A holding mechanism has a holding component including a base and a covering plate. The slide retaining unit is disposed between the cold light source and the projection lens, and is adapted to retain removably a projector slide between the cold light source and the projection lens when the image projector system is operated in a slide projection mode. A variable geometry turbine controller uses a sensor indicating the actuation position of the actuator to guide the operation of the vanes to the reference position. Further, the running state of each tire including air pressure is detected from the vibration level of the portion below the spring to estimate the running state of the vehicle.