Linghou Robotics' independently developed Kohler telecentric illumination lens primarily addresses the issues of uneven illumination and the large space occupied by external coaxial light sources in traditional internal coaxial telecentric lenses. This lens features a special optical design that eliminates stray light generated within the lens, ensuring parallel illumination and a more uniform illumination spot compared to ordinary internal coaxial telecentric lenses. This saves space compared to external coaxial light sources while achieving the same level of uniformity.
The material being tested is a highly reflective, mirror-like material, and the testing requirement is to detect scratches on the product surface.
A. Internal coaxial B. Kohler C. External coaxial
The three images shown above use the same camera parameters. Comparing images A and B, both show distinguishable scratches, but image B exhibits higher scratch contrast and more uniform lighting across the entire field of view. Comparing images B and C, both show relatively uniform lighting within the field of view, but image C lacks high contrast and fails to distinguish minor scratches.
Kohler lenses offer advantages such as small size, high uniformity, and good light parallelism. However, they also have some drawbacks, including a limited field of view in a single image, making them unsuitable for imaging large areas of material at once. Furthermore, to achieve optimal testing results, the material must be kept relatively perpendicular to the Kohler lens.
Kohler lenses are primarily used for surface defect detection (scratches, bumps, dents, dirt, etc.) on highly reflective materials (glass, screens, mirrors, metals, etc.).
