The narrow sense, as the optical light and see on the science, optics (optical) the word is used only for early stage, as with the eyes and see things associated. Today, it is often said optical broad sense, is to study from the microwave, infrared, visible light, ultraviolet light until the X-ray within the scope of broad-band, on the occurrence of electromagnetic radiation, transmission, reception and display, as well as interaction with the material science .

A Brief History of the development of optical
Optics is a subject that has a long history, the history of its development can be traced back over 2000 years ago.

Light of human research, the first major attempt to answer "how people can see objects around?" Issues like. About 400 years BC (on behalf of the Pre-Qin Dynasty), China's "Mojing" recorded in the world's first optical knowledge. It has the 8 on the optical records, described in the definition and generation of shadow, light, and the straight-line dissemination of pinhole imaging, as well as rigorous discussion in the text plane mirror, concave and convex spherical mirror mirror ball in the relationship between objects and the like.

Since the "Mojing), the 11th century Ibn Arabs invented wood Hessian lens; Year 1590 to the beginning of the 17th century, Johnson and Lee puhi microscope invented independently at the same time; until half of the 17th century only by the Sri Lanka Descartes and Fresnel light reflection and refraction of the observations, all comes down to today, usual and the law of refraction.

1665, Newton's experiments to sunlight, which the sunlight into simple components, these components form a color according to a certain order of the light distribution - spectrum. It allows people to come into contact with the first light of the objective and quantitative characteristics of the monochromatic light of the separation in space is determined by the nature of light.

Newton also found a large radius of curvature of the convex lens on the optical flat glass plate, when irradiated with white light, then see contact lens and glass plate color appeared a group of concentric circular fringes; when using a monochromatic light irradiation, then the emergence of a set of concentric rings of white light stripes, later said the Newton ring phenomenon. This phenomenon can be used with the first dark ring of the air gap thickness to quantitative characterization of the corresponding monochromatic light.

Huygens is that the particles of light opponents, he created a wave theory of light. The "one voice, like light, is the spread of spherical wave-front." And pointed out that the vibration of the light to reach every point can be regarded as a second wave of the vibration center, sub-surface-wave envelope for the spread of wave front (wave front). Throughout the 18th century, the light particle theory and wave theory of light have been put forward roughly, but not very complete.

The early 19th century, initially formed wave optics, in which Dr Thomas explained satisfactorily "color film" and the double-slit interference. Fresnel in 1818 in Young's interference principle to add the Huygens principle, which formed a well-known today for the Huygens - Fresnel principle, it can be successfully used to explain interference and diffraction of light phenomena, can also explain the rectilinear propagation of light.

In further studies, the observed polarization and the polarization of light interference. In order to explain these phenomena, Fresnel assumed that a continuous medium alone (Ethernet) in the S-wave transmission. To illustrate the different light in different media, speed, and it must be assumed that the characteristics of Ethernet in different materials are different; in anisotropic media is also a need for more complex assumptions. In addition, it must be more special to Ethernet in order to explain the nature of light rather than P-wave. So the nature of the Ethernet is difficult to imagine.

In 1846, Faraday discovered the surface vibration of light occur in the rotating magnetic field; in 1856, Weber found that the light speed in vacuum equal to the current strength of the electromagnetic units and the ratio of electrostatic units. Their findings show that the optical phenomena and magnetism, electrical phenomena there is a certain degree of internal relations.

Before and after 1860, the Maxwell pointed out that changes in electric and magnetic fields can not be confined to a certain part of space, but in units equivalent to the electromagnetic current and the ratio of electrostatic units of the speed of the spread of light is such an electromagnetic phenomenon. This conclusion in 1888 confirmed for Hertz experiment.

However, this theory can not explain, as light can produce such a high frequency oscillator of the nature of electricity, but also can not explain the phenomenon of light dispersion. Lorenz in 1896 to the creation of electronic theory, explain the light-emitting and light absorbing material phenomenon also explains the spread of light in the material in a variety of features, including the interpretation of the phenomenon of dispersion. In Lorentz's theory, Ethernet is not the vast infinite moving medium, is characterized by its unique, in which the optical medium has a certain vibration velocity.

Like hot blackbody radiation in the wavelength distribution of energy in accordance with such an important issue, Lorentz theory could not give a satisfactory explanation. And, if we think that the concept of Lorenz on the Ethernet is correct, may be fixed for the election of the Ethernet frame of reference, so that people can distinguish between absolute movement. In fact, in 1887 by Michelson interferometer test "ether wind", the negative results, indicating that the electronic theory of the Lorentz time, people's understanding of the nature of light, there is much one-sidedness.

In 1900, Planck material theory of molecular structure using the concept of discontinuity, the quantum theory of radiation. He believes that the various frequencies of electromagnetic waves, including light, can only determine the amount of their energy from the oscillator injection, the energy particles known as quantum, the quantum of light known as photons.

Quantum theory it is natural to explain not only the hot body by the wavelength distribution of radiation energy laws, it is also a new way of interaction between the light and the whole question of the material. Quantum theory not only to the optical, but also to the entire physics provides a new concept, and therefore it is usually the birth of modern physics as a starting point.

In 1905, the use of quantum theory Einstein explained the photoelectric effect. He made very clear to the photon's, said that the interaction between light and matter, light is the smallest unit of a photon is carried out.

September 1905, Germany, "Yearbook of Physics" Einstein published "On the electrodynamics media campaign," a text. The first time the basic principles of special relativity, the article pointed out that since the days of Galileo and Newton dominant classical physics, its application is limited to the speed of the situation is far less than the speed of light, and his new theory can explain and great velocity characteristics of the process, it abandoned the concept of Ethernet, a complete explanation of the optical phenomena of moving objects.

In this way, in the early 20th century, on the one hand from the optical interference, diffraction, polarization, and movement of objects confirmed the optical phenomena of electromagnetic waves alone; while on the other hand from the heat radiation, photoelectric effect, light pressure and chemical action of light, such as proved beyond reasonable doubt that the quantum nature of light - particulate.

Found in 1922 Compton effect, discovered in 1928, Raman effect, as well as the experiment has been obtained from atomic hyperfine structure spectrum, which indicate that the development of optical quantum physics and closely related. History has shown that the development of optics, modern physics in the two most important basic theory - quantum mechanics and special relativity in the light of research on the birth and development.

Since then, the optical entered a new period, so that modern physics and modern science and technology an important component of the frontier. One of the most important achievements is the discovery of Einstein in 1916 predicted the atoms and molecules by stimulated emission, and the creation of a number of concrete produced by stimulated emission of radiation technology.

Einstein Radiation Research, pointed out that under certain conditions, if the stimulated emission can continue to inspire other particles, causing a chain reaction amplification was like a avalanche effect, and finally there will be highly monochromatic radiation, ie laser . In 1960, Maiman made the first use of ruby laser visible light; made of helium-neon laser in the same year; in 1962 produced a semiconductor laser; in 1963 had a tunable dye laser. Due to the excellent monochrome laser, high brightness and good direction, it has been found that since 1958 has been rapid development and wide application of science and technology led to major changes.

Another important optical branch by imaging optics, holography and optical information processing components of the. This branch can be traced back as early as in 1873 microscope imaging of the theory, and in 1906 Porter was to verify the completion of the experiment; Zelnick in 1935 to phase contrast observation, and so the factory made by Zeiss phase contrast microscope, for which he received the Nobel Prize in Physics in 1953; in 1948 put forward by modern Gabor holography predecessor - the principle of wave front again, to that end, Gabor won the Nobel Prize in Physics 1971 .

Since the 50's since the 20th century, people began to mathematics, electronics and optical communication theory and combine the introduction of the optical spectrum, spatial filtering, carrier, linear transformation and the related concepts of operation, updating the classic optical image formed the so-called "Fourier Optics." In addition, as a result of coherent laser light provided by from Leith and improved within the Fox holography, the formation of a new academic field - optical information processing. Optical fiber communication is the basis of the theory in this regard an important achievement, it is for information transmission and processing of new technologies.

In modern optics itself, generated by the laser nonlinear optical phenomena are more and more attention to the people. Laser spectroscopy, including laser Raman spectroscopy, high-resolution spectra and ultrashort pulse picosecond and tunable laser technologies, has made the traditional spectroscopy has changed and become micro-structure of the material in-depth study, movement of energy conversion mechanism and an important means. For condensed matter physics, molecular biology and chemical study of the dynamics of the process provided an unprecedented technology.

Optics research
Optical is generally divided into geometrical optics, physical optics and quantum optics.

Geometrical optics is obtained from the experimental number of the basic principles of starting to study the propagation of light subjects. It uses the concept of light, refraction,反射定律to describe the light spread in a variety of media channels, it is usually always the result of wave optics in the approximation under certain conditions or limits.

Physical optics is the volatility from the point of light to study the spread of light in the course of the phenomenon occurred disciplines, therefore, also known as wave optics. It can be easier to study the light interference, light diffraction, polarized light, and light in anisotropic media when inserted in the Chuan-show phenomenon.

The basis of wave optics is the classical electrodynamics of Maxwell's equations. Unknown fluctuations of the optical dielectric constant and magnetic permeability of the relationship between structure and material, and focus on the interpretation of the law of light performance. Wave optics can be interpreted in light scattering media and anisotropic media when the phenomenon spread, as well as the optical media interface in the vicinity of the performance; also to explain the phenomenon of dispersion medium and a variety of pressure, temperature, acoustic, electric and magnetic fields of the phenomenon of light impact.

Planck Institute for Quantum Optics in 1900 when the black-body radiation in the study, in order to be theoretically consistent with the actual formula for a very good experience, he put forward bold and very different from the classical concept of the assumption, which is "composed of the oscillator blackbody continuous changes in the energy can not only take a discrete value of. "

In 1905, Einstein's photoelectric effect in the promotion of the Planck time of the above-mentioned quantum theory, which put forward the concept of photon. He believed that the electromagnetic wave theory of light is not as as described in the wave-front surface, but concentrated in the so-called photon particles. In the photoelectric effect, when the photon irradiation to the metal surface, a metal to absorb all of the electronics without the need for electromagnetic theory predicted that the cumulative energy of the time, the electronic part of this energy to overcome the metal surface it that is, for escaping the suction power, the remaining electron left on the metal surface into kinetic energy after.

This departure from the nature of photons to study the interaction between light and matter is the subject of quantum optics. It is based primarily on quantum mechanics and quantum electrodynamics.

Light to show that not only has the volatility of the phenomenon of particles not only wave-particle duality of light. Subsequent theoretical and experimental study on the indisputable proof: not only have this dual nature of light, the world of all substances, including electronics, protons, neutrons and atoms, as well as all the macro things, but also has its own quality and speed linked to the characteristics of the volatility.

Applied Optics Optics is composed of many closely associated with the physics component branches; because it has a wide range of applications, so the application of the background of a series of strong optical branch is also a range of disciplines. For example, the electromagnetic radiation measurement of physical quantities of light, radiation science degrees; to the normal average human eye for the receiver, to study the electromagnetic radiation caused by the color visual, physical and psychological measurements of color; and a large number of optical technology: optical system design and theory of optical instruments, optical manufacturing and optical testing, interferometry, thin film optics, fiber optics and integrated optics, etc.; interdisciplinary with other branches, such as optical astronomy, marine optics, remote sensing optics, atmospheric optics, physiological optics and optical and other weapons.

2. Luminous intensity (brightness) What is the unit?
A: The common unit of luminous intensity candlelight (cd, candela), the international standard candles (lcd) is defined as an ideal blackbody at the freezing point of platinum temperature (1769 ℃), the perpendicular to the blackbody (its specific surface area of 1m2) direction 60 one ten thousandth of the light, the so-called ideal black body radiation is the rate of objects equal to 1, objects can be absorbed by all the radiation energy out, so that the temperature has remained fixed uniform, international standard candles (candela) and the old standard candles (candle ) for the exchange of relations 1candela = 0.981candle

4. 1 feet What is the meaning of candlelight?
A: 1 feet away from a candlelight candlelight means of the light source (point source or non-point source) and one feet away and the surface of the orthogonal light illumination, the abbreviation for 1ftc (1 lm/ft2, lm / ft 2) , that is to receive per square foot by 1 lumen luminous flux at the time of illumination, and 1ftc = 10.76 lux

5. 1 meters What is the meaning of candlelight?
A: The one-meter candlelight candlelight refers to the distance of a light source (point source or non-point source) with one meter far from the surface of the orthogonal light illumination, known as the lux (lux, also written in lx), each received by the square of 1 lumen luminous flux at the time of illumination (lumens / m 2)

6. 1 lux What is the meaning?
A: per square meter received by 1 lumen luminous flux at the time of illumination

7. What is the meaning of illumination?
A: illuminance (E) is defined as: objects illuminated unit exposed area of the luminous flux received by, or by light irradiation of the objects in unit time per unit area of the light received by the unit in meters or feet candle candlelight light (ftc) .

9. Was the illumination according to body size and what factors?
A: According to the body by illumination with light source and the luminous intensity and according to the distance between the light source, while according to the body with the color, surface properties and surface area size