Optotune, a spinoff from ETH Zurich based in Switzerland is the market leader in focus tunable liquid lenses.
Due to the high repeatability and accurate performance, the lenses are beneficial in a variety of optical applications such as laser processing, augmented reality (AR), MedTech and machine vision.
With significant market growth and development of innovative products Optotune has grown rapidly, buoyed by being able to offer customised solutions besides the off-the-shelf imaging systems.
“We enable reliable high-speed imaging with a dynamic working distance,” says Mark Ventura, co-founder.
“It is great to build cutting-edge technologies together with our partners and customers.”
Optotune ensures that the lens is compatible with optical elements to plug and play. There is a great deal behind the working principle of the Optotune lens and its integration into conventional imaging systems.
In a wide range of applications such as logistics, quality control and sorting, machines now automate processes previously completed by humans. To image their targets, they use optical sensors. Computers process the acquired images and feed them into sophisticated decision algorithms.
Imaging systems often need to combine high resolution with a large field of view, which allows to identify small features on large objects. Conventional fixed-focus optical systems have a limited depth of field and therefore need to be adjusted or replaced when the working distance changes.
Optotune offers innovative products to address the focal depth issue. A tunable lens added to an imaging lens allows focusing on different z-positions without compromising image quality. Through eliminating the need for manual adjustments or multiple objectives and cameras, cost and system complexity decreases drastically. Optotune tunable lenses can be added to standard imaging systems comprising of a camera and an imaging objective, which enable rapid, electrical tuning of working distance within milliseconds, whilst preserving resolution and field of view of the image system.
Tunable lenses conceptionally follow the working principle of a human eye. An elastic polymer membrane covers a reservoir containing an optical liquid. A voice coil actuated system exerts pressure on the membrane outside of the clear aperture.
The increasing pressure changes the deflection of the membrane in the optical path as Figure 1 illustrates,
thereby changing optical power. Consequently, the current flow through the actuator is directly proportional to the resulting focal length of the lens.
Optotune offer clear aperture sizes of 3, 10, or 16 mm. The latter allow for a combination with large sensors and enable highest resolution. Depending on the size of the lens, focal power can be changed from one value to the other within up to 4ms. Computer actuation allows the liquid lenses to focus for billions of cycles, which equate to a very long lifetime.
Figure 2 depicts the EL-16-40-TC liquid lens in both industrial and OEM configurations. As a core technology in machine vision, Optotune lenses are either used in combination with off-the-shelf imaging optics or are integrated into complete imaging systems with optimized optical designs.
In package sorting objects of varying heights pass the optical scanning system at speed. The imaging system must adapt to a large field of view at different working distances rapidly. To track bar codes and addresses high resolution is required. Placing the liquid lens in front of the objective leads to a large range of achievable working distances. Vision systems can image with a wide focal range from infinity (tunable lens at 0 diopters) down to about 200 mm (tunable lens at 5 diopters).
Electronics inspection runs at high speed, requires relatively large field of views for inspection of multiple PCBs in parallel and most importantly high resolution to detect tiny production errors. By placing the focus tunable lens at the back of an imaging lens it is possible to achieve high resolution and image circles of up to 30 mm.
Robotics in precise manufacturing often rely on accurate measurements of features on objects at variable distance from the sensor. Placing the Optotune liquid lens right after the aperture stop of a telecentric lens creates an imaging system with variable focus at a constant magnification.
Designing the liquid lens into the imaging objective leads to optimal optical performance for a certain application. An objective with the liquid lens close to the aperture stop achieves larger fields of view, lower F-numbers and can accommodate large image sensors. In addition, integrated systems are compact and straightforward to implement in the production line. Recently, new lens models for 12 megapixel 1.1” sensors with 12mm and 50mm focal length lenses have been introduced by Optotune together with their partners VST and Chance for Change.
In conclusion, Optotune tunable lenses have been proven useful in a wide range of machine vision applications. Imaging systems with the Optotune liquid lens feature high temporal and spatial resolution and a long lifetime up to billions of cycles. Replacing multiple imaging systems with one single tunable solution reduces space and cost of the application. This is how Optotune has been defining the future of Optics since 2008 and continues to do so.