DE2129275C3 - Arrangement for automatic exposure control - Google Patents

Description

(Fig. 2).

4. Arrangement according to claim 1, characterized in that the sound device (S, S ₁ ; Sj to S ₃ ) has two working positions (b, c) and a neutral position and is coupled to the shutter release button in such a way that beirr, slight depression of the release button, the switching device is switched to a working position (b) , in which it connects the first capacitor (C ₁ ) to the voltage source (E) via the inner and outer electromotive element (P ₁ , P ₁ ) , and that with further Depressing the release button the switching device is switched to another working position (c) in which it connects the first capacitor (C ₁ ) to the first input (Q ₂ ) of the differential amplifier (A ₁ ; K) and the outer electromotive element (P ₂ ) with reverse polarity between the output and the second input (Q ₂ ) of the differential amplifier (A ₁ ; K) switches (Fig. 2).

5. Arrangement according to one of claims 1 to 4, characterized in that a potentiometer (Rf, R) is connected between the voltage source (B, E) and the electromotive elements (P ₁ , P ₂ ).

The invention relates to an arrangement for automatic exposure control in cameras Light measurement through the camera lens, especially in single-lens reflex cameras, with an outside of the optical path of the lens arranged outer light-sensitive element, which is used for direct Measurement of the object helplessness during the opening of the shutter «is provided, one in the image-side Beam path of the lens arranged, inner light-sensitive element, a voltage source for applying a voltage to the photosensitive elements, one to the photosensitive ones Elements connectable via a switching device and occurring between the elements Differential voltage-dependent voltage chargeable first capacitor, a second via a charging circuit chargeable and the opening time of the shutter determining capacitor, the bsim opening of the shutter depending on the voltage of the switchable on an input of the charging circuit first capacitor and from the voltage of the switching device alone to an input of the Charging switchable external light-sensitive Element is charged, and with a shutter depending on the charging voltage of the second capacitor closing shutter control circuit.

An arrangement for automatic exposure control of the type mentioned above has already been proposed been (German Patent 2 008 317), in which the light-sensitive elements are photo resistors are and the first capacitor before opening the shutter on the difference of the two Photoresistors tapped voltages is charged. This charging voltage becomes with the help the closing during the opening line of the

Finally, a correction voltage for the shutter is switched, in which it uses the first capacitor

Control circuit derived, which essentially connects the first input of the differential amplifier

VcischluLiη dependence on the charging voltage of the and the outer electromotive element with

two capacitor closes, the opposite polarity between the input and the when opening de

Closure only via the first phmo resistor S shackle the second output of the differential amplifier,

is chargeable. The exposure takes place solely in further subclaims relate to advantageous embodiments

Dependence on the light conditions before opening designs of the subject of the invention. On off-

of the closure If the brightness of the exemplary embodiment of the invention should now be based on the

photographing object changes, the figures are described in more detail. From the figures

Stored Hetiigkeitswert that shows the charging voltage of the io

corresponds to the first capacitor, of which when loading F i g. 1 is a block diagram of the invention

clearing actually existing holiness of ob- arrangement and

jekles different, so that no flawless loading is possible. FIG. 2 is a circuit diagram of an embodiment of FIG

clearing takes place. arrangement according to the invention.

Furthermore, an arrangement is: -Only automatic 15 The arrangement shown schematically in FIG.]

Exposure control in cameras _11L light measurement has a power source B, for example a battery,

through the camera lens * -? k * »nt (USA patent and one connected to the terminals of the power source

writing 3 324 799>, in the case of the em. ^ sensitive EIe series connection of a constant voltage

rnent in the optirchen AK _{e is} arranged. Before direction E and a potentiometer R / open. An im

Open the shutter r, so that the state of charge 20 can be eliminated.

of a storage coil. π -itors controlling light-sensitive electromotive element .t P ₁ and an outside of the

V he Ehment moved out of the beam path, the beam path of the OL>'ivs arranged outer

will. In the known arrangement, the electromotive element P ₀ is carried out with the aid of a

the control of the exposure as a function of contact pairs of a switch "S ₁ in series between

one before opening the shutter.-s master-whenden 25 the slider R of the potentiometer R _T and one

Brightness and not of the during the opening fixed contact b of a switch S switchable. the

the brightness of the shutter. electromotive elements can for example

The invention is therefore based on the object of being solar cells. The movable contact α ües Uman arrangement for the automatic exposure * - switch S is connected to the contact b , if steue-ur.g to create in cameras, in which a 3 ° the release button (not shown) for the camera exposure depending on the while the open shutter is depressed slightly. When the light-locked lock is sufficient for the lock, the movable holding pee is possible, i.e. a change in the light contact is in the neutral position. A first condensation ratio during the exposure takes into account capacitor C ₁ is connected to the movable contact α . 35 den, so that when contact is given between α and h

The arrangement according to the invention is characterized by the differential voltage of the output voltages in that the light-sensitive elements of the inner and outer electromotive flux are electromotive elements which are charged with opposing elements P ₁ and F _2, respectively. The other fixed set /. ^ R polarity in series with the first capacitor contact c of the switch S is connected to a first Einan c'le a constant voltage output voltage output of a differential amplifier A ₁ , the source are switchable, and that the Charging hook has a high input resistance. The second has a differential amplifier, at one input (λ, of the differential amplifier A ₁₎ the first additional pair of contacts of the switch S _{4 can be switched} with the capacitor via an input when the shutter is opened, while the outer electromotive hiement P _{2 can be connected at the same time} , outer electromotive element between the output 45 The switch S ₄ makes contact when the movable input and the other input of the differential contact α of the switch S to the fixed contact c can be switched on in such a way that the signal is switched on . The output of the differential amplifier. "Wide F input has a different polarity than A ₁ is - possibly via a further VerSignal at the first input. Stronger A ₂ - with the base of a first transistor T ₁

The arrangement according to the invention measures in front of the 50 connected, the collector of which has a forward

Open the closure, the ratio of the outer direction switched diode D to ground. Hamlet-

and inner brightness. When the \ er is opened, the output of the differential amplifier is A ₁ with

In conclusion, the exposure time is connected depending on the base of a second transistor, its

of this ratio and that of the outer collector via a second capacitor to ground

ni'jiuiisclicn Ciciiiciii gcmcsbciiL-ii Holiness 55 iiegi. The second capacitor is through one of the

set. If, therefore, the brightness of the object changes to the current corresponding to the brightness of an object.

λ changes during the opening of the shutter, charging. The capacitor C ₂ is a closure

this is immediately taken into account in the exposure. control circuit F connected in parallel, de previously

The switching device / wci is preferably open when the charging voltage closes

s (cllungs "and a cTNeutralstelluiiTg ^ ndrist with your 6q- ~ d_es Second Kndensalors-C, - a predetermined

Release button do3 camera lock such a coupled value reached.

pelt, because (3 when the push button is pushed down slightly The mode of operation of the arrangement is as follows:

The release button turns the switching device into a working position. If the release button (not shown) is slightly

luiiggcsch & het, in which it is depressed the other capacitor, becomes the movable contacts

with the voltage source connected via the inner and outer 65 of the switch S to the contact A, while

elektroinotoiische element connects, and that at the same time the electromotive elements Ρ _{Λ when rend}

further depressing the trigger button die and P ₁ Ausgnngsspunnungen depending on the

Switchgear; i (7 in a different working position gc- brightness of the object.

Conventional electromotive element flows cm can be taken into account, as the following equation Current / given by the following equation: shows

ι , al . ι '·. In '"", In2 ". <5)

¹ '"' ^cxp l * r) '''^<U5' / I '« · «ί

Mn using the size 2 "in equation (5) you can

where I ₀ cooling current. also reduce different I ilm sensitivities

V terminal voltage of the element. be locked.

li, - Fr.iosirom. When the shutter release button continues

q Charge of the LIcktron. io is depressed, the moving contacts.

A Boltzmann constants. at the same time as opening the lock on the

7 Absolute temperature (degrees K! Means. Contact "switched over, so that the first capacitor i", with the first input (J _{1 of} the differential

When the electromotive element is connected to an amplifier A ₁ . By glcirh circuit with a high Lingangsimpcdanz aufgc- 15-term closure of the switch .S _1, the external switches is i ".t the current flowing through the element current / electromotive f lemciit P ₂ between the / dwell negligibly small. Under the condition//. · / "Li.igang Q _{1 of} the differential amplifier * A ₁ and to the (this condition is always fulfilled when the light collector of the transistor 7 falls with such a polarity on the element) the terminal voltage of the is connected to the input (? _{2 of} the differential electromotive element given by 20 amplifier a negative potential is applied. If the

Capacitor C ₁ to the first input Q _{1 of} the

Y ^ In &quot;'(2) Differen / amplifies A ₁ and the outer clektromo-

qj tonsthe f-.lemcnt P ₂ with the polarity described

to the second input (J _{2 of} the differential amplifier

So if the inner electromotive EIe- aj is connected. the differential amplifier generates a ment P ₁ and the external electromotive L'cmeni P ₂ output signal. that the difference between the input voltages connected in series at the first and the second input with opposite polarity (cf. l · "i g. 1). i ^ t the voltage Vp ₁ P _{2 is} proportional to this. This output voltage is in the Elements given by the differential amplifier A, downstream Vcr-

. , 30 stronger 4 ^ amplified and attached to the base electrodes de>

y I ₁ , i _r I InI '| in | ² Ii first and / while transistor /, and I ₂ applied.

¹² '" q I \ Ι _ο ι · χ I \ / ₀ /' 2 / J In the 1 middle collector circuit of the first tran-

(3) sistors /, and by being connected to the collector ^

^, pkj., the diode D then flows a current which through the

35 initial voltage of amplifier A «is determined.

V _ri terminal voltage across element P ₁ . this current leads to a voltage drop I ".

V _Vz terminal voltage across the element P ₂ across the diode so that the difference between this

j _st voltage drop Γ /. and the voltage V _r . those of

the outer electromotive element P ₂ during

If the elements P ₁ and P _{2 have} the same characteristic 4 ° of the opening of the closure as the size, then / _o p, ^ - l _o v «applies. and the second input Q ₂ of differential amplifier 4, an equation (3) can be written as follows: lies.

If the input applied to the second input

. γ j input voltage is greater than that at the first input

Vp ₁ P-. >■>!'' / ·, L ⁿ ( ^/; ') · (4) 45 input voltage applied to input Q _{1, the}

q \ lLPi! Differential amplifier A ₁ its output voltage, so

that the output voltage of the amplifier A ₂

Since the photocurrents // », and f _r , the brightness of the and thus the collector current Ic _{1 of} the first light incident on the elements P ₁ and P _2, respectively, are reduced. The voltage V is thus proportional to the 5 ° but also the voltage drop across the diode D span ratio of the brightness at the front of niirig Vp. Thus, the on the second input Q ₂ the camera body and in the vicinity of the fotoempfind- of the differential amplifier A _1-fitting difference tensioning Lichen film. nung K _n - K, .. reduced.

The amount of light passing through the opening of an iris diaphragm, on the other hand, at the second input Q ₂ is proportional to 2 ". Where η 55 Hegende input voltage is smaller than the first corresponding to the set opening width of the diaphragm. Input voltage, the output voltage of the aid increases of the potentiometer R is now connected via the differential amplifier A _x to the output voltage of the inner and outer electromotive elements P _{1 of} the amplifier A ₂ and thus the collector current Ic ₁ and P ₂ to uen capacitor C ₁ and to the wiper R _{f of} the first transistor T ₁ . enlarge This tapped voltage V _n applied growing the selected ⁶ ° to the differential Blcndcnwcrt is similar to the second input Q ₂ An iris diaphragm itself amplifier A ₁ applied differential voltage V _D -. V _Pl is therefore r.tfht required After repeating this work cycle, the iris diaphragm for the main lens receives the corresponding information Di. reference amplifier A _{1 was} in a balanced Zumation electrically through the setting of the voltage, in which the at the first input ρ, an-

65 applied input voltage is the same as the input voltage applied to the second input: V _D - V _Pt

y _R 4. J _n 2 "=" - ^ c ₁ - This process runs almost instantaneously

q ab In the balanced state, the voltage

drop Vd at diode D can be given by equation (6) derived below:

Vr ₁ V ₁ , V _1. , With equation (5):

Equation (5) and Equation (4) and:

In

V ₁ , -

Ic ■ T

k-T

In 2 "" In

2 »

'LP:

(6)

where l ' _{LP is} the photocurrent

after the closure is opened. The current In flowing through the diode at a voltage drop of Vi at the diode D is given by

Id I _o d ■ exp

A -T

for the shutter is applied, the shutter closes when the voltage across the capacitor reaches a predetermined value. In this way, the shutter is kept open from the point at which the movable contact λ of the changeover switch S is brought into contact with the contact r until a point in time at which the terminal voltage of the second capacitor C ₁ reaches the desired value. This interval coincides with the charging time of the capacitor C ₂ and is proportional to the ratio of the output voltages of the outer and inner electromotive elements P _t and P divided by the output voltage of the outer electromotive element P ₂ during the opening of the shutter, and thus also proportional the light current incident on the film during photography.

In the proposed arrangement for automatic exposure control, in which the ratio

of the outer element ao between the inner brightness and the outer

If the magnitude assigned to the brightness prior to the photographing is multiplied by a corresponding magnitude assigned to the external brightness during the photographing, it is possible that the exposure takes place> n as a function of the internal brightness prevailing during the photographing. In FIG. 2 circuit details are shown. The Konslantspannungseinrichlung E is built up from the transistors T ₁ A, T ₂ A and T _z , \ . 30 Since the details of the constant voltage device / the saturation current of the external electrification F. do not form part of the invention , the saturation current of the diode D is the details of the sonication of these transistors on the motorized element P and I. Although these values change with the temperature through the resistances / ?, to R, and the diode D _1, the temperature has no express reference to the F ι ς. 2 referenced.
Influence on the ratio I "i, I ₀ . The designated by 35 the mn in F ig 2 A differential equation (7) given diode current / o is carried amplifier is the one _x of the transistors T to the collector current Ic _x of the first transistor T _x loading T- and Field effect transistors FET, and FET. If the first and the second transistor 7 ", built. 7 to amplify the output voltage of the and T have the same data, the transistor T ₁ is therefore two parallel-connected" Tran diode current Id essentially equal to the collector transistor 7 " _s and T ₉ provided. The connections current Ic of the second transistor T ₂ . The collector between the transistors T _H and T ₉ , in the currents Ic, and Zc _{2 of} the two transistors T ₁ and T ₂ F i g. _{Diode D 2} shown in FIG. of the capacitor C ₂ are determined by the low base currents and the voltage control circuit F are similar not so much by the size of the load and the size as in FIG. 1 wired. The switching of the emitter-collector voltages is affected. Therefore 45 direction consists of the switches 5 ,. S ₂ and S ₃ , the Slroi.i Ic _{2 is} the through the second condensate coupled with a release button, not shown, capacitor C flows equal to or proportional to the. These switches determine the interconnection KoIIektorstrom \ Ic _{1 of} the first transistor. For this device between the inner electromotive FIe reason, the voltage Vr ₂ builds up across the second _{element P 1} , the outer electromotive element P ₂ , capacitor C essentially linearly after the following 5 ° the first ¹ Om ¹ isator C, and the field effect trans - Correction to: 'sis! Or FE7

It is assumed that the grinder /? of the potentic meter Rf is fixed. If the release button is pressed a little, the

Ilp, Iw ₂

2 «I ₁

ir.

(7)

Kc ₂ =

Ic, C ₂

In C,

(8th)

With equation (7)

Vc ₂

2 "

(9)

There

this
himself

V constants or

C, I ₀ DIh, '' 1.P ₁ Hi-P ₂ «nd V are constants or comparable set parameters

(10)

where A is the constant ^c: nc for the exposure process to be carried out. Therefore, when the voltage across capacitor C _{2 is applied} to shutter control sound F

Switching contacts α of switches S ,, S ₂ and S _{3 brought} into contact with the stationary contacts b , so that the following circuit is set up: Slider inner electromotive element P ₁ , second electromotive element P ₂ (in reverse polarity),

first capacitor C ₁ . The first capacitor C1 is charged via this circuit.

If the release button is depressed further, at the same time as the shutter, not shown, is opened, the switching contacts α of the switches 5, S ₂ and S ₃ . transferred to the fixed contacts c to the output signal of the outer electromotive element P ₂ between da «. Gate of the field effect transistor FET, and the collector of transistor 7 ~ _R with

409 638/169

one with respect to the field effect transistor FET ₃ ent- through wl · i the collector current /, of the transistor T _e

opposite polarity. increased, whereby the voltage drop Vn across the

At the same time, the capacitor C, is connected to the gate diode D _t and thus the gate voltage V _{2 of} the field of the field effect transistor FET _x , so that the effect transistor FET _{2 is then} increased,
the sum of the voltage drop K / j across the diode D ₂ , 5 After repeating the cycle described, with d <-m collector current I _{3 of} the transistor 7 " _8, the differential amplifier K reaches a balanced state, and the output voltage V ' _P , state, in which the gate voltage V _{x of} the field effect of the external electromotive element P _{2 is applied} to the transistor FET ₁ equal to the gate voltage V _{2 of} the gate of the field effect transistor FET _2. (The other field effect transistor is FET ₃ The time required for the balanced state to be sufficient for the output voltage of the outer electrical interval is exceptionally short, since transistor- motor elements P _{2 are used} during the opening of the circuit
Closure acts.) If the transistors T _n and T _{a have} the same properties

. If Vo> Vp, is having transactions by the difference, the Kollektorströrne / ₃ and / Vn - V p ₂ given gate voltage V ₂ of the field 15 of these transistors the same size or at least positive proeffekttransistors FET _2, because V ₀ regarding the portional. Therefore, during exposure through the field effect transistor, it is positive while V ' _{Pj is} negative that connected to the collector of transistor T ₉ . Then, the gate voltage V ₂ is greater than the NEN capacitor C ren and ₂ flowing / ₄ the product given by the terminal voltage of the first condensation of the ratio of the output voltages of the inherent crystallizer C ₁ gate voltage V _x of the field-effect 20 of the outer electromotive element P ₁ transistor FET _x , so that the load current I _{2 of} the field or P ₂ immediately before exposure and the effect transistor FET »is greater than the load current /, the output voltage of the outer electromotive EIeanderen field effect transistor. Therefore, the Mentes P ₂ falls proportionally during exposure. As a result, the differential voltage I _x R ₅ - I ₂ R ₉ given forth, the second capacitor C _{2 is} charged with an in the base voltage of the transistor T _{5 to} the output 35 substantially constant current, so that the output voltage of the transistor T ₅ is reduced. Since the voltage Vc ₂ at the capacitance C ₂ rises linearly, the output voltage of the Tran- When the voltage Kr _{2 reaches} a predetermined value sistor T ₆ , the base of which is the collector of the Tran-, the previously opened shutter is opened the transistor T " _{5 is} connected. As a result, the shutter control circuit F is closed by connecting the output voltage of the transistor T ₁ , whose base is not shown, for example, to the collector of the transistor T ₆ Closure is closed in this way, is reduced. So that will also decrease, the movable switching contacts α of the collector currents I ₃ and /, the transistors T _s and switches S _x , S ₂ and S _{3 are returned} to their neutral position - T ₉ , the emitter of which is connected to the collector of transistor T _7. In this way, the shutter of the is connected In which the switching contacts α the switching current I ₃ leads to a reduction in the voltage «- ter S _x , S ₂ and S ₃ on the movable contacts c drop V _D through the diode D ₂ , the gate voltage will be placed up to the point in time kept open to reduce V ₂ = Vd - V ' _Pj. which the voltage Vc ₂ across the capacitor C ₂ den

When the gate voltage V _{2 reaches} the second field effect prescribed value.

transistor FET ₂ is smaller than the gate voltage V _x 40 As already mentioned, at the proposed the field effect transistor FET _x is increasing due to the arrangement of the wiper R of the potentiometer Rf beVerkleinerung of the load current I ₂ uses the Feldeffeki- be to at Use of films under transistor FET ₂ . to vary the base voltage of the transistor capacitor C given by the voltage difference of different sensitivity, the charging voltage of the I _x R ₅ - Z ₂ A _9. Also, as, so that the output change of the charging voltage of an "electronic voltages of the transistors T ₆ and T ₇ rise above 45 loading shift of the slider and corresponding Prescribed case of the comparison by T ₅ to a higher value. Da-Blende «can be effected.

For this purpose 2 sheets of drawings

Claims (3)

Patent claims: 1. Arrangement for automatic exposure control in cameras with light measurement through the camera lens, in particular in single-lens reflex cameras, with an outer light-sensitive element arranged outside the Sirah'enganges of the lens, which is provided for the direct measurement of the object helicity during the opening of the shutter, a. inner light-sensitive element arranged in the image-side beam path of the lens, a voltage source for applying a voltage to the light-sensitive elements, a first capacitor which can be connected to the light-sensitive elements via a switching device and a voltage that is dependent on a voltage difference between the elements, a second via a Charging circuit chargeable and cie opening time of the shutter determining the capacitor which, when the shutter is opened, is dependent on the voltage of the capacitor that can be switched on an input of the charging circuit and on the voltage of the external light-sensitive element that can be shaded by the switching device solely on an input of the charging circuit? is charged, and with a shutter depending on the charging voltage of the second capacitor closes shutter circuit, characterized in that the light-sensitive elements are electromotive elements \ P _t , P ₁ ) which are of opposite polarity in series with the first capacitor (C ₁ ) to which a constant voltage output voltage source (B, E) can be switched, and that the charging circuit has a differential amplifier (A ₁ ; K) , at one input (Q ₁ ) of which the first capacitor (C,) can be switched when the shutter is opened , while at the same time the outer electromotive element (.P ₂ ) between the output and the other input ((J ₂ ) of the differential amplifier (A ₁ ; K) can be switched in such a way that the signal at the second input (Q ₂ ) has a different polarity than the signal at the first input,). 2. Arrangement according to claim 1, characterized by a diode (D) and a transistor (T ₁ ) which conducts a current through the diode (D) as a function of the output voltage of the differential amplifier (A _x ; K) , the switching device ( S, S ₄ ; S ₁ to S ₃ ) the difference between the output voltage of the external electromotive tliciiiciiis (F ₂ ) and the voltage drop across the diode (Z?) Is applied to the second input (Q ₂ ) of the differential amplifier. 3. Arrangement according to claim 2, characterized in that the differential amplifier (A ") has two field effect transistors (FET ₁ , FET ₂ ) connected to one another in cascade connection, the gate electrode of the one field effect transistor through the switching device (S ₁ to S ₃₎ (FET ₁ ) is connected to the first capacitor (C ₁ ) and the gate electrode of the other field effect transistor (FET ₂ ) in such a way that the differential voltage across it / between the output voltage of the external electromotive element ^ ...) and the voltage drop across the diode (D)