Telecentric illumination is needed in a wide variety of applications including:
Any precision measurement application where accuracy, repeatability and high throughput are key factors.
The use of a collimated light in combination with a telecentric lens increases the natural depth of field of the telecentric lens itself by approximately +20/30% (this however also depends on other factors such as the lens type, light wavelength and pixel size).
Additionally, thanks to the excellent light coupling, the distance between the object and the light source can be increased where needed without affecting image quality. This happens because the illuminator’s numerical aperture (NA) is lower than the telecentric lens NA.
Therefore, the optical system behaves as if the lens had the same NA as the illuminator in terms of field depth, while maintaining the same image resolution given by the actual telecentric lens NA.
Collimated light is the best choice if you need to inspect objects with curved edges; for this reason, this illumination technique is widely used in measurement systems for shafts, tubes, screws, springs, o-rings and similar samples.