JP2002290804A - Digital camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a digital camera to operate at high-speed by removing unstable factors at the start of the closing operation of a mechanical shutter. SOLUTION: The digital camera is equipped with an image pickup element 1 which photographs a subject, a shutter blade 2 which is arranged in front of the image pickup element 1, an actuator 3 which opens and closes the shutter blade 2, a position detection part 4 which detects the position of the shutter blade 2 and outputs a trigger signal, and a control part 5 which perform on/off control over the image pickup element 1 and actuator 3 in seconds corresponding to the luminance of the subject according to the trigger signal. The control part 5 after turning on the actuator 3 according to a photography indication so that the shutter blade 2 begins to be closed, measures seconds according to the trigger signal outputted from the position detection part 4 and turns on the image pickup element 1 to start taking a picture, and then completes the photography when the shutter blade 2 is perfectly closed. The position detection part 4 comprises a cut 25 formed in the shutter blade 2 and an optical sensor 41 which optically detects it and outputs the trigger signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a digital camera. More specifically, the present invention relates to a shutter control technique for a digital camera.

[0002]

2. Description of the Related Art A digital camera includes an image pickup device for photographing a subject, a shutter blade disposed in front of the image pickup device, an actuator for driving the shutter blade to open and close, and an image pickup device in accordance with the brightness of the subject. A CPU for controlling on / off of the element and the actuator. The shutter control technology of the digital camera having such a configuration is
For example, it is disclosed in JP-A-4-281684. According to this, when the speed is relatively low (when the exposure time is long), an imaging element such as a CCD is turned on in response to the input of a shooting instruction (release signal) to start shooting. In other words, turning on the CCD corresponds to opening the electric shutter. At the same time as the opening of the electric shutter, the measurement of time is started. At the completion of the second measurement, the actuator is turned on, the shutter blades are closed, and the photographing is completed. In other words, closing the shutter blade, which was previously open,
This corresponds to closing of the mechanical shutter. As described above, the conventional digital camera performs a desired exposure operation by combining the opening of the electric shutter and the closing of the mechanical shutter.

However, as the time becomes faster (exposure time becomes shorter), the delay from the time when the actuator is turned on to the time when the shutter blade actually starts the closing operation becomes a problem. Since this mechanical response delay has individual differences, a high-speed and stable exposure operation cannot be obtained. Therefore, the above-mentioned Japanese Patent Application Laid-Open No. 4-281684 also proposes a shutter operation in the case of high-speed seconds. According to this, in the case of high-speed seconds, the actuator is first turned on in response to a release signal to start closing the shutter blades, and then the time is measured in response to a trigger signal output from the position detection unit to turn on the image sensor. Then, the photographing is started, and the photographing is ended when the shutter blades have been closed. After turning on the actuator first, C
By turning on an image sensor such as a CD, high-speed seconds can be handled.

[0004]

In the above-described operation at the high speed time, the time is measured in accordance with the trigger signal output from the position detecting section. In the above-described conventional technology, a mechanical switch is used as the position detection unit. However,
Since a mechanical switch uses contacts, the trigger signal itself also varies, so that precise exposure control cannot be performed. Further, since the switch is installed in the middle of the drive mechanism, it does not always provide a highly accurate closing position of the shutter blade due to variations in mechanical dimensions and the like.

[0005]

The following means have been taken in order to solve the above-mentioned problems of the prior art. That is, a digital camera according to the present invention includes, as a basic configuration, an image sensor for photographing a subject, a shutter blade disposed in front of the image sensor, an actuator for driving the shutter blade to open and close, and the shutter blade. And a control unit that controls the on / off of the image sensor and the actuator at a time corresponding to the brightness of the subject based on the trigger signal. The control unit includes:
After the actuator is turned on in accordance with a shooting instruction and the shutter blades are started to close, the time is measured in accordance with a trigger signal output from the position detection unit, the image sensor is turned on to start shooting, and the shutter is started. The photographing ends when the blades have been closed. The position detection unit includes at least one notch formed in the shutter blade and an optical sensor that optically detects the notch and outputs a trigger signal.

When the second time is larger than a predetermined value (low speed second time), the control unit turns on the image pickup device in accordance with a photographing instruction to start photographing and starts measuring the second time. At the completion of the measurement of the second, the actuator is turned on, the shutter blade is closed, and the photographing is completed. Preferably, the shutter blade is driven to rotate in an opening direction and a closing direction about a predetermined support shaft, and the thickness of the root portion close to the support shaft is increased while the thickness of the tip portion away from the support shaft is small. I have. In this case, the root of the shutter blade close to the support shaft hits the stopper.

The present invention includes a shutter blade for a digital camera. That is, the shutter blade according to the present invention is driven to rotate in the opening direction and the closing direction about a predetermined support shaft, and the thickness of the root portion close to the support shaft is small while the thickness of the tip portion away from the support shaft is small. And at least one notch for position detection is formed at the tip.

According to the present invention, in a digital camera, a high-speed operation is stabilized by providing a position detection unit directly on shutter blades to perform shutter control in order to eliminate an unstable factor at the start of a mechanical shutter closing operation. ing. At that time, an optical sensor is used in place of a conventional mechanical switch, so that the delay and variation in the output timing of the trigger signal are minimized.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1A is a schematic plan view illustrating a basic configuration of a digital camera according to the present invention. As shown in the figure, this digital camera includes an image pickup device 1 composed of a CCD or the like, a shutter blade 2, an actuator 3 composed of a moving magnet type motor (M), a position detection unit 4, and a control unit 5 composed of a CPU and the like. Have. The imaging device 1 is disposed behind an opening 6 formed in a shutter substrate (not shown), and is used for electrically photographing a subject via a lens (not shown). The shutter blade 2 is disposed in front of the image sensor 1 and opens and closes the opening 6 to perform an exposure operation. In this example, the number of the shutter blades 2 is two (only one side is shown), but one or three or more shutter blades may be combined. Actuator 3 consisting of moving magnet motor M etc.
Drives the shutter blades 2 to open and close. Specifically, the shutter blade 2 is mounted on the substrate so as to be able to rotate bidirectionally about the support shaft 21. Further, the shutter blade 2 is
Is provided with a through hole 22 in the vicinity of. The actuator 3 has an operating pin 31 which is engaged with the through hole 22 of the shutter blade 2. Actuating pin 31 of actuator 3
Is rotated in both directions, so that the shutter blades 2
Rotate bidirectionally around. Specifically, when the actuator 3 rotates clockwise, the shutter blade 2 also rotates clockwise, closing the opening 6. Conversely, when the actuator 3 rotates counterclockwise, the shutter blade 2 also rotates counterclockwise and retracts from the opening 6. In a standby state for photographing, the shutter blade 2 is previously retracted from the opening 6. The position detector 4 directly detects the position of the shutter blade 2 and outputs a trigger signal. In this example, after the actuator 3 is turned on, a position immediately before the shutter blade 2 retreats from the opening 6 and enters the opening 6 is detected, and a trigger signal is output. The control unit 5 includes the position detection unit 4
A desired exposure operation is performed by controlling on / off of the image sensor 1 and the actuator 3 at a time corresponding to the brightness of the subject which has been measured in advance based on the trigger signal output from the camera.

When the brightness of the subject is high and the exposure time is relatively short (at high speed), the control unit 5 turns on the actuator 3 and starts closing the shutter blade 2 in accordance with a photographing instruction (input of a release signal). After that, the control unit 5 measures the time according to the trigger signal output from the position detection unit 4 and turns on the image sensor 1. In other words, the electric shutter is opened to start photographing (exposure operation). Actuator 3
Is already turned on, the shutter blade 2 continues to rotate in the closing direction, and the photographing (exposure operation) ends when the opening 6 has been completely closed. At this time, the position detecting section 4 includes at least one cutout 25 formed in the shutter blade 2 and an optical sensor 41 that directly detects the cutout 25 and outputs a trigger signal. As the optical sensor 41, for example, a photo reflector or a photo interrupter in which a light emitting diode and a photo transistor are combined can be used. Since the position detection unit 4 uses an optical sensor unlike a conventional mechanical switch, the accuracy of the output timing of the trigger signal is increased, and the stability of the high-speed time control is increased.

When the brightness of the subject is relatively low (at the time of low speed), the control unit 5 first turns on the image sensor 1 according to the photographing instruction and starts photographing. That is, the electric shutter is opened first. After the measurement of the time is started after the electric shutter is opened, the actuator 3 is turned on and the shutter blade is closed when the measurement of the time is completed. Thus, the mechanical shutter is closed and the exposure operation is completed. Since the second time is relatively long, even if there is a mechanical delay from the time when the actuator is turned on to the time when the shutter blade is actually closed, a large exposure error does not occur.

FIG. 1B shows a cross-sectional shape of the shutter blade 2 along the line XX. As shown in the figure, the shutter blade 2 is driven to rotate in the opening direction and the closing direction about a predetermined support shaft 21, and the thickness of the tip portion remote from the support shaft 21 is small and the thickness of the root portion close to the support shaft is small. It is formed large. This makes it possible to reduce the overall weight while maintaining the mechanical strength of the shutter blade 2. By reducing the weight of the shutter blade 2, it becomes possible to cope with a faster high-speed operation. Further, the shutter blade 2 is
The root portion close to 1 hits the stopper S. The stopper S is used for positioning when the shutter blade 2 is fully opened. By using the stopper S in this manner, the position accuracy of the shutter blade 2 is further improved.
In particular, the position accuracy is increased by making contact with the stopper S at the base having high mechanical strength.

FIG. 2 is a timing chart for explaining the operation of the digital camera shown in FIG. 1, and particularly shows a case of high speed. As shown in the figure, first, an actuator (open / close motor) for opening and closing the shutter blade is turned on in response to the input of the release signal. As a result, the shutter blade starts running in the closing direction, and the effective opening diameter changes from fully open to fully closed. That is, the shutter blades travel from the fully open position to the fully closed position through the pinhole position after the opening / closing motor is turned on. At this time, the position sensor outputs a trigger signal P at a predetermined timing. In the illustrated example, the trigger signal P is output 0.5 ms after the opening / closing motor is turned on. Since the trigger signal P is output by directly detecting the position of the shutter blade optically, it becomes an extremely accurate reference signal. In response to the trigger signal P, the CPU starts measuring the time TAE1 until the CCD is turned on. In the case of this embodiment,
Exposure time of 1/1300 second or shorter is set to high speed. For example, when the exposure time is 1/1300 second, TAE1 is 0.0 m
When the exposure time is 1/2000 sec, TAE1 is set to 0.
TAE when 125ms and exposure time is 1/2600 seconds
1 is 0.25 ms, and TAE1 is 0.5 ms when the exposure time is 1/4000 second. The illustrated example shows a case where the exposure time is 1/4000 second and TAE1 is 0.5 ms. CPU sets TAE in response to trigger signal P
1 starts measurement, and when 0.5 ms elapses, CCD
Is turned on, and the electric shutter is opened. This starts the exposure operation. As is clear from the figure, the CCD is turned on and the electric shutter is opened after a lapse of 1 ms after the opening / closing motor is turned on. Thereafter, the shutter blade reaches the pinhole position with a predetermined delay ΔT and closes the lens opening. In other words, the mechanical shutter closes. Accordingly, as shown by hatching, the exposure amount at the time of high speed is from when the CCD is turned on until the shutter blade reaches the pinhole position. In practice, ΔT is on the order of 0.5 ms, which is quite fast. As described above, since the measurement of the second time TAE1 is performed with reference to the trigger signal P having high accuracy, a stable exposure operation can be performed even in the case of high speed second time.

FIG. 3 is a timing chart showing the exposure operation of the digital camera shown in FIG. 1, which is at a low speed. In this embodiment, the exposure time is 1/1300
The case where the time is longer than the second is regarded as the low speed time. First, the CCD is turned on when a release signal is input. This opens the electric shutter. At the same time when the electric shutter is opened, the CPU starts measuring the time TAE2 from when the CCD is turned on to when the opening / closing motor is turned on. When the measurement of TAE2 is completed, the opening / closing motor is turned on to rotate the shutter blade in the closing direction. The shutter blade passes through the fully open position and the pinhole position with a predetermined delay to complete the closing operation. As is apparent from the figure, the exposure amount at the low speed is indicated by a hatched portion from when the CCD is turned on to when the shutter blade passes the pinhole position.

FIG. 4 is a block diagram showing an example of a circuit configuration of the digital camera according to the present invention. As shown
The motor M for opening and closing the shutter blades is on / off controlled by a control circuit (sequencer) 5 via a driver DRV. In this embodiment, an aperture is also incorporated in the digital camera. Another motor Mx is used to set the aperture. The motor Mx for setting the aperture is controlled on / off by the control circuit 5 via the driver DRV.
An input / output circuit (I / O circuit) is also provided for the CPU constituting the control circuit 5. The I / O circuit is connected to an image sensor 1 such as a CCD, a photometric circuit 7 for measuring the luminance of a subject, a position detector 4, and the like. As described above, the position detection unit 4 includes the notch formed in the shutter blade 2 and the optical sensor. In the case of this example, the optical sensor is formed of a photo reflector, and is configured by a combination of a light emitting diode and a photo transistor.

FIG. 5 is a flowchart for explaining the operation of the circuit shown in FIG. The exposure process starts according to the input of the shutter release signal. First, photometry of a subject is performed in step S1, and an aperture value and a shutter value are determined in step S2. Subsequently, it is determined whether or not the aperture value determined in step S3 is fully opened. In the case of the fully opened state, the aperture is not used, and the trigger signal P1 is output immediately before the shutter blade reaches the fully opened position. On the other hand, when the aperture is set, the trigger signal P2 is output immediately before the shutter blade reaches the aperture diameter.

If it is determined in step S3 that the aperture value is fully open, the flow advances to step S4 to determine whether or not the shutter speed is smaller than a predetermined threshold T1. If the shutter time is smaller than T1, the process proceeds to step S5 to perform a high-speed time operation. That is, after the shutter closing drive is started in step S5, the output of the trigger signal P1 is waited in step S6, the measurement of the shutter time TAE1 is started in step S7, and the CCD is started in step S8X. afterwards,
The shutter is closed and the exposure is completed.

On the other hand, if it is determined in step S4 that the shutter time is equal to or greater than T1, the flow advances to step S8 to enter a low speed operation. That is, in step S8, C
The CD is started, and measurement of the shutter time TAE2 is started in step S9. In step S10, the shutter closing drive is performed together with the completion of the measurement of the shutter time TAE2, and the exposure is completed.

If it is determined in step S3 that the aperture value is not fully open, the flow advances to step S11 to start an exposure operation in a state where the aperture is set. The exposure operation when the stop is applied is basically the same as the exposure operation when the stop is not applied. However, the trigger signal is switched from P1 to P2, and the threshold for separating the high-speed operation and the low-speed operation is changed from T1 to T2. In the case of the high-speed operation, after the shutter closing drive is started in step S12,
13, the trigger signal P2 is detected, the measurement of the shutter speed TAE1 is started in step S14, and C is measured in step S15.
Start the CD. Thereafter, the shutter is closed and the exposure is completed. On the other hand, in the case of the low-speed second operation, step S1
In step S17, measurement of the shutter speed TAE2 is started, and in step S18, the CCD is started.
With the completion of the measurement of the shutter time TAE2, the shutter closing drive is performed to complete the exposure.

[0020]

As described above, according to the present invention, the position of the shutter blade is directly detected by the notch provided at the tip of the shutter blade, and the operation of the CCD is controlled based on the detected position. High-speed shutter control can be directly performed. In particular, by combining the notch provided in the shutter blade and the optical sensor, a precise trigger signal can be output, and the electric shutter can be opened based on this signal. In this way, stability in the high-speed time operation can be ensured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a digital camera according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the digital camera shown in FIG. 1;

FIG. 3 is a timing chart for explaining the operation of the digital camera shown in FIG. 1;

FIG. 4 is a circuit block diagram showing a specific example of a digital camera according to the present invention.

FIG. 5 is a flowchart for explaining the operation of the digital camera shown in FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image sensor, 2 ... Shutter blade, 3 ... Actuator, 4 ... Position detection part, 5 ... Control part

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Claims (5)

[Claims] An imaging device for photographing a subject; a shutter blade disposed in front of the imaging device; an actuator for driving the shutter blade to open and close; and detecting a position of the shutter blade to output a trigger signal. A digital camera, comprising: a position detection unit; and a control unit that controls on / off of the image sensor and the actuator at a time corresponding to the brightness of the subject based on a trigger signal, wherein the control unit turns on the actuator in accordance with a shooting instruction. Then, after the shutter blade starts to be closed, the time is measured according to the trigger signal output from the position detection unit, the image pickup device is turned on, and photographing is started. At the time when the shutter blade has been closed, Upon completion of the photographing, the position detection unit optically detects at least one notch formed in the shutter blade and outputs a trigger signal. Digital camera characterized by comprising the light sensor that. 2. When the second time is greater than a predetermined value, the control unit turns on the image sensor in accordance with a shooting instruction to start shooting, starts measuring the second time, and then completes the second time measurement. 2. The image pickup apparatus according to claim 1, wherein the actuator is turned on at a point in time to close the shutter blade to end photographing.
Digital camera as described. 3. The shutter blade is driven to rotate in the opening and closing directions about a predetermined support shaft, and has a small thickness at a distal end portion away from the support shaft and a large thickness at a base portion close to the support shaft. The digital camera according to claim 1, wherein: 4. The digital camera according to claim 3, wherein the shutter blade hits the stopper at a root portion near the support shaft. 5. A shutter blade for a digital camera, wherein the shutter blade is driven to rotate in an opening direction and a closing direction about a predetermined support shaft, and the thickness of a tip portion remote from the support shaft is small and is close to the support shaft. A shutter blade having a large thickness, and a notch for detecting a position is formed at the tip end.