EOSHD.com

Above: Panasonic's new DSLR image sensor fabrication plant in Japan

With Panasonic's recent camcorder update paving the way for 1920x1080 at 60p (Progressive) - the GH2's video spec certainly has to be impressive to stay state of the art, even by the company's own standards. Sony are ready to become a competitor once again too. (More on Sony's plans at the bottom of this article).

Panasonic engineer T. Azuma's talk at the International Solid State Circuits Conference (ISSCC) in San Francisco took place last week. (This builds detail on top of an earlier expose on sensor design made in advance schedule publications by ISSCC a few months ago).

His presentation dealt with Panasonic's innovations in sensor design for forthcoming digital cameras such as the GH2.

Here are the key points:

• Panasonic have developed a 4K x 2K image sensor (approx. 12 megapixel) based on 'dual exposure technique'
• The sensor is described as having new architecture that tries to improve sensitivity by a factor of 4 or more
• The architecture change is a new design which allows green pixels to be read independently of the blue and red ones on the sensor.
• The green pixels are exposed 4 times longer than the red and blue, thus achieving the sensitivity gain
• Motion artifacts are introduced as a result, but clever signal processing of the red and blue channels corrects the motion artifacts introduced in the green channel by the long exposure
• Red and blue channel gain achieved by pixel binning in 4x4 mode

The technique is similar to the Intelligent Resolution feature of the new Panasonic TZ10 sensor, but on a larger scale.

A factor of 4 increase in sensitivity will allow the Micro 4/3rds camera to surpass the full frame Canon 5DMkII. GH2 is currently slated for a September release date - partly due to delays last year in Panasonic commissioning their new Japanese sensor fabrication plant in Tonami and strategical decisions related to the worldwide economy and consumer electronics market performance.

I am told that since the fall of 2009, manufacture of the older GH1 sensor was transferred to the new Tonami plant to get things up and running there. Unforeseen circumstances resulted in a worldwide shortages of the GH1 at the same time period of the cross-over. These are now resolved and the plant is ready to produce the new GH2 sensor and other new Lumix G series image sensors. As a side note, I have noticed that newer stock of GH1s produce a slightly better image with less codec break up and banding than in the GH1's whose image sensors were produced at the older fab.



Azuma states that the sensitivity of solid-state image sensors has increased by a factor of 40,000 compared to the device originally invented by Boyle and Smith.

Now that is progress

Footnote: The GH1 is almost 1 year old, having been announced at PMA 2009 in February last year. This year's PMA begins on Friday so keep an eye on EOSHD.com for the latest video DSLR news.

PS - Sony were also presenting at ISSCC. Here is a rather verbose and technical description of their latest sensor. I believe it's already on the market in the form of the latest Sony compact cameras, like the TX7.

H. Wakabayashi et al from Sony says of the 10.3 Mpix back-side illuminated imager: "The device can run at 50 fr/s at full resolution of 10.3 Mpix with 10 bits resolution. In the case of 12 bits, the speed slows down to 22 fr/s, or in the case of 60 fr/s, the resolution goes down to 6.3 Mpix. Operation at 120 frames/s is also possible with then with only 3.2 Mpix."

Pretty interesting numbers were given for the angle dependency: for a ray angle of 10 deg, the sensitivity drop is only 9 %, and moreover the difference between the three colour channels is less that 1 %. At a ray angle of 20 deg. the remaining sensitivity is slightly less than 60 %, and the difference in colour channels is 3 % (based on the figure shown in the proceedings). Wakabayashi mentioned that the cross-talk of the back-side illuminated sensor is optimised by means of an extra metal shield at the back of the device, by optimized doping of the photodiode, by optimised doping of the substrate and by an optimized wiring of the metal layers on the front side. The chip has a 0.14 um process, 1P4M, LVDS output, lag below the measurement limit, power consumption 375 mW for the HD video mode.

Those are specs you won't see on the camera box!!

Earlier in the event, Sony's Suzuki sees the following trends in digital CMOS sensors:

• Ultra high speed
• Global shutter
• Wide dynamic range
• Increasing depth of field

It seems Panasonic aren't alone in pursuing a global shutter for their video DSLRs!!

At the end of the talk Suzuki-san referred to two new future imaging functions being 3D imaging and curved image sensors.

Curved image sensors curve around the back of an aspherical lens element, producing huge gains in image quality and lens design. It's actually similar in design to the human retina.

Behind all the jargon and the numbers, you can take one thing for sure - an interesting future lies ahead of us!!