Analysis and correction of phase calculation errors introduced by residual coherence in short-coherence heterodyne interferometry

Short-coherence heterodyne interferometry is believed to be a novel common-path interferometric measurement technique that relies on a short-coherence heterodyne laser source as its critical core component. This approach offers high precision and rapid phase shifting and eliminates the need for mechanical phase-shifting components. However, due to methodological constraints and manufacturing imperfections, the residual coherence (RC) in short-coherence lasers is difficult to suppress entirely, directly affecting phase calculation accuracy. This study establishes a four-beam interference fringe model that incorporates RC and derives a theoretical expression for phase calculation errors caused by RC, which provides a quantitative basis for the practical use of short-coherence heterodyne laser sources. Additionally, we introduce an iterative error correction algorithm that effectively reduces the influence of RC on heterodyne interferometric measurements, extending the application range of common-path heterodyne interferometry. This work reveals the impact mechanism of RC, offering valuable insights that complement existing RC analysis and research.