|
|
It was difficult to make. We tried optical methods but finished up using the oscilloscope.
|
|
A sinusoidal voltage was produced by a very low- frequency mechano-opto-electrical signal generator (a disc with an appropriately shaped mask that was rotated by a variable speed motor so that the amount of light falling on a photo-cell varied sinusoidally in time) and a device that charged a capacitor to the appropriate value at the beginning of each line-scan sweep and let it discharge exponentially during the sweep. It was all done at very low frequencies. The line frequency was about 100Hz and the frame duration at least 30 seconds. The signal generator had no sweep capability so one of us slowly turned the frequency knob during the 30+ seconds frame time as the other called out the frequency appropriate to how far the scan line had got across the screen.
|
|
It worked surprisingly well and we made a number of photographic prints about 3x4 inches that we gave out at our next presentation.
|
