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Graphene-based image sensor to enhance low-light photography

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May 30, 2013

Assistant Professor Wang Qijie from NTU’s School of Electrical & Electronic Engineering (P...

Assistant Professor Wang Qijie from NTU’s School of Electrical & Electronic Engineering (Photo: NTU)

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A team of scientists at Nanyang Technological University (NTU) in Singapore has developed a new image sensor from graphene that promises to improve the quality of images captured in low light conditions. In tests, NTU claims it has proved to be 1,000 times more sensitive to light than existing complementary metal-oxide-semiconductor (CMOS) or charge-coupled device (CCD) camera sensors in addition to operating at much lower voltages, consequently using 10 times less energy.

The new sensor is able to detect broad spectrum light, from the visible to mid-infrared, with great sensitivity. This will make it ideal for use in all types of cameras, including infrared cameras, traffic safety cameras, satellite imaging, and more. According to NTU, this technology will allow photographers to take much clearer images in harsh lighting conditions and, when mass produced, estimates are that graphene sensors will be up to five times cheaper than camera sensors today.

The research was led by Assistant Professor Wang Qijie from NTU’s School of Electrical & Electronic Engineering and has been ongoing for two years. “We have shown that it is now possible to create cheap, sensitive and flexible photo sensors from graphene alone. We expect our innovation will have great impact not only on the consumer imaging industry, but also in satellite imaging and communication industries, as well as the mid-infrared applications,” says Wang,

What is clearly exciting for the camera industry is how little needs to be done to introduce graphene to existing CMOS sensors.

“While designing this sensor, we have kept current manufacturing practices in mind," explains Asst. Prof Wang. "This means the industry can in principle continue producing camera sensors using the CMOS process, which is the prevailing technology used by the majority of factories in the electronics industry. Therefore manufacturers can easily replace the current base material of photo sensors with our new nanostructured graphene material.”

Graphene nano-structures

Graphene is a material composed of pure carbon with atoms arranged in a regular hexagonal pattern. It is a one-atom thick layer of the mineral graphite, a million times smaller than the thickest human hair and is known to have a high electrical conductivity and is very light, with a 1-square-meter sheet weighing only 0.77 milligrams.

Graphene is the basis of the new image sensor (Image: Shutterstock)

Asst. Prof Wang has devised a novel way to create nanostructures on graphene which "trap" light-generated electron particles for a longer period of time, translating into a stronger electrical signal. These electrical signals are then processed into an image, such as a photograph captured by a digital camera.

The "trapped electrons" are the key to achieving high photoresponse in graphene, which makes it far more effective than the normal CMOS or CCD image sensors, said Asst Prof Wang. Essentially, the stronger the electric signals generated, the clearer and sharper the photos.

"The performance of our graphene sensor can be further improved, such as the response speed, through nanostructure engineering of graphene, and preliminary results already verified the feasibility of our concept," Asst. Prof Wang says.

Camera ISO

Why is this so exciting for the photography industry? Camera ISO is one of the three pillars of photography (the other two being aperture and shutter speed). In simple terms, ISO is the level of sensitivity of your camera’s image sensor to available light.

The majority of people taking pictures have probably never adjusted the ISO setting on their cameras so here is an explanation. Essentially, a lower ISO setting reduces your cameras sensitivity to light creating higher quality images, while a higher ISO number increases sensitivity and your camera sensor can capture images in low-light environments without having to use a flash. But higher sensitivity comes at a cost – it adds grain or “noise” to the pictures.

ISO comparison in sports photography - click to enlarge (Photo: Colin Dunjohn)

ISO comparison in sports photography - click to enlarge (Photo: Colin Dunjohn)

Of course, not all grain is bad and we often see creative uses of it in black and white photography. But if you are a sports photographer shooting in a poorly lit indoor stadium, in order to freeze action, you have to shoot with a wide aperture (f 2.8 or lower) and try to keep your shutter speed above 500. The only way to do this is to increase ISO and live with the resulting grainy pictures. Asst. Professor Wang’s graphene sensor, being more sensitive, will negate the need to increase ISO in low light settings.

Canon and Nikon in particular, have been battling each other to develop the highest ISO levels with the least grain since the beginning of digital photography and no doubt “wires are buzzing" with these new developments. Asst. Prof Wang has already filed a patent through NTU’s Nanyang Innovation and Enterprise Office for his invention and plans to find industry partners to develop the graphene sensor into a commercial product. Our senses tell us that he won't have to look too far.

The NTU team's paper appears in the journal Nature Communications.

Source: NTU

13 Comments

Low light performance absolutely needs to be the next major focal area for digital photography.

In almost any camera/phone review I see example photos of the best the device can do but almost nobody ever does a good job showing the limitations of the device in poor lighting.

I walked into a photography store a while back and expressed my frustration at trying a decent camera for average lighting. The guy behind the counter handed me one and said "try this one".

I told my son to stand there and wave his arms around, and I took a photo of him in the middle of the mostly well lit store and there was a lot of motion blur. He didn't end up selling me the camera but it took me all of 5 seconds to effectively demonstrate the limitations of the technology which is something I rarely see in product reviews.

Benchmarking cameras based on optimal lighting means next to nothing in real world performance. Even putting a camera on a tripod to take pictures of fixed objects in a dimly lit room is a useless test because that's not how people use cameras and it allows the camera to compensate for low light sensitivity with a slower shutter speed without being penalized enough in motion blur.

I know fixed subjects like bowls of fruit make great apples to apples comparisons of cameras but unless we find better ways to benchmark light sensitivity we are going to be taking 40MP unusably blurry indoor photos years from now.

Daishi
31st May, 2013 @ 04:11 am PDT

Question is, will this sensor be able to dial down the ISO to say 100? If not it will run into a different set of problems regarding shutter speed in bright conditions.

Siegfried Gust
31st May, 2013 @ 04:16 am PDT

I also wonder being 1,000 times more sensitive to light than existing CMOS or CCD camera sensors translates to how much savings of ISOs.

thk
31st May, 2013 @ 06:39 am PDT

"Professor Wang’s graphene sensor, being more sensitive, will negate the need to increase ISO in low light settings." ISO is a measure of the sensitivity of the sensor to light. This new sensor would not negate the need to increase your ISO in low light. Instead, it would potentially enable you to shoot at higher ISOs while having image quality that is only achievable today at lower ISOs. Very exciting possibility!

MRF
31st May, 2013 @ 09:35 am PDT

There are also applications in telescopes and satellite imaging that would benefit from these graphene sensors. If the IR performance could be extended, satellites might be able to avoid the use of liquid helium as a coolant for the current IR applications. This coolant limits the life of IR satellites to a couple of years at most.

Robert Newman
31st May, 2013 @ 10:20 am PDT

I hate to be the Debbie Downer here, but how many times over the last decade have we read articles with the same headline? The articles always end exactly the same way this one does: "...plans to find industry partners to develop the graphene sensor into a commercial product."

These innovations never see the light of day (pun intended). Why? Take your pick.

Until Canon or Nikon (or Sony or Panasonic) actually step up to the plate and claim "We are bringing to market this Fall a new camera that can shoot perfect photos in extremely low-light conditions and it will be called such-and-suchand cost X amount of dollars", then I am going to continue to shrug apathetically at these breakthroughs.

Rolf Hawkins
31st May, 2013 @ 11:15 am PDT

How does it do color, lotsa little filters?

DonGateley
31st May, 2013 @ 07:32 pm PDT

Very interesting research, but how does it perform under low ISO then? how will the IQ be? The ISO performance is not the only main thing on a camera sensor alone. Colour seperation, details, dynamic range etc are equally as important. No point getting a clean ISO 51200 with no details or poor contrast. 5 times cheaper? are you referring to camera sensors in phones or full frame sized sensors? it's great for consumer/surveillance use, but for high end photography use, not quite so yet. It's a bit ironic in the first part of the article it says "We expect our innovation will have great impact not only on the consumer imaging industry," but when they explain what ISO is all about they talk about sports photographers. they don't expect the photographers to use a consumer grade equipment to shoot tennis players right?

shall reserve my judgement until further tests are carried out since there's quite a lot of loop holes in this article. it's a good start though!

Tan Zhi Shan
1st June, 2013 @ 09:03 pm PDT

@ Daichi:

While I get your point, that test you performed seems quite nebulous; who knows how the camera was adjusting or balancing its options for that shot? If you want a camera to optimize its settings specifically for freezing motion, you generally have to tell it via either manual control or semi-auto settings. Motion blur isn't directly related at all to low light performance; even if that camera had 1,000 times its current low-light performance, an auto mode might not know you wanted to optimize for minimal motion blur and, as such, still let some exist in the image. High-ISO performance and lens aperture are the only parameters limiting specifically low-light performance on a camera system.

@ Siegfried Gust:

Yeah, that's exactly what I was thinking. Still, unlike many pro cinema cameras, still photography cameras seem to all set their optimal gain at ISO 100-400 no matter how great they perform at the higher numbers. The 1D X, the best low-light camera on the market right now, still produces better images at ISO 100 than at 1600, even if 1600 is startlingly clean.

For video, hopefully manufacturers get creative with implementing in-built ND filters... I hear the new Red Dragon sensor will have a native ISO of 2000...

@ thk:

Well, since a stops of light are factors of two, 1000x more light would mean a difference of about ten stops. Ten stops is the same difference between ISO 100 and 102,400, so yeah, that's a lot of light.

@ Rolf Hawkens:

Especially what with how conservative many of the larger camera companies are with advancements in product capabilities, I wouldn't put it past some of them to take much, much longer than necessary to release products with this technology, were they to license it.

Mr. Blah
1st June, 2013 @ 09:28 pm PDT

Diachi,, you, "Test", does not mean much. What was the ISO on the camera you tried? What was the F-stop set too? What was the F-stop of the lens? Also your problem is no problem. It is called using your flash!

DonGately, color is done the same way it is with every camera. Read Wikipidia.

Siegfried Gust, if you have too much light sensitivity the answer is very simple and old, a light filter. I think this one is called a graduated neutral density filter.

Douglas E Knapp
1st June, 2013 @ 11:15 pm PDT

How does "1000 times more sensitive" compare to existing CCD sensors with > 90% quantum efficiency?

I don't think you can do better than detecting 100% of the photons that are there.

Sounds to me this is way overhyped - at best it means you'll be able to get away with simpler (cheaper) ADC conversion hardware in the camera. It may save a few pennies, but won't make any noticable difference to ultimate sensitivity or image quality.

Or, I'm confused.

Dave Lindbergh
2nd June, 2013 @ 09:05 am PDT

There is a major disconnect with this article compared to the original paper. This article states "...it has proved to be 1,000 times more sensitive to light than existing complementary metal-oxide-semiconductor (CMOS) or charge-coupled device (CCD) camera sensors..." Considering that most CCDs run at >99% quantum efficiency (as measured by the rate of conversion of photons to electrons), an increase in sensitivity to CCD detectors by a factor of 1000 is impossible. In fact, the abstract of the paper in Nature Communications (http://www.nature.com/ncomms/journal/v4/n5/full/ncomms2830.html) says that the factor of 1000 increase is over previous graphene-based detectors.

I don't want to denigrate the research done by the scientists at NTU. This is a very interesting prospect for detectors, especially the broadband coverage (which, to my knowledge, is not possible with CMOS or CCDs). However, the author of *this* article needs to be more careful about what they write and do their homework before sensationally reporting on things that do not exist.

Michael Pavel
2nd June, 2013 @ 05:08 pm PDT

What about graphene-based fiber optic substrates for lenses that are part of printed circuit "eyes' that will work to restore sight to the blind, as long as optic nerves exist. The reason for the printed circuit framework is to allow control over spectrum and intensity through programmed auto adjustment capability, which itself can be changed. The conept doesn't work without optic nerves totransmit tothe brain, but, nano-wiring may work to replace optic nerves.

Oh, and these could be "printed" on 3D printers., formulated like contact lenses, or permanently implanted with anti-rejection materials.

Barry Dennis
22nd April, 2014 @ 12:43 pm PDT
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