Lens system for projection type television
US4924244A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 14, 1988 |
| Grant date | May 8, 1990 |
| Priority date | — |
| Expiry date | Dec 14, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B13/18
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A lens system for a projection type television, having high focusing performance, a wide field angle and a reduced size. The lens system is composed of seven lenses, which are arranged successively from the screen side. The first lens, which is concave, and the second lens, which is convex, are cemented together to correct chromatic aberration. The third lens is a plastic lens for the correction of spherical aberration and astigmatism, at least one side of which is aspherical. The fourth lens, which is convex, and the fifth lens, which is concave, are cemented together to constitute an achromatic lens. In order to reduce the deterioration of focusing performance caused by changes in temperature, these two lenses are glass lenses and occupy the greater part of the power of the entire system. The sixth lens is an aspherical plastic lens for the correction of astigmatism and frame aberration, and the seventh lens is a plastic lens for the correction of image field curvature, using an aspherical surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.