SINGLE ELEMENT Lenses
Understanding Optical System Basics
FOCUSING AND COLLIMATION (infi nite/fi nite conjugates)
Common Applications: Autocollimators, light detection, laser collimation, and in nity corrected objectives
Single Element: Except in the case of in nity corrected objectives, this solution generally does not require use
of more than one element and the image can be found at the focal point of the lens. An important function of
an in nite/ nite conjugate system is the throughput ( ux per unit radiance or luminance) seen by the detector.
IMAGING (fi nite/fi nite conjugates)
Common Applications: Electronic imaging, relay systems, and image projection
Single Element: The simplest form of a nite/ nite conjugate system is one with a single element in which the
e ective focal length is equal to the focal length of the single lens in the system. Some advantages of this design
are its cost e ectiveness and its simplicity of design.
Two Element: You can combine elements to achieve di erent e ective focal lengths, while increasing the image
performance of the system drastically. The design becomes a bit more complex, though one method of simplifying
it is to place the object at the focal point of the object lens and the image at the focal point of the image lens.
IMAGE REDUCTION OR BEAM EXPANSION (infi nite/infi nite conjugates)
Common Applications: Telescopes and beam expanders
Two Positive Elements: Using two positive elements yields an intermediate image, which is useful for applications
requiring use of a crosshair or other type of reticle. Using two positive elements will result in an inverted image.
One Positive Element and One Negative Element: Most high power laser applications utilize this form for beam
expansion. One advantage of this form is that system length is greatly reduced while an erect image is maintained.
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