ABSTRACT
A telecentric optical system is one that has its exit pupil at infinity (the chief ray emerges parallel to the optical axis). An example of use is in a contour projector where one wants to accurately measure screw threads. Because the chief ray is parallel to the optical axis, measurements are the same regardless of the image location. The object can be placed anywhere within its depth of field. Systems have also been developed that are telecentric in both object and image spaces. Another use is in liquid crystal display (LCD) and digital light projector (DLP) projection lenses where, due to the dichroic coatings, a telecentric system is required (see the lenses in Figure 22.7 and Figure 22.8 in the previous section).
