WO2017014669A1

WO2017014669A1 - Positioning error reduction device for a ptz camera

Info

Publication number: WO2017014669A1
Application number: PCT/RU2015/000814
Authority: WO
Inventors: Иван Сергеевич ШИШАЛОВ; Андрей Викторович ФИЛИМОНОВ
Original assignee: Общество С Ограниченной Ответственностью "Дисикон"
Priority date: 2015-07-17
Filing date: 2015-11-23
Publication date: 2017-01-26

Abstract

The present invention relates to the field of video surveillance, and more particularly to video surveillance using panning (PTZ) cameras. A positioning error reduction device for a PTZ camera comprises a unit for determining interim positions of the camera, said unit being capable of recording and storing the coordinates of said interim positions of the camera, a unit for successively tilting the PTZ camera, a unit for establishing the target position of the camera, and a control unit, wherein the control unit is connected to the unit for establishing the target position of the camera, an output of which is connected to an input of the unit for determining the interim positions of the camera, which is connected to an input of the control unit, an input of which is connected to an output of the unit for successively tilting the PTZ camera. The technical result is a reduction in camera positioning error and an increase in the repeatability of positioning.

Description

POSITIONING ERROR DEVICE FOR PTZ CAMERA

TECHNICAL FIELD This technical solution relates to the field of video surveillance, in particular to video surveillance using PTZ cameras.

BACKGROUND OF THE INVENTION

Currently, PTZ cameras are widely used to monitor large areas. They are a device that supports remote control of viewing direction and zoom. ΡΤΖ-cameras are actively used when conducting video conferences, being a necessary attribute of a conference room or meeting room, when building security systems and other video surveillance systems. Due to their high prevalence at the moment, the range of cameras is quite extensive, cameras have different characteristics and cost.

When using a PTZ camera for video surveillance, an important characteristic of its functioning is the camera positioning error, it depends on the degree of wear of the mechanism, its initial accuracy, and camera calibration.

The prior art article is known [1], which describes the approaches that are used in solving the problem.

Sinha and Polleface proposed a positioning device for ΡΤΖ-cameras [2], in which the camera is first calibrated at low zoom, and then the internal parameters of the camera are calculated with increasing zoom. Since calibration is performed discretely from one zoom value to another, piecewise linear interpolation is used to calculate the internal parameters. Using this method provides the need for a large number of calibration steps to mitigate noise, which significantly increases the operating time. ESSENCE

This technical solution is aimed at eliminating the disadvantages inherent in solutions known from the prior art.

The technical result is to reduce errors and increase the repeatability of positioning. This technical result is achieved through the use of intermediate positioning points, which reduce the effect of inertia and "flight" of the required position. By reducing the positioning error, the positioning accuracy is improved.

Another technical result is the repeatability of positioning results. As a result, the positioning error becomes systematic and the same.

A device for reducing positioning errors for a PTZ camera, comprising a unit for determining intermediate positions of the camera, with the ability to record and store coordinates of intermediate positions of the camera, a unit for sequential rotation of the камеры-camera, a unit for obtaining the target position of the camera, a control unit, the control unit being connected to the unit for obtaining the target position camera, the output of which is connected to the input of the unit for determining intermediate positions of the camera, which is connected to the input of the control unit, the input of which is connected to the output of the unit поворота-camera rotation. BRIEF DESCRIPTION OF THE DRAWINGS

Signs and advantages of this technical solution will become apparent from the following detailed description and the accompanying drawings, in which: Figure 1 - shows a block diagram of a device;

DETAILED DISCLOSURE OF TECHNICAL SOLUTION

Below will be described the concepts and definitions necessary for the detailed disclosure of the ongoing technical solution. A panoramic angle (precession angle, Pan) is one of the Euler angles that describes the rotation of an object around the Z axis (for more details, see [9]). This angle corresponds to the rotation of the object in its own horizontal plane.

The angle of inclination (nutation angle, Tilt) is one of the Euler angles that describes the rotation of an object around the Y axis (for more details, see [9]). This angle corresponds to the rotation of the object in its own vertical plane.

Positioning error - the difference between the target position of the camera and the actual position of the camera after positioning in the target position. It is expressed by two angles: panoramic (corresponding to the difference between the panoramic angles of the actual and target position) and the angle of inclination (corresponding to the difference between the angle of inclination of the actual and target position).

Repeatability of a result is a characteristic that reflects the probability of a repetition of the result of an experiment subject to a certain set of initial conditions. The repeatability of the positioning result is a characteristic that reflects the probability of achieving the same values of the positioning error while maintaining the target position of the camera and changing the initial position. In the standard positioning mode, if necessary, rotate the camera, the control unit 101 (Fig. 1) sends a sequential rotation unit of the камеры-camera 103 the rotation command from the starting position to the target position:

Go To Pan _D , Tilt _D

RoB ^ Ra; Tilt ^) => Pos _D1 (Pan _D + Pan _Erl ; Tilt _D + Tilt _Erl )

Where is RoB ^ Ra; Tilt-i) - the initial position of the camera, which is characterized by a panoramic angle Ra and a tilt angle

Tilt-L, Pos _D1 (Pan _D + Pan _Erl ; Tilt _D + Tilt _Erl ) - the camera position when the camera moves from point 1 to the target position, it differs from the required target position Pos _D (Pan _D ; Tilt _D ) by the amount of error positioning.

In this case, turning to the same target position from a different starting position generally leads to other positioning errors:

So To Pan _D ; Tilt _D

Pos ₂ (Pan ₂ ; Tilt ₂ => Pos _D2 {Pan _D + Pan _Er2 , Tilt _D + Tilt _Er2 )

Pos2 (PcLn ₂ ; Tilt2) - the second initial position of the camera orientation, which differs from the first by the values of the panoramic angle and tilt angle, Pos _D2 {P n _D + Pan _Er2 ; Tilt _D + Tilt _Er2 ) - the orientation of the camera when it _comes to the target position from starting position 2, with other error values for the panoramic angle and tilt angle. The resulting position also differs from the desired target direction of the camera view.

With this approach, the scatter of Pan _Er values; Tilt _Er can achieve significant values, and for cameras with various mechanisms rotation error will be between 0.05 degrees and 0.5 degrees. Various rotation mechanisms are described in [4].

This technical solution proposes the introduction of at least one additional position through which the camera passes before reaching the target position, which allows to reduce the positioning error:

Go That Pan _Int ; Tilt _lnt

Pos ^ Pan ^, Tilt => Pos _lntl {Pan _Int + Pan _Erl ; Tilt _Int + Tilt _Erl )

Go To Pan _D ; Tilt _D

= => Pos _D1 (Pan _D + Pan _MErl ; Tilt _D + Tilt _MErl )

Go To Pan _lnt ; Tilt _lnt

Pos ₂ (Pan ₂ , Tilt ₂ ) == Pos _lnt2 (Pan _lnt + Pan _Er2 ; Tilt _Int + Tilt _Er2 )

Go To Pan _D ; Tilt _D

=> Pos _D2 (Pan _D + Pan _MEr2 ; Tilt _D + Tilt _MEr2 ) Similar to the previous one: PoB ^ Ra; Tilt ^) is the first starting position.

Pos _lntl (Pan _Int + Pari i. Tiltjnt + Tilt _Erl ) - an intermediate position with its own positioning error when repositioning from the first starting position.

Pos _D1 (Pan _D + Pan _MErl ; Tilt _D + Tilt _MErl ) - the end (target) position when repositioning from an intermediate position.

Pos _2. P n ₂ ; Tilt ₂ ) - second starting position, different from the first starting position.

Pos _Int2 {Pan _Int + Pan _Er2 ; Tilt _Int + Tilt _Er2 ) - an intermediate position with its own positioning error when repositioning from the second initial position.

Pos _D2 (Pan _D + Pan _MEr2 ; Tilt _D + Tilt _MEr2 - end position when coming from an intermediate position. Because the ΡΤΖ-camera is positioned at the final point from an intermediate point, the coordinates of which in the two described driving routes can differ by no more than a positioning error (from 0.05 to 0.5 degrees), the final error is Pan _MEr ; Tilt _MEr will be significantly smaller, and for cameras with a positioning accuracy of 0.05 degrees, it can already be about 0.01 degrees.

The necessary effect is achieved at the cost of some loss of time required for intermediate positioning and control of the installation of the rotary mechanism in the intermediate position. However, for many tasks, accuracy, which is achieved by reducing positioning error, is a priority. In addition, modern cameras have a very high positioning speed, which reduces the time spent on additional positioning to a minimum. According to FIG. 1, a device for implementing a technical solution includes a control unit 101. The control unit 101 may be configured as a client, server, mobile device or any other computing device that interacts with data in a collaboration system. In the most basic configuration, the control unit 101 typically includes at least one processor and a data storage unit. Depending on the exact configuration and type of computing device, system memory can be volatile (e.g., random access memory (RAM)), non-volatile (e.g. read only memory (ROM)), or some combination thereof. The data storage unit typically includes one or more application programs and may include program data.

The functional interaction of the blocks is as follows: the control unit 101 obtains the target rotation position of the камеры-camera from the block receiving the target position of the camera 104;

The target position is understood as the camera position defined by the camera control program or the operator. Thus, the target rotation position of the камеры-camera is transmitted to the control unit 101 from the unit for obtaining the target position of the camera 104. The essence of the technical solution does not depend on the method of obtaining the target position. the control unit 101 sends a command to the intermediate position determination unit 102 to determine at least one intermediate position of the camera and its coordinates based on the target rotation position of the camera;

Intermediate positions and their coordinates are determined by the intermediate position determination unit 102 by testing the device, or based on ideas about the configuration of the camera rotary mechanism. During testing, global optimization algorithms can be used to obtain optimal parameters of intermediate points [6,7,8].

Intermediate positions can be defined through absolute coordinates or through relative coordinates. The number of intermediate positions depends on the required speed and positioning accuracy. The higher the positioning speed is required, the less intermediate positioning points should be, and in some cases one intermediate positioning point may be sufficient. It is also obvious from general considerations that increasing the number of intermediate points beyond a certain limit will not increase the accuracy of positioning. Speed and positioning accuracy can be set in advance, depending on the specific application of the camera.

In some embodiments, the definition of intermediate points build an automatic procedure for calculating the resulting positioning accuracy at a given speed and vice versa, the resulting positioning speed at the required accuracy.

In a particular case, testing to determine intermediate positions can occur as follows:

1. The control unit 101 sends a command to the unit to obtain the target position of the camera 104 to determine the target position of the camera at random.

2. Then, the control unit 101 sends the unit for sequential rotation of the камеры-camera 103 to a command to move to an arbitrary point, then immediately sends the command to return to the unit to obtain the target position of the camera 104 to the target position according to a certain positioning algorithm, measuring the accuracy and speed of positioning.

3. After that, the control unit 101 changes the positioning algorithm and again takes measurements of positioning accuracy.

When changing the positioning algorithm, it implies both the choice of another algorithm and the setting of the current one.

In this case, various strategies for changing the positioning algorithm can be used, including the simplest ones. Here is an example of a simple strategy for determining a positioning algorithm: the control unit 101 selects one intermediate position that differs from the target one by the panoramic angle and angle of inclination by A. Then, using the global optimization algorithm [6,7,8] for a one-dimensional function choose a value A that corresponds to a minimum positioning error.

To determine the positioning error, computer vision algorithms can be used, for example, which implement the selection of control points on two frames and the determination of the displacement of control points between frames. The search for reference points can be performed as indicated in the information source [5]. In the particular case, two images can be used - the first obtained at the target point at the initial moment of time, and the second obtained at the target position after positioning from an intermediate position. Next, these images are compared and a positioning error is determined. the control unit 101 sends the command to the sequential rotation unit of the камеры-camera 103 to successively rotate to the target position through the aforementioned intermediate positions.

After receiving the target position and calculating a set of intermediate positions, the control unit 101 sends the command to the successive rotation unit of the камеры-camera 103 to successively rotate to the target position through the first intermediate position, then, if there is one, to the second, and so on. The final step is to rotate the camera to the target position.

The control unit 101 may have additional features or functionality. For example, the control unit 101 may also include additional data storage modules (removable and non-removable), such as, for example, magnetic disks, optical disks, or tape. Computer storage media may include volatile and non-volatile, removable and non-removable media implemented in any way or using any technology for storing information, such as machine-readable instructions, data structures, program modules or other data. The control unit 101 is an example of computer storage media. Computer storage media includes, but is not limited to, random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact ROM a disc (CD-ROM), universal digital disks (DVDs) or other optical storage devices, magnetic tapes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that may be used on to store the desired information and which can be accessed by the control unit 101.

The control unit 101 contains communication connections that allow the device to communicate with other computing devices. Communication connection is an example of a communication environment. Typically, a communication medium can be implemented using computer-readable instructions, data structures, program modules or other data in a modulated information signal, such as a carrier wave, or in another transport mechanism, and includes any information delivery medium. The term "modulated information signal" means a signal, one or more of its characteristics are changed or set in such a way as to encode information in this signal. By way of example, but without limitation, communication media include wired media such as a wired network or a direct wired connection. The term “machine-readable medium”, as used herein, includes both storage media and communication media. Elements of this device are in constructive unity and functional relationship, and their joint use leads to the creation of a new device with a new function. Thus, the design is performed in a rigid structure, all the blocks of which are connected, in any design, without affecting the essence of the technical solution.

The blocks used in the device can be implemented using electronic components used to create digital integrated circuits. Not limited to, microcircuits can be used, the logic of which is determined during manufacture, or programmable logic integrated circuits (FPGAs), the logic of which is set by programming. For programming, programmers and debugging environments are used that allow you to specify the desired structure of a digital device in the form of a circuit diagram or programs in special equipment description languages: Verilog, VHDL, AHDL, etc. Alternative FPGAs are: programmable logic controllers (PLCs), base matrix crystals ( BMK) requiring a factory production process for programming; ASIC - specialized custom large integrated circuits (LSI), which are much more expensive in small-scale and single-unit production.

Blocks can also be implemented using read-only memory devices (see O. Lebedev. Memory microcircuits and their application. - M.: Radio and communications, 1990. - 160 s; Large integrated circuits of memory devices: Reference / A.Yu. Gordenov et al. - M.: Radio and Communications, 1990. - 288 s).

Thus, the implementation of all used blocks is achieved by standard means based on the classical principles of implementing the foundations of computer technology. EXAMPLES OF IMPLEMENTATION

Let there be a camera model that allows positioning at different speeds. It is also known that due to the inertia of the mechanism, an attempt to position the camera at a point (Pan, Tilt) leads to positioning at a point (Pan + Perr, Tilt + Terr), where (Perr, Terr) is a positioning error, the magnitude of which depends on the speed the camera’s movement to the positioning point, and the direction depends on the motion vector that the camera possessed when it reached the target position. Thus, positioning at maximum speed results in a maximum error. The direction of the error is also unpredictable, because it depends on the position in which the camera was before the start of positioning. Positioning at a low speed would reduce the error, but would significantly increase the positioning time if the initial position of the camera and the target position are significantly different. During testing the capabilities of the camera’s rotary mechanism, it turned out that in order to achieve the minimum positioning error, it is enough to determine one intermediate point that differs from the target position by one degree in the panoramic angle and angle of inclination and move from the intermediate position to the target one with a minimum speed. Moreover, an increase in the distance between the target position and the intermediate one does not lead to a decrease in the error, but, of course, leads to an increase in the positioning time. At the same time, a further reduction in distance leads to an increase in positioning error. Thus, a distance of one degree at two angles is optimal in terms of reducing positioning errors.

The following is an example of the implementation of a technical solution in which there is one intermediate point (Pan - 1 °, Tilt - 1 °). The definition of the intermediate position (Pan - 1 °, Tilt - 1 °) is given in the absolute coordinates of the camera, but can also be determined in relative coordinates. In this case, if the initial position of the camera was (Figx, Tisx), then the relative position of the intermediate point will be (Pan - 1 - Figx, Tilt - 1 - Tisx) and will correspond to the offset by which the camera should be rotated to reach the intermediate position. Similarly, the coordinates of the target position relative to the intermediate position will be (1,1).

Previously, get the target position (Pan, Tilt). Next, one intermediate position is determined (Pan - 1 °, Tilt - 1 °), after which the camera is rotated at maximum speed from the initial position to the intermediate. From the intermediate position, turn the camera to the target position with minimal speed.

The result of this sequence of actions will be a reduction in positioning error at the target point, since the movement into it was carried out at a minimum speed. At the same time, the positioning time will increase insignificantly, since with a minimum speed the camera moved only a short interval of the positioning trajectory, namely, the path of one degree along the panoramic angle and tilt angle. In addition, the direction of the reduced error will be the same, since the camera’s vector of movement at the moment of reaching the target position will be the same, which will allow translating the error into a systematic category, taking into account and thus completely leveling.

In an example implementation with two intermediate points, the target position is first obtained, after which two intermediate positions are determined. The first position (Pan - 1 °, Tilt - 1 °), the second position (Pan, Tilt - 1 °). Then they are positioned in the first intermediate position with maximum speed, after which they are positioned in the second intermediate position with minimal speed. As a result, they are positioned at the target position with minimal speed.

One skilled in the art will appreciate that a technical result is achieved using one intermediate point. As the number of intermediate points increases, the positioning error decreases.

In addition to the technical result described for the method with one intermediate point, this device results in a further reduction in positioning error due to the fact that in the last two steps the movement is carried out only in one of the angles and there is no error associated with inaccurate synchronization of the positioning mechanism drives movement along each of the corners.

The present detailed description is made up of various non-limiting and exhaustive embodiments. At the same time, for specialists having an average level of competence in the considered field of technology, it is obvious that various replacements, modifications or combinations of any of the embodiments disclosed herein (including partially) can be reproduced within the scope of this technical solution. Thus, it is understood and understood that the present description of the technical solution includes additional embodiments, the essence of which is not set forth here in an explicit form. Such embodiments may be obtained, for example, by combining, modifying, or transforming any actions, components, elements, properties, aspects, characteristics, limitations, etc., related to the embodiments presented herein and not being restrictive. USED SOURCES

1. “Keeping a Pan-Tilt-Zoom Camera Calibrated)), authors: Ziyan Wu, Richard J. Radke, published: IEEE Trans. Pattern Anal. Mach. Intell - 2013.

2. S. N. Sinha and M. Pollefeys. Pan-tilt-zoom camera calibration and high-resolution mosaic generation. Computer Vision and Image Understanding, 103 (3): 170-183, Sept. 2006.

3. M. Sarkis, C. Senft, and K. Diepold. Calibrating an Automatic Zoom Camera With Moving Least Squares. IEEE Transactions on Automation Science and Engineering, 6 (3): 492-503, July 2009.

4. Internet resource: http://www.aktivsb.ru/article-infol052.html

5. Computer vision, a modern approach Computer Vision: A Modern Approach Authors: David A. Forsyth, Jean Pons Translators: A. Nazarenko, I. Doroshenko Languages: Russian Publisher: William ISBN 5-8459-0542-7, 0-13-085198 -one ; 2004 year

6. Strongin R. G. Numerical methods in multiextremal problems.

"Optimization and investigation of operations", The main edition of the physical and mathematical literature of the publishing house "Science", M., 1978, 240 pp.

7. Papadimitriou X., Steiglitz K. Combinatorial optimization:

Algorithms and complexity. M .: Mir, 1985

8. Batishchev D. I. Genetic algorithms for solving extreme problems. Ed. Lvovich Ya.E .: Textbook. allowance. Voronezh, 1995, 64 p.

9. Internet resource: https: //m.wikipedia.or^wiki/ynrcbi_3^epa

Claims

FORMULA

1. A device for reducing positioning errors for a PTZ camera, comprising a unit for determining intermediate positions of the camera, with the ability to record and store coordinates of intermediate positions of the camera, a unit for sequential rotation of the камеры-camera, a unit for obtaining the target position of the camera, a control unit, the control unit being connected to the receiving unit target position of the camera, the output of which is connected to the input of the unit for determining intermediate positions of the camera, which is connected to the input of the control unit, the input of which is connected to the output of the unit after ovatelnogo turn PTZ- camera.