Homodyne interferometer for basilar membrane vibration measurements. II. Hardware and techniques.

Selected mechanical features of the design of the homodyne interferometer are described. This interferometer was utilized for basilar membrane vibration measurements. The massive construction necessary to minimize mechanical vibration and noise is described. In order to measure basilar membrane vibrations, it was necessary to increase its reflectivity. Gold crystals were utilized as microscopic mirrors. The technique for fabrication of gold crystals is described. These crystals are small and fragile and required special handling. The method of picking up the crystals and placing them on a preselected location is described. In order to minimize the effect of the involuntary animal movements a reference mirror system is cemented to the skull. The design of the reference mirror system and the method of cementing it to the skull are described.