3D line confocal imaging

Line Confocal Imaging (LCI) technology can determine 3D microtopography of surfaces with sub-micron resolution, suitable for highly reflective, mirror-like, and transparent materials and multi-layered structures in various metrology and inspection applications of discrete parts, assemblies, and continuous products. Imaging results are used to characterize, for example, a product’s 3D form and dimensions; surface topography, roughness, and texture; and thickness, flatness, and 3D volume. LCI sensors can simultaneously acquire 2D gray-scale (intensity) images from the scanned surface with a depth of focus that covers the sensor’s entire Z-range, up to 5.50mm.

The LCI sensor’s transmitter has a light source that emits white light, containing all visible wavelengths. A complex optical assembly separates the light into wavelengths and focuses a horizontal line of each color at a different distance from the sensor, forming a focal plane. Depending on the vertical position of the imaged surface within the plane, corresponding wavelengths from 2,048 lateral measurement points reflect back to the sensor’s receiver, and its spectral camera captures wavelength and intensity information from each point, forming related height profile and intensity lines.

When the surface moves in front of the sensor, a 3D point cloud and a 2D gray-scale image are generated line-by-line from the scanned surface. Data can be processed, analyzed, and reported with 3D surface analysis and image processing software packages.

Depending on the imaged material, surface type, and resolution requirements, three sensor models are available:

• Vertical (Z) resolution: 100nm; Z range: 1.00mm
• Vertical (Z) resolution: 0.55µm; Z range: 2.80mm
• Vertical (Z) resolution: 0.98µm; Z range: 5.50mm

Lateral resolution in measurement line direction (X) varies from 2.20µm to 8.00µm, depending on the sensor model. Y resolution depends on line spacing which also affects the maximum surface motion speed in the application. The length of the sensors’ measurement line is from 4.5mm to 16.4mm. The sensors can be integrated in off-line and real-time metrology systems as they can operate up to approximately 5,000 lines per second – capturing more than 10 million 3D surface points per second. 2D intensity image data, potentially from several layers within the scanned area, can increase this number.

Benefits

Scanning an area that would take minutes with traditional 3D imaging methods, such as point confocal or interferometric technologies, can be completed within seconds with LCI.

Materials with highly reflective, mirror-like, high-contrast, and transparent surfaces can be evaluated with LCI. Surface color doesn’t affect the results and the sensor’s large numerical aperture and high tolerance for surface angle variation allows for imaging of steep mirrored slopes and glossy curved surfaces. LCI does not suffer from speckle noise, enabling surface imaging at much higher resolution than laser triangulation sensors.

Raw data produced by LCI sensors rarely needs filtering or other manipulation. Since the sensors capture 2,048 measurement points simultaneously, vibration of the imaged surface or the sensor seldom causes issues as relative point height positions within the measurement profile line remain unaffected.

Medical applications

Depth and shape of embossed and etched 3D features, parting line flash of molded parts, surface roughness and texture of extruded parts and continuous products, and burr in precision-stamped and micro-machined parts can be imaged with LCI in laboratory and production in real-time.

One of the first applications using the deep depth of focus tomographic LCI imaging is non-destructive inspection of completeness and integrity of heat seals in sterile medical packages.

FocalSpec LCI sensors

Bare LCI sensors can be integrated into custom systems for off-line and on-line metrology applications. The software development kit (SDK) allows integrators to control sensor functions and read 3D profile and 2D intensity data as the specific application may require. The SDK includes an application programming interface (API), drivers, and source code examples.

FocalSpec Inc.
www.focalspec.com