Design of an oblique camera based on a field-dependent parameter.

Area of Science:

• Optics and optical engineering.
• Remote sensing and photogrammetry.

Background:

• Characterizing optical system performance across a field of view is crucial for imaging applications.
• Off-axis reflective systems present unique challenges in maintaining uniform optical properties.

Purpose of the Study:

• Introduce a novel parameter, field focal length (FFL), to quantify optical properties per field point.
• Analyze the ground resolution (GR) of a freeform three-mirror off-axis reflective system using FFL.
• Design an oblique camera with consistent GR across its field of view.

Main Methods:

• Defined and applied the field focal length (FFL) parameter to an off-axis reflective system.
• Analyzed ground resolution (GR) variations across a 30° field angle under different working modes.
• Optimized the system design by leveraging FFL to control GR.

Main Results:

• The freeform three-mirror off-axis system exhibited varying FFLs across its field of view.
• Identified a working mode where larger FFL values directed at distant objects yielded more uniform GR.
• Achieved a constant GR within 99.41% over the entire field of view through FFL-guided design.

Conclusions:

• Field focal length (FFL) is an effective parameter for characterizing and controlling optical system performance.
• FFL-based design enables the development of high-performance oblique cameras with uniform ground resolution.
• This approach offers a method for optimizing imaging systems for specific remote sensing applications.