Published in Optica, Vol. 11, No. 2, February 2024
The SPIRAL project introduces a new class of freeform lenses capable of creating multiple focal points and an extended depth of field, all within a single, compact optical element. By applying a spiral pattern to the surface (diopter) of a lens, researchers have achieved a revolutionary form of “tubular focus,” where light is not concentrated at a single point but distributed across a continuum of focal zones. This innovation opens the door to major advancements in ophthalmology, wearable optics, virtual and mixed reality, and miniaturized imaging systems, where space and optical performance are critical.
Conventional lenses focus light at a single point, which limits sharpness and depth. SPIRAL lenses disrupt this paradigm by spiralizing the optical surface, redistributing focal power according to a Fermat spiral. This design generates several focal regions within a single pupil, improves image quality and depth perception without bulky components, and remains multifocal even at smaller apertures — something traditional trifocal lenses cannot achieve. Experimental and simulation results confirm the presence of up to four distinct focal zones, validated by optical bench measurements.
In direct comparison with classical trifocal lenses, spiralized lenses consistently match or surpass their performance. They show additional focal zones beyond the standard three, improved modulation transfer function (MTF) under various conditions, and a wider depth of focus with stable performance across different aperture sizes. The spiral geometry also naturally generates optical vortices — specific light structures that can be harnessed for advanced imaging and photonics applications.
This research marks a significant leap forward in optical engineering. By integrating spiral structures directly into the lens surface, the SPIRAL approach eliminates the need for complex or bulky devices while delivering superior multifocal performance. It paves the way for a new generation of contact lenses, intraocular implants, AR/VR displays, and miniaturized optical systems.
Spiralized freeform lenses combine compactness, versatility, and powerful optical behavior in a single element. They represent a paradigm shift in how we design lenses — from focusing light at a single point to shaping it across a tubular focus. This work lays the foundation for the next generation of wearable optics and embedded imaging technologies.
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