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86 PCB007 MAGAZINE I SEPTEMBER 2019 Figure 2 depicts the sensor's operating prin- ciple. The transmitter has a light source that emits white light containing all visible wave- lengths. An optical assembly separates the light into wavelengths and focuses each color at a different distance from the sensor, forming a focal plane (Figure 3). Depending on the vertical position of the im- aged surface within the plane, corresponding wavelengths from 2,048 lateral points are re- flected back to the sensor's receiver. The re- ceiver's spectral camera captures wavelength and intensity information from each point to form related height and gray-scale profile lines. When the surface is moved in front of the sen- sor (Figure 4), a 3D point cloud and 2D gray- scale image are generated from the scanned area line by line. The resulting data can be processed, analyzed, and reported with vari- ous 3D surface analysis and image processing software packages. Line Confocal Method Imaging Capabilities The line confocal sensors and systems work well in applications that require high-speed imaging of challenging materials at sub-mi- cron resolution. Scanning an area that would require minutes or hours for traditional 3D im- aging methods, such as point confocal or in- terferometric technologies, can be completed within a few seconds. Transparent materials and products with highly reflective or mirror-like surfaces are ide- al for the line confocal method. The sensors' large numerical aperture and high tolerance for surface angle allow for imaging of steep slopes and glossy curved surfaces. This method does not suffer from speckle noise; this enables sur- face imaging at a much higher resolution than laser triangulation sensors. The quality of the raw image data produced by the line confocal sensors is good and rarely needs filtering or other manipulation of any kind. Since the sensors capture 2,048 measure- ment points simultaneously, the vibration of the imaged surface or the sensor itself seldom causes issues; relative point height positions within the measurement profile line remain unaffected. Example 1: 3D Imaging of PCBs In this imaging example, a section of rigid PCB with fine lines at the top (Figure 5) was Figure 2: Line confocal method principle. Figure 4: Line confocal method principle. Figure 3: Focal plane.