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Microscope Optics and Facts

Brief history of the microscope. The microscope was invented by the Dutch spectacle maker Zaccharias Janssen around 1590. This was the time when Toyotomi Hideyoshi was unifying Japan into a single nation.
In 1655, the Englishman Robert Hooke produced a "compound microscope" that included an objective lens and an eyepiece lens. In 1665, he published Micrographia, the first book describing observations of a variety of organisms made through his microscope. In this book, Hooke named the numerous compartments partitioned by walls as "cells." The discovery of cells triggered the microscope's rapid advancement.
Antonie van Leeuwenhoek of Holland made his own simple microscopes using a single lens, which lead to his discovery of red blood cells in 1673, as well as the discovery of bacteria and human sperm.
Efforts to improve the microscope were made primarily in England in the 18th and 19th centuries. Microscopes developed by Leitz and Zeiss, both German companies, became popular in the last half of the 19th century and onward.

Features. Today there are dozens of microscope manufacturers around the world, making microscopes for education, research and industrial. All microscopes used today for gemological purposes are intended for general industrial use. So, selecting the proper optics for your gemological microscope that will last for long time is a matter of knowledge and expert advice.

The most suitable microscopes for gemological applications are the stereoscopic type allowing details in gems to be viewed in three dimensions. Stereo microscopes for gemological use are usually of low magnification (up to 50X), preferably equipped with continuous zoom magnification system. Step zoom magnification also available from several microscope manufacturers, but the desired 10X magnification is not always available. Zoom ratio and objective lens varied according to the optical design. The old Greenough 12° optical system is one the best.

For the glass wearers is of paramount importance to select eyepieces with high relief to facilitate easy observation. Also, individually adjustable diopter eye-tubes are recommended. Eyepieces having field of view 23 mm at 10X and depth of field around 4.00mm at 64X are highly desirable because the inclusions in the gems are easier observed. Another desirable feature is the adjustable interpupillary distance between the observer's eyes, usually 55 to 75 mm.

Long working distance is an important factor allowing easier manipulation of the gemstone, while observed under the microscope. Preferable working distance should be over 90mm.

Optic manufacturers. The prospective buyer should know what optical components are available in the market and select the most suitable for gemological applications. Gemological microscope fabricators do not make microscope pods, eyepieces and stands; they buy them from various sources, often with their logo, fit them in the microscope base they fabricate and selling them in the open market. Other gemological microscope marketers buy microscopes from various Chinese makers and then alter their appearance by replacing cover parts and adding their logo aiming to confuse the prospective buyer and preventing direct comparison with their competitors. Yet, other microscope marketers avoid to explain the technical specifications and features to prospective customers while pushing their own wares.

Certain microscope pod models from the Leica conglomerate (Zeiss, Wild, etc.) are on the top of the list, followed by some models of Nikon, Olympus and other Japanese manufacturers. At the bottom of the list include all the Chinese manufacturers producing "new" models or making copies of Bausch & Lomb, Nikon and other famous brand names. Others market their microscopes as "Olympus like", but these microscopes are not made in Japan, but in China. Extra caution should be exercised on certain microscope marketers who are selling Chinese copies of Leica microscopes. However, certain models made the Chinese manufacturers meet the minimum requirements for gemological use, but the majority are not acceptable for professional gemological applications due to their low quality. All Russian made microscopes marketed under the names Mikon, Lomo, Geck and MBS are of low quality, not recommended for professional gemological microscopes.

The bottom line. Until recently, Gemlab used the genuine (not copy) Leica optical pod (Model S6E) with 16X wide field eyepieces giving total zoom range from 10X to 64X, pod inclination angle (38o), long working distance (110mm). Moreover, Leica provides a 5-year warranty. However, the marketing practices imposed to the dealers by Leica and the high price do not justify the type of microscope used in gemological applications. At this this time, Gemlab uses the highest quality Chinese-made optical pods in the market, for the budget-cautious buyer.

Answering a common question: What is a digital gemological microscope? Some microscope salesmen point to the numeric digital LCD readout fixed in the gemological base showing the percentage of light intensity. It has nothing to do with the truth digital microscope. It is just a marketing trick addressed to naive and uninformed prospective buyer.

Carl Zeiss, a high quality German brand, has manufacturing facilities around the world; some of the low-end models (i.e. Zeiss PrimoStar) are made in China (by Motic) and in Mexico. The high-end microscope models are sold directly by Zeiss.
The Leica brand is a conglomerate formed by the merger of Wild, Leitz, American Optical, Bausch & Lomb, Cambridge, Reichert and Jung. Leica Microsystems is a multinational company with production facilities in India, China and Singapore. Models S4E and S6E are the most suitable for gemological use.
Wild-Leitz is now part of Leica, manufacturing the high quality M5 and MZ models (both models are suitable for gemological applications), but they are no longer made in Switzerland.
Aus Jena is the original Zeiss manufacturer located in Jena (former East Germany) had produced fine instruments in the Eastern Bloc until the unification of Germany in 1990. The control of the Jena was taken over by Carl Zeiss. Production of the Jena microscopes is discontinued.
American Optical (AO) pods 569, 570 and 580 were made in the USA and they were used in gemological microscopes for several decades. In the late 1980's, American Optical / Reichert and Bausch & Lomb were bought by Cambridge Instruments (Great Britain). Thereafter, Cambridge and Wild-Leitz merged to form the current Leica conglomerate. The AO microscopes are no longer made.
B&L microscopes were made in the US are best known for their Stereozoom 5 and 7 models used in gemological applications. These models were discontinued by Leica, but Chinese copies of unknown quality are available.
Nikon, a major Japanese manufacturer, has improved the quality of their microscopes to the point that they are now world-class. Certain models are of high quality used mainly for industrial applications. However, their low-end microscopes are of very low-quality, due to Chinese competition, and can no longer be recommended.
Olympus, another Japanese manufacturer, has become one of the top four microscope manufacturers in the world. Certain microscope models made in the Philippines are very good, but others, made in China, are disappointing. Motic offers better models for less money.
Meiji Techno microscopes are manufactured in Japan. Meiji microscopes have become top-selling brand for education and industry as they are rugged and reliable especially the EM series stereo microscopes. Equally good are those made by Carton Optical and produced in Thailand.
Gemlab resisted selling Chinese microscopes for many years, but now the majority of microscopes from all brands are Chinese made. Some models of Zeiss, Olympus, Leica and other brands are now made in China. Copies of Meiji, Bausch & Lomb and other brands are also manufactured in China, but their quality is inconsistent. Motic is one of the best Chinese-made microscope, but expensive and it is difficult to work with the marketing department of the company.
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