In order to
count boarding and alighting passengers as accurately as possible, the IRMA
passenger counting system uses a sensor which includes a passive and an active
infrared component.
The
function of the
passive component
of the sensor is based on the principle that:
-
every person emits heat radiation which
results in a temperature difference compared to the environment. This heat
radiation (long-wave and infrared radiation) can be measured with pyro-electrical
detection devices. The special feature of these detection devices is that
they do not register the heat radiation itself, but its changes. A uniformly
heated floor, for example, will produce no signal at the detector output.
However, if there are abrupt changes in the heat radiation, the detector will
emit a corresponding signal. This abrupt heat change will occur when a person
passes the measuring range of the detector.
The function of the
active component
of the sensor is based upon the principle that:
-
each person partly reflects the
radiation hitting him or her (short-wave infrared radiation). The active
component in the sensor consists of a transmitter and a receiver. The
transmitter sends infrared light to the floor. This light beam is reflected by
persons crossing or staying within the measuring range of the sensor. Parts of
this reflected beam reach the receiver.
The signals of the passive
component and the active component caused by persons passing the measuring range
of the sensor will then together undergo a pattern analysis. Persons boarding
and alighting are detected and the counts stored separately for each door during
the counting procedure. The principle of analyzing motion patterns in the
infrared spectral range delivered the name of the system: IRMA = InfraRed
Motion Analyser
In this
procedure, any identification of persons is of course excluded.
