The present invention relates to a method and an apparatus for inputting three-dimensional data that determines the shape of an object by irradiating a detection light beam toward the object so as to scan the object.
An apparatus for inputting three-dimensional data, which is a non-contact type and 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 a measurement method suitable for the three dimensional configuration measuring apparatus. By this method, a distance image (three-dimensional image) can be obtained by scanning an object optically. The method is one of active measurement methods for taking an image of an object by irradiating a specific detection light beam (reference light beam). The distance image is a set of pixels that indicate three-dimensional positions of plural parts of the object. In the slit light projection method, a slit light beam having a slit-like section of the irradiated light beam is used as the detection light beam. At a certain time point in the scanning, a part of the object is irradiated and an emission line that is curved corresponding to ups and downs of the irradiated part appears on the image sensing surface. Therefore, a group of data (three-dimensional input data) that determine the shape of the object can be obtained by periodically sampling intensity of each pixel of the image sensing surface in the scanning.
In the conventional method, the position of the object is calculated by triangulation from incident angle of the slit light beam reflected by the object and entering the image sensing surface, irradiation angle of the slit light beam, and length of the base line (distance between a starting point of the irradiation and a light receiving reference point), after determining the incident angle of the slit light beam in accordance with the position of the emission line in the image sensing surface. Namely, the position is calculated in accordance with the irradiation direction and the receiving direction of the detection light beam. The position of the object is calculated from the irradiation direction and the receiving direction in the case where the detection light beam, is a spot light beam (a light beam having a spot-like section) as shown in Japanese Unexamined Patent Application No. 10-2722.
The conventional method has so me disadvantages. Since the accuracy of the three-dimensional input data depends on the precision of the irradiation angle control of the detection light beam, the sufficient accuracy of the three-dimensional input data cannot be obtained. In order to maintain the accuracy, expensive components or much effort for adjusting the position of the irradiation system are necessary. It is difficult to secure the accuracy since the irradiation system has a movable mechanism for deflecting the detection light beam and the mechanism is easy to be affected by variation of operation environment such as temperature or humidity.
The object of the present invention is to realize three-dimensional data input without using information of the irradiation angle of a detection light beam so as to enable obtaining three-dimensional input data with high accuracy that does not depend on the precision of irradiation angle control, and to improve convenience by employing plural operation modes.
According to a preferred embodiment of the present invention, the method includes the step of irradiating a detection light beam toward an object, the step of sensing images of the object at a first position and a second position that is apart from the first position, the first calculation step of detecting reception angles of the detection light beam reflected by the object at the first and the second positions in accordance with the obtained image data, and calculating the position information of a predetermined part of the object in accordance with the detected first and second reception angles and the distance between the first position and the second position, the second calculation step of detecting the irradiation angle and the reception angle at the first position in accordance with the irradiation angle data of the detection light beam and the image data of the first position, and calculating the position information of a predetermined part of the object in accordance with the detected irradiation angle and the reception angle, and the step of obtaining the position information of a predetermined part of the object by one of the first and the second calculation steps.
According to another preferred embodiment of the present invention, the apparatus has a first mode and a second mode. In the first mode, images of an object are taken from two view points being apart from each other. The position of the object is calculated with high accuracy in accordance with the distance between the view points and the directions from each view point to the irradiated part on the object (the tilt with respect to the line connecting the view points) by triangulation. The calculated data or the data for calculation is output. In the second mode, the position of a part of the object is calculated in accordance with the irradiation angle and the reception angle in the same way as the conventional method of triangulation. In the first mode that does not use the irradiation angle information for calculating the position, it is necessary to memorize data up to the number of sampling points of the object multiplied by the number of view points, so more data should be handled than in the second mode that uses the irradiation angle information. Therefore, in the case where high accuracy is not required, the second mode using the irradiation angle information may be selected so that the load of data transmission and record can be reduced.