Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
1999-07-30
2001-06-05
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S692000, C359S663000
Reexamination Certificate
active
06243212
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to zoom lenses and more particularly, to a telecentric zoom lens having a telecentric forming aperture mechanically intermediate an objective lens and a zoom group.
BACKGROUND OF THE INVENTION
Telecentric optical systems are often employed in a measuring projector. The measuring projector allows a measurement of various values by illuminating the profile of an object to be measured, projecting the profile onto a screen, enlarging the projected image by a projection optical system and comparing the projection with a reference figure on the screen. For such systems, it is preferable that the projection be telecentric. That is, a principal ray passes through the optical system parallel with the optical axis.
However, the need exists for a telecentric zoom lens system having a reduced level of distortion in low tolerance applications. A further need exists for a telecentric zoom lens that has inherent color correction and reduced aberrations. A need also exists for a telecentric zoom lens that provides a constant speed on an image side of the lens. The need also exists for a method and apparatus of constructing such a telecentric zoom lens.
SUMMARY OF THE INVENTION
The present invention provides a telecentric zoom lens having a constant speed on an image side of the lens. Generally, the telecentric zoom lens includes a plurality of optical elements located along an optical axis. The optical elements include an objective lens having an object side and an image side; a zoom group moveable along the optical axis; and a telecentricity forming aperture mechanically intermediate the objective lens and the zoom group and thus optically intermediate the objective lens and the zoom group. Thus, the lens is telecentric in object space. In a further configuration, it is contemplated that the telecentricity forming aperture is a variable aperture. It is also contemplated, the telecentric zoom lens may include a first decollimator optically intermediate the objective lens and the telecentricity forming aperture.
More particularly, the present telecentric lens system includes a plurality of optical elements located on the optical axis, and specifically, a first collimator; a first decollimator, a zoom lens group, a second collimator, second decollimator, and a variable aperture optically intermediate the first decollimator and the zoom group. Further, it is contemplated that the zoom group may include a variator and a compensator.
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Sanson Mark C.
Zinter J. Robert
Amarel Precision Instruments, Inc.
Epps Georgia
Harter Secrest & Emery LLP
Lucas Michael A.
Salai Esq. Stephen B.
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