Shadow probe

• US 5,633,675 A
• Filed: 01/10/1995
• Issued: 05/27/1997
• Est. Priority Date: 02/16/1993
• Status: Expired due to Term

• Current Assignee: GE Inspection Technologies LP (General Electric Company)
• Original Assignee: Welch Allyn Incorporated
• Inventors: Lia, Raymond A., Danna, Dominick
• Primary Examiner(s): Au, Amelia
• Application Number:
  US08/370,866
• Time in Patent Office: 868 Days
• Field of Search: 348/65, 348/66, 348/67, 348/68, 348/72, 348/75, 348/76, 348/82, 348/84, 600/109, 600/112, 600/129, 600/130, 600/160, 600/171, 600/176, 600/181
• US Class Current: 348/65
• CPC Class Codes: A61B 1/00179 for off-axis viewing
• CPC Class Codes: A61B 1/05 characterised by the image sensor, e.g. camera, being in the distal end portion
• CPC Class Codes: A61B 1/0623 for off-axis illumination
• CPC Class Codes: A61B 5/1076 for measuring dimensions inside body cavities, e.g. using catheters A61B3/1005 takes precedence
• CPC Class Codes: G02B 23/2469 using optical fibres

Abstract

A device for measuring the size of targets viewed with a borescope having a housing with a longitudinal axis and a distal viewing end with an optically transparent window set therein, a source of target illumination which projects a cone of illumination so that the axis of the cone of illumination is at an angle of less than 90° with the housing axis, a contrasting shadow generated in association with the illumination source so as to project the contrasting shadow on the target, an image detector disposed adjacent to the source of illumination, directed so as to detect the image of the target and the contrasting shadow, a display for viewing the target and shadow as detected by the image detector, and a measuring device for measuring the parameters of the contrasting images on the display so that the actual size of the target can be determined.

Claims

1. A borescope having a compact imager head comprising:

an elongated cylindrical housing having a given wall thickness, a diameter (D), and a longitudinal axis;

said housing having a circular end face at its distal end that forms an angle θ

with a plane perpendicular to said longitudinal axis, said angle being less than 90°

;

an illumination window and an optic window mounted adjacent each other along a diameter of the end face;

an imager having a flat recording surface, said imager being mounted behind the optic window to view a target image outside of said housing, said recording surface being parallel with said end face, said imager being positioned a predetermined distance behind the optic window to establish a region behind the illumination window of a shape and size to accommodate the distal end of a light carrying fiber bundle for illuminating a target within the viewing range of the imager without interfering with the target image;

shadow generating means associated with said light carrying fiber bundle to produce a contrasting shadow in a target plane;

display means connected to said imager for viewing and measuring the target image and a shadow image in the target plane; and

measuring means for measuring parameters of the target image and the shadow image on said display so that the attached size of the target can be determined, wherein the diameter (D) of the imager head is substantially expressed by the relationship D=cos θ

(OW+IW+2t);

where;

OW=the length of the optic window along the diameter of the end face;

IW=the length of the illumination window along the diameter of the end face; and

2t=twice the wall thickness.

2. The borescope of claim 1 wherein the angle θ

is between 15° and

45°

.

3. The borescope of claim 1 wherein the angle θ

is about 20°

.

4. The borescope of claim 1 wherein said parameter measurements are used to adjust the target image on the display means in proportion to its distance from the imager.