BSI or Back Side Illumination

[Rohan B]

Hi guys,i am posting this new thread to know the answer of a question i have been asking for a couple of days,i hope u guys will help me find the answer.

A few days ago in an older thread i read about the BSI or back side illumination technology that can be used on an imaging sensor,which will enhance the dynamic range to 2 stops and improve the latitude and sensitivity, here's the link to that report
http://news.cnet.com/8301-30685_3-20048197-264.html?part=rss&subj=news&tag=2547-1_3-0-20

But then someone posted that this BSI technology cannot be used on a larger sensor and that is why it has been used mostly on mobile phone cameras, now, my question is that, is it true or not........

is it true that it cannot be used on a larger say super 35 sized cmos sensor, and if so, then why??

And yeah one more thing guys,mind it, i am not asking about any specs on the future red monstro dragon sensor.so don't mix this question with that......:undecided:

 

[Rohan B]

Guys i really need to know about these,plsssss repliessssss

 

[Stephen Matthews]

why ask it here if it is not directly related to red? I guess it makes sense with some of the smart people on here. But to me the general statement of two more stops is weird, compared to what? and if we know little of reds sensors then how do we know if this will indeed be better (and 2 stops at that), especially better than the next generation red sensors.

If anything why not ask it on cnet, or track down the team working on it and shoot them an email or someone else in the company.

These are just my assumptions that could be wrong.

 

[Rohan B]

Well what i have read so far this technology applied to any existing sensor will enhance the dynamic range to 2 stops and improve the latitude and sensitivity.i am not sure but i think sony is trying it on their next cinealta f65,but i not sure. And this question is if not directly but indirectly is related to red and its future but as jim said no talking about the monstro dragon until its ready to ship.........

 

[Stephen Matthews]

I still think throwing out 2 stops is a little arbitrary, though I could be wrong. But considering they don't know how red's sensor's work (I think) how could they flat out say it will get 2 stops more? at what cost if any? perhaps in regards to their sensors and their camera's yes but to apply that to all sensor to me does not make sense, but once again I'm no expert just a passionate storyteller or whatever I'm calling it these days.

have a good one, and I hope you find your answer!

ps. though as I have no idea about most of the real raw details of this stuff, who knows the new MX sensor could be BSI (though I don't think so) or some other derivative/similar technology. It just seems to have this discussion requires knowing intimate knowledge about sensors and camera's that most if not all companies would like to keep under their belt (obviously not stats and things like that but more the hows, whys, and whats...)

 

[Rohan B]

well i agree with you on theese points Stephen, lets just wait and see how the dragon turns out to be..........

 

[Anders Holck]

The enhancements of backside illumination depends on the pitch of the photosites on the sensor. The smaller the pitch the more the electronics/transistors will block light on a normal sensor as they generally take up the same space regardless of sensor sise/pixel density. A large sensor area, with smaller pitch photosites due to multi megapixel resolution could still benefit some from backside illumination. But a 1/8" 20mp mobile phone sensor will benefit the most. Thats why BSI is mostly used in the smaller sensors as the enhancement on larger photosites means less compared to the work of using a different process.

 

[Rohan B]

The enhancements of backside illumination depends on the pitch of the photosites on the sensor. The smaller the pitch the more the electronics/transistors will block light on a normal sensor as they generally take up the same space regardless of sensor sise/pixel density. A large sensor area, with smaller pitch photosites due to multi megapixel resolution could still benefit some from backside illumination. But a 1/8" 20mp mobile phone sensor will benefit the most. Thats why BSI is mostly used in the smaller sensors as the enhancement on larger photosites means less compared to the work of using a different process.

thanks anders,i was looking for an explanation like this,thank you very much........

 

[Jannard]

There are lots of ways to advance sensor technology... BSI is just one of them. The real advantage of BSI is for small (really small) pixels... like for cell phones. We are working on a lot of new stuff that you aren't reading about. Stuff that makes more sense for larger cinema sensors. Sleep tight. The RED sensor team is awake.

Jim

 

[Rohan B]

There are lots of ways to advance sensor technology... BSI is just one of them. The real advantage of BSI is for small (really small) pixels... like for cell phones. We are working on a lot of new stuff that you aren't reading about. Stuff that makes more sense for larger cinema sensors. Sleep tight. The RED sensor team is awake.

Jim

Thankx jim, really looking forward to a verry bright future and ofcourse DRAGON

 

[Keith Walters]

thanks anders,i was looking for an explanation like this,thank you very much........

At first I thought "Backside Illumination" was something offered by toilets in fancy hotel bathrooms, but the article cleared that up:redface:

(Don't you just love the catchy names those Asian companies come up with, almost as good as Samsung's "Film Retarded 3D" LCD screens).

As the article says, placing the photosensors on the "backside" means almost all the silicon "real estate" gets used for light gathering; none has to be sacrificed for the readout electronics.
With larger photodiodes such as those used with the RED and similar cameras, much the same improvement can be achieved with microlenses, which focus the incident light onto the photoactive area.
This is simply done by screen-printing tiny dabs of plastic powder onto the photosites, and then heating the chip until the powder melts, forming what look like an array of microscopic dew drops. This is not really possible with the tiny photosites used in compact cameras.

As far as "two stops" goes, it think it's perfectly reasonable to suggest that if the light-gathering area of the silicon is increased by four times, that will yield a 2-stop sensitivity increase.

However that will absolutely NOT give you a 2-stop improvement in dynamic range, although many people seem to imagine it will. To achieve that you need a fourfold improvement in signal-to-noise ratio.

 

[Henrik Andersson]

This technology can be used on big sensors too but it is a very expensive technology. Actually it was first used on big sensors for cameras on on satellites and aircrafts. Read: Military budgets ...
The small sensors on cellular phones and pocket cameras are very cheap and need the extra sensitivity the most ... Viola, thats the reason the commercial world only uses them in the smallest sensors yet.

/Henrik