Ball Lenses are commonly used to improve signal quality in fiber coupling applications, or for use in endoscopy or bar code scanning applications. Ball Lenses feature short back focal lengths to minimize the distance needed from the Ball Lens to the optical fiber. Zoolied offers a variety of Ball Lenses in a range of substrates for performance in the ultraviolet to the NIR. Half-Ball Lenses are also available to ease mounting or system integration.
Zoolied N-BK7 Ball Lenses are glass spheres commonly used in fiber optic applications. Ball lenses are ideal for focusing light into optical fibers, or for fiber coupling. Bk7 Ball Lens,K9 Ball Lens,K9 Optical Ball,5Mm Bk7 Ball Zoolied Inc. , https://www.zoolied.com
No.1 KKTV U40(Click for details)
Features: 4K Samsung screen, 64-bit processor 
KKTV, as a brand relying on Konka's 36 years of experience in TV production, is a hard brand. Equipped with A53 dual-core CPU, Mali-T720 quad-core GPU, dual-core VPU (video processor) strong configuration to help bright picture quality, easy to run sofa butler HD video, while using Samsung 4K screen, is 4 times the resolution of traditional 1080p TV H.265 hard decoding saves bandwidth loading faster and expands the interface to bring more convenience. Built-in double-receive dual-fire WiFi module, the signal is more stable, more penetrating power, new YIUI 5.5 system, open smart system, the application you want is in this! The video content is combined with a number of content resource service providers, whether it is hit TV series, trending variety shows, blood sports events, or colorful film and television, diverse video content, allowing you to have a variety of choices. 
Summary: KKTV produced by Konka, relying on Konka's decades of television production process, the product quality completely pass, and the original Samsung screen is used to allow consumers to have a better viewing experience, comparable to the desktop computer configuration Is also an important reason to choose KKTV U40, after all, smooth operation can bring a more pleasant experience.
Jingdong recommended price: 1699 yuan
No.2 TCL D40A620U(Click for details)
Features: Intelligent 10-core high-definition, high-fidelity Dolby audio 
This TCL D40A620U is known as the small screen viewing king. Rich in content to others, integrated multiple video platforms, specifically for Internet TV, video content, movies, TV dramas, variety shows, animation, sports live broadcast, etc., subdividing multiple content areas, differentiated content at a glance, convenient for you quick search. Covers HD genuine movies from the 70s to the present, including Hollywood blockbusters, and Japan and South Korea hits. If these are not enough, you can install a sofa housekeeper to get more free movie resources. The main frequency of the TV CPU reaches 1.4GHZ. In the multi-tasking scenario, the operation is still smooth, the operation response is very sensitive, and the Ultra HD 4K display brings the ultimate viewing experience! The performance of TV sound is also a standard to measure the quality of TV. TCL D40A620U uses the low-frequency enhancement technology to achieve a more complete performance in the full range and it is truly extraordinary. 
Summary: TCL also serves as the predecessor of domestic TV brands, and the products have been doing a good job in the market after iterative updating. TCL D40A620U super rich video content is very suitable for friends who like to watch TV at home, and massive libraries are accompanied by 4K. HD screen, living room change cinema!
Jingdong recommended price: 2299 yuan
No.3: Hisense LED 40EC520UA (Click for details)
Features: Colorful 4K screen, 64-bit 14-core processor 
Hisense LED 40EC520UA uses 4K color enhancement technology to achieve 4 times the full HD 4K ultra high-definition picture quality, clear display picture details, restore lively and vivid picture color, 2K to 4K technology even ordinary programs can also achieve comparable 4K Display effect, equipped with a 64-bit 4-core Cortex-A53 processor, to optimize the picture details to capture exciting moments, VIDAA third-generation operating system, according to the user's habits to adjust the interface details, create a simple smart TV operation experience, Hisense operations team The large-screen video platform built for television, film library resources include movies, TV shows, variety shows, VIP users can enjoy Hollywood movies, of course, if you want to watch movies for free, you can install a sofa butler, free movies can not finish! Through the strategic cooperation with Tencent to build a large-screen video game platform, many people can achieve the same screen, creating a new way of living room entertainment. 
Summary: Hisense LED 40EC520UA's 2K to 4K technology can be regarded as a more practical black technology, in the case of broadband is not very abundant, you can still experience the feeling of 4K, and the Dodo structure VIDAA third-generation operating system, operating methods Greatly simplified for use by more people.
Jingdong recommended price: 2599 yuan
No.4: Changhong 40U3 (Click for details)
Features: 4K Ultra HD, 18-core processor 
Changhong 40U3 as the new darling of the small-size TV, the screen resolution has reached the 4K standard, has 8.3 million pixels, can see a clearer picture quality at the viewing, amazing 4K colorful screen, has a high static Contrast makes the TV darker black, whiter white, and the details of the screen display are more. The HD image quality engine is adopted, and the edge sharpening processing technology enables each frame picture to be optimized in real time. The polymer light guide film is also Can make the screen level more abundant. The unique colorful color technology of Changhong makes the picture colorful, UMAX viewing system, restore film sense, 28-bit 64-bit SOC A53 chip processing data volume doubled, smooth viewing 4K movie in the sofa butler. Mali T720 image processing, effectively improve image quality, HD does not wait! With Tencent video platform, with rich content, stunning viewing experience to meet the needs of different viewing crowds. 
Summary: The colorful color technology of Changhong 40U3 and the application of UMAX viewing system make the video screen close to the film grade, and at the same time, it is accompanied by a 4K colorful screen, which shows more details of the picture and greatly enhances the viewing. Comfortable, small size can also see a more exciting world.
Jingdong recommended price: 2399 yuan
No.5 : Skyworth 40E6000 (Click for details)
Features: SOC chip, 4K smart 
The Skyworth 40E6000 adopts the design concept of “Windwellâ€. The nature of the Skyworth 40E6000 is inherently flashy. The simplicity is prior to the complexity. The SOC chip is equipped with excellent ten-core performance. Whether it is a large-scale game in a sofa butler or a 4K video, it can be performed with multiple tasks. .265 hard decoding, the same broadband can be more smooth viewing of 4K video, Galaxy video iQiyi as background, video resources are rich, and continues to update, let you enjoy the fun of viewing, you can swap the three modes, respectively The needs of audiences of all ages in the family, a key to start the old UI mode, each section is magnified, large icons and large fonts, so that older people's eyes can more easily see the content of the TV. And there are also programs tailored specifically for older people that are designed to be very intimate. 
Summary: Skyworth 40E6000 not only meets daily entertainment needs in terms of configuration, but is more intimate in content design. The three modes can be switched at random so that elderly and children at home can also enjoy customized content and UI, the real one. There are multiple functions of the box. If the family members are relatively old, this box is a good choice.
Jingdong recommended price: 2799 yuan
Summary: Xiao Bian recommended several 4K TVs here, all of which are domestically produced. The quality of the big brands is trustworthy. Although the size is not very big, the sparrows are small and well-organized. All the functions are available, and each has its own function. Its own characteristics, such as KKTV's Samsung original screen, and YIUI operating system, hardware and software are excellent in the industry, TCL D40A620U as a small screen viewing king, content super rich library allows you to see endless the film. The use of 4K color enhancement technology and 2K to 4K technology of Hisense LED 40EC520UA will allow you to enjoy a 4K viewing experience without a sufficient speed, which is very practical! Changhong 40U3 UMAX technology, with unique audio technology can give you the same as the cinema like a real viewing experience, Skyworth 40E6000 a variety of modes to switch, customized for all ages, the UI is very suitable for the elderly and children at home Users, and these small-size TVs are very affordable for small-sized users, and can experience 4K viewing experience at a low price.
Friends who know more about smart TVs should all know that these smart TVs cannot directly watch TV live broadcasts because of the restrictions of relevant policies. This is unfortunate, but we can solve this problem by installing some third-party applications, such as sofa butlers. After installing the sofa butler, you can easily watch live TV broadcasts from applications such as "little micro-broadcast", "TV cat" and "magic video" downloaded from the sofa butler client. 
Learn more about smart TV recommendations, click the following articles to view:
[60 inch 4k TV how to choose? 5 large screen smart TV recommended】
Five 40-inch 4K bedroom essential drama artifact recommended!
After introducing a 60-inch 4K TV recommendation to everyone last week, many of my friends said that the screen size is a bit large, there is no screen is relatively small, but the picture quality is still very good 4K TV, today the sofa network Xiaobian to introduce you to several Petite, but equally powerful 40-inch 4K smart TV.