Introduction
Ever taken a photo of a spinning fan or a speeding car and noticed the image looks distorted-vertical lines leaning, objects stretched? That's rolling shutter effect. It's common in most consumer cameras and many camera modules. But what causes it, and when does it matter? For applications like industrial inspection, medical imaging, and machine vision, understanding rolling shutter-and its alternative, global shutter-is essential. At Sincere, we've been manufacturing camera modules for over 30 years, helping clients choose the right sensor technology. This article explains rolling shutter, how it works, and when it matters.
What Is Rolling Shutter?
Rolling shutter is a method of image capture used by most cmos module camera sensors. Instead of capturing the entire image at once, the sensor reads the image line by line-typically top to bottom. Each row of pixels is exposed and read out sequentially. Different parts of the image are captured at slightly different times.
If the scene or camera moves during readout, distortion occurs:
- Skew: Vertical lines tilt
- Wobble: Objects bend or warp
- Partial exposure: Flashing lights appear only partially
Rolling shutter is standard for most sensors because it's cost-effective and allows smaller pixels.
How Rolling Shutter Works
Imagine a sensor as a grid of pixels. When you press the shutter:
- Reset: First row cleared
- Exposure: Light accumulates for set time
- Readout: Row's charge converted to digital
- Repeat: Process moves to next row
This takes time. For a 1080p sensor at 30fps, total readout might be about 30ms. If something moves during that time, different rows capture it in different positions.
Rolling vs. Global Shutter
| Feature | Rolling Shutter | Global Shutter |
|---|---|---|
| Capture method | Sequential rows | Entire frame at once |
| Motion distortion | Present | None |
| Cost | Lower | Higher |
| Complexity | Simpler | More complex |
| Sensitivity | Generally better | Slightly lower |
| Best for | General imaging | Fast motion, inspection |
Global shutter captures all pixels simultaneously, eliminating distortion, but costs more and may have slightly lower sensitivity.
When Rolling Shutter Matters
High-Speed Applications
Inspecting fast-moving objects on a production line? Rolling shutter can cause distortion. A 4k mipi camera module with rolling shutter might show parts as skewed.
Vibration or Movement
If the camera moves-on a drone, robot, or handheld scope-rolling shutter creates wobble. For stable applications, it's fine.
Flashing Lights
LED lights that pulse can appear as bands. Common in security and inspection.
Automotive
Cameras must capture moving objects accurately. Many automotive applications use global shutter or fast rolling shutter.
Where Rolling Shutter Is Acceptable
Medical Endoscopy
Movement is slow and controlled. A medical endoscope camera module with rolling shutter works well.
Industrial Inspection (Static)
If objects are stationary and camera stable, rolling shutter works perfectly. A camera usb module is common for quality control.
Consumer USB Cameras
Webcams and video conferencing use rolling shutter. A camera usb module for consumer use rarely needs global shutter.
Surveillance
Fixed cameras monitoring slow scenes are fine with rolling shutter.
Key Specifications
Readout Speed
Faster readout reduces distortion. High-end rolling shutter sensors have readout under 10ms.
Frame Rate
Higher frame rates mean faster readout. A 4k usb camera module at 60fps has less rolling shutter effect than at 30fps.
Interface
The interface affects data transfer speed. Mipi camera modules (MIPI CSI-2) are designed for high-speed transfer. A csi 2 camera module with fast readout minimizes effects.
Choosing Shutter Type
| Application | Recommended |
|---|---|
| Slow or stationary objects | Rolling shutter |
| Fast-moving objects | Global shutter |
| Handheld / moving camera | Global shutter |
| Flashing lights | Global shutter |
| Medical endoscopy | Rolling shutter acceptable |
| Industrial automation | Global shutter for motion |
| Drones / UAVs | Global shutter |
Sincere's Camera Modules
At Sincere, we offer both rolling and global shutter modules:
- Camera usb module: Rolling for general inspection; global available
- Mipi camera modules: High-speed for embedded systems
- 4k usb camera module: Ultra-HD with rolling; for stationary inspection
- 4k mipi camera module: High-res, high-speed for embedded vision
- Csi 2 camera module: Standard for Raspberry Pi, Jetson
- Cmos module camera: Available in both shutter types
Our manufacturing includes Class 10/100 dust-free facilities and Active Alignment (AA) for perfect focus.
Minimizing Rolling Shutter Effects
- Increase frame rate: Faster readout
- Reduce exposure time: Less time for movement
- Stabilize camera: Reduce camera movement
- Use consistent lighting: Avoid pulsed LEDs
- Post-processing: Software correction available
The Future
As cmos module camera technology advances:
- Faster rolling shutters: Readout times decreasing
- Stacked sensors: Fast readout with high sensitivity
- Global shutter costs: Decreasing, making it more accessible
Summary
Rolling shutter captures images row by row, which can cause distortion in fast-moving scenes. It's cost-effective and works well for:
- Stationary objects
- Slow movement
- Medical endoscopy
- Surveillance
For fast motion, global shutter is preferred.
Key points:
- Rolling shutter: Sequential readout; motion distortion possible
- Global shutter: Simultaneous capture; no distortion
- Interfaces: Camera usb module, mipi camera modules, csi 2 camera module
- Resolutions: HD to 4k usb camera module and 4k mipi camera module
At Sincere, we manufacture cmos module camera solutions in both shutter types. Whether you need a csi 2 camera module for an embedded project or a 4k mipi camera module for high-speed inspection, we can help you choose the right shutter. Contact us to discuss your requirements.
