Ultra-precision diamond machining is a promising technique for non-rotationally symmetrical surfaces with sub-micrometer form accuracy. The measurement and compensation processes in the fabrication process must be conducted carefully to achieve high form accuracy. However, significant challenges remain to improve the measurement accuracy and machining efficiency. Because of the remounting process, the off-machine measurements would reduce the efficiency. On the other hand, contact-type measurements can cause physical damage to some soft materials. To overcome these problems, a noncontact on-machine measurement (OMM) system is developed using two optical probes, and a two-step compensation strategy is proposed to generate a modified tool path. To verify the accuracy of the proposed measurement system, OMMs were performed on a spherical mirror using this system and were later compared with off-machine measurements. To evaluate the compensation strategy, an off-axis paraboloid mirror was diamond-machined and compensated using the proposed method. The results show that the OMM system and compensation strategy are effective for improving the form accuracy while simultaneously enhancing the machining efficiency.

Chemical–mechanical polishing (CMP) is widely adopted as a key bridge between fine rotation grinding and ion beam figuring in super-smooth monocrystalline silicon mirror manufacturing. However, controlling mid- to short-spatial-period errors during CMP is a challenge owing to the complex chemical–mechanical material removal process during surface morphology formation. In this study, the nature of chemical and mechanical material removal during CMP is theoretically studied based on a three-system elastic–plastic model and wet chemical etching behavior. The effect of the applied load, material properties, abrasive size distribution, and chemical reaction rate on the polishing surface morphology is evaluated. A microscale material removal model is established to numerically predict the silicon surface morphology and to explain the surface roughness evolution and the source of nanoscale intrinsic polishing scratches. The simulated surface morphology is consistent with the experimental results obtained by using the same polishing parameters tested by employing profilometry and atomic force microscopy. The PSD curve for both simulated surface and experimental results by profilometry and atomic force microscopy follows linear relation with double-logarithmic coordinates. This model can be used to adjust the polishing parameters for surface quality optimization, which facilitates CMP manufacturing.

The demand for high-quality, lightweight infrared imaging systems is rapidly increasing. Single-lens computational imaging, combining single-lens with post-processing algorithms, offers a promising solution to miniaturize imaging systems while maintaining performance. However, these post-processing algorithms are typically highly complex, posing significant challenges for real-time reconstruction on a neural network processing unit (NPU) chip. This study investigates the relationship between the complexity of post-processing algorithms and lens modulation transfer function (MTF), demonstrating that a single-lens system with highly consistent MTF can significantly reduce the complexity of post-processing algorithms. Building on this insight, we proposed an enhancing lens MTF consistency-based single-lens design method and developed a single-lens computational infrared imaging system featuring a small Res-Unet (S-Res-Unet) neural network. Compared to the traditional method using the large Res-Unet (L-Res-Unet) to achieve comparable reconstruction performance, the proposed system achieved a 16-fold reduction in computational demands. As a result, it performed real-time reconstructions at the rate of 25 frames per second (fps) with a resolution of 640×480 on the RK3588 NPU chip, while maintaining system MTF exceeding 0.42 at Nyquist frequency of 42 lp/mm. This research paves the way for the practical application of computational infrared imaging systems.

To accurately measure the surface figure of curved mirrors with large radius of curvature (RoC) using stitching interferometry methods, three types of measurement errors are systematically studied, including retrace error, defocusing error within a single subaperture, and stitching angle error among different subapertures. It was found that part of the retrace error caused by the mismatch between the reference wavefront and reflected wavefront has little effect, while the overall retrace error, including the influence of the imperfect optical elements, will cause an error of 1–2 nm RMS within a single subaperture. Defocusing error will enlarge the error due to amplification of optical path error caused by the deviation of the position of the CCD. Because the error is mainly in the edge area, a slope threshold, which controls the maximum surface slope of each subaperture, can be optimized to reduce the effect of the defocus on stitching measurement error. Constant angle error among neighboring subapertures has the biggest accumulation effect on the final stitched figure. For the spherical mirror with RoC of 100 m of 80 m m × 40 m m , the error of the one-dimensional residual profile is 4.67 nm PV, assuming a constant angle error of 2 × 10 − 7 r a d . For the elliptical mirror with RoC of 60–140 m, it is more than 15 nm peak-to-valley (PV). It is because the profile difference caused by constant angle error is closer to a circle, which can be mostly removed after subtraction of a best-fit sphere. Based on the above error analysis, the developed algorithm-based stitching method was used to measure an elliptical cylindrical mirror of 74 m m × 40 m m with RoC of 60–140 m, and the result was compared with a slope measurement instrument from the Beijing Synchrotron Radiation Facility. After removing the best fitting ellipse profile, the one-dimensional difference between the two results is only 0.77 nm RMS, which demonstrated good measurement accuracy.

For higher detection capability, dual band/dual field of view (FOV) infrared imaging systems are often used to recognize camouflaged targets. In this Letter, we report a dual band/dual FOV infrared imaging system with freeform prism, in which the optical path is folded drastically. Each spectral band will pass through the same entrance pupil and then is split off by a beam splitter so that each spectral band can match a different FOV. Compared to traditional infrared imaging systems, the proposed system has advantages of less volume, higher integration, and optical efficiency.

The nested grazing incidence telescope can achieve a large collecting area in x-ray astronomy, with a large number of closely packed, thin conical mirrors. Exploiting the surface metrological data, the ray tracing method used to reconstruct the shell surface topography and evaluate the imaging performance is a powerful tool to assist iterative improvement in the fabrication process. However, current two-dimensional (2D) ray tracing codes, especially when utilized with densely sampled surface shape data, may not provide sufficient accuracy of reconstruction and are computationally cumbersome. In particular, 2D ray tracing currently employed considers coplanar rays and thus simulates only these rays along the meridional plane. This captures axial figure errors but leaves other important errors, such as roundness errors, unaccounted for. We introduce a semianalytic, three-dimensional (3D) ray tracing approach for x-ray optics that overcomes these shortcomings. And the present method is both computationally fast and accurate. We first introduce the principles and the computational details of this 3D ray tracing method. Then the computer simulations of this approach compared to 2D ray tracing are demonstrated, using an ideal conic Wolter-I telescope for benchmarking. Finally, the present 3D ray tracing is used to evaluate the performance of a prototype x-ray telescope fabricated for the enhanced x-ray timing and polarization mission.