23 research outputs found

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    Development of the Correction Algorithm to Limit the Deformation of Bacterial Colonies Diffraction Patterns Caused by Misalignment and Its Impact on the Bacteria Identification in the Proposed Optical Biosensor

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    Recently proposed methods of bacteria identification in optical biosensors based on the phenomenon of light diffraction on macro-colonies offer over 98% classification accuracy. However, such high accuracy relies on the comparable and repeatable spatial intensity distribution of diffraction patterns. Therefore, it is essential to eliminate all non-species/strain-dependent factors affecting the diffraction patterns. In this study, the impact of the bacterial colony and illuminating beam misalignment on the variation of classification features extracted from diffraction patterns was examined. It was demonstrated that misalignment introduced by the scanning module significantly affected diffraction patterns and extracted classification features used for bacteria identification. Therefore, it is a crucial system-dependent factor limiting the identification accuracy. The acceptable misalignment level, when the accuracy and quality of the classification features are not affected, was determined as no greater than 50 µm. Obtained results led to development of image-processing algorithms for determination of the direction of misalignment and concurrent alignment of the bacterial colonies’ diffraction patterns. The proposed algorithms enable the rigorous monitoring and controlling of the measurement’s conditions in order to preserve the high accuracy of bacteria identification

    The schematic set-up of the PSDIHS configuration.

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    <p>Light generated by a coherent light source (LS) with a wavelength of 405 nm and output power of 25 mW is focused onto a 0.5-μm-diameter pinhole (PH), which acts as the point source emitting the divergent spherical wave. The wave illuminates an examined object, bacterial colonies grown on nutrient medium in a Petri dish on a sample holder with an X-Y translation stage, and forms magnified diffraction pattern in the recording plane (C) of the CMOS camera with the sensing area: 2048 × 2048 pixels (pixel size: 6 × 6 μm), mounted on a Z translation stage.</p
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