JP3072517B2 - Electronic still camera - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronic still camera, and more particularly to an electronic still camera using a solid-state imaging device.

[Conventional technology]

In recent years, an electronic still camera using a solid-state imaging device such as a CCD (charge coupled device) and a MOS (metal oxide semiconductor) has been put into practical use. Hereinafter, an example of this type of conventional electronic still camera will be described with reference to the drawings.

FIG. 6 is a schematic view showing an example of an exposure mechanism of a conventional electronic still camera. Reference numeral 1 denotes a CCD, 31 denotes an aperture shutter, which is opened and closed by a step motor (not shown) or the like, and is completely closed before and after photographing. Reference numeral 32 denotes a photometric element.
And the opening / closing timing of the aperture shutter 31 is determined. FIG. 7 is an example of a characteristic diagram showing a temporal change of the exposure amount B on the CCD 1 when photographing is performed by the exposure mechanism.

A from the closed state where the aperture shutter 31 is shielded from light
It begins to open at point, turns around and closes at point b, and ends at point c. Assuming that the slope of the straight line ab is m and the slope of the straight line bc is n, the slopes m and n correspond to the opening / closing speed (shutter speed) of the aperture shutter 51. Becomes m ', n'. Conversely, when the opening / closing speed decreases, the inclination becomes m ", n", and the exposure amount B to the CCD 1 changes. Furthermore, the positions of the points a, b, and c generally tend to vary in the direction of the time axis T due to mechanical and electrical factors, all of which are error factors, and deteriorate the exposure accuracy. .

Therefore, an attempt has been made to improve the exposure accuracy by performing readout photometry using the CCD1. 8th
FIG. 1 shows an example of an exposure operation sequence flowchart of a conventional electronic still camera including this kind of CCD re-reading photometry.

That is, when the photographer turns on the release 1 in step S11, external photometry is performed by the external photometric element 32 (step S12). The timing of opening and closing the aperture shutter is determined based on the information obtained by the external photometry.
Turn on the release 2 at S13 to open and close the aperture shutter 31,
In step S14, the CCD 1 is exposed ("exposure 1"). Next, based on the information read from the CCD 1 in step S15, the opening / closing timing of the aperture shutter 31 is calculated / corrected. In step S16, the aperture shutter 31 is opened / closed again (main exposure, "exposure 2"), and step S17 is performed. Then, the exposure is ended, and the video information is recorded on a floppy disk or the like in step S18.

Next, FIG. 9 shows an example of a timing chart of the above-described conventional imaging sequence.

(1) in the vertical synchronizing pulse V _P, 1V until the next pulse V _P
It is called a period and is set to 1/60 second. (2) is a vertical transfer pulses PS which is synchronous to the vertical sync pulse V _P, (3)
Represents the exposure amount B of the CCD 1 shown in FIG. (4)
Is a signal read from CCD1. Charge accumulated is exposed in CCD1 is synchronized to the vertical synchronization pulses V _P immediately after exposure, if "field imaging", is read in the next 1V period. Since the 1V period is 1/60 second, in the case of “frame shooting”, two fields are read out during 1/60 × 2 = 1/30 second.

(5), (6), the recording gate 1 a (hereinafter, RG1, RG2 and abbreviated), if the field photography, rise in synchronization with the vertical synchronizing pulse V _P, the image information for one field Is recorded. In the case of frame shooting, both RG1 and RG2 sequentially rise, and video information for two fields is recorded. (7) represents ON / OFF of relays 2.

Next, according to these timing charts, (7)
The timing of each pulse after the release 2 is turned on will be described. Reference numeral 41 in (3) denotes exposure (exposure 1) obtained by opening and closing the aperture shutter 31 at the determined timing as a result of external photometry in the release 1. After the exposure 1 is completed, in (1), between the next vertical synchronizing pulse V _P1 and the next vertical synchronizing pulse V _P1 ′, the data is read from the CCD 1 in (4). As a result of the calculation based on the read signal, the opening / closing timing of the aperture shutter 51 is corrected,
42 in (3), that is, exposure 2 is performed, and in the case of field photographing, data is read out from the next vertical synchronizing pulse _VP2 to the next pulse _VP2 'and at the same timing as in (5). Recording gate 1 RG1 rises and records during 1/60 second. In the case of frame photographing, after the signal of one field of the odd and even fields is read out and recorded during the vertical synchronization pulse V _P2 -V _P2 ′ of (1), the pulse
Between V _P2 ′ and the next pulse V _P2 ″, a signal for another field is read and recorded.

Next, FIG. 10 shows a schematic diagram of an example of a configuration in which the CCD is an interline CCD.

51 is each photodiode as a photoelectric conversion element, 52
Is a vertical transfer register, 53 is a signal read gate, 54
Is a horizontal register, and 55 is a charge detection unit, which converts the transferred signal charge into a signal voltage. Reference numeral 56 denotes a signal output terminal, and reference numeral 57 denotes each cleaning drain, which is used to discard unnecessary charges other than signal charges.

 Next, the operation will be described.

The photodiode 51 photoelectrically converts incident light from a subject to obtain signal charges. The signal charge is transferred to the vertical transfer register 52 in the right direction in the figure via the signal readout gate 53, is sequentially transferred to the horizontal register 54, is converted into a voltage by the charge detection unit 55, and is output from the signal output terminal 56. Obtained sequentially as a signal. The point-sequential signal becomes a television signal by signal processing.

Furthermore, in order to solve the problems of exposure accuracy and cost as described above, there is provided a means for controlling exposure by an electronic shutter that electrically controls the accumulation time of charges read from the CCD without using a mechanical shutter. It has been proposed (for example, JP-A-62-166661).

FIG. 11 shows an example of a timing chart of this type of electronic shutter.

The charge accumulated from the vertical synchronization pulse _{VP3 in} (1) is
The cleaning pulse 57 in FIG. 10 is discarded by the clear pulse ES (3), and the charge 61 is cleared on the CCD indicated by the hatched portion in FIG. Then, after being transferred to the vertical registers by the vertical transfer pulse PS ₃ in synchronization with the next vertical sync pulse V _P3 'of (the intersection of Figure 11 the shaded portion) accumulated charge 62 to the CCD vertical sync pulses V _P3, Next one
Read within the V period. Therefore, the shutter time T _V is from the clear pulse ES to the vertical transfer pulse PS ₃ , and the shutter time T _V can be changed by controlling the position of the clear pulse ES.

[Problems to be solved by the invention]

However, when exposure control is performed by the mechanical aperture shutter shown in the first conventional example, or
Even when exposure control is performed by the above-described electronic shutter, the following problems occur. That is: (1) When a mechanical aperture shutter is used Since the exposure accuracy required by the CCD is extremely high, the exposure amount for each shot changes due to play (play) and friction between members of the aperture shutter. The so-called "cut unevenness" occurs.

Further, by performing the re-measurement as described above, the photometry accuracy is improved, but the mechanical operation accuracy is not improved.

(2) When an electronic shutter is used Since an optical image is constantly radiated on the CCD, during the operation of reading out the charge stored in the CCD, that is, the vertical transfer register
During the transfer on the wire 52, the charge that has begun to accumulate in the photodiode 51 wraps around, and a phenomenon called "smear", in which white strings are drawn above and below a particularly bright image, occurs, which significantly degrades the image.

To solve this problem, for example, Japanese Patent Application No. 62-298282
As shown in the figures, it has been proposed to provide a light shielding unit for shielding the CCD image pickup unit from light during almost all periods other than the period of the electronic shutter operation. However, liquid crystal shutters and PLZT (lanthanum lead zirconate titanate) as light shielding means have not yet been put into practical use due to problems such as light shielding properties, responsiveness, and cost. Because there is some variation, it is necessary to expect a certain amount of time delay before the start of light shielding, and because it takes time from the start of light shielding to complete light shielding, Since charges are accumulated on the photodiode 51, the problem of the occurrence of smear has not been sufficiently solved.

The present invention has been made in order to solve the problems of the conventional example as described above, and provides an electronic still camera of this type which has high photometric accuracy and can obtain a still image without a smear phenomenon or the like. The purpose is.

[Means for solving the problem]

For this reason, in the present invention, there is provided an electronic shutter function, an imaging unit, a mechanical exposure control unit for controlling light incidence of the imaging unit, and a state in which the size of the diaphragm of the mechanical exposure control unit is fixed. Controlling the charge accumulation time of the image pickup means so as to perform a photometric operation in the image pickup means, and after performing the light measurement operation in the image pickup means, the mechanical exposure control means during the light measurement operation of the image pickup means A still image capturing is started by once clearing the accumulated charge of the image capturing unit while maintaining the size of the aperture, and the mechanical exposure control unit controls the image capturing unit based on a photometric result by a photometric operation of the image capturing unit. An electronic still camera, comprising: a control unit that controls a time during which light is blocked from entering the camera and controls to end still image capturing.

〔Example〕

Hereinafter, the present invention will be described based on examples. Fig. 1 ~
FIG. 4 is an explanatory view of an embodiment of the electronic still camera according to the present invention.

(Configuration) FIG. 1 is an explanatory perspective view of the exposure mechanism. Straight line l
Is an optical axis, 1 is a CCD which is an image sensor, 2 is a step motor, 3 is a rack gear that can move in the direction of the arrow 3a shown in the figure by meshing with a pinion gear 2a mounted on the axis of the step motor 2, and 4a is a rack gear. 3 and fixed to 5
And 4b are rods connecting the members of 5 and 7 in the same manner, 5 is a ring rotatable around the optical axis l, and 6 and 7 are Each is fitted with each rod 4a, 4b,
An aperture member 8 having apertures 6a and 7a for aperture, and a photoreflector 8 for reading the contrast of a striped pattern 7c on the aperture member 7.

(Operation) Next, an operation in the above configuration will be described.

When the step motor 2 starts rotating according to an exposure command from a microcomputer (not shown) for controlling the system, the rack gear 3
Moves in the direction of arrow 3a, and the throttle member 6 connected by the rod 4a moves in the direction of arrow 6b. In addition, since the ring 5 rotates in the direction of the arrow 5a by the movement of the rod 4a, the stop member 7 is moved by the arrow 4a connecting the ring 5 and the stop member 7 with the arrow.
It moves in the direction 7b, and the apertures 6a / 7a open greatly. The movement of the diaphragm member 7 causes the stripe pattern on the diaphragm member 7 to move.
7c also moves in the direction of the arrow 7b at the same time, so that the output of the photoreflector 8 reading it changes, and the microcomputer determines the current position and the moving speed of the diaphragm members 6 and 7 according to the number of detected pulses and the pulse interval. Can be read.

Conversely, when closing the apertures 6a / 7a, the step motor 2 may be rotated in the reverse direction.

(Exposure Operation) FIG. 2 shows an example of a timing chart of the exposure operation of the present embodiment. (1) is a vertical synchronizing pulse _VP , and (2) is a vertical transfer pulse PS, from which signal charges accumulated are read. (3) is a pulse SP for controlling the operation of the step motor 2 in FIG. 1, and (4) is a pulse SP.
The opening state of the shutter due to the opening and closing of the aperture members 6 and 7 is shown. (5) is the output pulse PR of the photoreflector 8,
(6) CCD that triggers the start of exposure of the electronic shutter
(7) is the exposure amount B accumulated in the CCD1, and (8) is the signal read from the CCD1.

2 will be described with reference to the exposure mechanism shown in FIG. 1 and the exposure operation sequence flowchart shown in FIG.

In step S1, when the operator presses the release 1 of the camera, the external photometry is performed by a photometry element (not shown) in step S2. As a result, the size of the aperture in exposure 1 and the shutter speed T _V1 (FIG. 2 (7)) are determined, and a predetermined pulse SP is given to the step motor 2 in FIG. Assuming that the time at which the first pulse is output is t ₀ (FIG. 2 (3)), a mechanical time lag is required from time t ₀ until the aperture members 6 and 7 start moving in the directions 6b and 7b, respectively.

In FIG. 2 (4), each of the aperture members 6, 7 is 6b
And the time when exposure to CCD1 is started by moving in the direction of 7b.
Assuming that t _{1 is} a time when the aperture value is opened to a predetermined aperture value is t ₂ , time (t _{0 to} t ₁ ) is a mechanical time lag, and time (t ₁ to t ₁ )
t ₂ ) is the time during which each of the aperture members 6, 7 is operating. Thus, at time (t ₁ ~t _2), the output pulse PR of the photo-reflector 8 is changed.

Shutter speed T _V1 = (t
₄ -t ₃₎ and so that raises the clear pulse ES that triggers an electronic shutter to time t _3. Then, the charge of the hatched portion 21 stored in the CCD 1 in FIG. 2 (7) is cleared through the cleaning drain. Then, at time t ₂ following the By raises vertical transfer pulse PS in synchronization with the appearing vertical synchronizing pulses V _P0 (FIG. 2 (5)) at time t _4, the time (t ₃ ~t ₄₎ Crossed diagonal lines accumulated between 22
Are transferred and read out. The microcomputer of the camera performs photometry again based on the read information, and moves the control pulse of the step motor 2 in the direction of closing the aperture shutter.
Determining the timing t ₆ for generating SP (Fig. 2 (3)).

Next, the exposure 2, ie during the exposure, CCD again starting accumulation to clear the charges accumulated at time t _5. At this time, the aperture shutter remains open. The time t ₆ in given closing direction of the pulse to the step motor 2, between the time (t ₇ ~t _8), each throttle member 6 and 7,
The aperture shutter moves in the opposite direction to 6b and 7b, respectively, and the aperture shutter is closed. Therefore, since the mechanical members such as the diaphragm members 6 and 7 block the light image, the exposure of the CCD 1 is completed. Therefore, the light image is not irradiated on the CCD 1 thereafter, and the smear phenomenon as described above occurs. Does not occur.

Vertical synchronization pulse V _P0 ′ after the end of exposure (FIG. 2 (1))
Exposure 2 by the vertical transfer pulse PS issued in synchronization with
At this time, the accumulated charges 23 (cross-hatched portions) are read (FIG. 2 (7)).

(Control of the operating speed of the aperture shutter) In FIGS. 2 and 3, as a result of the photometry / calculation in exposure 1 (step S5 in FIG. 3), the timing t ₆ of outputting a pulse to the step motor 2 is obtained. (Fig. 2 (3))
There were determined, after having a time lag, to move each diaphragm members 6 and 7 during the time (t ₇ ~t _8), but not the shutter closes, the play and the friction between the diaphragm shutter members , the time t ₇ to start moving the respective squeezing members 6 and 7 (FIG. 2 (4))
Is changed for each shot, so that a problem occurs that the exposure amount varies for each shot.

Hereinafter, the aperture shutter speed control for compensating the exposure amount will be described.

FIG. 4 shows a timing chart of the pulse PS to the step motor and the exposure amount to the CCD in the aperture shutter of FIG.

(1) SP and (2) SP 'correspond to (3) S in FIG.
P, that is, a pulse train for driving the step motor 2; (3) Exposure amount B is the same as in FIG.
FIG. 4 shows an exposure characteristic diagram of D. FIG.

Pulse SP to the step motor 2 at time t ₆ is sent, when the diaphragm member 6 begins to move, by the movement of the contrast stripes 7c on the throttle member 7 at the same time, the output PR of the photo-reflector 8 is changed, The microcomputer of the camera has each aperture member
The operation start time t ₇ ′ of 6, ₇ is detected. If the time t ₇ ′ matches the set value t ₇ previously registered in the microcomputer, the step motor 2 is operated at the same pulse rate as shown in FIG. In the exposure diagram of ()), the shutter closes via AB.

Further, the operation start of the diaphragm member 6 is delayed from the time t _7, becomes a point A, the microcomputer detects the time t ₇ ', the step motor in the middle as shown in FIG. 4 (2) 2
The operating speed of each of the diaphragm members 6 and 7 is increased by increasing the pulse rate of the exposure light, and the exposure diagram of (3) passes through A'-B 'in FIG. It can be made substantially equal to the case of passing through B. If the operation start of each of the aperture members 6, ₇ is earlier than the time t7, the stepping motor 2
It is clear that a similar effect can be obtained by lowering the pulse rate to.

Further, when the opening and closing of the aperture shutter performs exposure,
It is obvious that by changing the opening speed according to the opening start time of each of the aperture members 6, 7, the exposure accuracy can be improved also on the opening side of the aperture shutter.

(Other Embodiments) In the present embodiment, the case of the "field image" has been described. However, the same applies to the case of the "frame image".

Further, in FIG. 2 (7), since the start of the CCD1 accumulation for the exposure from the time t _5, when the shutter speed is short, the longer the time until the next vertical transfer pulse, CCD1
In some cases, dark current noise is mixed in the image and image quality is degraded. Therefore, if the accumulation time of the CCD 1 is brought very close to the next vertical transfer pulse PS, the influence of the dark current can be reduced. An example of implementing the method will be described with reference to the timing chart of FIG. (1) is vertical sync pulse
V _P , (2) is the CCD clear pulse ES, (3) is the exposure amount B accumulated in the CCD 1, and (4) is the signal read from the CCD 1.

Here, if the exposure amount indicated by reference numeral 23 in FIG. 2 (7) of the embodiment can be obtained, the proper exposure is obtained for the main photographing. First, the stepping motor is set so that the aperture shutter is completely closed immediately before signal reading. Issue a pulse to 2. afterwards,
By raises the time t ₉ the CCD clear pulse ES so that the exposure amount becomes an area of 23, accumulation starts at time t _9, since the exposure immediately before the signal at the diaphragm shutter readout is completed, the dark The influence of the current is small, and the photographing without the smear phenomenon can be performed.

〔The invention's effect〕

As described above, according to the electronic still camera of the present invention, since the photometric operation is performed by the output of the image sensor, the photometric accuracy is very good, and the size of the aperture of the mechanical exposure control means is continuously controlled after the photometric operation. Since the imaging operation is started by resetting the accumulated charge of the imaging element in a state where the image is kept constant, the still image imaging operation can be performed immediately, and the imaging by the mechanical exposure control unit is performed with the end of the still image imaging. Exposure accuracy is high because light incidence to the means is blocked,
The present invention has an effect that a still image without a smear phenomenon can be captured.

[Brief description of the drawings]

FIG. 1 is a perspective view of an exposure mechanism of one embodiment of an electronic still camera according to the present invention, FIG. 2 is an example of an exposure timing chart of FIG. 1, and FIG. FIG. 4 is an example of a timing chart of the pulse to the step motor and the exposure state to the CCD of FIG. 2, FIG. 5 is another example of the timing chart at the time of the main exposure, and FIG. FIG. 7 is a schematic view of an example of a conventional exposure mechanism of an electronic still camera, FIG. 7 is an example of a conventional temporal change characteristic of an exposure amount, FIG. 8 is an example of an exposure operation sequence flowchart of the conventional electronic still camera, Fig. 9
FIG. 10 is an example of a configuration diagram of an inline CCD, and FIG. 11 is an example of an operation timing chart of an electronic shutter. 1 is a CCD, 2 is a step motor, 6 and 7 are each aperture members, and 8 is a photo reflector.

Claims (1)

(57) [Claims] An electronic shutter function, an imaging means,
Mechanical exposure control means for controlling light incidence of the image pickup means, and photometry in the image pickup means by controlling the charge accumulation time of the image pickup means while keeping the size of the diaphragm of the mechanical exposure control means constant. After performing the photometric operation in the imaging unit, the accumulated charge of the imaging unit is temporarily cleared while maintaining the size of the diaphragm of the mechanical exposure control unit during the photometric operation of the imaging unit. To start capturing a still image, and based on the photometric result of the photometric operation of the image capturing unit, control the time during which the mechanical exposure control unit blocks light incidence on the image capturing unit, and terminate the still image capturing. Electronic still camera provided with control means for performing control as described above.