Optical manufacturing and testing

• Glass blank manufacturing • Batch mixing • Casting techniques • Annealing schedules and equipment • Physical characterization techniques • Index of refraction measurements and calculation of melt pedigree • Diamond shaping techniques • Diamond wheel curve generation processes and equipment • Diamond edging processes and equipment • Loose grit fabrication techniques: • Rough grinding • Fine grinding • Polishing and figuring • Glass moulding techniques • Precision glass moulding Unconventional techniques include single-point diamond turning (SPDT) and magnetorheological finishing (MRF). Free-abrasive grinding Free-abrasive grinding is a technique to grind down the surface of a material before polishing. It involves the use of small particles of grit to grind away small chips of material from the surface of an optical workpiece. The grit particles are known as free abrasives. The particles are added to a liquid slurry, which goes between a grinding plate and the material. Sliding motions between the grinding plate and the material are used. After grinding, there is a small amount of surface roughness, which is based on the size of the grit. There is also a small amount of fracturing below the surface of the material, known as subsurface damage (SSD). Polishing Optics are polished in a slurry of abrasive particles, a fluid carrier, and optional additives. Types of abrasive particles that can be used include cerium(IV) oxide, diamond, aluminum oxide, and colloidal silica. Optional additives include suspension agents, lubricants, and detergents. == Materials ==

There are various materials that can be used for optical components, including various types of glass, fused silica, silicon, and crystal quartz. Calcium fluoride (CaF2) can be used as an optical material, although it is easily fractured and scratched. Materials for infrared optical components include zinc selenide (ZnSe), zinc sulfide (ZnS), and gallium arsenide (GaAs). == Specifications ==

The specifications for optical components vary based on their type: Specifications for prisms include pyramidal error, beam path, beam displacement and deviation, base angle, roof edge chips, wavefront, and polarization. Specifications for aspheric lenses include base radius with tolerance, conic and polynomial coefficients, best-fit sphere reference, sag table reference, sag error tolerance, slope errors versus bandwidth, wavefront per specified test, tilt, and decenter. Surface quality Surface quality is the condition of the surface of an optical component. It indicates the presence of imperfections, such as scratches and pits. It is typically rated according to scratch-dig (S-D) specifications. Standards for specifying surface quality include the U.S. Military Performance Specification MIL-PRF-13830B and ISO 10110. MIL-PRF-13830B was formerly MIL-O-13830a. Other standards include MIL-C-48497a and MIL-F-48616, which are formally inactive and apply only to coatings. All three of these military standards lack specifications for statistical surface parameters, such as root-mean-square roughness, slope error, and ripple. An extension and improvement to MIL-PRF is the ANSI/OEOSC OP1.002 standard. == Testing techniques ==

• Direct surface profile measurement • Direct surface surveying (no intervening optics, for example Foucault knife-edge test, Ronchi test, Caustic test) • Auxiliary optics (null correctors, computer-generated holograms, etc.) • Interferometric testing The Fizeau interferometer is the standard type of interferometer that is used in optical fabrication. Stitching interferometry can be used for testing aspheres. It involves performing subaperture tests that are stitched together into a single-high resolution image. == See also ==

• Malacara, D., Optical Shop Testing - 2nd Edition, John Wiley and Sons, 1992, == External links ==