Depth-from-defocus optical apparatus with invariance to surface reflectance properties
US5912768A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 31, 1996 |
| Grant date | Jun 15, 1999 |
| Priority date | — |
| Expiry date | Dec 31, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/026
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A depth-from-defocus optical apparatus is provided for use with a depth-from-defocus three-dimensional imaging system for obtaining a depth image of an object. The invention facilitates the formation of depth images of objects exhibiting specular reflection, either alone or in combination with diffuse reflection, thereby allowing the application of depth-from-defocus three-dimensional imaging to objects such as microelectronic packages. The optical apparatus of the invention generally includes an illumination source, a projection lens assembly for converging rays of incident light towards an object, and a viewing lens assembly for converging rays of reflected light towards an image plane. Importantly, the viewing lens assembly is of the same working f-number as the projection lens assembly. In preferred embodiments, both the projection lens assembly and the viewing lens assembly exhibit object-side telecentricity so as to substantially eliminate vignetting of off-axis specular object features, and consequently, substantially eliminate specular false depth. The invention can also include an uncrossed polarizer/analyzer pair to balance the dynamic range of specular reflections with t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.