JP4846985B2 - Optical characteristic interpolation method, spectacle wearing simulation image processing method, spectacle wearing simulation image processing apparatus, spectacle lens evaluation method, spectacle lens evaluation apparatus - Google Patents

Description

The present invention relates to a data interpolation method in measurement of optical characteristics, simulation, and the like, and more particularly to an interpolation method for astigmatism and average power error. The present invention also relates to a simulation image processing apparatus and an image processing method for allowing a prescriber to experience a state of wearing a spectacle lens in a simulated manner, and further to a performance evaluation method and a performance evaluation apparatus for the spectacle lens.

  In recent years, as the optical performance required for spectacle lenses increases, improvement in the accuracy of evaluation of the optical performance has become one of the important issues. In order to realize high-accuracy evaluation of optical performance, it is necessary to measure or simulate the optical characteristics (mainly astigmatism and average power error) of the spectacle lens under various usage conditions.

  There are various usage conditions that should be considered when evaluating the optical performance of the spectacle lens, and there is mainly a distance to an object viewed through the spectacle lens (hereinafter simply referred to as an object distance). In particular, progressive-power lenses that correct presbyopia can be seen at different distances depending on the part of the lens. That is, the upper part of the lens is used to see a distant object, and the lower part of the lens is used to see a near object. The middle part of the lens is used for viewing an object at a distance between the far and near distances, with the object distance continuously changing as a use condition. The progressive-power lens is designed so as to obtain optimum optical performance at each object distance assuming the use conditions as described above. Therefore, the object distance is very important in the performance evaluation of the progressive power lens. Specifically, the object distance for evaluating the upper part of the lens may be evaluated at infinity. However, the evaluation object distance at the lower part of the lens is about 30 centimeters at hand, and the evaluation is performed assuming that the object distance continuously changes from infinity to about 30 centimeters at the middle part from the center to the lower part of the lens. There is a need to do.

  A lens meter is generally used as an apparatus for measuring the optical characteristics of an actual spectacle lens. When the lens to be examined is a single focal point, the lens meter measures the optical characteristics of the lens to be examined by measuring or calculating the light collection position when the light beam is incident from infinity. On the other hand, when the test lens is a progressive power lens as described above, it is necessary to measure optical characteristics at a finite distance in order to satisfy the actual use conditions as described above. Examples of the method for measuring optical characteristics at a finite distance include Japanese Patent Laid-Open Nos. 11-125580 and 11-125582 proposed by the present applicant.

  Each gazette discloses a lens meter that can constitute an optical system having a finite object distance by providing a detachable attachment lens. Such a lens meter is referred to as a variable object distance lens meter in the following text.

When measuring a progressive-power lens using the above variable object distance lens meter, it is necessary to replace the attachment lens according to the part of the lens and measure while changing the evaluation object distance. Further, when it is desired to change the object distance and the evaluation portion of the lens, for example, when it is desired to narrow the intermediate area, the measurement and evaluation must be performed again while exchanging the attachment lens with the variable object distance lens meter. As described above, the conventional lens meter has a problem in that it takes time and labor to measure the optical characteristics of the progressive power lens under observation conditions in accordance with actual use conditions.

  In addition, in recent years, the prescription person wears spectacles to acquire information necessary for performing tailor-made medical care in spectacle prescription or to provide information necessary for medical care as an informed consent to the prescriber. There is an urgent need for the development of a spectacle wearing simulation device that simulates what the appearance looks like. In order to obtain or provide more accurate information, it is indispensable to accurately calculate the optical characteristics necessary for the simulation. However, a great deal of labor is required to perform the above-described precise calculation process assuming various changes in use conditions.

  In general, in a spectacle wearing simulation apparatus, a simulation image that is observed when wearing spectacles to be simulated (that is, spectacles that a subject will wear in the future) is created. By observing the simulation image, the subject can experience the visual field when wearing glasses in the future. For this reason, it is desirable that the image be reproduced as faithfully as possible with respect to the blur caused by the aberration of the eyeglass lens to be simulated. In other words, in the simulation of spectacle lenses, particularly progressive-power lenses, the problem of obtaining a high-quality simulation image that satisfies the user's conditions such as prescription power and fitting state (positional relationship between the eye and the lens) is the lens blur. It is synonymous with the problem of how accurately the change to the object distance can be expressed. In order to solve this problem, it is indispensable to obtain a change in optical characteristics in accordance with a change in object distance at each part of the lens with high accuracy and in a short time.

  In order to reproduce blur with optically high accuracy at the time of simulation execution, conventionally, it is necessary to go through the following processing. First, at a specific pixel of the input original image without blur, a ray emitted from an object and incident on the pupil via a spectacle lens (glasses optical system) is traced. Then, a spot diagram on the imaging plane is obtained based on the result of the ray tracing. Next, a point spread function (PSF) is acquired from the spot diagram density on the imaging plane, that is, the retina. Furthermore, the luminance distribution on the retina is acquired by performing a convolution calculation between the acquired PSF and the luminance of the object. The above processing is performed for all pixels of the input original image.

In order to perform the series of processes as described above for all pixels, a large number of numerical operations are required. That is, it is almost impossible to acquire a simulation image within a realistic time that does not give a psychological burden to the prescriber or the operator. There is also a problem that the cost of hardware required for smoothly processing the series of processes is very high. Therefore, as some solutions, attempts have been made to obtain the PSF more simply by approximating it to a specific function. Such a PSF acquisition method is disclosed in, for example, Patent Document 1 and Patent Document 2 below.
JP 2000-29377 A JP 2000-107129 A

  In Patent Document 1, the PSF is approximated as a uniform function spreading in an elliptical shape. Then, the astigmatism of the target spectacle lens, the average power error, and the adjustment force assumed to be necessary for the prescriber are used to determine the spread of the ellipse. However, this document hardly takes into consideration that astigmatism and average power error vary depending on the object distance.

  In Patent Document 2, it is assumed that the PSF is a two-dimensional Gaussian distribution function. Then, a predetermined evaluation amount that does not require many times of ray tracing is adopted as a parameter of the Gaussian distribution, and a semi-empirical parameter is introduced. Thus, the Gaussian distribution function is approximated to the PSF distribution actually obtained from the spot diagram. Patent Document 2 discloses a method of interpolating the predetermined evaluation amount with respect to the object distance by a cubic spline interpolation method when the use condition of the spectacle lens changes, specifically, when the object distance changes. Adopted. However, it is completely unknown whether the predetermined evaluation amount has a property suitable for interpolation by a cubic spline interpolation method. Therefore, it is not certain whether the interpolation result corresponds to the result obtained when actually measured. Further, since the cubic spline interpolation method is complicated in the first place, further improvement in processing speed has been demanded in recent years.

  In view of the above circumstances, the present invention can quickly calculate an interpolation value closer to an actual measurement value of an optical characteristic for an arbitrary object distance based on optical characteristics for a plurality of object distances actually measured by a measuring device, a simulation, or the like. It is an object of the present invention to provide an optical characteristic interpolation method that can be easily acquired by the method, a spectacle wearing simulation image processing method and a lens evaluation method using the interpolation method, and a device for realizing each method.

In view of the above problems, the optical property interpolation method according to the present invention is based on optical properties observed for at least two object distances from a measuring device, simulation, etc., and optical properties for an arbitrary object distance. The interpolation value closer to the actual measurement value can be acquired.

First, the optical characteristics interpolated by the present invention will be described using the optical system shown in FIG. In FIG. 14, the distance from the rear surface vertex P1 of the spectacle lens L to the paraxial imaging point P2 is defined as a back focus fB. The length of the straight line connecting the eyeball rotation point C, which is the center of eye rotation, and the lens rear surface vertex P1 is the radius, and the spherical surface centered on the eyeball rotation point C is called the vertex spherical surface, of which the half surface on the rear vertex side Is the final surface Se of the optical system. The distance from the final surface Se to the imaging point on the maximum refractive power section of the spectacle lens 51 is Lm (unit: millimeter), and the distance from the final surface Se to the imaging point on the minimum refractive power section of the spectacle lens L is Ls (unit). : Millimeter), the average power error AP (unit: diopter) can be defined by the following equation (5).

  The present applicant paid attention to the fact that the average power error AP defined by the above equation (5) shows a substantially linear change with respect to the reciprocal of the object distance, as will be described later. Since the average power error has linearity with respect to the reciprocal of the object distance, an interpolation value can be obtained for a given object distance using a simple interpolation method such as a linear interpolation method.

The astigmatism magnitude AS (unit: diopter) can be defined by the following equation (6).

  Here, the astigmatism magnitude AS generally shows a non-linear change with respect to both the object distance and its reciprocal. However, according to the present invention, the interpolation value is obtained by a simple linear interpolation method or the like in the same manner as the average power error AP by following the procedure shown below.

The astigmatism interpolation method according to the present invention calculates the sum (difference) of astigmatism using two astigmatism magnitudes and azimuth angles twice astigmatism azimuth angles. Apply the principle that it can be handled as a vector composition operation. Hereinafter, a vector corresponding to the astigmatism component is referred to as an astigmatism basis vector. Specifically, the following processing is performed when astigmatism is interpolated. First, astigmatism is calculated by measuring or simulating the magnitude and azimuth of astigmatism at at least two object distances (calculation processing). Next, the calculated astigmatism is decomposed into two astigmatism components having different azimuth angles (decomposition processing) using the above two vector combining operation. Next, interpolation is performed for each component based on the value for the object distance between at least two locations (interpolation processing). Then, using the synthesis operation, the interpolated components are synthesized to obtain an astigmatism interpolation value (synthesis process).

  In the decomposition process, the astigmatism is decomposed into two astigmatism components whose azimuth angle difference is not an integral multiple of 90 °. The difference in the azimuth angle of the astigmatism component is an integral multiple of 90 °, which means that the difference in the azimuth angle of the corresponding astigmatism basis vector is a multiple of 180 °, that is, the two astigmatism basis vectors are Means primary dependency. Therefore, astigmatism cannot be decomposed into two astigmatism basis vectors (that is, two astigmatism components having different azimuth angles). By setting the difference between the azimuth angles of two astigmatisms not to be a multiple of 90 °, that is, the astigmatism basis vectors are linearly independent from each other, any astigmatism can be converted into two components having different azimuth angles. Can be broken down into

Furthermore, if the difference in azimuth between the two astigmatism components is 45 °, the corresponding two astigmatism basis vectors are orthogonal, so that the decomposition process is simplified. In particular, it is desirable to decompose into an astigmatism component with an azimuth angle of 0 ° and an astigmatism component with a 45 ° angle. According to this invention, the two astigmatism basis vectors corresponding to the astigmatism component having an azimuth angle of 0 ° and the astigmatism component of 45 ° are the basis vectors of 0 ° and 90 ° with respect to the coordinate axis, that is, Since the unit vector (1, 0) in the X-axis direction and the unit vector (0, 1) in the Y-axis direction are used, calculation for obtaining the size of each component becomes easy.

Here, a plurality of (i places, where i = 1 to n, the same shall apply hereinafter) object distances di, for example, if there are two object distances, measured values of astigmatism magnitudes for d1 and d2 are obtained. The measured value of ASi and azimuth is AXi. When the astigmatism obtained by the calculation process is decomposed into astigmatism components having azimuth angles of 0 ° and 45 °, the astigmatism component size Asix having an azimuth angle of 0 ° and an azimuth angle of 45 ° The astigmatism component magnitude ASy is expressed by the following equations (1) and (2), respectively.

When astigmatism is obtained for an arbitrary object distance d, the following is performed. First, the interpolated values ~ ASx (d), ~ ASy (d) are obtained from the above astigmatism component magnitudes ASix and ASyy, and substituted into the following equation (3) to obtain an arbitrary object distance. The astigmatism magnitude AS (d) with respect to d is obtained. Also, the azimuth angle AX (d) of astigmatism with respect to an arbitrary object distance d can be obtained by substituting the interpolated values ˜ASx (d), ˜ASy (d) into the following equation (4).

  The above expressions (3) and (4) are expressions derived from the astigmatism basis vector combining operation with an azimuth angle of 2AX. Further, the applicant of the present invention is that the astigmatism components ASix and ASyy defined by the above formulas (1) and (2) show a substantially linear change with respect to the reciprocal of the object distance, as will be described later. Pay attention. This means that an astigmatism interpolation value can be obtained with sufficiently high accuracy by a simple linear interpolation method or the like.

In the image processing method used in the spectacle wearing simulation apparatus, when performing simulation, optical performance is evaluated based on the object distance at each pixel on the image with respect to the original input original image. is required. Therefore, according to the spectacle wearing simulation image processing method according to the present invention , the above-described optical characteristic interpolation method may be used for the blur generating means for generating the blur experienced when wearing the spectacle lens.

  The eyeglass-wearing simulation apparatus that uses the above-described optical characteristic interpolation method as the blur generation means firstly has an object distance of at least two points or more at sample points (xli, yli) distributed two-dimensionally on the lattice points of the target lens. The optical characteristics are calculated in advance and stored in the main memory or storage medium. Next, it is determined which part (xl, yl) on the lens each pixel of the original image corresponds to, and from the optical characteristic corresponding to at least two object distances at the sample point, at the position (xl, yl). Interpolate the optical characteristics corresponding to a plurality of object distances, and finally calculate the optical characteristics of the object distance to be actually obtained from the optical characteristic values at the object distances of at least two points by an interpolation method such as a linear interpolation method. Obtained by interpolating distance. Here, as described above, the optical characteristics have very good linearity with respect to the reciprocal of the object distance. Therefore, it is possible to create a simulation image with sufficiently high accuracy by the processing by the linear interpolation method, in other words, a simulation image having substantially the same degree of blur as when it is actually worn.

  As described above, according to the spectacle wearing simulation apparatus and the simulation image processing method according to the present invention, the optical characteristics at an arbitrary object distance can be obtained by actually calculating the optical characteristics of the entire lens range with at least two object distances. It becomes possible to evaluate, and a high-quality and highly accurate simulation image can be obtained. As an interpolation method, in addition to the linear interpolation method, a higher-order interpolation method than the cubic spline method can be used. However, when using a higher-order interpolation method, the object distance for actual calculation is not sufficient in two places, and four or more places are required.

In the lens evaluation method according to the present invention, the light beam from the light source is incident on the test eyeglass lens, and the state of the light beam after passing through the test eyeglass lens is observed by the observation means, so that A lens evaluation method for obtaining characteristics, wherein a conjugate point of a light source or observation means is formed at a finite distance from an eyeglass lens to be examined, and at least two object distances (of which at least one object distance is A step of obtaining optical characteristics of the eyeglass lens to be examined at a finite distance , and a step of calculating optical characteristics of an arbitrary object distance using the optical characteristic interpolation method.

According to the lens evaluation method according to the present invention , the following method can be considered as a solution for avoiding the complexity of measurement in the conventional variable object distance lens meter. First, the entire range of the spectacle lens to be measured is measured under the condition that there is no attachment lens, that is, the object distance is infinite. Next, the entire range of the spectacle lens is measured by inserting an attachment lens having a refractive power that realizes the closest possible object distance. For the evaluation according to the actual use condition of each part of the lens, a value interpolated from the measured values of the two object distances is used. As the interpolation method, the optical characteristic interpolation method described above is used. As a result, by measuring the entire lens range at at least two object distances, it becomes possible to evaluate the optical performance of each part of the lens at an arbitrary object distance.

  As described above, according to the present invention, the optical characteristic for an arbitrary object distance is closer to the actually measured value based on the optical characteristics actually measured for at least two object distances from a measuring device or simulation. Interpolated values can be acquired. In addition, since the present invention utilizes the fact that each optical characteristic has linearity with respect to the reciprocal of the object distance, the interpolation value of the optical characteristic for an arbitrary object distance can be obtained in a simpler and shorter time than the conventional interpolation method. Can be acquired.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a hardware configuration of a spectacle wearing simulation apparatus 100 that uses the spectacle lens optical characteristic interpolation method of the present invention. The spectacle wearing simulation apparatus 100 according to the embodiment shown in FIG. 1 determines what field of view can be obtained when wearing spectacles for correcting presbyopia using a progressive power lens. This is a device for making a simulated purchase experience).

  As shown in FIG. 1, a spectacle wearing simulation apparatus 100 includes a CPU 21 that executes various processes, a program related to processes executed by the CPU 21, and various data generated or input during the processes. (RAM) 22 and a storage device 23 for storing a program executed by the CPU 21. Image processing performed mainly by the CPU 21 will be described in detail later.

  Further, the spectacle wearing simulation apparatus 100 includes a PC monitor 24 and a head mounted display (hereinafter referred to as HMD) 25 that function as an image display apparatus for displaying a simulation image reflecting the optical performance of the spectacle lens to be worn. . The subject sees the simulation image displayed on the PC monitor 24 or the like to experience the visual field when wearing glasses. In addition to the above, the apparatus 100 receives input data (keyboard 26, mouse 27) for appropriately inputting instructions to the CPU 21 that executes various processes, and various data necessary for the spectacle wearing simulation with an external device. Frame buffers 29A and 29B are provided for storing images related to the simulation process and simulation processing results to an image display device such as an input / output interface 28 and a PC monitor 21 for exchange. Each component is connected to each other by a bus SB.

  As described above, in the present embodiment, the storage device 23 stores in advance a program related to processing executed by the CPU 21. However, the program is not necessarily stored in the storage device 23. For example, the program can be supplied from an external storage medium such as a CD-ROM or a DVD-ROM by connecting an information reading device via the input / output interface 28. Further, the program can be supplied from the database by connecting to the database connected online via the Internet or the like.

  FIG. 2 is a block diagram relating to the image processing system 50 mounted on the spectacle wearing simulation apparatus 100. In the image processing system 50, an original image as a base of a simulation image is input via the original image input unit 11 (including the input / output interface 28 in FIG. 1). The original image may be an actual image from a digital camera or the like, or an artificial image created using computer graphics (CG) software or the like. The original image input unit 11 transmits the input original image to the image processing unit 12.

  The parameter input unit 13 is provided to input spectacle lens design parameters desired by the subject. Specifically, the parameter input unit 13 corresponds to the keyboard 26 and the mouse 27 shown in FIG. Examples of design parameters include prescription values such as spherical power, astigmatic power, and astigmatic axis direction. Further, when the progressive power lens wearing is set as a simulation target as in the present embodiment, parameters such as addition power, progressive zone length, usage distance, and the like are further added to the design parameters. The input design parameters are output to the lens data generation unit 14.

  The lens data generation unit 14 generates optical data related to a virtual spectacle lens that the subject intends to wear based on the design parameters. The optical data is, for example, optical information necessary for ray tracing, that is, lens arrangement such as lens refractive index, curvature, lens thickness, and distance between lenses. The generated optical data is transmitted to the image processing unit 12. The lens data generation unit 14 includes the controller 21, the RAM 22, the storage device 23, and the like shown in FIG.

  The image processing unit 12 is an image processing unit that generates a simulation image. Although specifically described later, the image processing unit 12 generates a simulation image using the original image output from the original image input unit 11 and the optical data transmitted from the lens data generation unit 14. The generated simulation image is output to the image display device 16 via the image output unit 15 (corresponding to the frame buffers 29A and 29B shown in FIG. 1). The image display device 16 is the PC monitor 24 or the HMD 25 shown in FIG. By observing the simulation image generated by such a system 50, the subject can experience the field of view when wearing glasses that he will own in the future.

  FIG. 3 is a flowchart showing a flow of a series of image processing performed by the image processing system 50. First, in step S <b> 1, the lens data generation unit 14 reads various design parameters input by the parameter input unit 13. Then, the lens data generation unit 14 designs a virtual lens desired by the subject based on the design parameters, and generates optical data necessary for ray tracing performed in a later step (S3).

  In S5, the original image input unit 11 reads the luminance value B (xo, yo) of the original image OI from an external device such as a personal computer or a digital camera or the built-in memory of the apparatus 100. Further, it is more desirable that the original image OI has distance information in the depth direction. Here, the artificial image created by using CG software or the like can be given the above distance information at the time of creation. Therefore, it is relatively easy to acquire distance information in S5. However, an actual image captured from a digital camera or the like usually does not have distance information. Therefore, when capturing an actual image, it is more desirable to further incorporate a distance information acquisition step of acquiring distance information based on the actual image into S5. Examples of the distance information acquisition process include a method of preparing real images taken from a plurality of viewpoints in advance and acquiring distance information using a stereo matching method or the like.

  In S7, the image processing unit 12 performs ray tracing using the optical data of the virtual lens obtained in S3, and evaluates the optical characteristics of the lens at a plurality of object distances. The part to be evaluated in the virtual lens is not the whole part of the lens corresponding to the object point, but only the sample point. This reduces the burden on the calculation process. At this time, it is desirable that at least one point of the object distance to be set is infinity. The evaluated optical characteristic data is stored on the RAM 22 as an optical characteristic table OT.

  Then, the image processing unit 12 performs image processing for obtaining a simulation image corresponding to the field of view when viewed through the virtual lens, using the data obtained by the above steps (S9). Details of this processing will be described later with reference to FIG.

  The simulation image generated by the image processing in S9 is output to the image display device 16 via the image output unit 15. Note that it is also possible to generate a simulation video image of the target virtual lens eyeglass optical system by preparing a large number of input original images and performing the above-described series of processing on all input original images.

  Next, the image processing (S9 in FIG. 3) performed by the image processing unit 12 will be described in detail with reference to FIG. First, in S <b> 11, the image processing unit 12 secures a work area on the RAM 22 for generating an output destination image (that is, a simulation image) SI. Next, the image processing unit 12 determines whether image processing has been performed for all the pixels of the simulation image SI (S13). If it is determined in S13 that the processing has been completed for all pixels, the image processing unit 12 ends the image processing in S9. If it is determined in S13 that there is a pixel that has not been subjected to image processing, the process proceeds to S15.

  The image processing unit 12 predefines the positions of the original image OI, the output image SI, and the lens part by two coordinates X and Y orthogonal to each other. First, in S15, the position (xl, yl) on the lens corresponding to the position (xs, ys) of the output image SI to be processed, the original image position (xo, yo), and the object distance do are obtained. Next, in S16, optical characteristics for a plurality of object distances at positions (xl, yl) on the lens are obtained by interpolation from the optical characteristics table OT. Next, in S17, the optical characteristics for a plurality of object distances are interpolated in the d direction to obtain the optical characteristics for the object distance do. A specific interpolation processing method in S17 will be described later.

  In the interpolation processing method of this embodiment in S17, the inverse of the object distance is taken and the linear interpolation method is used. However, the optical characteristic interpolation method according to the present invention may use a higher-order spline interpolation method. it can. However, when the linear interpolation method is used, two actual measurement values are sufficient, but when the higher-order spline interpolation method is used, four or more actual measurement values are required. Therefore, if the linear interpolation method is used, less actual measurement values are required, so that it is possible to reduce the time and labor required for simulation image generation including interpolation processing. Further, when the spline interpolation method is used, since there are many actual measurement values used for interpolation, a more accurate interpolation result can be obtained.

  In S19, a point spread function PSF approximated based on the optical characteristics obtained in S17 is obtained. Next, in S21, the range of the original image OI contributing to the position (xs, ys) of the output image SI is obtained from the approximate PSF, and the luminance value B (xo, yo) of the original image in the contributing range is used as a weight. The luminance value B ′ (xs, ys) of the output image SI is updated with the value added by applying the PSF. Subsequently, the next pixel is set (S23), and the processing from S13 is repeated. By executing the above processing, it is possible to generate a simulation image that reproduces the blur of the target spectacle lens.

  Here, the interpolation method of the optical characteristics of the progressive-power lens performed in S17 will be described. The progressive-power lens assumed in the following description has a refractive power of 1.67, a progressive zone length of 14 mm, a spherical refractive power of 4.00 diopter, and an addition refractive power of 2.00 diopter. 5A to 5F are contour graphs showing the average power error of the progressive-power lens and the distribution of astigmatism magnitudes based on the actual measurement results, respectively. In the order of FIG. 5A to FIG. 5F, each graph shows the case where the object distance is infinity, −1000 mm, −500 mm, −333 mm, −250 mm, and −200 mm. As can be seen from each graph, the distribution of the optical characteristics such as the average power error and astigmatism both change greatly with respect to the object distance.

  FIG. 6 is a graph showing the relationship between the average power error AP of the progressive-power lens and the reciprocal Do (unit: diopter) of the object distance. In FIG. 6, the vertical axis represents the average power error AP, and the horizontal axis represents the reciprocal Do of the object distance. The white circles in FIG. 6 are plots of measured values of the average power error of the pixel located at the point (20, -10) in the XY coordinates with the optical center as the origin in each graph shown in FIG. It is.

  The line in FIG. 6 is obtained by connecting a value when Do = 0 (object distance infinite) and a value when Do = −5 (object distance−200 mm) with a straight line. The origin of the graph is based on the front surface (first surface) of the spectacle lens, and the sign of the object distance is negative for the front (object side) with respect to the spectacle lens and positive for the face side with respect to the spectacle lens. . The method of determining these codes is the same for all graphs shown below. As is apparent from the graph shown in FIG. 6, the measured value of the average power error at other object distances is also almost on the straight line, that is, has a very good linearity. That is, according to the graph shown in FIG. 6, it can be seen that the average power error can be obtained as an interpolation value for an arbitrary object distance with sufficient accuracy by the linear interpolation method.

  The above is the description regarding the interpolation method of the average power error AP. Next, an astigmatism interpolation method will be described. FIG. 7 is a graph showing the relationship between the astigmatism AS of the progressive-power lens and the inverse Do of the object distance. In FIG. 7, the vertical axis represents astigmatism AS, and the horizontal axis represents the reciprocal Do of the object distance. Also, the white circles in FIG. 7 are plots of measured values of astigmatism of the pixel located at the point (20, −10) in the XY coordinates with the optical center as the origin in each graph shown in FIG. It is. As indicated by the white circles shown in the graph of FIG. 7, the astigmatism is not linear with respect to the reciprocal Do of the object distance, unlike the average power error. Therefore, in the present embodiment, when calculating the sum (difference) of astigmatism, the astigmatism has two astigmatism magnitudes and azimuths twice astigmatism azimuth angles. Astigmatism is interpolated using the principle that it can be handled as a vector combining operation.

  Specifically, first, the measured astigmatism (for example, the value of the place where Do = 0 (object distance infinite) and the value of the place where Do = −5 (object distance−200 mm)) are different in azimuth. Decomposes into two astigmatism components. Component decomposition is performed by making astigmatism basis vectors corresponding to two astigmatism components linearly independent from each other, that is, by making the difference in azimuth angle of each component not an integer multiple of 90 °. Realized. In this embodiment, the actually measured astigmatism is decomposed into two astigmatism components having azimuth angles of 0 ° and 45 °, respectively.

When the actually measured astigmatism is decomposed into two astigmatism components having azimuth angles of 0 ° and 45 °, the object distance at i points (where i = 1 to n, the same applies hereinafter). Assume that the measured value of the astigmatism magnitude with respect to di is ASi, and the measured value of the azimuth is AXi. When the astigmatism obtained by the calculation process is decomposed into astigmatism components having azimuth angles of 0 ° and 45 °, the astigmatism component size Asix having an azimuth angle of 0 ° and an azimuth angle of 45 ° The astigmatism component magnitude ASy is expressed by the following equations (1) and (2), respectively. In this embodiment, since the astigmatism is measured at two locations, where Do = 0 (object distance infinite) and Do = −5 (object distance−200 mm), i is 1 or 2.

  FIG. 8 is a graph showing the relationship between the astigmatism component size ASix having an azimuth angle of 0 ° and the reciprocal Do of the object distance. FIG. 9 is a graph showing the relationship between the astigmatism component magnitude Asiy having an azimuth angle of 45 ° and the reciprocal Do of the object distance. In each graph, the vertical axis represents the astigmatism component size Asix or ASiy, and the horizontal axis represents the reciprocal Do of the object distance. In addition, the white circles in each graph plot the values calculated by the above formulas (1) and (2). The lines in FIGS. 8 and 9 are obtained by connecting the value when Do = 0 (object distance infinite) and the value when Do = −5 (object distance−200 mm) with a straight line.

  As shown in FIG. 8 and FIG. 9, it can be seen that the calculated value of the astigmatism component at other object distances is also almost on the straight line, that is, has a very good linearity. . That is, according to the graphs shown in FIG. 8 and FIG. 9, it can be seen that each astigmatism component can be obtained an interpolation value for an arbitrary object distance with sufficient accuracy by the linear interpolation method.

Based on the above relationship between the astigmatism component and the reciprocal of the object distance, astigmatism for an arbitrary object distance d is obtained as follows. First, the interpolated values ~ ASx (d) and ~ ASy (d) are obtained from the astigmatism component magnitudes ASix and ASyy (see FIGS. 8 and 9) (where d is an arbitrary object distance). By substituting into the following equation (3), the magnitude of astigmatism ~ AS (d) with respect to an arbitrary object distance d is obtained. Also, the azimuth angle AX (d) of astigmatism with respect to an arbitrary object distance d is obtained by substituting the interpolated values ˜ASx (d), ˜ASy (d) into the following equation (4). Here, arctan is not a main value of −π / 2 to + π / 2, but an appropriate value from all quadrants (−π to + π) in consideration of the signs of ~ ASx (d) and ~ ASy (d). I need to take it.

  By the above processing, astigmatism interpolation of the progressive power lens is realized. Regarding the interpolation result obtained by the above processing, the magnitude of astigmatism is expressed as a curve shown in the graph of FIG. Further, the interpolation result of the azimuth angle of the astigmatism is expressed as a curve shown in the graph of FIG. Thus, astigmatism is divided into astigmatism components having linearity with respect to the reciprocal Do of the object distance and interpolated, so that the astigmatism itself is linear with respect to the reciprocal Do of the object distance. In spite of not having the ability, interpolation can be performed simply and with high accuracy in the same manner as the above average frequency error.

  The above is the embodiment of the present invention. Note that the optical characteristic interpolation method according to the present invention can be used in devices other than the above-mentioned spectacle wearing simulation device 100. The evaluation results when the optical property interpolation method according to the present invention is used in a variable object distance lens meter will be described below. In the following description, the progressive addition lens to be evaluated by the variable object distance lens meter is the same as that assumed in the above-described spectacle wearing simulation apparatus.

  FIG. 11A is a graph obtained by plotting the average power error of the progressive addition lens with respect to the rotation angle (unit: degree) of the eyeball when the object distance is infinite (Do = 0) using a variable object distance lens meter. FIG. 11B is a graph in which the astigmatism magnitude of the progressive addition lens is plotted against the rotation angle of the eyeball when the object distance is infinite using a variable object distance lens meter. The axes Vx and Vy of the graphs shown in FIG. 11A and FIG. 11B represent the eyeball rotation angles in the horizontal direction and the vertical direction, respectively. The same applies to FIGS. 12 and 13 shown below. From the graphs shown in FIGS. 11A and 11B, it can be seen that both the average power error and the magnitude of astigmatism are good in the upper part of the lens, but the performance deterioration becomes severe from the center of the lens to the lower part. I understand. This is conspicuous in the lower part of the lens, particularly in the peripheral part of the lens, because the observation condition with an infinite object distance is not originally assumed in the peripheral part of the lens.

  FIG. 12A is a graph obtained by plotting the average power error of the progressive power lens with respect to the rotation angle of the eyeball when the object distance is −200 mm (Do = −5) using a variable object distance lens meter. FIG. 12B is a graph in which the magnitude of astigmatism of the progressive power lens when the object distance is −200 mm using a variable object distance lens meter is plotted with respect to the rotation angle of the eyeball. It can be seen that neither the average power error nor the magnitude of astigmatism is suitable. This result originates from observations at an object distance different from the use conditions assumed at the time of design (for example, the object distance is infinite above the center of the lens and the object distance is approximately −300 mm below). In particular, since the object distance is assumed to be infinite at the time of designing, the performance at an object distance of −200 mm is considerably deteriorated.

  FIG. 13 is a graph created as a result of performing an interpolation process according to the optical characteristic interpolation method based on the measured values of the average power error and the astigmatism magnitude shown in FIGS. 13A is a graph in which astigmatism is plotted with respect to the eyeball rotation angle, and FIG. 13B is a graph in which the average power error is plotted with respect to the eyeball rotation angle. Each graph shown in FIGS. 13A and 13B reflects optical characteristics corresponding to the object distance assumed in each part of the lens. Specifically, the object distance is set to infinite (0 diopter) above the center of the lens, and the object distance is continuously changed from the lens center toward the bottom. That is, when the eyeball rotation angle Vy in the vertical direction is in the range of 0 <Vy, the object distance is set to be constant at 0 diopter. Further, when Vy <−35, the object distance is set to be constant at −300 mm (−3.333 diopter). Further, when −35 ≦ Vy ≦ 0, the linear change is made within the range of −3.333 ≦ Do ≦ 0.

  As described above, the graphs (FIGS. 13A and 13B) regarding the optical characteristics at the object distance substantially corresponding to the actual use conditions in each part of the progressive addition lens created by using the interpolation method described above are actually This is almost the same as the optical performance obtained as a result of actually measuring all parts of the progressive-power lens.

It is a block diagram showing an example of the hardware constitutions of the spectacles wearing simulator apparatus in embodiment of this invention. It is a block diagram regarding the image processing system mounted in the spectacles wearing simulator apparatus in embodiment of this invention. It is a flowchart which shows the flow of a series of image processing which an image processing system performs. It is a flowchart showing the flow of a process of the image processing process which produces | generates a simulation image. When the object distance is set to infinity (FIG. 5A), −1000 mm (FIG. 5B), −500 mm (FIG. 5C), −333 mm (FIG. 5D), −250 mm (FIG. 5E), and −200 mm (FIG. 5F), It is a contour graph showing the distribution of the average power error and astigmatism magnitude of the progressive power lens based on the actual measurement result. It is a graph showing the relationship between the average power error AP of a progressive-power lens, and the reciprocal number Do of an object distance. It is a graph showing the relationship between the astigmatism AS of a progressive-power lens, and the reciprocal number Do of an object distance. It is a graph showing the relationship between the size ASix of the astigmatism component with an azimuth angle of 0 ° and the reciprocal Do of the object distance. It is a graph showing the relationship between the astigmatism component size Asyy at an azimuth angle of 45 ° and the reciprocal Do of the object distance. It is a graph showing the relationship between the azimuth AX of the astigmatism of a progressive-power lens, and the reciprocal Do of object distance. FIG. 11A is a graph in which the average power error of the progressive addition lens is plotted against the rotation angle of the eyeball when the object distance is infinite using a variable object distance lens meter, and FIG. 11B is the object distance using the variable object distance lens meter. It is the graph which plotted the magnitude | size of the astigmatism of the progressive-power lens in the case of infinity with respect to the rotation angle of the eyeball. FIG. 12A is a graph in which the average power error of the progressive-power lens is plotted against the rotation angle of the eyeball when the object distance is 20 centimeters−200 mm (Do = −5) using a variable object distance lens meter, Is a graph plotting the astigmatism magnitude of the progressive power lens with respect to the rotation angle of the eyeball when the object distance is -200 mm using a variable object distance lens meter. It is the graph produced as a result of performing the interpolation process according to the interpolation method of an optical characteristic based on the measured value of the average power error and the astigmatism magnitude. 13A is a graph in which astigmatism is plotted with respect to the eyeball rotation angle, and FIG. 13B is a graph in which the average power error is plotted with respect to the eyeball rotation angle. It is a figure for demonstrating the astigmatism and average frequency error which are interpolated by this invention.

Explanation of symbols

12 Image processing unit 21 CPU
22 RAM
L spectacle lens 100 spectacle wearing simulation device

Claims (11)

A calculation process for calculating the magnitude and azimuth of astigmatism at at least two object distances;
A decomposition process for decomposing the calculated astigmatism into two astigmatism components whose difference in azimuth is not an integral multiple of 90 °;
Interpolation processing for interpolating between the at least two locations for each astigmatism component;
By combining the astigmatism components interpolated by the interpolation process, a combining process for obtaining an interpolation value for an object distance other than the at least two places of astigmatism;
A method for interpolating optical characteristics of a spectacle lens, comprising: The calculation process further calculates an average power error along the chief ray at the at least two locations,
2. The interpolation process further includes interpolating an average power error at an arbitrary object distance between the at least two locations using a relationship between an average power error calculated by the calculation process and an inverse of the object distance. The optical characteristic interpolation method of the spectacle lens described in 1. The method for interpolating optical characteristics of a spectacle lens according to claim 1 or 2 , wherein, in the decomposition process, the astigmatism is decomposed into two astigmatism components having a difference in azimuth angle of 45 °. The optical characteristic of the spectacle lens according to any one of claims 1 to 3, wherein, in the decomposition process, the astigmatism is decomposed into two astigmatism components having azimuth angles of 0 ° and 45 °. Interpolation method. In the calculation process, the astigmatism calculated at i points (where i = 1 to n, the same applies hereinafter) where the object distance is di is ASi, and its azimuth is AXi.
In the decomposition process, the astigmatism is decomposed into two astigmatism components ASix and ASyy expressed by the following equations (1) and (2):
The composition process uses the astigmatism components interpolated in the interpolation process, ~ ASx (d), ~ ASy (d), to the amount of astigmatism at an arbitrary object distance d using Equation (3). The method for interpolating optical characteristics of a spectacle lens according to any one of claims 1 to 4, wherein the interpolation value ~ AS (d) is calculated.
In the calculation process, the astigmatism calculated at i points (where i = 1 to n, the same applies hereinafter) where the object distance is di is ASi, and its azimuth is AXi.
In the decomposition process, the astigmatism is decomposed into two astigmatism components ASix and ASyy expressed by the following equations (1) and (2):
The composition processing uses the astigmatism components interpolated in the interpolation processing, ~ ASx (d), ~ ASy (d), to the astigmatism azimuth at an arbitrary object distance d using Equation (4). The method for interpolating optical characteristics of a spectacle lens according to any one of claims 1 to 4, wherein an angle interpolation value ~ AX (d) is obtained.
The optical characteristic interpolation method for spectacle lenses according to claim 1, wherein the interpolation processing uses a linear interpolation method. In the simulation image processing method for spectacle wearing that allows the visual information when wearing spectacle lenses to be simulated,
8. A spectacle wearing simulation image processing method using the spectacle lens optical characteristic interpolation method according to claim 1 as blur generating means for generating blur to be experienced when wearing the spectacle lens. . In the simulation image processing apparatus for spectacle wearing that simulates visual information when wearing spectacle lenses,
Having a blur generating means for generating blur to be experienced when wearing spectacle lenses;
The spectacle wearing simulation image processing apparatus using the spectacle lens optical characteristic interpolation method according to any one of claims 1 to 7. In a lens evaluation method for determining the optical characteristics of the eyeglass lens to be examined by causing the light flux from the light source to enter the eyeglass lens to be examined and observing the state of the light flux after passing through the eyeglass lens to be examined by an observation unit.
Creating a conjugate point of the light source or the observation means at a finite distance from the eyeglass lens to be examined;
Determining optical characteristics of the eyeglass lens at least at two object distances (at least one of which is the finite distance);
Calculating an optical characteristic of an arbitrary object distance using the optical characteristic interpolation method of the spectacle lens according to any one of claims 1 to 7;
A method for evaluating a spectacle lens, comprising: In a lens evaluation apparatus for obtaining optical characteristics of the eyeglass lens to be examined by causing a light flux from a light source to enter the eyeglass lens to be examined and observing the state of the light flux after passing through the eyeglass lens to be examined by an observation unit.
A conjugate point setting means for setting a conjugate point of the light source or the observation means at a position at a finite distance from the eyeglass lens to be examined;
Optical characteristic measuring means for measuring optical characteristics of the eyeglass lens at least at two object distances (at least one of which is the finite distance);
Optical characteristic calculation means for calculating an optical characteristic at an arbitrary object distance using the optical characteristic interpolation method for spectacle lenses according to any one of claims 1 to 7,
An eyeglass lens evaluation apparatus comprising: