A multifocal diffractive lens is a

diffractive optical element Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wav ...

(DOE) that allows a single incident

beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Radio beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially lo ...

to be focused simultaneously at several positions along the

propagation Propagation can refer to: *Chain propagation in a chemical reaction mechanism *Crack propagation, the growth of a crack during the fracture of materials *Propaganda, non-objective information used to further an agenda *Reproduction, and other forms ...

axis An axis (: axes) may refer to: Mathematics *A specific line (often a directed line) that plays an important role in some contexts. In particular: ** Coordinate axis of a coordinate system *** ''x''-axis, ''y''-axis, ''z''-axis, common names ...

Principle of operation

An incident

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...

beam is deflected by grooved

diffraction pattern Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wav ...

into axial diffraction orders along its

optical axis An optical axis is an imaginary line that passes through the geometrical center of an optical system such as a camera lens, microscope or telescopic sight. Lens elements often have rotational symmetry about the axis. The optical axis defines ...

. The foci appear around the

far field The near field and far field are regions of the electromagnetic (EM) field around an object, such as a transmitting antenna, or the result of radiation scattering off an object. Non-radiative ''near-field'' behaviors dominate close to the an ...

position. With an additional focusing lens, foci from multifocal lens will appear at certain distances from the focal point of the lens.

Theory

The multifocal spots location is a function of refractive

focal length The focal length of an Optics, optical system is a measure of how strongly the system converges or diverges light; it is the Multiplicative inverse, inverse of the system's optical power. A positive focal length indicates that a system Converge ...

''f''_Refractive and predetermined diffractive focal length ''f''_Diffractive The focal spot at the "zero" order refers to the refractive focal length of the lens being used. The distance between the focal spots can be described by the equation :

\frac  = \frac +\frac,\ \mathrm\ m = \pm 1, \pm 2, \pm 3...

, :where ''f_m'' is the focal length for the ''m''th diffractive order, :''f''_Refractive is the focal length of the refractive lens, and :''f''_Diffractive is the focal length of the diffractive lens.

Applications

Laser cutting Laser cutting is a technology that uses a laser to vaporize materials, resulting in a cut edge. While typically used for industrial manufacturing applications, it is now used by schools, small businesses, architecture, and hobbyists. Laser cutt ...

Laser drilling Laser drilling is the process of creating thru-holes, referred to as “popped” holes or “percussion drilled” holes, by repeatedly pulsing focused laser energy on a material. The diameter of these holes can be as small as 0.002” (~50 μm). ...

Microscopy Microscopy is the technical field of using microscopes to view subjects too small to be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of microscopy: optical mic ...

Ophthalmology Ophthalmology (, ) is the branch of medicine that deals with the diagnosis, treatment, and surgery of eye diseases and disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Following a ...

: Multifocal

contact lens Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic ...

es and multifocal intraocular lenses

External links

HOLOOR Application note for Multifocal Lenses

Beam Propagation through multifocal lens (Movie)

References

{{reflist Diffraction Lenses