JPH09218266A - Distance measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a distance measuring apparatus that can measure continuously with high accuracy. SOLUTION: This apparatus calculates a measuring distance G based on a phase difference obtained by extracting a static or low frequency component after multiplying an oscillation signal A of a modulated high frequency of a projecting laser light B and a detection signal D of a reflecting laser light C. This apparatus is provided with a means 75 which repeatedly multiplies the oscillation signal A and two oscillation signals A', A'' different only in phase from the oscillation signal A by the detection signal D in a time-sharing manner with an intermediate frequency at the same multiplication circuit 72 and a means 77a for carrying out an operation to obtain the phase difference with the use of these three multiplied values EE wherein offset component at the multiplication time is an independent variable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device, and more particularly to a distance measuring device for measuring a distance to an object to be measured based on a phase difference of a modulation signal due to an optical path length. Not only suitable for precise measurement from ranging devices to stationary objects,
The present invention relates to an improvement suitable for continuous measurement with movement of both or either.

[0002]

2. Description of the Related Art The conventional distance measuring device shown in FIG. 4 has a main body 2 mounted on a flat base plate 1. Inside the main body 2, a semiconductor laser 3 and a modulator 4 for intensity-modulating the laser light emitted from the laser 3 with an oscillation signal A are housed. Two
The modulated laser beam B is irradiated to the object to be measured 5 facing to. In addition, inside the main body 2,
A light receiving section 6 such as a photodiode that receives the laser beam C reflected by the DUT 5 and outputs a detection signal D corresponding to the laser beam C.
Alternatively, a distance calculation unit 7 that calculates the distance from the main body 2 to the DUT 5 based on the phase difference between the oscillation signal A and the detection signal D is also included, and the calculated distance G is displayed on the display unit 8. It has become so.

The distance calculation unit 7 has a high frequency ω of several hundred MHz.
Oscillation circuit 7 that oscillates at _M to generate a sinusoidal oscillation signal A
1, the oscillation signal A and the detection signal D are input, and the product signal E
And a multiplication circuit 72 that outputs the product signal E
A low-pass filter 73 that outputs a phase signal F by passing a signal component of z having a low frequency ω ₁ or less, and an oscillation signal A by π
Π / 2 phase shift circuit 74 for generating the phase shift oscillation signal A ′ by delaying by the phase of / 2, and multiplication for inputting the phase shift oscillation signal A ′ and the detection signal D and outputting the product signal E ′. Circuit 75
And a low-pass filter 76 that receives the product signal E ′ as an input and outputs a phase signal F ′, and an operation circuit 77 that performs an operation described later based on the phase difference between the phase signal F and the phase signal F ′ to obtain a calculated distance G. It consists of and. The multiplication circuit 75 has the same characteristics as the multiplication circuit 72, and the low-pass filter 76 has the same characteristics as the low-pass filter 73.

The distance to the object 5 to be measured using such a distance measuring device is measured as follows. Oscillation signal A
When the laser beams B and C modulated by the laser light are converted into an electric signal by the light receiving section 6 and become the detection signal D, the oscillation signal A and the detection signal D at that time are caused by the time delay corresponding to the optical path length.
And a phase difference θ corresponding to the optical path length is generated. That is, the oscillation signal A =
detection signal D = a × cos with respect to cos (ω _M × t)
(Ω _M × t−θ) is obtained.

[0005] Next, at the V75 offset of offset V72 Distant multiplication circuit 75 of the multiplier circuit 72, multiplying the signal _{E = a × cos (ω M} × t) × cos (ω M × t-
θ) + V72, product signal E ′ = a × sin (ω _M × t) ×
cos (ω _M × t−θ) + V 75 is obtained. After passing through the low-pass filter, DC components and low frequency components remain, and the phase signal F = a × cos (θ) + V72 and the phase signal F ′ = ax
sin (θ) + V75 is obtained.

Then, when the offsets V72 and V75 can be ignored, the arithmetic circuit 77 performs an arithmetic operation in which the above equations F and F'are made simultaneous to explicitly obtain θ with a and θ as independent variables. That is, the phase difference between the phase signal F and the phase signal F ′ θ = arctan ⁻¹ (sin (θ) /
cos (θ)) = arctan ⁻¹ (F ′ / F) is calculated. Further, the known basic length is set to b and c is the speed of light, and the calculated distance G = θ × c / ω _M + b is calculated. In this way, the distance from the main body 2 to the DUT 5 is calculated based on the phase difference θ between the oscillation signal A and the detection signal D. The calculated distance G is confirmed on the display unit 8 or the like.

Note that the offsets V72 and V75 of the multiplication circuits 72 and 75 are difficult to ignore because there are many restrictions on the circuit that operates at the high frequency ω _M and from the viewpoint of ensuring measurement accuracy.
A calibration means for removing this is also prepared. That is, inside the main body 2, a reflecting mirror 11, a calibration control circuit 12 that controls a calibration process periodically or according to a temperature change, and a motor driving control of the calibration control circuit 12, which rotates according to the motor drive control, and a modulation unit 4 during calibration.
And a rotating mirror 13 that guides the laser light from the reflecting mirror 11 to the light receiving unit 6. Then, in the arithmetic circuit 77, the offsets V72, V75 are measured in advance by the measurement corresponding to the predetermined distance at the time of calibration.
To obtain the offset V7 when measuring the DUT 5.
2. Subtract V75. Even during the distance measurement, the measurement is interrupted in consideration of the temperature change and the like, and the calibration is sometimes performed.

[0008]

However, in such a conventional distance measuring device, the offset of the multiplication circuit is ignored to endure the measurement accuracy, or a complicated optical system for calibration such as a reflecting mirror is added. Therefore, it was necessary to put up with the cost and usage patterns by limiting the intermittent measurement. Therefore, for example, it is inconvenient when constantly monitoring the machining accuracy of long rails that are continuously formed, or when continuously measuring long objects on the ground with a moving body. Therefore, it is an object to improve the measurement accuracy by removing the influence of the offset variation caused by the temperature change and the like without depending on the optical system, reduce the manufacturing cost, and enable continuous measurement.

The present invention has been made in order to solve such a problem, and an object thereof is to realize a distance measuring apparatus capable of continuous measurement with high accuracy.

[0010]

Means for Solving the Problems First and second solving means invented to solve such problems are as follows.
The configuration and operation and effect will be described below.

[First Solving Means] The distance measuring apparatus of the first solving means (as described in claim 1 at the beginning of the application) uses a high-frequency oscillating signal modulated from the irradiation laser light and a reflected laser light. In the ranging device for calculating the measurement distance based on the phase difference obtained by multiplying the detection signal and the static or low-frequency component, the oscillation signal and the phase with the oscillation signal are calculated during the multiplication. For each of the two phase-shift oscillation signals different from each other, means for repeatedly multiplying the detection signal by the same multiplication circuit at an intermediate frequency in a time-division manner, and for obtaining the phase difference, these three types of multiplication products are used. Means for performing an arithmetic operation using the product value as an independent variable, which is an offset component at the time of multiplication.

In this specification, the "phase-shifted oscillation signal" means a high-frequency oscillation signal generated by shifting the phase of the high-frequency oscillation signal by a predetermined amount, and these oscillation signals have a phase difference. It serves as a reference signal for detection. On the other hand, the "phase signal" means a signal of a static or low-frequency extracted component that is a signal that directly bears phase difference information corresponding to a distance that changes statically or at low frequency.

In the distance measuring device of the first solving means, the oscillation signal and the two phase-shift oscillation signals are used as the three signals.
A product signal of the detected signal and the reference signal is obtained from the two reference signals. 3
Since the two reference signals have different phase differences and different phase differences only, in this case, in comparison with the conventional case where the product signal with the detection signal is obtained from only two reference signals, in this case, You can increase the number of valid simultaneous equations without increasing the number of independent variables.

Then, using these three types of product values, an operation is performed using the offset component at the time of product as an independent variable.
In this case, since the multiplication circuit is common, there is only one offset component when multiplying. Since the number of valid simultaneous equations is increased by one, even if the number of independent variables is increased by one, it can be directly calculated by the arithmetic processing. Therefore, the offset component at the time of multiplication can be accurately removed only by calculation. Moreover, since this operation is repeated at intermediate frequencies, static or low frequency varying distances are measured substantially continuously.

This makes it possible to remove the influence of the offset fluctuation caused by the temperature change and the like by a simple calculation process without depending on the optical system. Therefore, according to the present invention, it is possible to realize a range finder capable of continuous measurement with high accuracy.

[Second Solving Means] The distance measuring apparatus of the second solving means (as described in claim 2 at the beginning of the application) is a high-frequency oscillation signal obtained by modulating the irradiation laser beam and a reflected laser beam. In the distance measuring device for calculating the measurement distance based on the phase difference obtained by multiplying the detection signal and the static or low-frequency component, the product of the detection signal is added prior to the multiplication. Means for inverting the phase of the signal of the other party at an intermediate frequency and then removing the static component or the component below the low frequency; and, after the multiplication, to the static or the low frequency component. Instead, it is provided with a means for obtaining the phase difference after extracting the intermediate frequency component.

In the distance measuring device of the second solving means, the oscillation signal and the phase-shift oscillation signal as the reference signal, which is the multiplication partner of the detection signal, are prior to the multiplication with the detection signal. Its phase is inverted at the intermediate frequency. And
From these reference signals, low frequency components and below are removed. Therefore, the reference signal does not include an undesired DC component and has a phase inverted at the intermediate frequency, and the reference signal is used for multiplication.

When the intermediate frequency modulated reference signal and the detection signal are thus multiplied, the phase difference component, which was a quasi-static component in the simple oscillation signal and detection signal multiplication, becomes
It is also included in the intermediate frequency component. On the other hand, the offset during multiplication, which is added for the first time during multiplication, remains quasi-static. Then, the phase difference is obtained after extracting the intermediate frequency component instead of the static component. Therefore, this phase difference no longer includes the offset at the time of multiplication.

As a result, the distance calculation based on the phase difference is performed by a simple calculation process that ignores the offset at the time of multiplication, and the influence of the offset fluctuation caused by the temperature change or the like is always obtained regardless of the optical system. It can be removed and an accurate distance can be measured. Therefore, according to the present invention, it is possible to realize a range finder capable of continuous measurement with high accuracy.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A mode for carrying out the distance measuring apparatus of the present invention achieved by the first and second solving means will be described.

[First Embodiment] In the first embodiment of the present invention, in order to carry out the above-mentioned first solving means, a laser beam irradiated to an object to be measured is oscillated at a high frequency. A means for modulating the signal, a means for multiplying the detection signal of the reflected laser light from the object to be measured, the oscillation signal and a phase-shift oscillation signal generated by shifting the phase of the oscillation signal, and a static signal from the multiplication signal. And a means for extracting a low-frequency component, and a distance measuring device for calculating a measurement distance to the object to be measured by obtaining a phase difference between the oscillation signal and the detection signal from the extracted component, Means for generating a first phase-shifted oscillation signal and a second phase-shifted oscillation signal having different phases as a phase oscillation signal, and the detection in time division at an intermediate frequency between the high frequency and the low frequency during the multiplication. Multiplying the signal with the oscillating signal, Means for repeatedly multiplying a signal by the first phase-shift oscillation signal and multiplying the detection signal by the second phase-shift oscillation signal by the same multiplication circuit, and obtaining the phase difference. In this case, there is provided means for performing calculation using these three kinds of product values as independent variables of the phase difference, the amplitude of the detection signal, and the offset component at the time of product.

[Second Embodiment] In the second embodiment of the present invention, in order to carry out the above-mentioned second solving means, a laser beam irradiated to an object to be measured is oscillated at a high frequency. Means for modulating with a signal, a multiplication means for multiplying the detection signal of the reflected laser light from the object to be measured, the oscillation signal and a phase-shift oscillation signal generated by phase-shifting the oscillation signal, and from this multiplication signal And a means for extracting a static or low-frequency component,
In the distance measuring device for calculating the measurement distance to the object to be measured by obtaining the phase difference between the oscillation signal and the detection signal from the extracted component, the distance measuring device is provided before the multiplication means, and the high frequency and the low frequency. A means for inverting the phases of the oscillation signal and the phase-shift oscillation signal at an intermediate frequency with the frequency, and removing the static component or the component below the low frequency; and the multiplication means instead of the extraction means. And means for extracting the component of the intermediate frequency from the product signal and extracting the amplitude of the signal of the extracted component.

[0023]

【Example】

[First Embodiment] A specific configuration of the first embodiment of the distance measuring apparatus of the present invention will be described with reference to the block diagram of FIG. This distance measuring device is an improved distance calculating unit that increases the number of reference signals and continuously removes the offset component at the time of multiplication by calculation. That is, the distance calculating unit 7 of FIG. 4 in the conventional example is replaced with the distance calculating unit 70 of FIG. 1, and the calibration means dependent on the optical system such as the reflecting mirror 11 in FIG. 4 of the conventional example is unnecessary. Therefore, the same components are designated by the same reference numerals, and the description thereof will be omitted. Hereinafter, the distance calculation unit 70 will be mainly described.

In the distance calculating section 70, a π phase shift circuit 74a for delaying the oscillation signal A by a phase of π to generate a phase shift oscillation signal A ″ is added in parallel with the π / 2 phase shift circuit 74. Subsequent to the above, a switching circuit 75a for inputting three signals of an oscillation signal A, a phase-shift oscillation signal A ', and a phase-shift oscillation signal A "and outputting any one of them according to a control signal is also provided. Instead of the oscillation signal A, the output signal of the switching circuit 75a is used as the signal input to the multiplication circuit 72 as the multiplication partner. The multiplication circuit 75 is unnecessary.

The control signal for the switching circuit 75a is generated by the switching control circuit 75b, but in order to cause the switching circuit 75a to select the oscillation signal A, the phase-shifted oscillation signal A ', and the phase-shifted oscillation signal A "sequentially and repeatedly. , High frequency of several hundred MHz ω _M
And the low frequency ω _{1 of} several Hz, the value changes cyclically at an intermediate frequency ω _K of several KHz. As a result, the distance calculation unit 70 causes the same multiplication circuit 72 to multiply the product of the oscillation signal A and the two phase-shifted oscillation signals A ′ and A ″ having different phases from the detection signal D by the same multiplication circuit 72. It is repeated in time division at ω _K.

The distance calculation unit 70 includes a low pass filter 7
A low-pass filter 76a having the same characteristics is additionally provided in parallel with the third and the third circuits 76, 76, and the multiplication circuit 72 and the low-pass filter 7
3, the output of the multiplication circuit 72 is input to the low-pass filter 7 in accordance with the control signal from the switching control circuit 75b.
3, a switching circuit 75 for selectively outputting an input signal to any one of the low-pass filter 76 and the low-pass filter 76a
c is also inserted. Then, at each duty (1/3), the product signal E of the oscillation signal A and the detection signal D is obtained.
Is processed by the low-pass filter 73, the product signal E ′ of the oscillation signal A ′ and the detection signal D is processed by the low-pass filter 76, and the product signal E ″ of the oscillation signal A ″ and the detection signal D ″ is processed by the low-pass filter 73. Therefore, the phase signals F and F'have only the signal level of 1/3 of the conventional level, and the phase signal F "has only the phase difference component with respect to the phase signal F. It will be inverted.

The arithmetic circuit 77a uses the phase signal F ″ in addition to the phase signal F and the phase signal F ′ to perform the later-described arithmetic operation based on the phase difference. The calculated distance G is calculated by using the product value to perform an operation using the offset component at the time of product as an independent variable.

The operation of the distance measuring device of this embodiment will be described.

As in the conventional case, the amplitude due to the light receiving gain is set to a and the offset of the multiplication circuit 72 is set to V72, and for the oscillation signal A = cos (ω _M × t), the phase shift oscillation signal A '
_{= Sin (ω M × t)} , phase-shift oscillation signal A "= - cos
(Ω _M × t), further detection signal _{D = a × cos (ω M} ×
t-θ) is obtained.

Next, the multiplication circuit 72, the switching circuit 75c, and at duty (1/3) at a frequency omega _K, multiplied signal _{E = a × cos (ω M} × t) × cos (ω M × t-
θ) + V72, product signal E ′ = a × sin (ω _M × t) ×
cos (ω _M × t−θ) + V72, product signal E ″ = − a ×
_{cos (ω M × t) ×} cos (ω M × t-θ) + V72 is obtained. After passing through the low-pass filter, the DC component remains, and the phase signal F = (a × cos (θ) + V72) / 3, the phase signal F ′ = (a × sin (θ) + V72) / 3, the phase signal F ″ = (−a × cos (θ) + V72) / 3 is obtained.

Then, the arithmetic circuit 77a performs an arithmetic operation to express the above equations F, F ', F "simultaneously to explicitly obtain .theta. With a, .theta. And V72 as independent variables. From the signal F and the phase signal F ″, V72 / 3 =
(F + F ″) / 2 is calculated to prepare for erasing the offset component V72, and then the phase difference θ between the phase signal F and the phase signal F ′ θ = arctan ⁻¹ (sin (θ) / c
os (θ) = arctan ^-1 ((F'-V72 / 3) /
(F−V72 / 3)) = ((2 × F′−F−F ″) / (F
-F ")) is calculated.

In this way, the offset component of the multiplication circuit 72 is explicitly removed, and an accurate phase difference that is not affected by the offset component is obtained. Then, without performing a special calibration process for removing the offset component, the calculation of the calculated distance G = θ × c / ω _M + b where the known basic length is b and c is the light velocity, and the display thereof is performed. It

In the case where the arithmetic circuit 77a is a digital circuit for sampling the phase signal F and the like at the frequency ω _K and performing arithmetic operation and is mainly composed of a microprocessor or the like, switching is performed from the viewpoint of circuit simplification. The functions of the circuit 75b and the low-pass filters 73, 76, 76a may be incorporated in the arithmetic circuit and may be performed by program processing. Alternatively, only the function of the switching circuit 75a may be incorporated in the arithmetic circuit, and a single low-pass filter may be collected and inserted in series with the signal line of the calculated distance G. In this case, the frequency ω _K is separable from the frequency ω ₁ and is preferably several tens Hz which is close to this.

[Second Embodiment] A specific configuration of a second embodiment of the distance measuring apparatus of the present invention will be described with reference to the block diagram of FIG. Here again, the characteristic distance calculator will be described.

This distance calculation unit in FIG. 2 intermediates the phases of the signals A and A'to be multiplied by the detection signal D prior to the multiplication to obtain the phase difference θ between the oscillation signal A and the detection signal D. In order to remove components below the low frequency ω ₁ after being inverted at the frequency ω _K , the oscillation circuit 710, the multiplication circuits 731 and 762, the high-pass filter 732, and the high-pass filter 762 are interposed before the multiplication circuits 72 and 75. It has been inserted.

The oscillation circuit 710 oscillates at an intermediate frequency ω _K of several KHz between a high frequency ω _M of several hundred MHz and a low frequency ω _{1 of} several Hz, and an oscillation of ± 1 at a duty of 50%. The signal H is generated. The multiplication circuit 731 is
The oscillation signal A and the oscillation signal H are input and the product signal E1 is output. As a result, the product signal E1 is an oscillation signal of high frequency ω _M , and its phase is inverted at the intermediate frequency ω _K.

The high pass filter 732 receives the product signal E1.
Is input and only the component of frequency ω _K or higher is passed to generate the product signal E2. This allows
The product signal E2 has the DC component and the low frequency component of the frequency ω ₁ removed. Then, the multiplication circuit 72 multiplies the detection signal D. The product signals E1 and E2 should be called the reference signals modulated for the product, but for simplicity, they are called in this way. The same applies to the next product signals E1 'and E2'.

Similar to the multiplication circuit 731, the multiplication circuit 761 produces, from the oscillation signals A ′ and H, a product signal E1 ′ which is an oscillation signal of high frequency ω _M and whose phase is inverted at the intermediate frequency ω _K. To generate. In addition, the high pass filter 762
In the same manner as the high pass filter 732,
A product signal E2 ′ from which the DC component and the low frequency component of the frequency ω ₁ are removed is generated from 1 ′. Then, the multiplication circuit 7
At 5, the product signal E2 'is multiplied with the detection signal D.

Further, the distance calculating section of FIG. 2 extracts the component of the intermediate frequency ω _K after the multiplication for obtaining the phase difference θ between the oscillation signal A and the detection signal D, and obtains the phase difference θ from it. , The multiplication circuits 72 and 75, and then the bandpass filter 7
33 and 763 and the amplitude detection circuits 734 and 764 are respectively inserted in series.

The bandpass filter 733 is a multiplication circuit 7
The product signal E3 output by 2 is input, and the product signal E4 is generated by passing a signal component in a predetermined band including the intermediate frequency ω _K. The amplitude detection circuit 734 is composed of a detection circuit, a low-pass filter, etc., and generates a phase signal F which is a signal of the amplitude from the product signal E4. As a result, the phase signal F is a quasi-static signal having a low frequency ω ₁ or less due to the low pass filter.

Similarly, the bandpass filter 763 receives the product signal E3 'output from the multiplication circuit 75 as an input and passes the signal component in a predetermined band including the intermediate frequency ω _K to generate a product signal E4'. And the amplitude detection circuit 764
Is to generate a phase signal F ′ which is a signal of the amplitude from the product signal E4 ′. The phase signal F ′ is also a quasi-static signal having a low frequency ω ₁ or less.

The arithmetic circuit 770, which receives the phase signal F and the phase signal F ′ and calculates the calculated distance G, is a multiplication circuit 7.
When the offsets V72 and V75 of 2,75 do not exist, the above-described calculation is performed to obtain the calculated distance G based on the phase difference between the phase signal F and the phase signal F '.
Thereby, the arithmetic circuit 770 is simpler than the conventional one.

The operation of the distance measuring apparatus of this embodiment will be described with reference to the signal waveform example of FIG.

As in the conventional case, the amplitude due to the light receiving gain is set to a and the offsets of the multiplication circuits 72 and 75 are set to V72 and
A description will be given centering on a case where the phase difference θ between the oscillation signal A and the detection signal D is obtained by setting the offsets of V75 and the alternate multiplication circuits 731 and 761 to V31 and V61, respectively (FIG.
(See (a) and (b)). First, the oscillation signal A = cos (ω
_M × t) (see FIG. 3C), the phase shift oscillation signal A ′ = sin (ω _M × t) and the detection signal D = a × c
os (ω _M × t−θ) is obtained.

Next, the frequency ω _K is generated by the oscillation circuit 710.
The positive and negative inversion oscillation signal H = ± 1 is supplied at (Fig. 3 (d)
See), alternating positive and negative of the product signal _{E1 = ± cos (ω M ×} t) + V31 is generated (FIG. 3 (e) at the frequency omega _K by multiplier circuit 731 references). And the high pass filter 7
32 removes V31 and obtains a product signal E2 = ± cos (ω _M × t) of alternating positive and negative at the frequency ω _{K. From} this and the detection signal D, the multiplication circuit 72 causes the frequency ω _K
Alternating positive and negative product signal E3 = ± a × cos (ω _M × t)
× cos (ω _M × t−θ) + V72 = ± a × (cos (2
× ω _M × t) + cos (θ)) + V72 is obtained (FIG. 3)
(F)).

After passing through the bandpass filter 733, the direct current component and the low frequency components drop, and further the components of the frequency ω _{M and} above drop, and only the component of the frequency ω _K remains in the product signal E4. Therefore, the product signal E4 = a × cos (ω _K
Xt) * cos (θ) is obtained. The product signal E4 no longer includes the offset V72 of the multiplication circuit 72. The phase signal F = a × cos (θ) is obtained from the product signal E4 by the amplitude detection circuit 734.

Although the repeated explanation is omitted, the multiplication circuit 7 is similarly calculated from the phase shift oscillation signal A'and the detection signal D.
5, the phase signal F ′ = a × sin (θ) is obtained. This also does not include the offset V75 of the multiplication circuit 75. In this way, the phase signals F and F ′ that do not include the offset components of the multiplication circuits 72 and 75 are always generated.

Then, there is no need to perform a special calibration process for removing the offset component, and the phase difference θ = arcta
An accurate phase difference θ is obtained by the calculation of n ⁻¹ (F ′ / F), and thereafter, a known basic length is set to b and a calculated distance G is defined as c is the speed of light G = θ × c / ω _M + b , And its display are made.

As a result, without using the optical system, and without using the switching circuit in which it is difficult to obtain good separation characteristics at high frequencies,
An accurate phase difference could be obtained easily and continuously by arithmetic processing using a general high-frequency band multiplication circuit or filter circuit.

[0050]

As is apparent from the above description, in the distance measuring device according to the first solution of the present invention, the reference signal is increased and the offset component at the time of multiplication is continuously removed only by calculation. By doing so, there is an advantageous effect that it is possible to realize a distance measuring device that can perform continuous measurement with high accuracy regardless of the optical system.

In the distance measuring apparatus according to the second solution of the present invention, the phase difference component is left as the intermediate frequency component and the offset during quasi-static multiplication is separated and removed. As a result, there is an advantageous effect that it is possible to realize a distance measuring device capable of performing continuous measurement with high accuracy simply and easily by calculation processing without depending on the optical system.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of a distance measuring device according to the present invention.

FIG. 2 is a block diagram of a second embodiment of the distance measuring device according to the present invention.

FIG. 3 is an example of the signal waveform.

FIG. 4 is a schematic diagram and a block diagram of a conventional distance measuring device.

[Explanation of symbols]

 1 Base plate 2 Main body 3 Laser 4 Modulator 5 Object to be measured 6 Light receiving part 7 Distance calculating part 8 Display part 11 Reflecting mirror 12 Calibration control circuit 13 Rotating mirror 70 Distance calculating part 71 Oscillation circuit 72 Multiplying circuit 73 Low-pass filter (LPF) 74 π / 2 phase shift circuit 75 multiplication circuit 73 low pass filter (LPF) 77 arithmetic circuit 74a π phase shift circuit 75a switching circuit 75b switching control circuit 77a arithmetic circuit 710 oscillation circuit 731 multiplication circuit 732 high pass filter (HPF) 733 band pass filter (BPF) 764 Amplitude detection circuit 761 Multiplier circuit 762 High-pass filter (HPF) 763 Band-pass filter (BPF) 764 Amplitude detection circuit 770 Operation circuit

Claims (2)

[Claims] 1. A measurement based on a phase difference obtained by multiplying a high-frequency oscillation signal obtained by modulating irradiation laser light and a detection signal of reflected laser light and then extracting a static or low-frequency component. In the distance measuring device for calculating the distance, the product of the oscillation signal and the detection signal of each of the two phase-shifted oscillation signals whose phases are different from that of the oscillation signal are time-divided at the intermediate frequency by the same multiplication circuit. A distance measuring device comprising means for repeatedly performing the calculation and means for calculating the phase difference by using these three types of product values and using the offset component at the time of the product as an independent variable. . 2. A measurement based on a phase difference obtained by multiplying a high-frequency oscillation signal obtained by modulating an irradiation laser beam and a detection signal of a reflected laser beam and then extracting a static or low-frequency component. In a range finder for calculating a distance, a means for inverting the phase of a signal of a product of the detection signal to be multiplied by the intermediate frequency before the product, and then removing the static component or the component of the low frequency or lower. And a means for obtaining the phase difference after extracting the intermediate frequency component instead of the static or low frequency component after the product, and the distance measuring device.