Telecentric Lenses

Related FAQs

• What is a telecentric lens?

  Telecentricity is a special case where the principal optical rays are parallel to the lens's optical axis. In an object-side telecentric, the lens on the object side (as opposed to the camera side) principal rays are parallel to the optical axis, this eliminates perspective errors . An object is always displayed the same size at different working distances, i.e. the magnification does not change with varying working distances. Telecentric lenses are generally used where distance and location of the test object can affect the measurement accuracy and are ideal for precision measurement applications. Due to the parallel beam path telecentric lenses can be used to image critical and awkward optical surfaces and material properties for example high gloss, optically active materials, variable edge shapes, glass etc.

• What is a entocentric or standard lens?

  Entocentric refers to the 'normal' perspective, i.e. the optical properties of such a lens corresponds to how the human eye works. The farther away an object is, the smaller it appears, this phenomenon arises because of the way the lens bends the light beams to reach the imaging sensor.
  With these lenses, the magnification changes with varying working distances therefore entocentric or standard lenses are only suitable for non-measurement applications. Often with the lower priced lenses other types of distortion can also be found, especially towards the edges of the lens
  These lenses can be sucessfully applied to color, presence, completeness, surface inspections, as well as characters, code and feature recognition.

• What do you mean by “working distance”?

  Working distance or WD is the distance between the test object [your component] and the front of the lens that it imaging the object. It is very important for determining the relative positions of the object and the lens/camera. Extra optical components, for example filters, protection glass, Prisms and mechanical accessories must be included in the calculation (these shorten the optical path). The working distance is normally given in mm.