Enabling single photon imaging at kHz frame rates using digital holography

Cameras designed to operate at kHz frame rates suffer from higher noise levels due to increased readout rate. This can mean in scenarios where it is not possible to increase the illumination level, for example biomedical imaging applications, that objects may be lost in noise. The coherent gain effect inherent in an unbalanced holographic imaging system provides a solution, by amplifying the information in the signal beam with a bright reference beam. The resulting interference pattern can be detected above the noise floor of the camera, and intensity and phase images of the object reconstructed with off-axis holography techniques. This allows for a large improvement in the signal to noise ratio (SNR) of images of the object without having to increase the illumination level. We show that using this method it is possible to obtain images with a SNR ≥ 1 down to a detected intensity on the camera of ∼ 1 photon per pixel per frame.