Abstract:
An optical mouse system with a high-angle optical path features small size and low power consumption. The illumination source and optical sensor are mounted in the same plane, directly on the PCB. The higher angle of the optical path causes more light to be reflected to the optical sensor, increasing optical efficiency and allowing a smaller, lower powered LED to be used. This also results in increased sensitivity of the optical sensor, allowing use of the mouse on surfaces on which conventional optical mice cannot function adequately. Sensitivity can be further increased by optional isolation of the optical sensor and illumination source. Lower power usage increases battery life for mobile or wireless-mouse use, while reducing thermal waste considerations. This allows the creation of a significantly smaller form factor for the overall package, thereby reducing materials costs and giving designers more flexibility for external design considerations.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to optics. More specifically, the present invention discloses an optical system for sensing motion of a surface relative to the optical system.  
         [0003]     2. Description of the Prior Art  
         [0004]     Traditionally, the optical computer mouse uses a light-emitting diode (LED) to graze a surface with illuminating light, and detects patterns in reflected light from the surface to compute motion. Please refer to  FIG. 1   a,  a diagram of a prior-art optical computer mouse  100 . Externally, the mouse has a housing  101  and a base plate  102 . Internal to the housing, a printed-circuit board (PCB)  110  has a light-emitting diode  140  (LED) and optical sensor  150  mounted to it. The LED  140  emits light, a light beam  170  of which is focused and guided through an illumination guide  130 . The illumination guide  130  typically extends through a hole in the PCB  110 . The light beam  170  enters the illumination guide  130  through a first flat surface  1311 , is reflected off a first reflector  1301 , is reflected off a second reflector  1302 , and exits the illumination guide  130  through a second flat surface  1312 . The light beam  170  exits the mouse body through an aperture  107  in the base plate  102 , reflects off a reference surface  10 , and reenters the illumination guide  130  through a third flat surface  1313 . The light beam  170  shines onto an optical sensor  150 , which detects patterns in the reference surface  10  revealed by the light. These patterns may be caused by roughness in the reference surface  10 , or may be caused by colorations of the surface  10 . Referring to  FIG. 1   b,  the angle  20  between the light beam  170  and the reference surface  10  is acute and is typically less than about twenty degrees and greater than about five degrees from the plane of the reference surface. The angle  70  between the light beam  170  and a normal  90  to the reference surface  10  is thus typically about seventy degrees or greater.  
         [0005]     However, this low angle causes most of the light emitted by the LED to be scattered to the sides, thereby being lost to the sensor. The LED  140  must therefore be of high intensity, consuming a large amount of power, which is then wasted on generating the lost light, and which also creates heat dissipation issues. Furthermore, this requires the LED  140  and other components to be correspondingly large, increasing the size of the mouse. In addition to increasing materials costs, this creates a lower limit on the attainable size of the mouse. Moreover, the structure of this design places the LED  140  and the optical sensor  150  in different planes, and requires cuts in the PCB  110 , thereby further increasing the design complexity of the mouse, and also increasing the required size.  
         [0006]     In addition, the structure of the prior art mouse is typically open internally, and in many cases transparent materials are used for the housing  101  and base plate  102  for aesthetic considerations, thereby allowing external light not generated by the mouse  100  to reach the optical sensor  150 , and internally, allowing randomly scattered light from the LED  140  to reach the optical sensor  150 . This undesirable light can only serve to interfere with the imaging performed by the optical sensor  150 .  
         [0007]     Therefore there is need for an improved optical system for the mouse which will allow smaller overall size and lower power consumption while also reducing design complexity.  
       SUMMARY OF THE INVENTION  
       [0008]     To achieve these and other advantages and in order to overcome the disadvantages of the conventional method in accordance with the purpose of the invention as embodied and broadly described herein, the present invention provides an optical mouse system that directs illumination at a surface from an angle of typically less than about thirty-three degrees in respect to a 90 degree angle from the surface, thereby increasing the optical efficiency of the system and reducing power requirements, and also thereby increasing the sensitivity of the system to the relative movement of the reference surface, and also thereby shrinking size requirements.  
         [0009]     The present invention further provides an optical mouse system in which the illumination source is mounted on the same surface or plane as the optical sensor, thereby simplifying construction and shrinking size requirements.  
         [0010]     The present invention further provides an optical mouse system in which the optical sensor may optionally be substantially isolated from extraneous light, both that which is generated by the mouse and that which is foreign to the system, thereby increasing the sensitivity of the system to the relative movement of the reference surface.  
         [0011]     These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of preferred embodiments.  
         [0012]     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:  
         [0014]      FIG. 1   a  is a diagram showing a cross section of a prior art optical computer mouse;  
         [0015]      FIG. 1   b  is a diagram illustrating the path of a light beam generated by a prior art mouse;  
         [0016]      FIG. 2   a  is a sectional diagram illustrating the preferred embodiment of the internal components of an optical computer mouse of the present invention;  
         [0017]      FIG. 2   b  is a sectional diagram illustrating a second embodiment of the internal components of an optical computer mouse of the present invention;  
         [0018]      FIG. 3   a  is a detail diagram illustrating an embodiment of an illumination guide for an embodiment of an optical computer mouse of the present invention;  
         [0019]      FIG. 3   b  is a diagram illustrating the path of an illumination beam generated by an embodiment of an optical computer mouse of the present invention;  
         [0020]      FIGS. 4   a  is a top view of a holder for an embodiment of an optical mouse of the present invention;  
         [0021]      FIG. 4   b  is a bottom view of a holder for an embodiment of an optical mouse of the present invention;  
         [0022]      FIG. 4   c  is a cross-section view of a holder for an embodiment of an optical mouse of the present invention;  
         [0023]      FIG. 5  is a diagram of an alternate embodiment of a holder for an embodiment of an optical mouse of the present invention;  
         [0024]      FIG. 6   a  is a perspective drawing of an embodiment of a clip for an embodiment of an optical computer mouse of the present invention;  
         [0025]      FIG. 6   b  is an internal view of an embodiment of a clip for an embodiment of an optical computer mouse of the present invention;  
         [0026]      FIG. 6   c  is an end view of an embodiment of the clip for an optical computer mouse of the present invention;  
         [0027]      FIG. 6   d  is a bottom view of the assembled optical mouse core;  
         [0028]      FIG. 7  is a detailed diagram of the preferred embodiment of an illumination guide for the embodiment an optical mouse of the present invention; and  
         [0029]      FIG. 8  is a ray-trace diagram of the preferred embodiment of the illumination guide for the embodiment of an optical mouse the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.  
         [0031]     Please refer to  FIG. 2   a,  which shows a cross-section diagram of the internal components of the preferred embodiment of an optical computer mouse of the present invention. (The cross-section traverses the exit aperture  2211  and entry aperture  2212 , thereby causing the holder  220  to appear as if in three pieces. This section is the same as used in  FIG. 4   c,  and is marked as the section A-A in  FIG. 6   c .) An illumination source  240  and an optical sensor  250  are mounted on a printed-circuit board (PCB)  210 . The illumination source  240  and the optical sensor  250  are mounted on a plane parallel to the surface of the PCB  210 , on which the electronic components are mounted. The illumination source  240  is typically a light-emitting diode (LED) in the SMD form factor, but the present invention may also use an infrared-emitting diode, a laser diode, or other suitable illuminating radiation emission source matched to the type of illumination that the optical sensor  250  can receive. A holder  220  is disposed over and around the illumination source  240 , such that the holder  220  in combination with the PCB  210  isolates the illumination source  240  inside a source cavity  2201  so that the illumination it generates can only exit through an exit aperture  2211 . Likewise, the holder  220  is disposed over and around the optical sensor  250 , such that the holder  220  in combination with the PCB  210  surrounds the optical sensor  250 , isolating the optical sensor  250  inside a sensor cavity  2202  so that the illumination the optical sensor  250  receives can only enter through an entry aperture  2212 . An illumination guide  230  rests in an illumination guide cavity  2203  of the holder  220 , retained securely in place by a clip  260 . (The retaining arrangement of the preferred embodiment is discussed in more detail below.) The clip  260  has a main aperture  267  through which the illumination exits, reflects off a reference surface  10 , and re-enters the optical computer mouse.  
         [0032]     Referring now to  FIG. 2   b,  which shows a cross-section diagram of the internal components of a second embodiment of an optical computer mouse of the present invention, this embodiment differs from the preferred embodiment in that it does not use a holder to isolate the illumination source  240  from the optical sensor  250 . The illumination guide may be held to the PCB  210  by a clip (not shown) or integrated fingers  2366 ˜ 2367 , or it may be attached to the housing (not shown) or the housing base (not shown), or it may be an integral part of the housing base (not shown).  
         [0033]     Please refer to  FIG. 3   a,  which is a diagram illustrating an embodiment of an illumination guide for the preferred embodiment of an optical computer mouse of the present invention, with reference to  FIG. 2   a  and  FIG. 2   b.  The preferred embodiment&#39;s illumination guide  230  has a first reflector  2301  and a second reflector  2302 . The preferred embodiment&#39;s illumination guide  230  further comprises a first lens  2311 , a second lens  2312 , a third lens  2313 , and a fourth lens  2314 . The preferred embodiment&#39;s illumination guide  230  further has a first mating surface  2321  and a second mating surface  2322 . The illumination guide  230  may be made of polymer, glass, or other refractive material which is substantially transparent to the wavelength of the illumination being used. Optically, the illumination beam  270  is emitted from the illumination source  240 , enters the illumination guide  230  through the first lens  2311 , is reflected from the first reflector  2301 , is reflected from the second reflector  2302 , and exits the illumination guide  230  through the second lens  2312  at an angle of, for example, less than about thirty-three degrees from a 90 degree angle to the reference surface. Optionally, to spread the illumination beam  270  more evenly, the first lens  2311  and second lens  2312  may be textured, for example by stippling or otherwise hazing their surfaces. Optionally, to spread the scattered illumination from the reference surface  10  to the optical sensor  250  for the purpose of removing detail from the image formed on the optical sensor  250 , the third lens  2313  may be textured. Please note that the first lens  2311 , the second lens  2312 , the third lens  2313 , and/or the fourth lens may be flat surfaces in some embodiments.  
         [0034]     In the preferred embodiment, the angle is thirty-two degrees from the normal. Note this angle can be adjusted according to design. It is understood that this angle is intended to be measured when the optical mouse is flat against a substantially planar reference surface, although in typical use the mouse may be picked up, turned, or used on an irregular surface in such a way that at times the angle varies substantially; such usage may result in a temporary loss of tracking.  
         [0035]     Continuing with discussion of  FIG. 3   a,  the illumination is scattered from the reference surface and re-enters the illumination guide  230  through the third lens  2313 , and travels through the illumination guide  230  to the fourth lens  2314 , where the illumination beam  270  then exits the illumination guide  230  to fall onto the optical sensor  250 .  
         [0036]     The illumination path of the preferred embodiment and the second embodiment is shown in  FIG. 3   b.  The illumination exits the illumination guide (not shown) such that it reaches the reference surface  10  at an angle  32  less than about thirty-three degrees from a normal  90  to the reference surface  10 . The optical sensor (not shown) receives illumination that has been scattered at an angle substantially near the normal  90  to the reference surface  10 . Referring to  FIG. 3   a  in combination with  FIG. 3   b,  it should be noted that it is possible to alter the angles of the first reflector  2301  and second reflector  2302  relative to each other while still generating an illumination beam  270  that reaches the reference surface  10  at a substantially similar angle  32 .  
         [0037]     Please refer to  FIG. 4   a,    FIG. 4   b,  and  FIG. 4   c,  which show three views of the holder  220  used in an embodiment of an optical mouse of the present invention.  FIG. 4   a  shows a top view of the holder  220 . The holder  220  has a source cavity  2201  which surrounds the illumination source  240 , and a sensor cavity  2202  which surrounds the optical sensor  250 . The source cavity  2201  has an exit aperture  2211  through which illumination from the illumination source  240  exits the source cavity  2201  and enters the illumination guide (see  FIG. 2   a ). The sensor cavity  2202  has an entry aperture  2212  through which illumination can reach the optical sensor  250 . Along the outer perimeter, three ears  2291 ˜ 2293  which hook into three tabs  2601 ˜ 2603  (not shown, see  FIG. 6   b ) on the clip  260  (not shown, see  FIG. 6   b ) for holding the overall assembly together are visible.  FIG. 4   a  also shows an outline of the PCB-side surface  2230  of the holder  220  where it contacts the PCB  210 . The holder thus isolates the illumination source  240  from the optical sensor  250 , providing only a single exit path for the illumination that the illumination source  240  emits, said exit path being through the exit aperture  2211 . The holder further provides only a single entry path through which illumination can reach the optical sensor  250 , said entry path being through the entry aperture  2212 . The holder is typically made of a material which absorbs the illumination generated by the illumination source  240 , such as a textured (e.g., stippled or otherwise made nonreflective) black polymer, thereby reducing any illumination scattered by internal reflections.  
         [0038]      FIG. 4   b  shows a view of the illumination guide cavity  2203  surface of the holder  220 . This surface is shaped to fit the contours of the illumination guide  230 , capturing the illumination guide  230  into its designed position and orientation and supporting it. From this viewpoint, looking down into the cavity, the area  2281  surrounding the exit aperture  2211  is lower than the area  2283  surrounding the entry aperture  2212 . Please refer to  FIG. 4   b  in combination with  FIG. 3   a,  a diagram showing a cross section of the illumination guide  230 . The middle area  2282  slopes at the same angle as the second reflector  2302  of the illumination guide  230  and a small wedge forms to one side where this middle area  2282  rises above the area  2281 . The upper exit surface  2314  of the illumination guide  230  fits against the area  2283 , and the first mating surface  2321  fits against the area  2281 . This orients and supports the illumination guide  230  from the holder surface. Additionally, the sides of the illumination guide  230  are substantially flat and parallel planar surfaces (not shown). These fit neatly between the two long walls  2251 ˜ 2252  of the illumination guide cavity  2203 . The short wall  2253  of the illumination guide cavity  2203  may optionally have an overhanging shelf  2254  to capture the end of the illumination guide  230 . The second short wall  2255  of the illumination guide cavity  2203  fits against the opposite end of the illumination guide  230 . Thus the illumination guide  230  is supported on all sides and underneath, holding the illumination guide  230  in its proper orientation.  
         [0039]      FIG. 4   c  shows a cross-section of the holder  220  and the PCB  210  through the line A-A of  FIG. 6   c.  The cross-section shows the exit aperture  2211  and the entry aperture  2212 , the contour of the illumination guide cavity  2203  (through the center, including the wedge), the source cavity  2201 , the sensor cavity  2202 , and one ear  2292  of the three ears. The cross-section traverses both the exit aperture  2211  and entry aperture  2212  (shown with dashed lines) thereby causing the holder  220  to appear as if in three pieces. Note that this section is the same as used in  FIG. 2   a.    
         [0040]     Please refer to  FIG. 5 , which shows an alternative embodiment of the holder  220  which, in addition to the other features already described, further comprises locating pins  2241 ˜ 2243  molded to project from the surface of the holder which is proximal to the PCB  210 . These locating pins  2241 ˜ 2243  are inserted into matching locating holes  2141 ˜ 2143  in the PCB  210 , and the locating pins  2241 ˜ 2243  are then softened and flattened against the rear surface of the PCB  210  during final assembly, after the illumination source  240  and optical sensor  250  (as well as any other electronic components) are mounted to the PCB  210 , to mount the holder permanently in place on the PCB. The locating pins  2241 ˜ 2243  are designed in an asymmetrical pattern to orient the holder  220  correctly so that the holder  220  cannot be improperly positioned during assembly.  
         [0041]     Please refer to  FIG. 6   a,  which is a perspective drawing of an embodiment of a clip for an embodiment of an optical computer mouse of the present invention. The clip  260  has a distal surface  265  with a main aperture  267 . The distal surface  265  is substantially flat. Tab  2601  and tab  2602  are visible from this angle; tab  2603  is on the long face to the back and right. In the preferred embodiment the clip  260  has three tabs  2601 ˜ 2603  which lock over three ears  2291 ˜ 2293  on the holder  220  shown in  FIG. 4   a  and  FIG. 4   b.  The tabs  2601 ˜ 2603  and ears  2291 ˜ 2293  are oriented asymmetrically so that the parts can only fit together in one orientation during assembly. This helps to ensure that the main aperture  267  ends up being located correctly over the illumination guide  230  (see  FIG. 2   a ).  
         [0042]     Referring now to  FIG. 6   b,  which is an internal view of an embodiment of a clip for an embodiment of an optical computer mouse of the present invention, The interior surface  2651  of the distal surface  265  (not shown) presses against the second mating surface of the illumination guide  230  (not shown), locking the illumination guide  230  (not shown) into place against the holder  220  (not shown) in the illumination guide cavity  2203  (not shown). This completes the assembly of the optical mouse core.  
         [0043]     Please see  FIG. 6   c,  an end view of the preferred embodiment of the clip for an optical computer mouse of the present invention. The tab  2602  is centered from side to side in the face, and is near the edge proximal to the PCB  210 . Visible inside the tab  2602  is the ear  2292  of the holder  2200 . The distal surface  265  is at the top of this diagram. Section line A-A marks the section shown in  FIG. 2   a  and  FIG. 4   c.    
         [0044]     Please see  FIG. 6   d,  a bottom view of the assembled optical mouse core. The main aperture  267  is visible on the distal surface  265  of the clip  260 . The second lens  2312  and third lens  2313  of the illumination guide  230  and an edge of the holder  220  are visible within the main aperture  267 . The second lens  2312  and third lens  2313  are positioned so that the path of the illumination beam (not shown) exits the second lens  2313 , exits the main aperture  267 , scatters off the reference surface (not shown), and re-enters the main aperture  267  to enter the third lens  2313 . Positions of the tabs  2601 ˜ 2603  are marked but are not directly visible in this drawing.  
         [0045]     Please refer to  FIG. 7 , which is a detailed drawing of the lens system of the illumination guide of the present invention and to  FIG. 8 , which shows the mathematical relationships of the optics. The illumination source  240  illuminates the first lens  2311  of the illumination guide  230  with about sixty degrees of its output. The first lens  2311  is designed with the correct focal length to collimate this illumination into an illumination beam  270 . Any illumination which is moving in other directions is scattered or absorbed by the holder  220  (not shown), which is preferably made of a black nonreflective material such as a polymer. The first reflector  2301  and second reflector  2302  reflect the illumination beam  270  through the second lens  2312 , which spreads the illumination beam  270  substantially to illuminate the reference surface  10  through the main aperture (not shown). Illumination which is scattered from the reference surface  10  re-enters the illumination guide  230  through the third lens  2313 , travels through the illumination guide  230 , exits through the fourth lens  2314 , and falls on the image plane  2501  of the optical sensor  250 .  
         [0046]     The required length of the first reflector  2301  is the width of the exit aperture  2211  divided by the sine of forty-five degrees. The required length of the second reflector  2302  is the width ‘e’, here identical to the width of the exit aperture  2211  (since the first reflector  2301  was selected to be at a forty-five degree angle) divided by the sine of the quantity forty-five degrees minus half the angle of incidence from the normal, chosen to be thirty-two degrees in the preferred embodiment; this simplifies to the sine of twenty-nine degrees.  
         [0047]     This optical mouse system thus provides a substantial improvement over the prior art by reducing power usage and materials costs, and by simplifying the internal construction of the optical mouse core. Isolation of the illumination source from the optical sensor, and of the optical sensor from external illumination, helps to increase sensitivity of the system. Furthermore, its smaller form factor gives designers more flexibility in housing design.  
         [0048]     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the invention and its equivalent.