T. Delbrck and C. A. Mead, "Analog VLSI phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits," in CNS Memo 30. Pasadena, CA: California Inst. Tech., 1994.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....VLSI circuit emulates the retina in many ways and the micro mirrors act like a deformable lens, we refer to the silicon adaptive optics systems as a silicon eye. III.ANALOG POSITION SENSORS Active pixel technologies offer tremendous advantages in massively parallel silicon based architectures [3]. For our silicon eye, we fabricated at the University of New Mexico Center for High Technology Materials (UNM CHTM) a simple planar back to back Schottky barrier Si position sensor. This detector enables high bandwidth (up to 1 GHz) nm scale position displacements independent of spot size. ....

T. Delbruck and C. Mead, "Analog VLSI phototransduction by continuous-time, adaptive

....architecture Object plane lens Image plane Out of focus Half silvered mirror Focus sensor defocus kernel E I ( 2 image = EI I Photoreceptors Difference computations 3. THE CIRCUIT ELEMENTS The pixel uses only two circuit elements: an 5 transistor adaptive photoreceptor [1] and a 7 transistor antibump circuit [2] In addition, the chip includes a bias generator that generates all circuit bias currents and an output circuit that produces a pulse frequency modulated output from the summed focus signal. 3.1 Adaptive photoreceptor [1] Over a range of 6 7 decades of ....

....5 transistor adaptive photoreceptor [1] and a 7 transistor antibump circuit [2] In addition, the chip includes a bias generator that generates all circuit bias currents and an output circuit that produces a pulse frequency modulated output from the summed focus signal. 3. 1 Adaptive photoreceptor [1] Over a range of 6 7 decades of illumination, the photoreceptor shown in Figure 3 outputs a signal V o whose variations in response to scenes with varying reflectivity are nearly invariant to illumination level. The output of the receptor V o is referenced around the past history of the ....

. T. Delbrck and C.A. Mead (1994). Analog VLSI Phototransduction by Continuous-Time, Adaptive, Logarithmic Photoreceptor Circuits. Caltech CNS Memo #30 http://www.pcmp.caltech.edu/anaprose/tobi/recep

.... that is in the pixel with several advantages including on site information concentration, increased reactivity and possibly active sensing [1] With about 10 transistors per pixel, it is already possible to perform some dedicated image preprocessing tasks, using analog circuit techniques [2,3]. However, much more visual versatility can be expected from a programmable architecture in the focal plane. We mean an on a chip SIMD array processor in which each processing element (PE) corresponds to one pixel and therefore contains a photosensitive device. We call such a circuit a ....

T. Delbrck and C.A. Mead. Analog VLSI phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits. Technical Report 30, CalTech/CNS, July 1994.

....at a pixel into a voltage, a nonlinear differentiator circuit which produces an analog voltage pulse for an abrupt change in photoreceptor voltage, and a thresholding circuit which converts the differentiator output into a larger voltage pulse. The photoreceptor has been fully characterized in [9]. The subsequent stages are discussed below. All three TED stages are shown in Figure 1; example oscilloscope traces for a passing edge are shown in Figure 2. The nonlinear differentiator circuit of [10] has been modified to allow response to both signs of derivative. This makes the TED responsive ....

....DEUTSCHMANN AND KOCH: PULSE BASED 2D MOTION SENSORS 3 V V thr dif V out V out V amp (a) Adaptive Photoreceptor (b) Nonlinear differentiator (c) Thresholding circuit V prout V dif C4 C3 M2 M3 V prout V prbias C2 C1 M1 M5 M4 V gain I dif Fig. 1. TED circuitry: a) adaptive photoreceptor [9]: transistor M1 allows long term adaptation to the light level; the ratio of C1 to C2 sets the transient gain. b) nonlinear differentiator [10] transistors M2 and M3 have been added to the original circuit to allow response to both signs of temporal edges; the ratio of C3 to C4 sets the ....

T. Delbruck and C. Mead, "Analog VLSI phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits," Tech. Rep. 30, Department of Computation and Neural Systems, California Institute of Technology, 1993.

....by Boahen; refer to the paper by Boahen [3] in this proceedings for further details. 4: Photosensor Sender Chip 4.1: Sender Architecture The core of the sender chip is a 12 Theta 12 array of sender pixels. See Figure 2 for a layout diagram. Each sender pixel contains an adaptive photoreceptor [4] and a nonlinear differentiator circuit [10] interfaced to the interchip communication circuitry. The photoreceptor adapts to the local light intensity on slow time scales (a few seconds) allowing high sensitivity to transient changes over a wide range of illumination without a change in bias ....

T. Delbruck and C. Mead. Analog VLSI phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits. Technical Report 30, Department of Computation and Neural Systems, California Institute of Technology, 1993.

....role in vision system, information loss in this stage is difficult to restore and causes system dysfunction. Since the light intensity present in natural environments can vary over six decades, employing a photoreceptor with large dynamic range is necessary. Logarithmic photoreceptor (see [2] [3] [5] 10] presents two major drawbacks: 1 poor sensibility; 2 its large fixed pattern noise (FPN) it s very difficult to cancel, even off chip, due to its nonlinear transformation. We see that an integration mode photoreceptor offers the several important advantages over a logarithmic ....

T. Delbruck and C.A. Mead, ˛Analog VLSI Phototransduction by Continuous-Time, Adaptive, Logarithmic Photoreceptor Circuits˛, CNS Memo #30, Computation and Neural Systems Department, California Institute of Technology, Pasdena CA 91125, 1994.

....that each pixel has a square lightcollection area of a Theta a. We illustrate how various system parameters scale with a. We shall only show the forms of the dependence on a without constant factors. Our theory and measurements are based on the adaptive photoreceptor characterized extensively in [11], but our discussion is of a general nature and applies to many common photoreceptor designs. 2.1 Spatial and Temporal Filtering For a photodiode, the photocurrent I is proportional to Ea 2 , where E is the irradiance and a 2 is the light collection area. The total capacitance on the ....

....with the photocurrent 2 . Thus, B a 2 a 2 p E : 1) The linear dependence of the bandwidth on the irradiance E can be seen from Figure 1A, showing the response of a photoreceptor to small signal, white noise for different irradiance levels. The data were provided by T. Delbruck from [11]. For a given irradiance E, the bandwidth rises with increasing a but eventually asymptotes to a constant value independent of a. 2 The bandwidth is proportional to g=C, where g = I=V k is the conductance of the photodiode sensing node and V k is a multiple of the thermal voltage kT=q. Since V ....

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T. Delbruck and C. A. Mead, "Analog VLSI Phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits", CNS Memo No. 30, California Institute of Technology, June 1995.

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T. Delbrck and C. A. Mead, "Analog VLSI phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits," in CNS Memo 30. Pasadena, CA: California Inst. Tech., 1994.

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T. Delbrck and C. A. Mead, "Analog VLSI phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits," in Vision Chips: Implementing Vision Algorithms with Analog VLSI Circuits, C. Koch and H. Li, Eds. Los Alamitos, CA: IEEE Computer Society Press, 1995, pp. 139--161.

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. T. Delbrck and C.A. Mead (1994). Analog VLSI Phototransduction by Continuous-Time, Adaptive, Logarithmic Photoreceptor Circuits. Caltech CNS Memo #30 http://www.pcmp.caltech.edu/anaprose/tobi/recep

No context found.

T. Delbruck and C. A. Mead, "Analog VLSI phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits," tech. rep., California Institute of Technology, 1996. CNS Memo No. 30.

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T. Delbruck and C. A. Mead, "Analog VLSI phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits," tech. rep., California Institute of Technology, 1996. CNS Memo No. 30.

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