The reflection signal in the inverse synthetic aperture radar is measured in the polar coordinate defined by the object rotation angle and the frequency. The reconstruction of fixed scene images requires the coordinate transformation of the polar format data into the rectangular spatial frequency domain, which is then processed by the inverse Fourier transform. In this paper a fast and flexible method of coordinate transformation based on the nearest neighbor interpolation utilizing the Delauney triangulation is at first presented. Then, the induced errors in the transformed rectangular spatial frequency data and the resultant fixed scene images are investigated by simulation under the uniform plane wave transmit-receive mode over the swept frequency 120-160 GHz, and the results which demonstrate the validity of the current coordinate transformation are presented.

A new system for high speed and continuous 3-D measurement is presented. It is based on slit-ray projection method. Remarkable features of our system--high speed and continuous measurement--mainly come from its image plane constructed by PSD array which is horizontally non-divided and linear, whereas vertically divided in numbers. Each row PSD element is attached to respective analog signal processor, A/D converter and memory element. By the virtue of this configuration of the image plane, we can store the positional information of slit-like image on the image plane into memory elements in real time, without waiting for one frame interval as is required in the conventional methods with scanning type image grabbers. As the result, we can scan the slit-ray at a constant high angular velocity and calculate the deflection angle of the slit-ray from scanning time of it, which is set on the address bus of memory elements in our system. Thus, basic datum for 3-D measurement are acquired during only one scanning of slit-ray at high speed in the form of addresses of memory elements and datum stored in them. Moreover, if we use large capacity and/or dual port memories, we may continuously obtain 3-D datum of as many scenes as we want. Trial system has verified our method showing data acquisition time per scene within a few milliseconds and enabling us to obtain 3-D datum continuously at a rate of hundreds scenes per second.