first of all , a first embodiment of the present invention will be explained with reference to fig1 to 4 , and the construction thereof will be explained in connection with fig1 and 2 . the image reading apparatus according to the first embodiment includes a supply tray 2 on which originals 1 each having code information thereon are stacked , a paper feed detection sensor 3 for detecting the presence of the originals 1 in the tray 2 , feed rollers 4 for feeding the original to a detecting means , and a double - feeding detection roller 5 which is mounted for movement in an up - and - down direction , as shown in fig2 . an overlap - feeding detection roller 6 is arranged in confronting relation to the double - feeding detection roller 5 . a bias spring 7 for holding the roller 5 in a predetermined position is arranged in the vicinity of an end of a center shaft of the roller 5 , and said end of the shaft is abutted against a shaft 9 of a differential transformer 8 . with this arrangement , the thickness of the original or originals 1 being passed through the roller 5 can be detected by moving the double - feeding detection roller 5 upwardly in response to the thickness of the original to cause the corresponding upward movement of the shaft 9 which causes the transformer 8 to generate an output corresponding to the amount of movement of the shaft 9 . the overlap - feeding detection roller 6 is connected through a driving belt 10 to an encoder 11 which can detect the length of the original 1 being fed , by outputting pulses corresponding to the timing of the presence of detection by means of an original detection sensor 12 . the reference numeral 13 designates conveying rollers for conveying the original 1 ; 14 designates a bar code reader as a means for reading the code information on the original 1 ; 15 designates a solenoid which is energized to be extended when the abnormal original ( due to the double - feeding and / or the overlap - feeding ) is detected or when the code bar is erroneously read ; and 16 designates a feeding path guide which can be changed in position by the solenoid 15 . the reference numeral 17 designates ejector rollers for feeding the abnormal original onto an abnormal original receiving tray 18 ; and 19 designates a driving roller for driving a conveyor belt 20 which feeds out the normal original onto a normal original receiving tray 22 . a camera 21 as a recording means for photographing the original is arranged above the conveyor belt 20 . next , an example of the operation of the apparatus according to the first embodiment will be explained with reference to fig3 and 4 . in the illustrated embodiment , the abnormal original detecting means 32 comprises a double - feeding detection means and an overlap - feeding detection means , and the conveying means 33 , reading means 14 and recording means 21 are controlled by a one - chip microcomputer 40 having memories ( ram 42 , rom 41 ). a reference value for the double - feeding detection means is determined as follows . first of all , a single sample original ( or actually used original ) having a predetermined dimension ( thickness and length ) is passed between the double - feeding detection roller 5 and the overlap - feeding detection roller 6 . in this case , the double - feeding detection roller 5 is shifted upwardly by an amount corresponding to the thickness of the sample original , with the result that the shaft 9 of the transformer 8 is lifted by an amount corresponding to the shift of the roller 5 . consequently , the differential transformer 8 emits an output corresponding to the difference between the amount of lifting movement of the roller 5 and that of the shaft 9 . this output is set as a double - feeding detection reference value ( used for judging the condition that two or more originals each having the predetermined thickness are doubled ) and is stored in the memory 42 ( ram ). on the other hand , a reference value for the overlap - feeding detection means is determined as follows . the rotation of the overlap - feeding detection roller 6 is continued during the duration from when the original sensor 12 detects the leading edge of the sample original to when the original sensor detects the trailing edge of such sample original and is transmitted through the driving belt to the encoder 11 , which outputs the number of pulses corresponding to an amount of rotation thereof . the number of such pulses is set as an overlap - feeding detection reference value used for judging the condition that two or more originals each having the predetermined length are overlapped in the feeding direction , and is stored in the memory 42 ( ram ). in this way , the setting of the reference values are completed . when the originals ( each having the same dimension as that of the sample original ) each having the bar code applied thereto are set on the supply tray 2 , the paper feed detection sensor 3 detects the presense of the original 1 . after a predetermined timing , the original 1 is fed by the feed rollers 4 to the nip between the double - feeding detection roller 5 and the overlap - feeding detection roller 6 ( step 1 ). after the original has passed through the nip , the value of the thickness of the original is obtained from the output value of the differential transformer 8 , which thickness value is compared with the double - feeding detection reference value . if the thickness value is noticeably larger than the reference value , it is judged that double - feeding has occurred ( step 2 ). similarly , the value of the length of the original is obtained from the counted number of pulses emitted from the encoder 11 , which length value is compared with the overlap - feeding detection reference value . if the length value is noticeably larger than the reference value , it is judged that overlap - feeding has occurred ( step 3 ). the originals which are judged to be included in double - feeding or overlap - feeding are treated as the abnormal originals , and the bar codes thereof are not read . the abnormal original is fed by the conveying rollers 13 to the solenoid 15 . in this point , the feeding path guide 16 is deflected toward the ejector rollers 17 by the extension of the solenoid 15 . accordingly , the abnormal original is fed to the ejector rollers 17 through which the abnormal original is ejected onto the abnormal original receiving tray 18 ( step 7 ). on the other hand , the original 1 judged as the normal original is fed to the bar code reader 14 , where the bar code of the original is read ( step 4 ). thereafter , it is judged whether the bar code is correctly read or not ( step 5 ). if an error in the bar code reading occurs , the original is ejected onto the abnormal original receiving tray 18 in the same manner as the above - mentioned step 7 ; whereas , if the bar code is correctly read , the original 1 is conveyed by the conveyor belt 20 , during which the original is photographed by the camera 21 at a predetermined position , and then the original is ejected onto the normal original receiving tray 22 ( step 6 ). fig5 and 6 show a second embodiment of the present invention , where the same elements as those of the first embodiment will be designated by the same reference numerals used in the first embodiment . in the second embodiment , as shown in fig5 the overlap - feeding detection means comprises a plurality of pairs of conveying rollers 30 , and a plurality of original sensors 31a , 31b , 31c , 31d each arranged between the adjacent roller pairs 30 for detecting the presence of the original 1 . in this case , the length of the original can be determined by the fact that , when the last original sensor 31a detects the leading edge of the original , it is judged which sensor among the remaining sensors 31b , 31c , 31d detects the original 1 . that is to say , in this embodiment , after the length of the sample original has been set as the overlap - feeding detection reference value , by comparing the length of the original 1 being actually fed with the reference value , it can be judged whether the overlap - feeding occurs or not . accordingly , in this embodiment , since the overlap - feeding detection means is arranged in the conveying system ( between the conveying rollers ), the conveying system can be compact . on the other hand , in the second embodiment , as shown in fig6 the double - feeding detection means comprises a detection roller 23 , and a rocking arm 25 having one end connected to a center shaft of the roller 23 and the other end connected to a pivot 24 around which the rocking arm can rotate . the rocking arm 25 is provided at its upper surface with a plurality ( three , in the illustrated embodiment ) of projections 28 1 - 28 3 cooperating with levers 27 1 - 27 3 of corresponding microswitches 26 1 - 26 3 . these projections 28 1 - 28 3 and microswitches 26 1 - 26 3 are arranged in different vertical positions , respectively . with this arrangement , when the roller 23 is shifted upwardly by an amount corresponding to the thickness of the sample original being fed , the maximum upward movement of the rocking arm 25 caused by the shift of the roller 23 causes the projection 28 1 or 28 2 to activate the microswitch 26 1 , 26 2 . on the basis of the activated microswitch , the thickness value of the sample original is set as the double - feeding detection reference value which is stored in the memory . for example , it is assumed that , when the sample original is fed , the microswitches 26 1 and 26 2 are activated . in this case , when the original 1 is actually fed , if the thickness of the original exceeds the predetermined value , i . e ., if two or more originals are fed in the stacked condition , the microswitch 26 3 is activated , thus detecting the double - feeding . accordingly , in this embodiment , by utilizing a plurality of microswitches as the double - feeding detection means , double - feeding can be detected with simpler construction than that of the first embodiment . the construction and function of the other elements are the same as those of the first embodiment , and , thus , the detailed explanation thereof will be omitted . according to the above - mentioned embodiments , since the means for detecting the thickness and the length of the original are provided , it is possible to positively discriminate the normal original from the abnormal original . further , since the reference values for the detection means can be set at will , an original having any dimension can be used . furthermore , since the reference values regarding the dimension of the original can be easily set merely by feeding the sample original , the setting operation can be simplified . in addition , since useless reading is abbreviated to keep the scanner portion of the bar code reader using the laser in an inoperative condition , the service life of the scanner can be extended .