Pinhole Camera Targets New Unmanned Aerial Vehicles
Daniel S. Burgess
A research fellow at the University of Sydney in Australia has developed a field-widened pinhole camera for the guidance and stabilization of miniature unmanned aerial vehicles with wingspans of tens of centimeters.
A compact pinhole camera for the guidance and stabilization of miniature unmanned aerial vehicles has a field of view of approximately 165°. It produces data that indicate translational and rotational motion in three dimensions in low-light conditions. Courtesy of Christel-Loic Tisse, University of Sydney.
Christel-Loic Tisse adopted a top-down design approach in the work, allowing a consideration of egomotion data processing methodology to determine how data should be acquired. Judging that the best approach would be to employ an imaging system with a single viewpoint and a wide field of view, he rejected solutions that could be expected to remain outside the weight limits of a miniature drone or that could not produce the nearly hemispherical images that yield indicators of motion even when confronted with high noise levels.
He thus settled on a pinhole camera design. Presuming that the camera’s sensor would be a CMOS device because it would demand less power and offer more opportunity for integration with signal processing electronics than a CCD imager, he determined that the best results would be had from the addition of a planoconvex lens to the far side of the pinhole relative to the sensor and a hemispherical lens to the near side.
Tisse constructed a prototype using a 510 × 492-pixel CMOS sensor from OmniVision Technologies Inc. of Sunnyvale, Calif., lenses of LaSFN and BK 7 glass, and a 500-µm-wide pinhole in blackened stainless steel. The mass of the optical system (pinhole and lenses) was approximately 0.2 g. The resulting camera offered a field of view of approximately 165° and produced data that indicated translational and rotational motion in three dimensions in low-light conditions.
Although the prototype displayed a slow response that would require the addition of corrective mechanisms, Tisse considers the results promising and suggests that the performance of control systems incorporating pinhole cameras be investigated.
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