Grinding glass lenses Start grinding glass lens by partly filling a small pan with #220 or #240 carborundum or Aloxite mixed with water. Apply the mixture to both the lens and the grinding tool, and then place the two with the upper glass held at the edge by fingers and thumb of your hands. With the sound of grinding becoming faint, slide the tool and add abrasive. Keep this up for 15-20 minutes to make the upper glass, if concave, become more concave and the lower glass more convex. After a spell of #220 grinding check the radius and the lens center thickness, and also the centering, commonly called OwedgeO. Wedge should be maintained at less than 0.001 during #220 grind and below 0.0004 inch for #400 grind. To measure wedge, place the clean dry lens on the fixture with the dial plunger resting inside the rim. If you are creating a cemented doublet and using the flint lens to grind the mating curve, lookout for the center thickness of the flint lens in order to leave sufficient material to grind the flat side. To bevel the edges, grind the sharp corners with a #220 carborundum stone held at a 45 degree angle with adequate water upon the lens and the stone. Polishing lenses Before dealing with the polishing process, make sure to use 15 inch fluorescent tube as the source of monochromatic light for interference fringe testing of the lens surface. Use gummed paper, duct or masking tape to wrap the edges of the two shellacked convex and concave wood discs to provide a circular dam three eighths of an inch high above the surface. Pour melted pitch level full into the concave disc and allow the pitch to cool to attain flexibility. Then press into it the convex R2 that has been tarnished with diluted Cerium Oxide or Barnesite. As the lens sinks into the pitch, material bulges out at the edge. Push it back against the glass lens while moving the lens around over the pitch until it is totally fitted. Remove the lens at this point and freeze the pitch by immersing in cool water, and then strip off the dam. Repeat this process with the second wood tool. The first polishing task includes polisher shaped by R3. This polisher is fastened to the pedestal, the concave lens rubbed over it until there is enough OshineO to perform a knife-edge and Ronchi test. When tests are done, polish the surface completely after verifying its radius and sphericity. Now take the plate glass tool that ground R1 for polishing. Press the concave side on warmed pitch polisher that finished R3. The next step involves polishing the flat surfaces of the R1 test glass and R4. Polish the flat of R1 test glass until it is clear enough to see through, and then begin polishing R4. R1 and R2 are next to be polished by using the polisher already made. Warm it and press it to whichever radius you wish to polish first. As polishing proceeds, use the test glass as needed to bring about a 3 fringe or better match for both sides of the biconvex lens. Article is provided by Optics- Sourcing. To compare your quotes from qualified optic vendors visit -http://optics-sourcing.com.
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