Patent ID: 11900634
Assignee: PENG CHENG LABORATORY
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 4:
5. The method for adaptively detecting chessboard sub-pixel level corner points according to claim 4, wherein step 6) comprises the following specific steps:
6-1) in the process of expanding outwards, obtaining the coordinates of the other two unknown corner points of the adjacent unit grid according to the homography matrix H, obtaining the lengths of the four sides of the adjacent unit grid according to the coordinates of the two corner points, naming the lengths of the four sides in the same direction (clockwise or counterclockwise) as d1, d2, d3, d4 and the corresponding included angles of every two adjacent sides as θ1, θ2, θ3, θ4 respectively; when the average value d of the four side lengths of the unit grid and the radius win of the iteration window satisfy the following fitting relation:, win
  =
  
   [
   
    
     
      k
      *
      
       d
       ¯
      
     
     +
     c
    
    
     
      ρ
      *
      
       
        ∑
        
         i
         =
         1
        
        4
       
       
        
         
          ❘
          "\[LeftBracketingBar]"
         
         
          
           θ
           i
          
          -
          
           π
           2
          
         
         
          ❘
          "\[RightBracketingBar]"
         
        
        4
       
      
     
     +
     b
    
   
   ], the sub-pixel level corner point detected is the most accurate, wherein k and ρ are coefficients of first order terms, and c and b are constants; based on the known k, ρ, c, b, d and θi, the initial value of the radius win of the window is taken as w0;
6-2) verifying the accuracy of the sub-pixel level corner point coordinates of the four points of the adjacent unit grid; naming the lengths of the four sides of the adjacent unit grid in the same direction (clockwise or counterclockwise) as d′1, d′2, d′3, d′4, the tangents of the four sides as ϕ1, ϕ2, ϕ3, ϕ4, and the corresponding included angles of every two adjacent sides as θ′1, θ′2, θ′3, θ′4 respectively; setting parameters μ1, μ2, λ1, λ2, η1, η2, δ1 and δ2, and taking μ1=λ1=η1=δ1=0.9 and μ2=λ2=η2=δ2=1.1; the side lengths needs to satisfy that:, μ
    1
   
   ≤
   
    
     d
     1
     ′
    
    
     d
     3
     ′
    
   
   ≤
   
    μ
    2
   
  
  ,
  
   
    λ
    1
   
   ≤
   
    
     d
     2
     ′
    
    
     d
     4
     ′
    
   
   ≤
   
    λ
    2
   
  
  ,
  
   
    
     η
     1
    
    ≤
    
     
      ϕ
      1
     
     
      ϕ
      3
     
    
    ≤
    
     
      η
      2
     
     ⁢
        
     and
     ⁢
        
     
      δ
      1
     
    
    ≤
    
     
      ϕ
      2
     
     
      ϕ
      4
     
    
    ≤
    
     δ
     2
    
   
   ;, if the above relations are not satisfied, the size of the iteration window win for calculating sub-pixel level corner points shall be dynamically adjusted until the relations are satisfied.