| Victor Roberts 2008-01-17, 3:25 am |
| On Thu, 17 Jan 2008 03:18:19 +0200, "I.N. Galidakis"
<morpheus@olympus.mons> wrote:
>Victor Roberts wrote:
>[snip]
>
>
>and also in another post:
>
>
>Let me see if I can use the above to demonstrate mathematically that there
>exists at least one kind of CFL which does not flicker.
>
>Count the original oscillator in both the above cases as ONE, and the video FPS
>rate as TWO. Vic, above, effectively says that we always have _some_ ripple even
>in the best possible cases and hence some light flicker. Therefore, when we
>video any (even so slightly) flickering light source, we effectively have two
>coupled oscillators, so the effects can be analyzed mathematically.
>
>It turns out that the slower oscillator (which in this case is the video)
>"captures" the behavior of the fastest one:
>
>http://ioannis.virtualcomposer2000.com/math/video.html
>
>For those who wish to forgo with the math, the above simply means that:
>
>"If there's light oscillation, then it shows on video. Hence, if nothing shows
>on video, there's no light oscillation".
>
>If, without loss of generality we try the above analysis for some ridiculously
>high value of light oscillation, say 67361 Hz or 67.3 kHz, the resulting
>Diophantine equation gives:
>
>k=33680+67361*n
>j=40+80*n.
>
>Let's pick j, which is easier. The first "flickering" ripple on the video should
>occur at 2*(40+80)/80 secs = 3 secs. The second flickering ripple on the video
>should occur at 2*(40+80*2)/80=5 secs. This means that if the light was
>oscillating at 67.361kHz, the video would have shown flickering ripples with a
>time amplitude of 2 seconds.
>
>Since the video of the CFL is much longer than 2-3 seconds, it follows that a
>high light oscillating frequency at least up to 67.361 kHz is not likely.
>
>Adjust the equation per your preferences, adding mayo and jalapeno peppers. I
>suppose I could solve the problem backwards and try to find what is the maximum
>oscillation frequency whose video ripple amplitude is larger than a minute worth
>of video, but it's a little late now and I need to pass to the other dimension
>for some rest.
>
>(Sorry about having the videos on QuickTime format, but that's my camera's
>capture mode and as I said, I am a little tired right now. For those who don't
>know about it, QuickTime is a free download from Apple).
>
>Anyone who disagrees with the above conclusion, please raise your hand... ;o)
I raise my hand in objection.
Instead of your complicated arrangement I just connect an
optical detector to my oscilloscope and point it at a CFL.
If the trace on the oscilloscope shows modulation, then the
CFL light output is modulated.
I've attached a trace of a CFL with small amount of 120
modulation of the light output. The zero level is about 1
division from the bottom of the screen, at the arrow marker.
--
Vic Roberts
http://www.RobertsResearchInc.com
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