JP2953133B2 - Imaging system with anti-fogging means - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographing system having anti-fogging means suitable for a camera such as a television camera or a video camera. The present invention relates to a photographing system having a fogging prevention means for effectively removing fogging generated on a lens surface by heating the lens surface.

[0002]

2. Description of the Related Art Conventionally, television cameras, video cameras,
Cameras such as photographic cameras are often used in environments where the temperature and humidity rapidly change, such as indoors and outdoors.

Generally, 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 fogged, making it impossible to take a picture.

For this reason, conventionally, for example, in a television camera or the like, when a heating means is provided inside the camera and the environmental conditions of the outside air suddenly change, the temperature inside the camera is raised by the heating means and the temperature is generated on the lens surface. The fogging was removed or fogging on the lens surface was prevented.

However, in general, it is very difficult to uniformly raise the temperature of each lens surface in the lens barrel to prevent fogging from occurring over the entire lens surface, and inevitably causes partial fogging. There were many things.

On the other hand, for example, Japanese Patent Laid-Open Publication No.
No. 17, the transparent conductive film is uniformly provided on the surface of a transparent substrate such as glass, and the positive and negative electrodes are appropriately provided on a part of the transparent conductive film. The proposed imaging system is proposed.

[0007]

Problems to be Solved by the Invention JP-A-1-185
In Japanese Patent No. 517, a transparent conductive film is applied to a lens surface having a diameter of 120 mm, and a pair of electrodes having an arc-shaped length of 80 mm are provided to face the periphery of the transparent conductive film on the lens surface. Then, a voltage of 12 V is applied to the electrode from a stabilized DC power supply, and a current of 0.5 A flows. Thus, the temperature of the surface of the transparent conductive film is raised by 32 ° C. to 46 ° C. 20 minutes after the start of energization.

In this publication, the fogging of the lens surface due to an environmental change is prevented. In general, the thickness of the lens differs between the center of the optical axis and the periphery. In particular, this difference is large on a lens surface having a strong curvature.

The transparent conductive film applied to the lens surface has a uniform thickness, and since the electrodes are provided in an arc on the periphery of the lens surface, the flow of current varies depending on the location and the temperature of the lens surface rises. Sometimes differed depending on the location.

[0010] In this case, there is a problem in that there is a variation in the removal of fogging due to a temperature difference between the lens surfaces, and there is a case where the lens is broken due to a partial difference in thermal expansion.

According to the present invention, when a current is supplied to the transparent conductive film provided on the lens surface to cause the transparent conductive film to generate heat and prevent the fogging of the lens surface and remove the fogging of the lens surface, the temperature difference of the lens surface is reduced. Is controlled so as not to exceed a predetermined value, thereby effectively removing the fogging of the lens surface and having an anti-fogging means for effectively preventing the lens from being damaged by a temperature difference of the lens surface. The purpose is to provide.

[0012]

According to the present invention, there is provided a photographing system having anti-fogging means, wherein a transparent conductive film is provided on at least one of a plurality of lens surfaces constituting the photographing system, and power is supplied from a power supply control circuit. In a photographing system having an anti-fogging means for supplying power to the transparent conductive film through means and heating the lens surface to remove the fogging generated on the lens surface, at least two temperature sensors are provided on the lens surface. The power supply control circuit uses an output signal from the temperature sensor to determine whether or not the temperature difference on the lens surface has reached a certain value. The power supply to the conductive film is stopped.

[0013]

FIG. 1 is a sectional view of a main part of a lens barrel structure according to a first embodiment of the present invention, FIG. 2 is an enlarged explanatory view showing the vicinity of a focus lens group in FIG. 1, and FIG. 3 is viewed from a direction A in FIG. FIG. 4 is a block diagram showing power supply to the transparent conductive film provided on the lens surface of FIG.

In FIG. 1, reference numeral 1 denotes a lens barrel, and reference numeral 2 denotes a focus lens group. FIG. 1 shows a case where the zoom lens comprises two lenses 2-1 and 2-2. Reference numeral 3 denotes a variable power lens group (variator lens group), which is linearly arranged on the optical axis via a guide pin 11-1 along a cam groove (curved cam groove) 12-1 formed in the cam cylinder 10 with the variable power. Or moving non-linearly.

Reference numeral 4 denotes a correction lens group (compensator lens group), which is provided with a guide pin along a cam groove (curved cam groove) 12-2 formed in the cam cylinder 10 in order to correct an image plane variation accompanying zooming. It moves (reciprocates) non-linearly on the optical axis via 11-2. Reference numeral 5 denotes a fixed imaging lens (relay lens group).

Reference numeral 6 denotes a focusing lens barrel, which holds the focus lens group 2. Reference numeral 7 denotes a guide roller which moves in a groove formed in the lens barrel 1 when the focusing barrel 6 is driven. Reference numeral 8 denotes a focus drive motor which rotates or drives the focusing lens barrel 6 straight through a focus drive screw 9. Reference numeral 13 denotes a linear cam for performing a zoom operation, which is formed on the lens barrel 1.

Reference numeral 19 denotes a spacer for adjusting the distance between the lens 2-1 and the lens 2-2 on the optical axis. A holding ring 21 fixes the two lenses 2-1 and 2-2 to the focusing lens barrel 6. 17-1, 17-2, 17
Reference numerals -3 and 17-4 denote transparent conductive films, respectively.
1, 2 and 2 lens surfaces 2-1a, 2-1b, 2-2a,
2-2b.

Reference numerals 18-1 and 18-2 denote arc-shaped electrodes, which are provided on the focusing lens barrel 6 for electrical connection with the transparent conductive film 17-4 on the lens surface 2-2b. 20
Reference numerals -1 and 20-2 denote arc-shaped electrodes, and the lens surface 2-2.
The spacer 19 is provided for electrical connection with the transparent conductive film 17-3 a. Reference numerals 20-3 and 20-4 denote arc-shaped electrodes, which are provided on the spacer 19 for electrical connection with the transparent conductive film 17-2 on the lens surface 2-1b.

Reference numerals 22-1 and 22-2 denote arc-shaped electrodes, and as shown in FIG. 3, the transparent conductive film 1 on the lens surface 2-1a.
It is provided on the presser ring 21 for electrical connection with 7-1. Reference numerals 24-1 and 24-2 denote temperature sensors provided on the surface of the transparent conductive film 17-4 around the lens surface. 25-
Reference numerals 1, 25-2 denote temperature sensors, which are provided on the surface of the transparent conductive film 17-3 around the lens surface. 26-1, 26-2
Denotes a temperature sensor and the transparent conductive film 17 around the lens surface
-2 surface. Reference numerals 27-1 and 27-2 denote temperature sensors, which are provided on the surface of the transparent conductive film 17-1 around the lens surface 2-1a as shown in FIG.

In this embodiment, at least two temperature sensors are provided on the transparent conductive film on one lens surface as described above.
The partial temperature difference on the lens surface is determined.

Reference numeral 14 denotes a power supply control circuit, which controls a voltage applied to each transparent conductive film electrode based on a signal relating to the temperature of the lens surface obtained from each temperature sensor. 1
Reference numeral 5 denotes a dew sensor, which detects whether or not there is a water drop or the like in the lens space. Reference numeral 16 denotes a power switch.

23-1, 23-2, 23-3, 23-
Reference numerals 4 and 23-5 denote lead wires, which are provided on the holding ring 21, the spacer 19, the focusing lens barrel 6, and the like, respectively, and correspond to the corresponding electrodes (18-1, 18-2, 20-).
1,20-2,20-3,20-4,22-1,22
The power is supplied from the power supply control circuit 14 via a switch described later in 2).

Reference numeral 28-1 denotes a switch for turning on / off a current to the transparent conductive film 17-1 provided on the lens surface 2-1a of the lens 2-1. A switch 28-2 is a transparent conductive film 17 provided on the lens surface 2-1b of the lens 2-1.
The current to -2 is turned ON / OFF. A switch 28-3 turns on / off a current to the transparent conductive film 17-3 provided on the lens surface 2-2a of the lens 2-2. 2
A switch 8-4 is a lens surface 2-2 of the lens 2-2.
ON / OFF of the current to the transparent conductive film 17-4 provided in b.
doing. The electrodes, lead wires, switches, and the like constitute one element of the power supply means. Further, the transparent conductive film 17-1 described above is used.
To 17-4, the temperature sensors 27-1 and 27-2, the power supply control circuit 14, the power supply means, and the like constitute one element of the fogging prevention means.

Next, the operation of this embodiment will be described.

In this embodiment, when the environment of the photographing system changes and fogging occurs on the lens surface (or when fogging is about to occur), a signal for removing fogging is input from the power supply switch 16.

The power supply control circuit 14 supplies a current to the transparent conductive films (17-1 to 17-4) based on a signal from the power supply switch 16.

For example, a signal from the power supply control circuit 14 passes through the switches 28-1 (28-2 to 28-4) and the presser ring 2
1 (spacer 19, focusing lens barrel 6), arc-shaped electrodes 22-1, 22-2 (20-1 to 20-4,
18-1, 18-2) to the lens surface 2-1a (2-1).
b, 2-2a, 2-2b)
(17-2 to 17-4) to supply current to the transparent conductive film 1
7-1 (17-2 to 17-4) generates heat. Thereby, the lens surfaces 2-1a (2-1b, 2-2a, 2-2)
The haze generated in b) is removed by evaporation.

At this time, two temperature sensors 27-1 and 27-2 (25-1, 25-25) provided on the lens surface 1-a are used.
2, 26-1, 26-2, 27-1, 27-2), the temperature difference on the lens surface 2-1a is detected. Then, it is determined whether or not the temperature difference has reached a preset value. When it is determined that the temperature difference has reached, the supply of the current to the transparent conductive film 17-1 is stopped. This prevents the temperature difference on the lens surface 2-1a from exceeding a predetermined value and prevents the lens from being damaged.

In the embodiment shown in FIG. 3, two temperature sensors are provided on the transparent conductive film surface of the lens surface. However, any number of two or more temperature sensors may be provided.

For example, as shown in FIG.
The six temperature sensors (27-1 to 27-6) are provided on the surface of the transparent conductive film 17-1 in the peripheral portion of the lens, and the temperature difference between the lens surfaces is detected using the output signals from the six temperature sensors. By doing so, the temperature of the lens surface can be controlled more accurately.

In this embodiment, when a water droplet or the like is detected by the dew sensor 15, the power supply control circuit 14 supplies an electric current to the transparent conductive film to heat the lens surface and evaporate the water droplet generated in the lens space. I try to remove it.

[0032]

According to the present invention, as described above, current is supplied to the transparent conductive film provided on the lens surface, and the transparent conductive film is heated to prevent the occurrence of fogging on the lens surface and remove the fogging on the lens surface. In this case, by controlling the temperature difference on the lens surface so as not to exceed a predetermined value, fogging on the lens surface was effectively removed and the lens was effectively prevented from being damaged by the temperature difference on the lens surface. It is possible to achieve a photographing system having fogging prevention means.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a lens barrel structure according to a first embodiment of the present invention.

FIG. 2 is an enlarged explanatory view near a focus lens group in FIG. 1;

FIG. 3 is a schematic view of a main part when viewed from a direction A in FIG. 2;

FIG. 4 is a block diagram showing power supply to the transparent conductive film of FIG. 1;

FIG. 5 is a schematic view of an embodiment when there are six temperature sensors according to the present invention.

[Explanation of symbols]

Reference Signs List 1 lens barrel 2 focus lens group 3 variable power lens group 4 correction lens group 5 relay lens group 6 focusing lens barrel 7 guide roller 8 focus drive motor 14 power supply control circuit 2-1 and 2-2 lenses 17-1 to 17- 4 transparent conductive films 20-1 to 20-4, 22-1, 22-2, 18-1,
18-2 Electrodes 24-1, 24-2, 25-1, 25-2, 26-1,
26-2, 27-1 to 27-6 Temperature sensor

Claims (1)

(57) [Claims] 1. A transparent conductive film is provided on at least one lens surface of a plurality of lens surfaces constituting a photographing system, and a power supply control circuit supplies power to the transparent conductive film via a power supply means to heat the lens surface. In a photographing system having a fogging prevention means for removing fogging generated on the lens surface, at least two temperature sensors are provided on the lens surface, and the power supply control circuit uses an output signal from the temperature sensor. Determining whether the temperature difference on the lens surface has reached a certain value, and stopping the power supply to the transparent conductive film provided on the lens surface when the temperature difference has reached the certain value. An imaging system having a prevention means.