Coherent anti-Stokes Raman scattering (CARS) microscopy is used to determine the distribution and concentration of selected compounds in intact human hair. By generating images based on ratiometric CARS contrast, quantitative concentration maps of both water and externally applied d-glycine are produced in the cortex of human hair fibers. Both water and d-glycine are found to homogeneously distribute throughout the cortical regions of the hair. The ability to selectively detect molecular agents in hair fibers is of direct relevance to understanding the chemical and physical mechanisms that underlie the performance of hair-care products.
Hyperspectral reflectance imaging in the visible and NIR spectral ranges has considerable utility for revealing spatial
and chemical complexity in both biological systems and manufactured products. Conventional imaging systems are
based on broad-band illumination in tandem with a spectrometer or tunable filter placed between the sample and the
detector. These systems are typically slow (require seconds of integration per wavelength step), and the CW broad-band
source can cause significant heating of the sample. An alternative method is to use a tunable, pulsed, high-peak-power
(low average power) source coupled with a broad-band detector. This approach offers a reduction in data acquisition
time, the inherent ability to stop motion, and data collection at ambient temperature. An integrated system based on a 5-
ns pulsed laser tunable from 430 nm to 2150 nm has been used to obtain hyperspectral images in both the visible and
NIR spectral ranges. A number of camera/lens options allow for varied spectral bandwidths and the FOV, ranging from
11 × 15 mm<sup>2</sup> to 15 × 20 cm<sup>2</sup>. An entire hyperspectral image stack can be collected in as little as 20 s. This method,
allowing fast, room-temperature data acquisition, has sufficient sensitivity to produce data that can be successfully
processed using spectral derivatives and multivariate analysis. We discuss several applications, both in vivo and
otherwise, of this alternative approach to visible/NIR hyperspectral imaging.