CN114441051B - Light field measuring method, light field measuring device and storage medium - Google Patents
Light field measuring method, light field measuring device and storage medium Download PDFInfo
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Abstract
The application relates to a light field measurement method, a light field measurement device and a storage medium, wherein the method comprises the following steps: the method comprises the steps of respectively splitting laser beams emitted by a laser device according to a plurality of preset phase differences in sequence to obtain a plurality of corresponding pairs of beams, wherein the phase difference of two beams in each pair of beams is a corresponding preset phase difference; respectively carrying out frequency multiplication on the multiple pairs of light beams to obtain multiple corresponding frequency multiplication light beams, and obtaining actual measurement spectrum information of the multiple frequency multiplication light beams; performing at least one iteration based on the measured spectral information to determine predicted light field information of the laser beam; according to the predicted light field information and a plurality of preset phase differences, determining predicted spectrum information of a plurality of frequency multiplication light beams; determining an accumulated error according to the predicted spectrum information and the actually measured spectrum information of the multiple frequency multiplication light beams; the light field measurement result of the laser beam is determined according to the accumulated error, thereby providing a new method for iteratively restoring the light field information of the laser, so as to shorten the time required for iteratively restoring the light field information of the laser (particularly the femtosecond laser).
Description
Technical Field
The present disclosure relates to the field of optical detection technologies, and in particular, to a light field measurement method, a light field measurement device, and a storage medium.
Background
For a laser whose time length is in the order of femtoseconds, how to accurately measure the light field information of the laser is one of the current research hotspots. In existing detection systems, there are methods that use autocorrelation to measure the pulse width of the femtosecond laser, but this method loses phase, carrier frequency information, and spectral distribution. Although time-domain spectral analysis and frequency-domain resolution optical switching methods are proposed later, the time required by the method for iteratively restoring the optical field information of the femtosecond laser matched with the time-domain spectral analysis and the frequency-domain resolution optical switching methods is long.
Disclosure of Invention
The embodiment of the application provides a light field measuring method, a light field measuring device and a storage medium, which are used for solving the problem of long time required by restoring light field information of a femtosecond laser by the existing iteration method.
In order to solve the above problems, an embodiment of the present application provides a light field measurement method, including:
the method comprises the steps of respectively splitting laser beams emitted by a laser device according to a plurality of preset phase differences in sequence to obtain a plurality of corresponding pairs of beams, wherein the phase difference of two beams in each pair of beams is a corresponding preset phase difference;
respectively carrying out frequency multiplication on the multiple pairs of light beams to obtain multiple corresponding frequency multiplication light beams, and obtaining actual measurement spectrum information of the multiple frequency multiplication light beams;
performing at least one iteration based on the measured spectral information to determine predicted light field information of the laser beam;
according to the predicted light field information and a plurality of preset phase differences, determining predicted spectrum information of a plurality of frequency multiplication light beams;
determining an accumulated error according to the predicted spectrum information and the actually measured spectrum information of the multiple frequency multiplication light beams;
and determining a light field measurement result of the laser beam according to the accumulated error.
Wherein, confirm the light field measuring result of the laser beam according to the accumulated error, include specifically:
when the accumulated error is smaller than a preset threshold value, taking the predicted light field information as a light field measurement result of the laser beam;
and when the accumulated error is greater than or equal to a preset threshold value, performing the next iteration to update the predicted light field information of the laser beam, and then returning to perform the step of determining the predicted spectrum information of the multiple frequency multiplication light beams according to the predicted light field information and the multiple preset phase differences.
The next iteration is performed to update the predicted light field information of the laser beam, which specifically includes:
determining corresponding amplitude gradient factors and phase gradient factors according to the results of the last two iterations;
updating the amplitude contained in the result of the last iteration based on the actually measured spectrum information and the amplitude gradient factor, and updating the phase contained in the result of the last iteration based on the phase gradient factor to obtain the result of the next iteration;
updating spectral domain information contained in the predicted light field information based on the updated amplitude and phase;
based on the updated spectral domain information, the time domain information contained in the predicted light field information is updated.
Wherein, according to the prediction spectrum information and the actual measurement spectrum information of a plurality of frequency multiplication light beams, confirm the accumulated error, specifically include:
determining the absolute value of the difference value between the predicted spectrum information and the actually measured spectrum information of each frequency multiplication light beam to obtain the prediction error of each frequency multiplication light beam;
root mean square values of the prediction errors of the plurality of multiplied beams are determined to obtain an accumulated error.
According to the predicted light field information and a plurality of preset phase differences, the predicted spectrum information of a plurality of frequency multiplication light beams is determined, and the method specifically comprises the following steps:
according to the time domain information contained in the predicted light field information and a plurality of preset phase differences, determining predicted time domain information of a plurality of frequency multiplication light beams;
and respectively carrying out Fourier transformation on the predicted time domain information of the multiple frequency multiplication light beams and multiplying the predicted time domain information by self conjugation so as to correspondingly obtain the predicted spectrum information of the multiple frequency multiplication light beams.
In order to solve the above-mentioned problems, an embodiment of the present application provides a light field measurement device, including:
the light splitting module is used for splitting the laser beams emitted by the lasers respectively according to a plurality of preset phase differences in sequence to obtain a plurality of corresponding pairs of light beams, and the phase difference of two light beams in each pair of light beams is a corresponding preset phase difference;
the frequency multiplication module is used for respectively carrying out frequency multiplication on the plurality of pairs of light beams to obtain a plurality of corresponding frequency multiplication light beams and obtaining actual measurement spectrum information of the plurality of frequency multiplication light beams;
a first determining module for performing at least one iteration based on the measured spectral information to determine predicted light field information of the laser beam;
the second determining module is used for determining the predicted spectrum information of the multiple frequency multiplication light beams according to the predicted light field information and the multiple preset phase differences;
the third determining module is used for determining an accumulated error according to the predicted spectrum information and the actually measured spectrum information of the multiple frequency multiplication light beams;
and the fourth determining module is used for determining the light field measurement result of the laser beam according to the accumulated error.
The fourth determining module is specifically configured to:
when the accumulated error is smaller than a preset threshold value, taking the predicted light field information as a light field measurement result of the laser beam;
and when the accumulated error is greater than or equal to a preset threshold value, performing the next iteration to update the predicted light field information of the laser beam, and triggering the second determining module to re-execute the predicted spectrum information of the multiple frequency multiplication light beams according to the predicted light field information and the multiple preset phase differences.
The next iteration is performed to update the predicted light field information of the laser beam, which specifically includes:
determining corresponding amplitude gradient factors and phase gradient factors according to the results of the last two iterations;
updating the amplitude contained in the result of the last iteration based on the actually measured spectrum information and the amplitude gradient factor, and updating the phase contained in the result of the last iteration based on the phase gradient factor to obtain the result of the next iteration;
updating spectral domain information contained in the predicted light field information based on the updated amplitude and phase;
based on the updated spectral domain information, the time domain information contained in the predicted light field information is updated.
The third determining module is specifically configured to:
determining the absolute value of the difference value between the predicted spectrum information and the actually measured spectrum information of each frequency multiplication light beam to obtain the prediction error of each frequency multiplication light beam;
root mean square values of the prediction errors of the plurality of multiplied beams are determined to obtain an accumulated error.
The second determining module is specifically configured to:
according to the time domain information contained in the predicted light field information and a plurality of preset phase differences, determining predicted time domain information of a plurality of frequency multiplication light beams;
and respectively carrying out Fourier transformation on the predicted time domain information of the multiple frequency multiplication light beams and multiplying the predicted time domain information by self conjugation so as to correspondingly obtain the predicted spectrum information of the multiple frequency multiplication light beams.
Embodiments of the present application also provide a computer readable storage medium storing a computer program adapted to be loaded by a processor to perform the light field measurement method of any one of the above.
According to the light field measuring method, the device and the storage medium, the laser beams emitted by the lasers are respectively split according to the preset phase differences in sequence to obtain the corresponding multiple pairs of beams, the phase difference of two beams in each pair of beams is the corresponding preset phase difference, then the multiple pairs of beams are respectively multiplied to obtain the corresponding multiple frequency multiplication beams, actual measurement spectrum information of the multiple frequency multiplication beams is obtained, at least one iteration is carried out based on the actual measurement spectrum information to determine predicted light field information of the laser beams, the predicted spectrum information of the multiple frequency multiplication beams is determined according to the predicted light field information and the preset phase differences, then the accumulated error is determined according to the predicted spectrum information and the actual measurement spectrum information of the multiple frequency multiplication beams, and the light field measuring result of the laser beams is determined according to the accumulated error, so that a novel method for iteratively recovering the light field information of the lasers is provided, and the time required for iteratively recovering the light field information of the lasers (particularly the femtosecond lasers) is shortened.
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Technical solutions and other advantageous effects of the present application will be made apparent from the following detailed description of specific embodiments of the present application with reference to the accompanying drawings.
Fig. 1 is a schematic flow chart of a light field measurement method provided in an embodiment of the present application;
FIG. 2 is a schematic diagram of a Michelson interferometer according to an embodiment of the present application for processing a laser beam emitted from a laser;
FIG. 3 is another flow chart of a light field measurement method according to an embodiment of the present disclosure;
fig. 4 is a schematic diagram of optical field information mode value distribution of a laser obtained by measurement in a time domain according to an embodiment of the present application;
FIG. 5 is a schematic diagram of the optical field information mode value distribution of the laser in the spectral domain obtained by measurement according to the embodiment of the present application;
fig. 6 is a schematic structural diagram of a light field measurement device according to an embodiment of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
The embodiment of the application provides a light field measurement method and device.
Referring to fig. 1, fig. 1 is a flow chart of a light field measurement method according to an embodiment of the present application, and a specific flow of the light field measurement method may be as follows:
s11, respectively carrying out light splitting on laser beams emitted by the lasers according to a plurality of preset phase differences in sequence to obtain a plurality of corresponding pairs of light beams, wherein the phase difference of two light beams in each pair of light beams is the corresponding preset phase difference.
In this embodiment, the above-described light field measurement method may be applied to light field information of a measurement laser (e.g., a femtosecond laser), and the light field information may include time domain information and spectral domain information of a light field. Specifically, two light beams of each pair of light beams may have the same vibration direction, and one of the two light beams may be used as reference light and the other may be used as test light. The phase difference between the test light and the reference light is equal to a preset phase difference currently used for splitting the laser beam to form a pair of light beams consisting of the test light and the reference light.
In some embodiments, the phases of the test light and the reference light in a pair of light beams may be the same or different, i.e., the above-described preset phase difference may be equal to zero or not. In one embodiment, the preset phase difference may be zero or a positive value.
S12, frequency multiplication is carried out on the multiple pairs of light beams respectively to obtain multiple corresponding frequency multiplication light beams, and actual measurement spectrum information of the multiple frequency multiplication light beams is obtained.
Specifically, in the process of sequentially and respectively splitting laser beams emitted from the lasers with a plurality of preset phase differences to obtain a plurality of corresponding pairs of beams including test light and reference light, each pair of beams is obtained, the pair of beams can be multiplied to obtain a corresponding frequency-multiplied beam, and each time a frequency-multiplied beam is obtained, spectrum information (i.e., actually measured spectrum information) of the frequency-multiplied beam can be obtained by a spectrometer.
In one embodiment, as shown in fig. 2, the modified michelson interferometer 20 may be used to process the laser beam 30L emitted from the laser 30 to obtain the measured spectrum information of the multiple frequency-doubled light beams L3 corresponding to the multiple preset phase differences one by one.
Specifically, the modified michelson interferometer 20 may include a spectroscopic unit 21, a phase delay unit 22, a frequency doubling unit 23, a spectral measurement unit 24, and a reference mirror 25. When a laser beam 30L emitted from the laser 30 is split by any one of the predetermined phase differences, the laser beam 30L irradiates the beam splitting unit 21 at a predetermined angle, a part of the light beam 30L passes through the beam splitting unit 21 to form the test light L1 emitted to the frequency doubling unit 23, and another part of the light beam is reflected by the beam splitting unit 21 to the phase delaying unit 22 and forms the reference light L2 emitted to the frequency doubling unit 23 after passing through the phase delaying unit 22. The test light L1 and the reference light L2 may be parallel to each other, and after being multiplied by the frequency multiplier unit 23, a corresponding frequency-multiplied light beam L3 can be formed. Then, the doubled light beam L3 may propagate in the direction of the spectrum measuring unit 24 and be detected by the spectrum measuring unit 24, so as to obtain the measured spectrum information of the doubled light beam L3.
In some embodiments, as shown in fig. 2, the light splitting unit 21 may be a beam splitter, the phase delay unit 22 may include a linear translation stage 221 and a pyramid prism 222, the frequency doubling unit 23 may include a focusing lens 231 and a nonlinear crystal (or frequency doubling crystal) 232, and the spectrum measuring unit 24 may be a spectrometer. Specifically, after the laser beam 30L irradiates the beam splitter, a part of the light beam passes through the beam splitter and is turned by 90 ° by the beam splitter to form the test light L1 directed to the focusing lens 231, and another part of the light beam is reflected by the beam splitter into the pyramid 222 and is turned by 180 ° by the pyramid 222 to form the reference light L2 directed to the focusing lens 231. The test light L1 and the reference light L2 may be converged at a point after being refracted by the focusing lens 231, and may be multiplied by the nonlinear crystal 232 at the point to form a corresponding multiplied frequency light beam L3.
In the above embodiment, the value of each preset phase difference can be controlled by adjusting the phase delay unit 22 in the michelson interferometer 20 of the above modification. Specifically, the magnitude of each preset phase difference can be controlled by moving the linear translation stage 221 in the phase delay unit 22 in the Z direction. It will be appreciated that moving the linear translation stage 221 in the Z direction substantially changes the optical path difference between the test light L1 and the reference light L2, for example, moving the linear translation stage 221 in the Z direction away from the beam splitter increases the optical path difference between the test light L1 and the reference light L2, and conversely, decreases the optical path difference between the test light L1 and the reference light L2.
In this embodiment, the plurality of pairs of light beams are in one-to-one correspondence with the plurality of preset phase differences, and the plurality of frequency-doubled light beams are in one-to-one correspondence with the plurality of preset phase differences. And, the preset phase difference may be represented by τ, so that the test light and the reference light in the pair of light beams corresponding to the preset phase difference τ may be represented as E, respectively T (t) and E R The frequency-doubled light beam corresponding to the preset phase difference tau can be expressed as E doubel_w And E is doubel_w ＝CE T (t)E R (t- τ), wherein C represents a constant. Correspondingly, the phase difference tau is presetCorresponding frequency-doubled light beam E doubel_w May be represented as I spectrum (w, τ), and I spectrum (w,τ)＝|FT[CE T (t)E R (t-τ]| 2 Where FT denotes a fourier transform operator for converting a signal in the time domain (i.e., time domain) t into a signal in the spectral domain (i.e., frequency domain) w.
It can be appreciated that compared with the direct measurement of the laser beam to obtain the measured spectrum information, the present embodiment obtains the measured spectrum information by measuring the frequency-doubled beam, which can have a larger spectrum measurement time range, thereby being beneficial to reducing measurement errors.
In a specific embodiment, as shown in fig. 2, the frequency doubling unit 23 may further include a small aperture diaphragm 233, where the small aperture diaphragm 233 can screen the light emitted from the nonlinear crystal 232 to screen the frequency doubling light L3, so as to reduce or avoid the non-frequency doubling light emitted from the nonlinear crystal 232 (i.e., the light passing through the nonlinear crystal 232 but not being frequency doubled in the test light L1 and the reference light L2) from entering the spectrum measuring unit 24, which improves the accuracy of the measured spectrum information of the frequency doubling light L3 measured by the spectrum measuring unit 24.
S13, performing at least one iteration based on the actually measured spectrum information to determine predicted light field information of the laser beam.
In this embodiment, the predicted light field information of the laser beam may include information such as spectral domain information and time domain information of the predicted light field.
Specifically, before the iteration starts, that is, before the 1 st iteration is performed, an initial value of the iteration (that is, a result of the zeroth iteration) may be set in advance, and the above-described laser beam initial predicted light field information is determined from the result of the zeroth iteration. The result of the zeroth iteration may include a plurality of initial amplitudes corresponding to the plurality of preset phase differences τ one by one and a plurality of initial phases corresponding to the plurality of preset phase differences τ one by one, and the initial predicted light field information determined by the zeroth iteration may include initial time domain information and a plurality of initial spectral domain information corresponding to the plurality of preset phase differences τ one by one.
In one embodiment, in the result of the zeroth iteration, the amplitude and phase corresponding to the preset phase difference τ may be represented as
And j phi (t, tau), and spectral domain information corresponding to the preset phase difference tau contained in the initial predicted light field information determined by the zeroth iteration may be expressed as +.>
And is also provided with
Based on this, the time domain information contained in the initial predicted light field information determined by the zeroth iteration can be expressed as +.>
And->
Wherein iFT is the inverse fourier transform operator. That is, it is possible to add the spectral domain information corresponding to the plurality of preset phase differences τ to the plurality of predetermined phase differences τ>
Respectively performing inverse Fourier transform and then accumulating to obtain corresponding time domain information +.>
In one embodiment, the at least one iteration may be specifically one iteration, and the corresponding S13 may be specifically: a first iteration is performed based on the measured spectral information to determine predicted light field information for the laser beam.
Specifically, performing a first iteration based on the measured spectral information to determine predicted light field information of the laser beam may include: respectively utilizing a plurality of phase differences tau corresponding to the preset phase differences tau one by oneFrequency-doubled light beam E doubel_w Is the measured spectral information I of (1) spectrum Amplitude Sqrt (I) of (w, τ) spectrum (w, τ)) corresponding updating is carried out on a plurality of amplitudes corresponding to the preset phase differences τ one by one in the result of the zeroth iteration so as to obtain the result of the first iteration; updating spectral domain information contained in the predicted light field information based on the updated amplitude; and updating time domain information contained in the predicted light field information based on the updated spectral domain information.
In the result of the first iteration, the amplitude and phase corresponding to the preset phase difference τ can be expressed as
And j phi (t, tau), and +.>
The spectral domain information corresponding to the preset phase difference tau contained in the predicted light field information corresponding to the first iterative determination may be expressed as +.>
And->
Based on this, the time domain information obtained by iteration 1 can be expressed as +.>
And->
S14, according to the predicted light field information and a plurality of preset phase differences, determining predicted spectrum information of a plurality of frequency multiplication light beams.
Specifically, after performing the above-mentioned at least one iteration (for example, k iterations, where k is greater than or equal to 1) and before performing the next iteration (for example, the (k+1) th iteration), the predicted spectral information of the multiple frequency-multiplied light beams corresponding to the multiple preset phase differences τ one-to-one may be determined according to the predicted light field information and the multiple preset phase differences τ. That is, the above-described predicted light field information and predicted spectrum information may be predicted light field information and predicted spectrum information, respectively, determined by the kth iteration.
In one embodiment, the step S14 may specifically include:
s141: and determining the predicted time domain information of the multiple frequency multiplication light beams according to the time domain information contained in the predicted light field information and the multiple preset phase differences.
Specifically, the time domain information included in the predicted light field information is the time domain information included in the predicted light field information obtained by the kth iteration determination
And the predicted time domain information of the frequency-doubled light beam corresponding to the preset phase difference τ can be expressed as +.>
And->
Where c represents the speed of light, K represents the wave vector, and j represents a constant.
S142: and respectively carrying out Fourier transformation on the predicted time domain information of the multiple frequency multiplication light beams and multiplying the predicted time domain information by self conjugation so as to correspondingly obtain the predicted spectrum information of the multiple frequency multiplication light beams.
Specifically, after performing the above-mentioned at least one iteration (for example, k iterations) and before performing the next iteration (for example, the (k+1) th iteration), the predicted spectrum information of the frequency-doubled light beam corresponding to the preset phase difference τ may be expressed as
And->
Where conj () is a conjugate function.
S15: and determining the accumulated error according to the predicted spectrum information and the actually measured spectrum information of the multiple frequency multiplication light beams.
Wherein, the step S15 may specifically include:
s151: and determining the absolute value of the difference value between the predicted spectrum information and the actually measured spectrum information of each frequency multiplication light beam to obtain the prediction error of each frequency multiplication light beam.
Specifically, after performing at least one iteration (for example, k iterations) and before performing the next iteration (for example, the (k+1) th iteration), the prediction error of the frequency-doubled light beam corresponding to the preset phase difference τ may be expressed as error k (w, τ), and
where abs () is a function that takes an absolute value.
S152: root mean square values of the prediction errors of the plurality of multiplied beams are determined to obtain an accumulated error.
Specifically, after performing at least one iteration (e.g., k iterations) as described above, and before performing the next iteration (e.g., the (k+1) th iteration), the accumulated error may be represented as calcul_error k (w, τ), and
where abs () is a function of absolute value, sqrt () is a function of square root, Σ is a summation formula, and N represents the number of preset phase differences τ.
S16, determining a light field measurement result of the laser beam according to the accumulated error.
As shown in fig. 3, the step S16 may specifically include:
s161, when the accumulated error is smaller than a preset threshold value, the predicted light field information is used as a light field measurement result of the laser beam.
S162, when the accumulated error is greater than or equal to a preset threshold, performing the next iteration to update the predicted light field information of the laser beam, and then returning to execute the step S14 (or S141).
In this embodiment, the preset threshold may be determined by the actually required light field measurement accuracy, and in one embodiment, the preset threshold may beTo be between 10 -6 ～10 -5 Between them. The smaller the accumulated error, the closer the predicted light field information obtained by the last iteration determination is to the real light field information of the laser beam.
Specifically, after performing at least one iteration (e.g., k iterations) and before performing the next iteration (e.g., the (k+1) th iteration), if the calculated accumulated error calcul_error k When (w, τ) is smaller than the preset threshold, it is indicated that the preset light field information obtained by the kth iteration determination can reach the light field measurement accuracy requirement of the laser, so that the iteration can be stopped, and the preset light field information obtained by the kth iteration determination can be output as the light field measurement result of the laser. In one embodiment, the optical field measurement result may include time domain information of the optical field of the measured laser beam as shown in fig. 4, and the optical field measurement result may include spectral domain information of the optical field of the measured laser beam as shown in fig. 5.
And if the calculated accumulated error is calculated k And (w, τ) is not smaller than the preset threshold, which indicates that the error of the predicted light field information obtained by the kth iteration determination relative to the actual light field information of the laser is larger. Thus, the number of iterations (e.g., the (k+1) th iteration) needs to be increased to update the predicted light field information determined by the kth iteration to reduce the error in measuring the light field information of the laser by the iterative method.
It will be appreciated that the above S162, S14 and S15 can form a loop, and that each time a loop is executed, the corresponding number of iterations increases once, and the loop stops once the calculated accumulated error can meet the requirement (i.e. is smaller than the above predetermined threshold). In some embodiments, an upper limit of the number of iterations may also be preset, so that when the number of iterations reaches the upper limit, the loop may be stopped (i.e., the loop may be forced to stop when the number of iterations reaches the upper limit) even if the calculated accumulated error is not able to meet the requirement.
In a specific embodiment, the performing the next iteration to update the predicted light field information of the laser beam may specifically include:
s1-1: and determining corresponding amplitude gradient factors and phase gradient factors according to the results of the last two iterations.
Specifically, when the next iteration is the (k+1) th iteration, the last two iterations are the kth iteration and the (k-1) th iteration, respectively, where k is greater than or equal to 1, for example, if k is equal to 1, the last two iterations are the 1 st iteration and the 0 th iteration, respectively, and if k is equal to 2, the last two iterations are the 2 nd iteration and the 1 st iteration, respectively. And, after the above-described kth iteration is performed, and before the (k+1) th iteration is performed, the corresponding amplitude gradient factor and phase gradient factor may be determined based on the result of the kth iteration and the result of the (k-1) th iteration.
Wherein the amplitude gradient factor can be expressed as
And is also provided with
/>
The phase gradient factor can be expressed as
And, in addition, the method comprises the steps of,
where angle () is a function of the phase angle.
Wherein, the liquid crystal display device comprises a liquid crystal display device,
for the amplitude corresponding to the preset phase difference tau contained in the result of the kth iteration,
amplitude corresponding to the preset phase difference tau contained as the result of the (k-1) th iteration,/->
The amplitude corresponding to the preset phase difference τ is included as a result of the (k+1) th iteration.
S1-2: and updating the amplitude contained in the result of the last iteration based on the actually measured spectrum information and the amplitude gradient factor, and updating the phase contained in the result of the last iteration based on the phase gradient factor to obtain the result of the next iteration.
Specifically, each amplitude modulus corresponding to each preset phase difference τ can be included in the result of the last iteration (i.e., the kth iteration)
Respectively replace the measured spectrum information I corresponding to each corresponding preset phase difference tau spectrum Amplitude sqrt (I) of (w, τ) spectrum (w, τ)) and the above-mentioned amplitude gradient factor +.>
And (3) summing. That is, the amplitude modulus +_corresponding to the preset phase difference τ included in the result of the (k+1) th iteration>
Is that
And, each phase corresponding to each preset phase difference τ included in the result of the last iteration (i.e., the kth iteration)
Respectively replaced by the phase corresponding to each corresponding preset phase difference tau contained in the result of the kth iteration>
Is in accordance with the above phase gradient factor->
And (3) summing. That is, the result of the (k+1) -th iteration includes a phase +.>
Is that
S1-3: and updating spectral domain information contained in the predicted light field information based on the updated amplitude and phase.
Specifically, spectral domain information corresponding to the preset phase difference τ contained in the predicted light field information obtained by the (k+1) -th iterative update may be expressed as
And is also provided with
S1-4: based on the updated spectral domain information, the time domain information contained in the predicted light field information is updated.
Specifically, the time domain information contained in the predicted light field information obtained by the (k+1) -th iterative update may be expressed as
And->
That is, the (k+1) th iteration updates the time domain information included in the predicted light field information>
By corresponding to the plurality of preset phase differences tauIs->
And performing inverse fourier transform and then superposition.
It will be appreciated that in this embodiment, from the second iteration, each iteration is performed to update the prediction result of the optical field in the spectral domain and the time domain, that is, by adding constraints in the spectral domain and the time domain, the spectral domain and the time domain are iteratively updated. On the basis, a phase gradient factor and an amplitude gradient factor are further introduced, so that double-gradient conjugate descent can be formed, convergence is accelerated, minimum values are skipped, minimum value searching can be realized, and light field information of the laser can be quickly reconstructed.
As can be seen from the foregoing, in the optical field measurement method provided in this embodiment, the laser beams emitted from the lasers are split by sequentially using a plurality of preset phase differences, so as to obtain a plurality of corresponding pairs of beams, the phase difference between two beams in each pair of beams is the corresponding preset phase difference, then the plurality of pairs of beams are multiplied to obtain a plurality of corresponding multiplied beams, actual measurement spectrum information of the plurality of multiplied beams is obtained, at least one iteration is performed based on the actual measurement spectrum information to determine predicted optical field information of the laser beams, the predicted optical field information of the plurality of multiplied beams is determined according to the predicted optical field information and the plurality of preset phase differences, then an accumulated error is determined according to the predicted optical field information and the actual measurement spectrum information of the plurality of multiplied beams, and an optical field measurement result of the laser beam is determined according to the accumulated error.
The present embodiment will be further described from the perspective of the light field measurement apparatus on the basis of the method described in the above embodiment, and referring to fig. 6, fig. 6 specifically describes a light field measurement apparatus provided in the embodiment of the present application, which may include: a light splitting module 601, a frequency doubling module 602, a first determining module 603, a second determining module 604, a third determining module 604 and a fourth determining module 604, wherein:
(1) Light splitting module 601
The beam splitting module 601 is configured to split the laser beams emitted by the lasers with a plurality of preset phase differences in sequence, so as to obtain a plurality of corresponding pairs of beams, where the phase difference between two beams in each pair of beams is the corresponding preset phase difference.
(2) Frequency doubling module 602
The frequency multiplication module 602 is configured to multiply the pairs of light beams to obtain a plurality of corresponding frequency-multiplied light beams, and obtain measured spectrum information of the plurality of frequency-multiplied light beams.
(3) First determination module 603
A first determining module 603 is configured to perform at least one iteration based on the measured spectral information to determine predicted light field information of the laser beam.
(4) The second determination module 604
The second determining module 604 is configured to determine predicted spectrum information of the multiple frequency-doubled light beams according to the predicted light field information and the multiple preset phase differences.
In one embodiment, the second determining module 604 may be specifically configured to:
according to the time domain information contained in the predicted light field information and a plurality of preset phase differences, determining predicted time domain information of a plurality of frequency multiplication light beams;
and respectively carrying out Fourier transformation on the predicted time domain information of the multiple frequency multiplication light beams and multiplying the predicted time domain information by self conjugation so as to correspondingly obtain the predicted spectrum information of the multiple frequency multiplication light beams.
(5) Third determination module 605
The third determining module 605 is configured to determine the accumulated error according to the predicted spectrum information and the actually measured spectrum information of the multiple frequency-multiplied beams.
In one embodiment, the third determining module 605 may be specifically configured to:
determining the absolute value of the difference value between the predicted spectrum information and the actually measured spectrum information of each frequency multiplication light beam to obtain the prediction error of each frequency multiplication light beam;
root mean square values of the prediction errors of the plurality of multiplied beams are determined to obtain an accumulated error.
(6) Fourth determination module 606
A fourth determining module 606 is configured to determine a light field measurement of the laser beam according to the accumulated error.
The fourth determining module 606 may be specifically configured to:
when the accumulated error is smaller than a preset threshold value, taking the predicted light field information as a light field measurement result of the laser beam;
when the accumulated error is greater than or equal to the preset threshold, the next iteration is performed to update the predicted light field information of the laser beam, and then the second determining module 604 is triggered to re-execute to determine the predicted spectrum information of the multiple frequency-doubled light beams according to the predicted light field information and the multiple preset phase differences.
In a specific embodiment, the performing the next iteration to update the predicted light field information of the laser beam may specifically include:
determining corresponding amplitude gradient factors and phase gradient factors according to the results of the last two iterations;
updating the amplitude contained in the result of the last iteration based on the actually measured spectrum information and the amplitude gradient factor, and updating the phase contained in the result of the last iteration based on the phase gradient factor to obtain the result of the next iteration;
updating spectral domain information contained in the predicted light field information based on the updated amplitude and phase;
based on the updated spectral domain information, the time domain information contained in the predicted light field information is updated.
It should be noted that, in the implementation, each module may be implemented as an independent entity, or may be combined arbitrarily and implemented as the same entity or a plurality of entities, and the implementation of each module may refer to the foregoing method embodiment, which is not repeated herein.
As can be seen from the above, the light field measuring device provided in this embodiment includes a light splitting module, configured to split laser beams emitted from a laser device respectively with a plurality of preset phase differences in sequence, so as to obtain a plurality of corresponding pairs of light beams, where a phase difference between two light beams in each pair of light beams is a corresponding preset phase difference; the frequency multiplication module is used for respectively carrying out frequency multiplication on the plurality of pairs of light beams to obtain a plurality of corresponding frequency multiplication light beams and obtaining actual measurement spectrum information of the plurality of frequency multiplication light beams; a first determining module for performing at least one iteration based on the measured spectral information to determine predicted light field information of the laser beam; the second determining module is used for determining the predicted spectrum information of the multiple frequency multiplication light beams according to the predicted light field information and the multiple preset phase differences; the third determining module is used for determining an accumulated error according to the predicted spectrum information and the actually measured spectrum information of the multiple frequency multiplication light beams; and a fourth determining module, configured to determine a light field measurement result of the laser beam according to the accumulated error, thereby providing a new method for iteratively restoring the light field information of the laser, so as to shorten the time required for iteratively restoring the light field information of the laser (especially, the femtosecond laser).
Accordingly, embodiments of the present application also provide a computer readable storage medium storing a computer program, and the computer program is capable of being loaded by a processor to perform steps in any of the light field measurement methods provided by embodiments of the present application. For example, the computer program may perform the steps of:
the method comprises the steps of respectively splitting laser beams emitted by a laser device according to a plurality of preset phase differences in sequence to obtain a plurality of corresponding pairs of beams, wherein the phase difference of two beams in each pair of beams is a corresponding preset phase difference;
respectively carrying out frequency multiplication on the multiple pairs of light beams to obtain multiple corresponding frequency multiplication light beams, and obtaining actual measurement spectrum information of the multiple frequency multiplication light beams;
performing at least one iteration based on the measured spectral information to determine predicted light field information of the laser beam;
according to the predicted light field information and a plurality of preset phase differences, determining predicted spectrum information of a plurality of frequency multiplication light beams;
determining an accumulated error according to the predicted spectrum information and the actually measured spectrum information of the multiple frequency multiplication light beams;
and determining a light field measurement result of the laser beam according to the accumulated error.
The specific implementation of each operation above may be referred to the previous embodiments, and will not be described herein.
Wherein the computer-readable storage medium may comprise: read Only Memory (ROM), random access Memory (RAM, random Access Memory), magnetic or optical disk, and the like.
Because the computer program stored in the computer readable storage medium can execute the steps in any light field measurement method provided by the embodiments of the present application, the beneficial effects that any light field measurement method provided by the embodiments of the present application can be achieved, which are detailed in the previous embodiments and are not described herein.
The foregoing description of the preferred embodiments of the present application is not intended to be limiting, but is intended to cover any and all modifications, equivalents, and alternatives falling within the spirit and principles of the present application.
Claims (10)
1. A light field measurement method, comprising:
the method comprises the steps of respectively carrying out light splitting on laser beams emitted by a laser device according to a plurality of preset phase differences in sequence to obtain a plurality of corresponding pairs of light beams, wherein the phase difference of two light beams in each pair of light beams is the corresponding preset phase difference;
respectively carrying out frequency multiplication on a plurality of pairs of light beams to obtain a plurality of corresponding frequency multiplication light beams, and obtaining actual measurement spectrum information of the plurality of frequency multiplication light beams;
performing at least one iteration based on the measured spectral information to determine predicted light field information for the laser beam;
determining predicted spectrum information of a plurality of frequency multiplication light beams according to the predicted light field information and a plurality of preset phase differences;
determining an accumulated error according to the predicted spectrum information and the actually measured spectrum information of a plurality of frequency multiplication light beams;
and determining a light field measurement result of the laser beam according to the accumulated error.
2. The light field measurement method according to claim 1, wherein the determining the light field measurement result of the laser beam according to the accumulated error specifically comprises:
when the accumulated error is smaller than a preset threshold value, taking the predicted light field information as a light field measurement result of the laser beam;
and when the accumulated error is greater than or equal to the preset threshold, performing the next iteration to update the predicted light field information of the laser beam, and then returning to execute the step of determining the predicted spectrum information of a plurality of frequency multiplication light beams according to the predicted light field information and a plurality of preset phase differences.
3. The light field measurement method according to claim 2, wherein the performing of the next iteration to update the predicted light field information of the laser beam comprises:
determining corresponding amplitude gradient factors and phase gradient factors according to the results of the last two iterations;
updating the amplitude contained in the result of the last iteration based on the actually measured spectrum information and the amplitude gradient factor, and updating the phase contained in the result of the last iteration based on the phase gradient factor to obtain the result of the next iteration;
updating spectral domain information contained in the predicted light field information based on the updated amplitude and phase;
and updating time domain information contained in the predicted light field information based on the updated spectral domain information.
4. The light field measurement method according to claim 1, wherein determining the accumulated error from the predicted spectral information and the measured spectral information of the plurality of frequency-doubled light beams comprises:
determining the absolute value of the difference value between the predicted spectrum information and the actually measured spectrum information of each frequency multiplication light beam to obtain the predicted error of each frequency multiplication light beam;
and determining root mean square values of the prediction errors of a plurality of the frequency multiplication beams to obtain accumulated errors.
5. The light field measurement method according to claim 1, wherein the determining predicted spectral information of the multiple frequency-doubled light beams according to the predicted light field information and the multiple preset phase differences specifically comprises:
determining predicted time domain information of a plurality of frequency multiplication light beams according to the time domain information contained in the predicted light field information and a plurality of preset phase differences;
and respectively carrying out Fourier transform on the predicted time domain information of the multiple frequency multiplication light beams and multiplying the predicted time domain information by self conjugation so as to correspondingly obtain the predicted spectrum information of the multiple frequency multiplication light beams.
6. A light field measurement device, comprising:
the light splitting module is used for sequentially and respectively splitting laser beams emitted by the lasers according to a plurality of preset phase differences to obtain a plurality of corresponding pairs of light beams, and the phase difference of two light beams in each pair of light beams is the corresponding preset phase difference;
the frequency multiplication module is used for respectively carrying out frequency multiplication on the plurality of pairs of light beams to obtain a plurality of corresponding frequency multiplication light beams and obtaining actual measurement spectrum information of the plurality of frequency multiplication light beams;
a first determining module for performing at least one iteration based on the measured spectral information to determine predicted light field information of the laser beam;
the second determining module is used for determining the predicted spectrum information of the multiple frequency multiplication light beams according to the predicted light field information and the multiple preset phase differences;
the third determining module is used for determining accumulated errors according to the predicted spectrum information and the actually measured spectrum information of the multiple frequency multiplication light beams;
and a fourth determining module, configured to determine a light field measurement result of the laser beam according to the accumulated error.
7. The light field measurement device of claim 6, wherein the fourth determination module is specifically configured to:
when the accumulated error is smaller than a preset threshold value, taking the predicted light field information as a light field measurement result of the laser beam;
and when the accumulated error is greater than or equal to the preset threshold, performing the next iteration to update the predicted light field information of the laser beam, and then triggering the second determining module to re-execute the predicted spectrum information of the multiple frequency multiplication light beams according to the predicted light field information and the multiple preset phase differences.
8. The light field measurement device of claim 7, wherein the performing the next iteration to update the predicted light field information of the laser beam comprises:
determining corresponding amplitude gradient factors and phase gradient factors according to the results of the last two iterations;
updating the amplitude contained in the result of the last iteration based on the actually measured spectrum information and the amplitude gradient factor, and updating the phase contained in the result of the last iteration based on the phase gradient factor to obtain the result of the next iteration;
updating spectral domain information contained in the predicted light field information based on the updated amplitude and phase;
and updating time domain information contained in the predicted light field information based on the updated spectral domain information.
9. The light field measurement device of claim 6, wherein the third determination module is specifically configured to:
determining the absolute value of the difference value between the predicted spectrum information and the actually measured spectrum information of each frequency multiplication light beam to obtain the predicted error of each frequency multiplication light beam;
and determining root mean square values of the prediction errors of a plurality of the frequency multiplication beams to obtain accumulated errors.
10. A computer readable storage medium, characterized in that it stores a computer program adapted to be loaded by a processor to perform the light field measurement method of any one of claims 1-5.
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