Most optics are listed in several grades, from precision optics of high accuracy to economical items for less critical applications. Whatever the grade, we take great care to ensure that the specification is met, and we are well known among our suppliers for our exacting attention to details. All incoming goods are quarantined until inspection, which includes both measurement of dimensions etc. and 100% visual check for cosmetic defects. Records are kept for future reference. Our main ranges of optics are made to specifications set by ourselves, which we are equipped to verify in-house. We also list some proprietary ranges from specialist manufacturers (e. g. eye pieces, polarisers, lamps); specifications given for these are generally as stated by the manufacturer.
- Stated in wavelengths (λ); 1λ = 633nm
- Often given for a specific test field, e.g. 1λ over 25mm diameter,meaning 1λ over any test field 25mm diameter within the optical aperture.
- For small areas the error often varies as the square of the test field size, so 1λ over 20mm is roughly equivalent to λ/4 over 10mm.
The two numbers give respectively the largest scratch and largest dig (circular defect) permitted. Digs are simply measured by diameter in 10μm units. Scratches are assessed by visual comparison with a standard. Since the scratch specimens referred to in MIL-0-13830A are not generally available,we offer an equivalent standard to help our customers:- 01 QS 00 Reference standard containing scratches 10, 20, 40, 60, 80, 120, 160 and digs 5, 10, 20, 40, 50, 70, 100.