In this final installment of our five-part series on selecting and setting up C/CS lenses, we cover the foundational step of calculating the focal length.

Why Focal Length Matters

The focal length is arguably a lens’s most critical parameter. It determines how much the lens can magnify an object and influences the field of view captured by your imaging system. To ensure that both the height and width of your subject are fully represented on the CCD chip, you’ll need to calculate the appropriate focal length.

The Calculation Process

The key is to find a single focal length that works for both dimensions—your object’s height and its width. Here’s how it’s done:

  1. Calculate the required focal length based on the object height.
  2. Calculate the required focal length based on the object width.
  3. Choose the smaller of these two values as your focal length.

Example from Various Applications

Let’s consider a practical example to illustrate this process:

  • A machine vision application requires imaging an object that is 10 mm high and 8 mm wide, with a CCD sensor size of 6.5 mm (height) by 5.2 mm (width).
    • Calculating for height: F = (sensor_height / object_height) * magnification (Note: This calculation assumes the desired field of view corresponds to the sensor dimensions at the calculated focal length)
    • Calculating for width: F = (sensor_width / object_width) * magnification
    • In this case, the value derived from height is larger than that from width. Therefore, we select the smaller value obtained from the width calculation as our system’s focal length.

Conclusion

Choosing the correct focal length ensures your C/CS lens captures a complete image of your object without distortion or vignetting issues related to cropping. This step sets the stage for selecting the right physical lens and configuring its other parameters appropriately, which we’ll explore in Part 5 (standalone).

This completes our series on selecting and setting up C/CS lenses. We hope these insights are helpful!

Last Updated: 2025-09-05 02:10:16