CN114465083A - Laser stability control method and system - Google Patents

Abstract

The invention relates to a laser stability control method and a system, which are used for acquiring the output optical power, the voltage of a discharge tube and the vertical acceleration of an optical resonant cavity in the working process of a laser; determining the output light power change degree in each set time period according to the output light power; obtaining the working stability of the laser corresponding to a set time period according to the output light power change degree and the voltage; matching every two set time periods based on the working stability and the vertical acceleration to obtain a plurality of matching pairs; calculating the difference of the lasers in the two set time periods of each matching pair, wherein the difference is used as a corresponding matching pair weight index, and the predicted output power is obtained based on the average value of the output power of the two set time periods of each matching pair and the weight index; and obtaining the predicted compensation output power according to the output light power and the predicted output power of the laser. Namely, the invention evaluates and adjusts the working stability of the laser by detecting the relevant parameters of the laser.

Description

A kind of laser stabilization control method and system

technical field

The invention relates to the technical field of laser measurement, in particular to a laser stabilization control method and system.

Background technique

In practical applications, the stability of the laser has a great influence on the performance of the laser measuring instrument, so it is necessary to correctly evaluate the stability of the laser.

Taking CO2 laser as an example, CO2 laser is composed of laser tube-hard glass, optical resonator, pump source, power supply and control system; CO2 laser is mostly used for laser cutting, welding, drilling and surface treatment, high-power CO2 laser It is very important to maintain constant power operation for a long time.

The laser power stability is one of the key parameters to measure the stability of the laser. Unpredictable changes in the pump source, resonator, working medium and transition quantum noise will cause the laser power to change, which will affect the output light. Measure the effect.

Therefore, a method for stable control of laser power is urgently needed.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned technical problems, the purpose of the present invention is to provide a laser stabilization control method and system, and the adopted technical solutions are as follows:

The technical scheme of a laser stabilization control method provided by the present invention includes the following steps:

Obtain the output optical power, the voltage of the discharge tube and the vertical acceleration of the optical resonant cavity at each moment in each set time period during the working process of the laser;

According to the output optical power, determine the change degree of the output optical power in each set time period;

According to the change degree of the output optical power and the voltage, the working stability of the laser corresponding to the set time period is obtained;

Based on the working stability of each set time period and the vertical acceleration, the matching of the two set time periods is performed to obtain several matching pairs;

Calculate the difference between the lasers of the two set time periods in each matching pair, and the difference is used as the weight index of the corresponding matching pair. Based on the average output power of the two set time periods of each matching pair and the corresponding weight index, the prediction is obtained. Output Power;

According to the output optical power of the laser and the predicted output power, the predicted compensation output power is obtained.

Further, it also includes determining whether there are more than the set number of unmatched independent time periods, and when there is, judging whether the laser continues to work:

According to the working stability and vertical acceleration of the laser in the independent time period and the matching time period, the correlation degree between the independent time period and each matching time period is calculated, and the correlation degree is normalized to obtain the maximum correlation degree and the minimum correlation degree. degree;

Use the maximum correlation degree and the minimum correlation degree to weight the vertical acceleration mean value of the independent time period to obtain the vibration index of the laser in the independent time period;

Comparing the vibration index with the set threshold, when the vibration index is greater than the set threshold, the optical resonator vibrates seriously and the laser stops working.

Further, the output optical power change rate is the ratio of the difference between the maximum power value and the minimum power value within the set time to the average power value.

Further, the matching process is:

According to the working stability of each set time period and the vertical acceleration, calculate the consistency of the laser operation in any two set time periods;

According to the consistency, combined with the maximum weight matching of the K-M algorithm, matching pairs with similar laser working times are obtained.

Further, the predicted output power is:

Wherein, mean(P _k ) is the mean value of the output optical power of the kth matched pair in two set time periods, C _k represents the kth matched pair weight index, and n is the number of matched pairs.

The present invention also provides a laser stabilization control system, comprising a processor and a memory, wherein the processor executes the technical solution of the above-mentioned laser stabilization control method stored in the memory.

The present invention has the following beneficial effects:

The invention analyzes the stability of the working process of the laser by acquiring the output optical power of each set time period, the voltage of the discharge tube and the vibration of the optical resonant cavity during the working process of the laser, so as to adjust the output power and ensure the stability of the laser. Stability of output light.

At the same time, by matching the working conditions of each set time period of the laser, the special working conditions that are different from other working conditions are extracted, and according to the number of occurrences of the special working conditions, it is determined whether it is an abnormal working condition, if it is an abnormal working condition If the laser is not stable, it is considered that the laser is unstable and needs to be stopped for maintenance; that is, if the special working condition occurs too many times, it proves that it is not an accident; otherwise, the output power is adjusted according to the matching working condition.

Description of drawings

In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description The drawings are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

FIG. 1 is a method flow chart of an embodiment of a laser stabilization control method according to the present invention.

Detailed ways

In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following describes the solution according to the present invention, its specific implementation, structure, features and effects in detail with reference to the accompanying drawings and preferred embodiments. as follows. In the following description, different "one embodiment" or "another embodiment" are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

The specific scheme of the laser stabilization control method provided by the present invention will be specifically described below with reference to the accompanying drawings.

The invention aims at the stability of the laser power, that is, analyzes the relevant parameters of the laser, measures the stability of the laser, and is used for the subsequent adjustment of the output light, so as to ensure the measurement effect of the laser.

Specifically, taking a CO2 laser as an example, please refer to FIG. 1 , which shows a flow chart of the steps of an embodiment of a laser stabilization control method provided by an embodiment of the present invention, and the method includes the following steps:

Step 1: Acquire the output optical power, the voltage of the discharge tube and the vertical acceleration of the optical resonator at each moment in each set time period during the working process of the laser.

In this embodiment, LBA (Laser Beam Analyser) is used to sample the laser output optical power P of the CO2 laser; wherein, the LBA records the output optical power p every 0.1s, and takes 2s as the time length to record data {P ₁ , P ₂ , ..., P ₂₀ }. Of course, the system analysis and measurement time can also be appropriately adjusted according to the accuracy of the experimental results.

Among them, LBA is a needle-type laser beam detection device, which is mainly composed of a motor, a pointer, and two pyroelectric sensors. The motor drives the pointer to rotate at a high speed to cut the laser beam, obtain a short section of laser beam power density that is approximately vertical, and reflect it to two pyroelectric sensors, which convert the received light energy into a voltage signal proportional to it , the voltage signal is transferred to the amplifier, and finally the laser beam power is displayed and controlled; it should be noted that each time the LBA measures a data, it discards an old data, and the control system analyzes it in real time. The above-mentioned time period for measuring the output optical power of the laser is known in the industry, and will not be repeated here.

In this embodiment, a Hall voltage sensor is used to measure the voltage U input to the laser discharge tube, wherein the Hall voltage sensor measures the voltage of the discharge tube every 0.1s, and the set time period is 2s, during which the measurement is performed The voltage signal of 20 data {U ₁ , U ₂ , ..., U ₂₀ } in total.

The installation position and measurement principle of the above Hall voltage sensor are in the prior art and need not be repeated here.

In this embodiment, the vertical vibration acceleration G of the optical resonant cavity is measured based on the MEMS resonant accelerometer; the MEMS resonant accelerometer is installed under the total reflection mirror and the partial reflection mirror of the optical resonant cavity, and can sense the external environment or resonance The extremely tiny vibration caused by the cavity resonance; after the laser works, the MEMS resonant accelerometer measures the vertical vibration acceleration of the resonant cavity every 0.1s, and the acceleration data measured within 2s are {G ₁ , G ₂ ,..., G ₂₀ }, The measured data is converted into an electrical signal through an A/D converter.

It should be noted that an optical resonant cavity is composed of a total reflection mirror, a partial reflection mirror, a cavity, an excitation source, etc., in which light waves are reflected back and forth to provide light energy, and then transmitted to the outside world through an optical fiber. During the operation of the optical resonator of the laser, slight vibrations caused by sound waves or walking will affect the output optical power of the laser.

The laser has high requirements on the working environment. The laser must be completely level during use, and no vibration can be generated in the working room. Therefore, in order to measure the vertical vibration acceleration of the optical resonant cavity, a resonant accelerometer with extremely high precision should be selected. The greater the fluctuation of the laser output optical power P and the input voltage U of the discharge tube in the laser tube within a period of time, indicates that the working stability of the laser is worse, and the working condition stability value is smaller, and conversely, the working condition stability value is larger. . Within a certain range, the greater the voltage U input to the discharge tube, the greater the laser beam power P output by the laser. The fluctuation of the vertical vibration acceleration of the optical resonator becomes larger in a certain period of time, indicating that the stability of the laser working condition is smaller, and vice versa.

Step 2, according to the output optical power of the laser, determine the degree of change of the output optical power in each set time period;

In this embodiment, the change degree of the output optical power is based on the ratio of the difference between the maximum value and the minimum value in the output optical power sequence in each set time period and the average value of the output optical power sequence.

Among them, the smaller the time variation value of the output optical power, the smaller the fluctuation of the laser output optical power in a period of time, the better the working stability of the laser, the larger the working condition stability value, and the smaller the vice versa.

Step 3, obtaining the working stability of the laser corresponding to the set time period according to the change degree of the output optical power and the voltage;

In this embodiment, the working stability of the laser is

Among them, Si is the change degree of the output optical power in the ith set time period, and std(U _i ) is the standard deviation of the voltage in the ith set time period.

In the formula, the average value mean(U _i ) and the standard deviation std(U _i ) of the input laser tube voltage U _i of the CO2 laser within 2s are calculated _. Larger, the greater the degree of dispersion, and vice versa. The smaller the degree of dispersion, the smaller the fluctuation of the voltage within a period of time, the better the working stability of the laser, the greater the stability value of the working condition of the laser, and vice versa.

At this point, the working condition stability of the laser has been obtained, and the working condition stability of the laser for the next 2s is ready to be calculated, new data is measured, and the above steps are repeated.

Step 4, based on the working stability of each set time period and the vertical acceleration, perform pairwise matching of the set time periods to obtain several matching pairs.

Specifically, the matching project in this embodiment is:

1) According to the working stability of each set time period and the vertical acceleration, calculate the consistency of laser operation in any two set time periods;

The consistency of the laser work in this embodiment is:

In the formula (i, j) represent two time periods of the laser, (G _i , G _j ), (W _i , W _j ) represent the vertical acceleration and the working stability measured by the laser in the two time periods respectively.

Dynamic time normalization DTW(G _i , G _j ) is performed on the vertical vibration acceleration (G _i , G _j ) measured in the time period (i, j), and its value range is (0, +∞). Normalize and combine the laser working condition stability to obtain the working time similarity R of the time period (i, j). The value range of the laser working time similarity R is [0, 1], and the closer its value is to 1 , indicating that the similarity between the two time periods of the laser is higher, and vice versa.

2) According to the consistency, combined with the maximum weight matching of the K-M algorithm, matching pairs with similar laser working times are obtained.

Based on the calculated laser working time similarity R, the maximum weight matching of the K-M algorithm is performed, and matching pairs with similar laser working time are obtained to form a reference relationship.

The significance of using the K-M algorithm to allocate the maximum laser in the above is to determine the two most similar time periods based on the vertical vibration acceleration measured and calculated by the laser control system and the stability of the working condition.

It should be noted that for those that cannot be matched according to the maximum weight of KM, it means that this time period is more dissimilar to other time periods, and it is possible that the optical resonator has slightly vibrated due to external environmental reasons or internal reasons during this time period. . Slight vibration of the resonator will affect the output optical power in a very short time, and the optical resonator will quickly reach a new balance after the vibration and continue to output the laser beam. Therefore, for this isolated time period, it does not participate in the calculation of the predicted output optical power.

Step 5: Calculate the difference between the lasers of the two set time periods in each matching pair, and the difference is used as the weight index of the corresponding matching pair, based on the average value of the output power of the two set time periods of each matching pair and the corresponding weight index , get the predicted output power;

According to the output optical power of the laser and the predicted output power, the predicted compensation output power is obtained.

The predicted compensation output power in this embodiment is:

P _complement = P _set - P _pre

Among them, the laser will set the output optical power P _of the laser in advance during operation. According to the maximum weight matching pair, the output optical power and the time change degree of the output power of the matching pair are obtained, and the predicted output optical power P for the next _2s is calculated. , calculate the predicted compensation output optical power P _complement for the next 2s.

The predicted output power P in the above is _assumed to be

Wherein, mean(P _k ) is the mean value of the output optical power of the kth matched pair in two set time periods, C _k represents the kth matched pair weight index, and n is the number of matched pairs.

The method for obtaining the weight index in the above is:

1) For each matched pair, calculate the difference of the laser working conditions in the two set time periods,

Among them, the value range of Q is located in [0.5, 1], the closer it is to 1, the higher the degree of difference, and vice versa.

2) Normalize all the differences obtained above and add the sum to 1 to obtain the weight index {C ₁ , C ₂ , ..., C _n }, n of the predicted output optical power time change of each matching pair is the number of matching pairs.

After updating the measurement data, repeat the calculation of the confidence.

Further, it also includes the steps of determining whether there are more than the set number of unmatched independent time periods, and when there is, judging whether the laser continues to work:

According to the working stability and vertical acceleration of the laser in the independent time period and the matching time period, the correlation degree between the independent time period and each matching time period is calculated, and the correlation degree is normalized to obtain the maximum correlation degree and the minimum correlation degree. degree;

Use the maximum correlation degree and the minimum correlation degree to weight the vertical acceleration mean value of the independent time period to obtain the vibration index of the laser in the independent time period;

Comparing the vibration index with the set threshold, when the vibration index is greater than the set threshold, the optical resonator vibrates seriously and the laser stops working.

The set number in the above is set according to the actual situation, and the value is 3 in this embodiment.

In this embodiment, the set threshold is G _threshold , then judging the vibration condition of isolated data and other data resonator cavity S=G _S -G _threshold , S≥0, indicating that the resonator is affected by vibration and cannot be ignored, and the laser should be inspected and maintained in time. , S<0 means that the vibration effect of the resonator can be ignored.

Among them, the vibration index is:

G _S =mean(G _m )*C' _Max +mean(G _m )*[1-C' _Min ]

where mean(G _m ) represents the average of the vertical acceleration data of the m-th isolated time segment, C′ _Max represents the maximum correlation degree between the isolated time segment and other matched pairs, and C′ _Min represents the isolated time segment The minimum degree of association of the time period with other completed matching matching pairs.

So far, the confidence level of the vertical vibration condition of the isolated time period is obtained.

The methods for obtaining the maximum correlation degree and the minimum correlation degree in the above are:

First, calculate how well the isolated time period is related to all other matching pairs:

where G _m is the vertical acceleration data sequence of the m-th unmatched isolated time period, G _k is the vertical acceleration data sequence of the k-th matched pair, and W _m is the m-th unmatched isolated time segment. The working stability of the time period, W _k is the working stability of the kth matching pair.

G _k in the above can be a vertical acceleration data sequence corresponding to any set time period in the matching pair, or a sequence composed of the mean value of the corresponding elements of the vertical acceleration data sequences corresponding to two set time periods. The W _k can be the work stability corresponding to any set time period in the matching pair, or it can be the mean value of the work stability corresponding to two set time periods.

Secondly, normalize the obtained correlation degrees of the isolated time period and add the sum to 1, and obtain the sequence of the value range of X located in [0, 1: {C' ₁ , C' ₂ ,... , C′ _n }, the closer it is to 1, the stronger the difference of vertical vibration conditions, and then the maximum difference degree C′ _Max and the minimum difference degree C′ _Min are determined.

So far, the laser control system not only calculates the predicted output optical power of the laser, but also can compensate the predicted output optical power, so as to achieve the effect of controlling the output optical power of the laser in advance. At the same time, the laser control system obtains the vibration status of the optical resonator, and senses and warns the vibration of the laser caused by the external environment or internal reasons of the laser.

It should be noted that: the above-mentioned order of the embodiments of the present invention is only for description, and does not represent the advantages and disadvantages of the embodiments. And the foregoing describes specific embodiments of the present specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in an order different from that in the embodiments and still achieve desirable results. Additionally, the processes depicted in the figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

The various embodiments in this specification are described in a progressive manner, and the same and similar parts between the various embodiments may be referred to each other, and each embodiment focuses on the differences from other embodiments.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection of the present invention. within the range.

Claims (6)

1. A laser stabilization control method is characterized by comprising the following steps:

acquiring output optical power, voltage of a discharge tube and vertical acceleration of an optical resonant cavity at each moment in each set time period in the working process of the laser;

determining the output light power change degree in each set time period according to the output light power; obtaining the working stability of the laser corresponding to a set time period according to the output light power change degree and the voltage;

matching every two set time periods based on the working stability of each set time period and the vertical acceleration to obtain a plurality of matching pairs;

calculating the difference of the lasers in the two set time periods in each matching pair, wherein the difference is used as a corresponding matching pair weight index, and the predicted output power is obtained based on the average value of the output power of the two set time periods in each matching pair and the corresponding weight index;

and obtaining the predicted compensation output power according to the output light power and the predicted output power of the laser.

2. The method of claim 1, further comprising the step of determining whether there are more than a set number of independent time periods in which the unmatching is successful, and if so, determining whether the laser continues to operate:

calculating the association degree of the independent time period and each matching time period according to the working stability and the vertical acceleration of the laser in the independent time period and the matching time period, and carrying out normalization processing on the association degree to obtain the maximum association degree and the minimum association degree;

weighting the vertical acceleration average value of the independent time period by using the maximum correlation degree and the minimum correlation degree to obtain a vibration index of the laser in the independent time period;

and comparing the vibration index with a set threshold value, and when the vibration index is larger than the set threshold value, the optical resonant cavity vibrates seriously and the laser stops working.

3. The method as claimed in claim 1, wherein the output optical power change rate is a ratio of a difference between a maximum power value and a minimum power value within a set time to a power average value.

4. The method of claim 1, wherein the matching process comprises:

calculating the working consistency of the lasers in any two set time periods according to the working stability of each set time period and the vertical acceleration;

and obtaining matching pairs with similar laser working time by combining the maximum weight matching of the K-M algorithm according to the consistency.

5. The method of claim 1, wherein the predicted output power is:

wherein mean (P)_k) Average value of output optical power of two set time periods in the kth matching pair, C_kAnd representing the weight index of the k matching pair, wherein n is the number of the matching pairs.

6. A laser stability control system comprising a processor and a memory, wherein the processor executes the steps of a laser stability control method according to any one of claims 1 to 5 stored in the memory.

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