A system and method (10) for heating objects (O) during a thermal treatment process in a production line (P) is described. The system (10) comprises a transport system (11), a mirror arrangement (201, 202, 203, 204, 205, 206) comprising a first mirror surface (21, 21', 21'') and a second mirror surface (22, 22', 22'') arranged at opposite sides, so that the objects (0) may be transported between the mirror surfaces (21, 22, 21', 22', 21'', 22'') along the production line and a radiation device (30) comprising a number of lasers for generating light (L). The radiation device (30) and the mirror arrangement (201, 202, 203, 204, 205, 206) are constructed such that the main direction (R) of light (L) that enters the mirror arrangement (201, 202, 203, 204, 205, 206) is directed towards the first mirror surface (21, 21', 21'') at an angle to the production line (P), and the light (L) subsequently undergoes multiple reflections between the mirror surfaces (21, 22, 21', 22', 21'', 22'') so that a series of multiple reflections of the light (L) travels in the transport direction (OT) along at least a section of the mirror surface (21, 22, 21', 22', 21'', 22'') or travels against the transport direction (OT) along at least a section of the mirror surface (21, 22, 21', 22', 21'', 22'') and heats the objects (0) being transported between the mirror surfaces (21, 22, 21', 22', 21'', 22'').