Solid-state optical scanning system for remote measurements in biomechanical systems

Abstract

A remote optical sensing system, employing a self-scanning photodiode array, is described, and its operation is demonstrated for measurements of rapid dimensional changes in contracting smooth muscle preparations. The single-line sensor array, a commercially available charge-coupled device integrated circuit, with 256 elements at 25-microns intervals, is mounted in the image plane of an optical system focused on a backlit test object. The amplitude profile of each scan is proportional to the illumination reaching the individual sensory elements. Auxilliary circuitry generates a raster of successive scan lines on the face of a storage oscilloscope. Spatial and temporal information about the target and its motions may be derived from the displayed raster scan. Performance is illustrated using an artificial target and a muscle fiber bearing opaque markers. Successive lines may be scanned in as briefly as 5 ms (at 10-ms intervals) or in as long as 50 ms (at 1-s intervals). Each raster may contain up to 256 lines, although not all of the lines need to be displayed. The spatial resolution is determined by the photodiode spacing in the sensory array and by the magnitude of the optical system in use; as described here, the resolution is on the order of 0.2 mm for a 20-mm scan length.