JP2832604B2 - Lightwave rangefinder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lightwave distance meter.

(Prior Art) A conventional lightwave distance meter is configured as shown in FIG. 2 and measures a distance as follows. First, when the optical path switching shutter g is disposed at the position indicated by the broken line, the light emitting element a
To output a modulated light, and the modulated light is radiated toward a reflecting mirror (not shown) placed at a target point via a light transmitting side objective lens c, and the reflected light is transmitted to a light receiving side objective lens d. The light then enters the light receiving element e as measurement light. When the optical path switching shutter g is moved to the position indicated by the broken line by the control circuit f, the modulated light is reflected by the prism h and the reflecting mirror i provided on the shutter g.
Is incident on the light receiving element e as reference light via an optical path k in the rangefinder body formed by The detector j measures the phase difference between the measurement signal and the reference signal obtained from the measurement light and the reference light with respect to the reference signal, and subtracts the phase difference between the reference signal and the reference signal from the phase difference between the measurement signal and the reference signal. This measures the distance to the target point.

(Problems to be Solved by the Invention) According to the above-described conventional lightwave distance meter, since the optical path switching shutter g is a mechanically movable part, there is a problem in terms of life. Further, since the shutter g does not always stop at the same position when the shutter g is repeatedly operated, an error is likely to occur in the measurement accuracy. Further, a space for installing the shutter g is required, and when the lightwave distance meter is used in an inclined state, the shutter g moves in the inclination direction, and the response speed of the forward and backward shutters differs due to the influence of gravity. And the measurement time becomes longer.

An object of the present invention is to solve such a conventional problem.

(Means for Solving the Problems) In order to achieve the above object, the present invention radiates modulated light from a light emitting element toward a reflector located at a target point, and uses the reflected light as measurement light as a light receiving element. And the operation of projecting the modulated light directly toward the light receiving element inside the rangefinder body and receiving the light as the reference light by the light receiving element is switched, and the measurement signal output from the light receiving element is referred to. In a lightwave distance meter configured to measure a distance from a phase difference of a signal to a reflecting mirror, the light emitting element includes a measuring light emitting element that emits emitted modulated light toward the reflecting mirror, and a emitted modulated light. A light-emitting element for reference light that projects directly toward the light-receiving element inside the rangefinder body, and the light-emitting element for measurement light and the light-emitting element for reference light are connected to a modulator via a switching element. , The light emitting element for measuring light 3. The light-emitting element for a reference beam and the light-emitting element for a reference light, which are arranged close to each other on the same stem so as to achieve good thermal coupling, and are packaged in the same case.
As described in above, it is desirable that the output light of the light emitting element for measurement light and the light emitting element for reference light is emitted toward the reflecting mirror and the light receiving element via an optical fiber, respectively.

(Operation) First, the control unit causes the light emitting element for measurement light to emit light, emits the modulated light toward the reflecting mirror, and causes the light receiving element to receive the reflected light as measurement light, and then emits light for the reference light. The element is caused to emit light, and the modulated light is directly received by the light receiving element as reference light inside the rangefinder, and the distance to the reflector is measured from the phase difference between the measurement signal output from the light receiving element and the reference signal. Further, the measurement light emitting element and the reference light emitting element,
Since the same wafers are used and arranged close to each other on the same stem so as to achieve good thermal coupling, and packaged in the same case, the difference in characteristics becomes negligible, and the surveying accuracy is improved.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a light-emitting unit, which comprises a light-emitting element 1a for measuring light and a light-emitting element 1b for reference light. The light emitting element for measurement light 1a and the light emitting element for reference light 1b are, for example, semiconductor lasers, using the same wafer whose properties can be regarded as the same, and usually, the thermal coupling is good on the same stem of a good thermal conductor. And housed in one package so that the difference in characteristics between them can be ignored. The two light emitting elements 1a and 1b are connected to a modulator 3 via a switching element, for example, a switching switch 2, and the switching switch 2 is switched by a control circuit 4. The modulated light output from the measuring light emitting element 1a is guided to the light transmitting side objective lens 6 by the optical fiber 5a as the measuring light, and is emitted from the objective lens 6 toward a reflecting mirror (not shown) at a target point. The modulated light output from the light-emitting element 1b for reference light is guided as the reference light by the optical fiber 5b directly to the light-receiving element 7 inside the rangefinder and emitted, and the light-receiving element 7 receives the modulated light as the reference light. It is supposed to. The light receiving element 7 receives the measurement light reflected by the reflecting mirror and entering through the light receiving side objective lens 8 and converts it into an electric signal, and is connected to the detector 9. The detector 9
Is to measure the phase difference between the measurement signal and the reference signal corresponding to the measurement light and the reference light output from the light receiving element 7 and to detect the distance from the measurement signal to the reflecting mirror, and a known circuit is used.

In the above-described embodiment, the changeover switch is used as the changeover element. However, as long as the changeover element has the same electrical characteristics, a semiconductor non-contact relay can be used and connected in series to both light emitting elements. In this case, the reliability is further improved.

(Effects of the Invention) Since the present invention is configured as described above, it has the following effects. According to the present invention, as described above, the switching between the measurement light and the reference light incident on the light receiving element does not depend on the mechanical switching of the optical path, and the light emitting element for the measurement light and the light emitting element for the reference are on the same wafer. And long distance, improved measurement accuracy, reduced size, and reduced measurement time because they are placed close to each other on the same stem for good thermal coupling and packaged in the same case. It has the effect of.

[Brief description of the drawings]

FIG. 1 is a diagram of one embodiment of the present invention, and FIG. 2 is a diagram of a conventional example. 1a: Light emitting element for measuring light, 1b: Light emitting element for reference light 2, ... Switching element, 3 ... Modulator 4, ... Control circuit, 5a, 5b ... Optical fiber 7, ... Light receiving element, 9 ... Detector

Claims (2)

(57) [Claims] An operation of radiating modulated light from a light emitting element toward a reflecting mirror placed at a target point and receiving the reflected light as a measuring light by a light receiving element; An operation of projecting the light toward the light receiving element and causing the light receiving element to receive light as the reference light is performed by switching, and a distance to the reflecting mirror is measured from a phase difference between the measurement signal output from the light receiving element and the reference signal. In the lightwave range finder,
The light-emitting element is a light-emitting element for measurement light that emits emitted modulated light toward the reflecting mirror and a light-emitting element for reference light that projects the emitted modulated light directly toward the light-receiving element inside the rangefinder body. The measuring light emitting element and the reference light emitting element are connected to a modulator via a switching element, and the measuring light emitting element and the reference light emitting element use the same wafer. And a lightwave distance meter, which is closely arranged on the same stem so as to achieve good thermal coupling, and is packaged in the same case. 2. The apparatus according to claim 1, wherein output lights of said measuring light emitting element and reference light emitting element are respectively radiated toward said reflecting mirror and said light receiving element via optical fibers. The lightwave distance meter according to 1.