A 150-nm mirror directs laser light onto the retina while keeping smart glasses transparent and suitable for daily use.
TDK Corporation has demonstrated a direct retinal projection display for smart glasses using a meta-optic mirror. The mirror is 150 nm thick, uses nanoscale reflectors, and can be embedded directly into a lens.
The mirror has about 80% visible-light transmittance, allowing the glasses to remain as transparent as ordinary eyeglass lenses. This can help create smart glasses that look and function more like conventional eyewear.
Direct retinal projection displays images by directing light into the user’s eye and onto the retina. Conventional systems use a curved mirror positioned in front of the eye. This can increase the size of the optical system and make it difficult to achieve a glasses-like form factor.
TDK’s meta-optic mirror replaces the curved mirror with a flat structure containing nanoscale reflectors. The reflectors are arranged so the reflection angle changes with the mirror’s position. This allows laser light entering from different angles to be directed towards the angle required for retinal projection.
The optical system also prevents the projected image from being visible to people facing the wearer. This reduces image leakage and can help protect the privacy of information displayed through the glasses.
TDK has also developed an ultra-compact full-colour laser module and a visible-light full-colour laser control device designed to support resolutions up to 4K. These technologies are being combined with the meta-optic mirror to develop optical systems for smart glasses.
Unlike conventional waveguide displays, which can require complex structures and manufacturing processes, the meta-optic mirror can be produced using processes similar to those used in semiconductor manufacturing. This could support mass production of the optical component.
The current meta-optic mirror supports monochrome operation. TDK plans to develop full-colour operation and target mass production in the coming years.
TDK is also working with QD Laser to develop optical technologies for smart glasses. The companies are combining QD Laser’s retinal projection technology and patents with TDK’s full-colour laser module, laser control devices and meta-optic mirrors. The work includes development of RGB light source modules and optical engines for smart glasses.
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