FOSSIL MICROSTRUCTURE USING 3D PROFILOMETRY

Transcription

1 FOSSIL MICROSTRUCTURE USING 3D PROFILOMETRY Prepared by Duanjie Li, PhD 6 Morgan, Ste156, Irvine CA P: F: nanovea.com Today's standard for tomorrow's materials NANOVEA

2 INTRODUCTION Fossils are the preserved remains of traces of plants, animals and other organisms buried in sediment under ancient seas, lakes and rivers. The soft body tissues usually decayed after death, but the hard shells, bones and teeth fossilized. Microstructure surface features are often preserved when mineral replacement of the original shells and bones takes place at a fine scale, which provide an insight into the evolution of creatures, change of weather and formation mechanism of fossils on the ancient earth. IMPORTANCE OF 3D NON-CONTACT PROFILOMETER FOR FOSSIL EXAMINATION 3D profiles of the fossil enable us to closely observe the detailed surface feature of the fossil sample from different angle. The high resolution and accuracy of the Nanovea profilometer allows detecting the intricate micro structure of the fossil surface which may not be discernable by the naked eye. The profilometer s analysis software offers a wide range of studies applicable to these unique surfaces. Unlike other techniques such as touch probes, the Nanovea 3D Non-Contact Profilometer measures the surface features without touching the sample. This allows preserving the true surface feature of certain delicate fossil samples. Moreover, the portable model JR25 profilometer enables 3D measurement on fossil sites, which substantially facilitates fossil analysis and protection after excavation. MEASUREMENT OBJECTIVE In this study, the Nanovea JR25 Profilometer is used to measure the surface of two representative fossil samples. The entire surface of each fossil was scanned and analyzed in order to characterize the surface features including roughness, contour and texture direction. Fig. 1: Non-contact optical pen scanning on the fossil sample. 2

3 RESULTS AND DISCUSSION Brachiopod fossil The first fossil sample presented in this report is a brachiopod fossil, which was from a marine animal that have hard "valves" (shells) on the upper and lower surfaces. They first appeared in the Cambrian, which is more than 550 million years ago i. The diagram and False Color View of The fossils are shown in Fig. 2 ii, and the 3D View in Fig. 3. (a) (b) Fig. 2: Diagram and False Color View of the brachiopod fossil. Fig. 3: 3D View of the brachiopod fossil. 3

4 The overall form was then removed from the surface in order to investigate the local surface morphology and contour of the brachiopod fossil as shown in Fig. 4. A peculiar divergent groove texture can be observed on the brachiopod fossil sample. (a) (b) Fig. 4: False Color View and Contour Lines View after form removal. Line profile is extracted from the textured area to show a crossectional view of the fossil surface in Fig. 5. The Step Height study measures precise dimensions of the surface features. The grooves possess an average width of ~0.38 mm and depth of ~0.25 mm. Fig. 5: Line profile and Step Height studies of the textured surface. 4

5 Crinoid stem fossil The second fossil sample is a crinoid stem fossil. Crinoids first appeared in the seas of the Middle Cambrian, about 300 million years before dinosaurs iii. The diagram and False Color View of The fossils are shown in Fig. 6, and the 3D View in Fig. 7. (a) (b) Fig. 6: Diagram and False Color View of the crinoid stem fossil. Fig. 7: 3D View of the crinoid stem fossil. 5

6 The surface texture isotropy and roughness of the crinoid stem fossil are analyzed in Fig. 8. The crinoid stem fossil has a preferential texture direction in the angle close to 90, leading to a texture isotropy of 69%. (a) (b) Fig. 8: Surface texture isotropy and roughness of the crinoid stem fossil. The 2D profiles along the axial direction of the crinoid stem fossil is shown in Fig. 9. The size of the peaks of the surface texture is fairly uniform. Fig. 9: 2D profile analysis of the crinoid stem fossil. 6

7 CONCLUSION In this application, we comprehensively studied the 3D surface features of a brachiopod fossil and a crinoid stem fossil using a JR25 Nanovea 3D Non-Contact Profilometer. We showcase that Nanovea 3D Non-Contact Profilometer can precisely characterize the 3D morphology of the fossil samples. The interesting surface features and texture of the fossil samples are further analyzed The brachiopod sample possesses a divergent groove texture, while the crinoid stem fossil shows a preferential texture isotropy. The detailed and precise 3D surface scan provides an ideal tool to the paleontologists and geologists to study the evolution of lives and formation of fossils. The data shown here represents only a portion of the calculations available in the analysis software. Nanovea Profilometers measure virtually any surface in fields including Semiconductor, Microelectronics, Solar, Fiber Optics, Automotive, Aerospace, Metallurgy, Machining, Coatings, Pharmaceutical, Biomedical, Environmental and many others. Learn more about the Nanovea Profilometer or Lab Services 7

8 MEASUREMENT PRINCIPLE: The Chromatic Confocal technique uses a white light source, where light passes through an objective lens with a high degree of chromatic aberration. The refractive index of the objective lens will vary in relation to the wavelength of the light. In effect, each separate wavelength of the incident white light will re-focus at a different distance from the lens (different height). When the measured sample is within the range of possible heights, a single monochromatic point will be focalized to form the image. Due to the confocal configuration of the system, only the focused wavelength will pass through the spatial filter with high efficiency, thus causing all other wavelengths to be out of focus. The spectral analysis is done using a diffraction grating. This technique deviates each wavelength at a different position, intercepting a line of CCD, which in turn indicates the position of the maximum intensity and allows direct correspondence to the Z height position. Unlike the errors caused by probe contact or the manipulative Interferometry technique, Chromatic Confocal technology measures height directly from the detection of the wavelength that hits the surface of the sample in focus. It is a direct measurement with no mathematical software manipulation. This provides unmatched accuracy on the surface measured because a data point is either measured accurately without software interpretation or not at all. The software completes the unmeasured point but the user is fully aware of it and can have confidence that there are no hidden artifacts created by software guessing. Nanovea optical pens have zero influence from sample reflectivity or absorption. Variations require no sample preparation and have advanced ability to measure high surface angles. Capable of large Z measurement ranges. Measure any material: transparent or opaque, specular or diffusive, polished or rough. Measurement includes: Profile Dimension, Roughness Finish Texture, Shape Form Topography, Flatness Warpage Planarity, Volume Area, Step-Height Depth Thickness and many others. A.1

9 1 z(x, y) dxdy A A 1 A A z2 (x, y)dxdy 1 Sq 3 [1 A A z3 (x, y)dxdy] 1 Sq 4 [1 A A z4 (x, y)dxdy] A.2