Very Odd Question

DigitalDj

Ok here i go!

Can anyone tell me if a infared beam(like the ones used in a tv remote)·can be reflected off of a persons retna in your eye? If not, what can be used to reflect from the retna?

I would like to see some discussion on this.

Thanks,
Kevin
·

Newzed

You're playing on dangerous ground.· IR, Lasers, and UV can all damage the retina.· Also, when visible light strikes the eye, the pupil will contract-
the brighter the light the greater the contraction.· When your eye doctor wants to look at your retina, he dilates your eye so the puplil can not contract, and he uses a very, very high intensity light to provide retina reflection.· Whatever you're thinking of, Keven, I don't think I would pursue it.· Just a headlight is enough to reflect off of an animal's eye surface, but that's a long way from the retina.· If you want more advice, talk to a retinal specialist.

Sid

DigitalDj

What i want is to get a reflection, maybe the retna is to far back. What causes redeye in a picture from a flash, does this come from the retna?

Kevin

David B

When you look me in the eye you are seeing a reflection of the ambient light off whatever in my eye is reflective.

So just by looking at my eyeball you are already getting a reflection, at a harmless light level. Is that not good enough?

knightofoldcode

Kevin,

My dad is a optometrist, and I would have to say, this is some REALLY dangerous stuff that you are talking about.

Think about this.... You've had sunburns rights?..... Imagine that on the back of your eye.

There is something called a "Welder's Flash". This is caused by UV light, however it can occur without the person even knowing that it is occuring. They wake up to an extreme amount of pain. It's literally unbearable.... My office is right in the next room, and we live in a farming community, I've had many many times that I hear the men screaming in pain from the burns. And the worst part is there is NOTHING that can be done by the doctors to heal it. All that can be done is to have the eye doctor check to make sure nothing is in there. (Foreign particles) However that's all that can be done. When the doctor needs to examine the eye, the patient has his/her eye closed shut, SOLID because of the pain, and so the doctor puts a pain killer on the eye (yeah, how can they get it in if the eye is closed? The doctor drops a few drops on the outside of the eye and a small amount gets in, this dulls the pain, then they can open their eye, then he puts several more drops into the eyes, and does the examination) after the pain killer the doctor examines, and the pain is completly gone, however it returns in less than 10 minutes.... we've had LOTS of patients literally begging to take the drops home. It's a huge amount of pain.... but it does go away.... however with lasers the blindness will NOT go away... it's not painful...but it's also permanent....

I would NOT suggest emitting any form of light, UV, Laser, even normal, "white" light. A large amount of white light can be dangerous too, it's just that most people won't stare at it....*most*

I assume with this project you're considering some for of a "retina scanner"?... They use the method that David B said. They simply collect ambient light, they do NOT project aditional light. The gov. (at least in the US) won't allow any form of projection of light, so they must use normal light to collet the information. (Last I have heard, things may have changed)

In short, I'd scrap the idea. If you need security access consider RFID, fingerprinting, standard keys, barcodes, or keypad based security codes.

Knight.

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