For a symmetric all-dielectric filter on a non-absorbing substrate, used near normal incidence at low optical power, flipping the part does not change the transmitted spectrum. Transmittance through a non-absorbing multilayer is the same in both propagation directions at the same angle of incidence. Optical…
A filter described as “850 nm,” “550 nm longpass,” or “10 nm bandpass” is not fully specified by those nominal numbers alone. Real optical filters are manufactured and measured against an allowable range. A nominal 850 nm bandpass filter, for example, may require its actual…
A machine vision system may use an 850 nm or 940 nm LED, a monochrome camera with good near-infrared sensitivity, and stable exposure settings—yet still produce images whose contrast changes with factory lighting, sunlight, or reflections from nearby equipment. The problem is often not the…
A dichroic mirror is a wavelength-selective optical component designed to reflect one spectral region while transmitting another. Unlike a conventional mirror that is intended to reflect a broad wavelength range, a dichroic mirror uses a carefully designed multilayer dielectric coating to control how different wavelengths…
A ghost image in a beamsplitter is a second, weaker image formed by light that reached the detector along an unintended optical path inside the component. In the large majority of cases the path is a reflection from the second surface of a plate beamsplitter,…
A beamsplitter is often described simply as an optical component that divides one incident beam into transmitted and reflected paths. In an actual optical system, however, an important question comes first: Should the splitting behavior depend on polarization? That question separates two major categories: polarizing…
Edge steepness describes how quickly an optical filter transitions between its passband and its blocking region. It is measured as the wavelength interval between two defined reference points on the transition — for example between the 50% transmission point and the wavelength where transmission drops…
An ultra narrow bandpass filter is used when an optical system needs to transmit a tightly defined wavelength region while strongly attenuating light outside that region. Typical ultra narrow bandpass filter applications include laser-line cleanup, LiDAR and active optical sensing, selected fluorescence channels, analytical spectroscopy,…
Protected aluminum and enhanced aluminum start from the same vacuum-deposited aluminum film. The difference is what goes on top: protected aluminum adds a single dielectric overcoat that stops oxidation and makes the surface cleanable, with almost no change to the reflectance curve, while enhanced aluminum…
Choosing a narrow bandpass filter manufacturer comes down to three questions: can their coating process hold your center wavelength tolerance across the full clear aperture, do they measure the filter under your actual angle and cone conditions, and is the blocking specification real across your…
Choosing a ZnSe lens manufacturer comes down to three things you can actually verify: the grade and traceability of the chemical vapor deposition (CVD) zinc selenide blank, the measured bulk absorption at your operating wavelength, and whether the polishing and coating processes hold surface figure…
Searching for a custom optics manufacturer in China usually means the optical function is already known, a drawing exists, or a prototype needs to be converted into a repeatable production component. The difficult part is not finding a company that can make a lens, filter,…
