We present SQUIDPOL, a low-cost, multi-channel optical imaging polarimeter that performs simultaneous linear polarization measurements using a rotating half-wave plate, a non-polarizing beam splitter, and four wire-grid filters. We show that the multilayer dielectric coating of the off-the-shelf non-polarizing beam splitter introduces different phase delays to the s- and p-polarized components, which introduces polarization-dependent systematics that can bias polarimetric measurements if left uncorrected. We quantify this effect for both transmitted and reflected beams and incorporate a correction scheme into the data-analysis pipeline. On-sky validation demonstrates stable and reproducible performance, achieving a polarization accuracy of σP ∼ 0.15% for bright polarimetric standard stars (V ∼ 2–3 mag). Mounted on the 60-cm Ritchey-Chrétien telescope (focal length of 4200mm, f/7) at the Pyeonchang Observatory of Seoul National University, SQUIDPOL provides an effective common field of view of 13.5′ × 8.2′ with a pixel scale of 0.45′′ pixel−1 and supports standard B, V , RC, and IC filters.

Introduction
Instrument Design
    Optical Layout
    Optomechanical Design
Performance Evaluation Results
    Test Observations
    Geometric Characteristics
    Optical Characteristics
    Basic Camera Properties
    System Stability
    Polarimetric Performance
Summary
Acknowledgments
References
Performance Verification of the HWP

• Sunho Jin(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Woojin Park(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Heeyoung Oh(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Chan Park(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Yoonsoo P. Bach(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Jooyeon Geem(Asteroid Engineering Laboratory, Luleå University of Technology, Kiruna, Sweden)
• Masateru Ishiguro(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea) Corresponding author
• Seungwon Choi(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea)
• Jinguk Seo(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea)
• Bumhoo Lim(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea)
• Myungshin Im(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea)
• Hyeonwoo Ju(Department of Physics, Konkuk University, Seoul 05029, Republic of Korea)