Right-angle Prism Research Articles

Three-dimensional posture changes of the vocal fold from paired intrinsic laryngeal muscles.

Although the geometry of the vocal fold medial surface affects voice quality and is critical in the treatment of glottic insufficiency, the prephonatory shape of the vocal fold medial surface is not well understood. In this study, we activated intrinsic laryngeal muscles individually and in combinations, and recorded the temporal sequence and precise three-dimensional configurational changes of the vocal fold medial surface. In vivo canine hemilarynx model. A hemilaryngectomy was performed in an in vivo canine model and ink was used to mark the medial surface of the in situ vocal fold in a grid-like fashion. The thyroarytenoid (TA), lateral cricoarytenoid (LCA), cricothyroid (CT), and posterior cricoarytenoid (PCA) muscles were stimulated individually and in combinations. A right-angle prism whose hypotenuse formed the glottal midline provided two distinct views of the medial surface for a high-speed digital camera. Image-processing package DaVis (LaVision Inc., Goettingen, Germany) allowed time series cross-correlation analysis for three-dimensional deformation calculations of the vocal fold medial surface. Combined TA and LCA activation yields an evenly adducted rectangular glottal surface. Addition of thyroarytenoid to cricoarytenoid adducts the vocal fold from inferior to superior in a graded fashion allowing formation of a divergent glottis. Posterior cricoarytenoid has a bimodal relationship with thyroarytenoid favoring abduction. Cricothyroid and lateral cricoarytenoid yield unique glottal postures necessary but likely not conducive for efficient phonation. Understanding the three-dimensional geometry of the vocal fold medial surface will help us better understand the cause-effect relationship between laryngeal physiology and phonation. NA Laryngoscope, 127:656-664, 2017.

Ultra-high resolution spectral domain optical coherence tomography using supercontinuum light source

An ultra-high resolution spectral domain optical coherence tomography (SD-OCT) was developed using a cost-effective supercontinuum laser. A spectral filter consists of a dispersive prism, a cylindrical lens and a right-angle prism was built to transmit the wavelengths in range 680–940 nm to the OCT system. The SD-OCT has achieved 1.9 μm axial resolution and the sensitivity was estimated to be 91.5 dB. A zero-crossing fringes matching method which maps the wavelengths to the pixel indices of the spectrometer was proposed for the OCT spectral calibration. A double sided foam tape as a static sample and the tip of a middle finger as a biological sample were measured by the OCT. The adhesive and the internal structure of the foam of the tape were successfully visualized in three dimensions. Sweat ducts was clearly observed in the OCT images at very high resolution. To the best of our knowledge, this is the first demonstration of ultra-high resolution visualization of sweat duct by OCT.

Solution refractive index sensor based on high resolution total-internal-reflection heterodyne interferometry

In this paper, a solution refractive index sensor is proposed based on a high resolution total-internal-reflection (TIR) interferometry. In the proposed sensor, a half-wave plate and a quarter-wave plate that exhibit specific optic-axis azimuths are combined to form a phase shifter. When an isosceles right-angle prism whose base contacts with a tested solution is placed between the phase shifter and an analyzer with suitable transmission-axis azimuth, it shifts and increases the phase difference of the s- and p-polarization states at one TIR. The increased phase difference relates to the solution refractive index; thus it can be easily and accurately measured by evaluating the phase difference. The feasibility was demonstrated by experimental results. This method has the merits of both common-path interferometry and heterodyne interferometry.

Quartz-Enhanced Photoacoustic Spectroscopy with Right-Angle Prism.

A right-angle prism was used to enhance the acoustic signal of a quartz-enhanced photoacoustic spectroscopy (QEPAS) system. The incident laser beam was parallelly inverted by the right-angle prism and passed through the gap between two tuning fork prongs again to produce another acoustic excitation. Correspondingly, two pairs of rigid metal tubes were used as acoustic resonators with resonance enhancement factors of 16 and 12, respectively. The QEPAS signal was enhanced by a factor of 22.4 compared with the original signal, which was acquired without resonators or a prism. In addition, the system noise was reduced a little with double resonators due to the Q factor decrease. The signal-to-noise ratio (SNR) was greatly improved. Additionally, a normalized noise equivalent absorption coefficient (NNEA) of 5.8 × 10−8 W·cm−1·Hz−1/2 was achieved for water vapor detection in the atmosphere.

Correlative principal indices of refraction of an anisotropic crystal

The principal indices of refraction are normally assumed to be independent quantities of an anisotropic crystal. Note that the energy of an electromagnetic wave is a function of the refractive index of the medium, and consider the energy conservation in a reversible transition from an ordinary to an extraordinary wave by a total internal reflection in a right-angle prism composed of the anisotropic crystal. It is found that the principal indices of refraction are correlative properties, which is confirmed by the experimental results of material dispersion.

Integrated Micro-Optics for Microfluidic Detection.

A method of embedding micro-optics into a microfluidic device was proposed and demonstrated. First, the usefulness of embedded right-angle prisms was demonstrated in microscope observation. Lateral-view microscopic observation of an aqueous dye flow in a 100-μm-sized microchannel was demonstrated. Then, the embedded right-angle prisms were utilized for multi-beam laser spectroscopy. Here, crossed-beam thermal lens detection of a liquid sample was applied to glucose detection.

Measurement of four-degree-of-freedom error motions based on non-diffracting beam

A measuring method for the determination of error motions of linear stages based on non-diffracting beams (NDB) is presented. A right-angle prism and a beam splitter are adopted as the measuring head, which is fixed on the moving stage in order to sense the straightness and angular errors. Two CCDs are used to capture the NDB patterns that are carrying the errors. Four different types errors, the vertical straightness error and three rotational errors (the pitch, roll and yaw errors), can be separated and distinguished through theoretical analysis of the shift in the centre positions in the two cameras. Simulation results show that the proposed method using NDB can measure four-degrees-of-freedom errors for the linear stage.

Design and fabrication of an angle-scanning based platform for the construction of surface plasmon resonance biosensor

A sensing system for an angle-scanning optical surface-plasmon-resonance (SPR) based biosensor has been designed with a laser line generator in which a P polarizer is embedded to utilize as an excitation source for producing the surface plasmon wave. In this system, the emitting beam from the laser line generator is controlled to realize the angle-scanning using a variable speed direct current (DC) motor. The light beam reflected from the prism deposited with a 50nm Au film is then captured using the area CCD array which was controlled by a personal computer (PC) via a universal serial bus (USB) interface. The photoelectric signals from the high speed digital camera (an area CCD array) were converted by a 16 bit A/D converter before it transferred to the PC. One of the advantages of this SPR biosensing platform is greatly demonstrated by the label-free and real-time bio-molecular analysis without moving the area CCD array by following the laser line generator. It also could provide a low-cost surface plasmon resonance platform to improve the detection range in the measurement of bioanalytes. The SPR curve displayed on the PC screen promptly is formed by the effective data from the image on the area CCD array and the sensing responses of the platform to bulk refractive indices were calibrated using various concentrations of ethanol solution. These ethanol concentrations indicated with volumetric fraction of 5%, 10%, 15%, 20%, and 25%, respectively, were experimented to validate the performance of the angle-scanning optic SPR biosensing platform. As a result, the SPR sensor was capable to detect a change in the refractive index of the ethanol solution with the relative high linearity at the correlation coefficient of 0.9842. This greatly enhanced detection range is obtained from the position relationship between the laser line generator and the right-angle prism to allow direct quantification of the samples over a wide range of concentrations.

Applying LED in full-field optical coherence tomography for gastrointestinal endoscopy

Optical coherence tomography (OCT) has become an important medical imaging technology due to its non-invasiveness and high resolution. Full-field optical coherence tomography (FF-OCT) is a scanning scheme especially suitable for en face imaging as it employs a CMOS/CCD device for parallel pixels processing. FF-OCT can also be applied to high-speed endoscopic imaging. Applying cylindrical scanning and a right-angle prism, we successfully obtained a 360° tomography of the inner wall of an intestinal cavity through an FF-OCT system with an LED source. The 10-μm scale resolution enables the early detection of gastrointestinal lesions, which can increase detection rates for esophageal, stomach, or vaginal cancer. All devices used in this system can be integrated by MOEMS technology to contribute to the studies of gastrointestinal medicine and advanced endoscopy technology.

High brightness beam shaping and fiber coupling of laser-diode bars.

The strong beam quality mismatch in the fast and slow axes of laser-diode bars requires a significant beam shaping method to reach the parameters needed for fiber coupling. An effective solution to this problem is proposed that is based on a right-angle prism array and a distributed cylinder-lens stack. Coupling 12 mini-bars into a standard 100μm core diameter and 0.15 numerical aperture fiber is achieved, and the output power can reach 400W. Using this technique, production of compact and high brightness fiber-coupled laser-diode modules is possible.

Generating polarization vortices by using helical beams and a Twyman Green interferometer.

A stable interferometric arrangement consisting of a polarizing beam splitter, a reflector, and a right-angle prism is designed to transform helical beams into polarization vortices. The computer-generated holograms are loaded on the liquid crystal spatial light modulator (LC-SLM) in order to generate different helical beams. Then the helical beams are transformed into polarization vortices with different kinds of intensity distribution successfully.

High-accuracy device for measuring the twist angle

This paper describes a high-accuracy optoelectronic device for measuring the twist angle, based on an autocollimation method and using a reflector in the form of a unit of right-angle prisms. The device makes it possible to measure the relative twist angle of objects in the range ±2.5° when there is a distance of 2.5–3.5 m between the reflector and the optoelectronic unit of the device. The rms deviation of the measured angle from the true value in this case does not exceed 2′′ in the range ±2.5°, and it does not exceed 1′′ in the range ±10′. A specially shaped mark is used in the device that makes it possible to measure the auxiliary angle between the direction of the edge of the prism reflector and a plane perpendicular to the optical axis of the device. The installation can be used to transfer the azimuthal direction vector.

Evanescent Wave Coupled Spectroscopic Sensing Using Smartphone

This letter demonstrates a technique that utilizes the camera of a smartphone for evanescent wave coupled spectroscopic sensing. Using simple optical components, the camera of the smartphone is converted into a highly resolved spectrometer (0.305 nm per pixel), and using a right-angled glass prism, the evanescent field of the internally reflected light signal from a broadband optical source is allowed to interact with the external medium. The primary advantages of the proposed sensing technique are its compactness, portability, and cost-efficiency.

Reduction of the angular dispersion in self-diffraction signals by using a prism

Self-diffraction effect has very important applications in the field of femtosecond laser, such as to improve the temporal contrast of femtosecond pulses, to be used as the reference pulse of self-reference spectral interferometry, and as the signal of self-diffraction frequency-resolved optical gating, etc. However, in the self-diffraction signal of femtosecond pulses with a broadband spectrum angular dispersion exists obviously, which will limit the application of self-diffraction effect. In this paper, the self-diffraction signal angular dispersion of femtosecond pulses is obviously reduced, when a right-angle prism is located in the light path of an incident beam with an incident angle of 23° to the prism. The experimental result provides a useful reference for the application of the self-diffraction effect to the research of femtosecond laser pulse in the future.

Zoom Lens Design for a 10x Slim Camera using Successive Procedures

This study presents a new design method for a zoom lens, in which real lens groups are designed successively to combine to form a lens modules zoom system. The lens modules and aberrations are applied to the initial design for a four-group inner-focus zoom system. An initial design with a focal length range of 4.2 to 39.9 mm is derived by assigning the first-order quantities and third-order aberrations to each module along with the constraints required for optimum solutions. After obtaining the lens module zoom system, the real lens groups are successively, not separately, designed to get a zoom lens system. Compared to the separately designed real lens groups, this approach can give a better starting zoom lens and save time. The successively designed groups result in a zoom system that satisfies the basic properties of the zoom system consisting of the original lens modules. In order to have a slim system, we directly inserted the right-angle prism in front of the first group. This configuration resulted in a compact zoom system with a depth of 12 mm. The finally designed zoom lens has an f-number of 3.5 to 4.5 and is expected to fulfill the requirements for a mobile zoom camera having high zoom ratio of 10x.

Experimental Evaluation of a Small-Displacement Sensing System Based on the Surface Plasmon Resonance Technology in Heterodyne Interferometry

In this article, a small-displacement sensing system based on the surface plasmon resonance technology in heterodyne interferometry is proposed and evaluated. The basic sensing unit is composed of a prism assembly and a displacement probe. The prism assembly consists of a halfwave (λ/2) plate, two right-angle prisms and two rotation stages. The small-displacement sensor is with high sensitivity and resolution due to the attenuated total reflection effect in heterodyne interferometry. Besides, we can obtain the results of the experiment in a distant place by uses of the USB data acquisition card (DAQ card) and a ZigBee module. It can be found that the displacement resolution of the small-displacement sensor can reach 0.155nm by numerical simulation. The small-displacement sensor has some merits, e.g., easy operation, high measurement accuracy, high resolution and rapid measurement, etc.

Solid-state interferometry of a pentaprism for generating cylindrical vector beam

We demonstrated the generation of a cylindrical vector laser beam using a pentaprism interferometer. The solid-state interferometer was made up of a trapezoid and right-angle prism, whose hypotenuse face was implemented with a polarization beam splitter coating that split a rotated TEM01 mode beam into two orthogonal polarizations. The Ppolarized beam was reflected inside the prism twice, allowing a mode pattern without inversion; however, the Spolarized beam was reflected once resulting in mode patterns that form P-polarized beams rotated by 90°. We also held the phase shift of the two beams to zero by use of a phase shifter, thus the output of the superimposed beam was a radially polarized beam. We demonstrated the mode pattern and polarization purity of the output beam through the use of this configuration.

Invisibility cloaking based on geometrical optics for visible light

Optical cloaking has been one of unattainable dreams and just a subject in fiction until recently. Several different approaches to cloaking have been proposed and demonstrated: stealth technology, active camouflage and transformation optics. The last one would be the most formal approach modifying electromagnetic field around an object to be cloaked with metamaterials. While cloaking based on transformation optics, though valid only at single frequency, is experimentally demonstrated in microwave region, its operation in visible spectrum is still distant from realisation mainly owing to difficulty in fabricating metamaterial structure whose elements are much smaller than wavelength of light. Here we show that achromatic optical cloaking in visible spectrum is possible with the mere principle based on geometrical optics. In combining a pair of polarising beam splitters and right-angled prisms, rays of light to be obstructed by an object can make a detour to an observer, while unobstructed rays go straight through two polarising beam splitters. What is observed eventually through the device is simply background image as if nothing exists in between.

A new static lighting concentrator with optical coupler

Currently, energy-saving and carbon dioxide reduction are the most critical issues faced by the globe. Therefore, solar energy should be used as much as possible. A possible use is to illuminate a solar cell so as to transform light energy directly into electricity. However, due to its low efficiency and high cost, the solar cell is not presently economically feasible. Utilization of solar energy, which is considered one of the most important renewable energy sources, not only reduces consumption of fossil fuel but also slows down the pace of global warming. In addition to the use of solar cells, daylight illumination is also an important access to solar energy. Our team has developed a technique that can guide the natural light to the interior for indoor illumination. It is called the “Natural Light Guiding System.” Our system can guide sunlight to the interior, but the distribution of light at the exit of the system is disordered. To solve this problem, we have proposed an optical coupling transmission structure with right-angled prism collecting modules. We analyzed the mathematical model of coupling transmission. And, we also analyzed the efficiency of this cascade structure at the exit surface of the concentrator. In this paper, we provide a high efficiency new concentrator coupled to a transmission device. We save 75% of the optical fiber cable expense usage and we improve efficiency by 47.46% when we add an optical coupling transmission structure to our static lighting concentrator. It is better than the original cascade prism static concentrator. Taking the fiber cost into consideration, we defined a key performance index—it is a ratio of luminous flux on an illuminated area. Our system can provide more powerful light for indoor illumination than existing methods The optical coupling can provide high transmission efficiency and provide parallel light beams at the export from the optical coupling module. We used optical simulation tools to design and simulate the efficiency of the active module. We can use this system as an ecological illumination system to offer steady illumination in indoor space to provide healthy illumination, save energy, and meet safety requirements.

Design considerations for a concentrator photovoltaic system based on a branched planar waveguide

A concentrator photovoltaic system can be built by coupling a lens array to a branched planar waveguide, which has one end with a solar cell attached and the other end divided into multiple branches. A right-angle prism is attached to each branch end, redirecting the focused sunlight into the waveguide via total internal reflection so that the light propagates inside the waveguide. With an appropriate design, the light leakage from the waveguide can be made negligible. Our ray-tracing simulations show that the ratio of the optical power exiting the waveguide to an optical power entering the lens-array is close to 87%, with the loss being mostly due to the Fresnel reflections at the lens (8%) and prism surfaces (3%). We can increase geometric concentration by cascading tapered waveguides. The number of cascades should be limited so that the light leakage from the tapered portions remains insignificant. A secondary optical element on each prism would collimate the light, easing this limitation, as well as making the system thinner. The absorption in the waveguide material imposes an inherent limit on the number of cascades and the concentration factor.