Noise reduction in digital fluoroscopy systems
US4367490A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 24, 1981 |
| Grant date | Jan 4, 1983 |
| Priority date | — |
| Expiry date | Apr 24, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/3205
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Apparatus for reducing the effect of x-ray statistical noise and electronic noise in a fluorographic system that displays an x-ray image on a television screen. Analog video signals based on the x-ray image are amplified logarithmically and digitized to yield live pixel signals. Processed pixel signals are averaged in a full image store or memory. Motion is detected by subtracting the stored pixels from the live pixels on a pixel-by-pixel basis in an ALU. The difference resulting from subtraction is used as part of an address to a look-up table (LUT) which contains values equivalent to the difference signals times a noise reduction multiplicative factor, K. The other part of the addresses is the live pixel value. There are several replications of the look-up tables each relating to a particular brightness level range. The one selected is determined by the live signal part of the address which relates to brightness. The K times the difference signals in the ranges are chosen so the amount of noise reduction varies with brightness level as desired for logarithmic signals. The pixels processed as explained above are added in-phase with the stored and averaged pixels and returned to th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.