JP3086869B2 - Telescope system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telescope system having a resolution exceeding the diffraction limit.

[0002]

2. Description of the Related Art Conventionally, in a Galileo telescope having an objective lens system of a convex lens and an eyepiece system of a concave lens, an upright virtual image can be obtained with a simple lens configuration. Has been used for

[0003]

However, in the Galileo telescope, the resolution (resolution) of the telescope is determined by the light diffraction phenomenon. Therefore, the telescope is used only in a range where the influence of the light diffraction phenomenon is not remarkable. Had the problem of not being able to do so.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and uses a concave lens in an eyepiece system of a telescope for transmitting and receiving light, and applies a wavefront of a spherical wave for a finite distance to the concave lens. With a spherical aberration, the telescope is distorted so that the curvature becomes smaller as the distance from the optical axis becomes larger at the aperture surface of the telescope,
An object of the present invention is to provide a telescope system that generates a special diffracted beam having a width smaller than the light intensity distribution at the diffraction limit to make the resolution higher than the diffraction limit.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of one embodiment of the present invention will be described below. Consider a Galileo telescope using a concave lens for the eyepiece 6 shown in FIG. Objective lens 5
By changing the position of the eyepiece 6 with respect to, it is possible to focus on infinity and finite distance according to the distance of the object. In each of these states, the light beam of the telescope is a parallel beam (plane wave) state and a convergent beam (spherical wave).
It is equivalent to being in a state.

Here, the focal lengths of the objective lens 5 and the eyepiece 6 are respectively f ₁ and f ₂ (in the case of a concave lens, they are defined as negative).
And the distance between the objective and eyepiece lenses is L, L = f
₁ + f ₂ a parallel beam, a convergent beam state in L> f ₁ + f _2. Here, an object at a finite distance is handled by setting the telescope to a convergent beam (spherical wave) state.

Next, a concave lens having an appropriate spherical aberration is used as the eyepiece 6 in FIG. Since the spherical aberration of the concave lens is a negative spherical aberration, a ray passing through the peripheral portion acts so that a focal length of the telescope becomes shorter than a ray passing through the central portion near the optical axis.

As a result, the light beam of the present telescope has a wavefront distorted so that the curvature becomes smaller toward the periphery in a spherical wave state when an object at a finite distance is targeted. The light beam at that time is as shown in FIG. In FIG. 2, 1 is a distorted spherical surface, 2 is a spherical surface, and 3 is an optical axis.

In the case of a special light beam state as shown in FIG. 2, a light beam having a large intensity is generated in the form of a narrow sub-beam at the center due to the light interference effect. To be more precise, the light intensity distribution in the beam at an arbitrary distance can be obtained by Fresnel integration. Approximately, the light intensity distribution is obtained as follows. The width at the center of this light intensity distribution is the resolution of the telescope.

When attention is paid to the generation of the center portion in the form of a sub-beam having a high intensity, as can be understood from FIG. 2, each part of the wavefront (which is annular due to the axial symmetry) has an optical axis 3 normal to the wavefront.
It can be considered that the Bessel beam is formed most contributing to the distance intersecting with. In the diffracted beam generated over a long distance, a far portion is a portion outside the aperture of the telescope, and a short portion is a portion inside the aperture of the telescope.

The shape of the center of the beam is a very good approximation of 0
Has a J ₀ ² follows Bessel, the full width at half maximum of the light intensity distribution (FWHM) and w _0, J ₀ ² is half (1/2) and made of the of the J ₀ variable is 1.125 Since it is time, this is represented by Equation (1).

[0012]

(Equation 1)

Where λ is the wavelength, z is the distance to the object,
ρ _a is the average radius of the first contributing first Fresnel zone in the aperture, which in this case is annular. The distance contributed by the vicinity of the opening end where ρ _a is the opening radius a is expressed by Expression (2). Here, D is the diameter of the opening.

[0014]

(Equation 2)

Meanwhile, J ₁ ² next 1 Bessel type as diffraction pattern corresponding to the resolution of the diffraction limit of a general telescope is well known, the half width (FWHM) w ₁
Then, the finite distance z is represented by Expression (3).

[0016]

(Equation 3)

From equations (2) and (3), w ₀ / w ₁ =
2.25 / π ≒ 0.72, the beam width is about 70% of the diffraction limit, and the resolution is improved accordingly. From equations (1) and (3), the radius ρ _a in the opening is ρ _a
It can be seen that the resolution of the super-diffraction limit can be obtained with respect to the distance of the periphery of the opening that satisfies ≧ 0.72a. (However,
Since the intensity of the main lobe of the diffracted beam decreases as the distance increases, the system is not effective for a distance equivalent to infinity. )

Therefore, when the telescope system of the present invention is used, an ultra-high resolution exceeding the diffraction-limited resolution of the conventional telescope can be obtained for the above distance.

[0019]

EXAMPLE In this example, the optical telescope system of the present invention was used, and an objective lens (aperture: 10 cm, focal length: 40 cm)
And an example of the light intensity distribution in the beam obtained by accurate Fresnel integration when an eyepiece lens (used effective diameter: 1.25 cm, spherical aberration at the effective diameter end = −0.58 mm) is used.

The light intensity distribution of the telescope system of the present invention at a distance of 1 km is shown in FIG. 4 when the beam is condensed to 1 km with a general telescope (corresponding to focusing on 1 km) (FIG. 4). 3 is shown in FIG.
The width of the main lobe in FIG. 3 is smaller than the width of the light intensity distribution at the diffraction limit in FIG. 4 (≒ 80%), which indicates that the resolution is at the super diffraction limit.

As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and may be implemented in any manner unless the configuration described in the claims is changed. it can.

[0022]

As described above, in the present invention, a super-diffraction-limited telescope is used for transmitting and receiving light, so that when it is used for transmitting laser light or the like, a thinner light beam than before can be obtained at a long distance. Also, when used for reception, a great effect is obtained, such as higher resolution than before can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a configuration of a telescope system according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a trajectory of a light beam on a light wavefront of a distorted spherical surface according to the present invention.

FIG. 3 is a characteristic diagram showing a light intensity distribution in the telescope system of the present invention.

FIG. 4 is a characteristic diagram showing a light intensity distribution in a conventional telescope system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Distorted spherical surface 2 Sphere 3 Optical axis 4, 4 'ray 5 Objective lens system 6 Eyepiece system

Claims (1)

(57) [Claims] 1. A concave lens is used in an eyepiece system of a telescope for transmitting and receiving light, and a wavefront of a spherical wave intended for a finite distance is made to have a spherical aberration so that the concave lens has a spherical aberration. Distort the curvature to be small,
A telescope system characterized in that a special diffraction beam having a width narrower than a diffraction-limited light intensity distribution is generated and the resolution is equal to or higher than the diffraction limit.