Method for individual measurement of the temperature of a preform

A method for measuring the temperature of a preform in an installation for manufacturing containers by forming preforms made of a thermoplastic material comprising:

• moving the preforms continuously in a line along a production path using a device;
• heating the preforms in a station which is passed through by the production path;
• contactlessly measuring the temperature of a part of the preforms using a device comprising a sensor which sensor measures the temperature of the preforms running continuously over a measurement section of the production path, the device and sensor thereof remaining spaced a distance from the preforms without making contact therewith as they move along the production path;
• wherein the measurement device is equipped with a convergent optical device which allows an image of the sensor to be projected in a measurement direction Y in a zone for measuring the temperature of each of the preforms, the measurement zone having a section of dimensions smaller than the outer diameter of the part of the preform to be measured in order to individually and successively measure the temperature of each preform.