3-D Particle Tracking

[Wesley2894]

I am currently working on a science project that involves writing a computer program that tracks particles 3 dimensionally. I am using Matlab's Simulink to write this program. I have already figured out how to determine the x and y location of the particle but I am having problems determining the z location. I have researched methods that I could use to accomplish this, and I have found something called:
"Focusing With Spectral Entropy" http://vision.fe.uni-lj.si/research/focus/index.html. The website gives a brief tutorial and demo for Matlab.
However I am not very adept at programming, explaining why I am using the Simulink drag and drop block interface. Is there some possible way that I could use Simulink blocks to achieve the same effect?

Here is a picture of my current program:

[deleted-42343]

Hi Wesley,

We are trying to find an Expert that can help with your project. Our experts check in on different days and since your question is very specific it is taking a while to find someone with this knowledge.

[Wesley2894]

Okay. I understand

[deleted-71788]

Hi Wesley,

Please post on this forum (preferably on the 'Math & Computer Science' forum) the specific details of exactly what you are trying to achieve. For example, do you have a 3-dimensional equation you are trying to plot? Post specific details.

What you mentioned in your earlier post and the reference (web link) that you gave is about '...spectral entropy' and something to do with 'cosine transform', for which they are using the Matlab/Simulink tool. Is that what you are trying to do or just trying to program a 3-dimensional equation? Please post details.

[Wesley2894]

I am currently working on a computer program that tracks particles under a microscope. I have already figured out how to find the x and y locations of the particle. I am currently trying to figure out how to find the z location of the particle. I am trying to incorporate spectral entropy into my computer program to help me do that. I am trying to determine the location of the particle by finding how focused it is.



As you can see above, there is a single focus position (optimal focus) that provides the sharpest picture. As you move left or right, the sharpness decreases. In my experiment, I will be looking at a single particle under the microscope. I will focus the microscope so that the particle is at its optimal focus so it provides the sharpest image. In my experiment, I will be looking at particles that are constantly moving. As the particle moves around, the sharpness of the particle will change. The further the particle drifts away, the less sharp it would be. In other words, the sharpness of the particle is proportional to the distance the particle traveled on the z axis. To sum it up, I will determine the z axis location of the particle by determining how focused the particle is.

My problem right now is I do not know how to add spectral entropy into my computer program.

Here is a copy of my computer program: http://www.mediafire.com/?tkdk4jymmon *You must have Matlab to open up this file*

[deleted-71788]

Unfortunately, I do not have Matlab, or much exposure to it.

However, there are hundreds of very good webinars (I attended one some time back) on Matlab's website categorized by topics, applications etc. For example, some relevant categories to what you are doing are Control Design, Image Processing, Computational Biology.

Check this site, you may find a good webinar/tutorial to help you out:

http://www.mathworks.com/company/events ... pplication

[Wesley2894]

Thanks for the info.

[5650Kelvin]

I am no expert in this field, but I do a lot of photography in my spare time.

There are two ways you could be tracking your particle, either by modifying the focus, or by measuring the amount of defocus. I think you are doing the latter, based on your description.

If you are planning to get the z value by measuring how "out of focus" the particle is, then you have two different problems. The size of the blur will increase as the distance from optimum focus increases, yes, but the edge of the blur will get fainter, too - that's unavoidable. So you'll have more difficulty detecting the exact edge of the blur as it gets further and further from focus. Also, you don't have an easy way of determining whether the distance from focus is positive or negative - is the particle getting closer to the lens, or further away? I don't know if that is important to you.

BTW: If you are depending on reflected light, you will want to have the light source a significant distance from the particles to avoid adding the complication of the amount of reflected light varying with distance of the particle from the light source. Basically, you want the distance of the light source to be many times the distance that the particles are travelling.

I recommend reading up on "circles of confusion" and "Airey discs" - these are somewhat advanced optics, but exactly relevant to what you are doing. You may find some of the mathematics involved useful, but be prepared to spend some time studying it.

I hope this helps.