Abstract:
An optical navigation device containing an adjustable depth of field light source is positioned with respect to a surface such that the depth of field of light source can be adjusted to match the Z dimension of a particular surface. In one embodiment, a plurality of individual light sources are used each having a different angle of reflection from the surface. By selecting the light source having an angle of reflection to match the Z dimension of the surface to be navigated the device can be used over a wide range of Z dimensions. In one embodiment, the selection of the proper light source is accomplished upon start-up of the device with respect to a particular surface and in another embodiment a user can adjust the light surface to obtain optimal performance.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to optical navigation devices and more particularly to such devices where the depth of field of the optics is variable.  
       BACKGROUND OF THE INVENTION  
       [0002]     Optical navigation devices are now commonly used, for example with personal computers, for allowing the computer user to “point” to a location on the display screen. An optical navigation device, often called a mouse, projects a light beam onto a surface. The light beam from a mouse moving across the surface reflects from imperfections (artifacts) on the surface. A sensor then picks up the reflections and the direction of travel of the mouse is determined from the surface artifacts as they are being reflected onto the sensor.  
         [0003]     This works well when the navigation surface is at a relatively fixed position (Z dimension) with respect to the light beam and the sensor. In existing navigation devices the optical beam has a depth of field (DOF) which is usually about +/−5 mm. Thus, if the navigation surface is positioned more than 5 mm below the surface of the device (as it would be if a 30 mm glass plate were to be positioned between the navigation device bottom and the navigation surface) the reflected light would not impact properly on the sensor due to the Z dimension falling outside the limits of the DOF. In such a situation, and depending upon the exact Z dimension of the navigation surface, directional determinations would either be impossible to make or would be severely affected.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     An optical navigation device containing an adjustable depth of field light source is positioned with respect to a surface such that the depth of field of light source can be adjusted to match the Z dimension of a particular surface. In one embodiment, a plurality of individual light sources are used each having a different angle of reflection from the surface. By selecting the light source having an angle of reflection to match the Z dimension of the surface to be navigated the device can be used over a wide range of Z dimensions. In one embodiment, the selection of the proper light source is accomplished upon start-up of the device with respect to a particular surface and in another embodiment a user can adjust the light surface to obtain optimal performance. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]     For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:  
         [0006]      FIG. 1  illustrates a schematic side view of one embodiment depicting operation of a multiple light source device at the proper Z dimension for one light sources of a multiple light source optical navigation device;  
         [0007]      FIG. 2  illustrates a schematic side view of one embodiment depicting operation of the multiple light source of  FIG. 1  at the proper Z dimension for a different light source;  
         [0008]      FIG. 3  illustrates a schematic side view of an alternate embodiment depicting light with different angles of incidence created by a moving light source;  
         [0009]      FIG. 4  illustrates a schematic side view of an alternate embodiment depicting the light from a single light source being split and reflected to create more than one angle of incidence;  
         [0010]      FIG. 5  illustrates a schematic side view depicting a refractive element creating multiple angles of incidence of light from a single light source;  
         [0011]      FIG. 6  illustrates a schematic side view depicting an implementation of a prior art optical mouse;  
         [0012]      FIG. 7  illustrates a simplified schematic side view depicting a prior art optical mouse being operated within the proper Z dimension; and  
         [0013]      FIG. 8  illustrates a simplified schematic side view depicting a prior art optical mouse operated with the wrong Z dimension. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]      FIG. 1  illustrates a schematic side view of one embodiment depicting operation of a multiple light source navigation device  10  at the proper Z dimension for one light sources of a multiple light source optical navigation device.  FIG. 1  shows light sources  12  and  13  having light beams or channels  120  and  130  respectively. Dimension Z is the distance within the depth of field for light column  120  allowing the light to reflect from work surface  16  and impact sensor  14  as shown in solid line  120 . Sensor  14  is any well-known sensor that operates to allow for the calculation of navigational movement of navigational device  10  as device  10  moves in horizontal relation to surface  16 . In this example, surface  16  is positioned with respect to bottom surface  11  of device  10  such that light reflecting from  16  will impact some (or all) of the pixels of sensor  14 . If dimension Z becomes too large (as seen in  FIG. 2 ), surface  16  will move beyond the depth of field of light channel  120  such that the reflected light will miss sensor  14  as shown by dotted line  120 .  
         [0015]     Continuing in  FIG. 1 , note that the Z dimension is too “shallow” with respect to the depth of field of light channel  130  from second light source  13  and thus reflected light from surface  16  misses sensor  14 , as shown by dashed line  130 .  
         [0016]      FIG. 2  illustrates a schematic side view of one embodiment depicting operation of the multiple light source of  FIG. 1  at the proper Z dimension for a different light source. As discussed above and as shown in  FIG. 2 , the depth of field (as measured from bottom surface  11  of device  10 ) is now large enough (in this embodiment, 30 mm) such that the Z distance is within the depth of field for light  13  positioned to allow light reflected from channel  130  to impact sensor  14  as shown in  FIG. 2  by dotted line  130 . This Z dimension is outside the depth of field for light  12  and thus, as shown by dashed line  120 , reflected light from column  120  does not impact sensor  14 .  
         [0017]     Although depicted with two light sources  12  and  13  yielding two distinct depths of field, additional light sources (not shown) could be added, thereby increasing the number or range of depths of field. For example, by adding a third light a thicker (or a second) transparent medium could be used. If the thicker medium were to be double the size of medium  25  then the Z dimension would be approximately 60 mm. The light channels are advantageously arranged such that the depths of field are adjacent to each other, increasing the overall depth of field and, correspondingly the overall operable range of Z distances in which the device will function properly.  
         [0018]     Using multiple light channels allows a transparent medium, such as medium  25 , to be inserted between bottom surface  11  of device  10  and actual work surface  16  so long as the Z distance remains within the operable range. The transparent medium need only be transparent to the particular light required by the sensor. If desired, the wavelengths of the different light sources could be different to yield different depths of field perhaps depending upon the intermediary medium.  
         [0019]     As depicted in  FIGS. 1 and 2 , the light from only one light source will impact upon sensor  14  for a given Z distance, thus the selection of a light source for a given Z distance may be accomplished by turning and leaving on both light source  12  and light source  13 . Since light from only one light source will impact upon sensor  14 , the Z distance will inherently select the proper light source.  
         [0020]     Alternatively, selection may also be accomplished by testing each light source. Starting with both light sources  12  and  13  off and then turning on light source  12 . If the reflect light from light source  12  impacts upon the sensor then light source  12  is selected to remain on. Otherwise light source  12  will be turned off and light source  13  will be turned on. If the reflected light from light source  13  impacts the sensor then light source  13  will be selected and will remain on. Otherwise the process will be started again with light source  12  until the Z distance of the device is brought to within the depth of focus for light  12  or light  13 .  
         [0021]     The selection process may also be invoked if the Z distance changes during the operation of the navigation device, such as when a mouse is moved from a mouse pad onto a plate of glass above a navigation surface. When the Z distance changes to a value that is outside of the current depth of focus, reflected light will no longer impact upon the sensor, thus triggering the selection process. Such selection process could be similar to the ones described above or the light sources with depths of field closest to the previous depth of field may be tested before the light sources with depths of field farthest from the current depth of field  
         [0022]     One or more buttons (not shown) may be arranged on device  10  such that pressing a particular button may invoke the automated selection process. If desired, the button could allow a user to select an individual light source, or change the selected light source in a predetermined manner, for example, by cycling through all the light sources with successive presses, thereby giving the user of the device control of the depth of field.  
         [0023]     Alternatively, the depth of field may be controlled by the system (such as by processor  19  connected by transmission path  18 ) to which the navigation device is connected. In the example of a personal computer with attached mouse, software on the computer may be used to interactively select the desired depth of field in an automated or user controlled fashion. Alternatively, CPU  17  within device  10  could control the selection of light sources.  
         [0024]     When using multiple light channels, the depths of field could partially overlap each other still increasing the overall depth of field but at the same time ensuring a smooth transition when changing light channels.  
         [0025]      FIG. 3  illustrates a schematic side view of an alternate embodiment depicting light with different angles of incidence created by a moving light source.  FIG. 3  depicts variable light channels  300  and  301  created by rotating light source  30  with reflections from light channel  301  on surface  16  impacting sensor  14  and reflections from light channel  300  reflecting from surface  16  missing sensor  14 . The multiple channels each with a different depth of field of light source  30  may be created with a rotatable light or with a rotatable mirror or prism in front of a focused light source. The mechanism (not shown) for controlling movement of light source  30  could be controlled by CPU  17  and/or could be controlled from processor  19  via communication path  18 .  
         [0026]      FIG. 4  illustrates a schematic side view of an alternate embodiment depicting the light from a single light source being split and reflected to create more than one angle of incidence. As is shown in  FIG. 4 , light from channels  420  and  410  created by light  400  from light source  40  is split by optical splitter  41 . Light  420  is reflected by reflector  42  onto surface  17  and then onto sensor  14 . Light  410  is reflected by reflectors  43  and  44  and because of its DOF (angle of impact with surface  16 ) it is reflected away from sensor  14 . As depicted, the device is within the depth of field for light column  420  and outside the depth of field for light column  440 .  
         [0027]      FIG. 5  illustrates a schematic side view depicting a refractive element creating multiple angles of incidence of light from a single light source. As shown light source  50  emits light  500  that passes through cylindrical lens  51  creating planar light sheet  510 , which reflects from work surface  16  becoming planar light sheet  512 , portions of which impact upon sensor  14 . The portion of light sheet  510  and light sheet  512  that are coincident are represented by element  511 .  
         [0028]      FIG. 6  illustrates a schematic side view depicting an implementation of a prior art optical mouse.  FIG. 6  is a side cut away view of a well known optical navigation device implementation. Light source  60  is mounted on printed circuit board (PCB)  600 , both of which are held in place relative to sensor  14  via clip  61 . Sensor  14  is attached to another PCB  62 , which is affixed to the bottom of the device housing. Bottom surface  11  of the device has low friction glides  63  enabling the device to move across work surface  16  and controlling the Z dimension. The bottom of the device has opening  64  through which light may pass out of and in to the device. Light from light source  60  passes out of the device through opening  64 , reflects from surface  16  and passes back into the device through opening  64  impacting sensor  14 .  
         [0029]      FIG. 7  illustrates a simplified schematic side view depicting a prior art optical mouse being operated within the proper depth of field with light channel  700  from light source  70  reflecting from surface  16  onto sensor  14 .  
         [0030]      FIG. 8  illustrates a simplified schematic side view depicting a prior art optical mouse operated with the wrong Z dimension.  FIG. 8  depicts the device from  FIG. 7  being operated outside of the proper depth of field having light channel  700  miss sensor  14 .  
         [0031]     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.