JP3204289B2 - Laser distance measuring device and laser distance measuring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser distance measuring apparatus and a laser distance measuring method for measuring a distance by scanning a target with a laser beam emitted from a laser light source.

[0002]

2. Description of the Related Art This type of laser distance measuring apparatus scans a transmission laser beam emitted from a laser light source using a rotating polygon mirror and receives a reception laser beam reflected by a target.
The distance to the target is measured based on the time difference between the transmission laser light and the reception laser light.

FIG. 3 is a circuit diagram schematically showing a laser beam distance detector. The distance detector includes a transmitting sensor 103 that receives a part of the transmitting laser light LT from the output unit 102 connected to the laser output circuit 101 as the reference light L1, and a receiving sensor 104 that receives the receiving laser light LR reflected by the target.
And the sensors 103 and 104 are connected to the detection circuit 107 via the respective amplifiers 105 and 106.

In the detection circuit 107, as shown in FIG.
The received laser light LR and the reference light L1 are converted into electric signals, and a detection signal that repeats on / off based on a time difference between the two is obtained. At this time, the width (time) t of the ON state in the drawing is proportional to the distance to the target, and this is output as distance data RD.

[0005] Incidentally, such a laser distance measuring apparatus is described in, for example, pages 406 to 408 of "Encyclopedia of Missile Engineering" published by Hara Shobo on December 10, 1990.

[0006]

However, in the above-mentioned conventional laser distance measuring apparatus, errors may occur in the output distance data RD due to environmental temperature and self-heating. The main reason for this is that when the reference light L1 that is input almost directly as compared with the received laser light LR that is reflected light is converted into an electric signal, the reference light L1 is affected by temperature.
, A relative shift occurs as shown by the dotted line in FIG. As a result, the width (t) of the detection signal in the ON state becomes the width te including the deviation, and the distance data RD
Results in errors.

[0007] For this reason, in the conventional laser distance measuring device, it is necessary to improve the accuracy of the measuring distance.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has a laser distance measuring apparatus and a laser capable of obtaining accurate distance data without being affected by temperature. It is intended to provide a distance measuring method.

[0009]

According to a first aspect of the present invention, there is provided a laser distance measuring apparatus for rotating a laser light source and a laser beam transmitted from the laser light source for reflecting the laser beam toward a target for scanning. A polygon mirror, a condensing means for receiving the received laser light reflected by the target, a distance detector for converting the transmitted laser light and the received laser light passing through the condensing means into an electric signal for comparison, An optical path for receiving and sending the distance to the distance detector is provided, and the rotating polygon mirror is configured to transmit the transmission laser light from the laser light source when reaching a predetermined rotation angle position and travel straight toward the optical path. According to a second aspect of the present invention, the optical path is an optical fiber, and the above configuration is a means for solving the problem.

Further, the laser distance measuring method according to the present invention is characterized in that the transmitting laser light is reflected toward a target by a rotary polygon mirror to perform scanning, and a time lag between the transmitting laser light and the receiving laser light reflected by the target is obtained. In the laser distance measuring method for measuring the distance to the target based on the transmitted laser light, when the rotating polygon mirror reaches a predetermined rotation angle position, the transmitted laser light is passed through an optical path of a fixed length and is used as a reference laser light. The optical path length is measured based on the time difference between the transmission laser light and the reference laser light, and the measurement distance to the target is corrected based on the measurement result. Means to solve the problem.

[0011]

In the laser distance measuring apparatus according to the first aspect of the present invention, the distance to the target is measured based on the time difference between the transmission laser light and the reception laser light reflected by the target, and the transmission laser light is measured. The length of the optical path is measured based on the time lag between the light and the transmission laser light passing through the optical path having a certain length such as the optical fiber according to the second aspect.

Thus, in the laser distance measuring device, if the signal of the transmitted laser beam has a deviation due to the temperature effect in the distance detector, the deviation of the measurement result of the optical path, which should be a certain length, is not included. It is possible to detect that an error corresponding to a minute has occurred, and to correct the target measurement distance based on the error.

In the laser distance measuring method according to a third aspect of the present invention, when the rotary polygon mirror for scanning the transmission laser beam is at a predetermined rotation angle position, the transmission laser beam is converted into an optical beam having a predetermined length. Through a static path and use it as a reference laser beam,
By measuring the length of the optical path based on the time difference between the transmission laser light and the reference laser light, if the transmission laser light signal has a deviation due to temperature effects, It is possible to detect that an error corresponding to the deviation has occurred in the measurement result of the optical path that should be, and correct the measurement distance to the target based on the measurement result (error). Distance data can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a laser distance measuring apparatus according to the present invention and a laser distance measuring method will be described below with reference to the drawings.

As shown in FIG. 1A, a laser distance measuring apparatus 1 uses a laser diode 2 with a collimator as a laser light source and a transmission laser beam LT emitted as parallel light from the laser diode 2 as shown in FIG. ),
A rotating polygon mirror 3 that reflects toward a target T, rotates about a rotation axis 3a by the output of a motor 4, and moves the transmission laser light LT in the rotation direction (X direction in FIG. 1B);
A rotating shaft 3a around an axis P passing through the center of the rotating polygon mirror 3
A nodding mechanism 10 for rotating the transmitting laser beam LT moving in the rotation direction by rotating the laser beam in a direction orthogonal to the rotation direction of the rotary polygon mirror 3 (vertical direction in FIG. 1A, Y direction in FIG. 1B); Focusing means 5 for receiving the reception laser light LR reflected by the target T via the rotary polygon mirror 3, and the transmission laser light L
There is provided a distance detector 8 for converting the T and the received laser light LR passing through the condensing means 5 into an electric signal and comparing the electric signal.

The distance detector 8 is installed on the rear wall 7a of the case 7 and includes a photodiode 6 as a light receiving unit. As described with reference to FIG. Part of the light LT is received as reference light (L1).

The laser distance measuring device 1 includes an optical fiber 20 as an optical path for receiving a transmission laser beam LT from a laser diode 2 as a laser light source. The rotating polygon mirror 3 is disposed between the laser diode 2 and the optical fiber 20 as shown in FIG. 1, and transmits from the laser diode 2 when a predetermined rotation angle position is reached as shown by a virtual line in the figure. The arrangement is such that the laser light LT is passed on the front side as shown by the arrow A and goes straight toward the optical fiber 20. The optical fiber 20 has a length such that an appropriate time difference is obtained with respect to the transmission laser light (reference light) LT, and sends the received transmission laser light LT to the photodiode 6 of the distance detector 8 as the reference laser light LS. .

The nodding mechanism 10 includes a pair of stands 11, 11 provided facing the bottom 7 b of the case 7, a base 12 rotatably provided between the stands 11, 11, and a base 12. And the resolver 14 for switching the direction of rotation of the base 12. The axis P passing through the center of the polygon mirror 3 and the center of rotation of the base 12 coincide with each other. By mounting the motor 4 on the base 12, the transmission laser light LT is moved in the vertical direction in FIG.

The focusing means 5 includes a first folding mirror 5a provided near the rotary polygon mirror 3, a second folding mirror 5b provided above the first folding mirror 5a, a second folding mirror 5b, and a photodiode. And a condensing lens 5c with an interference filter provided between the rotating polygon mirror 6 and the condensing means 5 in this embodiment.

In this case, the reflection area R of the rotary polygon mirror 3 that receives and reflects the received laser light LR is set to be divided into two quadrants in the rotation direction of the rotary polygon mirror 3. That is, the two reflection areas Ra and Rb are set, and each of the first folding mirrors 5a and 5a of the two condensing means 5 and 5 is connected to two.
The two reflecting regions Ra and Rb are opposed to each other, so that the rotating polygon mirror 3 can be used without reducing the amount of received light.
In this case, the area of each mirror surface can be reduced.

When the distance to the target T on the ground is measured obliquely from above by the laser distance measuring apparatus 1, first, the transmission laser light LT emitted in parallel from the laser diode 2 is transmitted from the rotary polygon mirror 3 to the target T. Reflected toward. At this time, the transmission laser light LT moves in the rotation direction (X direction in FIG. 1B) by the rotation of the rotary polygon mirror 3, and the rotation of the rotary polygon mirror 3 by the operation of the torquer 13 of the nodding mechanism 10. Direction perpendicular to the direction (Fig. 1
(B) Y direction), the scanning of the substantially fan-shaped plane in and around the target T is performed as shown in FIG. 1 (b).

The reception laser light LR reflected by the target T is
Each of the reflection areas R is reflected by reflection areas Ra and Rb set in two quadrants in the rotation direction of the rotary polygon mirror 3.
The light passes through the light collecting means 5 and 5 corresponding to a and Rb, and reaches the photodiode 6 of the distance measuring device 8. Then, the distance measuring device 8 converts the transmission laser light (reference light) LT and the reception laser light LR into an electric signal and compares them.
The distance to the target T is measured based on the time difference between the signals of the two laser beams LT and LR.

Here, in this type of laser distance measuring apparatus, as described with reference to FIG. 4 in the section of the prior art, the transmission laser directly input to the distance measuring device 8 due to the environmental temperature or self-heating. A shift may occur in the signal of the light (reference light L1). In this case, distance data including a shift indicated by a dotted line is obtained with respect to the original measurement data indicated by a solid line in FIG. 2, and the output signal V2 corresponding to the predetermined distance RT is reduced by the relative shift. Different output signal V1
Becomes

Therefore, the laser distance measuring device 1 measures the distance to the target T as described above, while transmitting the laser light L when the rotary polygon mirror 3 reaches a predetermined rotation angle position.
T is not reflected by the rotating polygon mirror 3 but travels straight as indicated by the arrow A in FIG. 1 and is received by the optical fiber 20, and the transmission laser light LT is used as the reference laser light LS as the photodiode 6 of the distance measuring device 8. Then, the distance measuring device 8 measures the length of the optical fiber 20 based on the time lag between the signal of the transmission laser light (reference light) LT and the signal of the reference laser light LS.

Thus, the laser distance measuring apparatus 1 can detect the deviation of the signal of the transmission laser light (reference light) LT due to the influence of the temperature on the measurement result of the optical fiber 20 having a certain length. It is possible to detect that an error corresponding to a minute has occurred, and to correct the measured distance of the target T based on the error.

That is, in FIG.
Since the reference output signal VS corresponding to the length RF is set in advance, the output signal VS and the optical fiber 20
It can be detected from the output signal VF when the length RF is measured that the error e due to the temperature effect has occurred. Therefore, by correcting the output signal V1 at the time of measuring the distance RT to the target based on the error e, an output signal V2 corresponding to the actual distance RT can be obtained.

The above correction may be performed at the time of image processing, for example, in an image recognition device using the laser distance measuring device as an input source.

[0028]

As described above, according to the laser distance measuring apparatus according to the first aspect of the present invention, reference distance data is obtained in a laser distance measuring apparatus that scans a transmission laser beam with a rotary polygon mirror. Therefore, even when an error occurs in the distance data measured due to the temperature effect, the error can be corrected, and the measurement accuracy can be improved.

Further, according to the laser distance measuring apparatus of the second aspect of the present invention, the same effect as that of the first aspect can be obtained, and in addition, by employing an optical fiber,
An optical path that is not easily affected by temperature can be formed, and the structure can be simplified.

Further, according to the laser distance measuring method according to the third aspect of the present invention, in a laser distance measuring device that scans a transmission laser beam with a rotary polygon mirror, an error may occur in the distance data measured due to temperature effects. Even in this case, it is possible to correct this and obtain accurate distance data.

[Brief description of the drawings]

FIGS. 1A and 1B are an explanatory perspective view and a scanning pattern explanatory view, respectively, showing a laser distance measuring device according to an embodiment of the present invention in a state in which a case is broken.

FIG. 2 is a graph illustrating a relationship between a distance to a target and an output signal of a laser distance measuring device.

FIG. 3 is a circuit diagram illustrating an outline of a distance detector.

FIG. 4 is a diagram illustrating a signal of a reception laser beam, a signal of a transmission laser beam, and a detection signal obtained from both signals.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser distance measuring device 2 laser diode (laser light source) 3 rotating polygon mirror 5 focusing means 8 distance detector 20 optical fiber (optical path) LR reception laser light LS reference laser light LT transmission laser light T target

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masahiko Kato 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside the Olympus Optical Co., Ltd. (72) Inventor Hiroshi Matsuzaki 2-43 Hatagaya, Shibuya-ku, Tokyo No. 2 Olympus Optical Co., Ltd. (72) Inventor Yasuhiko Iijima 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. Examiner Koichi Matsushita (56) References JP-A-7-72239 (JP, a) JP flat 6-102343 (JP, a) JP flat 6-186333 (JP, a) JitsuHiraku Akira 62-197015 (JP, U) (58 ) investigated the field (Int.Cl. ⁷ G01S 7/48-7/51 G01S 17/00-17/95

Claims (3)

(57) [Claims] 1. A laser light source; a rotary polygon mirror for reflecting and scanning a transmission laser beam emitted from the laser light source toward a target; and a condensing unit for receiving a reception laser beam reflected by the target. A distance detector that converts the transmission laser light and the reception laser light that has passed through the condensing means into an electric signal for comparison, and an optical path that receives the transmission laser light and sends it to the distance detector. A laser distance measuring device having a configuration in which a transmission laser beam from a laser light source is passed when the rotation angle position is reached, and the laser beam travels straight toward an optical path. 2. The laser distance measuring device according to claim 1, wherein the optical path is an optical fiber. 3. A laser for scanning a laser beam reflected by a rotary polygon mirror toward a target and scanning the laser beam, and measuring a distance to the target based on a time difference between the laser beam transmitted and the laser beam reflected by the target. In the distance measuring method, when the rotating polygon mirror is at a predetermined rotation angle position, the transmission laser light is passed through an optical path of a fixed length and used as a reference laser light,
A laser distance measuring method comprising: measuring a length of an optical path based on a time difference between a transmission laser beam and a reference laser beam; and correcting a measurement distance to a target based on the measurement result.