A display device is applied to a light sensing system. The display device includes a display module and a pattern layer. The pattern layer is made of optical material and formatted on the display module. The pattern layer includes patterned optical material and gaps without optical material. The pattern layer selectively reflects or absorbs invisible light with specific wavelength emitted from the display module, such that a light sensor cannot sense the invisible light reflected or absorbed by the optical material or just can sense a little invisible light through the optical material. However, the invisible light can be emitted out of the gaps without the optical material, such that the light sensor can selectively sense the invisible light. Based on the light sensing result, the light sensor can recognize the corresponding pattern.