Abstract:
A computer readable media having at least one program code recorded thereon. An interference image determining method can be performed when the program code is read and executed. The interference image determining method comprises: (a) controlling a light source to illuminate an object on a detecting surface to generate an image; (b) controlling a sensor to catch a current frame of the image; (c) utilizing an image characteristic included in the current frame to determine a interference image part of the current frame; and (d) updating a defined interference image according to the determined interference image part.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Taiwan Patent Application No. 101107630 filed Mar. 7, 2013, and incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an interference image determining method and an interference image determining apparatus utilizing the interference image determining method, and particularly relates to an interference image determining method utilizing the image characteristic of a caught current frame to update a defined interference image, and an interference image determining apparatus utilizing the interference image. 
     2. Description of the Prior Art 
     As related tech rapidly grows, the mouse utilizing a rolling ball or other apparatuses such as a tracking ball is replaced by an optical mouse or an optical touch control apparatus. Such optical mouse or optical touch control apparatus can be regarded as an optical replacement estimating apparatus, since these apparatuses determine a related displacement between a detecting surface of the apparatus and an object. 
       FIG. 1  is a schematic diagram illustrating a prior art optical displacement estimating apparatus  100 , for determining displacement for a finger on a detecting surface.  FIG. 1( a )  illustrates a cross sectional view of the optical displacement estimating apparatus  100 , and  FIG. 1( b )  illustrates a block diagram for a circuit controlling the operation for the optical displacement estimating apparatus  100 . The optical displacement estimating apparatus  100  includes a detecting surface  103 , a light source  105 , a detector  107 , lens  109 ,  111 , a processing unit  113 , a storage apparatus  115  and a light source controlling unit  117 . The operation of the light source  105  is controlled by the light source controlling unit  117  and illuminates the finger  101  on the detecting surface  103  to generate in image. The detector  107  catches the frame in the image, and the processing unit  113  computes displacement of the finger  101  according to the caught frame. Also, the processing unit  113  controls data accessing of the storage apparatus  115  and the operation of the light source controlling unit  117 . 
     However, some objects on the detecting surface  103 , such as scraping trace, finger print or dust, may form an interference image in the caught frame such that the displacement estimation becomes un-accurate. Some related techniques are developed to solve these problems, but these techniques need extra hardware cost or complicated algorithm. 
     SUMMARY OF THE INVENTION 
     One objective of the present invention is to provide an effective interference image determining method and interference image determining apparatus needing no extra hardware and complicated algorithm. 
     One embodiment of the present invention discloses a computer readable media having at least one program code recorded thereon. An interference image determining method can be performed when the program code is read and executed. The interference image determining method comprises: (a) controlling a light source to illuminate an object on a detecting surface to generate an image; (b) controlling a sensor to catch a current frame of the image; (c) utilizing an image characteristic included in the current frame to determine a interference image part of the current frame; and (d) updating a defined interference image according to the determined interference image part. 
     One embodiment of the present invention discloses a n interference image determining apparatus comprises: a detecting surface; a light source; a processing unit, for controlling the light source to illuminate an object on a detecting surface to generate an image; a sensor, for capturing a current frame of the image; and a storage apparatus, for storing a defined interference image; wherein the processing unit utilizes an image characteristic included in the current frame to determine a interference image part of the current frame, and updates a defined interference image according to the determined interference image part. 
     The above-mentioned embodiments can be performed via writing a firmware into a processing unit. Alternatively, the above-mentioned embodiment can be performed via writing a program code into a computer readable media and executing the program code. Therefore, unnecessary hardware and cost can be saved. Additionally, the interference image determining method provided by the present invention can compute the interference image part via simple steps, thus no complicated algorithm is needed. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a prior art optical displacement estimating apparatus. 
         FIG. 2  is a flow chart illustrating detail steps for an interference image determining method according to one embodiment of the present invention. 
         FIG. 3  is a schematic diagram illustrating the operation of the interference image determining method according to one embodiment of the present invention. 
         FIG. 4  is a flow chart illustrating summarized steps for an interference image determining method according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. 
     Please note the following description utilizes the optical displacement estimating apparatus  100  to explain the concept of the present invention, but it does not mean the concept of the present invention can only be applied to the optical displacement estimating apparatus  100  in  FIG. 1  (in this case, the optical displacement estimating apparatus can be regarded as an interference image determining apparatus). The interference image determining method can also be applied to other apparatuses that can perform the same function. Additionally, the following concept utilizes an optical displacement estimating apparatus having a detecting surface upward to detect displacement of a finger. However, an optical displacement estimating apparatus having a detecting surface downward such that the optical displacement estimating apparatus can be put on a plane to move a cursor such as an optical mouse should also fall in the scope of the present invention. 
     An optical displacement estimating apparatus can operate in two modes: an operating mode and a non operating mode. The non operating mode is a mode that a finger has a long distance away from the detecting surface, such that the sensor can not detect the displacement for the finger. Operating mode is a mode that a finger touches the detecting surface or a finger has a short distance away from the detecting surface such that the sensor can detect displacement for the finger. In these two modes, different consideration should be taken for updating the defined interference image. The embodiment according to the present invention shown in  FIG. 2  will take these two situations into consideration. 
       FIG. 2  is a flow chart illustrating detail steps for an interference image determining method according to one embodiment of the present invention, which includes the following steps: 
     Step  201   
     Control a light source to illuminate an object, such as a finger or any object that be utilized for touch control, on a detecting surface to generate an image. 
     Step  203   
     Catch a current frame I(x,y) of the image. 
     Step  205   
     Determine if the finger can be detected by the sensor? If yes, go to step  207 , if not go to step  213  to directly update defined interference image F(x,y) to generate a new defined interference image F′(x,y). The reason that the defined interference image F(x,y) can be directly updated in this embodiment is that if the finger can not be detected and interference objects generate interference images exist on the detecting surface, then the current frame caught in the step  203  includes only interference image part. Therefore such image can be directly utilized to update the defined interference image F(x,y), which can be stored in the storage apparatus shown in  FIG. 1 . 
     Step  207   
     Generate a compensated frame I′(x,y) according to the current frame I(x,y) and the defined interference image F(x,y). Other detail concept will be described as below. 
     Step  209   
     Perform displacement estimating for the finger according to the compensated frame I′(x,y). 
     Step  211   
     Determine if any displacement is estimated, if yes, go to step  213 , if not, go back to step  201  to prepare a next turn determining. 
     Step  213   
     Update the defined interference image F(x,y) to generate F′(x,y). 
     In this embodiment, the reason that the displacement is determined first then the interference image part is determined is that the caught current frame includes a still finger image and interference image part if the finger can be detected but has no displacement, thus the interference image part can not be determined. However, the image can be classified into a still image part and a moving image part if the finger has displacement, thus the interference image part can be determined thereby. In this embodiment, if the finger has displacement, the still image part can be directly regarded as an interference image part. 
       FIG. 3  is a schematic diagram illustrating the operation of the interference image determining method according to one embodiment of the present invention.  FIG. 3  depicts the concept of the steps  207 - 211  in  FIG. 2 . Please also refer to the apparatus shown in  FIG. 1  to understand the concept of the present invention for more clear. After the processing unit  113  receives the current frame I(x,y) caught by the sensor  107 , the defined interference image F(x,y) is utilized to process the current frame I(x,y) to generate the compensated frame I′(x,y). The compensating can utilize lightness of the pixels surrounding a specific pixel having lightness higher than a first predetermined value or lower than a second predetermined value (i.e. the pixel that is too bright or too dark), to compensate the specific pixel. Also, the compensating can be performed to a part including pixels having larger lightness variation level, since the part having scraping traces or dust may generate brighter or darker part, or an image having lightness variation level different from other parts. 
     After generating the compensated frame I′(x,y,), the compensated frame I′(x,y,) is compared with a reference frame R(x,y) to generate displacement estimation. The reference frame can be a frame that has already been processed and has no interference image. 
     Practically, the current frame I(x,y) in the embodiment of  FIG. 3 , includes the finger image FI 1  caused by finger moving and an interference image part II. Also, the processing unit  113  utilizes the defined interference image F(x,y) to compensate the interference image part II of the current frame I(x,y), to generate a compensated frame I′(x,y). As shown in  FIG. 3 , the compensated frame I′(x,y) only has the finger image FI and has no interference image part II. Then, the processing unit  113  compares the compensated frame I′(x,y) and the reference frame R(x,y). The displacement estimation of finger  101  can be acquired via comparing theses two images, since the reference frame R(x,y) also includes the above-mentioned finger image FI 2 . 
     Additionally, the processing mechanism shown in  FIG. 2  can be shown as following equations:
 
 F ′( x,y )= F ( x,y )*α+ I ( x,y )*(1−α)  Equation (1)
 
 I ′( x,y )= f ( I ( x,y ), F ( x,y ))  Equation (2)
 
corr(I′(x,y),R(x,y))  Equation (3)
 
     Equation (1) indicates the original defined interference image F(x,y) is multiplied with a weighting value α and the current frame is multiplied with (1−α), while updating the original defined interference image F(x,y) to a new defined interference image F′(x,y). By this way, too large difference for the new defined interference image F′(x,y) can be avoided. The weighting value can be a value generated by various experiments, or a value determined by detected image quality or lightness. 
     Equation (2) indicates the compensated frame I′(x,y) is generated via performing a logic operation to the current frame I(x,y) and the defined interference image F(x,y). In the embodiment shown in  FIG. 3 , the compensated frame I′(x,y) is generated via subtracting the defined interference image F(x,y) from the current frame I(x,y), that is, I′(x, y)=I(x,y)−F(x,y). Please note any logic operation that can remove the defined interference image F(x,y) from the current frame I(x,y), or decrease the affect that the interference image F(x,y) causes to the current frame I(x,y) should also fall in the scope of the present invention. Besides, the equation can be regarded as a step of utilizing lightness of the pixels surrounding the interference image part II to compensate the current frame I(x,y), since the defined interference image F(x,y) also includes pixels at edges of the interference image part II. 
     Equation 3 indicates comparing the compensated frame I′(x,y) with the reference frame R(x,y) to estimate displacement. 
     In view of above-mentioned embodiments, an interference image determining method including summarized steps can be acquired.  FIG. 4  is a flow chart illustrating summarized steps for an interference image determining method according to one embodiment of the present invention. The interference image determining method includes the following steps: 
     Step  401   
     Control a light source to illuminate an object, such as a finger or any object that be utilized for touch control, on a detecting surface to generate an image. 
     Step  403   
     Catch a current frame I(x,y) of the image. 
     Step  405   
     Utilize an image characteristic included in the current frame I(x,y) to determine an interference image part of the current frame. In view of above-mentioned description, the step of determining the interference image part can be regarded as utilizing an image characteristic included in the current frame I(x,y) to determine, since the compensated frame I′(x,y) is generated via compensating too light/too dark pixels, or via compensating pixels having lightness variation level different from other parts. 
     Step  407   
     Update a defined interference image F(x,y) according to the determined interference image part to generate a new interference image F′(x,y). 
     The above-mentioned embodiments can be performed via writing a firmware into a processing unit. Alternatively, the above-mentioned embodiment can be performed via writing a program code into a computer readable media and executing the program code. Therefore, unnecessary hardware and cost can be saved. Additionally, the interference image determining method provided by the present invention can compute the interference image part via simple steps, thus no complicated algorithm is needed. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.