describes the intensity distribution of electromagnetic radiation versus the wavelength. The area of interest for industrial photometry comprises light waves, i.e. visible light, ultraviolet light and infrared light. A prism- or grid-generated spectrum is able to visualize the spectral colors of selected light, including anything from short-wave violet to blue, green, yellow, orange and onto long-wave red light.

occurs when a previously straight beam of light is deflected from its path by an obstacle in an otherwise homogeneous optical medium, which results in a change of optical properties. This physical process is called scattering of light at particles. Light scattering gives rise to opaqueness.

are inhomogeneities of small spatial extent, typically appearing as thread-like or cord-like zones inside a glass volume. These can be visually perceived due to their refractive index that differs from that of the surrounding material. They are marked in accordance with ISO 10110 standard requirements.

is a synthetic fused silica type from Heraeus Quarzglas GmbH.

Small imperfections within the critical optical area caused by improper handling during or after the manufacturing process, for example, scratches, digs or surface spots that lack final finish-polish quality on the glass surface. They are marked in accordance with ISO 10110 standard requirements.

refers to the profile of an optical surface und provides a global statistical feature.