JP2518062B2 - Laser distance measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laser distance measuring device that measures a distance to a target using pulsed laser light.

[Conventional technology]

An example of a conventional laser distance measuring device is shown in FIG. The Q-switched pulse laser oscillator 21 of this laser distance measuring apparatus generates a laser beam of an extremely short pulse having a pulse width of several nanoseconds to several tens of nanoseconds. The semitransparent mirror 22 transmits most of the laser light, but sends part of the light to the photodetector 23. Photodetector 23
At, when the laser light is emitted, the pulsed laser light is converted into an electric pulse signal to detect the timing at which the pulsed laser light is emitted. Most of the output light from the Q-switch pulse laser oscillator 21 is incident on the transmission optical system 24, the beam divergence angle is narrowed, and then the light is transmitted to the distance measuring target 25.

The irradiating laser light 26 irradiating the distance measuring target 25 is scattered on the surface thereof. A part of the scattered laser propagates through the space to be subjected to distance measurement, and then is condensed by the receiving optical system 27. In the light receiving system 28, only the laser light is selectively transmitted by the optical filter and converted into an electric pulse signal by a preset threshold value, and the timing at which the laser light is received is detected. In the distance measuring counter 29, the time interval between the timing of emitting the pulse laser light and the timing of receiving the light is measured by the electric pulse signals of the photodetector 23 and the light receiving system 28, and the pulse laser light is measured by the laser distance measuring device and the distance measuring target 25 Determine the distance by determining the time to and from. The calculated distance value is displayed on the display circuit 30. The operation of the Q switch pulse laser oscillator 21, the distance measuring counter 29, and the display circuit 30 is controlled by the control circuit 31 at the same timing.

As described above, the conventional laser distance measuring device using the pulsed laser light has advantages that the retroreflector does not need to be placed on the distance measuring target, the device is simple, and the measurement does not take time. It is very convenient for ranging from several hundred meters to 10 km.

[Problems to be Solved by the Invention]

In the above-mentioned conventional laser distance measuring device, it is necessary to make it compact and lightweight so that it can be used easily.
Also, there is a limit to the output energy value of the Q-switched laser that can be used, and in order to increase the distance-measuring distance, it is necessary to raise the sensitivity of the light-receiving system and lower the threshold value when converting it into an electric pulse signal. . However, the noise generated in the light receiving system is not limited to that generated from the detector itself of the light receiving system,
Some are caused by extraneous light such as sunlight, and the level is not stable. Therefore, the threshold value is determined according to the maximum noise level. Therefore, there is a drawback that the measurable distance is kept low.

The object of the present invention is to eliminate such drawbacks and to lower the threshold value in the case of weak sunlight or at night, which enables distance measurement at a longer distance and improves performance. It is to provide a distance measuring device.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a Q-switch pulse laser oscillator, a photodetector that detects a part of the output laser light and converts it into a transmission electric pulse signal, and an output laser of the Q-switch pulse laser oscillator. A transmitting optical system for sending most of the light to the distance measuring target, a receiving optical system for receiving a part of the laser light scattered by the distance measuring target, and a pulsed laser light focused by this receiving optical system. Light receiving system for converting the received electric pulse signal into a received electric pulse signal, an analog gate which is connected to the light receiving system and is turned off during a time when the Q switch pulse laser oscillator is activated, and an analog gate which is turned off. The square root mean square converter that converts only the AC component in the output voltage of the light receiving system that passed through to the root mean square value and the DC signal of the root mean square value that is the output of the root mean square converter. A DC amplifier that performs DC amplification at a magnification, a comparator circuit that converts the received electric pulse signal into a digital pulse signal using the output level of this DC amplifier as a threshold, and a digital signal that is output from the comparator circuit that starts at the rising edge of the transmission pulse signal. A distance measuring counter that stops at the rising edge of the pulse signal to measure the distance measuring time interval, a display circuit that converts the distance measuring time interval into distance data and displays it, and a control circuit that operates at the operation timing of each part It is composed of.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The laser range finder shown in FIG. 1 comprises a Q-switch pulse laser oscillator 1, a semitransparent mirror 2, a photodetector 3, and
Transmitting optical system 4, receiving optical system 7, light receiving system 8, analog gate 12, rms (root mean square) converter 13, DC amplifier 14, comparator circuit 15, and distance measuring counter 9
And a display circuit 10 and a control circuit 11.

In the laser range finder having such a configuration, the Q switch pulse laser oscillator 1 generates a pulse laser beam having a short pulse width.

The semitransparent mirror 2 transmits the pulsed laser light from the Q switch pulsed laser oscillator 1 and sends it to the transmission optical system 4. At the same time, the semitransparent mirror 2 sends a part of the pulsed laser light to the photodetector 3.

The photodetector 3 converts the pulsed laser light from the semitransparent mirror 2 into an electric pulse signal. That is, when the pulsed laser light is emitted, the pulsed laser light is converted into an electric pulse signal by and the timing at which the pulsed laser light is emitted is detected.

The transmission optical system 4 narrows the beam divergence angle of the pulsed laser light from the semitransparent mirror 2 and sends it to the distance measurement target 5.

The receiving optical system 7 collects a part of the pulsed laser light scattered by the distance measuring target 5.

The light receiving system 8 converts the pulsed laser light focused by the receiving optical system 7 into a received electric pulse signal. In addition, the light receiving system 8
In addition to the received electric pulse signal, outputs an output voltage whose noise component is, for example, noise generated by the light receiving system 8 itself or noise related to sunlight incident on the receiving optical system 7.

The analog gate 12 is turned off during a period in which there is a possibility of receiving the electric pulse signal received by the light receiving system 8 after the Q switch pulse laser oscillator 1 is activated. It is turned on at other times. As a result, the analog gate 12 sends the noise component, which is the output voltage from the optical system 8, to the rms converter 13.

The rms converter 13 is a light receiving system 7 that has passed through the analog gate 12.
Only the AC component in the output voltage of is converted to rms value. Then, a DC electric signal having an rms value is generated.

The DC amplifier 14 amplifies the DC electric signal of the rms value, which is the output of the rms converter 13, to a certain factor and sends it as a threshold value.

The comparator circuit 15 converts the received electric pulse signal from the reception system 8 into a digital pulse signal by using the output level of the DC amplifier 14 as a threshold value.

The distance measuring counter 9 starts the rising of the electric pulse signal from the photodetector 3 and stops at the rising of the digital pulse signal output from the comparator circuit 15 to measure the distance measuring time interval.

The display circuit 10 converts the distance measurement time interval measured by the distance measurement counter 9 into distance data and displays the distance data.

The control circuit 11 includes a Q switch pulse laser oscillator 1 and
The analog gate 12, the distance measuring counter 9, and the display circuit 10 are connected to operate the respective parts at the same operation timing.

 Next, the operation of this laser range finder will be described.

The Q-switch pulse laser oscillator 1 generates pulse laser light having an extremely short pulse width. The semi-transparent mirror 2 transmits most of the pulsed laser light, but partially detects the light.
Send to The photodetector 3 converts the pulse laser light into an electric pulse signal when the pulse laser light is emitted,
A transmission pulse signal is generated to detect the timing at which the pulsed laser light is emitted.

The pulsed laser light that has passed through the semitransparent mirror 2, that is, the output light of the pulsed laser oscillator 1 and most of it is incident on the transmission optical system 4, and the beam divergence angle is narrowed before being sent to the distance measurement target 5. The target for distance measurement is a distance from several hundred meters to about 10 km.

The irradiation laser beam 6 with which the distance measuring target 5 is irradiated is scattered on the surface thereof, and a part of the irradiation laser beam 6 also propagates in space and is condensed by the receiving optical system 7. In the light receiving system 8, the focused pulsed laser light is selectively transmitted through an optical filter and then converted into a received electric pulse signal, which is used to detect the timing at which the pulsed laser light is received.

An analog gate 12 is connected to the light receiving system 8 and Q
After the switch pulse laser oscillator 1 is activated, the switch pulse laser oscillator 1 is turned off while the electric pulse signal of the light receiving system 8 may be received, and is turned on for the other time. While the analog gate 12 is on, the output voltage from the light receiving system 8 is applied to the rms converter 13 connected next. During the output voltage of the light receiving system 8 passing through the analog gate 12, the light receiving system 8
Noise generated by itself and noise components of external light such as sunlight incident on the receiving optical system are mixed as AC components, and the AC components of the output voltage are converted to DC electrical signals of rms value by the rms converter 13. To be done. This DC electric signal is amplified by the DC amplifier 14 to a value of about 5 times, and given to the comparator circuit 15 as a threshold value.

The comparator circuit 15 receives the electric pulse signal received from the light receiving system 8, converts a pulse signal having a peak value exceeding this threshold value into a digital pulse signal, and suppresses a pulse signal having a peak value below that value as noise. To do.
The reason why the threshold value is set to about 5 times the rms value of noise is to distinguish the noise from the received electric pulse signal and to let the received electric pulse signal pass as much as possible. The threshold value becomes large when the noise is large due to the sunlight, and the generation of the digital pulse signal due to the noise is prevented. On the contrary, when the sunlight is weak or at night, the threshold value is lowered, and a weak received electric pulse signal from a distance is converted into a digital pulse signal.

The distance measuring counter 9 starts at the rising edge of the transmission pulse signal from the photodetector 3 and stops at the rising edge of the digital pulse signal from the comparator circuit 15, and the distance measuring time interval at which the laser travels back and forth to the distance measuring target 5. To measure. The display circuit 10 converts the distance measurement time interval data measured by the distance measurement counter 9 and displays the distance data. Control circuit 11
Adjusts the operation timing of each part to allow the operation to be performed smoothly.

In this way, in this embodiment, the Q-switch pulse laser oscillator, the photodetector that detects a part of the output laser light and converts it into a transmission electric pulse signal, and the output laser light of the Q-switch pulse laser oscillator A transmission optical system that sends most of the laser beam to the distance measurement target, a reception optical system that receives a portion of the laser light scattered by the distance measurement target, and a pulsed laser light that is focused by this reception optical system A light receiving system for converting to an electric pulse signal, an analog gate which is connected to this light receiving system and is turned off during a time when the Q switch pulse laser oscillator may operate and a received electric pulse signal may be received, and an analog gate are passed. The rms converter that converts only the AC component in the output voltage of the light receiving system to the rms value, the DC amplifier that amplifies the DC signal of the rms value, which is the output of the rms converter, by a certain factor, and the DC amplifier A comparator circuit that converts the received electrical pulse signal into a digital pulse signal using the power level as a threshold value, and starts at the rising edge of the transmission pulse signal and stops at the rising edge of the digital pulse signal output from the comparator circuit to measure the distance measurement time interval. And a display circuit for converting distance measurement time intervals into distance data and displaying the distance data, and a control circuit for operating the operation timings of the respective parts. With such a configuration, the threshold value can be lowered when the sunlight is weak or at night, so that the distance can be measured at a longer distance.

[Effects of the Invention] As described above, the present invention adds some circuits to the conventional laser range finder, in the case where sunlight is weak due to a change in the measurement place or time, or at night, It enables distance measurement to a far greater distance than conventional ones.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional laser distance measuring device. 1 ... Q-switch pulse laser oscillator 2 ... Semi-transparent mirror 3 ... Photodetector 4 ... Transmitting optical system 5 ... Distance measuring target 6 ... Irradiation laser light 7 ... Receiving optical system 8 ... Receiving system 9 ...... Distance measurement counter 10 ...... Display circuit 11 ...... Control circuit 12 ...... Analog gate 13 ...... rms converter 14 ...... DC amplifier 15 …… Comparator circuit

Claims (1)

(57) [Claims] 1. A Q-switch pulse laser oscillator, a photodetector for detecting a part of its output laser light and converting it into a transmission electric pulse signal, and distance measurement for most of the output laser light of the Q-switch pulse laser oscillator. Transmitting optical system for sending to the target, receiving optical system that receives a part of the laser light scattered by the target, and converting the pulsed laser light collected by this receiving optical system into a received electric pulse signal Light receiving system, an analog gate that is connected to this light receiving system, and is turned off during the time when the Q switch pulse laser oscillator operates and a received electric pulse signal may be received, and an output of the light receiving system that passes through the analog gate DC that amplifies the DC signal of the root mean square value, which is the output of the square root mean square converter, which converts only the AC component in the voltage to the root mean square value A comparator, which converts the received electric pulse signal into a digital pulse signal using the output level of this DC amplifier as a threshold, and a digital pulse signal output from the comparator circuit that starts at the rising edge of the transmission pulse signal. It has a distance measuring counter that stops and measures the distance measuring time interval, a display circuit that converts the distance measuring time interval into distance data and displays the data, and a control circuit that operates at the operation timing of each part. Laser range finder.