The Olympus BH-2 is a family of 160mm finite-conjugate microscopes which were available in multiple variations, each bearing a unique model designation. The first two characters in the model designation for any BH-2 scope are “BH”. The third character is either a “T” (indicating 20W halogen illumination) or “S” (indicating 100W halogen illumination). There may be a fourth character, “U”, which designates those models with a reverse-facing nosepiece. The various BH-2 models are described below.
BHT Stand
The Olympus BHT utilizes a modular forward-facing nosepiece, a modular condenser, a modular viewing head, and a modular stage. The BHT features 20W halogen lighting integrated within the base, with the halogen lamphouse located on the rear of the base so that heating of the specimen stage is kept to a minimum. The BHT features pre-focused Kohler Illumination and an adjustable stage preset lock. The BHT can be configured for biological (including brightfield, darkfield, phase contrast, as well as Nomarski DIC), polarizing, metallurgical (brightfield and darkfield), and fluorescence applications.
BHTU Stand
The Olympus BHTU is similar to the BHT, differing in that is has a fixed (i.e., non-modular) 5-position reverse-inclined nosepiece, rather than compatibility with the modular forward-facing nosepieces. The BHTU was created to satisfy a large market demand in the United States (hence the “U” in the model name) for the improved ergonomics of the reverse-inclined nosepiece. The BHTU was Olympus’ answer to similar competing designs from Nikon, and successfully outsold the Nikon offerings in the US by a significant margin. The addition of the reverse-inclined nosepiece lowered the BHTU stage and condenser height (as compared to the BHS/BHT stands) and modified the geometry of the mounting recess for the modular viewing heads (the BHTU mounting recess contains an optical infinity element needed to correct the optical tube length back to 160mm). The presence of this optical infinity element limits compatibility of a few of the accessories in the BH-2 line, such as vertical illuminators with darkfield capability, but for the vast majority of users, this was not an issue. After all, the BHTU easily outsold the BHT model, which did not have these compatibility limitations. For a great may users, the improved ergonomics of the BHTU more than made up for the inability to do reflected darkfield.
BHS Stand
The Olympus BHS is similar to the BHT, differing in that it features 100W halogen illumination integrated within the base. Like the BHT/BHTU, the halogen lamphouse is located on the rear of the base to minimize heating of the specimen stage. The BHS can be easily differentiated from the BHT by the significantly wider base containing the 100W electronics, and by the much larger lamphouse on the rear of the base. Due to the large amount of light provided by the 100W halogen, the BHS was considered to be the “research stand” of the BH-2 line. The earlier BHS scopes contained red LEDs on the front for displaying the halogen lamp voltage. At some point in the production run of the BHS, the lighting electronics were significantly redesigned, and the front panel LEDs were changed to green so as to differentiate the two versions.
BHSU Stand
The Olympus BHSU is essentially a BHS with a fixed, reverse-inclined nosepiece. The BHSU offers the improved ergonomics of the BHTU with the retina-searing lighting intensity of the BHS. The BHSU is quite rare in the US, as it was not sold in North America in any significant volumes. The BHSU can be identified by the reverse-inclined nosepiece and the wide base containing the 100W electronics.