Key Engineering Materials Vols. 295-296

Abstract: Autocorrelation and cross-correlation functions are proposed for 2D and 3D surface texture comparisons. At the maximum correlation point of the two correlated surface textures, there is a peak shown at the cross-correlation curve. It is proposed to generate a difference function at the maximum correlation point for evaluation of the difference between the two compared surface textures. Based on this method, the National Institute of Standards and Technology (NIST) bullet signature measurement system is developed for the bullet signature measurements of NIST standard bullets.

Abstract: Linear filters are widely used for smoothing measurement data in dimensional metrology and surface texture analysis. In the past, the use of linear filters was mainly limited to Gaussian or even 2RC filters. Recent advances in spline filter theory have paved the way for the development of more flexible and powerful linear filters. This paper deals with the general characteristics of these filters.

Abstract: This paper is aimed to develop and implement a web-based 3D surface evaluation, analysis and simulation software. The software can provide users from all around the world with a means to conduct surface study through the Internet. The software automatically calculates all 3D surface roughness parameters and has options for the user to view various 2D and 3D graphical representations of the entire surface. All outputs calculated are viewed through a web browser or can be downloaded to a user computer, giving the user a complete numerical and graphical representation of any surface for which they have measured the surface data.

Abstract: For linear textures, widely exist on 3D engineering surfaces, a method for characterization based on the spectrum analysis is proposed. Through an angular spectrum analysis of the power spectrum of 3D surface signals, the directional characteristic parameters of the linear texture distribution on the surface are extracted. By using the directional parameters, the engineering surface can be roughly identified. A texture detector based on the directional Gabor wavelet transformation is used to detect the texture signals. The linear texture features of different directions and scales on a complex engineering surface can be decomposed. A weighting multi-scale correlative analyzing method is presented. The correlation analysis results of the texture features of different scales are weighted according to the significance and summed to obtain the final correlation results. Through Laplacian differential operation of the correlative output, a sharper correlative peak is obtained. This method has been successfully used to extract and identify bullet marks.

Abstract: A reliable reference is the key to characterize surface topography. Gaussian filtering is strongly recommended by experts in the international standardization field. However, it can be affected by abnormal surface features. Based on the principle of M-estimation, a novel robust weighting function is proposed to improve the Gaussian filtering and a 3D robust Gaussian filtering model is developed. Experimental results have proven them effective.

Abstract: As a special surface texture evaluation method, motif has received much attention since it was adopted as an ISO standard which is ISO12085 1996. However, like many other evaluation methods, it is based on 2 dimensional lines. The surface itself is three dimensional in nature. 3D motif evaluation should be more suitable. Until now, no 3D motif evaluation method has yet been proposed. A key issue is 3D motif combination to determine how the evaluation should be implemented. Three types of 3D MOTIF combination methods currently used are examined. Features such as algorithm complexity and application range are investigated. We conclude that the best 3D Motif combination method is not currently available. We should select a combination method based on the need for surface function analysis. Hybrid methods are also recommended.

Abstract: The development of a three-dimensional surface profilometer using digital fringe projection technology and phase-shifting principle is presented. Accurate and high-speed three-dimensional profile measurement plays a key role in determining the success of process automation and productivity. By integrating a digital micromirror device (DMD) with the developed system, exclusive advantages in projecting flexible and accurate structured-light patterns onto the object surface to be measured can be obtained. Furthermore, the developed system consists of a specially designed micro-projecting optical unit for generating flexibly optimal structured-light to accommodate requirements in terms of measurement range and resolution. Its wide angle image detection design also improves measurement resolution for detecting deformed fringe patterns. This resolves the problem in capturing effective deformed fringe patterns for phase shifting, especially when a coaxial optical layout of a stereomicroscope is employed. Experimental results verified that the maximum error was within a reasonable range of the measured depth. The developed system and the method can provide a useful and effective tool for 3D full field surface measurement ranging from µm up to cm scale.

Abstract: A two-dimensional surface profile imaging technique based on heterodyne interferometer is proposed. A piezo translator vibrated grating is used to generate a heterodyne signal. A high speed CCD camera is used to extract the interference signal using a five step method. The uncertainty in the displacement measurement is approximately 0.035 µm within a measurement range of 1.7 µm, confirming the two dimensional heterodyne interferometer is valid for measuring the surface profile. The method is also available for low coherence heterodyne interferometer due to the optical frequency shifts caused by the vibration of grating independent on the wavelength.

Abstract: A laser measurement technique based on polarized heterodyne astigmatic principle is proposed for high precision three-dimensional (3D) profile measurement. In the presented system, the defocus astigmatic signal coming from the polarized reflection of the detected 3D surface is used to determine the position of the surface. The work of tracing, scanning and processing of the detected 3D surface is performed by combining the system with an ultra precision laser coordinate measuring machine (CMM). Compared with the current heterodyne astigmatic measuring technique, a polarization incidence and Glan-Thompson prism (GP) is used in the novel polarized heterodyne astigmatic measuring method. The anti-interference ability of the optical sensing system is significantly improved. The undesired influence on the measurement results, caused by fluctuation of surrounding brightness, by the intensity disturbance of the laser source, and by the multi-reflection among optical elements, is effectively restrained. Experimental results show that the stability of the optical sensing system is better than 2%. The resolution of the system is better than 0.005µm.

Abstract: A nanometer profilometer in which the measuring force can be controlled is proposed. The key part is the nanometer profiling core, which consists of a voice coil motor with a short and movable voice coil and an inductive transducer. According to the A/D value of the transducer signal, the measuring force can be adjusted to approximately µN level by use of a PID control algorithm. The advantages of contact type and non-contact type profilometer are possessed by the proposed instrument.