JP2001051058A - Apparatus for measuring distance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a wasteful measurement and to shorten the measuring time by repeating measuring while scanning in a measuring direction, and altering the measuring accuracy to a measuring point at every part in a measuring area. SOLUTION: A pulse light of a laser light source 11 is reflected by a polarizing mirror 31, and externally directed. The reflected and returned pulse light is converged to a photodetector 15 by a condenser lens 14, and the photodetector 15 outputs a light quantity conversion signal S15 of an amplitude corresponding to the received light quantity. The signal S15 is amplified by a signal processor 22, sampled and quantized by an A-D converter 23. A CPU 61 specifies a photodetecting time point based on the photodetected data of given number of times, calculates a flying time Tf from a transmitting time point to a receiving time point, calculates distance data DL response to a distance between objects from the time Tf and a light propagating velocity, and outputs the distance. The CPU 61 also refers to a measuring accuracy map of a map memory 26, gives a designation responsive to a set accuracy at each measuring point to a scanner controller 63, sets a stopping time of the mirror 31 only to a measurement necessary time, and does not stop a projecting direction of a set value 0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring apparatus for projecting reference light to obtain distance information to an object.

[0002]

2. Description of the Related Art A so-called flight time (TOF: ti) from transmission of a light pulse to reception of a pulse reflected by an object and returned.
By measuring the me of flight, the distance between the objectives can be determined by applying a known light propagation velocity. In principle, the closer the pulse width is to zero, the higher the measurement accuracy is. However, in practice, the pulse width is equal to or larger than a value determined by constraints such as light source response and reception sensitivity. In a general distance measuring device, the pulse width is set to a value of about 50 to 100 ns at which a resolution of about several cm can be obtained, and the waveform is a single-peak mountain-like shape. By detecting the peak (peak) of the received light waveform and specifying the time of reception, highly accurate measurement can be performed regardless of the magnitude of the amplitude of the received light waveform.

As an application example of this distance measuring method to a range finder, Japanese Patent Application Laid-Open No. 7-218632 describes an apparatus configuration in which a plurality of laser light sources emit light in order and project light in different directions. . In addition, the present applicant has proposed a distance measuring device having a configuration in which the projection direction is changed by a deflecting mirror (Japanese Patent Application No. 11-74837). When projecting pulsed light in many directions to measure the object shape finely,
Scanning in which the projection angle is changed by the deflecting mirror is more advantageous than arranging a light source for each projection direction in terms of simplifying the device configuration.

[0004]

By providing a scanning mechanism such as a deflecting mirror as described above, measurement in multiple directions can be performed more quickly than in the case where the distance measurement is repeated by changing the position and orientation of the distance measurement device itself. Can be done. For example, if the deflecting mirror is intermittently driven at a constant angle so as to perform two-dimensional scanning, the distance measuring device can be used as a three-dimensional input device. However, ranging may be useless for a part of a number of projection directions (ranging directions) determined by the setting of the scanning operation. For example, ranging in a direction deviating from an object to be measured is useless. In particular, when repeating transmission and reception of pulsed light in each direction to improve measurement accuracy and average measurement data from multiple measurements or select measurement data with the least influence of noise, useless ranging The number of times increases. From the viewpoint of reducing the measurement time and the amount of measurement data, it is desirable to perform only effective distance measurement.

In some applications, highly accurate measurement data is required for a part of the object, and measurement is required for the other part, but the accuracy may be relatively low. Even in such a case, conventionally, it is necessary to perform measurement with uniform accuracy in all directions.

An object of the present invention is to reduce the measurement time and the amount of measurement data by eliminating useless distance measurement. Another object is to improve the practicability by enabling setting change of the measurement accuracy for each measurement direction.

[0007]

In the present invention, for example, a set value of the number of measurements for each direction is stored, and scanning is performed based on the set value. If the set value is set to zero (0), no distance measurement is performed. As the set value is increased, the number of measurements increases, and high-precision (high reliability) data can be obtained by averaging or the like. If the user interface is configured so that the scanning range is displayed on the monitor and the direction is specified by specifying the area of the monitor image, the user can easily set the number of measurements according to the application.

According to a first aspect of the present invention, there is provided a distance measuring apparatus for measuring a distance to an object by projecting reference light and receiving light reflected by the object. Scanning means for repeating the measurement while scanning, and control means for changing the measurement accuracy with respect to the measurement point for each portion in the measurement area that is a scannable range.

In the distance measuring apparatus according to the second aspect of the present invention,
The control unit changes the number of measurements as the measurement accuracy. 4. The distance measuring device according to claim 3, wherein the control means operates the scanning means at irregular intervals so as to increase or decrease the time for maintaining the measurement direction according to the number of measurements.

According to a fourth aspect of the present invention, there is provided a distance measuring apparatus, wherein: a photographing means for photographing with the measurement area as a field of view; a display for displaying a photographed image obtained by the photographing means; And an operation input means for designating the part as the part.

[0011] In the distance measuring apparatus according to the present invention,
The operation input means has a function of designating a change value of the measurement accuracy. The distance measuring device according to the sixth aspect does not measure a range other than the portion designated by the operation input means.

[0012] In the distance measuring apparatus according to the present invention,
The control means sequentially determines the measurement results for each of a plurality of measurement directions sequentially obtained during the scanning period, and changes the measurement accuracy in subsequent measurements according to the determination results.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view schematically showing a distance measuring operation according to the present invention. The pulse light is projected from the starting point A toward the virtual plane VS, and the flight time Tf of the pulse light is measured. The projection direction is sequentially changed by a predetermined angle in the vertical and horizontal directions by the deflecting mirror 31 so as to scan the virtual plane VS. The three-dimensional input of the object Q can be performed by measuring the inter-object distances in a number of directions from the starting point A to the virtual plane VS. Each projection direction is
This corresponds to a sampling point (measurement point) in three-dimensional input.

FIG. 2 is a block diagram of a three-dimensional input device according to the present invention. Solid arrows in the figure indicate the flow of data,
The broken arrows indicate the flow of the control signal. 3D input device 1
Is an optical system 10 for transmitting and receiving pulsed light, and a scanning mechanism 3
0, an optical system 40 for monitor photographing, various electric circuit elements, and an input means 70 for operation designation.
The optical system 10 includes a laser light source (semiconductor laser) 11, a light projecting lens 12 for defining a spread angle of a light beam, a reflecting prism 13 for setting an optical path, a light receiving lens 14, and a photodetector (photodiode) 15. Have been. The laser light source 11 emits pulsed light having a pulse width of about 100 ns in response to power supply from the light emitting driver 21.
The pulsed light enters the scanning mechanism 30 through the light projecting lens 12 and the reflecting prism 13 in order, is reflected by the deflecting mirror 31, and travels to the outside. The pulse light reflected outside and returned to the deflecting mirror 31 is condensed by the light receiving lens 14 and is detected by the photodetector 15.
Incident on. The photodetector 15 outputs a photoelectric conversion signal S15 having an amplitude corresponding to the amount of received light.

The photoelectric conversion signal S15 is supplied to a signal processing circuit 22.
After being appropriately amplified by the A / D converter 23, it is sampled and quantized by the A / D converter 23 at a constant period. The received light data obtained by the sampling is sequentially written into the waveform memory 24. The waveform memory 24 can store waveforms for a time corresponding to the maximum measurable distance. The CPU 61 is responsible for specifying the light receiving time based on the light receiving data and calculating the flight time (light propagation time) Tf from the transmission time to the light receiving time. By determining the peak of the pulse by calculating the center of gravity in specifying the light receiving point, the resolution can be improved as compared with the case where the local maximum value of the data is regarded as the peak. The transmission time is specified by starting waveform storage in synchronization with the light emission control. A timing controller 62 is provided for the control. However, the peak may be detected by monitoring the actual light emission amount.

In the calculation of the flight time Tf, the measurement accuracy can be improved by repeating the transmission and reception of the pulse light to increase the number of measurements per direction. CPU 61
Gives an instruction corresponding to the accuracy set for each measurement point to the timing controller 62 and the scanner controller 63 with reference to a measurement accuracy map described later stored in the map memory 26, The flight time Tf is calculated based on the received light data. Then, the distance data DL corresponding to the inter-object distance is calculated from the flight time Tf and the known light propagation speed (3 × 10 ⁸ m / s), and written to the output memory 25. The distance data DL is appropriately transferred to an external device (for example, a computer) connected via the connector 27. Output memory 25, map memory 2
6, and a data transfer controller 65 for accessing an image memory 53 described later. The device configuration related to output to the outside is not limited to the example. For example, the received light data may be output from the three-dimensional input device 1, and the distance data DL may be obtained by an external computer. Three
The output of the dimension input device 1 can be used as the photoelectric conversion signal S15. Further, there is a modification in which an external device controls the light emitting driver 21 and the like.

In the three-dimensional input device 1, the deflecting mirror 31 is intermittently driven to change the projection direction. During the distance measurement in one projection direction, the driving of the deflecting mirror 31 is temporarily stopped, and the projection direction is maintained. The suspension time of the deflecting mirror 31 is longer as the set value of the number of measurements in the projection direction is larger. That is, the deflecting mirror 31 is stopped for the time required for the measurement. For the projection direction in which the set value of the number of measurements is 0, the distance measurement is substantially omitted without stopping the deflection mirror 31. As a result, the time required for scanning can be reduced.

The optical system 40 includes a variable magnification lens 41, an infrared cut filter 42, and a two-dimensional imaging device (C
CD sensor, CMOS sensor, etc.) 43,
Imaging is performed with the scannable range (virtual plane) as the field of view. The lens 41 is arranged such that its optical axis is parallel to the projection direction when projecting the pulsed light in front of itself, and the principal point and the starting point of the projection are located in the same plane orthogonal to the optical axis, It is controlled by the lens controller 64. After the output of the imaging device 43 passes through the signal processing circuit 51, A /
The data is quantized by the D converter 52 and stored by the image memory 53. Then, the photographing data read from the image memory 53 is converted into an image signal by the D / A converter 54 and displayed on the monitor 55. In this example, n stages (here, three stages) of zooming are possible by controlling the lens 41, and the rotation angle range (scanning range) of the deflecting mirror 31 is set in conjunction with the zooming operation by the user. Table 1 shows the setting of the number of measurement points in the mode in which the deflection width (measurement interval) is constant, and Table 2 shows the setting of the deflection width in the mode in which the number of measurement points is constant.

[0019]

[Table 1]

[0020]

[Table 2]

The user can confirm and change the scanning range by looking at the monitor photographed image, and can operate a pointing device (not shown) provided on the input means 70 to specify the area on the monitor screen. The setting of the measurement accuracy (the number of times of measurement) at an arbitrary measurement point can be changed.

FIG. 3 is a perspective view showing the configuration of the scanning mechanism. The scanning mechanism 30 includes a deflecting mirror 31, a motor 32 for vertical deflection, a mirror box 33, and a motor 3 for horizontal deflection.
4 and a fixed frame 35. In the vertical deflection, the mirror box 33 is fixed,
The deflection mirror 31 in the mirror box 33 rotates. The horizontal deflection is performed by rotating the mirror box 33 together with the mirror box 33. Holes large enough to allow transmission light and reception light to pass therethrough are provided in the bottom portions of the mirror box 33 and the fixed frame 35.

In the illustrated mirror arrangement state, the pulse light P1 incident on the deflection mirror 31 from the reflection prism 13
Is deflected in a direction corresponding to the angular position of the deflecting mirror 31, and travels toward an external object Q. The pulse light P1 that has reached the object Q is reflected on the object surface. As long as the object surface is not specular, its reflection will be diffuse. Therefore, at least a part of the reflected pulse light P <b> 2 goes to the three-dimensional input device 1 even if the incidence on the object surface is not normal incidence. The pulse light P2 returned to the three-dimensional input device 1 is deflected by the deflecting mirror 31, and enters the photodetector 15 via the light receiving lens.

FIG. 4 is a schematic diagram of a scanning mode. FIG.
If the main scanning is of the reciprocating type as shown in FIG. 9A, the virtual plane can be efficiently scanned. However, when there is a deviation of the mirror position due to the rotation direction of the deflecting mirror, if the main scanning is of a one-way type as shown in FIG. 4B, the variation of the measurement position can be reduced.

FIG. 5 is an explanatory view of a modification of the photographing optical path.
When the optical axis of the monitor shooting is parallel to the projection direction when projecting directly in front, the designated point on the monitor image and the measurement point where the pulse light is actually projected are located between the optical axes as shown in FIG. It shifts by a distance. Usually, this deviation is not substantially a problem. However, if you want to minimize the deviation,
As shown in FIG. 5B, an optical system 40b having a configuration in which the optical axis of distance measurement and the optical axis of photographing are made to coincide with each other using the half mirror 45 is preferable. The half mirror 45 is arranged so that the optical path length p between the half mirror 45 and the projection start point is equal to the optical path length q between the main point of the lens 41.

FIG. 6 is an explanatory diagram of the area designation related to the setting of the measurement accuracy, FIG. 7 is a flowchart of the setting operation of the measurement accuracy, and FIG. 8 is a schematic diagram of the contents stored in the map memory. When the user specifies the accuracy setting mode, the measurement accuracy map M1 stored in the map memory 26 is initialized, and the monitor images G1 captured by the optical system 40 are displayed (# 1 to # 3 in FIG. 7). . The measurement accuracy map M1 is a data set indicating the number of measurements at each measurement point (projection direction). As shown in FIG. 6A, the user designates a rectangular area of an arbitrary position and size of the monitor image G1 in a well-known diagonal two-point designation format and inputs a desired accuracy level (# 4 to # 7). In this embodiment, it is possible to set the accuracy in five levels of levels 0 to 4. Table 3 shows the number of measurements at each level.

[0027]

[Table 3]

As shown in the monitor image G2 in FIG. 6B, the designated areas g1 and g2 are highlighted (#
8). Levels may be distinguished by color,
The level may be indicated by a letter. Since the same level can be specified for a plurality of different areas, a desired level can be specified for an area having a complex shape other than a quadrangle by repeating area specification and level input. The minimum size of the area may be a size corresponding to one measurement point or a size corresponding to a plurality of measurement points. That is, the level setting may be performed in units of measurement points, or a predetermined number of measurement points may be performed in block units.

In accordance with the specification on such a monitor,
As shown in FIG. 8, regions g1, g in the measurement accuracy map M1
The level values are rewritten for the address areas ag1 and ag2 corresponding to No. 2 (# 9 and # 10 in FIG. 7). In this example, since the default value is 0, the measurement is omitted for the measurement points corresponding to the area not specified on the monitor.

Since the measurement accuracy is set for each measurement point,
It is necessary to output information indicating the measurement accuracy of the distance data DL of each measurement point to an external device. Therefore, the measurement results of the measurement points are stored in the output memory 25 in the measurement order, and the measurement accuracy map M1 is also stored at the same time. As a result, it is possible to determine with which measurement accuracy the measurement result is obtained for each measurement point. The measurement results of the measurement points are not limited to the measurement order, but may be rearranged in a specific rule order. When the measurement accuracy is uniform, it is not necessary to save the measurement accuracy map M1, and it is sufficient to add and save a header indicating the arrangement order of the measurement result data and the measurement accuracy level. Also,
Even when the measurement accuracy is not uniform, there is a case where the user does not need the accuracy information for each measurement point, and in that case, there is no need to output the accuracy information. However, even when it is not necessary to output the accuracy information, when the level 0 setting is included, the measurement point map M2 (see FIG. 8) is simultaneously saved so that the measurement data and the measurement point can be associated with each other. I do. The measurement point map M2 is a data set of one bit per measurement point for identifying whether or not measurement has been performed at each measurement point.

FIG. 9 is a diagram showing a second example of setting the measurement accuracy. In the above-described example, the user performs the division of the scanning range. Alternatively, the accuracy may be set in advance by dividing the scanning range. In the example of FIG. 9, a setting is made such that the measurement accuracy changes stepwise from the center to the outside with respect to the scannable range (virtual plane) Am0. The accuracy level of the central portion Am1 is the highest, 4; the accuracy level of the portion Am2 of a predetermined width surrounding the central portion Am1 is 3, and the accuracy level of the peripheral portion Am3 is 2. Generally, the scanning range is determined so that the measurement target is located at the center. That is, the center portion Am1 is regarded as the most important. Therefore, according to the setting of FIG. 9, it is possible to perform measurement with appropriate accuracy according to the degree of importance.

FIG. 10 is a diagram showing a third example of the setting of the measurement accuracy, FIG. 11 is a diagram showing the contents stored in the map memory corresponding to FIG. 10, and FIG. 12 is a flowchart of the measuring operation corresponding to FIG.

The accuracy of subsequent measurements can be automatically changed according to the measurement results obtained sequentially during scanning. The scanning is advanced in accordance with the measurement accuracy map M1 (# 11 to # 15 in FIG. 12). If the latest measurement result falls within the range of interest (for example, 10 to 20 m), the measurement point and the measurement points in the vicinity of the adjacent 8 are measured. Then, the measurement accuracy level of the measurement point scanned thereafter is changed (# 16, # 17). If the number of measurements increases due to the level change, additional measurements for the increase are performed (# 18, # 21). In FIG. 11, the default value of the measurement accuracy is level 2 and the measurement accuracy is 5
The measurement accuracy of the measurement points is changed to level 4. When the measurement of the set level is completed, the distance data DL is calculated by averaging the received light data for the number of measurements (# 19).
This operation is repeated until the measurement at the final measurement point is completed (# 20, # 14 in FIG. 12).

By updating the accuracy level of each measurement point in this way, three-dimensional input of an object within a preset distance range becomes highly accurate. Note that the measurement accuracy may not be updated for a measurement point whose measurement result is within the attention distance range, and the measurement accuracy may be updated only for a measurement point that is scanned after that around the measurement point. The measurement accuracy may be updated only for the measurement points whose measurement results fall within the range of interest.
Further, the measurement accuracy may be updated not only for the measurement points and the vicinity thereof but also for all the measurement points scanned thereafter.

In the above-described embodiment, the result calculated based on a plurality of measurement data is stored as the measurement data at that point (that is, one data is stored for each measurement point). The measurement data of the measurement may be stored as it is (that is, the number of stored data corresponds to the accuracy of each measurement point). In this case, it is necessary to store the measurement accuracy map. This is because the number of data corresponds to which point based on the measurement accuracy map.

In the above-described embodiment, an example has been described in which the distance is measured based on the time from the projection of the pulsed light to the reception of the pulsed light. However, the present invention is not limited to this. When measuring the shape of an object, the present invention is applicable.

In the above-described third example, the measurement accuracy map M1 is changed according to the measurement result. However, the measurement at the next measurement point is performed according to the measurement result without using the measurement accuracy map. The accuracy (the number of measurements) may be controlled.
That is, if the measurement result of the range of interest is obtained at a certain measurement point during scanning, the subsequent accuracy is set to level 4, and if the measurement result deviates from the range of interest, the subsequent accuracy is set to level 2.

[0038]

According to the first to seventh aspects of the present invention,
Measurement accuracy can be set independently for each projection direction, eliminating wasteful measurement that would occur when setting measurement accuracy uniformly for all projection directions within the scanning range, reducing measurement time and measuring data volume. Can be reduced.

According to the fourth to sixth aspects of the present invention, the user can individually set the measurement accuracy in a plurality of measurement directions according to the application.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a distance measuring operation according to the present invention.

FIG. 2 is a block diagram of a three-dimensional input device according to the present invention.

FIG. 3 is a perspective view illustrating a configuration of a scanning mechanism.

FIG. 4 is a schematic diagram of a scanning mode.

FIG. 5 is an explanatory diagram of a modified example of a photographing optical path.

FIG. 6 is an explanatory diagram of area designation related to measurement accuracy setting.

FIG. 7 is a flowchart of a measurement accuracy setting operation.

FIG. 8 is a schematic diagram of the contents stored in a map memory.

FIG. 9 is a diagram illustrating a second example of the setting of measurement accuracy.

FIG. 10 is a diagram showing a third example of setting of measurement accuracy.

FIG. 11 is a diagram showing storage contents of a map memory corresponding to FIG. 10;

FIG. 12 is a flowchart of a measurement operation corresponding to FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Three-dimensional input device (distance measuring device) P1, P2 Pulse light (reference light) 10 Optical system (transmission means, reception means) 30 Scanning mechanism (scanning means) 31 Deflection mirror 61 CPU (control means) Tf Flight time DL Distance Data 26 Map memory (Memory) 40 Optical system (Photographing means) 55 Display 70 Input means (Operation input means)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Sukebe 2-3-113 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Hiroshi Uchino Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 2-3-1-3 Osaka International Building Minolta Co., Ltd. (72) Inventor Takashi Kondo 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka International Building Minolta Co., Ltd. 2F065 AA02 AA06 DD06 FF12 FF32. CA03 CA23 CA61 CA65 CA70 DA01 DA09 EA04 EA40

Claims (7)

[Claims] 1. A distance measuring device for measuring a distance to an object by projecting a reference light and receiving a reflected light from the object, wherein the measurement is repeated while scanning in a measuring direction. A distance measuring device comprising: a control unit that changes a measurement accuracy for a measurement point for each part in a measurement area within a scanable range. 2. The distance measuring apparatus according to claim 1, wherein said control means changes the number of measurements as said measurement accuracy. 3. The distance measuring apparatus according to claim 2, wherein said control means operates said scanning means at irregular intervals so as to increase or decrease the time for maintaining the measurement direction in accordance with the number of measurements. 4. A photographing means for performing photographing with the measurement area as a field of view, a display for displaying a photographed image obtained by the photographing means, and an operation for designating an arbitrary area of the photographed image as the portion. The distance measuring device according to claim 1, further comprising: input means. 5. The distance measuring apparatus according to claim 4, wherein said operation input means has a function of designating a change value of said measurement accuracy. 6. The distance measuring device according to claim 4, wherein the measurement of a range other than the portion designated by the operation input means is not performed. 7. The control unit according to claim 1, wherein the control unit sequentially determines the measurement results in each of a plurality of measurement directions sequentially obtained during a scanning period, and changes the measurement accuracy in subsequent measurements according to the determination results. The distance measuring device as described.