I. Preparation

      Placement Environment: Mount the target horizontally on an optical table, ensuring the substrate is free from warping, dust, and stains.

      System Focusing: Adjust the camera/lens to achieve sharp imaging of the target pattern.

      Lighting Setup: Use uniform coaxial illumination to avoid glare and shadows, ensuring high contrast between black and white regions.

II. Image Acquisition

      Multi-Angle Coverage: Capture images of the target at various angles, heights, and positions to ensure the pattern is evenly distributed across both the center and peripheral areas of the camera's field of view (FOV).

      Pose Diversity: Include diverse poses such as horizontal, tilted, and rotated orientations; avoid capturing images from a single angle only.

      Image Quantity: Typically, acquire 10–20 sharp images with varying poses.

III. Data Processing & Calibration

      Feature Extraction: Utilize algorithms (e.g., edge detection, contour fitting) to extract the edges and corners of the squares in each layer and calculate their geometric centers.

      Distortion & Intrinsic Parameter Estimation: Solve for the camera's intrinsic parameters (focal length, principal point) and distortion coefficients by analyzing the deviation between the theoretical centers of the multi-layer concentric squares and their actual positions in the image.

      Error Compensation: Import the calibration results into the system to perform distortion correction and error compensation for subsequent measurement/imaging data.

IV. Key Application Scenarios & Precautions

1. Typical Applications

      Distortion correction for industrial cameras (especially wide-angle lenses)

      Accuracy calibration for high-precision video measuring instruments / toolmaker's microscopes

      Imaging quality testing for optical lenses

      Reference point calibration for visual positioning systems

2. Pitfall Avoidance Guide

      Factors Affecting Accuracy: Substrate flatness, pattern fabrication accuracy (typically ±1 μm grade), lighting uniformity, and focus clarity.

      Common Mistakes: Capturing only a single image, insufficient target coverage within the FOV, edge glare, and failure to cover the entire field of view—all of which lead to inaccurate calibration results.

      Environmental Requirements: Avoid vibration during use and maintain stable temperatures to prevent thermal expansion/contraction of the substrate from compromising accuracy.