Phase-coded volume holographic gratings for spatial–spectral imaging filters
We present a design of phase-contrast filters embedded in a three-dimensional pupil to form phase-coded volume holographic gratings (VHGs) for spatial–spectral imaging. The phase-coded VHG improves image contrast and results in strong filtering properties to acquire weak phase structures of an object. In addition, incorporated with in-plane angle multiplexing, the multiplexed phase-coded VHGs enable obtaining weak phase information from multiple depths of an object. We experimentally demonstrate the multiplexed phase-coded VHGs for spatial–spectral imaging to enhance unstained features of spatial–spectral images of human breast cancer cells.