A bio-inspired analog silicon retina with Michaelis-Menten auto-adaptive pixels sensitive to small and large changes in light

Abstract

In this paper, we present: (i) a novel analog silicon retina featuring auto-adaptive pixels that obey the Michaelis-Menten law, i.e. V=V(m) I(n)/I(n)+σ(n); (ii) a method of characterizing silicon retinas, which makes it possible to accurately assess the pixels' response to transient luminous changes in a ±3-decade range, as well as changes in the initial steady-state intensity in a 7-decade range. The novel pixel, called M(2)APix, which stands for Michaelis-Menten Auto-Adaptive Pixel, can auto-adapt in a 7-decade range and responds appropriately to step changes up to ±3 decades in size without causing any saturation of the Very Large Scale Integration (VLSI) transistors. Thanks to the intrinsic properties of the Michaelis-Menten equation, the pixel output always remains within a constant limited voltage range. The range of the Analog to Digital Converter (ADC) was therefore adjusted so as to obtain a Least Significant Bit (LSB) voltage of 2.35mV and an effective resolution of about 9 bits. The results presented here show that the M(2)APix produced a quasi-linear contrast response once it had adapted to the average luminosity. Differently to what occurs in its biological counterparts, neither the sensitivity to changes in light nor the contrast response of the M(2)APix depend on the mean luminosity (i.e. the ambient lighting conditions). Lastly, a full comparison between the M(2)APix and the Delbrück auto-adaptive pixel is provided.

Taking Inspiration from Flying Insects to Navigate inside Buildings

“…Phototransduction: a logarithmic amplifier was originally used (five decades of lighting) [60,61], a linear amplifier was used (three decades of lighting) [64], or more recently autoadaptive photodetectors were designed as artificial retinas [58,65], which consisted of a logarithmic amplifier associated with a high-gain negative feedback loop (seven decades of lighting). Results with auto-adaptive pixels are reminiscent of analogous experiments carried out on single vertebrate [66] and invertebrate [67] photodetectors.…”

“…This functional prototype with its 630 pixels (forming 630 artificial ommatidia) offered a wide view field (180 Â 60 ) over a significant range of lighting conditions and weights~2 g [58] (see twin CurvACE version in Figure 8a). APix stands for Michaelis-Menten auto-adaptive pixel [65]) can auto-adapt in a 7 decade of lighting range and responds appropriately to step changes up to AE3 decades [82]. The pixels do not saturate thanks to the normalization process performed by the very large-scale integration (VLSI) transistors [65]; this is due to the intrinsic properties of the Michaelis-Menten equation [66].…”

“…APix stands for Michaelis-Menten auto-adaptive pixel [65]) can auto-adapt in a 7 decade of lighting range and responds appropriately to step changes up to AE3 decades [82]. The pixels do not saturate thanks to the normalization process performed by the very large-scale integration (VLSI) transistors [65]; this is due to the intrinsic properties of the Michaelis-Menten equation [66]. A comparison of the characteristics of auto-adaptive Michaelis-Menten and Delbrück pixels [83] under identical lighting conditions (i.e., integrated in the same retina) demonstrated better performance of the Michaelis-Menten pixels in terms of dynamic sensitivity and minimum contrast detection [65].…”

A quasi-panoramic bio-inspired eye for flying parallel to walls

“…1). Two 10-gram servo motors mounted in serial stabilize the 8 OF sensors (based on M 2 APix sensor [9], [14]) in pitch and roll ( Fig. 1) to avoid any perturbation coming from attitude disturbances.…”

“…In the present paper, a quasi-panoramic bio-inspired eye built with 8 custom-made OF sensors (based on M 2 APix sensor [9], [14]) is presented for local visual heading measurement purposes : it should allow a future micro flying robot devoid of a magnetic compass to stabilize its heading in an unpredictable indoor environment while visually following local flat surfaces. In section II, the eye design will be described.…”