Polarization Sensitive Current-Mode Sensor

Vision Systems Design: Proceeedings of the IEEE publishes an open-access invited paper "Bioinspired Polarization Imaging Sensors: From Circuits and Optics to Signal Processing Algorithms and Biomedical Applications" by Timothy York, Samuel B. Powell, Shengkui Gao, Lindsey Kahan, Tauseef Charanya, Debajit Saha, Nicholas W. Roberts, Thomas W. Cronin, Justin Marshall, Samuel Achilefu, Spencer P. Lake, Baranidharan Raman, and Viktor Gruev.

The paper proposes to use polarization imaging to detect cancer cells. For unknown reasons, the pixel is current-mode based:

Current-mode pixel schematic and peripheral readout circuitry of the imaging sensor. The pixel’s readout transistor operates in the linear mode, allowing for high linearity between incident photons on the photodiode and output current from the pixel.

Cross section of the pinned photodiode together with the reset,
transfer, readout, and select transistors. The diode is an n-type diode
on a p-substrate with an insulating barrier between. The readout
transistor operates as a transconductor, providing a linear
relationship between accumulated photo charges and an
output current.

The 7.4um-sized pixel in 180nm process shows excellent PRNU of less than 0.1% rms, in spite of Gm variations between the pixels:

Histogram of all responses of pixels in the imaging array to a uniform
illumination at room light intensity. The fixed pattern noise of the
current-mode imaging sensor

Omnivision Proposes Increasing Pixel Crosstalk in RGBC Sensors

Omnivision patent application US20140267848 "Image sensor with pixels having increased optical crosstalk" by the company's President Raymond Wu says "some RGBC patterns may suffer from color aliasing. [...] Color aliasing occurs at least partly due to the alignment of the clear filters within the RGBC pattern. Image sensors with clear pixels are more prone to color aliasing since clear pixels do not produce any color information of their own other than the intensity of light."

"Accordingly, embodiments of the present disclosure intentionally increase optical crosstalk in the pixel array in order to reduce the effect of color aliasing. [...] In conventional image sensors, optical crosstalk is an unfavorable effect that is mitigated because light straying from neighboring pixels may tend to distort the true color information of the target pixel. However, optical crosstalk has the unexpected benefit of blending the color of the target pixel with its neighboring pixels, thereby reducing color aliasing. Embodiments of the present disclosure intentionally induce and/or increase optical crosstalk as a desirable feature of CMOS image sensors to reduce the effects of color aliasing.

...it may be advantageous to have color pixels increase crosstalk, but to have clear pixels not. In other words, light incident on color pixels may be directed into neighboring clear pixels, but light incident on clear pixels will substantially remain within the clear pixels."

Few ways to increase the crosstalk are proposed. The one below shows a BSI example:

206 x 156 pix Thermal Camera for $199

PRNewswire: Following FLIR One steps, Seek Thermal announces the Seek thermal camera that plugs into iPhone and Android devices. The Santa Barbara, CA-based startup seems to be well funded to buy a thermal.com domain name to promote its sales. The spec is quite impressive for a $199 camera:

• True Thermal Sensor
• 206 x 156 Array
• 32,136 Thermal Pixels
• 12μm Pixel Pitch
• Vanadium Oxide Microbolometer
• Chalcogenide Lens
• 36° Field of View
• Magnesium Housing
• Long Wave Infrared 7.2 - 13 Microns
• -40C to 330C Detection
• Framerate < 9Hz

"Seek's breakthrough technology lets people see heat for the first time, something that only government agencies and companies could afford in the past," said Seek Thermal CEO, Robert Acker. "The Seek camera not only gives average consumers the capabilities in home improvement and safety and security that only professionals used to have, but we are also especially excited about the hundreds of new use cases for thermal that our camera will enable."

Thanks to JZ for letting me know!

Another FLIR One alternative, Hema-Imager Kickstarter project, fell short from its $205,000 fundraising goal recently. HemaImaging product was supposed to use German Heimann Sensors Gmbh thermopile array.

Caeleste Rad-Hard Design Tutorial

Caeleste publishes Bart Dierickx' tutorial "Radiation hard design in CMOS image sensors," presented at CPIX Workshop held in Bonn, Germany on Sept 15-19, 2014. It's a very nice overview of radiations effects combined with some countermeasures. Few slides out of 53 ones:

v6 of DxO Analyzer Announced

DxO Labs announces version 6 of its Analyzer with a slew of new features:

• HDR testing supporting up to 120dB
• Automated lighting system
• Video analysis now includes exposure, white-balance, sharpness and texture with changing lighting
• New MTF-based calibration for testing higher resolutions
• 6-Axis video image stabilization testing
• 3D camera characterization

Sony Product Sheets Restrict Applications

Sony publishes product sheets of its recent stacked sensors that have quite unusual restrictions on the sensor uses:

The 20MP 1/2.3-inch IMX220 document says:

The 13MP 1/3.06-inch IMX214 is intended for cellular phones or tablet devices. The note in the doc says:

The 1.07MP 1/8.32-inch IMX188 product sheet (non-stacked "regular" BSI) says:

Update: Apparently, most of the product briefs released recently have these restrictions. Few more examples: IMX208, IMX219, IMX135.

A Closer Look at iPhone 6 and 6 Plus Cameras

Chipworks publishes a more detailed report on iPhone 6 and 6 Plus cameras, both front and rear. All cameras have stacked sensors made by Sony. The front FaceTime camera has 2.2um pixels (up from 1.75um in iPhone 5s) and features an interesting CFA pattern: