Optical analyzer for identification of materials using transmission spectroscopy
A device and method for identifying solid and liquid materials use near-infrared transmission spectroscopy combined with multivariate calibration methods for analysis of the spectral data. Near-infrared transmission spectroscopy is employed within either the 700-1100 nm or the 900-1700 nm wavelength range to identify solid or liquid materials and determine whether they match specific known materials. Uses include identifying solid (including powdered) and liquid materials with a fast measurement cycle time of about 2 to 15 seconds and with a method that requires no sample preparation, as well as quantitative analysis to determine the concentration of one or more chemical components in a solid or liquid sample that consists of a mixture of components. A primary application of such analysis includes detection of counterfeit drug tablets, capsules and liquid medications.
1. An optical analyzer system for identifying materials through transmission spectra analysis, the system consists of a light source and a set of non-light source components, wherein:
the light source consists of a circular monolithic array of light-emitting diode (LED) chips continuously powered with a DC power supply and covering either the 700-1100 or 900-1700 nm wavelength range; and
the set of non-light source components comprises:
a sample holder system holding a sample of a drug tablet, or a drug capsule, or a capsule filled with powder, or a cuvette filled with liquid, or a piece of: plastic, carpet, plaster board, wood, cloth, mineral, or paper;
a sample aperture located between the LED chips and the sample holder system;
a solid waveguide with a polygonal cross section or an elliptically distorted polygonal cross section, the waveguide positioned between the LED chips and the sample aperture;
an optical encapsulant layer between the LED chips in the monolithic array and the waveguide, wherein the optical encapsulant layer contains an optical epoxy or an optical grade silicone sealant;
an optical spectrometer module operating in either of the 700-1100 nm spectral range or the 900-1700 nm spectral range, the optical spectrometer module positioned to receive light from the light source passing through the sample aperture and through an entire thickness of the sample within the sample holder system, the optical spectrometer system having:
an input slit;
a diffraction grating for wavelength dispersing;
a linear detector array with associated readout electronics to collect and integrate the signal from each detector element in the linear detector array, wherein the linear detector array has at least 128 detector elements, and wherein the detector elements respond within the wavelength range of 700-1100 nm or 900-1700 nm; and
a spectral resolution of 10 nm or better; and
a computer or microprocessor system interfaced with the optical spectrometer, wherein the computer or microprocessor system controls the collection of spectral data, storage of the collected spectral data, and performs processing of the spectral data using a qualitative multivariate calibration analysis algorithm.