ASME/ANSI Y14.18M:1986 pdf free download

ASME/ANSI Y14.18M:1986 pdf free download.OPTICAL PARTS.
3.1 Introduction
Specific methods of tolerancing and worknianship are inherent in optical manufacturing. This section lists and describes those items; however, it lists them for illustration and not as a design guide.
3.2 Apertures
3.2.1 Clear Aperture. The clear aperture i the portion of element surface filled with thc Image forming beam.
3.2.2 Mount Aperture. The mount aperture is the mechanically toicranced portion of the element surface. If not otherwise stated, the mount aperture Is the same as the clear aperture.
3.2.3 CoatIng Aperture. As elements may have to be supported by their edges In a vacuum chamber when being coated (see para. 6.1), the coating aperture needs to be specified. If not otherwise stated, the coating aperture is the same as the mount aperture.
3.2.4 Surface Sags. When desired, the sagitta depth (SAG) from a surface may be dimensioned. Surface sags shall be dimensioned as a reference dimension unless a control tolerance is required.
3.3 Edges
3.3.1 Protective Chamfer. In order to reduce chipping and to eliminate unnecessarily sharp edges, all edges with an included angle less than some value (typically 135 deg.) usually have a small chamfer (typicaLly 0.5 maximum face width at approximate symmetry). A default condition is often applied as a standard drawing note as shown in Fig. 1. The interpretation of the chamfer dimensions is per Fig. 8.
3.3.2 Roof Edges. When the application requires it, anedgeoredgesmaybeleft sharp, i.e., with noprotective chamfer. This shall be called out in the field of the drawing with a maximum chamfer tolerance.
3.3.3 Design Chamfers.All chamfers applied fora design purpose shall be called out on the field of thedrawing as noted in Fig. 2.
3.3.4 Edge Chips. Glass elements can chip at theedges with handling.The size and distribution of chipsshall be specified,typically by a default condition asnoted in Fig.1.
3.3.5 Edge Thickness. Edge thickness shall be di-mensioned as a reference dimension unless a controltolerance is required.
3.4 Spherical Radius Surface
3.4.1 Surface Curvature Tolerance (Mechani-cal). Each spherical radius shall be given a tolerancereflecting the limits, but not the geometric form,ofthe surface.This tolerance shall be given in the sameunits as the radius, except for plano surfaces which aretreated in para. 3.4.2.The radius shall be specifiedconcave or convex.
3.4.2 Surface curvature Tolerance (Power).Plano surfaces shall be toleranced as the difference insagitta between a perfect surface and the spherical sur-face of the smallest radius allowable.The measure-ment shall be given in the number of fringes of light ata specified wavelength. The fringe spacing shall cor-respond to a sagitta difference of one-half of thewavelength of the light per fringe. Plano-plano ele-ments may have their individual surfaces exemptedfrom this tolerance when the element is toleranced perpara.4.3.
3.4.3 lrregularity Tolerance.The nonspherical de-viation of a surface from its specified shape shall begiven in the number of fringes of light at a specifiedwavelength.The fringe spacing shall correspond to asagitta difference of one-half of the wavelength of thelight per fringe. The error is preferably given as an ab-solute limit (peak-to-valley – PV), but may be speci-fied as an average error (RMS) or as a gradient error(wave lengths/cm).