JP4469486B2 - Imaging apparatus and imaging method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention Imaging device and imaging method In particular, the present invention relates to an imaging apparatus that can be suitably used under various shooting conditions.
[0002]
[Prior art]
FIG. 11 shows an example of a conventional imaging device. As shown in FIG. 11, the imaging apparatus includes an aperture / shutter 100, a lens 101, an imaging device 102, a CDS 103, an A / D converter 104, an analog unit including a timing generator 105 (TG), a ROM 1108, a RAM 109, and a CPU 1106. , An operation unit 1107 for operating the device, and a recording unit 110 for recording a video signal.
[0003]
The image sensor 102 operates in accordance with a control signal from the TG 105, and settings for the TG 105, the CDS 103, and the A / D converter 104 are performed by the CPU 1106 via a serial communication line (not shown). The CPU 1106 controls each unit for photographing based on an input signal from the operation unit 1107.
[0004]
The imaging apparatus configured as described above operates as follows during imaging.
First, when a video shooting command is input from the operation unit 1107, the CPU 1106 turns on the power of an imaging system (not shown), and after the voltage has settled to a certain level, the TG 105, the CDS 103, and the A / D converter 104 are set arbitrarily. Go and start shooting.
[0005]
First, a clock and a horizontal / vertical synchronization signal are sent from the CPU 1106 to the TG 105. Based on this, the TG 105 outputs a drive signal to the image sensor 102 and outputs a sampling clock to the CDS 103 and the A / D converter 104.
[0006]
The video signal output from the image sensor is input to the A / D converter 104 and sent to the CPU 1106 as digital data in accordance with the sampling clock rate. The above operation is performed for a certain period of time to be an initialization operation after power-on.
[0007]
One shooting operation is as follows. That is, first, after completion of the initialization operation, AE and AF operations are performed. The image pickup device is driven based on a synchronization signal having a set cycle, and the CPU 1106 records digital data for one cycle output from the A / D converter 104 in an arbitrary area on the RAM 109. By performing an arbitrary calculation, the positions of the aperture / shutter 100 and the lens 100 are driven by an arbitrary control value to adjust the exposure and the focal length. Also, an exposure time t0 at the time of the main exposure is calculated. After the AE and AF operations are completed, the main exposure and readout operations for image shooting are performed.
[0008]
FIG. 12 shows the state of the drive waveform at this time. First, a VD signal that starts the main exposure period is sent, and during this period during which the readout pulse XSG is output, a high-speed readout pulse XSUB for discharging the charge on the image sensor is output. It becomes a period.
[0009]
Next, the main exposure operation is performed. After the readout pulse is output, an electronic shutter XSUB is output that is commensurate with the previously calculated exposure time t0, and the main exposure is performed after the output ends. After the elapse of an arbitrary exposure time, the diaphragm / shutter is closed to complete the exposure. The read operation starts after the next read pulse XSG is output.
[0010]
A video signal read from the image sensor 102 according to a transfer pulse (not shown) is converted into digital data via the CDS 103 and the A / D converter 104, and the CPU 1106 records this data in an arbitrary area on the RAM 109. Data on the RAM 109 is converted into an arbitrary format, and is recorded on a recording medium on the recording unit 110 by the CPU 1106 to complete the photographing operation.
[0011]
[Problems to be solved by the invention]
In a conventional imaging device, when performing a long exposure operation or high-sensitivity shooting, it is necessary to suppress the analog output voltage within a range that does not exceed the range of the analog unit of the A / D converter. Further, in the long exposure, there is a tendency that the signal component is decreased due to an increase in the dark current component and the S / N tends to be deteriorated.
[0012]
The present invention has been made in view of the above-described problems, and an object of the present invention is to obtain a good image quality without degrading the image quality even under various photographing conditions.
[0013]
[Means for Solving the Problems]
An imaging apparatus according to the present invention includes an imaging unit that converts subject light into an image signal, a determination unit that determines an exposure time of the imaging unit, the exposure time determined by the determination unit, and a predetermined value corresponding to a shooting mode. A comparison means for comparing values, and when the exposure time is less than or equal to the predetermined value, control is performed such that an image signal is read from the imaging means at a time according to the exposure time, and the exposure time is And control means for controlling the image signal to be read out in a plurality of times according to the exposure time when the image signal is longer than a predetermined value.
Another feature of the imaging apparatus of the present invention is that it has signal processing means for generating a predetermined image signal by adding the image signals read out in multiple times from the imaging means. Features.
Another feature of the imaging apparatus of the present invention is that the shooting mode is a plurality of modes including a single shooting mode and a continuous shooting mode.
Another feature of the imaging apparatus of the present invention is that the photographing mode is a plurality of modes including shutter priority and aperture priority.
[0014]
The imaging method of the present invention is an imaging method that performs an exposure operation of inputting an optical image to the imaging means, converts the optical image into an electrical signal by the imaging means, and generates a video signal, the exposure of the imaging means A determination step for determining a time, a comparison step for comparing the exposure time determined in the determination step with a predetermined value corresponding to a shooting mode, and the imaging when the exposure time is equal to or less than the predetermined value. When the exposure time is longer than the predetermined value, the image signal is divided into a plurality of times according to the exposure time. And a control step of controlling to read out.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
<First Embodiment>
Hereinafter, embodiments of an imaging apparatus, an imaging method, and a storage medium according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration example of a photographing apparatus according to the first embodiment of the present invention.
[0017]
As shown in FIG. 1, the imaging apparatus according to the present embodiment drives a lens 101, a diaphragm / shutter 100, a driving unit 112 that drives the lens 101 and the shutter, a CCD 102, a CDS 103, an A / D converter 104, and an imaging device. A timing generator 105 (hereinafter referred to as TG), a CPU 106, a ROM 108, a RAM 109, a recording unit 110 that records video signals, a display unit 111 that displays captured video and shooting conditions, and an operation unit 107.
[0018]
The operation unit 107 includes a release button (not shown), a switch for setting an aperture value, sensitivity, and exposure time, a single shooting / continuous shooting / valve setting button, and a main switch.
[0019]
The release button is configured to be capable of a two-stage pressing state, that is, a first pressing state S1 and a second pressing state S2, and the transition to the second pressing state S2 always passes through the first pressing state S1. Has been made.
[0020]
In the imaging apparatus of the present embodiment, the imaging sequence is switched between the normal exposure mode and the multiple exposure mode based on the relationship between the exposure time and the imaging conditions of single shooting / continuous shooting / bulb setting.
[0021]
First, FIG. 2 shows a flowchart for explaining the processing procedure for the shooting operation in the single shooting setting. Hereinafter, it demonstrates along this flowchart.
When the main switch is turned on from the operation unit 107 (step S1), the photographing apparatus shifts to a movie mode for displaying a moving image on the display unit 111 (step S2). The CPU 106 sets movie operations for the TG 105, the CDS 103, and the A / D converter 104, and starts outputting horizontal / vertical synchronization signals to the TG 105.
[0022]
When a synchronization signal that matches the video cycle of the movie is sent to the TG 105, exposure and readout of the CCD 102 are performed at an arbitrary cycle. A signal from the CCD 102 is converted into a digital signal via the CDS 103 and the A / D converter 104, then sent to the CPU 106, and temporarily recorded on the RAM 109.
[0023]
After recording a signal for one cycle, the CPU 106 performs arbitrary signal conversion on the video signal on the RAM 109 to convert it into a display signal. After the conversion, the CPU 106 sequentially sends video signals to the display unit 111 and sequentially displays them as movie videos.
[0024]
In this state, when the release button is in the first pressed state S1 (step S3), the photographing apparatus is in a distance measuring mode (step S17). In addition, when the release button is pressed sequentially in the first pressing state S1 and the second pressing state S2 (step S4), the mode immediately shifts to the main shooting without shifting to the distance measuring mode (step S5). In the distance measurement mode (step S <b> 17), the CPU 106 performs settings for still image shooting to each unit, and sends a still image synchronization signal to the TG 105.
[0025]
The TG 105 sends a still image drive signal to the CCD 102 to perform exposure and readout of the still image video signal, and the digital video signal is supplied to the RAM 109 via the CDS 103 and the A / D converter 104 and recorded.
[0026]
The CPU 106 performs arithmetic processing on the video signal recorded on the RAM 109 to obtain an aperture value, sends a control value to the drive unit 112 to obtain proper exposure, and then proceeds to exposure for obtaining an AF control value. .
[0027]
Further, the CPU 106 sequentially moves the lens position to a set number of positions, and performs photographing at each position. After recording a plurality of video signals whose lens positions are shifted on the RAM 109, an arithmetic operation for obtaining an AF control value is performed.
[0028]
If the AF control value is within an arbitrary threshold value (step S18), the AE / AF adjustment ends. If it is outside the threshold, the number of evaluations so far is set. If the number of evaluations is within an arbitrary number (step S19), the CPU 106 sends the obtained control value to the drive unit 112 and performs the AF operation again. . Thereafter, adjustment is performed any number of times until the evaluation value becomes an appropriate value.
[0029]
After the adjustment is completed or an arbitrary number of adjustments is completed, the AE / AF operation is terminated, and the CPU 106 shifts to the movie mode again. At this time, a video signal with proper exposure and focus is displayed. After the adjustment is completed, when the release button is further pressed to hold the first pressing state S1, the current AE and AF states are held.
[0030]
Next, when the release button is pressed so as to be in the second pressing state S2 (step S4), the photographing apparatus shifts to the main photographing mode (step S5). The CPU 106 first shifts to the distance measurement mode, performs the AE / AF operation again (step S6), and adjusts so that an image with an appropriate image quality is obtained.
[0031]
At this time, if the photographing parameters are set in advance by the photographer, AE and AF operations are performed under the restriction conditions to obtain the exposure time during the main exposure (step S7). At the time of single shooting, when the obtained exposure time is equal to or greater than a predetermined set value ts, the multiple exposure mode (step S8) is set, and when the exposure time is less than that, the normal exposure mode (step S14) is set. The operation in the normal exposure mode in which the determined exposure time t1 is not more than ts is as follows.
[0032]
After the AE / AF adjustment, the CPU 106 shifts to the main shooting mode. A part of the CCD drive signal at this time is shown in FIG. First, output of a synchronization signal for main exposure is started, and main exposure reading of the CCD 102 is started (step S15).
[0033]
The mechanical shutter is opened after the elapse of an arbitrary time for stabilizing the operation of each part. At this time, the CCD 102 is in a state of discharging electric charges by the electronic shutter. Then, the electronic shutter is stopped at the timing based on the previously calculated exposure time t1, and the main exposure is started. After the obtained exposure time t1 has elapsed, the CPU 106 closes the mechanical shutter and ends the main exposure.
[0034]
Reading of the exposed video signal is started at an arbitrary timing of the next synchronization signal (step S16). As in the movie mode, the main exposure data is converted into digital data through the CDS 103 and the A / D converter 104, and recorded in an arbitrary area on the RAM 109 by the CPU.
[0035]
The CPU 106 first performs defective pixel correction on the data recorded in the RAM 109, then performs signal conversion according to the image format to be recorded (step S20), and records it in another area on the RAM 109 again. The video signal converted into an arbitrary image format is sent to the recording unit 110 and recorded on the recording medium (step S21).
[0036]
After image recording, during single shooting (step S22), the CPU 106 performs signal conversion similar to that in the movie mode on the data before signal conversion, sends the converted signal to the display unit 111, and displays a captured image ( Step S24).
[0037]
At this time, when the release button is kept pressed to maintain the second pressing state S2 (step S25), the display of the photographed image on the display unit 111 is indicated by the second pressing state of the release button. Continue until released from state S2. Then, after the second pressing state S2 is released, at the time of single shooting, the mode switches from the main shooting mode to the movie mode (step S2), and the above-described movie shooting operation is performed.
[0038]
Next, the multiple exposure mode will be described. When an exposure time longer than the threshold value ts is set by the operation unit 107 or when the exposure time measured in the distance measurement mode is longer than the exposure time ts that is the threshold value, the CPU 106 starts the operation in the multiple exposure mode (step S8). ).
[0039]
In the multiple exposure mode, the exposure time is divided at predetermined time intervals ts to perform exposure / reading, calculate a plurality of output video signals, and finally obtain one video signal. .
[0040]
FIG. 4 shows drive signals in the multiple exposure mode. In FIG. 4, ts is a unit of one exposure time, and a plurality of video signals are obtained by repeating exposure for a plurality of ts times, and the captured video signals are added on a memory to obtain a final video signal. Get.
[0041]
As shown in FIG. 5, during the multiple exposure mode shooting, a signal in which a dark current component is added to the video signal is output from the CCD 102, and the value at the ts time of the signal added with the dark current is set to the maximum value. As a result, it is possible to capture a video signal without widening the input range of the A / D converter 104 even in long-second shooting longer than ts time, and a video signal with a wide dynamic range and good S / N can be obtained.
[0042]
The operation in the multiple exposure mode is shown below.
First, in the movie mode, it is assumed that the release button is pressed so as to be in the first pressing state S1, and an exposure time longer than the exposure unit ts is set based on the distance measurement result. The CPU 106 adjusts the aperture to an arbitrary value based on the AE data, and shifts to the movie mode.
[0043]
In the movie mode for long seconds, the exposure time is longer than the exposure unit time in the movie, so other parameters can be adjusted so that the exposure time becomes the movie rate. However, display at the same image rate as the actual exposure condition can also be performed by setting the operation unit 107.
[0044]
In this case, although the display rate of the movie is lowered, the same image as that at the time of actual shooting can be seen. Here, the operation when the exposure time is four times the movie rate Tm as shown in FIG. 6 will be described.
[0045]
First, in the movie mode, the CPU 106 performs setting for the TG 105 and the like. At this time, the CPU 106 performs setting so that the electronic shutter pulse to the sensor issued by the TG 105 is output only once at 4V, and starts driving the sensor.
[0046]
From the sensor, a signal corresponding to ¼ of the appropriate exposure time is read every 1V (step Tm), sent to the CPU 106 as digital data via the CDS 103 and the A / D converter 104, and arbitrarily stored in the RAM 109. Recorded in the area.
[0047]
In the CCD 102, the electric charge discharging operation by the electronic shutter is performed only once at 4V. Therefore, the 4V video signal to which no electronic shutter is applied is a continuously exposed video signal.
[0048]
First, the CPU 106 sequentially performs defective pixel correction of the CCD 102 on the video signal recorded on the RAM 109. When four video signals are recorded, the CPU 106 adds the four video signals and converts them into one video signal. Further, signal conversion for display is performed and recorded in another area on the RAM 109. The display signal is held on the RAM 109 for a period of 4 V while the next display signal is created, and displays the same video.
[0049]
Next, the main shooting mode will be described. When the release button is pressed so as to be in the second pressing state S2 during the movie mode (step S4), first, the CPU 106 shifts to the distance measurement mode (step S5), and performs AE and AF operations for the actual photographing. And make adjustments so that an image with appropriate image quality is obtained. When the exposure time t2 obtained at this time is equal to or longer than ts (step S7), the multiple exposure mode is set (step S8).
[0050]
In the multi-exposure shooting mode, as in normal exposure, first, output of a synchronization signal for main exposure is started, and main exposure reading of the CCD 102 is started. After an arbitrary time for stabilizing the operation of each part, the mechanical shutter is opened, the electronic shutter is stopped at a timing based on the previously calculated exposure time, and the main exposure is started (step S9).
[0051]
During the exposure time, the electronic shutter pulse is not output. When the read pulse XSG signal is received, the signals from the previous exposure are sequentially read out, digitized via the CDS 103 and the A / D converter 104, and then arbitrarily stored in the RAM 109. Record in the area. The CPU 106 sequentially performs defect correction on the recorded video signal.
[0052]
The CPU 106 calculates the remaining exposure time every time the video signal recording in the 1V period ends, compares the remaining exposure time with a threshold value ts equal to the maximum exposure time of 1V (step S10), and if it is longer than this, exposure / readout is performed. Is performed again (step S9). If the remaining exposure time is less than or equal to the threshold, the CPU 106 proceeds to the final exposure stage (step S11).
[0053]
After an arbitrary exposure time has elapsed, the CPU 106 closes the mechanical shutter, ends the main exposure, and starts reading the last video signal at an arbitrary timing of the next synchronization signal (step S12). After all the data is recorded on the RAM 109, the CPU 106 adds all the video signals and records it as a single video signal on the RAM 109 (step S13).
[0054]
The bit length at the time of video signal addition is set so as not to cause clipping due to overflow at the time of addition. This addition process can also be performed after completion of defect correction during exposure if the processing speed is sufficient, in which case the area of the RAM 109 can be saved.
[0055]
Next, 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 stored in another area on the RAM 109. To record. The video signal converted into an arbitrary image format is sent to the recording unit 110 and recorded on the recording medium (step S21).
[0056]
After image recording, during single shooting (step S22), 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 S24). ). After the image display, as in normal exposure shooting, after the second pressing state S2 is released (step S25), at the time of single shooting, the main exposure mode is exited and the movie mode is entered again (step S2). The movie is displayed on the unit 111.
[0057]
Next, the shooting operation in the continuous shooting setting will be described. In the continuous shooting setting, processing speed is required during shooting, compared to single shooting, and the multiple exposure mode is used to reduce the effect of the reduction in continuous shooting speed due to the shift to multiple exposure mode that requires more processing after shooting. The setting value tc of the exposure time that is the transition condition of is set to be larger than the setting value ts at the time of single shooting, and the multiple exposure transition condition is tightened.
[0058]
Here, tc = 2ts, and when the exposure time is longer than tc, the unit of processing is the same as the unit of processing ts for single shooting, the internal processing is the same, only the transition conditions are changed, The increase of the code is prevented.
[0059]
The flow of processing is almost the same as in single shooting, and the threshold value at the time of comparison between the exposure time and the multiple exposure mode transition threshold value (step S7) is doubled as described above. Done. As processing after shooting, after the recording of the video signal (step S21) ends (step S22), the state of the second pressing state S2 is detected during continuous shooting (step S23), and the second pressing state S2 is ON. In this case, the process shifts to the main shooting under the same shooting conditions (step S7).
[0060]
When the second pressing state S2 is released, signal conversion similar to that in the movie mode is performed on the last captured video signal, the converted signal is sent to the display unit 111, and the captured image is displayed ( Step S24).
[0061]
After the arbitrary time has elapsed, the second pressing state S2 is OFF at this point (step S25), so the process exits the main exposure mode and shifts back to the movie mode (step S2). A movie is displayed on the display unit 111.
[0062]
Next, the operation at the time of valve setting will be described. The operation at the time of the valve is almost the same as that at the time of single shooting, but the aperture value etc. are manually set values without performing photometric evaluation for AE / AF after being pushed so as to be in the second pressing state S2. The point that exposure is continued while being pressed to be in the second pressing state S2 is different.
[0063]
In bulb shooting, shooting is performed in the multiple exposure mode from the beginning, and the exposure time unit tb in the multiple exposure mode is shortened compared to that in single shooting in order to suppress saturation in the analog portion as much as possible. Here, tb = 1/2 ts.
[0064]
This suppresses saturation at the analog stage at the time of bulb, and widens the bit width at the time of addition on the memory in the later stage digital section, thereby suppressing exposure saturation for long-second exposure and shooting images with less noise be able to. Other operations are the same as in single shooting.
[0065]
As described above, in the present embodiment, by changing the exposure / readout processing method of the image sensor depending on the shooting mode, the operability suitable for the situation is maintained, and the wide dynamic range is achieved. A good video signal can be obtained.
[0066]
<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 7 is a block diagram illustrating a configuration example of an imaging apparatus according to the second embodiment of the present invention.
[0067]
The imaging apparatus according to the present embodiment includes a lens 101, an aperture 113, a shutter 114, an AF sensor 120, a driving unit 112 that drives the shutter, a CMOS sensor 115 that is an imaging element, an AMP 116, an A / D converter 104, and an imaging element. Timing generator 105 for driving (hereinafter referred to as TG), memory controller 117 for converting and recording video signals, memory controller process RAM 118, CPU 106, ROM 108, RAM 109, recording unit 110 for recording video signals, and displaying captured video The display unit 111 and the operation unit 107.
[0068]
The operation unit 107 includes a release button (not shown), a switch for setting an aperture value, sensitivity, and shooting time, a mode dial, and a main switch. The release button has a first pressing state S1 and a second pressing state S2. It is configured to be operable so as to be in a two-stage pressing state. The second pressing state S2 is set after passing through the first pressing state S1.
[0069]
The mode dial is for setting a plurality of shooting modes. As the shooting modes, a manual mode, an aperture priority mode, a shutter priority mode, and a program mode are provided. In the photographing apparatus of the present embodiment, the photographing sequence is switched to the normal exposure mode or the multiple exposure mode according to the set exposure time and photographing mode.
[0070]
FIG. 8 shows a flowchart for explaining the processing procedure.
Hereinafter, although it demonstrates along this flowchart, detailed description is abbreviate | omitted about the part which overlaps with 1st Embodiment.
[0071]
First, the photographing operation in the program mode will be described.
In the program mode, the exposure time and aperture value are determined based on the program diagram from the Ev value and subject distance obtained during metering.
[0072]
When the main switch is turned on from the operation unit 107 (step T1), the CPU 106 performs initial setting for each unit and enters a photographing standby state (step T2). First, the CPU 106 reads the lens position / aperture value from the driving unit 112, sets the normal shooting for the memory controller 117, and displays the current state of the photographing apparatus through the display unit 111. Wait for input from the operation unit 107.
[0073]
When the first pressing state S1 is pressed in this state (step T3), the photographing apparatus enters a distance measurement mode (step T20). At the same time, when the second pressing state S2 is pressed (step T4), the process immediately shifts to the main exposure mode (step T5). In the distance measurement mode, the CPU 106 sends commands for AE and AF operations to the drive unit 112.
[0074]
The driving unit 112 drives the AF sensor 120, detects a distance measurement signal from the video signal that has passed through the aperture 113 and the lens 101, and sends data to the CPU 106. The CPU 106 evaluates based on the sent data, and if the evaluation value is equal to or greater than the threshold value (step T21), obtains control values for AE and AF, sends them to the drive unit 112, and controls the aperture 113 and lens position. AE and AF operations are performed again. Thereafter, an arbitrary number of adjustments are performed until the evaluation value becomes an appropriate value (step T22).
[0075]
Also, during this time, power is turned on to the main photographing block such as the CMOS sensor 115 and the TG 105 and the photographing standby state is set. The AE / AF operation is completed as described above, and the CPU 106 obtains an appropriate aperture value and exposure time from the obtained AE, AF value, and program diagram, and sends a control value for obtaining an appropriate aperture value to the drive unit. The obtained aperture value and exposure time (shutter speed) are sent to the display unit and displayed to the photographer.
[0076]
Further, the exposure time obtained from the program diagram is compared with a threshold value tp for transitioning to a plurality of exposure modes in a predetermined program mode (step T23). Other than the above, the normal exposure mode is used. Here, first, the operation in the normal exposure mode in which the exposure time is shorter than the threshold will be described first.
[0077]
In this case, since the exposure time is shorter than the threshold value tp, the distance measuring mode is terminated here, and then the CPU 106 shifts to the standby state again. In this state, when the first pressing state S1 is released and a predetermined time has elapsed, the CPU 106 turns off the main photographing block. After the adjustment, when the first pressing state S1 is kept pressed, the current AE and AF states are maintained.
[0078]
When the second pressing state S2 is pressed after the first pressing state S1 is pressed (step T4), the CPU 106 shifts to the main exposure mode (step T5). First, the CPU 106 performs the AE / AF operation again (step T6), performs adjustment based on the program diagram so as to obtain an image with an appropriate image quality, and obtains the exposure time t3 during the main exposure. When the exposure time is less than or equal to the threshold value tp (step T7), after the AE / AF adjustment, the CPU 106 shifts to the normal photographing mode (step T15).
[0079]
The state at this time is shown in FIG. First, output of a synchronization signal for main exposure from the memory controller 117 is started, and main exposure reading of the CMOS sensor 115 is started. After an arbitrary time for stabilizing the operation of each part, the shutter 114 is opened, a reset signal is output to the CMOS sensor 115 at an arbitrary timing, a reset operation is performed, and excess charge on the sensor is discharged to start exposure ( Step T16).
[0080]
The shutter 114 is closed at a timing based on the previously calculated exposure time t3, and the exposure ends. After the exposure is completed, the synchronization signal is input again to the CMOS sensor 115, and reading of the video signal is started (step T17).
[0081]
The exposure data is converted into digital data through the AMP 116 and the A / D converter 104, and is temporarily recorded in an arbitrary area on the process RAM 118 by the memory controller 117. Next, the CMOS sensor 115 is driven again for the same t3 time as exposure with the shutter 114 closed, and a dark current image is photographed (step T18).
[0082]
Thereafter, a read operation is performed. At this time, the memory controller 117 reads the exposure image previously recorded on the process RAM 118 from the process RAM 118 in synchronization with the reading from the CMOS sensor 115, and calculates the exposure image and the dark current image. The dark current component at the time of exposure / reading is canceled, and this video signal is recorded as a main exposure video in another area of the process RAM 118 (step T19).
[0083]
In this way, the dark current component and fixed pattern noise of the CMOS sensor 115 can be canceled from the recorded video. Thereafter, the CPU 106 sends a command to the memory controller 117 to perform signal conversion corresponding to the image format to be recorded on the data on the process RAM 118 and record it again in another area on the process RAM 118 (step T25).
[0084]
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, causes display conversion to be performed on the data before signal conversion, sends the converted signal to the display unit 111, and displays a captured image (step T26).
[0085]
At this time, when the second pressing state S2 is kept pressed (step T27), the display of the captured image on the display unit 111 is continued until the second pressing state S2 is released. After the second pressing state S2 is released, the CPU 106 exits from the main exposure mode, shifts to the standby state again, makes arbitrary settings, and enters the photographing standby state.
[0086]
Next, the multiple exposure mode in the program mode will be described. When the first pressing state S1 is pressed to shift to the distance measuring mode and the exposure time t4 obtained from the program diagram is longer than the threshold value tp of the multiple exposure mode transition condition in the program mode (step T23), the CPU 106 The operation in the multiple exposure mode is started. The operation in the long second exposure mode is shown in FIG.
[0087]
FIG. 10 shows a case where the exposure time t4 is four times tp. The long-second shooting in this embodiment takes in a dark current signal for an arbitrary time tp including a dark current component and fixed pattern noise before the start of the main exposure, and the exposure time is fixed at a predetermined time during the main exposure. Exposure and readout are performed at intervals of time tp, and a plurality of output video signals and dark current signals are calculated to finally obtain one video signal.
[0088]
In addition, since the pixel signal is read independently in the CMOS sensor 115, there is a difference t5 in the exposure time between the read start position and the end position during continuous exposure. In order to correct this, the readout signal immediately after the first exposure is also used as an exposure signal for calculation, and after the exposure is completed, a dark current corresponding to t5 time is again photographed and used for correction.
[0089]
By doing so, it is possible to prevent a decrease in the dynamic range of the exposure signal in the A / D converter portion due to an increase in the dark current component for a long time, and to cancel the dark current component before memory recording so that only the signal component is obtained. Thus, the memory area can be used efficiently without increasing the bit width during memory recording.
[0090]
Although all exposure signals are recorded in the figure, it is also possible to sequentially calculate the previous exposure signal and record the result in the memory every time it is read out. In this case, the memory can be used more efficiently. Conversely, the dark current signal can be taken and calculated from the end of the main exposure.
[0091]
In this case, it is possible to reduce the shutter time lag because the time for photographing the dark current signal before the main exposure can be saved. The operation during multiple exposure will be described below.
First, it is assumed that the first pressing state S1 is pressed in the standby state (step T2) (step T3), and the exposure time longer than the exposure threshold tp in the program mode is set based on the distance measurement result (step T23).
[0092]
The CPU 106 turns on the main photographing block 119 and starts photographing the dark current signal (step T24). After the exposure unit tp is driven, reading is performed during time t5, 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.
[0093]
When the second pressing state S2 is pressed after the first pressing state S1 is pressed (step T4), the CPU 106 shifts to the main photographing mode (step T5). The CPU 106 performs the AE / AF operation again, and performs adjustment according to the program diagram so that an image with appropriate image quality can be obtained (step T6).
[0094]
After the AE / AF adjustment, when the exposure time is longer than the threshold value tp (step T7), the CPU 106 shifts to the multiple exposure mode (step T8). First, output of a synchronization signal for main exposure is started from the memory controller 117, the shutter 114 is opened, a reset signal is output to the CMOS sensor 115, reset operation is performed, and excess charge on the sensor is discharged, and then exposure is started. (Step T9).
[0095]
The memory controller 117 reads out the dark current signal recorded when the first pressing state S1 is pressed simultaneously with the reading of the exposure signal from the CMOS sensor 115, and subtracts the dark current signal from the exposure signal as an arbitrary signal in the process RAM 118. Record sequentially in the free space.
[0096]
The CPU 106 calculates the remaining exposure time every time the video signal recording in the 1V period is completed, and compares the remaining exposure time with a threshold equal to the maximum exposure time (Tp) of 1V (step T10). Read again.
[0097]
When the remaining exposure time is equal to or less than the threshold value tp, the CPU 106 proceeds to the final exposure stage (step T11). After the calculated remaining exposure time has elapsed, the shutter 114 is closed, the exposure is terminated, and the final exposure signal is recorded on the process RAM 118 (step T12). After the exposure is completed, dark current imaging for correcting the readout time difference is performed and similarly recorded in the process RAM 118 (step T13).
[0098]
After the photographing is finished, the CPU 106 sends a calculation command for a plurality of exposure signals on the process RAM 118 to the memory controller 117. The read memory controller 117 sequentially adds a plurality of exposure signals to create one main exposure video and records it on the process RAM 118 (step T14).
[0099]
In FIG. 10, the difference from the read 1 signal is obtained from the read 1 signal in FIG. 10 to be exposure 1, and the other read 2-5 signals are obtained from the difference from the read 0 signal to obtain exposure 2-6. It is assumed that the exposure image 1-6 is added to the main exposure image.
[0100]
Thereafter, as in the normal exposure mode, signal conversion corresponding to the image format to be recorded is performed on the data on the process RAM 118, and the data is recorded again in another area on the process RAM 118 (step T25). The video signal converted into an arbitrary image format is sent to the recording unit 110 and recorded on a recording medium.
[0101]
Further, the CPU 106 sends a command to the memory controller 117 again, causes display conversion to be performed on the data before signal conversion, sends the converted signal to the display unit 111, and displays a captured image (step T26).
[0102]
If the second pressing state S2 is kept pressed at this time (step T27), the display of the captured image on the display unit 111 is continued until the second pressing state S2 is released. After the second pressing state S2 is released, the CPU 106 exits from the main exposure mode, shifts to the standby state again, makes arbitrary settings, and enters the photographing standby state.
[0103]
In operations other than the program mode, the threshold value for switching between the normal exposure mode and the multiple exposure mode is changed in accordance with the operation characteristics of each mode. For example, in the shutter priority mode such as the sports mode, the operator sets the shutter speed. At this time, since the imaging apparatus performs a continuous shooting operation, as in the first embodiment, the multi-exposure mode in which subsequent processing becomes heavy is performed. In order to reduce the degree of transition, the threshold value tt in the shutter priority mode is set larger than the threshold value tp in the program mode.
[0104]
In the aperture priority mode, the threshold value ta is set smaller than tp in order to capture a video with a wide dynamic range and a better S / N. In the manual mode, the same threshold value as in the program mode is used here, and the same image quality as in the program mode is provided.
[0105]
In the present embodiment, the operation mode of the imaging apparatus is the program mode, shutter priority mode, aperture priority mode, and manual mode. However, the present invention can be applied to other modes such as portrait mode and macro mode. Needless to say.
[0106]
As described above, in the present embodiment, on the basis of the operation mode and the exposure time that the photographer is doing, by performing exposure / readout processing in a plurality of times in long-second shooting over a certain time, It is possible to prevent the input range of the analog stage from being compressed due to an increase in dark current.
[0107]
Moreover, by subtracting the dark current signal from the read signal and recording it in the memory, the dynamic range of the exposure signal can be secured without increasing the word length of the memory, and the memory can be used efficiently without degrading the image quality. it can.
[0108]
【The invention's effect】
As described above, according to the present invention, the determined exposure time is compared with a predetermined value according to the shooting mode, and an image signal is read out from the image sensor at one time or multiple times according to the comparison result. Since it is controlled to separately read out, it is possible to accurately control according to the photographing mode, and it is possible to obtain an image signal having a wide dynamic range and a good S / N.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing the flow of processing in the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an operation of normal exposure shooting in the first embodiment of the present invention.
FIG. 4 is a diagram showing an operation of multi-exposure shooting in the first embodiment of the present invention.
FIG. 5 is a diagram showing an image sensor output voltage at the time of long-second shooting in the first embodiment of the present invention.
FIG. 6 is a diagram showing a multiple exposure shooting operation in a movie mode according to the first embodiment of the present invention.
FIG. 7 is a block diagram showing a second embodiment of the present invention.
FIG. 8 is a flowchart showing a processing procedure in the second embodiment of the present invention.
FIG. 9 is a diagram illustrating a normal shooting operation in the second embodiment of the present invention.
FIG. 10 is a diagram showing a long-second shooting operation according to the second embodiment of the present invention.
FIG. 11 is a block diagram showing a conventional example.
FIG. 12 is a diagram illustrating a photographing operation of a conventional example.
[Explanation of symbols]
100 Shutter combined with shutter
101 lens
102 CCD
103 CDS
104 A / D converter
105 Timing generator (TG)
106 CPU
107 Operation unit
108 ROM
109 RAM
110 Recording unit
111 Display
112 Drive unit
113 aperture
114 Shutter
115 CMOS sensor
116 AMP
117 Memory controller
118 Process RAM
119 Main shooting block
120 AF sensor

Claims (5)

Imaging means for converting subject light into an image signal;
Determining means for determining an exposure time of the imaging means;
A comparison means for comparing the exposure time determined by the determination means with a predetermined value according to the photographing mode;
When the exposure time is less than or equal to the predetermined value, control is performed so that an image signal is read from the imaging unit at a time according to the exposure time, and when the exposure time is longer than the predetermined value, Control means for controlling the image signal to be read out multiple times according to the exposure time from the imaging means;
An imaging device comprising:   2. The imaging apparatus according to claim 1, further comprising a signal processing unit configured to add a plurality of image signals read out from the imaging unit and generate a predetermined image signal.   The imaging apparatus according to claim 1, wherein the shooting mode is a plurality of modes including a single shooting mode and a continuous shooting mode.   The imaging apparatus according to claim 1, wherein the photographing mode is a plurality of modes including shutter priority and aperture priority. An imaging method for performing an exposure operation of inputting an optical image to an imaging unit, converting the optical image into an electrical signal by the imaging unit, and generating a video signal,
A determining step for determining an exposure time of the imaging means;
A comparison step of comparing the exposure time determined by the determination step with a predetermined value according to the shooting mode;
When the exposure time is less than or equal to the predetermined value, control is performed so that an image signal is read from the imaging unit at a time according to the exposure time, and the imaging is performed when the exposure time is longer than the predetermined value. A control step of controlling the image signal to be read out in a plurality of times according to the exposure time from the means;
An imaging method characterized by comprising:

Images