The Olympus BX51 is a high quality research microscope that is capable of bright-field, dark-field, fluorescence, phase contrast and differential interference contrast (Normarski DIC) viewing of samples. The microscope can be customized at the time of purchase, depending on your needs.
Bright-field observation is powered by a 100W halogen lamp that offers such high intensity that we have found it rarely necessary to use anything past half-power. The lamp is controlled by an easily accessible dial on the front right of the microscope with a pre-set button for quick return to a desired light level. If required, two neutral density filters can be applied in the light path to reduce brightness. The light can be daylight-balanced with the supplied filter or colored by user-supplied filters (placed in the single empty slot on a filter holder). The field and illumination seems to be very even once aligned properly and alignment with the light source is quick and easy. Dark field observation using the BX51 is adequate, but the field appears to display less contrast than other, often much older, microscopes we have tested. However, the images obtained are very sharp and, by no means, unacceptable.
Observation of fluorescent samples is achieved by the use of the BX-URA2 fluorescence illuminator and again, this microscope is significantly brighter than others we have tested. The intensity can also be controlled with stops that can be placed in the beam path. We have found this microscope suitable even for very small and weak fluorescence signals, such as cellular localization studies of proteins in bacterial cells.
The microscope can accept 8 different objective lenses and a wide range are available including oil-immersion, water-immersion and dry lenses, ranging from 1.25x to 100x. At 22 mm, the field of view for all methods is very large (an accessory eye-piece and head are available to further enlarge the field). The field is very flat and sharp from edge to edge and offers excellent contrast. The overall design of the microscope makes all of the controls easily accessible without having to look away from the specimen. The frame is ‘Y-shaped’, with all controls at the front or sides of the microscope within easy reach. The illumination control, however, does lie directly behind the stage movement dial, which hangs down from the stage. This can sometimes lead to accidental movement of the stage while attempting to adjust the field brightness but it is not a serious issue once the user is aware of it. The stage is a large and ceramic coated to prevent scratching and damage. It is a matte finish surface which means that any oil spilled onto it is almost impossible to remove properly. The stage control is a single-bar, dual-action control that hangs from either the left or right of the stage, depending on preference. It is easy to use as both direction controls are on the same mechanism and it is low to the bench surface. This means that using the microscope for extended periods is not as uncomfortable as some other microscopes we have used.
Image recording is achieved by the attachment of film or digital cameras, including still and video. We purchased the digital camera and, unfortunately, it has relatively low resolution (virtual resolution can be increased using sensor position shifting). This works relatively well for static samples but it is not suitable for samples that are moving. We have found that it also results in slightly soft images in comparison to a static, but higher resolution, sensor. Of course, other cameras can be fitted to the microscope and just about any camera can be used with adaptors.
Overall, this is a very capable microscope with excellent optics and features. It is very versatile, as it has been designed for complete customization. Nearly all parts of the microscope can be customized at the time of purchase, including the cameras, eye pieces, nose piece, prisms, filter, stages, stage controls, light sources and so on.
Scott Coutts
Department of Microbiology
Monash University, Melbourne, Australia