Halftoning-Inspired Methods for Foveation in Variable-Acuity Superpixel Imager Cameras
We compare approaches for generating binary control signals for variable acuity superpixel imager (VASI™) cameras. We foveate a set of images using control signals generated by various halftoning approaches and then measure their performance via figures of merit (FOMs). We find that two novel approaches provide superior FOM values but inferior bandwidth control, making them unsuitable for use with VASI™ cameras. Floyd-Steinberg error diffusion gives the best combination of FOM values and bandwidth control. Our contributions include a comparison of approaches, a lookup table method to improve bandwidth control, and two novel methods for binarizing VASI™ control signals. I. INTRODUCTION Our objective is to compare how different halftoning- inspired approaches perform at generating the binary control signals used by Variable Acuity Superpixel Imager (VASI™) foveating cameras, in the context of an automatic target acquisition and recognition (ATA/ATR) application. To accomplish this, we measure five objective figures of merit (FOMs) after foveating a small set of test images with a variety of halftoning-inspired approaches. VASI™ cameras have a number of characteristics that are attractive for the ATR application, but to use them the user must specify a binary control signal that defines the camera's pixel-by-pixel behavior. The translation from a continuous- valued desired resolution signal to a binary VASI™ control signal can be based on halftoning. It must be efficient to avoid lowering the camera's effective frame rate. It must also accurately achieve the target resolution - or equivalently a target bandwidth reduction, which we express as percentage of original bandwidth (PBW) - because this drives the frame rate achieved by the VASI™ camera.