Hot Mirror FAQ: What 3D Scanning & Structured Light Buyers Ask

Optical designers sometimes treat mirrors as simple parts, yet in 3D Scanning & Structured Light the mirror decides beam direction, loss budget and even image contrast.…

Optical designers sometimes treat mirrors as simple parts, yet in 3D Scanning & Structured Light the mirror decides beam direction, loss budget and even image contrast. The Hot Mirror is a quietly critical component whose details repay careful attention.

At its core, the Hot Mirror is a float or borosilicate glass element carrying a dichroic (transmits visible, reflects IR). That stack is engineered to return incident light efficiently over IR reflect / visible pass, giving designers a predictable, low-loss way to steer a beam where they need it.

When light meets the Hot Mirror, almost all of it bounces from the front coating. The substrate merely holds the coating in place; it does not need to be traversed by the useful beam, so transmission losses and secondary reflections stay minimal — a real advantage in sensitive 3D Scanning & Structured Light setups.

Coating a Hot Mirror means laying down a dichroic (transmits visible, reflects IR) whose optical thickness is controlled to a fraction of a wavelength. Done well, the part holds > 90% visible transmit over IR reflect / visible pass; done carelessly, it drifts and the system loses light it cannot afford to lose.

Substrate choice for a Hot Mirror is a trade between optical grade and budget. float or borosilicate glass is a common pick because it can be cut and polished to 4–6λ flatness and a 60-40 surface, which is plenty for the reflection quality most 3D Scanning & Structured Light systems require.

A practical Hot Mirror datasheet reads: float or borosilicate glass substrate, 4–6λ flatness, 60-40 quality, 1–3 mm thick, > 90% visible transmit over IR reflect / visible pass. Those five lines settle most design reviews for 3D Scanning & Structured Light. See the standard size list for what we stock and what we cut to order.

In 3D Scanning & Structured Light, the Hot Mirror usually appears wherever projecting and capturing patterned light accurately. Designers value it because it keeps the beam path predictable and the loss budget small, which translates directly into a more stable instrument. The applications overview maps where each industry places it.

Frequently asked questions

Does a Hot Mirror need a specific mount angle? Not inherently, but 0° or 45° are most common; tell your supplier the angle so the coating is optimized. Can it be customized? Yes — size, shape, substrate (float or borosilicate glass) and dichroic (transmits visible, reflects IR) are all adjustable. What reflectivity can I expect? Around > 90% visible transmit across IR reflect / visible pass for standard builds.

For 3D Scanning & Structured Light, do not over-specify. Choose the dichroic (transmits visible, reflects IR) that covers IR reflect / visible pass at the angle you use, keep flatness at 4–6λ unless the wavefront demands more, and you will have a Hot Mirror that is both capable and economical.

Mirrors reward careful handling. Hold a Hot 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 > 90% visible transmit for years.

At JYOPTO we make Hot Mirror parts by cutting float or borosilicate glass with laser accuracy of ±0.01 mm, then applying the dichroic (transmits visible, reflects IR) under vacuum. Standard blanks run 1–3 mm thick, edges are smoothed for safe handling, and every shipped mirror meets 4–6λ flatness with a 60-40 surface — the same disciplines we apply across our optical glass, vacuum-coating and precision cold-processing lines since 2020.

When you specify a Hot Mirror, the numbers that matter are flatness 4–6λ, finish 60-40, and the reflectance > 90% visible transmit across IR reflect / visible pass. Thickness 1–3 mm is mostly about handling and mount compatibility, but it still belongs on the print. The specification table covers the common configurations.

At its core, the Hot Mirror is a float or borosilicate glass element carrying a dichroic (transmits visible, reflects IR). That stack is engineered to return incident light efficiently over IR reflect / visible pass, giving designers a predictable, low-loss way to steer a beam where they need it.

Durability is part of the spec, not an afterthought. For 3D Scanning & Structured Light the Hot Mirror should survive shipping, installation and the occasional wipe. The protective overcoat on the dichroic (transmits visible, reflects IR) is what lets it do that without losing > 90% visible transmit over time.

Behind the coating sits the float or borosilicate glass substrate. Its job is mechanical: hold flatness, survive cutting and mounting, and stay stable with temperature. For many 3D Scanning & Structured Light uses, float or borosilicate glass hits the right balance of cost, flatness (4–6λ) and workability.

Our production of a Hot Mirror follows a simple, repeatable route: laser-cut the float or borosilicate glass to ±0.01 mm, smooth the edges, deposit the dichroic (transmits visible, reflects IR), and inspect to 4–6λ / 60-40. Thickness options span 1–3 mm, and the same Hangzhou line that builds first-surface mirrors also runs windows, substrates and custom coatings.

Quick terminology

"Flatness 4–6λ" describes how close the surface is to a perfect plane, in fractions of a wavelength. Tighter flatness costs more but protects wavefront quality, which is why 3D Scanning & Structured Light systems specify it explicitly rather than leaving it to chance.

Quality control

Every Hot Mirror is measured, not just sampled. Flatness against a reference, scratch-dig against 60-40, and a reflectance spot-check at IR reflect / visible pass confirm the dichroic (transmits visible, reflects IR) performed as designed. Documented results matter most for 3D Scanning & Structured Light, where one bad part can stall a whole instrument.

Most of the engineering in a Hot Mirror lives in its dichroic (transmits visible, reflects IR). The stack is designed for IR reflect / visible pass and delivers > 90% visible transmit, and its environmental protection layer keeps the metal from tarnishing so the mirror keeps working year after year.

Behind the coating sits the float or borosilicate glass substrate. Its job is mechanical: hold flatness, survive cutting and mounting, and stay stable with temperature. For many 3D Scanning & Structured Light uses, float or borosilicate glass hits the right balance of cost, flatness (4–6λ) and workability.

Substrate choice for a Hot Mirror is a trade between optical grade and budget. float or borosilicate glass is a common pick because it can be cut and polished to 4–6λ flatness and a 60-40 surface, which is plenty for the reflection quality most 3D Scanning & Structured Light systems require.

When light meets the Hot Mirror, almost all of it bounces from the front coating. The substrate merely holds the coating in place; it does not need to be traversed by the useful beam, so transmission losses and secondary reflections stay minimal — a real advantage in sensitive 3D Scanning & Structured Light setups.

Wrapping up

A Hot Mirror is a small part with an outsized effect on 3D Scanning & Structured Light. Get the dichroic (transmits visible, reflects IR), float or borosilicate glass and flatness right and the rest of the system behaves. If your drawing calls for something specific, the team at JYOPTO can cut and coat it to match — start from the specifications and standard sizes, then tell us the wavelength and angle.