Ambient light detection: Difference between revisions
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Ambient light detection
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Note that XO-1.75 laptops have a built-in Ambient [[Light Sensor]]. The scheme outlined below hasn't ever been implemented, partially because of the privacy questions that it raises. |
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[[Image:Olpc_logo.jpg|center]] |
[[Image:Olpc_logo.jpg|center]] |
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<center><span style="font-size:200%">Ambient light detection</span></center> |
<center><span style="font-size:200%">Ambient light detection</span></center> |
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== Introduction == |
== Introduction == |
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* Don't store the picture (for privacy reasons) - instead, average the luminance of the image and square that number. (Why square? [http://en.wikipedia.org/wiki/Luminance See the formula] on how luminance is calculated.) |
* Don't store the picture (for privacy reasons) - instead, average the luminance of the image and square that number. (Why square? [http://en.wikipedia.org/wiki/Luminance See the formula] on how luminance is calculated.) |
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* Use this number (the square of the luminance) to control the backlight. |
* Use this number (the square of the luminance) to control the backlight. |
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* Allow the user to manually override the automatic backlight setting, and to easily turn the auto-backlight-setting mode on and off. |
* Allow the user to manually override the automatic backlight setting, and to easily turn the auto-backlight-setting mode on and off. |
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== How to help == |
== How to help == |
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Latest revision as of 17:28, 9 April 2012
Note that XO-1.75 laptops have a built-in Ambient Light Sensor. The scheme outlined below hasn't ever been implemented, partially because of the privacy questions that it raises.
Introduction
By using the XO's camera as an ambient light detector and using that data to control the backlight brightness, it may be possible to make the XO's battery life longer when used by kids (who may not walk around adjusting their backlight to optimal power-saving levels all the time).
Features to implement
- Every N seconds (suggested: 60 seconds, but we'll have to experiment to find a good polling interval), take a picture.
- Don't store the picture (for privacy reasons) - instead, average the luminance of the image and square that number. (Why square? See the formula on how luminance is calculated.)
- Use this number (the square of the luminance) to control the backlight.
- Allow the user to manually override the automatic backlight setting, and to easily turn the auto-backlight-setting mode on and off.
How to help
Contact Chris Ball.