DEVICE FOR DETECTING A THREE-DIMENSIONAL STRUCTURE

Abstract

The invention relates to a device for detecting a three-dimensional structure, comprising an imaging device, especially a camera, which is adjustable in the z-direction, a control device which is designed to record an image of a first plane and, after adjustment of the imaging device in the z-direction, to record an image of a second plane, and an evaluation device which is designed to interpolate a sub-plane between the first plane and the second plane.

Claims

1. Device for detecting a three-dimensional structure, comprising an imaging device (10), which is adjustable in the z-direction, a control device (12) which is designed to record an image of a first plane and, after adjustment of the imaging device (10) in the z-direction, to record an image of a second plane, and an evaluation device (16) which is designed to interpolate a sub-plane between the first plane and the second plane.

2. Device according to claim 1, characterised in that interpolation of the sub-plane proceeds pixel by pixel.

3. Device according to claim 1, characterised in that interpolation proceeds by means of a parabolic fit.

4. Device according to claim 1, characterised in that interpolation proceeds by means of a quadratic interpolation.

5. Device according to claim 1, characterised in that a filter is provided.

6. Device according to claim 1, characterised in that an exposure device is provided which is controlled by means of the control device such that the exposure times for the first plane and the second plane are different.

7. Device according to claim 1, characterised in that the exposure times are optimised by means of automated parameterisation.

8. Device according to claim 1, characterised in that the control device (12) records only partial areas of the first plane and/or the second plane.

9. Device according to claim 1, characterised in that the control device (12) records only images of certain planes in the event that there is a plurality of planes, and/or the evaluation device (16) evaluates only images of certain planes in the event that there is a plurality of planes.

10. Method for detecting a three-dimensional structure, comprising a device in accordance with any of the preceding claims, in which an image is recorded of a first plane, the imaging device (10) is adjusted in the z-direction, an image is recorded of a second plane, and a sub-plane is interpolated between the first plane and the second plane.

11. Method according to claim 10, characterised in that image capture and evaluation are performed in parallel.

12. Device according to claim 1, characterised in that the imaging device (10) is a camera.

13. Device according to claim 5, characterised in that the filter is a 16-bit median filter.

14. Device according to claim 1, characterised in that the evaluation device (16) evaluates only partial areas of the first plane and/or the second plane.

Description

[0088] The invention is described below by way of example with reference to the drawings. The drawings show in:

[0089] FIG. 1 A cross-sectional view of an embodiment of an inventive device.

[0090] FIG. 2 a focus value curve in three different pixels,

[0091] FIG. 3 A height image of a multi-layer scan, and

[0092] FIG. 4 A flow chart of an asynchronous evaluation in parallel with the image capture sequence.

[0093] First of all, it should be noted that the embodiments shown are purely exemplary. Thus, individual features can be realised not only in the combination shown, but also alone or in other technically useful combinations. For example, the features of one embodiment can be combined as desired with features of another embodiment.

[0094] Where a drawing contains a reference numeral which is not explained in the directly associated descriptive text, reference is made to the corresponding previous or subsequent deliberations in the description of the drawings. Thus, the same reference numerals are used for the same or comparable components in the drawings and are not explained again.

[0095] FIG. 1 shows a device for capturing a three-dimensional structure with a camera 10 which is adjustable in the z-direction (see double arrow) and constitutes the imaging device.

[0096] The device comprises a control device 12 which can capture images in different planes by means of the camera 10. The camera 10 can be adjusted in the z-direction by means of a drive device 14, whereby an image is captured at each of certain predetermined intervals.

[0097] Furthermore, the device comprises an evaluation device 16, which calculates a sub-plane between each of the captured planes.

[0098] An exposure device 18 can be used to expose the images in the individual planes. In particular, the planes can be exposed alternately at different exposure times, whereby each plane is preferably exposed at only one exposure time. In this way, for example, bright components can be shown in one layer and dark components in the next layer.

[0099] Through interpolation, all components can then be clearly visible in a composite image.

[0100] FIG. 2 shows a focus value curve in three different pixels, with the z-direction plotted on the x-axis and the focus value on the y-axis.

[0101] The shape of the focus value curve is parabolic. Proceeding therefrom, it is also possible to interpolate values between the discrete scanning points and to obtain increased accuracy.

[0102] FIG. 3 shows a possible curve of a multi-layer scan.

[0103] For example, if the reference surface during a pin height inspection is on a different plane from the pins themselves, then in principle two scans can be made at different z-positions. The offset of the first scan area 20 and the second scan area 22 can be factored in because the distance is known.

[0104] In particular, scanning does not take place between the first scanning area 20 and the second scanning area 22. Nevertheless, a height image 24 can be generated.

[0105] Finally, FIG. 4 shows a flow chart for asynchronous evaluation in parallel with the image capture sequence.

[0106] To boost performance, the image data are preprocessed asynchronously while the scanning process is in progress.

[0107] First, initialisation 26 takes place, and then the scan is started 28.

[0108] The capture process is started 30. Now the axis is moved 32. While this is in progress, images are captured 34. Finally, the capture process is finished 36.

[0109] In parallel with the capture process, processing is started 38. The images are processed 40 and a depth image is created 42. Finally, the depth image can optionally be enhanced 44.

[0110] Finally, a new scan 46 can be started, as required.

LIST OF REFERENCE SYMBOLS

[0111] 10 Camera, imaging device [0112] 12 Control device [0113] 14 Drive device [0114] 16 Evaluation device [0115] 18 Exposure device [0116] 20 First scanning area [0117] 22 Second scanning area [0118] 24 Height image [0119] 26 Initialisation [0120] 28 Start scan [0121] 30 Start capture [0122] 32 Move axis [0123] 34 Image capture [0124] 36 End capture process [0125] 38 Start processing [0126] 40 Process images [0127] 42 Generate depth image [0128] 44 Improve depth image [0129] 46 New scan