JP2013097014A - Position data calculation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position data calculation method of lens design information in glasses capable of calculating lens design information needed when attaching lenses to an eye glass frame.SOLUTION: An imaging apparatus 1 provided with an imaging optical system images a face part including the rims 21 of the eye glass frame while a subject wears the eye glass frame and visually inspects the front. The imaging optical system of the imaging apparatus 1 can drive a plane perpendicular to the line of sight of the subject, is configured to be able to be focused in a direction of approaching and leaving the face part of the subject, and can calculate three-dimensional position data of the rims 21 with respect to the eyes of the subject.

Description

  The present invention relates to a position data calculation method for calculating position data required for information generated in relation to the shape of a lens holding portion of a spectacle frame and the lens when the lens is mounted on the spectacle frame.

As information (hereinafter referred to as frame / lens information) generated in the positional relationship between the shape of the lens holding portion of the spectacle frame and the lens when the lens is mounted on the spectacle frame, for example, the distance between vertices (from the apex of the cornea to the back and front of the lens) Distance to the intersection of the line of sight). If the distance between the eye and the lens is different, the appearance will be different even if the lens is set to the same lens power. For example, even if a trial lens is used to determine the lens power of the user (subject) and the optimal lens power is obtained, the lens of the optimal power is used for a spectacle frame different from the spectacle frame for the trial lens. When is applied, the distance between vertices changes and is not necessarily optimal. Therefore, the distance between vertices is important as one piece of frame / lens information.
In addition, when a lens is mounted on a spectacle frame, the lens may be warped or tilted forward unlike a trial lens spectacle frame. If there is a slant angle or anteversion angle, the lens will be worn without facing the eye, so even a user without astigmatism will be in an astigmatism state. It is necessary to reflect the lens characteristics that correct the lens. The slant angle and forward tilt angle require the tangent angle of the lens surface at the eye point position of the lens mounted on the spectacle frame, but in reality it is possible to accurately measure the tilt angle and forward tilt angle at such a position. For this reason, for the sake of convenience, the angle of the lens holding part is often used as the sled angle or forward tilt angle.
The distance between the vertices, the warp angle, and the forward tilt angle are important as typical frame / lens information. In any case, the shape of the lens holding portion with respect to the position of the user's eye and the three-dimensional position of the lens are obtained. There is a need.

  For example, as a conventional method for determining the position of the eye (eye point position) with respect to the spectacle frame, for example, a technique disclosed in Patent Document 1 can be cited. This is done by marking an index at a predetermined position on the rim of the spectacle frame, actually wearing the spectacle frame on the subject, photographing the face part including the spectacle frame, and based on the position of the index obtained in advance. The optimum eye point position is calculated.

Japanese Patent No. 4536329

Patent Document 1 describes a method of recording a reference point on a dummy lens mounted on a frame, taking a face photograph from the front of the frame wearer, and specifying an eye point from a positional relationship with the reference point. . In this method, it is also possible to calculate the apex distance triangulated from the reference point on the two photographs taken at an oblique angle and the pupil center position. However, when a measurement test was performed using an actual machine, it was confirmed that the measurement accuracy was low because the measurement value used for the calculation was not sufficiently large compared to the parameter to be obtained. In addition, there is a problem that it is difficult to position the camera and the subject when taking a picture.
The present invention has been made paying attention to such problems existing in the prior art. An object of the present invention is to provide a method for calculating position data of lens design information in spectacles, which can calculate lens design information required for mounting a lens on a spectacle frame.

In order to solve the above-mentioned problem, in the invention of claim 1, the face part including the lens holding part of the spectacle frame is imaged by an imaging means equipped with an imaging optical system in a state in which the subject wears the spectacle frame and looks forward. The gist is that an image is taken and the three-dimensional position data of the lens holding unit with respect to the eye of the subject is calculated based on the imaging information.
Further, in the invention of claim 2, in addition to the configuration of the invention of claim 1, the imaging optical system can drive a plane perpendicular to the line of sight of the subject and in a direction in which it is in contact with or away from the face of the subject. The gist of the present invention is that the three-dimensional position data is defined by a movement amount and a focus position with respect to the measurement location of the imaging optical system.
Further, in the invention of claim 3, in addition to the configuration of the invention of claim 1, the imaging information captured by the imaging means is subjected to image analysis, and the three-dimensional position data of the lens holding unit with respect to the eye of the subject is calculated. The gist.
According to the invention of claim 4, in addition to the configuration of the invention of claim 1 or 2, a reference measurement point serving as a calculation reference is measured to calculate three-dimensional position data, and based on the position data of the reference measurement point. The gist of the invention is to calculate the three-dimensional position data of the lens holding portion.
In addition to the configuration of the invention of claim 4, the gist of the invention of claim 5 is that the reference measurement point is an arbitrary position on the face of the subject obtained as imaging information.
Further, the gist of the invention of claim 6 is that, in addition to the configuration of the invention of claim 5, the reference measurement point is a corneal apex position.
The gist of the invention of claim 7 is that, in addition to the configuration of the invention of claim 6, the corneal apex position is converted based on the pupil position.
The gist of the invention of claim 8 is that, in addition to the configuration of the invention of claim 6 or 7, the pupil position is converted based on the measured corneal refractive power.
Further, the gist of the invention of claim 9 is that, in addition to the configuration of the invention of claim 6, the corneal apex position is directly measured by a corneal curvature measuring device.
Further, in the invention of claim 10, in addition to the structure of any one of claims 1 to 9, the forward tilt angle and the warp angle of the lens mounted on the spectacle frame based on the three-dimensional position data of the lens holding portion. The gist is to calculate at least one of the following.

In the configuration as described above, the face part including the lens holding part of the spectacle frame is imaged by the imaging means equipped with the imaging optical system in a state where the subject wears the spectacle frame and the front is viewed, and based on the imaging information Then, three-dimensional position data of the lens holding part with respect to the eye of the subject is calculated.
As a calculation method, for example, the imaging optical system can be driven in a direction across the subject's screen (hereinafter referred to as a first direction), and a direction in which the imaging optical system is in contact with or separated from the subject's face (hereinafter referred to as a second direction). ) Can be calculated based on the movement amount of the imaging optical system in the first direction with respect to a certain reference position and the movement amount of the focusing lens at the time of focusing. . The lens holding portion is a concept that includes not only a rim that surrounds the entire circumference of the lens but also a holding means called “rimless” in which there is no rim or rim surrounding a part of the lens and the lens is fastened only at both ends.
It is also possible to calculate image information such as the edge of the lens holding unit and the contrast of the skin of the screen by performing image analysis.

It is preferable to measure the reference measurement point to calculate three-dimensional position data, and to calculate the three-dimensional position data of the lens holding unit based on the position data of the reference measurement point. The reference measurement point is preferably an arbitrary position on the subject's face obtained as imaging information. Here, since what is necessary as the position data is the arrangement state of the lens holding portion with respect to the face of the subject, it is only necessary to obtain three-dimensional position data of predetermined lens design information on the basis of somewhere on the face of the subject. It is. A preferable reference measurement point is the inside of the lens holding portion in imaging, and a more preferable position is the corneal apex position. However, in order to make it difficult to focus the imaging optical system when the corneal apex position is set as the reference measurement point, it is preferable to convert the second direction with a pupil position where the iris can be clearly seen.
Further, it is possible to calculate the forward tilt angle and the warp angle of the lens mounted on the spectacle frame based on the three-dimensional position data of the lens holding unit. If the spectacle frame does not have a forward tilt angle or a warp angle, the effects of these angles need not be considered, but if there is a forward tilt angle or a warp angle, it must be considered. By acquiring the three-dimensional position data of the lens holding unit, the forward tilt angle or the warp angle can be accurately calculated.

  In the inventions of the above claims, it is possible to calculate lens design information required when the lens is mounted on the lens holding portion of the spectacle frame.

Explanatory drawing explaining the one aspect | mode which images using an imaging device in Embodiment 1 of this invention. 2 is a block diagram illustrating an electrical configuration of an imaging device used in Embodiment 1. FIG. 4 is an explanatory diagram illustrating an example of imaging displayed on a monitor of the imaging apparatus in Embodiment 1. FIG. Explanatory drawing explaining the coordinate position set on a rim in Embodiment 1. FIG. Explanatory drawing explaining the concept of a curvature angle in the positional relationship with eyes, a frame, and a lens. Explanatory drawing explaining the concept of a forward tilt angle in the positional relationship with eyes, a frame, and a lens. Explanatory drawing for demonstrating the position of the curvature center coordinate of a lens surface spherical surface. The schematic diagram which cut out the predetermined | prescribed pixel area | region of the eye and eyelid periphery for demonstrating dividing an area | region by the difference of the gradation of imaging in Embodiment 2 of this invention. FIG. 9 is a histogram in which the horizontal axis representing the difference in gradation in FIG. 8 is the intensity of gradation and the vertical axis is the number of pixels. Explanatory drawing explaining the setting method of the focus target point set on a rim in Embodiment 2. FIG. (A) is a histogram when a predetermined pixel area is out of focus, and (b) is a histogram in a focused state.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
In the first embodiment, an imaging apparatus 1 as shown in FIG. 1 is used as an example of imaging means. An imaging mechanism and a three-axis motor mechanism (not shown) are disposed inside the housing 2 of the imaging apparatus 1. The casing 2 is installed on the bed 4 via the column 3. The bed 4 is installed on the base 5. An objective lens cylinder 6 is formed on the front surface (subject side) of the housing 2, and a monitor 7 is formed on the rear surface. The housing 2 includes a photographing optical system (not shown) having a light source therein. The facial imaging optical system captures an object illuminated by a light source (here, around the left or right eye including a frame (rim)) and acquires imaging data by the imaging element 9.
The housing 2 can move in the left-right direction (X-axis direction) and the front-rear direction (Z-axis direction) together with the column 3 with respect to the bed 4, and can move in the vertical direction (Y-axis direction) with respect to the column 3. It is said that. The three-axis motor mechanism is provided with three motors for moving the housing 2 and the column 3 forward and backward in the three axial directions of the X axis, the Y axis, and the Z axis. The X-axis direction and the Y-axis direction are the first directions that cross the subject's screen, and the Z-axis direction is the second direction that is in contact with and away from the face portion of the subject. The imaging mechanism is focused by the movement in the second direction. On the bed 4, a joystick 8 serving as an operating means for freely moving the housing 2 in the three-axis directions is disposed. The joystick 8 is provided with a slide switch 8a that can be slid up and down. By tilting the joystick 8 itself in the left-right direction, the housing 2 can be moved in conjunction with the Z-axis direction by tilting in the X-axis direction and in the front-rear direction. Further, the housing 2 can be moved in conjunction with the Y-axis direction in conjunction with the up / down movement of the slide switch 8a.
A stand device 10 for supporting the face of the subject at the time of imaging is disposed at the front position of the housing 2 on the base 5. The stand device 10 is provided with a slider 11 for placing the subject's chin so as to be movable in the vertical direction. A cushion 12 for abutting the frontal head of the subject is disposed at an upper position of the stand device 10.

Next, the electrical configuration of such an imaging apparatus 1 will be described. In addition, about the structure which is not directly related to this invention, it abbreviate | omits.
As shown in FIG. 2, the controller MC of the image pickup apparatus 1 includes the monitor 7, the joystick 8, the slide switch 8a, the image pickup device 9, the first to third step motors 15 to 17, and the first to third steps. Rotary encoders 18 to 20 are connected to each other.
The controller MC includes a known CPU, a memory such as a ROM and a RAM, a timer, and the like. In the ROM of the controller MC, a display program for displaying the image of the image sensor 9 on the monitor 7 and the image scale shown on the monitor 7 based on the pulse signals from the first to third rotary encoders 18 to 20 are displayed. Various programs such as a movement amount calculation program for calculating and displaying the movement amount and an OS (Operation System) are stored.
The first to third step motors 15 to 17 constitute a part of the three-axis motor mechanism, and the first step motor 15 moves the housing 2 with respect to the bed 4 in the left-right direction (X-axis direction). Move to. Similarly, the second step motor 16 is moved in the vertical direction (Y-axis direction). Similarly, the third step motor 17 is moved in the front-rear direction (Z-axis direction).
The first to third rotary encoders 18 to 20 respectively measure the rotation amounts of the first to third step motors 15 to 17 and output predetermined pulses according to the rotation amounts.
The controller MC executes drive control of the first to third step motors 15 to 17 on the basis of the operation of the joystick 8 and the slide switch 8a, and the first to third rotary encoders 18 to 20 obtained at that time are controlled. A three-dimensional movement amount of the housing 2 is calculated based on a pulse output corresponding to the rotation amount, and a numerical value is displayed on the monitor 7 together with the image. FIG. 3 is an example of a display screen displayed on the monitor 7. A face including the right eye and the rim 21 captured in a state in which the subject is telescopically viewed from the front is displayed. The center of the pupil is the eye point. A marker 23 as a target is displayed at the center of the monitor. The marker 23 indicates the eye point position on the drawing. The amount of movement (mm) from the reference position in the X, Y, and Z axis directions is shown in the upper left of the screen. The reference position can be set as (X, Y, Z) = (0, 0, 0) by a setting switch (not shown).

  In such use of the imaging apparatus 1, the vertical position of the slider 11 is adjusted so that either the left or right eye of the subject wearing the spectacle frame faces the front of the objective lens cylinder 6, and the horizontal direction is determined. Adjust by moving the face of the subject himself. The subject presses firmly against the forehead cushion 12 so that the face does not move during imaging. The operator operates the joystick 8 and the slide switch 8a to move the housing 2 in the X-axis, Y-axis, and Z-axis directions to obtain the position data of the center of the marker 23 for the image displayed on the monitor 7. get. Position data in the X and Y axis directions can be acquired as the amount of movement in the left and right and up and down directions (first direction) from a certain point (a reference point, anywhere), and the Z axis direction was in focus. It can be acquired by moving the current position in the front-rear direction (second direction) with a certain point as a reference and focusing.

Next, a specific measurement method using such an imaging apparatus 1 will be described. The calculation below may be performed either by a person calculating a numerical value obtained by the imaging apparatus 1 or by a computer provided in the imaging apparatus 1.
1) Measurement of reference measurement point In this embodiment, corneal vertex coordinates are used as a reference measurement point. Since the corneal vertex coordinates are position data necessary for acquiring the distance between the vertices in the first place, it is advantageous to use this as a reference with few errors. In the present embodiment, the X and Y coordinates in the corneal vertex coordinates are also eye point positions. Therefore, in the case of calculation, this is set as the reference measurement point position, and the calculation is performed with the corneal vertex coordinates (X, Y, Z) = (0, 0, 0).
Since the cornea is actually colorless and transparent, the position of the corneal vertex coordinates is not easy. Therefore, the corneal vertex coordinates are acquired using the iris forming the pupil.
As shown in FIG. 3, with the X and Y coordinates displayed on the monitor 7 set to 0, the subject pupil center position is made to coincide with the marker. In this state, the X and Y coordinates of the corneal apex coordinates are obtained. On the other hand, the Z coordinate of the pupil center coordinate is based on the iris plane. Table 1 shows the optical parameters of the average anterior segment of a person. The lens front surface position is considered to be the iris surface position, and the Z-axis coordinate position of the corneal vertex is obtained by adding the distance to the corneal vertex to the Z-axis coordinate position of the iris surface. Here, since the distance from the apex position of the cornea to the position of the front surface of the lens is 3.6 mm, by adopting this value, the value obtained by adding this distance to the Z coordinate of the iris plane is considered as the Z coordinate of the cornea apex coordinate. is there.
However, since the image displayed on the monitor 7 here displays an erecting virtual image due to the refraction of the cornea, the correction in consideration of this refraction, that is, here, how far the apparent distance is 3.6 mm due to the refraction of the cornea. It is necessary to calculate whether the subject is in focus. As described above, assuming that the lens front surface position is nearly equal to the iris position, and the apparent iris position is s', the relationship between the actual iris, the apparent iris position, and the corneal refractive power is expressed by the following equation (1).
By substituting the numerical values in Table 1 into this equation, the apparent iris position (Z-axis distance) from the corneal apex to the iris surface can be obtained. Here, the calculation result is 4.29 mm. In the following calculation, the corneal apex Z coordinate taking this 4.29 mm into consideration is set to zero.
Here, since the corneal refractive power (43.05D) shown in Table 1 merely refers to the average corneal refractive power of a human, the corneal refractive power of each subject actually measured is expressed as It is also possible to assign to an expression.

2) Calculation of the three-dimensional position of the frame Here, as shown in FIG. 4, the four points of the uppermost coordinate a, the lowest coordinate b, the coordinate c of the most nose side point, and the coordinate d of the most ear side of the rim 21 Find the dimension position. Of course, other positions may be obtained. At least these four points are necessary for calculating the boxing center required for lens processing and for calculating the forward tilt angle or the warp angle described later. The X, Y, and Z coordinates of a to d with respect to the corneal vertex coordinates (eye point position) can be acquired as shown in Table 2. The X and Y coordinates of the boxing center can be obtained from (X, Y) = ((cX + dX) / 2, (aY + bY) / 2). The X and Y coordinates of the boxing center obtained from Table 1 are (X, Y) = (− 2.45, −0.64), and the corneal vertex coordinates (eye point position) in FIG. The position is shifted by 2.45 mm on the nose side and 0.64 mm on the upper side.

3) Calculation of warp angle and forward tilt angle As shown in FIG. 5, the warp angle is the tilt in the XZ plane of the lens surface tangent at the intersection of the lens surface and the frontal line of sight. Also, as shown in FIG. 6, the forward tilt angle is the tilt in the YZ plane of the lens surface tangent at the intersection of the lens surface and the front-facing line of sight.
In order to obtain the warp angle and the forward tilt angle, it is first necessary to find the coordinates of the center of curvature of the lens surface spherical surface. When the frame to be used has a warp angle or a forward tilt angle, it is possible to provide feedback so that the lens can be provided with a characteristic that cancels aberrations generated based on the angle by calculating the exact angle. .
Since the warp angle and the forward tilt angle are inclinations generated by attaching the lens to the frame (rim 21), the lens parameters are calculated by applying the lens parameters to the lens as shown in Table 2. The data in Table 2 is an example, and is different information depending on the subject.

When the lens is attached to the frame (rim 21), it is necessary to determine how to arrange the lens thickness position with respect to the rim 21. Here, the lens surface is set so as to pass through the coordinate c of the point on the most nose side and the coordinate d on the most ear side. Since the surface curve is a spherical surface, the surface of the rim 21 in the first embodiment, which is short in the vertical direction with respect to the horizontal direction, is slightly forward with respect to the uppermost coordinate a and the lowest coordinate b as shown in FIG. Sometimes popping out. In addition, it is free to change the setting position.
Now, the center of curvature coordinates of the lens surface sphere are
A) It is on a straight line passing through the midpoint of the coordinates c and d and perpendicular to the two vectors ab and cd. The direction vector of this straight line is obtained by the outer product of the vector ab and the vector cd.
B) The center coordinate of curvature of the lens surface spherical surface is at a distance L from the midpoint of the coordinates c and d. This L is represented by L = sqrt (R ² −M ² ). Here, as shown in FIG. 7, R is a radius of curvature of the lens surface, and M is a length obtained by dividing a line connecting the coordinates c and d into two equal parts.
When this condition is applied, the center coordinates of curvature of the lens surface spherical surface are (X, Y, Z) = (− 4.572, −4.639, −125.307).

Next, the forward tilt angle and the warp angle are calculated based on the coordinates of the center of curvature of the lens surface spherical surface.
When the Z coordinate on the spherical surface is expressed as a function of the X coordinate and the Y coordinate in the three-dimensional space coordinates,
Z = fZ (X, Y)
Can be expressed as a function of variables X and Y. Specifically, if the spherical center coordinates are (X ₀ , Y ₀ , Z ₀ ) and the spherical radius is R,
(X−X ₀ ) ² + (Y−Y ₀ ) ² + (Z−Z ₀ ) ² = R ²
Than,
^{_{Z = sqrt (R 2 - (}} X-X 0) 2 - (Y-Y 0) 2) + Z 0
It becomes. That is,
^{fZ (X, Y) = sqrt} (R 2 - (X-X 0) 2 - (Y-Y 0) 2) + Z 0
The Z coordinate on the spherical surface can be expressed by the function
Here, when solving the spherical equation with respect to Z, out of the composite + − that precedes sqrt, the side used as the spectacle lens selects +.

Next, a point on the spherical surface where the X coordinate is 0 and the Y coordinate is 0 is defined as a point A. Here, there are two points on the spherical surface where X = Y = 0, but here it is a point used as a spectacle lens. It is naturally obtained as the value of Z in the above equation by selecting + from the complex before sqrt.
The warp angle can be obtained from a value (inclination of the surface in the X direction) in which the displacement of the Z coordinate value at the point A is fixed along Y = 0 and evaluated along the X axis direction. The value is obtained by substituting X = 0 and Y = 0 into the partial derivative ∂fZ / ∂X of the function Z at the point A to obtain the inclination and expressed as an angle with respect to the X axis.
_{^{∂fZ / ∂X = (1/2) ·}} (R 2 - (X-X 0) 2 - (Y-Y 0) 2) -1/2 · (-2X + 2X 0)
If X = 0 and Y = 0,
X ₀ · (R ² −X ₀ ² −Y ₀ ² ) ^−1/2
The warp angle is −tan ⁻¹ (X ₀ / sqrt (R ² −X ₀ ² −Y ₀ ² )).
X ₀ is a negative value, the bend angle than defining - a positive value with the.

On the other hand, the forward tilt angle can be obtained from the value (the tilt of the surface in the Y direction) obtained by evaluating the displacement of the value of the Z coordinate at the point A with X = 0 and evaluating along the Y axis direction. This is obtained by substituting X = 0 and Y = 0 into the partial derivative ∂fZ / ∂Y of the function Z at the point A to obtain the slope and expressing it as an angle with respect to the Y axis.
_{^{∂fZ / ∂Y = (1/2) ·}} (R 2 - (X-X 0) 2 - (Y-Y 0) 2) -1/2 · (-2Y + 2Y 0)
If X = 0 and Y = 0,
Y ₀ · (R ² -X ₀ ² -Y ₀ ² ) ^-1/2
The forward tilt angle is tan ⁻¹ (Y ₀ / sqrt (R ² −X ₀ ² −Y ₀ ² )).
Y ₀ is a positive value, and as it is anteversion.
When this condition was applied, the warp angle was 1.83 degrees and the forward tilt angle was 9.75 degrees.

4) Calculation of distance between vertices The distance between vertices is the distance from the corneal vertex to the intersection of the lens back surface and the frontal line of sight. In order to obtain the distance between the vertices, it is necessary to obtain the curvature center coordinates on the back surface of the lens in the same manner as the calculation of the warp angle and the forward tilt angle.
Since the distance between the vertices is a distance defined by attaching the lens to the frame (rim 21), here, the lens parameters are calculated by applying to the lens of the data as shown in Table 2 in the same manner as described above. And The data in Table 2 is an example, and is different information depending on the subject.
In order to obtain the curvature center coordinate of the lens back surface, the value of L when the curvature center coordinate of the lens surface is obtained is changed as follows.
L = sqrt (R ′ ² −M ² ) + CT
Here, R ′ is the radius of curvature of the rear surface of the lens, and M is the length obtained by dividing the line segment connecting the coordinates c and d into two equal parts. CT is the thickness at the geometric center of the lens.
The lens back spherical surface thus obtained is similar to the lens surface,
Z = fZ (X, Y)
Can be expressed as a function of variables X and Y. That is, the distance between vertices can be obtained from the value of Z when (X, Y) = (0, 0) is substituted.
The distance between the vertices determined from the above lens conditions and the measured ad coordinates was 15.9 mm.

(Embodiment 2)
In the second embodiment, as in the first embodiment, the subject's face does not move, and the digital camera as the imaging means includes the right and left eyes and the rim of the subject wearing the spectacle frame. Assume that an image is to be taken. The obtained imaging data is analyzed by an image analysis program in the controller MC of the analysis computer. In imaging, the iris is arranged at the center position of the pixel group as much as possible, and the imaging data focused at different approach positions in the Z-axis direction is acquired by changing as finely as possible.
1) Section of acquired imaging area First, it is assumed that the acquired image basically employs 256 gradations of a black and white image. Of course, other gradation patterns or color images can be analyzed. In the 256 gradations, the intensity 0 represents black and the intensity 255 represents white.
For example, for 200 × 200 = 40000 pixels surrounding the iris as shown in FIG. 8, the intensity distribution of each point is represented by a histogram as shown in FIG. In this histogram, the horizontal axis represents intensity values from 0 to 255, and the vertical axis represents “the number of pixels having the intensity value”. For simplicity, it is assumed that the 20 mm × 20 mm region does not include a frame, and eyelashes are ignored. Then, 4000 pixels are distributed in a) an iris having a relatively small pixel value, b) a skin-colored eyelid, and c) a white eye. Two appropriate threshold values can be set, and a set of points belonging to three intensity ranges can be divided into three regions.
For example, the threshold value can be determined from a condition that minimizes the ratio of the intra-group variance and the inter-group variance of the three groups. For the intra-group dispersion of the iris, the threshold between the iris and the eyelid is assumed to be 70.5, the average number of pixels per intensity of 0 to 70 is 110, and Σ (110−number of each intensity) ² is divided by 71. Obtained as a value. Intergroup variance is a variance of three values, which is the average intensity of the three groups. By appropriately changing the threshold value, a condition for minimizing the ratio of the intra-group variance and the inter-group variance of the group is determined.

The three regions divided in this way are not necessarily “a lump” and may be divided and distributed. For example, if there is a mole in the immediate vicinity of the eye, the area and the iris may be confused and classified as the same area, and the eyelid is divided into upper and lower parts. Therefore, shape feature evaluation is performed on which of the three regions is closest to the “circular shape with the vertical direction cut”.
For example, a pattern having the highest degree of matching may be selected as compared with a shape pattern prepared in advance. In other words, a kind of filtering is performed. The shape pattern prepared in advance is, for example, a pattern having a center coordinate of 200 × 200 pixels, a radius of 5 mm (50 pixels), and a width of 2 mm (20 pixels) hidden by the upper and lower eyelids. Is obtained by the ratio of pixels that match. Even if the position of the iris is deviated from the center of 200 × 200 pixels, it can be determined by the condition with the highest degree of matching by appropriately moving the center coordinates of the pattern.
Next, let us consider expressing the shape of the iris by five variables: 1) center position X, 2) center position Y, 3) radius R, 4) width hidden by upper eyelid, and 5) width hidden by lower eyelid. By appropriately changing these five variables, the center position of the iris can be determined according to the condition that the region matching degree is maximized. The position of the rim can also be determined by this concept of region division and shape feature evaluation.

2) Focusing In the second embodiment, four points on the rim and the iris are used as target points for focusing. These are positions required for calculating the distance between vertices and for calculating the sled angle and the forward tilt angle. As shown in FIG. 10, in order to determine four points on the rim, first, a rectangle circumscribing the frame is set. The horizontal side of this rectangle is horizontal and the vertical side is vertical. The center of this rectangle is the boxing center. Four points on the rim are the intersection points of the perpendicular line and the frame dropped from the boxing center to each side.
With respect to the four points on the frame determined as the target and the iris center, it is necessary to calculate at which position the focus of the camera is focused. For this reason, in the second embodiment, the intensity distribution of pixels near the target point is evaluated in each of a plurality of images picked up by finely changing the focal position of the camera. For example, as shown in FIGS. 11A and 11B, in 30 × 30 = 900 pixels surrounding the target point, the intensity distribution of each point is represented by a histogram. In this histogram, the horizontal axis represents intensity values from 0 to 255, and the vertical axis represents the number of pixels.
In the in-focus state, the area of the blurred area becomes larger as shown in FIG. 11B (in practice, it is more appropriate to evaluate by dispersion rather than area). That is, for each intensity of 0 to 255, a value obtained by summing the squares of the degree of difference (difference in the number of pixels) from the average number (900 ÷ 256) is referred to as a “numerical value for evaluating the degree of focus coincidence”. To do. This value changes depending on the change in the focal position of the camera, but becomes the maximum peak value when the subject is in focus. The position in the depth (Z-axis) direction can be determined by obtaining the maximum peak value for the target point.
As described above, since the three-dimensional positions of the four points on the rim and the iris can be acquired, the distance between vertices, the warp angle, and the forward tilt angle can be calculated using the values as in the first embodiment. .

It should be noted that the present invention can be modified and embodied as follows.
In the above embodiment, the present invention is applied to a single focus lens. However, the present invention can be applied to a lens other than the single focus lens, for example, a progressive power lens or a bifocal lens.
・ In the above, a lens that actually has a lens power is used, but it is only necessary to know the curvature and lens thickness of the front and back of the lens for calculation, so it is possible to use a dummy lens that does not contain the lens power. .
In the calculation of the second embodiment, a large number of images with different focus positions are acquired in order to acquire an accurate position with respect to the Z axis. However, if the ability of image processing is improved, such a large number of images are acquired. It is not always necessary. For example, a method may be used in which the face is imaged from two different directions and depth (Z-axis direction) information is acquired using a parallax difference on the image.
In the above embodiment, the corneal apex position is indirectly acquired based on the pupil position, but may be directly obtained by a corneal curvature measuring apparatus. The corneal curvature measuring device is a device that measures the corneal refractive power based on the reflected image of the test pattern projected on the corneal surface. By displaying the test pattern as an object at infinity, the corneal curvature can be obtained directly from the reflected image. With this method, the corneal refractive power can be directly obtained regardless of the distance between the apparatus and the eye, and at the same time, the corneal vertex distance can be obtained.
-It is free to implement in other modes that do not depart from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Imaging device as imaging | photography means, 21 ... Rim as a lens holding part.

Claims (10)

In a state where the subject wears the spectacle frame and the front is viewed, the face portion including the lens holding portion of the spectacle frame is imaged by an imaging means including an imaging optical system, and the eye with respect to the eye of the subject is based on the imaging information. A position data calculation method characterized in that three-dimensional position data of a lens holding part is calculated. The imaging optical system is configured to be able to drive a plane perpendicular to the subject's line of sight and to be able to focus in a direction in which the subject is in contact with or separated from the subject's face, and the three-dimensional position data is the imaging The position data calculation method according to claim 1, wherein the position data calculation method is defined by a movement amount and a focus position with respect to a measurement location of the optical system. The position data calculation method according to claim 1, wherein the imaging information captured by the imaging unit is subjected to image analysis to calculate three-dimensional position data of the lens holding unit with respect to the eye of the subject. A reference measurement point serving as a calculation reference is measured to calculate three-dimensional position data, and the three-dimensional position data of the lens holding unit is calculated based on the position data of the reference measurement point. The position data calculation method according to claim 1, wherein: The position data calculation method according to claim 4, wherein the reference measurement point is an arbitrary position on the face of the subject obtained as imaging information. The position data calculation method according to claim 5, wherein the reference measurement point is a corneal apex position. The position data calculation method according to claim 6, wherein the corneal apex position is converted based on a pupil position. The position data calculation method according to claim 6 or 7, wherein the pupil position is converted based on the measured corneal refractive power. The position data calculation method according to claim 6, wherein the corneal apex position is directly measured by a corneal curvature measuring apparatus. The at least one of a forward tilt angle and a warp angle of a lens mounted on the spectacle frame is calculated based on three-dimensional position data of the lens holding unit. The position data calculation method described.

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