Novel Information-Driven Smoothing Spline Linearization Method for High-Precision Displacement Sensors Based on Information Criterions.

A noise-resistant linearization model that reveals the true nonlinearity of the sensor is essential for retrieving accurate physical displacement from the signals captured by sensing electronics. In this paper, we propose a novel information-driven smoothing spline linearization method, which innovatively integrates one new and three standard information criterions into a smoothing spline for the high-precision displacement sensors' linearization. Using theoretical analysis and Monte Carlo simulation, the proposed linearization method is demonstrated to outperform traditional polynomial and spline linearization methods for high-precision displacement sensors with a low noise to range ratio in the 10-5 level. Validation experiments were carried out on two different types of displacement sensors to benchmark the performance of the proposed method compared to the polynomial models and the the non-smoothing cubic spline. The results show that the proposed method with the new modified Akaike Information Criterion stands out compared to the other linearization methods and can improve the residual nonlinearity by over 50% compared to the standard polynomial model. After being linearized via the proposed method, the residual nonlinearities reach as low as ±0.0311% F.S. (Full Scale of Range), for the 1.5 mm range chromatic confocal displacement sensor, and ±0.0047% F.S., for the 100 mm range laser triangulation displacement sensor.

Chromatically multi-focal optics based on micro-lens array design.

CCD arrays encode color information via uniformly distributed red, green and blue pixels. Therefore, even a perfectly achromatic system projecting an image onto a CCD plane cannot possibly associate a single object point with the 3 or more discrete pixels encoding color content. Here, we propose and demonstrate a micro-lens array (MLA) design that simultaneously corrects chromatic aberrations and separates color channels to spatially distinct pixels. Starting from a commercially available aspheric condenser lens, methods to design and assess the performance of a few microns deep MLA etched on the convex optical surface are detailed. Actual fabrication is carried out by fluid jet polishing, with an optical form deviation of 0.24 µm rms. Finally, the MLA is assessed with a narrowly collimated beam containing two wavelengths, which produces distinct spots of diameter 10-15 µm as expected.

A novel piezoelectrically actuated 2-DoF compliant micro/nano-positioning stage with multi-level amplification.

This article presents a novel two-degrees-of-freedom (2-DoF) piezo-actuated parallel-kinematic micro/nano-positioning stage with multi-level amplification. The mirror symmetric stage consists of four leverage mechanisms, two Scott-Russell mechanisms, and a Z-shaped flexure hinge (ZFH) mechanism. Taking advantage of the ZFH mechanism, 2-DoF motions with final-level flexural amplification and decoupled motion guidance are achieved. Analytical models of the stage are developed and validated through finite element analysis to characterize its working performance. Practical testing of a prototype stage is conducted to demonstrate the design process and to quantify its response characteristics. Due to the utilized multi-level amplification, a practical amplification ratio of 13.0 is realized by the prototype. The decoupled output motion guidance feature of the stage makes it amenable for implementation in raster scanning type of measurements.

Note: Symmetric modulation methodology applied in improving the performance of scanning tunneling microscopy.

A symmetric modulation methodology is proposed to combine robust control of external disturbance, rapid response to steep sidewalls with the high speed of a traditional scanning tunneling microscopy. The 1400 × 200 µm(2) topography of a comb-like steep sidewalls micro-structure with the depth of 23 µm was acquired at a high scanning speed of 120 µms(-1) and the detectable slope angle is up to 85°. The total measuring time was only 17 min. In addition, a 4 × 4 mm(2) aluminum dual-sinusoidal array has been successfully measured with a scanning speed up to 500 µms(-1). It improved the performance of the normal scanning tunneling microscope and enables efficient and stable measurement of large-area complex micro-structures, and thus can be introduced to engineering applications.