Abstract: A monocular borescope or endoscope is provided with an image relaying means (16) defining a longitudinal axis (L)(and with a viewing means comprising an ocular lens (20) and field mask (18) defining a central axis (C) which is parallel to and offset from the longitudinal axis (L). In one embodiment the ocular lens (20) is coincident with the central axis (C) of the mask (18), while in another embodiment the ocular lens (20) is coincident with the longitudinal axis (L). The mask (18) is arranged to be mountable in a number of different rotational orientations each providing a different offset between the longitudinal axis (L) and the central axis (C).

Abstract: A system for determining a dimension of a detail includes an optical scope for producing an image of the detail, an image scaling device for providing a scaled image size, and a processor. The system also includes a video camera which is either within the optical scope or external to the optical scope. The optical scope includes a focusing device for adjusting a focal position of the image of the detail and a device for providing a focus position signal based a position of the focusing device. The processor converts the focus position signal into an object distance signal, or a magnification signal, or both, and determines the dimension of the detail based on the scaled image size and based on the object distance signal, or the magnification signal, or both. The system further comprises means to compensate for changes in temperature of the optical scope to ensure that the measurement accuracy is not compromised by expansion or contraction of the scope.

Abstract: There is disclosed an anti-backlash focusing mechanism (10) for an optical instrument in which clearances between the focus control member (22) and the focusing lens cell (16) are eliminated. The mechanism (10) comprises a focusing lens means (16a) mounted in a first cylindrical member (16) which is slidable in a bore (12) in a housing (11). A focus control member (22) is rotatably mounted on the housing (11) and coupled to the first cylindrical member (16) such that rotation of the focus control member (22) causes axial movement of the first cylindrical member (16). A second cylindrical member (17) is provided adjacent the first, the second cylindrical member (17) also being coupled to the focus control member (22) for axial movement upon rotation of the latter.