Large-diameter laser energy meter with high surface uniformity and precision and laser energy measurement method

Abstract

The application belongs to the technical field of optical metrology, and discloses a large-aperture laser energy meter with high surface uniformity and precision, which comprises a shell and a probe assembly formed in an opening of one side of the shell, and the probe assembly comprises, from outside to inside, an absorber, a heat diffusion layer, a sensor and a backing plate; the heat diffusion layer is uniformly attached to the back of the absorber; the sensor adopts resistance wires, and the multiple resistance wires are uniformly fixed on the outer surface of the heat diffusion layer. The application also provides a laser energy measurement system and a measurement method. The application optimizes the layout of the measurement sensor, increases the collection channels, adds the heat diffusion layer behind the absorber of the energy meter, improves the surface uniformity of the energy meter, uses the multi-channel data processing to improve the signal-to-noise ratio, and further improves the measurement sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of optical metrology technology, and relates to a method for measuring laser energy, particularly a large-aperture laser energy meter with high surface uniformity and accuracy, and a method for measuring laser energy. Background Technology

[0002] Laser energy measurement in laser fusion is a crucial research topic. Accurate determination of the laser energy used in target fusion is essential for analyzing and processing experimental data and deriving correct physical laws. Laser energy measurement in laser fusion is the only means to achieve multi-channel energy balance and is also a necessary measurement for achieving multi-channel power balance. With technological advancements, the requirements for large-aperture, high-energy laser energy meters in laser fusion are becoming increasingly stringent.

[0003] Currently, the main method for measuring the energy of large-aperture lasers is calorimetry. However, due to factors such as thermal conduction in the laser energy absorber, surface uniformity is poor. Limited by measurement accuracy, the sensor layout of ordinary large-aperture energy meters only supports single-channel acquisition. This method also suffers from low sensitivity in laser energy measurement due to noise limitations. Summary of the Invention

[0004] (I) Purpose of the Invention

[0005] The purpose of this invention is to provide a large-aperture laser energy meter with high surface uniformity and accuracy, and a laser energy measurement method. The surface uniformity is improved by adding a heat diffusion layer to the laser energy meter absorber and increasing the number of sensor channels to increase sensor density. The signal-to-noise ratio is improved by optimizing the data collected from multiple channels, thereby improving the measurement sensitivity.

[0006] (II) Technical Solution

[0007] To solve the above-mentioned technical problems, the present invention first provides a large-aperture laser energy meter with high surface uniformity and accuracy, which includes a housing and a probe assembly with an opening formed on one side of the housing. The probe assembly includes an absorber, a heat diffusion layer, a sensor, and a liner arranged sequentially from the outside to the inside. The heat diffusion layer is uniformly attached to the back of the absorber. The sensor uses resistance wires, and multiple resistance wires are uniformly fixed on the outer surface of the heat diffusion layer.

[0008] The absorber absorbs laser radiation and converts it into heat energy; the heat diffusion layer is made of metal or other materials with good thermal conductivity. The heat diffusion layer and the absorber need to be uniformly bonded. The heat diffusion layer can be formed on the back of the absorber by coating or other processes, so that the temperature rise of the absorber and the heat diffusion layer is more even.

[0009] In the sensor, multiple resistance wires are evenly distributed to increase the sensor density and ensure good surface uniformity; the layout of the resistance wires should ensure that the resistance value is the same per unit area.

[0010] The substrate is made of polytetrafluoroethylene (PTFE).

[0011] Based on the aforementioned laser energy meter, the present invention also provides a laser energy measurement system, comprising: a beam shaping mirror assembly, a laser energy meter, a multi-channel signal acquisition box, and a computer; the beam shaping mirror assembly shapes the incident laser into a laser spot and incident it onto the center position of the energy meter probe assembly; the multi-channel signal acquisition box is connected to the sensor of the laser energy meter, acquires multiple signals from the laser energy meter probe assembly, and transmits them to the computer for data processing to obtain the final energy value.

[0012] Based on the above-mentioned laser energy measurement system, the present invention further provides a laser energy measurement method, comprising the following steps:

[0013] Step 1: Adjust the relative position of the laser and the energy meter so that the laser spot is located at the center of the energy meter;

[0014] Step 2: Acquire n sensor signals R1, R2, R3, ..., R n The value of R changing over time 1t R 2t R 3t ..., R nt Turn on the laser to output single-pulse light, and wait for R... 1t R 2t R 3t ..., R nt Data collection stops once the value starts decreasing from its maximum value.

[0015] Step 3: Calculate the average value of the n sensor signals. in, It is a quantity that changes over time, and it is an array;

[0016] Step 4: Calculation The difference between the maximum and minimum values, ΔR;

[0017] Step 5: Measure the reflectivity β of the absorber and calculate the absorption coefficient α(λ) = 1-β of the energy meter.

[0018] Step 6: Calculate the single-pulse laser energy E.

[0019] In this method, the laser energy value is further calculated using the change in resistance. The computer averages the data measured by the multi-channel signal acquisition box, and based on the pre-measured temperature-resistance curve, the temperature change curve and temperature rise ΔT corresponding to the absorber can be obtained. i The mass M of the absorber and the heat diffusion layer is determined in advance. i and the specific heat C of materials under different temperature conditions pi (T), calculate the energy of a single-pulse laser:

[0020]

[0021] Where: M i —Mass of absorber and heat diffusion layer (kg), C pi (T) – Specific heat capacity of the absorber and heat diffusion layer (J / kg·℃), ΔT i —Temperature rise of the absorber and heat diffusion layer (°C), α(λ) —Absorption coefficient of the energy meter.

[0022] (III) Beneficial Effects

[0023] The above-mentioned technical solution provides a method to improve the surface uniformity and measurement accuracy of large-aperture laser energy meters. By optimizing the layout of the measurement sensors and increasing the number of acquisition channels, the surface uniformity of the energy meter is improved by increasing the heat diffusion layer behind the energy meter absorber. Multi-channel data processing is used to improve the signal-to-noise ratio and thus improve the measurement sensitivity. Attached Figure Description

[0024] Figure 1 This is the layout of the energy meter probe in an embodiment of the present invention.

[0025] Figure 2 This is the layout of the multi-channel energy meter sensor in an embodiment of the present invention.

[0026] Figure 3 This is a block diagram illustrating the overall principle of the energy meter according to an embodiment of the present invention.

[0027] Figure 4 This is an overall block diagram of laser energy testing according to an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0029] like Figures 1 to 2 As shown, the large-aperture laser energy meter with high surface uniformity and accuracy in this embodiment includes a housing and a probe assembly with an opening formed on one side of the housing. The probe assembly includes an absorber, a heat diffusion layer, a sensor, and a liner arranged sequentially from the outside to the inside. The heat diffusion layer is uniformly attached to the back of the absorber. The sensor uses resistance wires, and multiple resistance wires are uniformly fixed on the outer surface of the heat diffusion layer.

[0030] The absorber absorbs laser radiation and converts it into heat energy. The heat diffusion layer is made of a metal or other material with good thermal conductivity. The heat diffusion layer and the absorber need to be uniformly bonded. A coating or other process can be used to form the heat diffusion layer on the back of the absorber, making the temperature rise of the absorber and the heat diffusion layer more even. In the sensor, multiple resistance wires are evenly distributed to increase the sensor density and ensure good surface uniformity; the layout of the resistance wires should ensure that the resistance value is the same per unit area. The substrate is made of polytetrafluoroethylene (PTFE).

[0031] like Figure 3 As shown, this embodiment also provides a laser energy measurement system, including: a beam shaping mirror group, a laser energy meter, a multi-channel signal acquisition box, and a computer; the beam shaping mirror group shapes the incident laser into a laser spot and incident it onto the center position of the energy meter probe assembly; the multi-channel signal acquisition box is connected to the sensor of the laser energy meter, acquires multiple signals from the laser energy meter probe assembly, and transmits them to the computer for data processing to obtain the final energy value.

[0032] like Figure 4 As shown, the laser beam emitted from the laser is shaped into a 300mm*300mm laser spot by a beam shaping mirror group and incident on the center of the energy meter probe. The energy meter has a diameter of 500mm*500mm and a built-in 6-channel resistance wire sensor.

[0033] The steps for laser energy measurement using the above system are as follows:

[0034] Step 1: Adjust the relative position of the laser and the energy meter to ensure that the laser spot is located near the center of the energy meter;

[0035] Step 2: Begin collecting the time-varying values ​​of the 6 sensor signals R1, R2, R3, R4, R5, and R6. 1t R 2t R 3t R 4t R 5t R 6t Turn on the laser to emit a single pulse of light with energy E, and wait for R... 1t R 2t R 3t R 4t R 5t R 6t The data collection stopped after it started to shrink.

[0036] Step 3: Calculate the average value of the 6 sensor signals.

[0037] Step 4: Calculation The maximum and minimum values ​​are ΔR = 5.36Ω;

[0038] Step 5: Calculate the laser energy as E 测 =k·ΔR=1306.2×5.36=7001.2J.

[0039] This invention replaces the single-channel sensor of the laser energy meter with a multi-channel sensor and adds a heat diffusion layer. This method can greatly improve the surface uniformity and sensitivity of the laser energy meter.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A large-aperture laser energy meter with high surface uniformity and accuracy, characterized in that, include: The housing and the probe assembly formed with an opening on one side of the housing. The probe assembly includes an absorber, a heat diffusion layer, a sensor, and a liner arranged sequentially from the outside to the inside. The heat diffusion layer is uniformly attached to the back of the absorber. The sensor uses resistance wires, and multiple resistance wires are uniformly fixed on the outer surface of the heat diffusion layer.

2. The large-aperture laser energy meter with high surface uniformity and accuracy as described in claim 1, characterized in that, The heat diffusion layer is made of metal and is formed on the back of the absorber through a coating process.

3. The large-aperture laser energy meter with high surface uniformity and accuracy as described in claim 1, characterized in that, In the sensor, the multi-wire layout ensures that the resistance value is the same per unit area.

4. The large-aperture laser energy meter with high surface uniformity and accuracy as described in claim 1, characterized in that, The lining is made of polytetrafluoroethylene (PTFE).

5. A laser energy measurement system, characterized in that, include: The laser energy meter comprises a beam shaping lens assembly, a laser energy meter, a multi-channel signal acquisition box, and a computer; the laser energy meter is the laser energy meter described in any one of claims 1-4; the beam shaping lens assembly shapes the incident laser into a laser spot and directs it to the center of the energy meter probe assembly; the multi-channel signal acquisition box connects to the sensor of the laser energy meter, acquires multiple signals from the laser energy meter probe assembly, and transmits them to the computer for data processing to obtain the final energy value.

6. A laser energy measurement method, characterized in that, Laser energy measurement is performed using the laser energy measurement system described in claim 5; the measurement method includes the following steps: Step 1: Adjust the relative position of the laser and the energy meter so that the laser spot is located at the center of the energy meter; Step 2: Acquire n-channel sensor signals R1, R2, R3 3、 …、R n The value of R changing over time 1t R 2t R 3t、 …、R nt Turn on the laser to output single-pulse light, and wait for R... 1t R 2t R 3t、 …、R nt Data collection stops once the value starts decreasing from its maximum value. Step 3: Calculate the average value of the n sensor signals. ; Step 4: Calculation The difference between the maximum and minimum values ; Step 5: Measure the reflectivity β of the absorber and calculate the absorption coefficient of the energy meter. =1-β; Step 6: Calculate the single-pulse laser energy E; In step 6, the single-pulse laser energy E is: (1) Where: M i —Mass of absorber and heat diffusion layer, kg; C pi (T) – Specific heat capacity of the absorber and heat diffusion layer, J / kg·℃; —Temperature rise of the absorber and heat diffusion layer, °C; —Absorption coefficient of the energy meter; In formula (1), the temperature change curve and temperature rise of the absorber and the heat diffusion layer are obtained according to the temperature resistance curve obtained by prior measurement. .

7. The laser energy measurement method as described in claim 6, characterized in that, In formula (1), the mass of the absorber and the heat diffusion layer is measured in advance. and the specific heat of materials under different temperature conditions .

8. An application of the laser energy measurement method according to claim 6 or 7 in the field of optical metrology.

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