Technology

2D and 3D line sensors are ideal instruments for scanning applications where high feed rates and / or continous measurements are needed. Solarius offers various 2D and 3D chromatic or monochromatic confocal line sensor technologies as well as triangulation sensors, based on different light sources and technical implementations, applicable to a wide range of surface measurement tasks.

Optical point sensors are a cost efficient and space-saving alternative for various scanning metrology applications or to replace tactile profile measuring systems with up to date non contact 3D metrology. Chromatic confocal and laser point triangulation sensor technologies provide most precise and acurate results for ISO compliant measurements in the Solarius portfolio of point sensor products.

Optical matrix sensors are most common for 2D vision applications as well as for edge of technology 3D microscopy systems. The Solarius product range of matrix based sensor systems are implemented as interferometric, confocal or focus variation principles. The 3D matrix sensor systems are dedicated to edge of technology 3D measurement tasks where highest resultion and accuracy are needed.

Monochromatic confocal microscopy is an optical imaging technique to derive 3D surface topographies by means of using a spatial pinhole to block out-of-focus light in image formation. Capturing multiple two-dimensional images at different depths in a sample enables the reconstruction of three-dimensional structures within an object. This technique is used extensively in the scientific and industrial communities and typical applications are in life sciences, semiconductor inspection and materials science. Strength of this technology is its capability to derive very high spatial resolution and contrasts making it ideal for roughness and geometry measurements on smoth and transparent multi layer materials, rough surfaces or strongly varying reflectivities within an object. The weakness of this technology is its inability to capture steeper edges, thin layers and its comparably low measuring speed. There are high speed confocal systems available nowadays, however copared to triangulationg systems the high volume manufacturing capabilties are limited to edge of technology applications. The confocal technology can be combined with the focus variation approch to improve image quality, especially on steeper edges.

Chromatic confocal microscopy is related in principle to the monochromatic confocal technology. However, instead of blocking the out-of-focus light by pin holes, optical dispersion is used to create different, independent confocal conditions in different distances to the sensor. By the usage of spectroscopes or, faster and simpler by colour filters, the confocal peaks can be detected for the different wavelengths. By this colour dependent distance measurements, 3D topographies can be derived from objects and geometries. Chromatic confocal probes can measure on, and through, transparent material, detect several interfaces between materials and, therefore, calculate thickness. The metrological characteristics of point chromatic confocal systems are close to those of stylus probes and they are often used as a non-contact substitute on stylus profilometers. Strengths and weaknesses of the chromatic confocal technology are comparable to those of the monochromatic confocal approach, main differentiation is found in the comparably lower lateral resolution, a slight color sensitivity, depending on the systems technical implementation, and as a significant benefit, its comparably higher cost efficiency.

3D Interferometry is a measurement method using the phenomenon of interference of waves to reconstruct topographies of surfaces. In particular, displacement measuring interferometry is extensively used for the characterisation of surfaces. By using two coherent light beams, where one of it is exposed to an object's surfaces and the second one remains without modulation, an interference pattern can be formed when these two beams superpose. Because the wavelength of the visible light is very short, small changes in the differences in the optical path lengths between the two beams can be detected. Similar to confocal technology, this technique is common in life sciences, semiconductor inspection and materials science. The inherent streght of the interferometric 3D imaging technology is a very high vertical resolution, allowing to measure transparent films and layers reliaby even in the sub micron range. While interferometry still is compareably slow to triangulation systems it is a little faster than confocal approaches. Core weakness of interferometry is its limited capability in lateral resolution in respect to the confocal systems, and its high sensitivity to vibrations.

Holographic interferometry is a technique enabling static or dynamic displacements of objects with optically rough surfaces to be measured to optical interferometric precision. The measurements can be applied to stress and strain as well as to vibration analysis. Also, it can be used to detect optical path length variations in transparent media which enables, for example, fluid flow to be visualised and analyzed. Moreover, it can be used to generate contours representing the form of the surface. Holography is a process of recording diffracted light scattered from an object, then performing 3D image rendering. This process can be achieved with with a digital sensor array in digital holography. If the recorded field is superimposed on the field scattered from an ideal and plane object, the two fields will be identical. However, in case there is a small deformation on the object surface the relative phases of the light will be different and interference can be observed. Holographic interferometry can improve 3D measurement of rough surfaces while it does not overcome lateral resoultion limits and sensitivity to vibration. Its range of application for industrial 3D metrology is limited while it became a commonplace in vibrometric applications.

Focus variation based 3D sensors combine a small depth of focus of an optical system with vertical scanning to provide topography and color information from an object's surface. Using an optical system with a small depth of focus, only such parts of an object's surface are imaged in high definition which are in a certain distance to the sensor. All other areas of the surface topography appear blurred. By capturing multiple 2D images in different distances to the objects, similar to confocal systems 3D surface topographies can be reconstructed selecting the regions in high definition from each 2D image. Differentiation in an image is made, other than with pin holes in confocal systems, by the means of image processing algorithms. Focus variation is used in industrial as well as scientific applications in laboratories and mass production. Strengths of the focus variation technology certainly are, compared to confocal and interferometric approaches, its higher speed, its ability to acquire steeper edges and its capability to maintain resolution on an above triangulation level. Drawbacks are its inability to detect smooth and transparent surfaces as well as many scattering or higly dynamic 3D object topographies.

Triangulation sensors consits of a light pattern generating projector unit and a matrix camera imaging system. A light pattern, which can be a point, a line or even a complex arragement of color coded lines or sinusoidal patterns are projected to an object's surface. Using the example of a single line, the line will appear distorted by an uneven surface geometry or may stay a straight line when a surface is even. This distortion can be acquired by the means of the array camera. As the camera and the projector are oriented in a certain distance to each other, including a known projection and imaging angle to the object, based on the trigonometric rules of a triangle, an object's distance can be calculated. Scanning an object, a 3D topography can be derived. Triangulation is a widespread in 3D imaging with applications ranging from large automobile  parts down to geometries in the micrometer range. Triangulation provides a comparaby unmatched measurement speed, is applicable to a wide range of parts and component size and is robust against most difficult production environments. Weakness of triangulation approaches are the limited capabilty to acquire mirroring surfaces, shadowing and limitation of resolution.