This is a quartz half-lambda retardation plate specific to a wavelength of 422nm. The 10mm diameter plate is mounted in a 1 inch diameter disk of 0.23 inches in thickness. Clear aperture of the plate is 8mm. The orientation of the fast ray is indicated by a groove in the side of the mount.

This type of plate is known as a zero-order plate – if it is tilted slightly in the correct direction between crossed polarizers the zero-order interference band is clearly seen. Zero-order plates are preferable to high-order plates because they are less sensitive to specific wavelength and fluctuations in temperature. They are constructed of two higher-order retardation plates cut and oriented in such a manner that the net result is the desired retardation. The zero-order plates from Melles Griot are differentiated from high-order plates by the radial groove in the mount. The two plates are optically contacted (not air-spaced).
***MPN QWPO-442-04-2-R10
***OEM Melles Griot
***SKU*** 23008