Optical: systems and elements – Lens – Eyepiece
Reexamination Certificate
2000-04-24
2001-08-28
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Lens
Eyepiece
C359S663000, C359S715000
Reexamination Certificate
active
06282030
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to eyepiece lens assemblies and more specifically, to an eyepiece lens assembly using a plastic aspheric element.
2. Description of Prior Art
It is often required that the eyepiece of a rifle scope provide an extended eye relief distance beyond 30 mm in order to prevent the event of rifle firing “kickback”, forcing the scope backwards, and injuring the user's eye. In addition, for rifle scopes with modern integrated displays and reticules, it is also desirable to provide an oversized exit pupil (over 10 degrees) to accommodate eye wander and make it easier to view the display. In many cases, the modern eyepiece display assemblies may include display sources such as Cathode Ray Tubes (CRT's) or Flat Panels (such as Liquid Crystal Displays), in which case it may be also required that a lightweight eyepiece (under 6 ounces) is used. The eyepiece must also provide its own distortion correction independent of any objective optics (under 5% distortion) to be useable with other devices. For certain types of Flat Panel displays, and for large amounts of dioptric focus adjustment, it is also desirable that the eyepiece provide a near-telecentric focal plane on the display device (at least within +or −{fraction (2/10)} diopter).
Eyepiece design is a thoroughly explored subject to the point where nearly all the best solutions based upon spherical glass optics have already been utilized. Many of these design types have been named after their primary proponents, such as “Kellner”, “Ramsden”, “Berthele”, and “Erfle.” For the case of rifle scopes, it is common for these eyepieces which use spherical, all-glass lenses to provide the extended eye-relief at the expense of exit pupil diameter. The Berthele eyepiece is known to consist of a desired eye exit pupil location, followed by two singlet lenses (usually of the same glass type), and then followed by a cemented glass doublet. Nearly all the common forms of eyepiece design, that cover extended field of 300 or more, will have about 5%-10% distortion which must be corrected for in the rest of the optical system. The general performance for the Berthele eyepiece includes 10× eyepiece magnifying power, field coverage up to 400, distortion about 8%, eye relief at about 25 mm, and an eye pupil diameter of about 5 mm.
While the prior art has reported using optical eyepiece assemblies, none have established a basis for a specific optical assembly that is dedicated to the task of resolving the particular problem at hand. What is needed in this instance is a lightweight optical assembly utilizing plastic lens element to achieve an extended field of view that covers over 30 degrees, provides eye relief greater than 30 mm, minimal distortion and astigmatism.
SUMMARY OF THE INVENTION
It is therefore one object of the invention to provide a lightweight optical assembly utilizing plastic lens element to achieve an extended field of view that covers over 30 degrees, provides eye relief greater than 30 mm, minimal distortion and astigmatism.
According to the invention, there is disclosed an eyepiece lens assembly for providing over 30 degrees extended field of view and a greater than 30 mm eye relief. A collecting lens collects incoming light which is then received by a glass spherical cemented doublet. A plastic singlet with a first and second surface on said optical axis after said glass spherical cemented doublet, said second surface includes a aspheric surface that allows for substantially simultaneous control of field flatness, astigmatism, and distortion. A glass spherical singlet provides final focus and color correction onto a focal plane. The eyepiece lens assembly provides over 30 degrees extended field of view, a greater than 30 mm eye relief, under 5% distortion, a substantially telecentric focal plane, and extremely lightweight.
REFERENCES:
patent: 5638213 (1997-06-01), Ueno
patent: 5726808 (1998-03-01), Suzuki
patent: 6104542 (2000-08-01), Omura
Bashore Alain L.
Holford John E.
Lee Milton W.
Schwartz Jordan M.
The United States of America as represented by the Secretary of
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