JP2754020B2 - Exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus, and more particularly to an exposure apparatus for an electronic still camera or the like using a solid-state imaging device for performing exposure with an opening / closing member. is there.

[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. 5 is a schematic view showing an example of a conventional exposure mechanism of an 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. 6 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. Seventh
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. 8 shows an example of a timing chart of the above-described conventional photographing sequence.

(1) in the vertical synchronizing pulse V _P, referred to as a 1V period until the next pulse V _P, and 1/60 sec. (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 during the next 1V . 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 the release 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. 9 shows a schematic diagram of an example of a configuration of a CCD 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 a signal charge.The signal charge is shifted rightward in the drawing through the signal readout gate 53 to the vertical transfer register 52, and then sequentially to the horizontal register 54. The signal is transferred, converted into a voltage by the charge detection unit 55, and obtained as a point-sequential signal from the signal output terminal 56. This dot-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. 10 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
Due to the (3) clear pulse ES, it is discarded to the cleaning drain 57 in FIG. 9, 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 Figure 10 cross-perspective partial) charges accumulated 62 to 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 in the case where the exposure control is performed by the electronic shutter described above, the above-described problem occurs in any case. 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 or PLZT (lead lanthanum 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. Due to mechanical variations, it is necessary to expect a certain amount of time delay before the start of shading, and because it takes time from the start of shading to complete shading, Since charges are accumulated on the photodiode 51, the problem of the occurrence of smear has not been sufficiently solved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the conventional example, and has as its object to provide an exposure apparatus of this kind which has a high exposure accuracy and can obtain a still image without a smear phenomenon or the like. And

[Means for solving the problem]

For this reason, in the present invention, for example, the exposure (exposure 1) at the time of the re-reading photometry is performed by an electronic shutter, thereby performing high-precision photometry while eliminating a mechanical factor that affects the exposure accuracy. The exposure (exposure 2) starts accumulation from charge transfer to the vertical transfer register of the solid-state imaging device or charge clearing by a clear pulse, and while changing the closing speed by a mechanical shutter opening / closing member according to the closing start time, The object is achieved by arranging to end the main exposure.

[Action]

In this type of electronic still camera or the like provided with the exposure device having the above-described configuration, it is possible to obtain a still image with extremely high exposure accuracy and without a smear phenomenon.

〔Example〕

Hereinafter, the present invention will be described based on examples. Fig. 1 ~
FIG. 4 is an explanatory view of an example of an electronic still camera provided with an embodiment of the exposure apparatus 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 by meshing with a pinion gear 2a mounted on the axis of the step motor 2, 4a is A rod fixed to the rack gear 3 and connecting the members 5 and 6 described later, 4b is a rod connecting the members 5 and 7 similarly, and 5 is a The rotatable rings 6, 7 are fitted with the respective rods 4a, 4b,
An aperture member as an optical image shielding member having apertures (apertures) 6a and 7a for the aperture, and a photoreflector 8 for reading the contrast of the 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.
Since 7c also moves in the direction of arrow 7b at the same time, the output of the photoreflector 8 for reading it changes, and the microcomputer reads 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. be able to.

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
Clear pulse ES, (7) is the exposure amount accumulated in CCD1
B, (8) is a signal read from 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 when the first pulse is emitted is t ₀ (FIG. 2 (3)), the time is changed from t ₀ to each of the aperture members 6 and 7.
There is a need for a mechanical time lag until they start moving in 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 launching 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
The charge of the portion 22 is transferred and read. 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 registered in advance 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 to the above, 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".

〔The invention's effect〕

As described above, in the electronic still camera provided with the exposure apparatus according to the present invention, for example, (1) “exposure 1”, that is,
(2) In "exposure 2", that is, in the main exposure, the charge transfer to the vertical transfer drain of the image sensor or the charge clear is started as the charge accumulation, and the mechanical exposure is performed by the electronic shutter. By closing the shutter with a suitable shutter opening / closing member to end the exposure, a still image without smear can be taken.

(3) Furthermore, since the mechanical speed of the shutter opening / closing member is changed in relation to the operation start time of the shutter opening / closing member, the variation in the exposure amount for each shot can be reduced.

That is, by the exposure control of the present invention as described above,
At the same cost as a conventional low-cost exposure mechanism, a still image with high exposure accuracy and no smear phenomenon can be taken.

(4) In addition, although aperture metering and main exposure and two exposures are performed for one photographing operation, only one opening and closing of the aperture shutter is required. Is also very advantageous.

[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, FIG. FIG. 4 is an example of a timing chart of the pulse to the step motor and the exposure state to the CCD in FIG. 2, FIG. 5 is a schematic view of one row of the exposure mechanism of the conventional electronic still camera, and FIG. FIG. 7 is an example of an exposure operation sequence flow chart of a conventional electronic still camera, FIG. 8 is an example of an exposure timing chart of the above, and FIG. FIG. 10 is an example of a configuration diagram of a CCD, and FIG. 10 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] A shielding member for shielding an optical image, a detecting means for detecting an operation of the shielding member, and a speed adjusting means for changing an operation speed of the shielding member; An exposure apparatus, wherein an operation speed of the shielding member is changed according to an operation start time.