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Comment by rayiner | Hacker News Reader

I'm really surprised Microsoft hasn't bought the company yet already. Kinect is the key differentiator for the Xbox versus the Playstation, and it can't be a positive thing for Microsoft's supply chain for a key manufacturer to be bought up by Apple.

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Microsoft doesn't use PrimeSense for the XBox one. It's all in-house now. Should have negligible effect on the supply chain.

Presumably Microsoft has a perpetual license to PrimeSense's IP? Or does someone else entirely own that?

They bought another company in the field(3dv systems), which used a totally different physical principles(instead of dual cameras, using time of flight of photons) in their tech.

Canesta. I looked into their stuff before the Kinect came out. I am no expert in the field, but I thought their time-of-flight sensor is really clever. Basically, the speed of light is too fast to get an accurate ToF measurement within living-room distances using timers. So they use a technique where the intensity of the reflected IR is directly proportional to the ToF. Since you can measure intensity with much more accuracy and precision (and ease) than the time taken for light to travel a few meters, you get a pretty accurate 3D point cloud of the space being sensed. I can't find their white paper that explains this, but it's a good read.

That's interesting...was it an effect based on attenuation of the light? i.e. reflected photons from close objects will attenuate less than ones further away therefore intensity will be higher?

Something along those lines, but they also did something clever with the timing of emitting IR flashes and correlating the received number of photons with those flashes. I really wish I could recall more clearly, but I looked into it around 2007 - 2008. I tried finding the white paper, but all the links are dead :-( I might have a copy lying around, though... I'll try to dig that up.

Don't sweat it, I just think that if that's the method, it's a really cool hack.

Eureka! Found it on scribd:

http://www.scribd.com/doc/40735369/Can-Esta-101

Thanks for the link :) Do you happen to know how to download the pdf off scribd? It looks like you need to pay scribd to do it (or to read past the first few pages), which doesn't quite seem fair since I'm assuming they don't have a license to the content themselves, in which case it'd be someone else's copyrighted content they're profiting off...

Can't get it off scribd, but thanks to the magic of archive.org (seriously! amazing stuff), the entire pre-purchase canesta website is still up. Just look prior to mid 2010 or so. Here's the exact pdf in question:

https://web.archive.org/web/20091122234143/http://www.canest...

Yeah, that was a pretty big turn-off. Scribd is already on my groan-when-I-go-there sites, but I'm pretty sure a service that lets me download a pdf is not something I'm interested in paying for since that was invented decades ago when it was called ftp.

Doesn't return the intensity of reflection depend on the color and surface finish of the target? i.e. a white sofa reflects more light than a black sofa?

Yes, it does, so I'm not sure how (or if) they addressed that. I'll try to dig up that white paper.

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