RESUMEN
An increase in power and therefore in luminous flux of medical illuminators with light guides proves the necessity of illuminance control of the studied object. Because of dazzling effect of powerful light sources it is impossible to observe simultaneously large and small details of oral cavity. Provision with light and illumination by a rapid change of illuminance levels in their different succession is the solution of the problem. Principal requirements to the ways of illuminance control of luminous flux regulators on the exit of light guides are: simplicity, smoothness of control, small losses, flat gain over the frequency range, drive and absence of side effects (to the luminous flux too). The regulator permits to increase considerably the productivity of labour and the quality of diagnosis.