JPS6345530B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens meter for measuring the refractive properties of lenses, mainly, but not exclusively, spectacle lenses and contact lenses.

Currently, it is used to measure the refractive properties of eyeglass lenses, contact lenses, etc., such as spherical refractive power, cylindrical refractive power, cylinder axis direction, prism refractive power, and prism base direction, or to measure the optical properties of unprocessed lens materials during processing and adjustment of eyeglasses. Lensmeters are widely used to mark the center and cylinder axis direction.

Conventional lensmeters use a collimator lens to convert the light beam from a target illuminated with light from a light source into a parallel light beam, and then input this parallel light beam into a telescope section consisting of an objective lens, focus plate, and eyepiece to create a target conjugate image. It is configured to form an image on the focus plate of this telescope section. Then, when the test lens to be measured is placed between the collimator lens and the objective lens, depending on the refractive power of the test lens, the parallel light flux from the collimator lens becomes a condensed light flux after exiting the test lens. , the target conjugate image on the reticle becomes out of focus because the beam becomes a divergent beam. This is focused by moving the collimator lens along the measurement optical axis, and the refractive power of the test lens is measured from the amount of movement of the collimator lens. In addition, in the so-called "centering process" of aligning the optical center of the test lens with the measurement optical axis of the lensmeter, the test lens is aligned perpendicular to the measurement optical axis so that the center of the target image matches the crosshair on the reticle. This is done by moving within a plane.

The lensmeter described above is generally called a telescopic lensmeter, but it uses a screen instead of the focusing plate of this telescopic lensmeter, and enlarges and projects the target conjugate image with the objective lens. There is also a projection lensmeter that directly observes the projected image on the screen without using a lens.

The targets of these lens meters include so-called corona targets, which have many small circles arranged on the circumference, cross-line targets, which have two sets of multiple straight lines orthogonal to each other, and corona targets and cross-lines. A corona cross-line target, which is a combination of targets, is known.

In the "centering work", if the lens to be tested is an astigmatic lens, when measuring using a lens meter with a built-in corona target or corona cross-line target, either of the two focal planes of the astigmatic lens can be measured. After focusing on one side, each small circle of the corona target becomes rod-shaped along the focal line direction due to the refractive characteristics of the astigmatic lens, and the corona target is elliptical as a whole. It is very difficult to find the center.The larger the cylindrical refractive power of the lens to be tested, the flatter the elliptical shape of the corona target image, and the greater the rate of change in the rod shape of the corona small circle. It will become increasingly difficult to locate the center of the coronavirus. For this reason, conventional "centering work" is performed by relying on visual measurements and intuition, which results in low centering accuracy, which reduces the accuracy of measuring the refractive properties of the tested lens, or causes problems such as not being able to align the optical center of the tested lens. This was the main reason for the decrease in marking accuracy. In particular, the accuracy of marking the optical center decreases because the cut of the lens to be tested, the insertion of the processed lens into the eyeglass frame, and the fitting adjustment are performed based on this marked center mark. This resulted in a decrease in accuracy.

A first object of the present invention is to provide a new lensmeter that solves the above-mentioned drawbacks of the conventional lensmeter.

The second object of the present invention is to eliminate the "centering work" by simply adding a center index optical system that is hardly affected by the measurement optical system, which will be described later, without changing the measurement optical system itself of the conventional lens meter. The object of the present invention is to provide a new lens meter that can be used very easily and accurately.

The structural features of the lens meter according to the present invention include the following features:
A light beam reflecting member is provided between the collimator lens and the objective lens for overlapping a part of the optical axis of the measurement optical path and the optical axis of the central index optical system,
The central index optical system includes a central index and its central index image that is placed near the rear apex of the test lens inserted into the measurement optical path and on the optical axis of the measurement optical path via the light beam reflecting member. and a projection means for projecting a beam of light, and the target is located at a point other than the vicinity of the optical axis of the measurement optical path.

With this configuration, there is a central index optical system dedicated to "centering work" that is separate from the target for measuring the refractive properties of the lens under test, and this central index optical system is almost immune to the influence of the refractive properties measuring optical system. This has the advantage that "centering work" can be performed very easily and accurately.

In the following, the invention will be explained in more detail with reference to the figures.

First, to explain the principle of the present invention, Fig. 1a is an optical principle diagram showing the measurement principle of a lens meter. Light from a target TA illuminated with light from a light source (not shown) is measured by a collimator lens C. The light beam is made into a parallel light beam parallel to the optical axis _O0 and enters the objective lens OB. The objective lens OB forms an image of this parallel light beam onto a focusing plate R placed at a focal position on the rear side. For example, if the target TA is a corona target, the target image TI formed on the reticle R will be as shown in FIG. 1b. When a test lens TL, which is a spectacle lens for hyperopic astigmatism, for example, is inserted into this measurement optical system as shown in FIG. 2a, so that its optical center O ₁ coincides with the optical axis O ₀ of the measurement optical system, The parallel light flux from the collimator lens C is focused by the refraction of the test lens and enters the objective lens OB, so the corona image TI is located at the position F in front of the focusing plate R at the first position of the test lens TL. An image is formed on the first focal plane by the refractive power of the principal meridian. Therefore, on the reticle R, the second b
As shown in the figure, the image becomes blurred. Therefore, the third a
As shown in the figure, the target TA is shifted in the direction of the arrow N so that a target image TI is formed on the focusing plate R. The amount of movement of the target TA becomes the refractive power _D1 of the first principal meridian of the lens to be tested. The target image TI on the reticle is, as shown in FIG. 3b, an image in which each small circle of the corona flows in a rod shape in a direction perpendicular to the direction of the first principal meridian of the lens to be examined.
If the target TA is further moved until a corona image flowing in the opposite direction to the flow direction of the corona shown in FIG. It is well known that Now, as shown in the shaded light flux diagram in Figure 3a, the lens to be tested is
When a light beam fl having a first image forming point P ₁ is incident on or near the rear vertex of TL and on the measurement optical axis, the second image forming point P ₂ of this light beam fl is on the objective lens.
Due to the action of the OB, an image is formed on the imaging plane F', which is slightly shifted from the position of the focusing plate R. However, this luminous flux fl
is sufficiently thin so that it becomes an image on the focusing plate R that is not very blurred, and the image is located on the measurement optical axis, that is, on the intersection of the cross hairs h of the focusing plate R. The reason why the first imaging point P ₁ of the light flux fl is focused at or near the rear apex position of the test lens TL is as follows. That is, as shown in Fig. 5, the focal length of the lens TL to be tested is f, its object side focal point is F ₁ and its image side focal point is F ₂ , and an object point A is set at a distance x from the focal point F ₁ . , this and the lens to be tested
Assuming that the conjugate image point B due to TL is located at a distance y from the focal point F ₂ , there is a relationship of x·y=f ² . And here, if x=-f, that is, the object point A is located at the object side vertex of the test lens TL, then y=f ² /-f=-f Also, the lateral magnification β is β=f/x=-f/f =-1. Here, the case where the sign of the magnification is negative is taken as an erect image. From this, if we place the object point at x=-f, its image will also be formed at the same position as the object point, which means that the same physical relationship exists even if the test lens TL does not exist. , From this, as shown in Figure 3a, the first imaging point of the light flux fl
When P ₁ is imaged at the rear apex of the test lens TL, that is, the object side apex, the light beam from this first imaging point is not subjected to the refraction action of the test lens TL, but is only affected by the objective lens OB. and the second imaging point P ₂
make a statue of it. However, as shown in Fig. 4a, the optical axis O ₁ of the lens TL to be tested _is
When the target TA is placed at a position shifted from the target TA, the image of the target TA is affected by the prism component PR of the test lens TL and is focused on the reticle R at a position shifted from the intersection of the cross hairs h, as shown in Figure 4b. imaged. Similarly, the light flux fl is not affected by the refraction effect of the test lens due to the above-mentioned principle, but is affected by the action of the prism PR of the test lens, and is shifted by the same amount as the target image.

Based on the above principle, the test lens is
By moving TL, the optical axis of the test lens O ₁ and the measurement optical axis
O ₀ can be matched, and this principle is much more "centering work" than finding the center visually using a flowing corona image like a conventional lens meter.
It can be seen that it is easy to do and accurate.

Embodiments of the present invention will be described below with reference to the drawings, taking a telescope lens meter as an example. In FIG. 6, the refractive power measurement system includes a light source 2, a target 3, a collimator lens 4, a beam splitting member 5, a test lens 6, an objective lens 7, a focus plate 8, and an eyepiece lens 9, arranged on an optical axis 1. It will be done. The target 3 is formed by forming a corona pattern 15 in which a large number of small circles are arranged on the circumference of a circle whose center coincides with the optical axis 1, as shown in FIG. It is formed by combining a cross target 18 made of straight lines of a book and the corona pattern 15 described above. As shown in FIG. 7, the focus plate 8 is formed with a cross pattern 10 whose intersections coincide with the optical axis 1. The target 3 and reticle 8 are conjugate. Further, a glass scale having a diopter scale that moves in synchronization with the movement of the target 3 is illuminated by the light source 2, and the scale scale image is focused on the focusing plate 8 via the prism 21, relay lenses 22, 23, and prisms 24, 25. Image is projected. On the optical axis reflected by the beam splitting member 5, an aperture 11, a first condensing lens 12, a second condensing lens 13, a light source 14, and an aperture plate 17 having a small aperture 17a through which the light from the light source passes are arranged. A central index optical system is configured. Small opening 1
7a and the vicinity of the rear vertex of the test lens 6 are conjugate. In the above configuration, when the test lens 6 is centered, as shown in FIG. As a result, it is possible to observe a central index, that is, a small circle 16, whose projected periphery is slightly blurred. When the centering work is completed using the central index, the light source 14 is turned off and only the target image is projected onto the focusing plate 8, thereby measuring the refractive characteristics of the lens to be tested.The central index does not get in the way when measuring the refractive characteristics. There isn't. Also, instead of the light source 14, the light from the light source 2 is guided by an optical fiber, the end of which is placed at the position of the light source 14, and the 1
When one light source is used for both target illumination and central index illumination, the central index image can be erased if necessary by using a flip-up reflecting mirror as the beam splitter 5. In addition, the light source 14 and the aperture plate 1
By inserting a color filter 19 between 7 and 7 to change the color of the central index image from that of the target image, the central index image and the target image can be easily distinguished.

Although a telescopic lens meter has been described in this embodiment, the present invention is not limited to this, and the focusing mirror shown in FIG. 6 may be used as a screen.
It goes without saying that a projection type lens meter configured to enlarge and project a target image using the objective lens 7 can also be used. Also,
The center indicator is not limited to the aperture of the aperture plate illuminated by an incandescent light bulb as shown in this embodiment, but a minute light emitting diode or a laser light source may be used directly as the indicator.

[Brief explanation of drawings]

Figures 1a, 2a, 3a, and 4a are principle diagrams of the measurement optical system of a lens meter for explaining the measurement principle of the present invention, and Figures 1b, 2b, 3b, and 4b are the above-mentioned figures 1a, 2a, 3a, and 4a. Figure 5 is an optical principle diagram showing that the central index optical system of the present invention is not affected by the refractive characteristics of the test lens, and Figure 6 is a diagram showing the state of the target image corresponding to each of the following. An optical layout diagram of a lens meter showing an embodiment of the invention,
FIG. 7 is a diagram showing an example of a target used in the above embodiment, and FIG. 8 is a diagram showing another example of a target used in the above embodiment. 1...Optical axis, 2...Light source, 3...Target,
4... Collimator lens, 5... Luminous flux splitting member,
6...Test lens, 7...Objective lens, 8...Focal plate, 11...Aperture, 17...Aperture plate.

Claims (1)

[Scope of Claims] 1. A lensmeter having a measurement optical path configured by sequentially arranging at least a light source, a target, a collimator lens, an objective lens, and a focus plate, wherein the light of the measurement optical path is provided between the collimator lens and the objective lens. It has a light beam reflecting member for overlapping the axis and a part of the optical axis of the central index optical system, and the central index optical system has a central index and its central index image inserted into the measurement optical path. and a projection means for projecting a thin beam of light through the light beam reflecting member near the rear apex of the test lens and onto the optical axis of the measurement optical path, and the target is a portion of the optical axis of the measurement optical path. A lens meter characterized by being configured excluding the surrounding area. 2. The lens meter according to claim 1, wherein the target has a corona shape with small circles arranged on the circumference. 3. The lensmeter according to claim 1 or 2, further comprising an eyepiece for observing the target image on the focus plate. 4. The lens according to claim 1 or 2, wherein the focusing plate is a screen, and the image of the target is enlarged and projected onto the screen by the objective lens. meter.