论文标题

实施大型双眼望远镜干涉仪的相位传感器PHASECAM的多波长附带跟踪

Implementing multi-wavelength fringe tracking for the Large Binocular Telescope Interferometer's phase sensor, PHASECam

论文作者

Maier, Erin R., Hinz, Phil, Defrère, Denis, Grenz, Paul, Downey, Elwood, Ertel, Steve, Morzinski, Katie, Douglas, Ewan S.

论文摘要

PHASECAM是大型双目望远镜干涉仪(LBTI)的边缘跟踪器。它是一款近红外摄像机,用于测量两个自适应光学器件(AO)校正的孔径之间的尖端/倾斜相和条纹相变的变化。目前以$ h $(1.65 $ $ m)和$ k $(2.2 $ $ $ m)的频段以1 kHz进行提示/倾斜度和相位感应,但仅使用$ k $ - 频段 - 带相位遥测来向系统发送校正,以维持边缘的连贯性和可见性。但是,由于条纹相的循环特性,只能测量相位的360度。试图减轻此问题的PhaseCam的阶段解开算法在快速,较大的相位变化或低信噪比的情况下偶尔会失败。这可能会导致边缘跳跃,在这种情况下,OPD校正将通过波长不正确。目前可以由操作员手动纠正。但是,随着LBTI委员会的进一步模式,需要鲁棒,主动的相控制,并且为之难以检测,包括多轴(Fizeau)干涉仪和双孔径非冗余的磁带掩盖干涉仪,需要更可靠和自动化的解决方案。我们提出了一种多波长的边缘跳跃捕获和校正方法,涉及$ k $ band和$ h $ band相位遥测之间的直接比较。我们演示了利用档案Phasecam遥测的方法,这表明它提供了一种可靠,可靠的方法来检测边缘跳跃的方法,该方法可能有可能恢复丢失的数据的很大一部分。

PHASECam is the fringe tracker for the Large Binocular Telescope Interferometer (LBTI). It is a near-infrared camera which is used to measure both tip/tilt and fringe phase variations between the two adaptive optics (AO) corrected apertures of the Large Binocular Telescope (LBT). Tip/tilt and phase sensing are currently performed in the $H$ (1.65 $μ$m) and $K$ (2.2 $μ$m) bands at 1 kHz, but only the $K$-band phase telemetry is used to send corrections to the system in order to maintain fringe coherence and visibility. However, due to the cyclic nature of the fringe phase, only the phase, modulo 360 deg, can be measured. PHASECam's phase unwrapping algorithm, which attempts to mitigate this issue, occasionally fails in the case of fast, large phase variations or low signal-to-noise ratio. This can cause a fringe jump, in which case the OPD correction will be incorrect by a wavelength. This can currently be manually corrected by the operator. However, as the LBTI commissions further modes which require robust, active phase control and for which fringe jumps are harder to detect, including multi-axial (Fizeau) interferometry and dual-aperture non-redundant aperture masking interferometry, a more reliable and automated solution is desired. We present a multi-wavelength method of fringe jump capture and correction which involves direct comparison between the $K$-band and $H$-band phase telemetry. We demonstrate the method utilizing archival PHASECam telemetry, showing it provides a robust, reliable way of detecting fringe jumps which can potentially recover a significant fraction of the data lost to them.

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