Abstract:
A device for determining a position of a film which has been stopped includes plural mutually spaced film characteristic sensors. The sensors are disposed along a film transport path and circuitry associated with the sensors provides output indication that the film is in a predetermined position responsively to inputs from the film characteristic sensors.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a device for determining the position of a film loaded on a camera or the like. 
     2. Description of the Related Art 
     Since, in a conventional camera, the positional relation of perforations provided in a film to a photographing picture frame is not always fixed, a film position detecting device has been configured to detect the relative positions of the perforations and the photographing picture frame when the film is being transported. 
     Meanwhile, there has been proposed a camera arranged to use a film in which only one perforation is assigned to each photographing picture frame and the absolute positional relation between the perforation and the photographing picture frame is fixed. The camera of this kind is arranged to mechanically fix the position of the perforation so as to hold the film in position. 
     However, the conventional camera first cited above has presented a problem in that, when the film happens to deviate from its predetermined position due to vibrations or a fall of the camera, the film position detecting device of the camera fails to detect the deviation of the film. In such a case, pictures taken might partly overlap each other. 
     In the case of the camera secondly cited above, the camera is provided with a member for fixing the position of the film perforation. The use of the fixing member not only prevents reduction in cost and size of the camera but also tends to impair the flatness of the film. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of this invention, there is provided an apparatus comprising a determination device for determining a position of a film which has been stopped, which is advantageous in terms of reduction in cost and size as the apparatus is arranged in a simple manner to be capable of adequately preventing pictures from overlapping each other due to a positional deviation of the film caused by a fall or vibrations of the apparatus. 
     The above and other aspects of this invention will become apparent from the following detailed description of embodiments thereof taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the circuit arrangement of a camera according to embodiments of this invention. 
     FIG. 2 is a circuit diagram showing the details of the concrete arrangement of a film position detecting circuit shown in FIG.  1 . 
     FIG. 3 shows the positional relation between photo-reflectors and a film. 
     FIG. 4 is a timing chart showing the outputs of the film position detecting circuit shown in FIG.  1 . 
     FIG. 5 is a flow chart showing the operation of a microcomputer of FIG. 1 according to a first embodiment of this invention. 
     FIG. 6 is a flow chart showing the operation of the microcomputer of FIG. 1 according to a second embodiment of this invention. 
     FIGS.  7 ( a ) and  7 ( b ) are diagrams explaining cases where a film is not in a predetermined photographing position in the second embodiment of this invention. 
     FIG. 8 is a timing chart showing the outputs of the film position detecting circuit of FIG. 1 in the second embodiment of this invention. 
     FIG. 9 is a flow chart showing the operation of the microcomputer of FIG. 1 according to a third embodiment of this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following describes by way of example some of preferred embodiments of this invention with reference to the drawings. 
     FIG. 1 is a block diagram of the circuit arrangement of a camera according to embodiments of this invention. Referring to FIG. 1, a microcomputer  1  is arranged to control the various actions of the camera. A film position detecting circuit  2  is arranged to detect the position of a film in use. A film transport circuit  3  is arranged to wind and rewind the film. A light measuring circuit  4  is arranged to measure the luminance of an object to be photographed. A distance measuring circuit  5  is arranged to measure a distance to the object. A photographing circuit  20  is arranged to perform a photographing action. A liquid crystal display circuit  6  is arranged to display information of varied kinds about the camera. A switch (SW 1 )  7  is arranged to turn on when a shutter release button is pushed halfway. A switch (SW 2 )  8  is arranged to turn on when the release button is pushed to the end of its full stroke to initiate an exposure action. A mode selection switch  9  is provided for switching the photographing mode of the camera from one mode to another. 
     FIG. 2 shows the details of the concrete arrangement of the film position detecting circuit  2 . Referring to FIG. 2, each of two photo-reflectors  10  and  11  is a photo-sensor arranged to detect the presence or absence of each perforation provided in the film. Hereinafter, the photo-reflectors  10  and  11  will be referred to respectively as PR 1  and PR 2 . Each of constant current circuits  12  and  13  is arranged to cause a current of a predetermined value to flow to the PR 1  or PR 2 . Resistors  14  and  15  are arranged to respectively convert the outputs of the PR 1  and PR 2  into voltages. The resistors  14  and  15  are set respectively at predetermined resistance values. Comparators  16  and  17  are arranged to respectively compare the outputs of the PR 1  and PR 2  with predetermined reference values. In the embodiments, the comparator  16  or  17  provides a low level output when the PR 1  or PR 2  faces uperferated surface of the film and provides a high level output when the PR 1  or PR 2  faces each perforation of the film. 
     The film transport circuit  3  is arranged to be controlled on the basis of the output of the film position detecting circuit  2 . Further, the constant current circuits  12  and  13 , the resistors  14  and  15  and the comparators  16  and  17  may be incorporated into the microcomputer  1  in one chip. 
     FIG. 3 shows the positional relation between the film used in the embodiments and the PR 1  and PR 2  obtained when the film is stopped in an apposite predetermined photographing position. The illustration includes the film  20 , the perforations  21  provided in the film  20 , and a photographing picture frame  22  which is at an N-th frame. An (N−1)th frame is a picture frame which has already been used for photographing. In the case of FIG. 3, the film  20  is assumed to be wound up to the right as viewed on the drawing (in the direction of the arrow). 
     As shown in FIG. 3, when the film is in the apposite predetermined photographing position, the PR 1  is just on a perforation of the film, while the PR 2  is located on uperferated surface of the film. 
     FIG. 4 is a timing chart showing an output CMP 1  of the comparator  16  and an output CMP 2  of the comparator  17  which are obtained when the film is being wound up. 
     Referring to FIG. 4, the outputs of the comparators  16  and  17  obtained when the film is in the apposite predetermined photographing position as shown in FIG. 3 are indicated at a position P 1  where the output CMP 1  is at a high level and the output CMP 2  is at a low level. When the film is normally wound up for one frame to come to an (N+1)th frame, the outputs of the comparators  16  and  17  come to another position P 2 . Completion of winding for one frame is determined by detecting the rises E 1  and E 2  to the high level of the output CMP 1  taking place in succession while the output CMP 2  is at a low level. 
     With the camera arranged as described above, the camera operates as described below with reference to FIG. 5 which is a flow chart of the operation of the microcomputer  1 . 
     At a step S 1 , a check is made for the state of the switch SW 1 . When the switch SW 1  turns on, the flow of operation comes to a step S 2 . At the step S 2 , the microcomputer  1  causes the light measuring circuit  4  to measure the luminance of an object to be photographed. At a step S 3 , the distance measuring circuit  5  is caused to measure a distance to the object. At a step S 4 , a check is made for the state of the switch SW 2 . When the switch SW 2  turns on, the flow comes to a step S 5 . At the step S 5 , the film position detecting circuit  2  is caused to begin to detect the position of the film. 
     At a step S 6 , a check is made to find if the film is stopped in an apposite predetermined photographing position. If the film is found to be in the predetermined photographing position as shown in FIG. 3, the flow proceeds to a step S 7 . At the step S 7 , since the film is in the predetermined photographing position, the photographing circuit  20  is allowed to perform photographing actions in a normal sequence of the camera. If the film is found to be not in the predetermined photographing position, the flow comes to a step S 8 . At the step S 8 , the photographing circuit  20  is inhibited from performing the photographing actions and the shutter release switch is locked. 
     While it is not shown in the flow chart of FIG. 5, the camera may be arranged to cause the liquid crystal display circuit  6  or the like to provide a warning display at the same time that the photographing action is inhibited at the step S 8 , if the film is found to be not in the predetermined photographing position. 
     The first embodiment is arranged, as described above, to confirm, during photographing, the position of the film by using the film position detecting circuit  2  and, if the film is found to have deviated from the predetermined photographing position due to vibrations or a fall of the camera, to inhibit photographing, so that photographing picture frames can be prevented from overlapping each other. In such a case, the arrangement of causing a liquid crystal display or the like to give a warning display would visually inform the photographer that a photographing operation is inhibited. 
     FIG. 6 is a flow chart showing the operation of a microcomputer  1  according to a second embodiment of this invention. FIGS.  7 ( a ) and  7 ( b ) show the positional relation between the PR 1  and PR 2  and the film when the position of the film has deviated in the film winding direction and in the film rewinding direction, respectively. 
     FIG. 8 is a timing chart showing the respective outputs CMP 1  and CMP 2  of the comparators  16  and  17 . In FIG. 8, reference symbols P 3  and P 4  indicate the states of the outputs CMP 1  and CMP 2  of the comparators  16  and  17  which are obtained in the events of FIGS.  7 ( a ) and  7 ( b ), respectively. 
     The illustrations given in FIGS. 1,  2  and  3  apply as they are to the arrangement of the second embodiment. 
     Referring to the flow chart of FIG. 6, the operation of the second embodiment of this invention is described as follows: 
     At a step S 11 , a check is made for the state of the switch SW 1 . If the switch SW 1  is found to have turned on, the flow comes to a step S 12 . At the step S 12 , the microcomputer  1  causes the light measuring circuit  4  to measure the luminance of an object to be photographed. At a step S 13 , the distance measuring circuit  5  is caused to measure a distance to the object. 
     At a step S 14 , a check is made to find if the switch SW 2  has turned on. If so, the flow comes to a step S 15 . At the step S 15 , the film position detecting circuit  2  is caused to begin to detect the position of the film. At a step S 16 , a check is made to find if the film is stopped in an apposite predetermined photographing position. If the film is found to be in the predetermined photographing position as shown in FIG. 3, the flow proceeds to a step S 17 . 
     At the step S 17 , since the film is in the predetermined photographing position, the photographing circuit  20  is caused to perform photographing actions in the normal sequence of the camera. If the film is found at the step S 16  to be not in the predetermined photographing position and to be in a position as shown in FIG.  7 ( a ) or  7 ( b ), the flow comes to a step S 18 . At the step S 18 , since the film is found to be not in the predetermined photographing position, the film transport circuit  3  is caused to perform a film winding action and the flow comes to a step S 19 . 
     At the step S 19 , a check is made for completion of one-frame blank transport of the film, by causing the film position detecting circuit  2  to detect the rises E 1  and E 2  of the output CMP 1  which take place in succession as shown in FIG.  8 . The flow then comes to the step S 17  to cause the photographing circuit  20  to perform photographing actions. At this time, a photographing frame of the film shifts to the (N+1)th frame and the outputs CMP 1  and CMP 2  of the comparators  16  and  17  come into the state shown at a point P 5  in FIG.  8 . 
     In the second embodiment described above, the position of the film is confirmed by means of the film position detecting circuit  2  during photographing. In a case where the film is thus found to have deviated from a predetermined photographing position due to vibrations or a fall of the camera, the film is subjected to one-frame blank transport. Although, in such a case, the one-frame blank transport of the film may cause an N-th frame portion of the film to be left unused for photographing, the possibility of having overlapped picture planes is effectively eliminated. 
     FIG. 9 is a flow chart showing the operation of the microcomputer  1  according to a third embodiment of this invention. The illustrations given in FIGS. 1,  2  and  3  apply as they are to the arrangement of the third embodiment. 
     Referring to FIG. 9, a check is made for the state of a mode selection switch  9 , which may be arranged in any known manner as desired. If the mode selection switch  9  is found to be in an on-state, the flow comes to a step S 22 . At the step S 22 , the film position detecting circuit  2  is caused to begin to detect the position of the film. At a step S 23 , a check is made to find if the film is stopped in an apposite predetermined photographing position. If the film is found to be in the predetermined photographing position as shown in FIG. 3, the flow comes to a step S 24 . At the step S 24 , since the film is in the predetermined photographing position, the photographing mode of the camera is shifted to a mode selected by the mode selection switch  9 . 
     If the film is found at the step S 23  to be not in the predetermined photographing position, the flow comes to a step S 25 . At the step S 25 , since the film is not in the predetermined photographing position, the film transport circuit  3  is caused to perform a film winding action. The flow then comes to a step S 26 . At the step S 26 , a check is made by the film position detecting circuit  2  to find if the one-frame blank transport of the film has been completed. Upon completion of the one-frame blank transport, the flow comes to the step S 24  to select the photographing mode of the camera by the mode selection switch  9 . 
     The third embodiment is arranged to cause the film position detecting circuit  2  to confirm the position of the film when some of switches of the camera are pushed. In a case where the film is found to have deviated from the predetermined photographing position due to vibrations or a fall of the camera or the like, the film is subjected to the one-frame blank transport. Therefore, in such a case, although an N-th frame may be left unused for photographing, photographing picture planes of the film can be prevented from overlapping each other. Further, the arrangement of making a check for the position of the film every time a switch is operated minimizes the probability of having the film deviating from the predetermined photographing position when the switch SW 2  is pushed for photographing. Therefore, the probability of performing the one-frame blank transport of the film when the switch SW 2  is pushed is very small, so that shutter opportunities are seldom missed. 
     The second and third embodiments described above are arranged to control the position of the film by performing the one-frame blank transport if the film is not stopped in an apposite predetermined photographing position. However, since the film does not much deviate in general, the arrangement may be changed to include some control means that is arranged to cause the film to be wound or rewound only to a very short extent to bring the film back to the predetermined photographing position (a point P 6  shown in FIG.  8 ), when the film is found by the film position detecting circuit  2  to have deviated from the predetermined photographing position (for example, at the point P 3  or P 4  shown in FIG.  8 ). Such a modification effectively prevents overlapping of photographing picture frames without causing any frame to be left unused for photographing, like in the cases of the second and third embodiments, because the N-th frame can be used for photographing by virtue of the control action of the control means. 
     Each of the embodiments described above detects the position of the film by using two photo-reflectors. However, in accordance with this invention, this detecting method may be replaced by any other suitable method. 
     Further, the embodiments described above are arranged to make a check for the position of the film at the commencement of an exposure action with the shutter release button fully pushed to the end of its stroke. The arrangement may be changed to make this check at any stage of the pushing operation on the shutter release button, such as when the shutter release button is pushed halfway or when it is pushed halfway and then fully pushed. 
     The embodiments described above are arranged to detect the position of a perforation of the film by means of the photo-reflectors. However, this detecting method may be replaced by some other suitable method. For example, a pulse disk or the like may be used in place of the photo-reflectors. Further, this invention applies also to image recording media other than films. 
     While the present invention has been described with respect to what is presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     The individual components shown in schematic or block form in the drawings are all well-known in the camera arts and their specific construction and operation are not critical to the operation or best mode for carrying out the invention. 
     This invention may be carried out by combining as necessary the embodiments or their technological elements described in the foregoing. 
     This invention applies to cases where either the whole or a part of claims or the arrangement of each embodiment described forms one apparatus or is used in combination with some other apparatus or as a component element of an apparatus. 
     Further, this invention is applicable to cameras of varied kinds, such as a single-lens reflex camera, a lens-shutter type camera, a video camera, etc., optical apparatuses other than cameras, other apparatuses, devices adapted for cameras, optical apparatuses and other apparatuses, and component elements forming these apparatuses and devices.