JPH03216630A - Light quantity controller - Google Patents

Abstract

PURPOSE:To smoothly actuate a stop blade and to save power by setting the winding diameter of the coil part of a torsion coil spring equal to or above the open diameter of a diaphragm and concentrically disposing the coil part on the optical axis of a photographing lens. CONSTITUTION:The winding diameter of the coil part of the torsion coil spring 24 is set equal to or above the open diameter of the diaphragm and the coil part is concentrically disposed on the optical axis of the photographing lens. Therefore, the load fluctuation of the spring is kept nearly constant even when the deflection angle of the spring 24 is varied by turning a ring 14, and the ring 14 smoothly turns. Since the load fluctuation of the spring is a little, the energizing force of the spring 24 on the diaphragm open side is made weak and the power for driving a servometer 22 is kept to the minimum. Thus, the stop blade 26 is smoothly actuated and the output of the driving means is made small, so that the power is saved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a light amount control device, and particularly in an aperture device that uses electromagnetic force to change the aperture diameter of the aperture blades, a coil spring is biased in the direction in which the blades close. Regarding the light amount control device.

[Conventional technology]

Generally, an aperture device for a camera is configured so that the diameter of the aperture changes by controlling the aperture blades by rotating a ring. The ring is provided with a servometer and a coil spring, and when the servometer is driven to rotate the ring against the biasing force of the coil spring, the aperture blades are controlled to open the aperture diameter. Furthermore, when the servometer is turned off, the ring is rotated by the biasing force of the coil spring in a direction opposite to the direction in which the servometer is driven, and the aperture blades are controlled so that the diameter of the aperture is closed. In this way, when the power is turned off, the amount of light to the imaging section is blocked by the coil spring.

[Problem to be solved by the invention]

However, conventional coil springs have a small coil diameter and a large variation in spring load with respect to the deflection angle of the coil spring, so there is a problem that a constant biasing force cannot be applied to the ring and the aperture blades cannot operate smoothly. be. Furthermore, since the servometer needs to be set so as to be able to handle the spring load at the maximum deflection angle, a servometer with a large output is required and there is a problem in that power saving cannot be achieved.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a light amount control device that can smoothly operate the aperture blades and save power.

[Means to solve problems]

In order to achieve the above object, the present invention provides an amount of light to open the aperture blades, which are biased in the closing direction by a torsion coil spring, to a desired aperture diameter by using an aperture driving means against the biasing force of the torsion coil spring. The control device is characterized in that the winding diameter of the coil portion of the torsion coil spring is greater than the aperture opening diameter, and the coil portion is disposed concentrically with the optical axis of the photographing lens.

[Effect]

According to the present invention, since the winding diameter of the coil portion of the torsion coil spring is set to be equal to or larger than the opening diameter of the aperture, it is possible to reduce the variation in spring load with respect to the deflection angle of the torsion coil spring. Therefore,
The biasing force of the torsion coil spring can be kept approximately constant and the opening side of the aperture can be kept small. This allows smooth rotation of the ring and smooth operation of the aperture blades. Furthermore, since the biasing force of the torsion coil spring can be reduced, the output of the driving means can be kept low.

〔Example〕

Preferred embodiments of the light amount control device according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of a light amount control device according to the present invention, and FIG. 2 is a sectional view taken along the line AA in FIG. The light amount control device 10 has a main body member 12, which is formed in an annular shape and is arranged concentrically around the optical axis L, and a ring 14 is rotatably fitted into the main body member 12. The outer peripheral edge of the fitted ring 14 is connected to the main body member 12
The ring 14 is rotatably supported by the main body member 12 because the ring 14 is in contact with the regulating member 15 that is engaged with the ring 14 .

A protrusion 14a is formed on the ring 14, and the protrusion 14a
A pin 18 is arranged in the elongated hole 16, and the pin 18 is connected to a drive shaft 20a of a servometer 22 via a lever 20. This servometer 22 is attached to the camera body or body member 12 (not shown). Note that a motor may be used instead of the servometer 22.

Further, a protruding piece 14b is formed on the inner peripheral surface of the ring 14,
One end of a torsion coil spring 24, which is fitted into the main body member 12 with a gap while being concentrically arranged, is locked to the protruding piece 14b. The other end of this torsion coil spring 24 is locked in a recess formed in the main body member 12.

Drive dowels 28, 28, . . . are implanted in the ring 14 for applying rotational driving force to the respective aperture blades 26, 26, . Incidentally, support dowels (not shown) for rotatably supporting each aperture blade 26 are implanted in the main body member 12, and the support dowels protrude so as to be approximately flush with the drive dowels 28. Therefore, each aperture blade 26, 26...
* is inserted into the drive dowels 28, 28... and support dowels (not shown), and then the second
The blade holding plate 30 shown in the figure is attached.

The operation of the light amount control device according to the present invention configured as described above will be explained.

First, when opening the aperture diameter, the servometer 22 is driven to rotate the drive shaft 22a counterclockwise (in the direction of arrow 8 in FIG. 1). Therefore, the ring 14 rotates clockwise (in the direction of arrow B in FIG. 1) via the pin 18 against the biasing force of the torsion coil spring 24. When the ring 14 rotates clockwise, the aperture blades 26, 26, . . . are controlled to open the aperture diameter via the drive dowels 28, 28, .

In this case, since the winding diameter of the torsion coil spring 24 is designed to be larger than the opening diameter of the aperture, even if the bending angle of the torsion coil spring 24 changes due to rotation of the ring 14, the spring load fluctuation remains approximately constant. maintained in condition.

Therefore, the ring 14 rotates smoothly. Furthermore, since the spring load fluctuation is small, the biasing force of the torsion coil spring on the aperture opening side can be lowered, and the electric power for driving the servometer 22 can be kept to a minimum.

Next, when the power to the servometer 22 is turned off, the ring 14 rotates counterclockwise (in the direction of arrow C in FIG. 1) due to the biasing force of the torsion coil spring 24, and as the ring l4 rotates, the drive dowel 28, 28... also rotate in the counterclockwise direction, so each aperture blade 26, 26... is controlled and the aperture diameter is closed.

〔Effect of the invention〕

As explained above, according to the light amount control device according to the present invention, it is possible to reduce the variation of the spring load with respect to the bending angle of the torsion coil spring, so that the biasing force of the biasing material is kept approximately constant, and the aperture opening side can be kept low. Therefore, the operation of the diaphragm blades can be made smoother, and the output of the driving means can be reduced, so that power can be saved.

[Brief explanation of drawings]

FIG. 1 is a plan view showing one embodiment of the light amount control device according to the present invention, and the second leap is a sectional view taken along the line AA in FIG. 1. 1O...Light amount control device, 12... main body parts,
14...Ring, 14a...Protrusion part,
l 8... Bin, 2 2... Servometer, 2 4... Torsion coil spring, 2 6... Aperture blade.

Claims (1)

[Scope of Claims] A light amount control device in which aperture blades urged in a closing direction by a torsion coil spring are opened to a desired aperture diameter by an aperture driving means against the urging force of the torsion coil spring, A light amount control device characterized in that the coil portion of the torsion coil spring has a winding diameter equal to or larger than an aperture opening diameter, and the coil portion is disposed concentrically with the optical axis of a photographing lens.