Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
  • G01M11/02—Testing optical properties
  • G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
  • G01M11/0257—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
  • G01B11/255—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring radius of curvature
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
  • G01M11/005—Testing of reflective surfaces, e.g. mirrors
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/0095—Relay lenses or rod lenses
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
  • G02B27/4233—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive element [DOE] contributing to a non-imaging application

Definitions

• the invention relates to an optical device of the deflectometer type, in particular phase detection, with a large measurement range.
• Document FR 2 647 913 describes an optical device, suitable for checking, by phase detection, any surface of an optical system, essentially comprising, along an optical path: emission means suitable for the constitution of a light source, a reflecting surface to be checked, a separating cube placed between the light source and the surface to be checked and provided with a semi-reflecting surface for deflecting the light beam reflected by the surface to be checked, a network such as a Ronchi grating, placed in the vicinity of the point of convergence of said reflected light beam, a lens for giving the image observable in the analysis plane of a camera with charge coupling device (CCD), that is to say say in the plane of the CCD sensor, and a camera coupled to computer processing means for the exploitation of the image by phase detection.
• emission means suitable for the constitution of a light source
• a reflecting surface to be checked a separating cube placed between the light source and the surface to be checked and provided with a semi-reflecting surface for deflecting the light beam reflected by the surface
• This optical device of the deflectometer type, with phase detection, allows precise, rapid measurement, for the entire surface, and without contact, of a wide variety of spherical and aspherical surfaces, without specific tools.
• it has limits in terms of the diameter of the measurable range, in particular due to the entrance pupil of its acquisition system.
• An object of the invention is to increase the entrance pupil of an imaging system, in particular a deflectometer, in order to increase its measurable range.
• Another object of the invention is to use a zoom for the observation of the image given by a deflectometer.
• the subject of the invention is an optical device, of the deflectometer type, in particular with phase detection, comprising a light source, a surface to be checked, a semi-reflecting surface between the light source and the surface to be checked to deflect the reflected light beam.
• a network placed in the vicinity of the point of convergence of said reflected light beam, and a CCD camera coupled to computer processing means, characterized in that it comprises, between the network and the CCD camera, a lens primary with large entrance pupil providing an intermediate image, a frosted surface intended to receive said intermediate image, and a secondary optical system taking up the intermediate image materialized on the frosted surface and forming a final image on the sensor of the CCD camera.
• the secondary optical system is a zoom.
• Fig. 1 a schematic view of an optical device of known type, with grating and separating element, for the control, by phase detection, of an optical surface;
• Fig. 2 a diagram of the rays emitted by a light source and reflected by an aspherical optical surface
• Fig. 3 a diagram illustrating the defocus with respect to the diagram in FIG. 2;
• Fig. 4 a block diagram of the optical device of FIG. 1;
• Fig. 5 a block diagram of the optical device according to the invention.
• a light source 1 a semi-reflecting surface 2, the optical surface to be checked 3, a Ronchi grating 4, a lens 5, a sensor 6 of a CCD camera not shown, and the computing means 7 for processing.
• the optical surface 3 being aspherical, a ray 8 from the source 1 reaches the surface 3 at point 9, and it is reflected at 10.
• the ray 10 is deflected at 11 by the semi-reflecting surface 2, and it reaches the network 4 at a point 12 distant by a distance d from the point 13 symmetrical with the source 1 with respect to the semi-reflecting surface 2.
• the distance d between the points 12 and 13 is the deflection undergone by the light ray coming from the source 1, after reflection on the surface 3 to be checked. For each point 9 of the surface 3, knowing the deflection d and the angle at which point 9 is seen from the source 1, makes it possible to know the slope at this point, and to reconstruct the surface 3 by integration.
• optical network device and separating element for the phase detection control of an optical system is given in the document.
• the objective 5 has the function of forming on the sensor 6 of the CCD camera, the image of the surface observed, on which is superimposed the pattern of fringes to be analyzed.
• the illumination at a point on the surface is characteristic of the slope of the surface at this point.
• the source 1 illuminates the surface 3, aspherical, the axis of which passes at points 1 and 15.
• the diameter of the light beam reflected by the surface 3 is not no. This diameter is symbolized by the arrows 16 and 17.
• a surface 3 will be measurable (pupillary imaging), if its CMD (possibly after recovery by an adaptation optic) is smaller in size than the pup i l l e input of the acquisition system.
• the interest of the user is to have a system with the largest possible entrance pupil, if he wants to measure an area without specific asphericity compensation tools.
• Fig. 4 the entrance pupil 14 and the circle of least diffusion 18 are shown.
• the sensor 6, which defines the size of the image, is of small dimensions.
• the entrance pupil 14 is of maximum size, and the opening is large on the image side.
• the optical device according to the invention is schematically represented in FIG. 5.
• the source 1 emits a beam towards the surface to be checked 3 which is aspherical.
• the beam deflected by the surface 3, after defocusing, has a circle of least diffusion (CMD) 18.
• CMD circle of least diffusion
• the primary objective 19 has a large entrance pupil 14, but it has a relative aperture limited by the possibilities and production costs , and therefore it gives a great picture.
• This image is materialized in the image plane of the primary objective 19, for example on a frosted surface 20, of small thickness.
• This image is taken up by an optical system 21 for secondary imaging which forms an image thereof on the sensor 6 of the CCD camera.
• the use of a frosted surface 20 between the primary objective 19 and the secondary optical system 21 makes it possible to resume the intermediate image, with the secondary optical system 21, at an opening angle ⁇ smaller than the opening angle image a of the primary objective 19.
• the secondary objective is therefore no longer subjected to the proportionality relationship that exists, in conventional deflectometers, between the size of the entrance pupil and that of the image on the CCD camera sensor.
• the size of the intermediate image can be very large, and the entrance pupil of the primary objective 19, that is to say in fact the entrance pupil of the optical acquisition system, can be greatly increased.
• the secondary optical system 21 can be a zoom, because its opening is independent of that of the primary objective.
• the optical device is applicable to systems for measuring surface areas by defectectometry. It essentially comprises a primary objective with a large entrance pupil forming an intermediate image materialized on a plane, for example with a frosted surface, and a secondary optical system for taking up the intermediate image, so that the size of the final image is compatible with any CCD camera sensor.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Optics & Photonics (AREA)
• Geometry (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Testing Of Optical Devices Or Fibers (AREA)

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• 1992
  • 1992-04-01 FR FR9203937A patent/FR2689653B1/fr not_active Expired - Fee Related
• 1993
  • 1993-03-31 EP EP93907915A patent/EP0592631A1/de not_active Ceased
  • 1993-03-31 JP JP5517164A patent/JPH06508218A/ja active Pending
  • 1993-03-31 WO PCT/FR1993/000323 patent/WO1993020416A1/fr not_active Ceased
  • 1993-03-31 US US08/150,127 patent/US5440383A/en not_active Expired - Fee Related

Non-Patent Citations (1)

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