SU711525A1 - Exposure determining and control device - Google Patents

Abstract

The exposure control has the photocell coupled to two transistors (1, 2) with base and collectors shorted. Their outputs are taken to a switching stage (7) via a third transistor (10). The transistors are connected to the battery supply. The system eliminates any mechanical switching with its inherent unreliability. It provides an indication of the preferred exposure settings or operates exposure limit indicators. The second transistor (2) is connected to a timing capacitor (6) and to the input of a switching stage (7). The output of the latter (7) is coupled to an electro-magnet (8) ending the exposure. The transistor (10) compensates for the base to emitter potential of the first transistor (1).

Description

The invention relates to photographic equipment and can be used to determine and control exposure.

A device is known comprising a photodetector, a signal processing circuit having switches ₅ associated with camera elements, and an actuator [1].

A device is known comprising a photodetector, a storage capacitor, a signal processing unit, a threshold device, an actuator, and a power source [2].

A disadvantage of the known devices is the presence of contact switches that reduce their reliability in operation,

The purpose of the invention. - increased reliability. jg The goal is achieved in that the photodetector is connected to a power source through the collector-emitter junction of the first transistor, and the base is connected to its collector and connected to the bases N of installed additional 20 transistors having identical parameters with the first transistor, and collectors of additional transistors connected to the inputs of actuator circuits having a different threshold of operation ^

In FIG. 1 shows a diagram of a device for determining and controlling exposure; in FIG. 2 is a diagram of inputting film sensitivity values; in FIG. 3 is a diagram for roughly aligning the tolerances of the photodetector.,.

A transistor 2 is connected in series with the photodetector '1. In parallel, a circuit consisting of a capacitor 3 is connected, in parallel to which a switch 4 and a transistor are connected. 5. The common point of the capacitor and transistor is connected to the input of the threshold actuator 6, the output of which is connected to the electromagnet '7.

In series with the actuator, transistor 8 is used, which serves to compensate for the voltage of the base and emitter of transistor 2. As well as transistor 5, transistors 9 and 10 are included, together with resistors And and 12 forming voltage dividers, the common points of which are respectively connected to the inputs of actuators 13 and 14, at the outputs of which the indicator lights 15 and 16 are turned on.

Transistors 17 and 18 are used to compensate for the voltage of the base and emitter of transistor 2.

The device is powered from a power source 19 through a switch 20.

The device operates as follows. After turning on the device, the switch 20 through the photodetector 1 current will flow

Zri R <p the voltage of the power source; voltage drop across the transistor 2.

current will flow through the collector as well, where U _o The same resistor 5, i.e.

When the shutter opens, the switch 4 opens and the capacitor 3 charges to a voltage, U _c , equal to their ^C \ ^C

The charge will continue until the voltage across the capacitor reaches a value sufficient to trigger the threshold element of the actuator 6.

(4) (5).

θ6 · ^υ 0 ^_υ ΒΕ ₈ ”where Cl is the coefficient characterizing the threshold ·. inclusion.

With equality, and _with ? Us ( ^b ) actuator 6 is activated, and electrode 7 is de-energized, ceasing exposure.

The exposure time obtained in this way takes into account the values of equations (5) and (6) in equation (3), (4),

On condition,

Фо ^ ΒΕβ- ^ Ф ^U o ~ ^υ ΒΕ ₂ that

CO (8) is obtained for equation (9) transistor exposure time

Current Pf acts but also on transistors is equal

AF

Voltage drop * f not only at 9 and 10. Transistor current = - (40)

Ф on the resistor 11 is equal to _{-and п₽} К ,.

About BEg 44 (.4 ’44 - ‘’

5, ^υ - '' ³ κ _ς ^κ

If the magnitude of this voltage is less than the threshold voltage, then the indicator light 15 remains dark, if the voltage exceeds the threshold, then it starts to glow, indicating insufficient exposure time.

The inclusion condition in this case is determined by the equation

R, CR.

f c

In the same way, the photodetector 1 controls the device 14. At the input: the last logic circuit NO is turned on, and the indicator light 16 lights up if, with a low illuminance of the subject, the resistance value of the photodetector 1 becomes quite large. The inclusion condition in this case is as follows:

1G

R ,,, OR f C

Along with the above functions, others can be implemented, for example, a preliminary indication of the holding time by supplementing the circuit in FIG. 1 indicator, adjustable in the same way by the photodetector 1.

Transistor 22 can be connected to transistor 2 through switch 21, and transistor 23 can be connected to transistor 5. This will allow taking into account the sensitivity value of the film.

The above scheme does not require special selection of the parameters of the photodetector 1.

Claims (2)

(54) DEVICE FOR DETERMINATION AND REGULATION OF EXPOSURE The device is powered from the power source 19 through the switch 20. The device operates as follows. After the device is switched on by the switch 20, a current will flow through the photodetector 1 a.- with the voltage supply voltage; voltage drop across the transistor. torus 2. The same current will flow through the collector of transistor 5, i.e. opening the shutter, the switch 4 is released and the capacitor 3 d voltage is charged, U is equal to IUo-UuE 3t3 The charge will continue until the voltage on the capacitor reaches the value Ug sufficient for actuating the threshold element of the actuator 6. 6,. (5) where d is the coefficient characterizing the horn-, inclusion. In case of equality, Uc U9 Sb) actuator 6 triggers, and electrode 7 is de-energized by stopping the exposure. The exposure time thus obtained takes into account the values of equations (3), (4) (5) and (6) in the equation t o-UBE “BEe-t Ф O-UBE. Provided that, for the exposure time, the equation is obtained, t-a fs. (9) Current Sf affects not only transistors but also transistors 9 and 10. Current transistor 9 is equal to o nf. 3 ..: j. .. ° g. (-10) k, - The voltage drop across the resistor 11 is equal to and. And because it is IF if the magnitude of this voltage is less than the horn voltage, then the indicator light 15 remains dark if the voltage preys the threshold, then it begins to shine, indicating that the expo time is insufficient. The switching condition in this case is determined by the equation T -dR - In the same way, the photodetector 1 controls the device 14. At the entrance: the last logical circuit is NO, and the light indicator 16 lights up if the resistance value of the photoreceiver 1 becomes sufficiently small . The condition of inclusion in this case is the following:. cht R ..- C3lTR -14 with others. Other functions, such as a preliminary indication of the exposure time, can also be implemented along with the above functions, in addition to the diagram in FIG. 1 indicator, regulated in the same way by the photodetector 1. To the transistor 2 through the switch 21 you can connect the transistor 22, and to the transistor 5 - the transistor 23. This will take into account the sensitivity of the film. The diagram does not require special selection of photodetector parameters. Formula of Invention The device for determining and controlling exposure includes a photodetector, a storage capacitor, a signal processing unit, a threshold device, a performance element and a power source, in order to increase reliability, the photodetector through the transition the collector of the first transistor is connected to the power source, and the base is connected to its same collector and is connected to the bases N of installed additional transistors stories having identical parameters to the first transistor, the collectors of the transistors are connected to additional inputs of executive devices circuits having different threshold. Sources of information taken into account in the examination 1. For France of France N 7500963, clb 03c 7/00, 1975. 2. US patent N 3931628, CL- 354-24, published. 01/06/76 (prototype).