JP3272825B2 - Camera static electricity protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera in which, when static electricity generated during a film winding operation or a film rewinding operation is discharged, noise is induced in an electronic circuit inside the camera, and the noise is generated. To prevent the electronic circuit from malfunctioning.

[0002]

2. Description of the Related Art In a camera, when a film is wound or unwound, static electricity is generated on the film by rubbing a part of the camera with a structural member of the camera. FIG. 2 and FIG. 3 show this state.

FIG. 2 shows the inside of the camera when the film is being rewound.
Shows a state where the film is unwound into the film cartridge 12 by a film unwinding mechanism (not shown). At this time, the film rubs against the film pressure plate 13 attached to the film rail surface 7 or the back cover 6 of the camera body. In FIG. 2, a portion where the film is rubbed against the film rail surface 7 is shown as a friction portion, and a portion where the film pressure plate 13 is rubbed with the film is shown as a friction portion.

FIG. 3 is an enlarged view of the frictional portion, showing that the film is rubbed against the film rail surface 7 so that a negative charge is accumulated on the film surface and a positive charge 16 is accumulated on the film rail surface 7. Is shown. Depending on the material of the film rail surface 7 and the type of the film, the voltage due to the accumulated electric charge may reach from 10,000 volts to 10,000 volts, and may discharge onto nearby metal parts and electronic circuits. FIG. 3 shows the moment when positive electric charges 16 accumulated near the film rail surface 7 are electrostatically discharged to the metal camera component 2 (arrows in the figure) through the perforation holes of the film (not shown). I have. At this time, the electric field in the surrounding space fluctuates greatly, and a voltage is induced on the pattern of the electronic circuit existing in the electric field and inside the IC by electrostatic induction and electromagnetic induction. May malfunction. In FIG. 3, a negative charge is stored on the film, and a positive charge 16 is stored on the film rail surface 7.
Depending on the type of film and the material of the film rail surface 7, the polarity of the accumulated charges may be reversed. In the past, noise was generated when static electricity generated during film winding and rewinding operations was discharged, and to prevent the electronic circuit of the camera from malfunctioning due to the noise, it was necessary to keep the electronic device at a sufficient distance from the film. A circuit is provided or, as shown in FIG. 4, a conductor 2 is provided between the film and the electronic circuit 3, and the conductor 2 is connected to a GND level of the electronic circuit 3 by a conductor 11 to connect the electronic circuit 3. A configuration is adopted in which a countermeasure is taken by shielding the noise with an electrostatic shield.

[0005]

However, in the prior art, if the electronic circuit is to be kept away from the film,
The design of the camera imposes restrictions on the arrangement of electronic circuit components, which is a major obstacle to miniaturizing the camera.

Further, even if a conductor is provided between the film and the electronic circuit and connected to the GND level, a sufficient effect may not be obtained. This will be described in detail below.

FIG. 4 shows a state in which the camera is left on a metal desk 8 and a motor (not shown) is rotating to rewind the film 1. At this time, the film and a part of the structure of the camera (not shown) The moment when the static electricity is generated by the rubbing and the static electricity is discharged to the conductor 2 is shown. When this discharge occurs, a positive charge is stored in the conductor 2 instantaneously, so that a negative charge is collected in the metal desk 8 and apparently between the conductor 2 and the metal desk 8. Form a capacitor. Although the electronic circuit 3 is located inside the capacitor, the electric field strength of the space 9 is determined by the electric charge stored in the conductor 2. Therefore, the conductor 2 before the electrostatic discharge occurs
Is zero, the electric field intensity in the space 9 around the electronic circuit 3 is also zero. However, after the electrostatic discharge, the electric field is rapidly changed by the electric charge stored in the conductor 2 to have a constant electric field intensity. . Accordingly, the electronic circuit 3 undergoes a sudden change in the electric field due to the electrostatic discharge. At this time, a high-frequency voltage of a certain level is induced in the electronic circuit 3 by the electrostatic induction.
This high-frequency voltage is noise, and if the level is not negligible, the electronic circuit 3 may malfunction.

If the polarity of the static electricity generated when the film rubs against a part of the structure of the camera is opposite to that described above, the electric charge stored in the conductor 2 by the electrostatic discharge becomes negative, and The desk 8 will collect positive charges. Therefore, the direction of the electric field in the space 9 is opposite, but noise still occurs on the electronic circuit 3. In addition, a similar phenomenon may occur even when a human body, for example, a palm, or the ground surface is used instead of the metal desk 8, because a capacitor is formed between the conductor 2 and the human body.

It is an object of the present invention to provide an electrostatic protection device which does not generate any noise in an electronic circuit installed near the film when static electricity generated during film winding and rewinding operations is discharged. With the goal.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a camera having a film winding and rewinding mechanism, comprising: a first conductor disposed near a film where static electricity is generated during a film winding operation or a film rewinding operation; A second conductor provided in the vicinity of the camera exterior member, and a lead wire for electrically connecting the first and second conductors without being connected to the ground are provided, and an electronic circuit mounted on the camera is provided with the first circuit. An electronic circuit malfunction due to electrostatic discharge, which is provided between the conductor and the second conductor, so that the electric field does not change in the space where the electronic circuit is arranged even when the two conductors are charged. This is to be an electrostatic protection device for a camera that has been prevented.

[0011]

By providing such means, even if static electricity generated by rubbing of the film and a part of the structure of the camera during the film winding and rewinding operations is discharged, the electronic device installed in the vicinity of the film is discharged. Noise is prevented from being generated in the circuit, and thus malfunction of the electronic circuit is prevented.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a camera placed on a metal desk 8 with the taking lens surface 15 facing upward. The electronic circuit 3 includes a display unit, has a function of displaying data transmitted from a control circuit of a camera body (not shown) to a photographer, and is installed inside the back cover 6. Therefore, when the back cover 6 is closed, the electronic circuit 3 is placed at a position close to the film.

In the camera having such a configuration, in this embodiment, the first conductor 2 is provided between the film and the electronic circuit 3, and the first conductor 2 is provided between the exterior member of the back cover 6 and the electronic circuit 3. A second conductor 4 is provided, and a first conductor 2 and a second conductor 4
Are electrically connected by a conducting wire 5.

In this camera, the film 1 wound on the spool is being rewound to a film cartridge (not shown), and static electricity is generated by rubbing against a film rail surface or a film pressure plate (not shown). FIG. 1 shows a state in which the first conductor 2 is electrostatically discharged. As soon as the first conductor 2 is charged with a positive charge by this electrostatic discharge, the conductor 5
Through the second conductor 4. Therefore, a capacitor is formed by the second conductor 4 and the metal desk 8, and a negative charge is accumulated in the metal desk 8, and the capacitor is formed in the space between the second conductor 4 and the metal desk 8. Produces an intense electric field.

The space 9 covered by the first conductor 2 and the second conductor 4 is surrounded by positive charges even after the electrostatic discharge, but the first conductor 2 and the second conductor 4 5, the same potential is maintained. Therefore, the electric field in the space 9 does not change. Therefore, the electronic circuit 3 installed in the space 9 is not exposed to the fluctuation of the electric field due to the electrostatic discharge, and therefore does not induce a voltage which becomes a noise, so that it does not malfunction.

In FIG. 1, a positive charge is applied to the first conductor by the electrostatic discharge. However, even if this is a negative charge, the same effect is exerted. Accumulates.

Although FIG. 1 assumes that the device is placed on a metal desk 8, the same effect can be obtained when the device is placed on the ground surface or in the palm of the photographer. .

The first conductor 2, the second conductor 4, and the conductor 5 in FIG. 1 need not necessarily be metal. Generally, it is sufficient if their electrical resistivity is 100 Ωm or less. Therefore, the second conductor 4 can be formed by depositing a metal compound such as indium tin oxide on a polyester film. Since the electronic circuit 3 has high transparency, even if the electronic circuit 3 includes a display unit such as a liquid crystal, the entire circuit can be covered without impairing its function. The conductive wire 5 can also be realized by using a conductive adhesive, a conductive tape, or mechanically pressing the first conductor 2 and the second conductor 4 into contact with each other.

[0020]

As described above, according to the present invention,
An electrostatic protection device having a function of preventing noise from being induced in an electronic circuit installed near the film when static electricity generated during film winding and rewinding operations is discharged, thereby preventing a camera from malfunctioning. Can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a camera having an electrostatic protection device according to the present invention, showing a configuration of a first embodiment.

FIG. 2 is a diagram showing a portion where static electricity is generated inside the camera.

FIG. 3 is an enlarged view of a part of a static electricity generation site in FIG. 2;

FIG. 4 is a diagram showing an example of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Film, 2 ... 1st conductor, 3 ... Electronic circuit which controls a camera, 4 ... Second conductor, 5 ... Conductor, 6 ... Camera back lid, 7 ... Camera body film rail surface, 8 ... Metal 9: Space around electronic circuit, 10: Battery as power source for driving electronic circuit, 11: GND line of battery, 12
... Film cartridge, 13 ... Film pressure plate, 15 ... Camera lens surface, 16 ... Accumulated positive charge.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kikuchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Yoshii 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-59-152428 (JP, A) Japanese Utility Model Laid-open No. 2-19043 (JP, U) Japanese Utility Model Application No. 3-129943 (JP, U) Japanese Utility Model Laid-open No. 4-53231 (JP, A) U) JP-A 3-108232 (JP, U) JP-A 62-91629 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03B 17/00-17/04

Claims (1)

(57) [Claims] 1. A camera having a film winding and rewinding mechanism, wherein a first conductor installed near the film where static electricity is generated at the time of film winding operation or rewinding operation, and a second conductor installed near the camera exterior member. Connect two conductors and these first and second conductors to ground.
A lead wire for electrical connection without connection, and an electronic circuit provided in the camera is installed between the first conductor and the second conductor, so that even when the two conductors are charged,
Electric field does not change in the space where child circuit is placed
Camera electrostatic protection device which prevents electronic circuit malfunction due to electrostatic discharge, characterized in that.