Tech Briefs Magazine - August 2022 - 38

Optics
LiDAR is a remote sensing method
that uses laser beams (pulses of invisible
light) to measure distances. The beams
of light bounce off everything in their
path and a sensor collects these reflections
to create a precise, three-dimensional
picture of the surrounding environment
in real time.
LiDAR can tell how far away each pixel is
in an image - it has been used for decades
in satellites and airplanes to conduct atmospheric
sensing and measure the depth of
bodies of water and heights of terrain.
In order to work broadly in the consumer
market, LiDAR must become even
cheaper, smaller, and less complex. The
simpler and smaller silicon chips can be
made - while retaining high resolution
and accuracy in their imaging - the more
technologies they can be applied to including
self-driving cars and smartphones.
For more information, contact Daniel
Strain at daniel.strain@colorado.edu; 303735-5875.
Metalens
for Virtual and Augmented Reality
The millimeter-sized flat lens can be used in wearable displays for virtual reality, which
requires compact, lightweight, and cost-effective components.
Harvard University, Cambridge, MA
D
espite all the advances in consumer
technology over the past
decades, one component has remained
frustratingly stagnant: the
optical lens. Unlike electronic devices,
which have gotten smaller
and more efficient over the years,
the design and underlying physics
of today's
optical
changed much.
Researchers have developed the
next generation of lenses that promises
to replace bulky curved lenses
with a simple, flat surface that uses
nanostructures to focus light. The
team created a two-millimeter achromatic
metalens that can focus
RGB (red, blue, green) colors without
aberrations and developed a
miniaturized display for virtual and
augmented reality applications.
Like previous metalenses, this
lens uses arrays of titanium dioxide
nanofins to equally focus wavelengths
of light and eliminate chromatic
aberration. By engineering
the shape and pattern of these nanoarrays,
the researchers could control
the focal length of red, green,
and blue light. To incorporate the
lens into a VR system, the team developed
a near-eye display using a
method called fiber scanning.
The display, inspired by fiber-scanning-based
endoscopic bioimaging
techniques, uses an optical fiber
through a piezoelectric tube. When
a voltage is applied onto the tube, the
fiber tip scans left and right and up and
down to display patterns, forming a
miniaturized display. The display has
high resolution, high brightness, high
dynamic range, and wide color gamut.
In a VR or AR platform, the metalens
would sit directly in front of the eye
38
Optical combiner:
e.g. Beamsplitter
Real-world scene path
Virtual-world scene path
Human eyeball
Floating image
RGB
Metalens
Display
lenses
haven't
Real-world scene
The two-millimeter achromatic metalens can focus RGB (red, blue, green) colors without aberrations. A
miniaturized display was created for VR and AR applications. (Image: Harvard University)
and the display would sit within the focal
plane of the metalens. The patterns
scanned by the display are focused onto
the retina, where the virtual image
forms with the help of the metalens. To
the human eye, the image appears as
part of the landscape in the AR mode,
some distance from our actual eyes.
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The team aims to scale up the lens
even further, making it compatible
with current large-scale fabrication
techniques for mass production at a
low cost.
For more information, contact Leah
Burrows at lburrows@seas.harvard.edu;
617-496-1351.
Tech Briefs, August 2022

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Tech Briefs Magazine - August 2022

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