Optical Autocorrelator with Special Application to MTF Measurement.

Area of Science:

• Optical engineering
• Interferometry
• Metrology

Background:

• Optical testing is crucial for lens characterization.
• Existing methods for measuring optical transfer function (OTF) can be complex or limited.
• The Sagnac interferometer offers a stable platform for optical measurements.

Purpose of the Study:

• To develop a novel optical autocorrelator for real-time lens testing.
• To utilize a modified Sagnac interferometer for aperture function autocorrelation.
• To demonstrate the system's capability in measuring the modulation transfer function (MTF) of lenses.

Main Methods:

• A modified Sagnac two-mirror interferometer operating in zero-fringe mode was employed.
• The real-time radiant flux output was configured to represent the square of the autocorrelation of the aperture function.
• The system was applied to measure the MTF of a lens by using its pupil function as the aperture function.

Main Results:

• The optical autocorrelator successfully measured the MTF of a lens.
• Experimental results were obtained and compared with theoretical calculations for both infinite-conjugate MTF and aperture autocorrelation.
• The system's scalability concerning aperture size was noted, limited only by component dimensions.

Conclusions:

• The described optical autocorrelator, based on a modified Sagnac interferometer, provides a viable method for real-time MTF measurement.
• The system is adaptable for measuring the phase of the transfer function and for finite conjugate testing.
• This approach offers a flexible and potentially more accessible tool for optical system characterization.