Aberrations of temporally modulated optical wavefronts in dispersive optical systems

摘要

Classical time-invariant lens aberrations, and methods for correcting them, are well known in the art. However, the design, analysis, and construction of optical components and systems for temporally modulated optical wavefronts-and in particular, wavefronts in optical time-of-flight or phase measurement instruments, such as laser trackers, heterodyne laser interferometers, and spherical retroreflectors, require additional considerations to correct for what will be called Optical Amplitude Modulation (OAM) aberrations. Ray tracing analysis is time-invariant and thus insensitive to temporal modulation of the rays. Secondary considerations must be given to the wavefront of the modulated envelope which is focused on a detector, i.e., while the rays converge to a focus, the phase of the modulated envelope will in general depend on the path of the rays. Elements from communications theory, including amplitude modulation (AM) and analysis in the Fourier transform frequency domain are unified with classical optics, where the optical wavelength of a laser is treated as a carrier signal and the AM produces two slightly offset sidebands. The sidebands produce the OAM aberration due to dispersion and different paths through the optical elements. Suggestions are made for methods for correcting OAM aberrations, such as lens designs that are achromatic at the two sidebands, the use of specific materials matched to the carrier wavelength, the use of corrector plates, and computer modeling tools. A review of relevant patent literature is included.