# Scanning projectors

The next steps after configuring the camera is to define settings for the scanning procedure based on the site-specific situation: lighting condition, projector setting, surface and camera setting.

For each projector, a series of settings is defined:

## 1. Adjust brightness

<figure><img src="/files/oOwo708VCyR1dBvrN3Tu" alt=""><figcaption></figcaption></figure>

This step determines the brightness of the projector depending on the camera exposure and reflectivity of the surface.&#x20;

{% hint style="info" %}
At first run, the ideal brightness for a projector is determined automatically.

If in doubt, go with this setting and manipulate only if there are obvious issues with the brightness detection.
{% endhint %}

* A value between 80 and 95 is ideal as it indicates a certain buffer for brightness adjustments.
* A value of 100 indicates that the projector signal perceived by the camera has reached it's maximum. Consider to increase the camera sensitivity (longer exposure, open iris)
* A value <50 usually indicates a way too high signal input, e.g. by a strong light source, reflection of metal, sunlight, etc. Try to remove this source. If not, consider to manually override the brightness until the perceived projection light is appropriate.

<figure><img src="/files/KLhajCT4y5lOS3Plr7zY" alt=""><figcaption></figcaption></figure>

Use the slider to adjust the brightness or re-run the automatic brightness detection by pressing `Automatic`.

Continue to the next step by pressing `Next`.

## 2. Adjust Dot Size

This visual feedback loop is crucial. It allows you to define the level of detail for the test pattern, which is essential for accurately capturing the projector’s mapping and the surface properties.

The success of the auto-alignment process hinges on how the camera perceives and interprets this pattern.

<figure><img src="/files/n8TVHxpHROKpPOhKJWqV" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
The objective: To see as many dots as possible that are clearly delineated, do not smudge and do not fade away
{% endhint %}

We always start with dot size = 1.2 and margin = 0, which surprisingly often works right from the spot

Depending on camera resolution, projector image size, projector resolution and camera distance any other value might be suitable. If in doubt and if the dot pattern looks like in the picture "OK", do not do not alter and give it a try by pressing `Next`.

<figure><img src="/files/VLCbA2JIxVOirpzCWoom" alt=""><figcaption></figcaption></figure>

If dots keep being blurry, smudged and not clearly delineated, go through these checklist:

* [ ] Check the focus of the camera. Check also the lens for dirt.
* [ ] Check the camera lens iris - open/close to gain better contrast
* [ ] Check the ambient lighting conditions. Low ambient light = better contrast = better dots
* [ ] Check the camera image settings - increase/decrease the camera exposure
* [ ] Check the camera image settings and deactivate all image enhancement features: NO sharpness enhancement, NO user gamma, NO brightness enhancement, etc.
* [ ] Increase or decrease the exposure (see [#id-1.-adjust-brightness](#id-1.-adjust-brightness "mention")) - a wrong exposure leads to bad dots
* [ ] Check the threshold (see [#id-3.-threshold](#id-3.-threshold "mention"))

`Next` will proceed to the scanning (see [Scan Result](/calibration/scanning/scan-result.md)).

## 3. Noise Filter Threshold

In case of troubles getting well detected dots, the threshold  for the built-in noise filtering can help to solve the issue. The threshold is determined automatically after the brightness adjustment.

A fading image with dots left out is a typical indicator for an improper threshold:

<figure><img src="/files/TBL016mIrIfhl8TG1BE4" alt=""><figcaption><p>most likely the noise filter threshold is wrong</p></figcaption></figure>

Klick `Threshold` to go back one step to the noise filter threshold dialog.

<figure><img src="/files/aEAN0QOacbKSzPRUPCzO" alt=""><figcaption></figcaption></figure>

The projector displays a line pattern and the camera tries to find a threshold for the noise filter to keep the lines clearly visible while cutting off noise. Whenever you change the slider `thickness`, the noise filter analyzes the camera image and tries to find a matching threshold setting.

Use the slider `threshold` to optimize the result on a line pattern that reflects more or less the size of the dots.

<figure><img src="/files/G73QAk6dsVy1qD6SdDui" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
Dont't be mislead by a morieè effect happening (see <https://en.wikipedia.org/wiki/Line_moir%C3%A9>). This is due to the fact that the lines are mostly finer than the camera can resolve. morieè effect has no impact on the scanning quality.
{% endhint %}

Once a good threshold setting has been determined, click `Next` to proceed to the dot pattern again.


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