Static camera calibration using motion of vehicle portion

Abstract

In a system and a method for extrinsic calibration of an image capture apparatus of a vehicle, the vehicle includes a vehicle body and a movable part configured to rotate around a known rotation axis relative to the vehicle body. The system includes an image capture apparatus having an image capture device mounted on the vehicle body and configured to capture at least two images of the movable part, an identification unit configured to identify at least two image features in the images, a calculation unit configured to calculate a calculated direction of the rotation axis relative to the image capture device based on the image features, and a calibration unit configured to determine extrinsic parameters of the image capture apparatus based on the calculated direction of the rotation axis relative to the image capture device and the known parameters of the rotation axis relative to the vehicle.

Claims

1. A system for extrinsic calibration of an image capture apparatus of a vehicle, wherein the vehicle includes a vehicle body and a movable part, wherein the movable part is configured to rotate around a rotation axis having a known position and orientation relative to the vehicle body, and wherein the system comprises: an image capture apparatus comprising an image capture device that is mounted on the vehicle body, and is configured to capture at least first and second images of the movable part; and at least one processor that is configured to identify image features of the movable part in the images, to calculate a calculated direction of the rotation axis relative to the image capture device based on the image features, and to determine extrinsic parameters of the image capture apparatus based on the calculated direction of the rotation axis relative to the image capture device and the known position and orientation of the rotation axis relative to the vehicle body.

2. The system according to claim 1, wherein the first image depicts the movable part in a first rotation position relative to the vehicle body, and the second image depicts the movable part in a second rotation position different from the first rotation position relative to the vehicle body.

3. The system according to claim 1, wherein the image features comprise at least two image features of the movable part in the first image and at least two corresponding image features of the movable part in the second image.

4. The system according to claim 1, wherein the movable part comprises a part selected from the group consisting of a boot, a bonnet, a mirror and a door of the vehicle.

5. The system according to claim 1, further comprising a memory configured to store at least one vehicle characteristic.

6. The system according to claim 5, wherein the vehicle characteristic comprises a position of the image capture device mounted on the vehicle body.

7. A vehicle comprising: a vehicle body; a movable part configured to rotate around a rotation axis having a known position and orientation relative to the vehicle body; and the system according to claim 1; wherein the image capture device is mounted on the vehicle body and is configured to capture the images of the movable part.

8. The vehicle according to claim 7, wherein the movable part comprises a part selected from the group consisting of a bonnet, a boot, a mirror and door of the vehicle.

9. A method for extrinsic calibration of an image capture apparatus of a vehicle, wherein the vehicle includes a vehicle body and a movable part, wherein the movable part is configured to rotate around a rotation axis having a known position and orientation relative to the vehicle body, wherein the image capture apparatus includes an image capture device mounted on the vehicle body, and wherein the method comprises: with the image capture device, capturing at least first and second images of the movable part; identifying image features of the movable part in the images; calculating a calculated direction of the rotation axis relative to the image capture device based on the image features; and determining extrinsic parameters of the image capture apparatus based on the calculated direction of the rotation axis relative to the image capture device and the known position and orientation of the rotation axis relative to the vehicle.

10. The method according to claim 9, wherein the first image depicts the movable part in a first rotation position relative to the vehicle body and the second image depicts the movable part in a second rotation position different from the first rotation position relative to the vehicle body.

11. The method according to claim 9, wherein the image features comprise at least two image features of the movable part in the first image and at least two corresponding image features of the movable part in the second image.

12. The method according to claim 9, performed when the vehicle is parked.

13. The method according to claim 9, further comprising capturing additional images of a second movable part that is configured to rotate around a second axis relative to the vehicle body, identifying additional image features of the second movable part in the additional images, and calculating a second direction of the second axis based on the additional image features, wherein the second axis is not parallel to the rotation axis, and wherein the determining of the extrinsic parameters is further based on the second direction of the second axis.

14. A non-transitory computer-readable storage medium storing thereon executable program instructions that perform the method according to claim 9 when executed.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 shows a vehicle with mounted image capture devices in a top view, side view, front view, and rear view.

(2) FIG. 2 shows a block diagram of a possible embodiment of a control unit of a vehicle.

(3) FIG. 3 shows a flowchart of a possible embodiment of a method for extrinsic calibration of an image capture system of a vehicle.

(4) FIG. 4 illustrates a possible embodiment of a readable storage medium comprising executable program instructions.

(5) FIG. 5 shows a vehicle with mounted image capture system in a side/rear view and a diagram illustrating the calculated door rotation axis in an image captures device frame using the multiple image capture device approach.

(6) FIG. 6 shows a vehicle with mounted image capture systems in a side/rear view and a diagram illustrating the calculated boot rotation axis in an image captures device frame using the multiple image capture device approach.

(7) FIG. 7 shows a diagram illustrating the calculated rotation axis and the full rotation between an image captures system frame and vehicle frame using the multiple image capture device approach.

(8) FIG. 8 shows a vehicle with a mounted image capture system in a side/rear view and a diagram illustrating the calculated door rotation axis in an image captures system frame using the single image capture device approach.

(9) FIG. 9 shows a mirror of a vehicle with a mounted image capture system in a side view and a diagram illustrating the calculated mirror rotation axis in an image captures system frame using the single image capture device approach.

(10) FIG. 10 shows a diagram illustrating the calculated rotation axis and the full rotation between an image captures system frame and vehicle frame using the single image capture device approach.

DETAILED DESCRIPTION OF EMBODIMENTS

(11) Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

(12) Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of including, comprising or having and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms connected, mounted and coupled are used broadly and encompass both direct and indirect connecting and coupling.

(13) It is also to be noted that the image capture devices are mounted on a vehicle portion by an interface that provides a detachable connection between the image capture device and the vehicle portion.

(14) FIG. 1 shows a vehicle 10 in a side view 11, in a front view 12, in a top view 13, and a rear view 14. The vehicle 10 comprises different image capture systems 21, 22, 23 comprising an image capture device 22 mounted on the mirror frame, an image capture device 21 mounted on the boot frame, and an image capture device 23 mounted on the bonnet frame. FIG. 1 also shows the rotation axes of the doors, boot (i.e. trunk), and bonnet (i.e. hood). As the left or right door of the vehicle is opened and closed, the left or right door rotates about the respective door axis 33. As the boot of the vehicle is opened or closed, the boot rotates about the boot axis 32. As the bonnet is opened or closed, the bonnet rotates about the bonnet axis 31.

(15) The orientation of the image capture device mounted on the mirror, boot, or bonnet, in the vehicle frame can be calculated by moving (opening and closing) the door, boot and bonnet about their respective axis 33, 32, 31. The apparent motion of image features (objects or features in the surrounding area of the vehicle, or body portion), detected in the images taken by the image capture device as the door or mirror, boot or bonnet is opened and closed allows the rotation axis of the vehicle's mirror, door, boot or bonnet to be measured. If two non-parallel rotation axes are measured, the three extrinsic parameters representing the camera's rotation about the x, y and z axes can be determined. For instance, if the rotation axes of the door and the boot are measured, the orientation of the image capture device relative to the vehicle 10 can be calculated.

(16) If only one rotation axis is measured, the orientation of the image capture device can only be determined around two axes perpendicular to the rotation axis observed. For instance, if the rotation axis of the boot (i.e. the y axis) is measured, then the orientation of the image capture device can be determined only around the x and z axes, and not around the y axis (assuming the boot's rotation axis is parallel to the y axis).

(17) In this case, the unknown orientation around the observed axis could be determined by observing a portion of the vehicle within the images.

(18) For instance, a portion of the boot could be observed in the fully open and closed positions within the images to determine the orientation of the image capture device around the boot's rotation axis (y axis).

(19) Alternatively, a portion of the boot could be observed in a known orientation between fully open and closed.

(20) The calculation of the orientation of the image capture device should not be limited to the image capture devices 21, 22, 23 as described above and presented in FIG. 1, and their respective mounting in the mirror/door, boot, and bonnet. Rather, there are further image capture systems comprising an image capture device mounted in different body portions of the vehicle 10 providing information for driver assistance systems that can be used to identify image features in the images of the body and/or surrounding area and/or body portion to calculate the direction of the rotation axis relative to the image capture device.

(21) FIG. 2 shows a block diagram of a possible embodiment of a control unit of a vehicle.

(22) In the illustrated embodiment, the control unit 40 of a vehicle 10 comprises the memory unit 41, the identification unit 42, the calculation unit 43, and the calibration unit 44.

(23) The control unit 40 is installed in the vehicle 10 and enables the calibration of the image capture systems 21, 22, 23 mounted on the mirror/door, boot, and bonnet in a parking position of the vehicle by only moving body portions of the vehicle 10 with an image capture and without moving of the whole vehicle.

(24) The memory unit 41 is adapted to store information and/or calculation results of motions from features or objects between at least two images captured by image capture devices 21, 22, 23. Furthermore, the memory unit 41 is adapted to store the calculation result of the rotation axis.

(25) The identification unit 42 is adapted to identify, on the images taken by the image capture device, at least two features or objects, such that the rotation axis of the vehicle portion can be determined. The identification unit may identify features on the vehicle body or in the surrounding area of the vehicle, if the image capture device is mounted on the vehicle portion, to compute the motion of the features or objects between the at least two images. Alternatively, the identification unit may identify features on the vehicle portion, if the image capture device is mounted on the vehicle body, to compute the motion of the features or objects between the at least two images.

(26) It is to be understood that also a video provided by a video camera consists of a plurality of images, wherein the number of images depends on the frame rate. The motion of the feature or object from the plurality of images can be extrapolated and used to calculate the rotation axis of the vehicle portion.

(27) The calculation unit 43 is adapted to calculate the direction of the rotation axis relative to the image capture device on the basis of the image features.

(28) The calibration unit 44 is configured to determine the extrinsic (intermediate) parameters of the image capture system 21, 22, 23 on the basis of the calculated direction of the rotation axis relative to the image capture device 21, 22, 23 and the rotation relative to the vehicle 10.

(29) FIG. 3 shows a flowchart of a possible embodiment of a method for extrinsic calibration of an image capture system 21, 22, 23 of a vehicle 10.

(30) In the illustrated embodiment, the method comprises four main steps.

(31) In a first step S1 at least two images are captured by an image capture device of the image capture system 21, 22, 23 such that the rotation axis of the body portion can be calculated. If the image capture device is mounted on the body portion, the image capture device captures a first image and a second image of the body and/or surrounding area of the vehicle 10. If the image capture device is mounted on the body, the image capture device captures a first image and a second image of the body portion. The first image is captured with the body portion in a first position. The second image is captured with the body portion in a second position.

(32) In a second step S2 at least two image features in the images are identified.

(33) In a third step S3 a direction of the rotation axis relative to the image capture device on basis of the image features in the images is calculated. The direction of the rotation axis can be defined as a unit vector parallel to the rotation axis.

(34) In a fourth step S4 the extrinsic parameters of the image capture system 21, 22, 23 are determined on the basis of the calculated direction of the rotation axis relative to the image capture device and the rotation relative to the vehicle 10.

(35) In the first step S1 while opening/closing the door/boot/bonnet the image capture system 21, 22, 23 captures images of the body of the vehicle 10 and/or surrounding area of the vehicle 10 and/or body portion. Within the images taken by the image capture device of the image capture system 21, 22, 23 features or objects are identified and the position and/or motion of the identified features or objects is tracked. In the third step the direction of the rotation axis is determined relative to the image capture device on the basis of the image features.

(36) Similarly, to the motion of the door/boot/bonnet, in a further embodiment, the motion of the wing mirror can be used to calculate the direction of the rotation axis of the wing mirror.

(37) The wing mirror can rotate over an angle at the fixation point with the door of the vehicle 10 and after closing the door, the mirror can be folded and unfolded, the motion of the features detected within the images taken by the image capture device of the image capture system 22 during the folding motion can be used to calculate the direction of the rotation axis relative to the image capture device of the image capture system 22.

(38) The observed rotation axis of a body part of a vehicle, in combination with the known location of this rotation axis relative to the vehicle, is used to determine some parameters of the image capture system's extrinsic calibration. The extrinsic calibration converts coordinates in the image capture system reference frame (e.g. the coordinate system where the z axis points down the optical axis) to the coordinates in the car reference frame (e.g. the coordinate system where the z axis points upwards). The extrinsic calibration consists of the image capture system's orientation and location. The orientation defines which direction the image capture system is pointing, i.e. its rotation as defined in the car reference frame. The location defines the image capture system's position with respect to a defined zero position on the car, such as the center of the rear axle.

(39) To determine the extrinsic orientation of the image capture system the direction of the rotation axis can be calculated. The rotation axis of a body part (such as a door) needs to be known in advance for this method to work. For instance, the rotation axis of the door may be known to be parallel to the z-axis of the car (measured in the car reference frame). When the image capture system on the vehicle observes image features moving due to the rotation of the door, the system can calculate the direction of the rotation axis of the door in the camera reference frame. The system can then determine the rotation needed such that this observed rotation axis in the image capture system reference frame is parallel with the known axis in the car reference frame. This will convert the coordinates of the rotation-axis into the car reference frame. This will provide information regarding the image capture system extrinsic calibration.

(40) The method can determine the image capture device orientation around two rotation axes (the x and y axis in this example) perpendicular to the rotation axis of the body part. It is possible to resolve the unknown orientation of the image capture system, around the rotation axis of the body part by using further information, such as by using a full 3D model of the car, or by observing a second (non-parallel) rotation axis of another body part of the vehicle 10.

(41) For instance, the image capture device could capture image features moving due to the rotation of the door, and image features moving due to the rotation of the door mirror (if the door mirror rotates around a rotation axis that is not parallel to the rotation axis of the door) to determine the full orientation of the image capture device around the x, y and z axes of the car.

(42) The direction of the rotation axis in the image capture reference frame provides information regarding the image capture system's orientation in the vehicle 10 reference frame, when compared with the known rotation axis.

(43) The location of the rotation axis in the image capture reference frame provides information regarding the image capture system's location in the vehicle reference frame, when compared with the known rotation axis.

(44) The rotation axis is calculated by tracking the motion of image features in the images. The minimum number of image features needed relates to the number of unknown parameters in the equations. To determine direction and position of the rotation axis five features are needed. A five-point Essential Matrix algorithm could then be used, such as the Nister's five-point relative pose algorithm, to recover the rotation and translation of the image capture system relative to the rotating body part. The rotation and translation of the image capture system could then be converted into the rotation axis direction and position.

(45) Many other alternative relative pose algorithms would also be suitable to calculate the relative motion of the image capture system. It may be possible to use a minimal solver that uses fewer features if only the direction of the rotation axis needs to be calculated.

(46) FIG. 4 shows an embodiment of a computer readable storage medium 50 comprising executable program instructions 60 that perform the method according to the present invention when executed. Using the program instructions 60, the direction of the rotation axis relative to an image capture device by observing a position and/or orientation of the features on the images is calculated, and the extrinsic parameters of the image capture device 21, 22, 23 on the basis of the calculated direction of the rotation axis relative to the image capture device and the rotation relative to the vehicle are determined.

(47) The computer readable storage medium 50 can be designed for example as a Random Access Memory (RAM), Read Only Memory (ROM), microSD/SDHC memory card, hard disc drive, and USB-Stick. The usage of different memory designs is not limited to the number of storage designs as listed, rather there are still other storage designs applicable.

(48) FIG. 5 shows a vehicle 10 with mounted image capture systems 21, 22 in a side/rear view and a diagram illustrating the calculated door rotation axis 33 in an image capture system reference frame using the multiple image capture system 21, 22 approach.

(49) In FIG. 5 the motion of the door is illustrated by the arrow A. While the door of the vehicle 10 is opened and closed, the door is moving around the door rotation axis 33. During the motion of the door around the door rotation axis 33, the image capture device 22 detects images of the body and/or body portion of the vehicle 10 and/or surrounding area of the vehicle 10 to identify different features and/or objects in the image. The image capture system can be mounted in the mirror. Further positions to mount the image capture system or to use for identifying features and/or objects are possible depending on the driver assistant systems. The motion of the identified features and/or objects will be computed using the plurality of different images detected by the image capture device of the image capture system 22. The motion can be used to calculate the direction of the door rotation axis 33 (door axis unit vector) with regard to the image capture device reference frame of the image capture device 22 as illustrated in the diagram.

(50) FIG. 6 shows a vehicle 10 with mounted image capture devices 21, 22 in a side/rear view and a diagram illustrating the calculated boot rotation axis 32 in an image capture device reference frame using the multiple image capture system 21, 22 approach.

(51) In FIG. 6 the motion of the boot is illustrated by the arrow B. While the boot of the vehicle 10 is opened and closed, the boot is moving around the boot rotation axis 32. During the motion of the boot around the boot rotation axis 32, the image capture device of the image capture system 21 captures images of the body and/or body portion of the vehicle 10 and/or surrounding area of the vehicle 10 to identify different features and/or objects in the images. Different positions to mount the image capture system or to use for identifying features and/or objects are possible depending on the driver assistant systems. The motion of the identified features and/or objects will be computed using the plurality of different images detected by the image capture device of the image capture system 21. The motion can be used to calculate a direction of the boot rotation axis 32 (boot axis unit vector) with regard to the image capture device reference frame of the image capture system 21 as illustrated in the diagram.

(52) FIG. 7 shows a diagram illustrating the calculated rotation axis and the full rotation between an image capture system reference frame and a vehicle reference frame using the multiple image capture device approach.

(53) In FIG. 7 the approach to calculate the extrinsic parameters of the image capture system by using the calculated rotation, both, around the door axis and the boot axis, is shown.

(54) The axes X, Y, and Z in FIG. 7 represent the axes of the intermediate reference frame. The axes i, j, and k represent the bases of the image capture device reference frame 21. The axes {circumflex over (B)} and {circumflex over (D)} represent the boot axis unit vector and door axis unit vector.

(55) To determine the extrinsic parameter, at first the door axis {circumflex over (D)} from the image capture system reference frame 22 (camD) is rotated to the image capture system reference frame 21 (camB):
{circumflex over (D)}.sub.camB=R.sub.camD/camB{circumflex over (D)}.sub.camD

(56) This assumes the rotation R.sub.camD/camB from image capture system 22 to image capture system reference frame 21 is known. Once the door axis unit vector {circumflex over (D)} and the boot axis unit vector {circumflex over (B)} have been found in the image capture system reference frame 21 (camB), they can be used to calculate the Y axis of an intermediate reference frame.

(57) $\hat{Y}=\frac{{\hat{D}}_{\mathrm{camB}}{\hat{B}}_{\mathrm{camB}}}{.Math.{\hat{D}}_{\mathrm{camB}}{\hat{B}}_{\mathrm{camB}}.Math.}$

(58) The Z axis of the intermediate reference frame is then calculated using the door axis in the image capture system reference frame ({circumflex over (D)}.sub.cam) and the unit vector .
{circumflex over (Z)}={circumflex over (D)}.sub.camB

(59) With the X axis of the intermediate frame being:
{circumflex over (X)}={circumflex over (D)}.sub.camB

(60) The rotation between the image capture system reference frame and the intermediate reference frame (R.sub.cam/inter) is then calculated as

(61) $R_{\mathrm{cam}/\mathrm{inter}}=\left[\begin{array}{ccc}\hat{X}.Math.i& \hat{X}.Math.j& \hat{X}.Math.k\\ \hat{Y}.Math.i& \hat{Y}.Math.j& \hat{Y}.Math.k\\ \hat{Z}.Math.i& \hat{Z}.Math.j& \hat{Z}.Math.k\end{array}\right]$
where i, j, and k are the bases of the image capture system B reference frame. Since the position and orientation of the door and boot axis are known in the vehicle reference frame, the rotation from the intermediate reference frame to the vehicle reference frame R.sub.inter/vehicle is known. This can then be used to calculate the rotation between image capture system reference frame 21 and vehicle reference frame R.sub.cam/vehicle.
R.sub.camB/vehicle=R.sub.inter/vehicleR.sub.camB/inter

(62) The extrinsic parameters of the other capture device can then be found using the known rotation between the image capture devices.

(63) The above illustrated approach provides an embodiment to calculate the extrinsic parameters with two image capture devices using two rotation axes such as the door axis and the boot axis.

(64) In a further embodiment the door axis and the bonnet axis can be used to calculate the extrinsic parameters.

(65) This approach according to the present invention has the advantage that the image capture systems 21, 22, 23 of a vehicle 10 can be quickly and simply calibrated by opening and closing the door and boot/bonnet. Further the approach provides a high accuracy orientation calculation. The features and/or objects in the images detected by the image capture device of the image capture system 21, 22, 23 will appear to move over a large arc because of the long motion of the door and boot/bonnet. With a small amount of motion there would be more errors within the calculation.

(66) Advantageously, the method according to the present invention does not require a vehicle motion. The method can be performed in the factory or garage in the parking position. Furthermore, the vehicle does not need a precise and measured position with regard to placed reference points (features such as straight lines on ground plane, calibration boards attached to the car, or any measured vehicle portions or vehicle features e.g. tire, hubcap).

(67) FIG. 8 shows a vehicle 10 with a mounted image capture device 22 in a side/rear view and a diagram illustrating the calculated door rotation axis 33 in an image capture device reference frame using the single image capture device of the image capture system 22 approach.

(68) In FIG. 8 the motion of the door is illustrated by the arrow A. While the door of the vehicle 10 is opened and closed, the door is moving around the door rotation axis 33. During the motion of the door around the door rotation axis 33, the image capture device of the image capture system 22 captures images of the body and/or body portion of the vehicle 10 and/or surrounding area of the vehicle 10 to identify different image features and/or objects. The image capture system can be mounted in the mirror. Further positions to mount the image capture systems or to use for identifying features and/or objects are possible depending on the driver assistant systems. The motion of the identified features and/or objects will be computed from the plurality of different images captured by the image capture device of the image capture system 22. The motion can be used to calculate the direction of the door rotation axis 33 (door axis unit vector) with regard to the image capture device reference frame of the image capture device 22 as illustrated in the diagram.

(69) FIG. 9 shows a mirror of a vehicle with a mounted image capture device 22 (not shown) in a side view and a diagram illustrating the calculated mirror rotation 34 axis in an image capture device reference frame using the single image capture 22 device approach.

(70) In FIG. 9 the motion of the wing mirror is illustrated by the arrow C. While the mirror of the vehicle 10 is folded and unfolded, the mirror is moving around the mirror rotation axis 34. During the motion of the mirror around the mirror rotation axis 34, the image capture device of the image capture system 22 captures images of the body and/or body portion of the vehicle and/or surrounding area of the vehicle 10 to identify different image features and/or objects in the images. The motion of the identified image features and/or objects will be computed from the plurality of different images detected by the image capture device of the image capture system 22. The motion can be used to calculate the direction of the mirror rotation axis 34 (mirror axis unit vector) with regard to the image capture device reference frame of the image capture device 22 as illustrated in the diagram.

(71) FIG. 10 shows a diagram illustrating the calculated rotation axis and the full rotation between an image capture device reference frame and vehicle reference frame using the single image capture device approach.

(72) In FIG. 10 the approach to calculate the extrinsic parameters of the image capture device by using the calculated rotation, both, around the door axis and the mirror axis of a single image capture device, is shown.

(73) The axes X, Y, and Z in FIG. 10 represent the axes of the intermediate reference frame. The axes i, j, and k represent the bases of the image capture system reference frame 22. The axes {circumflex over (M)} and {circumflex over (D)} represent a mirror axis unit vector and a door axis unit vector.

(74) If the door axis unit vector {circumflex over (D)} and the mirror axis unit vector {circumflex over (M)} have been calculated in the image capture system reference frame (cam), they can be used to calculate the Y axis of an intermediate reference frame.

(75) $\hat{Y}=\frac{{\hat{D}}_{\mathrm{cam}}{\hat{M}}_{\mathrm{cam}}}{.Math.{\hat{D}}_{\mathrm{cam}}{\hat{M}}_{\mathrm{cam}}.Math.}$

(76) The Z axis of the intermediate reference frame is then calculated using the door axis in the image capture system 22 ({circumflex over (D)}.sub.cam) and the unit vector .
{circumflex over (Z)}={circumflex over (D)}.sub.cam

(77) With the X axis of the intermediate reference frame being:
{circumflex over (Z)}={circumflex over (D)}.sub.cam

(78) The rotation between the image capture system reference frame and the intermediate reference frame R.sub.cam/inter is then calculated as:

(79) $R_{\mathrm{cam}/\mathrm{inter}}=\left[\begin{array}{ccc}\hat{X}.Math.i& \hat{X}.Math.j& \hat{X}.Math.k\\ \hat{Y}.Math.i& \hat{Y}.Math.j& \hat{Y}.Math.k\\ \hat{Z}.Math.i& \hat{Z}.Math.j& \hat{Z}.Math.k\end{array}\right]$

(80) Where i, j, and k are the bases of the image capture system reference frame. Since the position and orientation of the door and mirror axis are known in the vehicle reference frame, the rotation from the intermediate reference frame to the vehicle reference frame R.sub.inter/vehicle is known. This can then be used to calculate the rotation between image capture system reference frame and vehicle reference frame R.sub.cam/vehicle.
R.sub.cam/vehicle=R.sub.inter/vehicleR.sub.cam/inter

(81) In a further embodiment, to calculate the extrinsic parameters the motion caused by opening and closing the bonnet or boot and the motion of the image capture device around a mechanism (fixed point of the image capture device) in the boot and/or bonnet can be used. In this point the image capture system rotates and provides an extra rotation to the image capture system on the boot and bonnet that can be used to calculate the extrinsic parameters with the single image capture device approach.

REFERENCE NUMBERS

(82) 10 vehicle 11 side view of a vehicle 12 front view of a vehicle 13 top view of a vehicle 14 rear view of a vehicle 21 image capture device (frame) boot of a vehicle 22 image capture device (frame) mirror (l, r) of a vehicle 23 image capture device (frame) bonnet of a vehicle 31 rotation axis of the bonnet 32 rotation axis of the boot 33 rotation axis of the doors (l, r) 40 control unit 41 memory unit 42 identification unit 43 calculation unit 44 calibration unit S1 step of detecting S2 step of identifying S3 step of calculating S4 step of determining