CN113834449B - Visual angle detection method and device for medical display - Google Patents
Visual angle detection method and device for medical display Download PDFInfo
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Abstract
The invention relates to a visual angle detection method and a visual angle detection device for a medical display, which belong to the technical field of instrument optical detection, and the method comprises the steps of displaying an image target in the central area of the medical display, and converting the display coordinate system into a mechanical arm coordinate system; calibrating the relative positions of the camera, the mechanical arm and the medical display, and calculating and planning the motion track of the brightness meter held at the tail end of the mechanical arm; after each 1 degree angle shift, the luminance ratio at that position is calculated. The device is including being fixed in camera and the luminance meter at the arm end, and camera and luminance meter are parallel to each other, all are perpendicular with the axial of the terminal rotation axis of the activity of arm. The invention realizes the field automatic calibration of the visual angle parameter of the medical display. The complicated support building, positioning and adjusting processes are not needed, so that the field calibration and detection of the visible angle parameters of the medical display can be conveniently carried out, and the working quality and the working efficiency are greatly improved.
Description
Technical Field
The invention relates to a visual angle detection method and a visual angle detection device for a medical display, and belongs to the technical field of optical detection of instruments.
Background
With the continuous promotion of high-quality development of the medical industry, the digitalization process of hospitals at all levels is effectively promoted, and the popularity of digital medical displays (PACS) is increased year by year. The medical image diagnosis instruments including ultrasound, DR, CT, MRI and the like are equipped with professional medical displays as terminal presentation equipment of the PACS system, and the accuracy and reliability of the current medical image diagnosis depend on the quality of medical images presented by the medical displays to a great extent. Medical displays are more and more common in clinical use occasions such as operating rooms and multi-expert consultation, so that the requirement on visual angle parameters is more and more emphasized.
The published national calibration specification JJF 1746 and 2019 medical image diagnosis display system calibration specification take the visual angle as one of important measurement parameters, and provide a reference index that the horizontal visual angle and the vertical visual angle are not less than 150 degrees. The existing visual angle detection device mainly has two types, namely a guide rail type and a rotary table type, the size and the weight are not suitable for developing field detection, the detection of a vertical visual angle cannot be developed under the condition that a medical display does not have a rotary screen function, and when actual calibration work is developed, the measurement of a visual angle parameter is also one of the most time-consuming and labor-consuming items. Therefore, developing a set of measuring device for field calibration aiming at developing rapid and efficient automatic detection of visible angle parameters of a medical display is a research work with practical requirements in the field of current medical measurement.
Patent document CN107463789A provides an integrated automatic calibration device for medical display. The luminance meter and the colorimeter are fixed on the rotating table and the balance supporting mechanism, and the balance supporting mechanism moves back and forth, left and right and up and down along the guide rail. This calibration device is bulky and is only suitable for use in fixed locations. Also, when the display plane is not perpendicular to the desktop, calibration is difficult to perform. The existing design is not suitable for carrying out the field calibration work of the medical display, particularly the construction of a visual angle detection device, is relatively complex, has certain requirements on the size and the shape of a base of the medical display, and limits the application range of the medical display. Meanwhile, the high-resolution liquid crystal screen of the medical display belongs to fragile products, the transportation requirement is high in the process of a submission laboratory, and in addition, the medical display is an indispensable terminal display part of each medical imaging device, and the timeliness of the submission laboratory can hardly meet the clinical requirements of hospitals.
Disclosure of Invention
The invention aims to provide a method and a device for detecting visual angle parameters of a medical display, which solve the problem that the current medical display cannot be calibrated on site and meet the requirements of national calibration standards of the medical display on corresponding technical indexes of the visual angle parameters.
The technical solution for realizing the purpose of the invention is as follows:
a visual angle detection method of a medical display comprises the following operation steps:
step 1: displaying an image target in the central area of the medical display, obtaining a conversion relation between a camera pixel coordinate and a mechanical arm space coordinate through hand-eye calibration, and converting a display coordinate system into a mechanical arm coordinate system;
step 2: calculating the target pose under the mechanical arm coordinate system by using the conversion relation obtained by calibrating the hand eyes, resolving the obtained pose information into a specific output signal by a mechanical arm motion resolving controller through robot inverse kinematics, and driving the tail end of the mechanical arm to move towards the center of the display;
and step 3: calculating the position error between the image center and the target center after the target image is obtained by the camera, driving the mechanical arm to move by taking the position error as a control condition, and compensating the error introduced by the calibration precision and the coordinate conversion in the visual servo positioning process based on the position in the step 2;
and 4, step 4: after the vertical positioning of the tail end of the mechanical arm relative to the central area of the display is completed, calculating and planning the motion trail of the tail end of the mechanical arm: the central point of the display is taken as the center of sphere, the distance between the brightness meter at the initial position and the central point of the display is taken as the radius, and the brightness meter extends in four directions, namely vertical, horizontal and left and right directions;
and 5: taking a brightness meter vertical to the middle area of the display as an initial position, according to the track planned in the step 4, respectively moving the brightness meter held at the tail end of the mechanical arm in a stepping manner along the track in the horizontal left-right direction and the vertical up-down direction at an angle of 1 degree, always aligning the brightness meter to the center of the display in the moving process, reading the luminance measurement values of 100% full white field and 0% full black field of the display once after moving for each angle of 1 degree, and calculating the luminance ratio of the position;
step 6: in the process of moving towards each direction, when the brightness ratio of the position is less than 10, stopping moving continuously, and driving the mechanical arm to return to an initial position vertical to the center of the display;
and 7: the sum of the angles measured by moving according to the horizontal left and right direction tracks is the horizontal visual angle, and the sum of the angles measured by moving according to the vertical upper and lower direction tracks is the vertical visual angle.
Further, step a1, step a 1: the camera (2) and the brightness meter (3) are fixed at the tail end of the mechanical arm, the mechanical arm is fixed in front of the medical display through a support or a chassis, and the brightness meter held at the tail end of the mechanical arm can move along the circular arc tracks in the horizontal and vertical directions of the medical display by taking the center of the medical display as the center of a circle.
Further, the specific process of step 1 is as follows:
establishing a camera coordinate system by using the optical center of the camera, establishing a world coordinate system on the image target, wherein the Z axis of the world coordinate system is vertical to the medical display, the acquired image comprises the characteristic information of the image target, the coordinates of the characteristic points of the image target under the world coordinate system are known, and the following steps are obtained according to the relationship of the characteristic points under the world coordinate system and the camera coordinate system:
the above equation is a conversion relation of the camera coordinate system,
is a matrix of parameters in the camera and is,
is a pose matrix of the world coordinate system of the medical display under the coordinate system of the camera and is expressed as an external parameter matrix of the camera in the coordinate system of the camera,
for feature points in the camera coordinate system
Orientation coordinate and pose matrix
Correlation, in the positioning of medical displays, world coordinates of image target feature points on the medical display
And pixel coordinates
Are all known, camera intrinsic parameters
As known, the medical display image target is a pose transformation matrix from a world coordinate system to a camera coordinate system
And substituting coordinate information of a plurality of characteristic points into the formula to obtain a pose matrix
And positioning the medical display is completed.
Further, the specific process of calculating the target pose under the mechanical arm coordinate system in the step 2 is as follows:
the method comprises the steps of collecting image targets under different poses to carry out hand-eye positioning work of a mechanical arm, placing the image targets in front of the mechanical arm to be fixed, continuously changing the poses of the mechanical arm to collect the image targets with different relative poses, and calculating the positions of the image targets relative to a mechanical arm coordinate system according to the relationship between the poses of the image targets and a camera and the terminal poses of the mechanical arm when each image target is collected.
Further, the specific process of calculating the position error between the image center and the target center in step 3 is as follows:
let the camera coordinate system be
The coordinate system of the end of the mechanical arm
Coordinate system of medical display
The position of the mechanical arm is changed twice, the initial position is regarded as the first moving position, and before moving, the coordinate system of the camera and the coordinate system of the tail end of the mechanical arm are composed of
、
Represents; after moving, the camera coordinate system and the mechanical arm end coordinate system are composed of
、
Representing the medical display coordinate system
Inner point
In corresponding four coordinate systems
、
、
、
The point coordinates under the corresponding coordinates are set as
、
、
、
By using the position transformation between coordinate systems, the following relation equation between points is obtained:
from the above formula, one can obtain:
in the formula (I), the compound is shown in the specification,
as a terminal coordinate system
、
A homogeneous transformation matrix between them
Is a basic coordinate system of the mechanical arm,
、
as the end coordinate system of the robot arm
、
And base coordinate system
A homogeneous transformation matrix in between; wherein the content of the first and second substances,
、
obtained by reading the joint information of the mechanical arm and deducted
It is recorded as
；
As a terminal coordinate system
、
The camera coordinate system is obtained through the camera external parameters
、
Coordinate system of medical displayHomogeneous transformation matrix of cells
、
From which a relation matrix between the camera coordinate systems can be obtained
It is recorded as
(ii) a Since the position of the camera is fixed, the homogeneous transformation matrix between the camera coordinate system and the end coordinate system is also fixed and recorded as
；
The formula is written as:
，
the above formula is a basic equation for calibrating the hand and the eye, and the pose solving process of calibrating the hand and the eye is to obtain a plurality of basic equations according to the poses of a plurality of groups of mechanical arms so as to solve a matrix
。
The utility model provides a visual angle detection device of medical display, includes arm, camera and luminance meter are fixed in the activity of arm and are terminal, just camera and luminance meter are parallel to each other, all with the axial vertical of the terminal rotation axis of the activity of arm.
Further, the mechanical arm is a six-axis mechanical arm and comprises a first rotating arm, a second rotating arm, a third rotating arm, a fourth rotating arm, a fifth rotating arm and a sixth rotating arm which are sequentially connected and can rotate 360 degrees around respective central axes;
the first rotating arm is vertically arranged on the mounting platform, the central axis of the first rotating arm is perpendicular to the plane of the mounting platform, and the mounting platform is arranged on the bracket or the chassis;
the first rotating arm and the second rotating arm are connected, wherein the axes are vertical to each other;
an arm lever a is connected between the second rotating arm and the third rotating arm, the arm lever a is perpendicular to the central axes of the second rotating arm and the third rotating arm respectively, the central axes of the second rotating arm and the third rotating arm are parallel, when the second rotating arm rotates, the arm lever a rotates around the central axis of the second rotating arm, and the arm lever a drives the third rotating arm to move synchronously;
an arm lever b is connected between the third rotating arm and the fourth rotating arm, the arm lever b is perpendicular to the central axes of the third rotating arm and the fourth rotating arm respectively, the central axes of the third rotating arm and the fourth rotating arm are parallel, one end of the axis of the third rotating arm is provided with an L-shaped transition plate extending forwards, one side of the L-shaped transition plate is fixed with the end face of the third rotating arm, the other side of the L-shaped transition plate is parallel to the central axis of the third rotating arm and is fixed with the head end of the arm lever b, and the tail end of the arm lever b is connected with the axial outer wall of the fourth rotating arm;
the fourth rotating arm and the fifth rotating arm are connected, wherein the axes are vertical to each other;
the fifth rotating arm and the sixth rotating arm are connected, wherein the axes are vertical to each other;
the sixth rocking arm is the activity end, the luminance meter sets up in the axial direction center top of sixth rocking arm, and the luminance meter is parallel with the sixth rocking arm, the camera sets up in the luminance meter top, the axis coplane of camera and luminance meter.
Furthermore, the first rotating arm, the second rotating arm, the third rotating arm, the fourth rotating arm, the fifth rotating arm and the sixth rotating arm are respectively internally provided with an independently controlled servo motor and a communication module, and the independently controlled servo motor and the communication module are used for feeding back the position information of the corresponding rotating arm in time and receiving a control instruction of the servo motor.
Furthermore, the base plate is rectangular, suckers are arranged at positions, close to the four corners, of the bottom surface of the base plate, the suckers are of a cavity structure, and the side walls of the suckers are connected with vacuum-pumping pipes in a through mode.
Compared with the prior art, the invention has the following remarkable advantages:
the invention can realize the field automatic detection of the visual angle detection of the medical display. The method has the advantages that a complex positioning and adjusting process is not needed, the moving path of the tail end of the mechanical arm is automatically planned after hand-eye calibration is completed through machine vision, and the central axis extension line of the brightness meter is ensured to be always aligned to the central area of the display in the detection process. In addition, the current medical display is inconvenient to transport to a laboratory for detection, the cost is high, the risk is high, the field detection can be carried out in the use place of a user by adopting the scheme of the invention, and the detection quality and the working efficiency are greatly improved.
Drawings
Figure 1 is a schematic flow diagram of the present invention,
FIG. 2 is a flow chart of the pose algorithm of the mechanical arm of the present invention,
figure 3 is a schematic flow chart of the calibration of the mechanical arm of the present invention,
figure 4 is a schematic view of the coordinate system for calibration of the robotic arm of the present invention,
figure 5 is a schematic view of the robotic arm of the present invention facing a medical display,
figure 6 is a schematic view of the robotic arm of the present invention rotated to the left side of the medical display,
figure 7 is a schematic view of the robotic arm of the present invention rotated to the right of the medical display,
1-medical display, 2-camera, 3-luminance meter, 4-sixth mechanical arm, 5-fifth mechanical arm, 6-fourth mechanical arm, 7-third mechanical arm, 8-second mechanical arm, 9-first mechanical arm, 10-base, 11-sucking disc, 12-evacuation pipe, 13-mount table.
Detailed Description
The invention is further described with reference to the following figures and embodiments.
The luminance ratio is calculated according to the following formula:
LRthe ratio of the luminance brightness is expressed,L LR,maxindicating when a white field test image is displayed (e.g., 255 gray scale), brightMaximum luminance value, cd/m, measured by a photometer2； L LR,maxIndicating the maximum luminance value, cd/m, measured by a luminance meter when a black field test image is displayed (e.g., 0-gradation)2。
The ratio of the luminance of the light measured by the luminance meter at each angle is calculated and compared to the 0 ° angle, i.e., the ratio of the luminance of the light perpendicular to the display screen, and if greater than 1.0 or other value, the viewing angle requirement is deemed to be satisfied.
In the visual angle detection, the starting position was set to 0 ° when the luminance meter was vertically aligned with the center of the display. Setting the brightness as a calibration brightness value recommended by a manufacturer; if there is no recommended value, the brightness value is set to 60% of the maximum brightness value that the display can adjust to. Taking the horizontal visual angle as an example, the luminance meter needs to rotate concentrically from the initial position to the left and right along the same horizontal plane until the luminance meter is parallel to the display screen. Namely, the extension line of the central axis of the brightness meter is always aligned with the central area of the display, moves towards the left side and the right side of the display in an arc shape and keeps the distance from the center of the display constant. Similarly, for a vertically viewable angle, the luminance meter needs to be rotated concentrically upward and downward along the same horizontal plane from the starting position to be parallel to the display screen.
The invention aims to conveniently realize the movement of the brightness meter on site, thereby realizing the automation of the monitoring of the visual angle of the medical display; and the brightness ratio of the display is measured at intervals of 1 degree in the rotation and movement process of the luminance meter, so that the detection accuracy is improved.
As can be seen from fig. 1, the specific detection process of the present patent is as follows:
step 1: displaying an image target in the central area of the medical display 1, obtaining a conversion relation between a camera pixel coordinate and a mechanical arm space coordinate through hand-eye calibration, and converting a display coordinate system into a mechanical arm coordinate system;
step 2: calculating the target pose under the mechanical arm coordinate system by using the conversion relation obtained by calibrating the hand eyes, resolving the obtained pose information into a specific output signal by a mechanical arm motion resolving controller through robot inverse kinematics, and driving the tail end of the mechanical arm to move towards the center of the display;
and step 3: calculating the position error between the image center and the target center after the target image is obtained by the camera, driving the mechanical arm to move by taking the position error as a control condition, and compensating the error introduced by the calibration precision and the coordinate conversion in the visual servo positioning process based on the position in the step 2;
and 4, step 4: after the vertical positioning of the tail end of the mechanical arm relative to the central area of the display is completed, calculating and planning the motion trail of the tail end of the mechanical arm: the central point of the display is taken as the center of sphere, the distance between the brightness meter at the initial position and the central point of the display is taken as the radius, and the brightness meter extends in four directions, namely vertical, horizontal and left and right directions;
and 5: taking a brightness meter vertical to the middle area of the display as an initial position, according to the track planned in the step 4, respectively moving the brightness meter held at the tail end of the mechanical arm in a stepping manner along the track in the horizontal left-right direction and the vertical up-down direction at an angle of 1 degree, always aligning the brightness meter to the center of the display in the moving process, reading the luminance measurement values of 100% full white field and 0% full black field of the display once after moving for each angle of 1 degree, and calculating the luminance ratio of the position;
step 6: in the process of moving towards each direction, when the brightness ratio of the position is less than 10, stopping moving continuously, and driving the mechanical arm to return to an initial position vertical to the center of the display;
and 7: the sum of the angles measured by moving according to the horizontal left and right direction tracks is the horizontal visual angle, and the sum of the angles measured by moving according to the vertical upper and lower direction tracks is the vertical visual angle.
Referring to fig. 2, the pose algorithm process of the mechanical arm of the invention is as follows: the method comprises the steps of collecting image targets under different poses to carry out hand-eye positioning work of a mechanical arm, placing the image targets in front of the mechanical arm to be fixed, continuously changing the poses of the mechanical arm to collect the image targets with different relative poses, and calculating the positions of the image targets relative to a mechanical arm coordinate system according to the relationship between the poses of the image targets and a camera and the terminal poses of the mechanical arm when each image target is collected.
The visual servoing system in fig. 2 can use a camera, the camera shoots a calibration pattern (image target) on the display in real time, so as to position the poses of the camera and the luminance meter relative to the display in real time (because the camera and the luminance meter are relatively fixed, the pose of the luminance meter relative to the display screen can be directly obtained by the pose of the camera), the control system controls the movement of the mechanical arm based on the real-time pose of the luminance meter, so that the luminance meter rotates step by 1 degree each time, and the movement track of the luminance meter is required to be ensured in a concentric plane (including a horizontal vertical plane in the left-right direction and/or a vertical plane in the up-down direction) vertical to the display screen. The display alternately displays white field images and black field images, and when the target position is reached, the luminance information of the white field images and the black field images is captured by utilizing the machine vision driven luminance meter, and the luminance ratio is calculated. For example, when the horizontal deflection is 50 degrees to the left, the brightness ratio meets the measurement requirement, and when the horizontal deflection reaches 51 degrees, the brightness ratio exceeds the measurement requirement; and the horizontal deflection is 45 degrees to the right to obtain the brightness ratio meeting the measurement requirement, and the visual angle of the display in the horizontal direction is 95 degrees. Thereby, the process of measuring the light luminance ratio at each step point is completed. Similarly, the vertical direction is measured by deflecting upwards and downwards.
Referring to fig. 3, the calibration process of the mechanical arm of the present invention is: let the camera coordinate system be
The coordinate system of the end of the mechanical arm
Coordinate system of medical display
The position of the mechanical arm is changed twice, the initial position is regarded as the first moving position, and before moving, the coordinate system of the camera and the coordinate system of the tail end of the mechanical arm are composed of
、
Represents; after moving, the camera coordinate system and the mechanical arm end coordinate system are composed of
、
Representing the medical display coordinate system
Inner point
In corresponding four coordinate systems
、
、
、
The point coordinates under the corresponding coordinates are set as
、
、
、
By using the position transformation between coordinate systems, the following relation equation between points is obtained:
from the above formula, one can obtain:
in the formula (I), the compound is shown in the specification,
as a terminal coordinate system
、
A homogeneous transformation matrix between them
Is a basic coordinate system of the mechanical arm,
、
as the end coordinate system of the robot arm
、
And base coordinate system
A homogeneous transformation matrix in between; wherein the content of the first and second substances,
、
obtained by reading the joint information of the mechanical arm and deducted
It is recorded as
；
As a terminal coordinate system
、
The camera coordinate system is obtained through the camera external parameters
、
Homogeneous transformation matrix between medical display coordinate system
、
From which a relation matrix between the camera coordinate systems can be obtained
It is recorded as
(ii) a Since the position of the camera is fixed, the homogeneous transformation matrix between the camera coordinate system and the end coordinate system is also fixed and recorded as
；
The formula is written as:
，
the above formula is a basic equation for calibrating the hand and the eye, and the pose solving process of calibrating the hand and the eye is to obtain a plurality of basic equations according to the poses of a plurality of groups of mechanical arms so as to solve a matrix
。
Referring to fig. 4-6, the visual angle detecting apparatus for a medical display includes a robot arm, a camera 2 and a luminance meter 3, the camera 2 and the luminance meter 3 are fixed to a movable end of the robot arm, and the camera 2 and the luminance meter 3 are parallel to each other and are perpendicular to an axial direction of a rotation shaft of the movable end of the robot arm.
The mechanical arm is a six-axis mechanical arm and comprises a first rotating arm 9, a second rotating arm 8, a third rotating arm 7, a fourth rotating arm 6, a fifth rotating arm 5 and a sixth rotating arm 4 which are sequentially connected and can rotate 360 degrees around respective central axes;
the first rotating arm 9 is vertically arranged on the mounting table 13, the central axis of the first rotating arm 9 is perpendicular to the plane of the mounting table 13, and the mounting table 13 is arranged on the bracket or the chassis;
the first rotating arm 9 and the second rotating arm 8 are connected, wherein the axes are mutually vertical;
an arm rod a is connected between the second rotating arm 8 and the third rotating arm 7, the arm rod a is perpendicular to the central axes of the second rotating arm 8 and the third rotating arm 7 respectively, the central axes of the second rotating arm 8 and the third rotating arm 7 are parallel, when the second rotating arm 8 rotates, the arm rod a rotates around the central axis of the second rotating arm 8, and the arm rod a drives the third rotating arm 7 to move synchronously;
an arm lever b is connected between the third rotating arm 7 and the fourth rotating arm 6, the arm lever b is perpendicular to the central axes of the third rotating arm 7 and the fourth rotating arm 6 respectively, the central axes of the third rotating arm 7 and the fourth rotating arm 6 are parallel, one end of the axis of the third rotating arm 7 is provided with an L-shaped transition plate extending forwards, one side of the L-shaped transition plate is fixed with the end face of the third rotating arm 7, the other side of the L-shaped transition plate is parallel to the central axis of the third rotating arm 7 and is fixed with the head end of the arm lever b, and the tail end of the arm lever b is connected with the axial outer wall of the fourth rotating arm 6;
the fourth rotating arm 6 is connected with the fifth rotating arm 5, wherein the axes are vertical to each other;
the fifth rotating arm 5 is connected with the sixth rotating arm 4, wherein the axes are vertical to each other;
the sixth rotating arm 4 is a movable tail end, the brightness meter 3 is arranged above the axial center of the sixth rotating arm 4, the brightness meter 3 is parallel to the sixth rotating arm 4, the camera 2 is arranged at the top of the brightness meter 3, and the central axes of the camera 2 and the brightness meter 3 are coplanar.
The first rotating arm 9, the second rotating arm 8, the third rotating arm 7, the fourth rotating arm 6, the fifth rotating arm 5 and the sixth rotating arm 4 are respectively internally provided with an independently controlled servo motor and a communication module which are used for feeding back the position information of the corresponding rotating arm in time and receiving the control instruction of the servo motor.
The specific embodiment of the base plate 10 is given, the base plate 10 is rectangular, the positions of the bottom surface of the base plate, which are close to four corners, are provided with the suction cups 11, the suction cups 11 are in a cavity structure, and the side walls of the suction cups 11 are connected with the vacuumizing pipes 12 in a penetrating way. During the use, place medical display 1 in the place ahead of arm, the chassis adsorbs on the desktop, and the sucking disc bottom is pasted in the desktop, connects the suction pump through the evacuation pipe, forms the inside negative pressure of sucking disc, and sucking disc 11 stabilizes the absorption and the desktop, and the chassis is fixed, and the arm can not have the displacement deviation in the use.
Before the device is used, the mechanical arm is firstly fixed at a proper position right in front of the medical display, then the relative coordinates of the mechanical arm, the medical display and the camera are calibrated by using the method, after the calibration is finished, each path point passed by the mechanical arm is automatically planned, stepping rotation is realized by controlling each rotating arm of the mechanical arm, and the moving track of the camera is accurately controlled.
Claims (7)
1. A visual angle detection method of a medical display is characterized by comprising the following steps: the method comprises the following operation steps:
step 1: displaying an image target in the central area of the medical display, obtaining a conversion relation between a camera pixel coordinate and a mechanical arm space coordinate through hand-eye calibration, and converting a display coordinate system into a mechanical arm coordinate system;
the specific process is as follows:
establishing a camera coordinate system by using the optical center of the camera, establishing a world coordinate system on the image target, wherein the Z axis of the world coordinate system is vertical to the medical display, the acquired image comprises the characteristic information of the image target, the coordinates of the characteristic points of the image target under the world coordinate system are known, and the following steps are obtained according to the relationship of the characteristic points under the world coordinate system and the camera coordinate system:
the above equation is a conversion relation of the camera coordinate system,
is a matrix of parameters in the camera and is,
is a pose matrix of the world coordinate system of the medical display under the coordinate system of the camera and is expressed as an external parameter matrix of the camera in the coordinate system of the camera,
for feature points in the camera coordinate system
Orientation coordinate and pose matrix
Correlation, in the positioning of medical displays, world coordinates of image target feature points on the medical display
And pixel coordinates
Are all known, camera intrinsic parameters
As known, the medical display image target is a pose transformation matrix from a world coordinate system to a camera coordinate system
And substituting coordinate information of a plurality of characteristic points into the formula to obtain a pose matrix
Positioning the medical display is completed;
step 2: calculating the target pose under the mechanical arm coordinate system by using the conversion relation obtained by calibrating the hand eyes, resolving the obtained pose information into a specific output signal by a mechanical arm motion resolving controller through robot inverse kinematics, and driving the tail end of the mechanical arm to move towards the center of the display;
and step 3: calculating the position error between the image center and the target center after the target image is obtained by the camera, driving the mechanical arm to move by taking the position error as a control condition, and compensating the error introduced by the calibration precision and the coordinate conversion in the visual servo positioning process based on the position in the step 2;
and 4, step 4: after the vertical positioning of the tail end of the mechanical arm relative to the central area of the display is completed, calculating and planning the motion trail of the tail end of the mechanical arm: the central point of the display is taken as the center of sphere, the distance between the brightness meter at the initial position and the central point of the display is taken as the radius, and the brightness meter extends in four directions, namely vertical, horizontal and left and right directions;
and 5: taking a brightness meter vertical to the middle area of the display as an initial position, according to the track planned in the step 4, respectively moving the brightness meter held at the tail end of the mechanical arm in a stepping manner along the track in the horizontal left-right direction and the vertical up-down direction at an angle of 1 degree, always aligning the brightness meter to the center of the display in the moving process, reading the luminance measurement values of 100% full white field and 0% full black field of the display once after moving for each angle of 1 degree, and calculating the luminance ratio of the position;
step 6: in the process of moving towards each direction, when the brightness ratio of the position is less than 10, stopping moving continuously, and driving the mechanical arm to return to an initial position vertical to the center of the display;
and 7: the sum of the angles measured by moving according to the horizontal left and right direction tracks is the horizontal visual angle, and the sum of the angles measured by moving according to the vertical upper and lower direction tracks is the vertical visual angle.
2. The visual angle detection method of a medical display according to claim 1, characterized in that: step a1, step a 1: the camera (2) and the brightness meter (3) are fixed at the tail end of the mechanical arm, the mechanical arm is fixed in front of the medical display through a support or a chassis, and the brightness meter held at the tail end of the mechanical arm can move along the circular arc tracks in the horizontal and vertical directions of the medical display by taking the center of the medical display as the center of a circle.
3. The visual angle detection method of a medical display according to claim 1, characterized in that: the specific process of calculating the target pose under the mechanical arm coordinate system in the step 2 is as follows:
the method comprises the steps of collecting image targets under different poses to carry out hand-eye positioning work of a mechanical arm, placing the image targets in front of the mechanical arm to be fixed, continuously changing the poses of the mechanical arm to collect the image targets with different relative poses, and calculating the positions of the image targets relative to a mechanical arm coordinate system according to the relationship between the poses of the image targets and a camera and the terminal poses of the mechanical arm when each image target is collected.
4. The visual angle detection method of a medical display according to claim 1, characterized in that: the specific process of calculating the position error between the image center and the target center in the step 3 is as follows:
let the camera coordinate system be
End of arm coordinate systemIs composed of
Coordinate system of medical display
The position of the mechanical arm is changed twice, the initial position is regarded as the first moving position, and before moving, the coordinate system of the camera and the coordinate system of the tail end of the mechanical arm are composed of
、
Represents; after moving, the camera coordinate system and the mechanical arm end coordinate system are composed of
、
Representing the medical display coordinate system
Inner points in the corresponding four coordinate systems
、
、
、
The point coordinates under the corresponding coordinates are set as
、
、
、
By using the position transformation between coordinate systems, the following relation equation between points is obtained:
from the above formula, one can obtain:
in the formula (I), the compound is shown in the specification,
as a terminal coordinate system
、
A homogeneous transformation matrix between them
Is a basic coordinate system of the mechanical arm,
、
as the end coordinate system of the robot arm
、
And base coordinate system
A homogeneous transformation matrix in between; wherein the content of the first and second substances,
、
obtained by reading the joint information of the mechanical arm and deducted
It is recorded as
；
As a terminal coordinate system
、
The camera coordinate system is obtained through the camera external parameters
、
Homogeneous transformation matrix between medical display coordinate system
、
From which a relation matrix between the camera coordinate systems can be obtained
It is recorded as
(ii) a Since the position of the camera is fixed, the homogeneous transformation matrix between the camera coordinate system and the end coordinate system is also fixed and recorded as
；
The formula is written as:
，
the above formula is a basic equation for calibrating the hand and the eye, and the pose solving process of calibrating the hand and the eye is to obtain a plurality of basic equations according to the poses of a plurality of groups of mechanical arms so as to solve a matrix
。
5. A visual angle detection device of a medical display is characterized in that: the automatic detection device comprises a mechanical arm, a camera (2) and a brightness meter (3), wherein the camera (2) and the brightness meter (3) are fixed at the movable tail end of the mechanical arm, and the camera (2) and the brightness meter (3) are parallel to each other and are perpendicular to the axial direction of a rotating shaft at the movable tail end of the mechanical arm;
the mechanical arm is a six-axis mechanical arm and comprises a first rotating arm (9), a second rotating arm (8), a third rotating arm (7), a fourth rotating arm (6), a fifth rotating arm (5) and a sixth rotating arm (4) which are sequentially connected and can rotate 360 degrees around respective central axes;
the first rotating arm (9) is vertically arranged on the mounting table (13), the central axis of the first rotating arm (9) is perpendicular to the plane of the mounting table (13), and the mounting table (13) is arranged on the support or the chassis;
the first rotating arm (9) and the second rotating arm (8) are connected, wherein the axes are vertical to each other;
an arm lever a is connected between the second rotating arm (8) and the third rotating arm (7), the arm lever a is perpendicular to the central axes of the second rotating arm (8) and the third rotating arm (7), the central axes of the second rotating arm (8) and the third rotating arm (7) are parallel, when the second rotating arm (8) rotates, the arm lever a rotates around the central axis of the second rotating arm (8), and the arm lever a drives the third rotating arm (7) to move synchronously;
an arm lever b is connected between the third rotating arm (7) and the fourth rotating arm (6), the arm lever b is perpendicular to the central axes of the third rotating arm (7) and the fourth rotating arm (6), the central axes of the third rotating arm (7) and the fourth rotating arm (6) are parallel, one end of the axis of the third rotating arm (7) is provided with an L-shaped transition plate extending forwards, one side of the L-shaped transition plate is fixed with the end face of the third rotating arm (7), the other side of the L-shaped transition plate is parallel to the central axis of the third rotating arm (7) and fixed with the head end of the arm lever b, and the tail end of the arm lever b is connected with the axial outer wall of the fourth rotating arm (6);
the fourth rotating arm (6) is connected with the fifth rotating arm (5), wherein the axes are vertical to each other;
the fifth rotating arm (5) is connected with the sixth rotating arm (4), wherein the axes are vertical to each other;
sixth rocking arm (4) are the activity end, luminance meter (3) set up in the axial direction center top of sixth rocking arm (4), and luminance meter (3) are parallel with sixth rocking arm (4), camera (2) set up in luminance meter (3) top, the axis coplane of camera (2) and luminance meter (3).
6. The visual angle detection device of a medical display according to claim 5, wherein: the first rotating arm (9), the second rotating arm (8), the third rotating arm (7), the fourth rotating arm (6), the fifth rotating arm (5) and the sixth rotating arm (4) are internally provided with independently controlled servo motors and communication modules for feeding back the position information of the corresponding rotating arm in time and receiving the control instruction of the servo motors.
7. The visual angle detection device of a medical display according to claim 5, wherein: the base plate is rectangular, suckers are arranged at positions, close to four corners, of the bottom surface of the base plate, the suckers are of a cavity structure, and the side walls of the suckers are connected with vacuum-pumping tubes in a through mode.
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