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.

Zivid Projector

The projector brightness variable in Zivid is based on a relative value where 1.0 is default and 0.0 is projector off. The table below shows how the available projector brightness in Zivid One+ relates to stops.

Brightness		0.25	0.50	1.00	1.80
Stops		-2	-1	0	+0.85
Lumen	Zivid One+	100	200	400	720
	Zivid Two	90	180	360	650

Note

Zivid Two has a smaller projector area and a higher light density (w/m2) than Zivid One+ cameras.

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 1m.

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 and 50% at brightness 1.8.

• 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.

Version History

SDK	Changes
2.9.0	Thermal throttling is improved to throttle between acquisitions for a predicted time horizon instead of pausing the full capture.
1.2.0	Enable brightness larger than 1.0 for Zivid One Plus.