Optics: measuring and testing – By polarized light examination – With light attenuation
Reexamination Certificate
2000-04-05
2001-10-02
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By polarized light examination
With light attenuation
C356S370000, C356S389000, C250S332000, C250S334000
Reexamination Certificate
active
06297881
ABSTRACT:
This application is based on application No. Hei 11-100866 filed in Japan, the content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical type three-dimensional measurement method and a three-dimensional measurement device for obtaining measurement data or data based on measurement data.
2. Description of the Related Art
Three-dimensional measurement devices of the non-contact type are used for data input to computer graphics (CG) systems and CAD systems, three-dimensional measurements, and robotic visual recognition because of their high-speed measurement capability compared to devices of the contact-type.
Active methods for projecting reference light such as the slit projection method (also known as the light-sectioning method), spatial pattern encoding method, and striped pattern projection method are generally used as the measuring methods in portable three-dimensional measurement devices. Some devices also use the passive type stereo view method. For example, the slit projection method uses a slit light having a beam cross-section in the form of a linear band as a reference light, and scans in line sequence by deflecting the beam in the slit width direction. The slit length direction is the main scan direction, and the width direction is the subscan direction. Part of an object is illuminated at a point in time during scanning, and a bright line curved in accordance with the shape of the illuminated part appears on the photoreceptive surface of the image sensing system. Accordingly, a group od three-dimensional data which identify the object shape or the distances to various positions on the object is obtained by periodically sampling the brightness of each pixel of the photoreceptive surface during the scan.
In three-dimensional measurement via an active triangulation method, only the shape within a range of an object illuminated by a reference light and projected on the photoreceptive surface can be measured. Shadow areas on the photoreceptive surface cannot be measured even when illuminated by reference light. That is, a so-called occlusion is disadvantageously generated. To suppress the generation of occlusion, the baseline length of triangulation (i.e., the length of the line connecting the starting point of the projection light and the point of the received light) may be reduced to bring the principal point of the received light near the starting point of the projection light. However, this reduces resolution in the measurement depth direction, i.e., the distance direction. Even in the case of stereo view methods, resolution is reduced if the distance between the image sensing positions of two locations, i.e., the baseline length, is shortened.
When the frontal shape of an object is long and narrow, and the depth dimension is small, the majority of the photoreceptive surface is a region which does not receive the projection of the object image, thereby greatly reducing the efficiency of the photoreceptive surface. It is desirable that the projected object image is larger than the photoreceptive surface from the perspectives of measurement accuracy and reduction of unnecessary data.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a three-dimensional measurement method and device capable of ensuring a specific resolution while reducing occlusion or not increasing occlusion.
These objects are attained by the measurement method of the present invention which is a three-dimensional measurement method for measuring position of an object, comprising following steps of: forming an image of the object on a sensor by an anamorphic lens to have a magnification of the image in a direction along the baseline of triangulation greater than a magnification of the image in another direction; different from the direction along the baseline of triangulation and measuring position of the object by triangulating in accordance with data obtained by the sensor.
The three-dimensional measurement device of the present invention comprises a projector for projecting reference light from a starting point to an object; a sensor for receiving the reference light reflected by the object at a position separated from the starting point in a baseline direction; and an anamorphic lens system for forming an image on a photoreceptive surface of the sensor, wherein the image having greater magnification in the baseline direction than in another direction; and data output device for outputting data identifying a position of the object in accordance with data related to the object obtained from the sensor output.
REFERENCES:
patent: 5416591 (1995-05-01), Yoshimura et al.
Norita Toshio
Yahashi Akira
Font Frank G.
Minolta Co. , Ltd.
Punnoose Roy M.
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