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This module describes the application of compressive sensing to the design of a novel imaging architecture called the "single-pixel camera".

Architecture

Several hardware architectures have been proposed that apply the theory of compressive sensing (CS) in an imaging setting  [link] , [link] , [link] . We will focus on the so-called single-pixel camera   [link] , [link] , [link] , [link] , [link] . The single-pixel camera is an optical computer that sequentially measures the inner products y [ j ] = x , φ j between an N -pixel sampled version of the incident light-field from the scene under view (denoted by x ) and a set of N -pixel test functions { φ j } j = 1 M . The architecture is illustrated in [link] , and an aerial view of the camera in the lab is shown in [link] . As shown in these figures, the light-field is focused by a lens (Lens 1 in [link] ) not onto a CCD or CMOS sampling array but rather onto a spatial light modulator (SLM). An SLM modulates the intensity of a light beam according to a control signal. A simple example of a transmissive SLM that either passes or blocks parts of the beam is an overhead transparency. Another example is a liquid crystal display (LCD) projector.

Single-pixel camera block diagram. Incident light-field (corresponding to the desired image x ) is reflected off a digital micromirror device (DMD) array whose mirror orientations are modulated according to the pseudorandom pattern φ j supplied by a random number generator. Each different mirror pattern produces a voltage at the single photodiode that corresponds to one measurement y [ j ] .

The Texas Instruments (TI) digital micromirror device (DMD) is a reflective SLM that selectively redirects parts of the light beam. The DMD consists of an array of bacterium-sized, electrostatically actuated micro-mirrors, where each mirror in the array is suspended above an individual static random access memory (SRAM) cell. Each mirror rotates about a hinge and can be positioned in one of two states ( ± 10 degrees from horizontal) according to which bit is loaded into the SRAM cell; thus light falling on the DMD can be reflected in two directions depending on the orientation of the mirrors.

Each element of the SLM corresponds to a particular element of φ j (and its corresponding pixel in x ). For a given φ j , we can orient the corresponding element of the SLM either towards (corresponding to a 1 at that element of φ j ) or away from (corresponding to a 0 at that element of φ j ) a second lens (Lens 2 in [link] ). This second lens collects the reflected light and focuses it onto a single photon detector (the single pixel) that integrates the product of x and φ j to compute the measurement y [ j ] = x , φ j as its output voltage. This voltage is then digitized by an A/D converter. Values of φ j between 0 and 1 can be obtained by dithering the mirrors back and forth during the photodiode integration time. By reshaping x into a column vector and the φ j into row vectors, we can thus model this system as computing the product y = Φ x , where each row of Φ corresponds to a φ j . To compute randomized measurements, we set the mirror orientations φ j randomly using a pseudorandom number generator, measure y [ j ] , and then repeat the process M times to obtain the measurement vector y .

Questions & Answers

what does nano mean?
Anassong Reply
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Damian Reply
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s. Reply
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are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
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That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
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what is the Synthesis, properties,and applications of carbon nano chemistry
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Mostly, they use nano carbon for electronics and for materials to be strengthened.
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is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
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SUYASH
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of graphene you mean?
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or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
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Source:  OpenStax, Introduction to compressive sensing. OpenStax CNX. Mar 12, 2015 Download for free at http://legacy.cnx.org/content/col11355/1.4
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