Geometrical OpticsOn and on and on …Slide 3Most important case: converging lens Object to left of F1Most important case: converging lensSlide 6Slide 7Slide 8Slide 9Remember the Spectrum?DispersionChromatic AberrationExampleCorrection : achromatic lens coupleSlide 15Spherical AberrationSpherical Aberration - CorrectingBarrel DistortionComaSome useful stuffDiaphramCameraf stopsMore on CameraThe MicroscopeGeometrical OpticsChapter 24 + Other Tidbits1On and on and on …This is a short week.Schedule followsSo far, no room available for problem session. Still working on it.Today we try to complete lenses.Quiz on Friday?23November 2009SUNDAY MONDAY TUESDAY WEDNESDAY THURSDAY FRIDAY SATURDAY22 23COMPLETE THINLENSPROBLEMS SOLVING25Interference& Diffraction26THANKSGIVING27THANKSGIVINGHOLIDAY282930Interference DiffractionDecember 2009SUNDAY MONDAY TUESDAY WEDNESDAY THURSDAY FRIDAY SATURDAY1REVIEW SESSIONIf Room isAvailableNO ROOMAVAILAVLE2EXAMINATION #43 4INTERFERENCE&DIFFRACTION56 7OVERVIEW OFCOURSELAST DAY OF CLASS8 9 10 11 12FINALEXAMMost important case: converging lensObject to left of F14Most important case: converging lens5Most important case: converging lens6Most important case: converging lens7Most important case: converging lens89Aberrations are imperfections in the optical image formed by a spherical lens (or optical mirror). There are five main aberrations:1. Chromatic aberration. The refractive index of glass varies with wavelength. This results in different focal lengths and image magnifications for different colours.2. Spherical aberration. Lenses with spherical surfaces have a shorter focal length at their periphery than at their centre.3. Coma. The various circular zones of a lens produce an image of an off-axis point that is distorted radially into a comet shape known as a coma patch.4. Curvature of field. The focal surface is not a plane but a bowl shape.5. Astigmatism. Because a lens appears asymmetric to an off-axis beam, the image of a point is not a point but a short line radial from, or tangential to, the optic axis of the lens. These images are formed in different planes.6. Distortion. The image magnification is greater towards the edges of the field (pincushion distortion) or less (barrel distortion) than at its centre.Remember the Spectrum?10DispersionIndex of refraction depends on the wavelength, or color.f depends on the index of refraction.11fRRn111)1(21Chromatic Aberration12Example13Correction : achromatic lens couple1415Spherical AberrationResults from the assumption of paraxial conditions. Real lenses need a wider opening, larger apertures.16Spherical Aberration - Correcting17Barrel Distortion18Coma19Some useful stuf20Diaphram21Intensity~Areaarea double will 2by D ChangeFixed f stops will thereforego by factors of 2CameraThe intensity of the light striking the film or CCD array is proportional to the area of the lens.This is adjusted by the photographer by means of the aperture or diaphragm control.f-number is defined byEx: A lens of focal length f=50mm and an aperture diameter of 25mm has an f number of 2, often written as “f/2”22dfnumberf diameter aperturelength focalf stops23Multiplier sqrt(2) Designationsqrt(2)^2 2.0 f/2sqrt(2)^3 2.8 f/2.8sqrt(2)^4 4.0 f/4sqrt(2)^5 5.6 f/5.6sqrt(2)^6 8.0 f/8sqrt(2)^7 11.1 f/11sqrt(2)^8 16.0 f/16More on Camera24The
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