In recent years, there has been a growing awareness and emphasis on the importance of sustainable energy sources. This focus has led to the rapid development and popularity of solar lights as an alternative to conventional lighting solutions. Solar lights, also known as solar-powered lights, are becoming increasingly popular due to their eco-friendly nature, cost-effectiveness, and ease of installation. In this article, we will delve into the different types and models of solar lights, their specifications, advantages, installation process, applications, and storage capabilities.

Types and Models of Solar Lights:

Solar lights encompass a wide range of designs and functionalities to cater to various lighting needs. Some of the common types and models of solar lights include solar garden lights, solar street lights, solar spotlights, solar flood lights, and solar lanterns.

Solar Garden Lights: Solar garden lights are designed to light up outdoor spaces such as gardens, pathways, driveways, and landscapes. These lights are usually mounted on stakes that can be easily pushed into the ground. Solar garden lights come in various forms, including decorative lanterns, post lights, and string lights, making them aesthetically pleasing while providing illumination.

Solar Street Lights: Solar street lights are specifically designed for outdoor lighting in public areas such as streets, parks, and parking lots. These lights are equipped with high-powered LED bulbs and solar panels, ensuring optimal luminosity throughout the night. Solar street lights often incorporate advanced technologies such as motion sensors and dimming capabilities to conserve energy when not in use.

Solar Spotlights: Solar spotlights are ideal for highlighting specific areas or objects such as trees, sculptures, or architectural features. These lights are adjustable and usually come with a stake or wall-mounted options. Solar spotlights are known for their bright and focused illumination.

Solar Flood Lights: Solar flood lights are powerful light fixtures that are used for areas requiring high-intensity lighting, such as sports fields, billboard advertisements, or construction sites. Solar flood lights are designed to provide ample lighting over a large area and often come with adjustable features to accommodate various lighting requirements.

Solar Lanterns: Solar lanterns are portable lighting solutions that are used for outdoor activities such as camping, hiking, and emergency situations. These lanterns are lightweight, durable, and often have multiple brightness options. Solar lanterns are designed to charge during the day and provide illumination throughout the night.

Specifications and Advantages of Solar Lights:

Solar lights come with specific specifications that determine their performance and capabilities. Key specifications to consider when choosing solar lights include solar panel wattage, battery capacity, charging time, and working time.

Solar panel wattage refers to the power rating of the solar panel that converts sunlight into electricity. Higher wattage panels usually generate more electricity, leading to faster charging and increased illumination.

Battery capacity determines the amount of energy that can be stored by the solar light. Higher battery capacity generally allows for longer working times, ensuring consistent illumination throughout the night

Charging time is the amount of time required for the solar panel to fully charge the battery. This time can vary depending on factors such as solar radiation and panel efficiency. It is crucial to select solar lights with shorter charging times for faster and more efficient use.

Working time indicates the duration of illumination provided by the solar light after a full charge. Depending on the battery capacity and lighting requirements, solar lights can provide anywhere from a few hours to an entire night of illumination.

Advantages of solar lights are manifold and make them a favorable choice over traditional lighting options. Solar lights are powered by renewable energy, making them environmentally friendly and reducing the carbon footprint. Since they are not dependent on electricity grids, solar lights operate independently, reducing energy costs and providing an alternative energy source. Additionally, solar lights are low maintenance and require minimal operational costs, contributing to long-term savings.

Installation and Application of Solar Lights:

The installation process of solar lights is generally straightforward and user-friendly. Most solar lights come with simple instructions and can be easily installed without the need for electrical expertise. Here are some general steps for installing solar lights:

1. Select the desired location: Choose the area where you want to install the solar light, ensuring it receives sufficient sunlight throughout the day.
2. Mounting or placement: Depending on the type of solar light, secure it in the desired location using stakes, screws, or brackets.
3. Position the solar panel: Ensure that the solar panel is positioned in a way that it receives direct sunlight. Adjust it accordingly for optimal charging efficiency.
4. Test the light: After installation, test the solar light by covering the solar panel to activate the light. This step ensures the light is working correctly before complete installation.

Solar lights find numerous applications in both residential and commercial settings. In residential settings, solar lights are commonly used for outdoor lighting purposes, such as providing illumination to gardens, pathways, decks, and patios. They enhance the aesthetic appeal of outdoor spaces while minimizing energy consumption.

In commercial settings, solar lights are extensively used for street lighting, parking lots, signage illumination, and perimeter security lighting. Solar street lights, in particular, are gaining popularity in developing regions where grid electricity is unreliable or non-existent. These lights provide a sustainable and cost-effective solution for illuminating public spaces, improving safety and security.

Storage Capabilities:

Solar lights are equipped with built-in batteries that store solar energy during the day for use at night. The battery capacity determines the amount of energy that can be stored and utilized by the solar light. Depending on the model and specifications, solar lights can store enough energy to provide illumination throughout the night.

It is essential to consider the storage capabilities of solar lights while selecting the appropriate model for specific applications. For areas that experience extended periods of cloudy weather or limited sunlight, choosing solar lights with higher battery capacity ensures consistent illumination even during adverse conditions.

In conclusion, solar lights have emerged as a viable and sustainable solution for outdoor lighting needs. With their various types and models, one can easily find solar lights that cater to specific lighting requirements. Solar lights offer significant advantages such as energy efficiency, cost-effectiveness, and environmental friendliness. Their uncomplicated installation process and applications in diverse settings make them a popular choice. As the demand for renewable energy sources continues to rise, investing in solar lights is a step towards embracing clean energy and contributing to a greener future.

                                                                                                                                                                                          LED lighting and light color measurement led light measurement

Abstract: Solid-state lighting is the leading direction of future lighting, and LED lighting is the main component of solid-state lighting, which is an ideal next-generation lighting device. The development of the LED industry is inseparable from light and color measurement technology. Starting from the development requirements of LED lighting, the article introduces the light color measurement of LED lighting.

Key words: LED lighting; light color measurement; lighting evaluation;

1 Introduction

Light-emitting diode (LED), as an emerging illuminant, has the advantages of high electro-optic efficiency, small size, long life, low voltage, energy saving and environmental protection, etc., and is the preferred device for the new generation of lighting. The development of LED has been widely concerned at home and abroad, and new products and new technologies emerge in an endless stream. In recent years, the LED industry has developed rapidly, with increasing light efficiency and brightness. Today, LEDs have been widely used in many occasions, especially the continuous progress of white LED technology, making its application in the field of lighting gradually popular.

2. Working principle of LED

Light-emitting diode (LED) is a solid device that can convert electrical energy into light energy. Its structure is mainly composed of PN junction chips, electrodes and optical systems. The basic working principle of LED is a process of electro-optical conversion. When a forward bias voltage is applied to both ends of the PN junction, due to the reduction of the PN junction potential barrier, the positive charges in the P region will diffuse to the N region, and the electrons in the N region will also flow to the N region. The P region diffuses, forming a non-equilibrium charge accumulation in the two regions at the same time. Because the minority carriers generated by current injection are relatively unstable, for the PN junction system, the non-equilibrium holes injected into the valence band will recombine with the electrons in the conduction band, and the excess energy will radiate outward in the form of light. The greater the energy difference between electrons and holes, the higher the energy of the resulting photon. If the energy level difference is different, the frequency and wavelength of the light produced will be different, and the color of the corresponding light will be different.

3. Light parameters of LED

3.1 Luminous flux

Luminous flux is the amount of light emitted by a light source per unit time, that is, the effective equivalent of the radiant power (or radiant flux) that can be felt by the human visual system. The symbol of luminous flux is Φ, and the unit is lumen (Lm).

According to the spectral radiant flux Φ (λ), the luminous flux can be determined by the following formula:

Φ=Km Φ(λ)gV(λ)dλ

In the formula, V(λ)—relative spectral luminous efficiency;

Km—the maximum value of the spectral luminous efficacy of radiation, the unit is Lm/W. In 1977, the Km value was determined by the International Committee of Weights and Measures to be 683Lm/W (λm=555nm).

3.2 Light intensity

The luminous intensity I of a light source in a given direction is the quotient of the luminous flux dΦ transmitted by the light source in the solid angle element of this direction divided by the solid angle element dΩ, that is:

I=■

The unit of luminous intensity is candela (cd), 1cd=1Lm/1sr. The sum of light intensities in all directions in space is the luminous flux.

3.3 Brightness

The luminance L at a certain point on the light-emitting surface of the light source is the quotient of the luminous intensity of the surface element dS in a given direction divided by the orthographic area of the surface element on a plane perpendicular to the given direction, namely:

L=■

The unit is candela per square meter (cd/m2).

When the light-emitting surface is perpendicular to the measurement direction, then cosθ=1. 3.4 Illumination

The illuminance E of a point on the surface is the quotient of the luminous flux dΦ incident on the surface element containing the point divided by the area dS of the surface element. Right now:

E=■

The unit is lux (Lx), 1Lx=1Lm/m2.

3.5 Other parameters

The light parameters of LEDs also include: spectrum, chromaticity coordinates, dominant wavelength and color purity, color temperature and correlated color temperature, color rendering and color rendering index, etc.

4 Necessity of LED light color measurement

4.1 Avoiding Hazards

LED is different from traditional lighting, it has the characteristics of point light source, high brightness, narrow beam output and so on. When LEDs are used in lighting fixtures, strong glare will be produced if the light emitting angle is not strictly controlled, and some high-brightness LED products may even cause light radiation hazards to the human body. Photochromic measurement can provide guidance for the safe use of LEDs.

4.2 Promote the development of LED industry

The light and color measurement of LED can provide a large amount of experimental data, which can be used as a standard for judging whether LED products are qualified or not, and can provide a basis for improving the design and manufacture of LEDs.

5 LED light color measurement method

5.1 Measurement of luminous flux

5.1.1 Integral method

Measure the light intensity of the LED in all directions, and then calculate these light intensity values to obtain the total luminous flux of the LED (as shown in Figure 3).

5.1.2 Integrating sphere method

Integrating sphere, also known as luminous flux sphere, is a hollow complete spherical shell. The inner wall is coated with a white diffuse reflection layer, and each point on the inner wall of the ball diffuses evenly. The illuminance produced by the light source at any point on the wall of the sphere is superimposed by the illuminance produced by multiple reflected lights. According to the principle of integral theory, the illuminance at any point on the spherical surface is proportional to the luminous flux of the light source, so the luminous flux of the measured lamp can be obtained by comparing the standard lamp with known luminous flux with the measured lamp.

However, due to the difference in physical structure and properties (such as absorption) between the standard lamp and the tested lamp, it is necessary to correct the test results when using the integrating sphere method to test the luminous flux, and the auxiliary lamp method can be used.

5.1.32π solid angle luminous flux test

There is also a test structure when using the integrating sphere method to test the LED luminous flux, which is called the test of the front luminous flux or the 2π solid angle luminous flux. This test does not test the total luminous flux of the LED, but it is often confused with testing the total luminous flux of the LED.

5.2 Light intensity measurement

For the test of LED light intensity, CIE-127 stipulates two test conditions.

5.3 Brightness

The test of LED brightness is usually used in the process of testing the brightness of LED chips and evaluating the safety of LED light radiation. The test generally adopts the imaging method, and the test of the chip can be measured by microscopic imaging.

5.4 Illuminance measurement Strictly speaking, illuminance is not actually an optical parameter of LEDs. Illuminance is an optical quantity that indicates the degree of illumination of the illuminated surface, and it is not meaningful to test the illuminance of a single LED on a certain point or surface, because generally Under normal circumstances, the lighting of the actual occasion is jointly completed by multiple LEDs.

5.5 Measurement of other parameters

Other parameters such as chromaticity coordinates, dominant wavelength and color purity, color temperature and correlated color temperature, color rendering and color rendering index can be tested with a correlation colorimeter or a spectrometer.

6 LED optical radiation safety test and evaluation

In recent years, the light radiation safety of LEDs has received more and more attention, so this article also makes a brief introduction to it.

Zhejiang University Sanse Instrument Co., Ltd. first carried out the research on optical radiation safety testing in China, and jointly drafted the national standard for photobiological safety of incoherent light sources with the National Electric Light Source Testing Center. At present, Zhejiang University Tricolor has made new progress in LED light radiation safety testing. It has carried out lighting LED testing for Philips and completed the research and completion of LED radiation safety testing system with China’s independent intellectual property rights. The following is an introduction to the process of LED light radiation safety testing and evaluation based on our test examples.

6.1 Measured white light LED

6.1.1 LED working conditions

Lamp current 0.417A, voltage 12V DC, power 5w.

6.1.2 Physical map and spectral distribution

6.2 Test of apparent light source

As shown in Figure 9, we used the apparent light source test system to test the white LED. These 9 pictures are the apparent light source images taken at intervals of 10° in the directions of 0° (directly facing) and 90°. Theoretically, we should test and evaluate light safety according to each direction, but for the sake of simplicity, this article only tests and evaluates the situation in the 0° direction (because the light output in this direction is the strongest), other angles can be analogized by analogy. The apparent light source size in the 0° direction is a circular spot with a diameter of 2.5 cm.

6.3 Test conditions 1

According to the requirements of IEC-60825, the test shall be carried out according to the test condition 1 first. The white LED exit hole is 2m away from the light receiving port, and the diameter of the light receiving port is 50mm.

Analysis of test results:

Type 1 AEL calculation

Photochemical hazards at 400-600nm: not exceeding the specified AEL

400-700nm thermal hazard: not exceeding the specified AEL

AEL of 700-1400nm: does not exceed the specified AEL

Conclusion: The light radiation output of the white LED measured under test condition 1 does not exceed the AEL regulations for Class 1 laser products.

6.4 Test conditions 2

The light exit hole of the white LED is 100m away from the light receiving port, and the diameter of the light receiving port is 7mm.

Analysis of test results:

(1) Type 1 AEL calculation

Photochemical hazard AEL at 400-600nm: exceeding the specified AEL

Conclusion: The white light LED exceeds the AEL regulations for photochemical hazards of Class 1 laser products, and does not belong to Class 1 products.

(2) Calculation of Type 2 AEL

AEL of 400 ~ 700nm: does not exceed the specified AEL

AEL of 700 ~ 1400nm: not exceeding the specified AEL

Conclusion: The white LED under test condition 2 does not exceed the AEL regulations for Class 2 laser products.

6.5 Irradiance or radiance test conditions

In the above test process, the test structure of test condition 2 is the same as that of irradiance or radiance test conditions, and the 1M category AEL refers to the regulations of 1 category AEL, so it can be seen from the above analysis that the light radiation output of this white LED exceeds the 1M category AEL .

6.6 Conclusion

Based on the above analysis, it can be seen that the tested white light LED product belongs to the category 2 LED products, and looking directly at the LED for a long time will damage the human retina. However, under normal circumstances, since the human eye has a natural avoidance response such as blinking, it will not cause damage to the human eye.

Through the above introduction, we can see that the testing and evaluation of LED optical radiation safety is a very complicated process involving many aspects. However, the testing and evaluation of LED optical radiation safety has gradually become an indispensable content in LED product testing. test. Therefore, we should increase research investment in this field.

7. LED light color measurement and lighting evaluation

The ultimate goal of LED lighting is to obtain the best lighting effect, and judging the quality of the lighting effect depends on the light color measurement of the LED.

7.1 Evaluation of current lighting

The current lighting evaluation is mainly based on several main optical basic quantities: luminous flux, luminous brightness, light intensity and illuminance, among which the first three basic quantities are mainly used for the evaluation of the light source, and the illuminance is the evaluation of the light radiation action surface of the light source.

These basic optical quantities are obtained based on the biophysical characteristics of the human eye, and are also the result of a weighted integral of the spectral luminous efficiency function V(λ) and the corresponding radiance measure approved by the International Commission on Illumination (CIE), satisfying the following relationship:

Photometric (λ) = KmgV (λ) radiometric (λ), Km—683 Lm/W.

7.2 Existing problems and deficiencies

The biophysical mechanism of the human eye is very complex, and the response to light stimuli is different in different situations. It can be roughly divided into photopic vision, scotopic vision, and intermediate vision. Among them, intermediate vision is particularly complicated, so the above-mentioned spectral luminous efficiency is not accurate. accurately represent the actual effect of lighting. As shown in Figure 10, the same light source has significantly different stimulation values to human eyes under photopic and scotopic vision. In addition, the current domestic lighting evaluation lacks the consideration of photobiological safety, which may cause different degrees of harm to the human body.

7.3 Solutions

7.3.1 Test methods and instruments

The spectral distribution of the LED is measured by the full spectrum method, and then the spectrometer is used for spectroscopic testing.

7.3.2 Evaluation method

(1) Lighting effect According to different visual conditions, different spectral luminous efficiency functions are used to weight the LED spectral distribution data to obtain the actual lighting effect of the light radiation of the measured light source under corresponding visual conditions. For example, the scotopic spectral luminous efficiency function is used for scotopic vision, the photopic spectral luminous efficiency function is used for photopic vision, and the mesopic spectral luminous efficiency function is used for mesopic vision.

(2) Photobiological safety

According to the type of hazard, use the corresponding effect function to weight the LED spectral distribution data to obtain the actual hazard effect

In short, the evaluation of LED lighting should be in line with the actual biophysical needs of the human body.

8 Summary and Outlook

(1) The development of the LED industry is inseparable from the light and color measurement technology of LEDs. In order to adapt to the application of LED lighting, there should be new breakthroughs in the light and color measurement technology in the future.

(2) LED lighting and light color measurement should be people-oriented, and everything is oriented to meet the actual requirements of human beings.

(3) Current tasks:

①Strengthen research on basic biological theories related to the human body, and promote cross-disciplinary cooperation;

② In line with international standards, speed up the formulation and implementation of normative documents, and actively participate in the activities of internationally renowned organizations such as CIE and IEC;

③Increase investment in scientific research and develop light and color measuring instruments with independent intellectual property rights;

④Strengthen the research of various testing technologies, train professional testing personnel, and accelerate the improvement of the equipment level and testing capabilities of quality inspection institutions.

Ceramic high power led material

Ceramic high-power LEDs are composed of ceramic substrates, solid primers, chips, gold wires, fluorescent powder (white light), silica gel and other main materials.

1. The function of ceramic substrate:
Ceramic substrates are divided into alumina ceramic substrates and aluminum nitride ceramic substrates. The thermal conductivity of alumina ceramic substrate is 30W/M*K, generally used for 1-3W, aluminum nitride ceramic substrate is 100-200W/M*K, generally used for 5W.
Material of ceramic substrate:
Used for conduction, heat dissipation and connection. It is mainly to sinter ceramic powder into a ceramic substrate, and then distribute copper, nickel plating, copper plating, and silver plating on the substrate.

2. Solid primer: Different from low-power primer, ceramic high-power LED diodes use nano-silver glue and poured gold-tin alloy flux because of their high power and high heat. The crystal primer has the functions of fixing the chip and conducting electricity.

3. The role of the chip: The chip is the main component of the LED light source and is a luminous semiconductor material.
a) Chip composition: The chip is made of gallium phosphide (GaP), gallium aluminum arsenide (GaAlAs) or gallium arsenide (GaAs). Gallium nitride (GaN) and other materials, and its internal structure has unidirectional conductivity.
b) Chip structure: Weld single-wire positive polarity (P/N structure) wafers and double-wire wafers. Wafer size unit: mil. Wafer pads—typically gold or aluminum pads. The pad shape is round, square, cross and so on.
c) Luminous color: The luminous color of the chip depends on the wavelength. The classification of common visible light is roughly: far red light (700-7400nm), deep red light (640-660nm), red light (615-635nm), amber light (600nm) -610nm). Yellow light (580-595nm). Yellow-green light (565-575nm). Pure green light (500-540nm). Color (450-480nm). Purple (360-430nm).
4) High-power LED chip: It is divided into two processes: vertical structure and horizontal structure. The vertical structure chip needs gold wire.

4. Wire material
a) Gold wire: 99.99% gold wire, connect the chip PAD (welding pad) with the bracket, and make it conductive. Au: The elongation rate is 2-6%,
a) Gold wire size: 0.9mil.1.0mil.1.2mil.1.5mil etc.

5. Phosphor powder, mainly used to adjust the color of white light, monochromatic light does not need phosphor powder.

6. Mold top glue: mainly used to protect chips and gold wires.

LED waterproof tube structure

The waterproof lamp tube is composed of a lamp board, a lamp housing, a waterproof component and a heat-dissipating aluminum material, and it can also be called a waterproof lamp tube. That is, the outer ring is a sealed PC tube with an aluminum strip and D-shaped aluminum material added inside.

It is mainly aimed at solving the problems of the poor heat dissipation effect of the all-plastic pipe and the single matching plug, which can improve the safety performance of the finished product to a certain extent, and can use the aluminum structure to reduce the formation of plastic pipes after long-term lighting temperature rises. the camber.

At present, the outer shell of the lamp tube can be made into a full diffuser tube, a fully transparent tube, a blue-backed two-color tube, a white-backed two-color tube, and the waterproof lamp shell kit covers T5, T6, T8, T10, T12 and other series of products ,

Because aluminum is added, it is equivalent to a tube in a tube. Customers can choose different diameters, circuit board specifications, and lighting angles according to their needs. And our company’s waterproof lamp shell

Screw holes are designed on the aluminum material, which can be matched with various LED plugs provided by our company. At present, the shell of the lamp tube is widely used in LED waterproof tube.

1. Product Features

LED LED waterproof tube, high brightness and high color rendering index, soft light, easy installation, appearance and size are the same as traditional integrated brackets, and can be directly replaced by traditional integrated brackets;

The radiator is made of aluminum alloy with high thermal conductivity to ensure the product can effectively dissipate heat, ensure the stability and long life of the product, and the appearance is exquisite and beautiful;

Energy saving and environmental protection, high efficiency, low carbon, no ultraviolet rays, no glare.

Using LED light source, long life, low power consumption, durable

Adopt amorphous, odorless, non-toxic and highly transparent PC thermoplastic engineering plastics, which have excellent physical and mechanical properties and can be used for a long time at low temperature.

The circuit board adopts a full glass fiber circuit board with low water absorption and good moisture resistance, with a thickness of 1.2mm, which can dissipate heat quickly and is not easy to break.

The structure of the lamp body is made of waterproof stainless steel screws, filled with excellent performance sealant, the outer layer is tightly wrapped with waterproof silicone sleeve, double-layer waterproof, and the protection level reaches IP65/IP67.

LED waterproof tube has high brightness and high color rendering index, soft light, easy installation, the same appearance and size as the traditional integrated bracket, and can be directly replaced by the traditional integrated bracket

2. Product description

Specifications and models: T5 LED waterproof tube, T6 LED waterproof tube, T8 LED waterproof tube, etc.

Light source chip: Epistar 2835 LED lamp beads are light, which can save 80% energy than incandescent lamps.

Lamp bead brand: Philips, Osram, Hongli=

Service life: up to 50000 hours service life

Input voltage: AC100-240V 50/60HZ

Protection level: filled with high-quality performance sealed waterproof silicone, the outer layer is tightly wrapped with waterproof silicone sleeve, using transparent AB glue, protection level IP65/IP67

Heat dissipation solution: the circuit board adopts a full glass fiber circuit board with low water absorption and good moisture resistance, with a thickness of 1.2mm and fast heat dissipation

Shell material: PC, aluminum, PC+aluminum, all-plastic thermoplastic engineering plastic [Waterproof type is usually the best solution with all-plastic priority] IP67 waterproof lamps can effectively protect the farm when cleaning the farm.

The lamp tube avoids water ingress. The special all-plastic PC tube can resist cleaning chemicals, especially ammonia, and achieve the effect of anti-oxidation and aging.

Light transmission performance: The light transmittance of the transparent PC cover is 94-96%, and the light diffusion large stripe PC cover has a light transmittance of 90-92%. Light diffusion PC cover light transmittance 85-88%

Flame retardant grade: PC cover Flame retardant grade: 94-V2 or 94-V0

Energy saving and environmental protection: high efficiency, low carbon, no ultraviolet rays and energy savin

g of 60%. The LED light source has a long service life and low power consumption, and is durable. Odorless, non-toxic PC plastic, with excellent physical properties, can work at low temperature for a long time

3. Scope of application

Application fields: Mainly used in chicken farms, pig houses, chicken houses, poultry farms, etc. Planting plants, planting plants, fish tanks, fresh food, beverages, refrigerators, freezers, or indoor and outdoor humid areas, etc.

4. Product size

L1: 586mm, 1196mm, 1496mm L2: 605mm, 1215mm, 1515mm

Luminous intensity: The measurement units of luminous intensity include illuminance unit (lux), luminous flux unit (lumen Lumen), luminous intensity unit (candle power). 1CD (candle power) refers to a completely radiated object;

Luminous intensity per sixtieth square centimeter area at the freezing point of platinum. (It used to refer to a whale oil candle with a diameter of 2.2 cm and a mass of 75.5 grams, burning 7.78 grams per hour, a flame height of 4.5 cm, and the luminous intensity along the horizontal direction) 1L (lumen) refers to 1 CD candlelight irradiated at a distance of 1 cm , the luminous flux on a plane with an area of 1 cm2.

1Lux (lux) refers to the illuminance at which 1L of luminous flux is evenly distributed on an area of 1 square meter. Generally, the active luminous body adopts the unit of luminous intensity, candlepower;

CD, such as incandescent lamps, LEDs, etc.; reflective or penetrating objects use luminous flux unit lumen LM, such as LCD projectors, etc.; and illuminance unit Lux,

Generally used in photography and other fields. The three units of measurement are numerically equivalent, but need to be understood from different perspectives. For example: if the brightness (luminous flux) of an LCD projector is 1600 lumens, and the size of its projection onto a fully reflective screen is 60 inches (1 square meter), its illuminance is 1600 lux, assuming that its light outlet is 1 cm, and the area of the light outlet is 1 square centimeter, then the luminous intensity of the light outlet is 1600CD.

However, due to the loss of light transmission, loss of reflection or light-transmitting film, and uneven distribution of light, the brightness of a real LCD projector will be greatly reduced. Generally, an efficiency of 50% is good. In actual use, light intensity calculations often use data units that are easier to survey and map or change directions.

For active illuminants such as LED displays, CD/square meter is generally used as the unit of luminous intensity, and the viewing angle is used as an auxiliary parameter, which is equivalent to the illuminance unit lux on the surface of the screen; this value is compared with the effective display area of the screen. Multiplied together, the luminous intensity of the entire screen at the best viewing angle is obtained, assuming that the luminous intensity of each pixel in the screen is constant in the corresponding space,

Then this value can be considered as the luminous flux of the whole screen. Generally, the outdoor LED display must reach a brightness of more than 4000CD/square meter to have an ideal display effect under sunlight. For ordinary indoor LEDs, the maximum brightness is about 700-2000 CD/square meter.

The luminous intensity of a single LED is in CD, and it is equipped with viewing angle parameters. The luminous intensity has nothing to do with the color of the LED. The luminous intensity of a single tube varies from a few mCDs to five thousand mCDs. The luminous intensity given by the LED manufacturer refers to the point where the LED lights up at a current of 20mA, the best viewing angle and the center position with the highest luminous intensity.

The shape of the top lens and the position of the LED chip from the top lens when packaging the LED determine the LED viewing angle and light intensity distribution. Generally speaking, the larger the viewing angle of the same LED, the smaller the maximum luminous intensity, but the accumulated luminous flux on the entire three-dimensional hemisphere remains unchanged. When multiple LEDs are arranged closely and regularly, their luminous spherical surfaces overlap with each other, resulting in a relatively uniform distribution of luminous intensity across the entire luminous plane. When calculating the luminous intensity of the display screen, it is necessary to multiply the maximum point luminous intensity value provided by the manufacturer by 30% to 90% according to the LED viewing angle and the LED emission density, as the average luminous intensity of a single tube.

Generally, the luminous life of LEDs is very long, and manufacturers generally mark it as more than 100,000 hours. In fact, attention should also be paid to the brightness decay cycle of LEDs. Only half of the original. The brightness decay period has a lot to do with the material process of LED production.

Generally, four-element LEDs with slower brightness decay should be selected when economic conditions permit. Color matching and white balance: White is a mixture of red, green and blue according to the brightness ratio. When the brightness of green in the light is 69%, the brightness of red is 21%, and the brightness of blue is 10%. Arrived in pure white.

However, the chromaticity coordinates of the red, green and blue colors of LED cannot achieve the effect of the full spectrum due to the process and other reasons, and controlling the brightness of the primary colors including the deviation of the primary colors to obtain white light is called color matching. Before color matching for full-color LED displays, in order to achieve the best brightness and the lowest cost, try to choose LED devices with a ratio of 3:6:1 to form pixels. White balance requires that the three primary colors synthesized under the same gray value are still pure white. Primary color, primary color: Primary color refers to the basic color that can synthesize various colors. The primary colors in color light are red, green, and blue. The figure below is a spectrum table, and the three vertices in the table are ideal primary color wavelengths. If the primary color deviates, the area where the color can be synthesized will decrease, and the triangles in the spectral table will shrink. From a visual point of view, the color will not only deviate, but also reduce the richness.

The red, green and blue light emitted by LEDs can be roughly divided into purple red, pure red, orange red, orange, orange yellow, yellow, yellow green, pure green, emerald green, blue green, pure blue, blue purple, etc. according to their different wavelength characteristics and orange red. , Yellow-green, and blue-purple are much cheaper than pure red, pure green, and pure blue. Among the three primary colors, green is the most important, because green occupies 69% of the brightness of white, and is in the center of the color horizontal arrangement table. Therefore, when weighing the relationship between the purity of the color and the price, green is the most important object to consider.

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LED is an abbreviation taken from the three words Light Emitting Diode, a light emitting diode is an electronic device that can convert electrical energy into light energy and has the characteristics of a diode. At present, different light-emitting diodes can emit light of different wavelengths from infrared to blue, and light-emitting diodes that emit purple or even ultraviolet light have also been born. In addition, there are white LEDs that coat phosphors on blue LEDs to convert blue light into white light.

LED color and process:

Different materials for making LEDs can produce photons with different energies, so that the wavelength of light emitted by the LED can be controlled, that is, the spectrum or color.

The material used in the first LED in history is arsenic (As) gallium (Ga), its forward PN junction voltage drop (VF, which can be understood as lighting or working voltage) is 1.424V, and the light emitted is infrared spectrum .

Another commonly used LED material is gallium (P) phosphide (Ga), its forward PN junction voltage drop is 2.261V, and the light emitted is green. Based on these two materials,

the early LED industry used the GaAs1-xPx material structure, which can theoretically produce LEDs with any wavelength from infrared light to green light.

The subscript X represents the percentage of phosphorus replaced by arsenic. Generally, the wavelength and color of the LED can be determined by the voltage drop of the PN junction. Typical ones are red LEDs of GaAs0.6P0.4, orange LEDs of GaAs0.35P0.65, yellow LEDs of GaAs0.14P0.86, etc. Because gallium, arsenic, and phosphorus are used in the manufacture, these LEDs are commonly known as three-element light-emitting tubes. GaN (gallium nitride) blue LEDs, GaP green LEDs and GaAs infrared LEDs are called two-element light-emitting tubes. At present, the latest technology is a four-element LED made of AlGaInN four-element material mixed with four elements of aluminum (Al), calcium (Ca), indium (In) and nitrogen (N), which can cover all visible light and some ultraviolet light. The spectral range of light.

Ps.
1. Direct energy gap: The range of lattice constant X<0.49 is called direct energy gap, and the luminous efficiency is higher.
2. Indirect energy gap: The range of lattice constant X>0.49 is called indirect energy gap.

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LED Basic Principles

LED Light-emitting diodes (LEDs) are optoelectronic components made of III-V compound semiconductors, and their core is a PN junction. Under the forward voltage, electrons are injected into the P region from the N region, holes are injected into the N region from the P region, and part of the minority carriers entering the opposite region recombine with the majority carriers to emit light. The material properties (band gap width) forming the PN junction determine the wavelength of the emitted light, and for visible light, it determines the color of the light.

The main features of LEDs are: small size, low power consumption, long service life, high brightness and low heat, environmental protection and durability. Working under proper current and voltage, the service life of LED can be as long as 100,000 hours.

Classification and application of LED

According to the type of light emitted, LEDs can be divided into two types: visible light LEDs and invisible light LEDs.

At present, the packaging types of LED products mainly include Through Hole LEDs, Surface Mounting (SMD), Direct Bonding (Direct Bonding), etc. Among them, SMD LEDs are smaller than other traditional LEDs, so SMD LEDs are mainly used for mobile phone screen backlight and mobile phone buttons, and are greatly affected by mobile phone demand.

Visible light LEDs include red, orange, yellow, green, blue, and purple LEDs. Among them, GaP (binary system), AlGaAs (ternary system) and AlGaInP (quaternary system) are the main materials for red LEDs; GaN is the main material for blue/white LEDs.

The application of LED is very extensive, mainly including:

1. LED display screen: indoor and outdoor billboards, sports scoreboards, information display screens, etc.;
2. Signal indicator lights: urban traffic lights, expressway, railway and airport signal lights in major and medium-sized cities across the country, and electronic equipment function indications;
3. Light color lighting: outdoor landscape lighting and interior decoration lighting;
4. Special general lighting: portable lighting (flashlight, headlight), low-light lighting (corridor lights, house lights, family lights), reading lighting (reading lights for airplanes, trains, and cars), microscope lights, camera flashes, desk lamps , street lights;
5. Safety lighting: miner’s lamp, explosion-proof lamp, emergency lamp, safety indicator lamp;
6. Backlight: Backlight for LCD monitors and LCD TVs.
7. Automotive lights: including interior lighting and exterior lighting. The interior of the car includes dashboards, electrical product indicators (switches, audio, etc.), switch backlights, reading lights, and external brake lights, tail lights, side lights and headlights. lights etc.
8. Other applications: consumer use, such as children’s flash shoes, Christmas tree LED lights, etc.

LED industry chain

The entry threshold of the LED industry chain from upstream to downstream industries is gradually lowered. The upstream is single wafer and its epitaxy, the midstream is LED chip processing, and the downstream is packaging testing and application. Among them, the upstream and midstream areas have high technological content and high capital investment density, which are the areas with the most intense international competition and the greatest operating risks. In the LED industry chain, LED epitaxial wafers and chips account for about 70% of the industry’s profits, LED packaging accounts for about 10-20%, and LED applications account for about 10-20%.

A single wafer is the base for manufacturing LEDs, also known as a substrate, and sapphire, silicon carbide, GaAs, and GaP are mostly used as materials. Epitaxial wafers are grown on single crystals with multiple layers of single crystal films of different thicknesses, such as AlGaAs, AlGaInP, GaInN, etc., to realize LEDs of different colors or wavelengths. Common epitaxy methods include liquid phase epitaxy (LPE), vapor phase epitaxy (VPE), and metal organic chemical vapor deposition (MOCVD), among which VPE and LPE technologies are quite mature and can be used to grow LEDs with general brightness. The growth of high-brightness LED must adopt the MOCVD method. At present, the main manufacturers of MOVCD in the world are AIXTRON Company of Germany and VEECO Company of the United States. The former accounts for about 60% to 70% of the international market share, and the latter accounts for 30% to 40%. The equipment produced by Japanese manufacturers is basically limited to domestic sales in Japan.

The midstream is mainly chip design and processing. Midstream manufacturers carry out device structure and process design according to the performance requirements of LEDs, diffuse through epitaxial wafers, then metal coat, then perform photolithography, heat treatment, form metal electrodes, and then cut the substrate after grinding and polishing.

Downstream includes packaging, testing and application of LED chips. LED packaging refers to connecting the outer leads to the electrodes of the LED chip to form an LED device. The packaging plays the role of protecting the LED chip and improving the efficiency of light extraction. LED packaging technology is developed from the packaging technology of semiconductor discrete devices.

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1. LED light-emitting diode light-emitting color:

According to the luminous color of the luminous tube:

It can be divided into red, orange, green (subdivided into yellow-green, standard green and pure green), blue light and so on. In addition, some LED light-emitting diodes contain chips of two or three colors.

According to whether the light-emitting diode is mixed or not mixed with scattering agent, colored or colorless,

The above-mentioned light-emitting diodes of various colors can also be divided into four types: colored and transparent, colorless and transparent, colored scattering and colorless scattering. Scattering light-emitting diodes can be used as indicator lights.

2. LED light-emitting diode light-emitting surface points:

According to the characteristics of the light-emitting surface of the luminous tube, it is divided into a round lamp with a through hole, a square lamp with a through hole, a rectangular through-hole, a front luminous tube, a side tube, and a micro tube for surface mounting.

The through hole circle is divided into φ2mm, φ4.4mm, φ5mm, φ8mm, φ10mm and φ20mm according to the diameter. In foreign countries, the φ3mm light-emitting diode is usually recorded as T-1; the φ5mm is recorded as T-1 (3/4); the φ4.4mm is recorded as T-1 (1/4).

The angular distribution of circular luminous intensity can be estimated from the half-value angle. From the angular distribution of luminous intensity, there are three categories:

1) High directivity: Generally, it is a pointed epoxy package, or a package with a metal reflective cavity, and no scattering agent is added. The half-value angle is 5°~20° or less, with high directivity, it can be used as a local lighting source, or combined with a photodetector to form an automatic detection system;

2) Standard type: usually used as an indicator light, its half-value angle is 20°~45°;

3) Scattering type: This is an indicator light with a larger viewing angle, the half-value angle is 45°~90° or greater, and the amount of scattering agent is relatively large.

3. According to the structure of light-emitting diodes

According to the structure of light-emitting diodes, there are full epoxy encapsulation, metal base epoxy encapsulation, ceramic base epoxy encapsulation and glass encapsulation.

4. According to luminous intensity and working current

According to the luminous intensity and working current, there are LEDs with ordinary brightness (luminous intensity 100mcd);

The luminous intensity between 10~100mcd is called high-brightness LED light-emitting diode. Generally, the working current of LED is more than ten mA to tens of mA, while the working current of low-current LED is below 2mA (the brightness is the same as that of ordinary light-emitting tubes).

In addition to the above classification methods, there are also methods of classification by chip material and classification by function.

Its main categories are:

1) LED (Light emitting diode): We have LED products called LEDs, some called P2 products, and some called DIP LEDs. In any case, as long as they are in-line, they belong to one type. There are many types of LED types:

According to the shape of the colloid: 3mm, 4mm, 5mm, 8mm, 10mm, 12mm, square, oval, tombstone, and some special shapes, etc.;

According to the color of the colloid: colorless and transparent, colored and transparent, colored scattering, colorless scattering, etc.;

By color: red (red), orange (orange), yellow (yellow), yellow-green (green yellow), green (green), blue-green (blue green), blue (blue), purple (pink), ultraviolet (uv), white (white), infrared, etc.;

2) SMD (Suface mount device): Surface mount diodes or surface mount components are his names, and there are many categories in this:

Divided by shape and size: 0603, 0805, 1210, 5060, 1010, etc. Generally, SMD is diamond-shaped, so its name is based on the size of length * width. The industry is good at using inches, not millimeters. It is also called in millimeters, not as good as 1608 (1.6*0.8mm).

The luminous color and the type of colloid are the same as LED products, but the shape of the product has changed a lot.

3) Piranha (Flux led): This product is developed because the luminous efficiency of LED cannot meet the requirements of automobiles. It is a low-power product. The driving current is generally 50MA, and the maximum current is 20MA for ordinary LEDs. It can reach 70mA, because of its better heat dissipation, it is generally used in the rear lights of cars.

4) High power (power led): LED products for existing lighting, it has the following classifications:

①According to the power: 1w, 3w, 5w, etc.;

② According to the top light-emitting lens: flat head, spotlight, wine glass shape, etc.;

③According to the process, there are also aluminum substrates and anti-luminous ones.

5) LED digital tube (LED Display): It was first used as a display screen and digital display

According to the shape: 1, 2, 3, 4, etc.;

Surface color: gray surface black glue, black surface white glue, etc.;

Polarity: Common Yin, Common Yang;

The color can also be made into many kinds like LED.

6) Dot Matrix (LED Dot Matrix): This product is similar to a digital tube, and is used for information display. Changes in the spacing and diameter of the holes are different products. Now it is generally divided into 5*7 and 8*8, and its colors include single-color, double-color, three-color and so on.

① According to the color: single red, single green, double primary color, three primary colors, etc.;

② According to the diameter of the hole: Φ2.0, Φ3.0, Φ3.75, Φ5.0, etc.;

③According to points: 5*7, 8*8, 16*16, etc.;

④There are some other products: such as pixel tube (cluster), measuring light source (LED Side Light Source), infrared receiving and emitting products (Infrared & PhotoDiode) and so on.

Simply put, it is a kind of light intensity energy unit. The energy unit of light intensity is generally represented by J/m² and mJ/cm², that is, the light energy per unit area. So what is the conversion rate between these units?

1. UV energy unit conversion method

1J/cm² = 1000mJ/cm² = 1000000uJ/cm²

1J/m² = 1000mJ/m² = 1000000uJ/m²

1J/m² = 0.1mJ/cm²

In the parameter table of many uv energy meters on the market, there are not only “energy measurement range” but also “power measurement range”. In fact, simply speaking, the two are inseparable, because “energy = power * time”. Since power is mentioned in the formula, what is the unit of power in the instrument?

1 joule (J) = 1 Newton meter = 1 watt (W) second (S)

UV intensity unit conversion method:

1W/m² = 1000 mW/ m² = 1000000uW / m²

1W/m² = 1000mW/ 10000 cm² = 0.1mW/cm² = 100uW/cm²

And the unit of power: E = W *t

1 W = 10³ mW (milliwatts) = 106 uW (microwatts)