Μm Pixel Size Research Articles

Focus on lasers, imaging, and microscopy

Focus on lasers, imaging, and microscopy

Design and construction of a variable resolution cone-beam small animal mini-CT prototype for in vivo studies

We present the conceptual design and construction of a mini x-ray computed tomography (mini-CT) scanner designed and built for in vivo small-animal imaging. The imaging system includes an x-ray tube with 0.5 mm focal spot size and a flat panel detector that provides an active area of 41 × 41 cm2 with 200 µm × 200 µm pixel size. The scanner, designed based on the rotating sample idea, features variable imaging magnification and field-of-view (FOV). To this end, the detector and x-ray tube are mounted on linear motion systems, such that the object to detector or object to x-ray source distance can be easily changed. The variable magnification enables to acquire images at different spatial resolution depending on the size of the object being imaged. This design provides a trade-off between the scanner's FOV and imaging spatial resolution in which small objects are imaged at relatively high spatial resolution as smaller FOVs are required. Conversely, larger objects can also be imaged as the scanner's FOV is adjustable at the expense of spatial resolution degradation. The scanner's FOV varies from 43 cm down to 9 cm (in diameter) with a spatial resolution improving from 3.9 cycle/mm up to 14.4 cycle/mm, respectively. This mini-CT scanner is a self-standing versatile imager suitable for various preclinical imaging applications.

Quantum Efficiency of Back-illuminated CMOS Sensor with 1.4×1.4 μm2 Pixel Size

Quantum Efficiency of Back-illuminated CMOS Sensor with 1.4×1.4 μm2 Pixel Size

Focus on nanotechnology, lasers, and imaging

Focus on nanotechnology, lasers, and imaging

(Invited) Si(1-x)Gex/Si Mqw Based Uncooled Microbolometer Development and Integration into 130 nm BiCMOS Technology

The process of epitaxial SiGe layers are getting attractive as they offer a variety of advanced microelectronics devices compatible with silicon processing technology [1-3]. The large research effort of the last decade has focused on the growth of high quality strained SiGe layers. In particular, SiGe superlattice containing high Ge concentration is demanded in order to improve performances of the devices. Recently, IHP has achieved a significant breakthrough in SiGe/Si MQW processing technology [4]. The developed high quality of superlattice of SiGe/Si MQW structure containing 50% Ge has been successfully processed (Fig. 1) and presented as a potential thermistor material with its high performance for uncooled microbolometer applications [5]. The prototype of thermistor device with 50% Ge in SiGe wells exhibited an outstanding TCR of -5.5 %/K and a K1/f value of 3.4 × 10-15 for 200 µm× 200 µm pixel size, respectively, showing a concurrent achievement of a very high TCR and a low 1/f noise performance. One of the main challenge of SiGe/Si MQW structures is the high resistance values including high Ge concentration makes it difficult to integrate as a detector material in a complete microbolometer device. Large pixel resistances cause not only high noises and hence lower sensitivity but also a challenge to design and maximize the performance of the ROICs [6, 7]. A method to optimize and tune the resistance of the detector material in microbolometers is in-situ doping of quantum well layers in order to enhance the combined detector and ROIC performance. In [8], Boron (B) doping level in SiGe quantum wells are optimized in order to keep the pixel resistance of the thermistor in acceptable values for an ROIC design. B doping of SiGe MQWs is used for the resistance tuning of the detector. The main challenge of the method is simultaneous achievement of enough doping in the SiGe region of the MQWs while keeping the barrier intrinsic silicons non-doped. The initial pixel resistance of 3 period of SiGe/Si MQWs with 50% Ge concentration of 21 MΩ is reduced 210 kΩ for 25 × 25 µm2 pixel size by the optimization of in-situ B doping level in SiGe layers of the MQW stack [8]. The optimized B doping density of ~1 × 1018 cm-3 in SiGe wells did not cause any significant change in the TCR value whereas the 1/f noise performance is even enhanced due to the in-situ doping process. All the aforementioned results shows the successful demonstration of intrinsic thermistor based on SiGe/Si MQWs including 50% Ge with an acceptable pixel resistances. Although the successful demonstration of SiGe MQWs has been performed for high performance microbolometer applications, a full integration of the high performance SiGe/Si MQW based detector into a standard CMOS process is still challenging. SiGe/Si MQW process requires higher temperatures than the temperature budget of the post processing of CMOS process. Therefore, the transfer of the optimized detector structure to a CMOS/BiCMOS wafer needs a special layer transfer process (i.e. wafer bonding). More critically, due to the vertical working principle mechanism of the detector device, there is a challenge for full integration of the optimized detector structure into standard BiCMOS process because the suspended detector device needs to be contacted by both sides In this work, the recent progress on SiGe/Si type high performance detector structures will be presented. The process optimization of the detector by means of high TCR, low 1/f noise and appropriate resistance will be detailed. The method of integrating the developed SiGe/Si MQW structures into a 130 nm BiCMOS process will be provided. The integration method is based on the oxide-oxide fusion bonding of ROIC and detector wafer followed by post processing of the bonded wafer stack. The details of thermal conductance optimization of the microbolometer together with the mechanical stress optimization, required for the suspended detector device, will also be given. Finally, the low-pressure hermetic packaging of the microbolometer structure will also be proposed. Figure 1

Influence of Size and Current Density on the Optoelectrical Properties of Green III-Nitride Micro-Light-Emitting Diodes

High efficiency III-nitride light-emitting diodes (LEDs) have been applied to solid-state lighting. A luminous efficacy (about 150 lm/W) of InGaN/GaN-based LEDs is much higher than those of other self-emissive devices such as organic LEDs (OLEDs). As mobile electronics scale down, display technologies must also move to smaller form factors and ultra-high resolutions while maintaining high efficiencies to extend battery lifetime. III-nitride LEDs are an ideal candidate for achieving these goals. Current technologies including liquid crystal displays (LCDs) and organic light emitting diode (OLED) suffer from low efficiencies and brightness. For the realization of ultrahigh resolutions, around 10 μm or smaller light-emitting pixel sizes are required. In this regard, the InGaN/GaN μLED-based displays have emerged as a promising technology in terms of high brightness, contrast, luminous efficacies, resolution, compactness, operation under harsh conditions, and long lifetime, which cannot be satisfied by conventional LCD and OLED-based display technologies. Several groups have fabricated single-color μLED-based arrays with pixel dimensions as small as 12 μm. This self-emissive technology can be used in applications where high resolution, brightness, and efficiency are necessary such as smartphones, smartwatches, head-mounted and near-eye displays. In addition, μLEDs have exhibited improved thermal management, enhanced light extraction, and operation at higher current densities over their broad-area counterparts. Despite these benefits, surface recombination at small dimensions has been noted as a potential source for reducing device efficiencies. We have investigated the effect of chip size on the forward voltage, light output, emission image and spectral shift of InGaN based green LEDs (518 nm) as a function of current density. The size of the chips was varied from 10 to 100 μm. The smaller chips exhibited higher light output power although the lower output powers were obtained at the higher current densities. Furthermore, the smallest devices showed the better current spreading at higher current densities. It was observed that green μLEDs underwent spectral shift more pronouncedly when dc drive current increased than when chip size increased. It was observed that variation of dc drive current more pronouncedly affected the spectral shift of green μLEDs compared with change of chip size. The relation between the electroluminescence characteristics and current density of different-size devices exhibited that the devices experienced more dominantly blue shift than red shift. However, at the same current density, the peak of the devices was not shifted when the device size changed. Dependence of size and current density on the spectral shift of green μLEDs will be described and discussed in terms of band-filling and stress relaxation effects.

MTF measurements of a type-II superlattice infrared focal plane array sealed in a cryocooler

In operational electro-optical systems, infrared focal plane arrays (IR FPA) are integrated in cryocoolers which induce vibrations that may strongly affect their modulation transfer function (MTF). In this paper, we present the MTF measurement of an IR FPA sealed in its cryocooler. The method we use to measure the MTF decorrelates operational constraints and the technological limitations of the IR FPA. The bench is based on the diffraction properties of a continuously self imaging grating (CSIG). The 26 µm pixel size extracted from the MTF measurement is in good agreement with the expected value.

Use of material decomposition in the context of neurovascular intervention using standard flat panel and a high-resolution CMOS detector.

The imaging of endovascular devices during neurovascular procedures such as the coiling of aneurysms guided with CBCT imaging may be challenging due to the presence of highly attenuating materials such as platinum in the coil and stent marker, nickel-titanium in the stent, iodine in the contrast agent, and tantalum in the embolization agent. The use of dual-energy imaging followed by a basis material decomposition image processing-scheme may improve the feature separation and recognition. Two sets of testing were performed to validate this concept. The first trial was the acquisition of dual-energy micro-CBCT data of a 3D-printed simple aneurysm model using a 49.5 μm pixel size CMOS detector (Teledyne DALSA, Waterloo, ON.). Two sets of projection data were acquired using beam energies of 35 kVp and 70 kVp. Axial slices were reconstructed and used to carry out the material decomposition processing. The second trial was the acquisition of dual-energy CBCT images of a RS-240T angiographic head phantom (Radiology Support Devices Inc., CA.) with an iodine vascular insert using a Toshiba Infinix BiPlane C-arm system coupled to a flat panel detector. Two sets of image data were acquired using beam energies of 80 kVp and 120 kVp. Following image reconstruction, slices of the phantom were decomposed using the same processing as previously. The resulting image data over both trials indicate that the decomposition process was successful in separating the kinds of materials commonly used during a neurovascular intervention, such as platinum, cobalt-chromium, and iodine. The normalized root mean square error metric was used to quantitatively assess this. This indicates a basis for future more clinically relevant testing of our methods.

Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. Here we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolved neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.

First tests of Timepix detectors based on semi-insulating GaAs matrix of different pixel size

In this work, we have focused on Timepix detectors coupled with the semi-insulating GaAs material sensor. We used undoped bulk GaAs material with the thickness of 350 μm. We prepared and tested four pixelated detectors with 165 μm and 220 μm pixel size with two versions of technology preparation, without and with wet chemically etched trenches around each pixel. We have carried out adjustment of GaAs Timepix detectors to optimize their performance. The energy calibration of one GaAs Timepix detector in Time-over-threshold mode was performed with the use of 241Am and 133Ba radioisotopes. We were able to detect γ-photons with the energy up to 160 keV. The X-ray imaging quality of GaAs Timepix detector was tested with X-ray source using various samples. After flat field we obtained very promising imaging performance of tested GaAs Timepix detectors.

In-situ investigation of water distribution in polymer electrolyte membrane fuel cells using high-resolution neutron tomography with 6.5 µm pixel size

In this feasibility study, high-resolution neutron tomography is used to investigate the water distribution in polymer electrolyte membrane fuel cells (PEMFCs). Two PEMFCs were built up with two different gas diffusion layers (GDLs) namely Sigracet® SGL-25BC and Freudenberg H14C10, respectively. High-resolution neutron tomography has the ability to display the water distribution in the flow field channels and the GDLs, with very high accuracy. Here, we found that the water distribution in the cell equipped with the Freudenberg H14C10 material was much more homogenous compared to the cell with the SGL-25BC material.

Correlative mass spectrometry imaging, applying time-of-flight secondary ion mass spectrometry and atmospheric pressure matrix-assisted laser desorption/ionization to a single tissue section.

RationaleMass spectrometry imaging (MSI) is a powerful tool for mapping the surface of a sample. Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) and atmospheric pressure matrix‐assisted laser desorption/ionization (AP‐MALDI) offer complementary capabilities. Here, we present a workflow to apply both techniques to a single tissue section and combine the resulting data for the example of human colon cancer tissue.MethodsFollowing cryo‐sectioning, images were acquired using the high spatial resolution (1 μm pixel size) provided by TOF‐SIMS. The same section was then coated with a para‐nitroaniline matrix and images were acquired using AP‐MALDI coupled to an Orbitrap mass spectrometer, offering high mass resolution, high mass accuracy and tandem mass spectrometry (MS/MS) capabilities. Datasets provided by both mass spectrometers were converted into the open and vendor‐independent imzML file format and processed with the open‐source software MSiReader.ResultsThe TOF‐SIMS and AP‐MALDI mass spectra show strong signals of fatty acids, cholesterol, phosphatidylcholine and sphingomyelin. We showed a high correlation between the fatty acid ions detected with TOF‐SIMS in negative ion mode and the phosphatidylcholine ions detected with AP‐MALDI in positive ion mode using a similar setting for visualization. Histological staining on the same section allowed the identification of the anatomical structures and their correlation with the ion images.ConclusionsThis multimodal approach using two MSI platforms shows an excellent complementarity for the localization and identification of lipids. The spatial resolution of both systems is at or close to cellular dimensions, and thus spatial correlation can only be obtained if the same tissue section is analyzed sequentially. Data processing based on imzML allows a real correlation of the imaging datasets provided by these two technologies and opens the way for a more complete molecular view of the anatomical structures of biological tissues.

Applications of a pnCCD detector coupled to columnar structure CsI(Tl) scintillator system in ultra high energy X-ray Laue diffraction

Most charge coupled devices (CCDs) are made of silicon (Si) with typical active layer thicknesses of several microns. In case of a pnCCD detector the sensitive Si thickness is 450 μm. However, for silicon based detectors the quantum efficiency for hard X-rays drops significantly for photon energies above 10 keV . This drawback can be overcome by combining a pixelated silicon-based detector system with a columnar scintillator. Here we report on the characterization of a low noise, fully depleted 128×128 pixels pnCCD detector with 75×75 μm2 pixel size coupled to a 700 μm thick columnar CsI(Tl) scintillator in the photon range between 1 keV to 130 keV . The excellent performance of the detection system in the hard X-ray range is demonstrated in a Laue type X-ray diffraction experiment performed at EDDI beamline of the BESSY II synchrotron taken at a set of several GaAs single crystals irradiated by white synchrotron radiation. With the columnar structure of the scintillator, the position resolution of the whole system reaches a value of less than one pixel. Using the presented detector system and considering the functional relation between indirect and direct photon events Laue diffraction peaks with X-ray energies up to 120 keV were efficiently detected. As one of possible applications of the combined CsI-pnCCD system we demonstrate that the accuracy of X-ray structure factors extracted from Laue diffraction peaks can be significantly improved in hard X-ray range using the combined CsI(Tl)-pnCCD system compared to a bare pnCCD.

Understanding the neurovascular unit at multiple scales: Advantages and limitations of multi-photon and functional ultrasound imaging.

Developing efficient brain imaging technologies by combining a high spatiotemporal resolution and a large penetration depth is a key step for better understanding the neurovascular interface that emerges as a main pathway to neurodegeneration in many pathologies such as dementia. This review focuses on the advances in two complementary techniques: multi-photon laser scanning microscopy (MPLSM) and functional ultrasound imaging (fUSi). MPLSM has become the gold standard for in vivo imaging of cellular dynamics and morphology, together with cerebral blood flow. fUSi is an innovative imaging modality based on Doppler ultrasound, capable of recording vascular brain activity over large scales (i.e., tens of cubic millimeters) at unprecedented spatial and temporal resolution for such volumes (up to 10μm pixel size at 10kHz). By merging these two technologies, researchers may have access to a more detailed view of the various processes taking place at the neurovascular interface. MPLSM and fUSi are also good candidates for addressing the major challenge of real-time delivery, monitoring, and in vivo evaluation of drugs in neuronal tissue.

150万画素VMIS撮像素子 : 基板電荷変調方式を用いた新しい4.2μm,150万画素撮像素子(固体撮像技術および一般)

150万画素VMIS撮像素子 : 基板電荷変調方式を用いた新しい4.2μm,150万画素撮像素子(固体撮像技術および一般)

MP08-20 RAPID PHENOTYPING OF GENITOURINARY ANOMALIES IN MICE USING MICRO-CT

You have accessJournal of UrologyImaging/Radiology: Uroradiology I1 Apr 2017MP08-20 RAPID PHENOTYPING OF GENITOURINARY ANOMALIES IN MICE USING MICRO-CT Gene Huang, Marisol O'Neill, Meade Haller, Carolina Jorgez, and D.J. Lamb Gene HuangGene Huang More articles by this author , Marisol O'NeillMarisol O'Neill More articles by this author , Meade HallerMeade Haller More articles by this author , Carolina JorgezCarolina Jorgez More articles by this author , and D.J. LambD.J. Lamb More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.307AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Mouse models serve as an excellent tool for studying human disease. Yet, the small size of the mouse presents technical challenges in characterizing organ defects. The use of micro-computed tomography (micro-CT) in biomedical research has historically been limited to studying osseous structures. However, development of iodine staining techniques has allowed for improved ex vivo study of soft tissue structures. Images acquired through micro-CT allow for limitless virtual sectioning (as thin as 2 µm), a distinct advantage over traditional tissue sectioning. In this study, we demonstrate the successful use of iodine staining and micro-CT to rapidly phenotype genitourinary (GU) anomalies in mice. METHODS Mice GU specimens were excised, fixed in formalin, and dehydrated in 70% ethanol. Iodine staining was performed by soaking the tissue in 0.1 N iodine (Fluka). The specimen was suspended in agar in preparation for imaging. Images were acquired using the SkyScan 1272 High-Resolution X-Ray Microtomograph (Bruker microCT, Kontich, Belgium). A 0.5 µm aluminum filter was utilized. Imaging parameters were 5 µm and 11 µm pixel size for penis and kidney specimens, respectively, and 2016 x 1344 resolution. Images were reconstructed using NRecon (Bruker microCT) and visualized using 3D Slicer v4 (slicer.org). RESULTS Both embryonic and adult mice GU specimens were imaged. Micro-CT scan time varied with specimen size and desired resolution, but was at longest 120 minutes. Normal and pathologic GU phenotypes were characterized on three-dimensional, reconstructed images. Embryonic GU systems were examined, including a number of hydronephrotic kidneys (top left). Normal, hydronephrotic, duplex (top right), and polycystic kidneys (bottom left) were identified in adult specimens. Adult penile specimens (bottom right) were reconstructed to allow for morphometric measurements. CONCLUSIONS We demonstrate successful generation of three-dimensional, high-resolution, contrast-enhanced images of GU organs in the murine model using micro-CT. The use of micro-CT possesses a vast potential in rapid phenotyping and study of GU anomalies in the murine model. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e99 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Gene Huang More articles by this author Marisol O'Neill More articles by this author Meade Haller More articles by this author Carolina Jorgez More articles by this author D.J. Lamb More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Design of angularly tolerant zero-contrast grating filters for pixelated filtering in the mid-IR range.

Zero-contrast gratings (ZCG) can be used to implement narrow bandpass transmission filters. However, they suffer from poor angular tolerance, which hinders their use in pixelated applications. Combining ZCG with double-corrugation grating, we increase the resonance width and angular tolerance of the filter by more than 1 order of magnitude. Filters tunable around 4.6 μm with more than 90% transmission and compatibility with 140 μm pixel size are demonstrated.

Potential use of cubic phase masks for extending the range of clear vision in presbyopes: initial calculation and simulation studies.

In this paper we analyse the potential use of a non-symmetrical optical element, a cubic phase mask, for extending the range of clear vision of presbyopic eyes. Additionally, we will discuss the appropriateness of the visual Strehl ratio to analyse this sort of presbyopic solution based on non-symmetrical phase masks contrasted with through-focus retinal images. In order to evaluate the performance of the cubic phase mask we employed computational Fourier Optics to compute the different visual Strehl criteria as well as simulate the retinal images. The through focus real part of the modulation transfer functions and retinal images were computed for four object distances 6.0, 1.0, 0.6 and 0.4m which correspond to far, intermediate and near vision conditions for optotypes of visual acuity of 0.1 and 0.0 logMAR (Snellen 6/7.5 and 6/6; 0.8 and 1 in decimal Snellen). For the experimental validation we built an artificial eye consisting of a plano-convex lens with a focal length of 25.4mm and 0.5 numerical aperture, a variable diaphragm, a 3× objective and an ORCA 285 Hamamatsu Photonics camera 8.1μm pixel size (resulting in an effective pixel size of 2.7μm). A set of four different VA charts adapted to monitor different visual acuities (ranging between 0.0 and 0.20 logMAR) were placed at different object distances 6, 1.0, 0.6 and 0.4m from the artificial eye. Both numerical and experimental validation showed the suitability of the cubic phase mask for extending the range of clear vision of presbyopic eyes, providing at least a visual acuity of 0.1 logMAR (6/7.5 Snellen, 0.8 decimal Snellen) at all distances. The results show that it is possible to choose between promoting far or near vision by changing the magnitude of the defocus component. It is also possible to extend the range of clear vision, by increasing the magnitude of the cubic component. But this increment will cause a reduction in the contrast of the images as it can be observed from the Visual Strehl values and the retinal images generated numerically. A cubic phase mask in the shape 7.07μm×(Z9 -Z6 )-0.9μm×Z4 is a good solution for obtaining a range of clear vision with at least 0.1 logMAR visual acuity (and close to 0.0 logMAR, 6/6, 20/20 and decimal Snellen 1.0) between 6.0 and 0.4m for a pupil diameter of 5.0mm. Our results seem to be a good starting point for future studies of this type of cubic phase mask solutions for presbyopia.

High-resolution MALDI mass spectrometry imaging of gallotannins and monoterpene glucosides in the root of Paeonia lactiflora.

High-resolution atmospheric-pressure scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging (AP-SMALDI MSI) at 10 μm pixel size was performed to unravel the spatio-chemical distribution of major secondary metabolites in the root of Paeonia lactiflora. The spatial distributions of two major classes of bioactive components, gallotannins and monoterpene glucosides, were investigated and visualized at the cellular level in tissue sections of P. lactiflora roots. Accordingly, other primary and secondary metabolites were imaged, including amino acids, carbohydrates, lipids and monoterpenes, indicating the capability of untargeted localization of metabolites by using high-resolution MSI platform. The employed AP-SMALDI MSI system provides significant technological advancement in the visualization of individual molecular species at the cellular level. In contrast to previous histochemical studies of tannins using unspecific staining reagents, individual gallotannin species were accurately localized and unequivocally discriminated from other phenolic components in the root tissues. High-quality ion images were obtained, providing significant clues for understanding the biosynthetic pathway of gallotannins and monoterpene glucosides and possibly helping to decipher the role of tannins in xylem cells differentiation and in the defence mechanisms of plants, as well as to investigate the interrelationship between tannins and lignins.

Design of current mirror integration ROIC for snapshot mode operation

Current mirror integration (CMI) read out integrated circuit (ROIC) topology provides a low input impedance to photo-detectors and provides large injection efficiency, large charge handling capacity and snapshot mode operation without in-pixel opamps. The ROIC described in this paper has been implemented with a modified current mirror circuit, with matched PMOS pairs for detector input stage and its biasing. The readout circuit has been designed for 30 × 30 μm2 pixel size, 4 × 4 array size, variable frame rate, 5 Mega pixel per second (Mpps). Experimental performance of the test chip has achieved 15 Me charge handling capacity, a high dynamic range of 83 dB, 99.8% linearity and 99.96% injection efficiency. The ROIC design has been fabricated in 3.3 V 1P6M UMC 180 nm CMOS process and tested up to 5 MHz pixel rate at room and at cryogenic temperature.