JP2552325Y2 - Lightwave ranging device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightwave distance measuring device for determining a distance to a measurement point based on a phase difference between an internal optical path and an external optical path.

[0002]

2. Description of the Related Art As a conventional lightwave distance measuring device, Japanese Patent Publication No.
There is one as disclosed in Japanese Patent Publication No. 1-8338.

[0003] That is, an internal optical path (a reference optical path having a constant optical path length in which transmission light from the light emitting means reaches the detecting means directly or indirectly via a mirror or the like) is provided between the light emitting means and the detecting means. An external optical path (a measuring optical path in which the transmitting light is reflected by a reflecting mirror placed at the measuring point from the light emitting means and reciprocates between measuring distances) is formed, and an optical signal from the internal optical path and an optical signal from the external optical path are selected. There is provided an optical path switching device for selectively intermittently interposing both optical paths in order to be incident on the switching means. In the lightwave distance measuring device, in order to avoid a phase change in the detection means and a subsequent processing circuit due to a change in the level of the input signal, detection is performed so that the amounts of light incident on the detection means via the internal optical path and the external optical path are matched. There is provided a light quantity control means for adjusting the attenuation of the light quantity variable device provided in at least one of the optical paths using the output signal of the means.

In the lightwave distance measuring apparatus having such a configuration, first, an optical path switch is operated to select an optical path without a light quantity variable device, and an output signal of the detecting means at this time is input to a storage circuit and stored. Next, the optical path switching device is switched to select one of the optical paths having the light amount variable device, and the output signal of the detecting means is switched so as to be input to one input terminal of the comparator. The other input terminal of the comparator is stored in the other input terminal. By inputting the signal of the circuit, the difference signal between the light amount reaching the detection means via the optical path without the light amount variable device and the light amount reaching the detection means via the optical path with the light amount variable device is output as the output of the comparator. The light amount control means operates to drive the light amount variable device so that both light amounts fall within a predetermined range. Therefore, when the external light amount is large in the initial state, the external light amount is set to be larger than the internal light amount by a predetermined level even at the end of the light amount balance as shown in FIG. If the external light amount is small in the initial state, the external light amount is set to be smaller than the internal light amount by a predetermined level even at the end of the light amount equilibrium.

[0005] This method is the same also when a light quantity variable device is installed in both the internal optical path and the external optical path.

[0006]

However, in such a conventional lightwave distance measuring device, the internal light amount and the external light amount are limited within a predetermined error range due to the attenuation characteristics of the light amount variable device and the accuracy of the storage circuit and the comparator. Could not be matched. Then, there is a problem that a phase change occurs in a light receiving element (optical signal) or a subsequent processing circuit (electric signal) due to a change in the level difference between the internal light amount and the external light amount incident on the detecting means.

On the other hand, it is very difficult to manufacture a high-precision light quantity variable device that does not cause a phase change. In order to improve the accuracy of a memory circuit and a comparator, the circuit scale becomes larger. In addition, there is a problem that expensive components must be used.

The present invention has been made in view of such a conventional problem, without increasing the circuit scale.
It is an object of the present invention to provide a high-precision lightwave distance measuring device with reduced cost.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the gist of the present invention is as follows. 1. A light emitting means for emitting transmission light, and a detecting means for receiving an optical signal passing through an internal optical path or an external optical path. An optical path switching device that selects an optical path so that transmission light from the light emitting unit passes through the internal optical path and the external optical path alternatively to the detection unit, and a light amount variable device provided in the external optical path. ,
A light amount control unit that adjusts an attenuation amount of the light amount variable device according to light amount information obtained from the detection unit; and a light signal connected to the detection unit and a light signal when an internal light path is selected and a light signal when an external light path is selected. Calculating means for determining the distance to the measurement point based on the phase difference of the optical signal; and light emission control for limiting the emission of the transmission light for a fixed time after the optical path is switched from the internal optical path to the external optical path by the optical path switch. And a means for measuring the distance between light waves.

[0010] The light emitting means includes an oscillating means for outputting a predetermined frequency, and a light source intensity-modulated at the frequency, and the light emission controlling means stops the oscillation of the oscillating means for the predetermined time. 2. The lightwave distance measuring device according to claim 1, wherein

(3) Light emitting means for emitting transmission light, detection means for receiving an optical signal passing through an internal optical path or an external optical path, and transmission light from the light emitting means selecting between the internal optical path and the external optical path. An optical path switching device having a light blocking unit for temporarily blocking an optical signal received by the detecting means when the optical path is selected so as to reach the detecting means, and when switching from the internal optical path to the external light path, A light amount variable device provided in an optical path, light amount control means for adjusting an attenuation amount of the light amount variable device based on light amount information obtained from the detection means, and light which is connected to the detection means and which is used when an internal optical path is selected. There is provided a lightwave distance measuring device comprising: a calculating means for calculating a distance to a measurement point based on a phase difference between a signal and an optical signal when an external optical path is selected.

An optical path switching signal output means is provided for outputting a control signal to the optical path switching apparatus when the optical path switching apparatus selects an internal optical path and an external optical path.

[0013]

When the optical path is switched from the internal optical path to the external optical path, the light quantity variable device is driven to be in a light-shielded state electrically or optically for a certain period of time. Is controlled.

Therefore, as compared with the case where the light amount varying device is not kept in the light-shielding state for a certain period of time, even if the attenuation characteristics of the light amount variable device and the accuracy of the storage circuit and the comparator are the same, the range of the light amount adjustment error is smaller. Since the light amount is reduced to about half and the light amount variable device is controlled only from one direction, light amount adjustment with good reproducibility can be performed. As a result, the accuracy of lightwave distance measurement can be significantly improved.

[0015]

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

FIG. 1 and FIG. 2 show a first embodiment of the present invention.

In the basic block diagram of the lightwave distance measuring apparatus shown in FIG. 1, a plurality of different prescribed frequencies are created by the oscillating means 10. The transmission light from the light emitting means 20 having a light source such as an LED becomes an optical signal whose intensity is modulated by the frequency generated by the oscillation means 10.

The transmission light is selected in the optical path by the optical path switch 30, and when passing through the internal optical path 3, it passes through the inside of the device.
The light enters the detection means 40. On the other hand, when the external optical path 4 is selected, the light is emitted from the objective lens 50 to the outside of the device. The transmission light converted into a parallel light beam by the objective lens 50 is reflected by a reflecting mirror (not shown) placed at the measurement point, and then enters the apparatus body again through the objective lens 50. The light signal that has entered the apparatus main body and passed through the external light path 4 passes through the light quantity varying device 60 that can continuously adjust the attenuation, and then enters the detection unit 40.

A control section 70a is connected to the optical path switch 30 and the detecting means 40. The control unit 70a includes a calculation unit 70 and a determination unit 75. The determination unit 75 is connected to an optical path switching signal output unit 80 that issues a control signal to switch the optical path switch 30. Further, an oscillation control signal output unit 82 that outputs an oscillation control signal when switching the optical path switch 30 is connected to the determination unit 75. If the optical path switching signal output means 80 and the oscillation control signal output means 82 are set so that each output signal has the same level, one of the means may be omitted.

The rotation angle of the optical path switching device 30 is controlled by a motor or the like (not shown) based on the control signal of the optical path switching signal output means 80. When the rotation angle is controlled and an opening for the external optical path (not shown) of the optical path switch 30 comes before the light emitting means 20, the optical signal passing through the external optical path 4 is selected and the detecting means 4 is selected.
0, and an opening for an internal optical path (not shown) comes,
The optical signal passing through the internal optical path 3 is selected and made incident on the detecting means 40.

The detecting means 40 is connected to the control section 70a so that the optical signal is converted into a voltage signal by photoelectrically converting the optical signal, and is input to the control section 70a. It is connected. Control unit 70a
The control unit 70a is connected to the light amount control unit 90 so that the voltage signal input to the control unit 70a is input to the light amount control unit 90 via the determination unit 75 to the light path switching signal output unit 80 of the control unit 70a. The light quantity control means 90 is connected to the light quantity variable device 60.

The determining section 75 determines whether the signal from the detecting section 40 is due to the internal optical path 3 or the external optical path 4 based on a control signal from the optical path switching signal output section 80. The phase difference between the signal on the optical path 3 and the signal on the external optical path 4 is detected, and this phase difference is converted into the distance to the measurement point.

Next, the operation will be described.

In the lightwave distance measuring apparatus having this configuration, first, the optical path switching signal output means 80 selects the internal optical path 3 via the optical path switch 30 and not through the light quantity varying device 60. At this time, the changeover switch 76 is in a state of being switched to one input terminal side, and the output signal level of the detection means 40 is input to the storage circuit 73 and stored.

Next, the external optical path 4 is selected by the optical path switching signal output means 80 via the optical path switching device 30, and
The changeover switch 76 is switched by the optical path switching signal output means 80 so that the output signal of the detection means 40 is input to the other input terminal of the comparator 74. By inputting the signal of the storage circuit 73 to one input terminal of the comparator 74, the amount of light reaching the detecting means 40 via the internal optical path 3 as the output of the comparator 74 and the detecting means via the external optical path 4 40
To obtain a difference signal from the amount of light reaching.

At this time, the control signal of the optical path switching signal output means 80 is input to the light quantity control means 90, and both the control signal and the difference signal are input to the light quantity control means 90. Is activated, and the light amount variable device 60
Drives both light amounts to fall within a predetermined range.

At this time, when the optical path is switched from the internal optical path 3 to the external optical path 4, the controller 70 controls the intensity modulation frequency transmitted to the light emitting means 20 to be cut off for a certain time.
The oscillation control means 71 operates based on the control signal of the oscillation control signal output means 82 of a. Therefore, even when the external light amount is large in the initial state, as shown in FIG. 2, at the end of the light amount equilibrium, the external light amount is set to be smaller than the internal light amount by a predetermined level. For this reason, in the initial state, the external light amount is set to the same output signal level as when the external light amount is small, so that the error in light amount balance between the internal light amount and the external light amount is constant in any case.

The level difference between the internal light amount and the external light amount incident on the detecting means 40 is about half as compared with the case where the oscillation control means 71 and the like are not provided, and since the level difference becomes constant, the light receiving element ( There is no phase change in the optical signal) and the subsequent processing circuit (electrical signal). Therefore, it is possible to improve the light amount adjustment accuracy and to manufacture a high-precision lightwave distance measuring device without manufacturing a high-precision light amount variable device, a storage circuit, and a comparator.

The oscillation control means 71 can be achieved not only by cutting off the transmission of the modulation frequency from the oscillation means 10 to the light emitting means 20 but also by keeping the modulation frequency from a specified frequency. In other words, the light emitting means 20 only needs to be able to stop the oscillation of the oscillation means 10 by the oscillation control means 71 for a fixed time.

FIG. 3 shows a second embodiment of the present invention.
An opening 32 for an external optical path and an opening 33 for an internal optical path are respectively formed in the switching disk 31 of the optical path switching device 30 at positions opposed to each other with the central portion of the disk interposed therebetween. A light-shielding portion 34 is formed at a middle portion in the circumferential direction with respect to the opening 33 for the optical path. As a result, when the optical path is switched from the internal optical path 3 to the external optical path 4, the optical signal passes through the light-shielding portion 34, so that there is no optical signal incident on the detecting means 40 for a certain time. Therefore, the light amount adjustment is also as shown in FIG. 2, and in any case, the error of the light amount balance between the internal light amount and the external light amount is constant.

[0031]

According to the lightwave distance measuring device of the present invention,
When the light path is switched to drive the variable light amount device, the light or electric light is kept in the light-shielded state for a certain period of time, so that the accuracy of lightwave distance measurement can be significantly improved without significantly increasing the number of parts, and the price is low. It is possible to manufacture a lightwave distance measuring device with high accuracy. In addition, by improving the accuracy of light quantity adjustment, for example, a variable gain amplifier that has been electrically responsible for fine adjustment of the amplitude of an optical signal can be omitted, and a small and low-priced lightwave distance measuring device is manufactured. It is also possible to do.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a process of adjusting a light amount in the first embodiment of the present invention.

FIG. 3 is a schematic view of an optical path switching device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a conventional light amount adjustment process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 ... Internal optical path 4 ... External optical path 10 ... Oscillating means 20 ... Light emitting means 30 ... Optical path switcher 40 ... Detecting means 50 ... Objective lens 60 ... Light quantity variable device 70a ... Control part 70 ... Calculation means 71 ... Oscillation control means 73 ... Storage Circuit 74 Comparator 80 Optical path switching signal output means 82 Oscillation control signal output means 90 Light quantity control means

Claims (3)

(57) [Scope of request for utility model registration] A light emitting means for emitting a transmission light; a detecting means for receiving an optical signal having passed through an internal light path or an external light path; and a transmission light from the light emission means selectively switching between the internal light path and the external light path. An optical path switching device for selecting an optical path so as to reach the detection means as described above; a light amount variable device provided in the external light path; and a light amount for adjusting an attenuation amount of the light amount variable device based on light amount information obtained from the detection means. Control means, connected to the detection means, calculating means for calculating a distance to a measurement point based on a phase difference between an optical signal when an internal optical path is selected and an optical signal when an external optical path is selected, A lightwave distance measuring device comprising: light emission control means for restricting emission of the transmission light for a fixed time after an optical path is switched from an internal optical path to an external optical path by an optical path switch. 2. The light emitting means includes an oscillating means for outputting a predetermined frequency, and a light source intensity-modulated by the frequency, and the light emission controlling means stops the oscillation of the oscillating means for the predetermined time. The lightwave distance measuring apparatus according to claim 1, wherein: 3. A light emitting means for emitting transmission light; a detecting means for receiving an optical signal having passed through an internal optical path or an external optical path; and a transmitting light from the light emitting means selects between the internal optical path and the external optical path. An optical path switch having a light blocking unit for temporarily blocking an optical signal received by the detection means when switching from the internal light path to the external light path, and selecting an optical path so as to reach the detection means, A light-amount variable device provided in an external optical path; a light-amount control unit that adjusts an attenuation amount of the light-amount variable device based on light amount information obtained from the detection unit; a light-amount control unit that is connected to the detection unit and selects an internal light path. A lightwave distance measuring device comprising: a calculating means for calculating a distance to a measurement point based on a phase difference between an optical signal and an optical signal when an external optical path is selected.