16 August 2016

Keeping nighttime lighting under control

Yosemite National Park offers stunning views of mountain vistas during the day and star-filled skies at night. This view often includes the Milky Way -- invisible to almost one third of Earth’s population due to light pollution.

Artificial lighting is restricted in Yosemite, but some areas in the park require lighting, such as parking lots and pathways between buildings. Light pollution can not only have a negative effect on visitors’ experiences, but can also change the natural rhythms of the park’s wildlife.

University of California, Merced (UC Merced) graduate student Melissa Ricketts has found a solution – by turning one of her professor’s inventions upside down. In an article from UC Merced’s University News, Ricketts describes what she calls “prescribed irradiance distribution.”

Ricketts is a member of UC Solar, a multicampus research institute headquartered at UC Merced headed by Roland Winston, the inventor of nonimaging optics. His compound parabolic concentrator (CPC) is a key piece of solar-collecting equipment in the emerging solar energy industry. Ricketts has developed a way to make Winston’s CPC emit light rather than gather it.

“It’s the reverse of the solar collector,” Ricketts said. “We can make a perfect square of LED light, or a circle, or whatever shape works best to illuminate only what needs to be illuminated.

Ricketts has been working with Steve Shackelton, a UC Merced staff member and former Yosemite chief ranger, on what they call “The Sand Pile Project.” Although most of their work is done in the lab, designs are occasionally tested in Yosemite on a large pile of sand that snowplow operators spread on the park roads when needed. The park needs to keep the sand pile well-lit so it can be accessed at any time, but lighting should have minimum effects on the surrounding areas.

UC Merced graduate student Melissa Ricketts sets up her LED
 lighting solution in the Sand Pile at Yosemite National Park
Credit: Courtesy of UC Merced

Yosemite is cautious about introducing new technology into the park, but they have been supportive of Ricketts’ research toward managing light by letting her use the area as a test where her work could eventually have global implications for wildlife and park visitors.

“We’re hoping to show the park we can eliminate the unnecessary light,” Ricketts said. She’s currently seeking funding to make the project viable for Yosemite and other parks

08 August 2016

Laser-induced removal of space debris

If you never thought something as small as a paint chip could have the potential to destroy the International Space Station, think again. Traveling at speeds upwards of 17,500 mph, the ISS could be torn apart by debris smaller than a marble in an instant. NASA is currently tracking more than 500,000 objects orbiting Earth including non-operational satellites and obsolete disengagements from past rocket missions. But the greatest risk to active satellites and space missions comes from the millions of pieces of debris that are nearly impossible to track.
7 mm chip on ISS window caused by a small
fragment of space debris no larger than
a few microns across

An article from 12 May 2016 in the Washington Post reported the International Space Station’s recent collision with “something as unassuming as a flake of paint or a metal fragment just a few thousandths of a millimeter across.”

The fragment left a 7-millimeter chip in a window of the European-built Cupola module. ESA astronaut Tim Peake was the first to snap a picture of the damage, then shared it with the world on his twitter account.

So how might we deal with all this hazardous space material? Lasers!

Authors of Laser-based removal of irregularly shaped space debris, Stefan Scharring, Jascha Wilken, and Hans-Albert Eckel of the German Aerospace Center discuss a new method in applying laser-induced damage principles to clean up space junk, where the use of high-energy laser pulses modify the orbit of debris causing it to burn up in the atmosphere.

The greatest improvement from previous studies in laser-based removal of debris is the ability to target irregularly-shaped objects – a characteristic shared by most space material.

To get a better picture of how much debris we’re working with, watch this short video simulating the increasing amount of space junk that has accumulated over the years in low Earth orbit (LEO).

Claude Phipps of Photonic Associates, LLC and his colleagues have been researching laser orbital debris removal (LODR) for over 15 years and have concluded that it is a very promising technique. Laser technology is improving at an astounding rate and is proving to be the most cost-efficient solution to space junk clean up.

20 July 2016

Grilling robot takes over backyard barbecue

Photonics has already made profound contributions to such areas as medicine, energy, and communications to make our everyday lives more efficient. (Hence the name of this blog.) People in all walks of life benefit from the incorporation of photonics technologies. We look forward to future advancements when the technology may help find a cure for cancer, monitor and prevent climate change, and pave the way to other advancements we can’t even visualize yet.

But here’s a photonics-based invention -- already demonstrated – that breaks ground in a new area: the backyard barbecue. Talk about hot fun in the summertime!

The BratWurst Bot made its appearance at the Stallw├Ąchter-Party of the Baden-W├╝rttemberg State Representation in Berlin. It’s made of off-the-shelf robotic components such as the lightweight Universal Robots arm UR-10, a standard parallel gripper (Schunk PG-70) and standard grill tongs. A tablet-based chef’s face interacted with party guests.

Two RGB cameras and a segmentation algorithm with background subtraction were used to localize each sausage on the grill. A special challenge was the changing color of the sausages. As one was completely cooked and served, the robot replaced it with a new one on the grill.

The BratWurst Bot was developed by the FZI Research Center for InformationTechnology at the Karlsruhe Institute of Technology; FZI also has a branch office in Berlin. A press release from FZI points out that hardware and software components of the grilling robot are also applicable to other processes like cooperative assembly or difficult manipulation tasks.

24 June 2016

Sky survey, AMA recommendations say it's time to reduce light pollution

A major focus of the International Year of Light and Light-Based Technologies was raising awareness of light pollution. With the rapid dissemination of LED lighting, one unfortunate side-effect is the proliferation of a higher color-temperature illumination. This has many documented negative effects on wildlife behavior and migration, as well as on human circadian rhythms. In addition, scientists are studying further problems in human health that may be indirectly related to different lighting, including higher incidence of some cancers.

Meanwhile, cities and towns across the globe enthusiastically switch to LED street lighting. The energy savings are significant, but in news reports of the plans and projects, there is usually no mention of the technical specifics (or “warmth”) of the light. Early bright white LED streetlights were mostly above 4000K, whereas warmer versions are now available, 3000K or below.

One problem with extremely bright light is that it impairs vision in darker areas, so any illusion of safety at night vanishes as visibility diminishes once you get into a shadow. For drivers as well as pedestrians, this can be dangerous.

Now the American Medical Association (AMA) has issued guidance encouraging communities to adopt LED lighting that minimizes blue-rich light. The AMA also recommended that “all LED lighting should be properly shielded to minimize glare and detrimental human health and environmental effects, and consideration should be given to utilize the ability of LED lighting to be dimmed for off-peak time periods,” according to a press release.

“The guidance adopted by grassroots physicians who comprise the AMA's policy-making body strengthens the AMA's policy stand against light pollution and encourages public awareness of the adverse health and environmental effects of pervasive nighttime lighting,” the release says.

We requested a copy of the original report that led to these recommendations from the AMA. Here’s an excerpt:

More recently engineered LED lighting is now available at 3000K or lower. At 3000K, the human eye still perceives the light as “white,” but it is slightly warmer in tone, and has about 21% of its emission in the blue-appearing part of the spectrum. This emission is still very blue for the nighttime environment, but is a significant improvement over the 4000K lighting because it reduces discomfort and disability glare. Because of different coatings, the energy efficiency of 3000K lighting is only 3% less than 4000K, but the light is more pleasing to humans and has less of an impact on wildlife.

“Disability glare” is defined by the Lighting Research Center at Rensselaer Polytechnic Institute as “the reduction in visibility caused by intense light sources in the field of view [because of] stray light being scattered within the eye.”

One city that put the brakes on the brighter LEDs is Davis, California. In 2014, as new lights were being installed, the Davis city council put the project on hold after multiple complaints from residents. Later, the city decided to spend an additional $325,000 to replace those too-bright streetlights in residential areas. However, Davis is the exception. Places that have not yet committed to the switch are encouraged by the International Dark-Sky Association (IDA), the Lighting Research Center, and others to ask the right questions and study the issues involved beyond the simple let’s-save-energy approach. (In fact, that justification is up for debate as well -– it seems that when something gets cheaper, people tend to use more of it.)

Last fall, SPIE Newsroom published an article exploring these issues and collecting the advice of lighting experts. Recommendations for municipalities considering a change are included. (See “LED light pollution: Can we save energy and save the night?” by Mark Crawford.)

Just this month, a world atlas of artificial sky luminance, described in Science Advances reported that 80% of North Americans and one third of all humans are unable to see the Milky Way because of light pollution. Calculated with data from professional researchers and citizen scientists, the atlas also takes advantage of the newly available, low-light imaging data from the VIIRS DNB sensor on the Suomi National Polar-orbiting Partnership (NPP) satellite. The authors conclude:

"Light pollution needs to be addressed immediately because, even though it can be instantly mitigated (by turning off lights), its consequences cannot (for example, loss of biodiversity and culture)."

The IDA says this is a "watershed moment." The sky atlas and the AMA recommendations offer "an unprecedented opportunity to implore cities to transition to LEDs in the most environmentally responsible way possible." It's a good chance to start a conversation with your elected officials.

07 June 2016

Photonics on the farm: robotics to help feed the world

Simon Blackmore talks about farming with robots
for precision agriculture in an
SPIE Newsroom video interview [6:58].
Ten to 15 years ago, farmers used to laugh when Simon Blackmore and his colleagues talked about deploying robotics for such chores as weeding, protecting crops from disease or pests, or selecting harvest-ready vegetables — all while helping to cut costs and limit chemical and other impacts on the soil.

Now, he said in an SPIE Newsroom video interview posted last week, they’re asking questions about how robotics and other photonics-enabled technologies can help save energy and money, minimize soil damage, and improve crop yield.

Blackmore, who is Head of Engineering at Harper Adams University in Shropshire, director of the UK National Centre for Precision Farming (NCPF), and project manager of FutureFarm, also shared his ideas in a new conference at SPIE Defense and Commercial Sensing in April on technologies with applications in precision agriculture.

Blackmore and his NCPF colleagues are working to overhaul current farming practices by intelligently targeting inputs and energy usage. Their lightweight robots are capable of planting seeds in fields even at full moisture capacity, replacing heavy tractors that compact and damage the soil.

Simon Blackmore
Robots have also been designed with micro-tillage capabilities, to target the soil at individual seed positions, and for selective harvesting of crops for quality assurance.

“Now one of my former PhD students has developed a laser weeding system that probably uses the minimum amount of energy to kill weeds, by using machine vision to recognize the species, biomass, leaf area, and position of the meristem, or growing point,” Blackmore said.

A miniature spray boom of only a few centimeters wide can then apply a microdot of herbicide directly onto the leaf of the weed, thus saving 99.9% by volume of spray. Or, a steerable 5W laser can heat the meristem until the cells rupture and the weed becomes dormant. These devices could be carried on a small robot no bigger than an office desk and work 24/7 without damaging the soil or crop.

Not surprisingly, data is a hot topic in the field of precision agriculture.

Several speakers at the April event — among them John Valasek, and Alex Thomasson of Texas A&M University (TAMU), chairs of the conference, and Elizabeth Bondi of the Rochester Institute of Technology (RIT) — spoke about best practices for collecting data, and Kern Ding of California State Polytechnic University discussed data processing techniques.

Valasek also described several sensors and different ways they may be flown. Factors such as weather, speed, altitude, and frame rate can dramatically change the quality of the data products from UAV imagery.

Bondi discussed the calibration of imagery from UAVs (unmanned aerial vehicles, such as drones) to maintain consistency over time and under different illumination conditions.

Other speakers — Haly Neely of TAMU, Carlos Zuniga of Washington State University, and Raymond Hunt of the U.S. Agricultural Research Service — focused on the use of UAVs for such applications as soil variability, irrigation efficiency, insect infestation, and nitrogen management for crops including cotton, grapes, and potatoes.

Plant phenotyping — the analysis of crop characteristics such as growth, height, disease resistance, nutrient levels, and yield — is vital to increase crop production. Taking these data with current methods can damage plants, and is time-consuming and expensive. UAVs, carrying the right sensors, have the potential to make phenotyping more efficient and less damaging.

Speakers Yu Jiang of the University of Georgia, Andrew French of the U.S. Arid-Land Agriculture Research Center, and Grant Anderson of RIT described ground-based systems to expedite phenotyping, and Joe Mari Maja of Clemson University, Yeyin Shi of TAMU, Maria Balota of Virginia Polytechnic Institute, and Lav Khot of Washington State University discussed UAV-based systems.

With images and measurements from such devices, for example, cotton height may be determined and cotton bolls counted, soil temperature can be mapped, and nutrient levels in wine grapes were assessed remotely.

Small- and mid-sized farms are expected to see the largest yield increase from these initiatives. The ultimate result of all this photonics-enabled precision agriculture is profound: healthier food, more productive farms and gardens, and more nutritious food for a growing world population.

Thanks to Elizabeth Bondi and Emily Berkson, both of RIT, for contributions to this post.

06 April 2016

Cataract surgery: misnomer?

On left, the patient’s left eye has no cataract and all structures are visible. On right, retinal image from fundus camera confirms the presence of a cataract. (From Choi, Hjelmstad, Taibl, and Sayegh, SPIE Proc. 85671Y, 2013)

On left, the patient’s left eye has no cataract and all structures are visible. On right, retinal image from fundus camera confirms the presence of a cataract. (From Choi, Hjelmstad, Taibl, and Sayegh, SPIE Proc. 85671Y, 2013)
Article by guest blogger Roger S. Reiss, SPIE Fellow and recipient of the 2000 SPIE President's Award. Reiss was the original Ad Hoc Chair of SPIE Optomechanical Working Group. He manages the LinkedIn Group “Photonic Engineering and Photonic Instruments.”

The human eye and its interface with the human brain fit the definition of an "instrument system."  The human eye by itself is also an instrument by definition.

After the invention of the microscope and the telescope, the human eye was the first and only detector for hundreds of years, only to be supplemented and in most cases supplanted by an electro-optical detector of various configurations.

The evolution of the eye has been and still is a mystery.  In National Geographic (February 2016) an excellent article titled "Seeing the Light" has a very good explanation of the eye's development

Having recently had cataract surgery, my interest in the eye was stimulated. First, I wondered why "cataract surgery" is called "cataract surgery."

In cataract surgery, no surgery is performed on the cataracts (cataract material). A very small incision is made in the lens pocket and the cataract material is flushed out by using the opening to introduce the flushing substance, and the flushing substance carries out the cataract material through that opening. The cataract material may require ultrasonic fracturing to reduce particle size.  A man- and machine-made lens is inserted into the opening.  The opening may or may not require suturing. This procedure should more accurately be known as "lens replacement surgery."

Why are a large number of measurements made on the eye before the eye surgery?

Without invasion of the eyeball, a great many measurements from outside it must be made to determine the required focal length of the replacement lens. (Some people do need corrective glasses to achieve the correct value.) When I asked about all these measurements (made by high-precision lasers) other important factors were brought up, including knowledge of the instruments by the operator, guesswork, and finally…some luck.  Luckily, without glasses distance vision is infinite after surgery, but reading glasses are a necessity. Today, there are many options available to cataract patients, including multifocal lenses, which may enable complete independence from glasses.

After having lens replacement surgery myself, two haunting questions remain unanswered in my mind.

A. Where did the optical-quality fluid (vitreous) in the original eye lens and the eyeball come from, and how did it know where it belonged? Optical-quality liquid or gel occurs in the human eye but nowhere else in the human body.

B. How did the Creator (or whoever or whatever, a religious question) -- without Physics 101 or Optics 101 or Warren Smith's book on basic optics -- determine the focal length of the eye lens (the distance from the eye lens to the retina; some people do need corrective glasses to achieve the correct value). The focal length of the human eye lens is a mathematical value based on measurements and calculations or both and could not have just evolved without some knowledge and information about basic optics.

I wish I could answer either of these two questions but I will have to wait for someone smarter than me. Until then let’s at least change the name of the operational procedure to reflect what is actually being performed, so that people will understand that their cataracts are not being operated on but that their eye lens is being replaced.

Meanwhile, beyond these everyday procedures for improving vision, exciting advances are emerging from labs around the world, enabled by photonics. These include smart contact lenses for monitoring and even treating disease. Artificial retinas under development at Stanford, USC, and elsewhere offer the promise of vision to the blind. The results might not be as clear as what we are used to (yet), but imaging technologies and/or nanomaterials that send visual signals to the brain are helping counter the effects of age-related macular degeneration and other vision problems. New devices and treatments may offer a bright future to those with previously intractable vision problems.

09 March 2016

Graphene: changing the world with 2D photonics

In existing technologies, 2D technologies can be introduced
into products such as silicon electronics, semiconductor
nanoparticles, plastics and more for added new
functionality; above; a flexible 2d prototype sensor.
Graphene, anticipated as the next "killer" app to hit optical sensing, is expected to offer an all-in-one solution to the challenges of future optoelectronic technologies, says Frank Koppens. A professor at the Institute of Photonic Sciences (ICFO) in Barcelona, Koppens leads the institute's Quantum Nano-Optoelectronics Group.

Koppens, along with Nathalie Vermeulen of B-PHOT (Brussels Photonics Team, Vrije Universiteit Brussel), will lead a daylong workshop in Brussels on 5 April on transitioning graphene-based photonics technology from research to commercialization.

In his article on Light and Graphene in the current issue of SPIE Professional magazine, Koppens describes the 2D material's tunable optical properties, broadband absorption (from UV to THz), high electrical mobility for ultrafast operation, and novel gate-tunable plasmonic properties.

Two-dimensional materials-based photodetectors are among the most mature and promising solutions, Koppens notes. Potential applications include expanded communications networking and data storage, increased computing speeds, enhanced disease control utilizing increasingly larger and more complex data sets, and more accurate fire, motion, chemical, and other sensor systems including the next generation of wearables.

Graphene is gapless, absorbing light in the ultraviolet, visible, short-wave infrared, near-infrared, mid-infrared, far-infrared, and terahertz spectral regimes. A few of many advantages include:
  • Ability to be monolithically integrated with silicon electronics
  • Extremely fast -- exceeding 250GHz -- as a material-based photodetector
  • Able to bend, stretch, and roll while maintaining useful properties
  • Low-cost production with potential to integrate on thin, transparent, flexible substrates
  • Potential to be competitive against alternate applications in health, safety, security and automotive systems.

Koppens notes that the €1 billion European Union Graphene Flagship program is aiming to work through academia and industry to bring graphene into society within the next 10 years.

For more, read the complete article in the SPIE Professional, and watch Koppens' SPIE Newsroom video interview [7:09] on manipulating light with graphene.