Method and device for determining a three-dimensional distortion

Abstract

A method for determining a distortion of the image of an object formed by a reflection on a reflecting object includes capturing a reflected image of the reflecting object, determining, using the captured reflected image, a three-dimensional (3-D) shape of the surface of the reflecting object, calculating, based on the determined 3-D shape, distortion of the captured reflected image of the reflecting object from different viewing directions and using the calculated distortion from the different viewing directions, determining a three-dimensional (3-D) distortion of the surface of the reflecting object.

Claims

1. A method for determining a distortion in the image of an object formed by a reflection on a reflector, the method comprising the steps of: capturing an image of the object reflected by the reflector; using the captured reflected image for determining a three-dimensional (3-D) shape of the surface of the reflector; based on the determined 3-D shape, calculating the distortions of the images of the object formed by the reflection by the reflector from a plurality of different viewing directions; and using the calculated distortion from the plurality of different viewing directions, determining a three-dimensional (3-D) distortion in the image of the object formed by reflection on the reflector, wherein the step of calculating distortions from the different viewing directions includes assuming that a virtual camera is disposed in every direction of the different viewing directions and that one virtual image of the object reflected by the reflector is determined from each perspective of the virtual camera.

2. The method according to claim 1, wherein the step of capturing the image of the object reflected by the reflector is implemented with a camera and wherein the step of determining the 3-D shape of the surface of the reflector is implemented using deflectometry.

3. The method according claim 1, wherein the step of determining the 3-D distortion in the image of the object formed by reflection on the reflector is implemented in a viewing direction of the different viewing directions that corresponds to a direction normal to the surface of the reflector, for every point on the surface.

4. The method according to claim 1, further comprising varying a reflectance of the surface of the reflector.

5. The method according to claim 1, further comprising assessing the calculated 3D distortion in the image of an object formed by reflection on the reflector in order to determine whether the calculated 3D distortion is within an acceptable range specified therefor.

6. The device according to claim 5, wherein of the reflectance of the surface of the reflector is varied.

7. A device for determining a three-dimensional (3-D) distortion in an image of an object formed by a reflection on a reflector, comprising: a camera for capturing the image of the object reflected by the reflector; a determination device for determining, from the captured image of the object, a three-dimensional (3-D) shape of a surface of the reflector; a computing unit for calculating, on the basis of the determined shape of the 3-D shape of the surface of the reflector, the distortions in the images of the object formed by the reflection by the reflector from a plurality of different viewing directions and according to the calculated distortions from the different viewing directions, calculating a three-dimensional (3-D) distortion in the image of the object formed by reflection on the reflector, wherein the computing unit calculates the distortions from the different viewing directions in reliance upon a virtual camera virtually positioned in order to virtually capture the image of the object formed by reflection on the reflector from each of the different viewing directions and to determine the reflected image of the object reflected by the reflector from each perspective of the virtual camera.

8. The device according to claim 7, wherein the determination device determines the shape of the surface of the reflector using deflectometry.

9. The device according to claim 7, wherein the computing unit calculates the distortion in the image of the object formed by reflection on the reflector in a viewing direction of the different viewing directions, wherein the viewing direction corresponds to a direction that is normal on the surface of the reflector for every point on the surface.

10. The device according to claim 7, wherein the computing unit assesses the calculated 3-D distortion in the image of the object formed by reflection on the reflector to determine whether the calculated 3D distortion is within an acceptable range specified therefor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will become apparent from the description of embodiments that follows, with reference to the attached figures, wherein:

(2) FIG. 1 presents a view from the side of a first subsystem of a device configured according to the invention for determining a three-dimensional distortion; and

(3) FIG. 2 shows a second subsystem of a device configured according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) The following is a detailed description of example embodiments of the invention depicted in the accompanying drawings. The example embodiments are presented in such detail as to clearly communicate the invention and are designed to make such embodiments obvious to a person of ordinary skill in the art. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention, as defined by the appended claims.

(5) FIG. 1 depicts a reflective object in the form of a glass pane 1 for a window of an automobile. The glass pane has a reflective surface 2 which is observed by a camera (real camera) 3. In particular, the camera 3 observes the image of an object formed via reflection on the surface 2 of the glass pane 1, which object is in the form of a lattice such as a regular or square lattice 5. Any other type of functionally equivalent object also can be used for the deflectometric measurement. In the case of a large glass pane 1, it is also possible to use a plurality of cameras, which detect different regions of the surface of the glass pane 1.

(6) The three-dimensional shape of the surface 2 of the glass pane 1 is determined using deflectometry using a determination device of the device according to the invention on the basis of the image of the object captured by the camera 3. The determination device is part of or embodies a computing unit 10, including a memory, which is shown connected to camera 3. Please note that the connection of computing unit 10 is not limited to a hardwire connection to camera 3 as shown, but also may be connected wirelessly. When a plurality of cameras is used, the different measurements are used to compose the three-dimensional shape of the surface 2 of the glass pane 1.

(7) In order to determine the three-dimensional distortion of the lattice 5, the device according to the invention then calculates the distortion of the lattice 5 from the different viewing directions using a suitably designed computing unit, as shown in FIG. 2, on the basis of the ascertained three-dimensional shape of the surface 2, the resultant curvatures at all points on the surface 2 and refractive powers from different viewing directions. To this end, the computing unit assumes that a virtual camera 7 views the reflective object 1 from the particular viewing direction. On the basis thereof, the image of the (virtual) lattice 5, and the distortion thereof, is calculated while this lattice 5 is reflected on the surface 2 of the object 1, e.g., by ray tracing. On the basis thereof, the computing unit determines distortion effects when the viewing angle changes, i.e., the three-dimensional distortion. The lattice 5 is also provided as a virtual lattice for calculating the three-dimensional distortion.

(8) Within the scope of a quality inspection, the computing unit compares the ascertained three-dimensional distortion of the glass pane with the customer's requirements and makes a decision (determination) as to whether the ascertained distortion of the glass pane 1 meets the requirements. If this is not the case, the glass pane 1 is removed from the production process.

LIST OF REFERENCE NUMBERS

(9) 1 glass pane 2 surface of the glass pane 3 camera 5 lattice 7 virtual camera 10 computing unit

(10) As will be evident to persons skilled in the art, the foregoing detailed description and figures are presented as examples of the invention, and that variations are contemplated that do not depart from the fair scope of the teachings and descriptions set forth in this disclosure. The foregoing is not intended to limit what has been invented, except to the extent that the following claims so limit that.