scale/material used, while somewhat reducing its measurement accuracy. Screen size As for selection of screen size, one should carefully consider whether the entire part must be imaged on the screen. If the inspection can readily be done at a modest scale, there is no need for a larger screen. Projector manufacturers offer multiple screen sizes to meet various needs. Magnification The projection lens magnification is fixed. Different views of measured pieces often require different magnifications. However, the usual projector factory configuration is with a single lens, so according to needs, additional lenses may be purchased and used. Work table and accessories The work table is used to place and hold the measured piece. Its own volume, X, Y travel and carrying capacity are critical. Meanwhile, for the convenience of holding the workpiece, a precision rotary table, a V-block part holder and other accessories are generally added. Also, the projector must have a flexible and stable focusing mechanism and large working distance (the top surface of the workpiece relative to the lens pitch). The user selects appropriate data processing modes: without exception, all modern optical measuring projectors on market have been digitized. We will therefore also consider relevant data-processing capabilities. See also Shadowgraph References Bibliography Industrial equipment Metrology Metalworking measuring instruments