Optical inspection

Claim 3

A method according to claim 1, in which said two patterns of illumination are simultaneously formed respectively by means of light of two different wavelengths and respectively on two different photo-sensitive screens by means of which said two video signals are respectively derived.

Claim 4

A method according to claim 1, in which the correlation comprises deriving a unidirectional signal whose magnitude varies in accordance with the strength of the alternating components of the difference between said two video signals.

Claim 5

A method according to claim 1, in which the result of the correlation is itself displayed as a television picture whose brightness varies from point to point in accordance with the differences between said two patterns of illumination.

Claim 6

A method according to claim 1, in which the imaging of the light is effected using an aperture not greater than f/5.6.

Claim 7

A method according to claim 1, applied to the comparison of two nominally identical surfaces, in which each pattern of illumination is formed by two beams of light respectively scattered from the two surfaces and imaged in a similar manner on to a photo-sensitive screen, the two patterns of illumination being respectively formed under conditions which differ in respect of the optical (but not the geometrical) path lengths between the photo-sensitive screen and the two surfaces but are otherwise identical.

Claim 8

A method according to claim 6, in which the said patterns of illumination are formed successively on the same photo-sensitive screen, the correlation being effected between the video signal as derived and a delayed version of the other video signal.

Claim 9

A method according to claim 6, in which said two patterns of illumination are formed respectively by means of light of two different wavelengths.

Claim 10

A method according to claim 8, in which said two patterns of illumination are respectively formed simultaneously on two different photo-sensitive screens by means of which two video signals are respectively derived.

Claim 11

A method according to claim 1, in which said two patterns of illumination are formed successively in the same manner on the same photo-sensitive screen, the correlation being effected using a recorded version of the first signal to be derived.

Claim 12

A method according to claim 10, in which said two patterns of illumination are formed respectively by means of light of two different wavelengths.

Claim 13

A method according to claim 10, in which said two patterns of illumination are formed using light of the same wavelength respectively before and after a change in the state of an object of which said surface forms part, said second Beam being the same for both patterns of illumination.

Claim 14

A method according to claim 12, in which said second beam is constituted by light scattered from a different surface and imaged on to the photo-sensitive screen in the same manner as for said first beam.

Claim 15

A method according to claim 12, in which said second beam has a smooth wavefront such that the beam diverges from an effective point source disposed at a position optically equivalent to the centre of the optical system used for imaging the light of said first beam.

Claim 16

Apparatus for use in optical inspection, the apparatus comprising: a television camera operative to generate video signals representing the point-by-point variations of intensity in patterns of illumination formed on at least one photo-sensitive screen incorporated in the camera, the camera further incorporating an optical system for imaging on to said at least one screen light from surfaces viewed by the camera; illuminating means operative when a surface is viewed by said camera to irradiate each photo-sensitive screen incorporated in said camera with coherent light consisting of two interfering beams a first of which is constituted by light scattered from said surface and imaged on to the screen by said optical system and the second of which has a form such that at every point in the pattern of illumination formed on the screen by said two interfering beams the maximum angle between a ray of the first beam and a ray of the second beam is not greater than the maximum angle between rays of the first beam; and means for correlating two video signals derived from said camera.

Claim 17

Apparatus for use in optical inspection, the apparatus comprising: a television camera operative to generate video signals representing the point-by-point variations of intensity in patterns of illumination formed on at least one photo-sensitive screen incorporated in the camera, the camera further incorporating an optical system for imaging on to said at least one screen light from surfaces viewed by the camera; illuminating means operative when a surface is viewed by said camera to irradiate each photo-sensitive screen incorporated in said camera with coherent light consisting of two interfering beams a first of which is constituted by light scattered from said surface and imaged on to the screen by said optical system and the second of which has a form such that at every point in the pattern of illumination formed on the screen by said two interfering beams the maximum angle between a ray of the first beam and a ray of the second beam is not greater than the maximum angle between rays of the first beam; and means for correlating two video signals derived from said camera.

Claim 18

Apparatus according to claim 15, in which said illuminating means is operative so that said second beam has a smooth wavefront such that the beam diverges from an effective point source disposed at a position optically equivalent to the centre of the aperture of said optical system.

Claim 19

Apparatus according to claim 15, in which there are provided means enabling said camera to view two similar surfaces simultaneously in a similar manner, said illuminating means being operative to illuminate the two surfaces in a similar manner, whereby said two interfering beams will be constituted by light respectively scattered from the two surfaces.

Claim 20

Apparatus according to claim 15, in which the aperture of said optical system is not greater than f/5.6.

Claim 21

Apparatus according to claim 15, in which said illuminating means is operative at two different light wavelengths.

Claim 22

Apparatus according to claim 19, in which said television camera incorporates two photo-sensitive screens, and means rendering said screens respectively responsive to light of said two wavelengths.

Claim 23

Apparatus according to claim 15, in which said camera incorporates only a single photo-sensitive screen, and the correlating means is operative to correlate two video signals derived from said camera at different times.

Claim 24

Apparatus according to claim 21, in which said correlating means comprises means for recording the video signal which is derived at the earlier of said different times, and means for utilising the recorded version of that signal in effecting the correlation.

Claim 25

Apparatus according to claim 15, in which the correlating means comprises means for deriving a unidirectional signal whose magnitude varies in accordance with the strength of the alternating components of the difference between said two video signals.

Claim 26

Apparatus according to claim 23, comprising a cathode ray tube monitor operative in synchronism with said television camera, and means for applying said unidirectional signal to said monitor.

Claim 27

Apparatus for use in the optical comparison of two nominally identical surfaces, the apparatus comprising: a television camera operative to generate two video signals respectively representing the point-by-point variations of intensity in two patterns of illumination formed respectively by light of two different wavelengths on at least onE photo-sensitive screen incorporated in the camera, the camera further incorporating an optical system for imaging on to said at least one screen light from surfaces viewed by the camera; means for enabling the camera to view two surfaces to be compared in a similar manner; means for illuminating said two surfaces, while they are so viewed, in a similar manner with coherent light of said two different wavelengths; and means for correlating said two video signals.

Claim 28

Apparatus for use in the optical comparison of two nominally identical surfaces, the apparatus comprising: a television camera operative to generate two video signals respectively representing the point-by-point variations of intensity in two patterns of illumination formed respectively by light of two different wavelengths on at least onE photo-sensitive screen incorporated in the camera, the camera further incorporating an optical system for imaging on to said at least one screen light from surfaces viewed by the camera; means for enabling the camera to view two surfaces to be compared in a similar manner; means for illuminating said two surfaces, while they are so viewed, in a similar manner with coherent light of said two different wavelengths; and means for correlating said two video signals.

Claim 29

Apparatus according to claim 25, in which said television camera is operative to generate said two video signals simultaneously, the camera incorporating two photo-sensitive screens by means of which said two video signals are respectively derived.

Claim 30

Apparatus according to claim 25, in which said television camera is operative to generate said two video signals alternately, and the correlating means is operative to effect the correlation between one video signal as derived and a delayed version of the other video signal.