luminous flux

Today I will share with you the knowledge of LED lighting

Knowledge of light

Light propagates in the form of electromagnetic waves. The light source is an electromagnetic wave that can be felt by the human eye, with a wavelength range of 380nm-780nm (nm: nanometers, length unit 1nm=10-9 longer than 780nm has infrared, radio, etc., shorter than 380nm has ultraviolet, X-ray, cosmic rays, etc.

The visible light section is further divided into seven basic monochromatic lights: red, yellow, orange, green, cyan, blue, and violet.

Like all other electromagnetic radiation, light travels in a straight line at 300,000 kilometers per second in a vacuum. When light passes through substances such as water or air, its propagation slows down.

The ratio of the speed of light in a vacuum to the velocity in the medium is called the refractive index of the medium. At the interface of two media with different refractive indices, incident light produces refraction and emission phenomena. In addition, light scatters, diffuses reflections, diffuse reflections, etc. during propagation.

Units of measurement of light:

(1) Luminous flux: The amount of light emitted by the light source per unit time is called luminous flux, the symbol is φ, and the unit is lumens (Lm). Luminous flux is the human eye’s evaluation of energy radiation flux.

(2) Light intensity: The luminous flux emitted by the light source in a given direction at a unit solid angle is defined as the light intensity of the light source in that direction. The symbol is I, the unit is candela (cd), I = dφ/d. The unit of light intensity is the basic unit of photometric measurement.

(3) Illuminance, also known as brightness: the number of luminous fluxes emitted in a certain direction by a unit projection light source surface at a unit solid angle. The symbols are E, E = dφ/ ds in Lx (lux), I lx = 1 Lm/m2.

(4) Light efficiency: refers to the ratio of the luminous flux emitted by the light source to the electrical power P consumed by the light source.


Color knowledge:

Human visual organs cause a psychological response from the brain in color stimuli. That is, the visual organ is stimulated by different wavelengths of light, and at the same time, a color stimulus signal is generated and transmitted to the brain. The brain constantly converts the color signals it receives into color concepts and combines them with visual experiences stored in the brain to interpret them to form color perception.

Colors are divided into color and achromatic. Achromatic colors refer to various shades of white and black. Color refers to a variety of colors other than the black and white series.

Due to the association between emotional effects and objective things, the visual stimulation of color produces a series of psychological effects of color perception. This effect varies with specific time, place, and conditions (such as appearance and shape, natural conditions, personal preferences, lifestyle habits, shape and size, environmental location, etc.). In general, color can create a sense of temperature, distance, weight, space, and darkness.

Color temperature and color application:

(1) Color temperature of the light source:

The color table of a light source (the color that the human eye sees when it directly looks at the light source) is described by the absolute temperature of the complete heat sink equal to or approximate the color temperature of the light source, also known as the color temperature of the light source. The color temperature is expressed as the absolute temperature K, and different color temperatures can cause people to have different emotional responses. We generally divide the color temperature of the light source into three categories:

Color temperature chart

1. Warm light:

The color temperature of warm light is less than 3300K. Warm light is similar to incandescent lamp, and there are more red light components, giving people a warm, healthy and comfortable feeling. It is suitable for homes, residences, dormitories, hospitals, hotels and other places, or places with relatively low temperatures.

1. Warm white light:

Also known as intermediate color, its color temperature is between 3300K-5300K. The warm white light is soft, making people feel happy, comfortable and peaceful. Suitable for shops, hospitals, offices, restaurants, restaurants, waiting rooms and other places.

1. Cold light:

Also known as daylight color, its color temperature is above 5300K. The light source is close to natural light and has a bright sensation that makes people focus. It is suitable for offices, conference rooms, classrooms, living rooms, design rooms, library reading rooms, exhibition windows and other places.

1. Light source classification:

The classification of lighting sources is based on different forms of light emission. It can be divided into two categories: radiation source and gas discharge lighting source. The former uses an electric current to heat it to an incandescent state through a wire to emit visible light. The latter uses the atoms of certain elements to be excited by electrons to produce radiation.

2. Selection of light source:

The selection of electric light sources should be based on the implementation of green lighting projects. Green lighting projects aim to save energy and protect the environment. The specific content is: the use of high-efficiency, low-pollution electric light source. Improve lighting quality and protect vision. Improve labor productivity and energy efficiency. Save energy, reduce lighting costs, reduce the construction of hydropower projects, reduce the emission and escape of harmful substances, and achieve the purpose of protecting the human living environment.

1. Classification of lamps:

The variety of lamps is very rich, the appearance is ever-changing, and the performance is also very different. There are also various classification methods for lamps, mainly including:

· According to the power supply used: the lamps are divided into incandescent lamps, fluorescent lamps, high-pressure gas discharge lamps and LED lamps.

· According to the light distribution classification of lamps: lamps are divided into five categories: direct lighting, fully diffuse lighting, total reflection lighting, semi-indirect lighting and indirect lighting.

· According to the installation of the building, the lamps are divided into ceiling lights, chandeliers, wall lamps, recessed lights, foot lights, garden lights, automatic emergency lights, mobile lights and road square lights, etc.

· Classification according to the place of use of lamps: there are open lights, closed lights, sealed lights, explosion-proof lights, safety lights and shockproof lights.

2. Light distribution

The distribution of light intensity in space is an important feature of lamps, usually represented by curves, so it is also called light distribution curve. There are generally three ways to represent the light distribution curve: one is the polar coordinate method, the other is the rectangular coordinate method, and the third is the equal light intensity curve.

A. Polar coordinate light distribution curve:

On the metering plane passing through the center of the light source, the light intensity value of the luminaire at different angles is measured. Starting from a certain direction, mark the light intensity of each angle with a vector as a function of angle, and the connection to the top of the vector is the polar light distribution curve of the lighting fixture.

If the luminaire has a rotationally symmetrical axis, only the light intensity distribution curve on the photometric surface across that axis can be used to illustrate the spatial distribution of its light intensity. If the light distribution of the luminaire is asymmetrical in space, light intensity distribution curves of several photometric planes are required to account for the spatial distribution of its light intensity.

Polar coordinate light distribution curve

B. Cartesian light distribution curve:

For spotlights, because the beam is concentrated at a very narrow solid angle, it is difficult to represent the spatial distribution of its light intensity in polar coordinates, so the Cartesian light distribution curve representation method is adopted. The horizontal axis represents the light intensity map I, and the horizontal axis represents the projection angle of the beam. In the case of luminaires with symmetrical axes of rotation, only one light distribution curve is required. If it is an asymmetrical lamp, multiple light distribution curves are required.

Cartesian light distribution curve

C. Light intensity curve:

The curve that connects the top of a vector with equal light intensity is called an equal light intensity curve. Arrange the values of adjacent waiting light intensity curves in a certain proportion and draw a series of graphs consisting of equal light intensity curves, called waiting light intensity maps. Commonly used diagrams include circular network diagrams, rectangular network diagrams, and positive arc network diagrams. Since the rectangular network diagram can not only explain the light intensity distribution of the luminaire, but also explain the regional distribution of the amount of light, the current isolight intensity curve used by the current projection lamp is a rectangular network diagram.

Light intensity curve

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Color temperature chart