Patent ID: 8174581
Filing Date: 2012-05-08
Classification: G01S

Abstract:
1. A moving object image tracking apparatus comprising: a first rotation unit configured to rotate about an azimuth axis vertically oriented and rotatably supported; a second rotation unit configured to rotate about an elevation axis rotatably supported and horizontally oriented, the elevation axis being perpendicular to the azimuth axis; a driving unit configured to drive the first rotation unit and the second rotation unit to rotate independent of each other; an acquisition unit supported by the second rotation unit and configured to acquire image data of a moving object by photography; a first detection unit configured to detect, from the image data, a tracking error detection value indicating a tracking error as a deviation of the moving object from a center of a field of view of the acquisition unit; a second detection unit configured to detect a first angle indicating a first attitude of the first rotation unit; a third detection unit configured to detect a second angle indicating a second attitude of the second rotation unit; a first computation unit configured to compute a first angular velocity of the first rotation unit and a second angular velocity of the second rotation unit, using the tracking error detection value and the first angle and the second angle; a determination unit configured to determine whether the moving object falls within a correction range, referring to the second angle, the correction range being defined by a correction range angle threshold value set with respect to a zenith; a second computation unit configured to compute a moving velocity of the moving object by executing temporal differentiation on the first angle and the second angle; a third computation unit configured to compute a period of time in which the moving object falls within the correction range, based on the correction range angle threshold value and the moving velocity; a fourth detection unit configured to detect, as an approach angle, the first angle assumed when the moving object enters the correction range; a setting unit configured to set the first angular velocity and the second angular velocity as angular velocity instruction values for the first rotation unit and the second rotation unit when it is determined that the moving object falls outside the correction range, and configured to set the second angular velocity and a third angular velocity as the angular velocity instruction values when it is determined that the moving object falls within the correction range, the third angular velocity being obtained by dividing the approach angle by the period of time, the third angular velocity being used to rotate the first rotation unit toward a zero axis along which the moving object approaches the acquisition unit; a fifth detection unit configured to detect a fourth angular velocity and a fifth angular velocity of the first rotation unit and the second rotation unit, respectively; and a control unit configured to control the driving unit to eliminate a difference between the fourth angular velocity and an angular velocity indicated by one of the angular velocity instruction values corresponding to the first rotation unit, and configured to control the driving unit to eliminate a difference between the fifth angular velocity and an angular velocity indicated by another one of the angular velocity instruction values corresponding to the second rotation unit.