Problems of television cameras and camera tubes

Questions of sensitivity and signal-to-noise ratio are discussed. While the results are of general application, the subject is developed with particular reference to the image orthicon type of camera tube. The latter, in its standard form (the 3-in image orthicon), has a considerable sensitivity advantage compared with other types of tube. For some purposes, particularly studio use, it is desirable to exchange some of this sensitivity for other properties, such as signal/noise ratio. In this case the balance of properties can be improved by increase in target area, which leads to the large (4+¿-in) image orthicon. A description is given of a new camera designed around the large image orthicon with maximum exploitation of the properties of the latter. Three approaches to the colour television camera problem are described, and the repercussion of colour on sensitivity and signal/noise ratio is discussed.