Abstract:
A system and pupil position acquisition method and a device containing computer software for executing the same are provided. The system includes a shooting module, a scanning module, a signal transformation module, and a signal analysis module. The shooting module shoots an eyeball image using an image shooting device, such as a charge-coupled device (CCD) camera. The scanning module scans the eyeball image to acquire an eyeball signal. The signal transformation module performs a wavelet transform on the eyeball signal. The signal analysis module analyzes the eyeball signal after the wavelet transform to acquire a signal interval, and analyzes and acquires a position of a pupil with respect to the eyeball image according to the signal interval.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Taiwan Patent Application No. 097148389, filed on Dec. 12, 2008, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pupil position acquisition system and method and a device containing computer software for executing the same, and more particularly to a pupil position acquisition system and method and a device containing computer software for executing the same which use the wavelet transform to analyze an eyeball image signal so as to acquire a pupil position. 
     2. Related Art 
     The pupil tracking method is a technique used widely in the field of medicine, which is mainly applicable to the patients with severe disabilities, an extreme disability such as amyotrophic lateral sclerosis (ALS) or severe cerebral palsy deprive them of the use of their limbs and facial muscles. If eye motion is unaffected, the patient could rely on a pupil tracking method to attain or regain some degrees of independent living and control in conjunction with equipments having a human-machine interface. 
     However, in the conventional pupil tracking technique, for example, a cornea and pupil reflection, a camera receives the light reflected from the eye to form an eye image as different parts of the eye have different reflectivities to the light, and then the movement and the position of the eye are determined through image processing. In the cornea and pupil reflection, binary images are processed, and the Hough transform technique or circular sample is applied to look for or contrast a boundary of the pupil circumference based on the image processing technique, and thus it is time consuming when acquiring the threshold value of the pupil and the noise interference is easily generated, resulting in undesirable accuracy of the acquired pupil position. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a pupil position acquisition system and method and a device containing computer software for executing the same, which use a wavelet transform to analyze an eyeball image signal to acquire a pupil position. 
     Accordingly, the present invention provides a pupil position acquisition system, which includes a shooting module, a scanning module, a signal transformation module, and a signal analysis module. The shooting module shoots an eyeball image using an image shooting device, such as a charge-coupled device (CCD) camera. The scanning module scans the eyeball image to acquire an eyeball signal. The signal transformation module performs a wavelet transform on the eyeball signal. The signal analysis module analyzes the eyeball signal after the wavelet transform to acquire a signal interval, and analyzes and acquires a position of a pupil with respect to the eyeball image according to the signal interval. 
     The present invention further provides a pupil position acquisition method, which acquires an eyeball image using an image shooting device, such as a CCD camera, and performs a scanning procedure on the eyeball image to acquire an eyeball signal. Then a wavelet transform is performed on the eyeball signal, and the eyeball signal after the wavelet transform is analyzed to acquire a signal interval. A position of a pupil with respect to the eyeball image is analyzed and acquired according to the signal interval. 
     The present invention also provides a device containing computer software. A pupil position acquisition method is performed through the software. The pupil position acquisition method includes the following steps. An eyeball image is acquired, and a scanning procedure is performed on the eyeball image to acquire an eyeball signal. Then a wavelet transform is performed on the eyeball signal, and the eyeball signal after the wavelet transform is analyzed to acquire a signal interval. A position of a pupil with respect to the eyeball image is analyzed and acquired according to the signal interval. 
     The efficacy obtained by applying the present invention lies in that a position of a pupil with respect to an eyeball image can be easily analyzed and acquired through a wavelet transform. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus is not limitative of the present invention, and wherein: 
         FIG. 1  is an architectural view of a system of the present invention; 
         FIG. 2  is a schematic view of a working flow of the present invention; 
         FIG. 3  is a schematic view of acquiring an eyeball image according to the present invention; 
         FIG. 4A  is a schematic view of acquiring a high frequency signal after a wavelet transform performed on a digital eyeball signal at the longitudinal axis according to the present invention; 
         FIG. 4B  is a schematic view of acquiring a high frequency signal after a wavelet transform performed on a digital eyeball signal at the horizontal axis according to the present invention; 
         FIG. 4C  is a schematic view of matching the high frequency signal at the longitudinal axis in  FIG. 4A  with the high frequency signal at the horizontal axis in  FIG. 4B  to acquire a pupil position according to the present invention; 
         FIG. 5A  is a schematic view of acquiring a low frequency signal after an wavelet transform performed on a digital eyeball signal at the longitudinal axis according to the present invention; 
         FIG. 5B  is a schematic view of acquiring a low frequency signal after an wavelet transform performed on a digital eyeball signal at the horizontal axis according to the present invention; and 
         FIG. 5C  is a schematic view of matching the low frequency signal at the longitudinal axis in  FIG. 5A  with the low frequency signal at the horizontal axis in  FIG. 5B  to acquire a pupil position according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In order to make above purposes, features, and characteristics more apparent, the embodiments related to the present invention are illustrated as follows in detail in conjunction with the drawings. 
       FIG. 1  is an architectural view of a system of the present invention. Referring to  FIG. 1 , the pupil position acquisition system described in the present invention includes a shooting module  10  and a servo device  20 . The servo device  20  includes a scanning module  210 , a signal transformation module  220 , and a signal analysis module  230 . 
     The shooting module  10  shoots an eyeball image  101  of a subject utilizing an image shooting device. The scanning module  210  is used to scan the eyeball image  101  to acquire a digital eyeball signal  2100 . The signal transformation module  220  performs a wavelet transform on the digital eyeball signal  2100 . The signal analysis module  230  analyzes the digital eyeball signal  2100  after the wavelet transform to acquire a signal interval, and analyzes and acquires a position of a pupil with respect to the eyeball image  101  according to the signal interval. 
     Referring to  FIGS. 2 and 3 ,  FIG. 2  is a schematic view of a working flow of the present invention, and  FIG. 3  is a schematic view of acquiring an eyeball image according to the present invention. 
     When it is intended to acquire a position of a pupil  100  of a subject, the shooting module  10 , such as a CCD camera, can be used to shoot an eyeball image  101  of a pupil of the subject (Step S 100 ). An image capture card or an image program installed in the computer is utilized to capture the eyeball image  101  as shown in  FIG. 3 . Then a vertical scanning and a horizontal scanning are performed by the scanning module  210  on each of the longitudinal axis and the horizontal axis within the range of the eyeball image  101  respectively, so as to acquire a digital eyeball signal  2100  of the eyeball image  101  (Step S 110 ). 
     After the digital eyeball signal  2100  is acquired, a signal transformation module  220  is utilized to perform the wavelet transform on the digital eyeball signal  2100 . A high frequency analysis and a low frequency analysis are performed on the digital eyeball signal  2100  by the signal analysis module  230 . The formulas of the high frequency analysis and the low frequency analysis of the wavelet transform are as follows respectively:
 
 D =( s,H )  (Formula 1)
 
 A =( s,L )  (Formula 2),
 
     in which s is the digital eyeball signal  2100 , H is a high frequency filter factor of the wavelet transform, the high frequency signal D is a convolution result of the digital eyeball signal  2100  and the high frequency filter factor H. L is a low frequency filter factor of the wavelet transform, A is a low frequency signal of the digital eyeball signal  2100 , and the low frequency signal A is a convolution result of the digital eyeball signal  2100  and the low frequency filter factor L. 
     Referring to  FIGS. 4A ,  4 B and  4 C together,  FIG. 4A  is a schematic view of acquiring a high frequency signal after a wavelet transform performed on a digital eyeball signal at the longitudinal axis according to the present invention,  FIG. 4B  is a schematic view of acquiring a high frequency signal after a wavelet transform performed on a digital eyeball signal at the horizontal axis according to the present invention, and  FIG. 4C  is a schematic view of matching the high frequency signal at the longitudinal axis in  FIG. 4A  with the high frequency signal at the horizontal axis in  FIG. 4B  to acquire a pupil position according to the present invention. 
     After the wavelet transform at the longitudinal axis and at the horizontal axis is performed on the digital eyeball signal  2100 , a high frequency signal at the longitudinal axis as shown in  FIG. 4A  and a high frequency signal at the horizontal axis as shown in  FIG. 4B  are obtained respectively. It can be observed clearly from  FIGS. 4A and 4B  that the digital eyeball signals  2100  at the longitudinal axis and at the horizontal axis after wavelet transform have a signal interval  22  and a signal interval  24  respectively (Step S 120 ). 
     Normally, the variance of wavelet transform coefficients from the mutual subtraction of pixels is small when the pupil  100  is in the low frequency band. Therefore, the frequency of both signal intervals is zero, which is the position of the longitudinal axis and the horizontal axis of the pupil  100 . The signal interval  22  is the length of the pupil  100 , and the signal interval  24  is the width of the pupil  100 . The position of the pupil  100  is analyzed and obtained according to a zero-crossing rate principle. The zero-crossing rate is the number of times of the signal amplitude crossing zero in the digital eyeball signal. The range of the largest number of times of crossing zero consecutively is retrieved, and it is also necessary to set at least how many times to cross zero consecutively to obtain the position of the pupil  100 . Then, the high frequency signal at the longitudinal axis in  FIG. 4A  is matched with the high frequency signal at the horizontal axis in  FIG. 4B  to acquire the position of the pupil  100  accurately as shown in  FIG. 4C  (Step S 130 ). 
     Referring to  FIGS. 5A and 5B ,  FIG. 5A  is a schematic view of acquiring a low frequency signal after the wavelet transform performed on the digital eyeball signal at the longitudinal axis according to the present invention,  FIG. 5B  is a schematic view of acquiring a low frequency signal after the wavelet transform performed on the digital eyeball signal at the horizontal axis according to the present invention, and  FIG. 5C  is a schematic view of matching the low frequency signal at the longitudinal axis in  FIG. 5A  with the low frequency signal at the horizontal axis in  FIG. 5B  to acquire a pupil position according to the present invention. 
     Similarly, after the wavelet transform at the longitudinal axis and at the horizontal axis is performed on the digital eyeball signal  2100 , a low frequency signal at the longitudinal axis as shown in  FIG. 5A  and a low frequency signal at the horizontal axis as shown in  FIG. 5B  are obtained respectively. It can be observed clearly from  FIGS. 5A and 5B  that the digital eyeball signals at the longitudinal axis and at the horizontal axis after transform have a signal interval  32  and a signal interval  34  respectively (Step S 120 ). The signal interval  32  is the length of the pupil  100 , and the signal interval  34  is the width of the pupil  100 . 
     Normally, the variance of wavelet transform coefficients from the sum of pixels is small when the pupil  100  is in the low frequency band. Therefore, the frequency of both signal intervals is a particular constant value in a consecutive time, which is the position of the longitudinal axis and the horizontal axis of the pupil  100 . The signal interval  32  and the signal interval  34  are acquired by analyzing a signal length of the two low frequency signals crossing a particular ratio of the constant frequency in a consecutive time. Then, the low frequency signal at the longitudinal axis in  FIG. 5A  and the low frequency signal at the horizontal axis in  FIG. 5B  are matched to acquire a pupil position as shown in  FIG. 5C  (Step S 130 ). 
     It is known from above that the pupil position acquisition method described in the present invention has the following features. 
     1. The pupil position of a subject may be found quickly by utilizing the image processing technique of the wavelet transform. Thus, if the technique is applied to a wearable computer, the limb disabled people can enjoy the performance of eye operations by operating the cursor of a computer mouse through eye motions. 
     2. For the patients with severe disabilities, an extreme disability such as amyotrophic lateral sclerosis (ALS) or severe cerebral palsy deprives them of the use of their limbs and facial muscles, the person could rely on this technique to attain or regain some degrees of independent communication and control. 
     To sum up, the present invention is recorded only to present the preferred implementation methods or embodiments of the technology means adopted to solve the problems, instead of limiting the scope of the present invention. That is, equivalent variations or modifications consistent with the claims of the present invention all fall within the scope of the present invention.