A light modulator (e.g., for terahertz radiation) may be constructed using a prism in which light undergoes total internal reflection (TIR) at one surface. A tunable conductive layer is disposed on the TIR surface. The tunable conductive layer can have a conductivity that is dynamically controllable, e.g., by applying a voltage across the tunable conductive layer or by optically pumping the tunable conductive layer. The tunable conductive layer can absorb a portion of the reflected light beam, attenuating the beam, with the attenuation being a function of the electrical conductivity of the tunable conductive layer. The phase of the reflected light beam can also be altered as a function of electrical conductivity of the tunable conductive layer.

A flame detection system includes: an optical sensor that detects light generated from a light source; an applied voltage generating circuit that periodically applies a drive pulse voltage to the optical sensor, discharge determining portion that detects a discharge from the optical sensor, a discharge probability calculating portion that calculates a discharge probability based on a number of times of application of the drive pulse voltage and a number of times of discharge detected in the a first state in which the optical sensor is shielded from light and a second state in which the optical sensor can receive light, a sensitivity parameter storing portion storing known sensitivity parameters of the optical sensor; and a received light quantity calculating portion that calculates the received light quantity by the optical sensor in the second state based on the sensitivity parameters and the discharge probabilities calculated in the first and second states.

A method of estimating non-linearity in a response of an optical detector comprises emitting optical radiation at different intensities. The method includes, at each intensity: amplitude modulating the emitted optical radiation at a modulating frequency to produce amplitude modulated optical radiation; detecting the amplitude modulated optical radiation with the optical detector to produce a detected waveform; and generating a Fourier transform of the detected waveform that includes a fundamental frequency equal to the modulating frequency and harmonics thereof. The method further includes estimating the non-linearity in the response of the optical detector based on a change in an amplitude of a second harmonic of the fundamental frequency relative to an amplitude of the fundamental frequency across the Fourier transforms corresponding to the different intensities.

A system simultaneously tracks multiple objects. All or a subset of the objects includes a wireless receiver and a transmitter for providing an output. The system includes one or more wireless transmitters that send commands to the wireless receivers of the multiple objects instructing different subsets of the multiple objects to output (via their respective transmitter) at different times. The system also includes object sensors that receive output from the transmitters of the multiple objects and a computer system in communication with the object sensors. The computer system calculates locations of the multiple objects based on the sensed output from the multiple objects.

A system simultaneously tracks multiple objects. All or a subset of the objects includes a wireless receiver and a transmitter for providing an output. The system includes one or more wireless transmitters that send commands to the wireless receivers of the multiple objects instructing different subsets of the multiple objects to output (via their respective transmitter) at different times. The system also includes object sensors that receive output from the transmitters of the multiple objects and a computer system in communication with the object sensors. The computer system calculates locations of the multiple objects based on the sensed output from the multiple objects.

In one embodiment, an infrared (IR) imaging system for determining a concentration of a target species in an object is disclosed. The imaging system can include an optical system including an optical focal plane array (FPA) unit. The optical system can have components defining at least two optical channels thereof, said at least two optical channels being spatially and spectrally different from one another. Each of the at least two optical channels can be positioned to transfer IR radiation incident on the optical system towards the optical FPA. The system can include a processing unit containing a processor that can be configured to acquire multispectral optical data representing said target species from the IR radiation received at the optical FPA. Said optical system and said processing unit can be contained together in a data acquisition and processing module configured to be worn or carried by a person.

In one embodiment, an infrared (IR) imaging system for determining a concentration of a target species in an object is disclosed. The imaging system can include an optical system including an optical focal plane array (FPA) unit. The optical system can have components defining at least two optical channels thereof, said at least two optical channels being spatially and spectrally different from one another. Each of the at least two optical channels can be positioned to transfer IR radiation incident on the optical system towards the optical FPA. The system can include a processing unit containing a processor that can be configured to acquire multispectral optical data representing said target species from the IR radiation received at the optical FPA. Said optical system and said processing unit can be contained together in a data acquisition and processing module configured to be worn or carried by a person.

An optical assembly may include a thermal sensor and a temperature source between the optical assembly and a viewing area of the thermal sensor. The temperature source may provide a first reference temperature and a second reference temperature. A controller may cause the thermal sensor to sense thermal images of the temperature source at a first reference temperature and a second reference temperature and determine a contamination level of the optical assembly or a damage to the optical assembly based on the thermal images.

An infrared imaging device comprises an infrared imaging sensor to detect infrared light as heat, a temperature drift compensation amount calculator to calculate a temperature drift compensation amount in accordance with a temperature change of the substrate, with respect to a pixel output outputted from each of the plurality of pixels, a compensation amount calculation function generator to generate a function with the temperature of the substrate as an independent variable; and a timing controller to cause the infrared imaging sensor and the substrate temperature sensor to synchronously output data to the compensation amount calculation function generator for generating the function, wherein the compensation amount calculation function generator uses the data for generation output after the generation of the function as additional data for improving accuracy of the function.

An infrared imaging device comprises an infrared imaging sensor to detect infrared light as heat, a temperature drift compensation amount calculator to calculate a temperature drift compensation amount in accordance with a temperature change of the substrate, with respect to a pixel output outputted from each of the plurality of pixels, a compensation amount calculation function generator to generate a function with the temperature of the substrate as an independent variable; and a timing controller to cause the infrared imaging sensor and the substrate temperature sensor to synchronously output data to the compensation amount calculation function generator for generating the function, wherein the compensation amount calculation function generator uses the data for generation output after the generation of the function as additional data for improving accuracy of the function.