Optical Wavefront Error Research Articles

Experimental Validation of a Novel Concept to Reduce Optical Surface Wave Front Errors by Using Deformable Bushes at Opto-Mechanical Interfaces

One of the major objectives of the optomechanics is to support large optics required for the purpose and also to maintain high dynamic stability in operation. This requirement calls for more number of supports, to support large optics. While addressing this issue, the mounting system tends to become non-kinematic and distorts the optical surface and leads to poor image quality. The distorted optical surfaces bring in increased RMS surface wavefront errors which will result in poor image quality. In this context, a new concept is proposed in our previous publication ( Nagabhushana et al., 2021 ) which involves introduction of deformable bushes at the optomechanical interfaces. These are deformed by applied clamping forces and also enabling all degrees of freedom (DOF) to be arrested. This also ensures that the clamping force in axial DOF is limited to a minimal value. This technique enables to arrest of axial DOF without exerting the clamping force on the optomechanical assembly there by reduces optical aberrations and improves the mounting system’s dynamic stability. This is because deformable bushes absorb all the clamping forces and the strain has no impact on the mount and therefore does not lead deformation of the optical surface. The clamping forces are simulated by Finite Element (FE) methods. Further, in this paper, the concept is verified and validated by experiments. The simulation results are observed to be in close correlation with experiment results. Improved stability is also observed by additional constraints introduced to optomechanical mounts with no compromise in wavefront errors.

Optical alignment and wavefront error demonstration of a prototype LISA telescope

In this work, we document the first complete alignment of a subscale prototype telescope for the LISA mission. An optical wavefront error map, which meets current mission requirements, was attained using alignment techniques consistent with production of multiple identical copies of a telescope for flight. We find that the telescope wavefront error is dominated by the as-built surface figure error of the mirrors and not the residual design wavefront error of the telescope prescription. Furthermore, this work shows the ability to implement a wavefront error allocation specific to the LISA telescope, lending confidence to such allocations for future flight telescopes, and provides a verified reference point for ongoing research into many aspects of the LISA optical system.

Astronomy. Improving planet-finding spectrometers.

Adaptive optics will enhance the precision of exoplanet surveys

Single-pixel demonstration of innovative adaptive optics by use of a charge-transfer membrane light modulator

We have constructed and demonstrated a single-pixel implementation of an all-optical membrane-based spatial light modulator as a compact optical wave-front error correction device. High rates of response of as much as 20 kHz in an open-loop configuration were obtained. The device was then used in an adaptive-optics servo to compensate successfully for a 1-kHz sinusoidal phase error with a peak-to-peak excursion of approximately pi/7 rad. A small-signal servo gain of the order of 10 was inferred from the closed-loop measurements.

Acoustooptic signal processing and computing

Acoustooptic techniques have been used to perform computationally intensive signal processing operations and form subsystems of larger signal processing systems. Key aspects of acoustooptic devices and of the range of possible signal processing applications, including the advantages of acoustooptic implementation, are reviewed. Developments that improve acoustooptic device performance, increase system dynamic range such as by reduction of optical crosstalk from optical scatter and wavefront error, and implement data reduction operations that allow easier interfacing into a larger signal processing/computation system are described. >

Real-time atmospheric compensation

We have developed an active optical imaging system capable of correcting optical wave-front errors in real time at frequencies in the kilohertz range. Wave-front errors due to atmospheric turbulence in the propagation path, as well as optical figure aberrations and wave-front errors due to mechanical and thermal changes may be compensated. The system used an ac shearing interferometer, a parallel analog data processor, and a monolithic piezoelectric active mirror arranged in a closed-loop configuration. This compensation system can be applied to apertures of any size; experimental results are shown for a system with 21 correction zones.