Название: Optical Design for LED Solid State Lighting: A Guide
Автор: Ching-Cherng Sun, Tsung-Xian Lee
Издательство: IOP Publishing
Серия: IOP Series in Emerging Technologies in Optics and Photonics
Год: 2022
Страниц: 219
Язык: английский
Формат: pdf (true)
Размер: 47.1 MB

Light-emitting diodes (LEDs) are considered the most important light source of the 21st century owing to advantages of energy saving, long life, fast response, high colour performance, and environmental benefit. We believe that accurately understanding the light performances of LEDs and using them skilfully is an important capability for optical designers.

This book provides an overview of the light performance of LED SSL and can further effectively apply optical design to SSL at different levels. Optical Design for SSL is classified into four levels including LED die, package, component, and system. All approaches are aimed at teaching readers to precisely determine the spatial and chromatic light performance of an LED and increasing the optical utilization factor of an LED luminaire to achieve optical energy efficiency.

LED is a semiconductor device that can convert electrical energy into light energy. To understand the working principle of LEDs, we must first introduce the concept of semiconductors. Semiconductors are solid-state objects of which the electrical conductivity is between conductors and insulators. They are essentially a crystallized structure with atoms that are stacked up neatly. In general, when many atoms combine to form solid matter, there will be interactions between the peripheral electrons of the neighboring atoms. As the attractive and repulsive forces act simultaneously, a stable equilibrium state is finally reached. In the process of solid formation, some significant changes will be produced in the electron energy level, resulting in materials with different characteristics, such as conductors, insulators, and semiconductors. From the perspective of energy state, these stable electrons have lower energy and form a valence band. If some of the electrons obtain energy from the external actions, such as heating, illuminating, or electrifying, these excited electrons will then be free to move between atoms. Such free moving electrons can conduct electricity or heat. Because of their higher energy state, they form a conductive band. The energy difference between the conduction band and the valence band is called the ‘band gap.’ Generally speaking, physical systems tend to go to a low-energy state, so, electrons first fill up the valence band.

The book covers seven chapters. The first chapter introduces the background of SSL and knowledge for readers that four-level optical technologies will be discussed throughout the book. Besides, radiometry and photometry, the essential knowledge for handling illumination of SSL, is introduced to the readers. The second chapter briefly introduces basic optics to the readers. This is useful for a reader without an optics background, and it is also helpful to a reader in strengthening the necessary optical knowledge. The third chapter discusses the light extraction of an LED. This is an issue when the emission efficiency of an LED is concerned, and also is related to the light emission field owing to LED structures through the crystal epitaxy and chip processing. The fourth chapter discusses packaging technology, where phosphor modeling is one of the key issues. The reader will understand how to figure out the packaging efficiency when facing the related complex problem. The fifth chapter is important for an optical designer. The optical modeling technology of an LED light source is introduced with case studies. The sixth chapter discusses the secondary optical design, which is the main technique for an optical designer. The fundamental of energy transfer from a light source to a receiver is discussed. The seventh chapter introduces several different cases of optical design for LED SSL.

We believe that this book will be useful to a student learning optical technology, and helpful to an optical engineer in figuring out the optics of SSL.

Key Features:

- Presents an essential guidebook for optical design in LED Lighting
- Includes thorough explanations of LED light performance and limitations
- Proposes four-level optical design in LED lighting
- Includes chapter summaries
- Provides a reader-friendly approach to ensure precision