LIGHT SOURCES AND DETECTORS 



type, hermetically sealed in an all-glass envelope of frosted glass. Dimensions 

 are: diameter, 5-9 mm, length 15 mm. The photosensitive region is 7 mm^ 

 in area. Due to the diffusing properties of the glass envelope the cell is 

 sensitive to radiation reaching it either end-on or from directions around 

 the envelope. The spectral response is shown in Figure 28.52. The cell 

 must be used with an electrical power source of correct polarity, connected 

 to the emittor and collector leads. Figure 28.53 shows the current versus 

 applied voltage characteristics for an average OCP71 at various levels of 

 illumination. As can be seen from Figure 28.54 the characteristics of the 

 OCP71 vary markedly with temperature. 



REFERENCES AND BIBLIOGRAPHY 



^ Walsh, J. W. T. Photometry London; Constable. 1953 



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27(1950) 113 

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37 (1947) 420 

 1^ RoDDA, S. Photoelectric Multipliers London; Macdonald. 1953 

 1^ Preston, J. S. The relative spectral response of the selenium rectifier photocell 

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Fellgett, p. a current stabilized photomultiplier power supply /. sci. Instrum. 

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Holiday, E. R. and Wild, W. An image converter to extend the useful range of 

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 Le Grand, Y. Light, Colour and Vision. London; Chapman & Hall. 1957 

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Preston, J. S. The specification of a spectral correction filter for photometry 

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