You can freely build on How James Russell Invented the Digital Optical Disc

What this patent covers

This patent describes a system that converts analog audio signals into digital data and encodes them onto a light-sensitive photographic disc. During playback, a light source scans the disc, and a detector converts the reflected light pulses back into an electrical signal. This process eliminates the physical contact between a needle and a record, preventing the wear and tear that degrades sound quality over time. By using digital encoding, the system ensures that the audio signal can be perfectly reconstructed without the noise or distortion inherent in analog playback.

What is now free to use

All 0 claims of US 3501586 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover magnetic tape recording or playback systems.

• Does not cover the specific error-correction algorithms used in later commercial CDs.

• Does not cover non-optical storage media like hard disk drives.

• Does not cover the physical manufacturing process of mass-producing consumer CDs.

Who is building on this today

Companies like Sony and Philips eventually refined and commercialized this concept into the CD standard. Today, while optical storage is declining in favor of flash memory and cloud storage, the core principles of digital optical scanning remain a foundation for high-density data archival.

Products built on expired version of this technology

How to cite this patent in your documentation

Battelle Development Corp. US Patent 3501586. Analog to digital to optical photographic recording and playback system. Granted 1970, expired 1987. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.