Xiangyu Quan

Single-shot incoherent digital holography using a dual-focusing lens with diffraction gratings

A new optical configuration of incoherent digital holography is presented to improve the quality of reconstructed images when the random polarization state of incoherent light is used. The proposed system improves the signal-to-noise ratio of the holograms by suppressing the unmodulated terms of a spatial light modulator. To generate the self-interference of a quasi-incoherent point-like source, we use a dual-focusing lens with diffraction gratings. The preliminary experimental results confirm the validity of the proposed method by reconstructing two point-like sources generated by a LED light source. When the pixel pitch of the phase-mode SLM is small enough, the off-axis hologram can be generated. The single-shot recording of the incoherent digital holography is expected.

Image recovery from defocused 2D fluorescent images in multimodal digital holographic microscopy

A technique of three-dimensional (3D) intensity retrieval from defocused, two-dimensional (2D) fluorescent images in the multimodal digital holographic microscopy (DHM) is proposed. In the multimodal DHM, 3D phase and 2D fluorescence distributions are obtained simultaneously by an integrated system of an off-axis DHM and a conventional epifluorescence microscopy, respectively. This gives us more information of the target; however, defocused fluorescent images are observed due to the short depth of field. In this Letter, we propose a method to recover the defocused images based on the phase compensation and backpropagation from the defocused plane to the focused plane using the distance information that is obtained from a 3D phase distribution. By applying Zernike polynomial phase correction, we brought back the fluorescence intensity to the focused imaging planes. The experimental demonstration using fluorescent beads is presented, and the expected applications are suggested.

Multimodal Imaging Based on Digital Holography

Digital holography provides a method of the 3-D recording and numerical reconstruction by a simple optical system and a computer. Quantitative measurement and numerical refocusing are major characteristics. So far, many physical parameters such as amplitude, phase, polarization, fluorescence, and spectra can be obtained independently. Recently, multimodal imaging that can obtain simultaneously two or more physical parameters by combining digital holographic microscope and other optical microscopes such as a fluorescence optical microscope and a Raman scattering microscope has emerged. In this review, physical parametric imaging techniques based on digital holography are presented and then these techniques are enhanced to develop multimodal imaging based on digital holography.

Multi-modal Digital Holographic Microscopy and Demonstration on Dual-excitation Fluorescence

Multi-modal digital holographic microscopy is a combination of epifluorescence microscopy and digital holographic microscopy. The attractive property is to obtain images from fluorescence and quantified phase information, simultaneously. On the fluorescence side, it is typical to image only limited colors due to prefixed filter sets. Increasing the range of excitation wavelengths/filters would help to identify status of molecules in the fluorescence. This paper introduces the optical set-up of the multi-modal digital holographic microscopic system and demonstrates dual-excitation fluorescence with static micro-fluorescent beads. The result successfully shows quantitative phase and two-color fluorescent information from the same object.

Hybrid digital holographic microscope for simultaneous measurement of 3D phase and 3D fluorescence distributions and its signal processing

A hybrid digital holographic microscopic system that enables simultaneous detection of 3D phase and fluorescence images is proposed. The proposed microscopic system is designed by combination of a transmission type off-axis digital holographic configuration and a reflection type Fresnel incoherent holographic configuration, aimed for biological application. Owing to the single acquisition, signal processing which separates a superposed hologram is proposed.

Digital holography and its multidimensional imaging applications: a review

We introduce digital holographic techniques and recent progress in multidimensional sensing. Digital holography can be used to perform multidimensional imaging of three-dimensional structure, dynamics, quantitative phase, multiple wavelengths, and polarization state of light and sensing of a holographic image of nonlinear light and a three-dimensional image of incoherent light.

Live cell imaging of Physcomitrella patens using a multi-modal digital holographic microscope

Fluorescent imaging and phase contrast imaging are two major techniques for live cell studies. One can obtain those two types of images by switching illumination and filter sets, and this process usually consumes unnecessary time. In order to image dynamical cell behaviors, we have presented a multi- modal digital holographic microscopic method to obtain both quantitative phase images and fluorescent images at the same time. We used Physcomitrella patens the moss to test the proposed system. Two-dimensional images of chloroplasts and quantitative phase information were obtained simultaneously under continuous exposure of laser light. We observed shrinkage in cell size and concentration in the chloroplasts distribution.

A hybrid digital holographic microscopy for biological applications

It will be useful in biological applications if two or more physical parameters are simultaneously measured in a digital holographic microscope. In this paper, we present a hybrid digital holographic microscope that can measure simultaneously three-dimensional (3D) phase and 3D fluorescence distributions. This property has big advantage compared with conventional optical microscopes such as phase contrast microscope and fluorescence microscope. We present an optical setup for measuring both phase and fluorescence images. In the experiments, two objects that are fluorescence beads and egera densa are used. The separation method of phase and fluorescence images is presented.

Three-dimensional imaging based on common-path off-axis incoherent digital holography (Conference Presentation)

In this invited presentation, we will introduce our recent research on 3D imaging based on common-path off-axis incoherent digital holography. 3D imaging by single shot measurement is very attractive for biological imaging field. In the proposed technique, two focusing lenses with different diffraction gratings are implemented by a phase-mode spatial light modulator and then two diffracted incoherent light waves can interfere at the image sensor. This system can be compact and be stable. We will present several experiments including LED sources. We will discuss the potential of the biological imaging.

Multimodal digital holographic microscopy for simultaneous phase and fluorescence imaging

This paper introduces a new type of multimodal digital holographic microscopy for biological applications. Off-axis digital holography is applied both in 3D phase imaging and 3D fluorescence imaging. In addition, image recovery by iterative method to obtain focused fluorescence images are introduced.