Scan optical system, light scan device, and image formation device
US8027074B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 19, 2008 |
| Grant date | Sep 27, 2011 |
| Priority date | — |
| Expiry date | Nov 19, 2028 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2201/04755
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An imaging lens good in mass-productivity, compact, low in manufacturing cost, good in aberration performance is provided by effectively correcting aberrations without greatly varying the variation of the thickness of a curing resin. An imaging device having such an imaging lens and a portable terminal are also provided. A third lens (L3) has a flat surface on the object side, a convex surface near the optical axis on the image side, and a concave aspheric surface around the peripheral portion within the region where a light beam passes. Therefore, it is possible to reduce the other optical aberrations such as distortion and simultaneously to design the imaging lens so that the astigmatism takes on a maximum value at the outermost portion. Hence, the resolutions at low to middle image heights are high. In addition, such a shape does not cause a large variation of the thickness of the third lens (L3) from the region along the axis to the periphery. Therefore, the thickness of the third lens (L3) can be small, and the material cost can be reduced.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.