When Did The First Compact Disc Come Out –  Origin of the Compact Disc! The compact disc is popularly known as CD ( Compact Disc ). It is a revolutionary invention that allows you to store data digitally (photos, music, videos or documents). Its reproduction fidelity spelled the end of the analog age. At concordant-thought.com, we explain the origin and history of the Compact Disc and also who invented it.

1. Who Invented the Compact Disc
2. Origin of the compact disc
3. End of the analog age
4. Start of the digital age
5. How to read a compact disc

Who Invented the Compact Disc

In March 1979 , the presentation to the press of the first compact disc by the Philips company represents the result of almost twenty years of research in the field of electronic optics .

when was the compact disc invented?

The CD is the result of the work of many years of a large group of engineers. They got this digital recording and playback system based on the early studies of American scientist James Russel.

Origin of the compact disc

The compact disc is a direct evolution of the LaserDisc. However, studies on the laser-readable disc are not the property of the Dutch firm Philips. Starting in the late 1970s, the Japanese companies Sony and JVC developed models of audiumeric discs derived from videodisc systems perfected in 1972.

This is how, in August 1980, Philips and Sony signed an agreement on the common standards that they will adopt for the development of the compact disc and its reader. A group of engineers is created led by Toshinada Doi (Sony) and Kees Schouhamer Immik (Phillips).

what is the origin of the compact disc?

One year later, Philips / Sony audio-numeric disc and player licenses are purchased by some 40 companies, demonstrating the success of the new process.

• In less than ten years, from its introduction, the compact disc has definitely replaced the vinyl record.
• Even without taking into account its ability to not wear out (it does not scratch, it is not sensitive to dust or stains).
• CD represents an increase of more than 30 dB in dynamics, a harmonic distortion of only 0.0004% at 1 kHz (against 1 to 2% of the classic record), and a band that increases from 20 Hz to 20 kHz 0.5 dB (against 30 Hz- 20 kHz 2 dB). These figures speak volumes: the numerical sound ended the analog era.

End of the analog age

The revolution brought by the compact disc in the field of sound recording, storage and reproduction obviously causes a massive turn of manufacturers towards this new technology.

Indeed, since Edison’s invention of the phonograph in 1376, audio equipment has evolved very little. It remains of the analog type, that is, a physical quantity is made to correspond to a similar one (in this case the sound wave) by means of transducer devices. Like the microphone, the reading diamond, and the speaker.

• Thus, in the case of an electrical recording, when the sound wave, which is a mechanical vibration of the air, reaches the membrane of a microphone, it causes a displacement of the membrane that corresponds to the acoustic pressure acting on it.
• This displacement is transformed into electrical vibrations that correspond to the movement of the membrane.
• Then, when these electrical vibrations are used to stimulate the burin that etches the record, the resulting groove remains, after all these intermediate stages, a function of the sound wave from the beginning.
• Sound restitution takes the reverse analogue path: the displacement of the diamond over the groove causes an electrical vibration that, after amplification, causes the displacement of the membrane of a loudspeaker and the reproduction of the original acoustic wave.

The circle is closed but, of course, for the analogy to be perfect, the equipment must not have any distortion to restore the purest sound wave, which never happens.

Start of the digital age

In compact disc technology, everything changes. The analog treatment of the signal is put aside in favor of a numerical treatment. For this, the sequence of pulses caused by the sound signal is used and it is divided into “samples”, that is, instants separated by equal time periods.

Each sample is compared with reference pulses and numerically coded by computer (at a rate of 44,100 operations per second) according to the value of the closest reference pulse.

1. The encoding is done in binary form , by sequences of “0” and “1”. The extremely faithful reproduction that is sought requires a large number of reference pulses.
2. In 16-bit systems, 65,536 of them are counted, allowing for highly accurate numerical matching of the sound sample – the tiniest subtleties of timbre, pitch, and amplitude are captured and numerically encoded during sound recording.
3. In addition, an error correction system ensures, at the time of reading, a rectification of any defects ( drop-out ).
4. origin and history of the compact disc
   The numerical information obtained is laser engraved on a matrix, from which the disk itself is engraved.
5. It is in the form of a series of oblong, microscopic cavities that correspond to 0 in binary language, separated by flat spaces that correspond to 1.

The microcavities are arranged in a spiral with a very narrow pitch (1.6 thousandths of a millimeter), embedded in the disk, its width is 0.5 thousandths of a millimeter, its depth 0.1 thousandths of a millimeter, and its length varies according to the amount of information that contains, the same as for the intermediate spaces.

How to read a compact disc

The information is read by a laser that travels the surface of the disk from the inside out, the reverse of the microgroove. With a speed that progressively goes from 200 to 500 revolutions per minute to ensure a constant parade speed.

The laser is the only light source with a fairly cohesive and steerable light beam. In order to be able to accurately explore the microscopic surface of the cavity (the diameter of the light point is, after refraction, 1.7 thousandth of a millimeter).

The laser beam is reflected more or less brightly as it passes over a microcavity or a smooth space. Thus signaling the presence of one or a series of “0” or “1”. This differential reflection of the beam is then reflected onto a photoelectric cell that transforms it into a series of electrical pulses.

These are decoded by microelectronic circuits and sent to the amplifier, which then follows the same classic analog scheme.

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