Optical: systems and elements – Lens – With multipart element
Reexamination Certificate
1996-12-31
2001-10-30
Sugarman, Scott J. (Department: 2873)
Optical: systems and elements
Lens
With multipart element
Reexamination Certificate
active
06310733
ABSTRACT:
SUMMARY OF THE INVENTION
The improvement to optical elements having rises and faces (ones that are stepped, e.g. a Fresnel lens) disclosed herein employs a light-absorptive element adjacent the vertical rises so that the amount of light passing through or reflected from the rises is minimized.
Thus the present invention provides an improved optical element having rise portions and face portions, wherein light transmitting through or reflected from the rise portions is substantially prevented from being seen by an observer viewing an image formed by light passing through the annular lens. More particularly, the rise portions are coated with an opaque light-absorbent material.
The improved optical element may be a refractive optical element, in which event the rise portions are substantially opaque and the face portions are substantially transparent. It may also have an anti-reflective coating. It may, for example, be a Fresnel lens or a Fresnel semi-lens or a lenserF lens, as disclosed hereinbelow.
The improved optical element may be a reflective element, such as an annular mirror.
Various methods of making the improved optical element are part of the present invention. Such methods comprise the steps of producing an optical element having rise portions and face portions, and imparting a light-absorbent coating to the rise portions. The optical element may have a series of annular grooves, or the grooves may be linear. The element may be refractive, in which event an antireflective coating may also be applied, or the element may be reflective.
The light-absorbent coating may be imparted to the rises by applying light-absorbing material to the element and selectively cleaning it so as to leave a coat of light-absorbent material adhering to the rise portions but not to the face portions. Adherence may be enhanced by roughening the rise portions in advance, such as by scratching, scoring, or abrading
Positive or negative photoresist may be used in the process in various ways. A coating of negative photoresist may be applied to the optical element so as to coat all faces and rises, then illuminating the photoresist so that the rises are not illuminated, so that exposed photoresist is only on the faces. Alternatively, positive resist can be used, and only the rises are illuminated. In either case, the element is then developed to remove the photoresist from the rises, and opaque material that is capable of adhering to the rises is then applied to the element. The photoresist is then removed from the faces by more developing to dissolve away remaining resist together with any of the opaque material coated on it.
Alternatively, the photoresist itself may be dark colored or dyed and left on the rises. Negative photoresist may be made to coat the rises selectively by exposing the rises but not the faces to light and then developing the optical element to remove unexposed photoresist. Alternatively, dark positive photoresist may be made to coat the rises selectively by exposing the faces but not the rises to light and then developing the optical element to remove exposed photoresist.
Other means for reducing flare and the like with stepped optical elements that are disclosed herein are also within the present invention.
REFERENCES:
patent: 3647303 (1972-03-01), Kramer, Jr.
patent: 3784282 (1974-01-01), Yamazaki et al.
patent: 4670095 (1987-06-01), Negishi
patent: 5543870 (1996-08-01), Blanchard
Elman Gerry J.
Elman & Associates
Sugarman Scott J.
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