This document provides an introduction to geometric optics, including reflection, refraction, lenses, and ray tracing. It covers the basic laws and principles of reflection, including the law of reflection which states that the angle of incidence equals the angle of reflection. It also discusses refraction, including Snell's law, total internal reflection, and the use of lenses and curved mirrors to focus light. Key concepts are explained through diagrams tracing the paths of rays reflecting and refracting off surfaces. Examples of optical systems like telescopes and the Cassegrain telescope are also summarized.
This document provides information on various lens surface coatings and their types and purposes. It discusses why coatings are applied, including for protection, appearance, clarity and to prevent fogging. It then describes common coating types like MAR coating, tints, scratch resistant coating, mirror coating, polarized coating and edge coatings. It goes on to explain uncoated lenses, single side coated lenses, hard coatings, hydrophobic/oleophobic coatings, anti-reflection coatings, scratch resistance coatings, clean coats, drive safe coats and coatings that provide protection from blue light. The document provides details on how each of these coating types work and their benefits.
How spectacle lenses are made.
In this section you will get the information about lens manufacturing (part 1),i.e, how lens blanks are manufactured and in lens surfacing (part 2) you will get the information about how lenses are surfaced and a finished lens is manufactured.
The document describes the various types of bifocals that have been developed over time, including Benjamin Franklin's original design from 1785, solid upcurve bifocals, cemented bifocals, fused Kryptok bifocals, straight top or "D" bifocals, Ultex bifocals, and executive bifocals. Each type is explained in terms of its design, advantages, and disadvantages for the wearer.
This document contains questions and answers related to vision and eye health. It addresses topics like:
- The type of phoria that has more esophoria for distance than near fixation
- Where physiologic diplopia is manifest
- An example of a monocular clue excepted
- How exophoria can be corrected
- What occlusion is a treatment for
- What the TNO random test is for
The document discusses the base curve of lenses, which is the surface curve that forms the starting point for the remaining lens curve. It describes the importance of selecting the proper base curve, as it determines lens thickness, aberrations, and cosmetics. The document outlines different lens forms including Wollaston, Oswalt, and meniscus, discussing their optical properties. It notes that the best lens form follows mechanical and optical criteria, providing a thinner lens that is lighter in weight with reduced magnification and aberrations.
The document discusses the history and process of manufacturing glass and lenses. It provides details on:
1) Glassmaking has been traced back to 3500 BC based on the oldest glass beads, though its discovery is unknown. Glass was initially used for jewelry before being made into art objects in 16th century BC.
2) When heated to high temperatures, sand melts and becomes glass through a molecular structure change.
3) Lens manufacturing involves measuring a patient's prescription, selecting frames, grinding lenses to the correct optical power, and fitting lenses into frames through processes like cutting, edging and mounting.
4) Resin and glass are the two main materials used for ophthalmic lenses.
This document discusses astigmatic lenses, which have non-uniform curvature across their surface resulting in different focal lengths in different meridians. There are two main types: cylindrical lenses, which have one curved and one plane surface, and toric lenses, which are a spherical lens combined with a cylindrical lens. Cylindrical lenses form a line image rather than a point, while toric lenses exhibit rotational movement when tested. The power of astigmatic lenses is measured and expressed based on the spherical and cylindrical components as well as the axis orientation.
The document discusses different measurement systems used for eyeglasses, including the datum system and boxing system. It provides definitions for key optical and frame measurements such as:
- Eye size and lens size refer to the horizontal length of the lens or frame opening.
- Geometric center is the midpoint of the horizontal midline between the lens borders.
- Effective diameter is twice the distance from the geometric center to the lens bevel edge.
- Bridge size is the distance between the two lenses at the narrowest point of the frame.
- Segment height specifies the vertical distance of bifocal or progressive addition lenses.
This document provides information on various lens surface coatings and their types and purposes. It discusses why coatings are applied, including for protection, appearance, clarity and to prevent fogging. It then describes common coating types like MAR coating, tints, scratch resistant coating, mirror coating, polarized coating and edge coatings. It goes on to explain uncoated lenses, single side coated lenses, hard coatings, hydrophobic/oleophobic coatings, anti-reflection coatings, scratch resistance coatings, clean coats, drive safe coats and coatings that provide protection from blue light. The document provides details on how each of these coating types work and their benefits.
How spectacle lenses are made.
In this section you will get the information about lens manufacturing (part 1),i.e, how lens blanks are manufactured and in lens surfacing (part 2) you will get the information about how lenses are surfaced and a finished lens is manufactured.
The document describes the various types of bifocals that have been developed over time, including Benjamin Franklin's original design from 1785, solid upcurve bifocals, cemented bifocals, fused Kryptok bifocals, straight top or "D" bifocals, Ultex bifocals, and executive bifocals. Each type is explained in terms of its design, advantages, and disadvantages for the wearer.
This document contains questions and answers related to vision and eye health. It addresses topics like:
- The type of phoria that has more esophoria for distance than near fixation
- Where physiologic diplopia is manifest
- An example of a monocular clue excepted
- How exophoria can be corrected
- What occlusion is a treatment for
- What the TNO random test is for
The document discusses the base curve of lenses, which is the surface curve that forms the starting point for the remaining lens curve. It describes the importance of selecting the proper base curve, as it determines lens thickness, aberrations, and cosmetics. The document outlines different lens forms including Wollaston, Oswalt, and meniscus, discussing their optical properties. It notes that the best lens form follows mechanical and optical criteria, providing a thinner lens that is lighter in weight with reduced magnification and aberrations.
The document discusses the history and process of manufacturing glass and lenses. It provides details on:
1) Glassmaking has been traced back to 3500 BC based on the oldest glass beads, though its discovery is unknown. Glass was initially used for jewelry before being made into art objects in 16th century BC.
2) When heated to high temperatures, sand melts and becomes glass through a molecular structure change.
3) Lens manufacturing involves measuring a patient's prescription, selecting frames, grinding lenses to the correct optical power, and fitting lenses into frames through processes like cutting, edging and mounting.
4) Resin and glass are the two main materials used for ophthalmic lenses.
This document discusses astigmatic lenses, which have non-uniform curvature across their surface resulting in different focal lengths in different meridians. There are two main types: cylindrical lenses, which have one curved and one plane surface, and toric lenses, which are a spherical lens combined with a cylindrical lens. Cylindrical lenses form a line image rather than a point, while toric lenses exhibit rotational movement when tested. The power of astigmatic lenses is measured and expressed based on the spherical and cylindrical components as well as the axis orientation.
The document discusses different measurement systems used for eyeglasses, including the datum system and boxing system. It provides definitions for key optical and frame measurements such as:
- Eye size and lens size refer to the horizontal length of the lens or frame opening.
- Geometric center is the midpoint of the horizontal midline between the lens borders.
- Effective diameter is twice the distance from the geometric center to the lens bevel edge.
- Bridge size is the distance between the two lenses at the narrowest point of the frame.
- Segment height specifies the vertical distance of bifocal or progressive addition lenses.
Real subjective refraction in astigmatismBipin Koirala
1) The document discusses subjective refraction techniques for astigmatism, including determining the spherical and cylindrical corrections.
2) Key steps include controlling accommodation, finding the monocular best sphere using VA or bichrome tests, and determining the cylindrical component using fogging with targets like clock dials or Jackson cross cylinders.
3) The axis of the cylindrical correction must match the axis of the patient's astigmatism to fully correct their refractive error.
Bifocals are lenses with two optical powers, one for distance and one for near. There are several types of bifocal segments including round, flat top, curve top, ribbon, and Franklin style. Bifocals can be made through fused, one piece, or cemented constructions. When measuring for bifocals, the frame is positioned as it will be worn and the bifocal height is measured from the lower limbus or lid margin using a vertical ruler. This ensures the bifocal segment will be at the proper height for the wearer.
The document provides an overview of optical dispensing. It discusses defining optical dispensing and the steps involved, including frame selection based on facial shape, frame measurements, lens measurements, counseling patients on lens materials and coatings, and the process of fitting lenses into frames which involves marking, cutting, and edging lenses.
progressive addition lenses- optics, designs and performancessabina paudel
Progressive addition lenses (PALs) gradually increase power from the distance to the near zone to provide clear vision at all distances without visible lines. PALs come in various designs like hard and soft to suit patients' needs. Factors like unwanted astigmatism, prism, and binocular vision must be considered for optimal performance. PAL selection depends on lifestyle, occupation, and adaptation needs. They are generally suitable for most presbyopes but some may prefer other options due to visual or physical factors.
Bifocal lenses have two optical powers, one for distance vision and one for near vision. They are useful for presbyopia. There are several types of bifocal lenses including round, flat-top, and executive styles. Benjamin Franklin is credited with inventing the first bifocal lens in the late 18th century by cutting a single lens in half. Modern bifocals are manufactured using various techniques like fusing, cementing, or making from a single piece of plastic or glass. Proper positioning and design of the near segment is important to reduce issues like image jump and chromatic aberration. Bifocals come in many styles and materials to best suit individual needs and prescription requirements.
Detailed instumentaion and use of manual Lensometer and just a outline of automated lensometer.
I have used the picture of manual lensometer with out the parts describtion because i have explained orally by showing the picture..
Hope u all like it and may help you in learning better. :)
Keratometry is a technique used to measure the curvature of the anterior surface of the cornea. It works by reflecting light off the cornea's convex surface and measuring the size of the reflected image to calculate the radius of curvature. The cornea acts as a convex mirror. Keratometry is important for assessing corneal astigmatism, estimating refractive error, monitoring conditions like keratoconus, and calculating intraocular lens power. Factors like improper calibration, positioning, focusing, or corneal irregularities can introduce errors in keratometry measurements.
Plane polarized light occurs when light is reflected off smooth, non-diffusing surfaces like water and snow. Polarizing filters absorb this plane polarized light, reducing glare. Modern polarizing filters are made by stretching polyvinyl alcohol sheets and dipping them in iodine, aligning the molecules. Polarizing lenses have benefits like reducing driving fatigue and enabling fishermen to see below water surfaces more clearly. They also don't bleach colors and reduce blinding from bright snow like regular sunglasses.
This document discusses frame adjustment and quality checking. It describes 7 off-face adjustments including x-ing, temple spread, pantoscopic angle, temple fold angle, pad angles, face form, and 4-point touch. It also discusses 7 on-face adjustments including horizontal alignment, vertex distance, frame height, segment height, temple bend, pad contact, and skin/lash clearance. Key details are provided about properly adjusting specific angles and alignments during the fitting process.
This document describes different types of lenses:
1. Convex lenses include equiconvex, biconvex, and planoconvex lenses. Concave lenses include equiconcave, biconcave, and planoconcave lenses.
2. Periscopic lenses have one surface with positive power and one with negative power.
3. Meniscus lenses also have one positively powered surface and one negatively powered surface, but with a greater base curve than periscopic lenses.
This document summarizes guidelines for dispensing progressive lenses. It identifies the best candidates as previous progressive lens wearers, emerging presbyopes with low add powers, and highly motivated individuals. It notes that previous bifocal wearers and those with occulomotor imbalances may require consideration. The document outlines the procedure for fitting progressive lenses, which includes selecting a frame, pre-adjusting it, measuring the fitting height and PD, verifying the cut-out, and taking free form measurements. It provides tips for selecting an appropriate frame, including ones that maintain adjustment and avoid large styles that expose the wearer to distortions.
Astigmatic lens used in ophthalmology and eyeRACHANA KAFLE
different types and classifications of astigmatic lens used
availability of astigmatic lens
uses of astigmatic lens
advantages and disadvantages of astigmatic lens
Cellulose acetate, nylon, and titanium are common materials used for eyeglass frames. Cellulose acetate is lightweight but can cause allergic reactions. Nylon is strong, flexible, and hypoallergenic. Titanium is very lightweight and strong, resistant to corrosion, and hypoallergenic, but more expensive than other materials. Other materials used include aluminum, stainless steel, gold, and plastic materials like polycarbonate. The ideal frame material is lightweight, strong, resistant to corrosion and breakage, non-flammable, inexpensive, durable, adjustable, and non-allergic.
This document discusses methods of measuring lens power, including trial lens hand neutralization and lensometry. Trial lens hand neutralization involves using trial lenses to neutralize an unknown lens and estimate its power. It is less accurate than a lensometer. A lensometer more precisely measures front or back vertex power by neutralizing an unknown lens against a standard lens and moving a target until lines focus. It can measure spherical and cylindrical powers, including axes. Multifocal lenses require measuring front vertex powers of distance and near portions.
The document discusses Fresnel lenses and prisms. It describes how Fresnel prisms are thinner than conventional ophthalmic prisms but can provide the same optical power due to their array of small angular grooves. The document outlines several medical indications for using Fresnel lenses, including for the treatment of phorias, strabismus, nystagmus, and diplopia. It provides guidance on selecting, applying, cleaning, and caring for Fresnel lenses.
This document discusses aspheric lenses. It begins with a brief history of aspheric lens development from 1909 to 1980. It then covers terminology, the introduction of aspheric lenses which aim to reduce optical aberrations compared to spherical lenses. The document discusses various aspheric lens designs and how they can reduce peripheral aberrations and make lenses thinner. It also covers measuring aspheric lenses, uses of aspheric lenses, and benefits such as reduction of oblique astigmatism and thinner lens designs.
This document discusses methods for detecting the type and power of lenses. It covers hand neutralization techniques for spherical and astigmatic lenses using convex and concave lenses. It also describes using a Geneva lens measure and manual and automated focimeters. The manual focimeter involves aligning mires to determine spherical and cylinder power of single vision, bifocal, trifocal and progressive lenses. The automated focimeter uses a light beam to precisely measure lens parameters. Both tools have limitations, with the automated version providing more accuracy.
The optical center of a lens is the point where light rays pass through without deviation. It is important for the optical center to be directly in front of the pupil for optimum vision. Decentering a lens, or moving it so the optical center is no longer in front of the pupil, introduces a prismatic effect. The amount of prismatic effect, measured in prism diopters, is calculated by multiplying the distance the lens is decentered in centimeters by the lens power in diopters. Decentering a lens with a spherical prescription or cylinder introduces different prismatic effects depending on the orientation of the cylinder axis relative to the direction of decentration.
1) The document describes principles of reflection, refraction, and lenses. It explains that reflection follows the law that the angle of incidence equals the angle of reflection, and refraction follows Snell's law.
2) Curved mirrors and lenses bend light according to the same principles as flat surfaces, using local surface normals. Parabolic mirrors focus light to a precise point due to their shape.
3) Lenses can form real or virtual images, depending on the position of the object relative to the focal length. The lensmaker's formula relates the focal length to the lens's refractive index and radii of curvature.
This document discusses optics concepts including reflection, refraction, and optical systems. It begins by explaining the law of reflection - that the angle of incidence equals the angle of reflection. It then discusses refraction and how light bends when passing from one medium to another with a different refractive index. It provides Snell's law to describe this quantitatively. Finally, it discusses lenses and how curved lenses can focus light due to the refraction that occurs at each surface, relating this to the eye and camera systems.
Real subjective refraction in astigmatismBipin Koirala
1) The document discusses subjective refraction techniques for astigmatism, including determining the spherical and cylindrical corrections.
2) Key steps include controlling accommodation, finding the monocular best sphere using VA or bichrome tests, and determining the cylindrical component using fogging with targets like clock dials or Jackson cross cylinders.
3) The axis of the cylindrical correction must match the axis of the patient's astigmatism to fully correct their refractive error.
Bifocals are lenses with two optical powers, one for distance and one for near. There are several types of bifocal segments including round, flat top, curve top, ribbon, and Franklin style. Bifocals can be made through fused, one piece, or cemented constructions. When measuring for bifocals, the frame is positioned as it will be worn and the bifocal height is measured from the lower limbus or lid margin using a vertical ruler. This ensures the bifocal segment will be at the proper height for the wearer.
The document provides an overview of optical dispensing. It discusses defining optical dispensing and the steps involved, including frame selection based on facial shape, frame measurements, lens measurements, counseling patients on lens materials and coatings, and the process of fitting lenses into frames which involves marking, cutting, and edging lenses.
progressive addition lenses- optics, designs and performancessabina paudel
Progressive addition lenses (PALs) gradually increase power from the distance to the near zone to provide clear vision at all distances without visible lines. PALs come in various designs like hard and soft to suit patients' needs. Factors like unwanted astigmatism, prism, and binocular vision must be considered for optimal performance. PAL selection depends on lifestyle, occupation, and adaptation needs. They are generally suitable for most presbyopes but some may prefer other options due to visual or physical factors.
Bifocal lenses have two optical powers, one for distance vision and one for near vision. They are useful for presbyopia. There are several types of bifocal lenses including round, flat-top, and executive styles. Benjamin Franklin is credited with inventing the first bifocal lens in the late 18th century by cutting a single lens in half. Modern bifocals are manufactured using various techniques like fusing, cementing, or making from a single piece of plastic or glass. Proper positioning and design of the near segment is important to reduce issues like image jump and chromatic aberration. Bifocals come in many styles and materials to best suit individual needs and prescription requirements.
Detailed instumentaion and use of manual Lensometer and just a outline of automated lensometer.
I have used the picture of manual lensometer with out the parts describtion because i have explained orally by showing the picture..
Hope u all like it and may help you in learning better. :)
Keratometry is a technique used to measure the curvature of the anterior surface of the cornea. It works by reflecting light off the cornea's convex surface and measuring the size of the reflected image to calculate the radius of curvature. The cornea acts as a convex mirror. Keratometry is important for assessing corneal astigmatism, estimating refractive error, monitoring conditions like keratoconus, and calculating intraocular lens power. Factors like improper calibration, positioning, focusing, or corneal irregularities can introduce errors in keratometry measurements.
Plane polarized light occurs when light is reflected off smooth, non-diffusing surfaces like water and snow. Polarizing filters absorb this plane polarized light, reducing glare. Modern polarizing filters are made by stretching polyvinyl alcohol sheets and dipping them in iodine, aligning the molecules. Polarizing lenses have benefits like reducing driving fatigue and enabling fishermen to see below water surfaces more clearly. They also don't bleach colors and reduce blinding from bright snow like regular sunglasses.
This document discusses frame adjustment and quality checking. It describes 7 off-face adjustments including x-ing, temple spread, pantoscopic angle, temple fold angle, pad angles, face form, and 4-point touch. It also discusses 7 on-face adjustments including horizontal alignment, vertex distance, frame height, segment height, temple bend, pad contact, and skin/lash clearance. Key details are provided about properly adjusting specific angles and alignments during the fitting process.
This document describes different types of lenses:
1. Convex lenses include equiconvex, biconvex, and planoconvex lenses. Concave lenses include equiconcave, biconcave, and planoconcave lenses.
2. Periscopic lenses have one surface with positive power and one with negative power.
3. Meniscus lenses also have one positively powered surface and one negatively powered surface, but with a greater base curve than periscopic lenses.
This document summarizes guidelines for dispensing progressive lenses. It identifies the best candidates as previous progressive lens wearers, emerging presbyopes with low add powers, and highly motivated individuals. It notes that previous bifocal wearers and those with occulomotor imbalances may require consideration. The document outlines the procedure for fitting progressive lenses, which includes selecting a frame, pre-adjusting it, measuring the fitting height and PD, verifying the cut-out, and taking free form measurements. It provides tips for selecting an appropriate frame, including ones that maintain adjustment and avoid large styles that expose the wearer to distortions.
Astigmatic lens used in ophthalmology and eyeRACHANA KAFLE
different types and classifications of astigmatic lens used
availability of astigmatic lens
uses of astigmatic lens
advantages and disadvantages of astigmatic lens
Cellulose acetate, nylon, and titanium are common materials used for eyeglass frames. Cellulose acetate is lightweight but can cause allergic reactions. Nylon is strong, flexible, and hypoallergenic. Titanium is very lightweight and strong, resistant to corrosion, and hypoallergenic, but more expensive than other materials. Other materials used include aluminum, stainless steel, gold, and plastic materials like polycarbonate. The ideal frame material is lightweight, strong, resistant to corrosion and breakage, non-flammable, inexpensive, durable, adjustable, and non-allergic.
This document discusses methods of measuring lens power, including trial lens hand neutralization and lensometry. Trial lens hand neutralization involves using trial lenses to neutralize an unknown lens and estimate its power. It is less accurate than a lensometer. A lensometer more precisely measures front or back vertex power by neutralizing an unknown lens against a standard lens and moving a target until lines focus. It can measure spherical and cylindrical powers, including axes. Multifocal lenses require measuring front vertex powers of distance and near portions.
The document discusses Fresnel lenses and prisms. It describes how Fresnel prisms are thinner than conventional ophthalmic prisms but can provide the same optical power due to their array of small angular grooves. The document outlines several medical indications for using Fresnel lenses, including for the treatment of phorias, strabismus, nystagmus, and diplopia. It provides guidance on selecting, applying, cleaning, and caring for Fresnel lenses.
This document discusses aspheric lenses. It begins with a brief history of aspheric lens development from 1909 to 1980. It then covers terminology, the introduction of aspheric lenses which aim to reduce optical aberrations compared to spherical lenses. The document discusses various aspheric lens designs and how they can reduce peripheral aberrations and make lenses thinner. It also covers measuring aspheric lenses, uses of aspheric lenses, and benefits such as reduction of oblique astigmatism and thinner lens designs.
This document discusses methods for detecting the type and power of lenses. It covers hand neutralization techniques for spherical and astigmatic lenses using convex and concave lenses. It also describes using a Geneva lens measure and manual and automated focimeters. The manual focimeter involves aligning mires to determine spherical and cylinder power of single vision, bifocal, trifocal and progressive lenses. The automated focimeter uses a light beam to precisely measure lens parameters. Both tools have limitations, with the automated version providing more accuracy.
The optical center of a lens is the point where light rays pass through without deviation. It is important for the optical center to be directly in front of the pupil for optimum vision. Decentering a lens, or moving it so the optical center is no longer in front of the pupil, introduces a prismatic effect. The amount of prismatic effect, measured in prism diopters, is calculated by multiplying the distance the lens is decentered in centimeters by the lens power in diopters. Decentering a lens with a spherical prescription or cylinder introduces different prismatic effects depending on the orientation of the cylinder axis relative to the direction of decentration.
1) The document describes principles of reflection, refraction, and lenses. It explains that reflection follows the law that the angle of incidence equals the angle of reflection, and refraction follows Snell's law.
2) Curved mirrors and lenses bend light according to the same principles as flat surfaces, using local surface normals. Parabolic mirrors focus light to a precise point due to their shape.
3) Lenses can form real or virtual images, depending on the position of the object relative to the focal length. The lensmaker's formula relates the focal length to the lens's refractive index and radii of curvature.
This document discusses optics concepts including reflection, refraction, and optical systems. It begins by explaining the law of reflection - that the angle of incidence equals the angle of reflection. It then discusses refraction and how light bends when passing from one medium to another with a different refractive index. It provides Snell's law to describe this quantitatively. Finally, it discusses lenses and how curved lenses can focus light due to the refraction that occurs at each surface, relating this to the eye and camera systems.
This document discusses optics concepts including reflection, refraction, and optical systems. It begins by explaining the law of reflection - that the angle of incidence equals the angle of reflection. It then discusses refraction and how light bends when passing from one medium to another with a different refractive index. It provides Snell's law to describe this quantitatively. Finally, it discusses lenses and how curved lenses can focus light due to the refraction that occurs at each surface, relating this to the eye and camera systems.
This document discusses optics concepts including reflection, refraction, and optical systems. It begins by explaining the law of reflection - that the angle of incidence equals the angle of reflection. It then discusses refraction and how light bends when passing from one medium to another with a different refractive index. It provides Snell's law to describe this quantitatively. Finally, it discusses applications of these principles like lenses, cameras, the eye, and total internal reflection.
Step by step procedure in doing Ray Tracing Diagram for Plane Mirrors, Curved Mirrors, and Lenses. Bonus: Corrective Lens and Optical Devices are included in the presentation as well. Enjoy!
This document provides information about optical components and their properties. It discusses plane and spherical surfaces, Snell's law, and thin lenses. The key points are:
1) It defines optical terms like object and image conventions, focal length conventions, and radius of curvature conventions.
2) It explains how to model optical components like plane and spherical surfaces, thin lenses, and thick lenses using matrix methods. The matrix for a single component can be derived and components can be combined by multiplying their matrices.
3) Examples are given for calculating properties of simple lens systems like a thin lens in air using matrices and lensmaker's equation. Ray tracing is also demonstrated through matrix methods.
Dr Md Anisur Rahman Optics basics conceptsAnisur Rahman
1) The document discusses key concepts in optics, including geometrical optics, physical optics, and quantum optics.
2) Geometrical optics deals with light rays and concepts like reflection and refraction. Physical optics examines light as waves and phenomena like interference and diffraction. Quantum optics views light as particles.
3) Images formed by concave mirrors depend on the object's location relative to the mirror's center of curvature and focal point. If beyond the center, the image is real, inverted, and smaller.
1) The document discusses key concepts in optics, including geometrical optics, physical optics, and quantum optics.
2) Geometrical optics deals with light rays and concepts like reflection and refraction. Physical optics examines light as waves and topics such as interference and diffraction. Quantum optics views light as particles.
3) Images formed by a concave mirror depend on the object's location relative to the mirror's center of curvature and focal point. If beyond the center, the image is real, inverted, and smaller.
This document discusses reflection and refraction at surfaces and curved surfaces. It begins by explaining the fundamentals of reflection, refraction, and total internal reflection. It then discusses the laws of reflection and refraction. Specific examples of reflection and refraction are provided for plane mirrors, convex mirrors, concave mirrors, and refraction through lenses and the cornea. Clinical applications of reflection and refraction in the eye and optical instruments are described.
Lens history and physics.
For comments please contact me on solo.hermelin@gmail.com.
For more presentations visit my website at http://www.solohermelin.com.
This presentation is in the Optics folder.
The document discusses key concepts about light, including that it travels as a wave, undergoes reflection and refraction, and has different speeds in different materials. Reflection occurs when light bounces off a surface, following the law that the angle of incidence equals the angle of reflection. Refraction is when light changes speed and bends as it passes from one material to another with a different density, according to Snell's law. Total internal reflection occurs when light traveling through a denser medium hits the boundary at an angle greater than the critical angle and is reflected back inside.
This document provides an introduction to geometric optics and concepts of reflection and refraction of light. It discusses how light rays interact with surfaces and change direction at boundaries between different optical media based on Snell's law. Total internal reflection is described, in which light reflecting back into the original medium if the angle of incidence is greater than the critical angle. Applications like fiber optics and mirages are discussed. A simple model is provided of light propagation through materials involving absorption and re-emission of photons by atoms.
This document provides an overview of key concepts related to light and optics, including reflection, refraction, spherical mirrors, lenses, the human eye, polarization, and diffraction. It includes definitions of technical terms, descriptions of phenomena such as the laws of reflection and refraction, explanations of how ray diagrams are used to determine image characteristics, and examples of applications including corrective lenses and polarized sunglasses.
When light travelling in one medium falls on the surface of second medium the following three effect may occur.
1:- A part of incident light is reflected back into the same medium. This is called Reflection of light.
2:- A part of light is passes through the medium.This Is known as Refraction of light.
3:- And remaining part of the light is absorbed by the surface on which the light fall. This is known as Absorption of light.
This document provides information about ray optics and optical instruments. It begins by defining key concepts in ray optics like reflection, refraction, total internal reflection, and dispersion. It then discusses these phenomena through examples like mirages, diamonds, and prisms. The document also covers topics in geometric optics like mirrors, lenses, the lens maker's formula, and optical instruments like microscopes and telescopes. It provides formulas for magnification, focal length, and angular magnification. In summary, the document is an overview of ray optics concepts and how they apply to the design and use of common optical instruments.
This document provides an overview of optics concepts including reflection, refraction, Snell's law, total internal reflection, fiber optics, and mirages. Key points covered include:
- Reflection and refraction occur when light changes direction at an interface between two mediums. Snell's law relates the angles of incidence and refraction.
- Total internal reflection occurs when light travels from a higher to lower index of refraction material at an angle greater than the critical angle, causing the light to reflect back into the first medium.
- Fiber optics use total internal reflection to transmit light signals over long distances through thin glass or plastic strands.
- Mirages are optical illusions caused by the ref
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
Assessment and Planning in Educational technology.pptxKavitha Krishnan
In an education system, it is understood that assessment is only for the students, but on the other hand, the Assessment of teachers is also an important aspect of the education system that ensures teachers are providing high-quality instruction to students. The assessment process can be used to provide feedback and support for professional development, to inform decisions about teacher retention or promotion, or to evaluate teacher effectiveness for accountability purposes.
Physiology and chemistry of skin and pigmentation, hairs, scalp, lips and nail, Cleansing cream, Lotions, Face powders, Face packs, Lipsticks, Bath products, soaps and baby product,
Preparation and standardization of the following : Tonic, Bleaches, Dentifrices and Mouth washes & Tooth Pastes, Cosmetics for Nails.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
2. Winter 2012
UCSD: Physics 121; 2012
2
Reflection
• We describe the path of light as straight-line rays
– “geometrical optics” approach
• Reflection off a flat surface follows a simple rule:
– angle in (incidence) equals angle out
– angles measured from surface “normal” (perpendicular)
surface normal
same
angle
incident ray exit ray
3. Winter 2012
UCSD: Physics 121; 2012
3
Reflection, continued
• Also consistent with “principle of least time”
– If going from point A to point B, reflecting off a mirror, the
path traveled is also the most expedient (shortest) route
A
B
too long
shortest path;
equal angles
4. Winter 2012
UCSD: Physics 121; 2012
4
Hall Mirror
• Useful to think in terms of images
“image” you
“real” you
mirror only
needs to be half as
high as you are tall. Your
image will be twice as far from you
as the mirror.
5. Winter 2012
UCSD: Physics 121; 2012
5
Curved mirrors
• What if the mirror isn’t flat?
– light still follows the same rules, with local surface normal
• Parabolic mirrors have exact focus
– used in telescopes, backyard satellite dishes, etc.
– also forms virtual image
6. Winter 2012
UCSD: Physics 121; 2012
6
Refraction
• Light also goes through some things
– glass, water, eyeball, air
• The presence of material slows light’s progress
– interactions with electrical properties of atoms
• The “light slowing factor” is called the index of refraction
– glass has n = 1.52, meaning that light travels about 1.5 times
slower in glass than in vacuum
– water has n = 1.33
– air has n = 1.00028
– vacuum is n = 1.00000 (speed of light at full capacity)
7. Winter 2012
UCSD: Physics 121; 2012
7
n2 = 1.5
n1 = 1.0
A
B
Refraction at a plane surface
• Light bends at interface between refractive indices
– bends more the larger the difference in refractive index
– can be effectively viewed as a “least time” behavior
• get from A to B faster if you spend less time in the slow medium
1
2
Snell’s Law:
n1sin1 = n2sin2
8. Winter 2012
UCSD: Physics 121; 2012
8
Driving Analogy
• Let’s say your house is 12 furlongs off the road in the
middle of a huge field of dirt
– you can travel 5 furlongs per minute on the road, but only 3
furlongs per minute on the dirt
• this means “refractive index” of the dirt is 5/3 = 1.667
– Starting from point A, you want to find the quickest route:
• straight across (AD)—don’t mess with the road
• right-angle turnoff (ACD)—stay on road as long as possible
• angled turnoff (ABD)—compromise between the two
A B C
D (house)
leg dist. t@5 t@3
AB 5 1 —
AC 16 3.2 —
AD 20 — 6.67
BD 15 — 5
CD 12 — 4
road
dirt
AD: 6.67 minutes
ABD: 6.0 minutes: the optimal path is a “refracted” one
ACD: 7.2 minutes
Note: both right triangles in figure are 3-4-5
9. Winter 2012
UCSD: Physics 121; 2012
9
Total Internal Reflection
• At critical angle, refraction no longer occurs
– thereafter, you get total internal reflection
n2sin2 = n1sin1 crit = sin1(n1/n2)
– for glass, the critical internal angle is 42°
– for water, it’s 49°
– a ray within the higher index medium cannot escape at
shallower angles (look at sky from underwater…)
n2 = 1.5
n1 = 1.0
42°
incoming ray hugs surface
10. Winter 2012
UCSD: Physics 121; 2012
10
Refraction in Suburbia
• Think of refraction as a pair of wheels on an axle
going from sidewalk onto grass
– wheel moves slower in grass, so the direction changes
Note that the wheels
move faster (bigger space)
on the sidewalk, slower
(closer) in the grass
11. Winter 2012
UCSD: Physics 121; 2012
11
Even gets Total Internal Reflection Right
• Moreover, this analogy is mathematically equivalent
to the actual refraction phenomenon
– can recover Snell’s law: n1sin1 = n2sin2
Wheel that hits sidewalk starts to go faster,
which turns the axle, until the upper wheel
re-enters the grass and goes straight again
12. Winter 2012
UCSD: Physics 121; 2012
12
n1 = 1.5 n2 = 1.0
Reflections, Refractive offset
• Let’s consider a thick piece of glass (n = 1.5), and the
light paths associated with it
– reflection fraction = [(n1 – n2)/(n1 + n2)]2
– using n1 = 1.5, n2 = 1.0 (air), R = (0.5/2.5)2 = 0.04 = 4%
incoming ray
(100%)
96%
92% transmitted
0.16%
4%
4%
8% reflected in two
reflections (front & back)
image looks displaced
due to jog
13. Winter 2012
UCSD: Physics 121; 2012
13
Let’s get focused…
• Just as with mirrors, curved lenses follow same rules
as flat interfaces, using local surface normal
A lens, with front and back curved surfaces, bends
light twice, each diverting incoming ray towards
centerline.
Follows laws of refraction at each surface.
Parallel rays, coming, for instance from a specific
direction (like a distant bird) are focused by a convex
(positive) lens to a focal point.
Placing film at this point would record an image of
the distant bird at a very specific spot on the film.
Lenses map incoming angles into positions in the
focal plane.
14. Winter 2012
UCSD: Physics 121; 2012
14
Cameras, in brief
In a pinhole camera, the hole is so small that light hitting any particular point
on the film plane must have come from a particular direction outside the camera
In a camera with a lens, the same applies: that a point on the film plane
more-or-less corresponds to a direction outside the camera. Lenses have
the important advantage of collecting more light than the pinhole admits
pinhole
image at
film plane
object
image at
film plane
object
lens
15. Winter 2012
UCSD: Physics 121; 2012
15
Positive Lenses
• Thicker in middle
• Bend rays toward axis
• Form real focus
16. Winter 2012
UCSD: Physics 121; 2012
16
Negative Lenses
• Thinner in middle
• Bend rays away from the axis
• Form virtual focus
17. Winter 2012
UCSD: Physics 121; 2012
17
Raytracing made easier
• In principle, to trace a ray, one must calculate the
intersection of each ray with the complex lens
surface, compute the surface normal here, then
propagate to the next surface
– computationally very cumbersome
• We can make things easy on ourselves by making
the following assumptions:
– all rays are in the plane (2-d)
– each lens is thin: height does not change across lens
– each lens has a focal length (real or virtual) that is the same
in both directions
18. Winter 2012
UCSD: Physics 121; 2012
18
Thin Lens Benefits
• If the lens is thin, we can say that a ray through the
lens center is undeflected
– real story not far from this, in fact: direction almost identical,
just a jog
– the jog gets smaller as the lens gets thinner
19. Winter 2012
UCSD: Physics 121; 2012
19
Using the focus condition
real foci virtual foci
s = ∞
s’ = f
s = f
s’ = ∞
s = ∞
s’ = f
s = ∞
s’ = f
s = f
s’ = ∞
s = ∞
s’ = f
20. Winter 2012
UCSD: Physics 121; 2012
20
Tracing an arbitrary ray (positive lens)
1. draw an arbitrary ray toward lens
2. stop ray at middle of lens
3. note intersection of ray with focal plane
4. from intersection, draw guiding (helper) ray straight
through center of lens (thus undeflected)
5. original ray leaves lens parallel to helper
why? because parallel rays on one side of lens meet each
other at the focal plane on the other side
21. Winter 2012
UCSD: Physics 121; 2012
21
Tracing an arbitrary ray (negative lens)
1. draw an arbitrary ray toward lens
2. stop ray at middle of lens
3. draw helper ray through lens center (thus undeflected) parallel
to the incident ray
4. note intersection of helper with focal plane
5. emerging ray will appear to come from this (virtual) focal point
why? parallel rays into a negative lens appear to diverge from the
same virtual focus on the input side
22. Winter 2012
UCSD: Physics 121; 2012
22
Image Formation
• Place arrow (object) on left, trace through image:
– 1) along optical axis (no defl.); 2) parallel to axis, goes
through far focus with optical axis ray; 3) through lens
center; 4) through near-side focus, emerges parallel to
optical axis; 5) arbitrary ray with helper
• Note convergence at image position (smaller arrow)
– could run backwards just as well
23. Winter 2012
UCSD: Physics 121; 2012
23
Notes on Image Formation
• Note the following:
– image is inverted
– image size proportional to the associated s-value: ray 3
proves it
– both s and s’ are larger than f (s = 120; s’ = 80; f = 48)
• Gaussian lens formula (simple form):
24. Winter 2012
UCSD: Physics 121; 2012
24
Virtual Images
• If the object is inside the focal length (s < f):
– a virtual (and larger) image is formed
– non-inverted
• Ray numbers are same procedure as previous
• This time s’ is negative:
– s = 40; f = 60; s’ = 120
– negative image distances indicate virtual images
25. Winter 2012
UCSD: Physics 121; 2012
25
The lens-maker’s formula
• We saw the Gaussian lens formula before:
– f is positive for positive lenses, negative for negative lenses
– s is positive on left, s’ is positive on right
• But in terms of the surface properties:
– R1 is for the left surface (pos. if center of curvature to right)
– R2 is for right surface (pos. if center of curvature to right)
– bi-convex (as in prev. examples) has R1 > 0; R2 < 0
– n is the refractive index of the material (assume in air/vac)
26. Winter 2012
UCSD: Physics 121; 2012
26
Deriving Gaussian Formula from Rays
• Object has height, h; image height = h’
• tangent of ray 3 angle is h/s, so h’ = h(s’/s)
• ray 2 angle is h/f, so h’ = (h/f)(s’ f)
• set the two expressions for h’ equal, and divide by hs’
– the result will pop out
• can do the same trick using virtual images too
27. Winter 2012
UCSD: Physics 121; 2012
27
Lenses map directions into displacements
• Two objects at infinity an angle apart produce
distinct spots separated by
– following geometry, = f·tan f· for small
• hint: look at central rays
– so lens turns angle () into displacement ()
28. Winter 2012
UCSD: Physics 121; 2012
28
Telescope
• A telescope has an “objective” lens and an eyepiece
– sharing a focal plane; giving the eye the parallel light it wants
• Everything goes as ratio of focal lengths: f1/f2
– magnification is just M = 2/1 = f1/f2
• after all: magnification is how much bigger things look
• displacement at focal plane, = f11 = f22 relation above
– ratio of collimated beam (pupil) sizes: P1/P2 = f1/f2 = M
29. Winter 2012
UCSD: Physics 121; 2012
29
Reflector/Refractor Analogy
• For the purposes of understanding a reflecting system, one may
replace with lenses (which we know how to trace/analyze)
– focal length and aperture the same; rays on other side
– for a reflector, f = R/2 [compare to 1/f = (n 1)(1/R1 1/R2) for lens]
• for n = 1.5, R2 = R1 (symmetric lens), f = R
• so glass lens needs twice the curvature of a mirror
30. Winter 2012
UCSD: Physics 121; 2012
30
Parabolic Example
Take the parabola:
y = x2
Slope is y’ = 2x
Curvature is y’’ = 2
So R = 1/y’’ = 0.5
Slope is 1 (45) at:
x = 0.5; y = 0.25
So focus is at 0.25:
f = R/2
Note that pathlength to focus is the same for depicted ray and one along x = 0
31. Winter 2012
UCSD: Physics 121; 2012
31
Cassegrain Telescope
• A Cassegrain telescope can be modeled as as positive and
negative lens
– eyepiece not shown: only up to focus
• Final focus depends on placement of negative lens
– if |s| = |f2|, light is collimated; if |s| > |f2|, light will diverge
• both s and f2 are negative
• For the Apache Point 3.5 meter telescope, for example:
– f1 = 6.12 m; f2 = 1.60 m; d12 = 4.8 m; s = d12 f1 = 1.32 m
– yields s’ = 7.5 m using 1/s + 1/s’ = 1/f2
32. Winter 2012
UCSD: Physics 121; 2012
32
Cassegrain focus
• Abstracting mirrors as lenses, then lenses as sticks:
– trace central ray with angle 1
– figure out 2 and then focal length given s’ and d12
• y2 = d121 (adopt convention where 1 is negative as drawn)
• y1 = f21 (f2 is negative: negative lens)
• 2 = (y1 y2)/f2 = 1(f2 d12)/f2
• yf = y2 + 2s’ = 1(d12 + s’(f2 d12)/f2)
• feff = d12 + s’(f2 d12)/f2 = f1s’/s after lots of algebra
• for Apache Point 3.5 meter, this comes out to 35 meters
33. Winter 2012
UCSD: Physics 121; 2012
33
f-numbers
• The f-number is a useful characteristic of a lens or system of
lenses/mirrors
• Simply = f/D
– where f is the focal length, and D is the aperture (diameter)
• “fast” converging beams (low f-number) are optically demanding
to make without aberrations
• “slow” converging beams (large f-number) are easier to make
• aberrations are proportional to 1/2
– so pay the price for going “fast”
f/1 beam: “fast” f/4 beam: “slow”
D D
f = D f = 4D
34. Winter 2012
UCSD: Physics 121; 2012
34
f-numbers, compared
• Lens curvature to scale for n = 1.5
– obviously slow lenses are easier to fabricate: less curvature
35. Winter 2012
UCSD: Physics 121; 2012
35
Pupils
• Consider two “field points” on the focal plane
– e.g., two stars some angle apart
• The rays obviously all overlap at the aperture
– called the entrance pupil
• The rays are separate at the focus (completely distinct)
• Then overlap again at exit pupil, behind eyepiece
– want your pupil here
– just an image of the entrance pupil satisfying 1/s’ + 1/(f1 + f2) = 1/f2
– size is smaller than entrance pupil by magnification factor
• M = f1/f2; in this picture, f1 = 48; f2 = 12; M = 4; s’ = 15
36. Winter 2012
UCSD: Physics 121; 2012
36
Pupils within Pupils
• Looking at three stars (red, green, blue) through telescope, eye
position is important
• So is pupil size compared to eye pupil
– dark adapted pupil up to 7 mm diameter (2–3 mm in daylight)
– sets limit on minimum magnification (if you want to use the full
aperture)
• 210 mm aperture telescope must have M > 30
• for f/5 scope, means f2 < 35 mm; f/10 scope means f2 < 70 mm
• 3.5-m scope means M > 500; at f/10, f2 < 70 mm
37. Winter 2012
UCSD: Physics 121; 2012
37
Vignetting
• Rays that don’t make it through an optical system are
said to be vignetted (shadowed)
– maybe a lens isn’t big enough
– maybe your eye’s pupil isn’t big enough, or is improperly
placed
• Often appears as a gradual darkening as a function
of distance from the field center
– the farther out you go, the bigger your lenses need to be
– every optical system has a limited (unvignetted) field of view
– beyond this, throughput goes down
38. Winter 2012
UCSD: Physics 121; 2012
38
Infrared Cold Stop
• An infrared detector is very sensitive to terrestrial heat
– so want to keep off of detector
– if detector located at primary focal plane, it is inundated with
emission from surroundings and telescope structure
• note black lines intersecting primary focal plane
• Putting a “cold” stop at a pupil plane eliminates stray emission
– cool to LN2; image of primary objective onto cold stop
– only light from the primary passes through; detector focal plane
then limits field of view to interesting bit
• Also the right place for filters, who prefer collimated light
39. Winter 2012
UCSD: Physics 121; 2012
39
Raytrace Simulations
• In Google, type in: phet
– top link is one to University of Colorado physics education
page
– on this page, click: go to simulations
– on the left-hand bar, go to: light and radiation
– then click the geometric optics simulation link (picture)
• Can play with lots of parameters
– real and virtual images
– lens radius of curvature, diameter, and refractive index
– see principle rays (ones you’d use to raytrace)
– see marginal rays
– use a light source and screen
– see the effect of two sources
40. Winter 2012
UCSD: Physics 121; 2012
40
Aberrations: the real world
• Lenses are thick, sin
– sin 3/6 + 5/120 7/5040 + …
– tan + 3/3 + 25/15 + 177/315 + …
• Different types of aberration (imperfection)
– spherical aberration
• all spherical lenses possess; parabolic reflector does not
– coma
• off-axis ailment: even aspheric elements have this
– chromatic aberration
• in refractive systems only: refractive index is function of
– astigmatism
• if on axis, then lens asymmetry; but can arise off-axis in any
system
– field curvature/distortion
• detectors are flat: want to eliminate significant field curvature
41. Winter 2012
UCSD: Physics 121; 2012
41
Spherical Aberration
• Rays at different heights
focus at different points
• Makes for a mushy focus,
with a halo
• Positive spherical lenses
have positive S.A., where
exterior rays focus closer to
lens
• Negative lenses have
negative S.A., as do plates
of glass in a converging
beam
• “Overcorrecting” a positive
lens (going too far in making
asphere) results in neg. S.A.
lens side
neg. S.A.
zero S.A.
pos. S.A.
42. Winter 2012
UCSD: Physics 121; 2012
42
Coma
• Off-axis rays meet at different
places depending on ray height
• Leads to asymmetric image,
looking something like a comet
(with nucleus and flared tail)
– thus the name coma
• As with all aberrations, gets
worse with “faster” lenses
• Exists in parabolic reflectors,
even if no spherical aberration
43. Winter 2012
UCSD: Physics 121; 2012
43
Chromatic Aberration
• Glass has slightly different
refractive index as a function of
wavelength
– so not all colors will come to
focus at the same place
– leads to colored blur
– why a prism works
• Fixed by pairing glasses with
different dispersions (dn/d)
– typically a positive lens of one
flavor paired with a negative
lens of the other
– can get cancellation of
aberration
– also helps spherical aberration
to have multiple surfaces
(more design freedom)
44. Winter 2012
UCSD: Physics 121; 2012
44
Optical Alignment Techniques
• The performance of an optical system often depends
vitally on careful positioning of the optical elements
• A step-wise approach is best, if possible: aligning as
the system is built up
– if using a laser, first make sure the beam is level on the
table, and going straight along the table
– install each element in sequence, first centering the incident
beam on the element
• often reflections from optical faces can be used to judge
orientation (usually should roughly go back toward source)
– a lens converts position to direction, so careful translation
cross-wise to beam is important
• orientation is a second-order concern
• Whenever possible, use a little telescope to look
through system: the eye is an excellent judge
46. Winter 2012
UCSD: Physics 121; 2012
46
Lab 4: Raytracing
• While it may not be Zemax, I’ve cobbled together a
C-program to do raytracing of any number of lenses
– restricted to the following conditions:
• ray path is sequential: hitting surfaces in order defined
• ray path is left-to-right only: no backing up
• elements are flat or have conic surfaces
• refractive index is constant, and ignorant of dispersion
• We will use this package to:
– analyze simple lens configurations
– look at aberrations
– build lens systems (beam expanders, telescopes)
– learn how to compile and run C programs (and modify?)
– in conjunction with some geometrical design
47. Winter 2012
UCSD: Physics 121; 2012
47
Raytracing Algorithm
• Detailed math available on website under Lab Info
• Basically, compute intersection of ray with surface,
then apply Snell’s Law
• Can have as many surfaces as you want!
• Must only take care in defining physical systems
– e.g., make sure lens is thick enough for the diameter you
need
48. Winter 2012
UCSD: Physics 121; 2012
48
References and Assignments
• Optics, by Eugene Hecht
– a most excellent book: great pictures, clear, complete
• Text reading (see assignments page for sections):
– Ray Tracing; Paraxial Ray Tracing; other topics of interest
– Apertures, Stops, Pupils; Vignetting
– Geometrical Aberrations & skim 5 types thereof
– Simple and Gal. Telescopes; Laser beam expanders &
spatial filters; Lens aberrations
– Flip through rest of chapter 4 to learn what’s there
• Lab Prep: read raytrace.pdf on raytrace algorithm