JP2006098675A - Lens unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens unit capable of easily and reliably preventing whitening.
In a lens unit in which a plurality of lenses including a first lens in which at least one surface is a concave surface and a coating film is formed on the concave surface is provided in a lens barrel, the first lens has a concave surface. The holding member is pressed by the holding member from the side and is held in the lens barrel. The holding member presses the first lens through the coating film or the coating film formed continuously with the coating film, and the end of the coating film from the pressing portion. The part was to leave.
[Selection] Figure 1

Description

  The present invention relates to a lens unit, and more particularly to a structure for preventing whitening of a lens.

In general, in a lens unit of a camera including a plurality of lenses, the lens is fixed by being pressed from one surface side by a pressing tool in a lens barrel (for example, Patent Document 1).
However, recently, cameras have been used in harsh environments such as being mounted on automobiles, and as a result, a phenomenon called whitishness of lenses has become more problematic than before. . In camera lenses, whitening is a fatal deterioration, and various proposals have been made to prevent it.

Whitishness occurs when water drops on the lens surface elute the alkali metal or the like in the lens and deposit the metal. The main cause of this is the dew condensation phenomenon. Therefore, it is possible to prevent whitening by not causing condensation. Condensation is a phenomenon in which water droplets are generated on the surface of a low-temperature surface when the temperature changes from low to high. Therefore, a method of preventing condensation by making the temperature constant with a heater has been proposed.
JP 2002-040308 A

However, the method of suppressing temperature change using a heater requires an energy source and is not practical at present when miniaturization is required.
Moreover, the method of suppressing a temperature change using a heater leads to a significant cost increase.
Therefore, an object of the present invention is to provide a lens unit that can easily and reliably prevent whitening.

In order to solve the above-described problems, a lens unit according to the present invention includes a plurality of lenses including a first lens in which at least one surface is concave and a coating film is formed on the concave surface. In the lens unit provided,
The first lens is pressed by a holding member from the concave surface side and held in the lens barrel, and the holding member passes through the coating film or a coating film formed continuously with the coating film. , And the end of the coating film is separated from the pressing portion.

  In the lens unit according to the present invention configured as described above, since the end of the coating film of the first lens is separated from the contact portion between the first lens and the holding member, water generated by condensation on the contact portion. Even if it accumulates, it is possible to prevent moisture from penetrating from the end of the coating film and to prevent whitening.

Hereinafter, embodiments of the lens unit according to the present invention will be described with reference to the drawings.
FIG. 1 is a half sectional view showing a configuration of a lens unit according to Embodiment 1 of the present invention.
The lens unit of the embodiment shown in FIG. 1 is used, for example, in a white line recognition camera mounted on an automobile, and is provided in front of a substrate on which an image sensor and a peripheral circuit of the image sensor are formed. . Note that the lens unit of the embodiment may be configured integrally with a substrate holder (not shown) to which a substrate on which an imaging element and its peripheral circuit are formed is attached.

Hereinafter, the lens unit of the embodiment will be specifically described.
As shown in FIG. 1, the lens unit of this embodiment is configured by disposing a lens group including a plurality of lenses L1 to L6 at a predetermined interval inside the lens barrel 1 and tightening and holding the lens group 1 with a retainer 2. Has been. In FIG. 1, reference numeral 20 denotes an image sensor, and a filter F <b> 1 is disposed between the lens unit and the image sensor 20.

Here, in the lens unit of the first embodiment, the lenses L1 and L4 are concave on one side, and the lenses L1 and L4 are pressed by the holding members 11 and 12 from the concave side, respectively. It is held in the cylinder 1. And this invention has the following characteristics in the holding structure.
That is, in the first embodiment, in the lenses L1 and L4, the coating film provided on the concave surface is formed so as to extend to the outside of the concave surface, and the holding members 11 and 12 are arranged on the lenses L1 and L1 via the coating film. L4 is configured to be pressed.

Specifically, the lens L1 forms a coating film continuously on a concave surface and an annular flat surface outside the concave surface, and the holding member 11 is one of the annular flat surfaces on which the coating film is formed. The lens L1 is pressed and held so as to be in contact with the portion.
In addition, the lens L4 has a chamfered corner between the outer peripheral surface L4g (an outer peripheral surface substantially parallel to the optical axis) and the concave surface, and continuously forms a coating film so as to extend from the concave surface to the chamfered surface. However, the holding member 12 is pressed against the corner of the concave surface and the chamfered surface to hold the lens L4 (FIG. 2).

  As described above, in the lens unit according to the first embodiment, when the lenses L1 and L4 are pressed from the concave surface side, the holding members 11 and 12 press the lens lenses L1 and L4 through the coating film so as to coat the coating film. Is separated from the contact portion between the holding member and the lens to prevent whitening near the pressing portions of the lenses L1 and L4.

Hereinafter, the lens holding structure in the present embodiment will be described in more detail, including a method for forming a coating film, in comparison with a conventional example.
In general, a lens coating film is formed by using a vapor deposition or sputtering apparatus. Conventionally, in order to hold a lens in a vacuum chamber, a lens holder 32 as shown in FIG. 6 is used to form a coating film on a concave surface. Was forming. In FIG. 6, the direction indicated by the arrow indicates the film forming direction. As is apparent from FIG. 6, in the method using the conventional lens holder 32, a coating film is formed on the concave surface of the lens L4, but no coating film is formed on the chamfered portion L4c.

  In this way, a lens in which the coating film is formed only on the concave surface and the coating film is not formed on the chamfered portion, and the holding member 12 is pressed against the corner of the concave surface and the chamfered surface as shown in FIG. Is held, the end of the coating film is pressed by the holding member 12. When the lens unit having such a configuration is used under conditions where condensation occurs, water droplets generated by condensation accumulate in the contact portion between the lens and the holding member 12, and the accumulated water passes from the end of the coating film to the glass and the coating film. It has been found that it permeates during the period of time and causes whitening. That is, water droplets on the surface of the holding member 12 and the like are relatively easily evaporated and naturally dried, whereas moisture that has permeated between the glass constituting the lens and the coating film is difficult to eliminate. Will be exposed to moisture for a long time, and it becomes easy to generate whitishness.

On the other hand, in the present embodiment, for example, a lens holder 31 shown in FIG. 5 is used to hold the lens in a vacuum chamber and form a coating film on the concave surface of the lens. In this way, in the lens L4 in which the corner portion between the outer peripheral surface L4g and the concave surface is chamfered, it is possible to continuously form the coating film so as to extend from the concave surface to the chamfered surface.
Here, in the lens holder 31 shown in FIG. 5, the lens 31 is held on its outer peripheral surface by pressing the ball 31a with the spring 31b so that the coating film is formed on the chamfered surface as well as the concave surface. .

  In the present embodiment, the lens L4 in which the coating film is continuously formed on the concave surface and the chamfered surface as described above, and the holding member 12 is provided at the corner of the concave surface and the chamfered surface as shown in FIG. Press to hold the lens. Even when the lens unit according to the present embodiment configured as described above is used under conditions where condensation occurs, condensation occurs, and water droplets generated by the condensation accumulate in the contact portion between the lens and the holding member 12. However, in the present embodiment, since the end portion of the coating film exists outside the contact portion between the lens and the holding member 12, the water accumulated in the contact portion is removed from the end portion of the coating film between the glass and the coating film. It does not penetrate in between. Therefore, in the lens unit of the present embodiment, water droplets and water generated by condensation are present only on the surface of the holding member 12 and the lens and do not permeate between the glass and the coating film. Dried. As a result, the glass constituting the lens is not exposed to moisture for a long time, and the occurrence of whitening can be prevented.

As described above, in the present invention, an important configuration for preventing whitening is that when condensation occurs, the lens from the contact portion between the lens and the holding member 12 where water produced by the condensation will be stored. This is to separate the end portion of the coating film, thereby preventing moisture from penetrating from the end portion of the coating film and preventing whitening.
Therefore, the present invention is not limited to the configuration shown in FIG. 2 and the like, and various modifications can be made without departing from the idea of the present invention.

Modified example.
FIG. 4 shows a modification according to the present invention configured by using a holding member 14 having a lens pressing portion 14a instead of the holding member 12 of FIG. In this modification, the lens L4 is held by pressing the peripheral portion in the concave surface of the lens L4 by the lens pressing portion 14a.
Here, the portion of the lens L4 pressed by the lens pressing portion 14a is inside the corner (corner) between the concave surface and the chamfered surface, and is away from the end of the coating film.

In the lens unit of the modification according to the present invention configured as described above, even if water generated by condensation is stored in the contact portion between the lens and the holding member 12, the end portion of the coating film does not contact the stored water. Since it can, whitening can be prevented.
Further, in the configuration of this modification, for example, as shown in FIG. 6, even when a lens having a concave coating film is used, whitening can be prevented.

  In the above lens unit according to the present invention, the lens barrel 1 is preferably configured using a material having a relatively low thermal conductivity such as a plastic material or ceramic. If it does in this way, it can control that the temperature difference between lens-barrel 1 and a lens arises, and can control the generation of dew condensation. The low thermal conductivity material is selected in consideration of characteristics such as strength and linear expansion coefficient.

In the lens unit according to the present invention described above, the holding members 12 and 14 may have higher thermal conductivity than the lenses L1 to L6 and the lens barrel 1.
That is, in the lens unit according to the present invention, for example, even when the holding members 12 and 14 are made of a metal that can be easily processed, it is possible to prevent the whitening of the lens.

Further, in the lens unit according to the present invention, it is preferable that the thickness of the coating film at the position where the holding member is pressed is thicker than the thickness of the thin film tip in other portions.
Thus, if the coating film in the position where the holding member is pressed is thickened, the mechanical strength of the coating film can be increased.

  In the lens unit according to the present invention, the coating film is formed, for example, by forming a silicon oxide thin film on a magnesium fluoride thin film. However, the present invention is not limited to this. For example, the coating film is formed of various materials such as a combination of titanium oxide and silicon oxide, a combination of silicon oxide and magnesium fluoride, or a single film of magnesium fluoride. Can be formed. Further, the number of stacked layers may be two or more.

In the lens unit according to the present invention, it is preferable to form a vent hole in the lens barrel 1 so that the space inside the lens barrel 1, particularly the space around the portion where the holding member presses the lens, is connected to the outside air. .
If it does in this way, the dew condensation in the lens-barrel 1 will be suppressed and it can prevent a whitish more effectively.

Further, in the lens unit according to the present invention, in addition to opening a vent hole in the lens barrel 1 or replacing the vent hole in the lens barrel 1, the holding member presses the lens in the lens barrel 1. You may make it form a notch part on the outer periphery of a lens and the outer side of an effective diameter so that the space around a part may connect with external air (what is called D cut).
If it does in this way, the dew condensation in the lens-barrel 1 will be suppressed and it can prevent a whitish more effectively.

  According to the present invention described above, since it is possible to provide a lens unit that can easily and reliably prevent whitening, it can be mounted on a vehicle-mounted camera used in a harsh environment.

It is a half sectional view which shows the structure of the lens unit of embodiment which concerns on this invention. It is sectional drawing which expands and shows a part of cross section of FIG. It is sectional drawing of the lens used for the lens unit of embodiment. It is sectional drawing which expands and shows a part of cross section of the lens unit of the modification concerning this invention. In embodiment, it is sectional drawing which shows the structure of the lens holder at the time of coating a lens. It is sectional drawing which shows the structure of the general lens holder at the time of coating a lens.

Explanation of symbols

1 barrel,
2 Retainer,
11, 12, 13, 14 holding member,
14a Lens holding part,
31 Lens holder,
31a balls,
31b spring,
L1-L6 lens,
F1 Optical filter.

Claims (7)

In a lens unit in which a plurality of lenses including a first lens in which at least one surface is a concave surface and a coating film is formed on the concave surface is provided in the lens barrel,
The first lens is pressed by a holding member from the concave surface side and held in the lens barrel, and the holding member passes through the coating film or a coating film formed continuously with the coating film. The lens unit is characterized in that the end of the coating film is separated from the pressing portion.   The lens unit according to claim 1, wherein the holding member has higher thermal conductivity than the lens and the lens barrel.   A corner portion between the outer peripheral surface of the first lens and the concave surface is chamfered and the coating film is formed so as to extend to the chamfered portion, and the holding member is interposed through the extended coating film. The lens unit according to claim 1, wherein the first lens is pressed.   The lens unit according to claim 1, wherein the coating film in the pressing portion is thicker than other portions of the coating film.   The lens unit according to any one of claims 1 to 4, wherein the coating film is formed by forming a silicon oxide thin film on a magnesium fluoride thin film.   The lens unit according to claim 1, wherein a vent hole is formed in the barrel so that a space around the pressing portion is connected to outside air. The notch part is formed in the outer periphery of the at least 1 lens of the said several lenses, and the outer side of an effective diameter so that the space around the said press part may be connected with external air. The lens unit according to any one of the above.

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