JPH0333812A - Lens barrel applied with remedy for fogging - Google Patents

Abstract

PURPOSE:To heat lenses and to prevent the fogging of the lenses by applying transparent conductive films on lens faces and feeding electricity to the transparent conductive films from a pair of electrodes provided on a lens barrel side. CONSTITUTION:A photographic lens system consists of the lens barrel 1, a focusing lens group 2, a variator lens group 3, a compensator lens group 4, and a relay lens group 5. The transparent conductive films which consist of indium oxide, tin, etc., and generate heat when energized are uniformly applied on the respective lens surfaces. A pair of the electrodes 6d to 6f formed to an arc shape are provided in order to energize the transparent conductive films. The feeding of the electricity to the electrodes 6d to 6f is executed by feeding the electricity via a pair of brushes 12a, 12b for feeding fixed the lens barrel 1 to a pair of conductive plates 11a, 11b provided on the focusing lens barrel 6. The fogging of the lenses is prevented in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical member having a heat generating means, and in particular, in a camera or the like, an optical member such as a lens provided in a lens barrel is uniformly heated to change the environment. The present invention relates to an optical member having a heating means suitable for effectively preventing fogging caused by fogging.

(Prior Art) Cameras such as television cameras, video cameras, and photographic cameras are sometimes used in environments where temperature and humidity change rapidly.

For example, photography may be performed outdoors during the rainy season when the rain that fell the previous day turns into clear skies in the morning and the temperature rises. Generally, when the temperature of the outside air changes rapidly, the difference between the temperature inside the camera and the outside air of 4 degrees becomes large, and the lens surface of the photographic lens may become cloudy, making it impossible to take pictures.

For this reason, conventionally, for example, in television cameras, etc., a heating means is installed in the space inside the camera, and when the outside environmental conditions suddenly change, the heating means increases the temperature inside the camera and fogs up the lens surface. It was prevented from occurring.

However, it is time consuming and extremely difficult to uniformly raise the temperature of each lens surface within the lens barrel to prevent fogging from occurring over the entire lens surface, and fogging inevitably occurs in some areas. There were many things.

(Problems to be Solved by the Invention) Now, as a method for removing such fogging that has occurred on the lens surface, the present applicant proposed a method for heating the lens surface C in order to heat the lens in Japanese Patent Application No. 63-8665. We devised a technology in which a transparent conductive film was provided, an electrode was provided on the lens surface for electricity supply at a position outside the effective light beam, and a lead wire was connected to this electrode.

However, although this proposal discloses a structure for supplying electricity to a single lens surface, little consideration has been given to applying it to an actual lens barrel incorporating a plurality of lenses.

In other words, if we do not carefully arrange the transparent conductive film, electrodes, and lead wires for a lens barrel made up of multiple lenses, the structure of the lens barrel will not only become complicated, but the work process during assembly will increase. Teru.

An object of the present invention is to provide a lens barrel that simplifies the structure when assembling a lens into a lens barrel as disclosed in the above-mentioned Japanese Patent Application No. 63-8665 and is easy to assemble.

(Configuration for Solving the Problems) According to the present invention, a heat-generating transparent conductive film is applied to the lens surface, and power is supplied to the transparent conductive film from at least one pair of electrodes provided on the lens barrel side. The purpose is to prevent fogging that occurs on the lens by heating it.

〔Example〕

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a sectional view of a photographic lens system according to the present invention. 1 is a lens barrel, 2 is a focusing lens group, 3 is a variator lens group, 4 is a compensator lens group, 5
is a relay lens group.

The focusing lens group 2 is held by a focusing lens barrel 6, and moves in the optical axis direction via a guide roller 7 that fits into a groove cut in the lens barrel 1, as shown in FIG.

As shown in FIG. 4, the variator lens group 3 and the compensator lens group 4 have cam grooves 10a, 10 provided in a rotary barrel 1o that rotates with respect to the lens barrel 1 cut with a straight groove 1a.
Zooming is performed by sliding the guide rollers 3a, 4a along the direction b. Note that 12 is a zoom drive motor, and 13 is a zoom drive gear.

Now, on the surface of each lens, a transparent conductive film made of indium oxide, tin, etc. and which generates heat when electricity is applied is uniformly applied.

First, the structure for supplying electricity to the transparent conductive film provided on the focusing lens group will be explained with reference to FIGS. 2, 3, and 5. In addition, Figure 2 shows the disconnection A- shown in Figure 1.
A sectional view, FIG. 3 shows a side view, especially FIG. 3(B)
3 is a sectional view of the focusing lens section showing the main part, and FIG. 3(C) is an exploded perspective view.

First, the lens 2b constituting the focusing lens group 2
is held and positioned by an annular portion 6c integrally formed with the focusing lens barrel 6, and an annular spacer 6b that determines the distance between the lens 2a and the lens 2a. Next, the lens 2a is positioned by removing the spacer 6b and the holding ring 6a. The lens group 2 is assembled by stacking the lens 2b, the spacer 6b, the lens 2a, and finally the holding ring 6a in this order.

A pair of arcuate electrodes 6d, 6e, 6 are formed at a portion of each ring 6a, 6b, 6c in contact with each lens 2a, 2b in order to conduct electricity to the transparent conductive film formed on the lens surface.
f is provided. Power is supplied to each pair of electrodes by a pair of conductive plates 1l provided on the focusing lens barrel 6.
A pair of power supply brushes 12a fixed to the lens barrel 1 to a11b
, 12b, and is energized.

Therefore, the power feeding brushes 12a and 12b do not need to draw the electric wires for power feeding even if the focusing lens group moves during focusing, and can also prevent disconnection due to movement of the electric wires.

On the other hand, the variator lens group 3 and compensator lens group 4 are similarly coated with a transparent conductive film on the surface of each lens, but unlike the power feeding system to the focusing lens group, in this example, the zoom lens is at the wide end. When the contactors 3c and 4c provided on the lens surfaces of the verifier lens group 3 and the compensator lens group 4 contact the fixed contacts 1b and lc fixedly provided on the lens barrel 1, respectively. Supply power. It also prevents fogging.

Incidentally, 15 is a dew condensation sensor that detects whether or not clouding has occurred on the lens surface. Reference numeral 16 denotes a power supply control circuit that controls power supply to each transparent conductive film based on power from the camera body (not shown).

Next, a method of controlling energization for preventing fogging of a zoom lens according to the present invention will be described.

First, according to Japanese Patent Application No. 1986-8665 by the same applicant, when a transparent conductive film is applied to one lens surface with a diameter φw of 120 mm and a potential of 12 V (volts) is applied, 0.5
A current of about A (ampere) flows. In other words, it is shown that approximately 6 W (watts) of power is consumed for one lens surface. Therefore, if a transparent conductive film is simply applied to the surfaces of 10 lenses with the same diameter φ, then 60
W power is required.

By the way, there is a certain limit to the amount of power that can be supplied from the main body of a handheld TV camera to the lens side, and depending on the number of surfaces coated with a transparent conductive film, it may have a negative effect on the electrical control of the camera. become.

Focusing on this point, the power supply control circuit 16 supplies electricity to each transparent conductive film in a time-divided manner in order to cope with the limited power supply source from the camera body side.

This situation will be explained based on FIGS. 5 and 6.

Note that the dew condensation sensor 15 and the manual energization switch are connected to a power supply control circuit. In particular, the dew condensation sensor 15
It is also connected to a warning display device 18 that warns that the lens surface has become cloudy.

First, when the photographer learns from the display on the warning display device 18 or the shooting screen that fogging has occurred on the lens surface, the photographer sets the manual energization switch 17 to activate the power supply control circuit. .

As shown in Figure 6, the power supply control circuit first starts energizing the transparent conductive film applied to the focusing lens group, but at this time, the duty ratio is applied to the focusing lens group, which occupies the largest lens surface area among the zoom lens groups. The power supply brush 12 is controlled to supply a large voltage of .

Next, a voltage is sequentially supplied to the transparent conductive film applied to the compensator lens group, and then to the transparent conductive film applied to the variator lens group via the fixed contact.

As explained above, according to this embodiment, while preventing fogging, stable camera control can be performed without imposing too much burden on the limited voltage.

[Effects of the Invention] As explained above, according to the present invention, the lens barrel can be manufactured relatively easily without complicating the structure of the lens barrel and in terms of assembly. Become.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a zoom lens barrel according to the present invention, FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1 according to the present invention, and FIG. FIG. 4 is a diagram for explaining the configuration of the variator lens group according to the present invention, FIG. 5 is a block diagram showing the control system according to the present invention, and FIG. 6 is a diagram showing the flow of supplied power according to the present invention. . 1... Lens barrel 2... Focusing lens group coated with a transparent conductive film 3... Variator lens group coated with a transparent conductive film 4... Convencenter lens group coated with a transparent conductive film 16. ...Power supply circuit b

Claims (2)

[Claims] (1) A transparent conductive film is applied to the lens surface, power is supplied to the transparent conductive film from at least one pair of electrodes provided on the lens barrel side, and the lens is heated to prevent fogging of the lens. Lens barrel with anti-fog protection. (2) The lens barrel according to claim 1, wherein the electrode is formed in an arc shape.