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Sensors 2017, 17(10), 2439; https://doi.org/10.3390/s17102439

Spatiotemporal Pixelization to Increase the Recognition Score of Characters for Retinal Prostheses

1
Interdisciplinary Program of Bioengineering, Seoul National University, Seoul 03080, Korea
2
Department of Biomedical Engineering, College of Medicine, Seoul National University, Seoul 03080, Korea
*
Author to whom correspondence should be addressed.
Received: 26 September 2017 / Revised: 21 October 2017 / Accepted: 22 October 2017 / Published: 24 October 2017
(This article belongs to the Special Issue Biomedical Sensors and Systems 2017)
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Abstract

Most of the retinal prostheses use a head-fixed camera and a video processing unit. Some studies proposed various image processing methods to improve visual perception for patients. However, previous studies only focused on using spatial information. The present study proposes a spatiotemporal pixelization method mimicking fixational eye movements to generate stimulation images for artificial retina arrays by combining spatial and temporal information. Input images were sampled with a resolution that was four times higher than the number of pixel arrays. We subsampled this image and generated four different phosphene images. We then evaluated the recognition scores of characters by sequentially presenting phosphene images with varying pixel array sizes (6 × 6, 8 × 8 and 10 × 10) and stimulus frame rates (10 Hz, 15 Hz, 20 Hz, 30 Hz, and 60 Hz). The proposed method showed the highest recognition score at a stimulus frame rate of approximately 20 Hz. The method also significantly improved the recognition score for complex characters. This method provides a new way to increase practical resolution over restricted spatial resolution by merging the higher resolution image into high-frame time slots. View Full-Text
Keywords: spatiotemporal; subsampling; character recognition; stimulus frame rates; retinal prosthesis spatiotemporal; subsampling; character recognition; stimulus frame rates; retinal prosthesis
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Kim, H.S.; Park, K.S. Spatiotemporal Pixelization to Increase the Recognition Score of Characters for Retinal Prostheses. Sensors 2017, 17, 2439.

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