Lots of shoes are sold on the net and lots and lots of shoes are returned because of size issues and shoe sizing is not full consistent (to say the least) across manufacturers.
I know laser measurers exist for measuring building dimensions wall to wall based on the bounce time of the beam. Can you do the same for the small enclosed area in the inside of a shoe where you stick a laser or ultrasonic probe in and it tells you the exact interior dimensions of the shoe re interior footbed length, width and possibly toe box area?
I think it would be possible to do it by splitting the beam and projecting several patterns from slightly different angles, then analysing the resulting interference/moire pattern that appears on the inside surface.
Some shoes are pretty long and narrow though - and some have an upturned toe (like this, not this) - for these, there isn’t necessarily full and proper line of sight down to all parts of the toe - so optical measurement may miss something.
Maybe you are overthinking this. I would guess that there are some key dimensions: width at the base of the toes, length from heel to toe, height at the arch. Our local shoe shop measured these whenever we took our kids in to be sure that they got the right size for growing feet.
So instead of just putting a size on the shoes, maybe the suppliers could supply the key dimensions. No lasers required.
Plus the current technology for making dental crowns involves laser scanning the molded tooth impression and translating that to a CNC model for machining the new crown.
I would go farther and say it is definitely possible to build such a device. Check out this video of a 3D scanner that scans inside your mouth.
Of course, I doubt it would ever be cost effective. Shipping shoes back is quite cheap, and the manufacturers probably already know the dimensions (and could simply do a better job of supplying them to retailers). But it looks like fun to 3D scan things.
Sure I could. I have no idea how to make such a device practical for it’s limited application. Any one person is unlikely to use this more than once a year. I also don’t know if it’s the way to fit shoes, first because I’m not a shoe salesman, but second because the interior of shoe may have conformed to a foot but it’s also doing so based on the materials in use and a leather dress shoe with the same interior dimensions as a sneaker may not feel as comfortable. I would think that simple scanners would be able to measure a foot accurately enough to get close enough size-wise and ordering shoes on-line will still have the risk that whatever you order just doesn’t feel comfortable for that particular shoe. If you’re going to go for a measuring device at a minimum you would want the dimensions of both a known shoe and the foot that normally wears it to have some idea of how that foot fits into the shoe and what the person expects to feel when he puts his foot in that shoe.