Case study · Mahle Engine Systems

A Machine Vision Lens That Keeps a Whole Bore in Focus

Mahle Engine Systems needed to inspect the inside face of bearing bushes on a production line. We designed and built a lens system, using the Scheimpflug principle, that holds focus along bushes up to 80mm long without the camera ever moving. Designed, made and assembled in Rye in 10 weeks.

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Complete bearing bush inspection lens designed and made by Kingsview Optical
80mmBush length, up to
2:1Bush aspect ratio
F/5Lens system
600–650nmWorking wavelength
~150mmWorking distance
0 movesCamera fixed for all bush sizes
2 finishesDiffuse and polished surfaces
10 weeksConcept to delivery
The challenge

Inspecting Down the Inside of a Bore, in Focus From Top to Bottom

Mahle needed to inspect the internal face of bearing bushes for defects as they passed along an assembly line. They came to us with the problem rather than a design, and asked us to take on the complete package.

Looking down into a bore, the wall runs away from the camera, so a conventional lens can only hold part of it in focus at once. The system also had to:

  • Work on bushes up to 80mm long with a 2:1 aspect ratio
  • Inspect different bush sizes without moving the camera
  • Handle both diffuse and polished surfaces
  • Work at 600–650nm from about 150mm above the conveyor
Image of the inside of a bearing bush taken with the Kingsview inspection lens system
An image of the inside of a bush, taken with the finished system
Our approach

Using the Scheimpflug Principle to Tilt the Plane of Focus

A normal camera focuses on a flat plane square to the lens. The surface we needed to see, the inside wall of the bush, runs at an angle to that plane, so most of it would always be out of focus.

The Scheimpflug principle solves this. When the camera's sensor is tilted relative to the lens, the plane of sharp focus tilts too. Set correctly, the sensor plane, the lens plane and the plane of focus all meet at one line, and the plane of focus can be laid along the bore wall, so the whole length is in focus in a single image.

We designed the F/5 lens system around that tilted geometry, with enough depth to cover different bush sizes from one fixed camera position.

Optical ray trace of the Scheimpflug bush inspection lens, showing focus along the bore wall
Ray trace of the bush inspection lens, with the plane of focus laid along the bore wall
Machine vision lens system for bearing bush bore inspection
Machine vision lens system for bore inspection

One Supplier for the Complete Package

Mahle came to us with a problem, not a drawing, so we took responsibility for the whole system: the optical design, the lenses, the multilayer coatings, the metalwork and the final assembly.

Our design engineers work beside the people who make the parts, so every choice was checked against what our lens line, coating chambers and machine shop can actually produce. Mahle dealt with one company from first discussion to a working system on their line.

One supplier, one site

Made in Rye, Start to Finish

Every stage of the system was carried out at our site in Rye, East Sussex, with no hand-offs between a design house, a lens maker and an assembler.

CNC lens polishing lines at Kingsview Optical
CNC lens lines
Optics loaded into vacuum coating chamber tooling
Multilayer coating
Optical assembly at Kingsview Optical
Optical assembly
  • Optical designScheimpflug layout and tolerance analysis in Zemax.
  • Lenses and coatingsLenses made on our CNC line, with multilayer coatings applied in house.
  • MetalworkLens housings and mounts machined on site.
  • AssemblyAssembled and aligned in house before testing.
Performance

How Focus Along the Bore Was Proven

Resolution test showing focus held along the length of an internal bore
Resolution test along the length of the bore

  1. Predicted in Design

    A Monte Carlo tolerance analysis simulated many systems built with random errors within our tolerances, confirming the design would hold its performance once made.

  2. Resolution Tested in Rye

    Resolution testing confirmed that focus was held along the full length of the bush, not just at one depth.

  3. Proven on Real Bushes

    The system was tested on a range of bushes, with diffuse and polished surfaces, and performed well across them.

  4. Accepted on the Production Line

    Mahle carried out final acceptance on their own production line.

The result

A bore inspection system that holds focus along bushes up to 80mm long, works from one fixed camera position, and was delivered in 10 weeks and accepted on Mahle's production line.

Need to Inspect a Surface Your Camera Can't Keep in Focus?

Tell us what you need to see and where your camera has to sit. An engineer who works beside our production line will tell you what is possible before you commit.

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