Grey-scale imaging using protein based artificial retina
Lasse Lensu*, a, Jussi Parkkinenb, Sinikka Parkkinenb, Timo Jaaskelainenb
aDepartment of Information Processing, Lappeenranta University of Technology,
Lappeenranta FIN-53851 FINLAND
bUniversity of Joensuu
This is an abstract
for a presentation given at the
Ninth
Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is
available on the web.
Bacteriorhodopsin is the light-sensitive protein found in Halobacterium salinarium. It is responsible for the photochemically induced proton gradient across the cellular membrane. The proton gradient is vital for the energy balancing mechanism of the bacterium under anaerobic conditions [1]. Bacteriorhodopsin is a photochromic molecule with photoelectric properties. Due to it's modifiability to a specific application, it has been proposed as a material for a range of information processing applications. These include real-time holography, associative optical memories, optical neural networks, pattern recognition and imaging devices [2, 3, 4, 5].
We have studied bacteriorhodopsin applicability into an artificial retina by immobilizing wild-type bacteriorhodopsin in polyvinylalchohol thin-films through self-assembly. The single-pixel elements have been used to determine properties of the photoelectric signal, and the area, intensity and wavelength dependency of the elements [6, 7]. The prototype matrix shown in Fig. 1 contains 7x5 pixels of size 5x5 mm. The matrix-element uses surface-mounted electronics for signal preprocessing. The signal from the matrix is converted to the digital domain using a microcontroller which also transfers the information to a computer for visualization and postprocessing purposes.
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Figure 1. Bacteriorhodopsin in polyvinylalcohol matrix.
Properties of the bacteriorhodopsin-based artificial retina has been measured and analyzed using a flashlamp and a pulsed Xenon light source. The device is capable of imaging the input under varied illumination. The variation of the self-assembly in the thin-films causes differencies in the light sensitivity of the pixels. These differencies can be compensated by calibrating the electronics pixel by pixel or taking the calibration results into account in the postprocessing software. Color-sensitive version of the matrix based on three variants of bacteriorhodopsin has been prepared, and it will be analyzed in the near future.
In this report we evaluate properties of a bacteriorhodopsin-based matrix detector. We give an electronic design and show capability of bacteriorhodopsin as a light sensitive material in a digital camera.
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*Corresponding Address:
Lasse Lensu
Department of Information Processing, Lappeenranta University of Technology
P.O. Box 20, Lappeenranta FIN-53851 FINLAND
phone: +358 5 621 2841
fax: +358 5 621 2899
email: [email protected]
http://www.lut.fi/~ltl/
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