EVBUM2868/D
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7
Pixel−to−Pixel (Fixed Pattern Noise) Calibration
After enabling the iToF depth plugin in Devware, there’s
an option to enable either phase correction or depth
correction. These are two different means to achieve the
same corrected result. Therefore either one of the two
options should be selected and not both. For phase
correction in mode 3.2, two files should be selected (one for
each phase). This is not the case for the depth correction in
this mode or for mode 2.2 altogether. See also related Issue
2 in the Errata document.
The bin0 suffix in the calibration file name is the native
resolution of this specific mode (1.2 Mp for mode 2.2 and
VGA for mode 3.2). The bin1 suffix refers to the 2x2 binned
file.
Your AF0131 Evaluation Board should include all
relevant pixel−to−pixel calibration files. If not, please
contact your onsemi representative.
Depth Accuracy (High Harmonics) Calibration
Due to the pixel and laser modulation signals not being
perfect sine waves but rather square waves, high harmonics
calibration is needed for high accuracy applications. When
evaluating the sensor’s depth accuracy over distance
without high harmonics corrections, one will see a “wiggle”
of about 3cm distance offset variations.
These High Harmonics calibrations are not yet available
in the current hardware and software.
The final version of the sensor will contain a 64 value
Look−Up Table (LUT) for different modulation frequencies.
Defect Pixel Identification and Replacement
Current defect pixel identification and correction is done
in software. The final version will have this feature on chip.
Lens Calibration
This calibration is needed to create a proper 3D depth map
from the depth data. This calibration will not be supported
on the AF0130 sensor. DevwareX, currently assumes a basic
lens correction algorithm for its point cloud. A simple
pinhole model is assumed with its center in the center of the
image array.
The horizontal field of view can be adjusted ”Lens Angle”
parameter in the depth plug−in.
LIMITATIONS
See the Errata document (AF0130−ERR−D.PDF) for an
overview of all sensor limitations. If by further evaluation of
the sensor you find other features that may be limited. Please
do not hesitate to contact your onsemi representative.
Two−Wire Serial Interface Limited
See related issue 4 and 5 in Errata. This is why Four−Wire
Serial Interface was chosen for the current demo.
Four−Wire Serial Interface Request over USB May
Shift Phase Captures
Due to issue 1, described in the Errata document, the
sensor may shift its phase captures by 90 degrees when
reading a sensor register on the wrong moment. This is
because a register read request from the USB may interrupt
the continuous necessary 90 degree shift updates of the
FPGA to the sensor exposures.
This 90 degree shift in the RAW interleaved exposures
may occur randomly when changing for example exposure
time of the sensor while the sensor is streaming.
Furthermore, this is why it is recommended to disable the
Info Text file (register dump) when grabbing frames with
DevwareX. This can be set in the “Image Save Options”
panel of the “Control Panel” in DevwareX.
Limited Frame Rate
Because the depth processing for AF0131 is done in
software. The current version has a limitation on the frame
rate to allow enough time for processing and corrections in
software.
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