The Dual-Core 3D Measuring Microscope Leica DCM 3D offers a unique combination of confocal and interferometry in a single sensor head. The core technology is based on a fast reaction microdisplay placed in the position of the field diaphragm. Bright field, interferometric and confocal images can be generated by the control of the microdisplay. The non-moving part concept, the confocal microdisplay (MD), two light sources and two cameras (one color and one monochromatic) achieve high accuracy 3D measurements and unlimited depth of focus.
Confocal MD technology allows measurements of smooth to rough surfaces, of topographical differences ranging from 1 nm to several mm, and up to 70 degrees of local slope. In comparison to Laser Scan based systems or Spinning Disc, MD confocal technology needs no moving mechanical parts, increasing both image stability at high magnifications and light efficiency, and enhancing reliability and flexibility. Along with a LED based light source, MD technology prolongs instrument lifetime, reducing servicing and avoiding the cost of expensive spare parts.
Surface measurements are achieved in seconds. The system is easy to use. Just place your sample under the microscope, focus and click “Acquire”. It only takes a few seconds (typically less than 5) to get a 3D view of the surface comparable to those acquired with a scanning electron microscope, in a fraction of the time.
As an example, the paint adhesion ability on a steel surface was characterized. After polishing, the steel was too smooth to allow good adhesion of an enamel-based composition. To increase the adhesion the steel is processed with an acid attack to create micro-valleys. This enables the paint to penetrate further into the surface, increasing the effective contact area and improving adhesion to the upper layers. As a result the paint is fixed hard. If the micro-valleys are too deep, however, the upper layer of the paint tends to follow the shape of the valleys in the underlying steel surface. On the other hand, if the microstructures are not deep enough, there is no adhesion effect.
With the Leica DCM 3D it is possible to inspect the surface and obtain suitable quality parameters to decide if the surface treatment is adequate or not. Already after placing the surface under the microscope, it is easy to get a good idea of the depth of the micro-valleys. The real-time confocal image allows you to focus on top of the surface, move the focus down to the valleys and take a direct reading of the depth. After clicking the “Acquire” button to get a 3D view, the confocal scan was so fast that I didn’t get time to follow what was happening. A pseudocolor display of the topography was shown on the screen with clear presentation of the micro-valleys. Figures 3 and 4 show the result of such a measurement. In order to get a quantitative analysis of the micro-valleys, the 3D analysis software included with the system, called LeicaMap, was used.
The software automatically segments the regions of the upper structures and the regions of the valleys. The volume distribution of the segmented regions (Figure 4) was a suitable indicator for this purpose. Another useful parameter is Sdr. This parameter represents the proportion of the 3D surface that has been formed to the vertical projection of this area. Thus, a plane surface has a ratio of 1 : 1, while a surface with valleys increases the 3D area and thus this value. In our case we concluded that the optimum value should be 1 : 1.33, that is, a 33 % increase of effective area.