Measuring system employing a measuring method based on the triangulation principle for the non-contact measurement of a distance from the surface of a contoured object to a reference level. _

• US 4,701,049 A
• Filed: 06/19/1984
• Issued: 10/20/1987
• Est. Priority Date: 06/22/1983
• Status: Expired due to Fees

• Current Assignee: B.V. Optische Industrie "De Oude Delft"
• Original Assignee: B.V. Optische Industrie "De Oude Delft"
• Inventors: Beckman, Leo H. J. F., Oomea, Gysbert L.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/622,546
• Time in Patent Office: 1,218 Days
• Field of Search: 356/1, 356/4, 250/568, 250/569, 250/204
• US Class Current: 356/3.07
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01S 17/48 Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves

Abstract

An apparatus for dimensional inspection of an object. The apparatus is adapted to produce a slender beam of measuring radiation for irradiating an object under examination. Reflected light image receiving means are provided including a receiving lens for collecting radiation reflected from an object surface spot irradiated by the measuring beam, and a linear photo-sensitive detector. The receiving lens is dimensioned and disposed relative to the measuring beam and the linear detector as to exclusively project those object surface spots irradiated by a longitudinal section defining a measuring range, of the measuring beam, as focussed dots on the linear photo-sensitive detector area. For improving the resolution of the focussed dots produced on the detector, a beam forming lens is provided for causing the cross-sectional area of the measuring beam to gradually increase over the measuring range. The apparatus is further adapted to image one and same object surface spot irradiated by the measuring means as two separate dots on the detector wherein these dots are uniquely related to each other only, in case a true reflection has been received. Thereby a discrimination can be made between true and false reflections from the object under examination.

Claims

1. A measuring system for determining the distance between a reference level and a spot on the surface area of an object when said spot is within a measuring range extending from said reference level, by utilizing principle of triangulation, said system comprising:

light source means for producing measuring radiation;

optical collecting means optically coupled to said light source means for producing a beam of measuring radiation extending through said measuring range and towards an object spot under examination, reflected light image receiving means for receiving light radiation reflected from an object surface spot irradiated by said beam, and including receiving lens means for collecting radiation reflected from said object surface spot, and a radiation-sensitive detector optically coupled to said receiving lens means for receiving light radiation collected thereby and for converting the light radiation thus received into a corresponding signal;

said detector having a substantially linear radiation-sensitive area;

said receiving lens means being dimensioned and disposed relative to said beam and said detector as to image only those object surface spots irradiated by said beam within said measuring range, onto said linear radiation-sensitive area of said detector as focussed spots;

said optical collecting means optically coupled to said light source means including further lens means adapted to cause the cross-sectional area of said beam to gradually increase from said reference level and with increasing distance therefrom, thereby causing said focussed spots on said detector to be of substantially one and same size.

2. The measuring system according to claim 1 wherein said light source means is adapted to emit monochromatic radiation having a selected wavelength within a wavelength range of wavelength components which are substantially spaced from wavelength components corresponding to spurious background radiation to be expected;

and wherein an optical bandpath filter is disposed within the spatial viewing angle of said detector, said bandpass filter being dimensioned to have a wavelength of the pass-band thereof, preferably the medium wavelength thereof, to correspond to said selected wavelength.

3. The measuring system according to claim 1 wherein masking means are disposed in the optical path of said beam of measuring radiation for distorting said beam whereby a respective object surface area is irradiated with a measuring beam of asymmetric intensity distribution;

and said reflected light image receiving means includes a signal processor adapted to exclusively pass those signal portions of a detector output signal applied thereto that correspond to image dots being a projection on said detector of the object spot irradiated by said measuring beam and having an asymmetric intensity distribution as determined by said measuring beam.

4. A measuring system for determining the distance between a reference level and a spot on the surface area of an object when said spot is within a measuring range extending from said reference level, by utilizing principle of triangulation, said system comprising:

light source means for producing measuring radiation;

optical collecting means optically coupled to said light source means for producing a beam of measuring radiation extending through said measuring range and towards an object spot under examination;

first reflected light image receiving means for receiving light radiation reflected from an object surface spot irradiated by said beam, and including first receiving lens means for collecting radiation reflected from said object surface spot;

second reflected light image receiving means for receiving light radiation reflected from said object surface spot irradiated by said beam and including second receiving lens means for collecting radiation reflected from said object surface spot;

a common radiation-sensitive detector optically coupled to said first and second receiving lens means for receiving light radiation collected whereby and for converting the light radiation thus received into corresponding signals, said detector having a substantially linear radiation-sensitive area;

said first receiving lens means and said second receiving lens means being dimensioned and disposed relative to said beam and to said common detector as to image only any object surface spot irradiated by said beam within said measuring range, onto said linear radiation-sensitive area of said common detector as two focussed dots spaced a fixed distance from each other; and

signal processing means coupled to said common detector for performing an auto-correlation function in respect of the detector output signal containing two discrete signal components spaced apart an interval corresponding to said fixed distance.

5. A measuring system for determining the distance between a reference level and a spot on the surface area of an object when said spot is within a measuring range extending from said reference level, by utilizing principle of triangulation, said system comprising:

light source means for producing measuring radiation;

optical collecting means optically coupled to said light source means for producing a beam of measuring radiation extending through said measuring range and towards an object spot under examination;

first reflected light image receiving means for receiving light radiation reflected from an object surface spot irradiated by said beam, and including first receiving lens means for collecting radiation reflected from said object surface spot;

second reflected light image receiving means for receiving light radiation reflected from said object surface spot irradiated by said beam, and including second receiving lens means for collecting radiation reflected from said object surface spot;

two prisms seucred to each other to have one prism surface in common, said two prisms having one surface optically coupled to said first receiving lens means and having another surface optically coupled to said second receiving lens means thereby causing radiation received from said first receiving lens means to pass through said common prism surface in partially undiffracted fashion and radiation received from said second receiving lens means to be partially reflected by said prism surface in common;

a common radiation-sensitive detector optically coupled to said prism surface in common for receiving said light radiatioan passed therethrough and light radiation partially reflected thereby, and for converting the light radiation thus received into corresponding signals, said detector having a substantially linear radiation-sensitive area;

said first receiving lens means and said second receiving lens means being dimensioned and disposed relative to said beam and said detector as to image only any object surface spot irradiated by said beam within said measuring range, onto said linear radiation-sensitive area of said common detector as two focussed dots spaced a fixed distance from each other; and

signal processing means coupled to said common detector to perform an auto-correlation function in respect of the detector output signal containing two discrete signal components spaced apart an interval corresopnding to said fixed distance.

6. The measuring system according to claim 5 wherein said first reflected light image receiving means further includes a first reflector surface adapted to direct light radiation reflected from said object surface spot onto said prism surface in common;

said second reflected light image receiving means further including a second reflector surface operated to direct light radiation reflected from said object surface spot irradiated by said beam and to said prism surface in common;

said first reflector surface and said second reflector surface each is tilted through one and same angle about a respective one of two intersecting axes extending mirror-symmetrically relative to a plane extending through said beam;

said beam being directed along the line of intersection of two planes through which any object spot produced by said beam is imaged on said common detector.

7. The measuring system according to claim 5 wherein said prism surface in common is tilted relative to a plane extending through said beam, the tilting angle being determinative of said fixed distance.

8. The measuring system according to claim 6 wherein each one of said first and second reflected light image receiving means includes a reflector surface disposed to direct radiation reflected from one and same object surface spot irradiated by said beam, onto said prism surface in common;

each of said reflector surfaces together with said prism surface in common forming one of said two prisms.