US-12618769-B2 - Self-cleaning optical probe

US12618769B2US 12618769 B2US12618769 B2US 12618769B2US-12618769-B2

Abstract

An optical probe includes an elongate hollow probe body, an optical window mounted at a distal end of the probe body for transmitting light therethrough, an ultrasonic transducer mounted within the probe body for applying ultrasonic vibrations to the optical window for cleaning the optical window, and one or more light guides located within the probe body for transmitting light through the optical window to a measurement region and/or for receiving light transmitted through the optical window from the measurement region. The ultrasonic transducer is located within the distal end of the probe body adjacent the optical window to transmit ultrasonic vibrations directly from the ultrasonic transducer to the window.

Inventors

Khalid Thabeth
Raymond Acheson

Assignees

Inov8 Systems Limited

Dates

Publication Date: 20260505
Application Date: 20230428
Priority Date: 20220501

Claims (11)

1 . An optical probe for use in a high pressure medium, said optical probe comprising: an elongate hollow probe body having an inner wall; an optical window mounted at a distal end of said probe body for transmitting light therethrough; an ultrasonic transducer mounted within said probe body for applying ultrasonic vibrations to said optical window for cleaning said optical window, said ultrasonic transducer having an ultrasonic transducer body; one or more light guides located within said probe body for transmitting light through said optical window to a measurement region and/or for receiving light transmitted through said optical window from said measurement region; and a mounting flange extending between said ultrasonic transducer body and said inner wall of said probe body, said mounting flange being located at a zero point of said ultrasonic transducer; wherein said ultrasonic transducer is located within said distal end of said probe body via said mounting flange, adjacent said optical window, and is operable to transmit ultrasonic vibrations directly from said ultrasonic transducer to said window.
2 . The optical probe of claim 1 , wherein said optical window is mounted on a distal end of said ultrasonic transducer within an opening in said distal end of said probe body.
3 . The optical probe of claim 2 , wherein a seal is provided between said optical window and said opening in said distal end of said probe body.
4 . The optical probe of claim 1 , wherein said one or more light guides are provided within said probe body to cooperate with said optical window, said one or more light guides extending between said ultrasonic transducer and said inner wall of said probe body.
5 . The optical probe of claim 4 , wherein said one or more light guides extend through said mounting flange.
6 . The optical probe of claim 1 , wherein said ultrasonic transducer comprises one or more ceramic transducer elements and a reaction mass mounted against said one or more ceramic transducer elements at a rear end of said ultrasonic transducer, and a transducer shaft extending between said one or more ceramic transducer elements and said optical window.
7 . The optical probe of claim 6 , wherein said transducer elements and reaction mass are secured to said transducer shaft by a fastener passing therethrough.
8 . The optical probe of claim 6 , wherein a distal end of said transducer shaft has a diameter less than the diameter of said optical window such that said transducer shaft cooperates with a central region of said optical window to transmit ultrasonic vibrations thereto.
9 . The optical probe of claim 8 , wherein said one or more light guides cooperate with a peripheral region of said optical window outside of said central region of said optical window.
10 . The optical probe of claim 6 , wherein said transducer shaft comprises a solid shaft whereby ultrasonic energy is transmitted therethrough with minimum energy loss.
11 . The optical probe of claim 1 , wherein said one or more light guides comprise one or more optical fibres.

Description

CROSS REFERENCE TO RELATED APPLICATION The present application claims priority benefit of U.K. Pat. Application Ser. No. GB2206373.9, filed May 1, 2022, which is hereby incorporated herein by reference in its entirety. FIELD OF THE INVENTION This invention relates to a self-cleaning optical probe and in particular to a self-cleaning optical probe for use in a high pressure medium. BACKGROUND OF THE INVENTION There are many applications that require measurement of the quantity of oil and/or the identification of oil or other contaminants present in a liquid. For example, in pipes leading from oil production or refining facilities or the like it may be required to measure the amount of oil and/or the identity of oil present in the liquid (mainly water) flowing in the pipes. Oil in water analysers or probes are used for this purpose, either in side stream passages or as insertion probes. Oil has a natural fluorescence. Therefore oil in water analysers typically measure the quantity of oil present in water by the detection of fluorescence. Devices that detect and/or measure fluorescence are commonly referred to as fluorometers. A fluorometer usually includes a light source for causing fluorescence in a target substance and a detector for measuring the resultant fluorescence. A typical oil in water analyser has a measurement window located at a distal end of an elongate probe body through which the excitation light source is transmitted into the measurement region and through which the resultant fluorescent and/or reflected light is received to be analysed in order to determine the quantity and/or identify of oil and/or other contaminants present. Fouling of the measurement window by oil and other substances will occur without means for cleaning the measurement window. This problem may be addressed by using an ultrasonic transducer, typically located an inner end of the probe body, opposite the distal end, whereby the measurement window can be cleaned by ultrasonic cavitation created by the ultrasonic energy transmitted to the measurement window from the ultrasonic transducer through the probe body. A known optical probe of an oil in water analyser, as illustrated in FIG. 1, includes an elongate hollow probe shaft 2 (known as a sonitrode) having a sapphire window 4 (defining the measurement window) at a distal end thereof. An ultrasonic transducer 6 having ceramic transducer discs is mounted on an opposite end of the probe shaft 2 for transmitting ultrasonic energy 5 to the window 4 via the probe shaft 2. Optical fibres and electrical leads are typically passed through a central channel 8 of the hollow probe shaft 2, typically via an entry slot cut through side of the probe shaft or through a hollow bolt securing a back mass of the ultrasonic transducer 6 to the transducer discs. The central channel 8 through the hollowed probe in itself introduces large inefficiencies in the transmission of ultrasonic energy. The probe is typically provided with a mounting flange 9 welded to the outer periphery of the probe shaft 2 adjacent a rear end of the probe shaft 2. On a conventional ultrasonic probe the position of the ultrasonic transducer 6 at the rear of the probe, transmitting ultrasonic waves down the full length of the probe shaft 2, applies physical stress directly to the mounting flange welds. This can result in fracture of the welded joint. To try and mitigate this problem the mounting flange may be positioned at a low ultrasonic energy point. However, the flange position is primarily dictated by the probe penetration depth. If the mounting flange is not positioned at a low energy point on the body of the probe, it will not only cause stress to the flange weld, it may greatly impact the efficient transmission of ultrasonic energy to the front of the probe and the optical window. The loss of transmission energy in this arrangement limits the effective cleaning capability to applications where the medium pressure is low, typically less than 10 Bar. SUMMARY OF THE INVENTION According to the present invention there is provided an optical probe comprising an elongate hollow probe body, an optical window mounted at a distal end of the probe body for transmitting light therethrough, an ultrasonic transducer mounted within the probe body for applying ultrasonic vibrations to the optical window for cleaning the optical window, and one or more light guides located within the probe body for transmitting light through the optical window to a measurement region and/or for receiving light transmitted through the optical window from the measurement region, wherein the ultrasonic transducer is located within the distal end of the probe body adjacent the optical window to transmit ultrasonic vibrations directly from the ultrasonic transducer to the window. Optionally, the ultrasonic transducer is located within the probe body via a mounting flange extending between the body of the ultrasonic transducer and an inner wall of the