Automated measurement apparatus and method for fraunhofer diffraction

Abstract

The application relates to the fields of physical optics and optoelectronic detection technology, and discloses a Fraunhofer diffraction automatic measurement device and method.The device comprises an optical unit, a dynamic control unit and an image processing and analysis unit.The optical unit comprises a laser, a first convex lens, a diffraction element, a second convex lens and an image acquisition camera.The dynamic control unit is arranged at the diffraction element and comprises a nonlinear optical medium and a piezoelectric ceramic driver.The image processing and analysis unit comprises an image acquisition module, an image preprocessing module, a feature recognition module, a parameter calculation module and an interactive display module.The method comprises the following steps: building an optical path to meet the far-field condition, acquiring a diffraction pattern through the image acquisition camera, identifying the positions of wave crests and troughs after gray-scale and filtering preprocessing, automatically calculating the slit width, the diffraction angle or the grating constant based on the Fraunhofer diffraction formula, and displaying the results in real time through a graphical interface.The application realizes the automatic measurement of Fraunhofer diffraction, the analysis of nonlinear medium response and the piezoelectric dynamic control, and significantly improves the measurement efficiency and precision.

Description

Technical Field

[0001] This invention relates to the fields of physical optics and photoelectric detection technology, specifically to an automated measurement device and method for Fraunhofer diffraction. Background Technology

[0002] Diffraction of light is an important manifestation of the wave nature of light. Single-slit diffraction is mainly divided into Fresnel diffraction and Fraunhofer diffraction. Fraunhofer diffraction has important application value in optical detection, precision measurement and basic physics experiment teaching because both the incident light and the diffracted light can be approximated as plane waves.

[0003] Traditional Fraunhofer single-slit diffraction experiments and detection devices largely rely on manual adjustment of the slit width and manual acquisition of light intensity data. This process is cumbersome, unstable, and makes it difficult to achieve high-precision, continuous measurements. In diffraction experiments involving nonlinear media, the media's response characteristics to the external field are complex. Existing equipment lacks rapid and precise dynamic control methods, making it impossible to track and analyze the nonlinear optical response in real time. Furthermore, precision control technologies such as piezoelectric actuation are not deeply integrated with automatic diffraction intensity detection, resulting in low levels of automation in data acquisition, processing, and analysis, and significant measurement errors. This fails to meet the demands of modern optical research for high-precision, automated, and dynamic testing, thus hindering in-depth research on the response of nonlinear media and diffraction characteristics under piezoelectric control. Summary of the Invention

[0004] This invention provides an automated Fraunhofer diffraction measurement device and method to solve the above-mentioned problems.

[0005] This invention provides an automated Fraunhofer diffraction measurement device, comprising:

[0006] The optical unit consists of a laser, a first convex lens, a diffraction element, a second convex lens, and an image acquisition camera arranged sequentially along the optical path.

[0007] The first convex lens is used to collimate the laser beam into parallel light to satisfy the Fraunhofer diffraction far-field condition, and the second convex lens is used to converge the diffracted light onto the photosensitive surface of the image acquisition camera.

[0008] A dynamic control unit, disposed at the diffraction element, includes a nonlinear optical medium and a piezoelectric ceramic actuator;

[0009] The nonlinear optical medium is used to generate a nonlinear optical effect to modulate the diffraction field when the incident light intensity exceeds the nonlinear response threshold, and the piezoelectric ceramic actuator is used to generate a nanoscale displacement in response to an applied voltage to dynamically adjust the slit width parameter of the diffraction element.

[0010] The image processing and analysis unit includes:

[0011] The image acquisition module is connected to the image acquisition camera to acquire digital images of diffraction patterns;

[0012] The image preprocessing module is used to perform grayscale conversion and filtering on digital images to suppress noise;

[0013] The feature recognition module is used to identify the positions of the peaks and troughs of diffraction fringes in the preprocessed image;

[0014] The parameter calculation module automatically calculates the slit width, diffraction angle, or grating constant based on the identified peak and trough positions according to the Fraunhofer diffraction formula.

[0015] The interactive display module provides a graphical user interface to display diffraction patterns, light intensity distribution curves, and calculation results in real time.

[0016] In one alternative implementation, the image acquisition camera is a 4KHD industrial camera that converts the spatial distribution of diffracted light intensity into the grayscale value distribution of a digital image.

[0017] In one alternative embodiment, the nonlinear optical medium is a lithium niobate crystal, which generates second harmonics or photorefractive effects under a strong light field to form a dynamic refractive index grating to nonlinearly modulate the diffracted light field.

[0018] In one alternative embodiment, the piezoelectric ceramic actuator is attached to the adjustable slit of the diffraction element, and the nanoscale slit width is linearly adjusted by applying a controllable voltage based on the inverse piezoelectric effect.

[0019] In one alternative implementation, the piezoelectric ceramic actuator has two operating modes: static precision adjustment and periodic dynamic scanning.

[0020] In one optional implementation, the system further includes an error analysis unit that integrates a MATLAB computing environment for analyzing relative error, Type A uncertainty, Type B uncertainty, and total uncertainty of multiple sets of experimental data.

[0021] In one optional embodiment, the focal length of both the first convex lens and the second convex lens is 150mm, and the distance between the first convex lens and the laser and the distance between the second convex lens and the image acquisition camera are both 150mm, so as to satisfy the far-field condition of Fraunhofer diffraction.

[0022] In one alternative embodiment, all optical elements are arranged coaxially at the same height, and the optical unit also includes a small aperture stop disposed between the laser and the first convex lens along the optical path.

[0023] Secondly, this embodiment also provides an automated measurement method for Fraunhofer diffraction, comprising the following steps:

[0024] A laser, a first convex lens, a diffraction element, a second convex lens, and an image acquisition camera are sequentially arranged along the optical path. The distance between the first convex lens and the laser, and the distance between the second convex lens and the image acquisition camera are adjusted to meet the Fraunhofer diffraction far-field condition.

[0025] A nonlinear optical medium or a piezoelectric ceramic actuator is placed at the diffraction element. The nonlinear optical medium generates a nonlinear optical effect to modulate the diffraction field when the incident light intensity exceeds the nonlinear response threshold. The piezoelectric ceramic actuator generates a nanometer-scale displacement in response to the applied voltage to dynamically adjust the slit width parameter of the diffraction element.

[0026] Digital images of diffraction patterns are acquired using an image acquisition camera;

[0027] Digital images are preprocessed by grayscale conversion and filtering to suppress noise;

[0028] Identify the peak and trough positions of diffraction fringes in the preprocessed image;

[0029] Based on the Fraunhofer diffraction formula, the slit width, diffraction angle, or grating constant is automatically calculated according to the identified peak and trough positions;

[0030] The diffraction pattern, light intensity distribution curve, and calculation results are displayed in real time through a graphical user interface.

[0031] In one optional implementation, the nonlinear response threshold is determined by gradually increasing the laser output power while simultaneously monitoring the diffraction pattern in real time using an image acquisition camera. The minimum incident light intensity when the diffraction fringes exhibit nonlinear modulation characteristics is the nonlinear response threshold. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 A diagram showing a nonlinear optical medium in an automated Fraunhofer diffraction measurement device according to an embodiment of the present invention;

[0034] Figure 2 A diagram showing a piezoelectric ceramic actuator in an automated Fraunhofer diffraction measurement device according to an embodiment of the present invention;

[0035] Figure 3 This is a parameter graph for detection group one;

[0036] Figure 4 The parameter graph for detection group two;

[0037] Figure 5 The parameter graph for detection group three;

[0038] Figure 6 This is a parameter graph for detection group four;

[0039] Figure 7 This is a diagram of an automated Fraunhofer diffraction measurement device according to an embodiment of the present invention.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1. Laser;

[0042] 2. First convex lens;

[0043] 3. Diffraction elements;

[0044] 4. Second convex lens;

[0045] 5. Image acquisition camera;

[0046] 6. Nonlinear optical media;

[0047] 7. Piezoelectric ceramic actuator. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Diffraction of light is an important manifestation of the wave nature of light. Single-slit diffraction is mainly divided into Fresnel diffraction and Fraunhofer diffraction. Fraunhofer diffraction has important application value in optical detection, precision measurement and basic physics experiment teaching because both the incident light and the diffracted light can be approximated as plane waves.

[0050] Traditional Fraunhofer single-slit diffraction experiments and detection devices largely rely on manual adjustment of the slit width and manual acquisition of light intensity data. This process is cumbersome, unstable, and makes it difficult to achieve high-precision, continuous measurements. In diffraction experiments involving nonlinear media, the media's response characteristics to the external field are complex. Existing equipment lacks rapid and precise dynamic control methods, making it impossible to track and analyze the nonlinear optical response in real time. Furthermore, precision control technologies such as piezoelectric actuation are not deeply integrated with automatic diffraction intensity detection, resulting in low levels of automation in data acquisition, processing, and analysis, and significant measurement errors. This fails to meet the demands of modern optical research for high-precision, automated, and dynamic testing, thus hindering in-depth research on the response of nonlinear media and diffraction characteristics under piezoelectric control.

[0051] The following is combined with Figures 1 to 7 The following describes embodiments of the present invention.

[0052] According to an embodiment of the present invention, an automated Fraunhofer diffraction measurement device is provided, comprising an optical unit, a dynamic control unit, and an image processing and analysis unit. The optical unit includes a laser 1, a first convex lens 2, a diffraction element 3, a second convex lens 4, and an image acquisition camera 5 arranged sequentially along the optical path. The first convex lens 2 is used to collimate the beam emitted by the laser 1 into parallel light to satisfy the far-field condition of Fraunhofer diffraction, and the second convex lens 4 is used to converge the diffracted light onto the photosensitive surface of the image acquisition camera 5. The dynamic control unit is disposed at the diffraction element 3 and includes a nonlinear optical medium 6 and a piezoelectric ceramic actuator 7. The nonlinear optical medium 6 is used to generate a nonlinear optical effect to modulate the diffracted light field when the incident light intensity exceeds a nonlinear response threshold. The piezoelectric ceramic actuator 7 is used to generate nanoscale displacement in response to an applied voltage to dynamically adjust the slit width parameter of the diffraction element 3; the image processing and analysis unit includes an image acquisition module, an image preprocessing module, a feature recognition module, and an interactive display module. The image acquisition module is connected to the image acquisition camera 5 to acquire digital images of the diffraction pattern; the image preprocessing module is used to perform grayscale conversion and filtering on the digital image to suppress noise; the feature recognition module is used to identify the peak and trough positions of the diffraction fringes in the preprocessed image; the parameter calculation module automatically calculates the slit width, diffraction angle, or grating constant based on the identified peak and trough positions according to the Fraunhofer diffraction formula; the interactive display module provides a graphical user interface to display the diffraction pattern, light intensity distribution curve, and calculation results in real time.

[0053] In the specific implementation of this embodiment:

[0054] Laser 1 can be a semiconductor laser, outputting monochromatic light with a stable wavelength. The focal lengths of the first convex lens 2 and the second convex lens 4 are selected according to experimental requirements, usually ensuring that the distance between the lens and the light source and camera is equal to the focal length to meet far-field conditions.

[0055] The diffraction element 3 can be a single-slit diffraction plate or a multi-slit diffraction plate, used to generate Fraunhofer diffraction patterns.

[0056] The nonlinear optical medium 6 can be a crystal material with nonlinear optical effects, and its nonlinear response threshold is determined by the material properties and the intensity of incident light.

[0057] The piezoelectric ceramic actuator 7 can be made of a piezoelectric ceramic sheet, which is stretched and deformed by applying voltage, thereby driving the slit width adjustment mechanism of the diffraction element 3.

[0058] The image acquisition camera 5 can be a high-resolution digital camera that converts the spatial distribution of light intensity into grayscale values ​​of a digital image.

[0059] The image acquisition module, image preprocessing module, feature recognition module, parameter calculation module, and interactive display module can be integrated into a computer, with corresponding functions implemented through software. For example, the image preprocessing module performs grayscale conversion and digital filtering algorithms, the feature recognition module uses image processing technology to identify fringe extreme points, the parameter calculation module performs numerical calculations based on diffraction formulas, and the interactive display module provides a user interface and real-time display functionality.

[0060] During operation, the laser beam emitted by laser 1 is collimated by the first convex lens 2 and then perpendicularly illuminates the diffraction element 3, producing a Fraunhofer diffraction pattern. The diffracted light is converged by the second convex lens 4 onto the photosensitive surface of the image acquisition camera 5. The camera acquires the diffraction image in real time and transmits it to the image processing and analysis unit. The image preprocessing module performs grayscale conversion and filtering on the image to remove noise. The feature recognition module identifies the peak and trough positions of the diffraction fringes. Based on these positional information, combined with known parameters such as the laser wavelength and lens focal length, the parameter calculation module automatically calculates the slit width, diffraction angle, or grating constant using the Fraunhofer diffraction formula. Simultaneously, the interactive display module displays the diffraction pattern, light intensity distribution curve, and calculation results in real time. When dynamic adjustment is required, a light intensity exceeding a threshold can be applied to the nonlinear optical medium 6 to induce a nonlinear effect that modulates the diffraction field; or a voltage can be applied to the piezoelectric ceramic actuator 7 to precisely change the slit width, allowing for real-time observation of changes in the diffraction pattern.

[0061] This embodiment integrates an optical unit, a dynamic control unit, and an image processing and analysis unit to achieve automated measurement of Fraunhofer diffraction, as well as nonlinear medium response and piezoelectric dynamic control, effectively improving experimental efficiency and measurement accuracy.

[0062] In one embodiment, the image acquisition camera 5 is a 4KHD industrial camera that converts the spatial distribution of diffracted light intensity into the grayscale value distribution of a digital image.

[0063] Specifically, the 4KHD industrial camera features high spatial resolution and a high frame rate, enabling it to clearly capture the fine structure of diffraction fringes. The camera's photosensitive surface receives the diffracted light intensity signal; the grayscale value of each pixel corresponds to the light intensity at that location, thus discretizing the continuous spatial distribution of light intensity into digital image data. This digital image data is transmitted in real-time to the image processing and analysis unit via the image acquisition module, providing high-quality raw data for subsequent image preprocessing and feature recognition.

[0064] This embodiment abandons the traditional digital galvanometer and uses a 4KHD industrial camera as the core device for light intensity detection and image acquisition. It has high spatial resolution, high acquisition frame rate and wide spectral response range. It can convert optical signals into digital image signals and realize real-time quantization of diffracted light intensity through the conversion of pixels and gray values. It solves the problems of low sensitivity, data jump and limited spatial resolution of galvanometer, and greatly reduces human reading error.

[0065] In one embodiment, the image preprocessing module is implemented using the OpenCV computer vision library and includes a grayscale conversion unit, a Gaussian filtering unit, and an image angle automatic correction unit. The image angle automatic correction unit is used to fine-tune the diffraction fringes that deviate horizontally in a clockwise or counterclockwise direction.

[0066] The grayscale conversion unit is used to convert the color digital image acquired by the image acquisition module into a grayscale image. Since the light intensity information of the diffraction pattern can be completely preserved in the grayscale image, grayscale processing can reduce the amount of data and improve the speed of subsequent processing.

[0067] The Gaussian filtering unit is used to smooth grayscale images. By convolving the image with a Gaussian convolution kernel, high-frequency noise introduced during image acquisition can be effectively suppressed, while preserving the edge and contour features of diffraction fringes, providing a clearer image basis for subsequent extreme point identification.

[0068] The automatic image angle correction unit is used to detect whether the diffraction fringes deviate from the horizontal direction. In actual optical path construction, the diffraction element 3 may cause the fringes to tilt due to installation errors. This unit automatically calculates the tilt angle of the fringes through image processing algorithms and performs clockwise or counterclockwise rotation of the image for fine adjustment, so that the diffraction fringes are restored to a horizontal state, thereby ensuring the accuracy of subsequent peak and trough position identification.

[0069] This embodiment introduces the OpenCV computer vision library to perform image preprocessing, which significantly improves the quality and standardization of diffraction images, laying a good foundation for subsequent feature recognition and parameter calculation, while also enhancing the system's adaptability to different experimental environments.

[0070] In one embodiment, the feature recognition module uses a Python-based algorithm to identify the peak and trough positions of the diffraction fringes; the parameter calculation module integrates NumPy and SciPy libraries to automatically calculate the slit width, diffraction angle, and grating constant based on the Fraunhofer diffraction formula.

[0071] The feature recognition module receives the grayscale image processed by the image preprocessing module and uses an algorithm developed in Python to identify extreme points of the diffraction fringes. This algorithm scans the grayscale value distribution line by line along the horizontal direction of the image, determining the coordinates of peaks (centers of bright fringes) and troughs (centers of dark fringes) by detecting local maxima and minima. To improve recognition accuracy, the algorithm can combine the symmetry features of the diffraction fringes with correlation information from consecutive frame images for verification and correction.

[0072] The parameter calculation module receives peak and trough position data output by the feature recognition module and integrates the NumPy and SciPy scientific computing libraries for numerical calculations. Specifically:

[0073] The NumPy library is used for efficient array operations on positional data, such as calculating intermediate parameters like the distance between adjacent extreme points and the sine of the diffraction angle.

[0074] The SciPy library provides optimization and integration tools that can fit light intensity distribution curves according to the Fraunhofer diffraction formula.

[0075] In single-slit diffraction mode, the parameter calculation module calculates the slit width based on the position of first-order or multi-order dark fringes; in multi-slit diffraction mode, it calculates the grating constant and slit width by combining the missing-order phenomenon and the position of the principal interference maxima. All calculation processes are completed automatically without manual intervention.

[0076] This embodiment uses a Python algorithm combined with the NumPy and SciPy libraries to achieve feature recognition and parameter calculation, making full use of the efficiency and accuracy of scientific computing tools. This enables the system to quickly and accurately complete the automatic calculation of diffraction parameters, significantly improving data processing efficiency and reliability.

[0077] In one embodiment, the nonlinear optical medium 6 is a lithium niobate crystal, which generates second harmonics or photorefractive effects under a strong light field to form a dynamic refractive index grating to nonlinearly modulate the diffracted light field.

[0078] By introducing lithium niobate nonlinear optical crystals into the diffraction path and utilizing their nonlinear optical properties such as second harmonic generation and photorefractive effect under strong light fields, the refractive index of the medium is dynamically changed with the intensity of incident light, forming a dynamic refractive index grating. This grating, superimposed with the single-slit diffraction effect, produces new diffraction extrema and light intensity modulation, breaking through the traditional linear diffraction experiment scope and enabling the exploration of the laws governing the interaction between light and matter. At the same time, the experimental setup is expanded into a nonlinear optical property detection platform.

[0079] In one embodiment, the piezoelectric ceramic actuator 7 is attached to the adjustable slit of the diffraction element 3, and the nanoscale slit width is linearly adjusted by applying a controllable voltage based on the inverse piezoelectric effect.

[0080] By utilizing the inverse piezoelectric effect of piezoelectric ceramics, they are attached to the adjustable slit of the diffraction slit. Nanoscale mechanical deformation is achieved by applying a controllable voltage, thereby precisely and dynamically controlling the slit width (the slit width is linearly related to the applied voltage). This allows for precise static slit width adjustment, as well as dynamic scanning of diffraction fringes by applying periodic voltages. By changing the interference conditions of the diffracted light, controllable modulation of the position and intensity distribution of the diffraction pattern can be achieved. Simultaneously, subwavelength displacement control can be realized, improving the sensitivity of experimental parameter control.

[0081] In one embodiment, the piezoelectric ceramic actuator 7 has two operating modes: static precision adjustment and periodic dynamic scanning.

[0082] The piezoelectric ceramic actuator 7 is attached to the adjustable slit of the diffraction element 3 and operates based on the inverse piezoelectric effect. When an external voltage is applied, the piezoelectric ceramic undergoes mechanical deformation proportional to the voltage magnitude, thereby driving the slit width adjustment mechanism to achieve slit width changes with nanometer-level precision. The amount of slit width change exhibits a good linear relationship with the applied voltage, providing a basis for precise control.

[0083] Static Precision Adjustment Mode: In this mode, a stable DC voltage is applied to the piezoelectric ceramic actuator 7, keeping it in a fixed deformation state. By precisely adjusting the voltage value, the slit width of the diffraction element 3 can be set and stabilized at the target value. This mode is suitable for experimental scenarios that require maintaining a specific slit width for repeated measurements over a long period of time, such as studying the diffraction pattern characteristics under a fixed slit width or collecting multiple sets of data for statistical analysis.

[0084] Periodic Dynamic Scanning Mode: In this mode, a periodically varying voltage signal, such as a sine wave, triangular wave, or square wave, is applied to the piezoelectric ceramic actuator 7. The piezoelectric ceramic responds to the voltage change by periodically expanding and contracting, causing the slit width to change periodically over time. The slit width of the diffraction element 3 continuously scans between its maximum and minimum values, resulting in a dynamic evolution of the fringe positions and intensity distribution in the diffraction pattern. This evolution process is captured in real time by the image acquisition camera 5, allowing for the study of the real-time impact of the dynamic slit width change on Fraunhofer diffraction, such as observing the movement trajectories of bright and dark fringes at various levels and the periodic modulation patterns of the intensity distribution.

[0085] In one embodiment, the focal length of the first convex lens 2 and the second convex lens 4 are both 150mm, and the distance between the first convex lens 2 and the laser 1 and the distance between the second convex lens 4 and the image acquisition camera 5 are both 150mm, so as to satisfy the far-field condition of Fraunhofer diffraction.

[0086] In one embodiment, all optical elements are arranged coaxially at the same height, and the optical unit also includes a small aperture stop disposed between the laser 1 and the first convex lens 2 along the optical path.

[0087] To verify the actual effect of the Fraunhofer diffraction automated measurement device of the present invention, comparative experiments were conducted on diffraction elements 3 of the same specifications using both the traditional manual measurement method (original method) and the device of the present invention, and the measurement results were recorded.

[0088] Experimental conditions:

[0089] Laser 1: Semiconductor laser, output wavelength λ=632.8nm;

[0090] Lenses: The focal lengths of the first convex lens 2 and the second convex lens 4 are both f=150mm;

[0091] Diffraction element 3: Single-slit diffraction plate and multi-slit diffraction plate;

[0092] Nonlinear medium: Lithium niobate crystal;

[0093] Image Acquisition Camera 5: 4K HD Industrial Camera;

[0094] Image Processing and Analysis Unit: An automated system based on OpenCV, Python, and MATLAB.

[0095] Measurement results using the original method (control):

[0096] Traditional manual measurement methods (manual reading of digital galvanometer and manual calculation) were used to measure single slits with slit widths of 0.10 mm and 0.12 mm to obtain experimental values ​​of diffraction angles θ and relative light intensities I / I0 for each order of diffraction, and compared with theoretical values. The results are shown in Table 1.

[0097]

[0098] ΔX represents the fringe spacing, and Z represents the diffraction distance. As shown in Table 1, there is a certain deviation between the manual measurement results and the theoretical values, and the manual calculation process is cumbersome and inefficient.

[0099] Measurement results of the device of the present invention:

[0100] The automated measurement device of this invention is used to measure various diffraction elements 3. Each sample is measured repeatedly. The system automatically acquires images, processes data and outputs results.

[0101] Test Group 1: Theoretical seam width of a single seam is 0.10mm.

[0102]

[0103] Test Group 2: Theoretical value of the double-slit diffraction grating constant: 0.21 mm

[0104]

[0105] Test Group 3: Theoretical value of single slit width is 0.07mm (with the addition of nonlinear dielectric lithium niobate crystal).

[0106]

[0107] Test Group 4: Theoretical value of single slit width is 0.10 mm (with the addition of nonlinear dielectric lithium niobate crystal).

[0108]

[0109] This embodiment verifies, through comparative testing of the traditional original scheme and the improved scheme of the present invention, that the present invention significantly reduces the measurement error of the Fraunhofer diffraction experiment, while reducing the time required for a single set of experiments, eliminating human error caused by manual operation, and greatly improving the automation level, measurement accuracy and ease of operation of the experiment.

[0110] Secondly, this embodiment also provides an automated measurement method for Fraunhofer diffraction, comprising the following steps:

[0111] A laser 1, a first convex lens 2, a diffraction element 3, a second convex lens 4, and an image acquisition camera 5 are arranged sequentially along the optical path. The distance between the first convex lens 2 and the laser 1, and the distance between the second convex lens 4 and the image acquisition camera 5 are adjusted to meet the Fraunhofer diffraction far-field condition.

[0112] Specifically, the distance between the first convex lens 2 and the laser 1 is equal to the focal length of the first convex lens 2, and the distance between the second convex lens 4 and the image acquisition camera 5 is equal to the focal length of the second convex lens 4, so that both the incident light and the diffracted light can be approximated as parallel light.

[0113] A nonlinear optical medium 6 or a piezoelectric ceramic actuator 7 is provided at the diffraction element 3. The nonlinear optical medium 6 generates a nonlinear optical effect to modulate the diffraction field when the incident light intensity exceeds the nonlinear response threshold. The piezoelectric ceramic actuator 7 generates a nanoscale displacement in response to the applied voltage to dynamically adjust the slit width parameter of the diffraction element 3.

[0114] When a nonlinear optical medium 6 is set, the medium generates a nonlinear optical effect when the incident light intensity exceeds the nonlinear response threshold, thereby modulating the diffraction light field.

[0115] When the piezoelectric ceramic actuator 7 is set, the actuator responds to the applied voltage to generate a nanometer-level displacement, thereby dynamically adjusting the slit width parameter of the diffraction element 3.

[0116] Digital images of the diffraction pattern are acquired using image acquisition camera 5;

[0117] The image acquisition camera 5 converts the spatial distribution of diffracted light intensity into the grayscale distribution of the digital image in real time, and transmits it to the image processing and analysis unit through the image acquisition module.

[0118] Digital images are preprocessed by grayscale conversion and filtering to suppress noise;

[0119] The acquired digital images undergo grayscale conversion and filtering preprocessing to suppress image noise. Grayscale conversion transforms the color image into a grayscale image, reducing the amount of data. Filtering employs appropriate filtering algorithms (such as Gaussian filtering, median filtering, or moving average filtering) to remove high-frequency noise while preserving the edge and contour features of the diffraction fringes.

[0120] Identify the peak and trough positions of diffraction fringes in the preprocessed image;

[0121] Identify the peaks and troughs of diffraction fringes in the preprocessed image. By scanning the grayscale distribution along the horizontal direction of the image, detect local maxima as peaks (centers of bright fringes) and local minima as troughs (centers of dark fringes), and record the coordinates of each extreme point.

[0122] Based on the Fraunhofer diffraction formula, the slit width, diffraction angle, or grating constant is automatically calculated according to the identified peak and trough positions;

[0123] In single-slit diffraction mode, the slit width *a* is calculated based on the condition *asinθ=kλ* satisfying the position of the dark fringe. The diffraction angle *θ* can be obtained by converting the trough position coordinates into the lens focal length. *k* represents the diffraction order, an integer ranging from ±1 to ±2 to ±3, indicating the order of the dark fringe. *λ* is the wavelength of the incident monochromatic light, a known experimental parameter.

[0124] In the multi-slit diffraction mode, the grating constant d is calculated based on the position of the bright fringe, and the accuracy of the calculation results is verified by combining the missing order phenomenon.

[0125] The diffraction pattern, light intensity distribution curve, and calculation results are displayed in real time through a graphical user interface.

[0126] The graphical user interface displays diffraction patterns, light intensity distribution curves, and results such as slit width, diffraction angle, or grating constant calculated in the above steps in real time. The user interface supports real-time monitoring of the experimental process and instant output of measurement results.

[0127] This embodiment achieves an automated measurement process for Fraunhofer diffraction through the above steps. This method integrates optical setup, dynamic control, image acquisition and processing, feature recognition, and parameter calculation, effectively improving experimental efficiency and measurement accuracy. It also supports automated analysis of both nonlinear medium response and piezoelectric dynamic control modes.

[0128] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An automated Fraunhofer diffraction measurement device, characterized in that, include: The optical unit is provided with a laser (1), a first convex lens (2), a diffraction element (3), a second convex lens (4), and an image acquisition camera (5) arranged sequentially along the optical path. The first convex lens (2) is used to collimate the beam emitted by the laser (1) into parallel light to satisfy the Fraunhofer diffraction far-field condition, and the second convex lens (4) is used to converge the diffracted light to the photosensitive surface of the image acquisition camera (5). The dynamic control unit is located at the diffraction element (3) and includes a nonlinear optical medium (6) and a piezoelectric ceramic actuator (7). The nonlinear optical medium (6) is used to generate a nonlinear optical effect to modulate the diffraction field when the incident light intensity exceeds the nonlinear response threshold, and the piezoelectric ceramic actuator (7) is used to generate a nanoscale displacement in response to the applied voltage to dynamically adjust the slit width parameter of the diffraction element (3). The image processing and analysis unit includes: The image acquisition module is connected to the image acquisition camera (5) to acquire digital images of diffraction patterns; The image preprocessing module is used to perform grayscale conversion and filtering on digital images to suppress noise; The feature recognition module is used to identify the positions of the peaks and troughs of diffraction fringes in the preprocessed image; The parameter calculation module automatically calculates the slit width, diffraction angle, or grating constant based on the identified peak and trough positions according to the Fraunhofer diffraction formula. The interactive display module provides a graphical user interface to display diffraction patterns, light intensity distribution curves, and calculation results in real time.

2. The automated Fraunhofer diffraction measurement device according to claim 1, characterized in that, The image acquisition camera (5) is a 4KHD industrial camera, which converts the spatial distribution of diffracted light intensity into the gray value distribution of digital images.

3. The automated Fraunhofer diffraction measurement device according to claim 1, characterized in that, The nonlinear optical medium (6) is a lithium niobate crystal, which generates second harmonics or photorefractive effects under strong light fields to form a dynamic refractive index grating to nonlinearly modulate the diffraction light field.

4. The automated Fraunhofer diffraction measuring device according to claim 1, characterized in that, The piezoelectric ceramic actuator (7) is attached to the adjustable slit of the diffraction element (3) and achieves linear adjustment of the nanoscale slit width by applying a controllable voltage based on the inverse piezoelectric effect.

5. The automated Fraunhofer diffraction measuring device according to claim 4, characterized in that, The piezoelectric ceramic actuator (7) has two working modes: static precision adjustment and periodic dynamic scanning.

6. The automated Fraunhofer diffraction measuring device according to claim 1, characterized in that, It also includes an error analysis unit, which integrates the MATLAB computing environment to perform relative error, Type A uncertainty, Type B uncertainty and total uncertainty analysis on multiple sets of experimental data.

7. The automated Fraunhofer diffraction measuring device according to any one of claims 1-6, characterized in that, The focal lengths of the first convex lens (2) and the second convex lens (4) are both 150 mm, and the distances between the first convex lens (2) and the laser (1) and between the second convex lens (4) and the image acquisition camera (5) are both 150 mm, so as to satisfy the far-field conditions of Fraunhofer diffraction.

8. The automated Fraunhofer diffraction measuring device according to any one of claims 1-6, characterized in that, All optical elements are arranged coaxially at the same height, and the optical unit also includes a small aperture stop arranged between the laser (1) and the first convex lens (2) along the optical path.

9. An automated method for measuring Fraunhofer diffraction, characterized in that, Includes the following steps: A laser (1), a first convex lens (2), a diffraction element (3), a second convex lens (4), and an image acquisition camera (5) are arranged sequentially along the optical path. The distance between the first convex lens (2) and the laser (1) and the distance between the second convex lens (4) and the image acquisition camera (5) are adjusted to meet the Fraunhofer diffraction far-field conditions. A nonlinear optical medium (6) or a piezoelectric ceramic actuator (7) is provided at the diffraction element (3). The nonlinear optical medium (6) generates a nonlinear optical effect to modulate the diffraction field when the incident light intensity exceeds the nonlinear response threshold. The piezoelectric ceramic actuator (7) generates a nanoscale displacement in response to the applied voltage to dynamically adjust the slit width parameter of the diffraction element (3). Digital images of the diffraction pattern are acquired by the image acquisition camera (5); Digital images are preprocessed by grayscale conversion and filtering to suppress noise; Identify the peak and trough positions of diffraction fringes in the preprocessed image; Based on the Fraunhofer diffraction formula, the slit width, diffraction angle, or grating constant is automatically calculated according to the identified peak and trough positions; The diffraction pattern, light intensity distribution curve, and calculation results are displayed in real time through a graphical user interface.

10. The automated measurement method for Fraunhofer diffraction according to claim 9, characterized in that, The method for determining the nonlinear response threshold is as follows: gradually increase the output power of the laser (1), and at the same time monitor the diffraction pattern in real time through the image acquisition camera (5). The minimum incident light intensity when the diffraction stripe shows nonlinear modulation characteristics is the nonlinear response threshold.

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