Optimization design method of DOE diffraction efficiency and its application in a zoom lens.

Area of Science:

• Optical Engineering
• Infrared Optics
• Diffractive Optics

Background:

• Conventional single-layer diffractive optical elements (SLDOEs) suffer from reduced efficiency and imaging quality due to unaddressed temperature and incident angle variations.
• Existing designs often optimize for angle bandwidth integrated average diffraction efficiency (ABIADE), neglecting critical environmental factors.

Purpose of the Study:

• To develop a novel design methodology for SLDOEs that compensates for temperature-induced phase delay variations.
• To introduce and model the temperature angle bandwidth integrated average diffraction efficiency (TABIADE) for optimizing SLDOE performance.
• To design and validate an infrared continuous zoom system utilizing SLDOEs optimized with the TABIADE method.

Main Methods:

• Derived phase delay increment considering temperature effects on refractive index and thermal expansion.
• Developed the mathematical model for TABIADE.
• Employed an optimization algorithm to maximize TABIADE for microstructure height adjustment in SLDOEs.
• Integrated optimized SLDOEs into a cooled infrared continuous zoom system and analyzed modulation transfer function (MTF).

Main Results:

• The TABIADE-based SLDOE design demonstrated superior adaptability to temperature variations compared to ABIADE-optimized designs.
• SLDOEs designed using the TABIADE method resulted in less degradation of imaging quality in the infrared zoom system.
• The final system with three SLDOEs achieved MTF>1 at 33 lp/mm across 3.7-5 µm, with a 40-900 mm zoom range and F-number of 4.

Conclusions:

• The proposed TABIADE method enables the design of high-efficiency SLDOEs that maintain imaging quality under varying environmental conditions.
• This approach facilitates a balance between high zoom ratio, long focal length, and lightweight design in infrared continuous zoom systems.
• Provides a viable technical solution for integrating SLDOEs into refractive-diffractive hybrid systems, particularly for demanding infrared applications.