Sensing One Nanometer Over Ten Centimeters: A Microencoded Target for Visual In-Plane Position Measurement

Abstract

At the nanoscale, accurate control and position sensing are recurrent issues conditioning advances of technologies and instruments in diverse fields of application. Recent advances were reported that combine optical microscopy and computer vision for non-contact and multi-axis position sensing of end-effectors with a high accuracy. This paper contributes to this domain by introducing a micro-encoded target aimed to high accurate ( , , ) measurements over an extended range. The micro-encoded target is designed to allow linear phase measurements, leading to high accuracy in position sensing, and unambiguous binary encoding leading to absolute position determination. In this way, ultimate performances and allowed measurement ranges are independent of each other and a current zone of observation can be registered with respect to the whole encoded area with an extra-large range-to-resolution ratio. Experiments reported in this paper demonstrate a precision below one nanometer in lateral position and of 4 • 10 −6 rad. in rotation with an encoded target of more than 11 × 11 cm 2 . The device demonstrated can be either inserted into experimental setups to allow accurate position control or used to calibrate in-plane displacements of one to three degrees of freedom actuators.

Nanometer Precision With a Planar Parallel Continuum Robot

“…This algorithm provides position and orientation with a resolution of 0.5 nm and 1 µrad. [27] the robot, shown in Fig. 3 and presented in section IV, is captured by a vision measurement system that is composed of a camera IDS UI3880CP-C-HR-R2, an Edmund microscope tube and a Mitutoyo 10× zoom.…”

Characterization of Angle Accuracy and Precision of 3-Degree-of-Freedom Absolute Encoder Based on NanoGPS OxyO Technology

“…While the general principle of vision-based 3-degree-of-freedom (3-DOF) position sensors has been documented in works published by different groups, implementations differ depending on intended sensor uses. Sensors based on this principle were developed in the context of microscopy [4,5,12], robotics [8], metrology [6], quality assurance (QA)/quality control (QC) and motion control [10][11][12][13], or general purposes [3,6,9].…”

“…HORIBA France developed a vision-based 3-DOF encoder [5,[9][10][11][12] that was designed to provide motion control to scientific instruments and quality-control solutions for motion systems. It is commercially available under trademark nanoGPS OxyO ® .…”

“…The present understanding of the capabilities of 3-DOF vision-based sensors is limited from a metrology point of view. It was established that this method has subpixel resolution [3,4,[6][7][8][9]11]. When expressed in the object plane, reports on precision vary between nm fractions to several tenths of nm.…”

“…Several papers also provide indications on angle precision. Chen reported 1.2 µrad standard deviation and 2.5 µrad systematic error on a travel of 2 mrad [6], Kim reported a resolution of 0.001 • (i.e., 17 µrad) [7], and the Sandoz group reported a precision of 4 µrad [9]. The precision of the nanoGPS OxyO ® encoder was determined to be slightly better than 10 µrad [10].…”