Image-reading lens
US6147816A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 16, 1999 |
| Grant date | Nov 14, 2000 |
| Priority date | — |
| Expiry date | Sep 16, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B5/1876
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An image-reading lens is formed of a two lens elements of meniscus shape, one with its convex surface on the most object-side of the image-reading lens and one with its convex surface on the most image-side of the image-reading lens. An intermediate lens element of negative refractive power may be optionally provided. A zone plate diffractive optical surface having different depth zones surrounding a vertex is formed on at least one aspherical surface of the two lens elements of meniscus shape so as to correct simltaneously for both lateral color and curvature of field. Another surface, preferably of the same lens element having the zone plate diffractive/aspherical surface, is made aspherical. Of the two lens elements of meniscus shape, one is made of plastic material and the other is made of non-plastic material. The image reading lens provides a high image quality having a small temperature dependence, despite one lens element thereof being made of plastic material. Unlike prior art image-reading lenses employing only two or three lens elements, the image-reading lens of the present invention can be used with a broadband light source.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.