High Performance Silicon Imaging

Fundamentals and Applications of CMOS and CCD Sensors

Daniel Durini

• Publisher: Woodhead Publishing
• Year: 2019
• eBook ISBN: 9780081024355
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

High Performance Silicon Imaging: Fundamentals and Applications of CMOS and CCD Sensors, Second Edition, covers the fundamentals of silicon image sensors, addressing existing performance issues and current and emerging solutions. Silicon imaging is a fast growing area of the semiconductor industry. Its use in cell phone cameras is already well established, with emerging applications including web, security, automotive and digital cinema cameras. The book has been revised to reflect the latest state-of-the art developments in the field, including 3D imaging, advances in achieving lower signal noise, and new applications for consumer markets.The fundamentals section has also been expanded to include a chapter on the characterization and testing of CMOS and CCD sensors that is crucial to the success of new applications. This book is an excellent resource for both academics and engineers working in the optics, photonics, semiconductor and electronics industries.- Covers the fundamentals of silicon-based image sensors and technical advances, focusing on performance issues- Looks at image sensors in applications, such as mobile phones, scientific imaging, and TV broadcasting, and in automotive, consumer and biomedical applications- Addresses the theory behind 3D imaging and 3D sensor development, including challenges and opportunities

Part One

Fundamentals

1

Fundamental principles of photosensing

D. Durini^a; D. Arutinov^{b a} National Institute of Astrophysics, Optics and Electronics (INAOE), Tonantzintla, Puebla, Mexico
^b Central Institute of Engineering, Electronics and Analytics ZEA-2—Electronic Systems, Forschungszentrum Jülich GmbH, Jülich, Germany

Abstract

This chapter discusses the fundamental theory behind photosensing and imaging. It starts with a brief overview of the human vision system and continues with the basic ideas behind photometry and radiometry used as radiation measuring systems. Next, it presents a brief history of phototransduction explaining the origins of solid-state photosensing through the development of quantum mechanics and the different applications of the photoelectric effect and mentions some important developments in the field of photodetectors prior to silicon-based microelectronics.

Keywords

Human vision; Photometry; Radiometry; Photoelectric effect; History of photodetectors

Nature and nature's laws lay hid in night;

God said ‘Let Newton be’ and all was light.

Alexander Pope

It did not last: the devil, shouting ‘Ho.

Let Einstein be,’ restored the status quo.

Sir John Collins Squire

1.1 Introduction

Since ancient times, people have been trying to create images that could reflect their experiences, explain the world surrounding them, and conserve their memories in a visual form. Since the very first mosaic paintings (also known as an “abaciscus” or “abaculus”) (see Fig. 1.1), the same concept has been pursued: putting together hundreds or thousands of small colored tiled stones or pieces of clay (named “tesserae”), used as basic picture elements or “picture cells” (pixels), a much bigger single final image can be created. The human brain and the human vision system do the rest of the job. The smaller these picture elements are and the more different intermediate values between complete darkness and complete illumination or different individual colors they might possess, the better is the resolution and the quality of the resulting image in our brain. The concept of mosaic painting has been known for several thousand years: the earliest known mosaics made of different materials were found in the temple building in Abra in Mesopotamia, dated to the second half of the third millennium BC.

Fig. 1.1 Detail showing the Greek God Dionysus, part of the central image of the Dionysus Mosaic from around AD 220–230 currently situated in the Römisch-Germanisches Museum in Cologne in Germany (and still in its original place, where it was used as a kitchen floor). The Dionysus Mosaic has an area of 10.6 m × 7 m and was made out of approximately 1.5 million stone tiles Photograph taken by Daniel Durini in 2012.

1.2 The human vision system

The concept of mosaic painting proved to be very successful mainly because it was developed based on the empiric knowledge of the functionality of our own human vision system and the ability of our brain to interpret the incoming information in a logical manner. Human vision is based on an optical system projecting an image through a lens, the cornea, the vitreous fluid, and a layer of capillaries to focus it through several layers of neural membranes onto a system of passive cone photoreceptors located in the center of the retina directly beneath a small cavity called the fovea (Davson, 1976), as it can be observed in Fig. 1.2. Currently accepted vision theories suggest that human beings use a trichromatic system to detect and separate colors, with photonic energy being measured using three different types of band-pass cone-shaped absorbing photoreceptors (Curcio et al., 1990; Rosenthal et al., 2004), and the ability of the brain to combine separate fragments into one logical image entity.

Fig. 1.2 A schematic diagram of the human eye.

The light entering the human eye first interacts with the cornea (see Fig. 1.2), where the air-cornea interface transmittance happens to be of some 98% (Kaschke et al., 2014). This remarkable transparency of the human cornea is mainly caused by the stacked lamellae building the cornea tissue. They are constituted by collagen fibrils running parallel to each other and having regular spacing. These collagen fibrils happen to be very poor scatterers as their diameters (25–35 nm) are much smaller than the wavelengths forming part of the visible part of the spectra (380–780 nm) and their spatial distribution reduces additional scattering due to induced destructive interference (Kaschke et al., 2014). So, after the incident light rays have been minimally refracted by the cornea, they travel through the anterior eye chamber and cross the iris. The iris, with its variable inner aperture diameter, limits the so-called visual field of view (FOV) for incident light rays to 105 degrees at the outer parts of the human eyes, and to some 60 degrees on the nasal side (Kaschke et al., 2014) per eye. In ophthalmology and optometry, the term “pupil” is often referred to as the hole of the iris aperture, although technically the iris is actually the aperture stop. It is the image of this aperture that will finally be formed by the cornea.

After passing the iris, the light rays travel through the posterior chamber and enter the eye's lens, adjustable to the distance of objects being fixated. The eye's lens consists of multiple shells stacked layer by layer, each with a different refractive index starting with 1.42 found in the core and the varying downwards (Kaschke et al., 2014). Passing the eye's lens, the light rays pass through the vitreous humor and are eventually impinging the retina.

According to 'sterberg (1935, as cited by Ripps and Weale in Davson, 1976), the human retina contains approximately 110–125 million rods and 6.3–6.8 million cones, the two kinds of photoreceptors in the human eye. As concluded by Max Schultze (1866, as cited by Ripps and Weale in Davson, 1976), they are associated with scotopic (nocturnal) and photopic (diurnal) visions, respectively, which formed the basis for the so-called “duplicity theory” defined to explain the visual ability of the human retina, with their properties as listed in Table 1.1.

Table 1.1

The physiological basis of the duplicity theory in a human being (Ripps and Weale in Davson, 1976)

Parameter	Rods	Cones
Operating conditions	Dim light	Daylight
Sensitivity	High	Low
Spatial resolution	Poor	Good
Temporal resolution	Poor	Good
Maximal sensitivity	Blue-green	Yellow-green
Directional sensitivity	Slight	Marked
Rate of dark adaptation	Slow	Fast
Color vision	Absent	Present

As described in 'sterberg's thorough survey (Davs...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Contributors
• Preface
• Part One: Fundamentals
• Part Two: Applications
• Index