Principle of high Dynamic Range (HDR) measuring

With the development of the C4-1280-GigE 3D camera, AT has added a new dimension when it comes to 3D measurement options using laser triangulation. With the help of new HDR-3D (High Dynamic Range) functionality, it is now possible to scan materials and surfaces with inhomogeneous reflection properties. The recording of saturated intensity readings is now a thing of the past because HDR-3D expands the dynamics of image intensity up to 90dB.

Essentially, HDR-3D comprises two independent but combinable sensor functions:

The aim of the MultipleSlope function is to avoid the saturation of pixels during sensor chip exposure. To do this, the threshold values for the recorded light volume and the voltage produced are set. If, within a predefined time, the threshold is exceeded the voltage of the pixel is reset to the threshold value. Next, the light exposure is continued until the exposure is complete. This mode is known as DualSlope. There is also an option of resetting the pixel voltage after the first reset (TripleSlope mode). The reset level and reset times in DualSlope and TripleSlope mode can be configured independently of one another.

The Non-Destructive Readout (NDR) function makes multiple sensor-chip readout possible during the exposure time without having to reset the pixels. Up to 7 readouts are possible. To this end, the time for each readout is predefined. This makes it possible to read out the recording of highly reflective objects shortly after the start of the exposure, the image of darker areas being read at the end of the integration time. When combining part records, a homogenous, saturation-free image can be generated.