JPH0256643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a lens barrel suitable for a zoom lens for a video camera and the like.

[Background of the invention]

As shown in FIG. 5, the zoom lens is constructed by combining a zoom section 1 with a predetermined number of lenses, a connecting tube 2, a master section 3 with a predetermined number of lenses, and a mount 4.

By the way, zoom lenses used in video cameras are composed of 14 to 15 lenses and nearly 50 lens barrel parts, making them complex and large, making them extremely heavy and expensive. . In particular, the large size and weight of a zoom lens poses a problem in that it reduces the operability of a video camera equipped with the zoom lens, and it has been desired to streamline the structure and reduce the weight of the zoom lens. Among the components of zoom lenses, especially the lens barrel parts,
Since the number of parts is large and the weight ratio is large compared to other parts, there was an urgent need to rationalize the structure and reduce the weight.

As a measure to meet these demands, it may be possible to integrally mold lens barrel parts, which were conventionally made from metal turnings, from resin materials to reduce the number of parts and make them lighter; however, in general, resin molded parts teeth,
The accuracy required for high-end lenses such as zoom lenses cannot be obtained, and at present, the movable frames of pocket camera lens barrels and zoom lens lens barrels are made of resin at best. be.

By the way, even if there is such a problem, making the lens barrel of a zoom lens from resin is a very effective means from the viewpoint of reducing the number of parts and weight, and its realization is highly desired.
However, especially when the lens barrel (master barrel) 6 of the master unit 3 is made of a resin molded product, the master lens group consisting of 7 to 8 lenses 5 held by this lens barrel 6 is Since it controls the imaging performance of the lens, there is a large variation in the inner diameter of the lens receiving part in the lens barrel 6.
The lens 5 shakes within the lens barrel 6, making it impossible to obtain the required resolution performance.

This point will be explained in more detail by taking as an example the master section 3 consisting of seven lenses: five lenses in the front group with an outer diameter of about 30 mm and two lenses in the rear group with an outer diameter of about 18 mm.

In this master section 3, the maximum allowable amount of lens eccentricity among lenses with an outer diameter of 30 mm is approximately
There is a lens that must fit within 30 μm, and the inner diameter of the lens barrel 6 that holds such a lens can have an allowable error from the specified value of 30 mm to a maximum of 60 μm (30 μm×2). Furthermore, from the viewpoint of ease of inserting the lens into the lens barrel 6, it is common to allow a clearance of 30 μm in diameter between the lens barrel 6 and the lens. Therefore, the inner diameter of the lens barrel 6 for the above lens is +30 μm from the specified value of 30 mm.
It is necessary to increase the size within the range of 60 μm. The above is
This is a case where there is no error in the outer diameter of the lens, but in reality, the manufacturing error in the outer diameter of the lens is limited to approximately ±10 μm. Considering this point, the inner diameter of the lens barrel 6 should be changed from the above specified value. It is necessary to set it within the range of +30μm to +50μm.

However, the error in the inner diameter of the lens barrel 6 is 20 μm.
(50μm-30μm) is extremely difficult to set, and even if it were possible, it would be difficult to manufacture many high-precision lens barrels like the one above from one mold due to mold wear. It is not possible. Therefore, the master barrel in conventional zoom lenses has generally been made of turned metal.

[Object of the invention] The object of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
To provide a resin-molded lens barrel with high lens mounting accuracy.

[Summary of the invention]

In order to achieve this object, the present invention provides a plurality of protruding stripes integrally provided on the inner wall of the lens barrel along a circumference centered on the central axis of the lens barrel. The lens is characterized in that the lens is held by closely fitting into the stripe.

[Embodiments of the invention]

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

FIG. 1a is a partial longitudinal sectional view showing an embodiment of a lens barrel according to the present invention, and FIG.
7 is an inner wall, and 8 is a protruding stripe.

In this embodiment, a master barrel of a zoom lens is shown as an example, and as shown in FIG. 1A, a protruding stripe 8 is integrally provided on the inner wall 7 at the lens mounting position. The protruding streaks 8 are as shown in FIG.
A plurality of lenses (three in the figure) are provided at equal intervals in the circumferential direction around the central axis O, and the lens 5 is held in close fit with these protruding stripes 8.

FIG. 2 is a perspective view showing a specific example of the protruding stripe 8, and shows the state before the lens is attached.

In this specific example, the protruding stripe 8 is elongated in the insertion direction (arrow B) of the lens to be attached, and has a strip shape with an inclined side surface at least on the lens insertion port side, and the thickness of the protruding strip 8 is the same as that of the lens to be inserted. It is set so that it abuts all of the protruding stripes 8 provided with. Therefore, before the lens is inserted, the distance from the central axis O (FIG. 1b) to the protruding stripe 8 is smaller than the radius of the lens.

When the lens is inserted in the direction of arrow B, the lens 5 hits the inclined side surface of the protruding stripe 8 as shown in FIG. The outer diameter of the In this way, the outer diameter portion of the lens 5 is tightly fitted into each of the protruding stripes 8 and is held within the lens barrel.

The protruding stripes 8 are formed in a well-balanced manner in position, shape, and size. Therefore, when the inserted lens is pushed into the protruding stripes 8,
All the protruding stripes 8 are shaved in a well-balanced manner so that the lens can be attached with an amount of eccentricity below the allowable amount.

Therefore, now the protruding stripe 8 has a thickness of 80 μm and a width of 80 μm.
When manufacturing a lens barrel so that the diameter is 240μm, the aforementioned outer diameter is 30mm and the manufacturing error is +0μm to +
When attaching a 20 μm lens, the inner diameter of this lens barrel is determined by the diameter of the clearance between the lens and the inner wall of the lens barrel from the viewpoint of lens installation work.
Since it is necessary to set it to 30 μm, the specified 30 mm is required for lenses with a manufacturing error of at least +20 μm.
It must be 50 μm (30 μm + 20 μm) larger than. In this case, the clearance for a lens with a manufacturing error of +0 μm is 50 μm or more in diameter.

On the other hand, if the range in which the inner diameter of the lens barrel is larger than the specified value is 160 μm (80 μm x 2) or less, the above lens may hit all three protruding stripes 8, but there is a margin. 130μm or less. In other words, increase the inner diameter of the lens barrel by +
Increase the size in the range of 50μm to +130μm.

In this way, when the inner diameter of the lens barrel is set, the maximum eccentricity of the lens is 65 μm (130 μm ÷
2), which is more than twice the lens holding tolerance specification (30 μm) and the resolution performance deteriorates significantly. On the other hand, in the above embodiment, by forming the protruding stripes in a well-balanced manner, it is possible to lock and hold the lens so that there is no wobbling and the amount of eccentricity is within the allowable range. In addition, the manufacturing error in the inner diameter of the lens barrel is 80 μm (130 μm - 50 μm).
Sufficiently larger than 20μm in the above conventional technology,
The manufacturing precision of the lens barrel can be reduced to this extent. FIG. Corresponding parts are given the same reference numerals.

In this embodiment, a step 9 for regulating the position of the lens 5 in the optical axis direction is provided on the inner wall 7 of the lens barrel, and a protruding stripe 8 is provided along the step 9. The lens 5 is inserted from the direction of arrow B, and as explained in FIG. Accordingly, the mounting position of the lens 5 is set. Furthermore, lens 5
To prevent the lens from falling off, glue the lens 5 with adhesive 10.
It is adhered to the protruding stripes 8 by.

This produces the same effects as this embodiment, but furthermore, the spacing ring conventionally used for holding and locking the lens becomes unnecessary, resulting in further weight and cost reductions.

As described above, by providing three protruding stripes at each mounting position of each lens, each lens can be mounted without wobbling and with an amount of eccentricity within an allowable range.

Note that the number of protruding stripes provided at one lens mounting position may of course be four or more, but
The complexity of the lens barrel mold structure and the number of protruding stripes are 3.
Considering that if the number of protruding stripes is 3 or more, there is no difference in lens mounting accuracy, etc., it is preferable to set the number of protruding stripes to 3, which is the minimum necessary number.

Furthermore, although the above embodiment has been described using the master barrel of a zoom lens as an example, the present invention is not limited to this.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to eliminate the wobbling of the lens even with variations in the inner diameter of the lens barrel due to resin molding, and to set the amount of eccentricity of the lens within an allowable range. It is possible to achieve high-precision lens holding comparable to that of a turned metal lens barrel, and it is possible to reduce the number of parts, reduce weight, reduce costs, and achieve excellent optical performance. A lens barrel can be provided.

[Brief explanation of the drawing]

FIG. 1a is a partial vertical sectional view showing an embodiment of the lens barrel according to the present invention, FIG. FIG. 3 is a perspective view showing a lens attachment state, FIG. 4 is a perspective view of main parts showing another embodiment of the lens barrel according to the present invention, and FIG. FIG. 2 is a configuration diagram showing an example of a zoom lens. 7...Inner wall, 8...Protruding streak.

Claims (1)

[Scope of Claims] 1. A lens barrel molded from a resin material and provided with a lens holding means on an inner wall, wherein the lens holding means is formed integrally with the inner wall and is located along the central axis of the lens barrel. 3, which are formed at approximately equal intervals in the circumferential direction with the center at , and the distance from the central axis is smaller than the lens radius.
Consisting of more than one protruding stripe, the top of the protruding stripe is scraped off when the lens is inserted into the lens barrel, so that the lens is tightly fitted and held by the protruding stripe. A lens barrel characterized by: