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Telecentric
Region Object
Example 1
As shown in the example of the two cubes, one cube is
positioned so that it is closer to the forefront than the other.
The fixed focal length lens images the objects much like
one would expect two objects of equal size but unequal
distance would appear: the cube in the forefront appears
larger than the cube in the rear. The telecentric lens, on
the other hand, images the setup so that both cubes appear
equal in size and distance.
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TECHNICAL NOTE
Telecentric Lenses
Why use Telecentric Lenses?
Perspective errors, or parallax, are part of everyday human experience and allow the brain to interpret the three dimensional world; we expect closer objects
to appear relatively larger than those farther away. This phenomenon affects conventional imaging systems in that the magnification of the object changes
with its distance from the lens. Telecentric lenses optically correct for such perspective error, so that objects remain the same perceived size independent of
their location in space.
Example 2
As advancements in technology result in the further miniaturization
of electronic components, precision alignment
becomes increasingly more complex. As shown in the example
of a fixed focal length lens imaging the jumper pins
of a typical circuit board at a 45° angle, perspective errors
cause the image of the pins to tilt inward, making accurate
measurements difficult. With the use of a telecentric
lens, though, the pins are imaged accurately, removing the
perspective error causing the inward tilt, and allowing for
precise measurements.
Fixed Focal Length Lens
Fixed Focal Length Lens
Arrangement
Arrangement
Telecentric Lens
Telecentric Lens
Image on Monitor Object
Advantages:
• Lower Cost
• Greater Availability
• Greater Flexibility
Disadvantages:
• Change of Magnification
within Depth of Field
• Perspective Error
Applications:
• Imaging Large Objects
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Non-Telecentric Object
Region
TELECENTRIC LENS
Advantages:
• Constant Magnification within
Depth of Field
• No Perspective Error
Disadvantages:
• Higher Cost
• Larger Lens Diameters
• Larger Weight
Applications:
• Metrology
• CCD Based Measurement
• Microlithography
Image on Monitor Object
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