A laser micro-energy calibration device based on optical fiber devices

Abstract

The application discloses a kind of laser micro-energy calibration devices based on optical fiber device, structure is: stable laser beam is connected to first optical fiber beam splitter by tail fiber, first optical fiber beam splitter divides two beams of light, one is connected to standard energy meter, another is connected to electrically controlled optical fiber attenuator;Electrically controlled optical fiber attenuator is connected computer, attenuation is adjusted by computer, electrically controlled optical fiber attenuator output and second optical fiber beam splitter input are connected, second optical fiber beam splitter divides two beams of laser, two beams of laser beam are connected to the two input ends of optical gating device, and the optical switch of optical gating device is controlled by computer to select the laser path irradiated to the laser energy meter to be calibrated.The application combines the monitoring effect of standard energy meter, and the calibration uncertainty only comes from the repeatability of energy meter itself, without systematic attenuation transmission, with wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of laser energy measurement and metrology technology, and relates to a laser micro-energy calibration device based on fiber optic devices. Background Technology

[0002] With the rapid development of laser technology, lasers have been widely used in industrial processing, communications, medicine, and national defense. In particular, the application of lasers as detection beams is quite extensive, such as laser ranging, laser guidance, laser tracking, and laser warning. Related military laser instruments and weapons have demonstrated outstanding advantages in modern warfare.

[0003] Laser detection capabilities are developing towards large dynamic range, low noise, low minimum detectable power, large target area, and large-scale arrays. An important means of evaluating detection sensitivity is to excite the detection signal by laser radiation of known energy. The lower the laser radiation, the stronger the detection capability. Therefore, the measurement and calibration of weak laser radiation energy is crucial.

[0004] The generation of constant weak laser radiation can be achieved by two methods: one is to monitor it in real time with measuring equipment, and the other is to attenuate the output using an attenuation device with a known value.

[0005] Currently, commercial laser energy meters can reach the sub-pJ level; however, the minimum detectable laser energy of laser detectors has dropped to the fJ level. Common linear calibration methods for transferring values ​​downwards primarily include the attenuation method and the area method. The attenuation method uses a constant attenuation rate, transferring the value stage by stage. The measurement uncertainty introduced at each stage is mainly due to the attenuation rate of the attenuator itself, typically exceeding 1%. After multiple accumulations, the uncertainty is difficult to control. The area method uses apertures of different areas within a large laser spot to transfer the value, but it is mainly limited by the attenuation error caused by the uniformity of the spot distribution. Both methods have relatively large measurement uncertainties and cannot be verified in a closed loop, especially at the fJ level, where reliability is extremely low. Therefore, the measurement and calibration of their linear characteristics remain at a technical level characterized by high uncertainty and difficulty in verification.

[0006] It is evident that while laser energy calibration can be traced back to higher-level laser energy standards, it is merely a single-point calibration method. It exhibits relatively small measurement uncertainties at the mJ level, and further ranges require linear calibration for transfer. Detection linearity primarily employs the constant-rate attenuation method or the area comparison method. However, both methods are limited by the accuracy of the attenuation ratio of the constant-rate attenuator and the uniformity of the light spot, and the comparison results cannot be verified in a closed-loop manner. Laser standard values ​​originate from cryogenic radiometers; therefore, in conventional ranges, the accuracy of the transferred values ​​can be controlled within 3%. Taking the extension to lower ranges as an example, at the nJ level, the transferred uncertainty exceeds 8%. Currently, the minimum detectable energy of laser detectors is below the fJ level; therefore, the uncertainty of existing linear calibration, based solely on value transfer, is insufficient to meet the accuracy requirements.

[0007] The method of attenuating the output of a known attenuation device is as difficult as the problem mentioned above, therefore the calibration of weak energy still needs to be improved. Summary of the Invention

[0008] (I) Purpose of the Invention

[0009] The purpose of this invention is to provide a laser micro-energy calibration device based on fiber optic devices. Addressing the issue that linear calibration methods for laser energy / power rely on attenuation at constant rate or area comparison methods, which introduce significant measurement uncertainty, leading to large measurement uncertainties below mJ and exceeding 10% in the fJ range, this invention presents an automatic calibration design based on fiber optic devices. It provides fully automated operation and data processing, optimizing the measurement uncertainty to a level of 2%.

[0010] (II) Technical Solution

[0011] To address the aforementioned technical problems, this invention provides a laser micro-energy calibration device based on fiber optic devices, comprising: a stable laser beam 1, a first fiber optic beam splitter 2, a standard laser energy meter 3, an electrically controlled fiber optic attenuator 4, a second fiber optic beam splitter 5, an optical selector 6, a laser energy meter to be calibrated 7, and a computer 8. The stable laser beam 1 is connected to the first fiber optic beam splitter 2 via a pigtail. The first fiber optic beam splitter 2 splits into two beams, one of which is connected to the standard energy meter 3, and the other is connected to the electrically controlled fiber optic attenuator 4. The electrically controlled fiber optic attenuator 4 is connected to the computer 8, which adjusts the attenuation. The output of the electrically controlled fiber optic attenuator 4 is connected to the input of the second fiber optic beam splitter 5, which splits into two laser beams. The two laser beams are connected to the two inputs of the optical selector 6. The optical switch of the optical selector 6 is controlled by the computer 8 to select the laser path that illuminates the laser energy meter to be calibrated 7.

[0012] The stable laser beam 1 is output by a laser with a pigtail.

[0013] The first fiber optic splitter 2 is a 50:50 splitter.

[0014] The stable laser beam 1, the first fiber beam splitter 2, the standard laser energy meter 3, the electrically controlled fiber attenuator 4, the second fiber beam splitter 5, and the optical selector 6 are all connected by flanges.

[0015] The standard energy meter 3 is a laser energy meter with a measurement range of 200pJ to 20nJ and a stability better than 0.5%.

[0016] Among them, the electrically controlled fiber optic attenuator 4 is composed of two fiber optic attenuators connected in series.

[0017] The splitting ratio of the second fiber optic beam splitter 5 is selected between 2 and 10.

[0018] When the laser micro-energy calibration device is working, the attenuation of the electrically controlled fiber optic attenuator 4 is first set to the minimum. This makes the laser energy at the standard laser energy meter 3 and the laser energy meter under calibration 7 equivalent. The laser energy is measured using both the standard laser energy meter 3 and the laser energy meter under calibration 7. The computer 8 reads the laser energy meter reading Q1 at the standard laser energy meter 3 and the laser energy meter reading Q2 at the laser energy meter under calibration 7, calculates the beam splitting ratio, and assigns this parameter to the laser energy meter under calibration 7. Using this energy value as a reference, the energy value is reduced by the electrically controlled attenuator 4, and the beam splitting ratio of the beam splitter 5 is set to k1. At each energy point, the optical selector 6 controls the sequential output of two laser beams, and the laser energy value Q is recorded alternately on the laser energy meter under calibration 7. 31 Q 32 If the two values ​​are constant at k1 across the entire range, replace the beam splitter 5 with a beam splitting ratio of k2, repeat the calibration process to obtain the second set of data, and then use the minimum error control method to perform linear correction on the two sets of data.

[0019] When using the laser micro-energy calibration device to measure the monitoring ratio, a standard energy meter is placed at the location of the standard laser energy meter 3 and the location of the laser energy meter being calibrated 7 to measure the laser energy value, thus obtaining the monitoring ratio R:

[0020]

[0021] In the formula:

[0022] Q1—Measured laser energy at location 3, in J;

[0023] Q2—Laser energy measurement at location 7, in J;

[0024] The laser energy measurements mentioned above were all calculated by averaging six sets of data.

[0025] The correction factor for the standard value of the laser energy meter 7 being calibrated is:

[0026]

[0027] In the formula:

[0028] Q′1——The standard energy meter reading at location 3, in J;

[0029] Q′2——The reading of the energy meter at position 7, in J;

[0030] The above-mentioned standard energy meter monitoring values ​​and the energy meter readings under test were all obtained by recording 6 sets and taking the average value.

[0031] (III) Beneficial Effects

[0032] The laser micro-energy calibration device based on fiber optic devices provided by the above technical solution uses fiber optic devices, including an electric attenuator, beam splitters of different ratios, and optical gating devices, to form a stable monitoring optical path. It corrects the linearity of the same energy measurement range based on the different beam splits of the beam splitters as reference values. Compared with traditional constant-rate attenuation methods and area comparison methods, the beam splitting ratio adjustment is simple and controllable, and it avoids measurement uncertainty components introduced by inaccurate attenuation ratio calibration, inaccurate area calibration, and uneven spot distribution. Combined with the monitoring function of a standard energy meter, its calibration uncertainty only originates from the repeatability effect of the energy meter itself, without systematic attenuation propagation, and has broad application prospects. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the principle of the laser micro-energy calibration device based on fiber optic devices of the present invention.

[0034] In the diagram: 1-Fiber optic output stable laser beam, 2-Fiber optic beam splitter 1, 3-Standard laser energy meter, 4-Electrically controlled fiber optic attenuator, 5-Fiber optic beam splitter 2, 6-Optical selector, 7-Laser energy meter under calibration, 8-Computer control terminal. Detailed Implementation

[0035] 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.

[0036] In the embodiments described below, laser micro-energy calibration can be achieved, generating a linear calibration curve L of laser energy, a standard correction value C, and a beam splitting ratio.

[0037] Reference Figure 1As shown, the laser micro-energy calibration device based on fiber optic devices in this embodiment includes: a stable laser beam 1, a first fiber optic beam splitter 2, a standard laser energy meter 3, an electrically controlled fiber optic attenuator 4, a second fiber optic beam splitter 5, an optical selector 6, a laser energy meter to be calibrated 7, and a computer 8. The stable laser beam 1 is connected to the first fiber optic beam splitter 2 via a pigtail. The first fiber optic beam splitter 2 splits into two beams, one of which is connected to the standard energy meter 3, and the other is connected to the electrically controlled fiber optic attenuator 4. The electrically controlled fiber optic attenuator 4 is connected to the computer 8, and the computer 8 adjusts the attenuation. The output end of the electrically controlled fiber optic attenuator 4 is connected to the input end of the second fiber optic beam splitter 5. The second fiber optic beam splitter 5 splits into two laser beams, and the two laser beams are connected to the two input ends of the optical selector 6. The optical switch of the optical selector 6 is controlled by the computer 8 to select the laser path that illuminates the laser energy meter to be calibrated 7.

[0038] Among them, the stable laser beam 1 is output by a laser with a pigtail.

[0039] The first fiber optic beam splitter 2 is a 50:50 beam splitter.

[0040] The stable laser beam 1, the first fiber beam splitter 2, the standard laser energy meter 3, the electrically controlled fiber attenuator 4, the second fiber beam splitter 5, and the optical selector 6 are all connected by flanges.

[0041] Since the measured values ​​of commercial nJ-level energy meters are relatively stable and traceable to national standards, a laser energy meter with a measurement range of 200pJ to 20nJ was selected and calibrated as the standard energy meter 3; a 10nJ-level laser with a stability better than 0.5% was selected as the standard laser output source to output a stable laser beam 1.

[0042] The first fiber beam splitter 2 selects a splitting ratio for the two beams to be similar, ensuring that the energy at the standard laser energy meter 3 and the laser energy meter under calibration 7 is similar. This allows the standard energy value from the upstream traceability to be reproduced at these two locations, avoiding the potential influence of the linearity of the standard energy meter. The monitoring optical path is directly connected to the flange and placed on the photosensitive surface of the standard laser energy meter 3. Since the target surface of the laser energy meter with a measurement range of 200pJ to 20nJ is larger than 5mm in diameter, the fiber output light will not exit the receiving target surface of the energy meter. The output end of the measurement optical path is connected to the input end of the electrically controlled fiber optic attenuator 4 via the flange. Depending on the calibration range, two 30dB electrically controlled fiber optic attenuators can be connected in series to form a 60dB attenuation, covering the calibration capability up to fJ. The output end of the electrically controlled fiber optic attenuator is connected to the output end of the second fiber beam splitter 5. The function of the second fiber beam splitter 5 is to form two optical paths with stable energy ratios. The two beams are alternately irradiated onto the same laser energy meter 7 being calibrated via the optical selector 6. Through continuous adjustment of the electrically controlled fiber attenuator 4, two sets of corresponding measurement values ​​can be generated across the entire calibration range. Since these are values ​​measured simultaneously by the same energy meter, they are comparable and serve as the data benchmark for linear calibration. Therefore, the beam splitting ratio of the second fiber beam splitter 5 can be controlled between 2 and 10 times, thus forming data sequences with different ratios and obtaining a greater number of data points within the measurement range.

[0043] During operation, the attenuation of the electrically controlled fiber optic attenuator 4 is first set to the minimum. This ensures that the laser energy at the standard laser energy meter 3 and the laser energy meter under calibration 7 are equivalent. The laser energy is measured using both the standard laser energy meter 3 and the laser energy meter under calibration 7. The computer 8 reads the laser energy meter reading Q1 at the standard laser energy meter 3 and the laser energy meter reading Q2 at the laser energy meter under calibration 7, calculates the beam splitting ratio, and assigns this parameter to the laser energy meter under calibration 7. Using this energy value as a reference, the energy value is reduced by the electrically controlled attenuator 4. The beam splitting ratio of the beam splitter 5 is set to k1. At each energy point, the optical selector 6 controls the sequential output of two laser beams, and the laser energy value Q is recorded alternately on the laser energy meter under calibration 7. 31 Q 32 Therefore, the ratio of the two values ​​should be constant at k1 throughout the full range. Since k1 is unknown, the beam splitter 5 will be replaced with a splitting ratio of k2. The calibration process will be repeated to obtain the second set of data. The two sets of data will then be linearly corrected using the minimum error control method.

[0044] During the monitoring ratio measurement, the standard energy meter is placed at the location of the standard laser energy meter 3 and the location of the laser energy meter under calibration 7 to measure the laser energy value, thus obtaining the monitoring ratio R:

[0045]

[0046] In the formula:

[0047] Q1—Measured laser energy at position 3 of the standard laser energy meter, in J;

[0048] Q2——The measured laser energy at position 7 of the laser energy meter being calibrated, in J.

[0049] The correction factor for the standard value of the laser energy meter being calibrated is:

[0050]

[0051] In the formula:

[0052] Q′1——Standard laser energy meter reading at position 3, J;

[0053] Q′2——The reading of the laser energy meter under test at position 7 of the laser energy meter being calibrated, in J.

[0054] The above laser energy measurement values, standard energy meter monitoring values, and tested energy meter readings were all obtained by recording 6 sets and taking the average value.

[0055] This point serves as the standard value for the laser energy meter being calibrated, i.e., the reference value Q after linear correction. Based on this, the attenuation value of the electrically controlled fiber optic attenuator is gradually increased. After each attenuation adjustment, a command is sent to the fiber optic selector to sequentially measure the energy values ​​of the two laser beams split by the second fiber optic beam splitter in six groups. After the range scan is completed, two sets of energy value sequences J with q values ​​can be obtained. 1p1 J 2p1 Ideally, the ratio of two energy sequence values ​​should form a stable ratio k1. However, due to the linearity and stability of the calibrated energy meter, the value of k1 varies within a certain range.

[0056] Replace the second fiber beam splitter to change the splitting ratio, and repeat the above steps to form a new energy value sequence J. 1p2 J 2p2 The ideal ratio of the two energy sequences is denoted as k1.

[0057] By applying a fixed ratio correction to the two sets of sequences and iterating through them using the minimum error control method, the optimal ratios k1 and k2 are obtained. The corresponding energy linear correction value can then be obtained. Using the standard correction value point Q as a reference, the correction value for the entire range can be obtained.

[0058] The measurement uncertainty of this method mainly originates from the measurement uncertainty component introduced by the traceability of the standard energy meter, as well as the stability of the laser and the laser energy meter. Long-term experimental data shows that its stability can be controlled within 0.5% under multi-sample measurement conditions. With a standard energy meter measurement uncertainty of 3% (k=2), the combined measurement standard uncertainty C of the calibration result obtained by this calibration method is... n It can be controlled to reach 5% (k=2). Furthermore, it can be applied to the full range, rather than a single-point calibration.

[0059] Therefore, the measurement uncertainty for energy calibration from nJ to fJ levels is less than 5%, which is superior to traditional linear calibration methods. Furthermore, the entire process is electronically controlled, achieving full automation.

[0060] Another major advantage of this method is that the calibration results can be automatically verified in a closed loop by changing the fiber splitting ratio to ensure the reliability of the measurement uncertainty.

[0061] The parameters of each subsystem of the device of the present invention are shown in Table 1.

[0062] Table 1 Component parameters of the laser detection linear automatic calibration device

[0063]

[0064] As can be seen from the above technical solutions, traditional linear calibration methods mainly employ the constant attenuation rate method and the area comparison method. This invention uses an optical fiber beam splitter as the splitting element, making the splitting ratio adjustment simple and controllable. Furthermore, it avoids measurement uncertainty components introduced by inaccurate attenuation rate calibration, inaccurate area calibration, and uneven spot distribution. Combined with the monitoring function of a standard energy meter, its calibration uncertainty stems solely from the repeatability effect of the energy meter itself, without systematic attenuation propagation, thus possessing broad application prospects.

[0065] 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 laser micro-energy calibration device based on fiber optic devices, characterized in that, include: The system consists of a stable laser beam (1), a first fiber optic beam splitter (2), a standard laser energy meter (3), an electrically controlled fiber optic attenuator (4), a second fiber optic beam splitter (5), an optical selector (6), a laser energy meter under calibration (7), and a computer (8). The stable laser beam (1) is connected to the first fiber optic beam splitter (2) via a pigtail. The first fiber optic beam splitter (2) splits the light into two beams, one of which is connected to the standard laser energy meter (3), and the other is connected to the electrically controlled fiber optic attenuator (4). The electrically controlled fiber optic attenuator (4) is connected to the computer (8) and is adjusted by the computer (8). The output of the electrically controlled fiber optic attenuator (4) is connected to the input of the second fiber optic beam splitter (5). The second fiber optic beam splitter (5) splits into two laser beams, which are connected to the two inputs of the optical selector (6). The optical switch of the optical selector (6) is controlled by the computer (8) to select the laser path that is irradiated to the laser energy meter (7) under calibration. When the laser micro-energy calibration device is used to perform the monitoring ratio measurement, the standard energy meter is placed at the location of the standard laser energy meter (3) and the location of the laser energy meter (7) under calibration to measure the laser energy value.

2. The laser micro-energy calibration device based on fiber optic devices as described in claim 1, characterized in that, The stable laser beam (1) is output by a fiber-coupled laser.

3. The laser micro-energy calibration device based on fiber optic devices as described in claim 2, characterized in that, The first fiber optic splitter (2) is a 50:50 splitter.

4. The laser micro-energy calibration device based on fiber optic devices as described in claim 3, characterized in that, The stable laser beam (1), the first fiber beam splitter (2), the standard laser energy meter (3), the electrically controlled fiber attenuator (4), the second fiber beam splitter (5), and the optical selector (6) are all connected by flanges.

5. The laser micro-energy calibration device based on fiber optic devices as described in claim 4, characterized in that, The standard laser energy meter (3) is selected from laser energy meters with a measurement range of 200pJ to 20nJ, and its stability is better than 0.5%.

6. The laser micro-energy calibration device based on fiber optic devices as described in claim 5, characterized in that, The electrically controlled fiber optic attenuator (4) consists of two fiber optic attenuators connected in series.

7. The laser micro-energy calibration device based on fiber optic devices as described in claim 6, characterized in that, The splitting ratio of the second fiber optic splitter (5) is selected between 2 and 10 times.

8. The laser micro-energy calibration device based on fiber optic devices as described in claim 7, characterized in that, When the laser micro-energy calibration device is working, the attenuation of the electrically controlled fiber optic attenuator (4) is first set to the minimum, so that the laser energy at the standard laser energy meter (3) and the laser energy meter under calibration (7) are equivalent. The laser energy is measured by the standard laser energy meter (3) and the laser energy meter under calibration (7). The computer (8) reads the laser energy meter reading Q1 at the standard laser energy meter (3) and the laser energy meter reading Q2 at the laser energy meter under calibration (7), calculates the beam splitting ratio, and assigns this parameter to the laser energy meter under calibration (7). With this energy value as the reference value, the energy value is reduced by the electric attenuator (4), and the beam splitting ratio of the beam splitter (5) is set to k1. At each energy point, the optical selector (6) controls the sequential output of two laser beams, and the laser energy value Q is recorded alternately on the laser energy meter under calibration (7). 31 Q 32 Then, the two-value ratio is always k1 throughout the full range; replace the beam splitter (5), its beam splitting ratio is k2, repeat the calibration process, obtain the second set of data, and use the minimum error control method to linearly correct the two sets of data.

9. The laser micro-energy calibration device based on fiber optic devices as described in claim 8, characterized in that, When the monitoring ratio is measured using the aforementioned laser micro-energy calibration device, the monitoring ratio R is obtained: （1） In the formula: Q1—Laser energy measurement value at the location of the standard laser energy meter (3), J; Q2—The measured laser energy at the location of the laser energy meter under calibration (7), in J; The laser energy measurements mentioned above were all calculated by averaging six sets of data.

10. The laser micro-energy calibration device based on fiber optic devices as described in claim 9, characterized in that, The correction factor for the standard value of the laser energy meter being calibrated (7) is: （2） In the formula: Q'1——The standard laser energy meter reading at the location of the standard laser energy meter (3), J; Q'2——The reading of the laser energy meter under test at the position of the laser energy meter under test (7), J; The above-mentioned standard energy meter monitoring values ​​and the energy meter readings under test were all obtained by recording 6 sets and taking the average value.

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