CN114465083A - Laser stability control method and system - Google Patents
Laser stability control method and system Download PDFInfo
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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
Technical Field
The invention relates to the technical field of laser measurement, in particular to a laser stability control method and a laser stability control system.
Background
In practical applications, the stability of the laser has a great influence on the performance of the laser measuring instrument, so that the stability of the laser needs to be evaluated correctly.
Taking a CO2 laser as an example, the CO2 laser comprises a laser tube, namely hard glass, an optical resonant cavity, a pumping source, a power supply, a control system and the like; the CO2 laser is mainly used for laser cutting, welding, drilling and surface treatment, and whether the high-power CO2 laser keeps constant power operation for a long time or not is important.
The laser power stability is one of the key parameters for measuring the laser stability, and the influence factors of the laser power stability are caused by unpredictable changes of a pumping source, a resonant cavity, a working medium, transition quantum noise and the like, so that the output light is influenced, and the measurement effect is influenced.
Therefore, a method for stably controlling the laser power is urgently needed.
Disclosure of Invention
In order to solve the above technical problems, an object of the present invention is to provide a method and a system for controlling laser stability, wherein the adopted technical scheme is as follows:
the technical scheme of the laser stability control method provided by the invention comprises 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.
Further, the method also comprises the following steps of determining whether the independent time periods which are more than the set number and are not successfully matched exist, and judging whether the laser continues to work when the independent time periods exist:
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.
Further, the output optical power change rate is a ratio of a difference value between a maximum power value and a minimum power value within a set time to a power average value.
Further, the matching process is as follows:
calculating the working consistency of the lasers in any two set time periods according to the working stability and the vertical acceleration of each set time period;
and obtaining matching pairs with similar laser working time by combining the maximum weight matching of the K-M algorithm according to the consistency.
Further, the predicted output power is:
wherein mean (P)k) Is the average value of the output optical powers of two set time periods in the kth matching pair, CkAnd representing the weight index of the k matching pair, wherein n is the number of the matching pairs.
The invention also provides a laser stability control system, which comprises a processor and a memory, wherein the processor executes the technical scheme of the laser stability control method stored in the memory.
The invention has the following beneficial effects:
according to the invention, the output light power of each set time period, the voltage of the discharge tube and the vibration condition of the optical resonant cavity in the working process of the laser are obtained, and the stability of the working process of the laser is analyzed, so that the output power is adjusted, and the stability of the output light of the laser is ensured.
Meanwhile, through matching the working conditions of the laser in each set time period, extracting special working conditions different from other working conditions, determining whether the special working conditions are abnormal according to the occurrence frequency of the special working conditions, and if the special working conditions are abnormal, determining that the laser is unstable in working and needs to stop working and overhauling; that is, if the occurrence frequency of the special working condition is too many, the condition is proved not to be accidental; otherwise, adjusting the output power according to the matched working condition.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions and advantages of the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flowchart of a method of an embodiment of a laser stabilization control method according to the present invention.
Detailed Description
To further explain the technical means and effects of the present invention adopted to achieve the predetermined objects, the embodiments, structures, features and effects thereof according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Unless defined otherwise, 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 following describes a specific scheme of a laser stability control method provided by the present invention in detail with reference to the accompanying drawings.
The invention aims at the stability of the laser power, namely, the relevant parameters of the laser are analyzed to measure the stability of the laser for the adjustment of subsequent output light, thereby ensuring the measuring effect of the laser.
Specifically, taking a CO2 laser as an example, please refer to fig. 1, which shows a flowchart illustrating steps of an embodiment of a method for controlling laser stability according to an embodiment of the present invention, the method includes the following steps:
step 1, obtaining output optical power, voltage of a discharge tube and vertical acceleration of an optical resonant cavity at each time within each set time period in the working process of the laser.
In this embodiment, lba (laser Beam analyzer) is used to sample the laser output light power P of the CO2 laser; wherein, LBA records the output light power P every 0.1s, and takes 2s as the time length to record data { P }1，P2，……，P20}. Of course, the system analysis and measurement time can be adjusted appropriately according to the accuracy of the experimental results.
The LBA is a rotary-pin laser beam detection device, which mainly comprises a motor, a pointer, two pyroelectric sensors, etc. The motor drives the pointer to rotate at a high speed to cut the laser beam, a small segment of laser beam power density which is approximately vertical is obtained and is reflected to the two pyroelectric sensors, the two pyroelectric sensors convert the received light energy into voltage signals which are proportional to the light energy, the voltage signals are transmitted to the amplifier, and finally the laser beam power is displayed and controlled; it should be noted that, each time the LBA measures one piece of data, one piece of old data is discarded, and the control system analyzes the data in real time. The above-mentioned time periods for measuring the output optical power of the laser are known in the industry and will not be described in too much detail here.
In this embodiment, a hall voltage sensor is used to measure a voltage U input to a laser discharge tube, wherein the hall voltage sensor measures the voltage of the discharge tube once every 0.1s, wherein a set time period is 2s, and the voltage signals measured in this time period are 20 data { U } in total1，U2，……，U20}。
The installation position and the measurement principle of the hall voltage sensor in the above are prior art, and need not be described herein.
In the embodiment, the vertical vibration acceleration G of the optical resonant cavity is measured based on the MEMS resonant accelerometer; the MEMS resonant accelerometer is arranged below a total reflection mirror and a partial reflection mirror of the optical resonant cavity and can sense the minimal vibration caused by the external environment or resonant 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 in 2s is { G }1，G2，……，G20And converting the measured data into an electric signal through an A/D converter.
The optical resonant cavity is a cavity in which light waves are reflected back and forth to provide optical energy, and then transmitted to the outside through an optical fiber. In the working process of an optical resonant cavity of the laser, sound waves or tiny vibration caused by walking can affect the output optical power of the laser.
The laser has high requirements on working environment, the laser must be ensured to be completely horizontal in use, and vibration cannot be generated in a working room. Therefore, in order to measure the vertical vibration acceleration of the optical resonant cavity, a resonant accelerometer with extremely high precision is selected. The larger the fluctuation change of the output light power P of the laser and the input voltage U of a discharge tube in the laser tube in a period of time is, the worse the working stability of the laser is, the smaller the working condition stability value is, and otherwise, the larger the working condition stability value is. Within a certain range, the larger the voltage U input to the discharge tube, the larger the laser beam power P output by the laser. The fluctuation of the vertical vibration acceleration of the optical resonant cavity in a certain time is increased, which shows that the stability of the working condition of the laser is smaller, and vice versa.
Step 2, determining the output light power change degree in each set time period according to the output light power of the laser;
in this embodiment, the output optical power variation is a ratio of a difference between a maximum value and a minimum value in the output optical power sequence in each set time period to a mean value of the output optical power sequence.
The smaller the time variation value of the output light power represents that the fluctuation of the output light power of the laser within a period of time is smaller, the better the working stability of the laser is, the larger the stability value of the working condition is, and the smaller the fluctuation is otherwise.
Step 3, obtaining the working stability of the laser corresponding to the set time period according to the output light power change degree and the voltage;
in this embodiment, the laser has a working stability of
Wherein, Si is the output light power change degree of the ith set time period std (U)i) Is the standard deviation of the voltage for the ith set period.
In the formula, the voltage U of an input laser tube in the CO2 laser 2s is calculatediMean value of (U)i) And standard deviation std (U)i) The standard deviation represents the degree of voltage dispersion over a period of time, std (U)i) The larger the value of (c), the larger the degree of dispersion, and vice versa. The smaller the dispersion degree is, the smaller the fluctuation of the voltage in a period of time is, the better the working stability of the laser is, the larger the working condition stability value of the laser is, and the smaller the working condition stability value of the laser is, otherwise.
And obtaining the working condition stability of the laser, preparing to calculate the working condition stability of the next 2s laser, measuring new data, and repeating the steps.
And 4, 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.
Specifically, the matching engineering in this embodiment is as follows:
1) calculating the working consistency of the lasers in any two set time periods according to the working stability and the vertical acceleration of each set time period;
the working consistency of the laser in this embodiment is as follows:
wherein (i, j) represents two periods of the laser, (G)i，Gj)、(Wi，Wj) Indicating the vertical acceleration and the operating stability of the laser measured for two respective periods of time.
Vertical vibration acceleration (G) measured for a time period (i, j)i，Gj) Performing dynamic time warping DTW (G)i，Gj) The value range is (0, infinity), the working time similarity R of the time period (i, j) is obtained by normalizing the value range and combining the working condition stability of the laser, and the value range of the working time similarity R of the laser is [0, 1%]The closer its value is to 1, the higher the similarity of the two laser periods and vice versa.
2) And according to the consistency, combining the maximum weight matching of the K-M algorithm to obtain matching pairs with similar working time of the laser.
And performing K-M algorithm maximum weight matching based on the calculated working time similarity R of the laser to obtain matching pairs with similar working time of the laser, and forming a reference relation.
The meaning of using the K-M algorithm to maximally allocate the lasers in the above description is to determine the two most similar time periods based on the vertical vibration acceleration and the working condition stability measured and calculated by the laser control system.
It should be noted that for the time period which cannot be matched according to the KM maximum weight, the time period is not similar to other time periods, and the optical resonant cavity may be slightly vibrated in the time period due to external environmental reasons or internal reasons. The output light power can be influenced in a short time by slight vibration of the resonant cavity, and the optical resonant cavity can quickly reach a new balance after vibration to continuously output laser beams. Therefore, for this isolated period, no contribution is made to the calculation of the predicted output light power.
Step 5, 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.
The predicted compensated output power in this embodiment is:
Psupplement device＝PIs provided with-PPreparation of
Wherein, the output light power P of the laser can be set in advance during the operation of the laserIs provided withAccording to the maximum weight matching pair, the output light power and the output power time variation degree of the laser in the matching pair are obtained, and the predicted output light power P of the next 2s is calculatedPreparation ofCalculating the predicted compensated output optical power P of the next 2sSupplement device。
Predicted output power P in the abovePreparation ofIs composed of
Wherein mean (P)k) Is the average value of the output optical powers of two set time periods in the kth matching pair, CkAnd representing the weight index of the k matching pair, wherein n is the number of the matching pairs.
The method for acquiring the weight index comprises the following steps:
1) for each matching pair, calculating the difference of the laser working conditions in two set time periods,
wherein, the value range of Q is positioned in [0.5, 1], the closer to 1, the higher the difference degree is, and the lower the difference degree is.
2) All the differences obtained above are normalized and added to 1 to obtain a weight index { C ] of the predicted output light power time change of each matching pair1，C2，……，CnAnd n is the number of matched pairs.
After updating the measurement data, the confidence is repeatedly calculated.
Further, the method also comprises the steps of determining whether the independent time periods which are not matched successfully and have more than the set number exist, and judging whether the laser continues to work when the independent time periods exist:
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.
The set number is set according to actual conditions, and the value in this embodiment is 3.
The threshold value set in this embodiment is GThreshold(s)Judging the vibration state S ═ G of the isolated data and other data resonant cavitiesS-GThreshold(s)S is more than or equal to 0, which indicates that the resonant cavity is not influenced by vibration and the laser should be inspected and maintained in time, S<0 indicates that the resonant cavity is affected by negligible vibration.
Wherein, the vibration index is:
GS＝mean(Gm)*C′Max+mean(Gm)*[1-C′Min]
mean (G) in the formulam) Mean of vertical acceleration data representing the m isolated time periods, C'MaxRepresenting the maximum degree of correlation, C ', of the isolated time period with other matched pairs completing the match'MinRepresenting the minimum degree of association of an isolated time period with other matching pairs of completed matches.
Thus, the vertical vibration condition confidence of an isolated time period is obtained.
The method for acquiring the maximum correlation degree and the minimum correlation degree comprises the following steps:
first, the degree of association of an isolated time period with all other matching pairs is calculated:
in the formula GmIs a vertical acceleration data series for the m-th, unaided, isolated time period, GkIs the vertical acceleration data sequence of the kth matched pair, WmIs the operational stability, W, of the mth, not matched, isolated time periodkIs the operating stability of the kth matched pair.
G in the abovekThe vertical acceleration data sequence corresponding to any set time period in the pair can be matched, or the vertical acceleration data sequence corresponding to two set time periods can be a sequence formed by the mean values of corresponding elements of the vertical acceleration data sequence, wherein W iskThe working stability corresponding to any set time period in the matching pair can be obtained, and the average value of the working stabilities corresponding to the two set time periods can also be obtained.
Next, the obtained correlation degrees of the isolated time periods are normalized and added to 1, and the sequence of the value range of X located in [0, 1 is: { C'1，C′2，……，C′nThe closer to 1, the stronger the difference of the vertical vibration conditions is, and the maximum difference degree C 'is determined to be obtained'MaxMinimum degree of Difference C'Min。
Therefore, the laser control system not only calculates the predicted output light power of the laser, but also can compensate the predicted output light power, and the effect of controlling the output light power of the laser in advance is achieved. Meanwhile, the laser control system obtains the vibration condition of the optical resonant cavity, and senses and warns the vibration of the laser caused by the external environment or the internal reasons of the laser.
It should be noted that: the sequence of the above embodiments of the present invention is only for description, and does not represent the advantages or disadvantages of the embodiments. And specific embodiments thereof have been described above. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing may also be possible or may be advantageous.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
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, CkAnd 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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