90° Telecentric Lens + 90° Telecentric Light for AOI
A practical guide to compact telecentric imaging for space-constrained automated optical inspection, combining a 90° turning telecentric lens with controlled telecentric illumination.
Why Use a 90° Telecentric Lens for AOI?
A 90° turning telecentric lens uses a folded optical path to allow the camera to be positioned away from the conventional viewing axis while maintaining a telecentric imaging configuration. When combined with appropriately designed telecentric illumination, it can help integrate precision AOI imaging into machines with limited vertical clearance or restricted optical access.
Automated Optical Inspection (AOI) systems are becoming more compact while inspection requirements continue to increase. In many applications, optical performance is only part of the challenge. The physical space available for the camera, lens, and lighting can be equally important.
A conventional telecentric imaging system normally places the camera and lens directly above the inspection object. This configuration works well when sufficient vertical clearance is available. However, production equipment may contain robots, pick-and-place mechanisms, conveyors, fixtures, actuators, or other structures that make a straight optical path difficult to integrate.
A 90° turning telecentric lens provides an alternative by folding the optical path. When combined with a suitable 90° telecentric light, the system can be designed around both optical performance and mechanical constraints.
In This Guide
- What Is a 90° Telecentric Lens?
- Why Does AOI Need a 90° Optical Configuration?
- Why Not Simply Use a Mirror?
- Why Combine a 90° Telecentric Lens with 90° Telecentric Light?
- How Telecentric Illumination Supports AOI
- Complete 90° AOI Optical Architecture
- When Is a 90° Telecentric Lens Especially Useful?
- Applications for PCB, Electronics and Precision Inspection
- How to Design the 90° Telecentric Light
- How to Choose a 90° Telecentric Lens
- Frequently Asked Questions
1. What Is a 90° Telecentric Lens?
A 90° telecentric lens is a telecentric imaging system that incorporates a folded optical path, allowing the camera and inspection object to be positioned at approximately 90° relative to a conventional straight optical arrangement.
A conventional telecentric configuration can be represented as:
A 90° turning configuration changes the physical direction of the optical path:
The purpose is not simply to redirect the image. The optical system still needs to provide the required magnification, field of view, working distance, resolution, sensor coverage, and telecentric imaging characteristics.
2. Why Does AOI Need a 90° Optical Configuration?
In many AOI machines, the inspection object is surrounded by mechanical components. The camera may need to be located outside the area directly above the target.
Limited Vertical Clearance
Machine height may restrict the installation of a conventional top-down camera.
Moving Mechanisms
Robots, gantries, feeders, and pick-and-place mechanisms may occupy the space above the object.
Existing Machine Layout
A folded optical path can provide an alternative without requiring a complete machine redesign.
3. Why Not Simply Use a Mirror?
A mirror or prism can redirect an optical path, but adding a turning element to a conventional imaging system can introduce additional design considerations.
| Consideration | Independent Turning Optics | Integrated 90° Telecentric Design |
|---|---|---|
| Optical Path | Requires additional optical integration | Designed around a folded optical path |
| Alignment | Additional alignment considerations | Integrated optical architecture |
| Mechanical Integration | Depends on individual components | Designed for compact installation |
| Telecentric Performance | Must be evaluated as a complete system | Designed as part of the telecentric optical system |
For precision AOI, the complete optical system should be evaluated rather than assuming that any conventional lens combined with a turning mirror will provide equivalent performance.
4. Why Combine a 90° Telecentric Lens with 90° Telecentric Light?
Changing the camera direction solves only one part of the system-design problem. The inspection object still needs appropriate illumination.
In AOI, illumination affects the visibility of edges, surfaces, holes, pins, solder features, markings, and other inspection targets. Therefore, the lighting configuration should be considered together with the lens and camera.
Lens
Controls the imaging geometry, magnification, field of view, working distance, resolution, and telecentric characteristics.
Light
Controls illumination geometry, contrast, uniformity, reflection behavior, and feature visibility.
5. How Telecentric Illumination Supports AOI
Telecentric illumination is particularly useful when the inspection depends on controlled edge or silhouette representation.
Edges
Controlled illumination can help create clearer and more repeatable object boundaries.
Holes & Slots
Appropriate illumination can improve silhouette visibility for dimensional inspection.
Pins & Profiles
Controlled light geometry can support accurate edge and profile detection.
Reflective Parts
Illumination can be designed to reduce unwanted reflections and improve feature contrast.
The correct illumination depends on the object material, surface finish, inspection feature, working distance, and required image contrast. A telecentric light should therefore be evaluated as part of the complete AOI optical system.
6. Complete 90° AOI Optical Architecture
A practical 90° telecentric AOI system can be organized into four main elements.
Image Acquisition
Sensor size, pixel size, resolution, frame rate, and interface.
Optical Geometry
Magnification, FOV, working distance, resolution, distortion, and telecentricity.
Feature Visibility
Illumination direction, contrast, uniformity, and reflection control.
Inspection Processing
Measurement, positioning, pattern matching, defect detection, and OCR.
7. When Is a 90° Telecentric Lens Especially Useful?
A 90° configuration is most valuable when optical performance and machine integration must be solved simultaneously.
Limited Vertical Clearance
Useful when the space above the inspection object is restricted.
Moving Mechanisms
Helps keep the camera away from robots, gantries, or pick-and-place mechanisms.
Compact AOI Machines
Can provide greater flexibility when multiple inspection stations share limited machine space.
Existing Equipment
Provides another optical integration option when redesigning the machine is impractical.
8. Applications for PCB, Electronics and Precision Inspection
The 90° telecentric approach can be considered across a range of precision AOI applications.
PCB Inspection
Component placement, holes, connectors, PCB features, and dimensional inspection.
Connector Inspection
Pin alignment, terminals, connector geometry, and component positioning.
Semiconductor Components
High-resolution inspection where stable imaging and mechanical integration are important.
Precision Mechanical Parts
Holes, edges, profiles, pins, dimensions, and other precision features.
9. How to Design the 90° Telecentric Light
The light should be selected according to the inspection feature rather than simply matching the physical 90° orientation of the lens.
| Inspection Feature | Lighting Consideration |
|---|---|
| Edges & Silhouettes | Controlled or telecentric backlighting can help create a clear object outline. |
| Reflective Metal | Direction and diffusion should be selected to manage unwanted reflections. |
| Electronic Components | Contrast between component bodies, terminals, solder, and PCB surfaces may require controlled illumination. |
| Surface Defects | Lighting direction should be selected according to defect morphology and surface characteristics. |
In other words, a 90° telecentric light should be treated as part of the AOI optical architecture rather than simply as a mechanical accessory.
10. How to Choose a 90° Telecentric Lens
Selecting the correct lens starts with the inspection requirements. The 90° optical path is an important mechanical consideration, but it should not replace the normal optical selection process.
Step 1 — Define the Inspection Object
Determine object dimensions, material, surface characteristics, and height variation.
Step 2 — Define the Inspection Feature
Determine whether the application requires measurement, edge detection, defect inspection, positioning, or pattern recognition.
Step 3 — Determine the FOV
Define the physical inspection area that needs to be captured.
Step 4 — Select the Camera
Consider sensor size, pixel size, resolution, frame rate, and interface.
Step 5 — Select the Telecentric Lens
Match magnification, FOV, working distance, sensor coverage, optical resolution, and distortion requirements.
Step 6 — Determine the Optical Direction
If a straight optical path cannot fit into the machine, evaluate a 90° turning telecentric configuration.
Step 7 — Design the Illumination
Match the lighting geometry to the inspection feature and object surface.
Step 8 — Validate the Mechanical Layout
Check camera clearance, lens dimensions, light position, moving components, cable routing, and maintenance access.
Straight vs 90° Telecentric AOI Configuration
| Feature | Straight Telecentric Setup | 90° Turning Telecentric Setup |
|---|---|---|
| Optical Path | Straight | Folded |
| Camera Position | Typically above the object | Can be positioned away from the conventional vertical axis |
| Vertical Space | Requires sufficient clearance | Potentially easier to integrate in constrained layouts |
| AOI Applications | Broad | Particularly useful for space-constrained applications |
| Best Use Case | When mechanical space is available | When optical access or machine space is restricted |
90° Turning Telecentric Lens for AOI
Rapixel provides specialized telecentric imaging solutions for AOI, precision measurement, electronics, semiconductor inspection, and other industrial vision applications.
For space-constrained systems, a 90° turning telecentric lens can provide an alternative optical architecture by folding the imaging path while maintaining the requirements of a telecentric machine vision system.
For the best system configuration, evaluate the camera, lens, illumination, inspection object, and mechanical layout together.
Explore Rapixel Telecentric Lenses →Optical Performance Meets Mechanical Flexibility
A 90° telecentric lens is not simply a conventional lens with a different physical orientation. It is a specialized approach for integrating telecentric imaging into applications where a straight optical path is difficult to install.
When combined with appropriately designed telecentric illumination, high-resolution cameras, and vision processing, the configuration can provide a practical foundation for compact and precision AOI systems.
Frequently Asked Questions
What is a 90° telecentric lens?
A 90° telecentric lens is a telecentric imaging system with a folded optical path that changes the physical direction between the camera and inspection object. It is useful when a conventional straight optical path is difficult to integrate.
Why use a 90° telecentric lens for AOI?
It can help integrate telecentric imaging into AOI machines with limited vertical clearance, moving mechanisms, or restricted optical access while maintaining the required optical configuration.
What is a 90° telecentric light?
A 90° telecentric light is an illumination configuration designed to work within a constrained optical layout. Its purpose is to provide controlled illumination geometry while accommodating the mechanical arrangement of the AOI system.
Do I always need a 90° telecentric light with a 90° telecentric lens?
Not necessarily. Lighting should be selected according to the inspection feature, object surface, contrast requirements, and system geometry. A 90° lighting configuration becomes particularly useful when the illumination path is also constrained.
Can a 90° telecentric lens be used for PCB inspection?
Yes. It can be considered for PCB and electronic component inspection when stable telecentric imaging is required and the machine layout makes a conventional top-down optical path difficult to install.
Is a 90° telecentric lens better than a conventional telecentric lens?
Not inherently. A conventional telecentric lens is usually preferable when a straight optical path is easy to integrate. A 90° turning design becomes valuable when mechanical space or optical access requires a folded path.
How do I choose a 90° telecentric lens?
Start with object size, FOV, camera sensor, magnification, working distance, optical resolution, distortion, and inspection requirements. Then evaluate the mechanical envelope and determine whether a 90° optical path is necessary.
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Explore Vision Systems →Need Help Designing a 90° Telecentric AOI System?
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