Beck-Chapman Opaque Illuminator.

This illuminator was originally devised by Messrs. Chapman & Aldridge, and has been modified and sold under various trade names. A modification (patent applied for) is here introduced which simplifies the apparatus without injuring its utility. With the Beck aplanatic ring illuminator, the size of the object that can be examined is limited to about f in., whereas with the Beck-Chapman illuminator, the size of the object is immaterial.

The construction of this apparatus is shown in Fig. 6. The light from a small electric bulb (A) is thrown from the side into the microscope, through a condensing lens (B), upon a mirror (C) placed above the object glass (D). The mirror has an aperture in the centre. The mirror throws an annular ring of light, upon metal reflectors (E, E' and E"), which surround the object glass and concentrate the light upon the focal plane of the object glass giving a brilliant illumination upon any object or surface being examined. The light falls upon the object in the form of a hollow cone, so that no direct light enters the microscope and the object is rendered visible by reflected light.

To avoid the necessity of adjusting the height of an independant lamp when objects of a different thickness are being examined, a self-contained source of light is provided, consisting of a 6 volt lamp with condensing lens, in a well ventilated lamp-house, giving the necessary adjustments for the lamp. This lamp may be used with batteries or accumulators, or with suitable resistance or transformer from the mains. The mount of the illuminator, with its angular mirror, lamp-house and condenser, screws into the microscope by means of a revolving fitting (G). Its lower portion has a dovetailed slide (H) into which the various object glasses, with their reflectors are fitted. The illuminator is made with 1J in. (32 m/m.), fin. (16 m/m.), J in. (8 m/m.) and J in. (4 m/m.) object glasses. The construction of the reflectors is varied according to the magnifying power of the object glass, so that either a larger or smaller field of view is illuminated. The illustration shows the two different forms.

No. 2340.

4^4

If a specially intense source of light is required for photomicography, the 6 volt lamp can be withdrawn and light from our small arc lamp (No. 3635) or other powerful source can be directed into the aperture of the illuminator.

This will only be necessary for special purposes, and is generally too powerful for visual observation.

Both this form of illuminator and the aplanatic ring illuminator avoid any glare set up by reflections from the lenses of the object glass which are inevitable when so-called vertical illumination is used. The two methods are different in the results obtained. For polished metal specimens, vertical illumination is usually preferred, but for unpolished specimens the illumination given_by the Beck-Chapman or aplanatic ring illuminator is more satisfactory.

No. 2340. Beck-Chapman illuminator, mount only, with lamp-house, illuminant,

mirror and condenser, in case ... • • • • • • • • • • • • ... £5

No. 2341. ljin. (32 m/m.) Object glass, with reflector....................... ... 4

No. 2342. f in. (16 m/m.) Object glass, with reflector.......................... 4

No. 2343. Jin. (8 m/m.) Object glass, with reflector.......................... 6

No. 2344. J in. (4 m/m.) Object glass, with reflector............................ 8

No. 2345. Green and ground glasses to fit....................... ••• per pair 0 2

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Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 99,12 %.

La langue de reconnaissance de l'OCR est l'Anglais.

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