JP2000206448A - Beam converting device and laser range-finding device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system converting a Gaussian beam into a cylindrical beam, which is coaxially incorporated in the transmission optical system of a laser range-finding device which includes a Cassegrain telescope in a transmission and reception and can reduce the loss of transmitted energy by the shielding of the secondary mirror of the telescope. SOLUTION: This device is equipped with two conical surfaces 2 and 3 optically worked to be a mirror surface state. For the surfaces 2 and 3, the outer surface of the cone of either surface 2 or 3 is set as a reflecting surface and the inner surface of the cone of the other is set as the reflecting surface, and the surfaces 2 and 3 are arranged so that the axes 6 of two conical surfaces are aligned, and also arranged so that a beam 7 is made incident from the axis of the conical surface, whose outer surface is set as the reflection surface and reflected light beam on the reflecting surface which reflects axially symmetrically in similarly reflected axially symmetrically on the conical surface, whose inner surface is set as the reflection surface. The incident light beam passing through two conical reflection surfaces is enlarged, so that its diameter is doubled and converted into the cylindrical beam 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam converter for use in a laser radar device having a coaxial optical system for transmitting and receiving laser light passing through a Cassegrain type telescope. And send
The present invention relates to an artificial satellite laser distance measuring device for measuring a long distance with high accuracy, and a beam conversion device that is effective when applied to the artificial satellite laser distance measuring device.

[0002]

2. Description of the Related Art Conventionally, a laser ranging device using a Cassegrain-type telescope as an optical system for transmitting and receiving is structured so that a phenomenon that a central portion of a transmitting laser does not reach a target due to a shield of a secondary mirror of the telescope occurs. Was. The portion shielded by the secondary telescope mirror is the central portion of the beam approximated by a Gaussian distribution, and is the region with the highest laser energy density. For this reason, the transmission energy loss was large, and this was one of the causes of the decrease in the number of data acquisition in high-Earth orbit satellite ranging.

FIG. 5 shows a prior art laser distance measuring apparatus using a Cassegrain type telescope as an optical system for both transmission and reception.

In FIG. 5, reference numeral 14 denotes a pulse laser oscillator for outputting a laser, 15 denotes a beam splitter for separating laser light, 16 denotes a start signal detector for converting an optical signal into an electric signal, and 17 denotes a start signal detector. A rotating disk driven by a motor.The rotating chopper separates the transmitted and received light by alternately passing the light transmitting part and the light reflecting part outside the disk through the optical axis.18, 19, 20, 21 and 22 are lasers. Coupe mirror for guiding light to a telescope, 23 is a secondary mirror of a convex mirror-like telescope, 24 is a primary mirror of a concave mirror-like telescope, 25 is a target equipped with a retroreflector, and 26 is a device for converting an optical signal into an electric signal. A stop signal detector, 27 is a telescope altitude rotation axis, and 28 is a telescope azimuth rotation axis.

In the conventional laser distance measuring apparatus shown in FIG. 5, a transmission laser beam emitted from a pulse laser oscillator 14 is split into two directions by a beam splitter 15, one of which is incident on a start signal detector 16, and the other is incident on a start signal detector 16. The light enters the light reflecting portion of the rotating chopper 17. The transmission laser light incident on the start signal detector 16 is converted into an electric signal by the start detector 16 and recorded as a start signal.

The transmitted laser light reflected by the light reflecting portion of the rotary chopper 17 is reflected by the coup mirrors 18 to 22 and enters the telescope secondary mirror 23. The transmission laser light expanded to a predetermined beam diameter by the telescope secondary mirror 23 and the telescope main mirror 24 is emitted into the atmosphere, propagates in the atmosphere, and reaches the target 25.

[0007] The target 25 is equipped with a retroreflector.
The light is reflected in a direction parallel and opposite to the direction of incidence on 25. The received laser light is again focused on the telescope primary mirror 24 after propagating in the atmosphere, and the received laser light focused by the telescope primary mirror 24 is again
The light enters the rotary chopper 17 via 22 to 18.

[0008] Only the received laser light is transmitted by the light transmitting portion of the rotary chopper 17 and enters the stop detector 26.
The received laser light incident on the stop detector 26 is converted into an electric signal, the electric signal is recorded as a stop signal, and the distance measurement is completed.

[0009]

The problem of the transmission laser beam blocking by the secondary telescope, which has occurred in the conventional laser distance measuring apparatus, will be described with reference to FIG.

FIG. 6 shows a Cassegrain-type telescope generally used in a laser distance measuring apparatus (see FIG. 5). The Gaussian beam with the shape shown in Fig. 9 is a coup mirror 2
When the light enters 1, it is reflected by the coup mirror 21, further reflected by the coup mirror 22, and reaches the telescope secondary mirror 23.
The Gaussian beam 9 that has entered the secondary telescope mirror 23 is expanded to a predetermined beam diameter by the secondary telescope mirror 23, enters the primary telescope mirror 24, becomes a beam shape 30, and is emitted into the atmosphere.

The laser beam reflected by the telescope primary mirror 24 is blocked by the laser beam reflected by the telescope secondary mirror 23, where the hatched area 32 having the highest laser energy density at the center of the Gaussian beam is cut off and the laser energy density at the periphery of the Gaussian beam is blocked. A phenomenon occurs in which only the low region 31 is emitted into the atmosphere as transmission laser light.

That is, in the conventional laser distance measuring apparatus, there is a problem that the region having the highest energy density at the center of the Gaussian beam is blocked by the secondary mirror of the telescope. Was the cause.

An object of the present invention is to form a beam in which a portion corresponding to a Cassegrain telescope secondary mirror is made hollow in an incident beam so that transmission energy loss due to shielding of the telescope secondary mirror can be eliminated or reduced. To provide a beam conversion device.

Another object of the present invention is to remove the influence of blocking of the transmitted laser light in the Cassegrain type secondary telescope by adding the beam converter according to the present invention to the conventional laser distance measuring apparatus. It is an object of the present invention to provide a laser distance measuring apparatus which enables the laser distance measuring apparatus.

[0015]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a prism and a prism having two conical surfaces that are optically mirror-finished and converting an incident light beam into a cylindrical beam. It has a conversion optical system configured of one of the mirror members, of the two conical surfaces of the conversion optical system, one as the outer surface of the cone and the other as the reflection surface of the inner surface of the cone, The two conical surfaces are arranged so that their axes coincide with each other, and a light beam is incident from the axis of the conical surface having the outer surface as the reflecting surface. The reflected light of the reflecting surface which is reflected axially symmetrically has the inner surface as the reflecting surface. In the same manner as the former, they are arranged so as to be reflected axially symmetrically, so that the incident light beam passing through the two conical reflecting surfaces is enlarged to a double diameter and converted into a cylindrical beam.

Further, in order to achieve the above object, the present invention comprises two conical surfaces optically mirror-finished,
It has a conversion optical system that converts the incident light beam into a cylindrical beam, and among the two conical surfaces of the conversion optical system, one is an outer surface of the cone and the other is a reflective surface of the inner surface of the cone. ,
The axes of the two conical surfaces are arranged so as to coincide with each other, a light beam is made to enter from the axis of the conical surface having the outer surface as a reflecting surface, and the reflected light of the reflecting surface that is reflected axially symmetrically defines the inner surface as a reflecting surface. In the same manner as the former, it is arranged so as to reflect axially symmetrically on the conical surface, and the incident beam passing through the two conical reflecting surfaces is converted into a cylindrical beam. The relative positional relationship is determined according to at least one of the predetermined inner radius and outer radius of the cylindrical beam to be emitted.

Further, a reduction optical system for reducing an incident light beam is further added to the incident side of the conversion optical system of the beam conversion device, and the light beam incident on the device is converted into the reduction optical system and the conversion optical system. A configuration may be adopted in which the light beam is converted into a cylindrical beam having the same diameter as the incident light beam via a system.

According to another aspect of the present invention, there is provided a laser distance measuring apparatus including a Cassegrain type telescope on a transmission optical axis, wherein the laser beam is incident on the Cassegrain type telescope. The beam conversion device according to the present invention is arranged on the transmission optical axis.

Here, it is preferable that the diameter of the hollow portion of the cylindrical beam emitted from the beam conversion device and further expanded by the Cassegrain telescope is equal to or larger than the diameter of the secondary mirror of the Cassegrain telescope. Further, the inner diameter of the cylindrical beam may be made to substantially match the diameter of the secondary mirror of the Cassegrain telescope, and the outer diameter of the cylindrical beam may be made to substantially match the diameter of the main mirror of the Cassegrain telescope.

Further, the apparatus may further include an adjusting means for changing at least one of an inner radius and an outer radius of the cylindrical beam emitted from the beam converter.

According to another aspect of the present invention, there is provided a laser distance measuring apparatus including a Cassegrain type telescope on a transmission optical axis, and a reduction optical system for reducing a laser beam incident on the Cassegrain type telescope. A conversion optical system for converting a laser beam reduced by the reduction optical system into a cylindrical beam, and changing at least one of an inner radius and an outer radius of the cylindrical beam emitted from the conversion optical system. Adjustment means.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a beam conversion device to which the present invention is applied will be described with reference to FIG.

In the beam conversion device 1 of this embodiment, the conical surface 2 and the conical surface 3 formed by rotating the sectional shape as shown in FIG. Both conical surfaces are arranged at 45 degrees to the axis 6 and the conical axes coincide.

In the present invention, the concrete means for realizing the two conical surfaces 2 and 3 is not particularly limited. For example, a hollow conical mirror whose inner surface is optically mirror-finished. Alternatively, it is preferably realized by a prism.

The optical path of laser beam propagation in the beam converter 1 will be described with reference to FIG. A Gaussian-shaped incident beam (beam having a beam radius of w and a spot size defined by a radius w of a 1 / e ² power point) shown in 7 is incident on a plane 4 along an axis 6. Laser light incident on plane 4 is conical
Head to 2. The laser light is totally reflected by the conical surface 2 in a direction perpendicular to the optical axis 6 and symmetrically with respect to the axis 6. Conical surface 2
The laser light totally reflected by the laser beam goes to the conical surface 3. The laser light is totally reflected by the conical surface 3 in a direction parallel to the optical axis 6 and in the same direction as the propagation direction of the Gaussian-shaped incident beam 7. The laser light totally reflected by the conical surface 3 is emitted through the plane 5.

As shown in FIG. 1, by setting the distance between the two conical surfaces constituting the beam conversion device 1 to be twice as large as the incident beam radius w, the shape of the emitted beam 8 is smaller than that of the incident beam 7. At the same time, the beam radius doubles to 2w, and at the same time, the beam is converted into a cylindrical beam in which the area of the radius w from the beam center becomes a space and output.

The conical surface 2 and the conical surface of the beam conversion device 1
It is assumed that 3 has a high reflection coating.
When the beam conversion device 1 is constituted by a prism, the planes 4 and 5 are subjected to an anti-reflection coating process. By these coating processes, light attenuation in the beam conversion device 1 can be minimized.

In the beam conversion device of the present embodiment,
The outer conical surface 2 and the inner conical surface 3 are assumed to have a relative positional relationship such that the two conical surfaces are parallel and the distance therebetween is 1 / √2 W as shown in FIG. The relationship is not limited to this, and the relative positional relationship between the two conical surfaces may be different as long as the incident beam can be converted into a cylindrical beam having a hollow central portion.

Next, another embodiment of the beam conversion device according to the present invention will be described with reference to FIG.

The beam conversion device according to the present embodiment is the same as that shown in FIG.
This is realized by a combination of the beam conversion device 1 and the Galileo telescope shown in (1), and emits a hollow beam having the same diameter as the incident beam.

The Galileo telescope, as shown in FIG.
It is composed of a combination of a convex lens 12 and a concave lens 13. Here, the convex lens 12 has a focal length f, the concave lens 13 has a focal length −f / 2, and the concave lens 13 is installed coaxially with the convex lens 12 axis. The beam conversion device 1 is an optical element that has been described in the embodiment of FIG. 1 and converts the incident beam diameter to twice and simultaneously converts the beam profile to a cylindrical shape.

In the beam converter of the present embodiment, the above-described beam converter 1, convex lens 12, and concave lens 13 are respectively installed in series as shown in FIG. That is, the convex lens 12
The concave lens 13 is disposed at a distance of f / 2 from and the beam conversion device 1 is disposed at an arbitrary distance from the concave lens 13 at a position where the axes are aligned.

In the beam conversion device of the present embodiment,
First, a Gaussian beam with the shape shown in 9 (beam radius r
Then, a beam having a spot size defined by the radius r of the 1 / e ² power point) is incident on the convex lens 12 along the axis 6. The Gaussian beam 9 after the incidence is condensed by the convex lens 13 and converted into a beam radius r / 2, then collimated by the concave lens 12 and converted into a Gaussian beam having a radius r / 2 having the shape shown in FIG.

Next, a Gaussian beam having a shape shown in 10 (the beam radius is assumed to be r / 2, and the radius r / 2 of the 1 / e ² power point
(A beam having the same spot size) enters the entrance surface 4 of the beam conversion device along the axis 6. The Gaussian beam 10 after being incident on the incident surface 4 of the beam conversion device 1 is totally reflected by the conical inner surface 2, is further totally reflected by the conical inner surface 3, and is emitted from the emission surface 5.

The shape of the emitted beam 11 becomes r twice as large as the beam radius of the beam 10, and at the same time, a region having a radius of r / 2 from the beam center is converted into a hollow cylindrical beam and output. The shape of the emitted cylindrical beam 11 is radius r
As compared with the Gaussian beam 9, the beam radius becomes r having the same diameter, and at the same time, a region having a radius r / 2 from the beam center is converted into a hollow cylindrical beam and output.

Next, an embodiment of a laser distance measuring apparatus to which the present invention is applied will be described with reference to FIGS.

The laser range finder of this embodiment is the same as that shown in FIG.
A beam converter (hereinafter referred to as a beam converter having the same diameter) that emits a cylindrical beam having the same diameter as the incident beam described with reference to FIG.
Is added. Here, the same reference numerals are given to the same components as those in the above-described drawings, and detailed description thereof will be omitted.

That is, in the laser distance measuring apparatus of the present embodiment, as shown in FIG. 3, the same-diameter beam converter 29 is inserted between the beam splitter 15 and the rotary chopper 17. By inserting the same-diameter beam converter 29 in this way, the Gaussian beam emitted from the pulse laser oscillator 14 is converted into a cylindrical beam. For this reason, in the optical path after the same-diameter beam conversion device 29, the cylindrical beam propagates and reaches the Cassegrain telescope.

FIG. 4 is a diagram showing a state in which the problem that has occurred in the conventional laser distance measuring apparatus has been solved by the apparatus of the present embodiment.

The Gaussian beam is converted into the cylindrical beam 11 by inserting the same-diameter beam converter 29.
When a cylindrical beam having the shape shown in FIG. 11 is incident on a coup mirror 21 of a laser distance measuring apparatus, it is reflected by the coup mirror 22 and reaches a telescope secondary mirror 23. The cylindrical beam 11 that has entered the secondary telescope mirror 23 is expanded to a predetermined beam diameter by the secondary telescope mirror 23 and enters the primary telescope mirror 24. Here, the laser beam reflected by the telescope main mirror 24 passes through an optical path that does not pass through the telescope secondary mirror 23 because of its cylindrical shape,
The laser light is emitted into the atmosphere in a cylindrical shape 33.

As described above, the center of the beam, which is the region where the energy density of the Gaussian beam is the highest, is located at the telescope 2.
By forming an optical system that does not pass through the secondary mirror 23, the entire beam area 34 is emitted into the atmosphere as transmission laser light.

That is, according to the apparatus of the present embodiment, the region having the highest energy density at the center of the Gaussian beam is entirely emitted to the atmosphere without being blocked by the secondary telescope 23.

Further, according to the laser distance measuring apparatus of the present embodiment, it is possible to improve the laser transmission efficiency.
For this reason, the same effect as substantially increasing the transmission power can be obtained, and the distance measurement operation such as the initial supplementation of the satellite is facilitated.

It should be noted that other laser radar devices having a Cassegrain-type telescope on the transmission optical axis instead of the laser distance measuring device have the same structure as the present embodiment by including the beam conversion device according to the present invention. It is clear that the effect is obtained.

Next, another embodiment of the beam conversion device to which the present invention is applied will be described with reference to FIGS.

The beam conversion device of this embodiment is similar to that of FIG.
In addition to the beam conversion device according to the embodiment, there is provided means for adjusting the inner radius and the outer radius of the cylindrical beam emitted from the beam conversion device.

First, a method of making the inner radius of the cylindrical beam variable will be described.

In the beam conversion device of this embodiment, as shown in FIG. 7, the conical surfaces 2 and 3 are formed by mirror members 200 and 300 which are arranged so that the arrangement positions can be adjusted manually or automatically. In the state before the adjustment, the incident Gaussian beam having the radius w has an outer radius 2w and an inner radius w.
Shall be converted into a cylindrical beam. FIG.
Shows the cross-sectional shapes of the mirror members 200 and 300 and the laser light propagation optical path in the beam conversion device.

In order to change the inner radius of the cylindrical beam, the relative position of two conical surfaces arranged so that their axes coincide with each other is changed along the conical surface axis.

For example, as shown in FIG. 8, when the conical mirror member 200 is changed along the conical axis by a distance L in the direction indicated by the arrow in the figure, the mirror member 200a and the mirror member 300 are formed after the movement. The laser light propagation light path changes due to the two conical surfaces. That is, an incident Gaussian beam having a radius w is converted into a cylindrical beam, and the inner radius is changed from w to w + L. This shows that the inner radius is a function of the change L in the relative position of the two conical surfaces.

However, in the above method, the outer radius also changes from 2w to 2w + L as the inner radius changes. For this reason,
According to this method, the inner radius and the outer radius cannot be changed independently. Therefore, by using a method of changing the outer radius described below together, it is possible to change only the outer radius of the beam, and the ratio between the outer radius and the inner radius can be adjusted independently.

Next, a method for making the outer radius of the cylindrical beam variable will be described.

In this method, in order to change the outer radius, a Galileo telescope composed of lenses 12 and 13 is added to the beam conversion device shown in FIG. FIG. 9 shows a laser light propagation optical path in this case.

That is, when the Galileo telescope is added, an incident Gaussian beam having a radius w is converted into a cylindrical beam having an outer radius of w + nw and then emitted. From this, the outer radius is a function of the incident beam radius w and the Galileo telescope magnification n.

Finally, a method of independently changing the inner radius and the outer radius of the cylindrical output beam using the above two methods will be described. FIG. 1 shows the laser light propagation optical path in this case.
0 is shown.

As described above, the inner radius and the outer radius of the cylindrical exit beam are represented by the following equations.

Inner radius = w + L (Expression 1) Outer radius = nw + w + L (Expression 2) where, w: Incident beam radius L: Distance change of relative position of two conical surfaces along the axis of the conical surface Minute n: Magnification of Galileo telescope.

For example, when it is desired to convert an incident Gaussian beam of w = 40 mm into a cylindrical beam having an inner radius: outer radius = 3: 4 (formula 3), the above formulas 1 to 3 are satisfied. The following equation indicating the condition to be obtained is obtained.

120n = 40 + L (Equation 4) That is, in order to generate a cylindrical beam satisfying Equation (3), L and n satisfying Equation (4) may be selected. For example, when L = 20 mm, a Galileo telescope with n = 1/2 times may be used.

According to the above method, it is possible to arbitrarily set the inner radius and the outer radius of the cylindrical beam emitted from the beam converter.

The method of the present embodiment can be similarly applied to a laser distance measuring apparatus having a Cassegrain telescope. For example, in a conventional laser distance measuring apparatus as shown in FIG. 5, a beam conversion apparatus as shown in FIGS. 9 and 10 is arranged on a transmission optical axis for allowing a laser beam to enter a Cassegrain telescope.

According to the apparatus to which this embodiment is applied, when converting a laser beam having an arbitrary diameter emitted from a laser light source into a cylindrical beam, the telescope 2 of the Cassegrain telescope is used.
It is possible to make the ratio of the radius of the secondary mirror to the radius of the main mirror of the telescope coincide with the ratio of the inner radius to the outer radius of the cylindrical beam.

[0063]

According to the present invention, it is possible to suppress a decrease in the transmission efficiency due to the effect of the shielding of the secondary telescope, thereby increasing the transmission laser intensity and improving the capability for high altitude satellite ranging. Becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of a beam conversion device according to the present invention.

FIG. 2 is an explanatory view showing an embodiment of the same-diameter beam conversion device according to the present invention.

FIG. 3 is an explanatory diagram showing an application example of the present invention to a conventional laser distance measuring device.

FIG. 4 is an explanatory diagram showing a method of solving a problem that has occurred in a conventional laser distance measuring apparatus.

FIG. 5 is an explanatory diagram showing a conventional example of a laser distance measuring device.

FIG. 6 is an explanatory diagram showing a problem that has occurred in a conventional laser distance measuring device.

FIG. 7 is an explanatory view showing another embodiment of the beam conversion device according to the present invention.

FIG. 8 is an explanatory view showing another embodiment of the beam conversion device according to the present invention.

FIG. 9 is an explanatory view showing another embodiment of the beam conversion device according to the present invention.

FIG. 10 is an explanatory diagram showing another embodiment of the beam conversion device according to the present invention.

[Explanation of symbols]

1 ・ ・ ・ Beam conversion device 2 ・ ・ ・ Conical outer surface of beam conversion device (high reflection coating) 3 ・ ・ ・ Conical inner surface of beam conversion device (high reflection coating) 4 ・ ・ ・ Injection plane of beam conversion device (non-reflection) Coating) 5 ・ ・ ・ Output plane of beam converter (non-reflective coating) 6 ・ ・ ・ Optical axis of beam converter 7 ・ ・ ・ Gaussian beam (beam radius w) 8 ・ ・ ・ Cylindrical beam (beam radius 2w) 9 ... Gaussian beam (beam radius r) 10 ... Gaussian beam (beam radius r / 2) 11 ... cylindrical beam (beam radius r) 12 ... convex lens 13 ... concave lens 14 ... Pulse laser oscillator 15 ・ ・ ・ Beam splitter 16 ・ ・ ・ Start detector 17 ・ ・ ・ Rotating chopper 18 ・ ・ ・ Coup mirror 19 ・ ・ ・ Coup mirror 20 ・ ・ ・ Coup mirror 21 ・ ・ ・ Coup mirror 22 ・ ・ ・ Coup mirror 23 ・ ・ ・ Secondary telescope 24 ・ ・ ・ Primary telescope 25 ・ ・ ・ Target 26 ・ ・ ・ Stop detector 27 ・ ・ ・ Altitude rotation axis 28 ・ ・ ・ Azimuth rotation axis 29 ・..Equal diameter beam conversion device 30... Emitted laser light (when 29 is not used) 31... Area of laser light 30 not shielded by telescope secondary mirror 23 32. Area of laser light 33 to be shielded 33 ... Laser light to be emitted (when using 29) 34 ... Area of laser light 33 not to be shielded by telescope secondary mirror 23 f ... Focal length of convex lens 10- f / 2 Focal length of concave lens 11 w… Gaussian beam radius (beam radius of spot size defined by 1 / e ² power point) r… Gaussian beam radius (defined by 1 / e ² power point) Spot size beam radius).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Suzaki 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in the Information and Communication Division, Hitachi, Ltd. 5J084 AA05 BA03 BB01 BB14 BB21 CA03 DA01 EA07

Claims (7)

[Claims] 1. A conversion optical system having two conical surfaces that are optically mirror-finished and configured to convert an incident light beam into a cylindrical beam, the conversion optical system including one of a prism and a mirror member. Of the two conical surfaces of the conversion optical system, one is the outer surface of the cone and the other is the inner surface of the cone as the reflecting surface, and the two conical surfaces are arranged so that their axes coincide with each other. A light beam is made incident from the axis of the conical surface serving as the reflecting surface, and the reflected light of the reflecting surface that is axially symmetrically reflected is axially symmetrically reflected on the conical surface having the inner surface as the reflecting surface in the same manner as the former. A beam conversion device wherein an incident light beam passing through the two conical reflecting surfaces is enlarged to a double diameter and converted into a cylindrical beam. 2. A conversion optical system for converting an incident light beam into a cylindrical beam, comprising: two conical surfaces that are optically mirror-finished; and One is the outer surface of the cone and the other is the inner surface of the cone as the reflecting surface, the axes of the two conical surfaces are aligned with each other, and the light beam is transmitted from the axis of the conical surface having the outer surface as the reflecting surface. It is arranged so that the reflected light of the reflecting surface which is reflected axially symmetrically is reflected on the conical surface having the inner surface as the reflecting surface, similarly to the former, and the incident beam passing through the two conical reflecting surfaces is It is to be converted into a cylindrical beam, the relative positional relationship between the two conical surfaces, according to at least one of the inner radius and the outer radius predetermined for the cylindrical beam to be emitted Beam transformation characterized by being determined Location. 3. A conversion optical system according to claim 2, further comprising a reduction optical system for reducing an incident light beam, wherein said incident light beam enters said conversion optical system via said reduction optical system. And converting the incident light beam into a cylindrical beam having the same diameter as the incident light beam. 4. A beam converting apparatus according to claim 1, wherein a laser ranging device including a Cassegrain type telescope on a transmission optical axis is used to convert a laser beam incident on said Cassegrain type telescope. Is arranged on the transmission optical axis. 5. The laser ranging apparatus according to claim 4, wherein the diameter of the hollow portion of the cylindrical beam emitted from the beam conversion device and further enlarged by the Cassegrain telescope is equal to 2 of the Cassegrain telescope. A laser distance measuring device having a diameter equal to or larger than the diameter of the secondary mirror. 6. The laser distance measuring apparatus according to claim 4, further comprising adjusting means for changing at least one of an inner radius and an outer radius of the cylindrical beam emitted from the beam converter. Characteristic laser ranging device. 7. A laser distance measuring apparatus including a Cassegrain type telescope on a transmission optical axis, a reduction optical system for reducing a laser beam incident on the Cassegrain type telescope, and a laser beam reduced by the reduction optical system. A conversion optical system for converting into a shaped beam, and adjusting means for changing at least one of an inner radius and an outer radius of a cylindrical beam emitted from the conversion optical system, wherein the conversion optical system includes: A laser distance measuring device, which is a conversion optical system of the beam conversion device according to claim 1.