JP2005331427A - Refractive index measuring method for lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens refractive index measuring method capable of measuring easily and inexpensively a refractive index of a lens. <P>SOLUTION: In this measuring method using a lens meter capable of measuring a dioptic power of the lens, the examined lens L is arranged on a nose piece 9 serving as a measuring base point of the lens meter, and the first dioptic power of the lens is measured in the atmospheric air. Then, the lens L provided respectively with the first and second transparent gel bodies 16, 21 of the same material brought into close contact with close contact faces 18, 23 on obverse and reverse face sides of the examined lens L are arranged on the nose piece 9 to measure the second lens dioptic power of the examined lens L sandwiched with the both gel bodies 16, 21, in the atmospheric air. The refractive index of the examined lens L is calculated based on the obtained first and second lens dioptic power. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a measuring method for measuring the refractive index of a lens such as a spectacle lens.

The higher the refractive index of a spectacle lens, the more the thickness of the lens can be reduced. Therefore, it is preferable to use a lens having a high refractive index for a wearer whose power is advanced by myopia. On the other hand, since the higher the refractive index, the higher the price of the lens, the higher the price, the conventional eyeglass stores have stocked many lenses with different refractive indexes to provide lenses that match the customer's frequency and budget. ing.
By the way, there are cases where eyeglass stores demand glasses with the same lens as the glasses that the customer actually wears, in addition to customers who want new glasses. In this case, it is sufficient that the customer stores the past data of the customer, but if there is no data, it is necessary to measure what refractive index lens is used by borrowing the customer's glasses.
In addition to the reason of “customer's request”, there is a request to check whether a predetermined refractive index is obtained for a lens received from a manufacturer other than a reliable manufacturer at an eyeglass store. There is also.
The most practical means for measuring the refractive index of a lens is a reflection type measuring instrument. Patent Document 1 is cited as a prior art of such a reflection type measuring instrument. The reflection type measuring instrument described here uses a prism to form an interference fringe of light transmitted through the lens, and indirectly analyzes the refractive index of the lens from the phase of the interference fringe.
Japanese Patent Laid-Open No. 5-113398

However, it is difficult to actually measure the refractive index of a lens at an eyeglass store for the following reasons.
1) Since the reflection type measuring instrument as described above measures reflected light, when the spectacle lens to be measured is coated with a surface coating such as antireflection or anti-fogging, the error is too large and the measurement is performed. It becomes impossible.
2) Reflective measuring instruments are not always available at regular eyeglass stores, and those with high accuracy are very expensive and cannot be newly purchased. In addition, although there is a simple reflection type measuring instrument, the problem of the above 1) occurs in the same manner, and in addition to low accuracy, skill is required for measurement.
3) It is difficult to measure the refractive index of the lens at a spectacles store mainly because of the reasons 1) and 2) above. If there is a request from the customer as described above, the customer The lens must be selected by estimating the refractive index from the lens power and lens thickness.
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 lens refractive index measuring method that can easily and inexpensively measure the refractive index of a lens.

In order to achieve the above object, according to the first aspect of the present invention, a mark is disposed between the measurement light source and the test lens, and based on the amount of variation in image formation of the mark obtained through the test lens. A measurement method using a lens meter capable of measuring the lens power of the lens to be tested, wherein the lens to be tested is disposed at a measurement base point of the lens meter, and the lens meter is used to measure the lens power in the air. A first lens power measurement step for measuring a first lens power of the lens, and the same lens to be tested in which transparent first and second gel bodies made of the same material are adhered to the front and back lens surfaces, respectively. A second lens power measuring step for measuring a second lens power of the lens to be measured which is disposed at the measurement base point of the meter and is sandwiched between the gel bodies in the air by the lens meter; 2 Based on the lens power that it has to have a calculating step of calculating a refractive index of the subject lens and the gist thereof.
The gist of the invention of claim 2 is that, in addition to the configuration of the invention of claim 1, the gel body is formed into a plate shape.
Further, in the invention of claim 3, in addition to the configuration of the invention of claim 1 or 2, the adhesion surface of the gel body to the test lens is curved according to the unevenness of the lens curve. The gist.

Further, in the invention of claim 4, in addition to the structure of the invention of any one of claims 1 to 3, transparent first and second flat plates are brought into close contact with the back surfaces of the two gel bodies, respectively. A five-layer structure in which the first planar plate, the first gel body, the test lens, the second gel body, and the second planar plate are arranged in this order in a state where the gel body is in close contact with the test lens. The gist is that the second lens power is measured through the five-layer structure.
Further, the gist of the invention of claim 5 is that, in addition to the configuration of the invention of claim 4, the two transparent flat plates are arranged substantially in parallel.

In such a configuration, the lens lens measures the first lens power of the test lens in the air arranged at the measurement base point and is sandwiched between the transparent first and second gel bodies in the air. The second lens power of the test lens is measured. Then, the refractive index is calculated based on the obtained lens power. Using the lens power of the test lens alone in the air obtained by the lens meter and the lens power of the test lens sandwiched between both gel bodies in the air, the refractive power of the known air and the refractive power of the gel body are used as parameters. It is intended to obtain the refractive index of the test lens.
The refractive index can be calculated from the following calculation formula.
N = (n2 * Dv1-n1 * Dv2) / (Dv1-Dv2)
N: Refractive index of the test lens, Dv1: Lens power in air (first lens power), Dv2: Lens power through the first and second gel bodies (second lens power), n1: Refractive index of air, n2: refractive index of gel

Here, the gel body needs to be composed of a transparent gel having a uniform refractive index. The concept of transparency includes translucency. The material is not particularly limited as long as the material is soft enough to follow the lens curve and adhere to the surface. For example, a functional hydrogel based on a water-soluble polymer (eg, polyhydric alcohol or polyacrylic acid), a segmented polyurethane gel that does not use a dispersion medium (eg, polyester-based polyurethane resin, polycarbonate-based polyurethane resin, etc.) ), Silicone gel, natural polymer gel (for example, sodium alginate gel, chitosan gel) and the like.
The shape of the first and second gel bodies is a lens that exhibits a plate shape that is adhered along the front lens surface (lens object side surface) and the back lens surface (eyeball side surface) of the lens to be examined. It is preferable in terms of stability when it is arranged at the measurement base point of the meter. Specifically, a plate shape such as a rectangular parallelepiped shape having a low height such as a tile or a cylindrical shape having a low height can be given. In this case, it is preferable that at least the contact surface that is in close contact with the lens to be inspected is curved according to the unevenness of the lens curve. As a result, the adhesion of the gel body to the front and back lens surfaces of the test lens is improved. For example, the adhesion surface of the gel body arranged on the object side surface of the test lens is formed in a concave shape in accordance with the convex shape of the test lens. At this time, it is preferable to prepare a plurality of gel bodies having different degrees of curvature in order to cope with the fact that the degree of curvature of the test lens varies. The degree of curvature of the close contact surface of the gel body and the degree of curvature of the unevenness of the test lens do not need to be completely the same.

Moreover, it is preferable that the back surface (hereinafter referred to as the back surface) of the close contact surface in close contact with the test lens of the gel body extends in a direction orthogonal to the optical axis of the lens meter. That is, it is most preferable that the back surface of the gel body is formed in a planar shape and arranged perpendicular to the optical axis of the meter. If the back surface of the gel body is not orthogonal to the optical axis, a measurement error will occur, and if it is severe, error correction and measurement rework are required.
In this case, even if the close contact surface of the gel body is brought into close contact with the lens curve of the lens to be examined, the degree of curvature of the lens curve and the close contact surface of the gel body does not necessarily match completely. Therefore, even if the back surface of the gel body is configured in a planar shape so that it can be arranged orthogonally to the optical axis of the lens meter, the gel body deforms when the gel body is actually brought into close contact with the lens to be tested. Flatness may be lost. In order to solve such a problem, it is preferable that the transparent first and second flat plates are in close contact with the back surface of the gel body. Since the flat plate is hard, its flatness is not lost due to the deformation of the gel body. That is, a five-layer structure in which the first plane plate, the first gel body, the test lens, the second gel body, and the second plane plate are arranged in this order in a state where both gel bodies are in close contact with the test lens. Thus, the second lens power is measured through these five-layer structures.
When measuring the test lens having such a five-layer structure, each of the two transparent flat plates is orthogonal to the optical axis of the lens meter. That is, it is preferable for the two flat plates to be arranged substantially in parallel to reduce errors. Further, if the flat plate is very thin, it can be ignored when measuring the first lens power as an error. However, when measuring the first lens power, both planes are provided before and after the lens to be tested. A more accurate value can be obtained by measuring the first lens power with the plate placed.

  In the inventions of the above-mentioned claims, it is possible to individually measure the refractive index of a predetermined lens whose refractive index is unknown, which has been difficult to measure in the past, and the measurement work is easy using simple equipment. At a low cost.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for measuring a refractive index of a lens according to the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the lens meter 1 used in the present embodiment is composed of a housing 3 and a measurement unit 5 protruding in front of the housing 3. A CRT display 6 is disposed at an upper position of the housing 3. A power measuring optical system (not shown) for measuring the lens power is disposed inside the housing 3. The frequency measurement optical system includes a measurement light source such as an LED, a transparent target plate on which a mark is printed, a lens, a mirror, a prism, an image sensor, a controller, and the like. The principle of operation of the lens meter 1 is that the controller analyzes the amount of variation between the image of the mark passing through the test lens L captured by the image sensor and the image of the mark without the test lens L. . In the present embodiment, a known lens meter 1 provided with such a power measuring optical system is used.
The measuring unit 5 includes a light emitting side table 7 and a light receiving side table 8 disposed on the light emitting side table 7. A nosepiece 9 as a measurement base point is disposed on the upper side of the light projecting side table 7. A lens pad 10 is disposed on the back side of the nosepiece 9 (to the right of the nosepiece 9 in FIG. 1). A marking mechanism 11 and a lens pressing lever 12 are disposed between the tables 7 and 8. A leaf spring 13 is extended rearward from the lower end position of the lever 12. A pad 14 is attached to the tip of the leaf spring 13.
When the test lens L is set in such a lens meter 1, the test lens L is placed on the nosepiece 9 in contact with the lens pad 10, and the pad 14 is operated by operating the lever 12. It is lowered and clamped so as not to fall with the nosepiece 9. Basically, the lens power of the test lens L can be measured in this state, but the concave gel pad 15 and the convex gel pad 16 are brought into close contact with the front lens surface and the back lens surface of the test lens L. Thus, it is also possible to measure the lens power of the lens L to be tested through the gel pads 15 and 16.

As shown in FIGS. 2A and 2B, the concave gel pad 15 disposed on the front lens surface (the object-side surface of the lens) has a planar circular shape, and the transparent first gel body 16 and the first gel body 16 The glass plate 17 is a flat plate. The contact surface 18 of the first gel body 16 (the surface that is in close contact with the lens L) has a concave shape as if a part of the inner peripheral surface of a true sphere having a predetermined diameter is cut out. The meat is thickened so as to increase the thickness evenly from the center to the periphery. The first gel body 16 is homogeneous and has a predetermined refractive index. The back surface 19 of the first gel body 16 (the back surface of the close contact surface 18) has a planar shape. The glass plate 17 is a transparent flat plate and is in close contact with the back surface 19 of the first gel body 16. The frequency of the glass plate 17 is 0.
As shown in FIGS. 3A and 3B, the convex gel pad 20 arranged on the back lens surface (lens eyeball side surface) has a planar circular shape, and the second transparent gel body 21 and the second gel body 21 are transparent. The glass plate 22 is a flat plate. The contact surface 23 of the second gel body 21 (the surface that is in close contact with the lens L) has a convex shape as if a part of the outer peripheral surface of a true sphere having a predetermined diameter is cut out, and the second gel body 21 is centered. It is supposed to be meat-filled to reduce the thickness evenly from the outside. The refractive index of the second gel body 21 is the same as that of the first gel body 16. The back surface 24 of the second gel body 21 (the back surface of the contact surface 23) is planar. The glass plate 22 is the same as the glass plate 17 of the concave gel pad 15. As the first and second gel bodies 16 and 21 in the present embodiment, a polyester-based segmented polyurethane gel that does not use a dispersion medium is used.

Next, a specific method for measuring the refractive index of a lens using such a lens meter 1 will be described.
First, as shown in FIG. 5, glass plates 17 and 22 are respectively arranged on the front and back lens surfaces of the lens L to be examined with the O-rings 25 interposed therebetween, placed on the nosepiece 9 of the lens meter 1, and the pad 14 is lowered. Hold it. At this time, it arrange | positions so that both glass plates 17 and 22h may be parallel, and it may orthogonally cross with respect to the light beam E projected upwards from the center of the nosepiece 9. FIG. In this state, the lens power of the lens L (including the refractive indexes of the glass plates 17 and 22) in the air is first measured in accordance with normal operation. This lens power is defined as the first lens power. The glass plates 17 and 22 are prepared separately from the first and second gel bodies 16 and 21 in advance.
Next, as shown in FIG. 4, the concave gel pad 15 and the convex gel pad 20 are respectively arranged on the front and back lens surfaces of the lens L to be tested. The contact surfaces 18 and 23 of the first and second gel bodies 16 and 21 are reasonably brought into close contact with each other along substantially the curvature of the front and back lens surfaces of the lens L to be tested. Since the first and second gel bodies 16 and 21 are also sticky, once they are brought into close contact with each other, the first and second gel bodies 16 and 21 are held on the lens surface unless actively peeled off. The glass plate 17, the first gel body 16, the test lens L, the second gel body 22, and the glass plate 22 in which the test lens L is disposed in the middle with the concave gel pad 15 and the convex gel pad 20 disposed. A five-layered structure is formed in which no air layer enters in the middle.
As shown in FIG. 6, the test lens L having the concave gel pad 15 and the convex gel pad 20 placed thereon is placed on the nosepiece 9 of the lens meter 1 and the pad 14 is lowered and held. At this time, it arrange | positions so that both glass plates 17 and 22h may be parallel, and it may orthogonally cross with respect to the light beam E projected upwards from the center of the nosepiece 9. FIG. In this state, the lens power of the test lens L having a five-layer structure in air is first measured in accordance with a normal operation. This lens power is set as the second lens power.
Then, based on the first lens power and the second lens power, the refractive index of the test lens L is calculated using known parameters (refractive power of air and refractive power of the gel body). In addition, the refractive indexes of the glass plates 17 and 22 are canceled as a result by measuring the first and second lens powers.

With this configuration, the present embodiment has the following effects.
(1) The refractive index of a desired lens can be measured on the spot using the lens meter 1 that is always possessed by the spectacles store, and the refractive index of the lens at the spectacles store, which has been difficult in the past, can be confirmed. It becomes possible. In addition, since no special device for refractive index measurement is required, the cost is not burdened.
(2) The theory of refractive index calculation in the present invention uses two types of media (that is, air and the first and second gel bodies 16 and 21) having a known refractive index surrounding the lens L to be measured. Thus, the refractive index of the lens L to be measured is calculated from the measured power. In this case, since the first and second gel bodies 16 and 21 are solid, they are easier to handle than liquids such as water. For example, in a liquid such as water, if the liquid level is shaking, light is scattered and the error is too large, so the measurement work needs to be done very carefully and slowly, but such consideration is not necessary at all. It is possible to shorten the measurement time.
Further, if a liquid such as water is used instead of the first and second gel bodies 16 and 21, the test lens L is immersed in a dish such as a petri dish for measurement. If it is liquid, there is a possibility that it will spill around the measurement unit 5 of the lens meter 1 during such a measurement operation and cause the lens meter 1 to malfunction. However, in this embodiment, such a problem may occur. The measurement work can be done with peace of mind.
(3) The first and second gel bodies 16 and 21 are soft and follow the lens curve. As a result, it is difficult to make the back surfaces 18 and 24 of the gel bodies 16 and 21 that are preferably flat surfaces into a planar shape. ing. In the present embodiment, the glass plates 17 and 22 can be flattened by sticking to the back surfaces 18 and 24, so that errors during measurement can be minimized. Further, since the glass plates 17 and 22 are hard, the lens L can be stably held horizontally without being bent when placed on the nosepiece 9.
(4) Since the first and second gel bodies 16 and 21 are tile-shaped plate bodies, they are easy to be attached to the lens L and are not unnecessarily thick, so that they are set on the lens meter 1. It can be stably held between the nosepiece 9 and the pad 14.

It should be noted that the present invention can be modified and embodied as follows.
In the above embodiment, when the first lens power is measured, the glass plates 17 and 22 are arranged and measured. However, since the presence or absence of the glass plates 17 and 22 is actually a slight error, the glass plates 17 and 22 are measured. The first lens power may be measured without 22.
-The thickness and shape of the 1st and 2nd gel bodies 16 and 21 can be changed suitably.
The shape and type of the lens meter 1 are not limited to the above embodiment. The measurement base point is not limited to the above.
-The material of the glass plates 17 and 22 may be other than glass.
-Besides, it is free to implement in a mode that does not depart from the gist of the present invention.

The side view explaining the state which set the to-be-tested lens to the lens meter explaining embodiment of this invention. (A) is a perspective view of a concave gel pad, (b) is a cross-sectional view of the same concave gel pad. (A) is a perspective view of a convex gel pad, (b) is a cross-sectional view of the same convex gel pad. Sectional drawing in the state which stuck the concave gel pad and the convex gel pad to the to-be-tested lens. The partial enlarged view explaining the state which set the to-be-tested lens to the lens meter when measuring a 1st lens power. The elements on larger scale explaining the state which set the to-be-tested lens to the lens meter when measuring a 2nd lens power.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lens meter, 9 ... Nose piece as a measurement reference point, 16 ... 1st gel body, 17 ... Glass plate as 1st plane plate, 21 ... 2nd gel body, 22 ... As 2nd plane plate Glass plate.

Claims (5)

A lens meter that can measure the lens power of the test lens based on the amount of variation in image formation of the mark obtained by placing a mark between the measurement light source and the test lens. The measurement method used,
A first lens power measurement step of disposing the test lens at a measurement base point of the lens meter and measuring a first lens power of the test lens in the air by the lens meter;
The same test lens having the same first and second transparent gel bodies made of the same material in close contact with the front and back lens surfaces is placed at the measurement reference point of the lens meter, and both the gel bodies in the air by the lens meter. A second lens power measurement step of measuring a second lens power of the lens to be tested sandwiched between
A method for measuring a refractive index of a lens, comprising: a calculation step of calculating a refractive index of the lens to be tested based on the first and second lens powers. 2. The method for measuring a refractive index of a lens according to claim 1, wherein the gel body is formed into a plate shape. The method for measuring a refractive index of a lens according to claim 1 or 2, wherein the adhesion surface of the gel body with respect to the lens to be examined is curved according to the unevenness of the lens curve. In close contact with the first and second flat plates transparent to the back surfaces of the two gel bodies, the first flat plate, the first gel body, 5. A five-layer structure in which a test lens, a second gel body, and a second plane plate are arranged in this order, and the second lens power is measured through the five-layer structure. The method for measuring a refractive index of a lens according to any one of claims 1 to 3. 5. The method of measuring a refractive index of a lens according to claim 4, wherein the two transparent flat plates are arranged substantially in parallel.

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