Finger movement detection method and apparatus

A finger movement detection apparatus comprising:

• a fingerprint sensor that detects a fingerprint in an area smaller than a fingertip to obtain a first sensor image and a second sensor image;
• a pattern matching unit that extracts a plurality of partial image areas of the second sensor image as small blocks, searches the first sensor image for a plurality of image areas having a fingerprint pattern that agrees with a fingerprint pattern in one of the small blocks in the second sensor image, and obtains a plurality of vectors indicating a movement of a finger, based on a plurality of displacements of the small blocks in the second sensor image from the image areas in the first sensor image;
• a vector evaluation unit that selects a vector having a highest matching degree from the vectors as a vector indicating the finger movement, when a fingerprint image in the first sensor image and a fingerprint image in the second sensor image are superimposed on each other based on each of the vectors;
• and
• a vector correction unit that corrects a combined vector to a vector indicating the finger movement, the combined vector being obtained by combining a mean vector between a vector that is obtained by multiplying a vector newly selected by the vector evaluation unit by a first coefficient and a vector that is previously obtained by being multiplied by the first coefficient, with a vector obtained by multiplying a previously combined vector by a second coefficient.

A pointing method, comprising:

• obtaining a vector indicating a movement of a finger, by using a finger movement detection method including
• detecting a fingerprint in an area smaller than a fingertip to obtain a first sensor image and a second sensor image;
• extracting a plurality of partial image areas of the second sensor image as small blocks, searching the first sensor image for a plurality of image area each having a fingerprint pattern that agrees with a fingerprint pattern in one of the small blocks in the second sensor image, and obtaining a plurality of vectors indicating the movement of the finger, based on a plurality of displacements of the small blocks in the second sensor image from the image areas in the first sensor image;
• selecting a vector having a highest matching degree from the vectors as a vector indicating the finger movement, when a fingerprint image in the first sensor image and a fingerprint image in the second sensor image are superimposed on each other based on each of the vectors;
• and
• correcting a combined vector to a vector indicating the finger movement, the combined vector being obtained by combining a mean vector between a vector that is obtained by multiplying a vector newly selected at the selecting by a first coefficient and a vector that is previously obtained by being multiplied by the first coefficient, with a vector obtained by multiplying a previously combined vector by a second coefficient;
• and
• controlling a movement of a pointer displayed on a screen, based on the vector.

A pointing apparatus comprising:

• a finger movement detection apparatus including
• a fingerprint sensor that detects a fingerprint in an area smaller than a fingertip to obtain a first sensor image and a second sensor image;
• a pattern matching unit that extracts a plurality of partial image areas of the second sensor image as small blocks, searches the first sensor image for a plurality of image areas having a fingerprint pattern that agrees with a fingerprint pattern in one of the small blocks in the second sensor image, and obtains a plurality of vectors indicating a movement of a finger, based on a plurality of displacements of the small blocks in the second sensor image from the image areas in the first sensor image;
• a vector evaluation unit that selects a vector having a highest matching degree from the vectors as a vector indicating the finger movement, when a fingerprint image in the first sensor image and a fingerprint image in the second sensor image are superimposed on each other based on the respective vectors;
• and
• a vector correction unit that corrects a combined vector to a vector indicating the finger movement, the combined vector being obtained by combining a mean vector between a vector that is obtained by multiplying a vector newly selected by the vector evaluation unit by a first coefficient and a vector that is previously obtained by being multiplied by the first coefficient, with a vector obtained by multiplying a previously combined vector by a second coefficient;
• and
• a control unit that controls a movement of a pointer displayed on a screen, based on the vector indicating the movement of the finger obtained by the detection apparatus.

A finger movement detection method, comprising:

• detecting a fingerprint in an area smaller than a fingertip to obtain a first sensor image and a second sensor image;
• extracting a plurality of small blocks of said second sensor image and searching said first sensor image for a plurality fingerprint patterns matching a plurality of fingerprint patterns in said small blocks;
• and
• obtaining a plurally of vectors indicating a movement of a finger, based on a plurality of displacements of the fingerprint patterns in said small blocks of said second sensor image relative to the fingerprint patterns of said first sensor image;
• selecting a vector having a highest matching degree from the vectors as a vector indicating the movement of the finger, when a fingerprint image in the first sensor image and a fingerprint image in the second sensor image are superimposed on each other based on each of the vectors;
• and
• correcting a combined vector to a vector indicating the movement of the finger, the combined vector being obtained by combining a mean vector between a vector that is obtained by multiplying a vector newly selected at the selecting by a first coefficient and a vector that is previously obtained by being multiplied by the first coefficient, with a vector obtained by multiplying a previously combined vector by a second coefficient.