Here is a simple challenge for you geoff ...
Go find a spectrum for the laser diode in a CD ... should be easy. Now look at that spectrum.
There is not visible red in the spectrum of the laser, and yes, that cheap laser diode, like all laser diodes are pretty much monochromatic unless designed otherwise. It is not a super sharp wavelength single mode, but even a dirt cheap multi-mode is monochromatic. There may be leakage in the 700-720nm, but it is almost none and would required a dark room to see. Many transports added a red diode inside the assembly to give people comfort "something" was happening. Since the optical detector is focused on the spot, minor stray light is not much of an issue. Look at the second half of this video and how hard it is for the person to even detect the CD laser: http://www.youtube.com/watch?v=Df70YVAg-iI
Many green inks will absorb 780nm. That proves nothing at all except that people who promote things like using green ink (as opposed to some other color) don’t understand much about absorption spectrum of dies and inks. Let’s not forget the optics are also focused, so most scattered light is rejected.
And you are wrong, almost all black inks will absorb 780nm. Again easily proven, just look up absorption spectrums of black inks and dyes. The "color-wheel" only tells you what happens when the light is visible. It tells you nothing about what happens to light on a colored substance when you use non-visible light. You are guessing at what happens and guessing wrong.
All the ad-hominems in the world will not change that You Are Wrong. You keep slinging ad-hominems, I will keep slinging verifiable facts. Let’s see who most people believe.
Go find a spectrum for the laser diode in a CD ... should be easy. Now look at that spectrum.
There is not visible red in the spectrum of the laser, and yes, that cheap laser diode, like all laser diodes are pretty much monochromatic unless designed otherwise. It is not a super sharp wavelength single mode, but even a dirt cheap multi-mode is monochromatic. There may be leakage in the 700-720nm, but it is almost none and would required a dark room to see. Many transports added a red diode inside the assembly to give people comfort "something" was happening. Since the optical detector is focused on the spot, minor stray light is not much of an issue. Look at the second half of this video and how hard it is for the person to even detect the CD laser: http://www.youtube.com/watch?v=Df70YVAg-iI
Many green inks will absorb 780nm. That proves nothing at all except that people who promote things like using green ink (as opposed to some other color) don’t understand much about absorption spectrum of dies and inks. Let’s not forget the optics are also focused, so most scattered light is rejected.
And you are wrong, almost all black inks will absorb 780nm. Again easily proven, just look up absorption spectrums of black inks and dyes. The "color-wheel" only tells you what happens when the light is visible. It tells you nothing about what happens to light on a colored substance when you use non-visible light. You are guessing at what happens and guessing wrong.
All the ad-hominems in the world will not change that You Are Wrong. You keep slinging ad-hominems, I will keep slinging verifiable facts. Let’s see who most people believe.