Patent ID: 8781687

Claim:
A security system comprising: a sensor module ( 15 ) comprising at least one laser sensor ( 10 ) working with self-mixing interference, the laser sensor having a Rayleigh range; at least one optical element for focusing light; a control circuit ( 30 ) and security means; wherein the sensor module ( 15 ) comprises means to generate first measurement data which are directly or indirectly related to at least one first velocity component of an object ( 400 , 351 , 700 ) relative to the sensor module ( 15 ), and wherein the control circuit ( 30 ) comprises means to receive the first measurement data generated by the sensor module ( 15 ) and to activate the security means in dependence upon the first measurement data received from the sensor module as soon as the first measurement data exceeds a defined first threshold value; wherein the laser sensor ( 10 ) in combination with the at least one optical element has a focal region ( 12 ) between the optical element and the object, and the distance between the focal region ( 12 ) and the object is greater than one Rayleigh range.