Stereoscopic microscopes

90.11 - Corn ound optical microscopes, including cinep otomicrography or microprojection. \ those for photomicrography, - Stereoscopic microscopes 90 11.20 - Other microscopes, for photomicrography, cinephotomicrography or 901 1.10 microprojection 90 11.80 - Other microscopes 901 1.90 - Parts and accessories Whereas magnifiers of heading 90.13 have only a single stage of magnification of relatively low power, the corn ound optical microscope of this heading has a second stage of magmfication for the o servation of an already magnified image of the object. ! A compound optical microscope normally comprises : (I) An optical system consisting essentially of an objective desi ed to produce a magnified image of the object, and an eyepiece which fbrther magni ies the observed image. The o tical system usually also incorporates provision for illuminating the object from below mans of a mirror illuminated by an external or an integral light source), and a set of condenser lenses which direct the beam of light from the mirror on to the object. P (gy (XI) A specimen stage, one or two ey iece-holder tubes (according to whether the microscope is the monocular or binocular typ7,and an objective-holder (generally revolving). The whole is fixed on a stand to which a limb or bracket and various adjusting accessories may be attached. This heading covers microsco es as used by amateurs, teachers, etc., and those for industrial use or for research laboratories; !elty remain in the heading whether or not they are presented with their optical elements (objectives, eyepieces, mirrors, etc.). The heading includes universal microscopes; polarising microscopes; metallur ical microscopes; stereoscopic microscopes; phase contrast and interference microscopes; re ecting microscopes, microscopes with drawin attachments; special microscopes for examining clock or watch jewels; microscopes wit% heating or fi-eezing stages. rk Special purpose microscopes include : (1) Trichinoscopes, a type of projection microscope, used for examining pork suspected of threadworm. Microscopes for measuring or checking operations in certain manufacturin processes; these may be of the conventional types or may be special models designed or fittin to machines. These appliances include comparison microscopes (for comparing the s d x e finish of precision articles with that of a standard article); co-ordinate reading microscopes (for locating the osition of clock or watch parts); tool-makers' ox other measurin microscopes (for c ecking threads, rofiles, gear-cutters or cutting tool profiles, etc.); sma ortable microscopes for placing &rectly on the object to be examined (for the Briuell Rardness test, for printers type, printing blocks, etc.); centring microscopes (fitted on spindles of machine-tools, instead of the tool, to bring the work into the correct position before working); etc. P f fi Some of the last mentioned instruments (e.g., those for checking the profile of worked parts), may be fitted with pro ection devlces which are usually m the form of a small circular screen fitted on top o f t e microscope. i, (3) Laboratory measuring microscopes, e.g., for measuring line separation in spectrograms. (4) SurgicaI microscapes for use by surgeons when operating on a very small portion of the body. Their light sources result in independent light paths whch provide a threedimensional image. The heading also covers : (A) Microscopes for photomicrography and microscopes for cinephotomicrography. In addition to the visual observation of the specimen, these also permit the photographic recording of magnified ima es The may be composed either of a microsco e permanently incorporating a p otograp ic or cinernatographc camera usually specia y designed for this purpose), or of a conventional microscope to whic a conventional photographic or cinematographic camera can be temporarily fixed by means of a simple attachment. t* Z R Separately presented photo a hic or cinematoga hic cameras for photomicrography or cinephotomicrography are exc$B u ed (heading 90.06 or 0.07, respectively). g (B) Microsco es for microprojection with compound magnification. These are used for the horizondor vertical projection of images magnified by a microscope incorporated in the apparatus. They are equipped with s ecial microscopes enabling rapid change of focus, and are used in education, scientific an medical demonstration rooms, technical laboratories, etc. S PARTS AND ACCESSORIES Subject to the provisions of Notes 1 and 2 to this Chapter see the General Explanatory Note), parts and accessories identifiable as being solely or principal y for use with microscopes are also classified here. These include : (I Stands (brackets, bases, etc.); eyepiece-holder tubes and revolving objective-holder tubes (whether or not with lenses); specimen sta es (including heating or freezing stages); specimen-guides; optical attachments enabling tfle image to be sketched; diaphragm-adjusting levers; etc. The heading also excludes : (a) Specimen slides or covers, of glass (heading 70.17). (b) Ophthalmic binocular-type microscopes (heading 90.18). (c) Prepared sIides for microscopic study (heading 90.23). (d) Microtomes; refractometers (heading 90.27). (e) Profile projectors and other apparatus with optical devices for checking mechanical parts, not being microscopes or microprojection apparatus, e.g., optical comparators, measuring benches, etc. (heading 90.31).