DE2550802A1 - METHOD AND CIRCUIT FOR COUNTING PULSES IN AN ELECTRONIC DIGITAL SHUTTER - Google Patents

Description

PATENT ADVOCATE DR. GERHARD SCHAEFER DI PLOM PH YSIKER

8023 Munich-Pullach Seitnentra & s 13 Telephone 7 93 09 01

P 499

YUGENKAISHA SATO KENKYUSHO No.6-38-1 »Maenooho, Itabashi-ku, Tokyo / Japan

KABUSHIKIKAISHA YASHIMA No.28o, Kamikawaramachl Akishima-shi, Tokyo / Japan

Method and circuit for counting pulses in an electronic digital shutter

The invention relates to a method and a circuit for • counting pulses in a digital electronic shutter, in which the exact exposure time is set depending on the number of cell pulses.

In general, the exact exposure time is stored in terms of pulse numbers from a digital ZShI circuit an electrical closure, for example one

Single lens reflex camera, the output of a foto · y-. * electrical element exposed to scene brightness

Shh / ho. ./.

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integrated by a capacitor and a counter counts time pulses, until the voltage of the capacitor reaches a predetermined voltage and the counted pulses are stored and show the exact exposure.

However, if the scene brightness can be changed over a wide range and when the scene is dark, it takes a long time to finish the counting process. Here the so-called closure chance is lost. The time for counting must therefore be about 1/100 to 1/500 of the closure speed be shortened.

The invention is based on the object den.vorbeschrittenen To avoid the disadvantage of known electronic locks and to create a counting method in an electronic lock, in which the time for counting the pulses can be reduced to a minimum. A further object of the invention is to create a process in which information can be introduced at the same time, through which the pilm sensitivity and / or the aperture is taken into account in order to obtain an exact exposure time, irrespective of the film speed or aperture is inserted 1st.

This object is achieved in that the number of pulses required for the exact exposure is characteristic, is broken down into a characteristic part and an exponent part, as follows described 1st.

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• V

Details and advantages of the invention are explained using the exemplary embodiments shown in the drawing. Show it:

Figure 1 shows a circuit in which the principle of the invention is implemented,

FIG. 2 shows a circuit for the introduction of information relating to the film brightness and / or the aperture relate to the circuit of Figure 1,

FIG. 3 shows a modification of that shown in FIG Circuit with which a pulse number for an exact exposure time is obtained when during the Actuation of the circuit according to the invention either fully opens the aperture, or when it is in the desired position opening is held.

In general, the exact exposure time of a camera is reversed proportional to the intensity of the scene brightness. If the value is inversely proportional to the scene brightness, i.e., if it is assumed that the reciprocal number is 1236, for example, then the number 1200 is sufficient instead of the actual number from 1236 to determine the exposure time. This accuracy is sufficiently great because of the latitude of the film is large enough to cover the aforementioned difference.

If this reciprocal number is broken down into the identifying number part 1,2 and the exponent part 3 of the reciprocal number

609821/0744 ' ^{/ #}

1.2 χ ICr and counting the indicative number part and the exponent part according to the present invention, the time required for the counting is extremely reduced. A sufficiently high accuracy is obtained with a maximum error of 10 %.

In order to obtain the count of the number 1200 described above, for example, the timing pulses are first carried out a first counter is counted until a predetermined number of pulses, for example 100, are counted. Every time when 100 counts have been made in the first counter, a second counter counts once. After the first counter is reset, it starts counting again, shifting the number of digits by one, up to 100 counting steps and the second counter continues to count by one counting step each time there are 100 counting steps in the first counter are carried out. The above procedure is repeated until the count in the first counter is finished, even before the the aforementioned 100 counting steps have been reached. The identifying number part 1, 2 is obtained by the first counter. The ex ^ onent part 3 is obtained by the second counter. The count only requires 100 χ 3 + 12 counts. This enables extremely fast counting compared to the previous one Counting technique that required 1200 χ 100 counts. This involved a complicated and extensive circuit necessary, and there was an increase in the counting time.

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FIG. 1 shows a circuit according to the present invention, in which the bases of the transistors T 1 and T p are connected to one another and the emitters are connected to the positive pole of an electrical power source, so that a constant current circuit is formed. The collector of the transistor T. is connected to its base, while a series of parallel connected resistors r _Q , r ,, Γρ r is connected to the collector of the transistor T ^. The resistor r i has a resistance value which is numerically one digit greater than the resistance value of the resistor r _Q. In other words, the resistor r _Q has a resistance value of 1 Kft, for example, while the resistor r Q has a resistance value of 10K &. Similarly, the resistor r _{2 has} a resistance one place higher than the resistance of the resistor is, etc. Therefore, the resistors r _Q , r ,,

η resistance values of 1 KA, 10 κ £ 1 , 100 Κ & , 1 M ££, 10 Μβ ... .etc.

The photoelectric element CdS is connected between the collector of the transistor T ₂ and the negative pole of the electrical power source.

The resistors r _Q , r _{1 #} r _g ... r _n can be connected separately to the counter III, as will be described below. When the resistance r. is connected to the up-down counter III, the current that flows through the resistor r, and which, because of the constant circuit consisting of the transistors T ₁ and T ₂ , is equal to the current that flows through the

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Photoelectric element CdS flows one digit less in magnitude than the current flowing through photoelectric element CdS when resistor r _{Q is} connected to up-down counter III. As shown, the counter III is connected between the plus and minus poles of the electrical power source so that it can be operated by them. The same applies to the resistances r ₂ , r ^ ... r. As a result, the strength of the current flowing through the electrical element CdS is reduced by one digit each time a resistor having a higher resistance value is switched to the counter III.

The photoelectric element CdS is arranged to receive light of the scene to be recorded, so that the resistance value R of the photoelectric element CdS changes depending on the brightness of the scene. The photoelectric element CdS generates a comparison voltage which is determined by the brightness of the scene as well as by that of the resistors r _Q , r ₁ , r 2 ... r, which is connected to the counter III.

The bases of the transistors T- *, T ^, are with each other and theirs Emitters are connected to the positive pole of the electrical power source. The collector of transistor IV is with its base connected so that through the transistors T 1 and T ^ a constant current circuit is formed, which supplies the current that is fed to the capacitor C, which is between the collector of the

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Transistor T-, and the negative pole of the electrical power source is connected. This current is equal to the current that _{goes through the resistor R Q} , which is connected between the collector of the transistor Tj and the negative pole of the electrical power source. Therefore, the charging current that goes from the collector of transistor T- to capacitor C can be controlled _{by adjusting the resistance of R Q.}

The connection line between the collector of the transistor T and the photoelectric element CdS is connected to one input Ijt of the comparator Q in order to supply it with the comparison voltage as determined by the photoelectric element CdS, while the connection line between the collector of the transistor T -, and the capacitor C is connected to the other input Ij of the comparator Q, so that the voltage which is given by the charge of the capacitor C is fed to it. The comparator Q is constructed in such a way that a high output voltage is generated when the voltage at input I «deviates _{from the voltage at input I 1.} If the voltage at input I ₃ . equal to that at the input I _n , the output of the comparator Q is low.

The output of the comparator Q is connected to one of the inputs of the grid circuit G, while the other input of the grid circle G is at the time pulse generator 06C, so that output pulses from the pulse generator OSC through the grid circle G are passed through when the output of the comparator Q

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has a high level while the output pulses from the grid circle G can be interrupted when the output of the! Comparator Q has a low level.

The output of the grid circuit G is connected to the input C _{Q of} the up-down counters I and II as shown and receives the output pulses from the grid circuit G. The counter I is constructed so that it can, for example, the one of a number], and the Counter II counts the tens of a number. The reset terminal C- of the counter II is connected to the reset _{terminal C 1 of} the counter

Λ. Λ.

Lers I connected, while the transmission output C _{Q of} the counter II is connected to the input C _{Q of} the up-down counter III. The output voltage of the transmission output C _{Q of} the counter II is kept at a high level. However, when the counters I, II have counted 100 counts, the transmission output is brought to a low level and the counter III is activated by the applied low output voltage of the transmission output Cq, so that the counter III performs a count while the counters I and II are reset by a reset signal from the reset output Cj, of the counter II, which is applied to the counter I.

The counter III is activated by a low output voltage of the transmission output C _{Q of} the counter II, which switches the connection between one of the resistors r _Q> r., ... r and the counter III. That is, it switches the negative pole of the electrical power source in such a way that the connection between the resistor r _Q and the output 0 of the counter III

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interrupted and the resistor r is connected to the output 1 of the counter III, and the resistor r. is connected to the negative pole of the electrical power source when it is supplied with a transmission output voltage from the counter II, while the counter III is simultaneously counting a number. When another transmission output pulse is supplied to the counter III, the resistor r. switched off by the counter III and the resistance r _? is connected to output 2 of the counter, while another count is carried out in counter III. The above-described operations are repeated each time a transmission output voltage is applied to the counter III, so that the connection of the resistor to the counter III is made from one resistor to another which has a resistance value one digit higher than the previous one, while each time after receiving a transmission output voltage from the counter II a count is carried out by the counter.

One side of the switch SW is connected to the positive pole of the electrical power source, while the other side is connected to the reset terminals C _{R of} the counters I, II and III and the base of the transistor T ₁ - whose emitter and collector are connected in parallel to the capacitor C. are connected to short-circuit and discharge the capacitor C when the transistor Tf- is made conductive.

The base of the transistor T ₁ - is also connected to the collector of the transistor T / -, which also has a

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Resistance is connected to the positive pole of the electrical power source. The emitter of the transistor Tg is connected to the negative pole of the electrical power source, while the base of the transistor Tg is connected to the transmission output C _{Q of} the counter II via a resistor.

Therefore, when the switch SW is closed and the transistor Tg is changed by changing the transmission output of the counter II from a high to a low voltage after counting 100 counts in counters I and II to the non-conductive state comes, the transistor T ^. made conductive to the Discharge capacitor C.

The operation of this circuit arrangement is as follows: By closing the switch SW, the counters I, II and III are reset and the output 0 of the counter III is connected to the resistor r _Q. As a result, the resistance r ~ is connected to the negative pole of the electrical power source. This gives a current through the photoelectric element CdS which is the same size as that flowing _{through the resistor r Q.} Assuming that the current flowing through the resistor r _{Q is i 0 , a voltage R. Q} (the reference voltage) is generated between the terminals of the photoelectric element CdS. R is the resistance, which is determined by the intensity of the scene brightness that the photoelectric element CdS picks up.

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At the same time, by closing the switch SW, the transistor T ₁ - is put into the conductive state, so that the capacitor is kept in the discharged state.

At the beginning of counting, the switch SW is opened, and the transistor Tg is put into the conductive state by the high level transmission output of the counter II, so that the transistor T ₁ - becomes non-conductive and the capacitor C is charged by the from transistor T-. supplied constant current takes place.

Opening the switch SW also makes counters I, II III ready for the counting process.

Since the output is maintained at a high level because the voltage at the input 1 ^, which is the reference voltage R. _Q which CdSherrührt from the photoelectric element is higher than the voltage on capacitor C, which was initially discharged, the grid circuit is G triggered, and lets through time pulses of the pulse generator OSC, which are counted in the counters I and II.

As already described, the collector current of the transistor T- is controlled by the setting of the resistor R, that the voltage across the capacitor in the time in which the counters I and II count 100 counts, a predetermined th value reached.

.A 609821 / 07AA

When the voltage across the capacitor has reached a predetermined comparison voltage R ₁₀ before 100 times counts are counted by the counters I and II, the output of the comparator Q is brought to a low level, so that the grid circuit G is closed and the counting is ended. Then the number contained in counters I and II is the pulse number, which is indicative of a precise exposure time, given in terms of the indicative number part of the number of pulses without their exponent part.

If the voltage on the capacitor C _{does not reach the reference voltage R. o} when 100 counts have been carried out because the scene is too dark and the resistance and thus the voltage emitted by the photoelectric element CdS are too high, the transmission output C has _Q of the counter II has a low level, so that a count is effected in the counter III. This indicates the addition of an exponent part of one. At the same time, the resistor r, instead of the resistor Tq, is connected to the transistor Tg, which becomes non-conductive and the transistor Tp. Becomes conductive in order to discharge the capacitor C and reset the counters I and II.

The switching on of the resistor r causes the current which flows through the transistor T ₁ and therefore the current which flows through the photoelectric element CdS, since the transistors T ₁ and Tg form a constant current circuit. As described above, the photoelectric

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Element.CdS flowing current i, reduced to 1/10 of the current i _Q if the resistor r is switched on instead of the resistor r _Q. Therefore the comparison voltage r. »·, * Which is generated by the switching on of the resistor r. instead of the resistance r _{Q is} achieved, reduced to 1/10 of the comparison voltage RQ.

After the capacitor C has discharged and the transfer output Cq has been brought back to its high level in order to bring the transistor T ₁ - into the non-conductive state, and the capacitor is ready for recharging, while the counters I and II are ready for a count, the capacitor C begins to charge by the constant current supplied by the transistor T ^. The voltage of the capacitor C is reduced in the comparator Q with the comparison voltage RQ of the previous step, while the counters I and II begin to count the output pulses of the pulse generator OSC- coming via the grid circuit G until the voltage of the capacitor C dies Equivalent stress R. _{Q has} reached.

When the voltage of the capacitor C reaches the comparison voltage R .. before 100 counts in the counters I and II are, the counts in counters I and II represent the characteristic part of the number of pulses, the characteristic 1st for accurate exposure, while the counts in Counter III represent the exponent part of that number.

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- i4 -

If the voltage of the capacitor C does not reach the comparison voltage R. before 100 counts have been carried out in the counters I and II, then instead of the resistor r. in the same way as has already been described, the resistor r _{2 is} switched on, so that the count with the comparison voltage of the photoelectric element CdS is reduced to 1/10 of the comparison voltage R., and the described process is repeated until the voltage of the capacitor reaches the comparison voltage before 100 counts have been carried out by counters I and II.

Assuming that the resistance of the photoelectric element CdS is K when a resistor r _{Q is} used with the resistance 1 KÄ and the voltage across the capacitor C reaches the predetermined voltage V. _Q0 when 100 counts from the counters I and II are performed, then the value of the resistance R of the photoelectric element at the time of counting the number of pulses indicative of an accurate exposure time for each desired scene is represented by

R - 10 ⁿ KN / 100

η = number of counts counted by the counter III i.e. the number of the exponent part

N = number of counts made by counters I and II, i.e. the number of the identifying part of the number.

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Therefore, the above-described circuit enables the characteristic Part and the exponent part of the number of pulses, which is characteristic of an exact exposure time across the resistance R, which corresponds to the scene brightness, is to be counted and saved in counters I, II and III.

The counters can count according to anything other than the decimal system.

In order to reproduce the stored number of pulses, which is indicative of a precise exposure time, and to carry out the exposure, the timing circuit, which is determined by the above-described resistors r _Q , r ₁ , r 2 ..., is simultaneously activated by the output current of the transistor Tp with the opening of the shutter operated and the shutter is closed when the counters I, II and III have counted down the previously stored values of η and N.

Since the current flowing through the photoelectric element is automatically and successively reduced by one Place of the number, which is dependent on the scene brightness, is prevented according to the invention that the voltage of the photoelectric Elements CdS becomes too big. This will reduce the time required to operate the comparator Q extremely short, while the counting circuit is simple and compact.

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FIG. 2 shows a circuit according to the invention, which together with the circuit shown in Figure 1 can be used to introduce information relevant to the exposure set aperture and sensitivity of the film used in the camera to obtain an accurate exposure time regardless of any change the aperture and the film speed.

It is assumed that the fully open aperture Fmax and the aperture that is set for exposure are F is. The maximum sensitivity of the film that is in a Camera can be used is Smax, and sensitivity of the film actually used in the camera is S.

It is known to be used for obtaining the exact exposure time at the aperture F, if the measurement has been carried out with the aperture fully open, the exact exposure time T for the fully open aperture Fmax and for a film with the maximum sensitivity Smax with a compensation coefficient for the aperture F and for the sensitivity S of the film used, which can be expressed as follows

(F / Fmax) ²

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• A-

Assuming that Pilm sensitivity is expressed by the geometric series 2 ^m (where m is a positive or negative number, such as 16; 8; 4; 2; 1.0; 0.5; 0.25; 0.125; (im In the case of ASA sensitivity, this number is to be multiplied by 100) and the area between two adjacent terms or numbers in the geometric series is divided into three parts to define 1/3 step, then it is sufficient, for example, to set the exposure time T as it is has been described above, ^{to multiply by the compensation coefficient 2 n} ^ in order to obtain the exact exposure time with an alteration of the Pilm sensitivity by η steps (where a step 1/3 of the area between the two adjacent terms of the geometric series of the In other words, the multiplication of the exposure time T by 2 '^ is performed η times.

Therefore, to simplify the calculation, 2 '** is expressed

by 1.26 (* ^ f? = 2 ¹ ^) and the multiplication of the exposure time T by 1.26 is carried out η times.

Similarly, it suffices if the aperture is expressed by the geometric series 2 ^m , such as 32, 16, 8, 4, 2, 1, 1/2, 1/4, 1/8, 1/16, 1/22 , 1/64 and the range of two adjacent terms divided into three equal parts to give a 1/3 step, perform 2 ⁿ times the multiplication of the exposure time T by 1.26 to make in n steps

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the change in the aperture must be taken into account, since the exposure time depends on the square of the change the aperture changed.

As described above, the compensation coefficient A be expressed by

A = (l, 26) ⁿ .

FIG. 2 shows a circuit for carrying out the compensation described above for the diaphragm opening and the pilm sensitivity. The emitters of the transistors T ₁ ', T ₂ ', T ^ 'are connected to the positive pole of the electrical power source, while their bases are connected to one another. The collector of transistor Tp ¹ is connected to its base to form a constant current circuit in which the current flowing through each of the collectors of transistors T, 'and T,' is equal to the current flowing through the collector of transistor T. ₂ ¹ flows.

The collector of the transistor T. 'is connected to the movable contact of the switch Sr, to compensate for the exposure time when changing the aperture and the pilm sensitivity. The fixed contacts t ,, tp, t, ... t of the switch Sr are connected to the connections of adjacent resistors of a number of series connected resistors ^r i ** ¹ ^ '··· ^r _n ', the resistance τ ^ is connected to the negative pole of the electrical power source.

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The resistances r, ', i * ₂ ' ... correspond to the corresponding steps of the compensation coefficient described above.

The collector of the transistor T ₂ 'is connected to one side of the resistor R _Q ', the other side of which is connected to the negative pole of the electrical power source, so that the current flowing through each of the collectors of the transistors T, ¹ , Tp ', T , 'flows, is determined by the resistor R _Q '. The collector of the transistor T- * 'is connected to one side of the capacitor C', the other side of which is connected to the negative terminal of the electrical power source.

The input I 'of the comparator 1 is fed by the electrical current source which is connected to the connection between the switch Sr and the collector of the transistor T 1'. The other input Ip 'of the comparator 1 is connected to the connection line between the collector of the transistor T,' and the capacitor C ¹ . The output of the comparator 1 is connected to the input I ^ 'of the NAND-Oitterkreises j5. The input I- 'of the NAND grid circuit 3 is connected to the output of the pulse generator 2, which is supplied by the electrical power source. It consists of an unstable multivibrator that is able to keep its time

constant to change by 1/2. The effect of this measure will be described later.

Another input I ₅ ^{1 of} the NAND grid circuit J> is connected to the base of the transistor T ^ * via a switch S.

609821/07 44 ^{m /} '

whose collector is connected to the connection between the collector of the transistor T, ¹ and the capacitor C ¹ , and whose emitter is connected to the negative terminal of the electrical power source.

The resistance R ₁ . is connected between the positive terminal of the electrical power source and the connection between the switch S and the input I ₁ - 'of the NAND grid circuit J5. The output of the NAND grating circuit 3 is used as a multiplication requirement for the compensation of the exposure time as a function of the aperture and / or the film speed by introducing this multiplication requirement into the appropriate part of the circuit of FIG.

As in the case of the comparator Q in Figure 1, the output of the comparator 1 is brought to a high level when the voltage at the input I ₁ 'is higher than the input Ip' * while the output is at a low level when the voltage at Input I ₂ 'reaches that of input I. ¹ .

The operation of the circuit according to FIG. 2 is as follows: By closing the switch S, the transistor T ^ ^{1 is made} conductive, so that the capacitor C 'is discharged. Since the movable contact of the switch Sr is connected to the contact _{selected from the contacts ti., T 2} ··· for setting the compensation coefficient for the aperture and / or the film sensitivity, the output of the comparator 1 is high

-A

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Level because the capacitor C ^{f is} discharged. Therefore, the input L x ^{1 of} the NAND gate circuit j5 is held high. The input I ₁ - 'of the NAND grid circuit 3 is kept low because of the connection of the base of the transistor Tj, ¹ to the resistor R ₁ . Therefore, the output pulses of the pulse generator 2 do not appear at the output of the NAND grid circuit 2.

When the switch S is opened, the transistor T ^ ^{1 is} inactivated and the charging of the capacitor C ^f by the constant current coming from the collector of the transistor T 1 'begins. The voltage of the capacitor C ¹ is applied to the input I ₂ 'of the comparator and compared with the voltage generated by the selected number of resistors r ,, r ₂ ... and which is generated by the setting of the switch Sr and the constant current flowing through it from the collector of transistor T, 'is given.

At the same time, the input I ₅ 'of the NAND grid circuit 3 is at a high level.

Until the voltage at the input I ₂ 'of the comparator 1 reaches the voltage at the input I ₁ ' of the same, the high output voltage of the comparator 1 actuates the NAND grid circuit J5, so that the output pulses of the pulse generator 2 continuously in reverse at the output of the NAND Grid circle 3 appear. When the voltage at input I ₂ 'reaches that of input I _1',

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is the generation of output pulses at the output of the NAND grid circuit 3 finished.

Since the voltage at the input I ₁ 'increases due to the number of resistors r ,, r ₂ , ..., which are switched on by setting the switch Sr, the charging time for the capacitor C ^{1 is} lengthened. This increases the number of inverted output pulses at the output of the NAND grid circuit 3,

To compensate for the film sensitivity, the time constant or frequency of the pulse generator 2, the capacitance of the capacitor C ^f , the resistance value of each of the resistors r, ', r ₂ ', ..., and the resistance value of the resistor R ₀ 'become more appropriate Manner so that an output pulse is generated by the NAND grid circuit 3 at each switching step of the switch Sr, whereby the number of resistors ^r i ^f * ^r p '··· ^{connected in the circuit increases by} one.

To compensate for the aperture, the time constant of the pulse generator 2 is reduced to 1/2 with respect to the time constant used to compensate for the pilra sensitivity. Therefore, two output pulses are generated by the NAND grid circuit 3 for each switching step of the switch Sr, thereby increasing the number of resistors r. ^r , Vp ', ... which are switched in the circle to increase by one.

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Therefore, when the movable contact of the switch Sr comes into contact with the contact t ^ , so that the resistance r. * is switched in circuit to compensate for film sensitivity, one pulse is generated, while when the movable contact is switched to turn on resistors r ^ ¹ and Γρ ¹ , two pulses are generated, etc. Similarly, two pulses are generated when the moving contact is in contact with the contact t. _{comes to switch the resistor T 1} * in the circuit to compensate for the aperture, while if the movable contact is switched in such a way that it is in connection with the resistors r, 'and r', four pulses are generated, etc.

The output pulses generated in this way at the output of the NAND grid circuit 3 are used as a multiplication requirement which is applied to the operating circuit, as has been described in FIG. For this purpose, for example, the above-described number 1.26 (= 2 ^{/ J} ) is stored in the operating circuit and the number of pulses, which is characteristic of an exact exposure time under the condition of the fully open aperture and the maximum sensitivity of the film used, is multiplied by the aforementioned number 1 , 26 as often as determined by the number of pulses generated by the NAND grid circuit 3. This gives the compensated number of pulses, which is characteristic of an exact exposure time under the conditions of the set aperture for the exposure and the film speed actually used.

.A

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In the description above, the geometric series is given as 2 ^m and the area between two adjacent terms of the geometric series is divided into three, resulting in the number 1.26 = 2 ™ . However, the geometric series can also have any other shape and consist, for example, of the terms 2 '(M and N integers) and the area can be divided into q-sections (where q is whole and of any value), where the multiplication factor 2 will.

When performing the compensation described above, if, for example, a film with the ASA sensitivity in the range from 1600 to 25 and an aperture in Range from F 1.4 to F 16 is used, the compensation coefficient:

A = (F / Fmax) ² ^ p

Ci £ / i k \ ² τ, 1600 = (16 / 1.4) χ - ^ jT-

- 64 χ 128 - 8192.

If a compensation coefficient with a large value is used when multiplying the pulses, the characteristic are for an exact exposure time for the maximum aperture and the maximum film speed, the number of compensated pulse numbers becomes too large for an exact exposure time.

According to a further feature of the invention, the number of Impulse, which is characteristic of an exact exposure time

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for the maximum aperture and maximum film speed previously divided by 10,000, for example, a value that corresponds to the aforementioned compensation coefficient This means that the number of pulses is then only 0.8192 is multiplied. This allows the number of compensated pulses to exceed the number of pulses for the maximum opening and the maximum sensitivity is approximated. This greatly facilitates the counting process. aside from that the operating circuit can be extremely simplified and built up from cheap elements, since one extraordinarily high frequency is not required and a suitable frequency of the pulse generator can be selected for digitally counting the exposure time, since the highest shutter speed has a limit and a limit is also given at the aperture.

In order to describe the above in more detail, it is assumed that the resistance of the photoelectric element 1 is K 51 and the time required for the operation of the counting circuit is Ims to be 10 ms. The actuation must then be carried out during the time period from Ims to 10ms using a CR circuit with 8192 KjSS. This is due to the above-described compensation coefficient 8192 under the condition of the aperture of F 16 and the ASA sensitivity

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given by 25. The making of the elements for such a CR circle is difficult. Furthermore, a resistor with a resistance value of 8000 M £ is required to achieve this an exposure time of 1 to 10 seconds. Using such a high resistance value is impractical and requires a high cost.

According to the above-described invention, the CR circuit can be manufactured very easily and cheaply by the foregoing Division of the number of pulses required for the exposure time, for example 10,000, as described above because then the number of counts is greatly reduced.

Figure 3 shows a circuit similar to that shown in Figure 2, in which, however, the compensation for the aperture can be effected, also under the condition of fully open aperture before exposure, so that the exact exposure time for the on a set value for the Exposure closed aperture can be obtained.

The circuit shown in Figure 3 is essential similar to that shown in Figure 2, except that the portion bounded by a dashed line is so modified is that he does the above-described switchover of the measurement

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enables. The resistors r ', r _p ', .. connected in series are for the compensation of the pilm sensitivity similar to those in FIG. to the collector

rA

of the transistor T ₁ 'connected.

The resistance r, 'is a series of with the resistance r "

l η

Resistors r ", ^r p"»*%" * ... r "connected for the compensation of the aperture. The resistance r "is connected to the negative pole of the electrical power source. Since the resistors r" ^r p "" ··· ^ft * * ^the compensation of the aperture are provided ^, is the resistance value of each resistor r, "r", ". .. chosen so that it is twice as large as that of the resistors r. ^f , Γρ '* ··· ♦ ^{so that two} pulses are obtained for each addition of a resistor to the circuit instead of changing the time constant of the pulse generator 2.

The switch S -. Has a movable contact, which is switchable and selectively comes into contact with one of two fixed contacts, each with the associated one Connection between adjacent two resistors of the series of resistors r '' # r ", ... is connected.

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A switch S_ is connected to the switch S_ on one side, which is connected to the junction between the resistors r "and r", as well as to the movable contact of switch S. The other side of the switch SF is connected to the contact b of the switch S, which is connected to the Connection between the resistors r "and r" is connected. Therefore, when the switch S_, is closed, are the resistors r ", r", ..., r "short-circuited.

dj n

The switches S and S _ can by (not shown) Buttons in the camera body in which the circuit is used can be operated manually. The switch S_ can be coupled with shutter actuation means in the camera, so that the switch S_, is closed to switch the resistors r ", r",

Γ d J

..., r "to close when the aperture is set to a The value is closed by actuating the shutter actuating means.

If the measurement is carried out with the diaphragm fully open, the switch S_ is open, so that a selected number of resistors r " _f r", ..., r. "and r ', r' ... by setting the switches SA and SP with the collector of the

r r

Transistor T. 'are connected. This can reduce the tension.

609821/0744

which is determined by the number of connected resistors applied to input I 'of the! Comparator 1 in order to achieve the required output pulses in the NAND grid circle 3 to get.

In order to effect the measurement in the actually closed diaphragm opening for the exposure, the diaphragm actuating means are actuated in order to close the diaphragm to a desired opening; at the same time the switch S "
closed, so that the resistors for the compensation of the aperture are short-circuited and the compensation for the film sensitivity is carried out alone.

609821/0744

Claims (1)

- 30 ~ 25 5 0 8 Patent claims 1./Method of counting pulses in a digital electronic shutter in which the exact exposure time depends on the number of time pulses is set, counting until the through a constant current on a capacitor generated voltage equal to one of the scene brightness dependent and with the help of a constant current generated by a photoelectric element comparison voltage, characterized in that the number of Time impulses into a characterizing part and an exponent part which are counted separately. 2. The method according to claim 1, characterized in that the time pulses are counted by a first counter, until a predetermined number of pulses is reached and a second counter then counts while the first counter is reset and the capacitor is discharged, after which the photoelectric element to guided constant current and thus the comparative voltage P 499 · /. 609821/0744 is reduced by a power of ten and the first numerator counts again and this is repeated until the counting of the first counter is finished before the predetermined rate Number of pulses reaches 1st. J. The method according to claim 1 or 2, characterized in that that the number of pulses is multiplied by a compensation coefficient, that of the film speed and / or corresponds to the aperture. 4. The method according to claim 3 * characterized in that before the multiplication with the compensation coefficient first the number of pulses by a selected number is shared. 5. Circuit for counting pulses in a digital electronic A shutter as claimed in claim 1 including a capacitor, a photoelectric element that controls the brightness of the scene receives, a constant current circuit, to charge the capacitor and generate a voltage that increases with the charging time changed, another constant voltage circuit to generate a comparison voltage as a function of the exact Exposure time that corresponds to the brightness of the scene, the 609821/0744 connected to the photoelectric element, a comparator, which is connected to the capacitor and the fofcoelectric Element for generating a signal * when the voltage of the capacitor reaches the reference voltage, a time pulse generator, a grid circle, which is connected to the pulse generator and the comparator, for continuous Generation of output pulses until the signal is received from the grid circle and a counting circuit, which with is connected to the grid circle and counts the output pulses until the signal is obtained from the grid circuit, with the other constant current circuit connected to a series of resistors which are connected in parallel to each other, and where the resistance value of each resistor is chosen so that it is one place higher than the value of the previous resistor, the counting circuit having a first and a second counter and wherein the first counter is connected to the grid circuit and counting the output pulses serves until the counting has reached a predetermined number of times, at which time the first counter is reset while it generates an output signal and the second counter connected to the first counter every time it generates an output signal receives counts once, while the next larger of the resistors connected in series one after the other with the second 609821/07 A A J) '1550802 m ΊΊ m Counter is connected when the output signal is obtained, the constant current flowing through the photoelectric Element flows, is reduced by one place and the equivalent voltage is reduced by one place and a short circuit is connected to the capacitor and the first counter to discharge the capacitor each time when the output signal is obtained from the short circuit. 6. A circuit according to claim 5 »characterized in that a Compensation circle for pilm sensitivity and / or for the aperture is provided, which compensates for the number of pulses. 7. A circuit according to claim 5 or 6 built into a camera with a diaphragm and with a compensation circuit for the diaphragm opening, which is connected to the counting circuit, consisting from series-connected resistors, a selected number of which corresponds to the set aperture corresponds, is short-circuited and which generate a compensation coefficient that is included in the counting circuit is introduced, a first switch for shorting a selected number of the resistors and a second Switch for short-circuiting all resistors, whereby by actuating the first switch and not actuating it of the second switch, the number of pulses that characterize 609821/0744 is counted for an accurate exposure time with the aperture fully open while pressing the second Switch counting the number of pulses is carried out under the condition that the aperture is set to a certain aperture is set. 609821/0744 Blank page