Kerr Microscope - Revision history

Junherng: /* Setup 2: Microscope Setup */

2022-04-30T15:24:59Z

Setup 2: Microscope Setup

← Older revision		Revision as of 15:24, 30 April 2022
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	File: Microscope setup kerr.jpeg\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.		File: Microscope setup kerr.jpeg\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.
	</gallery>		</gallery>

	<!-- [[File: Kerr microscope schematic.png\|right\|thumb\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]		<!-- [[File: Kerr microscope schematic.png\|right\|thumb\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]
	[[File:Microscope setup kerr.jpeg\|right\|thumb\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]]		[[File:Microscope setup kerr.jpeg\|right\|thumb\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]]

Junherng: /* Setup 2: Microscope Setup */

2022-04-30T15:23:21Z

Setup 2: Microscope Setup

← Older revision		Revision as of 15:23, 30 April 2022
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	The use of a micrometer screw translation stage allowed for finer control over the position of our sample to a precision of <math>\pm 10</math> microns (5 micron contribution from both ends of the measurement).		The use of a micrometer screw translation stage allowed for finer control over the position of our sample to a precision of <math>\pm 10</math> microns (5 micron contribution from both ends of the measurement).

	To test the iterated setups, two main samples were used, in addition to a series of permanent magnets. The first, a standard empty Si/SiO2 substrate as a control sample. The second, a magnetic sample whose external field will be controlled by a magnet stack. This magnet stack was attached to a second translation stage and held close to our samples. The external field strength affecting our sample could then be controlled by moving the magnet closer or ~~father~~ from our samples, and the distance travelled can be read off from the micrometer screw gauge. In terms of imaging, if stripe domains are the brighter features, the expected overall intensity garnered from the setup will decrease as the field increases, and vice versa if the stripe domains turn out to be the darker features.		To test the iterated setups, two main samples were used, in addition to a series of permanent magnets. The first, a standard empty Si/SiO2 substrate as a control sample. The second, a magnetic sample whose external field will be controlled by a magnet stack. This magnet stack was attached to a second translation stage and held close to our samples. The external field strength affecting our sample could then be controlled by moving the magnet closer or farther from our samples, and the distance travelled can be read off from the micrometer screw gauge. In terms of imaging, if stripe domains are the brighter features, the expected overall intensity garnered from the setup will decrease as the field increases, and vice versa if the stripe domains turn out to be the darker features.

	<gallery widths=450px heights=200px>		<gallery widths=450px heights=200px>

Junherng: /* Experimental Setup */

2022-04-30T15:21:47Z

Experimental Setup

← Older revision		Revision as of 15:21, 30 April 2022
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	* Power Supply		* Power Supply
	* Red LED		* Red LED
			* Red Laser Diode
			* Red Laser Pen (Visual Fault Locator)
	* Pinhole Aperture		* Pinhole Aperture
	* Plano-convex lens (100mm)		* Plano-convex lens (100mm, 150mm, 300mm)
	* ~~Steel sheet & Copper Wire~~		* Translation stage x2
	* Sheet Polarizer x2		* Sheet Polarizer x2
	* CCD Array (Webcam)		* CCD Array (Webcam)
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	To test the iterated setups, two main samples were used, in addition to a series of permanent magnets. The first, a standard empty Si/SiO2 substrate as a control sample. The second, a magnetic sample whose external field will be controlled by a magnet stack. This magnet stack was attached to a second translation stage and held close to our samples. The external field strength affecting our sample could then be controlled by moving the magnet closer or father from our samples, and the distance travelled can be read off from the micrometer screw gauge. In terms of imaging, if stripe domains are the brighter features, the expected overall intensity garnered from the setup will decrease as the field increases, and vice versa if the stripe domains turn out to be the darker features.		To test the iterated setups, two main samples were used, in addition to a series of permanent magnets. The first, a standard empty Si/SiO2 substrate as a control sample. The second, a magnetic sample whose external field will be controlled by a magnet stack. This magnet stack was attached to a second translation stage and held close to our samples. The external field strength affecting our sample could then be controlled by moving the magnet closer or father from our samples, and the distance travelled can be read off from the micrometer screw gauge. In terms of imaging, if stripe domains are the brighter features, the expected overall intensity garnered from the setup will decrease as the field increases, and vice versa if the stripe domains turn out to be the darker features.

	<gallery widths=~~350px~~ heights=~~150px~~>		<gallery widths=450px heights=200px>
	File: Sample edge 60x.png\| OBS screen capture - Imaging the edge of our sample with a 60x microscope objective.		File: Sample edge 60x.png\| OBS screen capture - Imaging the edge of our sample with a 60x microscope objective.
	</gallery>		</gallery>

Junherng: /* Setup 2: Microscope Setup */

2022-04-30T15:17:24Z

Setup 2: Microscope Setup

← Older revision		Revision as of 15:17, 30 April 2022
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	When working with microscope objectives, it is important to be aware of the <i>tube length</i>, which is the distance between the objective and the image produced by the objective. We used an objective that was manufactured according to the DIN standard, which specifies a 160mm tube length. Hence, we positioned our CCD array 160mm away from the objective to capture the image. If working with an RMS objective, the tube length is 170mm instead<ref>DIN Standard Microscope Objective Lenses - [https://blog.microscopeworld.com/2012/09/din-standard-microscope-objective-lenses.html#:~:text=A%20typical%20DIN%20standard%20microscope,Most%20DIN%20optics%20are%20interchangeable\| Microscope World].</ref>. A second parameter that must be kept in mind is the <i>working distance</i>, which is the distance that the sample must be placed in front of the objective. For the 10x and 60x objective, these are 1.5mm and 0.15mm respectively<ref>10x Objective - [https://www.edmundoptics.com/p/10x-din-plan-commercial-grade-objective/5386/\| Edmund Optics]</ref><ref>60x Objective - [https://www.edmundoptics.com.sg/p/60x-din-achromactic-finite-intl-standard-objective/3137/\| Edmund Optics]</ref>. Hence, when using the 60x objective, the sample is practically kissing the objective.		When working with microscope objectives, it is important to be aware of the <i>tube length</i>, which is the distance between the objective and the image produced by the objective. We used an objective that was manufactured according to the DIN standard, which specifies a 160mm tube length. Hence, we positioned our CCD array 160mm away from the objective to capture the image. If working with an RMS objective, the tube length is 170mm instead<ref>DIN Standard Microscope Objective Lenses - [https://blog.microscopeworld.com/2012/09/din-standard-microscope-objective-lenses.html#:~:text=A%20typical%20DIN%20standard%20microscope,Most%20DIN%20optics%20are%20interchangeable\| Microscope World].</ref>. A second parameter that must be kept in mind is the <i>working distance</i>, which is the distance that the sample must be placed in front of the objective. For the 10x and 60x objective, these are 1.5mm and 0.15mm respectively<ref>10x Objective - [https://www.edmundoptics.com/p/10x-din-plan-commercial-grade-objective/5386/\| Edmund Optics]</ref><ref>60x Objective - [https://www.edmundoptics.com.sg/p/60x-din-achromactic-finite-intl-standard-objective/3137/\| Edmund Optics]</ref>. Hence, when using the 60x objective, the sample is practically kissing the objective.

	The use of a micrometer screw translation stage allowed for finer control over the position of our sample to a precision of <math>\pm 5</math> microns (5 micron contribution from both ends of the measurement).		The use of a micrometer screw translation stage allowed for finer control over the position of our sample to a precision of <math>\pm 10</math> microns (5 micron contribution from both ends of the measurement).

	To test the iterated setups, two main samples were used, in addition to a series of permanent magnets. The first, a standard empty Si/SiO2 substrate as a control sample. The second, a magnetic sample whose external field will be controlled by a magnet stack. This magnet stack was attached to a second translation stage and held close to our samples. The external field strength affecting our sample could then be controlled by moving the magnet closer or father from our samples, and the distance travelled can be read off from the micrometer screw gauge. In terms of imaging, if stripe domains are the brighter features, the expected overall intensity garnered from the setup will decrease as the field increases, and vice versa if the stripe domains turn out to be the darker features.		To test the iterated setups, two main samples were used, in addition to a series of permanent magnets. The first, a standard empty Si/SiO2 substrate as a control sample. The second, a magnetic sample whose external field will be controlled by a magnet stack. This magnet stack was attached to a second translation stage and held close to our samples. The external field strength affecting our sample could then be controlled by moving the magnet closer or father from our samples, and the distance travelled can be read off from the micrometer screw gauge. In terms of imaging, if stripe domains are the brighter features, the expected overall intensity garnered from the setup will decrease as the field increases, and vice versa if the stripe domains turn out to be the darker features.

Junherng: /* Setup 2: Microscope Setup */

2022-04-30T15:16:31Z

Setup 2: Microscope Setup

← Older revision		Revision as of 15:16, 30 April 2022
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	===Setup 2: Microscope Setup===		===Setup 2: Microscope Setup===

	<gallery widths=~~350px~~ heights=~~250px~~>		<gallery widths=450px heights=350px>
	File: Kerr microscope schematic.png\| Schematic of microscope setup. The two mirrors facilitate beam alignment.		File: Kerr microscope schematic.png\| Schematic of microscope setup. The two mirrors facilitate beam alignment.
	File: Microscope setup kerr.jpeg\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.		File: Microscope setup kerr.jpeg\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.

Junherng: /* Setup 1: Angled Setup */

2022-04-30T15:14:48Z

Setup 1: Angled Setup

← Older revision		Revision as of 15:14, 30 April 2022
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	As a first observation of the MOKE, we utilized a basic setup that reflected a linearly polarized light source off our sample - an electromagnet that consists of a steel sheet wrapped with copper wire. The light source is an off-the-shelf red laser pointer. The reflected beam is focused by a plano-convex lens and passed through an analyzer before it is finally captured on our CCD array (webcam). The open source video capture software [https://obsproject.com\| OBS] was used to display the captured image.		As a first observation of the MOKE, we utilized a basic setup that reflected a linearly polarized light source off our sample - an electromagnet that consists of a steel sheet wrapped with copper wire. The light source is an off-the-shelf red laser pointer. The reflected beam is focused by a plano-convex lens and passed through an analyzer before it is finally captured on our CCD array (webcam). The open source video capture software [https://obsproject.com\| OBS] was used to display the captured image.

	<!-- [[File: Kerr setup angled initial.jpeg\|200px\|right\|thumb\|Setup 1. The laser pointer is mounted on an acrylic stand shown in bottom left of image.]] -->		<!-- [[File: Kerr setup angled initial.jpeg\|200px\|right\|thumb\|Setup 1. The laser pointer is mounted on an acrylic stand shown in bottom left of image.]] -->

Junherng: /* Experimental Setup */

2022-04-30T15:14:11Z

Experimental Setup

← Older revision		Revision as of 15:14, 30 April 2022
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	<gallery widths=350px heights=250px>		<gallery widths=350px heights=250px>
	[[File: Kerr microscope schematic.png\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]		File: Kerr microscope schematic.png\| Schematic of microscope setup. The two mirrors facilitate beam alignment.
	[[File: Microscope setup kerr.jpeg\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]]		File: Microscope setup kerr.jpeg\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.
	</gallery>		</gallery>

	<!-- [[File: Kerr microscope schematic.png\|right\|thumb\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]		<!-- [[File: Kerr microscope schematic.png\|right\|thumb\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]
	[[File:Microscope setup kerr.jpeg\|right\|thumb\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]] ~~-->~~		[[File:Microscope setup kerr.jpeg\|right\|thumb\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]]
	[[File: Sample edge 60x.png\|300px\|left\|thumb\| OBS screen capture - Imaging the edge of our sample with a 60x microscope objective.]]		[[File: Sample edge 60x.png\|300px\|left\|thumb\| OBS screen capture - Imaging the edge of our sample with a 60x microscope objective.]] -->

	This change was made in an effort to increase the magnification of our imaging setup.		This change was made in an effort to increase the magnification of our imaging setup.
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	To test the iterated setups, two main samples were used, in addition to a series of permanent magnets. The first, a standard empty Si/SiO2 substrate as a control sample. The second, a magnetic sample whose external field will be controlled by a magnet stack. This magnet stack was attached to a second translation stage and held close to our samples. The external field strength affecting our sample could then be controlled by moving the magnet closer or father from our samples, and the distance travelled can be read off from the micrometer screw gauge. In terms of imaging, if stripe domains are the brighter features, the expected overall intensity garnered from the setup will decrease as the field increases, and vice versa if the stripe domains turn out to be the darker features.		To test the iterated setups, two main samples were used, in addition to a series of permanent magnets. The first, a standard empty Si/SiO2 substrate as a control sample. The second, a magnetic sample whose external field will be controlled by a magnet stack. This magnet stack was attached to a second translation stage and held close to our samples. The external field strength affecting our sample could then be controlled by moving the magnet closer or father from our samples, and the distance travelled can be read off from the micrometer screw gauge. In terms of imaging, if stripe domains are the brighter features, the expected overall intensity garnered from the setup will decrease as the field increases, and vice versa if the stripe domains turn out to be the darker features.

			<gallery widths=350px heights=150px>
			File: Sample edge 60x.png\| OBS screen capture - Imaging the edge of our sample with a 60x microscope objective.
			</gallery>

	In this final iteration, we are happy to report that imaging was a success. We were able to observe the presence of defects and dirt particles on the surface of our samples. And as a quick estimation of the size of our imaging region, we honed in on the edge of our magnetic sample and tuned the micrometer stage such that the edge moved from end of the screen to the other. The distance moved by the edge can then be read off from the screw gauge. In this manner, we found the 10x objective to give an image size 370 microns across and the 60x objective to give an image size 60 microns approximately (with the associated 10 microns uncertainty).		In this final iteration, we are happy to report that imaging was a success. We were able to observe the presence of defects and dirt particles on the surface of our samples. And as a quick estimation of the size of our imaging region, we honed in on the edge of our magnetic sample and tuned the micrometer stage such that the edge moved from end of the screen to the other. The distance moved by the edge can then be read off from the screw gauge. In this manner, we found the 10x objective to give an image size 370 microns across and the 60x objective to give an image size 60 microns approximately (with the associated 10 microns uncertainty).

Junherng: /* Setup 1.1: Double Mirror Alignment */

2022-04-30T15:10:52Z

Setup 1.1: Double Mirror Alignment

← Older revision		Revision as of 15:10, 30 April 2022
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	[[File: Red laser pointer dirty.jpeg\|200px\|right\|thumb\| Not all laser pointers are equal. The first laser pointer we used turned out to have a rather dirty beam. The pinhole aperture might have helped to remove some of these artifacts, but to be sure we decided to switch to a laser diode that produced a cleaner beam.]]		[[File: Red laser pointer dirty.jpeg\|200px\|right\|thumb\| Not all laser pointers are equal. The first laser pointer we used turned out to have a rather dirty beam. The pinhole aperture might have helped to remove some of these artifacts, but to be sure we decided to switch to a laser diode that produced a cleaner beam.]]
	[[File: Kerr mirror near.jpeg\|300px\|left\|thumb\|Pinhole near.]]		<!-- [[File: Kerr mirror near.jpeg\|300px\|left\|thumb\|Pinhole near.]]
	[[File: Kerr mirror far.jpeg\|300px\|left\|thumb\|Pinhole far.]]		[[File: Kerr mirror far.jpeg\|300px\|left\|thumb\|Pinhole far.]] -->

	This change to the setup was made in response to alignment woes.		This change to the setup was made in response to alignment woes.
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	The usage of the mirrors for alignment is as follows:		The usage of the mirrors for alignment is as follows:
			<gallery widths=300px heights=250px>
			File: Kerr mirror near.jpeg\| Pinhole near.
			File: Kerr mirror far.jpeg\| Pinhole far.
			</gallery>
	# Place a pinhole aperture near the second mirror and turn the knobs on the <i>first</i> mirror to adjust the pitch and yaw until the laser beam is centered on the pinhole.		# Place a pinhole aperture near the second mirror and turn the knobs on the <i>first</i> mirror to adjust the pitch and yaw until the laser beam is centered on the pinhole.
	# Swap the pinhole to a location farther down the beam path. Tune the knobs on the <i>second</i> mirror until the beam is centered.		# Swap the pinhole to a location farther down the beam path. Tune the knobs on the <i>second</i> mirror until the beam is centered.

Junherng: /* Experimental Setup */

2022-04-30T15:08:32Z

Experimental Setup

← Older revision		Revision as of 15:08, 30 April 2022
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	==Experimental Setup==		==Experimental Setup==

	[[File: Angled schematic kerr.png\|thumb\| Angled Setup Schematic. A polarized light source is reflected off our sample at an angle, passed through an analyzer and finally recorded on our CCD array.]]		<!-- [[File: Angled schematic kerr.png\|thumb\| Angled Setup Schematic. A polarized light source is reflected off our sample at an angle, passed through an analyzer and finally recorded on our CCD array.]] -->

	This section details the two main iterations of our experimental setup - the angled setup and the microscope setup.		This section details the two main iterations of our experimental setup - the angled setup and the microscope setup.
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	===Setup 1: Angled Setup===		===Setup 1: Angled Setup===

			<gallery widths=300px heights=250px>
			File: Angled schematic kerr.png\| Angled Setup Schematic. A polarized light source is reflected off our sample at an angle, passed through an analyzer and finally recorded on our CCD array.
			File: Kerr setup angled initial.jpeg\|Setup 1. The laser pointer is mounted on an acrylic stand shown in bottom left of image.
			</gallery>

	As a first observation of the MOKE, we utilized a basic setup that reflected a linearly polarized light source off our sample - an electromagnet that consists of a steel sheet wrapped with copper wire. The light source is an off-the-shelf red laser pointer. The reflected beam is focused by a plano-convex lens and passed through an analyzer before it is finally captured on our CCD array (webcam). The open source video capture software [https://obsproject.com\| OBS] was used to display the captured image.		As a first observation of the MOKE, we utilized a basic setup that reflected a linearly polarized light source off our sample - an electromagnet that consists of a steel sheet wrapped with copper wire. The light source is an off-the-shelf red laser pointer. The reflected beam is focused by a plano-convex lens and passed through an analyzer before it is finally captured on our CCD array (webcam). The open source video capture software [https://obsproject.com\| OBS] was used to display the captured image.

	[[File: Kerr setup angled initial.jpeg\|200px\|right\|thumb\|Setup 1. The laser pointer is mounted on an acrylic stand shown in bottom left of image.]]		<!-- [[File: Kerr setup angled initial.jpeg\|200px\|right\|thumb\|Setup 1. The laser pointer is mounted on an acrylic stand shown in bottom left of image.]] -->
	[[File: Red laser pointer dirty.jpeg\|200px\|right\|thumb\| Not all laser pointers are equal. The first laser pointer we used turned out to have a rather dirty beam. The pinhole aperture might have helped to remove some of these artifacts, but to be sure we decided to switch to a laser diode that produced a cleaner beam.]]

	The intention with this setup is that if we align the axes of the polarizer and analyzer, the beam would be completely extinguished for a non-magnetic sample. Then, regardless of which of the three MOKE effects were at play, a magnetic sample would alter the polarization of the reflected beam, causing it to only be partially extinguished by the analyzer. In practice, since we are working with non-ideal polarizers that have high extinction ratios (but not 100%), the image of a non-magnetic sample would have been used as a baseline for comparison with a magnetic sample. By exporting image captures from the OBS software and isolating the pixel intensities, a study could have been done by taking the differences in pixel intensities between the two images.		The intention with this setup is that if we align the axes of the polarizer and analyzer, the beam would be completely extinguished for a non-magnetic sample. Then, regardless of which of the three MOKE effects were at play, a magnetic sample would alter the polarization of the reflected beam, causing it to only be partially extinguished by the analyzer. In practice, since we are working with non-ideal polarizers that have high extinction ratios (but not 100%), the image of a non-magnetic sample would have been used as a baseline for comparison with a magnetic sample. By exporting image captures from the OBS software and isolating the pixel intensities, a study could have been done by taking the differences in pixel intensities between the two images.
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	===Setup 1.1: Double Mirror Alignment===		===Setup 1.1: Double Mirror Alignment===

			[[File: Red laser pointer dirty.jpeg\|200px\|right\|thumb\| Not all laser pointers are equal. The first laser pointer we used turned out to have a rather dirty beam. The pinhole aperture might have helped to remove some of these artifacts, but to be sure we decided to switch to a laser diode that produced a cleaner beam.]]
	[[File: Kerr mirror near.jpeg\|300px\|left\|thumb\|Pinhole near.]]		[[File: Kerr mirror near.jpeg\|300px\|left\|thumb\|Pinhole near.]]
	[[File: Kerr mirror far.jpeg\|300px\|left\|thumb\|Pinhole far.]]		[[File: Kerr mirror far.jpeg\|300px\|left\|thumb\|Pinhole far.]]
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	===Setup 2: Microscope Setup===		===Setup 2: Microscope Setup===

	[[File: Kerr microscope schematic.png\|right\|thumb\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]		<gallery widths=350px heights=250px>
	[[File:Microscope setup kerr.jpeg\|right\|thumb\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]]		[[File: Kerr microscope schematic.png\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]
			[[File: Microscope setup kerr.jpeg\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]]
			</gallery>

			<!-- [[File: Kerr microscope schematic.png\|right\|thumb\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]
			[[File:Microscope setup kerr.jpeg\|right\|thumb\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]] -->
	[[File: Sample edge 60x.png\|300px\|left\|thumb\| OBS screen capture - Imaging the edge of our sample with a 60x microscope objective.]]		[[File: Sample edge 60x.png\|300px\|left\|thumb\| OBS screen capture - Imaging the edge of our sample with a 60x microscope objective.]]

Junherng: /* Setup 2: Microscope Setup */

2022-04-30T14:54:54Z

Setup 2: Microscope Setup

← Older revision		Revision as of 14:54, 30 April 2022
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	[[File: Kerr microscope schematic.png\|right\|thumb\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]		[[File: Kerr microscope schematic.png\|right\|thumb\| Schematic of microscope setup. The two mirrors facilitate beam alignment.]]
	[[File:Microscope setup kerr.jpeg\|right\|thumb\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]]		[[File:Microscope setup kerr.jpeg\|right\|thumb\| Microscope setup, sans pinhole after Mirror 2. The light source is at the bottom left.]]
	[[File: Sample edge 60x.png\|~~250px~~\|left\|thumb\| OBS screen capture - Imaging the edge of our sample with a 60x microscope objective.]]		[[File: Sample edge 60x.png\|300px\|left\|thumb\| OBS screen capture - Imaging the edge of our sample with a 60x microscope objective.]]

	This change was made in an effort to increase the magnification of our imaging setup.		This change was made in an effort to increase the magnification of our imaging setup.