A PRACTICAL METHOD FOR MEASURING THE SPATIAL FREQUENCY RESPONSE OF LIGHT FIELD CAMERAS

The spatial frequency response (SFR) is one of the most important and unbiased image quality measures of a digital camera. It evaluates to which extent a lens/sensor combina-tion can resolve scene details. In this paper, we propose a sim-ple and practical method to measure the SFR of microlens-based light field cameras. The particularity of such cameras resides in their ability to capture both spatial and angular in-formation of the incoming light field thanks to an array of microlenses located in front of the sensor. Existing meth-ods for measuring the SFR of conventional cameras are thus no longer applicable as the interaction between the main lens and the micro-lenses results in different resolving powers over the image plane that depend on the scene depths. By us-ing a 3-dimensional target made of vertical lines printed on an inclined planar surface, we are able to measure the SFR across multiple depths in a single exposure. Our method al-lows SFR measurements from the raw light field itself as cap-tured by the camera, and is thus independent of subsequent post-processing algorithms such as image reconstruction, dig-ital refocusing or depth estimation. Our experimental results are consistent with theoretical bounds and reproducible