ABSTRACT
In this work, we present an analytic model for analyzing the range and frequency dependency of a monostatic coherent lidar measuring velocities of a diffuse target. The model of the signal power spectrum includes both the contribution from the optical system as well as the contribution from the time dependencies of the optical field. A specific coherent Doppler wind lidar system measuring wind velocity in the atmosphere is considered, in which a Gaussian field is transmitted through a simple telescope consisting of a lens and an aperture. The effects of the aperture size, the beam waist position, and pulse duration are analyzed.
ABSTRACT
Objective speckles produced by two beams overlapping and interfering on a rough object surface contain information about the angle of incidence of the two beams, and how well they overlap. We obtain the autocovariance function for such a speckle pattern, and demonstrate how the information carried by the objective speckles can be used to probe the distance between the object and the observation plane. From a distance of 75 mm to a distance of 150 mm, and using an angle of 0.3 deg between the two incident beams, we can measure the actual distance with an uncertainty of better than ±0.1% of the full range. As long as the beams overlap at the object surface, the proposed method can measure distance with an uncertainty inversely proportional to the spot size at the object.