Difference between revisions of "Temporary Optics Bootcamp"
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You will build something that looks like the picture below. There will be a light source (LED), an object being illuminated (a micrometer calibration slide), a lens for focusing, and a camera to view the final image. You will be able to adjust the positions of the object and lens to see what happens to the image formed on your camera. | You will build something that looks like the picture below. There will be a light source (LED), an object being illuminated (a micrometer calibration slide), a lens for focusing, and a camera to view the final image. You will be able to adjust the positions of the object and lens to see what happens to the image formed on your camera. | ||
− | [[Image: | + | [[Image: OpticsBootcampApparatus.png|thumb|400px|center|Imaging apparatus with illuminator, object, lens, and CCD camera mounted on an optical rail.]] |
The first step is to gather the materials required to build the lens measuring apparatus. Look at the image above to think about the parts you will need. | The first step is to gather the materials required to build the lens measuring apparatus. Look at the image above to think about the parts you will need. | ||
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|width="150"|[[Image: MountedLEDonTable.JPG|frameless|150px]] | |width="150"|[[Image: MountedLEDonTable.JPG|frameless|150px]] | ||
|align="left" colspan="2"|'''Optical posts, post holders, and mounting bases''' | |align="left" colspan="2"|'''Optical posts, post holders, and mounting bases''' | ||
− | Optical posts and post holders are used to mount your optical components to the table (or an optical breadboard). In addition, the post holder enables you to set the height of your optical components. In this bootcamp, you'll | + | Optical posts and post holders are used to mount your optical components to the table (or an optical breadboard). In addition, the post holder enables you to set the height of your optical components. In this bootcamp, you'll use the posts with their thumbscrews to ensure your components are all the same height. The images demonstrate how to use a 1/4-20 cap screw to connect the BA1 mounting base to a PH2 post holder. |
* Secure the BA1 mounting base to the PH2 post holder using one 1/4-20 x 5/16 cap screw and the 3/16 hex balldriver. | * Secure the BA1 mounting base to the PH2 post holder using one 1/4-20 x 5/16 cap screw and the 3/16 hex balldriver. | ||
− | * | + | * When you're ready to mount things to the table, you will use one or two washers and one or two 1/4-20 x 1/2 cap screws to secure the BA1 base to the table, as in the image on the right. |
|- | |- | ||
|width="150"|[[Image: 140729_OpticsBootcamp_05.jpg|frameless|130px]] | |width="150"|[[Image: 140729_OpticsBootcamp_05.jpg|frameless|130px]] | ||
|width="150"|[[Image: 140729_OpticsBootcamp_07.jpg|frameless|130px]] | |width="150"|[[Image: 140729_OpticsBootcamp_07.jpg|frameless|130px]] | ||
− | |align="left" rowspan = "2" colspan="2"|'''Mount the LED light source''' | + | |align="left" rowspan = "2" colspan="2"|'''Mount the LED light source''' |
* In the LCP01 cage plate, the LED will get sandwiched in-between two SM2RR retaining rings. First screw in one SM2RR only 1 mm deep. | * In the LCP01 cage plate, the LED will get sandwiched in-between two SM2RR retaining rings. First screw in one SM2RR only 1 mm deep. | ||
* Next place the LED above it. | * Next place the LED above it. | ||
* Finally tighten down the second SM2RR using the SPW801 adjustable spanner wrench. The SPW801 can be opened until its width matches the SM2RR diameter, the separation between the ring's notches. | * Finally tighten down the second SM2RR using the SPW801 adjustable spanner wrench. The SPW801 can be opened until its width matches the SM2RR diameter, the separation between the ring's notches. | ||
* Affix a TR2 optical post to the LCP01 cage plate (holding the LED) using an 8-32 set screw. | * Affix a TR2 optical post to the LCP01 cage plate (holding the LED) using an 8-32 set screw. | ||
− | * | + | * Place this optical post into a post holder and mount to the table (see previous section). |
− | '''Power the LED light source''' | + | '''Power the LED light source''' |
* The red LED will be connected to a DC power supply. Ensure that the current limit on the power supply (CH1) is set to a value below 0.5 A! | * The red LED will be connected to a DC power supply. Ensure that the current limit on the power supply (CH1) is set to a value below 0.5 A! | ||
* Connect channel CH1 to the red and black threads of the LED, using alligator clip cables. | * Connect channel CH1 to the red and black threads of the LED, using alligator clip cables. | ||
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|width="150"|[[Image: LensInLensTube.JPG|frameless|150px]] | |width="150"|[[Image: LensInLensTube.JPG|frameless|150px]] | ||
|width="150"|[[Image: LensTubeLCP02.JPG|frameless|150px]] | |width="150"|[[Image: LensTubeLCP02.JPG|frameless|150px]] | ||
− | |align="left" colspan="2" rowspan="1"|'''Mount a lens in a lens tube''' | + | |align="left" colspan="2" rowspan="1"|'''Mount a lens in a lens tube''' |
We typically mount our lenses in lens tubes so that we can easily add them to or remove them from cage plates in our optical systems. | We typically mount our lenses in lens tubes so that we can easily add them to or remove them from cage plates in our optical systems. | ||
* Carefully (use lens paper to protect the lens surface) place the 25 mm plano-convex lens into a 1" lens tube with the hemisphere facing up | * Carefully (use lens paper to protect the lens surface) place the 25 mm plano-convex lens into a 1" lens tube with the hemisphere facing up | ||
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|- | |- | ||
|width="150"|[[Image: TightenSetScrew.JPG|frameless|150px]] | |width="150"|[[Image: TightenSetScrew.JPG|frameless|150px]] | ||
− | |align="left" colspan="3"|'''Set up the cage rods''' | + | |align="left" colspan="3"|'''Set up the cage rods''' |
− | We will use cage rods to frame our optical system so that we can adjust the position of cage plates by sliding them along the rods. There are 4-40 set screws that you can tighten to set the cage plate positions | + | We will use cage rods to frame our optical system so that we can adjust the position of cage plates by sliding them along the rods. There are 4-40 set screws that you can tighten to set the cage plate positions. Cage rods also help us to make sure our optical components are aligned to one another. |
* Place three cage rods (ER8) through the holes in the LCP01 cage plate holding the LED. We will practice to use three cage rods instead of four, since when we use 1" cage plates, this will enable us to switch out lens tubes easily. | * Place three cage rods (ER8) through the holes in the LCP01 cage plate holding the LED. We will practice to use three cage rods instead of four, since when we use 1" cage plates, this will enable us to switch out lens tubes easily. | ||
* Once the cage rods are flush against the back of the LCP01 cage plate, set their position by tightening the 4-40 set screws (see picture). | * Once the cage rods are flush against the back of the LCP01 cage plate, set their position by tightening the 4-40 set screws (see picture). | ||
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|- | |- | ||
|width="150"|[[Image: 140729_OpticsBootcamp_17.jpg|frameless|150px]] | |width="150"|[[Image: 140729_OpticsBootcamp_17.jpg|frameless|150px]] | ||
− | + | |align="left" colspan="3"|'''Mount the CCD camera''' | |
− | |align="left" colspan=" | + | |
* Affix a TR2 optical post directly to the CCD camera plate using the 1/4-20 set screw. | * Affix a TR2 optical post directly to the CCD camera plate using the 1/4-20 set screw. | ||
* Place optical post into post holder with BA1 mounting base. | * Place optical post into post holder with BA1 mounting base. | ||
* Connect the CCD to the computer using a red ethernet cable. | * Connect the CCD to the computer using a red ethernet cable. | ||
* Power up the CCD using the Calrad 45-601 power adapter. | * Power up the CCD using the Calrad 45-601 power adapter. | ||
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* Make sure the heights of the components are adjusted by adjusting the position of the optical posts. | * Make sure the heights of the components are adjusted by adjusting the position of the optical posts. | ||
+ | |- | ||
|} | |} | ||
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Now that you've learned the basics of mounting, aligning and adjusting optical components, you will through this lab exercise | Now that you've learned the basics of mounting, aligning and adjusting optical components, you will through this lab exercise | ||
− | * | + | * Verify the lens maker and the magnification formulae: |
:<math> {1 \over S_o} + {1 \over S_i} = {1 \over f}</math> | :<math> {1 \over S_o} + {1 \over S_i} = {1 \over f}</math> | ||
:<math>M = {h_i \over h_o} = {S_i \over S_o}</math> | :<math>M = {h_i \over h_o} = {S_i \over S_o}</math> | ||
− | * | + | * Become familiar with image acquisition and distance measurement using the Matlab software. |
{|class="wikitable" | {|class="wikitable" | ||
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** Divide additional images into an equal number with the target, the object, placed at less than and greater than 2<math>f</math> from the lens | ** Divide additional images into an equal number with the target, the object, placed at less than and greater than 2<math>f</math> from the lens | ||
* Under the ''Device Properties'' tab, optimize the ''Exposure Time Abs'' field for good contrast without pixel saturation. | * Under the ''Device Properties'' tab, optimize the ''Exposure Time Abs'' field for good contrast without pixel saturation. | ||
+ | * You may need to reduce the current in your LED, and add an ND filter after your light source to decrease its intensity | ||
* Measure the distance <math>S_o</math> from the target object to the lens and the distance <math>S_i</math> from the lens to the CCD active imaging plane. | * Measure the distance <math>S_o</math> from the target object to the lens and the distance <math>S_i</math> from the lens to the CCD active imaging plane. | ||
** Does the lens maker formula <math> {1 \over S_o} + {1 \over S_i} = {1 \over f}</math> apply as it should when the image focus is optimized? | ** Does the lens maker formula <math> {1 \over S_o} + {1 \over S_i} = {1 \over f}</math> apply as it should when the image focus is optimized? | ||
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** This manipulation allows you to calculate the image size <math>h_i</math>, taking into account the CCD pixel size: 7.4 μm x 7.4 μm. | ** This manipulation allows you to calculate the image size <math>h_i</math>, taking into account the CCD pixel size: 7.4 μm x 7.4 μm. | ||
* Confirm the corresponding object size <math>h_o</math>: | * Confirm the corresponding object size <math>h_o</math>: | ||
− | ** | + | ** Each small tick mark is 10 um apart |
− | ** | + | ** Each larger tick mark is 100 um apart |
− | + | ||
* Do both magnification relationships <math>M = {h_i \over h_o} = {S_i \over S_o}</math> match ? | * Do both magnification relationships <math>M = {h_i \over h_o} = {S_i \over S_o}</math> match ? | ||
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* Given the sources of error, how far off could your measurements of magnification be? | * Given the sources of error, how far off could your measurements of magnification be? | ||
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Latest revision as of 21:32, 2 February 2016
Lab exercise 2: imaging with a lens
You will build something that looks like the picture below. There will be a light source (LED), an object being illuminated (a micrometer calibration slide), a lens for focusing, and a camera to view the final image. You will be able to adjust the positions of the object and lens to see what happens to the image formed on your camera.
The first step is to gather the materials required to build the lens measuring apparatus. Look at the image above to think about the parts you will need.
To help you familiarize yourself with the different components and get started, the lists below include part numbers and descriptive names of the components in the apparatus. It is likely that you will find some of the terms not-all-that-self-explanatory. Most of the parts are manufactured by a company called ThorLabs. If you have a question about any of the components, the ThorLabs website can be very helpful. For example, if the procedure calls for an SPW602 spanner wrench and you have no idea what such a thing might look like, try googling the term: "thorlabs SPW602". You will find your virtual self just a click or two away from a handsome photo and detailed specifications.
Optomechanics
These components are located in plastic bins on top of the center parts cabinet:
- 2 x 1" Lens tube (SM1L10)
- 2 x Lens tube slip ring (SM1RC)
- 2 x 2" Cage plate (LCP01, looks like an "O" in a square)
- 4 x Cage plate adapter (LCP02, looks like an "X")
- 2 x 2" Retaining rings (SM2RR)
These components are located on the counter above the west drawers.
- 3 x ER8 cage assembly rod (The last digit of the part number is the length in inches.)
- You may decide to add additional cage rods to extend the length of the ER8 rods.
- 2 x 1" Retaining rings (SM1RR)
Screws and posts
Stainless steel, ¼-20 size, socket head cap screws (SHCS), washers, posts, and post holders are located on top of the west parts cabinet. If you are unfamiliar with screw types, take a look at the main screw page on the McMaster-Carr website. Notice on the left side of the page that there are about ... links on the left side of the page. Click the links for more information about screw sizes and attributes. This link will take you to an awesome chart of SHCS sizes.
- 3 x Post holders (PH2)
- 3 x Optical posts (TR2)
- 3 x Mounting base (BA1)
- 3 x 8-32 set screws
- 3 x 1/4-20 x 5/16" socket cap screws
- 1 x 1/4-20 set screw
- 4 washers
- 4 x 1/4-20 x 1/2" socket cap screws
Optics
Lenses and microscope objectives are located in the west drawers.
- 1 x LA1951 plano-convex, f = 25 mm lens (this will be used as a condenser for your illuminator)
- 1 x LB1811 biconvex, f = 35 mm lens (this will be used to form an image of your object)
- 1 x ND filter (use this if your illumination is too bright, located on east cabinet)
Object
Imaging targets are located in a plastic bin on top of the east cabinet.
- 1 Micrometer Calibration Slide (each small division is 0.01mm, each larger tick mark is 0.1mm) mounted to a cage plate adapter (LCP02)
Optoelectronics
LEDs will be in a plastic bin on top of the center cabinet.
- 1 x red, super-bright LED (mounted)
Tools
Most of the tools are located in the drawers at your lab station. Be sure to put all of the tools you use back in their proper location.
Hex keys (also called Allen wrenches) are used to operate SHCSs. Some hex keys have a flat end and others have a ball on the end, called balldrivers. The ball makes it possible to use the driver at an angle to the screw axis, which is very useful in tight spaces. You can get things tighter (and tight things looser) with a flat driver.
- 1 x 3/16 hex balldriver for 1/4-20 cap screws
- 1 x 9/64 hex balldriver
- 1 x 0.050" hex balldriver for 4-40 set screws (tiny)
- 1 x SPW602 spanner wrench
You will also need to use an adjustable spanner wrench. The adjustable spanner resides at the lens cleaning station. There is only one of these in the lab. It is likely that one of your classmates neglected to return it to the proper place. This situation can frequently be remedied by yelling, "who has the adjustable spanner wrench?" at the top of your lungs. Try not to use any expletives. And please return the adjustable spanner wrench to the lens cleaning station when you are done.
- 1 x SPW801 adjustable spanner wrench
Things that should already be (and stay at) your lab station
- 1 x Manta CCD camera
- 1 x Calrad 45-601 power adapter for CCD
- 1 x ethernet cable connected to the lab station computer
Build the apparatus
Use the image of the apparatus to think about how to put your system together. The following guidelines should help get you started. If at any point you have questions, do not hesitate to ask an instructor for help.
Visualize, capture, and save images in Matlab
Now that you've learned the basics of mounting, aligning and adjusting optical components, you will through this lab exercise
- Verify the lens maker and the magnification formulae:
- $ {1 \over S_o} + {1 \over S_i} = {1 \over f} $
- $ M = {h_i \over h_o} = {S_i \over S_o} $
- Become familiar with image acquisition and distance measurement using the Matlab software.
Examine images in Matlab
Plot and discuss your results
- Repeat these measurements of $ S_o $, $ S_i $, $ h_o $, and $ h_i $ for several values of $ S_o $.
- Plot $ {1 \over S_i} $ as a function of $ {1 \over f} - {1 \over S_o} $.
- Plot $ {h_i \over h_o} $ as a function of $ {S_i \over S_o} $.
- What sources of error affect your measurements?
- Given the sources of error, how far off could your measurements of magnification be?