免费看欧美性生活黄片-成年人免费在线看大片-精品少妇人妻中文字幕-日本一区二区免费在线视频

Advantages of Fresnel Lenses

2014-02-09 admin1

  Our team is ready to assist you! Please visit our website at http://njst56.com/about/335-en.html

  Fresnel lenses consist of a series of concentric grooves etched into plastic. Their thin, lightweight construction, availability in small as well as large sizes, and excellent light gathering ability make them useful in a variety of applications. Fresnel lenses are most often used in light gathering applications, such as condenser systems or emitter/detector setups. They can also be used as magnifiers or projection lenses in illumination systems, and image formulation.

  A Fresnel (pronounced fray-NEL) lens replaces the curved surface of a conventional optical lens with a series of concentric grooves. These contours act as individual refracting surfaces, bending parallel light rays to a common focal length (Figure 1). As a result, a Fresnel lens, while physically narrow in profile, is capable of focusing light similar to a conventional optical lens but has several advantages over its thicker counterpart.

  Figure 1: Profile of a Fresnel Lens [View Larger Image]

  THE THEORY OF FRESNEL LENSES

  Interested in a short video? Check out Fresnel Lens Review. View Now

  The driving principle behind the conception of a Fresnel lens is that the direction of propagation of light does not change within a medium (unless scattered). Instead, light rays are only deviated at the surfaces of a medium. As a result, the bulk of the material in the center of a lens serves only to increase the amount of weight and absorption within the system.

  To take advantage of this physical property, 18th-century physicists began experimenting with the creation of what is known today as a Fresnel lens. At that time, grooves were cut into a piece of glass in order to create annular rings of a curved profile. This curved profile, when extruded, formed a conventional, curved lens – either spherical or aspherical (Figure 2). Due to this similar optical property compared to a conventional optical lens, a Fresnel lens can offer slightly better focusing performance, depending upon the application. In addition, high groove density allows higher quality images, while low groove density yields better efficiency (as needed in light gathering applications). However, it is important to note that when high precision imaging is required, conventional singlet, doublet, or aspheric optical lenses are still best.

  Figure 2: Side Profile Comparison of a Plano-Convex (PCX) and a Fresnel Lens [View Larger Image]

  MANUFACTURING FRESNEL LENSES

  The first Fresnel lenses were made by tediously grinding and polishing glass by hand. Eventually, molten glass was poured into molds, but it was only with the development of optical-quality plastics and injection-molding technology in the 20th-century that the use of Fresnel lenses in many industrial and commercial applications became practical.

  Fresnel lenses can be manufactured from a variety of substrates. They are manufactured from acrylic to polycarbonate to vinyl, depending on the desired wavelength of operation. Acrylic is the most common substrate due to its high transmittance in the visible and ultraviolet (UV) regions, but polycarbonate is the substrate of choice in harsh environments due to its resistance to impact and high temperature.

  APPLICATION EXAMPLES

  While French physicist Augustin-Jean Fresnel (1788 - 1827) was not the first to conceptualize a Fresnel lens, he was able to popularize it by integrating it into lighthouses. Since then, Fresnel lenses have been utilized in a variety of applications, from light collimation and light collection to magnification.

  Light Collimation

  A Fresnel lens can easily collimate a point source by placing it one focal length away from the source. In a finite-conjugate system, the grooved side of the Fresnel lens should face the longer conjugate (Figures 3 - 4) because this produces the best performance.

  Figure 3: Light Collimation of a Point Source with a Fresnel Lens [View Larger Image]

  Light Collection

  One of the most common applications for a Fresnel lens is the collection of solar light, which is considered very nearly parallel (an infinite-conjugate system). Using a Fresnel lens for light collection is ideal for concentrating light onto a photovoltaic cell or to heat a surface. For example, a Fresnel lens can be used for popular home maintenance such as heating a home or pool! In these cases, the overall surface area of the lens determines the amount of collected light.

  Figure 4: Light Collection of Collimated Light with a Fresnel Lens [View Larger Image]

  Magnification

  Another common application for a Fresnel lens is magnification. It can be used as a magnifier or projection lens; however, due to the high level of distortion, this is not recommended. Also, the image quality does not compare to that of a higher-precision system given the amount of distortion.

  While commonly found in solar applications, Fresnel lenses are ideal for any application requiring inexpensive, thin, lightweight positive lens elements. Fresnel lenses are not new technology, but their pervasiveness has increased with improvements in manufacturing techniques and materials. Fresnel lenses are truly unique optical lenses which make them a great tool for a range of interesting and fun optical designs.

蜜臀91精品视频在线观看| 亚洲黄色av在线免费观看| 亚洲av影片一区二区三区| 午夜精品亚洲一区二区| 亚洲男人的天堂一区二区| 亚洲美女性生活一级片| 日本一区二区不卡视频在线播放| 亚洲无吗视频在线观看| 国产自拍在线一区二区| 另类亚洲欧美专区第一页| 18禁止看的视频免费| 少妇被爽到高潮喷水免费福利| 十八禁网站免费在线播放| 女同专区中文字幕另类一区| 熟女一区二区免费视频| 成人亚洲精品国产精品| av人妻熟女少妇蒂亚| 亚洲精品一区二区三区蜜桃久| 国产精品丝袜一区二区三区| 91九色中文视频在线观看| 日本东京热国产精品视频| 亚洲av丝袜诱惑在线| 97视频在线观看免费| 日韩x级av免费在线观看| 中文字幕熟女人妻另类癖好| 日韩精品视频在线观看99| 亚洲精品在线视频视频| 亚洲一区国产二区日本三区| 亚洲精品第一页第二页| 在线观看中文字幕不卡二区| 内射国产老熟女综合导导航 | 我和熟女难忘的真实激情经历| 四虎日韩精品在线观看视频| 亚洲激情图区二区三区| 亚洲激情午夜福利视频| 中中文字幕一区二区三区| av国产老师国语对白国产| 在线观看一区二区中文字幕| 免费观看黄片的视频在线观看| 精品人妻一区二区三区在线av| 国产一区二区三区在线观看一区|