SELF-CLEANING OPTICAL PROBE

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.

Claims

1. An optical probe comprising: an elongate hollow probe body; 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; and 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; wherein said ultrasonic transducer is located within said distal end of said probe body, adjacent said optical window, and operable to transmit ultrasonic vibrations directly from said ultrasonic transducer to said window.

2. The optical probe of claim 1, wherein said ultrasonic transducer is located within said probe body via a mounting flange extending between a body of said ultrasonic transducer and an inner wall of said probe body, said mounting flange being located at a zero point of said ultrasonic transducer.

3. 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.

4. The optical probe of claim 3, wherein a resilient seal is provided between said optical window and said opening in said distal end of said probe body.

5. 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 an inner wall of said probe body.

6. The optical probe of claim 5, said ultrasonic transducer is located within said probe body via a mounting flange extending between a body of said ultrasonic transducer and an inner wall of said probe body, said mounting flange being located at a zero point of said ultrasonic transducer and wherein said one or more light guides extend through said mounting flange.

7. 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.

8. The optical probe of claim 7, wherein said transducer elements and reaction mass are secured to said transducer shaft by a fastener passing therethrough.

9. The optical probe of claim 7, 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.

10. The optical probe of claim 9, 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.

11. The optical probe of claim 1, wherein said transducer shaft comprises a solid shaft whereby ultrasonic energy is transmitted therethrough with minimum energy loss.

12. The optical probe of claim 1, wherein said one or more light guides comprise one or more optical fibres.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] An embodiment of the present invention will now be illustrated, by way of example, with reference to the accompanying drawing, in which:—

[0017] FIG. 1 is a longitudinal sectional view through a prior art optical probe;

[0018] FIG. 2 is a longitudinal sectional view through an optical probe in accordance with an embodiment of the present invention; and

[0019] FIG. 3 is a detailed sectional view through the front end of the optical probe of FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

[0020] As illustrated in FIGS. 2 and 3, an optical probe in accordance with an embodiment of the present invention includes a measurement window 10, defining a distal end of an insertion probe, the measurement window being mounted in an opening 12 in a distal end of a hollow elongate probe body 14. A resilient seal 16 is provided in the opening in the probe body 14 around the periphery of the measurement window 10.

[0021] As best shown in FIG. 3, an ultrasonic transducer 18 is provided within the hollow probe body 14 adjacent the measurement window 10 for transmitting ultrasonic energy 5 to the measurement window 10 in order to clean the window 10. The ultrasonic transducer 18 may include one or more ceramic transducer discs 20 located between a back mass 22 and a transducer shaft 24. A bolt 26 preferably passes through the rear of the back mass 22 and through the ceramic transducer discs 20 into the rear end of the transducer shaft 24 to secure the ceramic discs 20 and back mass 22 to the transducer shaft 24.

[0022] A distal end of the transducer shaft 24 of the ultrasonic transducer 18 is mechanically coupled to the measurement window 10 to directly transit ultrasonic energy from the transducer shaft 24 to the measurement window 10. As such, the measurement window 10 receives ultrasonic energy directly from the transducer 18 without the losses inherent in prior art arrangements wherein a hollow probe body 14 is disposed between the ultrasonic transducer 18 and the measurement window 10. Furthermore, the location of the measurement window 10 within the opening 12 in a distal end of the probe body 14, without direct mechanical coupling between the probe body 14 and the measurement window 10 further avoids the losses of ultrasonic energy inherent in prior art arrangements wherein the measurement window is mechanically coupled to the probe body 14. The resilient seal 16 seals the distal end of the probe body 14 while mechanically isolating the measurement window 10 from the probe body 14.

[0023] Light guides 28 (only one shown in FIG. 3), such as in the form of optical fibres, extend alongside the transducer shaft 24, distal ends of light guides 28 being mounted in an intermediate plate 30, secured between the transducer shaft 24 and measurement window 10, whereby the light guides 28 are located adjacent and alongside a distal end of the transducer shaft 24 to transmit and received light through the measurement window 10.

[0024] The measurement window 10 is secured to the intermediate plate 30 via a cap 32 extending over the measurement window 10 and having an opening for the passage of light into and out of the window 10, the seal acting between the opening 12 in the distal end of the probe body 14 and the outer sides of the cap 32.

[0025] The solid cylindrical transducer shaft 24 extending between the ceramic transducer discs 20 and the measurement window 10 and the location of the ultrasonic transducer 18 within the front end of the probe body 14 directly adjacent and in contact with the measurement window 10 minimises any loss of energy between the two and therefore greatly reduces the energy consumption of the ultrasonic transducer 18 required for the creation of cavitation and efficient cleaning of the measurement window 10.

[0026] Furthermore, the location of the light guides 28 to the side of the transducer shaft 24, and therefore to a side region of the window 10 advantageously increases the useful life of the measurement window 10. This is because ultrasonic energy from the ultrasonic transducer 18 is highest in a central region of the measurement window 10 (i.e. along the central axis of the transducer shaft 24), reducing towards the outer edges of the window 10. Therefore cavitation is greatest in this central region, leading to erosion and etching of this central region of the window 10.

[0027] The transducer shaft 24 of the ultrasonic transducer 18 is located within the hollow probe body 14 by means of a transducer mounting flange 34 affixed (for example by welds) to the transducer shaft 24 and extending between the transducer shaft 24 of the ultrasonic transducer 18 and the probe body 14. As shown in FIG. 3, the probe body 14 includes a distal portion 36 having the opening 12 at a distal end thereof within which the measurement window 10 is located, the mounting flange 34 of the ultrasonic transducer abutting a stepped seat 38 within the distal portion 36 of the probe body 14, the remainder of the probe body 14 including a tubular portion 40 having a distal end inserted within the distal end of the distal portion 36 and engaging the mounting flange 34 of the ultrasonic transducer 18 to secure the ultrasonic transducer 18 (and the window 10) within the probe body 14. The distal end of the tubular portion 40 of the probe body 4 may be threadedly engaged within the distal portion 36 of the probe body 14.

[0028] The transducer mounting flange 34 is located at a zero point of the ultrasonic transducer 18 (i.e. minimum point of ultrasonic energy) such that the probe body 14 is isolated from the ultrasonic vibrations generated by the ultrasonic transducer 18, preventing ultrasonic energy from being absorbed by the probe body 14.

[0029] The isolation of the probe body 14 from the ultrasonic transducer 18 and the direct coupling between the ultrasonic transducer 18 and the measurement window 10 avoids the losses in ultrasonic energy inherent in prior art optical probes. Furthermore, it allows the length of the probe body 14 and the position of a probe mounting flange 42 on the probe body 14 to be readily varied without requiring calibration of the position of the mounting flange 42 and length of the probe body 14, unlike prior art examples wherein the mounting flange location needs to be aligned with a zero point of the ultrasonic vibrations to try and avoid losses of ultrasonic energy and fracture of the mounting flange welds.

[0030] Because the ultrasonic transducer 18 is located at the front end of the probe body 14, isolating the ultrasonic waves from the probe body, the prior art problem of stressing of welds along the probe body, particularly at the mounting flange 42, is avoided and the location of a mounting flange on the probe body is not critical. In turn, vast improvement in transmission efficiency is achieved, reducing the power required (by as much as 85%) to achieve the desired effect of cleaning the optical window and allowing effective cleaning of the window in high pressure mediums (for example in excess of 80 Bar. Furthermore, because the probe body 14 does not have to transmit ultrasonic energy it can be made of lighter construction, allowing a significant reduction in the overall weight of the probe, further reducing stress on the welds of the mounting flange.

[0031] The invention is not limited to the embodiments described herein but can be amended or modified without departing from the scope of the present invention, which is intended to be limited only by the scope of the appended claims as interpreted according to the principles of patent law including the doctrine of equivalents.