EP2695374A1

EP2695374A1 - Method for determining adjustment deviations of an image data capture chip of an optical camera and corresponding adjustment verification devices

Info

Publication number: EP2695374A1
Application number: EP12703523.6A
Authority: EP
Inventors: Marzieh Asadeh PARCHAMI; Uwe Apel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2011-04-07
Filing date: 2012-02-09
Publication date: 2014-02-12
Also published as: DE102011006910A1; CN103493470A; WO2012136402A1; CN103493470B; US20140092240A1

Abstract

The invention relates to a method and an adjustment verification device for determining adjustment deviations of an image data capture chip of an optical camera (40;140) having the steps of aligning (S11) a laser beam (31;130a-c) of a laser source (11;120) by means of an adjustment verification device (1, 100) on a camera image to be captured by the optical camera (40; 140), on which camera image a visible laser image is formed by the laser beam (31; 130a-c), wherein the adjustment verification device (1, 100) has a camera holder (14, 15;123a, 123b) for the correct positional installation of the camera (40;140) and capturing (S12) the camera image by means of the optical camera (40;140), installed in correct position, and determining coordinates of the laser image captured in the camera image and measuring a deviation of the coordinates of the captured laser image from a target position of the camera image and deriving, on the basis thereof, the adjustment deviations of the image data capture chip of the optical camera (40; 140).

Description

Description title

A method for determining adjustment deviations of an image acquisition chip of an optical camera and corresponding Justierprüfvorrichtungen

The invention relates to a method for determining adjustment deviations of an image data acquisition chip of an optical camera and corresponding

Justierprüfvorrichtungen.

State of the art

DE 102 46 066 A1 describes a method for calibrating at least one image sensor system of a motor vehicle by means of at least one calibration object, wherein the image sensor system generates a first image information of the calibration object, preferably in the form of at least one image data set, and wherein the alignment of the image sensor system with respect to the geometric travel axis of Motor vehicle is determined.

It is well known that driver assistance systems based on optical

Cameras that monitor the apron of a vehicle, through features such as

Transverse guidance and object recognition can support the driver of the vehicle and increase safety.

An essential feature that such driver assistance systems must have is the correct determination of the object coordinates in the 3-dimensional world, such as lane markers and pedestrian locations, from the 2-dimensional image data acquired by the optical camera.

A further requirement of such driver assistance systems is that the viewing direction of the optical camera as a line of symmetry of the detection cone is matched as well as possible with the driving axis of the vehicle, since a skewness the

Reduces detection range of the optical camera and thus limits the function. Accordingly, the alignment check, which determines the deviation of the viewing direction of the camera from the nominal line of sight, is one of the most critical final optical checks. The determination of the device capability of measuring devices assumes that there is a normal, ie a reference, measure. For the determination of

Viewing direction of a camera so far no directly usable standard is available, since the viewing direction must be determined in each case in relation to the attachment or attachment points of a camera. That means that for every case shape and for each

Detection range of a camera, which is determined from the lens and image sensor data, a separate normal would be required.

So far, this task in the testing technology is solved so that the cameras are clamped in a test stand, the test specimens with a known orientation relative to a test point field. The image of the test point field recorded in this clamping is evaluated by means of a special image processing routine in such a way that the viewing direction of the camera and the distortion parameters of the objective can be determined. These data are then stored in the test object. The orientation of the camera in the clamping of the test stand is determined relative to the point coordinates on the test point field via two auxiliary steps in the field of surveying technology. In a first step, by means of the measurement on a 3D coordinate measuring machine, the contact points of the holder on which the camera to be tested is positioned are determined. Furthermore, the location of special

Reflector Brands - Hubbs Brands or Reflectance Spheres - Intended.

Based on the CAD data of the camera to be tested, the

Coordinates of the bearing points of the specimen recording the position of the main point and the viewing direction of the nominal optical camera are calculated. Starting from this point, the coordinates of the special reflector marks -

Hubbs Marks or Reflectance Spheres - determined in the coordinate system of the DUT. Building on this, in a second step, the positions of the

Reference reflector marks on the test chart of the test bench with respect to the

Coordinate system of the camera determined by means of a photogrammetric measurement. The results of the two measuring steps of the test bench must be in one

Coordinate transformation to give the parameter set for the image processing routines used in measuring the individual cameras. The calculation result of the coordinate transformation is used as a calibration, but as a result of the indirect determination of the measured variables, no calibration standard can be derived therefrom.

A camera that exactly matches the nominal design data can not be produced due to the relatively large influences of very small mechanical deviations. For example, results from the requirements that cameras for the night vision application, an angular resolution of 30 pixels (corresponding to 168 μηι) per degree of angle at a

Focal length of the lens of 10 mm, and that the maximum deviation from the nominal direction of view must not exceed +/- 1 °. This makes it clear that even the slightest deviations, for example in the placement of the image sensor on the printed circuit board, result in a significant error contribution.

Disclosure of the invention

Claim 1 defines a method for determining alignment deviations of an image acquisition chip of an optical camera, wherein a laser beam of a laser source is aligned by means of a Justierprüfvorrichtung on a camera to be recorded by the optical camera image on which a visible laser image is formed by the laser beam, wherein the Justierprüfvorrichtung has a camera holder for the correct position installation of the optical camera. Furthermore, in the method, the camera image is taken by the correct position built-in optical camera. Furthermore, coordinates of the laser image recorded in the camera image are determined, and a deviation of the coordinates of the recorded laser image from a desired position of the camera image is determined and based thereon a derivation of the

Adjustment deviations of the image data acquisition chip of the optical camera.

In claim 14, a Justierprüfvorrichtung for determining Wnkelabweichungen an optical camera is defined, comprising a camera holder for a reference camera, which support elements for installation of the reference camera in the

Camera mount and a support surface for a plane mirror has, and a Laser source, which is arranged in the Justierprüfvorrichtung such that a

Laser beam is adjusted at a position of an optical axis of the Justierprüfvorrichtung on the plane mirror and a reflected laser beam is aligned congruent to the laser beam.

Claim 15 defines an alignment test device for determining angular deviations of an optical camera, comprising a projection surface on which a line can be projected and which can be imaged by the optical camera, a laser source which is used to project the line perpendicular to the optical axis of the optical camera provided optical camera arranged projection surface, and a rocker unit, which is provided for rotatably supporting the laser source.

Advantages of the invention

The method defined in claim 1 and that defined in claims 14 and 15

Justierprüf device have the advantage that, for example, the position angle of an optical camera with respect to an external suspension on the housing of the camera can be determined with a simplified structure.

This determination is made independently of the determination of other parameters, such as the intrinsic calibration parameters of the optical camera. It is also independent of the mechanical dimensions of the optical camera, these need only be known with sufficient accuracy.

The features listed in the dependent claims relate to advantageous developments and improvements of the subject matter of the invention.

According to a preferred development, the following steps are carried out in the method prior to the alignment of the laser beam: Provision of a reference camera which has support elements for installation of the reference camera in the camera holder of the Justierprüfvorrichtung and a support surface for a plane mirror and used as part of the Justierprüfvorrichtung and loading the bearing surface of the reference camera with the plane mirror and clamping the reference camera in the

Camera mount. The advantage of doing so is that it's direct and easy Position angle of an optical camera in relation to an external suspension on the

Housing can be determined.

According to a further advantageous embodiment, the method is the

Aligning the laser beam in the test apparatus such that the laser beam is incident on the plane mirror at a location of an optical axis of the test apparatus and a reflected laser beam is reflected congruent to the laser beam, wherein the reference camera is replaced by the optical camera. By means of the alignment of the laser beam, the accuracy of the measurement is further improved.

According to a further advantageous embodiment of the method as

Adjustment deviations of the image data acquisition chip of the optical camera detects pitch and / or yaw deviations of the image data acquisition chip of the optical camera.

According to a further advantageous development of the method, a filter element is introduced into the beam path of the laser beam in such a way that no overexposure of the optical camera takes place. By suitable filtering with the filter element, the shape and size of the laser image and thus the accuracy of the measurement can be further improved.

According to a further advantageous embodiment of the method are in

Aligning the laser beam of the laser source in the Justierprüfvorrichtung Aperturelemente used to limit the diameter of the laser beam. The advantage achieved here is that it prevents a crossfading of the optical camera. In addition, the

Alignment of the incident and reflected beam from the plane mirror improved.

According to a further advantageous embodiment of the method is from the

Deviation of the coordinates of the recorded laser image from the target position of the camera image in the X direction calculated a yaw angle deviation of the optical camera.

According to a further advantageous embodiment of the method is from the

Deviation of the coordinates of the recorded laser image from the target position of the camera image in the Y direction, a pitch angle deviation of the optical camera

calculated. Brief description of the drawings

The present invention will be explained in more detail with reference to the exemplary embodiments indicated in the schematic figures of the drawing.

1 shows a method for determining adjustment deviations of an image acquisition chip of an optical camera according to an embodiment of the invention; an adjustment checking device for determining adjustment deviations of an image data acquisition chip of an optical camera according to another embodiment of the invention; an adjustment checking device for determining adjustment deviations of an image data acquisition chip of an optical camera according to another embodiment of the invention; and an adjustment checking device for determining adjustment deviations of an image data acquisition chip of an optical camera according to another embodiment of the invention. In the figures of the drawing are identical and functionally identical elements, features and components - unless otherwise stated - each with the same

Provided with reference numerals. It is understood that components and elements in the drawings are not for the sake of clarity and clarity

necessarily reproduced to scale to each other.

Embodiments of the invention

FIG. 1 shows a method for determining adjustment deviations of an image acquisition chip of an optical camera according to an embodiment of the invention. In a first step S1 1 of the method, a laser beam 31, 130a-c of a

Laser source 1 1, 120 aligned by means of a Justierprüfvorrichtung 1, 100 on a camera to be recorded by the optical camera 40, 140. The alignment takes place, for example, in relation to a mechanically accurately produced replica of the optical camera housing, which contains a plane mirror at the sensor position, after alignment of the laser beam, this replica is replaced by an optical camera 40, 140 with sensor, on which by the laser beam 31, 130a-c, a visible laser image is formed, wherein the Justierprüfvorrichtung 1, 100 a

Camera mount 14, 15, 123a, 123b for the correct installation of the optical camera 40, 140 has.

In a second step S12 of the method, the camera image is recorded by the correctly installed optical camera 40, 140. Furthermore, coordinates of the laser image recorded in the camera image are determined and a deviation of the

Coordinates of the recorded laser image determined from a desired position of the camera image and based thereon, deriving the adjustment deviations of the image data acquisition chip of the optical camera 40, 140. The method allows in addition to the determination of adjustment deviations of

Image data acquisition chips of the optical camera 40, 140 and the determination of adjustment deviations of another optical system of the camera 40, 140 such as a lens. FIG. 2 shows an alignment test device for determining adjustment deviations of an image data acquisition chip of an optical camera according to another

Embodiment of the invention.

FIG. 2 shows an alignment test device 1, which comprises a camera mount 14, 15 for a reference camera 20, which support elements 22a, 22b for installation of the

Reference camera 20 in the camera mount 14, 15 and a support surface 21 for a plane mirror has. Furthermore, the Justierprüfvorrichtung 1 comprises a laser source 1 1, which is arranged in the Justierprüfvorrichtung 1, that a laser beam 31 is adjusted at a position of an optical axis of the Justierprüfvorrichtung 1 on the plane mirror and a reflected laser beam 32 is aligned congruent to the laser beam 31. For example, the mechanical dimensions of the reference camera 20 and the fixed optical axis of the Justierprüfvorrichtung 1 from design data are known.

The spatial arrangement of an optic and the image capture chip of the optical camera 40 are also fixed, as well as the resolution of the image capture chip in pixels. The zero point of the image plane of the optics of the optical camera 40 is assumed, for example, in the center of the image sensor or image sensing chip. In the sense of the

Central projection of a pinhole camera, this point is the main point of the image and forms the base of the optical axis of the system and that of the projection center.

The straight line through the principal point in the image plane and the projection center represents the optical axis of the Justierprüfvorrichtung 1, wherein the attitude angle of the optical camera 40 or the reference camera 20 are given in relation to the projection center.

According to the design data of the optical camera 40, a milled camera dish or reference camera 20 is manufactured. The reference camera 20 has the property that the plane in which the image sensor of the optical camera 40 would be attached, is suitable for the attachment of a semi-transparent mirror or plane mirror. The location of the image sensor should be a symmetrical recess in the camera shell, which has approximately the same dimensions as the sensor itself.

Furthermore, this plane must have a direct relation to the later suspension of the camera body, which is determined by the support elements 22a, 22b.

This reference is important for the later positioning of the optical camera 40 relative to the laser beam 31 of the laser source 11. The details of the relation can only be defined in the sense of the application and construction. A semitransparent mirror is fixedly attached to the position of the image sensor, whereby bonding or mechanical fixation can be used. It's important to make sure that this interface is as level as possible.

The semitransparent mirror may, for example, be round or square and approximately correspond to the dimensions of the image sensor. The center of the semi-permeable Mirror must be marked so that it coincides with the center of the sensor position when mounting as far as possible.

As the laser source 11, for example, a He-Ne laser with a continuous

Power less than 1 mW and a beam diameter of about 1 mm used.

Furthermore, the Justierprüfvorrichtung 1 has at least two deflecting mirrors 12, 13, through which the laser beam 31 is guided so that it hits the reference camera 20 in the camera mount 14, 15.

The laser beam 31 is adjusted by means of the deflection mirrors 12, 13 so that it meets the center of the semitransparent mirror of the reference camera 20 vertically. This is ensured by the fact that a reflected laser beam 32 is aligned congruent with the laser beam 31.

The optical path of the laser beam 31 to the reference camera 20 is selected to be as large as possible, for example more than 3 m, so that small tilting of the laser beam 31 relative to the mirror of the reference camera 20 cause a large deflection of the reflected laser beam 32 and the tilting are well recognized can.

Further, for example, aperture elements 16, 17 for limiting the diameter of the laser beam 31 may be used to detect tilting of the laser beam 31

To facilitate laser beam 31. FIG. 3 shows an alignment test device for determining adjustment deviations of an image data acquisition chip of an optical camera according to another

Embodiment of the invention.

In FIG. 3, the reference camera 20 is replaced by an optical camera 40, which can record a camera image. When a camera image is taken with the optical camera 40, a laser image of the laser source 11 in the form of a laser spot or laser spot is visible on the recorded camera image of the optical camera 40.

For example, the difference between the position of the laser spot or laser spot to the image center or another desired position can be calculated. From the positional deviation of the laser spot or laser spot in the X direction of the Yaw angle and calculated by the positional deviation in the Y-axis of the pitch angle. The projection center represents the pivot point for the determination of both angles. This size can be taken from the design or a measurement. For this purpose, the laser spot may need to be attenuated in intensity. For example, filter elements or aperture elements 16, 17 are used for this purpose. The filter elements are designed for example as an optical filter and select the incident laser radiation according to certain criteria, eg. B. according to the wavelength, the polarization state or the direction of incidence.

The limitation of the diameter of the laser beam can be adapted, for example, to the respective optics of the optical camera 40. The larger the field of view of the optics of the optical camera 40, the more carefully it is checked that the laser beam 31 extends along the optical axis of the Justierprüfvorrichtung 1 and has a sufficiently small diameter. This ensures that the laser beam 31 hits the paraxial area of the optics of the optical camera 40 and thus the geometrical aberrations of the optics do not come into play.

Further reference numerals of Figure 3 are already described in the figure description of Figure 2.

FIG. 4 shows an alignment test device for determining adjustment deviations of an image data acquisition chip of an optical camera according to another

Embodiment of the invention.

The Justierprüfvorrichtung 100 includes a projection surface 1 10, on which a line 11 1 is projected and which can be imaged by an optical camera 140, a laser source 120, which for the projection of the line 1 11 on the perpendicular in front of the optical axis OA of the optical camera 140 arranged projection surface 110 is provided, and a Wppeinheit 121, which is provided for the rotatable mounting of the laser source 120.

The Justierprüfvorrichtung 100 further comprises fixed contact points in the form of a camera mount 123a, 123b for mechanical suspension of the optical camera 140, wherein the position of the optical camera 140 with respect to the optical axis OA of Justierprüfvorrichtung 100 is defined. Furthermore, the rocker unit 121 allows the optical camera 140 to be fixedly mounted on a tripod.

The laser source 120 is mounted, for example, parallel and vertically offset, above or below, to the optical axis OA of the Justierprüfvorrichtung 100.

A pendulum unit 122 allows the wobble unit 121 to continuously rock, with the laser source 120 of the alignment tester 100 during a

Oscillation laser beams 130a, 130b, 130c projected onto the projection surface 1 10 such that the line 1 11 is imaged as a laser image of the laser beams 130a, 130b, 130c.

The optical camera 140 is operated to capture a sequence of camera images with the appropriate software. The entire assembly of optical unit 121 and optical camera 40 is positioned such that the laser beams 130a, 130b, 130c are projected onto, for example, a wall or panel removed from the optical camera 140 about 5 meters.

The rocker unit 121 with the laser source 120 switched on is set in vibration relative to the optical camera 40. The optical camera 140 captures a sequence of camera images during this time of oscillation. For this example, a

Darkening be made.

The laser source 120 projects during the Wppbewegung a line 1 11 to the

Projection surface 110. For example, the sequence of recorded camera images is later assembled by addition, so that the line 1 11 is displayed.

In an ideally manufactured optical camera 140 without adjustment deviations, the line 11 is a vertical line in the image plane of the recorded camera image, the line 11 being along the central column of the image sensor.

An optical camera 140, which is subject to manufacturing tolerances, will record, for example, a line 11 which has a curvature to the horizontal of the projection surface 110. This deviation of such an oblique line to an ideally vertical results in the roll angle of the optical camera 140. In this case, the beschräge cross over and vertical line in the middle of the sensor. The roll angle is referred to this point, the puncture point of the optical axis OA by the image sensor.

When manufacturing the wobble unit 121, care must be taken that the light pointer runs parallel to the optical axis OA of the alignment test device 100.

Although the present invention has been described above with reference to preferred embodiments, it is not limited thereto, but modifiable in many ways.

Claims

Claims 1. Method for determining adjustment deviations of a

Image acquisition chips of an optical camera (40; 140) comprising the steps of:

Aligning (S1 1) a laser beam (31; 130a-c) of a laser source (11; 120) by means of an alignment test device (1; 100) with a camera image to be recorded by the optical camera (40; 140) on the laser beam

(31; 130a-c) a visible laser image is formed, wherein the

Justierprüfvorrichtung (1, 100) has a camera mounting (14, 15; 123a, 123b) for the correct installation of the optical camera (40; 140); and picking up (S12) the camera image by the correct position built-in optical

And determining coordinates of the laser image taken in the camera image and determining a deviation of the coordinates of the captured laser image from a target position of the camera image and deriving therefrom the adjustment deviations of the camera image

Image data acquisition chips of the optical camera (40; 140).

2. The method of claim 1, wherein prior to aligning (S11) the laser beam (31) the following steps are carried out: providing a reference camera (20), which support elements (22a, 22b) for

Installation of the reference camera (20) in the camera holder (14, 15) of

Justierprüfvorrichtung (1) and a bearing surface (21) for a plane mirror and is used as part of the Justierprüfvorrichtung (1); Equipping the support surface (21) of the reference camera (20) with the plane mirror and

Clamping the reference camera (20) in the camera holder (14, 15).

3. The method of claim 2, wherein the alignment (S11) of the laser beam (31) in the test apparatus (1) takes place such that the laser beam (31) at a location of an optical axis of the test apparatus (1) meets the plane mirror and a reflected Laser beam (32) is reflected congruent to the laser beam (31), wherein the reference camera (20) is replaced by the optical camera (40).

4. The method according to any one of the preceding claims, wherein as

Adjustment deviations of the image data acquisition chip of the optical camera (40) Nick and / or yaw deviations of the image data acquisition chip of the optical camera (40) are determined.

5. The method according to any one of the preceding claims, wherein a filter element in the beam path of the laser beam (31) is introduced such that no

Overexposure of the optical camera (40) takes place.

6. The method according to any one of the preceding claims, wherein when aligning (S11) of the laser beam (31) of the laser source (1 1) in the Justierprüfvorrichtung (1)

Aperture elements (16, 17) are used to limit the diameter of the laser beam (31).

7. The method according to any one of the preceding claims, wherein from the

Deviation of the coordinates of the recorded laser image from the target position of the camera image in the X direction, a yaw angle deviation of the optical camera (40) is calculated.

8. The method according to any one of the preceding claims, wherein from the

Deviation of the coordinates of the recorded laser image from the target position of the camera image in the Y direction, a pitch angle deviation of the optical camera (40) is calculated.

9. The method of claim 1, wherein prior to aligning (S11) of the laser beam (130a-c), there is provided a rocker unit (121) which oscillates

Laser source (120) allows, which on a perpendicular in front of the optical axis of the optical camera (140) arranged projection surface (1 10) radiates.

10. The method of claim 9, wherein recording (S22) an image sequence of individual images of the projection surface (110) by the optical camera (140) takes place during a vibration process of the rocking unit (121) and for determining the deviation for recording (S12) of the camera image an evaluation of the image sequence by a Image processing routine takes place, wherein by means of a deviation of the laser beam (130a-c) during the oscillation process swept line (1 11) from the vertical, the angular deviations of the optical camera (140) are determined.

5 1. The method of claim 10, wherein the rocker unit (121) is deflected such that in the vertical, the full image height of the optical camera (140) from the laser beam (130a-c) is swept during the vibration process.

12. The method according to any one of claims 10 or 11, wherein the deviation of the o laser beam (130a-c) swept line (1 11) from the vertical of the

Angular deviation of the optical camera (140) corresponds.

13. The method of claim 10, wherein the optical camera (140) uses a correction value based on the determined

5 adjustment deviations to set up testing and manufacturing facilities

is used.

14. Justierprüfvorrichtung (1) for determining angular deviations of an optical camera (40) with:

0

a camera mount (14, 15) for a reference camera (20), which support elements (22a, 22b) for installation of the reference camera (20) in the camera mount (14, 15) and a support surface (21) for a plane mirror has ; 5 of a laser source (11) which is arranged in the Justierprüfvorrichtung (1) that a laser beam (31) at a position of an optical axis of the Justierprüfvorrichtung (1) is adjusted to the plane mirror and a reflected laser beam (32) congruent to the Laser beam (31) is adjusted. 0 15. An adjustment test apparatus (100) for determining deviation of an optical camera (140) comprising: a projection surface (110) on which a line (11) can be projected and which can be imaged by the optical camera (140);

5 a laser source (120) which is provided for the projection of the line (11 1) on the projection surface (1 10) arranged perpendicularly in front of the optical axis (OA) of the optical camera (140); and a rocker unit (121) provided for rotatably supporting the laser source (120).