SU865619A1 - Method of working the aspherical surfaces of an optical component - Google Patents

Description

(54) METHOD FOR PROCESSING ASPHERIC SURFACES OF OPTICAL PARTS

one

The invention relates to the field of abrasive machining and can be used in the manufacture of optical components with aspherical surfaces.

Methods are known for the aspherization of optical parts, where the axes of the rotating parts and the tool are angled to each other, while the working surface of the tool has a configuration made depending on the equation of the given aspherical surface.

In these methods, the working profile of a convex tool is made along a radius of curvature equal to the linear radius of curvature of a given concave aspherical surface, and the working profile of a concave tool is made along a radius of curvature equal to the maximum radius of curvature of the convex surface 1.

The disadvantage of these methods is that the choice of the radius of curvature of the working surface of the tool equal to the extreme radius of curvature of a given spherical surface causes the contact between the tool and the part to touch the variable area when the current zones pass through the aspheric surface.

The variability of the contact spot area in different zones of the part does not allow to calculate with sufficient accuracy the distribution of material removal by zones. In addition, due to the wear of the working surface of the tool, the magnitude of which is different during the asphericization of different zones of the part, the required regularity of the aspherization process is disrupted.

The foregoing does not allow to achieve high precision of processing in the above methods due to the lack of proper grinding between the tool and the spot with the known constant ve, 5 area mask, which ensures the required regularity of the aspherization process.

Claims (2)

In this regard, the known methods are suitable only for aspherizing optical components by copying using non-installable tools, such as diamond-coated tools, that provide average processing accuracy. The closest to the proposed by the technical essence is a method of obtaining aspherical surfaces, in which, in order to increase the accuracy and productivity of processing, the asphericization is carried out with a toroidal tool, whose axis is angled to the plane of the linear movement of the tool. The method is intended for aspherization of parts rotating around a fixed axis by a rotating tool moving in a three-coordinate system from program control 2. The disadvantage of this method is that it is applicable only for aspherization by copying parts that have low accuracy, and this method allows to expand the range of machined details on asphericity, gives a sharp decrease in the accuracy of processing with an increase in the gradient of asphericity. When using the specified toroidal tool for aspherization by distributing work over zones, gradual wear of the toroidal working surface leads to uncertainty in the size of the contact spot area, as a result of which the aspherization process becomes uncontrollable due to the uncertainty in the value of the specific processing pressure and the area of the coating of the asparated zones. The purpose of the invention is to increase the accuracy and expand the range of parts to be processed in terms of asphericity. The goal is achieved by choosing the width of the working surface of the instrument equal to the diameter of the central zone of a given surface, within which the asphericity does not exceed the processing tolerance, the radius of curvature of the working surface of the instrument in the meridional section equal to the radius of the sphere adjacent to the said central zone, combine the sagittal section a tool with a meridional section of the treated surface and move the tool in the plane of the meridional section of the part. FIG. 1 and 2 depict schematics for carrying out the invention in the aspherization of concave and convex surfaces, respectively; in fig. 3 and 4 - the same, top view. The workpiece 1 of the workpiece with the original (closest to the specified aspheric) spherical or flat surface, made with the required interference accuracy, is re-aligned and fixed to the faceplate 2. On the carriage 3, performing a swinging motion according to a predetermined program around the O-O axis with respect to the aspherical surface, install the annular instrument 4, fixing it on the quill 5, located at an angle oCc of the axis of the asphericized surface so that the sagittal plane of the instrument is perpendicular to in the plane of the drawing, it passed through the middle of the annular part of the tool and through the axis of rotation of the aspheric surface. In this case, the width of the annular working surface of the tool a is chosen equal to the diameter d of the central zone of a given aspherical surface, within which the asphericity does not exceed the tolerance for processing the given aspheric surface as a whole. The radius of curvature of the annular working surface of the instrument in the meridional section is equal to the radius of the sphere closest to the specified central zone, which, therefore, deviates from the central zone of the given surface by asphericity not exceeding the tolerance on the machining accuracy of this aspheric surface. Processing details produced as follows. Before the start of aspherization, the calculated frequency of rotation of the part and the tool determined during the calculation of the treatment program is established. Moving the quill 5, having a degree of freedom along its axis of rotation, the tool 4 is lowered onto the aspheric surface of the part 1. After turning the carriage 3 around the axis O-O, the quill with the tool is mounted on the central zone of the aspheric surface. The tool 4 is loaded along the axis of the quill 5 using a pneumatic-hydraulic system or a load with a calculated load according to the norms of the specific processing pressure for the abrasive shaping of optical components. By means of the auto-feeding system, a grinding or polishing slurry is applied to the surface to be treated, depending on the type of treatment. Through the process control system, the machining of the workpiece 1, the tool 4, and the programmed movement of the carriage 3 are programmed. The programmed movement of the tool 4 by means of the carriage 3 is carried out in the plane of the meridional section of the spherical surface of the workpiece being machined. The aspheric surface is processed until the calculated layer of material is removed in the part area, where the surface is monitored during the process. After removing the design layer, the treatment is stopped and the entire aspherical surface of the part is measured in the annular zones selected for inspection. In the grinding operation, the control of an aspherical surface is carried out using spherometers of the IZS-7, IZS-8 and IZS-72 types with contact rings, and in the polishing operation, depending on the type of aspherical surface (second or higher order), the Foucault shadow method, interference or holographic methods . The proposed method of asphering optical parts by programmed movement of an annular tool positioned at a desired angle to the axis of rotation of the workpiece by selecting the optimal width of the annular working surface of the tool allows for contact between the tool and the part with a spotted spot sufficient to provide the necessary machining accuracy . At the same time, choosing the radius of the tool section radius equal to the radius closest to the central zone of a given surface of the sphere and the programmed movement of the tool in the plane of the meridional section of the part reduces the spot size in the direction of the meridional section of the part, which greatly extends the range of parts to be machined according to asphericity, since the size of the tangency spot in the said direction in this case is reduced to the size of a point contact. This, in combination with the optimal width of the ring tool, allows for increased machining accuracy, since the spot area of contact between the tool and the part, due to an increase in the size of the touch line in the sagittal section of the treated surface, where the asphericity is close to zero, is required aspheric value process. The invention of the method of processing aspherical surfaces of optical parts with an annular tool, in which the axes of the part and the tool are set at an angle to each other, they are given a rotational movement, and the tool is moved relative to the part according to the program, characterized in that, in order to increase the accuracy and extend the range machined parts according to asphericity, choose the width of the working surface of the tool equal to the diameter of the central zone of the given surface, within which the asphericity does not exceed The machining tolerance, the radius of curvature of the working surface of the instrument in the meridional m section equal to the radius closest to the said central zone of the sphere, combine the sagittal section of the instrumental with the meridional section of the treated surface and mix the instrument in the plane of the meridional section of the part. Sources of information taken into account in the examination 1. USSR author's certificate L 244142, cl. B 24 B 13/00, 1964. 2. USSR author's certificate No. 214328, cl. B 24 B 13/00, 1963.