Reference Light Intensity Research Articles

Common-path-based device for magnetomotive OCT noise reduction.

Magnetomotive optical coherence tomography (MMOCT) is a promising imaging method for noninvasive three-dimensional tracking of magnetic nanoparticle (MNP) motions in target tissues or organs. The external B-field is the driving force that provides MMOCT contrast. However, B-field modulation also introduces modulation noise, thereby decreasing the quality of the MMOCT image. In this paper, a common-path-based device is designed for modulation noise reduction. The device is capable of adjusting interference distance, reference light intensity, and imaging position (X-Y translation). The sensitivity of the MMOCT is increased by ∼20 times with the new device. Using the proposed device, the distribution of MNPs injected in zebrafish was imaged.

Research on Experimental Parameters of Reflective Off-axis Digital Holography

Summarized the research status of digital holography microscopy technology. Aiming at the experimental parameters which influences the quality of hologram recurrent image, the recording and reconstruction process of hologram are analyzed, the reconstruction distance are calculated which based on the reflective off-axis digital holographic light path. The experiment records the hologram of standard resolution board and reconstruct it under different light intensity ratio. The results show that the object and reference light intensity ratio have a significant impact on the quality of hologram recurrent image. Besides, it’s the key to determining an appropriate recording distance and object and reference light intensity ratio of improving the quality of hologram. The result would provide theoretical basis and technical conditions for studying the reflective digital holography based on 3-D reconstruction.

Simultaneous measurement of retardance and fast axis azimuth based on liquid crystal wave plate group

The simultaneous measurement of retardance and fast axis azimuth based on liquid crystal wave plate group (LCWPG) is presented. The laser beam propagates through an aperture and then splits into two beams by a non-polarizing beam splitter (NPBS). The intensity of the reflected beam is detected by a photomultiplier tube (PMT) as the reference light intensity. The transmitted beam, which passes through a polarizer, a quarter-wave plate, a retarder sample to be measured and the LCWPG successively, is finally detected by another PMT. The LCWPG is composed of four liquid crystal wave plates (LCWPs). In addition, the LCWPG works in six different polarized modulation modes dependent on the voltages applied on each LCWP. The six corresponding sets of light intensity are then measured by the two PMTs. By calculating and deriving from the six sets of light intensity, the retardance and fast axis azimuth of the measured sample can be obtained, respectively. In the experiment, the retardance of a quarter wave plate as the sample is measured when its fast axis is at different angles. The standard deviations of the retardance and the fast axis azimuth of the measured sample are 0.67˚ and 0.85˚, respectively. The effectiveness of the proposed method is verified.

Common-Path Optical Coherence Tomography Using a Conical-Frustum-Tip Fiber Probe

We demonstrated an in-fiber common-path optical coherence tomography (OCT) system using a conical-frustum-tip fiber probe. The probe had a circularly truncated conical shape to increase reflection of reference light while preserving focus without additional lens components. We analyzed the intensity of reference light back-reflected from the probe using a ZEMAX simulation, and the optimal height of the conical-frustum lens was 1.0 μm. Compared to various other types of conical-frustum-tip fiber probes, the probe in this paper showed the best lateral resolution with a relatively high reflectivity. Experimental results are compared to simulations. This conical-frustum-tip probe provided a 3.7 times larger reflectivity than a conventional conical lens. Due to the increased reflection, the signal-to-noise ratio (SNR) of an OCT image was enhanced by up to 5.6 dB. Furthermore, the lateral resolution was less than 4.4 μm as verified by B-scan profiles of a resolution target card. This probe can be utilized as a forward-viewing endoscopic probe to enhance OCT image quality through an increase in SNR, sensitivity, a small size, and effective focusing without additional lens components.

Effects of plant size, temperature, and light intensity on flowering of Phalaenopsis hybrids in Mediterranean greenhouses.

Mediterranean greenhouses for cultivation of Phalaenopsis orchids reproduce the warm, humid, and shaded environment of tropical underbrush. Heating represents the highest production cost, due to the high thermal requirements and the long unproductive phase of juvenility, in which plants attain the critical size for flowering. Our researches aimed to investigate the effect of plant size, temperature, and light intensity, during the phase of flower induction, on flowering of modern genotypes selected for Mediterranean greenhouses. Three experiments were carried out to compare (i) plant size: reduced size versus size considered optimal for flowering (hybrids “Sogo Yukidian,” “Chain Xen Diamond,” and “Pinlong”); (ii) temperature: moderate reduction of temperature versus standard thermal regime (hybrid “Premium”); (iii) light intensity: supplemental lighting versus reference light intensity (hybrid “Premium”). The premature exposure of plants to the inductive treatment delayed the beginning of flowering and reduced the flower stem quality, in all the tested hybrids. In “Premium,” the lower temperature did not affect flowering earliness and commercial quality of flower stems compared to the standard regime, whereas it promoted stem branching. In the same hybrid, supplemental lighting anticipated flowering and promoted the emission of the second stem and the stem branching, compared to the reference light regime.

Interplay among culture parameters, light, mixing, and photobioreactor configuration during H 2 production by sulfur-deprived Chlamydomonas reinhardtii

The interplay among the culture parameters, light intensity and illumination conditions, mechanical mixing conditions, and reactor configurations during O 2 evolution and H 2 production in sulfur-deprived Chlamydomonas reinhardtii cultures is studied in this work. The advective-diffusive reaction equation is used to describe the diffusion and the local biochemical reactions of the species involved in the biological process for H 2 production. Solutions of the diffusion equation are obtained for different boundary conditions. An empirical equation is used to describe the relation between the light attenuation coefficient and the initial chlorophyll concentration, which characterizes both the culture absorption property and the mechanical mixing condition. The dynamics of O 2 evolution and H 2 production in a tubular photobioreactor illuminated under three different light conditions on the boundary is studied for the cultures with different initial chlorophyll concentrations. For the culture with the initial chlorophyll concentration of 18 mg/L, the light attenuation level of K a 0 = 0.125, and the reference light intensity of 236.3 μE m −2 s −1, the results indicate that the maximum H 2 production is 166 ml for the tubular reactor under uniform light illumination, 163 ml for the flat plate reactor under two-side light illumination, 85 and 75 ml for the tubular and the flat plate reactors, respectively, under one-side light illumination.

An assessment of light-based geoposition estimates from archival tags

Archival tags record information about the environment of tagged animals over long periods of time (months to years). In theory, position can be estimated from a record of changes in light intensity with time. We describe two approaches to estimating geoposition based on estimating either the time of maximal rate of change in light intensity or the time that a reference light intensity is reached. Digital signal processing is investigated as a method of increasing the signal-to-noise ratio of the light record. Our test data suggest that the daily position of a tagged animal can potentially be estimated within an average error of about 140 km (SD's of 0.9° of longitude and 1.2° of latitude), approaching the resolution of the best eddy-resolving physical oceanographic models of ocean currents. The source of the remaining large-scale errors in geoposition appears to be extrinsic to the tags and may be related to large-scale weather systems. The accuracy of current archival tags is sufficient to permit an assessment of the open-ocean migration pathways of animals such as maturing salmon and may be sufficient for use in some parts of the continental shelf as well.

Uncertainty estimates for pressure sensitive paint measurements

A recently introduced surface pressure measurement technique for aerodynamic applications uses pressure sensitive luminescent coatings. The primary measurable is luminescent light intensity, but the determination of pressure also requires the measurement of other variables, such as a reference light intensity and surface temperatures. Each of the primary measurables is associated with an error that contributes to the uncertainty of the pressure computed from all inputs. This paper investigates these contributions to the resultant uncertainty, both in fundamental terms and in terms of commonly used wind tunnel parameters. The uncertainty is sharply dependent on both freestream and local flow conditions, such that a simple global characterization of error magnitude does not seem to be practical. Spatial surface temperature variations and temperature differences between reference and run conditions may significantly affect the results.

Use of a wedge cuvette in thin layer photometry and its application to oximetry.

A wedge cuvette was constructed by fixing 2 glass plates at a known angle with a spacer at one end. This resulted in a thin layer with thickness varying from 0 to 250 micrometer. By measuring the intensity of a beam of light through the thin layer as a function of distance along the wedge (and thus layer thickness), the absorption coefficient at the light wavelength used could be obtained without a separate measurement of I0, the reference light intensity. In addition, the difficult problem of determining accurate layer thickness as encoutered in conventional thin layer photometry has been avoided. Tests of the wedge cuvette method with Evans Blue and Malachite Green serial dilutions as well as with haemoglobin solutions at several oxygen saturations demonstrate that accuracy of the order of 1% can be obtained. Application of the wedge cuvette in experiments on oxygen uptake by layers of haemoglobin solution are discussed.