High resolution heterodyne interferometer without detectable periodic nonlinearity

Abstract

A high resolution heterodyne laser interferometer without periodic nonlinearity for linear displacement measurements is described. It uses two spatially separated beams with an offset frequency and an interferometer configuration which has no mixed states to prevent polarization mixing. In this research, a simple interferometer configuration for both retroreflector and plane mirror targets which are both applicable to industrial applications was developed. Experimental results show there is no detectable periodic nonlinearity for both of the retro-reflector interferometer and plane mirror interferometer to the noise level of 20 pm. Additionally, the optical configuration has the benefit of doubling the measurement resolution when compared to its respective traditional counterparts. Because of non-symmetry in the plane mirror interferometer, a differential plane mirror interferometer to reduce the thermal error is also discussed. ©2010 Optical Society of America References and links1. W. T. Estler, "High-accuracy displacement interferometry in air," Appl. Opt. 24(6), 808-815 (1985). 2. H. Bosse, and G. Wilkening, "Developments at PTB in nanometrology for support of the semiconductor industry," Meas. Sci. Technol. 16(11), 2155-2166 (2005). 3. N. Bobroff, "Recent advances in displacement measuring interferometry," Meas. Sci. Technol. 4(9), 907-926 (1993). 4. F. C. Demarest, "High-resolution, high-speed, low data age uncertainty, heterodyne displacement measuring interferometer electronics," Meas. Sci. Technol. 9(7), 1024-1030 (1998). 5. R. C. Quenelle, "Nonlinearity in interferometer measurements," Hewlett Packard J. 34, 10 (1983). 6. W. Hou, and G. Wilkening, "Investigation and compensation of the nonlinearity of heterodyne interferometers," Precis. Eng. 14(2), 91-98 (1992) 3195-3203 (2006). 13. M. Tanaka, T. Yamagami, and K. Nakayama, "Linear interpolation of periodic error in a heterodyne laser interferometer at subnanometer levels (dimension measurement)," IEEE Trans. Instrum. Meas. 38(2), 552-554 (1989). 14. C. M. Wu, J. Lawall, and R. D. Deslattes, "Heterodyne interferometer with subatomic periodic nonlinearity,"Appl. Opt. 38(19), 4089-4094 (1999). 15. J. Lawall, and E. Kessler, "Michelson interferometry with 10 pm accuracy," Rev. Sci. Instrum. 71(7), 2669-2676 (2000). 16. T. L. Schmitz, and J. F. Beckwith, "Acousto-optic displacement-measuring interferometer: a new heterodyne interferometer with Anstrom-level periodic error," J. Mod. Opt. 49(13), 2105-2114 (2002

Heterodyne displacement interferometer, insensitive for input polarization

“…This can be achieved by keeping the two source frequencies spatially separated throughout the interferometer system until detection takes place [12][13][14][15][16][17][18][19]. Spatial separation prevents frequency leakage occurring, thereby prohibiting PNL, but it also leads to possible optical path length inequality during source frequency delivery.…”

“…The interferometer designs discussed in this Letter [15][16][17], designed at TU Delft, are of equal optical complexity compared to coaxial systems and use spatially separated source frequencies (generated using [20]). Furthermore, the Delft designs allow for a high degree of system integration, as fiber coupling is possible for both frequency delivery and signal detection.…”

Fiber-coupled displacement interferometry without periodic nonlinearity

“…However, periodic nonlinearity in the measurement is more difficult to eliminate because it arises from a combination of source mixing, manufacturing tolerances, and imperfect alignment. Fiber delivery will inherently decrease polarization stability and add timevarying effects, which further complicates the signal processing for interferometers susceptible to periodic nonlinearity [17].Several heterodyne interferometer configurations have been developed that limit the chances for periodic nonlinearity [18][19][20][21][22][23]. These interferometers generally use a spatially separated source and limit all reference and measurement beam overlaps until the final interfering surface prior to detection.…”

“…In this Letter, we present a general, fiber-coupled Joo-type interferometer with a novel design based on previous Joo-type retroreflector (RR) and plane mirror target interferometers [21,23], which is more suitable for multiaxis systems and has the same footprint on the measurement target as a typical Michelson plane mirror interferometer. Additionally, we compare the results from periodic error analyses between fiber-and free-space-delivered variants and characterize the nominal drift from fiber-induced Doppler shifts.…”

“…Several heterodyne interferometer configurations have been developed that limit the chances for periodic nonlinearity [18][19][20][21][22][23]. These interferometers generally use a spatially separated source and limit all reference and measurement beam overlaps until the final interfering surface prior to detection.…”