JP2721399B2 - Zoom lens barrel with anti-fogging measures - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical member having a heat generating means, and more particularly to a camera or the like in which an optical member such as a lens provided in a lens barrel is uniformly heated to change an environment. The present invention relates to an optical member having a heat generating means suitable for effectively preventing fogging caused by the above.

[Conventional technology]

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

For example, there is a case where shooting is performed during the rainy season when the temperature rises due to the sunny weather from the morning when the rain that had fallen the day before outdoors has been fine. In general, when the temperature of the outside air changes suddenly, the difference between the temperature inside the camera and the temperature of the outside air increases, and the lens surface of the taking lens may become cloudy, making it impossible to take a picture.

For this reason, conventionally, for example, in the case of a television camera or the like, a heating means is provided in the space inside the camera, and when the environmental conditions of the outside air suddenly change, the temperature inside the camera is increased by the heating means, and the lens surface becomes cloudy. Was prevented from occurring.

However, it is time-consuming and very difficult to prevent the occurrence of fogging over the entire lens surface by uniformly raising the temperature of each lens surface in the lens barrel, and it is inevitable that partial fogging will occur. There were many things.

[Problems to be solved by the invention]

As a method of removing the fogging generated on the lens surface, the present applicant has disclosed a heat-generating transparent conductive film on the lens surface in order to heat the lens in Japanese Patent Application Laid-Open No. 63-8665. A technique was devised in which the arrangement of the lead wires or electrodes for energization at positions outside the effective light flux on the lens surface was devised.

However, although this proposal discloses an energization structure for a single lens surface, little consideration is given to its application to an actual zoom lens barrel.

In a zoom lens in which the lens moves along the optical axis, a member that holds the variator lens group and the compensator lens moves with respect to the fixed barrel. Therefore, in order to supply power from the fixed cylinder to the movable cylinder, if power is further supplied through a lead wire from a power supply circuit provided in the fixed cylinder, the lead wire also moves, and the lead wire may be broken. In addition, the lens barrel itself becomes large due to the need to secure space. Further, in some cases, the load fluctuates when the lens is moved.

[Means for solving the problem]

The present invention has been made in view of the above problems,
A fixed cylinder, a movable cylinder that holds a movable lens that moves for zooming with respect to the fixed cylinder, a heating unit that is provided on the movable lens and generates heat on the lens surface by being supplied with power, and a fixation provided on the fixed cylinder. A cylinder terminal, a movable cylinder terminal provided on the movable cylinder, connected to the heating means, and a power supply circuit for supplying power to the fixed cylinder terminal, the movable cylinder terminal and the fixed cylinder when the movable cylinder is in a predetermined zoom position. The fact that the heat is supplied from the power supply circuit to the heat generating means while the terminal is in contact with the lens means that the lens is protected from fogging.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a taking 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,
Reference numeral 5 denotes a relay lens group.

The focusing lens group 2 is held by the focusing lens barrel 6 while being guided in the optical axis direction via a guide roller 7 which fits into a groove cut in the lens barrel 1 as shown in FIG. Moving. Numeral 8 is a focusing lens drive motor, and 9 is a focusing drive screw.

The variator lens group 3 and the compensator lens group 4 are composed of a lens barrel 1 having a straight groove 1a as shown in FIG. 1 and FIG.
Cam grooves 10a, 10b provided in the rotary cylinder 10 rotating with respect to
Zooming is performed by sliding the guide rollers 3a and 4a along the axis.

Incidentally, reference numeral 12 denotes a zoom drive motor, and reference numeral 13 denotes a zoom drive gear.

Now, a transparent conductive film made of indium oxide, tin or the like, which generates heat when energized, is uniformly applied to each lens surface.

First, a configuration for applying a current to the transparent conductive film formed on the focusing lens group is shown in FIG. The description will be made based on FIGS. 3 and 5. FIG. 2 is a diagram showing the disconnection A shown in FIG.
3A is a cross-sectional view, FIG. 3 is a side view, and FIG. 3B is a cross-sectional view of a focusing lens part showing a main part.
FIG. 3 (C) is an exploded perspective view.

First, the lens 2b constituting the focusing lens group 2
Is determined by the annular portion 6c formed integrally with the focusing lens barrel 6 and the position sandwiched by the annular spacer 6b for determining the lens distance from the lens 2a. Next, the lens 2a is positioned via the spacer 6b and the holding ring 6a.

In addition, a pair of electrodes 6d, 6e, 6f formed in an arc shape to supply electricity to the transparent conductive film formed on the lens surface is provided at a part of each ring 6a, 6b, 6c in contact with each lens 2a, 2b. ing. The power supply to each pair of electrodes is performed by the focusing lens barrel 6.
The power is supplied to a pair of conductive plates 11a and 11b provided on the lens barrel 1 via a pair of power supply brushes 12a and 12b fixed to the lens barrel 1.

Therefore, the power supply brushes 12a and 12b can prevent each wire for power supply from being dragged even when the focusing lens group moves at the time of focusing, and can also prevent disconnection due to movement of the wires.

On the other hand, the variator lens group 3 and the compensator lens group 4 are similarly provided with a transparent conductive film on each lens surface. However, unlike the power supply method to the focusing lens group, in this embodiment, the zoom lens is wide-angle end. Are reached, the contacts 3c and 4c provided on the lens holding frame of the variator lens group 3 and the compensator lens group 4 come into contact with the fixed contacts 1b and 1c fixed to the lens barrel 1, respectively. To supply power. And it prevents fogging.

A condensation sensor 15 detects whether or not fogging 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 a power supply from a camera body (not shown).

Next, a description will be given of a power supply control method for preventing fogging of the zoom lens according to the present invention.

First, according to Japanese Patent Application No. 63-8665 filed by the same applicant, a transparent conductive film is applied to one lens surface having a diameter φ of 120 mm, and when a voltage of 12 V (volt) is applied, a current of about 0.5 A (ampere) is generated. Flows. That is, it is shown that power of about 6 W (watt) is consumed for one lens surface. Therefore, if transparent conductive films are simply applied to ten lens surfaces having the same diameter φ, 60 W of power is required.

By the way, there is a certain limit to the power that can be supplied to the lens side from a general handy-type TV camera body, and depending on the number of surfaces on which the transparent conductive film is applied, there is a negative effect on the electrical control of the camera. Become.

Focusing on this point, the power supply control circuit 16 time-divisionally supplies power to each transparent conductive film in order to correspond to a limited power supply source from the camera body.

This situation will be described with reference to FIGS. Note that the dew sensor 15 and the manual power supply switch are connected to a power supply control circuit. In particular, the condensation sensor 15 is also connected to a warning display device 18 that warns that the lens surface is fogged.

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

The power supply control circuit first starts energizing the transparent conductive film applied to the focusing lens group as shown in FIG.
At this time, control is performed such that a voltage having a large duty ratio is supplied to the focusing lens group occupying the largest lens surface area of the zoom lens group via the power supply brush 12.

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

As described above, according to the present embodiment, stable camera control can be performed without imposing a considerable load on a limited power supply while preventing fogging.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a zoom lens barrel in which the lens barrel structure can be simplified and durable and has excellent anti-fog measures.

[Brief description of the drawings]

1 is a cross-sectional view of a zoom lens barrel according to the present invention, FIG. 2 is a cross-sectional view along AA of FIG. 1 according to the present invention, and FIG. 3 shows a main part of a focusing lens group according to the present invention. FIG. 4, FIG. 4 is a diagram for explaining the configuration of a variator lens group according to the present invention, FIG. 5 is a block diagram showing a control system according to the present invention, and FIG. 6 is a diagram showing a flow of power supply according to the present invention. is there. DESCRIPTION OF SYMBOLS 1 ... Lens barrel 2 ... Focusing lens group provided with transparent conductive film 3 ... Variator lens group provided with transparent conductive film 4 ... Compensation center lens group provided with transparent conductive film 16 ... Power supply circuit

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sayoko Amano 53, Imaiue-cho, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Canon Inc. Kosugi Office (56) References -12118 (JP, U) Real opening 61-114434 (JP, U)

Claims (1)

(57) [Claims] A fixed cylinder, a movable cylinder for holding a movable lens that moves for zooming with respect to the fixed cylinder, a heating means provided on the movable lens for generating heat on the lens surface by being supplied with power, the fixed cylinder. Fixed cylindrical terminal provided in
A movable cylinder terminal provided on the movable cylinder and connected to the heat generating means, a power supply circuit for supplying power to the fixed cylinder terminal, wherein the movable cylinder terminal and the fixed cylinder terminal are arranged at a predetermined zoom position; A zoom lens barrel with anti-fogging measures, wherein power is supplied from the power supply circuit to the heating means in a contact state.