High-speed ghost imaging by an unpredictable optical phased array

Ghost imaging (GI) retrieves an image from the correlation between a sequence of illumination patterns on the object and their corresponding bucket detections. Traditionally, GI requires the precise information of the illumination patterns, which raises technology barriers on building a high-speed illumination source, limiting the scope of its application. In this study, we propose a high-speed GI system, which implements a self-correlation with a purely optical operation without determining illumination patterns. The light source is an optical phased array (OPA), built of a set of waveguide-type electro-optic phase modulators. The OPA is driven to randomly change the phases in every 200 ns, generating speckle patterns at a rate of 5 MHz. Although the speckle patterns are not predictable or post-determinable, with the help of the naked-eye GI scheme, the system in real time optically generates the images of the object at a frame rate of more than 1 kHz, which can be directly observed by eyes or using a camera. This method avoids acquiring the information of the illumination, thus providing a simple and easy way to realize high-speed GI. It also inspires a different way of applying OPAs to high-speed imaging.