CN110017793B - A dual-channel anti-vibration interferometric measurement device and method - Google Patents

Abstract

The invention discloses a dual-channel anti-vibration interferometric measurement device and method. The device comprises a light source beam expansion and collimation system arranged in sequence for expanding and collimating a light source, and is used to detect the auxiliary vibration phase plane of a measured piece. Interferometric measurement system, the main interferometric measurement system used to measure the phase distribution of the DUT in combination with the auxiliary interferometric measurement system, and the optical path system of the DUT; the light source beam expansion and collimation system and the optical path system of the DUT are coaxial, marked as the first The optical axis, the optical axes of the auxiliary interferometric measurement system and the main interferometric measurement system are respectively recorded as the second optical axis and the third optical axis, which are all perpendicular to the first optical axis; the light source beam expansion collimation system, the main interferometric measurement system and the measured The component optical path system constitutes the main Taiman-Green interference optical path; the light source beam expansion collimation system, the auxiliary interferometric measurement system and the measured component optical path system constitute the auxiliary Taiman-Green interference optical path. The device and method of the present invention not only have good anti-vibration effect and high measurement accuracy, but also have a simple and compact structure and low cost.

Description

A dual-channel anti-vibration interferometric measurement device and method

technical field

The invention belongs to the field of optical interferometric measurement, in particular to a dual-channel anti-vibration interference measurement device and method.

Background technique

Nowadays, optical interferometry technology is widely used to measure the surface shape of optical components. There are various traditional optical interference devices and measurement methods, such as Michelson interferometer, Tyman interferometer, Fizeau interferometer and other devices and phase-shifting interferometer. Measurement techniques such as measurement, Fourier transform interferometry, dislocation interferometry and heterodyne interferometry. However, these methods have evolved so far, and the requirements for the measurement environment are very strict, especially the measured phase cannot be accurately measured in a vibration environment.

The existing interference devices and measurement methods with good robustness to environmental vibration are mainly divided into two categories. One is to solve the vibration problem from the data processing algorithm. This kind of scheme does not make any changes in the interference device. A series of interference patterns are collected, and the error caused by the environmental vibration is calculated by the data processing algorithm, thereby making the phase calculation more accurate. There are many kinds of data processing algorithms in this kind of method, but the measurement error will appear when the number of fringes in the interferogram is small, especially the zero fringe interferogram. The other type is mainly from the interference device to overcome the influence of vibration. The more commonly used method is to use the synchronous four-step phase shifting method in the Fizeau-type common optical path interferometer. The Fizeau-type interference device itself has a certain resistance. Then, the interference beam is divided into four beams at the back of the optical path. In each beam, a different phase-shifting amount is introduced through a polarizing device, so that four pairs of phase-shifting interferograms can be collected at the same time, which can effectively overcome the impact of vibration on the measurement. . In this type of scheme, the spatial relative positional relationship between the phase shift diagrams is unknown, and the relative positions lack mature and reliable calibration technology, which easily leads to position matching errors and affects the measurement accuracy.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a dual-channel anti-vibration interferometric measurement device and method that overcomes the influence of environmental vibration during interferometric measurement and improves measurement accuracy.

The technical solution to achieve the purpose of the present invention is: a dual-channel anti-vibration interferometric measurement device, comprising: a light source beam expansion and collimation system for expanding and collimating the light source, which is arranged in sequence, and is used for detecting the vibration of the measured object The auxiliary interferometric measurement system of the phase plane, the main interferometric measurement system used to measure the phase distribution of the DUT in combination with the auxiliary interferometric system, and the optical path system of the DUT;

The optical axis of the light source beam expansion collimation system and the optical path system of the tested piece is the same as the optical axis, which is marked as the first optical axis. The first optical axis is vertical; the light source beam expansion collimation system, the main interferometric measurement system and the DUT optical path system constitute the main Taiman-Green interference optical path; the light source beam expansion collimation system, the auxiliary interferometric measurement system and the DUT optical path system are auxiliary Form the Tyman-Green interference light path.

The measurement method based on the above-mentioned dual-channel anti-vibration interferometric measurement device includes the following steps:

Step 1. The light source beam expansion and collimation system outputs linearly polarized light, and the auxiliary interferometric measurement system transmits and reflects the linearly polarized light;

Step 2. The main interferometric measurement system divides the transmitted light in step 1 into orthogonal p light and s light, and the s light passes through the main interferometric measurement system to form a first reference light that is orthogonal to the original s light; the p light is measured The component optical path system forms the test light and is reflected and transmitted by the main interferometric measurement system to obtain the first test light and the second test light respectively;

Step 3. The reflected light in Step 1 is reflected by the auxiliary interferometric measurement system to form a second reference light;

Step 4. The first test light and the first reference light are combined by the main interferometric measurement system to produce interference, adjust the optical path system of the tested piece to make the interference fringes sparse, and then collect the corresponding interference image sequence; at the same time, the second test light and the second The reference light is combined by the auxiliary interferometric measurement system to generate interference, and the auxiliary interferometric measurement system is adjusted to make the interference fringes dense, and then the corresponding interference image sequence is collected;

Step 5: Calculate the phase distribution of the DUT according to the interferogram obtained in Step 4.

Compared with the prior art, the present invention has the following significant advantages: 1) The present invention adopts a two-channel Taiman-Green interference device and a measuring method, which can simultaneously collect two-channel interference signals, solve the vibration plane in one way, and solve the Phase measurement can achieve effective and rapid measurement, and can overcome the influence of vibration during measurement; 2) the device of the present invention can not only solve the influence of environmental vibration on measurement, but also has a simple and compact structure, the measurement method is ingenious and easy to understand, and the cost Low.

The present invention will be described in further detail below with reference to the accompanying drawings.

Description of drawings

FIG. 1 is a schematic structural diagram of a dual-channel anti-vibration interferometric measuring device according to the present invention.

FIG. 2 is an interferogram collected by the main interferometric measurement system in the embodiment of the present invention.

FIG. 3 is an interferogram collected by the auxiliary interferometric measurement system in the embodiment of the present invention.

FIG. 4 is a schematic diagram of the phase distribution of an optical element measured by adopting the solution of the present invention in an embodiment of the present invention.

FIG. 5 is a schematic diagram of the phase distribution of the same optical element measured by using a traditional four-step phase-shifting scheme in an embodiment of the present invention.

Detailed ways

1, a dual-channel anti-vibration interferometric measurement device of the present invention includes: a light source beam expansion and collimation system 24 for expanding and collimating the light source, which is arranged in sequence, and is used for detecting the vibration phase plane of the measured object. The auxiliary interferometric measurement system 25, the main interferometric measurement system 27 for measuring the phase distribution of the measured object in combination with the auxiliary interferometric measurement system 25, and the measured optical path system 28;

The light source beam expansion and collimation system 24 is coaxial with the optical path system 28 of the device under test, which is denoted as the first optical axis, and the optical axes of the auxiliary interferometric measurement system 25 and the main interferometric measurement system 27 are respectively denoted as the second optical axis and the third optical axis. axis, all perpendicular to the first optical axis; the light source beam expansion collimation system 24, the main interferometric measurement system 27 and the measured object optical path system 28 constitute the main Taiman-Green interference optical path; the light source beam expansion collimation system 24, the auxiliary interferometric measurement The system 25 and the DUT optical path system 28 constitute an auxiliary Taiman-Green interference optical path.

Further, the light source beam expansion and collimation system 24 includes a laser assembly 1, a half-wave plate 2, a first objective lens 3, a first aperture 4 and a second objective lens 5 arranged in sequence along the first optical axis; the laser assembly 1 includes Linearly polarized lasers, or including lasers and polarizers;

The main interferometric measurement system 27 includes a first standard reference mirror 12, a first quarter wave plate 13, a polarizing beam splitter prism 7, a first polarizing plate 18, and a third objective lens 19, a second a first beam reduction imaging system composed of a diaphragm 20 and a fourth objective lens 21, and a first area array detector 23;

The auxiliary interferometric measurement system 25 includes a second standard reference mirror 11 arranged in sequence along the second optical axis, a beam splitting prism 6, a second polarizer 14, a fifth objective lens 15, a third aperture 16 and a sixth objective lens 17. a second beam reduction imaging system, and a second area array detector 22;

The polarizing beam splitting prism 7 and the beam splitting prism 6 are located on the first optical axis at the same time; the second standard reference mirror 11 and the first standard reference mirror 12 are fixed on the same adjustment frame 26, and the adjustment frame 26 is used to adjust the inclination of the reference mirror angle;

The DUT optical path system 28 includes a second quarter-wave plate 8 , a converging objective lens group 9 and the DUT 10 arranged in sequence along the first optical axis.

Further preferably, the light beam incident on the polarizing beam splitter prism 7 is divided into a transmitted p-wave and a reflected s-wave, the angle between the fast axis of the first quarter-wave plate 13 and the s-wave is 45°, and the second and fourth The angle between the fast axis of the one-wave plate 8 and the p wave is 22.5°.

Further preferably, the first area array detector 23 and the second area array detector 22 are CCD or CMOS cameras.

The measurement method based on the above-mentioned dual-channel anti-vibration interferometric measurement device includes the following steps:

Step 1. The light source beam expansion and collimation system 24 outputs linearly polarized light, and the auxiliary interferometric measurement system 25 transmits and reflects the linearly polarized light;

Step 2. The main interferometric measurement system 27 divides the transmitted light in step 1 into orthogonal p light and s light, and the s light passes through the main interferometric measurement system 27 to form a first reference light that is orthogonal to the original s light; The optical path system 28 of the DUT forms the test light and is reflected and transmitted by the main interferometric measurement system 27 to obtain the first test light and the second test light respectively;

Step 3. The reflected light in Step 1 is reflected by the auxiliary interferometric measurement system 25 to form a second reference light;

Step 4. The first test light and the first reference light are combined by the main interferometric measurement system 27 to generate interference, and the optical path system 28 of the tested piece is adjusted to make the interference fringes sparse, and then the corresponding interference image sequence is collected; The second reference light is combined by the auxiliary interferometric measurement system 25 to generate interference, and the auxiliary interferometric measurement system 25 is adjusted to make the interference fringes dense, and then a corresponding interference image sequence is collected;

Step 5: Calculate the phase distribution of the DUT 10 according to the interferogram obtained in Step 4 .

Further, step 1 is specifically:

The light source beam expansion and collimation system 24 composed of the linearly polarized laser 1, the half-wave plate 2, the first objective lens 3, the first diaphragm 4 and the second objective lens 5, which are arranged in sequence, emits the polarized light and enters the auxiliary interferometric measurement system. 25 beam splitting prism 6, the beam splitting prism 6 transmits and reflects linearly polarized light.

Further, step 2 is specifically:

The polarization beam splitter prism 7 of the main interferometric measurement system 27 divides the transmitted light in step 1 into orthogonal p light and s light;

After that, the s light becomes circularly polarized light through the first quarter-wave plate 13, and then reflected by the first standard reference mirror 12 and the first quarter-wave plate 13 forms the first reference light orthogonal to the original s light , the first reference light is incident on the polarizing beam splitter 7 and then transmitted;

The p light passes through the second quarter-wave plate 8 to become elliptically polarized light, passes through the converging objective lens group 9 and then is reflected by the tested object 10 to become test light, the test light returns to the original path through the quarter-wave plate 8 to become linearly polarized light and Incident to the polarizing beam splitting prism 7, and the angle between the linearly polarized light and the p light is 45°; the polarizing beam splitting prism 7 reflects and transmits the linearly polarized light, the reflected beam is recorded as the first test light, and the transmitted beam is recorded as the first test light. Two test lights.

Further, step 3 is specifically as follows: the reflected light in step 1 is reflected by the second standard reference mirror 11 and incident on the beam splitting prism 6 and then transmitted to form the second reference light.

Further, step 4 is specifically:

The first test light and the first reference light are combined by the polarizing beam splitter prism 7, and interfere with the first polarizer 18, and then pass through the first beam reduction composed of the third objective lens 19, the second diaphragm 20 and the fourth objective lens 21. The imaging system is then incident on the target surface of the first area array detector 23; during this process, the contrast of the interference pattern fringes received by the first area array detector 23 is adjusted by adjusting the half-wave plate 2 and the first polarizer 18 , adjust the optical path system 28 of the DUT to make the interference fringes sparse, and then collect the corresponding interference image sequence;

The second reference light and the second test light are combined by the beam splitter prism 6 , interfere with the second polarizer 14 , and then pass through the second beam reduction composed of the fifth objective lens 15 , the third aperture 16 and the sixth objective lens 17 The imaging system is then incident on the target surface of the second area array detector 22; during this process, the contrast of the interference pattern fringes received by the second area array detector 22 is adjusted by adjusting the half-wave plate 2 and the second polarizer 14 , the inclination of the second standard reference mirror 11 is adjusted by the adjusting frame 26 to make the interference fringes denser, and then the corresponding interference image sequence is collected.

Further, in step 5, according to the interferogram obtained in step 4, the phase distribution of the DUT 10 is calculated, specifically:

其中n＝1,2,3,…，N，N为第二面阵探测器22采集的干涉图的总数；Step 5-1. Use the Fourier transform method to obtain the phase of each interferogram collected by the second area array detector 22

where n=1, 2, 3,..., N, N is the total number of interferograms collected by the second area array detector 22;

对应的待测件相对于第二标准参考镜11的振动相位面

所用公式为：Step 5-2. Find the phase of each interferogram

The vibration phase plane of the corresponding DUT relative to the second standard reference mirror 11

The formula used is:

为第一幅干涉图的相位；In the formula,

is the phase of the first interferogram;

获取无噪声的振动相位平面P_n(x,y)：Step 5-3, according to the vibration phase plane

Obtain the noise-free vibration phase plane P _n (x,y):

P _n (x,y)=α _n x+β _n y+γ _n

获得；In the formula, α _n , β _n , γ _n are all coefficients, which are fitted by the least squares method

get;

Step 5-4, the expression of the light intensity of the interferogram collected by the main interferometric measurement channel is:

I _n =a(x,y)+b(x,y)cos(φ(x,y)+ _Pn (x,y))

In the formula, a(x, y) is the background light intensity, and b(x, y) is the modulation amplitude;

Combining In and P _n ( _x , y), the phase φ(x, y) of the DUT is solved by the least squares solution phase method.

The present invention will be described in further detail below in conjunction with the embodiments.

Example

In this embodiment, the laser 1 of the light source part in the dual-channel anti-vibration interferometry device is a helium-neon laser with an output power of 5mw, the wavelength is 632.8nm, and the beam diameter after the beam expansion and collimation system 24 is 10mm. The effective focal length is 50mm, the DUT 10 is a concave mirror, its radius of curvature is 125mm, the clear aperture is 25mm, the focal lengths of the fifth lens 15 and the sixth objective lens 17 are 150mm and 75mm respectively, the third lens 19 and the fourth objective lens 21 The focal lengths are also 150mm and 75mm, the sampling pixels of the second area array detector 22 and the first area array detector 23 are both 1920×1200, and the pixel size is 5.8um.

Measurement is performed by the above-mentioned device, a pair of interference fringe patterns collected by the main interferometric measurement system is shown in Fig. 2, and an interference fringe pattern collected by the auxiliary interferometric measurement system 25 is shown in Fig. 3. A set of interferograms are obtained. The phase distribution of the concave mirror 10 to be measured is calculated from the group interferogram as shown in Figure 4, PV=0.3306λ, RMS=0.0578λ; the phase distribution of the same concave mirror 10 measured by the traditional synchronous phase shift scheme is shown in Figure 5, the PV =0.3718λ, RMS=0.0594λ.

The phase distributions in Fig. 4 and Fig. 5 are approximately the same, which verifies the correctness of the measurement of the present invention. However, the traditional synchronous phase-shifting scheme will have the problem of inconsistent contrast between the four phase-shifting images, resulting in fringe errors. As shown in Figure 5, the phase has obvious fringe errors, while in Figure 4, there is no fringe error caused by vibration.

It can be seen that, compared with the traditional solution, the device and method of the present invention not only have good anti-vibration effect and high measurement accuracy, but also have a simple and compact structure and low cost.

Claims (10)

1. The utility model provides a binary channels formula anti-vibration interferometry device which characterized in that, including setting gradually: the system comprises a light source beam expanding and collimating system (24) for expanding and collimating the light source, an auxiliary interferometry system (25) for detecting the vibration phase plane of the measured piece, a main interferometry system (27) for measuring the phase distribution of the measured piece by combining the auxiliary interferometry system (25), and a measured piece optical path system (28);

the light source beam expanding collimation system (24) and the optical path system (28) of the measured piece have the same optical axis and are marked as a first optical axis, and the optical axes of the auxiliary interference measurement system (25) and the main interference measurement system (27) are respectively marked as a second optical axis and a third optical axis which are both vertical to the first optical axis; the light source beam expanding collimation system (24), the main interference measurement system (27) and the measured piece light path system (28) form a main Taemann-Green interference light path; the light source beam expanding collimation system (24), the auxiliary interference measurement system (25) and the measured piece light path system (28) form an auxiliary Taeman-Green interference light path;

the main interference measurement system (27) comprises a first standard reference mirror (12), a first quarter-wave plate (13), a polarization beam splitter prism (7), a first polaroid (18), a first beam reduction imaging system and a first area array detector (23), wherein the first standard reference mirror (12), the first quarter-wave plate (13), the polarization beam splitter prism (7), the first polaroid (18), the first beam reduction imaging system and the first area array detector are sequentially arranged along a third optical axis;

the auxiliary interferometry system (25) comprises a second standard reference mirror (11), a beam splitting prism (6), a second polaroid (14), a second beam reduction imaging system and a second area array detector (22), wherein the second standard reference mirror, the beam splitting prism (6), the second polaroid (14), the second beam reduction imaging system and the second area array detector are sequentially arranged along a second optical axis;

the polarization beam splitter prism (7) and the beam splitter prism (6) are positioned on a first optical axis simultaneously; the second standard reference mirror (11) and the first standard reference mirror (12) are fixed on the same adjusting frame (26), and the adjusting frame (26) is used for adjusting the inclination angle of the reference mirror.

2. The dual-channel anti-vibration interferometry device according to claim 1, wherein the light source beam expanding and collimating system (24) comprises a laser assembly (1), a half-wave plate (2), a first objective lens (3), a first diaphragm (4) and a second objective lens (5) arranged in sequence along a first optical axis; the laser assembly (1) comprises a linearly polarized laser, or comprises a laser and a polarizer;

the measured piece optical path system (28) comprises a second quarter-wave plate (8), a convergence objective lens group (9) and a measured piece (10) which are sequentially arranged along a first optical axis.

3. The dual-channel anti-vibration interferometry device according to claim 2, wherein the light beam incident on the polarizing beam splitter prism (7) is split into a transmitted p-wave and a reflected s-wave, the fast axis of the first quarter-wave plate (13) is at an angle of 45 ° to the s-wave, and the fast axis of the second quarter-wave plate (8) is at an angle of 22.5 ° to the p-wave.

4. The dual-channel anti-vibration interferometry device according to claim 3, wherein the first and second area-array detectors (23, 22) are CCD or CMOS cameras.

5. The measuring method of the dual-channel anti-vibration interferometry device based on claim 1, comprising the steps of:

step 1, a light source beam expanding collimation system (24) emits linearly polarized light, and an auxiliary interference measurement system (25) transmits and reflects the linearly polarized light;

step 2, the main interference measurement system (27) divides the transmitted light in the step 1 into orthogonal p light and s light, and the s light forms first reference light orthogonal to the original s light through the main interference measurement system (27); p light forms test light through a tested piece light path system (28), and the test light is reflected and transmitted through a main interference measurement system (27) to respectively obtain first test light and second test light;

step 3, the reflected light of the step 1 is reflected by an auxiliary interference measurement system (25) to form second reference light;

step 4, combining the first test light and the first reference light through a main interference measurement system (27) to generate interference, adjusting a light path system (28) of a measured piece to make interference fringes sparse, and then collecting a corresponding interference image sequence; meanwhile, the second test light and the second reference light are combined through the auxiliary interference measurement system (25) and generate interference, the auxiliary interference measurement system (25) is adjusted to enable interference fringes to be dense, and then a corresponding interference image sequence is acquired;

and 5, resolving the phase distribution of the measured piece (10) according to the interferogram obtained in the step 4.

6. The dual-channel anti-vibration interferometry method according to claim 5, wherein step 1 specifically comprises:

the linear polarization light source system comprises a light source beam expanding collimation system (24) and a beam splitting prism (6), wherein the light source beam expanding collimation system (24) is composed of a linear polarization laser (1), a half-wave plate (2), a first objective lens (3), a first diaphragm (4) and a second objective lens (5) which are sequentially arranged, linear polarization light is emitted and enters the beam splitting prism (6) of an auxiliary interference measurement system (25), and the linear polarization light is transmitted and reflected by the beam splitting prism (6).

7. The dual-channel anti-vibration interferometry method according to claim 6, wherein step 2 specifically comprises:

a polarization beam splitter prism (7) of a main interference measurement system (27) splits the transmitted light of the step (1) into orthogonal p light and s light;

then, the s light becomes circularly polarized light through the first quarter-wave plate (13), and then the circularly polarized light is reflected by the first standard reference mirror (12), the first quarter-wave plate (13) forms first reference light orthogonal to the original s light, and the first reference light is incident to the polarization beam splitter (7) and then is transmitted;

the p light becomes elliptical polarized light through the second quarter-wave plate (8), the elliptical polarized light is reflected by the tested piece (10) after passing through the converging objective lens group (9) to become test light, the test light original path returns to become linearly polarized light through the quarter-wave plate (8) and is incident to the polarization beam splitter prism (7), and the included angle between the linearly polarized light and the p light is 45 degrees; the polarization beam splitter prism (7) reflects and transmits the linearly polarized light, the reflected light beam is marked as first test light, and the transmitted light beam is marked as second test light.

8. The dual-channel anti-vibration interferometry method according to claim 7, wherein step 3 specifically comprises: the reflected light of the step 1 is reflected by a second standard reference mirror (11) and is transmitted to a beam splitter prism (6) to form second reference light.

9. The dual-channel anti-vibration interferometry method according to claim 8, wherein step 4 specifically comprises:

the first test light and the first reference light are combined through a polarization beam splitter prism (7), generate interference through a first polaroid (18), and then are incident to a target surface of a first area array detector (23) through a first beam reduction imaging system consisting of a third objective lens (19), a second diaphragm (20) and a fourth objective lens (21); in the process, the contrast of interference pattern fringes received by a first area array detector (23) is adjusted by adjusting a half-wave plate (2) and a first polaroid (18), an optical path system (28) of a tested piece is adjusted to make the interference fringes sparse, and then a corresponding interference image sequence is acquired;

the second reference light and the second test light are combined through the beam splitting prism (6), generate interference through the second polaroid (14), and then enter a target surface of the second planar array detector (22) through a second beam reduction imaging system formed by the fifth objective lens (15), the third diaphragm (16) and the sixth objective lens (17); in the process, the contrast of interference pattern fringes received by the second area array detector (22) is adjusted by adjusting the half-wave plate (2) and the second polaroid (14), the interference fringes are dense by adjusting the inclination of the second standard reference mirror (11) through an adjusting frame (26), and then a corresponding interference image sequence is acquired.

10. The dual-channel anti-vibration interferometry method according to claim 9, wherein step 5, calculating the phase distribution of the measured object (10) according to the interferogram obtained in step 4, specifically:

step 5-1, solving the phase of each interference pattern acquired by the second area array detector (22) by utilizing a Fourier transform method

Wherein N is 1,2,3, …, and N is the total number of interferograms collected by the second area array detector (22);

step 5-2, solving the phase of each interference pattern

The corresponding vibration phase plane of the piece to be measured relative to the second standard reference mirror (11)

The formula used is:

in the formula (I), the compound is shown in the specification,

is the phase of the first interferogram;

step 5-3, according to the vibration phase plane

Obtaining a noiseless vibration phase plane P_n(x,y)：

P_n(x,y)＝α_nx+β_ny+γ_n

in the formula, α_n、β_n、γ_nAre coefficients, which are fitted by the least square method

Obtaining; and 5-4, acquiring an interference pattern light intensity expression by the main interference measurement channel as follows:

I_n＝a(x,y)+b(x,y)cos(φ(x,y)+P_n(x,y))

wherein a (x, y) is background light intensity, and b (x, y) is modulation amplitude;

binding of I_nAnd P_n(x, y), and solving the phase phi (x, y) of the piece to be detected by using a least square solution phase method.

Images