Microscope Eyepiece Research Articles

Factors in the design of a microscope eyepiece graticule for routine dust counts

The limitations of existing microscope eyepiece graticules for use in routine dust counting work and the problems of determining the geometrical form and physical dimensions of a graticule for use with commercial microscope equipment are discussed. Comparison is made of the consistency and accuracy obtainable with three types of graticule: the Patterson-Cawood, a simplified globe and circle type and a parallel line graticule. The simple globe and circle graticule described has been taken into general use in the National Coal Board.

Photomicrography of Moving Specimens

AbstractThe equipment described consists of a micro-camera, and a flash tube unit. The micro-camera embodies a single leaf electromagnetic shutter. The leaf is inclined, and the lower side is silvered to reflect the microscope eyepiece light cone Into a viewing eyepiece. The shutter is actuated by a separate foot-operated timer, giving exposures from I sec.-I 300 sec. The flash-tube is used in conjunction with the camera, to give an exposure of 5 micro-seconds. It has mercury electrodes and forms a light source 3 millimetres in diameter, of great intrinsic brilliance. Using an I ford 109 filter, 94°, of the light output, as recorded on Panatomic X film, lies within the wavelength range 5000°-6400 A. This is the corrected range for achromatic objectives. The tube operates at 950 volts D.C., and dissipates 4 joules. The light output is sufficient for 2 mm. oil immersion phase contrast and dark ground photographs.The photographic technique used by the author is described.

III.—OBSERVATIONS ON MICROSCOPE CONDENSERS, OBJECTIVES, AND EYEPIECES.: III. Microscope Eyepieces

SYNOPSIS.The requirements for microscope eyepieces for visual use are considered and the possibilities of achieving them are discussed in relation to the conditions under which the system is required to work. Eyepieces of various types for both visual and photomicrographic purposes are described and illustrated.

Coating of Microscope Eyepiece Lenses

IN recent years the coating or ‘blooming’ of lenses has been widely practised and has proved a most effective means of eliminating undesirable reflexions. The process has been applied to the microscope, and the coating of objectives for use with normal incident illumination is quite common practice. It is not generally recognized, however, that in certain conditions the coating of eyepiece surfaces may be advantageous, and sweeping statements have appeared to the effect that no useful purpose is served by coating eyepiece lenses.

THE LATERAL CHROMATIC ABERRATION OF APOCHROMATIC MICROSCOPE SYSTEMS

Methods are described for the measurement of the lateral chromatic aberration and distortion of microscope objectives and eyepieces. Measurements have been made on 20 apochromatic microscope objectives of 4 different makes, and on 10 compensating eyepieces of 2 different makes. The results show that the compensating eyepieces in general do not entirely compensate the chromatic aberration of the objectives and that the complete microscope system is usually undercorrected. The bearing of this on the performance of the system in photomicrographic work by a three color process and in the direct visual observation of objects is considered in detail.

A portable string galvanometer for use at moderate frequencies

The instrument described has been designed for use in a portable apparatus. The string galvanometer has been constructed with a frequency of vibration of 150-200 per sec. In order to secure critical damping the string is arranged in an oil-filled case, and to maintain proportionality between deflection and current the string is supported at the ends by springs. With this arrangement the deflection is proportional to the current over the whole working range, and with a magnification of 60-80 photographic records can be obtained with the light from an 18-watt 6-volt lamp, the battery for which is easily transportable. The optical system consists of a low-power microscope objective and eyepiece, and is fitted with a double convex lens and a plano-convex cylindrical lens to obtain a sharp image. The motion of the string is recorded by a film camera. The motor for moving the film is spring driven and a spring-driven time marker is also fitted. In order to identify records a device is fitted for marking notches on the edge of the film. After exposure the film is coiled up in a cylindrical box, a spring-operated knife cutting off the film when the lid of the camera is opened, to enable the film box to be removed.

The lateral chromatic aberration of apochromatic microscope systems

Methods are described for the measurement of the lateral chromatic aberration and distortion of microscope objectives and eyepieces. Measurements have been made on 20 apochromatic microscope objectives of 4 different makes, and on 10 compensating eyepieces of 2 different makes. The results show that the compensating eyepieces in general do not entirely compensate the chromatic aberration of the objectives and that the complete microscope system is usually undercorrected. The bearing of this on the performance of the system in photomicrographic work by a three color process and in the direct visual observation of objects is considered in detail.

IRRITATION FROM MICROSCOPE EYEPIECE

To the Editor: —From personal experience, I wish to warn both the microscope user and the microscope manufacturer of the danger of the projecting corrugated rim of the ordinary microscopic eyepiece as an agent for producing an epithelioma in the region of the orbit. This applies especially to the binocular microscope, in which it is almost impossible to look through the microscope without scraping a piece of nasal epithelium with the eyepiece. Can any other procedure, if repeated day after day for year after year, be any more favorable for the production of an epithelioma on the side of the nose?