Diffraction is the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi coined the word diffraction and was the first to record accurate observations of the phenomenon in 1660.
A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. Lenses are made from materials such as glass or plastic and are ground, polished, or molded to the required shape. A lens can focus light to form an image, unlike a prism, which refracts light without focusing. Devices that similarly focus or disperse waves and radiation other than visible light are also called "lenses", such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses.
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.
Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution. It is used in optics applied to light waves, in antenna theory applied to radio waves, and in acoustics applied to sound waves. The colloquial use of the term "resolution" sometimes causes confusion; when an optical system is said to have a high resolution or high angular resolution, it means that the perceived distance, or actual angular distance, between resolved neighboring objects is small. The value that quantifies this property, θ, which is given by the Rayleigh criterion, is low for a system with a high resolution. The closely related term spatial resolution refers to the precision of a measurement with respect to space, which is directly connected to angular resolution in imaging instruments. The Rayleigh criterion shows that the minimum angular spread that can be resolved by an image forming system is limited by diffraction to the ratio of the wavelength of the waves to the aperture width. For this reason, high resolution imaging systems such as astronomical telescopes, long distance telephoto camera lenses and radio telescopes have large apertures.
An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electronic image sensors.
The field of view (FOV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation.
Fourier optics is the study of classical optics using Fourier transforms (FTs), in which the waveform being considered is regarded as made up of a combination, or superposition, of plane waves. It has some parallels to the Huygens–Fresnel principle, in which the wavefront is regarded as being made up of a combination of spherical wavefronts whose sum is the wavefront being studied. A key difference is that Fourier optics considers the plane waves to be natural modes of the propagation medium, as opposed to Huygens–Fresnel, where the spherical waves originate in the physical medium.
The resolution of an optical imaging system – a microscope, telescope, or camera – can be limited by factors such as imperfections in the lenses or misalignment. However, there is a principal limit to the resolution of any optical system, due to the physics of diffraction. An optical system with resolution performance at the instrument's theoretical limit is said to be diffraction-limited.
In optics, the Airy disk and Airy pattern are descriptions of the best-focused spot of light that a perfect lens with a circular aperture can make, limited by the diffraction of light. The Airy disk is of importance in physics, optics, and astronomy.
Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one, it refers to a reduction in size, sometimes called magnification or de-magnification.
In optics, the Fraunhofer diffraction equation is used to model the diffraction of waves when plane waves are incident on a diffracting object, and the diffraction pattern is viewed at a sufficiently long distance from the object, and also when it is viewed at the focal plane of an imaging lens. In contrast, the diffraction pattern created near the diffracting object and is given by the Fresnel diffraction equation.
An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings it to focus creating an image. The eyepiece is placed near the focal point of the objective to magnify this image. The amount of magnification depends on the focal length of the eyepiece.
The ring-imaging Cherenkov, or RICH, detector is a device for identifying the type of an electrically charged subatomic particle of known momentum, that traverses a transparent refractive medium, by measurement of the presence and characteristics of the Cherenkov radiation emitted during that traversal. RICH detectors were first developed in the 1980s and are used in high energy elementary particle-, nuclear- and astro-physics experiments.
Optical resolution describes the ability of an imaging system to resolve detail, in the object that is being imaged.
The small-angle approximations can be used to approximate the values of the main trigonometric functions, provided that the angle in question is small and is measured in radians:
Rotation around a fixed axis is a special case of rotational motion around a axis of rotation fixed, stationary, or static in three-dimensional space. This type of motion excludes the possibility of the instantaneous axis of rotation changing its orientation and cannot describe such phenomena as wobbling or precession. According to Euler's rotation theorem, simultaneous rotation along a number of stationary axes at the same time is impossible; if two rotations are forced at the same time, a new axis of rotation will result.
Angular distance or angular separation, also known as apparent distance or apparent separation, denoted , is the angle between the two sightlines, or between two point objects as viewed from an observer.
Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph (FGS-NIRISS) is an instrument on the James Webb Space Telescope (JWST) that combines a Fine Guidance Sensor and a science instrument, a near-infrared imager and a spectrograph. The FGS/NIRISS was designed by the Canadian Space Agency (CSA) and built by Honeywell as part of an international project to build a large infrared space telescope with the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). FGS-NIRISS observes light from the wavelengths of 0.8 to 5.0 microns. The instrument has four different observing modes.
NIRCam is an instrument aboard the James Webb Space Telescope. It has two major tasks, as an imager from 0.6 to 5 micron wavelength, and as a wavefront sensor to keep the 18-section mirrors functioning as one. In other words, it is a camera and is also used to provide information to align the 18 segments of the primary mirror. It is an infrared camera with ten mercury-cadmium-telluride (HgCdTe) detector arrays, and each array has an array of 2048×2048 pixels. The camera has a field of view of 2.2×2.2 arc minutes with an angular resolution of 0.07 arcsec at 2 microns. NIRCam is also equipped with coronagraphs, which helps to collect data on exoplanets near stars. It helps with imaging anything next to a much brighter object, because the coronagraph blocks that light.
MIRI, or the Mid-Infrared Instrument, is an instrument on the James Webb Space Telescope. MIRI is a camera and a spectrograph that observes mid to long infrared radiation from 5 to 28 microns. It also has coronagraphs, especially for observing exoplanets. Whereas most of the other instruments on Webb can see from the start of near infrared, or even as short as orange visible light, MIRI can see longer wavelength light.
