Concepts and principles behind camera parameters

“Exposure Time”

In photography, shutter speed or exposure time is the duration that the film or digital sensor inside the camera is exposed to light, i.e., when the camera’s shutter is open. Mech-Eye Industrial 3D Cameras utilize this time to capture multiple stripe images for calculating depth information. The 3D “Exposure Time” of these cameras can range from 0 ms to 100 ms.

Projector’s “Light Brightness”

Adjust “Light Brightness” to control the projector’s output power and thereby regulate its emitted light. Mech-Eye Viewer offers three brightness levels of the projector: High, Normal, and Low, each corresponding to different projector power settings. Set this parameter to maximize the signal received by the camera. As long as the reflected light from the projector does not make pixels over-saturated, the impact of noise will be minimized and the camera’s signal-to-noise ratio (SNR) will be increased subsequently.

Based on the SNR, selecting an appropriate “Light Brightness” helps to increase the SNR and ensures the quality of the point cloud.

“Gain”

“Gain” refers to the pre-amplification of the readout circuit in the pixels of an image sensor. In photography, it is commonly referred to as the ISO value. A large “Gain” value will amplify the pre-amplification of the sensor, thereby increasing its sensitivity to light and resulting in brighter images.

Applications

If there is a need to reduce the time in projection, the “Gain” is advantageous for expanding the dynamic range within the scene when using HDR capture. (Each pixel in the image counts the photons received during the readout stage or exposure process and outputs an intensity score. The dynamic range is defined as the ratio between the minimum and maximum measurable light intensities from black to white.) The “Gain” is also applicable for capturing point clouds in very dark areas.
However, larger “Gain” values have a significant drawback as they amplify everything captured by the sensor, including noise. This, in turn, impacts the dynamic range of a single capture and reduces the peak SNR. Therefore, to obtain the best low-noise 3D point cloud, it is recommended to maintain lower “Gain” values. And if a longer image capturing period is acceptable, the “Gain” option can be left unactivated.

Influences

Increasing the “Gain” value will increase the noise. When obtaining two images of the same greyscale value by only increasing the “Exposure Time” and only raising the “Gain”, the latter will lead to lower accuracy and increased noise.
When comparing multiple HDR exposures with a high “Gain” value to a single high exposure, the former effectively averages the noise caused by “Gain”, thereby reducing overall noise and potentially achieving the same level of accuracy as a single high exposure.
The image below illustrates the impact of “Gain” on the overall SNR: