https://scholar.dgist.ac.kr/handle/20.500.11750/10189 Sat, 04 Apr 2026 14:22:52 GMT 2026-04-04T14:22:52Z https://scholar.dgist.ac.kr/handle/20.500.11750/59951 Title: Simple and practical single-shot digital holography based on unsupervised diffusion model Author(s): Park, Seonghwan; Park, Jaewoo; Kim, Youhyun; Moon, Inkyu; Javidi, Bahram Abstract: Single-shot digital holography in Gabor mode offers cost-effective quantitative phase imaging but suffers from the fundamental twin image problem, where real and conjugate images are inherently superimposed, severely limiting phase reconstruction accuracy. Traditional iterative phase retrieval methods require computationally expensive multiple propagations, while off-axis holography demands complex optical setups with precise alignment. We present the first unsupervised diffusion model for automated phase image reconstruction from single-shot in-line holograms, eliminating both twin image artifacts and the need for expensive off-axis configurations. Our framework integrates cycle-consistency and denoising modules to enable training on unpaired hologram-phase image datasets, learning the mapping between low-cost in-line measurements and high-quality phase distributions without requiring labeled data pairs. Comprehensive evaluation on diverse biological specimens demonstrates that our approach significantly outperforms conventional unsupervised methods, achieving superior Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity Index Measure (SSIM) values for both red blood cells and cancer cells. Critically, the model maintains exceptional performance even with limited training data, consistently outperforming supervised learning approaches under data-constrained conditions. The framework exhibits remarkable generalization capabilities, successfully reconstructing phase images from holograms captured at different propagation distances and processing various cancer cell types not included in training data. This computational breakthrough enables accurate, scalable, and hardware-efficient quantitative phase imaging, democratizing access to high-quality phase microscopy for resource-constrained environments while maintaining reconstruction fidelity comparable to complex off-axis systems. © 2025 Elsevier B.V., All rights reserved. Wed, 31 Dec 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/59951 2025-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/12631 Title: Noise-free quantitative phase imaging in Gabor holography with conditional generative adversarial network Author(s): Moon, Inkyu; Jaferzadeh, Keyvan; Kim, Youhyun; Javidi, Bahram Abstract: This paper shows that deep learning can eliminate the superimposed twin-image noise in phase images of Gabor holographic setup. This is achieved by the conditional generative adversarial model (C-GAN), trained by input-output pairs of noisy phase images obtained from synthetic Gabor holography and the corresponding quantitative noise-free contrast-phase image obtained by the off-axis digital holography. To train the model, Gabor holograms are generated from digital off-axis holograms with spatial shifting of the real image and twin image in the frequency domain and then adding them with the DC term in the spatial domain. Finally, the digital propagation of the Gabor hologram with Fresnel approximation generates a super-imposed phase image for the C-GAN model input. Two models were trained: a human red blood cell model and an elliptical cancer cell model. Following the training, several quantitative analyses were conducted on the bio-chemical properties and similarity between actual noise-free phase images and the model output. Surprisingly, it is discovered that our model can recover other elliptical cell lines that were not observed during the training. Additionally, some misalignments can also be compensated with the trained model. Particularly, if the reconstruction distance is somewhat incorrect, this model can still retrieve in-focus images. © 2020 Optical Society of America Fri, 31 Jul 2020 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/12631 2020-07-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/12588 Title: Gold-Nanoparticle Layer Substrate Assisted Transmission-Mode Laser Desorption for Atmospheric Pressure Mass Spectrometry Imaging Author(s): Kim, Jae Young; Lim, Heejin; Sun Young Lee; Gwanjin, Lee; Lim, Dong-Kwon; Moon, DaeWon; Song, Cheol Abstract: We demonstrate continuous-wave laser-based ambient mass spectrometry imaging with the use of a gold-nanoparticle layer substrate. When a fresh tissue slice is placed on a gold-nanoparticle layer substrate and irradiated with a 532-nm continuous-wave laser, the transmission-mode laser configuration provides precise desorption performance to facilitate mass spectrometry imaging. The subsequent ionization process with non-thermal atmospheric pressure plasma jets generates sufficient amounts of molecular ions. By using this method, micrometer-spatial-resolution mass spectrometry imaging of humid tissues can be obtained. The gold-nanoparticle layer substrates can be prepared and stored in advance of the experiment, resulting in simplified specimen preparation and an advantage in faster preparing of fresh tissue specimen for analysis. Wed, 30 Sep 2020 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/12588 2020-09-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/11399 Title: Secure Random Phase Key Exchange Schemes for Image Cryptography Author(s): Kim, Youhyun; Sim, Minwoo; Moon, Inkyu; Javidi, Bahram Abstract: We propose novel random phase key exchange schemes for image cryptography, which are complex sinusoidal waveform versions of the Diffie-Hellman (DH) key exchange algorithm. We demonstrate that the proposed schemes can be particularly helpful to establish a shared secret key in Fourier optics-based image cryptosystems since the problem of symmetric secret key establishment is one of the fundamental difficulties in Fourier optics-based image cryptography. We also propose a ring-type key exchange system in which multiple users can securely share a secret key, which is an extension of the key exchange scheme for two users. The schemes are verified by numerical simulations. © 2014 IEEE. Sat, 30 Nov 2019 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/11399 2019-11-30T15:00:00Z