UV-visible-NIR Spectrophotometry

How a Spectrophotometer Works

 A spectrophotometer is an optical instrument for measuring the intensity of light relative versus wavelength.  A simple way of describing this would be that the spectrophotometer measures the intensity of each color of light (if we are just covering the visible region)

The system works when electromagnetic energy, called light in visible region, is collected from the sample and enters the monochromator through an aperture (the input light is shown by the yellow line).  There it is separated into its component wavelengths by an optical grating and the separated light is then focused onto a CCD array detector.  The CCD is made up of thousands of pixels (or individual light detectors) where the intensity of each wavelength is then measured. The CCD is then read-off to a computer and the result is a spectrum which displays the intensity of each wavelength of light.

UV-visible-NIR spectrophotometer diagram

In the visible region, we perceive such electromagnetic energy as different colors of light.  The system works when when white light enters the monochromator and is separated into a rainbow featuring each color.  This rainbow, with blue light on one end and red on the other, would be focused on to the CCD.  Each pixel of the CCD then measures the intensity of a color.  The results are a spectrum such as the one shown below.  As shown, the blue pixels emit blue light, the green pixels emit in the green portion of the spectrum and the red pixels emit red light.

Spectra of red, green and blue pixels of an OLED display using a spectrophotometer

In a microspectrophotometer, such as those made by CRAIC Technologies, the 508 PV™ Microscope Spectrophotometer adds uv vis spectroscopy of microscopic sample areas, color imaging, thin film thickness measurement and colorimetry capabilities to your optical microscope. It helps with diverse applications such as colorimetry of pixels on flat panel displays, reflectometry of vitrinite coal and thin film thickness measurements.