With the continuing trend toward device miniaturization in many engineering and scientific fields, the need to accomplish highly-precise measurements at the micro- or nano scale has emerged as a critical concern. In practice, the accuracy of high-precision machines is affected by the Abbe principle due to inevitable angular errors during motion. Therefore, this study focuses on the development of a high precision nanometer level co-planar XY stage with miniature multi-degree-of-freedom measurement system (MDFMS).
The symmetric structural design of the co-planar stage is considered to eliminate the structure deformation due to force and temperature changes. The MDFMS is constructed by a wavelength corrected Michelson interferometer and a coaxial dual-axis autocollimator. The wavelength correction of the miniature laser interferometer is achieved by employing a holographic grating so that the real-time mean wavelength of the laser diode can be detected to the resolution of 0.001 nm. Controlling the temperature within 20 ± 2°C, the wavelength stability is less than 10^-6. Conventional complicated frequency stabilization technique is no more needed. In addition, using the laser diode as the light source, the MDFMS can be reduced to a small physical size so as to be used as the feedback sensor in the stage. The autocollimator has a resolution of 0.1 arc-sec and accuracy of ±0.3 arc-sec within the range of ±30 arc-sec in both axes. These detected angular errors can be used to compensate for the Abbe error if the functional point of the stage is at a certain Z-height, or called the Abbe offset. Experimental results show that, after error compensations, the positioning error can be controlled to ±20 nm for the travel up to 20 mm long.

Non-destructive testing (NDT) describes a wide range of methods for measuring and comparing physical quantities against a nominal condition. The most familiar laser based optical non destructive methods are based on the interference of wave fronts of monochromatic light reflected from a test surface. This paper will focus primarily on the profound review of operating principles of laser based non destructive methods involved with the measurement principles at Measurement Standards Laboratory (MSL). Michelson Inteferometric Principles with emphasis on minimizing alignment errors for better results will be assessed. The paper also enlists the discussion about airy points and its impact on measurement results. Uncertainties associated with the measurement results have been estimated using the GUM: Evaluation of measurement data — Guide to the expression of uncertainty in measurement procedures. The Agilent 5530 Laser Calibration Facility does provide the much needed Flexibility and better control. The necessary compensation factors including wavelength, air and material compensation factors with their due influence on the repeatability of the measurement results are studied. The range of optics involved in the measurement process both in linear and angular measurement procedures will be evaluated. A summary overview of different errors like Cosine, Abbe, and Dead path Errors resulting from the measurement of laser based dimensional parameters will be discussed with profound insight. By virtue of the high quality of its calibration services, MSL has gained national and international recognition to the kingdom of Saudi Arabia. It provides expertise and state-of-the art measurement infrastructure to ensure that the accurate calibration results are achieved with high degree of reliability. Precision engineering measurements at MSL are traceable to national and international calibration laboratories such as National Institute of Standards and Technology (NIST), USA, Physikalisch Technische Bundesanstalt (PTB), Germany, National Physical Laboratory (NPL), UK, Commonwealth Scientific Industrial Research Organization (CSIRO), Australia and more.MSL operates under the Total Quality Management Scheme and in conformity with ISO/IEC-17025: General requirements for the competence of testing and calibration laboratories guidelines. The information presented in this paper is most useful to the metrological organizations, who want to get enriched with comprehensive and exhaustive study involving the laser based measurement systems. This research grade laser based non destructive system will improve the metrological capabilities and will be of greater importance to the industrial community at large in Saudi Arabia.

Optical microscopy enables the observation of highly magnified objects and material structures on micro surfaces, however with the weakness that it can only acquire 2D images. In order to observe the areal features more accurately and intuitively, 3D surface micro topography recovery is applied to form a 3D surface model of an object from its 2D image sequence. Optical microscope has a limited depth of focus in large magnification, which makes the area within the depth of focus cleared and other area blurred. So this paper firstly acquires image sequence which obtains all useful information in one view by vertical scanning of the microscope. Secondly, each image is calculated by an appropriate focus measure operator to find the maximum focus measure value and form a 2D fused image. Then the maximum value of each pixel is accurately transferred into a distance value, forming a discrete depth map. After conducting interpolation, fitting and color mapping, a smooth and authentic 3D color model of the measured surface is obtained. Various focus measure operators such as grey level variance are used to compare their performances in 3D model recovery. The superiority of the modified Laplacian operator proposed in this paper is proved by experimenting on measured objects with different micro topography features such as ditch shaped and slope shaped structure. In addition, surface roughness information of R_a and R_z is extracted from the formed 3D models.

SelfA (Self-calibratable Angle device) encoder is an epoch-making encoder with the angular error self-calibration function. SelfA encoder, which has the structure of arranged several sensor heads around the scale disc at the equal angular interval space, by analyzing the angle signal from each sensor heads output in one revolution, can detect several angular error factors, not only angle scale error but an attachment error (eccentricity error). Because SelfA can carry out this self-calibration analysis after attached to the axis shaft of the apparatus, even if measurement condition changes, the people can use the encoder keeping the same angle accuracy. The SelfA encoder can achieve angle accuracy more than 0.1" by this function.
In this SelfA study, we find out that there was slight difference between the output angle signals in each SelfA sensor heads, furthermore, understand the slight difference is generated from axis shaft run out of the apparatus.
In order to estimate the ability of run out detection function of SelfA encoder quantitatively, we developed an axis run out generating device and carried out the experiment. In this experiment results, SelfA can detect dynamic RRO (Repeatable Run Out) and (NRRO: Non Repeatable Run Out) with very high sensitivity of accuracy about 50 nm level.

We present various metrology techniques for small-size microlenses, which can be applied to a single lens or thousands of microlenses. An individual microlens can be characterized by its optical performance and surface profile characteristics. First, the optical performance is characterized by using a high-resolution interference microscope (HRIM), which consists of Mach-Zehnder interferometer and an optical microscope. Second, a confocal microscope is applied to investigate the surface profile parameters. Third, the three-dimensional (3D) intensity distribution near the focus can be measured by the axial scanning function of the HRIM. Such 3D intensity maps allow us to characterize the focal properties of microlenses in an array. By deeply understanding those characterization techniques and measurement outputs, we develop a new method to characterize a large number of microlenses, for instance, more than one million lenses. This method is currently applied to wafer-based manufacturing in a cleanroom fab.