SIGMA SD15 The Inside Story

The inceptions of the Foveon X3® direct image sensor

The invention of the Foveon X3® direct image sensor by Foveon, Inc. traces its roots back to the research of Caltech physicist, information engineer, and professor Carver Mead. One focus of Mead’s research was the modeling in semiconductors of human capabilities. Mead’s collaboration with a neural network research group on the simulation of human cognition eventually led to his research on image sensors.

Mead’s research led to a business venture supported by some of Silicon Valley’s leading firms with both financial and human resources. In August 1997, Foveon was founded, taking its name from an anatomical term: fovea centralis.

The origin of the name “Foveon”

The fovea centralis is the central portion of the human retina that has the most acute vision and the best color perception. The name “Foveon” signaled the company’s commitment to developing the world’s most advanced and high-performance image sensors for the professional market. From its first days as a startup company, Foveon gathered the best imaging engineering talent available and engaged in cutting-edge research and development.

Foveon’s first product was not an image sensor but instead a complete digital camera.

In this original system, a beam-splitter prism assembly separated the incoming light into its three primary colors, passing the red, green, and blue beams through separate color filters and directing them to three large image sensors. An extremely high-resolution image was then assembled from the data of the three colors.

This camera was extraordinary, high-end technology, but it was expensive to manufacture and ultimately too costly for the end user. By the time Foveon stopped prism digital camera production, it had already created a patented technology that would ensure its preeminence in the coming era of image processing research.

The invention of a revolutionary device that captures all three primary colors of light

Next, Dick Merrill, a leading semiconductor engineering working at Foveon, invented a device that could create a stack of RGB pixels in each pixel location. Thanks to his special genius and a unique career, Merrill had developed the creativity needed to realize artistic objectives through advanced technology. His ability as a photographer led to crucial technological contributions, and his passion for artistic expression became the driving force behind the invention and development of Foveon’s advanced, full-color image sensors.

A revolution in image processing

Merrill’s device proved the feasibility of capturing RGB information in each pixel location, but it was not immediately possible to develop an image sensor based on this technology.

Although it was well known that silicon absorbs shorter wavelengths of light closer to its surface and longer wavelengths of light further from its surface, additional advances in image processing were necessary to make use of this characteristic in creating high-quality images.

That task fell to Foveon Chief Scientist Dick Lyon, an image processing expert with a keen interest in photography.

New products offering ultra-high image quality

Through careful experiments and analysis, Lyon performed theoretical research into the light absorption characteristics of silicon, determining a set of red, green, and blue spectral sensitivity curves for theoretical R, G, and B photodiodes at specific depths. Based on his research, Lyon concluded it was possible to use the technology to produce color images of a high quality that would satisfy the discerning professional.

Through the efforts of Dick Merrill, Dick Lyon, and many other engineers, Foveon produced the prototype of the Foveon X3® direct image sensor and continued to refine it. At last in 2002, through trial and error, creativity, and powerful resolve, Foveon completed the development of an image sensor ready for a commercial digital camera.

In October 2002, the Sigma SD9 camera debuted, featuring the Foveon X3® direct image sensor. It was and is the world’s first single-chip, full-color image sensor.

The lens maker pursues its ideal of image quality

With its focus on creating lenses of the highest resolution possible, Sigma found the idea of using a resolution-reducing optical low-pass filter—on which conventional digital SLR cameras rely—completely unacceptable. A lens manufacturer with a philosophy of leveraging its own technology to offer the highest level of product quality, Sigma introduced the sigma SD9, its first digital SLR camera and the first camera in the world to feature the Foveon X3® direct image sensor.

Sigma had accepted the risk of implementing a new technology and selected the Foveon X3® direct image sensor for its flagship digital SLR camera. Having no need for an optical low-pass filter, the Foveon X3® direct image sensor made full use of the potential of Sigma’s high-resolution lenses to produce lifelike images rich in emotion and presence.

Best lenses, best image sensor—fulfilling the Sigma philosophy

Having selected the Foveon X3® direct image sensor to bring out the full potential of its lenses, Sigma once again dedicated itself to taking the quality of its lenses to a new level. Aiming not just for a high modulation transfer function (MTF) value, Sigma took a holistic approach to lens developing, pursuing the best photographs and best finished-image quality possible.

In November 2008, Sigma purchased Foveon, creator of the Foveon X3® direct image sensor. With strong synergy in goals and philosophy, the two companies make an ideal combination.

In addition, Sigma had always focused on developing its own technology and manufacturing its own products, including everything from tiny screws to injection molds. As a unified entity, Sigma and Foveon have continued to pursue the industry’s highest level of quality while offering products at a reasonable cost.

Having merged the best lens with the best image sensor, Sigma has not stopped asking the central question: what makes for the best overall photograph? Sigma has continued to pursue excellence in the body of the camera and all of the components to offer each photographer the best camera possible.

SIGMA SD15 Special Contents