Plasmonic color filter array based visible light spectroscopy

Compared with traditional Fabry–Perot optical filters, plasmonic color filters could greatly remedy the complexity and reduce the cost of manufacturing. In this paper we present end-to-end demonstration of visible light spectroscopy based on highly selective plasmonic color filter array based on resonant grating structure. The spectra of 6 assorted samples were measured using an array of 20 narrowband color filters and detected signals were used to reconstruct original spectra by using new unmixing algorithm and by solving least squares problem with smoothing regularization. The original spectra were reconstructed with less than 0.137 root mean squared error. This works shows promise towards fully integrating plasmonic color filter array in imagers used in hyperspectral cameras.

Dynamic Serosal Perfusion Assessment during Colorectal Resection Using Visible Light Spectroscopy

<b><i>Introduction:</i></b> Anastomotic leakage (AL) in colorectal surgery occurs with an incidence of up to 20%. Bowel perfusion is deemed to be one of the most important factors for anastomotic healing. However, not much is known about its variability during colorectal surgery and its impact on the outcome. Therefore, this study aims to evaluate serosal oxygen saturation patterns during colorectal resections with visible light spectroscopy (VLS). <b><i>Materials and Methods:</i></b> Bowel perfusion in patients undergoing left-sided colorectal resections was assessed at different timepoints during surgery using VLS on the colonic serosa. The primary outcome parameter was serosal oxygen saturation (StO₂) at the anastomosis during different timepoints of surgery. <b><i>Results:</i></b> We included 50 patients who underwent colorectal resection for bowel cancer (58%) and diverticular disease (34%). StO₂ at the proximal site of the anastomosis increased significantly throughout the surgery (mean difference 3.61%; 95% CI –6.22 to –1.00; <i>p</i> = 0.008). However, aberrancy from this identified perfusion pattern had no impact on the postoperative outcome. <b><i>Conclusion:</i></b> During colorectal resections, we could demonstrate an increase of the colonic StO₂ throughout surgery. Appearance of AL was not associated with lower StO₂, underlining the multifactorial genesis of developing AL.

Analysis of wood thermal degradation using 2D correlation of near infrared and visible-light spectroscopy

Wood changes its properties, especially color, as a result of thermal degradation. In this study, change in wood properties due to thermal degradation have been studied using the nondestructive test methods of near infrared spectroscopy, CIELAB color measurement, visible-light spectroscopy, and Arrhenius time–temperature superposition. Arrhenius time–temperature superposition allowed analysis of near infrared and visible-light spectra, and color parameters to predict thermal degradation and color change of wood at 120–180℃ for 6 min to nine months duration. Two-dimensional correlation spectroscopy for the complementary analysis of near infrared and visible-light spectroscopy was applied to investigate chemical changes during wood thermal degradation that cause the observed color change. Visible-light spectroscopy with CIELAB color measurement was used to obtain information on color changes, and near infrared spectroscopy was applied in the measurement of chemical changes during thermal degradation. Changes in spectral intensities in 2D correlation spectroscopy indicated that different chemical components are responsible for color change during heat treatment and accelerated aging of wood. With dry-thermal treatment, the hemicellulose content decreased following a color change, whereas cellulose and lignin/extractives decreased with hygro-thermal treatment.