Fowler 52-665-005 Pocket Optical Comparators, 7X Magnification

The Fowler 52-665-005 optical comparator has 7X magnification and a set of five reticles for measuring line thickness, angles, radii, circles, degrees, and length. A glass lens provides high-resolution images. Scales are photo-etched onto glass reticles for accuracy and distortion-free viewing. The set of five reticles includes one each Fowler 52-667-001 degree, circle, linear scale, and square reticle; Fowler 52-667-005 degree, linear scale, radii, line length, and line thickness reticle; Fowler 52-667-007 square and circle reticle; Fowler 52-667-008 linear metric reticle; and Fowler 52-667-013 linear inch reticle. Each reticle includes a protective plastic case and the set includes a fitted plastic case.

Diopter (D) is a technical term for the measurement of the light curvature and thickness of a lens. A dioptric number and a magnification number are not the same thing. Diopter strength represents a specific magnification power (X). For example, a 5-diopter provides 2.5X magnification (at a distance of 8"). The higher the diopter, the more magnification a lens can provide. As magnification increases, distance to the object (focal length), and field of view (diameter, or narrowness of view) decrease. Magnifiers and prescription eyeglasses have a diopter value, such as 1.5 or 2. The dioptric strength of an accessory lens, such as prescription eyeglasses or an eye loupe, must be added to the dioptric strength of the magnifier to calculate total magnification.

Magnifiers are devices used to enlarge the visual appearance of an object or image. Magnifiers come in a variety of styles such as hand-held, headband, standing, clip-on, eye loupe, and those that hang in a necklace form, or fit in a trouser pocket. Magnifiers are commonly made of plastic or glass. They can have one or more lenses with varying magnification abilities, and can have a binocular configuration with a single lens, or two separate lenses. They are sometimes used with LED or fluorescent light sources to help control viewing capabilities. Magnifier ability is often expressed as magnification at a specific length. For example, 1.75X at 14" means that when a magnifier is held at 14" from a viewer's eyes, the object will be magnified 1.75 times (X) its actual size. As magnification increases, viewing areas and focal length decrease. Magnifiers sometimes have a diopter number, expressed as + or - D, which is a measurement of strength (or power) of the lens. Some magnifiers are marked with a dioptric number on the lens. A high diopter number has a higher magnification than a low diopter number. Aspheric magnifiers, unlike spheric magnifiers, produce a sharp image to the edge of the lens for less distortion. Magnifiers are widely used in jewelry inspection and fabrication, watch-making, needlework, artwork, reading, print inspection, and stamp-collecting.

The Fred V. Fowler Company manufactures inspection and measurement instruments such as electronic indicators, calipers, bore gages, and digital scales. The company, founded in 1946, is headquartered in Newton, MA.

What's in the Box?

• Fowler 7X magnifying loupe
• Fowler 52-667-001 reticle
• Fowler 52-667-005 reticle
• Fowler 52-667-007 reticle
• Fowler 52-667-008 reticle
• Fowler 52-667-013 reticle
• Fitted case