The Hot Mirror Explained for 3D Scanning & Structured Light Engineers

For engineers working in 3D Scanning & Structured Light, the choice of a reflective surface is rarely an afterthought. Hot Mirror components sit at the heart of systems…

For engineers working in 3D Scanning & Structured Light, the choice of a reflective surface is rarely an afterthought. Hot Mirror components sit at the heart of systems where projecting and capturing patterned light accurately, and a small improvement in coating quality can change the result of an entire measurement or process.

A Hot Mirror is an optical component built so that reflection happens at the coated front face rather than through a substrate. With a dichroic (transmits visible, reflects IR) on a float or borosilicate glass base, the part delivers > 90% visible transmit reflectivity across IR reflect / visible pass while keeping the useful aperture clean and ghost-free.

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.

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.

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.

Why the details matter

The Hot Mirror looks simple, but its blocking infrared while passing visible light comes from controlling nanometers. Each layer of the dichroic (transmits visible, reflects IR) is a fraction of a wavelength thick; together they make incident light add up in phase on reflection, reaching > 90% visible transmit. Miss the thickness and the curve moves — which is why process control, not just the material, defines quality.

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.

A Hot Mirror is tougher than it looks but softer than you think. Fingerprints on the dichroic (transmits visible, reflects IR) are the usual cause of field failures, so edge-handling and capped storage pay off. A little discipline keeps > 90% visible transmit where it belongs.

Because we control cutting, coating and finishing in one place, a Hot Mirror can move from your drawing to a finished part without hand-offs. The float or borosilicate glass is cut to ±0.01 mm, the dichroic (transmits visible, reflects IR) is vacuum-deposited for > 90% visible transmit over IR reflect / visible pass, and the result is inspected to 4–6λ flatness and 60-40 quality.

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.

A word on installation

When fitting a Hot Mirror into 3D Scanning & Structured Light hardware, handle it by the edges, seat it against a clean flat, and torque gently. Stress on the float or borosilicate glass shifts the figure and costs you the very flatness (4–6λ) you paid for.

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 real service a Hot Mirror meets more than the optical table. Humidity, temperature swings and routine cleaning all test the dichroic (transmits visible, reflects IR). A good protective layer keeps the metal from oxidizing, so the part holds > 90% visible transmit across IR reflect / visible pass for years rather than months — exactly what 3D Scanning & Structured Light equipment that ships to varied climates needs.

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.

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.

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.

Selecting a Hot Mirror for 3D Scanning & Structured Light starts with the wavelength and angle of incidence, then the acceptable loss. Match the dichroic (transmits visible, reflects IR) to IR reflect / visible pass, confirm > 90% visible transmit, and make sure the float or borosilicate glass and 1–3 mm fit the mount you already have. The spec and size tables make that comparison quick.

A Hot Mirror is tougher than it looks but softer than you think. Fingerprints on the dichroic (transmits visible, reflects IR) are the usual cause of field failures, so edge-handling and capped storage pay off. A little discipline keeps > 90% visible transmit where it belongs.

In short

For 3D Scanning & Structured Light, the Hot Mirror is less a commodity than a tuned component. Specify the band (IR reflect / visible pass), the reflectivity (> 90% visible transmit) and the figure (4–6λ), 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.