Please image a CD-R or CD-RW
What's the white stuff on top of the needle? Some of it seems to be moving (or getting lighter?) from frame-to-frame about halfway up the part of the arm that's in focus, on each side.
Beneficial, the needle support arm is aluminum, but heavily corroded and covered with dust and debris (it was a used phonograph stylus). The dust is a good insulator and became charged inside the SEM, making it appear bright and dark, and distorting the electron beam. I coated the arm with conductive carbon glue, but some of the dirt is still present, showing the weird time-dependent charging effect.
Thank you so much for taking your time to create this. I wish I had the discipline to go back to school and learn electronics.
Interesting to see the RCA VideoDisc. I worked on that project for several years during my tenure at RCA Labs in Princeton. If I remember there were about 10,000 grooves per radial inch. The stylus was a small diamond bar about .025 square. The stylus had a prow like angled part that rode in the groove. The faceted prow had many different angles and each facet was ground. The grinding was done by playing the roughly shaped needed in a record groove that had a certain signal which in turn produced a particular shape on the needle tip. So, through a succession of varying signals the various angled facets were formed on the tip. Of course, this facet geometry was on the order of 2-8 microns (if I remember correctly). I remember talking to a RCA VideoDisc bigwig about laser technology and he just laughed saying there would never be a consumer product with a dangerous laser beam inside. I suppose he didn't know that another group in RCA Labs had been working on mini semiconductor lasers for a few years by then. I really enjoy your work, Ben. Jim Anders - firstname.lastname@example.org
Thanks! It's great to hear from an engineer involved with the VideoDisc. It's really an impressive mechanical system.