Industrial Camera Selection: Area Scan or Line Scan, and How Resolution Is Calculated
Industrial camera selection guide: it explains the applicable scenarios of area scan and line scan cameras, how to calculate resolution, the logic for choosing shutter and exposure, and how camera selection constrains and is constrained by illumination, lens and cycle time.
Clarify One Thing First
The order for choosing a camera is: first calculate how many pixels are needed, then decide on the form factor
For industrial camera selection, first convert the "smallest defect size" and the "inspection area" into the required pixel count, then decide between area scan and line scan: use an area-scan camera for intermittent feeding and single-sheet fixed-trigger imaging; use a line-scan camera for continuous material travel and wide areas. The camera is only one link in the imaging chain and must be considered together with the lens, light source, and cycle time.
There are two common wrong approaches to camera selection. One is "picking a camera with good specifications first," only to find that the pixel equivalent is excessive and the cost wasted, or conversely that it is not enough. The other is looking only at resolution and ignoring whether the shutter, frame rate and interface match the site.
The correct path is Work Backward from Requirements: First define the minimum defect size and the inspection area → calculate the required pixel equivalent → calculate the required total pixel count → then decide whether to use an area-scan or a line-scan camera and how many cameras are needed.
Only after that do you look at engineering details such as shutter type, interfaces and dimensions. Get the order right and the solution will not go off track.
selection Factors
Area-Scan Camera
A single capture produces a complete two-dimensional image. It suits intermittent feeding, single-sheet triggered capture and scenarios requiring multi-angle imaging. The structure is simple, making it the first choice for most station-based inspection.
Line-Scan Camera
It scans line by line and builds an image together with the continuous motion of the material. It suits roll materials, continuous material running and wide-format scenarios. The motion speed and the scan line rate must match strictly.
Monochrome and Color
Monochrome offers a better sensitivity-to-resolution cost ratio and suits shape and gray-level defects; color is used for color difference and color classification judgements.
Global Shutter vs. Rolling Shutter
Moving objects must use a global shutter, otherwise distortion occurs. A rolling shutter can be used for stationary workpieces.
Interface and Bandwidth
High resolution combined with a high frame rate produces large amounts of data, and insufficient interface bandwidth becomes a bottleneck. This must be considered together with the frame grabber and host configuration.
Field of View and Pixel Sampling
Do Not Mistake Pixel Scale for Inspection Accuracy
Required horizontal pixel count = field of view width ÷ required pixel equivalent. For example, with a field of view of 200 mm and a desired pixel equivalent of 0.05 mm, about 4000 pixels are needed, which means a 5 MP camera (about 2448×2048) is not wide enough horizontally, and a higher resolution or zone-by-zone imaging is required.
For line scan cameras, the line rate must also be calculated: line rate ≥ material speed ÷ pixel equivalent. For example, at a speed of 300 mm/s and a pixel equivalent of 0.05 mm, a line rate of about 6000 lines/s is required.
| specifications | Calculation Method | Notes |
|---|---|---|
| Horizontal pixels required | Field of view width ÷ target pixel equivalent | Then multiply by a safety factor (typically 1.2-2x) |
| Vertical pixels required | Field of view height ÷ target pixel equivalent | Area-scan cameras are limited by aspect ratio and may not satisfy both at the same time |
| Line-Scan Rate | Material feed speed ÷ target pixel equivalent | Must be strictly synchronized with motion speed |
| Data per Image | Horizontal pixels × vertical pixels × bit depth ÷ 8 | Affects interface bandwidth and processing time |
Light Source and illumination
Lens Working Distance and Field of View
Working distance, lens focal length, and field of view constrain one another. Site installation space usually limits the working distance first, and the lens focal length is then back-calculated.
Distortion and Telecentric Lenses
Standard lenses have distortion, which causes systematic deviation in edge measurement. Precision dimensional measurement usually requires low-distortion or telecentric lenses.
Depth of Field
Insufficient depth of field causes out-of-focus areas where the material undulates. This matters especially for flexible materials — the depth of field must cover the thickness variation and the posture variation of the material.
Coordination with the Light Source
The lens aperture affects both light throughput and depth of field: a smaller aperture gives a greater depth of field but less light throughput. Insufficient light throughput requires a stronger light source. This is a coupled relationship.
algorithm Selection
The inherent limitations of the camera and lens (distortion, depth of field, noise) can be partly compensated for in the algorithm layer but cannot be eliminated entirely. Solution design should follow the principle of "solving the problem at the imaging stage" rather than relying on the algorithm to cover for it.
Distortion Correction
Use a calibration target for distortion calibration and pixel equivalent calibration.
- Calibration results directly affect measurement accuracy
- Requires periodic re-inspection
Sub-pixel Edge
Sub-pixel interpolation on the gray-scale gradient improves positioning accuracy.
- Can be significantly better than pixel resolution
- Depends on good contrast
Image Stitching
Multiple cameras or multiple fields of view are stitched into a complete area.
- Must handle deformation in overlapping regions
- Stitching accuracy affects overall measurement
Multi-Frame Averaging
In static scenarios, multi-frame averaging reduces noise.
- Trading time for signal-to-noise ratio
- Not suitable for high-speed motion scenarios
Communication and interlocking
The camera interface (GigE / USB3 / Camera Link / CoaXPress) determines how fast data can be transferred to the host and also determines cable length and the feasibility of on-site wiring. This must be confirmed during the selection stage to avoid discovering later that bandwidth is insufficient or cables are too long.
- 01 Determine the minimum defect size and area
- 02 Calculate the required pixels and pixel equivalent
- 03 Choose area-scan or line-scan
- 04 Matching lens (focal length / working distance / distortion)
- 05 Determine the illumination method
- 06 Calculate data bandwidth and interfaces
- 07 Verify cycle time feasibility
- 08 Validate by measurement with samples
Common Question
Should my application use area-scan or line-scan?
Is higher resolution always better?
How do you choose between monochrome and color?
Why does a moving workpiece deform?
Is Choosing the Right Camera Enough?
What Information Do You Need to Provide?
Submit sample testing
The final camera selection conclusion is best confirmed by measurement. Please provide inspection samples and your minimum defect size requirement; we will carry out imaging validation and give configuration recommendations.
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Need to assess imaging conditions, defect criteria and cycle time item by item? Go to the Full Requirement Assessment →
The Most Effective Step in Selection: Test Your Own Sample
For the same workpiece, the inspection result differs greatly with different lenses, light sources, mounting distances and algorithm combinations. Sending us samples for measurement is more reliable than extrapolating from a specification table.