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Very low level LED observation

Last night I walked into room with lights off, just to grab something. Was alerted by a very faint flashing red light. VERY faint, switched on the light, could not see it. Light back off, turned out to be Chinese optical wireless mouse. About one flash per second.

Makes sense, this one (unlike some other one I have where you have to press a mouse button to wake it up) comes alive automagically.

But cannot see the light from my other logitech mouse... must be there though.

You have to wait about half a minute for the normal LED to switch to the faint mode.

Reply to
Jan Panteltje
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Depends on the mouse base proximity to a surface. Some will continually try to acquire positional info if near a surface. Turn it over (away from a surface)and watch how fast it sleeps. Same effect occurs eventually when zero movement on a reflected surface remains motion free. The determination and timeouts may differ.

Reply to
DecadentLinuxUserNumeroUno

It may be a healthy optical pulse, but very short. Get a photodiode and see!

Reply to
John Larkin

The mouse is typically a 256 pixel camera with illumination provided by the LED that you're seeing. When in standby, the LED produces a short pulse of light so that the camera can grab an image. If the previous image is the same as the current image, the mouse remains in standby. However, if something changes in the image, the mouse wakes up, the LED lights up full time, and the mouse begins to operate normally.

If you need entertainment value, try turning a mouse into a camera: etc...

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Reply to
Jeff Liebermann

Some IR diodes can be seen once your eyes adjust to low light, either because they're close to red or because they produce a little bit of red.

Pretty much anything can trigger your retina if it's powerful enough and aimed right at you.

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Reply to
Kevin McMurtrie

Scotopic vision is less sensitive in the deep red than photopic. The CIE scotopic curve at

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shows a peak at 504 nm, and by 700 nm it's down by a factor of 10**5. The normalized photopic response is 0.0041 at 700 nm. So night adaptation per se isn't relevant for seeing deep red LEDs. Your pupils do dilate in dim light, of course, which helps.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

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