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Telecentric Lens Application in AOI
Application
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Telecentric Lens Application in AOI

Explore the Micro World
What is AOI?

AOI, abbreviation for Automated Optical Inspection, refers to a system that uses cameras, industry lens and computer vision to automatically inspect products for defects, such as missing components or incorrect solder joints.

AOI Process
The 4 Steps of AOI Process

In AOI process, optical parts performs like human eyes, while image processing and analysis acts like human brain.

  • 01. Image Capture (Optical Scanning & Data Collection)
  • 02. Data Processing (Classification & Conversion)
  • 03. Image Analysis (Comparison against "golden standard")
  • 04. Defect Identification & Action
Lenses Used in AOI

Automated Optical Inspection (AOI) uses different types of lenses depending on the application:

  • Standard telecentric lenses: For high precision measurement and distortion-free views.
  • Macro lenses: For capturing details of small components.
  • Zoom lenses: Adjustable magnification for different object sizes.
Telecentric Lens
Working Principle
Working Principle

The photodiode receives the light reflected by the object, converting light energy into electric charges. These charges form a voltage analog signal which varies with light intensity. This is sequentially output and converted into digital gray-scale values (0-255), reflecting the intensity of the reflected light to identify different objects.

Optical Structure

The system is mainly composed of optical principles and image processing technology. The light source structure is often a ring-shaped optical RGB (red, green, blue) structure.

As shown in the figure, the optical LEDs from top to bottom are red, green, and blue LEDs.

RGB Structure
When is a Telecentric Lens a MUST?
① Inspected objects with large thickness requires inspection of several angles.
② Inspected objects form an angle with the lens.
③ Objects move up and down during inspection (WD changes).
④ Inspected objects have holes or uneven surfaces.
⑤ Low distortion and consistency of image brightness is required.
⑥ Defects can be only inspected under telecentric illumination.
⑦ Ultra high precision measurement (e.g., tolerance 1um).
Application in PCB Soldering

In the PCB soldering field, high accuracy, consistent scale, and clear images of object edges are critical due to the high density required. Ordinary lenses struggle here, making Telecentric lenses an essential tool.

Common defects tracked: insufficient solder, excessive solder, poor overlap, broken solder bridge connections, deviations, short circuits, etc.

Canrill Performance
Excellent Performance

The image performance of Canrill telecentric lenses in AOI (especially PCB field) has consistently been stable:

Resolution:
Achieve micron-level pixel details up to 4μm.
Distortion:
Controlled within 0.04%. Perfect for extensive image stitching.
Eliminating Parallax Errors

Canrill telecentric lenses applied in AOI eliminate parallax errors, providing accurate measurements and imaging even when the object is at varying depths.

✓ Reduces repair costs.
✓ Avoids disposal of repairable circuit boards.

No Parallax Error

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