SAIL image of a triangle cut from a piece of retroreflective material. The target is tilted away from the observer at 45 degrees to create the range depth, which is why the laser spot size appears elliptical. The SAIL image thus displays range in the vertical dimension and cross-range or azimuth in the horizontal dimension. Inset is a close-range photograph of the target triangle; the white lines on the target do not have the retroreflective material and appear as dark lines in the SAIL image. The fuzzy image above the figure is a "beam-scan" image, where the range has been focused but the azimuth processing has not been performed. The beam-scan image represents the real-aperture diffraction-limited spot scanned across the target shape; it gives an impression of the image quality and resolution that would be obtained in the absence of aperture synthesis. Phase-gradient autofocus techniques were used to estimate and remove the pulse-to-pulse phase errors, which, if not removed, would render the image unrecognizable. The dark diagonal lines through the target image are less than a millimeter wide. As a result of "laser speckle," this image has a signal-to-noise ratio of about 1. The eye ignores this speckle noise, and the image is still highly interpretable. The focus is reasonably good, although the number of SAIL range resolution elements per illuminating spot size is only about 60. This result indicates that synthetic-aperture ladar imaging is possible despite the nonlinearity and instability of the laser waveform.