Abstract:
A method for optical detection of residual soil on articles (such as medical instruments and equipment), after completion of a washing or a rinsing operation by a washer. A soil detection system provides an indication of soil on the articles by detecting luminescent radiation emanating from the soil in the presence of ambient light.

Description:
RELATED APPLICATION 
       [0001]    The present application is a continuation of U.S. application Ser. No. 13/777,053, filed Feb. 26, 2013, said patent application fully incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to the cleaning and decontaminating arts, and more particularly to a method and apparatus for optical detection of biological contaminants on articles, such as medical devices, food, agricultural products, forensic equipment and devices, and the like, after undergoing a decontamination process. 
       BACKGROUND OF THE INVENTION 
       [0003]    Medical washers are conventionally known and are used to clean articles (e.g., medical devices, such as medical instruments and equipment) that have been exposed to bio-contaminants. Such washers typically clean the articles to remove bio-contaminants by directing jets or streams of fluid at the articles from spray heads or nozzles located within the washer. A typical cleaning operation may include a preliminary rinse cycle, a pre-wash cycle, a wash cycle, a post-wash rinse cycle, a thermal rinse cycle and a drying cycle. During the rinse and wash cycles the articles are exposed to one or more chemical cleaning and rinsing solutions. 
         [0004]    It is not unusual for a cleaning operation to be followed by a visual inspection conducted by a human to insure that there are no residual bio-contaminants (hereinafter referred to as “soil”) on the articles. The soil may include organic residues including, but not limited to, blood, fat, mucous, lipids, carbohydrates, bone, hair, protein, and food product. Some articles have unique shapes, corners or crevices that make removal of the bio-contaminants therefrom difficult. Human visual inspection helps ensure that post-wash articles with soil thereon are not allowed to proceed to further processing (e.g., sterilization) without first removing any remaining bio-contaminants. 
         [0005]    As will be appreciated, a human visual inspection is both time-consuming and costly. Moreover, it is difficult to detect minute amounts of soil by human visual inspection, and such visual inspection is subject to human error (for example, person-to-person variations and individual biases). Furthermore, it is observed that human visual inspection is a binary qualitative process, not quantitative. 
         [0006]    Some prior art methods for optical detection of soil use a fluorescent dye or agent to detect the presence of soil on an article. In such systems, the fluorescent agent is applied to the article, for example, by exposing the article to a solution that includes the fluorescent agent. The fluorescent agent binds to organic residues (e.g., proteins), and thus affixes to the soil to label the bio-contaminant. Where there is no soil on the article, the fluorescent agent does not become affixed thereto, and thus can be washed off. To provide optical detection of the soil according to prior art methods, the article is exposed to “black light” (i.e., electromagnetic radiation in the ultraviolet range having wavelengths around 315-400 nm), which is absorbed by the fluorescent agent. Absorbance of this ultraviolet (UV) light causes the fluorescent agent (e.g., a fluorophore such as fluorescein) to emit visible light (i.e., to be fluorescent), thereby identifying the presence of soil to a human inspector. A typical human eye is responsive to light in the wavelength range of 390-750 nm. 
         [0007]    This prior art method does not allow personnel to carry out their task of reprocessing of articles in desirable ambient light conditions, and thus makes it difficult for personnel to disassemble, reassemble, and inspect articles for cleanliness. Recommended illuminance levels for such work environments can range from 200 lux to 2000 lux, and more typically range from 1400 lux to 2000 lux. 
         [0008]    The present invention provides a method and apparatus for optical detection of soil that operates in preferred ambient lighting conditions. 
       SUMMARY OF THE INVENTION 
       [0009]    According to a first aspect of the present invention, there is provided a soil detection system for detecting presence of soil on an article, the soil detection system comprising: (a) a scanning unit including: a light source for producing light to be incident on the article; a detector for detecting electromagnetic radiation emanating from said article and generating light data corresponding thereto, said electromagnetic radiation including ambient light reflected by the article and light emitted by an excited luminescent agent that is bound to the soil, and a light filter for filtering light of predetermined frequencies; and (b) a control unit for receiving the light data generated by the detector to determine the presence of soil on the article. 
         [0010]    According to another aspect of the present invention, there is provided a method for detecting presence of soil on an article, said method comprising: introducing a luminescent agent to a detergent during a wash cycle of a washing apparatus, wherein the luminescent agent is bound to soil present on the article; rinsing the article to remove unbound luminescent agent; exposing the article to laser light; detecting light emanating from said article and generating light data corresponding thereto, said light emanating from said article including ambient light reflected by the article and light emitted by exciting the luminescent agent bound to the soil; filtering the light emanating from said article at predetermined frequencies; and determining the presence of soil on the article based upon the filtered light received by a light detector. 
         [0011]    An advantage of the present invention is the provision of a method and apparatus that uses optical excitation and luminescence (such as fluorescence) to detect the presence of soil on articles that have undergone a washing or rinsing process. 
         [0012]    Still another advantage of the present invention is the provision of a method and apparatus that allows optical detection of soil on articles in the presence of ambient light. 
         [0013]    These and other advantages will become apparent from the following description of the present invention, taken together with the accompanying drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention may take physical form in certain parts and arrangement of parts, preferred embodiments of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof, and wherein: 
           [0015]      FIG. 1  is a schematic view of a soil detection system according to a first embodiment of the present invention; 
           [0016]      FIG. 2  is a schematic view of a soil detection system according to a second embodiment of the present invention; 
           [0017]      FIG. 3  is a detailed illustration of a soil detection system according to the first embodiment of the present invention; 
           [0018]      FIGS. 4A and 4B  illustrate internal components of a scanning unit for the soil detection system; 
           [0019]      FIG. 5  illustrates a soil detection system according to an alternative embodiment of the present invention; 
           [0020]      FIGS. 6A  is a graph illustrating the intensity of light emitted by an incandescent light bulb for a range of wavelengths; 
           [0021]      FIG. 6B  is a graph illustrating the intensity of light emitted by a fluorescent light tube for a range of wavelengths; and 
           [0022]      FIG. 6C  is a graph illustrating the intensity of light emitted by a computer monitor for a range of wavelengths. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    It should be appreciated that the term “medical devices” as used herein, includes, but is not limited to, such articles as surgical, dental, veterinary and mortuary instruments and equipment. The articles may be made of various materials, including, but not limited to, stainless steel. 
         [0024]    Referring now to  FIGS. 1 and 3 , there is shown a soil detection system  30  according to an embodiment of the present invention, generally comprised of a scanning unit  80  and a control unit  40 . Scanning unit  80  includes a detector  90 , a light source in the form of a laser  100  that produces a laser light  102 , a light filter  112 , and a dichroic beamsplitter  116  that are located within a housing  81 . In the illustrated embodiment, scanning unit  80  is handheld by the user. It should be understood that the light source can alternatively be located external to scanning unit  80  and an optical fiber used to transmit light from the external light source to scanning unit  80 . 
         [0025]    In the illustrated embodiment, detector  90  takes the form of a conventional digital video/still camera that includes a CMOS (complementary metal-oxide semiconductor) or CCD (charge-coupled device) image sensor  92  and a lens  94 . A CCD image sensor  92  represents pixels by p-doped MOSFET capacitors. These capacitors are biased above the threshold for inversion when image acquisition begins, allowing the conversion of incoming photons into electron charges at the semiconductor-oxide interface. Image sensor  92  is then used to read out these charges. Detector  90  is adapted to detect electromagnetic radiation emanating from said articles and generate corresponding information (i.e., light data) that is delivered to control unit  40 . It should be understood that detector  90  may take the form of any suitable device able to detect electromagnetic radiation and produce an image, including, but not limited to, a CMOS sensor, a CCD, a photodiode, and a photodiode array. In the illustrated embodiment, image sensor  92  takes the form of a color image sensor, such as CCD or CMOS with RGB (Red-Green-Blue) pixel matrix, or a three-dimensional image sensor where color RGB planes are stacked on the same chip, such as 3-CCD or 3-CMOS. These image sensors provide access to each color channel individually for image processing. 
         [0026]    In the illustrated embodiment, laser  100  is preferably a laser diode that predominantly emits light (“laser light”) at a wavelength of 488 nm (blue). As will be explained in further detail below, the laser light excites a fluorescent agent (e.g., a fluorophore such as fluorescein). Two- and three-dimensional images may be obtained since fluorescence takes place in all directions (i.e., the fluorescence signal is usually isotropic). Furthermore, the signal-to-noise ratio of the fluorescence signal is very high, providing a good sensitivity. In the illustrated embodiment, the fluorescent agent is fluorescein, which has a maximum excitation at light having a wavelength of about 490 nm. Once excited, the fluorescein emits light at a wavelength of about 513 nm. Since the emitted, fluorescent light is of a different frequency than the excitation light, the excitation light can be filtered out. The intensity of light emitted from a region having the fluorescent agent is correlated to the intensity of excitation energy and to the concentration of the fluorescent agent. 
         [0027]    It should be understood that the light source of the present invention for producing light emitted by scanning unit  80  may take a number of different forms, including, but not limited to, any kind of device being able to emit a monochromatic or broadband electromagnetic field. Examples of such devices include lasers, solid-state lasers, laser diodes, argon ion lasers, micro wire lasers, diode solid-state lasers, vertical cavity surface emitting lasers, light emitting diodes (LED), organic light emitting diode (OLED), polymer light emitting diode (PLED), quantum dot based light sources, white light sources, halogen lamps, phosphor-coated LEDs, thin-film electroluminescent devices, phosphorescence OLEDs, inorganic/organic LEDs, LEDs using quantum dot technologies, LED arrays, flood light systems using LEDs, white LEDs, filament lamps, arc lamps, gas lamps and fluorescent tubes. 
         [0028]    Dichroic beamsplitter  116  is used to both reflect and filter light, depending upon the direction the light is traveling toward dichroic beamsplitter  116 . In one direction, dichroic beamsplitter  116  reflects blue light emitted by laser  100  to direct laser light  102  through an opening  81   a  in housing  81 . In a second direction, dichroic beamsplitter  116  cuts blue light and allows green and red light to pass therethrough for reception by detector  90 . Accordingly, dichroic beamsplitter  116  prevents any excitation light (in this case, blue light emitted by laser  100 ) from being received by detector  90 . It should be appreciated that a combination of a reflective member (e.g., a dichroic mirror) and one or more light filters may be substituted for dichroic beamsplitter  116 . In the embodiment illustrated in  FIG. 1 , filter  112  is preferably a dual band filter that permits only red and green light to pass therethrough and be received by detector  90 . 
         [0029]    As shown in  FIG. 3 , housing  81  includes a handle grip  84 . A trigger  86  is provided to activate scanning unit  80 , as will be explained below. A cable  82  electrically connects scanning unit  80  with control unit  40 . 
         [0030]    In the illustrated embodiment of the present invention, control unit  40  includes a display unit  42  (e.g., an LCD or LED display unit), a user input interface  44  (e.g., buttons, knobs, keypad, and the like) for control and programming of control unit  40 , and an audio output  48  (e.g., a speaker) for emitting audible sounds. A power cord  50  connects control unit  40  to a power source (e.g., a conventional AC electrical outlet). The power source may also supply power to scanning unit  80  through control unit  40 . Control unit  40  includes a processing unit and data storage to perform image processing on the light data collected by detector  90  and provides an audible and/or visual soil detection feedback using audio output  48  and display unit  42 . A detailed description of the operation of control unit  40  and scanning unit  80  is provided below. 
         [0031]    The present invention will now be further described with reference to detection of soil on articles that have been exposed to a solution containing a fluorescent agent (e.g., fluorescein, which is biocompatible). For example, a medical washer (washing apparatus) may be provided to remove bio-contaminants from articles placed in a washing chamber by directing jets or streams of fluid at the articles from spray heads or nozzles located within the washer chamber. The washer may be configured to expose the articles to a solution containing the fluorescent agent during the washer&#39;s standard wash cycle and/or rinse cycle. The fluorescent agent (non-specifically) binds to organic residues (e.g., proteins), and thus affixes to soil on the articles to label the bio-contaminant. Where there is no soil on the article, the fluorescent agent does not become affixed thereto (i.e., is unbound), and therefore can be easily rinsed off of the article. In a preferred embodiment, no extra wash time is required for labeling the bio-contaminant and no extra rinse time is required to remove all of the unbound fluorescent agent. Accordingly, no changes are required of existing medical washers with respect to standard wash and rinse cycles (i.e., no additional “marking” cycle, or pre-wash cycle, etc. is required). In one embodiment of the present invention, fluorescein is used as the fluorescent agent at a concentration in the range of about 0.001 mM to 90 mM (for example, around 0.3 mM) with an exposure time in the range of 30 seconds to 5 minutes to label the bio-contaminant. 
         [0032]    It is contemplated that the washer may include a source of a fluorescent agent that is introduced into a water inlet line to the washing chamber during a desired stage of the washing and/or rinsing cycles. A valve controls the flow of the fluorescent agent into the water inlet line. Preferably, the solution containing the fluorescent agent is introduced into the washing chamber during a later stage of the washing cycle. Therefore, during a subsequent rinsing cycle, the fluorescent agent can be removed from unsoiled portions of the articles. The solution containing the fluorescent agent may be combined with a washing solution that includes a decontaminating agent or cleaning detergent. The decontaminating agent or cleaning detergent may initially be in a liquid or dry powder form. The fluorescent agent may be directly added to the decontamination or cleaning detergent before the detergent is added to the washing chamber. 
         [0033]    It should be appreciated that while an illustrated embodiment of the present invention is described herein with reference to “fluorescein” as the fluorescent agent, it is contemplated that alternative fluorescent agents may be substituted for fluorescein. A selected fluorescent agent preferably has the following properties: approval by government regulatory authorities (e.g., FDA); bio-compatible in such a way that remaining traces of the fluorescent agent on an article can be safely introduced into the human body without incurring health problems; binds rapidly to proteins (e.g., within a few seconds); has the ability to withstand exposure to harsh washing environment conditions (i.e., harsh chemicals and temperatures exceeding 80° C.); water soluble; and high quantum yield. Alternative fluorophores include, but are not limited to, rose bengal, acid red, phtalocyanine, and luminol. 
         [0034]    While the present invention has been described in connection with the use of a fluorescent agent, it is also contemplated that the present invention may be adapted for use with alternative chemical agents that provide luminescence, including but not limited to, chemical agents which provide phosphorescence, chemiluminescence, or bioluminescence. 
         [0035]    Referring now to  FIGS. 1 and 3 , one or more articles  10  (e.g., a tool or instrument) which have been exposed to a solution containing fluorescein are placed in a tray  5 . The articles are preferably arranged in a single layer to provide exposure to the light emitted by the light source, as will be described below. 
         [0036]    An operator of soil detection system  30  grabs handle grip  84  to manually move scanning unit  80  over the surfaces of an article  10  while activating laser  100  using trigger switch  86 . Activation of trigger switch  86  causes laser  100  to produce a laser light  102  at a wavelength of 488 nm (blue light). The laser light  102  is reflected by dichroic beamsplitter  116  and travels through opening  81   a  of housing  81  and is directed toward article  10 . 
         [0037]    Article  10  is exposed to both ambient light and laser light  102  as scanning unit  80  is moved over the surfaces of article  10 .  FIGS. 6A-6C  show the intensity of ambient light produced at various wavelengths for ambient lighting sources, such as an incandescent bulb, a fluorescent tube light, and a computer monitor screen, respectively. As discussed above, when the fluorescein that binds to soil is exposed to the laser light  102  at a wavelength of about 490 nm, the fluorescein emits light (i.e., fluoresces) at a wavelength of about 513 nm. 
         [0038]    Reflected ambient light (L R ) and fluorescent light (L F ) emitted by the excited fluorescein pass through dichroic beamsplitter  116  and filter  112  before traveling through lens  94  of detector  90 . Filter  112  allows only red and green light to pass therethrough to detector  90 . The light transmitted through lens  94  is received by image sensor  92 . 
         [0039]    As scanning unit  80  is moved across article  10 , the user squeezes trigger  86 , thereby activating laser  100  to produce laser light  102  that is emitted from housing  81  through opening  81   a.  Laser light  102  is incident on article  10  as scanning unit is moved across article  10 . Ambient light is also incident upon article  10 , thereby producing ambient light reflections that will include both red and green light. When the fluorescent agent (i.e., fluorescein) present in the soil is excited by laser light  102  the soil fluoresces thereby emitting light at a wavelength of about 513 nm (green light). Both the reflected ambient light (L R ) and the fluorescent light (L F ) of the soil pass through filter  112  which filters out all but red and green light. Therefore, image sensor  92  only receives red and green light. 
         [0040]    Referring now to  FIG. 1 , there is shown a sample input spectrum  120 . As scanning unit  80  is moved across article  10 , image sensor  92  acquires and transmits to control unit  40  detected light data indicative of input spectrum  120  that includes a green light waveform  122  and a red light waveform  124 . Green light waveform  122  is indicative of the intensity of green light detected by image sensor  92  and red light waveform  124  is indicative of the intensity of red light detected by image sensor  92 . 
         [0041]    Control unit  40  is programmed to spectrally discriminate between soil fluorescence (indicating the presence of soil) and specular ambient light reflections, based upon the measure of saturation of green light intensities relative to red light intensities (ratio). In the illustrated embodiment, the range of this measure of saturation is enclosed between zero and one. Accordingly, the system is robust to the variations of ambient light of the surrounding environment and changes of acquisition parameters. A value of saturation close to zero is indicative of the presence of specular ambient light reflections, whereas a large value close to one is indicative of the presence of soil. 
         [0042]    Control unit  40  may be programmed to display the detected light data to a user on display unit  42 . Control unit  40  may also be programmed to provide the user with a visual and/or audible indicator (e.g., warning/alarm/feedback) via display unit  42  and audio output  48  in the event that the ratio of green light intensity-to-red light intensity indicates the presence of soil. It is further contemplated that control unit  40  may present an image of article  10  and use display unit  42  to display the location of the detected soil (i.e., contaminated region) on article  10 . The image of article  10  may be acquired during optical scanning of article  10  or from a prestored image library comprised of images of a plurality of commonly used articles  10 . 
         [0043]    Referring now to  FIG. 2 , there is shown a soil detection system  30 A according to an alternative embodiment of the present invention. Soil detection system  30 A is similar to soil detection system  30  in several regards, and thus like components have been given the same reference numbers. Soil detection system  30 A includes scanning unit  80 A having laser  100 , detector  90 , a power modulator  34 , dichroic beamsplitter  116 , and a light filter  112 A that allows only green light to pass therethrough. Power modulator  34  produces a pulsed waveform that provides an ON/OFF signal to activate/deactivate laser  100 . When the pulse is an ON signal, laser  100  is activated to produce laser light  102 . The pulsed waveform causes laser  100  to be continuously pulsed ON and OFF at a laser modulation frequency. As scanning unit  80 A is moved across article  10 , the user squeezes trigger  86 , thereby activating power modulator  34  to produce the pulsed waveform that provides the ON/OFF signal to laser  100 . When the pulse is an ON signal, laser light  102  is emitted from housing  81  through opening  81   a.  It should be appreciated that power modulator  34  may alternatively take the form of a square wave modulation circuit to modulate the output of laser  100  (amplitude modulation). 
         [0044]    Laser light  102  is incident on article  10  as scanning unit is moved across article  10 . Ambient light is also incident upon article  10 , thereby producing ambient light reflections that will include green light. When the fluorescent agent (e.g., fluorescein) present in the soil is excited by laser light  102  the soil fluoresces thereby emitting light at a wavelength of about 513 nm (green light). Both the reflected ambient light (L R ) and the fluorescent light (L F ) of the soil passes through filter  112  which filters out all but green light. Therefore, image sensor  92  only receives green light. In this embodiment, image sensor may take the form of a color or gray-scale type sensor. 
         [0045]    The modulation frequency for laser  100  is set to be lower than the emission frequencies of ambient lighting sources. Detector  90  operates in a continuous (video) mode at a frame rate that is higher that the modulation frequency. Green blinking features on display unit  42  of control unit  40  at the modulation frequency are indicative of soil. Non-blinking features or blinking at frequencies other than the modulation frequency are identified as ambient light reflections. In one embodiment of the present invention the modulation frequency is around 10 Hz. The frequency of ambient lighting sources are ƒ=20-60 kHz (electronic ballast fluorescent tube), ƒ=120 Hz (incandescent light bulb and magnetic ballast fluorescent tube), and ƒ=240 Hz (computer monitor). 
         [0046]    As scanning unit  80 A is moved across article  10 , power modulator  34  produces the pulsed waveform that causes detector  90  and laser  100  to be continuously pulsed ON and OFF. As indicated above, filter  112 A only allows green light to pass therethrough to detector  90 . Image sensor  92  acquires and transmits to control unit  40  detected light data indicative of the intensity of green light detected by image sensor  92 . 
         [0047]      FIG. 5  illustrates a soil detection system  30 B according to an alternative embodiment of the present invention. Soil detection system  30 B includes a control unit  40 A having an inspection chamber  60  for inspecting articles  10  placed on a tray  5 . A plurality of scanning units  80 B are located within chamber  60  for exposing the plurality of surfaces of an article  10  to laser light  102 . Scanning units  80 B are similar in most respects to scanning units  80  and  80 A except that they are automatically activated by control unit  40 A. The embodiment shown in  FIG. 5  eliminates the need for the user to manually activate a handheld scanning unit  80 ,  80 A and manually expose all of the surfaces of an article  10  to laser light  102 . 
         [0048]    It is contemplated that tray  5  may also be connected with an apparatus (now shown) for rotating, shaking, or otherwise moving tray  5  within chamber  60 . It is further contemplated that scanning units  80 B may be mounted to moveable arms (not shown) to provide a range of motion for each scanning unit  80 B. Control unit  40  is programmed to control movement of tray  5  and scanning units  80 B. 
         [0049]    The foregoing description discloses specific embodiments of the present invention. It should be appreciated that these embodiment are described for purposes of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. For example, it is contemplated that the scanning unit of the present invention could communicate with the control unit via wireless communications. It is also contemplated that the method and apparatus of the present invention may also be used in combination with automated and human visual inspections using “white light” imaging. In addition, it is further contemplated that the present invention may be adapted to include a fiber optic accessory for point inspection of canulated instruments. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.