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This module contains the background of our object detection algorithm and 3-D sound synthesis system.

Object detection

Finding an object in an image can be done in various ways. One of the most common methods used is matching certain features in the image to those in the object that is being searched for. Traditionally, these features have included mostly edges and corners because these are relatively easy to find, but unfortunately these features are also often sensitive to even small amounts of noise and are also often neither scale nor rotation invariant. Another method of object detection in an image is color matching. This method works reliably and efficiently, but is very sensitive to things in the background and thus, in general, a very plain background must be used in order to track the desired object correctly. For this reason, we found that a good tradeoff between speed of computation and sensitivity to noise was the Speeded Up Robust Features (SURF) algorithm. Using this algorithm allows the program to track an object by simply providing a picture of the desired object, and it works both outdoors and indoors without any overly tight constraints on the environment.


The SURF algorithm is actually based on the earlier Scale Invariant Feature Transform (SIFT) algorithm, but has a few modifications that make the former a lot faster to compute. In order to use these algorithms, one first simply takes a picture of the object that is to be tracked; this image is called the "template." Then, the algorithm finds "keypoints" on another image; these are places with interesting features that might be useful for tracking an object, but not necessarily the object we're looking for. Each of these keypoints includes a scale, orientation, coordinates, and other identifying information ("descriptors"). In order to actually find where the object we're looking for is, one finds the keypoints whose descriptors are closest to those calculated for the template image. This is usually done by finding the keypoints in the test image with the least squares difference in their descriptor values as compared to those in the template descriptors.

SIFT will be described first because it is simpler, and then the differences between SIFT and SURF will be noted.

Creating the Scale-Space

The first step in the SIFT algorithm is to create what is known as a "scale-space." This basically creates a set of images that consist of versions of the original image, blurred to different extents. This is important because oftentimes there are objects of very different scales in an image. An example of this would be a large tree with lots of small leaves on it. Adding higher amounts of blur means that only larger objects will remain detectable while small amounts of blur will preserve small details. Additionally, this step is critical for maintaining scale invariance so that the object can be detected when it is farther or closer to the camera in the video than when the template image was taken. Blurring of the image is done by taking the 2-D convolution of the image with a Gaussian function. This has the same effect as passing the image through a low pass filter in the frequency domain. It is important to note that most current methods of generating scale-spaces use the Gaussian and not other types of low pass filters to perform this blurring because it has been mathematically proven that the Gaussian filter does not add any features to the source image that were not originally there. Other types of filters might potentially add things like edges in places where there were originally none.

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
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