Wednesday, September 29, 2010

Paper watch: Metal-Insulator-Semiconductor Photodetectors

A recent paper at the open access Sensors Journal: "Metal-Insulator-Semiconductor Photodetectors". The abstract reads:
The major radiation of the Sun can be roughly divided into three regions: ultraviolet, visible, and infrared light. Detection in these three regions is important to human beings. The metal-insulator-semiconductor photodetector, with a simpler process than the pn-junction photodetector and a lower dark current than the MSM photodetector, has been developed for light detection in these three regions. Ideal UV photodetectors with high UV-to-visible rejection ratio could be demonstrated with III-V metal-insulator-semiconductor UV photodetectors. The visible-light detection and near-infrared optical communications have been implemented with Si and Ge metal-insulator-semiconductor photodetectors. For mid- and long-wavelength infrared detection, metal-insulator-semiconductor SiGe/Si quantum dot infrared photodetectors have been developed, and the detection spectrum covers atmospheric transmission windows.

Tuesday, September 28, 2010

Paper watch: Custom transistor layout for RTS noise reduction in image sensors

I will make an effort to overlook the issues from the previous post and point to this nice paper at Electronics Letters describing a custom transistor layout for RTS noise reduction in image sensors: "Custom transistor layout design techniques for random telegraph signal noise reduction in CMOS image sensors". The abstract reads:
Interface and near oxide traps in small gate area MOS transistors (gate area ≪1 μm2) lead to RTS noise which implies the emergence of noisy pixels in CMOS image sensors. To reduce this noise, two simple and efficient layout techniques of custom transistors have been imagined. These techniques have been successfully implemented in an image sensor test chip fabricated in a 0.35 μm CMOS image sensor process. Experimental results demonstrate a significant reduction of the noisy pixels for the two different techniques.
I like that the techniques have been "imagined" but also measured: Inception paper? :-)

One possible problem I see is that their transistors are done in a technology with LOCOS. Advanced technologies use STI, so I don't know how well the techniques translate to e.g. the latest CIS technologies by tsmc and others.

Is anybody editing the papers for Electronics Letters?

Checking the weekly update of IEEXplore I see the following title for a paper in Electronics Letters: "nth-order multi-bit ΣΔ ADC using SAR quantiser". Being something I'm interested in, I follow the link to check what I think is a sigma-delta with a successive-approximation ADC as quantizer. To my excitement I read the following abstract: "An nth-order multi-bit delta-sigma (ΣΔ) analogue-to-digital converter (ADC) using a synthetic aperture radar (SAR) quantiser is proposed. By exploiting the residue voltage of a multi-bit SAR ADC, the proposed ADC performs as an nth-order noise shaping converter with only one opamp and removes the need for a feedback multi-bit DAC. In addition, the proposed architecture is very reconfigurable and can be implemented as a bandpass ADC.". Wow! That looks pretty cool, how do they manage to put a radar as quantizer and why don't they send it to ISSCC? :-D

Of course, thinking it's a typo that will not appear in the paper itself, I click and lo and behold, the same mistake is repeated in the abstract in the paper. Of course, checking the paper it's obvious it's a successive-approximation register quantizer.

Conclusion? Electronics Letters HUGE FAIL!

Friday, September 24, 2010

Commercial plenoptic cameras

This escaped me: "The first plenoptic camera on the market".

The technology by Adobe in the video was presented in this paper of the IEEE Computational Photography mentioned in the previous post: "Rich image capture with plenoptic cameras". The abstract reads:
The plenoptic function was originally defined as a record of both the 3D structure of the lightfield and of its dependence on parameters such as wavelength, polarization, etc. Still, most work on these ideas has emphasized the 3D aspect of lightfield capture and manipulation, with less attention paid to other parameters. In this paper, we leverage the high resolution and flexible sampling trade-offs of the focused plenoptic camera to perform high-resolution capture of the rich “non 3D” structure of the plenoptic function. Two different techniques are presented and analyzed, using extended dynamic range photography as a particular example. The first technique simultaneously captures multiple exposures with a microlens array that has an interleaved set of different filters. The second technique places multiple filters at the main lens aperture. Experimental results validate our approach, producing 1.3Mpixel HDR images with a single capture.

High resolution large format cameras

Hasselblad just announced today that they have developed a 200 Megapixel capture device (found via OISblog).

Coincidentally, yesterday the proceedings of the 2010 IEEE International Conference on Computational Photography were put on line at IEEEXplore, and among the papers there was this one by Moshe Ben-Ezra from Microsoft Research Asia: "High resolution large format tile-scan camera: Design, calibration, and extended depth of field". The abstract reads:
Emerging applications in virtual museums, cultural heritage, and digital art preservation require very high quality and high resolution imaging of objects with fine structure, shape, and texture. To this end we propose to use large format digital photography. We analyze and resolve some of the unique challenges that are presented by digital large format photography, in particular sensor-lens mismatch and extended depth of field. Based on our analysis we have designed and built a digital tile-scan large format camera capable of acquiring high quality and high resolution images of static scenes. We also developed calibration techniques that are specific to our camera as well as a novel and simple algorithm for focal stack processing of very large images with significant magnification variations.

Wednesday, September 15, 2010

Radiation testing of ICs with Ion-photon-emission microscopy

A news item at SPIE regarding a new instrument at Sandia National Labs: "Radiation testing and imaging of micro-electronics"
[...] as technology advances, features in satellites and spacecraft are getting smaller and, therefore, more susceptible to radiation damage. IPEM, once fully developed and validated as a means of testing the radiation hardness of micro-electronics, will contribute to the development of new and emerging radiation-tolerant IC technologies far into the future.

Tuesday, September 14, 2010

Engineering history

Most of us with access to it use IEEEXplore to check the latest issues of the IEEE journals. But they've also been busy uploading old issues of journals. This week, for example, they've uploaded several volumes from the late XIX century of the Transactions of the American Institute of Electrical Engineers. It is particularly interesting to see, after each paper, a written critical discussion of the contents of the paper by other experts. Why not bring this back?

Worth taking a look, if you have access.

Fuijitu's high speed ADC revisited

Remember their 56GS/s ADC? Fujitsu has announced their new version, fabricated in a 40nm CMOS technology. Here's their page with info. Here are some slides about this new version.

Thursday, September 9, 2010

New IEEE publication on affective computing

No it's not a typo, it's affective with an "a". The IEEE Transactions on Affective Computing start with a very nice introductory paper by Rosalind W. Picard:
I did not want to work on or be associated with emotion, yet emotion was starting to look vital for solving the hard engineering problems we needed to solve. A scientist has to find what is true, not just do what is popular. I was becoming quietly convinced that engineering dreams to build intelligent machines would never succeed without incorporating insights about emotion. I knew somebody had to educate people about the evidence I was collecting and act on it. But I did not want to risk my reputation and I was too busy. I started looking around, trying to find somebody, ideally male and established, whom I could convince to develop this topic, which clearly needed more attention than I had time for.

Tuesday, September 7, 2010

Samsung's BSI image sensors for consumer applications

Samsung reports their first BSI image sensors for consumer applications: press release.
Samsung's new BSI imagers show 30 percent enhancement in low light sensitivity over conventional front side illumination imagers of the same pixel size. By optimizing process parameters, Samsung was able to efficiently control crosstalk thereby improving the color, electrical and optical performance significantly.

The S5K4E5, a quarter-inch optical format 1.4 micron 5 megapixel (Mp) CMOS image sensor, is designed to support full resolution real-time video. By providing 30 frames per second (fps) full resolution frame rates it also enables the user to 'catch the shot' by capturing the frame as the user hits the shutter button thus reducing shot to shot lag time. The 5Mp imager has a wider chief ray angle that reduces the height of the imager package making it attractive for slim, small form factor smartphones with demanding z-height requirements.

The S5K2N1, a 1/2.33 inch optical format 1.4 micron 14.6Mp imager, offers 30fps capability at full resolution and leverages Samsung's low-power 90 nanometer logic process technology. Samsung is able to offer a dedicated thermal enhanced plastic lead ceramic carrier (TePLCC) package to more effectively dissipate the heat generated by the high performance device.

These imagers also offer the ability to capture full high definition (HD) resolution video images at 60fps.

Samples of the 5Mp S5K4E5 are available now with mass production starting in the fourth quarter of this year. The 14.6Mp S5K2N1 is expected to start sampling in the fourth quarter of 2010 with production scheduled in the first quarter of 2011.

EETimes: Researchers develop image sensor for rough environments

There's nothing yet at the IMS website yet, but EETimes Europe reports on a design by Fraunhofer IMS of an image sensor able to work in an extended temperature range of -40 to 115 degrees Celsius.

Other uses for microlenses

Although microlenses are mostly used at the "receiving end", in front of image sensors, they are also used (and useful) at the "transmitting end", in front of illuminators. This article at Photonics Spectra, from RPC Photonics, gives an introduction to this application for microlenses.

Monday, September 6, 2010

Paper watch: Machine hearing

The latest issue of the IEEE Signal Processing Magazine, besides a series of interesting articles on algorithms for security video applications, includes also a good article from a research scientist at Google on machine hearing. The abstract reads:
If we had machines that could hear as humans do, we would expect them to be able to easily distinguish speech from music and background noises, to pull out the speech and music parts for special treatment, to know what direction sounds are coming from, to learn which noises are typical and which are noteworthy. Hearing machines should be able to organize what they hear; learn names for recognizable objects, actions, events, places, musical styles, instruments, and speakers; and retrieve sounds by reference to those names. These machines should be able to listen and react in real time, to take appropriate action on hearing noteworthy events, to participate in ongoing activities, whether in factories, in musical performances, or in phone conversations.

Lenses and cameras

A somewhat old article which I missed, found at the OISBlog, on electrically tunable lenses.
As the predominant method of focusing images for over a century, mechanical lens motion sharply contradicts the biological methods found in nature. By leveraging principles based on these methods, manufacturers are now developing different types of small deformable lenses that can be tuned over various focal distances. Because these lens systems can be miniaturized relatively easily, they are finding applications in smart machine-vision cameras, endoscopy systems, and cell phones.
And a review of the Canon Expo 2010, with references to both their full wafer, 600 micron pixel and their 120Mpixel detectors. Cool stuff.

Thursday, September 2, 2010

Paper watch: Graphene photonics and optoelectronics

From Nature Photonics, a nice overview of the applications of graphene in the field of photonics: "Graphene photonics and optoelectronics": The abstract reads:
The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light-emitting devices to touch screens, photodetectors and ultrafast lasers. Here we review the state-of-the-art in this emerging field.

Paper watch: Surface plasmon enhanced responsivity in a waveguided germanium metal-semiconductor-metal photodetector

A paper at Applied Physics Letters which shows again possible advantages of plasmonics for photodetection. In this case for optical communications: "Surface plasmon enhanced responsivity in a waveguided germanium metal-semiconductor-metal photodetector". The abstract reads:
The authors report on high transverse magnetic (TM)-mode responsivity in a waveguided germanium Schottky-barrier metal-semiconductor-metal photodetector on silicon-on-insulator substrate for operating wavelength at 1550 nm. The employed aluminum interdigitated electrodes act as a one-dimensional rectangular grating above the depletion layer. By means of properly designed finger dimensions, surface plasmon polariton resonances can be excited at the interface of metal and silicon interfacial layer due to grating coupling. The resulting strong field intensities reach into active region, enabling high absorption under TM injection. At a voltage of 1 V, the TM-mode photocurrent is measured over three times than that of transverse electric mode, in spite of the relatively larger TM insertion loss in the silicon waveguide.

Wednesday, September 1, 2010

Miscellaneous entry: transmission lines, book excerpts, ...

Unfortunately not much time is left to prepare better entries, so I'm putting together here several topics in one blog entry.

Beginning with a short (but very informative) note from Mentor Graphics on the effects of bends in transmission lines for SerDes circuits.

Continuing with a series on Zigbee applications from EETimes, extracted from a book. parts one, two, three, four, five, six and seven (so far).

Another series from EETimes, extracted from a book on oscillators.

And yet another series extracted from a book on antennas.