| The television camera is rather like the human eye．Both the eye and the camera have a lens(镜头)，and both produce a picture on a screen．In each case the picture is made up of millions of spots of light． Let us see how the eye works．When we look at an object a person a house or whatever it may be we do not see all the details of the object in one piece．We imagine what we do but this is not the case．In fact the eye builds up the picture for us in our brain which controls our sight in millions of separate parts and although we do not realize it all these details are seen separately． This is what happens when we look at something．Beams of light of different degrees of intensity(强度) reflected from all parts of the object strike the lens of the eye．The lens then gathers together the spots of light from these beams and focuses them on to a light sensitive plate the retina(视网膜)at the back of the eyeball．In this way an image of the object is produced on the retina in the form of a pattern of lights． The retina contains millions of minute light sensitive elements each of which is separately connected to the brain by a tiny fibre in the optic(视力的)nerve．These nerve fibres working independently pick out minute details from the image on the retina and turn the small spots of light into nerve impulses(冲击)of different strengths．They then transmit these impulses to the brain．They do this all at the same time． All the details of the image are fed to the brain and as we have taught our brain to add them together correctly we see a clear picture of the object as a whole． Television which means vision at a distance operates on a similar principle．A television picture is built up in thousands of separate parts． Beams of light reflected from the subject being televised strike the lens of the television camera which corresponds to(相当于)the lens of the eye．The camera lens gathers together the spot of light from these beams and focuses an image of the subject on to a plate the surface of which is coated with millions of photo electric elements sensitive to light． |