Ocean Optics - Inventor of the World's First Miniature Spectrometer
Ocean Optics - Inventor of the World's First Miniature Spectrometer
 

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Ocean Optics - Inventor of the World's First Miniature Spectrometer
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Ocean Thin Films has developed a low-loss color imaging technology that is free from the limitations of cost and performance that make spectral imaging too expensive or unwieldy for most customers. Our new technology changes all that, by taking a single CCD array and turning it into a versatile multispectral imager for a wide variety of new applications.

About Multispectral Imaging

Multispectral imaging is remote sensing that obtains optical representations in two or more ranges of frequencies or wavelengths. The most common multi-spectral imagers, though they typically are not thought of as such, are color-sensitive cameras. Imaging companies utilize dyes for transforming a monochrome array into a color-sensitive camera. Color filters are used on image sensors to allow them to see color as humans do. These color filters are placed on or directly above photodiodes to selectively filter the unwanted wavelengths and selectively pass the desired wavelengths. Most commonly the dyes are coated on the wafer in what is called a Bayer pattern.  Each pixel is covered by one of four filters. The pattern of four colors -- two green, one red and one blue -- is repeated across the array. Green is coated twice to match the photopic response curve of the eye, which is much more sensitive to green.

Other methods of multispectral imaging include using multiple arrays and stitching them together; using the push-broom method of scanning the scene multiple times each at different wavelengths; and using methods involving acousto-optic tunable filters and tunable liquid crystals. Each method adds value but also has drawbacks. For example, the multiple array method allows for quick, single-shot acquisition, but the added arrays create a costly approach and alignment is critical. The push-broom method creates very high spectral and spatial content, but doesn’t allow for a dynamic scene. 

The Ocean Thin Films Approach

Ocean Thin Films has created the missing piece of the multispectral puzzle. Thanks to our patented coating processes, we are in a unique position to create patterned dichroic filters using microlithographic techniques. The process works much like the dye process works, but instead of screen printing organic materials, we apply the coating via an evaporative source using oxide (also called dielectric) materials. The finished product could have the same Bayer pattern or any other pattern chosen. In addition, the response of each filter can be tailored to the user’s specifications. 

For example, a user may purchase a hyperspectral imager to investigate an imaging application, or perhaps send samples for testing to someone with a multispectral imager. In most cases the user will identify between 3 and 10 frequency ranges of interest for the application. We can then take a monochrome imager and apply patterned coatings that match the ranges needed by the user. This method will allow the user to get to production quickly and in a cost-effective manner.  This is the only single-shot, compact, cost-effective multispectral camera technology on the market that conserves both spatial and spectral content.   

In addition to the filter technology, Ocean Thin Films also has the ability to increase the overall image resolution with set of trade-secret recursive algorithms. When an image array is broken up into imaging diodes that see only one band of color the resolution is reduced. For instance, if an 8 megapixel camera has 8 color filters applied, the overall image resolution is reduced to 1 megapixel for each color. We can then take those images and increase the resolution substantially by using a series of proprietary algorithms in combination with the patterned filters.  This process allows the 1 megapixel image to be increased to 4 megapixels. 

Possible Applications

  • Agriculture: surface mapping of vegetation, crop monitoring, soil analysis
  • Safety: detection of food pathogens
  • Entertainment: 3D animation and imaging
  • Homeland security: hazardous material identification
  • Environment: Smokestack monitoring

Where to Learn More

For more information about multispectral imaging and our dichroic filter processes, please contact us at 727.545.0741 or OTFinfo@oceanoptics.com. And please join us on Jan. 28, 2009 at 10:30 a.m. at SPIE’s Photonics West 2009 for the presentation "Ultracompact fully integrated megapixel multispectral imager," part of the show’s "Integrated Optics: Devices, Materials, and Technologies XIII" conference.

 

 

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