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+++
title = "Interferometers"
author = ["Thomas Dehaeze"]
draft = false
+++
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Backlinks:
- [Position Sensors ]({{< relref "position_sensors" >}} )
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Tags
: [Position Sensors ]({{< relref "position_sensors" >}} )
## Manufacturers {#manufacturers}
| Manufacturers | Links | Country |
|---------------|----------------------------------------------------------------------------------------------------------|-------------|
| Attocube | [link ](http://www.attocube.com/ ) | Germany |
| Zygo | [link ](https://www.zygo.com/?/met/markets/stageposition/zmi/ ) | USA |
| Smaract | [link ](https://www.smaract.com/interferometry ) | Germany |
| Qutools | [link ](https://www.qutools.com/qudis/ ) | Germany |
| Renishaw | [link ](https://www.renishaw.com/en/fibre-optic-laser-encoder-products--6594 ) | UK |
| Sios | [link ](https://sios-de.com/products/length-measurement/laser-interferometer/ ) | Germany |
| Keysight | [link ](https://www.keysight.com/en/pc-1000000393%3Aepsg%3Apgr/laser-heads?nid=-536900395.0&cc=FR&lc=fre ) | USA |
| Optics11 | [link ](https://optics11.com/ ) | Netherlands |
## Environmental Units {#environmental-units}
< div class = "table-caption" >
< span class = "table-number" > Table 1< / span > :
Characteristics of Environmental Units
< / div >
| | Temperature (\\(\pm\ ^oC\\)) | Pressure (\\(\pm\ hPa\\)) | Humidity \\(\pm\\% RH\\) | Wavelength Accuracy (\\(\pm\ \text{ppm}\\)) |
|-----------|------------------------------|---------------------------|--------------------------|---------------------------------------------|
| Attocube | 0.1 | 1 | 2 | 0.5 |
| Renishaw | 0.2 | 1 | 6 | 1 |
| Picoscale | 0.2 | 2 | 2 | 1 |
## Interferometer Precision {#interferometer-precision}
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([Jang and Kim 2017](#orgc0eaaa4))
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< a id = "orge2a3743" > < / a >
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{{< figure src = "/ox-hugo/position_sensor_interferometer_precision.png" caption = "Figure 1: Expected precision of interferometer as a function of measured distance" > }}
## Sources of uncertainty {#sources-of-uncertainty}
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Sources of error in laser interferometry are well described in ([Ducourtieux 2018](#org2c23555)).
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It includes:
- Laser Source Stability
- Variation of refractive index of air, which is dependent of:
- Temperature: \\(K\_T \approx 1 ppmK^{-1}\\)
- Pressure: \\(K\_P \approx 0.27 ppm hPa^{-1}\\)
- Humidity: \\(K\_{HR} \approx 0.01 ppm \% RH^{-1}\\)
- These errors can partially be compensated using an environmental unit.
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- Air turbulence (Figure [2 ](#org92b4926 ))
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- Non linearity
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< a id = "org92b4926" > < / a >
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{{< figure src = "/ox-hugo/interferometers_air_turbulence.png" caption = "Figure 2: Effect of air turbulences on measurement stability" > }}
## Bibliography {#bibliography}
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< a id = "org2c23555" > < / a > Ducourtieux, Sebastien. 2018. “Toward High Precision Position Control Using Laser Interferometry: Main Sources of Error.” < https: / / doi . org / 10 . 13140 / rg . 2 . 2 . 21044 . 35205 > .
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< a id = "orgc0eaaa4" ></ a > Jang, Yoon-Soo, and Seung-Woo Kim. 2017. “Compensation of the Refractive Index of Air in Laser Interferometer for Distance Measurement: A Review.” _International Journal of Precision Engineering and Manufacturing_ 18 (12):1881– < https: // doi . org / 10 . 1007 / s12541-017-0217-y > .
