Information processing apparatus that performs three-dimensional shape measurement, information processing method, and storage medium

1. An information processing apparatus comprising:

an input unit configured to input image data of a target object, onto which a pattern has been projected by a projection apparatus and which has then been photographed by an imaging apparatus, wherein the pattern varies in luminance only in a predetermined direction;

an association unit configured to associate a two-dimensional coordinate (x′ c , y′ c ) on the image data of the target object with a one-dimensional coordinate (y p ) in the predetermined direction on image data of the pattern based on the input image data;

a first correction unit configured to obtain a first corrected two-dimensional coordinate (x c , y c ) on the image data of the target object by correcting the two-dimensional coordinate (x′ c , y′ c ) on the image data of the target object based on a first distortion model which expresses an influence of distortion, by a lens of the imaging apparatus, to a reflected light reflected by the target object when the reflected light passes through the lens of the imaging apparatus;

a first viewing vector-deriving unit configured to derive a first viewing vector which is through the first corrected two-dimensional coordinate (x c , y c ) on the image data of the target object and an optical center of the imaging apparatus;

a second correction unit configured to obtain a second corrected two-dimensional coordinate (x′ p , y′ p ) on the image data of the pattern based on an equation derived from (i) the one-dimensional coordinate (y p ) in the predetermined direction on the image data of the pattern and (ii) a second distortion model which expresses an influence of distortion, by a lens of the projection apparatus, to an emitted light emitted from a light source of the projection apparatus, when the emitted light passes through the lens of the projection apparatus, and the first viewing vector, wherein the second corrected two-dimensional coordinate (x′ p , y′ p ) is obtained directly from the equation without processing of projecting a three-dimensional coordinate onto the image data of the pattern;

a second viewing vector-deriving unit configured to derive a second viewing vector which is through the second corrected two-dimensional coordinate (x′ p , y′ p ) on the image data of the pattern and an optical center of the projection apparatus; and

an intersection coordinate-deriving unit configured to derive coordinates of a point, in a three-dimensional space, of intersection between the first viewing vector and the second viewing vector.

2. The information processing apparatus according to claim 1 , wherein the pattern is a striped pattern image.

3. The information processing apparatus according to claim 2 , wherein a direction of stripes of the striped pattern image is a horizontal direction or a vertical direction on the image data of the striped pattern image.

4. The information processing apparatus according to claim 1 , wherein the pattern is a line pattern image.

5. The information processing apparatus according to claim 4 , wherein a direction of lines of the line pattern image is a horizontal direction or a vertical direction on the image data of the line pattern image.

6. The information processing apparatus according to claim 1 , wherein the image data of the pattern comprises multiple patterns for a space coding method or a phase shift method.

7. An information processing method executed by an information processing apparatus, the method comprising:

inputting image data of a target object, onto which a pattern has been projected by a projection apparatus and which has then been photographed by an imaging apparatus, wherein the pattern varies in luminance only in a predetermined direction;

associating a two-dimensional coordinate (x′ c , y′ c ) on the image data of the target object with a one-dimensional coordinate (y p ) in the predetermined direction on image data of the pattern based on the input image;

obtaining a first corrected two-dimensional coordinate (x c , y c ) on the image data of the target object by correcting the two-dimensional coordinate (x′ c , y′ c ) on the image data of the target object based on a first distortion model which expresses an influence of distortion, by a lens of the imaging apparatus, to a reflected light reflected by the target object when the reflected light passes through the lens of the imaging apparatus;

deriving a first viewing vector which is through the first corrected two-dimensional coordinate (x c , y c ) on the image data of the target object and an optical center of the imaging apparatus;

obtaining a second corrected two-dimensional coordinate (x′ p , y′ p ) on the image data of the pattern based on an equation derived from (i) the one-dimensional coordinate (y p ) in the predetermined direction on the image data of the pattern and (ii) a second distortion model which expresses an influence of distortion, by the lens, to an emitted light emitted from a light source of the projection apparatus, when the emitted light passes through the lens of the projection apparatus, and the first viewing vector, wherein the second corrected two-dimensional coordinate (x′ p , y′ p ) is obtained directly from the equation without processing of projecting a three-dimensional coordinate onto the image data of the pattern;

deriving a second viewing vector which is through the second corrected two-dimensional coordinate (x′ p , y′ p ) on the image data of the pattern and an optical center of the projection apparatus; and

deriving coordinates of a point, in a three-dimensional space, of intersection between the first viewing vector and the second viewing vector.

8. A non-transitory storage medium storing a program for causing a computer to function as each unit of an information processing apparatus, the program executable by the information processing apparatus to execute a method comprising:

inputting image data of a target object, onto which a pattern has been projected by a projection apparatus and which has then been photographed by an imaging apparatus, wherein the pattern varies in luminance only in a predetermined direction;

associating a two-dimensional coordinate (x′ c , y′ c ) on the image data of the target object with a one-dimensional coordinate (y p ) in the predetermined direction on image data of the pattern based on the input image;

obtaining a first corrected two-dimensional coordinate (x c , y c ) on the image data of the target object by correcting the two-dimensional coordinate (x′ c , y′ c ) on the image data of the target object based on a first distortion model which expresses an influence of distortion, by a lens of the imaging apparatus, to a reflected light reflected by the target object when the reflected light passes through the lens of the imaging apparatus;

deriving a first viewing vector which is through the first corrected two-dimensional coordinate (x c , y c ) on the image data of the target object and an optical center of the imaging apparatus;

obtaining a second corrected two-dimensional coordinate (x′ p , y′ p ) on the image data of the pattern based on an equation derived from (i) the one-dimensional coordinate (y p ) in the predetermined direction on the image data of the pattern and (ii) a second distortion model which expresses an influence of distortion, by the lens, to an emitted light emitted from a light source of the projection apparatus, when the emitted light passes through the lens of the projection apparatus, and the first viewing vector, wherein the second corrected two-dimensional coordinate (x′ p , y′ 2 ) is obtained directly from the equation without processing of projecting a three-dimensional coordinate onto the image data of the pattern;

deriving a second viewing vector which is through the second corrected two-dimensional coordinate (x′ p , y′ p ) on the image data of the pattern and an optical center of the projection apparatus; and

deriving coordinates of a point, in a three-dimensional space, of intersection between the first viewing vector and the second viewing vector.

9. The apparatus according to claim 1 ,

wherein the second distortion model is expressed by an equation (1) set forth below:

y p =y′ p {1 +k p1 ( x′ p 2 +y′ p 2 )+ k p2 ( x′ p 2 +y′ p 2 ) 2 }+p p1 ( x′ p 2 +3 y′ p 2 )+2 p p2 x′ p y′ p   (1)

wherein an epipolar constraint between the imaging apparatus and the projection apparatus is expressed by an equation (2) set forth below:

[

x

c

y

c

1

]

⁢

E

⁡

[

x

p

′

y

p

′

1

]

=

0

,

(

2

)

and

wherein the second correction unit solves the equation (1) and the equation (2) as simultaneous equations to thereby obtain the second corrected two-dimensional coordinate on the image data of the pattern.