Patent Publication Number: US-2019196223-A1

Title: Device and method for designing ophthalmic lens

Description:
FIELD 
     The subject matter relates to a device and a method for designing an ophthalmic lens. 
     BACKGROUND 
     Ophthalmic lenses are commonly worn by users to correct vision, or for cosmetic or therapeutic reasons. After a surface shape of the ophthalmic lens is designed, the ophthalmic lens is manufactured by precise machining or injection molding. The actual ophthalmic lens may shrink compared to the designed lens, so that the actual ophthalmic lens cannot meet the requirement of the user. A one-station service for designing and testing the ophthalmic lens is required. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is a block diagram of an exemplary embodiment of a device for designing an ophthalmic lens. 
         FIG. 2  is a flowchart of an exemplary embodiment of a method for designing an ophthalmic lens. 
         FIG. 3  is a diagram of a progressive addition lens made in the method of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure. 
     In general, the word “module,” as used hereinafter, refers to logic embodied in hardware or firmware, or to a collection of software instructions, written in a programming language, such as, for example, Java, C, or assembly. One or more software instructions in the modules may be embedded in firmware. It will be appreciated that modules may comprise connected logic modules, such as gates and flip-flops, and may comprise programmable modules, such as programmable gate arrays or processors. The modules described herein may be implemented as either software and/or hardware modules and may be stored in any type of non-transitory computer-readable storage medium or other computer storage device. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the like. 
       FIG. 1  illustrates an exemplary embodiment of a device  1  for designing an ophthalmic lens. The device  1  comprises a memory  10  and at least one processor  20 . The memory  10  stores a system  100  for designing a particular surface shape (target surface form) for the ophthalmic lens. The memory  10  can be an internal storage system of the device  1  such as a flash memory, a random access memory (RAM) for temporary storage of information, and/or a read-only memory (ROM) for permanent storage of information. The memory  10  can also be an external storage system, such as a hard disk, a storage card, or a data storage medium. The ophthalmic lens can be an eyeglass, a contact lens, or an intraocular lens. More specifically, the ophthalmic lens can be a progressive addition lens. 
     The system  100  comprises a number of modules, which are a collection of software instructions which can be executed by the processor  20  to perform the functions of the system  100 . The processor  20  can be a central processing unit (CPU), a microprocessor, or other data processor chip that performs functions of the system  100 . 
     The system  100  comprises a designing module  101 , a diopter calculating module  102 , an analyzing module  103 , a control module  104 , a measuring module  105 , and a modifying module  106 . 
       FIG. 2  illustrates an exemplary embodiment of a method for designing an ophthalmic lens. The method is provided by way of example, as there are a variety of ways to carry out the method. The method described below can be carried out using the configurations illustrated in  FIG. 1 , for example, and various elements of these figures are referenced in explaining example method. Each block shown in  FIG. 2  represents one or more processes, methods, or subroutines, carried out in the example method. Furthermore, the illustrated order of blocks is illustrative only and the order of the blocks can change. Additional blocks can be added or fewer blocks may be utilized, without departing from this disclosure. The example method can begin at block  21 . 
     At block  21 , the designing module  101  designs a target surface form of the ophthalmic lens according to a Zernike polynomial, and calculates a curvature of each point of the target surface form to obtain a curvature distribution over the target surface form. 
     Table 1 shows a sequence of polynomials and Zernike coefficients of the Zernike polynomial. Wherein, ρ and θ represent two variables of the polynomials, which are orthogonal on the unit disk. Each polynomial can be multiplied by the corresponding Zernike coefficient to obtain the target surface form. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 
                   
                 
                 polynomials 
               
               
                   
                   
               
             
            
               
                   
                 Z0 
                 1 
               
               
                   
                 Z1 
                 ρcosθ 
               
               
                   
                 Z2 
                 ρsinθ 
               
               
                   
                 Z3 
                 2ρ 2  − 1 
               
               
                   
                 Z4 
                 ρ 2 cos2θ 
               
               
                   
                 Z5 
                 ρ 2 sin2θ 
               
               
                   
                 Z6 
                 (3ρ 2  − 2)ρcosθ 
               
               
                   
                 Z7 
                 (3ρ 2  − 2)ρsinθ 
               
               
                   
                 Z8 
                 6ρ 4  − 6ρ 2  + 1 
               
               
                   
                 Z9 
                 ρ 3 cos3θ 
               
               
                   
                 Z10 
                 ρ 3 sin3θ 
               
               
                   
                 Z11 
                 (4ρ 2  − 3)ρ 2 cos2θ 
               
               
                   
                 Z12 
                 (4ρ 2  − 3)ρ 2 sin2θ 
               
               
                   
                 Z13 
                 (10ρ 4  − 12ρ 2  + 3)ρcosθ 
               
               
                   
                 Z14 
                 (10ρ 4  − 12ρ 2  + 3)ρsinθ 
               
               
                   
                 Z15 
                 20ρ 6  − 30ρ 4  + 12ρ 2  − 1 
               
               
                   
                 Z16 
                 ρ 4 cos4θ 
               
               
                   
                 Z17 
                 ρ 4 sin4θ 
               
               
                   
                 Z18 
                 (5ρ 2  − 4)ρ 3 cos3θ 
               
               
                   
                 Z19 
                 (5ρ 2  − 4)ρ 3 sinθ 
               
               
                   
                 Z20 
                 (15ρ 4  − 20ρ 2  + 6)ρ 2 cos2θ 
               
               
                   
                 Z21 
                 (15ρ 4  − 20ρ 2  + 6)ρ 2 sin2θ 
               
               
                   
                 Z22 
                 (35ρ 6  − 60ρ 4  + 30ρ 2  − 4)ρcosθ 
               
               
                   
                 Z23 
                 (35ρ 6  − 60ρ 4  + 30ρ 2  − 4)ρsinθ 
               
               
                   
                 Z24 
                 70ρ 8  − 140ρ 6  + 90ρ 4  − 20ρ 2  + 1 
               
               
                   
                   
               
            
           
         
       
     
     That is, the target surface form can be described by a function Z(ρ,θ). The obtained curvature distribution of the target surface form can be described by function f(x,y). Wherein, x=ρ cos θ, y=ρ sin θ. 
     At block  22 , the diopter calculating module  102  calculates a diopter distribution over the target surface form corresponding to the obtained curvature distribution. 
     In at least one exemplary embodiment, the calculated diopter distribution can be described as function H(x,y): 
         H =[(1 +f   y   2 )× f   xx −2 ×f   x   ×f   y   ×f   xy +(1 +f   x   2 )× f   yy ]/[2×(1 +f   x   2   +f   y   2 ) 1.5 ]
 
     Wherein, f(x,y) denotes the obtained curvature distribution of the target surface form, f x  denotes differentiating the obtained curvature distribution f(x,y) with respect to x, f y  represents differentiating the obtained curvature distribution f(x,y) with respect to y, f xx  represents differentiating the obtained curvature distribution f(x,y) with respect to x twice, f yy  represents differentiating the obtained curvature distribution f(x,y) with respect to y twice, and f xy  represents differentiating the obtained curvature distribution f(x,y) with respect to x and then y. 
     At block  23 , the analyzing module  103  determines whether the calculated diopter distribution matches a preset diopter distribution; if yes, the procedure goes to block  24 , otherwise, the procedure goes to block  27 . 
     Referring to  FIG. 3 , in at least one exemplary embodiment, the ophthalmic lens is a progressive addition lens  200  that comprises a distant region  201 , a near region  202 , and an intermediate region  203  between the distant region  201  and the near region  202 . The preset diopter distribution is the dioptric gradually and continuously increasing from the distant region  201  to the intermediate region  203  and the near region  202 , to obtain a desired diopter at the near region  202 . 
     At block  24 , the control module  104  controls a processing machine  2  to manufacture the ophthalmic lens according to the Zernike polynomial. 
     In at least one exemplary embodiment, the processing machine  2  can be a computer numerical control machine or an injection molding machine. The control module  104  outputs the Zernike polynomial to the processing machine  2 , thereby controlling the processing machine  2  to manufacture the ophthalmic lens by precise machining or injection molding. 
     At block  25 , the measuring module  105  measures an actual surface form of the manufactured ophthalmic lens. 
     At block  26 , the analyzing module  103  determines whether the measured actual surface form is sufficiently close to the target surface form. If no, the procedure goes to block  27 , otherwise, the procedure ends. 
     In at least one exemplary embodiment, the analyzing module  103  calculates a difference between the measured actual surface form and the target surface form, and determines whether the calculated difference is less than or equal to a preset value. If the calculated difference is less than or equal to the preset value, the analyzing module  103  determines that the measured actual surface form is sufficiently close to the target surface form. If the calculated difference is greater than the preset value, the analyzing module  103  determines that the measured actual surface form is not sufficiently close to the target surface form. The preset value can be varied according to need. For example, the preset value can be zero. 
     At block  27 , the modifying module  106  modifies the Zernike polynomial. Then, the block  21  is repeated (here, the target surface form is designed according to the modified Zernike polynomial) until the measured actual surface form is sufficiently close to the target surface form. 
     The device and method provides one-station service for designing and testing the ophthalmic lens. For the ophthalmic lens which at first does not meet the requirement, the device and method can modify the ophthalmic lens until the final ophthalmic lens is sufficiently close to the target ophthalmic lens. 
     Even though information and advantages of the present exemplary embodiments have been set forth in the foregoing description, together with details of the structures and functions of the present exemplary embodiments, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present exemplary embodiments, to the full extent indicated by the plain meaning of the terms in which the appended claims are expressed.