I began my work on write-once-read-many (WORM) optical disk
technology on my first job out of graduate school in 1979. I had
joined 3M's Central Research Laboratories to develop a digital audio
system that could demonstrate the efficacy of the WORM optical disk
media and recording technology that 3M was pursuing. Digital audio
was a logical choice at the time because 3M had pioneered digital
mastering using magnetic tape media, and on top of that, the
industry was abuzz with anticipation of incredibly high-fidelity
recorded music on CD, still only a glimmer in the future.
3M had hired me for my experience with data communications and
error-correcting codes, both critical elements of digital audio and
optical recording. My immediate colleagues were electrical
engineers, physicists, thin-film and material scientists, and
microscopists. This multi-disciplinary group was working together to
produce 14" glass disks with optically-tuned thin films, and an
optical recorder on a test bench.
While I was concentrating on the digital audio system, the
engineer who was working on the servo systems for the recording
equipment moved on to another job, and I was assigned his
responsibilities. I did have an academic background in control
theory, but I had never planned to be a servo engineer. But there I
was. I continued to work with another logic designer on the digital
audio electronics and I still developed a few modules such as the
phase-locked loop, and the line encoder/decoder, but I began work on
the automatic focusing and tracking servos, neither of which worked
properly. I was fortunate to obtain a former University of Minnesota
professor, who was somewhat of a servo specialist, as a mentor on
the project. Eventually, we designed new analog electronics for
focusing and tracking, characterized the electro-optical-mechanical
sensors and actuators, and optimized the compensation using
theoretical models. We successfully demonstrated the system and
media to 3M's top management on schedule.
After our initial success, we upgraded our recording apparatus.
We designed a new very high-performance optical head, changed our
method of sensing focus, and designed an extremely high-gain focus
servo. Shortly thereafter, I moved on to another project, and left
optical recording for the time being.
Twelve years later, I received a call from one of my original
optical recording colleagues. He was working on rewritable
magneto-optical disks, but instead of working in a cramped
laboratory, he was working in a building dedicated to developing and
manufacturing optical disks. They needed an engineer to work on a
tester for a new generation of rewritable magneto-optical (MO)
disks. The beginnings of a tester existed: a rack of test equipment,
control electronics, and an optical bench with a motor-driven disk
mount. I worked on all aspects of the tester, laser diodes,
diffraction-limited laser optics, mechanical fixtures, servo
controls, and electronics development until I got the tester working
properly. Then I developed a suite of tests and wrote the software
to automate it so we could evaluate disks quickly. I tested disks,
analyzed test data, and made presentations to both my client's
management and my client's OEM customers. Of course, the end of the
project did come, as it always does, and once again I moved on.
But my optical disk work had not yet ended. Once again, my
optical disk colleagues asked me to work on a high-density optical
disk project that used flying optical heads. The heads, extremely
small, molded aspheric lenses integrated with magnetic-head-like
aerodynamics for flying close to a spinning surface, promised a much
smaller spot size and finer track pitch than conventional optical
heads. I converted the old tester I described above so it would work
with the flying heads. I also worked with a tester that was supplied
by my client's partner.
My work in optical disk technology has supplied me with an
incredible breadth of experience in control systems, analog and
digital electronics, software development, magnetics, mechanical
design, optics, lasers, and electro-optics. It also taught me how to
work in groups of vastly diverse backgrounds and it has demonstrated
the value of a thorough grounding in physics and mathematics.
