A kind of rotatable phase shifting interferometer of tested surface and measurement method
Technical field
The present invention relates to a kind of optical interference instruments, and in particular to a kind of rotatable phase shifting interferometer of tested surface and survey
Amount method.
Background technique
Phase shift interference measuring technique is one of the important means of Optical Surface detection.In general, phase shifting method can divide
For two classes: hardware phase shift and frequency conversion phase shift.Frequency conversion phase shift interference is that phase-modulation, light are realized by the change of light source frequency
Source uses Wavelength tunable laser.Hardware phase shift is typically all that reference mirror is driven to make axial movement modulation by piezoelectric ceramics
The phase difference of two coherent lights, to realize the modulation to phase.
Phase shift interference measuring technique is that a corrugated in two relevant corrugateds is made to make staged or consecutive variations, is formed
Interference fringe.The light intensity that each point in interference field is obtained with video camera or CCD camera, in each measurement point, the variation of phase difference
Make the light intensity value of interference field that corresponding variation (constituting light intensity equation group) occur, obtains the measurement point by solving light intensity equation group
Phase value, so as to find out the phase information or wavefront figure on corrugated to be measured.
Summary of the invention
In view of the deficiencies of the prior art, the present invention proposes a kind of rotatable phase shifting interferometer of tested surface and measurement sides
Method.
A kind of rotatable phase shifting interferometer of tested surface, including laser emitter, collimating mirror, optical splitter, reference mirror,
Tested mirror surface, convex lens, mirror surface rotator and CCD camera, it is characterised in that: the laser emitter, collimating mirror, optical splitter,
On measured lens EDS maps and same axis, the reference mirror and imaging lens are distributed in the preceding survey of optical splitter and survey afterwards, described
Mirror surface rotator is located at tested mirror;The emergent ray of laser emitter is incident on collimating mirror, the collimated light of collimating mirror outgoing
Line reaches tested mirror surface transmitted through optical splitter by optical splitter, a part of light, and another part light is reflected by optical splitter
To reference mirror, this two-beam line all returns optical splitter by mirror-reflection;The reflected light of reference mirror transmitted through beam splitter,
The light that test surfaces are reflected back is reflected through optical splitter, at this point, this two-beam forms interference, and is passed through convex lens and is converged light
Gather CCD camera;Wherein the rotation of mirror surface rotator adjusts the angle between tested mirror surface and vertical plane;The tested mirror surface is
Single side mirror surface.
Preferably, it is the single-mode laser that wavelength is 632.8nm that the laser emitter, which is to emit laser,.
Preferably, the mirror surface rotator rotation adjusts the angle, θ of tested mirror surface and vertical plane, the model of the angle theta
Enclose is -90 ° to 90 °.
A kind of measurement method of the rotatable phase shifting interferometer of tested surface;This method is specific as follows:
Step 1: rotation m secondary mirror rotator obtains the interference light intensity I of m width phase shifthmAnd the phase-shift phase δ of tested mirror surfaceh;
The wherein expression formula of the interference pattern light intensity without phase shift are as follows:
A is background light intensity in formula, and B is light intensity system,For the Wave-front phase of testee;
The phase-shift phase δ of tested mirror surfacehExpression formula are as follows:
δh=h*tan (θ),
H indicates tested height value of the mirror surface different location relative to bottommost in formula, therefore after rotating an angle θ,
It is different when phase-shift phase is at different height, it needs individually to solve the Wave-front phase of each height;
Its dephased interference pattern light intensity expression are as follows:
In formula m indicate testee the m time rotation, be the m time rotate after different height light intensity, be the m times rotate after
The a certain height of tested surface phase shift;
Step 2: the 4 width interference fringe pictures that will be obtained calculate it by the wave of side shape by the algorithm of least square
Preceding phase
Dephased interference pattern light intensity expression is unfolded, is obtained:
Due to being to need the unknown quantity that acquires, above formula can be write as:
Ihm=a+b cos (δhm)+c sin(δhm),
A=A in formula,
The theoretical value of interference light intensityThe value I obtained with actual measurementhmBetween error be expressed as:
M indicates the light intensity for the interference fringe that different phase-shift phases obtains in above formula, according to the principle of least square:
X=A-1B,
In formula
X=[a b c]T,
After acquiring vector, by side phase distribution are as follows:
The present invention compared with the existing technology the utility model has the advantages that by the angle of side achieve the purpose that phase shift by rotating, and
Without using traditional phase-shifter, object can so save space, grow interferometer not without movement in orbit
The limitation of degree.
Detailed description of the invention
Fig. 1 is the phase shifting interferometer structural block diagram that embodiment provides;
Structural block diagram when Fig. 2 is the phase shifting interferometer phase shift of embodiment offer;
Fig. 3 is the detected element rotational structure block diagram that embodiment provides;
Fig. 4 is the face shape X-Y scheme for the simulation that embodiment provides;
Fig. 5 is the interference pattern measured by the face shape simulated that embodiment provides;
Fig. 6 is the face shape for the non-unpacking that embodiment provides;
Fig. 7 is the face shape for having solved package that embodiment provides.
In figure, laser emitter 1, collimating mirror 2, optical splitter 3, convex lens 4, reference mirror 5, tested mirror surface 6, CCD camera
7, mirror surface rotator 8
Specific embodiment
In order to more specifically describe the present invention, with reference to the accompanying drawing and specific embodiment is to technical solution of the present invention
It is described in detail.
Embodiment
Fig. 1 is the phase shifting interferometer structural block diagram that embodiment provides.A kind of rotatable phase shifting interferometer of tested surface, packet
Include laser emitter 1, collimating mirror 2, optical splitter 3, reference mirror 5, tested mirror surface 6, convex lens 4, mirror surface rotator 8 and CCD phase
Machine 7, the laser emitter, collimating mirror, optical splitter, on measured lens EDS maps and same axis, the reference mirror and imaging
Camera lens is distributed in the preceding survey and rear survey of optical splitter, and the mirror surface rotator is located at tested mirror;The emergent light of laser emitter
Line is incident on collimating mirror, and by optical splitter, a part of light reaches tested the collimated ray of collimating mirror outgoing transmitted through optical splitter
Mirror surface, another part light reflect it to reference mirror by optical splitter, this two-beam line all returns optical splitter by mirror-reflection;Ginseng
Examine mirror-reflection return light transmitted through beam splitter, the light that test surfaces are reflected back is reflected through optical splitter, at this point, this two
Beam light forms interference, and passes through convex lens and light is converged to CCD camera;Wherein the rotation of mirror surface rotator adjust tested mirror surface with
Angle between vertical plane;The tested mirror surface is single side mirror surface.
When measuring, rotator will will drive tested surface and rotate, as shown in Fig. 2, to reach the mesh of phase shift
, as shown in Figure 3, Figure 4, schematic diagram when rotating for testee, rotation is equivalent to the generation of testee different height
Mobile, after testee rotates the angle θ, the position apart from bottom h height is equivalent to the distance for moving L backward, L=h*
tan(θ).After rotator rotates an angle, it will obtain new interference fringe picture.After rotator rotates four times, it will
4 width interference fringe pictures are obtained, the wavefront phase information of tested surface will be obtained by carrying out least square using 4 width interference fringe pictures.
One face shape of this real case simulation, face shape formula are as follows:
X and y indicates face shape in the position of space pixel in formula, and unit is pixel.If rotating its rotation angle θ every time, then
The distance of the tested surface of different height mobile h*tan (θ), is equivalent to L for its distance, then 4 phase shifts are L respectively1, L2, L3,
L4, coefficient matrices A can be obtained according to phase-shift phase,
It, can be in the hope of formula I according to coefficient matrixhm=a+b cos (δhm)+c sin(δhm) in coefficient a, b and c.
Finally acquire face shape, face shape as shown in fig. 6, the face shape still obtained at this time be package face shape, need to pass through solution
Algorithm is wrapped up, keeps its face shape smooth, unpacking face is shaped like Fig. 7.