JPS6236647A - Diaphragm device for camera - Google Patents

Abstract

PURPOSE:To simplify the constitution of the titled device and to reduce the size of the device by detecting the displacement of a diaphragm on the basis of the change of magnetic flux density of a meter itself for opening/closing a diaphragm blade and manually adjusting the quantity of photographing light. CONSTITUTION:A voltage corresponding to the change of the magnetic flux density of a movable magnet M in a movable magnet type servo motor is detected by a magnetic field detecting element D in a detecting part II, applied to resistors R5, R6 in a detecting voltage amplifying part III and amplified by a comparator Q1. The amplified detecting voltage and the divided voltage of a common terminal of a sliding resistor VR4 to be varied in accordance with a required diaphragm value are applied to resistors R8, R9, the detecting voltage of the element D is increased/decreased in accordance with the resistance ratio of the resistor R8 to R9 and the controlled voltage is outputted to the manual terminal of an auto-manual changing switch SW1. Thus, the constitution of the device is made simple and the size of the device is made small, as compared with a case that a mechanical interlocking mechanism and a sliding resistance or a photocoupler are provided and the reversion from a manual operation to an automatic operation can be easily attained without changing a reference voltage.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is built into a camera such as a video camera or a cine camera, uses a movable magnet type therpometer as a driving source, and manually adjusts the amount of shooting light by switching from outside the camera. The present invention relates to an aperture device for a camera.

[Technical background of the invention]

Generally, this type of camera uses an automatic aperture device that can automatically detect changes in external light and control the aperture, but sometimes it is possible to set the aperture freely regardless of external light. Special photography 1 For example, when photographing a person standing by a window, automatic aperture devices tend to adjust the diaphragm according to the amount of light outside the window. There are cases where you can arbitrarily set the aperture according to the situation and take pictures with proper exposure.

Conventionally, when such manual adjustment was required, an aperture device was generally installed on the lens barrel, so an automatic/manual switching knob was installed on the lens barrel, etc., and a lever member was operated from outside the camera. A mechanical adjustment mechanism is provided to directly clamp the diaphragm drive member of the diaphragm device to drive the diaphragm, but it is possible to adjust the resistance value at that time by directly interlocking a sliding resistance or a photocoupler with the diaphragm itself or the diaphragm drive member. A device was provided for electrically capturing and adjusting changes in the aperture due to changes in the aperture or changes in the amount of light.

[Issues in the technical background]

However, with the former method, which uses a mechanical adjustment mechanism, the connection part may slip, making it difficult to operate, and the operability is particularly poor, resulting in increased space and complexity of the camera structure, making it difficult to implement. I hated missing things. The latter method that uses sliding resistance is an electrical detection method,
Although it has good operability, it is easily damaged due to poor contact between the sliding parts, and an excessive load is applied to the drive source.While the structure is extremely simple and inexpensive, the movable magnet type is driven by a minute current and has low driving force. It is impossible to operate with a servometer and it is inevitable to use an expensive motor that is uneconomical. Therefore, it is difficult to provide a small and inexpensive device, and a device that uses another photocoupler is oversized. Since there is no load applied to the drive source, an inexpensive movable magnet type servometer can be used, but on the other hand, it is necessary to provide an adjustment lever etc. to vary the light intensity, making the structure complex and requiring an external device to be introduced into the photocell. Consideration must be given to blocking light and the effects of the own light source on the image pickup tube and film, and there are disadvantages such as high power consumption due to the use of a light source. However, there were problems such as a complicated structure and an increase in the size of the device.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned drawbacks.

The amount of photographing light is manually adjusted by capturing the displacement of the diaphragm from changes in the magnetic flux density of the meter itself that drives the diaphragm blades to open and close, and the above-mentioned special mechanical adjustment mechanism, sliding resistor, or photocoupler is provided. The main object of the present invention is to provide an aperture device for a camera that is unnecessary, has a simple structure, is small in size, and is inexpensive.

[Summary of the invention]

In order to achieve the above objects, the present invention employs a so-called movable magnet type servometer as a drive source for opening and closing the aperture blades, and a magnetic field for detecting changes in magnetic flux density of the movable magnet. a detection element, a manual adjustment circuit that increases or decreases the output voltage of the magnetic field detection element at a desired rate by external operation, and a manual adjustment circuit that increases or decreases the difference between the output voltage of the manual adjustment circuit and a preset reference voltage. It consists of a differential amplification circuit that drives a moving magnet type servometer.
This system utilizes changes in the magnetic flux density of the meter itself to capture changes in the aperture and manually adjust the amount of photographing light.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A camera aperture device according to the present invention will be explained below with reference to the accompanying drawings.

First, to explain the servo mechanism of the device, the first
The figure is a schematic diagram of its mechanism, and Figure 2 shows a cross-sectional view of its driving source. The type servometer is attached to a base plate (not shown).The installation consists of a yoke Y fixed to a plate U, a pair of coil frames G that fit inside this yoke Y, and a fixed coil wound around this coil frame G. It consists of a coil and a movable magnet M rotatably supported in a space formed inside the pair of coil frames G. In particular, the movable magnet M has N and S as shown in Figure 81-2. It is magnetized in the radial direction shown, and when a positive current is applied to the drive coil t2 (see FIG. 3), for example, it rotates clockwise, and when a negative current is applied, it rotates counterclockwise.

Moreover, its operating range is limited to within 180 degrees, which is very different from a normal motor, and as mentioned above, the structure is extremely simple, so it is much cheaper than a motor. The aperture F is the rotation axis M of the movable magnet M of the servometer.
1 is connected and driven via an interlocking arm M2 and an interlocking bin MS, and 2 is fixed to a base plate (not shown) and has a supporting shaft F+'.
A ring receiver F'+ having a ring receiver F'+, a drive ring F2 that is slidably supported by the ring receiver Fl and has a drive pin F2' implanted therein, and a drive ring F2 that is fitted to the support shaft F+' and the drive pin F2'. diaphragm blades ps (only one of the plurality of blades is shown). D is a magnetic field detection element consisting of a Hall element or the like that detects the magnetic flux density of the movable magnet M. The two poles of N.

For example, a pair of coil frames around which a fixed coil K is wound, or It is provided on the yoke into which the coil frame fits. Therefore, the magnetic field detection element 1 generates an output voltage corresponding to the rotating state of the movable magnet M.

Next, the control circuit for controlling the servo mechanism of the aperture device will be explained using the circuit diagram shown in FIG.

It is roughly divided into a power supply section I, a detection section (2), a detection voltage amplification section (2), a manual operation section IV, and a servometer drive circuit section V.

The power supply section I consists of a power supply E and a main switch SWo.The detection section ■ mainly consists of a magnetic field detection element D (for example, a Hall element, etc.) that detects changes in the magnetic flux density B of a movable magnet M of a movable magnet type servometer. .

A constant current IC is connected between a and b that activates the magnetic field detection element.
It consists of resistors R1 and R2 for causing the magnetic field detection element to flow, and a sliding resistor VR+ provided as a means of compensating for an error voltage that occurs if the position of the Hall electrode of the magnetic field detection element is unbalanced, and resistors R5 and R4. A detection voltage related to a change in the magnetic flux density B of the movable magnet M is output from between c and d of the magnetic field detection element.

The detection voltage amplification section (■) connects the detection voltage of the detection section (■) to the resistor R5.
is received by R6, and this is sent to the input terminal of comparator Q (8L
(9) Amplify the detected voltage input during the period. The sliding resistor VR4 is used to adjust the gain of the comparator Q1, and the sliding resistor VR2 and the resistor R7 constitute a circuit that feeds back changes in the output of the comparator Q4 to the input terminal (8).

The manual (especially referred to when only manual is referred to) operation section 1v includes an automatic-manual changeover switch SW1 and a variable sliding resistance V whose resistance value corresponds to a desired aperture value (F value).
The detection voltage of the amplified magnetic field detection element outputted to the output terminal (1) of the comparator Q1 of the detection voltage amplification section (2) and the aforementioned sliding voltage are The divided voltage at the common end of the resistor VR4 is related to the resistor R6 and R9, and the detected voltage of the magnetic field detection element is increased or decreased in proportion to the resistance ratio of the resistors R8 and R9.
The voltage is output to the manual end of the automatic-manual changeover switch SW+. between, and for example using an operational amplifier,
The ratio of the input and output, that is, the gain, may be arbitrarily set using the sliding resistor VR4, and the output may be output as a composite voltage.The servometer drive circuit section V includes resistors R12 and R13, photographing conditions, etc. A reference bias circuit outputs a reference voltage consisting of a sliding resistance VRs arbitrarily set in advance at input terminal (a) + (
9), the comparator Q2 amplifies the difference.
And the output terminal of this comparator Q2 (2L (3) +
Transistor T r+ activated by the outputs from (4) and (5).

T r 2. A drive coil 12 which is configured in a movable magnet type servometer having a differential amplification circuit consisting of T r s and Tr4 and an aperture mechanism and rotates a movable magnet M which receives current from the differential amplification circuit; A braking coil to brake the rotation of the movable magnet M! , consists of.

2. Since the aperture F and the movable magnet M of the aperture device using the movable magnet servometer as a driving source according to the present invention are connected via a connecting member, they perform a series of operations, and the movable magnet M
The change in the output of the servometer drive circuit V is fed back to the detection section (2) through the servometer drive circuit (2).

The detection section (2) in FIG. 3 has a circuit configuration when using a constant current input type magnetic field detection element.

The detecting section 2' in FIG. 2 has a circuit configuration when a constant voltage input type magnetic field detecting element D' is used.

Therefore, a series of operations of the camera aperture device of the present invention will be explained using the state diagram shown in FIG. still.

Figure 5 shows the rotational position θ of the movable magnet M of the servometer, the magnetic flux density B of the movable magnet M involved in the magnetic field detection element at that time, the output voltage ■ output due to the involvement of this magnetic flux density B, and the movable magnet M at that time. This graph shows the relationship between the aperture value (F value) at rotational position 5. First, let us assume that the Fr state in Fig. 5 is the state to be set by electric manual operation, and the Fr state changes from automatic exposure to manual exposure. This is the state immediately after switching to manual operation, and F
The α state is a state in which the manual knob is rotated to set the Fr state, but the state is exceeded. Conversely, even in a state where the Fr state has gone too far just after the Fα state, the same circuit operation can be performed.

Therefore, when SW and o are first made conductive, the circuit is activated and the common point of the automatic-manual changeover switch 8W+ on the manual operation section ■ is in a conductive state with point A on the automatic side, and the servometer is automatically driven by changes in external light. So-called automatic exposure control, which operates the circuit section V, is performed.

Therefore, operate the automatic-manual changeover switch SW+ and the sliding resistor VRa on the manual operation section (■).

The common dot is switched from the automatic side A to the manual side M to make it conductive, and the sliding resistor VR4 is adjusted to the desired manual aperture value Fr using the aperture value (F value) scale or the like.

However, since the state immediately after switching is the Fr state, the magnetic flux density B that is involved in the magnetic field detection element resistance at the rotational position θr of the movable magnet M is Br, so the output voltage of the detection unit 11 changes due to the magnetic field detection element resistance at that time. is Va. This output voltage is amplified by the detection voltage amplifying section (2) and can be outputted. The output of the above-mentioned sliding resistance VR4 of the manual operation section ■
It is involved in the divided voltage outputted by the resistors R6 and R9 and outputted to the manual side M.

This output is input to the comparator Q2 together with the reference voltage of the reference bias circuit of the servometer drive circuit section V, and the amount of difference between the Fa state to be set and the Fr state at that time is compared and output. The circuit is operated to supply current to the drive coil 12 and move the movable magnet M to Fr.
The rotational position in FIG. 5 is rotated from σr to θβ direction. When the Fr state is reached, the movable magnet M changes its rotational position to θβ, and at that time, the magnetic flux density B involved in the magnetic field detection element changes to Bβ, and the output of the detection section H becomes Vβ.

This output voltage Vβ is compared with the reference voltage of the reference bias circuit of the servometer drive circuit section V by the detection voltage amplifying section (2) and the manual operation section (2) using the comparator Q2, as described above, but at this time, the manual operation section (2) Since the output of the comparator Q2 is set to be equal to the reference voltage by operating the sliding resistor VR4 using the manual operation described above, the output of the comparator Q2 makes the differential amplifier circuit stable and sets the drive coil 1 to be equal to the reference voltage.
It is possible to cut off the supply of current to the movable magnet M, stop the rotation of the movable magnet M, and set the aperture value (F value) to the manual setting value Fβ.

Then, the rotational force of the movable magnet M is strong enough to overcome the braking action of the braking coil 11, and the manually set aperture value Fr state may be exceeded and the state becomes Fa state. At this time, the rotational position θ of the movable magnet M is 0, and the magnetic flux density B involved in the magnetic field detection element becomes Bα, so the output voltage of the detection section ① becomes Va. 9 The divided voltage by the sliding resistor VR4 The comparator Q2 of the servometer drive circuit section V
The voltage is input to the input of the reference bias circuit together with the reference voltage of the reference bias circuit and compared.

In this case, the input terminal of comparator Q2 in the Fr state (
With respect to the input voltage application state between 8) + (9), an inverted input voltage is applied with the Fr state as the border, and therefore the output state of the comparator Q2 is the same as that of the differential amplification circuit, contrary to the Fr state. In order to control this, the direction of the current flowing through the drive coil 12 is reversed, and the direction of rotation of the movable magnet M is reversed.

Then, the rotational position 0 of the movable magnet M changes from θ4 to θβ, and the magnetic flux density B involved in the magnetic field detection element also changes from Bα to Bβ, and the output of the detection section ■ changes from Vα to ■β due to the output of the magnetic field detection element. The output is involved in the amplification circuit and is fed back to the comparator Q2 for comparison, thereby becoming an output for keeping the differential amplification circuit in a stable state, cutting off the current supply to the drive coil 12 and causing the movable magnet M to rotate. This allows the aperture value to be set and maintained at the manually set aperture value by stopping the operation of the aperture device, eliminating unnecessary power consumption.

The control circuit described above includes a manual adjustment circuit that increases or decreases the output voltage of the magnetic field detection element at a desired rate by external operation, and the difference between the output voltage of this manual adjustment circuit and a preset reference voltage. This is because the movable magnet type servometer is driven by a differential amplification circuit that increases the amplification.

For example, when configuring a circuit so that the output voltage of a magnetic field detection element is input directly to a servometer drive circuit, and the reference voltage of the servometer drive circuit is externally manipulated to compare the variable voltage, switch from manual to automatic. While it is necessary to return the reference voltage to the reference value in the auto state before manual operation each time, this operation is unnecessary and the operation required for switching between auto and manual is very simple. If the base voltage setting circuit of the servometer drive circuit is configured to be switched between automatic and manual settings separately, both input terminals of the differential amplifier will be electrically floated at the same time at the time of switching, and in this case, Problems such as large current flowing through the servometer and damaging the servo mechanism often occur, but it is possible to prevent both input terminals of the differential amplifier from floating electrically at the same time (this problem has also been solved). There is.

〔Effect of the invention〕

As explained above, the present invention detects the magnetic flux density of the movable magnet of the drive meter connected to the aperture blade with a magnetic field detection element,
This is because the output is increased or decreased to a desired ratio by a manual adjustment circuit, and the difference between the output and a preset reference voltage is used to drive the drive meter to manually adjust the amount of photographing light.

The device is simpler than the conventional mechanical interlocking mechanism, sliding resistance, or photo ratchet.

Not only is it small and inexpensive, but it also has features such as not changing the reference voltage during manual operation, making it easy to return from manual to auto mode.

[Brief explanation of drawings]

Fig. 1 is a schematic mechanical diagram of the diaphragm device, Fig. 2 is a cross-sectional plan view of the same as above, Fig. 3 is an electric manual diaphragm control servo circuit according to the present invention, and Fig. 4 is another implementation of the detection section (2) in Fig. 1. 5(a) and 5(b) are explanatory diagrams showing the relationship between the diaphragm and the movable magnet for explaining the present invention. ■...Power supply section, II...Detection section, II...
Detection voltage amplification section, ■...Manual operation section, V,...
Servometer drive circuit section, D...magnetic field detection element 2
M...Movable magnet, L...Fixed coil, F...Aperture, B...Magnetic flux density. Figure 1 Figure 2 Kbe

Claims (1)

[Scope of Claims] In an aperture device that connects a movable magnet that rotates in opposition to a coil to an aperture blade and drives the aperture blade to open and close, (a) a drive having a movable magnet that drives the aperture blade to open and close; meter. (b) A magnetic field detection element that detects changes in magnetic flux density of the movable magnet. (c) A manual adjustment circuit that increases or decreases the output voltage of the magnetic field detection element by external operation. (d) A differential amplification circuit that amplifies the difference between the output voltage of the manual adjustment circuit and a preset reference voltage to drive the drive meter. A camera aperture device having the configurations (a) to (d) above.