ABSTRACT
Several Applications for tunable laser diodes have strict constraints in terms of overall power consumption. Furthermore, the implementation in harsh environments with large temperature fluctuations is necessary. Due to the constraint in power consumption, the application of active cooling might not be an option. For this reason we investigate the temperature characteristics of an electrically pumped MEMS-VCSEL with wide continuous wavelength tuning. For the first time, a mode hop free single mode (side mode suppression ratio (SMSR) > 40dB) tuning range of 45nm at 70°C is demonstrated with a MEMS-VCSEL. An increase of the tuning range from 85nm at 20°C to 92nm at 40°C is measured and explained. In contrast to fixed wavelength VCSEL, the investigated device shows a negative temperature induced wavelength shift of -4.5nmK(-1), which is caused by the MEMS-mirror. At 1560nm, the fibre-coupled optical output power is above 0.6mW over the entire temperature range between 20°C to 70°C and shows a maximum of > 3mW at 20°C.
ABSTRACT
For the first time a vertical-cavity surface-emitting laser (VCSEL) with a single-mode wavelength-tuning over 102 nm in the range of 1550 nm is demonstrated. The fiber-coupled optical output power has a maximum of 3.5 mW and is > 2 mW over the entire tuning range. The sidemode suppression ratios are > 45 dB. The wavelength tuning is achieved with the micro-electro mechanical actuation of a mirror membrane fabricated with surface micro-machining for on-wafer mass production. The mirror membrane consists of low cost dielectric materials (SiOx/SiNy) deposited with low temperature (< 100°C) Plasma Enhanced Chemical Vapor Deposition (PECVD).
ABSTRACT
The slit lamp microscope is the most popular opthalmologic instrument comprising a microscope with a light source attached to it. The coupling of microscope and light source distinguishes it from other optical devices. In this paper an Auto Focus system is proposed that considers this mechanical coupling and compensates for movements of the patient. It tracks the patients eye during the focusing process and applies a robust contrast-measurement algorithm to an area relative to it. The proposed method proved to be very accurate, reliable and stable, even starting from very defocused positions.
Subject(s)
Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Lighting/instrumentation , Microscopy/instrumentation , Microscopy/methods , Ophthalmoscopes , Ophthalmoscopy/methods , Algorithms , Feedback , Image Enhancement/instrumentation , Image Interpretation, Computer-Assisted/instrumentation , Lighting/methods , Motion , Optical Devices , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
OBJECTIVE: To evaluate the potential effect of computer support on general practitioners' prescribing, and to compare the effectiveness of three different support levels. DESIGN: Crossover experiment with balanced block design. SUBJECTS: Random sample of 50 general practitioners (42 agreed to participate) from 165 in a geographically defined area of Oxfordshire. INTERVENTIONS: Doctors prescribed for 36 simulated cases constructed from real consultations. Levels of computer support were control (alphabetical list of drugs), limited support (list of preferred drugs), and full support (the same list with explanations available for suggestions). MAIN OUTCOME MEASURES: Percentage of cases where doctors ignored a cheaper, equally effective drug; prescribing score (a measure of how closely prescriptions matched expert recommendations); interview to elicit doctors' views of support system. RESULTS: Computer support significantly improved the quality of prescribing. Doctors ignored a cheaper, equally effective drug in a median 50% (range 25%-75%) of control cases, compared with 36% (8%-67%) with limited support and 35% (0-67%) with full support (P < 0.001). The median prescribing score rose from 6.0 units (4.2-7.0) with control support to 6.8 (5.8 to 7.7) and 6.7 (5.6 to 7.8) with limited and full support (P < 0.001). Of 41 doctors, 36 (88%) found the system easy to use and 24 (59%) said they would be likely to use it in practice. CONCLUSIONS: Computer support improved compliance with prescribing guidelines, reducing the occasions when doctors ignored a cheaper, equally effective drug. The system was easy to operate, and most participating doctors would be likely to use it in practice.
