JP2803689B2 - Aperture device for electronic still camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aperture device for an electronic still camera.

[0002]

2. Description of the Related Art An electronic still camera photoelectrically converts a still image formed on a solid-state imaging device such as a CCD image sensor and records the obtained video signal on a recording medium such as a magnetic disk. A solid-state imaging device generally has a narrow dynamic range, and requires accurate exposure control during photographing.

[0003] Exposure control of an electronic still camera is generally performed by programmed exposure using a combination of an exposure time and an aperture. To change the exposure time, the charge accumulation time of the solid-state imaging device is adjusted using a sensor shutter. However, in an electronic still camera using a sensor shutter,
The solid-state imaging device is still irradiated with the subject light even after the end of the charge accumulation time. For this reason, a noise charge is likely to be generated in the charge storage portion and the charge transfer path of the solid-state imaging device and around it before and after photographing. Then, when these noise charges leak into the charge transfer path, they cause so-called smear noise, which significantly lowers the quality of the reproduced image.

[0004] For this reason, the present applicant has proposed the following turret type aperture device. When shooting takes place,
A stop aperture having an aperture diameter corresponding to the photometric result is inserted into the optical path, and exposure starts with the start of charge accumulation in the solid-state imaging device. When the charge accumulation time elapses, the diaphragm driving means operates and the diaphragm plate is displaced, and instead of the diaphragm opening used for photographing, a shielding portion formed between adjacent diaphragm openings of the diaphragm plate is located in the photographing optical path. And the CCD enters a light-shielding state. Therefore, no unnecessary light is irradiated to the solid-state imaging device after the end of the charge accumulation time.

[0005]

However, such a turret type aperture mechanism of an electronic still camera has a drawback in that the aperture plate and the shielding portion are formed in the turret type aperture plate of a disk, so that the aperture plate becomes large. . Therefore, in order to reduce the size of the turret type aperture plate, there is an aperture plate in which the aperture holes are brought close to each other to such an extent that there is no light leakage, and further, a light shielding portion of the aperture is not provided. In that case, there was no problem in field shooting, but smearing and flicker occurred in frame shooting.

That is, when a frame is shot by an electronic still camera, the CCD signal is read out in the order of the A field and the B field. When reading the A field,
The signal of the B field remains in the image portion, and light from the aperture hole affects the signal of the B field, causing smear and flicker. The present invention
In an aperture device with a turret type aperture plate that is close to the aperture hole for miniaturization and further has no light-shielding part, smearing in frame shooting can be achieved by shielding the opening with a shielding member immediately after shooting is completed. The purpose is to eliminate flicker.

[0007]

According to the present invention, there is provided an electronic still camera for converting an electric signal obtained by imaging a subject with a solid-state image sensor into a video signal and recording the video signal on a recording medium. In the above, a turret type aperture plate provided with a plurality of aperture openings for restricting the subject light passing through the exposure aperture, and the turret type aperture plate so as to be driven in conjunction with the rotation operation of the turret type aperture plate A shielding member connected to a turret type aperture plate, and after the end of the charge accumulation time of the solid-state imaging device, when the turret type aperture plate is rotated, the shielding member is displaced to open the exposure opening. It is characterized by covering.

[0008]

According to the present invention, exposure is performed by selecting the aperture of the aperture plate. At this time, the shielding plate is at a position regulated by the stopper. When the photographing is completed, when a predetermined pulse is rotated in a direction opposite to the direction in which the diaphragm plate is rotated, the shielding member comes to a position covering the opening.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an aperture device for an electronic still camera according to the present invention will be described below in detail with reference to the accompanying drawings. As shown in FIG. 1, the turret type diaphragm plate 10 is rotatably supported on an iris base plate 12 via a support shaft 14.
A two-phase excitation stepping motor 16 is attached to the iris base plate 12. As shown in FIG.
It is fixed to the back of.

The output shaft 18 of the stepping motor 16
1 and 2, a gear 20 is fixedly engaged with the gear 10A formed on the entire periphery of the diaphragm plate 10. As shown in FIG. Thereby, the rotational driving force of the stepping motor 16 is transmitted to the diaphragm plate 10 via the gears 20 and 10A, and the diaphragm plate 10 is
4 can be rotated about a rotation axis. The gear 20
And the ratio of the number of teeth of 10A is 1: 4. Further, the stepping motor 16 is rotated by a desired amount in response to a pulse signal output from a pulse generation circuit (not shown).
0 rotation angle is controlled. Specifically, the stepping motor 16 rotates 18 ° each time one pulse is input from the pulse generation circuit, and rotates 360 ° when 20 pulses are input. Therefore, by outputting a signal of a total of 80 (= 20 × 4) pulses to the stepping motor 16 based on the gear ratio of the gears 20 and 10A, the diaphragm plate 10 can be rotated once.

A photo-interrupter 22 is fixed to the iris base plate 12, and the photo-interrupter 22 is
Thus, a notch (not shown) formed in the diaphragm plate 10 is detected, and the home position of the diaphragm plate 10 is detected from the time when the stepping motor 16 enters a certain excitation phase. By the way, the turret type diaphragm plate 10
Has a plurality of large and small apertures 24, 26, 28, 30, 32,
34 are formed on the concentric circles at predetermined intervals and alternately in size. The centers of the apertures 24 to 34 are aligned with the aperture plate 1
When 0 rotates, it is positioned at a position that matches the center of the opening 36 formed in the iris base plate 12.

A gear 40 meshes with the gear 10A of the diaphragm plate 10. A shield plate 44 is rotatably supported on a support shaft 42 of the gear 40, and the shield plate 44 is urged by a spring 46 toward one surface 40 </ b> A of the gear 40.
Therefore, when the gear 40 rotates, the shielding plate 44 rotates together with the frictional force. On the other hand, a stopper 48 is
A and 48B are provided. Stoppers 48A, 48B
When three pulses are given to the motor 16, the shielding plate 44
6 is provided in advance at a position for shielding the same. Since the shield plate 44 and the gear 40 are only integrally connected by frictional force, when the shield plate 44 comes into contact with the stoppers 48A and 48B and is restricted, only the gear 40 idles. Next, the operation of the camera having the turret type aperture plate configured as described above will be described.

First, the stepping motor 16 is rotated clockwise in FIG. 1, the gear 20 is rotated clockwise, the aperture plate 10 is rotated counterclockwise, and an arbitrary aperture is selected. At this time, the shielding plate 44 is regulated by the stopper 48B,
The gear 40 comes into sliding contact with the shielding plate 44 and slips. After the photographing is completed, when the stepping motor 16 is rotated in the direction opposite to the above-described direction by three pulses, that is, when the stepping motor 16 is rotated in the counterclockwise direction by three pulses,
The shielding plate 44 rotates counterclockwise in FIG. 1 to shield the opening 36 of the base plate 12 (see FIG. 3).

That is, as shown in FIG. 4, the charge stored in the photocell in the A field of the CCD exposed for a predetermined exposure time is transferred to the transfer path at time t ₁ by a field shift pulse, and thereafter at time t ₂ Is transferred to the storage unit at high speed (FIG. 4A). Then, the signal charges stored in the storage unit are read out line by line as a CCD output (FIG. 4C). Meanwhile, power storage charge of photocell B fields of the CCD that are exposed by the same time as the A field is transferred in the transfer path at time t ₃ by a field shift pulse, after the reading of the A field is completed, at time t ₄ The data is transferred to the storage unit at a high speed (FIG. 4B). Then, the data is read line by line from the storage unit similarly to the A field.

However, during the period from the time t ₃ to the time t _4, smear components are accumulated because light is incident on the transfer path, and the B field signal is larger than the A field signal by the smear component. Become. When the signal of the A field and the signal of the B field are alternately read out line by line to complete the frame signal, the signal including the smear component is mixed every other line, so that the horizontal scanning lines appear coarse, resulting in a poor image quality. Invite.

Therefore, after the photographing is finished, that is, as shown in FIG. 4D, the exposure end time of the B field (time t ₃ )
Then, the rotation of the shielding plate 44 is started, and the opening portion 36 of the ground plate 12 is immediately shielded to prevent the smear component from being mixed. When the stepping motor 16 is rotated counterclockwise and the shielding plate 44 is restricted by the stopper 48A, after the photographing is completed, when the stepping motor is rotated in the reverse direction, that is, three pulses clockwise, the shielding plate 44 becomes the first pulse. The opening 36 is closed by rotating clockwise in the drawing.

As described above, according to the present invention, the stepping motor 16 is rotated three times in reverse with respect to the direction of the diaphragm plate regardless of the stopper position (48A, 48B) of the shielding plate 44 after the photographing is completed. The light-shielding plate 44 shields the opening 36 from light. This can eliminate smear and flicker in frame shooting. In this embodiment, when the open stop shown in FIG. 1 is used, it is not known which stopper the shielding plate 44 is in contact with, so that the rotation direction of the stepping motor 16 is not known. Therefore,
In this case, when the stepping motor 16 first rotates forward six pulses and then reversely rotates six pulses, it always hits one of the stoppers. Thereby, the shielding direction of the shielding plate 44 is known, and the three-pulse stepping motor 16 is rotated forward to move to the shielding position.

[0018]

As described above, according to the camera having the turret type aperture plate according to the present invention, the smear or flicker is generated in the frame photographing because the shielding member is immediately located in the exposure opening after the photographing is completed. do not do. Further, since the light blocking portion is not provided on the aperture plate, the aperture plate can be formed small.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment in which a camera having a turret type aperture plate according to the present invention is disposed on an iris base plate.

FIG. 2 is a sectional view of the embodiment of FIG. 1;

FIG. 3 is an explanatory view showing the operation of the embodiment according to the present invention.

FIG. 4 is a timing chart used to explain the operation of the embodiment according to the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Aperture plate 16 ... Stepping motor 24-34 ... Aperture hole 36 ... Opening 44 ... Shielding plate

Continued on the front page (72) Inventor Yasunori Nishijima 2-26-30 Nishiazabu, Minato-ku, Tokyo Fuji Photo Photo Film Co., Ltd. (72) Inventor Yasumasa Kayanuma 2-26-30 Nishiazabu, Minato-ku, Tokyo Fuji Photo (56) References JP-A-2-209087 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04N 5 / 225,5 / 235-5/243

Claims (2)

(57) [Claims] An electronic still camera for converting an electric signal obtained by imaging a subject with a solid-state image sensor into a video signal and recording the video signal on a recording medium, for limiting subject light passing through an exposure aperture. A turret type diaphragm plate provided with a plurality of diaphragm apertures ,
Driven in conjunction with the rotation of the let-type aperture plate
A shielding member connected to the turret type diaphragm plate ;
After the end of the charge accumulation time of the solid-state imaging device,
When the turret type diaphragm plate is rotated, the shielding member is displaced.
An aperture device for an electronic still camera, wherein the aperture device covers the exposure opening . 2. A gear is provided on a peripheral edge of the aperture plate and meshes with a drive gear driven by a stepping motor.
The gear of the diaphragm plate meshes with the driven gear and the shielding member is provided coaxially with the driven gear, and the shielding member rotates integrally with the driven gear by frictional contact and its movement is regulated by a stopper, 2. The shielding member moves from a position regulated by the stopper to a position covering the opening when a predetermined pulse stepping motor is driven.
Electronic still camera aperture device.