大口径标准球面镜组研制与应用

As one of the coherent diffractive imaging (CDI) techniques, coherent modulation imaging (CMI) is a lensless phase imaging technology with diffraction limited resolution in theory. Unlike multiple measurement phase retrieval algorithms, the CMI can achieve fast convergence speed with single-shot measurement by introducing a pre-characterized random phase modulator. Besides, it has simple structure without reference wave based on iterative engine. Despite the fact that the matured phase imaging can be used to implement the on-line wave diagnostics of laser pulse, in this work we accurately measure the face-type of optical component with peak-to-valley value below 0.5<i>λ</i> (<i>λ</i> = 632.8 nm) by using the CMI for the first time. In order to verify its measurement capability, 10 quartz windows with a diameter of 80 mm and PV value between 0.1<i>λ</i> and 0.5<i>λ</i> are repeatedly measured. Compared with the results of commercial interferometer, the root mean square error (Root MSE) of the peak-to-valley (PV) ratio of the results of the CMI is 0.0305<i>λ</i>, and the Root MSE of the root mean square (RMS) is 0.00522<i>λ.</i> The measurement accuracy of PV ratio and RMS can reach 0.1<i>λ</i> and 0.01<i>λ</i> respectively. In addition, the parallel flat with PV ratio = <i>λ</i>/20 is measured and analyzed with CMI, and its noise level is also analyzed. Considering that the potential improvement of CMI is available in the future, the CMI is expected to become a new technique for optical metrology with high precision, which is different from interferometry.

We present a rapid process for producing flat and smooth surfaces. In this technical note, a fabrication result of a carbon mirror is shown. Electrolytic in-process dressing (ELID) grinding with a metal bonded abrasive wheel, then a metal-resin bonded abrasive wheel, followed by a conductive rubber bonded abrasive wheel, and finally magnetorheological finishing (MRF) were performed as the first, second, third, and final steps, respectively in this process. Flatness over the whole surface was improved by performing the first and second steps. After the third step, peak to valley (PV) and root mean square (rms) values in an area of 0.72 x 0.54 mm2 on the surface were improved. These values were further improved after the final step, and a PV value of 10 nm and an rms value of 1 nm were obtained. Form errors and small surface irregularities such as surface waviness and micro roughness were efficiently reduced by performing ELID grinding using the above three kinds of abrasive wheels because of the high removal rate of ELID grinding, and residual small irregularities were reduced by short time MRF. This process makes it possible to produce flat and smooth surfaces in several hours.

The Ritchey-Common test is widely adopted to measure large optical flats. The traditional Ritchey-Common test eliminates the defocus error with multiple tests by changing the position of the mirrors, which suffers from cumbersome steps, poor repeatability, coupled system error, extra mirror deformation, and potential overturning. The above problems increase the test time, decrease the reliability and accuracy, increase the test cost, and threaten manufacturing safety. We propose a single-test Ritchey-Common interferometry to avoid the obligatory position change in the traditional method. A sub-aperture of test flat is directly measured by a small-aperture interferometer before the test, which is easy to implement, to replace the extra system wavefront measurement in different positions. The defocus is calculated in sub-aperture at exactly the same position as the full-field measurement without the position change, then the surface form under test can be obtained with accurate optical path modeling. Measurement experiments for 100 mm and 2050 mm aperture flats were performed to demonstrate the feasibility of this method. Compared with a direct test in a standard Zygo interferometer, the peak to valley (PV) and root mean square (RMS) errors were 0.0889 λ and 0.0126 λ (λ=632.8 nm), respectively, which reaches the upper limit of accuracy of the interferometer. To the best of our knowledge, this is the first proposal of the Ritchey-Common test that can eliminate the defocus error and realize high accuracy measurement in a single test. Our work paves the way for reliable and practical optical metrology for large optical flats.

The complicated surface part generally possesses exceptional properties, then the developments of high-end equipment and the precision physics experiment are in pressing demand of it. To accurately manufacture the complicated surface part, this study presents a toolpath generation strategy for slow tool servo (STS) turning with position-velocity-time (PVT) interpolation under the constraint of the specified interpolation error. Based on the mathematical principle of PVT interpolation, the interpolation point is calculated. With the anticipant curve represented with a spatially circular arc, the cutter contact point (CCP) of the toolpath with PVT interpolation is derived under the constraint of the specified interpolation error by way of the presented bisection algorithm. Then the cutter location point (CLP) of the toolpath is calculated through the tool nose radius compensation for STS turning. The validated experiment shows that the workpiece machined with the toolpath with PVT interpolation generated through the proposed scheme satisfies the constraint of the specified interpolation error. The peak to valley (PV) value of the form error of the surface is 8.2 μm, besides the root mean square (RMS) value of the form error is 1.9 μm. The volume of CLPs of the toolpath is reduced by 51.7% compared with the toolpath discretized by an equal angle. The achievement of this study provides guidance for the STS precision turning with PVT interpolation for the complicated surface.

Nowadays, large-aperture optical components are increasingly used in high-power laser systems, remote-sensing satellites, and space-based astronomical telescopes. Fabricating these surfaces with submicron-scale shape accuracy and a nanoscale surface finish has been a great challenge for the optical industry, especially for hard and difficult-to-machine materials. Thus, to achieve the high-efficiency and high-precision polishing of large-aperture aspherical optical parts, this study combined robotic machining technology with computer-controlled optical surfacing (CCOS) technology and investigated the effect of robot motion accuracy on the surface topography of workpieces during polishing. First, a material removal model considering the normal error of the polishing tool was developed based on contact mechanics, kinematic theory, and the abrasion mechanism. Next, in combination with the polishing trajectory, the surface morphology and form accuracy after polishing were predicted under different normal-error conditions. Then, preliminary experiments were conducted to verify the model. The experimental data agreed with the simulation results, showing that as the normal error increased from 0° to 0.5° and 1°, the peak-to-valley (PV) values of the surface profile of the optical element decreased from 5.42, 5.28, and 4.68 μm to 3.97, 4.09, and 4.43 μm, respectively. The corresponding convergence rates were 26.8%, 22.5%, and 5.3%. The root mean square (RMS) values decreased from 0.754, 0.895, and 0.678 μm to 0.593, 0.620, and 0.583 μm, with corresponding convergence rates of 21.4%, 30.7% and 14.0%, respectively. Moreover, a higher motion accuracy enabled the polishing robot to reduce the mid- and high-frequency errors of the optical element.

Channel-cut monochromators can be easily incorporated in high-resolution image techniques. However, polishing on the inner diffracting surfaces is difficult because of blockage by the opposite face. To address this difficulty, an open-faced monolithic monochromator has been designed, produced and tested using x-rays at the Advanced Photon Source (APS). The open-faced channel cut has a "Z"-shape geometry with a hole in the mid section to allow passage of the diffracted beam. The open geometry allowed chemical mechanical polishing so that an optically smooth finish on both surfaces was achieved. The high-resolution x-ray imaging and topography measurements revealed that the new design introduces significantly less distortions in the phase-contrast images compared with conventional channel-cut monochromators produced using etching alone.

Carrier squeezing interferometry with π/2 phase shift at the synthetic wavelength: Phase extraction in simultaneous dual-wavelength interferometry

This paper investigates the feasibility of measuring form error of all the optical surfaces on a lens in a single setup using a dual tipped diamond stylus. Two lenses were measured with a dual, 2 μm conisphere tipped, diamond stylus on a tactile profilometer having a phase grating interferometer (PGI) gauge. When the lens was mounted in a horizontal orientation, one of the stylus tips was used to measure the optical surface on top of the lens (hereafter referred to as measurement using normal bias), whereas the other stylus tip (180˚ opposite) was used to measure the optical surface on bottom of the lens (hereafter referred to as measurement using reverse bias). To validate the results from the measurement using reverse bias, a given optical surface was measured using both normal bias and reverse bias of the PGI gauge with a suitable fixture. Moreover, this surface was also measured on a LuphoScan instrument, a 3D non-contact profiler based on multiwavelength interferometry, and an average form error profile was extracted from the 3D surface form error map. Surface form was quantified by evaluating peak-to-valley (PV), and root mean square (RMS) parameters to compare the results obtained from measurements using normal bias, reverse bias, and multiwavelength interferometer. It is shown that there is a good agreement not only between normal bias and reverse bias measurements using PGI gauge but also with measurement performed on multiwavelength interferometer. With this additional capability of PGI gauge to measure form error of all the optical surfaces in a single setup, results from both surfaces can be correlated to determine wedge, commonly referred to as inner centration, decenter error between the two surfaces, and thickness of the lens under test.

The purpose of this study was to evaluate which type of Ni-Ti files are able to maintain canal configuration better in the simulated canal with abrupt curvature near it's apex. Ninety six simulated root canals were made in epoxy resin and 15 finger spreader was used as root canal templates. The simulated root canals were made with radius of curvature of 1.5mm, 3.0mm, 4.0mm, 6.0mm respectively and the angle of curvature of all simulated canals were adjusted to 90 degree. The simulated canals were instrumented by ProFile, ProTaper, Hero 642, and at a 300 rpm using crown-down pressureless technique. Pre-instrumented and post-instrumented images were taken by digital camera and were superimposed with Adobe Photos hop 6.0 program. Images were compared by image analysis program. The changes of canal width at the inner and outer side of the canal curvature. canal transportation were measured at 9 measuring point with 1 mm interval. Statistical analysis among the types of Ni-Ti files was performed using Kruskal-Wallis test and Mann-Whitney U-test. The result was that ProFile maintain original canal configuration better than other engine driven Ni-Ti files in the canals above 3.0mm radius of curvature, and in the 1.5mm radius of curvature, most of Ni-Ti flies were deformed or separated during instrumentation.

This study addressed the critical challenge of systematic alignment errors in freeform surface measurement, which arose from spatial deviations between design and measurement coordinate systems. An enhanced Coherent Point Drift (CPD) registration method incorporating 3D-Harris feature point extraction was proposed. The methodology employed the 3D-Harris operator to extract local curvature feature points, significantly reducing data volume while preserving essential geometric characteristics. An initial coarse registration was achieved through coordinate transformation of the feature point set, followed by precision fine registration using the CPD algorithm enhanced with local structural constraints. Comprehensive experiments using the standard Bunny model and freeform surface measurement data demonstrated the superior performance of the proposed method. Compared to conventional CPD algorithms, the method achieved reductions of 34% in peak-to-valley (PV) error and 31% in root-mean-square (RMS) error on the Bunny model, along with a 77% reduction in computation time. For freeform surfaces, the method attained exceptional precision with PV = 11 nm and RMS = 7 nm registration errors, while maintaining high efficiency with a processing time of approximately 1.4 seconds. These results confirmed the effectiveness of the proposed approach in achieving high-precision and high-efficiency point cloud registration for freeform surfaces.

This study aimed to compare ocular wavefront aberrations for pupil diameters of 4 mm and 6 mm, and contrast sensitivity, in eyes with AcrySof IQ and AcrySof Natural intraocular lenses (IOLs). Sixty eyes of 60 patients were enrolled in this prospective randomized study. After phacoemulsification the eyes received either AcrySof IQ SN60WF or AcrySof Natural SN60AT IOLs. One month after surgery, all patients underwent complete ophthalmological examination including corneal topography, wavefront analysis for pupil diameters of 4 mm and 6 mm, and contrast sensitivity measurements with the CSV 1000E instrument under photopic and mesopic conditions with and without glare. There was no statistically significant difference between groups in age, sex or other preoperative ocular characteristics (p > 0.05). Patients with AcrySof IQ IOLs had higher contrast sensitivity at 6 c.p.d. under photopic conditions, at 6 c.p.d. and 18 c.p.d. under mesopic conditions, and at 6 c.p.d., 12 c.p.d. and 18 c.p.d. under mesopic conditions with glare (p < 0.05). Corneal spherical aberration was 0.273 ± 0.074 μm in the AcrySof Natural group and 0.294 ± 0.086 μm in the AcrySof IQ group (p = 0489). Ocular spherical aberration was 0.362 ± 0.141 μm and 0.069 ± 0.043 μm (p < 0.001) for 6-mm diameter pupils and 0.143 ± 0.091 μm and 0.017 ± 0.016 μm (p < 0.001) for 4-mm diameter pupils, with AcrySof Natural and AcrySof IQ IOLs, respectively. There were no significant differences in other higher-order aberrations between the groups (p > 0.05). Aspherical AcrySof IQ IOLs significantly reduced spherical aberration for pupil diameters of both 4 mm and 6 mm and also improved contrast sensitivity more than spherical AcrySof Natural IOLs, especially in mesopic conditions.

Cold-background multitarget compounding system provides infrared targets for hardware-in-the-loop simulation system, in which large aperture reflective mirrors are employed. In this paper, we proposed a combined belt-back structure and designed the flexible connection to solve support mechanism of large aperture mirrors for 100K temperature variations. By Finite Element Method analysis, root mean square (RMS) of optimized mirror was better thanλ/40 under self-gravity and 100K temperature variations. By Zernike polynomial fitting, MTF of multitarget compounding system was over 0.5 and RMS spot diameter was less than 0.05mrad. Results demonstrated that the proposed support mechanism was effective and provided analytical data for 1m level mirror in large environment temperature variations.

The phase diversity (PD) algorithm is an image-based co-phasing error detection method for segmented mirror synthetic aperture optical systems. Particle swarm optimization (PSO) is suitable for PD for its fast convergence speed and simple structure. However, with the increase of the numbers of subapertures, optimization of cost function formed by the PD algorithm becomes a high-dimension non-linear optimization problem, which would lead PSO to result in a premature solution. Regarding the problem above, this paper presented a modified PSO in the PD algorithm to co-phase the segmented primary mirror, which overcame drawbacks of the traditional PSO, such as premature convergence and deactivation of particles, and enhanced the dig ability of the algorithm. Vast simulation results show that the modified PSO in the PD algorithm can effectively restore the segmented primary mirror, reducing the peak-to-valley (PV) value to 0.0012λ and the root mean square error to 0.0007λ, and raising the Strehl ratio to over 0.999. A comparison was also conducted to show that the modified PSO has advantages over two existing algorithms in higher accuracy and faster convergence speed.

Force and vibration generated in apical direction by three endodontic files of different kinematics during simulated canal preparation: An in vitro analytical study.

We use the swing ion-beam etching method to fabricate short wave infrared convex blazed gratings. This method solves the consistency problem of blaze angles by swing etching through the meridian direction of the gratings. A geometric model is built to analyze the influence of swinging speed and beam slit width on groove evolution. Convex gratings with a 45.5 gr/mm groove density, 67 mm aperture, 156.88 mm radius of curvature and 2.2 blaze angle have been fabricated and measured. Experimental results validate that high-efficiency convex gratings of small blaze angle and high groove consistency can be produced by swing etching to satisfy the requirements for high spectral resolution and miniaturization of imaging spectrometers.