Patent ID: 7061001

Claim:
A method for automatically determining whether a photosensor in an apparatus is operational, the photosensor comprising a light emitter and a light detector, wherein when the photosensor is operational, the light emitter is capable of producing light for illuminating the light detector in response to a current applied to the light emitter; and the light detector has an output voltage indicative of the applied current to the light emitter, wherein the output voltage of the light detector falls in a first predetermined voltage range (ΔV1) when the applied current is substantially equal to a first current value (I — 0); and the output voltage of the light detector fails in a second predetermined voltage range (ΔV2) lower than the first predetermined voltage range when the applied current is substantially equal to a second current value, (I_nom), and wherein the apparatus comprises: a control module, adapted to provide a data signal indicative of the output voltage of the light detector, said method comprising the steps of: conveying a request signal to the control module for causing the control module to provide the data signal; measuring the output voltage of the light detector based on the data signal, when the applied current is set to one of the first and second current values, for obtaining a measured voltage value, and determining whether the measured voltage value falls in the corresponding predetermined voltage range, thereby indicating that the photosensor is operational.