hye guys, this is my final year proj. and indeed i need help from all the expertise out here do help me ya

Proj. Description:
im trying to used infrared emitter (SFH485) and receiver (SFH229FA). The detector is expected to detect the difference of light intensity that comes from the condition of eyelid either in opened or closed condition.

When the eyes closed for more than 2 seconds, a buzzer is expected to be activated to warn the driver that he/ she is in fatigue mode. For this time being, i need to build 3 circuits which are the voltage regulator to ensure 5v is being supply to the eye blink sensor, then the eye blink detector circuit and the buzzer circuit. I hope u people can help me to succesfully build up this proj.

It is expected to be build at the temple of commersial spectacles so that it can be worn by all users

 

The detector is expected to detect the difference of light intensity that comes from the condition of eyelid either in opened or closed condition.

How will you do the sensing, and how will you compensate for darkness broken by approaching headlights, or saturated illumination caused by driving into rising/setting sun?

 

A can offere two suggestion for the implementation.

1. Use a two BJT transistor current mirror to convert the photo-diode current to voltage.

2. Use a pulse to drive the IR emitter and set the receiver up to look for pulses rather than a constant light output level.

hgmjr

 

Where is the "Temple of Commercial Spectacles" Sounds like a cool place.

I wonder how bad this could be for people who have had cataract surgery and can now see IR.

Actually some people CAN see IR. And if you are shining it in there eyes whilst driving, it may not be a good thing.

 

It's probably a good idea to have a check around to see how dangerous IR is to healthy eyes. I think at high powers it is a pretty bad idea. Presumably there is some level considered safe. At the very least try to keep the current down as much as possible.

 

I thnk what Mark is saying is that even if we can't SEE the photons of the energy of the level IR transmitters, the photon's still hit our eyes. Don't have to see the light to go blind, or be distracted, a bulk photon stream even of the wrong frequency hitting our eyes will desensitize the cells of our eye site from the photons they're sensitive too. It's much like a basic RF receiever, even the bulk radiation of non sensitive frequencies can still massivly swamp a local receiver even if it's tuned.

 

I think a sample rate of 2 to 5 Hz will be fine.

I think a flash of IR only about 50 microseconds will be unnoticed by the driver.

It would be so momentary that you could use a bright enough LED so that ambient light conditions are not an issue.

Test it yourself first just to make sure you will honestly try not to overdo it.
Do some eye tests before and immediately after use -testing night vision which is where it would have the most effect.

I think that you could even flash alternate eyes to further reduce the flash bulb effect and any limited eyestrain.

So you flash your LED and the Photosensor collects a strength signal. Scope that signal with eyes open and closed and tell us what you see so we can decide what you need to do next.

Pretty simple first steps are just create your LED flashers, and test them out for eyestrain. Then bias up the photosensor and scope what the flashes look like in particular the difference between open and closed and several different users.

 

I suspect that after seeing the photosensor response you will realize that you have too much flash and turn down your LED currents. If open and closed eyes both give you a max signal in the photosensor then you have way too much flash. This is another reason why I DOUBT that the Infrared signal will be a danger if this is done right because I expect the photosensor will be much more sensitive than our eyes and need very little IR power for these measurements.

Safety first so assume I am wrong and treat the dangers with extreme caution. Permanent eye damage is a possibility with only a small mistake.

 

I agree with those who counsel researching the potential of adverse impact on the user's eyesight from the IR light.

At the same time I can imagine that the light can and should be directed at an oblique angle with the eye. It is afterall intended to reflect off the surface of the eye and is interrupted when the eyelid drops down.

hgmjr

 

I wonder how eye make-up (eyeliner, eye shadow) will affect the reflection.

I get some oily eyelids. So you would think that would give a good reflection, but a matte made-up eyelid could cause different responses.

There would need to be some sort of self-calibration routine.. Like taking the high and low samples over 30 seconds or so. That way the uC would know how THAT eyelid at THAT particular time of day responds to the sensor.

Take 30 seconds of samples and analyze the results. find the mean, then average the samples below the mean and average the samples above the mean.

That should give you average eye-open and eye-shut levels.

 

One thing that would mediate any damage would be to use narrow short duration pulses. With a duty cycle of 1% or less any adverse impact would likey be avoided. The IRLED need not be pulse more than a couple of times a second to permit detection of a closed lid.

retched, you have a good point about the possibility that makeup applied to the eyelid could interfere with the normal reflectivity of the eyelid and so affect the sensitivity of the system.

hgmjr

 

Question: doesn't the light intensity sensor need to be focused in a relatively narrow area around the eyes? If so, how will you guarantee that the sensor will be targeted correctly, since the height and the driving stance of a driver can greatly vary?

 

It is going to be attached to a pair of glasses.

But you still have a good point.. What about eyelid shape? Asians, bug-eyed caucasians, non-bug-eyed caucasians, bug-eyed or non bug-eyed-Latin, black, purple, polka-doted...etc..

 

What about Grays? It would be horrible if they fell asleep and crashed their flying saucer.
I hope they have their own version of AAA.

 

There are already similar devices in the market for keeping drivers from falling asleep at the wheel, one particular one clips on to the ear like a bluetooth headset, then when the driver starts to "nod" off, an alarm goes off to "wake" them... >>> http://www.napzapper.biz/

 

I'm not sure how significant the various problems mentioned with regards to hitting the eye with IR light. Certainly, higher power is a danger, but perhaps very low power will not be an issue. If it turns out to be a problem, then commercially available 1550 nm LEDs/Lasers, used for fiber optic communications, are an option. This wavelength is considered an eyesafe wavelength as long as the power levels are low, and this application can use very low power. The light will basically be absorbed by water on the surface of the eye, before entering the eye itself.

An important concern is to use very low power, and it's best to use all methods of maximizing sensitivity of the optical receiver. Optical filters and a modulation scheme are a must because headlights or sun will occationally hit the eyelid. Initial feasibility testing does not need to solve all problems, but it's a good idea to identify as many problems as possible and to have possible solutions available.

 

The light will basically be absorbed by water on the surface of the eye, before entering the eye itself.

That might create a problem. If the IR is absorbed, how do you tell open lids from closed? Will the IR reflect from a closed lid?

 

That might create a problem. If the IR is absorbed, how do you tell open lids from closed? Will the IR reflect from a closed lid?

Good point, it might indeed be a problem. For sure, there would need to be a difference in reflection/scattering between an open and closed eyelid. Personally, I don't know how the closed eyelid (or skin in general) behaves at 1550 nm. There is a possiblity that the idea could work, since skin is dry and maybe oily, typically. There are issues of sweating and crying too.

Keep in mind that even with absorption inside the medium, it is possible that the air/water interface can reflect a small percentage of light. One would need to calculate the reflection coefficient using complex permitivity of water at 1550 nm. One thing which gives some hope here is that 1550 nm is not exactly at the water absorption peak. Hence, the loss may be low enough to allow sufficient reflection, but would still be high enough to attenuate the transmitted light in the thin layer of tears and tissue.

The main benefit of eyesafe wavelengths is that they do not enter the eye and hit the sensitive retina. So, even with the additional research work and higher product cost, it may be the preferred approach in the end.

 

This is why I think an auto-calibrate function would have to be done every time they put them on.

Thing is, if you get out of an air conditioned office/home/whatever and get into a car, and decide not to use the AC, when you start driving, alls good. Eyelids are dry. but as you sweat (Its hit 106deg F here today) and the reflectivity of your eyelids change.

So if the initial calibration was done when you first got in the car, the conditions would change, in a few minutes.

This could lead to false triggering, or non-triggering.

 

I sort of expected a constant recalibration to be bult into the system.

It might be based on the last 100 or so samples.