JPH0333814A - Camera lens applied with remedy for preventing fogging - Google Patents

Abstract

PURPOSE:To prevent the fogging of lens faces by providing a control circuit to time-dividedly supply the electric power fed from a feeding circuit to the respective lenses at the time of heating the lens faces by feeding electricity thereto. CONSTITUTION:A photographic lens system consists of the lens barrel 1, a focusing lens group 2, a variable lens group 3, a compensator lens group 4, and a relay lens group 5. Transparent conductive films which consist of indium oxide, tin, etc., and generate heat when energized are uniformly formed on the respective lens surfaces. Whether the lens surfaces are fogged or not is detected by a frost setting sensor 15 in this case and the electricity is fed to the respective transparent conductive films time-dividedly by a feeding control circuit 16 in accordance with the power source from a camera body in this case. The fogging of the lens faces 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. This invention relates to an optical member having a heat generating means suitable for effectively preventing fogging caused by.

[Conventional technology]

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 temperature of the outside air 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.

[Problem that the invention seeks to solve]

Now, as a method for removing such fogging that has occurred on the lens surface, it may be possible to heat the lens when fogging occurs or when the environmental conditions are such that fogging is likely to occur.

Incidentally, in recent years, when controlling zooming and aperture in television camera devices, a method of automatically controlling the zooming and aperture based on electrical signals has become common.

Particularly in the case of hand-held television cameras, there is usually a certain limit or restriction on the ability of the power source to supply electric power.

Therefore, installing a new load, that is, a mechanism that heats the lens, based on this limited power supply source will adversely affect the video signal of the camera body, the aforementioned zooming, and even aperture control. It is possible to give

In view of this problem, the present invention removes fogging that has occurred on the lens surface by heating the lens, without placing much load on the limited power supply source, and by implementing other controls such as To provide a lens barrel for a camera that can perform stable control without significantly affecting the control of a zooming diaphragm or the like.

[Means and Structure for Solving the Problems] The present invention provides a method for preventing the occurrence of fog by reducing the amount of power supplied from the power supply circuit to each lens when heating a plurality of lens surfaces by supplying power. The reason is that a control circuit is provided that supplies the power in parts.

r 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 convencator 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.

Note that 8 is a focusing lens drive motor, and 9 is a focusing drive system.

As shown in FIG. 4, the variator lens group 3 and the convencator lens group 4 have cam grooves 10a, 10 provided in a rotary barrel 10 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, a configuration for supplying electricity to the transparent conductive film provided on the focusing lens group will be explained based on 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. The lens 2a includes a spacer 6b and a holding ring 6a.
The location is determined via the .

In addition, each ring 6a, 6b, 6c (D each lens surface a.

A pair of electrodes 6d, 6 formed in an arc shape at a part of the contact with the lens 2b to conduct electricity to the transparent conductive film formed on the lens surface.
e and 6f are provided. Power is supplied to each pair of electrodes by a pair of conductive plates Ila provided on the focusing lens barrel 6.

A pair of power supply brushes 12a fixed to the lens barrel 1 to 11b,
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 near the wide end. When the lens reaches the fixed contactors 1b and lc fixed to the lens barrel 1, the velier lens group 3 and the compensator lens group 4
Contactors 3c and 4c provided on the lens holding frame contact each other to supply power. The lens surface is heated to prevent 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. 63-8665 No. 4 filed by the same applicant, when a transparent conductive film is applied to one lens surface with a diameter φ = 120 mm and a voltage of 12 volts is applied, the voltage becomes zero.
．． A current of about 5A (ampere) flows. In other words, it is shown that approximately 6 W (watts) of power is consumed for one lens surface. Therefore, if we simply have the same diameter φ
If a transparent conductive film is applied to the surfaces of 10 lenses having the following characteristics, a power of 60 W will be 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 the 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 from 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. In this embodiment, the relay lens group has a transparent conductor.As explained above, according to this embodiment, while preventing fogging, stable camera control can be performed without placing a large burden on the limited power source.

〔Effect of the invention〕

As explained above, according to the present invention, even if there is a certain limit to the power supply capacity, it is possible to prevent the lens surface from fogging without significantly affecting other electrical controls such as zooming and aperture. can.

[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... Compensation center lens group coated with a transparent conductive film , 6...Power supply circuit.

Claims (1)

[Claims] (1) A control circuit that heats a plurality of lens surfaces constituting an imaging system by supplying power from a power supply circuit to remove fogging generated on the lens surfaces, and supplies power from the power supply circuit in a time-sharing manner. A camera lens with anti-fogging features.