JP2523610B2 - Aperture drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm drive device for a camera, especially for a surveillance camera for crime prevention, phenomenon observation, and the like.

[Conventional technology]

In such a surveillance camera, as a diaphragm driving device that automatically changes the diaphragm value of a taking lens according to the brightness of a subject, conventionally, a diaphragm member is driven according to the output of a diaphragm driving circuit having a photoconductive element. The one that operates the stepping motor, the one that drives the diaphragm blades by utilizing the shake of the exposure meter, and the diaphragm sensor that controls the servomotor for diaphragm driving by the position sensor that detects the rotation angle of the diaphragm member. There are those that operate members.

[Problems to be solved by the invention]

However, in such a conventional aperture driving device, the first one requires the aperture driving system to be reset and returned to the origin every time photographing is performed due to the characteristics of the stepping motor, so that the brightness of the subject does not change. Even if the aperture value is the same as that used in the previous shooting, the diaphragm member must be driven from the origin each time, so there is a risk of taking a lot of time and effort for shooting.

In the second type, the deflection angle of the meter must be adjusted by adjusting the urging force of the return spring and the magnetic force of the magnet. Therefore, the adjustment is troublesome, and the driving force is weak. It cannot be used except when directly driving two diaphragm blades, and there is a problem that the deflection angle changes due to the influence of dust and the like even with time.

Further, the third type requires a position sensor for detecting the operating angle of the diaphragm and a servomotor for driving, and thus has a drawback that the outer diameter of the lens barrel becomes significantly large.

It is an object of the present invention to provide a diaphragm driving device that can solve such conventional problems.

[Means for solving problems]

Therefore, the diaphragm drive device according to the present invention includes a toroidal coil having an iron core, and a diaphragm member that changes the diaphragm diameter by rotating concentrically with the toroidal coil.
A permanent magnet having both NS magnetic poles fixed to the outer peripheral portion of the diaphragm member and facing the inner peripheral portion of the toroidal coil at 180 degrees apart from each other; The first output unit connected to the second and third terminals respectively, which outputs a voltage signal that rises in proportion to the output of the photometry unit and is saturated at a predetermined voltage, and the output of the photometry unit up to the above predetermined voltage A second output section that outputs a voltage signal that maintains the predetermined voltage and that drops in proportion to the output when the voltage exceeds the predetermined voltage, and a third output section that outputs a constant voltage lower than the predetermined voltage. And are provided.

[Work]

With the above configuration, the magnetic field corresponding to the current flowing in each part of the winding is generated in the toroidal coil by the voltage from each output part, and the diaphragm member is rotated according to the output of the photometry part. It is possible to change the aperture diameter.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a toroidal coil in which a winding L is wound around an annular iron core 2. 2, 3rd terminal 1a, 1
b, 1c are pulled out.

Numeral 3 is concentric with the toroidal coil 1 and is a well-known equally-spaced diaphragm member configured to change the diaphragm value in proportion to the rotation angle by rotating. Magnetic pole plates 4a, 4b, which are fixed permanent magnets and are provided on both NS magnetic poles 180 degrees apart from each other, along the circumferential direction,
Each is opposed to the inner peripheral portion of the toroidal coil 1.

Also, 11, 12, and 13 are the first, second, and third of the toroidal coil 1.
Are the first, second and third output sections respectively connected to the terminals 1a, 1b and 1c, the first and second output sections 11 and 12 are variable, and the third output section 13 is fixed. Is.

FIG. 2 is a circuit diagram showing a configuration example of the first and second output units 11 and 12.

Reference numeral 14 is a photometric section comprising a photoconductive element having a condenser lens 15 disposed at the front and a signal output circuit thereof, and 16 is a zener voltage Vz = V.
A Zener diode 17 (predetermined voltage) is an operational amplifier for inputting the output voltage E of the photometry unit 14 through the resistor R ₁ , and forms a voltage follower circuit. With these, the first output unit 11 Are configured.

Reference numeral 18 is a zener diode having a zener voltage Vz = 2V, which makes the power supply voltage Vcc a constant voltage 2V (twice the predetermined voltage V) via the resistor R ₄ . Reference numeral 19 denotes an operational amplifier, which inputs a constant voltage of 2 V to the positive side input terminal via the resistor R ₃ and outputs a predetermined voltage via the output voltage E of the photometric unit 14 to the negative side input terminal via the resistor R ₂ and the diode 20. V is input, and these constitute the second output section 12.

Next, the operation of the embodiment thus configured will be described.

When the light from the subject reaches the photometric unit 14 through the condenser lens 15, a voltage E proportional to the amount of light is generated.

As a result, the first voltage signal E ₁ is output from the first output unit 11.
However, the second voltage signal E ₂ is output from the second output section 12, respectively.

The first voltage E ₁ is the voltage E _{1 as} shown by the solid line in FIG.
The voltage rises in proportion to the output voltage E of the photometry unit 14 from 0 until the voltage reaches a predetermined voltage V equal to the zener voltage Vz of the zener diode 16, but when the voltage E reaches the predetermined voltage V, the zener diode 16 becomes conductive. Since the input voltage of the operational amplifier 17 is clamped at V, the output voltage signal E ₁ of the first output section 11 is saturated and remains at V even if the voltage E rises thereafter.

In addition, the second voltage E ₂ output from the output unit 12 in FIG.
Is the output voltage E of the photometric unit 14 as shown by the broken line in FIG.
Since the diode 20 conducts and the predetermined voltage V is input to the operational amplifier 19 from 0 to the predetermined voltage V, E ₂
= 2V-V = V is output as a predetermined voltage, and after the voltage E reaches the predetermined voltage V, the diode 20 becomes non-conducting so that the voltage E is input to the operational amplifier 19 and becomes E ₂ = 2V-E. Voltage E
Falls in proportion to.

On the other hand, the third voltage E ₃ is always constant regardless of the value of the voltage E.

When such voltages are applied to the toroidal coil 1 from the terminals 1a, 1b, 1c shown in FIG. ₁ , currents I ₁ , I ₂ , I ₃ flow in the respective portions of the winding L of the toroidal coil 1, Magnetic fields H ₁ , H ₂ and H ₃ corresponding to respective currents are formed inside thereof (see FIG. 4).

 Now, assuming that the magnetic field is H, the current is I, and the number of coil turns is N, H∝IN is established.

The combined magnetic field H ₀ due to the currents I ₁ , I ₂ , and I ₃ is the vector sum of the magnetic fields H ₁ , H ₂ , and H ₃ as shown in FIG. 5, so that H ₀ = H ₁ + H ₂ + H _3, that is, the diaphragm member 3 is rotationally driven in the vector direction of the synthetic magnetic field H ₀ .

Here, as is clear from FIG. 4, each magnetic field H ₁ , H ₂ , H ₃
Since the angle between each vector is 60 degrees, the combined magnetic field H ₀ , the combined rotation angle θ ₀ , the combined magnetic field H _{12 of} the magnetic fields H ₁ and H ₂ , and the combined rotation angle θ ₁₂ are calculated taking these into consideration. And becomes like this.

From the formula A, when | H ₁ | = | H ₂ | + | H ₃ | is satisfied, the rotation angle of the diaphragm member 3 becomes the magnitude of the magnetic field H ₂ when the combined rotation angle θ ₀ is ₀ to 60 degrees. In proportion, and when | H ₂ | = | H ₁ | + | H ₃ | is satisfied, the rotation angle of the diaphragm member 3 is equal to the magnitude of the magnetic field H ₁ when the combined rotation angle θ ₀ is 0 to −60 degrees. It turns out to be proportional.

As a result, the aperture member 3 can be rotated by a total of 120 degrees, and even if the rotation angle per EV is as large as 19 degrees with a shooting lens having an aperture value of 2.8 to 22, a total rotation angle of 114 degrees is sufficient, The rotation angle of the diaphragm member is sufficient.

Here, each calculated value when | H ₁ | = | H ₂ | + | H ₃ | = 1 is shown in the table below.

FIG. 6 illustrates this.

Further, each calculated value when | H ₂ | = | H ₁ | + | H ₃ | = 1 can be similarly obtained.

In the above embodiment, the third terminal 1c of the toroidal coil 1 is connected to the third output section 13 of constant voltage.
If an alternating current is applied to the output section 13 to drive the third terminal 1c for modulation, the precision of the diaphragm can be further improved.

〔The invention's effect〕

As described above, the diaphragm driving device according to the present invention is
A diaphragm member is rotatably provided concentrically with the toroidal coil,
A permanent magnet is fixedly provided on the outer peripheral portion of the diaphragm member, the winding of the toroidal coil is divided into three equal parts, and respective terminals output voltage signals that change in opposite directions according to the output of the photometric portion. Since the first and second output sections and the third output section that outputs a constant voltage are respectively connected, it is necessary to reset the aperture drive system each time a picture is taken, as in the case of using a conventional stepping motor. There is no need for quick shooting.

In addition, since a much stronger driving force can be obtained without having to make adjustments unlike the one using a meter, a general iris diaphragm can be used as it is, and there is no fear of aging.

Further, unlike the one using a servo motor, there is no need for a position sensor, there is no need to increase the outer diameter of the lens barrel, and an accurate diaphragm driving device can be supplied at low cost.

[Brief description of drawings]

FIG. 1 is a configuration and circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of the photometric unit and first and second output units of the same, and FIG. , A characteristic diagram showing the relationship between the output voltages of the third output parts, FIG. 4 is an explanatory diagram showing each magnetic field generated in the toroidal coil, FIG. 5 is a vector diagram showing the combined magnetic field, and FIG. 6 is each magnetic field. FIG. 6 is a diagram showing the relationship between the rotation angle of the diaphragm member and the rotation angle of the diaphragm member. 1 ... Toroidal coil, 2 ... Iron core 3 ... Drawing member, 4 ... Permanent magnet 11 ... 1st output part, 12 ... 2nd output part 13 ... 3rd output part, 14 ... Metering unit

Claims (1)

(57) [Claims] 1. A toroidal drive device for changing an aperture according to the output of a photometric unit, a toroidal coil having an iron core, an aperture member for changing the aperture diameter by rotating concentrically with the toroidal coil, and the aperture. A permanent magnet having NS magnetic poles fixed to the outer periphery of the member and facing the inner periphery of the toroidal coil 180 degrees apart from each other, and the first and second windings of the toroidal coil divided into three equal parts. A first output unit connected to each of the third terminals and outputting a voltage signal that rises in proportion to the output of the photometric unit and is saturated at a predetermined voltage; and the output of the photometric unit up to the predetermined voltage. Is a second output section that outputs a voltage signal that maintains the predetermined voltage and drops in proportion to the output when the predetermined voltage is exceeded, and a third output that outputs a constant voltage lower than the predetermined voltage. And a section are provided. Ri drive.