Pairing Optics and illumination: Best practices Matching Ring Light Illumination to an Optical System.

Explore how matching ring light illumination to an optical system can enhance performance and efficiency in this case study, featuring best practices and actionable insights.

Enquiry

The University of Bristol sought technical advice, a configuration build, and a supplier for an optical zoom system paired with an appropriate illuminator. Their School of Physics needed an optical system with high magnification and short working distance to resolve their inspection samples effectively.

Design Brief

The client required an optical system with variable magnification to locate areas of interest at larger fields of view (lower magnification) before zooming in to smaller fields of view (higher magnification) for detailed study. Their specific requirements included:

• High-resolution, short working distance optics.
• Variable magnification.
• Brightfield illumination.
• Retrofit to an existing camera.
• Mounting hardware for integration.

Challenges

The client’s preferred lighting method was a ring illuminator, chosen for its ability to maintain consistent illumination across various system orientations. The main challenge was matching the optical system’s working distance with the LED ring light’s optimal working distance—a crucial yet often overlooked aspect for optimising vision systems.

Process

I determined that a 12x zoom system would provide an appropriate range of fields of view. By combining this with a suitable front lens and rear adapter tube, the system could be completed. Our portfolio includes systems with mounting clamp options and interchangeable camera interfaces, allowing secure mounting and integration with the client’s current camera. This setup provided flexibility to change various modular parts and refine the overall optical output.

The illumination needed to be paired precisely with the optical configuration, specifically ensuring the ring light’s working distance matched the lens. Given the fewer options for ring light working distances compared to front lens options, this presented a challenge. Ring lights typically require medium to longer working distances, whereas higher resolution through increased magnification demands inherently shorter working distance lenses.

Therefore, my approach was to balance:

• The client’s Wishlist.
• Available optical configurations.
• Available ring lights.

Configuration

Through evaluating product matrices, I selected the 12x Navitar zoom system, which offered the field of view range required by the client. I paired this with a higher magnification rear adapter tube to achieve higher magnification at a longer working distance, providing more options for matching the front lens working distance with a suitable ring light.

I specified the Navitar 1-50014 front lens (1.5x magnification) with a working distance of 51mm. This matched directly with a Starlight ring light with a working distance range of 30-150mm, optimized at 50mm. This exact match ensured optimal performance.

Additionally, I integrated a mounting clamp over the camera adapter tube, providing the necessary interface and secure mounting for retrofitting to the client’s rig.

Results

The supplied optical system enabled the client to visualise their sample effectively. Successfully matching the front lens and ring light working distance was particularly satisfying, ensuring perfect optimisation. However, testing revealed a potential pitfall: if the ring light is too close to the sample, it can create a halo effect as shown in image below left— a fine line during the optimisation process to be aware of.

 Conclusion

If you need new lenses, optics, or complete inspection systems, or if you have existing parts you want to utilize but are unsure of the result, please contact us for a consultation. We can accurately describe the optical properties you can expect from a retrofit system in advance of any purchase, avoiding surprises. All our solutions are carefully considered with your application in mind before making any recommendations.

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