CN111623958B - Wavelet peak-peak value extraction method in interference signal - Google Patents

Wavelet peak-peak value extraction method in interference signal Download PDF

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CN111623958B
CN111623958B CN202010421825.6A CN202010421825A CN111623958B CN 111623958 B CN111623958 B CN 111623958B CN 202010421825 A CN202010421825 A CN 202010421825A CN 111623958 B CN111623958 B CN 111623958B
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潘宏亮
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Changchun Ouyi Photoelectric Technology Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0207—Details of measuring devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/14—Measuring arrangements characterised by the use of optical techniques for measuring distance or clearance between spaced objects or spaced apertures

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Abstract

The invention relates to a method for extracting wavelet peak values of interference signals, which comprises the following steps: denoising and fitting the interference signal to obtain an envelope signal; filtering out sampling points with energy amplitude values smaller than a set threshold value, and taking the reserved sampling points as data points; the energy amplitude is compared by 2N1The energy amplitude of the data points with large data points and the corresponding positions thereof are taken as the wave peak value and the position thereof; the position difference is less than N2The sampling points and two adjacent wave crests of which the wave crest value difference is less than Vc are used as effective wave crests to store the peak values and the positions of the effective wave crests; for position difference less than N2Sampling points, two adjacent wave crests of which the wave crest value difference is greater than Vc, and taking the higher wave crest as an effective wave crest to store the peak value and the position of the effective wave crest; difference of the opposite positions is larger than N2Sampling points, wherein the two adjacent wave crests are used as effective wave crests to store peak values and positions of the peak values; n is a radical of1、N2And Vc is a set value. The invention can improve the accuracy of obtaining the wave peak value and the peak position.

Description

Wavelet peak-peak value extraction method in interference signal
Technical Field
The invention belongs to the technical field of interference signal peak value extraction, and particularly relates to a wavelet peak value extraction method in an interference signal.
Background
The optical adjustment is used as the last ring for manufacturing the lens, and is one of the keys for ensuring the performance of the optical lens by strictly controlling the central deviation and the mirror surface interval of the optical lens. In addition, the detection and verification of the interval of the assembled optical lens group is also a problem frequently encountered by optical personnel. The non-contact mirror surface interval measuring instrument can assist installation and adjustment personnel to monitor and measure the interval in real time in the lens installation process based on the low coherence interference principle, and can also accurately measure the interval of the finished optical lens group.
In the detection by using laser, the optical lens group is determined at intervals according to the size and position of the peak value of the interference signal, so the requirements on the extraction and position accuracy of the effective peak are very strict, and the final detection result is influenced. In the process of extracting peaks, peaks are generally lost or miscellaneous peaks are extracted, so that the improvement of the accuracy of acquiring peak values and peak value positions becomes a key for improving the laser detection performance.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a wavelet peak-to-peak value extraction method in interference signals, which can effectively prevent the loss and over-extraction of small peaks, thereby improving the accuracy of acquiring peak values and peak value positions.
In order to solve the above technical problem, the method for extracting wavelet peak-to-peak value of interference signal of the present invention comprises the following steps:
removing noise from an interference signal and fitting to obtain a smooth envelope signal;
filtering sampling points with energy amplitudes smaller than a set threshold value, and storing the reserved sampling points as data points into a data point array;
step three, the energy amplitude of each data point in the data point array and the front and back N1Comparing the energy amplitude of the data points, if the energy amplitude of the data points is 2N before and after1If the energy amplitude of the data point is large, recording the energy amplitude of the data point and the corresponding position of the data point as a wave peak value and the position of the wave peak value, otherwise, not recording the energy amplitude; finally, a group of wave peak value sets and position sets corresponding to the wave peak values are obtained;
step four, when the difference value of the positions of two adjacent wave crests is less than N2Sampling points, and when the wave peak value difference value is less than Vc, taking two adjacent wave peaks as effective wave peaks to store the peak values and the positions of the effective wave peaks; when the position difference of two adjacent wave crests is less than N2Sampling points, and when the difference value of adjacent wave peak values is greater than Vc, taking the higher wave peak as an effective wave peak and storing the peak value and the position of the effective wave peak; when the position difference of two adjacent wave crests is larger than N2Sampling points, and storing peak values and positions thereof by taking the two wave crests as effective wave crests; n is a radical of1、N2And Vc is a set value.
N1、N2According to the setting of the sampling frequency f, 0.0001f < N1 < 0.0002f and 0.00015f < N2 < 0.001 f.
Vc is set according to the maximum value V of two adjacent peaks, and Vc is more than 0.1V and less than V.
The invention has the beneficial effects that: the invention can avoid extracting the miscellaneous peak or losing the effective wave peak value, thereby improving the accuracy of obtaining the wave peak value and the peak value position and improving the performance of laser detection.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a schematic diagram of a measurement of a spacer gauge; in the figure, 1 is a measuring arm, and 2 is a reference arm; 01 is a super-radiation light-emitting diode, 02 is an optical fiber coupler, 03 is a measuring head, 04 is a measured mirror group, 05 is a collimating mirror, 06 is a reflecting mirror, and 07 is a detector; l is a delay line.
Fig. 2 is a flow chart of the present invention.
Fig. 3 is a waveform diagram of an original interference signal.
Fig. 4 is a waveform diagram of an envelope of an original interference signal with 3 peaks inside.
Fig. 5a, 5b, and 5c are enlarged images of 3 peaks, respectively.
Detailed Description
As shown in fig. 1, the measurement principle of the noncontact mirror surface interval measuring instrument is as follows: the light source adopts a super-radiation light-emitting diode 01, light emitted by the super-radiation light-emitting diode 01 is divided into two parts by an optical fiber coupler 02, one part enters a measuring arm 1, the light is collimated by a measuring head 03, is reflected by the surfaces of all lenses in a measured lens group 04 and then returns to the optical fiber coupler 02; one path enters a reference arm 2 which comprises a delay line L, light rays are collimated by a collimating mirror 05 and reflected by a reflecting mirror 06 to return to the optical fiber coupler 02, and the reflecting mirror 06 is installed on an electric translation table, and the position of the reflecting mirror is measured by an internal metering system based on a linear optical encoder. By adjusting the position of the measuring arm 1, when the optical path difference of the two reflected lights is matched within the coherence length, an interference signal is generated in the detector 07. The absolute position of each lens surface is determined by the position of the mirror 06 of the delay line L corresponding to the peak of the interference fringe envelope, and the distance between the two surfaces is proportional to the interval between the two interference peaks, so that the air gap or mirror thickness can be calculated. Accurate air space or mirror thickness can be obtained by accurately extracting the wavelet peak value of the interference signal and then calculating.
And moving the reflector, detecting interference signals of the two paths of reflected light by a detector 07, sampling at the frequency of 18 ten thousand points/second, and obtaining the energy amplitude of a sampling point. When the optical path difference of the two reflected lights is matched within the coherence length, the peak value corresponding to each optical surface can be obtained. The peak positions and the number thereof theoretically correspond to the positions and the number of the respective optical surfaces. Therefore, the accuracy of obtaining the peak value and the peak position is improved, and the key for improving the laser detection performance is realized.
As shown in fig. 2, the method for extracting wavelet peak-to-peak value of interference signal of the present invention comprises the following steps:
step one, acquiring interference signals, and obtaining smoothed envelope signals according to a formula (1), wherein the envelope signals are shown in figure 3;
Figure GDA0003251682450000031
pdata (i-2) represents the energy amplitude of the envelope signal corresponding to the (i-2) th sampling point, and data (i) represents the energy amplitude of the interference signal corresponding to the ith sampling point;
step two, defining a threshold value fcThe threshold value is determined according to oscillograms measured for multiple times and experience and is larger than most of miscellaneous peak values so as to filter the miscellaneous peak values as much as possible;
if pdata (i) > fc, making i ═ pos (j), and storing pos (k) in the data point array; pdata (i) represents the energy amplitude of the envelope signal corresponding to the ith sampling point, pos (j) represents the data point corresponding to the ith sampling point, wherein the energy amplitude of the data point corresponding to the ith sampling point is greater than a threshold value, pos (j) is defined as the jth data point, and j is 1,2,3, …;
step three, comparing the energy amplitude of each data point in the data point array with the energy amplitudes of 40 data points before and after the data point array, if the energy amplitude of the data point is larger than the energy amplitudes of 80 data points before and after the data point, recording the energy amplitude of the data point and the corresponding position as a wave crest value and the position of the wave crest value, otherwise, not recording the wave crest value and the position of the wave crest value; finally, a group of wave peak value sets and position sets corresponding to the wave peak values are obtained, namely if:
pdata(pos(j))＞pdata(pos(j-n))，n＝1，2，3，...，10； (2)
pdata(pos(j))＞pdata(pos(j+n))，n＝1，2，3，...，10； (3)
pdata (pos (j)) is an energy amplitude of an envelope signal corresponding to the jth data point; order:
V(k)＝pdata(pos(j))
P(k)＝pos(j)
saving V (k) as a wave peak value into a wave peak value array, and saving P (k) as a wave peak position into a wave peak position array;
step four, when the position difference of two adjacent wave crests is less than 150 sampling points and the wave crest difference is less than 0.05(v), taking the two adjacent wave crests as effective wave crests and storing the peak values and the positions of the effective wave crests; when the position difference value of two adjacent wave crests is less than 150 sampling points and the difference value of the adjacent wave peak values is more than 0.05(v), the higher wave crest is taken as an effective wave crest and the peak value and the position of the effective wave crest are stored; when the position difference value of two adjacent wave crests is larger than 150 sampling points, the two wave crests are used as effective wave crests to store the peak values and the positions of the effective wave crests; the specific operation method comprises the following steps:
as shown in fig. 5a, if the formulas (4) and (5) are satisfied, the peak 3 is the calculated effective peak, the peak value and the position of the peak 3 are saved, and the two side peaks are filtered;
|V(k)-V(k+1)|＞0.05 (4)
P(k+1)-P(k)＜150 (5)
as shown in fig. 5b, if the equations (6) and (7) are satisfied, the peaks 6 and 7 are the calculated effective peaks, the peaks 6 and 7 and their positions are saved, and the undesired peaks 4 and 5 are filtered out;
|V(k)-V(k+1)|＜0.05 (6)
P(k+1)-P(k)＜150， (7)
as shown in fig. 5c, if equations (8) and (9) are satisfied, the peak 8 is the calculated effective peak, and the peak of the peak 8 and its corresponding position are saved;
P(k)-P(k-1)＞150 (8)
P(k+1)-P(k)＞150 (9)
in the prior art, all the miscellaneous peaks are extracted or the peaks 3, 7 and 8 are extracted and the peak 6 is lost when other algorithms extract the peak value.

Claims (1)

1. A method for extracting wavelet peak value of interference signal is characterized in that the method for generating interference signal is as follows: the light source adopts a super-radiation light-emitting diode (01), light rays emitted by the super-radiation light-emitting diode (01) are divided into two parts by an optical fiber coupler (02), one part of the light rays enters a measuring arm (1), and the light rays are collimated by a measuring head (03), reflected by the surfaces of all lenses in a measured lens group (04) and then return to the optical fiber coupler (02); one path enters a reference arm (2) which comprises a delay line L, light rays are collimated by a collimating mirror (05), reflected by a reflecting mirror (06) and returned to an optical fiber coupler (02), the reflecting mirror (06) is installed on an electric translation stage, and the position of the reflecting mirror is measured by an internal metering system based on a linear optical encoder; by adjusting the position of the measuring arm (1), when the optical path difference of the two paths of reflected light is matched within the coherence length, an interference signal is generated in the detector (07); the method for extracting the wavelet peak value of the interference signal comprises the following steps:
removing noise from an interference signal and fitting to obtain a smooth envelope signal;
filtering sampling points with energy amplitudes smaller than a set threshold value, and storing the reserved sampling points as data points into a data point array;
step three, the energy amplitude of each data point in the data point array and the front and back N1Comparing the energy amplitude of the data points, if the energy amplitude of the data points is 2N before and after1If the energy amplitude of the data point is large, recording the energy amplitude of the data point and the corresponding position of the data point as a wave peak value and the position of the wave peak value, otherwise, not recording the energy amplitude; finally, a group of wave peak value sets and position sets corresponding to the wave peak values are obtained;
step four, when the difference value of the positions of two adjacent wave crests is less than N2Sampling points, and when the wave peak value difference value is less than Vc, taking two adjacent wave peaks as effective wave peaks to store the peak values and the positions of the effective wave peaks; when the position difference of two adjacent wave crests is less than N2Sampling points, and when the difference value of adjacent wave peak values is greater than Vc, taking the higher wave peak as an effective wave peak and storing the peak value and the position of the effective wave peak; when the position difference of two adjacent wave crests is larger than N2Sampling points, and storing peak values and positions thereof by taking the two wave crests as effective wave crests; n is a radical of1、N2Vc is a set value; n is a radical of1、N2According to the setting of the sampling frequency f, 0.0001f is less than N1 and less than 0.0002f, and 0.00015f is less than N2 and less than 0.001 f; vc is set according to the maximum value V of two adjacent peaks, and Vc is more than 0.1V and less than V.
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