CN106932921A - Progressive additional free surface lens method of evaluating performance - Google Patents

Abstract

The invention relates to a method for evaluating the performance of a progressive multi-focus free-form surface lens. In the design stage, starting from the perspective of multiple viewing axes, the optical power and astigmatism of the lens when the human eye wears a progressive multi-focus free-form surface lens under the multi-visual axis state and axial distribution evaluation method, which can not only give the influence of visual axis changes in far, near and surrounding areas on lens power, astigmatism and axial distribution when the human eye is wearing a progressive multifocal lens in a multi-visual axis state , can also give the coincidence degree and weight factor of different areas of the lens. After normalization, calculate the weight of the progressive multi-focal free-form surface lens in the multi-visual axis state to evaluate the grid point power, astigmatism and axial distribution of the lens. factor threshold. According to the weight factor threshold, the gap between the progressive multi-focus free-form surface designed in the multi-view axis state and the prescription is obtained, and the error of the parameters in the design process is known. This evaluation method can shorten the design cycle, reduce the processing waste rate, and improve the product qualification rate.

Description

Performance Evaluation Method of Progressive Multifocal Freeform Surface Lens

technical field

The invention relates to an optical performance, in particular to a method for evaluating the performance of a progressive multi-focus free-form surface lens.

Background technique

Progressive multifocal lens is a free-form surface lens designed on the basis of bifocals, trifocals and multifocal glasses, which overcomes the shortcomings of image jump caused by sudden changes in focal power and boundary marks on the surface of the lens. It is a lens whose optical power increases gradually from top to bottom. As the human eye observes from far to near, the focal power of this lens increases gradually, and only one lens can correct the vision of all fields of view.

For the performance evaluation of progressive multifocal lenses, optical power and astigmatism distribution diagrams are mainly used in optics, which are mainly two-dimensional or three-dimensional graphics used to express and evaluate the optical performance of progressive multifocal lenses. The drawing of the distribution diagram is mainly to connect the points with equal power or astigmatism on the progressive multifocal lens, so as to reflect the change characteristics of the refractive power of the progressive multifocal lens surface. However, the evaluation of the lens by the distribution map is only a rough subjective result, and it cannot evaluate the lens quantitatively. As for the quantitative evaluation, at present, most of the autofocusmeters (such as the autofocusmeter of Japan's NEDIK company) are used to measure the high beam, low beam focal power, astigmatism and axial direction on the lens. This lens meter measurement method only obtains the quantitative result of a certain point on the lens, and cannot give a comprehensive evaluation result of the entire lens. With the wide application of progressive multi-focal lens, its corresponding detection technology is also developing continuously. Measurement methods such as surface profilometry, Hartmann-Shack wavefront sensing and Moiré fringes are used to study the progressive multifocal lens, mainly to analyze the astigmatism, aberration and power distribution of the lens. From the above methods, it can be seen that the auto-focusmeter is a single-point measurement method, which can only obtain the optical information of each point on the lens, and has limitations in evaluating the optical characteristics of the entire surface of the progressive multi-focal lens; the Hartmann measurement method (For example, the VM series surface measuring instrument of VISIONIX company), the measurement method based on Moire deflection technology (FFV surface measuring instrument of Israel Roltex company), and the Ronchi grating measurement method, these three overall surface sampling measurement methods are parallel light Through the lens under test, the relevant optical parameters of the lens in the full aperture range are obtained.

Although there are many evaluation methods for progressive focus eyes at home and abroad, and some of them have been widely used in daily life, all of the existing methods have certain defects, and these evaluation methods do not affect the design of lenses in the design stage. Errors are analyzed, but after the lens surface design is completed, it is directly processed on the corresponding free-form surface processing machine tool, which greatly increases the defective rate of progressive multi-focal lenses. Therefore, it is the primary problem to be solved in the design process to study the evaluation method of the progressive multifocal free-form surface lens in the multi-visual axis state.

Contents of the invention

The present invention aims at the problems existing in performance measurement and evaluation of progressive multi-focal lenses, and proposes a performance evaluation method for progressive multi-focal free-form surface lenses. Starting from the angle of the visual axis, the evaluation method of the focal power, astigmatism and axial distribution of the lens when the human eye wears a progressive multi-focal free-form surface lens in the multi-visual axis state can not only give the human eye wearing a progressive multi-focal lens In the state of multiple visual axes, the influence of visual axis changes in far, near and surrounding areas on the focal power, astigmatism and axial distribution of the lens can also be given, and the conformity and weight factors of different areas of the lens can be given. After normalization processing , to calculate the weighting factor threshold value of the progressive multifocal free-form surface lens in the state of multi-visual axis to evaluate the grid point power, astigmatism and axial distribution of the lens. According to the weight factor threshold, the gap between the progressive multi-focus free-form surface designed in the multi-view axis state and the prescription is obtained, and the error of the parameters in the design process is known.

The technical solution of the present invention is: a method for evaluating the performance of progressive multi-focus free-form surface lenses,

1) Carry out grid division for the designed progressive multifocal free-form surface lens, the diameter of the lens is R, each grid is a square, and the grid side length is r, and the lens is divided into m×n grid points;

2) The connection line between any grid point (m, n) on the lens and the eyeball center of the human eye is used as a visual axis, and after obtaining the surface data of the lens, the design focal power of m×n grid points is obtained f _ij , astigmatism c _ij and astigmatism axis a _ij distribution matrix, i=1...m, j=1...n, calculate the difference between the design power, astigmatism and astigmatism axis and the wearer's prescription;

3) According to the international standard for progressive multifocal glasses, determine the degree of conformity between the optical power, astigmatism and axial distribution of the m×n grid points 4 under the design surface data and the prescription of the glasses wearer, and according to the actual use process Different weight factors are assigned to the degree of demand, and the matrix of conformity and weight factors is obtained;

4) Reselect the visual axis and repeat steps 2) and 3) until the design power, astigmatism and axis of the progressive multifocal free-form surface lens in all visual axis states are obtained in the far and near vision areas of the wearer's prescription , add the coincidence degree and weight factor matrix of the light channel and the astigmatism area, and normalize it, and normalize the conformity degree and weight factor as the evaluation index;

5) Evaluate the wearing performance of the lens according to the focal power, astigmatism, and the weight factor threshold of astigmatism axial compliance that meet the wearer's comfort.

The method of calculating the degree of compliance in step 3): on the m×n grid points of the progressive multi-focal free-form surface lens, when the absolute value of the difference between the design value and the prescription value is less than or equal to the standard allowable minimum value A, that is:

|Design value-prescription value|≤A

It is determined that this point meets the prescription requirements, and the degree of compliance is 1;

When the absolute value of the difference between the design value and the prescription value is greater than the standard allowable maximum value B:

|design value-prescription value|＞B

That is, it is determined that the point does not meet the prescription requirements, and the degree of compliance is 0;

For the absolute value of the difference between the design value and the prescription is between A and B, it is determined that this point partially meets the design requirements, and the compliance degree satisfies the linear distribution:

Then, for m×n grid points, the coincidence matrix can be used to represent the conformity of the whole lens, and the far beam, near beam, addition channel and astigmatic area of the lens are in the process of wearing the lens, so The degree of emphasis given is different, and each grid point has a different weight of focal power, astigmatism, and astigmatism axis, and the coincidence matrix is multiplied by the corresponding weight matrix to obtain the distribution of lens power, astigmatism, and astigmatism axis Indexes F _p , C _p , A _p .

The step 4) normalized evaluation index of the progressive multifocal free-form surface lens is:

Among them, σ ₁ , σ ₂ , and σ ₃ are the weight factor thresholds of distributions corresponding to F _p , C _p , and A _p after normalization.

The beneficial effect of the present invention is that: the method for evaluating the performance of the progressive multi-focus free-form surface lens of the present invention can shorten the design cycle, reduce the rate of processing rejects, improve the product qualification rate, and provide new ideas and innovations for the evaluation method of the progressive multi-focus free-form surface lens. approach, strong implementability, and very practical application prospects.

Description of drawings

Fig. 1 is a schematic diagram of the performance evaluation of the progressive multifocal free-form surface lens of the present invention;

Fig. 2 is a schematic diagram of the grid division standard of the progressive multi-focal free-form surface lens of the present invention.

detailed description

Figure 1 shows a schematic diagram of performance evaluation of progressive multifocal free-form surface lenses. Put the lens 3 directly in front of the human eye 1, the horizontal line passing through the center of the eyeball of the human eye 1 is the optical axis 6, the intersection point of the optical axis 6 and the front surface of the lens 3 is the front surface vertex 5, and the distance between the front surface vertex 5 of the lens 3 and the human body is The length of the center of the eyeball is 27mm. According to the facial features of the wearer, the lens 3 is tilted at a certain angle 7 along the straight line perpendicular to the optical axis 6, and the range is 10-12°, so as to simulate different wearing states, that is, the face shape.

As shown in Figure 2, the standard schematic diagram of grid division, the diameter 8 of the lens 3 is R, divided according to the radius r of the eye pupil of different wearers, the grid 9 is a square, and the grid side length 10 is r, and the lens 3 is divided into m×n grid points, coordinate coefficients can also be added, divided according to the radius r smaller than the pupil of the eyeball.

The connection line between any grid point 4(m,n) and the eyeball center of the human eye is regarded as a visual axis 2 . Here, the prescription refractive power value of progressive multifocal lens 3m×n grid point 4 (prescription is defined as: human eye optometry parameter) is defined as F _ij , where: i=1...m, j=1...n, theory The astigmatism is C _ij , the astigmatism axis is A _ij , the design focal power result is f _ij , the astigmatism is c _ij , and the astigmatism axis is a _ij . According to the prescription of the lens 3, the matrix F _ij , C _ij , A _ij of the power, astigmatism and astigmatism axial distribution of the lens 3m×n grid points 4 are obtained.

After obtaining the surface data of the lens 3 , the distribution matrix of the focal power f _ij , astigmatism c _ij and astigmatism axis a _ij of the m×n grid points 4 . Then, the difference between the design power, astigmatism, and axis of astigmatism and the wearer's prescription is:

ΔF _ij =F _ij -f _ij

ΔC _ij =C _ij -c _ij

ΔA _ij =A _ij -a _ij

Here, ΔF _ij , ΔC _ij and ΔA _ij are the difference between the prescription and design optical power, astigmatism and astigmatism axis, respectively.

In order to explore the coincidence between the design focal power and the focal power obtained by the design simulation, it is expressed by δ _(m,n) . According to the international standard of progressive multifocal glasses, when the power difference between the prescription and the design value is less than or equal to P ₁ , P ₁ =0.12D (D diopter is the abbreviation of the unit of optical power is D, and the unit of the International System of Units is m to the power of -1), it is determined that this point meets the design requirements, and the degree of compliance δ _(m,n) ＝1; when |f _ij -F _ji |＞P ₂ , among them, P ₂ ＝0.25D, it is determined that the point does not meet the design requirements, and the compliance degree δ _(m,n) = 0; when P ₂ ≥|f _ij - F _ij |＞P ₁ , it is determined that this point partially meets the design requirements, and the compliance degree satisfies the linear distribution:

which is:

The focal power compliance matrix δ _ij corresponding to the m×n grid points on the lens is:

For the focal power of each point on the m×n grid points 4, different weights λ _(m,n) are assigned according to the degree of demand in the actual use process (for example, the imaging effects of the near and far vision and the addition channel have a significant impact on wearing It is very important for those whose focal power error is smaller than P ₁ should also be larger), then the corresponding weight matrix λ _ij is:

The power distribution index F _p is calculated as follows:

and have:

The power distribution index F _p is calculated as follows:

F _p =∑λ _ij *δ _ij

and have:

For the degree of conformity between the prescribed astigmatism and the design value, here, according to the international standard for progressive multifocal glasses, we define: when | _{c ij} -C _ij | P ₃ ＝0.5D), it is determined that this point meets the design requirements, and the degree of compliance ε _(m,n) = 1; when |c _ij -C _ij |＞2*ADD, the point does not meet the design requirements, and the degree of compliance ε _{(m, n)} ＝0; when 2*ADD≥|c _ij -C _ij |＞P ₃ , it is determined that the point partially meets the design requirements, and the degree of compliance satisfies the linear distribution:

which is:

The astigmatism coincidence matrix corresponding to m×n grid points 4 on the lens is ε _ij .

For each point of astigmatism on the grid point 4, different weights k _(m,n) are assigned according to the degree of demand in the actual use process, (for example, the imaging effects of farsightedness and near vision and the addition of light channels are very important to the wearer , the weight of the astigmatism error smaller than P ₃ should also be larger), and the astigmatism weight matrix is k _ij .

The astigmatism distribution index C _p is calculated as follows:

C _p =∑k _ij *ε _ij

and have:

Σk _ij =1

For the degree of conformity between the prescription axis and the design value, according to the international standard of progressive multifocal glasses, the error value of astigmatism is different in different ranges of far beam astigmatism. Therefore, we define a letter A to indicate that in different astigmatism The absolute value of the error range limit in the lower axis of the value. We define: when |A _ij -a _ij |＝0° (the axial difference between the prescription and the design value is equal to 0°), it is considered that this point meets the design requirements, and the degree of compliance is ω _(m,n) = 1; when |A _ij -a _ij |＞H°, this point does not meet the design requirements, and the degree of compliance is ω _(m,n) = 0; when H°≥|a _ij -A _ij |＞0°, it is considered that this point partially meets the design requirements Requirements, the degree of compliance satisfies the linear distribution:

which is:

The axial coincidence matrix of astigmatism corresponding to m×n grid points 4 on the lens is ω _ij .

For each point of astigmatism on the grid point 4, different weights ρ _(m,n) are given according to the degree of demand in the actual use process, and the astigmatism axial weight matrix ρ _ij is:

The astigmatism axial distribution index _Ap is calculated as follows:

A _p =∑ρ _ij *ω _ij

and have:

∑ρ _ij =1

According to the above definition, the normalized evaluation index of progressive multifocal free-form surface lens is:

Here, σ ₁ , σ ₂ , and σ ₃ are the weight factor thresholds of distributions corresponding to F _p , C _p , and A _p after normalization.

According to the above scheme, the degree of compliance between the design focal power, astigmatism and axial direction of the progressive multifocal free-form surface lens 3 in the state of multi-vision axis 2 and the wearer's prescription in the far vision zone, near vision zone, addition channel and astigmatism zone is obtained and weight factor matrix. After normalization processing, the progressive multifocal free-form surface lens 3 under the state of multi-visual axis 2 is calculated, and the weight factor thresholds σ ₁ , σ ₂ , and σ ₃ of the evaluation lens grid point 4 power, astigmatism and axial distribution are calculated. According to the weight factor threshold, the gap between the progressive multi-focus free-form surface designed in the multi-view axis state and the prescription is obtained, and the error of the parameters in the design process is known. This evaluation method can shorten the design cycle, reduce the processing waste rate, and improve the product qualification rate.

We will use the degree of compliance and weight as the evaluation criteria and optimization goals, so that the final optimization design results meet the requirements of optometry prescriptions. The study of different compliance values is actually the weight of each compliance value in the lens evaluation model for the design of the lens, and it is normalized. The relative weight of each coincidence value after normalization was obtained through statistical analysis, and a relative weight calculation method was proposed to make up for the error caused by the design calculation of the progressive multifocal free-form surface lens in the initial design process, and a light that satisfied the wearer's comfort was proposed. The weight factor threshold value of focal power, astigmatism and axial coincidence degree, the distribution of weight factor, the determination of the degree of coincidence of each point and the accuracy of the solution will directly affect the reliability and reliability of the optimal design and processing of progressive multifocal glasses. Wearing comfort.

Claims (3)

1. a kind of progressive additional free surface lens method of evaluating performance, it is characterised in that

1) mesh generation, a diameter of R of eyeglass are carried out for the progressive additional free surface lens for designing, each grid is just Square, side length of element is r, and eyeglass is divided into m × n grid lattice point；

2) line at any one grid lattice point (m, n) and human eye eyeball center, as an optical axis, is obtaining eyeglass on eyeglass Face type data after, obtain the m × n design focal power f of grid lattice point_ij, astigmatism c_ijWith astigmatism axial direction a_ijThe square of distribution Battle array, i=1 ... m, j=1 ... n calculate design focal power, the difference between astigmatism and astigmatism axial direction and wearer's prescription；

3) according to progressive multi-focal lenses international standard determine m × n grid lattice point 4 design face type data under focal power, Astigmatism and axial direction are distributed and with the degree of conformity between mirror person's prescription, are assigned according to desirability in actual use different Weight factor, obtains degree of conformity and weight factor matrix；

4) optical axis, repeat step 2 are reselected) and 3), the progressive additional free form surface mirror under obtaining all optical axis states Piece design focal power, astigmatism and axially with wearer's prescription regarding far field, near reading range, plus optical channel and spread area degree of conformity and Weight factor matrix, and normalized, degree of conformity and weight factor are normalized as evaluation number；

5) weight factor threshold value according to the focal power, astigmatism and astigmatism axial direction degree of conformity for meeting wearer comfort evaluates eyeglass Wear performance.

2. progressive additional free surface lens method of evaluating performance according to claim 1, it is characterised in that the step 3) degree of conformity calculation in：On progressive additional free surface lens m × n grid lattice point, when design load and prescription values Difference absolute value less than or equal to standard allow minimum value A when：

| design load-prescription values |≤A

Assert that the point reaches prescription requirements, and degree of conformity is 1；

When the absolute value of design load and the difference of prescription values allows maximum B more than standard：

| design load-prescription values | ＞ B

Assert that the point is unsatisfactory for prescription requirements, degree of conformity is 0；

For design load and the difference of prescription absolute value between A and B, assert that the point part meets design requirement, degree of conformity is full Sufficient linear distribution:

So, for m × n grid lattice point, so that it may represent the degree of conformity of whole eyeglass with degree of conformity matrix, and eyeglass Distance light, dipped beam, plus optical channel and astigmatism area during eyeglass wearing, the attention degree for being assigned is different, each net Sound of laughing point just has different weight focal powers, astigmatism and astigmatism axial direction, degree of conformity matrix and respective weights matrix multiple, obtains mirror The profile exponent F of piece focal power, astigmatism and astigmatism axial direction_p、C_p、A_p。

3. progressive additional free surface lens method of evaluating performance according to claim 2, it is characterised in that the step 4) progressive additional free surface lens normalization evaluation number is：

$\left\{\begin{array}{c}g=F_p\·{\mathrm{\σ}}_1+C_p\·{\mathrm{\σ}}_2+{\mathrm{\σ}}_3\·A_p\\ g=1\end{array}\right.$

Wherein σ₁, σ₂, σ₃It is F after normalization_p, C_p, A_pThe weight factor threshold value of corresponding distribution.