Browsing by Author "Lin, Li-Ju"

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A CMOS Bio-Inspired 2-D Motion Direction Sensor Based on a Direction Computation Method Derived From the Directionally Selective Ganglion Cells in the Retina
(2011-12-01)
Yang, Wen-Chia
;
Lin, Li-Ju
;
Chiueh, Herming
;
Wu, Chung-Yu
;
電子工程學系及電子研究所
A CMOS bio-inspired motion direction sensor structure and its associated computation method are proposed. Both method and structure with excitation-inhibition operation are derived from the directionally selective ganglion cells (DSGCs) in the retina to mimic their functions. Edge-number normalization for direction calculation and pseudo-random tessellation (PRT) structure for pixel layout arrangement are also proposed to enhance the accuracy of the computation. An experimental chip based on the proposed method and structure has been designed, fabricated, and measured. The chip comprised 32 x 32 pixels with a pixel size of 63 x 63 mu m(2) and a fill factor of 12.8%. The total chip size is 3.3 x 4.2 mm(2) and the power consumption is 9.9 mW in the dark and 21 mW at a maximum clock rate of 10 MHz with 3.3-V power supply. The fabricated chip has been measured with different moving patterns, and a computation error of less than 11 degrees has been accomplished. This verifies the correct functions of the proposed motion direction sensor. With the capability of real-time motion detection and processing under low power dissipation, the proposed sensor is feasible for many applications.
A neuromorphic chip that imitates the ON brisk transient ganglion cell set in the retinas of rabbits
(2007-09-01)
Lin, Li-Ju
;
Wu, Chung-Yu
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Roska, Botond
;
Werblin, Frank
;
Balya, David
In this paper, a new CMOS design methodology is proposed to implement CMOS neuromorphic chips which imitate the ON brisk transient ganglion cell (GC) set of rabbits' retinas. The measurement results on the fabricated CMOS neuromorphic chip are consistent with the biological measurement results. Thus, the biological functions of the chip have been successfully verified. It can be used to understand more biological behaviors and visual language of retinas under different input optical images which have not yet been tested in biological experiments. Based on the results, the full GC sets of retina can be designed. Thus, many potential applications of retinal chips on motion sensors, computer vision, retinal prosthesis, and biomedical devices are feasible.
Responses of Rabbit Retinal Ganglion Cells to Subretinal Electrical Stimulation Using a Silicon-Based Microphotodiode Array
(2011-12-01)
Yang, Ya-Ting
;
Lin, Po-Kang
;
Wan, Chen
;
Yang, Wen-Chia
;
Lin, Li-Ju
PURPOSE. With subretinal prostheses, retinal ganglion cells (RGCs) are activated by electrical stimulation of the retinal neural network. The aim of this study was to evaluate the efficacy of silicon-based solar cells in evoking RGC responses by electrically stimulating the photoreceptor side of an isolated retina. METHODS. A light-bleached retina of an adult New Zealand White rabbit was placed with its photoreceptor side down onto a silicon chip that consisted of a 4 x 4 microphotodiode array (MPDA). The stimulating current was elicited by activating the solar cell with a 532-nm laser light source. Responses of the ON and OFF alpha RGCs on electrical stimulation were recorded extracellularly. Recorded RGCs were then injected with 4% N-(2-aminoethyl)-biotinamide hydrochloride to allow cell type identification. RESULTS. Using a design that includes a circumvented ground electrode, the authors successfully evoked spiking responses by the ON and OFF alpha RGCs in an isolated rabbit retina using low light power to activate the MPDA (equivalent to 39 mu C/cm(2)). The charge density-dependent response and the frequency-dependent pair-pulse suppression were characterized. The spike latency of the RGC responses triggered by electrical stimulation was equivalent to the latency of its light response, which supports the hypothesis that the activation is mediated by the retinal neural network. CONCLUSIONS. Reliable activation of RGCs by electrical stimulation in vitro using an MPDA demonstrates the feasibility of developing solar cell-based subretinal prostheses that potentially could be developed into a power-free device able to restore vision. (Invest Ophthalmol Vis Sci. 2011; 52: 9353-9361) DOI: 10.1167/iovs.11-7808