Medium having photographically recorded digital audio bits

DETAILED DESCRIPTION The invention is a medium (such as motion picture film) having digital audio signals photographically recorded thereon.
The medium can be motion picture film.
Multiple, photographically recorded digital and analog audio soundtracks on the medium can be read by employing a photosensitive detector array (such as a CCD array) for each of the digital audio soundtrack areas, and a separate means for reading the analog soundtrack (or soundtracks).
In a preferred embodiment of the invention, digital error detection and correction bits are recorded in a digital soundtrack area of the medium (along with digital audio bits), and error detection and correction are performed on the recorded digital audio bits read from the medium.
Preferably, the inventive apparatus includes a means for substituting a corresponding analog signal for one or more corrupted digital soundtrack channels, when one or more digital soundtrack channels have an error rate which exceeds a selected threshold.
In a class of preferred embodiments of the invention, recorded digital audio information is read by projecting a laser beam (preferably having a near infrared wavelength) on a row of a digital soundtrack area (of a motion picture film), to modulate the beam as it passes through the row.
The modulated beam is then expanded by a lens system (to increase its waist dimension) and the expanded, modulated beam is projected on a photosensitive detector array.
Use of laser radiation for this purpose has substantial optical benefits over use of incandescent lamp radiation, including longer source lifetime, and greater uniformity, stability, and reliability.
If a single laser beam is employed to illuminate two or more spatially separated digital soundtrack areas, optical elements are employed to split the beam and direct each beam portion from one of the digital soundtrack areas to a different detector array.
In a preferred embodiment, the radiation transmitted through each bit area of a digital soundtrack area is projected onto a spot (in the detector plane) that is substantially larger than the dimension of each individual detector which receives the radiation (the "receiving" detector)