System for compensatively correcting for displacements due to heat in machine tools

A correction system for compensatively correcting for thermal displacement in a machine tool of the type having a column, a main spindle head ascendably and descendably supported on the column, a main spindle rotatably supported on the main spindle head and having means for holding a machining tool, and a table for holding a workpiece to be machined by the tool, said correction system comprising:

• at least one light source mounted on the main spindle head in the vicinity of the main spindle and operating to emit diffused light;
• at least one lens mounted on the table in a state apart from and facing said at least one light source and functioning to receive said diffused light and to form an image of said at least one light source;
• at least one light point displacement detector for detecting a variation of a position of the light source image of said at least one light source and generating a corresponding detection signal;
• an amplifying circuit for amplifying said detection signal;
• and
• a control means operating to determine, from the signal thus amplified, any relative displacement of the table and the light source and, on the basis of said relative displacement, to correct the relative position of the table and the main spindle.