|
GX Optical provide one of the largest selections of magnifiers of all types in the world.
The magnifiers are from the world’s finest optical equipment manufacturers.
They will provide you with high quality images and are designed with highly durable materials for a prolonged life.
Our magnifier range includes almost every type of magnifier available.
Our experts are ready to help you make your choice.
All or magnifiers are supplied with our 14 day money back guarantee.
GX Optical Information
When choosing a magnifier the first thing to remember is that, generally speaking, the larger the lens the lower is the magnification. We are very frequently asked for high magnifications covering a large area which is not physically achievable.
Magnifier lenses are either made of glass or glass equivalents, glass equivalent polymers are most frequently used in hand held lenses to greatly reduce the weight. The finest quality glass equivalent polymer is PMMA.
Choosing a Magnifier
Faced with a very wide range of magnifier types it is often difficult to decide what type of magnifier you need. Most people concentrate most on the magnifying power of the lens first which may well be a mistake because the magnifying power is really determined by the size of lens you need and the focal length (or working distance) you need. High magnification lenses have shorter working distances/focal lengths.
The size of lens you need depends entirely on what you need to use it for. If you have to look at extremely small objects for inspection or sorting then a small lens is probably your only option because you need a high magnification. Many people need a magnifier to aid reading and often think that a large magnifier would be best but there also handy, portable magnifiers that are essentially domes or rods which sit directly on the page and magnify an individual; word of line of words which may be even more useful.
Another consideration is illumination which can help significantly in making the magnification task less of a strain and usable in any location. For the partially sighted it can make the difference between reading clearly or not at all.
Finally you need also to decide if you need hands free observation. This is both more relaxing and helpful in tasks where you need to manipulate the subject or even hold a book. There are several approaches to hands free magnification:
- Head mounted magnifiers which can be attached to a head band with flip-up lenses or attached to spectacles.
- Chest mounted magnifiers which hang on a strap around your neck and rest on your chest
- Desk, Floor or G-clamp magnifiers with a variety of articulated arms
- EyeLoupes for higher magnifications held in place in the orbit of your eye
1. Decide on the magnification you need, don’t be tempted to go for the highest magnification because your field of view and depth of focus will become more limited.
2. Some lenses only show their diopter value, look at the table to see the magnification.
3. If shown check the focal length and lens diameter and make sure they are suitable for your task.
4. As a general rule, because the working distance will be less than 20 cm above 5 diopter, stereo microscopes are recommended for close-up purposes only.
Technical Terms:
Diopter (D): This describes the refractive (light bending) capability of a lens, it is proportional to the curvature of the lens. The focal length (working distance) and diopter values of a lens are directly related. The diopter of a magnification lens, can be established by viewing from a distance of 25 cm above the lens, then move the object to the the greatest distance below the lens where it remains in sharp focus. Divide this distance into 100 cm. The result is the diopter of the lens - e.g., if the object is at a 33 cm distance than it is a 3-diopter lens (100/33 = 3D). Each diopter increases the size of the viewed object by 1/4 (25%) when the object is at its full focal length from the lens.
Field of View: The Observable Area while in focus. As magnification increases, the field of view and focal length decrease.
Magnification: The amount of enlargement (see table below).
|
Diopter
|
Magnification (X)
|
|
3
|
1.75
|
|
4
|
2.00
|
|
5
|
2.25
|
|
7
|
2.75
|
|
8
|
3
|
|
9
|
3.25
|
|
11
|
3.75
|
|
13
|
4.25
|
|
16
|
5.00
|
|
18
|
5.50
|
|
20
|
6.00
|
|
Using your Magnifier
For comfortable viewing:
1. Use both eyes.
2. Position the magnifier so that it is a suitable distance from the subject, yet close enough to your eyes to get the maximum magnification without distortion. Do not be tempted to lean back away from the lens to increase magnification.
3. Chair height and work surface should be positioned so the operator can maintain comfortable posture while working.
BASIC MAGNIFIER OPTICAL SYSTEMS
Simple Lens:
Simple lenses are satisfactory for work that requires only low power magnifiers, such as 2X or 3X reading magnifiers. Simple lens magnifiers distort color on the outer fringes of the image and thereby lose sharpness.
Doublet Lens:
The doublet lens is two simple lenses used in conjunction with each other but not cemented together. The doublet produces an image of better quality because it corrects some of the outer image color distortion. It does not necessarily have more power than the simple lens, but it does provide a better quality image.
Achromatic:
An achromatic is a positive simple lens cemented to a negative simple lens. The primary advantage is that it is corrected for two colors and works well at high powers. Most high quality magnifiers use achromatics to remove color fringing at the edge of objects.
Triplet:
Cementing three lenses together produces a triplet lens. Triplets produce a better quality image, are corrected for three colors, and give little or no image distortion. They are best used for jobs that require a great deal of precision at high magnifying levels of 10X to 12X. Comparators are examples of triplets.
BIFOCAL
This type of magnifier has a main lower power lens with a smaller, higher power lens occupying an area within it.
COLOUR DISTORTION
The lens may produce a prism effect giving the image colour fringes known as chromatic aberration. Simple lenses focus various colours at different points. Achromatics with two simple lenses cemented together correct this by causing many colors to focus at the same point.
FIELD FLATNESS
Due to physical laws, the outer part of the image formed by a simple lens may appear out of focus. The greater the magnification - and the greater curvature of the lens - the greater the problem. This can be easily overcome by designing a magnifier that has more than one lens. A triplet has a "flat field" which means the entire area of view is in focus and undistorted.
|
