Sensitivity balancing apparatus for photo responsive detecting circuits

Claim 3

The apparatus as set forth in claim 1 wherein said amplifier means includes first and second amplifier devices each having first and second input terminals and an output terminal, said first input terminal of said first amplifier device being connected to said common terminal, said first and second input terminals of said second amplifier device being connected across said storage means, said output terminal of said second amplifier device being connected to said second input terminal of said first amplifier device, said output terminal of said first amplifier device providing said compensated difference signal.

Claim 4

The apparatus as set forth in claim 1 wherein said first and second detecting devices are photoresistors.

Claim 5

The apparatus as set forth in claim 1 wherein said first and second detecting devices each Comprise a like plurality of photoresistors having first and second terminals, said first terminals of said photoresistors of said first detecting device being commonly connected to means for connection to a first voltage source, said first terminals of said photoresistors of said second detecting device being commonly connected to means for connection to a second voltage source, said second terminals of corresponding elements of said first and second detecting devices being connected together thereby forming a plurality of said common terminals, said apparatus including one of said circuit means connected to each of said plurality of said common terminals.

Claim 6

The apparatus as set forth in claim 4 wherein said apparatus includes a signal processing means which comprises: means for rectifying said compensated difference signals; and means connected to said rectifying means for providing a composite signal representative of the sum of said rectified, compensated difference signals.

Claim 7

The apparatus as set forth in claim 1 wherein said first and second detecting devices are photovoltaic elements.

Claim 8

The apparatus as set forth in claim 1 wherein said first and second detecting devices each comprise a like plurality of photovoltaic elements having first and second terminals, said first terminals of said photovoltaic elements being connected to a common reference potential; a plurality of differential amplifier circuits each having first and second input terminals and an output terminal, said second terminals of corresponding photovoltaic elements of said first and second detecting devices being connected to said first and second input terminals, respectively, of separate ones of said differential amplifier circuits, said output terminals of said differential amplifier circuits each being connected to a separate common terminal, said apparatus including one of said circuit means connected to each of said common terminals.

Claim 9

The apparatus as set forth in claim 7 wherein said apparatus includes a signal processing means comprising: means for rectifying said compensated difference signals; and means connected to said rectifying means for providing a composite signal representative of the sum of said rectified compensated difference signals.

Claim 10

The apparatus as set forth in claim 1 wherein said defining means further includes first and second lens means for receiving spatially separated segments of radiation from the object, said first lens means defining said first discretely identifiable portion and said second lens means defining said second discretely identifiable portion.

Claim 11

A focus detecting apparatus for use with means for focussing a principal image of an object on a predetermined plane, the focus detecting apparatus comprising: first and second means arranged to receive radiation from the object for defining a light path including first and second discretely identifiable portions of said radiation, said first and second portions being effective to form first and second auxiliary images of the object, respectively, said second auxiliary image being spatially separated from said first auxiliary image; first and second detecting devices positioned to receive radiation from said first and second auxiliary images, respectively; means operable conjointly with said means for focussing the principal image for introducing relative motion between at least one of said auxiliary images and the associated detecting device; said first and second detecting devices each including a similar array of a plurality of light responsive elements, each element being arranged to provide an electrical signal representative of the intensity of the light impinging thereon; means for comparing electrical signals from each element of one of said arrays with the electrical signal from a corresponding element of the other of said arrays, and deriving from each such comparison a difference signal which appears at a separate common terminal; Signal processing means; circuit means for receiving said difference signals, said circuit means being connected to said signal processing means; means selectively operable between a first position in said light path and a second position out of said light path, said selectively operable means, when in said first position, being effective to cause substantially equal amounts of radiation to fall on said first and second detecting devices, said circuit means including, for each of said difference signals, a storage means, a switching device connecting each of said common terminals with the associated storage means, said switching devices being operable, when said selectively operable means is in said first position, for providing a low impedance path between each common terminal and its associated storage means for rapidly charging said storage means to a balancing signal level representative of the respective difference signals generated while said first and second detecting devices are substantially equally radiated, said switching devices being further operable, when said selectively operable means is in said second position, for providing a high impedance path between each of said common terminals and the associated storage means to substantially preclude a discharging of the respective storage means, an amplifier means for comparing said stored balancing signals with difference signals generated when said selectively operable means is in said second position for providing compensated difference signals which are representative of the difference between said stored balancing signals and said difference signals, said compensated difference signals being compensated for any inequality in effective sensitivity between corresponding ones of said first and second detecting devices; said signal processing means being operable to process the compensated difference signals to produce an output signal which is representative of the condition of focus of the principal image on the predetermined plane.

Claim 12

A focus detecting apparatus for use with means for focussing a principal image of an object on a predetermined plane, the focus detecting apparatus comprising: first and second means arranged to receive radiation from the object for defining a light path including first and second discretely identifiable portions of said radiation, said first and second portions being effective to form first and second auxiliary images of the object, respectively, said second auxiliary image being spatially separated from said first auxiliary image; first and second detecting devices positioned to receive radiation from said first and second auxiliary images, respectively; means operable conjointly with said means for focussing the principal image for introducing relative motion between at least one of said auxiliary images and the associated detecting device; said first and second detecting devices each including a similar array of a plurality of light responsive elements, each element being arranged to provide an electrical signal representative of the intensity of the light impinging thereon; means for comparing electrical signals from each element of one of said arrays with the electrical signal from a corresponding element of the other of said arrays, and deriving from each such comparison a difference signal which appears at a separate common terminal; Signal processing means; circuit means for receiving said difference signals, said circuit means being connected to said signal processing means; means selectively operable between a first position in said light path and a second position out of said light path, said selectively operable means, when in said first position, being effective to cause substantially equal amounts of radiation to fall on said first and second detecting devices, said circuit means including, for each of said difference signals, a storage means, a switching device connecting each of said common terminals with the associated storage means, said switching devices being operable, when said selectively operable means is in said first position, for providing a low impedance path between each common terminal and its associated storage means for rapidly charging said storage means to a balancing signal level representative of the respective difference signals generated while said first and second detecting devices are substantially equally radiated, said switching devices being further operable, when said selectively operable means is in said second position, for providing a high impedance path between each of said common terminals and the associated storage means to substantially preclude a discharging of the respective storage means, an amplifier means for comparing said stored balancing signals with difference signals generated when said selectively operable means is in said second position for providing compensated difference signals which are representative of the difference between said stored balancing signals and said difference signals, said compensated difference signals being compensated for any inequality in effective sensitivity between corresponding ones of said first and second detecting devices; said signal processing means being operable to process the compensated difference signals to produce an output signal which is representative of the condition of focus of the principal image on the predetermined plane.