Bi-telecentric lenses are the most accurate type of telecentric lenses because their field of view is completely unaffected by changes caused by changes in object position or sensor position, nor does it operate any cos4θ attenuation. The diagram below shows the comparison of three different lenses: fixed focal length lens, object space telecentric lens, and double-telecentric lens. The X-axis represents the change in working distance (mm) from the nominal value, and the Y-axis represents the dimensional error percentage from the actual value.

As you can see, the bi -telecentric lens is the most accurate lens in the group, with a working distance offset of 4mm and an error of less than 0.2% during this period. Bi-telecentric lenses should be used in applications that require the highest accuracy and precision.

Non Telecentric Lens

The chief ray originated from optical axis has a angle θ with optical axis. For objects at different WD from the lens, the lens will have either smaller or larger mag.