... | ... | @@ -9,10 +9,10 @@ Reflective polariscopes allow for the visualization of the photoelastic fringes |
|
|
* A light source
|
|
|
* A single *polarizer*, which is ideally a circular polarizer located between the light source and photoelastic specimen. This is shown with both of its parts: a linear polarizer plus a quarter-wave plate.
|
|
|
* A reflective surface, that can be either a mirror below the sample or a coating on the particles.
|
|
|
* An *analyzer*, which is a circular polarizer located between the photoelastic specimen and the camera. For a darkfield polariscope, this matches the incident light (and can even be the same optical element); for a brightfield polariscope, this is complementary.
|
|
|
* An *analyzer*, which is a circular polarizer located between the photoelastic specimen and the camera.
|
|
|
* A camera.
|
|
|
|
|
|
Similar to the [transmissive polariscope](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/transmission-photoelasticity), both the *Polarizer* and the *Analyzer* are usually circular polarizers. Thus the principle axis of the quarter-wave plate in figure below must form $`45^{\circ}`$ angle with the direction of polarization of the linear polarizer. It is important to point out that a dark field reflective polariscope uses circular polarizers with same chirality for both the *Polarizer* and the *Analyzer* (see section 2. for mathematical proof), whereas the transmissive polariscope uses circular polarizers with different chirality.
|
|
|
Similar to the [transmissive polariscope](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/transmission-photoelasticity), both the *polarizer* and the *analyzer* should be circular polarizers. In assembling the circular polarizers, it is important for the principle axis of the quarter-wave plate to make a $`45^{\circ}`$ angle with the direction of polarization of the linear polarizer. Note that for a darkfield polariscope, the analyzer must match the chirality of the polarizer on the incident light path (see section 2. for mathematical proof), and can even be the same optical element. For a brightfield polariscope, the two polarizers are complementary.
|
|
|
|
|
|
![reflective_circular_4](uploads/9b9996db2ba507c78fd8e16f65a6144c/reflective_circular_4.png)
|
|
|
|
... | ... | @@ -29,8 +29,6 @@ There are two typical ways to implement the mirror in real granular physics expe |
|
|
|
|
|
A typical way to create the reflective surface for photoelastic particles is to coat one side of the particles with mirror effect paint. An empirical choice that works well is the [*Rust-Oleum Mirror Effect spray*](https://www.amazon.com/Rust-Oleum-267727-Specialty-Mirror-6-Ounce/dp/B00FMRXJW2/ref=sr_1_1?ie=UTF8&qid=1544796251&sr=8-1&keywords=rust-oleum+mirror+effect) (figure below). To ensure uniform coating, it is typical to first paint a sheet of photoelastic material and then cut particles from it. The lower right figure below shows a picture of the painted photoelastic sheet after [cutting of the particles](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/cutting-sample). The figure below also shows different angles of particles after this coating process.
|
|
|
|
|
|
|
|
|
|
|
|
![particles](uploads/ba1713b99aba580dd47cdeb73c15cc8d/particles.png)
|
|
|
|
|
|
|
... | ... | |