Wondering what you should know to choose between a rolling shutter and a global shutter for your camera-based application? It's essential to understand these two types of sensors, including their advantages and disadvantages, to make an informed decision.
Modern embedded vision systems utilize sensors that capture and record images for various processing and analysis purposes. These sensors employ an electronic shutter, which controls the exposure of photon wells on the sensor and determines whether pixels are exposed line by line or as a complete matrix.
Let’s explore the differences between global and rolling shutters, their pros and cons, and how to determine which one best suits your needs.
In global shutter mode, every pixel on an image sensor begins and ends its exposure simultaneously within the programmed duration for each image acquisition cycle. Once the exposure period is complete, the pixel data is read out systematically, row by row, until all pixel data has been extracted.
This mechanism is a fundamental characteristic of global shutter cameras, ensuring the capture of non-distorted images free from wobble or skewing artifacts. This is why global shutter sensors are commonly used in embedded vision applications that require precise imaging of high-speed moving objects.
Global shutter is capable of avoiding rolling shutter artifacts alone, not motion blur caused by fast-moving objects and exposure. Only at lower exposure levels does global shutter help capture sharp images of moving objects without any motion blur.
Rolling shutter mode in a camera exposes pixel rows sequentially, creating a temporal offset between each row, unlike the simultaneous exposure of global shutter cameras. The first row of pixels begins capturing light, completing its exposure cycle before the next row starts.
This method results in a temporal delay between the start and end times of light collection for each subsequent row. However, the duration of light collection remains consistent across all pixel rows, ensuring uniform exposure times despite the staggered readout. This temporal offset can affect image quality, often leading to artifacts such as skew or wobble during the capture of high-speed motion or when the camera moves rapidly.
The distinction in imaging between rolling shutter sensors and global shutter sensors is most apparent during dynamic image acquisition. The rolling shutter effect occurs when a rolling shutter sensor captures fast-moving objects.
In a rolling shutter, not all pixels in the image sensor are exposed simultaneously; instead, each row of sensor pixels is scanned sequentially. If an object moves faster than the exposure and readout times of the sensor, the resulting image can become distorted due to this staggered exposure. This distortion is referred to as the rolling shutter effect.
PROS | CONS |
1. Capturing fast-moving objects: As earlier mentioned, the global shutter exposes all pixels simultaneously, enabling it to capture high-speed motion without motion artifacts like skew or wobble. 2. Minimal image distortion: The simultaneous pixel exposure reduces motion-related image distortions, enabling accurate imaging of objects in rapid movement. 3. Effective multi-camera synchronization: Global shutter cameras ensure uniform synchronization across multiple cameras, which is crucial for industrial inspection, 3D scanning, etc. | 1. Higher ambient noise: Global shutter sensors can have higher ambient noise compared to rolling shutter sensors due to their architecture and simultaneous exposure. 2. High sensor cost: The manufacturing complexity of global shutter sensors results in higher production costs, making them more expensive compared to rolling shutter sensors. 3. Lower light sensitivity: The additional circuitry required for simultaneous pixel exposure often reduces the fill factor, leading to a decrease in light sensitivity. |
PROS | CONS |
1. Lower ambient noise: Rolling shutter sensors have a simpler architecture, leading to reduced electronic noise. 2. Lower sensor cost: The simpler design makes rolling shutter sensors easier and less expensive to manufacture, resulting in lower production costs. 3. Higher light sensitivity: Rolling shutter sensors generally have a higher fill factor, which means they capture more light and offer better low-light performance. | 1. Image distortion: Since rows are exposed sequentially, rolling shutter sensors are prone to artifacts like skew, wobble, etc., when capturing fast-moving objects. 2. Potential for flicker: Rolling shutters can struggle with flicker artifacts when shooting under artificial light sources. 3. Limited synchronization capabilities: Rolling shutter sensors are less suited to precise synchronization across multiple cameras. |
A global shutter camera is specifically designed for capturing high-speed moving objects without artifacts or motion blur. These cameras are utilized in various applications, including ball tracking, industrial automation, warehouse robots, drones, and live cell imaging.
On the other hand, rolling shutter sensors provide excellent sensitivity for imaging and are suitable for cost-effective applications. They are predominantly used for capturing slow-moving objects, such as agricultural tractors, slow-speed conveyors, and standalone applications like kiosks and barcode scanners.
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