JPH06147890A - Automatic vertical angle compensator - Google Patents

Abstract

PURPOSE:To allow detection of the inclination of a reference surface only by a uniaxial optical system by providing a lens system for equalizing variation of the reflection angle of optical axis, corresponding to the variation of the incident angle of optical axis, in all directions and offsetting variation of angle of reflection optical axis. CONSTITUTION:Liquid encapsulated in a container 4 forms a free liquid plane 1. Luminous flux is projected from a light source 6 through a concrete lens 5 onto the liquid plane 1 at a predetermined angle causing total reflection with the optical axis of luminous flux being set in yz coordinate plane. When the container 4 inclines to cause relative variation of the incident angle of luminous flux to the liquid plane 1, sensitivity for the variation of reflection angle varies depending on the inclining direction of the liquid plane 1. The difference of sensitivity is corrected by a lens system and the relative inclination of the liquid surface 1 is optically offset by a lens system for the luminous flux reflected from a reflector 14 in the vertical direction thus keeping verticality constantly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical angle automatic compensator for use in surveying instruments, measuring instruments, etc. for measuring changes in the amount of tilt or for holding the optical axis of the instrument vertically. Is.

[0002]

2. Description of the Related Art When surveying various types of surveying instruments, measuring instruments, etc., it is necessary to compensate the reference plane of the surveying instruments, the measuring instrument, or the verticality of the optical axis.

Conventionally, there are two types of automatic compensation.
If a pendulum body such as a lens or a prism is suspended in a pendulum shape with a book or three or more suspension lines and the surveying instrument or measuring instrument body is tilted, the pendulum body is braked by a magnetic type braking mechanism. , There are those that automatically compensate the optical path.

Further, as a method for detecting the inclination of the reference plane of the main body of a surveying instrument, measuring instrument, etc., there is a method utilizing reflection on a free liquid surface.

In this method, a light beam is made incident on the free liquid surface, and a change in the optical axis of the reflected light of the light beam is detected by a light receiver. When mercury or the like is used as a liquid having a free liquid surface, if a light beam is incident perpendicularly to this free liquid surface, a reflection angle with the same sensitivity to the inclination of the liquid surface in all two-dimensional directions can be obtained. It is possible to obtain the inclination of the reference plane.

However, in actuality, from the viewpoint of cost and safety, it is difficult to use the liquid such as mercury described above, and a transparent liquid such as silicon oil is practically used. When a transparent liquid is used, total reflection is used, but since there is a critical angle between the liquid and air, in order to totally reflect the light beam on the liquid surface, the incidence of the light beam on the free liquid surface is the critical angle. The incident angle θ corresponding to is required. Thus, in the conventional inclination detecting device using the free liquid surface, the light beam is incident on the free liquid surface at a predetermined angle.

When the light beam is incident on the free liquid surface at a predetermined angle, the change in the reflection angle of the reflected light in the two different axial directions with respect to the inclination of the liquid surface becomes uneven.
Therefore, it is necessary to take measures against the uneven variation of the reflection angle in the tilt detecting device using the free liquid surface. For this reason, light beams with different two optical axes are made incident on the free liquid surface at a predetermined angle, and the reflected light is received by the photodetectors, and each photodetector detects the light receiving position in only one direction, and each photodetector receives the reflected light. The inclination of the two optical axes is detected based on the change of the light receiving position, and the inclination of the reference plane such as a surveying instrument or measuring instrument with respect to the horizontal plane is calculated from the detected inclination of the two optical axes, and compensation is performed based on the calculation result. There is.

[0008]

However, in the former case of the above-mentioned conventional one, since the pendulum body is suspended, the structure is complicated and the work of suspending the pendulum body at the time of assembling the apparatus is not easy. Also, the adjustment was difficult. Furthermore, the length of the suspension wire changes with time, which makes it difficult to maintain accuracy. Further, since a special braking device for braking the pendulum body is required, this is also a factor that complicates the structure of the device. Further, there is a problem that the suspension structure of the pendulum body is delicate and weak against impact.

On the other hand, the latter, which utilizes the total reflection of the free liquid surface, is easy to assemble and adjust, does not change with time because there is no suspension wire, and can form a liquid-tight structure so that it has impact resistance and environment resistance. Excellent in performance. Furthermore, since a liquid is used, there is an advantage that braking can be performed by utilizing the viscosity of the liquid and a braking device is not required, and various advantages of the vertical angle automatic compensator with a pendulum suspended. The problem is solved.

However, since the light fluxes of two different optical axes with respect to the free liquid surface are made incident on the free liquid surface at a predetermined angle, the projection system of the light flux becomes two optical systems, so that the structure of the apparatus is complicated. There was a problem that became.

In view of such circumstances, the present invention utilizes the total reflection of the free liquid surface, and detects the inclination of the reference surface only by the uniaxial optical system or automatically compensates the vertical line. It was done.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a liquid encapsulation container in which a transparent liquid is enclosed so as to form a free liquid surface, and a light beam for totally reflecting the free liquid surface at a predetermined angle on the free liquid surface. A projection system for projecting, a mirror for vertically reflecting the light beam reflected by the free liquid surface, and a reflection angle of the optical axis provided at a required position in the optical path of the reflected light beam and corresponding to a change in the incident angle of the optical axis. And a lens system for canceling the change in the angle of the reflected optical axis corresponding to the change in the incident angle of the optical axis.

[0013]

When the liquid sealing container is tilted and the incident angle of the light beam with respect to the free liquid surface is relatively changed, the change of the reflection angle has different sensitivity depending on the tilt direction of the free liquid surface. This difference in sensitivity is optically corrected, and the light beam reflected in the vertical direction by the mirror optically cancels the relative inclination of the free liquid surface,
The light flux reflected in the vertical direction always maintains the vertical direction.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, when a light beam is incident on the free liquid surface at a predetermined angle and the light beam is totally reflected by the free liquid surface, when the free liquid surface is inclined relative to the light beam, the liquid surface is inclined. The difference in the sensitivity of the change in the reflection angle with respect to the direction will be described with reference to FIGS.

In reality, the free liquid surface is kept horizontal and the incident direction of the light beam changes, but the following description is made assuming that the incident direction of the light beam is constant and the free liquid surface is inclined.

In the figure, 1 is a free liquid surface, and it is assumed that an incident light beam 2 is incident on the free liquid surface 1 at an angle θ. Free liquid level 1
The xz coordinate plane formed by the coordinate axis x and the coordinate axis z substantially coincides with each other, and the coordinate axis perpendicular to the coordinate plane is y. It is assumed that the optical axis of the incident light beam 2 exists on the coordinate plane formed by the coordinate axis z and the coordinate axis y. If the free liquid surface 1 is tilted by an angle α about the coordinate axis x from this state, the optical axis of the reflected light beam 3 moves in the yz coordinate plane, and the reflection angle changes by ξ1x in the yz coordinate plane. . In this case, the relationship between the liquid surface displacement angle α and the reflection displacement angle ξ1x is ξ1x =
2α, and in this case, the reflection displacement angle ξ2x in the xy coordinate plane does not occur.

On the other hand, if the free liquid surface 1 is inclined by the angle α about the coordinate axis z, the reflected light flux 3 moves away from the xy coordinate plane and the yz coordinate plane, respectively. Therefore, the reflection displacement angle ξ1z and the reflection displacement angle ξ2z appear on the xy coordinate plane and the yz coordinate plane, respectively. Furthermore, the relationship between the reflection displacement angle ξ1z and the liquid surface displacement angle α of the free liquid surface 1 is

[0019]

[Equation 1] ξ1z = cos ^-1 (cos ² θ cos 2α + sin ² θ) ξ 2z = π / 2-cos ^-1 ((1- cos 2α) sin θ cos θ)

For example, α = 10 ', θ = 50
If it is °, then ξ2z = 1.7 ″, and ξ2z is a value that can be neglected in terms of precision.

[0021]

[Number 2] ξ1x '= 2nα ξ1z' = n · cos -1 a ^{(cos 2 θ cos2α + sin 2} θ).

Therefore, the reflection displacement angle ξ1x 'and the reflection displacement angle ξ1z' have different sensitivities to the liquid surface displacement angle α. In the present invention, the reflection displacement angle ξ1x ′ and the reflection displacement angle ξ
The difference in the sensitivity of the displacement angle from 1z 'is corrected by optical means so that the sensitivity becomes the same, so that an optical axis that deviates at a constant rate in all directions can be obtained.

Further explanation will be given with reference to FIG.

Reference numeral 4 in the figure denotes a liquid sealing container provided in the main body of a measuring instrument or the like, and the free liquid level 1 is formed by the liquid sealed in the liquid sealing container 4. Further, the light beam emitted from the light source 6 is projected on the free liquid surface 1 at a predetermined angle so as to be totally reflected by the free liquid surface 1 through the collimator lens 5, and the optical axis of the light beam is as described above. Like yz
Position in the coordinate plane.

With the free liquid surface 1 not tilted,
A cylindrical lens system 9 having a pair of cylindrical lenses 7 and 8 and a reflection mirror 14 are arranged along the optical axis of the reflected light beam 3 totally reflected by the free liquid surface 1. The cylindrical lenses 7 and 8 each have a curvature in only one direction, and the cylindrical lens 7 is a convex cylindrical lens or a cylindrical lens 8 having a focal length f1.
Is a concave cylindrical lens having a focal length f2.

The light beam that has passed through the cylindrical lens system 9 is vertically reflected by the reflection mirror 14, and the light beam reflected by the reflection mirror 14 is convex lens 1
The beam expander 12 composed of 0 and 11 is transmitted. If the focal length of the convex lens 10 is f3 and the focal length of the convex lens 11 is f4, the distance between the convex lens 10 and the convex lens 11 is set to f3 + f4.

The cylindrical lens system 9 may be provided in the optical path after being reflected by the reflection mirror 14.

The operation will be described below.

First, as shown in FIG. 4A, when a light beam enters from the radial direction of curvature of the cylindrical lens 7, the angle formed by the reflected light beam 3 and the optical axis of the cylindrical lens 7, the incident angle a, The relationship with the exit angle a ′ from the cylindrical lens 8 is

[0030]

## EQU3 ## a '= (f1 / f2) a.

Further, as shown in FIG. 4B, when the light beam enters from a plane including the generatrix of the curved surface of the cylindrical lens 7, the angle between the reflected light beam 3 and the optical axis of the cylindrical lens 7 and the incident angle. a, the relationship with the exit angle a ′ from the cylindrical lens 8 is

[0032]

## EQU4 ## a = a '.

Here, the cylindrical lens system 9 is arranged as shown in FIG. 4A with respect to the movement of the reflected light beam 3 when the free liquid surface 1 is tilted about the z axis. Therefore, with respect to the movement of the reflected light beam 3 when the free liquid surface 1 is tilted about the x axis, the arrangement of the cylindrical lens system 9 is arranged as shown in FIG. 4 (B).

Thus, in FIG. 3, the set incident angle to the liquid θ = 50 °, the inclination angle of the device, that is, the inclination angle α of the free liquid surface 1 =
10 ', and the refractive index n of the liquid is 1.4, the reflection displacement angle ξ1x' when the free liquid surface 1 is tilted about the x axis and the free liquid surface 1 is tilted about the z axis according to the mathematical formula 2. Reflection displacement angle ξ1z ′ of ξ1x ′ = 28 ′, ξ1z ′ = 1
8 '. Therefore, there is a difference in sensitivity between the reflection displacement angle ξ1x ′ and the reflection displacement angle ξ1z ′ of (ξ1x ′ / ξ1z ′) = 1.555 times. Therefore, under this condition,

[0035]

## EQU5 ## ξ1x '= 2nα and ξ1z' = 1.286nα.

Therefore, according to Equation 2, (f1 / f2) = 2 /
If it is 1.286, the displacement angle ξ1z ′ of the optical axis transmitted through the cylindrical lens system 9 is 1.286nα × 2 /
It is converted to 1.286 = 2nα, and after passing through the cylindrical lens system 9, ξ1x ′ = ξ1z ′, and even if the free liquid surface 1 tilts in any direction, the reflection displacement angle with the same sensitivity is always present for this tilt. Is obtained.

Furthermore, when the light beam that has passed through the cylindrical lens system 9 and is reflected upward by the reflection mirror 14 passes through the beam expander 12, the angular magnification of the beam expander 12 is 1 / 2n times. If,
The optical axis after transmission is

[0038]

[Equation 6] (ξ1x ′ = ξ1z ′ = 2nα) × 1 / 2n = α

The final optical axis after passing through the beam expander 12 is always orthogonal to the free liquid surface 1, that is, vertical. Here, the focal length of the convex lens 10 is f3
, And the focal length of the convex lens 11 is f4, the angular magnification of the expander 12 is f3 / f4.
By selecting, the angular magnification can be reduced to 1 / 2n.

Next, with respect to the embodiment shown in FIG. 3, the cylindrical lens system 9 is rotated by 90 °,

[0041]

## EQU7 ## (f2 / f1) = 1.555 (f3 / f4) = 1 / 1.286n may be set.

FIG. 5 shows the relationship between incidence and emission of the reflected light beam 3 when the cylindrical lens system 9 is rotated by 90 °.
This will be described in (A) and (B).

As described above, the reflection displacement angle of the optical axis of the reflected light beam 3 with respect to the free liquid surface 1 is the inclination angle α of the free liquid surface 1,
When the incident angle of the light flux is θ and the refractive index of the liquid is n, the reflection displacement angle ξ1x ′ = 2 when the free liquid surface 1 is tilted about the x-axis
When the free liquid surface 1 is tilted about the nα z-axis, the reflection displacement angle ξ1
Since z ′ = 1.286nα, the reflection displacement angle ξ1x ′ is after passing through the cylindrical lens system 9,

[0044]

## EQU1 ## ξ1x '= 2nα × 1 / 1.555 = 1.286nα

Therefore, the reflection displacement angle ξ1z 'is maintained as it is after passing through the cylindrical lens system 9,

[0046]

## EQU9 ## ξ1z '= 1.286nα.

Further, as described above, the beam expander 1
Since the angular magnification of 2 is f3 / f4 = 1 / 1.286n,

[0048]

(10) (ξ1x ′ = ξ1z ′) × (f3 / f4) = 1.286nα / 1.286n = α

As described above, the optical axis can always be kept vertical.

Another embodiment of the present invention will be described with reference to FIG.

In the other embodiment, the combination of the cylindrical lens system 9 and the beam expander 12 shown in FIG. 3 is replaced with an expander 13 composed of a pair of toric lenses 15 and 16. The toric lenses 15 and 16 are lenses having different x-direction focal points and z-direction focal points, and x-direction focal points are f1x and f2x, and z-directional focal points are f1z and f2z, respectively, and

[0052]

[Formula 11] f1x / f2x = 1 / 1.286n f1z / f2z = 1 / 2n

Then, as shown in FIGS. 7A and 7B, the exit angle from the toric lens 16 can be set to α,
After all, the optical axis can always be kept vertical.

As described above, according to the present invention, the optical axis of the emitted light beam can be always kept vertical. An application example of the present invention will be described below.

FIG. 8 shows a pentaprism or a pentamirror 17 rotatably arranged on the optical axis of the light beam emitted from the beam expander 12, and the emitted light beam is horizontally moved by the pentamirror 17. A horizontal reference plane can be formed by the emitted light by being emitted in the direction and further rotating the pentamirror 17. That is, the present invention can be applied to a leveler.

FIG. 9 shows still another application example.

In the applied example, the telescope system 18 is arranged on the light source side of the embodiment shown in FIG. 3, and with such a configuration, it can be used as a vertical unit.

In the above configuration, the slope of the entire configuration is usually limited when it is actually used. Therefore, in use, it is necessary to detect whether the tilt is within the required tilt limit. The following configuration may be added to such a request.

A half mirror 40 is provided in place of the reflection mirror 14 described above, and the reflected light beam from the free liquid surface 1 is split into a vertically reflected light beam 41 and a transmitted light beam 42. The transmitted light beam 42 passes through the convex lens 43, passes through the pinhole 45 formed in the light shielding plate 44, and is received by the light receiving element 46. The pinhole 45 is arranged at the focal point of the convex lens 43. Further, the diameter of the pinhole 45 is set to a size corresponding to the limit range.

When the entire structure is tilted, the reflected light beam from the free liquid surface 1 is displaced in the optical axis. Since the configuration has the cylindrical lens system 9 as described above, the reflected light flux exhibits uniform sensitivity in all directions with respect to the inclination angle of all configurations. The transmitted light flux 42 is received by the light receiving element 46 through the convex lens 43 and the pinhole 45. By the way, since the pinhole 45 and the light-receiving element 46 are arranged at the focal point of the convex lens 43, if the focal length of the convex lens 43 is f0, the optical axis is f0.tan.xi0 for the reflection displacement angle .xi.0. Move on.

The diameter of the pinhole 45 is determined so that the light receiving amount of the light receiving element 46 becomes a predetermined light amount or less when the amount of movement exceeds the required tilt limit.

Thus, by monitoring the amount of light received by the light receiving element 46, it is possible to determine whether or not the inclination of all components is within the limit angle.

For example, the incident angle θ on the free liquid surface 1 is 50.
°, tilt limit angle α of all components = 10 ', refractive index of liquid n =
Assuming that the focal length of the convex lens 43 is f0 = 100 mm and the diameter of the pinhole is R, the deviation of the optical axis after passing through the cylindrical lens system 9 is ξ0 = 2nα. Therefore, the amount of movement l of the optical axis at the pinhole 45 (focal position of the convex lens 43) is

[0064]

## EQU12 ## l = f0.tan .xi.0 = 100 × tan (2 × 1.4 × 10/60) = 0.81

When the pinhole 45 is opened with this diameter, as shown in FIG. 11, when the beam spot of the transmitted light beam 42 moves by 0.81 mm, the pinhole 45
The outer diameter of the light shielding plate 44 is reduced, and the amount of light received by the light shielding plate 44 is reduced. Therefore, by stopping the light emission of the light source 6 at the time when the decrease in the light amount is sensed, it is possible to use the light source only in the required range.

The pinhole 45 may be omitted, and the light receiving element 46 may be a light receiving element such as a CCD, and the light receiving element 46 may detect the position of the beam spot.

Next, a specific example of the liquid enclosure 4 described above will be described with reference to FIGS.

The liquid-filled container 4 is fixed to the main body of the apparatus together with another lens system or is formed as a part of the apparatus. In this case, when the device is used in an environment where a temperature difference occurs, for example, when it is carried out from the room to the outdoors, a temperature distribution occurs inside the liquid sealed in the liquid sealing container 4. When a temperature distribution is generated inside the liquid, the refractive index also shows a distribution corresponding to the temperature distribution, so that refraction of the optical axis occurs inside the liquid. The specific example of the liquid sealing container 4 shown in FIGS. 12 and 13 solves such a problem.

The details will be described below.

An inner case 21 similar to the outer case 20 is provided inside the outer case 20 having an inverted trapezoidal shape. A plate-like space 22 is formed along the upper side surface of the inner case 21, and a light introducing path 23 and a light guiding path 24 communicating with the space 22 are formed. The axis of the light introducing path 23 is aligned with the optical axis of the incident light beam, and the axis of the light guiding path 24 is aligned with the optical axis of the reflected light beam 3 when the free liquid surface 1 is horizontal. .

A heat transfer plate 25 is fixed to the bottom surface of the space 22. The heat transfer plate 25 has a window hole 26 formed in the center thereof so that the incident light flux and the reflected light flux can pass therethrough. In addition, the light introduction path 2
3, and a plug 27 made of transparent glass is fixed to the upper end of each of the light guiding paths 24, and the transparent liquid 28 is hermetically sealed by the plug 27. The amount of the transparent liquid 28 enclosed is determined so as to form a free liquid surface.

The outer case 20 accommodates the inner case 21, and a required surrounding space 2 is provided around the inner case 21.
9 is formed. In addition, the light introduction path 23 of the outer case 20
Then, a transparent glass window 30 and a glass window 31 are provided at positions where the respective axes of the light guiding paths 24 pass. The outer case 20 has an airtight structure, and the surrounding space 29 is evacuated or filled with gas.

Further, the outer case 20 and the inner case 21 are made of a material having a small thermal conductivity such as a synthetic resin in order to suppress heat radiation and heat absorption to the outside.

As described above, the space 22 in which the transparent liquid 28 is sealed is flat and thin, and the heat transfer plate 25 is provided on the bottom surface.
Is provided, the heat propagation speed is increased and the temperature uniformity of the transparent liquid 28 in the temperature changing state is improved.
Further, the surrounding space 29 forms a heat insulating layer for transferring heat to and from the inner case 21 to suppress the temperature change of the transparent liquid 28 or the temperature change speed.

Thus, the difference in temperature distribution inside the transparent liquid 28 is suppressed, and the change of the cross-sectional shape of the light beam due to the refraction of the optical axis of the light beam or the change of the refractive index can be prevented. In addition, the stability is increased even when the environmental temperature changes, and the measurement accuracy is improved.

Next, FIG. 14 shows another specific example of the liquid enclosing container 4. The inner case 21 is covered with an outer case 20 made of a heat insulating material without forming a surrounding space 29 around the inner case 21. , The inner case 21 by the outer case 20
A heat insulating layer is formed around the.

Needless to say, the shape of the liquid sealing container 4 is not limited to the above embodiment.

[0078]

As described above, according to the present invention, since the reflection of the free liquid surface which always maintains the horizontal level is utilized, it is not necessary to have a high-level assembly technique unlike the conventional pendulum type angle compensator. It can be easily assembled, and the work is remarkably simple because the work of injecting the liquid into the liquid-filled container is sufficient instead of the work of hanging the optical member like the conventional pendulum type angle compensator. There is no variation in the assembly accuracy due to the difference of, and because the liquid is completely sealed, it does not change over time, it has excellent environmental resistance, and it is possible to use the viscosity of the liquid against external vibration and shock to brake. It exhibits various excellent effects, such as not requiring a complicated braking device.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a change in a reflection angle of a reflected light beam when a free liquid surface is inclined.

FIG. 2 is an explanatory diagram illustrating a change in a reflection angle of a reflected light beam when a free liquid surface is inclined.

FIG. 3 is a configuration diagram of an embodiment of the present invention.

FIGS. 4A and 4B are explanatory diagrams showing changes in the optical axis of a transmitted light flux with respect to a cylindrical lens system.

5A and 5B are explanatory diagrams showing changes in the optical axis of a transmitted light flux with respect to a cylindrical lens system.

FIG. 6 is an explanatory diagram showing another embodiment of the present invention.

7A and 7B are explanatory diagrams showing changes in the optical axis of a transmitted light flux with respect to a toric lens expander.

FIG. 8 is an explanatory diagram showing an application example of the present invention.

FIG. 9 is an explanatory diagram showing another application example of the present invention.

FIG. 10 is an explanatory diagram showing still another application example of the present invention.

FIG. 11 is an explanatory diagram showing a relationship between a beam spot and a pinhole in the still another application example.

FIG. 12 is a front sectional view showing a specific example of a liquid sealing container.

13 is a view on arrow AA of FIG.

FIG. 14 is a front sectional view showing another specific example of the liquid sealing container.

[Explanation of symbols]

 1 Free Liquid Level 2 Incident Light Flux 3 Reflected Light Flux 4 Liquid Encapsulation Container 6 Light Source 9 Cylindrical Lens System 12 Beam Expander 14 Reflection Mirror 17 Penta Prism, Penta Mirror 18 Telescope System 28 Transparent Liquid 45 Pinhole 46 Photoreceptor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaaki Yamazaki 75-1 Hasunumacho, Itabashi-ku, Tokyo Topcon Co., Ltd. (72) Inventor Junichi Kodaira 75-1 Hasunuma-cho, Itabashi-ku, Tokyo Topcon Co., Ltd. Within

Claims (7)

[Claims] 1. A liquid encapsulation container enclosing a transparent liquid so as to form a free liquid surface, a light projecting system for projecting a light beam for totally reflecting on the free liquid surface onto the free liquid surface at a predetermined angle, A mirror that reflects the light beam reflected by the free liquid surface in the vertical direction, and the reflection angle change of the optical axis corresponding to the incident angle change of the optical axis provided at a required position of the optical path of the reflected light beam is made equal in all directions, An automatic vertical angle compensator further comprising: a lens system for canceling a change in angle of a reflected light axis corresponding to a change in incident angle of the light axis. 2. The vertical according to claim 1, wherein an optical path changing means for emitting a light beam in a horizontal direction is provided on an optical axis in the vertical direction which has passed through the lens system, and the optical path changing means is rotatable about a vertical axis. Direction angle automatic compensator. 3. The vertical angle automatic compensator according to claim 1, wherein a telescope system is arranged on the side of the incident light beam on the free liquid surface. 4. A half mirror is used as a mirror for reflecting the reflected light beam in the vertical direction, and the light beam transmitted through the half mirror is received by a light receiving element, and the movement of the optical axis of the transmitted light beam is detected by the light receiving element. The automatic vertical angle compensator according to claim 1. 5. The transparent liquid is sealed in a plate-like space.
Vertical angle automatic compensator. 6. The vertical angle automatic compensator according to claim 5, wherein a heat transfer plate is provided on the bottom surface of the plate-shaped space. 7. The vertical angle automatic compensator according to claim 1, wherein a heat insulating layer is formed around an inner case enclosing a transparent liquid.