Patent ID: 8159453

Claim:
A display device, comprising: a display panel; a backlight device disposed under the display panel, the illuminance of said backlight device being adjustable; a selection and measurement device for light intensity, said selection and measurement device being configured to measure the ambient light intensity of said display panel at a prescribed frequency when light intensity signals of a sensitivity range selected from a plurality of prescribed sensitivity ranges are outputted; and a control device determining whether a number of latest prescribed light intensity signals are all falling within a upper portion, a lower portion or a remaining portion of one of said plurality of prescribed sensitivity ranges, said control device comprising: a memory device for sequentially memorizing said light intensity signals; a first average device obtaining a first average value of a first prescribed number of light intensity signals read out from said memory device; a second average device for obtaining a second average value of a second prescribed number of light intensity signals read out from said memory device, wherein said second prescribed number is larger than said first prescribed number; and a calculation and control device calculating with said selection and measurement device and accordingly controlling the illuminance of said backlight device, wherein said calculating is performed based upon: the sensitivity range adjacent to said upper portion of said prescribed sensitivity range when said control device determines that all of said first prescribed number of light intensity signals fall within said upper portion and said first average value is greater than said second average value, the sensitivity range adjacent to said lower portion of said sensitivity range when said control device determines that all of said first prescribed number of light intensity signals fall within said lower portion and said first average value is smaller than said second average value, and the sensitivity range when said control device determines that all of said first prescribed number of light intensity signals fall within neither said upper portion nor said lower portion.