Method and apparatus for sensing moving ball

Abstract

Provided are an apparatus and method for sensing a moving ball, which extract a feature portion such as a trademark, a logo, etc. indicated on a ball from consecutive images of a moving ball, acquired by an image acquisition unit embodied by a predetermined camera device, and calculate a spin axis and spin amount of rotation the moving ball based on the feature portion and thus spin of the ball is simply, rapidly, and accurately calculated with low computational load, thereby achieving rapid and stable calculation of the ball in a relatively low performance system. The sensing apparatus includes an image acquisition unit for acquiring consecutive images, an image processing unit for extracting a feature portion from the acquired image, and a spin calculation unit for calculating spin using the extracted feature portion.

1 . An apparatus for sensing a moving ball, for acquiring and analyzing an image of the moving ball to calculate spin of the moving ball, the apparatus comprising:
 an image acquisition unit for acquiring consecutive images according to movement of a ball with a surface having a predetermined feature portion indicated thereon;   an image processing unit for extracting only a feature portion of a ball portion from each of images consecutively acquired by the image acquisition unit; and   a spin calculation unit for comparing and analyzing position information of each pixel of a feature portion obtained by applying a trial spin axis and a trial spin amount to position information of pixels constituting a feature portion of a ball portion on a first image as a preceding image among two consecutively acquired images of a moving ball, and position information of each pixel constituting a feature portion of a ball portion of a second image as a subsequent image among the two consecutively acquired images, to calculate a spin axis and spin amount according to ball movement to the second image from the first image.   
     
     
         2 . The apparatus according to  claim 1 , wherein the image acquisition unit is embodied as a three-dimensional camera or a stereo camera configured by a plurality of cameras installed at different positions with respect to the same ball. 
     
     
         3 . The apparatus according to  claim 1 , wherein the image processing unit comprises:
 a ball image extraction part for finding a ball portion on an image acquired by the image acquisition unit and extracting the ball portion as an image having a predetermined size; and   a ball feature extraction part for extracting the feature portion from the ball image to prepare a ball feature portion image.   
     
     
         4 . The apparatus according to  claim 3 , wherein:
 the ball image extraction part extracts a first ball image and a second ball image for the first image and the second image, respectively; and   the spin calculation unit calculates a spin axis and spin amount for converting the first feature portion image to the first feature portion image while the ball feature extraction part extracts a first feature portion image and a second feature portion for the first ball image and the second ball image, respectively.   
     
     
         5 . The apparatus according to  claim 2 , wherein the spin calculation unit comprises:
 a spin applying part for converting position information of each pixel constituting a feature portion of a ball portion on the first image into three-dimensional position information and applying a trial spin axis and a trial spin amount to the three-dimensional position information, and re-converting the three-dimensional position information into two-dimensional position information to calculate a trial spin feature portion information; and   a spin determination part for comparing the trial spin feature portion and a feature portion of a ball portion on the second image with each other to calculate similarity and determining corresponding spin axis and spin amount information as final spin axis and spin amount information when the similarity is equal to or greater than a preset value.   
     
     
         6 . The apparatus according to  claim 2 , wherein the spin calculation unit comprises:
 a spin applying part for converting position information of each pixel constituting a feature portion of a ball portion on the first image into three-dimensional position information and applying a trial spin axis and spin amount to the three-dimensional position information, and re-converting the three-dimensional position information into two-dimensional position information to calculate a trial spin feature portion information; and   a spin determination part for comparing information of the trial spin feature portion and position of each pixel constituting a feature portion of a ball portion on the second image to calculate the number of corresponding pixels and determining corresponding spin axis and spin amount information as final spin axis and spin amount information when the number of the corresponding pixels is equal to or greater than a preset value.   
     
     
         7 . The apparatus according to  claim 5 , wherein the spin calculation unit further comprises a position correction part for calculating position correction information for correcting a position and direction of a camera as if respective balls on consecutively acquired images are viewed at the same position and direction with respect to the camera and applies the position correction information to position information of each pixel constituting a feature portion on each feature portion image. 
     
     
         8 . The apparatus according to  claim 5 , wherein the spin applying part selects and applies a trial spin axis and a trial spin amount in consideration of characteristics of ball movement and a frame rate of the camera according to a preset limitation condition. 
     
     
         9 . (canceled) 
     
     
         10 . A method of sensing a moving ball, for acquiring and analyzing an image of the moving ball to calculate spin of the moving ball, the method comprising:
 acquiring consecutive images according to movement of a ball with a surface having a predetermined feature portion indicated thereon;   extracting the feature portion indicated on one side of a ball portion of each of the consecutively acquired images;   calculating position information of each pixel of a feature portion obtained by applying a trial spin axis and a trial spin amount to position information of pixels constituting a feature portion of a ball portion on a first image as a preceding image among two consecutively acquired images of a moving ball; and   comparing and analyzing position information of each pixel constituting a feature portion of a ball portion of a second image as a subsequent image among the two consecutively acquired images with the position information of each of the pixels of the feature portion obtained by applying the trial spin axis and spin amount, to calculate a spin axis and spin amount according to ball movement to the second image from the first image.   
     
     
         11 . The method according to  claim 10 , wherein the extracting of the feature portion comprises:
 converting position information of pixels constituting of each feature portion into three-dimensional position information, with regard to the extracted feature portion; and   calculating position correction information for correcting a position and direction of a camera as if respective balls on consecutively acquired images are viewed at the same position and direction with respect to the camera,   wherein the position correction information is applied to the converted three-dimensional position information to apply the trial spin information and to calculate spin information.   
     
     
         12 . The method according to  claim 10 , wherein the calculating of the position information of each pixel of a feature portion obtained by applying a trial spin axis and a trial spin amount comprises:
 converting position information of each pixel constituting the feature portion on the first image into three-dimensional position information;   extracting trial spin axis and spin amount information and applying the trial spin axis and spin amount information to the converted three-dimensional position information;   converting the three-dimensional position information to which the trial spin axis and spin amount are supplied into two-dimensional position information to calculate trial spin feature portion information.   
     
     
         13 . The method according to  claim 10 , wherein the calculating of the spin axis and spin amount according to ball movement to the second image from the first image comprises:
 comparing the position information of each of the pixels of the feature portion obtained by applying a trial spin axis and a trial spin amount and the position information of each of the pixels constituting the feature portion of the ball portion on the second image to calculate the number of corresponding similarity or pixels; and   determining corresponding spin axis and spin amount information as final spin axis and spin amount information when the similarity is equal to or greater than a preset value or the number of the corresponding pixels is equal to or greater than a preset value.   
     
     
         14 . The method according to  claim 12 , wherein the trial spin axis information applied to the converted three-dimensional position information comprises spin axis information arbitrarily selected from a range according to two components among a roll direction, a pitch direction, and a yaw direction with respect to rotation of an object. 
     
     
         15 . The method according to  claim 12 , wherein the trial spin axis information applied to the converted three-dimensional position information comprises spin amount information arbitrarily selected from a preset range according to maximum spin limitation for rotation by user hit and a frame rate of a camera for capturing an image. 
     
     
         16 . A method of sensing a moving ball, for acquiring and analyzing an image of the moving ball to calculate spin of the moving ball, the method comprising:
 acquiring consecutive images according to movement of a ball with a surface having a predetermined feature portion indicated thereon;   extracting a feature portion from a ball portion from each of the consecutively acquired images to prepare a feature portion image; and   searching for a spin axis and spin amount in three-dimensional space, for allowing a feature portion image of a first acquired image of two consecutively acquired images into a feature portion image of a second acquired image.   
     
     
         17 . The method according to  claim 16 , wherein the searching for of the spin axis and the spin amount comprises calculating position correction information for correcting a position and direction of a camera as if respective balls on consecutively acquired images are viewed at the same position and direction with respect to the camera and applying the position correction information to position information of each pixel constituting a feature portion on each feature portion image. 
     
     
         18 . The method according to  claim 16 , wherein the searching for of the spin axis and the spin amount comprises:
 applying trial spin information of a trial spin axis and a trial spin amount to position information of each pixel constituting a feature portion on a feature portion image of a first acquired image of two consecutive images;   comparing position information of the pixels to which the trial spin information is applied with position information of each pixel constituting a feature portion on a feature portion image of a second acquired image of the two consecutive images; and   determining the spin axis and spin amount of the trial spin information as final spin axis and spin amount information when the position information of the pixels to which the trial spin information is applied is similar to the position information of each pixel constituting a pixel portion on the second feature portion image to a preset level.   
     
     
         19 . The method according to  claim 18 , wherein the searching for of the spin axis and the spin amount comprises collecting based on a predetermined function a plurality of spin informations calculated by performing the step of applying trial spin information, the step of comparing position information, and the step of determining the spin axis and spin amount of the trial spin information as final spin axis and spin amount for each of a plurality of pairs, each pair of images comprising a preceding one and a later one of two consecutive images to calculate the spin information of the moving ball.