Non-causal attitude estimation for real-time motion compensation of sensed images on a moving platform

摘要

An attitude estimator provides non-causal attitude estimates for real-time motion compensation of sensed images on a moving platform. A non-causal filter processes uncompensated attitude samples received with a latency from an IMU at a high rate clock to provide an attitude estimate that is strictly non-causal but satisfies a just-in-time (JIT) criteria for real-time motion compensation of images captured at a low rate clock. On-average the error of the non-causal attitude estimate is less than the error of a causal attitude estimate. If the lag added by the non-causal filter is greater than the latency, the effective transfer function of the non-causal filter has a negative gain slope that attenuates high frequency noise of the uncompensated attitude samples. The attitude estimator may also include a causal filter to generate a causal attitude estimate for real-time active stabilization of the image sensor at the high rate clock.

主权项

1. An attitude estimator for providing attitude estimates for real-time motion compensation of images on a moving platform, wherein an IMU provides uncompensated attitude samples S(hT) of the moving platform at a high rate clock with a sampling period T and a dock index h, said samples S(hT) received with a latency L, an image sensor captures images O(kMT) at a low rate clock with a sampling period MT where M is greater than one and a clock index k, each image captured over an integration period having a center of integration (COI) at the center of the integration period synchronized to the low rare clock followed by a readout period, and a motion compensator that initiates real-time motion compensation on the captured image I(kMT) at the end of the readout period at a just-in-time constraint J measured in a number of high rate clock samples equal to one half the integration period plus the readout period after the COI, the attitude estimator comprising:
a non-causal sampling clock corresponding to the low rate clock kMT delayed by N high rate clock samples where N is less than or equal to J; and a non-causal filter that filters the uncompensated attitude samples S(hT) including at least one sample received after the COI to provide a non-causal attitude estimate A(kMT|(kM+N)T) for the previous COI that is delayed by N−L high rate samples and synchronized to the non-causal sampling clock, said motion compensator using the non-causal attitude estimate A(kMT|(kM+N)T) to initiate motion compensation on the captured image I(kMT).