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In response to the recent call for help with small markers, I'd like
to discuss our experience. We have been using the following set-up to
perform 2-D studies of soft tissue with the Motion Analysis System.
Minor modifications should allow you to perform 3D studies. We utilize
florescent markers for the following reasons:
- useful for inherently noisy fields of view, small or large (our
application is to wet soft tissue, which would produce a great deal of
reflections of white light, visible to the camera)
- Use uv light to excite markers, and a cut-off filter to eliminate
all other background makes for beautiful binary input image to the
camera prior to thresholding
- No problem with heat of intense white lights used in retro-
reflective markers
- CHEAP non-toxic Crayola brand florescent paint covered with clear
plastic spray works great
- cheap color filters (same as paint color) works great as cut off
filter in front of lens
- florescent type black lights best for UV light source.
- We use orange paint with orange filter with UV light and most of the
room lights out for best results.
We have been using tag board for our circular markers, but I would
think that you could use any material which would hold the paint to
generate spherical markers.
(No one in the lab stands to gain from the sale of any product
mentioned in this posting, and any of the other usual disclaimers.)
Tom Cahalan (with a great deal of technical support
from Eric Growney and Larry Berglund)
to discuss our experience. We have been using the following set-up to
perform 2-D studies of soft tissue with the Motion Analysis System.
Minor modifications should allow you to perform 3D studies. We utilize
florescent markers for the following reasons:
- useful for inherently noisy fields of view, small or large (our
application is to wet soft tissue, which would produce a great deal of
reflections of white light, visible to the camera)
- Use uv light to excite markers, and a cut-off filter to eliminate
all other background makes for beautiful binary input image to the
camera prior to thresholding
- No problem with heat of intense white lights used in retro-
reflective markers
- CHEAP non-toxic Crayola brand florescent paint covered with clear
plastic spray works great
- cheap color filters (same as paint color) works great as cut off
filter in front of lens
- florescent type black lights best for UV light source.
- We use orange paint with orange filter with UV light and most of the
room lights out for best results.
We have been using tag board for our circular markers, but I would
think that you could use any material which would hold the paint to
generate spherical markers.
(No one in the lab stands to gain from the sale of any product
mentioned in this posting, and any of the other usual disclaimers.)
Tom Cahalan (with a great deal of technical support
from Eric Growney and Larry Berglund)