The document discusses the keratometer, an instrument used to measure the curvature of the cornea. It describes the keratometer's parts including the focusing knob, rotating grip, and measuring drums. The optical principle is that the cornea acts as a convex refracting surface and the keratometer uses the doubling principle to measure the corneal curvature. The document outlines the procedure for taking keratometry measurements, which involves adjusting the instrument height, focusing on the patient's eye, and reading the values from the measuring scales to determine the corneal curvature and astigmatism. Keratometry is important for contact lens fitting, evaluating keratoconus, and determining intraocular lens power for cataract surgery.
The document discusses the keratometer, an instrument used to measure the curvature of the cornea. It describes the keratometer's parts including the focusing knob, rotating grip, and measuring drums. The optical principle is that the cornea acts as a convex refracting surface and the keratometer uses the doubling principle to measure the corneal curvature. The document outlines the procedure for taking keratometry measurements, which involves adjusting the instrument height, focusing on the patient's eye, and reading the values from the measuring scales to determine the corneal curvature and astigmatism. Keratometry is important for contact lens fitting, evaluating keratoconus, and determining intraocular lens power for cataract surgery.
The document discusses lensometry, which is the process of using a lensometer or lensmeter to measure the optical properties of lenses. A lensometer projects lines that allow optometrists to determine information like the sphere, cylinder, and axis measurements specified in a prescription. It can also verify the accuracy of lenses and detect their type (spherical, astigmatic, prismatic). Lensometers are used to properly fit lenses into frames and ensure prescriptions are correct. The document outlines the history of the lensometer's invention and provides details on its use, parts, manual operation, and the measurements it can obtain for different lens types like bifocals.
Lenses bend light to form images, either converging or diverging. Convex lenses are thick in the middle and thin at the edges, converging light, while concave lenses are thin in the middle and thick at the edges, diverging light. Ray diagrams illustrate the path of light through lenses using lines representing rays and key points like the optical center, principal axis, focal points, and images. Images can be magnified or diminished, inverted or upright, and real or virtual depending on their position relative to the lens and focal points. Magnification is calculated by comparing the size of the image to the object.
1. The document describes various types of corrective lenses and how their power is measured using trial lenses, a lensometer, or focimeter.
2. A lensometer or focimeter uses targets, power dials, and axis dials to separately measure the sphere, cylinder, and axis of a lens.
3. Key steps involve focusing the instrument, centering the lens, and adjusting dials until target lines are clear, taking note of the power and axis readings.
Cylindrical lens, also called a cylinder, is an optical lens which focuses light on to a line instead of on to a point, as a spherical lens would. The curved face or faces of a cylindrical lens are sections of a cylinder, and focus the image passing through it onto a line parallel to the intersection of the surface of the lens and a plane tangent to it. The lens compresses the image in the direction perpendicular to this line, and leaves it unaltered in the direction parallel to it (in the tangent plane).
Cylindrical lenses are used to correct the output from diode lasers, to produce a round beam from the diode’s elliptical output. They are also applied in optical systems to correct the shape of laser beams, change image aspect ratios, and illuminate in the shape of line source.
Photonchina’s cylindrical lens is among top-level in terms of surface quality, irregularity and dimension tolerance. It also provides the high precision, special shapes and specifications designed by customers.
The degree to which a beam of light is deflected as it
passes through the lens depends on the focal and prismatic power of the lens and the distance from its optical centre.
Most of the times this study confused me...so, i just put some important points in one place to easily keep them in mind..hope it will help other students as well..and inform me, if a reader find anything new to improve it further.
The document discusses the standards of perimetry measurement including the three international standards of measurement, background illumination, spot intensity, size, duration and speed, and how threshold testing works by bracketing the minimum light level the eye can detect at different points on the retina. It also covers different types of perimetry tests and factors that determine the reliability of a visual field test results.
Snell's law describes how light refracts as it passes from one medium to another. It states that the ratio of the sines of the angles of incidence and refraction is equal to the ratio of the indexes of refraction of the two media. When light passes from air into glass, it bends toward the normal. Prisms can be stacked to approximate convex lenses. Converging lenses bring light rays to a focus while diverging lenses spread them out. Chromatic aberration occurs because different wavelengths of light are refracted differently, producing colored fringes around objects. This can be reduced using an achromatic lens made of two materials with different refractive indexes.
Binocular Indirect Ophthalmoscopy is known to provide a wider view of the inside of the eye. It is one of the most commonly used ophthalmic instrument.
Ultrasonography uses high frequency sound waves to generate images of the eye and orbit. It can be used to evaluate the anterior and posterior segments when the media is opaque, detect tumors, orbital disorders, and intraocular foreign bodies. A-scan provides axial length measurements, while B-scan produces two-dimensional images to assess conditions like retinal detachments, tumors, infections, and more. Proper probe positioning and interpretation of real-time gray scale images allow ultrasonography to evaluate a wide range of ocular and orbital pathologies in a non-invasive manner.
Refraction of light at spherical surfaces of lensesMukesh Tekwani
This document contains 15 important theory questions about refraction of light at spherical surfaces and lenses. It includes questions about sign convention in optics, the optical center of a lens, focal length of concave and convex lenses, lens maker's formula, derivation of expressions for refraction at single spherical surfaces and thin lens combinations, linear magnification by a lens, location of a virtual image formed by a convex lens based on focal length, dependence of focal length on wavelength, definition and unit of power of a lens, definition of 1 dioptre, formula for combined power of two lenses in contact, and laws governing image formation by lenses. The questions cover key concepts like derivation, definition, diagrams, formulas, and image formation.
The slit lamp biomicroscope allows high-powered, stereoscopic examination of the eye. It has two main components: an illumination system that produces a thin slit of light using the Kohler principle, and an observation system consisting of binocular microscopes. There are two common types - Zeiss and Haag Streit - which differ in the position of the light source. Various illumination techniques like diffuse, direct, retro-illumination and specular reflection are used to visualize different ocular structures. The slit lamp enables in-vivo examination of the anterior segment in 3D and is invaluable for diagnostic and surgical procedures.
This document provides an overview of geometric optics, including reflection, mirrors, refraction, and lenses. It discusses how light rays reflect off mirrors according to the law of reflection, forming real images with plane mirrors and virtual images with spherical mirrors, whether concave or convex. Concave mirrors bring parallel rays to a focus at their focal point, while convex mirrors cause parallel rays to appear to diverge from a virtual focal point.
This document provides an overview of geometric optics, including the ray model of light, reflection, refraction, and image formation using plane mirrors, spherical mirrors, and thin lenses. Key concepts covered include the types of images that can be formed (real or virtual), sign conventions, lateral magnification, focal points and lengths, and graphical methods for solving problems involving mirrors and lenses. Sample problems are worked through as examples.
The document discusses lensometry, which is the process of using a lensometer or lensmeter to measure the optical properties of lenses. A lensometer projects lines that allow optometrists to determine information like the sphere, cylinder, and axis measurements specified in a prescription. It can also verify the accuracy of lenses and detect their type (spherical, astigmatic, prismatic). Lensometers are used to properly fit lenses into frames and ensure prescriptions are correct. The document outlines the history of the lensometer's invention and provides details on its use, parts, manual operation, and the measurements it can obtain for different lens types like bifocals.
Lenses bend light to form images, either converging or diverging. Convex lenses are thick in the middle and thin at the edges, converging light, while concave lenses are thin in the middle and thick at the edges, diverging light. Ray diagrams illustrate the path of light through lenses using lines representing rays and key points like the optical center, principal axis, focal points, and images. Images can be magnified or diminished, inverted or upright, and real or virtual depending on their position relative to the lens and focal points. Magnification is calculated by comparing the size of the image to the object.
1. The document describes various types of corrective lenses and how their power is measured using trial lenses, a lensometer, or focimeter.
2. A lensometer or focimeter uses targets, power dials, and axis dials to separately measure the sphere, cylinder, and axis of a lens.
3. Key steps involve focusing the instrument, centering the lens, and adjusting dials until target lines are clear, taking note of the power and axis readings.
Cylindrical lens, also called a cylinder, is an optical lens which focuses light on to a line instead of on to a point, as a spherical lens would. The curved face or faces of a cylindrical lens are sections of a cylinder, and focus the image passing through it onto a line parallel to the intersection of the surface of the lens and a plane tangent to it. The lens compresses the image in the direction perpendicular to this line, and leaves it unaltered in the direction parallel to it (in the tangent plane).
Cylindrical lenses are used to correct the output from diode lasers, to produce a round beam from the diode’s elliptical output. They are also applied in optical systems to correct the shape of laser beams, change image aspect ratios, and illuminate in the shape of line source.
Photonchina’s cylindrical lens is among top-level in terms of surface quality, irregularity and dimension tolerance. It also provides the high precision, special shapes and specifications designed by customers.
The degree to which a beam of light is deflected as it
passes through the lens depends on the focal and prismatic power of the lens and the distance from its optical centre.
Most of the times this study confused me...so, i just put some important points in one place to easily keep them in mind..hope it will help other students as well..and inform me, if a reader find anything new to improve it further.
The document discusses the standards of perimetry measurement including the three international standards of measurement, background illumination, spot intensity, size, duration and speed, and how threshold testing works by bracketing the minimum light level the eye can detect at different points on the retina. It also covers different types of perimetry tests and factors that determine the reliability of a visual field test results.
Snell's law describes how light refracts as it passes from one medium to another. It states that the ratio of the sines of the angles of incidence and refraction is equal to the ratio of the indexes of refraction of the two media. When light passes from air into glass, it bends toward the normal. Prisms can be stacked to approximate convex lenses. Converging lenses bring light rays to a focus while diverging lenses spread them out. Chromatic aberration occurs because different wavelengths of light are refracted differently, producing colored fringes around objects. This can be reduced using an achromatic lens made of two materials with different refractive indexes.
Binocular Indirect Ophthalmoscopy is known to provide a wider view of the inside of the eye. It is one of the most commonly used ophthalmic instrument.
Ultrasonography uses high frequency sound waves to generate images of the eye and orbit. It can be used to evaluate the anterior and posterior segments when the media is opaque, detect tumors, orbital disorders, and intraocular foreign bodies. A-scan provides axial length measurements, while B-scan produces two-dimensional images to assess conditions like retinal detachments, tumors, infections, and more. Proper probe positioning and interpretation of real-time gray scale images allow ultrasonography to evaluate a wide range of ocular and orbital pathologies in a non-invasive manner.
Refraction of light at spherical surfaces of lensesMukesh Tekwani
This document contains 15 important theory questions about refraction of light at spherical surfaces and lenses. It includes questions about sign convention in optics, the optical center of a lens, focal length of concave and convex lenses, lens maker's formula, derivation of expressions for refraction at single spherical surfaces and thin lens combinations, linear magnification by a lens, location of a virtual image formed by a convex lens based on focal length, dependence of focal length on wavelength, definition and unit of power of a lens, definition of 1 dioptre, formula for combined power of two lenses in contact, and laws governing image formation by lenses. The questions cover key concepts like derivation, definition, diagrams, formulas, and image formation.
The slit lamp biomicroscope allows high-powered, stereoscopic examination of the eye. It has two main components: an illumination system that produces a thin slit of light using the Kohler principle, and an observation system consisting of binocular microscopes. There are two common types - Zeiss and Haag Streit - which differ in the position of the light source. Various illumination techniques like diffuse, direct, retro-illumination and specular reflection are used to visualize different ocular structures. The slit lamp enables in-vivo examination of the anterior segment in 3D and is invaluable for diagnostic and surgical procedures.
This document provides an overview of geometric optics, including reflection, mirrors, refraction, and lenses. It discusses how light rays reflect off mirrors according to the law of reflection, forming real images with plane mirrors and virtual images with spherical mirrors, whether concave or convex. Concave mirrors bring parallel rays to a focus at their focal point, while convex mirrors cause parallel rays to appear to diverge from a virtual focal point.
This document provides an overview of geometric optics, including the ray model of light, reflection, refraction, and image formation using plane mirrors, spherical mirrors, and thin lenses. Key concepts covered include the types of images that can be formed (real or virtual), sign conventions, lateral magnification, focal points and lengths, and graphical methods for solving problems involving mirrors and lenses. Sample problems are worked through as examples.
This document discusses Smith charts and impedance matching. It begins with an introduction to resonators, Q factor, and resonant bandwidth. It then covers basic impedance matching networks including L, T, and π networks. The document explains how to use Smith charts to represent LC circuits and perform impedance matching. It also discusses loaded Q versus unloaded Q and how to match impedances for different cases. Matching bandwidth is defined and conversions between series and parallel circuits are covered. The document provides an overview of important concepts regarding resonators, Q factor, impedance matching, and the use of Smith charts.
3. Outline
26-1 The reflection of light
26-2 Forming images with a plane mirror
26-3 Spherical mirrors
26-4 Ray tracing and the mirror equation
26-5 The refraction of light
26-6 Ray tracing for lenses
26-7 The thin-lens equation
26-8 Dispersion and the rainbow
4. Light Propagation: Observations…
Shadows (eclipses); Pinhole camera; Human vision, etc…
Solar eclipse: shadows produced by the hands and leaves…
5. The angle of
incidence is equal
to the angle of
reflection.
Incident ray,
reflected ray and
the normal to the
mirror are in the
same plane.
The Reflection of Light
qi=qr
6. Light Reflection in Everyday Life
For both specular
and diffuse reflection
surfaces the law of
reflection works
perfectly. However,
because of the surface
structure the results
of the reflection are
very different!
qi = qr
20. 面鏡公式(The Mirror Formula)- 高斯
式
¢ ¢
A B = OF =
f
AB FB p -
f
¢ ¢ ¢ - = =
A B B F q f
AB OF f
f q f
p f f
pq pf qf f f
qf pf pq
-
- - + =
+ =
Þ + =
2 2
= -
1 1 1
p q f
