CN104515482B - White light interferometer interference fringe method for widening - Google Patents

Abstract

White light interferometer interference fringe method for widening, is related to a kind of interference fringe method for widening in field of optical detection.It is an object of the invention to provide a kind of automatic striped method for widening of white light interferometer, while measurement efficiency is improved, operation difficulty and workload are reduced.The method implementation steps are：First regulation white light interferometer to striped at screen center；Then the fringe intensity of the sub-regions of screen four is calculated；Calculate stripe direction of two stripeds compared with hadron region；Along respective stripe direction make virtual line by two regional centers and calculate intersection point screen coordinate；The screen coordinate is converted into physical location skew, and camera lens pendulum angle is controlled according to element curvature radius；Above procedure is repeated until striped meets measurement request.This method uses image processing techniques, is not required to additional sensor, calculates simple, and regulating cycle is short, for ordinary circumstance striped, measurement request can be met by 3~5 regulations.

Description

White light interferometer interference fringe method for widening

Technical field

The present invention relates to technical field of optical detection, and in particular to a kind of white light interferometer interference fringe method for widening.

Background technology

Optical element surface roughness is generally detected using white light interferometer.But due to the detection range of white light interferometer Very little, generally in a mm, so in order to obtain more real optical surface roughness information, generally on surface Multiple sampled points are taken to be averaging processing, and as the roughness measurement result on final surface.

So, each surface is both needed to measure more than ten to tens sampled points, if measurement surface is (sphere, non-curved surface Sphere, free form surface) when, each point needs to complete contraposition, repeatedly striped broadening, the link such as measurement, so as to cause optical surface The measurement efficiency of roughness is low.

Among these, interference fringe broadening is a very important link.Generally in white light interferometer, striped broadening Completed by regulation manually.Tester by observing the stripe information such as shape, density, position of interference fringe, then hand The two-dimentional inclination angle (being directed to objective table tilting white light interferometer) of dynamic regulation objective table or the pendulum angle of camera lens (incline for object lens Inclined white light interferometer), so as to gradually by striped broadening and adjust to zero striped measurement.But this process not only take compared with It is long, and depend critically upon the operating experience of tester.For beginner, the operation is very cumbersome, it tends to be difficult to by striped It is entirely on the center in both direction.For even for skilled operator, completing tens striped broadenings on a surface is also In huge workload, and striped spreading process, the change carved and focus on striped is taken, easily cause eyes uncomfortable.

The content of the invention

The present invention is generally adjusted manually to solve existing interference fringe method for widening, and it is cumbersome to there is regulation process, and work A kind of the problems such as amount is big and causes eyes uncomfortable, there is provided white light interferometer interference fringe method for widening.

White light interferometer interference fringe method for widening, the method is realized by following steps：

Step one, adjustment the distance between white light interferometer camera lens and the measured optical unit surface and angle, make interference bar Line is presented on screen；

Step 2, to be evenly dividing screen be four regions, and the fringe intensity in each region is calculated respectively；

The threshold value of fringe intensity is obtained in step 3, setting procedure two, two or more regions are judged whether Fringe intensity exceed the threshold value, if it is not, then prompting fringe intensity is too low, and return to step one；If it is, performing step Rapid four；

Step 4, two stripe directions in region of fringe intensity highest are asked for, and with the center in described two regions point Not as the reference point of corresponding region, straight line is made along stripe direction respectively by two reference points, obtain two straight-line intersections Screen coordinate；

Whether the distance of step 5, the screen coordinate for judging two straight-line intersections that step 4 is obtained and screen center is less than pre- Definite value, if it is not, then calculating white light interferometer camera lens needs the angle of adjustment, and carries out angle adjustment, return to step two；If It is, it is determined that striped broadening meets requirement.

Beneficial effects of the present invention：The present invention employs image processing method for the striped spreading process of white light interferometer Method, calculates the relevant parameter of interference fringe, and the automatic broadening by adjusting the two-dimentional pivot angle of camera lens to realize striped.This mistake Journey has broken away from the use experience of operator, the efficiency and stability of the striped broadening for greatly improving, while also reducing instrument Use difficulty and workload, more proper operation person's long-time operation.

Specific embodiment

Specific embodiment one, white light interferometer interference fringe method for widening, the method are realized by following steps：

First, the surface roughness of sphere is measured using white light interferometer.

1st, measured point position is determined first, then adjusts the distance between white light interferometer camera lens and measured surface and angle Degree, makes interference fringe be presented in screen and as far as possible in an intermediate position.

2 and then to be evenly dividing screen be upper left, lower-left, upper right, the square region of bottom right four, and obtain each sub-district The gray-scale map in domain.Gray-scale map for each region makees following computing：

A) by taking the region any point as an example：Its coordinate is (x, y), then the coordinate of its neighbouring 8 point, and with wherein right side Point is respectively in the counterclockwise direction as starting point：(x+1, y), (x+1, y-1), (x, y-1), (x-1, y-1), (x-1, y), (x-1, y+1), (x, y+1), (x+1, y+1), then the gray variance of 135 ° of four directions is along 0 °, 45 °, 90 ° this o'clock：

d₀(x, y)=[I (and x-1, y)-I (x+1, y)]²

d₄₅(x, y)=[I (x-1, y+1)-I (x+1, y-1)]²×0.5

d₉₀(x, y)=[I (x, y-1)-I (x, y+1)]²

d₁₃₅(x, y)=[I (x-1, y-1)-I (x+1, y+1)]²×0.5

Wherein I (x, y) represents the gray scale at (x, y) point.

B) each point, along the variance sum in aforementioned four direction, can scan for tiring out in units of lines in zoning Plus.Then along 0 °, 45 °, 90 °, the gray variance of 135 ° of four directions is whole region：

Wherein S represents the region to be calculated.

C) then the fringe intensity in the region is：C (x, y)=(D₀-D₉₀)²+(D₄₅-D₁₃₅)²；

3rd, fringe intensity threshold value is set, if exceeding the threshold value in the presence of two or more region fringe intensities, is selected Two regions of fringe intensity highest, go to step 4；If exceeding the threshold in the absence of two or more region fringe intensities Value, then point out fringe intensity too low, and return to step 1, the distance between regulation camera lens and surface so that striped is near screen Center.

4th, the region of fringe intensity highest two in step 3 is recorded, a-quadrant, B regions is set to.Counted in A, B region respectively The stripe direction in two subregions is calculated, the computational methods of stripe direction are as follows：

Wherein D₀, D₄₅, D₉₀, D₁₃₅Calculate in step 2, this Place has been not required to recalculate.

The stripe direction that A, B region can so be obtained is respectively：θ_A, θ_B.If the central point of A, B square region is M, N, then Cross M points and do direction for θ_AVirtual line, cross N points and do direction for θ_BVirtual line, then can calculate two by elementary geometry straight Screen coordinate (P of the line intersection point relative to screen centre position_x, P_y)。

5th, the screen coordinate (P of the intersection point is judged_x, P_y), if the intersection point is to the distance of screen centerLess than setting Definite value, the then it is believed that work of striped broadening has terminated.If the intersection point is more than setting value to the distance of screen center, according to following Step is adjusted：

A, the horizontal direction physical length l measured according to the length in pixels L and white light interferometer in screen level direction, obtain Unit screen pixel correspondence optical element surface actual range be：The parameter is constant under the conditions of identical object lens, Calculated in advance and can be stored among program.

B, with screen center as the origin of coordinates, record two straight-line intersections screen coordinate (P_x, P_y), and calculate the intersection point screen The actual range of element surface is corresponding to curtain coordinate：R_x=kP_x, R_y=kP_y

C, the radius of curvature r according to the measured optical unit, obtain white light interferometer camera lens is along the pendulum angle of A, B axle：

6th, control instruction is sent to white light interferometer control system so that camera lens swings along A, B axle respectivelyAnd Return to step 1, continuation judges whether striped is adjusted in place.The A, B axle are the rotary shaft rotating around X, Y-axis rotation, its side To meeting the right-hand rule.

Method described in present embodiment calculates simple, and regulating cycle is shorter, for the striped of ordinary circumstance, by 3~5 Secondary regulation can meet measurement request.

Claims (5)

1. the method for widening of white light interferometer interference fringe, it is characterized in that, the method is realized by following steps：

Step one, adjustment the distance between white light interferometer camera lens and the measured optical unit surface and angle, make the interference fringe be in Now on screen；

Step 2, to be evenly dividing screen be four regions, and the fringe intensity in each region is calculated respectively；

The threshold value of fringe intensity is obtained in step 3, setting procedure two, the bar in two or more regions is judged whether Line intensity exceedes the threshold value, if it is not, then prompting fringe intensity is too low, and return to step one；If it is, performing step Four；

Step 4, two stripe directions in region of fringe intensity highest are asked for, and made respectively with the center in described two regions It is the reference point of corresponding region, straight line is made along stripe direction respectively by two reference points, obtains the screen of two straight-line intersections Coordinate；

Whether the distance of step 5, the screen coordinate for judging two straight-line intersections that step 4 is obtained and screen center is less than predetermined Value, if it is not, then calculating white light interferometer camera lens needs the angle of adjustment, and carries out angle adjustment, return to step two；If It is, it is determined that striped broadening meets requirement.

2. white light interferometer interference fringe method for widening according to claim 1, it is characterised in that in described step two It is four regions that screen is evenly dividing, and specially makees level, vertical two straight lines along screen center, and screen is divided into a left side Upper, lower-left, upper right, the square region of bottom right four.

3. white light interferometer interference fringe method for widening according to claim 1 and 2, it is characterised in that described step Fringe intensity computational methods in two, are specifically realized by following steps：

Step 2 one, any point coordinate of the arbitrary region set in four regions are (x, y), then neighbouring eight points of the point Coordinate, and using wherein right-hand point as starting point, be respectively in the counterclockwise direction：(x+1, y), (x+1, y-1), (x, y-1), (x-1, y-1), (x-1, y), (x-1, y+1), (x, y+1), (x+1, y+1), then this o'clock is along 0 °, 45 °, 90 °, 135 ° of four directions Gray variance be：

d₀(x, y)=[I (and x-1, y)-I (x+1, y)]²

d₄₅(x, y)=[I (x-1, y+1)-I (x+1, y-1)]²×0.5

d₉₀(x, y)=[I (x, y-1)-I (x, y+1)]²

d₁₃₅(x, y)=[I (x-1, y-1)-I (x+1, y+1)]²×0.5

, along 0 °, 45 °, the 90 ° and 135 ° gray variances of four direction use formula for step 2 two, region described in calculation procedure 21 It is expressed as：

$D_{angle}\left(x,y\right)=\underset{\left(x,y\right)\∈S}{\Σ}{d}_{angle}(x,y)$

Wherein, angle is 0 °, 45 °, 90 ° or 135 °, and region fringe intensity C (x, y) is：C (x, y)=(D₀-D₉₀)2+(D₄₅- D₁₃₅) 2, I (x, y) represents gray scale at (x, y) point, S represents the region to be calculated.

4. white light interferometer interference fringe method for widening according to claim 3, it is characterised in that in described step four The computational methods of stripe direction, specially：

5. white light interferometer interference fringe method for widening according to claim 1, it is characterised in that described step five is counted The angle that white light interferometer camera lens needs to adjust is calculated, detailed process is：

Step 5 one, the horizontal direction physical length l measured according to the length in pixels L and white light interferometer in screen level direction, The actual range for obtaining unit screen pixel correspondence optical element surface is：

Step 5 two, with screen center as the origin of coordinates, record two straight-line intersections screen coordinate (P_x, P_y), and calculate the intersection point The actual range of element surface corresponding to screen coordinate is：R_x=kP_x, P_y=kP_y

Step 5 three, the radius of curvature r according to the measured optical unit, obtain white light interferometer camera lens along A, the pendulum angle of B axle For：