2D Dot Peen Bar Code on Gear Assembly – Automotive Machine Vision

Description of Application:

The goal of this inspection is the verification of the 2D dot peened data matrix code. The code is located on a ring gear assembly located inside the gear housing.

Setup for Inspection

Illumination: S75-625 [75mm Spot Light 625nm Red – “Brick Light”]
Lens Filter: BP635
(A) Lens Working Distance: 32” from tip of lens to the 2D inspection area of the part
(B) Light Working Distance: 32” from front of the light to the 2D inspection area of the part
(C) Light Angle to 2D Barcode: 20 Degrees


The current inspection requires a Dark Field Lighting approach. The key to creating contrast is low angle lighting. The light will then create bright spots and shadows on the markings highlighting them. The camera needs to be at about a 20 degree angle to the 2D code surface. There is at the maximum only about +/- 2-3 degrees of angle tolerance. The camera needs to be positioned perpendicular to the 2D code surface. The 2D code needs to be positioned near the center of the gear housing opening for repeatable and consistent readings. With the 2D code markings dot peened on a rounded surface, the surface having machined grooves, and the light positioned on a severe angle to the part surface there is no way to grade the 2D code. At this point the 2D code can only be read. As the 2D code marking degrades then vision filters may need to be incorporated to enhance the 2D code cells to help keep the readability robust.

Application Image

NOTE: The difference in dot peened markings indicated by the variance in cell intensities. This is due to marking on a rounded surface and the surface having machined ridges.