| Autor: |
Hill, M. J., Pownall, D. R. |
| Zdroj: |
The British Journal of Radiology; August 1966, Vol. 39 Issue: 464 p633-635, 3p |
| Abstrakt: |
Most of the C.E.G.B. film laboratories which have been approved by the Ministry of Power use the Baldwin radiological densitometer for the determination of the densities of personnel monitoring films. Although the legal requirements for the wearing of film badges are strict and the design of film and holder has to be approved together with their manufacturers, there are no minimum specifications laid down for the performance of the density measuring equipment.The need to measure films whose densities were higher than those capable of being measured with the Baldwin instrument could not be disregarded. This led to a study of the instrument with a view to extending its range. Some experimental work was carried out, described later in this article, and forms the basis of this report.The manufacturer's handbook on the radiological densitometer states that the British Standard diffuse density (1947) is measured by the instrument. The definition of diffuse density states that for the geometrical conditions the “incident radiant flux shall be normal to the plane of the sample and all of the transmitted radiant flux shall be collected and equally evaluated: or (in accordance with the optical reversibility principle) the incident radiant flux shall be perfectly diffuse and only the normally transmitted component shall be collected and evaluated”.An examination of the system used in the Baldwin instrument shows that the incident light is not normal to the film under measurement but comes to a focus at a position about 1 cm beyond the film. |
| Databáze: |
Supplemental Index |
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