Pyramid Wavefront Sensor Using a Discrete Modulated Operation Method

The adaptive optics system (AOS) incorporating a modulated pyramid wavefront sensor (PWFS) represents a key area of exploration in current research aimed at enhancing the capabilities of future extremely large astronomical telescopes. However, incorporating a conventional modulated PWFS into an AOS presents several challenges, including complex optical pathways, intricate alignment procedures, and issues related to deviation in the exit pupil image. This paper introduces a novel discrete modulated operation method for the pyramid wavefront sensor, while the sensor concept has been already presented in authors' last paper, termed the DM-PWFS. The DM-PWFS integrates the modulation mirror with the pyramidal prism, reducing the number of conjugate planes in the system and significantly simplifying the optical pathways and alignment processes. Moreover, the M-PWFS replaces the traditional method of incident light modulation by modulating the center point of pyramidal prism, ensuring that the primary optical axis remains stationary during modulation and effectively eliminating the impact of pupil image deviation. The theoretical model and geometrical optical analysis explain the wavefront sensing principle of the DM-PWFS. Simulation analysis discusses the system parameters and dynamic performance of the DM-PWFS. Experimental results demonstrate that an AOS equipped with the DM-PWFS successfully corrects wavefront distortion, achieving a residual wavefront Root Mean Square (RMS) value of approximately 0.02λ and a focal plane image Strehl Ratio value of around 0.83.