Abstract:
A produce data collector and produce recognition system which illuminates a produce item with substantially uniform light to enhance the accuracy of collected produce data and subsequent identification of the produce item as part of a transaction in a transaction establishment. The produce data collector includes a light source for illuminating the produce item with substantially uniform light during the transaction, a light separating element for splitting light collected from the produce item into a plurality of different light portions having different wavelengths, a detector for converting energy in the plurality of light portions into a plurality of electrical signals, and control circuitry which digitizes the plurality of electrical signals to produce a digital spectrum from the produce item which contains information to identify the produce item for the purpose of determining its unit price.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention is a division of the following commonly assigned and co-pending U.S. application: 
     “An Item Checkout Device Including A Bar Code Data Collector And A Produce Data Collector”, filed Nov. 10, 1998, invented by Collins, and having a Ser. No. 09/189,783. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to product checkout devices and more specifically to a produce data collector and a produce recognition system. 
     Bar code readers are well known for their usefulness in retail checkout and inventory control. Bar code readers are capable of identifying and recording most items during a typical transaction since most items are labeled with bar codes. 
     Items which are typically not identified and recorded by a bar code reader are produce items, since produce items are typically not labeled with bar codes. Bar code readers may include a scale for weighing produce items to assist in determining the price of such items. But identification of produce items is still a task for the checkout operator, who must identify a produce item and then manually enter an item identification code. Operator identification methods are slow and inefficient because they typically involve a visual comparison of a produce item with pictures of produce items, or a lookup of text in table. Operator identification methods are also prone to error, on the order of fifteen percent. 
     Therefore, it would be desirable to provide a produce recognition system which can minimize operator involvement in produce identification and entry into a transaction. 
     SUMMARY OF THE INVENTION 
     In accordance with the teachings of the present invention, a produce data collector is provided. 
     The produce data collector includes a light source for substantially uniformly illuminating the produce item with light during the transaction, a light separating element for splitting light collected from the produce item into a plurality of different light portions having different wavelengths, a detector for converting energy in the plurality of light portions into a plurality of electrical signals, and control circuitry which digitizes the plurality of electrical signals to produce a digital spectrum from the produce item which contains information to identify the produce item for the purpose of determining its unit price. 
     It is a feature of the present invention that the produce data collector provides substantial uniformity in both spectrum and luminosity across a sample collecting window, without the use of complicated optical devices. 
     It is accordingly an object of the present invention to provide a produce data collector and system. 
     It is another object of the present invention to provide a produce data collector which is light in weight and inexpensive. 
     It is another object of the present invention to provide a produce data collector which digitizes a color spectrum for a produce item. 
     It is another object of the present invention to provide a produce recognition system which compares digitized produce color spectra from a produce data collector with historical reference spectra. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a block diagram of a transaction processing system including the produce data collector of the present invention; 
     FIG. 2 is a block diagram of the produce data collector; 
     FIG. 3 is an exploded view of the produce data collector; 
     FIG. 4 is an exploded view of the optical components of the produce data collector; 
     FIG. 5 is a top view of the assembled optical components of the produce data collector; 
     FIG. 6 is a side view of the assembled optical components of the produce data collector. 
     FIG. 7 is a perspective view of an alternate turning mirror design; and 
     FIGS. 8A and 8B illustrate an electromechanical shutter arrangement. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, transaction processing system  10  includes bar code data collector  12 , produce data collector  14 , and scale  16 . 
     Bar code data collector  12  reads bar code  22  on merchandise item  32  to obtain an item identification number, also know as a price look-up (PLU) number, associated with item  32 . Bar code data collector  12  may be any bar code data collector, including an optical bar code scanner which uses laser beams to read bar codes. Bar code data collector  12  may be located within a checkout counter or mounted on top of a checkout counter. 
     Produce data collector  14  collects data for produce item  18  or any other non-barcoded merchandise item. Such data may include color and color distribution data, size data, shape data, surface texture data, and aromatic data. Reference produce data is collected and stored within produce data file  30 . During a transaction, operation of produce data collector  14  may be initiated by placement of produce item  18  on scale  16  or in by operator-initiated commands from transaction terminal  20 . 
     Scale  16  determines a weight for produce item  18 . Scale  16  works in connection with bar code data collector  12 , but may be designed to operate and be mounted separately. Scale  16  sends weight information for produce item  18  to transaction terminal  20  so that transaction terminal  20  can determine a price for produce item  18  based upon the weight information. 
     Bar code data collector  12  and produce data collector  14  operate separately from each other, but may be integrated together. Bar code data collector  12  works in conjunction with transaction terminal  20  and transaction server  24 . 
     In the case of bar coded items, transaction terminal  20  obtains the item identification number from bar code data collector  12  and retrieves a corresponding price from PLU data file  28  through transaction server  24 . 
     In the case of non-bar coded produce items, transaction terminal  20  executes produce recognition software  21  which obtains produce characteristics from produce data collector  14 , identifies produce item  18  by comparing produce data in produce data file  30  with collected produce data, retrieves an item identification number from produce data file  30  and a corresponding price from PLU data file  28 . 
     In an alternative embodiment, identification of produce item  18  may be handled by transaction server  24 . Transaction server  24  receives collected produce characteristics and compares them with produce data in produce data file  30 . Following identification, transaction server  24  obtains a price for produce item  18  and forwards it to transaction terminal  20 . 
     PLU data file  28  and produce data file  30  are stored within storage medium  26 , but either may also be located instead at transaction terminal  20 , or bar code data collector  12 . 
     To assist in proper identification of produce items, produce recognition software  21  may additionally display candidate produce items for operator verification. Produce recognition software  21  preferably arranges the candidate produce items in terms of probability of match and displays them as text and/or color images on an operator display of transaction terminal  20 . The operator may accept the most likely candidate returned by or override it with a different choice. 
     Turning now to FIG. 2, produce data collector  14  primarily includes light source  40 , spectrometer  51 , control circuitry  56 , transparent window  60 , auxiliary transparent window  61 , housing  62 , and shutter  63 . Produce data collector  14  may additionally include color balancing filter  42 , light source sensor  44 , and ambient light sensor  46 . 
     Light source  40  produces light  70 . Light source  40  preferably produces a white light spectral distribution, and preferably has a range from four hundred 400 nm to 700 nm, which corresponds to the visible wavelength region of light. 
     Light source  40  preferably includes one or more light emitting diodes (LEDs). A broad-spectrum white light producing LED, such as the one manufactured by Nichia Chemical Industries, Ltd., is preferably employed because of its long life, low power consumption, fast turn-on time, low operating temperature, good directivity. Alternate embodiments include additional LEDs having different colors in narrower wavelength ranges and which are preferably used in combination with the broad-spectrum white light LED to even out variations in the spectral distribution and supplement the spectrum of the broad-spectrum white light LED. Feedback from light source sensor  44  may additionally be employed by control circuitry  56  to adjust desired intensity levels by varying the drive current to the LEDs. Use of these techniques may remove the necessity to use color balancing filter  42 , thereby reducing cost, easing packaging constraints, and improving mechanical reliability. 
     Other types of light sources  40  are also envisioned by the present invention, although they may be less advantageous than the broad spectrum white LED. For example, a tungsten-halogen light may be used because of its broad spectrum, but produces more heat and optimally requires color balancing filter  42 . 
     A plurality of different-colored LEDs having different non-overlapping wavelength ranges may be employed, but may provide less than desirable collector performance if gaps exist in the overall spectral distribution. 
     Color balancing filter  42  balances spectral throughput and increases the system signal-to-noise ratio when using light sources which alone or in combination with other light sources fail to produce a broad range of intensities across the entire spectral distribution. Color balancing filter  42  is designed to take into account the fact that system spectral throughput or intensity will not be equal for all wavelengths of light due to the intrinsic nature of light source  40 , light separating element  52 , and photodetector array  54 . In designing color balancing filter  42 , the spectral emissivity of light source  40 , the spectral transmissivity of light separating element  52 , and spectral responsivity of photodetector array  54  are all considered. 
     When employed, color balancing filter  42  preferably includes an absorptive glass filter or a thin-film filter on a glass substrate or a combination of absorptive and interference filters. Light  72  from color balancing filter  42  passes through windows  60  and  61  to illuminate produce item  18 . 
     Light source sensor  44  monitors the spectrum of light  72  for changes in light source intensity and stability, which would adversely affect the operation of produce data collector  14 . Light source sensor  44  includes one or more photodiodes and may include a bandpass filter to monitor only a portion of the emitted spectrum. Light source sensor  44  may also include light source current and voltage monitors for monitoring light source  40  for stability. Output signals  86  are processed by control circuitry  56 . Light source sensor  44  could be mounted anywhere within the direct line of sight of light source  40  and can monitor light source  40  directly, instead of monitoring filtered light from color balancing filter  42 . In the preferred embodiment, light source sensor  44  looks down at light source  40 . 
     Ambient light sensor  46  senses the level of ambient light through windows  60  and  61  and sends ambient light level signals  88  to control circuitry  56 . Ambient light sensor  46  is mounted anywhere within a direct view of window  61 . In the preferred embodiment, light source sensor  44  looks down at light source  40 . 
     Spectrometer  51  includes light separating element  52 , photodetector array  54 . 
     Light separating element  52  splits light  76  in the preferred embodiment into light  80  of a continuous band of wavelengths. Light separating element  52  is preferably a linear variable filter (LVF), such as the one manufactured Optical Coating Laboratory, Inc., or may be any other functionally equivalent component, such as a prism or a grating. 
     Photodetector array  54  produces waveform signals  82  containing spectral data. The pixels of the array spatially sample the continuous band of wavelengths produced by light separating element  52 , and produce a set of discrete signal levels. Photodetector array  54  is preferably a complimentary metal oxide semiconductor (CMOS) array, but could be a Charge Coupled Device (CCD) array. 
     Control circuitry  56  controls operation of produce data collector  14  and produces digitized produce data waveform signals  84 . For this purpose, control circuitry  56  includes an analog-to-digital (A/D) Converter. A twelve bit A/D converter with a sampling rate of 22-44 kHz produces acceptable results. 
     Control circuitry  56  also receives signals from light source sensor  44  and ambient light sensor  46 . In response to changes in light source monitor output signals  86 , control circuitry  56  compensates for the changes and/or alerts an operator of transaction terminal  20 . 
     In response to ambient light level signals  88 , control circuitry  56  waits for ambient light levels to fall to a minimum level (dark state) before turning on light source  40 . Ambient light levels fall to a minimum level when produce item  18  covers window  60 . After control circuitry  56  has received waveform signals  82  containing produce data, control circuitry  56  turns off light source  40  and waits for ambient light levels to increase before returning to waiting for the dark state. Ambient light levels increase after produce item  18  is removed from window  60 . 
     Control circuitry  56  controls shutter  63 . Control circuitry  56  opens shutter  63  when it detects placement of produce item  18  over window  60 . Control circuitry  56  closes shutter  63  when it fails to detect placement of produce item  18  over window  60 . 
     Control circuitry  56  establishes periodic reference readings. Reference readings are desirable since component aging, dirt, and temperature and voltage changes may cause inaccuracies in collected produce data if significant. Control circuitry  56  may take as many readings as necessary. For example, control circuitry  56  may take ten reference readings per second, or one reference reading for each produce item, or five times a day. 
     Housing  62  contains light source  40 , color balancing filter  42 , light source sensor  44 , ambient light sensor  46 , stray light baffle  96 , light separating element  52 , photodetector array  54 , control circuitry  56 , and auxiliary transparent window  61 . Housing  62  additionally contains transparent window  60  when produce data collector  14  is a self-contained unit. When produce data collector  14  is mounted within the housing of a combination bar code reader and scale, window  60  may be located in a scale weigh plate instead. 
     Transparent window  60  is mounted above auxiliary transparent window  61 . Windows  60  and  61  include an anti-reflective surface coating to prevent light  72  reflected from windows  60  and  61  from contaminating reflected light  74 . 
     Housing  62  is approximately five and a half inches in length by two and three quarters inches in width by one and three quarters inches in height. 
     Windows  60  and  61  may be rectangular, elliptical, and circular, instead of square. Windows  60  and  61  are about three quarters inches in width and length (square) or diameter (circular). 
     Window size affects the size of produce data collector  14 . In order to minimize the angle of light reflected off of produce item  18  and received at light separating element  52 , while maintaining as large of an output window as possible (in order to provide as a large of a sample area as possible) a minimum distance of approximately five inches is needed between window  60  and light separating element  52 . If window  60  is reduced in diameter, thereby reducing the sampled area on produce item  18 , the distance between object  18  and light separating element  52  can be reduced, keeping the angle the same. 
     Shutter  63  is mounted below transparent window  61 . Shutter  63  may include a polymer dispersed liquid crystal (PDLC) or a motor-driven door (FIGS. 8A-8B) mounted to the underside of the top wall of housing  62 . 
     The PDLC shutter allows about fifteen percent of ambient light to pass through it when de-energized. Produce data collector  14  takes reference illumination readings with the PDLC shutter energized and de-energized. When produce item  18  is placed over window  60 , control circuitry  56  energizes the PDLC shutter, allowing about eighty-five percent of light  72  and eighty-five percent of light  74  to pass through it. 
     The motor-driven shutter includes a milky-white optically opaque screen with a white (or gray) diffusively-reflecting surface facing down towards detector  54 . This surface serves as an internal reference for system calibration. The screen is moved to an open position and a closed position by a motor. Control circuitry  56  controls the motor. 
     When closed for taking reference readings, the motor-driven&#39;shutter prevents substantially all ambient light from passing through while reflecting about eighty-five percent of light  72 . When open for taking reference readings or recognizing produce item  18 , the motor-driven shutter allows substantially all of light  72  and  74  to pass through, as well as substantially all ambient light. 
     Operation of produce data collector  14  is automatic. An operator places produce item  18  on window  60 . Control circuitry  56  senses low level ambient signals  88  and turns on light source  40 . Light separating element  52  separates reflected light  74  into different wavelengths to produce light  80  of a continuos band of wavelengths. Photodetector array  54  produces waveform signals  82  containing produce data. Control circuitry  56  produces digitized produce data signals  84  which it sends to transaction terminal  20 . Control circuitry  56  turns off light source  40  and waits for ambient light levels to increase before returning to waiting for the dark state. Control circuitry additionally monitors light source monitor output signals  86  for changes and compensates and/or alerts an operator of transaction terminal  20 . 
     Advantageously, produce data collector  14  captures image data in about two tenths of a second, well within normal produce handling time. 
     Transaction terminal  20  uses produce data in digitized produce data signals  84  to identify produce item  18 . Here, produce data consists of digitized waveforms which transaction terminal  20  compares to a library of digitized waveforms stored within produce data file  30 . After identification, transaction terminal  20  obtains a unit price from PLU data file  28  and a weight from scale  16  in order to calculate a total cost of produce item  18 . Transaction terminal  20  enters the total cost into the transaction. 
     With reference to FIGS. 3-6, produce data collector  14  is shown in further detail. 
     Produce data collector  14  additionally includes printed circuit board  90 , light source assembly  92 , turning mirror  94 , stray light baffle  96 , and turning mirror  98 . 
     Printed circuit board  90  contains control circuitry  56  and forms a base for mounting color balancing filter  42 , light source sensor  44 , ambient light sensor  46 , mount  49 , light separating element  52 , photodetector array  54 , light source assembly  92 , turning mirror  94 , stray light baffle  96 , and turning mirror  98 . Printed circuit board  90  fastens to housing  62 . Printed circuit board  90  serves as a carrier for all of the active components in this system, thus when it is manufactured and tested, the entire system can be tested by testing printed circuit board  90 . 
     Light source assembly  92  includes light source  40 , lower light source mount  100 , and upper light source mount  102 . 
     Light source  40  preferably includes a number of white LEDs which are arranged close to window  60  and in direct line of sight of window  60 . Light source mount  92  is designed such that each individual LED is pointed at the top surface of window  60  so that there is uniform luminosity over the entire top surface of window  60  for illuminating produce item  18 . In the preferred embodiment, the LEDs are all aimed at the center of window  60  and oriented at an angle of about 31.75 degrees. The LEDs are located at a distance of about 1.657 inches from the center of window  60 , and 1.075 inches from the center of light source assembly  92 . 
     The preferred embodiment provides uniformity in both spectrum and luminosity. Since it is highly desirable to avoid using complicated optical devices, such as lens systems and light pipes, for simplicity, the preferred embodiment envisions arrangements of multiple LEDs. The LEDs are spectrally matched in groups, and their placement and orientation achieves optimal uniformity in both spectrum and luminosity across the illuminated surface area. 
     To achieve uniformity in both spectrum and luminosity with multiple LEDs, the LED samples are first sorted into spectrally matched groups by computing and analyzing the matrices of linear correlation coefficients. The direct illumination from LEDs in a matched group will have a uniform spectrum regardless of their positions and beam orientations. 
     Second, LED positions and beam orientations are arranged to achieve uniform luminosity. If higher luminosity is needed to achieve adequate signal level, multiple groups can be used. The total illumination from multiple groups will be uniform in both spectrum and luminosity even if the spectra from different groups are different. 
     FIG. 4 shows sixteen white LEDs arranged in four groups of four LEDs on four sides of lower light source mount  100 . Other arrangements are also envisioned by the present invention, such as two or four groups of four and eight LEDS. The use of a single white LED is also envisioned because it provides spectral uniformity, providing acceptable luminosity across window  60  only if window  60  is smaller. To achieve higher system efficiency, LEDs with a narrow, concentrated beam are preferred. 
     Lower light source mount  100  is generally circular in shape. This arrangement supports the LEDs in the preferred arrangement and orientation. Lower light source mount  100  connects mechanically and electrically to printed circuit board  90  and includes terminal connections  104  for light sources  40 . 
     Upper light source mount  102  is also generally circular in shape and connects mechanically in mating relationship to lower light source mount  100 . Upper light source mount  102  mechanically hold the LEDs in a preferred orientation for even illumination across the area of window  60 . Upper light source mount  102  includes gap  103  which allows reflected light  74  to be directed to photodetector array  54 . Upper light source mount  102  further includes apertures  106  through which light sources  40  emit light from positions below top surface  108 . Top surface  108  angles downwardly from outer wall  110  to inner wall  112  perpendicular with the inclination angles of lights sources  40 . 
     Turning mirror  94  routes reflected light  74  from produce item  18  through stray light baffle  96  towards turning mirror  98 . Deflector mirror  94  is mounted at about a forty-five degree angle on base  114 , which is incorporated into upper light source mount  102 . Turning mirror  94  is preferably substantially planar and has a rectangular shape. 
     Turning mirror  98  directs reflected light  74  to light separating element  52 . Turning mirror  98  is mounted at about a forty-five degree angle on mount  49 . In the preferred embodiment (FIG.  4 ), turning mirror  98  is substantially planar and has a rectangular shape. 
     Alternate embodiments (FIG.  7 ), may incorporate turning mirrors  94  and  98  that are non-planar, i.e., have one or more radii of curvature and/or have the possibility of being segmented into multiple sections, each section with one or more radii of curvature. 
     In one such alternate embodiment, turning mirror  98  not only directs reflected light  74 , but also produces equalized light of average reflected illumination by mixing reflected light  74 . For this purpose, turning mirror  98  includes inner concave surface  113  and substantially planar textured surface  115 . Textured surface  115  diffuses and scatters reflected light  74 . Inner concave surface  113  converges the scattered light to reduce loss. 
     Alternate turning mirror  98  is made of a molded transparent acrylic and is mounted at about a forty-five degree angle on mount  49 . Surface  115  is coated with aluminum using an evaporation process. The aluminum is an enhanced aluminum to provide the highest possible reflectance across the visible spectrum. Enhanced aluminum is ninety-seven percent reflective versus ninety-four percent reflective for regular aluminum coating. 
     All embodiments of mirrors  94  and  98  serve to direct light  74  to photodetector array  54 . 
     Stray light baffle  96  mounts directly to printed circuit board  90  and helps to minimize the amount of light from light sources  40  that reaches photodetector array  54  directly, as well as any other sources of light other than the light reflected from produce item  18 , such as ambient light. For this purpose, stray light baffle  96  includes outer walls  118 - 124 , inner walls  125 - 132 , top wall  134 , and bottom wall  136 . Outer walls  118 - 124  form a generally rectangular assembly. Outer wall  124  is adjacent to upper and lower light source mounts  100  and  102 . 
     Walls  118 ,  120 ,  122  and  132  define a chamber containing turning mirror  98 , mount  49 , light separating element  52 , and photodetector array  54 . Photodetector array  54  is mounted directly to printed circuit board  90 . Light separating element  52  is held within mount  49 , which rests directly upon photodetector array  54 . Light separating element  52  is held in close proximity to photodetector array  54 . 
     Walls  118 - 132  cooperate to channel light turning mirror  98  through an ever-narrowing tunnel  133 . Walls  125 ,  126 , and  130  are generally U-shaped walls and provide a lower bound for tunnel  133 . Walls  124 ,  128 , and  132  are generally inverted U-shaped walls and provide an upper bound for tunnel  133 . Tunnel opening  138  at wall  124  for receiving reflected light  74  from deflector mirror  94  is larger than tunnel opening  140  at wall  132 . Tunnel openings  138  and  140  are optimally sized to allow as much light energy in reflected light  74  as possible to be incident on photodetector array  54 , while restricting the angles of incidence of reflected light  74  to less than six degrees. 
     Advantageously, the preferred embodiment reduces spectral distortion without significant loss of reflected light levels. Reduction of spectral distortion is particularly important when light separating element  52  is an LVF or a dispersing element, such as a prism or a grating. 
     To reduce such spectral distortion, the present embodiment reduces the size of the field-of-view in at least two ways. First, light sources  40  are inwardly inclined in order to accommodate a smaller size for window  60  without significant loss in outgoing light levels. Second, distance between window  60  and light separating element  52  is increased to an optimum distance, consistent with the fact that the angle for light incident upon light separating element  52  must be less than six degrees. If the angle is greater than six degrees then there is unequal attenuation through light separating element  52  which adds error to the system. In other words, produce item  18  will appear to have different spectra characteristics when located at different locations on window  60 . 
     As an alternate embodiment, a light pipe, or a light pipe in combination with a preceding condenser lens, may also be used between window  60  and light separating element  52  to further reduce the field-of-view effect by adding distance. 
     A third technique is to shift the LVF center such that its longer wavelength (red) end is closer to the center line of window  60 , instead of aligning the LVF center along an optical path to the center of window  60 . By placing the red end closer to the center, average incident angle is reduced for the longer wavelengths. Therefore, the absolute wavelength shift is smaller for longer wavelengths, while the opposite is true for the shorter wavelengths (the blue end). This technique works regardless of window shape. 
     Advantageously, housing  62  is small in size. In particular, it is much smaller than other produce data collectors, such as video cameras. Produce data collector  14  is even small enough in size to be mounted within an existing bar code reader or packaged as a light-weight (less than about eight ounces) hand-held unit. 
     Turning now to FIGS. 8A-8B, electromechanical shutter  63  is mounted below and adjacent window  61 . FIG. 8A shows both housing  62  and printed circuit board  90 , while FIG. 8B shows only printed circuit  90 . 
     Shutter  63  includes motor  150  and door  152 . Motor  150  is mounted to printed circuit board  90 . Door  152  is mounted to the shaft of motor  150 . Control circuitry  56  energizes motor  150  to place door  152  in an open position (FIG. 8A) and a closed position (FIG.  8 B). 
     Although the invention has been described with particular reference to certain preferred embodiments thereof, variations and modifications of the present invention can be effected within the spirit and scope of the following claims. In particular, alternate embodiments may be further reduced or enlarged in size as window  60  is made smaller or larger. Also, the number light source  40  may change, but all of these variations are incorporated in the scope of present invention and may be considered alternative embodiments.