JP7033875B2 - Surveying device - Google Patents

Description

The present invention relates to a measuring device that irradiates a measurement object with ranging light, receives reflected light from the measurement object, and measures the distance to the measurement object.

In recent years, a single device has a measurement function in prism mode that reflects the distance measurement light on a prism to measure the distance to the object to be measured, and the distance measurement light is directly applied to the object to be measured to measure the object. There is known a surveying device that has a measurement function in a non-prism mode and can select a distance measuring method according to the purpose of measurement (Patent Document 1).

In such a device, since the measurement in the non-prism mode requires high-output ranging light, an optical system is used in which the light flux emitted from the light source is taken in as much as possible to improve the light utilization efficiency. On the other hand, in the measurement in the prism mode, the distance measuring light with the output as in the non-prism mode is not required, so that the output output is lowered by an attenuation filter or the like.

However, when the prism mode is measured using an optical system whose light utilization efficiency is improved in accordance with the non-prism mode, the distance measurement value is caused by the prism being slightly deviated from the center of the intensity of the distance measurement light to be irradiated. There was a problem that the deviation (hereinafter referred to as "mispointing error") became large.

The cause of the mispointing error will be described with reference to FIG. First, since the beam Bn for the non-prism mode is required to have a high output, the peripheral light from the light emitting element 12 is also taken in with high efficiency by using the collimating lens 13 with a high NA (numerical aperture), and the aperture for non-prism distance measurement is performed. The aperture 14 limits the light to a large beam diameter D, which is the diffraction limit light, and emits the light. The intensity of the beam Bn for the non-prism mode shows a so-called Gaussian distribution, as shown in the graph in the center of the figure, in which the center of the beam is higher and becomes lower toward the periphery.

When the prism is measured using this non-prism mode beam Bn, as shown in the graph on the left side of the figure, the distance value between the beam intensity and the distance value decreases as the intensity decreases with respect to the center of the beam intensity. There is a correlation that the error becomes large. Further, at a long distance such as when measuring a prism, the size of the prism becomes relatively small with respect to the size of the beam of the distance measuring light. Will be measured at.

As a result, the emission timing of the light source deviates from the internal reference signal based on the reference light in the beam, and the time difference from the internal reference signal depends on which part of the beam the light is irradiated and reflected on the object to be measured. As a result of the change in, the measured distance value changes within the beam, causing a mispointing error.

On the other hand, when measuring the prism mode, the applicant inserts an aperture diaphragm in the distance-finding optical path of the light transmission unit, partially shields the beam, and uses only the light near the center of the intensity of the beam. We have found that mispointing errors during prism mode measurement can be reduced by making the intensity in the beam uniform, and filed a patent application for such an invention (see Japanese Patent Application No. 2017-035922).

Specifically, the horizontal and vertical widths of the aperture aperture are greater than 0, and are 0.5 times or less of the half-value full width of the intensity distribution in each of the horizontal and vertical cross sections of the non-prism mode beam, or the aperture. The mispointing error was reduced by limiting the beam for the reflected prism mode to a range of 84% or more of the center intensity of the beam for the non-prism mode.

Japanese Unexamined Patent Publication No. 2004-21259

However, according to the further study by the inventor, when an aperture diaphragm is inserted in the distance measuring optical path of the light transmitting unit for the purpose of reducing mispointing error, the error at a short distance may become large in the measurement in the prism mode. all right.

The cause of the large error at a short distance will be described with reference to FIGS. 9 and 10. FIG. 9 schematically shows a light receiving element 104 that receives the reflected light from the prism 102, and FIG. 10 schematically shows a light emitting element 107 that emits distance measuring light. The ranging light emitted from the light emitting element 107 is collimated by a collimating lens (not shown) and controlled to be parallel light, and is applied to the prism 102. As shown in FIG. 9A, the light receiving element 104 is usually designed so that the optical axis (reflected light axis) 101 of the reflected light from the prism 102 is the center of the light receiving surface 104a of the light receiving element 104. There is.

However, in reality, when the prism 102 is located at a long distance, as shown in FIG. 9A, the reflected light is emitted so that the reflected light axis 101 is at the center of the light receiving surface 104a, but the prism. When the 102 is at a short distance, as shown in FIG. 9B, the reflected light spreads so as to pass on the reflected light axis 101 and the axes 105 and 106, and is separated from the center of the light receiving surface 104a of the light receiving element 104. Is irradiated to the position.

The light receiving element 104 does not have uniform sensitivity and responsiveness over the entire surface of the light receiving surface 104a due to manufacturing, and the sensitivity and responsiveness differ depending on the portion on the light receiving surface 104a. Therefore, when the reflected optical axis 101 is deviated, the responsiveness of the light receiving signal from the light receiving element 104 may differ depending on the light receiving position of the light receiving surface 104a. If the responsiveness of the received light signal is different, it will appear as a distance measurement error when measuring the distance.

When the light receiving surface 104a is irradiated with the reflected light as a planar beam having an intensity distribution in which the center is high and the periphery is low without arranging the aperture diaphragm, even if the beam spreads due to the deviation of the reflected optical axis 101. The central light with high intensity spreads to the periphery, and the unevenness of the beam intensity of the reflected light is made uniform as a whole. As a result, the variation in responsiveness depending on the light receiving position of the light receiving surface 104a becomes relatively small.

On the other hand, when the aperture diaphragm is arranged, since the irradiation is performed in a relatively narrow area with a certain intensity or more, the influence of the spread due to the deviation of the reflected optical axis 101 is large, and the responsiveness depending on the light receiving position of the light receiving surface 104a. The effect of the variation of is noticeable. Therefore, in the device in which the aperture stop is arranged, the distance measurement error when measured at a short distance becomes large.

Further, also in the light emitting element 107, the phase 109 from the center position of the light emitting surface 107a shown in FIG. 10 and the phases 108 and 110 from the position away from the center do not have uniform light emission. The emission power and characteristics vary depending on the position on the light emitting surface 107a.

Therefore, as shown in FIG. 9B, when the prism at a short distance is measured and the reflected light axis 101 shifts, the phase 109 of the light emitting signal disappears, and the light emitting element 107 depends on the light receiving position of the light receiving surface 104a. Only the phases 108 and 110 of the light emission signal from the above appear as a distance measurement error when measuring the distance.

In this way, when measuring a prism at a short distance, in a device with an aperture aperture, an error due to the deviation of the reflected optical axis (hereinafter, the deviation of the reflected optical axis that appears at a short distance when measuring in prism mode) The error caused by this is called "short-range error").

Short-range error can be reduced by using high-quality components for the light-receiving element and the light-emitting element, that is, elements having uniform response sensitivity, but high-quality components are expensive.

Therefore, the inventor has found that the short-distance error can be reduced by adjusting the bias voltage (sensitivity) of the light receiving element and the light emitting output of the light emitting element, and proposes the present invention.

The present invention has been made in view of such circumstances, and provides a surveying apparatus capable of reducing short-distance errors while reducing mispointing errors by a simple method that suppresses costs. The purpose.

In order to achieve the above object, the measuring device according to one aspect of the present invention includes a light emitting unit that emits distance measuring light, a light receiving unit that receives reflected distance measuring light from a measurement object, and the distance measuring light. A range-finding optical system that has an aperture throttle that limits the shape of the beam so that the beam intensity of the beam is uniform within the beam, and guides the range-finding light through the measurement object to the light-receiving part. A prism mode is provided with a light receiving sensitivity adjusting unit that electrically adjusts the light receiving sensitivity of the light receiving unit by adjusting a bias voltage (V), and an arithmetic control unit that calculates a distance based on the light receiving signal of the reflected distance measurement light. It is a measuring device capable of measuring a distance by selecting measurement and non-prism mode measurement, and when prism mode measurement is selected, the aperture throttle is arranged in a distance measuring optical path, and the light receiving sensitivity adjusting unit measures. It is characterized in that the bias voltage (V) is reduced so that the error becomes equal to or less than a predetermined value.

Further, in the measuring device according to another aspect of the present invention, the light emitting unit that emits the distance measuring light, the light receiving unit that receives the reflected distance measuring light from the measurement object, and the beam intensity of the distance measuring light are within the beam. It is equipped with an aperture throttle that limits the shape of the beam so that it becomes uniform, and the distance measuring optical system for guiding the distance measuring light through the measuring object to the light receiving part and the light emitting output of the light emitting part. It is a measuring device that has a light emission adjusting unit for adjustment and an arithmetic control unit that calculates a distance based on the received signal of the reflected distance measuring light, and can select distance measurement by selecting prism mode measurement or non-prism mode measurement. When prism mode measurement is selected, the aperture throttle is arranged in the distance measuring light path, and the light emitting adjusting unit reduces the light emitting output of the light emitting unit so that the measurement error becomes a predetermined value or less. And.

Further, in still another aspect of the present invention, the light emitting unit that emits the distance measuring light, the light receiving unit that receives the reflected distance measuring light from the measurement object, and the beam intensity of the distance measuring light are uniformly in the beam. It is provided with an aperture throttle that limits the shape of the beam so that the distance measuring optical system for guiding the distance measuring light through the measuring object to the light receiving portion, and a bias voltage (bias voltage) for the light receiving sensitivity of the light receiving portion. A light receiving sensitivity adjusting unit that electrically adjusts by adjusting V), a light emitting adjusting unit that adjusts the light emitting output of the light emitting unit, and an arithmetic control unit that calculates a distance based on the light receiving signal of the reflected distance measurement light. It is a measuring device capable of measuring a distance by selecting prism mode measurement and non-prism mode measurement, and when prism mode measurement is selected, the aperture throttle is arranged in a distance measuring optical path and the light receiving sensitivity is adjusted. The unit is characterized in that the bias voltage (V) is reduced so that the measurement error is equal to or less than a predetermined value, and the light emission adjusting unit reduces the light emission output of the light emitting unit so that the measurement error is equal to or less than a predetermined value. And.

In the above embodiment, it is also preferable that the light receiving sensitivity adjusting unit reduces the bias power (V) to the range of 91% RV> V ≧ 85% RV with respect to the breakdown voltage (RV).

Further, in the above embodiment, it is also preferable that the light emission adjusting unit reduces the light emission output (LD) to the range of 4.5 mW> LD ≧ 1.5 mW.

Further, the horizontal width and the vertical width of the opening of the aperture diaphragm are larger than 0 and 0.5 times or less of the half-value full width of the intensity distribution in each of the horizontal and vertical cross sections of the beam for non-prism mode. It is also preferable.

It is also preferable that the aperture stop limits the prism mode beam to a range of 84% or more of the center intensity of the non-prism mode beam.

According to the above aspect, it is possible to provide a surveying device capable of reducing short-distance error while reducing mispointing error without using high-cost parts.

It is a figure which shows the structure of the optical system of the surveying apparatus which concerns on embodiment of this invention. It is a block diagram explaining the operation of the surveying apparatus which concerns on the same form. It is a figure which shows an example of the aperture diaphragm for prism mode measurement which concerns on the same form. It is a figure which shows the luminous flux around the light emitting part and the aperture diaphragm of the surveying apparatus which concerns on the same form, (a) is a plan view, and (b) is a side view. It is a figure which shows the relationship between the beam width and the beam intensity of the distance measuring light of the surveying apparatus which concerns on the same form. (A) to (d) are graphs showing distance measurement errors when prism mode measurement is performed using a surveying device according to the same embodiment. (A) and (b) are graphs showing distance measurement errors when prism mode measurement is performed using a surveying device according to the same embodiment under conditions different from those in FIG. It is a figure explaining the correlation of the light intensity and the distribution of a distance value when a prism is measured with a beam for conventional non-prism mode measurement. (A) is a diagram showing an optical axis near a light receiving element when a long-distance prism is measured in a conventional prism mode measurement, and (b) is a diagram showing a short-distance prism in a conventional prism mode measurement. It is a figure which shows the optical axis in the vicinity of a light receiving element at the time of measurement. It is a figure explaining the phase of the light in the vicinity of a light emitting element in the conventional prism mode measurement.

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

(Embodiment)
FIG. 1 is a diagram showing an optical system of a surveying apparatus 1 according to an embodiment of the present invention, and FIG. 2 is a block diagram illustrating an operation of the embodiment. The surveying device 1 is a total station and includes a light emitting unit 10, a distance measuring optical system 20, a reference optical system 30, a light receiving unit 40, an eyepiece optical system (telescope) 50, and an arithmetic control unit 60 shown in FIG.

The light emitting unit 10 has a light emitting optical axis 11, and a light emitting element 12, a collimating lens 13, a non-prism mode aperture diaphragm 14 and a shutter unit 15 are arranged on the light emitting optical axis 11 so that the optical axes match. ing. The light emitting element 12 is, for example, a laser light emitting element that emits visible light of 690 nm as distance measuring light. The collimating lens 13 is a lens that collimates the light from the light emitting element 12 to make it parallel light and guides it to the shutter unit 15.

The aperture diaphragm 14 for the non-prism mode is a diaphragm having a rectangular or circular aperture on a black plate, and limits the beam diameter of the ranging light so as to be adapted to the non-prism ranging. The shutter unit 15 includes a fixed beam splitter 16 and a shielding plate 17 that is movable as shown by an arrow X by an actuator 28 (FIG. 2), and the shielding plate 17 allows distance measurement through the distance measuring optical system 20. The optical path is switched by shielding either the optical path OP ₂₀ or the reference optical path OP ₃₀ passing through the reference optical system 30.

As shown in FIG. 2, the light emitting element 12 is connected to a light emitting adjusting unit 18 as a light emitting adjusting unit. The light emission adjusting unit 18 is, for example, a digital potentiometer. The light emission adjusting unit 18 controls the light emission of the light emitting element 12, that is, the light emission of the light emitting unit 10.

The distance measuring optical system 20 has a distance measuring optical axis 21 that matches the extension of the light emitting optical axis 11, and an aperture diaphragm for prism mode (hereinafter, simply referred to as “aperture diaphragm”) 22 on the distance measuring optical axis 21. The dimming member 23 and the first deflection mirror 24 are arranged, and the second deflection mirror 26 is arranged so as to match on the reflected optical axis 25 of the first deflection mirror 24.

The aperture diaphragm 22 is, for example, a black plate having a rectangular aperture. FIG. 3 is a front view of the rectangular aperture stop 22. 4 (a) and 4 (b) are views showing the light flux around the light emitting unit 10 and the aperture diaphragm 22, FIG. 4 (a) is a plan view, and FIG. 4 (b) is a side view. The opening 22A of the aperture stop 22 is a rectangle having a horizontal width Ah and a vertical width Av.

As shown in FIG. 4A, the non-prism mode beam Bn shows an intensity distribution in which the center is high and the periphery is low in its horizontal cross section, but the horizontal width Ah of the opening 22A is larger than 0. It is set to be 0.5 times or less of the half-value full width FWHMh of the intensity distribution in the horizontal cross section of the beam Bn for the non-prism mode.

Further, as shown in FIG. 4B, the non-prism mode beam Bn shows an intensity distribution in which the center is high and the periphery is low in its vertical cross section, but the vertical width Av of the opening 22A is larger than 0. It is set to be large and 0.5 times or less of the half-value full width FWHMv of the intensity distribution in the vertical cross section of the beam Bn for the non-prism mode.

By this opening 22A, the prism mode beam Bp is limited to the size of the opening 22A (horizontal width Ah, vertical width Av) as shown in FIGS. 4 (a) and 4 (b). .. With such a configuration, the numerical aperture (NA) of the collimating lens 13 is limited, and the effect of making the intensity distribution of the ranging light substantially uniform is obtained. As a result, the deviation of the emission timing of the light beam in the distance measuring light beam of the light source becomes small, and the mispointing error can be reduced.

Further, as shown in FIG. 5, when the horizontal width Ah of the opening 22A is set to 0.5 times the half-value full width FWHMh of the intensity distribution in the horizontal cross section of the non-prism mode beam Bn, the horizontal width of the prism mode beam Bp is set. The width Wh is 0.5 times the half-value full width FWHMh of the intensity distribution in the horizontal cross section of the beam Bn for non-prism mode. At this time, only the light having an intensity of 84% or more of the peak intensity Bn _max is the beam Bp for prism mode. Will be emitted as. This also applies to the vertical direction of the beam.

Therefore, if the horizontal width Ah and the vertical width Av of the opening 22A are set to be 84% or more of the peak intensity of the non-prism ranging beam Bn _max in the horizontal direction and the vertical direction, the numerical aperture of the collimating lens 13 is increased. This has the effect of making the intensity distribution of the ranging light almost uniform. Therefore, the deviation of the emission timing of the light beam in the ranging beam is reduced, and the mispointing error is reduced.

The aperture diaphragm 22 is not limited to the configuration in which an opening is provided in the plate as described above, and the beam diameter of the distance measuring light is limited to the size of the opening 22A, and the distribution of the beam intensity is one in the beam. In this way, any type of aperture that is suitable for prism mode measurements can be used. For example, the element may change the transparency of the light to partially block the light and limit the shape of the beam. Further, the shape of the opening is not limited to the above example, and can be designed to be any shape such as an ellipse, a circle, a square, and a polygon.

Returning to FIG. 1, the dimming member 23 is a so-called ND (neutral density) filter, and attenuates the amount of light for distance measurement to a light amount suitable for prism mode measurement. Both the aperture diaphragm 22 and the dimming member 23 are connected to the actuator 28 shown in FIG. 2, and are evacuated from the distance measuring optical path OP ₂₀ when performing non-prism distance measurement, and are measured when performing reflection prism distance measurement. It is designed to be inserted into the distance light path OP ₂₀ . The first deflection mirror 24 and the second deflection mirror 26 may be any one that reflects light, and a mirror that totally reflects light or a dichroic mirror can be used.

The reference optical system 30 is provided between the light emitting unit 10 and the light receiving unit 40 described later, has a reference optical axis 31 that matches the optical axis of the branched light of the beam splitter 16, and collects light on the reference optical axis 31. One end 33a of the lens 32 and the optical fiber 33 is provided. The other end 33b of the optical fiber 33 is arranged in the vicinity of the light receiving portion 40, and the light receiving element 45 is arranged on the optical axis of the emitted light. The light receiving element 45 is irradiated through the light receiving element 45.

The light receiving unit 40 has a light receiving optical axis 41 whose distance measuring light coincides with the optical axis of the reflected light reflected by the object to be measured. The objective lens 42 and the dichroic prism 43 are arranged on the light receiving optical axis 41, and the light receiving element 45 is arranged on the reflected optical axis 44 of the dichroic prism 43.

As the light receiving element 45, for example, an avalanche hot diode (APD) or the like is used, but the light receiving element 45 is not limited thereto.

A bias setting unit 46 as a light receiving sensitivity adjusting unit is electrically connected to the light receiving element 45. The bias setting unit 46 is, for example, a reverse voltage circuit when the light receiving element is APD, and applies a bias voltage so that the light receiving element 45 has a required light receiving sensitivity.

The light receiving element 45 outputs a light receiving signal that changes according to the applied bias voltage, and the intensity of the light receiving signal increases as the bias voltage increases. That is, as the bias voltage increases, the sensitivity of the light receiving unit 40 increases. On the other hand, the noise included in the light receiving signal output from the light receiving unit 40 has a property of rapidly increasing as the bias voltage applied to the light receiving element 45 approaches the breakdown voltage (RV). In the present specification, the breakdown voltage (RV) means a voltage at which the light receiving element 45 is saturated.

As described above, the sensitivity and responsiveness of the light receiving element 45 change depending on the bias voltage. The light receiving surface 45a of the light receiving element has a predetermined area, that is, a finite area, and does not have the same light receiving sensitivity and responsiveness over the entire area of the light receiving surface when considering a minute portion of the light receiving surface.

The eyepiece optical system 50 has an eyepiece optical axis 51 that matches the extension of the light receiving optical axis 41, and a focusing lens 52, an erecting prism 53, a collimation plate 54, and an eyepiece lens 55 are arranged on the eyepiece optical axis 51. It is a so-called telescope. The focusing lens 52 is attached so as to be movable back and forth on the eyepiece optical axis 51 to adjust the focus. The upright prism 53 is a prism that converts into an erect image, such as a polo prism. The collimation plate 54 is a transparent plate provided with a collimation line (reticle) such as a cross. The user can visually collimate with the eyepiece 55.

The arithmetic control unit 60 includes a CPU 61 and a storage unit 62. The arithmetic control unit 60 controls the light emission adjusting unit 18 and controls the light emitting output of the light emitting element 12 via the light emitting adjusting unit 18. The arithmetic control unit 60 measures the distance to the object to be measured based on the received signal of the reflected distance measuring light received by the light receiving unit 40 received via the signal processing unit 71 and the internal reference light.

Further, the arithmetic control unit 60 emits a control signal to the bias setting unit 46, controls the bias voltage applied to the light receiving element 45 from the bias setting unit 46, and sets or adjusts the sensitivity of the light receiving element 45. Further, the arithmetic control unit 60 sets the measurement mode of the surveying device based on the input from the operation unit 73 and the operation. Further, the arithmetic control unit 60 outputs the measurement result and displays it on the display unit 72.

Hereinafter, the operation of the surveying apparatus 1 will be described with reference to FIG. The surveying device 1 is capable of two types of measurement, non-prism mode measurement and prism mode measurement. In the non-prism mode measurement, the measurement object 80 is an arbitrary measurement point, but in the prism mode measurement, the measurement object 80 is a prism.

Non-prism mode measurement Non-prism mode measurement will be described. First, the operation unit 73 sets the measurement mode to non-prism mode measurement.

When the non-prism mode measurement is selected, the arithmetic control unit 60 commands the bias setting unit 46 to apply the measurement maximum bias voltage to the light receiving element 45. Here, the measured maximum bias voltage means the maximum value of the bias voltage used for the measurement. The measured maximum bias voltage is, for example, 91% of the breakdown voltage (RV).

Further, when the aperture stop 22 is arranged in the distance measurement optical path OP ₂₀ , the arithmetic control unit 60 drives the actuator 28 to retract the aperture stop 22 from the distance measurement optical path OP ₂₀ .

Next, the light emission adjusting unit 18 is driven by a command from the arithmetic control unit 60, and by driving the light emitting adjusting unit 18, light is emitted from the light emitting element 12, collimated by the collimating lens 13, and guided to the shutter unit 15. .. At this time, the output of the light emission adjusting unit (light emission output (LD)) is, for example, 4.5 mW.

The arithmetic control unit 60 controls the shutter unit 15 to selectively switch between the range-finding optical path OP ₂₀ and the internal range-finding optical path OP ₃₀ . When the range-finding optical path OP ₂₀ is selected, the light that has passed through the shutter unit 15 is guided to the range-finding optical path OP ₂₀ as the range-finding light, and is irradiated on the measurement object 80 shown by the broken line, and the measurement object 80 is irradiated. After being reflected by, it is guided to the light receiving element 45.

On the other hand, when the reference optical path OP ₃₀ is selected, the light branched by the shutter unit 15 is condensed as reference light by the condenser lens 32 and incident on one end 33a of the optical fiber 33 to be incident on the optical fiber 33. It is emitted from the other end 33b of the above, is condensed by the condenser lens 34, and is guided to the light receiving element 45.

The light receiving element 45 selectively injects the range-finding light and the reference light. The reference light is light quantity adjusted by a light quantity adjusting means (not shown).

The light receiving unit 40 is connected to the calculation control unit 60, and the distance to the measurement object 80 is calculated based on the light receiving signals of the ranging light and the reference light. The result obtained by the calculation is displayed on the display unit 72. The reference light is used to correct the fluctuation of the ranging value due to the temperature change of the light emitting element 12.

Prism mode measurement Next, prism mode measurement will be described. When the prism mode measurement is selected from the operation unit 73, the arithmetic control unit 60 commands the bias setting unit 46 to apply a bias voltage to the light receiving element 45. Here, the bias voltage (V) is constant regardless of the distance measured, but is reduced from the measured maximum bias voltage, and is 91% RV> V ≧ 85% with respect to the breakdown voltage (RV). It is preferable to satisfy the relationship of RV. The value of the bias voltage can be appropriately set in this range according to the required sensitivity.

Further, the arithmetic control unit 60 drives the actuator 28 to insert the aperture stop 22 into the distance measuring optical path OP ₂₀ .

Next, the light emission adjusting unit 18 is driven by a command from the arithmetic control unit 60, and by driving the light emitting adjusting unit 18, light is emitted from the light emitting element 12, collimated by the collimating lens 13, and guided to the shutter unit 15. .. At this time, the output of the light emission adjusting unit (light emission output (LD)) is smaller than the light emission output in the non-prism mode measurement, and it is preferable that 4.5 mW> LD ≧ 1.5 mW.

The light emitted from the light emitting element 12 is reflected by the prism, which is the measurement target 80, through the same path as in the non-prism mode measurement, and is similarly guided to the light receiving element 45.

(Examples 1 to 3, Comparative Example 1)
FIG. 6 is a graph showing a distance measurement error when prism mode measurement is performed using the surveying device 1 according to the embodiment. As the measuring device 1, a laser diode was used as the light emitting element, an APD was used as the light receiving element 45, and an aperture diaphragm 22 having a horizontal width of 2.0 mm and a vertical width of 0.3 mm was used. This is a value corresponding to 0.5 times or less of the full width at half maximum in each of the horizontal direction and the vertical direction of the intensity distribution of the beam for non-prism mode measurement.

6 (a), 6 (b), 6 (c), and 6 (d) show the results of Comparative Example 1, Example 1, Example 2, and Example 3, respectively. The measurement conditions of each example are as shown in Table 1. In each figure of FIG. 6, the horizontal axis indicates the distance (m) to the prism, and the vertical axis indicates the error (mm) from the baseline. Further, the broken line in the center of the vertical axis, which is parallel to the horizontal axis, indicates that the error from the baseline is 0 mm, and the two broken lines parallel to the horizontal axis, drawn above and below the baseline, are the relevant ones of the surveying device 1. An error (hereinafter referred to as “required error”) (mm) allowed for a predetermined measurement accuracy (standard value) in the apparatus is shown. It has already been confirmed that the mispointing error is reduced in this device.

With reference to FIG. 6A, in the comparative example measured under the same emission output (LD) and same bias voltage (V) conditions as in the non-prism mode measurement, the values vary as a whole, and an error occurs from 0 m to 20 m. It can be seen that the error deviates from the required error, especially at a short distance of 1 m to 4 m. This indicates that, as described above, the short-distance error appears remarkably due to the deviation of the optical axis due to the prism being at a short distance and the insertion of the aperture stop.

Referring to FIG. 6 (b), by lowering the bias voltage (V) to 87% of the breakdown voltage (RV), there is an overall error, especially at a distance of 2 m to 20 m, as compared to Comparative Example 1. Can be seen to be decreasing. Under the conditions of the first embodiment, the distance measuring error is within the range of the required error of the surveying device 1.

In this way, the short-distance error can be reduced by reducing the bias voltage (V) by the bias setting unit 46 during the prism mode measurement.

Referring to FIG. 6 (c), by lowering the light emitting output (LD) of the light emitting element 12 from 4.5 mW to 2.6 mW, as compared with Comparative Example 1, in particular 1.3 m to 14 m as a whole. It can be seen that reducing the error and lowering the emission output (LD) at the distance of 2 is effective in reducing the error at a short distance. Under the conditions of the second embodiment, the error is within the range of the required error of the surveying device 1.

In this way, when the prism mode measurement is performed, the light emission adjusting unit reduces the light emission output (LD), so that the short-distance error can be reduced.

Referring to FIG. 6 (d), the bias voltage (V) is lowered to 87% of the breakdown voltage (RV), and the emission output (LD) is lowered to 2.6 mW. In particular, it can be seen that the error is significantly reduced at a distance of 1.3 m to 20 m, and the variation in the error due to the distance is reduced.

In this way, when the bias setting unit reduces the bias voltage (V) and the light emission adjustment unit reduces the light emission output (LD) during prism mode measurement, the respective effects act synergistically to reduce the short-distance error. Can be reduced.

The inventor made measurements by changing the bias voltage (V) and the emission output (LD) in various ways, and found that the bias voltage (V) was 91% RV> V ≧ 85% with respect to the breakdown voltage (RV). In the range where the RV relationship is satisfied and the emission output (LD) is 4.5 mW> LD ≧ 1.5 mW, the short-range error is significantly reduced and the range-finding error is suppressed within the range of the required error of the measuring device 1. I understand.

Even when the bias voltage (V) is lowered to less than 85% of the breakdown voltage (RV), this tendency does not change, and the ranging error can be suppressed to the range of the required error. However, if the bias voltage (V) is lowered, the sensitivity of the light receiving element 45 is lowered, and the measurable distance may be shortened.

On the other hand, even when the light emission output (LD) is lowered to less than 1.5 mW, this tendency does not change, and the distance measurement error can be suppressed to the range of the required error. However, if the light emission output (LD) is lowered, the amount of light is reduced and the measurable distance may be shortened.

(Example 4)
Further, as another embodiment, another machine having the same configuration as the surveying apparatus 1 according to the embodiment of the first to third embodiments is used, and the aperture diaphragm 22 has a horizontal width of 5.4 mm and a vertical width of 0.3 mm. Prism mode measurement was performed using. This is a value corresponding to 0.5 times or less of the full width at half maximum in each of the horizontal direction and the vertical direction of the intensity distribution of the beam for non-prism mode measurement. The results are shown in FIG.

The measurement conditions of each example are as shown in Table 2.

As can be seen from FIG. 7, even when the widths of the aperture diaphragms 22 are different, the short-distance error is reduced by reducing the bias voltage as in the first embodiment. Further, although not shown, the same results as in Examples 2 and 3 were obtained even when the emission output (LD) was reduced.

Although the preferred embodiments of the present invention have been described above, the above embodiments and examples are examples of the present invention, and these can be combined based on the knowledge of those skilled in the art, and such embodiments are possible. Is also included in the scope of the present invention.

1 Surveying device 10 Light emitting unit 18 Light emitting unit 22 Aperture diaphragm 30 Distance measuring optical system 40 Light receiving unit 45 Light receiving element 46 Bias setting unit (light receiving sensitivity adjustment unit)
Ah Horizontal width of aperture stop Av Vertical width of aperture stop

Claims (1)

A light emitting part that emits range-finding light with an intensity distribution in which the center is high and the periphery is low,
A light receiving part that receives reflected distance measurement light from the object to be measured,
The shape of the beam is limited so as to be in the range of 84% or more of the center intensity of the non-prism distance measuring beam of the distance measuring light, or the horizontal width and the vertical width of the opening are larger than 0 and the non. It is equipped with an aperture aperture that is 0.5 times or less of the half-value full width of the intensity distribution in each of the horizontal and vertical cross sections of the prism distance measuring beam, and the distance measuring light is passed through the measurement object to receive the light. A range-finding optical system for guiding to the unit, a light-receiving sensitivity adjustment unit that electrically adjusts the light-receiving sensitivity of the light-receiving unit by adjusting the bias voltage (V), and a light-receiving sensitivity adjustment unit.
A light emitting adjustment unit that adjusts the light emitting output of the light emitting unit,
It is a surveying device that is equipped with an arithmetic control unit that calculates a distance based on the received signal of the reflected distance measuring light and can measure a distance by selecting prism mode measurement and non-prism mode measurement.
If prism mode measurement is selected
The aperture diaphragm is arranged in the distance measuring optical path, and the aperture diaphragm is arranged in the distance measuring optical path.
The light receiving sensitivity adjusting unit adjusts the bias power (V) in the range of 91% RV> V ≧ 85% RV with respect to the breakdown voltage (RV), and the light emitting adjusting unit adjusts the light emitting output (LD). ) Is adjusted in the range of 4.5 mW> LD ≧ 1.5 mW so that the error of the measured distance value is equal to or less than the allowable value for a predetermined measurement accuracy.

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