Light integrating type light detector circuit with photovoltaic cell

Claim 2

A light sensitive circuit comprising: a. a photovoltaic cell; b. a capacitor element; c. switch means actuatable for initiating a variable time interval; d. said photovoltaic cell, said capacitor element and said switch means being connected in a parallel circuit with each other, whereby upon opening of said switch means, said capacitor element is charged with a signal; and e. circuit means responsive to the signal of said parallel circuit of a threshold level to provide an output signal after the timing interval, said threshold level being selected within a range of a signal charged on said capacitor element with a charging current substantially equal to a short circuit current of said photovoltaic cell, whereby said timing interval is inversely proportional to the intensity of light directed onto said photovoltaic cell.

Claim 3

A light sensitive circuit comprising: a. a photovoltaic cell; b. an integrating capacitor element; c. switch means actuatable to initiate a timing interval; d. said photovoltaic cell, said integrating capacitor element and said switch means being connected in a parallel circuit whereby upon opening of said switch means, said photovoltaic cell applied a signal to charge said integrating capacitor element; and e. circuit means responsive to the signal developed on said integrating capacitor element of a threshold level to provide an output signal after the timing interval, said threshold level being selected to be approximately one-tenth of the open circuit voltage of said photovoltaic cell at the lower limit of light intensity to be measured by said light sensitive circuit, whereby the timing interval is inversely proportional to the intensity of illumination directed onto said photovoltaic cell.

Claim 4

A light sensitive circuit comprising: a. a photovoltaic cell; b. an integrating capacitor element; c. switch means actuatable to initiate a timing interval; d. said photovoltaic cell, said integrating capacitor element and said switch means being connected in a parallel circuit whereby upon opening of said switch means, said photovoltaic cell applied a signal to charge said integrating capacitor element; and e. circuit means responsive to the signal developed on said integrating capacitor element of a threshold level to provide an output signal after the timing interval, said threshold level being selected to be approximately one-tenth of the open circuit voltage of said photovoltaic cell at the lower limit of light intensity to be measured by said light sensitive circuit, whereby the timing interval is inversely proportional to the intensity of illumination directed onto said photovoltaic cell.

Claim 5

A light sensitive circuit responsive to scene illumination for controlling the exposure interval of a shutter mechanism, said light sensitive circuit comprising: a. a photovoltaic cell disposed to receive the scene illumination said photovoltaic cell responsive to scene illumination to provide a linear output corresponding to the scene illuminaTion; b. a capacitor element; c. switch means responsive to the opening of the shutter mechanism to initiate the exposure interval; d. said photovoltaic cell, said capacitor element and said switch means being connected with each other in a parallel circuit, whereby upon opening of said switch means, said capacitor element is charged with the cell output; and e. trigger circuit means responsive to the charged signal on said capacitor element of a threshold level, for providing an output signal, said threshold level being set within said range of said photovoltaic cell whereby said output of said trigger circuit means occurs after an exposure interval inversely proportional to the intensity of the scene illumination incident on said photovoltaic cell.

Claim 6

A light sensitive circuit responsive to scene illumination for controlling the exposure interval of a shutter mechanism, said light sensitive circuit comprising: a. a photovoltaic cell disposed to receive the scene illumination said photovoltaic cell responsive to scene illumination to provide a linear output corresponding to the scene illuminaTion; b. a capacitor element; c. switch means responsive to the opening of the shutter mechanism to initiate the exposure interval; d. said photovoltaic cell, said capacitor element and said switch means being connected with each other in a parallel circuit, whereby upon opening of said switch means, said capacitor element is charged with the cell output; and e. trigger circuit means responsive to the charged signal on said capacitor element of a threshold level, for providing an output signal, said threshold level being set within said range of said photovoltaic cell whereby said output of said trigger circuit means occurs after an exposure interval inversely proportional to the intensity of the scene illumination incident on said photovoltaic cell.

Claim 7

A light sensitive circuit for controlling the exposure interval of a shutter mechanism, said light sensitive circuit comprising: a. a photovoltaic cell disposed to receive scene illumination; b. switch means responsive to the opening of the shutter mechanism to initiate the exposure interval; c. an integrating capacitor element; d. said photovoltaic cell, said switch means and said capacitor element being connected in parallel with each other whereby a signal is charged on said integrating capacitor element; e. means coupled to said integrating capacitor element for converting the impedance of its charged signal; f. amplifier means responsive to the converted output of said conversion means after said switch means is actuated by the shutter mechanism to initiate the exposure interval; g. time constant means coupled to the output of said amplifier means for absorbing a long period drift of said amplifier means; h. trigger circuit means responsive to the output of said amplifier means of a threshold level to provide an output signal; and i. actuating means responsive to the output of said trigger circuit means for actuating the shutter mechanism to terminate the exposure interval.

Claim 8

A light sensitive circuit for controlling the exposure interval of a shutter mechanism, said light sensitive circuit comprising: a. a photovoltaic cell disposed to receive scene illumination; b. switch means responsive to the opening of the shutter mechanism to initiate the exposure interval; c. an integrating capacitor element; d. said photovoltaic cell, said switch means and said capacitor element being connected in parallel with each other whereby a signal is charged on said integrating capacitor element; e. means coupled to said integrating capacitor element for converting the impedance of its charged signal; f. amplifier means responsive to the converted output of said conversion means after said switch means is actuated by the shutter mechanism to initiate the exposure interval; g. time constant means coupled to the output of said amplifier means for absorbing a long period drift of said amplifier means; h. trigger circuit means responsive to the output of said amplifier means of a threshold level to provide an output signal; and i. actuating means responsive to the output of said trigger circuit means for actuating the shutter mechanism to terminate the exposure interval.

Claim 9

The light sensitive circuit as claimed in claim 4, wherein said time constant means comprises a second capacitor element and a resistor element.

Claim 10

The light sensitive circuit as claimed in claim 4, wherein said time constant means includes a resistor and a second capacitor element, at least one of said resistor and said second capacitor being altered to vary the amplification factor of said amplifier means.

Claim 11

The light sensitive circuit as claimed in claim 6, wherein said amplification factor is varied dependent on the sensitivity of a photographic medium exposed by the shutter mechanism.

Claim 12

The light sensitive circuit as claimed in claim 4, wherein said time constant means comprises a resistor and a second capacitor element connected in a second parallel circuit, said amplifier means comprising an amplifying transistor, said second parallel circuit connected to said amplifying transistor for providing an emitter bias therefor, said amplifying transistor providing a signal across said resistor in proportion to a drift or relatively long period whereby the amplification factor of said amplifying transistor is maintained relatively low, in response to a drift of short period, said second capacitor element of said time constant means being charged and discharged to tend to cancel the signal across said resistor whereby the amplification factor of said amplifying transistor is raised.

Claim 13

The light sensitive circuit as claimed in claim 4, wherein said time constant means comprises a second capacitor element, a resistor and a switch, said switch responsive to the opening of the shutter mechanism to be opened.

Claim 14

The light sensitive circuit as claimed in claim 4, wherein said time constant means comprises a second capacitor element and a resistor, and there is further included second switch means connected in series with said second capacitor element of said time constant means, said second switch means responsive to the opening of the shutter mechanism to be opened.

Claim 15

The light sensitive circuit as claimed in claim 10, wherein said second switch means is coupled to said first-mentioned switch means to be actuated together in response to the opening of the shutter mechanism.

Claim 16

The light sensitive circuit as claimed in claim 11, wherein said amplifier means comprises a differential amplifier circuit having first and second input terminals, said first input terminal being connected in series by said second switch means to said second capacitor element and to a reference signal source, said second input terminal being connected to the point of interconnection between said second capacitor element and said second switch means.

Claim 17

The light sensitive circuit as claimed in claim 11, wherein said amplifier means comprises a differential amplifier circuit having first and second input terminals, said first input terminal being associated with the output of said conversion means, said second input terminal being connected to the point of interconnection between said second capacitor element and said second switch means whereby said time constant means receives an amplified signal in-phase with the signal applied to said differential amplifier circuit.

Claim 18

The light detector circuit as claimed in claim 4, wherein said time constant means comprises a first resistor and a second capacitor element connected in series with a variable resistor, said series connected variable resistor and said second capacitor element being connected in parallel with said first resistor, and a switch connected in parallel with said variable resistor, the resistance of said variable resistor being dependent upon the sensitivity of a photographic medium exposed by the shutter mechanism.

Claim 19

A light measuring circuit comprising: a. a photovoltaic cell disposed to receive light, the intensity of which is to be measured; b. an integrating capacitor element; c. switch means actuatable for applying the output of said photovoltaic cell to be integrated by said integrating capacitor; d. said integrating capacitor and switch means being connected to form a first parallel circuit; e. amplifier means for amplifying the output of said parallel circuit; and f. means for absorbing a long-period drift of said amplifier means comprising a resistor and a capacitor element connected together to form a second parallel circuit; g. said amplifier means comprising an amplifying transistor, said second parallel circuit being connected to said amplifying transistor for providing an emitter bias therefor, said amplifier means applying a signal across said resistor dependent upon a long-period drift of said amplifier means to maintain an amplification factor of said amplifying transistor low, in response to a drift or relatively short period, said second capacitor element of said absorbing means being charged and discharged for cancelling the signal applied across said resistor of said absorbing means, whereby the amplification factor of said amplifying transistor is raised.

Claim 20

A light measuring circuit comprising: a. a photovoltaic cell disposed to receive light, the intensity of which is to be measured; b. an integrating capacitor element; c. switch means actuatable for applying the output of said photovoltaic cell to be integrated by said integrating capacitor; d. said integrating capacitor and switch means being connected to form a first parallel circuit; e. amplifier means for amplifying the output of said parallel circuit; and f. means for absorbing a long-period drift of said amplifier means comprising a resistor and a capacitor element connected together to form a second parallel circuit; g. said amplifier means comprising an amplifying transistor, said second parallel circuit being connected to said amplifying transistor for providing an emitter bias therefor, said amplifier means applying a signal across said resistor dependent upon a long-period drift of said amplifier means to maintain an amplification factor of said amplifying transistor low, in response to a drift or relatively short period, said second capacitor element of said absorbing means being charged and discharged for cancelling the signal applied across said resistor of said absorbing means, whereby the amplification factor of said amplifying transistor is raised.

Claim 21

The light measuring circuit as claimed in claim 15 adapted for use with a shutter mechanism for controlling the exposure of scene illumination onto a photographic medium, wherein said absorbing means further comprises a switch responsive to the opening of the shutter mechanism to be opened.

Claim 22

The light measuring circuit as claimed in claim 15, adapted for use with a shutter mechanism for controlling the exposure of scene illumination onto a photographic medium, wherein said absorbing means comprises a switch connected in series with said second capacitor of said absorbing means and responsive to the opening of the shutter mechanism to be opened.

Claim 23

The light measuring circuit as claimed in claim 15, adapted for use with a shutter mechanism for controlling the exposure interval of a photographic medium, wherein said absorbing means further comprises a variable resistor, said second capacitor connected in series circuit with said variable resistor, said seriEs circuit being connected in parallel with said first-mentioned resistor, and a switch connected in paralell with said variable resistor, the resistance of said variable resistor being set in accordance with the sensitivity of the photographic medium.

Claim 24

The light measuring circuit as claimed in claim 18, wherein said amplifier means comprises a differential amplifier circuit having first and second inputs, said first input being connected to said switch of said absorbing means and to a reference potential source, said second input being connected to the point of interconnection between said second capacitor element and said switch of said absorbing means.

Claim 25

The light measuring circuit as claimed in claim 18, wherein said amplifier means comprises a differential amplifier circuit having first and second inputs, said first input being asoociated with the output of said first parallel circuit, said second input being connected to the point of interconnection of said second capacitor element and said switch of said absorbing means whereby the output of said amplifier means is applied to said absorbing means in-phase with the signal applied to said second input of said differential amplifier circuit.

Claim 26

A light measuring circuit for controlling the exposure interval of a shutter mechanism, said light measuring circuit comprising: a. a light sensitive element disposed to receive the light whose intensity is to be measured and to provide an output indicative of the light intensity; b. means for providing an output control signal for controlling the exposure interval of the shutter mechanism in accordance with the output derived from said light sensitive element, the output control signal provided by said signal providing means having a relatively long-period drift; and c. absorbing means associated with said signal providing means including a capacitor for absorbing a long-period drift of the output control signal of said signal providing means.

Claim 27

A light measuring circuit for controlling the exposure interval of a shutter mechanism, said light measuring circuit comprising: a. a light sensitive element disposed to receive the light whose intensity is to be measured and to provide an output indicative of the light intensity; b. means for providing an output control signal for controlling the exposure interval of the shutter mechanism in accordance with the output derived from said light sensitive element, the output control signal provided by said signal providing means having a relatively long-period drift; and c. absorbing means associated with said signal providing means including a capacitor for absorbing a long-period drift of the output control signal of said signal providing means.

Claim 28

The light measuring circuit as claimed in claim 21, wherein said signal providing means includes amplifier means for amplifying the output derived from said light sensitive element and said capacitor of said absorbing means is connected with said amplifier means with a resistor connected in parallel therewith to form a time constant circuit of a time constant substantially larger than the lowest shutter speed of the shutter mechanism for lowering the amplification factor of said amplifier means in a range of particularly low frequencies.

Claim 29

The light measuring circuit as claimed in claim 21, wherein said absorbing means includes a plurality of time constant circuits, each of which comprises a capacitor and a resistor connected in parallel therewith and has a time constant larger than the lowest shutter speed for lowering the amplification factor of said amplifier means in a range of particularly low frequencies.

Claim 30

The light measuring circuit as claimed in claim 23, wherein said amplifier means includes amplifying transistors and said plurality of time constant circuits are connected in series to the emitters of said amplifying transistors, respectively.

Claim 31

The light measuring circuit as claimed in claim 21, wherein said signal providing means includes amplifier means for amplifying the output derived from said light sensitive element and trigger circuit means responsive to the output from said amplifier means of a threshold level for providing said signal for controlling the exposure interval, and said capacitor of said absorbing means is connected between the output of said amplifier means and the input of said trigger circuit means with a switch connected between the input of said trigger circuit means and a point of fixed voltage, said switch being opened upon initiation of exposure.

Claim 32

The light measuring circuit as claimed in claim 25, wherein said capacitor of and absorbing means is connected to the input of said trigger circuit means through a variable resistor connected in parallEl with said switch, said variable resistor being set in accordance with the sensitivity of a photographic medium used.

Claim 33

The light measuring circuit as claimed in claim 21, wherein said signal providing means includes amplifier means for amplifying the output derived from said light sensitive element, said amplifier means including a differential amplifier circuit having first and second inputs, and said capacitor of said absorbing means is connected between the output of said light sensitive element and said first input of said differential amplifier circuit with a switch connected between said first and second inputs of said differential amplifier circuit, said switch being opened upon initiation of exposure.

Claim 34

The light measuring circuit as claimed in claim 21, wherein said signal providing means includes amplifier means for amplifying the output derived from said light sensitive element, said amplifier means including a differential amplifier circuit having a first input supplied with the output derived from said light sensitive element and a second input, and said capacitor of said absorbing means is connected between said second input and a point of fixed voltage with a negative feedback circuit connected to said second input through a switch, said switch being opened upon initiation of exposure.

Claim 35

The light measuring circuit as claimed in claim 21, wherein said signal providing means includes a first circuit for receiving the output derived from said light sensitive element and a second circuit for producing said signal for controlling the exposure interval, and said capacitor of said absorbing means is connected between the output of said first circuit and the input of said second circuit with a switch connected between the input of said second circuit and a point of fixed voltage, said switch being opened upon initiation of exposure.