19 February 2007 Contrast enhancement in biomedical optical imaging using ultrabright color LEDs
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The recent emergence of bright, inexpensive colored LEDs offers several advantages over traditional light sources, including reduced size and increased portability, low power consumption and heat production, increased durability and longer life, and high temporal resolution. We assembled a modular array of different Phillips LUMILED LUXEON LEDs, white and seven colors with peak wavelengths between 450 and 640 nm and bandwidths of 20-30 nm. LED illumination was fiber-optically coupled to the transmitted light path of an inverted microscope, and digital images of sectioned human tissue stained with absorbing dyes were acquired using combinations of the white and color LEDs. The LED array was also coupled to an endoscope and used to image human and mouse tissue in situ. Image contrast was assessed (1) qualitatively by looking down the microscope and by viewing the digital images, and (2) quantitatively by using entropy analysis in the real and frequency domains to assess the dependence of contrast enhancement on spatial frequency. Contrast in image features of a given color range was enhanced by LEDs conjugate to that color, whereas LED colors spanning a wider range enhanced contrast in the entire image, with white LEDs often maximizing contrast of tissue. This analysis demonstrates the utility of LED illumination in modulating contrast in light microscopy and endoscopy, which may facilitate spectral segmentation and classification of image features.
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Kevin Burton, Raphael Zelikowsky, Danny Shandling, Erik Lindsley, Daniel L. Farkas, "Contrast enhancement in biomedical optical imaging using ultrabright color LEDs", Proc. SPIE 6441, Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues V, 64411I (19 February 2007); doi: 10.1117/12.712401; https://doi.org/10.1117/12.712401

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