JP3618804B2 - Light control device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a light amount adjusting device such as a diaphragm device of an imaging device.
[0002]
[Prior art]
In a diaphragm device of a video camera, a diaphragm blade is driven to open and close by a motor (hereinafter referred to as an IG meter) as a drive source, and the aperture diameter of the diaphragm blade is detected by, for example, setting the rotation angle of the rotor of the IG meter to a hole. It is detected by a detector composed of elements. Then, the detection information from the detector is output to a control circuit, and the aperture diameter of the aperture blade can be controlled to an arbitrary value by feedback control, and an imaging device such as a video camera capable of shooting in aperture priority mode and program mode is provided. Proposed.
[0003]
The IG meter of this image pickup apparatus will be described generally below.
[0004]
FIG. 4 is a block diagram of this IG meter. Reference numeral 10 denotes a drive coil wound around a yoke (not shown), and reference numeral 11 denotes a magnet rotor integrally formed with a permanent magnet magnetized in two poles. The magnet rotor 11 is rotatable about a shaft 11a sandwiched between two poles of the yoke and supported by a bearing (not shown). Reference numeral 12 denotes a diaphragm blade drive plate that rotates integrally with a magnet rotor 11 that is press-fitted and fixed to a shaft 11a, and pins 12a and 12b are provided at both ends thereof. A spring 13 biases the diaphragm blade drive plate 12 clockwise in the drawing.
[0005]
14a and 14b are stoppers for restricting the rotation of the diaphragm blade drive plate 12, and are provided at the same angular positions in the clockwise and counterclockwise directions with respect to the Y axis. These stoppers 14a and 14b move the diaphragm blade drive plate 12 within a range of approximately 30 ° in the clockwise and counterclockwise directions with respect to the Y axis perpendicular to the X-axis direction in which the diaphragm blades, which will be described later, total 60 °. It is restricted to be rotatable. The aperture blades 15a and 15b have openings 15c and 15d, respectively, and are coupled with the pins 12a and 12b of the aperture blade drive plate 12 and the holes 15e and 15f, so that the aperture blade drive plate 12 rotates. It is held by a mechanism (not shown) so as to translate in the X direction in opposite directions. Reference numeral 16 denotes a hall element that detects a rotation amount of a permanent magnet integrally provided in the rotor 11 as a voltage. The excitation magnetic pole of the yoke is disposed opposite to the Y axis, and the magnetic pole of the magnet rotor 11 faces the excitation magnetic pole when the diaphragm blade is located at the center of the movable range.
[0006]
Here, when no current is passed through the drive coil 10, the diaphragm blade drive plate 12 is urged clockwise by the spring 13 and is positioned at the position shown in FIG. 4A by the stopper 14a. When a current is passed through the drive coil 10, the yoke is excited by the current, and an electromagnetic force is generated by interaction with the two-pole magnetized permanent magnet of the magnet rotor 11. For example, it rotates counterclockwise.
[0007]
As the magnet rotor 11 rotates, the biasing force of the spring 13 also increases, and the rotation of the magnet rotor 11 stops at a position where the magnetic interaction between the yoke and the magnet rotor 11 and the biasing force of the spring 13 are balanced. With this rotation, the diaphragm blade 15a is translated in the X (−) direction and the diaphragm blade 15b is translated in the X (+) direction, and the aperture 15c of the diaphragm blade 15a and the opening 15d of the diaphragm blade 15b intersect each other. An opening diameter is formed. When the current passed through the drive coil 10 is further increased, the magnet rotor 11 rotates to a position where the position of the diaphragm drive plate 12 is regulated by the stopper 14b, and the diameter of the diaphragm opening is maximized as shown in FIG. become.
[0008]
FIG. 5 shows the relationship between the rotation amount of the magnet rotor 11 and the output voltage of the Hall element 16.
[0009]
A predetermined current is passed through the hall element 16 in advance, and the hall element 16 is disposed, for example, at a position where the magnetic flux density of the magnet rotor 11 is penetrated. When the magnet rotor 11 is rotationally moved in a direction in which the magnetic flux density penetrating the hall element 16 increases or decreases from the magnet rotor 11, the Hall voltage increases or decreases linearly in proportion thereto. In FIG. 5, the range of the state in which the rotation amount (degree) of the magnet rotor 11 and the output voltage (V) of the Hall element 16 are inversely proportional to the linearity is set.
[0010]
Next, the amount of rotation of the magnet rotor 11 and the amount of movement of the aperture blades 15a and 15b are defined by the following equations.
[0011]
S = L {cos θ1-cos (θ1 + θ2)}
Here, S: movement amount of the diaphragm blade 15a in the X (−) direction movement amount L of the diaphragm blade 15b in the X (+) direction; length of the arm of the diaphragm blade driving plate 12 (in FIG. 4A) Show)
θ1; an angle formed by the X axis and the diaphragm blade drive plate 12 when no current flows through the drive coil 10 (initial position) (shown in FIG. 4A)
θ2 is the rotational angle of movement of the aperture blade drive plate 12 from the initial position.
[0012]
Conventionally, θ1 = 60 ° and θ2 = 0 ° to 60 °, and FIG. 6 shows the relationship between the amount of rotation of the magnet rotor 11 and the amount of movement of the aperture blades 15a and 15b obtained under these conditions.
[0013]
From the relationship between the amount of rotation of the magnet rotor 11 and the output voltage of the Hall element 16, the relationship between the amount of rotation of the magnet rotor 11 and the amount of movement of the aperture blades 15a and 15b, and the shape of the openings 15c and 15d of the aperture blades 15a and 15b. The relationship between the output voltage of the element 16 and the aperture opening FNO is as shown in FIG. As apparent from this figure, since the relationship between the Hall element output voltage and the opening FNO is 1: 1, the current applied to the drive coil 10 is feedback controlled with respect to the output voltage of the Hall element 16 to thereby restrict the aperture FNO. Can be controlled to a free value, and a photographing apparatus capable of photographing in the aperture priority mode and the program mode becomes possible.
[0014]
[Problems to be solved by the invention]
However, as is clear from FIG. 7 described above, the relationship between the output voltage of the Hall element and the aperture opening FNO is not linear, and the Hall element output with respect to the change in the aperture FNO toward the small aperture side (the side with the larger value of the aperture FNO). The amount of change in voltage decreases rapidly. Therefore, when the current applied to the drive coil 10 is controlled with respect to the Hall element output voltage with the same accuracy, there is a problem that the aperture accuracy on the small aperture side is lowered. Conversely, in order to control with FNO with the same accuracy, it is necessary to perform feedback control with respect to the Hall element output voltage with higher accuracy on the small aperture side. There will be a problem of complexity.
[0015]
For example, when it is considered using FIG. 7 to control the target diaphragm FNO with two stages of aperture accuracy, the difference in Hall element output voltage between F11 that is two stages lower than the small diaphragm side F22 and F22. Is about 0.15V, the difference of the Hall element output voltage between F5.6 of the relatively large diaphragm and F2.8, which is two steps lower than F5.6, is about 0.65V. It can be seen that the control accuracy is more than 5 times.
[0017]
An object of the invention according to the present application is to provide a light amount adjusting device that reduces the amount of movement of the diaphragm blades on the small diaphragm side and improves the diaphragm control accuracy on the small diaphragm side of the diaphragm blades.
[0018]
[Means for Solving the Problems]
The structure which realizes the object of the invention according to the present application includes a magnet rotor, a drive coil for rotating the magnet rotor when energized, a center fixed to the output shaft of the magnet rotor, and engaging portions formed at both ends. Drive plate, two diaphragm blades that are respectively engaged with engaging portions at both ends formed on the drive plate, and move in opposite directions by the rotation of the drive plate, and the rotation of the drive plate A stopper for restricting the range and a detecting means for detecting the rotation angle of the magnet rotor, and controlling the energization to the drive coil based on the detection information from the detecting means to adjust the aperture diameter of the diaphragm in the light amount adjusting device, the stopper is the aperture with respect to the axis perpendicular to the moving direction of the blades, the rotating axis inclined by a predetermined angle as viewed in the direction in which the drive plate is rotated in small aperture side of the drive plate Characterized by restricting the range of rotation of said drive plate so that the center of the circumference.
[0019]
In this configuration, the rate of change in the amount of movement of the light shielding member such as the aperture blade with respect to the amount of rotation of the magnet rotor can be made as small as possible.
[0020]
The configuration for realizing the object of the second invention according to the present application is characterized in that, as described in claim 2, in claim 1, the predetermined angle is shifted to the aperture opening diameter side.
[0021]
In this configuration, even when a light-shielding member having the same aperture shape as that of the conventional light amount adjusting device is used, the accuracy of control on the small aperture side is greatly improved as compared with the conventional example.
[0022]
【Example】
FIG. 1 shows an embodiment of a light amount adjusting device according to the present invention.
[0023]
Reference numeral 10 denotes a drive coil wound around a yoke (not shown), and 11 a magnet rotor integrally formed with a permanent magnet. The magnetic pole of the yoke faces the magnet rotor 11 at the Y-axis position in the figure. Has been placed. The magnet rotor 11 is rotatable around a shaft 11a supported by a bearing (not shown). Reference numeral 12 denotes a diaphragm blade drive plate having an arm length L that rotates integrally with a magnet rotor 11 press-fitted and fixed to a shaft 11a, and pins 12a and 12b are provided at both ends thereof. A spring 13 biases the diaphragm blade drive plate 12 clockwise in the drawing. Reference numerals 14 a and 14 b denote stoppers that restrict the rotation of the diaphragm blade driving plate 12.
[0024]
These stoppers 14a, clockwise rotation of the blade drive plate 12 14b is squeezed, the center line Z axis rotated by θ in the clockwise direction with respect to the Y axis Cartesian in the X-axis direction of movement of the diaphragm blades described later・ The angle is approximately 30 ° in the counterclockwise direction, and is regulated to be rotatable within a total angle of 60 °.
[0025]
Reference numerals 15a and 15b denote diaphragm blades, which have respective openings 15c and 15d (the opening shape is the same as that of the conventional example), and are coupled to the pins 12a and 12b of the diaphragm blade drive plate 12 through holes 15e and 15f. As the diaphragm blade drive plate 12 rotates, it is held by a mechanism (not shown) so as to be translated in opposite directions in the X direction. Reference numeral 16 denotes a hall element that detects a rotation amount of a permanent magnet integrally provided in the magnet rotor 11 as a voltage.
[0026]
Here, when no current is passed through the drive coil 10, the yoke is not magnetized. Therefore, the diaphragm blade drive plate 12 is urged clockwise by the spring 13, and the stopper 14a causes (a) in FIG. As shown in FIG. 4B, the lens is positioned at a position inclined clockwise with respect to the Y axis.
[0027]
When a current is passed through the drive coil 10, the yoke is excited by the current, and the magnet rotor 11 is caused by the magnetic interaction between each magnetic pole of the yoke and the two-pole magnetized permanent magnet of the magnet rotor 11 facing the yoke. Electromagnetic force is generated in the aperture, and the diaphragm blade drive plate 12 rotates counterclockwise. As the magnet rotor 11 rotates, the urging force of the spring 13 also increases, and the rotation of the magnet rotor 11 stops at a position where the magnetic interaction between the yoke and the magnet rotor 11 and the urging force of the spring 13 are balanced. The plate 12 stops. With this rotation, the diaphragm blade 15a is translated in the X (−) direction and the diaphragm blade 15b is translated in the opposite directions in the X (+) direction, and the opening 15c of the diaphragm blade 15a and the opening 15d of the diaphragm blade 15b intersect. Thus, the aperture diameter is formed.
[0028]
As the current passed through the drive coil 10 is further increased, the magnetism of the yoke increases, and the magnet rotor 11 continues to rotate further due to the magnetic interaction with the two-pole magnetized permanent magnet of the magnet rotor 11, and the diaphragm blade drive plate 12 is restricted by a stopper 14b provided on the opposite side to the stopper 14a with respect to the Z axis and at a symmetrical angular position, and rotates to a position inclined substantially counterclockwise with respect to the Y axis. At this time, the aperture diameter is maximized as shown in FIG.
[0029]
As the magnet rotor 11 rotates, the magnetic flux density penetrating from the magnet rotor 11 through the Hall element 16 changes, and the Hall voltage of the Hall element 16 changes linearly in proportion to the amount of rotation. Here, the relationship between the rotation amount of the magnet rotor 11 and the output voltage of the Hall element 16 is the same as in the conventional example of FIG. 5, and the rotation amount (degree) of the magnet rotor 11 and the output voltage (V) of the Hall element 16 are It is set to a state range that is inversely proportional to the linearity.
[0030]
Next, the amount of rotation of the magnet rotor 11 and the amount of movement of the aperture blades 15a and 15b are defined by the following equations.
[0031]
S = L {cos θ3-cos (θ3 + θ2)}
Here, S: movement amount of the diaphragm blade 15a in the X (−) direction movement amount L of the diaphragm blade 15b in the X (+) direction; length of the arm of the diaphragm blade driving plate 12 (in FIG. 1A) Show)
θ3: an angle formed by the X axis and the diaphragm blade drive plate 12 when no current flows through the drive coil 10 (initial position) (shown in FIG. 1A)
θ2 is the rotational angle of movement of the aperture blade drive plate 12 from the initial position when a current is passed through the drive coil 10.
[0032]
Here, if θ = 30 ° (angle formed by the Y axis and the Z axis), θ3 = 30 ° (90 ° -30 ° -30 ° = 30 °) · θ2 = 0 ° -60 °, and under these conditions The relationship between the required amount of rotation of the magnet rotor 11 and the amount of movement of the aperture blades 15a and 15b is shown in FIG. Here, the relationship between the amount of rotation of the magnet rotor 11 and the amount of movement of the diaphragm blades 15a and 15b is such that the angle between the diaphragm blade drive plate 12 and the X axis is smaller than that of the conventional example, that is, the diaphragm opening. 15c and 15d are slanted on the small aperture side, that is, the moving amount of the aperture blades 15a and 15b is small.
[0033]
The relationship between the amount of rotation of the magnet rotor 11 and the output voltage of the Hall element 16, the relationship between the amount of rotation of the magnet rotor 11 and the amount of movement of the diaphragm blades 15a and 15b, and the shapes of the openings 15c and 15d of the diaphragm blades 15a and 15b (opening) The relationship between the output voltage of the Hall element 16 and the aperture opening FNO is as shown in FIG.
[0034]
As is apparent from this figure, the relationship between the output voltage of the Hall element and the aperture FNO is 1: 1, and the relationship between the output voltage of the Hall element and the aperture opening FNO is also relatively linear. Feedback control is possible with respect to the output accuracy of the same Hall element on the large aperture side.
[0035]
For example, considering that the target aperture FNO is controlled with two stages of aperture accuracy using FIG. 3, the difference in Hall element output voltage between F11 which is two stages lower than the small diaphragm side F22 and F22. Is 0.65V, whereas the difference in output voltage of the Hall element between F5.6, which is two steps lower than F5.6 and F5.6, which is relatively large aperture, is 0.45V. It suffices to perform feedback control with the same reasonable accuracy.
[0036]
In the above embodiment, the case of θ = 30 ° has been described, but it is obvious that the larger θ is, the more advantageous the control accuracy on the small aperture side.
[0037]
【The invention's effect】
According to the present invention, it is possible to reduce the amount of movement of the diaphragm blades on the small aperture side, and it is possible to improve the control accuracy on the small aperture side .
[Brief description of the drawings]
1A and 1B are schematic configuration diagrams showing an embodiment of the present invention, in which FIG. 1A shows a state before rotor rotation driving, and FIG. 1B shows a state after rotor rotation driving;
FIG. 2 is a graph showing the relationship between rotor rotation angle and diaphragm blade movement according to an embodiment of the present invention.
FIG. 3 is a graph showing a relationship between an opening FNO and a Hall element output voltage according to an embodiment of the present invention.
4A and 4B are schematic configuration diagrams showing a conventional technique, in which FIG. 4A shows a state before rotor rotation driving, and FIG. 4B shows a state after rotor rotation driving;
FIG. 5 is a graph showing the relationship between the rotor rotation angle of the present invention and the conventional Hall element output voltage.
FIG. 6 is a graph showing a relationship between a conventional rotor rotation angle and a diaphragm blade movement amount.
FIG. 7 is a graph showing a relationship between a conventional opening FNO and a Hall element output voltage.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Drive coil 11 ... Rotor 12 ... Diaphragm blade drive plate 13 ... Spring 14 ... Stopper 15 ... Diaphragm blade 16 ... Hall element

Claims (1)

A magnet rotor,
A drive coil that rotates the magnet rotor by energization;
A drive plate having a center fixed to the output shaft of the magnet rotor and engaging portions formed at both ends;
Two diaphragm blades that respectively engage with engaging portions at both ends formed on the drive plate and move in opposite directions by rotation of the drive plate;
A stopper for restricting the rotation range of the drive plate;
Detecting means for detecting the rotation angle of the magnet rotor,
In a light amount adjusting device for controlling energization to the drive coil based on detection information from the detection means and adjusting a diaphragm aperture diameter,
The stopper is tilted by a predetermined angle with respect to the axis perpendicular to the moving direction of the diaphragm blades so that the driving plate rotates in the direction of the small diaphragm. A light amount adjusting device characterized by restricting a rotation range of the drive plate.

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