JPH0868936A - Afocal imaging optical device and laser device using the optical device - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide an afocal imaging optical device in which the total length of the optical system can be shortened and the transfer distance can be lengthened. In an afocal imaging optical device for converting an image of a predetermined object plane A with a magnification M and transferring it to a predetermined image formation plane B, a focal length is provided between the object plane and the image formation plane. Is f
_{The first to} third optical elements 11 to 13 set to ₁ , f ₂ and f ₃ are sequentially arranged on the same optical axis under a predetermined setting condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an afocal image forming optical device used in a telescope, a beam forming optical system and the like, and a laser device using the optical device.

[0002]

2. Description of the Related Art A conventional afocal image-forming optical device has a first lens 1 having focal lengths fa and fb as shown in FIG.
The second lens 2 is arranged on the same optical axis at a predetermined interval, and has a function of transferring the image of the object on the object plane A to the image forming plane B at a magnification M. The image forming condition at this time is realized by selecting the arrangement condition of the two lenses 1 and 2 as follows.

Da = d (1) expression db = fa + fb (2) expression dc = (1-M) fb -M ² .d (3) expression M = -fb / fa (4) expression Where da is the distance between the object plane A and the first lens 1, db is the distance between the first lens 1 and the second lens 2, and dc is the distance between the second lens 2 and the image plane B. A distance between them, M: imaging magnification, fa: focal length of the first lens 1, fb: focal length of the second lens 2.

By the way, such two lenses 1, 2
According to the afocal image-forming optical device constructed by, the transferred image is an inverted image of the object image. Therefore, in order to obtain an erect image, it is necessary to arrange two image forming optical devices in series, which sometimes causes an increase in size of the device.

Further, in the case of the two-lens configuration of the first lens 1 and the second lens 2, the following may occur.
That is, when the image transfer distance, which is the distance between the object plane A and the image plane B, is L, this distance L is as follows. L = da + db + dc = (1-M) · db + (1-M 2) · d where, considering the M <0, the maximum when d = 0, Lmax is, Lmax = (1-M ) .Db.

Therefore, the transfer distance L is the distance between lenses db.
Will be limited to (1-M) times. For example, as shown in FIG. 8, when the magnification is 10 times (M = -10), db = 1
If fa = 90mm and fb = 900mm, assuming m,
Since db = 0.99m, the maximum value of the transfer distance L is 10.9m.
However, the transfer distance may not be sufficient.

[0007]

As described above, the conventional 2
In the afocal image forming optical device including two lenses, two devices must be arranged in series to obtain an erect image, and a sufficient transfer distance cannot be obtained in some cases.

The present invention has been made in view of the above circumstances. A first object of the present invention is to provide an afocal image forming optical device which can not only obtain an erect image or an inverted image but also can lengthen a transfer distance. To provide.

A second object is to provide a laser device capable of transferring laser light outputted from a laser oscillator by the afocal image forming optical device to a long distance with a constant beam diameter. To provide.

[0010]

The first means of the present invention is an afocal image-forming optical device for converting an image of a predetermined object plane at a magnification M and transferring it to a predetermined image-forming plane. The focal lengths f ₁ , f ₂ , and f are between the surface and the image plane.
Afocal imaging optics characterized in that the first to third optical elements set to ₃ are sequentially arranged on the same optical axis under the conditions of the following expressions (A) to (D). On the device.

[0011]

[Equation 2]

Where d _{1 is} the distance between the object plane and the first optical element, d _{2 is} the distance between the first optical element and the second optical element, and d _{3 is} the second optical element. the distance between the third optical element, d _4; distance between the third optical element and the image plane.

A second means of the present invention has a laser oscillator, and is for transmitting the laser light on the optical path of the laser light output from the laser oscillator. 1 is a laser device characterized in that the afocal optical device described in 1 is arranged.

[0014]

According to the first means, one of the three optical elements is selected to be a predetermined one, so that the image of the object plane can be inverted or upright on the image plane. An image can be formed, and the transfer distance can be sufficiently expanded. According to the second means, since the laser light is transferred by the imaging optical device of the first means, the laser light can be transferred far without changing the cross-sectional shape of the light flux.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a first lens 11 made of a convex lens, a second lens 12 made of a concave lens, and a third lens 13 made of a convex lens as an optical element are provided between the object plane A and the image formation plane B as an optical axis. Is an afocal image forming optical device which is arranged at a predetermined interval so as to coincide with each other.

FIG. 2 shows a first lens 11 composed of a convex lens as an optical element between the object plane A and the image plane B.
a, the second lens 12a and the third lens 13a are afocal imaging optical devices arranged at a predetermined interval.

First to third lenses 11 to 13 and 11
Assuming that the focal lengths of a to 13a are f _{1 to} f ₃ , as shown in FIG. 1, f ₁ , f ₃ > 0, f ₂ <0 constitute an inverted imaging optical system, and FIG. F ₁ , f
_By setting ₂ and f ₃ > 0, an erecting type imaging optical system is constructed.

The image forming optical apparatus shown in FIGS. 1 and 2 has an object plane A.
Of the first lens to the third lens 11 shown in FIG.
To 13 and the first to third lenses 11a to 1 shown in FIG.
3a is arranged under the conditions of the following expressions (5) to (8).

[0019]

(Equation 3)

Where d _{1 is} the distance between the object plane and the first optical element, d _{2 is} the distance between the first optical element and the second optical element, and d _{3 is} the second optical element. the distance between the third optical element, d _4; distance between the third optical element and the image plane. That is,
The present invention is characterized in that three optical elements are arranged between the object plane A and the image plane B under the conditions of the above equations (5) to (8).

Next, the operation relating to the transfer distance will be described by comparison with FIG. 5 with reference to FIG. Like the configuration shown in FIG. 1, the configuration shown in FIG. 3 is an inverted imaging optical system, and in order to facilitate comparison with the configuration in FIG. 5, d ₁ =
da and fa = f ₁ , and the magnification was M. At this time, if the second lens 12 and the third lens 13 are considered as a pair, the following equation holds.

1 / f = 1 / f ₂ + 1 / f ₃ − (d ₃ / f ₂ ) · f ₃ (9) Expression h ₁ = (f / f ₂ ) · d ₃ (10) Expression h ₂ = (F / f ₂ ) · d ₃ (11) where, f: synthetic focus of lens pair f ₂ and f ₃ , h ₁ ; position of first principal plane of lens pair f ₂ and f ₃ , h ₂ The position of the second principal plane of the lens pair f ₂ and f ₃ . By substituting the equation (7) into the equation (9), M = f / f ₁ (12) is obtained.

Comparing the equation (12) with the equation (4) showing the magnification M of the structure of FIG. 5, it can be seen that f = f _b . From the above equations (10) and (11), h ₁ > 0, h
Considering that ₂ <0, the configuration shown in FIG. 3A is equivalent to the afocal imaging optical system shown in FIG. 3B. In the figure, 4 is the second lens 12 and the third.
5 is a second main plane when the lenses 13 are paired, and 5 is a second main plane.

In the structure shown in FIG. 3B, (dc =
d ₄ + h ₂ ), and ΔL ₁ becomes ΔL ₁ = db − (d ₂ + d ₃ ) = d ₃ −h ₁ = d ₃ · {1- (fb / f ₃ )} (13) . ΔL ₁ represents the difference in the total length of the optical system between the two-lens afocal imaging optical system shown in FIG. 7 and the three-lens optical system of the present invention.

Further, in FIG. 3B, ΔL ₂ is ΔL ₂ = (da + db + dc)-(d ₁ + d ₂ + d ₃ + d ₄ ) = d _3- (h ₁ + h ₂ ) = d ₃ {1- fb · (1 / f ₂ −1 / f ₃ )} (14).

ΔL ₂ represents the difference in the transfer distance of the image on the object plane A between the optical system having two lenses and the optical system having three lenses. According to the above equations (13) and (14), if the following conditions are satisfied, the total length of the three-piece afocal optical system of the present invention can be made shorter and the transfer distance can be made larger than the conventional two-piece set. I understand. f ₃ <fb (14) Equation 1 / f ₂ + 1 / f ₃ <1 / fb (15) Equation From the above, the concrete operation is shown in FIG. 4. At this time, in order to compare with the conventional two-disc structure shown in FIG.
_{M = -10, d 1 = 0} , fa = 90mm, was fb = 900mm. That is, in FIG. 4, f ₁ = 90 mm, f ₂ = −30
mm, f ₃ = 300 mm, and at this time ΔL ₁ = −560 mm
, ΔL ₂ = 7840 mm.

Therefore, according to the configuration of the present invention, the total length of the optical system can be set to about 40% as compared with the conventional configuration shown in FIG. 7, and the transfer distance is enlarged by about 1.7 times. Will be done.

Moreover, the optical system can be selected from the inverted type and the upright type depending on whether the second lens is a concave lens or a convex lens. In the above embodiment, the case where each lens is a thin single lens has been described, but the present invention can be applied to a case where each lens is a thick lens or a combination lens composed of two or more lenses. it can. The configuration at that time is shown in FIG.

That is, in FIG. 5, 21 to 23 are the first
To a third thick lens or a combination lens, and their effective or combined focal lengths are f _{1 to} f ₃ . Two
Reference numerals 1a and 21b denote a first main plane and a second main plane of the first lens, and 22a and 22b denote a first main plane of the second lens 22.
And the second and second principal planes 23 a and 23 b are the first and second principal planes of the third lens 23. And
If d _{1 to} d ₄ are defined as shown in the figure and these values are set as in equations (5) to (8), the same operational effect as in the above-described one embodiment can be obtained.

FIGS. 6A to 6C show application examples of the above-mentioned image forming optical device. In FIG. 6A, an imaging optical device 51 is arranged on the emission side of the laser oscillator 21, and the laser oscillator 2 is provided.
The laser light L oscillated and output from the image forming optical device 1
When it is introduced into No. 1, it is guided to a predetermined position.

That is, the exit image of the laser oscillator 21 is the object plane A, and an enlarged image is formed on the image plane B. Since the image forming optical device 51 can suppress the beam divergence angle, energy dissipation due to diffraction, and deterioration of the beam intensity distribution, highly efficient long-distance beam transfer becomes possible.

In FIG. 6B, the laser light L oscillated and output from the laser oscillator 31 and shaped by the beam shaping means 32 is made incident on the imaging optical device 51. The laser light L emitted from the image forming optical device 51 is incident on the laser amplifier 32, amplified, and then emitted.

That is, the output beam from the laser oscillator 31 is
The shaping image is shaped by the shaping means 32 into a shape similar to the shape of the laser amplifier 32, and the shaped image is made incident on the image forming optical device 51 as the object plane A, and the incident surface of the laser amplifier 32 is connected. The image plane B is used, and the image is amplified by the amplifier 32.

With such a configuration, energy can be incident on the amplifier 32 without being affected by the beam spread angle and diffraction, so that the amplification efficiency can be improved. FIG. 6C shows the laser light L output from the laser oscillator 31.
Is incident on the imaging optical device 51, and the imaging optical device 51
The laser light L emitted from the laser is changed in its optical path by the reflection mirror 34 and used as the excitation light for exciting the excited laser oscillator 35 such as a dye laser oscillator. In this case, the exit surface of the laser oscillator 31 is the object surface A, and the entrance surface to the excited laser oscillator 35 is the imaging surface B.

With such a configuration, the laser light L can be transferred far enough without changing its characteristics, so that there is no restriction on the arrangement of the excited laser oscillator 24. Beam transfer can be performed with high efficiency.

[0036]

As described above, according to the present invention described in claim 1, the optical element is changed from the conventional two-element set to the three-element set, and these three optical elements are made to have the same optical axis. At the same time, they were arranged at intervals satisfying a predetermined relationship.

As a result, not only the total length can be shortened but also the transfer distance can be lengthened as compared with the conventional afocal imaging optical system. Further, there is a case where one of the three optical elements is a concave lens or a convex lens so that either inverted image formation or erect image formation can be set.

According to the present invention described in claim 2,
By disposing the afocal optical system described in claim 1 on the optical path of the laser light, the laser light is sufficiently long without causing energy loss or deterioration of the beam intensity distribution. The distance can be transferred.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inverted afocal imaging optical device showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of an upright afocal imaging optical device.

FIG. 3A is a diagram for explaining the operation of the inverted afocal imaging optical device, and FIG. 3B is an equivalent diagram of the optical device of FIG.

FIG. 4 is an explanatory diagram showing an actual calculation result of the optical device shown in FIG.

FIG. 5 is an equivalent diagram of an afocal imaging optical device according to another embodiment of the present invention.

6A to 6C are explanatory views of a laser device using an afocal imaging optical device.

FIG. 7 is a configuration diagram of a conventional two-lens afocal imaging optical device.

FIG. 8 is an explanatory diagram showing an actual calculation result.

[Explanation of symbols]

11 ... 1st lens (optical element), 12 ... 2nd lens (optical element), 13 ... 3rd lens (optical element), 31
... laser oscillator, A ... object plane, B ... imaging plane.

Claims (2)

[Claims] 1. An afocal imaging optical device for converting an image of a predetermined object plane at a magnification M and transferring it to a predetermined image formation plane, wherein a focal length is provided between the object plane and the image formation plane. Is f ₁ , f
_2, first to third three optical elements that are configured to f ₃ is characterized by comprising sequentially disposed on the same optical axis with the following conditions (A) formula ~ (D) type afocal - Cal Imaging optics. [Equation 1] Where d _{1 is} the distance between the object plane and the first optical element, d _{2 is} the distance between the first optical element and the second optical element, and d _{3 is} the second optical element and the third optical element. the distance between the optical elements, d _4; distance between the third optical element and the image plane. 2. The aforesaid aspect of claim 1, further comprising a laser oscillator, wherein the laser light is transferred onto an optical path of the laser light output from the laser oscillator. A laser device in which a cull optical device is arranged.