A lidar with a laser transmitter for transmitting a laser beam and a receiver having receiving optics for detecting radiation reflected back from the beam by aerosol particles in the atmosphere, the receiver having an optical axis aligned with the beam. The receiver includes a number of radiation receiving elements such as concentric radiation detector elements placed in the receiving optics focal plane so that these concentric detector elements can measure backscatter radiation from the beam at several fields of view simultaneously. Backscattered signals at fields of view larger than the laser beams's divergence are due to multiple scattering. The unknown backscatter coefficient can then be eliminated by ratioing the lidar returns at the different fields of view.
For automated visual range measurement by a LIDAR system, a distance measuring range is first determined through repeated evaluation of a voltage level U(R) which indicates the intensity of a threshold value. After random initialization of a start value, the start value is then replaced each time with a new mean visual range, resulting in iterative improvements, and the mean visual range in the determined range is then displayed automatically as soon as the visual range lies within the measuring range of the LIDAR system. Using the Klett method, the accuracy can be determined with the aid of a breaking-off criterion in the form of a threshold value with respect to a deviation percentage between a new and a previous calculation. With this method the deviation can be identified to an order of magnitude of about 10%.
A holographic optical element transforms a spectral distribution of light to image points. The element comprises areas, each of which acts as a separate lens to image the light incident in its area to an image point. Each area contains the recorded hologram of a point source object. The image points can be made to lie in a line in the same focal plane so as to align with a linear array detector. A version of the element has been developed that has concentric equal areas to match the circular fringe pattern of a Fabry-Perot interferometer. The element has high transmission efficiency, and when coupled with high quantum efficiency solid state detectors, provides an efficient photon-collecting detection system. The element may be used as part of the detection system in a direct detection Doppler lidar system or multiple field of view lidar system.
A light-sensing module and arrays of two or more light-sensing modules are described. Each light-sensing module comprises a mounting support structure that may include an air vehicle guidance section and an optical element adapted to direct incident light to a detector array that comprises an array of photodiodes and is attached to the mounting support structure. The detector array is adapted to receive the directed light and convert the received light to a set of electrical pulses via a plurality of photodetectors each of which is operatively coupled to an amplifier and a threshold circuit adapted to output a detection to a memory store adapted to associate a detection with a time-of-arrival. The light-sensing module may be adapted to output the associated detection and time-of-arrival. Air vehicles including the light-sensing modules are also disclosed.
The present invention provides systems and methods for modeling the impact of a medium on the appearances of encompassed light sources using a Legendre polynomial series solution to a Radiative Transfer Equation for Spherical Media (RTE-SM) called an Atmospheric Point Spread Function (APSF). Using this APSF, it is possible to determine characteristics of the medium causing the multiple scattering of the light from the encompassed light source. For example, by observing a street light in bad weather at night, using the APSF, it is possible to determine whether the bad weather is haze, mist, fog, or rain. Similarly, the APSF may be used to estimate the size of particles in a liquid. It is also possible using the APSF to remove and/or add an effect of the medium on a light source captured in an image.
A multiplexed set of light sources having outputs of light with various wavelengths which are combined into one beam. The beam may impinge a particle in a flow channel of a cytometer. The light leaving the flow channel may be sensed by a detector and the light distinguished according to wavelength.
