Acousto-optic devices. Optical elements for spectroscopy.
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Acoustics↗
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Results for “Optical Devices”
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Visualisation of tibiofemoral contact in total knee replacement using optical device.
An in situ optical visualization technique (OVT) has been developed to identify the tibiofemoral contact (TFC) area during prosthesis indentation. An artificial total knee replacement (TKR) with borosilicate glass femoral component has been reproduced similarly to the original one. The medial and lateral contact areas have been observed, located and measured by means of in situ OVT. Therefore, it was experimentally possible to ensure a good axial alignment of the femoral component and tibial polyethylene insert. In addition, experimental measurement for load-displacement curves became reproducible. Furthermore, the evolution of the medial and lateral TFC areas as a function of the normal load was established. Finally, this study has shown that the in situ OVT is a simple in vitro method that provides comparable results with well-known methods such as Fuji film technique.
Arthroplasty, Replacement, Knee↗
Artificial neural networks as a method to improve the precision of subcutaneous adipose tissue thickness measurements by means of the optical device LIPOMETER.
The LIPOMETER is an optical device for measuring the thickness of a subcutaneous adipose tissue layer. It illuminates the interesting layer, measures the backscattered light signals and from these, it computes absolute values of subcutaneous adipose tissue layer thickness (in mm). Previously, these light pattern values were fitted by nonlinear regression analysis to absolute values provided by computed tomography. Nonlinear regression analysis might provide slight limitations for our problem: a selected curve type cannot be changed afterwards during the application of the measurement device. Artificial neural networks yield a more flexible approach to this fitting problem and might be able to refine the fitting results. In the present paper we compare nonlinear regression analysis with the behaviour of different architectures of multilayer feed forward neural networks trained by error back propagation. Specifically, we are interested whether neural networks are able to yield a better fit of the LIPOMETER light patterns to absolute subcutaneous adipose tissue layer thicknesses than the nonlinear regression techniques. Different architectures of these networks are able to surpass the best result of regression analysis in training and test, providing higher correlation coefficients, regression lines with absolute values obtained from computed tomography closer to the line of identity, decreased sums of absolute and squared deviations, and higher measurement agreement.
Adult↗
[Peritoneoscopy with 2 optical devices: reduced risk - better diagnostic results (author's transl)].
Peritoneoscopy with 2 optical devices was performed in two cases; the technique of this procedure is described. The method allows inspection of areas, which cannot be seen during routine peritoneoscopy, especially of the anterior abdominal wall and of intraabdominal organs covered by adhesions. In addition, this method allows to find out, whether the anterior abdominal wall and vessels in it were injured by the troikart; the risk of the procedure is reduced thereby. Using a second optical device allows to visualize areas, which cannot be studied during routine peritoneoscopy because of intraabdominal adhesions. Thus better diagnostic results can be achieved with this method as compared to the routine technique.
Aged↗
A comparison of patient reading performance and preference: optical devices, handheld CCTV (Innoventions Magni-Cam), or stand-mounted CCTV (Optelec Clearview or TSI Genie).
BACKGROUND: Clinicians frequently prescribe reading devices for low vision patients having a central field loss. This study seeks to provide comparative information the clinician can use to assist patients in selecting the most cost-effective device(s) for reading. METHOD: In this study we compared optical devices with two types of closed-circuit televisions (CCTVs) that differed in two important characteristics: price, and whether the camera was stand-mounted with an X-Y table or whether the camera was handheld. A "within-subjects" design was used with 22 subjects. The primary comparisons between devices were subject reading speed, duration, and preference. RESULTS: Subject reading speed and duration were significantly greater with the CCTV systems than with optical devices; however, no significant performance differences were found between the two types of CCTVs. Patients did express a clear preference for one versus the other type of CCTV, with an overall preference for the stand-mounted system. When asked to consider the price differential between types of CCTVs, patient preferences were about equally divided. CONCLUSIONS: Clinicians can expect significantly better initial reading performance for patients with central visual-field losses when reading with CCTVs versus optical devices. Handheld CCTVs, when compared with stand-mounted systems, are less expensive, provide equal performance, and have slightly lower subject preference ratings. The current study provides clinicians with objective performance data and subjective preference data that can be used to help patients with central visual-field losses select the most cost-effective reading device.
Aged↗
Estimating percentage total body fat and determining subcutaneous adipose tissue distribution with a new noninvasive optical device LIPOMETER.
A newly developed optical device was applied to measure the subcutaneous adipose tissue (SAT) thickness of 20 healthy women and 18 healthy men at specified body sites. These measurements were used to derive equations to estimate percentage total body fat (TBF%). Total body electrical conductivity (TOBEC) was employed as a reference method; caliper techniques and measurements of absorbances of infrared light in fat versus lean tissue were also compared. The LIPOMETER results show good agreement with TOBEC data (r = 0.96). The technique allows the precise determination of the distribution of SAT thickness at specified body sites. The method also permits the construction of profiles of SAT thicknesses, e.g., the profiles are significantly different between women and men. Based on the normal profiles of healthy subjects, patients with proven type-2 diabetes mellitus were also evaluated. The patients showed significantly different profiles. By linear discriminant analysis, classification functions were extracted with good predictive accuracy classification of subjects according to the presence or absence of type-2 diabetes mellitus. The data suggest that measurement of SAT thickness might aid in the diagnosis and/or classification of metabolic disorders. Am. J. Hum. Biol. 12:221-230, 2000. Copyright 2000 Wiley-Liss, Inc.
Journal Article↗
Refinement of an optical device that stabilizes vision in patients with nystagmus.
An optical device that produces partial stabilization of retinal images has been described. It consists of a high-plus spectacle lens used in combination with a large, high-minus, polymethyl methacrylate (PMMA) contact lens. This device is designed to provide more clear and stable vision in patients with acquired nystagmus due to neurological disease. We report success in using a smaller, rigid, gas permeable (RGP) contact lens that achieves the required degree of stabilization, but is more comfortable for patients than the PMMA contact lens originally described. We have confirmed that the degree of retinal image stabilization is similar to that achieved with the PMMA lens. We present a case report to illustrate its use.
Adult↗
Optical devices used for image analysis of pigmented skin lesions: a proposal for quality assurance protocol using tissue-like phantoms.
Different technological tools have been developed to aid in the diagnosis of pigmented skin lesions, including cameras working with conventional RGB colour systems, epiluminescence microscopy and spectrophotometric methods using visible and near infrared wavelengths. All the different procedures should provide in an objective and reproducible fashion quantitative measurements of the colour and shape features of a given skin mole. At present, many devices have been introduced in experimental stages for clinical diagnosis, mainly used to provide to the clinicians an objective, computer-assisted second opinion. As for any diagnostic instruments, optical devices should also be subjected to a dedicated quality assurance protocol in order to evaluate the response repeatability of each device (intra-instrument agreement) and to check the accordance among the responses of different devices (inter-instrument agreement). The aim of this study was to design a quality assurance protocol for optical devices dedicated to image analysis of pigmented skin lesions and, in case, to detect cutaneous melanoma by using suitable tissue-like phantoms as standard references that enable testing of both hardware and software components. As an example, we report the results of intra-instrument and inter-instrument agreement when the protocol was applied on a series of 30 SpectroShade instruments, a novel optical device based on multi-spectral image analysis of colour and shape features of pigmented skin lesion.
Biophysical Phenomena↗
[Utilization of optical devices and equipments by students with visual impairment].
PURPOSE: To verify perceptions and conduct of students with visual impairment regarding devices and equipment utilized in schooling process. METHODS: A transversal descriptive study on a population of 12-year-old or older students in schooling process, affected by congenital or acquired visual impairment, inserted in the government teaching system of Campinas during the year 2000. An interview quiz, created based on an exploratory study was applied. RESULTS: A group of 26 students, 46% of them with low vision and 53.8% affected by blindness was obtained. Most of the students were from fundamental teaching courses (65.4%), studying in schools with classrooms provided with devices (73.1%). Among the resources used in reading and writing activities, 94.1% of the students reported they used the Braille system and 81.8% reported that the reading subject was dictated by a colleague. Most of the students with low vision wore glasses (91.7%), and 33.3% utilized a magnifying glass as optical devices. Among the non-optical devices, the most common were the environmental ones, getting closer to the blackboard (75.0%) and to the window (66.7%) for better lighting. CONCLUSIONS: It became evident that students with low vision eye-sight made use of devices meant for bearers of blindness, such as applying the Braille system. A reduced number of low vision students making use of optical and non-optical devices applicable to their problems were observed, indicating a probable unawareness of their visual potential and the appropriate devices to improve efficiency.
Child↗
Optical phase shifting with acousto-optic devices.
A novel optical phase-shifting method based on a well-known acousto-optic interaction is proposed. By using a pair of acousto-optic modulators (AOMs) and properly aligning them, we construct an optical phase shifter that can directly control the phase of a collimated beam. The proposed phase shifter is insensitive to the polarization of the incident beam when polarization-insensitive AOMs are used, and no calibration is necessary. The proposed approach is confirmed with experimental results.
Journal Article↗
La3Ga5SiQ14 single-crystal Q switch used as an electro-optic device.
A new kind of electro-optic Q switch is designed by use of a La3Ga5SiQ14 (LGS) crystal. Because the LGS crystal is optically active, the Q switch is based on the consideration that the total rotation angle of the polarization plane is zero, whereas the polarized wave propagates through the Pockels cell back and forth, with the polarization plane gyration and electro-optic effect existing simultaneously. The LGS Q switch is a practical electro-optic device that can be used in medium output energy lasers to partially take the place of deuterated potassium dihydrogen phosphate and lithium niobate Q switches.
Journal Article↗
The effect of optical devices and repeated trials on the velocity of saccadic eye movements.
OBJECTIVE: The purpose of this prospective study was to analyze the effect of glasses and contact lenses on the latency and velocity of visually evoked saccadic eye movements. MATERIAL AND METHODS: A saccadic test was performed 10 times on 20 emmetropic controls (Group A) and 20 ametropic test subjects with myopia (Group B) who were using glasses (Subgroup Bg) or contact lenses (Subgroup Bc). RESULTS: No training or fatigue effect on either latency or eye velocity was registered. Regardless of visual acuity (Group A or B) or of the optical device used (Subgroup Bg or Bc), no significant intergroup difference in latency could ultimately be established. Subgroup Bc showed a significantly slower eye velocity than Group A. Regardless of the optical device used, subjects with a higher degree of myopia (> 6 D) showed a lower eye velocity than the Group A controls. Additionally, saccadic velocity was lower in this subgroup ( > 6 D) in subjects using contact lenses than in those using glasses. CONCLUSION: These results demonstrate that optical devices have an influence on the electronystagmographical analyses of the vestibulo-ocular reflex that must be taken into consideration, particularly in scientific investigations.
Adult↗
[Method and optical device for exactly hinge axis localization tested on original phantom].
The quickly and exactly method of location of the hinge-axis is based on the moiré effect, produced between two superposed optical nets, one of it being moved. A face bow is fixed on the mandible to the occlusion rim. Two optical devices are mounted on the bottoms of the face bow. Two other optical nets are applied on the skin, corresponding to the TMJ. During the opening movements of the mandible when a pure rotation of the mandibular condiles take place on the TMJ, the optical nets are displaced and me exactly register the place corresponding to the rotation axe and we can note on the skin the hinge axis. The checkout was done using a phanthom achieved in our department, consisting of a skull made up of polyestheric resins and an elastic element made up of PVC.
Cephalometry↗
[Light-optical device for fiber light guides].
The paper gives a calculation method for a lighting optical device consisting of light flux concentrator lamps rigidly installed in an ellipsoid reflector with heat-permeable coating, and the parameters of two big concentrator lamps for fibre endoscopes.
Endoscopes↗
A simple optical device for measuring free surface deformations of nontransparent liquids.
In this paper, a novel optical device for measuring the deformation of liquid free surfaces is presented. The device employs a laser beam, which can be focused on any chosen location on the free surface. The key measurement is of the intensity of the beam reflected from a location on the free surface where the deformation exhibits a local extremum. The optics of the device is so designed as to measure a maximum intensity when the distance between the focusing lens and the selected point on the free surface is equal to the focal length, thus enabling a height measurement. The device is tested in ferrofluid pools where the height of the spikes of the normal field instability is measured. The simplicity of the suggested technique enables the fabrication of a quite cheap device for measuring surface deformation of nontransparent liquids, which provides good accuracy and reproducibility.
Journal Article↗
Comparison of central corneal thickness measurements with a new optical device and a standard ultrasonic pachymeter.
PURPOSE: To compare central corneal thickness (CCT) values obtained with ultrasonic pachymetry and a new optical method using partial coherence interferometry (PCI). SETTING: Department of Ophthalmology, Medical Health and Science Center, University of Debrecen, Debrecen, Hungary. METHODS: The study comprised 136 eyes of 70 patients whose spherical refractive error was not greater than +/-6.0 diopters (D) and whose keratometric astigmatism was not greater than 2.0 D. Central corneal thickness was measured 5 times with a new optical device (ACMaster, Zeiss) and with an ultrasonic pachymeter (AL-2000, Tomey). All measurements were obtained by the same investigator. RESULTS: Mean CCT was 531.2 microm +/- 3.9 (SD) with PCI and 547.8 +/- 36.0 microm with the ultrasonic device. The difference between groups was significant (P = .001). There was no difference between CCT values measured in right and left eyes (P = .55) with ultrasonography and PCI (P = .67). The coefficient variation was 0.73% for PCI and 6.5% for ultrasonography. Correlation between the CCT measurements with both devices was strong and statistically significant (Spearman correlation = .91, P = .001). CONCLUSIONS: Mean CCT values measured by the PCI method were significantly smaller than those measured by the ultrasonic device. Central corneal thickness measured with PCI is more reproducible and seems to be more reliable than that measured by ultrasonography.
Adult↗
An infra-red fibre optic device for cardiac cycle timing and photoplethysmography.
In this work a simple fibre optic device using infra-red radiation is used to obtain information on the timing of the cardiac cycle and blood volume changes in the flow of blood in the body. The device is small, non-invasive and free from interference by surrounding electromagnetic fields enabling it to be used in the environment of such devices as NMR scanners.
Cardiography, Impedance↗
The matching of physical models to three-dimensional electron-density maps: a simple optical device.
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Biophysics↗