JPH11119104A - Catadioptric system for observing wide visual field - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate manufacture, and to sufficiently fetch a visual field in a direction perpendicular to an optical axis by constituting this system of a first lens group having a convex mirror, a second lens group having a concave mirror or a plane mirror and a third lens group having a refracting lens in order from an object side. SOLUTION: This system is constituted of the first lens group G1 having the convex mirror M1 , the second lens group G2 having the concave mirror M2 or the plane mirror M3 , and the third lens group G3 having the refracting lens in order from the object side. A luminous flux from an object is reflected by the groups G1 and G2 in order, transmitted through the group G3 , and image- formed on an image surface. In this case, a Gaussian optical system is adopted as the group G3 . Since this system is the one for an ultra wide angle lens, the luminous flux made incident on the two reflecting mirrors of groups G1 and G2 is comparatively small. Consequently, spherical aberration and coma aberration hardly occur in the reflecting system, and the occurrence is restrained by the group G3 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical system capable of observing a wide field of view, and more particularly to an optical system capable of observing 360 ° in a circumferential direction.

[0002]

2. Description of the Related Art FIG.
1 shows a schematic configuration of an observation optical system capable of observing 60 °. As shown in the figure, this optical system is composed of one convex mirror and a refractive optical system, and the convex mirror has a spherical or hyperboloidal shape. Next, FIG. 10 shows a schematic configuration of a catadioptric optical system of a monitoring system capable of monitoring 360 ° in the horizontal direction disclosed in Defense Technology Journal. Vol. 16, No. 12, pp. 36-39. It is. This monitoring optical system is composed of a primary mirror and a secondary mirror, all of which are convex mirrors, and a refractive lens. To explain this catadioptric optical system very simply, an off-axis light beam having an angle of view of 70 ° to 110 °, that is, ± 20 ° in a direction perpendicular to the optical axis,
In the circumferential direction, a 360 ° light beam is formed on the image plane. In this document, the shape of the reflector is not shown in detail, but it is indicated that the two reflectors are specially shaped aspherical surfaces. An optical system almost similar to this optical system was reported at a joint lecture of the Japan Society of Applied Physics in March 1997, and it was also disclosed that the shape of the two reflecting mirrors was a higher-order aspherical surface. ing.

[0003]

As described above, this type of conventional optical system is composed of one or two convex mirrors and a refractive lens. Here, in the conventional example shown in FIG. 9, it is difficult to widen the field of view in the direction perpendicular to the optical axis. Further, in the conventional example shown in FIG. 10, since two aspherical convex mirrors are used, there is a disadvantage that the manufacturing cost is increased.

[0004] In view of these problems, the present invention has an object to provide a catadioptric optical system which is relatively easy to manufacture and can sufficiently capture a field of view in a direction perpendicular to the optical axis. And

[0005]

In order to achieve the above object,
In the present invention, in order from the object side, a _first mirror having a convex mirror M ₁ is provided.
A lens group G ₁ , a second lens group G ₂ having a concave mirror M ₂ or a plane mirror M _3, and a third lens group G having a refractive lens
_{3. A} catadioptric optical system for wide-field observation, comprising:

[0006]

As described above, according to the present invention, a reflecting mirror is used.
Use two, especially the second lens group G_TwoConcave reflector shape
Or, it was flat. A concave or flat surface is generally
The surface can be easily inspected, so it is possible to work with high accuracy
Noh. In addition, convex mirror M₁Has a large refractive power,
The contribution to Petzval sum is very large. So here
Field curvature and astigmatism caused by
You. Since a good image cannot be obtained as it is, the convex mirror M
₁Field curvature and astigmatism caused by
There is need. Conventionally, as shown in FIG.
In the present invention, the second lens group G is used._TwoFor
By making the reflecting surface concave or flat,
Value to the convex mirror M₁Value opposite to or convex mirror M ₁The value of that
In the direction perpendicular to the optical axis.
To provide an optical system with a sufficiently corrected image plane
become.

Hereinafter, description will be made with reference to a first embodiment of the present invention. The luminous flux from the object is a convex mirror M ₁
More first lens group G ₁ consisting reflects the order of the second lens group G ₂ composed of the concave mirror M _2, forming on the image plane is transmitted through the third lens group G ₃ composed of refractive lenses Image. As described above, since the convex mirror M ₁ has a large refractive power,
The contribution to Petzval sum is very large. This remains in good image has not obtained, there is a need to cancel the convex mirror curvature generated by M ₁ and the astigmatism. In the present invention, further a third lens group G ₃ by employing a Gaussian optical system, solves this problem. this is,
This is because two concave surfaces sandwiching the stop S of the Gaussian optical system contribute to correction of Petzval sum. Further, the two concave surfaces satisfactorily correct the imaging performance on the image plane by utilizing the effect of correcting astigmatism.

Since the optical system of the present invention is a system of an ultra-wide-angle lens, the light beams incident on the two reflecting mirrors of the first lens group G ₁ and the second lens group G ₂ are relatively small. for that reason,
Spherical aberration and coma is hardly generated in the reflection system, to suppress the occurrence in the third lens group G ₃ composed of refractive lenses. Here, it is preferable that the shape of the convex mirror M ₁ of the first lens group G _{1 be} an aspheric surface, particularly a hyperboloid. By using an aspheric surface, aberration correction can be performed more favorably.

The concave mirror M ₂ has a concave spherical surface and has some effects of Petzval sum correction and astigmatism correction. In particular, since the concave mirror M ₂ is a spherical mirror,
Compared with the conventional example, the number of aspherical surfaces is reduced by one, which makes it easy to manufacture parts and reduce costs. Also, as disclosed in the second embodiment according to the present invention, even when the second lens group G ₂ and the plane mirror M _3, basically, a method of correcting aberration of the convex mirror M ₁ and a refractive lens is exactly the same . In the case of using the plane mirror M _3, it is easy to further manufacture than a spherical mirror, it is possible to further reduce the manufacturing cost. In the conventional example shown in FIG. 9, a convex mirror has been difficult to image the vertically above the scene for a downward, by using the plane mirror M _3, more extensive image the vertical direction by folding a plane mirror be able to.

[0010]

The embodiments of the present invention will be described below. In each table of each embodiment, the leftmost number indicates a surface number, r indicates a radius of curvature, d indicates a surface interval, n (d) indicates a refractive index at d-line, and ν.
(D) represents the variance based on the d line. The optical system of each embodiment according to the present invention has a configuration in which a direction perpendicular to the optical axis is 22 ° to 110 ° (a depression angle of 68 ° to an elevation angle of 20 °).
°), a 360 ° image is formed in a donut shape in the circumferential direction.

The projection system of the optical system of each embodiment according to the present invention is represented by a stereoscopic projection system (Y = 2f · tan (θ / 2) when an image height Y, a focal length f, and an angle of view θ). (Projection method), and an image is taken to be about ４ of the size of the image near the angle of view of 90 ° on the axis. However, since the optical system of each embodiment according to the present invention is a reflection system, the light flux near the axis is blocked.

In each aberration diagram, the solid line is the d-line (578.6).
nm), the dotted line represents the C line (656.3 nm),
The dashed line represents the F line (486.7 nm). [First Embodiment] Table 1 shows optical data of the first embodiment according to the present invention. FIG.
The aberration diagram is shown in FIG. Incidentally, the first surface of the present embodiment is represented by κ = −
It is a hyperboloid of 1.347066.

[0013]

TABLE 1 r d n (d) ν ( d) 1 42.92284 -100.000 -1 G 1 M 1 2 520.73052 106.033 -1 G 2 M 2 3 6.73890 2.300 1.64049 60.10 G 3 4 15.00421 0.200 5 4.26284 2.200 1.76180 26.95 6 2.11912 2.272 7 0.00000 0.676 S 8 -5.92842 1.000 1.80518 25.43 9 15.28604 3.500 1.64049 60.10 10 -4.65928 0.900 11 13.53996 2.000 1.69673 56.42 12 -25.80949 8.880 As shown in FIGS. Up to 110 °, various aberrations are well corrected. [Second Embodiment] Table 2 shows optical data of the first embodiment according to the present invention. FIG.
The aberration diagram is shown in FIG. Incidentally, the first surface of the present embodiment is represented by κ = −
It is a hyperboloid of 1.594168.

[0014]

TABLE 2 r d n (d) ν ( d) 1 48.44101 -97.966 -1 G 1 M 1 2 0.00000 102.816 -1 G 2 M 2 3 6.88655 2.300 1.64049 60.10 G 3 4 13.81611 0.200 5 4.45075 2.200 1.76180 26.95 6 2.32741 2.701 7 0.00000 0.676 S 8 -5.78718 1.000 1.80518 25.43 9 24.18148 3.500 1.64049 60.10 10 -4.96114 0.900 11 14.42286 2.000 1.69673 56.42 12 -31.30077 10.562 As shown in FIGS. 6 to 8, the direction perpendicular to the optical axis is from 22 °. Up to 110 °, various aberrations are well corrected.

In each of the above embodiments, the light flux near the axis is shielded, but as disclosed in the Defense Technology Journal. Vol. 16, No. 12, pp. 36-39 described in the section of the prior art. For the on-axis portion, using a normal imaging optical system, in the center of the donut-shaped image formed by the optical system of the embodiment,
It is conceivable to form an image of a normal imaging optical system.

As described above, the primary mirror of the convex mirror of the catadioptric optical system, the secondary mirror of the concave mirror or the plane mirror, and the two mirrors sandwiching the stop
Combination with a refracting lens having two concave surfaces enables imaging in a wide field of view, and by making the secondary mirror a spherical surface or a flat surface, it is possible to simplify the production of parts and reduce the production cost.

[0017]

According to the present invention, it has become possible to provide a catadioptric optical system which is relatively easy to manufacture and can sufficiently take in a visual field in a direction perpendicular to the optical axis.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical system according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating spherical aberration and astigmatism of the optical system according to Example 1.

FIG. 3 is a lateral aberration diagram of the optical system according to Example 1.

FIG. 4 is a lateral aberration diagram of the optical system according to the first example.

FIG. 5 is a configuration diagram of an optical system according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating spherical aberration and astigmatism of the optical system according to Example 2.

FIG. 7 is a lateral aberration diagram of the optical system according to Example 2.

FIG. 8 is a lateral aberration diagram of the optical system according to Example 2.

FIG. 9 is a diagram of a conventional catadioptric optical system for observation.

FIG. 10 is a diagram of a conventional catadioptric optical system for observation.

[Explanation of symbols]

G ₁ first lens group G ₂ second lens group G ₃ third lens group M ₁ convex mirror M ₂ concave mirror M ₃ plane mirror S diaphragm

Claims (8)

[Claims] 1. A first lens group having a convex mirror, a second lens group having a concave mirror or a plane mirror, in order from the object side,
A catadioptric optical system for wide-field observation, comprising: a third lens group having a refractive lens. 2. The catadioptric optical system for wide-field observation according to claim 1, wherein a combined refractive power of said first lens group and said second lens group is a negative value. 3. The catadioptric optical system for wide-field observation according to claim 1, wherein the concave mirror is a spherical mirror. 4. The catadioptric optical system for wide-field observation according to claim 1, wherein said convex mirror has an aspherical shape. 5. A catadioptric optical system for wide-field observation according to claim 4, wherein said convex mirror has a hyperboloidal shape. 6. A catadioptric optical system for wide-field observation according to claim 1, wherein said third lens group has a stop. 7. The catadioptric optical system for wide-field observation according to claim 1, wherein said third lens group is a Gaussian optical system having two opposing concave surfaces. 8. The catadioptric optical system for wide-field observation according to claim 1, wherein the projection system is a stereoscopic projection system.