A MEASUREMENT SYSTEM FOR THE VISUAL ANALYSIS OF INTEGRATED MICROMECHANICAL DEVICES

Research on micromechanical devices in silicon often requires visual inspection 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 is required for this purpose. Such a research tool has, therefore, been developed. It is especially suited for the visual inspection of a micromechanical 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 motion frequency, the apparent motion frequency and the aperture time. The maximum motion frequency can be set to 400 kHz. The frequency difference between the motion frequency, f(m), and the sampling frequency, f(s), results in the apparent motion frequency, f(a), which can be controlled in between 0.03 and 3 Hz. The aperture time can also be programmed 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 wanted position. The hardware of the stroboscope enables remote computer control of all settings.