Constant Precision Indirect Time of Flight Range Images Using Variable Frame Rate Imaging

This paper expands on variable frame rate imaging, a technique for improving the dynamic range of indirect time of flight range imaging cameras. Variable frame rate imaging varies the effective integration time across the scene being measured. A theoretical model describing the technique is developed and experimentally verified. Variable frame rate imaging is extended by the introduction of a new quality metric, allowing the system to capture an approximately constant precision range image regardless of the properties of the scene being measured. In previous implementations of this technique, the darker areas of the scene suffer from significantly lower precision than bright areas. A comparison is provided between the new metric and the metric previously reported in the literature. Finally, the effect of variable frame rate imaging on known systematic errors in indirect time of flight systems is examined, namely measurement nonlinearity and motion error.