fig1 schematically shows an endoscope . the endoscope includes a shaft 10 that contains elements that are conventionally provided . the shaft has a longitudinal axis 12 . an objective optical system is provided at the distal end of the shaft to give the endoscope a view vector 14 and a field of view 16 . the objective optical system comprises components such as lenses , prisms , reflectors , etc . the objective optical system may be adjustable or mounted adjustably to provide a variable direction of view . a housing 18 is provided at the proximal end of the shaft 10 . an image sensing device or camera 20 is mounted in the housing 18 . it is configured to receive images 22 from the objective optical system . the housing 18 encases an electronic microprocessor ( not shown ) for performing calculations . the microprocessor is in communication with an image rotator ( not shown ), also contained within the housing . image rotation can be accomplished in one or more of three ways : physical rotation of the image sensor ; optical rotation of the received image prior to incidence upon the image sensor ; and electronic rotation of the image within a processor . the details of these methods are not necessary for an understanding of this invention , but are described in chatenever and other prior art . electronic rotation pick - up means , in the preferred embodiment three accelerometers 24 , 26 , 28 responsive to gravity , are mounted to the housing 18 . each accelerometer measures a component of gravity along a particular measurement axis . the accelerometers provide pulse - width - modulated signals to the processor which can convert each signal into a gravitational force measurement . changes in the gravitational force measurements from the accelerometers are related to rotations of the endoscope . in order to adequately describe the method of the current invention , an appropriate mathematical framework needs to be defined . the housing 18 has a longitudinal axis 30 and a lateral axis 32 which are horizontal when the housing is in its upright position , and an upright axis 34 which is vertical when the housing is in its upright position . these axes 30 , 32 , 34 are orthogonal . each accelerometer axis is aligned with an axis of the housing 18 . the first accelerometer 24 measures a component of gravity along the longitudinal axis 30 . the second accelerometer 26 measures a component of gravity along the lateral axis 32 . the third accelerometer 28 measures a component of gravity along the upright axis 34 . the force from the longitudinal accelerometer 24 is z . the force from the lateral accelerometer 26 is x . the force from the upright accelerometer 28 is y . the endoscope has a view vector 14 . the camera upright projection 36 is the projection of the default upright axis 38 of the camera 20 through the optics and along the view vector 14 . a view vector pivot axis 40 is defined at the distal end of the endoscope , initially aligned with the housing upright axis 34 . the pivot axis 40 may or may not exist in the actual implementation of the endoscope , but is defined as part of the mathematical framework . the pivot axis 40 may be realigned by rotating it about the longitudinal axis 12 . the variable theta is used to describe the angle of the pivot axis 40 relative to the upright axis 34 as rotated about the longitudinal axis 12 . the variable phi is used to describe the angle of the view vector 14 relative to the longitudinal axis 12 as rotated about the pivot axis 40 . the variable zeta is used to describe the angle of the camera upright projection 36 relative to the pivot axis 40 as rotated about the view vector 14 . it should be noted that the above parameterization uses zyz euler angles , which are commonly used to describe three dimensional rotations . for simple oblique , side , or retro viewing endoscopes , the above parameterization variables theta , phi , and zeta will be fixed constants defined for each endoscope . variable direction of view endoscopes require that one or more of the variables change during operation to reflect the changing direction of view . during use , the endoscope will be positioned with an attitude as shown in fig2 . the attitude is parameterized as pitch and roll . the variable alpha is used to describe the pitch angle of the longitudinal axis 12 relative to horizontal 42 . the variable beta is used to describe the roll angle of the endoscope about its longitudinal axis 12 . both pitch and roll may be adjusted during use . the microprocessor calculates pitch and roll from the accelerometer outputs according to the formulas : as shown if fig3 , the camera upright projection 36 is offset from gravity upright 44 by a correction angle . the variable gamma is used to describe the correction angle as a rotation about the view vector 14 . the microprocessor calculates gamma according to the formula : the image rotator rotates the image by the angle gamma to align the image in the gravity upright orientation . a video display ( not shown ) is used to provide the corrected image to the user . the video display may be any device suitable for displaying images from the endoscope . in an alternative embodiment , one or more gyroscopes can be used as the electronic rotation pick - up means . the gyroscope output is used to determine the attitude of the endoscope . a gyroscope creates a signal representative of a force proportional to the angular displacement relative to its axis of rotation . methods of determining attitude using gyroscopes are described in chatenever , but the details of these methods are not necessary for an understanding of this invention . in a further embodiment of the present invention , a machine vision system is used to compute the attitude of the endoscope . in such a system , the endoscope has thereon or therein at least one signal emitting element which emits some form of energy which is received by a receiver located at some location remote from the endoscope , such is in the ceiling of the operating room , mounted on a tripod or the like , or in a wall . by analyzing the energy received from signal emitting elements , receiver calculates the attitude of the endoscope . signal emitting elements may themselves generate the energy , such as in the case of light emitting diodes , magnets , or the like , or may comprise reflectors for reflecting energy emitted from some transmitting source located at some location remote from the endoscope , such is in the ceiling of the operating room , mounted on a tripod or the like , or in a wall . transmitting source thus transmits energy , which is reflected off signal emitting elements , and is received by receiver . the energy may comprise , for example , infrared energy , light in the visual spectrum , magnetic energy , or the like . the present invention has been described above in terms of a presently preferred embodiment so that an understanding of the present invention can be conveyed . however , there are many alternative arrangements for a method for providing gravity referenced endoscopic image orientation not specifically described herein but with which the present invention is applicable . for example , and alternative mathematical framework describing the endoscope will lead to an alternative formula for the necessary orientation correction . in addition , while the examples were given with respect to endoscopes for use in surgical procedures , the present invention is equally applicable with respect to borescopes or the like for use within various mechanical structures . therefore , the term “ endoscope ” as used herein , refers to an endoscope ( used for medical procedures ) or any similar device such as a borescope , a fiberscope , etc . this invention is not to be limited by the embodiments shown in the drawings and described in the description , which are given by way of example and not of limitation , but only in accordance with the scope of the appended claims .
a method is disclosed in for presenting an endoscopic image in an upright orientation . an electronic rotation pick - up means is fixed to the housing of an endoscope . the electronic rotation pick - up means produces signals indicating rotations of the endoscope . a microprocessor uses these signals to calculate a necessary amount of rotational correction for the endoscopic view orientation . the calculation includes factors to account for endoscope roll , endoscope pitch , and endoscope viewing direction . an image rotator rotates the endoscopic image by the calculated correction amount . the rotated image is displayed on a video display device .