FIELD: optical engineering. SUBSTANCE: flexible member is installed between groups of lenses of optical device with space maintained between them. Flexible member is made as device which prevents light from getting into space between groups of lenses. It is essentially spiral-shaped band mounted for stretching, when compresses. When stretched, spiral turns positioned concentrically overlap one another partially. Internal turn of spiral band is coupled to first group of lenses, and external turn is coupled to second group of lenses. Band folded like spiral, when developed and flat, may have of parallel longitudinal edges and par of transverse edges positioned at some angle to longitudinal edge. In second variant optical device has first group of lenses installed in first holder, second group of lenses is positioned on common longitudinal axis with first group of lenses in second holder positioned telescopically in first holder and capable of moving relative to the latter. Device which does not pass light and installed between two groups of lenses is made flexible. It allows flexible compression, when stretched. EFFECT: more effective design. 11 cl, 5 dwg
