The Dutch engineer started working for Philips in 1952 and in 1960 he became head of the newly started product development department.
Two years later, he presented his groundbreaking invention.
Ottens was tired of the awkward tape recorders and wanted something small enough to fit a jacket pocket.
When the cassette tape was introduced to the outside world at a trade fair in Berlin in 1963, it was with the slogan "Less than a pack of cigarettes!".
In an interview with Time in connection with the cassette band's 50th anniversary, Ottens said that it was "a sensation from day one".
Liked the CD better
Lou Ottens was also involved in the work of producing the CD, but always emphasized that it was teamwork that was behind the two inventions.
However, he thought that the CD had far superior sound quality and was incomprehensible to the cassette band's increasing popularity in recent years.
- Nothing can match the CD sound.
It is absolutely noise and noise free.
It never works with a band, he said in an interview with the newspaper NRC.
New cassette scale
Despite this, sales of cassette tapes have increased and several artists, such as Lady Gaga and The Killers, have released their music on cassette.
What annoyed Lou Otten the most was that it was arch-rival Sony and not Philips who was first with the portable cassette player.
- It still hurts, he said in an interview after retirement in 1986.