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Overview of Optical Filter Classifications and Coating Technologies Optical filters are essential components in various optical systems, designed to transmit specific wavelengths while blocking others. Their classification is based on functional mechanisms and application scenarios, with coating technologies playing a critical role in enhancing performance. Classification of Optical Filters Primary Classification by Working Principle Absorptive FiltersThese filters are typically made of glass doped with organic or inorganic compounds that absorb specific wavelengths. For example, certain compounds in the glass matrix block unwanted light, allowing only target wavelengths to pass through. Dichroic Filters (Interference Filters)Unlike absorptive filters, dichroic filters rely on optical coatings to reflect unwanted wavelengths and transmit desired ones. The coating's thickness and material properties determine precise wavelength control, making them widely used in scientific instruments and cameras. Key Role of Coatings in Dichroic Filters Dichroic filters owe their precision to advanced coating technologies Coating Materials and ThicknessMultilayer coatings (e.g., dielectric materials) are deposited to create interference effects. The thickness of each layer is engineered to reflect specific wavelengths, enabling high transmittance for target ranges. Performance AdvantagesCompared to absorptive filters, dichroic filters exhibit lower heat generation (since reflection replaces absorption) and higher wavelength selectivity, making them ideal for scientific research and precision optical systems Application-Specific Coating and Design Examples Projection Display Devices In projection systems, optical filters may integrate polarizing plates, flat glass substrates, and silicone gel bonding layers. The silicone gel layer, with a higher refractive index than air, reduces reflection losses and improves surface smoothness, enhancing light transmission efficiency. This design ensures optimal polarization and image clarity. Pattern Recognition Systems Hybrid optical processors for pattern recognition use filters encoded with phase-coded pattern functions. These filters, often created as computer-generated holograms, enable efficient computation of inner products between input patterns and reference functions, critical for classification tasks. Summary Optical filter are classified into absorptive, dichroic, and application-specific types, with dichroic filters leveraging coating technologies for superior precision. Coatings determine wavelength selectivity, while innovative designs (e.g., silicone gel bonding) further optimize performance in specialized applications like displays and pattern recognition.

When it comes to high-performance infrared and laser optics, conventional optical glass is not always sufficient. Different systems demand materials with exceptional transparency, durability, and thermal stability across specific wavelength ranges. Below are several specialty optical materials that play a critical role in aerospace, defense, spectroscopy, laser systems, and scientific research. ? ZnSe (Zinc Selenide)With low absorption and high thermal expansion resistance, ZnSe is widely used in high-power CO₂ laser systems as substrates for mirrors and beam splitters. However, its relative softness (Knoop hardness ~120) makes it less suitable for harsh environments, requiring careful handling and cleaning. ? ZnS (Zinc Sulfide)CVD ZnS is chemically inert, highly pure, and easy to machine. It offers excellent transmission in the 8–12 μm range, making it ideal for IR windows, domes, and imaging optics. Compared with ZnSe, it provides higher hardness and fracture strength, ensuring better durability in demanding conditions. ? CaF₂ (Calcium Fluoride)Transparent from 250 nm to 7 μm, CaF₂ is perfect for prisms, windows, and lenses, especially in broad-spectrum applications. With low absorption and high laser damage threshold, it is widely used in excimer laser systems. ? BaF₂ (Barium Fluoride)Covering a wide range of 0.13–14 μm, BaF₂ is suitable for optical windows, prisms, and lenses. It is commonly used in FTIR gas analysis, IR power distribution, oil & gas detection, and high-power laser systems. ? Ge (Germanium)Known for its high hardness and refractive index, Ge is commonly coated with AR films (3–12 μm or 8–12 μm). Best suited for use below 100 °C due to thermal sensitivity, it is ideal for IR optics where strength and stability are required. ? Si (Silicon) Single-crystal silicon transmits well from 1.2–7 μm and 30–300 μm, making it unique among IR materials. With excellent thermal conductivity and low density, it is widely used in MWIR windows, optical filters, and lightweight laser mirrors.   Each of these materials—ZnSe, ZnS, CaF₂, BaF₂, Ge, and Si—offers unique optical and mechanical properties that make them indispensable in advanced infrared technologies. At China Star Optics Technology, we custom-produce optics using these materials according to customer requirements, ensuring broad spectral coverage, high durability, and resistance to extreme environments—delivering the precise, reliable performance demanded by modern optical systems.  

Every time light passes from one medium to another, part of it is transmitted, part is reflected, and part may be absorbed by the material. While absorption losses depend mainly on the choice of glass, reflection losses can be effectively minimized with anti-reflection (AR) coatings. Let’s look at the numbers: Uncoated optical glass reflects about 8% per surface. A typical photographic lens with 7 elements has 14 air-to-glass surfaces. Without coatings, each surface transmits only 92% of incoming light. Multiply that over 14 surfaces ≈ 31% transmission. In other words, nearly 70% of the light never makes it through the lens. Now consider AR coatings: With coatings, reflection per surface can be reduced to below 2%. Transmission per surface rises to about 98%, giving ≈ 75% transmission. That’s more than double the light efficiency compared to an uncoated lens. This improvement is not just about brightness—it also means reduced glare, higher contrast, and sharper imaging. From professional photography to telescopes, microscopes, and advanced optical instruments, AR coatings are a fundamental step in achieving high-performance optics. At China Star Optics Technology, we combine advanced coating technologies with precision polishing to ensure that every optical component delivers maximum light transmission and long-term reliability. Whether you need single-layer AR coatings or multi-layer broadband solutions, we provide tailored coatings for demanding applications.  

When a laser beam passes through an optical substrate, its energy is divided into three parts: transmission, reflection, and absorption. Among these, absorption refers to the fraction of laser energy that is converted into heat inside the material. Even small absorption levels can have a significant impact on high-power laser systems.   Causes of Absorption ·         Material Properties: Different optical materials absorb differently across the spectrum. For example, fused silica provides excellent transmission from UV to near-IR, while germanium (Ge) and silicon (Si) are better suited for the mid-IR range. ·         Impurities and Defects: Trace ions, inclusions, or lattice defects inside the substrate increase absorption. ·         Surface Quality: Roughness, scratches, or micro-cracks on the surface can cause localized scattering and higher thermal absorption. 2. Effects on Laser Systems ·         Thermal Loading: Absorbed laser energy converts to heat, raising the substrate temperature. ·         Beam Distortion: Excessive heating can cause thermal lensing or optical distortion. ·         Component Damage: Under high laser power, substrates with high absorption risk cracking, warping, or catastrophic failure. 3. Typical Absorption Levels ·         Fused Silica: At 1064 nm (Nd:YAG lasers), absorption can be as low as 10⁻⁶–10⁻⁷ cm⁻¹, making it ideal for high-power applications. ·         Zinc Selenide (ZnSe): Commonly used for CO₂ lasers (10.6 µm), with low absorption and high transmission. ·         Ge and Si: Excellent transmission in the mid- to far-infrared, but strong absorption in the visible range. 4. Engineering Solutions ·         Material Selection: Match the substrate material to the laser wavelength for minimal absorption. ·         High-Purity Materials: Using ultra-pure crystals and glasses reduces impurity-related absorption. ·         Advanced Coatings: Anti-reflection and protective coatings lower surface reflection and can help minimize absorption losses. ·         Thermal Management: Cooling systems or heat sinks are often integrated into high-power optics to dissipate absorbed energy.     Conclusion Substrate absorption directly impacts the efficiency, stability, and lifetime of laser optical systems. Selecting the right material and controlling absorption to the lowest possible level is essential in modern laser engineering. At China Star Optics Technology, we specialize in producing low-absorption optical components tailored for demanding laser applications. From fused silica windows to ZnSe and Ge optics for infrared systems, our products are manufactured with advanced polishing and coating technologies to ensure high transmission, low absorption, and long-term reliability. Contact us to learn how our custom optics can optimize the performance of your laser system.

In the world of optics, diffraction gratings play an irreplaceable role. They precisely separate composite light into its constituent wavelengths, producing a vivid spectrum. From revealing the elemental composition of distant planets, to serving as core components in modern laser communication, and even enabling spectral sensors in our smartphones, diffraction gratings are everywhere. At the heart of their performance lies the precisely arranged periodic microstructures on their surface. At China Star Optics Technology, we specialize in designing and manufacturing high-performance diffraction gratings for a wide range of applications — from laboratory research to industrial integration. Types of Diffraction Gratings   1. By Material and Fabrication Principle   Ruled Gratings: The “pioneers” of optical gratings. They are created by mechanically ruling parallel grooves directly onto a reflective coating (usually aluminum) on an optical substrate such as glass using a diamond-tipped tool. Their key advantage is precise control over the blaze angle, producing blazed gratings that concentrate most diffraction energy into a specific order and wavelength range, greatly enhancing efficiency. While extremely accurate, they are time-consuming and expensive to produce, and are mainly used in high-end spectrometers. Replica Gratings: Developed to overcome the low productivity of ruled gratings. First, a precision master grating (often a ruled or high-quality holographic grating) is made. A release layer and reflective coating (e.g., aluminum) are applied, followed by optical adhesive and a blank substrate. After curing and separation, the groove structure of the master is “replicated” onto the new substrate. This approach is much more cost-effective and enables large-scale commercialization. Holographic Gratings: Fabricated using the interference of coherent light beams. Two laser beams intersect on a photosensitive layer coated onto an optical substrate, forming alternating bright and dark fringes. After development, sinusoidal or near-sinusoidal relief patterns remain. These are often transferred to the substrate via ion beam etching. Holographic gratings have no periodic errors (low ghosting), low stray light, and are well-suited for large-area production, but are less efficient for blaze applications. Volume Holographic Gratings: Unlike surface-relief gratings, these feature refractive index modulation within the material (e.g., dichromated gelatin or photopolymers). Created by recording interference patterns inside a photosensitive medium, they are commonly used for narrowband filtering, beam coupling, and augmented reality (AR) waveguide displays. Fiber Bragg Gratings: A special type of volume grating directly inscribed into the fiber core with periodic refractive index modulation, typically using UV laser interference or phase mask methods. They are essential in fiber-optic communication (e.g., WDM multiplexers/demultiplexers), fiber lasers, and sensing applications. Special Material Gratings: Silicon Gratings: Produced using semiconductor microfabrication techniques on silicon wafers, fundamental in integrated photonics (e.g., waveguide grating couplers and filters in silicon photonic chips). Metal Gratings: Grooves directly patterned into metal surfaces or made from metallic lines, widely used in THz, infrared, and plasmonics research.   2. By Working Surface   Reflection Gratings: Diffract light from a reflective surface with periodic grooves. The most common type, widely used in spectrometers. Transmission Gratings: Diffract light through a transparent medium with periodic structures, which may be surface-relief (etched into glass or fused silica) or volume refractive index modulations. Common in compact spectrometers and pulse compression systems.   3. By Geometry   Plane Gratings: Flat working surfaces, often requiring focusing optics for use. Concave Gratings: Spherical (or aspherical) working surfaces that combine dispersion and focusing in a single element, simplifying spectrometer design and reducing aberrations. Classic applications include the Rowland circle and Paschen–Runge setups.   4. By Groove Shape   Blazed Gratings: Sawtooth-shaped grooves that direct most energy into a specific diffraction order and wavelength. Traditionally made via ruling, though modern holography combined with ion beam etching can produce near-blazed profiles. Sinusoidal Gratings: Grooves with sinusoidal cross-sections, typical of conventional holographic gratings. Rectangular (Binary) Gratings: Grooves with rectangular profiles, often made with micro- and nanofabrication methods such as photolithography or e-beam lithography, for applications like diffraction order separation or beam shaping.   The world of diffraction gratings is both historic and cutting-edge. From mechanically ruled masters to today’s nanometer-scale lithographic and holographic techniques, gratings have continuously advanced optical science and technology. Whether in astronomy, telecommunications, laser engineering, or emerging AR displays, high-quality gratings are the key to precise spectral control. At China Star Optics Technology, we are committed to delivering precision-engineered gratings that meet the highest standards of performance and reliability. With advanced fabrication capabilities and customizable solutions, we help our customers turn optical concepts into reality.  

Munich, 24 June 2025 — China Star Optics is proud to join LASER World of PHOTONICS 2025, the world’s leading photonics trade fair that welcomed over 42 000 visitors from 80 countries this week. At Hall A2–425 we showcased our latest precision optics, met old partners and made new ones.   We expect this presence to translate into concrete orders before the year ends and to strengthen our R&D roadmap. Back home, we will speed up innovation, add more high-performance products to our line-up and extend global service coverage. Your next inquiry will be answered faster, shipped sooner and supported longer—this is our promise after Munich. If you are interested: Cylinder Lens,Aspheric Lens,Optical Glass Dome,Plane Ruled Grating Manufacturer and Supplier in China Pic cr: LinkedIn account      

China Star Optics Showcases Cutting-Edge Large-Diameter Optical Dome Technology at Singapore Photonics Expo 2025 Singapore, February 26, 2025 — China Star Optics, a leading provider of precision optical solutions, made a significant impact at the 2025 Singapore Photonics Expo (Asia Photonics Expo, APE) held at the Sands Expo & Convention Centre from February 26 to 28. The company spotlighted its revolutionary large-diameter optical dome technology, demonstrating its dominance in advanced optical manufacturing for industries including  security, automotive, and smart infrastructure. Unveiling Large-Diameter Optical Dome Leadership At the expo, China Star Optics showcased its high-precision optical domes with diameters exceeding 350mm, designed to meet the growing demand for robust, optically superior enclosures in surveillance cameras, laser radar (LiDAR) systems, and industrial sensors. The company highlighted its proprietary micro-nano processing and injection molding techniques, which enable unmatched surface accuracy (micro-nano level) and durability while reducing production costs. “Our large-diameter optical domes are engineered to withstand extreme environmental conditions, from harsh weather to high-impact scenarios, without compromising light transmittance or image clarity,” said a senior engineer from China Star Optics. “This technology addresses a critical gap in the market for scalable, reliable solutions in smart cities and autonomous driving.”

1. Why use Dome Lens for Underwater Photography?•   Domes make it better - Domes help correct aberrations that occur when light travels thru water as opposed to air. Domes can deliver better results compared to flat ports, and also make it easier or possible some results that flat ports would not capture. •   Size matters - Bigger domes are better than smaller domes, for a number of reasons. The tradeoffs are; heavier, bulkier, pricier than smaller domes. •   Customized specially for you - CSOPT manufactures dome lenses in various sizes and various glass materials, like K9, sapphire, quartz.Whether it's for aerospace or underwater photography it will ensure the safety of your lens and the clarity of the image. •   Domes are ideal for split-level and underwater use - While dome ports will not take anything away from your work above water, their impact or difference above the surface is irrelevant. Domes are ideal for split-level and underwater work. 2. DOME SIZE   All domes are sharp in the center, so when we are comparing the image quality of domes we are concerned more with the corners and edges. In general the larger the dome the better the corner sharpness. Knowing this, it seems like the solution is to use the largest dome possible but this is not always necessary, practical or the best solution. Smaller sensor cameras can use smaller domes and still retain good image quality. This is also more practical as most users of smaller sensor cameras are concerned with size. Fisheye lenses can also use smaller domes and still retain acceptable corners. In fact, in most cases a small dome is preferred over a large dome for a fisheye. This is because fisheye lenses are able to focus extremely close and the smaller dome allows us to get physically closer to our subject. This makes them better suited for close focus wide angle and the smaller size has less drag and is easier to use in tight spaces. Rectilinear lenses will benefit from a larger size dome but you want to use what is appropriate for your sensor size and focal length. Split images also benefit from a larger size dome, creating a thinner meniscus or water line. Whenever your image contains important information in the corners it's a good idea to stop down to retain good detail.

China Star Optics Technology Co., Ltd., as a company with 20 years of manufacturing and processing optical components, invites you to attend <span font-size:20px;text-wrap:wrap;background-color:#ffffff;"="" style="box-sizing: border-box; font-family: Arial, sans-serif; background-color: rgb(255, 255, 255); color: rgba(0, 0, 0, 0.9);" data-mce-style="box-sizing: border-box; font-family: Arial, sans-serif; background-color: #ffffff; color: rgba(0, 0, 0, 0.9);">PHOTONICS. WORLD OF LASERS AND OPTICS'2025. We'll show you our newest optical lenses, aspherical lenses, optical mirrors, cylindrical lens, diffraction gratings and new camera lenses etc. Welcome to visit us at Booth FH032. We believe this exhibition presents a fantastic opportunity not just to showcase our products but also to engage with peers from around the world. Whether you are a professional in the laser and optics industry or an enthusiast with a keen interest in the field, we look forward to meeting you at the event. The fair also provides a platform for the presentation of devices and technologies for processing, manufacturing, and testing of optical components and systems. Overall, Photonics is an important trade fair for the photonics and optics industry, which offers professionals from various industries the opportunity to present their products and solutions and to find out about the latest trends and developments in the field of optical technologies. See you at Booth FH032. <span font-size:20px;text-wrap:wrap;background-color:#ffffff;"="" style="box-sizing: border-box; font-family: Arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255); color: rgba(0, 0, 0, 0.9);">

Held on 26th to 28th February 2025 at Marina Bay Sands Expo and Convention Centre, Singapore, Asia Photonics Expo (APE) is the one-stop photonics exhibition for industry players to technical communication, networking, and product sourcing. It covers the entire optoelectronic ecosystem to showcase the latest products and technologies from materials, components, modules, devices to various photonics applications in optical communication, precision optics, laser, infrared, sensor, and display fields. APE will attract a wide range of buyers and audiences from different application industries, ensuring that you meet your target audience at the event. By participating in APE, you will have the opportunity to get in touch with key decision makers and potential collaborators across these industries. CSOPT (China Star Optics Technology Co., Ltd.), as a company with 20 years of manufacturing and processing optical components including optical lens, prisms, aspherical lens,optical windows, diffraction gratings, cylindrical lens etc, we invite you to attend Asia Photonics Expo 2025 |26 to 28 February 2025, Marina Bay Sands®, Singapore .We believe this exhibition presents a fantastic opportunity not just to showcase our products but also to engage with peers from around the world. Whether you are a professional in the laser and optics industry or an enthusiast with a keen interest in the field, we look forward to meeting you at our booth D106. 

China Star Optics Technology Co., Ltd. is one of China`s leading optical manufacturing companies, which was registered and established in Changchun,Jilin province in 2005. Our company has been engaged in manufacturing of optical components for nearly 20 years, we have wide experience and advantages in processing high precision optical components, such as optical lenses, aspherical lens, optical dome, optical windows, optical coatings and infrared optical parts etc. The components are widely used in medical instrument,optical communications, photography, biochemical analysis,laser systems, aerospace and other fields. We have strict quality control in the production of optical components, to improve our inspection capabilities, we have been equipped with advanced inspection equipments, including ZYGO Verifire Interferometer, Goniometer,Autocollimator, Theodolite and Spectrophotometer etc. Ensures that we can provide high quality prodcuts and efficiency service. We look forward to hearing from you with developing a long-term friendly business relationship in near future.

The optical properties of quartz glass are unique. It can pass through the far-ultraviolet spectrum, and is the best for all UV-transparent materials, as well as visible and near-infrared. The user can arbitrarily select the desired variety from the range of 185-3500 mμ band as needed. Due to its high temperature resistance, quartz glass has a very small thermal expansion coefficient and good chemical thermal stability. Bubbles, stripes, uniformity and birefringence are comparable to those of ordinary optical glass, so it is a highly stable optical system that works in a variety of harsh environments. Essential optical material. The structure of quartz glass, impurity content, OH gene, NO, CO and other content are the main factors affecting the spectral transmittance. The oxygen atom binding failure has an absorption peak at 0.24μ, and quartz glass containing OH group at 2.7μ. Due to the molecular vibration, a significant absorption peak will be produced, and the low ultraviolet transmittance is mainly caused by the atomic absorption spectrum caused by the metal impurities. Spectral characteristic curve of quartz glass Fused silica glass is a very good infrared transparent material, but the ultraviolet transmittance is low due to the presence of impurities. The quartz glass obtained by melting the crystal of the oxyhydrogen flame has an absorption peak at 0.24 μ and an OH group due to the oxygen structure defect, so the infrared transmission is extremely low. High-purity optical quartz glass smelted with synthetic raw materials is the best UV-permeable material, but has a severe OH absorption peak at 2.7 μ. Only the optical quartz glass which is formed by melting the synthetic raw material by electrofusion or hydrogen-free flame can well penetrate the continuous spectrum from far ultraviolet to near infrared.

British astronomer Herschel discovered infrared technology in 1800. In the constant efforts of the scientific community, infrared technology has also been applied to various occasions. The most typical one for security applications is the infrared camera. Infrared cameras can be divided into 2 categories, analog infrared cameras and infrared network cameras. But they all have the same characteristics, which are mainly manifested in the different characteristics of infrared light source and the choice of low illumination camera. Only by combining these two points with an infrared camera can you become an excellent product. In selecting different infrared light sources and distances, the main infrared light source characteristics for different applications are as follows: Infrared light is an invisible light with a wavelength greater than 780 nm. Generally, the infrared lamps of current infrared cameras have the following types. 1. Use infrared light emitting diode LEDs or LED arrays to generate infrared light. Such devices generate infrared light by recombining electrons and holes in a gallium arsenide (GaAs) semiconductor. 2. The infrared laser diode LD can also be used as an infrared light source. However, it is necessary to excite or pump electrons in a lower energy state to a higher energy state, and maintain the stimulated radiation infrared light by reversing a large amount of particle distribution and resonating. The first is an infrared lamp composed of a semiconductor gallium arsenide LED array, especially an array-type integrated light-emitting chip LEDArray that is now developed using a new technology. Its LED-Array has an optical output of 800mw-1000mw, which has become a replacement for ordinary LEDs. The LED-Array has a half-power angle of 10-120° (variable angle). Since the LED-Array is a highly integrated LED and the size is only one penny coin, its life span is 50,000 hours. The second is to use an infrared laser diode LD. For the monitoring of ultra-long-distance scenes of more than 1km, it is still necessary to select an infrared LD source. Because semiconductor lasers have higher brightness and better directivity than LEDs. Infrared camera installation and debugging need to pay attention to the following issues: First of all, debugging infrared lights must be done at night. The infrared beam illumination position is adjusted at night by a rendering device such as a monitor. And can effectively adjust the lens aperture settings. Secondly, the infrared light can't directly face the camera. The infrared light seen by the camera is like the sunlight seen by humans, which will make the image appear white. Again, the infrared light is not necessarily mounted in the same position as the camera. If the camera is far away from the object being illuminated, consider installing the infrared light between the two. The best way to install in the same position is to overlap the camera with the infrared light and the camera. Finally, users should first read the instruction manual carefully when using the infrared light, especially the precautions for ensuring the safety of personal equipment. Check whether the matching aspects described above meet the requirements, and whether the influencing factors should be taken into consideration, if the requirements are not met, the equipment used can be adjusted in time. The use of large-angle infrared light with a small angle of view lens, there is a waste of light. Secondly, the larger the emission angle of the infrared light, the better the picture effect. The relative aperture determines the light-passing ability of the lens. The relative light-through of the lens with a relative aperture of f1.0 is four times that of the lens with a relative aperture of f2.0. The same camera and infrared light are matched with the above two lenses, and the infrared distance is It can be doubled. The large-aperture lens is four to ten times better than the conventional lens in infrared monitoring. It is reasonable to say that it should be an essential accessory for infrared night vision monitoring. However, due to the high cost and technical difficulty, most infrared products Manufacturers do not have the ability to supply. The problem of focus shift: visible light and infrared light are different in wavelength, the imaging focus is not on a plane, resulting in clear image under visible light conditions in the daytime, blurred under nighttime infrared light conditions, or clear image under nighttime infrared light conditions, daytime visible light conditions The image below is blurred. All black and white cameras are infrared light. Infrared light is a kind of stray light for color cameras under visible light conditions, which will reduce the sharpness and color reproduction of color cameras. The color camera filters prevent infrared rays from participating in imaging. There are two ways to make the color camera sense infrared. First, switch the filter to block the infrared light from entering under visible light conditions; remove the filter in the absence of visible light and let the infrared light enter. The image quality is good, but the cost is high and the switching mechanism will cause a certain failure rate. Second, open a specific infrared channel on the filter, allowing infrared light of the same wavelength as the infrared light to come in. This method does not increase. Cost, but the color reproduction is slightly worse. At present, infrared night vision distance has been more than 500 meters, and price is also one of the reasons. Among them, infrared light, infrared camera technology, infrared lens is the core.

Many of my friends are wondering why the same focal length lens will be divided into ordinary lenses and infrared lenses. What is the difference between ordinary lenses and infrared lenses? Next we will briefly explain the difference between the two: First of all, the use of the two is different: In the surveillance environment that does not require infrared light subsidies, an ordinary lens can be used. In an infrared light-subsiding surveillance environment, an infrared lens must be used for better monitoring effects; Can see the picture, but the picture will become blurred, this point I believe everyone has a deep understanding. Second, the prices of the two are different: The price of a professional infrared lens is several times that of an ordinary lens. Why? Because the use of an infrared lens is both clear during the day and at night, and the effect is natural and expensive. Oh, this is nonsense. Finally, I talk about the reasons why the performance and price of the two are so different: Because the refractive index of the glass for different wavelengths of light is different, the position of the focused point will be different. Currently on the market, ordinary lenses can achieve the wavelength difference of about 250nm on the same plane, that is, 430 ~ 650nm or 650 ~ The light in the 900 nm range can be successfully focused and present a clear image. This is why the ordinary lens is clear during the day, the night vision is blurred, or the night vision is clear and the daytime is blurred. Professional-infrared lens uses special lenses, can achieve the 430 ~ 900nm or even longer wavelength range of the light gathered on the same plane, so regardless of the day or night vision is clear. Due to the special lens material, so the cost Naturally high. Professional infrared lens cost is high, new problems come again, everyone has to do a high cost of the machine, the profit is low, how to do? The people are very smart, do point coating to the lens, amend the light, hey, Cheap infrared lens comes out slightly ~ and no matter how good or bad, all are called - infrared lens! But how is the effect? How long will the coating be removed?... Will it be evaporated after being heated?... The plating is not as uniform as it should be, but sometimes it will be a little blurry. How can I do it? The goods requirement is not too high.. In any case, the best is cheap! We all recommend that everyone use good equipment, after all, a penny and a piece of goods, you buy it and use it comfortably, and we sell it comfortably. Although we just added more costs, our profits are the same, but if the equipment Praised by the majority of customers, the effect is different response. Finally, I wish you all a happy and prosperous business.

Many of my friends are wondering why the same focal length lens will be divided into ordinary lenses and infrared lenses. What is the difference between ordinary lenses and infrared lenses? Next we will briefly explain the difference between the two: First of all, the use of the two is different: In the surveillance environment that does not require infrared light subsidies, an ordinary lens can be used. In an infrared light-subsiding surveillance environment, an infrared lens must be used for better monitoring effects; Can see the picture, but the picture will become blurred, this point I believe everyone has a deep understanding. Second, the prices of the two are different: The price of a professional infrared lens is several times that of an ordinary lens. Why? Because the use of an infrared lens is both clear during the day and at night, and the effect is natural and expensive. Oh, this is nonsense. Finally, I talk about the reasons why the performance and price of the two are so different: Because the refractive index of the glass for different wavelengths of light is different, the position of the focused point will be different. Currently on the market, ordinary lenses can achieve the wavelength difference of about 250nm on the same plane, that is, 430 ~ 650nm or 650 ~ The light in the 900 nm range can be successfully focused and present a clear image. This is why the ordinary lens is clear during the day, the night vision is blurred, or the night vision is clear and the daytime is blurred. Professional-infrared lens uses special lenses, can achieve the 430 ~ 900nm or even longer wavelength range of the light gathered on the same plane, so regardless of the day or night vision is clear. Due to the special lens material, so the cost Naturally high. Professional infrared lens cost is high, new problems come again, everyone has to do a high cost of the machine, the profit is low, how to do? The people are very smart, do point coating to the lens, amend the light, hey, Cheap infrared lens comes out slightly ~ and no matter how good or bad, all are called - infrared lens! But how is the effect? How long will the coating be removed?... Will it be evaporated after being heated?... The plating is not as uniform as it should be, but sometimes it will be a little blurry. How can I do it? The goods requirement is not too high.. In any case, the best is cheap! We all recommend that everyone use good equipment, after all, a penny and a piece of goods, you buy it and use it comfortably, and we sell it comfortably. Although we just added more costs, our profits are the same, but if the equipment Praised by the majority of customers, the effect is different response. Finally, I wish you all a happy and prosperous business.

Many of my friends are wondering why the same focal length lens will be divided into ordinary lenses and infrared lenses. What is the difference between ordinary lenses and infrared lenses? Next we will briefly explain the difference between the two: First of all, the use of the two is different: In the surveillance environment that does not require infrared light subsidies, an ordinary lens can be used. In an infrared light-subsiding surveillance environment, an infrared lens must be used for better monitoring effects; Can see the picture, but the picture will become blurred, this point I believe everyone has a deep understanding. Second, the prices of the two are different: The price of a professional infrared lens is several times that of an ordinary lens. Why? Because the use of an infrared lens is both clear during the day and at night, and the effect is natural and expensive. Oh, this is nonsense. Finally, I talk about the reasons why the performance and price of the two are so different: Because the refractive index of the glass for different wavelengths of light is different, the position of the focused point will be different. Currently on the market, ordinary lenses can achieve the wavelength difference of about 250nm on the same plane, that is, 430 ~ 650nm or 650 ~ The light in the 900 nm range can be successfully focused and present a clear image. This is why the ordinary lens is clear during the day, the night vision is blurred, or the night vision is clear and the daytime is blurred. Professional-infrared lens uses special lenses, can achieve the 430 ~ 900nm or even longer wavelength range of the light gathered on the same plane, so regardless of the day or night vision is clear. Due to the special lens material, so the cost Naturally high. Professional infrared lens cost is high, new problems come again, everyone has to do a high cost of the machine, the profit is low, how to do? The people are very smart, do point coating to the lens, amend the light, hey, Cheap infrared lens comes out slightly ~ and no matter how good or bad, all are called - infrared lens! But how is the effect? How long will the coating be removed?... Will it be evaporated after being heated?... The plating is not as uniform as it should be, but sometimes it will be a little blurry. How can I do it? The goods requirement is not too high.. In any case, the best is cheap! We all recommend that everyone use good equipment, after all, a penny and a piece of goods, you buy it and use it comfortably, and we sell it comfortably. Although we just added more costs, our profits are the same, but if the equipment Praised by the majority of customers, the effect is different response. Finally, I wish you all a happy and prosperous business.

Modern communication systems often use dual band bandpass filters to isolate different operating bands in the same network. The traditional design dimensions of such filters are relatively large and require an additional combined network for the two filters. However, the dual-band bandpass filter design method discussed in detail in this paper can be made very small. Its structure is relatively simple, consisting of two asymmetric split spiral resonators (ASSR) cascaded with a microstrip line. Due to the inherent spiral geometry of the ASSR, the ASSR can be fully embedded in the microstrip line, so the final design size can be minimized. This paper also further analyzes this innovative design and validates this design approach with a pair of prototypes. The two dual band filters operate between 1.16 GHz and 1.84 GHz and between 1.80 GHz and 2.45 GHz, respectively. The industry has made a lot of efforts to miniaturize the dual-band bandpass filter. For example, a cross-coupled filter is a relatively efficient solution. In this design method, an isometric split-ring resonator with dual resonant frequency response characteristics is used as the basis for the design of the filter. In one example, a cross-coupled dual-band bandpass filter is synthesized using four resonators, and the relative positions of these resonators must be carefully tuned in order to obtain a suitable coupling coefficient. Unfortunately, the use of four resonators results in reduced insertion loss performance and the difficulty of achieving compact dimensions (especially cross-sectional dimensions). Another approach is to use an open-loop resonator and a parallel open stub as the basis for the design of a compact dual-band bandpass filter. Designed and manufactured here are three dual-band filters optimized for out-of-band rejection. In these prototypes, the second passband can be controlled by adjusting the position and length of a particular parallel open stub. There is also a micro-planar dual-band bandpass filter based on a curved stepped impedance resonator (SIR). The dual-band response of this filter depends on the main geometric parameters of the SIR, while the compact size is achieved by integrating the U-shaped SIR with the latest coupling mechanism. A miniature dual-band bandpass filter is also implemented using a combined coupling structure of short and open quarter-wavelength SIR. In summary, these different dual-band filter design methods rely on a basic unit with a dual resonant mode. This article provides different design methods for creating compact, dual-band bandpass filters. In this new approach, the filter consists of two cascaded ASSRs connected by microstrip lines. These ASSRs are an improved version of a single plane double helix resonator unit and a symmetric split type spiral resonator. Due to its special geometry, this ASSR can be fully embedded in the microstrip feed line to directly form the corresponding component with a compact cross-sectional dimension. In general, ASSR is a band-pass unit that operates by electromagnetic (EM) coupling. In the current design, the first passband is dependent on the inherent passband of the ASSR, while the second passband is created by a combination of an equal impedance network of ASSRs and connected microstrip lines. Thus, the second passband can be adjusted independently of the first passband by using the length of the connected microstrip line as a variable parameter. This conclusion will also be verified by circuit model analysis. Based on this analysis, we designed and fabricated two different dual-band bandpass filters to demonstrate the effectiveness of the analysis. According to our knowledge, these dual-band bandpass filters are the narrowest filters reported in all the literature to date due to their particularly compact cross-sectional dimensions. Figure 1: The layout shows ASSR(a) and the recommended dual-band bandpass filter (b). This filter uses a pair of ASSRs and a microstrip transmission line connected to it. Figure 1 shows the ASSR layout (a) and recommended filter (b) used in this dual-band bandpass filter. Each ASSR consists of two separate, asymmetrical rectangular spiral patterns. Due to the rotational geometry of the rectangular helix, a given unit can be fully embedded within the microstrip line, resulting in a particularly compact cross-sectional dimension. Thus, the ASSR Broadband W1 remains unchanged at 4.6 mm, which is equivalent to the width of a 50Ω microstrip line fabricated on Rogers' RT/duroid 5880 printed circuit board (PCB) substrate. The relative dielectric constant of this substrate is 2.2. The thickness is 1.5mm. These material values are also used for simulation. The values for dimensions W3 and W4 are limited due to limitations imposed by circuit manufacturing tolerances (approximately 0.1 mm at W1 = 4.6 mm). For these dual band bandpass filter designs, the values for W3 = 0.6 mm and W4 = 0.3 mm are used here. In a common model of a coupled microstrip line filter, these values will support the effective bandpass properties through electromagnetic coupling. This prediction will be verified by the parameter analysis method of L1 (the main adjustment parameter of the bandpass filter), and the result is shown in Fig. 2.

Modern communication systems often use dual band bandpass filters to isolate different operating bands in the same network. The traditional design dimensions of such filters are relatively large and require an additional combined network for the two filters. However, the dual-band bandpass filter design method discussed in detail in this paper can be made very small. Its structure is relatively simple, consisting of two asymmetric split spiral resonators (ASSR) cascaded with a microstrip line. Due to the inherent spiral geometry of the ASSR, the ASSR can be fully embedded in the microstrip line, so the final design size can be minimized. This paper also further analyzes this innovative design and validates this design approach with a pair of prototypes. The two dual band filters operate between 1.16 GHz and 1.84 GHz and between 1.80 GHz and 2.45 GHz, respectively. The industry has made a lot of efforts to miniaturize the dual-band bandpass filter. For example, a cross-coupled filter is a relatively efficient solution. In this design method, an isometric split-ring resonator with dual resonant frequency response characteristics is used as the basis for the design of the filter. In one example, a cross-coupled dual-band bandpass filter is synthesized using four resonators, and the relative positions of these resonators must be carefully tuned in order to obtain a suitable coupling coefficient. Unfortunately, the use of four resonators results in reduced insertion loss performance and the difficulty of achieving compact dimensions (especially cross-sectional dimensions). Another approach is to use an open-loop resonator and a parallel open stub as the basis for the design of a compact dual-band bandpass filter. Designed and manufactured here are three dual-band filters optimized for out-of-band rejection. In these prototypes, the second passband can be controlled by adjusting the position and length of a particular parallel open stub. There is also a micro-planar dual-band bandpass filter based on a curved stepped impedance resonator (SIR). The dual-band response of this filter depends on the main geometric parameters of the SIR, while the compact size is achieved by integrating the U-shaped SIR with the latest coupling mechanism. A miniature dual-band bandpass filter is also implemented using a combined coupling structure of short and open quarter-wavelength SIR. In summary, these different dual-band filter design methods rely on a basic unit with a dual resonant mode. This article provides different design methods for creating compact, dual-band bandpass filters. In this new approach, the filter consists of two cascaded ASSRs connected by microstrip lines. These ASSRs are an improved version of a single plane double helix resonator unit and a symmetric split type spiral resonator. Due to its special geometry, this ASSR can be fully embedded in the microstrip feed line to directly form the corresponding component with a compact cross-sectional dimension. In general, ASSR is a band-pass unit that operates by electromagnetic (EM) coupling. In the current design, the first passband is dependent on the inherent passband of the ASSR, while the second passband is created by a combination of an equal impedance network of ASSRs and connected microstrip lines. Thus, the second passband can be adjusted independently of the first passband by using the length of the connected microstrip line as a variable parameter. This conclusion will also be verified by circuit model analysis. Based on this analysis, we designed and fabricated two different dual-band bandpass filters to demonstrate the effectiveness of the analysis. According to our knowledge, these dual-band bandpass filters are the narrowest filters reported in all the literature to date due to their particularly compact cross-sectional dimensions. Figure 1: The layout shows ASSR(a) and the recommended dual-band bandpass filter (b). This filter uses a pair of ASSRs and a microstrip transmission line connected to it. Figure 1 shows the ASSR layout (a) and recommended filter (b) used in this dual-band bandpass filter. Each ASSR consists of two separate, asymmetrical rectangular spiral patterns. Due to the rotational geometry of the rectangular helix, a given unit can be fully embedded within the microstrip line, resulting in a particularly compact cross-sectional dimension. Thus, the ASSR Broadband W1 remains unchanged at 4.6 mm, which is equivalent to the width of a 50Ω microstrip line fabricated on Rogers' RT/duroid 5880 printed circuit board (PCB) substrate. The relative dielectric constant of this substrate is 2.2. The thickness is 1.5mm. These material values are also used for simulation. The values for dimensions W3 and W4 are limited due to limitations imposed by circuit manufacturing tolerances (approximately 0.1 mm at W1 = 4.6 mm). For these dual band bandpass filter designs, the values for W3 = 0.6 mm and W4 = 0.3 mm are used here. In a common model of a coupled microstrip line filter, these values will support the effective bandpass properties through electromagnetic coupling. This prediction will be verified by the parameter analysis method of L1 (the main adjustment parameter of the bandpass filter), and the result is shown in Fig. 2.

The optical component is a very precise component, and the manufacturing cost is high. If the thickness of the component can be reduced, or even a sheet lens, the size of the optical component can be reduced, thereby reducing the size of the lamp or other equipment, and saving material. cut costs. As the thickness is reduced, the light absorption is also reduced, and the efficiency of the luminaire or instrument is also increased. Therefore, it is one of the goals of optical design to make high-quality sheet-shaped optical parts. The Fresnel lens is a sheet-like thin lens that has been used in some aspects for its lightness, thinness and low cost. However, the Fresnel lens on the market is mostly concentric circle structure with equal radius. The fabrication lacks precise optical design process, resulting in low image quality, and some even simple corrugated structures, and its optical quality is even worse. . Even a better Fresnel lens is usually formed by dividing a common lens into small segments, which are approximately broken lines, and are formed by simple translation of different distances. The defects in these design methods result in low quality of the Fresnel lens. LEDs are small in size, but most of the LED lenses on the market are thicker than 10mm, which is a fatal problem for LEDs in some applications, although Fresnel lenses can be used to reduce the thickness of the lens and reduce light absorption. However, how to carry out accurate optical design is rarely reported in the literature. This article describes the design method for obtaining accurate ultra-thin zigzag lenses with good optical quality and high light utilization. Because the general Fresnel lens is theoretically wasteful, that is, the light passing through the lens theoretically has a part that cannot reach the destination of the design, and the lens obtained by the method has no theoretical waste. In addition, the distance between the small serrations can also be different according to needs, and the zigzag spacing at different positions in the same lens can also be changed, so that the zigzag lens designed by this method has wider adaptability, that is, it can Adapt to different conditions of use and different processing conditions. This zigzag lens is suitable for secondary optical lenses in which the LED is a light source. For a small-sized light source such as an LED, it is very meaningful to have a small and thin optical lens. First, the design principle A single lens is generally a transparent material whose surface shape is curved, and its function is to change the direction of the light to form a desired spatial distribution of light intensity. The disadvantage is that it tends to be relatively thick, so it is bulky and costly, and the absorption is large, especially for lenses with large curvature. For the sake of simplicity, an example of a plano-convex lens is shown in Fig. 1(a). Correspondingly, the conventional Fresnel lens is shown in Fig. 1(b). For the sake of explanation, the pitch of the figure is relatively large. Figure 1 The formation principle of the traditional Fresnel lens The design principle of Fresnel lens is to replace the entire continuous large surface with several small faces. Figure 1 (c) shows the design principle of a conventional Fresnel lens. The function of the sawtooth Fresnel lens of Fig. 1(b) is the same as that of the original lens of Fig. 1(a). The traditional design method can be represented by Figure 1 (c). Actually, the Fresnel lens of Fig. 1(b) can be regarded as that a plurality of rectangular portions are deleted from the lens of Fig. 1(a), and the remaining portion is moved downward into a sheet shape to become a Fresnel lens. See Figure 1(c), where the stepped shadow is the part of the multiple rectangles that are deleted. It is obvious that the Fresnel lens of Fig. 1(b) is thinner than the lens (a), so that the absorption is small and the material is saved. However, this conventionally designed lens is correct only for parallel light, in which case the shaded portion of (c) has no effect on the light. However, in the case of non-parallel light, such as when the LED is a light source, the shaded portion of (c) has an effect on the light. If it is removed into a Fresnel lens, it will cause a lot of stray light. In addition, if the cross section of the lens is replaced by a broken line instead of a small arc, an optical error will also occur. In order to overcome the above shortcomings, we propose to design Fresnel lenses in two new ways. Here we design for a single LED. For other light sources, the design principle is the same, so in principle it can be extended to other light sources. The basic idea of the new method is to divide the edge of the deleted invalid part along the light, and the effective remaining part moves along the light while changing its size in a certain proportion, so that the light will not propagate in the lens. Hit the invalid part of the edge and it will be refracted in the original direction. This reduces the scattered light and increases the optical efficiency of the lens. Second, the design method 1, the angle method Figure 2 angle method We assume that the incident surface of the original lens is a plane, and the exit surface (the surface on which AB is located in Figure 2) is a curved surface. As for how to design the original surface, it is beyond the scope of this article. The new exit surface is the zigzag we want to design. In this paper, we can assume that the O point is the position of the virtual image point after the light source passes through the incident surface, that is, the light from the O point passes through the exit surface and reaches the image surface (the lens may not be "imaged" but illuminated). So we will include the role of the entrance surface. We can divide the surface where AB is located into small segments at the angle of the point O. In the figure, AB is one of the small segments. Instead of moving these small segments vertically as in the first section, we moved them in the direction of the light and scaled them while scaling. Thus, AB is scaled to A'B'. According to the principle of linear optics, the direction of light refraction caused by facet A'B' is exactly the same as that of facet AB, except that the position of the light is slightly different. Since the lens size is much smaller than the image distance, and the distance difference between OA and OA' is a second-order small amount, we can only care about the angle of the outgoing light before and after the design without concern for the position of the light. Minor changes, that is to say the facets before and after the change, will not make a significant difference in the optical effect of the entire lens, especially for illumination lenses. In addition, the division of the angles may be equal or unequal, and neither of these cases affects the optical effect. To illustrate the problem, Figure 2 only divides the lens into 8 parts. In fact, the larger the number of divisions, the thinner the lens can be. However, as mentioned below, a larger number will bring new problems. However, it can be seen that one disadvantage of the above method is that the sawtooth thickness of the lens will be different, which may affect the strength of the lens. Another method is proposed below, which can achieve the same thickness of the sawtooth. Although the design process is more complicated, it can not only overcome the problem of uneven thickness, but also eliminate stray light. 2, thickness method Figure 3 thickness method 3 is the same as the original lens of FIG. 2, but in FIG. 3, the original lens is divided into several parts in the thickness direction by equal distance (see the horizontal dotted line of FIG. 3), and then the same method is used in the upper section angle method. Each segment is linearly reduced while moving along the light to form a lens of substantially the same thickness. This method not only achieves the same sawtooth depth, but also increases the strength of the lens, and can reduce the thickness at the same number of teeth compared to the angle-angle method, or reduce the number of saw teeth at the same thickness. It can be seen from the analysis below that this result can also reduce stray light of the lens, thereby improving image quality and light utilization efficiency. It should also be pointed out that in general, as long as one of the two faces of the incident and outgoing faces is made into a serrated surface, the design requirements can be met. If the entrance surface is desired to be a sawtooth surface and the exit surface is flat, the above analysis is the same. For example, the outer surface can be a smooth surface and the inner surface can be a serrated surface, which prevents dust from accumulating. More importantly, if the side of the sawtooth is not a flat surface but a curved surface, the result is the same. In this way, we can not only make a flat-plate Fresnel lens, but also other Fresnel lenses such as curved tiles or bowls. Third, stray light analysis It can be seen from the analysis below that the sawtooth lens designed by the new method not only retains the advantages of the original method, but also reduces the stray light caused by the machining error. Because in the actual processing, the tip and bottom of the sawtooth can not be infinitely small, but have a certain rounded corner, this rounded corner will affect the light can not reach the place that should be reached, causing stray light. Figure 4 is a simulation result of a single sawtooth stray light. Figure 4 Simulation results of a single sawtooth stray light The amount of stray light is related to the accuracy of the processing. Assuming that the average width of the sawtooth is d, the radius of the corner of the sawtooth tip is r, and it is roughly assumed that the light in the r range becomes stray light, and the ratio of light loss is r/d. For example, the sawtooth width is 1 mm, and the machining accuracy is caused. Some r is 0.05mm, the light loss is 5%. This is the light loss that the Fresnel lens has to have, which is also a disadvantage of the Fresnel lens. However, compared to Fresnel lenses designed by other methods, the new method and other thickness methods can relatively reduce this loss. The reason for this is that the equal thickness method can have fewer sawtooth numbers under the same thickness conditions as compared with other methods, so that the average width d is larger, r/d is relatively smaller, and thus light loss is less. Further analysis knows that since the LED light source has a large luminous intensity in the optical axis portion and a small edge portion, the thickness obtained by the thickness method has a larger pitch in the middle portion than in the edge portion (see Fig. 3). There is less loss in places where the light intensity is high, that is, there can be less light loss overall. Figure 5 Example of two Fresnel lenses A three-dimensional lens can be obtained by rotating or stretching the designed section. Figure 5 is an example of two Fresnel lenses. The stretched (a) can be used for a strip spot, and the rotated (b) can be used for a circular spot. The design method uses a method of dividing the ideal optical surface and moving in the direction of the light while scaling, while maintaining the optical performance of the lens while minimizing the optical loss, and achieving higher efficiency than other methods. The method can obtain good effects on an LED light source with a small light source scale.

Microscope lenses are of different types, but even for the same type of lens, the imaging quality is very different, mainly due to factors such as material, processing accuracy and lens structure, and also leads to different grades of lens prices. A huge difference from a few hundred yuan to several tens of thousands. More famous such as four three-piece Tiansei lens, six four-group double Gauss lens. For the lens design and manufacturer, the optical transfer function OTF (Optical Transfer Function) is generally used to comprehensively evaluate the lens imaging quality. The optical system transmits the information along the spatial distribution of the brightness. The optical system is transmitted when transmitting the information of the subject. The sinusoidal signal of each spatial frequency, the degree of modulation and the change of phase in the actual image, are all functions of spatial frequency. This function is called the optical transfer function. The OTF is generally composed of a modulation transfer function MTF (Modulation Transfer Function) and a phase transfer function PTF (Phase Transfer Function). Aberration is an important aspect that affects image quality. Common aberrations are as follows: Ball difference: A monochromatic conical beam emitted from an object point on the main axis to the optical system is refracted by the optical series. If the original beam has different angles of light, it cannot be placed at the same position on the main axis, so that the ideal image on the main axis At the plane, a diffuse spot (commonly known as a blur circle) is formed, and the imaging error of the optical system is called a spherical aberration. Hypothesis: A monochromatic conical beam emitted from an off-axis object located outside the main axis to the optical system, after being refracted by the optical series, cannot form a clear point at the ideal image plane, but is formed by dragging a bright tail The illuminating star spot, the imaging error of this optical system is called coma. Astigmatism: An oblique monochromatic conical beam emitted from an off-axis object located outside the main axis to the optical system, after being refracted by the optical series, cannot form a clear image point, but can only form a diffuse spot. The imaging error of the optical system is called astigmatism. Field music: A clear image formed by a plane object perpendicular to the main axis through the optical system, if not in a plane perpendicular to the image plane of the main axis, and on a curved surface symmetrical on the main axis, that is, the best image plane is a curved surface, then The imaging error of the optical system is called field curvature. When the image is adjusted to the center of the screen, the image around the screen is blurred. When the image is blurred until the image around the screen is clear, the image at the center of the screen begins to blur. Color difference: A white object emits a white light to the optical system. After being refracted by the optical system, the light of each color cannot converge on one point, and a color image spot is formed, which is called chromatic aberration. The reason for the chromatic aberration is that the same optical glass has different refractive indices for light of different wavelengths, the short-wave light has a large refractive index, and the long-wave light has a small refractive index. distortion: The straight line outside the main axis in the object plane becomes a curve after being imaged by the optical system, and the imaging error of this optical system is called distortion. Distortion aberrations only affect the geometry of the image without affecting the sharpness of the image. This is the fundamental difference between distortion and spherical aberration, coma, astigmatism, and field music. When evaluating lens quality, we usually judge several practical parameters such as resolution, sharpness and depth of field. Resolution: Also known as discrimination rate, resolution, refers to the ability of the lens to clearly distinguish the details of the fiber of the scene, the reason for restricting the resolution of the lens is the diffraction phenomenon of light, that is, the diffraction spot (Eryer spot). The unit of resolution is line pair / mm. Acutance: Contrast, also known as contrast, refers to the contrast of the brightest and darkest parts of the image. Depth of Field (DOF): In the scene space, the scene located within a certain distance from the plane of the focus object can also form a relatively clear image. The depth distance between the above-mentioned scenes that can form a relatively clear image before and after the focus plane, that is, the depth range of the scene space that can obtain a relatively clear image on the actual image plane, is called the depth of field. Maximum relative aperture and aperture factor: Relative aperture refers to the ratio of the incident aperture diameter (indicated by D) to the focal length (indicated by f) of the lens, ie relative aperture = D / f. The reciprocal of the relative aperture is called the aperture scale, also known as the f/aperture coefficient or the aperture number. The relative aperture of a typical lens is adjustable, and its maximum relative aperture or aperture factor is often indicated on the lens, such as 1:1.2 or f/1.2. If the scene is dark or the exposure time is short, you need to choose the lens with the largest relative aperture. The interaction between the parameters of the lens A good lens has a good reflection in terms of resolution, sharpness, depth of field, etc. It is also better for correcting various aberrations, but at the same time its price will increase several times or even hundreds of times. If we have some rules and experience, we can use the same grade lens to achieve better results. 1. The effect of the focal length The smaller the focal length, the greater the depth of field; The smaller the focal length, the larger the distortion; The smaller the focal length, the more severe the vignetting phenomenon, and the illumination of the aberration edge is reduced; 2. Influence of aperture size The larger the aperture, the higher the brightness of the image; The larger the aperture, the smaller the depth of field; The larger the aperture, the higher the resolution; 3. Center and edge of the field Generally, the image center has higher resolution than the edge. Generally, the image center has higher illumination than the edge light field. 4. Effect of light length Under the same camera and lens parameters, the shorter the wavelength of the light source of the illumination source, the higher the resolution of the resulting image. Therefore, in a vision system that requires precise size and position measurement, short-wavelength monochromatic light is used as an illumination source as much as possible, which has a great effect on improving system accuracy.