Model eyes with curved multilayer structure for the axial resolution evaluation of an ophthalmic optical coherence tomography device

Optical coherence tomography(OCT)has been widely applied to the diagnosis of eye diseasesduring the past two decades.However,valid evaluation methods are stil not available for theclinical OCT devices.In order to assess the axial resolution of the OCT system,standard modeleyes with micro-scale multilayer structure have been designed and manufactured in this study.Mimicking a natural human eye,proper Titanium dioxide(TiO_(2))materials of particles withdifferent concentrations were selected by testing the scattering coefficient of PDMS phantoms.The artificial retinas with multilayer films were fabricated with the thicknesses from 9.5 to 30 micrometers using spin coating technology,Subsequently,standard OCT model eyes were ac-complished by embedding the retina phantoms into the artificial frames of eyes.For ease ofmeasurement processing,a series of model eyes were prepared,and each contained flms withthree kinds of thicknesses.Considering the traceability and accuracy of the key parameters of the standard model eyes,the thicknesses of multilayer structures were verfed using ThicknessMonitoring System.Through the experiment with three different OCT devices,it demonstratedthe model eyes fabricated in this study can provide an effective evaluation method for the axialresolution of an ophthalmic OCT device.

Optical Test of Local Hidden—Variable Model

An inequality is deduced from local realism and a supplementary assumption. This inequality defines an experiment that can be actually performed with the present technology to test local hidden-variable models, and it is violated by quantum mechanics with a factor 1.92, while it can be simplified into a form where just two measurements are required.

New Test Light Spectrum Design for L/U-Band Extended Optical Fiber Line Testing System

This paper describes a new design for the test light source of an L/U-band extended optical fiber line testing system and the side-band suppresser ratio of the test light should be more than 70 dB.

Problems on fabrication of computer-generated holograms for testing aspheric surfaces

Interferometric optical testing using computer-generated hologram （CGH） can give highly accurate measurement of aspheric surfaces has been proved. After the system is designed, a phase function is obtained according to the CGH＇s surface plane. For the requirement of accuracy, an optimization algorithm that transfers the phase function into a certain mask pattern file is presented in this letter, based on the relationship between the pattern error of CGH and the output wavefront accuracy. Then the writing machine is able to fabricate such a mask with this kind of file. With that mask, an improved procedure on fabrication of phase type CGH is also presented. Interferometrie test results of an aspherie surface show that the whole test system obtains the demanded accuracy.

Fabrication and measurement of optical characterization of one dimensional photonic crystal with defect

Numerical calculations based on the transfer matrix method are carried out, and the results of band gap with resonance peaks are obtained. The electron beam lithography technology （EBL） and induction coupling plasma （ICP） etching are used to make the photonic crystal （PC） structures, and from several scanning electron microscope images, the PC structures are observed with features closing to the design. In order to create the tiny PC structures in the right places of the waveguide by the EBL technology at different time, some alignment markers are deposited on the chip, which are made of gold that deposited on titanium for its good adhesion to the underlying Si. An optical testing bed is designed for measurement of the optical characterization of PC structures. Through the analysis of the measured data, a △λ value of 0.8 nm is obtained and for the centre frequency of 1547 nm, a very high quality factor value of 1933 can be obtained. The 3-rim difference represents only a 0.2% error from the theoretical centre.

High precision mode of subaperture stitching for optical surfaces measurement

Subaperture stitching （SAS） provides us with an attractive way of extending the effective aperture and dynamic range of phase measuring interferometers. Accuracy of stitching algorithm becomes the key factor in the SAS technology. In this paper, the basic principle of SAS was introduced and four modes of SAS were discussed. The stitching experiments were done through the SSI-300 workstation designed and developed indepen- dently. There were several comparisons between the four different stitching methods and the measurement of full aperture. The results suggest that the global error averaging mode with reference of subaperture near optic axis is of high precision.

An approach for machining distortion measurements and evaluation of thin-walled blades with small datum

Inspection techniques for aero-engine blades are a hot topic in industry. Since these blades have a sculptured surface and a small datum, measurement results may deviate from an actual position. There are few proper approaches compensating for non-uniform distribution errors that are within specified tolerance ranges. This study aimed to develop a meshing structure measuring approach for the distortion of blades via non-contact optical 3D scanning. A rough measurement and a registration procedure are initially adopted to rectify the coordinate system of a blade, which avoids the initial coordinate system errors caused by the small datum. A measurement path with meshing structure is then unfolded on the blade surface. For non-uniform distribution errors, the meshing structure measurement is more visual and clear than the traditional constant height curves method. All measuring points take only 7 min to complete, and the distribution of error is directly and accurately presented by the meshing structure. This study provides a basis for future research on distortion control and error compensation.

Simultaneous measurements of s- and p-polarization reflectivity with a cavity ring-down technique employing no polarization optics

The cavity ring-down （CRD） technique is adopted for simultaneously measuring s- and p-polarization reflectivity of highly reflective coatings without employing any polarization optics. As the s- and p-polarized light trapped in the ring-down cavity decay independently, with a randomly polarized light source the ring-down signal recorded by a photodetector presents a double-exponential waveform consisting of ring-down signals of both s- and p-polarized light. The s- and p-polarization reflectivity values of a test mirror are therefore simultaneously determined by fitting the recorded ring-down signal with a double-exponential function. The determined s- and p-polarization reflectivity of 30° and 45° angle of incidence mirrors are in good agreement with the reflectivity values measured with the conventional CRD technique employing a polarizer for polarization control.

Four-quadrant demodulation fiber sensor for wavelength monitoring of a wavelength phase-shifting interferometer

Real-time monitoring of wavelength is important for high-speed wavelength phase-shifting interferometry.In this paper,a wavelength sensor based on a polarization-maintaining fiber interferometer with four-quadrant demodulation was proposed.We built the wavelength sensing system with resolution better than 0.005 pm and 0.1 ms sampling interval and measured the response time of the tuned wavelength at 35 ms in the phase-shifting process of a commercial wavelength phase-shifting free-space interferometer,as well as the wavelength drift velocity of 0.01 pm per second in the hysteresis process.The optical fiber wavelength sensor with four-quadrant demodulation provides a real-time wavelength sensing scheme for high-speed wavelength phase-shifting interferometers.

Accuracy and analysis of long-radius measurement with long trace profiler

The long trace profiler （LTP） is proposed to measure radius of curvature （R） and surface figure of a longradius spherical surface in an optical shop. Equipped with a motorized rotary stage and a two-dimensional tilt stage, the LTP scans the full aperture and calculates the absolute radius of curvature of each scanning line based on the least square method. Nonlinear error and manufacture error difference between center and the edge are obtained by comparing R results. The R-limit is validated and expressed as D/R, where D is the aperture of the mirror under test. A full-aperture three-dimensional figure is also reconstructed based on triangle interpolation.

On the technologies of Hα imaging spectrograph for the CHASE mission

The Hα imaging spectrograph(HIS) is the scientific payload of the first solar space mission, the Chinese Hα solar explorer(CHASE), supported by the China National Space Administration(CNSA). The CHASE/HIS achieves, for the first time in space, Hα spectroscopic observations with high spectral and temporal resolutions. Separate channels for the raster scanning mode(RSM) and continuum imaging mode(CIM) are integrated into one, and a highly integrated design is achieved through multiple folding of the optical path and ultra-light miniaturized components. The design of HIS implements a number of key technologies such as high-precision scanning of the optical field of view(FOV), high-precision integrated manufacturing inspection, a large-tolerance pre-filter window, and full-link solar radiation calibration. The HIS instrument has a pixel spectral resolution of 0.024 ? and can complete a full-Sun scanning within 46 s.