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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

who was the first nanotechnologist
Lizzy Reply
technologist's thinker father is Richard Feynman but the literature first user scientist Nario Tagunichi.
Norio Taniguchi
I need help
anyone have book of Abdel Salam Hamdy Makhlouf book in pdf Fundamentals of Nanoparticles: Classifications, Synthesis
Naeem Reply
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pedro Reply
It could change the whole space science.
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sibaram Reply
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synthesis of nano materials by chemical reaction taking place in aqueous solvents under high temperature and pressure is call?
hydrothermal synthesis
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Eke Reply
is this allso about nanoscale material
are nano particles real
Missy Reply
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
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where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
has a lot of application modern world
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
STM - Scanning Tunneling Microscope.
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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