Laser Distance Measurer - Revision history

Arya: /* Results */

2025-04-29T11:55:55Z

Results

← Older revision		Revision as of 19:55, 29 April 2025
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	\| [[File:final2.png\|600px]]		\| [[File:final2.png\|600px]]
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	\| '''Table 5.''' Uncertainty of Distance Difference from delay time ~~vs manually measured distance difference between LED and photodetector~~ without mirror.		\| '''Table 5.''' Uncertainty of Distance Difference from delay time without mirror.
	\| '''Table 6.''' Uncertainty of Distance Difference from delay time ~~vs manually measured distance difference between LED and photodetector~~ with a mirror acting as the "object"		\| '''Table 6.''' Uncertainty of Distance Difference from delay time with a mirror acting as the "object"
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Arya: /* Results */

2025-04-29T11:55:17Z

Results

← Older revision		Revision as of 19:55, 29 April 2025
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	\| [[File:final2.png\|600px]]		\| [[File:final2.png\|600px]]
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	\| '''Table 5.''' ~~Graph~~ of ~~Calculated Average~~ Distance Difference from delay time vs manually measured distance difference between LED and photodetector without mirror.		\| '''Table 5.''' Uncertainty of Distance Difference from delay time vs manually measured distance difference between LED and photodetector without mirror.
	\| '''Table 6.''' ~~Graph~~ of ~~Calculated Average~~ Distance Difference from delay time vs manually measured distance difference between LED and photodetector with a mirror acting as the "object"		\| '''Table 6.''' Uncertainty of Distance Difference from delay time vs manually measured distance difference between LED and photodetector with a mirror acting as the "object"
	\|}		\|}

Jonathan: /* Results */

2025-04-29T11:54:56Z

Results

← Older revision		Revision as of 19:54, 29 April 2025
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	\| [[File:data2.png\|600px]]		\| [[File:data2.png\|600px]]
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	\| '''Table 3.''' Calculated Average Distance Difference from delay time vs Manually measured distance between LED and photodetector. Separation distance of '''~~10cm~~''' was taken as the "reference" distance and the successive distances were subtracted from it to give "absolute" values.		\| '''Table 3.''' Calculated Average Distance Difference from delay time vs Manually measured distance between LED and photodetector. Separation distance of '''10 cm''' was taken as the "reference" distance and the successive distances were subtracted from it to give "absolute" values.
	\| '''Table 4.''' Calculated Average Distance Difference from delay time vs Manually measured distance between LED and photodetector with the mirror acting as the "object". Separation distance of '''46.~~5cm~~'''was taken as the "reference" distance and the successive distances were subtracted from it to give "absolute" values.		\| '''Table 4.''' Calculated Average Distance Difference from delay time vs Manually measured distance between LED and photodetector with the mirror acting as the "object". Separation distance of '''46.5 cm'''was taken as the "reference" distance and the successive distances were subtracted from it to give "absolute" values.
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Jonathan: /* Results */

2025-04-29T11:47:02Z

Results

← Older revision		Revision as of 19:47, 29 April 2025
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	The measured delay time is in the order of 20-30 ns, which, when calculated, gives about 6-9 m of distance. However, our incremental changes in the distance between the LED and the photodetector were in the order of 10-80 cm. Hence, it was evident that this additional delay time was occurring due to all the cables attached to the oscilloscope and function generation and the distance between the laser and the detector. The length of the BNC cables was ~~410cm~~. This would lead to an additional delay of 13.7 ns. We hypothesise that the rest of the delay is due to the internal wiring functions of the oscilloscope.		The measured delay time is in the order of 20-30 ns, which, when calculated, gives about 6-9 m of distance. However, our incremental changes in the distance between the LED and the photodetector were in the order of 10-80 cm. Hence, it was evident that this additional delay time was occurring due to all the cables attached to the oscilloscope and function generation and the distance between the laser and the detector. The length of the BNC cables was 410 cm. This would lead to an additional delay of 13.7 ns. We hypothesise that the rest of the delay is due to the internal wiring functions of the oscilloscope.

Jonathan: /* Results */

2025-04-29T11:46:46Z

Results

← Older revision		Revision as of 19:46, 29 April 2025
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	The measured delay time is in the order of 20-30 ~~nanoseconds~~, which, when calculated, gives about 6-9m of distance. However, our incremental changes in the distance between the LED and the photodetector were in the order of 10-~~80cm~~. Hence, it was evident that this additional delay time was occurring due to all the cables attached to the oscilloscope and function generation and the distance between the laser and the detector. The length of the BNC cables was 410cm. This would lead to an additional delay of 13.~~7ns~~. We hypothesise that the rest of the delay is due to the internal wiring functions of the oscilloscope.		The measured delay time is in the order of 20-30 ns, which, when calculated, gives about 6-9 m of distance. However, our incremental changes in the distance between the LED and the photodetector were in the order of 10-80 cm. Hence, it was evident that this additional delay time was occurring due to all the cables attached to the oscilloscope and function generation and the distance between the laser and the detector. The length of the BNC cables was 410cm. This would lead to an additional delay of 13.7 ns. We hypothesise that the rest of the delay is due to the internal wiring functions of the oscilloscope.

Jonathan: /* Experiment Setup */

2025-04-29T11:45:46Z

Experiment Setup

← Older revision		Revision as of 19:45, 29 April 2025
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	==Experiment Setup==		==Experiment Setup==
	For a visual of the completed setup, please refer to figure 5.		For a visual of the completed setup, please refer to figure 5 and the accopmanying circuit diagram.

	====Laser Modulation and System Initialisation====		====Laser Modulation and System Initialisation====

Jonathan: /* Results */

2025-04-29T11:45:14Z

Results

← Older revision		Revision as of 19:45, 29 April 2025
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	==Results==		==Results==
	{\| style="border:none; margin:auto; text-align:center;"		{\| style="border:none; margin:auto; text-align:center;"
	\|+ '''Figure 6.''' Delay between the function generator and the received signal by the photodetector on the oscilloscope. Green graph represents the function generated by the function generator and the yellow graph represents the function produced from received the laser beam by the detector.
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	\| [[File:reference.png\|700px]]		\| [[File:reference.png\|700px]]
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			\| '''Figure 6.''' Delay between the function generator and the received signal by the photodetector on the oscilloscope. Green graph represents the function generated by the function generator and the yellow graph represents the function produced from received the laser beam by the detector.
	\|}		\|}

Jonathan: /* Recording the Time Delay vs. Distance Mapping */

2025-04-29T11:44:24Z

Recording the Time Delay vs. Distance Mapping

← Older revision		Revision as of 19:44, 29 April 2025
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	====Recording the Time Delay vs. Distance Mapping====		====Recording the Time Delay vs. Distance Mapping====
	Turn on the LED and ensure that the beam is collimated by adjusting the distance of the lens to the LED. With the light from LED hitting the photodetector, observe the function generated on the oscilloscope. Use the oscilloscope’s cursor measurement function to determine the relative time delay Δt between the modulation reference signal (Channel 1) and the return signal (Channel 2). Correlate the measured delay values with corresponding distances to establish the system’s delay–distance response curve. ~~The~~ following procedure outlines how to measure the time delay and the corresponding distance:		Turn on the LED and ensure that the beam is collimated by adjusting the distance of the lens to the LED. With the light from LED hitting the photodetector, observe the function generated on the oscilloscope. Use the oscilloscope’s cursor measurement function to determine the relative time delay Δt between the modulation reference signal (Channel 1) and the return signal (Channel 2). Correlate the measured delay values with corresponding distances to establish the system’s delay–distance response curve.

			With the apparatus in place, the following procedure outlines how to measure the time delay and the corresponding distance:

	# Fix the LED source and the photodetector on a linear translation stage, ensuring proper alignment for the beam return to the detector at all positions along the translation stage; the detector and the laser diode were mounted on a postholder so that the height of the detectors was adjustable.
	# Use a meter ruler to mark the distance along the translation stage.		# Use a meter ruler to mark the distance along the translation stage.
	# Move the LED source to the marked positions (e.g. 30 cm from detector) and adjust the beam until it is centralised on the photodetector.		# Move the LED source to the marked positions (e.g. 30 cm from detector) and adjust the beam until it is centralised on the photodetector.
	# Measure the time delay on the oscilloscope. Record the minimum, maximum and mean time delay—take three readings per distance and average them.		# Measure the time delay on the oscilloscope. Record the minimum, maximum and mean time delay—take three readings per distance and average them.
	# '''Repeat steps ~~1–4~~ for different distances''' on the translation stage.		# '''Repeat steps 1–3 for different distances''' on the translation stage.
	# Insert a mirror in the setup to act as the “object we are trying to measure the distance of”, so that the beam path is reflected off the mirror to the photodetector.		# Insert a mirror in the setup to act as the “object we are trying to measure the distance of”, so that the beam path is reflected off the mirror to the photodetector.
	# Measure the total path length manually and '''repeat steps ~~1–4~~''' for each mirror position.		# Measure the total path length manually and '''repeat steps 1–3''' for each mirror position.

Jonathan: /* Experiment Setup */

2025-04-29T11:43:12Z

Experiment Setup

← Older revision		Revision as of 19:43, 29 April 2025
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	====Optical Alignment====		====Optical Alignment====
	Mount the 650 nm laser diode on the linear translation stage and use the aspheric lens to collimate and focus the beam onto the reflective target surface. The lens should be placed in a cage plate and mounted in a position such that the distance between the lens and the LED is the focal length of the lens.		Mount the 650 nm laser diode on the linear translation stage and use the aspheric lens to collimate and focus the beam onto the reflective target surface. The lens should be placed in a cage plate and mounted in a position such that the distance between the lens and the LED is the focal length of the lens. (Note: the LED--and the detector below--should be mounted on the translation stage via postholders so that their heights are adjustable.)

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	====Recording the Time Delay vs. Distance Mapping====		====Recording the Time Delay vs. Distance Mapping====
	~~(Note: the detector and LED should be mounted on the translation stage via postholders so that their heights are adjustable.)~~
	Turn on the LED and ensure that the beam is collimated by adjusting the distance of the lens to the LED. With the light from LED hitting the photodetector, observe the function generated on the oscilloscope. Use the oscilloscope’s cursor measurement function to determine the relative time delay Δt between the modulation reference signal (Channel 1) and the return signal (Channel 2). Correlate the measured delay values with corresponding distances to establish the system’s delay–distance response curve. The following procedure outlines how to measure the time delay and the corresponding distance:		Turn on the LED and ensure that the beam is collimated by adjusting the distance of the lens to the LED. With the light from LED hitting the photodetector, observe the function generated on the oscilloscope. Use the oscilloscope’s cursor measurement function to determine the relative time delay Δt between the modulation reference signal (Channel 1) and the return signal (Channel 2). Correlate the measured delay values with corresponding distances to establish the system’s delay–distance response curve. The following procedure outlines how to measure the time delay and the corresponding distance:

Jonathan: /* Experiment Setup */

2025-04-29T11:42:26Z

Experiment Setup

← Older revision		Revision as of 19:42, 29 April 2025
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	====Laser Modulation and System Initialisation====		====Laser Modulation and System Initialisation====
	Configure the function generator to output a 10 MHz square wave with an amplitude of 1 to 3.1 V (High level: 3.1 V, Low level: 1.0 V, output impedance: 50 Ω) to modulate the laser diode. Connect the function generator to the oscilloscope and verify that the signal output from the function generator can be observed on the oscilloscope. Use a T-section to connect the oscilloscope (same port used by the function generator) to the laser LED, and verify that visible light is emitted from the laser. Connect the DC power supply set to constant voltage (5.0 V in this setup) to the photodiode.		Configure the function generator to output a 10 MHz square wave with an amplitude of 1 to 3.1 V (High level: 3.1 V, Low level: 1.0 V, output impedance: 50 Ω) to modulate the laser diode. Connect the function generator to the oscilloscope and verify that the signal output from the function generator can be observed on the oscilloscope. Use a T-section to connect the oscilloscope (same port used by the function generator) to the laser LED, and verify that (when the function output is on) visible light is emitted from the laser. Connect the DC power supply set to constant voltage (5.0 V in this setup) to the photodiode.

	====Optical Alignment====		====Optical Alignment====
	Mount the 650 nm laser diode and use the aspheric lens to collimate and focus the beam onto the reflective target surface. The lens should be placed in a cage plate and mounted in a position such that the distance between the lens and the LED is the focal length of the lens.		Mount the 650 nm laser diode on the linear translation stage and use the aspheric lens to collimate and focus the beam onto the reflective target surface. The lens should be placed in a cage plate and mounted in a position such that the distance between the lens and the LED is the focal length of the lens.

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	====Detection and Amplification Circuit Configuration====		====Detection and Amplification Circuit Configuration====
	For the photodetector, mount the Hamamatsu S5971 silicon photodiode to a position such that it can detect the light signal. To amplify the signal linearly without saturation, the detector output is connected to a high-speed preamplifier (bandwidth >100 MHz, gain ∼10³–10⁵). Connect the detector/amplifier combination to Channel 2 of a digital oscilloscope; compare it to the reference signal from the function generator (Channel 1) as the modulation phase reference; the two signals should be out of phase.		For the photodetector, mount the Hamamatsu S5971 silicon photodiode to a position on the translation stage such that it can detect the light signal. To amplify the signal linearly without saturation, the detector output is connected to a high-speed preamplifier (bandwidth >100 MHz, gain ∼10³–10⁵). Connect the detector/amplifier combination to Channel 2 of a digital oscilloscope; compare it to the reference signal from the function generator (Channel 1) as the modulation phase reference; the two signals should be out of phase.

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	====Time Delay vs. Distance Mapping====
	~~Fix~~ the LED ~~source and the photodetector~~ on ~~a linear translation stage, ensuring that the beam returning to the detector at all positions is aligned along~~ the translation stage~~; the detector and the laser diode were mounted on a postholder~~ so that ~~the height of the detectors was~~ adjustable. Turn on the LED and ensure that the beam is collimated by adjusting the distance of the lens to the LED. ~~Incident~~ the LED ~~onto~~ the photodetector ~~and~~ observe the function generated on the oscilloscope. Use the oscilloscope’s cursor measurement function to determine the relative time delay Δt between the modulation reference signal (Channel 1) and the return signal (Channel 2). Correlate the measured delay values with corresponding distances to establish the system’s delay–distance response curve. The following ~~are the steps carried out~~ to measure the time delay and the corresponding distance:		====Recording the Time Delay vs. Distance Mapping====
			(Note: the detector and LED should be mounted on the translation stage via postholders so that their heights are adjustable.)
			Turn on the LED and ensure that the beam is collimated by adjusting the distance of the lens to the LED. With the light from LED hitting the photodetector, observe the function generated on the oscilloscope. Use the oscilloscope’s cursor measurement function to determine the relative time delay Δt between the modulation reference signal (Channel 1) and the return signal (Channel 2). Correlate the measured delay values with corresponding distances to establish the system’s delay–distance response curve. The following procedure outlines how to measure the time delay and the corresponding distance:

	# Fix the LED source and the photodetector on a linear translation stage, ensuring proper alignment for the beam return to the detector at all positions along the translation stage; the detector and the laser diode were mounted on a postholder so that the height of the detectors was adjustable.		# Fix the LED source and the photodetector on a linear translation stage, ensuring proper alignment for the beam return to the detector at all positions along the translation stage; the detector and the laser diode were mounted on a postholder so that the height of the detectors was adjustable.