Pressure variations within a solid propellant rocket motor produce like variations in the optical radiance of the motor exhaust plume. The periodicity of the variation is related to the length L of the rocket motor or speed of sound in the rocket motor combustion chamber to length ratio a/L. The optical radiance is collected and converted to electrical signals that are sampled at or above the Nyquist rate. An array of single-pixel photo detectors is well suited to provide amplitude data at high sample rates. The sampled data from the one or more detectors is assembled to form a high fidelity time sequence. A window of sampled data is processed to form a signal frequency spectrum. The mode structure in the frequency spectrum is related to the rocket motor length or speed of sound in the rocket motor chamber to length ratio. The rocket motor length or speed of sound to length ratio is used alone or in combination with other information to either classify or identify the rocket motor.

A device images radiation from a scene. The scene can include two materials with spectral characteristics in different radiation wavelength regions. A static filtering arrangement includes two filters with different passbands corresponding to the two wavelength regions. An image forming optic forms an image of the scene on a detector. The radiation from the scene is imaged simultaneously through an f-number of less than 1.5 onto two detector pixel subsets. The imaged radiation on one pixel subset includes radiation in one wavelength region. The imaged radiation on the other pixel subset includes radiation in the other wavelength region. Electronic circuitry produces a pixel signal from each detector pixel. The pixel signals include information associated with absorption or emission of radiation in one of the respective wavelength regions by the two materials. The electronic circuitry determines the presence or absence of each of the two materials based on the pixel signals.

A metrology system includes an optical frequency separation apparatus in the path of the pulsed light beam and configured to interact with the pulsed light beam and output a plurality of spatial components that correspond to the spectral components of the pulsed light beam; a plurality of sensing regions that receive and sense the output spatial components; and a control system connected to an output of each sensing region. The control system is configured to: measure, for each sensing region output, a property of the output spatial components from the optical frequency separation apparatus for one or more pulses; analyze the measured properties including averaging the measured properties to calculate an estimate of the spectral feature of the pulsed light beam; and determine whether the estimated spectral feature of the pulsed light beam is within an acceptable range of values of spectral features.

A photoelectric conversion element is realized in which the movement direction of electrons in the element changes according to the wavelength of light to be converted. A photoelectric conversion unit includes an active layer on which light to be converted is incident, an intermediate layer that is arranged on the active layer on a side opposite to the side on which the light to be converted is incident, and a reflection layer that is arranged so as to oppose the active layer with the intermediate layer interposed therebetween. The active layer includes a plasmonic material, which is a material in which plasmon resonance occurs due to a reciprocal action with the light to be converted. The intermediate layer has both a semiconductor property and transparency with respect to the light to be converted. The reflection layer has reflectivity with respect to the light to be converted.

An optoelectronic module includes a light guide arranged to receive light, such as ambient light or light reflected by an object. The light guide has a diffractive grating that includes multiple sections, each of which is tuned to a respective wavelength or narrow band of wavelengths. The module further includes multiple photosensitive elements, each of which is arranged to receive light diffracted by a respective one of the sections of the diffractive grating. The module can be integrated, for example, as part of a spectrometer or other apparatus for optically determining characteristics of an object.

The present disclosure describes optical radiation sensors and detection techniques that facilitate assigning a specific wavelength to a measured photocurrent. The techniques can be used to determine the spectral emission characteristics of a radiation source. In one aspect, a method of determining spectral emission characteristics of incident radiation includes sensing at least some of the incident radiation using a light detector having first and second photosensitive regions whose optical responsivity characteristics differ from one another. The method further includes identifying a wavelength of the incident radiation based on a ratio of a photocurrent from the first region and a photocurrent from the second region.

An optical module of a micro spectrometer with tapered slit and slit structure thereof. The optical module includes an input section and a micro diffraction grating. The input section includes a slit structure, which receives a first optical signal and outputs a second optical signal travelling along a first optical path. The slit structure includes a substrate and a slit, which penetrates through the substrate and has a gradually reduced dimension from a first surface of the substrate to a second surface of the substrate. The micro diffraction grating, disposed on the first optical path, receives the second optical signal and separates the second optical signal into a plurality of spectrum components travelling along a second optical path. The optical module of the micro spectrometer with the tapered slit and slit structure thereof according to the embodiment of the invention can be manufactured in a mass-production manner using the semiconductor manufacturing processes, so that the cost can be decreased, and the slit can have a smooth surface, which avoids the negative effect on the incident light.

An imaging sensor comprises: an array of light-detecting elements, wherein each light-detecting element in the array of light-detecting elements is arranged in the imaging sensor so as to detect a respective wavelength interval, wherein the respective wavelength interval differs for different light-detecting elements; a pattern arranged on the array of light-detecting elements, wherein the pattern defines a plurality of transparent areas, each transparent area being associated with a corresponding light-detecting element in the array of light-detecting elements, wherein a size of a transparent area among the plurality of transparent areas is dependent of the corresponding light-detecting element with which the transparent area is associated.

A spectrophotometer includes a photodetection unit configured to convert received light into an electric signal to output the electric signal; a circuit unit including a plurality of gain amplifiers and a plurality of AD converters configured to amplify an output signal from the photodetection unit by a plurality of gains using the plurality of gain amplifiers and configured to convert the amplified output signals into digital signals using the plurality of AD converters to output the digital signals as a plurality of pieces of light amount data; a saturation determination unit configured to determine whether or not each of the plurality of pieces of light amount data from the circuit unit has been saturated; and a measurement result calculation unit configured to calculate, in accordance with a result of the determination by the saturation determination unit, a measurement result of the received light using a part or all of the plurality of pieces of light amount data.

An apparatus and corresponding method for line-scan imaging includes a 2D array of light-sensitive detector elements divided into a plurality of sub-arrays. An electrical circuit can be configured to determine a correction for parallax based on detector element values from at least two rows of parallax detecting elements to enable images captured by the sub-arrays to be co-aligned with each other. The 2D array and parallax detecting elements can be located on the same substrate chip. Image data from sub-arrays can be co-aligned with each other based on parallax data from the parallax detecting elements and used to produce hyperspectral images corrected for parallax.