Magnifiers are inspection instruments that enlarge the image of a sample. The level of magnification (generally less than 50 times) differentiates magnifiers and microscopes.

 

Operation

 

Magnifiers are used to increase the speed of assembly, improve inspections, enhance quality control, facilitate the manufacturing of small parts, and investigate or observe small objects. They are commonly used in electronics manufacturing and during medical procedures.magnifier

 

Magnifiers are evaluated on the parameters of task distance and task duration. Task distance is the space between the viewer and the object being viewed. Near tasks, such as reading, are usually done at distances of 16 inches or less. Intermediate tasks are those done at arm's length or slightly more—between 17 and 40 inches. Distance tasks are completed at approximately 5 feet or more.

 

The task duration refers to the time period during which the magnifier is utilized. Short-term activities are only a few minutes long, while extended viewing tasks are for longer periods of time. The grid below can be used to identify the best magnifier based on task distance and duration.

 

  

Magnifier selection

Magnifier selection grid

Table credit: eschenbach

 

Types

 

Mounting

 

  • Floor stand: The device location is maintained via a stand which rests on the floor. The magnifier is mounted on a boom or extension for more ergonomic use.
  • Desktop/tabletop: The magnifier includes a weighted stand or clamp for fixed positioning on a tabletop.
  • Handheld/wearable: Personnel manipulate a magnifier's position with their hands, or the device is integrated into a garment for easy access and use. 
  • Magnetic: A paramagnetic mechanism adheres the magnifier to attracted materials.
  • Suspended: An articulated arm or boom magnifier extends from an overhead structure, providing a versatile range without interrupting floor space.

 Configurations

 

Product image for Luxo IFM Magnifier -- 16345LG

Arm, boom or clamp

The magnifier's position is managed by a rigid boom, gooseneck arm, or other articulating mechanism. They are common for quality assurance, jewelry manufacturing, and electronics assembly as they free the hands of the operator..

Page Magnifier, DM-21, DM21, Magnifier

Sheet

This type of magnifier is long and wide, but thin. It facilitates the examination of documents, photos, textiles, and other flat-surfaced specimens. A hemispherical or Fresnel-type lens is most common with this style and it may include an integrated scale.

 

K bino TTL professional mit Sportfassung und Saphiro²

Binocular

Two magnifiers are unified into a chassis to add stereoscopic or depth perception. This type of magnifier is handheld or worn.

folding magnifiers

 

Folding/linen

Instances where the lens retracts or folds into a storage position enhance the portability of the device. Cube-like collapsing magnifiers often used on desktops are known as linen magnifiers. 

Magna Visor 814212

Headband/visor

This wearable style of magnifiers provides the user convenient analysis lenses, often with several levels of magnification. 

Loupe -- 243-1021-ND-Image

Loupe

A jeweler's loupe is either handheld or withheld by orbital muscles in the user's face. An eyeglass loupe clips onto prescription or safety glasses.

 

 

Pocket magnifier

Pocket

A magnifier whose volume is less than the average garment pocket and its lens is retractable.

Computer Screen Enlarger for 14-17

Screen magnifier

A visual aid which enhances the magnification of a monitor or television. They are commonly flat magnifiers with characteristic mounting hardware and corrected viewing angles.

Macro Series Zoom 7000 PK M1

Video/digital

These types capture images via CCD, CMOS, or CID technology and recreate a magnified visualization on a monitor. Though the technology is digital, the lenses usually remain optical.

dynameter

Optical dynameter / measuring magnifier

Dynameters measure the diameter of the exit pupil, the distance of the exit pupil to the eyepiece shoulder, and the magnification of telescopes. The magnifying power is determined by comparing the diameter of the glass with the measured diameter of the image of the glass. Magnification = D/d = (entrance pupil diameter)/(exit pupil diameter)

 

Specifications

 

Magnification is the ratio of the size of an image to its corresponding object, which is determined by linear measurement. This value is often represented by an "x," an indication that the number is a multiple. For example, a 2x magnifier doubles the apparent size of an object. This specification represents the entire magnification range, including both the eyepiece magnification and the objective magnification. If a high magnification is required, a microscope should be considered.

 

The magnification chart below shows how magnification, diopter, and focal length affect the object in view.

 

 

Magnification Chart

% MagnificationDiopterFocal LengthSample View

Normal Newsprint

+75% magnification

3-diopter lens

Focal length of 13"

+125% magnification

5-diopter lens

Focal length of 8"

+275% magnification

11 diopters (3-diopter lens plus ADD-A-LENS)

Focal length of 3.75"

+400% magnification

16-diopter lens system

Focal length of 2.5"

Chart credit: Dazor

 

Additional specifications include:

 

  • Diopter: Diopter refers to the curvature of a lens. As the diopter increases, the lens becomes thicker and the curvature greater. As the curvature increases, light rays are redirected to fill a greater portion of the user's retina, which makes the object look bigger. The relationship between diopters and power is: the number of diopters divided by four equals power. For example, an eight-diopter lens would make an object look two times bigger, over and above what the unaided eye already sees (8 diopters ÷ 4 = 2x power).
  • Illumination: Illumination describes the built-in lighting within the magnifier. If the application requires additional illumination there are several options including LED, halogen, and fluorescent lighting.
  • Field of view: The extent of the visible image field that can be seen when the magnified image is in focus. As the power increases, the magnifier's field of view decreases.
  • Focal length: Focal length, also known as working distance, is the distance between the front lens and specimen when the specimen is in focus. In most instances, the working distance of a magnifier decreases as magnification increases. For example, a 2x magnifier at a focal length of 5 in. means that the magnifier will provide double the magnification power and be clear in focus at 5 in. The shorter the focal length, the higher the magnification power. The image at right represents this concept. If the application uses low magnifications then a magnifier can give the user a longer focal length and also give more room to work side-to-side. Microscopes are great for focusing on a small point, but magnifiers provide a more comprehensive field of view. Working distance values are not included on all magnifiers and their presence varies depending upon the manufacturer. 
  • Scale/reticle resolution: Scale or reticle resolution refers to the minimum scale or reticle that can be resolved with the magnifier. An optical device reveals the fineness of detail in an object. Objectively, resolution is specified as the minimum distance between two lines or points in the object that are perceived as separate by the human eye. Subjectively, the images of the two resolved points must fall on two receptors (rods or cones), which are separated by at least one other receptor on the retina of the eye. 
  • Depth of field: The depth of field is the range of distance the magnifier can be moved from the object and maintain an acceptable degree of focus. The depth of field varies with the focal length and as the power increases, the depth of field shortens.

Features

 

Common features of magnifiers include:

 

  • Bifocal lens: Magnifiers with a bifocal lens provide two or more, magnification levels. This style includes traditional bifocal lenses that have two different strength lenses melded together, as well as swing lens or drop alignment types.
  • ESD safe: Electrostatic discharge (ESD) can damage sensitive electronic components. An ESD safe magnifier is designed so that random or static charge energy cannot be released.
  • Scale/comparator reticle: The magnifier has an internal scale or reticle grid for comparative measurements of dimensional or orientation features. A reticle is a flat, transparent component inscribed or etched with a grid or graduations. Reticles can be placed with the magnifier, on top of, or along the side of the product being examined.
  • Variable magnification: The magnifier provides several magnification levels. It may produce discrete or continuous changes in magnification using multiple, independent, or aligned lenses, or an optical or digital zoom system. The lenses themselves may swing or drop into alignment on some magnifiers.
  • Work holders/manipulator: Magnifiers constructed with integral clamps, clips, or magnet holders for manipulating or holding the sample being viewed.

 

Applications

 

Applications that use magnifiers include assembly, document and photograph inspection, electronics manufacturing, forensics, industrial inspection, jewelry and gemology, medical and life science, vision aid, tool and die, machining, and textiles.

 

Standards

 

Magnifiers must adhere to certain standards and specifications to ensure proper design and function. Additional standards can be found on the IHS standards store

  • BS 5165: Characteristics of single-element, multi-element and twin-system magnifiers. Recommendations for their selection.

  • BS 7522 P1: Specifies requirements, both optical and mechanical, for handheld and stand-mounted magnifying appliances for use as near-vision aids. Includes simple and compound magnifiers. 

References

 

Working Distance

 

Technical Magnifiers: Finding a Commercial or Industrial Magnifier

 

How to Select a Magnifier

 

How to Choose a Lighted Magnifier

 

Image Credit:

 

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