EETimes quotes UBM TechInsights' reverse engineering of Microsoft Kinect revealing that of the roughly $56 BOM, about $17 is attributed to the cost of the PrimeSense 3D sensing reference system. Microsoft is planning to retail the Kinect system for $149, and stands to make a healthy profit on each unit, UBM TechInsights said.
17$ 3D system BOM is a tough target to meet for TOF camp.
just having tried a Kinect, the laser power is dangerous. If you point your mobile phone camera to the laser at short distance to the Kinect, you can see a big glare of light. Please note that there is a IR-cut filter in front of the sensor!!!!
ReplyDeleteThere seem to be 3 possibilities about the safety of IR light sources in 3D systems.
ReplyDelete1. The power is safe and we are sure about that.
2. The power is claimed to be safe but we really don't know.
3. The power is claimed to be safe but we know it is not.
In case #3, we have a moral duty to at the very least speak up about this to the manufacturers and consumers and the press.
In case #2 we still have the moral duty to express our concerns until we find a conclusive report about the eye safety of these systems. Does anyone know anything about such safety?
If it is case #1 then claiming the power is dangerous is actually libel.
Since I am working on 3D TOF I'd love to know what anyone else has found about eye safety. I keep hearing it is all fine but I am guessing that conditions under which these systems will be used have not been fully explored (power lvel + exposure time) especially from a quasi point source illuminator.
Your 3 conditions don't include human behavior. If you measure the laser power at the normal gaming conditions, it should be safe. But as it's a gaming device, kids can be curious about the sensor and can look into the laser, that will be dangerous. Like Sun eclips observation, we repeat endless to kids to use protection device.
ReplyDeleteI've worked before on car night vision system. This close-looking condition has been studied serious and even today the use of a laser illuminator is still questionned.
I've just scanned the MS website on the Kinect page, there is no any information concering the laser eye safty issue. Even when you buy a 1mW laser pointer for powerpoint presentation, you have a warning message, but on Kinect with 200-300mW, there is no any warning message at all. Do you think that this is normal?
From a scientific's point of view we have question to ask Microsoft guys.
http://www.youtube.com/watch?v=nvvQJxgykcU
ReplyDeletehttp://www.youtube.com/watch?v=6CFoOFZ6ifc&feature=related
ReplyDeleteImpressive patterns - seems to be coded and not repeating. I'm not sure that Primesense light source really emits 200-300mW of power, but let's assume you are right, for the sake of argument.
ReplyDeleteI'm not a safety expert, but it looks to me that what matters here is power density, rather than absolute power. 1mW laser pointer is pretty much a point source with huge power density. On the other hand, Primesense IR illuminator window is quite big in comparison and I'd guess its power density is lower than one of the laser pointer. So peering directly into laser pointer might be more dangerous than doing so with Primesense illuminator - this is my guess why Microsoft is feeling safe on this.
The key point is that if you look into the illuminator closely, you will get all the optical power. Your eyes don't have the natural reflexion againt strong IR light because you can not see it. You can count the number of points in the projected pattern. Even each point represents 0.01mW, the total laser power is huge. At least one year ago, PrimeSense uses a 300-500mW laser with a TE cooler for temperature stabilization.
ReplyDeleteIf you want to see the laser spots during the daytime, you have no choice. They use Aptina CMOS sensor with rolling shutter inside, so short-exposure time with a pulsed laser is not possible.
You can see that on youtube, people starts to be aware of the potential danger. Microsoft cannot hide this for long time.
@ "if you look into the illuminator closely, you will get all the optical power."
ReplyDeleteI disagree with it. If peering directly into the illuminator one only gets a part of the power, just because the illuminator's output pupil is much bigger than the eye's one. And once this light enters the eye, it's more evenly distributed over retina than, say, laser pointer's ray. All in all, I think more investigation should be put into safety issue than just comparing the power with one of laser pointer.
Thinking about this some more, the main source of energy transfer is probably by heating the tissue. The NIR absorption coefficient in water is quite low (0.1-0.01 cm^-1) but isnce people are not transparent in the NIR realistically in body tissue it has to be of the order of 1-10. Let's choose 10 or 1 mm absorption depth.
ReplyDeleteLet's say the laser illumination is focused on 1 mm x 1mm. So, the laser energy is roughly absorbed in 1mm x 1mm x 1mm of tissue.
If the specific heat of body tissue is like water, then it is 4 J/cm^3/C. 300 mW x 1 sec = 300 mJ divided by 0.001 cm^3 is 300J/cm^3. Divide by 4 to get 75C rise in temp per sec.
So, this estimate seems dangerous.
But, if the power is spread over 3mm x 3mm and the absorption depth is 10 mm, then the temperature rise is 0.75C per second. Depending on blood flow rate in the retinal tissue etc, this may not be dangerous if the heat is dissipated.
So, it seems like the answer depends on these parameters, and changing them slightly can make a big difference in the result.
Perhaps there are non-heating effects as well. There is not much energy in 800 nm photons to ionize anything, but perhaps there are some random coincident effects that can cause molecular damage. I don't know.
I remember we were not supposed to get our eyeballs too close to old TV sets due to x-rays emission or something like that but I don't remember warnings on any TVs.
I would be satisfied I suppose if Bill Gates stuck his eyeball up close to the Kinect system and stared at the (invisible) source for half an hour.
(A Sunday musing)
I find that Eric's suggestion is very honest indeed. Let's make petition on this blog?
ReplyDeletehttp://en.wikipedia.org/wiki/File:IEC60825_MPE_W_s.png
ReplyDeleteI think that the long time gaming should be taken into consideration too.
Bill Gates is out. Need to ask Steve Ballmer to do it. But he won't be able to sit still for 1/2 hour:
ReplyDeletehttp://www.youtube.com/watch?v=wvsboPUjrGc
OK understand. It's hard to target this guy a laser spot, so no danger at all.
ReplyDelete