Q: “The goal is to find the distance between two light emitters that are both within a single pixel. One will go dark after a period of time and the other will go dark after another period of time. …we are looking to see if you see an issues in some of the techniques we are using or can propose better algorithms.”

Let me summarize.

Problem:

• Given a few emitters going on and off, find their coordinates from a video.

Challenges:

• The emitters are blurred forming spikes.
• There is other noise.
• The spikes are just a few pixels in size.
• The sources are sometimes closer than the size of the pixel leading to overlapping spikes.

Main methods:

• Enhancing the images: smoothing and background removal.
• Averaging the corresponding spikes throughout the frames.
• Fitting a Gaussian to each spike, then the mean of this distribution is supposed to be the location of the emitter [2].
• MATLAB is used.
• A lot more is done…

The main issue is this:

• Averaging the spikes obscures the fact that the coordinates of each spike varies from frame to frame.

How much do they vary? The answer will give you the best possible accuracy of the measurement.

The goal was to test the approach in order to see of it’s possible to track emitters from frame to frame and for that I used Pixcavator. I picked a couple of frames, fairly far apart from each other and converted them to bmp images. I analyzed each with Pixcavator with the same settings. Then I matched the locations. These are the distances between the best matches:

0.30 0.07 0.69 0.15 0.41 0.19 0.92 0.72 0.40 0.60 0.97 0.64 0.15 pixels.

Is this accurate enough?

More details here…