Abstract:
A portable device includes a transparent surface; a microlens array having lenslets, each lenslet forming a corresponding image of an object using light received through the transparent surface; a light sensor having pixels, each pixel corresponding uniquely to one of the plurality of lenslets, to detect the formed images of the object; and a controller to use the detected images to determine a motion of the object relative to the transparent surface, and to output the detected motion to a display for use in navigating a cursor and/or a menu on the display according to the determined motion. The portable device can be used in a telephone, personal digital assistant, and/or other handheld devices which control navigation on a display included in the device or external to the device.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     Aspects of the invention relate to optical navigation using a microlens array, and more particularly, to an electronic device having an integrated optical navigation module using a flat-type microlens array.  
         [0003]     2. Description of the Related Art  
         [0004]     Conventionally, navigation modules (i.e., computer mice) come in a wide variety of shapes having different features, sizes and prices. Navigation modules are categorized according to how the motion is sensed. Specifically, optical navigation modules use optical motion sensing. In contrast, mechanical navigation modules use mechanical motion sensing. While the mechanical mice were the earlier of the two types of navigation modules, the optical navigation modules have begun to gain increased acceptance.  
         [0005]     Early versions of optical navigation modules were used in the context of personal computers and relied upon fine lines on a specific grid in order to perform tracking operations. However, with the advent of an optical position sensor by Agilent Technologies in 1999, optical mice are now able to work on a wide variety of surfaces without requiring the fine line grids. The optical position sensor works by taking a picture of the surface on which the mouse is navigating, and comparing images taken sequentially to detect the speed and direction of the movement of the surface relative to the mouse. In this manner, the optical mouse is able to navigate across a wide variety of surfaces without requiring such a grid.  
         [0006]     In contrast to early optical mice and mechanical mice which used a ball to perform the tracking operation, an optical mouse typically does not use a ball. Specifically, the mouse includes a clear lens underneath. Light from a light source (generally an LED emitting a red wavelength light) reflects off the surface and is received through a window at the lens. The lens focuses the received light on a sensor, which detects the image. As such, as the mouse is moved, the sensor takes continuous images of the surface and compares the images to determine the distance and direction traveled utilizing digital signal processing. The comparison results are then sent to a personal computer in order to move the cursor on the screen.  
         [0007]     With the emergence of increasing numbers of handheld electronic devices, such as cell phones and PDAs, with small displays and increased functionality, there is an increased need for more flexible and sophisticated navigation technologies to allow the user to easily access this functionality. However, while optical mice are used with computers, optical navigation modules are not used for these handheld devices. This is because computers are of a larger scale and are expected to use external optical mice on a desk in order to navigate on a screen. In contrast, handheld devices have a constrained size so as to fit in the hand and/or pocket. Thus, handheld devices are not typically used with external devices to perform on-screen navigation, making the inclusion of conventional optical navigation technologies impractical with the handheld devices.  
         [0008]     Instead, conventional handheld devices, such as cell phones and personal digital assistants (PDAs), use mechanical navigation devices to perform on screen navigation. Examples of mechanical navigation devices include a button, rocker switch, a click wheel, and/or touch screen displays. As such, when a user needs to select an item or navigate through an on screen menu, the user presses the button, rocker switch and/or presses (such as with a stylus) the screen itself.  
         [0009]     However, such mechanical devices have drawbacks in terms of overall aesthetic appeal, are liable to wear out from prolonged use, and are limited in terms of the navigation directions. For instance, on a cell phone using the rocker switch, the rocker switch is under a circular disk and typically allows navigation in one of four directions (i.e., up/down and left/right). As such, when pressed by the user, the user can only navigate in one of the four directions. Therefore, in order to increase range of on screen movement, there need to be increased numbers of switches, which increases the complexity of the navigation module and exacerbates space constraints in a typical hand held device. Thus, existing rocker switch technology is not suitable for providing cursor movement similar to that performed on computers using mice.  
         [0010]     For other technologies such as that used in BLACKBERRIES and IPODs, a mounted track wheel is used to allow rapid up-down cursor navigation. However, the track wheel allows only one dimensional movement, and does not allow left-right (i.e., two dimensional) navigation.  
         [0011]     Moreover, mechanical devices such as buttons, rocker switches and sidewalls have drawbacks in terms of overall aesthetic appeal, and are liable to wear out from prolonged use.  
         [0012]     Additionally, while touch screen technology allows increased cursor motion, the user is typically is forced to obstruct the display itself to perform navigation. While suitable for desktop computer screens, this obstruction is problematic for small displays. Thus, when used in a handheld device such as a PDA, a separate stylus is often used for increased cursor movement accuracy. The use of the stylus has drawbacks in that the stylus is easy to misplace, aggravating the user. Moreover, unless a stylus is used, the display is likely to become dirty as users touch the display to navigate thereon. Thus, touch screen technology also has limitations when used in the context of navigating cursors.  
       SUMMARY OF THE INVENTION  
       [0013]     Aspects of the invention relate to optical navigation using a microlens array, and more particularly, to a portable electronic device having an optical navigation module using a flat type microlens array.  
         [0014]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
         [0015]     According to an aspect of the invention, a portable device comprises a display on which information and/or images are displayed; a transparent surface; one or more lenses forming a corresponding image of an object using light received through the transparent surface; a light sensor comprising a plurality of pixels to detect the formed image of the object; and a controller to use the detected image to determine a motion of the object relative to the transparent surface, and to navigate a cursor and/or a menu on the display according to the determined motion.  
         [0016]     According to an aspect of the invention, the portable device further comprises a housing on which the display and the transparent surface are mounted and having a cavity housing the one or more lenses, the light sensor, and the controller.  
         [0017]     According to an aspect of the invention, the portable device comprises a handheld device, and the housing is shaped to be held in one hand.  
         [0018]     According to an aspect of the invention, the object is a fingertip, and the detected motion corresponds to a motion of the fingertip relative to the transparent surface.  
         [0019]     According to an aspect of the invention, the portable device further comprises an aperture array between the one or more lenses and the light sensor which blocks portions of the light to prevent the portions from being received at a non-corresponding pixel.  
         [0020]     According to an aspect of the invention, each portion of the one or more lenses corresponds to one of the pixels and directs a portion of the image to the corresponding pixel, and the aperture array blocks the portions of the image portion directed to the non-corresponding pixel.  
         [0021]     According to an aspect of the invention, a distance between the transparent surface and the sensor is substantially 1 mm.  
         [0022]     According to an aspect of the invention, the portable device further comprises a light source directed to the object and which is used by the light sensor to detect the formed image of the object.  
         [0023]     According to an aspect of the invention, the light source comprises an LED.  
         [0024]     According to an aspect of the invention, the light source comprises a laser which produces an interference pattern using the object used to produce the image of the object.  
         [0025]     According to an aspect of the invention, a portable device comprises a transparent surface; a microlens array comprising a plurality of lenslets, each lenslet forming a corresponding image of an object using light received through the transparent surface; a light sensor comprising a plurality of pixels, each pixel corresponding uniquely to one of the plurality of lenslets, to detect the formed images of the object; and a controller to use the detected images to determine a motion of the object relative to the transparent surface, and to output the detected motion to a display for use in navigating a cursor and/or a menu on the display according to the determined motion.  
         [0026]     According to an aspect of the invention, the portable device further comprises a display.  
         [0027]     According to an aspect of the invention, the sensor is disposed substantially 1 mm from the transparent surface.  
         [0028]     According to an aspect of the invention, the portable device further comprises a light source directed to the object and which is used by the light sensor to detect the formed image of the object.  
         [0029]     According to an aspect of the invention,the microlens array is directly bonded to the light sensor according to a resist reflow process or injection molding process.  
         [0030]     According to an aspect of the invention, the microlens array further comprises an aperture system which blocks portions of light from non-corresponding lenslets so as to prevent the portions from being received on a same pixel.  
         [0031]     According to an aspect of the invention, each lenslet forms the corresponding image of the surface on the corresponding pixel at a corresponding offset from a centerline of the lenslet, and an amount of the offset varies as a function of distance from an edge of the light sensor.  
         [0032]     According to an aspect of the invention, each lenslet has a diameter, the diameter is in a range at or between 5 to 200 microns, and a height of the microlens array is in a range at or between 5 to 500 microns.  
         [0033]     According to an aspect of the invention, each lenslet corresponds to one of the pixels, and a number of pixels of the light sensor is in a range at or between 50 to 2,000 pixels.  
         [0034]     According to an aspect of the invention, the portable device comprises a telephone having the display. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0036]      FIG. 1  is a portable telephone having an optical navigation module according to an embodiment of the invention;  
         [0037]      FIG. 2A  is a top view of a microlens array shown in  FIG. 1  and  FIG. 2B  is a top view of a sensor array according to an aspect of the invention;  
         [0038]      FIG. 3  is a cross section across section A-A of the microlens and sensor arrays of  FIGS. 2A and 2B  and showing an offset between lenslets and the corresponding pixels according to an aspect of the invention;  
         [0039]      FIG. 4  is an example of the optical navigation module of  FIG. 1  using a set of apertures according to an aspect of the invention;  
         [0040]      FIG. 5  is an example of the microlens array of  FIG. 4  showing the apertures and an offset according to an aspect of the invention;  
         [0041]      FIG. 6  is a result of a computer simulation of an example of the optical navigation module of  FIG. 4  showing amounts of amounts of light imaged by a single lenslet and which is received at a corresponding pixel relative to non-corresponding pixels;  
         [0042]      FIGS. 7A and 7B  shown an example of a light source integrated on a periphery of the sensor according to an aspect of the invention;  
         [0043]      FIGS. 8A and 8B  shown an example of a light source integrated on between pixels of the sensor according to an aspect of the invention; and  
         [0044]      FIG. 9  shows an example of a light source not using a light guide according to an aspect of the invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0045]     Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
         [0046]      FIG. 1  shows a phone  100  utilizing an optical navigation device  140  according to an aspect of the invention. The phone  100  is shown as a cellular phone, but may be a wired or wireless phone in other aspects. The phone  100  includes a primary keypad  110 , including alphanumeric and other like keys for use and entering numbers and/or characters. The phone  100  includes specific function keys  120  which provide specific functionalities such as send, end-call, and other like commands. Above the specific function keys  120  is a display  130 . The display  130  displays information relevant to the user, and can include preset images and video received at the phone  100 .  
         [0047]     The display  130  can be any type of display, such as an OLED or LCD type display. Moreover, the phone  100  can be of a clam shell design, in which the display  130  is on a separate half of the phone  100  as compared to the primary keypad  110  and/or keys  120 , and/or can be supplemented by an exterior display (not shown). Moreover, the phone  100  is merely one example of a hand-held device utilizing an optical navigation device  140 . Other examples of such a device include personal digital assistants (PDAs), Smartphones, and Blackberry type communication devices. Moreover, while describing the context of a portable phone  100 , it is understood that the optical navigation device can be used in MP3 and other multi-media type players and recorders, such as an IPOD. Moreover, the optical navigation device  140  could be implemented using cameras and camcorders in order to navigate through screens and menus on the display  130 , and can also be used for remote controls and hand-held devices such as wireless game controllers and/or remote controllers. For these hand-held computer devices, the display  130  may not be included on the hand-held device itself and instead may be in communication with the optical navigation device  140  and other aspects of the invention.  
         [0048]     The optical navigation device  140  shown in  FIG. 1  is a circular embodiment. However, it is understood that the device  140  can be other shapes, such as rectangular. Moreover, while shown in  FIG. 1  as being on the front of the phone  100  between keys  120  and above the keypad  110 , the optical navigation device  140  could instead be on the back or side, on the outside of a clam shell, or as part of a separate flip-out from the phone  100 .  
         [0049]     The operation of the optical navigation device  140  will be explained in relation to  FIGS. 2A through 4  according to aspects of the invention. As shown in  FIG. 4 , optical navigation is performed through the use of a finger  400  moving across a cover glass  405 . This movement allows for detection of the finger  400  motion within the plane of the cover glass  405 . However, it is understood that it might be possible to detect motion out of plane of the cover glass  405  in other aspects of the invention in order to further increase the ability to interact with the phone  100  through the device  140 .  
         [0050]     When the finger  400  is on the cover glass  405 , an image of the finger  400  is detected at a sensor array  210  using a flat lens array  200 . The sensor array  210  includes sensor pixels  215 . Each pixel  215  of the sensor array  210  receives a corresponding image from one of the microlenses  201  through  207  of the flat lens array  200 . The sensor array  210  can be a conventional CMOS image sensor or a CCD sensor according to aspects of the invention.  
         [0051]     The images from the pixels detected at the sensor array  210  are detected by a chip (not shown). The chip performs a comparative analysis over time of successive images in order to determine a direction and speed of the movement of the finger  400  relative to the cover glass  405 . Specifically, the chip includes firmware which compares present images detected by the pixels  215  of the sensor array  210  with images taken at a previous time, and the difference reveals the relative motion of the finger  400  to the cover glass  405 . An example of this comparative analysis is found in U.S. Pat. No. 5,644,139, the disclosure which is incorporated by reference. The resulting output is output to move a cursor on the display  130 .  
         [0052]     While existing optical navigation devices use a single objective lens to focus an image onto a sensor as a single image, as shown in  FIGS. 2A and 4 , the microlens array  200  (alternately referred to as a flat lens array) has a plurality of lenslets  201 ,  202 ,  203 ,  204 ,  205 ,  206 ,  207 . Each lenslet  201 ,  202 ,  203 ,  204 ,  205 ,  206 ,  207  focuses individual images onto corresponding pixels  510 ,  520 ,  530 ,  540 ,  550 ,  560 ,  570  of the sensor array  210 . This allows the lens array  200  to be placed closer to the cover glass  405 , thereby reducing the form factor (i.e., physical size) of the overall optical navigation device  140 . As shown in  FIG. 4 , the microlens array  200  is designed to be close to the sensor array  210 . While not required in all aspects, the microlens array  200  can be layered on and/or bonded to the sensor array  210  so as to further decrease the form factor.  
         [0053]      FIG. 3  shows an embodiment of the invention in which the microlens array  200  includes lenslets  201  through  207 . As can be seen in  FIG. 3 , light entering each lenslet is focused at a different angle, and therefore has an offset Δx when reaching the sensor array  210 . The offset Δx of each lenslet varies according to a distance from a center of the microlens array  200 . Specifically, the lenslet  204  has substantially no offset Δx and images along a center line. In contrast, lenslets  203 ,  205  have an increased offset Δx, lenslets  202 ,  206  have a larger offset, and lenslets  201 ,  207  have the largest offset Δx of the shown microlens array  200 . Using these offsets Δx, the microlens array  200  steers each image to a corresponding location chosen to reduce or prevent cross talk between adjacent pixels  510 ,  520 ,  530 ,  540 ,  550 ,  560 ,  570 . In this manner, the light is received radially. However, it is understood that the offset can increase or decrease according to other factors beyond distance from a center or edge, and need not be used for all of the lenslets of a particular array.  
         [0054]     Moreover, it is understood that, while shown in  FIG. 3 , there need not be offsets in all aspects of the invention. Specifically, for small distances between the cover glass  405  and the microlens array  200 , there is less overlap between images formed by the microlens array  200 . Thus, a distance between the glass  405  and the microlens array  200  of roughly 1 millimeter, there would not be appreciable overlap and offset would not be needed. In contrast, where the distance between the glass  405  and the microlens array  200  is 3 millimeters, there would be image overlap and some mechanism, such as an offset or an aperture, is more desirable to use in order to improve performance. The distance at which overlap occurs can be other than 3 millimeters depending on the design of the microlens array  200 .  
         [0055]     While many different shapes of the microlens array  200  are possible,  FIG. 2A  shows a circular embodiment of the microlens array  200  in which the lenses  201 ,  202 ,  203 ,  204 ,  205 ,  206 ,  207  shown in  FIGS. 2A and 3  correspond to concentric circles. In this manner, light is received radially as shown in  FIG. 3 .  
         [0056]     However, it is understood that the microlens array  200  can also be rectilinear or other shapes according to aspects of the invention. In this embodiment, the sensor array  210  has a corresponding rectilinear shape and receives light normally to the microlens array  200 , and the lenslets  201 - 207  extend in parallel to the pixels  215 . Moreover, the size of the sensor array  210  is substantially the size of the object field of the microlens array  200  and/or to a size of the finger  400  tip contacting the cover glass  405 . However, it is understood that the light need not be received normally in all aspects of this embodiment, such as when the light is imaged at a common angle to the pixels  215 , and that the sensor array  210  can have dimensions relative to the microlens array  200  and/or the object field.  
         [0057]     While the use in existing optical navigation modules is possible if the cover glass  405  is a few tens of centimeters from the microlens array  200 , the microlens array  200  allows for smaller distances on the order of a few millimeters. As such, the microlens array  200  allows for a small form factor, which is suitable for handheld devices such as the phone of  FIG. 1 . Preferably, for a small form factor and to reduce optical cross talk, the distance from the microlens array  200  to the cover glass  405  is less than three millimeters.  
         [0058]     Moreover, whereas existing uses of lens arrays, such as that shown in PCT Publication WO 00/64146 in  FIGS. 1 and 2 A as well as lenticular lenses exist and are usable in aspects of the present invention, these existing lens arrays require extensive effort to prevent ghosting and cross-over of the images, which makes these lens arrays less desirable for use even for human consumption. By way of example, the lens array of PCT Publication WO 00/64146 requires the use of a specific offset in order to produce an image suitable for a camera. In contrast, the microlens array  200  according to aspects of the present invention is used for optical navigation and does not need such a precise image and can have a simpler design. Further the microlens array  200  has a nearly zero angle field of view, and is thus able to image a larger total field of view. This ability simplifies the alignment of the lenslets with any aperture array so as to reduce fabrication costs.  
         [0059]     While not required in all aspects of the invention, the microlens array  200  has a thickness in a range between a few microns to a few hundred microns thick. According to an aspect of the invention, the diameter of each lenslet  201  through  207  is on the order of 5 to 200 microns, and a height of the microlens array  200  is in a range at or between 5 to 500 microns. As such, light from a small area of the lens array  200  (such as a 100 micron by 100 micron area) is directed to a corresponding pixel  215  of the sensor array  210 .  
         [0060]     Additionally, while the microlens array  200  can be separately attached and/or have a layer between the array  200  and the sensor array  210 , the microlens array  200  may be bonded directly to the sensor array  210  according to an aspect of the invention. Such direct bonding would allow for reduced fabrication cost, greater ease in pixel-lenslet alignment, and a lower form factor as compared to conventional lenses. Any aperture set(s) could be disposed as layers in such a construction which further facilitates an alignment of pixels and the aperture set openings. The microlens array  200  can be fabricated using any optical material normally used for lenses. By way of example, glass, plastic or a plastic photoresist may be used according to an aspect of the invention.  
         [0061]     According to an aspect of the invention, the photoresist is used at a wafer level scale by forming the lenses  201  through  207  through a resist reflow process. In the resist reflow process, the resist is placed on a wafer, the resist is lithographically patterned to correspond to the pixel layout, and then heat is generated in order to reflow the resist to form the individual lenses  201  through  207  through surface tension. Alternately, the photoresist or other optical material can be formed into the microlens array  200  through processes such as injection molding, preferably at wafer level.  
         [0062]     While seven lenslets  201  through  207  are shown in  FIGS. 2A and 3  for simplicity, it is understood that additional lenslets and detectors often will be needed. Specifically, for a one lenslet per pixel embodiment, there may be between 10×10 or 30×30 pixels in an array according to aspects of the invention. As such, a corresponding number of lenslets would be used. However, it is understood that for other applications, the pixel array of the sensor array  210  can be between 50 to 2,000 pixels. As such, a corresponding number of lenslets would be needed for the microlens array  200 . Moreover, while a one-to-one pixel to lenslet arrangement is described, it is understood that other ratios can be used in other aspects of the invention. While shown as focusing light along the centerline, it is understood that each lenslet could focus light at a same angle according to another aspect of the invention.  
         [0063]     Preferably, the field of view for each lenslet is restricted in order to prevent overlap and ghost images. Overlap and ghosting occur due to optical cross talk when light from a lenslet forms an image on or contacts an unintended pixel. According to an aspect of the invention, the field of view of each lenslet is reduced by reducing a distance between the glass  405  and the microlens array  200 . Essentially, the greater the distance, the greater likelihood of overlap. Thus, the field of view of each lenslet is directed at a small angle so that the field of view of one lens does not overlap substantially with a field of view of an adjacent lenslet. As such, offsets need not be used in all aspects of the invention to prevent cross talk.  
         [0064]     While not required in all aspects, the effective field of view can be reduced and better controlled through blocking of the light focused by each image using an aperture array. The aperture array can include single or multiple opaque layers with apertures therein according to aspects of the invention. By creating the aperture array, the ghosting and cross talk can be reduced by blocking light causing the ghosting. Moreover, since the existence of ghost images is not fatal in the context of optical navigation and depending on the use of offset and the distance between the flat lens array  200  and the sensor array  210 , the use of the aperture array need not be used in all aspects of the invention.  
         [0065]     An example of the relationship between the lens array  200 , an aperture array, and the sensor array  210  is shown in  FIG. 4 . As shown, the finger  400  contacts the cover glass  405  and moves relative to the cover glass  405 . The finger  400  is illuminated by a light source  460 . Light reflected from the finger  400  passes through the cover glass  405  and is imaged by the microlens array  200 . The microlens array  200  is disposed on one side of a glass  410 . On the other side of the glass  410  is disposed a first aperture set  420 . Light imaged by the lens array  200  passes through the glass  410  and is at least partially blocked by the first aperture set  420 . The remaining light which passed through the apertures of the first aperture set  420  sequentially passes through apertures of a second aperture set  430 , a second piece of glass  440 , and apertures of a third aperture set  450  prior to being received at the sensor array  210 . While not required in all aspects, the third aperture set  450  is in contact with the sensor array  210 .  
         [0066]     In the shown example, the optical navigation device  140  has a diameter of roughly 3 mm. The cover glass  405  has a thickness of 0.5 mm. The distance between the bottom of the cover glass  405  and the flat lens array  200  is 0.3 mm. Moreover, the distance between the microlens array  200  and the sensor array  210  is 0.25 mm, thereby making the device  140  only 1.05 mm thick. However, it is understood that other arrangements and thicknesses can be used. For instance, in order to allow the average fingertip to navigate, the diameter of the glass  405  would be on the order of 10 to 30 mm.  
         [0067]     As shown in greater detail in  FIG. 5 , three sets of apertures  420 ,  430 , and  450  are shown. The aperture sets  420 ,  430 ,  450  provide a restricted field of view so as to effectively block light from being received at the sensor array  210  except at image points  512 ,  522 ,  532 ,  542 ,  552 ,  562 ,  572  on corresponding sensor pixels  510 ,  520 ,  530 ,  540 ,  550 ,  560 ,  570 . The number of aperture sets can be other than the three sets shown in the embodiment in  FIGS. 4 and 5  according to other aspects of the invention. For instance, a single aperture set is suitable in some implementations, such as where a controlled illumination field is used and/or a distance between the microlens array  200  and the sensor array  215  is small. Thus, the use and number of aperture sets is dependent on the orientation of the various elements relative to each other.  
         [0068]     By way of example, assuming the cover glass  405  is at least 20 to 30 mm across, and a sensor array  210  is 10 mm across, the light received at the sensor array  210  at about a 40 to 45 degree angle. As such there is an increased risk of cross-talk and a need to improve the image in order to reduce this cross-talk such that an aperture array might be used. The greater the number of aperture sets, the more likely that the cross-talk will be reduced so as to improve optical navigation.  
         [0069]     An example of the improvement is readily seen in the simulation shown in  FIG. 6 .  FIG. 6  shows the result of a computer simulation in which aperture sets  420 ,  430 ,  450  were exposed to light from an extreme left of the cover glass  405 . The measured amount on the x axis relates to a normalized amount of light flux for light imaged by the left most lenslet of the flat lens array  200  and received at positions on the sensor plane corresponding to the positions of pixels  215 . The leftmost lenslet is designed to correspond with the leftmost position such that ghosting occurs for light received at the remaining positions to the right of the leftmost position. Each of the apertures of the aperture set  420  had a diameter of 50 μm, each of the apertures of the aperture set  430  had a diameter of 30 μm, and each of the apertures of the aperture set  450  had a diameter of 5 μm.  
         [0070]     According to the shown computer simulation, for light originating at the extreme left of the cover glass  405  which passed through the leftmost lenslet, very little of the light received at pixel locations other than the corresponding leftmost pixel position (i.e., the location corresponding to the left most lenslet). The shown amounts are normalized by the light received at the corresponding leftmost pixel location, which is denoted with a 100%. In contrast, for the adjacent pixel position, at most 1.2% of the light from the leftmost lenslet is received at the adjacent pixel position. As such, the use of multiple aperture sets reduces optical cross-talk so as to improve the contrast and the optical navigation. However, it is understood that other sizes of the apertures and/or distances can be determined according to other aspects of the invention.  
         [0071]     According to an aspect of the invention, in order to further prevent ghosting and other effects caused by optical cross-talk, a controlled illumination field matching the imaging field of the microlens array  200  is used to reduce cross-talk. As such, where a controlled illumination field is provided, the apertures are not needed, but still are preferable. However, if ambient light is used for illumination, the apertures is preferred since there is more likely to be ghosting and optical cross-talk where the illumination field is variable.  
         [0072]     The light source  460  can used in order to provide an illumination field sufficient to illuminate the finger  400  as shown in  FIG. 4 . As such, according to an aspect of the invention, the microlens array  200  would have a field of view matching the illumination field provided by the light source  460 . Examples of such light sources  460  include an LED, a laser, or other like light emitting device. According to an aspect of the invention, where the light source  460  is the laser, the laser produces interference patterns due to features of the surface such that the formed image is of the interference patterns imaged by the microlens array  200  to detect motion.  
         [0073]     However, it is understood that ambient light can be used in addition to the light source  460  or instead of the light source  460  according to an aspect of the invention. Moreover, light used to generate the display  130  might also be sufficient in other aspects.  
         [0074]     Additionally, while shown in  FIG. 4  as being separate from the sensor array  210 , it is understood that the light source  460  can be integrated with the sensor array  210  in order to further reduce the form factor and the thickness of the optical navigation device. Such integration can be performed using semiconductor and/or lithography techniques. Examples of such integrated light sources  460  and sensor arrays  210  are shown in  FIGS. 7A through 9 .  
         [0075]      FIG. 7A  shows a cross sectional view of the integrated light source shown in  FIG. 7B . As shown in  FIGS. 7A and 7B , the light source  460  is included on a wafer W holding the sensor array  210  and the microlens array  200 . The light source  460  includes a light input  710  and a light guide  720 . The light input  710  emits light into the light guide  720 , which is disposed on a periphery of the sensor array  210 . In this manner, the light guide  720  and light input  710  are disposed in an area normally used for circuitry and not required for receiving images. The light input  710  can be an LED or laser according to an aspect of the invention, but could also be light supplied from the display  130 . The light guide  720  guides the input light to illuminate the cover glass  405 . It is understood that, while only one light input  710  is shown and is disposed at a corner of the light guide  720 , multiple light inputs can be used and/or can be otherwise located.  
         [0076]     Alternately, as shown in  FIGS. 8A and 8B , the light source  460  can be between pixels of the sensor array  210  according to an aspect of the invention.  FIG. 8A  shows a cross sectional view of the integrated light source shown in  FIG. 8B . Specifically, the light inputs  710  input light into the light guide  720 . The light guide  720  is shaped as a cross hatched matrix so as to emit light between the lenslets-pixel pairs. While shown as being between discrete lenslets of the flat lens array  200  so as to emit light between the lenslets, it is understood that the light guide  720 , could instead send light at least partially through the lenslets. Further, it is understood that the light guide  720  can have other shapes, need not form a cross hatch pattern, and need not pass between each adjacent pair of pixels as shown.  
         [0077]      FIG. 9  shows an example of an integrated light source  460  not using a light guide according to an aspect of the invention. Specifically, in  FIG. 9 , only light inputs  710  are used. However, the use of the light guides  720  allows the light to be emitted from a point closer to the cover glass  405  as compared to the examples shown in  FIGS. 4 and 9 .  
         [0078]     While shown in  FIGS. 7A through 9  as using separate light input  710  and light guides  720 , it is understood that the shown patterns can be replaced with light emitting layers, such as those used in organic electroluminescent displays (OELDs) and organic light-emitting diodes (OLEDs). In this manner, strips of light emitting material can be deposited between pixels and/or around pixels to provide the light without increasing a distance between the microlens array  200  and the cover glass  405  and/or increasing a form factor of the phone  410  or other like optical navigation modules.  
         [0079]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.