Automatic exposure control for photographic apparatus

Claim 2

In a photographic apparatus, a shutter movable between open and closed positions with variable delay to furnish a range of exposure times; a picture taking objective; adjustable diaphragm means for controlling the amount of light passing through said objective and incident on the light-sensitive film; bridge means comprising two arms respectively containing first and second photosensitive means and respectively exposed to scene light through said objective and to direct scene light to provide electrical signals proportional to the intensity of the respective lights; meter means connected in said bridge means to adjust said diaphragm as a function of the difference in said signals; control means for closing said shutter for a predetermined exposure time; and switch means for switching said second photosensitive means from said bridge means into said control means, said second photosensitive means being operative to determine the exposure time furnished by said shutter while said diaphragm is adjusted as a function of said signal difference.

Claim 3

In a photographic apparatus as defined in claim 1, wherein said meter means comprises a moving-coil instrument.

Claim 4

In a photographic apparatus as defined in claim 1, wherein said bridge means further comprises two further arms respectively containing first and second equal resistance means connected together at a common junction.

Claim 5

In a photographic apparatus as defined in claim 3, wherein said first and second photosensitive means are connected together at a common junction, and said meter means is connected between said common junction of said first and second photosensitive means and said first and second resistance means.

Claim 6

In a photographic apparatus as defined in claim 1, further comprising auxiliary adjustable diaphragm means coupled to said adjustable diaphragm means and located to intercept direct scene light to said second photosensitive means.

Claim 7

In a photographic apparatus as defined in claim 1, wherein said meter means comprises an output member movable from a starting position in proportion to the difference in signals between said first and seconD photosensitive means, and said diaphragm means comprises blade means and first and second independently movable diaphragm blade controlling means, and further including adjustable stop means for limiting the movement of said first diaphragm blade controlling means; and adjusting means controlled by the position of said output member for moving said second diaphragm blade controlling means as a function of scene brightness.

Claim 8

In a photographic apparatus as defined in claim 6, including first motion-transmitting means for transmitting movements of said adjusting means to said second diaphragm blade controlling means.

Claim 9

In a photographic apparatus as defined in claim 6, wherein said photographic apparatus is a single-lens reflex camera, and said bridge means operates before said control means, and further including pivotal light-reflecting means normally positioned in a first position in the light path passing through said objective and pivotal to a second position out of said path to permit exposure of the light-sensitive film after operation of said bridge means; and second motion-transmitting means for normally preventing movement of said first and second diaphragm blade controlling means operated by movement of said light-reflecting means to said second position to free said first and second diaphragm blade controlling means.

Claim 10

In a photographic apparatus as defined in claim 8, wherein said second motion-transmitting means comprise first and second click means respectively normally preventing movement of said first diaphragm blade controlling means and of said first motion-transmitting means.

Claim 11

In a photographic apparatus as defined in claim 6, including two said adjusting means for respectively moving said second diaphragm blade controlling means in one of two different directions for reducing or increasing the size of the aperture of said diaphragm means.

Claim 12

In a photographic apparatus having a shutter movable between open and closed positions with variable delay to determine the exposure time, a combination comprising a picture-taking objective, adjustable diaphragm means for controlling the amount of light incident on the light-sensitive film; exposure control means comprising a electric circuit having a light-measuring first portion and a second portion operative to close the shutter; said first portion including electrical bridge means comprising two arms respectively containing first and second photosensitive means connected together at a common junction and respectively exposed to scene light through said objective and to direct scene light to provide each a signal proportional to the light incident upon it, said electric circuit second portion operating after said electric circuit first portion, electrical means connected in said bridge to respond to the difference in signals between said first and second photosensitive means to adjust said diaphragm means as a function of scene brightness; and switch means for switching said second photosensitive means out of said electrical bridge means and into said second portion of said electric circuit for operation of said electric circuit second portion.

Claim 13

In a photographic apparatus having a shutter movable between open and closed positions with variable delay to determine the exposure time, a combination comprising a picture-taking objective, adjustable diaphragm means for controlling the amount of light incident on the light-sensitive film; exposure control means comprising a electric circuit having a light-measuring first portion and a second portion operative to close the shutter; said first portion including electrical bridge means comprising two arms respectively containing first and second photosensitive means connected together at a common junction and respectively exposed to scene light through said objective and to direct scene light to provide each a signal proportional to the light incident upon it, said electric circuit second portion operating after said electric circuit first portion, electrical means connected in said bridge to respond to the difference in signals between said first and second photosensitive means to adjust said diaphragm means as a function of scene brightness; and switch means for switching said second photosensitive means out of said electrical bridge means and into said second portion of said electric circuit for operation of said electric circuit second portion.

Claim 14

In a photographic apparatus having a shutter movable between open and closed positions with variable delay to determine the exposure time, a combination comprising a picture-taking objective; adjustable diaphragm means for controlling the amount of light incident on the light-sensitive film; exposure control means comprising an electric circuit having a light measuring first portion and a second portion operative to close the shutter, said first portion including electrical bridge means comprising two arms respectively containing first and second photosensitive means connected together at a common junction and respectively exposed to scene light through said objective and to direct scene light to provide each a signal proportional to the light incident upon it, said bridge further comprising two further arms respectively coNtaining first and second equal resistance means connected together at a common junction, said electric circuit second portion operating after the operation of said electric circuit first portion; electrical means connected in said bridge to respond to the difference in signals between said first and second photosensitive means to adjust said diaphragm means as a function of scene brightness; and switch means for disconnecting said first photosensitive means and said electrical means from said electrical bridge means after operation of said electric circuit first portion.

Claim 15

In a photographic apparatus having a shutter movable between open and closed positions with variable delay to determine the exposure time, a combination comprising a picture-taking objective; adjustable diaphragm means for controlling the amount of light incident on the light-sensitive film; exposure control means comprising an electric circuit having a light measuring first portion and a second portion operative to close the shutter, said first portion including electrical bridge means comprising two arms respectively containing first and second photosensitive means connected together at a common junction and respectively exposed to scene light through said objective and to direct scene light to provide each a signal proportional to the light incident upon it, said bridge further comprising two further arms respectively coNtaining first and second equal resistance means connected together at a common junction, said electric circuit second portion operating after the operation of said electric circuit first portion; electrical means connected in said bridge to respond to the difference in signals between said first and second photosensitive means to adjust said diaphragm means as a function of scene brightness; and switch means for disconnecting said first photosensitive means and said electrical means from said electrical bridge means after operation of said electric circuit first portion.

Claim 16

In a single-lens reflex camera having a shutter movable between open and closed positions with variable delay to determine the exposure time, a combination comprising a picture-taking objective; adjustable diaphragm means for controlling the amount of light incident on the light-sensitive film; exposure control means comprising an electric circuit having a light measuring first portion and a second portion operative to close the shutter, said fist portion including electrical bridge means comprising two arms respectively containing first and second photosensitive means connected together at a common junction and respectively exposed to scene light through said objective and to direct scene light to provide each a signal proportional to the light incident upon it, said electric circuit second portion operating after the operation of said electric circuit first portion; pivotal light-reflecting means normally positioned in a first position in the path passing through said objective and pivotal to a second position out of said path to permit exposure of the light-sensitive film after operation of said electric circuit first portion, and a plurality of switch means operated by the movement of said light-reflecting means from said first to said second position for switching said second photosensitive means out of said electrical bridge means and into said electric circuit second portion and for disconnecting said electrical means from said electrical bridge means.

Claim 17

In a single-lens reflex camera having a shutter movable between open and closed positions with variable delay to determine the exposure time, a combination comprising a picture-taking objective; adjustable diaphragm means for controlling the amount of light incident on the light-sensitive film; exposure control means comprising an electric circuit having a light measuring first portion and a second portion operative to close the shutter, said fist portion including electrical bridge means comprising two arms respectively containing first and second photosensitive means connected together at a common junction and respectively exposed to scene light through said objective and to direct scene light to provide each a signal proportional to the light incident upon it, said electric circuit second portion operating after the operation of said electric circuit first portion; pivotal light-reflecting means normally positioned in a first position in the path passing through said objective and pivotal to a second position out of said path to permit exposure of the light-sensitive film after operation of said electric circuit first portion, and a plurality of switch means operated by the movement of said light-reflecting means from said first to said second position for switching said second photosensitive means out of said electrical bridge means and into said electric circuit second portion and for disconnecting said electrical means from said electrical bridge means.