Self-Calibration of a Large-Scale Variable-Line-Spacing Grating for an Absolute Optical Encoder by Differencing Spatially Shifted Phase Maps from a Fizeau Interferometer
A new method based on the interferometric pseudo-lateral-shearing method is proposed to evaluate the pitch variation of a large-scale planar variable-line-spacing (VLS) grating. In the method, wavefronts of the first-order diffracted beams from a planar VLS grating are measured by a commercial Fizea...
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MDPI AG
2022-12-01
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| Online Access: | https://www.mdpi.com/1424-8220/22/23/9348 |
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| author | Xin Xiong Chenguang Yin Lue Quan Ryo Sato Hiraku Matsukuma Yuki Shimizu Hideaki Tamiya Wei Gao |
| author_facet | Xin Xiong Chenguang Yin Lue Quan Ryo Sato Hiraku Matsukuma Yuki Shimizu Hideaki Tamiya Wei Gao |
| author_sort | Xin Xiong |
| collection | DOAJ |
| description | A new method based on the interferometric pseudo-lateral-shearing method is proposed to evaluate the pitch variation of a large-scale planar variable-line-spacing (VLS) grating. In the method, wavefronts of the first-order diffracted beams from a planar VLS grating are measured by a commercial Fizeau form interferometer. By utilizing the differential wavefront of the first-order diffracted beam before and after the small lateral shift of the VLS grating, the pitch variation of the VLS grating can be evaluated. Meanwhile, additional positioning errors of the grating in the lateral shifting process could degrade the measurement accuracy of the pitch variation. To address the issue, the technique referred to as the reference plane technique is also introduced, where the least squares planes in the wavefronts of the first-order diffracted beams are employed to reduce the influences of the additional positioning errors of the VLS grating. The proposed method can also reduce the influence of the out-of-flatness of the reference flat in the Fizeau interferometer by taking the difference between the measured positive and negative diffracted wavefronts; namely, self-calibration can be accomplished. After the theoretical analysis and simulations, experiments are carried out with a large-scale VLS grating to verify the feasibility of the proposed methods. Furthermore, the evaluated VLS parameters are verified by comparing them with the readout signal of an absolute surface encoder employing the evaluated VLS grating as the scale for measurement. |
| first_indexed | 2024-03-09T17:31:47Z |
| format | Article |
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| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-03-09T17:31:47Z |
| publishDate | 2022-12-01 |
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| series | Sensors |
| spelling | doaj.art-461ac434e6a647a7a094009e63ab7c592023-11-24T12:12:44ZengMDPI AGSensors1424-82202022-12-012223934810.3390/s22239348Self-Calibration of a Large-Scale Variable-Line-Spacing Grating for an Absolute Optical Encoder by Differencing Spatially Shifted Phase Maps from a Fizeau InterferometerXin Xiong0Chenguang Yin1Lue Quan2Ryo Sato3Hiraku Matsukuma4Yuki Shimizu5Hideaki Tamiya6Wei Gao7Department of Finemechanics, Tohoku University, Sendai 980-8579, JapanDepartment of Finemechanics, Tohoku University, Sendai 980-8579, JapanDepartment of Finemechanics, Tohoku University, Sendai 980-8579, JapanDepartment of Finemechanics, Tohoku University, Sendai 980-8579, JapanDepartment of Finemechanics, Tohoku University, Sendai 980-8579, JapanDepartment of Human Mechanical Systems and Design, Hokkaido University, Sapporo 060-0808, JapanMagnescale Co., Ltd., Suzukawa 45, Isehara 259-1146, JapanDepartment of Finemechanics, Tohoku University, Sendai 980-8579, JapanA new method based on the interferometric pseudo-lateral-shearing method is proposed to evaluate the pitch variation of a large-scale planar variable-line-spacing (VLS) grating. In the method, wavefronts of the first-order diffracted beams from a planar VLS grating are measured by a commercial Fizeau form interferometer. By utilizing the differential wavefront of the first-order diffracted beam before and after the small lateral shift of the VLS grating, the pitch variation of the VLS grating can be evaluated. Meanwhile, additional positioning errors of the grating in the lateral shifting process could degrade the measurement accuracy of the pitch variation. To address the issue, the technique referred to as the reference plane technique is also introduced, where the least squares planes in the wavefronts of the first-order diffracted beams are employed to reduce the influences of the additional positioning errors of the VLS grating. The proposed method can also reduce the influence of the out-of-flatness of the reference flat in the Fizeau interferometer by taking the difference between the measured positive and negative diffracted wavefronts; namely, self-calibration can be accomplished. After the theoretical analysis and simulations, experiments are carried out with a large-scale VLS grating to verify the feasibility of the proposed methods. Furthermore, the evaluated VLS parameters are verified by comparing them with the readout signal of an absolute surface encoder employing the evaluated VLS grating as the scale for measurement.https://www.mdpi.com/1424-8220/22/23/9348variable-line-spacing gratingdiffraction gratingsself-calibrationoptical encoderinterferometryinterferometric pseudo-lateral-shearing method |
| spellingShingle | Xin Xiong Chenguang Yin Lue Quan Ryo Sato Hiraku Matsukuma Yuki Shimizu Hideaki Tamiya Wei Gao Self-Calibration of a Large-Scale Variable-Line-Spacing Grating for an Absolute Optical Encoder by Differencing Spatially Shifted Phase Maps from a Fizeau Interferometer Sensors variable-line-spacing grating diffraction gratings self-calibration optical encoder interferometry interferometric pseudo-lateral-shearing method |
| title | Self-Calibration of a Large-Scale Variable-Line-Spacing Grating for an Absolute Optical Encoder by Differencing Spatially Shifted Phase Maps from a Fizeau Interferometer |
| title_full | Self-Calibration of a Large-Scale Variable-Line-Spacing Grating for an Absolute Optical Encoder by Differencing Spatially Shifted Phase Maps from a Fizeau Interferometer |
| title_fullStr | Self-Calibration of a Large-Scale Variable-Line-Spacing Grating for an Absolute Optical Encoder by Differencing Spatially Shifted Phase Maps from a Fizeau Interferometer |
| title_full_unstemmed | Self-Calibration of a Large-Scale Variable-Line-Spacing Grating for an Absolute Optical Encoder by Differencing Spatially Shifted Phase Maps from a Fizeau Interferometer |
| title_short | Self-Calibration of a Large-Scale Variable-Line-Spacing Grating for an Absolute Optical Encoder by Differencing Spatially Shifted Phase Maps from a Fizeau Interferometer |
| title_sort | self calibration of a large scale variable line spacing grating for an absolute optical encoder by differencing spatially shifted phase maps from a fizeau interferometer |
| topic | variable-line-spacing grating diffraction gratings self-calibration optical encoder interferometry interferometric pseudo-lateral-shearing method |
| url | https://www.mdpi.com/1424-8220/22/23/9348 |
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