JPS61140929A - External photometric type exposure control device - Google Patents

Abstract

PURPOSE:To prevent the generation of an exposure error caused by a variation of the running characteristic of a shutter blade by providing an aperture detecting means for detecting a variation of the aperture of a photographic lens, and correcting the charging characteristic of an integration circuit in accordance with its detecting means. CONSTITUTION:The output of an operational amplifier 33 for constituting a photometric circuit 30 is connected to the ground through a transistor 35, and only when the transistor 35 is cut off, a charging operation of a capacitor 37 is executed. Accordingly, when a ratio of a cut-off time of the transistor 35 is raised by following the opening of a shutter blade 1, the charging characteristic of the capacitor 37 can be followed to the variation of the integral characteristic of an exposure quantity which follows an opening of the shutter blade. Therefore, by a pulse generated by a duty converting circuit 80, the transistor 35 is made to execute a switching operation, and also off-time of a pulse generated by the duty converting circuit 80 by following the rise of a counting value in a counter 20 is raised. Variation of the charging characteristic of the photometric circuit can be followed to the variation of an opening characteristic of the shutter blade, therefore, exposure control can be executed exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an external light metering type exposure control device for a camera equipped with a program shutter using a shutter blade that also serves as an aperture blade.

[Conventional technology and its problems]

When photographing with a still camera, in order to properly expose the film, it is necessary to stop the exposure when the integral value of the amount of light irradiated onto the film surface reaches a certain value determined in accordance with the film sensitivity. Most of today's still cameras are equipped with an automatic exposure control device whose main components are a light-receiving element and an integrating circuit that is charged by the photocurrent flowing through the light-receiving element. The integrating circuit is charged by a photocurrent flowing through the light receiving element, and when the charged value reaches a level determined corresponding to the film sensitivity, or in response to the field brightness and the film sensitivity, the photocurrent flows to the light receiving element. The integrating circuit is charged by a photocurrent, and when the charged value reaches a certain level, the exposure is completed.

As is well known, the amount of exposure to the film surface is ultimately F.
In the case of a camera where the F value and exposure time can be controlled independently, once the F value is determined, the appropriate exposure can be obtained by determining the exposure time in accordance with the field brightness. Furthermore, once the exposure time is determined, proper exposure can be obtained by determining the F value in accordance with the brightness of the field.

However, in order to perform such exposure control, it is necessary to provide independent drive devices for the aperture blades and shutter blades (shutter curtain), which is expensive in terms of cost.
In the case of so-called compact cameras, a programmed shutter that serves both as a shutter blade and an aperture blade is generally used.

In the case of such a programmed shutter that functions as both a shank blade and an aperture blade, as shown in Figure 11, the shank blade that also functions as an aperture blade is opened to a near linear value, and the shutter blade is closed when the appropriate exposure is obtained. .

Even in such a program shank, the exposure control circuit basically integrates the photocurrent flowing through the light receiving element in response to the field brightness, and closes the shutter blade when the integrated value reaches a certain value. However, in this kind of program shutter, the exposure amount is proportional to the exposure time after the shutter blade reaches the open aperture, and in the high brightness area until the shutter blade reaches the open aperture, the aperture of the shutter blade becomes proportional to the exposure time. At the same time, since the amount of exposure per unit time is increasing every moment, proper exposure control cannot be performed unless the characteristics of the photometric circuit are corrected.

Various methods have been known for this correction, but they can basically be divided into the following two types.

First, the first method is to form sub-diaphragm blades that open and close the light-receiving element integrally with the shutter blade, and increase the light-receiving area of the light-receiving element in conjunction with the aperture of the shutter blade. According to the method, when the field brightness is constant, the photocurrent per unit time increases with the aperture of the shafter blade, so the integral value of the actual exposure amount and the integral value of the photocurrent roughly correspond, This allows for accurate exposure control.

However, in the case of this method, there are problems in that the locations where the light-receiving element can be placed are extremely limited, and the shape of the shutter blade itself is also restricted in order to arrange the light-receiving element. It is also possible to place the light-receiving element at an arbitrary position and simultaneously operate the shutter blades and sub-diaphragm blades using an interlocking mechanism, but if an interlocking mechanism is used, the exposure error will be amplified by the interlocking mechanism. There is a risk.

A second method is known in which the aperture characteristics of the shutter blades are predicted in advance and the integral value of the photocurrent is electrically corrected. However, in order for the above prediction to hold true, it is assumed that the running characteristics of the shutter blades are extremely stable, so a complicated speed regulating mechanism such as a governor is essential. At the same time, it has been pointed out that the inertial weight of the actuating member increases due to these speed regulating mechanisms, causing a rise in the shutter stability. It has also been pointed out that exposure errors occur when the running characteristics of the shutter blade change due to changes over time, changes in camera posture, changes in temperature, or the like.

[Means for solving problems]

The present invention has been made to solve these problems, and provides a novel exposure method that allows flexibility in the placement of the light receiving element while preventing exposure errors from occurring due to fluctuations in the running characteristics of the shutter blade. The purpose is to provide a control device.

In summary, the exposure control device of the present invention is equipped with an integrating circuit that integrates a photocurrent flowing through a light receiving element in accordance with field brightness, and when the integrated value of the integrating circuit reaches a predetermined value, the aperture is stopped. An external photometry type exposure control device in which a shutter blade which also serves as a blade is closed, is provided with an aperture detection means for detecting a change in the aperture of the photographing lens, and the charging characteristic of the integrating circuit is determined in response to the detection output of the aperture detection means. It is designed to correct.

[Effect]

The external photometry type exposure control device according to the present invention detects changes in the aperture of the photographic lens and corrects the charging characteristics of the photometry integrating circuit, so mechanically the sub-aperture blades are used to add so-called γ correction. This eliminates the need for the light-receiving element, which increases the degree of freedom in the placement of the light-receiving element, and even if the aperture characteristics of the photographing lens change due to some reason, the charging characteristics of the photometry integrating circuit can follow this, resulting in extremely high performance. Accurate exposure control becomes possible.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

The present invention is applicable to a program shutter equipped with a shutter blade that also functions as an aperture blade. First, an example of the basic configuration of a program shutter that has a shutter blade that also functions as an aperture blade is shown in FIG. show.

In FIG. 1, numerals 1 and 2 each indicate shutter blades that also serve as aperture blades, and the shutter blades 1 and 2 are rotatably supported on shafts 1a and 2a, respectively. 3 indicates a blade opening/closing ring which is rotatably held around the optical axis,
The blade opening/closing ring 3 is always biased counterclockwise by a spring 4, and the bottle 3a installed in the blade opening/closing ring 3 is
・3b is the long groove 1b formed in the shaft blades 1 and 2, respectively.
・Engaged with 2b. Further, 5 indicates a solenoid, which is an example of an actuator for rotating the blade opening/closing lever 3 clockwise.

To explain its operation, first, in the initial state, the solenoid 4 is demagnetized, and the blade opening/closing ring 3 is biased counterclockwise by the spring 4. Therefore, the blade opening/closing ring 3 is stopped at the position where the claw 3C contacts the stopper 6, and the shutter blades 1 and 2 close the aperture 7.

When the solenoid 5 is energized in this state, the blade opening/closing ring 3 keeps the pins 3a and 3b locked in the long grooves 1b and 2b.
It rotates clockwise against the tension of spring 4, so
The shaft blades 1 and 2 rotate counterclockwise about the shafts 1a and 2a, respectively, to gradually open the aperture 7, and when the claw 3d of the blade opening/closing ring 3 comes into contact with the stopper 6, the aperture is closed. 7 is an open aperture. Then, when the solenoid 5 is demagnetized at the timing when proper exposure is obtained, the blade opening/closing ring 3 is rotated counterclockwise by the tension of the spring 4, and the shutter blade III/2 closes the aperture 7 to complete the exposure operation. do.

Although the structure and operation of a programmable nuclide shutter for exposure control are conventionally well known, in the present invention,
Its characteristic feature is that it is provided with means for detecting the actual aperture of the photographic lens.

As means for detecting the aperture of the photographic lens, there are various possible methods, such as a method of detecting the amount of rotation of the shutter blade 1 (or 2), a method of detecting the amount of rotation of the blade opening/closing ring 3, etc., but in this embodiment, An example is adopted in which a photoelectric encoder 8 for detecting the amount of rotation of the shutter blade 1 is formed.

The photoelectric encoder 8 will be described in detail with reference to FIGS. 2 and 3, but to explain its basic structure and operation, the shutter blade 1 has a part that does not interfere with the operation of other mechanical members. A large number of slits 8a are formed on the circumference around the axis 1a, and the pulses generated each time the slits 8a open and close the optical path from the light emitting element 8b to the light receiving element 8C are counted. It is designed to detect the amount of rotation.

FIG. 2 is an enlarged view of this encoder 8, and FIG. 3 is a sectional view cut along A in FIGS. 1 and 2. The shafter blade l is supported so as to float in the gap between the base plate 8d and the base plate 8e, and a light guide 8f with extremely low reflectance and transmittance, which is a feature of this embodiment, is installed in the through hole formed in the base plate 8e. It is buried. A light guide slit 8g whose area is sufficiently smaller than the slit 8a formed in the shutter blade 1 is formed approximately in the center of this light guide 8f, and the light beam irradiated from the light emitting element 8b passes through the light guide slit 8g. Pass through the main plate 8d or the main plate 8
The light is reflected by the shutter blade 1, which has a reflectance different from d, and reaches the light receiving element 8C. The characteristic points of the encoder 8 in this embodiment are: ■Light guide 8f
The reflectance of the light guide slit 8g is sufficiently small compared to the reflectance of the base plate 8d and the shutter blade 1, and the area of the light guide slit 8g is sufficiently small compared to the area of the slit 8a formed in the shutter blade 1. (The line segment connecting the light emitting element 8b and the light receiving element 8c is formed on the shutter blade l)
For example, it is perpendicular to the traveling direction of 8a. Therefore, in this embodiment, only the light that passes through the pinhole-like light guide slit 8g among the light beams emitted from the light emitting element 8b reaches the light receiving element 8C, and furthermore, the boundary line between the shutter blade 1 and the slit 8a is the light guide slit 8g. Surin)
8g instantaneously, the photocurrent generated by the light-receiving element 8C exhibits rapid falls and rises, making it possible to form accurate pulses. Also, considering the case where the shutter blade 1 runs unstable due to a change in camera posture, etc., normally in such a case, the shutter blade 1 tilts back and forth in the direction of movement of the slit 8a. As mentioned above, since the line segment connecting the light emitting element 8b and the light receiving element 8c is perpendicular to the traveling direction of the shutter f-8a formed on the shutter blade 1, the shutter of the light emitted from the light emitting element 8b The angle of incidence with respect to blade 1 is shutter blade l
The passage of Surin 8a can be detected with high accuracy, almost unaffected by the inclination of .

Then, if the change in the photocurrent of the light receiving element 8c that occurs every time the slit 8a passes through the light guide slit 8g is converted into a pulse, and this pulse is counted, the aperture position of the shutter blade 1 (that is, the F value ) can be known.

In this embodiment, the charging characteristics of the photometry circuit for exposure control are corrected in accordance with the aperture position of the shutter blade 1 detected in this way, and the light receiving element for photometry is connected to the shutter blades 1 and 2. Even if it is placed at a location unrelated to the operation of the integrating circuit, it is possible to make the charging characteristics of the integrating circuit follow the aperture characteristics of the shutter blades 1 and 2.

Next, with reference to FIG. 4, an example of an exposure control circuit including a circuit that corrects the charging characteristics of a photometric circuit for exposure control in accordance with the opening position of the shirt blade 1 detected by the light receiving element 8C will be explained. do.

First, in FIG. 4, 8b and 8C indicate the light-emitting element and light-receiving element, respectively, which have already been explained, and 10 indicates the light-emitting element 8.
A waveform shaping circuit 20 pulses the output of the waveform shaping circuit 0, and a counter 20 counts the output pulses of the waveform shaping circuit 0. Further, 30 is a photometry circuit that determines the exposure time in accordance with the brightness of the field, 40 is a drive circuit that drives the shutter blades, 50 is a sequence circuit that performs various sequence controls, and 60 is a DX film cartridge. There are 7 contact groups for meter breaking corresponding to the conductive patterns provided on the
0 indicates a DX circuit which codes film sensitivity in accordance with the pattern obtained by the meter break of the contact group 60, and 80 indicates a duty conversion circuit which is a feature of this embodiment.

Although this embodiment assumes a camera compatible with DX film, the film sensitivity may be manually input as, for example, the terminal level of a variable resistor, and this may be digitally coded.

The embodiment shown in FIG. 4 basically controls the duty ratio of the photometry circuit 30 in accordance with the aperture position of the shutter blade l, and the film sensitivity information output from the DX circuit 70 and the counter 20 are The ratio of the on time and off time of the pulse generated by the duty conversion circuit 80 is changed according to the aperture position of the shutter blade 1 digitized as a count value, and the photometry circuit changes the ratio of the on time and off time of the pulse generated by the duty conversion circuit 80. I am trying to operate 30.

In addition, as mentioned above, the count value of the counter 20 is equal to the shutter blade 1.
-2 aperture position (that is, the F value of the photographing lens), in this embodiment, the strobe synchronization timing in the so-called flashmatic mode is also controlled by the count value of the counter 20.

In other words, the guide number, which is a numerical value that indicates the amount of light emitted by a strobe, is defined as the product of the shooting distance and F-number when the film sensitivity is 150100, and when the film sensitivity is changed, the shooting distance is proportional to the square root of the film sensitivity ratio. .

Therefore, when using a strobe with a fixed guide number, the F-number to be used will be determined once the shooting distance and film sensitivity are determined, and if the strobe is synchronized at the timing when this F-number is obtained, the normal exposure will be achieved. You will get it.

In this embodiment, since the counted value of the counter 20 indicates the F value, the film sensitivity information output from the DX circuit 70 and the shooting distance information output from the distance measuring circuit 90 are sent to the arithmetic circuit 100.
In addition to this, the arithmetic circuit 100 calculates the F value that will give the appropriate exposure from the film sensitivity, shooting distance, and guide number and provides it to the digital comparator 110. EF at the timing that matches the output
A trigger pulse is given to the U circuit 120 (abbreviation for electronics-flash-unit circuit, which is well known) to cause the strobe to emit light. Note that the distance measuring circuit 90 may be configured to detect the amount of helicoid extension, or, for example, an autofocus distance measuring mechanism using near-infrared light may be used.

Next, a more specific configuration and operation of this embodiment will be explained.

First, a mechanism for quantifying the opening position of the shutter blade 1 will be explained.

First, the light emitting element 8b is a light emitting diode, and the light receiving element 8c is a phototransistor.
The light emitted from the light guide slit 8g passes through the light guide slit 8g, is reflected by the base plate 8d or the shutter blade 1, and reaches the light receiving element 8c. Since the reflectance of the base plate 8d and the shutter blade l are different, the light energy incident on the light receiving element 8c changes every time the slit 8a crosses the light guide slit 8g, and is added to the waveform shaping circuit 10 as the terminal level of the resistor R1. It will be done.

FIG. 5 shows a specific configuration example of the waveform shaping circuit 10, in which the terminal level of the resistor R1 is determined by removing an amount equivalent to the dark current of the light receiving element 8c with the DC cut capacitor 11, and then amplifying it with the operational amplifier 12. and is applied to the inverting input of comparator 13. A reference level is applied to the non-inverting input of the comparator 13 from the power supply 14, and the comparator 13 compares the output of the operational amplifier 12 with the reference level and converts it into a pulse. A pulse is generated each time the shutter blade 1 passes, and this pulse is applied to the clock terminal of the counter 20 and amplifies the counter 20 (countdown is also possible), so the opening position of the shutter blade 1 is quantified as the count value of the counter 20. Ru.

Next, the photometry circuit 30 will be explained.

In this embodiment, the 5PD 31, which is a light receiving element, is used without bias in order to eliminate the influence of dark current, and the log diode 32 is used as a feedback resistor of the operational amplifier 33 in order to cope with the extreme brightness range. . in particular,
The 5PD 31 has its anode side connected to the non-inverting input of the operational amplifier 33, and its cathode side connected to the inverting input of the operational amplifier 33, and preferably, its light-receiving surface faces directly to the subject and can be placed at any location on the camera body. It is located. Further, a voltage V is applied from a bias power supply 34 to a non-inverting input of the operational amplifier 33, and a log diode 32 is connected as a feedback resistor.

To explain its effect, when light corresponding to the field brightness is incident on the 5PD 31, a photocurrent flows in the 5PD 31 in the opposite direction, and a voltage drop v2 is generated across the log diode 32 due to this photocurrent. If the switching transistor 35 is cut off at this time, the output terminal of the operational amplifier 33 will have a voltage drop (2) of the log diode 32 caused by the photocurrent in the output voltage v1 of the bias power supply 34.
A superimposed level is generated. The output voltage of the operational amplifier 33 is applied to the base of the logarithmic expansion transistor 36 to control its collector current, and the capacitor 37 is charged by the collector current of the transistor 36, so the charging characteristic of the integration capacitor 37 becomes 5PD31. It will be determined by the flowing photocurrent. The charge level of this capacitor 37 is then applied to the inverting input of the comparator 38, and the power supply 39 is applied to the non-inverting input of the comparator 38.
The shutter closing signal generated by the comparator 38 when matched with the reference level applied from the shutter is applied to the sequence circuit 50 to cause the shutter closing operation to be executed. Note that the transistor 310 is connected in parallel with the capacitor 37.

It is shut off in conjunction with the shirt release, and transistor 3
10 is cut off, the charging operation of the capacitor 37 is started.

The characteristic point of this embodiment is that the ratio of the operating time to the non-operating time of the photometric circuit 30 (i.e., the ratio of the operating time of the photometric circuit 30 to the non-operating time By controlling the ratio), the integral characteristic of the exposure amount with respect to the film surface is made to match the integral characteristic of the photometric circuit 30.

As already explained, the shutter blades, which also serve as aperture blades,
In the case of a program shutter using 2, the exposure amount per unit time increases moment by moment as the exposure time passes until the shutter blades 1 and 2 reach the open aperture. By increasing the duty ratio of the photometric circuit 30 in accordance with the curve, the integral characteristic of the exposure amount with respect to the film surface can be matched with the integral characteristic of the photometric circuit 30, and accurate exposure control can be performed.

In this embodiment, the output of the operational amplifier 33 constituting the photometric circuit 30 is connected to the ground via the transistor 35, and the capacitor 37 is charged only when the transistor 35 is cut off. Therefore, shutter blade 1
By increasing the ratio of the cut-off time of the transistor 35 as the shutter blade opens, it is possible to make the charging characteristic of the capacitor 37 follow the change in the integral characteristic of the exposure amount caused by the opening of the shutter blade. Therefore, in this embodiment, the transistor 35 is caused to perform a switching operation by the pulses generated by the DT conversion circuit 80, and as the count value of the counter 20 increases, the off time ratio of the pulses generated by the DT conversion circuit 80 is increased. I'm doing it like that.

Specifically, the duty conversion circuit 80 includes an oscillator 81 that generates a reference clock and a pulse width conversion circuit 82.

This pulse width conversion circuit determines the ratio of on time and off time in the period of the reference clock generated by the oscillator 81 in accordance with the count value of the counter 20 and the film sensitivity information given from the DX circuit 70. A table and a counter 20 for determining the ratio of output pulse on time and off time in accordance with film sensitivity information.
and a table for determining the ratio of the on time and off time of the output pulse in accordance with the count value of the output pulse.

Therefore, first, we created a table that determines the ratio of output pulse on time and off time in accordance with film sensitivity information.
Shown in the table.

Table 1 As is well known, when the field brightness is constant, the required exposure amount is inversely proportional to the film sensitivity.

In the embodiment shown in FIG. 4, the capacitor 37 is charged during the off-time of the transistor 35, and the exposure operation ends when the charge level of the capacitor 37 reaches the reference level. Width conversion circuit 8
2, when the film sensitivity is halved, the off-time ratio of the transistor 35 is halved, so that the amount of exposure until the charge level of the capacitor 37 reaches the reference level is doubled.

Next, Table 2 shows a table for determining the ratio of the on time and off time of the output pulse in accordance with the count value of the counter 20.

Table 2 As already explained, in the case of a program shutter with a shutter blade that also serves as an aperture blade, the amount of exposure per unit time increases as the shutter blades 1 and 2 open.
It is required to increase the off-time ratio of the transistor 35 as the shutter blades 1.2 are opened.

As explained with reference to Table 1, the charging characteristics of the photometric circuit 30 are determined based on when the shutter blades 1 and 2 are fully open, so until the open aperture is reached, the charging characteristics of the photometric circuit 30 are increased as shown in Table 2. The ratio of the on time of the transistor 35 is increased by the rate, and the ratio of the off time of the transistor 35 is increased by decreasing the rate of increase of the on time of the transistor 35 as the count value of the counter 20 increases as the aperture approaches the open aperture. I try to let it happen.

Next, the operation of this embodiment will be explained with reference to the above matters.

First, the operation in normal automatic exposure mode will be explained.

In the initial state, the sequence circuit 50 is connected to the drive circuit 40.
The level of the signal applied to the base of the transistor 41 constituting the solenoid 5 is low, and the transistor 41 is cut off, so the solenoid 5 is demagnetized. Therefore, the blade opening/closing ring 3 is rotated counterclockwise by the tension of the spring 4, the pawl 3C is in contact with the stopper 6, and the pins 3a and 3b implanted in the blade opening/closing ring 3 are connected to the long groove 1b.
- Since the shutter blades 1 and 2 are rotated counterclockwise while locking the shutter blade 2b, the aperture 7 is closed by the shutter blades 1 and 2.

In addition, in the initial state, the level of the signal applied by the sequence circuit 50 to the base of the transistor 310 of the photometry circuit 30 is also low, and the transistor 310 is conductive, so the terminal level of the capacitor 37 is pulled up to the power supply level, and the capacitor 37 is not charged.

When the power switch is turned on, the contact group 60 makes and breaks in accordance with the DX pattern marked on the cartridge of the film being sent, and the DX circuit 70 encodes the make and break pattern of the contact group 60. Film sensitivity information is generated, and this film sensitivity information is provided to a pulse width conversion circuit 82.

Now, when the shutter button is pressed and a release signal is applied to the sequence circuit 50, the sequence circuit 50 will
The base inputs of the transistor 41 of the drive circuit 4o and the transistor 310 of the photometric circuit 30 are each set to high level, and a drive voltage is applied to the light emitting element 8b.

First, the transistor 41 becomes conductive when its base becomes high level, and the solenoid 5 is energized accordingly. Therefore, since the blade opening/closing ring 3 rotates clockwise against the tension of the spring 4, the pins 3a and 3b implanted in the blade opening/closing ring 3 lock the long grooves 1b and 2b, respectively, while holding the shutter blade 1. 2 is rotated clockwise, the shutter blade l.2 opens the aperture 7 with a characteristic as shown by curve a in FIG. 6, and exposure to the film surface is started.

In FIG. 6, the horizontal axis shows the exposure time, and the vertical axis shows the F value.

Further, in the photometry circuit 30, the base of the transistor 310 becomes high level, so that the transistor 310 is cut off and the capacitor 37 can be charged.

In the case of this kind of program shutter, in the triangular area before reaching the open aperture, the amount of exposure per unit time changes moment by moment as the shutter blades 1 and 2 open, so that the capacitor 37 changes as the open aperture changes. It is required to correct the charging characteristics of

Therefore, in this embodiment, the opening position of the shutter blade 1 is digitized as the count value of the counter 20, and the charging characteristic of the capacitor 37 is corrected in accordance with the count value of the counter 20.

More specifically, when the shutter blades 1 and 2 start opening the aperture 7 by rotating the blade opening/closing ring 3 clockwise as described above, the slit 8a formed in the shutter blade 1 becomes a light guide slit. Cross 8g in sequence. At this point, the sequence circuit 50 is connected to the light emitting element 8.
Since a driving voltage is applied to b, the luminous flux emitted from the light emitting element 8b passes through the light guide slit 8g and enters the light receiving element 8c, and the reflectance of the shutter blade 1 and the reflectance of the base plate 8d are as follows. Therefore, each time the slit 8a crosses the light guide slit 8g, the amount of light incident on the light receiving element 8c changes, and the terminal level of the resistor R1 also changes.

The waveform shaping circuit 10 then compares the terminal level of the resistor R1 with a reference level and generates a pulse as shown in FIG. 7a. This pulse is added to the counter 20 and the counter 2o
, the opening position of the shutter blade 1 is digitized as the count value of the counter 20, and this count value of the counter 20 is added to the pulse width conversion circuit 82.

Then, the pulse width conversion circuit 82 determines the ratio of the on time and off time of the pulse applied to the transistor 35 in accordance with the film sensitivity information applied from the DX circuit 7° and the count output of the counter 20. In addition, the pulse width conversion circuit 8
The period of the pulses generated by oscillator 81 itself is determined by the reference clock generated by oscillator 81.

For example, if a film of 15O400 is currently set, the DX circuit 70 provides film sensitivity information of 15O400 to the pulse width conversion circuit 82. When the film sensitivity is 15O400, the ratio of the on time when the shutter is fully open is 7/8 as shown in Table 1, and the pulse width conversion circuit 82 converts the count value of the counter 20 into the on time when the shutter is fully open. The ratio of the on time and off time of the pulse applied to the transistor 35 is determined by multiplying by the correspondingly determined increase rate shown in Table 2.

More specifically, for example, when the count value of the counter 20 is 1 or 2, the ratio of the off time and on time of the pulse generated by the pulse width conversion circuit 82 (that is, the duty ratio of the photometry circuit 30) is 1:1. 7×32, and when the count value of the counter 20 is 3, the duty ratio is 1:7×22, and so on, each time the count value of the counter 20 increases, the duty of the photometry circuit 30 increases.
The ratio increases, and after the count value of the counter 20 reaches 12, the photometry circuit 30 operates at the duty ratio when fully opened, that is, the duty ratio of 1:7.

In Table 2, the reason why the on-time increase rate does not change when the count value of the counter 20 is 1 and 2 is that the aperture 7 actually changes after the shutter blades 1 and 2 start opening.
This is because there is a slight time lag before the counter 20 starts to open, and when the count value of the counter 20 reaches 12, the on-time increase rate is already 1 (the on-time increase rate of 1 means that the photometry is Duty when circuit 30 is fully open
This means that it operates in ratio. ) is that the shutter blade 1 actually changes after the shutter closing signal is generated.
This is because there is a slight time lag until 2 is closed, and this increase rate itself is set in accordance with mechanical or electrical characteristics.

On the other hand, in the photometric circuit 30, the transistor 310 is cut off in conjunction with the shirt release, allowing the capacitor 37 to be charged.
At the timing when is cut off, a level determined corresponding to the photocurrent flowing through the light receiving element 31 corresponding to the field brightness is applied to the base input of the transistor 36 to control the collector current of the transistor 36, Capacitor 37 is charged by the collector current of transistor 36.

In this embodiment, when the pulse generated by the pulse width conversion circuit 82 is at a low level, the transistor 35 is cut off.
As the count value of the counter 20 increases, the time ratio at which the pulses generated by the pulse width conversion circuit 82 are at a low level increases. It will rise as the blade 1 opens.

Then, the charge level of the capacitor 37 is determined by the comparator 3.
8, the output of comparator 38 is inverted.

When the output of the comparator 38 is inverted in this way, the sequence circuit 50 lowers the base of the transistor 41 to a low level, so the solenoid 5 is demagnetized.
The blade opening/closing ring 3 is rotated counterclockwise by the tension of the spring 4, and the shutter blades 1 and 2 close the aperture 7 to complete the exposure operation.

At this time, the sequence circuit 50 lowers the base level of the transistor 310 of the photometric circuit 30 and the drive voltage of the light emitting element 8b, so the photometric circuit 30 and the encoder 8 also end their operations.

By the way, as explained above, solenoid 5
The shutter blades 1 and 2 open the aperture when the shutter blades are excited, but the opening characteristics of the shutter blades 1 and 2 vary with time, changes in camera position, or in the case of electromagnetic shutters, changes in power supply voltage, etc. It cannot be denied that this is a possibility.

For example, if the curve a already explained with reference to FIG. 6 is the ideal aperture characteristic in the design of the shutter blades 1 and 2, the shutter blades l and 2 are It is quite conceivable that the opening would have the characteristics shown in the curve.

In order to give proper exposure to the film surface, it is necessary to stop the exposure when the integral value of the exposure amount reaches a value determined corresponding to the film sensitivity, so the shutter blades 1 and 2 are curved. In the case of an aperture characteristic as shown in curve a, proper exposure cannot be provided unless the exposure time is made longer than in the case of an ideal aperture characteristic as shown in curve a.

However, in this embodiment, the actual aperture characteristics of the shutter blades 1 and 2 are fed back as the count value of the counter 20 to control the duty ratio of the photometry circuit 30. Even if the integral characteristic of the exposure amount with respect to the film surface changes due to fluctuations, it is possible to make the charging characteristic of the photometry circuit 30 follow the integral characteristic of the exposure amount with respect to the film surface, and the shutter blade l.2
Accurate exposure control is possible even when the aperture characteristics of the lens vary.

That is, as the shutter blade 1 opens, the waveform shaping circuit 10
generates a pulse, and this pulse is applied to the counter 20 as a count-up clock, but the waveform shaping circuit 1
0 corresponds to the actual aperture position of the shaft blade l, so when the shaft blade 1 exhibits an aperture characteristic like the curved line in FIG. Since a slightly delayed pulse is generated as shown in FIG. 2, the rate at which the count value of the counter 20 increases also decreases. Therefore, the rate of increase in the charging speed of the capacitor 37 of the photometric circuit 30 also decreases as shown by the curve in FIG. 8, and the time required for the charging level of the capacitor 37 to match the reference level is also delayed. Exposure time is extended.

In this way, in this embodiment, even if the aperture characteristics of the shutter blades 1 and 2 change due to some reason, the charging characteristics of the photometry circuit also change in accordance with the change in the aperture characteristics. It becomes possible to provide appropriate exposure regardless of variations in the aperture characteristics of No. 2.

Next, the operation during flash photography will be explained.

When the photographer specifies the strobe mode, the sequence circuit 50 activates the EFU circuit 120 and starts charging the main capacitor (not shown).

At the same time, the sequence circuit 50 includes a distance measuring circuit 90 and an arithmetic circuit 1.
00 and the digital comparator 110 are activated.

First, the distance measuring circuit 90 is activated, and the calculation circuit 10 receives shooting distance information indicating the distance to the target object.
Give to 0. Further, the arithmetic circuit 100 is given film sensitivity information from the DX circuit 70.

In the case of a strobe with a fixed guide number, once the shooting distance and film sensitivity are determined, the F number that provides the appropriate exposure is uniquely determined, so the arithmetic circuit 100 uses the shooting distance information and film sensitivity information to obtain the correct exposure. F indicating F value
Value information is calculated, and this F value information is digitized and provided to the digital comparator 110.

When the photographer presses the shutter button after the charging of the EFU circuit 120 is completed, the shutter blades 1 and 2 open the aperture 7 in the same manner as during normal shooting, and the shutter blades 1 and 2 open the aperture 7 in a manner corresponding to the opening position of the shutter blade 1. The count value of the counter 20 is updated. Therefore, the count value of the counter 20 always corresponds one-to-one with the actual F value, regardless of the aperture characteristics of the shutter blades. Therefore, the digital comparator 110 compares the counted value of the counter 20 with the F value information generated by the arithmetic circuit 100, and at the timing when the two match, the digital comparator 110
By applying a trigger signal to 0, the strobe can be synchronized at the timing when an appropriate F value is obtained.

Incidentally, the trigger signal generated by the digital comparator lli<Q at this time is given to the sequence circuit 50, and the sequence circuit 50 uses this trigger signal to stop the exposure operation.

In addition to using a strobe as the main light source when the subject brightness is low, as mentioned above, you can also use it to match the field brightness ratio with the film's exposure range, as in so-called daytime synchronization. It may be used as an auxiliary light source for capturing images.

In such a case, if the background is bright enough, if the output of the comparator 38 is inverted at the timing when the background is properly exposed, the output of the comparator 38 will be
The output is given as a trigger signal to the EFU circuit 120 via the OR gate 130 to cause the strobe to emit light, so the background will not be overexposed.

Next, FIG. 9 is a circuit diagram showing another embodiment of the present invention, and the same elements as those in the embodiment shown in FIG. 4 are given the same reference numerals as in FIG. do.

The biggest difference from the embodiment shown in FIG. 4 is that the embodiment shown in FIG. By controlling the off-time ratio of the pulses generated by the width conversion circuit 82 and controlling the duty ratio of the photometry circuit 30, the charging characteristics of the capacitor 37 are made to follow the actual aperture characteristics of the shutter blade l. , in the embodiment shown in FIG.
By increasing the bias voltage V in response to the increase in the count value of 0, the charging characteristic of the capacitor 37 is made to follow the actual aperture characteristic of the shutter blade 1.

That is, in FIG. 9, when a photocurrent corresponding to the field brightness flows through the log diode 32 to the 5PD 31, a voltage 2 corresponding to this photocurrent is generated across the log diode 32. Therefore, a voltage is generated at the output terminal of the operational amplifier 33 by superimposing the bias voltage (1) applied to the non-inverting input terminal of the operational amplifier 33 with the voltage v2 corresponding to the photocurrent.

Then, the output voltage of the operational amplifier 33 is applied to the base of the transistor 36 to control the collector current of the transistor 36, and the capacitor 37 is charged by the collector current of the transistor 36. By increasing the voltage v1, the charging characteristics of the capacitor 37 can be made to follow the actual aperture characteristics of the shutter blade 1.

Therefore, in this embodiment, the film sensitivity information generated by the DX circuit 70 and the counter 2 indicating the opening position of the shutter blade l are used.
A count value of 0 is applied to the arithmetic circuit 83, and the output of the arithmetic circuit 83 is converted into a voltage v1 by an analog-to-digital conversion circuit 84 and is applied to the non-inverting input of the operational amplifier 33.

The specific calculation contents executed by the calculation circuit 83 vary depending on the characteristics of the photometry circuit 30 and other mechanical characteristics, but the higher the film sensitivity, the more it is necessary to increase the charging speed of the capacitor 37. - Since it is necessary to increase the charging speed of the capacitor 37 as the count value of the counter 20 increases as the chain 7 opens, the arithmetic circuit 83 multiplies the film sensitivity information added from the DX circuit 70 by the count value of the counter 20; This may be multiplied by a constant determined by the characteristics of the photometric circuit 30 or other mechanical characteristics.

Note that the content of this calculation is shown in (Equation-1).

Answer constant number×film sensitivity×count value (Formula-1) Next, the operation of the embodiment shown in FIG. 9 will be explained.

First, in the embodiment shown in FIG. 9, the operation during strobe photography is exactly the same as the embodiment shown in FIG. 4, so the description will be omitted and the operation during normal photography will be explained.

Similar to the embodiment shown in FIG. 4, when the shutter blade l.2 starts opening the aperture 7, the transistor 310 of the photometric circuit 30 is cut off and charging of the capacitor 37 starts. At the same time, the counter 20 is counted and amplified by pulses generated by the waveform shaping circuit 1O in conjunction with the opening operation of the shutter blade 1, and the count value of the counter 20 is added to the arithmetic circuit 83.

Further, film sensitivity information is added to the arithmetic circuit 83 from the DX circuit 70, and the arithmetic circuit 83 calculates (Equation-1) using this film sensitivity information and the counted value of the counter 20, and digitally converts the numerical value that becomes the answer. -Analog conversion circuit 8
Add to 4. Accordingly, the digital-to-analog conversion circuit 84 applies a voltage v1 corresponding to the output value of the arithmetic circuit 83 to the non-inverting input of the operational amplifier 33, and applies the output voltage vi of the digital-to-analog conversion circuit 84 to the output of the operational amplifier 33 by photocurrent. A voltage is generated that is a superposition of the voltage drop v2 occurring in the log diode 32. Since the count value of the counter 20 is updated in conjunction with the opening operation of the shutter blade 1,
The output voltage v1 of the digital-to-analog conversion circuit 84 rises in a stepwise manner, and the output voltage of the operational amplifier 33 also rises in a stepwise manner as shown in FIG.

The charging speed of the capacitor 37 is controlled by the output voltage of the operational amplifier 33, so when the output voltage of the operational amplifier 33 increases as the shutter blade opens, the charging speed of the capacitor 37 increases.
When the charging speed of the capacitor 37 increases and the terminal level of the capacitor 37 matches the reference level, the output of the comparator 38 is inverted, and the sequence circuit 50 completes the exposure operation in the same manner as in the embodiment of FIG.

In this way, even in the case of this embodiment, even if the amount of exposure per unit time changes ε due to the opening of the shutter blades 1 and 2, the charging speed of the capacitor 37 also changes accordingly. Appropriate exposure control can be performed regardless of variations in the aperture characteristics.

By the way, when photographing a subject under low brightness, the shutter speed naturally becomes slow, and hand-held photography may cause so-called camera shake. Therefore, when the field brightness is low compared to the film sensitivity, it is desirable to display a low brightness warning in the viewfinder to encourage flash photography or the use of a tripod. In the case of the example shown, the shutter speed is determined in accordance with the output level of the operational amplifier 33, and since the output level of the operational amplifier 33 reflects the film sensitivity and field brightness as described above, the half of the shutter button If the output level of the operational amplifier 33 is monitored during a stroke, it can be used as a so-called low brightness warning.

That is, during the half stroke of the shutter button, since the shutter blade l is not performing an opening operation, the counter 20
The count value of is 0, therefore, the value output by the arithmetic circuit 83 reflects only the film sensitivity, and the output voltage v1 of the digital-to-analog conversion circuit 84 is also determined only by the film sensitivity, and the higher the film sensitivity, the higher the value. The output voltage (1) of the digital-to-analog conversion circuit 84 becomes high. Also, 5
The voltage v2 generated across the log diode 32 by the photocurrent flowing through the pD 31 increases as the subject brightness increases.

Since the output level of the operational amplifier 33 is the superposition of the output voltage v1 of the digital-to-analog conversion circuit 84 and the voltage ■2 generated across the log diode 32 by the photocurrent, the output level of the operational amplifier 33 is The output voltage reflects only the film sensitivity and subject brightness. The final shutter speed will reflect the aperture characteristics of the shutter blade 1 introduced as the count value of the counter 20 on the output level of the operational amplifier 33 at this initial time, and it is expected that the aperture characteristics of the shutter blade 1 will vary slightly. However, it has sufficient accuracy as a low-luminance warning.

Therefore, in this embodiment, a low brightness warning can be issued using a current comparator that compares the output current of the transistor 311 and the current value of the constant current source 313.

More specifically, transistor 311 and transistor 3
12 is connected in parallel between the constant current source and the ground, and the base of the transistor 311 is connected to the output of the operational amplifier 33.
The base of transistor 312 is connected to constant current source 313. Further, the base of the transistor 314 is connected to the constant current source 313, the collector of the transistor 314 is connected to the sequence circuit 50, and the emitter of the transistor 314 is connected to the ground.

The current value of the constant current source 313 is set so that the collector current of the transistor 311 becomes low when a low brightness warning is to be issued, and the constant current is determined by the output level of the operational amplifier 33 applied to the base of the transistor 311. source 313 to collector emitter of transistor 311 (
It is designed to control the amount of current injected between the ground and ground. That is, by controlling the current flowing into the transistor 311 from the constant current source 313, the transistor 314
The transistor 314 is turned on and off by controlling the current flowing through the base of the transistor 314, and the transistor 312 functions as a diode that determines the current supply level to the transistor 314 and turns it on and off.

Therefore, when the output level of the operational amplifier 33 is lower than the level determined corresponding to the handheld limit shutter speed during the half stroke of the shutter button, the constant current source 313
Since only a portion of the current flows to the transistor 311 and the rest flows to the base of the transistor 314, the transistor 314 becomes conductive. When the transistor 314 becomes conductive, the sequence circuit 50 determines that the field brightness is low relative to the film sensitivity, and issues a low brightness warning to an LED or the like in the finder (not shown).

On the other hand, when the output level of the operational amplifier 33 is higher than the level determined corresponding to the hand-held limit shutter speed during the half stroke of the shutter button, all the current of the constant current source 313 flows into the collector of the transistor 311, and the constant current Since no current is supplied from source 313 to the base of transistor 314, transistor 314 is cut off. When the transistor 314 is cut off, the sequence circuit 50 determines that the field brightness is sufficient for the film sensitivity and does not issue a low brightness warning.

In the embodiment shown in FIG. 4, the output of the pulse width conversion circuit 82 reflects the film sensitivity and the count value of the counter 20, and in the embodiment shown in FIG. Although we have explained an example in which the sensitivity and the count value of the counter 20 are reflected, the pulse width conversion circuit 82
Alternatively, the output of the digital-to-analog conversion circuit 84 may reflect only the counted value of the counter 20, and the film sensitivity may be reflected as the reference level of the comparator 38.

〔effect〕

As explained above, according to the present invention, the charging characteristics of the photometric circuit can be varied in accordance with the aperture position of the shutter blade.
Overall, the degree of freedom in design can be significantly improved.

In addition, in the case of the present invention, since the charging characteristics of the photometry circuit are varied by detecting the actual aperture position of the shutter blade, the aperture characteristics of the shutter blade may change over time, fluctuations in power supply voltage, changes in photographing posture, etc. Even if there are fluctuations, the fluctuations in the charging characteristics of the photometric circuit follow the fluctuations in the aperture characteristics of the shutter blades.
It becomes possible to perform accurate exposure control.

Further, according to the present invention, since the opening position of the shutter blade is digitized as a count value of a counter, it is easy to introduce microcomputers, which have become particularly popular in recent years.

Furthermore, in the present invention, since the count value of the counter has a one-to-one correspondence with the F value at that point, it can also be used as a criterion for determining strobe synchronization timing in flashmatic mode, which improves exposure accuracy in flashmatic mode. It also improves.

[Brief explanation of drawings]

Fig. 1 is a mechanical diagram of a shutter mechanism according to an embodiment of the present invention, Fig. 2 is an enlarged view of the main part of Fig. 1, Fig. 3 is a sectional view cut along A in Figs. The figure is a circuit diagram of one embodiment of the present invention, Figure 5 is a circuit diagram showing an example of a waveform shaping circuit, and Figure 6 is a circuit diagram showing an example of a waveform shaping circuit.
The figure shows the aperture characteristic diagram of the shutter mechanism shown in Figure 1, Figure 7 shows the characteristic diagram showing the output pulse of the waveform shaping circuit, Figure 8 shows the characteristic diagram showing the charging waveform of the photometric capacitor, and Figure 9 shows the characteristic diagram of the present invention. FIG. 10 is a characteristic diagram showing the output voltage of a digital-to-analog conversion circuit, and FIG. 11 is an aperture characteristic diagram of a general program shutter. 1, 2...Shutter blade 5...Solenoid 8...
・Encoder 8f...Light guide 8g...
・Light guide slit 20...Counter 30...Photometering circuit 31・
・・SPD 35・・Transistor 37・
... Capacitor 82 ... Pulse width conversion circuit 84
...Digital-analog conversion circuit patent applicant Konogu 11 Co., Ltd. Agent Patent attorney Koji Murakami Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Scope of Claims] It is equipped with an integrating circuit that integrates the photocurrent flowing through the light-receiving element in accordance with the brightness of the field, and when the integrated value of the integrating circuit reaches a predetermined value, a shutter blade that also serves as an aperture blade is activated. The external photometric exposure control device is configured to be closed, and includes an aperture detection means for detecting a change in the aperture of the photographing lens, and the charging characteristic of the integrating circuit is corrected in accordance with the detection output of the aperture detection means. An external metering type exposure control device characterized by: