Low phosphor response or fast decay shouldn't be as much trouble if you can mount some UV LEDs inside the hood so they can be left on continuously during the shot, or right up to it if there's visible interference. If you use a color camera it should be blind to any true UV reflections - but not necessarily the "visible" part of deep blue or near-UV emission. These cameras usually have bandpass filters so the white balance won't be upset by UV or IR illumination. Some experimenting should be able to assess the camera response. If there's a problem it may be possible to cascade another white balance filter (since true color response isn't needed) to sharpen the passband edges, or a filter that will pass mostly the phosphor emission wavelengths but block the rest.
Ed
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--- In TekScopes@..., "Dennis Tillman" <dennis@...> wrote:
I did solve one problem with this little UV LED experiment: I now know how
to take a photo of the Wiltron 640 RF Analyzer CRT.
This instrument is built into a Tek 5000 series scope with a special purple
long persistence phosphor because the sweep speeds can sometimes be slow.
Before taking the photograph I 'paint' the CRT with the LED 4" to 6" away.
By waving the LED around with my hand I excite the long persistence phosphor
which glows in a purple-green color for >10 sec. As I wave the LED I can
easily see any spots I missed so it is quite simple to stimulate all of the
CRT to glow uniformly. The long persistence gives me plenty of time to hook
the scope camera hood over the bezel and snap the picture. The graticule is
plainly visible against the now faint purple-green glow.
This doesn't help me with the 577/D1 which has a different phosphor that
doesn't glow much or for very long with the LEDs I have tried so far.
Dennis
