Researchers in Lebanon and France develop laser biospeckle method to help farmers harvest climacteric fruits -- like apples, bananas, pears and tomatoes -- at their precise peak in ripeness
The ability to detect when to harvest "climacteric" fruits -- such as apples, bananas, pears and tomatoes -- at the precise moment to ensure "peak edibleness" in terms of both taste and texture may soon be within reach for farmers, thanks to the work of a team of researchers from Saint Joseph University in Lebanon and the Université de Bretagne Occidentale de Brest in France.
The team's setup to measure speckle patterns involves coherent light, a laser beam, polarizers and quarter-wave plates to generate different incident polarizations, and a CMOS or CCD camera to record the fruits' speckle pattern.
As the team reports in a paper published in The Optical Society's (OSA) journal Applied Optics, they recently demonstrated a laser biospeckle technique capable of detecting fruits' climacteric peak.
What's the significance of this climacteric peak? "Fruits are divided into two categories: climacteric or nonclimacteric fruits," explained Rana Nassif, a postdoctoral researcher affiliated with both Saint Joseph University and the Université de Bretagne Occidentale de Brest. "Climacteric fruits continue their maturation off the tree or vine, so these fruits emit ethylene and are characterized by a climacteric peak--indicating a maximum ethylene release.
"This peak signals that the fruit has reached its maturity." After this point, the fruit is more susceptible to fungal invasion or begins to degrade from cell death.
By tapping biospeckle activity, generated by illuminating a biological medium with coherent light, the researchers studied the evolution of two batches of Golden apples' speckle patterns as they underwent the ripening process in both low- and room-temperature environments.
To do this, the team uses a rather simple setup that involves coherent light, a laser beam, polarizers and quarter-wave plates to generate different incident polarizations, and a digital camera to record the speckle pattern. "Simplicity and low cost are the key advantages of our technique," noted Nassif.
How does it work? Laser light interacts with any medium through different processes such as scattering, absorption and reflection. Photons scattered by the medium interfere with the incident light field to create a speckle pattern. "A group of sparkling and dark grains called 'speckle grains' make up this pattern. If the medium is biological -- meaning that it presents some sort of cell activity -- its speckle pattern will show changes with time," she said. "And this pattern depends on the medium's scattering properties, as well as its own nature."
Once obtained, speckle patterns can be correlated with a reference standard, which is based on emitted ethylene concentrations obtained by a principal component analysis. "This approach allows us to validate biospeckle as a noninvasive alternative method to respiration rate and ethylene production, which are used today for climacteric peak detection and as a ripening index," said Nassif.
The team explored the diffusion properties and inner activity aspects of the apples via speckle grain size, recording the temporal correlation between a set of images, consecutively, in different light polarizations. "On one hand, the changes the speckle grain size underwent marked an inflection point corresponding to the climacteric peak for apples stored at room temperature. While on the other hand, the time correlation coefficient behavior demonstrated a rise in the apples' activity until the day of climacteric peak was reached, followed by a decrease that marked the beginning of the deterioration stage."
Beyond apples, Nassif and colleagues are also monitoring the ripening of "Conference" pears -- performing backscattered speckle images on the fruits during the ripening phase. They supplemented these images with fluorescence and biochemical measurements.
"By doing this, we were able to show that as the glucose content increases, the circular degree of polarization decreases," Nassif said. In technical terms, she added, "This signature is expected for a medium that constituted a significant portion of small 'scatterers,' in which the Rayleigh diffusion regime outweighs the Mie regime. We also noticed a decreasing speckle grain size, which can be attributed either to increasing glucose or the decreasing of absorption."
What's next for the team? "In the near term, we're working on speckle theoretical studies based on Monte Carlo simulations -- taking into account light polarization and media characteristics," said Nassif. "These simulations can be used to differentiate and quantify the diffusion coefficient variations and its effect from those of absorption on the fruits' speckle image."
Then, they'll focus on comparing these simulations with experiments done on latex spheres -- a mix of spheres of varying diameters -- to vary the diffusion and absorption coefficient.
And, of course, one of the team's ultimate goals is to develop a portable tool to enable farmers to noninvasively assess their fruits' maturity in orchards or fields to detect the optimal time to harvest their crops. "This is of great interest to fruit farmers--especially since most tests used today are either destructive or based on visual criteria that are often wrong," noted Nassif.
Paper: "Detection of Golden apples climacteric peak by laser biospeckle measurements," by R. Nassif et al., Applied Optics, Vol. 53, Issue 35, pp. 8276-8282(2014).
About Applied Optics
Applied Optics publishes articles emphasizing applications-centered research in optics, moving the potential of science and technology to the practical. Published three times each month, Applied Optics reports significant optics applications from optical testing and instrumentation to medical optics...from holography to optical neural networks...from lidar and remote sensing to laser materials processing. Each issue contains content from three divisions of editorial scope: Optical Technology; Information Processing; and Lasers, Photonics, and Environmental Optics. It is edited by Joseph Mait of the U.S. Army Research Laboratory. For more information, visit http://www.OpticsInfoBase.org/AO
Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and entrepreneurs who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. OSA is a founding partner of the National Photonics Initiative and the 2015 International Year of Light. For more information, visit http://www.osa.org
Jason Socrates Bardi | EurekAlert!
Forest Management Yields Higher Productivity through Biodiversity
14.10.2016 | Technische Universität München
Farming with forests
23.09.2016 | University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES)
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences