OPTM 4101 Principles of Optics PDF - University of Western Australia

1/24/24 OPTM 4101 Principles of Optics Object, Images and Blur Danuta Sampson, Discipline of Optometry, SAH...

1/24/24 OPTM 4101 Principles of Optics Object, Images and Blur Danuta Sampson, Discipline of Optometry, SAH [email protected] 1 Acknowledgement of country The University of Western Australia acknowledges that its campus is situated on Noongar land, and that Noongar people remain the spiritual and cultural custodians of their land, and continue to practise their values, languages, beliefs and knowledge. Artist: Dr Richard Barry Walley OAM 2 1  1/24/24 Learning objectives 1. Understand the difference between primary and secondary light sources. 2. Explain the difference between a point source and an extended light source. 3. Define the aperture and blur circle. 4. Understand the pinhole effect and calculate the characteristics of the image formed by a pinhole camera. 5. Explain basic concepts related to objects and images. 3 3 Sun e. g. source , Primary moon e g.. per source. 2TY & Secondary Light sources – Objects for an optical element Secondary light source Primary light source Reflects light from a Creates the light it primary source emits Person Candles Surface Light sources (both primary and secondary sources) = “Object” emitting light Photo credit: Internet 4 4 2  1/24/24 Light sources – Objects for an optical element Remember: light does not stop unless there is an obstacle! Cross‐section Direction of light Point source = object Image point = Point source Convergent Optical axis Optical system Diverging wavefronts Converging wavefronts Diverging wavefronts 5 5 Point sources and extended sources A Extended source On-axis source Off-axis source/point /point A axis axis B Optical axis On-axis source/point /point B axis Point source 5 times rule: the distance from an optical system to the light source should be greater than 5 times the largest dimension of the source/object for it to be called a point source. 6 Loshin 6 3  1/24/24 On-axis and off-axis sources/objects at infinity Indicates long distance (∞) Ind i ca tes l on gd ista nc e( ∞) Loshin 7 7 Point sources and extended sources off-axis on-abis ax3 --- off-axis. Extended source ↳ contain both on + off axis - 8 8 4  1/24/24 Point images and extended images Direction of light Image Converg- ent Axis Off-axis optical \ image system Converging wavefronts On-axis image On-axis image Point image Loshin 9 9 Point images and extended images Off-axis image C’ Axis axis On-axis image B’ Extended image Keating 10 10 5  1/24/24 Pencils, Beams and Chief rays Diverging pencil emanating from point of the object Converging pencil reaching point of the image len s LENS Chief ray Axis Chief ray 11 11 Pencils, Beams and Chief rays ↳ Beam emanating from the object Beam aimed lens towards the image Axis 12 12 6  1/24/24 Blur circles Convergent refractive surface/ lens/ optical system Image plane A Point object The clearest point. Optical axis A’ Point image Blur circle Keating 13 13 Blur circles 14 14 7  1/24/24 Extended images and blur Convergent refractive surface/lens/ optical system A B’ Image plane Optical axis B A’ Extended image Extended object The smaller the blur circle, D the clearer the image. Image plane: Smallest blur circle Keating 15 15 Blur circles and Pinhole camera Can we have a sharp image without a converging optical system? L 7 red green Uniform illumination object screen APERTURE SMALLER APERTURE PINHOLE Green red point red green red green green red red green Red green point Smaller Aperture* ® smaller the pencil of rays ® smaller blur circle ® clearer image 16 16 8  1/24/24 Pinhole camera pinhole axis physicsmax.com/the-pinhole-camera-6725 17 17 Pinhole camera Object Pinhole Image Box Object height: y axis a a y' Image height Object distance l Image distance l’ REMEMBER: l ! "! Similar triangles: = l " 18 18 9  1/24/24 Blurred images in the eye retina=our “screen” Optical system of the eye (convergent lenses) Retina=screen Emmetropia Because the image Yes perfect or near perfect vision. on the retina is sharp Light converges on the retina ≡ image position 19 19 Blurred images in the eye refers to any conditions where the eye's > optical system cannot focus light - retina Retina=screen Ametropia directly on the. Hyperopia (long-sightedness) Sharp image No, Because the image formed on the retina is blurred Retina=screen Myopia (short-sightedness) Sharp image No, Because the image formed on the retina is blurred 20 20 10  1/24/24 Blurred images in the eye Without using any lens/optical system, can you think of a way to make the image at the retina sharper in ametropic eyes? 21 21 Pinhole effect https://www.jdharris.com/image/cache/catalog/pinh ole-glasses-effect-on-eye-500x500.jpg Schwartz 22 http://www.eyesfirst.eu/pinhole-okkluder.html?___store=en&___from_store=de 22 11  1/24/24 Important concepts related to objects and images 23 23 Object space light Object Space Lens Object: Image Object distance (l)