Sunday, July 30, 2017

3D VOLUME SCANNER IDEA

I recently learned about an innovative method to get 3D scans of objects. It overcomes line of sight problem and captures the inner shape of the object also. It looks like a robot arm dips the object into water in different orientations. Each time how water level changed over time gets measured and from these measurements 3d object shape is calculated like a CAT scan.

I think these method can be improved upon greatly as follows:

Imagine we put a tight metal wire ring around the object we want to scan, maybe using a separate machine.
It could be a bendable but rigid, steel wire ring, or maybe bicycle wire ring, could be even a suitable kind of plastic.
The object could be in any orientation, hold tight by the ring.

Imagine we have an aquarium tank filled with liquid mercury
(which would keep the object dry unlike water, and also tank walls so that measurements would be more precise).
(Also mercury is conductive which would also make measurements easier using electronic sensor(s).)
(It could also be a cylindrical tank.)

Imagine inside of the tank we have a vertical bar that can move up and down a horizontal bar using electronic control.
Imagine that horizontal bar at its middle (down side) has a hook/lock for the wire ring (around the object).
That hook/lock has an electronically controlled motor that can rotate the wire ring (so the object) to any (vertical) angle.
(To prevent the ring/object moving like a pendulum when it is dipped into liquid (fast) each time, we could add a second horizontal bar with adjustable height, that has a hook/lock for the wire ring at its middle (up side). So the ring would be hold in place from its top and bottom points by two horizontal bars.)

Now imagine to take new measurements each time, we rotate the object a small and equal angular amount (within 360 degrees).
Then we dip the object fully inside the liquid (at constant speed) and take it out fully back (at constant speed).
Every time as we dip the object we record the changes in the liquid level in the tank over time.
(While the object fully dipped we could rotate it again and then record liquid level changes while we take the object fully out back
to get two sets of measurements at each cycle, instead of one.)

Of course mercury is highly toxic and reacts with some metals.
So it would be best to find a better liquid.
The liquid would need to be non-stick to keep scanned objects, tank walls dry. Minimal viscosity and density as possible, maximal temperature range with linear volume change based on temperature, constant volume under common different air pressures would be better. Stable (non-chemically active) and non-toxic are must.
Also electric conductivity would be a plus.

References:
https://www.sciencedaily.com/releases/2017/07/170721131954.htm
http://www.fabbaloo.com/blog/2017/7/25/water-displacement-3d-scanning-will-this-work
https://3dprintingindustry.com/news/3d-scanning-objects-dipping-water-118886/