Optics: measuring and testing – Position or displacement
Reexamination Certificate
2001-02-16
2003-03-25
Epps, Georgia (Department: 2873)
Optics: measuring and testing
Position or displacement
C356S622000, C356S623000, C356S624000, C356S602000, C356S003100
Reexamination Certificate
active
06538751
ABSTRACT:
This patent application claims priority based on a Japanese patent applications Nos. 2000-37771 filed on Feb. 16, 2000, 2000-247034 filed on Aug. 16, 2000 and 2000-275176 filed on Sep. 11, 2000, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image capturing apparatus and a distance measuring method for obtaining information regarding a depth-direction distance of a subject. More particularly, the present invention relates to an image capturing apparatus and a distance measuring method for obtaining the information regarding the depth-direction distance of the subject by capturing outgoing light beams from the subject that is illuminated with light.
2. Description of the Related Art
As a method for obtaining information regarding a distance to an object or information regarding a position of the object, a three-dimensional image measuring method is known in which light having a pattern of, for example, a slit or a stripe, is cast onto the object and the pattern cast onto the object is captured and analyzed. There are a slit-light projection method (light cutting method) and a coded-pattern light projection method as typical measuring methods, which are described in detail in “Three-dimensional image measurement” by Seiji Inokuchi and Kosuke Sato (Shokodo Co., Ltd.).
Japanese Patent Application Laid-open No. 61-155909 (published on Jul. 15, 1886) and Japanese Patent Application Laid-open No. 63-233312 (published on Sep. 29, 1988) disclose a distance measuring apparatus and a distance measuring method in which light beams are cast onto a subject from different light-source positions and the distance to the subject is measured based on the intensity ratio of the reflected light beams from the subject.
Japanese Patent Application Laid-open No. 62-46207 (published on Feb. 28, 1887) discloses a distance detecting apparatus that casts two light beams having different phases onto the subject and measures the distance to the subject based on the phase difference between the light beams reflected from the subject.
Moreover, “Development of Axi-Vision Camera”, Kawakita et al., 3D Image conference '99, 1999, discloses a method for measuring the distance to the subject in which the subject that is illuminated with light having the intensity modulated at a very high speed is captured by a camera having a high-speed shutter function, and the distance to the subject is measured from the degree of the intensity modulation that varies depending on the distance to the subject.
The conventional measuring method using light projection measures the distance to a region of the subject onto which the projection pattern is projected based on the principle of trigonometrical measurement. Thus, in order to obtain a high resolution in the distance measurement, it is necessary to arrange a projection optical system at a position sufficiently distant from a capturing optical system in principle, thus increasing the size of the measuring apparatus inevitably. Moreover, since an optical axis of the projection optical system is apart from that of the capturing optical system, there is a shadow region in which the projected pattern cannot be viewed because of the shadow of the subject when the region is viewed from the capturing optical system, thereby generating a “blind region” from which distance information cannot be obtained.
In the distance measuring apparatus and the distance measuring method disclosed in Japanese Patent Applications Laid-open Nos. 61-155909 and 63-233312, the time difference occurs in the measurement because it is necessary to successively cast the light from the different emission positions to measure the reflected light beams. Thus, in a case of the moving subject, the distance cannot be measured. In addition, during a time period in which the position of the light source is changed to change the emission position, the measurement difference may occur because of waver of the capturing apparatus.
Moreover, in a case of using light beams having different wavelength characteristics, the light beams can be emitted simultaneously and the reflected light beams can be separated by a filter selected in accordance with the wavelength characteristics of the light beams so that the intensities of the reflected light beams can be measured. However, if the reflectivity of the object varies depending on the wavelength, the intensities of the reflected light beams are also different depending on the wavelength thereof. The difference of the reflected-light intensities between the wavelengths may cause an error when the depth-direction distance is calculated from the ratio of the intensities of the reflected light beams, thereby preventing the precise calculation of the depth-direction distance.
The distance measuring apparatus disclosed in Japanese Patent Application Laid-open No. 62-46207 requires a high-precision phase detector for detecting the phase difference. This makes the apparatus expensive and loses the simplicity of the apparatus. In addition, since this apparatus measures the phase of the reflected light beam from a point of the subject, it cannot measure the depth distribution of the whole subject.
Moreover, in the distance measuring method using the intensity modulation disclosed in “Development Axi-Vision Camera” by Kawakita et al. (3D Image Conference '99, 1999), it is necessary to perform the light modulation and the optical shutter operation at very high speed. This causes the measuring apparatus to become large and expensive and prevents the simple measurement.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a image capturing apparatus and distance measuring method which overcomes the above issues in the related art. This object is achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to the first aspect of the present invention, an image capturing apparatus for obtaining information regarding a depth of a subject, comprises: an illumination unit operable to cast a first illumination light beam mainly having a first wavelength and a second illumination light beam mainly having a second wavelength and a third wavelength from optically different emission positions onto the subject, the second and third wavelengths being different from the first wavelength; and a depth calculator operable to calculate a depth-direction distance to the subject based on outgoing light beams from the subject.
The illumination unit may cast the first and second illumination light beams onto the subject simultaneously. Moreover, the image capturing apparatus may further comprises: an optically converging unit operable to converge the outgoing light beams from the subject onto which the first and second illumination light beams are cast; a separation unit operable to optically separate the outgoing light beams from the subject into a first outgoing light beam having the first wavelength, a second outgoing light beam having the second wavelength and a third outgoing light beam having the third wavelength; a light-receiving unit operable to receive the first, second and third outgoing light beams that are separated by the separation unit and are converged by the optically converging unit; and a light intensity detector operable to detect intensities of the first, second and third outgoing light beams received by the light-receiving unit, wherein the depth calculator calculates the depth-direction distance to the subject by using the intensities of the first, second and third outgoing light beams.
The light-receiving unit may include three panels of solid state image sensors, while the separation unit separates the first, second and third outgoing light beams by using an optical path splitter so as to allow the first, second and third outgoing light beams to be received by the three panels of solid state image sensors, respectively. Alterna
Birch & Stewart Kolasch & Birch, LLP
Epps Georgia
Fuji Photo Film Co. , Ltd.
Hasan M.
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