DE2253685A1 - DEVICE FOR ELECTRIC EXPOSURE CONTROL FOR A SINGLE-EYED MIRROR REFLEX CAMERA - Google Patents

Description

Minolta Camera Kabushiki Kaisha

Toyota Building 18, 4-chome, Shiomachidori

Minami-ku * Osaka Ü Japan)

Device for electrical exposure control for a single-lens reflex camera

The invention relates to a device for electrical Exposure control for a single-lens reflex camera and in particular a device for electric exposure control for a one-eyed Single-lens reflex camera in which the scene light entering through the lens is transmitted through light-receiving elements is recorded to store a brightness value of an object to be photographed and at which the Exposure according to the stored brightness value and by one corresponding to the values of the brightness of the object to be photographed, the film speed and the shutter speed set manually is controlled by the aperture.

In the single-lens reflex camera, it is basically

It is known that when the exposure is controlled by measuring the incident light through the lens, the axial release operation causes the camera to move from the viewfinder to the exposure condition and to move the reflex mirror from the viewfinder to the exposure position. Before you let the aperture take a predetermined opening, the brightness of the an object to be photographed is detected as a voltage by a detection circuit; which determined Voltage is stored in the storage means. The time circuit (timer) is saved by the Voltage actuated simultaneously with the beginning of the exposure, and when the level detection circuit determines that the level of the voltage of the timing circuit has reached a predetermined value, the actuation circuit is actuated to terminate the exposure.

It is also known that the brightness value of the object to be photographed, which is detected by the detection circuit, is converted into a logarithmic Value is compressed or compressed; the logarithmically compressed tension is stored in the storage means and then converted anti-logarithmically into a logarithmic expansion. By such an arrangement can be the capacity of the capacitor of the storage means and the voltage of the power source can be lowered.

However, it is evident that by these operations of

- 3 -309820/0673

the logarithmic compression for the anti-logarithmic conversion into the logarithmic expansion is already a small in the logarithmically compressed, stored voltage introduced a large error in exposure time caused when it is logarithmically stretched. It can also be seen that there is an error in the Exposure time, which is inversely proportional to the logarithmically expanded storage voltage, becomes long, especially when the brightness of the object to be photographed Object is large, in other words, when a high shutter speed is set.

In order to keep the error to a minimum, the first thing was envisaged eliminating errors due to fluctuations in the voltage of the power sources. To this Purpose, the logarithmic amplifier must be operated by the output of the power source circuit.

There will be lots of P-N connections like transistors and diodes Used in the generator circuit for constant current, in the logarithmic amplifier and in the time circuit. The P-N connection is known to have a characteristic that changes with temperature. Accordingly, there is a consideration to compensate for the error caused by temperature changes at the P-N connections of the respective circuits necessary·. When actually applying the exposure control according to the storage system to a one-eyed SLR cameras are used except for one.

309820/06 7 3

value of the object to be photographed Values of the film speed and aperture as input variables for used the photography process. When the camera is in the viewfinder mode, the aperture will be adjusted accordingly the brightness of the lens is left completely open, as has already been said above, and is set to a predetermined value set, accordingly, the value of the diaphragm opening is usually a predetermined value.

Both the value of the film speed and the specified value of the aperture change digitally in the Way that the former ASA 25,50,100 ... and the latter 1,4; 2; 2.8; 4 is, and the values must be used as input quantities are fed to the logarithmic amplifier.

The object of the invention is to provide an electrical exposure adjustment device for a single-lens reflex camera to create, in the case of a memory system for controlling the exposure, in which a determined brightness value of a to be photographed object is logarithmically compressed, this value is stored in a memory means before the exposure and at the time of exposure this is controlled according to the stored value and the Introduction of a bug based on voltage fluctuations in the Energy source and a temperature change based, is prevented.

* when the camera is brought into exposure mode.

309820/0673

In the case of a camera with a focal plane shutter consisting of two screens, the exposure error that from the overlap of the rear edge of the leading screen and the leading edge of the trailing screen, when the shutter is cocked, follows', to be compensated.

In the exposure control circuit of the storage system, part of the circuit is said to consist of a monolithic integrated circuit exist for the purpose of miniaturization. According to the invention, this is achieved in that the output variable of the photosensitive elements through a logarithmic amplifier as one of the value of the logarithm the voltage proportional to the brightness of the light can be determined, this potential can be stored in storage means is, the time circuit at the time of exposure by the anti-logarithmically converted from the stored voltage Current can be actuated and an actuation circuit for the termination of the exposure is provided that for Prevention of current fluctuations resulting from voltage fluctuations of the energy source a generator circuit for constant current is provided, the voltage of which is fed to the logarithmic amplifier that a circuit is available, to which the electricity generated in the G-enerator circuit for constant electricity can be fed, in which Photosensitive elements and resistors are included and in which a voltage is proportional to a logarithmic Value of the illumination of the light-sensitive areas

- 6 309820/0673

it is possible to produce a logarithmic amplifier connected in series with the circuit mentioned in the second place is provided, the bias voltage dependent on the set value of the film speed and the aperture opening The generating circuit contains that through the logarithm! see the amplifier through the output current of the generator circuit for constant current generated voltage of both circuits can be evaluated and one one logarithmic value of the exposure time proportional voltage can be generated that storage means for storage . the output voltage of the logarithinic amplifier are provided by a switch before exposure that a Timing circuit is present to generate an anti-logarithmically converted from the storage voltage of the storage means Current simultaneously with the exposure and that one to terminate the exposure by the time circuit operable actuating circuit is provided.

In the exposure adjusting device of the present invention, there are provided

(A) a dry cell battery

(B) A constant current generator circuit that contains

(a) a fixed resistor consisting of a first resistor, one of which is connected to the positive pole of the dry cell battery is connected, and consists of the second resistor connected in series with the first resistor,

- 7 309820/067 3

(b) a first NPN transistor whose collector is connected to the outer connection of the second resistor, whose emitter to "the negative pole of the dry cell battery and its Base is connected to the connection point between the first and the second resistor of the fixed resistor,

(e) a second NPN transistor whose base is connected to the Collector of the first IPN transistor and its emitter for the generation of the collector current proportional to the absolute temperature via a third fixed resistor to the negative pole of the energy source is connected,

(d) a first transistor circuit consisting of a PNP transistor, the emitter of which is connected to the positive pole of the energy source via a resistor, and from the third NPN transistor whose base to the collector this ΡϊΙΡ transistor whose collector to the emitter this PNP transistor and its emitter is connected to the collector of the second liPN transistor,

(e) a second transistor circuit equivalent to the The first transistor circuit is connected and consists of a PHP transistor whose base is connected to the base of the PNP Tranoistor in the first transistor circuit and its emitter connected through a resistor to the positive terminal of the dry cell battery and off. ordered an NPN transistor,

where each transistor and each resistor has a mono-

309820/0673

is a lithic, integrated circuit,

(C) A logarithmic amplifier is also provided with a circuit connected to the emitter of the NPN transistor of the second transistor circuit has connected photo element and one of the logarithmic value of the illuminance has a proportional output voltage on the photosensitive surface of the photo element,

(D) a storage means for storing the output voltage this logarithmic amplifier as well

(E) a timing circuit that has the integrated fourth NPN transistor contains, at the base of which the storage voltage of the storage circuit is applied during exposure.

The device according to the invention also has a third transistor circuit which is used in the generator circuit for constant current is connected to the first transistor circuit equivalent and from a PNP transistor, its base to the base of the PNP transistor in the first Transistor circuit and its emitter connected to the positive pole of the dry cell battery via a resistor and consists of an NPN transistor, as well one with the fourth NPN transistor the same Characteristic of the fifth integrated NPN transistor, the collector of which is connected to the circuit, which has the PhotoeJenent and which the logarithmic Value of the illuminance on the light-sensitive surface

- 9 _
309820/0673

of the photo element generated proportional voltage and a variable resistance, its resistance value according to a certain aperture as well as a certain Film speed is variable, one connection to the emitter of the fifth NPI transistor and at the same time to the emitter of the NPN transistor of the third Generator circuit transistor circuit for. constant current is connected and its other Terminal is connected to the negative terminal of the dry cell battery.

The time circuit has the parallel to the collector of the fourth NPN transistor and the first capacitor, to the second variable by a switch according to a specific aperture and a specific one Film speed variable resistor connectable second capacitor. A changeover switch is provided for the optional setting of the automatic and manual control of the exposure time, as well as a level detection circuit, through the switch with its one terminal to one terminal of the first or second capacitor can be connected to determine the charging voltage of this capacitor and to generate a signal when this Voltage reaches a certain level, and an electromagnet that terminates the level-detecting circuit is excitable. '

- 10 -

309820/0 6 73

mm j [^ J mm

The storage means has a capacitor for storing the output voltage of the logarithmic amplifier and a fixed resistor, which is used to correct the through the line of the electromagnet in the actuation circuit caused a voltage drop of the dry cell battery to the capacitor and the negative pole of the dry cell battery connected. A fourth transistor circuit of the integrated circuit is provided which is connected to the first transistor circuit in the generator circuit for constant current is connected equivalent and off a PNP transistor whose base connects to the base of the PNP transistor in the first transistor circuit and its emitter through a resistor to the positive pole of the Dry cell battery is connected, and consists of an NPN transistor, and a measuring circuit to which the Emitter current of the NPN transistor of the fourth transistor circuit and the output voltage of the logarithmic amplifier can be supplied as input variables.

A delay circuit is provided between an Ausgarigsklemme of the level detection circuit and an input terminal of the actuation circuit is for the temporal correction of the overlap of the rear edge of the leading screen with the front one Edge of the trailing screen of the focal plane shutter in the tensioned position.

The invention is described below with reference to the accompanying drawings described in more detail:

- 11 309820/0673

Fig. 1 is a block diagram showing the structure of an

Guide form according to the present invention reproduces i

Fig. 2 is a graph showing the temperature dependency

of the output current in a generator circuit for shows constant current as drawn in the block diagram of FIG. 1;

Fig.3 is a diagram showing the spring logarithm of the brightness of an object to be photographed proportional Output voltage in a logarithmic amplifier according to FIG. 1 in relation to the respective set Shows film speed and aperture;

Fig.4 shows in a diagram the relationship between a Output voltage of the logarithmic amplifier, which is generated according to the setting values of the film speed and aperture and the logarithm of the exposure time, which are controlled

5 shows a circuit diagram of an embodiment according to of the present invention; Fig. 5 (A) shows part of it, Fig. 5 (B) shows the other part;

Fig. 6 (A) shows the detail of a circuit diagram in

which is another embodiment of a light receiving Element of the logarithmic amplifier in the embodiment of Fig. 5 reproduces;

- 12 -

309 8 20/067 3

Fig. 6 (B) is a diagram showing the relationship between

the logarithm of the brightness of a light-receiving surface of the photosensitive element according to Fig. 6 (A) and the value of a combined resistance;

Fig. 7 is a diagram showing the relationship between

a terminal voltage of a series resistor Rs and set which is variable for setting the values of film speed and aperture Values of aperture and film speed in the same embodiment according to FIG. 5;

8 shows a diagram at different temperatures a ratio between an output voltage of the logarithmic amplifier and a logarithm the brightness on the light receiving surface of the scene light receiving element of the same embodiment;

Fig. 9 is a diagram showing a relationship between

a base-emitter voltage of an input transistor of a timing element of the same embodiment when a storage voltage of the storage element is supplied to it, and a logarithm of the collector current this transistor;

Fig. 10 shows the value of an exposure time

by a measuring instrument of a measuring circuit again, and an allowable range of the automatic control is also shown; and

- 13 -

309820/0673

Fig. 11 is a diagram showing a relationship between the gain of an NPN transistor and of a PHP transistor and the ambient temperature.

1 shows, in a block diagram, a structural principle of the present invention. for constant current generates a stable output current even if there are fluctuations in the voltage supply thereof in relation to an absolute temperature changes. The characteristic of the output current and the temperature is shown in FIG. This generator circuit for Constant current serves as an energy source for a measuring circuit M and a logarithmic amplifier P.

The logarithmic amplifier P is a circuit to convert a quantitative change in incident light into a voltage change. Change in general the brightness value of an object to be photographed, values of the lens opening and fi & i sensitivity, all of which are used as input values, digitally, for example 1 lux, 2.4. »... lux at Brightness value of the object to be photographed,

* during an output current

- 14 -

309820/0673

1.4,2,2.8,4 .... for the aperture and ASA 25,50,100 for the value of the film speed. if these digitally changing values are used as they are as outputs of the measured light, change accordingly the outputs of the

measured light digitally. For example, suppose that the range of exposure time is limited is 1 to 1/1000 of a second and the output voltage of the logarithmic amplifier P 0.1 volts per second, then the output voltage for 1/1000 of a second is 100 volts. Therefore the power of the source of energy becomes great, so that it is impossible is to use miniaturized or low voltage energy sources. Should be digitally changing output voltages of the measured light are used as they are, would consequently, as was shown in the example above, the practical utility of the circuit is greatly reduced, and the use of one energy source is reduced Performance would degrade accuracy. ,

In the device according to the present invention, in order to avoid the above-mentioned difficulties, the logarithmic amplifier P is used, which is designed in such a way that a digitally changing input variable can be transformed into one evenly

- I5 -

309820/0673

receives differential changing output of measured light; the characteristic curve in this regard is shown in FIG. 3.

In connection with a storage circuit Me arrives at the single-lens reflex camera the scene light of the object to be photographed through a recording lens system, from where it is projected into the viewfinder system through a reflex mirror. Are light receiving elements arranged behind the reflective mirror so that they carry out the light measurement. At the time of recording when the If the reflex mirror is rotated to block the incidence of light on the light-receiving elements, the values fluctuate of the light receiving elements to such an extent that an output voltage of the logarithmic amplifier P does not represent an exact value. Therefore, in this case, the exposure time can not go through the exit of the logarithmic amplifier P can be controlled. To such influence due to the rotation of the reflex mirror or the like, the storage circuit Me is provided, in which the output voltage of the logarithmic Amplifier P into a capacitor of the storage circuit is loaded. This makes the output voltage of the logarithmic amplifier P during a control the exposure time required.

- 16 -

309820/0673

In the event that the automatic control is selected, a time circuit Tc comes into action around the digitally changing exposure time using the uniformly differentially changing storage voltage to control the storage means Me for example by means of a transistor and capacitors, while if the value the exposure time is set by hand, a circuit is operated, which consists of a fixed resistor and Capacitors.

A level detection circuit D is a circuit for Determining the level of the output variable of the timing circuit Tc and generating output signals, if the output of the timing circuit Tc reaches a predetermined level.

A delay circuit De can be added according to the needs. This delay circuit is required in the event that a shutter how to use a focal plane shutter that has a leading and trailing screen. In order to use the shutter of this type at the time of shutter tensioning to switch off the penetration of light, this delay circuit De is actuated to a value deviation electrically adjust the exposure time, resulting from the difference between the starting positions of the rear Edge of the leading screen and the leading edge of the trailing screen, both of which are partially mutually exclusive

- 17 -309820/0673

overlap, arises. By making a delay circuit is provided, the precise adjustment of the "two screens" during assembly is simplified.

An actuation circuit A is a section for amplifying an output signal of either the level detection circuit D or the delay circuit De and for controlling magnetization of an electromagnet to convert electrical signals into mechanical signals. Finally, a measuring circuit M is actuated by output signals of the logarithmic amplifier P, which are fed to it as input signals, in order to display the value of the exposure time by a suitable measuring instrument and thereby to show a condition of the light measurement (the light conditions) at the time of exposure the storage means Me, the timing circuit Tc, the level detection circuit D, the delay circuit De and the actuation circuit A are shown in FIG. The above relationships among the respective circuits are represented by the following formulas.
First in amplifier P:

Vp = K1 log L + K2

where L is the brightness of the object to be photographed, K1 a constant, K2 a depending on a combination of the Values of the film speed and aperture value determined expression and Vp an output signal of the logarithmic ratio

- · 18 -

309820/0673

stronger P is, which latter the time circuit Tc than Input signal is supplied.

For the time circuit Tc, the level detection circuit D, the delay circuit De and the actuation circuit A is the formula:

Vp = K ₃ log

T + a

where K? is a constant, T is the exposure time and a is a delay time in the delay circuit De, the latter being a fixed value that can be set by the camera. As can be seen from formula 2, if the values of K1, K2 and K3 are determined in a suitable manner, the expression _T 1 and thus automatically one is obtained

T
The value of the exposure time T in relation to the fluctuation in the brightness value of the object to be photographed. Figures 5 (A) and (B) are circuit diagrams of an embodiment of the invention drawn separately for the sake of clarity and therefore both combined in one complete circuit diagram. Referring to the drawings, the constant current generator circuit I in Fig. 1 includes transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, QO, Q10, Q11, Q2y, 030, fixed resistors R1, R2, R3, R4. R5, semi-fixed resistors R6, R12, R39 and diodes 1) 1, D2, in which the output current is obtained from the Emit Lürori of the transistors Q, 6, Q11 _t Q30,

309820/0673

In detail, the emitter current of the transistor Q6 feeds constant current in the photosensitive elements Rcds1, Rcds2 and resistors E7 »R8 of the logarithmic amplifier P ·, the emitter current of the transistor Q11 feeds constant Current .in a variable bias resistance Rs, the resistance of which depends on a set value of the • Film speed and the aperture of the logarithmic Amplifier P changes, and the emitter current of transistor Q30 feeds constant current into the measuring circuit M.

It is now the circuit structure of the G-enerator circuit of the constant current in detail with reference to the embodiment described in Fig. 5 (A). Two resistors R1 and R2 connected in series are connected to the The collector of a first NPN transistor Q1 connected, while an external connection of the resistor R1 via a switch S1 to the positive pole of an energy source E and emitter of this first NPN transistor Q1 with the negative pole of the energy source E is connected. The base of transistor 0.1 is with the connection point connected between the two resistors R1, R2. A second NPlI transistor Q2, its base to the collector of the first NPN transistor Q1 is suitable, generate a collector current proportional to the absolute temperature; the emitter of this transistor is Q2

- 20 -,
309820/0673

Via a resistor R3 to the negative pole of the energy source E and its collector is one with the emitter third NPN transistor Q3 connected. The collector of this third NPN transistor Q3 is on the one hand with the positive pole of the via a resistor R4 and the switch S1 Power source E and, on the other hand, connected to the emitter of a PNP transistor Q4. The collector of this PNP transistor Q4 is connected to the base of the third NPN transistor Q3 and to the base of another NPN transistor

LA-q —— 3 ... iy \ ./ i Tin 1 * 1- r \ r% ί » Wο * i ο ο λ ι y> f \ ο ca yt /" j Qy η yi vA tJlV l * Pνι ** _ ι η ο * ι ο τ f \ * y * o C] / "tr q" ν *

bound. The collector of this transistor Q7 is across the Switch S1 to the positive pole of the energy source E and its emitter is to the collector of a transistor QO verbudnen whose base is connected to the base of the second NPN transistor Q2. The emitter of transistor Q8, which has the equivalent current characteristic of the transistor Q2 is connected to the negative pole via a resistor R5 the energy source E connected.

The emitter of transistor Q7 is also grounded through series connected diodes D2 and D1 of the PNP transistor 0.4 connected.

A circuit consisting of a PNP transistor 03 and an NPN transistor Q6 is connected to the positive pole of the energy source E via a resistor R6 and the switch S1; this circuit has an equivalent connection

3 (T98 ¹ 2Ö / 0873

- 21 -

to the circuit consisting of the PNP transistor Q4 and the third NPN transistor Q3, and the emitter of this NPN transistor is connected to a circuit which is a Output voltage proportional to the value of the logarithm of the brightness of the object to be photographed is generated in the logarithmic amplifier P '. In the same way, a Circuit consisting of a PNP transistor Q10 and an NPN transistor Q11 via a resistor Ii.12 and the Switch S1 connected to the positive pole of the energy source E. This circuit has an equivalent connection to the circuit consisting of the PHP transistor Q4 and. the third NPN transistor Q3 and the emitter of this NPN- ' Transistor QH is connected to a circuit which depending on the set value of the film speed and the aperture in the logarithmic amplifier logarithmically compressed prestress generated. .

Similar is a circuit consisting of a PNP transistor Q29 and an NPN Troncistor Q30 via a resistor R39 and the switch SI connected to the positive pole of the energy source E. This circuit has an equivalent connection to the circuit consisting of the PNP transistor Q4 and the third NPN transistor Q3 and the emitter of the transistor Q30 is connected to the measuring circuit M. The bases of these PNP transistors Q5, Q10, Q29 are all with the Connected to the base of the PITP-Tr meter Q4. Accordingly, the actuation current of the transistor QI decreases when the Voltage of the energy source in relation to the resistors

309820/0673

- 22 -

R1, R2, R3 and the transistors Q1, Q2 go down, which is a decrease the base-emitter voltage BE of this transistor Q1 results. However, the voltage between the terminals of the resistor R2 also decreases, and therefore the collector potential of the transistor Q2 is against fluctuations the voltage of the energy source E is kept stable.

This is shown numerically below. Assuming that a temperature corresponds to the absolute temperature Te, is the saturation current of transistor QJ at temperature Te Is., The saturation current of the transistor Q2 is Isp (the saturation current is a constant that is determined by a transistor and changes depending on the temperature), then one obtains the following formula:

K - Te _t Ij KT _e I ₂

¹ : ^{= R} 2 ^X 1 f in + RT ₀

where so that the emitter current I2 of the transistor Q2 against Fluctuations in the emitter current I1 of the transistor Q] are stable. is the value

is and therefore

KT
R ^ I. =. (approximately R ,, Ii = 26mV

q if Te = 300 ° Κ)

and therefore the resistors R2, R3 must be chosen so that they satisfy the above formula.

309820/0673

- 23 -

Between the base and emitter of the transistor QI and the transistor Q2 becomes a difference in the base-emitter voltage BE either by a difference between the emitter currents L · and Io or by a difference between the Areas of these emitter layers generated. The temperature coefficient of the base-emitter voltage BE is:

1 ■ ¹ BI

then you get the following formula:

^dV BE ^V BE ■ ^KT e ^V BE dT 81 ^dV BE < O ^aT e ^T e increases e ■ m Correspondingly at Increase in Worth

the difference in the BE value between the transistors changes Q1 and Q2 how the temperature changes. In other words, the emitter current Ip of the transistor Q2 becomes communicated to the temperature change. According to the present invention, the difference therebetween is a few 10 mV given so that the value of the collector current of the transistor Q2 is set proportional to the absolute temperature will. If by the difference between the emitter currents L · and Ip of the transistors Q1 and Q2 there is a difference

- 24 τ
309820/0673

is given in the voltage value BE and when the transistors Q1 and Q2 are transistors with the same characteristic and their degree of reinforcement is sufficiently large, then the formulas are:

a -

KT

hit, " 'Γ P ²

"IS " 4 3 ~ ~ "q"" ^{x £ / i} " s2

= I.

where I'ρ is a value of the emitter current of the transistor Q2, when the temperature is T2.

Suppose the above formulas are replaced by the formulas _T , _T ' _T ' _φ9 where _TT

¹ Sl ^{fc i} s2 2 ~ ff "I ₂ si" ⁱ s2 ·

then you get the formula

T2

XiI ₁ -

rn-i mn Λ-i I J C-

In the above formulas are. T ₁ and T ^ determined by the required temperature range, and the emitter current I ^ of the transistor Q2 is determined because it is also a required otrom.

309820/0673

- 25 -

If the resistor R3 is given a value as it can be assumed for a stabilized circuit, then one obtains the value of the emitter current I ^ of the transistor Q1,

In connection with the transistors Q3, Q4, the transistors Q5, Q6, the transistors Q10, -QH and the transistors Q29, 0.30 it should be said that _f should they belong to an integrated circuit, the gains of PIP transistors be significantly degraded to such an extent that it is impossible to use PHP transistors alone; therefore, in the present invention, PIIP transistors and NPN transistors are used in combination to thereby increase the gain. As can be seen from Fig. 5 (A), the values or emitter currents of the transistors 0, 6, 0, 11 and Q30 are approximated by the respective following formula:

₆ = _JL ii ₌ 4

^H 6 ^{2; 11} "XT" ^ .; ho

This means that the emitter current Ip of the transistor Q2 against the voltage fluctuation of the energy source E stable remains and since a value proportional to the absolute temperature is obtained, the output current is. Ir »I-i- | or I ^ q

-26 -

309820/0673

stable against the voltage fluctuation of the energy source E and v / e is proportional to the absolute temperature Value on.

A circuit consisting of transistors Q7, 0.8, den Diodes D1, D2 and the resistor Pi 5 serves to control the base current of the combined PNP-NPN transistor circuits to flow. This circuit is designed so that the Base current flows to the diodes D1, D2 while through the Difference between the base current and the current of transistor Q8, which is equivalent to a constant current characteristic the current characteristic of the transistor has 0.2, the current is supplied to the transistor Q7; when the gains / PNP transistors are extremely low, this does not affect the characteristics of the emitter current Ig, L ·. or I ™ off, even if the base current is high.

The logarithmic amplifier P will now be described with reference to Fig. 5 (A).

As already said above, the logarithmic amplifier P is a circuit that changes analogously, photographic input data, such as values of the brightness of the object to be photographed, an aperture, film sensitivity etc. converts into an arithmetically changing emergence voltage.

Two photoconductors RcdSI and RcdS2 form what is known as one

- 27 309820/0673

photoconductive
compound / element. As shown in Fig. 6 (A), each conductor is composed of a photoconductive element CdS, high sensitivity and a photoconductive element CdS, low sensitivity. are connected in parallel to each other. The highly sensitive photoconductive element CdS-, is connected to a resistor ri in series ", and a resistor r ^ is connected in series with the parallel circuit. Values of the logarithm of the combined resistance of these resistors have a linear course that corresponds to the width Area related to the values of the logarithm of the received scene light, as shown in Fig. 6 (B).

Two of the photoconductive elements shown in Fig. 6 (A) are used in the circuit of Fig. 5 (A), the photoconductive elements on the high sensitivity side (on the low resistance side) being interconnected by a semi-fixed resistor R9; in parallel, the photoconductive elements on the low sensitivity side (on the high resistance side) are directly connected to each other and a semi-fixed resistor R9 ¹ is connected in series with these parallel circuits. These two photosensitive elements are arranged on a finder light path system (for example, on a front edge and a rear edge of a roof-shaped reflection surface of a pentagonal prism). When derailing

309820/0673

If the resistance value between these semi-fixed resistances Uq and HJ _{1 is} to be adjusted, the output voltage changes arithmetically in relation to the analogously changing value of the brightness of the object to be photographed, which is known as the CLC effect and a photographically favorable result of the semi-solid Resistance Rq ^{1 can be} achieved. Then, these resistors Rq and Rq ^{1 are} connected to the emitter of the transistor Q6 in the constant current generator circuit, and the output current is input to the logarithmic amplifier.

A circuit consisting of the series-connected resistors ΠγιΗο is parallel to the above-mentioned circuit intended. Both circuits are connected to the collector of transistor Q9, the base of which is connected to the junction point this resistors Ry and Rn is connected. This transistor Q9 causes temperature compensation for the base-emitter voltage of a transistor Q12, what will be described later.

A resistor R10 and a thermistor R1 are connected to the emitter of the transistor Q9. Since the emitter current Ir of the transistor Q6, in other words the actuation current of the transistor Q9, is proportional to the absolute

29 -

309820/0673

When the temperature changes, the base-emitter voltage of the transistor Q9 has a change in relation to the temperature change which is different from the case where the emitter current Ir of the transistor Q6 is constant. Specifically, the change in the base-emitter saving, when the emitter current Ir decreases as the temperature drops, is less than in the case in which the emitter current Ig. is constant. This difference is compensated for by the resistors ILq and Pi ,,. This is represented numerically by the following formula:

TCT FT

9 β 9 9 / T

6 6

Q. ^c l T *

with a change in temperature of 50 ⁰ G, the difference that is compensated is approximately 4 mV.

A variable resistor R is a resistor -for feeding data such as the values of the aperture and film sensitivity, and the voltage generated therein is ¹ G * ^E s ^{= 1} G ^x ( ^nr) > where? Is the number of setting thresholds and r is ^T < / is the resistance value per 1 ^. With the setting of η corresponding to the fourth of the aperture and film sensitivity, the voltage generated across the resistor Π shows the change as shown in FIG. The sum of the outputs V of the logarithmic amplifier P (the

- 30 -

309820/0673

Voltage between the ■ positive side of the resistor R9 ¹ and the negative side of the energy source 10 is given by the formula:

71 ρ t ρ ρ I ^U 7. ^ll O -Wi ' ¹ VfIo

V - \ J 4- fT L ⁿ ' ) T f ^T> P O UiJ N τ

^ T ^ G ^ cds ^

where R ^{1 is} a resistance value combined from the resistances Ii. ,,,, R ,, and R ..., Rcds is a resistance value _{combined from the resistances Reels 1, Rcds2 and R c} <. This is shown in Fig. Ü by a typical example, in

der.i R and R _η , that is, the value of the aperture, s cds ^u

the film sensitivity and the brightness of the object to be photographed are shown with the change in temperature. As can be seen from this sketch, as far as the characteristic of the output voltage is considered, since the limit current I.,. or I, - is stable with respect to the voltage of the energy source E, this output voltage is stabilized. Meanwhile, this voltage is shifted in parallel with respect to temperature because the Llasis-Einit gate

the base-emitter saving BEQ9 of the transistor QS ¹ increases as the ambient temperature falls and, since the emitter currents I., and Ir are proportional to the absolute temperature, the gradient of the output voltage becomes V kLcin.

- 31 -

309820/0673

In conjunction with that shown in Figures 5 (A) and (B) Storage means Me, the V of the outputs of the logarithinic amplifier P is charged therein and the output voltage V is cut off with the help of a switch S2 when the mirror is rotated and so the value the output voltage V for a control of the loading

the required period of time is held / so that it can be fed to the following time circuit Tc as an input variable and the change in the output voltage V sets a negligible capacity value for the duration of the exposure.

In this invention, under the condition of a few F, it is possible to maintain a sufficient holding time, which is negligible for an error in the exposure time.

The timing circuit (timer) Tc is as in FIG. 5 (B) from a circuit in which a transistor Q12 is controlled by a switch S4 which is set in the Connection with the triggering of the lock according to an input variable of the storage device, which is the output variable V of the logarithmic amplifier P store, opened will. This transistor Q12 and a capacitor C2 are connected in series to be connected to one another point to generate input variables; whereby the loading. lichtungndauor automa! if3ch is controlled by the values dor lüeridenöffnimp and Filmenipfindliclikeit discontinued

3
30 9 H 20/0673, -. _:

BAD ORIQtNAL.

v / earth. In addition, the timing circuit includes a circuit in which an optionally available, variable resistor R _m and a capacitor CU are connected in series with one another to produce output variables at their connection point, so that a desired exposure time by actuating the switch AM- included therein. and AMp can be set manually.

Assuming that a reference voltage of the level detection circuit D, in other words the voltage between the base of the transistor Q14 and the positive pole of the power source E, is given by Vq ₁ , the exposure time T ^{1 is} obtained by the following formula. In the case of manual adjustment, as is well known, the formula is:

1
T '= C ₅ R _T , Cn C flp—)

_5T flp

¹ - E

In the case of automatic control, if the collector current of the transistor is 0.12 Iqq-io ^unc * ^if ^ xr = 0, since it is the case of a constant current charge, the exposure time T ^{1 is} :

¹ CQI2

The exposure time T ¹ in the case of manual setting is given by the preceding formula; As you know, it is stable either to changes in the voltage of the energy source E or to changes in temperature, and therefore becomes

- 33 309820/0673

no further description is given, only the Case of automatic control is related to the Change in voltage of the energy source E and the change the ambient temperature.

First , with respect to the voltage fluctuation of the power source E, referring to Fig. 5 (B), in the aforementioned formula, Vm is given by the formula

. 'V ^B 16 ^{+ H} 13 -

and if

₆ ), - then applies

^{+ R} 16

The exposure time T ¹ b, ei Span- is correspondingly subject. voltage fluctuations of the energy source E no change and it is sufficient that the. To change the value of.Iqq. ^ At a fixed rate, i.e. it is sufficient to change the base potential of the transistor Ql2.

In the event that the resistor E13 and the capacitor G, for storage are connected in the manner shown in Fig. 5 (B), Lpp 'changes from 1 ·' to I ₀ , if ^{1 is} the voltage of the power source E changes from EV to E ₉ ; ' defr fluctuation amount VgrjAVp of the basic F.mitter-Spammng

- 34 309820/0673

of transistor Q12 is obtained from the general as follows Transistor formula:

¹ I ^KT e ¹ Z

O J.

KT

η I

^f [

1 / ^X 2

and assuming that the exposure time T ^{1 is} constant,

PP P

^G 2 ^ll i5 ° 2 R, p-

T _ "γ ft ¹ T _ ___" __ γ ¹ ^. , L ¹

Φ · Px T? * - Φ · P ill ^

Accordingly, the oMge form is] KT _a

v / odurch, uenu ^ K = ß, - E ₀ i ^£; t, the following formula will be obtained:

KT

the amount of the i'pnnnimrs'iolu / anlviirji; de. >noL'gi.efjile Vi bodru.Lot and dor U'lcIol ·: -: ti: tu! i: wüft don I- LJt ■. ■ '.: ■ ί'κ .'! ^; ··

309820/0673

BAD ORfQW ^ iAL

jL · is determined to satisfy the above formula. If, for example, E = 6V and E = 2V, then the voltage between the terminals of the resistor R ^ _{7 is} approximately 60 mV. . .

This means that essentially all of the tension is against this voltage fluctuation of the energy source E, which instead of- ν found when the electromagnet Mg, whose power consumption is high, is made conductive, compensates.

In order to keep the value of the exposure time T ¹ free from fluctuations in the case of a temperature change, the collector current I ™ -io ^ ^es transistor 0.12 must be kept stable, the values of the capacitor Cp and Vm should be constant. In general, a transistor is represented by

KT I
^V BEQ12 φ -2- In ~ ^ - ² and its characteristic is in

q p

Fig. 9 reproduced.

As can be seen from the sketch, it is noted in the characteristic that a component has a parallel displacement and a component has a change in its gradient when the temperature changes. The Grr-serves of the component in question changes proportionally to the absolute temperature, as shown in the previous formula

3 0 9820/0 6 73

So / eit the exposure time T 'is concerned, accordingly the compensation is carried out so that these two effects of the base-emitter voltage Vr »™ ..ρ of the transistor Q12 to be balanced »

Regarding the formula that the output voltage V of the logarithmic amplifier P compensates for the change in the base-emitter voltage Vd-pao of the transistor Q9 the change in the component causing a parallel shift in the base-emitter voltage Vn ^ n-io of the tran-

. , / Q12 on we is.t «if a transistor, 7. ,.,,. sistoivverwenaex, which has the same characteristics like transistors Q9 and 0.12, while what the components concerned, the gradient of which changes proportionally to the absolute temperature, the compensation, since the emitter currents 1.,. ,, Ir are proportional to absolute temperature, by this is achieved.

Particularly in the case of a short exposure time, the _{charge charged to the capacitor C 1} for storage is easily discharged through the transistor Q12 and the resistor IL. When the base current of the transistor Q12 ibQ-, ρ is ^ », the potential applied to the base of the transistor Q12 is lowered by the amount ibQ12 χ IL, and thereby the characteristic of the exposure time is formed, at which a substantially fixed value by a the value corresponding to the voltage drop is added; for example 1.1mS for 1/1000 C = 1mS, 2.1 mf; for 1/500 S = 2 mS, 4.1 mS for 1 / 25O: -3 = 4 mS.

- 37. - 309820/0673

Compensate this EU ^ if a semi-fixed resistor E ^ c is connected between the transistor _{0, 12 and the capacitor C 2} "as in -Figo 5

C 2 ^

in ; τ »=

For the formalities ^ u is seen that ,, tin solid "seconds value of the delay element may be equivalent ^ p% 5 ^a bgsi®itet. When §mn Example 1" is to be made 1 × mS wunschgemäi gu 1 mS and, when C2 ^β 1 / iF is _e so the value of the resistance IUr "is introduced to I00 8 ]

The Ii? Iin ^ feffllttlragiitromkr © ieS in Ii§ ₀ 5 (S) is constructed in such a way that il @ duroh the width city R ₁ Kpl * / - .. or © inen changing resistance! Lp g® "tsilt © spanning a connection the input side of the level <= detection circuit D is supplied ο so that this, voltage, _r as its reference voltage;

^& 2. above- mentioned ^ (? Rofe ^ Y ™ isxi,.

serves (welehas / while the other insciiluß on the input QQI T (S Wi- * f τ fißVi ¹ "\ ΓΩ * ν» * Κ ΤΤΙΠΊΊΉίϊ ¹ ΠΩ © Alles ^ VQVl Gf ^ Tiiil ^ inlrT © © OfS) Q 7ai γο ΤΤ? ΠΤΠοα

toi tV '* - ¹ ^ i

circular. Te Terbunden is? the charge voltage eex capacitors Cn. and G _x is matched with the reference pairing and thus ■ @ auo determined. "'

In Fig _o 5 (Β), the transistors 0.13 and 0.14 "form one

309820/0673

known differential amplifier, in which a transistor Q16 serves as a supply source with constant current »A circuit consisting of the transistor Q17 and the resistors R ^, ILg has the same structure as the circuit consisting of the transistor Q1 and the resistors R-pRp in the generator circuit I for constant current exists. Since the collector of the transistor is stable with respect to voltage fluctuations in the power source Q1, the collector current of the transistor Q12 is extremely stable "Concerning the relationship zn temperature changes, follows in terms of voltage fluctuations in the power source so should be the base of the transistor Q16 directly to the collector of the transistor Q17 must be connected so that the collector current of the transistor Q16 is subject to changes, and therefore a buffer circuit consisting of the diodes -Dz ₉ D. and the resistors R ^ q, Rp ^ is provided to stabilize the collector current ,, by effect of this circuit, the transistors Q13 and Q14 are constantly operated ρ to generate a stable output at the collector of the transistor Q22, which is a starting point of the level detection circuit D.

The In Fi.g _o 5 (B) delay circuit shown is used in the case that the device of the present invention is applied to a camera with a focal plane shutter, and that in this case, a fixed second value to the set from the time circuit Tc value of the exposure period

_ 39 309820/0673

must be added because of the difference in the starting position of the movement between the leading and trailing screen, as already mentioned above. In this delay circuit De are a semi-fixed resistor ELo and a capacitor C connected in series with each other. Both terminals of this capacitor C are connected to a transistor 0.23 in order to make this transistor Q23 conductive or non-conductive in accordance with the output signal of the level detection circuit D, with this capacitor G in a short-circuit state or in an open state "With the help of the charging characteristic of the capacitor C. and the semi-fixed resistor Rpn, a fixed rate of time delay is provided. In the circuit, the connection between the resistor Rpn and the capacitor C serves as the starting point _β."

The actuation circuit A is able to control the voltage change at the starting point of the delay circuit De to detect and amplify to operate the electromagnet Mg.

In Figo 5 (B), the voltage of the energy source E is divided by the diodes D5, D6 and the resistors ^ αι ^ ο at the connection point of the resistors R ^ R ™ a reference ™ voltage / and the reduction of the output voltage at the starting point of the Delay circuit De are compared to

/ ". The reference voltage

- 40 -

309820/0673

to be detected by transistor Q24 and through the transistors 0,25, Q26 and Q27 to be amplified.

In the same way, the two in Series-connected diodes D5 and D6 to compensate for the voltage fluctuation of the energy source E and Temperature change needed.

In this case it follows from the formula

¹ '" ^V BEQ24
^W 4 ^il 29 ⁱ " ⁿ 30

Jö

_E .V _BEQ24 _

^R 29 ^{+ R} 30

after which. if V _D5 = V ^ = V _{BEQ24 and R = R}

2y

t = C ₄ R ₂₀ In 2,

so that / maintains a stabilized rate of time lag.

In the camera equipped with a focal plane shutter, the electromagnet actuates the armature, which is connected to the fastening of the

- 41 309820/0673

trailing shield are connected. A resistor R ^ - connected in series with the electromagnet Ma serves to bring the current flow through the electromagnet Md to the most suitable value. Diodes B7, D8 and B9 are arranged for the purpose of protecting the transistor Q27 from damage by the back electromotive force of the electromagnet Mg. A capacitor C ₁ - is -with the electric-. Magnet Mg and a resistor R ^ connected in parallel and compensates for the change between the separation intervals of the armature from the electromagnet Mg, and this contributes to increasing the accuracy in the functioning of the circuit, especially when a short exposure time is established. Both the resistor R ™ and a transistor Q32, the collector of which is connected to a terminal on the input side of the level detection circuit D, are provided to prevent oscillation in the circuit caused by the following reason:

There is always an effort to reduce the size of an energy source to be used in a camera because of the conditions surrounding it and the dimensions of the camera; therefore, dry cells used therein must be extremely miniaturized. In this case, if a large amount of current (for example 30 mA) were to be fed into the electromagnet Mg, this would lead to a voltage drop in the dry cells. On the other hand, if the electromagnet is made non-conductive, the load on the

- 42 -309820/0673

Dry cells decrease drastically and as a result the tension of the dry cells immediately increases slightly and reverses then return to the initial state. Accordingly, Tc changes in the time circuit and in the level detection circuit D, assuming the immediate voltage rise in the supply source is ΔΕ, the base voltage of the transistor Q14 of the level detection circuit

R ₁₅

on A E χ while the base of the other

The transistor Q13 of the differential amplifier does not follow the change in the voltage of the energy source E due to the capacitors C ₉ and C i connected to it. Consequently

SiQh ₁ changes the base voltage ^ά ■>

of transistor Q13 by ^ E »This causes the Circuit is reset to its initial state from the state of termination of control, and that will repeats and causes the circuit to oscillate.

The measuring circuit M shown in Fig. 5 (A) operated by output signals of the logarithmic amplifier P, which are fed to it as input signals, a measuring instrument Met. As shown in FIG. 10, this measuring instrument shows a set value of the exposure time and is able to emit a warning signal if a set value of the exposure time, which is derived from a combination of the values of the aperture, the film sensitivity

- 43 -309820/0673

possibility and the brightness of what is to be photographed Object "was determined, the permissible range of the interlock exceeds. As shown in Fig. 5 (A), the input signal of the measuring circuit M becomes the base of a transistor Q31 is supplied, and when this potential changes, the emitter potential of the transistor Q31 becomes as follows Formula reproduced:

(Emitter potential of Tr. Q30) = V +

Accordingly, the emitter potential changes in the same way as the output potential V of the logarithmic Amplifier P. An emitter potential of the transistor Q34 is represented by the following formula:

^{+ V} BEQ31 ⁺ high ~ ^V BEQ33 " ^V BEQ34

Accordingly, the change in the emitter potential of the Tran- ■ sistor Q34 is equivalent to that of the output voltage V des logarithmic amplifier P. The output voltage V of this circuit remains with voltage fluctuations of the Energy source unchanged, and the emitter current I ™ of the transistor Q30, which is an input current, is kept stable, thereby ensuring the accuracy of the gauge. Meanwhile, in terms of the change in ambient temperature a, compensation-for temperature change accomplished between the sums of temperature change in the oumme the basic emitter spanmmg ^ -dpqo 3 es transistor Q9

3 0.9 820/0673

- 44 - '"■ -. ■ · ■

and VpT ₁ V- ^ .. of the transistor Q31 and the temperature change in the sum of the base-emitter voltage V ^ ₁₁₀ -,., of the transistor Q33 and ^ twq ^ a of the transistor Q34, and the emitter current I, q of the transistor Q30 changes it]] proportionally to the absolute temperature. The temperature coefficient is approximately 33OOPPM / ° C, while the temperature coefficient of the internal contradiction of the measuring instrument Met is approximately 3000PPM / Cict, since its -.pulcm is also wound with copper wire. These two compensate each other and thus ensure the stable and accurate display of the measuring instrument Met. In addition, a semi-fixed resistor H-zjf , which is connected in series with the measuring instrument Met, to the emitter of the transistor Q34, is used to reduce the Adjust the gradient characteristic of the measuring instrument Met.

Since the emitter current I ₇ Q of the transistor Q30 changes in proportion to the absolute temperature, as already stated, the actuation current of the transistor Q31 also has an equivalent change.

In particular, this means the base-emitter voltage VmYjz-i of transistor Q31 changes in the same way as the base-emitter voltage Vnpno of transistor Q9 des logarithmic amplifier Ijtind causes a slight Error in the measuring instrument Met. Although this error is so small that no special consideration needs to be given to compensation is, is in the present invention to "wock

309820/0673

the compensation a resistor R ₇ Q between the output side of the logarithmic amplifier P and the transistor Q51, to which the inputs are applied, switched on. When a transistor belonging to an integrated circuit, generally increases the gain of an NPN-Tran ~ sistpffs at a particular temperature decrease of 50 ⁰ C to> approximately $ 30, while that of a PNP transistor decreases by approximations, 50 T. Accordingly, if the transistors 031 and Q32 used in the measuring circuit belong to an integrated circuit, their gain decreases by approximately a total of 65 1 ° . In detail, this means that the base current of the transistor Q31 increases with the decrease in temperature, and then the voltage drop across the resistor Ti-zQ corrodes with the change in temperature.

If the value of a voltage change across the resistor IUg on one of the change in the base-emitter voltage Y ^, / of the transistor Q31 is brought to an equivalent level, the error of the display on the measuring instrument Met can accordingly can be reduced to a negligible extent.

When transistors Q31 and Q32 are normal transistors, the decrease in gain of either an NPN or a PNP transistor * is approximately 30 $> and therefore the resistance of resistor R _ZQ must be adjusted accordingly.

- 46 -

309820/0673

Elements that are in the previous description of the respective Circuits that have been omitted are described below:

(i) In the constant current generator circuit, with regard to the resistor Rr connected to the base or collector of the two series-connected transistors Qc and Qir , it can be seen that changes in the resistance of this resistor IL - a change in the emitter current L. of the transistor (L- cause. Because in the logarithmic amplifier P, the change in the characteristics of the two composite photoconductive elements Rp ^ qi and Rpjqo is balanced by the semi-fixed resistors Rq and RA, the gradient that the change in the set values of the brightness of the The object to be photographed shows the characteristics of the input transistor CLp of the time circuit. In other words, in order to change the collector current Ιπη-ι2 ^ ^es transistor Q ^ by two digital values, the value per step must be in view of the general transistor formula:

W - - f - ^ln2

The value is approximately 17.8 mV at 25 ^° C. Accordingly, the resistance value of the resistor R must be determined so that the value of the emitter current Ir of the transistor £ L · is set according to this value.

309820/0673

- 47 -

(ii) Considering the resistor R12 of the constant current generator circuit, it is also evident that with the change in the resistance of the resistor R12, the emitter current L ·., the transistor 0.11 and the emitter current Ir of the transistor (L- combined the variable resistance E are supplied by

.what data the values of the aperture and film speed can be set.

The resistor band of the resistor R ^, for setting the The values of the aperture and the film speed are generally not uniform but rather irregular Manufacturing standpoint. In the present invention is the change in the component that changes its gradient due to the emitter current L · .. of transistor 0.11 adjustable. In the event that the output voltage increases. due to a change in the resistance value of the resistor R changes, the resistor R acts in such a way that it contains the component

8 p

which changes its gradient, according to the 4 «* · characteristic the base-emitter voltage V-o-pn-io of the input transistor of the time circuit Tc.

(iii) In connection with a semi-fixed resistor R ^ shifts the characteristic of the output voltage V of the logarithmic amplifier P in parallel by changing the resistance value of this semi-fixed resistor R ^ (see Fig. 3). This resistor R ^ is used to mainly the change the base-emitter voltage V-DW) Q of the transistor 0.9 and Vd-pq-io ⁽ ^ ^eG transistor Q12; e.g. be

309820/0673

the voltage change of approximately + 2mV calculated in the event that these transistors belong to an integrated circuit and the change in capacitance of the capacitor C «due to this resistance precisely adjusted.

(iv) With regard to the resistor R _{59, it} is apparent that when the resistance of this resistor B, q changes, the emitter current of the transistor Q30 changes, and the change in the emitter current I, «causes the emitter potential of the transistor Q33 to change of the measuring circuit, that is, the emitter potential of the transistor Q34. If this means a change in the current flow to the measuring instrument Met, the zero point of the measuring instrument Met can be set by adjusting the resistance value of the resistor R39.

(v) The variable resistor R22 of the level detection circuit D is provided for setting the reference voltage of this circuit D, which is necessary when the exposure time is set manually. By Adjusting the resistor R22 can cause a change in the delay elements of the capacitor C, and des Resistance RT can be compensated.

(vi) A resistor R14 in the timing circuit Tc is used to a discharge of the capacitor Cp or C to bring about. This resistor RI4 is used to the capacitors Cp or C, to keep free from heat damage caused by their too

- 49 -

309820/0673

A sudden discharge occurs, and it is usually convenient to apply an actuation voltage of 3 && per volt to it in order to stabilize _{the capacitors C ^ and C x.}

(Vii) In a switch system, the changeover switches are used A-M (D, A-M (2) and A-M (3) to the circuit of the manual control, in which the exposure time is set manually, to automatic control, in which the exposure time is controlled automatically, to switch and vice versa. With these switches, position M applies to manual control and A to automatic control Steering; both are operated essentially simultaneously, whichever case is chosen.

(Viii) The other Sohalter S ^ _t Sg »S ,, S _A and Sr- described, 4 5

(a) In the event that the circuit is for manual Setting the exposure time is used, the respective contacts of the changeover switch A-M folded over to the M side, see Fig. 5 (B). The variable resistance RT is required to be Resistance value is set, and at the same time the shutter is released, it is in the off position Switches left in place are rendered conductive in order to Time circuit Tc, the Mveau detection circuit D, to operate the delay circuit De and the actuation circuit A in FIG. Then the im

-50 -309820/0673

conductive state switch S, switched on, and if the switch S. is made conductive at the same time as the start of the exposure, the delay capacitor C becomes through the variable resistor RT charged until a voltage becomes equal to the reference voltage set by the variable resistor R22, whereby asr level detection circuit D is operated to drive the solenoid Mg through the delay circuit De and the actuation circuit A to make non-conductive and thereby the actuation signal for the termination of the exposure to a mechanical one Transfer system.

(b) In the event that the exposure time is automatically controlled, the contacts of the changeover switches AM are set to the Α side in FIGS. 5 (A) and (B), and a sliding intermediate contact b is moved to a connection point a, the is provided at one terminal of the resistance region of the variable resistor RT Then, the variable resistor R _{n is} adjusted to adjust a value of the film sensitivity, and the switch S in the non-conductive state is turned to the conductive state to thereby switch the measuring circuit M to operate the constant current generator circuit I, the logarithmic amplifier P and the storage means Me. A value of the diaphragm opening is set with the aid of the variable resistor R so that the measuring instrument Met a desired value

- 51 -

309820/0673

Can display exposure time. At this point in time, the switch Sp has become conductive in order to apply the potential equivalent to the output voltage Vp of the logarithmic amplifier P for storage on the capacitor Cj, thereby charging this capacitor brought the conductive state to the non-conductive state before the value of the illuminance of the light-receiving surfaces of the light-receiving elements Rn ^ c-if ^ cdS2 fluctuates due to the rotation of the mirror, whereby their data-containing voltage, such as the values of the aperture, the The sensitivity and the brightness of the object to be photographed are stored in the storage capacitor (L is stored _e ¥ ¥ If the processes continue, the switch Sc, which is in the non-conductive state, is made conductive in order to connect the time circuit Tc, the level detection circuit D, the delay circuit De and the, Message stream To operate circuit A, the electromagnet Mg is made effective in a short time. Thereafter, the conductive switch S 1 is turned off, while the non-conductive switch S _{4 is} made conductive simultaneously with the start of the exposure, whereby the charging of the delay capacitor Cg by the transistor Q12 starts. The charged voltage is applied to the base of the transistor Q13 of the level detection circuit D. When the voltage is equal to the

- 52 -309820/0673

Reference voltage is whose value is given by the resistors R15, R16 and R13 is set and attached to the base of the transistor Q12 is applied, the level detection circuit D is operated to operate the electromagnet To make Mg conductive through the delay circuit De and the actuation circuit A and thereby transmit the actuation signal for the termination of the exposure to the mechanical system. Although in the previous Description of the variable resistor R22, the fixed resistors R 15, R16 and the capacitors Cp, C * through two changeover switches A-M (D and A-M (2) are operated, it goes without saying that on one of the two, namely the Switch A-M (D can be dispensed with, since the capacitors Cp and C can be operated by a single switch.

In the event that the device according to the present invention is based on such a camera as a one-eyed SLR is used, it is necessary to the pentaprism around the MeßStromkreis M, the Generator circuit I for constant current, the logarithmic amplifier P, the storage means Me and the Time circuit Tc and in the camera housing the level detection circuit D, the delay circuit De and to arrange the actuating circuit A. Such an arrangement of the circuits in the camera allows this Reinstallation of the viewfinder system in various ways, and the provision of a switch system A-M (D, A-M {2) and A-M (3) help make the realization easier.

- 53 -309820/0673

As can be seen from the preceding description, energy consumption is saved to a great extent by the provision of the switch Sc by the the current only during the exposure time to the electromagnet Mg, which in the circuit consumes the highest current has "supplied". Since the conventional circuit intended for such use is after the Differen / principle works, there were additional ones Disadvantages that a lot of current had to be fed into the measuring instrument and that in the event that that Resistance values decrease and that the photoconductive elements consist of a light-receiving element, which adjusts the values of the aperture and film speed, the current increases. If for example the brightness value of an object to be photographed is high must depend on the set value a current of a few mA can be fed into the aperture. This was the reason for the short lifespan the power source used in the camera, which is poorly efficient.

On the other hand, according to the present invention, values such as the values of the current flowing through the instrument Met, the brightness of the object to be photographed, the aperture and film sensitivity are obtained by the constant current generator circuit, and whatever the combination thereof, the power consumption is reduced. It is advantageous that with the current of some 10 ^ A to 100 M A, the circuit is practical

- 54 309820/0673

is operated with the electricity consumption corresponding to that of the conventional light beam meter, which consists of photoconductive elements, the energy source and resistors, is equivalent.

In the previous sections it is described that resistors and corresponding transistors of the generator tromkreises I for constant current, the transistor Q9 of the logarithmic amplifier P, the transistor Q12 of the time circuit each to a monolithic integrated circuit. However, it is possible to use one of the circuit of the present invention equivalent circuit from the conventional equivalent individual parts or mixed integrated To form circuits; in this case these transistors can be replaced by transistors with opposite polarity; for example a php transistor can work for one NPN transistor and one NPN transistor for one FNP transistor can be used

309820/0673

Claims (1)

, -55- Patent applications 2253685 Device for electrical exposure control for a single-lens reflex camera, in which the scene light incident through the lens is picked up by light-receiving elements in order to store a brightness value of an object to be photographed and in which the exposure corresponds to the stored brightness value and by a corresponding to the values of the brightness of the object to be photographed, the film speed and the aperture opening manually set shutter speed is controlled,
characterized, that the output of the light receiving elements through a logarithmic amplifier (P) as one of the value of the Logari.thmus proportional to the brightness of the light Tension can be determined, this potential in memory tte In (Me) can be saved, the time circuit (Tc) for Time of exposure can be actuated by the current converted from the stored voltage in an anti-logarithmic manner and an actuation circuit (A) for termination the exposure is present, that to prevent voltage fluctuations from the Energy source (E) resulting from current fluctuations, a generator circuit (I) is provided for constant current whose voltage can be fed to the logarithmic amplifier (P),. - that there is a circuit similar to that in the generator circuit (I) current generated for constant current can be supplied, in which photoconductive elements (Ελλο-ι 3 -56-309820 / 0673 and resistors are included and in which a voltage is proportlnal to a logarithmic value of the illumination of the photosensitive surfaces can be generated that a circuit to the second mentioned circuit in Series connected logarithmic amplifier (P) is provided, one of the set value of the Film speed and the aperture dependent bias voltage generating circuit contains, that through the logarithmic amplifier (P) through the output current of the generator circuit (I) for constant current generated voltage of both circuits can be evaluated and a voltage proportional to a logarithmic value of the exposure time can be generated, that storage means (Me) for storing the output voltage of the logarithmic amplifier (P) by a Switches (Sp) are provided in front of the exposure, that a time circuit (Tc) is available for generation a current converted from the storage voltage of the storage means (Me) anti-logarithmically at the same time as the exposure and that an actuating circuit (A) which can be actuated to terminate the exposure by the time circuit (Tc) is provided. 2. Device according to claim 1, marked (A) by a dry cell battery (E); (B) a generator circuit (I) for constant current, -57-309820 / 0673 which contains (A) a fixed resistor which is connected to the first resistor (R1) _f one terminal of which is connected to the positive pole of the Troekenzellbatterie (S), and consists of the second resistor (R2) "connected in legs with the first resistor (R1) ; (b) the first NPN transistor (QD> its collector to the external connection of the second resistor (R2), its emitter to the negative pole of the dry cell battery (E) and its base to the connection point between the first resistor (RD and the second resistor (R2) of the fixed resistor connected; (c) the second NPN transistor (QZ) ₉ its base to the collector of the first KPN transistor (QD and its emitter for generating the collector current proportional to the absolute temperature via the third fixed resistor (R3) to the negative pole of the energy source ( E) is connected; (d) the first transistor circuit, which consists of a PNP transistor (Q4), the emitter of which is connected to the positive pole of the energy source via a resistor (R4) (E) is connected, and from the third NPU transistor (Q3), whose base is connected to the collector this PNP transistor (Q4) whose collector is on the emitter of this PNP transistor (Q4) and its Emitter to the collector of the second NPN transistor ($ 2) is connected, is there? -58-309820 / 0673 (e) the second transistor circuit, which is equivalent to the first transistor circuit and consists of a PNP transistor (Q5) _f whose base is connected to the base of the PNP transistor (Q4) in the first transistor circuit and its emitter through a resistor (R6) connected to the positive PqI of the dry cell battery (E) and composed of an HHi transistor (Q6); each transistor and each resistor belonging to a monolithic integrated circuit; (C) through a logarithmic amplifier (P) with a « Circuit having one connected to the emitter of the KPN transistor (Q6) of the second transistor circuit Photo element and one of the logarithmic should word the lighting unit on the receiving surface of the photo element has proportional output voltage, (D) by a storage means (Me) for storing the output voltage of this logarithmic amplifier (P) as (S) through a time circuit (Tc), the ix the integrated fourth NPN transistor (Q12) at its base the storage voltage of the storage circuit is applied during exposure. -59- 309820/0673 2253685 3; Device according to claim 2, marked, through the third transistor circuit, which is connected in the generator circuit (I) for constant current equivalent to the first transistor circuit and from a PHP transistor (Q10), its base to the base of the PNP transistor (Q4) in the first transistor circuit and dtssen Emitter is connected to the positive pole of the dry cell battery via a resistor (R12), and from one HPH-T transistor (Q11) consists; by the same as with the fourth NPN transistor (Q12) A fifth integrated NPN transistor (Q9), the collector of which is connected to the circuit is, which has the photo element and which is the logarithmic value of the illuminance at the liekteapfangenden Voltage proportional to the area of the photo element generated? and by a variable resistor (R_), its resistance value according to a certain aperture as well as a certain film speed can be changed, one terminal of which is connected to the emitter of the fifth NPN transistor (09) and at the same time to the emitter of the NFN tramsistor (QII) of the third transistor circuit of the 4e # generator circuit (I) is connected for constant current and the other terminal of which is connected to the negative terminal of the dry cell battery (E). -6p- 309820/0673 4. Apparatus according to claim 2,
characterized, that the time circuit (Tc) is connected to the collector of the fourth NPN transistor (Q12) connected first Capacitor (C2) and the one to the fourth NPN transistor (Q12) and the first capacitor (C2) standing parallel to the second variable, through the changeover switch (A-M1, A-M2) according to a certain aperture and a certain film speed variable resistance (RT) can be connected second capacitor (C3) has. 5. Apparatus according to claim 4,
marked by a switch (A-M1, A-M2), for the optional setting of the automatic control and manual Control of the exposure time, a level detection circuit (D), which is controlled by the switch (A-M1, A-M2) with its one terminal can be connected to one terminal of the first (C2) or second capacitor (C3) for the purpose of detection the charging voltage of this capacitor and for generating a signal when this voltage is a certain Level reached, and an electromagnet (Mg) that terminates the exposure by the signal from the level detection circuit is excitable. 6. Apparatus according to claim 5,
characterized, that the storage means (Me) has a capacitor (CD for storing the output voltage of the logarithmic Amplifier (P) and a fixed resistor (R13), -61- 3 0 9 8 2 0/0673 the one to correct the caused by the conduction of the electromagnet (Mg) in the actuation circuit (A) Voltage drop of the dry cell battery across the capacitor (C1) and the negative pole of the dry cell battery connected. 7. Apparatus according to claim 4,
marked, through the fourth transistor circuit of the integrated Circuit that starts with the first transistor circuit in the Generator circuit (I) equivalent for constant current is connected and consists of a PNP transistor (029), its base to the base of the PNP transistor (Q4) im first transistor circuit and its emitter through a resistor (R39) to the positive pole of the dry cell battery is connected, and consists of an NPN transistor (Q30) and a measuring circuit (M) to which the Emitter current of the NPN transistor (Q30) of the fourth transistor circuit and the output voltage of the logarithmic amplifier (P) can be supplied as input variables. 8, device according to claim 6,
marked by a delay circuit (De) between a Output terminal of the level detection circuit (D) and an input terminal of the actuation circuit (A) is connected for the temporal correction of the overlap of the rear edge of the leading screen with the front edge of the trailing screen * of the focal plane shutter in a tense position. IfIItIIfIlItI 309820/0673