US4029992A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Flash apparatus with flash terminating switch controlled by photosensor
Assignee: Braun GmbH
•
Filing: 1975-05-02
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Granted: 1977-06-14
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Expires: 1995-05-02
Abstract
Abstract The light sensitive circuit which controls the voltage at the control electrode of the thyristor used to control the termination of the flash includes a photosensor and a resistor-capacitor integrator circuit connected to the photosensor. The voltage across the capacitor is applied to the control electrode of the thyristor. In accordance with the present invention, a diode connected in series with a variable resistor is connected in parallel with the resistor of the integrator circuit. An additional resistor may be connected in parallel with the capacitor and a further resistor in parallel with the whole integrator circuit in order to allow adjustment of the operating region of the diodes such that it has a very low resistance only when a very high quantity of light as reflected by a very close object impinges upon the photosensor.
Inventors
- 👤 Heinz Engelstatter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:08
CPC Classifications
H; H05; H05B; H05B41/00; H05B41/14; H05B41/30; H05B41/32; H05B41/325
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
229 words
In the electronic flash unit of the type operative for producing flashes the duration of which is automatically controlled in dependence upon the scene brightness during the flash, in combination, a flash element; means for igniting the flash element; terminating means for terminating the flash produced by the flash element and including an electronic flash-terminating switch having a control electrode and operative when activated for causing the terminating means to terminate the flash; an integrating capacitor and means providing a current path for the capacitor; a charging resistor connected in the current path of the integrating capacitor and carrying a component of the integrating capacitor current, the charging resistor being operative for affecting the rate at which the integrating capacitor charges; means connecting the junction between the charging resistor and the integrating capacitor to the control electrode of the electronic flash-terminating switch for controlling the conductivity of the switch in dependence upon the voltage across the integrating capacitor; a light-sensing element connected in the current path of the integrating capacitor operative for making the capacitor current a function of sensed scene light; and a diode connected across the charging resistor with a polarity such as to carry a further component of the integrating capacitor current, the diode presenting to such further current component a resistance which varies in inverse dependence upon variations in the voltage across the charging resistor.
Claim 2
Dependent Claim
229 words
In the electronic flash unit of the type operative for producing flashes the duration of which is automatically controlled in dependence upon the scene brightness during the flash, in combination, a flash element; means for igniting the flash element; terminating means for terminating the flash produced by the flash element and including an electronic flash-terminating switch having a control electrode and operative when activated for causing the terminating means to terminate the flash; an integrating capacitor and means providing a current path for the capacitor; a charging resistor connected in the current path of the integrating capacitor and carrying a component of the integrating capacitor current, the charging resistor being operative for affecting the rate at which the integrating capacitor charges; means connecting the junction between the charging resistor and the integrating capacitor to the control electrode of the electronic flash-terminating switch for controlling the conductivity of the switch in dependence upon the voltage across the integrating capacitor; a light-sensing element connected in the current path of the integrating capacitor operative for making the capacitor current a function of sensed scene light; and a diode connected across the charging resistor with a polarity such as to carry a further component of the integrating capacitor current, the diode presenting to such further current component a resistance which varies in inverse dependence upon variations in the voltage across the charging resistor.
Claim 3
Dependent Claim
22 words
The electronic flash unit defined in claim 1, including a further resistor connected in series with the diode across the charging resistor.
Claim 4
Dependent Claim
16 words
The electronic flash unit defined in claim 2, wherein the further resistor is an adjustable resistor.
Claim 5
Dependent Claim
38 words
The electronic flash unit defined in claim 1, including a further resistor connected across the integrating capacitor for diverting away from the integrating capacitor a portion of the current flowing in the current path of the integrating capacitor.
Claim 6
Dependent Claim
44 words
The electronic flash unit defined in claim 1, including a further resistor connected across the combination of the charging resistor and the integraring capacitor for diverting away from the latter a portion of the current flowing in the current path of the integrating capacitor.
Claim 7
Dependent Claim
15 words
The electronic flash unit defined in claim 1, wherein the diode is a zener diode.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-06-13 | 1980-12-13 | 1981-06-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-06-13 | 1984-12-13 | 1985-06-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-06-13 | 1988-12-13 | 1989-06-14 | $7700.00 | Window Closed / Lapsed |