
- 2026-07-28
AI Technical Summary
Existing crystal birefringence measurement devices are complex in structure, have many components, are complicated to assemble and adjust, and are costly, making them difficult to use in the field.
It employs a simplified optical system design, including a light source, a half-wave plate, a polarizing beam splitter, a focusing objective, and a CCD camera. Combined with the rotating scanning total internal reflection measurement method, it uses a semiconductor laser and a prism, simplifies the optical path layout, reduces the light source wavelength, and is suitable for field measurements.
It simplifies the device structure, reduces costs, and makes it easy to carry and adjust. It is suitable for field crystal birefringence measurement and ensures measurement results.
Smart Images
Figure CN224568882U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of crystal birefringence measurement technology, and specifically to an auxiliary device for crystal birefringence measurement. Background Technology
[0002] Existing technologies have proposed methods based on the principle of total internal reflection critical angles, utilizing the different critical angles of total internal reflection for o-ray and e-ray to create a double light-dark boundary, which is then inverted through angle scanning. Ordinary refractive index, The rotating scanning total internal reflection measurement method for unusual light refractive index and cross-sectional direction is applicable to the measurement of uniaxial and biaxial crystals; For example, Chinese patent CN112557344B, entitled "A Device and Method for Measuring Birefringence," uses a trapezoidal prism-total internal reflection critical angle as its core technology. It rotates the sample to image the critical angles of the o-ray and e-ray on a CCD camera, and then inverts the image. Ordinary refractive index, Unusual refractive index and optical axis direction; However, existing devices of this type have complex optical structures based on accuracy requirements, generally requiring more than a dozen components. They are complicated to assemble and adjust, difficult to carry, costly, and have low safety, which limits the use of the entire device to laboratory use and makes it completely unsuitable for field work. Based on this, those skilled in the art urgently need to improve the existing technical solutions to ensure measurement results while simplifying the overall structure, making them both portable and easy to assemble and adjust. Utility Model Content
[0003] Therefore, the technical problem to be solved by this utility model is to overcome the defects existing in the prior art, thereby providing a crystal birefringence measurement auxiliary device.
[0004] A crystal birefringence measurement auxiliary device includes: a light source, a half-wave plate, a focusing objective lens, a prism, a CCD camera, and a turntable, and further includes: a polarizing beam splitter prism; The laser module, measurement module, and camera module are connected optically in sequence. The laser module consists of a light source, a rotatable half-wave plate, a polarizing beam splitter, and a focusing lens connected in sequence via optical paths. The prism in the measurement module is a triangular prism; the focusing objective lens and the prism are connected in the optical path. The light source is a semiconductor laser with an output wavelength of 515nm.
[0005] Preferably, a CCD camera is used as the camera module; The CCD camera and prism optical path are connected to receive images of reflected light spots.
[0006] Preferably, the fast axis of the polarizing beam splitter is at a 45-degree angle to the vertical axis of the sample under test.
[0007] Preferably, the prism has an equilateral triangular cross-section.
[0008] Preferably, the prism is a triangular prism with a side length of 25.4 mm.
[0009] Preferably, the equivalent focal length of the focusing objective is 45mm.
[0010] The technical solution of this utility model has the following advantages: Compared with existing optical systems that also use the rotating scanning total internal reflection measurement method, this invention reduces the wavelength of the light source and improves the arrangement of various components in the overall device using existing optical elements. This results in a final optical system that simplifies the device, maintains the same performance, reduces costs, and is more portable and adaptable to field measurements of birefringent crystals. In this invention, a turntable is used to adjust the rotation of the sample while maintaining the fixed spatial positions of other components in the overall system during sample rotation. Attached Figure Description
[0011] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0012] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a schematic diagram of a captured image of a reflected light spot. Figure 3 The main graph showing the refractive index variation for any set of data; Figure 4 To and Figure 3 A graph showing the birefringence variation of the same data; Figure 5 To and Figure 3 Same data Error bar chart; Figure 6 To and Figure 3 Residual plots of the same data; Figure 7 To and Figure 3 Polar coordinate distribution plot of the same data; Figure 8This is a structural example diagram of an optical system that uses the traditional rotating scanning total internal reflection measurement method.
[0013] Explanation of reference numerals in the attached figures: 1-Light source, 2-Half-wave plate, 3-Polarizing beam splitter, 4-Focusing objective lens, 5-Prism, 6-CCD camera, 7-Turntable, 8-Sample placement position. Detailed Implementation
[0014] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.
[0015] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0016] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0017] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.
[0018] Example 1 Before detailing the composition and structure of this embodiment, the principle of this embodiment will be briefly introduced below. The principle used in the structure of this embodiment belongs to the existing rotating scanning total internal reflection measurement method; such as Figure 8 This is a schematic diagram of the structure of an existing crystal birefringence measurement optical system based on the rotating scanning total internal reflection measurement method; like Figure 8In the middle, from left to right, are a 632.8nm measurement light source, a beam expander, a waveplate, a converging objective, a trapezoidal prism, an objective lens, a microscope tube, and a detector; the microscope tube needs to contain built-in filters, polarizers, and pinhole diaphragms; the trapezoidal prism is mounted on the stage; like Figure 1 This embodiment discloses a crystal birefringence measurement auxiliary device, including: a light source 1, a half-wave plate 2, a focusing objective lens 4, a prism 5, a CCD camera 6, and a turntable 7, and also includes: a polarizing beam splitter prism 3. The laser module, measurement module, and camera module are connected optically in sequence. Unlike existing technologies, in this embodiment, the laser module is composed of only a light source 1, a rotatable half-wave plate 2, a polarizing beam splitter prism 3, and a focusing objective lens 4 connected in sequence via optical paths. The light source 1 is a semiconductor laser with an output wavelength of 515nm, and the prism 5 in the measurement module is a triangular prism. The focusing objective lens 4 and the prism 5 are connected via optical paths. This optical path arrangement ensures that the critical angle can be effectively obtained, as well as the adaptability to field conditions and the cost of application. Specifically, the incident angle range of the triangular prism is 56.18° to 63.82°, covering a measurable refractive index range of 1.4780 to 1.5964.
[0019] It should be noted that although both the scheme in this embodiment and the existing technical solutions are optical systems based on the rotating scanning total internal reflection measurement method, and both are optical systems composed of existing optical components, the arrangement order of the components is different. Furthermore, the existing technology often requires a measurement light source that outputs a linearly polarized beam. In conventional optical structure design, researchers generally believe that complex optical systems perform better than simple structures under the same principles. This is because complex optical systems are generally better able to meet multiple performance indicators compared to simple structures.
[0020] In this embodiment, the fast axis of the polarizing beam splitter 3 forms a 45-degree angle with the vertical axis of the sample under test. In this embodiment, the polarizing beam splitter 3 functions as both a quarter-wave plate, converting linearly polarized laser light into approximately circularly polarized light, and a light intensity reduction operation for the 515nm wavelength laser light from the light source 1, simplifying the light source module structure. Although quarter-wave plates are also used in existing technologies, they require a beam expander with a magnification of at least 5x between the quarter-wave plate and the measurement light source to ensure the accuracy of the final technical effect.
[0021] Prism 5 specifically adopts a traditional triangular prism with an equilateral triangular cross-section. Prism 5 is a triangular prism with a side length of 25.4 mm. It should be noted that, in the prior art, the triangular prism 5 is a common optically dense medium in the field of optics. However, in this embodiment, by applying prism 5 in conjunction with the aforementioned optical module, it is easier to operate and assemble compared to complex trapezoidal prisms and traditional complex light source modules, and it can also meet the needs of fieldwork. Furthermore, by combining this with a focusing objective lens 4 with an equivalent focal length of 45mm, the structural composition of the detection module can be further simplified, so that in the actual application of this embodiment, the camera module only needs a CCD camera 6, without the need for a layer-by-layer optimization structure before detecting the image as in the prior art.
[0022] The CCD camera 6 and prism 5 are optically connected to receive images of reflected light spots.
[0023] Example 2 Based on Example 1, taking a uniaxial crystal as an example, specifically a quartz crystal, this example further discloses how to use a crystal birefringence measurement auxiliary device to measure crystal birefringence, in order to elaborate on the effects of this application. Specifically, the process includes the following steps: S1. Initialize the assembly of the sample and the device of Example 1. The installation relationship between the sample and the device of Example 1 is consistent with that in the prior art. Figure 1 The sample is placed at position 8 as shown, so we will not elaborate on this further. S2. Every time the turntable 7 rotates 10 degrees, the CCD camera 6 takes a picture of the reflected light spot, and at the same time takes a background image and a reference image, for a total of 36 sets of pictures; in practical applications, it is recommended that the CCD camera 6 be a device with a resolution of 1920×1080 or higher.
[0024] In this reference image, all other components remain unchanged, except that the sample is mounted on the bottom surface of the prism 5, and the CCD camera 6 captures the complete laser spot after total internal reflection in the air as the reference light field. The captured image is used as the reference image.
[0025] The background image is an image in which other components remain unchanged, light source 1 is turned off, and the background light intensity and noise are measured in a dark field.
[0026] S3. Image Processing: Process the acquired reflected light spot image as follows... Figure 2 As shown, the background image and reference image are vertically summed, and further calculated according to the formula. Calculate the reflectivity curve to intuitively reflect the relationship between the change in light spot intensity and the critical angle. Light intensity of the light spot Background light intensity : Reference light intensity; R represents refractive index.
[0027] S4. Based on a pre-defined isolation degree + prominence dual-threshold peak-finding algorithm, two peak positions are extracted. The critical angles corresponding to the o-ray and e-ray critical angles are then extracted. Furthermore, the refractive index-pixel relationship obtained from prism 5 with a known refractive index is used to convert the critical angle positions into refractive index values. In practical applications, measurements need to be performed on a series of optical glasses with different refractive indices to establish an accurate refractive index-pixel correspondence table. For a pre-constructed refractive index-pixel correspondence table, subsequent measurements can be directly applied without re-establishing it. Parameter inversion: A nonlinear least squares fitting method is used to fit the refractive index curve obtained from the rotation measurement, inverting parameters such as the principal refractive index and tangential direction of the sample. During the fitting process, the parameters are continuously optimized by minimizing the sum of squared errors between the measured values and the theoretical model to obtain accurate crystal optical parameters. For example... Figure 3-7 For any set of measurement data, the principal refractive index variation plot and the birefringence variation plot are provided. Error bar plot, fitting residual plot, and polar coordinate distribution plot are shown in the figure. Indicates the fit; This represents the difference in refractive index between the ordinary ray and the extraordinary ray; This indicates the rotation angle of turntable 7. Among them, Figure 3 middle express Figure 3 The highest refractive index is corresponding to the middle; express Figure 3 The angle of refraction corresponding to the highest refractive index; Table 1 below shows the comparison table of actual measured values and characteristic parameters, with 275 degrees selected as the characteristic point; Table 1 is a comparison table of actual measured values and characteristic parameters.
[0028] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.
Claims
1. A crystal birefringence measurement auxiliary device, comprising: The light source (1), half-wave plate (2), focusing lens (4), prism (5), CCD camera (6) and turntable (7) are characterized in that they further include: polarizing beam splitter (3); The laser module, measurement module, and camera module are connected optically in sequence. Among them, the light source (1), the rotatable half-wave plate (2), the polarizing beam splitter (3) and the focusing lens (4) are connected in sequence to form a laser module; In the measurement module, the prism (5) is a triangular prism; the focusing objective (4) and the prism (5) are connected in the optical path; The light source (1) is a semiconductor laser with an output wavelength of 515nm.
2. The crystal birefringence measurement auxiliary device according to claim 1, characterized in that, CCD camera (6) serves as a camera module; The CCD camera (6) and the prism (5) are optically connected to receive the reflected light spot image.
3. The crystal birefringence measurement auxiliary device according to claim 1, characterized in that, The fast axis of the polarizing beam splitter (3) is at a 45-degree angle to the vertical axis of the sample to be tested.
4. The crystal birefringence measurement auxiliary device according to claim 1, characterized in that, The cross section of the prism (5) is an equilateral triangle.
5. The crystal birefringence measurement auxiliary device according to claim 4, characterized in that, The prism (5) is specifically a triangular prism with a side length of 25.4 mm.
6. The crystal birefringence measurement auxiliary device according to claim 1, characterized in that, The equivalent focal length of the focusing objective (4) is 45mm.