JPH0682467A - Movement measuring instrument with high accuracy - Google Patents

Abstract

PURPOSE:To provide a high-accuracy movement measuring instrument whose resolution is enhanced by the close-up image pickup of a measuring range while maintaining excellent controllability available in conventional methods using television techniques and which enables measurement over a wide range by the continuous tracking of a subject for measurement and also enables measurement of high accuracy to be performed over a wide range by removal of the influence of distortion of image pickup systems. CONSTITUTION:Two television cameras TV1, TV2 which take into view in different directions a measuring range where a label 1 for measurement is present and which can be switched between wide-angle photographing and closeup photographing are installed. A pair of high-speed, high-accuracy mirror controllers 2a-2d, having rotating mirrors 3a-3d for moving the optical axes of the television cameras in ortogonally intersecting directions and driving the mirrors to rotate at high accuracy, are disposed on the optical axes of the television cameras. A servo control mechanism, which drives the high-speed, high-accuracy mirror controllers 2a-2d to oscillate the rotating mirrors 3a-3d so as to always hold the image of the label at the center of the visual field of each television camera, is connected to each television camera.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the movement of a sign made of a high- or low-brightness object or an object of a specific color taken in close-up by an imaging system such as a television camera or a semiconductor position detector (PSD). The present invention relates to a dynamic measuring instrument capable of measuring with high accuracy and in a wide range, and for example, it is effectively utilized for the development of welfare equipment through highly accurate motion analysis of a human who moves around in a range of several meters to several tens of meters, or It can be effectively used when, for example, the assembling of a building is verified with high accuracy from a position about 100 m away, and the building can be built easily and accurately.

[0002]

2. Description of the Related Art The existing main three-dimensional position measuring method is (1)
Method of using the moire pattern of light, (2) Method of using the activating force of orthogonal coils placed in a uniform magnetic field, (3) Digitizing and inputting the measurement points shown in photographs, movies, etc. manually. Method, (4) Method of making infrared light emitting diode (LED) emit light in a time-division manner and sequentially measuring its position using PSD, (5) Applying TV technology to automatically track and measure measurement points on the screen There are two main methods.

A comparison of the relative performances of the above measurement methods is summarized in Table 1. In the table, the approximate performance is shown by numerical values, and the evaluations are shown in order of goodness by ○, △, and ×. According to this, the method of No. 4 is relatively excellent, but a cable for lighting and synchronizing the LED is required, and there is a difficulty in operability. The method of No. 5 cannot be said to have sufficient performance in any of resolution, speed, and measurement point, but is excellent in operability. Moreover, TV technology is
It is expected that the performance will be further improved in the near future, as the high-definition TV comes into practical use.

[0004]

[Table 1] As described above, none of the above-mentioned existing methods has satisfactory performance for the dynamic measurement required to measure the movement of a specific sign with high accuracy and in a wide range with good operability.

[0005]

The technical problem of the present invention is to obtain a dynamic measuring instrument that has only the advantages of the methods of No. 4 and No. 5 described above. While maintaining the excellent operability in the method of 0.5, the resolution is increased by taking a close-up image of the measurement area, and the servo control system based on the null method uses only the central area of the imaging system. The main purpose of the present invention is to obtain a high-accuracy dynamic measuring instrument capable of performing high-accuracy measurement over a wide range by removing the influence of the distortion and further by controlling the mirror with high speed and high accuracy.

[0006]

A high-precision dynamic measuring instrument of the present invention for solving the above-mentioned problems is capable of taking a close-up image by placing a measurement region in which a marker to be measured is present in a field of view from a different direction. A pair of imaging systems are installed, and on each of the optical axes of these imaging systems, there are rotary mirrors that move the optical axes of the imaging systems in directions orthogonal to each other, and that rotate and drive them with high accuracy. The high-speed and high-accuracy mirror controllers are installed, and by driving these high-speed and high-accuracy mirror controllers to swing the rotating mirror, the image of the sign is always kept in the center of the visual field of the imaging system. A servo control system based on the null method is connected to the image pickup system.

[0007]

[Operation] With the high-precision dynamic measuring instrument having the above-mentioned configuration,
In measuring the movement of the marker, first, the marker on the object to be measured is photographed by the imaging system, the marker is captured by the measuring system, and then close-up photographing is performed. Then, the rotary mirrors are rotationally driven by two high-speed and high-accuracy mirror controllers placed on the optical axis of the imaging system, and when the measurement is performed following the sign, the sign image is captured by servo control based on the null method. Since it comes to the center of the screen of the system, by measuring the angle of the mirror in that case, the direction in which the sign exists can be found, and the excellent operability is maintained by finding the intersection of the two straight lines indicating those directions. However, the three-dimensional position of the sign is measured with high accuracy.

As a result, the resolution can be increased by the magnification due to the close-up photography. Therefore, the accuracy of the rotation angle of the mirror must be increased by the increased resolution, but the present inventors have previously developed it. (Japanese Patent Application No. 4-1
It is possible to achieve sufficiently high accuracy by using a high-speed and high-accuracy angle measuring device (No. 02172). On the other hand, the control based on the null method eliminates the influence of the distortion of the image pickup system by using only the central region of the image pickup system, and the high-speed, high-precision mirror control enables a wide range of high-precision measurement. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows the basic structure of the high-precision dynamic measuring device of the present invention when used as a high-precision three-dimensional position measuring system. The dynamic measuring device in the same figure is for performing highly accurate motion analysis of a sign 1 on a human or other appropriate object that moves within a range of several meters to several tens of meters.
As the high- or low-luminance object on the measured object, or an object of a specific color, a light-emitting diode (LE) is used when there is no suitable marker on the measured object.
D) is attached to the object to be measured and used as a marker.

In order to detect the mark 1, the measuring range in which the mark moves (the range of the angle of view of about 40 ° vertically and horizontally)
We have installed _two TV cameras TV ₁ and TV ₂ that can fit within the field of view. Instead of the TV cameras TV ₁ and TV ₂ , a PSD or other imaging system can be used. It should be noted that, in the description of this embodiment, the description will be made with the idea of improving the method of No. 5 in the prior art described above, but the position detection described below is the same for the PSD method of No. 4. Can be applied to. In that case, noise removal due to illumination or the like becomes a big problem, but higher accuracy can be expected.

These television cameras TV ₁ and TV ₂ respectively include rotating mirrors 3a and 3 in a pair of high-speed and high-accuracy mirror controllers 2a, 2b and 2c and 2d arranged on the optical axis.
The sign is photographed via b, 3c, and 3d, and at this time, it is possible to perform close-up photographing of the entire measurement range and a part of the measurement range by arbitrary means, for example, switching to wide-angle photography and close-up photography. When the wide-angle shooting is performed, the entire measurement area is included in the field of view, and when a close-up image is taken of a part of the measurement area in order to improve the resolution, the pair of mirrors 3a, 3b and 3c, 3d are used. By rotating, the entire measurement area is covered and an arbitrary part of the measurement area can be photographed.

The pair of high-speed and high-accuracy mirror controllers 2a, 2b and 2c, 2d provided on the optical axes of the _two TV cameras TV ₁ , TV ₂ are rotary mirrors 3a, 2b, 2c, 2d whose rotation is controlled. The axes of rotation of 3b, 3c, and 3d are arranged so that the optical axis of the television camera moves in the vertical and horizontal directions orthogonal to each other in the measurement range, as shown in FIG. In FIG. 2, L indicates a lens system. By driving these high-speed and high-accuracy mirror controllers, when the sign 1 moves around the measurement range, the image of the sign comes to the center of the screen of the TV cameras TV ₁ and TV ₂ as described later. Is controlled so as to follow the movement of the sign 1, and the control is performed.

As shown in FIG. 3, the high-speed and high-accuracy mirror controller detects the light passing through the slit 5 having a special shape by using the one-dimensional semiconductor position detector 7 to determine the rotation angle of the motor 8. It is equipped with an angle measuring device that measures with high accuracy. More specifically, as an apparatus for measuring this angle, a light source (not shown) and a high-speed, high-torque motor 8 are rotationally driven, and a distance r from the central axis 6 is used.
Is provided with a shield plate 4 provided with a spiral slit 5 proportional to the rotation angle θ, and a one-dimensional semiconductor position detector 7 for measuring the position of light passing through the slit 5.

The spiral slit 5 is provided at a position given by r = aθ (where a is a constant). Therefore, when the shield plate 4 is rotated, the slit 5 is formed.
On the one-dimensional semiconductor position detector 7, the position of the light projected on the straight line along the line and passing through the slit 5 is the rotation angle θ.
Since it changes in proportion to, the rotation angle of the motor 8 can be measured with high accuracy by the position. In particular, since the semiconductor position detector has extremely high resolution and is stable, it is possible to measure the rotation angle of the motor 8 with high accuracy based on the position of the light passing through the slit 5.

Further, a controller for controlling the motor 8 at high speed and with high accuracy using the measurement data is connected to the angle measuring device. The controller can be called an integral control type optimum tracking controller with initial value compensation,
The inventor has a configuration as shown in FIG. 4, and regarding the theoretical basis, the present inventor has proposed that the Institute of Instrument and Control Engineers, Volume 20, No. 1, “Initial Value Compensator for Linear Multiple Input / Output Optimal Tracking Control System”. In detail.

The integral control type optimum tracking controller of FIG. 4 basically has a constant K _{2 with} respect to the difference e between the set input r and the output y.
An integral control system having an integral control element (Im / S) for performing integral control on the element for multiplying by and the result, and a feedback control system for feeding back the state variable x to be controlled by a constant K ₁ Is equipped with. Furthermore, in these control systems, since an undesired control operation appears when the integral control element has an initial value, a compensation control system for performing initial value compensation of the manipulated variable for eliminating it, that is,
When the system starts up, the value of the manipulated variable u is sampled to 0
Next hold circuit holds the value (-K ₁ x (0)
A compensation control system is added to eliminate the influence of the initial value by feeding back + z (0)) and subtracting it from the output of the integral control system.

This compensation control system samples the value of the manipulated variable u and holds the value when the differential value of the input r exceeds a certain value due to system startup or a large change in the set value. It can also be realized by an element having various functions. Further, since the operation amount u is not excessively sampled and held, a refractory element may be added to the sampler. Therefore, in the above-mentioned integral control type optimum tracking controller, the manipulated variable u
Is a component in which the state variable x to be controlled is multiplied by a constant K ₁ and fed back, a component z in which the difference e between the input r and the output y is multiplied by a constant K ₂ is subjected to integral control, and the input r fluctuates greatly. Sometimes, the operation amount u is sampled and held, and the value is fed back and added to and subtracted from the component.

Here, the constants K ₁ and K ₂ are adjusted so that the output y can follow the input r as quickly as possible while keeping the square value of the manipulated variable u, that is, the energy as small as possible. As can be seen from the above, these constants K ₁ and K ₂ are obtained by minimizing the quadratic evaluation function, but a method of determining the constants K ₁ and K ₂ is also possible without this method. is there. However, even in that case, if the constants K ₁ and K ₂ are increased in order to increase the quick response, an undesired initial fluctuation will occur when the system is started, so the above initial value compensator is indispensable.

When the motor 8 is controlled by the integral control type optimum follow-up controller using the measurement data of the one-dimensional semiconductor position detector 7 described above, the stability is excellent and the speed is high because the optimum control system is formed. Since it is controllable and an integral controller is directly attached to the input and output ends, an offset of zero is guaranteed, and by providing the motor 8 with mirrors 3a to 3d for reflecting the light from the marker 1 in a required direction, It is possible to realize a mirror controller that guarantees the accuracy of angle measurement data.

Further, in the above-mentioned high precision dynamic measuring instrument,
It is equipped with an XY tracker that is connected to a TV camera to detect the position of the sign in the measurement image, and drives the high-speed and high-precision mirror controller based on the output of the XY tracker to swing the rotating mirror to display the image of sign 1. It is equipped with a servo control system based on the null method, which is always kept at the center of the field of view of the TV camera. When the marker is captured in the center of the screen by the servo system control system based on the null method, only the central region of the image pickup system can be used to remove the distortion of the image pickup system and high-precision measurement can be performed over a wide range.

FIG. 5 is for explaining the control based on the null method. That is, when the marker 1 moves and moves to a white circle point on the TV screen, the position of the white circle is measured, and the controller rotates so as to move to the black circle point, that is, the measurement origin (0, 0). Rotate the mirror. At this time, when the integral control type optimum tracking control system as shown in FIG. 4 according to the present inventors is used, since the position error is directly attached to the integrator, the offset is always within the error of the sensor. Since an optimum control system can be configured, it is possible to design a control system with excellent stability and high speed.

When the movement of the sign 1 is measured by the high-accuracy dynamic measuring device having the above structure, first, the sign 1 on the object to be measured is photographed by the TV cameras TV ₁ and TV _{2 at a} wide angle, and the sign 1 is taken. TV camera TV after capturing the
₁ , Switch TV ₂ to close-up shooting. The rotary mirrors 3a to 2d are respectively provided with two high-speed and high-accuracy mirror controllers 2a to 2d placed on the optical axes of the TV cameras TV ₁ and TV _2.
3d is rotated and the image of the sign 1 moving around in the measurement area is made to come to the center of the screens of the TV cameras TV ₁ and TV ₂ by the servo control based on the null method.
By measuring the angle of ~ 3d, the directions in which the sign 1 exists can be found, and the three-dimensional position of the sign 1 can be measured by finding the intersection of two straight lines indicating those directions.

As described above, the resolution can be increased by the magnification due to the close-up photography. Therefore, the accuracy of the rotation angle of the mirror has to be increased by the amount corresponding to the increased resolution, but when the high-speed and high-accuracy angle measuring instrument developed by the present inventors is used, the accuracy is about 10 times higher than that of the conventional one. Sufficient high accuracy is possible. On the other hand, the movement of the sign becomes faster due to the close-up photographing, which can be covered by the speed of the mirror controller. In addition, the control based on the null method eliminates the influence of distortion of the imaging system by using only the central region of the imaging system,
High-speed, high-accuracy mirror control enables high-accuracy measurement to be performed over a wide range.

With standard television equipment, position measurement is 1/6
Since it can be done only every 0 seconds, there is a limit to high-speed control, but various methods are known to solve the problem. For example, the first is to increase the shooting speed of the television, and there is no technical problem. Second
Is a method adopted by each company, limiting the measurement range, and measuring the limited range each time in a short time of horizontal recovery, or crushing the image vertically and horizontally using a cylindrical lens, For example, a method for performing high-speed measurement by operating only a fraction of the screen.

When the sign is photographed in close-up,
Since it becomes difficult to capture it in the field of view and it takes time and labor for measurement, it is desirable to separately prepare a means for photographing at a wide angle, perform close-up photographing after completing the setup, and start measurement.

Next, a method of importing the measurement data of the angles of the mirrors 3a to 3d into a computer and calculating the three-dimensional position coordinates of the marker 1 will be described. As shown in FIG.
The coordinate origin O of the measurement system (X, Y, Z; O) is placed in the center of the measurement range, and the coordinate system with the optical centers of the two TV cameras is (Xi, Yi, Zi; Oi) (i = 1, 2) However, Y,
Yi is vertical and faces upward. Further, the coordinate system at the midpoint of the line segment O ₁ O ₂ is expressed as (X ₃ , Y ₃ , Z ₃ ; O ₃ ), and the line segment O ₁ O ₃ = line segment O ₂ O ₃ = a and the line segment OO _It is expressed as ₃ = b.

Now, suppose that the position of the image of the sign is x _i , y _i (i = 1, 2) on the image pickup surface placed on O ₁ and O ₂ . In addition,
In this system, the mirror actually moves and the sign is always captured at the origin. However, considering the case where the sign moves and the mirror is fixed, x _i , y _i can be easily obtained from the angle of the mirror.
Then, the following equation is established.

[Equation 1]

The coordinate conversion between the coordinate systems O ₃ and Oi (i = 1,2) may be performed by considering rotation about the Yi axis, and is expressed by the following equation.

[Equation 2]

Substituting equation (3) into equation (1) and rearranging,

[Equation 3] Becomes To summarize the two conditional expressions,

[Equation 4] Becomes Therefore,

[Equation 5] To get Further, the conversion of O and O ₃ can be easily obtained by the following equation.

[Equation 6]

According to the above calculation, even if the measured value includes an error and the two straight lines estimated from the two image pickup systems do not intersect, the point giving the minimum distance between the two straight lines. Is obtained as a solution. By the way, since the equation (9) includes the calculation of the inverse matrix, when the number of measurement data is large, the calculation time becomes long and may not be practical. here,
When the formula (7) is written down concretely,

[Equation 7] Becomes

Therefore, when the element of F is represented by f _ij and the first and third equations of equation (11) are extracted,

[Equation 8] From this,

[Equation 9] To get Substituting equation (13) into the second and fourth equations of equation (11) and taking the average, the following equation is obtained.

[Equation 10]

This means that the intersection of the two straight lines obtained by projecting the straight line in the three-dimensional space on the horizontal plane is obtained by the equation, and then Y ₃ is obtained from the remaining two equations. According to equations (13) and (14),
It can be calculated with a fraction of the calculation amount of Eq. (9).

In the above, the image pickup system such as a television camera is used to photograph the measurement area through the rotating mirror. However, the measurement is performed by placing the rotating mirror on the focal point of the relay optical system and rotating it. The object can be measured by following over a wider range, and the high-precision measurement equivalent to dividing the measurement range into a large number becomes possible.

[0034]

As described in detail above, according to the high-precision dynamic measuring instrument of the present invention, the measurement range is divided and closed while maintaining the excellent operability in the conventional system using the television technology. The resolution is increased by up-imaging, and the servo control system based on the null method eliminates the influence of distortion of the imaging system by using only the central region of the imaging system.
High-speed and high-accuracy mirror control makes it possible to obtain a high-accuracy dynamic measuring instrument capable of performing high-accuracy measurement over a wide range.

[Brief description of drawings]

FIG. 1 is a schematic block configuration diagram showing a state in which a high-precision dynamic measuring device of the present invention is applied to a high-precision three-dimensional position measuring system.

FIG. 2 is a perspective view showing an arrangement state of a rotary shaft of a rotary mirror in FIG.

FIG. 3 is a front view showing a configuration of an angle measuring device in a high-speed / high-accuracy mirror controller.

FIG. 4 is a block diagram for explaining the operation of an integral control type optimum tracking controller with initial value compensation.

FIG. 5 is an explanatory diagram for explaining control based on the null method.

FIG. 6 is an explanatory diagram for calculating three-dimensional position coordinates of a sign.

[Explanation of symbols]

1 sign, 2a ~ 2d high speed and high precision mirror controller,
3a-3d rotating mirror, TV ₁ , TV ₂ TV camera.

Claims (1)

[Claims] 1. A measurement area in which a marker to be measured is present is included in a field of view from different directions, and two image pickup systems capable of close-up photographing are installed. It has a rotating mirror that moves the optical axis of the image pickup system in a direction orthogonal to each other, and a pair of high-speed and high-accuracy mirror controllers that rotate and drive it with high accuracy are arranged. A servo control system based on the null method, in which the controller is driven and the rotating mirror is shaken to keep the image of the sign at the center of the visual field of the image pickup system, is connected to the image pickup system. Precision dynamic measuring instrument.