Television camera

[edit] Apollo 15

To save size, weight and power consumption, the TV camera on board the CM has only one imaging tube, rather than the three or four found in contemporary colour cameras. The red, green and blue imaging is achieved by spinning a filter wheel at 600 revs per minute in front of the tube face. The wheel has two sets of three filters for the three primary colours, red, green and blue. At 10 revs per second, it filters the image in one colour for the duration of a TV field, 1/60th of a second. Thus, the resulting black and white video signal emerging from the camera actually consists of fields which sequentially represent red, green and blue. In black and white, the image looks rather flickery, especially in areas of strong colour. Back on Earth, a converter reconstructs a standard NTSC colour signal by combining the images from three consecutive fields. This scheme works well enough for still or slow moving images. However, moving highlights in the scene break up into separate coloured images. (ap15fj)