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Re: Anybody with an oscilloscope as an Apple II display?
Charlie Springer wrote:
On Tue, 1 Apr 2008 12:52:56 -0700, Michael J. Mahon wrote
(in article <07CdnQbALc4HD2_anZ2dnUVZ_oOnnZ2d@comcast.com>):
Fun with scopes is probably what led me to interactive graphics
as my first excursion into interactive computer programs (around
1964). The graphical capabilities of the Apple II were one of
its strongest attractions to me in 1980.
Micheal, you may not be aware, but Jef Raskin's thesis from 1967 is entitles
"QuickDraw, A graphical computer interface". I think I have it right.
I've been curious about his thesis, but haven't yet found it.
I was strongly influenced by Ivan Sutherland's Sketchpad--it led me
to think seriously about how many data reduction problems could be made
easier and more effective if the experimenter were placed in interactive
contact with his data in manipulable graphical form.
Subsequently, I saw Glen Culler's amazing graphical programming system
at the University of Santa Barbara, and was hooked on graphics for life.
People have largely forgotten about the history of computer developments
and the people who changed the way we use them.
I remember the first time I used a phototransistor to drive the vertical on a
scope and the weird stuff I got when I placed it near or against the scope
display, especially when the trace was set very slow, like a second or more.
If I had seen it as other than a novelty I might have invented the light pen.
Yes, I did similar experiments with a 931A photomultiplier tube around
1954. I had the photomultiplier tube "viewing" the scope trace in a
darkened room, and was displaying the output of the photomultiplier
on the vertical axis. As I moved my finger in front of the scope,
it would "push down" the trace so that the outline followed my
fingertip! Great fun!
When the photomultiplier was pointed toward an operating TV, the
video waveform was visible on the scope, and could be displayed
(with some smearing) on another monitor. This same approach, when
used with a telescope, can be used to see what TV shows are on in
nearby houses, even if the light from the screen is only indirect!
This led me to some very interesting flying-spot scanner experiments,
culminating in a very simple, medium-resolution slow-scan TV system
with video frequencies in the audio range.
Of course, it won't work unless the display is raster-scanned.
LCDs and plasma displays won't reproduce the video, though the
global brightness/color changes can be easily correlated to the
channel being watched.
BTW, you may have been a little late for the light pen, since the
first use of a light-sensitive device (a light "gun") that I know
of was developed in the 1950s (using a photomultiplier) to designate
targets on a computer-driven radar scope. It was the SAGE system,
running on IBM's AN/FSQ-7, IIRC.
-michael
NadaPong: Network game demo for Apple II computers!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
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