Low Light and Near IR

Aptina’s low-light and near-IR imaging solutions

There are numerous situations or times when you want your camera system to be able to see in the dark, so we offer über-sensitive DigitalClarity® CMOS imagers capable of capturing pictures and video in sub-one-lux conditions. These very sensitive imagers enable applications like the ones below and make possible new and potentially unique solutions.

Automotive

• Adaptive or bending headlights
• Backup assistance
• Drowsy driver warning
• Lane departure or keeping
• Night vision
• Occupant classification for smart airbag systems
• Pedestrian detection
• Sign recognition

Medical

• Minimally invasive endoscopy
• Emergency video-assisted tracheotomy
• Easy-to-swallow pill cameras

Mobile

• Assault prevention

PC Camera

• Web cameras

Surveillance

• Site monitoring
• Intrusion prevention
• Homeland security
• Firefighting
• Home security
• Intelligent video and pattern recognition

Now is the time to design for these markets

Many of the markets where low-light or near-IR sensitivity is important, for example automotive, surveillance, medical, etc., are considered young or emerging markets for camera systems. But the time to design for these applications is now. Our customers who design for these applications right now have the potential to ride huge waves of demand in the next few years.

iSuppli, a respected market-intelligence company, recently predicted that by 2011 the automotive industry would be consuming something like 20.1 million image sensor-based systems a year, up from just 5.4 million in 2006. That means that Aptina’s automotive customers could see a four-fold increase in demand.

Source: iSuppli 2007

Social networks and homeland security concerns have combined to fuel rapid growth in the PC cam and surveillance camera markets. Together, these markets (excluding the slow-growing CCTV flavor of security camera) are known as network camera systems. Industry and market analysts IDC predicted in 2007 that network camera systems would enjoy a 62.8 percent CAGR from 2006 to 2011, making the network camera market the fastest-growing segment in digital imaging.

Source: IDC 2007

When there just isn’t much visible light

Electromagnetic (EM) radiation and illuminance are important to any discussion about low-light or near-IR imaging solutions since both visible light and infrared light are bands in the EM spectrum and since perceiving them can depend on illuminance.

What we call visible light is really EM radiation with a wavelength range of about 400 to 700nm and a color range from violet to red that can be detected with the typical and healthy human eye. Put simply, visible light is that light which people are capable of seeing.

But just because you can see something, doesn’t necessarily mean you will see that thing. The light intensity is critical. Illuminance is a description of the intensity of light at a given point, in a given space, or on a particular surface. We measure illuminance in lux. A candle held about 30cm or 1 foot away from your eye generates approximately 10 lux of visible light at your eye. The brightly lit office you work in might be 400 lux. And a shadowy parking lot on a clear night might be 0.25 lux.

This is all well and good for the human eye, but image sensors have another problem. Switch gears for a moment and imagine that these wavelengths of light are made up of teensy light particles of energy (photons). At the same time, consider that image sensors like the ones we make are composed of hundreds of thousands (VGA) or even millions (megapixel) of tiny pixels. In order to take a picture or produce video, the sensor must capture the photons in these tiny pixels. The process is analogous to catching rain drops in a thimble. In low-light situations there are even fewer raindrops meaning that it’s even harder to fill your thimbles.

Aptina’s heritage in memory and silicon’s response

Lux, EM radiation, and thimbles are all helpful for understanding the problem of low-light imaging; now for the solution.

Two things help us–and therefore our customers–get great low-light sensitivity.

The first has to do with basic semiconductor manufacturing. Aptina is a division of Micron Technology, one of the world’s leading memory producers. Micron is known for its semiconductor process prowess and was one of the pioneers in memory semiconductor production. It turns out that memory chip processes, which were generally designed to hold a charge in a particular memory cell for very long periods of time, also make for some of the best and most sensitive CMOS image sensors. You see, there is a direct correlation between how well a memory cell holds a charge and how many photons can be held in a pixel. Because our sensors are based on memory semiconductor processes, they can capture and hold more photons. They can catch and hold more raindrops, if you will, in every thimble thus making them better in low lux conditions.

CMOS processes designed to build logic chips (the type of process that many Aptina competitors use) are focused on moving an electrical charge, not holding it, so that sensors made with logic processes generally do not perform as well in low-light situations.

The second factor that helps many Aptina customers develop cutting-edge, darkness-parting camera systems has to do with silicon’s response to the EM spectrum.

As mentioned above, the human eye responds to light in a range of about 400 to 700nm, but silicon, the raw material for our CMOS image sensors, perceives a much broader range of the EM spectrum, reaching well into near-infrared light. A sensor can use this near-IR light energy to illuminate a scene. Basically, it does not matter to the pixel, the thimble in our analogy, whether you fill it with visible light energy or near-IR light energy. Some of our customers, particularly in the automotive and surveillance industry, have even added an IR light to their camera system.

In the future

We fully expect there to be many new and exciting low-light and near-IR applications in the near and distant future—applications which will revolutionize and protect. We have customers using our sensors to develop thermal- and visual-light cameras for mobile phones, so that you can thermally scan a dark parking lot for would-be perpetrators and take a picture at a brightly lit office party with the same camera phone. We have customers developing special low-light vision systems for miners working hundreds of feet below the surface of the earth. And we have customers building robots that must see in virtual darkness to monitor oil pipelines.

No matter what low-light or near-IR solution you are planning we’ll be here with best-in-class imaging solutions.