U.S. patent application number 10/306663 was filed with the patent office on 2004-05-27 for back side plate illumination for biological growth plate scanner.
Invention is credited to Graessle, Josef A., Lea, Michael C., Schenk, Stephen B..
Application Number | 20040101954 10/306663 |
Document ID | / |
Family ID | 32325747 |
Filed Date | 2004-05-27 |
United States Patent
Application |
20040101954 |
Kind Code |
A1 |
Graessle, Josef A. ; et
al. |
May 27, 2004 |
Back side plate illumination for biological growth plate
scanner
Abstract
A biological growth plate scanner includes a multi-color
illumination system that illuminates a biological growth plate with
different illumination colors. A monochromatic image capture device
captures images of the biological growth plate during illumination
of the growth plate with each of the illumination colors. A
processor combines the images to form a composite multi-color
image, and/or individual components of the composite image, and
analyzes the composite image to produce an analytical result such
as a colony count or a presence/absence result. The biological
growth plate scanner may include both front and back illumination
components. The back illumination component may include a diffuser
element disposed under the biological growth plate. The diffuser
element receives light from one or more laterally disposed
illumination sources, and distributes the light to illuminate a
back side of the biological growth plate. The illumination sources
in the front and back illumination components may take the form of
sets of light emitting diodes (LEDs) that can be independently
controlled by the processor.
Inventors: |
Graessle, Josef A.;
(Meerbuscher, DE) ; Schenk, Stephen B.; (Cottage
Grove, MN) ; Lea, Michael C.; (Berkshire,
GB) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Family ID: |
32325747 |
Appl. No.: |
10/306663 |
Filed: |
November 27, 2002 |
Current U.S.
Class: |
435/288.7 ;
435/34 |
Current CPC
Class: |
G01N 15/1475
20130101 |
Class at
Publication: |
435/288.7 ;
435/034 |
International
Class: |
C12M 001/34 |
Claims
1. A device comprising: an optical diffuser element; and an
illumination source oriented to direct light into the optical
diffuser element, wherein the optical diffuser element directs the
light toward a side of a biological growth plate.
2. The device of claim 1, wherein the optical diffuser element
defines a first major surface, a second major surface and two or
more side surfaces, and the illumination source includes a
plurality of illumination sources oriented to direct the light into
the optical diffuser element via at least some of the side
surfaces.
3. The device of claim 2, wherein the illumination sources are
oriented to direct light into the optical diffuser element via two
of the side surfaces.
4. The device of claim 2, wherein the optical diffuser element
includes a diffusing material adjacent the first major surface, and
a reflecting element adjacent the second major surface, and the
optical diffusing material directs the light toward the side of the
biological growth plate via the first major surface.
5. The device of claim 2, wherein the optical diffuser element is
movable to support and transport the biological growth plate to a
scanning position for scanning of the biological growth plate.
6. The device of claim 5, wherein the optical diffuser element is
movable relative to the illumination sources between a position to
receive the biological growth plate and the scanning position.
7. The device of claim 2, wherein the optical diffuser element
includes a diffusing film formed on the first major surface, and a
reflecting film formed on the second major surface, and reflection
of the light from the reflecting film causes the optical diffusing
film to direct the light toward the side of the biological growth
plate via the first major surface.
8. The device of claim 1, wherein the illumination source
selectively produces one or more different illumination colors, the
device further comprising: a monochromatic camera oriented to
capture an image of the biological growth plate; and a processor
that controls the camera to capture one or more images of the
biological growth plate during illumination with each of the
different illumination colors.
9. The device of claim 8, wherein the different illumination colors
are red, green and blue, and the camera captures images of the
biological growth plate during the red, green and blue
illumination.
10. The device of claim 8, wherein the processor controls the
illumination sources to sequentially illuminate the biological
growth plate with each of the different illumination colors, and to
control an illumination duration for each of the different
illumination colors.
11. The device of claim 1, wherein the illumination source
includes: a set of red light emitting diodes to produce red
illumination; a set of green light emitting diodes to produce green
illumination; and a set of blue light emitting diodes to produce
blue illumination.
12. The device of claim 11, further comprising a processor to
selectively control activation of the red, green and blue light
emitting diodes according to illumination requirements of the
biological growth plate.
13. The device of claim 1, wherein the biological growth plate
carries a biological agent in the group consisting of aerobic
bacteria, E. coli, coliform, enterobacteriaceae, yeast, mold,
Staphylococcus aureus, Listeria, and Campylobacter.
14. The device of claim 1, wherein the biological growth plate is a
thin film culture plate.
15. The device of claim 1, wherein the optical diffuser element
defines a first major surface, a second major surface and four side
surfaces, and the illumination source includes a plurality of
illumination sources oriented to direct the light into the optical
diffuser element via at least two of the side surfaces, the device
further comprising a reflective material formed adjacent at least
one of the side surfaces.
16. A method comprising directing light into an optical diffuser
element to illuminate a side of a biological growth plate.
17. The method of claim 16, wherein the optical diffuser element
includes a first major surface, a second major surface and two or
more side surfaces, the method further comprising directing the
light into the optical diffuser element via at least some of the
side surfaces.
18. The method of claim 17, further comprising directing the light
into the optical diffuser element via two of the side surfaces.
19. The method of claim 17, wherein the optical diffuser element
includes a diffusing material adjacent the first major surface, and
a reflecting element adjacent the second major surface, and the
optical diffusing material directs the light toward the side of the
biological growth plate via the first major surface.
20. The method of claim 17, further comprising moving the optical
diffuser element to support and transport the biological growth
plate to a scanning position for scanning of the biological growth
plate.
21. The method of claim 20, further comprising moving the optical
diffuser element relative to the illumination sources between a
position to receive the biological growth plate and the scanning
position.
22. The method of claim 17, wherein the optical diffuser element
includes a diffusing film formed on the first major surface, and a
reflecting film formed on the second major surface, and reflection
of the light from the reflecting film causes the optical diffusing
film to direct the light toward the back surface of the biological
growth plate via the first major surface.
23. The method of claim 16, further comprising: selectively
illuminating the side of the biological growth plate with one or
more different illumination colors via the optical diffuser
element; and capturing one or more images of the biological growth
plate with a camera during illumination with each of the different
illumination colors.
24. The method of claim 23, wherein the different illumination
colors are red, green and blue, the method further comprising
capturing images of the biological growth plate during the red,
green and blue illumination.
25. The method of claim 23, further comprising sequentially
illuminating the biological growth plate with each of the different
illumination colors, and controlling an illumination duration for
each of the different illumination colors.
26. The method of claim 25, further comprising producing the
illumination colors with: a set of red light emitting diodes to
produce red illumination; a set of green light emitting diodes to
produce green illumination; and a set of blue light emitting diodes
to produce blue illumination.
27. The method of claim 26, further comprising selectively
controlling activation of the red, green and blue light emitting
diodes according to illumination requirements of the biological
growth plate.
28. The method of claim 16, wherein the biological growth plate
carries a biological agent in the group consisting of aerobic
bacteria, E. coli, coliform, enterobacteriaceae, yeast, mold,
Staphylococcus aureus, Listeria, and Campylobacter.
29. The method of claim 16, wherein the biological growth plate is
a thin film culture plate.
30. A device comprising: an optical diffuser element; a first
illumination source oriented to direct light into the optical
diffuser element, wherein the optical diffuser element directs the
light toward a first side of a biological growth plate; a second
illumination source oriented to direct light toward a second side
of the biological growth plate; and means for scanning the second
side of the biological growth plate during illumination of the
first and second sides by the optical diffuser element and the
second illumination source.
31. The device of claim 30, wherein the optical diffuser element
includes a first major surface, a second major surface and two or
more side surfaces, and the illumination source includes a
plurality of illumination sources oriented to direct the light into
the optical diffuser element via at least some of the side
surfaces.
32. The device of claim 31, wherein the illumination sources are
oriented to direct light into the optical diffuser element via two
of the side surfaces.
33. The device of claim 31, wherein the optical diffuser element
includes a diffusing material adjacent the first major surface, and
a reflecting element adjacent the second major surface, and the
optical diffusing material directs the light toward the side of the
biological growth plate via the first major surface.
34. The device of claim 31, wherein the optical diffuser element is
movable to support and transport the biological growth plate to a
scanning position for scanning of the biological growth plate.
35. The device of claim 31, wherein the optical diffuser element
includes a diffusing film formed on the first major surface, and a
reflecting film formed on the second major surface, and reflection
of the light from the reflecting film causes the optical diffusing
film to direct the light toward the side of the biological growth
plate via the first major surface.
36. The device of claim 30, wherein the first and second
illumination sources selectively produce one or more different
illumination colors, and the scanning means includes a
monochromatic camera oriented to capture an image of the biological
growth plate, the device further comprising a processor that
controls the camera to capture one or more images of the biological
growth plate during illumination with each of the different
illumination colors.
37. The device of claim 36, wherein the different illumination
colors are red, green and blue, and the camera captures images of
the biological growth plate during the red, green and blue
illumination.
38. The device of claim 36, wherein the processor controls the
illumination sources to sequentially illuminate the biological
growth plate with each of the different illumination colors, and to
control an illumination duration for each of the different
illumination colors.
39. The device of claim 30, wherein each of the first and second
illumination sources includes: a set of red light emitting diodes
to produce red illumination; a set of green light emitting diodes
to produce green illumination; and a set of blue light emitting
diodes to produce blue illumination.
40. The device of claim 39, further comprising a processor to
selectively control activation of the red, green and blue light
emitting diodes according to illumination requirements of the
biological growth plate.
41. The device of claim 30, wherein the biological growth plate
carries a biological agent in the group consisting of aerobic
bacteria, E. coli, coliform, enterobacteriaceae, yeast, mold,
Staphylococcus aureus, Listeria, and Campylobacter.
42. The device of claim 30, wherein the biological growth plate is
a thin film culture plate.
43. The device of claim 30, wherein the optical diffuser element
defines a first major surface, a second major surface and four side
surfaces, and the illumination source includes a plurality of
illumination sources oriented to direct the light into the optical
diffuser element via at least two of the side surfaces, the device
further comprising a reflective material formed adjacent at least
one of the side surfaces.
Description
FIELD
[0001] The invention relates to scanners for analysis of biological
growth media to analyze bacteria or other biological agents in food
samples, laboratory samples, and the like.
BACKGROUND
[0002] 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.
[0003] 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 and
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.
[0004] 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.
[0005] Biological growth plate scanners refer to devices used to
read or count bacterial colonies, or the amount of a particular
biological agent on a biological growth plate. For example, a food
sample or laboratory sample can be placed on a biological growth
plate, and then the plate can be inserted into an incubation
chamber. After incubation, the biological growth plate can be
placed into the biological growth plate scanner for automated
detection and enumeration of bacterial growth. In other words,
biological growth plate scanners automate the detection and
enumeration of bacteria or other biological agents on a biological
growth plate, and thereby improve the biological testing process by
reducing human error.
SUMMARY
[0006] In general, the invention is directed to a biological growth
plate scanner. The biological growth plate scanner may include a
multi-color illumination system that illuminates the biological
growth plate with different illumination colors. A monochromatic
image capture device captures images of the biological growth plate
during illumination of the growth plate with each of the
illumination colors. A processor combines the images to form a
composite multi-color image, and analyzes the composite image to
produce an analytical result such as a colony count.
[0007] The biological growth plate scanner may include both front
and back illumination components. The front illumination component
provides illumination for a front side of the biological growth
plate, which is scanned by the scanner. The back illumination
component provides illumination for a back side of the biological
growth plate. The back illumination component may include an
optical diffuser element disposed behind the biological growth
plate, e.g., under the biological growth plate when the major plane
of the growth plate is oriented horizontally. The diffuser element
receives light from one or more laterally disposed illumination
sources, and distributes the light to illuminate a back side of the
biological growth plate. The illumination sources in the front and
back illumination components may take the form of light emitting
diodes (LEDs) that can be controlled by the processor.
[0008] In one embodiment, the invention provides a device
comprising an optical diffuser element, and an illumination source
oriented to direct light into the optical diffuser element, wherein
the optical diffuser element directs the light toward a side of a
biological growth plate.
[0009] In another embodiment, the invention provides a method
comprising directing light into an optical diffuser element to
illuminate a side of a biological growth plate.
[0010] In an added embodiment, the invention provides a device
comprising an optical diffuser element, a first illumination source
oriented to direct light into the optical diffuser element, wherein
the optical diffuser element directs the light toward a first side
of a biological growth plate, a second illumination source oriented
to direct light toward a second side of the biological growth
plate, and means for scanning the second side of the biological
growth plate during illumination of the first and second sides by
the optical diffuser element and the second illumination
source.
[0011] The invention can provide a number of advantages. For
example, the use of a monochromatic camera results in resolution
benefits and cost savings. In particular, a monochromatic camera
offers increased spatial resolution relative to multi-color cameras
and a resulting cost reduction per unit resolution. Rather than
obtaining a single, multi-color image, the monochromatic camera
captures multiple high resolution images, e.g., red, green and
blue, and then combines them to produce a high resolution,
multi-color image.
[0012] The use of different illumination colors can be achieved by
independent sets of color LEDs, e.g., red, green and blue LEDs. The
LEDs offer an extended lifetime relative to lamps and have
inherently consistent output spectra and stable light output. A
processor can control the LEDs to perform sequential illumination
of the biological growth plates with different colors.
[0013] In addition, the color LEDs can be controlled independently
to provide different output intensities and exposure durations.
This feature is advantageous because the LEDs may exhibit different
brightness characteristics, and reflector hardware or other optical
components associated with the LEDs may present
nonuniformities.
[0014] Also, the camera and associated lens, or different types of
culture films, may exhibit different responses to the illumination
colors. For example, the camera may be more or less sensitive to
red, green and blue, presenting additional nonuniformities.
However, the LED's can be independently controlled to compensate
for such nonuniformities.
[0015] A back illumination component as described herein offers a
convenient structure for effectively illuminating the back side of
the biological growth plate with good uniformity while conserving
space within the scanner. For example, the back illumination
component may provide a diffuser element that serves to support a
biological growth plate and distribute light injected into the
diffuser element from laterally disposed illumination sources. In
addition, the back illumination component may incorporate a set of
fixed illumination sources that do not require movement during use,
thereby alleviating fatigue to electrical wiring and reducing
exposure to environmental contaminants.
[0016] 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
[0017] FIG. 1 is a perspective view of an exemplary biological
growth plate scanner.
[0018] FIG. 2 is another perspective view of an exemplary
biological growth plate scanner.
[0019] FIGS. 3 and 4 are front views of an exemplary growth plate
bearing an indicator pattern for image processing profile
selection.
[0020] FIG. 5 is a block diagram illustrating internal operation of
a biological growth plate scanner.
[0021] FIG. 6 is a block diagram illustrating the biological growth
plate scanner of FIG. 5 in greater detail.
[0022] FIG. 7 is a side view illustrating a front illumination
component for a biological growth plate scanner.
[0023] FIG. 8 is a front view illustrating a front illumination
component for a biological growth plate scanner.
[0024] FIG. 9 is a side view illustrating a back illumination
component for a biological growth plate scanner in a loading
position.
[0025] FIG. 10 is a side view illustrating the back illumination
component of FIG. 9 in a scanning position.
[0026] FIG. 11 is a bottom view illustrating the back illumination
component of FIGS. 9 and 10.
[0027] FIG. 12 is a side view illustrating the combination of front
and back illumination components for a biological growth plate
scanner.
[0028] FIG. 13 is a circuit diagram illustrating a control circuit
for an illumination system.
[0029] FIG. 14 is a functional block diagram illustrating the
capture of multi-color images for preparation of a composite image
to produce a plate count.
[0030] FIG. 15 is a flow diagram illustrating a technique for the
capture of multi-color images for preparation of a composite image
to produce a plate count.
[0031] FIG. 16 is a flow diagram illustrating the technique of FIG.
15 in greater detail.
DETAILED DESCRIPTION
[0032] The invention is directed to a biological growth plate
scanner for biological growth plates. A biological growth plate can
be presented to the biological growth plate 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 growth plate scanner automates the analysis
of biological growth plates.
[0033] A biological growth plate scanner, in accordance with the
invention, may include a multi-color illumination system that
illuminates the biological growth plate with different illumination
colors. A monochromatic image capture device captures images of the
biological growth plate during illumination of the growth plate
with each of the illumination colors. A processor combines the
images to form a composite multi-color image, and analyzes the
composite image and/or individual components of the composite image
to produce an analytical result such as a colony count or a
presence/absence result.
[0034] In addition, the biological growth plate scanner may include
both front and back illumination components. The back illumination
component may include a diffuser element disposed under the
biological growth plate. The optical diffuser element receives
light from one or more laterally disposed illumination sources, and
distributes the light to illuminate a back side of the biological
growth plate. The illumination sources in the front and back
illumination components may take the form of light emitting diodes
(LEDs) that can be controlled by the processor. Various embodiments
of a biological growth scanner will be described.
[0035] 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 and/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.
[0036] FIG. 1 is a perspective view of an exemplary biological
growth plate scanner 10. As shown in FIG. 1, biological growth
plate 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 growth plate
scanner 10 for scanning and analysis.
[0037] Biological growth plate 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 16 may present to a user an image of
the growth plate scanned by biological growth plate scanner 10. The
displayed image may be optically magnified or digitally scaled
upward.
[0038] A mounting platform 18 defines an ejection slot 20 through
which the growth plate can be ejected following analysis by
biological growth plate scanner 10. Accordingly, biological growth
plate 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.
[0039] 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 monochromatic line scanner or an area
scanner, in combination with a multi-color illumination system to
provide front and back illumination to 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.
[0040] When drawer 14 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 growth plate
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
plate via slot 20.
[0041] FIG. 2 is another perspective view of biological growth
plate scanner 10. As shown in FIG. 2, drawer 14 extends outward
from biological growth plate 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 growth plate 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 plate is optically scanned.
[0042] FIGS. 3 and 4 are front 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 some embodiments,
biological growth plate 22 may carry a plate type indicator 28 to
facilitate automated identification of the type of biological media
associated with the growth plate.
[0043] 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.
[0044] A wide variety of optical patterns such as characters, bar
codes, two-dimensional bar codes, optical gratings, holograms 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 growth plate
scanner 10.
[0045] 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,
Campylobacter and the like. The use of PETRIFILM plates, or other
growth media, can simplify bacterial testing of food samples.
Moreover, biological growth plate 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 analyze biological growth plate 22, e.g., by
counting bacterial colonies on an image of the plate.
[0046] 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 quantifies 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.
[0047] 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.
[0048] FIG. 5 is a block diagram illustrating internal operation of
a biological growth plate scanner 10. As illustrated in FIG. 5, a
biological growth plate 22 is positioned within biological growth
plate scanner 10 on a platform (not shown in FIG. 5). The platform
places biological growth plate 22 at a desired focal plane of an
imaging device 32. In accordance with the invention, imaging device
32 may include multi-color illumination systems for front and back
illumination of growth pate 22, as well as a monochromatic line or
area scanner that captures an image of the surface of growth plate
22. In some embodiments, for example, imaging device 32 may take
the form of a two-dimensional, monochromatic camera.
[0049] In general, imaging device 32 captures images of biological
growth plate 22, or, at least a growth region within the biological
growth plate, during illumination of the biological growth plate
with one or more different illumination colors. In some
embodiments, illumination durations and illumination intensities
may be controlled according to requirements of different biological
growth plates. In addition, selective illumination of a first side
and a second side of the biological growth plate can be controlled
according to requirements of different biological growth
plates.
[0050] A processor 34 controls the operation of imaging device 32.
In operation, processor 34 controls imaging device 32 to illuminate
biological growth plate 22 with different illumination colors, and
capture images of biological growth plate 22. Processor 34 receives
image data representing the scanned images from imaging device 32
during illumination with each of the different illumination colors,
and combines the images to form a multi-color composite image.
Processor 34 analyzes the composite image of biological growth
plate 22 and analyzes the image to produce an analytical result,
such as a colony count or a presence/absence result.
[0051] In some embodiments, processor 34 may extract or segregate a
portion of the image to isolate plate type indicator 28. Using
machine vision techniques, for example, processor 34 may analyze
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 circuit (ASIC), field
programmable gate array (FPGA) or other integrated or discrete
logic circuitry programmed or otherwise configured to provide
functionality as described herein.
[0052] Using the image processing profile, processor 34 loads
appropriate image processing 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 processing parameters may vary with the image processing
profile and detected plate type, and may specify particular imager
analysis conditions, including parameters such as color, size,
shape and proximity criteria for analysis of the scanned image. 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 growth plate scanner 10.
The image processing profile also may specify image capture
conditions such as illumination colors, intensities, and durations
suitable for a particular type of biological growth plate. Suitable
techniques for plate type identification and use of image
processing profiles are further described in copening and commonly
assigned U.S. application Ser. No. ______ filed ______, to Green et
al., entitled "BIOLOGICAL GROWTH PLATE SCANNER WITH AUTOMATED IMAGE
PROCESSING PROFILE SELECTION," and bearing attorney docket no.
58025US002, the entire content of which is incorporated herein by
reference.
[0053] Upon selection of the appropriate image processing
parameters, processor 34 processes the scanned image and produces
an analytical result, such as a colony count or a presence/absence
result, 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 growth plate 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 growth plate
scanner 10 for analysis.
[0054] Automated selection of image processing profiles within
biological growth plate 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.
[0055] FIG. 6 is a block diagram illustrating biological growth
plate scanner 10 of FIG. 5 in greater detail. Imaging device 32
(FIG. 5) of biological growth plate scanner 10 may include, as
shown in FIG. 6, a camera 42, front illumination component 44 and
back illumination component 46. In accordance with the invention,
front and back illumination systems 44, 46 may produce different
illumination intensities, colors and durations on a selective
basis. In particular, processor 34 controls front and back
illumination systems 44, 46 to expose biological growth plate 22 to
different illumination colors. In addition, processor 34 controls
camera 42 to capture images of biological growth plate 22 during
illumination with the different colors.
[0056] For example, processor 34 may provide coordinated control of
illumination systems 44, 46 and camera 42 to capture multiple
images of biological growth plate 22. Processor 34 then combines
the multiple images to form a multi-color, composite image. Using
the multi-color, composite image, and/or individual components of
the composite image, processor 34 analyzes biological growth plate
22 to produce an analytical result such as a detection or colony
count. In one embodiment, front and back illumination systems 44,
46 may expose biological growth plate 22 to red, green and/or blue
illumination colors on a selective basis under control of processor
34. In this example, camera 42 captures red, green and blue images
of biological growth plate 22. Processor 34 then combines the red,
green and blue images to form the multi-color, composite image for
analysis.
[0057] As an illustration, processor 34 may first activate red
illumination sources within front and back illumination components
44, 46 to expose biological growth plate 22 to red illumination. In
particular, processor 34 may control the intensity and exposure
duration of the red illumination sources. In synchronization with
the red illumination exposure, camera 42 captures a red image of
biological growth plate 22 and stores the captured image in an
image memory 47 within scanner 10.
[0058] Processor 34 then activates green illumination sources
within front and back illumination components 44, 46 to expose
biological growth plate 22 to green illumination, followed by
capture of a green image by camera 42. Similarly, processor
activates blue illumination sources within front and back
illumination components 44, 46 to expose biological growth plate 22
to blue illumination, followed by capture of a blue image by camera
42.
[0059] Camera 42 captures monochromatic images for each of the red,
green and blue illumination exposures, and may store the images in
separate files. Using the files, processor 34 combines the captured
images to form the composite image for analysis. The order in which
biological growth plate 22 is exposed to the multiple illumination
colors may vary. Therefore, exposure to red, green and blue
illumination sources in sequence should not be considered limiting
of the invention.
[0060] The individual images captured by camera 42 may be
represented in terms of optical intensity or optical density. In
other words, camera 42 captures gray scale data that can be used to
quantify the reflected output of biological growth plate 22 for
each exposure channel, e.g., red, green and blue. The use of a
monochromatic camera 42 to capture the individual images can result
in image resolution benefits and cost savings. In particular, a
less expensive monochromatic camera 42 may offer increased spatial
resolution relative to multi-color cameras that capture red, green
and blue spectra simultaneously. Accordingly, camera 42 can obtain
high resolution imagery needed for effective analysis of biological
growth plate 22 with reduced cost. Rather than obtain a single,
multi-color image monochromatic camera 42 captures multiple high
resolution images, e.g., red, green and blue, and then processor 34
combines them to produce a high resolution, multi-color image.
[0061] The different illumination sources within front and back
illumination systems 44, 46 may take the form of LEDs. In
particular, the different illumination colors can be achieved by
independent sets of color LEDs, e.g., red, green and blue LEDs. As
an advantage, LEDs offer an extended lifetime relative to other
illumination sources such as lamps. LEDs also may provide
inherently consistent output spectra and stable light output.
[0062] Also, processor 34 can readily control the output
intensities and exposure durations of the LEDs to perform
sequential illumination of the biological growth plates 22 with
appropriate levels of illumination. Processor 34 can be programmed
to control the different sets of color LEDs independently to
provide different output intensities and exposure durations for
each illumination color applied to biological growth plate 22.
[0063] This ability to independently control the LEDs via processor
34 can be advantageous because the LEDs may exhibit different
brightness characteristics, and reflector hardware or other optical
components associated with the LEDs may present nonuniformities. In
addition, camera 42 and one or more associated camera lenses may
exhibit different responses to the illumination colors. For
example, camera 42 may be more or less sensitive to red, green and
blue, presenting additional nonuniformities in the color response
for a given illumination channel.
[0064] Processor 34 can independently control the LEDs, however, in
order to compensate for such nonuniformities. For example, scanner
10 may be calibrated at the factory or in the field to characterize
the response of camera 42 to the different illumination sources,
and then compensate the response by storing appropriate drive
values to be applied by processor 34. Hence, processor 34 may apply
different drive values to the LEDs for different illumination
colors and intensity levels to produce a desired degree of
uniformity in the images captured by camera 42.
[0065] In some embodiments, scanner 10 may process images of
different biological growth plates 22 according to different image
processing profiles. The image processing profiles may be selected
by processor 34 based on user input or identification of the type
of biological growth plate 22 presented to scanner 10. The image
processing profile may specify particular image capture conditions,
such as illumination intensities, exposure durations, and colors,
for capturing images of particular plate types. Thus, the scanner
may apply different image capture conditions, including different
illumination conditions, in processing images of different
biological growth plates 22.
[0066] As an illustration, 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. Alternatively, 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. For these
reasons, processor 34 may control illumination in response to image
capture conditions specified by an image processing profile.
[0067] FIG. 7 is a side view illustrating a front illumination
component 44 for biological growth plate scanner 10. As shown in
FIG. 7, front illumination component 44 may be integrated with
camera 42. For example, camera 42 may include a camera body with a
CMOS or CCD camera chip 48 mounted to a camera backplane 50, such
as a printed circuit board, which may carry circuitry to drive
camera chip 48 and receive image data for processor 34. A camera
lens 52 may be oriented to capture images of a biological growth
plate 22 via an aperture 53 in a housing defined by front
illumination component 44. In the example of FIG. 7, front
illumination component 44 includes a side wall 54, a front wall 56,
and an optical platen 58. Optical platen 58 may simply be a
transparent sheet of glass or plastic that permits transmission of
illuminating light and capture of imagery from biological growth
plate 22 by camera 42. In some embodiments, optical platen 58 may
be eliminated such that the growth area 26 of plate 22 is
illuminated with no intervening structure between growth area 26
and the emitted light. Biological growth plate 22 may be elevated
into contact or close proximity with optical platen 58 to permit
camera 42 to capture images.
[0068] A number of components may be housed within front
illumination component 44. For example, front illumination
component 44 may include one or more illumination sources 60A, 60B,
preferably arranged in linear arrays about a periphery of growth
area 26 of biological growth plate 22. In particular, a linear
array of red, green and blue illumination sources 60A, 60B may
extend along each of four edges of biological growth plate 22,
e.g., in a square pattern. In other embodiments, the illumination
sources may be arranged in alternative patterns, e.g., circular
patterns. Again, illumination sources 60A, 60B may take the form of
LEDs and may be arranged in groups of one red, one green and one
blue LED.
[0069] Illumination sources 60A, 60B may be mounted within
illumination chambers 62A, 62B. Reflective cowels 64A, 64B are
mounted about illumination sources 60A, 60B and serve to reflect
and concentrate the light emitted by the illumination sources
toward inwardly extending walls 66A, 66B of chambers 62A, 62B. The
reflective material may be coated, deposited, or adhesively affixed
to an interior surface of reflective cowels 64A, 64B. An example of
a suitable reflective material for reflective cowels 64A, 64B is
the 3M Radiant Mirror Reflector VM2000 commercially available from
3M Company of St. Paul, Minn.
[0070] Walls 66A, 66B may carry an optical diffusing material, such
as a film 68A, 68B, that serves to diffuse light received from
illumination sources 60A, 60B. The diffuse light is transmitted
into an interior chamber of front illumination component 44 to
illuminate growth region 26 of biological growth plate 22. An
example of a suitable diffusing material for diffusing film 68A,
68B is the Mitsui WS-180A diffuse white film, commercially
available from Mitsui & Co., Inc., of New York, N.Y. The
diffusing film 68A, 66B may be coated or adhesively affixed to an
interior surface of walls 66A, 66B.
[0071] FIG. 8 is a front view illustrating front illumination
component 44 in greater detail. As shown in FIG. 8, front
illumination component 44 may include four illumination chambers
62A, 62B, 62C, 62D arranged around a periphery of biological growth
plate 22. Each illumination chamber 62 may include two sets of
illumination sources 60. For example, chamber 62A may contain
illumination sources 60A, 60C, chamber 62B may contain illumination
sources 60B, 60D, chamber 62C may contain illumination sources 60E,
60F, and chamber 62D may contain illumination sources 60G, 60H. In
addition, chambers 62A, 62B, 62C, 62D may include respective walls
66A, 66B, 66C, 66D carrying diffusing film. In other embodiments,
each respective chamber 62 may include any number of illumination
sources 60, which may or may not be the same number of illumination
sources in other chambers.
[0072] Illumination sources 60 may include an array of illumination
elements grouped together, e.g., in groups of three. In particular,
each illumination source 60 may include a red LED, a green LED, and
a blue LED that can be separately activated to illuminate
biological growth plate 22. Upon activation of the individual LEDs,
an inner chamber defined by front illumination component 44 is
filled with diffused light to provide front illumination to
biological growth plate 22. Camera 42 captures an image of
biological growth plate 22 during successive exposure cycles with
each of the different illumination colors.
[0073] FIG. 9 is a side view illustrating back illumination
component 46 for a biological growth plate scanner 10 in a loading
position, i.e., a position in which biological growth plate 22 is
initially loaded into the scanner. In some embodiments, biological
growth plate 22 may be loaded into scanner via drawer 14, as shown
in FIG. 2. In particular, drawer 14 carries a diffuser element 74
that serves as a platform for biological growth plate 22. Drawer 14
may be configured to permit retraction of biological growth plate
22 into the interior of scanner 10, and elevation of the biological
growth plate into a scanning position.
[0074] Once loaded, biological growth plate 22 can be supported by
optical diffuser element 74 or, alternatively, supported by a
transparent platform in close proximity to the optical diffuser
element. Optical diffuser element 74 serves to diffuse light that
is laterally injected into the diffuser element and radiate the
light upward to provide back side illumination of biological growth
plate 22. Back illumination component 46 effectively illuminates
the back side of biological growth plate 22 with good uniformity
while conserving space within scanner 10.
[0075] In addition, back illumination component 46 incorporates a
set of fixed illumination sources 76A, 76B that do not require
movement during use, thereby alleviating fatigue to electrical
wiring and reducing exposure to environmental contaminants. Rather,
biological growth plate 22 and diffuser element 74 are elevated
into position in alignment with the fixed illumination sources 76A,
76B. In summary, back illumination component 46 offers good
illumination uniformity across the surface of biological growth
plate 22, a flat illumination surface, a fixed arrangement of
illumination sources 76A, 76B, and an efficient size and volume for
space conservation.
[0076] Illumination sources 76A, 76B are positioned adjacent a
lateral edge of diffuser element 74, when the diffuser element
occupies the elevated, scanning position. Each illumination source
76A, 76B may include a reflector cowl 78A, 78B to reflect and
concentrate light emitted by the illumination sources toward
respective edges of diffuser element 74. In this manner,
illumination sources 76A, 76B inject light into optical diffuser
element 74. The reflective material may be coated, deposited, or
adhesively affixed to an interior surface of reflective cowels 78A,
78B. An example of a suitable reflective material for reflective
cowels 78A, 78B is the 3M Radiant Mirror Reflector VM2000
commercially available from 3M Company of St. Paul, Minn.
[0077] A platen support 80A, 80B may be provided to support an
optical platen 58 (FIG. 7), and provide an interface for engagement
of back illumination component 46 with front illumination component
44. As further shown in FIG. 9, a support bracket 82A, 82B provides
a mount for optical diffuser element 74. In addition, illumination
sources 76A, 76B are mounted to backplanes 84A, 84B, which may
carry a portion of the circuitry necessary to drive the
illumination sources. However, backplanes 84A, 84B and illumination
sources 76A, 76B may be generally fixed so that travel of the
illumination sources and associated fatigue to wiring and other
electrical components is not necessary, and exposure to
environmental contaminants is reduced.
[0078] A back side of diffuser element 74 may be defined by a
reflective film 88 that promotes inner reflection of light received
from illumination sources 76A, 76B, i.e., reflection of light into
an interior chamber defined by diffuser element. In this manner,
the light does exit the back region of diffuser element 74, but
rather is reflected inward and upward toward biological growth
plate 22. Reflective film 88 may be coated, deposited, or
adhesively bonded to a wall defined by diffuser element 74.
Alternatively, reflective film 88 may be free-standing and define
the back wall of diffuser element 74. An example of a suitable
material for reflective film 88 is 3M Radiant Mirror Film,
2000F1A6, commercially available from 3M Company of St. Paul,
Minn.
[0079] A front side of diffuser element 74, adjacent biological
growth plate 22, may carry an optical diffusing material such as an
optical light guide and diffusing film 86. Diffuser element 74 may
define an internal chamber between reflective film 88, optical
light guide and diffusing film 86, and respective light
transmissive layers 89A, 89B forming side walls adjacent
illumination sources 76A, 76B. As will be described, opposing side
walls of optical diffuser element 74 on sides not adjacent
illumination sources 76A, 76B may be formed by reflective layers to
promote internal reflection of light injected into the diffuser
element.
[0080] The internal chamber defined by optical diffuser element 74
may simply be empty and filled with air. Optical light guide and
diffusing film 86 serves to diffuse light emitted from diffuser
element 74 toward biological growth plate 22. An example of a
suitable optical light guide and diffusing film is 3M Optical
Lighting Film, printed with a pattern of diffuse white dots having
30% area coverage, with prism orientation facing down toward the
diffuser element. In particular, the prisms of optical light guide
and diffusing film 86 face into diffuser element 74 and the
orientation of the prisms is generally perpendicular to
illumination sources 76A, 76B. The 3M Optical Lighting Film is
commercially available from 3M Company of St. Paul, Minn.
[0081] In addition, diffuser element 74 may include a
scratch-resistant, light transmissive layer 87 over optical light
guide and diffusing film 86. Biological growth plate 22 may be
placed in contact with scratch-resistant layer 87. Additional
scratch-resistant, light transmissive layers 89A, 89B may be
disposed adjacent the lateral edges of diffuser element 74. In
particular, layers 89A, 89B may be disposed between illumination
sources 76A, 76B and diffuser element 74.
[0082] Scratch-resistant, light transmissive layers 89A, 89B are
placed over light entry slots at opposite sides of diffuser element
74 to permit transmission of light from illumination sources 76A,
76B into the diffuser element, and also provide a durable surface
for upward and downward sliding movement of the diffuser element.
An example of a suitable scratch-resistant, light transmissive
material for use as any of layers 87, 89A, 89B resides in the class
of acrylic glass-like materials, sometimes referred to as
acrylglass or acrylplate. Alternatively, layers 87, 89A, 89B may be
formed by glass.
[0083] An acrylic or glass plate as layer 87 can be used to provide
a stable, cleanable platform for the biological growth plate, and
protect diffuser element 74 from damage. An approximately 1 mm gap
may be provided between layer 87 and light guide and diffusing film
86 to preserve the optical performance of the light guide and
diffusing film, which could be altered by contact with materials
other than air.
[0084] FIG. 10 is a side view illustrating the back illumination
component 46 of FIG. 9 in a scanning position. In particular, in
FIG. 10, diffuser element 74 is elevated relative to the position
illustrated in FIG. 9. Diffuser element 74 may be elevated by a
variety of elevation mechanisms, such as camming, lead screw or
pulley arrangements. As diffuser element 74 is elevated into
scanning position, biological growth plate 22 is placed in
proximity or in contact with optical platen 58 (FIG. 7).
[0085] Upon elevation into scanning position, illumination sources
76A, 76B inject light into diffuser element 74, which diffuses the
light and directs it upward to provide back illumination for
biological growth plate 22. As will be described, illumination
sources 76A, 76B may incorporate differently colored illumination
elements that are selectively activated to permit camera 42 to
separate monochromatic images for each color, e.g., red, green and
blue.
[0086] FIG. 11 is a bottom view illustrating back illumination
component 46 of FIGS. 9 and 10. As shown in FIG. 11, multiple
illumination sources 76A-76H may be disposed in linear arrays on
opposite sides of diffuser element 74. FIG. 11 provides a
perspective of back illumination components from a side opposite
biological growth plate 22, and therefore shows reflective layer
88. Each illumination source 76 may include three illumination
elements, e.g., a red (R) element, a green (G) element, and a blue
(B) element. The red, green and blue elements may be red, green and
blue LEDs. Back illumination component 46 may be configured such
that all red elements can be activated simultaneously to illuminate
the back side of biological growth plate 22 with red light in order
to capture a red image with camera 42. The green elements and blue
elements, respectively, may be similarly activated
simultaneously.
[0087] As further shown in FIG. 11, reflective layers 93A, 93B form
opposing side walls of diffuser element 74 on sides not adjacent
illumination sources 76. Reflective layers 93A, 93B may be formed
from materials similar to reflective layer 88, and may be affixed
to interiors or respective side walls or form free-standing walls
themselves. In general, reflective layers 88, 93A, 93B serve to
reflect light injected by illumination sources 76 into the interior
chamber defined by diffuser element 74, preventing the light from
escaping from the back side or side walls of the diffuser element.
Instead, the light is reflected inward and toward diffusing
material 86. In this manner, the light is concentrated and then
diffused by diffusing material 86 for transmission to illuminate a
back side of biological growth plate 22.
[0088] FIG. 12 is a side view illustrating the combination of front
and back illumination components 44, 46, as well as camera 42, for
biological growth plate scanner 10. As shown in FIG. 12, optical
platen 58 serves as an interface between front illumination
component 44 and back illumination component 46. In operation,
biological growth plate 22 is elevated into proximity or contact
with optical platen 58. Front and back illumination components 44,
46 then selectively expose biological growth plate 22 with
different illumination colors to permit camera 42 to capture images
of the biological growth plate. For example, front and back
illumination component 44, 46 may selectively activate red, green
and blue LEDs in sequence to form red, green and blue images of
biological growth plate 22.
[0089] FIG. 13 is a circuit diagram illustrating a control circuit
90 for an illumination system. Control circuit 90 may be used to
control illumination sources in front and back illumination
components 44, 46. In the examples of FIGS. 7-12, front and back
illumination components 44, 46 each include eight separate
illumination sources 60, 76. Each illumination source 60, 76
includes a red, green and blue illumination element, e.g., red,
green and blue LEDs. Accordingly, FIG. 13 illustrates an exemplary
control circuit 90 equipped to simultaneously drive eight different
LEDs on a selective basis. In this manner, control circuit 90 may
selectively activate all red LEDs to illuminate biological growth
plate 22 with red light. Similarly, control circuit 90 may
selectively activate all green or blue LEDs for green and blue
illumination, respectively. FIG. 13 depicts control circuit 90 as
controlling eight LEDs simultaneously, and hence controlling either
front illumination component 44 or back illumination component 46.
However, the output circuitry controlled by processor 34 may
essentially be duplicated to permit control of sixteen LEDs
simultaneously, and therefore both front illumination component 44
and back illumination component 46.
[0090] As shown in FIG. 13, processor 34 generates digital output
values to drive a set of LEDs. Digital-to-analog converters (DAC)
91A-91H convert the digital output values to an analog drive
signals. Buffer amplifiers 92A-92H amplify the analog signals
produced by DACs 91A-91H and apply the amplified analog drive
signals to respective arrays of LEDs 94A-94H, 96A-96H, 98A-98H.
DACs 91A-91H and amplifiers 92A-92H serve as controllers to
selectively control illumination durations and illumination
intensities of LEDs 94A-94H, 96A-96H, 98A-98H. Processor 34 drives
the controllers, i.e., DACs 91A-91H and amplifiers 92A-92H,
according to requirements of different biological growth plates 22
to be processed by scanner 10.
[0091] Advantageously, processor 34 may access particular sets of
digital output values to produce a desired output intensity for
LEDs 94A-94H, 96A-96H, 98A-98H. For example, the digital output
values can be determined upon factory or field calibration of
scanner 10 in order to enhance the uniformity of the illumination
provided by the various LEDs 94A-94H, 96A-96H, 98A-98H. Again, the
red, green and blue LEDs may be characterized by different output
intensities and responses, and associated reflector and optics
hardware may present nonuniformities, making independent control by
processor 34 desirable in some applications.
[0092] Also, the digital output values may be determined based on
the requirements of different biological growth plates 22, i.e., to
control the intensity and duration of illumination applied to the
growth plates. Accordingly, processor 34 may selectively generate
different output values for different durations, enable different
sets of LEDs 9494H, 96A-96H, 98A-98H, and selectively enable either
front illumination, back illumination or both, based on the
particular types of biological growth plates 22 presented to
scanner 10.
[0093] The anodes of all LEDs 94A-94H, 96A-96H, 98A-98H are coupled
to the respective outputs of drive amplifiers 92A-92H for
simultaneous activation of selected LEDs. To permit selective
activation of LEDs for particular illumination colors, the cathodes
of LEDs 94A-94H (Red) are coupled in common to a switch, e.g., to
the collector of a bipolar junction transistor 100A with an emitter
coupled to a ground potential. Similarly, the cathodes of LEDs
96A-96H (Green) are coupled in common to the collector of a bipolar
junction transistor 100B, and the cathodes of LEDs 98A-98H (Blue)
are coupled in common to the collector of a bipolar junction
transistor 100C.
[0094] Processor 34 drives the base of each bipolar transistor
100A-100C with a RED ENABLE, GREEN ENABLE or BLUE ENABLE signal. In
operation, to expose biological growth plate to red illumination,
processor 34 selects digital values for the red LEDs 94A-94H, and
applies the digital values to DACs 91A-911H, which produce analog
drive signals for amplification by buffer amplifiers 92A-92H. In
synchronization with application of the digital values for the red
LEDs 94A-94H, processor 34 also activates the RED ENABLE line to
bias transistor 100A "on," and thereby pull the anodes of red LEDs
94A-94H to ground.
[0095] Using the ENABLE lines, processor 34 can selectively
activate red LEDs 94A-94H to expose biological growth plate 22 to
red illumination. Simultaneously, processor 34 controls camera 42
to capture a red image of biological growth plate 22. To capture
green and blue images, processor 34 generates appropriate digital
drive values and activates the GREEN ENABLE and BLUE ENABLE lines,
respectively. As an advantage, the ENABLE lines can be used to
independently control the exposure durations of the illumination
colors. For example, it may be desirable to expose biological
growth plate 22 to different durations of red, green and blue
illumination.
[0096] FIG. 14 is a functional block diagram illustrating the
capture of multi-color images for preparation of a composite image
to produce a plate count. As shown in FIG. 14, monochromatic camera
42 captures a red image 102A, green image 102B and blue image 102C
from biological growth plate 22. Processor 34 then processes the
red, green and blue images 102 to produce a composite image 104. In
addition, processor 34 processes the composite image to produce an
analytical result such as a colony count 106. Once the composite
image has been prepared, combining the red, green and blue images,
processor 34 may apply conventional image analysis techniques to
produce the colony count.
[0097] FIG. 15 is a flow diagram illustrating a technique for the
capture of multi-color images for preparation of a composite image
to produce a plate count. As shown in FIG. 15, the technique may
involve selective illuminating of a biological growth plate 22 with
different illuminant colors (108), and capturing plate images
during exposure to each of the illumination colors (110). The
technique further involves forming a composite image (112) based on
the separately captured images for each illumination color, and
processing the composite image (114) to produce an analytical
result such as a colony count (116). The colony count may be
displayed to the user and logged to a date file. As mentioned
above, techniques for capture of some images may involve
illumination with one, two or more illumination colors, as well as
front side illumination, back side illumination or both, depending
on the requirements of the particular biological growth plate 22 to
be processed by scanner 10.
[0098] FIG. 16 is a flow diagram illustrating the technique of FIG.
15 in greater detail. As shown in FIG. 16, in operation, processor
34 first outputs digital values to drive the red illumination LEDs
94A-94H (FIG. 13) (118), and activates the front and back red
illumination LEDs with the RED ENABLE line (120) to illuminate
biological growth plate 22. Camera 42 then captures an image of
biological growth plate 22 during illumination by the red LEDs
94A-94H (122).
[0099] Next, processor 34 outputs digital values to drive the green
illumination LEDs 96A-96H (124), and activates the front and back
green illumination LEDs with the GREEN ENABLE line (126) to
illuminate biological growth plate 22. Camera 42 then captures an
image of biological growth plate 22 during illumination by the
green LEDs 96A-96H (128). Processor 34 then outputs digital value
to drive the blue illumination LEDS 98A-98H (130), and activates
the blue illumination LEDs with the BLUE ENABLE line (132).
[0100] After the blue image is captured by camera 42 (134),
processor 34 combines the red, green and blue images to form a
composite red-green-blue image (136). Processor 34 then processes
the composite red-green-blue image (138) and/or individual
components of the composite image to generate a colony count (140).
Again, in some embodiments, processor 34 may process the individual
red-green-blue images prior to combining the red, green and blue
images to form a composite image. Again, the red-green-blue order
of illumination and capture is described herein for purposes of
example. Accordingly, biological growth plate 22 may be illuminated
and scanned in a different order.
[0101] 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.
[0102] Various modification may be made without departing from the
spirit and scope of the invention. For example, it is conceivable
that some of the features and principles described herein may be
applied to line scanners as well as area scanners. These and other
embodiments are within the scope of the following claims.
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