Friday, October 29, 2010

Indefinite hiatus

This blog is put on indefinite hiatus.

Friday, October 1, 2010

Gone for two weeks

The blog will not be updated the coming two weeks due to absence of its owner.

Paper watch: recent imaging papers

A few recent papers (some of them open access).

First, via Austin's imaging blog, a history of confocal microscopy at

At NanoLetters: "Very Black Infrared Detector from Vertically Aligned Carbon Nanotubes and Electric-Field Poling of Lithium Tantalate". From the abstract:
Vertically aligned multiwall carbon nanotubes were grown by water-assisted chemical vapor deposition on a large-area lithium tantalate pyroelectric detector. The processing parameters are nominally identical to those by which others have achieved the “world’s darkest substance” on a silicon substrate. The pyroelectric detector material, though a good candidate for such a coating, presents additional challenges and outcomes. After coating, a cycle of heating, electric field poling, and cooling was employed to restore the spontaneous polarization perpendicular to the detector electrodes. The detector responsivity is reported along with imaging as well as visible and infrared reflectance measurements of the detector and a silicon witness sample. We find that the detector responsivity is slightly compromised by the heat of processing and the coating properties are substrate dependent. However, it is possible to achieve nearly ideal values of detector reflectance uniformly less than 0.1% from 400 nm to 4 μm and less than 1% from 4 to 14 μm.
And finally, seen at Nature Photonics, an open access paper at the Virtual Journal for Biomedical Optics: "Wavefront image sensor chip". The abstract reads:
We report the implementation of an image sensor chip, termed wavefront image sensor chip (WIS), that can measure both intensity/amplitude and phase front variations of a light wave separately and quantitatively. By monitoring the tightly confined transmitted light spots through a circular aperture grid in a high Fresnel number regime, we can measure both intensity and phase front variations with a high sampling density (11 µm) and high sensitivity (the sensitivity of normalized phase gradient measurement is 0.1 mrad under the typical working condition). By using WIS in a standard microscope, we can collect both bright-field (transmitted light intensity) and normalized phase gradient images. Our experiments further demonstrate that the normalized phase gradient images of polystyrene microspheres, unstained and stained starfish embryos, and strongly birefringent potato starch granules are improved versions of their corresponding differential interference contrast (DIC) microscope images in that they are artifact-free and quantitative. Besides phase microscopy, WIS can benefit machine recognition, object ranging, and texture assessment for a variety of applications.

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.