JPH0633453Y2 - Aperture control device for camera lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to an aperture control device for a camera lens, for example, an aperture control device suitable as a lens aperture for an industrial television camera.

"Prior Art" A camera lens aperture control device controls the lens aperture according to the brightness of a subject so that the amount of light received by the camera is constant, and has been widely known.

FIG. 5 is a schematic view showing an example of an automatic aperture control device for an industrial television camera, wherein 1 is a front lens, 2 is a rear lens, and 3 is a vidicon incorporating a photoelectric conversion circuit.

Reference numeral 4 denotes a diaphragm mechanism provided between the front lens 1 and the rear lens 2, and a driving coil 6 arranged in the magnetic field of the magnet 5.
Is fixed to the rotor 7, and the diaphragm 8 is integrally linked by the rotor 7.

Further, a spiral spring is stretched over the rotor 7 as a restoring spring, and the rotor 7 has a weak rotational force to fully close the diaphragm 8.

Although there is a diaphragm that is not fully closed, in the case of this diaphragm, it is narrowed down to the minimum diaphragm diameter by the restoring spring.

Reference numeral 9 denotes an operational amplifier as an electric signal generating circuit, which inputs the output signal of the vidicon 3 and supplies an electric signal to the drive coil 6.

The operational amplifier 9 is an amplifier circuit that compares the output signal of the vidicon 3 with a reference voltage, and has a high amplification factor that produces a slight current signal when they have a predetermined relationship, for example, the same voltage value.

In the above automatic diaphragm device, the rotor 7 is pulled back by the restoring spring before the power supply voltage is applied, and the diaphragm diameter of the diaphragm 8 is fully closed or the minimum diaphragm diameter.

When the power switch is turned on and the power supply voltage is applied under the above-mentioned condition, the vidicon 3 is in the operating condition, but the output signal is almost zero because no light enters the field light.
A reference voltage is applied as a non-inverting input to one input terminal of the operational amplifier 9.

As a result, since the operational amplifier 9 outputs a sufficient electric signal, the rotor 7 driven by the drive coil 6 is rotated against the elastic force of the restoring spring to gradually open the aperture diameter.

When the diaphragm 8 is opened, the field light that has passed through the diaphragm 8 enters the vidicon 3 and the vidicon 3 generates an output signal having a magnitude corresponding to the amount of incident light.

This output signal is applied to the other input terminal of the operational amplifier 9 as an inverting input.

However, while this output signal is lower than the reference voltage, a sufficient current signal is supplied to the drive coil 6, so that the aperture diameter of the aperture 8 increases as the rotation of the rotor 7 progresses.

The output signal increases as the aperture diameter increases and the incident field light increases, and when this output signal reaches approximately the same level as the reference voltage, the output of the operational amplifier 9 becomes It is decreased, and a slight current signal is generated.

This current signal is continuously supplied to the drive coil 6, and the rotor 7 receives the rotational driving force due to the current signal,
Since the restoring spring acts on the rotor 7, the driving force of the driving coil 6 and the pulling force of the restoring spring are in balance, and the rotor 7 stops at the rotating position.

As a result, the aperture 8 keeps the aperture diameter in the above-described state as long as the field light and other shooting conditions do not change, and makes the proper field light enter the vidicon 3.

When the field light changes, for example, when the field changes in the dark direction, the output signal of the vidicon 3 decreases,
Since the current signal from the operational amplifier 9 increases, the rotation of the rotor 7 continues and the aperture diameter increases. When the subject changes in the bright direction, the operational amplifier 9 inverts as the output signal increases, and the current signal flows in the opposite direction.
The rotor 7 is pulled back, and the aperture diameter of the aperture 8 is reduced.

[Problems to be Solved by the Invention] As described above, in this type of aperture control device, the rotor 7 stops at a rotational position where the driving force by the driving coil 6 and the pulling force of the restoring spring are balanced, and When the power switch is opened to cut off the power supply voltage of the diaphragm device, the current signal of the drive coil 6 is cut off and the rotor 7 is rotated to the initial position by the pulling force of the restoring spring. Be reactivated. As a result, the diaphragm 8 is fully closed or reduced to the minimum diaphragm aperture.

By the way, in order to surely return the throttle 8 to the fully closed state or the minimum aperture as described above, it is necessary to use a restoring spring having a considerably strong elastic force. It is necessary to set a large current signal in order to increase the driving torque.

However, it is not preferable in terms of power consumption to continuously supply such a large current signal for balancing with the restoring spring.

From this fact, many of these types of diaphragm control devices use a restoring spring having a weak elastic force such as a spiral spring.
Therefore, the diaphragm 8 may not return to the squeezed state, and may remain stationary with the diaphragm aperture having a predetermined size.

In addition, since the restoring spring is weak, the device may move so as to open even when the device receives a weak impact, and the device may be stretched and left as it is with a predetermined aperture size.

If the iris 8 is stationary with the aperture open, high-intensity light such as sunlight will enter the camera, resulting in a seizure damage accident. Therefore, when the device is not powered, the iris 8 must be reliably cut off. That is, it is necessary to make it fully closed or the minimum aperture size.

"Means for solving the problem" In consideration of the above-mentioned situation, the present invention uses a weak restoring spring, while surely returning the diaphragm to the squeezing position, and
The purpose is to develop an aperture control device that does not open even if it receives some impact.

Therefore, in the present invention, a rotor for driving an aperture, which has a magnet and a coil around a hollow shaft through which light passes and which is rotated by electromagnetic force, is provided. In the aperture control device that is linked to the minimum aperture by returning to the rotor, a magnetic body that returns the rotor to the initial position of rotation by receiving the attraction force of the magnet when the aperture is linked near the minimum aperture is used in this rotor. We propose a diaphragm control device for a camera lens, which is characterized by being provided.

When the throttle is interlocked by the rotor and contracts to the minimum aperture and its vicinity, the restoring spring has the weakest elastic force.
Since the magnetic body is attracted by the magnet to rotate the rotor to the initial position all at once, the diaphragm surely returns to the squeezing position, and the magnetic body receives a constant attraction force when no power is supplied. The rotor will be kept in the initial position even if it receives some impact, and the diaphragm will not move.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is an example in which the present invention is embodied as a lens diaphragm control device for an industrial television camera, and this drawing is an exploded perspective view of a diaphragm mechanism. In this figure, the same members as those in the conventional example shown in FIG. 5 are designated by the same reference numerals.

In the figure, 10 is a fixing plate made of a magnetic material for fixing the magnet 5, and 11 is a magnetic path forming plate, which are fixed to a hollow shaft (not shown) for the optical path with a certain distance. Alternatively, only the magnetic path forming plate 11 may be fixed to the hollow shaft, and the fixed plate 10 may be fixed to the magnetic path forming plate 11.

The elongated hole 11a provided in the magnetic path forming plate 11 penetrates the connecting pin 8a of the diaphragm 8, and the pin 8a is fitted into the locking hole 7a provided in the rotor 7.

The rotor 7 is positioned between the fixed plate 10 and the magnetic path forming plate 11, and is rotatably attached to the hollow shaft.

The four drive coils 6 arranged on the rotor 7 are connected to each other and are supplied with power via a spiral spring as described later.

Power is supplied via a spiral spring.

The spiral spring 12 is a conductive material having a weak restoring force, one end of which is fixed to the copper foil portion of the printed circuit board 13 provided on the rotor 7 and the other end of which is made of a conductive material. It is fixed to the member 14.

The spiral spring 12 forms a restoring spring that restores the rotor 7 to the initial rotation position, that is, to the position where the diaphragm 8 is fully closed or has a minimum diaphragm aperture.

Further, the copper foil portion of the printed circuit board 13 and the drive coil 6 are electrically connected to each other, and the support member 14 and the spiral spring are connected.
The drive coil 6 is supplied with power via 12.

The projecting member 15 provided on the rotor 7 is a magnetic body, and in this embodiment, it contacts one end of the left magnet 5 when the diaphragm 8 is fully closed or has a minimum diaphragm aperture as shown in FIG. It is set to be in the position.

The magnetic body 15 may be a magnet, and can be formed of other metal material, and the arrangement thereof is
When the diaphragm 8 is fully closed or has a minimum diaphragm aperture, it may be provided on the rotor 7 that is in contact with one end of the left or right magnet 5 and is close to that end. Further, the number of the magnetic body 15 is not limited to one, and another magnetic body may be provided at a symmetrical position of the magnetic body 15 with the center point of the rotor 7 as a symmetrical point.

Next, the operation of the above diaphragm control device will be described.

When the diaphragm control device is in the non-power-supply state, it is attracted by the attraction force of the magnet 5 of the magnetic body 15 as shown in FIG. 3, and the diaphragm 8 is closed at this initial rotation position of the rotor 7. State, that is, fully closed or the minimum aperture size.

In the above-mentioned stopped state of the apparatus, the rotor 7 does not rotate unless it receives an impact force greater than the attraction force of the magnet 5 to the magnetic body 15. In general, such a large impact force is rarely received, so that the diaphragm 8 is reliably kept at the diaphragm cutting position.

When power is supplied to the diaphragm control device, a current signal is applied to the drive coil 6 and drive torque is generated in the rotor 7, as in the conventional example.

Since the rotor 7 is kept in the initial rotation position by the magnetic body 15 which receives the attraction force of the magnet 5, the drive torque that overcomes the attraction force causes the rotor 7 to start to rotate in the direction of the arrow in the figure.

After the rotor 7 starts to rotate, the current signal of the drive coil 6 decreases due to the appropriate incident light on the vidicon 3 as in the above-described conventional example, and the rotation of the rotor 7 is driven by the current signal. The balance is stopped by the balance between the force and the restoring force of the spiral spring 12, and the diaphragm 8 is maintained at a predetermined diaphragm aperture.

When the current signal to the drive coil 6 is cut off by opening the power switch or the like, the rotor 7 is pulled back by the restoring force of the spiral spring 12, and when the diaphragm 8 is fully closed or interlocked to near the minimum diaphragm aperture, the magnetic material 15 Is attracted by the magnet 5. After that, regardless of the restoring force of the spiral spring 12, the rotor 7 is swung back to the initial position of rotation by the magnetic force acting on the magnetic body 15 at once, and the throttle 8 is fully closed or surely throttled to the minimum aperture diameter. Controlled.

FIG. 4 is a graph in which the horizontal axis represents the size of the aperture of the diaphragm 8 and the vertical axis represents the restoring force of the rotor 7, and in this figure, the straight line OA including the dotted line is a spiral spring.
12, the two-dot chain line 16 is the attraction force acting on the magnetic body 15, and the solid line 17 is the restoring force by the spiral spring 12 and the magnetic body.
Each of the combined forces with the adsorption force acting on 15 is shown.

Although the aperture control device for the industrial television camera has been described in the above embodiments, the present invention can be similarly implemented as an aperture control device for other cameras, photographing devices and the like.

[Advantages of the Invention] As described above, in the present invention, a magnetic body is provided in the rotor that is rotated by electromagnetic force to control the diaphragm, and when the diaphragm is linked near the minimum diaphragm, the magnetic body is attracted by the attractive force of the magnet. Since the rotor is configured to return and rotate, the diaphragm surely returns to the minimum diaphragm position, and a constant holding force is applied at the minimum diaphragm position, so the state of the minimum diaphragm is maintained even if the device receives some impact. To be kept.

Further, since a restoring spring having a weak elastic force can be used, it is not necessary to continuously supply a large current signal to the drive coil, which is advantageous in terms of power consumption.

Further, since the present invention can be constructed only by providing the rotor with a magnetic material, the construction is simple and suitable for productivity.

[Brief description of drawings]

1 is an exploded perspective view showing an aperture mechanism of an aperture control device according to an embodiment of the present invention, FIG. 2 is a partially enlarged perspective view of the aperture mechanism, and FIG. 3 is an enlarged view of a rotor included in the aperture mechanism. FIG. 4 is a plan view, FIG. 4 is a graph showing the relationship between the drive torque of the rotor and the aperture diameter, and FIG. 5 is a simplified diagram showing a conventional aperture control device for an industrial television camera. 1 ... Front lens, 2 ... Rear lens 5 ... Magnet, 6 ... Drive coil 7 ... Rotor, 8 ... Aperture 10 ... Fixed plate, 11 ... Magnetic path forming plate 12 ... Spiral spring , 15 ... Magnetic material.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-53-36227 (JP, A) JP-A-59-115507 (JP, A) JP-A-59-116630 (JP, A) JP-A-59- 116631 (JP, A) Actual development Sho 59-90927 (JP, U)

Claims (2)

[Scope of utility model registration request] 1. A diaphragm driving rotor which has a magnet, a coil, etc. around a hollow shaft through which light passes and which is rotated by an electromagnetic force. The rotor is returned to an initial rotation position by a restoring force of a spring member. In this way, in the aperture control device that interlocks with the minimum aperture, the rotor is provided with a magnetic body that returns the rotor to the initial position of rotation by receiving the attraction force of the magnet when the aperture is interlocked near the minimum aperture. A diaphragm control device for a camera lens, characterized in that 2. The spring member is a spiral spring provided on a rotor, and the rotor is rotated and returned by the spring member, and the diaphragm is interlocked near the minimum diaphragm so that the magnetic body attracts the magnet. The diaphragm control device for a camera lens according to claim (1), wherein the utility model registration is configured to receive force.