| 摘要 |
A projection television display apparatus comprises a display device (CRT) with an image (M) formed for projection and a display screen (700) for receiving the projected image (M). A plurality of photo sensors (S1-S8) are located adjacent to edges of the display screen (700) and each generates an output signal (Isen) responsive to an intensity of illumination by the projected image (M). A detector (275) with controllable detection threshold (Iref) is coupled to the photo sensors (S1-S8) for generating a signal (202) having a first state when the output signal (Isen) generated by each of the plurality photo sensors (S1-S8) is greater than the detection threshold (Iref), and a second state when the output signal (Isen) generated by each of said plurality photo sensors (S1-S8) is less than the detection threshold (Iref). A controller (301/900) is coupled to the display device (CRT) and to the detector (275) for setting the detection threshold (Iref) for the output signal (Isen) generated by each one of the plurality of photo sensors (S1-S8). In response to the signal (202) having the first state, the controller (301/900) moves the image (M) on the display device (CRT) to sequentially illuminate another one of the plurality of photo sensors (S1-S8). <IMAGE> |
