JP2778577B2 - Light beam angle detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam angle detector, and more particularly to a corner cube reflector (hereinafter referred to as "corner cube reflector").
(Referred to as “CCR”).

[0002]

2. Description of the Related Art Conventionally, as a light beam angle detector using this kind of CCR, for example, "M. Shimizu, K. Shiratama,
& Y.Ohgushi: "POINT-AHEAD MECHANISM FOR ETS-VI OPTI
CAL ISLEXPERIMENT ", SPIE Vol.1218 Free-Space Laser
Communication Technologies II (1990) ”, page 652, FIG. 2. The angle detector disclosed in this document captures a reception beam from the target and a transmission beam to the target, and measures the output angle of the transmission beam toward the target from these positional deviations. ) And downlink (transmitted signal) beam angles are detected by the same angle detector. The beam of the uplink (received signal) passes through the beam splitter (BS) as it is and enters the four image limit detector (4QD), which is an angle detector, while the beam of the downlink (transmitted signal) has a CCR. 4QD which is an angle detector
Is incident.

[0003]

However, in the above prior art, since the CCR is used for detecting the light beam angle, a dark band portion due to the edge of the CCR is projected on the beam pattern on the angle detection surface. Even if the beam slightly moves on the sensor surface of the angle detector due to a slight change in the beam angle, the output of the angle detector does not change due to the influence of the dark band portion of the beam pattern. That is, there is a problem that the detection angle accuracy and the resolution are deteriorated when the CCR is used.

Accordingly, an object of the present invention is to provide a beam angle detector using a CCR which can detect the directivity angle of a light beam with high precision and high resolution in view of the above-mentioned problems of the prior art.

[0005]

In order to achieve the above object, the present invention provides a light beam angle detector using a corner cube reflector, comprising at least driving means for rotating the corner cube reflector; A light beam is incident on the detection surface of the beam angle detector via a corner cube reflector rotated by the driving means. Specifically, a transmission optical system for transmitting the light beam while changing it at a predetermined angle,
A beam splitter that branches a light beam that has passed through the transmission optical system into transmitted light and reflected light as an output beam, a corner cube reflector that reflects transmitted light from the beam splitter again to the beam splitter, and the corner A drive unit for rotating the cube reflector, and a light beam angle detector for detecting an output angle of the output beam by receiving a light beam from the corner cube reflector rotated by the drive unit via the beam splitter. It is.

In the above-mentioned light beam angle detector, it is preferable that the rotation of the corner cube reflector is performed at a frequency equal to or higher than the frequency band of the light beam angle detector. It rotates about an axis that vertically connects a surface to be formed and a vertex opposed to this surface. Further, the light beam angle detector may be composed of four image limit detectors.

In the light beam angle detector of the present invention configured as described above, the beam pattern incident on the sensor surface of the angle detector includes an image of a dark band due to the edge of the corner cube reflector. Since the cube reflector is rotated by the driving means, the image of the dark band due to the edge of the corner cube reflector in the incident beam pattern is spatially averaged. Therefore, angle detection can be performed with high accuracy and high resolution even when the incident beam slightly moves on the detection surface.

[0008]

Embodiments of the present invention will be described below. FIG. 1 is a schematic diagram showing a configuration of an embodiment of a beam angle detector using a corner cube reflector of the present invention.

In FIG. 1, a beam angle detector 5 of the present embodiment is shown.
Is a beam splitter 4 that reflects most of the light beam as an output beam and transmits a small part of the remaining light beam, and a transmission optical system 1 that transmits the light beam to the beam splitter 4 while changing the light beam at a predetermined angle. A corner cube reflector (CCR) 2 which reflects the light beam transmitted through the beam splitter 4 in the direction in which it came, that is, has a declination of 180 degrees;
A driving means 3 for rotating R2;
A part of the light beam reflected by the beam splitter 4
After being reflected by and passing through the imaging lens 6, it is incident as an imaging beam. The transmission optical system 1 is formed from optical elements such as a lens and a mirror, or a beam angle driving mechanism. The CCR 2 is attached to the driving means 3, and the whole CCR rotates around an axis that vertically connects a surface through which the light beam enters and exits and a vertex facing the surface. A motor or the like can be considered as the driving means 3, and a four-image limit detector, a CCD or the like can be considered as the angle detector 5. Also, C
When the beam diameter reflected by the CR 2 and reflected again by the beam splitter 4 and incident on the angle detector 5 is sufficiently smaller than the detection surface of the angle detector 5, the imaging lens 6 may not be used.

Next, the operation of this embodiment will be described with reference to FIGS.

In FIG. 1, a light beam passes through a transmission optical system 1 and is split into two beams by a beam splitter 4, and the reflected light becomes an output beam. On the other hand, the light beam transmitted through the beam splitter 4 is reflected by the CCR 2, reflected again by the beam splitter 4, then condensed by the imaging lens 6 and incident on the angle detector 5, and the output angle of the beam is detected. .

In this way, the output angle of the beam can be detected. However, when the CCR 2 is fixed, the pattern of the beam incident on the detection surface has CC as shown in FIG.
An image by the edge of R2 is included. Therefore, in the present invention,
By driving the driving means 3 and rotating the CCR 2, the CCR in the beam pattern incident on the angle detector 5 is obtained.
The images due to the two edges are spatially averaged.

For this reason, even when the imaging beam slightly moves on the detection surface due to slight fluctuation of the light beam by the transmission optical system 1, the angle detector 5 is not affected by the image due to the edge of the CCR 2 and is high. It can be detected with high accuracy and high resolution.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a schematic diagram showing a configuration of an embodiment of a beam angle detector using a corner cube reflector of the present invention. In this figure, the same components as those in the above embodiment are denoted by the same reference numerals.

In FIG. 3, the beam angle detector of the present embodiment is a four-image limit detector 7, which is a beam splitter 4 that reflects most of the light beam as an output beam and transmits the remaining small portion. A mirror driving mechanism 8 for transmitting the light beam to the beam splitter 4 while changing the light beam at a predetermined angle;
It has a corner cube reflector (CCR) 2 that reflects a light beam transmitted through the beam splitter 4 in an incoming direction, that is, a declination of 180 degrees, and a motor 9 that rotates the CCR 2. A part of the beam is reflected again by the beam splitter 4, passes through the imaging lens 6, and then enters as an imaging beam.

Next, the operation of this embodiment will be described with reference to FIGS.

In FIG. 3, the light beam passes through a mirror driving mechanism 8 and is split into two beams by a beam splitter 4, and the reflected light becomes an output beam. On the other hand, the light beam transmitted through the beam splitter 4 is reflected by the CCR 2, reflected again by the beam splitter 4, then condensed by the imaging lens 6, and enters the four-image limit detector 7.

FIG. 4 shows the state of an imaged beam on the detection surface when the four image limit detector 7 is used as an angle detector, and the principle of detecting the beam emission angle will be described. In the above-described configuration of the optical system, when the emission angle of the emission beam is changed by the mirror driving mechanism 8, the imaging beam moves on the sensor surface of the four-image limit detector 7 accordingly. The signal output from each channel of the four image limit detector 7 is proportional to the optical power of the beam incident on each channel. Therefore, by comparing the signal output of each channel with a predetermined reference and calculating the position, the position of the optical axis of the imaging beam on the sensor surface can be easily determined, and the output angle of the output beam can be obtained.

The output angle of the beam can be detected in this manner. However, if the CCR 2 is fixed, the beam intensity distribution is distorted due to the CCR edge, and the beam is incident on the sensor surface of the four-image detector 7. The pattern of the imaging beam includes an image (dark band portion) due to the edge of CCR2 as shown in FIG. Then, by driving the motor 9, the CCR
When 2 is rotated, the beam pattern incident on the 4-image limit detector 7 is spatially averaged by the image of the edge of the CCR 2. The rotation of the CCR 2 must be performed at a frequency equal to or higher than the frequency band of the four-image limit angle detector 7.

As described above, even when the imaging beam slightly moves on the sensor surface of the four-image limit detector 7 due to a slight change in the output beam by the mirror driving mechanism 8, the four-image limit detector 7 can be used. A signal change from each channel can be detected with high accuracy and high resolution without being affected by the image due to the edge of the CCR2.

[0021]

As described above, the present invention comprises at least a driving means for rotating the corner cube reflector, and the detection surface of the light beam angle detector is provided with the corner cube reflector rotated by the driving means. When the light beam is incident on the detection surface, an image of the edge of the corner cube reflector in the light beam incident on the detection surface is spatially averaged. Accuracy and high resolution angle can be detected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an embodiment of a beam angle detector using a corner cube reflector of the present invention.

FIG. 2 is a diagram illustrating a state in which an image due to an edge of a corner cube reflector is included in a pattern of a beam incident on a detection surface.

FIG. 3 is a schematic diagram illustrating a configuration of an embodiment of a beam angle detector using a corner cube reflector according to the present invention.

FIG. 4 is a diagram illustrating a state of an imaging beam on a detection surface when a four image limit detector is used as an angle detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission optical system 2 Corner cube reflector (CCR) 3 Driving means 4 Beam splitter 5 Angle detector 6 Imaging lens 7 4 Image limit detector 8 Mirror drive mechanism 9 Motor

Claims (4)

(57) [Claims] 1. A light beam angle detector using a corner cube reflector, wherein the corner cube reflector
And the vertex opposite to this surface
At least a driving unit for rotating the corner cube reflector about an axis connecting the light beam vertically, and a light beam is incident on the detection surface of the light beam angle detector via the corner cube reflector rotated by the driving unit. A light beam angle detector. 2. A transmission optical system for transmitting a light beam while changing the light beam at a predetermined angle, and a beam splitter for splitting the light beam passing through the transmission optical system into transmitted light and reflected light as an output beam. And a corner cube reflector for reflecting the transmitted light from the beam splitter to the beam splitter again, and a light beam of the corner cube reflector enters and exits.
A driving unit for rotating the corner cube reflector around an axis vertically connecting a surface and a vertex opposed to the surface, and a light beam from the corner cube reflector rotated by the driving unit via the beam splitter. And a light beam angle detector for detecting an outgoing angle of the outgoing beam. 3. The light beam angle detector according to claim 1, wherein the rotation of the corner cube reflector is performed at a frequency equal to or higher than a frequency band of the light beam angle detector. 4. The light beam angle detector according to claim 3, wherein said light beam angle detector comprises four image limit detectors.