Programmable Spectrometry: Per-pixel Material Classification using Learned Spectral Filters

Abstract

Many materials have distinct spectral profiles, which facilitates estimation of the material composition of a scene by processing its hyperspectral image (HSI). However, this process is inherently wasteful since high-dimensional HSIs are expensive to acquire and only a set of linear projections of the HSI contribute to the classification task. This paper proposes the concept of programmable spectrometry for per-pixel material classification, where instead of sensing the HSI of the scene and then processing it, we optically compute the spectrally-filtered images. This is achieved using a computational camera with a programmable spectral response. Our approach provides gains both in terms of acquisition speed - since only the relevant measurements are acquired - and in signal-to-noise ratio - since we invariably avoid narrowband filters that are light inefficient. Given ample training data, we use learning techniques to identify the bank of spectral profiles that facilitate material classification. We verify the method in simulations, as well as validate our findings using a lab prototype of the camera.