Frequency stability of a self-phase-locked degenerate continuous-wave optical parametric oscillator

The properties of a self-phase-locked by-2-divider optical parametric oscillator are presented. A locking range of up to 156 MHz is measured, and the divider's relative frequency stability is shown to be better than 6/spl times/10/sup -14/

Incremental concept learning with few training examples and hierarchical classification

Object recognition and localization are important to automatically interpret video and allow better querying on its content. We propose a method for object localization that learns incrementally and addresses four key aspects. Firstly, we show that for certain applications, recognition is feasible with only a few training samples. Secondly, we show that novel objects can be added incrementally without retraining existing objects, which is important for fast interaction. Thirdly, we show that an unbalanced number of positive training samples leads to biased classi er scores that can be corrected by modifying weights. Fourthly, we show that the detector performance can deteriorate due to hard-negative mining for similar or closely related classes (e.g., for Barbie and dress, because the doll is wearing a dress). This can be solved by our hierarchical classi cation. We introduce a new dataset, which we call TOSO, and use it to demonstrate the e ectiveness of the proposed method for the localization and recognition of multiple objects in images.This research was performed in the GOOSE project, which is jointly funded by the enabling technology program Adaptive Multi Sensor Networks (AMSN) and the MIST research program of the Dutch Ministry of Defense. This publication was supported by the research program Making Sense of Big Data (MSoBD).peer-reviewe

Letter from [?] to John Muir, 1907 Aug 14.

A. G. BARBER, PRES. & TREAS.F. A. BARBER, VICE PRES.FOUNDED 1889.INCORPORATED 1894.R. C. THOMPSON, ASST. TREAS.,MANAGER.W. W. SLADE, SECRETARY,SUPERINTENDENT.GLOBE OPTICAL COMPANYTHE HOUSE OF NEW ENGLANDMANUFACTURERS IMPORTERS EXPORTERSOPTICAL GOODS.MARLBORO BUILDING, 403 WASHINGTON ST.SURGICAL INSTRUMENTS,EYE, EAR, NOSE & THROAT.NEW ENGLAND AGENTSHARDYS OPHTHALMOMETERSDE-ZENGS LUMINOUSINSTRUMENTSSHUR-ON & SO-EASYMOUNTINGSMAKERS OFTORIC AND SPECIAL LENSES.INVISIBLE BIFOCALS.OPTICAL MACHINERYAND WORK BENCHES.GLOBE TABLES AND CABINETS.GLOBE EAR-PHONES.Los Angeles, Calif.August 14, 1907.John Muir,Martinez, Cal.Dear Mr. Muir:As you will see by this letter, I have returned from the Sierra Club outing, and am feeling finely; ready for another year of hard work.I am sending you under separate cover, catalogue of Microscopes and Accessories, made by the Bausch & Lomb Optical Co., of Rochester, New york. I wrote Mr. Edw. Bausch from camp, explaining what you wanted in the way of a Microscope, and a letter just received, advising Stands AH or BH, illustrated on pages 21 and 22 of catalogue.I should advise Stand BH4 as being the best all round Microscope for such work as you want. By reference to page 63, you will see that with the two-inch eye-piece, and the 2/3 objective, you will get 41 diameters, while with the one-inch eye-piece and 1/6 objective, you will get 585 diameters; thus giving you quite a range of power, with a very low priced Microscope.For the proper illumination of opaque objects, I should recommend using the new Vertical Illuminator, illustrated on page 72. This illuminator has recently been improved, and the price changed to $7.50.I believe I mentioned Dissecting Microscopes; the Y Stand illustrated on page 52, is very good, but you can get only 40 diameters magnification, and the lens giving\u27 this power is of short focus, with very small field.Pocket Magnifiers are illustrated on page 59, and as you will note, have recently been raised in price. These are not mounted in Aluminum, as you mentioned to me, but the German Silver is said to be stiffer and meanly as light.I shall be in San Francisco, Monday, the 19th inst., and if you would like to have me send you a Microscope and some Magnify-0391

The content of optometric eye examinations for a presbyopic patient presenting with symptoms of flashing lights

Background:  Standardised patients (SPs) are the gold standard methodology for evaluating clinical care. This approach was used to investigate the content of optometric eyecare for a presbyopic patient who presented with recent photopsia. Methods:  A total of 102 community optometrists consented to be visited by an actor for a recorded eye examination. This actor received extensive training to enable accurate reporting of the content of the eye examinations, via an audio recording and a checklist completed for each clinical encounter. The actor presented unannounced (incognito) as a 59-year-old patient seeking a private eye examination and complaining of recent onset flashing lights. The results of each clinical encounter were recorded on a pre-designed checklist based on evidence-based reviews on photopsia, clinical guidelines and the views of an expert panel. Results:  The presence of the symptom of photopsia was proactively detected in 87% of cases. Although none of the optometrists visited asked all seven gold standard questions relating to the presenting symptoms of flashing lights, 35% asked four of the seven questions. A total of 85% of optometrists asked the patient if he noticed any floaters in his vision and 36% of optometrists asked if he had noticed any shadows in his vision. The proportion of the tests recommended by the expert panel that were carried out varied from 33 to 100% with a mean of 67%. Specifically, 66% recommended dilated fundoscopy to be carried out either by themselves or by another eyecare practitioner, and 29% of optometrists asked the patient to seek a second opinion regarding the photopsia. Of those who referred, 70% asked for the referral to be on the same day or within a week. Conclusion:  SP encounters are an effective way of measuring clinical care within optometry and should be considered for further comparative measurements of quality of care. As in research using SPs in other healthcare disciplines, our study has highlighted substantial differences between different practitioners in the duration and depth of their clinical investigations. This highlights the fact that not all eye examinations are the same but inherently different and that there is no such thing as a ‘standard sight test’. Future optometric continuing education could focus on history taking, examination techniques and referral guidelines for patients presenting with symptoms of posterior vitreous detachment, retinal breaks and secondary retinal detachment

Time resolution of the plastic scintillator strips with matrix photomultiplier readout for J-PET tomograph

Recent tests of a single module of the Jagiellonian Positron Emission Tomography system (J-PET) consisting of 30 cm long plastic scintillator strips have proven its applicability for the detection of annihilation quanta (0.511 MeV) with a coincidence resolving time (CRT) of 0.266 ns. The achieved resolution is almost by a factor of two better with respect to the current TOF-PET detectors and it can still be improved since, as it is shown in this article, the intrinsic limit of time resolution for the determination of time of the interaction of 0.511 MeV gamma quanta in plastic scintillators is much lower. As the major point of the article, a method allowing to record timestamps of several photons, at two ends of the scintillator strip, by means of matrix of silicon photomultipliers (SiPM) is introduced. As a result of simulations, conducted with the number of SiPM varying from 4 to 42, it is shown that the improvement of timing resolution saturates with the growing number of photomultipliers, and that the 2 x 5 configuration at two ends allowing to read twenty timestamps, constitutes an optimal solution. The conducted simulations accounted for the emission time distribution, photon transport and absorption inside the scintillator, as well as quantum efficiency and transit time spread of photosensors, and were checked based on the experimental results. Application of the 2 x 5 matrix of SiPM allows for achieving the coincidence resolving time in positron emission tomography of $\approx$ 0.170 ns for 15 cm axial field-of-view (AFOV) and $\approx$ 0.365 ns for 100 cm AFOV. The results open perspectives for construction of a cost-effective TOF-PET scanner with significantly better TOF resolution and larger AFOV with respect to the current TOF-PET modalities.Comment: To be published in Phys. Med. Biol. (26 pages, 17 figures

From white elephant to Nobel Prize: Dennis Gabor’s wavefront reconstruction

Dennis Gabor devised a new concept for optical imaging in 1947 that went by a variety of names over the following decade: holoscopy, wavefront reconstruction, interference microscopy, diffraction microscopy and Gaboroscopy. A well-connected and creative research engineer, Gabor worked actively to publicize and exploit his concept, but the scheme failed to capture the interest of many researchers. Gabor’s theory was repeatedly deemed unintuitive and baffling; the technique was appraised by his contemporaries to be of dubious practicality and, at best, constrained to a narrow branch of science. By the late 1950s, Gabor’s subject had been assessed by its handful of practitioners to be a white elephant. Nevertheless, the concept was later rehabilitated by the research of Emmett Leith and Juris Upatnieks at the University of Michigan, and Yury Denisyuk at the Vavilov Institute in Leningrad. What had been judged a failure was recast as a success: evaluations of Gabor’s work were transformed during the 1960s, when it was represented as the foundation on which to construct the new and distinctly different subject of holography, a re-evaluation that gained the Nobel Prize for Physics for Gabor alone in 1971. This paper focuses on the difficulties experienced in constructing a meaningful subject, a practical application and a viable technical community from Gabor’s ideas during the decade 1947-1957

astroplan: An Open Source Observation Planning Package in Python

We present astroplan - an open source, open development, Astropy affiliated package for ground-based observation planning and scheduling in Python. astroplan is designed to provide efficient access to common observational quantities such as celestial rise, set, and meridian transit times and simple transformations from sky coordinates to altitude-azimuth coordinates without requiring a detailed understanding of astropy's implementation of coordinate systems. astroplan provides convenience functions to generate common observational plots such as airmass and parallactic angle as a function of time, along with basic sky (finder) charts. Users can determine whether or not a target is observable given a variety of observing constraints, such as airmass limits, time ranges, Moon illumination/separation ranges, and more. A selection of observation schedulers are included which divide observing time among a list of targets, given observing constraints on those targets. Contributions to the source code from the community are welcome