Optics: measuring and testing – Angle measuring or angular axial alignment – Relative attitude indication along 3 axes with photodetection
Reexamination Certificate
2001-12-07
2003-07-15
Tarcza, Thomas H. (Department: 3662)
Optics: measuring and testing
Angle measuring or angular axial alignment
Relative attitude indication along 3 axes with photodetection
C356S152100, C702S152000
Reexamination Certificate
active
06594007
ABSTRACT:
BACKGROUND
This application relates to a method and apparatus for mapping system calibration. An example of the application of the method is to a three-dimensional mapping system for determining the coordinates in space of identifiable locations on a crashed automotive vehicle. Specific embodiments described below relate to an optical system for three-dimensional automotive vehicle mapping and diagnostics operations. Certain of the broader aspects may be applicable to mapping systems (particularly but not exclusively for automotive diagnostic and repair work) utilizing other energy sources than optical energy.
Existing techniques for the calibration of equipment used in relation to dimensional and coordinate mapping and the like operations tend to be based on the obviously applicable technique of carrying out a series of dimensional mapping steps using known dimensional data (whereas in future use of the equipment that dimensional data will be to be determined), so that the unknown parameters, perhaps in relation to the equipment itself, can be accurately determined.
Thus, in relation to optical camera equipment, typically the technique is employed of using the optical equipment in a manner corresponding generally closely to that which will be employed when using the equipment in the field, and identifying the coordinates of a series of calibration locations by means of a calibration measurement machine (CMM).
Such a technique is somewhat laborious and slow and expensive as a basis for calibration of cameras on a production line, as is required. The step by step procedure is obviously slow. The technique also requires a substantial amount of space, since the calibration locations need to be, generally speaking, disposed at least as far from the camera as will occur in use, and preferably further, in order to enhance the accuracy of the determination. Thus, the technique is relatively slow, relatively costly and relatively inconvenient. An example of a published disclosure relating to in-field calibration of dimensional measuring equipment (applicable to vehicle wheel alignment) is disclosed in WO 08/12503 (Snap-on Technologies Inc). This technique utilizes for calibration purposes moveable targets which are disposable in either of two calibration positions for use in a sequential calibration process.
SUMMARY
An important aspect is to provide a method and apparatus particularly adapted to the calibration of optical and other mapping systems offering improvements relative to one or more of the matters discussed above, or generally.
Specifically in the embodiments, there are disclosed methods and apparatus for accurately determining the dimensional and locational parameters of certain critical internal components of a camera system employed in an optical measurement system used in three-dimensional automotive mapping. In these embodiments, the optical camera apparatus which is to be calibrated is itself manufactured to a relatively very high standard of constructional quality or accuracy, and accordingly the internal dimensions and locational parameters are, in principle, accurately known on the basis of the dimensional data relating to the components used and the assembly techniques employed. These dimensional parameters are, however, only nominal and do not provide a sufficiently accurate basis to be used as the dimensional starting point for calculating the coordinates of points to be mapped, in view of the relatively large distances between the camera and the points to be mapped, as compared with the internal camera dimensions under consideration.
In the embodiments described below it is disclosed that the techniques concerned enable the calculation of the relevant internal camera dimensional and locational data for three critical parameters of the camera. In its specific aspects, the invention is well-adapted to enable such data to be calculated. In its broader aspects, the invention provides a basis for very accurate calibration of mapping apparatus without the necessity for, in all cases, the calculation of the specific internal camera dimensions discussed in relation to the described embodiments.
In embodiments described below the method and apparatus is well adapted for use by way of calibrating production line equipment on a rapid and convenient basis and without adopting the step-by-step approach which has been necessary in relation to the use of CMM machines as described above. Moreover, in the embodiments described below, the apparatus described is constructed so that, and the corresponding method employs the apparatus so that, the dimensional and locational accuracy which can be readily built into the apparatus (of which only one example may be needed for a camera production line), is built into the apparatus and inherently controls the accuracy of the resultant calibration steps.
Thus, in the embodiments described below, we provide the means whereby optical camera apparatus forming part of a three-dimensional mapping system can be readily mounted in relation to the calibration apparatus at a location in which its dimensional position is very accurately known in relation to the relevant parts of the remainder of the apparatus. Then, the apparatus can be employed to provide simultaneously to the camera system energy signals from precisely known dimensional and locationally determined points so that (since these coordinates are known), the internal dimensions and locational data relating to the camera can be determined. Moreover, since the apparatus is extremely simple in construction its cost is relatively low. Also, since the apparatus is itself easily constructed to standards of dimensional accuracy which are better than those required for the mapping procedure itself, the overall dimensions of the apparatus can be significantly smaller than those of the typical three-dimensional article (such as an automobile) to be mapped.
In the embodiments, the energy source for calibration of the camera is a series of light-emitting diodes which are mounted on a pair of planar supports or mounting planes which are themselves disposed at spaced apart positions, one in front of the other and both in front of the camera unit.
By this arrangement, there is provided, conveniently, an accurately constructed three-dimensional array of energy sources which are precisely positioned and defined with respect to the camera unit, the latter being mounted at a fixed central front location with respect to the mounting planes and being connected thereto at a fixed distance by the structure of the apparatus, constituting spacer means.
Thus by adopting a simple mechanical structure providing merely a mounting for the camera module and connection means therefrom to a pair of mounting planes of simple planar construction and supporting, in each case, an array of energy sources, there is provided a simple and relatively cost effective mechanical means for effecting in a largely simultaneous manner the series of steps which have hitherto been necessary to take using CMM apparatus. Moreover, the simple mechanical structure of the apparatus enables the above-discussed provision of accuracy of dimensional construction enabling minimization of space requirements.
An important aspect of the embodiments relates to the simplicity of construction arising from the ability to transmit and receive energy signals between the transmitting and receiving energy modules despite the adoption of a simple mechanical construction in which the mounting planes are disposed one in front of the other, with one of these between the other and the camera.
The adoption of mounting planes, for example in form of boards or like rigid constructions, in the embodiments enables the precision location and position definition needed for the purposes of the system, without significant cost. However, such construction leads to the need either for an arrangement in which the energy signal can pass around the nearer board in order to reach the camera from the remote board, or else, some other arrangement is needed.
In order to allow fo
Andrea Brian K
Seyfarth Shaw
Snap-on Technologies, Inc.
Tarcza Thomas H.
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