Abstract:
In a camera, one photosensor is located next to the taking lens and another photosensor is located next to a built-in flash unit for sensing whether a camera user&#39;s fingers are obstructing the taking lens and/or the flash unit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to the field of photography, and in particular to apparatus in a photographic camera for detecting that a camera user&#39;s finger (or other portion of the user&#39;s hand) may be in front of a taking lens or a built-in flash unit. 
     2. Description of the Prior Art 
     As photographic cameras get smaller in size, it becomes more likely that a camera user may inadvertently position a finger in front of the taking lens or a built-in flash unit before the user depresses the shutter release button to take a picture. Should the user take a picture with a finger over the taking lens or the flash unit, the picture will of course be ruined. 
     Various designs have been proposed for preventing the camera user from positioning a finger in front of the taking lens. For example, U.S. Pat. No. 4,866,470, issued Sep. 12, 1989, suggests surrounding a lens opening in the front face of the camera body with a large number of small projections which, when touched, alert the camera user that at least one of his or her fingers may be positioned over the taking lens. 
     Another example, U.S. Pat. No. 4,547,054, issued Oct. 15, 1985, suggests surrounding a lens opening in the front face of the camera body with a pressure-sensitive plate which, when touched, is slightly tilted to energize a warning lamp. The energized lamp alerts the camera user that at least one of his or her fingers may be positioned over the taking lens. 
     SUMMARY OF THE INVENTION 
     According to the invention, a photographic camera comprising a camera body having a front face and a taking lens inset in the camera body to not project outwardly substantially from the front face, is characterized in that: 
     photosensor means is located in the vicinity of the taking lens for emitting a light beam towards a camera user&#39;s finger that may be positioned over the taking lens and for detecting reflection of the light beam from the camera user&#39;s finger; and 
     alarm means is connected to the photosensor means for providing a warning that a camera user&#39;s finger may be positioned over the taking lens when the photosensor means detects reflection of a light beam from the camera user&#39;s finger. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front perspective view of a photographic camera with respective photosensors for detecting that a camera user&#39;s finger may be positioned over the taking lens and/or a built-in flash unit, according to a preferred embodiment of the invention; 
     FIG. 2 is an elevation view of one of the photosensors, illustrating its manner of operation; and 
     FIG. 3 is a schematic view of an electronic circuit including the photosensors. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention is described as being embodied in a 35 mm still camera with a built-in electronic flash unit. Because such a type of camera is well known, this description is directed in particular only to those elements forming part of or cooperating directly with the preferred embodiment. It is to be understood, however, that other elements not specifically shown or described may take forms known to persons of ordinary skill in the art. 
     Referring now to the drawings, FIG. 1 shows a 35 mm still camera 1 with a camera body 3 having a front face 5 and a top face 7. A taking lens 9 is inset behind an opening 11 in the front face 5 of the camera body 3 to not project outwardly beyond the front face. A conventional built-in electronic flash unit 13, shown only in FIG. 3, is located behind a flash emission window 15 in the front face 5 of the camera body 3. A shutter release button 17 is supported by known means, not shown, for manually depression at the top face 7 of the camera body 3 to take a picture. 
     According to the invention, a first photosensor 19 is located in the vicinity of the opening 11 to the taking lens 9. See FIG. 1. The first photosensor 19 includes an infrared (IR) emitter 21 for emitting a beam of infrared light towards a camera user&#39;s finger that may be positioned over the taking lens 9 and an infrared (IR) detector 23 for detecting reflection of the beam of infrared light from the camera user&#39;s finger. A second photosensor 25 is located in the vicinity of the flash emission window 15. The second photosensor 25 includes an infrared (IR) emitter 27 for emitting a beam of infrared light towards a camera user&#39;s finger that may be positioned over the flash illumination window 15 and an infrared (IR) detector 29 for detecting reflection of the beam of infrared light from the camera user&#39;s finger. See FIG. 2. A first light-emitting diode (LED) 31 is located to be seen in a camera viewfinder 33 for providing a warning visible in the viewfinder that a camera user&#39;s finger may be positioned over the taking lens 9. A second light-emitting diode (LED) is located to be seen in the viewfinder 33 for providing a warning visible in the viewfinder that a camera user&#39;s finger may be positioned over the flash illumination window 15. The first and second LED&#39;s 31 and 35 are connected to the first and second photosensors 19 and 25 via an integrated circuit (IC) 37. See FIG. 3. Known shutter disablement means 39 is connected to the first and second photosensors 19 and 25 via the IC 37 for disabling a conventional camera shutter 41, to prevent the taking of a picture, when the IR detector 23 of the first photosensor detects reflection of a beam of infrared light from a camera user&#39;s finger that may be positioned over the taking lens 9 and/or when the IR detector 29 of the second photosensor detects reflection of a beam of infrared light from a camera user&#39;s finger that may be positioned over the flash illumination window 15. Preferably, known flash disablement means 43 is connected to the first and second photosensors 19 and 25 via the IC 37 for disabling the flash unit 13, to prevent its use, when the IR detector 23 of the first photosensor detects reflection of a beam of infrared light from a camera user&#39;s finger that may be positioned over the taking lens 9 and/or when the IR detector of the second photosensor detects reflection of a beam of infrared light from a camera user&#39;s finger that may be positioned over the flash illumination window 15. 
     OPERATION 
     When the shutter release button 17 is manually depressed to take a picture, it closes a trigger switch 45 connected to the first and second photosensors 19 and 25 via the IC 37. See FIG. 3. This causes the IR emitter 21 of the first photosensor 19 and the IR emitter 27 of the second photosensor 25 to emit respective beams of infrared light. If, however, known ambient light sensing means, not shown, determines that flash illumination of the subject is not required, the second photosensor 25 is prevented from operating, i.e. the IR emitter 27 of the second photosensor will not emit a beam of infrared light. 
     If the IR detector 23 of the first photosensor 19 detects reflection of a beam of infrared radiation from a camera user&#39;s finger that may be positioned over the taking lens 9 and/or the IR detector 29 of the second photofinisher 25 detects reflection of a beam of infrared radiation from a camera user&#39;s finger that may be positioned over the flash illumination window 15, the shutter disablement means 39 will disable the camera shutter 41 and the flash disablement means 43 will disable the flash unit 43 (assuming the ambient light sensing means determines that flash illumination of the subject is required). Morever, the first LED 31 and/or the second LED 35 will provide a warning visible in the viewfinder 33. 
     The invention has been described with reference to a preferred embodiment. However, it will be appreciated that variations and modifications can be effected within the ordinary skill in the art without departing from the scope of the invention.