Knowledge Q&A


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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.

  • The magical effects of magnifying glass and telescopes

    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.