CN111497043B - Method for manufacturing magnesium fluoride wave plate element - Google Patents

Abstract

The invention provides a manufacturing method of a magnesium fluoride wave plate element, which comprises the following steps: s1, cutting the magnesium fluoride crystal blank to obtain a rectangular strip blank with two sides a and b respectively, wherein a is along the (001) direction; s2, cutting the rectangular strip blank into rectangular sheets with the same thickness along the (100) plane; and S3, roughly grinding the rectangular thin sheet on an outer circle grinding machine, wherein the center point of the grinding machine corresponds to the center of the long edge of the blank sheet, and the diameter is ground to the required size. The invention adopts a pulling method to grow a magnesium fluoride monocrystal blank in a <100> direction, a (001) crystal face of the crystal is determined by a cross-shaped measuring method on a cylindrical surface by using an X-ray orientation instrument after processing a wave plate, then the crystal is directly sliced according to the (100) face according to the growth direction, and finally the crystal is processed to the required size by using an external grinding machine. The method is simple to operate, high in machining precision, capable of effectively improving the yield and reducing the cost of products.

Description

Method for manufacturing magnesium fluoride wave plate element

Technical Field

The invention belongs to the field of instruments and meters, and particularly relates to a manufacturing method of a magnesium fluoride wave plate element.

Background

The magnesium fluoride crystal is an excellent optical crystal material and can be used for manufacturing ultraviolet and infrared lenses, windows, polarization optical elements and the like. The magnesium fluoride crystal belongs to a tetragonal system, the lattice constants and expansion coefficients of a <100> direction (a axis or b axis) and a <001> direction (c axis) are greatly different, and a magnesium fluoride crystal blank grown by adopting a traditional Bridgman method can only select the c axis direction, otherwise the crystal has a serious cracking phenomenon. The magnesium fluoride crystal has birefringence and anisotropy, and when used as a polarizing element, it is necessary to utilize the birefringence characteristics, that is, the light passing direction is perpendicular to the crystal optical axis direction (c-axis). The wave plate is a typical polarization element, the magnesium fluoride crystal processing wave plate must be sliced according to a plane vertical to <100> (a axis), the growth direction of the wave plate is not consistent with the growth direction of a crystal blank, meanwhile, the polarization element requires that the deviation of the crystal orientation is less than 10 minutes for the orientation precision and the processing precision, the current processing method is to cut the plane first and then grind a platform, the method has low precision and large orientation error, the platform is easy to generate the condition of angular deviation when being processed, and the yield is greatly reduced.

Disclosure of Invention

The invention provides a processing method of a polarization element, aiming at solving the problems of large orientation deviation and low yield of the existing magnesium fluoride wave plate.

To achieve the above object, the present invention provides a method for manufacturing a magnesium fluoride wave plate element, comprising the steps of:

s1, cutting the magnesium fluoride crystal blank to obtain a rectangular strip blank with a short side a and a long side b, wherein the length of a is the diameter of the finished wave plate plus 0-1 mm along the (001) direction on the cylindrical surface of the crystal, and the length of b is the diameter of the finished wave plate plus 0.5-3 mm; s2, cutting the rectangular strip blank into rectangular sheets with the same thickness along the (100) plane; and S3, roughly grinding the rectangular sheet on an outer circle grinding machine, wherein the center point of the grinding machine corresponds to the center of the long edge of the blank sheet, and the diameter is ground to the required size.

Furthermore, the magnesium fluoride crystal blank is a magnesium fluoride single crystal with the <100> direction grown by a pulling method.

Further, S1 includes the steps of:

s11, finding out the (001) surface of the magnesium fluoride crystal blank, and grinding the (001) surface to be flat;

s12, adhering the (001) surface to a base of an inner circle cutting machine, and cutting a magnesium fluoride crystal blank to ensure that the thickness in the (001) direction is a, and a is the diameter of the finished wave plate plus 0-1 mm;

and S13, rotating the magnesium fluoride crystal blank by 90 degrees, and cutting the magnesium fluoride crystal blank again to obtain a rectangular strip blank with two sides a and b respectively, wherein b is the diameter of the finished wave plate plus 0.5-3 mm.

Further, an X-ray orientation instrument having a three-dimensional rotation stage is used for finding the (001) plane.

Furthermore, a (001) plane is accurately determined by adopting a cross orientation method.

Further, S2 includes the steps of:

s21, finding out the (100) surface of the magnesium fluoride crystal blank, and grinding the (100) surface to be flat; (ii) a

S22, adhering the (100) surface to a base of the inner circle cutting machine;

and S23, cutting the rectangular strip blank into rectangular sheets with the same thickness along the (100) plane.

Further, the (100) plane is found using an X-ray orientation machine with a three-dimensional rotating table.

Furthermore, a cross orientation method is adopted to accurately determine the (100) surface.

The method for manufacturing the magnesium fluoride polarization element (wave plate and the like) can be used for automatically completing the whole process by a machine without manual operation and repair in the later period, has simple operation method and high orientation precision, greatly reduces the labor cost in the processing process and improves the production and processing efficiency.

The invention adopts a pulling method to grow a magnesium fluoride monocrystal blank in a <100> direction, a (001) crystal face of the crystal is determined by a cross-shaped measuring method on a cylindrical surface by using an X-ray orientation instrument after processing a wave plate, then the crystal is directly sliced according to the (100) face according to the growth direction, and finally the crystal is processed to the required size by using an external grinding machine. The method is simple to operate, high in machining precision, capable of effectively improving the yield and reducing the cost of products.

Drawings

FIG. 1 is a schematic representation of a magnesium fluoride waveplate element made in accordance with the present invention.

FIG. 2 is a schematic diagram of the processing of a blank of a magnesium fluoride waveplate element of the present invention.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, these information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present invention. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.

The present invention will be described in detail below by way of examples.

Take the magnesium fluoride wave plate with the diameter of 25.4 multiplied by 2mm and the platform width of 10 plus or minus 3mm as an example:

firstly, selecting a magnesium fluoride single crystal growing in a pulling method in a <100> direction, fixing a crystal blank on an X-ray orientation instrument with a three-dimensional rotating table, finding out the position of a (001) surface 1 on a cylindrical surface by rotating the crystal, grinding the surface to be flat, accurately determining the (001) surface 1 by adopting a cross orientation method, namely, the angles of 4 directions in a cross shape are all equal to the theta angle of the magnesium fluoride crystal (001) surface 1 (when the diffraction angle is wave diffraction, the angle between a line in the advancing direction and a normal line, the diffraction angle is the included angle changed by a light path when the light is diffracted, for example, in the X-ray diffractometer, 2theta (2 theta) is taken as the diffraction angle, namely, the angle changed by the X-ray after the diffraction is taken as the 2theta (2 theta), then adhering the (001) surface 1 on a base of an inner circle cutting machine, cutting out a magnesium fluoride crystal blank block, and ensuring that the thickness in the <001> direction is 25.5mm of the finished product diameter, then, the blank is rotated for 90 degrees (four (001) surfaces are cut by clockwise rotation), and is cut again according to the distance of 26.5mm, and finally the rectangular strip-shaped blank with two sides respectively as a and b is obtained, wherein the length of a is 25.5mm, and the length of b is 26.5 mm; the invention relates to a cross-shaped orientation method, which comprises the steps of (adhering a crystal on a base of a cutting machine, cutting a wafer with the thickness of 1mm from the crystal, marking the wafer with a cross-shaped mark, marking four directions of the cross-shaped mark respectively, forming an included angle of 90 degrees in the four directions, placing the wafer on an X-ray orientation instrument in one direction, rotating a lower disk by a 2theta angle, observing the diffraction peak intensity of X-rays until the intensity is maximum, recording the angle value at the moment, calculating the difference value between the angle value and a standard theta angle of a crystal direction, rotating the wafer by 90 degrees clockwise or anticlockwise, measuring the difference value between the second direction angle value of the cross-shaped mark and the theta angle of the crystal direction according to the method for adjusting the angle of the cutting machine blade, rotating a blade in a two-dimensional plane by the four difference values respectively, repeating the operations for a plurality of times, until the four difference values are all less than 2 minutes)

Secondly, placing the cut crystal blank block on an X-ray orientation instrument again to accurately determine a (100) surface, grinding the surface to be flat, wherein the orientation method is the same as that of the (001) surface 1, adopting a cross orientation method, finally finding out planes with 4 directions of cross and the same theta angle of the (100) surface through rotation of a rotating table, adhering the planes to a base of an inner circle cutting machine, and cutting a rectangular sheet with the thickness of 2mm along the (100) surface;

thirdly, roughly grinding the rectangular magnesium fluoride blank sheet on an excircle grinding machine, finding out a central point o of the blank (the central point of the blank is the center of a rectangle with a short side as a short side and a long side as b) by using a square die with 26.5mm x 26.5mm, grinding the excircle of the central point corresponding to the center of a fixture of the excircle grinding machine, grinding the diameter to 25.4mm, wherein the short side of the rectangle with 25.5mm is a platform with 10 +/-3 mm because the two sides of the rectangle are unequal, and cleaning to obtain the magnesium fluoride wave plate element (as shown in figure 1).

The a side, the b side and the center point o involved in the rough machining process of the magnesium fluoride wave plate element are shown in fig. 2.

Comparative example

The comparative example is used for manufacturing the magnesium fluoride wave plate according to the prior art, the prior art mainly cuts out the wave plate firstly and then grinds the platform, and the specific process is as follows:

take the magnesium fluoride wave plate with the diameter of 25.4 multiplied by 2mm and the platform width of 10 plus or minus 3mm as an example:

accurately determining a (001) surface 1 by adopting a cross orientation method, namely angles in 4 directions of the cross are the same as the angle theta of the (001) surface 1 of the magnesium fluoride crystal, then adhering the (001) surface 1 to a base of an inner circle cutting machine, cutting a magnesium fluoride crystal blank block, ensuring that the thickness in the (001) direction is 25.5mm of the diameter of a finished wave plate, then rotating the blank by 90 degrees, cutting again according to the distance of 26.5mm, and finally obtaining a rectangular strip blank with two sides respectively being a and b, wherein the length of a is 25.5mm, and the length of b is 26.5 mm;

secondly, placing the cut crystal blank block on an X-ray orientation instrument again to accurately determine a (100) surface, wherein the orientation method is the same as that of the (001) surface 1, adopting a cross orientation method, finally finding out planes with 4 directions of cross and the same theta angle of the (100) surface through rotation of a rotating table, adhering the planes on a base of an inner circle cutting machine, and cutting a rectangular sheet with the thickness of 2mm along the (100) surface;

and thirdly, roughly grinding the rectangular magnesium fluoride blank sheet on an excircle grinding machine, finding out the central point of the blank by using a 26.5mm square die, grinding the excircle of the blank corresponding to the central point of an excircle grinding machine fixture, grinding the diameter to 25.4mm, then grinding the 25.5mm rectangular short edge to obtain a 10 +/-3 mm platform, and cleaning to obtain the magnesium fluoride wave plate element.

The magnesium fluoride wave plates prepared in the examples and the comparative examples are subjected to quality detection, and the detection indexes comprise yield and processing efficiency, wherein the yield of the preparation method can reach 95.8% or more, and the yield of the preparation method in the comparative example is only 67.8%; the processing efficiency of the invention is more than doubled compared with the comparison.

Claims (7)

1. A manufacturing method of a magnesium fluoride wave plate element is characterized by comprising the following steps:

s1, cutting the magnesium fluoride crystal blank to obtain a rectangular strip blank with a short side a and a long side b, wherein the length of a is the diameter of the finished wave plate plus 0-1 mm along the (001) direction on the cylindrical surface of the crystal, and the length of b is the diameter of the finished wave plate plus 0.5-3 mm;

the step S1 specifically includes the following steps:

s11, finding out a (001) surface of the magnesium fluoride crystal blank, and grinding the (001) surface to be flat;

s12, adhering the (001) surface to a base of an inner circle cutting machine, and cutting the magnesium fluoride crystal blank to enable the thickness in the (001) direction to be a, wherein the a is the diameter of the finished wave plate plus 0-1 mm;

s13, rotating the magnesium fluoride crystal blank by 90 degrees, cutting the magnesium fluoride crystal blank again to obtain a rectangular strip blank with two sides a and b respectively, wherein b is the diameter of the finished wave plate plus 0.5-3 mm;

s2, cutting the rectangular strip blank into rectangular slices with the same thickness as the finished product along the (100) plane;

and S3, roughly grinding the rectangular thin sheet on an outer circle grinding machine, wherein the center point of the grinding machine corresponds to the center of the long edge of the blank sheet, and the diameter is ground to the required size.

2. The method of claim 1, wherein the magnesium fluoride crystal blank is a <100> direction magnesium fluoride single crystal grown by a Czochralski method.

3. The method of claim 1, wherein an X-ray orientation tool having a three-dimensional rotational stage is used to find the (001) plane.

4. The method of claim 3, wherein the (001) plane is precisely defined by a cross-orientation method.

5. The method of claim 1, wherein the step S2 includes the steps of:

s21, finding out a (100) surface of the magnesium fluoride crystal blank, and grinding the (100) surface to be flat;

s22, adhering the (100) surface to a base of the inner circle cutting machine;

and S23, cutting the rectangular strip blank into rectangular sheets with the same thickness along the (100) plane.

6. The method of claim 5 wherein said (100) plane is identified using an X-ray orientation machine having a three-dimensional rotational stage.

7. The method of claim 6, wherein the (100) plane is precisely defined by a cross-orientation.

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