Kyong Woo Kim

Compact soft x-ray transmission microscopy with sub-50 nm spatial resolution

In this paper, the development of compact transmission soft x-ray microscopy (XM) with sub-50 nm spatial resolution for biomedical applications is described. The compact transmission soft x-ray microscope operates at lambda = 2.88 nm (430 eV) and is based on a tabletop regenerative x-ray source in combination with a tandem ellipsoidal condenser mirror for sample illumination, an objective micro zone plate and a thinned back-illuminated charge coupled device to record an x-ray image. The new, compact x-ray microscope system requires the fabrication of proper x-ray optical devices in order to obtain high-quality images. For an application-oriented microscope, the alignment procedure is fully automated via computer control through a graphic user interface. In imaging studies using our compact XM system, a gold mesh image was obtained with 45 nm resolution at x580 magnification and 1 min exposure. Images of a biological sample (Coscinodiscus oculoides) were recorded.

Nano X-ray Computed Tomography System

A nano computed tomography (nano-CT) system has been developed for three-dimensional (3-D) noninvasive biomedical imaging with sub-micrometer resolution. Using modern technologies in x-ray sources, precision mechanics and detection systems, a compact nano-CT scanner has been created for non-invasive imaging of internal microstructure of objects with sub-micrometer resolution. The system allows the imaging of previously unattainable details of internal 3-D micro-architecture in a wide range of applications. The nano-CT scanner consists of a nanofocus x-ray source, a precision object manipulator and high resolution CCD detectors. The source is of the open tube type (transmission) and the minimum focal spot size is < 1um. The object manipulator is composed of three linear motion stages for magnification adjustment (x), alignment(y), positioning(z) and rotating motion stage(θ) for sample rotation. The x-ray detector contains a straight fiber-optic coupled CCD. The source-to-detector distance (SDD) is 500 mm and the magnification is from 1.1 to 25 times respectively. All parts of the system operate under computer control from integrated software. In this paper, the reconstructed images using the developed nano CT system for 3-D non-invasive biomedical imaging are presented. The characteristics of nano-CT system are also depicted.

Small Field Scanning Mammography Using Polycapillary Optics Collimating Beam

Mammography is a unique diagnostic tool to detect breast cancer by identification of tumor masses and microcalcifications. High spatial resolution and image contrast is essential at mammography system with lowest dose as possible. We considered a small field scanning system which can achieve high spatial resolution with low dose. The X-ray source coupled with a polycapillary optic for collimating X-rays and a CCD detector of a 24 µm × 24 µm pixel size were used. The spatial resolution obtained from the experimental setup was 12 lp/mm at 10% of MTF.

A compact soft x-ray microscope for high resolution hydrated cell imaging

In this presentation, the development of compact transmission soft x-ray microscopy (XM) as a imaging tool for sub-50nm spatial resolution hydrated cell imaging is described. The compact transmission soft x-ray microscope operates at λ = 2.88 nm (430eV) and is based on a tabletop regenerative x-ray source in combination with tandem ellipsoidal condenser mirror (TECM) for sample illumination, objective micro zone plate (OZP) and thinned back-illuminated charge coupled device (CCD) to record an x-ray image. The spectral resolution of illumination soft x-ray has been shown to be E/□E=1000. The new, compact x-ray microscope system requires the fabrication of proper x-ray optical devices in order to obatain high-quality images. For an application-oriented microscope, the alignment procedure is fully-automated via computer control through a graphic user interface. On imaging studies using our compact XM system, the gold mesh image was obtained with 45 nm resolution at ×580 magnification and 1 minute exposure. The images of the biological sample were recorded.

Nano-positioning control of 5-DOF manipulator for alignment of condenser in soft x-ray microscopy system

This paper presents a method of a nano-positioning control for the high precision focusing of a doubled ellipsoidal condenser reflective mirror using 5-axis manipulator. We have developed the compact vertical type of soft X-ray microscopy system with 50nm resolution for biomedical application. This microscopy system is composed of a laser plasma x-ray source, doubled ellipsoidal condenser reflective optics, diffractive zone plate optics and MCP coupled with CCD to record an x-ray image. The X-ray source was focused on a sample by a doubled ellipsoidal condenser reflective mirror. X-ray source focusing will increase the photon density in the object plane and is very important to approach high resolution imaging. Required degree of freedom (DOF) of optics aligner in X-ray microscope is dependent on the kind of optics, but generally 5-DOF is needed. We used 5-axis manipulator that consists of three linear motions (X, Y and Z) and two tilting motions (θx, θy). A linear translation stage is adopted a kind of DC motor with a linear resolution 50nm and travel range of 5mm. The mechanism was controlled with PID controller augmented with closed feedback loop for precision control. A two axis tilt stage is employed a design resolution of 0.23μrad and tilt range of ±7deg. We have designed 5-axis manipulator for the precision position control of condenser mirror optics and have developed to control algorithm by inverse kinematics. The performance of the proposed 5-DOF manipulator is evaluated by using a laser interferometer system with two plane mirror reflectors. The experimental results are depicted in this paper.