JPH0353572B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lensmeter for measuring the refractive properties of eyeglass lenses, etc., and a target plate used therefor. To measure the refractive properties of optical members for eye refractive correction such as eyeglass lenses and contact lenses (hereinafter simply referred to as test lenses), such as spherical refractive power, cylindrical refractive power, and their axial angles, and prismatic refractive power and their base direction. A lens meter is well known as an optical device. Examples of measurement targets for conventional lensmeters include a corona target, which is made up of small circles arranged in an annular shape, and a cross-line target, which is made up of two sets of line patterns made up of two lines and three lines orthogonal to each other. . In the method of measuring the cylindrical axis direction of the astigmatic lens to be tested using these conventional lens meters with targets, in the case of a corona target, the flow direction of the corona small circle is measured as the cylindrical axis direction, and in the case of a cross-line target, the line is measured as the cylindrical axis direction. The running direction of the line pattern at the position where the distortion of the small rectangular groups at the pattern intersections was corrected was measured as the cylinder axis direction. However, with these conventional lensmeters, if the astigmatic lens to be tested is a weakly astigmatic lens whose cylindrical refractive power is only a minute amount, for example, about 0.12 Dioptor or 0.25 Dioptor, the above-mentioned flow rate of the corona target and cross line Since the amount of distortion in the small rectangular group of targets is minute, it is difficult to determine the cylinder axis direction, and therefore the refractive characteristics of the lens to be tested cannot be accurately measured. Other examples of conventional lensmeter measurement targets include small circles arranged in two directions at right angles, as disclosed in Utility Model Application No. 55-14506 and British Patent No.
Proposed by No. 1147452. These methods utilize the fact that small circular images flowing in the cylindrical axis direction of the astigmatic lens to be tested mutually overlap with other small circular images, making them easier to detect. However, even with this configuration, the minimum cylindrical power of commercially available eyeglass lenses C = 0.125
It is difficult to make measurements on the order of diopters quickly and accurately. The present invention was made to solve the drawbacks of the conventional lensmeter, and its first purpose is to improve the measurement accuracy compared to the conventional lensmeter, especially for lenses to be tested with weak cylindrical refractive power. An object of the present invention is to provide a lens meter that can measure the axial direction of a cylinder with higher accuracy. A second object of the present invention is to solve the drawbacks of conventional target plates for lens meters, and to improve measurement accuracy, especially for a target plate having weak cylindrical refractive power, compared to conventional target plates for lens meters. It is an object of the present invention to provide a target plate for a lens meter having a novel target pattern capable of measuring the cylindrical axis direction of a test lens with higher accuracy. A feature of the present invention for achieving the above object is that the target pattern of the target plate includes at least one dotted straight line and at least one dotted straight line parallel to the dotted straight line.
By using a straight line group pattern consisting of straight lines, and by configuring the diameter of the point pattern constituting this point straight line, the width of the straight line, and the interval between the dotted line and the straight line to have a quantitative relationship described in detail later, When the orientation of the linear group pattern differs from the cylinder axis direction of the test lens in the measurement of the minimum measurable cylinder power of the test lens required for measurement and the test lens astigmatism of a cylinder power higher than that, the straight line of the above-mentioned linear group pattern The flow image of the point pattern that makes up the image and the point line becomes inclined, and conversely, when the orientation of the straight line group pattern coincides with the cylindrical axis direction of the test lens, the straight image and the flow image of the point pattern touch each other. In addition, there is a lensmeter that functions so that the two are perpendicular to each other, and a target plate for the lensmeter used therein. The present invention focuses on the visual characteristics of the examiner's eyes, that is, when visually perceiving whether or not a large number of small straight lines (corresponding to a flow image of a dot pattern in the present invention) is inclined with respect to the direction in which they are arranged. , visual perception accuracy is improved by comparing the slope with a straight line extending parallel to the arrangement direction of the small straight line group, rather than simply looking at the small straight line group, and furthermore, the above-mentioned straight line is in contact with the small straight line group. This method effectively utilizes the visual characteristics of the human eye, which further improves the accuracy of visual perception of the amount of inclination. Furthermore, in a more limited embodiment of the present invention, the above-mentioned target pattern can be achieved by configuring a target pattern in which two dotted straight lines and a further straight line are arranged between them so that these three lines are parallel to each other. In addition to this characteristic, another visual characteristic of the human eye is also effectively utilized, in that it is possible to more accurately judge whether or not a small straight line is sloped based on whether or not the end portions of the small straight lines that face each other match or do not match. The configuration, operation, and effects of the present invention will become clearer through the following detailed explanation of principles and embodiments based on the drawings. First, the principle of the present invention will be explained. FIG. 1 is a perspective view showing the principle of the configuration of an optical system of a lensmeter. The configuration and operation of this optical system when the test lens TL is not placed in the measurement optical path are as follows. Collimator lens with focal length f ₁ when the test lens TL is not placed in the optical path
The emitted light beam from the point target t of the target plate T placed at the front focal position of CL exits the collimator lens CL and then heads toward the objective lens OL. This objective lens OL has a focus plate L placed at a focal point _f2 on the rear side. The parallel light beam from the collimator lens that is incident on the objective lens OL is formed into an image of the target t on the focus plate L by the objective lens OL.
Make t′. Here, the light flux used to form the target image t' is determined mainly by the effective diameter φ of the test lens receiving portion S for placing the test lens in the measurement optical path. Next, considering the state in which the test lens TL, which is an astigmatic lens, is placed in the measurement optical path by the test lens receiver S, the light beam after exiting the test lens TL does not become a parallel light beam, but is a parallel light beam to the target t. The image is no longer formed on the focusing plate L. Therefore, the target plate T is moved on the measurement optical axis to form a target image on the focus plate L.
The focus must be adjusted so that t′ is imaged. However, in this case, since the lens TL to be tested is an astigmatic lens, the target image t' is not formed as a point image even though the target t is point-shaped, but is the main character of either the strength or weakness of the lens to be tested. It becomes a straight line flowing in a direction perpendicular to the meridian direction. Let the length of this linear image be 2n as shown in Figure 1,
Hereinafter, the measurement optical system of the lens meter having the above configuration and the lens to be tested will be considered as a thin lens system. The amount of movement of the target plate T has a linear relationship with the refractive power of the test lens TL, and the amount of movement m ₀ of the target plate T per unit refractive power is m ₀ = f ₁ ² /1000mm/dioptor (1). Become. Here, f ₁ is the focal length of the collimator lens CL as described above. Therefore, assuming that the cylindrical refractive power of the lens TL to be tested is a C diopter, the movement width of the target plate T due to it is =f ₁ ² /1000C mm (2). In other words, in FIG. 1, when the target plate T is moved by the movement width of equation (2) above from a state in which the first focal line _F1 is imaged on the focusing plate L, the focusing plate L
The first focal line F ₁ above moves and becomes the second focal line instead.
This means that F ₂ is imaged onto the reticle L. Next, consider the magnification relationship of the target image (focal line image). As mentioned above, when the lens to be tested is placed in the measurement optical path, the lens meter moves the target plate T in the direction of the measurement optical axis to convert the light beam exiting the lens to be measured into a parallel light beam. The light beam is focused on a focus plate placed at the focal point of the objective lens, so that a target image can be formed.
The refractive power of the lens to be tested is determined from this state, that is, the position after the target plate T has been moved. In general, two lenses with focal lengths f _i and f _j are separated by l
The composite focal length f ₀ when the two lenses are placed apart from each other is given as 1/f ₀ =1/f _i +1/f _j −l/f _i f _j (3). Therefore, the composite focus of the collimator lens CL having a focal length _f1 and the test lens TL having a focal length F (if the test lens is an astigmatic lens, the focal length of the first or second principal meridian) In principle, distance F ₀ is the focal length of test lens TL, collimator lens CL, and collimator lens CL, f ₁
In the case of arranging them at a distance from each other, from the above equation (3), 1/F ₀ =1/f ₁ +1/F−f ₁ /f ₁ ·F (4) = 1/f ₁ . That is, the combined focal length is always the focal length f ₁ of the collimator lens. On the other hand, since the test lens TL and the objective lens OL are connected by a parallel light beam, the lateral magnification of the entire optical system is β
is β=f ₂ /f ¹ ...(5). From the above, the first focal line F ₁ and the second focal line in Fig.
The focal line distance D _F between the focal line F ₂ and the focal line F 2 is: D _F = P−f ₂ = f ₁ ² /1000・C・β ² =f ₁ ² /1000・C・(f ₂ /f ₁ ) ² = f ₂ ² /1000·C ...(6) It can be obtained. From this, the length h of the focal line (here, the length h of the focal line is the length of one side of the optical axis as h. The length of the entire focal line is expressed as 2h) is a proportional relationship. From this, h=(1-f ₂ /P)・φ/2 = (f ₂・C/f ₂・C+1000)・φ/2 ……(7). Calculating the length h _T of the focal line on the focusing plate T from equation (7), h _T = h/β = f ₁ / f ₂ (f ₂・C/f ₂・C+1000)・φ/2 = f ₂ · C / f ₂ · C + 1000 · φ / 2 ... (8). Here, if the cylindrical power is C and the minimum measurable cylindrical power required for this lens meter is C = 0.125 diopter, which is the minimum cylindrical power of commercially available eyeglass lenses, then the length h _T on the target plate T is:
From equation (8), it is given as h _T =f ₁ ×0.125/f ₂ ×0.125+1000×φ/2 (9). From this, as shown in FIG. 2A, the distance K between the centers of the point pattern t ₀ on the target plate T and the straight line l is
If they are selected so that they match at the minimum cylindricity C, then k=2h _T ...(10). In addition, the diameter a of the point pattern t ₀ and the width d of the straight line l are set so that ka=h _T and k-d=h T, a=h _T d=h _{T ……} (11) I choose. When measuring a test lens having the minimum measurable cylindrical power C (C = 0.125 in equation (9)) with this lens meter, the first cylinder axis direction of the test lens and a straight line group on the target plate T. When the orientation directions of the patterns are orthogonal (in other words,
The second cylindrical axis direction of the test lens and the target plate T
When the orientation directions of the straight line group patterns above match),
As shown in FIG. 2B, the point pattern image t' and the straight line image l' on the focus plate L flow in the direction of the second cylinder axis under the action of the second cylinder refractive power of the test lens. The dot pattern image t' and the straight line pattern image l' can be made to be in contact with each other. In other words, depending on whether the intersection angle γ between the flow image t' of this point pattern and the straight line image l' is a right angle, it is possible to determine whether the alignment direction of the straight line group pattern matches the direction of the cylindrical axis of the test lens. It is possible to detect whether or not. As described above, the present invention utilizes the "inclination perception of a small straight line using the standard straight line as a comparison guide," which has extremely high visual perceptual accuracy for the human eye, and therefore can make the measurement accuracy in the cylinder axis direction extremely high. can. Specific embodiments of a lens meter and a target plate for a lens meter based on the principle explained above will be described in detail below with reference to the drawings. First, a first embodiment of a target plate for a lens meter will be described with reference to FIGS. 3 to 6. As shown in FIG. 3, the target plate 1 has a large number of dot patterns 21,
A straight line group pattern 4 is formed of a dotted straight line 2 made up of 22, 23, . . . 2n and a straight line 3 arranged parallel to the dotted straight line 2. The distance between the dotted line 2 and the straight line 3 that make up the straight line group pattern 4 has the relationship shown in equation (10) above, and the diameter of the dotted pattern that makes up the dotted line 2 and the width of the straight line 3 are expressed by the equation (11) above.
It has the relationship of Eq. Furthermore, on the target board 1,
A second straight line pattern 5 is formed that is perpendicular to the straight line group pattern 4 described above. This second linear pattern 5 is provided to facilitate reading of the cylindrical axis angle of the lens to be tested, as will be described later, and is not necessarily an essential element of the present invention. 4 to 6 are diagrams schematically showing a method for measuring the refractive characteristics of the lens to be tested TL using the target plate T shown in FIG. It shows the relationship between the projected image and the cylindrical axis arrangement of the lens TL to be tested. The first cylindrical axis 8 of the lens to be tested TL is aligned with the reference horizontal line (0°-
The second cylinder axis 9 is assumed to be in the direction θ ₁ having an angle α with respect to the 180° target line 7), and the second cylinder axis 9 is in the direction θ ₂ =θ ₁ +90°. Here, as shown in FIG. 4, the orientation direction of the straight line group pattern image 4' is projected onto the focus plate 6 such that it is different from the direction of the second cylindrical axis 9, and the first cylindrical axis 8
If it is focused on the focal position of , each point pattern image 2n'(n'=1, 2, 3...) of the point straight line image 2'
is a flow image parallel to the axial direction θ ₁ of the first cylindrical shaft 8, and since this flow image has a tendency toward the running direction of the straight line image 3', the examiner can quickly find the direction of the target to be inspected. It is possible to detect a mismatch with the direction of the cylindrical axis of the lens. Next, as shown in FIG. 5, the flow image 2n' of the point pattern on the target plate T becomes a straight line 3' (the straight line pattern 3' is blurred, but its linearity is not lost). Rotate until they are orthogonal. When the flow images are perpendicular to each other, the orientation direction of the straight line group pattern image 4' coincides with the direction θ ₂ of the second cylindrical axis 9, and at the same time, the second straight line pattern image 5' coincides with the direction θ ₁ of the first cylindrical axis 8. , and since the target image is focused on the focal position of the first cylindrical axis 8, this second linear pattern image 5' becomes a clear focused image. Then, the direction of the second linear pattern image 5' is read using the angle scale 10 formed on the focus plate 6 to obtain the first cylinder axis angle θ ₁ . Next, when the target plate is simply moved in the direction of the measurement optical axis without rotating the target plate, the straight line group pattern image 4' becomes the second one, as shown in FIG.
It is focused on the focal position of the cylindrical axis 9. At this time, both the straight line image 3' and the dotted line image 2' become clear images, and each of the dotted straight line point pattern images is parallel to the second cylinder axis direction _θ2 , so each dot pattern image is partially overlapped. together, forming a single straight image as a whole. The second cylinder axis direction θ ₂ can be read on the angle scale 10 from the alignment direction of the straight line image 3' that has become clear and the dotted line pattern image 2' that has become a single straight line image. FIG. 7 is a plan view showing a second embodiment of the target plate of the present invention. The target plate 20 in this embodiment has two straight line group patterns 21, 2.
2 are formed to be orthogonal to each other. Furthermore, the straight line group pattern 21 consists of two parallel dotted straight lines 2
3 and 24, and a straight line 25 parallel to these and placed between them. Then, dot patterns 26n, 27 forming dotted straight lines 23, 24
The diameter of n (n=1, 2, 3...) and the width of the straight line 25 are given by the above equation (11), and
As in the first embodiment, the distance between the straight line 25 and the dotted straight lines 23 and 24 is given by the above equation (10). Similarly, the straight line group pattern 22 is also formed from two dotted straight lines 30 and 31 and a straight line 32. FIG. 8 is a schematic diagram showing the relationship between the projected image of the target plate 20 on the focus plate 6 of FIG. 7 and the test lens TL, and the arrangement relationship between the two is similar to that of FIG. They are the same, and the same components are given the same reference numerals and the description thereof will be omitted. When the alignment direction of the straight line group pattern images 21', 22' is different from the cylindrical axis direction of the test lens, the dotted straight line images 23', 24',
The flow images of the dot pattern images 30' and 31' flow in directions oblique to the straight line images 25' and 32', respectively, and their intersection angles ε are not at right angles. Furthermore, in this embodiment, the dot patterns constituting a set of dot straight lines are configured to face each other in pairs. Therefore, if the orientation of the straight line group pattern and the orientation of the cylinder axis are different, the flow images of the respective point patterns will be shifted laterally by Δ ₁ or Δ ₂ , as shown in FIG. Then, when the target plate is rotated so that the orientation of the linear group pattern and the cylindrical axis direction of the lens to be tested coincide, the flow images of the dot patterns are free from lateral deviation and coincide with each other, as shown in FIG. As described above, in this embodiment, not only the inclination of the flow image of the dot pattern with respect to the straight line image, but also the agreement/non-coincidence of the flow images with each other can be used for the cylinder axis measurement, and higher measurement accuracy can be obtained. FIG. 10 is a plan view showing a third embodiment of the target plate for a lens meter according to the present invention. On this target plate 40, two straight line group patterns 21 and 22 are formed so as to be perpendicular to each other, as in the second embodiment, and a known circular corona pattern 41 is further formed at the cut intersection. has been done.
The target plate of this example measures the cylindrical axis direction using a linear group pattern for a test lens having a weak cylindrical refractive power, and measures the cylindrical axis direction for a test lens having a strong cylindrical refractive power. The method uses a circular corona pattern to measure the cylindrical axis direction. In addition, when specific numerical examples of the diameter a of the dot pattern and the interval k between the dotted straight lines 2a and 2b in the above-mentioned first and second embodiments are obtained using equations (9) and (11), they are as shown in Table 1. Become.

[Table] FIG. 11 is an optical system layout diagram showing an example of the configuration of a lens meter having the above-mentioned target plate. On the measurement optical axis 0, there are a target plate 1, a light source 100 for illuminating the target plate 1, a collimator lens 101, a test lens receiving means 102,
Objective lens 103, focus plate 6, eyepiece lens 104
They each have The target plate 1 is attached to a cylindrical shaft 113, and the cylindrical shaft 113 is connected to the pinion 1.
The bearing member 112 is rotatably fitted into a bearing member 112 having a rack 111 that moves back and forth as the rack 10 rotates.
Further, a shaft tube 115 having a rotating handle 114 is fitted into the cylindrical shaft 113. This shaft tube 11
Slots 116, 117 are provided in the axial direction on the inner surface of the tube 5.
are formed, and these slots 116, 117
There are pins 120 and 12 implanted in the cylindrical shaft 113.
1 is inserted in each. With this configuration,
The target plate 1 can be rotated around the optical axis 0 by rotating the rotation handle 114, and the pinion 110 can be rotated.
By rotating the target plate 1, the target plate 1 can be moved back and forth in the direction of the optical axis 0. In addition, the amount of movement of the target plate 1 is determined by the scale 1 attached to the rack 111 as a diopter value.
It can be read from 30. A graduation image 130' of this scale plate 130 is projected onto the focus plate 6 by the graduation relay optical system 200. Although the embodiment of the lens meter described above is about a so-called telescopic lens meter, the present invention is not limited thereto, and can also be applied to a so-called projection type lens meter having a configuration in which the focusing plate 24 is used as a screen. There is no need to explain what it does.

[Brief explanation of drawings]

FIG. 1 is an optical layout diagram of a lens meter for explaining the principle of the present invention, FIGS. 2A and B are diagrams showing the relationship between dot patterns and straight lines, and FIG. 3 is a diagram showing the first target plate of the present invention. 4 to 6 are schematic diagrams for explaining the operation of the first embodiment, and FIG. 7 is a plan view showing the second embodiment of the target plate of the present invention.
8 and 9 are plan views showing the embodiment of
FIG. 10 is a plan view showing a third embodiment of the target plate of the present invention, and FIG. 11 is an explanatory diagram showing an embodiment of the lens meter of the present invention. . T, 1, 20, 40...Target board, CL,
101... Collimator lens, 102... Test lens receiving member, OL, 103... Objective lens,
6... focus plate, 4, 21, 22... straight line group pattern.

Claims (1)

[Scope of Claims] 1. A target plate that is rotatable about a measurement optical axis as a rotation axis, a light source for illuminating the target plate, a collimator lens having a focal point at the position of the target plate, and the collimator lens. an objective lens for condensing a parallel light beam from the target onto a focusing plate and forming an image of the target plate on the focusing plate; and a test lens disposed between the collimator lens and the objective lens. In a lens meter having at least a test lens receiving means for mounting, the target plate has a straight line group pattern consisting of at least one dotted straight line and at least one straight line parallel to the dotted straight line. The focal length of the collimator lens is f ₁ (mm), the focal length of the objective lens is f ₂ (mm), and the effective luminous flux diameter of the test lens receiving means is φ (mm). The minimum measured cylindrical power of the tested lens is C (day of ter).
When respectively, the diameter of the point pattern constituting the point straight line and the width of the straight line have a size h _T given as h _T = f ₁ · C / f ₂ · C + 1000 · φ / 2 (mm), and a distance between the dotted straight line and the straight line is 2h _T. 2. The lens meter according to claim 1, wherein the target plate has two linear group patterns formed so as to be perpendicular to each other. 3. The straight line group pattern consists of first and second dotted straight lines that are parallel to each other, and one straight line that is arranged between and parallel to the first and second dotted straight lines, and 3. The lens meter according to claim 1, wherein the distance between the first point straight line and the straight line and the distance between the second point straight line and the straight line are each _2hT . 4. The lens according to claim 2 or 3, wherein the intersection of the two straight line group patterns is cut, and a circular corona pattern is arranged at this cut part. meter. 5. A light source for illuminating a target plate that is rotatable around the measurement optical axis, and a focal length f ₁ (mm) for making the light beam of the target plate a parallel light beam.
A collimator lens, a test lens receiving member with an effective light flux diameter φ (mm) used for mounting the test lens, and a light flux from the collimator lens is focused onto a focusing plate to create an image of the target plate. an objective lens having a focal length f ₂ (mm) for forming an image on the focusing plate, the target plate having at least one dotted straight line and the dotted straight line; and at least _one straight line _parallel to the object. The diameter of the point pattern constituting the point straight line and the width of the straight line, where the effective luminous flux diameter used by the lens receiving means is φ (mm) and the required minimum measured cylindrical power of the lens to be tested is C (day obturer). has a size h _T given as h _T = f ₁・C/f ₂・C+1000・φ/2 (mm), and the distance between the point straight line and the straight line has an amount of 2h _T. A target plate used in a lens meter. 6. A target plate for use in a lens meter according to claim 5, wherein the two straight line group patterns are formed so as to be orthogonal to each other. 7. The straight line group pattern consists of first and second dotted straight lines that are parallel to each other, and one straight line that is arranged parallel to the first and second dotted straight lines, and Used in the lens meter according to claim 5 or 6, wherein the distance between the first point straight line and the straight line and the distance between the second point straight line and the straight line are each _2hT. target board. 8. The method according to claim 6 or 7, wherein the intersection of the two straight line group patterns is cut, and a circular corona pattern is disposed at the cut part. Target plate used in lens meters.