CN105643395A - Grinding forming method for optical free-form surface - Google Patents

Abstract

The invention discloses a method for grinding and forming an optical free-form surface, which adopts a numerically controlled grinding center and a spherical grinding wheel for grinding and forming. S1: describe the designed target surface using a point cloud matrix to obtain a point cloud design matrix M _design ; S2 : Grinding the curved surface to be processed according to the point cloud design matrix _Mdesign , and detecting the surface obtained after grinding to obtain the point cloud detection matrix M _measure ; S3: combining the point cloud detection matrix M _measure with the point Comparing the cloud design matrix M _design to obtain a point cloud error matrix M _err ; S4: performing compensation grinding on the ground surface according to the point cloud error matrix M _err . The forming method can effectively improve the grinding precision of the numerical control grinding center, and has the advantages of wide application range, low processing cost and the like.

Description

A grinding method for optical free-form surface

technical field

The invention relates to the field of optical processing, and in particular provides an optical free-form surface grinding forming method.

Background technique

Introducing a free-form surface into an optical system can greatly improve the imaging quality and energy transmission efficiency of the optical system. The application of free-form surfaces in modern optical systems can design specific free-form surfaces for the special aberrations of the system, compensate system aberrations, and improve system imaging quality. Due to the multi-degree-of-freedom characteristics of the free-form surface, it is usually possible to further reduce the number of components in the optical system and reduce the size of the optical system under the condition of ensuring the imaging quality of the optical system, so it is more and more widely used in medical, military, aerospace, etc. field.

Advanced CNC ultra-precision manufacturing technology for processing free-form optical elements can effectively solve the technical bottleneck of free-form optical element processing, but the general free-form surface grinding method involves the use of CNC grinding processing centers that directly affect the processing quality of optical free-form surfaces , Improving processing accuracy often means higher processing costs, such as the introduction of ultra-precision hydraulic or air-floating processing centers, which have great restrictions on the use environment and processing materials.

Therefore, how to solve the above problems has become an urgent problem to be solved.

Contents of the invention

In view of this, the object of the present invention is to provide a kind of optical free-form surface grinding forming method, to solve the need to use ultra-precise numerical control center when performing free-form surface processing in the past, all have very big restriction to use environment and processing material, and High processing costs and other issues.

The technical solution provided by the present invention is specifically a method for grinding and forming an optical free-form surface, which adopts a numerically controlled grinding center and a spherical grinding wheel for grinding and forming, and is characterized in that:

S1: Describe the designed target surface using a point cloud matrix to obtain a point cloud design matrix M _design ;

S2: Grinding the curved surface to be processed according to the point cloud design matrix M _design , and detecting the curved surface obtained after grinding to obtain the point cloud detection matrix M _measure ;

S3: Comparing the point cloud detection matrix M _measure with the point cloud design matrix M _design to obtain a point cloud error matrix M _err ;

S4: Perform compensation grinding on the ground surface according to the point cloud error matrix M _err .

Preferably, said step S4 includes:

S401: Comparing the point cloud error matrix M _err with a threshold;

S402: When the point cloud error matrix M _err is greater than a threshold, calculate and obtain a point cloud correction matrix M _{design_1} according to the point cloud error matrix M _err ;

S403: Perform compensation grinding on the ground surface according to the point cloud correction matrix M _{design_1} , perform point cloud detection on the compensation ground surface, and compare the detected point cloud detection matrix with the point cloud design matrix M _design , get the point cloud error matrix M _err again;

S404: Repeat steps S401-S403 until the point cloud error matrix M _err is less than or equal to the threshold.

Further preferably, in the step S402, according to the point cloud error matrix M _err , the formula for calculating and obtaining the point cloud correction matrix M _{design_1} is:

M design — ₁ =M _design +M _err .

Further preferably,

The method of detecting the curved surface obtained after grinding in step S2 is contact detection;

The method of detecting and compensating the ground surface in step S403 is contact detection.

Further preferably, the positions of the detection points in step S2 and step S403 are the same as the sampling point positions of the point cloud design matrix of the target curved surface.

Further preferably, both the point cloud design matrix M _design and the point cloud detection matrix M _measure include three-dimensional coordinate data of a curved surface in X, Y, and Z.

The optical free-form surface grinding forming method provided by the present invention uses a point cloud method to evaluate and measure the free-form surface, calculates the point cloud error matrix, and performs compensation processing with the point cloud error matrix to correct the processing results. The forming method for grinding can effectively improve the grinding accuracy of the CNC grinding center without using an ultra-precision CNC center, which reduces processing costs and is conducive to the manufacture and application of free-form optical components.

The optical free-form surface grinding forming method provided by the present invention has the following advantages:

1. Carry out surface design and detection description through point cloud, which can be applied to most free-form surface optical components, effectively expanding its scope of application;

2. Through the flexible processing method of compensation processing, the requirements on the processing center are reduced, which can effectively reduce the manufacturing cost of free-form surface optical elements.

Description of drawings

Fig. 1 is the structural representation of spherical emery wheel;

Fig. 2 is a schematic diagram of the grinding and forming process of the free-form surface optical element.

detailed description

The present invention will be further explained below in conjunction with specific embodiments, but it is not intended to limit the protection scope of the present invention.

In order to solve the problem that in the past, when processing free-form optical elements, it is necessary to use ultra-precision machining centers, there are many restrictions on the use environment and processing materials, and the problem of high cost, this embodiment provides an optical free-form surface grinding forming The method, which can be applied to ordinary numerical control centers, can improve the machining accuracy of ordinary numerical control centers, and then can use ordinary numerical control grinding machining centers and spherical grinding wheels to process optical free-form surfaces, reducing the cost of free-form surface processing, and for the use of There are no strict requirements on the environment and processing materials.

The present invention is described in detail with a specific embodiment below:

Using CNC grinding machining center and spherical grinding wheel, the free-form surface z=a ₁ x ² +a ₂ y ² +a ₃ x ³ +a ₄ y ³ is ground and shaped by single-point grinding. The aperture of the optical element is D, since the equation of the free-form surface includes a cubic term, it is a non-rotationally symmetric free-form surface.

Wherein, the structure of spherical grinding wheel can refer to Fig. 1, comprises cylindrical grinding wheel shank 1, and the cylindrical grinding wheel substrate 2 that is fixedly connected with cylindrical grinding wheel shank 1, is provided with grinding wheel abrasive layer 3 on the periphery of grinding wheel substrate 2, and grinding wheel abrasive material The grinding surface of layer 3 is arc-shaped, and its curvature changes to the diameter of the grinding wheel, that is, the grinding wheel base 2 and the grinding wheel abrasive layer 3 can be regarded as a section of a sphere. The advantage of this is that the actual grinding process is the grinding of the arc-shaped grinding working surface of the grinding wheel abrasive layer 3, which can improve the surface finish and processing efficiency. Since the actual grinding wheel contact position is a part of the spherical shape, it can be used to a certain extent. Make up for the impact of machining center motion accuracy and dynamic characteristics on actual machining. The caliber of the spherical grinding wheel is smaller than the radius of curvature of the best fitting sphere of the processed free-form surface.

Discretize the free-form surface z=a ₁ x ² +a ₂ y ² +a ₃ x ³ +a ₄ y ³ internal surface of caliber D, set the sampling interval as d, the surface shape point cloud design matrix M _design of the surface can be obtained

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; g</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& {\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}& {\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]$

Wherein, the point cloud design matrix includes X, Y, Z three-dimensional coordinate data;

According to the point cloud design matrix M _design and the specific parameters of the above-mentioned spherical grinding wheel, select the appropriate processing path, generate the processing program and import it into the CNC grinding machining center for processing. The processing schematic diagram is shown in Figure 2, where A is the spherical grinding wheel and B is the For the surface to be processed, the contact detection method is used after the processing is completed. The detection point position is the same as the point cloud sampling point position of the free-form surface, and the point cloud measurement matrix M _measure is obtained after detection;

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& {{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}& {{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]$

Analyze the deviation between the point cloud measurement matrix M _measure and the point cloud design matrix M _design to obtain the point cloud error matrix M _err ,

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; \&Delta;z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& {\mathrm{<span\; class="notranslate">\; \&Delta;z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {\mathrm{<span\; class="notranslate">\; \&Delta;z</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; .</span>\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}& {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}& {\mathrm{<span\; class="notranslate">\; \&Delta;z</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]$

This error can be considered to include the processing error caused by the combination of machining center performance, processing parameters, processing environment, grinding wheel wear and other factors. Therefore, if this error can be compensated, the processing error can be effectively reduced;

Add the alignment position of the point cloud error matrix M _err to the point cloud design matrix M _design to obtain the point cloud correction matrix M _{design_1} , the calculation formula is as follows:

M _{design_1} = M _design + M _err

Based on the new point cloud design matrix M _{design_1} and the specific parameters of the spherical grinding wheel, re-select the appropriate processing path, generate a processing program and import it into the CNC grinding machining center for processing, and then use the contact detection method for detection after processing is completed, and the detection The obtained point cloud detection matrix is compared with the design matrix to obtain the point cloud error matrix. If the point cloud error matrix is greater than the set threshold, the point cloud correction matrix is regenerated, and then processed. This iterative processing gradually reduces the processing error. , to reduce the point cloud error matrix until the processed surface point cloud matrix meets the design requirements, that is, the point cloud error matrix is smaller than the threshold, and the threshold can be actually set according to different needs.

The optical free-form surface grinding forming method proposed in the above embodiment involves the use of a general-purpose CNC grinding machining center, which can effectively reduce processing and maintenance costs, and the single-point grinding method of spherical grinding wheels improves the grinding efficiency and reduces For the requirement of the maximum spindle speed, the point cloud method is used to evaluate and measure the free-form surface, and the point cloud error matrix is calculated, and the processing data is compensated to correct the processing results. In this way, iterative processing gradually reduces the processing error, and finally meets the design requirements. free-form optical elements. The method can effectively improve the processing precision of the free-form surface, reduce the processing cost, and is beneficial to the manufacture and application of the free-form surface optical element.

This method is also applicable to the free-form surface processing that cannot be described by equations but can be described by a point cloud matrix. The present invention will be further described with a specific embodiment below.

Example 1

The processed optical free-form surface is shown in Figure 2, where A is the grinding wheel used for grinding, with a diameter of 150 mm and a cutting edge radius of 75 mm, and B is the processed optical free-form surface component. The optical free-form surface element B cannot be described by equations, but can only be described by the following point cloud matrix M _design , where each row includes x, y, and z coordinates of different positions, and there are 70 coordinates in total. The first 20 coordinates are given as follows:

The grinding path is calculated according to the point cloud matrix M _design and the grinding wheel used, and the NC machining program is generated after post-processing, which is imported into the NC grinding process for grinding processing. After processing, the contact detection method is used for measurement to obtain the measurement matrix M _measure , as follows Given the first 20 coordinates:

The error point cloud matrix M _err is calculated by the point cloud matrix M _design and the measurement point cloud matrix M _measure . Only the first 20 coordinates are given as follows, and the maximum deviation of the coordinate Z is 0.066mm. This deviation is greater than the threshold and can be passed through the CNC grinding center. Make corrections. Calculate M _{design_1} = M _design + M _err , and regenerate the machining path, post-process to generate the machining program, import the CNC grinding process for grinding, cycle iterations, and finally the error point cloud matrix M _err meets the design requirements.

The above are only preferred implementations of the present invention, and it should be noted that the above preferred implementations should not be regarded as limiting the present invention, and the scope of protection of the present invention should be based on the scope defined in the claims. For those skilled in the art, without departing from the spirit and scope of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (6)

1. a freeform optics surface grinding-shaping method, adopts numerical control grinding machining center and spherical emery wheel to carry out grinding-shaping, it is characterised in that:

S1: the target surface of design adopts some cloud matrix be described, invocation point cloud design matrix M_design;

S2: according to described some cloud design matrix M_designTreat processing curve and carry out grinding work, and gained curved surface after grinding is detected, invocation point cloud detection matrix M_measure;

S3: by described some cloud detection matrix M_measureWith described some cloud design matrix M_designCompare, it is thus achieved that some cloud error matrix M_err;

S4: according to described some cloud error matrix M_errGrinding rear curved surface is compensated grinding.

2. freeform optics surface grinding-shaping method described in claim 1, it is characterised in that described step S4 includes:

S401: by described some cloud error matrix M_errCompare with threshold value;

S402: as described some cloud error matrix M_errDuring more than threshold value, according to described some cloud error matrix M_err, calculate and obtain some cloud correction matrix M_{design_1};

S403: according to described some cloud correction matrix M_{design_1}Grinding rear curved surface is compensated grinding, carries out a cloud detection to compensating grinding rear curved surface, and by the some cloud detection matrix of detection gained and some cloud design matrix M_designRelatively, some cloud error matrix M is again obtained_err;

S404: repeat step S401��S403, until some cloud error matrix M_errLess than or equal to threshold value.

3. freeform optics surface grinding-shaping method described in claim 2, it is characterised in that: in described step S402, according to described some cloud error matrix M_err, calculate and obtain some cloud correction matrix M_{design_1}Formula be:

M_{design_1}=M_design+M_err��

4. freeform optics surface grinding-shaping method described in claim 2, it is characterised in that:

In step S2, after detection grinding, the method for gained curved surface is contact measurement;

In step S403, detection compensates the method for grinding rear curved surface is contact measurement.

5. freeform optics surface grinding-shaping method described in claim 4, it is characterised in that: step S2 is identical with the some cloud design matrix sampling point position of target surface with the test point position in step S403.

6. freeform optics surface grinding-shaping method described in claim 1, it is characterised in that: described some cloud design matrix M_designWith described some cloud detection matrix M_measureIn all include curved surface at X, Y, Z three-dimensional coordinate data.