# Light Tunnel Mk2

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<figure><img src="https://3492874807-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FUqYDL9yvLTNUYW7H1Q6t%2Fuploads%2FNB1EuTFi2dgKBNs8mclg%2Flt_light_backround.png?alt=media&#x26;token=8376721f-3c81-4a76-a8b0-0b9179c0038b" alt=""><figcaption></figcaption></figure>
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The Light Tunnel produces [**i.i.d.**](#user-content-fn-1)[^1] **data and images** from a controlled **optical experiment.**

It contains a controllable light source, linear polarizers mounted on rotating frames, and sensors to measure light intensity at different frequencies and locations. A camera captures images from inside the tunnel.
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The chamber produces images and i.i.d. data from up to 99 variables, including sensor measurements, control inputs, and sensor parameters.

<figure><picture><source srcset="https://3492874807-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FUqYDL9yvLTNUYW7H1Q6t%2Fuploads%2FnYJuFQnkOl8xbktsrMQE%2Flt-data-dark-images.png?alt=media&#x26;token=e800929c-0d71-4d84-b054-9170c08bf9c5" media="(prefers-color-scheme: dark)"><img src="https://3492874807-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FUqYDL9yvLTNUYW7H1Q6t%2Fuploads%2Fb832TwJNi2O8XlQ4dj9N%2Flt-data-light-images.png?alt=media&#x26;token=5a623acb-3b1a-4437-ad64-a5389b5d3052" alt="" width="563"></picture><figcaption><p><strong>Top right</strong>: infrared-intensity measurements produced by the first sensor (<code>ir_1</code>) for different intensities of the light-source channels (<code>red/green/blue</code>). <strong>Top left</strong>: examples of images produced by the tunnel in the linked_leds (left) and the camera_fast (right) <a href="#hardware-configurations">hardware configurations</a>. <strong>Bottom:</strong> observing Malus' law in the effect of the polarizer positions (<code>pol_1, pol_2</code>) on the infrared intensity at the third sensor (<code>ir_3</code>).</p></figcaption></figure>

<details>

<summary>Chamber diagram &#x26; variables</summary>

You can find a description of each variable in the documentation for each [hardware configuration](#hardware-configurations) below.

<figure><img src="https://3492874807-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FUqYDL9yvLTNUYW7H1Q6t%2Fuploads%2FKz8F7gs9Apgai4h7xHBc%2Flt_diagram_light_background.png?alt=media&#x26;token=4a8cd377-6467-46df-b383-cefe553b7798" alt=""><figcaption><p>Right click to download the image (available under a <a href="https://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC 4.0</a> non-commercial license).</p></figcaption></figure>

</details>

<details>

<summary>Simulators</summary>

See the [Simulator Index](https://github.com/juangamella/causal-chamber-package/tree/main/causalchamber/simulators) for a list of the simulators we offer for this chamber, including documentation and example code.

</details>

### Hardware configurations

Like all chambers, the wind tunnel can automatically load different [hardware configurations](https://docs.causalchamber.ai/how-they-work#hardware-configurations). See the corresponding PDF for a chamber diagram, a complete description of all variables, and the causal ground-truth graph.

<table><thead><tr><th width="127.375732421875">Name</th><th width="79.828125" data-type="checkbox">Img. data</th><th width="243.657958984375">Description</th><th width="149.1961669921875">Documentation</th><th>Causal ground-truth</th></tr></thead><tbody><tr><td><code>standard</code></td><td>false</td><td>Standard configuration with all variables (excl. motor parameters).</td><td><a href="https://cchamber-box.s3.eu-central-2.amazonaws.com/config_doc_lt_mk2_standard.pdf" class="button secondary">.pdf</a></td><td><a href="https://box.causalchamber.ai/gt_graph_lt_mk2_standard.pdf" class="button secondary">.pdf</a></td></tr><tr><td><code>linked_leds</code></td><td>false</td><td>Additional tunable causal effects.</td><td><a href="https://cchamber-box.s3.eu-central-2.amazonaws.com/config_doc_lt_mk2_linked_leds.pdf" class="button secondary">.pdf</a></td><td><a href="https://box.causalchamber.ai/gt_graph_lt_mk2_linked_leds.pdf" class="button secondary">.pdf</a></td></tr><tr><td><code>camera_fast</code></td><td>true</td><td>Provides images and camera variables.</td><td><a href="https://cchamber-box.s3.eu-central-2.amazonaws.com/config_doc_lt_mk2_camera_fast.pdf" class="button secondary">.pdf</a></td><td><a class="button secondary">.pdf</a></td></tr><tr><td><code>led_matrix</code></td><td>true</td><td>Same as <code>camera_fast</code> but with individual control of the light-source LEDs.</td><td><a href="https://cchamber-box.s3.eu-central-2.amazonaws.com/config_doc_lt_mk2_led_matrix.pdf" class="button secondary">.pdf</a></td><td><a class="button secondary">.pdf</a></td></tr></tbody></table>

[^1]: i.e., independent and identically distributed observations given a fixed set of inputs, up to negligible effects like small sensor drifts