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An introduction the Rice University ELEC 301 Fall 2006 coin recognition project.


Many tedious processes can be automated using computers. Counting and sorting objects, especially in large numbers, is an area where humans are simply less efficient. Applying this knowledge to the problem of identifying and counting coins, a software system can be developed to recognize and tally a handful of change. The following modules describe the challenges associated with building a system that accomplishes these tasks. Good luck on your journey!


Object recognition and identification are important aspects of machine vision. Coin recognition in particularposes a special challenge for two reasons: 1. Coins are notoriously difficult to photograph. They are reflective, and there aretrade-offs in evenness of lighting vs. visibility of details when determining lighting. 2. Coins are circular objects. Unlike playingcards, where long edges can be determined and the original image can be transformed to a standard angle from which comparisons canbe made, coins can have arbitrary orientations and there is no way to determine them without knowing the identity of the coin.

Process overview

There is a systematic process that the machine must follow to determine the identity of a coin. The rest of thiscourse will go into greater detail in each step.

Image acquisition

First, an image must be acquired. You might imagine that this part of the process would be the simplest, but itactually ended up being one of our steps that was most fraught with difficulties. Lighting ends up becoming a big issue, leading tomisidentification in systems with uneven lighting and necessitating the use of diffuse light sources.

Circle recognition

Once the image is in the computer, the first step is to locate the coins in the scene. This can be accomplishedusing off-the-shelf code that implements a feature extraction technique known as the Circular Hough Transform. Feeding thefunction the image and a range of radii to detect, it will, with high accuracy, return the radius and center of every circle (coin,in this case) in that range in the picture.

Coin fft creation

Radius and center data in hand, now we get to the meat of the project: recognizing the coins. The key difficultyin recognizing coins is their very circular nature. As mentioned previously, they can have any phase. Normally you might use amatched filter to try to determine identity of an object (the filter with the greatest resulting magnitude is the filter of thecoin). If you were going to do that in this case, you would need a separate matched filter not only for each coin surface, but foreach coin surface at every possible rotation. We take a different approach. Exploiting the properties of Fourier transforms and goingthrough an “unwrapping process”, we are able to create unique FFTs that are orientation agnostic.

Coin identification

Once we have the FFT of the coin, we have to determine which coin it is. Beforehand, we create adatabase of FFTs of known coins we want to recognize. Then, using one of many possible comparison algorithms, we compare the FFT ofthe current coin to each coin in the database, selecting the comparison with the closest match as the identity of thecoin.

Output display

Once the information about each coin is known, we can display it in any way we want. Because we record lots ofmetadata for each coin, in addition to the sum we can display all sorts of interesting statistics about the coins in the image. Wealso created a way to allow rapid error checking by superimposing the values of the coins onto the image of the coins.

Flow chart

This is a pictorial representation of the process described above.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Elec 301 projects fall 2006. OpenStax CNX. Sep 27, 2007 Download for free at http://cnx.org/content/col10462/1.2
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