Design of an Internal Focusing Tube Lens for Optical Inspection Systems

Abstract

The numerical aperture (NA) of objective lens optical (inspection) systems has been increased to achieve higher resolution. However, the depth of focus decreases with an increase in the NA, and focusing becomes difficult. Therefore, the entire optical lens in currently developed optical inspection systems must be moved to focus within the depth of focus. To achieve a high resolution, many lenses are used in optical inspection systems, increasing the size and weight of the optical systems. To address this issue, a focus control group was placed on a tube lens that could adjust its focus based on the movement of the sample in front of the objective lens. Therefore, we developed a focus range increment to focus on the range of the optical inspection system. Using objective lenses with focal lengths of 30 and 60 mm and tube lenses with a focal length of 300 mm, optical systems for 10× and 5× inspection were constructed. In the designed optical systems, the weights of the objective lenses with focal lengths of 30 and 60 mm were calculated to be approximately 844 and 570 g, respectively. These values confirm that the weight of the moving group can be reduced.

A Novel Analytical Interpolation Approach for Determining the Locus of a Zoom Lens Optical System

“…Based on the corrected results, the Padé approximation can be repeated to establish a rational function for computing the zoom locus. Figure 2 depicts the optical path representation when a specific i th lens group moves by a distance ∆z i in an optical system with an infinite object point [43]. In this context, k and z denote the refractive power of each lens group and the distance between the main points of each lens group, respectively.…”