6,657 research outputs found

    Standing-wave-excited multiplanar fluorescence in a laser scanning microscope reveals 3D information on red blood cells

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    Standing-wave excitation of fluorescence is highly desirable in optical microscopy because it improves the axial resolution. We demonstrate here that multiplanar excitation of fluorescence by a standing wave can be produced in a single-spot laser scanning microscope by placing a plane reflector close to the specimen. We report that the relative intensities in each plane of excitation depend on the Stokes shift of the fluorochrome. We show by the use of dyes specific for the cell membrane how standing-wave excitation can be exploited to generate precise contour maps of the surface membrane of red blood cells, with an axial resolution of ~90 nm. The method, which requires only the addition of a plane mirror to an existing confocal laser scanning microscope, may well prove useful in studying diseases which involve the red cell membrane, such as malaria.Comment: 15 pages, 4 figures; changed the discussion of narrow-band detected fringes (Fig. 3) to describe the phenomenon as a moire pattern between the excitation and emission standing-wave fields, rather than a beats pattern; added DiI(5)-labelled red blood cell in Fig. 4 to show that standing-wave fringes are present even when the dye excitation wavelength is outside the haemoglobin absorption ban

    Demonstration of integrated microscale optics in surface-electrode ion traps

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    In ion trap quantum information processing, efficient fluorescence collection is critical for fast, high-fidelity qubit detection and ion-photon entanglement. The expected size of future many-ion processors require scalable light collection systems. We report on the development and testing of a microfabricated surface-electrode ion trap with an integrated high numerical aperture (NA) micromirror for fluorescence collection. When coupled to a low NA lens, the optical system is inherently scalable to large arrays of mirrors in a single device. We demonstrate stable trapping and transport of 40Ca+ ions over a 0.63 NA micromirror and observe a factor of 1.9 enhancement in photon collection compared to the planar region of the trap.Comment: 15 pages, 8 figure

    RGB fluorescence imaging by changing illumination

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    High density pixel array and laser micro-milling method for fabricating array

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    A pixel array device is fabricated by a laser micro-milling method under strict process control conditions. The device has an array of pixels bonded together with an adhesive filling the grooves between adjacent pixels. The array is fabricated by moving a substrate relative to a laser beam of predetermined intensity at a controlled, constant velocity along a predetermined path defining a set of grooves between adjacent pixels so that a predetermined laser flux per unit area is applied to the material, and repeating the movement for a plurality of passes of the laser beam until the grooves are ablated to a desired depth. The substrate is of an ultrasonic transducer material in one example for fabrication of a 2D ultrasonic phase array transducer. A substrate of phosphor material is used to fabricate an X-ray focal plane array detector

    Digital Color Imaging

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    This paper surveys current technology and research in the area of digital color imaging. In order to establish the background and lay down terminology, fundamental concepts of color perception and measurement are first presented us-ing vector-space notation and terminology. Present-day color recording and reproduction systems are reviewed along with the common mathematical models used for representing these devices. Algorithms for processing color images for display and communication are surveyed, and a forecast of research trends is attempted. An extensive bibliography is provided

    A tribological investigation of windscreen wiper performance

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    This project focused on understanding windscreen-wiper/glass interactions with an aim to reduce friction and wear, improve wiping quality and prevent friction induced vibration, (also known as squeak). To achieve this, the contact between windscreen and wiper was simulated under laboratory conditions using a UMT2 Tribometer, which loaded a stationary rubber profile against a rotating glass disc. Then, a range of measurement and analytical techniques were used to characterize the effect of conditions on different aspects of wiper performance. Different surface conditions were reproduced by applying a range of common treatments to the glass, including hydrophobic and hydrophilic coatings. In addition to this, a new method of partially forming self-assembled monolayers was devised in order to produce test specimens with a controlled range of surface energies. It was shown that friction reduces with increasing surface energy, which is attributed to a smaller volume of water being entrained into the contact. Following this, a range of non-steady state friction behaviours were studied. These included combined friction and wear tests, where under severe conditions it was shown how friction performance is dominated by the formation and removal of burs, which prevents water from being entrained into the contact. In addition, drying tests were conducted to understand “tacky” behaviour (i.e., the peak in friction peak under partially lubricated conditions). This was shown to be controlled by decreasing the surface tension of the water, through the addition of detergent, and provided evidence to support the theory that water menisci are responsible for increasing surface area. Static friction behaviour was also investigated, and the effects of start-up velocity and stationary duration on friction were quantified and explained. The practical implications of these results are discussed in terms wiper design and material selection. To study friction induced vibration, (FIV), friction, sound and high speed video measurements were combined with finite element modelling of a rubber wiper/glass contact. In agreement with previous research, FIV only occurs when the friction versus speed curve has a negative gradient; a factor, which, in combination with the low stiffness of the materials, can lead to vibrational instabilities in the mixed regime. Results also showed that friction induced vibration is strongly affected by surface condition, and only occurs for a certain range of surface energies. This is explained by the fact that both high and low surface energies alter the gradient of the Stribeck curve thereby preventing FIV (i.e., low surface energies prevent sufficient liquid entering the contact and high surface energies attract water molecules to the surface of the glass producing a film that reduces friction). In order to study the source of squeak, simultaneous measurements were realised by a high speed camera, microphone, and laser Doppler vibrometer (LDV). This showed that although both the wiper and glass vibrate with the same frequency, it is the latter that transmits sound to the air. Results from the high-speed camera and microphone have shown that the frequency of the rubber vibration equals to the frequency of the emitted sound and the water vibration. This frequency is the same as the eigen frequencies determined from a finite element model of the wiper, which was developed. These observations led to the conclusion that friction induced noise occurs only when bending modes of the wiper are excited and this has important implications for the control of FIV since it shows that emitted sound can be eliminated by modifying the blade geometry during the design stage. Another important observation is that the frequency of squeak decreases with increasing volume of water present on the glass. This is attributed to the water effectively adding mass onto the vibrating system and hence reducing its natural frequency. Additionally, capillary waves have been for the first observed in the water surrounding the wiper contact. Based on the understanding gained, a number of recommendations are made regarding means of reducing windscreen wiper noise. Finally, in order to monitor the wiping performance of the rubber wiper, a fluorescence microscopy technique was developed to view the sliding contact. This has enabled the fluid film thickness within the blade/glass contact to be assessed and also manufacturing defects, such as notches and inclusions, to be identified as the cause of wipe quality issues, such as hazing and hairlines.Open Acces

    Effect of light source on the sorting performance of a vision-based robot system

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    Industries look toward computer vision as a means to automate materials handling. To make this choice more appealing, useful and feasible vision applications must be explored. However, illuminance variation in the factory environment can undermine the capability and applicability of vision-based control systems. The purposes of this study were (a) to design and develop a vision-based robot material sorting system, (b) to determine the optimal settings for this system under fluorescent and incandescent lighting for two different color parts on a moving conveyor, and (c) to determine the sorting performance of this system under each light source. The main components of this experimental system consisted of: (a) a SCORBOT ER-V plus (ESHED ROBOTEC) robot system with a slide base and a speed controlled conveyor, (b) a ROBOTVISIONplus vision system, (c) an incandescent lamp light intensity controller, and (d) two PCs. By integrating these components, color sorting applications were developed. This study was limited to the sorting of two parts with different colors and similar geometry from a moving conveyor. The system performance (sorting) data were collected on the developed application under fluorescent and incandescent light sources with a conveyor speed of 50 mm/s at various illuminations. This study explored two sorting methods. Method A used the difference in object descriptors to separate the dominos. Method A worked in a limited range of illuminance and identification tolerance for both light sources. Method B used the difference in the observed “saturation” response of the charge coupled device camera to difference in the observed “saturation” response of the charge coupled device camera to separate the dominos. The “saturation” response region described the interval of illuminance where changes in illuminance did not produce a corresponding change in objects’ measured grayvalue. Method B worked in a wide range of illumination with no stipulation on identification tolerances for both light sources. Unexpectedly, the light sources in the laboratory setting exhibited a large amount of illuminance variation, and these variations caused applications developed using Method A to perform erratically for both light sources. However, Method B sorted reliably over a wide illuminance range: 150 to 1500 lux for incandescent and 214 to 760 lux for fluorescent

    Fluorescence and Adaptation of Color Images

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    Color plays a vitally important role in the world we live in. It surrounds us everywhere we go. Achromatic life, restricted to black, white and grey, is extremely dull. Color fascinates artists, for it adds enormously to aesthetic appreciation, directly invoking thoughts, emotions and feelings. Color fascinates scientists. For decades, scientists in color imaging, printing and digital photography have striven to satisfy increasing demands for accuracy in color reproduc- tion. Fluorescence is a very common phenomenon observed in many objects such as gems and corals, writing paper, clothes, and even laundry detergent. Traditional color imaging algo- rithms exclude fluorescence by assuming that all objects have only an ordinary reflective com- ponent. The first part of the thesis shows that the color appearance of an object with both reflective and fluorescent components can be represented as a linear combination of the two components. A linear model allows us to separate the two components using independent component analysis (ICA). We can then apply different algorithms to each component, and combine the results to form images with more accurate color. Displaying color images accurately is as important as reproducing color images accurately. The second part of the thesis presents a new, practical model for displaying color images on self-luminous displays such as LCD monitors. It shows that the model accounts for human visual system’s mixed adaptation condition and produces results comparable to many existing algorithms
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