CN104534978B

CN104534978B - Detection vibration suppressing method is interfered in a kind of phase shift

Info

Publication number: CN104534978B
Application number: CN201410838076.1A
Authority: CN
Inventors: 于杰; 张海涛; 马冬梅; 金春水
Original assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Current assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Priority date: 2014-12-29
Filing date: 2014-12-29
Publication date: 2017-04-05
Anticipated expiration: 2034-12-29
Also published as: CN104534978A

Abstract

Detection vibration suppressing method is interfered in a kind of phase shift, belongs to field of optical detection, and in order to improve the repeatability for interfering detection, repdocutbility and precision, the method is：Step 1, gathers one group of N width phase-shift interference using phase-shifting interferometer, and N is more than or equal to 3, calculates PHASE DISTRIBUTION Ф using N step phase shift phase extraction algorithms₁；Step 2, using the phase shifter of phase-shifting interferometer itself, the chamber for adjusting interference cavity is long, so that change of cavity length λ/8, gather one group of interferogram after interferometer is stable, consistent in the quantity of interferogram and phase shift interval and step 1, employing calculates tested phase place Ф 2 with step 1 identical algorithm；Same step 3 and step 4 calculate tested phase place Ф 3 and tested phase place Ф 4 respectively；4 measurement results that step 1,2,3 and 4 obtain are carried out the phase average of pixel for pixel, are calculated average phase by step 5；Step 6, is calculated average corrugated W using formula, completes whole measurement.

Description

Detection vibration suppressing method is interfered in a kind of phase shift

Technical field

The present invention relates to detection vibration suppressing method is interfered in a kind of phase shift, belong to technical field of optical detection, effectively can press down The dynamic impact for interfering accuracy of detection to phase shift of damping, hence it is evident that improve repeatability, repdocutbility and the precision of phase shift laser interferometer, should Method can apply to optical surface profile and system wave aberration interferes the fields such as detection, holographic interference detection.

Background technology

With the Quality advance of optical imaging system, especially optical component surface shape required precision more and more higher, photoetching neck Domain, is to realize that exposure optical system meets diffraction limit, it is desirable to which optical component surface shape precision reaches Subnano-class not, and this is just to light Learn Wave-front measurement and propose extremely harsh requirement.

In detection is interfered in phase shift, vibration can introduce the change in location of a cycle, change interference cavity length, from interference The phase place change of a cycle is introduced in figure.Vibration is (can to use simple harmonic oscillation table by the oscillating component of various different frequencies Show) composition, when there is vibration, the light distribution of interferogram can be represented with following formula,

In formula, I (x, y, t) is in the gray value of t, Ι for (x, y) coordinate points in interferogram₀(x, y) and V (x, y) point Background light intensity and contrast that Wei be in interferogram at (x, y) coordinate points, Φ (x, y) be the phase place comprising wavefront information to be measured point Cloth, r_i、ν_iAnd α_iThe amplitude of respectively i-th oscillating component, frequency and initial phase.

It is which causes phase shift to be forbidden that vibration introduces the essence of measurement error, for phase-shift interference at equal intervals, preferable phase shift Amount and due to vibrating the phase shift that causes and forbidden it is,

Wherein, t₀For the time interval of phase-shift interference collection.

Common phase-shift interference phase extraction algorithms can be represented with equation (3),

In formula, N is total phase-shift interference frame number, and In is n-th frame phase-shift interference, and what Sn and Cn was Phase-shifting algorithm is Number.

The local derviation for asking PHASE DISTRIBUTION Ф to be forbidden with regard to phase shift, can obtain vibrating caused measurement error and be,

For common least square phase extraction algorithms, have

Therefore equation (4) is represented by

For the vibration effect described in equation (6), Leslie Deck reported a kind of side for suppressing vibration in 1996 Method, but this method needs to have using two cameras, and the temporal resolution to two cameras, spatial resolution and the time of integration It is strict with；Leslie Deck reported a kind of spectrum analyses of utilization phase error bar graph to reduce vibration in 2009 The method of impact, but this method requires that the fringe number of interferogram is no less than 1, and this can cause extra hysterisis error.

The content of the invention

The present invention can cause extra hysterisis error to solve the existing method for interfering reduction vibration effect in detection Problem, there is provided detection vibration suppressing method is interfered in a kind of phase shift, to suppress phase shift to interfere the impact that introducing is vibrated in detection, improves Interfere repeatability, repdocutbility and the precision of detection.

Detection vibration suppressing method is interfered in a kind of phase shift, it is characterized in that, the method comprises the steps：

Step 1, gathers one group of N width phase-shift interference using phase-shifting interferometer, and N is more than or equal to 3, walks phase shift phase place using N Extraction algorithm calculates PHASE DISTRIBUTION Ф₁, phase-shift interference phase shift interval need to meet algorithm requirement, algorithm meets following formula：

In formula, N is total phase-shift interference frame number, and In is n-th frame phase-shift interference, and what Sn and Cn was Phase-shifting algorithm is Number；

Step 2, using the phase shifter of phase-shifting interferometer itself, the chamber for adjusting interference cavity is long so that change of cavity length λ/8, treats Gather one group of interferogram after interferometer is stable, consistent in the quantity of interferogram and phase shift interval and step 1, employing and step 1 Identical algorithm calculates tested phase place Ф 2；

Step 3, using the phase shifter of phase-shifting interferometer itself, the chamber for adjusting interference cavity is long so that change of cavity length λ/8, chamber Long change direction is identical with the change direction of step 2, gathers one group of interferogram after interferometer is stable, the quantity of interferogram with Phase shift interval with it is consistent in step 1, using calculating tested phase place Ф 3 with step 1 identical algorithm；

Step 4, the chamber for adjusting interference cavity are long so that change of cavity length λ/8, the change direction of chamber length and step 2, step 3 Change direction is identical, and one group of interferogram, in the quantity of interferogram and phase shift interval and step 1 are gathered after interferometer is stable Cause, adopt and tested phase place Ф 4 is calculated with step 1 identical algorithm；

Step 5, the corrugated that four measurement results that step 1,2,3 and 4 obtain are carried out with pixel for pixel are average, calculate To average phase Ф ave=(Ф 1+ Ф 2+ Ф 3+ Ф 4)/4.

Step 6, using formulaAverage corrugated W is calculated, whole measurement is completed.

Beneficial effects of the present invention：

1) the method should not increase extra hardware, it is adaptable to various forms of phase-shifting interferometers；2) the method is to vibration The rejection ability for introducing measurement error is not limited by tested beam quality and interferogram fringe number；3) the method causes vibration to draw The measurement error for entering is identical in each location point, eliminates impact of the vibration to Wave-front measurement；4) the method is applied to each frequency The vibration of rate section；5) the method is applied to all Phase-shifting algorithms for meeting equation 3.

Description of the drawings

Fig. 1 is that detection vibration suppressing method flow chart is interfered in phase shift of the present invention.

Specific embodiment

Below in conjunction with the accompanying drawings the present invention is embodied as being described in detail.

The present invention proposes a kind of phase shift and interferes detection vibration suppressing method, can effectively eliminate vibration and interfere inspection to phase shift Survey method-OPD controls-averaging method that precision affects.By increasing λ/8 to optical path difference (OPD) successively, (λ is used the method for detection Optical source wavelength) four measurements be averaged to realize.Its principle is as follows：

An interferometry is carried out in interferometer initial position, N width phase-shift interferences are obtained, N is not less than 3, is walked most using N A young waiter in a wineshop or an inn takes advantage of phase extraction algorithms to calculate phase place Ф to be measured for obtaining first location point₁, the corrugated includes corrugated truthful data Ф The measurement error Δ Ф introduced with vibration₁, wherein Δ Ф₁Can be expressed as：

Using the phase shifter control OPD of phase-shifting interferometer itself so as to increase λ/8, wavelength of the λ for test light source. This position carries out second measurement.The phase-shift interference quantity of this time measurement collection and the algorithm of employing and measurement one for the first time Cause, it is possible to obtain phase place Ф to be measured of second location point₂, the measurement that the corrugated is introduced comprising corrugated truthful data Ф and vibration Error delta Ф₂, wherein Δ Ф₂Can be expressed as：

Using the phase shifter control OPD of phase-shifting interferometer itself so as to increase λ/8 again, carry out third time in this position Measurement.The phase-shift interference quantity of this time measurement collection and the algorithm of employing are consistent with measurement for the first time, it is possible to obtain the 3rd Phase place Ф to be measured of location point₃, the measurement error Δ Ф that the corrugated is introduced comprising corrugated truthful data Ф and vibration₃, wherein Δ Ф₃Can be expressed as：

Using the phase shifter control OPD of phase-shifting interferometer itself so as to increase λ/8 again, carry out the 4th time in this position Measurement.The phase-shift interference quantity of this time measurement collection and the algorithm of employing are consistent with measurement for the first time, it is possible to obtain the 4th Phase place Ф to be measured of location point₄, the measurement error Δ Ф that the corrugated is introduced comprising corrugated truthful data Ф and vibration₄, wherein Δ Ф₄Can be expressed as：

Average four measurement results, obtain final result Ф_aveCan be expressed as

Tested corrugated W is obtained using calculated PHASE DISTRIBUTION

Wavelength of the wherein λ for test light source.When as can be seen from the above equation by using this method, final measurement and face Deviation between shape true value is identical in each location point size, is a constant unrelated with vibration, therefore can eliminate vibration Affect.

The method can also be realized using following scheme：Four are carried out using phase shifter precise control OPD of interferometer itself Secondary measurement, the OPD for measuring every time are sequentially reduced λ/8, and four measurement results are carried out averagely, obtaining the knot for suppressing vibration effect Really.

Embodiment：

As shown in figure 1, using four step normalized phase extraction algorithms, the tool of the present invention for the phase-shifting interferometer of 632.8nm Body is comprised the following steps：

Step 1, gathers four width phase-shift interferences, calculates PHASE DISTRIBUTION Ф using four step normalized phase extraction algorithms₁；

Step 2, using the phase shifter of interferometer itself, adjusts measured lens position, makes interference cavity increase 79.1nm, collection four Width phase-shift interference, calculates PHASE DISTRIBUTION Ф using four step normalized phase extraction algorithms₂；

Step 3, using the phase shifter of interferometer itself, adjusts measured lens position, further increases on the basis of step 2 Interference cavity 79.1nm, gathers four width phase-shift interferences, calculates PHASE DISTRIBUTION Ф using four step normalized phase extraction algorithms₃；

Step 4, using the phase shifter of interferometer itself, adjusts measured lens position, further increases on the basis of step 3 Interference cavity 79.1nm；Four width phase-shift interferences are gathered, and PHASE DISTRIBUTION Ф are calculated using four step normalized phase extraction algorithms₄；

Step 5, to four PHASE DISTRIBUTION Ф for obtaining₁, Ф₂, Ф₃And Ф₄Carry out corrugated average, obtain average phase Ф_ave=(Ф₁+Ф₂+Ф₃+Ф₄)/4, finally give tested corrugated distributionObtain and suppress vibration Testing result, and then complete whole measurement process.

Claims

1. detection vibration suppressing method is interfered in a kind of phase shift, it is characterized in that, the method comprises the steps：

Step 1, gathers one group of N width phase-shift interference using phase-shifting interferometer, and N is more than or equal to 3, walks phase shift phase extraction using N Algorithm calculates PHASE DISTRIBUTION Ф₁, phase-shift interference phase shift interval need to meet algorithm requirement, algorithm meets following formula：

φ (x, y) = a r c t a n [\frac{Σ_{n = 1}^{N} S_{n} I_{n} (x, y)}{Σ_{n = 1}^{N} C_{n} I_{n} (x, y)}] - - - (3)

In formula, N is total phase-shift interference frame number, and In is n-th frame phase-shift interference, and Sn and Cn is the coefficient of Phase-shifting algorithm；

Step 2, using the phase shifter of phase-shifting interferometer itself, the chamber for adjusting interference cavity is long so that change of cavity length λ/8, waits to interfere Gather one group of interferogram after instrument is stable, consistent in the quantity of interferogram and phase shift interval and step 1, employing is identical with step 1 Algorithm calculate tested phase place Ф 2；

Step 3, using the phase shifter of phase-shifting interferometer itself, the chamber for adjusting interference cavity is long so that change of cavity length λ/8, chamber length Change direction is identical with the change direction of step 2, after interferometer is stable gathers one group of interferogram, the quantity of interferogram and phase shift Interval with it is consistent in step 1, employing calculate tested phase place Ф 3 with step 1 identical algorithm；

Step 4, the chamber for adjusting interference cavity are long so that change of cavity length λ/8, change direction and step 2, the change of step 3 of chamber length Direction is identical, gathers one group of interferogram after interferometer is stable, consistent in the quantity of interferogram and phase shift interval and step 1, Tested phase place Ф 4 is calculated using with step 1 identical algorithm；

Step 5, the corrugated that four measurement results that step 1,2,3 and 4 obtain are carried out with pixel for pixel are average, are calculated flat Equal phase place Ф ave=(Ф 1+ Ф 2+ Ф 3+ Ф 4)/4；

2. detection vibration suppressing method is interfered in a kind of phase shift according to claim 1, it is characterised in that institute in step 1-4 Change of cavity length λ/8 are stated for growth λ/8 are all in each step or reduction λ/8 are all, wherein, wavelength of the λ for test light source.