You are inspecting a moving cavity of shiny metal, hundreds a minute, for a fleck you must not miss. Beverage-can inner-wall inspection is defined by three physical facts — it is a recessed cavity, the surface is specular, and the line is fast — and every one of them fights the camera before the model is even considered.
DomainIndustrial AI, high-speed inspection
PlatformsFaststream Vision
ScopeOptical access to reject
Binding constraintInspect a specular cavity moving faster than the eye
DisclosureRepresentative programme; customer not named
CONTEXT
Where this started.
Inspecting the inside of a beverage can for contamination, coating gaps or foreign matter is deceptively hard. The target is a recessed cavity, the aluminium is specular so it throws glare instead of showing detail, and the line runs at hundreds of cans a minute, so each can offers a few milliseconds of view.
Get the optics and lighting wrong and there is nothing for a model to work with: glare hides a defect, a shadow invents one, and motion blur consumes the resolution. The imaging problem is the inspection problem; the model is downstream of it.
So the system is engineered from the light inward: illumination geometry that reads a curved specular cavity without glare, capture fast enough to freeze the can, and inference sized to answer within the few milliseconds the line allows before the reject.
CHALLENGES
4 problems, named.
Stated before any of them had an answer.
01
It is a cavity, not a surface
The defect is on the inner wall of a recess; getting light in and an image out without glare or shadow is a genuine optical design task.
02
Specular metal throws glare
Polished aluminium reflects the source rather than revealing the surface; the wrong geometry produces a bright image with no usable information.
03
The line is unforgiving
Hundreds of cans a minute means a few milliseconds per can for capture, inference and decision — the whole loop has to fit that window.
04
Motion blur eats resolution
If exposure and strobe are not short enough, the resolution the optics bought is lost to blur, and small defects vanish.
ARCHITECTURE
How it was built.
A camera pointed at a shiny cavity sees glare. The engineering is the lighting that turns a specular recess into an image a model can read — inside a few milliseconds.
CONTRIBUTION
What Faststream did.
The scope of the work, rather than a capability list.
Cavity illumination design — lighting geometry that reads the curved specular inner wall evenly, without glare or shadow.
Optical access and depth of field — getting a focused image across the recess despite the geometry.
Strobe and exposure — freezing the can so motion blur does not consume the resolution.
Registration — locating the cavity per can so the model looks where the defect can be.
In-window inference — a model sized to answer inside the few milliseconds the line speed allows.
Reject and traceability — firing against the tracked can and logging every verdict.
WHAT WAS HARD
The parts that consumed the schedule.
Rarely the subsystem that sounds difficult.
01
Lighting a specular recess
This is the crux; a curved, shiny cavity is one of the harder machine-vision imaging problems, and no model recovers a badly lit image.
02
Fitting the cycle
Capture, transfer, inference and decision all have to fit inside a few milliseconds, which constrains camera, resolution and model simultaneously.
03
Freezing motion
At line speed even a short exposure can blur; strobe timing and exposure are budgeted against the resolution the defect needs.
04
Rejecting the right can
A verdict is useless unless it reaches the can it belongs to; part tracking on a fast line survives stops and restarts.
OUTCOME
What resulted.
The cavity, imaged
A clean, glare-free image of the inner wall that a model can actually work from.
At full line speed
Capture-to-reject inside the cycle the line runs at, not a slowed-down demo.
Defects caught, motion frozen
Small contamination visible because the resolution survived exposure and strobe design.
Traceable rejects
Every rejected can logged and accounted for, fired against the right can.
Confidentiality
Customer projects are presented at property, capability, outcome and integration level. Customer names, internal architecture, confidential deliverables and commercial terms are not disclosed. Where a detail would identify a customer it is omitted rather than approximated. More is available under a non-disclosure agreement, within the limits the customer has agreed.
Three physical facts make it hard: the target is a recessed cavity, so light and imaging have to reach a curved inner wall; the aluminium is specular, so it reflects the light source as glare instead of showing surface detail; and the line runs at hundreds of cans a minute, leaving milliseconds per can. Each of these fights the camera, and the imaging has to be solved before a model can help at all.
02
Isn't this a job for a better AI model?
No amount of model quality recovers an image that has no information in it. If glare hides the defect or motion blur erases it, the model has nothing to learn from. The accuracy is won in the lighting, optics and exposure that turn a specular cavity into a readable image; the model is downstream of that and only as good as its input.
03
How does it keep up with the line?
By budgeting the cycle first. The few milliseconds each can allows constrain the camera resolution, the strobe and exposure, and the model size together, and inference runs on edge hardware beside the machine so there is no cloud round-trip. Part tracking ensures the verdict reaches the correct can at the reject point even through line stops.