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Historic as it is...
Olympus has an OlympusImageJPlugin ( http://imagej.net/OlympusImageJPlugin ) that supports the OIR (and VSI) format.
The plugin opens the file as a hyperstack with the correct calibration, LUT etc. but is limited by the file size and has some limitations with regard to scripting.
AFAIK there is no alternative open plugin (e.g. Bio-Formats).