JP7389987B2 - Galilean wide-angle foveal telescope - Google Patents

Description

The present invention relates to a Galilean wide-angle foveal telescope.

Telescopes such as binoculars and monoculars for magnifying distant objects have a Keplerian-style lens configuration that uses a convex lens for the objective and eyepiece, and a Galileo-style lens that uses a convex lens for the objective and a concave lens for the eyepiece. This lens configuration is known. A Galilean lens configuration results in an erect image, but a Keplerian lens configuration results in an inverted image. Therefore, when binoculars or monoculars have a Keplerian lens configuration, a lens system such as a relay lens or a prism for inverting an image is provided between the objective lens and the eyepiece.

On the other hand, an imaging lens (imaging system) called a wide-angle foveal optical system that is modeled on the human eye and has a wide field of view and high resolution at the center is known from Patent Document 1. In such a wide-angle foveal optical system, by making the optical magnification at the center of the field of view higher than at the periphery, a large amount of image information about the object of interest can be obtained from the center, and a wide range of information can be obtained from the periphery. I have to.

Japanese Patent Application Publication No. 2005-10521

By the way, when realizing a wide-angle foveal optical system with a telescope (afocal system), the Keplerian type is advantageous. This is because the degree of decrease in the width of the field of view as the magnification increases is more remarkable with the Galilean lens configuration than with the Keplerian lens configuration. However, in order to obtain an erect image, Keplerian telescopes require a lens system such as a relay lens or prism as described above, which increases the overall length and weight of the telescope, making it difficult for the user to handle and carry. There is a problem that convenience is lost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a Galilean wide-angle foveal telescope that is a wide-angle foveal optical system and is advantageous in terms of shortening the overall length.

The Galilean wide-angle foveal telescope of the present invention is an afocal optical system, and is composed of one or more lenses in order from the object side, with the central part having a positive refractive power and the peripheral part having a negative refractive power. It consists of a front group that has a refractive power and a rear group that is made up of one or more lenses and has a central portion that has a negative refractive power and a peripheral portion that has a positive refractive power.

According to the Galilean wide-angle foveal telescope of the present invention, the front group has a front group having a positive refractive power in the center and a negative refractive power in the periphery, and a front group having a negative refractive power in the center and a positive refractive power in the periphery. Since the lens structure is made up of a rear group having a refractive power of , the total length of a telescope with a wide-angle foveal optical system that has a wide field of view and high magnification at the center can be shortened.

FIG. 2 is a cross-sectional view showing the lens configuration of the telescope of Numerical Example 1. FIG. 3 is a cross-sectional view showing a lens configuration of a telescope in Numerical Example 2. It is an explanatory view explaining each angle of incidence to a telescope and a pupil. This is an image showing a simulation image of a telescope observation image. This is an image showing the observation range and image size of a conventional telescope. 2 is a graph showing the relationship between the angle of incidence θ ₁ and the angle of incidence θ ₂ to the pupil for the telescope of Numerical Example 1. 3 is an aberration diagram showing aberrations of the telescope of Numerical Example 1. FIG. 7 is a graph showing the relationship between the angle of incidence θ ₁ and the angle of incidence θ ₂ to the pupil for the telescope of Numerical Example 2. 7 is an aberration diagram showing aberrations of the telescope of Numerical Example 2. FIG.

An example of a lens configuration of a Galilean wide-angle foveal telescope according to an embodiment of the present invention is shown in FIGS. 1 and 2. 1 and 2 correspond to Galilean wide-angle foveal telescopes (hereinafter simply referred to as telescopes) 10 of Numerical Example 1 and Numerical Example 2, respectively, which will be described later, and have the same basic configuration. Below, a telescope 10 according to an embodiment of the present invention will be described with reference to the configuration of FIG.

The telescope 10 is a wide-angle foveal optical system that provides a wide angle, that is, a wide field of view (actual field of view), and a higher magnification in the center of the field than in the periphery. This telescope 10 can be used as a monocular or as a pair of telescopes 10 as binoculars. When using this telescope 10, it is possible to capture the observation target in the center of the field of view and observe it in detail, and when the observation target moves or the direction of the telescope 10 changes, the observation Even if the direction of the object changes significantly, it is possible to keep the observation object within the field of view of the telescope 10, and it is possible to easily return the observation object to the center of the field of view and continue detailed observation. .

In the telescope 10, while reducing distortion in the center of the field of view, the coefficient of distortion is greatly changed from the center to the periphery, and large negative distortion is generated in the periphery. Thereby, the telescope 10 has a wide angle and the magnification of the central part of its field of view is made higher.

The telescope 10 is an afocal lens composed of a front group Gf and a rear group Gr in order from the object side, and allows preferable observation through the telescope 10 with the observation eye located at the eye point EP. The front group Gf consists of one first lens L1. The rear group Gr is composed of a first lens group Gr1 and a second lens group Gr2 in order from the object side, the first lens group Gr1 is composed of one second lens L2, and the second lens group Gr2 is It consists of one third lens L3.

The first lens L1 serving as the front group Gf has a positive refractive power (lens power) P1c at the center and a negative refractive power P1p at the periphery. In the rear group Gr, the refractive power Prc of the central portion is negative and the refractive power Prp of the peripheral portion is positive for the entire rear group Gr.

In this example, the second lens L2 has a negative refractive power P2c at the center and a positive refractive power P2p at the periphery. This controls the refractive power of the rear group Gr. On the other hand, the third lens L3 mainly makes the diameter of the light beam from each incident direction at the eye point uniform, shortens the eye relief (exit pupil distance), and increases the apparent field of view (=magnification x actual field of view). . In this way, by increasing the apparent field of view, that is, by projecting the image within the field of view widely onto the retina, it is advantageous in securing a wide field of view while increasing the image magnification on the retina.

That is, the telescope 10 satisfies the following conditions (1) to (3).
(1) P1c>0, P1p<0
(2) Prc<0, Prp>0
(3) P2c<0, P2p>0

Conditions (1) and (2) above are conditions for obtaining a wider field of view while increasing the magnification in the central part of the field of view.With these conditions, the telescope 10 has a Galilean-style central part of the field of view. The peripheral part has an inverted Galilean lens configuration.

In the example shown in FIGS. 1 and 2, the front group Gf, the first lens group Gr1, and the second lens group Gr2 are each composed of one lens, but the first lens L1, the second lens L2, and the Each of the front group Gf, the first lens group Gr1, and the second lens group Gr2, or a part thereof, may be configured with a plurality of lenses so as to have the same function as the three lenses L3. Further, the rear group Gr may be composed of one lens. The relationship between the refractive powers of the front group Gf and the rear group Gr corresponding to the above conditions (1) and (2) is as follows, where the refractive power of the central part of the front group Gf is Pfc, and the refractive power of the peripheral part is Pfp. The conditions are as shown in (1a) and (2a). As shown in the examples shown in FIGS. 1 and 2, configuring the rear group Gr with a plurality of lenses increases the degree of freedom in the surface shape of each lens in the rear group Gr. This is a preferred embodiment from the viewpoint of facilitating lens processing.
(1a) Pfc>0, Pfp<0
(2a) Prc<0, Prp>0

With the above lens configuration, the telescope 10 can have a short overall length. Furthermore, since the number of lenses constituting the telescope 10 can be reduced, this is advantageous in reducing the weight of the telescope 10.

From the viewpoint of obtaining a sufficiently wide field of view while obtaining high magnification at the center of the field of view, the telescope ₁₀ has a magnification ratio of 3 or more ( _{α 1 /} α ₂ It is preferable that ≧3). As shown in FIG. 3, the magnifications α ₁ and α ₂ here refer to the appearance of the same object when viewed through the telescope 10 relative to the angle of the object seen with the naked eye (angle of incidence on the telescope) θ ₁ (°). The ratio of the image angle (angle of incidence on the pupil or retina) θ ₂ (°) (= θ ₂ /θ ₁ ), which is the ratio of the angle to the optical axis of the conjugate ray passing through the conjugate point on the optical axis. (angular magnification).

Incidentally, the incident angles θ _{1 and} θ ₂ corresponding to the magnification α ₁ at the center of the visual field are both “0°,” but in this case, the magnification α ₁ at the center of the visual field is, for example, as shown in FIGS. 8, it can be determined by the slope of the image height curve showing the relationship between the incident angle θ ₁ and the incident angle θ ₂ .

FIG. 4 shows a simulation image obtained by simulating an observed image observed by the telescope 10. This simulation image was created from the wide-angle image shown in FIG. The wide-angle image shows the range and size of the observed image observed by a telescope with a wide field of view equivalent to the real field of view of the telescope 10, but in reality, the range and size of the image are different from the observation position of the telescope 10 assumed by the simulation image. , is an image taken using a wide-angle lens whose diagonal angle of view is comparable to the actual field of view of the telescope 10. As can be seen from the wide-angle image in Figure 5, if the actual field of view of a telescope is widened, it is possible to observe a wide range without changing the direction of the telescope (direction of the optical axis). Difficulty fully recognizing what is being observed. On the other hand, with the telescope 10, as can be seen from the simulation image in FIG. 4, the object to be observed in the center can be observed at high magnification while observing a wide range similar to a wide-angle image.

Next, numerical examples of the telescope 10 will be described.

[Numerical Example 1]
As shown in FIG. 1, the telescope 10 of Numerical Example 1 includes, in order from the object side, a first lens L1 as the front group Gf, a second lens L2 as the first lens group Gr1 of the rear group Gr, and a second lens L2 as the first lens group Gr1 of the rear group Gr. It has a three-lens configuration including a third lens L3 as a second lens group Gr2. The first lens L1 has a positive refractive power P1c at the center and a negative refractive power P1p at the periphery. The entire rear group Gr has a negative refractive power Prc at the center and a positive refractive power Prp at the periphery. Further, the second lens L2 has a negative refractive power P2c at the center and a positive refractive power P2p at the periphery.

Table 1 shows the lens data of the telescope 10 of Numerical Example 1. The "surface number" in Table 1 is a number assigned to the lens surface in order from the object side. The "*" attached to the surface number indicates that the surface is an aspherical surface. The "Radius of curvature" column shows the radius of curvature of each lens surface, and the "Surface spacing" column shows the lens thickness or air gap between each lens surface and the next lens surface on the optical axis. ing. The eye relief of the telescope 10 is shown in the "plane spacing" column of the plane number "6". The unit of the radius of curvature and the interplanar spacing is "mm". The "nd" column shows the refractive index of each optical element for the d-line (wavelength 587.6 nm), and the "vd" column shows the Abbe number of each optical element for the d-line. The "Materials" column shows the material (in this example, the type of resin) of each optical element, and "PMMA" is polymethyl methacrylate resin. Note that "air" is written in the "Materials" column corresponding to the air interval. The eye relief is the distance from the rearmost surface of the third lens L3 on the pupil side to the exit pupil (eye point) on the optical axis.

The aspheric shape of the lens is expressed by the following aspheric formula using the conic coefficient k and the aspheric coefficients A ₂ , A ₄ , A ₆ . . . shown in Table 2.

Each value in the above formula is as follows.
Z: Sag amount in the optical axis direction (mm)
s: Distance from optical axis (mm)
C: Curvature (reciprocal of paraxial radius of curvature)
k: conic constant A ₄ , A ₆ , A ₈ ...: 4th, 6th, 8th... aspheric coefficients

The main specifications of the telescope 10 of Numerical Example 1 shown in the above lens data are as follows. The total length of the lens is the distance from the frontmost surface of the lens to the rearmost surface of the lens on the optical axis. Further, FIG. 6 shows the relationship (image height curve) between the above-mentioned incident angle θ ₁ and incident angle θ ₂ for the telescope 10 of Numerical Example 1. The slope of the image height curve in FIG. 6 indicates the magnification of the telescope 10.
Lens total length: 29.97mm
Exit pupil diameter: 2.0mm
Actual field of view (2ω): 30°
Magnification ratio (α ₁ /α ₂ ): 20 (magnification α ₁ : 5.0 times, magnification α ₂ : 0.25)

As described above, although the telescope 10 of Numerical Example 1 has a short overall length of about 30 mm, it has a wide field of view of 30° and a high magnification of 5 times in the center of the field of view. Furthermore, from the graph in FIG. 6, a large magnification is obtained in the center of the field of view of the telescope 10, and the magnification decreases rapidly from the center to the periphery, resulting in a wide field of view. I understand.

The curvature of field and distortion of the telescope 10 are shown in FIG. 7, respectively. Figure 7 shows the field curvature for the F-line (wavelength 486.1 nm), d-line, and C-line (wavelength 656.3 nm), where the solid line represents the field curvature of the tangential image plane, and the broken line represents the sagittal image. It shows the curvature of field in the plane. Further, as can be seen from the field curvature and distortion shown in FIG. 7, the telescope 10 can obtain good imaging over the entire field of view. Especially, very good imaging with little distortion can be obtained in the central part of the visual field that corresponds to a small incident angle of 0.5° or less. Furthermore, in the field of view range from 1.5° to 10°, particularly good imaging can be obtained while the distortion gradually increases.

[Numerical Example 2]
As shown in FIG. 2, the telescope 10 of Numerical Example 2, like the telescope 10 of Numerical Example 1, includes, in order from the object side, a first lens L1 as the front group Gf and a first lens of the rear group Gr. It has a three-lens configuration including a second lens L2 as a group Gr1 and a third lens L3 as a second lens group Gr2. The first lens L1 has a positive refractive power P1c at the center and a negative refractive power P1p at the periphery. The entire rear group Gr has a negative refractive power Prc at the center and a positive refractive power Prp at the periphery. Further, the second lens L2 has a negative refractive power P2c at the center and a positive refractive power P2p at the periphery.

Lens data of the telescope 10 of Numerical Example 2 is shown in Table 3 below. Further, the aspheric shape of each lens of the telescope 10 is expressed by the above-mentioned aspheric formula using the conic coefficient k and the aspheric coefficients A ₂ , A ₄ , A ₆ . . . shown in Table 4. FIG. 8 shows an image height curve showing the relationship between the incident angle θ ₁ and the incident angle θ ₂ for the telescope 10, and FIG. 9 shows the field curvature and distortion aberration for the telescope 10. The items in Tables 3 and 4 and the field curvature and distortion in FIG. 9 are shown in the same manner as in Numerical Example 1.

The main specifications of the telescope 10 of Numerical Example 2 shown in the above lens data are as follows.
Lens total length: 23.57mm
Exit pupil diameter: 4mm
Actual field of view (2ω): 30°
Magnification ratio (α ₁ /α ₂ ): 3.0 (magnification α ₁ :1.5, magnification α ₂ :0.5)

The telescope 10 of Numerical Example 2 also has a wide field of view of 30° and a high magnification of 1.5 times at the center of the field of view, although the overall length is short to about 20 mm. Furthermore, as can be seen from the graph in FIG. 8, the telescope 10 of Numerical Example 2 also has a large magnification in the center of the field of view, and then the magnification decreases rapidly from the center of the field of view toward the periphery. It can be seen that a wide field of view is obtained. Furthermore, as can be seen from the field curvature and distortion shown in FIG. 9, the telescope 10 provides particularly good imaging over the entire field of view.

10 Telescope Gf Front group Gr Rear group Gr1 1st lens group Gr2 2nd lens group L1 to L3 Lens

Claims (3)

It is an afocal optical system,
Consisting of one first lens in order from the object side, the central part has a positive refractive power that narrows the incident parallel light beam , and the peripheral part has a negative refractive power that widens the incident parallel light beam. It consists of a front group with a front lens, one second lens and one third lens in order from the object side , and as a whole, the central part has a negative refractive power that spreads the incident parallel light flux, and the peripheral part has a negative refractive power that spreads the incident parallel light flux. A Galilean wide-angle foveal telescope characterized by comprising a rear group having a positive refractive power that narrows an incident parallel beam of light . The Galilean wide-angle foveal telescope according to claim 1, wherein the second lens has a negative refractive power at a central portion and a positive refractive power at a peripheral portion. The Galilean wide-angle foveal telescope according to claim 1 or 2, wherein the magnification ratio α1/α2 is 3 or more, where α1 is the magnification at the center of the visual field and α2 is the magnification at the outer periphery of the visual field.

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