Questions tagged [optics]
Anything related to optics applied to electronics. Optics is a branch of physics studying the properties of light and its interactions with physical media.
128
questions
-1
votes
1answer
36 views
What is Multimode Delay Distortion?
I understand that the data has been distorted through the multimode fiber but is this due to a bandwidth that is longer than what the fiber can handle? What causes the distortion and how is it dealt ...
1
vote
2answers
65 views
What does the term "boresight", and what do the phrases "boresight adjustment" or "boresight calibration", mean in the context of laser scanning?
I have been studying the laser scanning literature. In doing so, I often come across the term "boresight", and the phrases "boresight adjustment" or "boresight calibration&...
30
votes
4answers
4k views
Why are most COB LEDs physically yellow?
Many "LEDs" found on devices nowadays appear to be yellow where the light comes from (when the device is off). Why yellow?
I put LEDs in quotes because COB leds can consist of many ...
0
votes
5answers
201 views
How is the measurement light frequency shifted with respect to the reference light frequency by some carrier frequency in practice?
I've been studying heterodyning in interferometry. My understanding is that heterodyning is achieved by shifting the measurement light frequency with respect
to the reference light frequency by some ...
1
vote
3answers
77 views
Design an RF amplifier for a photodiode
I've been asked to present a possible solution to design an optical system aimed at estimating the arrival time of the following light signal:
$$s(t)=[\Sigma_{i=1}^∞rect(\frac{t-t_i}{T})]\cdot Acos(...
4
votes
2answers
158 views
Building laser doppler vibrometer
I'm interested in building my own laser doppler vibrometer using laser diodes. The reason I mention laser diodes is because (1) I want it to be cheap and (2) I want to incorporate it into robotics ...
0
votes
1answer
72 views
Floating node in 4T CMOS camera pixel
I know how a 3 Transistor CMOS camera pixel works. As I understand, 4T CMOS pixels have one additional transistor that connects the photodiode to a so-called floating node.
What is that floating node ...
0
votes
2answers
35 views
Determination detection of direction with 2 optic sensors which are on opposite sides of disc
I would like to ask you is it possible to detect the direction of rotation with 2 optic sensors which are on opposite sides of disc? In the disc is small hole, when the part with hole goes through the ...
0
votes
1answer
96 views
What does this vertical bar in an equation mean?
I'd like to know what the vertical line followed by an E represents in this image. I would Google it, but I don't know what to type in to Google.
1
vote
0answers
43 views
Fiber optic transceiver for lower speeds
I am trying to figure out if a QSFP-DD transceiver can break out 8x 10G lanes if I make/use a 1:8 fiber optic breakout cable. It seems like most Transceivers are rated for one speed only, so if I get ...
0
votes
0answers
28 views
How can I at least estimate the optical power that an RGB LED radiates given the typical parameters?
How can I at least estimate the optical power that an RGB LED radiates given the typical parameters - say luminous intensity in Candela or Luminous efficiency - from a data sheet? Assume this is a ...
1
vote
0answers
45 views
Fourier transform of the electrical conductivity function
In this pdf https://studylib.net/doc/18704299/chapter-1 the author writes that the Fourier transform of the current density is:
$$
\Delta j_{i}(\mathbf{k}, \omega) \equiv \frac{1}{(2 \pi)^{2}} \iiiint ...
0
votes
0answers
27 views
Trying to build custom electronics connection to a motorized zoom/focus lens
I'm a beginner when it comes to electronics, I had some success with pretty simple arduino based projects like blue tooth controlled stepper motor assemblies using well documented drivers and ...
0
votes
0answers
38 views
A circularly polarized EM wave is perfectly absorbed by any interface?
According to the Fresnel equations, the effective reflectivity of an arbitrarily polarized electromagnetic wave is given as:
$$
\Gamma = \frac{\Gamma_p + \Gamma_s}{2} ,
$$
where \$\Gamma_p\$ and \$\...
-1
votes
1answer
43 views
What are the limits to parallel shift registers in electronics (in comparison to optics)?
Brackenbury and Mason in 1988 (https://iopscience.iop.org/article/10.1088/0022-3727/21/10S/044) said, on comparing parallel shift registers in electronic and optical computing, 'When implementing such ...
0
votes
1answer
75 views
Photodiode operating modes - confusion about wording
The more I read about the operating modes of photodiodes, the more confused I get since it seems that people are using the same wording for different stuff.
Please consider photoconductive (PC) mode ...
1
vote
1answer
35 views
Calculating transmittance LED
I am solving the following problem:
Consider a GaAs emitter. Calculate the transmittance for the interface GaAs/glass/air. Assume near
normal incidence. GaAs: n= 3.4; glass: n=1.5. Answer: 81.6%
My ...
0
votes
3answers
114 views
Controlling for ambient temperature changes in a transimpedance amplifier
I'll start by saying I'm new to electronics, and have only minor working knowledge. I am designing a transimpedance amplifier to measure the opacity of a surface that is changing over time. The ...
0
votes
2answers
97 views
Why do simple optical fibers usually support only half-duplex communication?
I'm a newbie to the subject, so a thorough answer would be very helpful.
I was curious as to why simple (single) optical fibers usually don't allow full-duplex communication. To my understanding, all ...
0
votes
0answers
47 views
Tuning the "frequency corners" of a PID system (with two integrals)
I am having some trouble understanding the language used in control theory.
I have a laser that is set up in a "Pound-drever-Hall" lock. This lock basically sets up a feedback loop between ...
3
votes
3answers
267 views
What is the response current of a photodiode to an LED emitting light at different intensities?
Let's say I have one of those conventional through-hole LEDs and I'm applying a sinusoidal voltage to it. From what I understand, at a given time, the same LED is either on or off, and to virtually ...
0
votes
3answers
223 views
A laser driver (MLD203P1) with an external Bias-Tee for modulation
As the title says, I would like to add an external Bias tee to modulate a high frequency signal into a laser diode, because the laser driver I have chosen does not have a built-in modulation circuit. ...
0
votes
4answers
205 views
Laser scanning: why are things like deflection and mirrors used instead of just a mount and servo?
In the Wikipedia article for laser scanning, it is said that laser scanning is the controlled deflection of laser beams, visible or invisible. It then lists some of the technologies used, such as ...
0
votes
1answer
128 views
How do we choose refractive index value in optical fiber design?
It is known that, given two media with refractive indeces \$n_1\$ and \$n_2 < n_1\$, if rays come from medium 1 they will be totally reflected if their angle of incidence is higher than the ...
2
votes
3answers
271 views
How can I model an optical filter using python?
Say I have an RGB LED which transmit intensity modulated signals, at one symbol transmission I want to send a symbol with all three chips.. Can I just model three bandpass optical filters like RF ...
0
votes
1answer
56 views
Dielectric slab waveguide
let's consider the so called dielectric slab waveguide (references for image and equations: here, page 53):
I do not know much about it, I know only that it is a planar guiding structure which is ...
2
votes
0answers
48 views
General question about convolution and Fourier
I'm working on a system that includes a bunch of elements and I arrived at the following general expression for the output:
$$\mathcal{F}\left\{ T\cdot\left(\left[T\cdot\mathcal{F}\left\{ E_{1}\right\...
5
votes
1answer
336 views
Measuring pulse durations with microsecond precision or better
Problem
I'll be receiving pulses and want to know the relative times of pulse start/end with microsecond precision (or better).
Pulse characteristics:
pulse frequency: probably 1Hz to 10Hz
pulse ...
0
votes
0answers
60 views
How to detect light polarization?
I want to build a proof of concept implementation of the BB84 algorithm.
I plan on having an Adruino send a pulse across a fiber optic cable, with a polarizer that it controls. On the other end is an ...
1
vote
1answer
283 views
Non-contact thermometers used by China in screening for coronavirus (2019-nCoV) [closed]
I'm not sure if this is off-topic, but if it is, then please inform me, and I'll delete it.
In media reports of the spread of the "coronavirus" (2019-nCoV), we often see images of Chinese officials ...
0
votes
1answer
103 views
Photodiode not working in reverse bias
I'm using a photodiode module, model: coaxial InGaAs, Gtel.
I set it in reverse bias with 5V and tested it with a laser but it doesn't give any output voltage. Unfortunately I don't know the laser ...
0
votes
3answers
384 views
Why does an optical drive use laser light?
Nowadays, lasers are cheap, but back in the day when CDs were first introduced, they were expensive. What is the reason for using a laser instead of a normal light source in optical drives?
2
votes
2answers
120 views
Can linearity of photoreceptor be improved by calibration?
I am trying to determine if equipment I already have can be used to take a reading in mcd/m2, for a quality control test. I have a sensor which meets all the requirements listed in the standard test ...
0
votes
1answer
84 views
How does one match irradiance to Luminous Intensity in Candela of source?
A light source has an Irradiance of about 1.6 W/m²/nm at wavelenght 385nm and an LED:
Peak Wavelength 385nm
Viewing Angle 30 °
Luminous Intensity 80 mcd
If this light source shines on a ...
2
votes
4answers
2k views
How to make affordable DIY low-res absolute rotatory optical encoders with fibers? [closed]
I have zero knowledge of optics and want to make a very low resolution (~10°) absolute rotary optical encoder using rapid manufacturing (I have 3D printers, laser cutter, and desktop CNC). Digging the ...
1
vote
1answer
126 views
Do electronic fiber optic selector switches exist?
From my research, I have been having a tough time finding and specifying a fiber optic selector switch or multiplexer. Do fiber optic selector switches exist?
Background - Simple
I have an ...
0
votes
1answer
61 views
How does a fiber optic receiver converts the optical signal to an electrical signal
A fiber optic receiver needs to convert the incoming optical signal to an electrical signal so it can be sampled. How is this achieved in practice?
I believe a photodiode is used, but would a ...
0
votes
1answer
128 views
Help me to build some devices for measuring LEDs optical power[mW] with range (1 -100)mW included [closed]
I have an application of photoactivation device with 10-20 LEDs for every color; with the following wavelengths : red 630-670nm ;yellow 575-595nm , green 510-540nm .
In order to obtain an uniform ...
0
votes
2answers
53 views
Specificity? "High-Contrast and spectroscopic-based specificity of optical imaging."
I came across the following phrase:
High-Contrast and spectroscopic-based specificity of optical imaging.
I'm wondering what is meant by "specificity" in this context?
Thanks for any ...
-7
votes
1answer
95 views
speed of light measurement [closed]
u can video call one smartphone from another via wireless internet connection, ie: the signal travels from one device to a satellite and then to the other device. but i want to avoid network noise and ...
0
votes
1answer
76 views
Classification of LED type
Out of curiosity, I recently opened a damaged measurement device (it´s some kind of lab spectrometer, but I am not sure) that contains a LED with a package like I have not seen before (see picture).
...
0
votes
2answers
265 views
Measure laser with photoresistor (LDR)?
I want to make a simple setum, where I can measure the opacity of air. I want to use a simple laserbeam, which I shoot across the room, and on the other side I want to measure how much is blocked/...
1
vote
0answers
56 views
Generate ultrashort rise times with photoconductive switch or photodiode
I am trying to produce voltage pulses with very short rise time (<15 ps), medium width (20 ns) and amplitudes up to 15 V. As a promising candidate I selected photoconductive switches and ultrafast ...
1
vote
1answer
134 views
Material dispersion in fiber optics transmission
In plain English, why does material dispersion increase with wavelength in fiber optic transmission? I am aware that refraction index decreases with wavelength increase, i.e. pulse travels faster, but ...
1
vote
4answers
215 views
Fiber-optic transceiver ICs for applications other than fiber-optic Ethernet? [closed]
When we talk about fiber-optic transmission, we almost always talk about copper to fiber-optic Ethernet conversion using fiber-optic transceivers.
But since fiber-optic communication is just ...
2
votes
1answer
704 views
Reducing LED spread via pinhole
I am making an infrared break beam to detect insects, using an IR emitter LED and detector. The insects fall into a channel and then eventually cross the beam, which travels the length of the channel.
...
1
vote
1answer
213 views
wifi baseband access
I've got an unusual use case (optical communications) that would benefit from access to the wifi baseband signal before it is upconverted/modulated at 2.5Ghz. However most modern wifi chips combine ...
0
votes
0answers
190 views
concave conical lenses on 5050 SMD LEDs?
Is there any way to put plano-convex conical lenses, or something broadly equivalent, on 5050 SMD LEDs?
The lenses I'm talking about are the type commonly built into cheap christmas-tree lights:
As ...
1
vote
4answers
528 views
Method to determine angle of a rotating stage
I am currently working on a project that requires the rotation of polarizers to very specific angles. It is necessary that we are able to determine what angle the polariser is currently at so that we ...
1
vote
1answer
80 views
principle about SPAD for ToF ranging module from ST
My colleagues are using VL53L0 from ST which is one ToF ranging module. I am trying to understand the principle about the SPAD(single-photon avalanche diode) and have read many materials on it.
From ...
