OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-1 Section 17 Camera Systems OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-2 W /#     Bz NA B  2   O PEP X    DD BL   DOF DOF b B f b may result from the detector resolution or fore the resulting blur exceeds the blur fore the resulting blur exceeds quirement. This blur requirement results in the detector can be shifted from the the detector can defines the performance requirement of an z ongitudinal position of the object or image   B   b  -b Nominal Focus  DOF = b B O  . ' L XP XP D optical system. This maximum acceptable blur just the overall system or display resolution re a first-order geometrical tolerance for the l diffraction or aberrations are included. plane. No describes the amount The depth of focus DOF nominal image position for a given be diameter criterion B There is often some allowable image blur that Depth of Focus and Depth of Field Depth of Focus and OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-3 z  B  2 1 B DOF DOF Nominal Focus  B h is stopped down (its f/# is increased), an (its f/# is increased), down is stopped h  B O  L W /# oportional to the f/# of lens:  XP  XP1 DOF B f D XP2 D The depth of focus is directly pr As a result, as a lens of given focal lengt increased depth of focus results. Depth of Focus and F/# OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-4 z  B O  L is the corresponding image plane is the corresponding , there is some range of object in focus for a given detector or O O ' f EP XP iterion B' is met for these object positions. detector is located at this position. ns with the stop at lens. O a particular object distance L L , the depth of field, that will appear  NEAR EP XP O to L L< 0 L< DDD FAR is the object plane where the camera is focused, and L and the camera is focused, is the object plane where O L where an in-focus image is produced. The where an in-focus image is produced. These results assume a thin le positions L When a camera is focused at image plane position. The image plane blur cr image plane position. The the nominal object location: Consider Depth of Field OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-5 z , this blur equals z  NEAR  B B . At L . At O O  O  L L the lens. A blur will form and be the lens. A blur will form and f f EP XP EP XP intained. When an object is at a distance NEAR L object at a distance less than L O , this blur equals the criteria , B'. O L L FAR FAR L , the resulting image will move closer to O The similar scenario exists for an the blur criteria B'. greater than L The same image plane/detector location is ma The seen on the detector. At L seen on Depth of Field OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-6 z  B  O . ' will produce images on the images on will produce O  O  L LfD DLB f NEAR  f and L NEAR L c depth of focus as it depth constrains the blur c FAR EP XP sed –sed this nominal object plane is conjugate will to be in meet the blur criteria appear and in diameter. Historically, this was probably this was Historically, in diameter.  NEAR NEAR O L O to L  urs less than the blur criterion B LfD DLB f FAR ns with the stop at lens. O  L FAR L  FAR L EP XP O L< 0 L< DDD is the object plane where the camera is focu is the object plane where O detector that have geometrical bl detector that have This linear blur condition is called the photographi on a print or film to be smaller than a certa related to the grain size in film. These results assume a thin le L to the detector. All objects positioned between L All objects positioned between to the detector. focus. All object positions between L All object positions between Depth of Field OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp  O L 17-7  O  O  D    F  D BL  L BL   11 BD  O   L   F  L 11 DB D      DB  F  OF  D L LL        O 11 DB D B FN  DB  D     ON N BL  N LL L L        N LLLDOF L z Limit  N L Near Object  B  F L Nominal Focus Limit Far Object O  L Consider the image side: Consider Depth of Field – Derivation D OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-8  O  D BL    O   O  OO  L O  O   L ()   f O fL   O  () () f   LDB  O zL LL O f fL ()     2  DLB    O O  fL D B f OO O 111 LfD B L LLf : DLDB Lf D B fD f    L NEAR L L and L : O ' FAR  is conjugate to L is conjugate  O  ()  O ()  O  OO  LL  LBLD ()   (/)  O O   OO LfD B   LBLDf DLDB O () f (/) f f      L 1 LLLf 1111 L zLLLf Solve for the corresponding object positions L Solve for the corresponding The image distances corresponding to the image limits image distances corresponding The are: The nominal object position L The Depth of Field – – Derivation Continued OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-9     O O z     zL L zLL  B O  L f   EP XP O O LfD LfD NEAR  L      OO    OO    O  O   DLB fDLB L f DLB fDLB O  f  O Lf D B Lf D B DLB f  O  Lf D B   NEAR FAR FAR L L L L EP XP O L< 0 L< DDD Depth of Field – – Derivation Continued OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp f 17-10 D  /# f  extends to OH LL FAR , and all , and objects from H  D  B f     ? H The near focus object limit is approximately half the hyperfocal object distance. Hyperfocal Focus Position   O LfD OH LL    e far point of the depth of field L e far point of the depth    2   H OH  /# L OO  /        DB DLB fDLB f 0 22 B OH fD DLB fDLB DfD f 22 f f LfDB LfDB O    Lf D B BfB fD f     H      NEAR NEAR NEAR H L L L FAR L when the system is focused at L the system is focused when fD L B L NEAR to infinity meet the image plane blur criterion are in focus. and Where is L NEAR infinity. The optical system is focused at the hyperfocaloptical system is focused infinity. The distance L An important condition occurs when th An important condition occurs when L Hyperfocal Distance OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp x   17-11 1   x B 1  /# 1  H  /#     ffB BD BD D   1/ DOF B f DOF L        HH H   H H 111 1 11 / LLf fDf Lf Lf LfBffDOF z  NEAR L focal point is given by the Depth of Focus. the Depth by focal point is given Near Object Focus e rear focal point of the lens, but produce an e rear focal point of the lens, but produce  B -DOF DOF  Detector Location F Infinity Focus  H L f Rays from the edge of the pupil acceptable blur on the detector. acceptable blur on the rear the sensor and separation between The Objects at the Near Point will focus a Depth of Focus behind the sensor, the detector. an acceptable blur on will also produce and The detector is placed at the conjugate to the hyperfocaldetector is placed at the conjugate The distance: at th objects at infinity will focus course, Of Hyperfocal Distance and Depth of Focus OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-12 /2 H = L Limit NEAR Near Focus L Distance Hyperfocal H digital-photography-school.com = L O Focus L Camera Position maximizes the use of available depth  D B f e depth of field actually extends beyond  Depth of Field OH LL ∞ = FAR L If the camera were focused at infinity, th If the camera were focused at infinity, infinity. Focusing at the hyperfocalinfinity. distance infinity. of field that includes Hyperfocal Distance OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-13 Focus/Field calculations. The two most Focus/Field calculations. The y disc) and that there are no aberrations. that there are no y disc) and infinity to half the hyperfocal distance. as the limitations to system performance are be determined within a zone. - of Number autofocus zones - Artistic considerations e stop at the lens is assumed. Hyperfocal Distance - fixed-focus cameras work Why Depth of FocusDepth of Field - Film plane flatness - Focus precision -from will be most distant zone The -from half the hyperfocalextends zone second The distance to its near point. -starts next zone The at this near point, etc. -the zones. can be overlap between There - object position The only needs to - zones get shorter The as the object distance get closer. Number of autofocus zones: important are that there is no diffraction (Air important are that there is no again, a thin lens with th Once these results important are very However, often these first-order geometrical considerations: There are many assumptions in these Depth of Hyperfocal Distance and Depth of Focus Field OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-14 38 .038 he film provides about 632 x 947 effective he film “pixels.” effective provides about 632 x 947  mm    fD B fD f 44 2 8 2438  .006 .15 2.44       /# / /15.5  H H NEAR f Lfmm Dmm Bmm LL ftmm Print Magnification 4X 4R Print mm) (4 x 6 inch or 100 150 mm) (0.15 Maximum blur on the print is 0.006” Near focus is 4 ft (1200 mm) with film) mm (sets FOV Focal length = 38 angular The exposure is set by the shutter speed and the film speed (ISO). Dividing the format size with the blur on t resolution. This is approximately SVGA System specification: 35 mm film (24 x 36 mm) Example – Fixed-Focus Camera The OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-15 Filter Array Bayer Color (35 mm equivalent = 38 mm) 4.8 m    fD  B fD f 2 8 2438  2.8 .0028 1.4      /# / /2.9  H H NEAR Lfmm f Bm mm LL ftmm Dmm Set the image blur equal to twice pixel size. Near focus is 4 ft (1200 mm) Focal length = 4.8 mm Number of Pixels = 3264 x 2488 (8MP) Number of Pixels x 2488 = 3264 1.4 Pixel Size = Most camera phones seem to operate at f/2.5 f/2.2. Most camera phones System specification: Sensor 1/3.2” Format (4.54 x 3.42 mm) Example – Fixed-Focus Digital The Phone Camera OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-16 z  B 2 O   f L field increases with the Bf H 22/# L  NEAR L  NEAR L NEAR L is stopped down), the hyperfocal distance also the hyperfocal down), is stopped /# 2 ength is stopped down, the depth of ength is stopped down,  Df BBf f FAR L  FAR L   H L moves closer to the lens: increased depth of focus. As the f/# of a lens increases (the As a lens of given focal l Depth of Field and F/# OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-17 f/5.6 f/32 wikipedia Depth of Field and F/# OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-18 otoshop.com photographyplusph Depth of Field and F/# OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-19 photographywisdom.com Depth of Field and F/# OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp z 17-20 z  Nominal Focus Blur  zorf XP XP D PEP X DD he image is averaged over the active area of each image is averaged he Assume Assume W  z the pixel size is lost. /#  f/# f   in microns XP D f/#  Blur ≈  zz D D = 2.44  Blur Various factors can affect the recorded image quality: Various factors can affect the recorded -circular blur results. or defocus: A Focus - of the imaging system Aberrations - Diffraction: The diameter of the Airy Disk is pixel. Detail finer than pixel. - Pixel Area and Number of Pixels: T Image Quality OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-21 z Ray Error Focus Paraxial h as a function of radial of the lens increases quadratically with 3  P as the cube of the location within as the cube   Blur r on of the power or focal lengt on of the power ). P P r pupil radius; the focal length decreases quadratically. pupil radius; the focal length decreases increases ray error associated with SA The the aberration blur. greatly reduce can a lens down pupil. Stopping For a singlet (undercorrectedthe power SA), Spherical aberration is a variati location within the pupil (r Spherical Aberration OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-22 the Pupil Sampling in Square Grid Variance Minimum Wavefront Wavefront Mid Focus Spot Size Minimum RMS Paraxial Focus Diagrams at Focus Positions Diagrams at Focus Minimum Circle Marginal Focus Spherical Aberration – Spot OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-23 pupil diameter (or the inverse cube of the f/#) cube inverse The spot scales as size the cube of the entrance the cube f/3 f/5 f/4 F-Number and Spherical Aberration OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 21-24 close to paraxial as possible. Plano-Convex lit between the surfaces. This minimizes This surfaces. the lit between he light is bent the same amount at each index, as is often found in the IR, best as is often found index, require different bendingsrequire different to minimize he lens should always face the infinite always he lens should es spherical aberration. It can only be he ray bending occurs at one surface. In the he ray bending Convex-Plano aces and makes the situation as aces and ented towards the finite ented towards conjugate. In the plano-convex configuration, all of t In the plano-convex convex-planois sp configuration, the ray bending the angles of incidence at surf side of t the convex For an index of about 1.5, The planoconjugate. side is ori that completely eliminat There is no bending object/image conjugates minimized. Different spherical aberration. At high The optimum shape varies with index. shape is a meniscus. lens surface. Object at Infinity: The minimum spherical aberration occurs when t minimum The spherical aberration occurs when Lens Bending and Minimum Spherical Aberration OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 21-25 the lens bending, or shape of the lens or shape the lens bending, Spherical Aberration vs. Lens Shape Spherical aberration is a function of OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 21-26 z z z required to minimize spherical aberration. o lenses in their infinite conjugate minimum on. At 1:1 imaging, an equiconvex lens is spherical aberration results than in the bi- on is to split the biconvex lens into two plano- on is to split the biconvex sometimes used in fast condenser lenses. fast condenser in sometimes used two lenses can be changed to match the object be changed two lenses can This final vertex-to-vertex arrangement uses tw uses This final vertex-to-vertex arrangement spherical aberration configuration. Much less The focal lengths of the solution. convex This solution is also image conjugates. and convex lenses and then flip each of the lenses: then flip each lenses and convex A trick to further minimize spherical aberrati A The particular shape depends on the magnificati used. At finite singlet image conjugates, a bi-convex is Spherical Aberration and Finite Spherical Aberration and Conjugates OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 21-27 z z lenses to further minimize spherical nite conjugate minimum spherical aberration minimum spherical nite conjugate to obtain minimum spherical aberration. Spherical Aberration and Finite Spherical Aberration and Conjugates At non-unity conjugates, the lens is bent Equal ray deviation at both surfaces is desired. also be split This lens can into two plano-convex aberration by using each element in their infi configuration. OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-28 f/# For many camera lenses, For many rather for their radiometric performance field errors are dominant, and the blur Faster camera lenses are not produced because Faster camera lenses are not produced on of the f/# of an objective can be drawn. on of the f/# an objective can be drawn. shutter speeds. The best image quality is The shutter speeds. he system has a small aperture, diffraction dependence of blur on the f/#. dependence

Blur Quality With large apertures, aberrations and depth of With large apertures, aberrations and grows quickly with faster f/#s. When t there is a linear dominates, and A qualitative A plot of image blur as a functi the minimum blur occurs at about f/5.6-8. the minimum blur occurs at about but diffraction blur, reduced potential for the of in low light level conditions or with fast produced when the lens is stopped down several stops. Quality vs. F-Number OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-29 gn parameter for an optical he system or its light collecting ability. ed, they all derive from different physical from all derive ed, they e performance aspects of the system: stop is very important desi • system The determined by vignetting. FOV • radiometric The or photometric speed of t • depth of focus and field The of the system. •image quality. amount of aberrations degrading The • diffraction-based The performance of the system. system as it controls five separat phenomena. The diameter of the aperture The While some of these aspects are interrelat Uses of the Stop OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-30 (mm x mm) Diagonal (mm) (mm x mm) Diagonal A lens with a focal length equal to the A mm camera (135 format) is historically mm camera (135 50- ed standard. There is considerable variation ed standard. V are called wide angle lenses, and lenses V is one that produces an image perspective and image perspective an that produces is one FOV that somewhat matches FOV human vision. diagonal of the format is usually consider lens for 35 in this definition as a standard FO a larger that produce mm. Lenses 55 are long focus lenses. that a smaller produce FOV In photographic terms, a standard lens 120 (4:3)220 (1:1)220 (7:6)220 (3:2)126 (1:1)110 (4:3)135 (3:2) 61.5Disc (4:3) 61.5APS Classic (3:2) 61.5 (16:9) HDTV APS 61.5APS Panoramic (3:1) 35.0 16.0 24.0 60 x 45 24.0 35.0 24.0 60 x 60 70 x 60 90 x 60 28 x 28 25.0 x 16.7 17 x 13 30.2 x 16.7 30.2 x 10.0 75.0 36 x 24 84.9 92.2 11 x 8 108.2 40.0 30.1 34.5 31.8 21.4 43.3 13.6 Film format Film width (mm) Frame size Film Formats OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-31 oldfilmprocessing.com 120:135:126: 60 x 45 mm 110: 36 x 24 mm Disc: 28(26) x mm 17 x 13 mm x 8 mm 11 126 & 120 Disc 126 Film Formats 110 135 126 Wikipedia OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-32 (and the larger 35 mm (and the larger us the increasing use of date/time, and exposure information The Advanced Photo System (APS) was Advanced The introduced in 1996, and provided several advances over 35 mm film: - image formats Three (aspect ratios) -optical recording for aspect ratio, and Magnetic - Film cartridge could be removed and reinserted - Smaller format with two perforations per frame 25.0 x 16.7 mm 30.2 x 16.7 mm 30.2 x 10.0 mm The APS format never caught on due to the popularity of The point-and-shoot 35 mm cameras pl professionals) for film size APS classic the While discontinued, digital cameras. digital SLRs. the format for many format serves as Classic (3:2) (16:9) HDTV Panoramic (3:1) mycameracabinet.wordpress.com archivemymemories.blogspot.com APS Film Format OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-33

Wikipedia er of the glass tube ensors in the HDTV aspect ratio (16:9). ensors in the HDTV deo sensors or focal plane arrays are usually deo s are the outer diamet size (i.e. 2/3 inch) has little to do or nothing ronic or digital cameras derives from video The charge density pattern on the photoconductor The charge 2/3 inch1/2 inch1/3 inch1/4 inch 8.8 x 6.6 6.4 x 4.8 4.8 x 3.6 3.6 x 2.7 11.0 8.0 6.0 4.5 Video format Image size (mm x mm)(mm) Diagonal To match standard television/monitor format, vi To produced in a 4:3 format. Note that the format produced These video format with the actual active area. required for the given active area. Modern, dedicated video cameras will likely have s The notation for sensor formats in elect The used camera tubes, in particular vidicon tubes. detector is read by a scanning electron beam. Sensor Formats OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-34  0.42" 1/ 2.4 " 1/2 22 mm inch Diagonal  5.76 4.29 7.18  25.4 /   1.5  A large variety of sensor formats exist for large A scientific and digital photography applications. Digital single lens reflex cameras seem to be evolving into “full frame” formats, mm film, matching 35 and “APS-C the sensors about format” cameras with 24 Classic format (about APS size of the x 16 mm). smaller For the formats, there is some variation in image size between manufacturers. determine the Rule sensor of Thumb: To format or type, multiply the sensor diagonal by 1.5 and convert to inches. Example: 1/2.5” DiagonalFormat mm Digital Sensors Wikipedia OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-35 Wikipedia 3:2 4:3 a 4:3 or TV format. The larger-format larger-format The format. TV a 4:3 or about the 1/3” format, with a diagonal of SLR cameras use sensors with the film-based 3:2 format. cameras use tiny sensors in Most mobile phone about 6.0 mm. Small format cameras generally use sensors with Digital Sensors OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-36 length of the lens o different cameras can terms of FOV. The crop The terms of FOV. ocus, etc.). In fact, FOV and ocus, etc.). In fact, FOV ltipliers applied to that must be  hf h on a 35 mm camera. “35 mm equivalent” focal length.  1/2  film and film-based cameras is likely to film-based cameras film and tan( ) / 36 mm) along with the focal these DSLRs have sensors that these DSLRs are smaller than ensors sizes, so the focal length means nothing digital single lens reflex cameras, are “crop focal lengths, many manufacturers are not focal lengths, many is means that using a 50 mm lens produces a is means that using a 50 mm lens produces a narrower FOV than would be expected based enced photographer instinctively what knows focal same focal length on tw equivalent focal lengt 75 mm lens on a full-frame camera. of the lens, but rather (normal, wide angle, long f FOV he lens. These terms are the mu the 35 mm equivalent focal length in the 35 produce very different FOVs. of the familiarity Because of 35 mm camera the actual focal length providing defines the FOV of the system. An experi of the system. An defines the FOV length to use get a particular terms. synonymous focal length almost become In digital available s cameras, there are many without reference to the sensor size. The as the lens covers the same FOV The Other terms especially in that are appearing, factor” or “focal length multiplier”. Many of the 35 mm film format and therefore cover the focal length of t simply on the lens focal length to give Th sensor is factor about 1.5. for an APS-C approximately equivalent to a FOV the terminology of film away, though is going Even be with us for quite a while. In a 35 mm camera, the fixed film format (24 x Focal Lengths and Digital Cameras OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-37 m  m (0.003 in or 3 mils) is  m the detector to determine color encoding must also factor into color encoding is corresponds to the resolution of the resolution of to the is corresponds oderate quality (0.005 in) requires about quality (0.005 oderate m) on the negative. It is easy to see that to see It is easy the negative. m) on ber of pixels or resolution elements across pixels or of ber  is about 4X. A blur of 3 mils on the print A is about 4X. resolution requirements on the lens. of 250 mm. Blurs larger than about 200 ith excellent image quality (0.003 in) requires ith excellent image quality (0.003 . For a 35 mm negative (24 x 36 mm) enlarged . For a 35 mm negative (24 x 36 mm) enlarged int, a blur diameter of 75 int, a 0.0003rad ed by the enlargement ratio fro ed by the enlargement m μ 75 250mm 1arc min 1arc  

  using smaller negatives places additional This analysis also leads to the required num For example, a 4R print w the detector. about 1300 x 2000 pixels (2.6 megapixels). M The method of pixels (1 megapixel). 800 x 1200 this analysis. a blur requirement for the imaging lens to a 4R print (4 x 6 in), this magnification corresponds to a blur of about .75 mils to a blur of about .75 (19 corresponds These blur sizes can be scal (0.008 in or 8 mils) (0.008 are typically unacceptable. considered excellent image quality. Note that th excellent image quality. Note considered eye (1 arc min) at the standard near point On a small-format photographic pr Image Quality OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp

4photos.net/blog 17-38 Optical zoom increases the size of the image falling on the sensor. The inherent resolution of the sensor is maintained. Digital zoom crops or uses a portion of the image recorded by the sensor and blows it up image. No or resamples it to create the zoomed additional resolution is produced. The amount of digital zoom that can be used with good results depends on the number of the pixels (image resolution) and recorded display resolution. Optical Zoom: Digital Zoom: Digital Zoom Original: support.nikonusa.com OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-39 Frame era systems. and perspective of The FOV a eyesight to place the eye relative to an Eyesight OV and perspective recorded by the camera. OV the viewfinder should match the F the viewfinder should The simple open-frame viewfinder consists of magnification is produced. No accurate. not very Simple, but frame. open Viewfinders allow for framing the scene in cam Viewfinders OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-40 Mirror Ground Glass Lens e a viewfinder lens separated for Viewfinder A brilliant reflex a viewfinder produces A much brighter image by replacing the The glass with a field lens. ground aperture of the viewfinder lens is imaged onto the eyes of operator. viewfinder image is still The erect but reverted. Mirror Because both of these viewfinders us Because the camera objective, parallax in viewfinder image will result. Lens Field Lens Viewfinder A reflex viewfinder is a waist-level viewfinder that uses an auxiliary objective on the camera. The dim glass screen is erect but on a ground image produced reverted. Reflex Viewfinders OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-41 goedlicht.blogspot.com is often at the eye. Eye Lens  OBJ EYE t = ft = f cameras is slightly more wide angle than angle cameras is slightly more wide an intermediate image plane prevents the use OV. The viewfinder stop ewfinder. Reverse Galilean viewfinders are Objective Viewfinder EYE f OBJ f  OBJ EYE F F Parallax in the viewfinder image will also result as the viewfinder is displaced (in both The directions) from the camera objective. for close objects. parallax error is worse Blue: Viewfinder Image Red: Recorded human vision requiring a MP < 1 for the vi human common in these cameras, however the lack of of a reticle for framing marks to define the F The image perspective of most point-and-shoot The Reverse Galilean Viewfinders OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-42 Eye Lens Marks Framing s by placing a partially reflecting coating a placing by s FOV and the viewfinder FOV is and the viewfinder a FOV problem FOV the positive eye lens) to the front focal lens) to the the positive eye , reflex and reverse Galilean). They are also , reflex and reverse Galilean). now imaged to infinity by the eye lens, are ean viewfinder. This resulting concave mirror This resulting concave ean viewfinder. Objective Viewfinder EYE Semi-Transparent f ough viewfinder image of the scene. Scene For near objects, parallax between the camera (simple with all of the viewfinders discussed to use with interchangeable lenses. very difficult on the negative lens of reverse Galil on images a framing mask or reticle (surrounding plane of the eye lens. The framing marks, superimposed on the straight-thr The Van Albada viewfinder adds framing mark Van Albada Viewfinder OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-43 Image Sensor Eye Lens Mirror by using the camera Movable Prism Reflex Lens Objective Screen Viewing ves the parallax problem to the film, and the eye lens serves as a to the film, the eye and age sensor. The ground glass or matte surface ground age sensor. The ng screen. The reflex prism corrects the image ovable mirror directs the light path either mirror directs the light path ovable The single lens reflex SLR/DSLR system sol reflex SLR/DSLR single lens The objective also for the viewfinder. The m The objective also for the viewfinder. the viewfinder or to film through or im of the viewing screen is optically conjugate magnifier to view the image on this viewi parity and provides eye-level viewing. Single Lens Reflex Viewfinder Single Lens The ground glass viewing screen prevents vignetting by scattering light from the entire image into be replaced by lens. It can the eye a field lens, often a Fresnel lens, Commonly, for light efficiency. the combination of a Fresnel lens is also a scattering surface and used. the viewfinder shares Because system is objective lens, the SLR ideal for use with interchangeable There is no camera lenses. parallax. OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp

Wikipedia 17-44 Used for lighthouse lenses and Used automobile taillights! images add incoherently, so that the that is collapsed into radial zones. It can be It can into radial zones. that is collapsed although the face of each prism may be curved. produced by computer-controlled lathes. is that of a single zone. is that of a Side View View Top The lens can be comprised of hundreds rings. considered to be a collection of prisms, diffraction-based resolution Usually molded, the master is Conceptually, a Fresnel lens is thick Conceptually, An image is produced by each zone, and these Fresnel Lens OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-45 Focused on Building Focused on Doll Focusing Screens OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp B A 17-46 Angles Wedge B B B A A A to turn focusing into an image alignment to turn focusing ing thin prisms placed in the center of thin prisms placed ing B hen the image is out of focus, the image will lens and changing the image distance in changing lens and sual evaluation of the image sharpness. A sual evaluation of the image sharpness. vernier acuity of the eye (about 5 arc sec) B A B A In FocusLong Focus A B A A B B Focus Short A camera. This is often done by subjective vi by camera. This is often done to the SLR viewfinder focusing aid can be added task. This method also makes use of the instead of the resolution of the eye (1 arc min). A split focusing aid consists wedge of two oppos of the viewfinder (SLRs). W the image plane appear sheared by the prisms. Focusing is accomplished by translating the Split Prism Focusing Aid Split Prism Focusing OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-47 Sciencephoto.com screens (ground surface plus a Fresnel lens) screens (ground When the image is properly focused, a clear the image is properly focused, When Each prism shifts Each the image in same focus, the image will appear to sparkle or manner as the split-prism focusing screen. the image is out of When image is seen. shimmer. Combinations of a split prism and microprisms can be used. On cameras with autofocus, simpler focusing are used. An array of small prisms can also be used. Microprisms OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-48 Focused on Building Focused on Doll Focusing Screens OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-49  zsf dd is related to the s z     ds zz z d s  z f f ween images produced by separated objectives images produced ween to an object. The object distance to an : d z = Object Distance Object relative image displacement relative image can be used to triangulate the distance The perspective difference or parallax bet The Parallax Triangulation OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-50 BS Mirror s Rotating  45°object at infinity. to an corresponding llax. The optical path through the reverse as a visual aid for focusing compact r into two separate optical paths. A separate optical paths. r into two directly coupled to the motion of lens directly coupled z s   z

 tan

   s  

 2 tan 2

   z Object is measured from the nominal mirror position of from the nominal is measured cameras. It is based upon triangulation and para triangulation and upon It is based cameras. a beamsplitte Galilean viewfinder is directed by mirror in one path is rotated until the two images viewed overlap. The mirror tilt angle encodes the scene distance. An image coincidence rangefinder is often used image coincidence An Image Coincidence Rangefinder The mechanical motion of the mirror The is often required for proper focus.  OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-51 m the ambient light received from the m the ambient light received towards the scene and the reflected energy is is important to understand these modes and pick If no focus position is detected, the camera it on the closest object detected. focuses Triangulation Image Contrast finity (or to the hyperfocalthe finity (or to distance). Passive Autofocus Sensors:Passive Autofocus Triangulation used to determine the object distance. used Passive – object distance is determined fro the scene. All focus sensors have a failure mode. It the system that is best for application. usually defaults to an object at in The camera usually scans near to far and Further Classifications: Sensors:Active Autofocus Echo Autofocus sensors can be classified Autofocus into two basic types: Active –from the camera is directed energy Autofocus Sensors OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-52 t The chirped pulse The ore distance) to be better than that allowed lated with the original waveform. This lated with the original waveform. and receiving the pulse. . The frequency of the pulse is chirped from . The frequency Because of the speeds and time intervals that ses can be used for increased signal to noise. SX-70 camera. A piezoelectric camera. A (PZT) SX-70 em. A pulse of energy is directed at em. A pulse of energy the scene Pulse Chirped and we measure the round trip transit time. is used instead of light. results, sound This system first on the Polaroid appeared transducer is used to emit an ultrasonic pulse to allow better trip 50-60 kHz resolution. The round time is 5.8 msec/m. The same transducer is used for both sending is used so that the returned signal can be corre theref allows the system resolution (in time and the total pul by length of the pulse. Longer This type of sensor is a time-of-flight syst Echo Sensors OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-53 d s Detector Array LED  z f f on the image detector. the subject. The subject is assumed to arrangements of source and detector can be finity a returned spot at the rear will produce be kept in focus by tilting the detector array ned spot from the axis of the second lens is a ned spot from the axis of second a single moving LED and a single fixed is captured by a second lens and imaged onto a  z required focus zones will depend on the focal required focus zones will depend d he required blur size s  z z = Object Distance Object be a diffuse reflector. The reflected light diffuse reflector. The a be separation of the retur detector array. The object at in measure of subject distance. An of focal point of the lens. The number length of the camera lens, its t f/#, and The light from an LED is collimated and aimed at aimed is collimated and LED an light from The Active Triangulation Sensors The returned spot on the detector array can returned spot on The and using the Scheimpflug condition. Other multiple used: single detector and LEDs; a fixed LED. detector and detector; a single moving OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-54 CCDs Reference ent light level is required. ent light level is required. Far Near Tilting Mirror Tilting ith parallax are imaged onto two detector ith parallax are imaged onto detectors sweeps across the detector. The detectors sweeps moves from close focus to infinity. As the he camera is in focus. The lens is stopped, and lens is stopped, he camera is in focus. The and the two detectors signals are fed into a rn onto the scene at low illumination at low levels. rn onto the scene camera focuses on the closest object. visual image coincidence rangefinder. The mirror rangefinder. The tilt visual image coincidence ght is used, so a reasonable ambi Line of Sight Near Far By starting close and working out, the The camera may also project a light patte The rangefinder, images w automated coincidence In an arrays. This is the direct analog of the the lens to the lens focus position, and is coupled one of the images on focus position changes, other detector contains the reference image, comparator circuit. the images match, t When is made. the exposure In a passive system, only existing li Passive Triangulation Systems OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-55 Image Sensor Focus Detector ax by using light from Viewfinder ens. The geometry creates two images that that creates parall Most SLR cameras use a focus detection system subaperturesof the objective l at the opposite edges to determine object position. are compared The focus detector is usually located in the The SLR/DSLR bottom of the mirror of an box camera by using a partially reflective flip mirror. small auxiliary a mirror and Focus detection can occur while the (flip mirror down). is active viewfinder Through the Lens (TTL) Phase Matching Focus Sensor Through OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-56 Focus Detector Unfolded System Lenslets the objective lens aperture onto Field Mask Field Lens e to the image sensor) selects portion of e he focus detector with a specific separation. the two lenslets selects light from different ng subapertures the triangulation. for The focus (lenslets) image this mask (and the object/image) Image Plane (Image Sensor) (black). The field (black). The lens images Subapertures – Conjugate to the Lenslets Objective the lenslets (dashed red). The size and offset of parts of the pupil objective lens defini to the image plane. detector array is conjugate A field (optically A mask in the image plane conjugat the FOV to measure. The two small two lenses to measure. The the FOV onto the focus detector arrays A point in the object will produce two images on t point in the object will produce A Through the Lens (TTL) Phase Matching Focus Sensor Through OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-57 Focus Detector Detector Outputs Lenslets lens is also ignored. Field Mask Field Lens In Focus Focus Short front of the defined image plane. It will be fraction at the field The lenslets The the reimaging on are slow and Image Plane (Image Sensor) Subapertures – Conjugate to the Lenslets Objective The separation of the two images The produced on the focus detector by an object point is reduced. Now consider an object point that focuses in Now out of focus on the image sensor. For clarity, only the central rays are shown. focus detector has a large depth of focus. Re Through the Lens (TTL) Phase Matching Focus Sensor Through OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-58 Focus Detector Detector Outputs Lenslets Field Mask Field Lens In Focus Focus Long rger separation than the in-focus object. focuses behind the defined image plane will focuses behind Image Plane (Image Sensor) Subapertures – Conjugate to the Lenslets Objective Calibrated against an in-focus images separation, the measured separation determines the direction and amount to refocus the lens in order to bring the image into focus. In a similar manner, an object point that produce a focus detector output that has a la a focus produce Through the Lens (TTL) Phase Matching Focus Sensor Through OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-59 of being fast and also works when the flip – field aperture A multipoint autofocus. ise with objectives having slow maximum f/#s. ise with objectives having used at each field point to be measured. The used at each field point to be measured. lly to detect horizontal scene detail. Detector Outputs In Focus Focus Short Focus Long The system is calibrated for the in-focus image separation. system is calibrated for the The Multiple regions of the scene can be measured a pair of lensletswith a field lens and is lenslet pair can also be oriented vertica This method of focus detection has the advantage mirror is in the viewfinder position. Issues ar Through the Lens (TTL) Phase Matching Focus Sensor Through OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-60 The diagrammed system measures three central position The field positions. measures horizontal detail; the other two measure vertical The aperture detail. mask defines the lenslet apertures. Applied Photographic Optics Applied Photographic Through the Lens (TTL) Phase Matching Focus Sensor Through F: Filter, M: Mask. C: Condenser or Field C: Condenser M: Mask. F: Filter, A&S: Lenslets Lens, K: Mirror, with Apertures, D: Focus Detector S. Ray; OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-61 na-2012-20300 Nikon D4 Camera n-at-photoki ephotozine.com/article/niko Through the Lens (TTL) Phase Matching Focus Sensor Through OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-62 In Focus Move Lens Move Lens three detector arrays the arrays (B) is optically Detector Signals AB C detection. A small portion of the light is light is then directed to light is then on of lens motion needed to get the image in on of lens motion needed rast of the three detector images can be Image Sensor so be used and the lens is moved back and forth to optimize longitudinal positions. One of One longitudinal positions. CCDs ABC Viewing Screen Viewing allowed to pass through the flip mirror. This at different that are located cont The coincident with the image sensor. for contrast to determine the directi analyzed focus. A single detector array can al SLR cameras also use image contrast for focus SLR the image quality on this the image quality on single detector. Through the Lens (TTL) Image Contrast Measurement Through OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-63 obtain maximum image contrast. The lens obtain maximum image contrast. The work towards more distant work objects. This slower than phase matching. SLR camera, a separate image sensor is used. reflex mirrors (non-SLR), the image captured by the camera’s image sensor can be examined to be examined the camera’s image sensor can image contrast is measured. the is shifted and focus start at near focus and camera lens would The can be an iterative process and is generally in an In order to use live-view autofocus In cameras that do not have shutters or not have In cameras that do Live-View Autofocus OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-64 Wikipedia s. The image on the detector image on s. The distance and the camera obtain a large magnification without the the required large image distance. For high llows or extension tubes to position the ect, so the optical magnification can exceed ger than the object ger than not approach 1:1 magnification, not approach and only the ital cameras, can use internal focusing use can ital cameras, aking pictures of small object aking  z z  m can sometimes be larger than the actual obj many macro systems do 1:1. However, displayed image is larger than the object. uses a be Traditionally, macro photography from the detector to obtain camera lens away magnifications, the image distance is lar use of extension tubes. situations, In both a limited distance often results. working Macro Photography refers to t Macro Photography arrangements (complex lens element motions) to objective is often reversed. Modern macro lenses, especially on dig Close-Up or Macro Photography OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-65 iopter D Objective f f  u u   m m graeter than that of z lens is imaged to the rear ens so that in the nominal a camera objective to allow for O F ' u ens. In this case, the magnification is the diopter lens is iopter to +7 diopters. An advantage of this D Objective z es with powers of +1, +2 and +4 diopters. special lens or extension tubes.  u uz ance is preserved, however high magnification however ance is preserved, point of the diopter lens can be imaged by point of the diopter lens can be  objective lens is focused at infinity. lens is focused objective m Camera Objective ont focal point of the diopter tly in front of the objective l Diopter Lens a simple lens that is added to simple lens that is added a u D F configuration, an object at the fr focal point of the objective lens. The set of diopter lenses usually contains lens A They can be combined to obtain a range of +1 configuration is that dist a long working the focal length of ratios because are not obtained the objective. objects not at the front focal Of course, setting the focus of the camera objective l changing given by close-up photography without requiring a close-up photography diopter lens is placed direc The A close-up or diopter lens is A Close-Up or Diopter Lenses OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp z 17-66  F A fMPf    u h h ff f hh   AA  Camera Objective f u A f  h  h  A  P A Afocal Adapter 1 mh  h h   A A ng an afocalng adapter. These come in both MP m ean telescope changes the focal length of the ean telescope changes cover the new FOV without vignetting. h Telephoto Example: Telephoto 0.75X wide angle and telephoto versions. This Galil system. to lens diameters The must be designed The FOV of a camera lens can be changed by addi be changed of a camera lens can FOV The Afocal Adapters 1.6X OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-67 ent back to the source. ent back Reflective street signs and reflective and Reflective street signs incorporating by this effect paint use The paint glass or beads as lenses. coating serves as a matrix to hold the beads away from a reflective back surface. diffuse reflector instead of a mirror, a mirror, reflector instead of diffuse ens and a mirror. On axis, all a mirror. On of the light ens and ed. The light is s ed. The guration is limited by vignetting of the and directed back to the source, however the A cat’s eye retroreflector is constructed out of a l The angular performance cam be improved by using a is reflected back through the lens and re-collimat and the lens through is reflected back is reduced. the light efficiency however Off axis, the beam is also re-collimated or efficiency of this confi angular acceptance the lens aperture. reflected beam by Cat’s Eye Reflection OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-68 strength of the red-eye prove light sensitivity. It is especially as possible. The retroreflection as possible. The will be by the camera lens. Because of spot the eye’s pupil. Less light gets into eye usually lies immediately the retina behind not red because the retinal reflection occurs he cat’s eye reflection from the blood-rich he cat’s eye ould predict that the oreflected beam will not be “collimated” and will sulting cat’s eye effect is called Eyeshine. sulting cat’s eye human retina. The retina can be considered as a scattering surface. To minimize red eye: - the flash as far from camera lens Position will to the flash and not be seen directed back size on the retina and scattering, the retr have an angular spread. - Use a pre-flash or light to reduce the size of the smaller and pupil size allows less of the scattered light to be returned in retroreflection. A simple area argument w Red eye in flash photography is caused by t reflection as the pupil diameter will go to the fourth power. reflection is cat’s eye animals, the In many from the tapetum lucidum. This tissue layer im retinal to the through reflects light back and prevalent in nocturnal animals. This re Red Eye OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-69 Media Input or Output Input or Direction Page Scan Image of Linear Array Array Linear or detector configuration: area, line or ectronic signal or digital image or to into an image. There are three basic ensor. This is really just a camera. This ensor. A linear array scanner or push broom A uses a linear detector array or scanner One as LEDs. linear array of sources such at a line of the scene is imaged or recorded the moving by is scanned scene The time. 2-dimension output media or scene through the image of linear array. are thermal printers, high Examples flatbed document resolution film scanners, scanners and earth resources satellites. convert a digital image or electronic signal the source upon based configurations for scanners spot. The area scanner uses a two-dimensional s Scanners are used to convert a scene into an el Scanners OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-70 Red Green Blue Glass Platen with Document the paper by a motor and belt drive. and the light source. It is mounted to a It is mounted the light source. and 1 magnification onto the paper surface with array is used. Each line is covered by a by line is covered Each array is used. about 1 inch long. The three about 1 inch color long. signals are Light Source Lens folded with a series of mirrors. Mirror CCD Carriage To obtain color images, a tri-linear CCD To array is The CCD color filter. different registered in software. a single lens. The optical path is carriage contains the entire optical system The metal ground rod and driven along the length of A linear CCD array is imaged with about an 8: array is imaged with about an linear CCD A Linear Array Scanner – – Example Flatbed Computer Scanner OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 17-71 Scan Page every other line in the every Line Scan . Each field contains Each . two fields two into a single image without 30 Hz, and the field rate is 60 Hz. Phosphor e written in a single pass down the screen (HDTV the screen (HDTV e written in a single pass down point detector or source scan in an optical flying and some scientific cameras). -frame fields are written per scan: two Interlace the frame rate is (NTSC), image. In the U.S. lag and the response of the eye combine the noticeable flicker. Two pertinent television definitions related to scanners: Two -lines ar TV scan: all of the Progressive In a flying spot scanner, a In a flying spot scanner, is scanned in a two-dimensional pattern over the is scanned scene or output surface. The two common options for the fast line are a galvanometer mirror spot scanner or a polygon scanner. The primary example is a laser printer where the page scan is accomplished by medium. the photosensitive recording moving Laser light use two galvanometer mirrors. shows CRTs are electron based flying spot scanners. Flying Spot Scanners