Phys 462 – Lab Session 5
Contents
1. the curvature of the other surface such that the effective focal length remains fixed at 100 mm As it does this we ll get OSLO to update the spot diagram plots in real time so we can see how the image quality varies with lens shape Ok slider wheel time In the main OSLO window click the window s setup window toolbar button El and ensure that the Optimization Tools option is checked Co No name Phys462_Lab5_Lens1 len OSLO Light File Lens Evaluate Optimize Tolerance Source Tools Window Help Eeer E gale Tile windows New graphics window Switch text window s SS right click actions Set Toolbars Row Standard Tools Optimization Tools Tolerancing Gaussian Beams Extended Sources This makes sure you have toolbar items displayed for various optimization tasks Now click on the open slider wheel spreadsheet button Enter 1 into the number of sliders field and press return ES Slider wheel Setup lt Surface Data oO x 4 ce x _ HE P 4 No Internal evaluation w Draw only O Ray intercept O OPO Field sag Spot diagram Long SA Number af sliders jm Use drag processing Surt Tg Item Value Lo O Lo O Enable swocallback CCL function Setup name D oZ o Oef zi 16 Now set the surface number for the slider to 1 double click on the Item to specify what parameter of surface 1 to adjust and select Curv2. Y Obj Frac Obj Min Fupil Max Pupil offset Fut FX Ay Draw rays to image surface 0 000000 0 000000 1 000000 1 000000 0 000000 700000 0 000000 0 000000 0 000000 0 000000 1 000000 0 000000 1 000000 1 000000 0 000000 Ok but where is the image surface We could put it 100 mm behind surface 2 which is where we expect the focus to be for an infinite object distance But here s a better idea let s get OSLO to put it in the right spot for us In the thickness column for the image screen IMS click the setup button and choose Autofocus gt paraxial focus as shown below 11 Sp Surface Data Ol x wf Select image surace thickness option yx TE ok EE j z Leen j Setup_ _wavelengths variantes j oran off _Group motes JA Lens No name ET g9 999979 Ent beam radius 25 000000 Field angle 15 000000 Primary wayln 0 587560 RADIUS THICKNESS APERTURE RADIUS GLASS SPECTAL 0 000000 __ 1 c000e z0 2 6795e 19 Aar O 680000 __ 8 449232 25 000000 BK 000000 o oooooof _ 2s o00000 air O oooooo 94 429547 Direct specification Variable vy Special variable Autofocus paraxial focus Autofocus minimum RMS spot size Autofocus minimum RMS OPO Now click on the Draw system 2D toolbar button IF again in your graphics window You should now see maw UW 2 Lens Drawing a el ES HETG S Blin Ne name UNITS WM FOCAL LENGTH 10
3. be 50 mm in diameter and the maximum off axis angle to be 15 E5 Paraxial Setup Editor Surface Data aff 7 T Aperture Field Conjugates Entr beam rad Field angle EI Object dist Object NA Object height Object to PPL Ax Pay 5 ope Gaus image Ht Gaus img dist Image NA PP2 to image working f nbr Magnification Aperture diwisions across pupil for spot diagram 17 0230000 gaussian beam Click the green tick symbol to accept the newly entered values and dismiss this spreadsheet uff Bs oj A GEN Now we re back at the lens data entry spreadsheet and its time to define some surfaces The spreadsheet is organized with one row for each surface and one column for each surface parameter Notice that the object is surface number zero but is conveniently labeled Obj We don t need to touch it anymore we already have it setup The front surface of the lens we re creating is surface 1 in our system although its labeled Ast in the spreadsheet This is because it is currently hard designated to be the aperture stop We can change this later but for now its fine There are two types of data that need to be entered for the surfaces There are properties of the surface itself such as radius of curvature or aperture But there are also properties that strictly apply to the media between surfaces such as thickness or material type In OSLO both data types are actually entered as if they
4. diagram Long SA Use dr Item mher af sliders processing Value 0 025350 Enable swocallback CCL function Level pe Setup name TT zl urt Now adjust the slider for surface 1 s curvature You should see the lens diagram update automatically and the lens shape changing continuously The focal length should stay at 100 mm This is good stuff If you go too 21 far the optimizer will blow up and fail to find a solution You may even need to manually enter some lens data to restore it to a reasonable region Ahhh out what about optimizing the image quality We can see even from a few rays in the lens diagram that some shapes are better than others But what is Once again click on the open slider wheel spreadsheet button Now enable the spot diagram and all points options Set the che scale to 5 Accept the spreadsheet by pressing the green E Slider wheel Setup lt Surface Data 3 No Intel evaluation O Draw on C4 sie dale O OPO O Field sag amp Spot diagra 4 Long SA Graphics scale 4 1 Field point at ATT points Number af sliders Use drag processing SUPT cfg Item walue 0 016350 Enable 5w callback CCL function Level Setup name oT zi Now move the slider around Examples of what you should see are shown below ix T lol x O C H A x fs FeY 1 2 Lens No name 100 000484 Ent beam radius 25 000000 Field angle
5. main OSLO window The graphics window should look something like this ma GW 2 O xX iS OG Oe S t Click on the Draw system 2D toolbar button JE The result should be 10 fae UW 2 Lens Drawing olx AFTOS GA Gl l He name WAITS BM FOAL LENGTH 100 Ma 0 25 DES GALE Interesting but not that helpful yet Click on the last item of the Lens pull down menu This is the Edit lens drawing conditions function You can also access this spreadsheet by pressing the IE button in the graphics window tool bar and selecting Operating Conditions In the resulting spreadsheet form select Draw rays to image surface as shown below and accept the spreadsheet by pressing the green EesiLens Drawing Conditions lt Surface Data lolx Enter drawlen raystosrt y img Be x _ Fe F ai Initial distance o 000000 Final distance o o000000 Horizontal view angle Vertical view angle First surface to draw Last surface to draw x shift 0 000000 Y shift 0 000000 DXF IGES view Apert Quadrant Rings 2 Spokes 4 I Fina dist a pertures quadrar ings pokes mage space rays inal dis a Draw aperture stop off On Hatch back of reflectors off amp On Shaded solid color Red Green 185 Blue Draw rays to wavefront Number of field points for ray fans Points for aspheric profiles 42 Draw rays to last drawn surface Frac
6. 0 Ma 0 35 DES GFL Hmmm better but we ve got some rays missing the lens note they are still traced as if the lens was there because we haven t told OSLO to check the beam diameter against the surface aperture We forgot that a real lens needs to be a bit larger than the diameter of the beam Let s fix that by increasing the apertures of the lens surfaces and the image screen to 30 mm radius by entering this value into the relevant spreadsheet cells 12 And don t forget we now have to update our thickness solve for surface 1 to give 2 mm thickness at a 30 mm aperture radius rather than at 25 mm Click on the Draw system 2D toolbar button JF again to obtain EFTE DEGBE Ne nome UNITS h FAL LENGTH 100 MA 0 75 DES QALI 13 4 H This is starting to look good We can already see that the rays don t focus too well off axis Now experiment with the lens viewing options by trying some of the other buttons on the toolbar FTG pS As you go through this section want you to right click in a few of the graphics windows and choose the copy to clipboard option Then paste the images into say a word document for a few examples of what you ve been doing You can then use these in your lab report Testing the image OK so how good is this planoconvex lens anyway Let s make some spot diagrams First we need to setup the number of rays to trace like lots Go to the main lens entry spreadsheet
7. 15 000000 Primary wavin 0 587560 SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPECIAL OB 0 000000 __ 1 0000e 20 __ 2 6795e 19 ar L AST 150 372439 __ 12 743059 5 30 000000 A ez c L L 2 29 572207 o oo0000 _ 30 000000 arD I Co ms o ooo0oo0o _ 94 429547 _ 30 000000 J Ea z FBY 0 7 wi 0 006650 x Bi l BEGGS OS Bc FeY O 22 ap eee i BELEAAN x _ P Lens No name 100 025351 Ent beam radius 25 000000 Field angle 15 000000 Primary wavin 0 587560 SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPECIAL OB 0 000000 1 0000e 20 2 6795e 19 ar I Lj 37 950887 __ 13 083318 5 30 000000 A BK7 rT 2 125 988793 fe o 000000 Ss 30 000000 arD I o mms o ooo0oo0o _ 34 429547 __ 30 000000 __ at Window 0 026350 SS UL me GW 32 BEGGS OS iis Data l x A Jn _ i Lens No name 100 000806 Ent beam radius 25 000000 Field angle 15 000000 Primary wavin 0 587560 SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPECIAL OB 0 000000 1 0000e 20 __ 2 6795e 19 ar LJ 61 162659 __ 11 306848 5 30 000000 BK7 Lj 2 312 354404 o c00000 30 000000 arD J D mms o o0o00o00 _ 34 429547 _ 30 000000 _ Slider Window ioj x wi 0 016350 KI H Step0 001 Heme GW 32 SSS Bes FEY O Obviously there is a lens shape that is much better than any other because the spot size is smallest But there s still on
8. Shared Private This will bring up a list of glasses EES Glass Catalog lt Surface Data Se E J T vA BK7 n 1 516800 64 17 dens 2 51 hard 610 chem 20122 gt dndT 1 5 TCE 71 bub 0 trans 0 991 cost 1 00 avail V sort Sort by Name Index gt v number _ _ _ _ _ _ _ Name amp Index v number si BAF 13 BAF3 BAF4 BAFSO BAFS1 BAFS2 BAFS BAFS BAFN1O BAFN11 BAFNG BAK1 BAK2 BAK4 BAKS BAKSO BALF4 BALFS BALFSO BALKN3 BASF1 BASF10 BASF12 BASF13 BASF2 BASFS1 BASFS2 BASFS4 BASFS6 BASFS7 BASF BASF64A BK1 BK10 BK3 BKG BKS F1 F13 F14 F15 F2 F3 F4 F5 F6 F7 FS F9 FK3 FK5 FK51 FK52 FK54 FN11 K10 K11 K3 K4 K5 K50 K7 KF3 KF6 KF9 KZFN1 KZFN2 KZFS1 KZFS6 KZFS7A KZFSS8 KZFSN2 KZFSN4 KZFSNS KZFSN9 LAF1I1A LAF13 LAF2 LAF20 LAF22A LAF3 LAFS LAFN1O LAFN21 LAFN23 LAFN24 LAFN28 LAFN LAFNS LAK1O LAK11 LAK16A LAK21 LAK23 LAK28 LAK31 LAK33 LAKS LAKS LAKL12 LAKL21 LAKN12 LAKN13 LAKN14 LAKN22 LAKNG LAKN LASF18A LASF3 LASF32 LASF33 LASF35 LASF36A LASFN1S LASFN30 LASFN31 LASFNS LFS LF LFS LLF1 LLF2 LLF6 LLF7 PK1 PK2 PK3 PK50 PKS1A PSK2 PSK3 PSKSO PSKS2 PSKS3A PSKS4 SF1 SF10 SF11 SF12 SF13 SF14 SF15 SF16 SF18 SF19 SF2 SF3 SF4 SFS SFS3 SFS4 SFSS SF56A SF57 SF58 SFS9 SFG SF63 SF64A SFS SF9 SFL4A SFLS6 SFLS 7 SFL6 SK1 5K10 SK11 5K12 5K13 5K14 SK15 SK16 SK18A SK2 SK3 SK4 SKS SK51 SK55 SK6 SK SK8 SSK1 SSK2 SSK3 SSK4A ssksoO SSK51 SSKNS SSKNS TIF3 TIFS6 TIFNS UBK UKSO ZK1 ZKN z Choose BK7 by clicking on th
9. University of Alaska Fairbanks Phys 462 Lab Session 5 Introduction to Computer Ray Tracing Format 4 8049nm x 4 8049mm 2 4024mm 2 4024mm 2 4024mm 4 Distortion um gases eee M 3 s g g ov oo a pa g 2 3 5 3 g g ae ey a a u l 2 4024mm T Jamieson SCALE 2 40244 TH 1 IR Fisheye Lens WAVELENG DISTORTION PLOT Field 45 de ASTIGMATISM LONGITUDINAL CHROMATIC 0 1 mm SPHERICAL ABER mm FOCAL SHIFT mm Field 31 5 deg 0 1 oe DISTORTION 50 k XH 50 LATERAL COLOR mm 0 002 0 002 On IR Fisheye Lens Ea WAVELGTH 10 00 4 8 00 RAY TRACE ANALYSIS 01 56 PM General Information Location Reichardt room 113 Optics Lab Session Times Thursday February 27 2014 Report due Thursday March 06 2014 Overview Title Introduction to Computer Ray Tracing Purpose Equipment Methods To gain an introduction to ray tracing techniques in general and the OSLO ray tracing program in particular To use these tools to optimize a simple optical system PC computer OSLO software This lab is unusual it is a virtual lab that will be done by computer have setup a problem that will introduce you to the possibilities for lens design using a modern software package like OSLO Note OSLO is only one of perhaps a half dozen packages that advertise similar capab
10. and click on the setup button below the message area In the resulting spreadsheet form set the Aperture divisions across pupil for spot diagram to 51 as shown and accept the spreadsheet by pressing the green 13 E Paraxial Setup Editor Surface Data E x i BE j e Aperture Field conjugates al Entr beam rad Field angle Object dist Object NA Object height Object to PPL ax pay slope 0 250000 Gaus image ht 26 794914 Gaus img dist Image NA FF2 to image Working T ner 2 000000 Magnification 0 000000 Aperture diwisions across pupil for spot diagram gaussian beam Next in the graphics window click the setup window toolbar button Ei and select spot diagram fae UW 32 Lens Drawing _ joyx i GGG Oe S ae New graphics window Mo name WIMITS hh ar earn ete GTH 100 NA 0 25 DES OSLO Set window title Invert background Right click actions a an Standard Tools wa ae aa Ray Analysis wavefront Spot Diagram PSF KAT F Energy Analysis The toolbar options will change Click the newly available spot diagram to obtain toolbar button 14 fae UW 32 Spot Diagram Analysis Bed OlA 40 FULL FIELC jadeq G 7 FIELD 10 6deq 5 ON AsIS Odeg a 5 T FOCUS SHIFT SPOT SOE amp FEAE SHIFT MITS om ELI WNL ae CESS SPOT DIAGRAM ANALYSIS A This shows how a distant point source would be imaged at 5 differ
11. ature CV You should see the following Eee Slider wheel Setup lt Surface Data Shel Ez ff Delect variable type a x Jao P 4 No Internal evaluation Draw only O Ray intercept O OPO Field sag 3 Spot diagram Long SA i nm Number of sliders Use drag processing SUr cq Item Walue Curvature Cw gt Enable sw callback CEL function E 00 Cems cc Aperture radius AF decentration DCX Y decentration OC Z decentration DEZ Alpha tilt angle TLA Beta tilt angle TLB Gamma tilt angle TLC Tilt vertex offset in x TOX Tilt vertex offset in y TOY Tilt vertex offset in z TOZ Setup name Accept the spreadsheet by pressing the green This should now create a slider control that can be used to adjust the curvature of surface 1 Go ahead and try it The screen should now contain items like this iSO 6 Oo S ie as Step 0 001 17 Note the slider control that has appeared Note also how the lens edge thickness stays constant as you adjust the slider that s no accident OSLO is calculating that for you on the fly This is nice but unfortunately the focal length changes as you adjust the slider which we didn t want So we better fix that We need to setup an optimization error function Go to the menu in the main OSLO window and choose optimize gt generate error function gt aberration operands ti No name Phys462_Lab5_Lens1 le
12. belong to a surface If you enter a thickness or a material type into the row for a particular surface these data apply to the region between that surface and the next_one following it Note that the column labeled Glass initially shows air as the material associated with all surfaces To make a lens we will need to change the material between surfaces 1 and 2 to be some suitable glass We enter this selection into the row of data for surface 1 In this case we will designate our lens to be made from the very common Schott BK7 glass by choosing this material from OSLO s glass catalog Click the glass setup button in the row for surface 1 ast and select Catalog gt Schoit as indicated below E Surface Data me Ed k AEEA v eas lass option x Te a 2 cen setup wavelengths variables J oraw off croup J nores J Lens No name Ef 7 5421e 35 Ent beam radius 25 000000 Field angle 15 000000 Primary wavin 0 587560 SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPECIAL OBJ 0 000000 1 0000e z0 2 6795e 19 ar i L AST 0 000000 o o0000o0o 25 000000 AIR E T 2 o oo0oo0o0 o o00000 _ 25 000000 5 Ar ms o o000o0o0o o 0o0000o0 25 000000 5 Reflect Reflect hatch Pickup P Cata log C Schott Model M Schott 2000 Direct Ohara we eee i Chf Tra Ref Fan Spd Auf Var One lte Sps Wy MtF F Hoya Corning Sumita Hikari Misc Obsolete
13. e 54 Ent beam radius 72966 05 Primary wavln 0 587560 SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPECIAL OBI 0 000000 __ 1 0000e z0 __ 1 0000e 14 Aar I Lj AST 0 000000 __ o cooooo 1 000000 ar D 0 000000 __ o cooooo 1 000000 ar O IMS 0 000000 __ o cooooo 1 000000 D A Click on the Gen button A new spreadsheet form now appears in the spreadsheet window lt overlays the previous form which will reappear when are finished with the new one Verify that your settings are as below General Conditions lt Surface Data Eje ES a EE x f F F Evaluation mode Focal JuUnits mm Ray aiming mode Tentrel Petero PE wavefront ref sph pos Exit pupil Aperture checking Designer Aberration mode OPD in wawes O off on zernike poly reference axis Y O x Global ref surf for ray data Ray aiming type Aplanatic Paraxial Source astigmatic distance o 000000 Temp 20 000000 Pressure 1 000000 You should not need to change anything unless you want your name in the designer field Just dismiss this spreadsheet form by clicking on the red Click on the Setup button Click on the spreadsheet cell for Entr beam rad and set its value to 25 mm by typing this number Then click on the Field angle cell and set it to 15 Notice the object distance is already set very large We have now defined the object to be at effectively infinite distance the input beam to
14. e more step The auto focus condition that we set for the image screen isn t automated at this level It is automatically calculated each time you select this function but not when you adjust the slider This means the focusing screen is staying at approximately the best place 23 after all the effective focal length is being kept at 100 mm But as the aberrations come and go perhaps there s a better place for it To experiment with this you need to make the thickness of surface 2 variable But you also need to give OSLO some constraint to optimize as it varies this thickness So go back to the menu bar in the main OSLO window and once again choose optimize gt generate error function gt aberration operands This time we ll keep all the aberration terms but weight them all at 1 apart from the OCM21 term Set it to OCM21 100 as before but set its weight to 20 Now we re telling OSLO to adjust both the image screen distance and the curvature of the lens back surface We re also saying we strongly prefer the focal length to stay at 100 mm but we do also want the minimum blur at the image screen Go ahead and try moving the slider You re not seeing effects of un optimized focusing now recall we are solving for the image screen location that minimizes the blur Explore the other options for diagnosing image quality as you adjust the lens shape Quantitative Exercises e Notice that the lens spreadsheet gives real time upda
15. ect specification Ar M 000000 LI z Solves 5 Curvature pickup F Minus curvature pickup P Variable v Special variable vy Notice that a new toolbar button is now available in OSLO s main window 2 This invokes the optimize function Try it now by first setting the curvature of surface 1 to give an efl of around 75 mm Then with a text window open and visible press The text window prints diagnostics as OSLO iterates toward a solution Hopefully you should now have an efl of almost exactly 100 mm Click on the Draw system 2D toolbar button IF in a convenient graphics window to obtain 20 Oo Xx ie Hame UNITS WM FOCAL LENGTH 100 NA 0 25 DES OSL H G Well its not much of a lens for this job but at least the efl is 100 mm as required We can now force the efl to 100 mm for any reasonable choice of curvature for surface 1 but manually optimizing each time is tiresome Let s automate it Click on the open slider wheel spreadsheet button again Now we ll tell OSLO to run the optimization every time the slider changes the curvature of surface 1 Select the enable sw_callback CCL function option and set the level to 2 This tells OSLO to invoke call back the optimizer for 2 iterations every time the slider is moved Accept the spreadsheet by pressing the green w Draw only O Ray intercept OPD Field sag 3 Spot
16. ent image screen locations centered on the paraxial focus and at 3 different angles to the axis There are other toolbar options available for spot diagram analysis too l Go ahead and try them although for now none of the others will be of much interest Again please make a copy of the spot diagram analysis by copy and paste into word to use in your report Also again using the graphics window s setup window toolbar button Ei experiment with some of the other analysis options We won t pursue these today Optimizing a lens So far we ve just made a static lens and looked at some rays going through it But is it the best we can do for our imaging application Could we improve on it The answer is of course yes But first we need to define a little more precisely what our application actually is We ll choose here an example application that is about as simple as possible image an object at Se with a lens of 30 mm aperture and 100 mm effective focal length We could have OSLO do this all automatically but it wouldn t be much fun at this early stage Rather let s setup a slider wheel to vary the curvature You can get some more control over the report spot diagram output by directly calling this plot routine from the command line The syntax is rpt_spd nrays max_defocus_ dist no_of_focus_shifts scale airy_yn 15 of one surface of our lens continuously We ll then get OSLO to solve for
17. ickups P Chief ray height Variable Edge thickness Special variable This will generate two dialogs First you are asked what radius you want to specify the thickness at Enter 25 mm Then you are asked for a thickness to solve for at that radius Enter 2 mm Your lens spreadsheet should now look like this Es Surface Data a el ES ff x E E P Coen J setup wavelengths _variables eran of arcup mores J Lens No name ETI 29 999979 Ent beam radius 25 000000 Field angle 15 000000 Primary wawl 0 587560 SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPECIAL OB 0 000000 __ 1 0000e za _ 2 67a5e 19 Aar O AST 51 680000 _ 8 449232 25 000000 BK i o coooo0 a cooooo 25 099984 ain O IMS o coooo0 a cooooo 25 099984 CS Sf Notice the S label in the thickness button for surface 1 Ok let s take a look at what we ve built using some viewing tools There are several types of window created by OSLO one of which is a graphics window The graphics window title bar identifies its type and id There are two basic types of graphics windows called UW and GW windows UW windows are updateable in that they can be automatically rewritten with current data GW windows are static and cannot be updated they must be cleared and rewritten Choose any open GW or UW If there is no such window open a new one using the Window gt Graphics gt New option from the menu bar of the
18. ility We will be using the following functions of the software Lens surface data specification via the lens spreadsheet simple 2 D and 3 D graphical views of the lens and of rays passing through it Automatic solve functions for edge thickness and for image screen position Optimization of designated lens parameters according to a user defined error function Slider wheel input for rapidly varying one or more design parameters Automatic optimization of lens parameters in real time in response to slider wheel adjustments Evaluation of aberrations using ray fans and spot diagrams These functions are a small subset of the possibilities with this program Note that we will be using the student version of OSLO here Anyone can download this for free from http Wwww lambdares com The student version is however limited to only 10 surfaces Detailed procedure Getting started We will begin the session with an overview of our objective the tasks ahead of us and content that will be required in your report Find yourself a computer in the Astronomy Lab that has the OSLO program installed on it Start OSLO by clicking on the OSLO icon on the desktop OSLO Dismiss any annoying dialogs about user tips or recently used files strongly recommend that you read the user manual pages that have attached to the lab handout preferably before we start the lab itself Entering a lens Our first task is to examine the beha
19. is item from the list Notice that the glass list displays lots of potentially useful data in the spreadsheet message area most critical for now is that it tells us that n 1 516800 for this glass BE n 1 516800 Y 64 17 dens 2 51 hard 610 chem 201 22 dnd 1 5 TCE 71 bub 0 trans 0 991 cost 1 00 avail With BK7 highlighted click on the green check symbol to accept this selection Notice that the glass type changes to BK7 in the lens data spreadsheet Now we set the aperture radii of the two lens surfaces and the image screen to be 25 mm which corresponds of course to elements with a physical diameter of 50 mm To do this just enter the number 25 into these three cells in the Aperture radius column i e ES Surface Data joy x off m x z F Leen J setup wavelengths variables oraw ort aroup rores Lens No name ET 7 5421e 35 Ent beam radius 25 000000 Field angle 15 000000 Primary wawr 0 587560 SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPECIAL OB 0 000000 __ 1 0000e za 2 6795e 19 ar L AST 0 000000 __ o oooooa 25 000000 BK 0 000000 __ o oooooa 25 000000 ar L IMS 0 000000 __ o oooooa _ 25 000000 L Next we set the radii of curvature for the lens surfaces Let s start with a singlet planoconvex lens of 100 mm effective focal length We better make the first surface the curved one given that our object is at In OSLO you can use a Curvature of
20. l Notice the mode is set to min This means efl will as of now be set to zero we don t want that But if efl minus 100 mm was zeroed this would be good It would mean efl itself was set to 100 mm Now at this point OSLO has been setup to store the current value of efl in the 21 element of an internal array that is referred to as the OCM array To tell OSLO to make efl 100 mm we actually ask it to make OCM21 100 mm equal to zero Double click in the Definition column of the one remaining spreadsheet row and the value to OCM21 100 Also make sure the weight is set to 1 Accept the spreadsheet by pressing the green ES Operands Data Editor lt Surf OP MODE waT MAME DEFINITION 1 000000 EFL OCM2 1 100 0 19 But we still can t actually minimize this error function because we haven t allowed OSLO to vary anything that would change the focal length So we now go back to the main lens data entry spreadsheet and set the curvature of surface 2 to be variable as shown below ESS Surface Data jo x ff Select curvature o tHon am i x Wariable v E T j e een setup wavelengths variables oraw off croup mores J Lens No name ETI 70 749362 Ent beam radius 25 000000 Field angle 15 000000 Primary wawl 0 587560 RADIUS THICENESS APERTURE RADIUS GLASS SPEC DAL 000000 1 0000e z0 _ 2 6795e 19 aR L 563278 __ 17 661764 5 320 000000 aA ek7 c L 000000 i Dir
21. n OSLO Light File Lens Evaluate Optimize Tolerance Source Tools Window Help Abe ss i Generate Error Function Singlet Operands Cemented Doublet l GENII Ray Aberration Variables Slider WWwheel Design Aberration Operands Ray Operands terate y P Advanced Optimization Optimization Conditions Support Routines This should open a spreadsheet with lots of entries All these are terms that are currently selected as contributors to the error function We want to remove all but one the last one so that our error function only includes effective focal length efl Click on the button labeled 1 in the leftmost column of the spreadsheet Then shift click on the button labeled 20 to select items 1 20 Press the delete key to remove these from the spreadsheet and from the error function 18 E x EE Operands Data Editor of mit x Foe P OP MODE WST NAME DEFINITION 1 000000 FY OCM1 1 000000 PU OcM2 1 000000 PYZ OcM3 1 000000 PUZ ocM4 1 000000 PAC OcMs gt 1 000000 PLC OCM 1 000000 SAC OcM g 1 000000 SLC oOcMs gt 1 000000 SA3 OcMS 1 000000 CMA OcM10 1 000000 AST3 OZM11 1 000000 PTZ3 CCM 12 1 000000 O153 OCM13 1 000000 SAS ocM14 1 000000 CMAS OZM15 1 000000 ASTS OCM16 1 000000 PTZ5 OCML 1 000000 DIS5 OZM18 1 000000 SA OZM19 1 000000 TOTAL_SPH OcM20 1 000000 EFL OcM2 1 xj Now we ll setup the ef
22. sion 2 Tabulation of data Provide a few screen grabs and some brief explanations for the various analysis tools that you experimented with Tabulate the best performing lens configurations that you found in the final section Include plots of the lens layouts together with a brief description of each one You should include at least a description of the best forms for the following cases e BK 7 lens 2mm edge thickness e High index lens 2 mm edge thickness e High index lens 8 mm edge thickness 3 Analysis and results For the BK7 lens with 2mm edge thickness use the RMS Spot Size versus Field tool to estimate the RMS spot size on axis for a range of Coddington shape factors Plot how the spot size depends on shape factor Is there a best shape 4 Additional Discussion Your discussion should address at least the following specific questions e How does the best shape for a singlet lens working at infinite conjugate ratio depend on the lens thickness and refractive index e What are the best shapes for imaging at unit conjugate ratio e Would you recommend using high or low index glasses for lenses like these e Do thin or thick lenses appear to work better or does it not matter e What types of aberration remain even at the best shape e What limitations do you think this analysis might have 5 Original Notes Attach a photocopy of your original notes taken during the lab The purpose of this is to demonstrate tha
23. t you were not only present in the lab but also that you participated fully enough for you to show that the content of your report is based on your own measurements and your own understanding of what was actually done 25 These notes are usually not neatly prepared but they do represent your only true record of what you did Your goal is to record enough information to convince me that you could in principle at least still adequately write up what you did at some time in the distant future when your immediate memory has faded You may type your measurements directly into a computer file if you wish but these results must be accompanied with ample free text explanation of what each measurement actually is And you ll still need lots of diagrams 26
24. tes of the lens data as you move the slider Using this compute the Coddington Shape Factor of the lens when it is giving the smallest on axis spot size The shape factor is calculated from the signed radii of curvature of the two lens surfaces using q r2 r r2 r1 e Experiment with changing the aberration operands and their weightings Does the best choice of Coddington Shape Factor change e ry changing the glass at surface 1 to something of higher index approximately 2 How does the minimum RMS spot size change What is the Coddington Shape Factor for best focus with this glass e Try setting a greater edge thickness for the lens 8 mm say Now what is the best shape factor Is the final image better or worse as the lens is made thicker e Try setting up an object at an object distance of 200 mm so that the 100mm lens will be working at unit conjugate ratio Now what is the best lens shape factor e lf time permits we may attempt to compare the performance of the best form singlet lens with a similar optimized doublet from OSLO s lens library will determine during the class if we have time for this Make sure you capture some relevant graphics during the above work to include in your lab report 24 Content of Report Your work for each lab report will be graded out of 100 points according to the description below 1 Title Page Provide your name the experiment date and the title of the lab ses
25. vior of a single two surface lens From the File menu of the main window choose New Lens Fill out the initial dialog box as shown File new New file name Phys462_Lab5_Lens File type E Custom lens Catalog lens Perfect a Humber of surfaces 2 1 000000 Focal length of pertect lens o o00000 Maanitication 0 050000 mage numerical aperture Cancel Help This should get you to a screen that looks like TA No name Phys462_Lab5_Lensi len OSLO Light File Lens Evaluate Optimize Tolerance Source Tools window Help Blick wf Omus Fe surface Data APERTURE RADIUS 1 0000 14 i onanan EE noone Text output Page mode Graphics autockear We will begin by setting up a suitable object entering a simple and static planoconvex BK7 glass lens and tracing some rays through it onto an image screen The window named Surface Data is the spreadsheet window It is the primary location for entering the surface and the setup data that will define your optical system Note the row of buttons located below the command input and user message areas of the spreadsheet window 1 If the surface data spreadsheet is not on your screen you can always open it from the first item on the Lens pull down menu ES Surface Data e Es lt E TE E E A _variables _oraw of E _Notes_ j z Lens No name EF 1 0000
26. zero to designate a plane surface although of course a mathematician may not consider this good practice So we can leave surface 2 and just set the curvature of surface 1 Using the paraxial lens maker s formula we find that R should be set to n 1 51 68 mm for a thin lens Enter this value into the spreadsheet cell for surface 1 curvature Notice that OSLO has now calculated that the effective focal length is 99 999979 mm which is gratifying Now what about lens thickness We ll certainly need a bit of that if the lens is to be realistic We really need to calculate a reasonable thickness based on the surface curvature and the lens aperture doable sure but it is a bit tedious Time for our first trick Instead of entering a thickness directly for surface 1 recall this is the thickness from surface 1 to surface 2 we ask OSLO to solve it for us Click the button next to the thickness cell and select Solves S gt Edge thickness as shown E ourface Data _ joy x F Select thickness option C Edge thickness a T x E m P i cen L setup_ waveTengens variables oran off J _croup_ L_notes_ Lens No name ET 99 999979 Ent beam radius 25 000000 Field angle 15 000000 Primary wavdn 0 587560 RADIUS THICKNESS APERTURE RADIUS GLASS SPECIAL 0 000000 _ 1 0000e z0 __ 2 6795e 19 ar L sso000 J a ano000 LL E amas i Lj 000000 g oooo00 __ z ae E oooo0o o o00000 ieee Axial ray height P
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