JPH0546009Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a lens device that can perform focus adjustment or magnification adjustment by extending the lens.

[Prior Art] Lens barrel extension mechanisms for lens focus adjustment and zoom magnification adjustment are broadly classified into linear type and helicoid type. Many techniques have been proposed in which these drives, which were conventionally performed manually, are performed using actuators such as electromagnetic driving force. However, those using electromagnetic driving force have a complicated structure and require a considerable volume for installation, which has been an obstacle to reducing the size and weight of lens devices.

In addition, in order to enable direct manual operation,
There were many unresolved problems, such as the need for a clutch mechanism to protect the actuator.

On the other hand, shape memory alloys are attracting attention as new actuators, and applications are also being attempted in the field of optical equipment. For example, JP-A-61-
No. 144631 proposes a technology in which a shape memory alloy is formed into a coil spring shape as a drive source for the aperture device, and the aperture ring is driven by memorizing the contracted shape of the coil spring.

[Problems to be solved by the invention] However, these technologies are limited to miniaturizing the actuator part, and because a coil spring-like actuator with a corresponding thickness is provided inside the lens device, the endoscope It is necessary to secure a space between the barrel and the outer lens barrel for installing the actuator, and the objective of reducing the size and weight of the lens device cannot be sufficiently achieved.

[Means for Solving the Problems] The present application provides a lens device that extends a lens by rotationally driving a lens barrel using a linear contraction force of a shape memory alloy wire formed into a linear shape.

[Example] This will be explained below with reference to the drawings.

Figure 1 shows one of the lens drive devices according to the invention of the present application.
A partially cutaway perspective view showing the embodiment, and FIG. 2 are reference views for explaining the driving principle.

The lens device is an outer lens barrel 3 that is attached to a camera, etc.
and an inner lens barrel 2 engaged by a helicoid mechanism 8.

A Teflon resin coating layer 5 is applied to the outer surface of the inner barrel 2, and the coated portion has a linear shape whose one end 7 engages with the inner barrel and the other end 6 engages with the outer barrel 3. A shape memory alloy wire 4 is wound. This linear shape memory alloy wire is memorized in advance as a shape in the longitudinal direction to have a length that is equal to or shorter than the required length of the winding wire in the helicoid's maximum unrolled state.
In addition to memorizing the length, the inner diameter of the inner barrel 2 is larger than the outer diameter of the outer barrel 2.
It is desirable to memorize the shape of the coil wound so that the outer diameter is smaller than the inner diameter of the coil.

The inner barrel 2 is biased in the retracting direction by a charging means such as a coil spring 9 shown in FIGS. 2A and 2B, and the wound shape memory alloy wire 4 is biased by this biasing force. It is deformed (elongated). This charging means is preferably a shape memory alloy wire wire having a composition that exhibits superelastic properties at room temperature, which is wound around the inner barrel so as to oppose the shape memory alloy wire of the present invention. .

The shape memory alloy wire 4 is connected to an electric circuit so that a voltage is applied to both ends thereof, as shown in FIGS. 2A and 2B. The switch SW is controlled by a control means such as an automatic focus mechanism or a zoom mechanism (not shown).
When closed, a current flows through the shape memory alloy wire 4, which self-heats due to its own internal resistance,
When the temperature for restoring the memorized shape is reached by this heating, the shape memory alloy wire 4 resists the tension of the charging means 9 and restores to its original memorized shape.
Then, since both ends 6 and 7 are engaged with the outer barrel and the inner barrel, respectively, the inner barrel begins to rotate as the line length contracts, and the inner barrel is extended by the helicoid mechanism. (Figure 2B). When the photographing is completed and the electricity is turned off and the temperature drops, the tension of the charging means 9 described above stretches (deforms) the shape memory alloy wire 4, drives the inner lens barrel, and returns the lens barrel to the extending start position. (Figure 2A).

(Example 1) The outer diameter of the inner tube is 50 mm, and the inner tube is 2 mm in 1/4 turn.
For an unrolling lens device, the retracted length of the shape memory alloy wire is required to be approximately 40 mm. Assuming that the practical displacement of a shape memory alloy wire with a diameter of 0.5 mm is 10%,
The total length of the wire is required to be approximately 400 mm, which is enough to be wrapped around the inner lens barrel in two and a half turns. In addition, the thickness of the wire is only about 0.5mm,
Requires almost no space for installation.

[Effect] The lens driving device of the present invention has a linear shape memory alloy wire wound around the outside of the inner lens barrel so that the linear contraction force directly drives the inner lens barrel to rotate. There is no need for any special space and there is almost no increase in weight, as only there is enough space for arranging the shape memory alloy wire and wiring.

By forming the shape memory alloy into a coil with an inner diameter larger than the outer diameter of the inner barrel and an outer diameter smaller than the inner diameter of the outer barrel, the coil comes into contact with the inner and outer barrels when the shape is restored. This reduces friction loss.

By coating the outer surface of the inner tube with Teflon resin, which has excellent heat resistance and electrical insulation, there is less friction loss between the wire and the outer surface of the inner tube due to elongation (deformation) of the shape memory alloy wire during charging. It is preferable because there is no lock due to aperture. Furthermore, electrical leakage to the lens barrel can be prevented.

By using a superelastic metal wire wound around the inner lens barrel as the charging means, almost no space is required for disposing the charging means as well as the driving means for the shape memory alloy wire, thereby increasing the size of the lens device.

The invention of the present application does not require a mechanism for transmitting driving force, so there is very little chance of failure, etc., and it provides a small, lightweight, and highly reliable lens driving device.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing one embodiment of the present invention. Figure 2 is a reference diagram showing the configuration. DESCRIPTION OF SYMBOLS 1... Lens device, 2... Inner barrel, 3... Outer barrel, 4... Shape memory alloy wire, 5... Teflon resin coating layer, 6, 7... Engaging portion, 8...
Helicoid mechanism section, 9...Charge means, 10...
...Power supply, SW... switch.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a lens device equipped with a helicoid type feeding mechanism consisting of an outer lens barrel and an inner lens barrel, a shape memory alloy wire is wound around the outside of the inner lens barrel, and one end of the wire is wound around the inner lens barrel. 1. A lens device characterized in that the other end of the cylinder is disposed in engagement with an outer lens barrel, and the lens barrel is rotationally driven by energizing and heating the shape memory alloy wire to cause linear contraction. (2) The lens device according to claim 1, wherein at least the outer surface portion of the inner barrel around which the shape memory alloy wire is wound is coated with Teflon resin.