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<h1 class="title">NASS - Short Stroke Metrology</h1>
<div id="table-of-contents">
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#orge8c6134">1. Measurement Principle</a></li>
<li><a href="#org4742c55">2. X-Y-Z measurement</a></li>
<li><a href="#org0ca496a">3. Tilt measurement</a></li>
<li><a href="#org4a349c9">4. Conclusion</a></li>
</ul>
</div>
</div>
<p>
The goal of this document is to analyze the feasibility of a short stroke metrology system for the NASS using fixed interferemoter and the same reflector as for the long stroke metrology system.
</p>
<p>
It is structured as follow:
</p>
<ul class="org-ul">
<li>Section <a href="#orgcce215b">1</a>: the meaurement principle is described.</li>
<li>Section <a href="#org7f61293">2</a>: the requirements for the interferometers measuring translations are described</li>
<li>Section <a href="#orgd21778d">3</a>: the same is done for the rotations</li>
</ul>
<div id="outline-container-orge8c6134" class="outline-2">
<h2 id="orge8c6134"><span class="section-number-2">1</span> Measurement Principle</h2>
<div class="outline-text-2" id="text-1">
<p>
<a id="orgcce215b"></a>
</p>
<p>
Here are the defined wanted displacement of the reflector that should be inside the measurement stroke of the metrology system.
The defined translations and rotations are defined with respect to the frame shown in Figure <a href="#org26e55bb">1</a>.
</p>
<div class="org-src-container">
<pre class="src src-matlab">d_x = 0; <span class="org-comment">% Wanted translation of the reflector in the x direction [m]</span>
d_y = 1e<span class="org-type">-</span>3; <span class="org-comment">% Wanted translation of the reflector in the y direction [m]</span>
d_z = 1e<span class="org-type">-</span>3; <span class="org-comment">% Wanted translation of the reflector in the z direction [m]</span>
R_x = 10e<span class="org-type">-</span>3; <span class="org-comment">% Wanted rotation of the reflector along the x axis [rad]</span>
R_y = 0; <span class="org-comment">% Wanted rotation of the reflector along the y axis [rad]</span>
</pre>
</div>
<div id="org26e55bb" class="figure">
<p><img src="figs/short_stroke_metrology_concept.png" alt="short_stroke_metrology_concept.png" />
</p>
<p><span class="figure-number">Figure 1: </span>Short Stroke Metrology - Concept. Blue interferometers are used to measure the X-Y-Z motion of the reflector. Red interferometers are used to measure tilt motion of the reflector.</p>
</div>
<p>
Here are the approximate dimensions shown in Figure <a href="#org26e55bb">1</a>:
</p>
<ul class="org-ul">
<li>\(d_0 \approx 10\,[mm]\)</li>
<li>\(L \approx 150\,[mm]\)</li>
<li>\(R \approx 250\,[mm]\)</li>
</ul>
<div class="org-src-container">
<pre class="src src-matlab">d0 = 10e<span class="org-type">-</span>3; <span class="org-comment">% [m]</span>
L = 150e<span class="org-type">-</span>3; <span class="org-comment">% [m]</span>
R = 250e<span class="org-type">-</span>3; <span class="org-comment">% [m]</span>
</pre>
</div>
</div>
</div>
<div id="outline-container-org4742c55" class="outline-2">
<h2 id="org4742c55"><span class="section-number-2">2</span> X-Y-Z measurement</h2>
<div class="outline-text-2" id="text-2">
<p>
<a id="org7f61293"></a>
</p>
<p>
The geometry for the interferometers measuring translations is shown in Figure <a href="#org98aebff">2</a>:
</p>
<ul class="org-ul">
<li>\(R = 250\,[mm]\)</li>
<li>\(d_0 > 10\,[mm]\)</li>
<li>\(d_x = \pm 1\,[mm]\)</li>
<li>\(d_y = \pm 1\,[mm]\)</li>
</ul>
<div id="org98aebff" class="figure">
<p><img src="figs/translation_interferometers.png" alt="translation_interferometers.png" />
</p>
<p><span class="figure-number">Figure 2: </span>Interferometers that are measuring translation</p>
</div>
<p>
The angle of the reflected beam is approximately equal to:
</p>
\begin{equation}
\theta \approx 2 \frac{d_y}{R}
\end{equation}
<p>
And we obtain:
</p>
<p>
\[ \theta \approx 8.0\,[mrad] \]
</p>
<table id="org7dbf661" border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<caption class="t-above"><span class="table-number">Table 1:</span> Specifications for the translation interferometers</caption>
<colgroup>
<col class="org-left" />
<col class="org-left" />
</colgroup>
<thead>
<tr>
<th scope="col" class="org-left">Specification</th>
<th scope="col" class="org-left">Value</th>
</tr>
</thead>
<tbody>
<tr>
<td class="org-left">Axial Acceptance</td>
<td class="org-left">\(\pm 1\,[mm]\)</td>
</tr>
<tr>
<td class="org-left">Angular Acceptance</td>
<td class="org-left">\(\pm 8\,[mrad]\)</td>
</tr>
<tr>
<td class="org-left">Distance to target</td>
<td class="org-left">\(10\,[mm]\)</td>
</tr>
</tbody>
</table>
</div>
</div>
<div id="outline-container-org0ca496a" class="outline-2">
<h2 id="org0ca496a"><span class="section-number-2">3</span> Tilt measurement</h2>
<div class="outline-text-2" id="text-3">
<p>
<a id="orgd21778d"></a>
</p>
<p>
The tilt \(\theta\) of the flat mirror is directly equal to the tilt of the reflector.
However, the \(z\) displacement on the flat part is equal to:
</p>
\begin{equation}
z \approx d_z + L \theta_y
\end{equation}
<p>
And we obtain:
</p>
<p>
\[ z \approx 2.5\,[mm] \]
</p>
<p>
The geometry for the interferometers measuring rotations is shown in Figure <a href="#orgb2621f2">3</a>:
</p>
<ul class="org-ul">
<li>\(d_0 > 10\,[mm]\)</li>
<li>\(\theta = \pm 10\,[mrad]\)</li>
<li>\(z = \pm 2.5\, [mm]\)</li>
</ul>
<div id="orgb2621f2" class="figure">
<p><img src="figs/rotation_interferometers.png" alt="rotation_interferometers.png" />
</p>
<p><span class="figure-number">Figure 3: </span>Interferometers that are measuring tilt</p>
</div>
<table id="org53ac3fe" border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<caption class="t-above"><span class="table-number">Table 2:</span> Specifications for the rotation interferometers</caption>
<colgroup>
<col class="org-left" />
<col class="org-left" />
</colgroup>
<thead>
<tr>
<th scope="col" class="org-left">Specification</th>
<th scope="col" class="org-left">Value</th>
</tr>
</thead>
<tbody>
<tr>
<td class="org-left">Axial Acceptance</td>
<td class="org-left">\(\pm 2.5\,[mm]\)</td>
</tr>
<tr>
<td class="org-left">Angular Acceptance</td>
<td class="org-left">\(\pm 10\,[mrad]\)</td>
</tr>
<tr>
<td class="org-left">Distance to target</td>
<td class="org-left">\(10\,[mm]\)</td>
</tr>
</tbody>
</table>
</div>
</div>
<div id="outline-container-org4a349c9" class="outline-2">
<h2 id="org4a349c9"><span class="section-number-2">4</span> Conclusion</h2>
</div>
</div>
<div id="postamble" class="status">
<p class="author">Author: Dehaeze Thomas</p>
<p class="date">Created: 2021-02-19 ven. 11:10</p>
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