Coaxial Light Source Research Articles

Prediction of milling surface roughness based on DGLCM and neural network

With the manufacturing industry’s increasingly automated and intelligent development, traditional workpiece roughness measurement methods can no longer meet the requirements for short time, high efficiency, and online measurement. Therefore, this article proposes a roughness evaluation model for vertical milling workpiece roughness measurement and improves upon the traditional Gray Level Co-occurrence Matrix (GLCM) method to achieve high accuracy and robustness in measuring milling surface roughness. First, the milled surface is illuminated by a coaxial light source, and an image is captured using an industrial camera and a telecentric lens. Then, four features of the image are extracted using the Direction Measure-based Gray Level Co-occurrence Matrix (DGLCM) to construct a feature descriptor. Finally, Finally, create an RBF network to predict surface roughness. Through experimental comparison with traditional GLCM feature extraction methods, our proposed feature extraction method has a prediction error of only 2.01%, which is superior to traditional methods.

Kinematics of the Upper Eyelid and the Globe During Downward Excursion With Comparative Analysis in Patients With Thyroid Eye Disease.

To analyze the kinematics of the upper eyelid and the globe on downward excursion for potential use in monitoring thyroid eye disease (TED) progression in an objective manner. Ten normal volunteers and 10 patients with TED were studied. A high-speed (240 fps) digital camera with a coaxial light source set at a constant distance from the subjects' eyes was used to record the excursion of the upper eyelid and the globe from extreme upgaze to extreme downgaze. Clinical data, including age, gender, race, thyroid function tests, Vision, Inflammation/Congestion, Strabismus/motility restriction, Appearance/exposure score (primary surgeons' preference of TED grading system), exophthalmometry, and eyelid measurements were collected for all patients with TED. Frame-by-frame analyses of the videos were performed using Python software (version 3.6) and the Open Source Computer Vision Library. Temporal resolution was obtained by measuring the number of frames from initiation of eyelid and globe movement from extreme upgaze (t 0 ) to extreme downgaze (t f ). Spatial resolution was obtained by measuring the number of pixels the eyelid margin and the globe traversed from t 0 to t f . The data were then plotted on a graph to calculate the velocity of the upper eyelid and the globe during downward excursion. Velocimetric calculations using high-speed photography suggests that downward excursion of the upper eyelid, and the globe occurs in 2 phases: the acceleration phase and the deceleration phase. Comparative analysis of slow-motion videography demonstrates that patients with TED were found to have attenuation in the early acceleration phase of upper eyelid excursion compared with normal subjects. In patients with TED, the difference in velocity between the eyelid and the globe occurs in the early deceleration phase. The upper eyelid normally synchronizes intimately with the globe during downward eye movement. Data from this study reveal that attenuation mostly in the early deceleration phase of eyelid movement relative to the globe accounts for the dynamic eyelid lag seen on clinical examination. Further analysis is needed to show if a quantified von Graefe sign can be used as an objective means of monitoring progression in TED.

Infrared All-Dielectric Metasurface Beam Splitter Based on Transflective Structures

Beam splitters are widely applied in various optical systems as a common beam-splitting device. The conventional stereoscopic and flat-type beam splitters greatly limit the packaging and integration of optical systems due to their large size and restricted emitting direction. Recently, beam-splitting devices made of various transmissive or reflective metasurfaces have shown the potential to overcome these challenges. However, in optical systems such as machine vision, these single-ended beam splitters increase the design complexity of the signal feedback link due to the limitation of the beam-splitting path direction. Here, we proposed and numerically simulated a transflective all-dielectric metasurface beam splitter by applying incompletely transmissive structural designs to the metasurface and using the transmission phase modulation mechanism. It can realize the beam separation for arbitrarily polarized incident light on the same side of the normal at both transmissive and reflective ends with a single-layer unit cell arrangement structure and has a similar emergence angle. The results reveal that at 1550 nm, the angular tolerance bandwidth is about 32°, the total splitting efficiency is over 90%, and the splitting ratio is approximately 1:1. After comparison and verification of simulation results, this transflective metasurface beam splitter is hopeful to be applied in new compact optical systems that require real-time signal feedback, such as coaxial light sources and photoelectric sensing.

Multilayer Soft Photolithography Fabrication of Microfluidic Devices Using a Custom-Built Wafer-Scale PDMS Slab Aligner and Cost-Efficient Equipment.

We present a robust, low-cost fabrication method for implementation in multilayer soft photolithography to create a PDMS microfluidic chip with features possessing multiple height levels. This fabrication method requires neither a cleanroom facility nor an expensive UV exposure machine. The central part of the method stays on the alignment of numerous PDMS slabs on a wafer-scale instead of applying an alignment for a photomask positioned right above a prior exposure layer using a sophisticated mask aligner. We used a manual XYZR stage attached to a vacuum tweezer to manipulate the top PDMS slab. The bottom PDMS slab sat on a rotational stage to conveniently align with the top part. The movement of the two slabs was observed by a monocular scope with a coaxial light source. As an illustration of the potential of this system for fast and low-cost multilayer microfluidic device production, we demonstrate the microfabrication of a 3D microfluidic chaotic mixer. A discussion on another alternative method for the fabrication of multiple height levels is also presented, namely the micromilling approach.

Imaging the pediatric retina: An overview.

Recent decade has seen a shift in the causes of childhood blinding diseases from anterior segment to retinal disease in both developed and developing countries. The common retinal disorders are retinopathy of prematurity and vitreoretinal infections in neonates, congenital anomalies in infants, and vascular retinopathies including type 1 diabetes, tumors, and inherited retinal diseases in children (up to 12 years). Retinal imaging helps in diagnosis, management, follow up and prognostication in all these disorders. These imaging modalities include fundus photography, fluorescein angiography, ultrasonography, retinal vascular and structural studies, and electrodiagnosis. Over the decades there has been tremendous advances both in design (compact, multifunctional, tele-consult capable) and technology (wide- and ultra-wide field and noninvasive retinal angiography). These new advances have application in most of the pediatric retinal diseases though at most times the designs of new devices have remained confined to use in adults. Poor patient cooperation and insufficient attention span in children demand careful crafting of the devices. The newer attempts of hand-held retinal diagnostic devices are welcome additions in this direction. While much has been done, there is still much to do in the coming years. One of the compelling and immediate needs is the pediatric version of optical coherence tomography angiography. These needs and demands would increase many folds in future. A sound policy could be the simultaneous development of adult and pediatric version of all ophthalmic diagnostic devices, coupled with capacity building of trained medical personnel.

Size Detection Method of Embedded Ball Based on Aviation Bearing Image

In the aerospace industry, bearing is widely used in various rotating machinery. The performance of bearing affects the operation of the whole machinery and even aviation equipment. The wrongly assembled ball due to size is an important reason for unqualified bearing. To solve this problem, an accurate ball detection method based on the bearing image is proposed. Firstly, according to the imaging characteristics of bearing and light propagation characteristics, an image collection system based on the coaxial light source is designed. Then, aiming at the problem that the embedded ball is occluded by the bearing ring and the cage, only partial ball in the narrow gap can be used to predict the full ball and the high-precision requirement of ball detection, a ball segmentation model based on DeepLab v3+ network is used to segment the local ball, and CBAM is added in the Xception network of the original network. According to the characteristics of the segmentation result, a circle detection algorithm based on circle fitting evaluation designed for incomplete short arc is proposed. Finally, according to the detection results, judge whether the bearing is qualified or not and evaluate the feasibility of this method. Experimental results show that the ball detection accuracy is about 27 microns, and the wrongly assembled ball with a size difference of only 198 microns can be distinguished. The false detection rate of unqualified bearing is 1%. As the last line of defense of bearing quality inspection, this method can achieve zero false detection rate of unqualified bearing in the industry.

Influence of different loupe systems and their light source on the vision in endodontics

The aim of this study was to evaluate the performance of Galilean and Keplerian loupes in the endodontic lumen with and without integrated light. Although the use of an operating microscope is widely recommended in endodontics it is uncertain whether an adequate loupe system with coaxial light source might replace the microscope for some endodontic work. Twenty-four dentists (age 27–64 years) underwent a miniaturized visual test inside the endodontic lumen of a natural molar: at the canal entrance, 5 mm inside the canal, and at the apex. The tooth was mounted in a phantom head in a simulated clinical setting. The naked eye (negative) and the microscope 6× (positive) served as control groups, and Galilean loupes 2.5× and Keplerian loupes 4.3× with and without a coaxial light source as experimental groups. A structure of 0.05 mm corresponding to the smallest instrument (06) was the threshold for sufficient vision. The loupe type, coaxial light source and the dentists’ age had a statistically significant influence at all locations. None of the loupes helped to visualize structures at the apex. At the canal entrance, the visual threshold was reached by dentists < 40 years with Galilean loupes, by dentists ≥ 40 years with Keplerian loupes, with and without coaxial light. Dentists < 40 years detected structures < 0.05 mm inside the root canal with Keplerian loupes and coaxial light. The microscope offered highly superior results. The naked eye was insufficient to reach the visual threshold at any location.

Influence of different loupe systems and their light source on the vision in endodontics

The aim of this study was to evaluate the performance of Galilean and Keplerian loupes in the endodontic lumen with and without integrated light. Although the use of an operating microscope is widely recommended in endodontics it is uncertain whether an adequate loupe system with coaxial light source might replace the microscope for some endodontic work. Twenty-four dentists (age 27–64 years) underwent a miniaturized visual test inside the endodontic lumen of a natural molar: at the canal entrance, 5 mm inside the canal, and at the apex. The tooth was mounted in a phantom head in a simulated clinical setting. The naked eye (negative) and the microscope 6× (positive) served as control groups, and Galilean loupes 2.5× and Keplerian loupes 4.3× with and without a coaxial light source as experimental groups. A structure of 0.05 mm corresponding to the smallest instrument (06) was the threshold for sufficient vision. The loupe type, coaxial light source and the dentists’ age had a statistically significant influence at all locations. None of the loupes helped to visualize structures at the apex. At the canal entrance, the visual threshold was reached by dentists < 40 years with Galilean loupes, by dentists ≥ 40 years with Keplerian loupes, with and without coaxial light. Dentists < 40 years detected structures < 0.05 mm inside the root canal with Keplerian loupes and coaxial light. The microscope offered highly superior results. The naked eye was insufficient to reach the visual threshold at any location.

Influence of different loupe systems and their light source on the vision in endodontics

The aim of this study was to evaluate the performance of Galilean and Keplerian loupes in the endodontic lumen with and without integrated light. Although the use of an operating microscope is widely recommended in endodontics it is uncertain whether an adequate loupe system with coaxial light source might replace the microscope for some endodontic work. Twenty-four dentists (age 27–64 years) underwent a miniaturized visual test inside the endodontic lumen of a natural molar: at the canal entrance, 5 mm inside the canal, and at the apex. The tooth was mounted in a phantom head in a simulated clinical setting. The naked eye (negative) and the microscope 6× (positive) served as control groups, and Galilean loupes 2.5× and Keplerian loupes 4.3× with and without a coaxial light source as experimental groups. A structure of 0.05 mm corresponding to the smallest instrument (06) was the threshold for sufficient vision. The loupe type, coaxial light source and the dentists’ age had a statistically significant influence at all locations. None of the loupes helped to visualize structures at the apex. At the canal entrance, the visual threshold was reached by dentists < 40 years with Galilean loupes, by dentists ≥ 40 years with Keplerian loupes, with and without coaxial light. Dentists < 40 years detected structures < 0.05 mm inside the root canal with Keplerian loupes and coaxial light. The microscope offered highly superior results. The naked eye was insufficient to reach the visual threshold at any location.

Smartphone guided wide-field imaging for retinopathy of prematurity in neonatal intensive care unit - a Smart ROP (SROP) initiative.

Purpose:To suggest a low cost, non-contact smartphone-based screening system in retinopathy of prematurity (ROP), and to illustrate its potential clinical application as a potential future tool for teleophthalmology.Methods:Neonatal intensive care unit (NICU)-based bedside ROP screening done between January 2018 and May 2018. Documentation of ROP was done by using a smartphone and +40D, +28D, or +20D indirect non-contact condensing lenses. By using the coaxial light source of the phone, this system works as an indirect ophthalmoscope that creates a digital image of the fundus. With smartphone-based camera we extracted high-quality still images extracted from the video clip.Results:Total of 228 eyes of 114 infants screened for ROP between January 2018 and May 2018. Incidence of total ROP was 23.68%, out of which incidence of type 1 ROP was 8.77%. After initial screening with indirect ophthalmoscope, we uesd smartphone imaging to document ROP in 28 eyes out of 55 eyes having ROP. Image quality was good in 89.28% eyes. Field of view vary from 46°, 53°, and 90° with +20D, +28D, and +40D indirect condensing lenses, respectively, which gives excellent images for bedside ROP documentation.Conclusion:The described technique of smartphone fundus photography is a light weight, cost-effective, user friendly, high-quality wide-field fundus photographs for bedside documentation of ROP in NICUs using readily available instruments that are handy and portable with simple power sources. Smartphones has the potential to be operated with only one hand. It can also be used as a future telescreening device.

Augmenting Photometric Stereo with Coaxial Illumination under Water

In this paper, two coaxial light sources are added to four light sources based on Photometric Stereo (PMS), and we put forward a kind of gradient fast algorithm. The simulation and underwater experiments show that the proposed algorithm can eliminate the influence of the shadow in four light photometric stereo algorithm and also reduce Mean Square absolute Error (MSE) and Relative Mean Square Error (RMSE) of underwater target 3D reconstruction, and can get underwater target albedo. This algorithm can be widely used in underwater target fast 3D reconstruction.

Simple, Inexpensive Technique for High-Quality Smartphone Fundus Photography in Human and Animal Eyes

Purpose. We describe in detail a relatively simple technique of fundus photography in human and rabbit eyes using a smartphone, an inexpensive app for the smartphone, and instruments that are readily available in an ophthalmic practice. Methods. Fundus images were captured with a smartphone and a 20D lens with or without a Koeppe lens. By using the coaxial light source of the phone, this system works as an indirect ophthalmoscope that creates a digital image of the fundus. The application whose software allows for independent control of focus, exposure, and light intensity during video filming was used. With this app, we recorded high-definition videos of the fundus and subsequently extracted high-quality, still images from the video clip. Results. The described technique of smartphone fundus photography was able to capture excellent high-quality fundus images in both children under anesthesia and in awake adults. Excellent images were acquired with the 20D lens alone in the clinic, and the addition of the Koeppe lens in the operating room resulted in the best quality images. Successful photodocumentation of rabbit fundus was achieved in control and experimental eyes. Conclusion. The currently described system was able to take consistently high-quality fundus photographs in patients and in animals using readily available instruments that are portable with simple power sources. It is relatively simple to master, is relatively inexpensive, and can take advantage of the expanding mobile-telephone networks for telemedicine.

Construction of 3D solder paste surfaces using multi-projection images

This paper aims to develop the 3D surface construction applications for the solder pastes using multi-projection images and the neural network approach. The proposed solution uses the image features of multi-projection angles as the inputs and the laser surface scanning results as the outputs of the neural network model to perform precise 3D solder paste surface construction. In this manner, the proposed methodology can measure the 3D solder paste surfaces in a precise way like the laser scanning results. The advantages of this work is to use a low cost and high speed image solution to overcome the disadvantages of high cost and slow speed laser solution while the inspection accuracy is maintained. The multi-projection images are captured from the multi-channel light source and the coaxial light source to perform precise and efficient inspections, respectively. On the other hand, the back-propagation (BP) neural network approach is used to construct the 3D solder paste surface models for various solder pad geometries. Finally, the proposed system was experimentally verified. The experimental results showed that the multi-channel light source solution with pad based learning achieves 95% volumetric accuracy in average, and the coaxial light source with sub-area based learning just achieves 80% volumetric accuracy in average when compared to the actual laser surface scanning.

Static Ocular Counterroll: Video-based Analysis After Minimizing the False-Torsion Factors

To determine the validity and usefulness of a newly developed measurement method of static ocular counterrolling (s-OCR) that eliminates false-torsion factors and to test the Jampel hypothesis that s-OCR does not exist. A lightweight measurement device, consisting of a video camera, a coaxial light source, and a laser pointer projecting a fixation target on the wall, was fixed to a subject's head by means of a mouthpiece. In 11 healthy adults (mean age: 30 +/- 15 years), digital images of the right eye were captured while the subject kept his head tilted at a randomly selected angle ranging from 0 degrees to 50 degrees . By a frame-by-frame analysis of movements of the corneal light reflex and the iris patterns, OCR was evaluated. Torsional eye movement in the opposite direction to head tilt was found in all subjects. The amount of torsion continuously increased until the head-tilt angle reached 40 degrees. The average (+/- SD) amplitude of a fitted sine curve was 7.6 +/- 3.2 degrees (range: 4.3 degrees-10.3 degrees), and the individual amplitude was significantly larger than the test-retest repeatability of the measurement (+/-1.7 degrees). The measurement method used in this study provided good test-retest repeatability and ease of application. The characteristics of torsional eye movements that we observed after minimizing the false-torsion factors agree with previous reports supporting the existence of s-OCR.

Multipurpose skin microscope–an aid to the assessment of treatment efficacy of skin disorders

High quality epiluminescence stereomicroscopes for the study of skin disorders are too massive and expensive to acquire for routine clinical use. Some dermatologists use otomicroscopes or operation microscopes for investigational purposes. Their construction is not suitable for the examination of the skin in general and their coaxial light sources provide flat illumination causing loss of contrast on the skin surface. In order to satisfy the apparent need for a suitable and economic stereomicroscope the author has constructed a moderately priced and versatile instrument for clinical use.

An ideal headlamp for overseas surgery.

A battery-powered headlamp with a point-source halogen bulb and rechargeable batteries is ideal for operating in underdeveloped facilities. It offers a coaxial light source that rivals the quality of fiberoptic illumination.

Powerful microsecond discharges in flash lamps

This paper develops practical recommendations for the matching of the electric circuitry with coaxial flash lamps in the case of micro-second discharges. Coaxial light sources were selected because they have superior characteristcs for the pumping of lasers on the basis of organic compounds. The instantaneous values of the discharge current and of the voltage at the coaxial flash lamp were determined from oscillograms of the pulses applied simultaneously to the input of an s8-2 double-beam oscilloscope from a Rogowski coil and from a resistive voltage divider. The relative difference between the calculated and experimental values of the peak power of the discharge are shown. The results allow one to combine an electric circuit and a flash lamp with certain discharge characteristics.

Brückner Test

Brückner, in 1962, published a paper in German describing a "trans-illumination" test extremely useful in the diagnosis of small angle deviations and amblyopia in young uncooperative children. A bright coaxial light source, such as a direct ophthalmoscope, is used. Both eyes of the patient are simultaneously illuminated from approximately one meter distance. First, the position of the corneal light reflex, (Hirschberg test), along with brightness difference of the fundus reflex as seen in the pupil through the ophthalmoscope, is evaluated. When strabismus is present. the fixing eye has a darker reflex than the deviated eye. The second step evaluates pupil size, pupil reaction, and fixation movement of the eyes on "successive" illumination of one eye at a time. This is useful in detecting amblyopia.