Glossary: M

Magnesium Fluoride (MgF2)

BBAR coating with reflection minimized at one specified wavelength, typically 550nm. Retains good transmission throughout visible into the NIR.

Magneto-Rheological Finishing (MRF)

Deterministic process using a precise interferometrically documented sub aperture tool to correct waveform errors by selectively removing material under a controlled and predicted process. It provides high performance finishing in less time than standard polishing techniques because of its precise control of the removal location and high removal rate. 


Optical and imaging magnification is a ratio of image angular subtense to object angular subtense. Electronic, or linear, magnification is the ratio of monitor size to sensor size. For example, 13" monitors are between 38 and 39 times as large as ½" size format sensor cameras when comparing horizontal, vertical, or diagonal measures.

Marginal Ray

In geometric optics, the marginal ray of an optical system determines the paraxial image location, and hits the edge of all pupils in the optical system. Along with the chief ray, it describes the entire paraxial image.

  See also Paraxial Rays , Chief Ray

Meniscus Lens

A type of singlet lens with one convex (outwardly curved) surface and the other concave (inwardly curved). It has a positive focal length. Shows less aberrations compared to a plano-convex lens when used for infinite/finite conjugate imaging.


A technique for producing micron-size structures on surfaces by using short-wavelength light or electron beams.

Mid-Spatial Frequency (MSF) Errors

Deviations in the surface form of an optical surface relative to its ideal shape at higher spatial frequencies than Zernike polynomial aberrations but lower frequencies than surface roughness. The mid-spatial frequency range is defined somewhat ambiguously as the region which causes optical blur or image degradation in optical systems. These errors must be controlled for during optical manufacturing, particularly when fabricating aspheric lenses.


Unit of measurement equal to 10-3 inches (0.001") or 0.0254 mm. 

Minimum Sensitivity

The minimum level of illumination required to produce a full video signal from a camera, expressed as luminous flux per unit area (lux or footcandles) through a specified imaging lens.

  See also Lux , Luminous Flux , Footcandle

Modulation Bandwidth

The pulse bandwidth of a modulatable laser. 

  See also Laser

Modulation Frequency

Rate at which optical radiation or a signal is varied through the use of a mechanical or electronic chopper, also called chopping frequency.

Modulation Transfer Function (MTF)

A measure of contrast as a function of spatial frequency. Defined as 100% at zero-frequency, MTF continuously declines with increasing spatial frequency to zero contrast at a theoretical maximum resolution frequency defined by the diffraction limit of the optical system.

Moment Load

The forces that are offset (cantilevered) from the bearing centers of mechanical components producing uneven loading on the bearings. Uneven loading means that some bearings are supporting more of the load than others. Moment forces are categorized by the direction in which they act: pitch, roll or yaw. When loading results in moments acting in only one of the moment directions, it is called a single direction moment. If it is in more than one direction, it is referred to as compound moment loading.

  See also Normal Load Capacity , Yaw , Roll , Pitch


Refers to one specific wavelength or color.

  See also Polychromatic

Monochrome Sensor

A camera sensor that outputs grayscale images. It is ideal for machine vision applications due to the absence of Bayer pattern color filters which reduce sensitivity and spatial resolution. 

  See also Color Sensor

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