Abstract:
A robot system comprises a base ( 2 ), a robot arm ( 1 ) connected to the base, a camera ( 10 ), at least one objective lens in the camera ( 10 ) being movable with the robot arm ( 1 ), and a screen ( 16 ). A control unit ( 15 ) is configured to detect a change in the distance between an object ( 21 ) detected by the camera ( 10 ) and the objective lens, and to vary the zoom factor of a zoom function of the camera ( 10 ) according to the change in distance.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a robotic system, in particular for operating room applications. 
       BACKGROUND INFORMATION 
       [0002]    Robots have been widely used for many years in the field of industrial manufacturing where, thanks to their ability to reproduce pre-programmed sequences of operations within a short time, an infinite number of times, they make possible significant rationalizations in production. Since such robots are in most cases also designed to relieve humans of fatiguing working steps like handling heavy workpieces, they are correspondingly robust in construction and at most can only be deflected slightly through an external impact. Conversely, due to their considerable mass and rapid movements, these robots are quite capable of injuring personnel working in their vicinity. In order to avoid a collision with persons, industrial robots are therefore generally surrounded by a cage when in use. 
         [0003]    Robots which are designed for use in the operating theatre cannot, for practical reasons, be shielded by means of a cage, since in general they do not perform an operation on their own; medical personnel are also working on the same patient at the same time. A collision between such a robot and the personnel cannot therefore be prevented with absolute  certainty. Since a surgical robot is generally lighter and slimmer in construction than a production robot, in order to avoid unnecessarily blocking the personnel&#39;s view of a surgical field, in the event of a collision a deflection of the robotic arm cannot be wholly prevented. If a tool being handled by the robotic arm is also thereby deflected, this could injure the patient. 
         [0004]    It is possible to equip a robotic system with appropriate sensors for detecting any impending collision and with a control unit which, when a collision is predicted, controls an evasive movement of the robotic arm in order to avert the impending collision. However, the possibilities for such an evasive movement are limited when the robotic arm is handling a tool on or in the patient&#39;s body which may not be moved at will. 
         [0005]    It would be ideal if, in such a situation, only a central section of the robotic arm which connects the base with the tool could perform an evasive movement, while the tool itself remained in position. However, the number of degrees of freedom of the robotic arm is generally only as large as is necessary in order to perform the desired movements of the tool. Therefore, there is a not insignificant likelihood that the degrees of freedom of the robotic arm are not sufficient for an evasive movement in which the tool remains immovable. In such a case, an evasive movement can at  best be performed in which the resulting movement of the tool is safe for the patient. 
         [0006]    If the tool is a camera, in particular an endoscope camera, the problem arises that any movement of the camera changes the image which it provides of its surroundings. Any movement of the camera can therefore lead to a user who is observing the images supplied by the camera on a screen losing sight of an object which is of interest to him. This possibility exists both with a movement of the camera controlled by the user himself as well as when it moves due to the robotic arm being jolted or in connection with an evasive movement of the robotic arm. In the latter two cases the likelihood is, however, particularly high. 
         [0007]    Known from WO 2012/078989 A1 is a robotic system with a movable camera on a robotic arm which can be introduced into the body of a patient through a trocar sleeve in order to monitor a tool. A control unit calculates, on the basis of a known aperture angle of the field of view of the camera and known positions of camera and tool, whether the tool lies in the field of view of the camera. If this is not the case, then the camera is moved away from the tool in order to bring the tool into the field of view. If the tool is to be shown larger, the camera is moved towards the tool, insofar as this is possible without losing the tool from the field of view.  The monitoring of other objects, in particular of tissue parts of a patient, is not facilitated with this robotic system. 
         [0008]    There is therefore a need for a robotic system with a camera in which the likelihood that an observed object is lost from sight through a movement of the camera is reduced. 
       SUMMARY 
       [0009]    In order to satisfy this need, according to one embodiment of the invention, in a robotic system with a base, a robotic arm connected with the base and a camera, wherein at least one lens of the camera can be moved with the robotic arm, a control unit is configured to register a change in the distance between an object captured by the camera and the lens and to vary the zoom factor of a zoom function of the camera according to the change in distance. 
         [0010]    This variable zoom function makes it possible to limit changes in the size in which the object is represented on a screen in the event of a movement of the lens along its optical axis and in this way make it easier for a user to recognise the object following the movement of the lens. 
         [0011]    Ideally, the control unit should be configured to keep the size of the object on the screen constant independently of distance.  
         [0012]    The zoom function can be implemented in that the lens has a focal length which can be adjusted by means of the control unit. 
         [0013]    Alternatively, the camera can include an image processing unit which implements the zoom function in that it transforms a raw image recorded by the camera into an output image using a variable scale. 
         [0014]    Various objects can be visible in a raw image generated by the camera. It can be the case that a user specifies to the image processing unit one of these objects, which he wishes to be displayed on the screen with distance-independent size. However, if the movement of the lens is attributable to a collision avoiding movement, then the likelihood is high that the user has not selected an object at the decisive moment. Therefore, the control unit is preferably configured to assume the object to be in a plane on which the camera is focused, since it can be assumed that, if the user wishes to follow an object in view of the camera he will focus the camera on this object. 
         [0015]    The lens of the camera can be rotatable around its optical axis by the robotic arm. In this case it is practical for the image processing unit to be configured to output a raw image supplied by the camera on the screen rotated in the opposite direction to the rotation of the lens. In this way, a rotation of the lens which can be necessary in connection with  an evasive movement of the robotic arm does not affect the image visible on the screen. 
         [0016]    It is practical for the control unit to be connected with means for detecting the approach of a foreign body to the robotic arm and configured to control an evasive movement of the robotic arm on detecting such an approach. 
         [0017]    The means for detecting the approach can comprise at least one proximity sensor or a camera. 
         [0018]    While a camera can preferably be arranged separately from the robotic arm in order to survey it together with an approaching foreign body, proximity sensors are preferably arranged distributed on the robotic arm in order in each case to detect an approach locally. In particular, this makes possible a simple control of the evasive movement, since the individual proximity sensors can in each case be assigned different strategies for evasive movements according to their positioning on the robotic arm. 
         [0019]    The control unit can also be connected with a further robotic arm and can be configured, on detecting a convergence of the robotic arms, to control an evasive movement of the robotic arm. 
         [0020]    In particular, a movement of the lens in the direction of its optical axis can be considered as an evasive movement. 
         [0021]    In such a case, the control unit can be configured to vary the zoom factor if a movement of the lens in the  direction of its optical axis is an evasive movement, but not to vary the zoom factor if the movement is caused by an external command, because if the user issues a corresponding command while observing the image on the screen then he expects to be able to recognize and assess the movement of the camera on the basis of the change in the relationship between the sizes of objects represented in the image, and failure of an intuitively anticipated change in size to occur can leave the user uncertain whether or not the robotic arm has performed the commanded movement. 
         [0022]    However, it can also be practical, on a user interface, to offer the user the option of choosing whether, in the case of a movement of the lens controlled by him, the size of the object should be distance-dependent or fixed. This makes it possible, for example, after precisely examining the object by means of the camera from a close proximity between camera and object, to create space for a tool for manipulating the object without having to relinquish the detailed view of the object on the screen. 
         [0023]    The control unit can also be configured to control a rotation of the lens around its optical axis as an evasive movement. Although this would not lead to a change in the size of an object displayed on the screen, the rotation of the image associated with the rotation of the camera can hinder the recognition of the object which is of interest, for which  reason the rotation of the image should be at least partially compensated by the image processing unit installed downstream. 
         [0024]    In this case the image processing unit can, practically, be configured to rotate the raw image supplied by the camera if a rotation of the camera around the optical axis of the lens is an evasive movement, but not to rotate the raw image if the rotation is caused by an external command. 
         [0025]    It is practical for the aforementioned user interface also to be used to generate said external commands. 
         [0026]    The camera can in particular be part of an endoscope. 
         [0027]    If the optical axis of the lens coincides with the longitudinal axis of the endoscope, then an extraction movement of the endoscope does not generally present any risk of injury to the patient and can therefore be performed in connection with an evasive movement, if necessary. A rotation of the endoscope around its axis is also generally possible without any risk of injury. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    These and other features and advantages of the present invention will be better understood by reading the following detailed description, taken together with the drawings wherein:  
           [0029]      FIG. 1  shows a diagrammatic representation of a robotic system according to a first embodiment of the invention; 
           [0030]      FIG. 2  shows the robotic system from  FIG. 1  following an evasive movement; 
           [0031]      FIG. 3  shows steps of the image processing in a control unit of the robotic system from  FIG. 1 ; 
           [0032]      FIG. 4  shows the robotic system performing a second evasive movement; 
           [0033]      FIG. 5  shows a diagrammatic representation of the lens and sensor chip of an endoscope camera of the robotic system before the evasive movement shown in  FIG. 4 ; and 
           [0034]      FIG. 6  shows a representation analogous to  FIG. 5  following the evasive movement. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]      FIG. 1  shows, in diagrammatic form, a robotic system according to an embodiment of the present invention. The system comprises a robotic arm  1  with a base  2  mounted in fixed position, in this case for example on the ceiling of an operating room, a first arm section  3 , which is connected with the base via a first articulated module  4 , a second arm section  5  which is connected with the first arm section  3  via a second articulated module  6 , and an endoscope  7  which is detachably attached to a holder  9  connected with the second arm section  5  via the articulated module  8 .  
         [0036]    The articulated modules  4 ,  6 ,  8  are in this case designed as two-axis joints with two shafts arranged orthogonally in relation to one another which are in each case anchored non-rotatingly to an adjacent component of the robotic arm, i.e. the base  2  and the arm section  3  in the case of the module  4 , the arm sections  3 ,  5  in the case of the module  6  and the arm section  5  and the holder  9  in the case of the module  8 , and can be rotated with the aid of servomotors housed in the articulated modules  4 ,  6 ,  8 . 
         [0037]    In this case the endoscope  7  comprises a miniaturized camera  10  which is attached to the tip of a flexible insertion tube  11 . A base  12  for attachment to the holder  9  can be immovably connected with the insertion tube  11 , so that each movement of the camera  10  requires a corresponding movement of the holder  9 . However, in order to facilitate the introduction of the endoscope  7  into a lumen of a patient&#39;s body, the insertion tube  11  can also be movable with respect to the base  12  and the base  12  can be equipped with servomotors for the longitudinal displacement of the insertion tube  11  or rotation of the insertion tube  11  around its axis. 
         [0038]    A data bus  13  extends from a plug connection  14  on the holder  9  via the arm sections  5 ,  3  and articulated modules  8 ,  6 ,  4  of the robotic arm  1  up to a control unit  15  and an image processing unit  20 . Although in this case the image  processing unit  20  is represented located separately from the endoscope  7 , functionally it forms a part of its camera  10 . A screen  16  for displaying the images supplied by the camera  10  is connected to the image processing unit  20 . 
         [0039]    A user interface  17  for controlling movements of the robotic arm  1  or of the endoscope  7  is represented diagrammatically in  FIG. 1  as a joystick. The control unit  15  receives positioning commands from a user via the user interface  17  and converts these into actuating commands for the servomotors of the articulated modules  4 ,  6 ,  8  as well as, if present, servomotors of the endoscope  7 . It can be provided that the control unit  15  queries the endoscope  7  for technical data relating to the endoscope  7 , in particular concerning the presence of servomotors and the degrees of freedom of movement of the insertion tube  11  in relation to the base  12 , in order if necessary to use the servomotors of the endoscope  7  to drive a movement of the camera  10 . 
         [0040]    The data bus  13  also connects a plurality of proximity sensors  18  with the control unit  15 . In particular, capacitive sensors can be used as proximity sensors  18 , since these are capable of detecting the proximity of foreign bodies made of virtually any materials. In this case the proximity sensors  18  are only represented in exposed positions on the arm sections  3 ,  5 ; in practice, they can be distributed in larger numbers over the housing of the arm sections  3 ,  5  in order if necessary not only to register the fact that a  foreign body is approaching but, on the basis of a comparison of the signal strengths of differently placed proximity sensors  18 , also to make it possible to determine the direction from which the foreign body is approaching, or the point at which it is expected to collide with the robotic arm  1 . 
         [0041]    Fundamentally, proximity sensors  18  can also be provided on the articulated modules, in particular the articulated modules  6 ,  8 . The articulated module  4  does not require such sensors, since it is connected directly with the fixed-location base  2  and is therefore not capable of evading an approaching foreign body; however, a collision of a foreign body with the articulated module  4  also would not lead to a deflection of the robotic arm  1 . 
         [0042]    For reasons of efficiency of manufacture and maintenance it can be desirable for all the articulated modules  4 ,  6 ,  8  to be of identical design. In such a case, in order to make it possible also to detect the approach of a foreign body to the articulated modules  6 ,  8  without needing to equip these themselves with sensors, it can be practical to provide proximity sensors on the ends of the arm sections  3 ,  5  adjacent to the articulated modules  6 ,  8 . 
         [0043]    In order to assist the proximity sensors  13  or as a substitute for these, one or more cameras  19  can be provided which are pointed at the robotic arm  1 , the images from these  being analysed by the control unit  15  in order to recognise the approach of a foreign body to the robotic arm  1 . 
         [0044]      FIG. 2  shows a typical application situation of the robotic system according to the invention. The endoscope  7  is placed within the body of patient, not shown in the figure, and a surgeon bends his head over the patient in order to have an unobstructed view of a surgical field. If, in this situation, the robotic arm  1  was in the position shown in  FIG. 1 , the surgeon&#39;s head  25  could collide with the arm section  3 . This proximity is registered by the control unit  15  by means of the proximity sensors  18  and/or the camera  19 . The arm section  3  is moved out of the area in which there is a danger of collision through a rotation of the articulated module  4  around its vertical shaft fixed to the base  2 . In the configuration shown in  FIG. 2 , the arm sections  3 ,  5  are rotated by approx. 90 degrees in relation to the configuration shown in  FIG. 1 , so that a central part of the roughly u- formed arm section  3  and the articulated module  8  at the end of the arm section  5  face the viewer. In order to keep the position of the endoscope  7  unchanged during this rotation, the holder  9  is rotated from the position shown in  FIG. 1 , extending from the articulated module  8  towards the viewer, into a position extending diagonally downwards, and the articulated module  8  is raised through increased angling of the arm sections  3 ,  5  in relation to the vertical. Although the position of the endoscope  7  remains unchanged as a result,  it is rotated around the longitudinal axis of its base  12  or, due to the flexibility of the insertion tube  11 , around the optical axis of the camera  10 . 
         [0045]    The effect of such a rotation on an image supplied by the camera  10  is illustrated in  FIG. 3 . The camera  10  supplies a raw image to the image processing unit  20  which, in the configuration shown in  FIG. 1 , before the evasive movement of the robotic arm  1 , is output to the screen  16  untransformed by the image processing unit  20  and contains representations of several objects  21 ,  22  located in front of the lens  24 . A diagrammatic view of the screen  16 , on which the objects  21 ,  22  can be seen, is shown in the left-hand part of  FIG. 3 . The camera is focused on the object  21 , the objects  22  lie outside of a focused plane and therefore appear in the image more or less out of focus. 
         [0046]    The rotation of the camera  10  around its optical axis during the course of the evasive movement causes the images of the objects  21  on the sensor chip of the camera  10  also to rotate around the optical axis, so that the raw image supplied by the camera  10  to the image processing unit  20  assumes, for example, the form shown in the center part of  FIG. 3 . 
         [0047]    Since the control unit  15  knows all of the movements performed during the course of the evasive movement of the robotic arm  1 , it is able to calculate the rotation of the  camera  10  resulting from the evasive movement and to supply a corresponding angle of rotation to the image processing unit  20 , on the basis of which the image processing unit  20  calculates a transformed image in which this rotation is reversed. This transformed image  23  is represented in the right-hand part of  FIG. 3  as a rectangle outlined in a broken line. In the transformed image  23  the objects  21  have the same position as before the evasive movement and remain visible. If an object  21  has been successfully located within the patient&#39;s body, it is thus not lost again as a result of the evasive movement, and the surgeon is not irritated by a rotating movement of the image visible on the screen  16 . 
         [0048]    A corresponding image transformation can also be carried out by the image processing unit  20  in the case that the user commands, on the user interface  17 , a translation movement of the camera  10  but, due to limitations in the freedom of movement of the robotic arm  1 , this can only be realized simultaneously with a rotation—not commanded by the user and therefore also not expected—of the camera  10  around its optical axis. 
         [0049]    If, in contrast, the user commands, on the user interface  17 , a rotation of the camera  10 , then he also expects to see this on the screen. In this case the control unit  15  can actually control a physical rotation of the camera  10 , without the image processing unit  20  compensating the rotation, or the rotation can be effected purely  arithmetically in the image processing unit  20 , without the camera  10  being physically rotated. 
         [0050]    In a variant of the invention, the camera has a sensor chip which is mounted in the camera such that it can rotate around the optical axis of the lens. In this case no image transformation in the image processing unit  20  is necessary. Instead, the sensor chip is adjusted rotationally around the optical axis, contrary to the rotation of the camera, so that the rotational orientation of the sensor chip remains unchanged in relation to the image which is to be recorded. 
         [0051]      FIG. 4  shows another evasive movement of the robotic arm. In this case the robotic arm  1  is initially in a position represented with solid lines and evades a foreign body approaching from the left at approximately the height of the articulated module  6  through transition into the position represented with broken lines. This evasive movement does not involve any rotation of the endoscope  7  around its optical axis, instead it involves a movement withdrawing its camera  10  from the patient&#39;s body. 
         [0052]      FIG. 5  shows, in diagrammatic form, a lens  24  and a sensor chip  26  of the camera  10  before the evasive movement. Several objects  21 ,  22  are located before the lens  24  of the camera  10 . The object  21  is located in a plane  27  on which the lens  24  is focused, i.e. it is imaged in sharp focus on the sensor chip  26 . The focusing of the lens  24  is controlled by  the control unit  15  on the basis of commands issued by the user on the user interface  17 , therefore the distance d between the lens  24  and the plane  27  is known to the control unit  15 . 
         [0053]    During the course of the evasive movement, the distance between the object  21  and lens  24  increases to d′, as shown in  FIG. 6 . The control unit  15  increases the focal length of the lens  24  by the factor d′/d and the distance between lens  24  and sensor chip  26 , so that the plane  27  remains imaged in sharp focus on the sensor chip  26  and at the same time the size of the image  28  of the focused object  21  on the sensor chip  26  does not change. Although the position and sizes of images  29  of the other objects  22  change all the more the further distant these are from the plane  27 , this has only little influence on the image supplied by the camera  10 , since these objects  22  are only projected onto the sensor chip  26  out of focus. The object  21  thus remains clearly recognizable following the evasive movement. 
         [0054]    According to an alternative embodiment, in the event of an evasive movement of the camera  10  the control unit  15  only adjusts the focusing of the lens  24 , not its focal length. In this case too, the image  28  of the object  21  remains in sharp focus, but its size is changed. In order nonetheless to be able to display the object  21  in unchanged  size on the screen  16 , the image processing unit  20  enlarges a section of the raw image digitally. 
         [0055]    Both embodiments can be combined together, for example such that the control unit  15  switches over to digital enlargement of the raw image if the focal length of the lens  24  has reached its maximum. 
         [0056]    If the camera  10 , controlled by user commands, is moved along its optical axis, the image correction described above should generally not take place, since in this case the user also expects to see a changed image on the screen in reaction to a movement of the camera  10 . Nonetheless, the user can be given the option of selecting on the user interface  17  whether or not he wishes for the image correction to take place in the case of a movement of the camera  10  controlled by him; for example the possibility can be provided that the user can first inspect an object  21  which is to be operated on with the camera  10  from such a close distance that there is hardly space for the foreign bodies  22  obstructing the view between lens  24  and object  21 , and then increase the distance while maintaining the image size, in order to create space for a surgical tool between lens  24  and object  21 . 
       REFERENCE NUMBERS 
       [0000]    
       
           1  robotic arm 
           2  base 
           3  arm section 
           4  articulated module 
           5  arm section  
           6  articulated module 
           7  endoscope 
           8  articulated module 
           9  holder 
           10  camera 
           11  insertion tube 
           12  base 
           13  data bus 
           14  plug connection 
           15  control unit 
           16  screen 
           17  user interface 
           18  proximity sensor 
           19  camera 
           20  image processing unit 
           21  object 
           22  object 
           23  transformed image 
           24  lens 
           25  head 
           26  sensor chip 
           27  plane 
           28  image 
           29  image 
       
     
         [0086]    Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the allowed claims and their legal equivalents.