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Ambient Light Rejection Integrated Circuit for Autonomous Adaptation on a Sub-Retinal Prosthetic System

Authors
Kang, HosungChoi, HojongKim, Jungsuk
Issue Date
Aug-2021
Publisher
MDPI
Keywords
Active pixel sensor; Ambient light; Image sensor; Retina implant
Citation
Sensors, v.21, no.16
Journal Title
Sensors
Volume
21
Number
16
URI
https://scholarworks.bwise.kr/gachon/handle/2020.sw.gachon/82066
DOI
10.3390/s21165638
ISSN
1424-8220
Abstract
This paper introduces an ambient light rejection (ALR) circuit for the autonomous adaptation of a subretinal implant system. The sub-retinal implants, located beneath a bipolar cell layer, are known to have a significant advantage in spatial resolution by integrating more than a thousand pixels, compared to epi-retinal implants. However, challenges remain regarding current dispersion in high-density retinal implants, and ambient light induces pixel saturation. Thus, the technical issues of ambient light associated with a conventional image processing technique, which lead to high power consumption and area occupation, are still unresolved. Thus, it is necessary to develop a novel image-processing unit to handle ambient light, considering constraints related to power and area. In this paper, we present an ALR circuit as an image-processing unit for sub-retinal implants. We first introduced an ALR algorithm to reduce the ambient light in conventional retinal implants; next, we implemented the ALR algorithm as an application-specific integrated chip (ASIC). The ALR circuit was fabricated using a standard 0.35-μm CMOS process along with an image-sensor-based stimulator, a sensor pixel, and digital blocks. As experimental results, the ALR circuit occu-pies an area of 190 µm2, consumes a power of 3.2 mW and shows a maximum response time of 1.6 sec at a light intensity of 20,000 lux. The proposed ALR circuit also has a pixel loss rate of 0.3%. The experimental results show that the ALR circuit leads to a sensor pixel (SP) being autonomously adjusted, depending on the light intensity. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
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Choi, Hojong
반도체대학 (반도체·전자공학부)
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