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#optics

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j_bertolotti

#PhysicsJournalClub
"Model-free estimation of the Cramér–Rao bound for deep learning microscopy in complex media"
by I. Starshynov et al.

Nat. Photon. (2025)
doi.org/10.1038/s41566-025-016

As everybody who ever tried to orient themselves while immersed in thick fog knows, scattering scrambles information. The question "how much information is still there?" is not particularly interesting as the answer is "essentially all of it", as elastic scattering can't destroy information. A much more interesting question is "how much information can we retrieve?" In order to even try to give an answer we need to be a bit more specific, so the authors placed a small reflective surface behind a scattering layer and asked how much information about its transverse position could be retrieved. This is a well-posed question, and the answer takes the form of a "Cramér–Rao bound" (en.wikipedia.org/wiki/Cram%C3%).
After estimating this upper bound, the authors investigate how well a trained neural network can do at this task, and show that a specifically built convolutional neural network can almost reach the theoretical bound.

[Conflict of interest: Ilya Starshynov (the first author) did his PhD in my group.]

#Physics#InformationTheory#Optics
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Soh Kam Yung

"Rather than rely on clever computation to make the best of conventional camera hardware, some engineers are instead experimenting with optical components such as new apertures, and animal-inspired sensors, that together can gather high-quality visual data that requires less intensive processing."

nature.com/articles/d41586-025

www.nature.comHow the natural world is inspiring the robot eyes of the futureIntelligent machine vision could get a boost from unconventional hardware design.
#Computers#Vision#Nature
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j_bertolotti

#PhysicsFactlet
Scattering scrambles coherent light into a speckle pattern, where the field at each point can be seen as the superposition of a large number of random phasors. At some point the result is brighter, and at some points the result is dimmer, creating the "speckly" pattern.
By changing the phase of the incident light one can change the phase of the phasors making up the resulting field, and since elastic scattering is linear, changing the phase of different input modes is going to rotate different phasors without cross-talk.
As a result it is possible to find an incident wavefront such that all the phasors making up the field at one point are in a straight line (constructive interference), resulting in a single bright dot (a focus) through a completely scattering material.

GIF
#Optics#Physics
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Spaceflight 🚀

Future applications of space 🌌 might include manufacturing materials like #pharmaceuticals, #optics, and #semiconductors in space; #mining the Moon and #asteroids; capturing energy, generating power 🔋, and beaming it to Earth and in-space #logistics, servicing assembly, and manufacturing (#ISAM) capabilities setr.stanford.edu/technology/s

Stanford Emerging Technology ReviewSpaceThe Stanford Emerging Technology Review helps America’s public and private sectors better understand transformational technologies.
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j_bertolotti

#PhysicsFactlet
A Shack-Hartmann sensor is made my an array of small lenses and a camera. If the light hitting the lenses is collimated, we will get a number of equispaced foci on the camera. But if the light is not collimated, the position of the foci will change in a predictable way, so we can reconstruct where the ray were coming from.
#Optics #Physics

GIF
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Soh Kam Yung

"[Researchers] developed a system that uses multiple laser beams to illuminate a distant target and uses a pair of small telescopes to collect the reflected light. The team demonstrated that this intensity interferometer can image millimeter-wide letters at a distance of 1.36 km, a 14-fold improvement in spatial resolution compared with a single telescope."

physics.aps.org/articles/v18/9

Physics · Interferometer Device Sees Text from a Mile AwayA high-resolution imaging system captures distant objects by shining laser light on them and detecting the reflected light.
#Lasers#Telescopes#Interferometry
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Artemis

Tired brain day.
My supervisor asked me to analyze our test data and prove that the quantum efficiency of our detector meets requirements.

Before this, all I know is that quantum efficiency is the rate that a detector turns photons into electric current.
Now I'm diving into a master's thesis that shows the derivations for modeling QE and trying to follow what's going on and how I can apply this to the images I was sent.
#science #optics #engineering #electronics

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