Optical: systems and elements – Lens – Anamorphic
Reexamination Certificate
2002-07-23
2003-12-16
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
Anamorphic
C355S025000, C355S052000, C355S075000, C399S204000
Reexamination Certificate
active
06665128
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to copying methods and apparatus and, more particularly, to a method and apparatus for correcting for the distortion that results when copying pages of a book pressed against the document support glass of a copying machine or a document scanner.
BACKGROUND OF THE INVENTION
Ever since the introduction of xerographic photocopiers many users have experienced difficulty in producing clear, non-distorted copies from opened books or volumes that have been pressed upon the flat document glass. This difficulty is mainly due to the fact that conventional photographic copiers are designed to produce copies from documents (generally, single sheets) that lay flat upon the document glass. Textbooks with hard bindings cannot be so oriented.
The crease of a typical textbook generally pyramids upwardly away from the glass, thus causing an upside-down “V-shaped” surface. This is especially so for thick books with hard covers. The crease falls outside of the focal length range for which the copier lens can properly project the image of the book onto the image receiving medium or pre-charged paper. In other words, the crease cannot be focused properly to provide an undistorted image. As a result, the copied crease is often blurred, distorted, and darkened.
In order to make the copies more legible, the operator of the copier is required to forcibly press on the backing of the book as it rests upon the glass. Sometimes this will work. However, many times the binding is too stiff and the crease cannot be projected into the fold. pressing with excessive force is also risky, as it may cause damage to the binding. In some cases, an immoderate amount of force may even break the glass.
DISCUSSION OF THE RELATED ART
In the last twenty-five years numerous apparatus have been invented or proposed to solve this problem. Most of them either do not work, or are impractical. A simple one-piece optical corrective or compensation lens was invented to cure these problems and was described in U.S. Pat. No. 6,313,954, granted to the present inventor on Nov. 6, 2001 for CORRECTIVE LENS FOR COPYING BOOKS.
The optical corrective lens of the '954 patent is basically composed of three parts: a thick curvilinear optical lens in the center, and two very thin extension leaves or arms spread outward from each side of the center lens. The only optically functional part of the lens is the center portion. The main purpose of the extension leaves is to eliminate the glitches in the copies caused by light deflections along the edges of the center lens. The surface contours of the center lens are basically a composition of sections of circular surfaces or circular-like elliptical and parabolic surfaces.
Although the results were not perfect, the lens worked for making duplications from book pages using a commercial xerographic copier. However, it was later revealed that the lens was difficult to manufacture using any of the existing conventional and economical plastic fabrication processes like injection molding, blowing, or continuous extruding. This is due to the extremely thin cross-section of the large extension leaves, which had to be seamlessly fabricated as an integral part of a relatively thick center lens. To improve the lens's manufacturability, the thickness of the extension leaves must be substantially increased. However, the increase of the extension leaves will also increase the profile of the center lens; otherwise, the radius of each constituent section of the top surface of the center lens must be reduced accordingly. Either way, the optical performance of the lens will be substantially worsened.
Several such lenses were built to fine tune this design for thicker (0.050 inch) extension leaves. The quality of a typical xerographic copy of the pages of a thick reference book produced using a typical xerographic copier with any of these trial lenses is obviously much poorer than the similar copy demonstrated in Tai's patent application. There are two darkened strips proximate the centerline. Characters close to these darkened strips are over-magnified and darker than the rest of the characters in the copy. Characters in center areas a little bit farther away from the centerline are still somewhat insufficiently decompressed or under-magnified. Copies with such poor quality are unsightly but may still be considered acceptable for reading purposes. However, its application to text scanning and digitizing is questionable due to more stringent decompression requirements.
After a laborious attempt to improve the performance of the lens, it was clear that the types of surfaces proposed and suggested to construct the lens's most crucial bottom surface are inadequate. Thus, it was found that to make the basic design of this lens work properly, adequate curvature must be found for the constituent sections of the most crucial bottom surface. Without scientific theory or principle available to guide the work, some innovation or breakthrough was needed.
In U.S. Pat. No. 3,609,030, issued to Meyer L. Sugarman et al. on Sep. 28, 1971 for ELECTROSTATIC BOOK COPIER, a tabletop electrostatic book copier is illustrated, having an exposure station on its top. The book to be copied is placed on top of a vertical exposure station and the image of the book is projected directly to the pre-charged paper through a mirror and an optical lens. The image of the book surface is projected using an ordinary optical lens and a mirror found in conventional copiers. The image is projected directly onto a charged paper instead of onto an image-receiving medium. There is no teaching or suggestion of using a distorted lens to refocus the page of the document.
In U.S. Pat. No. 4,585,334, issued to Brian R. Malyon on Apr. 29, 1986 for DOCUMENT COPIERS, a document copier is shown that incorporates a scanner with a forty-five degree slanted scanning window glass mounted at the end of a rectangular housing. The ninety-degree corner, or the so-called wedge, between the window glass and one of the sidewalls points downwardly. The book to be copied is placed on a rack below the scanner window glass. The rack is constructed from two flat frames connected together at a ninety-degree angle, with its opening facing upward. The book to be copied is faced upwardly and rests on the rack with its inside pages opened at a ninety-degree angle. During the copying process, the rack first moves up, bringing the half opened book toward the scanner. It then stops at a predetermined position and keeps a surface of the book page away from the scanner window to prevent damaging the book. In this position, the opposite inside page of the book is under the scanner housing, facing the sidewall. It may or may not touch the slanted sidewall. The scanner then scans the surface of the inside page of the book under its window.
In U.S. Pat. No. 4,763,173, issued to Michael E. Harrigan et al. on Aug. 9, 1988 for IMAGING SYSTEM FOR COMPENSATING FOR IMAGE DISTORTION DUE TO WRINKLED OR CURLED DOCUMENTS, a document imaging system is shown including a positive, aspheric, Fresnel lens. The purpose of the system is to compensate for small, smooth wrinkles and curls of the original document to be copied.
In U.S. Pat. No. 5,071,252, issued to William Howseman, Jr. on Dec. 10, 1991 and Japanese patent No. JP 360,186,360A, issued to Kenich Watabiki, it is suggested that book size bundles of numerous short optical fibers shaped in a nearly flat triangular prism be placed between an opened book and the copier's document glass to optically bring the images of the book pages to the copier's document supporting glass. Neither of these inventors addressed the solutions of other related problems such as the illumination of the book page's surfaces, the solution to the decompression of the text recorded on the book pages, etc. The principles and mechanisms they employed are very different from that used in the invention proposed in this application.
In Japanese patent Number JP 63,254,437A issued to Tatsuya Shimoda on
Choi William
Epps Georgia
Salzman & Levy
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