Abstract-Shape-from-focus for real-time terahertz 3D imaging

J.-B. Perraud, J. P. Guillet, O. Redon, M. Hamdi, F. Simoens, and P. Mounaix

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-3-483

Thanks to significant advances in real-time terahertz imaging in terms of resolution and image quality, adapting and extending optical methods for 3D imaging at the millimeter scale is now promising. The shape-from-focus algorithm is a post-processing tool used in optical microscopy to reconstruct the external shape surface of a convex surface object. Images acquired at different distances from the object-side focal plane are implemented in this algorithm. We localize the best focus position in the stack of images for each pixel and then reconstruct the object in 3D due to the short depth of field. In this Letter, we propose an application of this algorithm in active and real-time terahertz imaging. We achieve the experimental reconstruction in 3D with a terahertz waves imaging system composed of a powerful source and a real-time terahertz camera.

Abstract-Shape-from-focus for real-time terahertz 3D imaging

J.-B. Perraud, J.-P. Guillet, O. Redon, M. Hamdi, F. Simoens, P. Mounaix,

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-3-483

Thanks to significant advances in real-time terahertz imaging in terms of resolution and image quality, adapting and extending optical methods for 3D imaging at the millimeter scale is now promising. The shape-from-focus algorithm is a post-processing tool used in optical microscopy to reconstruct the external shape surface of a convex surface object. Images acquired at different distances from the object-side focal plane are implemented in this algorithm. We localize the best focus position in the stack of images for each pixel and then reconstruct the object in 3D due to the short depth of field. In this Letter, we propose an application of this algorithm in active and real-time terahertz imaging. We achieve the experimental reconstruction in 3D with a terahertz waves imaging system composed of a powerful source and a real-time terahertz camera.

Abstract-Three-Dimensional Imaging of Space Debris with Space-Based Terahertz Radar

 Xu Yang, Yiming Pi,  Tong Liu,   Haijiang Wang

http://ieeexplore.ieee.org/document/8207424/


The increasing natural or man-made space debris could pose a serious threat to orbital space-based systems and their operators. Consequently, their detection, reorganization, and tracking are of considerable significance. However, the traditional solutions, including ground-based radar and optical telescope, can not exactly observe the debris with small diameter. Imaging with space-based terahertz (THz) radar in combination with inverse synthetic aperture radar (ISAR) technique enables us to obtain high-resolution three-dimensional (3-D) image. In this paper, we have developed a high-resolution THz radar that operates at 340 GHz with a bandwidth of 28.8 GHz and the output peak power of 5 mW for proof-of-concept. In addition, using the characteristic that space debris rotates its main axis, we have established a 3-D ISAR imaging geometry as well as its corresponding signal model. Then, a 3-D wavenumber-domain image formation algorithm is presented and has been validated by point target simulation. The experimental results have confirmed that the THz radar can effectively achieve high-resolution 3-D imaging of the spinning space debris.

Abstract-2D and 3D Terahertz Imaging and X-Rays CT for Sigillography Study

• M. Fabre, 
• R. Durand, 
• L. Bassel, 
• B. Recur, 
• H. Balacey, 
• J. Bou Sleiman, 
• J.-B. Perraud, 
• P. Mounaix, 

http://link.springer.com/article/10.1007%2Fs10762-017-0356-3

Seals are part of our cultural heritage but the study of these objects is limited because of their fragility. Terahertz and X-Ray imaging are used to analyze a collection of wax seals from the fourteenth to eighteenth centuries. In this work, both techniques are compared in order to discuss their advantages and limits and their complementarity for conservation state study of the samples. Thanks to 3D analysis and reconstructions, defects and fractures are detected with an estimation of their depth position. The path from the parchment tongue inside the seals is also detected.

Abstract-Three-dimensional sparse image reconstruction for terahertz surface layer holography with random step frequency

Wei Liu, Chao Li, Zhaoyang Sun, Qunying Zhang, and Guangyou Fang
https://www.osapublishing.org/ol/abstract.cfm?URI=ol-40-14-3384

In this Letter, a sparse image reconstruction approach is proposed for three-dimensional (3D) terahertz (THz) surface layer holography by a sharply dwindled amount of frequency samples, without reducing the high quality of the final reconstructed 3D THz images. To avoid the range ambiguity resulting from the reduction of frequency samples, a random step frequency method is adopted to evaluate the rough range profile of the 3D surface layer. With the obtained range profile, a de-ambiguity procedure is proposed to demodulate the sparse echoed data to greatly compress the maximum nonambiguous range and recover all the information for 3D holography image reconstruction. Proof-of-state experiments are performed in 0.2-THz band. The results verify the effectiveness and the efficiency of the sparse imaging scheme for THz surface layer 3D holography.

© 2015 Optical Society of America

Full Article  |  PDF Article

Algebraic reconstruction technique for 3-D imaging in the terahertz frequency range

The team used techniques ranging from macroscopic to nanoscale to improve THz generation and detection for their imaging system

 http://phys.org/news/2015-01-algebraic-reconstruction-technique-d-imaging.html#jCp

Researchers at the Shanghai Institute of Microsystem and Information Technology and Fudan University in China have used an algebraic reconstruction technique (ART) for 3D imaging in the terahertz frequency range. They developed their technique in conjunction with computerised tomography (CT) based on a THz quantum cascade laser (QCL) and a quantum well photodetector.

Two-to-one

CT was first developed in the X-ray frequency band to reveal the cross-sectional image of an object by combining the different projections from different angles. The basic principle of CT relies on the Fourier-slice theorem, which states "that if the projections of each angle of a 2D image are obtained, the pixel value for any point can be calculated," explained Tao Zhou, lead author of the research. From a more mathematical standpoint, he said, "the 1D Fourier transform of a parallel projection of an object is a line of the 2D Fourier transform of the object."

Extending CT into the THz band was first achieved using time-domain spectroscopy (TDS). In these systems, THz pulses are generated using a femtosecond laser and a photoconductive antenna. The sample is placed on a translation-rotation stage to achieve a parallel scan mode for CT, and the transmitted THz signal is detected by a linearly chirped optical probe beam. The cross-section is then reconstructed by using a conventional filtered back projection (FBP) algorithm, and the 3D image is created by stacking the slices sequentially.

Low-power phase

For 3D THz imaging, the TDS technique is widely used and could provide information about the phase and amplitude of the signal from a single detection, as well as a high signal-to-noise ratio. Due to the relatively low output power of THz radiation, the reconstruction work is generally based on phase information, which corresponds to the refractive index of the material.

For the THz region, the FBP algorithm is the most commonly used for image reconstruction as it has the advantages of simple hardware requirements and high accuracy. However, it suffers from several disadvantages such as beam hardening, noise sensitivity, image aberration, and a long data acquisition time.

Rayleigh length

Although most THz applications are based on the TDS technique, there remain problems to be solved. TDS demands a complicated and sophisticated system design and imaging reconstruction is mainly based on phase information.

Advanced reconstruction algorithms helped the system to create accurate and clear images of hidden objects

In the experiment, to address some of these issues, Zhou told us that "a QCL and a QWP were adopted for THz CT. The system was placed in an open environment and the image reconstruction was based on the amplitude of the THz signal in contrast to TDS." This is also in contrast to most THz CT research that uses the traditional FBP algorithm, which demands sufficient angle samplings (usually more than 36) and is very sensitive to signal noise. "Consequently," said Zhou, "we successfully used an iterative ART algorithm to prove that the iterative reconstruction methods of X-ray CT are also suitable for THz waves."

In CT, Rayleigh length plays a dominant role. The reconstruction algorithm is based on the projection data, which represents the integral of attenuation along a transmission line. "So," said Zhou "a beam with a larger Rayleigh length is a better analogue of the line pattern, which ensures the basic conditions for the algorithm to operate effectively." To further improve the case for their technique, Zhou told us that "a better spatial resolution could be realized by a short focal length, but Rayleigh length is considered to be more important in THz CT. Therefore, parabolic mirrors with long-focal length are chosen for CT imaging."

As well as advantages in processing and reconstruction, the team's system features advances in generation and detection of radiation. Traditionally, at THz frequencies, the detectors are mostly broad-band detectors, such as cryogenically cooled bolometers, which are intrinsically slow and the main responsive frequency band is located in the mid-infrared. Zhou and the team, therefore, chose a spectra-matched QWP for THz detection and rebuilt the image with equal quality.

Quantum cascade lasers are an effective source of THz radiation

Raising the bar

The QCL/QWP based approach, combined with the ART algorithm, has been used before, but previous applications were for frequencies far below 1 THz. The images the group obtained proves that the amplitude-based reconstruction method does work very effectively in the THz band, which decreases the necessary sampling and facilitates image reconstruction.

However, Zhou said, there are still a number of challenges ahead: "most works choose point-scan mode for which the imaging speed is limited, and the reconstruction algorithm is borrowed from the X-ray CT, which is not completely suitable for the THz frequency band due to the inhomogeneity of the metal area."

A better source

The Chinese team are already working on these problems, as Zhou explained: "recently, we used a line-focus mirror and a THz array detector to improve the data acquisition and speed; for the reconstruction algorithms, we are trying to understand the inhomogeneous effect caused by reflection – reflection invalidates the assumptions of the algorithm and some modifications should be made and this is a complicated mathematic issue."

The group are also aiming to produce high quality THz sources and detectors by improving the quality and implementation of the QCL and QWP. Significantly, their work based on these devices very strongly indicates their potential in the CT/3D imaging field.

THz CT is a natural extension of X-ray CT, which is already a powerful technique in the imaging field. "For the next decade," said Zhou, "this technique will become faster (real-time), more accurate (high resolution) and simpler (low complexity of system, room temperature operation). As these demands are met, I look forward to seeing the technique applied in biomedical and industry fields, just as X-ray CT."

 Explore further: Broadband THz wave generation with metamaterials demonstrated

More information: "Three-dimensional imaging with terahertz quantum cascade laser and quantum well photodetector." Electronics Letters, Volume 51, Issue 1, 08 January 2015, p. 85 – 86 DOI:  10.1049/el.2014.3873

Journal reference: Electronics Letters  

Terahertz Spectroscopy Promises Better Diagnosis, Safer Drugs

Marie Freebody, Contributing Editor, marie.freebody@photonics.com

With terahertz imaging systems getting smaller and cheaper – and performing better – applications are stacking up in cancer imaging as well as drug detection and development.

http://www.photonics.com/Article.aspx?AID=54396
Terahertz spectroscopy is a fast-growing area of research with some hugely promising applications, now that cumbersome, expensive and hard-to-use systems are in the past. Its low-photon-energy radiation makes it safe for tissue imaging, and its high absorption in water, which is often a key indicator of the presence of tumor cells, makes it a hopeful weapon in fighting cancer.

Revealing tumors in more detail

Cancer is the second most common cause of death in the US, second only to heart disease, and accounts for nearly 1 in every 4 deaths, according to the American Cancer Society. Early detection could mean the difference between life and death for many patients, but there is a shortfall in the current imaging techniques.

X-ray imaging and MRI provide images of living tissues at the macroscopic level, but with low resolution and specificity. Microscopic imaging can be used on biopsy samples to provide structural and functional information, but there is not yet a technique that can noninvasively image tissue at a high resolution – effectively combining both macroscopic and microscopic imaging.

New terahertz spectroscopic studies of cancer could potentially fill this niche. Since terahertz frequencies are readily absorbed by water and other polar liquids, the method lends itself well to imaging most organic tissue.

Although the high absorption loss limits the depth of imaging, it does promote extreme contrast between substances with lesser or higher degrees of water content, which helps to show distinctive contrast in

 medical imaging.

“High absorption of water and other polar liquids in terahertz frequency range limits the sensitivity of terahertz imaging in water-rich samples,” said Dr. Trung Quan Luong of the Applied Competence Cluster Terahertz at Ruhr University Bochum in Bochum, Germany. “The focus of current biomedical application is on skin imaging. Further improvements require high-power terahertz sources.”


(Left) Outside and inside a package of omeprazole. (Right) Terahertz image of the packaged omeprazole showing that the terahertz beam can penetrate the paper and plastic packages to observe the inner drug content. Courtesy of Applied Competence Cluster Terahertz, Ruhr University Bochum.

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In a bid to further improve image contrast, Korean scientists introduced gold nanoparticles to label cancer cells (Optics Express 2009;17:3469-75). In a paper reviewing various forays into terahertz imaging, published in March 2012, professor Emma MacPherson at the Chinese University of Hong Kong and colleagues explain the innovative approach in more detail.
Gold nanorods (GNR) are engineered to be readily absorbed by cancer cells and injected into the specimen. At first, terahertz imaging reveals nothing, but once an IR laser is used to heat the nanoparticles, a notable increase in reflected terahertz signal is detected. Interestingly, since the positioning of IR light illumination can be controlled with micron resolution, the image resolution of the terahertz-differential image measurement can also be on the order of microns – much higher than with conventional terahertz imaging.

What’s more, with high enough concentrations of GNRs and intense exposure of near-IR light, cells can be destroyed. This means that if the GNRs can target the cancer cells with high enough specificity, the technique also has potential for hyperthermia therapy for cancer.

But MacPherson is quick to point out that further research into the safety of the technique needs to be fully investigated first.

“In terms of developing terahertz imaging/spectroscopy into a clinical technique for cancer diagnosis, there is still a long way to go,” MacPherson said. “More studies and clinical trials are needed to determine whether terahertz imaging has significant advantages over existing techniques.”

At National Taiwan University, Dr. Chi-Kuang Sun and colleagues demonstrated in vivo breast cancer detection in a mouse model for the first time. The group used a terahertz-fiber-scanning transmission imaging system to continuously monitor the growth of human breast cancer in mice. Cancer cells were first implanted into the mice; then continuous screening distinguished cancer development from the surrounding fatty tissue.

“Early cancer development was detected on the twenty-third day, and the induced terahertz absorption coefficient change was 0.25 mm⁻¹, corresponding to a cancer volume of 1.3 mm³,” Sun said. “This change is mainly due to the change in the water content in these tissues.”

While this study indicates the potential for noninvasive early cancer detection with high sensitivity and without the need for labeling, it does not prove that this imaging system can be directly applied to humans in vivo.

The problem is enhancing the image contrast of cancerous cells buried within fibrous breast tissue rather than fatty breast tissue. In addition, gland tissue – which also has high water content – shows up with similar contrast to cancerous tissue under terahertz illumination. Since breast tissue can be fatty and originates from glandular tissue, the potential of this technology could be seriously limited for human screening.

One possible solution is to perform time-lapsed imaging to provide a base from which cancerous tissue can be distinguished from other gland tissues, but Sun admits that further work still needs to be done.

Although progress is being made in many areas, the competition from more developed imaging modalities is fierce. Ultrasound, OCT, near-IR and Raman spectroscopy, MRI, positron emission tomography, in situ
confocal microscopy, and x-ray techniques have all received much more attention and currently offer enhanced resolution, greater penetration, higher acquisition speeds and specifically targeted contrast mechanisms.

But terahertz imaging is catching up fast and offers some elements that existing techniques do not. For example, no technique can readily distinguish benign from malignant lesions macroscopically at the surface or subdermally. Furthermore, the sensitivity of terahertz signals to skin moisture (which is often a key indicator) is very high, and competing techniques such as high-resolution MRI are less convenient and more costly.

Drug detection, development

Today, more terahertz systems are commercially available than ever before – and with more competition come many improvements.

“Advances in recent years have been on the source and detector side,” said Dr. David Armstrong, marketing director at M Squared Lasers in Glasgow, Scotland. “At M Squared, we have developed a turnkey tunable terahertz source, the Firefly-THz, using licensed technology developed at [the University of] St. Andrews [in Scotland] – namely, a pulse OPO [optical parametric oscillator] approach that yields high peak power and narrow linewidth, suitable for standoff imaging and resolving spectral components.”

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M Squared Lasers’ Firefly-THz is a hands-free, pulsed nanosecond terahertz laser source that provides a tunable narrow-linewidth output, thanks to its novel optical parametric oscillator design. Courtesy of M Squared Lasers.

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Building on 15 years of experience in developing parametric generators for the UV-VIS-IR spectral ranges, researchers at St. Andrews have developed a compact, efficient and transportable parametric generator of terahertz radiation.

The system has the potential to identify

The system has the potential to identify and characterize illegal drugs that are concealed about a person, sent
through the mail or on a contaminated surface. Unlike x-ray scanners, canine detection or external swiping,
terahertz waves can noninvasively penetrate a wide range of materials such as paper, wood, plastic, fabrics, ceramics, bone and tissue.
Not only can terahertz imaging detect a concealed drug, but it can also provide a spectral fingerprint, making drug identification possible.

Advances in 3-D terahertz imaging are opening up new avenues in pharmaceutical applications, where it can improve the quality and uniformity of pharmaceutical products. Many pharmaceutical materials can exist in multiple solid forms, known as polymorphic forms: They have the same chemical composition but different crystalline structures and as such behave differently in terms of solubility and stability.

Terahertz spectroscopy can pinpoint at which step in the manufacturing process the polymorphic transitions are emerging, giving pharmaceutical makers a better understanding of the causes of changes in structure.

But it’s not just what’s on the inside that matters; the tablet coating is also a crucial component that impacts how the drug interacts with our body. For oral drugs, the coating protects the active ingredients from being released before the tablet reaches the small intestine, where they are absorbed.

Coatings can also prolong a tablet’s shelf life by protecting the components from moisture and oxygen degradation. Therefore, characterizing the tablet coating and ensuring uniformity within a single tablet or an entire batch is important.

Here, terahertz pulse imaging measures the thickness of coatings by a change in refractive index of reflected light. Although the technique provides results similar to ultrasound measurements, there remains one common practice in the pharmaceutical industry in which terahertz triumphs.

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The interaction of a terahertz pulse with a protein and its hydration shell. Courtesy of Trung Quan Luong, Konrad Meister and Martina Havenith, Ruhr University Bochum.

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Terahertz data compiled from measuring the coating thickness has been found to strongly correlate with the dissolution profile of the tablet. Determining how a drug dissolves is currently performed using a dissolution apparatus, often requiring lengthy time analysis. Terahertz, on the other hand, offers a promising way to reduce the cost and time involved.

In terms of pharmaceutical applications, extending the spectral range of current instruments from 100 to 300 cm⁻¹ would allow coverage of both the intermolecular and some of the intramolecular vibration modes of pharmaceuticals. This would not only provide better spectral specificity for chemical discrimination and mapping, but would also help to characterize thinner coatings with higher spatial resolution.
References

1. C. Yu et al (March 2012). The potential of terahertz imaging for cancer diagnosis: A review of investigations to date. Quant Imaging Med Surg, Vol. 2, pp. 33-45.

2. American Cancer Society Cancer Facts & Figures 2011. American Cancer Society, Atlanta. Available online at http://www.cancer.org/Research/CancerFactsFigures/CancerFactsFigures/cancer-facts-figures-2011.

3. L.M. Ingle et al (2013). Terahertz spectroscopy for pharmaceutical applications. Int J Pharm Pharm Sci Res, Vol. 3, pp. 48-52.

Terahertz Lasers Reveal Information for 3D Images at NASA

(My Note: This article dates back to 2011, but I am posting it, because I just came across the article and because I had never heard of LongWave Photonics LLC, or their work with NASA, in developing the use of 3D THz imaging.)

http://spinoff.nasa.gov/Spinoff2012/ip_5.html
Industrial Productivity

NASA Technology
After taking off her shoes and jacket, she places them in a bin. She then takes her laptop out of its case and places it in a separate bin. As the items move through the x-ray machine, the woman waits for a sign from security personnel to pass through the metal detector. Today, she was lucky; she did not encounter any delays. The man behind her, however, was asked to step inside a large circular tube, raise his hands above his head, and have his whole body scanned.
If you have ever witnessed a full-body scan at the airport, you may have witnessed terahertz imaging. Terahertz wavelengths are located between microwave and infrared on the electromagnetic spectrum. When exposed to these wavelengths, certain materials such as clothing, thin metal, sheet rock, and insulation become transparent.

NASA worked with LongWave Photonics LLC to advance terahertz imaging technology for examining the materials on future spacecraft like the Multi-Purpose Crew Vehicle. Here, the vehicle is shown at Lockheed Martin’s Vertical Testing Facility. Image courtesy of Lockheed Martin

At airports, terahertz radiation can illuminate guns, knives, or explosives hidden underneath a passenger’s clothing. At NASA’s Kennedy Space Center, terahertz wavelengths have assisted in the inspection of materials like insulating foam on the external tanks of the now-retired space shuttle.
“The foam we used on the external tank was a little denser than Styrofoam, but not much,” says Robert Youngquist, a physicist at Kennedy. The problem, he explains, was that “we lost a space shuttle by having a chunk of foam fall off from the external fuel tank and hit the orbiter.”
To uncover any potential defects in the foam covering—such as voids or air pockets—that could keep the material from staying in place, NASA employed terahertz imaging to see through the foam. For many years, the technique ensured the integrity of the material on the external tanks.
Technology Transfer
In 2009, NASA’s Kennedy started looking for new capabilities to examine foam materials and other thermal coatings being considered for use on future space vehicles. “We had systems that provided 2D information, but we wanted to invest in technology to provide 3D imaging,” says Youngquist. “Going from 2D to 3D is a huge step in making a determination of whether something is severely or deeply damaged.” For NASA, 3D terahertz imaging can provide more complete information such as size, location, and depth of defects in thermal materials.
To gather ideas on potential technologies to create 3D images of the materials that might be used on future spacecraft, Kennedy solicited proposals from academia and industry through the Small Business Technology Transfer (STTR) program. One of the responses that garnered NASA’s interest was from Boston-based LongWave Photonics LLC and the Massachusetts Institute of Technology (MIT).

The Easy QCL could help to improve the uniformity of coatings on drug capsules.

Alan Lee, president of LongWave Photonics, launched the company soon after graduating from MIT. At MIT, Lee had gained experience working with terahertz technology, and he felt there were opportunities to commercialize a unique terahertz device. Called the quantum cascade laser (QCL), the technology is a high-power source of terahertz radiation. “The basic idea is that you use a QCL to illuminate a sample and cause the reflected light to interfere with itself,” says Lee. “An algorithm is applied to the interference signal to measure the distances between reflections, which results in a signal similar to an ultrasound scanner.”
According to Lee, the QCL was first developed to produce infrared frequencies at Bell Labs in 1994. By 2002, it was demonstrated at terahertz frequencies; a capability was later developed to adjust the terahertz frequency. Through the NASA partnership, LongWave Photonics was afforded the time and resources to advance the QCL to a point where it could be sold for research purposes. “The STTR funding has allowed us to develop a research system, the Easy QCL, to access niche markets that will help to grow the business while we explore larger markets,” says Lee.
According to Youngquist, the technology has been shown to be very powerful, and was proven to generate 3D scanning for NASA’s potential needs.
Benefits
In 2011, LongWave Photonics started selling the Easy QCL commercially as a turnkey terahertz source for academic, industrial, and government researchers. It has already been demonstrated for use in imaging, spectroscopy (looking at the energy emitted from an object), and tomography (imaging a section inside a solid object).
Over the last year, LongWave Photonics has sold several Easy QCLs, and one system is currently being used as
an illumination source for an experimental biological microscope at the University of Tokyo.
The Easy QCL emits light that is detected by a terahertz-specific uncooled camera, the IRV-T0831 fabricated by NEC Corporation. This combination of a high powered QCL with an uncooled terahertz imager has resulted in sensitive, real-time imaging. Lee says the system is designed to determine the binding state
of proteins, which often have observable features at terahertz frequencies.
An interesting future application, notes Lee, is to examine the coatings on controlled-release pharmaceutical tablets. “As it turns out, many of the polymer coatings are terahertz-transparent and, therefore, a 3D non-destructive system has the potential to improve the tolerances of these coatings,” he says. The main benefit of 3D terahertz imaging is that it provides information on the subsurface defects in a sample without damaging or otherwise modifying it, Lee explains. Defects in the tablet coatings can affect the performance and reliability of the drugs, but Easy QCL’s imaging capabilities could optimize the manufacturing and improve the uniformity of the coatings.
As the STTR work continues between Kennedy, LongWave Photonics, and MIT, Lee looks forward to producing a new compact, multi-frequency QCL system. Youngquist, meanwhile, looks forward to seeing
how LongWave’s QCL hardware might be used in NASA’s future.
“We don’t know all our plans for the future, but there will probably be applications looking for voids and defects in insulative materials,” says Youngquist. “Lockheed is currently working on a crew capsule at Kennedy, so if we get something promising, we will coordinate with them.”

Single-pixel device may spot cancer

http://www.dgstandard.co.uk/dumfries-news/scottish-news/2013/05/17/single-pixel-device-may-spot-cancer-51311-33342968/#.UZWokVFfpW4.blogger

My Note: Thanks to Mike Favale for posting this article on his blog thztechnology.blogspot.com

A new method of producing 3D images could improve cancer screening tests, scientists have said.

The technology uses four single-pixel detectors and has been developed at University of Glasgow's physics and astronomy department. It allows for the creation of 3D pictures without expensive digital cameras.

The technique is called 3D computational imaging, or ghost imaging, and can detect wavelengths that digital cameras cannot pick up. It could be used to look under the skin to detect cancer or other medical conditions quickly.

Oil industry firms could also use the technology to detect gases hidden from the naked eye that leak from the ground near oil wells.

Professor Miles Padgett, Kelvin chair of Natural Philosophy at the university, said: "Single-pixel detectors in four different locations are used to detect light from a data projector which illuminates objects with a rapidly shifting sequence of black-and-white patterns similar to crossword puzzles.

"Four detectors give images, each of which contain shadows, giving us clues about the 3D shape of the object. Combining the four images using a well-known technique known as shape-from-shade allows us to create a full 3D image of the object."

Details of the discovery appear in a report entitled 3D Computational Imaging With Single-Pixel Detectors in the current Science journal.

Research assistant Matthew Edgar, who contributed to the paper, said: "A more portable version of the system could be created quite easily, making it much more practical to use outside the lab. It could be used to look for the tell-tale gases which leak from the ground where oil can be found, for example, or it could be tuned into the terahertz range to probe just below the skin to search for tumours or other medical conditions."

The technology is in its early stages and commercial partners are being sought to help develop it.

Baoqing Sun, lead author of the paper, said: "This means that single-pixel detectors which cost just a few pounds each are now capable of producing images across a far wider spectrum than 3D imaging systems currently on the market which cost tens of thousands of pounds."

Connecting the dots from THz to 3d printing-"Will Gun Scanners Create a Market for Anonymous Objects?"

My Note: I came across the blog post, found below on the internet last night. I didn't have time to provide any explanation, on how this post enlightened me, concerning how THz, and 3D printing may interrelate. The "buzz" on the internet recently has been that Advanced Photonix (API), is somehow involved in 3D printing, but if they are, that is news to me, and there is nothing I am aware of that supports such a viewpoint. But, the article below, woke me up on how API's anomaly detection system, the Saf-T-Chek, may play a role in detecting the  plastic and other disguised guns or devices manufactured using 3D printing. The article below, doesn't discuss the fact that THz, time-domain spectroscopy can in fact, detect the chemical composition of items, and the Saf-T-Chek, which uses proprietary algorithms, can detect & identify a large number of  harmful or suspicious devices, bombs, guns, etc. whether they are plastic or some other non-metallic composition. I hope this clarifies the connection, that I see. If readers are aware of others please let me know.

http://reason.com/blog/2013/01/29/will-nypd-scanners-create-a-market-for-d

J.D. Tuccille|Jan. 29, 2013 6:21 p

Last week, as noted on Reason 24/7, The New York City Police Department announced that it's rolling out portable terahertz scanners that will let police "see" if people on the street are carrying metal objects, like firearms. It'll give the cops yet one more reason to hassle people going about their business — a practice that's already raising judicial eyebrows. Of course, the scanners are premised on the idea that the items people carry are necessarily recognizable, but their very existence may create demand for versions of forbidden, suspicious or valuable goods that aren't so easy to spot.

As CNet described the new scanners:

The scanner is a device small enough to fit in a police van or set up on a street corner that reads terahertz radiation, which is energy emitted by both humans and inanimate objects. When aimed at a person, it's possible to see anything that is blocking the specific energy coming off the human -- such as a gun.

"If something is obstructing the flow of that radiation, for example a weapon, the device will highlight that object," Police Commissioner Raymond Kelly said, according to the New York Daily News.

Since anything metal will block the radiation, police will be looking for recognizable outlines. Specifically, they're assuming that a gun will look like a gun. That's traditionally been a safe assumption, since disguised weapons are generally categorized as Any Other Weapons under the National Firearms Act and subject to strict regulation. But guns that don't look like guns were a bit of a craze in 19th century America, and there's a market — usually illegal — for them elsewhere. Pen guns are old hat, and European headline writers worked themselves into a frenzy a decade ago when officials discovered that somebody in the Balkans was manufacturing four-shot .22 pistols that looked like cell phones.

With desktop manufacturing coming to a workshop near you, and eager activists already hard at work to circumvent gun controls, it's easy to imagine Defense Distributed, or somebody similar, creating downloadable plans for guns that don't look at all like guns, the better to befuddle the snoops in blue.

But gun-toters aren't the only people who might not be comfortable with the idea of law-enforcement officers lifting the veil, so to speak. Journalists have long had a ... strained relationship with the powers-that-be, and they may not want police so-easily identifying them by the cameras and recording equipment stuffed in their pockets. Neither would activists monitoring police behavior at a demonstration or during an arrest. Most of this gear has been miniaturized in recent years anyway. So why not anonymize it, too? Sunglasses that record video and audiohave already been developed for the upload-my-skydive-to-Youtube set, so we're not far off.

Even people who usually consider themselves to have nothing to hide from the police may begin to feel uncomfortable revealing their possession of expensive watches or high-end electronics to public employees who aren't always on the up-and-up. Or, for that matter, public agencies seeking new applications for their toys. Why, of course, scanners would never be used to reveal the ownership of valuables that might contradict the claims made in a tax return.

Unless scanner-blocking metal-mesh clothing comes into wide vogue (limited use would just advertise a suspicious sense of modesty), we may soon live in a world in which  many items are designed to be unidentifiable.

Advantest 3D Imaging Analysis of particulate matter in Diesel Filters

http://www.dieselnet.com/advantest/tas7000.pdf

MY NOTE: THANKS TO NUMBRCRUNTCHR FOR POSTING THIS ON THE IV BOARD