Modeling the Aural canal and 3D scanning

From: Bill Richards (
Date: Fri Mar 08 2002 - 20:12:41 EET

I must agree with Dr. Bibb: Never stick anything in your ear (except your elbow).

Hearing specialists routinely make castings of a patient's ear canal with a soft material in order to create a custom fit hearing aid. Please go to your doctor to find out where you can have this done safely. I can't imagine that anyone would find having their eardrum ripped out of their body to be a pleasant experience...

3D scanning technology is not up to the level that many people would like to believe. I would put scanning technology at least several years behind rapid prototyping.

Laser scanners can only scan what can be seen on a straight line. Over hangs and folds will never be scanned. Metals, transparent materials, and materials with translucence or specularity will cause problems with the scanner determining just where the light beam actually touched the surface.

Mechanical arm scanners can overcome that issue, so long as the probe can be worked into the tight places. But the quality of your data depends on the number of times you touch your probe to the target surface.

Another type of scanner actually destroys the subject, by shaving it away layer by layer and imaging each layer. This technique guarantees that hidden geometries will be scanned. The only other way would be to use MRI or CAT scanning.

For creating a model of an ear, I don't believe you are going to get a true scan without using MRI or creating some custom probe-scanner. Perhaps an endoscope with a laser scanning from its tip. I think the best way is as Dr. Bibb suggested: Have a doctor create a casting of your subject's ear, and then scan the casting.

Bill Richards
Delta Search Labs
T: 617-551-4615
F: 617-551-4651

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