JPH0697197B2 - Lens meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention is directed to refraction characteristics of eyeglass lenses and contact lenses,
That is, the present invention relates to a lens meter that automatically measures spherical power, cylindrical power, cylindrical axis power, and the like.

(Background Art) 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.

(Problems to be Solved by the Invention) In a lens having an aspherical refracting surface such as a progressive multifocal lens or a bifocal contact lens,
In order to measure the distance and near refraction characteristics, the measurement field (the area where the measurement light beam can be incident on the lens to be measured) must be small. However, with the conventional lens meter, it is difficult to measure the above-mentioned progressive multifocal lens, bifocal contact lens, etc. because of the wide measurement field.

In particular, the conventional lens meter has a wide measurement field, and since the measurement field cannot be changed, it is not possible to measure a bifocal contact lens that requires measuring both the central part and the peripheral annular zone. Met.

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

A second object of the present invention is to provide a lens meter useful for measuring the refractive characteristics of bifocal contact lenses.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve this object, according to the present invention, a light source arranged on the optical axis of the device and a mask pattern for transmitting a light beam from the light source are formed. By having a mask plate, projecting a light flux that has passed through the mask pattern onto a photodetector via a lens under test, and detecting the position of the light flux on the photodetector,
In the lens meter that measures the refractive power of the lens under test,
The lens meter is arranged between the light source and the mask plate, and has a deflecting means for deflecting a light beam from the light source and changing an inclination angle of the light beam passing through the mask pattern with respect to the optical axis. is there.

(Example) First Example The lens meter of the present invention has a conical prism 11 (deflecting means) as shown in FIG. This conical prism 11
It has an apex 11a on the optical axis O of the device, a base 11b outside the optical axis O, and is provided so as to be movable and adjustable in the direction along the optical axis O shown by an arrow 18. Further, behind the conical prism 11, as shown in FIG. 2, a mask plate 12 having an annular opening 12a as a light transmitting portion is arranged. The collimator lens 13 is arranged so that its front focal point lies in a plane including the opening 12a of the mask plate 12. Therefore, the ring-shaped (linear) light flux passing through the opening 12a in the circumferential direction is collimated by the collimator lens 13 and reflected by the mirror 14 when the lens L to be inspected is not in the optical path.
Area that is fixed on the optical axis, for example, by the imaging lens 16.
An image is formed as an annular pattern on the photodetector 17 composed of a CCD.

The optical conjugate position of the light source 10 by the collimator lens 13 is at the position C.

Further, the front focus of the imaging lens 16 is the conjugate position C.
In the position.

The lens L to be inspected is placed close to the conjugate position C on a lens pedestal (not shown) and placed in the optical path.

When the conical prism 11 is moved in the direction of the arrow 18, the deflection position of the light beam from the light source 10 changes, so the opening of the mask plate 12
The inclination angle of the light beam passing through 12a with respect to the optical axis O changes, the diameter of the ring-shaped light beam passing through the lens L to be tested changes, and the measurement field can be changed.

FIG. 3 shows a method for obtaining the refraction characteristics of the test lens from the size of the annular pattern projected on the photodetector 17 (the test lens has an elliptical shape when it has a cylindrical power). is there.

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 (1 ) Further, considering that the lens L to be inspected is placed at the conjugate position C, when the radius of the annular pattern on the photodetector 17 changes to a, a is expressed as a = ftan θ (2) .

When the annular opening 12a of the mask plate 12 is imaged on the photodetector 17 by the lens L to be inspected, the radius y of the image at the imaging position X of the annular aperture 12a by the lens L to be inspected (imaging Lens 1
6 is not considered), y = ltan θ ₀ (3) y, where h is the radius of the light source ring image at the conjugate position C and l is the distance between the conjugate position C and the imaging position X. = Ltan θ−h (4), and from equations (3) and (4), l (tan θ ₀ −tan θ) = − h Becomes From the above equations (1) and (2) and the above equation (5), Is obtained. Since the lens L to be inspected is actually separated from the conjugate position C, the distance between the conjugate position C and the lens L to be inspected is Δ.
If d, Is required as.

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 their axial angles by using the equation (6).

Incidentally, 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 under test, but the center position of the pattern Since it is possible to obtain a circular or elliptical shape by obtaining, it is possible to measure.

The calculation according to the equation (6) is executed by the calculation control circuit 20 including a microprocessor, and the calculation result is displayed on the display 21 and printed out by the printer 22 as necessary.

In the present embodiment, by moving the conical prism 11 along the optical axis O as described above, the measurement field φ of the lens L to be measured is changed as shown in FIGS. 4 (A) and 4 (B). Since it can be changed, lenses with small measurement fields such as progressive focus lenses and bifocal contact lenses,
Alternatively, it becomes possible to measure a lens or the like which needs to change the measurement field.

The present embodiment can be applied to the case where the lens L to be inspected is thin, the difference in curvature between both refracting surfaces thereof is small, and h in FIG. 4 (A) does not change depending on the lens.

When the curved shape or thickness of the refractive surface of the lens under test is large,
A stop 15a having an annular opening 15a may be arranged at the conjugate position C as shown in FIG. 4, and the stop opening may be changed according to the movement of the conical prism.

Second Embodiment In the second embodiment, a diaphragm 15 is provided according to the moving amount P of the conical prism 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 annular light-transmitting portions 151, 152, 153 having different radii are constituted by photoelectric elements such as liquid crystal elements and photochromic elements.
Pattern electrodes (not shown) provided on 152 and 153 are connected to contacts 205a, 205b and 205c of the switch circuit 205.
On the other hand, the common (-) side electrode (not shown) is the DC power source 206.
Is connected to the (-) side of. Moreover, the (+) side of the power supply 206 is connected to the movable contact 205d of the switch circuit 205. This switch circuit 205 has fixed contacts 205a, 205b, 205
It has c 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. A portion of the diaphragm 15 other than the light-transmitting portions 151 to 153, that is, a central portion indicated by 154 is a light-shielding circular light-shielding portion, and a peripheral portion indicated by 155 is not light-transmitting. It is configured as a light-shielding band.

The moving amount of the conical prism 11 is regarded as a voltage change from the volume 201, and its output voltage Q is the comparators 202 and 203.
Is input to one of the input terminals. Moreover, the reference voltage aV is input to the other input terminal of the comparator 202, and the comparator 203
The reference voltage bV (a> b) is input to the other input terminal of the. 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. Upon receiving the signal S ₁ from the comparator 202, the control circuit 204 determines that the conical prism 11 is on the mask plate 12 side, controls the switch circuit 205, and moves the movable contact 205d to the fixed contact 205a as illustrated. Connect to the outer translucent part
The pattern electrode (not shown) of 151 is energized so that only the light transmitting 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 causes the switch circuit 2 to
The movable contact 205d of 05 is connected to the fixed contact 205b to energize the pattern electrode (not shown) of the central light transmitting portion 152 so that only the light transmitting portion 152 can pass the measurement light. Furthermore, when the signal S ₂ from the comparator 203 is input to the control circuit 204, the conical prism 11 moves to the most light source side. At this time, the control circuit 204 connects the movable contact 205d of the switch circuit 205 to the fixed contact 205c, and the inner light transmitting portion 15 is connected.
The pattern electrode (not shown) of 3 is energized, and the transparent portion 153
Only the measuring beam can pass through.

In order to secure the measurement range by increasing the movement amount P of the conical prism 11 and the change amount of the measurement field φ,
If you need to change the radius of the opening 12a of the mask plate 12,
Alternatively, when it is necessary to change the radius of the opening 12a of the mask plate 12 in order to secure the measurement range due to the refraction characteristics of the lens under test, a plurality of transparent lenses having different radii with the same configuration as the diaphragm 15 are used. It suffices to construct a mask plate capable of selecting the light portion.

EFFECTS OF THE INVENTION Since the present invention is configured as described above, the measurement field of a progressive power multifocal lens, a bifocal contact lens, etc. is small, and this small measurement field is in the radial direction from the optical center of the measurement optical system. At any position, the size of the measurement light beam from the mask pattern that passes through the lens to be measured is changed by changing the inclination angle of the measurement light beam that passes through the mask pattern with respect to the optical axis. Is changed, or the luminous flux for measurement is guided through the portion of the lens to be measured in the radial direction to be measured to the photodetection means.

As a result, it becomes possible to measure lenses with small measurement fields such as progressive multifocal lenses and bifocal contact lenses, which were difficult to measure in the past, and lenses with large measurement fields by changing the measurement area without changing the measurement accuracy. Can be measured accurately.

Further, it is possible to provide a lens meter capable of measuring a lens such as a bifocal contact lens that must be measured at both the central portion and the peripheral annular zone portion.

[Brief description of drawings]

FIG. 1 is an optical layout diagram showing a first embodiment of the lens meter according to the present invention, FIG. 2 is a plan view showing the aperture shapes of the mask plate and diaphragm plate, and FIG. 3 shows the refractive power of the lens under test. FIG. 4 (A) and FIG. 4 are optical path diagrams for explaining the obtaining method.
FIG. 6B is an optical path diagram showing the operation of the first embodiment, FIG. 5 is an optical path arrangement diagram and block diagram showing the second embodiment of the lens meter according to the present invention, and FIG. FIG. 10 …… Light source 11 …… Conical prism (deflecting member) 12 …… Mask plate 12a …… Aperture (translucent part) 13 …… Collimator lens 15 …… Aperture 151,152,153 …… Transparent part 16 …… Imaging lens 17 …… Photodetector L …… Lens to be inspected.

Claims (3)

[Claims] 1. A light source arranged on the optical axis of the device, and a mask plate on which a mask pattern for transmitting a light beam from the light source is formed. The light beam transmitted through the mask pattern is transmitted through a lens to be inspected. A lens meter for measuring the refractive power of a lens to be inspected by projecting it on a detector and detecting the position of a light beam on the photodetector, is arranged between the light source and the mask plate, and A lens meter having deflection means for deflecting a light flux and changing an inclination angle of the light flux passing through the mask pattern with respect to the optical axis. 2. The lens meter according to claim 1, wherein the deflecting means is a conical prism. 3. A collimator lens having a front focal point on the mask plate, and a connection for forming an image of a light beam transmitted through the mask plate mask pattern, which is collimated by the collimator lens, on the photodetector. Has an image lens,
The lens meter according to claim 1 or 2, wherein a lens to be inspected is arranged at a position substantially conjugate with a light source with respect to the collimator lens.