Working Distance Research Articles

Optical OAM tweezer based on graded-index multimode fibers.

A fiber-optic probe consisting of a section of graded-index multimode fiber (GIMF) fused onto a few-mode fiber (FMF) is proposed in this paper. The orbital angular momentum (OAM) mode guided by the FMF was launched into the GIMF, and a focused OAM beam profile was obtained by tailoring the length of the GIMF. Based on the analysis of the propagation trajectory, the intensity distributions, and the phase distributions of the vortex beam in GIMF, the focusing properties of the OAM mode were investigated. It is found that there exists a maximum working distance at an optimal GIMF length, and a trade-off between the beam size and working distance should be taken into account for optical tweezer applications. These results are expected to be applied to optical fiber tweezers for more flexible and efficient optical manipulation of particles.

Expansion tomography for large volume tissue imaging with nanoscale resolution.

Expansion microscopy enables conventional diffraction limit microscopy to achieve super-resolution imaging. However, the enlarged tissue lacks an objective lens with sufficient working distance that can image tissues with whole-brain-scale coverage. Here, we present expansion tomography (ExT) to solve this problem. We have established a modified super-absorbent hydrogel (ExT gel) that possesses high mechanical strength and enables serial sectioning. ExT gel enables tissue and cell imaging and is compatible with various fluorescent labeling strategies. Combining with the high-throughput light-sheet tomography (HLTP) system, we have shown the capability of large volume imaging with nanoscale resolution of mouse brain intact neuronal circuits. The ExT method would allow image samples to support super-resolution imaging of intact tissues with virtually unlimited axial extensions.

Dual-axis confocal configuration for depth sensitive fluorescence spectroscopy.

The dual-axis confocal (DAC) configuration provides a high axial resolution, long working distance (WD), and large dynamic range. These properties can reveal depth-resolved fluorescence spectra. We present a depth sensitive fluorescence spectroscopy based on the DAC configuration. The system enables high axial resolution of 3.23 µm and a long WD of 3.73 mm compared to that of 4.68 µm and 2.1 mm for comparable single-axis confocal configurations, respectively. Besides, a DAC configuration also offers a superior dynamic range and rejection of out-of-focus scattered light based on the principle of Huygens-Fresnel integrals. Additionally, to locate the target layer, the collection path of the DAC configuration will be used as the other illumination path, forming a dual-axis illumination configuration. These beam paths are used to locate the target layer using a white light imaging system with a commercial low numerical aperture objective. A multi-layer fluorescence phantom of Barrett's esophagus containing fluorescein isothiocyanate and Alexa Fluor 514 was used to verify the principle of depth-resolved fluorescence spectroscopy. The results show that the DAC configuration can collect fluorescence spectra from microscopic regions with high axial resolution.

Off-axis multilayer zone plate with 16 nm × 28 nm focus for high-resolution X-ray beam induced current imaging.

Using multilayer zone plates (MZPs) as two-dimensional optics, focal spot sizes of less than 10 nm can be achieved, as we show here with a focus of 8.4 nm × 9.6 nm, but the need for order-sorting apertures prohibits practical working distances. To overcome this issue, here an off-axis illumination of a circular MZP is introduced to trade off between working distance and focal spot size. By this, the working distance between order-sorting aperture and sample can be more than doubled. Exploiting a 2D focus of 16 nm × 28 nm, real-space 2D mapping of local electric fields and charge carrier recombination using X-ray beam induced current in a single InP nanowire is demonstrated. Simulations show that a dedicated off-axis MZP can reach sub-10 nm focusing combined with reasonable working distances and low background, which could be used for inoperando imaging of composition, carrier collection and strain in nanostructured devices.

A method of fine size measurement for telecentricity-based error compensation

Focusing on the stable magnification, near zero distortion, and wide field of depth (DoF), the telecentric optical system is well suited for size measurements with a large range of working distances. However, suffering from the telecentricity-based error (TBE), the size measurement is connected with the working distances and imaging position of the image sensor, even within the DoF. Therefore, a model of TBE compensation is established, inspired by the radial distortion model in the camera calibration. With the correction of radial distortion coefficients for different working distances, the TBE is evidently improved. The feasibility of the proposed method is verified both in the theory and experiment. Our results show that the uncertainty of size measurement at different working distances of the DoF is improved obviously after the TBE compensation, which is attractive for fine size measurements in industry.

Reported Patient Satisfaction and Spectacle Independence Following Bilateral Implantation of the PanOptix® Trifocal Intraocular Lens.

PurposeTo assess the spectacle independence and satisfaction of subjects after bilateral implantation of the PanOptix® trifocal intraocular lens (IOL) at the time of cataract surgery.DesignSingle site, prospective, single-arm study.MethodsEligible subjects interested in a trifocal IOL to potentially reduce dependence on spectacles for near, intermediate and distance vision were enrolled and followed for 3 months after the second eye surgery. Visual acuity and refractive data were collected 1 month and 3 months postoperative, including the uncorrected and best distance-corrected binocular visual acuities at distance (4m), intermediate (60 cm) and near (40cm). A patient satisfaction and spectacle independence questionnaire were administered at the 3-month visit.ResultsA total of 30 subjects successfully completed the study. Eighty-five percent of eyes (51/60) had a refraction within 0.50 D of plano with ≤ 0.50 D of refractive cylinder. One subject (3%) reported needing glasses for distance work, 3 (10%) for intermediate work and 4 (13%) for near work. Ninety percent or more of all subjects reported never wearing glasses or wearing them only a little at all working distances. Ninety percent or more were able to function without glasses at all 3 working distances all or most of the time. More than ninety percent of subjects reported being “com.pletely” or “mostly” satisfied with their vision without glasses or contact lenses at all three distances and overall.ConclusionA high percentage of patients are likely to achieve spectacle independence for distance, intermediate and near vision with this trifocal IOL.

Handheld optical coherence tomography scanner using a common-path probing arm with long working distance

In this study, a bending insensitive handheld optical coherence tomography (OCT) scanner is developed by means of common-path interferometric technique. The OCT source light is sent into a fiber based Michelson interferometer firstly and split into two portions. Light output from the Michelson interferometer, which consisting of two light components with different optical delay, is then guided into a common-path OCT probing arm with the extended working distance. The distal end of the probing fiber is polished with a small angle to serve as the reference plane of the OCT system. Theoretical analysis is carried out to derive the expression of the interference signal for the proposed imaging method, which agrees with experimental results. Measured OCT sensitivity is 100.9 dB at the sampling power of 580 μW. The performance of the OCT scanner is demonstrated through imaging biological samples.

Higher-order harmonic generation and strong field ionization with Bessel–Gauss beams in a thin jet geometry

A promising alternative to Gaussian beams for use in strong field science is Bessel–Gauss (BG or Bessel-like) laser beams, as they are easily produced with readily available optics and provide more flexibility of the spot size and working distances. Here we use BG beams produced with a lens-axicon optical system for higher-order harmonic generation (HHG) in a thin gas jet. The finite size of the interaction region allows for scans of the HHG yield along the propagation axis. Further, by measuring the ionization yield in unison with the extreme ultraviolet (XUV), we are able to distinguish regions of maximum ionization from regions of optimum XUV generation. This distinction is of great importance for BG fields, as the generation of BG beams with axicons often leads to oscillations of the on-axis intensity, which can be exploited for extended phase-matching conditions. We observed such oscillations in the ionization and XUV flux along the propagation axis for the first time. As is the case for Gaussian modes, the harmonic yield is not maximum at the point of highest ionization. Finally, despite Bessel beams having a hole in the center in the far field, the XUV beam is well collimated, making BG modes a great alternative when spatial filtering of the fundamental is desired.

Optimizing image contrast of second phases in metal alloys

Novel imaging strategies in the scanning electron microscope aimed at significantly improved image contrast of second phases in metal alloys are described. These include the use of low accelerating voltages, small working distances, and a novel detection system. Contrast is assessed as a function of voltage and optimized imaging conditions which result in much improved image quality are presented. These strategies are applied to two precipitation hardened Ni-base alloys, a cast single crystal and a hot isostatically pressed sample.

Long-GRIN-Lens Microendoscopy Enabled by Wavefront Shaping for a Biomedical Microdevice: An Analytical Investigation.

We analytically investigate the feasibility of long graded-index (GRIN)-lens-based microendoscopes through wavefront shaping. Following the very well-defined ray trajectories in a GRIN lens, mode-dependent phase delay is first determined. Then, the phase compensation needed for obtaining diffraction limited resolution is derived. Finally, the diffraction pattern of the lens output is computed using the Rayleigh–Sommerfeld diffraction theory. We show that diffraction-limited resolution is obtained for a 0.5 mm diameter lens with a length over 1 m. It is also demonstrated that different imaging working distances (WDs) can be realized by modifying the phase compensation. When a short design WD is used, a large imaging numerical aperture (NA) higher than 0.4 is achievable even when a low NA lens (NA = 0.1) is used. The long- and thin-GRIN-lens-based microendoscope investigated here, which is attractive for biomedical applications, is being prioritized for use in a clinical stage microdevice that measures three-dimensional drug responses inside the body. The advance described in this work may enable superior imaging capabilities in clinical applications in which long and flexible imaging probes are favored.

Continuous optical zoom microscopy imaging system based on liquid lenses

In this paper, a continuous optical zoom microscopy imaging system based on liquid lenses is proposed. Compared with traditional microscopes, which have discrete magnification, requiring manual conversion of the objective lens to change the magnification, the proposed microscope can continuously change the magnification of the targets in real-time. An adaptive zoom microscope, a liquid lens driving board, a microscope bracket, an adjustable three-dimensional stage and a light source are stacked to form the main framework of the continuous optical zoom microscopy imaging system. The adaptive zoom microscope which is composed of four electrowetting liquid lenses and six glass lenses form the main imaging element of the microscope. By changing the driving voltage which is applied to the four liquid lenses, the focal length of the liquid lenses can be modulated to achieve continuous zooming. By contrast, in traditional microscopes, the zooming process can only be achieved by rotating the eyepieces at different magnifications. At a fixed working distance, the magnification of the proposed microscope can change continuously from ∼9.6× to ∼22.2× with a response time of ∼50ms. Moreover, an axial depth scanning of ∼1000µm can be achieved without any mechanical movement. Our experiments proved that the microscope has stable performance and high consistency during zooming. Therefore, the proposed microscope has obvious advantages over the traditional microscopes in observing dynamic samples with different magnifications and can be commercialized for further expanding the applications in biochemical and pathological analysis.

Enhancing Microsurgical Assistant Experience with Bifocal Safety Glasses: A Low-Cost Alternative to Surgical Loupes.

The standard flap harvest is performed under loupe dissection. It is not infrequently that a medical student or physician assistant participates in the role of first or second assist. Such scenarios have impressed upon us the observation that these surgical assistants seldom use loupes or any other form of visual magnification. The reasons for this are likely multifaceted and may be related to cost as well as perceived opinions of colleagues. The benefit of encouraging optical aid use among surgical assistants encompasses an augmented surgical and learning experience. The aforementioned barriers, however, prohibit the use of loupes. We have found bifocal safety glasses to be an adequate alternative (Fig. 1). As compared to Galilean or prismatic loupes, which utilize multiple lenses and can magnify up to eight times without distortion (in the case of prismatic loupes), single-lens magnifiers can magnify up to 1.5 times without distortion or significant loss of working distance. Although this level of magnification is not acceptable for the primary surgeon, the added benefit of single-lens magnification is certainly superior to total lack of magnification typically utilized by nonresident surgical assistants.Fig. 1.: Standard bifocal safety glasses with +1.00 diopter strength.Bifocal safety glasses need to be selected in order to allow for maximal magnification at the optimal working distance. With this in mind, we recommend lower-powered magnifiers (i.e., diopters between +0.75 and +1.50 diopters), as these allow for crisp magnification and accommodation without causing eye fatigue. It is important to note the conversion of diopter to magnification is described by the equation m = d/4 + 1, therefore a +1.00 diopter would result in m = ¼ + 1 = 1.25× magnification. As compared to surgical loupes, bifocal safety glasses have the added benefit of being lightweight. The detrimental effect of loupes on cervical spine health has been well documented in surgeons of all levels and across multiple specialties; surgeons with severe cervical spine pain can use bifocal safety glasses as an alternative to loupes in cases where high-power magnification is not needed.1,2 In addition, single-lens magnifiers are not cost-prohibitive. They can be purchased for less than $15, which is markedly less than the typical price of loupes.3 The design of bifocals is discreet, as they resemble safety glasses typically worn in the operating room, and this mitigates any worry about eliciting negative opinions from colleagues. Bifocal safety glasses are a cost-conscious, comfortable, and inconspicuous optical aid that should be utilized by microsurgical assistants when loupes are not available. DISCLOSURE The authors have no financial interest to declare in relation to the content of this article.

Impact of C-shaped skin incision on surgical operability in the retrosigmoid approach: when a good start is half of the job.

The retrosigmoid approach (RSA) is one of the routes of choice to approach tumors and vascular lesions of the cerebellopontine angle. Among different types of skin incisions and soft tissue dissection techniques, the most widely used variants comprise the straight/lazy S-shaped and the C-shaped incisions. Several reports discuss advantages in terms of functional and clinical outcomes of the C-shaped incision, but scientific considerations about the critical impact of this kind of incision on surgical operability are still extremely limited. Authors comparatively analyze the advantage provided by C-shaped incision in RSA in terms of anatomic exposure and surgical operability, compared with straight/lazy S-shaped one. A comparative microanatomical laboratory investigation was conducted. The operability score (OS) was applied for quantitative analysis of surgical operability. C-shaped incision, providing a significant reduction of the overall working distance (-13%) together with an overall increase of the maneuverability area (+ 204.9%), did improve the conizing effect on the surgical corridor. It optimized overall maneuverability of surgical instruments, in terms of angle of attack (+ 27.7%), as well as maneuverability arc (+ 122%), on the entire surgical field. C-shaped incision ensured good operability on all surgical targets (OS ranging from 2 to 3), most significantly improving surgical maneuverability at the porus trigeminus and internal acoustic meatus. C-shaped incision in the RSA significantly improves anatomic exposure and surgical operability as compared with straight/lazy S-shaped incision.

HEALTH AND SAFETY PRACTICES DURING COVID 19: HOW TO ENSURE WORKPLACE ENVIRONMENT SAFETY AND HEALTH?

<p align="center"><strong><em>Abstract</em></strong></p><p>The COVID 19 pandemic is a challenge in various sectors in the world, one of which is the workplace. The large population of workers in the workplace which can lead to clusters of the spread of COVID-19, requires workplaces to be able to ensure that workers are healthy and safe. This is done to break the chain of spreading COVID-19. Various efforts that have been made by workplaces in various countries were reviewed based on searches through ScienceDirect, Springer, and Google Scholar which were adapted to research questions. COVID-19 has an impact on economic and business instability at the beginning of the pandemic, which is a challenge for the workplace to be able to adapt to these changes. Work from home is one effort that can be done, but not all jobs can be done at home. The workplace makes various efforts so that workers are healthy and safe, including the provision of personal protective equipment, a safe working distance of about 2 meters, workplace disinfection, engineering, redesign of work stations, development of digital technology, administrative control with work shifts, workload adjustment and various trainings that can be done, one of which is psychological support for workers. Every workplace has a challenge to break the chain of the spread of COVID-19, so a control program must be implemented optimally to ensure workers are safe and secure.</p><p><strong> </strong></p><p><strong>Keywords: </strong>workplaces, health and safety practice, COVID-19<strong></strong></p>

A Surgical Pen-Type Probe Design for Real-Time Optical Diagnosis of Tumor Status Using 5-Aminolevulinic Acid.

A surgical microscope is large in size, which makes it impossible to be portable. The distance between the surgical microscope and the observation tissue is 15–30 cm, and the adjustment range of the right and left of the camera is a maximum of 30°. Therefore, the surgical microscope generates an attenuation (above 58%) of irradiation of the optical source owing to the long working distance (WD). Moreover, the observation of tissue is affected because of dazzling by ambient light as the optical source power is strong (55 to 160 mW/cm2). Further, observation blind spot phenomena will occur due to the limitations in adjusting the right and left of the camera. Therefore, it is difficult to clearly observe the tumor. To overcome these problems, several studies on the handheld surgical microscope have been reported. In this study, a compact pen-type probe with a portable surgical microscope is presented. The proposed surgical microscope comprises a small and portable pen-type probe that can adjust the WD between the probe and the observed tissue. In addition, it allows the adjustment of the viewing angle and fluorescence brightness. The proposed probe has no blind spots or optical density loss.

A method for noise attenuation of straightness measurement based on laser collimation

The accuracy and stability of the straightness measurement based on laser collimation are severely affected by atmospheric turbulence, especially at long working distances. To address this problem, a method for noise attenuation of straightness measurement based on laser collimation is proposed in this paper. The turbulence shield was designed to reduce intensity of atmospheric turbulence on the beam path and weaken its impact on the straightness measurement. Subsequently, the effectiveness of the turbulence shield was simulated by the method of multi-phase screen. To verify the simulation results, the straightness measurement experiment was carried out on the laser five-degree-of-freedom (5-DOF) measurement system. The experimental results showed that the standard deviations of horizontal and vertical straightness noise were reduced by 95.6% and 87.4%, respectively. The experimental results were basically consistent with the simulation results. The turbulence shield effectively improved the accuracy and stability of straightness measurement based on laser collimation.

Synthesis of Self-healing Magnetic Microcapsules with Targeted Delivery through Magnetizing Emulsifiers

Targeted delivery self-healing microcapsules have higher self-healing effect and lower cost, but there are few preparation methods. Here, we have shown a novel method to synthesize targeted delivery self-healing magnetic microcapsules containing Tung oil (MMCTO) through introducing magnetic emulsifiers (ME). Compared to microcapsules containing Tung oil (MCTO), the MMCTO can migrate desirably and the average working distance of MMCTO is shortened almost by 50% under a magnetic field. The novel method is simple and economical, which is beneficial to guide future design of magnetic microcapsules.

On-axis sample viewer with flexible working distance for an X-ray spectroscopy beamline.

Conducting research using micrometer-sized X-ray beams with small samples is common at modern synchrotron X-ray sources. Often, the relative alignment between the X-ray beam and sample is time consuming. An on-axis or coaxial camera system with a view of the sample in a direction along the path of the X-ray beam with its depth of field set to coincide with the location of the focal spot of the X-ray beam is preferred. Besides the use of a drilled mirror, I propose the use of a Pellicle mirror to create an on-axis viewer that allows various sample environments and X-ray beam sizes.

Changes in vergence and accommodation parameters after smartphone use in healthy adults.

Purpose:To assess pre and post vergence and accommodation parameters after monitored reading on a smartphone device.Methods:This prospective comparative study was performed in a tertiary eye care center for a duration of 6 months (December 2017 – May 2018). A total of 47 healthy emmetropic subjects of age group ranging from 18-30 years were recruited for the study. Participants underwent an initial visual screening protocol, followed by accommodation and vergence parameters assessment. The subjects were given reading text of optotype N6 at 40cm working distance for 30 minutes in a smart phone device. Pre and post measurements were documented.Results:Among 47 subjects there were 17 male and 30 females with mean age group of 21.2+2.06 years. There was a statistically significant worsening of accommodative components (negative & positive relative accommodation, lag of accommodation). In vergence parameters, a statistically significant deterioration of negative (12.8 + 1.65 to 12.38 + 1.93 PD) and positive fusional vergence (15.48 + 1.53 to 16.08 +1.61 PD) was observed. The mean vergence facility also showed a statistically significant change in pre and post task measurements (13.51 + 1.64 to 10.71 + 1.91 cpm (cycles per minute)).Conclusion:The current study investigated that perusing text with a smart phone for 30 minutes shows significant effect on accommodative and vergence components for near task, with greater impact on vergence parameters. Drawn out exposure to digital screens at near, may bring about visual quality dysfunction.

Melt electrowriting stacked architectures with high aspect ratio

Melt electrowriting (MEW) approach with constant working distance has been developed to weaken the charge interferences and to enhance the architecture mechanical strength, by which various stacked architectures with high aspect ratio can be achieved. The deposited fiber guides the subsequent jet to print layer by layer along the pre-designed patterns without fiber pulsing. The position of the nozzle is raised simultaneously during the direct-writing process to maintain a constant working distance, and then, the deposition offset of the fiber layer can be decreased. The effects of the processing parameters on the MEW fibers with diameters distributed in the range of 50–125 µm have been studied. Patterns of polygon and characters with fiber layer number of 200 and aspect ratio higher than 180 are direct-written accurately. The maximum height of the direct-written patterns reaches 9 mm. The proposed approach is a good method to realize the direct additive manufacturing of high-aspect-ratio architectures and to promote its industrial applications.