Ambient dimming is now becoming a standard feature in AR and AI smart glasses. In a previous blog we’ve explained that the ability to dim the real world ensures that virtual objects in AR glasses can be seen clearly against the real world, whether the wearer is in a dimly lit office or outside on a sunny day. When the virtual object is intended to be dark or black then it’s even more important to have dimming, because light engines can only add more photons to your view of the real world; they cannot produce black. In short, dimming is a key part of achieving all-day wearable smart glasses.
Colour-changing dimmers
Most of the development of dimmers has primarily been for colour-neutral dimming, but recently we have seen the launch of some products with colour-changing dimmers – most notably Xiaomi’s AI glasses, which can switch between pink, blue and purple tints.
Whereas colour-neutral dimmers enhance the contrast of the virtual image for the primary user, colour-changing dimmers have the potential to provide other benefits, and not only for the wearer’s eyes.
Firstly, for the wearer there can be visual advantages in being able to filter out certain colours of light. For example, in sports such as skiing, it’s well known that certain colours of lenses increase contrast and visibility when it’s bright and sunny (eg blue filter), but other colours are better when it’s cloudy or overcast. Glasses could therefore automatically adjust the tint based on lighting conditions.
Customising the colour of lenses to particular user’s needs for all-day wearing is also of value – for example to reduce colours known to trigger or exacerbate migraines, or to improve colour vision for people with colour-blindness.
Another reason for the interest in colour-changing lenses is fashion: Colour changing glasses also give the wearer an opportunity to change the lenses to match their style preference and express their personality. In the same way that people customise their phones with different cases and backgrounds, smart glasses could be customised through the colours the wearer chooses. The ability to customise and personalise consumer electronics products is often an important factor in driving adoption beyond technology enthusiasts.
How do colour-changing dimmers work?
Whilst there are several technologies for ambient dimming, the most practical approach for coloured dimmer is to use Guest-Host Liquid Crystal (GHLC), since different colours can be engineered by changing the liquid crystal mixture.
GHLC work by dispersing a small quantity of dichroic dye(s) into a liquid crystal host. Applying a voltage across the thin layer of the liquid crystal causes the molecules to rotate, which also rotates the dye molecules inside it, changing the level of light absorption through the thin layer.
It’s common to use three different dyes mixed together: one which absorbs mostly red light, one mostly green and one mostly blue, so that together they can substantially absorb all wavelengths of visible light.
FlexEnable liquid crystal technology on plastic enables colour-dimming. By adjusting the blend, we can create any hue through subtractive colour mixing (like mixing pigments): from red to yellow to blue, to orange or green or purple. Stacking GHLC allows multi-coloured switching from a single module. We can also vary the depth or intensity of the colour produced by tuning the cell gap and the dye concentration.
Contact us at info@flexenable.com for more information.
Colour wheel
