Exposure control system for document copying apparatus

Claim 2

Apparatus for controlling intervals of photographic exposure in accordance with the brightest portion of an illuminated object comprising: shutter means operable to control the interval of said photographic exposure; actuator means for opening said shutter means to initiate an exposure; a timing network having a plurality of branches connected in parallel and arranged respectively for the photometric evaluation of selected regions of said illuminated object, each said branch including an element having an electrical characteristic variable in relation to the brightness of at least one said selected region and producing an output in response to the said initiation of exposure which changes with time in a manner functionally dependent upon said variable electrical characteristic; discrete unilaterally conductive means coupled with each said branch output and interconnected to form a selector circuit for conveying only the said output representing a photometric evaluation of the said region of highest brightness; and trigger means responsive to the output of said selector circuit for closing said shutter means when said output reaches a preselected trigger level.

Claim 3

Apparatus in accordance with claim 1 wherein each said element of said timing network branch is a light dependent resistor arranged for exposure to light from at least one said region and having a resistance value varying inversely with the intensity of light incident thereon.

Claim 4

Apparatus in accordance with claim 1 wherein said element of said timing network branch is a light dependent resistor whose resisTance values vary inversely with the magnitude of said selected region brightness.

Claim 5

Apparatus in accordance with claim 3 wherein each said timing network branch further includes capacitor means, the current through which changes in response to said initiation of exposure with a time constant dependent on at least the resistance of said light dependent resistor.

Claim 6

Apparatus in accordance with claim 1 including a manually adjustable variable resistance means coupled with said timing network for adjusting the output response characteristic of the network.

Claim 7

Apparatus in accordance with claim 1 wherein said unilaterally conductive means are mutually interconnected in a manner wherein that coupled with the said branch output representing a photometric evaluation of said region having highest brightness functions to isolate the outputs presented from the remaining branches.

Claim 8

Apparatus in accordance with claim 6 wherein each said unilaterally conductive means is a diode coupled for conductive response with said branch output.

Claim 9

Apparatus in accordance with claim 7 wherein said branch coupled diodes are mutually interconnected so as to permit a forward biasing only of that diode responding to the branch output of highest magnitude.

Claim 10

Apparatus in accordance with claim 1 wherein each said branch output is present as a voltage having a variable and rising value; and said selector circuit is arranged to effect a conveyance of that branch output having the highest rate of voltage rise.

Claim 11

Apparatus for controlling intervals of photographic exposure in accordance with the brightest portion of an illuminated object comprising: shutter means operable to control the interval of said photographic exposure; actuator means for opening said shutter means to initiate an exposure; a timing network having a plurality of branches connected in parallel and arranged respectively for the photometric evaluation of selected regions of said illuminated object, each said branch including an element having an electrical characteristic variable in relation to the brightness of at least one said selected region and producing an output in response to the said initiation of exposure, said output being present as a time variable voltage having a rising value functionally dependent upon said variable electrical characteristic; discrete unilaterally conductive means coupled with each said branch output and interconnected to form a selector circuit for conveying only the said output representing that branch output having the highest rate of voltage rise; and trigger means including a field effect transistor conductively responsive to the output of said selector circuit for closing said shutter means when said output reaches a preselected trigger level.

Claim 12

Apparatus for controlling intervals of photographic exposure in accordance with the brightest portion of an illuminated object comprising: shutter means operable to control the interval of said photographic exposure; actuator means for opening said shutter means to initiate an exposure; a timing network having a plurality of branches connected in parallel and arranged respectively for the photometric evaluation of selected regions of said illuminated object, each said branch including an element having an electrical characteristic variable in relation to the brightness of at least one said selected region and producing an output in response to the said initiation of exposure, said output being present as a time variable voltage having a rising value functionally dependent upon said variable electrical characteristic; discrete unilaterally conductive means coupled with each said branch output and interconnected to form a selector circuit for conveying only the said output representing that branch output having the highest rate of voltage rise; and trigger means including a field effect transistor conductively responsive to the output of said selector circuit for closing said shutter means when said output reaches a preselected trigger level.

Claim 13

Apparatus in accordance with claim 10 wherein said trigger means further includes transistor means coupled for conductive response with said field effect transistor and operative to conduct in the absence of a said output at said trigger level.

Claim 14

Apparatus for controlling intervals of photographic exposure in accordance with the brightest portion of an illuminated object comprising: shutter means for controlling said photographic exposure; actuator means for opening said shutter means to initiate an exposure; a timing network having a plurality of branches connected in parallel and arranged for the photometric evaluation of select regions of said illuminated object, each said branch including at least one light-dependent resistor exposed to light from at least one said region and having a resistance value dependent upon the intensity of light incident thereon, each said branch further including capacitor means, the current through which changes in response to initiation of exposure with a time constant dependent on at least the resistance of said light-dependent resistor, each said branch producing an output in response to initiation of exposure which changes with time in a manner functionallY dependent on said resistance of said light-dependent resistor and hence upon the brightness of said region; discrete unilaterally conductive means coupled with each said branch output and interconnected to form a selector circuit for conveying only the said output of predominant potential and hence representative of the said region of highest brightness; and trigger means responsive to the output of said selector circuit for closing said shutter means when said output reaches a preselected trigger level.

Claim 15

Apparatus for controlling intervals of photographic exposure in accordance with the brightest portion of an illuminated object comprising: shutter means for controlling said photographic exposure; actuator means for opening said shutter means to initiate an exposure; a timing network having a plurality of branches connected in parallel and arranged for the photometric evaluation of select regions of said illuminated object, each said branch including at least one light-dependent resistor exposed to light from at least one said region and having a resistance value dependent upon the intensity of light incident thereon, each said branch further including capacitor means, the current through which changes in response to initiation of exposure with a time constant dependent on at least the resistance of said light-dependent resistor, each said branch producing an output in response to initiation of exposure which changes with time in a manner functionallY dependent on said resistance of said light-dependent resistor and hence upon the brightness of said region; discrete unilaterally conductive means coupled with each said branch output and interconnected to form a selector circuit for conveying only the said output of predominant potential and hence representative of the said region of highest brightness; and trigger means responsive to the output of said selector circuit for closing said shutter means when said output reaches a preselected trigger level.

Claim 16

Apparatus in accordance with claim 12 including manually adjustable variable resistance means coupled with said timing network for adjusting the output response characteristic of the network.

Claim 17

Apparatus in accordance with claim 12 wherein said unilaterally conductive means are mutually interconnected in a manner wherein that coupled with the said branch output representing a photometric evaluation of said region having highest brightness functions to isolate the outputs presented from the remaining branches.

Claim 18

Apparatus in accordance with claim 14 wherein each said unilaterally conductive means is a diode coupled for conductive response with said branch output.

Claim 19

Apparatus in accordance with claim 15 wherein said branch coupled diodes are mutually interconnected so as to permit a forward biasing only of that diode responding to the branch output of highest magnitude.

Claim 20

Apparatus in accordance with claim 12 wherein each said branch output is present as voltage having a variable and rising value; and said selector circuit is arranged to effect a conveyance of that branch output having the highest rate of voltage rise.

Claim 21

Apparatus for controlling intervals of photographic exposure in accordance with the brightest portion of an illuminated object comprising: shutter means for controlling said photographic exposure; actuator means for opening said shutter means to initiate an exposure; a timing network having a plurality of branches connected in parallel and arranged for the photometric evaluation of select regions of said illuminated object, each said branch including at least one light-dependent resistor exposed to light from at least one said region and having a resistance value dependent upon the intensity of light incident thereon, each said branch further including capacitor means, the current through which changes in response to initiation of exposure with a time constant dependent on at least the resistance of said light-dependent resistor, each said branch producing an output in response to initiation of exposure which is present as a time variable rising voltage functionally dependent on said resistance of said light-dependent resistor and hence upon the brightness of said region; discrete unilaterally conductive means coupled with each said branch output and interconnected to form a selector circuit for conveying only the said output having the highest rate of voltage rise and hence representative of the said region of highest brightness; and trigger means including a field effect transistor conductively responsive to the output of said selector circuit for closing said shutter means when said output reaches a preselected trigger level.

Claim 22

Apparatus for controlling intervals of photographic exposure in accordance with the brightest portion of an illuminated object comprising: shutter means for controlling said photographic exposure; actuator means for opening said shutter means to initiate an exposure; a timing network having a plurality of branches connected in parallel and arranged for the photometric evaluation of select regions of said illuminated object, each said branch including at least one light-dependent resistor exposed to light from at least one said region and having a resistance value dependent upon the intensity of light incident thereon, each said branch further including capacitor means, the current through which changes in response to initiation of exposure with a time constant dependent on at least the resistance of said light-dependent resistor, each said branch producing an output in response to initiation of exposure which is present as a time variable rising voltage functionally dependent on said resistance of said light-dependent resistor and hence upon the brightness of said region; discrete unilaterally conductive means coupled with each said branch output and interconnected to form a selector circuit for conveying only the said output having the highest rate of voltage rise and hence representative of the said region of highest brightness; and trigger means including a field effect transistor conductively responsive to the output of said selector circuit for closing said shutter means when said output reaches a preselected trigger level.

Claim 23

Apparatus in accordance with claim 18 wherein said trigger means further includes transistor means coupled for conductive response with said field effect transistor and operative to conduct in the absence of a said output at said trigger level.