Basics
Plan line-scan inspection for moving web, roll-to-roll and continuous material by width, speed, encoder timing and line-light stability.
Direct answer
A line scan camera captures one row repeatedly and turns material motion into image length. It is useful only when web speed, encoder timing, exposure and line-light uniformity are controlled together.
Primary topic route: line scan camera
Sources and editorial review
Content updated: September 25, 2026. Calculations and selection guidance; no new physical test is claimed.
Manufacturer documentation explains fixed line rate for predictable motion and encoder triggering when roller-driven material speed varies. Example numbers above are declared assumptions.
Use a line scan route when the target moves continuously, the inspection width is large or area-scan snapshots would miss material between frames.
Line scan projects fail when material speed changes, exposure is too short for the light, or illumination is uneven from edge to center.
The first RFQ should include web width, target defect size, line speed, encoder plan, surface finish and available line-light mounting space.
The camera captures 1 row at a time. As the product moves, rows are assembled into a full 2D image, which is why motion control is part of the imaging system.
Short exposure and fast material speed require enough light intensity along the scan line. Uneven illumination becomes a repeating defect in the final image.
An encoder links image rows to real material movement. Without synchronization, speed variation can stretch or compress features in the inspected image.
How to test before buying
Run the material at target speed and check whether encoder pulses, line rate and light intensity keep defects the same shape from edge to center. A still sample cannot prove web geometry.
Decision checks
Roll-to-roll, web, film, textile, paper, metal strip and continuous conveyors.
Encoder, line rate, exposure and light intensity must match.
Uneven line light creates false surface defects.
Engineering method and assumptions
Illustrative sizing exercise, not a Deyi camera specification or a measured defect-detection result: assume a 200 mm inspection width, a 2,048-pixel line sensor, web speed of 1,000 mm/s and a target of 0.10 mm travel per acquired row. Use the active pixels across the inspected width; leave any edge margin out of this simplified calculation.
| Input or check | Calculation | What still needs verification |
|---|---|---|
| Across-web sampling | 200 mm ÷ 2,048 pixels = 0.0977 mm/pixel | Verify the actual sensor active width, optical field, focus and usable edge coverage. |
| Along-web sampling | 1,000 mm/s ÷ 0.10 mm/row = 10,000 rows/s (10 kHz) | Confirm the selected camera and interface can sustain the required line rate at the actual pixel format. |
| Time between rows | 1 ÷ 10,000 rows/s = 0.0001 s (100 µs) | Exposure, readout and trigger timing must fit the model-specific acquisition limits. |
| If speed rises by 20% | 1,200 mm/s ÷ 0.10 mm/row = 12,000 rows/s | A fixed 10 kHz line rate would stretch the along-web pixel spacing to 0.12 mm/row. Review encoder-triggered acquisition for variable speed. |
| Uncompressed Mono8 image payload | 2,048 pixels/row × 10,000 rows/s × 1 byte/pixel = 20.48 MB/s | Transport overhead, buffering, processing and storage are additional; check the actual output format. |
Across-web sampling and along-web sampling are separate. A nominal 0.10 mm grid does not prove a 0.10 mm defect can be detected; test contrast, blur, defect orientation and false rejects with representative moving material.
At variable speed, use an encoder and verify the trigger-to-row relationship on the real transport. Encoder pitch, mechanical slip and direction handling must be checked; a stationary sample cannot validate geometry.
Send material width, minimum defect size, speed range, surface finish, available line-light geometry, encoder details and sample good/bad images before selecting a camera or illumination route.
Technical basis: GigE Line Scan Use Case Descriptions and Diagrams.
Decision table
| Factor | Practical rule | RFQ impact |
|---|---|---|
| Best fit | Roll-to-roll, web, film, textile, paper, metal strip and continuous conveyors. | Send material width and line speed. |
| Key control | Encoder, line rate, exposure and light intensity must match. | Include encoder availability and speed range. |
| Common risk | Uneven line light creates false surface defects. | Provide surface material and defect samples. |
Application proof
Common mistakes
Factory handoff
The factory route review starts by checking whether the image can be made stable with lighting and fixture control. Then the camera, lens, reader or 3D sensor route is sized against speed, resolution, interface and installation constraints.
If you already have a Keyence, Cognex, Basler, OPT, LMI, Hikrobot or barcode-reader reference, include it as a reference model. Deyi Vision uses it to understand the application class; final selection still depends on real samples and production limits.
Guide to RFQ
Use the guide to frame the question, then send the details so engineering can recommend a route.
Request engineering RFQGuide FAQ
A line scan camera captures one row of pixels repeatedly and uses product motion to build a full 2D image.
Use line scan when the target is continuous, very wide, moving fast or better inspected as a synchronized stream rather than a single frame.
Line rate, material speed, encoder timing, lighting intensity, web width and surface behavior must be reviewed together.
