Apparatus and method for temperature measurement by radiation

An apparatus for measuring the temperature of an object by thermal radiation, said apparatus comprising:

• a thermal radiation sensor for receiving radiation from said object;
• shutter means adapted for reversible interruption of said radiation from said object to said sensor,
• electrically operated means forming an integral part of a portion of said shutter means for maintaining said portion of said shutter means at a predetermined temperature for comprising a thermal reference portion for said sensor,
• means for alternatively exposing said thermal radiation sensor to radiation from said object and to radiation from said thermal reference portion of said shutter means,
• said thermal radiation sensor also being for providing a first signal representative of the radiation it receives from said object, and a second signal representative of the radiation it receives from said portion,
• electronic circuit means connected to said sensor for receiving said first signal and said second signal, for calculating the temperature of said object, and for providing a signal representative of said calculated temperature.