here will be disclosed the first embodiment of the present invention with reference to fig2 and 3 . as shown in fig2 and 3 , ultrasonic scanner 11 , pickup means 12 and photoconductive fibre tube 13 are installed in a tip container 14 at the detector end of an endoscopic pickup means to effect the optical pickup and ultrasonic tomography of an object 15 to be examined . the pickup means 12 are composed of an optical lens 16 , solid state image pickup element 17 and preamplifier 18 and are installed in a container defined by an electromagnetic shield casing 19 and lead glass plate 20 . the lead glass plate is lined with a transparent electroconductor 21 formed from tin oxide and the electromagnetic shield casing 19 and transparent electroconductor 21 are grounded through a ground bar 22 . in the detector end of the present means incorporating such a pickup means 12 , due to ( a ) the installation of pickup means 12 in an enclosed container defined by the electromagnetic shield casing 19 and the transparent conductor 21 and ( b ) due to the potential drop at the electromagnetic shield casing 19 and transparent conductor plate 21 to the ground potential , the electromagnetic noise is grounded from the electromagnetic shield casing 19 and transparent electroconductor 21 through the ground bar 22 in the combined use of the pickup means 12 and any means which emits electromagnetic noise such as an electric knife , thereby performing the imaging pickup of the object 15 without being affected by such electromagnetic noise . in particular , electromagnetic noise from the optical axis is shielded by the transparent conductor plate 21 . as the transparent electroconductor plate 21 is made of optically transparent material , it does not have an affect on the optical pickup system . the second and third embodiments will be now set forth with reference to fig4 ( a ) and 5 ( b ). in order to omit further description of such details , the same parts as those in fig2 and 3 are designated with the same reference numerals . fig4 is a sectional view of the second embodiment . the electromagnetic shield means as shown in fig4 is formed by bonding an electromagnetic shield net 23 made by forming permalloy into a parallel plate with the transparent electroconductor plate 21 for the electromagnetic shielding means as shown in fig2 and 3 . the electromagnetic shield net 23 is provided with a great number of optical perforations 24 at the zone intersecting with the optical axis of the optical lens 16 and solid state image pickup element 17 . fig5 ( a ) and 5 ( b ) are sectional views of the third embodiment . the electromagnetic shield means is comprised by providing electromagnetic shield net 23 as shown in fig4 and providing optical perforations 24 over the zone thereof equivalent to the effective diameter of the flux of light at the pupil position of the optical lens members therebetween . this optical perforation zone 24 of electromagnetic shield net 23 is designed so that the modulation transfer function ( mtf ) of the optical lens is reduced only within a spatial frequency higher than the resolving power of solid state image pickup element 17 . modification of the electromagnetic shield means as in the second and third embodiments can prevent the external electromagnetic effects as in the first embodiment . in addition , the electromagnetic shield net 23 may be prepared by laminating a permalloy plate and another metal plate such as a lead plate and providing therethrough a great number of optical perforations , providing the shield plate with x ray - shielding effectiveness . accordingly , the present invention provides an endoscopic pickup means capable of providing a distinct image of an object to be examined without electric trouble in the combined use of a means emitting electromagnetic noise such an as electric knife , by installing the solid state image pickup means in a container defined by a shield casing and a transparent electroconductor plate and optionally an electromagnetic shield net , and grounding the container . it is apparent that various embodiments and modifications can be made widely without departing from the spirit and scope of this invention . accordingly , the present invention should not be restricted to any particular embodiments except the items as claimed in the attached claims .
electromagnetic shield means are provided on the optical axis of the detector end of an endoscope incorporating pickup means for providing an optical image and converting the image photoelectrically . the electromagnetic shield means are mounted at the preceding end of the endoscopic pickup means for preventing external electromagnetic effects so as to provide distinct image pickup of an object to be examined .