Virtual reality system with an optical position-sensing facility

A virtual reality system permanently connected with a device to be worn by a user, comprising:

• an optical position-sensing facility which comprises at least one radiation detector defining a fixed reference point in space;
• at least one optical transmitting system permanently connected with said device, said optical transmitting system comprising at least a first radiation source, a second radiation source, and a third radiation source whose optical axes, a first optical axis, a second optical axis, and a third optical axis respectively, are parallel to each other and, in a basic position, point at the at least one radiation detector;
• the first radiation source has an intensity pattern which has, in a first plane defined by the first optical axis, and by a first direction determined by the optical transmitting system, in a first angular range including the first optical axis, a rising/falling sensitivity characteristic which is essentially monotonic;
• the second radiation source has an intensity pattern which has, in a second plane defined by the second optical axis and by a second direction determined by the optical transmitting system, in a second angular range including the second optical axis, a rising/falling intensity characteristic which is essentially monotonic;
• and
• the third radiation source has a uniform intensity pattern which has, at least within the first and second angular ranges, an intensity characteristic which varies slowly in comparison with the intensity characteristic of the first or second radiation source.