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Stellar Displays
Optical stack

The lens in front of the panel decides how much light gets back out.

On a reflective LCD (RLCD) the light crosses the cover lens twice. Every interface it meets on the way costs contrast, so the lens is part of the optical specification, not a mechanical afterthought.

A reflective monitor with a hinged reflector panel, annotated for natural and overhead light

What does a cover lens cost and buy?

4%lost at each uncoated face
2 crossingslight passes the lens in and out
AR coatingrecovers most of the loss
IK impactwhy the lens is there at all

Characteristic behaviour of the technology, not the rating of a specific module. Per-module figures are issued as a datasheet with the conditions behind each one.

How much light does a cover lens lose?

Ambient light enters through the lens, reflects off the panel and leaves through the lens again. With an air gap behind it, that path crosses four optical interfaces. Each uncoated air-to-material boundary sends roughly four per cent straight back to the viewer as veiling glare, which lands on the dark state and closes the contrast ratio.

01

Light enters the lens

The first surface reflects a share immediately, before any of it reaches the panel.

02

It crosses the gap

With an air gap there are two more interfaces on the way in and two on the way out.

03

What returns is the image

Coating or bonding removes interfaces, which is why lens choice changes measured reflectance.

When should you specify a cover lens?

Specify it when

Impact or vandal resistance is required and the panel cannot be exposed.
The product is touched, so the lens is also the touch surface and the cleaning surface.
Anti-reflective coating is available and the budget can carry it.
The lens can be optically bonded, which removes two interfaces outright.

Consider something else when

Nothing protects the panel and the lens is being added purely for appearance.
A thick uncoated lens is specified with an air gap, which costs more contrast than the protection is worth.
The material is chosen on cost alone without checking scratch resistance against the cleaning regime.
Compare

Three cover lens materials compared

Criterion Chemically strengthened glass Acrylic (PMMA) Polycarbonate
Optical clarity Highest High Good
Scratch resistance Highest Low without hard coat Low without hard coat
Impact resistance Good Moderate Highest
Weight Heaviest Light Light
Takes anti-reflective coating Yes Yes Yes
Typical use Touch and outdoor Indoor, cost-led Vandal-resistant

Typical behaviour for the technology class, not a specific part. Request the datasheet for the module you are evaluating.

Panels supplied with a specified lens

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Resources on cover lens choice

Request Documentation
On request

Datasheets

Each module is characterised before its datasheet publishes, so we issue the current specification directly rather than list a stale one.

Not yet published

Integration guides

Written against real integrations rather than in advance. If you are driving a panel now, an application engineer walks the interface and timing through with you.

Available now

Power calculator

Size a reflective panel against your power budget before samples arrive. A sizing aid, with its assumptions stated on the page.

Specifying a lens over a reflective panel?

Send the enclosure drawing and the operating environment. An application engineer specifies the lens, the coating and the bonding method together.