Quick Guide to Precision Measuring Instruments

46/76

PG44Telecentric Optical SystemAn optical system based on the principle that the principal ray is aligned parallel to the optical axis by placing a lens stop on the focal point on the image side. Its functional feature is that the image will not vary in size though the image blurs as the object is shifted along the optical axis.For measuring projectors and measuring microscopes, an identical effect is obtained by placing a lamp lament at the focal point of a condenser lens instead of a lens stop so that the object is illuminated with parallel beams. (See the gure below.)Optical axisProjection lensFocal point on the image sideTelecentric contour illuminationCondenser lensWorkpieceProjectionscreen surfacePrincipal rayObject surfaceLight source(lamp)Optical axisProjection lensFocal point on the image sideTelecentric contour illuminationCondenser lensWorkpieceProjectionscreen surfacePrincipal rayObject surfaceLight source(lamp)Prole Projectors