Apparatus, method and program for distance measurement

A distance measurement apparatus in which a depth distance down to a target point is measured as a phase is entered to said apparatus as an input, said phase being a quantity representing a change of a pattern projected on a target point whose depth distance is to be measured;

• said pattern being varied depending on directions of projection from pattern projection unit;
• said phase being measured by observing a reflection of said pattern;
• said apparatus comprising:
• an image projection point search unit that receives a reference phase image which is a phase measured of a linear part of an object, phases and depth distances of three reference points lying on said line of sight on which said target point has been measured, and a phase of said target point;
• said image projection point search unit searching for positions of image projection points on said reference phase image which are points having phase values coincident with phase of said reference points and said target point;
• said image projection point search unit calculating distances among said image projection points and outputting the calculated distances as image distances;
• an image distance cross ratio calculating unit that receives said image distances, calculating a cross ratio of distances among said image projection points as an image distance cross ratio, and outputting said image distance cross ratio calculated;
• and
• a depth distance calculating unit that receives depth distances of said reference points and said image distance cross ratio and for calculating a depth distance of said target point by exploiting the equality of said image distance cross ratio and a depth distance cross ratio of the depth distances among said reference points and said target point.

A distance measurement apparatus, in which a depth distance down to a target point is measured as a phase is entered to said apparatus as input, said phase being a quantity representing a change of a pattern projected on a target point whose depth distance is to be measured;

• said pattern being varied depending on directions of projection from pattern projection unit;
• said phase being measured by observing a reflection of said pattern;
• said apparatus comprising:
• an image projection point search unit for taking a phase image measured for a linear area that stands for a three-dimensional shape of a target object for measurement, as a reference phase image, and searching for image projection points on said reference phase image;
• said image projection points being points having phases coincident with a phase of said target point and with phases of three reference points lying on the line of sight on which said target point has been measured;
• said image projection point search unit calculating distances among said image projection points and outputting the calculated distances as image distances;
• an image distance cross ratio calculating unit that receives said image distances, calculating a cross ratio of distances among said image projection points as an image distance cross ratio, and outputting the image distance cross ratio calculated;
• and
• a depth distance calculating unit that receives the depth distances of said reference points and the image distance cross ratio and for calculating a depth distance of said target point by exploiting the equality of said image distance cross ratio and a depth distance cross ratio of the depth distances among said reference points and said target point.

A distance measurement method, in which a depth distance down to a target point is measured based on a phase which is a quantity representing a change of a pattern projected on a target point whose depth distance is to be measured;

• said pattern being varied depending on directions of projection from pattern projection unit;
• said phase being measured by observing a reflection of said pattern;
• said method comprising:
• calculating a phase cross ratio based on a phase of said target point and phases of three reference points lying on a line of light on which the said target point has been measured, and for outputting the phase cross ratio calculated;
• and
• calculating a depth distance of said target point, based on depth distances of said reference points and said phase cross ratio, by exploiting the equality of said phase cross ratio and a depth distance cross ratio of depth distances among said reference points and said target point, termed as “depth distance calculating step” hereafter.

A distance measurement method in which a depth distance down to a target point is measured based on a phase which is a quantity representing a change of a pattern projected on a target point whose depth distance is to be measured;

• said pattern being varied depending on directions of projection from pattern projection unit;
• said phase being measured by observing a reflection of said pattern;
• said method comprising:
• searching for image projection points which are points of coincidence of phase values of said target point and phases of said reference points on said reference phase image, based on a reference phase image, phases and depth distances of three reference points on a line of sight on which said target point has been measured, and on the phase of said target point;
• said reference phase image being phases measured of a straight line on a surface of said object;
• said image projection point search step calculating distances among said image projection points and taking the distances calculated as image distances;
• calculating a cross ratio of distances among said image projection points as an image distance cross ratio, based on said image distances, termed as “image distance cross ratio calculating step” hereafter;
• and
• calculating a depth distance of said target point, based on the depth distances of said reference points and said image distance cross ratio, by exploiting the equality of said image distance cross ratio and a depth distance cross ratio of the depth distances among said reference points and said target point, termed as “depth distance calculating step” hereafter.