how to calibrate camera location in wafer inspection?

wafer

In wafer inspection, camera location calibration is an important step in ensuring accurate and reliable inspection results. The calibration process typically involves the following steps:

Prepare a calibration target: A calibration target, such as a high-precision stage or a special calibration wafer, is used to establish a reference frame for the camera system.

Capture calibration images: Using the camera system, capture images of the calibration target from different angles and positions. It is important to cover a wide range of camera positions and angles to ensure accurate calibration.

Extract feature points: Use computer vision algorithms to extract feature points from the calibration images. These feature points can include corners, edges, or other distinctive patterns on the calibration target.

Compute camera parameters: Using the extracted feature points, compute the camera's intrinsic and extrinsic parameters. The intrinsic parameters include the focal length, principal point, and distortion coefficients, while the extrinsic parameters describe the camera's position and orientation in the reference frame.

Evaluate calibration accuracy: To ensure that the calibration is accurate, it is important to evaluate the calibration results. This can be done by comparing the predicted camera positions and orientations with the actual camera positions and orientations.

Apply calibration to inspection: Once the calibration is complete, the camera system can be used for wafer inspection. The calibration parameters are used to correct for any distortion or misalignment in the images, ensuring accurate and reliable inspection results.

Overall, camera location calibration in wafer inspection requires careful preparation, precise measurements, and advanced computer vision algorithms. It is important to follow a standardized procedure to ensure accurate and reliable calibration results.