Patent Publication Number: US-6992846-B2

Title: Micro reader scan engine with prism

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional application of application U.S. Ser. No. 09/668,105, filed on Sep. 22, 2000, now U.S. Pat. No. 6,775,077, the entirety of which is hereby incorporated by reference as if fully set forth herein. 

   TECHNICAL FIELD 
   The present invention relates generally to data collection devices adapted for reading bar codes and other dataforms, and more particularly to a micro reader scan engine with a prism. 
   BACKGROUND OF THE INVENTION 
   Portable data collection devices are widely used in the manufacturing, service and package delivery industries to perform a variety of on-site data collection activities. Such portable data collection devices often include integrated bar code dataform readers adapted to read bar code dataforms affixed to products, product packaging and/or containers in warehouses, retail stores, shipping terminals, etc. for inventory control, tracking, production control and expediting, quality assurance and other purposes. 
   Bar code dataforms come in a variety of different formats including one and two dimensional bar codes, matrix codes and graphic codes, as well as words and numbers and other symbols, which may be printed or etched on paper, plastic cards and metallic and other items. For example, a one dimensional bar code dataform typically consists of a series of parallel light and dark rectangular areas of varying widths. The light areas are often referred to as “spaces” and the dark areas as “bars”. Different widths of bars and spaces define different characters in a particular bar code dataform. 
   Data originally encoded in a dataform is recovered for further use in a variety of ways. For example, a printed bar code may be illuminated to derive reflectance values which are digitized, stored in buffer memory and subsequently decoded to recover the data encoded in the bar code. The printed bar code may be illuminated using a laser, an array of LEDs, ambient light, or the like. The light reflected from the printed bar code typically is captured using a photosensor such as, for example, a CCD detector, CMOS detector, etc, which may take the form of a sensor array integrated circuit including a plurality of such device. 
   As data collection devices are used in more specialized applications, it is desirable to scan bar codes and other dataforms from different angles. Conventional scan engines include an image sensor component with an aperture adapted to receive incoming light from a scanned dataform. The light typically passes through an opening in the housing of the scan engine, and the housing may further include a protective cover for the opening. The trend in such devices is toward smaller and smaller packages, as a result of which it is desirable to reduce the size of the scan engine housing opening through which incoming light from a dataform enters. However, the image sensor components used in the data collection device scan engine may be too large to directly receive incoming light from a scanned dataform through a reduced size housing opening. Although the size of the aperture on such an image sensor may be reduced, the footprint of the integrated circuit on which the sensor aperture resides remains relatively large. Custom image sensor integrated circuits may be developed, however, it is desirable to use existing image sensor components to keep the data collection device scan engine cost low. Thus, there remains a need for a data collection device scan engine which may successfully scan dataforms from an angle using existing image sensor components through a reduced size housing opening, and which may scan bar code dataforms at an angle. 
   SUMMARY OF THE INVENTION 
   The present invention includes a scan engine for use in a data collection device, which minimizes or overcomes the above mentioned problems and shortcomings encountered in conventional scan engines. The invention further provides a method for producing a scan engine and a scan engine image sensor assembly which further address these shortcomings. 
   In accordance with an aspect of the present invention, there is provided a scan engine which includes a housing or enclosure with an opening for receiving light from a scanned dataform, an image sensor with an aperture, the image sensor being located within the housing and operative to sense light entering the aperture, and a prism located within the housing and adapted to receive light from the opening along a first path and to provide at least a portion of the received light to the aperture along a second path. In order to utilize existing image sensor integrated circuits, the prism allows the image sensor aperture to be mounted in the housing at an angle to the housing opening, which may be 90 degrees, whereby the second path is perpendicular to the first path. The invention thus allows the use of existing image sensor integrated circuits which may have a component width which is wider than the desired housing opening, in order to provide a reduced size scan engine in which existing image sensor components may be employed. 
   The prism may include a first planar face generally perpendicular to the first path and a second planar face generally perpendicular to the second path. In addition, the second face may be mounted on the aperture. The first face of the prism may be mounted proximate the opening located in a first wall of the housing. In this fashion, the prism may further operate as a protective cover for the housing opening, for example, wherein the first face of the prism is further adapted to cover the opening. In addition, the front surface of the prism may have a spherical convex shape, so as to serve as an imaging lens, and to thereby further reduce the scan engine cost and size. Moreover, the prism may be adapted to provide a seal around the opening of the first housing wall. Thus, an additional window or other protective cover for the housing opening is unnecessary, the elimination of which advantageously reduces the light signal losses associated therewith, and reduces manufacturing and assembly costs. 
   According to yet another aspect of the invention, there is provided a method for producing a data collection device scan engine. The method includes providing a housing with an opening for receiving light from a scanned dataform, mounting an image sensor within the housing, the image sensor having an aperture and being operative to sense light entering the aperture, and mounting a prism within the housing for receiving light from the opening along a first path and providing at least a portion of the received light to the aperture along a second path. The prism may comprise a first planar face generally perpendicular to the first path and a second planar face generally perpendicular to the second path, wherein the method may further include mounting the second face on the aperture. This may be accomplished, for example, using a low loss transparent adhesive. In this way, no gap exists between the second face of the prism and the image sensor aperture, thus further reducing incoming light signal loss. 
   In addition, where the opening is located in a first wall of the housing, the method may include locating the first face of the prism so as to cover the opening. Moreover, where a seal is desirable between the interior and exterior of the scan engine housing, the method may further include providing a seal around the opening of the first enclosure wall using the first face of the prism. The method thus eliminates additional housing windows associated with conventional scan engines, and the losses associated therewith. 
   According to still another aspect of the invention, there is provided a data collection device scan engine image sensor assembly. The assembly includes an image sensor having an aperture and being operative to sense light entering the aperture, and a prism mounted on the aperture and adapted to receive light along a first path and to provide at least a portion of the received light to the aperture along a second path. The prism may comprise a first planar face generally perpendicular to the first path and a second planar face generally perpendicular to the second path, wherein the first planar face may be further adapted to cover an opening in a scan engine housing. In addition, the first face of the prism may be further adapted to provide a seal around the opening of the scan engine housing. 
   To the accomplishment of the foregoing and related ends, certain illustrative aspects and implementations of the present invention are hereinafter described with reference to the attached drawing figures. The following description and the annexed drawings set forth in detail certain illustrative applications and aspects of the invention. These are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other aspects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram illustrating an exemplary data collection device in which various aspects of the present invention may be employed; 
       FIG. 2  is a schematic diagram illustrating another exemplary data collection device having a scan engine component in accordance with the invention; 
       FIG. 3  is a side elevation view in section illustrating a conventional scan engine with a sensor array and a lens; 
       FIG. 4  is a side elevation view in section illustrating an exemplary scan engine with a prism in accordance with an aspect of the invention; 
       FIG. 5A  is a side elevation view in section illustrating another exemplary scan engine with a prism in accordance with an aspect of the invention; 
       FIG. 5B  is a side elevation view in section illustrating another exemplary scan engine with a prism and a removable lens in accordance with another aspect of the invention; and 
       FIG. 6  is a flow diagram illustrating an exemplary method of producing a scan engine in accordance with another aspect of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. The following description and the attached drawings are provided in order to illustrate the various aspects of the present invention, and should not be interpreted as a limitation thereof. The invention provides a data collection device scan engine including an image sensor and a prism adapted to direct light from a bar code or other dataform onto an image sensor, which provides low signal loss and allows the image sensor to be located at an angle to the path of the light from the dataform. Although the invention finds particular utility in association with reduced size data collection devices, such as a micro reader, it will be appreciated that the invention may be employed in other applications as well. 
   Referring initially to  FIG. 1 , an exemplary data collection system  2  is schematically illustrated including a scan engine component  3  operatively coupled to a scanner processing system  6  via a system bus  9 . The scan engine  3  projects a light ray  7   a  through an aperture window  4  and a focusing system  5  on to an exemplary bar code or dataform target  8 . The bar code target  8  (e.g., a sequence of vertical black and white bars) is scanned from an X+direction (depicted as light ray  7   a ) to an X-direction (depicted as light ray  7   b ). It is to be appreciated that scanning may also take place in the opposite direction. 
   A plurality of light rays  7   c  (one ray is shown for simplicity) reflect from the target  8  back through the focusing system  5  on the scan engine  3 . The focusing system  5  may be a single optical lens system for directing and receiving light or may include a separate directing and receiving lens for sending and receiving light to and from the target  8 . Although conventional focusing systems variously include lenses and/or mirrors, the present invention advantageously provides a prism, as illustrated and described in greater detail hereinafter, which overcomes shortcomings associated with previous focusing system components. 
   The scan engine  3 , receives a light ray  7   c  and converts the ray to an electrical signal. The electrical signal is digitized and sent over the system bus  9  to the scanner processing system  6  for analysis and storage. It is to be appreciated that signal processing and analysis may take place at the scan engine  3 , or the scanner processing system  6 , or such processing tasks may be shared between the two system components  3  and  6 . For example, the scanner processing system  6  may provide a plurality of application software systems to process the bar code dataform information. Such application software systems may include, for example, accounting controls, inventory controls, pricing information, location information, and other information and/or functions suitably relevant to the dataforms and/or the items being scanned. 
   Turning now to  FIG. 2 , a block diagram of an exemplary data collection device  10  is provided, including a scan engine component  3  and a host interface component  50 . In the scan engine component  3 , a microprocessor  100  controls the various operations and performs image analysis in decoding a target dataform. For example, the microprocessor  100  may be programmed to carry out the various control and processing functions utilizing conventional programming techniques. A memory  116  coupled to the microprocessor  100  serves to store the various programs and other data associated with the operation of the data collection device  10  as described herein. A person having ordinary skill in the art will be able to program such operations without undue effort. Hence, additional detail is omitted for sake of brevity. 
   The microprocessor  100  is coupled to an address generator  102 , via a local bus  108 , which is designed to output a sequence of pixel addresses corresponding to a desired pixel data readout pattern from an image sensor or photosensor array  48 . For example, the microprocessor  100  may be configured to read out consecutive horizontal lines of pixel data from multiple zones so that such pixel data can be processed to reconstruct the entire dataform provided within the field of view of the data collection device  10 . 
   The addresses are provided from the address generator  102  to the photosensor array  48  via an address bus  106 . The photosensor array  48  provides, as its output data, pixel data on data bus  107  which corresponds to the address provided on the data bus  106 . The address generator  102  in turn provides the pixel data to the microprocessor  100  via bus  108 . Data may therefore be collected from the photosensor array  48  substantially in real time according to a predefined data readout pattern. It will be appreciated that while the present embodiment depicts the address generator  102  as being physically separated from the photosensor array  48 , it is possible for both components to be provided on a single image sensor chip. 
   The device  10  further includes a host interface board  50  including a trigger switch  26  and associated data form read trigger circuitry  104 . In order to carry out a dataform reading operation, the operator points a focusing system  5  towards a target dataform (e.g., dataform  8  of  FIG. 1 ). Light from the scanned dataform is directed by the focusing system  5  to an aperture window  4  which presents the light to the photosensor array  48 . The operator then initiates the dataform read operation via the trigger switch  26  or other methods. The dataform read trigger circuit  104  generates an interrupt signal which is provided to the microprocessor  100  indicating the initiation of a dataform reading operation. The microprocessor  100  communicates with the address generator  102  via the control bus  205  which causes the address generator  102  to begin generating addresses for the predefined readout pixel pattern. 
   The image data from the photosensor array  48  consists of digital data indicative of the instantaneous illumination of the pixel. For example, in the exemplary device  2  illustrated in  FIG. 1 , it is assumed that the target dataform  8  is made up of a series of black bars and white spaces. The photosensor array  48  of device  10  includes an analog to digital (A/D) converter  20  for converting analog pixel data obtained from the addressed pixels to digital pixel data. The A/D converter  20  has adjustable gain which may be adjusted via a gain adjust control signal provided on line  111  from the microprocessor  100 . The digitized pixel data from the photosensor array  48  is provided via the address generator  102  to the microprocessor  100 . The microprocessor  100  evaluates the range of the acquired pixel data on-the-fly to see if the full range of the A/D converter  20  is utilized. If not, the microprocessor  100  adjusts the gain of the input to the A/D converter  20 . The microprocessor  100  then proceeds to decode the image of the target dataform. 
   Additionally, the microprocessor  100  is coupled to the illumination assembly  42  via switching circuitry  126  which enables the microprocessor  100  to control the illumination assembly  42  to provide general illumination of a scanned target dataform and targeting during operation. The illumination assembly  42  of the present embodiment may employ any of various light sources having output light which is sculpted to be spread across such a dataform. Moreover, the microprocessor  100  may be coupled to an LED  32  to adjust its color state and/or to an audible annunciator or speaker  126  in order to indicate the current mode of operation. 
   The host interface board component  50  of the data collection device  10  may further include a communications transceiver  122  (e.g., RS-232, RS-485) and an associated connector  124  for transmitting and receiving data to and from remote devices, such as computers, modems, transmitters, etc, along with the LED  32  and a speaker  126 . In addition, the interface  50  may include power circuitry  130  and electrical connections  132  for providing electrical power from a power source  24  to the various components of the interface  50  as well as the scan engine component  3 . The power source  24  may include, for example, rechargeable batteries, and the like. 
   Referring now to  FIG. 3 , a conventional scan engine  200  is illustrated having an enclosure or housing  202  with a cover  204  in an opening therein, and a focusing lens  206 . Incoming light L reflected from the surface of a scanned dataform (not shown) passes through first and second surfaces  204   a  and  204   b  of the cover  204 , as well as first and second surfaces  206   a  and  206   b  of the lens  206 , and onto an aperture window  208  of an image sensor component  210 . The image sensor component  210  may be an integrated circuit mounted along with other components  212  on a printed circuit board (PCB)  214  mounted in the enclosure  202 . 
   It will be appreciated by those skilled in the art that the strength of the light signal L is reduced through signal losses associated with the materials used in making the cover  204  and the lens  206 , and further that there is a non-zero signal loss associated with each of the surfaces  204   a ,  204   b ,  206   a , and  206   b  associated therewith. In order to reduce these losses, the present invention provides a prism which may be employed to replace both the window  204  and the lens  206 , as illustrated and described in greater detail hereinafter. Thus, the invention reduces the signal losses found in conventional scan engines such as scan engine  200 . In addition, it will be recognized that the image sensor device  210  has a certain physical width W determined by the standard integrated circuit package sizes known in the art. As the size of scan engine components continues to decrease, it is desirable to decrease the overall height H 1  of such devices, and also to decrease the height H 2  of the enclosure opening for window  204 . However, the width W of the image sensor component  210  may be fixed for available standard components. 
   Referring now to  FIG. 4 , an exemplary scan engine  300  is illustrated in accordance with an aspect of the invention, including a low profile enclosure or housing  302  having a reduced height opening  304  with a window or protective cover  306  therein. The cover  306  may provide a seal between the interior and exterior of the scan engine housing  302 . The scan engine  300  further includes an image sensor component  310  with an aperture  308  thereon, wherein the sensor component  310  is mounted along with other components  312  on a PCB  314 . The image sensor  310  is operative to sense light entering the aperture  308  for processing as is known in association with bar code and other dataform readers. In accordance with an aspect of the invention, the scan engine  300  also includes a prism  320  located within the housing  302  and adapted to receive light L through the opening  304  along a first path  322  via an imaging lens  326  and to provide at least a portion of the received light L to the aperture  308  along a second path  324 . 
   The Prism  320  advantageously provides for mounting of a standard sensor  310  within the low profile housing  302  such that the first and second paths  322  and  324 , respectively, are generally perpendicular, although other angular arrangements are contemplated as within the scope of the invention. This allows use of standard sensors  310  which are too wide to be mounted in a plane parallel to the window  306 , particularly in low profile micro readers and the like. The prism  320  comprises a first planar face  320   a  generally perpendicular to the first path  322  and a second planar face  320   b  generally perpendicular to the second path  324 . 
   The second face  320   b  may further be mounted directly onto the image sensor aperture  308 , for example, using a low loss transparent adhesive (not shown). It will be noted in this regard, that while a gap (not shown) may be provided between the second face  320   b  of the prism  320  and the sensor aperture  308 , light signal losses associated with such a gap may be advantageously reduced according to an aspect of the invention through mounting the second face  320   b  of the prism  320  directly onto the aperture  308 . Furthermore, it will be appreciated that mounting the prism  320  directly onto the aperture  308  of the image sensor component  310  further reduces the size of the image sensor assembly. Moreover, the use of a prism  320  mounted to the aperture  308  provides for repeatable angular reflection of light from path  322  to path  324 . In conventional scan engines employing mirrors, the placement of such mirrors required careful manufacturing and assembly steps to ensure the desired angular reflection. In addition, the light signal losses associated with mirrors is greater than that of prisms. Thus, the present invention provides for a cost effective improvement over such conventional devices and manufacturing methodologies. 
   In accordance with another aspect of the invention, the first face  320   a  of the prism  320  may be further located proximate the opening  304  in the housing  302 , thereby reducing or eliminating the signal losses associated with a gap (not numerically designated) therebetween. In addition, the invention further allows the elimination of the cover  306  and the light losses associated with the front and rear surfaces  306   a  and  306   b , respectively, thereof. 
   Referring also to  FIG. 5A , another exemplary scan engine  400  is illustrated in accordance with the invention. The scan engine  400  includes a housing  402  having an opening  404  in a first wall  406  thereof, and through which light L is introduced to a first face  420   a  of a prism  420  along a path  422 . Scan engine  400  further includes an image sensor component  410  with an aperture  408  thereon, wherein the sensor component  410  is mounted along with other components  412  on a PCB  414 . As shown, the first face  420   a  of prism  420  is mounted within the housing  402  so as to provide a seal between the exterior and interior of the scan engine  400 , whereby the need for an additional window (e.g., window  204  of  FIG. 3 ) is eliminated. 
   The image sensor  410  is adapted to sense light L entering the aperture  408  along a second path  424 . In accordance with an aspect of the invention, the scan engine  400  also includes the prism  420  located within the housing  402  and adapted to receive light L from the opening  404  along the first path  422  and to provide at least a portion of the received light L to the aperture  408  along a second path  424 . Although there may be non-zero surface losses associated with the first and second faces  420   a  and  420   b , respectively, of the prism  420 , it will be appreciated that the invention provides for the reduction in total light signal loss through the elimination of the window (e.g., window  204  of  FIG. 3 ), and the mirrors, lenses, and/or air gaps along the light paths of prior conventional scan engines. 
   The prism  420  furthermore advantageously provides for mounting of a standard sensor component  410  (e.g., having a standard integrated circuit footprint size) within the low profile housing  402  such that the first and second paths  422  and  424 , respectively, are generally perpendicular, although other angular arrangements are contemplated as within the scope of the present invention. Standard sensors  410  may thus be employed which are too wide to be mounted in a plane parallel to the window  406 , particularly in low profile micro readers and the like. The prism  420  comprises a first face  420   a  generally perpendicular to the first path  422  and a second planar face  420   b  generally perpendicular to the second path  424 . 
   In addition, the first face  420   a  may include a spherical convex shape, whereby the prism  420  may also serve as an imaging lens. Thus, the prism  420  advantageously allows cost and/or size reduction through the elimination of a separate lens (e.g., lens  326  of  FIG. 4 ). According to another aspect of the invention, the second face  420   b  of the prism  420  may be further adapted to cover the opening  404  in the housing wall  406 . In addition, the prism face  420   a  may be adapted to provide a seal around the opening  404  of the enclosure wall  406 , thus eliminating the need for a window or other protective cover therein. 
   The second face  420   b  of prism  420  may further be mounted directly onto the image sensor aperture  408 , for example, using a low loss transparent adhesive (not shown). It will be noted in this regard, that while a gap (not shown) may be provided between the second face  420   b  of the prism  420  and the sensor aperture  408 , light signal losses associated with such a gap may be advantageously reduced according to an aspect of the invention through mounting the second face  420   b  of the prism  420  directly onto the aperture  408 . 
   In addition, mounting the prism  420  directly onto the aperture  408  of the image sensor component  410  further reduces the size of the image sensor assembly. Furthermore, it will be appreciated that the invention comprises an image sensor assembly, including the image sensor  410  having an aperture  408 , and a prism  420  mounted on the aperture  408  and adapted to receive light L along the first path  422  and to provide at least a portion of the received light L to the aperture  408  along the second path  424 . 
   Referring now to  FIG. 5B , the first face  426   a  of the prism  420  may be planar, and the scan engine  400  may further comprise a lens  426  adapted for detachable mounting on first wall  406  for imaging of the light L prior to passage thereof through the opening  404 . Lens  426  may be mounted onto wall  406  using engagement members  428  adapted for retractable engagement with one or more portions of the lens  426 . In this manner, a user may selectively change the lens  426  allowing for multi-configuration usage of the scan engine  400  depending on desired focal length or other application considerations. 
   Referring now to  FIG. 6 , an exemplary method  500  of producing a scan engine (e.g., scan engines  300  and/or  400  of  FIGS. 4 and 5 , respectively) is illustrated in accordance with another aspect of the invention. The exemplary method  500  begins at step  502 , whereat a housing is provided (e.g., housing  302  of  FIG. 4 ) with an opening for receiving light from a scanned dataform (e.g., barcode dataform  8  of  FIG. 1 ). At step  504 , an image sensor (e.g., sensor  310 ) is mounted within the housing. A prism (e.g., prism  320 ) is mounted at step  506  on an aperture (e.g., aperture  308 ) of the image sensor. The prism may be mounted on the aperture using, for example, a low loss transparent adhesive. At step  508 , a seal may be provided around the opening in the housing using the prism. 
   Although the invention has been shown and described with respect to a certain aspects and implementations, it will be appreciated that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, systems, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure, which performs the function in the herein illustrated exemplary aspects of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other aspects as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms “includes”, “including”, “has”, “having”, and variants thereof are used in either the detailed description or the claims, these terms are intended to be inclusive in a manner similar to the term “comprising.”