Astronomy

Are digital adaptive optics possible?

Are digital adaptive optics possible?


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Adaptive optics generally apply slight changes to mirrors to account for atmospheric turbulence. These generally require either a mirror to be broken up into smaller mirrors, each with their own actuator, or for a single large mirror to be slightly deformed by many different actuators.

Is it possible to do much of this digitally?

Couldn't software slightly attenuate or amplify each pixel at each time-slice collected from a passive mirror? These changes would depend on the distortions measured by a guide star or laser (this digital system would still require a guiding light)? I suspect this would probably be less accurate than true adaptive optics, but it would also be far less expensive (as you wouldn't need so many actuators).

Has this approach been studied and dropped? Is it ridiculous and not even theoretically possible? I'm curious if anything has researched this idea.


The problem with your approach is that the deformable mirror changes the phase of the light across the mirror, where the light is not focussed. The light at the sensor array is focussed, and what you get is the intensity which is, roughly, the Fourier Transform of the phase front at the mirror. By the time you have intensity, the phase information has been lost.

Edit for clarity:

The sensor array measures the intensity, at which point the phase info is irretrievable. If you remove the sensor array and re-measure past the focal plane, yes, you can get phase info -- see "Plenoptic cameras."

Now, there are other techniques -- you might be interested in searching for papers on "Lucky Imaging" , which basically takes as many images as possible and throws away the distorted ones.


With enough computational power every pixel of a camera sensor could be processed individually. Outputs amplified or reduced to compensate for variations of light levels across the sensor. Stacking algorithms can discard those pixels that do not receive a constant input.

Photo shopping to the max. Make the Astro Photographers life easier. The problem for everyone else would be in deciding where science becomes art.


Each part of the mirror contributes to every pixel in the image, and the pockets of atmospheric distortion may be only 10-20 cm wide. If you look at a bright planet through a 30+ cm telescope in poor seeing conditions, the image looks like a stack of several sub-images shifting in and out of alignment, each from a different part of the mirror. To oversimplify, adaptive optics systems continually tweak the mirror segments to keep those sub-images aligned.

If you can accept a much higher detector cost in exchange for eliminating the actuator cost, it's possible to make an array of small telescopes, each with its own video camera, and align the shifting sub-images in software. But then diffraction by the smaller apertures would limit the system resolution unless you built an optical interferometer, which has its own category of difficulties to overcome.


@CarlWitthoft's answer is misleading if not wrong.

The Fourier transform of a field does not lose phase information. If you let the light drift another focal length and then use an identical mirror, you completely recover the initial electric field distribution incident at the telescopes entrance aperture. Information is not lost here.

The problem is not related to the optics at all.

The problem is that the detector (silicon CCD or photographic plate or whatever) measures time-averaged intensity of the light, which is the absolute value squared of the field at the detector's surface. It's this squaring and averaging in conventional detection schemes that makes phase information unrecoverable.

There is a whole field of research into trying to make phase-sensitive pixels for cameras but it's pretty academic, and you lose significantly in resolution and other performance metrics when you try to do this.

But what about longer wavelengths?

Your idea can and indeed does work in radio astronomy, even for microwaves and millimeterwaves. This is because the electric field received by each pixel (which is one dish antenna of an array of them) can indeed be absolutely digitized. They down-convert frequencies as high as a THz to one or two GHz and then amplify and digitize it with extremely fast ADCs.

Once that is done, you can correct for distortions in the wavefront arriving at your array of antennas in software. This process is explained further in answers to Would Adaptive Optics be Useful in Radio Astronomy?


Lucky & Adaptive Optics

There is no doubt that Adaptive Optics techniques have been successful in certain areas. When the reference star is bright enough it has been possible to achieve very high Strehl ratios, and Adaptive Optics has been used extensively in the near infrared where we have not yet tried to apply Lucky Imaging techniques due to the lack of suitable detector systems. However there are a number of circumstances where the achievements of Lucky Imaging have exceeded those of Adaptive Optics. In order to understand the circumstances under which Lucky imaging excels we need to look at the way that Adaptive Optic systems generally work.

Adaptive Optics works by breaking up the telescope aperture into cells of size of the order of r0 and detecting the reference star in each cell. This is most often done with the Shack Hartmann sensor:

The images produced show an array of image is of a star, one from each of the lenslets in the Shack Hartmann sensor.

A movie showing a typical image sequence can be seen (1.3 MBtyes) by clicking on the image. This shows images from the 4.2m William Herschel Telescope on La Palma using an 8x8 lenslet array in a Shack-Hartmann sensor (JOSE Camera).

The relative motions and positions of the star within each cell are then used to work out what the phase errors in the wavefront are at any instant and a computer controlled flexible mirror is distorted to compensate for these phase errors. A schematic of such a system is shown below, where the blue light from the star is used for the wavefront sensor to give an image like those shown above, and the deduced wavefront errors drive a wavefront corrector (here a flexible mirror) to remove the errors in the input wavefront, and therefore pass a corrected (and ideally diffraction limited) wavefront on to the science instrument.


(Image from Gordon Love, Durham).

If the reference star is very bright then it may be possible to work out what the phase errors are and to correct them before they change (and remember that they are changing very rapidly on timescales of the order of milliseconds). The reference star has to be very bright anyway because it must be detected with good signal-to-noise in each of the cells of the sensor rather than over the whole aperture of the telescope as is the case with the Lucky Imaging technique. Typically perhaps 20 cells in the sensor would be used with a 2.5 metre telescope. In practice it means that there is a very small probability that a reference star will be found close enough to the object of scientific interest for adaptive optics to be usable whereas with Lucky Imaging we are able to work with very much fainter reference stars. We find that we therefore have a much higher probability of finding a reference star within our field of view. For more information on reference star magnitudes and availability click here.

Isoplanatic Patch Size

The other problem which greatly affects the application of Adaptive Optics is the limited isoplanatic patch. There are a few cases in astronomy when we are happy simply to resolve two objects. We may wish to look at a very close pair of stars so that we can separate the components and look at their relative motions. However virtually all astronomy depends on comparing the brightness of the object under study with others in the field so that we can measure positions and brightnesses with useful accuracy. The problem with adaptive optics is that the shape of the star images changes very rapidly with the distance of an object from the reference star. This arises because adaptive optics tries to compensate for the phase fluctuations in the atmosphere at every instant, including when they are particularly bad. The poorer these conditions are the more rapidly the image shape changes with distance from the reference star. With Lucky Imaging we discard images formed when the phase fluctuations are bad and only use those which are least affected. This gives us star image profiles that vary much more slowly across the image. Not only does this mean that we get images that are much easier to work with for astronomers but we are also able to find reference stars over a much larger area of sky than is possible with adaptive optics. This larger area to search for reference stars means that we have a much higher probability of finding one. The mean size of the isoplanatic patch measured at Paranal, the site of the European Southern Observatory VLT, is only about 2.6 arc seconds in V band (equivalent to about 4.5 arcsec in I-band at 850nm) whereas our measurements given isoplanatic patch approaching one arc minute in diameter. For more information on why Lucky imaging gives an isoplanatic patch so much larger than does Adaptive Optics click here.

Atmospheric Turbulence Model Problems

One final problem which is only becoming clear now that Adaptive Optics systems are being commissioned and found to be less good than expected is due to the fact that although atmospheric turbulence has a power spectrum very similar to that predicted by models based on Kolmogorov turbulence theory, the turbulence actually found in practice is significantly different in a way that makes the construction of Adaptive Optic systems very much harder. For more information on the complexities of atmospheric turbulence click here.


Are digital adaptive optics possible? - Astronomy

The turbulence of the Earth's atmosphere distorts images obtained at even the best sites in the world for astronomy, including Chile's Cerro Armazones, home to the ELT.

The telescope will employ incredibly sophisticated 'adaptive optics' technologies to ensure its images are sharper than those of any other telescope.

The telescope will employ incredibly sophisticated 'adaptive optics' technologies to ensure its images are sharper than those of any other telescope.

The turbulence of the Earth's atmosphere distorts images obtained at even the best sites in the world for astronomy, including Chile's Cerro Armazones, home to the ELT.

The telescope will employ incredibly sophisticated 'adaptive optics' technologies to ensure its images are sharper than those of any other telescope.

Turbulence in the Earth’s atmosphere causes the stars to twinkle in a way that delights poets but frustrates astronomers since it blurs the finest details of the cosmos. Observing directly from space can avoid this atmospheric blurring effect, but the high costs of operating space telescopes compared to using ground-based facilities limits the size and scope of the telescopes we can place off-Earth.

Astronomers have turned to a method called adaptive optics. Sophisticated, deformable mirrors controlled by computers can correct in real-time for the distortion caused by the turbulence of the Earth's atmosphere, making the images obtained almost as sharp as (or, in the case of the ELT, sharper than) those taken in space. Adaptive optics allows the corrected optical system to observe finer details of much fainter astronomical objects than is otherwise possible from the ground.

This illustration aims to show how the nebula NGC 3603 could be seen by three different telescopes: the NASA/ESA Hubble Space Telescope, ESO’s Very Large Telescope with the help of its adaptive optics modules, and the Extremely Large Telescope. Credit: ESO

Adaptive optics requires a fairly bright reference star that is very close to the object under study. This reference star is used to measure the blurring caused by the local atmosphere so that the deformable mirror can correct for it. Since suitable stars are not available everywhere in the night sky, astronomers can create artificial stars instead by shining a powerful laser beam into the Earth's upper atmosphere. Thanks to these laser guide stars, almost the entire sky can now be observed with adaptive optics. The ELT will have up to eight of these lasers.

From the largest adaptive mirror ever built to advanced control systems, the ELT will have some of the most sophisticated technologies ever employed on a telescope to correct for the blurring effects of the Earth’s atmosphere. This page, currently under construction, will explore those technologies.

This video explains the principles of adaptive optics, a technique used in many ESO telescopes. Credit: ESO


ADAPTIVE OPTICS and ASTRONOMY

SciMeasure cameras are designed to give the best performance possible in real world situations. Focusing on multi-port traditional CCDs means that our cameras yield better signal-to-noise at real world signal levels than CCDs that rely on electron multiplication. Focusing on back-illuminated CCDs means that our cameras have much better QE, MTF and cosmetics than all front-illuminated sensors, including CMOS sensors. Focusing on deeper-well CCDs with large pixels means that our cameras have a higher real dynamic range and higher signal-to-noise than small pixel CCDs and CMOS sensors. Large pixels also make it much easier to couple the target to the sensor.

NIRSPEC/MAGIQ guide camera image
Credit: Diane Wooden, NASA Ames/Mike DiSanti, NASA GSFC/Eliot Young SwRI/Al Conrad, Jim Lyke and Terry Stickel, WMKO


Adaptive Optics: An Introduction

16.2.a SOME BASIC RELATIONS

In order to illustrate the requirements for adaptive optics systems, we first present some of the necessary relations needed in our discussion. In this section, we draw on an excellent review by Beckers (1993) .

Detection and compensation of the phase variations on the wavefront are usually done by measuring the wavefront of a reference object near the target object. This method succeeds if the angular separation between these two objects is less than the isoplanatic angle θ0. A good approximation to this angle is

where H is the average distance of the turbulent layer. This angle corresponds to a lateral shift of 0.3r0 between wavefronts from sources separated by θ0, hence the overlap in common area between the wavefronts is approximately 60%.

At separations of θ0 the rms difference between the reference and target wavefronts is ≅ λ/6. For r0 = 26 cm, from the first line in Table 16.1 , and H = 5 km, we find θ0 = 3.4 arc-sec. In the visual range only a small fraction of the desired targets have suitable reference objects within the isoplanatic angle. This has led to development of laser guide stars, a topic we comment on briefly in the following section. The situation for natural reference objects in the infrared is decidedly more favorable.

Another angle related to θ0 is the isoplanatic angle for image motion θm. This is the angular distance over which image motions are very similar. An approximate relation for this angle is θm ≅ 0.3(D/H) ≅ θ0(D/r0).

Another factor of crucial importance in applying the techniques of adaptive optics to correct for the phase variations is the rate at which the wavefront changes. This rate depends on wind velocities at different heights in the atmosphere. An approximate time scale for significant change is

For r0 = 26 cm and Vwind = 10 m/sec, we find τ0 ≅ 0.008 sec. It is again evident that the situation for detection and compensation of phase variations is more favorable in the infrared than in the visual range.


Adaptive optics: a breakthrough in astronomy

Until the 1970s, atmospheric seeing was considered as an absolute limitation for angular resolution of ground-based optical telescopes, exactly at the time of the conception of the new generation of giant optical telescopes, as the VLT and the Keck. Emerging in the context of the cold war with many constraints due to the research being classified, but with the new possibilities of digital control, astronomical adaptive optics was shown to be feasible in 1989 and gradually convinced an initially skeptical astronomical community of its potential. Twenty years later, it is a mandatory ingredient for the planning of Extremely Large Telescopes on the surface of the Earth, and has allowed many discoveries concerning galactic and extragalactic objects. Some directions for new developments are discussed.

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Are digital adaptive optics possible? - Astronomy

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Instrumental Limitations In Adaptive Optics For Astronomy

1 Litton-Itek Optical Systems (United States)

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The technology and components required to implement discrete adaptive optics systems capable of compensating wavefront errors caused by atmospheric turbulence in ground-based astronomical telescopes are reviewed. Characteristics of the major types of deformable mirrors, wavefront sensors and wavefront reconstructors are described. The effects of device limitations such as the size of the compensation subapertures and the signal to noise ratio of the wavefront sensor detector on the overall performance of adaptive optics systems are discussed. This review indicates that the technology exists to enable conventional adaptive optics systems to perform close to their inherent performance limits, the major impediment being the high cost of the components required. However, a larger problem exists in that the usefulness of adaptive optics for ground-based astronomy is severely limited by external factors such as the small size of the isoplanatic patch and the small photon flux available from most astronomical objects. The conclusion is that new system concepts are needed to overcome these external limitations and to make adaptive optics a useful technique for ground-based astronomy. Among the new approaches that have already been proposed are laser guide stars and multiple wavefront correctors.

© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.


Are digital adaptive optics possible? - Astronomy

You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither SPIE nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.

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Development of an experimental optical adaptive optics for small telescopes

Takeo Minezaki, 1 Yukihiro Kono, 1 Leonardo Vanzi, 2 Abner Zapata, 2 Mauricio Flores, 2 Sebastian Ramirez, 2 Keiichi Ohnaka 3

1 The Univ. of Tokyo (Japan)
2 Pontificia Univ. Católica de Chile (Chile)
3 Univ. Católica del Norte (Chile)

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We are developing an optical adaptive optics (AO) system for small telescopes. An AO instrument in optical wavelength mounted on a 1-2 m class telescope located at a good seeing site will make it possible to achieve high angular resolution of 0.1-0.2 arcsec. Such capability will enable us to perform unique astronomical programs, as well as to provide good opportunity in education for both astronomy and engineering. In order to examine the AO capability on small telescopes, we developed an experimental AO instrument, in which inexpensive commercial devices are extensively used to reduce cost for development. We designed the weight and the physical size so small that it is portable and easy to be mounted on a small telescope, which is a unique feature of our AO instrument. After the engineering observations performed in Japan, we mounted it on the 1-m telescope of the European Southern Observatory of La Silla in Chile in March 2018 to examine the performance. We found that there were approximately 4 times and 5 times improvements in the full-width-halfmaximum (FWHM) and Strehl ratio of the PSF from the natural seeing, respectively. The best AO-corrected PSF obtained during the observation achieved FWHM=0.18 arcsec and the Strehl ratio = 0.18. Based on the detailed analysis of the timeseries wavefront and deformable-mirror-operation data, further improvement in AO performance is expected by adjustment of the system parameters. We succeeded in demonstrating the feasibility of an inexpensive optical AO system for small telescopes.

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Xinetics Adaptive Optics Solutions

The Intelligent Optics (IO) Business Area at AOA Xinetics specializes in the design, development and manufacturing of products and systems which require state-of-the-art integration of optical, electro-optical, and opto-mechanical technologies.

The Intelligent Optics (IO) Business Area at AOA Xinetics specializes in the design, development and manufacturing of products and systems which require state-of-the-art integration of optical, electro-optical, and opto-mechanical technologies. It has supplied laser beam control systems and adaptive optical systems for over 30 years for government, industrial and commercial applications including high energy lasers, free space optics, astronomy and advanced imaging for ISR.

IO has a proven track record of providing innovative products for wavefront sensing and correction for a wide variety of beam control applications. Many of our products are vertically integrated using the finest materials and optical coatings that have been tested in environmentally extreme conditions.

IO supports all program lifecycles phases from concept development and prototype, through system design, integration, test and field support. IO's customer base includes the Air Force Research Labs, Starfire Optical Range, US Army, NASA, DARPA, the High Energy Laser Joint Technology Office, Office of Naval Research, multiple Observatories, Universities and prime contractors.

Products

Intelligent Optics is a vertically integrated manufacturer of Deformable Mirrors, Wavefront Sensors, Driver Electronics, Actuators and complete Adaptive Optical Systems. Our products have been developed and tested over the last two decades under extreme environmental conditions and high level performance requirements for many government programs and applications.

Our family of Deformable Mirrors (DM) are designed to have high spatial resolution correction with various levels of stroke. From our conventional Surface Normal mirrors, our high resolution Photonex Integrated Module mirrors, and our high stroke Surface Parallel Arrays, we have Commercial Off The Shelf (COTS) and custom solutions for your beam control application. In addition, our Integrated Wavefront Control (IWC) deformable mirror offers a Tip and Tilt capability for an all-in-one performance. Electronic drivers are available for all of our DM products.

Technology

The Intelligent Optics (IO) Business Area at AOA Xinetics is a leader in the technology development and product deployment of wavefront control systems for real-time wavefront sensing and correction. It develops and manufactures world-class products in precision motion control devices. These products include active optics such as deformable and hybrid mirrors that are scalable to very large sizes for applications in space, airborne and naval platforms, and ground telescopes.

AOX Xinetics precision control technologies begin with our Lead Magnesium Niobate (PMN) electrostrictive actuators used in our deformable mirrors. PMN material technology offers a mechanically stable actuator featuring extremely low hysteresis, minimal creep and is the material of choice for precision positioning. Additionally, advancements in imaging science technologies have complemented our precision control systems to offer multiple imaging modalities.

Contact us to discuss how we can assist your project.

Applications

The Intelligent Optics (IO) Business Area at AOA Xinetics specializes in the design, development, and manufacturing of systems which require state-of-the-art integration of optical, electro-optical, and opto-mechanical technologies. It has supplied laser beam control systems as well as adaptive optics systems for over 30 years for government, industrial, and commercial applications including high energy lasers, free space optics, astronomy, and advanced imaging for ISR.

IO has a proven track record of applying innovative solutions in wavefront sensing and correction for a wide variety of beam control applications. It supports all program phases from concept development and system design through prototype, integration, test and evaluation and field support. IO's customer base includes the Air Force Research Labs, Starfire Optical Range, US Army, NASA, DARPA, the High Energy Laser Joint Technology Office, Office of Naval Research, multiple Observatories, Universities and prime contractors.


Keck Observatory captures rare high-resolution images of exploded star

An image of the gravitationally lensed iPTF16geu Type Ia supernova taken in near-infrared with W. M. Keck Observatory. The lensing galaxy visible in the center has distorted and bent the light from iPTF16geu, which is behind it, to produce multiple images of the same supernova (seen around the central galaxy). The position, size and brightness of these images help astronomers infer the properties of the lensing galaxy. Credit: W.M. Keck Observatory

Scientists will now be able to measure how fast the universe is truly expanding with the kind of precision not possible before.

This, after an international team of astronomers led by Stockholm University, Sweden, captured four distinct images of a gravitationally lensed Type Ia supernova, named iPTF16geu.

To get a high-resolution view, the discovery team used the W. M. Keck Observatory’s OSIRIS and NIRC2 instruments with laser-guided adaptive optics at near-infrared wavelengths.

The resolution of the Keck adaptive optics images was equivalent to being able to distinguish the individual headlights of a car in San Francisco as viewed from Hawaii. The measurements confirmed the four separate images originated from iPTF16geu and that its light traveled for 4.3 billion years before reaching Earth.

“Resolving for the first time, multiple images of a strongly lensed supernova is a major breakthrough,” said Ariel Goobar, Professor at the Oskar Klein Centre at Stockholm University and lead author of the study. “We can measure the light-focusing power of gravity more accurately than ever before, and probe physical scales that may have seemed out of reach until now.”

The research, titled “iPTF16geu: A multiply-imaged gravitationally lensed Type Ia supernova,” published last week in the journal Science.

iPTF16geu was initially observed by the intermediate Palomar Transient Factory (iPTF), a Caltech-led international project that uses the Palomar Observatory to scan the skies and discover, in near real-time, fast-changing cosmic events such as supernovas using a fully-automated, wide-field survey.

This composite image shows the gravitationally lensed type Ia supernova iPTF16geu, as seen with different telescopes. The background image shows a wide-field view of the night sky as seen with the Palomar Observatory located on Palomar Mountain, California. The leftmost image shows observations made with the Sloan Digital Sky Survey (SDSS). The central image was taken by the NASA/ESA Hubble Space Telescope and shows the lensing galaxy SDSS J210415.89-062024.7. The rightmost image was also taken with Hubble and depicts the four lensed images of the supernova explosion, surrounding the lensing galaxy. Credit: ESA/Hubble, NASA, Sloan Digital Sky Survey, Palomar Observatory/Caltech

It took some of the world’s leading telescopes to gather more detailed information about iPTF16geu. In addition to Keck Observatory, the discovery team also used the NASA/ESA Hubble Space Telescope and the European Southern Observatory (ESO) Very Large Telescope in Chile.

“The discovery of iPTF16geu is truly like finding a somewhat weird needle in a haystack,” said Rahman Amanullah, co-author and research scientist at Stockholm University. “It reveals to us a bit more about the universe, but mostly triggers a wealth of new scientific questions.”

Astronomers detect thousands of supernova every year, but only a few of those found are gravitationally-lensed. Because they are only visible for a short time, spotting them can be difficult.

“iPTF is known for finding supernova candidates, but the key is to image them with Keck Observatory’s cutting-edge adaptive optics while the supernova is still bright,” said Shri Kulkarni, John D. and Catherine T. MacArthur Professor of Astronomy and Planetary Science and co-author of the study. “Thanks to Keck Observatory’s ability to respond to such supernova events on short notice, the discovery team was able to produce fine images, which allowed them to successfully observe the light rise and fall from each of iPTF16geu’s four images.”

Standard candle sheds new light on expansion of Universe

This discovery is highly interesting to scientists because Type Ia supernovas can be used as a “standard candle” to calculate galactic distances.

A standard candle is an astrophysical object that emits a certain, known amount of light. In this case, the object is a Type Ia supernova, a class of dying stars that always explode with the same absolute brightness. If astronomers know such an object’s true luminosity, they can infer its distance from Earth. The dimmer the object, the farther away it is.

The magnifying power of gravitational lensing

This rare discovery is made possible through gravitational lensing, a phenomenon that was first predicted by Albert Einstein in 1912. As light of the distant object passes by a massive object such as a galaxy cluster in the foreground, it gets bent by gravity, just as light gets bent passing through a lens. When the foreground object is massive enough, it will magnify the object behind it. In iPTF16geu’s case, its light was magnified by up to 50 times and bent into four separate images by a galaxy in front of it.

The discovery team analyzed the four lensed images of iPTF16geu, measured how long it took for the light from each image to journey to Earth (light is not bent in the same way in each image, so the travel times are slightly different), then used the differences in the arrival times to calculate the expansion rate of the universe — known as the Hubble constant.


Adaptive optics in biology

For centuries, astronomers looking up at the heavens through a telescope had a problem on their hands – the quality of their images depended on the strength and direction of the wind in the air. Trouble is, the Earth’s atmosphere isn’t uniform because its density – and thus its refractive index – varies from point to point as the wind blows. Result: distorted images.

In 1953, however, astronomer Horace Babcock proposed a clever solution, which was to bounce incoming light off a device that can rapidly correct for changes in optical path-length, which flattens the wave-front and so counteracts the effects of aberration. Any remaining wave-front errors are measured after the correction, before a feedback control loop uses the measurement to continuously adjust the corrections applied to the wave-front.

That was the principle behind “adaptive-optics” technology, which has since gone on to become a routine and invaluable part of astronomy. Turns out, however, that the same principles can be used in microscopy too, leading to many applications of adaptive optics in medicine and biology too, as I’ve discovered by commissioning and editing a new short-form Physics World Discovery ebook by Carl Kempf.

Kempf is a senior systems engineer at the California-based firm Iris AO, Inc, which is heavily into adaptive-optics technology, having worked on sensing, actuation, and control systems for high-precision devices for more than 30 years. I’m pleased to say that Kempf’s short ebook, Adaptive Optics in Biology, is now available for you to read free in EPUB, Kindle and PDF format via this link.

To give you some more idea of what the book is about and his career to date, I put some questions to Kempf, which you can read below. Don’t forget either that there are plenty of other books in the Physics World Discovery series, ranging from multimessenger astronomy to quantitative finance.

1. Carl, can you tell us about how you ended up working for Iris AO?

My background is in control systems, and adaptive optics is an interesting area that a lot of traditional control engineers overlook. When the chance to build the controller for the Iris adaptive-optic mirror came along, I couldn’t resist.

2. What does the firm mostly do and what’s your role there?

The company’s core product is a family of deformable mirrors build using techniques from micro-electromechanical systems (MEMS). Unlike most other mirrors, the devices have an optical surface that is an array of individual hexagonal segments. This offers some significant advantages, but requires a little bit of sophistication in the controller design. We also build some closed-loop systems our customers can use in simple applications or use a starting point for their own development of more sophisticated systems. My role is to oversee the development of the electronics and software that our customers use.

3. Why do you find adaptive optics such an exciting technology?

First, it is just such a simple but clever idea. As an engineer, I appreciate that. Second, to see an image sharpen up dramatically when the adaptive-optics controller is turned never gets old. It is just a neat thing to see.

4. What’s been your favourite application of it so far?

Probably retinal imaging. Being able to see details like blood flow in real time is fascinating. There is so much complex biology at work in the eye it is really pretty amazing to me, particularly coming from an engineering background. Knowing that the technology we build enables this is rewarding. Another aspect is that researchers often image themselves when first testing out a system, just because we are readily available. Taking these hi-tech “selfies” is fun.

5. Why would you encourage other scientists to take an interest in the field?

Adaptive optics is basic enabling technology that is going to be present in all the highest performance optical imaging systems regardless of whether it is astronomy, biology, or other fields. A basic knowledge of what adaptive optics is and how it works is useful to a scientist, particularly if they are lucky enough to get some time on an adaptive-optic-equipped system.

You can read Kempf’s Physics World Discovery book Adaptive Optics in Biology completely free via this link. For all titles in the series, please go here.