Three-Step, Four-Step, and Five-Step Phase Shifting Methods with Corresponding Phase Unwrapping Algorithms

Three-step, four-step, and five-step phase shifting methods with their corresponding phase unwrapping programs are commonly used algorithms in digital image processing and optical measurement applications. These algorithms are designed to extract phase information from images or measurement data, enabling 3D reconstruction and other shape analysis operations. The phase shifting methods typically involve capturing multiple images with precisely controlled phase shifts between them. For implementation, each method requires specific phase shift intervals: three-step uses 120° increments, four-step uses 90° increments, and five-step uses 72° increments. The core algorithm calculates phase maps using arctangent functions applied to the intensity variations across the phase-shifted images. Phase unwrapping programs are essential for addressing phase discontinuities in images or measurement data to obtain more accurate phase information. These programs employ various implementation approaches, including image-based methods that use quality-guided path following or minimum discontinuity algorithms, and physics-based methods that incorporate physical constraints or model-based predictions. Key functions in phase unwrapping typically involve residue calculation, quality map generation, and reliable phase path determination to resolve 2π ambiguities in the wrapped phase data. Code implementations often utilize matrix operations for efficient computation, with phase calculation functions handling the arctangent operations and unwrapping algorithms managing the phase continuity restoration through iterative or global optimization techniques.