When dealing with small objects, it’s common for the required working distance to be smaller than the minimum working distance (MOD) specified by your lens. To resolve this issue, you can use extension rings placed between the lens and the camera body.

How It Works in Practice

Let’s consider an example involving inspecting a birthmark:

  • Object width: 5 mm
  • Required Working Distance: 30 mm
  • CCD format: 1/4″ (CCD width = 3.2 mm)

With a focal length of 14.7 mm, the appropriate lens selection is the H1214-M(KP). However, its MOD (0.25 m or 25 cm) significantly exceeds the needed working distance (3 cm or 30 mm).

Solution: Using Extension Rings

The table below shows that a 5 mm extension ring effectively reduces the effective working distance to meet the requirement while maintaining image quality.

This approach prepares us for the practical setup phase detailed in Step 4.

Last Updated: 2025-09-05 02:09:10