My first impressions - and some info...

Started Jul 28, 2001 | Discussions thread
OP Wayne DeWitt Senior Member • Posts: 1,259
Re: Some moer info...

Hi Bryan,

I had come to the same conclusion as you did. What I didn't understand is that the EVF turns off when I turn on the flashlight. An I.R. proximity sensor alone should not have behaved that way.


Bryan Biggers wrote:
Hi Wayne,

The way that these sensors work is that there is an IR emitter and
sensor pair. Probably the emitter is behind one of the little
windows to the right of the EVF, the sensor behind the other. When
an IR reflective object approaches (and just about everything
relfects near IR, which is why even glasses work), some of the
light from the emitter is reflected into the sensor. The reason
that the flashlight worked is probably just because it too
reflected some IR. The actual light emitted is probably a pattern
of pulses so that ambient IR does not trigger the EVF. Just cheap
stuff, the same as you might find in an IR TV remote control.

And for the people who asked about the nature of the proximity
sensor for the EVF I have a puzzling observation. It turns on the
EVF when an object is about 2" away from the eyepiece. I placed a
flashlight (torch to some of you) up against the eyepiece, the EVF
came on. When I switched the flashlight on the EVF went off. Think
you got it? Think again! I then passed my eyeglasses in front of
the sensors (there are 2 windows), the EVF turns on when my glasses
are held in front of the sensors (without my head being in them).
It also turned on when I passed transparent cellophane in front of
them. Very curious indeed. Could they have gone to the trouble of
haveing a proximity sensor AND a light sensor incorporated? The
dual-window setup would lead me to believe that it's a proximity
sensor. But then the question is how is it accomplished? I.R.
radiation? If it's a specific band it may reflect off of the glass
and the cellophane the same as it would off of your face. Wouldn't
explain the flashlight reaction though.

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