Abstract:
The present invention discloses an optical input device, which comprises a display panel having a displaying area functioning as an interface for detecting a position of an object; a backlight module providing light sources for the display panel; and at least one image sensor arranged behind the backlight module and capturing a positional image, which is formed on the displaying area by an object reflecting the light emitted by the light sources. The present invention not only can decrease the thickness of the optical input device but also can reduce the complexity of the optical system.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an input device, particularly to an optical input device. 
         [0003]    2. Description of the Related Art 
         [0004]    Generally, signals are input into an electronic device, such as a computer or a mobile phone, via an external keyboard. However, such a design is hard to achieve a slim and compact electronic product. 
         [0005]    To reduce the volume of devices, the keyboard function is incorporated into the display panel to form the so-called touchscreen. The touchscreens may be categorized into the resistive type, the capacitive type, the ultrasonic type and the optical type. The optical type touchscreen operates via receiving reflected light. Refer to  FIG. 1  and  FIG. 2  for a conventional optical type touchscreen. Infrared sources  12  and infrared cameras  14  are arranged below a projection screen  10  to form arrays. An object  16  contacting the projection screen  10  reflects light to the infrared cameras  14 . The infrared cameras  14  send signals to a control computer; the computer locates the position of the object  16  and then controls a projector  18  to project a related image on the projection screen  10 . In such a design, each infrared camera  14  can only cover a limited area. Besides, the infrared sources  12  have to uniformly illuminate the projection screen  10 . Thus, the projection screen  10  has to be elevated to increase the coverage of the infrared cameras  14  and make the infrared sources  12  illuminate the projection screen  10  uniformly. However, such a measure greatly increases the thickness of the display device (a thickness as great as a shown in  FIG. 2 ). Further, the optical system, wherein a projector cooperates with infrared sources, has a higher complexity. Therefore, the conventional optical type touchscreen has a high price. 
         [0006]    Accordingly, the present invention proposes an optical input device, which applies to general flat panel displays and has a smaller thickness and a lower system complexity, to solve the abovementioned problems. 
       SUMMARY OF THE INVENTION 
       [0007]    The primary objective of the present invention is to provide an optical input device, wherein the image sensors are incorporated in a display panel and arranged behind the backlight module to reduce the thickness of the device and decrease the complexity of the system. 
         [0008]    To achieve the abovementioned objectives, the present invention proposes an optical input device, which comprises a display panel having a displaying area functioning as an interface to detect the position of an object; a backlight module providing light for the display panel; and at least one image sensor arranged behind the backlight module and obtaining a positional image formed on the displaying area by the light reflected from the object. 
         [0009]    Below, the embodiments are described in detail in cooperation with the attached drawings to make easily understood the characteristics, technical contents and accomplishments of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view schematically showing a conventional optical type touchscreen; 
           [0011]      FIG. 2  is a front view schematically showing a conventional optical type touchscreen; 
           [0012]      FIG. 3  is a perspective view schematically showing an optical input device according to a first embodiment of the present invention; 
           [0013]      FIG. 4  is a front view schematically showing an optical input device according to the first embodiment of the present invention; 
           [0014]      FIG. 5  is a perspective view schematically showing an optical input device according to a second embodiment of the present invention; 
           [0015]      FIG. 6  is a front view schematically showing an optical input device according to the second embodiment of the present invention; 
           [0016]      FIG. 7  is a perspective view schematically showing an optical input device according to a third embodiment of the present invention; 
           [0017]      FIG. 8  is a front view schematically showing an optical input device according to the third embodiment of the present invention; 
           [0018]      FIG. 9  is a perspective view schematically showing an optical input device according to a fourth embodiment of the present invention; and 
           [0019]      FIG. 10  is a front view schematically showing an optical input device according to the fourth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    As the projector and the infrared sources cause the thickness of the device to increase in the conventional technology, the present invention replaces the projector with a flat panel display and replaces the infrared sources with a backlight module. Refer to  FIG. 3  and  FIG. 4  for a first embodiment of the present invention. The optical input device  20  of the present invention comprises a display panel  22 , a backlight module  26  and at least one image sensor  32 . The display panel  22  has a display area  24  functioning as an interface to detect the position of an object  34 , such as a finger. The backlight module  26  provides light sources for the display panel  22 . The image sensor  32  obtains a positional image formed on the displaying area  24  by the light reflected from the object  34 . The optical input device  20  of the present invention further comprises a processor  32  coupled to the image sensor  32 , receiving a signal from the image sensor, processing the image captured by the image sensor  32  to obtain a complete detection image. The processor may be a single-core or multi-core processor integrated with a computer. 
         [0021]    In the present invention, the backlight module  26  is arranged between the image sensor  32  and the display panel  22 . The backlight module  26  cannot have any metallic reflecting layer lest the sensitivity that the image sensor  32  detects the positional image of the object  34  be affected. In the first embodiment, the backlight module  26  includes a light guide plate  28  and a light-emitting device  30 . The light-emitting device  30  is arranged on a lateral of the light guide plate  28  and provides lights, including visible light and infrared light. The visible light is used to present images on the display panel  22 . The infrared light is used to detect the position of the object  34 . The light guide plate  28  is used to distribute light uniformly. 
         [0022]    Below is described the operation of the optical input device  20  of the present invention. When approaching or contacting the displaying area  24  of the display panel  22 , the object  34  shields the light emitted by the backlight module  26  and forms a positional image on the displaying area  24 . At the same time, infrared light is reflected by the object  34  to pass through the light guide plate  28  of the backlight module  26  and then reach the image sensors  32 , whereby the image sensor  32  obtains the positional image. Next, the image sensor  32  outputs a signal to the processor. The processor receives the signal and processes the positional image obtained by the image sensor  32  into a complete detection image. Thereby, the processor can accurately determine the position where the object  34  contacts the displaying area  24 . 
         [0023]    The optical input device  20  of the first embodiment has a thickness b, which is smaller than the thickness a of the conventional optical type touchscreen shown in  FIG. 2 . 
         [0024]    A single image sensor  32  can only have a limited view field except the distance between the display panel  22  and the image sensor  32  is increased. To increase the view field without increasing the thickness, a second embodiment of the present invention replaces the single image sensor  32  with a plurality of image sensors  32  arranged into an array. At the same time, the displaying area  24  is divided into a plurality of blocks each corresponding to one image sensor  32 . 
         [0025]    Refer to  FIG. 5  and  FIG. 6  for the second embodiment of the present invention. The second embodiment is different from the first embodiment in that the second embodiment has four image sensors  32  and that the displaying area  24  is divided into four blocks. The image sensors  32  are arranged into a square array. Each image sensor  32  is corresponding to a block most near to it. When an object  34  shields light and generates a positional image, the image sensors  32  respectively receive reflected infrared light through the corresponding blocks. The processor may be a single-core or multi-core processor. If the processor is a single-core processor, the processor simultaneously processes the signals sent out by all the image sensors  32  and integrates the images obtained by the image sensors  32  into a complete detection image. If the processor is a multi-core processor, the cores thereof respectively receive the images obtained by the image sensors  32 , process the signals and then integrate the images, whereby the processor can faster obtain a complete detection image. 
         [0026]    The optical input device  20  of the second embodiment has a thickness c, which is smaller than the thickness b of the optical input device  20  of the first embodiment shown in  FIG. 4 . 
         [0027]    Refer to  FIG. 7  and  FIG. 8  for a third embodiment of the present invention. The third embodiment is different from the first embodiment in that the third embodiment has a reflecting plate  36  facing the displaying area  24  and corresponding to the image sensor  32 . The reflecting plate  36  has an area sufficient to reflect the light from the displaying area  24 . When an object  34  shields light and generates a positional image, the reflecting plate  36  reflects the infrared light, which has been reflected by the object  34  beforehand, to the image sensor  32 , whereby the transmission path of the light is shortened. Thus, the image sensor  32  receives the positional image. Via the reflecting plate  36 , the optical input device  20  of the third embodiment has a smaller thickness than the optical input device  20  of the first embodiment. In other words, the optical input device  20  of the third embodiment has a thickness d, which is smaller than the thickness b of the optical input device  20  of the first embodiment shown in  FIG. 4 . 
         [0028]    Refer to  FIG. 9  and  FIG. 10  for a fourth embodiment of the present invention. The fourth embodiment is different from the second embodiment in that each image sensor  32  has a reflecting plate  36  facing a block (of the displaying area  24 ) corresponding to the image sensor  32 . The reflecting plate  36  has an area sufficient to reflect the light from the corresponding block on the displaying area  24 . When an object  34  shields light and generates a positional image, each reflecting plate  36  reflects the infrared light, which has been reflected by the object  34  to pass through the corresponding block, to the corresponding image sensor  32 , whereby the transmission path of the light is shortened. Thus, the image sensor  32  receives the positional image. Via the reflecting plates  36 , the optical input device  20  of the fourth embodiment has a smaller thickness than the optical input device  20  of the second embodiment. In other words, the optical input device  20  of the fourth embodiment has a thickness e, which is smaller than the thickness c of the optical input device  20  of the second embodiment shown in  FIG. 6 . 
         [0029]    In conclusion, the present proposes an optical input device, whose backlight module replaces the infrared device used in the conventional technology. Therefore, the present invention needn&#39;t use an additional optical device to provide infrared light. Thus is reduced the thickness, complexity, design difficulty, and cost of the display device containing the optical input device. 
         [0030]    The embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Any equivalent modification or variation according to the shapes, structures, characteristics, or principles of the present invention is to be also included within the scope of the present invention.