Patent Publication Number: US-7901933-B2

Title: Methods of processing a biological growth plate in a biological growth plate scanner

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/934,175, filed on Nov. 2, 2007; which was a divisional application of U.S. patent application Ser. No. 10/306,579, filed Nov. 27, 2002, now U.S. Pat. No. 7,298,885; the disclosures of which are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The invention relates to techniques for analysis of biological growth media to analyze bacteria or other biological agents in food samples, laboratory samples, and the like. 
     BACKGROUND 
     Biological safety is a paramount concern in modern society. Testing for biological contamination in foods or other materials has become an important, and sometimes mandatory requirement for developers and distributors of food products. Biological testing is also used to identify bacteria or other agents in laboratory samples such as blood samples taken from medical patients, laboratory samples developed for experimental purposes, and other types of biological samples. Various techniques and devices can be utilized to improve biological testing and to streamline and standardize the biological testing process. 
     In particular, a wide variety of biological growth media have been developed. As one example, biological growth media in the form of growth plates have been developed by 3M Company (hereafter “3M”) of St. Paul, Minn. Biological growth plates are sold by 3M under the trade name PETRIFILM plates. Biological growth plates can be utilized to facilitate the rapid growth and detection or enumeration of bacteria or other biological agents commonly associated with food contamination, including, for example, aerobic bacteria,  E. coli , coliform, enterobacteriaceae, yeast, mold,  Staphylococcus aureus, Listeria, Campylobacter , and the like. The use of PETRIFILM plates, or other growth media, can simplify bacterial testing of food samples. 
     Biological growth media can be used to identify the presence of bacteria so that corrective measures can be performed (in the case of food testing) or proper diagnosis can be made (in the case of medical use). In other applications, biological growth media may be used to rapidly grow bacteria or other biological agents in laboratory samples, e.g., for experimental purposes. 
     Biological scanners refer to devices used to read or count bacterial colonies, or the amount of a particular biological agent on a biological growth medium. For example, a food sample or laboratory sample can be placed on a biological growth medium, and then the medium can be inserted into an incubation chamber. After incubation, the biological growth medium can be placed into the biological scanner for automated detection and enumeration of bacterial growth. In other words, biological scanners automate the detection and enumeration of bacteria or other biological agents on a biological growth medium, and thereby improve the biological testing process by reducing human error. 
     SUMMARY 
     In general, the invention is directed to a biological scanner that automates selection of image processing profiles to scan and analyze different types of biological growth plates. The scanner automatically identifies the type of plate to be scanned, and then selects one of the image processing profiles appropriate for the identified plate type. 
     The scanner may identify the plate type by reference to a variety of machine-readable indicators, such as optically or magnetically readable marks, carried on the plate. Accordingly, the invention also is directed to biological growth plates carrying particular indicators that permit plate type identification for selection of image processing profiles. 
     The plates may be scanned in order to read or count different types of bacterial colonies, or the amount of a particular biological agent on the biological growth plate. In operation, the scanner identifies the plate type, e.g., upon presentation of the biological growth plate to the scanner. The scanner then processes the image according to an image processing profile associated with the identified plate type. 
     The image processing profile may specify particular image capture conditions, such as illumination intensities, durations, and colors, for capturing images of particular plate types. The image capture conditions also may include camera gain, resolution, aperture, and exposure time. In addition, the image processing profile may specify particular image analysis criteria, such as color, shape, size and proximity criteria, for detecting or enumerating different types of bacterial colonies within a captured image. Thus, the scanner may apply different image capture conditions, different image analysis criteria, or both in processing an image of the biological growth plate. 
     In operation, upon plate type identification, the biological scanner may select a corresponding image processing profile. The biological scanner may illuminate the biological growth plate using image capture conditions specified by the image processing profile and capture one or more images of the plate. The biological scanner then may perform an analysis of the captured image using image analysis criteria specified by the image processing profile. In this manner, the biological scanner automates the scanning and analysis of different types of biological growth plates. 
     In one embodiment, the invention provides a device comprising a memory that stores a set of image processing profiles, and an image processing device that selects one of the image processing profiles based on a plate type associated with a biological growth plate. 
     In another embodiment, the invention provides a method comprising detecting a plate type associated with a biological growth plate, selecting one of a plurality of image processing profiles based on the detected plate type, and processing an image of the biological growth plate according to the selected image processing profile. 
     In an additional embodiment, the invention provides a computer-readable medium comprising instructions for causing a processor to select one of a plurality of image processing profiles based on a detected plate type for a biological growth plate, and control an image processing device to process an image of the biological growth plate according to the selected image processing profile. 
     In a further embodiment, the invention provides a biological growth plate comprising a plate surface to support growth of a biological agent, and a machine-readable plate type indicator that identifies a type of the biological growth plate. 
     In another embodiment, the invention provides a system comprising a biological growth plate including a machine-readable plate type indicator that identifies a plate type of the biological growth plate, and an imaging device to capture an image of the biological growth plate and process the image according to one of a plurality of image processing profiles selected based on the plate type indicator. 
     The invention can provide a number of advantages. For example, automated image processing profile selection can provide a convenient and accurate technique for selecting the appropriate image processing profile. Automated image processing profile selection can promote the accuracy of bacterial colony counts and other analytical procedures, enhancing quality assurance. In particular, appropriate image capture conditions and image analysis criteria can be automatically selected and applied for each plate type. Automatic image processing profile selection can avoid the need for a technician to visually identify and manually enter the plate type, and thereby eliminate plate identification errors sometimes associated with human intervention. Analytical accuracy can be a critical health concern, particularly when testing food samples. In addition, automated image processing profile selection can promote efficiency and convenience, and improve workflow for laboratory technicians. A biological growth plate carrying a machine-readable plate type indicator that permits automated plate type identification by a biological scanner can contribute to the foregoing advantages. 
     Additional details of these and other embodiments are set forth in the accompanying drawings and the description below. Other features, objects and advantages will become apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an exemplary biological scanner. 
         FIG. 2  is another perspective view of an exemplary biological scanner. 
         FIGS. 3 and 4  are top views of an exemplary growth plate bearing an indicator pattern for image processing profile selection. 
         FIGS. 5A-5D  are diagrams illustrating exemplary plate type indicator patterns carried by a biological growth plate for image processing profile selection. 
         FIG. 6  is a block diagram illustrating a biological scanner configured for automated image processing profile selection. 
         FIG. 7  is a block diagram illustrating another biological scanner configured for automated image processing profile selection. 
         FIG. 8  is a block diagram illustrating the biological scanner of  FIG. 6  in greater detail and depicting plate illumination hardware. 
         FIG. 9  illustrates sample display content produced on a display by a biological scanner upon plate type detection. 
         FIG. 10  illustrates sample display content produced on a display by a biological scanner  10  upon rejection of an automated plate type detection by a user. 
         FIG. 11  illustrates sample display content produced on a display by a biological scanner upon determination of a colony count. 
         FIG. 12  illustrates sample display content produced on a display by a biological scanner upon determination of a colony count and including an image of a scanned plate. 
         FIG. 13  is a flow diagram illustrating a process for image processing profile selection in biological scanner. 
         FIG. 14  is a flow diagram illustrating a process for image processing profile selection in a biological scanner involving detection of a plate type indicator. 
         FIG. 15  is a flow diagram illustrating a process for image processing profile selection in a biological scanner involving extraction of a plate type indicator from a scanned plate image. 
         FIG. 16  is a flow diagram illustrating a process that permits a user to override an automatic plate type identification by a biological scanner. 
     
    
    
     DETAILED DESCRIPTION 
     The invention is directed to a biological scanner for biological growth plates. A biological growth plate can be presented to the biological scanner, which then generates an image of the plate and performs an analysis of the image to detect biological growth. For example, the scanner may count or otherwise quantify an amount of biological agents that appear in the image, such as a number of bacteria colonies. In this manner, the biological scanner automates the analysis of biological growth plates, thereby improving such analysis and reducing the possibility of human error. 
     A biological scanner, in accordance with the invention, also automates selection of image processing profiles to scan different types of biological growth plates and analyze plate images. The scanner automatically identifies the type of plate to be scanned by the scanner, and then selects one of the image processing profiles appropriate for the identified plate type. The image processing profiles may specify image capture conditions, image analysis criteria or a combination of both for different types of biological growth plates. For example, the image processing profile may specify illumination intensities, durations, and colors for illumination of particular plate types for image capture. The image capture conditions also may include camera gain, resolution, aperture, and exposure time. In terms of image analysis criteria, the image processing profiles may specify different color, shape, size and proximity criteria in counting different types of bacterial colonies within a captured image to promote accuracy in the analytical result, e.g., a count. Hence, the image processing profiles may pertain both to image capture and analysis. Accuracy is critical in both food and laboratory sample test environments. For food safety, in particular, accurate results permit verification of sanitation at critical control points throughout the food processing operation, including line production, equipment and environmental testing. 
     The scanner may identify the plate type by reference to a variety of machine-readable plate type indicators, such as optically or magnetically readable marks, carried on the plate. Accordingly, the invention also contemplates biological growth plates carrying a particular indicator that permits plate type identification. In addition, the invention may eliminate or reduce reliance on human judgment in making plate type identifications, thereby reducing the potential for human error and resulting inaccuracy in colony counts or other analyses. 
     The invention may be useful with a variety of biological growth plates. For example, the invention may be useful with different plate-like devices for growing biological agents to enable detection or enumeration of the agents, such as thin-film culture plate devices, Petri dish culture plate devices, and the like. Therefore, the term “biological growth plate” will be used broadly herein to refer to a medium suitable for growth of biological agents to permit detection and enumeration of the agents by a scanner. In some embodiments, the biological growth plate can be housed in a cassette that supports multiple plates, e.g., as described in U.S. Pat. No. 5,573,950 to Graessle et al. 
       FIG. 1  is a perspective view of an exemplary biological scanner  10 . As shown in  FIG. 1 , biological scanner  10  includes a scanner unit  12  having a drawer  14  that receives a biological growth plate (not shown in  FIG. 1 ). Drawer  14  moves the biological growth plate into biological scanner  10  for scanning and analysis. Scanner  10  may incorporate features that permit automated plate type identification, and automated selection of image processing profiles based on plate type, in accordance with the invention. 
     Biological scanner  10  also may include a display screen  16  to display the progress or results of analysis of the biological growth plate to a user. Alternatively or additionally, display screen may present to a user an image of the growth plate scanned by biological scanner  10 . The displayed image may be optically magnified or digitally scaled upward. A mounting platform  18  defines an ejection slot  20  through which the growth plate can be ejected following image capture by biological scanner  10 . Accordingly, biological scanner  10  may have a two-part design in which scanner unit  12  is mounted on mounting platform  18 . The two-part design is depicted in  FIG. 1  for purposes of example, and is not intended to be required by or limiting of the inventions described herein. 
     Scanner unit  12  houses an imaging device for scanning the biological growth plate and generating an image. The imaging device may take the form of a line scanner or an area scanner, which ordinarily will be provided in combination with an illumination system to provide front and/or back illumination of the biological growth plate. In addition, scanner unit  12  may house processing hardware that performs analysis of the scanned image, e.g., in order to determine the number or amount of biological agents in the growth plate. For example, upon presentation of the biological growth plate via drawer  14 , the plate may be positioned adjacent an optical platen for scanning. 
     When the drawer is subsequently opened, the growth plate may drop downward into the mounting platform  18  for ejection via ejection slot  20 . To that end, mounting platform  18  may house a conveyor that ejects the growth plate from biological scanner  10  via ejection slot  20 . After a biological growth plate is inserted into drawer  14 , moved into scanner unit  12 , and scanned, the biological growth plate drops downward into mounting platform  18 , where a horizontal conveyor, such as a moving belt, ejects the medium via slot  20 . 
       FIG. 2  is another perspective view of biological scanner  10 . As shown in  FIG. 2 , drawer  14  extends outward from biological scanner  10  to receive a biological growth plate  22 . As illustrated, a biological growth plate  22  may be placed on a platform  24  provided within drawer  14 . In some embodiments, platform  24  may include positioning actuators such as cam levers to elevate the platform for precise positioning of growth plate  22  within biological scanner  10 . Upon placement of biological growth plate  22  on platform  24 , drawer  14  retracts into scanner unit  12  to place the biological growth plate in a scanning position, i.e., a position at which the biological growth medium is optically scanned. 
       FIGS. 3 and 4  are top views of an exemplary biological growth plate  22 . By way of example, a suitable growth plate  22  may comprise biological growth plates sold by 3M under the trade name PETRIFILM plates. Alternatively, biological growth plate  22  may comprise other biological growth media for growing particular bacteria or other biological agents. In accordance with the invention, biological growth plate  22  carries plate type indicator  28  to facilitate automated identification of the type of biological media associated with the growth plate. 
     Plate type indicator  28  presents an encoded pattern that is machine-readable. In the example of  FIGS. 3 and 4 , plate type indicator  28  takes the form of an optically readable pattern. In particular,  FIGS. 3 and 4  depict a four-square pattern of light and dark quadrants formed in a corner margin of biological growth plate  22 . In other words, plate type indicator  28  defines a two-dimensional grid of cells modulated between black and white to form an encoded pattern. A wide variety of optical patterns such as characters, bar codes, two-dimensional bar codes, optical gratings, holograms, phosphorous inks and the like are conceivable. 
     In addition, in some embodiments, plate type indicator  28  may take the form of patterns that are readable by magnetic or radio frequency techniques. Alternatively, plate type indicator  28  may take the form of apertures, slots, surface contours, or the like that are readable by optical or mechanical techniques. In each case, plate type indicator  28  carries information sufficient to enable automated identification of the type of biological growth plate  22  by biological scanner  10 . Plate type indicator  28  will be described in greater detail below. 
     Biological growth plates may facilitate the rapid growth and detection and enumeration of bacteria or other biological agents including, for example, aerobic bacteria,  E. coli , coliform, enterobacteriaceae, yeast, mold,  Staphylococcus aureus, listeria , and  campylobacter , and the like. The use of PETRIFILM plates, or other growth media, can simplify bacterial testing of food samples. Moreover, as outlined herein, biological scanner  10  can further simplify such testing by providing automated plate type detection, and automated selection of image processing profiles based on the detected plate type to illuminate and/or analyze biological growth plate  22 , e.g., by counting bacterial colonies on an image of the plate. 
     As shown in  FIG. 3 , biological growth plate  22  defines a growth area  26 . A determination of whether a given sample being tested in plate  22  is acceptable, in terms of bacterial colony counts, may depend on the number of bacterial colonies per unit area. Accordingly, scanner  10  may quantify the amount of bacterial colonies per unit area on plate  22 , and may compare the amount, or “count,” to a threshold. The surface of biological growth plate  22  may contain one or more growth enhancing agents designed to facilitate the rapid growth of one or more types of bacteria or other biological agents. 
     After placing a sample of the material being tested, typically in liquid form, on the surface of biological growth plate  22  within growth area  26 , plate  22  can be inserted into an incubation chamber (not shown). In the incubation chamber, bacterial colonies or other biological agents being grown by growth plate  22  manifest themselves, as shown in biological growth plate  22  of  FIG. 4 . The colonies, represented by various dots  30  on biological growth plate  22  in  FIG. 4 , may appear in different colors on plate  22 , facilitating automated detection and enumeration of bacterial colonies by scanner  10 . 
       FIGS. 5A-5D  are diagrams illustrating exemplary plate type indicator  28  carried by a biological growth plate  22  for image processing profile selection. Again, plate type indicator  28  may take the form of patterns, marks, apertures, surface contours and the like, which permit optical or mechanical readability. For example, different optical patterns can be read by optical decoders, bar code scanners, optical character recognition (OCR) processors or the like. In the case of apertures or contours, mechanical styli may interact with the apertures or contours to detect different patterns and produce an electrical signal. Alternatively, plate type indicator  28  may be magnetically encoded stripes or markers or carry radio frequency identifications to permit magnetic or radio frequency readability. 
     Optically readable patterns may be formed by printing or deposition of ink on the surface of biological growth plate  22 , e.g., outside of growth area  26 . Apertures or surface contour patterns can be formed in biological growth plate  22  by punches, stamps, embossers, die cutters and the like. A magnetic stripe or radio frequency identification may be affixed to the surface of biological growth plate  22 , e.g., by adhesive or lamination techniques. In addition, a magnetic or radio frequency indicator need not be carried on the surface of biological growth plate  22 , but may be interposed between layers of the growth plate in the event the growth plate has a multi-layer structure. In each case, the various plate type indicators  28  may be formed at the factory to identify the type of biological growth plate  22 . 
     In addition, if desired, plate type indicator  28  may further include information that identifies a particular manufacturer, lot number, expiration date, security authorization, and the like. Such additional items of information may be important in verifying quality and suitability of biological growth plate  22  for used in biological scanner  10 . For example, one or more manufacturers may be specifically validated, e.g., on the basis of plate production quality and plate performance criteria, to provide biological growth plates  22  for use in biological scanner  10 . In this case, biological scanner  10  may be configured to reject biological growth plates  22  that, according to plate type indicator  28 , are not associated with validated manufacturers. 
     In addition, plate type indicator  28  may carry security information, such as serial number codes or the like, that serve to authenticate biological growth plate  22  and prevent fraudulent introduction of unauthorized growth plates, e.g., to thwart the food inspection or laboratory analysis process. Although such information may be integrated and encoded within biological growth plate  22 , it may alternatively be encoded within separate indicator patterns carried by the growth plate. Accordingly, biological growth plate  22  may carry one or more indicator patterns, in addition to plate type indicator  28 , which serve different security and quality assurance purposes. 
     To enhance security, plate type indicator  28 , as well as any other indicators that may be carried by biological growth plate  22 , may benefit from a variety of security mechanisms. For example, in some embodiments, a printed plated type indicator  28  may be printed with a particular phosphorous ink so that it can be conspicuously identified according to the wavelength of light emitted by the indicator when it is scanned. In addition, plate type indicators  28  may take the form of more complex patterns that carry encryption keys to unlock biological scanner  10  for operation. In this case, processor  34  in biological scanner  10  ( FIG. 6 ) would perform decryption of the pattern in order to proceed with image processing. 
     In the example of  FIGS. 5A-5D , plate type indicator  28  takes the form of a four-square pattern having four quadrants  29 ,  31 ,  33 ,  35  that can be either dark or light, permitting ready optical processing. In  FIG. 5A , plate type indicator  28  has four light quadrants, and may identify a first type of biological growth plate  22 . In  FIGS. 5B ,  5 C and  5 D, plate type indicator  28  include one black quadrant, two black quadrants, and four black quadrants, respectively. Selection of the number and position of the black quadrants permits up to sixteen (2 4 ) different encoded patterns to be formed and, accordingly, up to sixteen different plate types to be identified by machine-readable plate type indicator  28 . As examples, different encoded patterns could represent Aerobic Count, Coliform,  E. Coli, Staphylococcus aureus , Yeast and Mold, and other plate type designations. 
     Although the form of plate type indicator  28  may be subject to wide variation, the 4-square pattern shown in  FIGS. 5A-5D  provides one type of pattern that is relatively simple and easy to identify using optical pattern recognition techniques, i.e., machine vision. As will be described, plate type indicator  28  may be scanned by a dedicated optical code reader, such as a bar code reader or custom reader. In this case, plate type indicator  28  can be scanned prior to or in parallel with scanning of biological growth plate  22 , but before processing of the growth plate image. Alternatively, plate type indicator  28  may be captured in a scanned image of biological growth plate  22 , and then extracted for image processing to identify the plate type. In this case, the plate type can be identified before further image processing of the scanned growth plate image. 
       FIG. 6  is a block diagram illustrating internal operation of biological scanner  10 . As illustrated in  FIG. 6 , a biological growth plate  22  is positioned within biological scanner  10  on a platform (not shown in  FIG. 6 ). The platform places biological growth plate  22  at a desired focal plane of an imaging device  32 . Imaging device  32  may include illumination hardware for top and back illumination of growth plate  22 , as well as a line or area scanner that captures an image of the surface of growth plate  22 . Imaging device  32  may apply standard image capture conditions, or a user may specify image capture conditions. Alternatively, as will be described below, scanner  10  may automatically control image capture conditions based on an image processing profile that corresponds to a plate type. 
     In some embodiments, for example, imaging device  32  may take the form of a two-dimensional camera, although line scanners can be used in configurations in which either the canner or biological growth plate  22  is translated relative to the other. In general, image device  32  captures an image of biological growth plate  22 , or at least a growth region within the biological growth plate. A processor  34  controls the operation of imaging device  32 . In operation, processor  34  controls imaging device  32  to capture an image of biological growth plate  22 . Processor  34  receives image data representing the scanned image from imaging device  32 , and extracts or segregates a portion of the image to isolate plate type indicator  28 . 
     Using machine vision techniques, processor  34  analyzes plate type indicator  28  to identify a plate type associated with biological growth plate  22 . Processor  34  then retrieves an image processing profile from image processing profile memory  36 . The image processing profile corresponds to the detected plate type. Processor  34  may take the form of a microprocessor, digital signal processor, application specific integrated circuitry (ASIC), field programmable gate array (FPGA) or other integrated or discrete logic circuitry programmed or otherwise configured to provide functionality as described herein. 
     Using the image processing profile, processor  34  loads appropriate image analysis parameters and proceeds to process the scanned image of biological growth plate  22 . In this manner, processor  34  forms an image processing device in the sense that it processes the image data obtained from biological growth plate  22 . The image analysis parameters may vary with the image processing profile and detected plate type, and may specify particular parameters such as colony color, size, shape and proximity criteria for analysis of the scanned image. 
     For some plate types, for example, the color of surrounding nutrient media may be an indicator of high colony counts. Also, in the case of plates containing a specific carbohydrate and pH indicator, color may be an indicator of the type of organism. Adjacent objects, such as gas bubbles also may be an indicator of the type of organism. Accordingly, a variety of image processing criteria and associated parameters may be specified for various plate types. The criteria may differ according to the type of plate  22  to be analyzed, and may significantly affect colony count or other analytical results produced by biological scanner  10 . 
     Upon selection of the appropriate image processing parameters, processor  34  processes the scanned image and produces an analytical result, such as a colony count, which is presented to a user via display  16 . Processor  34  also may store the analytical result in memory, such as count data memory  38 , for later retrieval from scanner  10 . The data stored in count data memory  38  may be retrieved, for example, by a host computer that communicates with biological scanner  10  via a communication port  40 , e.g., a universal serial bus (USB) port. The host computer may compile analytical results for a series of biological growth plates  22  presented to biological scanner  10  for analysis. 
     Automated selection of image processing profiles within biological scanner  10  can provide a convenient and accurate technique for selecting the appropriate image processing profile. Automated selection of image processing profiles can promote the accuracy of bacterial colony counts and other analytical procedures. In particular, automatic image processing profile selection can avoid the need for a technician to visually identify and manually enter the plate type. In this manner, plate identification errors sometimes associated with human intervention can be avoided. Consequently, the combination of a scanner  10  and a biological growth plate  22  that carries plate type indicator  28  can promote efficiency and workflow of laboratory technicians while enhancing analytical accuracy and, in the end, food safety and human health. 
       FIG. 7  is a block diagram illustrating another biological scanner  10 ′ configured for automated image processing profile selection. Biological scanner  10 ′ conforms substantially to biological scanner  10  of  FIG. 6 , but further includes a code reader  42 . Instead of extracting plate type indicator  28  from a scanned image of biological growth plate  22 , code reader  42  serves as a dedicated reader to obtain plate type information. For example, depending on the form of plate type indicator  28 , code reader  42  may take the form of a dedicated optical reader, bar code reader, magnetic reader, radio frequency or mechanical reader. 
     In each case, code reader  42  serves to identify the plate type from plate type indicator  28  and communicates the plate type to processor  34 . Processor  34  then selects an image processing profile from memory  36  based on the identified plate type. Imaging device  32  scans biological growth plate  22  and provides the image date to processor  34 . Processor  34  then applies the image processing parameters specified by the retrieved image processing profile to process the image and produce an analytical result such as colony count. In this manner, processor  34  applies the appropriate image processing profile on an automated basis in view of the automatically identified plate type, offering enhanced accuracy, efficiency and convenience to the user. In particular, in such an embodiment, the invention eliminates the need for the user to enter the plate type identification manually, and reduces the likelihood of analytical error due to erroneous human input. 
       FIG. 8  is a block diagram illustrating biological scanner  10  of  FIG. 6  in greater detail and depicting plate illumination hardware. As shown in  FIG. 8 , biological scanner  10  may include a front illumination system  44  and a back illumination system  46 . Front illumination system  44  illuminates a front side of biological growth plate  22 , and back illumination system  46  illuminates a back side of the biological growth plate. Front and bottom illumination systems  44 ,  46  may produce different illumination intensities, colors and durations on a selective basis. In particular, processor  34  controls front and bottom illumination systems  44 ,  46  to expose biological growth plate  22  to different illumination colors. Front and back illumination systems  44 ,  46  may incorporate LEDs as illumination sources. The LEDs can be readily controlled by processor  34  and appropriate driver circuitry to achieve desired illumination intensities and durations. 
     In addition, processor  34  may control camera  43  to capture images of biological growth plate  22  during illumination with the different colors. For example, processor  34  may provide coordinated control of illumination systems  44 ,  46  and camera  43  to capture one or more images of biological growth plate  22 . Camera  43  captures one or more images of biological growth plate  22  during illumination by front illumination system  44 , back illumination system  46  or both, and may store the images in an image memory  47 . In some cases, processor  34  may control camera gain, resolution, aperture, exposure time or the like in response to the image capture conditions specified by the image processing profile. 
     Using the stored images, processor  34  performs image analysis according to the image analysis criteria specified by the image processing profile. In particular, processor  34  then may analyze the individual images or combine the multiple images to form a composite image. In some embodiments, for example, processor  34  may control illumination systems  44 ,  46  to capture red, green and blue images of biological growth plate  22  and analyze the images individually or as a composite multi-color image. 
     Some types of biological growth plates  22  may require illumination with a particular color, intensity and duration. In addition, some biological growth plates  22  may require only front or back illumination, but not both. For example, an aerobic count plate may require only front illumination as well as illumination by only a single color such as red. Also, an  E. coli /Coliform plate may require only back illumination and a combination of red and blue illumination. Similarly, particular intensity levels and durations may be appropriate, as well as different camera gain, resolution, aperture, and exposure time. For these reasons, processor  34  may control illumination and camera conditions in response to image capture conditions specified by an image processing profile. In other words, scanner  10  can be configured to select not only image analysis criteria based on plate type, but also image capture conditions to be applied to capture the image. 
     To permit identification of plate type in advance of illumination, scanner  10  may apply techniques similar to those described with respect to  FIGS. 6 and 7 . As described with respect to  FIG. 7 , for example a dedicated code reader may be provided to identify plate type in advance of illumination for image capture. Upon identification of the plate type using the dedicated reader, processor  34  selects a corresponding image processing profile from image processing profile memory  36  and controls illumination according to image capture conditions specified in the image processing profile. 
     Alternatively, scanner  10  may be configured to apply machine vision techniques to identify the plate type from a capture image, as discussed with respect to  FIG. 6 . In this case, scanner  10  may apply a set of default illumination conditions to capture an initial image of biological growth plate  22 , or a portion thereof, for purposes of analyzing plate type indicator  28  for plate type identification. Then, processor  34  may select a corresponding image processing profile and apply the specified image capture conditions to capture an image for analysis of biological growth. 
     The image processing profiles are generally described herein as specifying illumination conditions, image analysis criteria or both. However, separate profiles could be used for image capture and image analysis. For example, following plate type identification, processor  34  may access an image capture profile specifying image capture conditions such as illumination colors, intensities and durations. Then, for analysis of a captured image, processor  34  may access a separate image analysis profile specifying image analysis criteria such as color, shape, size and proximity. 
     Although the examples of  FIGS. 6-8  refer to automated selection of image processing profiles based on plate type, the selection may be semi-automated in some embodiments. In particular, upon detection of the plate type via plate type indicator  28 , processor  34  may present a preliminary plate type identification to a user via display  16 . In addition, processor  34  may permit the user to either confirm or reject the automatically identified plate type before proceeding with image capture or analysis using a corresponding image processing profile. The user may confirm or reject a preliminary plate type identification, for example, by actuating a pointing device or depressing regions of a touch screen. If the user believes that the automatically detected plate type identification is in error, processor  34  may permit the user to change the plate type identification. 
       FIG. 9  is a sample display content produced on display  16  by biological scanner  10  upon plate type detection. As shown in  FIG. 9 , display  16  presents a preliminary plate type identification, i.e., a plate type identification automatically made by processor  34 . In the example of  FIG. 9 , display  16  indicates that the “PLATE TYPE=LISTERIA.” In addition, display  16  presents two touch screen regions  52 ,  54  that accept user input to indicate whether the preliminary plate type identification is confirmed or rejected, respectively, by the user. 
       FIG. 10  is sample content produced by display  16  of biological scanner  10  upon rejection of the automated plate type detection by the user. For example, in the event the user rejects a preliminary plate type identification as shown in  FIG. 9 , processor  34  may drive display  16  to present an “ENTER PLATE TYPE” dialog by which the user may choose the correct plate type identification, as shown in  FIG. 10 . Display  16  may present a vertical scroll bar menu  56  that permits the user to choose an alternative plate type identification, e.g., by depressing an appropriate touch screen region. Upon selection of an alternative plate type identification, processor  34  may select an alternative image processing profile containing, for example, image capture conditions, image analysis criteria, or both. 
       FIG. 11  is sample content produced by display  16  of biological scanner  10  upon determination of a colony count. As shown in  FIG. 11 , processor  34  may drive display  16  to present a message that the “PLATE SCAN COMPLETED” and identify the plate type (“PLATE TYPE=LISTERIA”). In addition, upon completion of the analysis of biological growth plate  22 , processor  34  drives display  16  to present a count  58  (“COUNT=XX”). Display  16  may present other types of analytical results as well. 
       FIG. 12  is sample content produced by display  16  of biological scanner  10  upon determination of a colony count and including an image of a scanned plate. In the example of  FIG. 12 , display  16  presents information similar to that shown in  FIG. 11 , but further includes a representation  60  of the actual image scanned by biological scanner  10  from the surface of biological growth plate  22 . In this manner, the user can view both the analytical result, such as count  58 , and a representation  60  of the scanned image. In some embodiments, image representation  60  may present a sufficient amount of detail to permit the user to verify the automatically determined count. In other embodiments, image representation  60  may be a lower resolution representation. 
       FIG. 13  is a flow diagram illustrating a process for image processing profile selection in biological scanner  10 . As shown in  FIG. 13 , the process may involve identifying a plate type ( 62 ) for a biological growth plate  22  presented to scanner  10 . The process may further involve selection of an image processing profile based on the plate type ( 64 ), either before or after scanning a plate image ( 66 ). If the image processing profile specifies image capture conditions, the image processing profile should be selected prior to scanning the plate image so that illumination conditions, camera properties or both may be controlled. Using image analysis criteria specified by the selected image processing profile, the process further involves processing the plate image to produce an analytical result ( 68 ). In particular, the process may generate a bacterial colony count ( 70 ). In the example of  FIG. 13 , the plate type is identified before the plate image is scanned. 
       FIG. 14  is a flow diagram illustrating a process for image processing profile selection in a biological scanner involving detection of a plate type indicator. As shown in  FIG. 14 , the process involves reading the plate type indicator carried by a biological growth plate ( 72 ), e.g., with a dedicate plate type indicator reader such as an optical reader, bar code reader, magnetic reader, radio frequency reader, mechanical reader or the like. Upon determination of the plate type based on the plate type indicator ( 74 ), the process involves selecting an image processing profile based on the detected plate type ( 76 ). In addition, the process involves scanning an image of the biological growth plate ( 78 ), and processing the plate image according to parameters specified by the selected image processing profile ( 80 ). The process then produces an analytical result such as a colony count ( 81 ). 
       FIG. 15  is a flow diagram illustrating a process for image processing profile selection in a biological scanner involving extraction of plate type indicator from a scanned plate image. As shown in  FIG. 15 , the process involves scanning an image of a biological growth plate ( 82 ), and extracting a plate type indicator area from the scanned image ( 84 ). The process further involves processing the extracted plate type indicator area ( 86 ) to determine the plate type ( 88 ). Upon determination of the plate type based on the plate type indicator ( 88 ), the process involves selecting an image processing profile based on the detected plate type ( 90 ). The process then may involve scanning the plate again ( 91 ), e.g., using image capture conditions specified by the selected image processing profile, and processing the plate image according to image analysis criteria specified by the selected image processing profile ( 92 ). The process then produces an analytical result such as a colony count ( 94 ). 
       FIG. 16  is a flow diagram illustrating a process that permits a user to override an automatic plate type identification by a biological scanner. As shown in  FIG. 16 , the process involves automatically determining a plate type associated with a biological growth plate  22  ( 96 ), and presenting the determined plate type to a user via display  16  ( 98 ). The process further involves accepting user input to accept or reject the automatically determined plate type ( 100 ), e.g., via touch screen input. If the plate type is not accepted by the user, the process involves accepting user input to receive a plate type from the user ( 102 ). Upon entry of a plate type by the user ( 102 ) or acceptance of an automatically determined plate type ( 100 ), the process involves selection of an image processing profile based on the plate type ( 104 ). Using the selected image processing profile, the process scans a plate image ( 105 ), processes the plate image ( 106 ) and generates a colony count ( 108 ) or some other desired analytical result. 
     In operation, processor  34  executes instructions that may be stored on a computer-readable medium to carry out the processes described herein. The computer-readable medium may comprise random access memory (RAM) such as synchronous dynamic random access memory (SDRAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, magnetic or optical data storage media, and the like. 
     Various modifications may be made without departing from the spirit and scope of the invention. These and other embodiments are within the scope of the following claims.