Retinal Prosthesis Dissertation - Student Home Pages

Pulse generation is not part of the receiver chip design per se rather it’s the driver
(circuitry driving the electrodes) post processing interface, typically mounted as part
of the retinal implant, typically atop the electrode array. The negative going phase of
the pulse lasts for one quarter of the biphasic pulse time in this case 1ms and the
positive going phase of the pulse again lasts for one quarter of the biphasic pulse
time i.e. 1ms. In this case the biphasic pulse time matches with the 4ms incurred by
the biological action potential shown earlier in this chapter.
Spike plus off time equals the time for the biological action potential; represented by
the biphasic pulse, plus the interspike interval which in the case of maximum pulsing
i.e. full hue intensity, will be 20ms. NB the spike time will never alter only the off
time will vary according to the shade of colour (hue intensity) between 16ms at full
pulsing and 196ms at minimum pulsing.
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