Front Surface Mirrors Research Articles

A Novel Lightweight Navigation System for Oral and Maxillofacial Surgery Using an External Curved Self-Identifying Checkerboard

This paper presents a novel lightweight navigation system for oral and maxillofacial surgery (OMS). An external curved checkerboard with self-identifying markers is set as the reference object around the surgical scene. A customized oral clip with a micro camera is designed for oral localization by tracking the external checkerboard. Similarly, the dental handpiece is also equipped with a micro camera, which can be localized like the clip. The spatial model of the markers is provided by binocular stereoscopic reconstruction. A front surface mirror is taken up for the registration between the oral cavity and the camera on the clip. The pivot calibration of the dental handpiece is accomplished by our proposed calibration method. We set up an experimental group and a control group for evaluation. The surgical tools of the experimental group were approximately 30% lighter, 35% less bulky, and 90% cheaper than those of the control group. Our system yielded the comprehensive navigation accuracy of 0.92 mm whereas the accuracy of the control group was 0.87 mm. Results revealed that our system can achieve similar accuracy compared with a prevailing system at a lighter weight, a more compact volume, and a lower cost. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The motivation of this work is to reduce the burden on patients and surgeons during OMS. Current commercial navigation systems are still limited by the burden of extra cumbersome fiducial markers and high hardware costs. Their high accuracy benefits from the large size of fiducial markers. To take full advantage of the camera’s localization effect, we propose the concept of “marker-camera inverse projection”, i.e., reversing the roles of the camera and the markers. In this way, cameras on surgical tools detect more points with a more uniform distribution. Our proposed system achieves a decent balance between navigation accuracy and hardware cost, which facilitates the development of surgical tools to be lighter and more economical, and involves tremendous potential for commercialization.

Simple and additive-free synthesis of highly reflective thin silver films and their application on large-scale surfaces

There is a growing demand for highly reflective coatings especially on non-conducting surfaces for use in various industries. Additionally, focus is arising on green production and cost reduction in terms of energy, time, etc., which require detailed investigation of coating process parameters. Therefore, in this work, silver thin films with high reflectance were synthesized on glass substrates in short durations at room temperature by electroless plating (ELP) method in one-step and without using any additives. Effects of deposition time, concentration of the reactants (AgNO3, Glucose, NaOH), and also the surface pretreatment and activation steps were investigated in detail to improve the reflectance and structural properties of silver films. Contact angle measurements were realized to examine the effects of each surface modification step. Surfaces subjected to etching, sensitization and Ag activation were found to yield more homogeneously distributed nanoparticles in short deposition period. Scanning electron microscopy (SEM) also showed smaller-sized spherulite-shaped crystals, forming a close packed structure with an optimum film thickness of ∼110 nm. The continuity of the silver coatings on the surface was verified by the low sheet resistance of 0.18 Ωsq−1. Atomic force microscopy (AFM) analysis revealed a smoother film structure with an RMS of 10.7 nm after sensitization. X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy analysis (XPS) analysis proved the growth of highly crystalline silver nanoparticles with high purity. All these morphological improvements led to high values of light (∼97%), near-infrared (99%) and solar (96%) reflectance for the coatings. Finally, based on the optimized concentrations and bath conditions, large-scale (700×500 mm2) first-surface mirrors were successfully produced (96.2%R and 0.25 Ωsq−1) by spray coating technique combined with ELP. Overall, the results indicate that the obtained films have potential usage in applications such as solar energy, electronics and aeronautics.

Design, testing and characterization of a proton central axis alignment device for the dynamic collimation system

Objective. Proton therapy conformity has improved over the years by evolving from passive scattering to spot scanning delivery technologies with smaller proton beam spot sizes. Ancillary collimation devices, such the Dynamic Collimation System (DCS), further improves high dose conformity by sharpening the lateral penumbra. However, as spot sizes are reduced, collimator positional errors play a significant impact on the dose distributions and hence accurate collimator to radiation field alignment is critical. Approach. The purpose of this work was to develop a system to align and verify coincidence between the center of the DCS and the proton beam central axis. The Central Axis Alignment Device (CAAD) is composed of a camera and scintillating screen-based beam characterization system. Within a light-tight box, a 12.3-megapixel camera monitors a P43/Gadox scintillating screen via a 45° first-surface mirror. When a collimator trimmer of the DCS is placed in the uncalibrated center of the field, the proton radiation beam continuously scans a 7×7 cm2 square field across the scintillator and collimator trimmer while a 7 s exposure is acquired. From the relative positioning of the trimmer to the radiation field, the true center of the radiation field can be calculated. Main results. The CAAD can calculate the offset between the proton beam radiation central axis and the DCS central axis within 0.054 mm accuracy and 0.075 mm reproducibility. Significance. Using the CAAD, the DCS is now able to be aligned accurately to the proton radiation beam central axis and no longer relies on an x-ray source in the gantry head which is only validated to within 1.0 mm of the proton beam.

An automated fast neutron computed tomography instrument with on-line focusing for non-destructive evaluation.

A fast neutron tomography imaging instrument has been designed, built, and tested at The Ohio State University 500 kW Research Reactor on a fast neutron beamline with a peak neutron flux ≈5.4 × 107 n·cm-2·s-1 at 1.6MeV median neutron energy. The instrument and beamline are also configurable for thermal neutron imaging. The imaging apparatus is composed of a lens coupled, water-cooled Electron Multiplying Charge Coupled Device camera, a front-surface mirror, and a high light yield plastic Polyvinyl toluene scintillator. The instrument sits on a mobile cart. A total of 5 motion-control stages are built into the system for XYZ and rotational degrees of freedom for sample positioning; the fifth stage fine tunes the focal distance between the camera and the scintillator to achieve on-line focusing. A Python code with a user-friendly graphical user interface controls the fully automated image acquisition, not requiring user interaction, yet facilitating tracking of the image acquisition. A complete fast neutron computed tomography dataset with 360 projections requires less than 3 h, with 30s per projection. On-line focusing is accomplished with a commercial, off-the-shelf, dielectrically actuated liquid lens. Finally, tomographic reconstructions are visualized using the Livermore Tomography Tools software package. The effective pixel size (width and height) is ≈0.1058mm, yielding a minimum voxel size of 0.1058 × 0.1058 × 0.1058mm3, and produces a spatial resolution of 231μm when calculated from knife-edge measurements.

2nd mesiobuccal canals in maxillary molars of Korean population

It has been well known that mesiobuccal roots of maxillary molars tend to have more than 1 canals. 2nd mesiobuccal canals are in many cases calcified. So clinicians often have difficulty in finding these 2nd mesiobuccal canals. Moreover, the root canal morphology of mesiobuccal roots of maxillary molars is complex in many cases. To find and treat 2nd mesiobuccal canals, knowledge on incidence, type, and location of 2nd mesiobuccal canals is necessary. Use of Cone-Beam computed tomography (CBCT) is also helpful for finding 2nd mesiobuccal canals. And also, it is recommended to use proper illumination and magnification along with the use of instruments such as front surface mirror, long shank bur, and ultrasonic tips.

EVALUATING THE EFFECT OF USING MIRRORS IN 3D RECONSTRUCTION OF SMALL ARTEFACTS

Abstract. Small artefacts pose many challenges to 3D documentation techniques due to their often complex details, which are very difficult to capture completely in 3D. Small objects may also have characteristics that are not optimal for 3D documentation, e.g. glossiness, shininess, textureless surfaces, etc. Furthermore, hidden parts of the artefact cause occlusions and obstructions, which may complicate the data acquisition process, since additional images or scan data are necessary in order to compensate for these restrictions. All these aspects increase acquisition and data processing times. Currently, the two main categories of 3D documentation methods are Image Based Modelling (IBM) and Range Based Modelling (RBM). In this paper, preliminary investigations aimed at evaluating the accuracy and performance of a front surface mirror in Image Based Modelling for small artefacts are presented. These results are then compared to a reference model generated from the artefact using a structured light system.

Three-dimensional (3D) dose distribution measurements of proton beam using a glass plate

The measurements of the three-dimensional (3D) dose distribution of proton beams in water are critical for proton therapy for quality assessment (QA). Although ionization chambers are commonly used for this purpose, such measurements take a long time to calculate precise 3D dose distribution. To solve this problem, we measured 3D dose distributions using a glass plate. We placed a 1-mm thick float glass plate on the upper inside of a black box with a water tank set above the float glass plate outside the black box and irradiated the proton beam to the water tank from the upper side. The attenuated proton beam by water in the tank was detected by the float glass plate and a scintillation image was formed in the plate. The image was reflected by a first-surface mirror set below the float glass plate and detected by a cooled charge-coupled device (CCD) camera from the side. We changed the water depths in the tank and measured the scintillation images at each depth. Then we calculated the 3D scintillation images from the measured images by stacking them in the depth direction. Measurements were made for 71.2- and 100-MeV proton pencil beams and a spread-out Bragg peak (SOBP) using the imaging system. From the images, we successfully formed 3D scintillation images without quenching. The depth profiles measured from the scintillation images showed almost identical distribution with those measured by the ionization chamber within a maximum difference less than 5%. The lateral profiles were also almost identical within width differences less than 2 mm. We conclude that our proposed method is promising for the 3D dose distribution measurements of proton beams.

Experimental investigation of wind and temperature induced scintillation effect on optical wireless communication link

Atmospheric disturbances due to randomly distributed wind flow and temperature results in fluctuation of intensity as well as in the phase of the received light signal, impairing an optical wireless link performance. In this work, turbulence-induced scintillation on Optical Wireless Communication (OWC) is investigated experimentally on the basis of optimized signal wavelength, link length and launched power level. To mimic the outdoor environmental conditions, an indoor chamber equipped with fans and heating coil is made up, which gives manual control of the temperature and wind velocity within the chamber. The received signal bearing data rate of 100 Mbps is measured after traversing through the designed chamber and used to characterize the turbulence strength in terms of scintillation index (S.I.). To establish a long-range OWC link, the atmospheric channel length is increased using round-trip reflection by placing plane front surface mirrors at both ends of the chamber, also front concave mirror is used to collect distributed irradiance onto aperture area of the detector at the receiver. Experimentally, we have tried to characterize the combined effect of the wind and the temperature on the free space communication system. Various communication metrics like bit error rate (BER), signal to noise ratio (SNR) and Q factor have been evaluated and it is reported that the BER performance of an OWC link having wind flow of 15 km/h gets degraded by 109 as compared to still air.

Ocular anatomic changes for different accommodative demands using swept-source optical coherence tomography: a pilot study.

The purpose of our study was to assess the changes in ocular parameters for different accommodative demands using a new optical biometer based on swept-source optical coherence tomography (SS-OCT). Seven subjects were included in this pilot study, and only one eye per participant was analyzed. Each eye was measured six times with the optical biometer IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany). As this instrument is not able to change the vergence of the stimulus, to enable measurements at different accommodative states, a tilted first-surface mirror attached to the optical biometer was used to place the fixation stimulus at different vergences. Measurements were taken on the right eye of the subject while the left eye was looking through the mirror. Central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), axial length (AL), white-to-white (WTW) distance and keratometric readings were evaluated for three different accommodative states: 0.0 diopters (D), 1.5 D, and 3.0 D. No statistically significant differences were found for CCT, AL, WTW, K1 and K2 between the three accommodative states. As expected, changing the accommodative condition did not change CCT, AL, WTW, and keratometric outcomes. Nevertheless, statistically significant differences between the accommodative states were found for ACD and LT measurements. In addition, variations in ACD correlated linearly with variations in LT (R2 ≥ 0.99) when changing the vergence of the optotype. A practical methodology to assess the changes in ocular parameters for different accommodative demands using the IOLMaster 700 based on SS-OCT has been described. Statistically significant changes that have been found that agree well with previous reports.

Fourier-Based Diffraction Analysis of Live Caenorhabditis elegans.

This manuscript describes how to classify nematodes using temporal far-field diffraction signatures. A single C. elegans is suspended in a water column inside an optical cuvette. A 632 nm continuous wave HeNe laser is directed through the cuvette using front surface mirrors. A significant distance of at least 20-30 cm traveled after the light passes through the cuvette ensures a useful far-field (Fraunhofer) diffraction pattern. The diffraction pattern changes in real time as the nematode swims within the laser beam. The photodiode is placed off-center in the diffraction pattern. The voltage signal from the photodiode is observed in real time and recorded using a digital oscilloscope. This process is repeated for 139 wild type and 108 "roller" C. elegans. Wild type worms exhibit a rapid oscillation pattern in solution. The "roller" worms have a mutation in a key component of the cuticle that interferes with smooth locomotion. Time intervals that are not free of saturation and inactivity are discarded. It is practical to divide each average by its maximum to compare relative intensities. The signal for each worm is Fourier transformed so that the frequency pattern for each worm emerges. The signal for each type of worm is averaged. The averaged Fourier spectra for the wild type and the "roller" C. elegans are distinctly different and reveal that the dynamic worm shapes of the two different worm strains can be distinguished using Fourier analysis. The Fourier spectra of each worm strain match an approximate model using two different binary worm shapes that correspond to locomotory moments. The envelope of the averaged frequency distribution for actual and modeled worms confirms the model matches the data. This method can serve as a baseline for Fourier analysis for many microscopic species, as every microorganism will have its unique Fourier spectrum.

Fourier-Based Diffraction Analysis of Live &lt;em&gt;Caenorhabditis elegans&lt;/em&gt;

This manuscript describes how to classify nematodes using temporal far-field diffraction signatures. A single C. elegans is suspended in a water column inside an optical cuvette. A 632 nm continuous wave HeNe laser is directed through the cuvette using front surface mirrors. A significant distance of at least 20-30 cm traveled after the light passes through the cuvette ensures a useful far-field (Fraunhofer) diffraction pattern. The diffraction pattern changes in real time as the nematode swims within the laser beam. The photodiode is placed off-center in the diffraction pattern. The voltage signal from the photodiode is observed in real time and recorded using a digital oscilloscope. This process is repeated for 139 wild type and 108 "roller" C. elegans. Wild type worms exhibit a rapid oscillation pattern in solution. The "roller" worms have a mutation in a key component of the cuticle that interferes with smooth locomotion. Time intervals that are not free of saturation and inactivity are discarded. It is practical to divide each average by its maximum to compare relative intensities. The signal for each worm is Fourier transformed so that the frequency pattern for each worm emerges. The signal for each type of worm is averaged. The averaged Fourier spectra for the wild type and the "roller" C. elegans are distinctly different and reveal that the dynamic worm shapes of the two different worm strains can be distinguished using Fourier analysis. The Fourier spectra of each worm strain match an approximate model using two different binary worm shapes that correspond to locomotory moments. The envelope of the averaged frequency distribution for actual and modeled worms confirms the model matches the data. This method can serve as a baseline for Fourier analysis for many microscopic species, as every microorganism will have its unique Fourier spectrum.

Deposition of multifunctional TiO2 and ZnO top-protective coatings for CSP application

Abstract In this work, high quality, transparent multifunctional and smart anatase TiO 2 and wurtzite ZnO top protective coatings used for CSP silver-based first-surface thick glass mirrors are studied. The TiO 2 and ZnO top-coatings are deposited using chemical spray pyrolysis technique which conserves a very good specular reflectance of the mirrors (94% reflectance in the Near Infrared range). The photocatalytic activity of the prepared top-coatings is evaluated using the methylene blue dye (MB) as a model molecule, and the highest activity is observed for ZnO top-coating, with a degradation efficiency of 42%. Moreover, the effect of post-annealing treatment on the photocatalytic degradation of the top-coatings is pointed out, and is explained in terms of crystallinity and surface morphology. The increase of the photocatalytic activity can be achieved by increasing surface roughness, which is a conflicting requirement with optical transparency needed for concentrated solar power (CSP) top-coating application. Furthermore, it is pointed out that TiO 2 and ZnO top protective thin films exhibit a photo-induced switching of their wetting properties only after 30 min of UV exposure, and their usability as multifunctional top-protective layers for CSP application is discussed.

A Preliminary Discrimination of Cluster Disqualified Shape for Table Grape by Mono-Camera Multi-Perspective Simultaneously Imaging Approach

Sorting table grape based on external indices of cluster can not only assure consumer satisfaction but also enhance the industry’s competitiveness and profitability. This paper proposed a method of synchronously imaging from different perspectives to present the whole surface of “kyoho” table grape with the front-surface reflective mirrors. A preliminary grade was conducted to distinguish the disqualified cluster by multi-perspective imaging method using the mirrors and mono-camera. A grape image with three bunches in every 120° perspective was simultaneously imaged by once acquisition of mono-camera, and meanwhile, the weight of grape was weighed by a weighing senor. After series of image process stages, the grape bunches of one actual and two virtual regions were segmented out and the size of virtual regions was affined to the size of the actual region. The compactness of grape cluster was estimated by the deviating percentage between the sensing weight and the fitting weight which was regressed with the average area by exponential function. The ratio of contour curve’s width was extracted from the bunch region and was used to classify the disqualified shoulder pole of grape shape. Finally, the disqualified shape of table grape was classified by the weight, region size, compactness, and ratio and got a 95.5 % correct rate. Results show this preliminary grade is feasible to inspect the disqualified cluster shape of table grape by the multi-perspective simultaneously imaging method.

Single-Monitor-Mirror Stereoscopic Display

A new single-monitor-mirror stereoscopic display is presented. The stereoscopic display system is composed of one monitor and one acrylic first-surface mirror. The mirror reflects one image for one ...

Development of an on-axis-visualization stage to observe and align sample with an x-ray beam

An on-axis-visualization stage for accurate sample alignment respect to X-ray beam has been designed and implemented at the diffraction and absorption/fluorescence stations of the BM25-SpLine synchrotron beamline at the ESRF. It is mostly intended for studies involving heterogeneous samples where the analysis is restricted to a particular area of the sample. The OAV system provides a parallax-free image of the sample. This is accomplished by a front-surface mirror at an angle of 45° degrees to reflect the visible sample image 90° up to a zoom optics and digital colour CCD camera. A pinhole (PH) on the mirror in combination with a second PH 100 mm backward provides an on-axis collimated X-ray beam at image centre. The collimator is aligned to the beam axis by two angular and two translational high-precision motorized motions. The OAV stage is synchronized with the sample positioning stage, by a computer software so that the desired sample region is aligned on the X-ray beam by selecting it on the image produced by the video camera. In this work, a complete description of the on-axis-visualization system will be presented including the experimental determination of the alignment accuracy.

Measurement of the accumulation of water ice on optical components in cryogenic vacuum environments

Standard vacuum practices mitigate the presence of water vapor and contamination inside cryogenic vacuum chambers. However, anomalies can occur in the facility that can cause the accumulation of amorphous water ice on optics and test articles. Under certain conditions, the amorphous ice on optical components shatters, which leads to a reduction in signal or failure of the component. An experiment was performed to study and measure the deposition of water (H2O) ice on optical surfaces under high-vacuum cryogenic conditions. Water was introduced into a cryogenic vacuum chamber, via a hydrated molecular sieve zeolite, through an effusion cell and impinged upon a quartz-crystal microbalance (QCM) and first-surface gold-plated mirror. A laser and photodiode setup, external to the vacuum chamber, monitored the multiple-beam interference reflectance of the ice-mirror configuration while the QCM measured the mass deposition. Data indicates that water ice, under these conditions, accumulates as a thin film on optical surfaces to thicknesses over 45 microns and can be detected and measured by nonintrusive optical methods which are based upon multiple-beam interference phenomena. The QCM validated the interference measurements. This experiment established proof-of-concept for a miniature system for monitoring ice accumulation within the chamber.

P.8.a.003 Polypharmacy among psychiatric outpatients in Kuwait

With the disappearance of the radiuscope, alternative methods must be developed to accurately measure gas-permeable (GP) lenses. The purpose of this study was to design, manufacture, and test a novel attachment for the evaluation of spherical base curves of GP rigid contact lenses using a corneal topographer.A topographer attachment was devised with the intent of measuring the surface radii of GP lenses. A front-surface mirror was fixed at a 45° angle above a hemispherical GP lens mount taken from a radiuscope. The device was set in the chin rest of a Humphrey Atlas topographer (Carl Zeiss Meditec, Inc., Jena, Germany) such that the image from the back of a GP surface was focused. The base curve radii of 9 rigid polymer buttons nominally ranging from 5.00 mm to 9.00 mm in 0.5-mm steps were measured 3 times with a Neitz Auto CG (Neitz Instruments Co., Ltd., Tokyo, Japan), Reichert Radiuscope (Reichert Ophthalmic Instruments, Depew, New York), and Humphrey Atlas topographer using the base curve (BC) attachment.An analysis of variance with replication and without interaction, using the main effects of measurement method (n = 5) and nominal button radius (n = 9), found that there was no statistically significant effect of the base curve measurement method (F[4, 122] = 1.23; P = 0.303), although there was a statistically significant effect of nominal button radius (F[8, 122] = 4.70; P = 0.003).Although the optical system of the corneal topographer was designed for measurement of convex surfaces, measurement of base curve radii from concave surfaces was performed without a correction factor using the prototype attachment. The mean SimK and Axial radii were within the tolerance for GP base curve radius, 0.05 mm, cited in ANSI Z80.20-2004 and ISO 18369-2:2006. Thus, the clinical feasibility of this prototype BC attachment to support measurement of spherical base curve radii for GP lenses by a corneal topographer was demonstrated.

Development and mean life of aluminum first-surface mirrors for solar energy applications

Aluminum solar mirrors are an alternative for solar concentrators. This paper presents the first aluminum-surface solar mirrors, which, after 12 years of exposure to the aggressive weather conditions of Mexico City, have a reflectance decrease of only 3% (from 0.85 to 0.82), with only small scratches on the SiO 2 layer. Furthermore, two alternatives are presented for solar aluminum mirrors: mirrors with integrated first and second surfaces and first-surface compound mirrors. Each mirror and its fabrication are described, along with their weather tests. The aluminum first-surface solar mirror lasts for at least 12 years, and is a good alternative material for parabolic troughs, heliostats, CPC, Fresnel technology and dish concentrators.

Prototype base curve attachment for the topographer: What will replace the vanishing radiuscope?

Background With the disappearance of the radiuscope, alternative methods must be developed to accurately measure gas-permeable (GP) lenses. The purpose of this study was to design, manufacture, and test a novel attachment for the evaluation of spherical base curves of GP rigid contact lenses using a corneal topographer. Methods A topographer attachment was devised with the intent of measuring the surface radii of GP lenses. A front-surface mirror was fixed at a 45° angle above a hemispherical GP lens mount taken from a radiuscope. The device was set in the chin rest of a Humphrey Atlas topographer (Carl Zeiss Meditec, Inc., Jena, Germany) such that the image from the back of a GP surface was focused. The base curve radii of 9 rigid polymer buttons nominally ranging from 5.00 mm to 9.00 mm in 0.5-mm steps were measured 3 times with a Neitz Auto CG (Neitz Instruments Co., Ltd., Tokyo, Japan), Reichert Radiuscope (Reichert Ophthalmic Instruments, Depew, New York), and Humphrey Atlas topographer using the base curve (BC) attachment. Results An analysis of variance with replication and without interaction, using the main effects of measurement method (n = 5) and nominal button radius (n = 9), found that there was no statistically significant effect of the base curve measurement method (F[4, 122] = 1.23; P = 0.303), although there was a statistically significant effect of nominal button radius (F[8, 122] = 4.70; P = 0.003). Conclusions Although the optical system of the corneal topographer was designed for measurement of convex surfaces, measurement of base curve radii from concave surfaces was performed without a correction factor using the prototype attachment. The mean SimK and Axial radii were within the tolerance for GP base curve radius, 0.05 mm, cited in ANSI Z80.20-2004 and ISO 18369-2:2006. Thus, the clinical feasibility of this prototype BC attachment to support measurement of spherical base curve radii for GP lenses by a corneal topographer was demonstrated.

High-accuracy small-angle measurement of the positioning error of a rotary table by using multiple-reflection optoelectronic methodology

To improve upon and provide a methodological alternative to published optoelectronic angle measurement systems, the paper performs high-accuracy angle measurement by use of laser diodes, dual-axis position sensing detectors, and a series of reflections between two first-surface mirrors. Measurement accuracy improves from 0.5 to 0.05 arc sec as the light ray is reflected back and forth several times between the mirrors. Analytic ray tracing is used to model the reflected light ray so as to determine the system equations implicitly in terms of the measured angles. The first-order Taylor series expansion provides a linear form of the system equations. To validate the system, a prototype is built. Calibration and stability experiments are performed. Experimental results show the resolution, accuracy, and measurement range are, respectively, 0.008, 0.05, and ±250 arc sec. Compared with traditional optical angle measurement systems, this method has many merits such as low cost, simple configuration, high sensitivity, and high linearity.