Abstract:
A barcode reader having a light source illuminating a barcode, a diffuser disposed between the light source and the barcode, a camera opening at least partially surrounded by the diffuser, light reflected from the barcode passing through the camera opening and a camera oriented to acquire light reflected from the barcode after passing through the diffuser from the light source.

Description:
BACKGROUND 
   1. Field of the Invention 
   The present invention relates to a system for scanning optical codes formed on specular backgrounds. More specifically, the invention relates to systems for aiming and acquiring a code on a specular background with a portable scanning device. 
   2. Background 
   In many situations it is advantageous to identify and track items that are used in some task or that pass through a supply or distribution chain. For certain items it is not practical to attach tags or other identifying implements, such as when the items are very small or are designed to operate in harsh environments. In those cases, a solution is to direct mark the items, meaning that a barcode or other identification element is directly formed on the item&#39;s surface. 
   Direct marking of items is often used for surgical instruments that are tracked during medical procedures, and for other types of small tools. These often have a specular surface which reflects impinging light. This is often problematic for conventional optical code readers, because the mirror-like surface may reflect images to the camera that make it difficult to read the code. 
   SUMMARY OF THE INVENTION 
   A barcode reader having a light source illuminating a barcode, a diffuser disposed between the light source and the barcode, a camera opening at least partially surrounded by the diffuser, light reflected from the barcode passing through the camera opening and a camera oriented to acquire light reflected from the barcode after passing through the diffuser from the light source. 
   A method for providing light through a diffuser to a barcode and a specular background and collecting, by a camera, light reflected from the barcode, the light passing through an opening in the diffuser. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a diagram of an exemplary barcode reader having a camera in the center of a diffuser according to the present invention. 
       FIG. 2  is a diagram of an exemplary field of view of the barcode reader shown in  FIG. 1 . 
       FIG. 3  is a diagram of another exemplary embodiment of a barcode reader having a camera in the periphery of a diffuser according to the present invention. 
       FIG. 4  is a diagram of a third exemplary embodiment of a barcode reader having an aiming device according to the present invention. 
       FIG. 5  is a front view of the barcode reader shown in  FIG. 4 . 
       FIG. 6  is a diagram of a fourth exemplary embodiment of a barcode reader having a curved diffuser according to the present invention. 
       FIG. 7  is a diagram of a fifth exemplary embodiment of a barcode reader having a funnel shaped diffuser according to the present invention. 
       FIG. 8  is a perspective view showing an exemplary image scanner according to the present invention. 
       FIG. 9  is a perspective view of a funnel shaped diffuser according to the present invention, useable in the image scanner of  FIG. 8 . 
       FIG. 10  is a side view showing the funnel shaped diffuser shown in  FIG. 9 . 
   

   DETAILED DESCRIPTION 
   The present invention may be further understood with reference to the following description and to the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to a system for scanning optical codes formed on specular backgrounds. More specifically, the invention relates to systems for aiming and acquiring a code on a specular background with a portable scanning device. Throughout this description, the term specular will be used consistent with its common meaning, e.g., of, relating to, or having the qualities of a mirror. That is, the specular background may be any reflective surface to which a barcode is directly applied (e.g., engraved), affixed, etc. 
   Specular background surfaces offer difficult challenges for barcode reading systems. Those surfaces reflect the illumination source, create highlights that destroy the data of the barcode within the highlight, and reflect images of the reader device back to the reader. To reduce these problems, a diffuse light source rather than a point source is used to illuminate the barcode. The exemplary embodiments of the present invention provide a barcode reader system that can read a barcode formed on a reflective surface. Further exemplary embodiments provide a simple way of aiming the device so the barcode may be acquired. 
     FIG. 1  shows an exemplary barcode reader  100  used to read a barcode  120  from a specular background surface  122 . The barcode reader  100  comprises a housing  102  with a diffuser  104  at one end, designed to provide diffuse light to illuminate the barcode  120 . The diffuser  104  may be formed of a light scattering translucent material or from a transparent material modified with a surface texture to provide the diffuse light. The diffuser  104  is illuminated by one or multiple light sources  106 . Typically the diffuser  104  is disposed between the barcode  120  and the light sources  106 . For example, the diffuser  104  may be circular, oval, or have another shape to fit in the housing  102  of the device  100  The light sources  106  may include LED&#39;s, incandescent lights or other light emitters. 
   A camera  110  is located adjacent to the diffuser  104 , so that its image receiving opening  114  faces the barcode  120 . In this example, the camera  110  is placed centrally behind a central opening  108  in the diffuser  104 . However, placing the camera  110  at the center of the diffuser  104  may be problematic. In the example of  FIG. 1 , the lines  130  define the boundary of a field of view (“FOV”)  132  of the diffuser  104  illuminating the barcode  120 . Throughout this description, the term diffuser FOV is used to describe this FOV. However, those skilled in the art will understand that the diffuser itself does not have an FOV. Rather, the term diffuser FOV describes the view of the diffuser  104  by the camera  110 . More specifically, the camera  110  sees the reflection of the diffuser  104  from the specular background  122 . The barcode  120  prevents some of the light from the reflection of the diffuser  104  from reaching the camera  110  and thus forms a contrast on the image. This contrast is then analyzed to read the barcode  120 . However, in the arrangement shown in  FIG. 1 , the diffuser FOV  132  will include the central opening  108 , i.e., the camera  110  will not see a contiguous portion of the diffuser  104 . This absence of a reflection of the diffuser  104  in the area of the central opening  108  may cause a black spot or other shadow on the image captured by the camera  110  leading to an unreadable barcode. 
   Another issue illustrated in  FIG. 1 , is that if the camera  110  of the reader  100  is aimed orthogonally at the surface  122  containing the barcode  120 , the camera rays  116  define a camera FOV  112 . As can be seen from  FIG. 1 , the reflection of the camera  110  may occur within the FOV  112  and may be superimposed on the image of the barcode  120 . This may make the barcode  120  unreadable. 
   Another problem that may occur by placing the camera  110  in the center of the diffuser  104  is illustrated in  FIG. 2 . In the configuration shown in  FIG. 2 , the camera rays shown as lines  116 ′ define a camera FOV  112 ′ for the upper half of the reader  100 . In addition, the lines  130 ′ define the diffuser FOV  132 ′. If the barcode  120  is moved slightly away from the centerline of the camera opening  114 , the reflection of the camera  110  may no longer be problematic, but it becomes difficult to maintain the barcode  120  within the FOV  132 ′. A barcode acquisition region  126  is delimited by the intersection of the FOV  132 ′ and the target surface  122 . From the diagram it can be seen that the barcode  120  has substantially the same dimensions as the barcode acquisition region  126 . This means that any movement of the barcode  120  relative to the reader  100  puts it outside of the barcode acquisition region  126 , leaving no margin of error in placing the reader  100  relative to the barcode  120 . As would be understood by those skilled in the art, the placement of the barcode  120  toward the lower half of the reader  100  would result in the same issues since the diffuser  104  is symmetric with respect to the optical axis of the camera  110 . 
   Thus, the system described with respect to  FIGS. 1 and 2  becomes impractical because of the small or non-existent margin of error in placing the reader  100  to successfully read the barcode  120 . Except for a small range of relative positions, either the reader&#39;s image is reflected back into the camera  110 , or the light from the diffuser  104 , as reflected by the barcode  120 , does not reach the camera opening  114 . The analysis above also applies to the bottom half of the diffuser  104 , since the diffuser  104  is symmetrical with respect to the optical axis of the camera  110 . 
     FIG. 3  shows an exemplary embodiment of a barcode reader  200  according to the present invention. The barcode reader  200  includes a housing  202 , a diffuser  204 , LEDs  206 , and camera  210 . In a preferred embodiment of a barcode reader  200  according to the present invention, the camera  210  is located on a side of the diffuser. It should be noted that the placement of the camera  210  at the lower extremity of the diffuser  204  is only exemplary. The camera  210  may be placed anywhere on the periphery of the diffuser  204  to obtain the benefits described herein. The placement shown in  FIG. 3  shows a configuration that may be comfortable and intuitive for a user of a reader shaped like the reader  200 . Furthermore, the placement of the LEDs  206  is only exemplary and the LEDs  206  (or other light source) may be placed in any location that provides sufficient illumination through the diffuser  204  to illuminate the barcode  120 . 
   This configuration shown in  FIG. 3  almost doubles the FOV  232  of the diffuser, so that it is much easier to locate the barcode  120  within the diffuser&#39;s FOV  232 . There is a much wider range of positions of the barcode  120  relative to the reader  200  that will allow the camera opening  214  to see the light from the diffuser  204  reflected by the barcode  120 , without distortions from the reflected image of the camera  210  being also visible. 
   As shown, the lines  230  define the FOV  232  of the diffuser  204 , while the lines  216  define the FOV  212  of the camera. In turn, the intersection of the FOV  232  and the surface  122  delimits the barcode acquisition region  226  where the barcode  120  can be found so that it reflects the light from the diffuser  204  to the camera opening  214 . The wider the angular FOV  232 , the easer it is to acquire the barcode  120  because the barcode  120  may be located within any portion of the FOV  232  and still be acquired by the camera  210 . In this exemplary embodiment, substantially all the locations of the barcode  120  within the barcode acquisition region  226  avoid distortion due to the image of the camera  210  being reflected back to the camera opening  214 . 
   Because of the conical shape of the FOV  232 , the size of the barcode acquisition region  226  decreases as the distance between the reader  200  and the barcode  120  increases. This effect can be offset by increasing the size of the diffuser. However, an optimum use for the exemplary barcode reader  200  is to read small, high density barcodes applied to reflective surfaces which are read from small distances. An example of this situation is the tracking of medical instruments during surgical procedures. 
   In the above embodiment, the barcode acquisition region  226  is not aligned with the center of the diffuser  204 . This complicates aiming the device, such that an aiming mechanism may be beneficial. In another exemplary embodiment of a barcode reader  250  shown in  FIG. 4 , an aiming device  252  is included to facilitate acquisition of the barcode  120 . The barcode reader  250  includes the same components as the barcode reader  200  including a housing  152 , a diffuser  204 , LEDs  206  and a camera  210 . As described above, the configuration of these components is only exemplary. The laser aiming device  252  is provided with the barcode reader  250  to facilitate acquisition of the barcode  120  by the camera  210 . The exemplary laser aiming device  252  may be placed behind the diffuser  204 , and may shine through an aiming window  256  formed therein. The aiming device  252  projects a visible dot of light  254  at an optimum location of the barcode  120 . For example, the dot of light  254  may mark the center of the barcode acquisition region  226 . The aiming device  252  may be any device that can project a laser light or any defined beam of light through the aiming window  256 . 
   A front view of the barcode reader  250  is shown in  FIG. 5 . The small size of the aiming window  256  reduces or eliminates any optical distortion that a reflected image of the aiming device  252  may cause to the acquisition of the barcode image by the camera  210 . The camera opening  214  is also small, and is located at the periphery of the diffuser  204  so that its reflection will not degrade the image of the barcode  120 . 
   Those skilled in the art will understand that it is not necessary to physically locate the camera outside the periphery of the diffuser to obtain the results described above. For example, the objective of the camera opening may be located there, while the body of the camera is at another location. As described in greater detail below, optical elements such as mirrors, light pipes, optic fibers etc. may be used to place an effective camera opening at a location remote from the camera itself. 
   Another exemplary embodiment of a barcode reader  300  according to the present invention is shown in  FIG. 6 . The reader  300  comprises a housing  326  having a transparent exit window  324  on one side. The diffuser  304  according to this embodiment is curved, so that one edge meets the housing  326  along a portion of the exit window  324 . This layout ensures a common boundary of the diffuser  304  and exit window  324 , maximizing the dimensions of the diffuser  304  relative to the exit window  324 . Because the diffuser  304  is generally concave, it size is further maximized. 
   A camera mirror  320  is disposed adjacent to an edge of the diffuser  304 , to make the camera  310  appear to be located outside of the diffuser  304 . Using this mechanism it is possible to generate an effective camera opening  322  that is located away from the edge of diffuser  304 , while the camera  310  is located somewhere else, for example behind the diffuser  304 . This exemplary embodiment allows more freedom in locating the camera  310  within the housing  326 . It also allows the minimization of the size of the effective camera opening  322 , and to locate it as desired, such as at the edge of the exit window  324 . 
   As in the exemplary embodiments described above, the diffuser  304  is illuminated by one or more light sources  306 . These may comprise LED&#39;s or other light elements, and may be coupled to the diffuser  304  by a light pipe  334 . A mirrored reflector  328  can be placed behind the diffuser to increase the light efficiency of the diffuse surface light source. In addition, the laser aimer  352  is also included in this embodiment. 
   As can be seen in the diagram of  FIG. 6 , the light rays depicted by lines  330  define an angular camera FOV  332 . This FOV  332  is larger than an FOV possible with a centrally located camera (e.g., FOV  112  of  FIG. 1 ), and allows easier acquisition of the image from the barcode  120 , without the distortion of the image characteristic of a centrally located camera. 
   For certain applications it may not be practical to design a diffuser and camera arrangement where the camera opening is beyond the edge of the diffuser, or uses a mirror arrangement to create an effective camera opening remote from the camera. For example, to remain compatible with pre-existing readers, it may be necessary to place the camera within the area of the diffuser. 
   A further exemplary embodiment of a barcode reader  400  according to the present invention is shown in  FIG. 7 . In this exemplary embodiment, the centrally located camera  410  configuration of  FIGS. 1 and 2  is used. However, the diffuser  404  of the reader  400  extends backwards in a funnel shape towards an opening  414  of the camera  410 . Shaping the diffuser  404  as a funnel maximizes its dimensions relative to the size of the exit window of the device  400 . The increased size of the diffuser  404  results in a larger diffuser FOV  432  than if the diffuser  404  was planar, thereby improving the illumination of the barcode  120 . Thus, this exemplary embodiment may solve the orthogonal reflection issue with respect to the camera  410  in centrally located camera configurations by providing for a smaller camera opening and also provides for a larger diffuser FOV. 
     FIG. 8  shows an embodiment of a hand held barcode reader  450  having a funnel shaped diffuser  452  with a centrally located camera opening  454 . As described above, such an arrangement may be used with a current design of a barcode reader. For example, the diffuser  452  and camera (not shown) may be able to be placed within a housing of a currently available barcode reader  450  without having to redesign the housing and other portions of the barcode reader  450 . Thus, a supplier of devices may provide users with the benefit of the larger field of view without having to completely redesign the housing of their barcode readers. 
     FIGS. 9 and 10  show in more detail the funnel shaped diffusers according to the exemplary embodiment described above. The funnel shaped diffuser  452  comprises a camera opening  454  through which a camera can acquire the reflected image of a barcode. This exemplary embodiment of the funnel shaped diffuser  452  may be used with existing barcode readers, such as the DS6607 and DS6707 manufactured by Symbol Technologies. In this case, some of the advantages obtained by placing the effective camera opening outside of the diffuser may be limited to make the device compatible with existing barcode readers. 
   The present invention has been described with reference to specific exemplary embodiments. Those skilled in the art will understand that changes may be made in details, particularly in matters of shape, size, material and arrangement of parts. Accordingly, various modifications and changes may be made to the embodiments without departing from the scope of the claims below. The specifications and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.