Four Different Types of Illuminations in a Single Scan
Different allPixa cameras can be used to trigger up to four different flash controller channels synchronized to its line acquisition. This can be used to acquire several images with different illumination geometries (dark field, bright field, or backlight, co-axial) and/or colors (white, red, green, UV, IR) simultaneously in only one scan by line-multiplexing.
Image 1 | Flash mode acquisition of metal sample with two different illumination geometries.
Left: raw camera output. Right: Separated individual images with color plane correction. (Bild: Chromasens GmbH)
This means multi-channel flashing enables the system to scan the object using with up to four different type of illuminations in a single scan. Various types of defects are possible to be captured with this kind of vision system. Examples are cracks, scratches, stains, chipping, etc. The multi-channel flash control feature of the cameras can acquire multiple images, whereas every image is recorded under different illumination conditions in a single scan. In addition, high color fidelity and a high dynamic range help to achieve excellent results in defect detection. The high-quality color images can give more information about the defect class and extent of the defects on the object. The large full well capacity of the sensor enables a high dynamic range and the blooming resistance is outstanding, which is very import for strong local reflections in bright field configuration.
Image 3 | HDR demonstration on ball grid array sample.
Left: Interlaced image.
Middle: Separated images with different exposure times. Right: HDR image. (Bild: Chromasens GmbH)
Flash Controller Synchronization
One application where this is useful is in inspection tasks where different kinds of defects are identified either in images captured with brightfield illumination (e.g. scratches) while other defects require darkfield illumination (e.g. dust particles). Figure 1 illustrates this: The left side shows the raw camera image output for a metal sample with activated flash mode for one brightfield and one darkfield illumination. The size of this image in scan direction is enlarged by a factor of two as each line is captured twice with alternating illumination. The result is an image that is interlaced line by line repeatedly. This image needs to be deinterlaced and a correction for the color plane shift needs to be applied which results in the images shown on the right. The separation of these images is not part of the camera function and needs to be done in a postprocessing step.
