Abstract:
A protective mechanism terminates the emission of a laser beam from an inadvertently inverted laser input device. A transmitting/detecting circuit is positioned under a laser input device that emits laser beams from a laser light. The transmitting/detecting circuit projects an infrared ray to a working surface to be reflected therefrom, with the reflected infrared ray detected by the transmitting/detecting circuit. The laser light is turned off if the transmitting/detecting circuit fails to detect the reflected infrared ray.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical input device, and in particular, to a protective mechanism which detects whether a laser-emitting input device has been inverted during use. 
     2. Description of the Prior Art 
     A conventional optical mouse typically uses an optical detecting system to detect the movement of the mouse on a working surface, such that a cursor on a computer display can be controlled simultaneously. This type of technology is illustrated in U.S. Pat. Nos. 5,644,139 and 6,433,780, where an LED (light emitting diode) is adopted as a light source for detecting the movement of an optical mouse. 
     In order to overcome the divergence of the projected light from the LED, a so-called coherent light is introduced to the optical detecting system. An early example of such a laser optical detecting system for a computer mouse is disclosed in U.S. Pat. No. 4,794,384, in which the coherent light can be a laser beam or the like. U.S. Pat. No. 6,927,758 also discloses a dual lens laser detecting system for more accurate control of the movement of the cursor on the computer display. 
     Regardless of the type of laser or the type of laser detecting system used, there is still a possibility that the optical input device is inadvertently overturned (i.e., inverted) so that the laser beam is being emitted into the open work area occupied by the user. Even though the manufacturers of these existing optical input devices claim that the laser beam emitted from an inverted optical input device is harmless to the human eye, there is always a potential for harm. Thus, there remains a need to minimize harm arising from exposure to the laser beam from an optical input device. 
     SUMMARY OF THE DISCLOSURE 
     It is an object of the present invention to provide a simple and low-cost protective mechanism for use with a laser optical detecting system within an optical input device, which will minimize harm arising from exposure to the laser beam from an optical input device. 
     To accomplish the objectives of the present invention, the present invention provides a protective mechanism that terminates the emission of a laser beam from an inadvertently inverted laser input device. A transmitting/detecting circuit is positioned under a laser input device that emits laser beams from a laser light. The transmitting/detecting circuit projects an infrared ray to a working surface to be reflected therefrom, with the reflected infrared ray detected by the transmitting/detecting circuit. The laser light is turned off if the transmitting/detecting circuit fails to detect the reflected infrared ray. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit diagram of a first embodiment of a protective mechanism for use with an optical input device according to the present invention. 
         FIG. 2  is a circuit diagram of a second embodiment of a protective mechanism for use with an optical input device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following detailed description is of the best presently contemplated modes of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating general principles of embodiments of the invention. The scope of the invention is best defined by the appended claims. 
     Referring to  FIG. 1 , a protective mechanism for an optical input device includes an infrared transmitting/detecting circuit  10  which is positioned under the input device. The input device can be an optical mouse. A MCU (micro control unit)  20  can communicate with a computer via a wired or wireless connection according to principles that are well-known in the art. The MCU  20  is coupled between the infrared transmitting/detecting circuit  10  and a light sensor  30 . The light sensor  30  is further coupled between a laser light  40  and the MCU  30 . The power is commonly supplied from the V BUS , which can be a power supply from a power source such as a battery, a capacitor, a solar cell or the like. A switching circuit  50  is coupled between the V BUS  and the light sensor  30 . 
     The following description of the operation of an optical input device is well-known in the art. The laser light  40  is driven by a driving signal which is generated by the light sensor  30 . This driving signal causes the laser light  40  to project a laser beam on to a working surface, such as the surface of a table, a desk or the like. The light sensor  30  receives a reflected laser beam from the working surface, which causes the light sensor  30  to generate a cursor-moving signal to the MCU  20 , which in turn causes the MCU  20  to generate a cursor control signal for moving a cursor on a computer display simultaneously which is proportional to the cursor-moving signal. 
     The infrared transmitting/detecting circuit  10  includes an infrared diode  11  and an infrared receiving transistor  12 . The infrared diode  11  projects an infrared ray to the working surface, which reflects the infrared ray. The infrared receiving transistor  12  then receives the reflected infrared ray from the working surface. If the transistor  12  of the infrared transmitting/detecting circuit  10  fails to detect the reflected infrared ray, the infrared transmitting/detecting circuit  10  will generate an enabling signal to the MCU  20 . When the MCU  20  receives the enabling signal, the MCU  20  outputs a switching signal to the switching circuit  50 , causing the switching circuit  50  to turn off the light sensor  30 , so that the light sensor  30  stops generating the driving signal forwarded to the laser light  40 . 
     In other words, if the input device is turn over or inverted, the infrared transmitting/detecting circuit  10  will not receive the reflected infrared ray. The infrared transmitting/detecting circuit  10  will then generate an enabling signal to the MCU  20 . When the MCU  20  receives the enabling signal, it will output a switching signal to the switching circuit  50 , causing the switching circuit  50  to turn off the light sensor  30 , and the laser beam emitted by the laser light  40  will be terminated immediately. 
       FIG. 2  illustrates another embodiment of the protective mechanism according to the present invention. The protective mechanism for a laser mouse in this embodiment includes an infrared transmitting and detecting circuit  110 , an MCU  120 , a light sensor  130  and a laser light  140  that can be same as the corresponding elements  10 ,  20 ,  30  and  40  in  FIG. 1 . The MCU  120  can communicate with a computer via a wired or a wireless connection. The MCU  120  is also coupled between the infrared transmitting and detecting circuit  110  and the light sensor  130 . The light sensor  130  is further coupled between the laser light  140  and the MCU  120 . The power is supplied from the V BUS . 
     One difference between the embodiments of  FIGS. 1 and 2  is that, in the embodiment of  FIG. 2 , the laser light  140  is directly powered by V BUS . Another difference is that the switching circuit  150  in  FIG. 2  is coupled between the V BUS  and the laser light  140 . The switching circuit  50  can be the same as the switching circuit  50 . The laser light  140  is also driven by a driving signal which is generated by the light sensor  130  such that the laser light  140  can project a laser beam over a working surface, such as the surface of a table, a desk or the like. The light sensor  130  receives a reflected laser beam from the working surface, which causes the light sensor  130  to generate a cursor-moving signal to the MCU  120 , which in turn causes the MCU  120  to generate a cursor control signal for moving a cursor on a computer display. 
     The infrared transmitting/detecting circuit  110  includes an infrared diode  111  and an infrared receiving transistor  112 . The infrared diode  111  projects an infrared ray to the working surface, which reflects the infrared ray. The infrared receiving transistor  112  then receives the reflected infrared ray from the working surface. If the transistor  112  of the infrared transmitting/detecting circuit  110  fails to detect the reflected infrared ray, the infrared transmitting/detecting circuit  110  will generate an enabling signal to the MCU  120 . When the MCU  120  receives the enabling signal, the MCU  120  outputs a switching signal to the switching circuit  150 , causing the switching circuit  150  to shut off the power supply to the laser light  140  directly. 
     In other words, if the input device is turn over or inverted, the infrared transmitting/detecting circuit  110  will not receive the reflected infrared ray. The infrared transmitting/detecting circuit  110  will then generate an enabling signal to the MCU  120 . When the MCU  120  receives the enabling signal, it will output a switching signal to the switching circuit  150 , causing the switching circuit  150  to shut off the power supply of the laser light  140 , so that the laser beam emitted by the laser light  140  will be terminated immediately. 
     While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.