Natural compound-eyes consist of a large number of ommatidia that are arranged on curved surfaces and thus are able to detect signals from a wide field of view. We present an integrated artificial compound-eye sensor system with enhanced field of view of 180° × 60° due to the introduction of curvature. The system bases on an array of adaptive logarithmic wide-dynamic-range photoreceptors for optical flow detection and compound-eye optics for increasing sensitivity and expanding the field of view. Its assembling is mainly done in planar geometry on a flexible printed circuit board. The separation into smaller ommatidia blocks by dicing enables flexibility and finally allows for mounting on curved surfaces. The signal processing electronics of the presented system is placed together with further sensors into the concavity of the photoreceptor array, and facilitates optical flow computation for navigation purposes.
In the framework of our biologically inspired robotics approach, we describe a visually-guided demonstration model aircraft, the attitude of which is stabilized in yaw by means of a novel, non-emissive optical sensor having a small visual field. This aircraft incorporates a miniature scanning sensor consisting of tow photoreceptors with adjacent visual axes, driving a Local Motion Detector (LMD), which are made to perform a low-amplitude scanning at a varying angular speed. Under these conditions, the signal output from the motion detector varies gradually with the angular position of a contrasting object placed in its visual field, actually making the complete system a non- emissive optical 'position sensor'. Its output, remarkably, (i) varies quasi-linearly with the angular position of the contrasting object, and (ii) remains largely invariant with response to the distance to the object, and its degree of contrast. We built a miniature, twin-engine, twin-propeller aircraft equipped with this visual position sensor. After incorporating the sensor into a visuomotor feedback loop enhanced by an inertial sensor, we established that the 'sighted aircraft' can fixate and track a dark edge placed in its visual field, thus opening the way for the development of visually-guided system for controlling the attitude of micro-air vehicles, of the kind observed in insects such as hover-flies.