A MEASUREMENT SYSTEM FOR THE VISUAL ANALYSIS OF INTEGRATED MICROMECHANICAL DEVICES

Research on micromechanical devices in silicon often requires visual i nspection of the dynamic behaviour. Applications include the analysis of harmonic and parasitic modes in resonant sensors and accelerometers , the lateral eccentric travel in a micromotor and the lateral motion of the comb drive. A highly flexible stroboscopic measurement system i s required for this purpose. Such a research tool has, therefore, been developed. It is especially suited for the visual inspection of a mic romechanical structure under a microscope using light-emitting diodes for generating the sampling light pulses. Digital frequency synthesis has been used to allow easy, stable and independent control of the mot ion frequency, the apparent motion frequency and the aperture time. Th e maximum motion frequency can be set to 400 kHz. The frequency differ ence between the motion frequency, f(m), and the sampling frequency, f (s), results in the apparent motion frequency, f(a), which can be cont rolled in between 0.03 and 3 Hz. The aperture time can also be program med to allow the selection of the optimum illumination as a compromise between image sharpness and luminous intensity. A zoom option is also included to enable the investigation of a part of the periodic motion and a freezing option is available to obtain a fixed image at any wan ted position. The hardware of the stroboscope enables remote computer control of all settings.