Tissue refractive index provides important information about morphology at the nanoscale. Since the malignant transformation involves both intra- and inter-cellular changes in the refractive index map, the tissue disorder measurement can be used to extract important diagnosis information. Quantitative phase imaging (QPI) provides a practical means of extracting this information as it maps the optical path-length difference (OPD) across a tissue sample with sub-wavelength sensitivity. In this work, we employ QPI to compare the tissue disorder strength between benign and malignant breast tissue histology samples. Our results show that disease progression is marked by a significant increase in the disorder strength. Since our imaging system can be added as an upgrading module to an existing microscope, we anticipate that it can be integrated easily in the pathology work flow.

Holographic recording methods require the use of a reference beam that is coherent with the signal beam carrying the information to be recorded. In this paper, we propose self-referential holography (SRH) for holographic recording without the use of a reference beam. SRH can realize purely one-beam holographic recording by considering the signal beam itself as the reference beam. The readout process in SRH is based on energy transfer by inter-pixel interference in holographic diffraction, which depends on the spatial phase difference between the recorded phase and the readout phase. The phase-modulated recorded signal is converted into an intensity-modulated beam that can be easily detected using a conventional image sensor. SRH can be used effectively for holographic data storage and phase-to-intensity conversion.

The feasibility and the properties of shift-multiplexed self-referential holographic data storage (SR-HDS) were investigated. Although SR-HDS has attractive features as typified by referenceless holographic recording, its multiplexing properties, which are consummately important for holographic data storage, have not been clarified until now. The results of numerical and experimental evaluations of medium shift dependence in SR-HDS clarified that the shift selectivity is almost the same as in collinear holography. Furthermore, 25 datapages were successfully shift-multiplexed with the shift pitch of 8.3 μm by the numerical simulation.

According to the World Health Organization, cancer is a major cause of death globally.¹ Effective treatment strategies require early and accurate diagnosis of the disease. The gold standard method for cancer diagnosis is the microscopic investigation of a stained tissue biopsy by a trained clinical pathologist. Through this investigation, the pathologist looks for morphological signatures of either normal or abnormal tissue. Being qualitative, this type of assessment leads not only to interobserver discrepancy but also to automation of some or part of the process through machine learning where image analysis is complicated by stain variability.^2,3 Ensuring consistency in the disease signatures extracted through image analysis of stained tissue remains a significant challenge due to variations in tissue preparation.⁴

We propose a two-channel holographic diversity interferometer (2ch-HDI) system for single-shot and highly accurate measurements of complex amplitude fields with a simple optical setup. In this method, two phase-shifted interference patterns are generated, without requiring a phase-shifting device, by entering a circularly polarized reference beam into a polarizing beam splitter, and the resulting patterns are captured simultaneously using two image sensors. However, differences in the intensity distributions of the two image sensors may lead to serious measurement errors. Thus, we also develop a two-channel algorithm optimized for the 2ch-HDI to compensate for these differences. Simulation results show that this algorithm can compensate for such differences in the intensity distributions in the two image sensors. Experimental results confirm that the combination of the 2ch-HDI and the calculation algorithm significantly enhances measurement accuracy.

Two methods are proposed to improve the readout quality of signals in self-referential holographic data storage (SR-HDS), in which no reference beam is required to record and read digital data holographically: the off-the-focus (OtF) method and the oversampling additional pattern (OsAP) method. The focal point is located outside of the recording medium in the OtF method, and the signal pattern is recorded with an additional pattern that possesses a higher spatial frequency than the signal pattern in the OsAP method. Experimental results show that both methods are effective for drastically improving the signal-to-noise ratio (SNR). In addition, through numerical simulation, it can be observed that the readout quality is improved by the achievement of homogeneous hologram distribution.