White Diffuser Glass is a semi-opaque soda lime glass, which acts like a diffuser designed to create even illumination profiles. Soda Lime glass has a thermal co-efficient expansion of 93 (10-7) which is approximately 10 ppm (parts per million), and a transmittance value of 88% at 375-750nm, with a glass flatness class of 5um

It transmits a very wide variety of light sources from 350nm upwards, with an excellent UV transparency. The glass is optically good, very flat and has no imperfections. Soda Lime Glass is the most common substrate used for targets, due to its good quality/price ratio. Clearance at centre is 0.30mm, giving a minimum spoke width of 0.002mm at the centre SL1-4 314 Spoke design, where l= D / 100 for simpler calculations.Clearance at centre is 0.25mm, giving a minimum spoke width of 0.003mm at the centre SL1-3 120 Spoke design, giving 3 deg rotation.Clearance at centre is 0.20mm, giving a minimum spoke width of 0.004mm at the centre SL1-2 72 Spoke design, giving 5 deg rotation.Clearance at centre is 0.15mm, giving a minimum spoke width of 0.006mm at the centre

SL1-1 36 Spoke design, giving 10 deg rotation.

The outer diemater of the pattern is 2' / 50mm. There are 4 different patterns to choose from, each having a different spoke count.

Material: Chrome on White Glass, 1.25mm thick, available as 4' (100mm).

Material: Chrome on Transparent Soda Lime Glass, 1.5mm thick, available as 3' (75mm).

It consists of a pattern of bright 'spokes' on a dark background that radiate from a common center and become wider as they get further from it. It is used to identify the aberration of the optical system - determining the resolution of an optical system by noting how close to the center of the pattern an optical system is able to resolve adjacent bars A Siemens star is a device used to test the resolution of an Optical instrument.