WO2010006894A1

WO2010006894A1 - Method for detecting moving objects

Info

Publication number: WO2010006894A1
Application number: PCT/EP2009/057810
Authority: WO
Inventors: Detlef Gerhard
Original assignee: Siemens Aktiengesellschaft
Priority date: 2008-07-15
Filing date: 2009-06-23
Publication date: 2010-01-21
Also published as: EP2297568A1

Abstract

The invention relates to a method for detecting fast and/or unevenly moving objects, comprising the following steps: an object region is detected using at least one first, one-dimensionally resolving camera (K1) having at least one line (Z1), wherein the image of the first camera runs longitudinally to the direction of motion of objects, a detected object (1, 2) is scanned line by line using at least one second, one-dimensionally resolving camera (K2) having at least one line (Z2), wherein the image of the second camera runs transversely to the direction of motion of objects, and a two-dimensional image of the object is produced, wherein the image fields of the two cameras (K1, K2) overlap at least at one image point which is present in an image produced by the second camera. The method for detecting fast and/or unevenly moving objects using at least one first one-dimensionally resolving camera (K1) having at least one line (Z1) detects the image longitudinally to the direction of motion of objects, wherein a predefined line profile which describes the object is recorded and recognized by the camera (K1).

Description

description

Method for detecting moving objects

The invention relates to the taking of object images, wherein moving objects move relative to the camera in an object space, which is received by the camera.

Are one-dimensional imaging camera systems, for example, line scan cameras, for the optical inspection of on one

Moving belt used moving parts, the image quality depends crucially on the synchronization of the line scan camera in relation to the belt speed. Especially for images consisting of image lines, an unstable tape speed will produce larger artifacts or image distortions in the captured image of an object. In the case of small image scales, the triggering of the line scan cameras via a rotary encoder which picks up the signal at the drive or a roller of the conveyor belt is only conditionally suitable for regulation.

In the prior art, if a line scan camera is used for the object image, it is synchronized by means of a rotary encoder. This means that is triggered by means of the pulses of the encoder.

In other words, in the optical inspection of moving parts, the image recording is to be taken at the appropriate time. If the image acquisition is started too late, the object to be recorded is already partially or completely outside the image field or the object space. Normally, a sensor, such as a light barrier, is used to trigger the camera in such a way that timely image acquisition takes place. However, cases are conceivable in which triggering with an external sensor is no longer possible. This is the case, for example, with strongly fluctuating movement of objects. It is aggravating that, if it concerns the objects to be imaged Sub-objects of a larger object is, for example, the optical inspection of semiconductor chips on wafers, different magnifications are required.

In this case, a photoelectric sensor has been used with an external sensor to trigger the system.

The invention is based on the object of describing the imaging of moving objects by means of a stationary camera system, wherein irregular or fast object movements are to be controlled with regard to image acquisition.

The solution of this task is done by the respective feature combination according to claim 1 or 2. Advantageous embodiments can be taken from the subclaims.

The invention is based on the finding that for the object image used, one-dimensional resolution two cameras are arranged offset in a measuring head relative to an optical axis about 90 ° from each other, that the respective image of these cameras or camera optics on the object in the direction of movement Object is aligned longitudinally aligned. In this case, this camera system is used to determine the image distortion, for example due to uneven movement of the objects. Overall, the object shift in the consecutively captured images is analyzed and used for the image correction.

The second camera is generally used to capture the object image, i. H. that the test object is scanned line by line by the second camera, followed by any intermediate storage and assignment of the individual image lines to a two-dimensional image.

Another solution to the same problem is based on the combination of two camera systems in a single measuring head, wherein the one-dimensionally imaging camera constantly picks up the object surface and only when a suitable Abbr. education profile, the two-dimensional resolution camera triggers a synchronization circuit. Again, the two cameras used relative to the optical axis offset by about 90 ° to each other. The first camera is also aligned here so that their image is formed on the object approximately parallel to the direction of movement. If an object is detected by recording a corresponding line profile, whereby the type of object is detected, the second camera is activated after a predetermined delay time.

It is particularly advantageous to provide different image scales for different cameras. The individual cameras can advantageously be line scan cameras with associated optics and illumination.

In the event that both cameras used one-dimensional resolution, they can be triggered against each other at certain times. The triggering is advantageously done via a synchronization circuit.

In the following, the invention will be described with reference to schematic, accompanying figures, non-limiting embodiments.

FIG. 1A shows a system for object detection with a first one-dimensionally resolving camera K1 having its image F1 and a second two-dimensionally resolving camera K3 having the image F3 on an object,

FIG. 1B shows a representation correspondingly

FIG. 1A, wherein both cameras used are one-dimensionally resolving types and their images each represent a row Z1, Z2 on an object, FIGS. 2A and 2B show the form of object scanning associated with FIGS. 1A and 1B;

FIGS. 3A and 3B show, with reference to FIGS. 2A and 2B, a variant with a synchronization and an image evaluation, the synchronization in each case relating to the two cameras used, based on the results of FIG

Image evaluation of the line Zl is triggered.

In particular, the following features with corresponding effects in connection with the invention may be mentioned:

A measuring system and a method for detecting moving objects are each associated with at least two one-dimensional imaging cameras, which may be either line scan cameras K1 and K2, or a line camera and a two-dimensionally resolving camera.

The cameras Kl, K2, are arranged in relation to an optical axis which runs in the z-direction of a Cartesian coordinate system, rotated about 90 ° to each other about the axis. This means that the image Z1 of the first line scan camera Kl runs longitudinally to the movement direction BR of the object to be recorded 1,2, while the image Z2 of the second camera is oriented transversely to the movement direction of the inspection object.

The line scan cameras K1, K2 can have different numbers of pixel elements. At the same time, the magnification of each camera may differ from that of other cameras.

The image fields of both cameras overlap, wherein the images of the cameras in the object space can also be T-shaped, as can be seen in FIGS. 2A and 2B. examples The recording cameras Kl and K2 are triggered at certain times. A special case of the triggering is the simultaneous triggering of the image acquisition of both cameras.

The camera K1 accommodating along the direction of movement BR of objects 1, 2 serves to determine the image distortion which arises due to the uneven movement of objects. For this purpose, the object shift is analyzed in successive recorded images and used for the image correction.

The camera K2 is used to capture the object image, which means that the test object is scanned line by line with the second camera K2, stored and associated with respect to the individual image line a two-dimensional image to be created.

The line scan camera Kl is also used in connection with a synchronization circuit for triggering the second camera K2, K3. Here, the magnification used for the camera Kl is used. On the basis of this, the most favorable trigger time for activating the second camera K2, K3 can be derived by appropriate pixel evaluation and the triggering can be started accordingly.

The first camera Kl is a line scan camera which is connected to a picture capture of several lines. The additional image parts are used to determine the position of the object or the test object.

The method described is particularly suitable for imaging along an optical axis with moving objects at an undefined speed, wherein different corrections in the image recording are possible, whereby the quality of the optical inspection is improved. In addition, by means of the corresponding method, in particular measuring devices can be integrated more easily and thus cost-savingly into a production line. In the case that the invention is realized by means of a system of two cameras, a one-dimensionally resolving and a two-dimensionally resolving camera can also be used for the combination. The one-dimensionally resolving camera K1 is constantly functioning on the object surface and only when a suitable imaging profile of an object 1, 2 the second two-dimensionally resolving camera K3 is triggered via a synchronization circuit. The described method uses at least one one-dimensionally resolving camera K1 and a two-dimensionally resolving camera K3. As a constantly operated, one-dimensionally resolving camera, a line scan camera with several lines can be used, with which a plurality of image lines is scanned simultaneously. When using multiple line scan cameras in the camera system, the additional information is used to improve object recognition. The image analysis is done by means of an image processing hardware and corresponding analysis software.

The triggering of the two-dimensionally resolving camera K3 takes place when a suitable line profile, which describes the object to be recorded, is recorded with the one-dimensionally imaging camera K1. After the finding of this predefined suitable profile of a test object, a defined delay time will elapse before the image acquisition is started with the two-dimensionally resolving camera K3.

The image field of both cameras overlaps in such a way that at least one image element imaged by camera Kl lies on the image imaged by camera K2, K3.

The optical reproduction scales for both cameras Kl and K2 and also K3 can be different. The camera K1 consists of a line scan camera which scans at least one line at a time and if necessary consists of an optical system Ol and a lighting BR. The camera K2 consists of a two-dimensional resolution camera, a two-dimensional imaging optics and illumination B. The cameras Kl and K2 or K3 have common optical elements for imaging the object, ie, they overlap at least one pixel on the object surface.

The described method is particularly suitable for imaging along an optical axis along which objects are moved at undefined rates, such as microstructures on a conveyor belt or printed microstructures to be inspected on a film. An application of the invention, in particular in the representation of a measuring needle assembly for testing electronic components, with a corresponding optical arrangement is advantageous.

FIGS. 1A, 2A and 3A show the solution variant with a one-dimensionally resolving camera K1, corresponding to the line Z1 and combined with the two-dimensionally resolving camera K3, which corresponds to the surface F3. Relative to the central optical axis AX, the cameras Kl, K3 are arranged rotated by approximately 90 °. A coupling of the beam paths via beam splitter ST. Each camera is assigned a camera optics oil, 02. Furthermore, a common optic 012 with an illumination B is provided in the central beam path. The line Zl is aligned according to the direction of movement BR, d. H. parallel to this. The line Z1 corresponds to the image of the line camera K1 on the object. The line Z1 and the surface F3 overlap at least in one pixel.

Figures IB, 2B and 3B show the solution variant with two one-dimensional resolution cameras Kl, K2. Incidentally, the system components are essentially the same. On the object 1 and the camera Kl associated line Zl, which is aligned in the direction of movement, indicated. Instead of the area F3, the image of the line of the camera K2 can be seen in FIG. 1B on the object 1 with the designation Z2. The lines Z1 and Z2 overlap at least in one pixel. In FIG. 2B, an object scan is indicated, wherein Z1 and Z2 can touch and overlap in one pixel or have an overlap in a larger number of pixels. FIGS. 3A and 3B contain a synchronization and an image evaluation for the variant with a two-dimensionally resolving camera K3.

Claims

claims

1. A method for detecting objects moving rapidly and / or non-uniformly, comprising the following steps: - an object region is detected with at least one first one-dimensionally resolving camera (Kl) with at least one line (Z1), the image of the first camera being longitudinal to the direction of movement the objects runs,

- With at least one second, one-dimensionally resolving camera (K2) with at least one line (Z2), a detected object (1, 2) is scanned line by line, wherein the image of the second camera is transverse to the direction of movement of the objects, and it is a generates two-dimensional image of the object, - wherein the image fields of the two cameras (Kl, K2) overlap at least at one pixel, which is present in an image generated by the second camera.

2. Method for detecting fast and / or irregularly moving objects with the following steps:

- With at least a first one-dimensionally resolving camera (Kl) with at least one line (Zl) an object area is constantly detected, the image of the first camera is longitudinal to the direction of movement of objects, - is a predetermined line profile, which describes the object of the Camera (Kl) recorded and detected, so after a predetermined delay time with a second, by the camera (Kl) triggered, two-dimensionally resolving camera (K2) an image taken, created,

- Where the image fields of the two cameras (Kl, K2) overlap at least at one pixel, which is present in an image generated by the second camera.

3. The method of claim 1 or 2, wherein the optical imaging scales for different cameras are different.

4. The method according to any one of claims 1-3, wherein the camera (Kl) is a line scan camera with at least one line and additionally comprises optics and illumination.

5. The method according to any one of claims 1-4, wherein when using two one-dimensional resolution cameras at predetermined times both are triggered against each other.

6. The method according to any one of claims 1-5, wherein the triggering proceeds via a synchronization circuit.

7. The method according to any one of claims 1-6, wherein a one-dimensionally resolving camera for better object detection has a plurality of lines.

8. The method according to any one of claims 1-7, wherein two cameras located in a measuring head (Kl, K2) in the direction of the optical axis of an entire system record and these are offset in their mutual alignment relative to the optical axis by 90 °.