Phase sensing and scanning time of flight LADAR using atmospheric absorption bands

摘要

A phase-sensing and scanning time-of-flight LADAR method and device are disclosed that take advantage of an atmospheric absorption bands within the solar IR spectrum. In the phase-sensing LADAR embodiment, an object is illuminated with electromagnetic energy such as a laser beam having a wavelength substantially equal to a predetermined atmospheric absorption band such as 1.39 microns. The transmitted laser beam is modulated at a predetermined frequency and has a first phase. The phase of the reflected and returned laser beam is altered proportional to the distance of the object and has a second phase. The first phase of the transmitted signal and the second phase of the received signal are compared and used to determine the distance of the object from the device. The system may comprise a modified laser that is tuned to operate in an atmospheric absorption band. A method to identify range ambiguity is disclosed by periodically altering the modulation frequency from a first modulation frequency to a second modulation frequency. In the scanning LADAR embodiment, an object is scanned or illuminated with electromagnetic energy having a wavelength substantially equal to a predetermined atmospheric absorption band at a first time and detects the reflection of the beam at a second time. The difference in time from the transmission of the scanning beam and the detection of the reflection of the beam from the object is used to calculate the range of the object.