1. Field of the Invention
The present invention relates to an adjusting apparatus for automatically adjusting positional deviation of stereoscopic images by means of geometrical image transformation processes.
2. Discussion of the Background Art
In recent years, a stereoscopic vehicle surrounding monitoring apparatus using a pair of left and right cameras (stereoscopic camera having solid image element like CCD) mounted on the vehicle has been interested by automobile engineers. To detect a distance to an object, first respective picture element blocks having coincidence of brightness are found in left and right images (stereo matching), then distance data are calculated according to the principle of triangulation from a parallax, namely a relative deviation amount, between both picture element blocks. Consequently, in order to calculate distance data with high reliability, it is desirable that there exists no positional deviation other than the parallax in a pair of left and right images (stereoscopic images). In actual world, however, the stereoscopic camera has some amount of positional error caused when the camera is installed on the vehicle.
With respect to this, Japanese Patent Application Laid-open No. Toku-Kai-Hei 10-307352 discloses a technology in which the positional deviation of the stereoscopic camera is corrected by applying a geometric transformation to the stereoscopic image. That is, when an initial adjustment of the positional deviation is made or when a readustment of the positional deviation generated by aged deterioration is made, a dedicated correction detecting device is connected with an image correction apparatus performing the affine transformation to calculate the difference of angle of view, a rotational deviation or a parallel deviation of the stereoscopic image obtained by imaging a specified pattern for adjustment and to establish (reestablish) parameters of the affine transfomation according to the result of the calculation. The positional deviation is equivalently corrected by applying the affine transformation to images based on thus established affine parameters.
However, according to the prior art, a special adjustment pattern is imaged by the stereoscopic camera and the deviation is corrected based on the position of the pattern in images. Accordingly, when the correction is performed, it is necessary to interrupt the ordinary surroundings monitoring control and as a result this prior art is not suitable for a real time processing in which the monitoring control is carried out concurrently.
It is an object of the present invention to provide an adjusting apparatus capable of correcting the positional deviation of stereoscopic images in real time in parallel with the surroundings monitoring control.
In order to attain the object, a positional deviation adjusting apparatus of a stereoscopic camera taking a first image or a reference image and a second image or a comparison image, comprises an image correcting means for transforming an image geometrically according to transformation parameters, a reference area establishing means for establishing a plurality of reference areas in a first image transformed by the image correcting means, a reference point establishing means for establishing a reference point in the reference area for each of the reference points, a reference line establishing means for establishing a reference line passing through the reference points, a searching area establishing means for establishing a searching area corresponding to the reference area in a second image, a correlation point identifying means for identifying a correlation point having a correlation with the reference point for each of the searching areas, an approximation line calculating means for calculating an approximation line based on the correlation points and a parameter correcting means for correcting the transformation parameters such that the approximation line coincides with the reference line.