Helium-Neon (He-Ne) laser is a mature laser. Until now, it is still an irreplaceable light source in the field of precision instruments, and there is no competitor in terms of high precision. The Chaps. 1 and 2 of this book introduce the birefringent laser based on He-Ne laser and its physical properties. This chapter introduces the precision measuring instruments with He–Ne birefringence dual-frequency laser as the light source, including birefringence Zeeman dual frequency laser interferometer (not Zeeman laser interferometer based on traditional Zeeman laser), Laser nanometer ruler (dual-polarized light competitive displacement measurement laser), Optical wave-plate phase difference measuring instrument (which has become a national standard), Optical phase difference measurement instruments based on laser feedback (online in place), He–Ne laser feedback interferometer, Nano fringe interferometer. This chapter does not include instruments with microchip lasers as light sources, which are the subject of Chap. 4 . The instrument with He-Ne laser as the light source has the advantage of high precision, while the instrument with microchip laser as the light source has the advantage of not contacting the measurement target at all. The goal of our efforts is to form two types of precision measurement instruments with helium-Neon laser as the light source and microchip laser as the light source, which complement each other and have their own advantages, providing more and better precision measurement means and expanding the application field.