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Liquid Lenses in Imaging
The Future of Microscope Objectives

Liquid Lenses
in Imaging

June 2018 | See all Trending in Optics Topics

Quickly Autofocus and Overcome Depth of Field Limitations

 

Integrate liquid lenses into imaging assemblies for quick autofocus

 

Compensate for different object sizes and working distances

 

Increase throughput in high-speed machine vision systems

 

Ideal for barcode reading, rapid automation, package sorting, and security

Conventional imaging lenses struggle to capture sharp and accurate images in high-speed or precise applications that require quick refocusing. Liquid lenses overcome these limitations by quickly adjusting focus to accommodate for objects located at various working distances or objects of different heights. Liquid lenses are small cells containing optical-grade liquid that change their shape when a current or voltage is applied. This occurs within a matter of milliseconds and causes the lens’ optical power, and therefore focal length and working distance, to shift. Integrating liquid lenses into imaging systems is an ideal solution for applications requiring rapid focusing, high throughput, and accommodation for depth of field and working distance.

Liquid Lenses for Machine Vision

Machine vision applications such as high-volume assembly lines require fast, accurate, and precise measurements to ensure high throughput. Integrating a liquid lens is a compact and economical solution when quickly focusing at multiple distances is required.

Figure 1 (right): Liquid lens adjusting working distance to image objects of different heights as they pass by on a fast-moving conveyor belt. While a conventional imaging lens requires mechanical refocusing for every object height, a liquid lens refocuses without requiring mechanical translation.

Size Comparison of an Ultra-Compact Microscope Objective with a Standard Microscope Objective

Liquid Lenses for Life Sciences

In addition to machine vision applications, the versatility of liquid lenses is beneficial to a number of life science applications including focus stacking in microscopy and ophthalmology. Focus stacking, or z-stacking, is the combining of images taken at different focus distances. Liquid lenses can be integrated into tube lenses or in infinity space within a microscope to quickly and precisely focus to various object planes.

Liquid lenses are also commonly used in ophthalmology, where depth of field adjustment is essential to diagnosing ailments of the eye. Multiple conventional lenses can be replaced with a single liquid lens, reducing diagnosis time and the overall size of ophthalmic equipment such as phoropters and optical coherence tomography (OCT) systems.

Size Comparison of an Ultra-Compact Microscope Objective with a Standard Microscope Objective

Figure 2: Liquid lenses can be integrated into microscope systems to facilitate focus stacking, adjusting focus to capture a series of images at slightly different working distances

Understanding Liquid Lens Technology

Liquid lenses can function by several slightly different processes: electrowetting, current-driven polymers, or sound piezoelectrics. Electrically-focused liquid lenses consist of a container filled with optical fluid and a surrounding polymer membrane. A current-driven actuator applies pressure to the edges of the membrane, causing the curvature of the lens (and therefore its optical power) to change. Electrically-focused tunable lenses focus within milliseconds and function with low operating voltages. They do not alter polarization, typically have high laser damage thresholds, and introduce minimal aberrations.

Electrically-focused liquid lens technology.

Figure 3: Electrically-focused liquid lens technology.

The video below shows a demonstration of how liquid lens technology can be used to inspect objects of different heights.

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Liquid Lenses in Imaging

To learn more about liquid lens applications, features, and technologies, please read our application note.

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Liquid Lenses at Edmund Optics®

FAQ's

FAQ   How quickly can liquid lenses change between different focus positions?
Liquid lenses change focus to different working distances in a matter of miliseconds.
FAQ  What aperture sizes are available in liquid lenses from Edmund Optics®?

Variable Focus Liquid Lenses come in aperture sizes ranging from 2.5-3.9mm and Optotune Electrically Focus-Tunable Lenses come in aperture sizes ranging from 3-26mm.

FAQ   Can I integrate a liquid lens into another type of lens, such as a fixed focal length lens?

Yes, we can integrate liquid lenses into other types of lenses as a custom request. We also offer the modular Cx Series Fixed Focal Length Lenses, in which you can integrate interchangeable accessories including liquid lenses, fixed apertures, and internal filter holders.

FAQ   How do I use a C-Mount Focus Tunable Lens in combination with a fixed focal length lens assembly?

A thread adapter can be used to connect a C-Mount Focus Tunable Lens directly onto the filter threads of a fixed focal length lens assembly. To learn more, visit our Using C-Mount Focus Tunable Lenses application note.

Resources

Application Notes

Technical information and application examples including theoretical explanations, equations, graphical illustrations, and much more.

Introduction to Liquid Lenses
Read  

Liquid Lenses in Imaging
Read  

Using C-Mount Focus Tunable Lenses
Read  

Videos

Informative corporate or instructional videos ranging from simple tips to application-based demonstrations of product advantages.

Understanding Liquid Lens Technology
Watch  

Related Pages

Additional webpages that describe related products, capabilities, or concepts.

Diamond Turning Capabilities
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Laser Optics
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Technical Articles

Links to technical articles appearing in industry publications authored by Edmund Optics or featuring contributions from Edmund Optics' engineering team and key management.

"Electrically Tunable Lenses in Imaging and Machine Vision" by Boris Ecker - Inspect
Read  

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