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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Simulate photodiode in ltspice
I am trying to simulate a photodiode output in LTSpice. I was wondering if it is possible to have an independent current source wave that goes up to xyz uA (min 0 uA and max xyz uA) with a rise and ...
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Sending arbitrary bitstream to SFP transceiver: minimum bitrate?
I'm trying to use a Small Form-factor Pluggable (SFP) as the laser source for a homebuilt laser gas analyzer, which means I don't actually care about transmitting data. The plan is to send an ...
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If we increased the frequency of HV-AC lines, could we get atmospheric air to excite and illuminate?
I had a thought experiment I wanted to run past some experts.
It starts with CFL light bulbs. CFL light bulbs are light bulbs that use ~500 VAC @ ~20 kHz or more to excite a gas in a light vacuum.
...
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Laser diode control without PD
I'm currently looking for a new light source for a system. The laser diode seems to be an excellent candidate. However, for the specific wavelength I need (488 nm), diodes with an integrated ...
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What is the tension member in IEC 61000-6-8:2020 Table 6?
In IEC 61000-6-8:2020 3.1.10, an optical fiber port is defined as port at which an optical fiber is connected to an equipment. In Table 6 – Requirements for conducted emissions, other wires ports, it ...
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Interruption in waveguides
I want to fabricate a PE waveguide.I deposited a layer of aluminum with a thickness of 180 nm on Lithium niobate.I lithographed the design of the waveguide,After developing photoresist and etching the ...
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Different Vertical and Horizontal full well capacities for CCD image sensors
I want to use a line sensor for a medical imaging application. I understand that the full well capacity of the pixel is the maximum number of photo-electrons it can store before it gets saturated.
I ...
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LED : Perceived Light Intensity Greater Than Actual Light Intensity (via Weber-Fechner Law)
Background
In this question, user @glen_geek posited (with linked references) that perceived light from an LED versus actual light from an LED is greater at lower duty cycles:
@kando For PWMing LEDs, ...
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Designing an amplifier circuit for a BPW34 photodiode
I'm designing a laser seeker circuit. I need to amplify the photodiode so that the photodiode can detect laser beams reflected from the wall. I couldn't achieve this with the amplifier circuit you see ...
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Transducer for ultrasonic lens cleaning
I recently discovered TI's ULC1001 driver chip for ultrasonic lens cleaning. I'd like to try this in my next project, but I'm not sure what transducer to use.
For an application like his, are ...
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Minimum light bulb wattage for solar simulator
I am trying to design a simple homemade solar simulator. I have picked metal-halide lamps as my light source.
To achieve an irradiance of 1000 W/m2, I don't know what wattage of light bulbs are needed....
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How much does an LCD projector attenuate an 8000 lumen LED light source?
I am attempting to replace a high-pressure lamp in a 3 LCD (red, green & blue) projector with a 100 W LED array. This resulted in a very disappointing (dim) projected image.
From this stack ...
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Why is the frequency response of an LED important?
I'm working on visible light communication where I fabricate my own organic LEDs. One of the ways to characterize them is "small signal analysis." I understand we are applying this analysis ...
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Why aren't there displays which explicitly emit certain frequencies?
Rather than building displays that emit RGB, why not build displays that emit certain frequencies instead? What are the technical challenges of doing this?
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Why does isotropic radio transmission appear to be better than optical for communications?
I have a walkie-talkie that supposedly has a range of 5 km in open country, line of sight, that puts out 1 W in all directions.
Now, if I replaced that RF transmitter with a 1 W light source and the ...
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Is birefringence exploited or otherwise meaningfully observed anywhere in electronics?
Birefringence is a property of certain materials where the refractive index of the material is dependent upon the polarization and direction of propagation of light through it. I recently learned ...
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What is the technical difference between audio CD-R(W) and data CD-R(W) discs?
I just repaired a Sony RCD-W100 CD-recorder and want to test the recorder functionality. The manual 'says' I can only use audio CD-R(W) discs. Never heard of CD-R(W) discs just for audio. On the ...
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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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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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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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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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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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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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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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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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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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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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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 said, on comparing parallel shift registers in electronic and optical computing:
When implementing such a scheme in electronics, the shift length is usually limited to ...
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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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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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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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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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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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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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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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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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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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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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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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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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