JP2711699B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device, and more particularly to an imaging device for recording a still image of a subject.

[Conventional technology]

In recent years, an imaging device for inputting a still image of a subject has
It is used for various purposes as a so-called electronic still camera or as an industrial inspection camera. In such a camera, a mechanical shutter is used to cope with a wide range of light amount and exposure time, and a CCD or the like is used as an imaging device due to a demand for a small and lightweight camera and high reliability. Is used.

FIG. 5 shows a block diagram of an example of a conventional still video camera of this type. 1 is an optical lens for imaging, 2
Is a half-open type mechanical shutter, 3 is a solid-state imaging device such as a CCD, 4 is a photometric circuit for determining an appropriate exposure,
5 is a colorimetric circuit for determining white balance, 6
Is a drive circuit for generating a gate pulse of the solid-state imaging device 3, 7 is a system control circuit for generating and controlling operation timing pulses of the entire device, and 8 is an output signal of the solid-state imaging device 3. From the color difference signal (R
−Y and BY) and a luminance signal + a synchronization signal (Y + Sync)
An image signal processing circuit 9 for generating a signal; a modulation circuit for FM modulating a signal from the image signal processing circuit 8;
Is REC (recording) for amplifying the signal from the modulation circuit 9
An amplifier 11 is a magnetic head for electromagnetically converting a signal from the REC amplifier 10, a magnetic sheet 12 for recording a magnetic signal from the magnetic head 11, and a motor 13 for rotating the magnetic sheet 12. , 14 are servo circuits for controlling the rotation of the motor 13.

FIG. 6 shows an example of the operation timing of the image pickup apparatus using such a half-open mechanical shutter 2. ΦT
Is a transfer pulse of the solid-state imaging device 3. T1 discharges the charge stored in the storage element of the solid-state imaging device 3,
It shows a time for performing a clear operation for preparing to store an optical signal corresponding to a subject into an electrical signal by storing the storage element in an empty state. T3 is the effective exposure time of the shutter, T5
Is a time for reading out a signal stored in the solid-state imaging device 3.

.PHI.S1 is a pulse of a shutter opening command, and the mechanical shutter 2 starts opening after a time delay of T2 from the pulse .PHI.S1. This time T2 is determined in addition to the structural delay time of the mechanical shutter 2 and all the factors such as individual variations caused by the accuracy of the mechanism, the speed of the motor 13 for driving the shutter 2 and the speed fluctuation due to the voltage of the magnet and the like. And is substantially longer than about 10 ms. .PHI.S2 is a pulse of a shutter closing command, which is a time including a structural delay time of the mechanical shutter 2, a variation in operation time of each shutter, and the like, which is also substantially about 10 ms or more. Φ
R is a pulse for notifying the read timing, and T5 is a time from when the shutter 2 is closed to when the shutter 2 is read.

[Problems to be solved by the invention]

However, in the conventional example described above, the delay time of the operation of the mechanical shutter 2, the variation of the operation time of each shutter caused by the variation of the accuracy of the mechanism, the voltage fluctuation of the motor for driving the shutter, the electromagnet and the like. Since the accumulation operation of the solid-state imaging device 3 is performed including the time of the variation, the accumulation time of the solid-state imaging device 3 becomes extremely long.

Known drawbacks of this type of solid-state imaging device 3 are dark current and white (dot) flaws called fixed pattern noise. The characteristics of these are proportional to the storage time of the solid-state imaging device 3. To increase. The dark current and the white spot significantly deteriorate the output image when the charge amount exceeds a certain amount. On the other hand, as described above, in the conventional example using the mechanical shutter, since the accumulation time of the solid-state imaging device is generally extremely long, the output image becomes rough due to dark current and white spots, Appears everywhere in the image, deteriorating the image quality and causing discomfort to the viewer.

The present invention has been made in order to solve the problems of the conventional example as described above, shortening the charge accumulation time of the solid-state imaging device, reducing the level of the dark current and white spots,
It is an object of the present invention to provide this type of imaging device capable of obtaining a high-quality output image.

[Means for solving the problem]

For this reason, in the present invention, a solid-state image pickup device is used as an image input means, and in an image pickup apparatus having a mechanical shutter for adjusting the amount of exposure, the shutter is electrically operated in accordance with the movement of the shutter curtain before the opening of the shutter curtain. A means for generating a static pulse is provided, and the charge discharging operation of the solid-state imaging device is performed immediately before the opening of the shutter by detecting an electric pulse signal corresponding to the movement of the shutter curtain. An object of the present invention is to achieve the above object by adopting means for storing the number of the pulse signal at which the discharging operation of the solid-state imaging device is started in a storage device linked to a system control circuit.

[Action]

With the above configuration, the imaging device according to the present invention is
By performing the charge discharging operation of the solid-state imaging device immediately before the opening of the mechanical shutter, the accumulation time of the solid-state imaging device can be reduced, so that image deterioration due to dark current due to white spots is prevented, and a high-quality output image is obtained. Can be obtained.

〔Example〕

 Hereinafter, the present invention will be described based on examples.

FIG. 1 is a block diagram showing the configuration of an electronic still camera according to an embodiment of the present invention, in which the same components 1 to 14 as those in FIG.

(Structure) When the symbols 1 to 14 are redundantly described, 1 is an optical lens for photographing, 2a is a signal indicating that the operation of the aperture blade has started before the aperture and a pulse signal according to the aperture diameter of the aperture according to the present invention. 3 is a solid-state image sensor such as a CCD, 4 is a photometric circuit for determining an appropriate exposure, and 5 is a colorimetric circuit for determining a white balance. , 6 are solid-state imaging devices 3
A drive circuit 7 for generating the gate pulse of
A system control circuit 8 for generating and controlling the operation timing pulse of the entire apparatus is provided with a color difference signal (RY and BY) from the output signal of the solid-state imaging device 3.
And an image signal processing circuit 9 for generating a luminance signal + a synchronization signal (Y + Sync).
A modulation circuit for FM modulation, 10 is a REC (recording) amplifier for amplifying a signal from the modulation circuit 9, 11 is a magnetic head for electromagnetically converting a signal from the REC amplifier 10, 12
Is a magnetic sheet for recording a magnetic signal from the magnetic head 11, 13 is a motor for rotating the magnetic sheet 12, and 14 is a servo circuit for controlling the rotation of the motor 13. Reference numeral 15 denotes an EEPROM (electrically erasable semi-fixed recording device) provided in accordance with the principle of the present invention, which number of pulses of a pulse signal from the shutter 2a is obtained before the charge discharging operation of the solid-state imaging device 3 is performed. This is a storage device for recording.

(Shutter Operation) FIG. 2 is a timing chart showing the operation of the half-open mechanical shutter 2 used in the present embodiment. Second
In FIG. 7A, the horizontal axis represents the time T from the start of the shutter curtain operation.
(S), the vertical axis indicates the aperture value F-No. The curve in the table represents the operation of the shutter 2 at the longest time,
For example, depending on the brightness of the subject, assuming that F5, 6 has proper exposure, the shutter closes rapidly after reaching F5, 6. FIG. 2 (b) corresponds to the horizontal axis in FIG. 2 (a), and the vertical line indicates a pulse ΦF generated according to the operation of the shutter.

Here, FIG. 3 shows an exploded perspective view of the half-open shutter structure, and the configuration / operation of the shutter 2a and the pulse generation mechanism will be described with reference to FIG. Reference numeral 21 denotes a forward / reverse rotation motor for driving the shutter 2a;
The gear train 24 for decelerating the rotation is moved rightward in the figure by the forward rotation of the motor 21, and the rack gear whose movement range is regulated by a stopper provided on a fixed portion (not shown) is connected to the rack gear 24. The clutch is fitted into the provided bearing portion 24a, is held rotatably in the vertical direction in the drawing around the bearing portion 24a, and is urged downward by a torsion coil spring 29 in the drawing.

Reference numeral 30 denotes a control plate having a projection 30a that abuts against a tip end portion 28a of the clutch 28, and is rotatably held around a bearing 30d. 31 is a plurality of light beams integrally formed with the control plate 30. A pulse plate having a transmission slit 31a, 32 is a shutter spring (tensile coil spring) for urging the control plate 30 in the clockwise direction until it abuts a stopper (not shown), and 33 is a pulse plate When turning 30, the photo-interrupters 34 and 35 for detecting the slit portion of the pulse plate 31 and outputting it as a pulse have openings 34b and 35b for adjusting the amount of light, respectively. The aperture blades having grooves 34a, 35a into which the protruding shafts 30b, 30c are inserted, 36 are each aperture blade 34,
Each of the long grooves provided in 35 and a shaft penetrating through the bearing 30d of the control plate 30, the shaft 38 is held rotatably about the rotating shaft 40 and is attracted to the coil 39 when the coil 39 is energized. Thus, the armature is rotated upward in the drawing to push up the clutch 28.

In order to perform the shutter operation in the above configuration, the motor 21
When the rack gear 24 is energized in the forward rotation direction, the rack gear 24
It is guided by the fixed shafts 25 and 26 via 3 and moves rightward in the figure. At this time, the tip 28a pushes the projection 30a of the control plate 30 while the clutch 28 also moves integrally with the rack gear 24. Therefore, the control plate 30 is rotated counterclockwise about the shaft 36. Each shaft 36, 37 is protruded by each shaft 30b, 30c protruding from the control plate 30.
The diaphragm blade 34 is moved leftward, and the diaphragm blade 35 is moved rightward. At this time, the openings 34b and 35b initially approach each other from the sharp portion of each opening from a closed state in which both openings are closed, and correspond to the shape in which the openings 34b and 35b are overlapped. The amount of transmitted light is controlled. The amount of movement of the diaphragm blades 34 and 35 at this time, that is, the control plate 3
An arbitrary aperture value is determined according to the zero rotation amount. Therefore, the relationship between the time from the start of the operation of the shutter 2 and the aperture value is determined by detecting a pulse generated when each slit 31a provided on the pulse plate 31 passes through the detecting unit of the photo interrupter 33, as shown in FIG. It is expressed as the relationship shown in a) and (b).

Here, as described above, when the coil 39 is energized for a certain period of time when the number of pulses corresponding to the proper aperture value F5, 6 which is temporarily determined to be proper exposure is detected, the armature 38 is attracted, and the clutch 28 Is lifted upward in the drawing, the control plate 30 is rapidly rotated clockwise by the shutter spring 32, the aperture blade is returned to the closed state, and the shutter operation is completed. Thereafter, the rack gear 24 and the clutch 28 are returned to the initial state by rotating the motor 21 in the reverse direction for a certain period, thereby completing a series of shutter operations.

(Imaging Apparatus / Operation) FIG. 4 is a timing chart showing the operation of the imaging apparatus of the present embodiment.

Hereinafter, the operation of the image pickup apparatus according to this embodiment will be described with reference to FIGS. 1, 2, 3, and 4.

In FIG. 4, Φ SS is a shutter operation command, the first pulse is a command to “open the shutter”, and the second pulse is a command to “close the shutter”. The shutter mechanism operates with the first pulse of ΦSS, and the motor, magnet,
The shutter curtain starts moving at a delay time _Td due to a mechanical structure such as a gear. _Td differs for each shutter due to variations in the accuracy of each component constituting the shutter, and the like. Shutter blade starts to open the light entrance window of after a time T _o starts the motion. The time T _o is different by the individual shutter by accuracy variation of each component constituting the shutter, thus the number of generated pulses ΦF of the shutter during the time T _o is different by the shutter individually.

The time required for discharging the charge of the solid-state imaging device 3 is determined by the device structure, and there is no large variation. In this embodiment, it is assumed that a pulse ΦF generated from the shutter 2 for discharging electric charges takes a little less than four shots. Then, in the shutter shown in FIG. 4, a pulse ΦF of the shutter until the time T _o is generated 7 shots. Therefore,
The EEPROM 15 in FIG. 1 stores that the shutter 2 starts opening from the seventh pulse ΦF.

If the shutter to be used is opened at the sixth pulse ΦF, the fact that the shutter is opened at the sixth pulse may be stored in the EEPROM 15. System control 7 is EEPROM15
The pulse ΦF before the number n of shutter opening start pulses stored in the image storage unit and corresponding to the interval before the charge is discharged from the solid-state imaging device 3.
The (n-4) th pulse is emitted from the shutter 2a, and at the same time, a pulse for discharging the charge of the solid-state imaging device 3 is applied to the solid-state imaging device 3.

By operating in this manner, the shutter 2a starts opening immediately after the charge discharge of the solid-state imaging device 3 is completed. In addition, since the individual variation of the shutter 2a stores in the EEPROM 15 the number of the actual opening of the shutter, the discharge of the charge of the solid-state imaging device 3 is always completed immediately before the opening of the shutter, and after the opening of the shutter. There is no fear that the solid-state imaging device 3 is discharged and smear development occurs.

After the shutter is opened, the operation according to the conventional example is performed, and the description is omitted here.

Although the above embodiment has been described with reference to the case where the mechanical shutter is the half-open type shutter 2a, the principle of the present invention can be applied to the case where the mechanical shutter is a focal plane shutter by the same means.

〔The invention's effect〕

As described above, according to the present invention, since the charge discharging operation of the solid-state imaging device is performed immediately before the opening of the mechanical shutter, the charge accumulation time of the solid-state imaging device of the imaging device using the mechanical shutter can be reduced. Can,
It has become possible to obtain a high-quality output image by lowering the levels of dark current and white spots.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a still video camera according to the present invention. FIGS. 2 (a) and 2 (b) are examples of operation timing charts of the half-open type shutter, and FIG. FIG. 4 is an exploded perspective view of the shutter type shutter structure.
5 is an example of an operation timing chart of the imaging apparatus according to the fifth embodiment.
FIG. 1 is a configuration block diagram of an example of a conventional still video camera, and FIG. 6 is an example of an operation timing chart of the example of FIG. 2,2a ... Semi-open mechanical shutter 3 ... Solid-state image sensor 7 ... System control circuit 15 ... EEPROM 31/33 ... Pulse plate / photo interrupter (pulse generating means) ΦF ... Pulse electric signal

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshihiko Kudo 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Inside the Tamagawa Office of Canon Inc. (56) References JP-A-62-185475 (JP, A)

Claims (2)

(57) [Claims] 1. A solid-state imaging device is used as image input means.
As a means for giving a necessary exposure amount to the solid-state image pickup device, an image pickup apparatus provided with either a half-open shutter having a stop and a shutter function at the same time, or a combination of a focal plane shutter having only a shutter function and a stop One of the half-open shutter and the focal-plane shutter further includes a signal generating unit for generating a pulse-like electric signal in accordance with the movement of a shutter curtain before the shutter is opened, and An imaging apparatus, wherein a charge discharging operation before an accumulation operation is performed immediately before the shutter opening by detecting the pulse-like electric signal. 2. The apparatus according to claim 1, wherein an instruction is given to execute the charge discharging operation of said solid-state imaging device at an arbitrary number of pulses of said pulsed electric signal.
An imaging device according to any one of the preceding claims.