Method and device for measuring peak power of pulse laser
By establishing a measurement optical path and signal processing circuit, and using a comparator and FPGA processor to control the AD sampling module, the accuracy and cost of peak power measurement of pulsed lasers are solved, and an efficient and low-cost measurement method is realized.
Patent Information
- Application Number
- CN202411523508.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-29
- Publication Date
- 2025-02-07
AI Technical Summary
The prior art has difficulty accurately measuring the peak power of a pulsed laser, especially in terms of cost and complexity.
By establishing a measurement optical path, using a spectrometer to divide the pulsed laser into two beams, using a photodiode as a receiver, generating a photocurrent signal, and filtering and amplifying through a signal processing circuit, and controlling the AD sampling module with a comparator and FPGA processor to ensure that The sampling moment appears at the peak position.
Accurate measurement of the peak power of the pulsed laser is achieved, reducing system cost and complexity, and is suitable for industrial applications.
Smart Images
Figure CN119394597A_ABST
Abstract
Description
[Technical field]:
[0001] The invention relates to the technical field of laser power measurement, in particular to a method and a device for measuring peak power of a pulsed laser. [Background technology]:
[0002] As a commonly used light source, laser is widely used in many technical fields such as measurement and processing. For lasers, the laser power they output is their basic technical parameter, especially in the field of laser processing, where the laser power directly determines the quality and effect of the processing.
[0003] In order to increase the output power of lasers, pulsed lasers have emerged, which gather laser energy for a period of time and then output it in a concentrated manner to produce instantaneous huge energy light pulses. Figure 1 As shown in the figure, pulse laser is a laser that outputs in the form of pulses, forming a series of short, high-energy pulses in time. The peak power of this laser is very high, and the energy is concentratedly released in a short time, which has a small heating effect and is conducive to protecting the processed materials or human tissues from excessive damage. It is widely used in micro-machining, surface treatment, laser beauty, ophthalmic surgery and other special fields.
[0004] Since the pulse laser output time of the pulse laser is short and its output pulse width is in the nanosecond, picosecond or even femtosecond level, how to accurately measure its output power is a difficult problem. The commonly used methods in technology now include thermopile method measurement and high-speed A / D measurement. Thermopile is a thermoelectric sensor device that uses the thermal effect generated by the laser to cause temperature changes, thereby measuring the energy of the laser. However, due to its own characteristics of slow response time, what is measured is the integral effect of the laser power, that is, the average power of the laser, not the peak power of the pulsed laser. The measurement using high-speed A / D is to first measure the laser power with a high-speed photoelectric sensor. The photoelectric sensor can respond to the change of the laser power in time and reflect its instantaneous power change. Then, a high-speed A / D is used for sampling to calculate the instantaneous peak power of the laser. This method can accurately measure the peak power of the laser, but the acquisition and processing circuit of the high-speed A / D is complex and costly, which limits its application in ordinary industrial pulsed lasers. Therefore, providing a low-cost pulse laser peak power measurement method and device is of great significance for the industrial application and development of pulsed lasers. [Contents of the invention]:
[0005] The purpose of the present invention is to provide a method and device for measuring the peak power of a pulsed laser, which can overcome the shortcomings of the prior art and is a method and device for measuring the peak power of a pulsed laser with a simple structure, easy implementation and low cost.
[0006] The technical solution of the present invention is a method for measuring the peak power of a pulsed laser, characterized in that it comprises the following steps:
[0007] (1) Establishing the measurement optical path: Using a spectroscope, the laser output from the pulsed laser to be measured is divided into two beams of measurement light in a certain ratio. One of the beams of measurement light is transformed from a point light source into a uniform surface light source. The internal photoelectric effect is generated by the measurement light receiver, and a photocurrent signal is output. The other beam of measurement light is sent to the standard laser power meter as a reference light for subsequent calibration.
[0008] The laser power of one of the two beams of measuring light with different energies obtained in the step (1) is no more than 10 mW, i.e., the measuring light with weaker energy. This measuring light is transformed from a point light source into a uniform surface light source, and an internal photoelectric effect is generated by the measuring light receiver to output a photocurrent signal.
[0009] The measuring light in step (1) uses a photodiode as a receiver, and is provided with a pre-aperture, an attenuation mirror, and a scattering mirror to transform the measuring light from a point light source into a uniform surface light source; the photodiode is located at the center of the surface light source, with a fixed relative position, and after receiving the measuring light, an internal photoelectric effect is generated to output a photocurrent signal.
[0010] The spectroscope in step (1) is a spectroscope with a fixed ratio.
[0011] (2) filtering and amplifying the photocurrent signal obtained in step (1) by using a signal processing circuit, and converting it into a voltage signal through a load resistor, and connecting the voltage signal to an oscilloscope to display it as an original waveform to be measured;
[0012] The signal processing circuit in step (2) is composed of a filtering circuit and a small signal amplifying circuit; the filtering circuit is used to reduce the noise in the signal to improve the quality of the small signal; the small signal amplifying circuit is used to amplify the collected weak electrical signal to obtain the required voltage level.
[0013] (3) using a comparator to compare the amplitude of the filtered and amplified signal obtained in step (2) with a comparison threshold; if the amplitude is greater than the comparison threshold, the signal is a high-level signal; otherwise, the signal is a low-level signal; and so on, a set of square wave signals with the same frequency as the laser repetition frequency will be obtained, which will serve as a trigger signal for a sampling measurement cycle of the processor;
[0014] (4) The processor receives the trigger signal obtained in step (3), controls the AD sampling module to perform sampling measurement, and calculates and processes the measurement results to obtain a power value;
[0015] The processor module adopts a processor structure with FPGA as the core.
[0016] Considering the strong timing requirements of the whole system, the processor module uses FPGA as the core processor. The trigger signal enters the FPGA and becomes the start signal for the measurement after being processed by the internal clock of the FPGA; since the comparator has a certain response time, there is a delay time Δt1 between the square wave signal output by the comparator and the original waveform to be measured. Since the response time of the comparator is fixed, the delay time Δt1 is a fixed value; Figure 2 As shown, after receiving the trigger signal, the FPGA starts timing at the rising edge of the square wave signal, that is, at time T2, and after the set delay time Δt2, sends a sampling signal to the AD sampling module to control the AD sampling module to sample the amplified analog signal; the delay time Δt2 is adjusted to adjust the position of the sampling moment relative to the original waveform to be measured, so that the sampling moment is at the peak position of the original waveform to be measured, thereby realizing the sampling process of the laser power peak; the value sampled by the AD sampling module is sent to the FPGA, which is calculated and processed to obtain the power value of the laser.
[0017] The step (4) includes two parts: determining the sampling time and power calibration, and specifically includes the following contents:
[0018] (4-1) Determine the sampling time, that is, adjust the sampling time t so that it is sampled at the peak power;
[0019] (4-1-1) Use an oscilloscope to simultaneously measure the square wave signal output by the comparator, the original waveform signal to be measured, and the sampling time signal;
[0020] (4-1-2) Assuming that the delay time Δt2 is the time between the rising edge of the square wave signal, i.e., time T2, and the next peak value of the original waveform to be measured, i.e., time T4, the delay time Δt2 is adjusted so that the sampling time t appears at the peak position of the original waveform signal to be measured. At this time, the A / D value output of the AD sampling module is the maximum, i.e., the sampling time is determined; the A / D value of the AD sampling module obtained at this time is the corresponding laser power peak value, thereby realizing the sampling of the pulse laser power peak value;
[0021] The process of determining the sampling time in step (4-1-2) can also be implemented by software traversal, that is, continuously increasing the value of the delay time Δt2 from 0 until the A / D value is the maximum, which is the determined sampling time value.
[0022] (4-2) Power calibration, that is, the laser power measurement system can be calibrated;
[0023] (4-2-1) When the pulse laser to be tested has no laser output, read the current A / D output value of the AD sampling module at this time. This value is the initial value of the system, recorded as A0;
[0024] (4-2-2) Adjust the output power of the pulse laser to be tested to the maximum value. After the system is stable, read the current A / D output value of the AD sampling module, which is the peak value of the laser power, recorded as A1;
[0025] (4-2-3) Use a standard laser power meter to measure the laser power corresponding to the laser power peak value obtained in step (4-2-2), denoted as W1, and then the proportional coefficient between the A / D output value and the laser power can be obtained, as shown in formula (1). At this time, the power calibration is completed;
[0026]
[0027] (5) When the laser power needs to be measured, the A / D output value of the current AD sampling module is read, recorded as A. The peak power at this time, that is, the current laser output power value P, is obtained by formula (2):
[0028] P=K×(A-A0)#(2)
[0029] The power calibration in step (4-2) is performed by a linear method.
[0030] (6) The measured output power value P of the laser is output through the communication port for use by other systems; it can also be displayed on the display screen of the human-computer interaction module.
[0031] A schematic diagram of a pulse laser peak power measurement device is shown in Figure 3 As shown, it includes a pulse laser to be tested, a high-speed photoelectric sensor, a signal processing circuit, a signal comparator, an AD sampling module, a processor, a human-computer interaction module, etc., and its connection is a conventional connection method; the pulse laser to be tested emits a pulse laser, and irradiates the laser to be tested onto the high-speed photoelectric sensor to generate a photoelectric signal; the signal enters the signal processing circuit module, is filtered and amplified, and then divided into two paths, one of which enters the comparison circuit, and becomes a square wave pulse digital signal after comparison with the standard voltage, and enters the processor for use as a trigger and signal source; the other enters the AD sampling module for sampling, and enters the processor after being converted into a digital signal; the A / D value collected by the AD sampling module is calculated by the processor to obtain the current peak power, which is displayed or transmitted in the human-computer interaction module to achieve the measurement of the peak power of the laser.
[0032] The measuring principle and working principle of the present invention:
[0033] The pulse laser to be tested emits a pulse laser when it is working. Due to its large energy, a beam of weak light to be tested is separated by a spectroscopic system, which is irradiated onto a high-speed photoelectric sensor through an optical compensation module to generate a photoelectric signal. The signal enters the signal processing circuit module, where it is filtered and amplified and then divided into two paths: one path enters the comparison circuit, where it is compared with the standard voltage and becomes a square wave pulse digital signal, which enters the processor as a trigger and signal source; the other path enters the AD sampling module for sampling, becomes a digital signal and enters the processor. The collected A / D value is calculated to obtain the current peak power, which is displayed in the human-computer interaction module or transmitted to other devices to achieve the measurement of the peak power of the laser.
[0034] 1. Measurement principle:
[0035] like Figure 4 As shown in the figure, the core problem of measuring the peak power of a pulsed laser is that the A / D acquisition time needs to be controlled to appear at the peak of the laser power, so that the collected value truly reflects the peak power value of the laser. The way to use high-speed A / D is to use high-frequency sampling to include enough sampling points in the entire sampling area to cover the location where the peak power appears, and then query the A / D value to find its maximum value to obtain the peak power of the laser. The sampling frequency of ordinary A / D chips is low, and its sampling frequency and the pulse repetition frequency of the pulsed laser are relatively independent and there is no synchronization relationship. Therefore, its sampling position is random and cannot be guaranteed to appear at the peak power position. Therefore, how to ensure that the sampling point position of the ordinary A / D can appear at the peak of the laser power becomes the core problem of measuring the peak power of a pulsed laser.
[0036] From the analysis, it can be seen that when measuring power, the pulse laser is converted into an electrical signal through the high-speed power supply sensor, and then enters the comparator after being amplified by the signal processing circuit, and a square wave pulse signal can be obtained. This signal is generated by the pulse laser, so it is completely the same frequency as the repetition frequency of the pulse laser. It is just that there is a response time for the comparison circuit, so there is a delay Δt1 between it and the original pulse laser signal. Figure 5 As shown, since the response time of the comparison circuit is fixed, Δt1 can be considered to be a certain value.
[0037] If the square wave signal generated by the comparator is used as a trigger source to control the A / D sampling time, the A / D sampling time can be controlled to appear at the peak of the laser pulse, thereby performing accurate measurement. Figure 2As shown, T0 is the moment when the laser pulse appears; T1 is the peak moment of the laser pulse; T2 is the rising edge moment of the square wave obtained after comparison, T3 is the falling edge moment of the square wave; T4 is the peak moment of the next laser pulse. If the square wave signal is transmitted to the processor, the processor takes the rising edge of the square wave (T2 moment) as the starting moment and starts the AD sampling module to start sampling. The processor has a fixed circuit inside, which starts the AD sampling module sampling after receiving the trigger signal and responds, and the time required is fixed; the time required for AD chip sampling is also fixed; the repetition frequency of the pulse laser is stable, that is, the time interval between two adjacent laser pulses is also fixed; so after the processor receives the trigger signal, it starts the AD sampling module for acquisition after a delay of Δt2 time. By adjusting Δt2, the AD sampling moment can be controlled to appear at the T4 position, that is, the sampling is at the peak position of the laser power, thereby realizing the use of ordinary AD to measure the real-time power of the pulse laser.
[0038] 2. Working principle:
[0039] (1) Collecting pulsed laser: The instantaneous power of the pulsed laser generated by the pulsed laser to be measured is relatively large and cannot be directly irradiated onto the photoelectric sensor. Otherwise, a large amount of heat may accumulate on the surface of the detection equipment, causing damage to the photosensitive element. Therefore, a beam splitter is used in the measurement optical path to separate a weaker measurement light beam, which enters the photoelectric sensor after passing through an attenuation plate and a scattering mirror. The photoelectric sensor receives the light signal and converts it into internal photogenerated charges, which form a photocurrent under the drive of the electric field. The size of the photocurrent reflects the strength of the laser power. By measuring the photocurrent, the power of the laser can be measured.
[0040] (2) Signal processing circuit: The current signal output from the photoelectric sensor has a small amplitude and may contain various interference factors such as noise, which is not conducive to subsequent signal processing and cannot be measured directly. It is necessary to use a signal processing circuit to process the photocurrent signal and then amplify it after filtering. Use a high-bandwidth operational amplifier to amplify the amplitude of the original signal to improve the strength and clarity of the signal. Use a filter with an appropriate frequency to filter out the noise and invalid interference frequency components in the signal, improve the quality of the signal, and obtain a suitable electrical signal.
[0041] (3) Comparison circuit: The processed electrical signal is divided into two paths, one of which enters the comparison circuit module. The core of this module is a comparator, which receives a pulse voltage signal reflecting the pulse laser power amplitude and obtains a square wave signal after comparing it with the reference voltage signal. This signal is consistent with the repetition frequency of the laser, but the phase is slightly delayed. After de-jittering, the square wave signal eliminates the burrs and then enters the processor as a trigger signal.
[0042] (4) AD acquisition circuit: The other path after processing enters the AD acquisition circuit, which is mainly an AD sampling module responsible for converting analog voltage signals into digital signals, and then sending them to the processor for calculation and processing. The operation of this AD module is controlled by the processor. After receiving the trigger signal from the processor, it starts sampling and outputs the results, and then waits for the next trigger, that is, it works in the trigger mode to achieve synchronization with the signal to be sampled.
[0043] (5) Processing and calculation: Processing and calculation are the core parts of the entire system, responsible for managing and controlling the work of each module. Its main function is to receive the square wave signal from the comparator module, use its rising edge as a trigger signal, control the signal acquisition circuit, and start a cycle of sampling and calculation. This process is divided into two parts: determining the sampling time and calibrating the power value.
[0044] Determine the sampling moment: that is, adjust the sampling time so that it is sampled at the peak power. The method is to use an oscilloscope to simultaneously measure the square wave signal output by the comparator, the original waveform to be measured, and the sampling moment signal, and then continuously adjust the delay time Δt2 so that the sampling moment appears at the peak position of the waveform signal to be measured. At this time, the A / D value output is the largest, and the sampling moment is determined. It can also be achieved through software traversal: the method is to continuously increase the value of Δt2 from 0 until the A / D value is the largest, which is the determined sampling moment value t. The A / D value obtained at this time is the corresponding laser power peak, which realizes the sampling of the pulse laser power peak.
[0045] Power calibration. After determining the sampling time t, the laser power measurement system can be calibrated. Since the photoelectric sensor, operational amplifier circuit, A / D, etc. are all linear, a linear method is used to calibrate them. The method is: when there is no laser output, read the output value of A / D, which is the initial value of the system, recorded as A0. Adjust the laser output power to the maximum value, and read the current A / D value after the system stabilizes, that is, the laser power peak value, recorded as A1. At the same time, use a standard laser power meter to measure the current laser power, recorded as W1, then:
[0046]
[0047] K in the formula is recorded as the proportional coefficient between the AD value and the laser power, and the calibration is completed.
[0048] When using this module to measure laser power, read the current A / D value, recorded as A, then the peak power is:
[0049] P=K×(A-A0)#(2)
[0050] Where P is the current output power value of the laser.
[0051] (6) Human-computer interaction module: This module is responsible for human-computer interaction operations, receives parameters set by the user, and displays the calculated power value. It also sends the power value to other systems through the communication port.
[0052] The power measurement device involved in the present invention is constructed based on embedded system technology. The appearance of the measurement device is designed to make it easy to install and deploy, and to match the optical path of the laser. Based on this, the mechanical structure is designed, and optical devices such as the aperture, attenuation mirror, and scattering mirror are sequentially placed in the front section of the photoelectric sensor, and a special circuit board is designed and manufactured, integrating system functions such as sensors, signal processing circuits, comparison circuits, signal acquisition circuits, processors, and human-computer interaction modules. Then, the embedded system software is designed to realize the system functions of signal acquisition, driving, processing, display, and transmission. In this way, a special device for measuring the power of the laser is obtained.
[0053] The advantages of the present invention are as follows: through the coordination between the modules of the control system, the synchronization logic between the measurement timing and the repetition frequency of the laser is established, and the measurement of the peak power of the pulsed laser is realized. The method does not require complex high-speed signal processing circuits, effectively reduces the cost and complexity of the system, realizes low-cost measurement of the peak power of the pulsed laser, and provides support for the industrial application and development of pulsed lasers.
Description of the drawings
[0054] Figure 1 The figure is a schematic diagram of the power waveform of the pulsed laser in the prior art involved in the present invention.
[0055] Figure 2 The present invention is a schematic diagram of a method for accurately measuring peak power in a method for measuring peak power of a pulsed laser.
[0056] Figure 3 The present invention is a schematic block diagram of the structure of a pulse laser peak power measurement device.
[0057] Figure 4 Schematic diagram of the working principle of the A / D acquisition circuit selected in the pulse laser peak power measurement device involved in the present invention (wherein, Figure 4 -a is a high-speed A / D sampling card, Figure 4 -b is a common A / D sampling card).
[0058] Figure 5 The present invention is a schematic diagram of the time deviation between a square wave signal and a standard pulse signal in a method for measuring the peak power of a pulsed laser.
[0059] Figure 6 The present invention is a schematic diagram of the principle of an installation and fixing method of a pulse laser peak power measurement device. [Specific implementation]:
[0060] Embodiment: A method for measuring peak power of a pulsed laser, characterized in that it comprises the following steps:
[0061] (1) Establishing the measurement optical path: Using a spectroscope, the pulse laser generated by the pulse laser to be measured is divided into two beams of measurement light with different energies, one of which has a weaker energy (laser power is not higher than 10 mW) as the measurement light; using a photodiode as the measurement light receiver, with a pre-aperture, attenuation mirror, and scattering mirror, the measurement light is transformed from a point light source into a uniform surface light source; the photodiode is located at the center of the surface light source, and the relative position is fixed; after receiving the measurement light, an internal photoelectric effect is generated, and a photocurrent signal is output;
[0062] The spectroscope in step (1) is a spectroscope with a fixed ratio of 1:99.
[0063] (2) filtering and amplifying the photocurrent signal obtained in step (1) by using a signal processing circuit, and converting it into a voltage signal through a load resistor;
[0064] The signal processing circuit in step (2) is composed of a filtering circuit and a small signal amplifying circuit; the filtering circuit is used to reduce the noise in the signal to improve the quality of the small signal; the small signal amplifying circuit is used to amplify the collected weak electrical signal to obtain the required voltage level.
[0065] (3) using a comparator to compare the amplitude of the filtered and amplified signal obtained in step (2) with a comparison threshold; if the amplitude is greater than the comparison threshold, the signal is a high-level signal; otherwise, the signal is a low-level signal; and so on, a set of square wave signals with the same frequency as the laser repetition frequency will be obtained, which will serve as a trigger signal for a sampling measurement cycle of the processor;
[0066] (4) The processor with FPGA as the core receives the trigger signal obtained in step (3), controls the AD sampling module to perform sampling measurement, and calculates and processes the measurement results to obtain the power value;
[0067] Considering the strong timing requirements of the entire system, the processor module uses FPGA as the core processor. After the trigger signal comes in through the FPGA pin, it is processed by the internal clock of the FPGA and becomes the start signal for the measurement. After receiving the signal, the FPGA starts timing at the rising edge of the square wave signal. After the set delay time Δt2, it sends a sampling signal to the AD module, and the AD module samples the original waveform signal to be measured. The delay time Δt2 is adjusted to adjust the position of the sampling time t relative to the original waveform signal to be measured, so that the sampling time is at the peak position of the original waveform signal to be measured, realizing the sampling process of the laser power peak. The value sampled by the AD module is sent to the FPGA, which is calculated and processed to obtain the power value of the laser.
[0068] (4-1) Determine the sampling time, that is, adjust the sampling time t so that it is sampled at the peak power, such as Figure 2 As shown;
[0069] (4-1-1) Use an oscilloscope to simultaneously measure the square wave signal output by the comparator, the original waveform signal to be measured, and the sampling time signal;
[0070] (4-1-2) Assuming that the delay time Δt2 is the time between the rising edge of the square wave signal, i.e., time T2, and the next peak value of the original waveform to be measured, i.e., time T4, the delay time Δt2 is adjusted so that the sampling time t appears at the peak position of the original waveform signal to be measured. At this time, the A / D value output of the AD sampling module is the maximum, i.e., the sampling time is determined; the A / D value of the AD sampling module obtained at this time is the corresponding laser power peak value, thereby realizing the sampling of the pulse laser power peak value;
[0071] The process of determining the sampling time in step (4-1-2) can also be implemented by software traversal, that is, continuously increasing the value of the delay time Δt2 from 0 until the A / D value is the maximum, which is the determined sampling time value.
[0072] (4-2) Power calibration, that is, the laser power measurement system can be linearly calibrated;
[0073] (4-2-1) When the pulse laser to be tested has no laser output, read the current A / D output value of the AD sampling module at this time. This value is the initial value of the system, recorded as A0;
[0074] (4-2-2) Adjust the output power of the pulse laser to be tested to the maximum value. After the system is stable, read the current A / D output value of the AD sampling module, which is the peak value of the laser power, recorded as A1;
[0075] (4-2-3) Use a standard laser power meter to measure the laser power corresponding to the laser power peak value obtained in step (4-2-2), denoted as W1, and then the proportional coefficient between the A / D output value and the laser power can be obtained, as shown in formula (1). At this time, the power calibration is completed;
[0076]
[0077] (5) When the laser power needs to be measured, the A / D output value of the current AD sampling module is read, recorded as A. The peak power at this time, that is, the current laser output power value P, is obtained by formula (2):
[0078] P=K×(A-A0)#(2)
[0079] (6) The measured output power value of the laser is output through the communication port for use by other systems; it can also be displayed on the display screen of the human-computer interaction module.
[0080] A schematic diagram of a pulse laser peak power measurement device is shown in Figure 3 As shown, it includes a pulse laser to be tested, a high-speed photoelectric sensor, a signal processing circuit, a signal comparator, an AD sampling module, a processor, a human-computer interaction module, etc., and its connection is a conventional connection method; the pulse laser to be tested emits a pulse laser, and irradiates the laser to be tested onto the high-speed photoelectric sensor to generate a photoelectric signal; the signal enters the signal processing circuit module, is filtered and amplified, and then divided into two paths, one of which enters the comparison circuit, and is compared with the standard voltage to become a square wave pulse digital signal, and enters the processor for use as a trigger and signal source; the other enters the AD sampling module for sampling, and enters the processor after being converted into a digital signal; the A / D value collected by the A / D value is calculated to obtain the current peak power, which is displayed or transmitted in the human-computer interaction module to achieve the measurement of the peak power of the laser.
[0081] It should be noted that when using the laser of this measuring device, you should first select an appropriate location to install and fix the device. Figure 6 As shown, in the optical path at the output end of the laser, by installing a beam splitter, the laser output from the laser is split into two, and a weaker beam is used as the measuring light, generally a few milliwatts. Through the optical system, the measuring light is directed to the measuring device and directly irradiated to the aperture, so that the measured light can pass through the aperture, attenuation mirror, and scattering mirror, and directly irradiate the photoelectric sensor. After adjusting the optical path, fix the relative positions of each component and keep them fixed, and the installation is completed.
[0082] Due to the existence of components such as spectroscopes and measuring optical paths, power calibration is required according to the specific system when using it. The calibration process is as follows: the laser emitted by the pulsed laser is divided into two beams by a spectroscope, one of which is a weak-energy light for measuring light. The optical path is adjusted so that it shines directly on the aperture to form the measured light; the other beam is the main optical path, and a standard laser power meter is placed in the optical path as a calibration tool. During calibration, turn on the laser, adjust the power output to the maximum value, wait for a period of time, and when the working state of the laser is stable and its output power remains basically unchanged, calibration can be performed. Measure the actual optical power value in the standard laser power meter, and input the value into the device as a system parameter through the human-computer interaction interface of the device, and the power calibration is completed. Remove the standard power meter and use the device to measure the power. The current laser power value can be read out on the human-computer interaction interface to achieve the peak power measurement of the pulsed laser.
Claims
1. A method for measuring peak power of a pulsed laser, characterized in that It includes the following steps: (1) Establishing the measurement optical path: Using a spectroscope, the laser output from the pulsed laser to be measured is divided into two beams of measurement light in a certain ratio. One of the beams of measurement light is transformed from a point light source into a uniform surface light source. The internal photoelectric effect is generated by the measurement light receiver, and a photocurrent signal is output. The other beam of measurement light is sent to the standard laser power meter as a reference light for subsequent calibration. (2) filtering and amplifying the photocurrent signal obtained in step (1) by using a signal processing circuit, and converting it into a voltage signal through a load resistor, and connecting the voltage signal to an oscilloscope to display it as an original waveform to be measured; (3) using a comparator to compare the amplitude of the filtered and amplified signal obtained in step (2) with a comparison threshold; if the amplitude is greater than the comparison threshold, the signal is a high-level signal; otherwise, the signal is a low-level signal; and so on, a set of square wave signals with the same frequency as the laser repetition frequency will be obtained, which will serve as a trigger signal for a sampling measurement cycle of the processor; (4) The processor receives the trigger signal obtained in step (3), controls the AD sampling module to perform sampling measurement, and calculates and processes the measurement results to obtain a power value; (5) When the laser power needs to be measured, the A / D output value of the current AD sampling module is read, and the peak power at this time is recorded as the output power value of the current laser; (6) The measured output power value of the laser obtained in step (5) is output through the communication port for use by other systems and can be displayed on the display screen of the human-computer interaction module.
2. A method for measuring peak power of a pulsed laser according to claim 1, characterized in that The laser power of one of the two measuring lights with different energies obtained in the step (1) is no more than 10 mW, that is, the measuring light with weaker energy.
3. A method for measuring peak power of a pulsed laser according to claim 2, characterized in that The measuring light receiver in step (1) adopts a photodiode, and is provided with a front aperture, an attenuation mirror, and a scattering mirror to transform the measuring light from a point light source into a uniform surface light source; the photodiode is located at the center of the surface light source, and its relative position is fixed. After receiving the measuring light, it generates an internal photoelectric effect and outputs a photocurrent signal; the spectroscope in step (1) adopts a spectroscope with a fixed ratio.
4. A method for measuring peak power of a pulsed laser according to claim 1, characterized in that The signal processing circuit in step (2) is composed of a filtering circuit and a small signal amplifying circuit; the filtering circuit is used to reduce the noise in the signal to improve the quality of the small signal; the small signal amplifying circuit is used to amplify the collected weak electrical signal to obtain the required voltage level.
5. A method for measuring peak power of a pulsed laser according to claim 1, characterized in that The processor module adopts a processor structure with FPGA as the core.
6. A method for measuring peak power of a pulsed laser according to claim 1, characterized in that The step (4) includes two parts: determining the sampling time and power calibration, and specifically includes the following contents: (4-1) Determine the sampling time, that is, adjust the sampling time t so that it is sampled at the peak power; (4-1-1) Use an oscilloscope to simultaneously measure the square wave signal output by the comparator, the original waveform signal to be measured, and the sampling time signal; (4-1-2) Assuming that the delay time Δt2 is the time between the rising edge of the square wave signal, i.e., time T2, and the next peak value of the original waveform to be measured, i.e., time T4, the delay time Δt2 is adjusted so that the sampling time t appears at the peak position of the original waveform signal to be measured. At this time, the A / D value output of the AD sampling module is the maximum, i.e., the sampling time is determined; the A / D value of the AD sampling module obtained at this time is the corresponding laser power peak value, thereby realizing the sampling of the pulse laser power peak value; (4-2) Power calibration, that is, the laser power measurement system can be calibrated; (4-2-1) When the pulse laser to be tested has no laser output, read the current A / D output value of the AD sampling module at this time. This value is the initial value of the system, recorded as A0; (4-2-2) Adjust the output power of the pulse laser to be tested to the maximum value. After the system is stable, read the current A / D output value of the AD sampling module, which is the peak value of the laser power, recorded as A1; (4-2-3) Use a standard laser power meter to measure the laser power corresponding to the laser power peak value obtained in step (4-2-2), denoted as W1, and then the proportional coefficient between the A / D output value and the laser power can be obtained, as shown in formula (1). At this time, the power calibration is completed; 7. A method for measuring peak power of a pulsed laser according to claim 6, characterized in that The process of determining the sampling time in step (4-1-2) can also be implemented by software traversal, that is, continuously increasing the value of the delay time Δt2 from 0 until the A / D value is the maximum, which is the determined sampling time value.
8. A method for measuring peak power of a pulsed laser according to claim 6, characterized in that The power calibration in step (4-2) is performed by a linear method.
9. A method for measuring peak power of a pulsed laser according to claim 1, characterized in that The step (5) specifically means: when it is necessary to measure the laser power, the A / D output value of the current AD sampling module is read, recorded as A, and the peak power at this time, that is, the output power value P of the current laser, is obtained by formula (2). P=K×(A-A0)#(2) 10. A device for implementing the pulse laser peak power measurement method according to claim 9, characterized in that It includes a pulse laser to be tested, a high-speed photoelectric sensor, a signal processing circuit, a signal comparator, an AD sampling module, a processor, and a human-computer interaction module; the pulse laser to be tested emits a pulse laser, and irradiates the laser to be tested onto the high-speed photoelectric sensor to generate a photoelectric signal; the signal enters the signal processing circuit module, is filtered and amplified, and then is divided into two paths, one of which enters the comparison circuit, is compared with the standard voltage, and becomes a square wave pulse digital signal, and enters the processor to be used as a trigger and signal source; the other enters the AD sampling module for sampling, and enters the processor after being converted into a digital signal; The A / D value collected by the AD sampling module is calculated by the processor to obtain the current peak power, which is displayed or transmitted in the human-computer interaction module to achieve the measurement of the laser peak power.