Laser frequency scanning interferometer dispersion phase compensation method based on focusing definition evaluation function

A technology of frequency scanning interference and focusing clarity, applied in instruments, optical devices, measuring devices, etc., it can solve the problems of low measurement resolution and measurement signal influence, and achieve the effect of large-scale high-resolution measurement

Active Publication Date: 2015-12-09
HARBIN INST OF TECH
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  • Abstract
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Problems solved by technology

[0003] The present invention aims to solve the problem that the existing method has low measurement resolution and the influence on the measurement signal needs t

Method used

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  • Laser frequency scanning interferometer dispersion phase compensation method based on focusing definition evaluation function
  • Laser frequency scanning interferometer dispersion phase compensation method based on focusing definition evaluation function
  • Laser frequency scanning interferometer dispersion phase compensation method based on focusing definition evaluation function

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specific Embodiment approach 1

[0022] Specific implementation mode one: the dispersion phase compensation method based on the focusing sharpness evaluation function, which is implemented in the following steps:

[0023] (3) Establish the beat frequency model of the measurement signal under the fiber dispersion condition of the high-resolution laser frequency scanning interferometer;

[0024] (4) Compensate the optical fiber dispersion of the beat frequency model of the measurement signal by using the phase method:

[0025] (1) The measured signal is multiplied by the complex phase compensation item, and the dispersion phase distortion in the measured signal is compensated by adjusting the dispersion compensation coefficient. When the dispersion phase distortion of the measured signal is compensated, the full width at half maximum of the frequency spectrum of the signal will be narrowed;

[0026] (2) The focusing sharpness evaluation function is proposed as a criterion for judging whether the phase distortio...

specific Embodiment approach 2

[0031] Specific implementation mode two: the difference between this implementation mode and specific implementation mode one is: step (1) is specifically:

[0032] (1) The beat frequency ω formed by the auxiliary interferometer of the high-resolution laser frequency scanning interferometer aux Expressed as formula (6):

[0033]

[0034] Among them, the τ aux Indicates the time delay corresponding to the length difference of the two fiber arms in the auxiliary interferometer, μ is the frequency modulation slope, β 2 =-20ps 2 / km represents the group velocity dispersion of single-mode fiber, υ g Indicates the group velocity, t indicates the frequency modulation time of the laser;

[0035] (2) Since the beat frequency of the measuring interferometer and the auxiliary interferometer is directly proportional to the time delay, after sampling the measurement signal using the frequency sampling method, the delay ratio between the measuring interferometer and the auxiliary int...

specific Embodiment approach 3

[0044] Specific implementation mode three: the difference between this implementation mode and specific implementation mode one or two is: step (2) (1) is specifically:

[0045] (1) indicates that after each adjustment of the phase compensation factor, the S value is calculated to see if it reaches the maximum value. When the S value is the maximum, it is considered that the dispersion compensation is completed. However, in this process, a fixed step size is usually set to change the phase compensation factor, and the S value is judged each time until the S value reaches the maximum, and the compensation speed is relatively slow. And (2) the method of thirds avoids setting a fixed step size, and the maximum value of S can be found through fewer calculation times. Therefore, the method of thirds improves the efficiency of compensation.

[0046]Dispersion compensation is realized by calculating whether the S value of the focusing sharpness evaluation function reaches the maximum...

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Abstract

The invention discloses a laser frequency scanning interferometer dispersion phase compensation method based on a focusing definition evaluation function, which relates to a high-resolution laser frequency scanning interferometer dispersion compensation method and aims at solving the problems that the in the existing method, the measurement resolution is low, and influences on measurement signals need to be compensated. A measurement signal beat frequency model in a high-resolution laser frequency scanning interferometer fiber dispersion condition is built; and a phase method is adopted to compensate fiber dispersion of the measurement signal beat frequency model: (1) the measurement signal is multiplied by a complex phase compensation item, and through adjusting a dispersion compensation coefficient, dispersion phase distortion in the measurement signal is compensated; (2) a focusing definition evaluation function is put forward to serve as a standard to judge whether phase distortion in the measurement signal beat frequency model obtains compensation; and (3) trichotomy is adopted to find the best dispersion compensation coefficient to compensate the fiber dispersion of the high-resolution laser frequency scanning interferometer. The method of the invention is applied to the field of high-resolution laser frequency scanning interferometers.

Description

technical field [0001] The invention relates to a dispersion compensation method of a high-resolution laser frequency scanning interferometer. Background technique [0002] Laser frequency scanning interferometers play an important role in the fields of industrial parts measurement, aircraft surface processing, and three-dimensional shape modeling of objects. As production progresses, higher resolution frequency scanning interferometers are required. The key to improving the measurement resolution is to increase the sweep bandwidth. However, as the sweep bandwidth increases, the fiber dispersion of the auxiliary interferometer used to correct the beat frequency nonlinearity of the measurement signal increases accordingly, and the measurement signal is corrected by the auxiliary interferometer. After nonlinearity, the target spectrum is broadened and the measurement resolution is reduced. Therefore, the influence of the fiber dispersion of the auxiliary interferometer on th...

Claims

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Application Information

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IPC IPC(8): G01B9/02
Inventor 刘国栋甘雨刘炳国许新科陈凤东庄志涛
Owner HARBIN INST OF TECH
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