JPS63177104A - plastic lens barrel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a holding structure for a plastic lens used in a video camera, etc., and in particular, it prevents plastic deformation of the plastic lens due to temperature, improves durability, and reduces weight. The present invention relates to a plastic lens barrel suitable for reduction.

- [Prior Art] Conventionally, as a measure to prevent plastic lenses from being deformed due to expansion due to temperature changes, an elastic member has been interposed between the plastic lens and the holding lens barrel, as described in Japanese Patent Application Laid-Open No. 58-125004. Some models had an elastic member integrated into either the plastic lens or the lens barrel. However, plastic deformation due to thermal expansion could not be completely eliminated.

[Problem that the invention seeks to solve]

The above conventional technology does not take into consideration plastic deformation due to stress generated in the elastically deformed portion. When an elastic deformation portion is integrally provided in a plastic lens, plastic generally undergoes deformation due to creep, so if deformation continues for a long time in a high temperature environment, plastic deformation occurs. When placed in a low-temperature environment, this deformation results in a decrease in retention accuracy.

Providing the elastic deformation portion on the lens barrel side or as a separate component similarly involves a decrease in holding accuracy. Furthermore, both methods require a space between the lens and the lens barrel to provide an elastically deformable portion, and also have the disadvantage of increasing the outer diameter of the assembled lens.

To address the above problems, in order to absorb expansion caused by temperature changes, it is possible to match the linear expansion coefficients caused by temperature changes between the plastic lens and the lens barrel, but simply matching the linear expansion coefficients causes the following problems. A point occurs.

In a lens assembly, it is necessary to combine lenses made of two or more types of materials in order to ensure optical performance, as shown in, for example, Japanese Unexamined Patent Publication No. 59-31920. Therefore,.

Generally, different materials are used for the lens barrel and the plastic lens. On the other hand, different plastic materials have different thermal properties such as thermal conductivity, heat distortion temperature, and mechanical properties such as elastic modulus. Therefore, the temperature distribution and expansion and contraction of the lens barrel and plastic lens do not occur at the same speed in high-temperature and low-temperature environments, and as a result, either the plastic lens or the lens barrel undergoes plastic degeneration. This will cause it to happen.

An object of the present invention is to provide a glass lens barrel that can be used in a lens assembly and has environmental resistance characteristics that cause no practical problems.

[Means for solving problems]

The above objective is to take into account the holding accuracy tolerance allowed for each lens, which is determined by the configuration and function of the lens assembly, and to select the material of the lens barrel.
This can be achieved by making the holding precision the same as that for the plastic lens, which requires the most precision, and by adopting a method that satisfies the holding precision required for each of the other lens holding methods.

[Effect]

By making the plastic lens, which requires the most precision in holding, the same material as the lens barrel, the stress bond that occurs when expanding and contracting due to environmental changes is the same, and even if deformation occurs due to this stress, the plastic lens Both the lens and barrel deform uniformly.

Therefore, either the plastic lens or the lens barrel will not be significantly deformed and the holding accuracy will not be reduced.

As a result, there is no need to insert parts such as a spacing ring or an elastic member between the plastic lens and the lens barrel, and it is possible to improve the holding precision of the plastic lens, and to minimize the increase in the outer diameter. can.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a cross-sectional view showing this embodiment, and FIG. 2 is a cross-sectional view showing this embodiment.
1 is a cross-sectional view showing the configuration of a zoom lens to which this example is applied.

In Figure 1, numeral 1 is a plastic lens made of borica τponate and acts as a concave lens, 2 is a plastic lens made of acrylic resin and acts as a convex lens, 3 is a glass lens that acts as a convex lens, and 4 is polycarbonate. A holding lens barrel 5 and 6 suppress and hold the plastic lens 1 and the plastic lens 2. Lens holder, 10 indicates glass lens 3 and plastic lens 2
A spacing ring made of polycarbonate that maintains a zero spacing, 7 an outer lens barrel for connecting the lens group shown in FIG. 1 held by the holding lens barrel 4 with other lens groups, 8 the holding lens barrel 4 This is a set screw for fixing to the outer lens barrel 7.

In Fig. 2, the lens group I shown in Fig. 1 adjusts the focus position of the zoom lens, converts it to the desired magnification by the variable magnification group (■), and then uses the imaging action of the relay group (■) to position the focal point. By focusing the image on the lens, it functions as a zoom lens.

The operation will be explained with reference to FIG. Lens group I is the group with the largest lens diameter among the zoom lenses, and considering that the specific gravity of the plastic lens is 1/3 to 115 compared to that of glass, the zoom lens This has a great effect on reducing the weight of the lens, and the lens arrangement shown in Figure 1 is used to correct aberrations.At this time,
The holding precision required for the plastic lens 1 is about 10 μm, which is 3 to 5 times higher than that of the plastic lens 2, for example, even with respect to eccentricity in which the center of the lens shifts. On the other hand, since the holding lens barrel 4 is made of the same material, the precision of the parts is improved, and it is possible to fit and fit with the plastic clamp 1, and the central axis of the holding lens barrel 4 (
(not shown) and the center of the plastic lens 1 can be easily aligned.・The glass lens 3 is attached to the holding lens barrel 4
By fitting and holding it in the same way as plastic lens 1,
Obtain the required holding accuracy. A conventional holding structure may be used for the plastic lens 2, but in this embodiment, the plastic lens 2 is provided with a collar 9 with a flatness of about 2 μm, and a gap of about 20 μm between it and the holding lens barrel 4. The structure is such that it can be held in place and tightened using a lens holder.

By setting the initial assembly accuracy to the required value, the optical performance will be satisfactory.

The deformation of the plastic lens 1 due to changes in environmental temperature occurs in a reversible manner because the same material is used for the holding lens barrel 4, and the necessary lens surface of the plastic lens 1 The accuracy of the lens is not irreversibly deformed due to changes over time, and there is no deterioration in the holding accuracy such as an increase in the distance between the plastic lens 1 and the holding lens barrel 4.

Compared to the holding lens barrel 4, the glass lens 3 undergoes 115 to 1/10 fewer changes in shape due to changes in environmental temperature. If the holding lens barrel 4 expands, a gap may be created between it and the glass lens 3, which may reduce the holding accuracy. prevent the decline of The deformation stress generated in the holding lens barrel 4 at this time is absorbed between the parts holding the plastic lens 1 and has no effect on the plastic lens 1.

The plastic lens 2 and the holding lens barrel 4 mutually expand and contract due to the difference in materials (repeatedly, but the distance between them is maintained, so even if the holding accuracy decreases, the deterioration of the precision of the lens surface does not occur in practical use) This is not a problem.

'According to this embodiment, the lens group I, which uses large-diameter lenses that are highly effective in weight reduction, can be made of plastic, which has the effect of making it possible to obtain a lightweight zoom lens.

Further, the next embodiment will be explained with reference to FIG.

FIG. 3 is a cross-sectional view showing the lens group I in this embodiment.

Components that are the same as those in the first embodiment shown in FIG. 1 are designated by the same numbers and will not be described further.

What is different from FIG. 1 is the holding structure for the glass lens 3, in which an elastic member 11 is inserted between the glass lens 3 and the holding barrel 4, and a spring 12 is used to hold the glass lens. It is held compressed in the axial (not shown) direction. Further, between the outer lens barrel 7 and the outer lens barrel 7, a lens barrel collar 13 provided on the holding lens barrel 4 is tightened and held by a screw ring 14.

The initial operation of the plastic lens 1 and the plastic lens 2 of this embodiment and the operation due to changes in environmental temperature are the same as those of the first embodiment. The difference is that the deformation of the holding lens barrel 4 due to the difference in the amount of expansion and contraction between the glass lens 3 and the holding lens barrel 4 is absorbed by the elastic member 11, thereby reducing the deformation of the holding lens barrel 4. Similarly, since the conventional plastic lens and lens barrel holding structure is used between the outer lens barrel 7 and the holding lens barrel 4, deformation of the holding lens barrel 4 is further reduced. Both have a conventional plastic lens holding structure,
This is applied between the glass lens 3 and the holding lens barrel, and between the holding lens barrel and the outer lens barrel.

The effect of this embodiment is that a means for absorbing deformation using an elastic member or the like is provided between the glass lens 3, which does not deform compared to plastic, and the holding lens barrel, which has a thicker deformation tolerance compared to plastic lens IK. Therefore, since a relatively high-rigidity elastic member is used, higher component accuracy, that is, higher holding accuracy can be obtained compared to the case where an elastic member is inserted between the plastic lens 1 and the holding lens barrel 4. Moreover, it is possible to reduce the amount of deformation stress generated in the holding lens barrel 4 due to changes in environmental temperature.

〔Effect of the invention〕

According to the present invention, it is possible to maintain the holding precision required for practical use and to prevent plastic deformation due to changes in environmental temperature, so that it has environmental resistance characteristics that do not pose any practical problems when used in assembled lenses. A plastic lens barrel can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a horizontal half sectional view showing an embodiment of the present invention, FIG. 2 is a horizontal half sectional view showing a zoom lens to which this embodiment is applied,
FIG. 3 is a transverse half-sectional view showing a second embodiment of the present invention. 1...Plastic lens, 2...Plastic lens, 3...Glass lens, 4...Holding lens barrel.

Claims (1)

[Claims] Among a plurality of lenses arranged coaxially, in order from one direction, a first lens having a concave lens action and made of plastic, a second lens having a convex lens action and made of glass, and a convex lens having a concave lens action. In a lens assembly consisting of a third lens that has a function and is made of plastic, and a lens barrel that fits and holds approximately three lenses and maintains them coaxially, the material of the lens barrel is different from that of the first lens. A plastic lens barrel characterized by being made of the same material.