JPH06105291B2 - Laser distance measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser distance measuring device that detects a phase difference of reflected light by using intensity-modulated laser light to perform distance measurement.

2. Description of the Related Art Conventionally, various types of laser distance measuring devices using intensity-modulated laser light have been proposed. The applicant of the present invention has previously proposed a laser range finder having a structure shown in FIG. 3 in Japanese Patent Application No. 61-217417 (Japanese Patent Laid-Open No. 63-71675).

The laser light oscillated by the laser oscillator 1 is modulated by the modulator 2
Intensity is modulated by. Next, the intensity-modulated laser light is split into two optical paths by the beam splitter 14, and one of them is applied to the object 3 to become a reflected laser light and become a detector 4
Is detected and replaced by the reflected light signal 11. The other is detected by the detector 6 to monitor the laser output and generate a reference signal 12 for distance measurement. The intensity of the reflected signal 11 is first detected by the intensity detector 7 and becomes intensity information. On the other hand, the reflected light signal 11 becomes the input of the phase detector 8 together with the reference signal 12, the phase difference between them is detected, and becomes the phase signal 13. The phase signal 13 is phase information after the phase shift is corrected by the phase shift correction device 10 using the correction value calculated from the correction value generator 9 with the intensity information of the intensity detector 7 as an input. The phase shift here means
Specifically, the intensity of the reflected light signal 11 input to the phase detector 8 is adjusted to AGC (not shown) in consideration of the fact that the intensity of the reflected light from the target object 3 is scattered at the time of reflection and so becomes low. Since it is amplified by an amplifier such as a gain controller), it indicates the phase delay of the output signal generated by this amplification. The correction value generator 9 described above is
The correlation between the intensity of the reflected signal 11 and the phase shift in the phase detector 8 is stored as a characteristic map, and a correction value is generated based on the fixed characteristic map.

Problems to be Solved by the Invention In the configuration of FIG. 3, the phase shift depending on the reflected light signal having a wide dynamic range, which is a problem in phase detection of the laser range finder, is previously stored in the correction value generator 9. , A reflected light signal intensity and a phase shift characteristic map (hereinafter referred to as a characteristic map) are stored, the reflected light signal 11 is compared with the characteristic map to calculate a correction value, and the phase shift correction apparatus 10 is used. It was confirmed by using a means to correct it. However, in the above-described configuration, the input signal strength to the amplifier may be changed due to the environmental change or the secular change in the amplifier (not shown) provided in the phase detector 8 or in the previous stage of the phase detector 8. If the correlation with the phase shift of the output signal after amplification fluctuates, that is, if the phase shift causes a drift or the like, the characteristic map for correcting the phase shift is fixed and cannot be dealt with.

It is an object of the present invention to provide a structure that can immediately respond to a phase shift drift.

Means for Solving the Problems The present invention is directed to a laser oscillator that emits a laser beam, an intensity modulating unit that intensity-modulates the laser beam emitted from the laser oscillator, and a laser beam intensity-modulated by the intensity modulating unit. Irradiating means for irradiating the object to be measured, detection means for detecting reflected light from the object to be measured of the laser beam irradiated by the irradiating means and sending out a corresponding detection signal, the detection signal and the reference signal Phase detecting means for detecting the phase difference of, the map creating means for creating while updating the map for correcting the phase shift corresponding to the intensity of the reflected light generated in the phase difference detected by the phase detecting means, A characteristic map can be updated by configuring a laser range finder having a correction unit that corrects the phase shift using the map created by the map creation unit. And solve the above problems.

Effect In the present invention, the conventional laser distance measuring device is provided with the characteristic map creating device capable of updating the characteristic map, so that an appropriate characteristic map is immediately created for the drift of the phase shift at the time of phase detection, and the laser measuring device is provided. It is possible to improve the distance measurement accuracy of the distance measuring device.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a laser distance measuring device according to the present invention. In the figure, the same parts as those in FIG. In this embodiment, a characteristic map creating device 15 for creating a characteristic map based on the output of the phase detector 8 and a changeover switch 16 are provided.

When the laser range finder is activated, the characteristic map creating device 15 first controls the changeover switch 16 to select an input from the characteristic map creating device 15. The characteristic map creating device 15 creates a characteristic map and delivers the characteristic map to the correction value generator 9. After passing the characteristic map to the correction value generator 9, the characteristic map creating device 15 switches the changeover switch 16 to the side that receives the reflected light signal 11, and waits until the next instruction to create the characteristic map is given. The laser range finder operates in the same manner as in the case of FIG. 3 from the time the characteristic map generator 15 enters the standby state until the next characteristic map generation instruction is issued. When the operator determines that the phase shift drift has occurred, the operator gives a characteristic map generation instruction to the characteristic map generation device 15 from the outside. The characteristic map creating device, which has received an instruction to create a characteristic map from the outside, carries out the same operation as at the time of startup to create a characteristic map, and then repeats the above-described operation.

Next, the procedure for creating the characteristic map will be described in detail with reference to FIG.

In the laser range finder, the characteristic map creating device 15, the changeover switch 16 and the phase detector 8 form a closed circuit when the operation is started or when the operator issues an instruction to create or update the characteristic map. This is because the characteristic map generator 15 sends the control signal 21 to the changeover switch 16 as described above. On the other hand, the laser light generated from the laser oscillator 1 is input to the phase detector 8 as the reference signal 12 with a constant intensity. At the time when the closed circuit is generated in this way, the characteristic map creating device 15 responds to the same signal as the reference signal 12 input to the characteristic map creating device 15 as shown in FIG.
Is transmitted to the phase detector 8 via the changeover switch 16. The sample signal 22 has the same frequency and the same phase as the reference signal 12, but is a signal in which only the intensity is weakened in several steps, and for example, the sample signal 22 having the weakest intensity is used. Therefore, both the reference signal 12 and the sample signal 22 having the weakest intensity are input to an amplifier (not shown) in the phase detector 8, but this amplifier uses the reference signal 12 as a reference signal and outputs the sample signal 22 as a reference signal. The amplified signal amplified to the strength of the reference signal is created, and the phase detector 8 detects the phase difference between the reference signal and the amplified signal by a phase detection unit (not shown), and corresponds to the sample signal 22 set to the weakest strength. Phase shift signal 23
Is sent to the characteristic map creating device 15. Here, since the characteristic map creating device 15 changes the intensity of the sample signal 22 in several steps while timing with the internal clock, first, the phase shift signal 23 corresponding to the intensity of the sample signal 22 of the weakest intensity is generated. Can be received. Then, the phase shift signal 23 corresponding to the intensity is similarly received in the order of the second weakest setting. Thus, the sample signal 22
By receiving the phase shift signal 23 corresponding to the intensity of, the characteristic map creation device 15 causes the phase shift amount corresponding to the amplification amount of the amplifier of the phase detector 8, that is, the phase shift amount corresponding to the reflected light intensity. A characteristic map of can be created. Here, it is needless to say that the respective intensities of the sample signal 22 and their differences can be appropriately set by considering the properties of the object 3 and the measurement conditions. Then, after completing the characteristic map including the required amount of sampling phase shift determined by these settings, the characteristic map creating apparatus 15 sends the characteristic map data to the correction value generator 9. At this time, the characteristic map creating device 15 switches the changeover switch 16 to the input side of the reflected signal 11, the closed circuit is released, and the state shifts to the standby state.

In the above description, the reference signal 12 which is the reference wave for phase detection is taken from the detector 6, but even if the signal from the oscillator 5 is used, there is no essential difference. Further, although the example in which the laser light is not scanned has been described, it is clear that the present invention is also effective in the case of scanning the laser light to acquire a range image.

As described above, the phase shift corresponding to the reflected light intensity from the object is compensated by the updatable characteristic map, and the reflected light intensity which is a problem at the time of phase detection of the laser range finder It is possible to prevent the deterioration of the distance measurement accuracy due to the phase shift and to eliminate the unstable measurement due to the drift of the phase shift during the operation of the apparatus, which is a great effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing the entire configuration of an embodiment of a laser distance measuring device according to the present invention, FIG. 2 is a block diagram for explaining the operation of the main parts of FIG. 1, and FIG. FIG. 3 is a block diagram of a laser range finder according to a prior application of the present applicant. 1 ... Laser oscillator, 2 ... Modulator, 3 ... Object, 4
...... Detector, 8 …… Phase detector, 9 …… Correction value generator,
10 …… Phase shift correction device, 15 …… Characteristic map creation device, 16 …… Changeover switch.

Claims (1)

[Claims] 1. A laser oscillator for emitting a laser beam, an intensity modulator for intensity modulating the laser beam emitted from the laser oscillator, and a laser beam intensity-modulated by the intensity modulator for irradiating an object to be measured. Irradiation means, detection means for detecting reflected light of the laser light emitted by the irradiation means from the object to be measured, and transmitting a corresponding detection signal, and a phase for detecting a phase difference between the detection signal and a reference signal The detecting means, the map creating means for creating while updating the map for correcting the phase shift corresponding to the intensity of the reflected light generated in the phase difference detected by the phase detecting means, and the map creating means A laser range finder having a correction means for correcting the phase shift using a map.