| ... | @@ -5,7 +5,7 @@ Imaging with different wavelength |
... | @@ -5,7 +5,7 @@ Imaging with different wavelength |
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### 1.1. Best wavelength for a particular polariscope?
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### 1.1. Best wavelength for a particular polariscope?
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The *Polarizer* (the circular polarizer between the light source and the sample) and the *Analyzer* (the circular polarizer between the camera and the sample) of a polariscope ([transmissive](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/transmission-photoelasticity) or [reflective](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/reflection-photoelasticity)) contain same type of quarter-wave plate. This quarter-wave plate sets a particular wavelength that works best for this polariscope to probe the photoelastic fringes. A different light wavelength would create larger noise, since passing the quarter-wave plates twice no longer gives a $`\pi`$ phase difference between the two perpendicular components of the light. Thus using different wavelength can not give a perfect dark field for this polariscope.
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The *Polarizer* (the circular polarizer between the light source and the sample) and the *Analyzer* (the circular polarizer between the camera and the sample) of a polariscope ([transmissive](/transmission-photoelasticity) or [reflective](/reflection-photoelasticity)) contain same type of quarter-wave plate. This quarter-wave plate sets a particular wavelength that works best for this polariscope to probe the photoelastic fringes. A different light wavelength would create larger noise, since passing the quarter-wave plates twice no longer gives a $`\pi`$ phase difference between the two perpendicular components of the light. Thus using different wavelength can not give a perfect dark field for this polariscope.
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### 1.2. White light or monochromatic light?
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### 1.2. White light or monochromatic light?
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| ... | @@ -14,7 +14,7 @@ Monochromatic light works best for the photoelastic fringes detection. If a whit |
... | @@ -14,7 +14,7 @@ Monochromatic light works best for the photoelastic fringes detection. If a whit |
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## 2. Position detection and light color
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## 2. Position detection and light color
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There are two choices to record a image for [position detection](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/detect-and-follow), where no photoelastic fringe should be visible.
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There are two choices to record a image for [position detection](/detect-and-follow), where no photoelastic fringe should be visible.
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* The first choice is to use the same kind of light source but record another image without the *Analyzer*, which is the polarizer between the camera and the sample. An example image from this method is shown in the right figure below, where the light source is white light. (from [*J. Ren et al.*](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.018302)) This method needs only one light source and avoids any possible noise caused by the photoelastic fringes on the position detection.
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* The first choice is to use the same kind of light source but record another image without the *Analyzer*, which is the polarizer between the camera and the sample. An example image from this method is shown in the right figure below, where the light source is white light. (from [*J. Ren et al.*](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.018302)) This method needs only one light source and avoids any possible noise caused by the photoelastic fringes on the position detection.
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| ... | @@ -43,4 +43,4 @@ The rotation of the discs can be tracked by drawing a ultra-violet(UV) sensitive |
... | @@ -43,4 +43,4 @@ The rotation of the discs can be tracked by drawing a ultra-violet(UV) sensitive |
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[<go back to home](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/home) |
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[<go back to home](/home) |
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