The e.m.i. four-tube colour television camera

Abstract

The first part of the paper describes the background to the decision taken on the number and type of pickup tubes used in the camera. The argument for the use of a separate luminance tube is presented together with an explanation of the delta-L system for providing accurate colorimetry in a four-tube camera.Part 2 covers the considerations leading to the particular optical and mechanical arrangement adopted and the advantages which result from this arrangement. The key part of the design is the use of a pre-aligned beam splitter system, and the way in which this was achieved is described.Part 3 deals with the design of the more important circuits used. General requirements such as stability, serviceability and ease of adjustment are discussed first. This is followed by a description of the scanning circuits and the monitoring arrangements used for adjusting registration. The video circuits are then discussed in detail with particular reference to such problems as the tracking of the master gain and gamma correction controls applied to the four signals. Luminance correction is applied by the delta-L system and its practical realization in a form which gives three output signals suitable for direct monitoring and encoding is described. The final section deals with power supplies and in particular the stabilizer module which is used for all the low-voltage supplies including the camera supplies which are required to work through 600 m of cable by remote sensing.