CN105606338B - A kind of centre wavelength error compensating method based on white light interference test system - Google Patents

Abstract

The invention discloses a kind of centre wavelength error compensating method based on white light interference test system, belong to fiber end face measuring instrument technical field.Described calculation method changes the optical path difference between reference beam and test beams by phase-shifter first, while gathering some width interference patterns, then interference pattern is carried out to solve the height for obtaining fiber end face.Phase only pupil filter is carried out to the intensity maxima for extracting based on Carr é phase shift algorithms, computational accuracy is influenceed because the centre wavelength of light source has calibrated error, therefore piezoelectric ceramics step pitch is calibrated first by single groove standard sample, online demarcation is carried out to wavelength by the step pitch after check and correction.Can reduce by the error that light source characteristic and environmental perturbation are brought, improve computational accuracy.

Description

A kind of centre wavelength error compensating method based on white light interference test system

Technical field

The present invention relates to a kind of centre wavelength error compensating method based on white light interference test system, belong to fiber end face Measuring instrument technical field.

Background technology

Fiber end face measuring instrument is the principle based on white light interference, and bar is interfered so as to realize fiber end face using phase shift The change of line.Fiber end face tester can be with non-contacting measurement optical fiber surface pattern accurately and fast.As the biography of optical signal Defeated medium, fiber end face form directly affects optical signal transmission performance in a fiber, therefore fiber end face measurement to end face shape The measurement of state is most important in Fibre Optical Sensor and transmission.Because fiber end face measuring instrument disclosure satisfy that optical fiber in production, application During on-line testing demand, therefore, it is possible to be widely used in high power laser, military opto-electronic device, fiber-optic current sensor The high-grade, precision and advanced sciemtifec and technical sphere such as device.

Fiber end face measuring instrument during interferometry, changed by phase-shifter reference beam and test beams it Between optical path difference, while gathering some width interference patterns, then interference pattern is carried out to solve the height for obtaining fiber end face.Using When Light bulb phase-shift interfering method is demodulated relevant peak, influence to calculate essence because the centre wavelength of light source has calibrated error Degree, therefore a kind of online real-Time Compensation light source center wavelength error is designed, high precision, fireballing white light interference algorithm is particularly weighed Will.

The content of the invention

The invention aims to solve the above problems, a kind of centre wavelength based on white light interference test system is proposed Error compensating method, can be used for reducing centre wavelength calibrated error in fiber end face measuring system, and anti-interference, speed is fast, right The linearity error of phase-shifter is insensitive.

Plant the centre wavelength error compensating method based on white light interference test system, including following steps：

The first step, demarcates piezoelectric ceramic motor step pitch；

Second step, with the centre wavelength of the online real-time calibration white light source of the step pitch demarcated；

3rd step, relative altitude is resolved based on Carr é phase shift algorithms using the wavelength for extracting；

The advantage of the invention is that：

The present invention can demarcate step pitch when fiber end face height value is resolved by single groove sample block, and real-time calibration is calculated Light source center wavelength, anti-interference with reducing due to the centre wavelength calibrated error that environmental perturbation brings, speed is fast, to phase shift The advantages of linearity error of device is insensitive.

Brief description of the drawings

Fig. 1 is fiber end face measuring system schematic diagram；

Fig. 2 is the graph of a relation of white light interference light intensity and optical path difference；

Fig. 3 is single groove sample block pictorial diagram；

Fig. 4 is that actual measurement height is the standard sample interference pattern of 663nm；

Fig. 5 is flow chart of the method for the present invention.

Specific embodiment

The present invention is described in detail with reference to the accompanying drawings and examples.

As shown in Fig. 1 the principle schematic of fiber end face measuring system, light source is by condenser, and aperture diaphragm is accurate Straight beam expanding lens reaches Amici prism, and a portion light can reach tested optical fiber end face, and another part reaches reference mirror, after reflection Microcobjective is reached simultaneously, finally reaches CCD imagings.When interfering, formed after the interference fringe superposition that each wavelength light is produced White-light fringe, as shown in Figure 2.When piezoelectric ceramics (PZT) phase-shifter drives index plane to move, interference fringe can become Change.

Fiber end face measuring system measures three-dimensional appearance, is the light intensity value according to the interference fringe image for being gathered, and obtains The relative altitude value of body surface, it is critical only that the maximum relevant peak of the position i.e. light intensity value for accurately finding zero optical path difference Position.White light interference light intensity has relation as shown in Figure 2 with optical path difference, and when optical path difference is 0, light intensity reaches maximum.

When step pitch is demarcated using single groove sample block, it is extracted respectively to the point outside the point and groove in same a line groove The corresponding number of image frames of light strong extremum, the actual step pitch of piezoelectric ceramic motor can be drawn by groove height.

By the relation between wavelength and phase, centre wavelength is calculated with the step pitch demarcated in real time online.

Based on above-mentioned fiber end face measuring system, and optical path difference and light intensity relation, it is of the invention a kind of based on white The centre wavelength error compensating method of interference of light test system, flow is as shown in figure 5, including following steps：

The first step, demarcates piezoelectric ceramic motor step pitch；

First, the step pitch of piezoelectric ceramic motor, single groove standard sample such as Fig. 3 institutes are demarcated by single groove standard sample Show, the interference fringe that Fig. 4 is arrived for actual acquisition, Fig. 4 more intuitively illustrates the interference at interference fringe at groove and non-groove Striped has the changing of the relative positions, therefore can demarcate piezoelectric ceramic motor by the movement of interference fringe when known groove depth H Step pitch.The method that the present invention is used to extract its light strong extremum pair respectively to the point outside the point and groove in same a line groove The number of image frames answered, respectively N₁, N₂, groove depth is H, then actual step pitch d can be by formulaTry to achieve；

Second step, with the centre wavelength of the online real-time calibration white light source of the step pitch demarcated；

When being scanned to measured object, the picture frame number P that zero order fringe is included can be extracted, be counted in real time by following formula Calculate centre wavelength

3rd step, relative altitude is resolved based on Carr é phase shift algorithms using the wavelength for extracting；

The intensity level of the light synthesized by two-beam vibration：

In formula：I_aRepresent the light intensity value of the light reflected by optical fiber surface, I_bRepresent the light intensity value of the light reflected by reference mirror, I The intensity level of the light of synthesis is represented,Represent light source by the light and light source after the reflection that spectroscope reaches measured object by light splitting Mirror reaches the position difference with reference to light after reflection, so

Wherein, I_maxIt is intensity maxima, I_minIt is light intensity minimum, γ is intetference-fit strengthening.

Make I₀=I_a+I_b, then can obtain：

When optical path difference is zero, i.e.,When being zero, luminous intensity is peak value.Because sampling precision etc. is asked in actually measurement Also there is the φ phase extraction errors of with zero optical path difference in topic, the maximum extracted, it is therefore desirable to solve φ and it is entered Row amendment；In measurement process, it is accurately linear mobile that PZT drives reference mirror to carry out.Piezoelectric ceramics step pitch is set to d, then two-phase Phase place change between adjacent imageDue to the presence of piezoelectric ceramics linearity error ε, phase place change is designated as：

Wherein,It is phase change value

Phase only pupil filter is carried out to the intensity maxima for extracting based on Carr é phase shift algorithms, its general principle is as follows：

Wherein：I_bgIt is background light intensity value, I_-3、I_-1、I₁、I₃Respectively relative to before the zero order fringe light intensity value for being positioned 3 Frame, preceding 1 frame, rear 1 frame, the corresponding light intensity value of rear 3 frame.

Solve

From above formula, the extraction of phase is unrelated with the linearity error ε of piezoelectric ceramics.

By the resolving to phase, using the centre wavelength of online real-time calibrationThe relative altitude of measured object can be tried to achieve：

Wherein, h is relative altitude, and N is the corresponding picture frame number of intensity maxima.

Claims (1)

1. a kind of centre wavelength error compensating method based on white light interference test system, including following steps：

The first step, demarcates piezoelectric ceramic motor step pitch；

First, the step pitch of piezoelectric ceramic motor is demarcated by single groove standard sample, the step pitch of piezoelectric ceramic motor is：

$d=\frac{H}{|N_1-N_2|}$

Wherein, N₁、N₂It is that its corresponding picture frame of light strong extremum is extracted respectively to the point outside the point and groove in same a line groove Number, H is groove depth；

Second step, with the centre wavelength of the online real-time calibration white light source of the step pitch demarcated；

When being scanned to measured object, the picture frame number P that zero order fringe is included is extracted, centre wavelength is calculated in real time

$\stackrel{\‾}{\mathrm{\λ}}=2P\×d$

3rd step, relative altitude is resolved based on Carr é phase shift algorithms using the wavelength for extracting；

Obtain the intensity level of the light of two-beam vibration synthesis：

In formula：I_aRepresent the light intensity value of the light reflected by optical fiber surface, I_bThe light intensity value of the light reflected by reference mirror is represented, I is represented The intensity level of the light of synthesis,Represent and reached with reference to warp with by spectroscope by the light after the reflection that spectroscope reaches measured object The position difference of the light after reflection, if：

$I_{max}=I_a+I_h+2\sqrt{I_a{I}_h}$

$I_{\min }=I_a+I_b-2\sqrt{I_a{I}_b}$

$\mathrm{\γ}=\frac{I_{\max }-I_{\min }}{I_{\max }+I_{\min }}$

Wherein, I_maxIt is intensity maxima, I_minIt is light intensity minimum, γ is intetference-fit strengthening；

Make I₀=I_a+I_b, obtain：

When optical path difference is zero, i.e.,When being zero, luminous intensity is peak value；

To phase extraction error φ, it is modified, piezoelectric ceramics step pitch is d, the phase place change between two adjacent images isThen phase place change is：

Wherein,It is phase change value, ε represents piezoelectric ceramics linearity error；

Phase only pupil filter is carried out to the intensity maxima for extracting based on Carr é phase shift algorithms, its general principle is as follows：

Wherein：I_bgIt is background light intensity value, I_-3、I_-1、I₁、I₃Respectively relative to 3 frames before the zero order fringe light intensity value for being positioned, preceding 1 frame, rear 1 frame, the corresponding light intensity value of rear 3 frame；

Solve

${\tan }^2\mathrm{\φ}=\frac{|\[(I_{-3}-I_3)+(I_{-1}-I_1)\]\[3(I_{-1}-I_1)+(I_{-3}-I_3)\]|}{{\[(I_{-1}+I_1)+(I_{-3}+I_3)\]}^2}$

By the resolving to phase, the relative altitude of measured object is obtained：

$h=N\×d-\frac{\stackrel{\‾}{\mathrm{\λ}}}{4\mathrm{\π}}\mathrm{\φ}$

Wherein, h is relative altitude, and N is the corresponding picture frame number of intensity maxima.