Hacker News Reader

Comment by marze | Hacker News Reader

Suggestion: why not use three cameras simultaneously, each from a different angle, then classify the three images? Those cameras must be nearly free in cost.

Also, to get more training data, what about setting up a puffer to blow the part back on the belt and tumble it? If you could configure the loader belt to load parts slowly and stop after one is seen, you could automatically re-image the first part an arbitrary number of times by blowing it backwards before letting it move along and restarting to first belt to get another.

And question: do you normalize out color at any stage? As in, classify a black and white image, with a separate classifier for the color?

View on HN

> why not use three cameras simultaneously, each from a different angle, then classify the three images? Those cameras must be nearly free in cost.

Because you really only need one camera (and two mirrors).

> Also, to get more training data, what about setting up a puffer to blow the part back on the belt and tumble it?

That's an interesting and novel idea. It probably will not work because the difference between the heaviest and the lightest parts are such that you'd blow most of the parts clear off the belt. Also the camera is sampling fast enough that the part would end up imaged in many positions without the ability to stitch the parts together again. But interesting.

> And question: do you normalize out color at any stage? As in, classify a black and white image, with a separate classifier for the color?

No, but I am considering using HSV or LAB as the colorspace to see if that improves accuracy or reduces training time to get to a given accuracy.

Could you have another belt going back the other way, and blow lego to hit a wall and drop on to it, instead of in a bin? Send it back towards the ramp, and find a mechanical or air powered way of getting the part over the plywood wall to be sent back round. That way you could just send a batch of 3-4 of the same part round repeatedly for a bit.

Simpler to put up side walls and a back barrier to prevent the blown piece from leaving the belt.

Changing to a different fixed color space is unlikely to help. However adding a learnable color space transformation is a great (and rarely known) trick. Both are discussed and compared in this terrific paper: https://arxiv.org/abs/1606.02228

What about something easier? Instead of a puffer, just take a big bin of the same part and loop it through the hopper for a few hours. Presto, as much accurately-labeled training data as you want (though limited to a single part at a time).

If I had big bins of sorted parts I wouldn't need the machine ;)

This is an approach that will work for parts that are so common that even after a few runs you have lots of them but the 'long tail' of lego parts is the vast majority of parts and they are quite rare.

Reply on news.ycombinator.com