Portable high-end instrument for in-vivo infrared spectroscopy using spread spectrum modulation

Near infrared spectroscopy (NIRS) can be employed to monitor noninvasively and continuously local changes in hemodynamics and oxygenation of human tissues. In particular, the technique can be particularly useful for muscular functional monitoring during unattended physical activity. A portable NIRS research-grade acquisition system, dedicated to low-noise measurements during muscular exercise, is presented. A spread-spectrum multiplexing scheme significantly enhances system performance. The resulting instrument is compact, lightweight and efficient. Preliminary tests on oxygen consumption during exercise and venous occlusion show excellent detectivity and time response

Photometric compliance of tablet screens and retro-illuminated acuity charts as visual acuity measurement devices

Mobile technology is increasingly used to measure visual acuity. Standards for chart-based acuity tests specify photometric requirements for luminance, optotype contrast and luminance uniformity. Manufacturers provide some photometric data but little is known about tablet performance for visual acuity testing. This study photometrically characterised seven tablet computers (iPad, Apple inc.) and three ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts with room lights on and off, and compared findings with visual acuity measurement standards. Tablet screen luminance and contrast were measured using nine points across a black and white checkerboard test screen at five arbitrary brightness levels. ETDRS optotypes and adjacent white background luminance and contrast were measured. All seven tablets (room lights off) exceeded the most stringent requirement for mean luminance (≥ 120 cd/m2) providing the nominal brightness setting was above 50%. All exceeded contrast requirement (Weber ≥ 90%) regardless of brightness setting, and five were marginally below the required luminance uniformity threshold (Lmin/Lmax ≥ 80%). Re-assessing three tablets with room lights on made little difference to mean luminance or contrast, and improved luminance uniformity to exceed the threshold. The three EDTRS charts (room lights off) had adequate mean luminance (≥ 120 cd/m2) and Weber contrast (≥ 90%), but all three charts failed to meet the luminance uniformity standard (Lmin/Lmax ≥ 80%). Two charts were operating beyond manufacturer’s recommended lamp replacement schedule. With room lights on, chart mean luminance and Weber contrast increased, but two charts still had inadequate luminance uniformity. Tablet computers showed less inter-device variability, higher contrast, and better luminance uniformity than charts in both lights-on and lights-off environments, providing brightness setting was >50%. Overall, iPad tablets matched or marginally out-performed ETDRS charts in terms of photometric compliance with high contrast acuity standards

3D reconstruction of the fundus of a phantom eye through stereo imaging of slit lamp images

In the detection of glaucoma, the second leading cause of blindness worldwide, the alteration of the optic disc's morphology is a key clinical indicator. The current gold standard test, stereo funduscopy using stereo fundus cameras, is subjective. Quantitative devices exist but are prohibitively expensive. Work carried out elsewhere has demonstrated quantitative results from stereo matching fundus camera images. Building on this idea, the slit lamp microscope (a mainstay of eye diagnostics, present in practically all ophthalmology and optometry practices) has the potential to be used as a quantitative device. This study explored the feasibility of uncalibrated 3D reconstructions of retinal structures of a phantom eye's fundus using a slit lamp

Photometric compliance of standard and digital infant acuity tests

Amblyopia or “lazy eye” affects approximately 2–5% of the general population in the UK[1]. Treatment must be started as early as possible as it is less effective after age 8[2]. The current gold standards for infant acuity testing are based on printed cardboard targets (‘standard tests’) and have been in place for almost 35 years[3]. In spite of this, no national nor international standard criteria are in place to quality assure them. Electronic platforms show promise to replace card-based tests[4]. However, the fast-changing nature and photometric differences across manufacturers of electronic devices makes them potentially inaccurate when used for visual testing[5]. This work studied the photometric compliance of three standard tests (Teller cards, Keeler cards, Lea Paddles) and four electronic displays (phone, tablet, laptop and 4k monitor)

Capacitance-conductance investigation on the phase transitions in Ga nanoparticles

We have reported on coupled capacitance-conductance measurements on Ga nanoparticles embedded in vitreous matrices. The melting of nanoparticles was clearly detected as an abrupt increase in the capacitance vs. temperature scans. The influence of the embedding matrix and of the frequency of the applied field on the dielectric response was checked. The presence of a hysteresis cycle between melting and solidification has been detected. The technique allows the identification of the various solid phases of confined Ga

The BepiColombo laser altimeter (BELA): Concept and baseline design

The BepiColombo Laser Altimeter (BELA) has been selected for flight on board the European Space Agency's BepiColombo Mercury Planetary Orbiter (MPO). The experiment is intended to be Europe's first planetary laser altimeter system. Although the proposed system has similarities to the Mercury Laser Altimeter (MLA) currently flying on board NASA's MESSENGER mission to Mercury, the specific orbit and construction of the MPO force the use of novel concepts for BELA. Furthermore, the base-lined range-finding approach is novel. In this paper, we describe the BELA system and show preliminary results from some prototype testing. (c) 2007 Elsevier Ltd. All rights reserved