1. A method for suppressing the interference of wave plate delay error in dynamic interferometer is characterized by comprising the following steps: the method comprises the following steps:

s1: experiment preparation, namely detecting the flatness and the light transmittance of the half-wave plate (83) and the quarter-wave plate to ensure that the numerical values of the half-wave plate (83) and the quarter-wave plate are within a standard value, and installing the half-wave plate (83) and the quarter-wave plate in a dynamic interferometer;

s2: placing a piece to be measured, and adjusting the dynamic interferometer to ensure that four interference patterns acquired by the camera are distributed in a dense fringe manner;

s3: calculating a gray average value, manually selecting or automatically identifying a fringe area in an interference image, acquiring the gray average value of pixel points in the area in real time, calculating the root mean square value of the gray average value of four images, and calculating for multiple times to ensure that the best value is obtained integrally, wherein the gray average value calculation comprises the following two steps:

a1: taking points for multiple times to obtain an average value, selecting stripe regions in the interference pattern for multiple times, repeatedly measuring to obtain different values, calculating data sampled by multiple points, and calculating the gray level average value of pixel points in different regions;

a2: calculating root mean square values according to different average values, and substituting a plurality of groups of average values into a root mean square value calculation formula of the gray level average value to obtain the root mean square of the optimal average value;

s4: and (3) adjusting and measuring, manually or automatically rotating and adjusting the half wave plate (83) in a unidirectional mode through a motor, calculating the root mean square value of the gray average value of the four images in real time, and stopping adjusting the half wave plate (83) when the value is smaller than a set threshold value.

2. The method for suppressing interference of the delay error of the wave plate in the dynamic interferometer of claim 1, wherein: half wave plate (83) are including mounting bracket (1), mounting bracket (1) upper end fixedly connected with mounting panel (2), mounting panel (2) one end is rotated and is connected with worm wheel (3), mounting panel (2) inside is rotated and is connected with collar (4) that are used for installing worm wheel (3), through-hole (5) have been seted up to worm wheel (3) inside, the inside fixedly connected with wave plate body (6) of worm wheel (3), mounting bracket (1) one end fixedly connected with drives rotatory adjustment mechanism (7) of worm wheel (3).

3. The method for suppressing interference of the delay error of the wave plate in the dynamic interferometer of claim 2, wherein: the mounting plate (2) and the mounting ring (4) are both of an internal hollow structure, the hollow part of the mounting plate (2) is matched with the shape and size of the mounting ring (4), and the hollow part of the mounting ring (4) is matched with the shape and size of the wave plate body (6).

4. The method for suppressing interference of the delay error of the wave plate in the dynamic interferometer of claim 2, wherein: the mounting ring (4) is close to one side of the worm wheel (3) and is provided with a fixing screw hole (41), the worm wheel (3) is internally matched with a fixing screw (31) in a threaded manner, and the fixing screw (31) penetrates through the worm wheel (3) to be mutually clamped with the fixing screw hole (41).

5. The method for suppressing interference of the delay error of the wave plate in the dynamic interferometer of claim 4, wherein: the fixing screw holes (41) and the fixing screws (31) are distributed correspondingly, and the fixing screws (31) are located on the outer side of the wave plate body (6).

6. The method for suppressing interference of the delay error of the wave plate in the dynamic interferometer of claim 2, wherein: adjustment mechanism (7) are inside including fixing locating plate (71) in the mounting bracket (1) outside, locating plate (71) upper end fixedly connected with driving motor (72), driving motor (72) output end fixedly connected with drives worm wheel (3) pivoted action wheel (73).

7. The method of suppressing interference of the chip delay error in the dynamic interferometer of claim 6, wherein: the driving wheel (73) is meshed with the worm wheel (3), the driving wheel (73) is matched with the worm wheel (3), and the circle center line of the worm wheel (3) is overlapped with that of the wave plate body (6).

8. The method for suppressing interference of the delay error of the wave plate in the dynamic interferometer of claim 2, wherein: mounting bracket (1) one end fixedly connected with is used for fixed plate (11) of installation, the inside screw-thread fit of fixed plate (11) has mounting screw (12), mounting screw (12) pass fixed plate (11) and extend to fixed plate (11) lower extreme, mounting screw (12) are about fixed plate (11) horizontal center line symmetric distribution.

Background

The dynamic interferometer adopts a space synchronous phase shifting technology, can acquire four interferograms with fixed phase difference in real time, has the advantages of vibration resistance, airflow disturbance resistance and the like, and is widely applied to large-caliber and high-precision optical processing sites.

As shown in fig. 1, the conventional dynamic interferometer includes a light source 8 and a polarization camera 9, the light source 8 sequentially passes through a collimating mirror 81, a polarizing plate 82, a half-wave plate 83, a first quarter-wave plate 84 and a test optical path lens 85 to be diffracted on a to-be-tested mirror 86, the polarization camera 9 sequentially passes through an afocal system 91, a second quarter-wave plate 92 and a third quarter-wave plate 93 to be diffracted on a reference mirror 94, and an interference pattern is obtained by calculating an image obtained by the polarization camera 9 through a micro-polarization array.

In practical application, limited by a processing technology, delay of the quarter-wave plate usually has a certain error, the error causes inconsistency of background light intensity of four interferograms, so that correct phase information cannot be extracted, an accurate measurement result cannot be calculated, most direct expression is that a ripple error occurs in the measurement result, at present, people suppress the error through a software means, a least square method is used for carrying out polynomial fitting on the background and the modulation degree in the light intensity of the interferograms to solve corresponding coefficients, light intensity normalization of the four interferograms is completed, and then the phase and a final result are solved.

The above prior art solutions have the following drawbacks: although the software normalization process can suppress ripple errors in the result, the normalization process itself will interfere with the result of the normal phase, which will cause inaccuracy of the measurement result and reduce the overall measurement effect, thereby increasing the error generated in the overall measurement process.

Disclosure of Invention

The invention aims to provide a method for increasing measurement accuracy and inhibiting interference of a quarter-wave plate delay error in a dynamic interferometer on a measurement result.

In order to achieve the purpose, the invention provides the following technical scheme:

a method for suppressing the interference of wave plate delay error in dynamic interferometer includes the following steps:

s1: experiment preparation, namely detecting the flatness and the light transmittance of the half-wave plate and the quarter-wave plate to ensure that the numerical values of the half-wave plate and the quarter-wave plate are within a standard value, and installing the half-wave plate and the quarter-wave plate in a dynamic interferometer;

s2: placing a piece to be measured, and adjusting the dynamic interferometer to ensure that four interference patterns acquired by the camera are distributed in a dense fringe manner;

s3: calculating a gray average value, manually selecting or automatically identifying a fringe area in an interference image, acquiring the gray average value of pixel points in the area in real time, calculating the root mean square value of the gray average value of four images, and calculating for multiple times to ensure that the best value is obtained integrally, wherein the gray average value calculation comprises the following two steps:

a1: taking points for multiple times to obtain an average value, selecting stripe regions in the interference pattern for multiple times, repeatedly measuring to obtain different values, calculating data sampled by multiple points, and calculating the gray level average value of pixel points in different regions;

a2: calculating root mean square values according to different average values, and substituting a plurality of groups of average values into a root mean square value calculation formula of the gray level average value to obtain the root mean square of the optimal average value;

s4: and adjusting and measuring, namely adjusting the half wave plate manually or automatically and unidirectionally by a motor, calculating the root mean square value of the gray average value of the four images in real time, and stopping adjusting the half wave plate when the value is smaller than a set threshold value.

By adopting the technical scheme, the complexity of the reconstruction calculation of the interference surface shape is reduced by using the device of the dynamic interferometer, the method is convenient and quick, the influence of inconsistent light intensity of the interference pattern caused by the delay error of the quarter-wave plate is reduced, and the reliability of dynamic interferometry is improved.

Further, half wave plate includes the mounting bracket, mounting bracket upper end fixedly connected with mounting panel, mounting panel one end is rotated and is connected with the worm wheel, the inside collar that is used for installing the worm wheel that rotates of mounting panel, the inside through-hole of having seted up of worm wheel, the inside fixedly connected with wave plate body of worm wheel, mounting bracket one end fixedly connected with drives the rotatory adjustment mechanism of worm wheel.

Through adopting above-mentioned technical scheme, make adjustment mechanism drive the worm wheel and rotate to make things convenient for whole collar and the wave plate body of driving to rotate, so that wholly adjust the angle of half wave plate, make things convenient for wholly to adjust.

Furthermore, the mounting plate and the mounting ring are both of an internal hollow structure, the hollow part of the mounting plate is matched with the shape and size of the mounting ring, and the hollow part of the mounting ring is matched with the shape and size of the wave plate body.

Through adopting above-mentioned technical scheme, use inside hollow structure's mounting panel and collar to wholly carry out the printing opacity to guarantee the penetrating of whole inside light path, guarantee whole good formation of image effect.

Furthermore, a fixing screw hole is formed in one surface, close to the worm wheel, of the mounting ring, a fixing screw is matched with the inner thread of the worm wheel, and the fixing screw penetrates through the worm wheel to be clamped with the fixing screw hole.

Through adopting above-mentioned technical scheme, use set screw to pass the worm wheel and carry out threaded connection with fixed screw and can install and dismantle the worm wheel to the convenience is carried out dismouting and cleanness to half wave plate.

Furthermore, the fixing screw holes and the fixing screws are distributed correspondingly, and the fixing screws are located on the outer side of the wave plate body.

Through adopting above-mentioned technical scheme, use fixed screw and set screw to carry out the block, guarantee that worm wheel and collar carry out stable installation to guarantee that whole can fully drive the wave plate body and rotate.

Furthermore, the inside locating plate of fixing in the mounting bracket outside that is included of adjustment mechanism, locating plate upper end fixedly connected with driving motor, driving motor output end fixedly connected with drives worm wheel pivoted action wheel.

Through adopting above-mentioned technical scheme, driving motor drives the action wheel and rotates, and action wheel pivoted in-process drives the worm wheel and rotates, guarantees whole good rotation regulation effect.

Further, the driving wheel is meshed with the worm wheel, the driving wheel is matched with the worm wheel, and the worm wheel is overlapped with the circle center line of the wave plate body.

Through adopting above-mentioned technical scheme, action wheel pivoted in-process drives the worm wheel and rotates to the convenient whole wave plate body to the worm wheel inside carries out the regulation of angle, makes things convenient for whole regulation, has increased holistic practicality.

Further, mounting bracket one end fixedly connected with is used for the fixed plate of installation, the inside screw-thread fit of fixed plate has the mounting screw, the mounting screw passes the fixed plate and extends to the fixed plate lower extreme, the mounting screw is around fixed plate horizontal center line symmetric distribution.

Through adopting above-mentioned technical scheme, the mounting screw passes the fixed plate and fixes with the installed part to guarantee that whole can carry out abundant fixed to the mounting bracket, increased holistic fixed effect.

In conclusion, the beneficial technical effects of the invention are as follows:

1. the rotation adjustment is carried out by adopting the half wave plate, so that the complexity of the reconstruction calculation of the interference surface shape is reduced, the operation is convenient and quick, the influence of inconsistent light intensity of an interference pattern caused by the delay error of the quarter wave plate is reduced, the reliability of dynamic interference measurement is improved, and the effect of reducing the error is generated;

2. the gray average value is calculated, the average value is obtained by multiple points, and the data generated integrally are collected for multiple times, so that the data obtained integrally for multiple times can be conveniently calculated, and the effect of measuring, calculating and obtaining the average value for multiple times is generated;

3. the adjusting mechanism and the worm wheel are adopted, the worm wheel and the wave plate body are conveniently and integrally driven to rotate, so that the angle of the wave plate is conveniently and integrally adjusted, and the effect of convenient adjustment is generated.

Drawings

FIG. 1 is a schematic diagram of the optical path structure of the present invention;

FIG. 2 is a schematic perspective view of a half-wave plate according to the present invention;

FIG. 3 is a schematic perspective view of a half-wave plate according to the present invention;

FIG. 4 is a schematic view of a half-wave plate splitting structure according to the present invention;

FIG. 5 is a schematic perspective view of a second embodiment of the present invention;

fig. 6 is a schematic three-dimensional structure according to an embodiment of the present invention.

In the figure, 1, a mounting frame; 2. mounting a plate; 3. a worm gear; 4. a mounting ring; 5. a through hole; 6. a wave plate body; 7. an adjustment mechanism; 8. a light source; 9. a polarization camera; 11. a fixing plate; 12. mounting screws; 31. a set screw; 41. fixing screw holes; 71. positioning a plate; 72. a drive motor; 73. a driving wheel; 74. installing a frame body; 75. a worm; 76. a manual lever; 77. an electric motor; 81. a collimating mirror; 82. a polarizing plate; 83. a half wave plate; 84. a first quarter wave plate; 85. testing the light path lens; 86. a mirror to be tested; 91. a non-coke system; 92. a second quarter wave plate; 93. a third quarter wave plate; 94. reference is made to a mirror.

Detailed Description

The process of the present invention is described in further detail below.

A method for suppressing the interference of wave plate delay error in dynamic interferometer includes the following steps:

s1: the method comprises the following steps of preparing an experiment, detecting flatness and light transmittance of a half wave plate 83 and a quarter wave plate to ensure that the numerical values of the half wave plate 83 and the quarter wave plate are within a standard value, installing the half wave plate 83 and the quarter wave plate inside a dynamic interferometer, simultaneously collecting four interference patterns with fixed phase differences by the dynamic interferometer, extracting phase distribution by using a four-step phase-shifting algorithm, and further reconstructing the surface shape of a piece to be detected, wherein the light intensities of the four collected interference patterns are I1, I2, I3 and I4, the phase differences among the four patterns are pi/2, and if no wave plate phase delay error exists, the light intensity expression is as follows:

；

the phase distribution of the surface shape of the to-be-measured piece obtained by the above formula is as follows:

in practical situations, however, due to the processing precision factor, the quarter-wave plate inevitably has a certain phase retardation deviation, and it is assumed that the retardation is superposed with the deviationThe light intensity distribution expression of the four interferograms becomes:

the result obtained by the traditional phase solving method is as follows:

obviously, byCorrect phase distribution cannot be obtained;

s2: placing a piece to be measured, and adjusting the dynamic interferometer to ensure that four interference patterns acquired by the camera are distributed in a dense fringe manner;

s3: calculating the average gray value, manually selecting or automatically identifying a fringe area in an interference image, acquiring the average gray value of pixel points in the area in real time, calculating the root mean square value of the average gray value of four images, and calculating for multiple times to ensure that the best value is obtained integrally, wherein the calculation of the average gray value comprises the following two steps:

a1: taking points for multiple times to obtain an average value, selecting stripe regions in the interference pattern for multiple times, repeatedly measuring to obtain different values, calculating data sampled by multiple points, and calculating the gray level average value of pixel points in different regions;

a2: calculating root mean square values according to different average values, and substituting a plurality of groups of average values into a root mean square value calculation formula of the gray level average value to obtain the root mean square of the optimal average value;

s4: adjusting and measuring, manually or automatically rotating and adjusting the half wave plate 83 in a unidirectional way through a motor, calculating the root mean square value of the gray average value of the four images in real time, stopping adjusting the half wave plate 83 when the value is less than a set threshold value,

the light intensity distribution of the four interferograms is corrected as follows:

at this time, the phase distribution of the surface shape of the piece to be measured can be corrected as follows:

delta delta pair formula under normal machining precisionThe resulting effect is negligible.

The invention will be further elucidated with reference to an example,

example (b): the suppression of the delay error of the quarter-wave plate is realized by utilizing a dynamic interferometer;

the method comprises the following steps: building a light path shown in the figure 1, adjusting the position of a dynamic interferometer, and obtaining an interference fringe pattern, wherein fringes are densely distributed;

step two: and selecting a circular area where the interference fringes are located, obtaining the gray average value of the area of the four images, and calculating the root mean square value of the four gray average values, wherein the gray average values of the four interference images are 62.3178,70.0997,63.9684 and 53.8701 respectively, and the root mean square value of the four gray values is 5.7966.

Step three: setting the threshold value to be 1, starting the motor to rotate the half-wave plate 83, stopping the motor when the root mean square value is less than 1, obtaining four interference fringe graphs, wherein the gray average values are 66.7999,66.6066,65.9841 and 64.324 respectively, the root mean square value is 0.9743, and the phase information with the surface shape of the piece to be measured can be represented by a formula:

。

referring to fig. 3 and 4, the half-wave plate 83 includes a mounting frame 1, a mounting plate 2 is fixedly connected to the upper end of the mounting frame 1, a worm wheel 3 is rotatably connected to one end of the mounting plate 2, a mounting ring 4 for mounting the worm wheel 3 is rotatably connected to the inside of the mounting plate 2, a through hole 5 is formed in the worm wheel 3, a wave plate body 6 is fixedly connected to the inside of the worm wheel 3, an adjusting mechanism 7 for driving the worm wheel 3 to rotate is fixedly connected to one end of the mounting frame 1, the adjusting mechanism 7 can drive the worm wheel 3 to rotate, so as to ensure good adjusting effect of the whole body, the mounting plate 2 and the mounting ring 4 are both of an internal hollow structure, the hollow part of the mounting plate 2 is matched with the mounting ring 4 in shape and size, the hollow part of the mounting ring 4 is matched with the wave plate body 6 in shape and size, the hollow parts of the mounting plate 2 and the mounting ring 4 can ensure light path to pass through, so as to ensure good light passing effect of the whole body, the one side that collar 4 is close to worm wheel 3 has seted up fixed screw 41, the inside screw-thread fit of worm wheel 3 has set screw 31, set screw 31 passes worm wheel 3 and the mutual block of fixed screw 41, fixed screw 41 corresponds the distribution with set screw 31, set screw 31 is located the 6 outsides of wave plate body, when guaranteeing the overall stability and connecting, prevent that set screw 31 from leading to the fact the influence to wave plate body 6, 1 one end fixedly connected with of mounting bracket is used for the fixed plate 11 of installation, the inside screw-thread fit of fixed plate 11 has mounting screw 12, mounting screw 12 passes fixed plate 11 and extends to fixed plate 11 lower extreme, mounting screw 12 is about 11 horizontal central line symmetric distribution of fixed plate, symmetric distribution's mounting screw 12 can carry out stable installation to whole, guarantee holistic fixed effect.

Example one

Referring to fig. 2, the adjusting mechanism 7 includes a positioning plate 71 fixed on the outer side of the mounting frame 1, a driving motor 72 is fixedly connected to the upper end of the positioning plate 71, and a driving wheel 73 for driving the worm wheel 3 to rotate is fixedly connected to the output end of the driving motor 72.

Action wheel 73 and worm wheel 3 intermeshing, action wheel 73 and worm wheel 3 looks adaptation, the centre of a circle line overlap of worm wheel 3 and wave plate body 6 drives action wheel 73 through driving motor 72 and rotates to make things convenient for action wheel 73 to drive worm wheel 3 and wave plate body 6 and rotate, make things convenient for whole the adjusting.

Example two

Referring to fig. 5, the adjusting mechanism 7 is internally provided with an installation frame 74 fixed on the outer side of the installation plate 2, the installation frame 74 is internally connected with a worm 75 driving the worm wheel 3 to rotate in a rotating manner, the upper end of the worm 75 is fixedly connected with a manual control rod 76, the manual control rod 76 penetrates through the inner side of the installation frame 74 and extends to the upper end of the installation frame 74, the worm 75 is rotated by rotating the manual control rod 76, and the worm 75 rotates in-process to drive the worm wheel 3 and the wave plate body 6 to rotate, so that the whole angle of the wave plate body 6 is adjusted conveniently.

EXAMPLE III

Referring to fig. 6, the inside installation framework 74 who fixes in the mounting panel 2 outside of adjustment mechanism 7, the inside rotation of installation framework 74 is connected with and drives worm wheel 3 pivoted worm 75, installation framework 74 upper end fixedly connected with motor 77, the motor 77 output passes installation framework 74 upper end and worm 75 fixed connection, it is rotatory to drive worm 75 through motor 77, and the rotatory in-process of worm 75 drives worm wheel 3 and wave plate body 6 and rotates, thereby guarantee that whole convenience adjusts the angle of wave plate body 6.

The embodiments of the present invention are preferred embodiments of the present invention, and the scope of the present invention is not limited by these embodiments, so: all equivalent changes made according to the structure, shape and principle of the invention are covered by the protection scope of the invention.