High Dynamic Range (HDR)
- Without HDR
High-dynamic-range imaging (HDRI) is a high dynamic range (HDR) technique used in imaging and photography to reproduce a greater dynamic range of luminosity than what is possible with standard digital imaging or photographic techniques. Standard techniques allow differentiation only within a certain range of brightness. Outside of this range, no features are visible because there is no differentiation in bright areas as everything appears just pure white, and there is no differentiation in darker areas as everything appears pure black.
- After HDR mode
- HDR mode for VSEMI ToF Cam
This mode allows to acquire one image with two different integration time in oder to increase the dynamic range. Both groups provide exactly the same phase modulation signals. One stops earlier than the other due to different integration times. As a consequence, the two pixels collect different amount of light simultaneously.
Example I : ToF HDR of long distance for VSEMI ToF cam
Example II : ToF HDR short distance for VSEMI ToF cam
Embedded Software Filters
- Median Filter
This spatial filter uses a 3x3 pixel sliding window. It selects the median value of the 9 pixel in the window and places the result to the center pixel in the 3x3 window . The sliding window is shifted all across the image. First and last row as well first and last column of the image remain as they are.
- Average Filter
This spatial filter uses a 2x2 pixel sliding window. It averages the distance values of the four pixels and places the result to the upper left pixel in the 2x2 window. The sliding window is shifted all across the image. The last row and column of the image remain as they are.
- Temporal Filter
The temporal filter is a Kalman filter, which uses two parameters: A threshold 'T' and a filter value 'k'. As long as new distance measurement values are in between ±'T' to the former distance measurement, the filter takes the average of previous distance measurement values, depending on the 'k' value. The temporal filter applies to all pixels individually.
Set Region-of-Interest (ROI)
A full image of the Sentinel has a pixel-field of 160x 60 pixels in WFOV mode. A “region of interest” acquires only a selected number of pixels which are necessary for the application. This reduces the amount of readout data and increases the frame rate. The ROI is active for the WFOV image only.