JPH10136251A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve focusing and exposure in the case of main exposure. SOLUTION: Each section is initialized in the monitor mode (S1), an exposure control mode is set (S2). An image pickup element is exposed, a drive frequency, an electronic shutter time and an aperture of the image pickup element are calculated based on the exposure level (S3, S4), and the calculated values are set (S5-7). A distance of an object is measured and a focus lens is driven up to a focal position (S8). When in an afocal state (S9), the distance is measured again and the focus lens is adjusted (S10). A recording sequence is started with respect to the operation of a recording trigger switch (S11). That is, at first, the drive frequency of the image pickup element is changed into that for the main exposure mode (S12), an aperture is driven to obtain the aperture for the main exposure (S14). A mechanical shutter is driven at a proper shutter time decided from the measured values and the aperture for the main exposure mode and the image pickup element 14 is exposed (S15). A picked-up image is transferred to a recording medium 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup apparatus having an image pickup device such as a CCD.

[0002]

2. Description of the Related Art FIG. 5 is a schematic block diagram of a conventional digital electronic camera. Reference numeral 110 denotes an optical lens that forms an optical image of a subject, and 112 denotes an aperture shutter that controls the amount of incident light rays from the optical lens 110 and is also used as a shutter. An image sensor 114 converts an object image formed by the optical lens 110 into an electric signal, and is an image sensor generally used in a movie video camera, for example, a color difference sequential interline having a complementary color checkerboard filter. Type CCD image sensor.

Reference numeral 116 denotes a CDS circuit for removing noise from an output signal of the image sensor 114, and 118 denotes a CDS circuit 11.
6, an amplifier 120 amplifies the output signal of the amplifier 118; a clamp circuit for fixing the zero (black) level of the output signal of the amplifier 118;
An A / D converter 22 converts an analog output of the clamp circuit 120 into a digital signal, an imaging signal processing circuit 124 processes an output data of the A / D converter 122 as an imaging signal, and 126 an imaging signal processing circuit 124 Is a recording medium interface for outputting image information processed by the computer to an external recording medium 128 or a computer.

Reference numeral 130 denotes a luminance level detection circuit for calculating a luminance level (integral value) of a specific area on the screen from the luminance signal generated by the imaging signal processing circuit 124. Reference numeral 132 denotes a luminance generated by the imaging signal processing circuit 124. This is a focus information detection circuit that detects a high frequency component from a signal and uses it as focus information.

Reference numeral 134 denotes a focus driving circuit for driving a focus adjusting lens of the optical lens 110, and 136 denotes an aperture shutter 1.
An aperture shutter drive circuit 138 that drives the 12 apertures and changes the aperture of the aperture is an image sensor drive circuit that drives the image sensor 114.

Reference numeral 140 denotes a system control circuit for controlling the whole, 142 denotes an oscillator for generating a basic clock serving as a reference for the whole, and 144 denotes an imaging signal processing circuit in accordance with the output clock of the oscillator 142 under the control of the system control circuit 140. A synchronization signal generation circuit (SSG) for generating a pulse signal necessary for the signal 124 and video synchronization signals HD and VD for the timing signal generation circuit (TG) 146. Under the control of the system control circuit 140, the timing signal generation circuit 146 receives an image sensor drive circuit 138, a CDS circuit 116, a clamp circuit, in accordance with the clock signal from the oscillator 142 and the video synchronization signals HD and VD from the synchronization signal generation circuit 144. A predetermined timing signal is supplied to the A / D converter 120 and the A / D converter 122. The system control circuit 140 controls the exposure time of the image sensor 114, that is, the electronic shutter speed via the timing signal generation circuit 146 and the image sensor drive circuit 138.

The exposure control in such a conventional example will be described. The purpose of the exposure control is to maintain the illuminance (image surface illuminance) of the light receiving surface of the image sensor 114 at a constant amount by controlling the opening area of the aperture shutter 112. Image sensor 114
The amount of light incident on the image sensor 114 can be detected by converting the output signal of the image sensor 114 into a luminance signal by the image signal processing circuit 124 and integrating the luminance signal in a specific area of the light receiving area of the image sensor. Luminance level detection circuit 130 detects an integrated value of the luminance level in the specific area and transmits the integrated value to system control circuit 140.

The system control circuit 140 compares the brightness level from the brightness level detection circuit 130 with the reference brightness level, and controls the aperture shutter 112 by the aperture shutter drive circuit 136 so that the brightness level from the circuit 130 matches the reference brightness level. Control the opening area of Specifically, if the luminance level from the circuit 130 is higher than the reference luminance level, the system control circuit 140 instructs the aperture shutter drive circuit 136 to reduce the aperture area of the aperture shutter 112, and conversely, the circuit 130 Is smaller than the reference luminance level, the aperture shutter drive circuit 136 is instructed to increase the aperture area of the aperture shutter 112, and the aperture shutter drive circuit 136
The optical diaphragm of the diaphragm shutter 112 is driven in accordance with a command from 40.

By such a feedback operation, the exposure amount is kept at an appropriate amount. Note that a galvanometer or a stepping motor is used for driving the aperture.

Exposure can also be controlled by utilizing the electronic shutter function of the image sensor 114. FIG. 6 is a plan view showing the configuration of the interline CCD type image pickup device. Fifteen
Numeral 0 denotes a photodiode for converting incident light into electric charge corresponding to the amount of light, and a complementary color filter corresponding to a pixel position is disposed on each incident surface. Reference numeral 152 denotes a vertical transfer CCD for reading out the charges in the columns of the photodiodes 150 arranged vertically and transferring the charges in the vertical direction. Reference numeral 154 denotes horizontal transfer CCDs 156 for transferring the charges transferred from the vertical transfer CCD 152 horizontally for each horizontal line. Is a floating diffusion amplifier that converts the electric charge transferred from the horizontal transfer CCD 154 into a voltage signal and outputs the voltage signal.

FIG. 7 shows a cross-sectional structure of a photodiode 120 of an interline CCD type image pickup device, and FIG.
8 shows a potential on line AA in FIG. 7. As can be seen from these figures, a vertical overflow drain structure is employed as a mechanism for anti-blooming and electronic shutter. The substrate potential is usually a potential Vs at an appropriate saturation charge amount and at which antiblooming functions appropriately.
ub (DC). When a pulse of ΔVsub is further applied, signal charges already accumulated in the photodiode can be discarded.

FIG. 9 shows vertical transfer pulses ΦV1 to ΦV1 during a period from immediately before charge reading from the photodiode 150 to the vertical transfer CCD 152 to immediately after the next charge reading.
FIG. 7 is a timing chart of V4 and an electronic shutter pulse ΦVsub. The electronic shutter pulse ΦVsub is typically applied during the horizontal blanking interval. A period (1) from a charge read pulse instructing charge read from the photodiode 150 to the vertical transfer CCD to a next charge read pulse.
V or one field), the time te from the last electronic shutter pulse to the next charge readout pulse is the accumulation time (exposure time or shutter speed).

Therefore, normally, in the exposure control method using an electronic shutter, the vertical transfer CC
The exposure time is controlled by how far the electronic shutter pulse is issued from the charge readout pulse for instructing D152 to read out the charge. That is, the system control circuit 140
If the brightness level from the brightness level detection circuit 130 is higher than the reference brightness level, the timing signal generation circuit 146 is instructed to shorten the exposure time, and the number of electronic shutter pulses is increased. The electronic shutter pulse is a charge readout pulse for causing the vertical transfer CCD 152 to read out the charge of the photodiode 150, and the exposure time becomes shorter as the number of charge readout pulses increases.

Conversely, if the luminance level from circuit 130 is lower than the reference luminance level, system control circuit 140
Timing signal generation circuit 146 so as to extend the exposure time
To reduce the number of electronic shutter pulses. By such feedback control, the exposure amount is maintained at an appropriate amount.

In the above-described system, in a typical electronic still camera of the related art, the image pickup device 114 often uses a CCD image pickup device for a video camcorder for reasons such as cost. Therefore, the timing signal generation circuit 146 for driving the image sensor 114 and the CDS / AGC
Circuits, signal processing ICs, synchronization signal generation (SSG) ICs and the like are also used for video camcorders. Each unit is basically driven at a video rate. The charge signal of the odd-numbered line and the charge signal of the even-numbered line of the image sensor 114 are added and read. This addition is performed while being alternately shifted by one line for each field of the television signal, that is, interlaced. As a result, the image captured by the image sensor 114 is displayed as a moving image on a screen of a video display device such as an electronic viewfinder EVF, and the subject can be framed.

The optical lens 110 can be focused by detecting the high-frequency component of the captured image signal and adjusting the focus of the optical lens 110 by the focus driving circuit 134. Hereinafter, for the sake of explanation, an operation mode for finder output and focusing will be referred to as a monitor mode.

To obtain a high-resolution image as a still image, the aperture shutter 112 is used. That is, the aperture shutter 11
In step 2, the pixels of the odd-numbered line and the even-numbered line of the image sensor 114 are simultaneously exposed for a certain time, and then the image sensor 112 is shielded from light by the aperture shutter 112. Then, the charge signal of the odd-numbered line and the charge signal of the even-numbered line are read out in a time division manner without being added. For the sake of description, this is hereinafter referred to as a main exposure mode. An image consisting of the read-out charges of the odd-numbered lines;
An image composed of the charges of the even lines is subjected to image signal processing as synthetic paper and a frame image, and is recorded on the recording medium 128.

That is, in the conventional example, a mechanical shutter is used in the main exposure mode, and an electronic shutter is used in the monitor mode.

[0019]

By the way, in the case of focusing control, it is necessary to expose the image pickup element 114 and focus the optical lens 110 in advance before main exposure (that is, photographing for recording). There is. For example, the optical lens 110 is controlled to be in a focused state by continuously photographing in the monitor mode and driving the focus adjustment lens of the optical lens so that the high-frequency component of the luminance signal at that time is increased. After the in-focus state is obtained, the main exposure mode is set by a recording trigger signal corresponding to the depression of the shutter button or the like, and the image is captured by the mechanical shutter as described above, and the captured image is recorded on the recording medium 128. The aperture diameter in the main exposure mode must be the same as or smaller than that in the monitor mode. This is because the larger the aperture diameter of the aperture, the shallower the depth of field becomes. Therefore, if the aperture diameter of the aperture in the main exposure mode is larger than that in the monitor mode, the focus previously adjusted is blurred.

It is assumed that the shortest exposure time of the mechanical shutter can be controlled to be shorter than the shortest exposure time of the electronic shutter. If the shortest exposure time of the mechanical shutter is 1 / 8,000
Seconds, the shortest exposure time of the electronic shutter is 1 /
Assume a 2,000 second camera. Then, for example, the photographer sets the shutter speed in the main exposure mode to 1 / 8,000 seconds in a so-called shutter priority exposure control mode,
It is assumed that an appropriate aperture is F1.4. In this case, in order to obtain an appropriate exposure amount in the monitor mode, the minimum exposure time of the electronic shutter is 1/2000 sec.
It is necessary to squeeze to 5.6. Then, in the main exposure mode, the aperture diameter becomes wider, the focus of the optical lens is shifted, and the image is blurred.

In the case of interlaced reading, the charge signal of the odd line and the charge signal of the even line on the image sensor are added and read. Therefore, when the aperture value is set to a relatively wide aperture value, since the addition reading is performed, the sensitivity is relatively good. Therefore, it is necessary to make the exposure amount smaller in the monitor mode than in the main exposure mode. In other words, in this exposure mode, a longer shutter time is required than in the monitor mode. However, as the shutter time becomes longer, it becomes more difficult to shoot a fast-moving subject.

An object of the present invention is to provide an image pickup apparatus which solves such a problem.

That is, an object of the present invention is to provide an image pickup apparatus which prevents the depth of field from becoming shallow due to the opening of the aperture during the main exposure and the focus is not shifted, and realizes appropriate exposure control and distance measurement. .

The present invention is also directed to an image pickup apparatus using an image pickup device having an operation mode in which charge signals of a plurality of pixels are added and read out. And an imaging device for realizing distance measurement.

The present invention further provides an image pickup apparatus which realizes appropriate exposure control and distance measurement in a system having a distance measuring means for obtaining focus information of an image pickup lens from a shift amount of a plurality of optical images by a pupil dividing means. The purpose is to:

It is a further object of the present invention to provide an image pickup apparatus which realizes appropriate exposure control and distance measurement when the brightness of a subject image is equal to or higher than a predetermined value.

A further object of the present invention is to provide an image pickup apparatus which realizes appropriate exposure control and distance measurement when the aperture priority exposure control mode is set.

[0028]

According to a first aspect of the present invention, there is provided an image pickup device for converting an optical image by an image pickup lens into an electric signal, a focusing unit for focusing the image pickup lens,
An image sensor driving timing control means for controlling a timing for driving the image sensor, wherein a time required for reading an image signal for one screen of the image sensor differs between photographing and at least distance measurement. And

Thus, even when the aperture is opened in the main exposure and the depth of field becomes shallow, it is possible to prevent the focus from being shifted. Therefore, at the time of the main exposure, appropriate exposure control and distance measurement can be simultaneously realized.

According to a second aspect of the present invention, there is provided an image pickup device for converting an optical image by an image pickup lens into an electric signal, focusing means for focusing the image pickup lens, and one of the image pickup devices.
An image sensor driving timing control unit for controlling a time for reading a photoelectric conversion signal for a screen, the image sensor having a mode in which a plurality of pixels are added and read, and a plurality of pixels of the image sensor are added It is characterized in that the time for reading out the photoelectric conversion signal for one screen of the image sensor is changed according to the number of pixels.

Thus, in an image pickup apparatus using an image pickup device having an operation mode in which charge signals of a plurality of pixels are added and read out, appropriate exposure control and measurement are performed for each of a plurality of exposure modes having different numbers of pixels to be added. Distance can be realized.

According to a third aspect of the present invention, there is provided an image pickup device for converting an optical image by an image pickup lens into an electric signal, focusing means for focusing the image pickup lens, and one of the image pickup devices.
An imaging device drive timing control unit for controlling a time for reading a photoelectric conversion signal for a screen; and a distance measurement unit for obtaining focus information of the imaging lens from a shift amount of a plurality of optical images by a pupil division unit. The time for reading the photoelectric conversion signal for one screen of the image sensor differs at least between the time of distance measurement and the time of distance measurement.

This makes it possible to realize appropriate exposure control and distance measurement in a system having a distance measuring unit that obtains focus information of the imaging lens from a shift amount of a plurality of optical images by the pupil dividing unit.

According to a fourth aspect of the present invention, there is provided an image pickup device for converting an optical image by an image pickup lens into an electric signal, focusing means for focusing the image pickup lens, and a photoelectric conversion signal for one screen of the image pickup device. Image sensor drive timing control means for controlling the time for reading the image, and photometric means for measuring the brightness of the image of the subject. It is characterized in that the time for reading out the photoelectric conversion signal for one screen is shorter than that for shooting.

Thus, when the brightness of the subject image is equal to or more than a predetermined value, appropriate exposure control and distance measurement can be realized.

According to a fifth aspect of the present invention, there is provided an image pickup device for converting an optical image obtained by a photographing lens into an electric signal, focusing means for focusing the image pickup lens, and one of the image pickup devices.
Image sensor drive timing control means for controlling the time to read out the photoelectric conversion signals for the screen; photometric means for measuring the brightness of the subject image; exposure control means for controlling the amount of exposure to the image sensor; Exposure control setting means for setting the conditions of the above, when the aperture priority haze control mode is set by the exposure control setting means, the optical aperture diameter at the time of exposure at the time of distance measurement, the aperture priority exposure control It is characterized in that the time for reading out a photoelectric conversion signal for one screen of the solid-state imaging device is appropriately changed so as to be larger than the aperture diameter set in the mode.

Thus, appropriate exposure control and distance measurement can be realized when the aperture priority exposure control mode is set.

[0038]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram showing an embodiment of the present invention. 10 is an optical lens, 12 is an aperture shutter, 14 is an image sensor, 16 is a CDS circuit, 18 is an amplifier, 20 is a clamp circuit, 22 is an A / D converter, 24 is an image signal processing circuit, 26 is a recording medium interface,
28 is a recording medium, 30 is a luminance level detection circuit, 32 is a focus information detection circuit, 34 is a focus drive circuit, 36 is an aperture shutter drive circuit, and 38 is an image sensor drive circuit. These elements 10 to 38 are respectively elements 110 to 110 shown in FIG.
138 and perform the same function.

40 is a system control circuit for controlling the whole,
Reference numeral 42 denotes an oscillator for generating a basic clock serving as a reference, and 43 denotes an oscillator 42 under the control of the system control circuit 40.
A frequency divider 44 divides and multiplies the output frequency of the image signal. A pulse signal 44 necessary for the image signal processing circuit 24 and a timing signal generation circuit (44) are controlled by the system control circuit 40 in accordance with the output clock of the frequency divider 43. TG) Synchronization signal generation circuit (SSG) for supplying video synchronization signals HD and VD to 46
It is. Under the control of the system control circuit 40, the timing signal generation circuit 46 controls the clock signal from the frequency divider / multiplier 43 and the video synchronization signal H from the synchronization signal generation circuit 44.
In accordance with D and VD, the image sensor driving circuit 38 and the CDS circuit 1
6. A predetermined timing signal is supplied to the clamp circuit 20 and the A / D converter 22. The system control circuit 40 controls the exposure time of the image sensor 14, that is, the electronic shutter speed via the timing signal generation circuit 46 and the image sensor drive circuit 38.

In this embodiment, the exposure amount is adjusted by changing the driving speed, and the focusing is controlled by the time-division phase difference focusing method.

First, a method of adjusting the exposure amount by changing the driving speed will be described. As described above, the electronic shutter utilizes the fact that the charge accumulation time can be changed by changing the number of electronic shutter pulses. here,
The output clock frequency element of the oscillator 42 is fs (Hz). The frequency fs is arbitrarily determined depending on the purpose of use, specifications, and the like.

Consider a case where the luminance level detected by the luminance level detection circuit 30 is lower than the reference luminance level.
In such a case, the synchronizing signal generation circuit 44 and the timing signal generation circuit 46 are driven at the clock frequency fs, and the exposure time is equal to or less than the proper exposure amount even when the electronic shutter is set to the maximum exposure time (that is, there is no electronic shutter pulse). When only the amount is obtained, the system control circuit 40
3 divides the output frequency of the oscillator 42 by half. As a result, the output frequencies of the synchronization signal generation circuit 44 and the timing signal generation circuit 46 are all halved, and the interval between the electronic shutter pulses ΦVsub is doubled. Under this clock condition, the system control circuit 40 tries to adjust the exposure amount again by controlling the electronic shutter. If fs
When the exposure amount equal to or less than the appropriate exposure amount can be obtained even when the image pickup device 14 is set to the maximum exposure time at / 2 (Hz), the system control circuit 40 outputs the output of the oscillator 42 to the frequency divider 43. Divide by / 4. Until an exposure amount equal to or more than an appropriate exposure amount can be obtained when the image pickup device 14 is set to the maximum exposure time, such a frequency divider / multiplier 4 is used.
The control of 3 is repeated.

Conversely, consider a case where the luminance level from the luminance level detection circuit 30 is higher than the reference luminance level. In this case, when only the exposure amount equal to or more than the appropriate exposure amount is obtained even when the electronic shutter is set to the minimum exposure time (that is, the number of electronic shutter pulses is maximum), the system control circuit 40
Controls the frequency divider / multiplier 43 so as to multiply the output frequency of the oscillator 42. As a result, the frequency divider / multiplier 43 becomes 2 ·
fs (Hz) clock pulse to the synchronization signal generation circuit 4
4 and a timing signal generation circuit 46. Then, under this clock frequency, the system control circuit 40
Adjusts the exposure amount by controlling the electronic shutter.

If an exposure amount equal to or more than the proper exposure amount can still be obtained with the minimum exposure time even at 2 · fs (Hz), the system control circuit 40 increases the multiplication factor of the frequency divider / multiplier 43 and outputs the output of the oscillator 42. Quadruple the frequency. That is, 4 · fs
(Hz). Since the clock frequency is increased, the interval between the electronic shutter pulses is shortened, and the amount of change in the exposure amount due to the increase or decrease of one electronic shutter pulse is also reduced. This makes it possible to increase the accuracy of controlling the exposure amount for a high-brightness subject.

In this manner, by changing the driving frequency of the image pickup device 14, the exposure time by the electronic shutter, that is, the charge accumulation time can be adjusted.

Next, the time division phase difference focusing method will be described.
FIG. 2 is a plan view showing a configuration of a pupil stop for the time-division phase difference focusing method. In the time-division phase-difference focusing method, two optical images having different optical paths are obtained by switching two aperture holes opened so that the optical paths are different from each other, as shown in FIG. The two optical images thus obtained enter the image sensor in a time-division manner.

The output of the image sensor is output to a predetermined line (for example,
As shown in FIG. FIG.
(1) is a focused state, (2) is a front focus state, and (3) is a rear focus state. As can be seen from FIG.
The interval between the two images differs depending on whether the state is the front focus state or the rear focus state. The focusing lens of the optical lens 10 is moved and focused so that the image interval becomes the interval of the focused state. The amount of movement of the focusing lens,
That is, the moving amount of the image plane can be obtained by calculating from the interval between the two images.

FIG. 4 shows a flowchart of the characteristic operation of this embodiment. The overall operation of the present embodiment will be described with reference to FIG. In FIG. 4, general operations not directly related to the present embodiment are omitted for the sake of simplicity and clarity of the features of the present embodiment. Also in the present embodiment, an operation mode for outputting a subject image to a viewfinder such as an EVF or the like for determining the composition of photographing, or an operation mode for measuring a distance is referred to as a monitor mode, and is a predetermined mode before and after exposure for recording the subject image. The period is referred to as a main exposure mode.

First, initialization is performed in the monitor mode (S
1). However, at this point, no image is displayed on the viewfinder yet, and an appropriate image is displayed on the viewfinder after exposure control and focusing control in the following sequence. In the initialization process (S1), the drive frequency, sensitivity, electronic shutter time, and aperture value of the image sensor 14 are set to initial values. Here, suppose that the initial value of the driving frequency is 10 MHz,
The initial value of the sensitivity is set to ISO200, the initial value at the time of the electronic shutter is 1/1000 second, and the initial value of the aperture value is set to F8.0. The shortest electronic shutter time when the driving frequency is 10 MHz is 1 / 4,000 second. The shortest electronic shutter time is determined in terms of image quality such as the amount of smear.

Next, an exposure control mode is set (S
2). For example, through operation means and communication means (not shown),
The exposure control mode set by the photographer is determined. Here, as a simple example for explanation, it is assumed that the F-number is set to 5.6 in the aperture priority mode. That is, in the actual exposure mode, it means that the aperture value at the time of actually photographing is set to F5.6. Therefore, the aperture has not been stopped down yet, and the actual aperture at this point remains at the initial value F8.0.

The image pickup device 14 is exposed in an exposure state based on the initial value, and an exposure level (first photometric value) is measured from an output luminance level of the image pickup device 14 (S3). Based on the first photometric value, the drive frequency, electronic shutter time, and aperture value of the image sensor 14 for the monitor mode are calculated (S4). The aperture value for the monitor mode is set so that the aperture is not smaller than the aperture value for the main exposure mode. Since the aperture value for the main exposure mode is set to F5.6 in S2, the aperture value for the monitor mode is set to, for example, F4.0 (Av = 4). Assuming that the sensitivity is ISO200 and the first photometry value is Ev = 16, the electronic shutter time Tv =
13, ie 1 / 8,000 seconds. As described above, the driving frequency of the image sensor 14 is 10 MHz.
In this case, since the shortest electronic shutter time is 1 / 4,000 second, the drive frequency of the image sensor 14 is set to twice, that is, 20 MHz to enable 1/8000 second.

The drive frequency of the image sensor 14 is changed based on the calculation result in S4 (S5), the electronic shutter time is changed (S6), and the aperture is driven so as to obtain the calculated aperture value (S7).

The relative driving amount from the current lens position is calculated from the two image positions obtained by the image pickup device 14 by the above-described distance measuring method, and the focusing lens of the optical lens is moved by the driving amount. It is driven (S8). It is checked whether or not the camera is in focus (S9). If the camera is not in focus (S9), the distance is measured again to adjust the position of the focusing lens of the optical lens (1).
0).

After the focusing control (S9, S10), it is checked whether or not the recording trigger switch has been pressed (S1).
1) If not pressed (S11), it is determined that there is no intention to record, and the process returns to S2. If pressed (S1
1) The recording sequence (S12 and subsequent steps) is executed.

In the recording sequence, the main exposure mode is set. First, the drive frequency of the image pickup device 14 is set to a predetermined frequency (here, 10 MHz) in the main exposure mode.
(S12). The electronic shutter time is changed to that for the main exposure mode (S13), and the aperture is driven to the aperture value (S14). In this embodiment, the exposure time is controlled only by the mechanical shutter without using the electronic shutter. The aperture is driven so that the value becomes F5.6 previously set as the aperture priority mode.

The shutter is driven at the appropriate shutter time determined from the previous photometric value and the aperture value for the main exposure mode, and the image pickup device 14 is exposed. The previous photometry value was Ev = 16, the aperture value was F5.6 (Av = 5), and the ISO sensitivity was 200 in the monitor mode. In the main exposure mode, the odd / even lines were not added. Since the data is read from the image sensor 14, the ISO sensitivity is lowered. Therefore, the exposure is performed at an appropriate Tv of 11, that is, 1/2000 second of the shutter time.

The image data obtained by exposing the image pickup device 14 is processed, transferred to the recording medium 28 and recorded (S1).
6).

Since the main exposure mode is completed, the monitor mode is set and the process returns to S2. That is, the set value set in the main exposure mode is returned to the set value in the monitor mode, and S2
Return to

In FIG. 4, from S2 to S11, distance measurement and photometry are repeatedly performed until a recording trigger occurs. Accordingly, S2 to S11 are in a measurement state, and S12 to S17 are in a shooting state for obtaining a desired image.

With the above operation, in the main exposure mode, the aperture is narrowed down more than in the monitor mode, so that the photographing can be performed in the main exposure mode while maintaining the in-focus state in the monitor mode.

In the above embodiment, the driving frequency of the image pickup device is changed between the time of the main exposure and the other times. However, the driving frequency of the image pickup device is changed between the exposure for the distance measurement and the other times. You may make it. This is because the inability to change the aperture diameter for pupil division at the time of distance measurement is a major hindrance to exposure control at the time of distance measurement, and other factors such as display on the EVF other than at the time of distance measurement. This is also effective in a case where the increase in sensitivity due to pixel addition at the time can be handled by ordinary exposure control. Since the drive frequency of the image sensor can be lowered except when necessary, power consumption can be reduced.

Alternatively, when the driving frequency of the image sensor cannot be changed due to display timing or the like when displaying on an EVF or the like, at the time of distance measurement, an image taken for distance measurement is not displayed, and the image immediately before distance measurement is not displayed. What is necessary is just to store it in a memory, display it, and drive the image sensor at the original frequency after imaging for distance measurement is completed.

In the above-described embodiment, the distance measurement method is the time-division phase difference method. However, the present invention can be applied to a TV-AF method. In other words, a focusing method in which a high-frequency component in a predetermined range in the imaging screen is extracted and the optical lens is driven so as to increase the high-frequency component may be used. in this case,
There is an advantage that the number of components of optical and mechanical members for distance measurement can be reduced. In the time-division phase difference method, since the pupil position is different from that at the time of the original photographing, if the image at the time of imaging for distance measurement is displayed as it is on the finder, it will appear as a double image when not in focus. In the TV-AF system, such an unnatural image is not displayed.

Further, the time division phase difference method and the TV-AF
The present invention can be implemented even when the methods are used together. In this case, it is possible to combine the advantage of the high speed of the time division phase difference method with the naturalness of the display of the TV-AF method.

[0066]

As can be easily understood from the above description, according to the present invention, since the depth of field at the time of photographing for obtaining a desired image does not become shallower than at the time of distance measurement, an appropriate distance measurement is possible. And can realize shooting.

Further, in an image pickup apparatus using an image pickup device capable of equivalently increasing the sensitivity by adding a large number of pixels, the sensitivity of the image pickup device is increased by using pixel addition during distance measurement.
Distance measurement can be performed without stopping down more than at the time of main exposure. Therefore, the distance measurement accuracy for a dark subject is improved.

The range of exposure control by the electronic shutter can be widened at the time of pupil division distance measurement in which the aperture diameter cannot be changed, so that high-speed focusing and high-precision focusing which are the original features of pupil division distance measurement are realized. It is possible to realize an imaging device capable of performing appropriate distance measurement and photographing without defocusing during exposure.

When the brightness of the subject is equal to or more than a certain level, the charge reading time of the image pickup device is shorter than that at the time of photographing at the time of distance measurement, so that the distance to the subject can be measured without stopping down the aperture and the lens can be adjusted. Focus control is possible. In particular, the pupil-division ranging method that cannot change the aperture allows the exposure control range of the electronic shutter to be widened when the subject is bright, realizing high-speed focusing and high-precision focusing that are the original features of the pupil-division ranging method. However, it is possible to realize appropriate distance measurement and photographing in which the focus is not deviated during the main exposure.

Even in the aperture priority exposure control mode as the exposure control mode, appropriate exposure control and distance measurement can be realized. That is,
It is possible to take a picture that reflects the intention of the photographer, and the expression range of the photographer is expanded.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a pupil stop for a time-division phase difference AF method.

FIG. 3 is an explanatory diagram of a distance measurement principle of the time division phase difference AF method.

FIG. 4 is an operation flowchart of the embodiment.

FIG. 5 is a schematic block diagram of a conventional example.

FIG. 6 is a plan view showing the configuration of an interline CCD imaging device.

FIG. 7 is a sectional structural view of a pixel portion of the CCD image sensor.

FIG. 8 is a potential profile of a CCD image sensor.

FIG. 9 is a timing chart related to an electronic shutter pulse of the CCD type imaging device.

[Explanation of symbols]

 10: Optical lens 12: Aperture shutter 14: Image sensor 16: CDS circuit 18: Amplifier 20: Clamp circuit 22: A / D converter 24: Image signal processing circuit 26: Recording medium interface 28: Recording medium 30: Brightness level detection Circuit 32: Focus information detection circuit 34: Focus drive circuit 36: Aperture shutter drive circuit 38: Image sensor drive circuit 40: System control circuit 42: Oscillator 43: Divider / multiplier 44: Synchronous signal generation circuit (SSG) 46: Timing Signal generation circuit (TG) 110: Optical lens 112: Aperture shutter 114: Image sensor 116: CDS circuit 118: Amplifier 120: Clamp circuit 122: A / D converter 124: Image signal processing circuit 126: Recording medium interface 128: Recording Medium 130: luminance level detection circuit 132: focus information Report detection circuit 134: Focus drive circuit 136: Aperture shutter drive circuit 138: Image sensor drive circuit 140: System control circuit 142: Oscillator 144: Synchronous signal generation circuit (SSG) 146: Timing signal generation circuit (TG) 150: Photodiode 152: Vertical transfer CCD 154: Horizontal transfer CCD 156: Floating diffusion amplifier

Claims (5)

[Claims] An imaging device that converts an optical image from the imaging lens into an electric signal; a focusing unit that focuses the imaging lens; and an imaging device driving timing control unit that controls a timing at which the imaging device is driven. An imaging apparatus, comprising: a time required for reading an image signal for one screen of the image sensor at the time of shooting and at least at the time of distance measurement. 2. An image pickup device for converting an optical image by an image pickup lens into an electric signal, a focusing unit for focusing the image pickup lens, and an image pickup for controlling a time for reading a photoelectric conversion signal for one screen of the image pickup device. Element drive timing control means, the image pickup device has a mode in which a plurality of pixels are added and read out, and the number of pixels of the image sensor corresponding to one screen is added in accordance with the number of pixels to which the plurality of pixels are added. An imaging device, wherein a time for reading a photoelectric conversion signal is changed. 3. An image pickup device for converting an optical image by an image pickup lens into an electric signal, a focusing unit for focusing the image pickup lens, and an image pickup for controlling a time for reading a photoelectric conversion signal for one screen of the image pickup device. An element drive timing control unit; and a distance measuring unit that obtains focus information of the imaging lens from a shift amount of a plurality of optical images by the pupil splitting unit. An imaging device, wherein the time for reading out the photoelectric conversion signal for each minute is different. 4. An image pickup device for converting an optical image from an image pickup lens into an electric signal, focusing means for focusing the image pickup lens, and an image pickup device for controlling a time for reading out a photoelectric conversion signal for one screen of the image pickup device. A drive timing control unit; and a photometric unit that measures the brightness of the subject image. When a photometric light amount by the photometric unit is equal to or more than a predetermined amount, a photoelectric conversion signal for one screen of the image sensor is measured at the time of distance measurement. An image pickup apparatus characterized in that a readout time is shorter than that in photographing. 5. An image pickup device for converting an optical image by a photographing lens into an electric signal, a focusing unit for focusing the image pickup lens, and an image pickup for controlling a time for reading a photoelectric conversion signal for one screen of the image pickup device. Element drive timing control means, light metering means for measuring the brightness of the subject image, exposure control means for controlling the amount of exposure to the image sensor, and exposure control setting means for setting conditions for the exposure control. Where, when the aperture priority haze control mode is set by the exposure control setting means, so that the optical aperture diameter at the time of exposure at the time of ranging is larger than the aperture diameter set by the aperture priority exposure control mode, An imaging apparatus, wherein a time for reading a photoelectric conversion signal for one screen of the solid-state imaging device is appropriately changed.