Circuits to generate the intensity reading and the coordinates of the brightest pixel in each image would be added to imaging photodetector arrays of the active-pixel-sensor (APS) type, according to a proposal. For a given APS, the additional circuitry for locating the brightest pixel would be installed at the periphery of the basic APS circuit. The additional circuitry would thus not degrade the original optical properties or interfere with the original electronic functions of the APS. The APS could be operated in its normal image-readout mode or, optionally, it could be operated with the additional circuitry in the brightest-pixel mode. Potential applications could include star tracking or fast tracking of a moving laser-beam spot in laser communication system.
The brightest-pixel mode would be a winner-take-all mode. The pixel intensities would be read out row by row as in ordinary imaging, but unlike in ordinary imaging, the column intensity values for each row would be processed through a winner-take-all circuit (see figure) that would select the brightest pixel in the row. The intensity reading of the brightest pixel in the row most recently read out would be compared with the previous winner; that is, with the stored intensity reading of the brightest pixel (if any) found in all previous rows. If the greatest intensity reading from the most recent row were greater than the stored intensity reading, then the pixel with this reading would become the new winner, and its intensity reading and coordinates would be stored. Once the intensity readings from all the rows in the APS had been processed in this way, the final winner would be the brightest pixel in the image.
There are several design options for the winner-take-all circuit and the overall mode of operation. In one option, the winner-take-all function would be implemented by a fast current- or voltage-mode analog circuit. In another option a hybrid analog/digital circuit would generate and compare an increasing voltage (ramp voltage waveform) with intensity-reading voltages for all the columns and would latch the address and intensity value for the column that most recently matched the ramp voltage.
In yet another option, each column pixel in the row read out most recently would be compared with the previous winning pixel in that column and would, if appropriate be declared the new winner. Once the last row had been thus read out and processed, the final column winners would be processed through a winner-take-all circuit to obtain the intensity reading and the address of the brightest pixel in the image. The advantage of this option would be speed, in that the somewhat time-consuming winner-take-all operation would be performed only once per frame period.
This work was done by Orly Yadid-Pecht, Eric Fossum, and Carver Mead of Caltech for NASA's Jet Propulsion Laboratory. In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
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Refer to NPO-20212
This Brief includes a Technical Support Package (TSP).
Active-pixel sensors with "winner-take-all" mode
(reference NPO20212) is currently available for download from the TSP library.
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Overview
The document is a technical support package from NASA, detailing advancements in active-pixel sensors (APS) that incorporate a "winner-take-all" (WTA) mode. Authored by Orly Yadid-Pecht, Eric Fossum, and Carver Mead, the report highlights the integration of additional functionalities into APS arrays without compromising their imaging performance.
The WTA mode allows the sensor to identify and report the value and coordinates of the brightest pixel in a scene, enhancing the sensor's ability to process visual information efficiently. This capability is particularly beneficial in applications requiring rapid response to changes in the environment, such as in robotics, autonomous vehicles, and various aerospace applications.
The document outlines the operational principles of the APS with WTA functionality, emphasizing its two modes: the standard APS readout and the WTA mode. The WTA mode operates without the need for full frame readout, which significantly reduces processing time and power consumption. This efficiency is crucial for systems that require real-time data processing.
Figures included in the document illustrate the potential circuit designs for implementing the WTA functionality, showcasing the technical aspects of the system. The report also references previous works and studies that have contributed to the development of this technology, indicating a solid foundation of research and innovation in the field.
Additionally, the document provides a list of references for further reading, including notable publications on neural networks and CMOS active pixel sensor arrays. These references highlight the ongoing research and development efforts in the area of imaging technology and neural network applications.
Overall, the document serves as a comprehensive overview of the advancements in APS technology, particularly focusing on the WTA mode's capabilities and applications. It underscores the potential for improved imaging systems that can operate more efficiently and effectively in various high-demand environments, paving the way for future innovations in sensor technology. The report is a valuable resource for researchers and engineers interested in the intersection of imaging technology and neural network applications.
