Traditionally, the photographic world has subscribed to the bigger-is-better philosophy when it comes to camera design. The bigger the optical aperture, the better the transmission of light through those optics onto film or, in the case of digital cameras, silicon.
That philosophy could soon be reversed into a smaller-is-better perspective given the potential impact that tiny semiconductor particles called quantum dots could have on photography. Quantum dots are nano-particles of a semiconductor material, like cadmium or zinc, which range from 2 to 10 nm.
Because of their minute size, these dots have specific optical and electrical properties that are different in character from those of the corresponding bulk material. The most immediately apparent of these is the emission of photons under excitation, which are visible to the human eye as light. Moreover, the wavelength of these photon emissions depends not on the material from which the quantum dot is made, but its size.
The sensors used in today’s digital cameras employ silicon technology to turn the image light into an electronic charge that the sensor then measures. An image is created from those measurements, but it’s not a perfect system. Light entering the camera lens can be partially obscured before it reaches the actual sensor because of the electronic connections to the sensor.
Also, silicon can only employ about 30% of the light available in an image. Combined with the fact that silicon can turn only half of the incident light into electric charge, capturing light using silicon throws away about 75% of the light. Quantum dots could resolve these fundamental flaws.
Research by a company involved in quantum dots called Invisage has led to the development of what it calls QuantumFilm. Because each quantum dot is so small, up to three times as many “pixels” can be squeezed into a given space. The higher sensitivity provides better performance in low-light conditions.
QuantumFilm with these tiny semiconductor particles has been integrated into the sensors used in mobile phone cameras for pictures that often have much higher quality than those from larger dedicated cameras. But what about cost, particularly bearing in mind the highly competitive price environment that mobile phone manufacturers exist in?
Quantum dots don’t come cheap. They typically will cost around €1500/gram. The solvents used to manufacture the dots absorb much of that cost. However, research into alternative production solvents is starting to indicate that those costs can be reduced. The question is if they can be reduced to a level that makes the application of quantum dots in mobile phones financially viable.