Global VS Rolling Shutters

In machine vision applications the sensor is central to the camera performance and the image outcome. The primary two sensors in industrial grade cameras are CCD and CMOS, with CMOS becoming the dominant sensor of the two, and the most widely used in machine and industrial vision cameras. These sensors use electronic shutters to control exposure and complete pixel readout. Thus, the way in which the shutter functions, influences the resulting images. Of shutter options there are just two- global shutter and rolling shutter.

The global shutter is the newest of the two and has become the favored option for most industrial vision camera manufactures. When a sensor uses global shutter, it scans the entire image (completes pixel readout) simultaneously, in effect, it stops the action through simultaneous exposure and produces a non-distorted image, regardless of the speed of the object. Because of this unique ability it is ideal for fast motion applications such as:

Traffic Management
Metrology
Robotics Inspection
Bar code Scanners
Drone Collision Detection

So why hasn’t global shutter forced the obsoletion of rolling shutter? While global shutter is great in fast moving applications, it creates higher read-out noise levels and generates more heat. In applications where these attributes are problematic, and movement is not an issue, a rolling shutter may be the better option.

Rolling shutter scans an image in sequence from one side of the sensor to the other, line by line (not simultaneously as its global shutter counterpart). Because of this sequential exposure, there is a minor delay in the exposure time of the top and bottom of the sensor. This limits the speed of the sensor and produces distorted images on fast moving objects such as vehicles or plane propellers in motion. However, the rolling shutter sensor has useful attributes when motion and speed are not relevant to the user’s application. The rolling shutter has a wider dynamic range and generates less heat in addition to having lower noise levels. The internal camera components are less complex than a global shutter camera so it is typically less expensive. Some of the common rolling shutter applications are:

DSLR Cameras
Wearable Devices
Security Cameras
High Resolution applications without high speed objects
Where Ultra-High Resolution is needed

Below are two videos from Sony showing how the images differ from a rolling versus global shutter.

For more in depth support, please reach out to a Lore Tech representative to discuss your application. Let us help you find the right machine vision camera.