Re: fun things to try / laser pen questions

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Thu, 14 Nov 1996 17:25:43 -0600
>From: P3D Gabriel Jacob <jacob@xxxxxxxxxxxxxx>
>Subject: Re:  fun things to try / laser pen questions

>John W Roberts writes
>>anyone know the spectral sensitivity of typical consumer CCD video cameras?)

>The CCD sensor in consumer video cameras are sensitive past the sensitivity
>range of the human eye. For most people, the threshold of visible light is
>in the region of 720nm. CCD in video cams peak at around 960nm but
>manufacters usually put in a infrared filter to block it. My guess it won't
>allow radiant energy past the 700nm wavelength, which is where infrared
>region begins. 

Thanks.

Since you posted that, I came across an ad for 780nm IR laser diodes, which
claims "highly visible to CCD cameras".

I've noticed that in some videotapes of lectures where a laser pointer is
used, the spot is very hard to see. Maybe that's because of the encoding
NTSC uses to represent color, or maybe the pointer just wasn't very bright.

John R


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