Scientific Specialties, Inc.
 

Looksmall Microscope

Trekker’s ultra compact shape is achieved by the use of folded optics which compress the normal 150mm tube length of a conventional microscope by the use of precision mirrors. A similar method is used in the Swift microscopes which uses two-dimensional optical folding, but the Trekker takes the concept a stage further by using a third mirror to fold the light path three-dimensionally. This allows the top of the microscope to be used as a large uncluttered specimen stage with all the optics arranged beneath the stage in an incredibly neat and compact package.

The Trekker is therefore a modified inverted microscope.

Optical Layout

The optical layout consists of eight elements - three mirrors, a two-element objective and a three-element eyepiece. The objective power is x 3.5 and that of the eyepiece x 10, giving an overall magnification of x 35. The eyepiece may be removed. for cleaning and for use as x 10 loupe.

Objective

This is a two-element achromatic ‘doublet’ comprising two elements cemented together; one element is bi-convex and the other convex/concave. The diameter of the objective is 10mm, with 8mm clear. The NA (numerical aperture) is 0.12 and the working distance 32mms. Resolution is typically 3-4 microns.

The objective travels in a precision focusing mechanism consisting of a machined brass leadscrew of 4mm pitch which is attached to a machined aluminium focus wheel. This assembly is mounted on a sub chassis which also holds the three mirrors in perfect alignment. It is possible for focus to be reached from a point slightly below the specimen stage to a point approximately 15mm above the stage. This generous focus range allows a wide range of objects to be viewed easily.

Eyepiece

The eyepiece is of modified Ramsden design and comprises three elements - a single element field lens air-spaced from a two element eye lens. This gives a wide field of view with excellent eye relief. Because the field lens is contained within the body of the microscope it was possible to add a unique feature in that the field lens is enlarged to form a square. This gives a modern ‘user-friendly’ image in line with current day presentation of photographic images and documentation. Furthermore the eyepiece can be pulled out for cleaning, or for use as a handy x10 loupe.

Mirrors

The three mirrors are front silvered and are polished to a high degree of flatness – typically 2-3 fringes. The first mirror is situated between the object plane and the objective and the second and third mirrors are positioned between the objective and the eyepiece.

Coating

All optical air surfaces are coated with magnesium fluoride.

Illumination

Transmitted lighting for examining transparent specimens is simply achieved by the use of available light, whether in or outdoors. With the lower magnification of x 35 a sub stage is unnecessary and would furthermore complicate the simplicity of the Trekker and impede the use of the specimen stage.

Solid objects, however, do require illumination because the object blocks light from the viewing aperture. This is achieved with a daylight- corrected white LED which is situated adjacent to a clear annular ring surrounding the viewing aperture. This light ring is manufactured from highly polished acrylic which disperses light through 360’ around the specimen. The light output is biased to one side to create shadow relief which is a useful feature when viewing very fine detail on objects like coins and jewellery. Power is provided by a single 9 volt battery which is enclosed within the microscope case. Depending on the quality of the battery employed this can give over 100 hours of continuous light

Specimen stage

This is manufactured from steel to provide a durable specimen stage and this material enables specimens, and in particular slides, to be held using a simple ring magnet. The magnetic principle will also be used for the attachment of various planned accessories.

Tripod bush

A tripod location is centrally placed on the underside of the microscope. This consists of the photographic standard ¼” UNC internal thread fitted to all cameras. A small table tripod is thus ideal for converting the Trekker microscope into a simple bench instrument.