Global Shutter vs. Rolling Shutter

Global shutter and rolling shutter sensors differ primarily in how they capture and read out image data. When comparing the two technologies, the key distinction lies in the sensor's exposure method.

A global shutter sensor exposes all pixels simultaneously, which helps reduce motion-related image distortion in applications involving fast-moving objects or rapid camera movement. A rolling shutter sensor exposes and reads out the image sequentially, typically row by row. This approach is common in many CMOS sensors and can offer advantages in areas such as cost, resolution, and low-light performance, depending on the sensor design.

Selecting between global shutter and rolling shutter technology depends on factors such as object speed, lighting conditions, image quality requirements, and system cost constraints.

The Core Tradeoff

In CMOS image sensor design, pixel architecture influences how efficiently a sensor can capture light and how it behaves under motion. One of the key differences between global shutter and rolling shutter sensors is the amount of circuitry integrated within each pixel.

Global shutter sensors typically incorporate additional pixel-level storage elements that allow all pixels to begin and end exposure simultaneously. This additional circuitry occupies space that might otherwise be available for the photodiode, potentially reducing the effective light-sensitive area of each pixel.

Rolling shutter sensors generally require less in-pixel circuitry because image data is exposed and read out sequentially. Depending on the sensor design, this can allow a larger proportion of the pixel area to be dedicated to light collection.

As a result, global shutter and rolling shutter sensors often exhibit different performance characteristics. Global shutter sensors are commonly preferred in applications involving fast motion or where geometric accuracy is important. Rolling shutter sensors may offer advantages in areas such as sensitivity, noise performance, resolution, or cost, depending on the specific sensor architecture and application requirements.

Global Shutter vs. Rolling Shutter: Application Considerations

Rather than automatically specifying the more expensive global architecture, system integrators evaluate the specific mechanical and environmental constraints of the inspection task.

How Strobe Lighting Can Reduce Motion Artifacts?

A common assumption is that applications involving moving objects always require a global shutter sensor. In some machine vision systems, however, motion-related image distortion can also be mitigated through careful control of illumination and image acquisition timing.

In controlled inspection environments, high-intensity strobe lighting can be synchronized with camera exposure to significantly reduce the effects of motion. By operating the system in a darkened enclosure and using a short-duration light pulse, the effective exposure time can be reduced to only a few microseconds, helping to minimize motion blur.

In certain applications, this approach allows rolling shutter sensors to be used successfully even when objects are moving. However, achieving reliable results typically requires precise triggering, carefully controlled lighting conditions, and validation for the specific inspection task.

Cost and Resolution Scaling

Sensor architecture can also influence system cost and available resolution options. Rolling shutter sensors are often available in a broader range of high-resolution formats and may offer cost advantages depending on the sensor family and application requirements.

For applications where motion-related distortion is not a primary concern, rolling shutter sensors are commonly used in high-resolution inspection systems. In these cases, the choice may be driven by factors such as sensor availability, image quality requirements, interface bandwidth, system cost, and overall application constraints.

For example, stationary inspection applications such as PCB inspection, document imaging, or other high-resolution measurement tasks often use rolling shutter sensors because the advantages of global shutter operation may provide limited benefit in the absence of significant motion.