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9 MODULES – DISTORTION
8.6.
DISTORTION
The distortion module enables you to evaluate the distortion and the lateral chromatic aberration in one step. Therefore iQ-Analyzer uses a test patterns, crosses or points, which are distributetd over the complete image. The center of the crosses (points) are located with sub pixel precision for RGB. The distortion and the chromatic aberration can be calculated from these locations.
“Distortion” tab
There are some requirements for the image as they could affect the results:
• make sure that the camera is not tilted in any direction
• the center cross in the chart (surrounded by markers) has to be the center cross in the image as well
• arrange the camera in such a way that the image shows the full chart height.The image aspect ratio specifies how many crosses you cover in width
• the image must show only complete crosses
• the chart should be illuminated homogeneously
TE251 – the test chart for calculation of distortion and the chromatic aberration
LGD – Lens Geometric Distortion
the four quadrants (Q1, Q2, Q3, Q4) iQ-Analyzer
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9 MODULES – DISTORTION
Undistorted Grid Barrel Distortion (negative) Pincushion Distortion (positiv)
Lens Geometric Distortion Definition
The lens geometric distortion is defined as
LGD
=
100
⋅
(
H
`
−
H
)
H
H’ = dot distance from center of image
H = undistorted dot position
The geometric distortion for a grid position is the delta between the radial distance of the actual grid position H’ and radial distance to the ideal grid position H, devided by the ideal grid position H.
H’<H indicates negativ distortion (barrel distortion)
H’>H indicates positive distortion (pincushion distortion)
8.6.1.
Settings
Before starting analysis of the distortion charts you have to define some settings.
ADVANCED SETTINGS
By using the ‘Adanced’ button the Advanced menu opens.
“Advanced” button and the opening Advanced menu iQ-Analyzer
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