Opti-mechanical displacement indicator with high sensitivity

A device for visually indicating extremely small changes in displacement between two points of a structure through changes in color or brightness comprising:

• an unstressed actuating pin wherein said unstressed actuating pin remains fixed at a stationary position within the structure while displacement between the two points in the structure occurs;
• an indicator window fixedly attached to the structure in axial relationship with said unstressed actuating pin;
• a detachable head movably attached to said unstressed actuating pin in axial relationship with said indicator window wherein the direction and amount of axial motion of said detachable head is predetermined;
• a colored indicator portion attached to said detachable head at one end thereof;
• biasing means for resiliently biasing said detachable head in the direction of said indicator window;
• flexible indicator means filled with light-absorbing fluid having a portion of one side thereof fixed to said detachable head while a portion of the other side thereof is fixed to said indicator window for indicating a change in displacement in the structure by altering the amount of light reflected to said indicator window from said colored indicator portion in response to changes in thickness of the light-absorbing fluid contained between the two fixed portions of said flexible indicator means, wherein a change in thickness of the light-absorbing fluid occurs only as displacement between the two points within the structure approaches a preselected, desired magnitude.

A device for visually indicating extremely small changes in displacement between two points of a structure through changes in color or brightness comprising:

• an unstressed actuating pin fixedly attached within the structure at one end while displacement between the two points in the structure occurs;
• an indicator window fixedly attached to the structure in axial relationship with said unstressed actuating pin;
• a plunger having a colored circular area on one end thereof;
• a detachable tubular head fixedly attached to said actuating pin having a central circular borehole drilled therein and an outer circular borehole countersunk therein to form a stop wherein the boreholes are made from one end thereof while a colored annular area is on the opposite end thereof;
• biasing means for resiliently biasing said plunger in the direction of said indicator window through the central circular borehole in said detachable tubular head;
• flexible indicator means filled with light-absorbing fluid having a portion of one side thereof fixed to both the colored annular area of said detachable tubular head and the colored circular area of said plunger while a portion of the other side thereof is fixed to said indicator window for indicating a change in displacement in the structure by altering the amount of light. reflected to said indicator window from the colored annular area of said detachable head and from the colored circular area of said plunger in response to changes in thickness of the light-absorbing fluid contained between the fixed portions of said flexible indicator means wherein a change in thickness of the light-absorbing fluid occurs in the colored annular area of said detachable head throughout the period during which displacement in the structure occurs whereas a change in thickness of the light-absorbing fluid occurs in the colored circular area of said plunger only as displacement between the two points in the structure approaches a preselected, desired magnitude.