Borescope

Details Borescope Borescope

1999-08-12

2001-12-25

Nguyen, Thong (Department: 2872)

Optical: systems and elements

Compound lens system

Right angle inspector

C359S399000, C359S424000, C359S428000

Reexamination Certificate

active

06333812

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to apparatus for use as a borescope and in particular to an orbital scanning borescope. Such borescopes are commonly used for inspection of gas turbine engines to determine if there are any cracks or defects in components such as turbine blades. It is known in this field to incorporate a reticle (or graticule) in the borescope which allows a user to estimate the size of a crack or defect which is viewed through the scope, in order to determine whether the engine is airworthy.
Typically, these reticles have been fixed in the borescope in two ways. Firstly, the reticle may be fixed in position in relation to the handle/control section of the proximal end of the borescope. This means that when a borescope is orbitally scanned the reticle does not rotate with the image but stays in a fixed orientation. Secondly, the reticle may be fixed in relation to the insertion tube containing the lens system. In this version, when the borescope is orbitally scanned, the reticle always rotates with the image.
Both of these approaches present certain problems in that it may not be possible to correctly align the reticle with the feature to be measured, making the measurement far more difficult.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides apparatus for use as a borescope comprising a tube having a distal end which is insertable in use into an inaccessible location and a proximal end connected to a housing, a viewing port adjacent the distal end and an associated reflector through which an object at the inaccessible location may be laterally viewed in use, an image relaying means operable to relay an image of the object to a viewing means provided in the housing, an image inverter operable to correct image inversion created by the reflector, a scanning means operable to rotate the reflector relative to the housing about a rotation axis extending longitudinally of the tube, and focusing means operable to adjust the position of the viewing means relative to the housing in a direction along an optical axis defined by the viewing means, wherein the viewing means comprises an ocular lens received in an ocular mount, said ocular mount being supported by said housing so as to be axially movable with respect to said reflector and to be rotatable relative to the housing and the tube, the apparatus further comprising reticle means secured to the ocular mount at a location distal to the ocular lens and alignment means operable to rotate the ocular mount with the ocular lens and the reticle means relative to the tube.
An advantage of such apparatus is that the reticle can be rotated independently of the rotation of the tube and reflector. Therefore, the reflector can be scanned to allow a particular feature to be viewed and the reticle can then be aligned with the feature at the correct orientation to allow the feature to be measured.
Preferably, the focusing means comprises a focus actuator operable to provide adjustment along the optical axis of the position of the ocular mount relative to the housing.
Conveniently, the ocular mount is slidably received in a tubular portion of the housing, the focus actuator comprises a first collar rotatably mounted on the tubular portion, and the alignment means comprises a second collar secured to the tubular portion, the apparatus further comprising a coupling mechanism operable to axially displace the ocular mount in response to rotation of the first collar and to rotate the ocular mount in response to rotation of the second collar.
The coupling mechanism may comprise a ball bearing located in an axially extending slot defined by the tubular portion of the housing, the ball bearing projecting radially inwardly and outwardly of the tubular portion into respective engagement with a circular recess formed in a cylindrical surface of the ocular mount and a helical groove formed in the first collar.
Preferably, the scanning means is operable to rotate the tube relative to the housing such that the rotation axis of the tube is collinear with the optical axis of the viewing means.
Typically, the image relaying means comprises an optical relay having a plurality of lenses spaced axially within the tube.
In addition, the image inverter may comprise a dove prism.


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patent: 4721375 (1988-01-01), Van Dulmen
patent: 5170775 (1992-12-01), Tagami
patent: 5243399 (1993-09-01), Koop et al.
patent: 1260181 (1968-02-01), None
patent: 0350603 (1990-01-01), None
patent: 0636915 (1995-02-01), None
patent: 954629 (1964-04-01), None

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