Inline battery foil inspection using strobedPhotometric Stereo

Battery technology is a key component in current
electric vehicle applications and an important building block
for upcoming smart grid technologies. The performance of
batteries depends largely on quality control in their production
process. Defects introduced in the production of electrodes
can lead to degraded performance and, more importantly,
to short circuits that can cause accidents. In this contribution,
we propose an inspection system that can detect
defects, like missing coating, agglomerates, and pinholes on
coated electrodes and acquire valuable production quality
control metrics, like surface roughness. By employing Photometric
Stereo (PS), a shape from shading algorithm, our system
sidesteps difficulties that arise while optically inspecting
the black to dark gray battery coating materials. We present
in detail the acquisition concept of the proposed system, and
analyze its acquisition-, as well as, its surface reconstruction
performance. Further, we demonstrate the acquisition results
of several common defect types that arise in foil production.
Our system acquires at a production speed of 500 mm/s at a
resolution of 50 μm per pixel resolution.