JP4199723B2 - Optical lens polishing method - Google Patents

Description

  The present invention relates to a polishing method for an optical lens, and more particularly to a polishing method for an optical lens whose surface to be polished is non-rotationally symmetric.

  Conventionally, in order to polish a concave surface of a lens, which has been cut into a spherical or toric surface shape by an NC control curve generator, with a polishing apparatus, a polishing pad is attached to a metal polishing jig having a convex surface that substantially matches the shape of the concave surface to be polished. Is applied by sliding the polishing jig and the lens relative to each other in a state where the polishing jig is pressed against the concave surface to be polished. However, when polishing by such a method, it is necessary to prepare a different polishing jig for each concave shape of the lens to be polished. For example, in the case of a toric lens for correcting astigmatism, a toric surface (a part of a surface obtained by rotating an arc around the axis that is in the same plane as the arc and does not pass through the center of curvature of the arc) is 3000 to 4000. Since there are many types, it was necessary to prepare as many polishing jigs as there were. For this reason, not only the manufacturing cost of the polishing jig is increased, but also a large storage space is required for storage, and its management is complicated.

  Also, not only spherical and toric surfaces, but also aspherical surfaces (part of a rotating surface whose curvature continuously changes from the apex to the periphery), non-toric surfaces (surfaces having mutually perpendicular principal meridians with different curvatures, On the other hand, a concave surface with a complicated shape such as a free-form surface such as a progressive multifocal lens may be formed. There was a problem that the shape could not be accommodated and could not be polished.

  Accordingly, as a method for solving such a problem, a polishing jig made of an elastic material and polished in a state in which a fluid is sealed inside and inflated has been proposed (for example, see Patent Document 1). . In addition, this invention relates to the improvement of the method grind | polished using the grinding | polishing jig | tool described in patent document 1. FIG.

  The polishing jig described in Patent Document 1 includes a balloon member that is formed into an oval cup shape with an elastic material and has a top surface that expands into a dome shape when a fluid is introduced therein. The polishing surface of the lens is polished by a polishing pad provided on the upper surface of the lens. If the concave surfaces of the lens are toric surfaces and the curvatures in directions orthogonal to each other are significantly different, the spherical dome may not be able to follow such a concave surface. For this reason, the balloon member has an elliptical shape in plan view, and the curvature of the upper surface of the balloon member is made different between the short axis direction and the long axis direction orthogonal to each other so as to be close to the toric surface of the lens. During polishing, the lens is reciprocated in the left-right direction and reciprocally rotated in the front-rear direction, and the polishing jig is swung in a swivel motion, so that the polishing trajectory slightly deviates every round. The polishing surface is polished.

  According to such a polishing jig, since the curvature of the dome can be changed by changing the internal pressure of the balloon member, it is a special part for changing the curvature of the dome according to the curvature of the surface to be polished. No means is required, and the types of polishing jigs can be greatly reduced, and polishing can be reliably performed.

JP 2003-266287 A

  Conventional progressive-power lenses generally have a progressive surface on one of two optical surfaces. In addition, the progressive power lens uses a toric surface obtained by fusing a spherical shape and a toric component on a surface paired with the progressive surface as an optical surface. The spherical shape is rotationally symmetric, and the toric component is rotationally symmetric. Therefore, the toric surface is rotationally symmetric. When such a spectacle lens is polished using the polishing jig and the polishing apparatus described in Patent Document 1, the direction of the astigmatic axis and the long axis of the polishing jig are described. Were matched and polished. Here, the necessary size of the toric component is appropriately determined depending on the degree of astigmatism. Since the astigmatism magnitude and its axial direction are included in the prescription and can be referred to from the prescription when the lens is ordered, it is easy to match the astigmatic axis direction with the major axis of the polishing jig.

  However, in recent years, progressive-power lenses form an optical surface with a fusion surface of a progressive surface shape and a toric component, or an aspherical shape that is not rotationally symmetric (part of a progressive element) and a toric component are distributed to each optical surface of the lens. Thus, the desired progressive refractive power and astigmatism correction refractive power are constituted by the transmission refractive power on both sides. These optical surfaces are not simple rotationally symmetric surfaces (hereinafter, non-rotational symmetry is referred to as non-rotational symmetry). Here, the “non-rotationally symmetric lens” means a lens having a non-rotationally symmetric surface whose refractive power continuously changes over a part or the whole of the lens, for example, a progressive power lens, an aspherical power having a progressive element. It is a lens etc. (ISO13666.JP REV.030 spectacle lens).

  Furthermore, since the toric component is distributed on both sides, the toric component per one side may be small, or the absolute value of the prescription value of the toric component may be small. However, when the shape change due to the toric component is smaller than the non-rotationally symmetric change such as the progressive surface other than the toric component, when polishing is performed with the axial direction of the toric component and the major axis of the polishing jig matched, There is a problem that the entire surface to be polished cannot be polished with high accuracy due to the difference in curvature between the surface to be polished and the polishing jig. That is, when the surface to be polished is a non-rotationally symmetric surface, when the lens is mounted on the polishing apparatus with the axial direction of the toric component aligned with the long axis direction of the polishing jig, the minimum curvature of the lens and its axial direction are the toric component. And the minimum curvature is smaller than the curvature of the toric component, creating a gap between the outer peripheral edge of the lens surface to be polished and the outer periphery of the polishing jig, and the entire surface to be polished Cannot be uniformly polished.

  Therefore, the inventors of the present invention particularly determine the non-rotationally symmetric polished surface of the optical lens using the polishing jig described in Patent Document 1 described above. As a result of examining various arrangements and polishing, and calculating the axial direction of the minimum curvature for each lens, the axial direction of the minimum curvature is matched with the major axis direction of the polishing jig. It was confirmed that the entire surface to be polished could be satisfactorily polished without creating a gap between the outer peripheral edge of the surface to be polished of the lens and the outer periphery of the polishing jig.

  The present invention has been made based on the above-described findings, and an object of the present invention is to provide an optical lens polishing method that can satisfactorily polish a non-rotationally symmetric polished surface over the entire surface. .

  In order to achieve the above object, the present invention provides a balloon member that is formed into a cup shape with an elliptical shape in plan view and is inflated into a curved surface by introducing a fluid therein, and an upper surface of the balloon member. A polishing method for an optical lens that polishes a non-rotationally symmetric polished surface of an optical lens using a polishing pad attached to an optical lens, and calculates an axial direction that minimizes the average curvature of the polished surface of the optical lens. A step of identifying, a step of attaching the optical lens to a polishing apparatus so that an axial direction in which an average curvature of a surface to be polished of the optical lens is minimum coincides with a major axis direction of the balloon member, The balloon member is swung and swung while the polishing surface is in contact with the polishing pad, and the optical lens is reciprocated in the axial direction that minimizes the average curvature of the surface to be polished. By reciprocating rotation in a direction perpendicular to the axial direction is also one in which the locus of the polishing and a step of polishing the surface to be polished with non-orbital polishing path deviates slightly every one rotation.

  In the present invention, the step of calculating and specifying the axial direction in which the average curvature of the surface to be polished of the optical lens is minimum is determined by the geometric center on the surface to be polished and two point symmetric points of the outer periphery. A plurality of virtual curves along the to-be-polished surface to be connected are determined by shifting by a required angle in the circumferential direction of the to-be-polished surface, at least three arbitrary points are defined on each virtual curve, and the virtual curve is determined from the coordinates of these points The average curvature is calculated, the virtual curve having the smallest average curvature is selected, and the axial direction is specified.

  Furthermore, in the present invention, the optical lens is applied to a meniscus lens.

  In the present invention, since the axial direction in which the average curvature of the polished surface of the optical lens is minimized and the major axis direction of the balloon member are matched, the outer peripheral edge portion of the polished surface of the lens is used. There is no gap between the outer periphery of the balloon member and the entire surface to be polished can be brought into contact with the polishing pad. Therefore, the entire surface to be polished can be reliably polished.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIGS. 1A and 1B are a plan view of a lens polished by the polishing method according to the present invention and a cross-sectional view of the lens. In the figure, reference numeral 1 denotes a plastic lens for correcting astigmatism (hereinafter abbreviated as “lens”), which is formed in a circular shape. A meniscus lens is formed by the surface 2c. The lens 1 is a semi-finished lens made of urethane or epithio resin in which only the convex surface 2a is finished to a predetermined optical surface and the concave surface 2b is cut. The concave surface 2b forms a non-rotationally symmetric polished surface in which the axial direction 3 of the toric component and the axial direction 4 of the minimum curvature of the concave surface 2b are different and is polished by the polishing method according to the present invention to a predetermined optical surface. It will be finished.

FIG. 2 is a flowchart showing the procedure of the optical lens polishing method according to the present invention. In the figure, the optical lens polishing method according to the present invention includes a step (step S1) of calculating and specifying the axial direction 4 at which the average curvature of the polished surface 2b of the lens 1 is minimized. In order to calculate the minimum curvature of the lens 1 and specify the axial direction 4, first, a plurality of virtual curves U ₁ , U ₂ , U ₃ ... Are defined on the polished surface 2 b as shown in FIG. These virtual curves U ₁ , U ₂ , U ₃ ... Are two point-symmetric points (point Q ₁ and point Q ₁ , point Q ₂ and point Q ₂₎ on the polished surface 2b and the geometric center O. Q ₂ ... Are curves that are each shifted by a required angle (θ) in the circumferential direction of the polished surface 2b. Projection lines obtained by projecting the virtual curves U ₁ , U ₂ , U ₃ ... Onto the horizontal plane are straight lines.

Next, at least three arbitrary points (P ₁ , P ₂ , P ₃ ) are determined on each virtual curve U ₁ , U ₂ , U ₃ ..., And each of these points P ₁ , P ₂ , P ₃ The average curvatures of the virtual curves U ₁ , U ₂ , U ₃ ... Are calculated (the calculation method will be further described later). Then, the virtual curve having the smallest average curvature is selected from the calculated average curvatures, and the axial direction is specified. The average curvature of each virtual curve U ₁ , U ₂ , U ₃ ... Takes two points (for example, point P ₁ and point P ₃ ) separated by a distance S on the virtual curve, and these points P _1. DOO point P tangential direction in the ₃ difference [psi (= tangent of the angle α _1, -α ₂₎ and is the ratio of the length S of the arc between the points P ₁ ~ point P ₃ ([psi / S).

  The optical lens polishing method according to the present invention includes a step of aligning a major axis direction of a polishing jig to be described later with an axial direction 4 in which the average curvature of the polished surface 2b of the lens 1 is minimized (step S2); And a step (step S3) of polishing the surface 2b to be polished by a polishing apparatus. The surface 2b to be polished is polished by the polishing jig and the polishing apparatus described in Patent Document 1 described above.

  The step of matching the major axis direction of the polishing jig with the axial direction 4 in which the average curvature of the polished surface 2b of the lens 1 is the smallest is that the axial direction 4 in which the average curvature of the polished surface 2b is minimized is the polishing jig. The lens 1 is attached to the polishing apparatus so as to coincide with the major axis direction of the lens. In this case, the lens 1 is held by a lens holder and attached to the polishing apparatus.

  The step of polishing the polished surface 2b of the lens 1 by the polishing apparatus is performed by swinging and swinging the polishing jig and the polishing pad while the polished surface 2b of the lens 1 is in contact with the polishing pad attached to the polishing jig. Then, the lens 1 is reciprocated in the axial direction in which the average curvature of the surface to be polished 2b is minimized, and is reciprocally rotated in the direction orthogonal to the axial direction, so that the track of polishing is slightly shifted every round. This is a step of polishing the surface 2b to be polished by the polishing pad along a locus. As the polishing jig, a balloon member is used which is formed into an elliptical cup shape with an elastic material and the upper surface side expands into a predetermined curved surface shape by introducing a fluid therein. The balloon member swings and swings while maintaining the direction of the major axis and the minor axis constant during polishing. The polishing jig and the polishing apparatus will be described later.

Next, a method for calculating and specifying the axial direction of the minimum curvature of the polished surface 2b of the lens will be described in detail.
As a method for calculating the minimum curvature k of the polished surface 2b of the lens 1, at least three arbitrary points (P ₁ , P ₂ , P ₃ ) on the virtual curves U ₁ , U ₂ , U _3. There are a method of calculating by solving simultaneous equations from the coordinates of, and a method of calculating by the least square method from the coordinates of _three or more points (P ₁ , P ₂ , P ₃ ...). In the former calculation method, since there are few coordinate points, an error becomes larger than the latter calculation method depending on the shape of the polished surface 2b. For this reason, in the present invention, for each lens, the minimum curvature of the surface to be polished 2b is calculated by the former simultaneous equations and the latter least square method, respectively, and the results are compared. Polishing is performed based on a calculation result obtained by a simple calculation method, and if there is a problem in polishing accuracy, polishing is performed based on the calculation result obtained by the latter method.

  The surface (surface to be polished) shape of the lens 1 is represented by giving the height of the lens surface as a numerical value on each lattice of a lattice matrix (for example, 110 × 110) divided vertically and horizontally. In this case, the shape of the polished surface 2b is a free-form surface including a progressive shape. The height Z at the (X, Y) point on the polished surface 2b is expressed by Equation 1. Formula 1 can use a known interpolation function that can calculate the interpolation data of the point sequence data. In the present invention, the B-spline function is used.

A. Method of calculating an average curvature by solving simultaneous equations from three coordinate values In FIG. 3, an approximate radius of curvature r of the surface to be polished 2b is calculated from simultaneous equations of circle equations. The curvature radius r is the reciprocal of the curvature k. Therefore, using the coordinates of arbitrary three points (P ₁ , P ₂ , P ₃ ) on each virtual curve U ₁ , U ₂ , U ₃ ... Passing through the center O of the lens 1, each virtual curve U ₁ , The average curvature of U ₂ , U ₃ ... Is calculated. In this case, since it is necessary to detect the minimum curvature of the surface 2b to be polished and its axial direction, a plurality of virtual curves U _{1 to} U _m are set on the surface 2b to be polished over the entire circumference in the circumferential direction at a pitch of angle θ. Then, using the coordinates of arbitrary three points (P ₁ , P ₂ , P ₃ ) on the virtual curves U _{1 to} U _m , the average curvature of the polished surface 2b in the virtual curves is calculated. In the present invention, the angle pitch (θ) between adjacent virtual curves is set to 1 °. Therefore, if the average curvature r is calculated for ₁₈₀ virtual curves Q _{1 to} Q ₁₈₀ from> 0 ° to 179 °, the average curvature in all directions over 360 ° is obtained.

In FIG. 4, a method of calculating the average curvature of the i-th virtual curve inclined by an angle θ with respect to the X axis as Ui will be described.
Any three points on the virtual curve Ui are defined as P ₁ (X ₁ , Y ₁ ), P ₂ (X ₂ , Y ₂ ), and P ₃ (X ₃ , Y ₃ ). If the coordinate axis in the direction of the virtual curve Ui is the W axis, the coordinate values of the points P ₁ , P ₂ , P _{3 on} the ZW section are P ₁ (W ₁ , Z ₁ ), P ₂ (W ₂ , Z ₂ ), P ₃ (W ₃ , Z ₃ ). As described above, the coordinate values of W ₁ , W ₂ , and W ₃ are set on the virtual curve Ui that passes through the geometric center O of the lens 1 having the diameter D and connects the points (points P ₁ and P ₃ ) at both ends. This is performed in advance as three points (P ₁ , P ₂ , P ₃ ). The coordinate values of W ₁ , W ₂ , and W ₃ are the same when calculating for any direction. The equation for calculating the XY coordinate based on the set W coordinate value and the equation for calculating Z from the calculated XY coordinate are the following equations from the above equation 1.

Therefore, the following simultaneous equations can be solved in order to obtain an equation of a circle passing through the three points P ₁ , P ₂ , and P ₃ in the ZX cross section. However, it is a condition that these three points P ₁ , P ₂ , and P ₃ are not on a straight line in the ZW cross section.

a and b are the coordinate values of the W and Z values at the center of the circle, respectively, and r is the radius of the circle.
a, b, and r are calculated | required by Formula 4, Formula 5, and Formula 6, respectively.

  Further, since the average curvature k to be obtained is the reciprocal of the curvature radius r,

It becomes.
In this way, the average curvature k of each of the virtual curves U _{1 to} U ₁₈₀ is sequentially calculated, and the smallest average curvature (k _O ) is selected.

An example of calculating the average curvature k by the above method is shown in Table 1 below.

The calculation target lens is a progressive addition lens that is a non-rotationally symmetric lens.
Table 1 is an example of calculating the average curvature for ₁₈ virtual curves U _{1 to} U ₁₈ that pass through the geometric center O of the non-polished surface and are shifted in the circumferential direction at a pitch of θ = 10 °. Points P ₁ , P ₂ and P ₃ indicate coordinate values on the virtual curves U _{1 to} U _{18 of the} surface to be polished. From Table 1, the minimum curvature k _O is 1.103 × 10 ^−0.2 and the axial direction is θ = 170 °.

B. Method for calculating average curvature from least three coordinate values by least square method In FIG. 5, three or more points, for example, nine points P _{1 to} P passing through the geometric center O on the polished surface 2 b of the lens 1. Using the coordinate value on the polished surface 2b passing through ₉ , the approximate radius of curvature of the virtual curve U ₁ is calculated from the equation of the circle by the method of least squares.

Further, since it is necessary to detect the minimum curvature and its direction, a plurality of virtual curves U _{1 to} U _m are set on the polished surface 2b over the entire circumference in the circumferential direction at a required angular pitch, Using the coordinates of the points P _{1 to} P ₉ , the average curvature of the polished surface 2b in the virtual curve is calculated. Here, the angle pitch θ between adjacent virtual curves was set to 1 °. Therefore, also in this case, if the average curvature is calculated for ₁₈₀ virtual curves U _{1 to} U ₁₈₀ from 0 ° to 180 °, the average curvature in all directions over 360 ° is obtained.

Next, a method of calculating the average curvature of the angle θ as the i-th virtual curve U _i will be described.
The above three coordinate values, e.g., FIG. 5 (b) virtual curve as shown in U _i on the lens diameter of 8 equal parts of nine points _{P 1 (X 1, Y 1} ,), P 2 (X ₂ , Y ₂ )... P ₉ (X ₉ , Y ₉ ). If the coordinate axis in the direction of the virtual curve U _i is the W axis, the coordinate values of the points P _{1 to} P _{9 on} the ZW section are P ₁ (W ₁ , Z ₁ ), P ₂ (W ₂ , Z ₂ ). the _{··· P 9 (W 9, Z} 9). The coordinate values W _{1 to} W ₉ are set in advance at positions (points P _{1 to} P ₉ ) on the virtual curve U _i that divides the diameter D of the lens 1 at equal intervals. The coordinate values of W _{1 to} W ₉ are the same when calculating for any direction. The equation for calculating the XY coordinates based on the set W coordinate value and the equation for calculating Z from the calculated XY coordinates are the following equation (8).

In the ZW cross section, to obtain the equation of the circle closest to the coordinate values of these points P _{1 to} P ₉ , the simultaneous equations of Equation (10) are solved using the least square method (Equation 9). However, it is a condition that all the points P _{1 to} P ₉ are not on a straight line in the ZW cross section.

  When S in Equation 9 is minimum, the equation of the circle that is most approximated is obtained. Therefore, in order to obtain a, b, and r that minimizes S, S is differentiated by a, b, and r, and is set to 0.

Then, when these are solved together, it becomes as follows.

And put
a, b, and r are obtained by Expression 12, Expression 13, and Expression 14, respectively.

Further, since the average curvature k to be obtained is the reciprocal of the curvature radius r,

It becomes. In this way, the average curvature k of each of the virtual curves U _{1 to} U ₁₈₀ is sequentially calculated, and the smallest average curvature k _O is selected.

An example of calculating the average curvature according to the above calculation method is shown in Table 2 below.

The calculation target lens is a progressive addition lens that is a non-rotationally symmetric lens.
Table 2 shows an example of calculation for ₁₈ virtual curves U _{1 to} U ₁₈ that pass through the geometric center O of the non-polished surface and are shifted at a pitch of θ = 10 ° in the circumferential direction. Points P ₁ , P ₂ and P ₃ indicate coordinate values on the virtual curves U _{1 to} U _{18 of the} surface to be polished. From Table 2, the minimum curvature k _O is 1.103 × 10 ^−0.2 and the axial direction is θ = 170 °.

Further, when the results of Table 1 and Table 2 are compared, the minimum curvature k _O and the axial direction thereof coincide. Although depending on the lens shape, in the embodiment of the present invention, the minimum curvature k _O and its axial direction can be calculated with sufficient accuracy even by simple calculation using the three points P ₁ , P ₂ and P ₃ .

Next, lens polishing by the polishing apparatus will be described.
FIG. 6 is a schematic configuration diagram of a polishing apparatus used in the polishing method according to the present invention.
In the figure, a polishing apparatus generally indicated by reference numeral 30 has an apparatus main body 32 installed on the floor, and a horizontal axis 33 that can move in the left-right direction (arrow X direction) on the apparatus main body 32 in the drawing. An arm 34 rotatably disposed in a direction orthogonal to the paper surface (arrow AB direction), and a drive device (not shown) that reciprocates the arm 34 in the left-right direction and rotates in a direction orthogonal to the paper surface, A lens mounting portion 36 provided on the arm 34 for holding the convex surface 2a of the lens 1 via a lens holding body 37, and disposed in the apparatus main body 32 so as to be positioned below the lens mounting portion 36, not shown. A swinging device 38 that swings (does not rotate) around a vertical axis K by a driving device is provided. Further, a polishing jig 39 detachably provided on the rocking device 38, a polishing pad 40 detachably attached to the polishing jig 39, an elevating device 41 for raising and lowering the lens attaching portion 36, and the like are provided. ing. Such a polishing apparatus 30 is the same as the polishing apparatus described in Patent Document 1 described above.

  As described above, the lens 1 is made of a plastic semi-finished lens for correcting astigmatism with only a convex surface, and the concave surface 2b is a non-rotationally symmetric polished surface. The surface 2b to be polished is cut in advance into a predetermined surface shape by a curve generator that performs three-dimensional NC control (processing accuracy within 3 μm: outer diameter 50φ, surface roughness Ry 0.3 to 0.5 μm).

FIG. 7 is a cross-sectional view showing a state where the lens is attached to the lens holder 37.
In the figure, a lens holder 37 that holds the lens 1 is composed of a metal (tool steel, etc.) yatoi 44 and an adhesive 45 that joins the yatoi 44 and the lens 1. A fitting recess 47 that fits into the lens mounting portion 36 is formed on the back side of the yatoi 44. The fitting recess 47 has a hame-eye orientation. As the adhesive 45, an alloy having a low melting point (for example, an alloy of Bi, Pb, Sn, In, and Ga, a melting point of about 49 ° C.) is used. A scratch-preventing protective film 46 is interposed between the convex surface 2 a of the lens 1 and the adhesive 45. In order to join the lens 1 to the Yatoi 44 with the adhesive 45, for example, an apparatus called a layout blocker manufactured by LOH is used. The lens 1 is attached to the yatoe 44 in consideration of the axial direction of the minimum curvature of the polished surface 2b calculated by the above-mentioned simultaneous equations or the least square method. Specifically, when the yatoi 44 is attached to the lens attachment portion 36, the lens 1 is attached to the yatoi 44 so that the axial direction of the minimum curvature of the surface 2b to be polished matches the major axis direction of the polishing jig 39. . As the Yatoi 44, those having different sizes according to the power of the lens 1, the outer diameter, and the curvature of the convex surface 2a are used.

  In FIG. 6, the rocking device 38 is attached to the upper end of the vertical rotating shaft 21 at a required angle (α) in the vertical direction, and the polishing jig 39 is detachably installed on the upper end surface. Yes. The rotating shaft 48 rotates around the axis during polishing. The swinging device 38 is configured to swing around the axis of the rotating shaft 48 when the rotating shaft 48 rotates. The inclination angle α of the swing device 38 with respect to the rotation shaft 48 is, for example, 5 °. FIG. 8 shows the trajectory 50 of the swinging movement of the swinging device 38 and the polishing jig 39. The oscillating device 38 only revolves around the rotation shaft 48 in the swinging and swinging motion, and does not rotate.

  9 to 12, the polishing jig 39 includes a balloon member 51 formed in a cup shape by an elastic material and having a lower surface opened, and a lower surface side opening of the balloon member 51 is closed to keep the inside airtight. The fixture 52 and a valve 53 for supplying compressed air to the balloon member 51 are configured.

  The balloon member 51 has an elliptical shape in plan view and a dome portion 51A having a flat or gentle convex curved surface, and a substantially elliptical tube integrally extending downward from the outer periphery of the dome portion 51A. The portion 51B and an annular inner flange 51C extending integrally with the lower end of the cylindrical portion 51B are configured.

  As a material of the balloon member 51, for example, synthetic rubber (for example, IIR) or natural rubber close to natural rubber having a hardness of 20 to 50 degrees is used. The thickness of the balloon member 51 is uniform throughout and is about 0.5 to 2 mm (usually about 1 mm).

  The fixing member 52 is composed of two members, an inner fixing member 55 and an outer fixing member 56. By sandwiching the inner flange 51C of the balloon member 51 from the inner side and the outer side by these members, the lower surface side opening of the balloon member 51 is hermetically sealed. Is sealed. For this reason, a sealed space 57 is formed inside the balloon member 51. The inner fixture 55 is formed of an elliptical plate having the same size as the inner shape of the cylindrical portion 51B of the balloon member 51, and an annular groove 58 into which the inner flange 51C is fitted is formed on the outer peripheral portion of the lower surface.

  The outer fixture 56 is formed in a cup shape that opens upward, and thus includes a disk-shaped bottom plate 56A and a cylindrical portion 56B that protrudes integrally from the outer periphery of the upper surface of the bottom plate 56A. The inner fixture 55 is fitted and inserted into the cylindrical portion 56 </ b> B together with the cylindrical portion 51 </ b> B of the balloon member 51. The cylindrical portion 56 </ b> B has a circular outer shape, and an inner shape is formed in an elliptical shape having substantially the same size as the outer shape of the cylindrical portion 51 </ b> B of the balloon member 51. Then, after the inner fixing device 55 is integrally coupled by a plurality of set screws 60, the outer fixing device 56 is arranged on the upper surface of the swinging device 38 in the major axis direction of the balloon member 51 (the arrow in FIG. 9). F direction) is attached so as to coincide with the reciprocating direction of the arm 34 (X direction in FIG. 6).

  The valve 53 is a check valve and is attached to the inner fixture 55.

  When compressed air is supplied to the sealed space 57 of the dome member 51 via the valve 53, the dome portion 51A expands upward, and the radius of curvature of the cross section including the central axis of the dome portion 51A is in the short axis direction (see FIG. 9 is the shape closest to the toric surface in the minimum (G direction of arrow G) and maximum in the long axis direction (direction of arrow F). In this case, since the radius of curvature of the dome portion 51A changes corresponding to the center height (vertex height) of the dome portion 51A as shown in FIG. 13, the height of the dome center is measured and adjusted by an appropriate device. Thus, the radius of curvature of the dome portion 51A can be set to a desired radius of curvature. In order to bring the shape of the dome 51A closer to the concave surface 2b of the lens 1, a plurality of types of dome members having different major axis and minor axis dimensions or ratios thereof are prepared, and the one close to the shape of the concave surface 2b of the lens 1 is prepared. It is preferable to select and use. In this case, it is preferable that the radius of curvature of the dome portion 51A in the major axis direction is set to be approximately equal to the maximum radius of curvature (minimum curvature) of the concave surface 2b of the lens 1.

  Here, in the present embodiment, the concave surface 2b is a toric surface, the lens diameters 65φ, 70φ, 75φ, 80φ (mm), the refractive index 1.7, and the base curve 0.00-11.25 [D] of the concave surface 2b. When polishing a lens with an astigmatic power range of 0.00 to 4.00 [D], the ratio of the short axis to the long axis of the balloon member 51 is 0.9, and the long axis dimensions are 65φ, 70φ, and 75φ. , 80φ, 85φ, 90φ, 95φ, 100φ (mm), and 9 types of polishing jigs 39 in total, one type having a balloon member 51 of a substantially circular shape and an outer diameter of 100 mm, are prepared as lenses. Select and use them appropriately according to the diameter.

  Selection of the polishing jig 39 is appropriately selected according to the lens diameter and the curvature of the surface to be polished 2b. However, in the case of a lens having the same diameter, it is preferable to use a polishing jig having a shorter major axis as the curvature increases. For example, when a toric lens having a diameter of 70 mm is polished, when the base curve is 0.00 to 1.50 [D] and the astigmatic power is 0.00 to 2.00 [D], the long axis 100φ (mm) is polished. If the base curve has an astigmatic power of 2.25 to 4.00 [D] or more, a 90φ polishing jig, and a base curve of 1.75 to 6.00 [D] has an astigmatic power of 0.00 to 4.00. In the case of [D], a long axis 90 φ polishing jig (however, in the case of a base curve of 2.75 to 6.00 [D] and an astigmatic power of 2.25 to 4.00 [D], 80 φ), base When the curve is 6.25 to 11.25 [D] and the astigmatic power is 0.00 to 4.00 [D], the long axis 80φ polishing jig (however, the base curve is 10.00 to 11.25 [D]) And the astigmatic power is 2.25 to 4.00 [D]).

  10 and 14, the polishing pad 40 used for polishing the concave surface 2b of the lens 1 has a thickness of about 1 mm made of, for example, a fibrous cloth such as polyurethane foam, felt, or nonwoven fabric, or a synthetic resin. A polishing member 70 formed of a sheet material and formed in an oval shape having a size substantially the same as the front view shape of the dome portion 51A of the balloon member 51, and a plurality of polishing portions 70 extending outward from the outer periphery of the polishing portion 70 It is integrally formed with the fixed piece 71 of the book. The polishing portion 70 is composed of eight petal pieces 73 that are radially formed by a plurality of grooves 72 formed from the outer periphery toward the center. Each petal piece 73 is formed in a trapezoidal shape in plan view so that the width on the center side is narrow and the width on the outer peripheral side is wide, and is connected to each other at the center. The fixed piece 71 is extended in the radial direction on the outer edges of a total of four petal pieces 73 located in the major axis direction (F direction) and the minor axis direction (G direction) among the eight petal pieces 73. Yes. The width of the fixed piece 71 is set narrower than the width of the outer edge of the petal piece 73. This is because the deformation of the balloon member 51 during polishing and the bending of the fixing piece 71 when the fixing piece 71 is pulled out from the fastening member 76 shown in FIG. 15 are facilitated.

  If the width of the fixing piece 71 is too wide, the fixing piece 71 lacks flexibility and is difficult to bend. If the width is too narrow, the fixing piece 71 is weak in strength, and thus is easily broken during polishing. Therefore, the width of the fixed piece 71 is determined in consideration of strength and flexibility. For example, when a 1 mm thick felt is used, the width is preferably about 5 to 15 mm. If it is 5 mm or less, the durability is lowered, and if it is 15 mm or more, the flexibility is lowered and the balloon member 51 does not follow the deformation. The number of the fixing pieces 71 is preferably two or more and provided at a constant interval. If the number of the fixing pieces 71 is too large, the contact area between the fixing pieces 71 and the fastening members 76 increases, and the pressure of the fastening members 76 applied to the fixing pieces 71 is dispersed and becomes small, so that the fixing pieces 71 are easily detached. On the other hand, if the amount is too small, stable fixing of the polishing pad 40 to the polishing jig 39 cannot be obtained. Therefore, the number of the fixing pieces 71 is more preferably about 3 to 5.

  Such a polishing pad 40 is detachably attached to the polishing jig 39 by the fastening member 76. The fastening member 76 is obtained by plastically deforming a wire spring having an appropriate thickness into a ring shape and superimposing both ends, and has a diameter smaller than the outer diameter of the outer fixture 56 in a natural state. The portions 76a and 76b are bent outward at substantially right angles.

  In order to attach the polishing pad 40 to the polishing jig 39, first, the dome portion 51A of the balloon member 51 is expanded into a predetermined dome shape by supplying compressed air, and then the polishing portion 70 of the polishing pad 40 is mounted thereon. Put. Next, both ends 76a and 76b of the tightening member 76 are sandwiched between fingertips, and the distance between the end portions 76a and 76b is narrowed against elasticity, so that the tightening member 76 is expanded in diameter. The fixing pieces 71 are pressed from above, and the fixing pieces 71 are bent downward and brought into contact with the outer periphery of the outer fixture 56. When the fingertips are released from both end portions 76a and 76b, the fastening member 76 returns to its original shape, and the fixing piece 71 is fastened and fixed to the outer periphery of the outer fixing tool 56, whereby the attachment of the polishing pad 40 is completed.

The lens 1 is polished by the polishing apparatus 30 having such a structure according to the following procedure.
First, the lens 1 is mounted on the lens mounting portion 36 of the arm 34 via the lens holder 37. Next, a polishing jig 39 to which a polishing pad 40 is attached is installed on the upper surface of the rocking device 38. When the lens 1 is attached to the lens attachment portion 36, the lens 1 is attached so that the axial direction of the minimum curvature of the polished surface 2b of the lens 1 coincides with the reciprocating movement direction of the arm 34 (the arrow X direction in FIG. 6). When the polishing jig 39 is installed on the swing device 38, the major axis direction (F direction) of the balloon member 51 is set to coincide with the reciprocating movement direction (arrow X direction) of the arm 34.

  When the lens 1 is attached to the lens attachment portion 36, the lens 1 is lowered by the elevating device 41, and the concave surface 2 b is pressed against the surface of the polishing pad 40. In this state, an abrasive is supplied to the surface of the polishing pad 40, and the arm 34 is reciprocated in the left-right direction and rotated in the front-rear direction around the shaft 33. The movement locus of the lens 1 due to the movement of the arm 34 is shown in FIG.

  Further, as the rotating shaft 21 rotates, the swinging device 38 is swung as shown in FIG. By such movement of the lens 1 and the swinging device 38, the concave surface 2b of the lens 1 is polished by the polishing pad 40 and the abrasive with a trackless polishing locus in which the polishing locus is slightly shifted every round, and a desired toric surface is obtained. Finish. The polishing allowance by the polishing pad 40 is about 5 to 9 μm. As the abrasive, for example, a solution in which an abrasive (abrasive grains) such as alumina oxide and diamond powder is dispersed in a polishing liquid is used.

  Since the concave surface 2b cut by the curve generator includes a machining step due to backlash or the like by NC control, it is necessary to remove this step by polishing. For this reason, it is preferable to polish the concave surface 2b by dividing the polishing step into two steps of rough polishing and finish polishing. For example, in rough polishing, an abrasive having an average particle diameter of 1.6 to 1.8 μm is used, and the temperature is controlled to 8 to 14 ° C. for polishing. The polishing time is 2 to 6 minutes, the polishing pressure is 5 to 400 mbar, and the rotation speed is 400 to 1000 rpm.

  Next, in finish polishing, polishing is performed using an abrasive having an average particle diameter of about 0.8 μm. The polishing time is about 30 seconds to 1 minute, the polishing pressure is 5 to 400 mbar, and the rotation speed is 400 to 1000 rpm. If the polishing is performed with the polishing conditions changed as described above, the processing step can be surely removed.

As described above, in the present invention, the minimum curvature k _O of the surface to be polished 2b of the lens 1 is calculated, and the surface to be polished 2b is polished with its axial direction coinciding with the major axis direction of the balloon member 51. Even if the surface to be polished is a non-rotationally symmetric curved surface, the minimum curvature of the surface to be polished 2b and its axial direction can be made to substantially coincide with the curvature of the major axis direction of the balloon member 51 and its long axis direction. Therefore, there is no gap between the outer peripheral edge in the major axis direction of the minimum curvature of the non-polished surface 2b and the outer peripheral part in the major axis direction of the polishing jig 39, and the entire surface to be polished can be polished well and uniformly. And a desired optical surface can be obtained.

  In the above-described embodiment, the example of polishing the concave surface 2b made of the toric surface of the aspherical astigmatism correction spectacle lens having a progressive element has been described. However, the present invention is not limited to this, and the spherical surface It can be used for polishing non-spherical surfaces, non-toric surfaces, progressive surfaces, surfaces where progressive surfaces and toric components are combined, aspheric surfaces with progressive elements, concave surfaces made of free-form surfaces such as composite surfaces, and convex surfaces. . In addition, what is necessary is just to use the balloon member which elastically deforms to a concave surface shape where an upper surface is an ellipse by injection | pouring of compressed air, when grinding | polishing a convex surface.

(A), (b) is the top view and sectional drawing of a spectacles lens. It is a flowchart which shows the grinding | polishing process of a lens. (A), (b) is a figure which shows the virtual curve and coordinate position on a to-be-polished surface. (A), (b) is a figure which shows the virtual curve and coordinate position when calculating | requiring the minimum curvature from three points. (A), (b) is a figure which shows the virtual curve and coordinate position when calculating | requiring the minimum curvature from nine points. It is a schematic block diagram of the grinding | polishing apparatus used for the grinding | polishing method of the lens which concerns on this invention. It is sectional drawing which shows the state which attached the lens to the lens holding body. It is a figure which shows the swivel turning motion of a rocking | fluctuation apparatus and a grinding | polishing jig | tool. It is a top view of a grinding jig. It is a top view of the polishing jig to which a polishing pad is attached. It is a bottom view of the grinding jig. It is the XII-XII sectional view taken on the line of FIG. It is a figure which shows the relationship between the height of a grinding | polishing jig | tool, and a curvature radius. It is a top view of a polishing pad. It is a perspective view of a fastening member. It is a figure which shows the movement locus | trajectory of a lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lens, 2a ... Convex surface, 2b ... Concave surface (surface to be polished), 2c ... Edge surface, 30 ... Polishing device, 32 ... Device main body, 34 ... Arm, 36 ... Lens holder, 37 ... Lens holder, 38 ... Oscillator, 39 ... polishing jig, 40 ... polishing pad, 51 ... balloon member.

Claims (3)

An optical lens using a balloon member which is formed into an elliptical cup shape with an elastic material and a top surface is expanded into a curved shape when a fluid is introduced therein, and a polishing pad attached to the upper surface of the balloon member An optical lens polishing method for polishing a non-rotationally symmetric polished surface,
Calculating and identifying an axial direction in which the average curvature of the polished surface of the optical lens is minimized; and
Attaching the optical lens to the polishing apparatus so that the axial direction in which the average curvature of the polished surface of the optical lens is minimized coincides with the long axis direction of the balloon member;
The balloon member is swung and swung while the polished surface of the optical lens is in contact with the polishing pad, and the optical lens is reciprocated in an axial direction in which the average curvature of the polished surface is minimized and the shaft Polishing the surface to be polished in a track-free polishing locus in which the polishing locus is slightly shifted every round by reciprocatingly rotating in a direction perpendicular to the direction;
An optical lens polishing method comprising:   The step of calculating and specifying the axial direction in which the average curvature of the surface to be polished of the optical lens is the minimum is performed on the surface to be polished that connects the geometric center on the surface to be polished and two point-symmetric points on the outer periphery. A plurality of virtual curves along the circumferential direction of the surface to be polished are determined by shifting the required angle, and at least three arbitrary points are determined on each virtual curve, and the average curvature of the virtual curve is calculated from the coordinates of these points, respectively. 2. The method of polishing an optical lens according to claim 1, wherein an imaginary curve having the smallest average curvature is selected and its axial direction is specified. The optical lens polishing method according to claim 1, wherein the optical lens is a meniscus lens.

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