White Light Source For Illumination Research Articles

Preparation and characterization of green emitting NASO:Tb3+ and red emitting NASO:Eu3+ glasses derived from ions exchanged LTA zeolite

NASO:Tb3+ and NASO:Eu3+ glasses derived from ions exchanged LTA zeolite were successfully prepared by melt quenching method. The microstructure, mechanical and thermal properties were demonstrated, due to the porous structure and low Si/Al ratio of LTA, the Tb3+-doped and Eu3+-doped prepared glasses exhibited the good phase stability, high Vickers hardness (825 kg/mm2 and 807 kg/mm2) and quality thermal conductivity (2.523 W m−1 K−1 and 2.496 W m−1 K−1). The emission intensity of NASO:Tb3+ and NASO:Eu3+ glasses showed strong green and red luminescence corresponding to the transitions of 5D4→7F5 and 5D0→7F2, and the values maintained about 73% and 67% at the temperature of 200 °C, indicating the prepared glasses possess good thermal quenching performance. The CIE coordinates of the prepared glasses were calculated to be (0.321, 0.594) and (0.628, 0.361), and the CCT of green and red light were measured to be 1892 K and 5345 K. The results show that the straightforward technique to synthesize NASO:Tb3+ and NASO:Eu3+ glasses is promising for white light illumination source.

Ultralow-light-level color image reconstruction using high-efficiency plasmonic metasurface mosaic filters

As single-photon imaging becomes progressively more commonplace in sensing applications such as low-light-level imaging, three-dimensional profiling, and fluorescence imaging, there exist a number of fields where multispectral information can also be exploited, e.g., in environmental monitoring and target identification. We have fabricated a high-transmittance mosaic filter array, where each optical filter was composed of a plasmonic metasurface fabricated in a single lithographic step. This plasmonic metasurface design utilized an array of elliptical and circular nanoholes, which produced enhanced optical coupling between multiple plasmonic interactions. The resulting metasurfaces produced narrow bandpass filters for blue, green, and red light with peak transmission efficiencies of 79%, 75%, and 68%, respectively. After the three metasurface filter designs were arranged in a 64 × 64 format random mosaic pattern, this mosaic filter was directly integrated onto a CMOS single-photon avalanche diode detector array. Color images were then reconstructed at light levels as low as approximately 5 photons per pixel, on average, via the simultaneous acquisition of low-photon multispectral data using both three-color active laser illumination and a broadband white-light illumination source.

Living cell dry mass measurement using quantitative phase imaging with quadriwave lateral shearing interferometry: an accuracy and sensitivity discussion.

Single-cell dry mass measurement is used in biology to follow cell cycle, to address effects of drugs, or to investigate cell metabolism. Quantitative phase imaging technique with quadriwave lateral shearing interferometry (QWLSI) allows measuring cell dry mass. The technique is very simple to set up, as it is integrated in a camera-like instrument. It simply plugs onto a standard microscope and uses a white light illumination source. Its working principle is first explained, from image acquisition to automated segmentation algorithm and dry mass quantification. Metrology of the whole process, including its sensitivity, repeatability, reliability, sources of error, over different kinds of samples and under different experimental conditions, is developed. We show that there is no influence of magnification or spatial light coherence on dry mass measurement; effect of defocus is more critical but can be calibrated. As a consequence, QWLSI is a well-suited technique for fast, simple, and reliable cell dry mass study, especially for live cells.

Large area diffraction-based inspection of submicron periodic structures

An experimental study of diagnostics possibilities of periodic structures using visible light diffraction principles is presented. The goal of the study is to develop a simple method suitable for use in the inspection of large scale area periodically structured surfaces. It is shown that diffraction-based methods can be applied for surface feature size determination in the submicron region as well as for assessment of the surface profile modulation depth. In order to observe the periodic structure defects on the whole surface of 6–8 inch wafers, an optical filtration set-up is proposed using a white light illumination source. Diffraction efficiency has been acquired by photoelectric sensing of laser beam diffraction. Determined values, – of both the surface feature size and the depth of modulation coincide well with that obtained by AFM and SEM.

An array of highly selective Fabry–Perot optical channels for biological fluid analysis by optical absorption using a white light source for illumination

This paper describes a laboratory microsystem (Microlab) used to measure the concentration of biomolecules in biological fluids. Rather than just one measurement channel, it comprises 16 optical channels that enable the measurement of the concentration of 16 different biomolecules with the same device. An array of 16 optical filters based on Fabry–Perot thin-film optical resonators has been designed. Each optical channel is sensitive in a single wavelength with a FWHM less than 6 nm and with a peak intensity higher than 86%. The 16 optical channel array fabrication requires only four masks, used with different deposition time. The Microlab can easily be tuned during fabrication to analyse different biomolecules only by adjusting the deposition times without affecting the device layout. A commercially available passband optical filter with a passband wavelength in the range 450–650 nm is used. Th eM icrolab requires only a white light source for illumination due to the use of selective optical filters. The quantitative measurement of uric acid in urine is demonstrated. Such a device is extremely suitable for clinical diagnosis application in clinical laboratories and at a patient’s home because of its small size, low cost and portability.

An array of Fabry-Perot optical-channels for biological fluids analysis

This paper describes a biosystem (biological system) used to measure the concentration of biochemical substances in urine, serum, plasma or cerebrospinal fluid. Rather than just one channel, it comprises 16 optical-channels that enable the measurement of the concentration of 16 different biochemical substances. An array of 16 optical filters based on Fabry-Perot thin-films optical resonators has been designed. Each optical-channel is sensitive in a single wavelength with a full-width-half-maximum (FWHM) of 7 nm. The filter fabrication requires only four masks, used with different etch time. A commercially available band-pass optical filter with a band-pass wavelength in 450–650 nm is used. The biosystem requires only a white light source for illumination due the use of selective optical filters.

Inspection of micro-solderballs on a semiconductor bumped wafer using optical shadowgraph

We describe a simple way to effectively measure the height of a micro-solderball of a micro-ball grid array (micro-BGA) on a bumped wafer. The proposed method derived using a white-light illumination source can perform a speedy whole field inspection of the micro-solderballs. The optical system consists of a white-light telecentric configuration and a long-working-distance microscope with a telecentric objective. The optical axes of the illuminating light and microscope are symmetrically arranged with respect to the normal of the test surface and hence the technique is applicable to optical measurement on a mirror-like test surface, such as a silicon wafer. The height of a solderball is computed from a simple formula based on the geometry of the specimen and the system configuration. Experimental results demonstrate that the height of a micro-solderball can be readily measured with accuracy in the order of micrometers.

A new optical technique for detection of defects in ferromagnetic materials and components

In this paper, we present the details of a new optical technique to detect the defects present in a ferromagnetic material or component, using a ferrofluid emulsion. This new flux leakage probe consists of monodispersed ferrofluid confined between two thin transparent glass slides or in a cuvette and a white light source for illumination. By employing ferrofluid droplets of suitable size and surfactant concentration, one can qualitatively identify the region where the defect is located in the test specimen by visually observing a color change in the ferrofluid cell, in the vicinity of a crack or defect in the test specimen. The origin of this color change in the back scattering direction is due to Bragg scattering from the droplet chains, formed by the leaked magnetic flux in the presence of a defect. We discuss in detail the procedure, the merits and potential uses of this new technique for non-destructive testing and evaluation (NDT and E) applications.

An optical technique for the detection of surfacedefects in ferromagnetic samples

We discuss the details of a new optical technique developed for the detection of defects in ferromagnetic materials or components, using a ferrofluid emulsion. This new flux leakage probe consists of a monodispersed ferrofluid either confined between two thin transparent sheets or in a cuvette, and a white light source for illumination. By employing ferrofluid droplets of suitable size and surfactant concentration, and mounting the cell on the test specimen surface, one can detect the region where the defect is located in the test specimen by visually observing a colour change in the ferrofluid cell, in the vicinity of the defect. The origin of this colour change in the backscattering direction is Bragg scattering from the droplet chains, which are formed by the leaked magnetic flux in the presence of a defect. The details of the defect detection procedure and typical experimental results obtained in a ferromagnetic specimen with a rectangular slot (i.e. an artificial defect) are presented.

Spectroscopic Contrast by Colour Photon Scanning Tunnelling Microscopy

A colour photon scanning tunnelling microscope (Colour-PSTM) using a white light illumination source has been designed in order to provide spectroscopic contrast with three colour channels. True colour images can be put together from independently measured topography and normalized red, green and blue signals. The measurement of tip–sample distance curves in the respective spectral ranges is consistent with theoretical considerations. Material contrast is demonstrated with two different dyes, which can be clearly distinguished. As an example for measuring intrinsic material properties, surface plasmon polaritons in thin silver films are recorded at different coupling conditions of the momentum vectors. This new Colour-PSTM offers one of the most desirable features in scanning probe microscopy, with a high potential of application: local material contrast by colour spectroscopy.© 1997 John Wiley & Sons, Ltd.