System and method for detecting and indicating proper focal distance in a fixed lens camera
US5666569A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 25, 1994 |
| Grant date | Sep 9, 1997 |
| Priority date | — |
| Expiry date | Aug 25, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B7/365
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A fixed lens camera comprises a fixed focus lens, an infrared filter, and an optical low pass filter, all disposed in succession within a housing, coaxial with an optical axis. Light from a target passes through an aperture in the housing, and then through the lenses and filters. An image sensor receives the filtered light, and outputs a two-dimensional array signal of corresponding voltages proportional to the incident light striking each sensing element. The voltage signal from the image sensor is filtered using a high pass filter, and the high frequency components of the signal are measured to determine the relative focus of the light from the target. The signal measurement is displayed on a bar LCD to enable focusing of the lens by moving the camera along the optical axis while observing the LCD output.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.