AU2002301484B2 - A Method for Evaluating An Ocular Optical Lens - Google Patents

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

Name of Applicant: Actual Inventors: Address for Service: Invention Title: HOYA CORPORATION, of 7-5, Nakaochiai 2-chome, Shinjyuku-ku, Tokyo 161-8525, Japan AKIYAMA, Hisanori QI, Hua TANAKA, Norihisa YODA, Toshiro DAVIES COLLISON CAVE, Patent Attorneys, of 1 Little Collins Street, Melbourne, Victoria 3000, Australia A Method For Evaluating An Ocular Optical Lens The following statement is a full description of this invention, including the best method of performing it known to us: Q:\OPER\GCP\7000]div c do 16/10/02 P.OPERIGCM M]div spe doc-16/102 -1- A METHOD FOR EVALUATING AN OCULAR OPTICAL LENS Field of the Invention The present invention relates to a method for evaluating an ocular optical lens.

Prior Art The properties required for a lens material of spectacle are a high refractive index, a high Abbe number, a low specific gravity, excellent workability, excellent tinting performance and chemical resistance. Among these properties, the refractive index and the Abbe number are important as the optical properties. With respect to a spectacle lens having a great dioptric power, the higher the refractive index of the lens, the smaller the thickness and, therefore, the better the appearance and the lighter the weight of the lens.

The higher the Abbe number of the lens, the smaller the chromatic aberration in peripheral portions of the lens.

Since it has been difficult that a lens material having a high refractive index and a high Abbe number is developed, a spectacle lens having a higher refractive index tends to have a lower Abbe number. However, as the production technology has made progress, materials having a high refractive index and a high Abbe number and suited for the material for spectacle lenses have been developed and spectacle lenses prepared by -2using these materials and having excellent optical properties are becoming commercially available.

In general, a difference in the refractive index of a spectacle lens appears as a difference in the external shape, the thickness, of the lens when spectacle lenses having the same dioptric power are compared.

Therefore, the difference in the refractive index can be easily understood by a person wearing spectacles. However, a difference in the Abbe number of a spectacle lens cannot be shown by a difference in the external shape and 1o cannot be easily understood by a person wearing a spectacle. To help the person wearing spectacle glasses understand the effect of the Abbe number of the spectacle lenses, for example, an image of actual vision based on the Abbe number used for simulating retinal image is exhibited by using the Snellen's visual mark. In this image of actual vision, peripheral portions of the image are blurred with unfocussed colors and the degree of the blur depends on the Abbe number.

It is required by professional shops of spectacle glasses that, based on the difference in vision due to the difference in the Abbe number, persons wearing spectacle glasses easily understand that the lenses of spectacle worn by the persons are made of an excellent glass material. Thus, it is expected that the excellent spectacle lenses can be recognized as distinguished products different from ordinary spectacle lenses by emphasizing the excellence of the spectacle lenses. However, in the image of actual vision described above, blur with slightly unfocussed colors appearing in the Snellen's visual mark is exhibited in a manner close to that appearing in the actual retinal image and it is very difficult that the slight blur with unfocussed colors due to the difference in the Abbe number is recognized. Thus, it is heretofore difficult that an ordinary person wearing the spectacle recognizes the effect of the difference in the Abbe number from the image of actual vision unless the person is a professional P:\OPER\DH2581695 spal.doc-27/02/04 -3person skilled in the art.

According to the present invention there is provided a method for evaluating an ocular optical lens which comprises: arbitrarily selecting a point inside a lens shape of one ocular optical lens and, based on prism characteristics at the selected point, creating an equivalent visual region in which a specific value of visual acuity is surely obtained; creating an equivalent visual region of another ocular optical lens in accordance with a same method; and displaying the two equivalent visual regions on a same screen in a manner such that the regions can be compared.

Preferred Embodiments of the Invention The preferred embodiments of the present invention will be described in the following with reference to the drawings, in which: Fig. 1 shows a screen exhibited when the Abbe numbers treated by the apparatus for evaluation of an ocular optical lens are different in a great degree; PAOPERkGCto)tI Idiv spe. doc-16/JII)2 -4- Fig. 2 shows a screen exhibited when the Abbe numbers treated by the apparatus for evaluation of an ocular optical lens are different in a medium degree; Fig. 3 shows a screen exhibited when the Abbe numbers treated by the apparatus for evaluation of an ocular optical lens are different in a small degree; Fig. 4 shows a block diagram describing the apparatus for evaluation of an ocular optical lens; Fig. 5 shows a diagram describing the steps of simulation of an ocular optical lens; and Fig. 6 shows a diagram describing the angle of deviation of a ray by a prism having an angle ofi.

Fig. 4 shows a block diagram describing an apparatus for evaluating a spectacle lens which is an ocular optical lens. The apparatus is constituted with input means 10 for inputting data of the optical system of a spectacle lens for creating the region of comfortable vision in which a specific value of visual acuity is surely obtained, such as an Abbe number; an Abbe number simulator 20 for obtaining the region of comfortable vision of the spectacle lens based on the data of the optical system, such as the Abbe number; and output means 30 for outputting the region of comfortable vision obtained by the Abbe number simulator. The region of comfortable vision is a region marked out on the spectacle lens in a manner such that the specific value of visual acuity can be surely obtained within the region and is mainly determined by the Abbe number.

The Abbe number simulator is designed in a manner such that data for the region of comfortable vision and data for the image of actual vision can be output based on the data of the optical system such as the Abbe number using a simulation program which will be described later. The image of actual vision is an image simulating a retinal image and is already disclosed (for example, Japanese Patent Application Laid-Open No. Heisei 8(1996)-266472). The Abbe number simulator 20 can be constituted with a personal computer.

The input means 10 comprises two input lines. One of the input lines is an external input means 11 and the other is a manual input means 12.

Any of the input lines can be selected for the input. The external input means 11 is a means for entering outputs from an apparatus for measuring the Abbe number 13, a lens meter 14 and a frame tracer 15 into the Abbe number simulator 20. External data can be entered into the Abbe number simulator 20 from these external input means 11 via a communication cable such as an RS232C cable.

The manual input means 12 is constituted by an apparatus such as a keyboard, a mouse, a trackball, a trackpad, an apparatus for pen input and a pointing device. Data such as the Abbe number, the dioptric power and the shape of a spectacle lens can be manually input into the Abbe number simulator using the above means.

The output means is constituted by an apparatus for controlling a display 31 and a display apparatus 32 controlled by the apparatus for controlling display 31 such as a CRT, a liquid crystal display, a printer and a plotter. The region of comfortable vision can be displayed based on the data of the region of comfortable vision output from the Abbe number simulator Among the apparatuses connected to the Abbe number simulator the apparatus for measuring the Abbe number 13 derives the Abbe number which is the reverse of a dispersive power. When the e-ray is used as the reference, the Abbe number v e can be obtained in accordance with the following equation: ve (ne- (1) In the above equation, v e represents the refractive index of a medium 6 with respect to the e-ray n

F

p represents the refractive index of the medium with respect to the F'-ray (Cd) and n

C

represents the refractive index of the medium with respect to the C'-ray (Cd).

The lens meter 14 automatically measures the data of the optical system such as the spherical dioptric power, the cylindrical dioptric power, the angle of the cylindrical axis and the additional dioptric power of a spectacle lens inserted into the optical system for the measurement and outputs the data to the outside.

The frame tracer 15 traces the outline of the held spectacle frame, and automatically derives the data of the lens shape and outputs the data to the outside.

is In the apparatus for evaluating an ocular optical lens described above and shown in Fig. 5, the data of the optical system and the lens shape shown in the following to are successively entered into the Abbe number simulator 20 from the input means 10 and the simulation is conducted.

Abbe number (v) v e represents the Abbe number with respect to the e-ray.

6i) Lens dioptric power C, Ax, Px, Py and ADD) S represents the spherical dioptric power, C represents the cylindrical power, Ax represents the angle of the cylindrical axis, Px represents the prism dioptric power in the vertical direction and ADD represents the additional dioptric power.

(iii) Lens shape The lens shape provides the data for the outline of the spectacle -7frame.

(iv) Layout of lens shape (IN/OUT and UP/DOWN) The layout of the lens shape is the displacement between the geometrical center and the optical center of the lens shape.

IN/OUT represents the displacement in the direction of the Xaxis. UP/DOWN represents the displacement in the direction of the Y-axis.

Value of vision acuity The value of vision acuity indicates the condition of vision. In the use of spectacle lenses, it is recommended that a vision acuity of 0.7 or greater is obtained.

The Abbe number simulator 20 externally takes various data of the optical system from the apparatus for measuring the Abbe number 13, the lens meter 14 and the frame tracer 15 described above via communication cables 16. The data can be modified on the screen of a display operated by a simulation program which will be described later. For the manual input, the data of the optical system are entered into the Abbe number simulator via a manual input means such as a keyboard 12.

The Abbe number simulator 20 performs the operation of simulation which will be described later and data of the region of comfortable vision on the lens and (ii) data of the image of actual vision are obtained.

The data obtained as indicated above are transferred to the output means 30 from the Abbe number simulator 20. The apparatus for controlling the display 31 which is a part of the output means 30 displays (i) the region of comfortable vision on the lens and (ii) the image of actual vision on the screen of the display apparatus 32. The image of actual vision 8 displayed on the screen of the display apparatus 32 is an image containing the effect of the chromatic aberration actually formed. The region of comfortable vision is an image created in a manner such that the center of the image is placed at the optical center. The image of actual vision is a retinal image obtained as follows: using data of the optical system at a plurality of wavelengths which are set in advance, monochromatic retinal images at the plurality of wavelengths are formed from data of an original image and then the retinal image is synthesized from the obtained monochromatic retinal images. The image of actual vision is already known.

The method for obtaining the region of comfortable vision will be described in the following.

The Abbe number and the chromatic aberration used in the calculation by the Abbe number simulator 20 will be described in the following.

A. Abbe number and chromatic difference in the angle of deviation To calculate the refractive index n(k) at an arbitrary wavelength X from the refractive index ne with respect to the e-ray and the Abbe number ve, the following equation l+(ne- (2) is used.

In the above equation, A(X) -1.4955487241077+0.0885672084113 2 +0.3649396625563/(X 2 -0.035)+0.005720016 1544/(X 2 -0.035) 2 B(X) 0.0008271206802-0.0070364882344 2 9 +0.0011576188189/(2-0.035)-0.0002166266192(k 2 -0.035) 2 (3) Since the Abbe number is defined as: Ve (ne- (4) the following relations hold: 1 The angle of deviation of a ray by the prism having the angle of i shown in Fig. 6 is: 1}i (ne- 1)i{l+BO)+A(X)/ve} (6) The difference in the angle of deviation between the F'-ray and the C'-ray is expressed as: (0.01P)/ve (7) B. Chromatic difference in angle of deviation and visual acuity When the chromatic difference in the angle of deviation A5 derived in accordance with the equation increases, blur in the color increases and the visual acuity decreases. The empirical equation describing the relation between the chromatic difference in the angle of deviation A5 and the value 10 of visual acuity Va is as follows: Va 0.001389/A8 0.1389ve/P (8) wherein P: the prism diopter.

For example, to obtain a value of visual acuity of 0.7 or greater, the prism diopter P which is the unit used for expressing the ability of the prism in the direction of polarized light is in the range of: P S 0.1389ve/0.7 0.19844ve (9) When the lens dioptric power D is decided, the following relation is obtained: 0.19844ve In the above equation, h represents the radius of the circle of the region of comfortable vision in which a value of visual acuity of 0.7 or greater can be surely obtained. Therefore, the radius h of the circle placed within the range of the lens shape and having the center placed at the optical center is: h 1.9844 v e /lIDI (11) When specific values are input into the above equation, the following results can be obtained.

When the radius of the region of the lens in which a value of visual acuity of 0.7 or greater can be surely obtained is as follows: 11 When ve 58, 19.2 mm or 4 38.4 When ve 42, 13.9 mm or 27.8 When v e 38, 12.6 mm or 25.2 When ve 31, 10.2 mm or 20.4 The above simulation program used by the Abbe number simulator is memorized in a medium. As the medium for memorizing the program, for example, a flexible disk, a CD-ROM or a memory card can be used. The program memorized in the medium is installed into a memory apparatus disposed in the Abbe number simulator 20 such as a hard disk apparatus.

By running the program, the decrease in the visibility due to the chromatic aberration is calculated at each point on a spectacle lens. The region of comfortable vision is obtained based on the result. The difference in the visibility due to the difference in the Abbe number of the spectacle lens is evaluated based on the area of the region of comfortable vision. The program contributes to the construction of the above apparatus for evaluation of an ocular optical lens in the manner described above.

Fig. 1 shows an example of the region of comfortable vision displayed on the screen of a display apparatus based on output data from the Abbe number simulator 20. Two regions of comfortable vision corresponding to two different Abbe numbers are displayed and compared on a single screen.

This shows just an example and the display can be changed in various manners.

As shown in Fig. 1, a START button 51 is shown on the screen When this button is clicked, the Abbe number simulator is connected to the apparatus for measuring the Abbe number 13, the lens meter 14 and the frame tracer 15. The data of the optical system of a spectacle lens are entered into the Abbe number simulator via these apparatuses and the 12 entered data are displayed on the data display windows 61 to 67.

In the Previous_Abbe window 61, the Abbe number before change is displayed for comparison with the Abbe number after change. In the Recent_Abbe window 62, the Abbe number after change is displayed.

In the Sph window 63, the spherical dioptric power is displayed. In the Cyl window 64, the cylindrical dioptric power is displayed. In the Ax window 65, the angle of cylindrical axis is displayed. In the Dx window 66, the X value of the prism characteristics is displayed. In Dy window 67, the Y value of the prism characteristics is displayed. In the example shown in Fig. 1, the value in the Cyl window is zero and astigmatism is absent. The values in the Dx window 66 and the Dy window 67 are both zero and the spectacle lens has no correction in the values of the prism characteristics.

The Abbe numbers which are compared are 44.0 and 31.0 and the difference in the Abbe number is relatively great, 13.0.

To fix the data entered into the Abbe number simulator 20 and displayed in the windows 61 to 67, a SET button 53 is clicked. To clear these data, a CLEAR button 54 is clicked. When the data are manually input, the data are input directly into the data display windows 61 to 67 without clicking the START button 51 and then the SET button 53 is clicked.

When the data are fixed, the calculation of simulation is conducted based on the Abbe number set at first. In this case, the value of visual acuity was set at 0.7. Based on the result of the calculation, the Snellen's E marks which are images of actual vision 72 are displayed with blur in the outlines in the right portion B of the left area of the screen. The images of actual vision 72 are retinal images synthesized from images of the F-ray, the e-ray and the C-ray. As shown in the figure, the positions of the retinal images of the F-ray (blue), the e-ray (yellowish green) and the C-ray (red) 13 are displaced from each other. The displacement between the colors depends on the Abbe number. Therefore, when spectacle lenses having different Abbe numbers are used, the displacement between colors due to the chromatic aberration becomes different.

In correspondence to the image of actual vision 72 described above, the region of comfortable vision 82 obtained by the Abbe number simulator is displayed in the right area of the screen as the area of the region marked out with and contained in a circle, an ellipse or a dlosed curve whose center is placed at the optical center 0 of an image of a shape of a spectadle frame In other words, the Abbe number is recognized not as blur or density but as the area of the region marked out with and contained in the circle, the ellipse or the closed curve whose center is at the optical center 0. The closed curve corresponds to the case in which the spectacle lens is constituted with is a progressive multifocal lens.

It is also possible that at least one of the Abbe number, the value of visual acuity, the spherical dioptric power, the cylindrical dioptric power, the angle of cylindrical axis, the additional dioptric power and the values of IN/OUT and UP/DOWN of the region of comfortable vision 82 on the spectacle lens for the person wearing the spectacle lens, which are displayed in the right area of the screen, is changed and the change in the region 82 due to the above change is simulated. It is also possible that desired values of the Abbe number, the value of visual acuity, the spherical dioptric power, the cylindrical dioptric power, the angle of cylindrical axis, the additional dioptric power and the values of IN/OUT and UP/DOWN are entered.

As described above, regions of comfortable vision 82 based on various data can be displayed. It is possible that a region of comfortable Vision 81 based on a specific Abbe number is memorized as the reference and this region as the reference and a region of comfortable vision 82 based on 14 another Abbe number set afterwards are displayed on the same screen and compared with each other. When a single region of comfortable vision is displayed, the evaluation of the performance of a spectacle lens can be made easily. When a plurality of regions of comfortable visions are displayed and compared, a more excellent spectacle lens can be found easily among spectacle lenses which are based on different specifications. When the GET_IMAGE button 52 is clicked, the Abbe number and the image of actual vision of the Snelen's E mark 72 which are displayed on the right portion B of the left area are saved and transferred to the left portion A of the left area of the screen. The region of comfortable vision 81 remains in the right area 81. When the GET_IMAGE button 52 is not clicked, the data in the Recent_Abbe window 61, the image of actual vision 72 and the image of the region of comfortable vision 82 are overwritten by new data and a new image and updated every time the new data are set.

When the image of actual vision 71 based on the Abbe number displayed on the Previous_Abbe window 61 is saved and then a new Abbe number is set in the RecentAbbe window 62, an image of actual vision 72 based on the new Abbe number is displayed in the right portion B of the left area of the screen. In the right area C of the screen, a Recent region of comfortable vision 82 is displayed as an image overlapping the Previous region of comfortable vision 81. Therefore, the images of actual vision 71 and 72 based on the above Abbe numbers are displayed simultaneously with the regions of comfortable vision 81 and 82. The displayed image of actual vision 72 is transferred from the present portion B to the adjacent portion A for comparison and a plurality of images of actual vision are displayed in this portion so that the images of actual vision can be compared also with the image of actual vision 72 which will be displayed afterwards.

The regions of comfortable vision 81 and 82 are displayed in the region surrounded by the image of the shape of the spectacle frame 80 as 15 two concentric circles 81a and 82a corresponding to two different Abbe numbers. The centers of the concentric circles 81a and 82a are placed at the center of the spectacle frame in the examples shown in Fig. 1 for convenience. However, the center of the concentric circles is actually placed at the optical center. The difference between the two images of actual vision 71 and 72 which are based on different Abbe numbers and displayed in the portions A and B of the left area of the screen cannot be visually recognized.

In contrast, the difference between the two regions of comfortable vision 81 and 82 which are based on different Abbe numbers and displayed in the right area of the screen is expressed as the difference in the area of the region and can be easily recognized. In the figure, the two concentric circles 81a and 82a are shown by using a full line and a broken line, respectively, for convenience. It is preferable in the actual operation that the two circles are distinguished from each other by using different colors. For example, when the Previous_Abbe window 61 and the Recent_Abbe window 62 have red color and blue color, respectively, and the two circles 81a and 82a have red color and blue color, respectively, in correspondence to the colors of the windows, the comparison can be understood easily and the difference in the visibility depending on the difference in the Abbe number of the spectacle lens can be evaluated or understood easily.

In Fig. 1 described above, spectacle lenses having Abbe numbers relatively greatly different from each other are compared. In Fig. 2, spectacle lenses having Abbe numbers closer to each other, 39.0 and 31.0, the difference being 8.0, are compared. In Fig. 3, spectacle lenses having Abbe numbers further closer to each other, 36.0 and 33.0, the difference being 3.0, are compared. As shown in the displays of these figures, by displaying the region of comfortable vision in which a specific visual acuity is surely obtained, which is based on the Abbe number, as the area of a circle, an ellipse or a closed curve as shown in the embodiments of the present invention, clear visual display of the difference in the vision due to 16 the difference in the Abbe number is successfully achieved even when the difference in the Abbe number is small.

As described above, in accordance with the embodiments of the s present invention, the difference in the vision of an image due to the difference in the Abbe number is displayed not by the simulation of a retinal image containing chromatic aberration in the actual use of a spectacle lens but by the simulation expressed as the area of the region of comfortable vision in which the specific visual acuity is surely obtained within the image of the shape of the spectacle frame. Therefore, the difference in the Abbe number can be directly and clearly recognized visually from the difference in the area of the region. As a result, the difference in the Abbe number of spectacle lenses can easily be understood by a person wearing the spectacle lens and the difference in the performance of the spectacle lens can be recognized easily. Moreover, since the regions of comfortable vision before and after a change in the data of an optical system of a spectacle lens such as the Abbe number can be displayed as overlapping images on the same screen, the difference in the vision due to the difference in the Abbe number can be easily examined based on the comparison. As a result, the Abbe number which is not easily understood by a person wearing the spectacle lens heretofore can be understood more easily.

Since the center of the circle, the ellipse or the closed curve forming the outline of the region of comfortable vision is placed at the optical center of the spectacle lens, not only the area of the region of comfortable vision but also the range of the region in which the specific value of visual acuity is surely obtained in the spectacle lens can be easily understood. It has been difficult that the difference in the Abbe number between spectacle lenses based on different specifications is understood by a person wearing the spectacle lens. In accordance with the present invention, this difference can 17 be clearly shown and demonstrated and the difference in the performance can be easily recognized.

In the embodiments of the present invention described above, the region of comfortable vision in which a specific value of visual acuity can be surely obtained is created for one spectacle lens based on the Abbe number at each point of the spectacle lens. Then, the region of comfortable vision corresponding to the above value of visual acuity is created for another spectacle lens and the two regions are displayed in the same screen and compared. In another manner, a point may be selected arbitrarily inside the lens shape. Based on the prism characteristics of the selected point, a visual region may be created for one spectacle lens so that a specific value of visual acuity can be surely obtained at the selected point. Thereafter, an equivalent visual region of another spectacle lens corresponding to the value of visual acuity may be created and the two visual regions are displayed in the same screen and compared. In the case, it is preferable that an image of actual vision at the selected point is created and the image of actual vision is displayed in the same screen so that the image can be compared with the equivalent visual region.

In the results of simulation described above, the lateral chromatic aberration in magnification alone is considered and the spherical aberration, the coma aberration and the astigmatism are not considered for convenience.

The lateral chromatic aberration in magnification is obtained not in accordance with a rigorous method of ray tracing but in accordance with an approximate equation assuming that the angle of deviation of a ray is proportional to the prism diopter. For the practical purpose, the above approximate method is sufficient since the object of facilitating the understanding of a person wearing a spectacle lens can be achieved.

However, it is also possible that a highly accurate simulation is conducted by considering data of the optical system which are not considered above.

P:\0PERGCP\700MLdiv spe.doc-L6/iJA2 -18- In the above embodiments, the optical system is constructed by using a spectacle lens as the optical lens. The method can be used for selection of a contact lens or an in-eye lens when the optical system is constructed by using a contact lens or an in-eye lens, respectively, as the optical lens and an image is obtained by simulation based on the optical system. It is also possible that a scenery image of a Landolt's ring is used for the above image of vision in place of the Snellen's E marks. Of course, the layout of the display is not limited to those shown in the embodiments and can be changed in various manners as long as the object of the present invention is not adversely affected. The number of images simultaneously shown on the screen is not limited to one or two but may be three or more.

Since the difference of vision due to the difference in the Abbe number is expressed as the area of the region of comfortable vision in which a specific value of visual acuity can be surely obtained, the Abbe number or the difference in the Abbe number which has been difficult to understand easily can be easily understood.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Claims (3)

1. A method for evaluating an ocular optical lens which comprises: arbitrarily selecting a point inside a lens shape of one ocular optical lens and, based on prism characteristics at the selected point, creating an equivalent visual region in which a specific value of visual acuity is surely obtained; creating an equivalent visual region of another ocular optical lens in accordance with a same method; and displaying the two equivalent visual regions on a same screen in a manner such that the regions can be compared.

2. A method for evaluating an ocular optical lens according to claim 1, wherein an image of actual vision at the selected point is created and the image of actual vision and the equivalent visual region are displayed on a same screen in a manner such that the image and the region can be compared.

3. A method for evaluating an ocular optical lens substantially as hereinbefore described with reference to the accompanying drawings and/or Examples. DATED this 27th day of February, 2004 HOYA CORPORATION By its Patent Attorneys DAVIES COLLISON CAVE