MICROSCOPE

PURPOSE:To obtain an invariably constant visual field light quantity and to minimize a long-period drift quantity by providing a photoelectric transducer which detects a light reflected by a body to be observed or transmitted light on the optical path of an observation optical system or its prolonged optical path and adjusting the quantity of light of a lighting optical system with the output of the photoelectric transducer. CONSTITUTION:A reflected light illumination optical system 16 irradiates the body 15 to be observed with illumination light from above through a lamp 21 for reflected light, a condenser lens 20, a half-mirror 19, and an objective 14. This illumination light is reflected by the body 15 to be observed and reaches the eye of an observer through an ocular 11 and part of it is transmitted through an optical path split prism 12 to reach the photoelectric transducer 30. A tracking circuit 33 compares the photoelectric output which is amplified by an amplifier 31 with a set value 32 and controls a lamp dimming circuit 34 so that the photoelectric output of the photoelectric transducer 30 becomes equal to the set value 32. Consequently, the constant visual field light quantity can be secured with high trackability.