An adjustable optical component, for example an optical slit having adjustable slit width, comprises a movable member for providing an optical function, for example a slit and/or a shutter, and resilient suspension elements for connecting the movable member to a frame. The essential parts of the movable member, of the resilient suspension elements and of the frame consist of microstructures which are made of a common base material. Preferably, these parts are manufactured from a silicon chip by a micromechanical technique comprising, for example, anisotropic etching. In the case of an optical slit, the movable member comprises a plurality of openings of different widths which constitute a step slit. In order to adjust different slit widths, the member is moved along a line parallel to the center line of the step slit, with the force for moving the member being applied at an opening. When the member is moved by an external force, the resilient silicon beams are bending and the bars are moving. The movable member has an integrated shutter position. A high reproducibility of the adjustment of the center positions of the openings constituting the step slit during repeated movement of the member is ensured.