1. Field of the Invention
The present invention relates to a method and an apparatus for inputting three-dimensional data of an object.
2. Description of the Prior Art
An optical three-dimensional data input apparatus (a three-dimensional camera), which enables rapid measurement compared with a contact type, is used for data input into a CG system or a CAD system, physical measurement, visual sense of a robot or other applications. A slit light projection method (also referred to as a light cutting method) is known as the measurement method suitable for this three-dimensional data input apparatus.
FIG. 13 shows an input principle of a three-dimensional camera 80 utilizing the slit light projection method.
In FIG. 13, a three-dimensional camera 80 includes a light projection portion 81 and a light reception portion 82. The light projection portion 81 irradiates a slit light beam S having a linear section. The light reception portion 82 has an image sensing surface 83 and an imaging lens (not shown). The light projection portion 81 and the light reception portion 82 are separated from each other by a predetermined distance and are integrally installed in one housing.
The object Q1 is irradiated by the slit light beam S from the light projection portion 81, and the reflected light is captured on the image sensing surface 83 as a slit image. A space coordinate of the point p on the object Q1 corresponding to a point p′ of this slit image is determined as the coordinates of the intersection point of the plane formed by the slit light beam S and the line L connecting the point p′ and the center point 0 of the imaging lens. Therefore, the space coordinates of points on the surface of the object Q1 corresponding to the slit image are derived from one slit image obtained by the slit light beam S. The slit light beam S is moved horizontally so as to scan the object Q1 and the slit image at each scanning position is input. Thus, the three-dimensional data (three-dimensional shape data) of the front portion of the object Q1 are inputted, which is irradiated by the slit light beam S.
In order to obtain the three-dimensional data of the all-around surface of the object Q1, it is necessary to input from plural directions of the object Q1. Two methods are known for the purpose. In the first method, the three-dimensional camera 80 is moved on a predetermined track around the object Q1 while the shooting direction of the camera is directed to the object Q1 so as to take images of the object Q1 from plural directions. In the second method, a rotation stage is used on which the object Q1 is placed. The three-dimensional camera 80 is placed at a predetermined position for taking images of the object Q1 from plural directions.
The plural sets of three-dimensional data of the object Q1 taken from plural directions are processed for registration using a conversion parameter derived from a position on the track along which the three-dimensional camera 80 moves or the position of the rotation stage. Thus, the three-dimensional data of the all-around surface of the object Q1 are obtained.
However, the above-mentioned method causes a high cost since the position of the three-dimensional camera 80 or the angular position of the rotation stage should be detected in high accuracy for improving the registration accuracy.
In addition, since the three-dimensional camera 80 should be placed on a moving device, it is impossible to take images with holding the three-dimensional camera 80 in hand. Accordingly, the object that can be inputted is limited. Namely, the object such as a stone or bronze statue that cannot be moved cannot be inputted as the three-dimensional data by this method.
An apparatus that can solve this problem is disclosed in U.S. Pat. No. 5,990,895. This apparatus can take images of the object Q1 from any direction for inputting three-dimensional data. After inputting, three-dimensional shapes inputted from plural directions as well as a color image inputted simultaneously from the same view and corresponding to the three-dimensional data are displayed. A user designates corresponding points in the three-dimensional shape manually viewing the displayed color image, in accordance with a variation of color or other factors. The registration among the inputted three-dimensional data is performed on the basis of the corresponding points designated by the user.
However, according to the above-mentioned conventional apparatus, the user has to designate corresponding points for the registration among plural sets of three-dimensional data. This process is extremely troublesome.
Furthermore, there is no method for confirming whether proper images have been taken or not for all-around surface of the object Q1 when three-dimensional data input is performed. Accordingly, if the plural three-dimensional data are not continuous having proper overlaps, or if there is some lack of data, it is difficult to make proper corresponding points between three-dimensional data. In that case, accuracy of the registration between the three-dimensional data may be deteriorated. In the worst case, it is necessary to take images again.