Optics: measuring and testing – Position or displacement
Reexamination Certificate
2001-06-12
2004-04-20
Shafer, Ricky D. (Department: 2872)
Optics: measuring and testing
Position or displacement
C356S622000, C356S623000, C356S051000, C356S003100, C356S004070, C250S559050
Reexamination Certificate
active
06724490
ABSTRACT:
This patent application claims priority based on a Japanese patent application No. 2000-176142 filed on Jun. 12, 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 to a subject. More particularly, the present invention relates to an image capturing apparatus and a distance measuring method for obtaining the information regarding a depth 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 Laying-Open No. 61-155909 (published on Jul., 15, 1986) and Japanese Patent Application Laying-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 Laying-Open No. 62-46207 (published on Feb. 28, 1987) 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.
Japanese Patent Application Laying-Open Nos. 10-48336 and 11-94520 disclose an actual time-range finder that calculates the distance to the subject by casting different light patterns having different wavelength characteristics onto the subject and extracting wavelength components of light reflected from the subject incident light.
In the conventional distance measuring apparatus and method, the time difference occurs in the measurement because it is necessary to successively cast the light from the different emission positions so as to measure the reflected light beams, as disclosed in Japanese Patent Applications Laying-Open Nos. 61-155909 and 63-233312. 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 error 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 prepared 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 spectral reflectance of the subject 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 actual time-range finder disclosed in Japanese Patent Applications Laying-Open Nos. 10-48336 and 11-94520 also uses the light having different wavelength characteristics for calculating the distance to the subject. In a case where spectral reflectance is varied depending on a position of the illuminated portion of the subject, however, the error may be caused, thus preventing the precise calculation of the depth-direction distance.
The distance measuring apparatus disclosed in Japanese Patent Application Laying-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 at a very high speed in order to realize the intensity-modulation. Thus, a simple measurement cannot be realized. In addition, the measurement may include the time difference, thus preventing a precise measurement for the moving subject.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an image capturing apparatus and a distance measuring method that overcome 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 containing a first wavelength and having a first intensity distribution on a plane perpendicular to an optical axis of the first illumination light beam and a second illumination light beam mainly containing a second wavelength and a third wavelength and having a second intensity distribution on a plane perpendicular to an optical axis of the second illumination light beam onto the subject, the second and third wavelengths being different from the first wavelength, the second intensity distribution being different from the first intensity distribution; and a depth calculation unit operable to calculate a depth-direction distance to the subject based on outgoing light beams from the subject.
The first illumination light beam may have an intensity that monotonously increases along a first direction on the plane perpendicular to the optical axis thereof, and the second illumination light beam may have an intensity that monotonously decreases along a second direction on the plane perpendicular to the optical axis thereof, the second direction being opposite to the first direction.
The first illumination light beam may have the first intensity distribution in which, with increase of a distance from the optical axis thereof on the plane perpendicular to the optical axis, an intensity monotonously increases or decreases, and the second illumination light may have the second intensity distribution in which, with increase of a distance from the optical axis thereof on the plane perpendicular to the optical axis, an intensity monotonously decreases when the first illumination light increases or increases when the first illumination light decreases.
The illumination unit may cast the first and second illumination light beams onto the subject simultaneously.
The image capturing apparatus may further comprise: an optically converging unit operable to converge the outgoing light beams from the subject onto w
Birch & Stewart Kolasch & Birch, LLP
Fuji Photo Film Co. , Ltd.
Shafer Ricky D.
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