Typically, high gray-scale imaging requires a high dynamic range camera. High dynamic range is even more crucial to conventional lensless imaging methods such as coherent diffraction imaging, since the dynamic range highly determines the resolution of recovered images. We here propose that ptychographic intensity interferometry imaging (PIII) can detect a complicated-structure object under 1-bit dynamic range (each pixel outputs zero or one only), and reconstruct a high resolution gray-scale image. PIII ptychographically illuminates an object with random speckle light, generating a speckle-like intensity pattern on a detection plane. The second-order correlation of the speckle pattens reveals the power spectrum of the object. Although the depth information of the speckle patterns will be lost because of low dynamic range detections, a small number of multiple detections with different illuminating fields can effectively recover a high dynamic range power spectrum, resulting in a high resolution gray-scale image. A theoretical analysis and comprehensive simulations for the “cameraman” photo are given in this work, which shows that the image under 1-bit dynamic range deteriorates no more than 0.4 dB (peak-signal-to-noise ratio) in comparison to the 16-bit dynamic range one. This method reduces the cost and complexity of implementing a lensless imaging.
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.
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