Effect of wavefront error on 10^−7 contrast measurements

High-Contrast Imaging using Adaptive Optics for Extrasolar Planet Detection

“…In imaging mode, the testbed consists of a laser source (532 nm) passed through an optical fiber and a high-quality lens. The beam passes through a pupil stop, reflects off a flat mirror, and Figure 4.1: Simplified schematic of the ExAO testbed [26]. The testbed has two modes of operation: Imaging and phase shifting diffraction interferometry.…”

“…I identified laboratory contrast limitations through experiments with a flat mirror and shaped pupils on the testbed [26]. Using wavefront data from the phase shifting diffraction interferometer, I simulated performance and compared to experimental results.…”

“…The testbed was designed with high-quality optics to ensure that end-to-end wavefront error (WFE) would be small (< 1.5 nm RMS). Initial high-contrast measurements focused on measurement techniques and instrumentation without active correction, in particular, suppressing diffraction, understanding the high-contrast regime and developing experimental methods for high-contrast imaging (i.e., controlling scattered light) [26]. After initial tests, a 1024-actuator MEMS deformable mirror, developed by Boston Micromachines Corporation (BMC) [50], was installed for active wavefront control.…”

“…After initial tests, a 1024-actuator MEMS deformable mirror, developed by Boston Micromachines Corporation (BMC) [50], was installed for active wavefront control. [26]. The testbed has two modes of operation: imaging and phase shifting diffraction interferometry (PSDI).…”

“…Our ExAO testbed is uniquely suited to testing MEMS deformable mirrors in the high-contrast regime. We have already demonstrated an ability to operate at contrast levels of 10 −7 to 10 −8 [26]. The extremely accurate optical metrology of the phase shifting diffraction interferometer (PSDI) [51] allows absolute measurements of the MEMS DM.…”