Light transmitting display system, image output method thereof and processing device thereof

A light transmitting display system, an image output method thereof and a processing device thereof are provided. The light transmitting display device is located between a background object and a user. The image output method includes the following steps. The locations of the user, the light transmitting display device and the background object are detected. A coordinate conversion relationship between the user, the light transmitting display device and the background object is established. An eyes midpoint and an eyes offset of the user are detected. A left eye viewpoint and a right eye viewpoint of the user on the light transmitting display device are calculated according to the coordinate conversion relationship, the eyes midpoint and the eyes offset of the user. As a head-mounted device is switched, an image is alternately displayed at the left eye viewpoint and the right eye viewpoint.