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Crystran Newsletter July 2016

08th Jul 2016

Crystran Newsletter July 2016 - Metrology

The world of optics can often be very confusing with many different ways of specifying a single parameter. We at Crystran strive to stay on top of the latest measuring techniques and methods of testing for all the optics that we supply.

Crystran are proud to announce the newest addition to our metrology department, the Optilux SD. This next generation scratch dig evaluation system allows us to certify the quality of optical surfaces without subjectivity, adding even more weight to the Crystran stamp of quality assurance.

Scratch Dig measurement finally enters the 21st Century. Long regarded as a subjective measurement, scratch/dig remains one of the main industry standards defining the cosmetic finish of optical surfaces. In practice however, the practicalities of performing this assessment leads to a result that is highly subjective and prone to discussion. Although the use of "comparator plates" enables the inspector to roughly qualify the level of any gross imperfection, the intricacies of MIL13830 calls for the operator to make a pass/fail against the combined length of all scratches relative to the size of the optic; a challenging feat for even the most experienced technician.

Over recent years Crystran has seen an increase in the number of customers specifying against MIL13830 so we’ve decided to do something about it. Working with an advanced metrology company, we commissioned the design and development of a dedicated scratch/dig instrument to automatically assess components up to a clear aperture of 300mm. This instrument is calibrated against a set of industry recognised Davidson Optronics standards, and is able to resolve surface imperfections as small as 5µm using a dark-field measurement technique.

The instrument analyses the complete optic and provides an objective measure of scratch/dig that accounts for all the accumulation rules specified in the MIL standard. Additionally, any individual imperfection (or group of imperfections) can also be accurately assessed via an integration of the total amount of light being scattered.

Crystran would be pleased to discuss the use of this new instrument with you and, if you like, measure any samples you’d care to send our way.

One of our horizontal interferometers mounted on 3m optical bench with rail, SIOS laser and Heidenhain digital encoder for testing lens ROC.
Trioptics PrismMaster and OptiAngle measuring system for measuring parallelism and wedge angles up to 5 arc seconds.

A selection of our current equipment is listed below, which we use to test everything that goes through our quality system. 

- 12″ inch (300mm) Vertical Bespoke Interferometer and 2” High Resolution System Capability λ/20

- 4 inch (100mm) Intellium Z100 Horizontal Interferometer expandable to 6 inch (150mm) with Jenoptik attachment. Capability λ/20

-  3 Metre Optical Bench with rail, SIOS laser and Heidenhain digital encoder for testing ROC’s of lenses up to approx. +650mm Convex & -900mm Concave (C/A dependent on diameter of lenses and best fit sphere to radius f 1.0, f 3.3 &f 7.0 Spheres). Lens form errors can also be checked.

- Trioptics PrismMaster and OptiAngle measuring systems. Capability to <5 arc sec for parallelism and angles

- Baty Venture Vision 3-axis automated non-contact measuring system. 0.5µm resolution

- Redlux Optilux SD scratch-dig evaluation system

- Taylor Hobson CCI 6000 Talysurf for measuring Roughness Average. Resolution 0.1 Angstroms

- Perkin Elmer Frontier FT-IR Spectrometer (2—25µm)

- Perkin Elmer Lambda 750 UV/VIV/IR Spectrometer (195 to 3000nm)

- Vacuum UV rig for specific testing at Lyman Alpha wavelength (121.6nm)

- Trioptics Spherocompact for contact measuring the ROC of lenses up to 2µm resolution