How does Fresnel zone plate work?
Unlike lenses or curved mirrors, zone plates use diffraction instead of refraction or reflection. A zone plate consists of a set of concentric rings, known as Fresnel zones, which alternate between being opaque and transparent. Light hitting the zone plate will diffract around the opaque zones.
How many Focii are there in a zone plate?
Zone plate has one focus whereas lens has multiple focii.
Which lens is used in zone plate?
circular lens
Zone plates behave in many respects like a circular lens with focusing behaviour which approximates that described by the thin lens formula 1/p +1/q = 1/f. The main difference is that a zone plate has different diffraction orders and therefore several focal spots.
Does zone plate behave like?
lens
zones, behaves like a lens which is simultaneously both converging and diverging. Improvements in the performance of such zone plates has recently led to some attention being given to their potential use as lenses in certain applications. of the zone plats and a hologram may be considered as a generalized zone plate.
What are the positive and negative zone plates?
(2) Positive zone plate : When odd zones are kept transparent to the light and even zones are made opaque, then it is called positive zone plate. (3) Negative zone plate : when even zones are kept transparent to light and odd zones are made opaque, then it is called negative zone plate.
Why a zone plate has multiple foci?
Zone plate has multiple foci For a fixed distance of the object, a lens produces only one image, where as a zone plate produces a number of images. In other words, it has multiple foci. It is because the number of half-period zones contained in an area depends upon the position of the screen.
What is the difference between Fresnel and Fraunhofer diffraction?
The basic difference between fresnel and Fraunhofer diffraction is that in Fresnel diffraction the source of light and screen is at a finite distance from the obstacle, while in Fraunhofer diffraction if the source of light and screen is at an infinite distance from the obstacle.
What is difference between zone plate and convex lens?
➢ A convex lens has only one focus while a zone plate has a number of foci. amplitude from successive zones will help each other and the intensity of the image approaches that for an equivalent lens.
Does zone plate have multiple foci?
What is half period zone plate?
The distance between wavefront and point P is OP = b. point O is called the ‘pole’ of the wavefront corresponding to P. To find resultant intensity at point P due to wavefront, we divide the wavefront into a concentric half period zone. These period zone are known as fresnel’s half period zone.
What is a Fresnel zone plate?
A Fresnel Zone Plate (ZP) is a circular diffraction grating, with radially varying line period such that the diffracted light forms a focal spot at some distance f from the ZP. In diffraction limited conditions, the size of the focal spot is equal to 1.22 * drn, where drn is the width of the outermost zone of the ZonePlate.
What is a Fresnel zone in a microscope?
A zone plate consists of a set of concentric rings, known as Fresnel zones, which alternate between being opaque and transparent. Light hitting the zone plate will diffract around the opaque zones. The zones can be spaced so that the diffracted light constructively interferes at the desired focus, creating an image there.
What is the focusing ability of zone plates?
The zone plate’s focusing ability is an extension of the Arago spot phenomenon caused by diffraction from an opaque disc. A zone plate consists of a set of concentric rings, known as Fresnel zones, which alternate between being opaque and transparent. Light hitting the zone plate will diffract around the opaque zones.
What is the difference between phase gratings and absorbance of Z-Zone plates?
Zone plates with absorbing gratings show about two times more absorption than zone plates using phase gratings. Additionally, light passing into unused orders is lost. The diffraction efficiency of a zone plate used in the m th diffraction order is defined as with the incoming intensity I0 and the intensity in the m th diffraction order Im.