JP3412139B2 - Calibration method of three-dimensional distance measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calibration method for a three-dimensional distance measuring device in which a light projector capable of irradiating a light beam in an arbitrary direction and a light receiver for observing its reflection are combined.

[0002]

2. Description of the Related Art Generally, when three-dimensional measurement is performed using a visual sensor, it is necessary to calibrate the sensor. At this time, the parameters that must be obtained are the focal length of the visual sensor, distortion, image center, and the position and orientation of the sensor itself in the three-dimensional space. Of these, the focal length,
The distortion and the image center are values unique to the sensor and are called internal parameters. The position and orientation of the sensor itself in the three-dimensional space are values related to the installation of the sensor and are called external parameters.

If the three-dimensional distance measuring device is limited to a two-dimensional surface range sensor (to be referred to as 2DS hereinafter) which will be described later, internal parameters can be adjusted at the time of shipment and measurement is not necessary. Regarding external parameters,
Although it is necessary to calculate for each of the light emitting device and the light receiving device,
In 2DS, the detection range and the detection accuracy are determined by the positional relationship between the light receiving device and the light projecting device (hereinafter referred to as an external parameter). Conventionally, the following method has been adopted as a method for determining the external parameter.

First, a planar light emitting device is fixed to a plurality of points whose positions in space are known, and this is observed by a light receiver. The position and orientation of the light receiver in the space are calculated from this observation information and the positional relationship between the light emitting points fixed in the space. next,
The light emitting device is replaced with a projection plate, and the projection plate is irradiated with light rays from a projector. At this time, the irradiation direction is sequentially changed so as to include the entire measurement area. In the receiver,
Reflected light is detected when the projection plate is illuminated, and the irradiation direction of the projector at the time of detection is recorded. An external parameter of the projector is calculated from position information of the plurality of projection plates and irradiation direction information of the projector for each projection plate. Finally, the two external parameters are converted into a coordinate system with the focal point on the light receiver side as a reference.

[0005]

The present inventor has found the following problems as a result of examining the above-mentioned prior art.

In the conventional calibration method for the three-dimensional distance measuring apparatus, the apparatus for calibration is complicated and the operation is complicated. Therefore, when performing highly accurate calibration, there is a problem that a strict operation is required and the time required for calibration becomes long.

An object of the present invention is to provide a highly accurate calibration method using a simple and easy method in a three-dimensional distance measuring device.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0009]

The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, according to the present invention, a light emitting device capable of irradiating a light beam in an arbitrary direction projects the light beam on an object, and the light beam reflected by the object is observed from another angle by a light receiving device, and the light beam projected at this time is projected. Calibration of a three-dimensional distance measuring device for measuring a distance to an object using light information and light receiving information
A method, wherein the object is replaced with a plane projection plate having a figure with different reflectance at a predetermined position and movable horizontally or vertically, and a light beam is emitted from the light emitting device to the projection plate.
And the light rays reflected by the figures with different reflectances on the projection plate are observed by the light receiving device, and the amount of light received by the light receiving device.
The operation of detecting the figure position on the projection plate from the difference of
By performing a plurality of times while changing the position of the projection panel, the
A plurality of light projection direction of the light beam is projected from the light-emitting device, and a front
Serial receiving position information of the light receiving device in each light projection direction, parallel
Further, it is characterized in that graphic position information on the projection plate in each of the projection directions is calculated as reference data.

In a preferred embodiment of the present invention, the above 3
The dimensional distance measuring device is a device using a two-dimensional surface range sensor.

That is, according to the present invention, a figure is drawn on the plate in regions having different laser reflectivities, and a projection plate movable horizontally and vertically is provided. To detect. This operation is performed multiple times by changing the position of the projection plate, and the position (X, Y, Z) in the three-dimensional space
A combination of data of the light projecting direction and the light receiving position is obtained. This data group is used as reference data, and a conversion matrix is created from reference data in the vicinity of unknown inputs (light emitting direction and light receiving position) to calculate a three-dimensional position.

Here, a laser beam is used as the light source of the light projecting means, and the beam diameter of the laser beam is the minimum size of a region or a figure on the projection plate where the reflectance is different. Smaller than.

According to the above-mentioned means, even if the optical system of the apparatus has distortion, it is possible to obtain 3 from the neighborhood data that can be expected to be measured with high accuracy.
Since the dimensional position is derived, the camera calibration becomes simple and highly accurate.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments (examples) of the present invention will be described in detail below with reference to the drawings.

The embodiment of the present invention shows a calibration when a two-dimensional surface range sensor (2DS) is used as a three-dimensional distance measuring device.

Here, a two-dimensional surface range sensor (2DS)
Means a projector that can perform laser scanning in an arbitrary direction by driving a lens with a two-degree-of-freedom actuator, and a means for observing this reflected light with a two-dimensional light receiving element. This is a device for measuring the dimensional position. This 2
For detailed configuration of the dimensional surface range sensor, refer to "JAPAN-USA SYMP
OSIUM ON FLEXIBLE AUTOMATION -A Pacific Rim Confer
ence- July, 11-18,1994, Kobe, Japan ”, Tomoichi Takahashi, Akinor, pp. 1065-1068
i Watabe's article title “A Range Finder using a Two-d
imensional Lens Actuator ”.

The calibration method of the two-dimensional surface range sensor is a two-dimensional surface range provided with a device capable of irradiating a laser in an arbitrary direction in space and a light receiving device for observing reflected light with respect to the projected light. In the sensor, a conversion formula for outputting the three-dimensional position (Xp, Yp, Zp) of the irradiation point based on the laser irradiation direction (X1, Y1) output from the sensor and the observation information (X2, Y2) by the light receiving device It is about how to ask. Specifically, the conversion function “F” shown by the equation 1 is obtained.

[0019]

## EQU1 ## Xp = fx (X1, Y1, X2, Y2) Yp = fx (X1, Y1, X2, Y2) Zp = fx (X1, Y1, X2, Y2) P = F (X1, Y1 , X2, Y2) FIG. 1 is a configuration diagram of an implementation device for explaining a calibration method of a three-dimensional distance measurement device according to an embodiment of the present invention, where 1 is a two-dimensional surface range sensor (2DS) and 2 is a Projection plate, 3 is a fixing jig, 4 is a projection plate fixing device, 5 is a 2DS fixing device, and 6 is a host computer.

The projection plate fixing tool 4 has a movable part, and its moving direction is parallel to the optical axis of 2DS1.

FIG. 2 is a block diagram of the projection plate 2 used in the embodying apparatus of the present embodiment, where A is the area of the white paint portion and B is the area.
Is an area of a different color paint portion or a specular reflection portion. Here, it is assumed that the grid of the area A is drawn at regular intervals. Two
The laser projected by the DS1 projector is not observed unless it is totally reflected in the region B and the reflection direction does not coincide with the light receiving surface.

When the area B is a mirror surface, it can be observed even if the reflection direction and the light receiving surface match, but in this case, the amount of light received is too large to be undetectable. It Therefore, only the region A is observed on the light receiving surface.

FIG. 3 is a view showing the relationship between the projection plate 2 of the present embodiment and the projector and the light receiving surface of the 2DS1, 11 is the projection plate (cross section of the projection plate 2), 12 is the light receiver (cross section), 13 Is a projector, and 14 is a received light amount graph. As shown in the received light amount graph 14 of FIG. 3, the light receiving position can be specified only when the region A is irradiated with the laser.

FIG. 4 is a flow chart for explaining an algorithm for creating a reference table using the host computer 6 of the embodiment apparatus, and FIG. 5 is a view for explaining data acquisition of the reference table. . Figure 5
5A is a diagram in which the result of threshold processing is drawn on the XY plane, and FIG. 5B is a diagram in which line segment extraction and intersection detection are drawn on the XY plane.

The reference table is created by the host computer 6, as shown in FIG. 4, in the embodiment shown in FIG. In step 2, uniform irradiation is performed on the entire surface by raster scanning or the like, and the received light data is recorded (step 102). In the threshold processing section,
A portion where the amount of received light is equal to or more than a certain amount is extracted, and the laser irradiation direction (X1, Y1) and the light receiving position (X2, Y2) at that time are recorded (step 103) (FIG. 5a).

A straight line detection process (Hough transform) is performed on this data to find the intersection of each straight line (step 10).
4) (Fig. 5b).

When the moving position of the projection plate 2 is Z3, the coordinate values (X3, Y3, Z3) and (X1, Y1) (X of the intersections are set.
2, Y2). After repeating the above operation a specified number of times (step 106), Pn =
(X3n, Y3n, Z3n, X1n, Y1n, X2n,
Y2n) is output as a reference table (step 10).
7).

Using the reference table, unknown input (X1
The three-dimensional position (X3k, Y3k, Z3k) for k, Y1k) (X2k, Y2k) is calculated according to the following procedure.

(1) Input (X1k, Y1k) (X2k,
Y2k) and table data (X1n, Y1n, X2n,
Y2n) and the distance dn are calculated.

[0030]

## EQU2 ## dn = (X1n-X1k) ² + (Y1n-Y1
k) ² + (X2n−X2k) ² + (Y2n−Y2k) ² (2) Calculate the weight Wn of each reference value.

[0031]

## EQU3 ## Wn = 1 / dn (3) The following equation is used as the residual matrix, and the coefficients a, b, c, d are obtained by the least squares method.

[0032]

[Equation 4]

(4) Input (X1k, Y1k) (X2k,
Y2k), the following matrix is obtained (X3k, Y3k,
Z3k) is output.

[0034]

[Equation 5]

As described above (X3k, Y3k, Z3k)
If is obtained, it is possible to calibrate the three-dimensional distance measuring device by using these as correction values.

That is, the calibration method of the three-dimensional distance measuring apparatus of this embodiment uses the position (Zp) of the projection plate 2.
And the lattice position (Xp, Yp) on the plate is used (Xp, Y
p, Zp) = F (X1, Y1, X2, Y2). Arbitrary output (Xi, Yi,
(X, Y, Z) for (Xj, Yj) can be sequentially calculated and output, and the three-dimensional distance measuring device can be calibrated.

As described above, the invention made by the present inventor is
Although the specific description has been given based on the above-described embodiments, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

[0038]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

At the time of measurement, only the moving device of the projection plate is required, so that the camera calibration becomes easy. Further, by changing the density of the reference table, it is possible to change the accuracy to any accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an implementation device for explaining a calibration method of a three-dimensional distance measurement device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a projection plate used in the embodying device of the present embodiment.

FIG. 3 is a diagram showing a relationship between a projection plate and a projector and a light receiving surface of a two-dimensional surface range sensor (2DS) according to the present embodiment.

FIG. 4 is a flowchart for explaining an algorithm for creating a reference table for three-dimensional measurement using the host computer of the implementation device of this embodiment.

FIG. 5 is a diagram for explaining data acquisition of a reference table for three-dimensional measurement according to the present embodiment.

[Explanation of symbols]

1 ... Two-dimensional surface range sensor (2DS), 2 ... Projection plate, 3
... Fixing jig, 4 ... Projection plate fixing tool, 5 ... 2DS fixing tool, 6
… Host computer, A… White paint area, B
Areas of different-color paint portions or specular reflection portions, 11 ... Projection plate (cross section of projection plate 2), 12 ... Light receiver (cross section), 13 ... Emitter, 14 ... Light reception amount graph.

Front Page Continuation (72) Inventor Kenji Mochizuki 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nihon Telegraph and Telephone Corporation (56) Reference JP-A-8-210816 (JP, A) JP-A-6 -137840 (JP, A) JP-A-5-248819 (JP, A) JP-A-9-329417 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 11/00- 11/30

Claims (2)

(57) [Claims] 1. A light emitting device capable of irradiating a light beam in an arbitrary direction projects the light beam onto an object, and the light beam reflected by the object is observed from a different angle by a light receiving device. It is a calibration method for a three-dimensional distance measuring device that measures the distance to an object using information .
Then, the object has a figure with different reflectance at a predetermined position,
Further, the light emitting device is replaced with a plane projection plate that can move horizontally or vertically, the light emitting device irradiates the projection plate with a light beam, and the light receiving device receives the light beam reflected by a pattern having a different reflectance on the projection plate.
Observed at, and the projection plate from the difference in the amount of light received by the light receiving device
Change the position of the projection board to detect the position of the figure above
The light is emitted from the light-emitting device by performing the operation multiple times.
A plurality of light projection direction of the light ray, and put to the each light projection direction
Light receiving position information of the light receiving device and each of the light projecting methods
A method for calibrating a three-dimensional distance measuring device, characterized in that the position information of the figure on the projection plate in the orientation is calculated as reference data. 2. The calibration method for a three-dimensional distance measuring device according to claim 1, wherein the three-dimensional distance measuring device is a device using a two-dimensional surface range sensor.