Etendue, Miniaturization, and More: Considerations in Illumination Design for Advanced Endoscope Visualization Systems

Adaptive optics (AO) was first used by astronomers in the 1990s to correct for distortions in astronomical data due to fluctuations in the Earth’s atmosphere. Today, AO is critical in many applications in the machine vision, life sciences, and medical device fields. In many of these applications, AO can be used to increase the depth of field and signal intensity. In other applications, AO can be used to correct wavefront errors and extend the effective operating range of the optical systems. There are several commercially available AO components and ongoing research continues to produce more reliable and cost-effective technologies.

3D imaging systems, particularly those used in endoscopes, continue to benefit from advancements in visualization technology. Within these systems, the design of the illumination system is a key factor in providing superior image quality, allowing the surgeon to observe tissues, blood vessels, and more with the greatest detail. When developing a new endoscope or other handheld medical device it’s important to understand some key terms and concepts to ensure that the optical system and the illumination system work together to deliver your performance specifications.

Etendue and Controlling Light

All optical systems, no matter what the application, face similar challenges regarding how light will be controlled along the optical path, from the illumination source to the sample, then on to the detector. Etendue is a principal that explains how optical systems transmit light in area and angle. It is related to the optical invariant and is generally conserved and never decreases in an optical system where power is conserved.

Size and Space Constraints

Endoscopes pose a significant challenge for illumination design due to their compact size and often large field of view (FOV) requirements. Current state of the art endoscopes take advantage of miniaturization and miniature CMOS image sensors, which are now available in packages smaller than a millimeter on a side. These chip-on-tip endoscopes offer incredible imaging performance and are rapidly replacing traditional rod endoscopes because they offer stereo 3D imaging capabilities that support robotic surgery applications.

The white paper, A Guide to Illumination Design in Biomedical Imaging Systems, offers a comprehensive explanation of illumination design terms and concepts. Armed with this knowledge, you’ll be more effective at communicating with your optical system engineering team to achieve the device’s performance requirements all while paving the way for an efficient, faster product development timeline.