Objective lens for optical pick-up
Number of patents in Portfolio can not be more than 2000
United States of America Patent
Stats
-
Sep 12, 2000
Grant Date -
N/A
app pub date -
Jun 29, 1999
filing date -
Jun 26, 1998
priority date (Note) -
In Force
status (Latency Note)
Importance
Abstract
An objective lens includes a refractive lens having a positive refractive power, and a diffractive lens structure having a plurality of concentric ring-shaped steps that are formed on at least one lens surface of the refractive lens. The objective lens is a biconvex plastic lens having first and second aspherical surfaces. A diffractive lens structure is formed on the first surface of the objective lens. The diffractive lens structure is similar to a Fresnel lens, it is formed as many concentric rings each of which has a wedge sectional shape. The boundary between the adjacent rings is formed as a step giving a predetermined optical path difference. The diffractive lens structure has wavelength dependence such that at least two light beams having different wavelength with an identical diffractive order form appropriate wavefronts for at least two kinds of optical discs respectively provided with cover layers having different thickness.
First Claim
Other Claims data not available
Family
International Classification(s)
Cited Art Landscape
Patent Citation Ranking
- 80 Citation Count
- G02B Class
- 97.61 % this patent is cited more than
- 25 Age