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==== RIQA-Camera Distortion Module ====
Distortion is a geometric aberration in optical systems (such as lenses) where the magnification varies across different positions in the field of view, causing the true geometric shape of the subject to be distorted in the image (e.g., straight lines becoming curved). This module supports automatic distortion analysis for **dot charts** and **checkerboard charts**.

**Test Charts Supported by the Distortion Module**\\ 
|  Dot  |  Checkerboard  |  Concentric Test Card  |
|  [[https://www.yanding.com/product/detail?id=1584|{{ yanding:成像质量评价:工具:riqa图像质量分析软件:dot.png?250 |}}]]  |  [[https://www.yanding.com/product/detail?id=1615|{{ yanding:成像质量评价:工具:riqa图像质量分析软件:checkerboard-.png?250 |}}]]  |  {{ yanding:成像质量评价:工具:riqa图像质量分析软件:畸变2.jpg?170 |}}  |

** DOT**\\ 
**Operation Steps**\\
(1) Open the software and select "Dot" in the "Distortion" module.
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(2) Click "Add" to import the images to be analyzed.
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{{ yanding:成像质量评价:工具:riqa图像质量分析软件:d2.png?600 |}}
(3) Select the image and click "Start" to proceed to the next step.
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(4) View the analysis results.
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(5) Click "Generate Report", enter the file name, select the save directory and file format, and click "Export" to view the saved report in the specified path.
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{{ yanding:成像质量评价:工具:riqa图像质量分析软件:d5-.png?400 |}}
** Result Interpretation**\\
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|  **Metric**  |  **Definition**  |
|  Rotation Angle(°)  |  Rotation angle  |
|  Distortion SMIA(%)  |  SMIA TV distortion percentage  |
|  Image Radius(pixel)  |  Half of the diagonal length  |
|  Dot Number  |  Number of dots  |
|  Max LCA(pixel)  |  Maximum lateral chromatic aberration in pixels  |
|  Max LCA@0.7F(pixel)  |  Maximum lateral chromatic aberration at 70% field in pixels  |
|  Max LCA(%)  |  Maximum lateral chromatic aberration as a percentage  |
|  Max LCA@0.7F(%)  |  Maximum lateral chromatic aberration at 70% field as a percentage  |
|  Optical Distortion(%)  |  Optical distortion percentage  |
(1) Optical and SMIA TV Distortion Curves
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The red crosses represent the actual measurement results, the blue curve represents the best-fit optical distortion curve using the least squares method, and the green curve represents the best-fit SMIA TV distortion curve using the least squares method. If the maximum distortion percentage is positive, the image exhibits pincushion distortion; if it is negative, the image exhibits barrel distortion.

(2) Grid Distortion Visualization
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:dd-2-_3_.png?400 |}}
Optical distortion is illustrated by comparing it with an ideal undistorted grid. Superimposed on the image is an undistorted Cartesian grid. Thin green lines connect the centers of the distorted dots to the centers of their corresponding undistorted points.

(3) Lateral Chromatic Aberration
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The aberration is summarized by three metrics: the pixel difference between the red and green channels, the pixel difference between the blue and green channels, and the pixel difference between the red and blue channels. The measured data and the best-fit model are displayed. According to CPIQ, the values are expressed in pixels and as a percentage of the image height.

**Checkerboard**\\ 
**Operation Steps**\\
(1) Open the software and select "Checkerboard" in the "Distortion" module.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:c1.png?600 |}}
(2) Click "Add" to import the images to be analyzed.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:c2.png?600 |}}
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:c3.png?600 |}}
(3) Select the image, specify the number of columns and rows of the checkerboard, and click "Start" to proceed to the next step.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:c4.png?600 |}}
(4) View the analysis results.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:c5.png?600 |}}
(5) Click "Generate Report", enter the file name, select the save directory and file format, and click "Export" to view the saved report in the specified path.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:c6.png?600 |}}

**Result Interpretation**\\
[[yanding:成像质量评价:工具:riqa图像质量分析软件:riqa-camera畸变模块#结果解读|Click to view]]

** Concentric Test Chart**\\ 
** Operation Steps**\\
(1) Open the software and select "Concentric Test Chart" in the "Distortion" module.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:ctc-1.png?600 |}}
(2) Click "Add" to import the images to be analyzed.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:ctc-2.png?600 |}}
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:ctc-3.png?600 |}}
(3) Select the image and click "Start" to proceed to the next step.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:ctc-33.png?600 |}}
(4) View the analysis results.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:ctc-4.png?600 |}}
(5) Click "Generate Report", enter the file name, select the save directory and file format, and click "Export" to view the saved report in the specified path.
{{ yanding:成像质量评价:工具:riqa图像质量分析软件:ctc-5.png?600 |}}
**Result Interpretation**\\
Segmented Distortion Plot: The distortion circle test measures the average distortion rate in various directions along the concentric circles.\\
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Segment(i) refers to dividing the concentric circles into eight equal parts using eight straight lines and calculating the distortion rate along each line (i.e., in each direction). For example, Segment 1 refers to the distortion value in the first of the eight divided regions, and Segment 2 refers to the distortion value in the second region.