Low-Cost Laboratory-Grade Refractometer for DEF Fluid Quality

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An optical refractometer has a uniquely designed and patented low-cost hybrid optical prism that channels light from a light source to an optical surface interfacing with the fluid to be detected. Depending on the refractive index of the fluid and other determining factors, a portion of the light is reflected by the surface while a portion is refracted into the fluid. A low-cost high resolution digital image optical sensor positioned on the prism has a large matrix of pixels, with each pixel being capable of distinguishing between 4,096 different brightness levels of visible light. The digital image sensor is also capable of operation at a high frame rate in full resolution.

With an exemplary optical sensor module having a resolution of 5 megapixels and 4,096 brightness levels per pixel, it has been found that image data of the fluid being measured can be captured to a very high degree of resolution with minimal processing and memory requirements using patented processing techniques. Accordingly, very high accuracy measurements have been obtained for determining the type and/or quality of the measured fluid. The information gathered from the image area of the optical array includes pixel brightness and pixel location within each predefined reference, measurement, and calibration areas. Various functions can be performed on the pixel data including summing pixels above and/or below the predetermined or dynamic threshold, performing a normalization routine between the measurement and reference sensor array areas, and so on. When summing the pixels, the number of pixels above the brightness threshold can be counted, the value of the pixels above the brightness threshold can be added, the number of pixels below the threshold can be added, the value of each pixel below the threshold can be added, and/or the values of the pixels for the entire reference or measurement area can be added without setting the threshold.

Other functions can include adding and/or averaging the data from multiple readings of the image area, which provides increased magnitude in resolution of the signal strength. The shift of data patterns relative to previously gathered or recorded image areas can also be used as an identifier of change in fluid characteristics. The under/over threshold and over/under limit characteristics can be utilized to include or exclude the data from each pixel within the totals or averages. Accordingly, one or more of the above-described functions can be used to determine one or more fluid properties or characteristics. A change of fluid characteristics, such as concentration, will cause a change of signal magnitude as well as a change of pixel signal concentration location within the measurement and reference sensor array areas. Identifying this shift in signal concentration can be utilized to identify additional characteristics of the fluid with high accuracy.

Although this product has been developed for determining the accuracy of DEF fluid, it can be used for determining the quality of virtually any fluid in any industry.


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  • Name:
    Alvin Wirthlin
  • Type of entry:
  • Patent status: