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Multispectral Cameras Multispectral Cameras Expanding Beyond the Visible Modern vision and imaging applications rely on interpretation of information acquired by an image sensor. Typically the sensor is designed to emulate human vision, resulting in a color or monochrome image of the field of view as seen by the eye. This is accomplished by sensing light at wavelengths in the visible spectrum (400-700 nm). However, additional information can be gained by creating an image based on the light that is outside the sensitivity of the human eye. The information available can be maximized by combining information found in multiple spectral bands. The photonic spectrum includes energy at wavelengths ranging from the ultraviolet through the visible, near infrared, far infrared, and finally, x-rays. The color image from a Charge Coupled Device (CCD) array is acquired by sensing the wavelengths corresponding to red, green, and blue light. CCD sensors are capable of detecting light beyond the visible wavelengths out to 1100 nm. The wavelengths from 700 nm to 1100 nm are known as the near infrared (NIR) and are not visible to the eye. In standard color video cameras the infrared light is usually blocked from the CCD sensor because it interferes with the quality of the visible image. GSI’s multispectral cameras give you access to the full power of the CCD’s capabilities by providing one imaging array that performs color imaging and two more that sense the invisible light from 700-1100 nm. The wavelengths detected by each array can be further limited by adding narrowband optical filters in the imaging path. Combining the information from all three sensors provides image data in five spectral bands: red, green, blue and the two infrared bands. Multispectral Imaging GSI’s multispectral cameras can acquire images from up to five spectral bands. Light enters the camera through the lens and is separated by a dichroic prism. The visible wavelengths (400-700 nm) are directed to a color CCD array that images the red, green, and blue bands. Near infrared wavelengths (700-1100 nm) are split between two monochrome CCDs. Optional narrowband filters can be placed in front of the arrays to select specific wavebands. These trim filters can be customer specified and custom built at the factory allowing optimization for your specific application requirements. The color array can be replaced with a monochrome array providing a custom three-color, three-CCD camera. The prism can be fabricated with user specified dichroic coatings for OEM applications. Pixel data from each of the three arrays is digitized and processed by the Digital Signal Processing module. This module is programmable and can be customized to meet application requirements. A variety of operations such as comparisons between images or thresholding and overlays can be performed in real time. The image data from each of the three CCDs and any processed images can be selected for display. An encoder synthesizes analog NTSC, PAL, and S-Video formats. An optional digital interface allows direct access to the digital pixel data. Advanced optical design and CCD alignment features result in images from all three channels that are the same size and registered to within a fraction of a pixel. This image registration and square pixels provide high quality images ideal for advanced vision applications. 125 Tech Park Drive, Rochester, NY 14623 1-585-427-8310 (voice) 1-585-427-8422 (fax) www.geospatialsystems.com © 2006 Geospatial Systems, Inc. Multispectral Benefits The ability to “see” objects with a camera and detect color is a powerful tool. By processing the data from an image, additional information can be extracted. Multispectral imaging expands the camera’s capability to include the power to image features that can not be seen with the eye. By selectively combining both visible and infrared images, the available information from a field of view can be maximized. Food Processing In applications like produce sorting, the elimination of pigmentation effects Infrared allows easier identification of defects. By combining color and infrared imaging, a single camera can be used to Color sort for defects and grade for color appearance or ripeness. Color Infrared Defects such as bruising on fruit are more easily isolated in an infrared image. A single camera can sort for ripeness and defects. Precision Agriculture Plants have very high spectral reflectivity in the NIR. THis reflectivity is associated with chlorophyll and xanthophyll content. By studying changes in reflectivity, growers can identify plant stress resulting from problems such as water shortage, nutrient deficiencies, or toxins long before there is any visible indication. Color Infrared Although this ivy and its silk imposter look the same in the visible, the real plant is easily identified in the infrared by its high reflectivity. Most vegetation shows a large increase in reflectivity in the near infrared. Environmental Imaging and Reconnaissance Infrared film has long been used to analyze the health Color and composition of vegetation. However, working with film requires delays for processing and handling. By Infrared mapping the green, red, and a NIR band to the blue, green, and red channels of the output video signal real- time false color-IR video is created. The different characteristics of spectral imaging can provide a number of unique advantages in vision systems. The longer wavelengths of infrared penetrate False Color haze and fog better than visible wavelengths, resulting These images illustrate the use of in enhanced visibility under these conditions. color mapping. The plastic bag and Differences in spectral reflectivity can distinguish shirt are well camouflaged in the different objects that appear the same in the visible. visible image and very obvious in the infrared. The false color image further distinguishes the vegetation. 125 Tech Park Drive, Rochester, NY 14623 1-585-427-8310 (voice) 1-585-427-8422 (fax) www.geospatialsystems.com © 2006 Geospatial Systems, Inc..
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