Optical distance meter and method for calculating optical noise signal

Abstract

To provide a light-wave distance meter that reduces an error in a distance value due to noise without preparing a special contrivance for components and wiring.SOLUTION: A light-wave distance meter 100 comprises received light quantity adjustment means 21, measures an electrical noise signal with the received light quantity adjustment means 21 completely blocking light, measures a distance measurement signal with the received light quantity adjustment means 21 being in a proper state, and calculates a distance by subtracting the electrical noise signal and an optical noise signal from the distance measurement signal. With attachment of a jig for noise measurement 80 configured to be removably attachable, removing reflected light incident on a light receiving element when attached, and having a unique jig-derived noise signal, an arithmetic control unit 40 measures a first noise signal with the received light quantity adjustment means 21 completely blocking light. With attachment of the jig for noise measurement 80, the arithmetic control unit measures a second noise signal with the received light quantity adjustment means 21 transmitting light most, and calculates the optical noise signal by subtracting the first noise signal and the jig-derived noise signal from the second noise signal to store it.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical distance meter, and more particularly to an optical distance meter that emits distance measuring light toward a target and receives the distance measuring light reflected by the target to measure the distance to the target, and a method for calculating an optical noise signal of the optical distance meter. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a known electronic rangefinder is one that emits distance measuring light toward a target, receives distance measuring light reflected by the target, and measures the distance to the target, as disclosed in Patent Document 1.

[0003] In an optical distance meter, noise generated by the reference signal or various electronic circuits can enter the circuitry of the light-receiving unit through electrostatic coupling, electromagnetic coupling, electromagnetic radiation, etc., without traveling round trip to the target, resulting in electrical noise and resulting in errors in the distance value. The optical distance meter in Patent Document 1 (1) closes the aperture immediately in front of the light-receiving element to its narrowest position before measuring the distance, (2) activates the light source, and (3) measures the noise while controlling the light-receiving element's multiplication factor to an appropriate value, and calculates and stores the resulting amplitude and initial phase in a memory unit. During distance measurement, the distance is calculated based on the amplitude and initial phase, eliminating errors due to noise (see paragraph

[0045] ). This makes it possible to reduce errors without modifying components or wiring. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-258006 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-032421 Summary of the Invention [Problem to be solved by the invention]

[0005] However, noise that causes errors in distance values ​​in an electronic distance meter is not only electrical noise, but also optical noise caused by distance measuring light being reflected inside the electronic distance meter and incident on the light receiving element. The electronic distance meter in Patent Document 1 did not take into consideration reducing optical noise.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide an optical distance meter that further reduces errors in distance values ​​caused by noise without requiring special modifications to components or wiring. [Means for solving the problem]

[0007] In order to achieve the above object, an electronic distance meter according to one embodiment of the present invention comprises a first light source that emits distance measurement light toward an object to be measured, a first light receiving unit that includes a first light receiving element that receives the distance measurement light reflected by the object to be measured and converts it into a distance measurement signal, and a first received light amount adjustment means that adjusts the amount of light incident on the first light receiving element, a first objective lens that focuses the reflected distance measurement light on the first light receiving unit, a first calculation control unit that calculates the distance to the object to be measured from the initial phase of the distance measurement signal, and a first memory unit that stores the distance measurement signal, distance value data, and an optical noise signal, and the first received light amount adjustment means is set to a state in which it completely blocks light, the first light source is caused to emit light, an electrical noise signal is measured, and the first received light amount adjustment means is set to an appropriate state, and the distance to the object to be measured is measured. an optical distance meter that measures a distance measurement signal and calculates a distance by subtracting the electrical noise signal and the optical noise signal from the distance measurement signal, wherein the first calculation control unit is configured to be detachable from the optical distance meter and, when attached, removes reflected distance measurement light that enters the light receiving unit, and, with a noise measurement jig having a unique jig-derived noise signal attached, sets the first received light amount adjustment means to a state that completely blocks light, causes the first light source to emit light, and measures the first noise signal; with the noise measurement jig attached, sets the first received light amount adjustment means to a state that allows maximum light transmission, causes the light source to emit light, and measures a second noise signal; and subtracts the first noise signal and the jig-derived noise signal from the second noise signal to calculate the optical noise signal and store it in the memory unit.

[0008] In the above aspect, the jig-derived noise signal is calculated by using an optical distance meter including a second light source that emits distance measurement light toward the measurement object, a second light receiving unit that includes a second light receiving element that receives the distance measurement light reflected by the measurement object and converts it into a distance measurement signal, and a second received-light amount adjustment means that adjusts the amount of light incident on the second light receiving element, a second calculation control unit that calculates the distance to the measurement object based on the distance measurement signal, and a second memory unit, by: aiming at the night sky, setting the second received-light amount adjustment means to a state that completely blocks light, causing the second light source to emit light, measuring a third noise signal; setting the second received-light amount adjustment means to a state that most transmits light, causing the light source to emit light, measuring a fourth noise signal; and subtracting the third noise signal from the fourth noise signal to calculate an optical noise signal specific to the second optical distance meter; It is also preferable that the noise measurement jig is attached, the second light receiving amount adjustment means is set to a state in which it completely blocks light, the second light source is turned on to emit light, a fifth measurement noise signal is measured, the noise measurement jig is attached, the second light receiving amount adjustment means is set to a state in which it transmits the most light, a sixth measurement noise signal is measured, and the sixth measurement noise signal is obtained by subtracting the fifth measurement noise signal and the intrinsic optical noise signal from the sixth measurement noise signal.

[0009] In the above aspect, it is also preferable that the noise measuring jig comprises a cylindrical housing with a bottom, a glass filter that absorbs light of the wavelength of the distance measurement light, and a laser light absorber that absorbs the distance measurement light reflected by the glass filter, and that the glass filter is installed so that the distance measurement light emitted through the objective lens is incident at Brewster's angle when installed.

[0010] A method for calculating optical noise according to another aspect of the present invention includes a light receiving unit including a light source that emits distance measurement light toward a measurement object, a light receiving element that receives the distance measurement light reflected by the measurement object and converts it into a distance measurement signal, and a received light amount adjustment means that adjusts the amount of light incident on the light receiving element, a memory unit that stores an optical noise signal, and the received light amount adjustment means is set to a state in which light is completely blocked, causing the light source to emit light, measuring an electrical noise signal, setting the received light amount adjustment means to an appropriate state, measuring a distance measurement signal of the measurement object, and subtracting the electrical noise signal and the optical noise signal from the distance measurement signal to calculate a distance. and a calculation control unit for reducing reflected distance measuring light incident on the light receiving unit when attached, and measuring a first noise signal by setting the received light amount adjustment means to a state in which it completely blocks light and causes the light source to emit light while a noise measurement jig having an inherent jig-derived noise signal is attached, measuring a second noise signal by setting the received light amount adjustment means to a state in which it transmits light most while the noise measurement jig is attached, and calculating the optical noise signal by subtracting the first noise signal and the jig-derived noise signal from the second noise signal. [Effects of the Invention]

[0011] According to the above aspect, it is possible to provide an optical distance meter that further reduces errors in distance values ​​due to noise without requiring special modifications to components or wiring. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram of an electronic distance meter according to an embodiment of the present invention; [Figure 2] 3A and 3B are diagrams illustrating an example of a light-receiving-light-amount adjusting means of the optical distance meter. [Figure 3] 1A is a diagram showing sampling data of a distance measurement signal of the optical distance meter, and FIG. 1B is a diagram showing synchronously added data of the distance measurement signal. [Figure 4] 4 is a diagram showing the relationship between a distance signal vector and a noise signal vector in the optical range finder. FIG. [Figure 5] 1A and 1B are diagrams illustrating an example of a noise measurement method in the optical distance meter, where FIG. 1A illustrates a method for measuring an electrical noise signal, and FIG. 1B illustrates a method for measuring an optical noise signal. [Figure 6] 10A and 10B are diagrams illustrating a method for calculating the average amplitude and initial phase of an optical noise signal and the initial phase of a true ranging signal in the optical distance meter. [Figure 7] FIG. 2 is a longitudinal sectional view of an example of a noise measurement jig attached to the optical distance meter. [Figure 8] 10A and 10B are diagrams illustrating a noise measurement method using the noise measurement jig in the optical distance meter. [Figure 9] FIG. 10 is a diagram showing the relationship between the noise signal measured using the noise measuring jig, the optical noise signal, and the electrical noise signal. [Figure 10] 10 is a flowchart showing a process for measuring an optical noise signal in the optical distance meter. [Figure 11] 4 is a flowchart of a process performed when measuring distance in the light-wave distance meter. [Figure 12] 10 is a flowchart of a procedure for measuring jig-derived noise of a noise measurement jig using another light-wave distance meter. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. In addition, in each embodiment, the same components are given the same reference numerals, and duplicated descriptions will be omitted.

[0014] (Embodiment) The optical distance meter 100 according to this embodiment is a so-called phase difference type optical distance meter. As shown in Fig. 1, it generally comprises a light transmitting unit 10, a light receiving unit 20, an A / D converter 30, an arithmetic and control unit 40, a memory unit 50, and an objective lens 60, all of which are housed in a housing configured like a telescope.

[0015] The light-transmitting unit 10 includes a light source 11, a light-transmitting optical system (not shown), a modulator 12, and a reference signal oscillator 13. The light source 11 is a light-emitting element such as a laser diode, and emits distance measurement light L along a collimation axis toward the light-transmitting optical system, an objective lens, and a target 70, which may be a prism placed on the measurement point. The light source 11 is connected to the modulator 12, which is connected to the reference signal oscillator 13. The reference signal oscillator 13 generates a reference signal K with a constant frequency. The modulator 12 modulates the reference signal K into a modulated signal K1.

[0016] The light receiving section 20 includes a light receiving optical system (not shown), received light amount adjusting means 21, 21A, a light receiving element 22, a high frequency amplifier 23, a band pass filter 24, a frequency converter 25, and a low pass filter .

[0017] The light-receiving-light-amount adjusting means 21 is disposed immediately before the light-receiving element 22 and adjusts the amount of light incident on the light-receiving element. The light-receiving-light-amount adjusting means 21 is, for example, a variable density filter made of a thin, disk-shaped film as shown in FIG.

[0018] 2 has a central hole 21a at the center and an opening 21b around the central hole 21a, and is formed so that the filter density increases continuously from the opening 21b to the other end region 21c in the circumferential direction indicated by arrow X in Fig. 2, with the light intensity attenuation rate increasing from 0% to 100%. The light receiving adjustment means 21 is rotated by a rotating shaft (not shown) of a motor inserted through the central hole 21a.

[0019] When the opening 21b of the light-receiving light amount adjusting means 21 is positioned to match the light-receiving element 22, the light amount attenuation rate is 0% (a state in which the most light is transmitted), and when the other end region 21c is positioned to match the light-receiving element 22, the light amount attenuation rate is 100% (a state in which the most light is blocked), and the calculation control unit 40 controls the rotation of the motor, thereby controlling the opening and closing of the light-receiving light amount adjusting means 21 (filter).

[0020] The light receiving amount adjusting means 21 is not limited to the variable density filter, but may be a known diaphragm used in an electronic distance meter.

[0021] The light receiving element 22 is, for example, an avalanche photodiode (APD), and the bias voltage applied to the light receiving element 22 can be controlled by a reverse voltage control unit (not shown). The reverse voltage control unit changes the bias voltage according to commands from the calculation control unit 40, and controls the light receiving element 22 to an appropriate multiplication factor depending on the ambient brightness. The light receiving element 22 receives the distance measurement light L reflected by the target 70 via the light receiving optical system and the light receiving light amount adjustment unit 21, and converts it into a distance measurement signal, which is an electrical signal.

[0022] This electrical signal is amplified by a high frequency amplifier 23, and then noise is removed by a band pass filter 24.

[0023] The frequency converter 25 includes a mixer and a local oscillator. The frequency converter inputs the local oscillation signal generated by the local oscillator and the ranging signal after noise removal into the mixer and multiplies them to generate a frequency component that is the difference in frequency between the two signals and a frequency component that is the sum of the frequencies of the two signals. Here, only the ranging signal converted to the intermediate frequency IF that is the difference in frequency between the two signals is filtered by the low-pass filter 26.

[0024] The ranging signal converted to the intermediate frequency IF is amplified by the intermediate frequency amplifier 27. The amplified ranging signal is converted to a digital signal by the A / D converter 30, and stored in the memory unit 50 via the calculation control unit 40. In the following description, the ranging signal converted to the intermediate frequency IF and then converted to a digital signal will be referred to as ranging signal M.

[0025] The arithmetic control unit 40 is a processing device that controls the light transmitting unit 10 and the light receiving unit 20 to measure distance and calculates distance based on the obtained distance measurement signal M. For example, a central processing unit (CPU) or the like can be used as the arithmetic control unit 40. The functions of the arithmetic control unit 40 described below can be realized by a program, a circuit, or a combination of these. When realized by a program, the functions are realized by reading and executing a program stored in the storage unit 50.

[0026] The calculation control unit 40 also removes an optical noise signal IR and an electrical noise signal EL, which will be described later, from the measured distance measurement signal M to obtain a true distance measurement signal M. T The true ranging signal M T The initial phase β T Based on this, the distance value is calculated.

[0027] The storage unit 50 is configured with a recording medium that stores, preserves, and transmits information in a format that can be processed by a computer, and includes a so-called main storage device and an auxiliary storage device. The storage unit 50 stores sampling data and calculated distance value data. The storage unit 50 also stores the average amplitude a of the optical noise signal IR. IR and the initial phase η IR The storage unit 50 also stores programs for implementing the functions of the arithmetic and control unit 40 and the electronic distance meter 100. The storage unit 50 may be, for example, a non-volatile memory such as a flash memory or a ROM (Read Only Memory), or a volatile memory such as a RAM (Random Access Memory). The electronic distance meter 100 also includes an input unit such as buttons and keys and a display unit such as a liquid crystal display as user interfaces, both of which are not shown. The electronic distance meter 100 also includes an external interface, both of which are not shown, such as a communication unit and a USB port, that allows data stored in the memory unit 50 and data processed by the calculation control unit 40 to be input to and output from the outside.

[0028] (Calculating the theoretical distance) First, we will explain how the optical distance meter 100 measures a theoretical distance. When the optical distance meter 100 measures a distance, the reference signal oscillator 13 sends a synchronization signal P to the calculation control unit 40 and the A / D converter 30, and also sends a reference signal K to the modulator. The A / D converter performs sampling synchronized with the reference signal K. During distance measurement, the amount of light transmitted through the received light amount adjustment means 21 is fixed.

[0029] 3A is a diagram showing how the digitized distance measurement signal M is sampled in the optical distance meter 100. The sampling timing of the A / D converter 30 is determined so that one period of the distance measurement signal M is always sampled at a constant phase angle position, for example, by dividing one period into a (a≧3) equal parts. The distance measurement signal M is sampled continuously over several thousand periods at this sampling timing. At this time, sampling data of the distance measurement signal M that exceeds the input range of the A / D converter 30 or is too small for the input range is discarded.

[0030] To store the sampling data in the memory unit 50, N pieces of data for one period of the ranging signal M are prepared in the memory area of ​​the memory unit 50, and the N pieces of sampling data at the same phase positions are synchronously added and stored. In this way, as shown in Figure 3(B), synthesized data S of one period of the ranging signal M with large amplitude is created by synchronously adding the sampling data at the same phase positions. This synthesized data S is applied to a synthesized sine wave S1 by the least squares method to find the initial phase β of this synthesized sine wave S1. This synthesized sine wave S1 can also be expressed as follows: Nasin(θ-β)+Nb (Equation 1) (Here, N is the number of added ranging signals M, a is the average amplitude of ranging signal M, b is the bias level, θ is the coordinate that defines the angle corresponding to the sampling position, and β is the initial phase.)

[0031] The initial phase β is equal to the phase difference between the signal obtained by dividing the reference signal K to the same frequency as the intermediate frequency signal and the distance measurement signal M, and the distance D to the target 70 is calculated based on this initial phase β using equation 2. D=(β / 2π)(c / F)(1 / 2)=(βc) / (4πF) (Formula 2) (Here, β is the initial phase, c is the speed of light, and F is the modulation frequency of the distance measurement light L.)

[0032] The light source 11 can also emit distance measuring light L as reference light R, which can be passed through the inside of the optical distance meter 100 and received light amount adjustment means 21A having the same configuration as the received light amount adjustment means 21, and then guided to the light receiving element 22. When measuring distance, the measured value is corrected based on the result of measurement using the reference light R by a known method.

[0033] (Actual distance calculation) However, the actual distance measurement signal contains noise. The noise generated during distance measurement includes an electrical noise signal EL generated from the reference signal and various electronic circuits, and an optical noise signal IR generated when the distance measurement light L emitted from the light source 11 is reflected inside the device, such as the objective lens, and unintentionally enters the light receiving element 22.

[0034] Figure 4 shows the true ranging signal M T , the actual ranging signal M, the optical noise signal IR, and the electrical noise signal EL. As shown in Equation 3, the true ranging signal M T can be obtained by subtracting the optical noise signal IR and the electrical noise signal EL from the actually measured distance measurement signal M.

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[0035] (Noise measurement method)

[0036] The electrical noise signal EL can be measured, for example, by operating the electronic distance meter 100 under the following condition I. [Condition I] (1) The light receiving amount adjusting means 21 is set to a state in which light is completely blocked (transmittance 0%), (2) Light source 11 is turned on; (3) The bias voltage applied to the light receiving element is controlled to an optimum value (i.e., the multiplication factor is set to an optimum value).

[0037] 5(A) shows a schematic diagram of a method for measuring electrical noise. Under condition I, when distance measurement light L is emitted, it is emitted via the light-transmitting optical system and the objective lens 60. At this time, even if there is reflected distance measurement light incident via the objective lens 60 or light La reflected inside the instrument, such as on the back surface of the objective lens 60, it is blocked by the received light amount adjustment means 21 and does not enter the light receiving element 22, so no signal is generated by the incident light. However, the reference signal generated by the reference signal oscillator and other noise generated by various electronic circuits enter the circuits subsequent to the light receiving element 22, generating an electrical noise signal EL. Therefore, the measurement noise signal N measured under condition I is I is the electrical noise signal EL.

[0038] On the other hand, the optical noise signal IR can be measured, for example, as follows: (0) The aiming direction of the electronic range finder 100 is directed toward the night sky with no obstacles, i.e., the reflected light of the distance measuring light L is not incident on the objective lens 60, and the electronic range finder 100 is operated under condition II. [Condition II] (1a) The light receiving amount adjusting means 21 is set to a state where it transmits the most light (transmittance 100%), (2) Light source 11 is turned on; (3) The bias voltage applied to the light receiving element 22 is set to an optimum value (that is, the multiplication factor is set to an optimum value).

[0039] FIG. 5B shows a schematic diagram of a method for measuring the optical noise signal IR. Under conditions (0) and (II), the distance measurement light L emitted from the light source 11 is projected through the objective lens 60 toward an unobstructed night sky. Because there are no obstacles in the direction of the night sky to reflect the distance measurement light L, the distance measurement light L is not reflected, and the reflected distance measurement light does not enter the objective lens 60. However, a portion of the distance measurement light L, La, is reflected inside the instrument, for example, on the back surface of the objective lens 60, and travels through the light receiving optical system. It then passes through the light receiving amount adjustment means 21 and enters the light receiving element 22. The incident light La generates an optical noise signal IR. At this time, the light receiving element 22 also detects an electrical noise signal EL generated by electronic circuits, etc.

[0040] Measurement noise signal N measured under condition II II As shown in Figure 4, the optical noise signal IR is the resultant vector of the simultaneously generated optical noise signal IR and the electrical noise signal EL. Therefore, the optical noise signal IR is the measured noise signal N measured under condition II. II From the above, the measured noise signal N measured under condition I under the same condition (0) is I (i.e., the electrical noise signal EL) by vector subtraction.

[0041] (Distance value calculation method) The distance value calculation method according to this embodiment will be described below. I and N II shows the same behavior as the ranging signal M shown in Fig. 3(A). Therefore, in the same way as in the case of obtaining the synthesized data S and synthesized sine wave S1 of the ranging signal M shown in Fig. 3(B), the measured noise signal N I and N II When the composite data and composite sine wave are obtained, the composite sine wave of this noise signal is expressed by the general formula in Equation 4. Na·sin(θ-η)+Nb (Equation 4) (Here, N is the number of waves of added noise, a is the average amplitude of the noise, b is the bias level, η is the initial phase, and θ is the coordinate that defines the angle corresponding to the sampling position.)

[0042] Therefore, under the condition I, the measurement noise signal N I One wave of can be expressed by the following equation 5. a I sin(θ-η I )+b I (Formula 5) (where a I is the measured noise signal N I The mean amplitude of η I is the same initial phase, b I is the bias level.)

[0043] Also, the measurement noise signal N measured by operating the optical distance meter 100 under condition II II The first wave of can be expressed by the following equation 6. a II sin(θ-η II )+b II (Formula 6) (where a II is the measured noise signal N II The mean amplitude of η II is the same initial phase, b II is the bias level.)

[0044] Measurement noise signal N measured under condition II II is a composite noise signal of the electrical noise signal EL and the optical noise signal IR, and is therefore expressed as a vector as shown in FIG.

[0045] Measurement noise signal N measured under condition I I is the electrical noise signal EL. Therefore, the average amplitude a of the electrical noise signal EL EL and the initial phase η EL are respectively a EL =a I ,η EL =η I It can be calculated as follows.

[0046] Therefore, from Fig. 6, the average amplitude a of the optical noise signal IR IR and the initial phase η IR can be expressed by the following Equations 7 and 8, respectively.

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[0047] The distance measurement signal M obtained during distance measurement is expressed by Equation 1, but this Equation 1 includes noise signals (optical noise signal IR + electrical noise signal EL). Therefore, the true distance measurement signal M obtained by removing noise from Equation 1 is T The initial phase β T can be calculated from the following equation 9.

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[0048] Therefore, β in Equation 2 is β in Equation 9. T By replacing Equation 10 with T can be obtained. D T =(β T c) / (4πF) (Equation 10)

[0049] In this way, the true ranging signal M T The initial phase β T is the average amplitude a of the electrical noise signal EL contained in the ranging signal M EL and the initial phase η EL , and the mean amplitude of the optical noise signal IR a IR and the initial phase η IR It is possible to calculate it using

[0050] (Optical noise measurement using a noise measurement jig) To measure under conditions where reflected distance measuring light does not enter the light receiving unit 20, it is necessary to install the electronic distance meter 100 for each instrument in an outdoor location at night with no obstacles. However, this is a very time-consuming task. Therefore, the electronic distance meter 100 is fitted with a noise measurement jig 80 for measurement.

[0051] The noise measurement jig 80 is detachably attached to the telescope 100a of the optical distance meter 100 so as to block the objective lens 60, and has the optical property of absorbing distance measurement light and eliminating reflected light when attached. As an example, a jig such as that disclosed in Patent Document 2 can be used.

[0052] 7 shows a noise measurement jig 80 similar to that described in Patent Document 2. The noise measurement jig 80 includes a cylindrical housing 81 with an opening on one side, and a donut-shaped lid 82 with an opening in the center that closes the opening of the housing 81. The housing 81 is made of an opaque metal or resin. Inside the housing 81, a glass filter 83 that absorbs light of the wavelength of the distance measurement light L and a laser light absorber 84 such as black flocked paper are provided.

[0053] The noise measuring jig 80 is attached to the electronic distance meter 100 so that the axis C of the housing 81 coincides with the optical axis B of the distance measuring light L. The glass filter 83 is positioned so that the distance measuring light L is incident at Brewster's angle α. The laser light absorber 84 is also positioned so that reflected light from the glass filter 83 is incident thereon. The noise measuring jig 80 is configured to be attached so that the polarization plane of the distance measuring light L, which is linearly polarized light, is the plane of incidence on the glass filter 83.

[0054] With the above configuration, most of the distance measurement light L becomes P waves, is refracted and enters the glass filter 83, and is absorbed by the glass filter 83. Although the distance measurement light L is not completely linearly polarized light, S waves are reflected by the glass filter 83 and absorbed by the laser light absorber 84.

[0055] In this way, it was thought that when the noise measuring jig 80 was attached, the distance measuring light L would be almost completely absorbed and the returning light to the electronic distance meter 100 would be eliminated. However, in reality, due to diffuse reflection at the boundary surface of the glass filter 83, a small amount of returning light enters the electronic distance meter 100 via the objective lens 60.

[0056] FIG. 8(A) illustrates the noise measured under condition I with the noise measurement jig 80 attached. [Condition I] (1) The light receiving amount adjusting means 21 is set to a state in which light is completely blocked (transmittance 0%), (2) Light source 11 is turned on; (3) The bias voltage applied to the light receiving element is controlled to an optimum value (i.e., the multiplication factor is set to an optimum value). Hereinafter, this condition (noise measurement jig + condition I) will be referred to as "condition Ia."

[0057] When the light source 11 is turned on, distance measurement light L enters the noise measuring jig 80 via the objective lens 60. At this time, part of the distance measurement light L travels as internally reflected light La to the light receiving element 22. Most of the distance measurement light L that has entered the noise measuring jig 80 is absorbed by the noise measuring jig 80, but part of it travels as return light Lb to the light receiving element 22. However, the light receiving light amount adjusting means 21 blocks the internally reflected light La and return light Lb, and the light receiving element 22 outputs a measurement noise signal N Ia As a result, only the electrical noise signal EL is detected.

[0058] FIG. 8(B) illustrates the noise measured under condition II with the noise measurement jig 80 attached. [Condition II] (1a) The light receiving amount adjusting means 21 is set to a state where it transmits the most light (transmittance 100%), (2) Light source 11 is turned on; (3) The bias voltage applied to the light receiving element 22 is set to an optimum value (that is, the multiplication factor is set to an optimum value). Hereinafter, this condition will be referred to as "Condition IIa."

[0059] When the light source 11 emits light, the internally reflected light La and the return light Lb are directed to the light receiving element 22, as in FIG. 8(A). The internally reflected light La and the return light Lb pass through the light receiving light amount adjusting means 21 and are detected by the light receiving element 22. The light receiving element 22 detects a measurement noise signal N IIa In addition to the electrical noise signal EL and the optical noise signal IR originating from the internal reflection light La, the jig-derived noise signal IR originating from the return light Lb is also included. j is detected.

[0060] Figure 9 shows the measured noise signal N IIa , optical noise signal IR, jig-derived noise signal IR J and the electrical noise signal EL. As explained above, the measured noise signal N IIa are the electrical noise signal EL, the optical noise signal IR, and the jig-derived noise signal IR j The result is a composite vector of

[0061] Therefore, the measured noise signal N IIa From the jig noise signal IR j and the electrical noise signal EL, the optical noise signal IR can be obtained.

[0062] Here, the electrical noise signal EL is measured under condition Ia and is converted into the measured noise signal N Ia On the other hand, the jig-derived noise signal IR j cannot be measured directly.

[0063] The electrical noise signal EL fluctuates significantly due to environmental changes such as the ambient temperature and the voltage of the power supply (battery), as well as changes in the machine over time. On the other hand, the optical noise signal IR and the jig-derived noise signal IR j is a value specific to the instrument (electronic distance meter 100) or jig, which does not fluctuate due to measurement conditions, environmental changes, or aging.

[0064] Therefore, the measurement noise signal N measured in advance under condition II using the light-wave distance meter 100 while aiming at the night sky is II From the above, the measured noise signal N measured under condition I while aiming at the night sky is I (i.e., the electrical noise signal EL) is subtracted to obtain the optical noise signal IR, which is known.

[0065] Next, using the same optical distance meter 100, the measurement noise signal N IIa and the measured noise signal N Ia By measuring the electrical noise signal EL, the jig-derived noise signal IR is calculated from Equation 11 using the optical noise signal IR obtained in advance. j Ask for.

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[0066] Jig-derived noise signal IR jis a value specific to the jig, and will be the same even if measured with another unit, provided that the conditions of the distance measuring light L, such as the wavelength and energy of the laser light, and the method of reading the received light signal are the same, i.e., if the light-wave distance meter has the same configuration as the light-wave distance meter 100, then the measured noise signal N IIa and the measured noise signal N Ia By measuring the above, the optical noise signal IR specific to the optical distance meter 100 used in the measurement can be obtained from Equation 12.

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[0067] Note that the above noise signals all behave in the same way as the ranging signal M, and the synthesized sine wave obtained by synchronizing and adding N of these signals for one period and applying them to a sine wave is expressed by the general formula 4. Therefore, for each of these noise signals, the average amplitude a Ia ,a IIa ,a IRj and the initial phase η Ia ,η IIa ,η IRj By calculating the average amplitude a of the optical noise signal IR and performing vector addition and subtraction, IR and the initial phase η IR is the mean amplitude a Ia ,a IIa ,a IRj and the initial phase η Ia ,η IIa ,η IRj It can be expressed as a function of

[0068] By applying the result to Equation 9, the true ranging signal M T The initial phase β T Also, the initial phase β T Using this, the distance D is calculated by removing the noise error. T Ask for.

[0069] (Operation of the optical distance meter) An example of the operation of the electronic distance meter 100 according to this embodiment will be described with reference to the flowcharts of Figures 10 to 12. Figure 10 is a flowchart showing the process of adjustment before shipping from the factory or at an agency. Figure 11 is a flowchart showing the process of measurement.

[0070] For noise measurement before shipping from the factory, the jig-derived noise signal IR j The noise measurement jig 80 is used. The surface of the housing 81 of the noise measurement jig 80 is used to measure the jig-derived noise signal IR j The average amplitude of a j and the initial phase η j The value is displayed.

[0071] First, in step S01, the jig-derived noise signal IR is input to the calculation control unit 40. j The average amplitude of a j and the initial phase η j For example, the calculation control unit 40 may display the jig-origin noise signal IR j The average amplitude of a j and the initial phase η j The input screen for the noise measurement jig 80 is displayed, and the jig-derived noise signal IR j The average amplitude of a j and the initial phase η j is input from the input unit. Alternatively, an execution program for measuring jig-induced noise may be called from a general-purpose computer terminal connected via an external interface, and input may be made from the computer terminal. This general-purpose computer terminal is configured with, for example, a CPU, RAM, ROM, hard disk, external storage device, network interface, etc.

[0072] Next, in step S02, the calculation control unit 40 operates the light-wave distance meter 100 under the condition Ia to obtain the measurement noise signal N Ia Measurements are taken.

[0073] Next, in step S03, the calculation control unit 40 calculates the measured noise signal N Ia The average amplitude of a Ia and the initial phase ηIa is calculated and stored in the storage unit 50.

[0074] Next, in step S04, the calculation control unit 40 operates the optical distance meter 100 under condition IIa to generate the measurement noise signal N IIa Measurements are taken.

[0075] Next, in step S05, the calculation control unit 40 calculates the measured noise signal N IIa The average amplitude of a IIa and the initial phase η IIa is calculated and stored in the storage unit 50.

[0076] Next, in step S06, the calculation control unit 40 calculates the average amplitude a Ia ,a IIa ,a IRj and the initial phase η Ia ,η IIa ,η IRj Using the measured noise signal N IIa Measured noise signal N Ia and jig-derived noise signal IR j The average amplitude a of the optical noise signal IR after subtraction IR and the initial phase η IR is calculated and stored in the storage unit 50 as the optical noise signal IR.

[0077] In addition, the average amplitude a Ia and the initial phase η Ia and the average amplitude a in step S04 IIa and the initial phase η IIa is the average amplitude a of step S05 IR and the initial phase η IR After being used to calculate the value, it may be discarded or retained.

[0078] Next, when a measurement is to be performed, the measurement object (for example, a target) is collimated and the measurement is performed. First, in step S11, under condition I, the calculation control unit 40 operates the optical distance meter 100 to generate a measurement noise signal N I Measurements are taken.

[0079] Next, in step S12, the calculation control unit 40 calculates the measured noise signal N as the electrical noise signal EL. I The average amplitude of a I and the initial phase η I Calculate the average amplitude a of the electrical noise signal EL EL and the initial phase η EL and stores it in the storage unit 50.

[0080] Next, in step S13, the calculation control unit 40 operates the optical distance meter 100, adjusts the light receiving amount adjustment means 21 so that the amount of light received is appropriate (appropriate conditions), emits distance measuring light, sets the multiplication factor of the light receiving element to an appropriate value, and measures the distance measuring signal M based on the reflected distance measuring light L.

[0081] Next, in step S14, the calculation control unit 40 obtains the average amplitude A and initial phase β of the measured distance measurement signal M.

[0082] Next, in step S15, the calculation control unit 40 reads the average amplitude a of the optical noise signal IR from the storage unit 50. IR and the initial phase η IR Read out.

[0083] Next, in step S16, the average amplitude a IR ,a EL , A and initial phase η IR ,η EL , β, the optical noise signal IR and the electrical noise signal EL are subtracted from the ranging signal M to obtain a true ranging signal M T The initial phase β T Calculate.

[0084] Next, in step S17, the calculation control unit 40 calculates the calculated initial phase β T Distance D after removing noise-induced errors from T is calculated and the process ends.

[0085] Figure 12 shows the jig-induced noise signal IR j 1 is a flowchart for measuring the jig-derived noise signal IR jThe measurement uses an optical distance meter 100x with the same mechanical configuration as the optical distance meter 100. To avoid confusion, the components of the optical distance meter 100x are designated by the same reference numerals as those of the optical distance meter 100 with an x ​​added. The same applies to noise caused by the optical distance meter 100x.

[0086] First, in step S21, the arithmetic and control unit 40x aims at the night sky and operates the light-wave distance meter 100x under condition I to generate a noise signal N Ix Measurements are taken.

[0087] Next, in step S22, the calculation control unit 40x calculates the noise signal N Ix The average amplitude of a Ix and the initial phase η Ix is calculated and stored in the storage unit 50x.

[0088] Next, in step S23, the arithmetic and control unit 40x aims at the night sky, operates the light-wave distance meter 100x under condition II, and outputs a noise signal N IIx Measurements are taken.

[0089] Next, in step S24, the calculation control unit 40x calculates the noise signal N IIx The average amplitude of a IIx and the initial phase η IIx is calculated and stored in the storage unit 50x.

[0090] Next, in step S25, the calculation control unit 40x calculates the average amplitude a Ix ,a IIx and the initial phase η Ix, η IIx Using the noise signal N IIx to noise signal N Ix The optical noise signal IR X The average amplitude of a IRX and the initial phase η IRX and calculate the optical noise signal IR X and stores it in the storage unit 50x.

[0091] In step S26, the calculation control unit 40x operates the optical distance meter 100x under the condition Ia to obtain the noise signal N Iax Measurements are taken.

[0092] Next, in step S27, the calculation control unit 40x calculates the measured noise signal N Iax The average amplitude of a Iax and the initial phase η Iax is calculated and stored in the storage unit 50x.

[0093] Next, in step S28, the calculation control unit 40x operates the optical distance meter 100x under condition IIa to obtain the measurement noise signal N IIax Measurements are taken.

[0094] Next, in step S29, the calculation control unit 40x calculates the measured noise signal N IIax The average amplitude of a IIax and the initial phase η IIax is calculated and stored in the storage unit 50x.

[0095] Next, in step S30, the calculation control unit 40x calculates the average amplitude a Iax ,a IIax, a IRx and the initial phase η Iax, η IIax ,η IRx Using the measured noise signal N IIax Measured noise signal N Iax and the optical noise signal IRx, which is the jig noise signal IR j The average amplitude of a IRj and the initial phase η IRj is calculated and stored in the storage unit 50x.

[0096] Next, in step S31, the jig-derived noise signal IR calculated by the arithmetic control unit 40x j The average amplitude of a IRj and the initial phase η IRjThe output may be, for example, a display unit that displays the value. Alternatively, the output may be made possible to output to a data collector, an external terminal, a USB memory, or the like via an external interface.

[0097] The optical noise signal IRx of the 100x of the light-wave distance meter can be made known by the procedure of FIG. 13 and stored in the storage unit 50x.

[0098] In the optical distance meter 100 configured to perform the above operation, a true distance measurement signal M is obtained by subtracting an optical noise signal IR stored in advance in a storage unit and an electrical noise signal EL measured before distance measurement from the distance measurement signal M. T Since the distance value is calculated from the above, it is possible to reduce errors in the distance value due to noise without requiring special measures for components or wiring.

[0099] According to the above-described optical distance meter 100, an accurate optical noise signal IR can be obtained using the noise measurement jig 80. This improves the accuracy of distance calculation. Furthermore, the optical noise signal IR is usually small and takes a long time to measure. The optical distance meter 100 does not need to measure the optical noise signal IR when measuring distance, so the time required from distance measurement to calculation can be shortened. Furthermore, the electrical noise signal EL can be removed in accordance with fluctuations in the electrical noise signal EL, which also enables more accurate distance calculation.

[0100] In particular, with the optical distance meter 100, the optical noise signal IR can be measured by attaching the noise measurement jig 80, which eliminates the need to measure the optical noise signal IR outdoors at night every time, thereby reducing the workload.

[0101] The noise measurement jig 80 also measures the jig-derived noise signal IRx by using the light-wave distance meter 100x, whose optical noise IRx has been previously known. j If is known, it can be used any number of times to measure the optical noise signal IR of another optical distance meter 100.

[0102] In this embodiment, the noise measuring jig 80 used is the noise measuring jig 80 shown in Patent Document 2, which is configured to absorb light incident on the jig and hardly return it to the light-wave distance meter 100. The noise measuring jig 80 is not limited to this, and may be a jig-derived noise signal IR j For example, a deflection mirror may be placed at 45° with respect to the optical axis of the distance measurement light in a similar cylindrical housing, and a laser absorber may be placed at the position where the reflected light is incident. However, if a configuration is used in which there is almost no return light, as in the noise measurement jig 80, the jig-derived noise signal IR j The absolute value of the jig noise signal IR becomes smaller. j is an inherent value with almost no fluctuation, but in reality it may fluctuate slightly due to temperature or aging. However, if the absolute value of the jig-induced noise signal is small, the fluctuation value will also be small, making it possible to measure optical noise more precisely.

[0103] In addition, compared to the optical noise signal IR due to internal reflection, the jig noise signal IR j is small. For example, when the optical noise signal IR is 4, the jig-derived noise signal is approximately 0.1 to 1. However, under conditions where the received distance measurement signal is small, such as in non-prism distance measurement or when the object to be measured is far away, even such a small noise signal cannot be ignored. In this embodiment, the optical noise signal IR derived from internal reflection can be accurately calculated, so even the smallest signal can be used, improving measurement accuracy.

[0104] In addition, the jig-derived noise signal IR j is smaller than the optical noise signal IR, so it takes more time to measure. j By determining the optical noise signal IR based on the previously known values, the number of time-consuming operations can be reduced, and the efficiency of the operations can be improved.

[0105] The above describes preferred embodiments of the present invention, but the above embodiments are merely examples of the present invention, and these can be combined based on the knowledge of those skilled in the art, and such forms are also included in the scope of the present invention. [Explanation of symbols]

[0106] 10: Light transmitting unit 11:Light source 20: Light receiving part 21: Received light amount adjustment means 22: Light receiving element 40: Calculation control unit 50: Storage section 52: Electrical noise 53: Optical noise 60: Objective lens 70: Target 100:Lightwave distance meter

Claims

1. a first light source that emits distance measurement light toward a measurement object; a first light receiving unit including a first light receiving element that receives the distance measuring light reflected by the object to be measured and converts the light into a distance measuring signal, and a first light receiving amount adjusting means that adjusts the amount of light incident on the first light receiving element; and a first objective lens that focuses the reflected distance measuring light on the first light receiving unit; a first calculation control unit that calculates a distance to the object from an initial phase of the distance measurement signal; a first storage unit that stores the distance measurement signal, the distance value data, and an optical noise signal; a first light receiving amount adjusting means for adjusting the amount of light received by the measuring means for measuring an electrical noise signal by causing the first light source to emit light while completely blocking light; and a first light receiving amount adjusting means for adjusting the amount of light received by the measuring means for measuring an electrical noise signal by causing the first light receiving amount adjusting means to be in an appropriate state while measuring a distance measuring signal of the measuring object. The initial phase of the distance measurement signal is calculated using an average amplitude and an initial phase of an electrical noise signal included in the distance measurement signal, and an average amplitude and an initial phase of an optical noise signal included in the distance measurement signal, and the distance is calculated as an initial phase of a true distance measurement signal, The first arithmetic and control unit includes: a noise measuring tool configured to be detachable from the light-wave distance meter, which removes reflected distance measuring light incident on the first light receiving unit when the jig is attached, and which has a unique jig-derived noise signal, and in a state in which the first light receiving light amount adjusting means is set to a state in which light is completely blocked, the first light source is caused to emit light and a first noise signal is measured; With the noise measuring tool attached, the first light receiving amount adjusting means is set to a state in which light is most transmitted, and the first light source is caused to emit light to measure a second noise signal; an optical noise signal is calculated by subtracting the first noise signal and the jig-derived noise signal from the second noise signal, and the optical noise signal is stored in the first memory unit.

2. The jig-derived noise signal is using another optical distance meter including a second light source that emits distance measuring light toward a measurement object, a second light receiving unit that includes a second light receiving element that receives the distance measuring light reflected by the measurement object and converts it into a distance measuring signal, and a second light receiving adjustment means that adjusts the amount of light incident on the second light receiving element, a second calculation control unit that calculates the distance to the measurement object based on the distance measuring signal, and a second memory unit, while aiming at the night sky, setting the second light receiving amount adjustment means to a state in which light is completely blocked, causing the second light source to emit light and measuring a third noise signal, setting the second light receiving amount adjustment means to a state in which light is most transmitted, causing the light source to emit light and measuring a fourth noise signal, and calculating an optical noise signal specific to the other electronic range finder by subtracting the third noise signal from the fourth noise signal; the noise measuring tool is attached, the second light receiving amount adjustment means is set to a state in which light is completely blocked, the second light source is caused to emit light, and a fifth measured noise signal is measured; the noise measuring tool is attached, the second light receiving amount adjustment means is set to a state in which light is most transmitted, and a sixth measured noise signal is measured; 2. The optical distance meter according to claim 1, wherein the fifth measurement noise signal and the intrinsic optical noise signal are subtracted from the sixth measurement noise signal.

3. The noise measuring tool is a cylindrical housing with a bottom, a glass filter that absorbs light having a wavelength of the distance measuring light, and a laser light absorber that absorbs the distance measuring light reflected by the glass filter; 3. The optical distance meter according to claim 1, wherein the glass filter is arranged so that, in an attached state, the distance measuring light emitted through the first or second objective lens is incident at a Brewster's angle.

4. a light receiving section including a light source which emits distance measuring light towards a measurement object, a light receiving element which receives the distance measuring light reflected by the measurement object and converts it into a distance measuring signal, and a received light amount adjustment means which adjusts the amount of light incident on the light receiving element; a memory section which stores an optical noise signal; the received light amount adjustment means is set to a state in which light is completely blocked, the light source is caused to emit light, an electrical noise signal is measured, and the received light amount adjustment means is set to an appropriate state and the distance measuring signal of the measurement object is measured; and an arithmetic control unit that calculates an initial phase of the distance measurement signal using an average amplitude and initial phase of an electrical noise signal and an average amplitude and initial phase of an optical noise signal contained in the distance measurement signal, and calculates a distance to the object to be measured based on the initial phase as an initial phase of a true distance measurement signal, the initial phase being calculated using the average amplitude and initial phase of an electrical noise signal and the average amplitude and initial phase of an optical noise signal contained in the distance measurement signal, the reflected distance measurement light incident on the light receiving unit is removed when the distance measurement signal is attached, and a noise measurement jig having a unique jig-derived noise signal is attached, the light source is caused to emit light and a first noise signal is measured with the light receiving light amount adjustment means in a state where it completely blocks light, With the noise measuring tool attached, the light receiving light amount adjusting means is set to a state in which light is most transmitted, and a light source is caused to emit light to measure a second noise signal; The first noise signal and the jig-derived noise signal are subtracted from the second noise signal to calculate the optical noise signal.

13. A method for calculating an optical noise signal, comprising:

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