Very low level LED observation

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.

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

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...

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.

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

Cheers

Phil Hobbs