Fig. 6-1 shows a system with a double lens (f =94 mm). The aperture stop (30
mm) is located at the lens. Object width and image width are both 2 * 94 mm,
resulting in an 1 : 1 projection.
Fig. 6-1: Simple system with double lens
Fig. 6-2 shows a the same system converted to a basic telecentric system as it
is used in metrology. The aperture stop (3 mm) is now located at the focus F`
(94 mm), being the exit pupil. The entrance pupil is in infinity (to the left).
Principal rays are parallel to
the optical axis at the object and go through the focus.
A displacement of the object does (more or less) not affect the image height of
the projection on the screen (most
right), magnification is constant. The object heights are 0, 5, and 10 mm for
the yellow, green and red ray bundles,
Fig. 6-2: Telecentric system with aperture stop of 1 mm
Constant magnification with changing object distance is demonstrated by
animation of object distance (Fig 6-3). The object width varies between 300 and
20 mm in step of 10 mm.
By VOB++ an animation sequence was produced and
recorded as avi file. In order to minimize file size the avi file was converted
to an animated gif.
Fig. 6-3: Animated telecentric system with aperture stop of 1 mm
Fig. 6-2 shows a record of the corresponding spot size for three object
heights. Note the increasing chromatic aberration (false colors) with
increasing object height.
Fig. 6-4: Variation of spot sizes for telecentric system with aperture stop of
Fig. 6-5 and 6-6 show results for aperture stop of 3 mm. For more information
about telecentric systems see
Gottfried Schröder, Technische Optik, 1990, Vogel Buchverlag, Würzburg
Warren J. Smith, Modern Optical Engineering, 2nd Ed., McGraw-Hill, NY
Fig. 6-5: Animated telecentric system with aperture stop of 3 mm
Fig. 6-6: Variation of spot sizes for telecentric system with aperture stop of
Soon (ehem, in the next weeks ;-) we will add synthesized images for this
telecentric system. Suggestions for example systems are welcomed. Please come
The trial version of VOB Pro with Micro Optics plug-in contains hundreds of samples covering nearly any application of optical design programs. Use these samples as starting points for own designs.
See the Feature Table for a summary of features supported in each edition.