During on-site commissioning, this situation is often encountered:

The screen flickers between bright and dark, and even displays horizontal lines.

Many people’s first reaction is:

Is the camera broken?

In fact, the more common reason is:

The light source is “flashing”; it’s just that the human eye doesn’t notice.

Industrial vision is highly sensitive to light source stability; what appears normal to the naked eye does not necessarily translate to stable imaging with a camera.

01｜Why can’t the human eye see it, but a camera can?

Many LED and fluorescent lights do not emit light steadily at all times.

They may flicker continuously in response to the power supply frequency or PWM dimming.

The human eye usually cannot perceive it,

But the camera’s exposure time is very short, so one frame might happen to be captured at a “bright” moment, while the next is taken at a “dark” one.

Thus, the following arises:

Flickering, with fluctuating brightness.

Basler cameras even offer dedicated 50 Hz and 60 Hz Anti-Flicker modes to minimize brightness fluctuations caused by such lighting flicker..

02｜How do striations form?

Especially when using a rolling shutter,

The sensor does not expose the entire image at once; instead, it reads the image line by line.

If the brightness of the light source is also changing rapidly at this moment,

The top few lines might capture some bright light,

However, the next few lines happened to capture low-light conditions.

In the end, it will become:

One is bright, one is dark.

When a flickering light source is combined with progressive-scan exposure, distinct bright-and-dark stripes may appear.

Basler also cautions that PWM lighting, when used with very short exposure times, may cause brightness fluctuations; in cameras equipped with a rolling shutter, it can even result in banding.

03｜Why does the problem become more pronounced as the exposure time gets shorter?

When the exposure time is relatively long,

The camera will “average” the variations in brightness over a period of time.

But if the exposure is only:

500μs, 200 μs, or even shorter

The camera captures only a brief instant of the light source’s variation.

At this point, stroboscopic effects are particularly easy to capture.

So, high-speed projects often encounter:

As the exposure was shortened, the horizontal streaks suddenly appeared.

04｜How to solve it?

Start by checking these few places:

First, try turning off the workshop’s general lighting.

If the horizontal stripes disappear immediately, it’s very likely due to ambient light interference.

Second, use stable industrial vision lighting whenever possible.

Industrial vision demands stable, repeatable brightness—not merely “bright enough to the eye.” Teledyne also stresses that lighting for vision systems must be stable and controllable, preventing variations in the light source from being misinterpreted by the system as product‑related changes.

Third, check whether the light source uses PWM dimming.

In particular, short-exposure projects are even more worth checking.

Fourth, high-speed projects could be considered.Strobe light source.

Synchronize the light source and camera triggers:

Product in place → Light source flashes → Camera takes a photo.

High-speed vision systems typically synchronize the camera with a strobe light source, ensuring that each exposure delivers consistent and adequate illumination.

A very practical troubleshooting method

If transverse striations suddenly appear on the scene,

Don’t tweak a bunch of camera settings just yet.

Let’s do a test directly:

Turn off the surrounding lights, leaving only the industrial light source on.

If the screen returns to normal immediately,

The problem has basically been identified.

Finally, remember this one sentence.

Horizontal lines on the screen don’t necessarily mean the camera is broken.

Often it is:

Exposure time + Light source flicker + Shutter mode

They just bumped into each other.

What industrial vision truly needs is more than just “brightness.”

Rather:

Stably lit.