Projector Brightness

Introduction

Projector brightness controls the output power and thus the amount of light that is emitted by the projector. Using the projector brightness is the most efficient way to maximize signal-to-noise ratio (SNR). Maximizing projector brightness will maximize the amplitude of the signal received by the camera. This minimizes impact from noise, as long as the reflected light from the projector does not over-saturate the pixel. At the same time as improving the peak signal amplitude, increased brightness also affects the mean intensity of the image. This also means that projector brightness can be used to control exposure, measured in stops.

Projector

The projector brightness variable is based on a relative value that controls the amount of lumens emitted from the projector. The table below shows how the available projector brightness in Zivid cameras relates to stops. Turning the projector brightness to 0 will turn the projector off.

Brightness		0.25	0.50	1.00	1.80	2.00	2.50
Stops		-2	-1	0	+0.85	+1	+1.32
Lumen	Zivid 2	90	180	360	650	N/A	N/A
	Zivid 2+	90	180	360	650	720	900

For example, by increasing the projector brightness from 0.50 to 1.00, the average intensity of the image will increase by 1 stop.

It is recommended to keep the concept of SNR in mind when selecting projector brightness, and therefore keep it high when possible. This is especially true in the presence of strong ambient light or imaging at distances above one meter.

Note

The Zivid 3D cameras are fitted with thermal throttling which prevents the camera from overheating.

Thermal throttling

To limit peak temperatures in the projector, the camera always enforces a duty cycle ceiling when capturing. This ceiling depends on two factors:

• Projector brightness: The maximum achievable duty cycle is 100% at brightness 1.0, 50% at brightness 1.8, and 30% at brightness 2.5 (for typical temperatures).

• Projector temperature: The maximum achievable duty cycle is derated by the projector temperature, which depends on duty cycle, projector brightness and ambient temperature.

The way that one will experience thermal throttling is that the camera will take short pauses during capture. This lets the camera cool off for a short amount of time before it can continue to capture.

Zivid 2+ maximum projector brightness limitation

By default, the maximum projector brightness for Zivid 2+ cameras depends on the color of the light used by the projector. For 3D capture, the color of the light is determined by the Sampling::Pixel setting. For 2D capture, the color is always white.

With Zivid::Settings::Sampling::Pixel::blueSubsample2x2 or Zivid::Settings::Sampling::Pixel::redSubsample2x2

the maximum projector brightness is 2.5.

With Zivid::Settings::Sampling::Pixel::all or in 2D capture

the maximum projector brightness is capped at 2.2 to keep the camera’s power consumption during operation under 100 W.

If your application allows more than 100 W power consumption, you can increase this limitation with a configuration file to allow projector brightness 2.5, even when using Zivid::Settings::Sampling::Pixel::all or in 2D capture.

How to increase the maximum projector brightness limit for Zivid 2+

You can increase projector brightness limit by updating the Config.yml file. If the file already exists and its located in %LOCALAPPDATA%\Zivid\API for Windows or "${XDG_CONFIG_HOME-$HOME/.config}"/Zivid/API for Ubuntu, update it with the following information:

__version__:
    serializer: 1
    data: 18
Configuration:
    Camera:
        Power:
            Limit: unlimited

Note

Ensure that the data number in the __version__ section is 18 or higher.

If the file does not exist:

1. Download the Config.yml file.

2. Place the downloaded Config file in the following directory.

   Windows

   mkdir %LOCALAPPDATA%\Zivid\API
   move %HOMEPATH%\Downloads\Config.yml %LOCALAPPDATA%\Zivid\API\
   

   Ubuntu

   mkdir --parents "${XDG_CONFIG_HOME-$HOME/.config}"/Zivid/API
   mv ~/Downloads/Config.yml "${XDG_CONFIG_HOME-$HOME/.config}"/Zivid/API/
   

   Caution

   Any existing Config file will be overwritten.

Caution

Zivid configuration files must use .yml file extension ( not .yaml).

Version History

SDK	Changes
2.10.1	Maximum projector brightness for Zivid 2+ is limited by default, when capturing with white light, with an option to increase the limit using a Config.yml.
2.10.0	Zivid 2+ series is added.
2.9.0	Thermal throttling is improved to throttle between acquisitions for a predicted time horizon instead of pausing the full capture.