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.

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How to calculate radiant intensity in watts/cm^2 of a green and UV LED [duplicate]

I have a PN junction photodetector (the target) and two LED sources, one UV and one green. My aim is to calculate radiant intensity in watts/cm^2 that is falling on the target corresponding to both UV ...
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-1 votes
2 answers
80 views

Procedure to express radiantion intensity of a LED in watts/cm^2 , given luminous intensity or total radiant power [closed]

I am calculating Responsivity of a PN junction photodiode by irradiating radiation from LED sources. For this purpose, I have two LEDs, one UV and another green LED. Note that LEDs are placed close to ...
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2 answers
65 views

Mixing light from multiple leds

I'm trying to design a device that produces visible light with a somewhat controllable spectrum. My goal is to measure the human eye cone cell responses by switching between two different spectra and ...
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2 votes
4 answers
556 views

Text Projection in Smart Glasses

Say I have a pair of glasses such that each lens is densely pixelated and each pixel can be controlled to block (or attenuate) light coming through. Can I use this technology to project text (say &...
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Modulator in lasercom: from theory to practice

Hello everyone! We are working on a realisation of an optical modulator and have a doubt. Mr Noel Miller posted already a question, but it was suggested this community. I will repost his question ...
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Semi-opaque red coloring spots on LCD, potentially dead pixels

I've been researching how LCD screens work on a technical level. One thing I had a hard time finding any detailed information about is failure modes and how to identify the cause of failures. Are ...
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1 answer
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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 ...
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2 answers
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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&...
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4 answers
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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 ...
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5 answers
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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 ...
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1 vote
3 answers
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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(...
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3 votes
2 answers
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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 ...
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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 ...
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2 answers
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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 ...
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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.
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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 ...
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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 ...
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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 ...
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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 ...
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40 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 \$\...
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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 ...
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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 ...
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1 answer
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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 ...
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3 answers
182 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 ...
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2 answers
101 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 ...
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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 ...
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3 votes
3 answers
293 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 ...
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3 answers
390 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. ...
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4 answers
220 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 ...
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1 answer
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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 ...
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2 votes
3 answers
364 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 ...
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1 answer
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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 ...
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2 votes
0 answers
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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\...
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5 votes
1 answer
557 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 ...
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0 answers
64 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 ...
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0 votes
1 answer
289 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 ...
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0 votes
1 answer
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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 ...
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3 answers
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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?
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2 votes
2 answers
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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 ...
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1 answer
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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 ...
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2 votes
4 answers
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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 ...
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1 vote
1 answer
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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 ...
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0 votes
1 answer
82 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 ...
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0 votes
1 answer
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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 ...
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2 answers
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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 ...
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-7 votes
1 answer
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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 ...
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0 votes
1 answer
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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). ...
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0 votes
2 answers
369 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/...
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1 vote
0 answers
57 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 ...
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1 vote
1 answer
156 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 ...
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