JP2001326850A - Image pickup device, its control method and computer- readable medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device that can obtain excellent image quality even at the long time exposure photographing. SOLUTION: Whether or not an exposure time exceeds a predetermined threshold in the photographing is discriminated and when the exposure time exceeds the threshold, a CCD 102 is read for a plurality of times during one exposure, and a RAM 109 records video signals obtained by the reading operation and the recorded video signals are calculated to generate one video signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus which performs a read operation on an image pickup element during an exposure operation, converts a video signal into digital data and records it on a recording medium, a control method thereof, and a computer readable method. Regarding the medium.

[0002]

2. Description of the Related Art FIG. 14 is a block diagram showing a configuration of a conventional imaging apparatus. The photographing device includes an aperture / shutter 100
a, lens 101a, image sensor 102a, timing generator (TG) 105a, correlated double sampling circuit (CDS) 103a, and A / D converters 104a, C
It comprises a PU 106a, a ROM 108a, a RAM 109a, a recording unit 110a, and an operation unit 107a. Among them, the CDS 103a and the A / D converter 104a are analog units.

[0003] The image sensor 102a operates in accordance with a control signal from the TG 105a. TG105a, CDS
The setting of the 103a and the A / D converter 104a is performed by the CPU 106a via a serial communication line (not shown). The CPU 106a controls each unit for photographing according to an input signal from the operation unit 107a. The operation unit 107a is used for operating the device.

The operation at the time of image pickup is as follows. First,
When a command for capturing an image is input from the operation unit 107a, the CPU 106a turns on a power supply (not shown) of the imaging system, and after the power supply voltage has settled down to a constant level, the TG 105
a, the CDS 103a, and the A / D converter 104a are arbitrarily set to start photographing.

First, a clock and horizontal / vertical synchronization signals are sent from the CPU 106a to the TG 105a. Based on this signal, the TG 105a outputs a drive signal to the image sensor 102a, and the CDS 103a and the A / D converter 104
The sampling clock is output to a. Image sensor 102
The video signal output from a is input to the A / D converter 104a and sent to the CPU 106a as digital data according to the sampling clock rate.
The above operation is performed for a certain period of time, which is an initialization operation after the power is turned on.

One photographing operation is as follows. First, after the initialization operation, the AE / AF operation is performed. The image sensor 102a is driven based on a synchronization signal having a set cycle. The CPU 106a records one cycle of digital data output from the A / D converter 104a in an arbitrary area of the RAM 109a, and performs an arbitrary operation on the data to thereby execute the aperture / shutter 100a and the lens 10a.
The position of 1a is driven by an arbitrary control value, the exposure and the focal length are adjusted, and the exposure time at the time of the main exposure is calculated.

After the AE / AF operation is completed, a main exposure and readout operation for photographing an image is performed. FIG. 15 is a timing chart showing changes in drive signals during main exposure and reading. First, a VD signal, which is the start of the main exposure period, is sent, and a high-speed readout pulse XSUB for discharging electric charges accumulated in the image sensor 102a is output from this time until a readout pulse XSG is output.
This period is the blank reading period.

After the output of the read pulse XSG, the electronic shutter pulse XS corresponding to the previously calculated exposure time
After the UB is output, the main exposure operation starts. Then, after an arbitrary exposure time has elapsed, the aperture / shutter 100a is closed to end the exposure. The read operation starts after the output of the next read pulse XSG.

Thereafter, in accordance with a transfer pulse (not shown), the video signal read from the image sensor
When converted into digital data via the DS 103a and the A / D converter 104a, the CPU 106a records this data in an arbitrary area of the RAM 109a, and completes the photographing operation.

[0010]

However, in the conventional photographing apparatus, when performing a long-time exposure operation, the image pickup device 1 is required.
It is necessary to keep the sensor output voltage from 02a within a range that does not exceed the dynamic range of the analog section. Also, in long-time exposure, the signal component decreases due to an increase in dark current component and the like, and the SN ratio tends to deteriorate. It was difficult to shoot for a long time without deteriorating the image quality.

The present invention has been made in view of such circumstances, and an image pickup apparatus capable of obtaining good image quality even during long-time exposure photographing, a control method thereof, and a computer-readable medium. The purpose is to provide.

[0012]

In order to achieve the above object, an image pickup apparatus according to a first aspect of the present invention performs a read operation on an image pickup element during an exposure operation to convert a video signal into digital data. An imaging device that converts and records the data on a recording medium, wherein at the time of photographing, a determination unit that determines whether an exposure time exceeds a predetermined threshold, and when the exposure time exceeds the threshold, during one exposure operation, Reading means for performing a plurality of reading operations on the image sensor, recording means for recording a plurality of video signals obtained by the plurality of reading operations on the recording medium, and the recorded plurality of video signals And generating means for generating a single video signal by calculating

[0013] A control method of an image pickup apparatus according to claim 8 is
A method of controlling an image pickup apparatus that performs a read operation on an image sensor during an exposure operation, converts a video signal into digital data, and records the digital data on a recording medium, wherein an exposure time exceeds a predetermined threshold during shooting. If the threshold value is exceeded, a plurality of reading operations are performed on the image sensor during one exposure operation, and a plurality of video signals obtained by the plurality of reading operations are output. Record on a recording medium,
A single video signal is generated by calculating the plurality of recorded video signals.

According to a ninth aspect of the present invention, a computer readable medium performs a read operation on an image sensor during an exposure operation to convert a video signal into digital data and record it on a recording medium. It is determined whether the time exceeds a predetermined threshold.
Performing a plurality of read operations on the image sensor during the first exposure operation, recording a plurality of video signals obtained by the plurality of read operations on the recording medium, and recording the plurality of recorded video signals. Is calculated to generate a single video signal.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an imaging apparatus, a control method thereof, and a computer-readable medium according to the present invention will be described with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing a configuration of an imaging apparatus according to a first embodiment. This photographing apparatus includes a lens 101, an aperture / shutter 100,
Driver 112, interline CCD 102, correlation 2
Double sampling circuit (CDS) 103, A / D converter 1
04, timing generator (TG) 105, CPU
106, ROM 108, RAM 109, recording unit 110,
It comprises a display unit 111 and an operation unit 107. Among them, the CDS 103 and the A / D converter 104 are analog units.

The drive section 112 drives the lens 101 and the aperture / shutter 100. The TG 105 generates a timing signal for driving the imaging device (CCD) 102. The recording unit 110 records a video signal. Display 1
Numeral 11 displays the captured video.

The operation unit 107 is provided with a release button (not shown), a switch for setting an aperture value, sensitivity, and a photographing time, and a main switch. The release button has a two-stage state in which the switches S1 and S2 are turned on, and the on state of the switch S2 is always realized after passing through the on state of the switch S1.

In the present photographing apparatus, the photographing sequence is switched between the normal exposure mode and the long-time exposure mode according to the exposure time. This switching is performed according to the exposure time set by the operation unit 107 or the exposure time obtained by calculation before photographing.

FIGS. 2 and 3 are flowcharts showing the procedure of the photographing operation process. This processing program is stored in the ROM1
08 and is executed by the CPU 106. First, shooting in the normal exposure mode will be described. Operation unit 10
When the main switch is turned on at step 7 (step S1),
The imaging device shifts to a movie mode in which a moving image is displayed on the display unit 111 (step S2). In this movie mode, the CPU 106 sets a movie operation for the TG 105, the CDS 103, and the A / D converter 104, and starts outputting a horizontal / vertical synchronization signal to the TG 105.

When a synchronizing signal corresponding to the movie video cycle is sent to the TG 105, the CCD 102 is exposed and read at an arbitrary cycle. The signal from the CCD 102 is converted into a digital signal through the CDS 103 and the A / D converter 104, and then sent to the CPU 106,
Recorded temporarily in AM109. After recording the signal for one cycle, the CPU 106 performs an arbitrary signal conversion on the video signal of the RAM 109 and converts it into a signal for display. After the conversion, the CPU 106 sequentially sends the video signal to the display unit 111 and displays it as a movie video.

In this state, it is determined whether or not the switches S1 and S2 have been pressed (steps S3 and S4).
If 1 has not been pressed, the process returns to step S2.
On the other hand, the switch S1 is pressed and turned on, and the switch S1 is turned on.
When the button 2 is not pressed, the photographing apparatus shifts to the distance measurement mode (step S17). On the other hand, switch S
If both of the buttons 1 and S2 are pressed at the same time and turned on, the mode immediately shifts to the exposure mode of the main shooting without shifting to the distance measuring mode (step S5).

In the distance measurement mode, the CPU 106 makes settings for photographing a still image for each unit, and sends a synchronization signal for a still image to the TG 105. The TG 105 sends a still image driving signal to the CCD 102, performs exposure and reading of the still image video signal, and records the digital video signal read via the CDS 103 and the A / D converter 104 in the RAM 109. The CPU 106 performs arithmetic processing on the video signal recorded in the RAM 109 to obtain an aperture value, sends a control value to the drive unit 112 to perform appropriate exposure, and then shifts to exposure for obtaining an AF control value.

The CPU 106 sequentially moves the lens 101 to several set positions, and performs photographing at each position. After recording a plurality of video signals with the lens positions shifted in the RAM 109, an operation for obtaining an AF control value is performed. It is determined whether the control value is within an arbitrary threshold (Step S)
18) If the control value is within an arbitrary threshold, AE · A
The F adjustment ends. On the other hand, if the control value is larger than the threshold, the number of evaluations so far is set, and it is determined whether or not the set number of evaluations is within an arbitrary number (threshold) (step S19). In the case, the CPU 106
Sends the obtained control value to the drive unit 112 and performs the AF operation again. Thereafter, the process returns to the process in step S17 until the evaluation value becomes an appropriate value, and adjustment is performed an arbitrary number of times. After the adjustment, if the switch S1 is kept pressed, the current AE / AF state is maintained. After the adjustment or any number of adjustments, the AE / AF operation ends,
The CPU 106 returns to step S2 again and shifts to the movie mode. At this time, a video signal with proper exposure and focus is displayed.

On the other hand, when the switch S2 is pressed and turned on in step S4, the photographing apparatus shifts to the main photographing (exposure) mode as described above. First, the CPU 106 shifts to the distance measurement mode, repeats the AE / AF operation again, adjusts the image so as to obtain an image of appropriate quality, and obtains the exposure time at the time of the main exposure (step S6).

It is determined whether or not the exposure time is longer than the threshold (step S7).
After the E / AF adjustment, the CPU 106 shifts to a normal shooting (exposure) mode (Step S14).

FIG. 4 is a timing chart showing changes in the CCD drive signal in the normal exposure mode. First, the output of the synchronization signal for the main exposure is started, and the main exposure reading of the CCD 102 is started. After an elapse of an arbitrary time for stabilizing the operation of each unit, the mechanical shutter is opened. At this time, the CCD 102 is in a state of discharging electric charges by the electronic shutter.

The electronic shutter is stopped at the timing based on the previously calculated exposure time, and the main exposure is started (step S15). After the determined exposure time has elapsed, the CPU 10
Reference numeral 6 closes the mechanical shutter and terminates the main exposure.

The reading of the exposed video signal is started at an arbitrary timing of the next synchronization signal XSG (step S16). This exposure data is the same as the movie mode,
The data is converted into digital data through the CDS 103 and the A / D converter 104, and the
Is recorded in any area.

The CPU 106 performs signal conversion on the data recorded in the RAM 109 in accordance with the image format to be recorded (step S20), and again executes the RAM 109
Record in another area. The video signal converted into an arbitrary image format is sent to the recording unit 110 and recorded on a recording medium.

The CPU 106 performs the same signal conversion on the data before the signal conversion as in the movie mode.
The converted signal is sent to the display unit 111, and the captured image is displayed (Step S21). At this time, it is determined whether or not the switch S2 is kept pressed (step S22). If the switch S2 is kept pressed, it is determined whether or not the continuous shooting mode is set (step S23).

When the shooting mode is the single shooting mode,
Returning to the processing of step S21, the display of the captured image on the display unit 111 is continued until the switch S2 is released.
On the other hand, if the continuous shooting mode is set in step S23, the process returns to step S7 and shooting is performed again. At this time, A
Without shifting to the distance measurement mode in which the E / AF adjustment process is performed, the main exposure mode is continued using the same parameters as in the first image capturing, and the sequence of signal reading, video signal conversion, and recording is repeated. On the other hand, when the switch S2 is released in step S22, the CPU 106 exits the main exposure mode, shifts again to the movie mode in step S2, performs any setting, and displays a movie on the display unit 111.

Next, the long-time exposure mode will be described. If the exposure time set by the operation unit 107 or the exposure time measured in the distance measurement mode is longer than the preset exposure time in step S7, the CPU 106 starts the operation in the long-second exposure mode (step S8).

In the long-time exposure mode, exposure and reading are performed by dividing the exposure time at predetermined intervals, and a plurality of output video signals are added to finally obtain one video signal. Mode. FIG. 5 is a timing chart showing changes in the CCD drive signal in the long exposure mode. In the drawing, t1 is a unit time of one exposure time, and exposure of the unit time t1 is repeated a plurality of times to obtain a plurality of video signals, and the captured video signals are added on a memory to make a final image. Get video signal.

FIG. 6 is a graph showing a change in the CCD output voltage with respect to the exposure time. At the time of long-time shooting, a signal in which a dark current component is superimposed on a video signal is output from the CCD 102. By setting the increase in the dark current as the maximum value at the unit time t1, the signal over the unit time t1 is set. Even in long-time shooting, it is possible to capture a video signal without expanding the input range of the A / D converter 104. Thereby, the dynamic range can be widened, and the S / N
A video signal with a high ratio can be obtained. Hereinafter, the operation in the long exposure mode will be described in accordance with the flowcharts of FIGS.

First, it is assumed that the switch S1 is pressed in the movie mode, and an exposure time longer than the time t1, which is a unit of the exposure time, is set based on the result of distance measurement. CPU
106 adjusts the aperture to an arbitrary value based on the AE data and shifts to the movie mode. In the long movie mode, the exposure time is a multiple of the normal exposure unit time t1, so the display frame rate is reduced. However, display without addition processing can be performed by setting the operation unit 107.

Here, the operation when the exposure time is four times the unit time t1 will be described. FIG. 7 is a timing chart showing an imaging operation when the exposure time is four times the normal exposure unit time t1. FIG. 8 is a timing chart showing changes in the CCD drive signal in the case of FIG. First, CPU
106 sets the TG 105 and the like in the movie mode. At this time, the electronic shutter pulse XSUB output from the TG 105 to the CCD (sensor) is set so as to be output only once in a 4 V (vertical synchronization) period, and driving of the sensor is started.

From the sensor, an appropriate exposure time of 1
The signal of ４ is read, sent to the CPU 106 as digital data via the CDS 103 and the A / D converter 104, and recorded in an arbitrary area of the RAM 109.

In the CCD 102, the charge discharging operation by the electronic shutter is performed only once every 4V period. Therefore, the video signal in the 4 V period to which no electronic shutter pulse is applied is a continuously exposed video signal.

The CPU 106 first sequentially performs defective pixel correction of the CCD 102 on the video signal recorded in the RAM 109. When four video signals have been recorded, the CPU 106 adds the four video signals, converts them into one video signal, and further performs signal conversion for display.
It is recorded in another area of AM109. The display signal is held in the RAM 109 for 4 V until the next display signal is created, and the same image is displayed.

If the switch S2 is pressed in step S4 during the movie mode, the mode shifts to the main exposure mode (step S5), and the AE / AF is used to check the exposure time and the like.
Perform the operation. The AE / AF operation is performed using a signal for a 1 V (vertical synchronization) period in order to suppress a shutter time lag, and for an aperture value or the like, a control value when an appropriate exposure time is set from a signal for a 1 V period is obtained. It is determined whether the AE / AF operation has been completed and the AE / AF evaluation value is larger than a threshold value (step S6). If the AE / AF evaluation value is larger than the threshold, the process returns to step S2.
If the AF evaluation value is equal to or smaller than the threshold, it is determined whether the exposure time is longer than the threshold (step S7). If the exposure time is longer than the threshold, the mode shifts to the long-second shooting mode (step S8).

In the main photographing mode, as in the normal photographing, the output of the synchronizing signal for the main exposure is started, and the main exposure reading of the CCD 102 is started. After an elapse of an arbitrary time for stabilizing the operation of each unit, the mechanical shutter is opened, the electronic shutter is stopped at a timing based on the exposure time calculated previously, and the main exposure is started (step S9).

During the exposure time, the electronic shutter pulse is not output, and when the read pulse XSG signal comes, the signals from the previous exposure are sequentially read out and digitized via the CDS 103 and A / D converter 104 as in the movie mode. After that, it is recorded in an arbitrary area of the RAM 109. C
The PU 106 sequentially performs defect correction on the recorded video signal. The CPU 106 calculates the remaining exposure time every time the video signal recording for the 1V period ends, and compares the remaining exposure time with a threshold value equal to the maximum exposure time of 1V (step S10). If the remaining exposure time is equal to or longer than the threshold value, the process returns to step S9, and exposure and reading are performed again.

When the remaining exposure time becomes shorter than the threshold, the CPU 106 shifts to the final exposure stage (step S1).
1). After an arbitrary exposure time has elapsed, the CPU 106 closes the mechanical shutter, terminates the main exposure, and starts reading the last video signal from an arbitrary timing of the next synchronization signal (step S12). The CPU 106 determines that all data is RA
After being recorded in M109, all video signals are added and recorded as one video signal in RAM 109 (step S1).
3).

The bit length at the time of addition of the video signal is set so that clipping due to overflow at the time of addition does not occur. This is because, for example, in the case of recording with 10 bits per pixel during normal shooting, if the number of exposures is n for a long time, the minimum (10+
log ₂ n) bits are required. If there is a margin in the processing speed, the addition process can be performed after the completion of the defect correction during the exposure. In this case, the area of the RAM 109 can be saved.

Then, signal conversion is performed according to the image format to be recorded (step S20). At this time, the black level of the video signal is read from the added data, and the converted data is recorded in another area of the RAM 109. The video signal converted into an arbitrary image format is sent to the recording unit 110 and recorded on a recording medium.

Further, the CPU 106 performs signal conversion on the added data in the same manner as in the movie mode, sends the converted signal to the display unit 111, and displays a captured image (step S21). After the image is displayed, similarly to the normal exposure shooting, after the switch S2 is released, the CPU 106 exits the main exposure mode, shifts to the movie mode again, performs any setting, and displays the movie on the display unit 111.

In the first embodiment, in long-time shooting for a fixed time or longer, the exposure / readout processing is performed in a plurality of times, so that the dynamic range can be changed by the digital signal processing in the subsequent stage without changing the input range of the analog stage. A video signal with a wide range can be obtained, and a video signal with a high S / N ratio can be obtained.

[Second Embodiment] FIG. 9 is a block diagram showing the configuration of a photographing apparatus according to a second embodiment. The photographing apparatus includes a lens 101, an aperture 113, a shutter 11
4. AF sensor 120, drive unit 112, CMOS sensor 115 serving as an image sensor, AMP 116, A / D converter 1
04, timing generator (TG) 105, memory controller 117, memory controller process R
AM 118, CPU 106, ROM 108, RAM 10
9, a recording unit 110, a display unit 111, and an operation unit 107.

The drive unit 112 drives the shutter 114 and the like. The TG 105 drives the image sensor. The memory controller 117 converts and records a video signal. Recording unit 11
0 records a video signal. The display unit 111 displays the captured video.

The operation unit 107 is provided with a release button (not shown), a switch for setting an aperture value, sensitivity, a photographing time, and the like, and a main switch. The release button has a two-stage state in which the switches S1 and S2 are turned on.
Is realized after passing through the ON state.

In this photographing apparatus, the photographing sequence is switched between the normal exposure mode and the long-time exposure mode according to the exposure time. This switching is performed according to the exposure time set by the operation unit 107 or the exposure time calculated by calculation before photographing.

FIG. 10 and FIG. 11 are flowcharts showing the procedure of the photographing operation in the second embodiment. This processing program is stored in the ROM 108,
This is executed by the PU 106.

First, in photographing in the normal exposure mode, when the main switch is turned on from the operation unit 107 (step S).
31), the CPU 106 performs initial setting of each unit, and enters a shooting standby state (step S32). The CPU 106 reads out the lens position and the aperture value from the drive unit 112, makes settings for normal photographing in the memory controller 117, displays the current state of the photographing device on the display unit 111, and in this state the operation unit 107 Wait for input from.

The state of the switches S1 and S2 is determined (steps S33 and S34). If the switch S1 has not been pressed, the process returns to step S32. On the other hand, switch S
When 1 is pressed to turn on and the switch S2 is off, the photographing apparatus shifts to the distance measurement mode (step S5).
0). On the other hand, when the switch S2 is pressed at the same time as the switch S1, the mode immediately shifts to the main exposure mode (step S35).

In the distance measurement mode, the CPU 106 outputs a command for the AE / AF operation to the drive unit 112. The drive unit 112 drives the AF sensor 120, detects a distance measurement signal from a video signal that has passed through the aperture 113 and the lens 101,
The data is sent to the CPU 106.

The CPU 106, based on the transmitted data,
The AE / AF operation is evaluated, and it is determined whether or not the evaluation value is larger than a threshold (step S51). If the evaluation value is larger than the threshold, it is determined whether or not the number of evaluations is larger than the threshold (step S52). If the number of evaluations has not reached the threshold, the process returns to step S50 to perform the AE / AF operation. The control value is obtained, sent to the drive unit 112, and the AE / AF operation is performed by controlling the aperture 113 and the lens position again. After this, adjustment is performed an arbitrary number of times until the evaluation value becomes an appropriate value. On the other hand, if the number of evaluations has reached the threshold in step S52, the process returns to step S32. If the AE / AF evaluation value is equal to or smaller than the threshold value in step S51, the power is turned on and the apparatus enters a shooting standby state.

After the adjustment of the AE / AF operation is completed, it is determined whether or not the exposure time is longer than the threshold value (step S53). If the exposure time is equal to or less than the threshold value and the switch S1 is kept pressed, the current AE is determined. -Hold the AF state. On the other hand, if the exposure time is longer than the threshold in step S53, the CMOS
The sensor 115 is driven to capture a dark current image (step S54). Then, the AE / AF operation ends, and the CPU
106 shifts to the standby state again. In this state, if the switch S1 is released and a certain time has passed, the CPU
106 turns off the power of the main photographing block.

On the other hand, if the switch S2 is pressed after the switch S1 in steps S33 and S34, the CPU 106
Shifts to the main exposure mode (step S35). CP
U106 performs the AE / AF operation again, and
It is determined whether or not the evaluation value is larger than the threshold value (step S
36) If the evaluation value is larger than the threshold, step S32
Return to the processing of. If the AE / AF evaluation value is equal to or less than the threshold value, adjustment is performed so that an image of appropriate image quality is obtained, and the exposure time t0 during the main exposure is obtained.

It is determined whether or not the exposure time is longer than the threshold value (step S37).
After the AE / AF adjustment, the CPU 106 shifts to the normal shooting mode (Step S45). FIG. 12 is a timing chart showing the shooting operation in the normal shooting mode. First, the output of the synchronization signal for main exposure from the memory controller 117 is started, and the reading for main exposure of the CMOS sensor 115 is started.

After an elapse of an arbitrary time for stabilizing the operation of each unit, the shutter 114 is opened, a reset signal is output to the CMOS sensor 115 at an arbitrary timing, the reset operation is performed, and extra charges on the sensor are discharged. Exposure is started after ejection (step S46).

The shutter 114 is closed at the timing based on the previously calculated exposure time t0, and the exposure ends. After the exposure, the synchronization signal is input to the CMOS sensor 115 again to start reading the video signal (step S4).
7). Exposure data (exposure image) is AMP116, A /
The data is converted into digital data through the D converter 104, and is temporarily recorded in an arbitrary area of the process RAM 118 by the memory controller 117.

Then, while the shutter 114 is kept closed, the CMOS sensor 115 is driven again for the same time t0 as the exposure, and a dark current image is photographed (step S48). Thereafter, a read operation is performed. At this time, the memory controller 117 reads out the exposure image previously recorded in the process RAM 118 from the process RAM 118 in synchronization with the readout from the CMOS sensor 115, and outputs the exposure image and the dark current image. An arithmetic operation is performed to cancel the dark current component at the time of exposure and reading, and this video signal is recorded as a main exposure video in another area of the process RAM 118 (step S4).
9).

In this way, the dark current component of the CMOS sensor 115 and the fixed pattern noise can be canceled from the recorded exposure video. Further, thereafter, the CPU 106 sends a command to the memory controller 117 to cause the data in the process RAM 118 to perform signal conversion according to the image format to be recorded, and to record the data again in another area of the process RAM 118 (step S55). ).

The video signal converted into an arbitrary image format is sent to the recording unit 110 and recorded on a recording medium. Further, the CPU 106 sends a command to the memory controller 117 again to cause the data before signal conversion to be converted for display, sends the converted signal to the display unit 111, and displays the captured image (step S56). .

At this point, it is determined whether or not the switch S2 is kept depressed (step S57). If the switch S2 is kept depressed, the process returns to step S56 to display the photographed image on the display unit 111. Continue until switch S2 is released. On the other hand, in step S57, the switch S2
Is released, the CPU 106 exits the main exposure mode, shifts to the standby state again, performs any setting, and enters the shooting standby state.

Next, the long-time exposure mode will be described. If the exposure time set by the operation unit 107 or the exposure time measured in the distance measurement mode is longer than a preset threshold in step S37, the CPU 106 starts operation in the long-second exposure mode.

FIG. 13 is a timing chart showing a photographing operation in the long-second exposure mode. Here, a case where the exposure time is four times the unit time t1 is shown. In the long-time shooting according to the present embodiment, a dark current signal for an arbitrary unit time t1 including a dark current component and a fixed pattern noise is captured before starting the main exposure, and the exposure time is set to a predetermined constant value during the main exposure. Exposure / readout is performed for each unit time t1 of the above, and a plurality of output video signals and a dark current signal are calculated.
Finally, one video signal is obtained.

In the CMOS sensor 115, pixel signals are read out independently of each other. Therefore, during continuous exposure, the time difference t2 between the read start position and the read end position is the exposure time.
Exists. In order to correct this, a read signal immediately after the first exposure is also used as an exposure signal in the calculation, and after the end of the exposure, a dark current corresponding to the time difference t2 is photographed again and used for correction.

By doing so, it is possible to prevent the dynamic range of the exposure signal in the A / D converter from becoming narrow due to the increase in the dark current component during a long time, and to cancel the dark current component before recording in the memory. By using only signal components, the memory area can be used efficiently without increasing the bit width during memory recording.

In FIG. 13, all the exposure signals are recorded. However, it is also possible to sequentially calculate the exposure signals for each reading and to record the result in a memory. In this case, the memory can be used more efficiently. Conversely, the dark current signal can be photographed from the end of the main exposure and calculated. In this case, it is possible to save the time for photographing the dark current signal before the main exposure, and to reduce the shutter time lag. Hereinafter, the operation at the time of long-time exposure will be described in accordance with the flowcharts of FIGS.

First, in the standby state of step S32, it is assumed that the switch S1 is pressed (step S33) and an exposure time longer than the unit time t1 is set based on the distance measurement result (step S53). The CPU 106 turns on the power to the main photographing block 119 and starts photographing a dark current signal (step S54). After driving for the unit time t1, the time difference t2 is read, and the read dark current signal is recorded in the process RAM 118. After recording the dark current signal, the CPU 106 shifts to a standby state in step S32.

When the switch S2 is pressed after the switch S1 (step S34), the CPU 106 shifts to the main photographing mode (step S35). The CPU 106 performs the AE / AF operation again, and performs adjustment so that an image of appropriate image quality is obtained (step S36).

After the AE / AF adjustment, it is determined whether or not the exposure time is longer than a threshold value (step S37). If the exposure time is longer than the threshold value, the CPU 106 shifts to a long-second shooting mode (step S38). In the long-time shooting mode,
The output of the synchronization signal for the main exposure from the memory controller 117 is started, the shutter 114 is opened, and the CMOS sensor 1 is opened.
Then, a reset signal is output to 15 to perform a reset operation, and after exposing extra charges on the sensor, exposure is started (step S39). The memory controller 117
Simultaneously with the reading of the exposure signal from the MOS sensor 115, the dark current signal recorded when the switch S1 is pressed is read, and a signal obtained by subtracting the dark current signal from the exposure signal is sequentially recorded in an arbitrary empty area of the process RAM 118. Go.

The CPU 106 calculates the remaining exposure time every time the recording of the video signal in the 1V period ends, compares the remaining exposure time with a threshold value equal to the maximum exposure time in the 1V period (step S40), and If the time is equal to or greater than the threshold, the process returns to step S39, and exposure and readout are performed again. On the other hand, when the remaining exposure time becomes shorter than the threshold, the CPU 106 shifts to the final exposure stage (Step S41).

After the calculated remaining exposure time has elapsed,
The shutter 114 is closed to end the exposure, and the final exposure signal is recorded in the process RAM 118 (step S42).
After the exposure is completed, dark current photographing for correcting the read time difference is performed, and similarly recorded in the process RAM 118 (step S43).

After the end of the photographing, the CPU 106 sends to the memory controller 117 an operation command for a plurality of exposure signals in the process RAM 118. The memory controller 117 creates one main exposure image by sequentially adding a plurality of exposure signals, and records it in the process RAM 118 (step S44).

In this state, in FIG. 13, the difference between the signal of read 1 and the signal of read 6 is determined to obtain exposure 1, and the difference between the signals of read 2 to read 5 and the signal of read 0 is determined. Exposure 2 to Exposure 5, and the final exposure image is obtained by adding the signals of Exposure 1 to Exposure 5.

Thereafter, as in the normal exposure mode, the data in the process RAM 118 is subjected to signal conversion in accordance with the image format to be recorded, and the process RAM 1 is again processed.
18 is recorded in another area (step S55).

The video signal converted into an arbitrary image format is sent to the recording unit 110 and recorded on a recording medium. Further, the CPU 106 sends a command to the memory controller 117 again to cause the data before signal conversion to be converted for display, sends the converted signal to the display unit 111, and displays the captured image (step S56). . At this time, it is determined whether or not the switch S2 is kept pressed (step S57). When the switch S2 is kept pressed, the display of the captured image on the display unit 111 is switched by the switch S2.
Continue until 2 is released. After the switch S2 is released, the CPU 106 exits the main exposure mode, shifts to the standby state again, performs any setting, and enters the shooting standby state.

As described above, in the second embodiment, when shooting for a long period of time longer than a certain time, the exposure / readout processing is divided into a plurality of times to reduce the input range of the analog stage due to an increase in dark current. Also, by storing the dark current signal in the memory after subtracting it from the read signal, the dynamic range of the exposure signal can be secured without expanding the word length of the memory, and the memory can be used efficiently without lowering the image quality can do.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations of the embodiments, and the functions described in the claims or the functions of the embodiments are not limited to the embodiments. Any configuration that can achieve the function of the configuration is applicable. For example, when reading out n times during one exposure operation, the aperture control value may be multiplied by n times.

The present invention may be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), or may be applied to an apparatus including one device. . Also,
The software configuration and the hardware configuration of the above embodiment can be appropriately replaced. In addition, the present invention may combine the above-described embodiments or the technical elements as needed. In addition, the present invention may be applied to a case where the whole or part of the configuration of the claims or the embodiment forms one device or is combined with another device. , Which may be a constituent element of the device.

The present invention also relates to an electronic still camera for photographing a still image, a video movie camera for photographing a moving image, and the like.
The present invention can be applied to various types of cameras, imaging devices other than cameras, devices applied to these cameras and imaging devices, and elements constituting these devices.

Further, it goes without saying that the present invention can be applied to a case where the present invention is attained by supplying a program to a system or an apparatus using a recording medium storing software program codes for realizing the functions of the above-described embodiments. Nor. In this case, the program code itself read from the storage medium implements the novel function of the present invention, and the storage medium storing the program constitutes the present invention.

In the above embodiment, FIG. 2, FIG. 3, FIG.
The program code shown in the flowchart of FIG. 11 is stored in a ROM serving as a storage medium. The storage medium for supplying the program code is not limited to the ROM, and may be, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R,
DVDs, magnetic tapes, non-volatile memory cards, downloads from other computers, and the like can be used.

[0087]

According to the present invention, even during long-time exposure shooting, a signal output from the image sensor can be shot without exceeding the dynamic range of a subsequent analog section, and the image quality of a shot image is improved. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an imaging device according to a first embodiment.

FIG. 2 is a flowchart illustrating a shooting operation processing procedure;

FIG. 3 is a flowchart illustrating a shooting operation processing procedure following FIG. 2;

FIG. 4 is a timing chart showing a change in a CCD drive signal in a normal exposure mode.

FIG. 5 is a timing chart showing a change in a CCD drive signal in a long second exposure mode.

FIG. 6 is a graph showing a change in a CCD output voltage with respect to an exposure time.

FIG. 7 is a timing chart showing an imaging operation when the exposure time is four times the normal exposure unit time t1.

FIG. 8 is a timing chart showing a change in a CCD drive signal in the case of FIG. 7;

FIG. 9 is a block diagram illustrating a configuration of a photographing device according to a second embodiment.

FIG. 10 is a flowchart illustrating a shooting operation processing procedure according to the second embodiment.

FIG. 11 is a flowchart showing a shooting operation processing procedure continued from FIG. 10;

FIG. 12 is a timing chart showing a shooting operation in a normal shooting mode.

FIG. 13 is a timing chart showing a shooting operation in a long-second exposure mode.

FIG. 14 is a block diagram illustrating a configuration of a conventional imaging device.

FIG. 15 is a timing chart showing changes in drive signals during main exposure and reading.

[Explanation of symbols]

 102 CCD 104 A / D converter 106 CPU 107 Operation unit 108 ROM 109 RAM 115 CMOS sensor 118 Process RAM

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H04N 5/225 H04N 5/225 FF term (Reference) 2H002 AB03 CC09 JA07 2H054 AA01 2H104 AA12 5B057 BA02 BA11 BA28 CE08 CH08 5C022 AA13 AB02 AB12 AB17 AB22 AB37 AC32 AC42 AC52 AC54 AC69

Claims (9)

[Claims] 1. An image pickup apparatus for performing a read operation on an image sensor during an exposure operation, converting a video signal into digital data and recording the digital data on a recording medium, wherein a predetermined threshold value for an exposure time at the time of photographing is provided. Determination means for determining whether or not the value exceeds the threshold value; reading means for performing a plurality of reading operations on the image sensor during one exposure operation when the threshold value is exceeded; An imaging apparatus comprising: recording means for recording a plurality of recorded video signals on the recording medium; and generating means for calculating the recorded plurality of video signals to generate a single video signal. . 2. The imaging apparatus according to claim 1, wherein the operation of discharging the charge accumulated in the imaging element is performed only once at the start of the one exposure operation. 3. When the exposure time exceeds a predetermined threshold, the reading means performs a plurality of read operations during the one exposure operation with the threshold being a maximum exposure time. The imaging device according to claim 1. 4. The imaging apparatus according to claim 1, wherein a dark current signal read before and after the main exposure is used for correcting a video signal of the main exposure. 5. The imaging apparatus according to claim 1, wherein one dark current signal read before and after the main exposure is used for calculating video signals of a plurality of main exposures. 6. The method according to claim 1, wherein the data bit length of the digital data recorded on the recording medium is increased to log ₂ n bits or more when n reading operations are performed during the one exposure operation. The imaging device according to 1. 7. The image pickup apparatus according to claim 1, wherein, when performing the read operation n times during the one exposure operation, the aperture control value is set to n times. 8. A control method of an image pickup apparatus for performing a read operation on an image pickup device during an exposure operation, converting a video signal into digital data and recording the digital data on a recording medium, wherein a predetermined exposure time is set at the time of photographing. It is determined whether the threshold value is exceeded. If the threshold value is exceeded, a plurality of read operations are performed on the image sensor during one exposure operation, and a plurality of read operations obtained by the plurality of read operations are performed. Recording the video signal on the recording medium and calculating a plurality of the recorded video signals to generate a single video signal. 9. During an exposure operation, a read operation is performed on an image sensor to convert a video signal into digital data and record it on a recording medium. If the threshold value is exceeded, a plurality of read operations are performed on the image sensor during one exposure operation, and a plurality of video signals obtained by the plurality of read operations are stored in the recording medium. A computer-readable medium applied to an imaging apparatus, characterized in that the medium has a content recorded on a computer and calculates a plurality of recorded video signals to generate a single video signal.