JP3826504B2 - Lightwave ranging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light wave distance measuring device that projects light toward a target, receives the reflected light, and measures the distance to the target.
[0002]
[Prior art]
There are two types of optical wave distance measuring devices depending on whether the light projected toward the target is a continuous wave or a pulse wave. A light wave distance measuring device using a continuous wave projects light toward a target as a wave whose intensity is continuously modulated. Then, the reflected light from the target is received and the phase of the received continuous wave is compared with the phase of the projected continuous wave to determine the distance from the light wave distance measuring device to the target.
[0003]
In addition, in a light wave distance measuring device using a pulse wave, a pulse light with a narrow pulse width is projected toward a target, a reflected pulse light from the target is received, and the travel time of the pulse light from light projection to light reception Find the distance from the target to the target.
[0004]
In these lightwave distance measuring devices, light from the light emitting element is projected toward the target, the light reflected by the target is received by the light receiving element, and the light from the light emitting element passes through the path inside the apparatus. And an internal optical path until the light is received by the light receiving element.
[0005]
And, in order to correct the measurement distance by the external optical path to the distance from a predetermined reference point of the light wave distance measuring device (machine center point where the light wave distance measuring device is installed so as to be located on the vertical line of the reference point of surveying) The distance of the internal optical path is obtained by comparing the phase of the light received from the internal optical path with the phase of the projected light.
[0006]
By the way, the amount of light received through the external optical path and reflected by the target varies depending on the distance to the target and the reflectance of the target. Furthermore, the amount of light received from the external optical path and the amount of light received from the internal optical path are greatly different. In order to prevent measurement errors from occurring due to differences in the amount of light received from the external optical path and from the internal optical path and fluctuations in the amount of received light, the optical distance measuring device equalizes the amount of light received from the external optical path and the amount of light received from the internal optical path. The distance measurement is performed after performing the light quantity balance.
[0007]
[Problems to be solved by the invention]
As described above, the light wave distance measuring device needs to perform light amount balance that makes the received light amount of the external optical path equal to the received light amount of the internal optical path before the distance measurement. In the conventional optical distance measuring apparatus, this light quantity balancing operation is always performed while the power switch is on.
[0008]
The light quantity balance operation involves the following series of operations. That is, the light path is set as the internal optical path, the light emitting element emits light, the internal light is received by the light receiving element, and the amount of the internal light is stored. Next, the optical path is switched to the external optical path, and the light emitting element emits light and projects toward the target. The light receiving element receives the reflected light reflected by the target and stores the amount of light. Then, the amount of light passing through the internal optical path is compared with the amount of light passing through the external optical path, and the amount of light passing through the external optical path is adjusted so that the level of the amount of light is equal.
[0009]
Thus, the light quantity balancing operation involves an operation that consumes a lot of power, such as light emission of the light emitting element, driving of the optical path switching drive motor and the light quantity balancing attenuator. In the conventional optical wave distance measuring device, when the power switch is turned on, the light amount balancing operation is repeated even when the distance measuring operation is not yet required, such as when the target is moving, and the light amount balance in the latest state is always completed, The subsequent ranging operation can be started immediately. Therefore, more power is consumed than necessary.
[0010]
Therefore, when distance measurement is not being performed, an operator can frequently turn off the power switch to prevent the battery of the optical distance measuring device from being consumed. However, if the power switch is turned off, when the power switch is turned on after that, it takes time for the apparatus to stabilize in a steady state and to complete measurement preparation. In particular, an oscillator serving as a measurement reference has a temperature characteristic, and requires a considerable time until the output signal is stabilized. Accordingly, if the time until the reference oscillator shifts to the stable state is waited, the entire distance measurement time becomes long. Therefore, the optical distance measuring device is often used in a power-on state, and battery consumption is accelerated. In addition, in the conventional optical wave distance measuring device, the power consumed for the light quantity balancing operation described above occupies about 50% of the power consumption of the entire device.
[0011]
Accordingly, an object of the present invention is to provide an optical distance measuring device that suppresses the power consumption and reduces battery consumption.
[0012]
It is another object of the present invention to provide an optical distance measuring device that can reduce power consumption, can start a distance measuring operation quickly in measurement, and can shorten a distance measuring time.
[0013]
[Means for Solving the Problems]
According to the present invention, the above object is to control an optical path switcher that switches light from a light emitting element to an external optical path or an internal optical path, an attenuator that adjusts the amount of light from the external optical path, and adjustment of the amount of light by the attenuator. A distance measuring device that measures the distance to the measurement object after performing a light amount balancing process that adjusts the attenuator to equalize the light amount from the external optical path and the light amount from the internal optical path. In the light wave distance measuring apparatus that performs processing, the controller provides a light wave distance measuring apparatus characterized by having a standby mode in which the light amount balance process is not performed for a predetermined time after the light amount balance process is first performed. Is achieved.
[0014]
That is, according to the present invention, even when the power switch is turned on, a standby mode in which the light intensity balancing process that consumes a large amount of power is not performed for a certain period of time is provided. Can be reduced.
[0015]
Further, the controller of the light wave distance measuring device according to the present invention is characterized in that when the difference between the light amount from the external optical path and the light amount from the internal optical path is within a predetermined range, the controller shifts to the standby mode. To do.
[0016]
That is, according to the present invention, the light quantity balancing process that consumes a large amount of power is not repeated many times, the battery power consumption is reduced, and the standby mode is entered when the light quantity balance is maintained. Substantial light quantity balance is maintained, and measurement with high accuracy can be performed quickly.
[0017]
Further, the controller of the light wave distance measuring device according to the present invention is characterized in that it shifts to the standby mode when the distance measurement process is not performed after the light amount balancing process is completed.
[0018]
That is, for example, it is not necessary to repeat the light quantity balance until the target is set at the target point and measurement preparation is completed, and power consumption can be reduced by providing a standby mode for a certain period of time.
[0019]
Further, the controller of the light wave distance measuring device according to the present invention shifts to the standby mode after the light amount balancing process is completed and when the distance measuring process is not performed, and the light amount balanced state after the predetermined time has elapsed. If it is maintained, it further shifts to the standby mode.
[0020]
Therefore, since it is detected whether the light quantity in the external optical path is equal to the light quantity in the internal optical path at regular intervals, the light quantity balance is not significantly shifted, and power consumption can be reduced, and the light quantity can be reduced again at the start of measurement. Even when the balancing process is performed, it is possible to shorten the time until the balancing of the light amount is completed, and to start the distance measurement work quickly.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention.
[0022]
The present invention can be applied to both a light wave distance measuring device using a continuous wave phase difference and a light wave distance measuring device using a pulse wave time difference. Hereinafter, the present invention is applied to a light wave distance measuring device using a continuous wave phase difference. The case will be described.
[0023]
FIG. 1 shows a configuration block of a lightwave distance measuring device according to an embodiment of the present invention. The reference oscillator 1 with temperature compensation generates a stable sine wave signal 30 having a frequency f1, which is a reference for distance measurement based on a phase difference. A signal 30 generated by the reference oscillator 1 with temperature compensation is amplified by the light emitting element driving circuit 2 to a size necessary for driving the light emitting element 3. The light emitting element 3 converts the electric signal 31 from the light emitting element driving circuit 2 into an optical signal, and emits light toward the optical path switch 5 as a sine wave optical signal 4. In addition, the electric signal 31 from the light emitting element driving circuit 2 is input to the calculation unit 13 described later, and is used to calculate the distance to the target.
[0024]
The optical path switch 5 opens only one of the optical paths every predetermined time in order to guide the light 4 emitted from the light emitting element 3 to either the external optical path or the internal optical path. The external optical path means that the light 4 emitted from the light emitting element 3 is projected as external light 6 by the optical path switch 5 toward the outside of the optical distance measuring device and reflected by the target 7 installed at the distance measuring point. An optical path until the external reflected light 9 is received by the light receiving element 10. On the other hand, the internal optical path refers to an optical path until the internal light 8 projected from the optical path switch 5 is received by the light receiving element 10 through the internal path of the light wave distance measuring device.
[0025]
In this way, the optical distance measuring device has an internal optical path that serves as a reference for the amount of received light inside the apparatus, and selects an external optical path or an internal optical path by the optical path switch 5. Then, after equalizing the light receiving level of the light passing through the external optical path and the internal optical path, the light that has been projected (electrical signal 31 for causing the light emitting element 3 to emit light) and the respective light received from the external optical path and the internal optical path The distance to the target is calculated from the phase difference.
[0026]
At that time, the measurement distance error due to temperature change or secular change is removed from the measurement result by the external optical path and the measurement result by the internal optical path. For example, even if the phase detected in an electric circuit that converts reflected light into an electric signal varies depending on temperature, the measurement distance La by the phase difference φa obtained from the external optical path and the phase difference obtained from the internal optical path By obtaining the difference in the measurement distance Lb due to φb, the measurement error is removed and the measurement accuracy is improved. That is, the phase variation depending on the temperature or the like is common to both of the measurement distances of the external optical path or the internal optical path, so that the measurement error due to the temperature fluctuation or the like is canceled by taking the difference La−Lb between the two measurement distances. .
[0027]
The externally reflected light 9 projected toward the outside by the optical path switch 5 and reflected by the target 7 passes through the light amount balancing attenuator 19, is adjusted to a predetermined light amount, and is received by the light receiving element 10. The light quantity balancing attenuator 19 is driven by the motor 22 so that the light transmittance changes, and is positioned at a position where the light quantity levels of the external reflected light 9 and the internal light 8 are equal.
[0028]
The internal light 8 also passes through a position different from the portion through which the external reflected light 9 of the light quantity balancing attenuator 19 passes. The internal light passage portion of the light amount balancing attenuator 19 is driven by the motor 22 when the light receiving amount of the light receiving element 10 is not more than a predetermined value even when the light amount balancing attenuator 19 transmits the external reflected light 9 to the maximum. The light transmittance is changed so that the light amount of the internal light 8 is the same as the light amount of the external reflected light 9.
[0029]
That is, the amount of light received by the external reflected light 9 that has passed through the external optical path varies greatly depending on the reflectivity and distance of the target. The amount of light is adjusted to be the same as the amount of received light 8.
[0030]
The reason why the light quantity balance is made to equalize the light quantity levels is that the difference in signal level in the measurement circuit caused by the difference in the quantity of received light causes measurement errors.
[0031]
On the other hand, the reference signal 30 having the frequency f1 generated by the reference oscillator 1 with temperature compensation is also input to the PLL 14. The PLL 14 generates a reference signal 32 having a frequency f 2 that is phase-synchronized with the input reference signal 30. The reference signal 32 of the frequency f2 generated by the PLL 14 is mixed with the signal 33 of the frequency f1 output from the light receiving element 10, and is converted into a low frequency signal 34 of f1-f2.
[0032]
The signal 34 converted to the low frequency is amplified by the AMP 11 and further compensated for fluctuations in the amount of received light by the AGC 12 to obtain a signal level suitable for the controller 25. Then, a distance calculation based on a phase difference is performed in the calculation unit 13 in the controller 25. As described above, since processing is performed by the signal 34 or the like converted to a low frequency after the AMP 11, the measurement resolution can be increased with a simple circuit.
[0033]
When the distance measuring button 24 is pressed, the calculation unit 13 in the controller 25 calculates the distance to the target 7 from the phase difference of the external reflected light 9 and the phase difference of the internal light 8. That is, the phase difference φa from light emission to light reception in the external optical path and the phase difference φb from light emission to light reception in the internal optical path are obtained, and the distance L from these to the measurement object is
L = c (φa−φb) / 4πf
(C is the speed of light in the atmosphere, f is the modulation frequency of the light emission signal)
As required. The modulation frequency uses a plurality of frequencies, and the distance L to the target 7 is calculated based on the distance obtained from each modulation frequency.
[0034]
Since the optical distance measuring device is often used outdoors, when the battery 21 is mounted and the power switch 23 is turned on, the voltage of the battery 21 is the voltage required for each circuit in the power supply means 20. Is converted into and supplied to each circuit. However, the light-emitting element 3 and the optical path switch 5 are supplied through the switch 16 or the switch 15. The switches 16 and 15 are controlled to be turned on / off by a signal 38 and a signal 37 from the controller 25. Further, a signal 39 for controlling the driving of the motor 22 for driving the light quantity balancing attenuator 19 is input from the controller 25.
[0035]
The present embodiment is different from the conventional example in that a standby mode for a predetermined time is provided when a distance measuring operation is not performed even when the power switch 23 is turned on. And in standby mode, since the light quantity balance operation which consumes big electric power like light emission of the light emitting element 3 or drive of the motor 22 etc. is not performed, the use time of the battery 21 can be extended significantly.
[0036]
That is, in the standby mode, the switch 16 for supplying the drive voltage to the light emitting element 3 and the switch 15 for supplying the drive voltage to the optical path switch 5 are turned off by the signal 38 and the signal 37 from the controller 25. Further, the controller 25 does not output the drive signal 39 to the motor 22 that drives the light quantity balancing attenuator 19. Accordingly, the light emitting element 3 that consumes a large amount of power, the drive motor of the optical path switching unit 5, and the drive motor 22 of the light amount balancing attenuator 19 are not operated, so that the power consumed in the standby mode is greatly reduced.
[0037]
Further, when the CPU constituting the calculation unit 13 in the controller 25 has a sleep mode, if the CPU is also set to the sleep mode in conjunction with the standby mode, the power consumption of the entire optical distance measuring device is further reduced.
[0038]
However, even in the standby mode, the reference oscillator 1 with temperature compensation, the PLL 14 and the AGC 12 are supplied with power and operate stably. Therefore, even when the distance measurement operation is resumed, the phase signal serving as the reference for distance measurement is stably oscillated and amplified, so that the distance measurement operation can be quickly performed.
[0039]
FIG. 2 is a process flowchart of the light wave distance measuring device according to the embodiment of the present invention. The measurement start of the optical distance measuring device is started by turning on the power switch 23 (step 50). First, a light amount balance flag indicating whether or not light amount balance has been completed is initially set to OFF (step 51). On / off of the power switch 23 is monitored by the CPU 13 of the calculation unit (step 52), and when the power switch 23 is turned off, the CPU 13 ends the processing after performing termination processing (step 53). If the power switch 23 is turned on, the process proceeds to the confirmation of the light quantity balance flag (step 55).
[0040]
In step 55, it is confirmed whether or not the light quantity balancing process has already been performed by turning on and off the light quantity balancing flag. If the light quantity balancing flag is off, the light quantity balancing process is performed (step 56). In the light quantity balancing process, the switch 16 is turned on to cause the light emitting element 3 to emit light, the switch 15 is turned on to drive the optical path switch 5, and the light 4 emitted from the light emitting element 3 is switched between the external optical path and the internal optical path. Then, the light quantity balancing attenuator 19 is driven by the motor 22 so that the received light quantity from the external optical path is equal to the received light quantity from the internal optical path.
[0041]
When the above light quantity balance processing is completed, the light quantity balance flag in the CPU 13 is turned on (step 57), and a transition is made to the standby mode (step 54). In the standby mode, the loop from step 52 to steps 55, 58, 59, 54 is repeated, and during that time, the passage of a fixed time is measured by the timer in the calculation unit. In this standby mode, the switch 16 and the switch 15 are turned off, the drive signal 39 of the attenuator drive motor 22 is prohibited, and the light quantity balancing process is not performed. Therefore, the power consumption of the apparatus is greatly reduced, and the battery 21 can be prevented from being consumed.
[0042]
Further, in the standby mode, the CPU 13 in the calculation unit monitors the on / off of the distance measuring button 24 for starting the distance measuring process of the light wave distance measuring device (step 58), and when the distance measuring button 24 is turned on, the measurement is performed. Distance processing (from step 63 to step 66) is started.
[0043]
If the distance measuring button 24 is not turned on at step 58, the CPU 13 monitors the elapse of a fixed time without the distance measuring button 24 being turned on (step 59). If the predetermined time has not yet elapsed, the CPU 13 continues the standby mode (step 54). On the other hand, when a predetermined time has passed without the distance measuring button 24 being turned on, the process proceeds to external light quantity acquisition processing (step 60).
[0044]
When the external light quantity acquisition process newly obtains the light quantity value of the external light path and compares it with the light quantity value obtained during the previous light quantity balance (step 61). Turns off the light quantity balance flag in the CPU 13 (step 62), and shifts to the start state. Thereafter, the light quantity balance process (step 56) is executed. On the other hand, when the difference between the light quantity values is within a certain amount and the light quantity balanced state is maintained, the process again shifts to the standby mode (step 54). Therefore, when the light quantity balanced state is maintained, the light emitting element 3 is merely driven, and it is not necessary to drive the optical path switch 5 and the attenuator 19, so that the power consumption is small.
[0045]
In this way, in the state where the distance measuring button 24 is OFF, the light amount balancing process is performed only when the fixed amount of time elapses and the light amount balanced state is not reached. Accordingly, the light emitting element 3 that consumes a large amount of power in the optical distance measuring device, the drive motor of the optical path switch 5 and the drive motor 22 of the light amount balancing attenuator 19 only operate intermittently. This can reduce battery consumption.
[0046]
On the other hand, the external light intensity value is acquired every time a certain amount of time elapses, and if a change of a certain amount or more occurs, the light intensity balancing process is performed, so that the light intensity balancing state can be always maintained or close to it. Even when the light amount balance is performed again before performing the step, the driving distance of the attenuator 19 is small, the time required for the light amount balance process can be shortened, and the distance measurement operation can be quickly performed.
[0047]
If the distance measuring button 24 is turned on in step 58, the distance measuring process is started. In the distance measurement process, first, an external light quantity acquisition process (step 63) is performed. The light quantity in the external optical path and the light quantity in the internal optical path have already been adjusted to the same level by the light quantity balancing process (step 56). Prior to the distance measurement, the light quantity in the external optical path is acquired again to check the light quantity balance. .
[0048]
The external light quantity acquired again is compared with the light quantity of the already acquired internal light quantity (step 64). If the respective light quantity values are the same, the process immediately proceeds to the distance measuring operation (step 66). If the amount of light in the external optical path is different from the amount of light in the internal optical path, the light amount balancing process is performed again (step 65), and then the process proceeds to the distance measuring operation (step 66). After the distance measurement is completed, the process returns to the start state, and if the power switch 23 is not turned off, the standby mode (step 54) is set and power consumption is reduced.
[0049]
The light quantity value comparison in steps 61 and 64 is to confirm whether or not the newly obtained light quantity of the external optical path is within a range where the light quantity balanced state can be maintained. Accordingly, the newly acquired light amount of the external optical path may be compared with the already acquired light amount of the internal optical path, or may be compared with the previously acquired light amount of the external optical path.
[0050]
【The invention's effect】
As described above, by using the light wave distance measuring device according to the present invention, the battery usage time can be extended and the efficiency of surveying work can be improved.
[0051]
Further, in the standby mode, the portion that consumes a large amount of power in the optical distance measuring device is stopped, so that the battery usage time can be increased.
[Brief description of the drawings]
FIG. 1 is a block diagram of a lightwave distance measuring device according to an embodiment of the present invention.
FIG. 2 is a processing flowchart of the light wave distance measuring device according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reference oscillator with temperature compensation 2 Light emitting element drive circuit 3 Light emitting element 5 Optical path switch 10 Light receiving element 11 AMP
12 AGC
13 Calculation unit 14 PLL
19 Attenuator 20 for balancing light quantity 20 Power supply means 21 Battery 22 Attenuator driving motor 25 for balancing light quantity 25 Controller

Claims (2)

An optical path switcher that switches light from the light emitting element to an external optical path or an internal optical path;
Reflected light that is projected from the external optical path and reflected by the measurement object, and a light receiving element that receives the light projected to the internal optical path;
An attenuator for adjusting the amount of the reflected light ;
Controlling the light amount adjustment by the attenuator, the row intends controller the amount balancing process to equalize the amount of light from the light quantity and the internal optical path from the external light path,
A calculation unit that calculates a distance to the measurement object based on an output from the light receiving element;
The controller is in a standby mode in which the light quantity balancing process is not performed for a certain period of time while the calculation is not performed by the calculation unit. In the light wave ranging apparatus according to claim 1,
The controller maintains the standby mode when a difference in light amount between the reflected light received by the light receiving element and light projected on the internal optical path is within a predetermined range. Lightwave distance measuring device.

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