JPH11125581A - Automatic lens meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic lens meter that can rapidly obtain optical measurement values that are near the optical characteristic values of a manual- type lens meter with a simple optical configuration. SOLUTION: In the automatic lens meter, a pattern 18 for measuring optical characteristics with at least three openings at a projection light path 13 of measurement luminous flux P for measuring the optical characteristics of a lens 17 to be inspected is provided, at the same time, a two-dimensional image reception element 20 for receiving the light-point image of the measurement luminous flux P being transmitted through each opening is provided, the position of each light-point image on the two-dimensional image reception element 20 is detected, the optical characteristics of the lens 17 to be inspected are automatically calculated and measured, and distance Z from the two-dimensional image reception element 20 to a vertex position 17a of the rear surface of the lens 17 to be inspected is set to a value that is smaller than back focus distance Z1 when the lens 17 to be inspected that has plus power with the measurable maximum degree is set to the projection light path 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic lens meter capable of obtaining an optical measurement value close to an optical characteristic value of a manual lens meter by automatic measurement with a quick and simple optical configuration.

[0002]

2. Description of the Related Art Conventionally, a lens to be measured is set on a light beam path of a measuring light beam, and a measuring light beam having a diameter of 5 to 8 mm is projected on the lens to be measured with the optical axis as a center. 2. Description of the Related Art There is known a manual lens meter that reads a power of a lens to be inspected by adjusting a diopter handle to an appropriate position. The optical characteristic value of this manual lens meter is close to the measured value at the position where the luminous flux transmitted through the pupil of the eye is most concentrated when the lens to be inspected is worn, and when the lens to be inspected is actually worn on the eye. Corresponding favorable measurements are obtained.

[0003] On the other hand, an auto lens meter has a structure shown in FIG.
As shown in FIG. 2A, an optical characteristic measuring pattern 4 having a large number of openings 3 is provided on a light projecting optical path 2 of a measuring light beam P for measuring optical characteristics of a lens 1 to be measured, as shown in FIG. A two-dimensional image receiving element 5 for receiving a light spot image of the measurement light beam transmitted through each of the apertures 3 is provided, and the position of each light spot image on the two-dimensional image receiving element 5 is detected to be inspected. A configuration in which the optical characteristics of the lens 1 are automatically calculated and measured is known. In FIG. 1A, reference numeral 6 denotes a measurement light beam generation light source, 7 denotes a pinhole, 8 denotes a collimator lens, and 9 denotes a lens receiver.

According to the automatic lens meter, there is a merit that the variation in measurement is smaller than that of a manual lens meter.

[0005]

Incidentally, the test lens 1 has a spherical aberration as shown in FIG.
Since the contact lens has a small radius of curvature on the back surface (the back surface has a large curvature), the spherical aberration is large as compared with other lenses. In such a lens having a large spherical aberration, as shown in FIG. 3, due to the intersection of the measurement light beams P, the distance from the vertex position 1a on the rear surface of the test lens 1 to the two-dimensional image receiving element 5 shown in FIG. If the distance is designed to be larger than the back focus distance fb of the lens to be inspected, the positional relationship between the light spot images intersects as shown in FIG. 1 (b). There is.
In FIG. 1, the solid-line light beam indicates a light beam deflected by the test lens 1, the broken-line light beam indicates a light beam deflected by the test lens having a power different from that of the test lens 1, and is indicated by a broken line. When the two-dimensional image receiving element 5 is placed at the indicated position, the light spot images can be located at the same position even with the test lenses having different degrees of power.

In addition, a deviation occurs between the optical characteristic value obtained by the manual lens meter and the optical characteristic value obtained by the automatic lens meter. That is, in the case of a manual type lens meter, as shown in FIG. 3, the optical characteristic value is at a point fa where all the rays are gathered. When measured with a light beam n having a small value of h, the back focus distance on the optical axis is fb
On the other hand, the apparent back focus distance becomes fb ′ due to the influence of aberration, the power as an optical characteristic value becomes stronger, and the back focus distance (power) fa different from the back focus distance (power) fa by the manual lens meter. The focus distance (frequency) is obtained.

[0007] Even when the lens 1 to be inspected has a spherical aberration, the optical characteristic value (frequency) of the optical characteristic by the automatic lens meter should be as close as possible to the optical characteristic value (frequency) by the manual lens meter. Is desirable for the reasons described above.

Therefore, in a conventional auto lens meter,
A large number of apertures are required, and the position of each light spot image at each ray height on the two-dimensional image receiving element 5 is obtained by calculation, and the calculated value may be used to determine the fb position or the fa position. In addition, since the number of light spot images is very large, it takes a long time to perform arithmetic processing, and it is difficult to perform measurement in real time.

The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain an optical measurement value close to an optical characteristic value of a manual lens meter by automatic measurement with a quick and simple optical configuration. To provide an auto-lens meter capable of performing such operations.

[0010]

According to an aspect of the present invention, there is provided an automatic lens meter, comprising: an optical characteristic measuring pattern having at least three apertures in a projection optical path of a measuring light beam for measuring optical characteristics of a lens to be measured; And a two-dimensional image receiving element for receiving a light spot image of the measurement light beam transmitted through each of the apertures, detecting a position of each of the light spot images on the two-dimensional image receiving element, An auto-lens meter for automatically calculating and measuring the optical characteristics of an inspection lens, wherein a two-dimensional lens having the highest measurable positive power is set in the light projecting optical path. The distance from the image receiving element to the position of the vertex of the rear surface of the test lens is set smaller than the back focus distance.

The apertures are calculated so that the power calculated based on the light spot image on the two-dimensional image receiving element is close to the power obtained by measuring the test lens with a manual lens meter. It is desirable that a convergent lens be provided in each of the apertures, and the focal length of the convergent lens be the most frequently used lens in the range of the optical characteristic value ± 5 diopters. It is desirable that the size of the light spot image be set to a minimum when it is set to.

When a test lens having the highest measurable positive power is set in the light projecting optical path, each light spot image has a size that does not make close contact with each other on the two-dimensional image receiving element. More preferably, it is performed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG.
1 is a diffusion plate, and 12 is a pinhole. The LED 10, the diffusion plate 11, and the pinhole 12 constitute a light source unit for generating a measurement light beam, and the pinhole 12 functions as a diffusion secondary point light source. The luminous flux emitted from the pinhole 12 is transmitted through the light projecting optical path 13.
The light is converted into a parallel light beam by a collimator lens 14 provided in the camera. A lens receiver 15 is provided in the light projecting optical path 13, and a lens 17 to be measured is set in the lens receiver 15. The lens receiver 15 has a diameter of about 8φ (mm) when the test lens 17 is a spectacle lens, but has a diameter of about 5φ (mm) when a contact lens is set as the test lens 17. Is replaced by the lens receiver 15.

As shown in FIG. 5, an optical characteristic measuring pattern 18 having openings 18a is provided behind the lens receiver 15, but the number of openings 18a may be at least three or more. This is because the optical characteristic value can be calculated with at least three. On the other hand, if the number of the openings 18a is too large, it takes a long time to perform the calculation.
Here, each of the openings 18a is circular, and is arranged at a position equidistant from the measurement optical axis O and shifted by 90 degrees. Test lens 17 that is not rotationally symmetric such as a progressive lens
However, in order to be able to measure,
8a is desirably provided.

A converging lens 19 is provided in each opening 18a. The size of the opening 18a is desirably as large as possible in order to make the measured value of the optical characteristic by the auto lens meter as close as possible to the optical characteristic value by the manual lens meter. When the test lens 17 is a contact lens, the lens receiver 15
Is about 5φ, the circumscribed circle of the four openings 18a is required to be 5 mm or less. The opening 18
If the value of “a” is too large, when measuring the test lens 17 having a plus power, the light spot images come into close contact with each other and the center of gravity of each light spot image cannot be calculated.
When the distance l from the measurement optical axis O to the center position O1 of the center position O1 is short, the measurement sensitivity becomes low. On the contrary, when the distance l is too large, the light spot image is formed in the case of the test lens 17 having a minus power. In order to protrude from the effective area of the two-dimensional image receiving sensor described later, a distance l from the measurement optical axis O to the center position O1 is set.
Is preferably about 1 mm and the size of the opening 18a is about 1φ.

As the pattern plate 18 for measuring optical characteristics, for example, a glass plate provided with a metal frame and a microlens fixed to the metal frame may be used. For example, one resin plate or glass plate may be used. A mold lens in which four converging lenses 19 are formed on a plate may be used, or a lens in which a condensing lens 19 utilizing a diffraction phenomenon is formed on a glass plate by etching may be used. Further, it is desirable to shield the portion other than the converging lens 19 from light using a substance such as chrome.

Behind the optical characteristic measuring pattern 18, an area CCD 20 as a two-dimensional image receiving element is provided. The distance Z from the area CCD 20 to the lens receiver, that is, the distance from the two-dimensional image receiving element 20 to the lens
The distance Z from the rear surface vertex position 17a of the lens 1 to the test lens 1 having the strongest positive power that can be measured in the light projecting optical path 13
7 is set smaller than the back focus distance Z1. This is for avoiding overlapping of the light spot images or reversal of the measurement light beam transmitted through the lens 17 to be measured.

That is, as shown in FIG.
When D20 is provided at the position shown by the broken line, the measurement light flux P1 passing through the area above the test lens 17 forms an image on the area below the area CCD 20, and the measurement light flux P2 passing through the area below the area CCD 20 is focused on the area CCD 20. This is because the measurement light flux P is reversed and the measurement light flux P passing through the lens 17 to be measured cannot be determined to which light spot image on the area CCD 20 corresponds.

Therefore, for example, when the measurement frequency of the test lens 17 that can be measured by the auto lens meter is ± 25 diopters, the back focus distance Z1 is 40 mm, so the distance Z from the lens receiver 15 to the area CCD 20 is 20 mm. Desirably, it is ３０30 mm. When the distance Z is set to be equal to or less than 20 mm, the measurement sensitivity deteriorates. This is not the case when a relay lens is provided between the lens receiver 15 and the area CCD 20.

The lens 1 to be measured having a high frequency of measurement
7. For example, when the test lens 17 having a weakness (−2.5 D) is set in the light projecting optical path 13, the setting is such that the size of the light spot image on the area CCD 20 is minimized. It is preferable in that it is hardly affected by the measurement of scratches and dirt.

The measurement light beam n incident on the lens 17 to be inspected is
The light is deflected after passing through the test lens 17, and the degree of the deflection is determined by the incident height h and the power of the test lens 17 at the incident position. Assuming that the deflection angle θ of the transmitted measurement light beam is S = tan θ / 10h, the incident height h is known, and as shown in FIG. 7, when the height from the center line O ′ on the area CCD 20 is hi, θ = (h−hi /
Since Z), if the barycentric positions G1 to G4 are obtained, the power S of the lens 17 to be measured is obtained.

When the test lens 17 has a positive power, the interval between the light spot images PM1 to PM4 becomes narrow, and when the test lens 17 has a negative power, the light spot images PM1 to PM4
4 are widened and the lens 17 to be inspected is a spherical lens, the center position G0 of each of the light spot images PM1 to PM4 is located at substantially the same distance from the center line O ′, If there is, the distance from the center position G0 of each of the light spot images PM1 to PM4 to the center line O 'will be different.

According to the present invention, since the aperture 18a is formed as large as possible, a large number of thin light beams pass through each one aperture 18a under the influence of the aberration of the lens 17 to be measured. Each light spot image PM of one opening 18a
Areas C1 to PM4 deviate from the center position (center of gravity position) G0 based on one thin ray and the center of gravity G1 to G4 of area C
The power is formed on the CD 20, and a power close to the power obtained by the manual lens meter can be obtained.

Further, even if a small flaw or dirt is present in a local area of the lens 17 through which the measurement light beam P passing through the opening 18a passes, even if the measurement light beam going toward the opening 18a is partially blocked, the light beam is blocked. Since the ratio is smaller than in the case of a thin light beam, the barycentric positions G1 to G of the light spot images PM1 to PM4
4 is small, and therefore, the measurement error due to dust and dirt is small, and the measurement accuracy is improved.

[0025]

As described above, the present invention has an effect that an optical measurement value close to the optical characteristic measurement value of a manual lens meter can be obtained by automatic measurement.

Further, even when dust and dirt are present on the lens to be inspected, a measurement error caused by dust and dirt is reduced, and the measurement accuracy is improved.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing an optical system of a conventional auto lens meter, wherein FIG. 1A is an optical diagram for explaining the principle of measurement, and FIG. 1B is a diagram showing an example of the problem.

FIG. 2 is a plan view of the optical characteristic measurement pattern shown in FIG.

FIG. 3 is a ray diagram showing a ray path of a measurement light beam transmitted through a test lens.

FIG. 4 is an optical diagram for explaining the measurement principle of the auto lens meter according to the present invention.

FIG. 5 is a plan view of the optical characteristic measurement pattern shown in FIG.

FIG. 6 is a schematic diagram showing a positional relationship between an optical characteristic measuring pattern, a light beam path of a measuring light beam of a test lens, and a two-dimensional image receiving element according to the present invention.

FIG. 7 is a plan view showing a light spot image received by the two-dimensional image receiving element according to the present invention.

[Explanation of symbols]

 Reference Signs List 13 Projecting light path 17 Lens under test 17a Backside vertex position 18 Optical characteristic measuring pattern 18a Opening 20 Two-dimensional image receiving element P Measurement light beam Z1 Back focus distance

Claims (4)

[Claims] An optical characteristic measurement pattern having at least three openings is provided in a light projecting optical path of a measurement light beam for measuring optical characteristics of a test lens, and a light spot of the measurement light beam transmitted through each of the openings. An auto lens meter for providing a two-dimensional image receiving element for receiving an image, detecting the position of each of the light spot images on the two-dimensional image receiving element, and automatically calculating and measuring the optical characteristics of the lens to be inspected; The distance from the two-dimensional image receiving element to the vertex position of the rear surface of the test lens, when the test lens having the strongest measurable positive power is set in the light projecting optical path. However, the auto lens meter is set smaller than its back focus distance. 2. The method according to claim 1, wherein the power calculated based on the light spot image on the two-dimensional image receiving element is a value close to the power obtained by measuring the test lens with a manual lens meter. The auto lens meter according to claim 1, wherein the size of each opening is set, and each of the openings is provided with a converging lens. 3. The focal length of the converging lens is set such that the size of the light spot image is minimized when any one of optical characteristic values ± 5 diopters is set in the light projecting optical path. The auto lens meter according to claim 2. 4. When the lens having the highest measurable positive power is set in the light projecting optical path, the light spot images do not adhere to each other on the two-dimensional image receiving element. 3. The auto lens meter according to claim 2, which is sized.