A time-wavelength optical sampling system may be configured to determine a substance's composition based on variations in optical pulses caused by the substance's absorption of wavelengths of the pulse. A dispersion medium may disperse pulses to form stretched signal pulses that are incident on a substance under test. Optical gating is used to overlap each signal pulse with a portion of a reference pulse to generate a cross-correlation signal corresponding to a portion of the signal pulse, which may be detected by a slow detection speed detector. A controller controls delay introduced to the reference pulses so that different wavelength ranges are sampled for various signal pulses, thereby enabling the entire wavelength range for the signal pulses to be sampled over time without requiring an expensive high-speed optical detector. By analyzing absorption across the entire wavelength range as indicated by cross-correlation signals, the composition of the substance can be identified.

An optical phantom produces a time-resolved diffuse reflectance spectrum and includes: a light source; a spatial light modulator; and an optical delay line including optical fibers of different length that produce different time-of-flight distributions, such that different time-of-flight distributions are combined and produce phantom light having the time-resolved diffuse reflectance spectrum.

An optical phantom produces a time-resolved diffuse reflectance spectrum and includes: a light source; a spatial light modulator; and an optical delay line including optical fibers of different length that produce different time-of-flight distributions, such that different time-of-flight distributions are combined and produce phantom light having the time-resolved diffuse reflectance spectrum.

Evaluating a fluid, including transmitting a light beam through the fluid to a detector while oscillating a path length traveled through the fluid by the light beam at a first frequency of oscillation; measuring a time-dependent intensity of incident light at the detector responsive to an interaction of the light beam with the fluid to produce a time-dependent intensity signal; filtering the time-dependent intensity signal to recover a path-dependent signal oscillating at the first frequency and indicative of an absorbance property of the fluid; and estimating a parameter of interest of the fluid using the path-dependent signal. The time-dependent intensity may be indicative of the true absorbance at multiple wavelengths of the fluid or fluids over the maximum path length difference so as to permit quantification of the percentages of each of these fluids. Filtering may include frequency filtering alone or using a phase-sensitive lock-in amplifier.

An apparatus may include a platen, an electromagnetic interference (EMI)-reducing system including a first EMI-reducing layer, a light source system and a receiver system. The light source system may include a light-emitting component, light source system circuitry and a light guide system and may be configured to emit light through the first EMI-reducing layer to a first platen area via a light pipe between the first EMI-reducing layer and the platen. The light guide system may include a light-directing element for directing light from the first EMI-reducing layer to the light pipe. The receiver system may be configured to detect acoustic waves corresponding to a photoacoustic response of a target object in contact with the first platen area to light emitted by the light source system. The first EMI-reducing layer may reduce a level of EMI emitted by the light source system circuitry that is received by receiver system circuitry.

An apparatus may include a platen, an electromagnetic interference (EMI)-reducing system including a first EMI-reducing layer, a light source system and a receiver system. The light source system may include a light-emitting component, light source system circuitry and a light guide system and may be configured to emit light through the first EMI-reducing layer to a first platen area via a light pipe between the first EMI-reducing layer and the platen. The light guide system may include a light-directing element for directing light from the first EMI-reducing layer to the light pipe. The receiver system may be configured to detect acoustic waves corresponding to a photoacoustic response of a target object in contact with the first platen area to light emitted by the light source system. The first EMI-reducing layer may reduce a level of EMI emitted by the light source system circuitry that is received by receiver system circuitry.

Pulsed light in which an elapsed time in a pulse and a wavelength of light correspond to each other on a one-to-one basis is emitted from a pulsed light source and radiated to a product multiple times, and a plurality of beams of the pulsed light transmitted through the product is incident on a light receiver. An output of the light receiver is digitized by an AD converter, values at times regarded as having the same wavelength in beams of the pulsed light are integrated by an FPGA as an integration unit, and then the integrated value is input to a calculator, an absorption spectrum is calculated by a measurement program, and a quality determination program quantifies a specific component to determine quality of a product.