How a Protected Gold Mirror Solved a Projection & Display Problem

For engineers working in Projection & Display, the choice of a reflective surface is rarely an afterthought. Protected Gold Mirror components sit at the heart of systems…

For engineers working in Projection & Display, the choice of a reflective surface is rarely an afterthought. Protected Gold Mirror components sit at the heart of systems where routing and combining light engines in compact housings, and a small improvement in coating quality can change the result of an entire measurement or process.

A Protected Gold Mirror is an optical component built so that reflection happens at the coated front face rather than through a substrate. With a protected gold on a silicon, copper or glass base, the part delivers 98%+ in the IR reflectivity across 700 nm to 10.6 µm while keeping the useful aperture clean and ghost-free.

The working principle is the law of reflection applied to a coated plane. Mount the Protected Gold Mirror at 45° and a beam turns 90°; stack several and you fold a long path into a short box. That simplicity is why mirrors remain the fastest way to route light in Projection & Display.

The protected gold is where performance is won or lost. Deposited by vacuum processes, it is tuned so the reflected wave adds constructively across 700 nm to 10.6 µm, reaching 98%+ in the IR. Getting the layer thickness right is a precision task: a few nanometers off and the reflectivity curve shifts.

A Protected Gold Mirror starts as a silicon, copper or glass blank. We hold it to λ/4 flatness and 40-20 surface quality, then apply the protected gold. The substrate never sees the beam directly, but its figure sets the limit on how straight the reflected wavefront stays.

A practical Protected Gold Mirror datasheet reads: silicon, copper or glass substrate, λ/4 flatness, 40-20 quality, 0.5–6 mm thick, 98%+ in the IR over 700 nm to 10.6 µm. Those five lines settle most design reviews for Projection & Display. See the standard size list for what we stock and what we cut to order.

Where routing and combining light engines in compact housings, a Protected Gold Mirror earns its place by doing one job reliably: turning the beam without adding noise. In Projection & Display that reliability is the difference between a prototype and a shippable product. More application examples are worth a look if the use case is close to yours.

A typical situation

Consider a Projection & Display builder who needed routing and combining light engines in compact housings. Starting from a stock part caused ghosting and loss. Switching to a made-to-print Protected Gold Mirror — protected gold on silicon, copper or glass, flatness λ/4 — removed the ghost and recovered the lost light, turning an erratic bench setup into a repeatable instrument.

Selecting a Protected Gold Mirror for Projection & Display starts with the wavelength and angle of incidence, then the acceptable loss. Match the protected gold to 700 nm to 10.6 µm, confirm 98%+ in the IR, and make sure the silicon, copper or glass and 0.5–6 mm fit the mount you already have. The spec and size tables make that comparison quick.

Mirrors reward careful handling. Hold a Protected Gold Mirror by the edges, keep the coated face away from fingers and aerosols, and clean only with approved optics tissue and solvent when truly needed. Store it in its packaging, coated face protected, and it will hold 98%+ in the IR for years.

Because we control cutting, coating and finishing in one place, a Protected Gold Mirror can move from your drawing to a finished part without hand-offs. The silicon, copper or glass is cut to ±0.01 mm, the protected gold is vacuum-deposited for 98%+ in the IR over 700 nm to 10.6 µm, and the result is inspected to λ/4 flatness and 40-20 quality.

Mirrors reward careful handling. Hold a Protected Gold Mirror by the edges, keep the coated face away from fingers and aerosols, and clean only with approved optics tissue and solvent when truly needed. Store it in its packaging, coated face protected, and it will hold 98%+ in the IR for years.

Mirrors reward careful handling. Hold a Protected Gold Mirror by the edges, keep the coated face away from fingers and aerosols, and clean only with approved optics tissue and solvent when truly needed. Store it in its packaging, coated face protected, and it will hold 98%+ in the IR for years.

A word on installation

When fitting a Protected Gold Mirror into Projection & Display hardware, handle it by the edges, seat it against a clean flat, and torque gently. Stress on the silicon, copper or glass shifts the figure and costs you the very flatness (λ/4) you paid for.

Typical specs worth putting on a drawing: surface flatness λ/4, surface quality 40-20 (scratch-dig), substrate silicon, copper or glass, thickness 0.5–6 mm, and reflectivity 98%+ in the IR over 700 nm to 10.6 µm. Stating these up front saves rounds of sampling later. Our full technical specifications and standard sizes list the tolerances we hold routinely.

When you specify a Protected Gold Mirror, the numbers that matter are flatness λ/4, finish 40-20, and the reflectance 98%+ in the IR across 700 nm to 10.6 µm. Thickness 0.5–6 mm is mostly about handling and mount compatibility, but it still belongs on the print. The specification table covers the common configurations.

At JYOPTO we make Protected Gold Mirror parts by cutting silicon, copper or glass with laser accuracy of ±0.01 mm, then applying the protected gold under vacuum. Standard blanks run 0.5–6 mm thick, edges are smoothed for safe handling, and every shipped mirror meets λ/4 flatness with a 40-20 surface — the same disciplines we apply across our optical glass, vacuum-coating and precision cold-processing lines since 2020.

Every Projection & Display system eventually meets the same question: where does the light go, and how much of it survives the turn? A well-specified Protected Gold Mirror answers both, which is why it earns a place on the bill of materials long before the enclosure is drawn.

Mounting notes

A Protected Gold Mirror is only as good as its mount. Use edge contact rather than clamping the face, avoid over-tightening that bends the silicon, copper or glass and degrades λ/4, and keep the coated side clear of adhesive. In Projection & Display a kinematically supported mirror stays aligned through thermal cycles and shipping.

The protected gold is where performance is won or lost. Deposited by vacuum processes, it is tuned so the reflected wave adds constructively across 700 nm to 10.6 µm, reaching 98%+ in the IR. Getting the layer thickness right is a precision task: a few nanometers off and the reflectivity curve shifts.

The Protected Gold Mirror is not exclusive to Projection & Display. Universities, service centers and R&D groups use it wherever a beam must turn, which makes a flexible, customizable part a quiet workhorse across the optics world.

In short

For Projection & Display, the Protected Gold Mirror is less a commodity than a tuned component. Specify the band (700 nm to 10.6 µm), the reflectivity (98%+ in the IR) and the figure (λ/4), and you will spend less time debugging light you cannot see. That is the whole game. Where your application sits among the sectors we serve changes the details, not the method.