phenomena needs explaining?

IR diode flashing..?

it is new phyiscal phenomena to me that when I press any Remote Control
Keys the IR diode will radiate invisible radiation (light).but,When I Use my
mobile phone camera the flashing radiation will be seen .

my question
why I couldn't see that with my bare eye ,but I did throug mobile phone camer?
what make my camera see more spectrum than me?

Re: IR diode flashing..?

Cameras are quite sensitive to infrared beams and therefore they have IR filters installed just in front of the pick-up device (CCD, for example) ..
It looks like your mobile phone camera doesn't have such a filter, or, if it has, it is not very good one ..
Regards,
IanP

is it not hard to believe that CCD sensor chip has better sensitivity at longer wavelengths, is it?

The remote control emits "near infrared" light that is slighly beyond the wavelength limit of your eye. However, CCD and CMOS image sensors (such as the one in your camera) are somewhat sensitive to that wavelength. More expensive digital cameras normally include an IR blocking filter, because the lens usually focuses differently at IR, so it's best to block that light.

Question is why we see flickering in the picture when remote is activated. Theotetically we should not see it. It is in infrared spectrum.
Remote IF light is strong enough to modulate or saturate CCD. So we can see intermodulation products os simply result of overloading CCD which produces white light.

I think that the scanning rate of the camera is much faster than that of the human eye, so when you look through the camera, you will see thing scanned with a faster rate.

Try to get the camera and look to the TV through it, you wil see horizontal lines scanning the screen.

The scanning rate of the human eye I'm certain is much much higher than that of a CCD or CMOS camera. I can personally see flicker on a CRT monitor (mostly at my peripheral vision) at 60hz and even 75hz possibly slightly higher but I've never tested. I know CMOS can't match that scan rate and CCD's are almost completly phase out of digital camera's nowdays. Also, the IR filters on even the most expensive digital cameras still can't block ALL of it, even on those you're likley to see some degree of exposure on a remote control, depending on exposure time and other ambient lightning. I have a friend that had his camera dismantled and the IR filter removed in order to do near IR photography (look it up it makes some beautiful pictures of outdoor scenes) And being able to see the scan lines on a TV through a camera is because the scan rate of the camera is both slower and out of sync with the TV's refresh rate. Persistence of vision in the human eye reduces that flicker to the point where its all but invisible. I can't see flicker on a TV even in my peripheral visiont even though it's at 60hz because it's a moving image as opposed to a PC image which is static, the 'flicker' on a TV isn't normally noticeable because the eye is too busy processing incredible amount of information it's being flooded with to notice a simple desync.

Another thing is that IR remote transmit light bursts with repetition frequency about 35kHz. Scanning rates of CCD module and light bursts frequency produces interference which we see as flickering.
The reason why we can see it at all is in the CCD module nonlinearities and maybe saturation or in the way the colours are analyzed and reproduced.