Differential imaging device
US4881818A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 22, 1986 |
| Grant date | Nov 21, 1989 |
| Priority date | — |
| Expiry date | Apr 22, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/178
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus for forming a differential image of a specimen is disclosed. The two images whose difference is used to generate the differential image are made by illuminating said specimen with polarized light, each image corresponding to illuminating the specimen with light of a different polarization. The intensity of the differential image at each point is related to the difference in intensities observed when the point in question is illuminated with light having the different polarizations divided by the sum of said observed intensities. The present invention includes a light source for illuminating the image with polarized light having a polarization which oscillates between first and second preselected states of polarization, said oscillations occurring at a predetermined frequency. The intensity of light leaving each of a preselected plurality of points on the specimen is measured as a function of time by a light detecting apparatus which generates an electrical signal which is related to the intensity of light at the preselected point in question. This electrical signal is used as input to a lock-in amplifier referenced to said predetermined frequency. The output of this am…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.