A method and system for optical vortex transmissometry. The method uses optical orbital angular momentum (OAM) and optical vortices to discriminate coherent non-scattered light from incoherent scattered light. The system includes a laser which transmits a Gaussian laser beam through a medium. An OAM generating device is placed before a photodetector receiver. Coherent, non-scattered light passing through the OAM generating device forms an optical vortex, used to discriminate against the unwanted scattered signal that doesn't form a vortex. Alternatively, the system includes a transmitter which generates one or more OAM modes which are transmitted through a turbid medium. At the receiver, an OAM detection device analyzes the OAM mode spectrum of the received light. Coherent non-scattered light retains the OAM encoded at the transmitter, while scattered light does not. The attenuation of the channel is determined by comparison of the received OAM mode spectrum relative to the transmitted OAM mode spectrum.

A visibility meter, a street light device and an operation method thereof are provided. The visibility measurement method includes: transmitting a visible laser through an optical transmitter; receiving the visible laser through an optical sensor to generate a sensed result; and calculating a visibility according to the sensed result.

Methods and systems in accordance with the present invention provide a continuum measure of visibility from a single image without prior knowledge of the camera system or the cameras in the system. This may be, for example, a score on the weather visibility quality of the image, ranging from good to poor, or a numeric score representing the weather visibility quality of the terrain in the image. This may be done without prior knowledge of the camera system, the camera that took the image, or the environment. It is also done with the single image without using multiple images, or reference images. The system derives a real-time continuum measure of visibility from a single daytime image, with unknown camera quality, system configuration, and environmental conditions.

Methods and systems in accordance with the present invention provide a continuum measure of visibility from a single image without prior knowledge of the camera system or the cameras in the system. This may be, for example, a score on the weather visibility quality of the image, ranging from good to poor, or a numeric score representing the weather visibility quality of the terrain in the image. This may be done without prior knowledge of the camera system, the camera that took the image, or the environment. It is also done with the single image without using multiple images, or reference images. The system derives a real-time continuum measure of visibility from a single daytime image, with unknown camera quality, system configuration, and environmental conditions.

An example forward scatter sensor comprises: a transmitter to emit a light sheet; a receiver to observe light scattered from particles that fall through a measurement volume; and a control entity comprising an analyzer to record a measurement signal descriptive of intensity of light captured by the receiver as a function of time and to: carry out a precipitation analysis on basis of a time segment of the measurement signal; carry out a verification of analysis performance based on magnitudes of first peaks of at least one identified double peak and on respective residence times for said at least one identified double peak; and invoke a predefined maintenance action responsive to said verification indicating a threshold-exceeding difference between respective size estimates derived based on magnitudes of the first peak of said at least one identified double peak and based on residence times of said at least one identified double peak.

A method and system for optical vortex transmissometry. The method uses optical orbital angular momentum (OAM) and optical vortices to discriminate coherent non-scattered light from incoherent scattered light. The system includes a laser which transmits a Gaussian laser beam through a medium. An OAM generating device is placed before a photodetector receiver. Coherent, non-scattered light passing through the OAM generating device forms an optical vortex, used to discriminate against the unwanted scattered signal that doesn't form a vortex. Alternatively, the system includes a transmitter which generates one or more OAM modes which are transmitted through a turbid medium. At the receiver, an OAM detection device analyzes the OAM mode spectrum of the received light. Coherent non-scattered light retains the OAM encoded at the transmitter, while scattered light does not. The attenuation of the channel is determined by comparison of the received OAM mode spectrum relative to the transmitted OAM mode spectrum.

A method is provided for detecting a property of a gas comprising: emitting a light, comprising a plurality of wavelengths covering a plurality of absorption lines of the gas, along a first axis, the light being scattered by particles of the gas resulting in a scattered light, generating a sensor image using a detection arrangement configured to receive the scattered light and comprising: an optical arrangement having an optical plane and being configured to direct the scattered light on to a light sensor, the light sensor having at least one pixel columns, wherein the pixel columns are aligned to an image plane and configured to output a sensor image, wherein the first axis, the optical plane, and the image plane intersect such that a Scheimpflug condition is achieved, determining, from the sensor image, properties of the gas at a plurality of positions along the first axis.

The present disclosure provides a Scheimpflug LIDAR apparatus for detecting a property of a gas comprising: a light source configured to emit a light along at least a first axis, a light detection arrangement, and an optical configuration fulfilling the Scheimpflug condition and Hinge rule. The light source comprises an expander aperture, and wherein the expander aperture and light detection arrangement are configured such that: a spot size of the emitted light along the first axis is matched to a pixel footprint of pixels configured to receive light from corresponding distances along the first axis, and an effective range resolution of at least one column of pixels or probe volume deteriorates linearly with respect to the range.

A passive thermal imaging system is described. The system includes at least one detector array configured to detect thermal electromagnetic radiation (EMR), imaging optics, and processing electronics. The imaging optics are configured to receive thermal EMR from an object, and to image the received thermal EMR onto pixels of each of the at least one detector array. The processing electronics are configured to receive a detected signal from each of the pixels of the at least one detector array, to calculate a correlation value based on a correlation between the received detected signals from the pixels, and to compare the correlation value with a threshold correlation value to determine whether a detection event has occurred.

An example forward scatter sensor comprises: a transmitter arranged to emit a single light sheet; a receiver to observe light scattered from particles that fall through a measurement volume; and a control entity comprising an analyzer arranged to record a measurement signal descriptive of intensity of light captured by the receiver as a function of time and to carry out a precipitation analysis on basis of a time segment of the measurement signal, the precipitation analysis comprising: identifying, in said time segment, one or more double peaks that each represent a respective droplet and comprise a first peak that represents light refracted from a bottom of the respective droplet upon entry to the measurement volume and a second peak that represents light reflected from a top of the respective droplet upon exit from the measurement volume; and deriving one or more precipitation parameters and one or more precipitation indications.