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?

    With a wide range of styles and features to choose from, finding the right magnifying glass for your needs may seem a rather daunting task. But instead of exploring every option on the market, think of finding the right magnifier as shopping for your next pair of shoes: you want comfort and the best style, but above all you want the right fit. To help with your selection, consider these two simple steps:


  • 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) +1 For 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


  • 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 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.


  • Will magnifier work when touching a page?

    No. It won't get the magnification effort when touching a page. Because the magnifier need 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 focal length (working distance) is the ideal distance between the lens and the object, not too close (or the lens won't magnify) and not too far (or the image appears wavy). And if you hold the lens MUCH too far from the object, the image will appear upside down. According to the almighty Wikipedia the 'normal' working distance for a lens is 10 inches. This is rather neat because (as you will see if you read the extra-technical stuff below) 10 inches is about 25cm, and 25cm X4 = 1 meter (near enough), and physicists use 1 meter as the definition of 'standard' focal length (not very practicable as a 'working distance')...but don't worry about that, all you need to know is - the way I calculate magnification now falls in line with the 'official' method you find online, like this: 1 inch = 10X magnification 2 inch = 5X magnification 2½ inch = 4X magnification 3 inch = 3.4X magnification 3½ inch = 2.8X magnification 4 inch = 2.5X magnification 5 inch = 2X magnification 6 inch = 1.7X magnification 7 inch = 1.5X magnification 8 inch = 1.3X magnification 9 inch = 1.1X magnification