Laser energy monitoring system and method

Abstract

The embodiment of the invention discloses a laser energy monitoring system and method. The system comprises a laser used for generating a laser beam containing an ultraviolet band and a visible band; the high-reflectivity mirror is used for receiving the laser beam, reflecting part of the ultraviolet band beam to an application end and transmitting the remaining ultraviolet band and visible band to form a remaining laser beam for energy monitoring; the light splitting element is used for carrying out dispersion light splitting on the residual laser beams, removing visible wave band light beams and leaving ultraviolet wave band light beams; the diaphragm is used for filtering stray light by limiting the aperture of an ultraviolet band light beam to ensure that the size and energy of the light beam entering a subsequent light path are stable; the scattering element is used for homogenizing the ultraviolet band light beam passing through the diaphragm through a scattering effect and converting coherent laser into a uniform area light source; and the photoelectric detector is used for receiving the homogenized ultraviolet light signal and converting the homogenized ultraviolet light signal into an electric signal so as to realize real-time monitoring of ultraviolet laser energy.

Description

Technical Field

[0001] This invention relates to the field of optical technology. More specifically, it relates to a laser energy monitoring system and method. Background Technology

[0002] With the widespread application of meteorological lidar, the demand for lasers with flat-topped output spot energy density distribution that can operate continuously for a long time is increasing. Therefore, a monitoring system that can detect energy in the 200nm~400nm band in real time is very important in the system.

[0003] Solid-state lasers mostly use frequency combining to generate light with higher single-photon energy. Therefore, the output beam contains lasers of multiple frequencies. By using a suitable dichroic mirror to separate the light of different frequencies, the ultraviolet light band is output separately. However, due to the precision of the lens coating, some lasers of other bands will still be mixed in the output beam.

[0004] Current technologies mostly use broadband photodiodes as the main body for energy monitoring. These typically involve either introducing the diffuse reflection beam outside the cavity via optical fiber or directly detecting it inside the cavity. Using optical fiber detection consumes some of the ultraviolet laser's energy, requiring an increase in the solid-state laser's output energy, which significantly increases the product's technical complexity and cost. Directly detecting the diffuse reflection beam inside the cavity can only detect changes in a small portion of the energy range, and it cannot effectively detect some energy failure modes; optical fiber detection also suffers from this problem. Using pyroelectric probes for testing is costly and has a slow response time, and it is sensitive to environmental temperature and humidity, easily affected by external interference leading to measurement errors. Summary of the Invention

[0005] The purpose of this invention is to provide a laser energy monitoring system and method to solve at least one of the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a laser energy monitoring system, the system comprising: Lasers are used to generate laser beams that include both ultraviolet and visible wavelengths. A high-reflectivity mirror is used to receive the laser beam, reflect part of the ultraviolet band beam to the application end, and transmit the remaining ultraviolet and visible bands to form a remaining laser beam for energy monitoring. A beam splitter is used to disperse the remaining laser beam, removing the visible light beam and leaving the ultraviolet light beam. An aperture, by limiting the beam aperture in the ultraviolet band, filters stray light and ensures the stability of the beam size and energy entering the subsequent optical path; The scattering element homogenizes the ultraviolet light beam passing through the aperture through scattering, converting coherent laser into a uniform surface light source. A photodetector is used to receive homogenized ultraviolet light signals and convert them into electrical signals to enable real-time monitoring of ultraviolet laser energy.

[0007] Optionally, the beam-splitting element is a blazed grating; the scattering element is a frosted glass plate; and the photodetector is a broadband photodiode.

[0008] Optionally, the center wavelength of the ultraviolet band is 266 nm, and the center wavelength of the visible band is 532 nm.

[0009] Optionally, the system also includes: The data acquisition module is used to acquire the electrical signal to obtain real-time sampled data; The data processing module is used to calculate real-time pulse energy data based on the real-time sampling data and store the real-time pulse energy data in a buffer area. The feedback adjustment module is used to calculate the target pulse energy data and adjust the angle of the crystal in the laser using the dichotomy method based on the target pulse energy data, so that the laser energy monitoring system outputs a laser beam with the target pulse energy.

[0010] Optionally, the data processing module is further configured to determine whether the buffer is full at the current moment; if the buffer is full at the current moment, calculate the first key calculation index parameter of the pulse energy data at the current moment and calculate the second key calculation index parameter of the pulse energy data in the time period before the current moment; determine whether the first key calculation index parameter is greater than or equal to the second key calculation index parameter; if the first key calculation index parameter is greater than or equal to the second key calculation index parameter, issue an alarm signal.

[0011] Optionally, the first key calculation indicator parameter includes a first peak fluctuation value, and the second key calculation indicator parameter includes a second peak fluctuation value; Alternatively, the first key calculation indicator parameter may include a first relative standard deviation, and the second key calculation indicator parameter may include a second relative standard deviation.

[0012] Optionally, the first key calculation index parameter includes the first peak fluctuation value and the first relative standard deviation; The second key calculation index parameters include the second peak fluctuation value and the second relative standard deviation; The step of determining whether the first key calculation indicator parameter is greater than or equal to the second key calculation indicator parameter includes: Determine whether the first peak fluctuation value is greater than or equal to the second peak fluctuation value; If the first peak-to-peak fluctuation value is greater than or equal to the second peak-to-peak fluctuation value, an alarm signal is issued and the target pulse energy data is calculated. Based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using the dichotomy method so that the laser energy monitoring system outputs a laser beam with the target pulse energy. If the first peak-to-peak fluctuation value is less than the second peak-to-peak fluctuation value, then determine whether the first relative standard deviation is greater than or equal to the second relative standard deviation; If the first relative standard deviation is greater than or equal to the second relative standard deviation, an alarm signal is issued and the target pulse energy data is calculated. Based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using the dichotomy method so that the laser energy monitoring system outputs a laser beam with the target pulse energy. If the first relative standard deviation is less than the second relative standard deviation, energy monitoring continues.

[0013] Optionally, the system also includes: A temperature control module is used to adjust the phase matching angle of the crystal in the laser according to temperature changes; the formula for adjusting the phase matching angle of the crystal in the laser according to temperature changes is:

[0014] In the formula, The change in temperature The initial temperature; The temperature after the change; This is the offset; The phase matching angle; The initial angle for the fourth harmonic phase matching of the crystal; It is the temperature refractive index coefficient of visible light in a crystal; It is the temperature refractive index coefficient of ultraviolet light in a crystal; for At that time, the refractive index of the o-ray corresponding to the visible band light; for At that time, the refractive index of the e-ray corresponding to the ultraviolet band light.

[0015] A second aspect of the present invention provides a laser energy monitoring method for an energy monitoring system as described in the first aspect of the present invention, the method comprising: Using lasers to generate laser beams that include both ultraviolet and visible wavelengths; The laser beam is received by a high-reflectivity mirror, which reflects part of the ultraviolet band beam to the application end and transmits the remaining small amount of ultraviolet and visible bands to form a residual laser beam for energy monitoring. The remaining laser beam is dispersed and split using a beam splitter to separate and remove the visible wavelength beam, leaving the ultraviolet wavelength beam. By using an aperture to filter stray light by limiting the beam aperture in the ultraviolet band, the size and energy of the beam entering the subsequent optical path are kept stable. By using scattering elements to homogenize the ultraviolet light beam passing through the aperture through scattering, coherent laser light is converted into a uniform surface light source. By using a photodetector to receive homogenized ultraviolet light signals and convert them into electrical signals, real-time monitoring of ultraviolet laser energy can be achieved.

[0016] Optionally, the method further includes: The electrical signal is acquired using a data acquisition module to obtain real-time sampled data; The real-time pulse energy data is calculated based on the real-time sampled data using the data processing module, and the real-time pulse energy data is stored in the buffer area; The target pulse energy data is calculated using a feedback adjustment module. Based on the target pulse energy data, the angle of the crystal in the laser is adjusted using a binary method so that the laser energy monitoring system outputs a laser beam with the target pulse energy.

[0017] Optionally, the method further includes: The data processing module determines whether the buffer is full at the current moment; if the buffer is full at the current moment, the first key calculation index parameter of the pulse energy data at the current moment and the second key calculation index parameter of the pulse energy data in the time period before the current moment are calculated; it is determined whether the first key calculation index parameter is greater than or equal to the second key calculation index parameter; if the first key calculation index parameter is greater than or equal to the second key calculation index parameter, an alarm signal is issued.

[0018] Optionally, the first key calculation indicator parameter includes a first peak fluctuation value, and the second key calculation indicator parameter includes a second peak fluctuation value; Alternatively, the first key calculation indicator parameter may include a first relative standard deviation, and the second key calculation indicator parameter may include a second relative standard deviation.

[0019] Optionally, the first key calculation index parameter includes the first peak fluctuation value and the first relative standard deviation; The second key calculation index parameters include the second peak fluctuation value and the second relative standard deviation; The step of determining whether the first key calculation indicator parameter is greater than or equal to the second key calculation indicator parameter includes: Determine whether the first peak fluctuation value is greater than or equal to the second peak fluctuation value; If the first peak-to-peak fluctuation value is greater than or equal to the second peak-to-peak fluctuation value, an alarm signal is issued and the target pulse energy data is calculated. Based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using the dichotomy method so that the laser energy monitoring system outputs a laser beam with the target pulse energy. If the first peak-to-peak fluctuation value is less than the second peak-to-peak fluctuation value, then determine whether the first relative standard deviation is greater than or equal to the second relative standard deviation; If the first relative standard deviation is greater than or equal to the second relative standard deviation, an alarm signal is issued and the target pulse energy data is calculated. Based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using the dichotomy method so that the laser energy monitoring system outputs a laser beam with the target pulse energy. If the first relative standard deviation is less than the second relative standard deviation, energy monitoring continues.

[0020] The beneficial effects of this invention are as follows: The technical solution described in this invention can effectively suppress the influence of stray light while ensuring detection accuracy, improve the signal-to-noise ratio, further optimize the stability and repeatability of energy monitoring, and is more suitable for long-term industrial operation. Attached Figure Description

[0021] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0022] Figure 1 A schematic diagram of a laser energy monitoring system provided in one embodiment of the present invention is shown.

[0023] Figure 2 A schematic diagram of a laser energy monitoring system provided in another embodiment of the present invention is shown.

[0024] Figure 3 A flowchart of the operation of a laser energy monitoring system provided in one embodiment of the present invention is shown.

[0025] Figure 4 A flowchart of the operation of a laser energy monitoring system provided in another embodiment of the present invention is shown.

[0026] Figure 5 This diagram illustrates the workflow of a laser energy monitoring system according to yet another embodiment of the present invention.

[0027] Figure 6 This diagram illustrates a flowchart of the laser energy monitoring system for calculating target pulse energy data, as provided in an embodiment of the present invention. Detailed Implementation

[0028] To more clearly illustrate the present invention, the following description, in conjunction with embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0029] Current technologies mostly use broadband photodiodes as the main body for energy monitoring. These typically involve either introducing the diffuse reflection beam outside the cavity via optical fiber or directly detecting it inside the cavity. Using optical fiber detection consumes some of the ultraviolet laser's energy, requiring an increase in the solid-state laser's output energy, which significantly increases the product's technical complexity and cost. Directly detecting the diffuse reflection beam inside the cavity can only detect changes in a small portion of the energy range, and it cannot effectively detect some energy failure modes; optical fiber detection also suffers from this problem. Using pyroelectric probes for testing is costly and has a slow response time, and it is sensitive to environmental temperature and humidity, easily affected by external interference leading to measurement errors.

[0030] In view of this, one embodiment of the present invention provides a laser energy monitoring system, comprising: a laser for generating a laser beam containing ultraviolet and visible wavelengths; a high-reflectivity mirror for receiving the laser beam, reflecting a portion of the ultraviolet wavelength beam to an application end, and transmitting the remaining ultraviolet and visible wavelengths to form a residual laser beam for energy monitoring; a beam splitter for dispersing and splitting the residual laser beam, removing the visible wavelength beam and leaving the ultraviolet wavelength beam; an aperture for filtering stray light by limiting the aperture of the ultraviolet wavelength beam, ensuring the stability of the beam size and energy entering the subsequent optical path; a scattering element for homogenizing the ultraviolet wavelength beam passing through the aperture through scattering, converting the coherent laser into a uniform surface light source; and a photodetector for receiving the homogenized ultraviolet light signal and converting it into an electrical signal to realize real-time monitoring of the ultraviolet laser energy.

[0031] In a specific example, such as Figure 1 As shown, the system includes: a laser 10 for generating a laser beam 101 containing ultraviolet and visible wavelengths; a high-reflectivity mirror 20 for receiving the laser beam 101, reflecting a portion of the ultraviolet beam 201 to the application end, and transmitting the remaining ultraviolet and visible wavelengths to form a residual laser beam 202 for energy monitoring; a beam splitter 30 for dispersing and splitting the residual laser beam, removing the visible wavelength beam 301, and leaving the ultraviolet beam 302; an aperture 40 for filtering stray light by limiting the aperture of the ultraviolet beam 302, ensuring the stability of the beam size and energy entering the subsequent optical path; a scattering element 50 for homogenizing the ultraviolet beam passing through the aperture through scattering, converting the coherent laser into a uniform surface light source; and a photodetector 60 for receiving the homogenized ultraviolet light signal and converting it into an electrical signal to achieve real-time monitoring of the ultraviolet laser energy.

[0032] In a specific example, the laser is a deep ultraviolet solid-state laser.

[0033] In a specific example, the high-reflectivity mirror is a deep ultraviolet high-reflectivity lens with a reflectivity of 99.9% in the ultraviolet band. The high-reflectivity mirror reflects part of the ultraviolet band beam to supply the application end with high energy density. The remaining ultraviolet and visible bands with similar transmission energy levels form the remaining laser beam for energy monitoring. The energy of the two wavelengths is on the same order of magnitude, with the energy of the ultraviolet band being slightly lower than that of the visible band. The energy of the ultraviolet band main light used by the customer is basically the same as that of the laser output port.

[0034] In a specific example, the aperture of the stop is 4 mm. This stop is located in the outgoing light path of a specific diffraction order and is used for spatial filtering; the visible light beam is blocked by the stop due to spatial distribution differences, and the final output is a purified ultraviolet light beam.

[0035] The technical solution described in this example can effectively suppress the influence of stray light while ensuring detection accuracy, improve the signal-to-noise ratio, further optimize the stability and repeatability of energy monitoring, and is more suitable for the long-term operation requirements of industrial applications.

[0036] In one possible implementation, the system further includes: a temperature control module for adjusting the phase matching angle of the crystal in the laser according to temperature changes; the formula for adjusting the phase matching angle of the crystal in the laser according to temperature changes is:

[0037] In the formula, For temperature change; This is the offset; The phase matching angle; The initial angle for the fourth harmonic phase matching of the crystal; It is the temperature refractive index coefficient in the visible band of a crystal; It is the temperature refractive index coefficient in the ultraviolet band of the crystal; for At that time, the refractive index of the visible light corresponding to the o-wavelength; for At that time, the e-ray refractive index corresponding to the ultraviolet band.

[0038] In a specific example, the crystal is barium metaborate (BBO) crystal. Furthermore,

[0039]

[0040] In the formula, λ is the wavelength.

[0041]

[0042]

[0043] In the formula, λ is the wavelength.

[0044] Furthermore, based on experiments with the laser energy monitoring system, we can conclude that:

[0045]

[0046] Furthermore, the initial angle for the fourth harmonic phase matching of the BBO crystal is:

[0047] Furthermore, We can obtain:

[0048] This example quantifies the impact of thermal effects on phase matching conditions through the correlation between temperature, refractive index, and phase matching angle. This is a crucial basis for the quantitative adjustment of laser energy monitoring systems. For every 10°C increase in temperature, the shift is approximately... .

[0049] In one possible implementation, the beam-splitting element is a blazed grating; the scattering element is a frosted glass plate; and the photodetector is a broadband photodiode.

[0050] In a specific example, the beam splitter is a specific blazed grating, and the ultraviolet beam is incident at 35°; this causes beams of different wavelengths to be diffracted and dispersed in space at specific angles.

[0051] In a specific example, a frosted glass attenuator reduces the intensity of the light beam while improving beam uniformity.

[0052] In a specific example, the photodetector is a photodiode.

[0053] In one possible implementation, the center wavelength of the ultraviolet band is 266 nm, and the center wavelength of the visible band is 532 nm.

[0054] In one possible implementation, the system further includes: a data acquisition module for acquiring the electrical signal to obtain real-time sampling data; a data processing module for calculating real-time pulse energy data based on the real-time sampling data and storing the real-time pulse energy data in a buffer; and a feedback adjustment module for calculating target pulse energy data and adjusting the angle of the crystal in the laser using a binary method based on the target pulse energy data, so that the laser energy monitoring system outputs a laser beam with the target pulse energy.

[0055] In a specific example, such as Figure 2 As shown, the system also includes: a data acquisition module 70, i.e., a voltage acquisition module, which collects the electrical signals of the photodiode at a specific sampling rate and transmits the sampled data to the data processing module; a data processing module 80, i.e., a data analysis module, which obtains pulse energy data by calculating the sampled data and monitors the laser energy by analyzing the pulse energy data; and a feedback adjustment module 90, which calculates the target pulse energy data and adjusts the physical parameters of the crystal in the laser using a binary method based on the target pulse energy data, so that the laser outputs the target pulse energy.

[0056] In a specific example, such as Figure 2 As shown, the laser energy monitoring system includes an amplification and voltage regulation circuit module 100, which is used to amplify and regulate the electrical signal.

[0057] In one possible implementation, the data processing module is further configured to determine whether the buffer is full at the current moment; if the buffer is full at the current moment, calculate the first key calculation index parameter of the pulse energy data at the current moment and calculate the second key calculation index parameter of the pulse energy data in the time period before the current moment; determine whether the first key calculation index parameter is greater than or equal to the second key calculation index parameter; if the first key calculation index parameter is greater than or equal to the second key calculation index parameter, issue an alarm signal.

[0058] In a specific example, the data processing module processes the sampled data from the data acquisition module to obtain pulse energy data; it continuously receives pulse energy data and stores it in a buffer while waiting for new pulse energy data to be continuously imported; it calculates and analyzes the key calculation index parameters of the pulse energy data in the buffer; if the first key calculation index parameter is greater than or equal to the second key calculation index parameter, the system's energy operation is unstable, triggering an alarm signal for abnormal energy; it then starts the feedback adjustment module, which corrects the laser's energy output by adjusting the physical parameters of the laser crystal (such as angle and position). After the adjustment is completed, the entire process restarts, forming a continuous closed-loop monitoring and adjustment.

[0059] In a specific example, if the first key calculation indicator parameter is less than the second key calculation indicator parameter, the system is determined to be stable, and the process returns directly to continue monitoring.

[0060] In one possible implementation, the first key calculation indicator parameter includes a first peak-to-peak fluctuation value, and the second key calculation indicator parameter includes a second peak-to-peak fluctuation value; or the first key calculation indicator parameter includes a first relative standard deviation, and the second key calculation indicator parameter includes a second relative standard deviation.

[0061] In a specific instance, peak-to-peak fluctuation is the percentage of the difference between the maximum and minimum output power values ​​to the average power value, representing the range of output power variation over a certain period of time.

[0062] In a specific instance, such as Figure 3 As shown, pulse energy data is input, the buffer is updated, and it is determined whether the buffer is full. If not, it waits for new data to be imported. If so, the current peak-to-peak fluctuation is calculated. It is determined whether the current peak-to-peak fluctuation value is greater than or equal to the historical peak-to-peak fluctuation value. If not, the system is determined to be stable and monitoring continues. If so, an alarm signal for abnormal energy is triggered, and feedback is sent to the nonlinear crystal adjustment module (i.e., the feedback adjustment module) for correction.

[0063] In a specific instance, the relative standard deviation (RSD) is an important statistic describing the dispersion of data, typically expressed as a percentage by comparing the standard deviation to the mean.

[0064] In the formula, This is the average value.

[0065] In a specific instance, such as Figure 4 As shown, pulse energy data is input, the buffer is updated, and it is determined whether the buffer is full. If not, it waits for new data to be imported. If so, the current relative standard deviation is calculated. It is then determined whether the current relative standard deviation is greater than or equal to the historical relative standard deviation. If not, the system is determined to be stable and monitoring continues. If so, an alarm signal indicating an abnormal energy is triggered, and the nonlinear crystal adjustment module (i.e., the feedback adjustment module) is fed back for correction.

[0066] In a specific example, the real-time monitoring decision logic includes setting a buffer interval value based on the recorded values ​​of the relative standard deviation and peak-to-peak fluctuation of the laser energy obtained from the output of the solid-state laser. Once the buffer data is full, the current relative standard deviation and current peak-to-peak fluctuation data are calculated and compared with the recorded relative standard deviation and recorded peak-to-peak fluctuation. If an anomaly is found, the nonlinear crystal adjustment module (i.e., the feedback adjustment module) is fed back for correction.

[0067] This embodiment can more accurately represent the output energy by setting key calculation index parameters, including peak-to-peak fluctuation value and relative standard deviation.

[0068] In one possible implementation, the first key calculation index parameter includes a first peak-to-peak fluctuation value and a first relative standard deviation; the second key calculation index parameter includes a second peak-to-peak fluctuation value and a second relative standard deviation; determining whether the first key calculation index parameter is greater than or equal to the second key calculation index parameter includes: determining whether the first peak-to-peak fluctuation value is greater than or equal to the second peak-to-peak fluctuation value; if the first peak-to-peak fluctuation value is greater than or equal to the second peak-to-peak fluctuation value, an alarm signal is issued and target pulse energy data is calculated; based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using a bisection method so that the laser energy monitoring system outputs a laser beam with the target pulse energy; if the first peak-to-peak fluctuation value is less than the second peak-to-peak fluctuation value, the first relative standard deviation is determined whether it is greater than or equal to the second relative standard deviation; if the first relative standard deviation is greater than or equal to the second relative standard deviation, an alarm signal is issued and target pulse energy data is calculated; based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using a bisection method so that the laser energy monitoring system outputs a laser beam with the target pulse energy; if the first relative standard deviation is less than the second relative standard deviation, energy monitoring continues.

[0069] In a specific instance, such as Figure 5 As shown, pulse energy data is input, the buffer is updated, and it is determined whether the buffer is full. If not, it waits for new data to be imported. If so, the current peak-to-peak fluctuation and the current relative standard deviation are calculated. It is then determined whether the current peak-to-peak fluctuation value is greater than or equal to the historical peak-to-peak fluctuation value. If so, an alarm signal indicating an energy anomaly is triggered, and the nonlinear crystal adjustment module (i.e., the feedback adjustment module) is fed back for correction. If not, it is determined whether the current relative standard deviation is greater than or equal to the historical relative standard deviation. If not, the system is deemed stable and monitoring continues. If so, an alarm signal indicating an energy anomaly is triggered, and the nonlinear crystal adjustment module (i.e., the feedback adjustment module) is fed back for correction.

[0070] In a specific instance, in actual production, in order to ensure that the waveform envelope is not distorted, the sampling frequency should be greater than 10 times the actual frequency.

[0071] In a specific example, the time-pulse waveform of the laser is a Gaussian-like waveform, and the output electrical signal is also Gaussian. Therefore, a Gaussian function is used to describe this waveform:

[0072] In the formula, A is the peak amplitude of the pulse; σ represents the time center of the pulse peak; σ is the standard deviation of the Gaussian distribution, reflecting the pulse width characteristics. This refers to the voltage at the receiving end when there is no sampling signal input. It is an exponential function.

[0073] The model uses A, The three parameters σ are variables to be optimized, aiming to minimize the difference between their calculated values ​​and the actual acquired and corrected pulse data through fitting.

[0074] In a specific example, such as Figure 6 As shown, the calculation of target pulse energy data includes: acquiring raw voltage-time data; preprocessing the raw voltage data; estimating the initial parameters of the variable to be optimized; optimizing the parameters using the nonlinear least squares method and determining whether the convergence condition is met; if so, obtaining the optimal parameters; calculating the target pulse energy by integrating the optimal parameters; if not, re-estimating the initial parameters of the variable to be optimized.

[0075] In a specific example, preprocessing the raw voltage data includes: the acquired raw voltage is the sum of the pulse signal amplitude and the voltage amplitude generated by the circuit module itself, and the raw voltage needs to be calibrated. The calibration formula is:

[0076] In the formula, The voltage after calibration; This is the original voltage; This is the receiving voltage without a sampling signal input.

[0077] In a specific example, parameter optimization using the nonlinear least squares method includes: Step 10: Initial Parameter Estimation. Since the Levenberg-Marquardt algorithm is a nonlinear least squares optimization technique, its convergence speed and the accuracy of the final result heavily depend on the selection of initial parameter values. An initial value estimation method based on pulse time-domain waveform characteristics is adopted: from the corrected pulse data sequence, the maximum absolute value of the voltage is identified, and this value is directly used as the initial estimate A0 of the peak amplitude A; simultaneously, the specific time point corresponding to this maximum value is recorded, and this is used as the initial estimate t of the time center. 00 The initial value σ0 of the pulse width parameter is calculated using the mathematical relationship between the full width at half maximum (FWHM) of the pulse waveform and its standard deviation. Specifically, based on the characteristics of the Gaussian function, the following relationship exists: By measuring the actual value of the full width of the upper half of the corrected pulse waveform, the initial estimate of the standard deviation σ0 can be calculated by inverse solution.

[0078] The initial value estimation method in this embodiment provides a high-quality starting point for subsequent iterative optimization, effectively avoiding slow convergence or getting trapped in local optima due to improper initial guesses.

[0079] Step 20: Function definition and initialization.

[0080] Furthermore, the parameter vector for:

[0081] Furthermore, the initial parameter vector for:

[0082] Furthermore, the objective function for:

[0083] Furthermore, the objective function is optimized as follows:

[0084] In the formula, the scaling factor V = 2; the convergence tolerance... Initial damping factor Maximum number of iterations M=500; Current number of iterations K=0.

[0085] Step 30: Calculate the Taylor expansion and Jacobian matrix.

[0086] Furthermore, let the parameter update amount be... ; Furthermore, Taylor expands to:

[0087] In the formula, for Jacobian matrix, .

[0088] Furthermore, The element in the i-th row and j-th column is:

[0089] Furthermore,

[0090]

[0091]

[0092]

[0093] Step 40: Parameter update equation.

[0094] Furthermore, the following parameter update equation is calculated:

[0095] In the formula, This is the initial damping factor; It is an identity matrix.

[0096] Furthermore, the parameter update amount is obtained. Update parameter formula:

[0097] In the formula, It is the parameter vector of the Kth iteration. The peak amplitude of the Kth iteration is given. The time center of the pulse peak occurrence in the Kth iteration is... Let $\frac{ ... The parameter vector for the (K+1)th iteration.

[0098] Step 50: Adjust the damping factor for the next iteration.

[0099] Furthermore, calculate the scaling factor. :

[0100] Furthermore, when Accept the step size parameter, continue to reduce the damping factor by scaling factor, and adopt Gaussian and Newton models in the next iteration; when If the step size parameter is not accepted, the damping factor is increased by the scaling factor, and the gradient descent method is adopted. Step 60: Check if the convergence condition is met. If it is, output the optimal parameters: .

[0101] Step 70: Calculate the target pulse energy. The pulse energy is proportional to the integral of the optical power over time, and therefore proportional to the area under the voltage-time curve.

[0102] This embodiment uses the Levenberg-Marquardt algorithm, which is a combination of gradient descent and Gaussian and Newton's methods. It introduces a damping factor to dynamically adjust the iteration step size and direction, thereby ensuring stability while pursuing convergence speed.

[0103] In view of this, one embodiment of the present invention provides a laser energy monitoring method, the method comprising: generating a laser beam containing ultraviolet and visible wavelengths using a laser; receiving the laser beam using a high-reflectivity mirror, reflecting a portion of the ultraviolet wavelength beam to an application end, and transmitting the remaining small amount of ultraviolet and visible wavelengths to form a residual laser beam for energy monitoring; performing dispersive beam splitting on the residual laser beam using a beam splitter to separate and remove the visible wavelength beam, leaving the ultraviolet wavelength beam; filtering stray light using an aperture to limit the aperture of the ultraviolet wavelength beam, ensuring the stability of the beam size and energy entering the subsequent optical path; homogenizing the ultraviolet wavelength beam passing through the aperture using a scattering element through scattering, converting the coherent laser into a uniform surface light source; and receiving the homogenized ultraviolet light signal using a photodetector and converting it into an electrical signal to achieve real-time monitoring of the ultraviolet laser energy.

[0104] The technical solution described in this example can effectively suppress the influence of stray light while ensuring detection accuracy, improve the signal-to-noise ratio, further optimize the stability and repeatability of energy monitoring, and is more suitable for the long-term operation requirements of industrial applications.

[0105] In one possible implementation, the method further includes: adjusting the phase matching angle of the crystal in the laser according to temperature changes using a temperature control module; the formula for adjusting the phase matching angle of the crystal in the laser according to temperature changes is:

[0106] In the formula, For temperature change; This is the offset; The phase matching angle; The initial angle for the fourth harmonic phase matching of the crystal; It is the temperature refractive index coefficient in the visible band of a crystal; It is the temperature refractive index coefficient in the ultraviolet band of the crystal; for At that time, the refractive index of the visible light corresponding to the o-wavelength; for At that time, the e-ray refractive index corresponding to the ultraviolet band; for; for; for; for.

[0107] In a specific example, the crystal is barium metaborate (BBO) crystal. Furthermore,

[0108]

[0109] In the formula, λ is the wavelength.

[0110]

[0111]

[0112] In the formula, λ is the wavelength.

[0113] Furthermore, based on experiments with the laser energy monitoring system, we can conclude that:

[0114]

[0115] Furthermore, the initial angle for the fourth harmonic phase matching of the BBO crystal is:

[0116] Furthermore, We can obtain:

[0117] This example quantifies the impact of thermal effects on phase matching conditions through the correlation between temperature, refractive index, and phase matching angle. This is a crucial basis for the quantitative adjustment of laser energy monitoring systems. For every 10°C increase in temperature, the shift is approximately... .

[0118] In one possible implementation, the method further includes: acquiring real-time sampling data by using a data acquisition module to acquire the electrical signal; calculating real-time pulse energy data by using a data processing module based on the real-time sampling data, and storing the real-time pulse energy data in a buffer; calculating target pulse energy data by using a feedback adjustment module, and adjusting the angle of the crystal in the laser by using a bisection method based on the target pulse energy data, so that the laser energy monitoring system outputs a laser beam with the target pulse energy.

[0119] It should be noted that the relevant content of the methods in this example corresponds to the relevant content of the system, and will not be repeated here.

[0120] In one possible implementation, the method further includes: using a data processing module to determine whether the buffer is full at the current moment; if the buffer is full at the current moment, calculating a first key calculation index parameter of the pulse energy data at the current moment and calculating a second key calculation index parameter of the pulse energy data in the time period before the current moment; determining whether the first key calculation index parameter is greater than or equal to the second key calculation index parameter; if the first key calculation index parameter is greater than or equal to the second key calculation index parameter, issuing an alarm signal.

[0121] It should be noted that the relevant content of the methods in this example corresponds to the relevant content of the system, and will not be repeated here.

[0122] In one possible implementation, the first key calculation indicator parameter includes a first peak-to-peak fluctuation value, and the second key calculation indicator parameter includes a second peak-to-peak fluctuation value; or the first key calculation indicator parameter includes a first relative standard deviation, and the second key calculation indicator parameter includes a second relative standard deviation.

[0123] It should be noted that the relevant content of the methods in this example corresponds to the relevant content of the system, and will not be repeated here.

[0124] In one possible implementation, the first key calculation index parameter includes a first peak-to-peak fluctuation value and a first relative standard deviation; the second key calculation index parameter includes a second peak-to-peak fluctuation value and a second relative standard deviation; determining whether the first key calculation index parameter is greater than or equal to the second key calculation index parameter includes: determining whether the first peak-to-peak fluctuation value is greater than or equal to the second peak-to-peak fluctuation value; if the first peak-to-peak fluctuation value is greater than or equal to the second peak-to-peak fluctuation value, an alarm signal is issued and target pulse energy data is calculated; based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using a bisection method so that the laser energy monitoring system outputs a laser beam with the target pulse energy; if the first peak-to-peak fluctuation value is less than the second peak-to-peak fluctuation value, the first relative standard deviation is determined whether it is greater than or equal to the second relative standard deviation; if the first relative standard deviation is greater than or equal to the second relative standard deviation, an alarm signal is issued and target pulse energy data is calculated; based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using a bisection method so that the laser energy monitoring system outputs a laser beam with the target pulse energy; if the first relative standard deviation is less than the second relative standard deviation, energy monitoring continues.

[0125] It should be noted that the relevant content of the methods in this example corresponds to the relevant content of the system, and will not be repeated here.

[0126] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A laser energy monitoring system, characterized in that, The system includes: Lasers are used to generate laser beams that include both ultraviolet and visible wavelengths. A high-reflectivity mirror is used to receive the laser beam, reflect part of the ultraviolet band beam to the application end, and transmit the remaining ultraviolet and visible bands to form a remaining laser beam for energy monitoring. A beam splitter is used to disperse the remaining laser beam, removing the visible light beam and leaving the ultraviolet light beam. An aperture, by limiting the beam aperture in the ultraviolet band, filters stray light and ensures the stability of the beam size and energy entering the subsequent optical path; The scattering element homogenizes the ultraviolet light beam passing through the aperture through scattering, converting coherent laser into a uniform surface light source. A photodetector is used to receive homogenized ultraviolet light signals and convert them into electrical signals to enable real-time monitoring of ultraviolet laser energy.

2. The laser energy monitoring system according to claim 1, characterized in that, The beam-splitting element is a blazed grating; the scattering element is a frosted glass plate; and the photodetector is a broadband photodiode.

3. The laser energy monitoring system according to claim 1, characterized in that, The center wavelength of the ultraviolet band is 266 nm, and the center wavelength of the visible band is 532 nm.

4. The laser energy monitoring system according to claim 1, characterized in that, The system also includes: The data acquisition module is used to acquire the electrical signal to obtain real-time sampled data; The data processing module is used to calculate real-time pulse energy data based on the real-time sampling data and store the real-time pulse energy data in a buffer area. The feedback adjustment module is used to calculate the target pulse energy data and adjust the angle of the crystal in the laser using the dichotomy method based on the target pulse energy data, so that the laser energy monitoring system outputs a laser beam with the target pulse energy.

5. The laser energy monitoring system according to claim 4, characterized in that, The data processing module is further configured to determine whether the buffer is full at the current moment; if the buffer is full at the current moment, it calculates the first key calculation index parameter of the pulse energy data at the current moment and the second key calculation index parameter of the pulse energy data in the time period before the current moment; it determines whether the first key calculation index parameter is greater than or equal to the second key calculation index parameter; if the first key calculation index parameter is greater than or equal to the second key calculation index parameter, it issues an alarm signal.

6. The laser energy monitoring system according to claim 5, characterized in that, The first key calculation indicator parameter includes a first peak fluctuation value, and the second key calculation indicator parameter includes a second peak fluctuation value; Alternatively, the first key calculation indicator parameter may include a first relative standard deviation, and the second key calculation indicator parameter may include a second relative standard deviation.

7. The laser energy monitoring system according to claim 5, characterized in that, The first key calculation index parameters include the first peak fluctuation value and the first relative standard deviation; The second key calculation index parameters include the second peak fluctuation value and the second relative standard deviation; The step of determining whether the first key calculation indicator parameter is greater than or equal to the second key calculation indicator parameter includes: Determine whether the first peak fluctuation value is greater than or equal to the second peak fluctuation value; If the first peak-to-peak fluctuation value is greater than or equal to the second peak-to-peak fluctuation value, an alarm signal is issued and the target pulse energy data is calculated. Based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using the dichotomy method so that the laser energy monitoring system outputs a laser beam with the target pulse energy. If the first peak-to-peak fluctuation value is less than the second peak-to-peak fluctuation value, then determine whether the first relative standard deviation is greater than or equal to the second relative standard deviation; If the first relative standard deviation is greater than or equal to the second relative standard deviation, an alarm signal is issued and the target pulse energy data is calculated. Based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using the dichotomy method so that the laser energy monitoring system outputs a laser beam with the target pulse energy. If the first relative standard deviation is less than the second relative standard deviation, energy monitoring continues.

8. The laser energy monitoring system according to claim 1, characterized in that, The system also includes: A temperature control module is used to adjust the phase matching angle of the crystal in the laser according to temperature changes; the formula for adjusting the phase matching angle of the crystal in the laser according to temperature changes is: In the formula, The change in temperature The initial temperature; The temperature after the change; This is the offset; The phase matching angle; The initial angle for the fourth harmonic phase matching of the crystal; It is the temperature refractive index coefficient of visible light in a crystal; It is the temperature refractive index coefficient of ultraviolet light in a crystal; for At that time, the refractive index of the o-ray corresponding to the visible band light; for At that time, the refractive index of the e-ray corresponding to the ultraviolet band light.

9. A laser energy monitoring method for an energy monitoring system as described in any one of claims 1 to 8, characterized in that, The method includes: Using lasers to generate laser beams that include both ultraviolet and visible wavelengths; The laser beam is received by a high-reflectivity mirror, which reflects part of the ultraviolet band beam to the application end and transmits the remaining small amount of ultraviolet and visible bands to form a residual laser beam for energy monitoring. The remaining laser beam is dispersed and split using a beam splitter to separate and remove the visible wavelength beam, leaving the ultraviolet wavelength beam. By using an aperture to filter stray light by limiting the beam aperture in the ultraviolet band, the size and energy of the beam entering the subsequent optical path are kept stable. By using scattering elements to homogenize the ultraviolet light beam passing through the aperture through scattering, coherent laser light is converted into a uniform surface light source. By using a photodetector to receive homogenized ultraviolet light signals and convert them into electrical signals, real-time monitoring of ultraviolet laser energy can be achieved.

10. The laser energy monitoring method according to claim 9, characterized in that, The method also includes: The electrical signal is acquired using a data acquisition module to obtain real-time sampled data; The real-time pulse energy data is calculated based on the real-time sampled data using the data processing module, and the real-time pulse energy data is stored in the buffer area; The target pulse energy data is calculated using a feedback adjustment module. Based on the target pulse energy data, the angle of the crystal in the laser is adjusted using a binary method so that the laser energy monitoring system outputs a laser beam with the target pulse energy.

11. The laser energy monitoring method according to claim 10, characterized in that, The method also includes: The data processing module determines whether the buffer is full at the current moment; if the buffer is full at the current moment, the first key calculation index parameter of the pulse energy data at the current moment and the second key calculation index parameter of the pulse energy data in the time period before the current moment are calculated; it is determined whether the first key calculation index parameter is greater than or equal to the second key calculation index parameter; if the first key calculation index parameter is greater than or equal to the second key calculation index parameter, an alarm signal is issued.

12. The laser energy monitoring method according to claim 11, characterized in that, The first key calculation indicator parameter includes a first peak fluctuation value, and the second key calculation indicator parameter includes a second peak fluctuation value; Alternatively, the first key calculation indicator parameter may include a first relative standard deviation, and the second key calculation indicator parameter may include a second relative standard deviation.

13. The laser energy monitoring method according to claim 11, characterized in that, The first key calculation index parameters include the first peak fluctuation value and the first relative standard deviation; The second key calculation index parameters include the second peak fluctuation value and the second relative standard deviation; The step of determining whether the first key calculation indicator parameter is greater than or equal to the second key calculation indicator parameter includes: Determine whether the first peak fluctuation value is greater than or equal to the second peak fluctuation value; If the first peak-to-peak fluctuation value is greater than or equal to the second peak-to-peak fluctuation value, an alarm signal is issued and the target pulse energy data is calculated. Based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using the dichotomy method so that the laser energy monitoring system outputs a laser beam with the target pulse energy. If the first peak-to-peak fluctuation value is less than the second peak-to-peak fluctuation value, then determine whether the first relative standard deviation is greater than or equal to the second relative standard deviation; If the first relative standard deviation is greater than or equal to the second relative standard deviation, an alarm signal is issued and the target pulse energy data is calculated. Based on the target pulse energy data, the physical parameters of the crystal in the laser are adjusted using the dichotomy method so that the laser energy monitoring system outputs a laser beam with the target pulse energy. If the first relative standard deviation is less than the second relative standard deviation, energy monitoring continues.

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