Measuring instruments

• US 4,218,144 A
• Filed: 09/08/1978
• Issued: 08/19/1980
• Est. Priority Date: 09/09/1977
• Status: Expired due to Term

• Current Assignee: Rank Taylor Hobson Limited
• Original Assignee: The Rank Organisation Ltd.
• Inventors: Whitehouse, David J., Jungles, John
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Arnold, Bruce Y.
• Application Number:
  US05/940,665
• Time in Patent Office: 711 Days
• Field of Search: 356/445-448, 250/578
• US Class Current: 356/446
• CPC Class Codes: G01B 11/303 using photoelectric detection means
• CPC Class Codes: G01N 21/55 Specular reflectivity

Abstract

An optical sensing instrument for detecting specular and/or non-specular reflections of light from a surface under test has a sensor head with a plane face having a semi-circular recess in which are housed a plurality of light sources and a plurality of photodetectors each having an associated lens, the optical axis of which passes through the center of curvature of the semi-circular recess. The photodetectors and the light sources are positioned such that respective source/detector pairs are located on optical axes which form mirror angles with respect to the axis of symmetry of the sensing head. Means are provided for simultaneously energizing one or more selected light sources and one or more of the photodetectors.

Claims

1. In an optical sensing instrument for inspecting surfaces by detecting reflection therefrom at various different angles of incidence and reflection,

a sensing head;

means defining a plane in which a surface under test lies in use of said instrument;

a plurality of light sources carried on said sensing head;

a plurality of first lenses each associated with a respective one of said light sources, said first lenses directing light from their respective associated sources along respective optical axes towards a common area on said plane;

a plurality of photodetectors mounted on said sensing head;

a plurality of second lenses each associated with a respective one of said photodetectors for directing light reflected from a surface located at said plane to respective associated said photodetectors, the optical axis of each said first lens passing through said common area and lying at an angle, with respect to a normal to said plane, which is equal and opposite to the angle with respect to said normal formed by the axis of a respective one of said second lenses; and

means for selecting which of said light sources and which of said photodetectors is to be energised at any one time during operation of said instrument.

3. The optical sensing instrument of claim 1 or claim 2, wherein there is further provided:

a pulse generating system connected to said light sources and operating to drive at least one selected light source.

4. The optical sensing instrument of claim 3, wherein there is further provided:

a pulse detector system connected to said photodetectors and operating to provide an output signal in response to detection of pulses.

5. The optical sensing instrument of claim 4, wherein said pulse detector system includes an amplifier circuit, the system having a non linear response comprising said pulse detector and said amplifier,

means for adjusting said non-linear response of said pulse detector and amplifier system to match with different surface reflectance characteristics.

6. The optical sensing instrument of claim 4, wherein there is further provided:

a meter display, and

a pulse integrating network operating to provide a linear relationship between input pulse height and a D.C. voltage output for feeding to said meter display.

7. The optical sensing instrument of claim 1, wherein said sensing head has a plane face in which is formed a recess the shape of which, in section taken on a plane normal to said plane face, constitutes a part of a circle, said light sources and photodetectors being mounted in said recess so that the optical axes of said first and second lenses associated therewith all meet at the centre of curvature of said recess.

8. The optical sensing instrument of claim 7, wherein the centre of curvature of said recess lies in the plane of said plane face.

10. The optical sensing instrument of claim 5, wherein there is further provided;

a meter display, and

a pulse integrating network operating to provide a linear relationship between input pulse height and a D.C. voltage output for feeding to said meter display.

2. In an optical sensing instrument,

a sensing head;

a plurality of light sources carried on said sensing head;

a plurality of first lenses each associated with a respective one of said light sources,

a plurality of photodetectors mounted on said sensing head;

a plurality of second lenses each associated with a respective one of said photodetectors, the optical axis of each of said first lens lying at an angle, with respect to an axis of said measuring head, which is equal and opposite to the angle with respect to said axis formed by the axis of a respective one of said second lenses; and

switching means connected to said light sources and said photodetectors and operating to energise one of a selected one and any selected combination of light sources and detectors.

9. The optical sensing instrument of claim 2, wherein there are further provided means for energising a selected light source and at least one photodetector other than the one associated with the one of said second lenses the optical axis of which lies at an equal and opposite angle, with respect to said sensing head axis, to the one of said first lenses associated with said selected light source.