Optical manufacturing and testing spans an enormous range of manufacturing procedures and

optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...

test configurations. The manufacture of a conventional spherical

lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements ...

typically begins with the generation of the optic's rough shape by grinding a glass blank. This can be done, for example, with ring tools. Next, the lens surface is polished to its final form. Typically this is done by

lapping Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine. Lapping often follows other subtractive processes with more aggressive material removal as a first ste ...

—rotating and rubbing the rough lens surface against a tool with the desired surface shape, with a mixture of abrasives and fluid in between. Typically a carved pitch tool is used to polish the surface of a lens. The mixture of abrasive is called slurry and it is typically made from cerium or zirconium oxide in water with lubricants added to facilitate pitch tool movement without sticking to the lens. The particle size in the slurry is adjusted to get the desired shape and finish. During polishing, the lens may be tested to confirm that the desired shape is being produced, and to ensure that the final shape has the correct form to within the allowed precision. The deviation of an optical surface from the correct shape is typically expressed in fractions of a

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...

, for some convenient wavelength of light (perhaps the wavelength at which the lens is to be used, or a visible wavelength for which a source is available). Inexpensive lenses may have deviations of form as large as several wavelengths (λ, 2λ, etc.). More typical industrial lenses would have deviations no larger than a quarter wavelength (λ/4). Precision lenses for use in applications such as

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The ...

interferometer Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber o ...

s, and

holography Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other applications. In principle, i ...

have surfaces with a tenth of a wavelength (λ/10) tolerance or better. In addition to surface profile, a lens must meet requirements for surface quality (scratches, pits, specks, etc.) and accuracy of dimensions.

Fabrication techniques

*Glass blank manufacturing ** Batch mixing **

Casting Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a ''casting'', which is ejecte ...

techniques ** Annealing schedules and equipment ** Physical characterization techniques **

Index of refraction In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

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 Polishing is the process of creating a smooth and shiny surface by rubbing it or by applying a chemical treatment, leaving a clean surface with a significant specular reflection (still limited by the index of refraction of the material accordin ...

and

figuring Figuring is the process of final polishing of an optical surface to remove imperfections or modify the surface curvature to achieve the shape required for a given application. Types An example of figuring is that used in reflecting telescope pr ...

* Single-point diamond turning processes and equipment * Glass moulding techniques ** Precision glass moulding

Testing techniques

* Direct surface profile measurement * Direct surface surveying (no intervening optics, for example

Foucault knife-edge test The Foucault knife-edge test is an optical test to accurately measure the shape of concave curved mirrors. It is commonly used by amateur telescope makers for figuring primary mirrors in reflecting telescopes. It uses a relatively simple, inexpens ...

Ronchi test In optical testing a Ronchi test is a method of determining the surface shape (figure) of a mirror used in telescopes and other optical devices. Description In 1923 Italian physicist Vasco Ronchi published a description of the eponymous Ronchi tes ...

, Caustic test) * Auxiliary optics (

null corrector A null corrector is an optical device used in the testing of large aspheric mirrors. A spherical mirror of any size can be tested relatively easily using standard optical components such as laser, mirrors, beamsplitters, and converging lenses. O ...

s, computer-generated holograms, etc.) * Interferometric testing

Notes and references

*Malacara, D., ''Optical Shop Testing - 2nd Edition'', John Wiley and Sons, 1992,

External links

Virtual Lens Plant, Canon Camera Museum
Instructional videos of the processes, within a flash web interface. {{DEFAULTSORT:Fabrication And Testing Of Optical Components Optics Optical components, fabrication Glass engineering and science

Fabrication techniques

Testing techniques

See also

Notes and references

External links