High power LED lens knowledge

High-power LED lens /reflector cup is mainly used for focusing and guiding high-power LED cold light source series products. High-power LED lens is designed according to the angle of different LED output light distribution curves , by increasing optical reflection, reducing light loss and improving light efficiency (and setting aspherical optical lens). The following focuses on the secondary focusing high-power LED lens of PMMA material.

Types of materials for LED lens
1. Silicone lens;
a. Because silicone has high temperature resistance (can also be reflow soldered), it is often directly encapsulated on LED chip ;
b. Generally, silicone lens is small in size, with a diameter of 3-10mm;
2, PMMA lens
a. Optical grade PMMA (polymethyl methacrylate, commonly known as: acrylic)
b. Plastic material, advantages: high production efficiency (can be completed by injection molding); high light transmittance (penetration rate is about 93% when the thickness is 3mm); disadvantages: temperature resistance of 70% (thermal deformation temperature of 90 degrees);
3. PC lens
a. Optical grade nylon material Polycarbonate (PC for short)
b. Plastic material, advantages: high production efficiency (can be completed by injection molding); high temperature resistance (above 130 degrees); disadvantages: slightly low light transmittance (87%);
4. Glass lens
Optical glass Material, with high light transmittance (97%) and high temperature resistance, disadvantages: fragile, difficult to achieve aspheric precision, low production efficiency, high cost, etc.

2. Application classification of LED lenses
1. Primary lens
a. The primary lens is directly packaged (or bonded) on the LED chip bracket and becomes a whole with the LED;
b. Theoretically, the LED chip emits 360 degrees, but in fact, the chip is fixed and packaged on the LED bracket, so the maximum emitting angle of the chip is 180 degrees. In addition, there will be some stray light from the chip. In this way, the primary lens can effectively collect all the light from the chip and obtain a light output angle of 160 degrees, 140 degrees, 120 degrees, 90 degrees or even 60 degrees (different needs);
c. The primary lens is mostly made of PMMA or silicone.
2. Secondary lens
a. The secondary lens and LED are two independent objects, but they are inseparable when used;
b. The function of the secondary lens is to refocus the large-angle light of the LED (generally 90-120 degrees) into any desired angle from 5 degrees to 80 degrees;
c. The secondary lens material is mostly PMMA or glass.

III. LED lens specification classification
1. Transmission type (convex lens)
a. When the LED light passes through a curved surface of the lens (double convex has a curved surface), the light will be refracted and focused, and when the distance between the lens and the LED is adjusted, the angle will also change (inversely proportional). The curved surface designed with aspheric technology will have a very uniform light spot , but due to the limitation of the lens diameter, the light on the side of the lens cannot be used (light leakage);
b. Generally used for focusing at a large angle (40-80 degrees), such as table lamps, street lamps, indoor lamps, etc.;
2. Total reflection type (cone or cup type)
a. The design of the lens uses a transmissive focusing method in front, and the conical surface can collect and reflect all the side light, and the overlap of these two kinds of light (at the same angle) can obtain the most perfect light utilization and beautiful light spot effect;
b. You can also make some changes to the surface of the conical lens, which can be designed into a mirror surface, frosted surface, bead surface, striped surface, threaded surface, convex or concave surface, etc. to obtain different light spot effects.
3. LED lens module
a. It is a multi-lens that is completed as a whole by injection molding multiple single lenses. It can be designed into a 3-in-1, 5-in-1 or even dozens of lenses in one lens module according to different needs;
b. This design effectively saves production costs, achieves consistency in product quality, saves space for lamp mechanisms, and makes it easier to achieve "high power " and other characteristics.

Design and mold processing of four LED lenses
1. First of all, it depends on the light source (high-power LED). Different brands of high-power LEDs (such as CREE , lumileds, Seoul, OSRAM , Edison, Changsenyuan, etc.) have different chip structures, packaging methods, and light characteristics, which will cause the same lens to be different when paired with different specifications and brands of LEDs; so targeted development (oriented to mainstream brands) is required to meet actual needs;
2. Use optical design software (such as Trace pro, CodeV, Zemax , etc.) to design and simulate optical light scattering, and design the corresponding optical aspheric surface;
3. LED lens itself is a precision optical component, so it has extremely high requirements for mold precision, especially the processing precision of the lens optical surface must reach 0.1μm, and the lens eccentricity must reach within 3μm. Generally, the following equipment must be used for the processing of such high-precision molds: ultra-precision processing machines (for example: PRECITECH NANOFORM 350), CNC integrated processing machines, surface grinders, milling machines, CNC EDM machines, surface profilers, etc.
4. The most precise part of the mold is the optical mold core. First, special mold core steel is selected to complete the initial embryo, and then the ultra-precision processing machine is used to process the surface with aspheric technology after nickel plating. 5. Materials and

production of LED lenses
1. As an optical-grade product, LED lenses have extremely high requirements for light transmittance and shrinkage. The raw materials generally use high-grade optical-grade PMMA. At present, Japan's Mitsubishi PMMA material is the best (the current VH5 and VH001 are of higher quality), and the Nantong material of Mitsubishi is slightly inferior;
2. A dust-free workshop of Class 10,000 or higher must be equipped. Operators must wear anti-static clothing, finger cots, masks and other anti-static and dust-proof measures, and the workshop must be inspected and cleaned regularly.
3. Professional optical injection molding machines (electric) such as Falak, Toyo, Haitian, Garmin and other brands with a power of more than 35T are required, and the injection temperature and time are strictly controlled to reduce the shrinkage rate of the product. The nozzle material must not be added for reuse to ensure that the product is more in line with the design plan;
4. The product must be packaged in anti-static and dust-proof PV C, and must be completely sealed. The temperature and humidity must be controlled during storage, and it is best not to store it for more than one year.