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Optics
Optics is a science that studies the origin and propagation light, as well as the changes it experiences and produces. There are also other phenomena closely related to optics. There are two main branches to physical and geometrical. Physical optics focuses on the properties and nature of light. Geometrical optics deals with the principles that control the image-forming capabilities of mirrors and lenses. This also covers optical data processing. It involves manipulating the information content of images formed by coherent optical system. The term optics was originally used in reference to vision and the eye. As lenses and other devices to aid vision developed, they were called optical instruments. The meaning of optics was eventually expanded to include any light application, even though the ultimate receiver of light is not the eye, but a physical detector such as a photographic plate, or a television camera.
GEOMETRICAL OPTICS BASICS
Geometrical optics or ray optics describes light propagation using rays. Geometric optics uses the ray to approximate light propagation paths under certain conditions. Geometrical optics can be very simple or very complex. We mean that we can study it superficially so that we can create instruments roughly using rules that are so easy that they don't need to be dealt with here. Or, if we are interested in the details of lenses and other similar issues, it becomes too complicated to discuss here. It is a good idea to either read up on the subject, or to simply trace the rays through various surfaces using the law of reflection from one side to another. If they are forming a satisfactory image, it is advisable to analyze aberrations and find out the source.
HISTICAL BACKGROUND
The processes of image formation were a mystery to the ancients. There was much debate about vision for a long period. It was not clear if something moved from the object towards the eye, or if something reached out from it to the object. However, by the end of the 17th century it was well known that light rays travel in straight lines. Johannes Kepler, an English astronomer, wrote a book about optics in 1604. He suggested that an extended object could be considered a collection of points emitting light in all directions. Some of these rays would travel through a lens. They would then be bent around to meet a point. This point is where the rays originate. The eye's lens was no different than other lenses. It formed images of external objects on its retina, giving rise to the sensation of vision.
RESOLUTION and THE AIRY DISH
A well-corrected lens can be used to replace a pinhole. The geometrical ray divergence of the pinhole is eliminated by the lens's focusing action. In this case, the diffraction spreading is very small. A perfect lens creates an image of a point. This is made up of tiny rings of light that are concentric and gradually fainter around a central dot. The whole structure is called the Airy disc after George Biddell Airy who was an English astronomer who first described the phenomenon in 1834. An Airy disk in a practical lens has a small diameter. It is approximately equal to the f number of the lens in microns (0.001 meter). An f /4.5 lens's Airy disk measures approximately 0.0045 millimeter in size (ten times the wavelength blue light). If the eyepiece magnification of sufficient magnitude is adequate, however, you can still see the Airy disk created by a microscope objective or telescope.
GEOMETRICAL OPTICS BASICS
Geometrical optics or ray optics describes light propagation using rays. Geometric optics uses the ray to approximate light propagation paths under certain conditions. Geometrical optics can be very simple or very complex. We mean that we can study it superficially so that we can create instruments roughly using rules that are so easy that they don't need to be dealt with here. Or, if we are interested in the details of lenses and other similar issues, it becomes too complicated to discuss here. It is a good idea to either read up on the subject, or to simply trace the rays through various surfaces using the law of reflection from one side to another. If they are forming a satisfactory image, it is advisable to analyze aberrations and find out the source.
HISTICAL BACKGROUND
The processes of image formation were a mystery to the ancients. There was much debate about vision for a long period. It was not clear if something moved from the object towards the eye, or if something reached out from it to the object. However, by the end of the 17th century it was well known that light rays travel in straight lines. Johannes Kepler, an English astronomer, wrote a book about optics in 1604. He suggested that an extended object could be considered a collection of points emitting light in all directions. Some of these rays would travel through a lens. They would then be bent around to meet a point. This point is where the rays originate. The eye's lens was no different than other lenses. It formed images of external objects on its retina, giving rise to the sensation of vision.
RESOLUTION and THE AIRY DISH
A well-corrected lens can be used to replace a pinhole. The geometrical ray divergence of the pinhole is eliminated by the lens's focusing action. In this case, the diffraction spreading is very small. A perfect lens creates an image of a point. This is made up of tiny rings of light that are concentric and gradually fainter around a central dot. The whole structure is called the Airy disc after George Biddell Airy who was an English astronomer who first described the phenomenon in 1834. An Airy disk in a practical lens has a small diameter. It is approximately equal to the f number of the lens in microns (0.001 meter). An f /4.5 lens's Airy disk measures approximately 0.0045 millimeter in size (ten times the wavelength blue light). If the eyepiece magnification of sufficient magnitude is adequate, however, you can still see the Airy disk created by a microscope objective or telescope.
17 pages, Kindle Edition
Published December 6, 2021
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