JPH08210947A - Lens meter - Google Patents

Abstract

PURPOSE: To easily measure the refractive characteristic of a lens with small measuring field such as a progressive multifocus lens or contact lens by varying the projecting position of a measuring luminous flux to a lens to be inspected in the radial direction of the lens to be inspected by a conical prism. CONSTITUTION: A conical prism 11 having an apex 11a on a device optical axis 0 and a base bottom 11b on the outside of the optical axis 0 is set in such a manner as to be movable and adjustable in an arrowed direction 18 along the optical axis O. According to such a constitution, since the deflecting position of the luminous flux from a light source 10 is changed when a lens L to be inspected is put adjacent to the optical conjugate position C by a collimator lens 13 of a light source 10 within the optical path, and the prism 11 is moved in the arrowed direction 18, the inclination of the circular measuring luminous flux passing the opening (light transmitting part) 12a of a mask plate 12 is changed, the projecting position to the lens L is changed in the radial direction to change the diameter of the measuring luminous flux, so that the measuring field can be changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens meter for automatically measuring refraction characteristics of spectacle lenses and contact lenses, that is, spherical power, cylindrical power, cylindrical axial power and the like.

[0002]

2. Description of the Related Art As a conventional lens meter, as shown, for example, in Japanese Utility Model Publication No. 44-22912, an illumination light flux which is parallel to a lens to be inspected is projected, and the illumination light flux transmitted through this lens is inspected. There is a system in which the astigmatic axis and the degree of refraction are measured by observing with an eyepiece through a variable diaphragm and a target. This lens meter is capable of measuring the axis of astigmatism and the degree of refraction by increasing the diameter of the variable diaphragm in measuring the axis of astigmatism and decreasing the diameter of the variable diaphragm in measuring the degree of refraction.

As a conventional lens meter, for example, as disclosed in JP-A-60-210735, the illumination light from the illumination light source is diffused by a diffusion plate, and the diffused illumination light is rotated. Of the light from the slit extending in the radial direction onto the lens to be measured through the objective lens, and the light flux that has passed through the lens to be tested is projected onto the one-dimensional position detection element through the plurality of small holes and the projection lens provided on the diaphragm plate. There are things I tried to do. Incidentally, the small holes of the aperture plate are arranged so as to form a hexagon in a circular shape having a predetermined radius.

On the other hand, in recent years, progressive multifocal lenses and contact lenses have been frequently used for refraction correction. Further, so-called bifocal contact lenses, which have a refractive surface formed of a rotating aspherical surface, have been put into practical use in order to make contact lenses bifocal.

[0005]

In a lens having an aspherical refraction surface such as a progressive multifocal lens or a bifocal contact lens, the distance and near refraction characteristics of the lens must be measured by using a measurement field. The area in which the measurement light beam can enter the lens to be measured) must be reduced.

However, the above-mentioned Japanese Utility Model Publication No. 44-22912.
The lens meter disclosed in Japanese Patent Application Laid-Open Publication No. H10-209,197, projects an index through a lens to be inspected, observes this index image with a microscope, adjusts the optical system until the index image is in focus, and adjusts the optical system from the in-focus position. Since the refractive index of the lens to be measured is calculated, the numerical aperture greatly affects the detection accuracy, it is difficult to specify which position is the in-focus position, and it is difficult to identify a progressive multifocal lens or a bifocal contact lens. The measurement was difficult.

That is, according to the lens meter disclosed in this publication, when the numerical aperture is small, the depth of focus is deep, so that it is difficult to accurately specify which position is the in-focus position, and the index image becomes dark. Moreover, when the numerical aperture is large, a clear index image cannot be observed, and it is difficult to specify which position is the in-focus position. Therefore, according to the measurement principle of this lens meter, changing the measurement area also changes the measurement accuracy, so that the measurement area cannot be changed while maintaining the required measurement accuracy. As a result, with the lens meter disclosed in Japanese Utility Model Publication No. 44-22912, it was difficult to measure the above-described progressive multifocal lens, bifocal contact lens, and the like.

In the lens meter disclosed in Japanese Patent Application Laid-Open No. Sho 60-210735, the rotating body is rotated to change the transmission position of the slit image on the test lens in the circumferential direction. Since the size of the slit image projected on the image does not change, the measurement area does not change. Therefore, this lens meter cannot measure a lens such as a progressive multifocal lens having a small measurement area.

As described above, in the conventional lens meter, since the measurement field cannot be changed, it is impossible to measure a biological contact lens which needs to measure both the central portion and the peripheral orbicular zone. there were.

The present invention has been made based on the above technical background, and an object thereof is to provide a lens meter capable of measuring even a lens having a small measurement field such as a progressive multifocal lens or a contact lens.

[0011]

In order to achieve this object, the invention of claim 1 projects the measurement light beam from the measurement light beam projection means onto a lens to be measured, and the measurement light beam transmitted through the lens to be measured. In a lens meter provided with a measurement optical system for measuring the refractive power of the lens to be inspected by receiving light on a photodetector via the It is a lens meter having a projection position changing means for changing the projection position to the radial direction of the lens to be inspected.

Further, the invention of claim 2 is a lens meter provided with a measuring optical system for guiding light from a light source to a photodetector through a lens to be inspected and measuring a refraction characteristic of the lens to be inspected. A lens provided with light beam projection position changing means for changing the projection position of the light beam incident on the photodetector in the radial direction of the measurement optical axis of the measurement optical system when the test lens is not arranged in the measurement optical system. It is characterized by being a meter.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> The measurement optical system of the lens meter of the present invention has a measurement light beam projection means for varying the projection position of the measurement light beam of a predetermined pattern onto the lens L to be inspected in the radial direction of the lens L to be inspected. This measurement light beam projection means has a light source 10, a conical prism 11 (light beam projection position changing means), a mask 12, and a collimator lens 13. Further, the measuring optical system has an imaging lens for guiding the measuring light beam transmitted through the lens L to be detected onto the photodetector 17 as a light receiving optical system.

The conical prism 11 has a vertex 11 on the optical axis O of the apparatus.
a, the base 11b outside the optical axis O, and the arrow 18
It is provided so as to be movable and adjustable in the direction along the optical axis O indicated by. Further, behind the conical prism 11, a mask plate 12 having an annular opening 12a as a light transmitting portion is arranged as shown in FIG.

The collimator lens 13 is arranged so as to have its front focal point in a plane including the opening 12a of the mask plate 12. For this reason, when the test lens L is not in the optical path, the ring-shaped light beam that has passed through the opening 12a is converted into a parallel light beam by the collimator lens 13 and reflected by the mirror 14, and then, by the imaging lens 16, for example, on the optical axis. Area CC fixedly located at
An image is formed as an annular pattern on the photodetector 17 made of D. The optical conjugate position of the light source 10 by the collimator lens 13 is at the position C. The front focus of the imaging lens 16 is located at the conjugate position C.

The test lens L is placed on a lens holder (not shown) near the conjugate position C, and is placed in the optical path. When the conical prism 11 is moved in the direction of arrow 18, the deflection position of the light beam from the light source 10 changes.
The inclination angle of the measurement light flux of the annular pattern (circle) passing through the opening 12a with respect to the optical axis O (measurement optical axis) changes, and the projection position of the measurement light flux onto the test lens L is changed to the test lens L.
Since the diameter of the ring-shaped measuring light flux passing through the lens L to be measured is changed in the radial direction of, the measurement field can be changed. When the lens L to be inspected is not arranged in the measurement optical system, the inclination angle of the measurement light beam of the annular pattern (circle) passing through the opening 12a of the mask plate 12 with respect to the optical axis O changes, and The projection position of the measurement light beam on the detector 17 is changed in the radial direction of the measurement optical axis O. That is,
This makes it possible to change the position at which the measurement light beam transmitted through the lens L to be extracted is extracted toward the detector 17 in the radial direction of the lens L to be inspected.

FIG. 3 shows a method for obtaining the refraction characteristics of a lens to be measured from the size of an annular pattern projected on the photodetector 17 (an elliptical shape when the lens has a cylindrical power). It is shown.

Assuming that the focal length of the imaging lens 16 is f, the radius a _{0 of the} annular pattern on the photodetector 17 when the lens L to be inspected is not in the optical path is: a ₀ = ftan θ ₀ from FIG. (1) Further, assuming that the test lens L is inserted at the conjugate position C, when the radius of the annular pattern on the photodetector 17 changes to a, a becomes a = ftan θ (2) Is represented as

The annular opening 12a of the mask plate 12 is
When an image is formed on the photodetector 17 by the
The radius y of the image at the image forming position X of the annular aperture 12a by L (assuming that the refraction of the image forming lens 16 is not considered) is defined as h, where the radius of the light source ring image at the conjugate position C is h. Assuming that the distance to the imaging position X is D, y = Dtan θ ₀ (3) y = Dtan θ-h (4), and from the expressions (3) and (4), D (tan θ ₀ −tan θ) = − h Therefore, D = −h / (tan θ ₀ −tan θ) (5) From the above equations (1), (2) and the above equation (5), D = −h / [(a ₀ / f) − (a / f)] D = −f · h / (a ₀ −a) can get. Actually, since the test lens L is far from the conjugate position C, the distance between the conjugate position C and the test lens L is Δ
If d, then S = (a−a ₀ ) / [fh + Δd (a ₀ −a)] (6)

When the lens L to be inspected is an astigmatic lens, the refraction characteristics can be obtained from the minor axis and major axis of the elliptical pattern projected on the photodetector 17 and the axis angle thereof using the equation (6). it can.

In the present invention, since the photodetector 17 is fixedly arranged, the pattern projected on the photodetector 17 becomes a blurred pattern due to the refractive power of the refractive lens of the lens to be measured. Since the circle or the elliptical shape can be obtained by obtaining the center position of, measurement is possible.

The calculation according to the above formula (6) is executed by a calculation control circuit 20 composed of a microprocessor or the like, and the calculation result is displayed on a display 21 and printed out by a printer 22 as required.

In this embodiment, by moving the conical prism 11 along the optical axis O as described above,
Since the measurement field φ of the test lens L can be changed as shown in FIGS. 4A and 4B, a lens having a small measurement field such as a progressive lens or a bifocal contact lens, or Lenses that need to change fields can be measured.

This embodiment can be applied to the case where the thickness of the lens L to be measured is small, the difference in curvature between the two refraction surfaces is small, and h in FIG. 4 (A) does not change depending on the lens.

When the curved shape and the thickness of the refraction surface of the lens to be examined are large, the conjugate device C has a diaphragm 15a having an annular aperture 15a.
May be arranged as shown in FIG. 4, and the aperture of the stop may be changed according to the movement of the conical prism.

<Second Embodiment> A second embodiment is a conical prism.
A diaphragm 15 (light beam projection position changing means) according to the movement amount P of 11
This shows an example in which the radius h of the annular opening 15a is variable and has the configuration shown in FIG. The same components as those in the first embodiment described above are designated by the same reference numerals to avoid redundant description.

In the diaphragm 15, as shown in FIG. 6, concentric ring-shaped light transmitting portions 151, 152, 153 having different radii are composed of photoelectric elements such as liquid crystal elements and photochromic elements.
The pattern electrodes (not shown) provided on the respective light transmitting portions 151, 152, 153 are connected to the contacts 205a, 205b, 205c of the switch circuit 205. On the other hand, a common (−) side electrode (not shown) is connected to the (−) side of the DC power supply 206. And this power supply 2
The (+) side of 06 is connected to the movable contact 205d of the switch circuit 205. This switch circuit 205 has fixed contacts 205a, 205b, 2
05c and a movable contact 205d, and the movable contact 205d can be switched and connected to any of the fixed contacts 205a, 205b, 205c under the control of the control circuit 204. As a result, the measurement light beam can pass through only one of the light transmitting portions 151 to 153 of the diaphragm 15. The portion of the diaphragm 15 other than the light-transmitting portions 151 to 153, that is, the central portion indicated by 154 is a light-impermeable circular light-shielding portion, and the peripheral portion indicated by 155 is light-impermeable. It is configured as a light-shielding band.

The moving amount of the conical prism 301 is regarded as a voltage change from the volume 201, and its output voltage Q is input to one input terminal of the comparators 202 and 203. Moreover, the reference voltage aV is input to the other input terminal of the comparator 202,
The reference voltage bV (a> b) is input to the other input terminal of the comparator 203. The comparator 202 outputs the signal S ₁ to the control circuit 204 when the output voltage Q from the volume 201 becomes larger than the reference voltage a, and the comparator 203 outputs the signal S ₂ when the output Q from the volume 201 becomes smaller than the reference voltage b. It is configured to output to the control circuit. The control circuit 204 is
When the signal S ₁ from the comparator 202 is received, it is determined that the conical prism 11 is on the mask plate 12 side, the switch circuit 205 is controlled, and the movable contact 205d is connected to the fixed contact 205a as shown in the drawing. The pattern electrode (not shown) of the transparent portion 151 is energized so that only the transparent portion 151 can pass light.

When neither of the comparators 202 and 203 outputs a signal, the output Q of the volume 201 and the reference voltages a and bV are a>
Q> b. At this time, the control circuit 204
Connects the movable contact 205d of the switch circuit 205 to the fixed contact 205b, and forms a pattern electrode (not shown) of the central light-transmitting portion 152.
, So that the measurement light can pass through only the light transmitting portion 152. Further, the signal S ₂ from the comparator 203 is
When input to 04, the conical prism 11 has moved to the light source side most. At this time, the control circuit 204 connects the movable contact 205d of the switch circuit 205 to the fixed contact 205c, energizes a pattern electrode (not shown) of the inner light transmitting portion 153, and only passes the measuring light flux Pass through.

As described above, by selecting any one of the light transmitting portions 151, 152, and 153 so that the measurement light beam is transmitted, the measurement light beam can be varied in the radial direction of the measurement optical axis O. That is, the position at which the measurement light flux transmitted through the lens L to be extracted is extracted toward the detector 17 in the radial direction of the lens L can be varied.

Further, by increasing the amount of movement P of the conical prism 11 and the amount of change in the measurement field φ, it is necessary to change the radius of the opening 12a of the mask plate 12 in order to secure the measurement range. Alternatively, depending on the refraction characteristics of the test lens, the opening of the mask
When it is necessary to change the radius of 12a, a mask plate that can select a plurality of light-transmitting portions having different radii from each other may be configured in the same configuration as the stop 15. In this case, the light source 10, the conical prism 11, the mask having the same configuration as the diaphragm 15 used in place of the mask 12, the collimator lens 13 and the like serve as the measurement light beam projection means, and this mask serves as the light beam projection position changing means.

Further, if the illuminating light beam from the light source 10 is a parallel light beam, a combination of a mask having the same configuration as the diaphragm 15 used in place of the mask 12 serves as a light beam projection position changing means.

[0033]

Since the present invention is configured as described above, the measurement field of a progressive power multifocal lens, a contact lens or the like is small, and this small measurement field is either radial from the optical center of the measurement optical system. Position of the measurement light beam to the lens to be measured in the radial direction is changed, or the measurement light beam transmitted through the lens to be measured is taken out in the radial direction of the lens to be measured. Can be changed to change the position of the measurement light beam incident on the photodetector in the radial direction of the optical axis of the measurement optical system. As a result, it is possible to measure a lens having a small measurement field such as a progressive multifocal lens or a contact lens, which has conventionally been difficult to measure, and to accurately measure a lens having a large measurement field by changing the measurement area.

[Brief description of drawings]

FIG. 1 is an optical layout diagram showing a first embodiment of a lens meter according to the present invention.

FIG. 2 is a plan view showing an opening shape of a mask plate and an aperture plate shown in FIG.

FIG. 3 is an optical path diagram for explaining a method for obtaining the refractive power of the lens to be inspected in FIG.

FIGS. 4A and 4B are optical path diagrams showing the operation of the first embodiment.

FIG. 5 is an optical path layout diagram and a block diagram showing a second embodiment of the lens meter according to the present invention.

FIG. 6 is a plan view showing the configuration of the stop shown in FIG. 5;

[Explanation of symbols] 10 ... Light source 11 ... Conical prism 12 ... Mask plate 12a ... Aperture (transparent portion) 13 ... Collimator lens 15 ... Stoppers 151, 152, 153 ... Transparent portion 16 ... Imaging lens 17 ... Photodetector L ... Target Inspection lens

Claims (2)

[Claims] 1. A measuring light beam from a measuring light beam projection means is projected onto a lens to be measured, and is received on a photodetector via the measuring light beam transmitted through the lens to be measured. In a lens meter provided with a measurement optical system for measuring refractive power, the measurement light beam projection means changes a projection position for changing a projection position of the measurement light beam onto the lens under test in a radial direction of the lens under test. A lens meter having means. 2. A lens meter provided with a measurement optical system that guides light from a light source to a photodetector through a lens to be measured and measures refraction characteristics of the lens to be measured. A lens meter provided with a light beam projection position changing means for changing a projection position of a light beam incident on the photodetector when it is not arranged in an optical system in a radial direction of a measurement optical axis of the measurement optical system.