Deep learning-based hologram generation using a white light source taesik Go 1 , Sangseung Lee 2 , Donghyun You 2 ✉ & Sang Joon Lee 1 ✉ Digital holographic microscopy enables the recording of sample holograms which contain 3D volumetric information. However, additional optical elements, such as partially or fully coherent light source and a pinhole, are required to induce diffraction and interference. Here, we present a deep neural network based on generative adversarial network (GAN) to perform image transformation from a defocused bright-field (BF) image acquired from a general white light source to a holographic image. Training image pairs of 11,050 for image conversion were gathered by using a hybrid BF and hologram imaging technique. The performance of the trained network was evaluated by comparing generated and ground truth holograms of microspheres and erythrocytes distributed in 3D. Holograms generated from BF images through the trained GAN showed enhanced image contrast with 3-5 times increased signalto-noise ratio compared to ground truth holograms and provided 3D positional information and light scattering patterns of the samples. The developed GAN-based method is a promising mean for dynamic analysis of microscale objects with providing detailed 3D positional information and monitoring biological samples precisely even though conventional BF microscopic setting is utilized. Conventional bright-field (BF) microscopy using a white light source is a widespread imaging technique used in various areas, including industrial, biological, and medical fields. BF images have been commonly used to observe microscale objects, such as emulsions, microorganisms, and biological samples 1-5. Detection or diagnostic sensitivity is not high (usually less than 90% accuracy), and 3D monitoring of samples in a large volume is especially limited because BF images only provide two-dimensional (2D) amplitude information within the shallow depth of focus (DOF). Digital holographic microscopy (DHM) is a powerful imaging technique that encrypts the 3D information of a test sample into a single shot of 2D interference patterns (i.e., hologram). DHM has a deep observation depth that can overcome the technical limitations of BF microscopy by using a coherent light source. Therefore, DHM has been used in various fields including accurate biological sample monitoring 6-14 , environmental monitoring 15-17 , and particle or cell dynamic analysis 18-20 , because amplitude and phase information can be noninvasively obtained from the hologram without any labeling and mechanical scanning procedures. DHM systems with off-axis configuration can directly obtain phase information related to 3D morphological, mechanical, and biochemical properties 21. However, a complicated interferometric experimental setup, such as common-path and Mach-Zhender setups, is required in such systems. Digital in-line holographic microscopy (DIHM) has a relatively simple optical setup, that is, it only requires a single beam path. DIHM has been widely used in inve...