1. Field of the Invention
The present invention relates to a micromechanical component and a method for operating such a micromechanical component.
2. Description of Related Art
A micromechanical component for an optical beam deflection often has a mirror adjustable about at least one axis of rotation. For example, the mirror may be gimballed opposite an immovable frame, so that the mirror is adjustable about two axes of rotation oriented perpendicularly to one another. A micromechanical component having a mirror adjustable about two axes of rotation is used, for example, for scanning a surface with a light beam in a projector or in a scanner. It is advantageous here if information about an instantaneous position of the mirror with respect to the frame about the two axes of rotation is ascertainable during operation of the projector or the scanner. This makes it possible to verify whether the instantaneous position of the mirror corresponds to a desired mirror position.
A first possibility known from the related art for ascertaining an instantaneous position of the mirror with respect to the frame is based on a placement of piezoresistive elements on the torsion springs by which the mirror is connected to the frame. The piezoresistive elements may be designed as Wheatstone bridges, for example. When the torsion springs are rotated, mechanical stresses occur, causing a change in the electrical resistances of the piezoresistive elements. The instantaneous position of the mirror with respect to the frame is settable by analyzing the electrical resistances of the piezoresistive elements.
However, to ascertain the electrical resistances of the piezoresistive elements, electrical feeder lines connecting the piezoresistive elements to an evaluation unit are guided over the torsion springs (or on the gimbal ring). A piezoresistive element designed as a Wheatstone bridge requires four such electrical feeder lines, for example. The electrical feeder lines must be designed to be relatively narrow for them to be able to be guided over the torsion springs. As a power supply, relatively high currents must be fed to the piezoresistive elements. However, the useful electrical signals generated on the piezoresistive elements are very weak and susceptible to interference.
The manufacture, placement and shielding of the electrical feeder lines are therefore comparatively difficult. In addition, the electrical feeder lines are often subject to mechanical destruction due to the spring deformation. Furthermore, the electrical feeder lines affect the flexural rigidity and torsional rigidity of the torsion springs, which has a negative effect on the adjustability of the mirror.
In a second option which is known from the related art for ascertaining an instantaneous position of the mirror with respect to the frame, at least one first electrode is fixedly situated on a movable element, for example, the mirror or a torsion spring. Depending on an adjusting movement of the movable element, a capacitance between the first electrode and a second electrode situated fixedly with respect to the frame changes. The signal used for the analysis with respect to the capacitance between the two electrodes is, however, comparatively low and is susceptible to interference accordingly. The position of the mirror determined on the basis of the signal is thus often inaccurate. Furthermore, this traditional option for ascertaining the instantaneous position of the mirror also requires an electrical feeder line guided over a torsion spring for contacting the first electrode. The disadvantages described in the paragraph above therefore also occur when ascertaining the instantaneous position of the mirror by analyzing the capacitance between the two electrodes.