Apparatus for optical detection of bio-contaminants by comparing intensities of filtered light at two predetermined wavelengths

A soil detection system for detecting presence of soil on an article, the soil detection system comprising:

• a scanning unit for scanning the article treated with a fluorescent agent bound to soil present on the article, the fluorescent agent emitting fluorescent light at a fluorescence wavelength, said scanning unit including:
• a light source for producing incident light on the article, the incident light having an excitation wavelength for producing the fluorescent light at the fluorescence wavelength,
• a light filter for filtering the light emanating from said article at the fluorescence wavelength and a second predetermined wavelength,
• a light detector for detecting the filtered 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 fluorescent agent bound to the soil, and
• a control unit for receiving the light data generated by the detector to determine the presence of soil on the article by spectrally discriminating between the fluorescent light and the ambient light reflections based upon a measure of saturation of light intensities of combined fluorescent light and ambient light at the fluorescence wavelength relative to light intensities of ambient light at the second predetermined wavelength.