The Swiss High-tech Startup Optotune launched new products for LED lighting applications with its innovative tunable lens technology. Thanks to a variable lens shape, the beam angle of a spotlight can be flexibly adjusted. While being very efficient, this technology offers a compact solution to combine a flood- and a spotlight in one product, hence reducing complexity and offering new possibilities.
When designing a spotlight, there are components available for many different beam angles. As they are fixed, the customer has to decide in the design phase which angles to use for an installation. Sometimes it’s possible to exchange optics for different beam angles. However, this is time consuming and cumbersome, especially as lamps are often hard to access after installation.
There are solutions available to vary the beam angle without exchanging components, but they are not efficient and can be complex. It’s possible to shift a lens away from an LED to focus the beam (up to a certain point), however, rings and shadows typically appear in the spot and with increasing distance from the LED, a lot of light is lost. On the other hand, large show lights or even some museum lights are equipped with a zoom lens for the adjustment of the spot size.
While requiring lots of space and not being efficient, such a zoom lens is expensive in development and manufacturing, making it unsuitable for mass lighting applications. Optotune’s tunable lens technology allows to set the beam angle on site and to adjust it whenever necessary. There is even a possibility to motorize the tuning process for remote controlled adjustments. While lowering complexity costs by having just one product from flood to spot, it also offers new opportunities with changing beam angles for different settings, for example in a museum with changing exhibitions.
▲ Figure 1: Working Principle
The principle of Optotune’s tunable lens technology is outlined in figure 1. A ring or so called “lens shaper” is pressed into a poly carbonate container filled with an optical liquid and sealed with a thin polymer membrane. This causes a spherical lens to form, which changes the focal length proportionally with the liquid pressure. The clear aperture remains constant throughout the whole tuning range. While being very efficient and compact, this technology allows a flexible adjustment of the beam angle when implemented in a spot light. Turning a ring controls the movement of the lens shaper into the liquid filled container and therefore the shape of the lens. A cogwheel in the housing offers the possibility to motorize this process, allowing to remote control the beam angle.
▲ Figure 2: Lumilens
In figure 2, a spotlight design using Optotune’s ML-25-50 Lumilens is shown, illustrating the compact design possibilities for a spotlight. When designing a spotlight with a tunable lens, the optical design is outlined as shown in figure 3.
The LED and the secondary optics define the maximum beam angle. It’s important to use secondary optics with an even light distribution for a good tuning result. The tunable lens is then used to focus the beam from the wide flood angle to a small spot. For the spotlight design presented in this article, the range goes from 40° down to 10°. It varies depending on the design and optical components used.
▲ Figure 3: Optics Design Lumilens
While being a very new technology, Optotune’s tunable lenses have been extensively tested in various environments. Based on these results, the expected lifetime of the tunable lens is over 10 years in constant operating temperatures of -20°C to 85°C. The lenses are built in a dust free environment (clean room) and have a well protective housing to keep them clean. However, the current products do not have waterproof housings. Hence, the lens can only be used indoors.
The lens presented in figure 2 is one of Optotune’s standard products. It has a clear aperture of 25mm with an outer diameter of 50mm. The largest lens currently available has a clear aperture of 55mm, designed for large LED spotlights with lighting power of 2000 – 4000 lumen. Prices for these standard lenses are starting around € 20-30 depending on the volume and lens size. From the technology perspective, it would be possible to build even larger lenses or lenses as small as 2mm in clear aperture.