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I/O Metric - the disc lost to time https://forum.lddb.com/viewtopic.php?f=14&t=10625	Page 1 of 1

Author:	greenlaser [ 18 Nov 2022, 03:07 ]
Post subject:	I/O Metric - the disc lost to time
I am reading "Revolutionary Technology: an introduction to the video and digital audio disc" by David K. Matthewson. I was surprised to learn about the following! In the mid-1970s, an American company called I/O Metric Corporation created videodiscs which could be reproduced photographically: Attachment: iometric1.jpg [ 498.96 KiB \| Viewed 937 times ] The author says it demonstrated all of the benefits that laser videodiscs have. However, the I/O Metric system vanished without a trace. I could only find one mention of I/O Metric Corporation on Google. They worked with the US NOAA in 1974 on an atmospheric analysis system. Has anyone heard of I/O Metric before?

Author:

greenlaser [ 01 Dec 2022, 20:06 ]

Post subject:

Re: I/O Metric - the disc lost to time

I found more information! The creators published an article in the Journal of the SMPTE, 1974. I was able to get a digital copy from a library. Here is what I know:

the master used ordinary silver halide film
duplication of the master could be done through simple contact printing
multiple layers could be sandwiched together for greater capacity (like DVD/Blu-Ray does)

for playback, the disc could be illuminated by white light (no laser needed)
the disc had ~7Mhz bandwidth. The limiting factor was how fast they could modulate their recording laser
a video signal could be recorded directly without using a carrier (no FM needed). They called this the "analog mode"

copies: a silver halide copy could be made by use of an internegative
alternatively, a diazo copy could be made directly, without an internegative.
"diazo materials are significantly less expensive than silver emulsions"
such copies were "essentially indistinguishable" from the master

at least 4-layer sandwich discs were possible (an micrograph shows a 4-layer disc)
both CAV and CLV recording were possible. One layer held 14.1 minutes of video at CAV. CLV "yields an increase in playing time of about a factor of two".
speculation: with four CAV layers, could you fit ~113 minutes on a disc? (14.1 * 2 * 4)

The claimed advantages of the system were "archival image quality, ease of duplication, and low cost".

Attachment:

recording.jpg [ 193.15 KiB | Viewed 865 times ]

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