Tech Notes » Definitions
Material —The substance of which the optic is made. Material selection is dependent upon application requirements including operable spectral range, transmission/reflectance requirements, and optical mechanical and environmental damage characteristics.
Surface Figure — The deviation from the ideal surface. RMI specifies surface figure in terms of wave peak-to-valley at 633nm, prior to coating. RMI can produce flats to λ/40 and spherical surfaces to λ/10 accuracy on a routine basis. Surface figure on coated optics may also be application specified. Please contact us for more information.
Surface Quality — The quality of the substrate surface as defined by scratch-dig and military specifications found in MIL-0-13830A and ISO 10110. Tighter tolerances are available in some cases.
Wedge — The angle between the two surfaces of an optical element. RMI's standard window parts have < 3 arc min wedge and some are < 1 arc sec depending on the type of optic.
Radius of Curvature — The radius of the sphere or cylinder coincident with the optical surface. The reciprocal of the radius is called the curvature of the surface. RMI's standard radius covers from flat curvature equal to infinity to a few millimeters tolerance of ± 0.5% and ± 0.1% depending on selected radii.
Concentricity — The deviation between the optical and mechanical axes of a lens. Concentricity error is the measured maximum edge thickness variation. RMI's standard concentricity is .025" edge thickness variation.
Clear Aperture — The central area (in terms of the diameter of linear dimensions) over which the optical specifications apply. RMI's standard clear aperture is 85%.
Chamfer — The angle at which the edge of the optical component is shaped. Chamfer is used to protect against chipping and also against injury when handling optics.
Damage Threshold — Damage threshold is a very complex issue in optical coating technology and depends on many parameters. When ordering, please specify wavelength, pulse energy, duration, and repetition rate. RMI is a pioneer and leader in high damage threshold, Thin Film Coatings for optical components used in laser systems.
Angle and Plane of Incidence — The angle formed between the normal to the optical surface (0º) and the incident ray. The plane of incidence is the plane containing the incident, reflected, and refracted ray.
Polarization — The orientation and phase shift of the electric field when resolved into components parallel and perpendicular to the plane of incidence. P-polarized light has the electric field parallel to the plane of incidence (on the plane of incidence). S-polarized light has the electric field perpendicular to the plane of incidence (normal to the plane of incidence). U refers to unpolarized light, which is a random mixture of S- and P-polarization