Knowledge Q&A



Best Sale

E-Tay Knowledge Q&A Introduction

E-TAY INDUSTRIAL CO., LTD. is Taiwan supplier and manufacturer in Optical Industry. E-Tay has been offering our customers high quality Magnifying Glass, Magnifying Sheet, Headband Magnifier, Lighted Magnifier, Page Magnifier since 1980. With both advanced technology and 38 years experience, E-Tay always make sure to meet each customer's demand.

Knowledge Q&A


Over 30 years experience of making magnifiers and fresnel lenses, we also have some useful knowledge to share with the public.
It's our pleasure to help people find a suitable magnifier so that their vision will be clear and bright.

  • What is Fresnel Lens?

    Fresnel lenses are portable and lightweight sheets used for light gathering or magnifying. The frensel lens was first invented by a French physicist namely Augustin-Jean Fresnel. Augustin Fresnel first used this lens design to build a glass Fresnel lens - lighthouse lens in 1822.Unlike typical spherical or aspherical optical lenses, fresnel lenses are composed of a series of concentric grooves etched into one side of a sheet of plastic. A fresnel lens is a thin, flat optical lens which consists of a series of a series of small narrow concentric grooves on the surface of a lightweight plastic sheet in order to reduce the thickness, weight and cost. Each groove is at a slightly different angle than the next and with the same focal length in order to focus the light toward a central focal point. Every groove can be considered as an individual small lens to bend parallel Fresnel light waves and focus the light. The lens actually eliminates some spherical aberration.The Fresnel lens is a special optical lens. lt can now be made from plastic such as acrylic fresnel lens, PMMA, polyvinyl cholride (PVC), polycarbonate (PC) and HDPE. A traditional glass convex lens would be thick, heavy and very expensive, but a plastic Fresnel lens is a thin, flat, lightweight and low cost alternative.A high groove density has a better quality projection image. The Fresnel lens is a good solution for quality image and efficiency at a significantly lower cost. The Fresnel lens is usually corrected for spherical aberration.

  • How To Choose A Good Magnifying Glass?

    When one thinks of a magnifying glass, they tend to think of the big classic type lens. However, in actual use, you want a lightweight, and powerful magnifier that has impeccable optics and is simple to use. Utilizing the best magnifier for demanding jobs like inspecting diamonds and gemstones is essential to their occupation, while hobbyists who collect rocks and minerals just need to buy a decent magnifier that they can afford to lose.Let we know "What is a good magnifier" before we choose the good magnifier:

  • What is the relationship between diopter and magnification of a magnifying lens?

    Diopter refers to the curvature of the lens. As the diopter increases, the lens become thicker and the curvature greater. As the curvature increases, light rays are redirected to fill a greater portion of the viewer’s retina which makes the object look bigger. Powers refers to how much larger an object is made to look through a magnifying lens. Power is typically indicated by an X such 2X or 4X. There is more than one formula to converts the diopter of a lens into its power, we as a company use the common formula: Magnification = (Diopter / 4) +1For example an 3 diopter lens makes an object look 75% times larger, over and above what the unaided eye already sees. As you increase the magnification the lens size effectively decreases. It is not possible to get a high power lens in a large diameter. Opticical combinations are a compromise for the “ideal” magnifier.We have tabulated a guide for magnification levels,as compared to Diopter:2Diopter=1.50x Mag 3 Diopter = 1.75x Mag 4 Diopter = 2.00x Mag 5 Diopter = 2.25x Mag 7 Diopter = 2.75x Mag 8 Diopter = 3.00x Mag 9 DIOPTER = 3.25x Mag 11 Diopter = 3.75x Mag 13 Diopter = 4.25x Mag 16 Diopter = 5.00x Mag 18 Diopter = 5.50x Mag 20 Diopter = 6.00x MAG

  • How do I calculate magnification for my magnifier?

    An aspheric lens is an ideal magnifier from several points of view. When used at its conjugates, there is no distortion of the image (a rectangular grid remains a rectangular grid after magnification). If the lens is large enough for the object to be viewed with both eyes, the view is stereosopic. To calculate magnification, use the following formula: M (magnification) = the height of the image ÷ by the height of the object. Plug your data into the formula and solve. If your answer is greater than 1, that means the image is magnified. If your answer is between 0 and 1, the image is smaller than the object.

  • Differences Between A Magnifier and A Reading Glasses

    The lens of the eye is equivalent to a convex lens. It also works according to the theory of the actual image is inverted and minimized when object distance is greater than 2 times of the focal length. However, eyes to see close objects or distant object are not by changing distance to object or distance to image (because the distance of the lens and the retina are basically the same). It works by the expansion of ciliary muscles to change curvature of the lens to adjust self focal length leading to accurately reflect an image on the retina. Lighting on the retina is conducted to the brain through the nerves to analyze what the "object" is.Normally, as human lens gets fiberosis and is gradually hardened after age 40, the elasticity of ciliary muscles can be weakened and leading to the eyeball becomes short. Also, focus ability of lens is reduced. The result is to see distant objects clearly, but blurring of near objects. Then the eye condition is called presbyopia. By the condensation of positive meniscus, wearing reading glasses is supplementary and can make image of the object falls on the retina.

  • What is a magnifier used for?

    A magnifying glass (called a hand lens in laboratory contexts) is a convex lens that is used to produce a magnified image of an object. The lens is usually mounted in a frame with a handle (see image). A magnifying glass can be used to focus light, such as to concentrate the sun's radiation to create a hot spot at the focus for fire starting. A magnifier can be used in many ways in our daily life. But, firstly, let’s find out the function of magnifier tool.

  • Will magnifier work when touching a page?

    Usually. It won't get the magnification effort when touching a page. Because a magnifier with convex lens needs some distance between object and lens as focal length. In order to achieve maximum magnification without distortion, the user should position the lens a proper distance from the object. The distance from the 3x magnifier to the object viewed is about 8-10 cm. This distance offers user better viewing experience.


    People usually assume magnifying glasses only help seniors physically, but rarely aware magnifying glasses can help psychologically. We would like to share paragraphs excerpted from “99 years old, no matter how old” by Yoshizawa Hisako, a famous Japanese column writer and essayist.


    Usually, Fresnel lens is cut into spherical surface shape in order to minimize the optical aberration of the image during imaging. The lens can better align an ideal point light source into a parallel light source. In real life, no light source is a real point light source, but solid state light emitters such as LEDs are very small, so as long as the distance between the lens and the LED is appropriate, it can be used as a point light source. Therefore, the Fresnel lens produced by Yutai can align the LED output light to parallel light, while the traditional incandescent light source generates a large amount of radiant heat, which limits the application of plastic optical materials very close to the light source.


    The Fresnel lens has been used in many ways of our daily consumption. You can find it in the camera;s focusing screen, LED spotlight, ATM machines, buses, trucks, solar panel cells, magnfiers, traffic lights, 3D/VR glasses, and infrared sensor of human body.


    In order to make the VR headset lens thinner and lighter, some lenses use Fresnel lenses. This lens has the same curvature as a normal lens, but has threads of different sizes on one side. But using a Fresnel lens means you need to make a certain sacrifice. You can make a multi-threaded lens so that you can see clearer images. But the light cannot be focused on one point, and the curvature is always incorrect. In addition, you can also use a Fresnel lens with fewer threads to help focus the beam and improve contrast, but the sharpness of the image will be impaired. The VR head-mounted display device uses the characteristics of the Fresnel lens in short distances...


    Application of Fresnel lens in projection system. Fresnel lens proved to be the best use in the projection system, its role is to collimate light and focus light. The Fresnel lens tunes the light source retracted by the light source into parallel light, which obviously improves the brightness of the display panel and eliminates the hot spot effect, thereby improving the uniformity of the overall display brightness. Fresnel lenses are generally used together with other display components (such as cylindrical lenses). The advantage of the Fresnel lens used in the projection system is that after focusing or adjusting the light collimation to increase the brightness of the increased volume, if the collimator lens is eliminated, the light will be lost a lot when passing through the panel, showing...


    The Fresnel lens is a sheet, round or other shape that is injected or molded from polyolefin materials. There are two main functions of the Fresnel lens acting on the probe: one is focusing, which is to refract (reflect) the pyro-infrared signal on the PIR, and the second is to divide the detection area into several bright and dark areas. Zone, so that the moving objects entering the detection area can produce a changing pyro-infrared signal on the PIR in the form of temperature changes. Simply put, there are equidistant tooth patterns on one side of the lens. Through these tooth patterns, the optical bandpass (reflection or refraction) of the specified spectral range can be achieved.


    Positive Fresnel lens: The light enters from one side, and exits through the lens on the other side to focus into a point or exit as parallel light. The focus is on the other side of the light and is finitely conjugated. This type of lens is usually designed as a collimator lens (such as a Fresnel lens for projection, a magnifying glass, etc.) and a condenser lens (such as a heat-collecting and concentrating Fresnel lens for solar energy. Negatiive Fresnel lens, on the contrary, the focus and the light are on the same side, and the surface is usually coated as the first reflecting surface.


    If the LED lamp lens element is made of optical glass, the production cost is relatively high and it is fragile. If the thickness of the element can be reduced, or even a sheet lens, the size of the optical element can be reduced, and the size of the lamp or other equipment can be reduced. It can also save materials and reduce costs. As the thickness is reduced, the light absorption is also reduced, and the efficiency of lamps or instruments will also increase. Therefore, making high-quality thin-film optical parts has always been one of the goals pursued by optical design. The Fresnel lens is a sheet-like thin lens. It has always been light, thin, inexpensive, and cut in any shape.


    The infrared PIR Fresnel lens sensing method is static, and there is infrared light in the space. Because the dual-element probe adopts complementary technology, no electrical signal output will be generated. Under dynamic conditions, the human body is sensed by element A or element B successively through the sensor, and Sa<Sb or Sa>Sb produces a difference, and the dual elements lose their complementary balance effects and sensitively generate signal output. A person moves in a vertical state towards the probe, and Sa=Sb does not produce a difference, and it is difficult for the dual element to produce a signal output. Therefore, it is advisable to install the detector in parallel with the walking direction of the person. According to the above principle, the combination of the probe and the lens can make the human body detection with the following induction methods


    The design principle of the Fresnel lens is that the lens is no longer regarded as a whole during processing, but as an entity composed of many microstructures. These microstructures retain the curvature radius of the original convex lens, and remove the intermediate light The deflection does not work or affects a small part. The design process of the Fresnel lens is shown in Figure 1, and Figure 2 is a physical diagram of a flat Fresnel lens. In the early days, due to material limitations, lenses were all made of glass, and Fresnel lenses were no exception. However, if the traditional grinding and polishing method is used to process Fresnel lenses, it not only takes a long time, but also consumes manpower, which leads to cost Too high. Later people invented...


    Infrared sensing systems can be divided into five categories according to their functions. They are measurement systems that use infrared as the medium. According to the detection mechanism, they can be divided into photon detectors and thermal detectors. Infrared sensing technology has been used in modern science and technology, national defense, industry and agriculture, etc. It has been widely used. Infrared technology has developed to this day and is already well known to everyone. This technology has been widely used in modern technology, national defense technology, industrial and agricultural technology and other fields. Infrared sensing system is a measurement system using infrared as the medium, which can be divided into functions Five categories: (1) Radiometer, used for radiation and spectrum measurement; (2) Search and tracking system, used to search and track infrared target, determine its spatial position and track its movement; (3) Thermal imaging system , It can produce the distribution image of the entire target's infrared radiation; (4) Infrared ranging and communication system; (5) Hybrid system refers to a combination of two or more of the above various systems.


    The first reaction to seeing the "Fresnel lens" is that I don't know what it is! Only after seeing the practical application of these Fresnel lenses, we know that it has already entered our daily lives. Infrared Fresnel lens is used in the field of sensor lights and intelligent robots: Infrared Fresnel lens is used in security smart home: Fresnel lens is used in LED lights: Fresnel lens is used in the field of wide-angle lens: in projectors, solar power, The field of magnifying glass has also been very well applied: with the development of Fresnel (threaded) lens technology, the application has become more and more extensive. In our daily life, there are temperature measuring guns, sensor lights, automotive or ATM rear mirrors. ...


    Traditional lenses are relatively thick and heavy and small in size; Fresnel lenses are light, thin and large in size.


    Frensnel lens for LED light distribution Fresnel lens can be moulded or injection mold depending on light source model, COB light source (value of luminous), light angle, distance from lamp bead to lens d lens size, thickness, material. Application: Good for night vision, stage lights, high bay lights, flood lights, wall wash lights, traffic lights, film and television lighting, etc. Extended application: Use sandblasting, compound eyes, atomization, anti-glare, diffuser and other methods to make the light spot more uniform and soft...

  • How to clean a PVC Fresnel magnifying sheet?

    The PVC Fresnel mangifying sheet can be cleaned by glass cleaning spray like Windex or lens cleaner spray. With clean water then wiped by a soft cloth or eyeglasses cloth and dray naturely.