Paraxial focal length measurement method with a simple apparatus

Area of Science:

• Optics and Photonics
• Image Processing
• Metrology

Background:

• Accurate measurement of lens focal length is crucial in optical system design.
• Existing methods may require complex apparatus or lack flexibility.
• Developing a practical and precise focal length measurement technique is essential.

Purpose of the Study:

• To introduce an accurate and flexible measurement method for paraxial focal length.
• To demonstrate the method's efficacy using a simple experimental setup.
• To achieve high precision in focal length determination.

Main Methods:

• Utilizing the Gaussian optical formula and geometrical relationships of camera-lens systems.
• Employing image processing techniques, including image sharpness evaluation.
• Implementing system calibration to correct for apparatus-induced errors.
• Accounting for optical aberrations for precise paraxial focal length calculation.

Main Results:

• The proposed method accurately determines paraxial focal length.
• Image sharpness evaluation confirms adherence to Gaussian optics.
• System calibration effectively compensates for experimental errors.
• Repeatability error of the measurement system is less than 0.11% for most lenses.

Conclusions:

• The developed method offers an accurate and flexible approach to paraxial focal length measurement.
• The technique is practical for use with simple apparatus.
• High accuracy and repeatability are demonstrated, making it suitable for various lens types.