Self cleaning optical probe

An optical probe comprising:

• an optical window for transmitting light therethrough;
• an ultrasonic transducer operable to apply ultrasonic vibrations to said optical window for cleaning said optical window;
• one or more light guides for transmitting light through said optical window to a measurement region or for receiving light transmitted through said optical window from said measurement region;
• and
• an elongate body comprising a solid shaft having a first end positioned at said ultrasonic transducer and a second end proximate said optical window, wherein when said ultrasonic transducer is energized said solid shaft transmits ultrasonic vibrations along its length from said ultrasonic transducer to said optical window;
• wherein said ultrasonic transducer is coupled to said optical window via said elongate body;
• wherein at least a distal end of said one or more light guides extends alongside said elongate body;
• and
• wherein said one or more light guides communicate with said optical window adjacent said elongate body.