Contrast adjustment system for a display device

A contrast adjustment system (100) for a display device of a watch (10) including a case (12) which is configured to be removably arranged in a thermal protection housing (1) for mechanical and/or functional components (5) of said watch (10), the system (100) comprising:

• said housing (1), comprising:
• an enclosure (4) for thermally protecting the mechanical and/or functional components (5) of said watch (10), said enclosure (4) being formed by functional elements (15) of this housing (1), these elements (15) comprising a middle (9a), a back (9b) and a crystal (6) including a device (7) for dynamically varying the brightness on a visible face of the display device;
• a fastening device (13) fastening said case (12) of the watch (10) in said enclosure (4) while keeping the case away from the functional elements (15);
• a control unit (8) connected to the dynamic brightness variation device (7) of the crystal (6), said control unit (8) comprising event sensors (25) capable of causing a variation in the ambient brightness in an environment of the housing;
• the watch (10) comprising the display device and the case (12) capable of being removably arranged in said enclosure (4) with the display device facing the crystal (6) of said housing (1);
• an electronic device (110) configured to contribute, alongside the control unit (8) provided with its sensors (25), to controlling the dynamic brightness variation device (7) so as to adjust a contrast of the display device.