JP2002290823A - Imaging apparatus and exposing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus and an exposing method which start exposure with a small time lag or no time lag after an exposure mode is entered. SOLUTION: When a shutter release button 128 is half-pressed, an exposure calculation control function part 12A performs photometry and determines an exposure time. When the shutter release button 128 is fully pressed, a timing signal generation part 120 is switched from a movie mode to the exposure mode. Consequently, a driver part 122 supplies a fixed number of >1 electronic shutter output pulses 122a to an image pickup part 104 and the exposure is started at a fixed point of time. Then a system control part 12 controls an AE control part 108 so that a mechanical shutter 108d is closed at the end of the exposure time obtained by the photometry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup apparatus such as a digital camera and an exposure method therefor.

[0002]

2. Description of the Related Art In a digital camera, means for controlling an exposure time of an image pickup element (light receiving element) such as a photodiode (PD) is classified into the following two types. One is a mechanical shutter (mechanical shutter; hereinafter, abbreviated as “mechanical shutter”) that physically blocks irradiation of light from the object scene. The other is an element shutter which switches the energization of the image sensor to substitute for the shutter, that is, an electronic shutter.

[0003] Of these two types of shutters, the mechanical shutter is mainly used for an interlace scan type digital camera. In the interlaced scanning method, the odd-numbered scanning lines and the even-numbered scanning lines are alternately read. Therefore, while one of the scanning lines is being scanned, the object field is set so that the image sensor constituting the other scanning line does not receive light. This is because it is necessary to completely block light from the light source.

On the other hand, the electronic shutter uses a vertical overflow drain (VOD; Verti
Dispose in the direction of the substrate using cal overflow drain). Thereby, the image pickup device can start the exposure from the state where the signal charge becomes zero. Therefore, the electronic shutter is used for a progressive scan system. This is because, in this method, since all pixels are read at once, there is no need to shut off the light source as in the interlace scan method.

Although it is possible to control the exposure time only with the electronic shutter, as described above, if the exposure time control is performed using only the electronic shutter in the interlace system, the difference in reading for each scanning line is large. It is too much and cannot be put to practical use. Further, although it can be used for a progressive system, since light from the object field is not completely blocked, smear may be generated by an intense light source during reading out of signal charges.

[0006] From this viewpoint, it is preferable to use an electronic shutter capable of high-speed switching to start exposure, and to use a mechanical shutter capable of completely shutting off the light source to end exposure. However, the mechanical shutter has a problem in that the shutter speed is slow. This is because if the shutter is closed with a delay from a desired timing due to a mechanical delay of the mechanical shutter, charges due to an excessive amount of light are accumulated in the image sensor, and an overflow of signal charges occurs.

Therefore, in order to overcome the slow shutter speed while utilizing the advantages of the mechanical shutter, there has been proposed a system using a combination of an electronic shutter and a mechanical shutter. For example, in Patent No. 2649882 and Patent No. 2649883, exposure start is performed by an electronic shutter,
Exposure is terminated by a mechanical shutter. The error due to the delay of the mechanical shutter is compensated for by fine adjustment on the electronic shutter side.

[0008]

However, in the case of the above-mentioned prior art, even if the blanking period or the like is ended and the exposure mode is set, fine adjustment by the electronic shutter is required until the exposure actually starts. There is a time lag, and for example, there is a drawback that an object moving at a very high speed is missed.

One mode (exposure mode) is assigned to the exposure, but the time lag wastes time and unnecessarily extends the period of the exposure mode.
As a result, performance degradation such as a decrease in the number of continuous shots occurs. In order to solve this, a method of optimizing the imaging time by assigning a time of “shake time limit + mechanical shutter close time” as an exposure mode can be adopted. However, when the exposure time is shorter than the camera shake time limit Is also a waste of time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image pickup apparatus and an exposure method for solving the above-mentioned drawbacks of the prior art and for starting exposure with a small or no time lag after shifting to an exposure mode.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention includes a plurality of two-dimensionally arranged imaging elements for photoelectrically converting incident light from an object field into signal charges and storing the signal charges. An imaging apparatus that operates in accordance with at least an operation mode selected from a movie mode, an exposure mode, and a signal readout mode has the following features.

That is, the present apparatus is integrally connected to an image pickup device and calculates a desired exposure time based on the amount of incident light radiated from the object field, and extracts the signal charges accumulated in this device. Possible charge removal means;
It is connected to the charge extracting means and the image pickup device, and is usually in the movie mode, and it is possible to switch the operation mode in synchronization with the synchronization signal transmitted by itself, and to switch the operation mode to the exposure mode, at the same time,
Signal generation means for giving the charge extraction means one or more times over a predetermined time period the signal charge extraction instruction and switching the operation mode to the signal readout mode, instructing the image sensor to read out the accumulated signal charge. When,
A mechanical shutter means that is normally open, and that physically closes the image sensor from the field of view when closed.
An exposure adjusting means connected to the mechanical shutter means for opening and closing the means, and a calculating means, a signal generating means, and an exposure adjusting means connected to the exposure adjusting means for receiving the exposure time calculated by the calculating means; To the signal generation means,
And control means for controlling the exposure adjusting means so that the mechanical shutter means closes at the same time as the end of the exposure time started when a predetermined period elapses when the operation mode is the exposure mode.

According to the present invention, exposure is performed by an instruction to switch to an exposure mode transferred from the control means to the signal generating means, and a signal is issued by an instruction to switch to a signal reading mode transferred from the control means to the signal generating means. The charge is read.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an image pickup apparatus and an exposure method of the image pickup apparatus according to the present invention; Illustration and description of parts not directly related to the present invention are omitted. Also, the reference number of a signal is represented by the reference number of the connection line in which it appears.

FIG. 1 shows a case where the image pickup apparatus of the present invention is applied to a digital camera 10. The digital camera 10 has
As shown in FIG. 1, an imaging system 10A, a signal processing system 10B, a drive signal generation unit 10C, a signal output system 10D, a mode designation unit 10E, and a system control unit 12 are provided.

The imaging system 10A includes an imaging lens 102, an imaging unit 10
4. AF (Auto Focus; including focus adjustment mechanism not shown)
Auto focus) adjustment unit 106, AE (Auto Exposure)
A mechanical shutter mechanism (hereinafter, abbreviated as “mechanical shutter”) 10 on the side of the incident light of the adjusting unit 108 and the imaging unit 104
Including 8d. The mechanical shutter is normally open, and when closed, can completely completely block incident light from the object field irradiated on the image pickup device of the image pickup section 104.
The mechanical shutter is driven by a drive signal 108c, which will be described later, and is characterized in that it takes a certain time to open and close. Imaging lens
Reference numeral 102 denotes an optical system that condenses incident light from the object scene so as to focus on the light receiving surface of the imaging unit 104.

Although not shown, the image pickup section 104 includes a photodiode (PD) for photoelectrically converting incident light supplied thereto.
ode), and these are two-dimensionally arranged in a grid pattern in a row direction and a column direction to form a light receiving surface. The array of the imaging elements may be a honeycomb-shaped array in which the grid-like array is shifted vertically and horizontally and the pixel row interval is 1 / √2 times. The image pickup unit 104 is provided with a color filter segment for color-separating the incident light on the side of the incident light from the image pickup device, and is integrally formed as a single-plate color separation filter CF corresponding to each of the image pickup devices. ing. By disposing the color separation filter CF, incident light that has been color-separated so as to have, for example, each of the three primary colors RGB has the attribute of each color. The imaging unit 104 outputs the imaging signal 10a to the signal processing system 10B.

Next, the configuration of the image pickup unit 104 will be described. A transfer gate (signal read gate) for preventing leakage of signal charges is provided between a transfer element (not shown) disposed adjacent to the image pickup element, that is, a vertical transfer element. Is formed. The transfer gate opens and closes the gate in response to a field shift pulse included in a vertical synchronization signal supplied via an electrode, and transfers (field shifts) signal charges from the image sensor to the vertical transfer path. The vertical transfer path is a charge-coupled device (Ch
arge Coupled Device (hereinafter, referred to as CCD), and sequentially transfers read signal charges in the column direction, that is, in the vertical direction in response to the vertical synchronization signal VD. By the vertical transfer, the signal charges are line-shifted and supplied to the transfer elements in the row direction, that is, the horizontal transfer paths. Horizontal transfer path is also CC
D, in response to the supplied horizontal synchronization signal, and outputs the signal charge as a signal 10a to the signal processing system 10B via the amplifier as described above.

Although not shown, the image pickup unit has a vertical overflow drain (VOD) disposed on the substrate side with respect to the image pickup device. VOD is determined by the reverse bias voltage applied to the substrate.
This is an element for extracting the signal charges accumulated by the imaging element in the direction of the substrate. As a result, an electronic shutter function for extracting signal charges at high speed is realized.

As described above, the image pickup section has two types of means for removing charges from the image pickup device. One is a transfer gate, and the other is an electronic shutter. From the time when charge is extracted from the image sensor by these means,
Exposure is newly started, which will be described later in the description of the operation of this embodiment.

The signal for driving the image pickup unit 104 is a drive signal 122a output from a drive signal generation unit 10C described later.
This includes, in addition to an electronic shutter drive signal or a transfer gate drive signal (field shift pulse) for extracting signal charges from the image sensor, a line shift pulse, a vertical
The horizontal synchronization signal VD / HD is included.

The AF adjustment unit 106 arranges the imaging lens 102 at an optimum position according to information obtained by measuring the distance between the subject and the camera 10 by a focus adjustment mechanism (not specifically shown). This position adjustment is performed as follows. At this time, the calculation of the ranging information is performed by the signal processing unit 114 at the subsequent stage, and the ranging information is processed by the system control unit 12 to determine the control amount. As a result, in response to the supplied control signal 12a, the AF adjustment unit 106 drives the focus adjustment mechanism with the drive signal 106a, and moves the imaging lens 102 along the optical axis in the direction of arrow A.

The AE adjustment unit 108 is provided with a drive signal 108a based on a control signal 12a from an exposure calculation control function unit 12A in the system control unit 12 for calculating a photometric value of an object scene including a subject.
Is supplied to the aperture shutter mechanism 108b to displace the aperture position and adjust the amount of incident light flux. The AE adjustment unit 108
The drive signal 108c is supplied to the mechanical shutter mechanism 108d to give opening / closing timing, and the mechanical shutter 108d is opened / closed accordingly. The light blocking timing of the mechanical shutter 108d is also given by a control signal 12a from the system control unit 12. Note that the control signal 12a may be supplied as separate signals for AE adjustment and AF adjustment.

The signal processing system 10B includes a pre-processing unit 110, an A / D conversion unit 112, a signal processing unit 114, a buffer unit 116, and a compression /
An extension processing unit 118 is provided. The signal processing system 10B
, A control signal 12b is supplied from the system control unit 12 so as to control each unit described above in accordance with the mode, and timing signals 20a to 20e are supplied. Preprocessing section
110 is connected to the output 10a of the imaging system 10A, for example, performs correlated double sampling (CDS) processing on the supplied signal charge 10a to reduce noise, performs gamma correction on the signal, A / D converter 11 amplifies this signal 10a.
Output to 2. These pre-processes are performed in synchronization with the timing signal 20a. The gamma correction is not limited to this position, and may be performed by the signal processing unit 114 in the subsequent stage.

The A / D converter 112 is connected to the output 10b of the preprocessor 110, and receives a control signal 12b from the system controller 12.
The analog signal 10b supplied via the pre-processing unit 110 is sampled using the timing signal 20b and quantized into a digital signal (or image data) 10c. The timing signal 20b may be a clock signal for high-speed processing. The converted digital signal 10c is supplied to a signal processing unit 114.
Supplied to In the present embodiment, processing and control related to the control of the AF adjustment unit 106 and the AE adjustment unit 108 are performed by the system control unit 12.
Is done. Therefore, the digital signal 10c is also supplied to the system control unit 12, as shown in FIG.

The signal processing section 114 outputs the output 10c of the A / D conversion section 112.
And performs white balance adjustment (AWB), aperture correction, and the like that are generally performed. The signal processing unit 114 can be set to also perform processing (AE) for calculating an automatic aperture value. In the present embodiment, this AE processing is performed by the exposure calculation control function unit 12A. The signal processing unit 114 performs these processes, and further performs signal processing according to each of the three modes. In the present embodiment, in the signal reading mode, for example, all pixels, two-line thinning, frame reading, and the like are set according to the recording capacity and the image quality to be recorded by the key switch 130 described later. Also,
In the movie mode, the image of the imaging system 10A is simply displayed, and photometry including AF and AE is also performed. The photometry is set to two-line thinning-out reading from the demand for high speed. In this configuration, the mode is not limited to the three types of modes, and a larger 1/4 thinning may be used.

This photometry and control are performed by the exposure calculation control function unit 12A and the system control unit 1 as described later in this embodiment.
2, the signal processing unit 114 may perform arithmetic processing for performing optimal exposure of the object scene. In this case, the signal processing unit 114 uses the data of the predetermined area of the supplied image data 10c to calculate the photometric value and calculate the aperture value and the exposure time based on the calculated photometric value. The signal processing unit 114 supplies the value 10c obtained by the calculation to the system control unit 12. The system control unit 12 generates a control signal 12a corresponding to the supplied value and supplies the control signal 12a to the imaging system 10A.

In addition, in the digital still camera 10, which mode is currently selected is controlled by the control signal 12b described above. This system control unit 1
By the control of 2, the signal processing unit 114 performs, in addition to the above-described signal processing, signal processing associated with predetermined digital in the signal readout mode, for example, increasing the bandwidth of a luminance signal.

The signal processing section 114 converts the image pickup signal 10a from the image pickup section 104 into a recordable video signal by signal processing in the signal readout mode. Then, the signal processing unit 114
Outputs the signal 10d of the mode in which display / recording is selected to the buffer unit 116.

The above-described gamma correction processing may be performed here, or may be performed at a later stage. Since these series of signal processing are performed digitally, the signal processing unit
114 may be configured as a single unit in a DSP (Digital Signal Processor).

The buffer unit 116 receives the output 10 of the signal processing unit 114.
d, which amplifies the supplied video signal 10d to a predetermined amplitude and has a function of adjusting time during recording. The buffer unit 116 includes the system control unit 1
The image 10e is output to the signal output system 10D or the compression / decompression processing unit 118 under the control of a recording control unit (not shown) provided in the unit 2.

The compression / expansion processing section 118 is connected to the output 10e of the buffer section 116, and captures and records the image signal 10e according to the control signal 12b from the system control section 12. The supplied image signal 10e includes, for example, JPEG (Joint Photo
Graphic coding Experts Group) compression processing is performed. When reading and reproducing the signal 10f recorded from the recording / reproducing unit 126, the original image signal is reproduced by performing signal processing such as the inverse conversion of the above-described compression processing, and the image signal is restored although not shown. Display image signal
It is supplied to 124 and displayed.

The signal output system 10D includes a display unit 124 and a recording / reproducing unit 126. The display unit 124 includes a buffer unit
116 connected to the output 10e
It is equipped with a VGA (Video Graphics Array) standard liquid crystal display monitor with B input. The recording / reproducing unit 126 is a storage unit, and records the video signal 10f supplied to a semiconductor memory used for a memory card or the like, a magnetic recording medium, an optical recording medium, or a magneto-optical recording medium. The recording / reproducing unit 126 reads out the recorded video signal 10f, and
Can also be displayed. The recording / reproducing unit 126
However, if the recording medium can be detached, the recording medium may be removed and the video signal recorded by an external device may be reproduced and displayed, or the image may be printed. These are controlled by the control signal 12c.

The mode designating unit 10E is provided with a shutter release button 128 and a key switch 130, and is a device for determining an operation mode of the digital camera 10.
The operation mode referred to herein includes at least three modes: an exposure mode and a signal readout mode for capturing an obtained still image and capturing it in the recording / reproducing unit 126 of the signal output system 10D, and a movie mode for simply displaying a moving image. means. In this embodiment, the shutter release button 128 is a push button having a two-step pressing function. When the shutter release button is not pressed, the movie mode is set, and this is the initial mode. In the half-pressed state of the first stage, an instruction signal 28 for performing photometry described below is output to the system control unit 12 in the movie mode, and in the fully-pressed state of the second stage, the switching signal 28 to the exposure mode is controlled by the system control. Part 12
Output to

The key switch 130 sets the CCD signal reading method according to the mode. For example, when photometry is performed, reading is performed by thinning out two lines because reading must be performed at high speed. In addition, all-pixel reading or frame reading can be selected. The selected information is sent to the system control unit 12 via the signal line 30.

The system control unit 12 outputs the output of the mode designating unit.
The controller is connected to 28 and 30 and controls the operation of the entire camera. The system control unit 12 includes a central processing unit (CPU). The system control unit 12 determines which mode has been selected based on the input signal (or the designation signal) 28 from the shutter release button 128. However, the actual mode switching is performed by the timing signal generator 120 as described later. Further, the system control unit 12 controls the reading of the camera image signal based on the selection information 30 from the key switch 130. As described above, the system control unit 12 supplies the operation mode information 12b to a signal processing system described later based on the information supplied from the mode designating unit 10E. In addition, a reset signal for supplying the selected mode switching instruction 12d to the timing signal generation unit 120 of the drive signal generation unit 10C, which will be described later, and resetting the vertical synchronization signal VD generated by the timing signal generation unit 120. 12e
Can be output.

As described above, the system control unit 12 includes the exposure calculation control function unit 12A and the recording control unit.
The recording control unit controls the buffer unit 116 and the recording / reproducing unit 12D of the signal output system 10D according to a control signal 12c from the system control unit 12.
The operation of 6 is controlled.

The exposure calculation control function unit 12A performs photometry in the movie mode. When the photometry instruction signal 28 is input to the system control unit 12 due to the half-press state of the shutter release button 128, photometry is performed using the imaging signal 10c directly supplied from the signal processing unit 114 to the system control unit 12. Will be Next, based on the photometric value calculated by the control unit 12 and converted into a digital signal, the exposure amount is calculated by the exposure calculation control function unit 12A of the system control unit 12, and the actual exposure time for achieving this exposure amount is determined. Is done. To ensure this exposure time, the system control unit 12 sends a mechanical shutter
A control signal 12a for determining the timing for closing 108d can be supplied to the AE adjustment unit 108.

Here, when determining the timing of closing the mechanical shutter, it is considered that a certain time is required for closing the mechanical shutter. That is, the closing timing signal 12
The mechanical shutter cannot be closed at a desired timing unless the delay from when a is issued until the actual closing operation is started and the time required for the mechanical shutter to completely close are not considered. This is called “mechanical shutter closing time”). Therefore, the system control unit 12 calculates the substantial exposure time for obtaining an appropriate exposure amount as “substantial exposure time = mechanical shutter opening time + mechanical shutter closing time”, and calculates an earlier exposure time in consideration of the mechanical shutter closing time. The closing signal 12a is supplied to the AE adjusting unit 108. With this adjustment, exposure can be optimized. Further, as will be described later in the description of the operation of this embodiment, the exposure mode length can be adjusted to the substantial exposure time.

The control section 12 can also control the timing of opening the mechanical shutter by sending an opening signal 12a to the AE adjusting section 108. At this time, the AE adjusting unit 108 can be controlled so that the mechanical shutter 108d is opened at the same time as the completion of the reading of the signal charges accumulated in the imaging unit 104, and the timing signal generating unit 120 switches to the exposure mode again at the same time as the reading is completed. The timing signal generation unit 120 can be controlled so as to perform These controls enable continuous shooting.

The drive signal generator 10C includes a system controller 1
Timing signal generator 120 connected to outputs 12d and 12e of 2
And a driver unit 122 connected to the output 120a of the generation unit 120. The timing signal generation unit 120 generates the synchronization signal 20c based on the clock of the original oscillation generated so as to drive the digital still camera 10 in the current broadcasting system (NTSC / PAL), and outputs the synchronization signal 20c to the signal processing unit 114, for example. Supply.
The timing signal generation unit 120 includes a pre-processing unit 110, an A / D conversion unit 1
12, timing signals 20a, 20b, 20d, and 20e are also supplied to the buffer unit 116 and the compression / expansion processing unit 118 as clocks that serve as operation references for the sampling signal and the write / read signal. If these timing signals can be shared, the number of components of the timing signal generation unit 120 can be reduced.

The timing signal generator 120 is connected to the outputs 12d and 12e of the system controller, generates a synchronization signal from the clock of the original oscillation, and generates various timing signals 120a generated by using these signals. Output to the driver unit 122. As the output timing signal 120a, a timing signal used for reading out the signal charge obtained by the imaging unit 104, for example, a vertical synchronization signal VD for supplying a drive timing for a vertical transfer path, and a drive timing for a horizontal transfer path are supplied. There are a horizontal synchronizing signal HD, a timing pulse for performing a field shift and a line shift, a charge extraction pulse for an electronic shutter, and operation mode information.

It is the timing signal generator 120 that determines the operation mode of the camera 10. The generation unit 120 is normally in the movie mode, and receives a mode switching instruction 12 from the control unit 12.
Upon receiving d, the operation mode is switched in synchronization with the next vertical synchronizing signal VD transmitted by itself. However, from the system control unit, for example, simultaneously with the mode switching instruction 12d, the signal line 12e
When the reset pulse is sent through the switch, the vertical synchronization signal VD is reset, so that the operation mode is switched at the same time as the mode switching instruction 12d.

The driver unit 122 includes a timing signal generation unit 1
It is connected to an output 120a from 20 and generates a drive signal 122a for the imaging unit 104 based on the various signals 120a. At this time, the driver unit 122 can be set to perform an operation unique to the present invention. That is, when the operation mode is switched from the movie mode to the exposure mode, at the same time, it is possible to set so as to output one or more fixed number of charge extraction pulses (pulses for electronic shutter) over a predetermined period. is there. When the operation mode is switched to the signal reading mode, the imaging unit 104
To read out signal charges.

The driver section 122 also outputs the vertical synchronizing signal VD and the horizontal synchronizing signal HD to the system control section 12 through a signal line 122b. This is the CPU in the system controller
This is because (not shown) counts these timing signals to output the mode switching instruction 12d and output the reset pulse 12e.

The operation of the embodiment of the present invention configured as described above will be described below.

First, the prior art will be described for comparison. Although the hardware configuration of this prior art is not shown, if necessary, Japanese Patent No. 2649882 and Japanese Patent No. 26249
See No. 83. FIG. 2 shows a time chart of the related art in which exposure is started by an electronic shutter and exposure is ended by a mechanical shutter. In FIG. 2, when a still image shooting command is issued, the vertical synchronization signal VD shown in FIG. 2 (a) is synchronized with a timing 200 at which the polarity changes to negative immediately after the command, as shown in FIG. 2 (e). Exposure mode 2 from the previous operation mode
Switching to 02 is performed.

Here, an error occurs in the exposure time due to a delay variation in the mechanical shutter closing time. That is, even if the closing pulse is given to the mechanical shutter at the timing 204, the immediate closing operation as shown by the dotted line 206 is not performed,
The closing operation is performed with a slight delay. Therefore, there is a possibility that a delay corresponding to the time indicated by reference numeral 208 occurs, and an excess charge is generated due to an increase in the exposure time, thereby causing an overflow.

Therefore, in the prior art, the fine adjustment 210 is performed on the electronic shutter side where exposure is started using a vertical overflow drain structure so that an appropriate exposure amount can be obtained. While the electronic shutter pulse is being given, the charge of the CCD is repeatedly extracted, and each time the charge becomes zero and the accumulation of charge is restarted. In this way, the start of exposure is delayed by a necessary time, and the delay variation of the mechanical shutter is compensated to obtain a substantial exposure time (mechanical shutter open time + mechanical shutter close time) 211. The fine adjustment 210 is performed using a photometric mechanism that has been conventionally used, and after a substantial exposure time 211 is grasped in advance.

However, in such a method of compensating for the delay of the mechanical shutter on the electronic shutter side, the time lag 212 from the start of the exposure mode 202 to the start of the actual exposure becomes long. In particular, in the case of a bright subject, since the surplus electric charge increases, the electronic shutter needs to frequently extract the electric charge, and the output frequency becomes high. As a result, there is a disadvantage that an object moving at a very high speed is missed. Also, due to this time lag, unnecessary exposure mode 20
There is also a disadvantage that the number of images is reduced when continuous shooting is performed by extending the number 2.

FIG. 3 is a time chart of a first embodiment of the exposure method according to the present invention which solves the above-mentioned problems of the prior art. Hereinafter, the operation of this embodiment will be described with reference to FIG. In this embodiment, the timing signal generator 120 in FIG. 1 is initially in the movie mode. When the photometry instruction signal 28 is sent to the system control unit 12 by half-pressing the shutter release button 128, the exposure calculation control function unit 12A uses the imaging signal 10c supplied from the signal processing unit 114 to the system control unit 12. And perform photometry.
The system control unit 12 determines a substantial exposure time so as to achieve an exposure amount based on the calculated photometric value, and based on the determined exposure time, sends a control signal 12a that determines a timing for closing the mechanical shutter 108d to the AE adjustment unit 108. Supply. The timing here is the timing 222 of the rise of the mechanical shutter drive pulse in FIG. The driving is set so as to be earlier than the rising timing 224 of the mechanical shutter driving pulse before adjustment shown in FIG.

When the shutter release button 128 is fully depressed, a switch signal 28 for switching to the exposure mode is transmitted, and the system controller 12 sends this to the timing signal generator 120 as a switching instruction 12d for switching to the exposure mode. Timing signal generator 1
20 switches to the exposure mode in synchronization with the timing 226 at which the immediately following vertical synchronizing signal VD turns negative, and outputs the switched mode information to the driver unit 122. The driver unit 122 gives the electronic shutter output pulse 122a one or more fixed times to the imaging unit, and starts actual exposure from the fixed time point 228. As described above, the charge extraction pulse to the electronic shutter shown in FIG. 3B may be output any number of times, but is fixed as described above. Therefore, the exposure start time is fixed to an earlier time. Then, the exposure is completed, as described above, with the mechanical shutter 10 adjusted by photometry.
According to 8d. By expediting the closing of the mechanical shutter 108d, the substantial exposure time 232 is moved forward. That is, the delay of the mechanical shutter 108d is compensated not by the electronic shutter but by the mechanical shutter itself. This results in a substantial exposure time
Although 232 is the same as the conventional case, the time lag 230 from the start of the exposure mode to the start of the actual exposure is significantly shorter than that of the related art.

FIG. 4 is a time chart of a second embodiment of the exposure method according to the present invention. In this embodiment, unlike FIG. 3, the exposure start point is determined by generating a field shift pulse instead of an electronic shutter. The same operation timing as in FIG. 3 is represented by the same reference numeral as in FIG. FIG. 4 differs from FIG. 3 in that the driver unit 122 supplies a field shift pulse 122a instead of an electronic shutter pulse to the transfer gate of the imaging unit 104 at the same time as the shift to the exposure mode 220. Thereby, the imaging unit
Unnecessary charges accumulated in the image sensor 104 are field-shifted to the vertical transfer path.

In this embodiment, the exposure mode 22
The actual exposure is started substantially simultaneously with the transition to zero. Corresponding to this, the drive timing of the mechanical shutter 108d is also earlier than that of FIG. 3, a drive pulse is started at timing 236, and closing is started at timing 238. Thus, the present embodiment has an advantage that the time lag is substantially eliminated. Further, in this embodiment, the electronic shutter mechanism used in FIG. 3 is unnecessary. However, the operation as in the present embodiment can also be realized by using an electronic shutter pulse. In that case, the electronic shutter pulse need only be output once at the same time as the shift to the exposure mode.

When the field shift pulse is used to designate the exposure start time as in this embodiment, the charges shifted to the vertical transfer path are transferred to the vertical transfer path by the time the signal read mode 234 starts. It is necessary to sweep from the road.

FIG. 5 is a time chart showing a third embodiment of the exposure method according to the present invention. The timing signal generator 120 in FIG. 1 is initially in the movie mode 300 in FIG.
When the shutter release button 128 is half-pressed, a photometric instruction signal 28 is input to the system control unit 12. Accordingly, the exposure calculation control function unit 12A performs photometry using the imaging signal 10c supplied from the signal processing unit 114 to the system control unit 12.

This embodiment is characterized in that AE (Auto Exposure) information acquired in the movie mode 300 before shifting to exposure,
Specifically, the imaging signal 10c supplied to the system control unit 12
Is based on the photometry, and the length of the exposure mode 304 is determined in advance. In this respect, the present embodiment differs from the embodiment of FIG. 3 or FIG. 4 in that not only the actual exposure time is calculated but also the exposure mode 30
Also shorten the length of 4. That is, “exposure mode length = substantial exposure time = mechanical shutter open time + mechanical shutter close time”, and only the calculated exposure time
Keep 304. The system control unit 12 sends a control signal 12a for determining the timing of closing the mechanical shutter 108d to achieve the calculated substantial exposure time.
To supply.

When the shutter release button 128 is fully pressed, a switching signal 28 for switching to the exposure mode is transmitted. When the system control unit 12 sends this to the timing signal generation unit 120 as the mode switching instruction 12d, this appears as a shooting command 302 in the vertical synchronization signal VD of FIG. System control unit 1
2 starts the timing of the exposure mode 304 at the same time. Thereby, the shift to the exposure mode 304 of FIG. 5E is performed. The driver unit 122 outputs the electronic shutter pulse 305 once at the same time as the shift to the exposure mode 304, and immediately starts the actual exposure. Although a fixed number of electronic shutters can be output from the shift to the exposure mode as performed in FIG. 3, here, unnecessary exposure mode length is reduced and the exposure mode length is substantially reduced. Only one output is used to match the exposure time. The end of exposure is performed by the mechanical shutter 108d adjusted by photometry. Thus, FIG.
Is output only once to start the substantial exposure time 306 and the exposure mode 304.
With the start of

At the same time as the previously calculated exposure time elapses, the system control unit 12 uses the timing signal 12e of FIG. 1 to generate the timing signal irrespective of the normal frequency of the vertical synchronizing signal VD of FIG. It instructs the generation unit 120 to forcibly reset output 308 of the vertical synchronization signal VD. The timing of the exposure time by the system control unit 12 may be performed by timing a synchronization signal as shown in FIG. FIGS. 8A and 8C are enlarged views of FIGS. 5A and 5C, and FIGS. 8B and 8D are output timings of the horizontal synchronizing signal HD and the reset pulse. As shown in FIG. 8, transition to the exposure mode 304,
That is, the timing 302 of the vertical synchronization signal VD shown in FIG.
At the same time, the measurement may be performed by counting the number of horizontal synchronization signals HD (this is provided from the driver unit via the signal line 122b in FIG. 1) in the period 307 shown in FIG. 8B. When a predetermined number of signals HD have been counted, a reset pulse 303 shown in FIG. 8D is output. This corresponds to the output 308 of the signal VD shown in FIG.
Appears as.

As described above, the start of the exposure mode coincides with the start of the actual exposure, so that there is no time lag. In addition, the exposure mode is forcibly terminated at the same time as the actual exposure is completed. You can move to 310. In FIG. 5, the exposure mode itself is shorter than in FIG. 3 or FIG. Therefore, the exposure time can be further reduced.

FIG. 6 is a time chart showing a fourth embodiment of the exposure method according to the present invention. The operation of this embodiment is substantially the same as that of the third embodiment shown in FIG. 5, and the same pulses and timings are represented by the same reference numerals. FIG.
However, the difference from FIG. 5 is that the exposure is started not by the electronic shutter but by the transfer gate of FIG. 6C. Hereinafter, only differences from FIG. 5 will be described.

FIG. 6 is the same as FIG. 5 up to the transition from the movie mode 300 to the exposure mode 304. In this embodiment, the field shift pulse 312 is output to the transfer gate shown in FIG. 6C instead of the electronic shutter pulse shown in FIG. 6B simultaneously with the start of the exposure mode 304. Thus, exposure is started. Field shift pulse
Unnecessary signal charges swept out to a vertical transfer path (not shown) of the imaging unit 104 in FIG.
Transferred vertically and horizontally inside and discarded. The point that the exposure mode 304 is adjusted to the substantial exposure time 306 started by the field shift pulse 312 is the same as in FIG. 5, and a forced reset pulse 308 is applied to the vertical synchronization signal VD in FIG. Thus, the exposure mode is shifted to the signal reading mode 310 in the shortest time.

FIG. 7 is a time chart showing a fifth embodiment of the exposure method according to the present invention. This embodiment shows an exposure method in the case of performing continuous shooting using the fourth embodiment (exposure is started by a field shift pulse) in FIG. However, the third embodiment of FIG. 5 (exposure is started by an electronic shutter) can also realize the embodiment of performing continuous shooting shown in FIG.

Hereinafter, FIG. 7 will be described only with respect to differences from FIG. The same reference numerals as those in FIG. 6 are used for the same pulses and timings. FIG. 6 is the same as FIG. 6 until the exposure mode 304 is set to substantially coincide with the exposure time 306, and the reset pulse 308 is output simultaneously with the end of the exposure to forcibly shift to the signal reading mode.

Thereafter, the signal charges are read in the signal read mode 310, and the last vertical synchronizing signal 314 in the signal read mode 310 is output, and any signal before the reading of the signal charges from the vertical transfer path is completely completed. For example, at time 318, the system controller 12 again identifies the state of the shutter release button 128. At this time, if the shutter release button 128 has returned to a state other than the full press, the system control unit 12 returns the timing signal generation unit 120 to the movie mode.

However, when performing continuous shooting as in the present embodiment, the shutter release button 128 is kept fully pressed. In this case, the system control unit 12 instructs the AE adjustment unit 108 to finish reading the signal charge and
Is opened as the control signal 12a. The AE adjustment unit 108 inverts the mechanical shutter drive pulse in FIG.
This is supplied to the mechanical shutter as a drive signal 108c, and the mechanical shutter is opened at the same time when the signal reading is completed (start of the exposure mode 316). On the other hand, the timing signal generator 120 is again set to the exposure mode 316, and repeats the same operation as that performed in the previous exposure mode 304 and signal readout mode 310. That is, the switching instruction 12d to the exposure mode
Is sent to the timing signal generator 120, and the generator 120 switches to the exposure mode 316 again. At the same time as the start of the exposure mode 316, the field shift pulse 322 is output and substantial exposure is started, and the system control unit 12 already has
In response to the exposure time 326 based on the AE information, a mechanical shutter drive pulse 323 is output, and the mechanical shutter 108d
Completely closed at the end of 26. At the same time, a reset pulse 324 is output from the system control unit 12 to the timing signal generation unit, and the exposure mode 316 is forcibly terminated at the same time when the actual exposure 326 is completed. Then, the signal read mode 328 is started. Thus, the exposure mode and the signal readout mode are repeated in the shortest time, and the number of continuous shots is increased.

The embodiments of the present invention have been described using the digital camera. However, the present invention is not limited to the above embodiments, and is applicable to all types of image pickup apparatuses in which the start of exposure is performed by an electronic shutter or a transfer gate, and the end of exposure is performed by a mechanical shutter.

[0068]

As described above, according to the present invention, substantial exposure can be started with a small time lag from the transition to the exposure mode. This improves the feeling of use. Further, since the electronic shutter outputs only a constant number of times, the number of cases in which a subject moving at high speed is missed is reduced. on the other hand,
The same effect can be obtained when a field shift pulse is output to the transfer gate instead of the electronic shutter to set the timing of exposure start. In that case, the electronic shutter and circuits related thereto are not required.

Further, the exposure mode length can be made substantially equal to the exposure time. That is, the substantial exposure is started at the same time as the shift to the exposure mode, and the exposure mode can be forcibly terminated at the same time as the substantial exposure is completed. Thereby, the time lag is substantially eliminated, and the photographing time is reduced. Therefore, there is an advantage that the number of continuous shots is increased particularly when continuous shooting is performed.

Further, since the electric charge accumulated in the image pickup device by the exposure can be transferred to the vertical transfer path in the shortest time, the charge can be prevented from being discharged and the image pickup device can be prevented from being saturated.

Further, the mechanical shutter used by the image pickup apparatus according to the present invention can be mounted anywhere on the camera, and is less subject to restrictions on the mounting location as compared with the electronic shutter.

Further, if the exposure is performed only by the electronic shutter pulse, so-called white spots appear on the screen, the exposure is terminated by using the mechanical shutter.
The advantage is that the image quality is not affected.

[Brief description of the drawings]

FIG. 1 is a block diagram in which an imaging device according to the present invention is applied to a digital camera.

FIG. 2 is a time chart according to the related art.

FIG. 3 is a time chart of the first embodiment of the exposure method according to the present invention.

FIG. 4 is a time chart of a second embodiment of the exposure method according to the present invention.

FIG. 5 is a time chart of a third embodiment of the exposure method according to the present invention.

FIG. 6 is a time chart of a fourth embodiment of the exposure method according to the present invention.

FIG. 7 is a time chart of a fifth embodiment of the exposure method according to the present invention.

FIG. 8 is a diagram illustrating output timing of a reset pulse output by the system control unit in FIG. 1;

[Explanation of symbols]

 10 Digital camera 12 System control unit 104 Imaging unit 108 AE adjustment unit 120 Timing signal generation unit 122 Driver unit 128 Shutter release button

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/225 H04N 5/225 G 5/238 5/238 Z 5/335 5/335 F // H04N 101 : 00 101: 00 F term (reference) 2H002 AB01 CC01 CC10 DB02 HA02 JA07 2H054 AA01 2H081 CC02 CC57 CC62 DD02 DD03 DD06 5C022 AA13 AB03 AB17 AB18 AC32 AC42 AC52 5C024 AX01 BX01 DX04 DX07 GY01 GZ01 HX23

Claims (7)

[Claims] 1. An image pickup device comprising: a plurality of two-dimensionally arranged image pickup elements for photoelectrically converting incident light from an object field into signal charges and storing the signal charges, and is selected from at least a movie mode, an exposure mode, or a signal readout mode. An imaging device that operates in accordance with the operation mode, the device further includes: an exposure calculation unit configured to calculate an exposure time of the imaging device based on an amount of incident light emitted from the object scene; Charge extracting means for extracting the signal charge; and when the operation mode is switched from the movie mode to the exposure mode, at the same time, a charge extracting instruction is given to the charge extracting means at least once over a predetermined period, and A signal generating unit for instructing the image sensor to read out accumulated signal charges when switching to a signal readout mode; Mechanical shutter means for physically blocking the image sensor from the object field; exposure adjusting means for adjusting exposure by opening and closing the mechanical shutter means; When the operation mode is the movie mode and the operation mode is the exposure mode, the time from the end of the charge extraction over the predetermined period to the closing of the mechanical shutter means is equal to the calculated exposure time. Control means for controlling the exposure adjusting means, wherein exposure is performed by switching to the exposure mode by the control means, and reading of signal charges is performed by switching to the signal reading mode by the control means. Imaging device. 2. The apparatus according to claim 1, wherein the control unit controls the timing at which the mechanical shutter is closed to perform the exposure over the exposure time. 3. The apparatus according to claim 1, wherein the charge extracting means extracts the signal charge only once so that the exposure is started simultaneously with switching to the exposure mode. Imaging device. 4. The apparatus according to claim 1, wherein said electrification extracting means is an electronic shutter for discarding signal charges in a direction of a substrate on which said image pickup device is disposed. Imaging device. 5. An apparatus according to claim 1, wherein said electrification extracting means is a transfer gate for transferring a signal charge to a charge transfer path provided in parallel with said image pickup device. Characteristic imaging device. 6. A movie process for irradiating a plurality of two-dimensionally arranged imaging elements with incident light from an object field, and mechanically shuttering by starting exposure by extracting electric charges accumulated in the imaging elements. An exposure method comprising: closing an image sensor to physically close the image sensor from an object field to end exposure, and a signal reading step of reading signal charges accumulated in the image sensor by the exposure.
An electronic shutter step of, at the same time as switching from the movie step to the exposure step, extracting a signal charge and starting exposure from the image pickup device at least once over a predetermined period; and Closing the mechanical shutter means simultaneously with the elapse of the exposure time. 7. The method according to claim 6, wherein in the electronic shutter step, simultaneously with switching to the exposure step,
An exposure method, wherein the exposure is started simultaneously with switching to the exposure step by extracting signal charges only once from the image sensor.