JP2013027022A - Imaging apparatus and timing signal control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption of an imaging element.SOLUTION: An imaging apparatus comprises: a CCD image sensor 121; a timing generator 125 that outputs a horizontal synchronization signal and an electronic shutter pulse to the CCD image sensor 121; and an image processing processor 110 to control the timing generator 125. Exposure time is adjusted by outputting the electronic shutter pulse to the CCD image sensor 121. The image processing processor 110 controls so that the timing generator 125 outputs the electronic shutter pulse at intervals of a multiple of two or more integers of a cycle that the horizontal synchronization signal is outputted.

Description

  The present invention relates to an imaging apparatus and a timing signal control method. More specifically, the present invention relates to electronic shutter pulse oscillation control by a timing generator in an imaging apparatus.

  In an image pickup apparatus using a CCD image sensor (hereinafter also simply referred to as a CCD) as an image pickup device, when performing a continuous view capture such as a live view function for checking a subject on a liquid crystal monitor or moving image shooting, the exposure time is controlled. In general, an electronic shutter is used.

  The electronic shutter of this CCD image sensor is realized by, for example, applying a pulse having an amplitude of about 20V (hereinafter referred to as an electronic shutter pulse) to the N-type substrate to release the charge accumulated in the photodiode to the N-type substrate. Is done.

  Here, the application of the electronic shutter pulse is performed during the horizontal blanking period of pixel readout so as not to affect the operation of the FD amplifier. That is, in continuous frame imaging, the application of the electronic shutter pulse is started from the horizontal blanking period immediately after the photodiode is read out in the frame, and the electronic shutter pulse is continuously applied every horizontal blanking period. Thus, the exposure period is controlled by stopping the application of the electronic shutter pulse during the horizontal blanking period before the exposure of the photodiode of the next frame.

  The application of the electronic shutter pulse is controlled by a timing generator, and a desired exposure period is obtained by setting the number of horizontal scanning lines to which the electronic shutter pulse is applied in the timing generator.

  Regarding the application of such an electronic shutter pulse, for example, in Patent Document 1, electronic shutter pulses having two types of amplitudes are generated by synthesizing pulses generated by two different amplitude conversion circuits. A technique relating to a solid-state imaging device that reduces power consumption by selectively using the electronic shutter pulse depending on the period is disclosed.

  However, in the above-described electronic shutter control method, the electronic shutter pulse is applied continuously every horizontal blanking period from the reading of the photodiode to the start of the exposure period of the next frame. As described above, since the electronic shutter pulse requires high amplitude, power consumption is large, and as the exposure time is shortened, many electronic shutter pulses are required, so that power consumption increases. .

  In Patent Document 1, power consumption is reduced by controlling an electronic shutter pulse to be applied. However, since a complicated control mechanism such as two amplitude conversion circuits and a pulse synthesizer is required, the device configuration is as follows. There was a problem that it became complicated and cost increased.

  Accordingly, an object of the present invention is to provide an imaging apparatus and a timing signal control method capable of reducing power consumption of an imaging element by adjusting an application interval of an electronic shutter pulse.

  In order to achieve such an object, an imaging apparatus according to the present invention includes an imaging unit, a timing signal generation unit that outputs a horizontal synchronization signal and an electronic shutter pulse to the imaging unit, and a control unit that controls the timing signal generation unit. In the image pickup apparatus that adjusts the exposure period of the image pickup means by outputting an electronic shutter pulse to the image pickup means, the control means is an integer multiple of 2 or more of a cycle in which the horizontal sync signal is output by the timing signal generation means. The electronic shutter pulse is controlled to be output at intervals of.

  The timing signal control method according to the present invention is a timing signal control method for outputting a horizontal synchronization signal and an electronic shutter pulse to an imaging unit that converts light incident from an optical system into an electrical signal and outputs it as an imaging signal. Thus, an electronic shutter pulse is output to the imaging unit at intervals of an integer multiple of 2 or more of the cycle in which the horizontal synchronization signal is output, so that the exposure period of the imaging unit is adjusted.

  According to the present invention, the power consumption of the image sensor can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS It is an example of the external view of the digital camera which is one Embodiment of the imaging device which concerns on this invention, (a) is a top view, (b) is a front view, (c) shows a back view. It is an example of the functional block diagram of the imaging device which concerns on this embodiment. It is a functional block diagram concerning timing signal control. It is a timing chart which shows a charge accumulation of a synchronizing signal, a reading pulse, an electronic shutter pulse, and a photodiode. It is explanatory drawing which shows the relationship between the period of a horizontal synchronization, and an electronic shutter. It is explanatory drawing of the register in a timing generator. It is a flowchart which shows the control of the counter performed at the time of horizontal synchronization within a timing generator, and an electronic shutter pulse output. FIG. 5 is a timing chart showing the relationship of each register together with the synchronization signal, readout pulse, electronic shutter pulse, and photodiode charge accumulation shown in FIG. 4. FIG. It is explanatory drawing of the register in the timing generator of the imaging device which concerns on this embodiment. It is a flowchart which shows the control of the counter performed at the time of horizontal synchronization within the timing generator of the imaging device which concerns on this embodiment, and an electronic shutter pulse output. 6 is a timing chart showing a charge accumulation of a synchronization signal, a readout pulse, an electronic shutter pulse, and a photodiode according to the present embodiment. It is a functional block diagram concerning timing signal control provided with a saturated pixel count means. It is an example of the set value table of the output interval of the electronic shutter by the combination of the saturated pixel by the saturated pixel counting means and the exposure time.

  Hereinafter, the configuration according to the present invention will be described in detail based on embodiments shown in the drawings.

(Configuration of imaging device)
In the present embodiment, a digital camera will be described as an example of an imaging apparatus. FIG. 1 shows an external view of a digital camera, (a) shows a top view of the camera, (b) shows a front view of the camera, and (c) shows a rear view of the camera.

  As shown in FIG. 1A, the digital camera has a sub LCD 1, a release shutter 2 (SW1), and a mode dial 4 (SW2) on the upper surface.

  As shown in FIG. 1B, the digital camera has a strobe light emitting unit 3, a distance measuring unit 5, a remote control light receiving unit 6, a lens unit 7, and an optical viewfinder (front) 11 on the front. Have. A memory card throttle 23 indicates a throttle for inserting a memory card 34 such as an SD card, and is provided on the side of the camera.

  As shown in FIG. 1C, the digital camera has an AFLED (autofocus LED) 8, a strobe LED 9, an LCD monitor (display means) 10, an optical viewfinder (back surface) 11, and a zoom on the back surface. It has a button (zoom lever) TELE12 (SW4), a power switch 13 (SW13), a zoom button (zoom lever) WIDE14 (SW3), and a self-timer / deletion switch 15 (SW6).

  Furthermore, the menu switch 16 (SW5), the OK switch 17 (SW12), the left / image confirmation switch 18 (SW11), the down / macro switch 19 (SW10), the up / strobe switch 20 (SW7), the right A switch 21 (SW8) and a display switch 22 (SW9) for displaying an image are provided.

  FIG. 2 is a functional block diagram of a control system of the digital camera shown in FIG. The system configuration inside the digital camera will be described below.

  As shown in FIG. 2, in this digital camera, a CCD (CCD image sensor) 121 serving as a solid-state imaging device on which a subject image incident through a photographing lens system installed in the lens unit 7 forms an image on a light receiving surface, Front end IC (F / E, analog front end) 120 that processes electrical signals (analog RGB image signals) output from the CCD 121 into digital signals, and digital signals output from the front end IC (F / E) 120 A signal processing IC (image processing processor) 110, an SDRAM 33 for temporarily storing data, a ROM 30 in which a control program and the like are stored, a motor driver 32, and the like are provided.

  The lens unit 7 includes a zoom lens, a focus lens, a mechanical shutter, and the like, and is driven by a motor driver 32. The motor driver 32 is controlled by a microcomputer (CPU, control microcomputer) 111 included in the signal processing IC 110.

  The CCD 121 is a solid-state imaging device for photoelectrically converting an optical image, and an RGB primary color filter as a color separation filter is arranged on a plurality of pixels constituting the CCD, and an electrical signal (analogue) corresponding to RGB three primary colors. RGB image signal) is output.

  A front-end IC (F / E) 120 is a CDS 122 that performs sampling hold (correlated double sampling) on the CCD output electrical signal (analog image data), and an AGC (Auto Gain Control) 123 that adjusts the gain of the sampled data. A vertical synchronization signal (VD) and a horizontal synchronization signal (HD) are supplied from an A / D converter (A / D) 124 that performs digital signal conversion and a CCD I / F 112, and drive timing signals for the CCD 121 and the F / E 120 are supplied. A TG (timing generator: control signal generator) 125 is generated.

  The oscillator (clock generator) supplies a clock to the system clock of the signal processing IC 110 including the CPU 111, the TG 125, and the like. The TG 125 receives the oscillator clock and supplies a pixel clock for pixel synchronization to the CCD I / F 112 in the signal processing IC 110.

  A digital signal input from the F / E 120 to the signal processing IC 110 is temporarily stored as RGB data (RAW-RGB) in the SDRAM 33 by the memory controller 115 via the CCD I / F 112.

  The signal processing IC 110 includes a CPU 111 that performs system control, a CCD I / F 112, a resizing processing unit 113, a memory controller 115, a display output control unit 116, a compression / expansion unit 117, a media I / F unit 118, a YUV conversion unit 119, and the like. ing.

  The CCD I / F 112 outputs a vertical synchronizing signal (VD) and a horizontal synchronizing signal (HD), takes in a digital (RGB) signal input from the A / D 124 in accordance with the synchronizing signal, and passes through the memory controller 115. RGB data is written to the SDRAM 33.

  The display output control unit 116 sends the display data written in the SDRAM 33 to the display unit, and displays the captured image. The display output control unit 116 can display on the LCD monitor 10 built in the digital camera, or output it as a TV video signal and display it on an external device.

  The display data here is OSD (on-screen display) data for displaying a natural image YCbCr, a shooting mode icon, etc., and the memory controller 115 reads and displays the data placed on the SDRAM 33. The data is sent to the output control unit 116, and the data synthesized by the display output control unit 116 is output as video data.

  The compression / decompression unit 117 compresses the YCbCr data written in the SDRAM 33 during recording and outputs JPEG-encoded data. During reproduction, the compression / decompression unit 117 decompresses the read JPEG-encoded data into YCbCr data and outputs the YCbCr data.

  The media I / F 118 reads data in the memory card 34 to the SDRAM 33 or writes data on the SDRAM 33 to the memory card 34 in accordance with an instruction from the CPU 111.

  The YUV conversion unit 119 converts the RGB data temporarily stored in the SDRAM 33 into luminance Y and color difference CbCr data (YUV data) based on the image development processing parameters set by the CPU 111, and writes back to the SDRAM 33.

  The resizing processing unit 113 reads out YUV data and performs size conversion to a size necessary for recording, size conversion to a thumbnail image, size conversion to a size suitable for display, and the like.

  In addition, the CPU 111 which is a control unit that controls the overall operation loads a control program and control data for controlling the camera stored in the ROM 30 at the time of startup into, for example, the SDRAM 33, and performs the overall operation based on the program code. Control.

  The CPU 111 performs imaging operation control, setting of image development processing parameters, in accordance with an instruction by a button key of the operation unit 31, an external operation instruction from a remote controller (not shown), or a communication operation instruction by communication from an external terminal such as a personal computer. Performs memory control and display control.

  The operation unit 31 is used by the photographer to instruct the operation of the digital camera, and a predetermined operation instruction signal is input to the control unit by the operation of the photographer. For example, as shown in FIG. 1, various button keys such as a two-stage (half-pressed and fully-pressed) release shutter 2 for instructing shooting, zoom buttons 12 and 14 for setting an optical zoom and an electronic zoom magnification are provided.

  When the operation unit 31 detects that the power key of the digital camera is turned on, the CPU 111 performs a predetermined setting for each block. With this setting, an image received by the CCD 121 via the lens unit 7 is converted into a digital video signal and input to the signal processing IC 110.

  The digital signal input to the signal processing IC 110 is input to the CCD I / F 112. The CCD I / F 112 performs processing such as black level adjustment on the photoelectrically converted analog signal and temporarily stores it in the SDRAM 33. The RAW-RGB image data stored in the SDRAM 33 is read by the YUV conversion unit 119, and subjected to gamma conversion processing, white balance processing, edge enhancement processing, and YUV conversion processing, and is written back to the SDRAM 33 as YUV image data. .

  The YUV image data is read by the display output control unit 116. For example, if the output destination is an NTSC system TV, the resizing processing unit 113 performs horizontal / vertical scaling processing according to the system, and Is output. By performing this process for each VD, monitoring which is a display for confirmation before still photographing is performed.

(Operation of imaging device)
Next, the monitoring operation and still image shooting operation of the digital camera will be described. This digital camera performs a still image shooting operation while performing a monitoring operation as described below in the still image shooting mode.

  First, when the photographer turns on the power switch 13 and sets the mode dial 4 to the photographing mode (still image photographing mode), the digital camera is activated in the recording mode. When the CPU 111 detects this, the CPU 111 outputs a control signal to the motor driver 32 to move the lens unit 7 to a photographing position, and the CCD 121, F / E 120, signal processing IC 110, SDRAM 33, ROM 30, LCD monitor 10 And so on.

  Then, by directing the photographic lens system of the lens unit 7 toward the subject, a subject image incident through the photographic lens system is formed on the light receiving surface of each pixel of the CCD 121. An electrical signal (analog RGB image signal) corresponding to the subject image output from the CCD 121 is input to the A / D 124 via the CDS 122 and AGC 123, and converted into 12-bit RAW-RGB data by the A / D 124.

  This RAW-RGB data is taken into the CCD I / F 112 of the signal processing IC 110 and stored in the SDRAM 33 via the memory controller 115. The RAW-RGB data read from the SDRAM 33 is input to the YUV conversion unit 119 and converted into YUV data that can be displayed, and then the YUV data is stored in the SDRAM 33 via the memory controller 115. .

  The YUV data read from the SDRAM 33 via the memory controller 115 is sent to the LCD monitor 10 via the display output control unit 116, and a captured image (moving image) is displayed. At the time of monitoring in which a photographed image is displayed on the LCD monitor 10, one frame is read out in a time of 1/30 seconds by thinning out the number of pixels by the CCD I / F 112.

  In this monitoring operation, the photographed image (moving image) is only displayed on the LCD monitor 10 functioning as an electronic viewfinder, and the release button 2 is not yet pressed (including half-pressed).

  By displaying the photographed image on the LCD monitor 10, the composition for photographing a still image can be confirmed. In addition, it can output as a TV video signal from the display output control part 116, and a picked-up image (moving image) can also be displayed on external TV (television) via a video cable.

  Then, the CCD I / F 112 of the signal processing IC 110 determines an AF (automatic focus) evaluation value, an AE (automatic exposure) evaluation value, an AWB (auto white balance) evaluation value (WB evaluation value) from the captured RAW-RGB data. (Also referred to as AWB evaluation value).

  The AF evaluation value is calculated by, for example, the output integrated value of the high frequency component extraction filter or the integrated value of the luminance difference between adjacent pixels. When in the in-focus state, the edge portion of the subject is clear, so the high frequency component is the highest. By using this, at the time of AF operation (focus detection operation), AF evaluation values at each focus lens position in the photographing lens system are acquired, and AF operation is performed with the maximum point as the focus detection position. Is executed.

  The AE evaluation value and the WB evaluation value are calculated from the integrated values of the RGB values in the RAW-RGB data. For example, the screen (image area) corresponding to the light receiving surface of all the pixels of the CCD 121 is equally divided into 256 blocks (areas) (horizontal 16 divisions and vertical 16 divisions), and the RGB integration of each block is calculated.

  Then, the control unit reads the calculated RGB integrated value, and in the AE process, calculates the luminance of each area (block) of the screen and determines an appropriate exposure amount from the luminance distribution. Based on the determined exposure amount, exposure conditions (the number of electronic shutters of the CCD 121, the aperture value of the aperture unit, the insertion and removal of the ND filter, etc.) are set. In the AWB process, an AWB control value that matches the color of the light source of the subject is determined from the RGB distribution. By this AWB process, white balance is adjusted when the YUV conversion unit 119 performs conversion processing to YUV data. Note that the AE process and the AWB process are continuously performed during monitoring.

  Then, when a still image shooting operation in which the release button is pressed (half-pressed to fully pressed) is started during the monitoring operation, an AF operation that is a focus position detection operation and a still image recording process are performed.

  That is, when the release button is pressed (half to full), the focus lens of the photographing lens system is moved by a drive command from the control unit to the motor driver 32. For example, contrast evaluation called so-called hill-climbing AF is performed. The AF operation of the method is executed.

  When the AF (focusing) target range is the entire region from infinity to close, the focus lens of the taking lens system moves to each focus position from close to infinity or from infinity to close, and the CCD I / F 112 The control unit reads the AF evaluation value at each focus position calculated in step (1). Then, the focus lens is moved to the in-focus position with the point where the AF evaluation value at each focus position is maximized as the in-focus position, and in-focus.

  Then, AE processing is performed, and when the exposure is completed, the mechanical shutter unit is closed by a drive command from the control unit to the motor driver 32, and an analog RGB image signal for a still image is output from the CCD 121. Then, as in the monitoring, the data is converted into RAW-RGB data by the A / D 124 of the F / E 120.

  The RAW-RGB data is taken into the CCD I / F 112 of the signal processing IC 110, converted into YUV data by the YUV conversion unit 119, and stored in the SDRAM 33 via the memory controller 115. The YUV data is read from the SDRAM 33, converted into a size corresponding to the number of recording pixels by the resizing processing unit 113, and compressed to image data in the JPEG format or the like by the compression / decompression unit 117. The compressed image data such as JPEG format is written back to the SDRAM 33, read from the SDRAM 33 via the memory controller 115, and stored in the memory card 34 via the media I / F 118.

(Timing signal control)
Hereinafter, the control of the timing signal by the imaging apparatus will be described in detail. First, a basic control example that is a premise of timing signal control by the imaging apparatus according to the present embodiment will be described with reference to FIGS.

  FIG. 3 is a functional block diagram for explaining a portion related to timing signal control of the imaging apparatus according to the present embodiment. As described above, the timing generator 125 is an IC that generates a CCD drive signal, an electronic shutter pulse signal, an analog front end control signal, and the like of the CCD image sensor 121. Further, the analog front end 120 performs processing for converting the output signal from the CCD image sensor 121 into a digital signal.

  Further, the image processor 110 processes a digital signal from the analog front end 120 and executes various controls such as display on a display, data conversion, and storage in a flash memory. Further, the image processor 110 includes a control microcomputer (CPU 111) and a program storage area, and controls the timing generator 125 through serial communication under the control of the program.

  The photodiode of the CCD image sensor 121 includes a P-well layer 41 and an N-type substrate 42 (not shown), and the Vsub terminal 43 connected to the N-type substrate 42 applies an electronic shutter pulse. Used for.

  Signal charges generated by photoelectric conversion during exposure are accumulated by the potential of the P-well layer 41. When the electronic shutter pulse φSUB is applied to the Vsub terminal 43 connected to the N-type substrate 42, the potential of the P-well layer 41 is increased. The accumulated signal charge is discharged through the N-type substrate 42. Thereby, it functions as an electronic shutter by returning the amount of signal charge to the state before exposure.

  FIG. 4 is a timing chart showing a synchronization signal (vertical synchronization, horizontal synchronization), a readout pulse, an electronic shutter pulse, and charge accumulation of a photodiode. Note that the vertical axis represents signal output, the amount of accumulated charge (charge accumulation in the photodiode), and the horizontal axis represents time.

  Here, the vertical synchronization is a synchronization signal output for each frame of the video, the horizontal synchronization is a synchronization signal output for each line of the video, and the readout pulse reads the charge accumulated in the photodiode to the vertical transfer CCD. The timing of the pulse signal is shown. The electronic shutter pulse indicates the application timing of the electronic shutter, and the charge accumulation of the photodiode schematically indicates the amount of charge accumulated in the photodiode over time.

  As shown in FIG. 4, the charge of the photodiode is reset each time the electronic shutter is applied. The exposure time is a period obtained by subtracting the period during which the electronic shutter is output from the vertical synchronization period.

  FIG. 5 is an explanatory diagram showing the relationship between the horizontal synchronization period and the electronic shutter. Here, since the electronic shutter pulse has a high amplitude of about 20 V, if it is applied during pixel transfer, it causes noise in the FD amplifier or the like in the analog front end 120. Therefore, the electronic shutter pulse is applied during the horizontal blanking period 44 during which no pixel signal is output during the pixel output period. On the other hand, a period during which the pixel signal is output is a horizontal video period 45.

  FIG. 6 is a schematic diagram showing the configuration of the register 50 in the timing generator 125. VD_Cnt51 is a register that counts the vertical synchronization signal, HD_Cnt52 is a register that counts the horizontal synchronization signal, and nHD53 is a register that holds the number of horizontal synchronization signals in one frame.

  SUB_Start 54 is a register that holds a position at which application of the electronic shutter pulse is started. The position here is held by the number of horizontal synchronizing signals after the vertical synchronizing signal. SUB_Cnt55 is a register for counting electronic shutters.

  The nSUB 56 is a register that holds the electronic shutter output period in units of the number of horizontal synchronization signals. The larger the nSUB 56, the shorter the exposure time, and the smaller the nSUB 56, the longer the exposure time. The range of nSUB 56 is 0 to nHD.

  FIG. 7 is a flowchart showing counter control and electronic shutter pulse output performed in the timing generator 125 during horizontal synchronization.

  First, processing related to a register that is updated every horizontal synchronization is performed. Specifically, HD_Cnt52 and SUB_Cnt55 are counted up (S101), and then HD_Cnt52 is reset. That is, when HD_Cnt52 is counted up to nHD-1 (S102: y), it is reset to 0 (S103).

  Next, a reset process of SUB_Cnt55 is performed. That is, when HD_Cnt 52 is counted up to Sub_Start 54 (S104: y), SUB_Cnt 55 is reset to 0 (S105).

  Next, an electronic shutter application process is performed. That is, from when SUB_Cnt55 = SUB_Start54 (S106: y), nSUB electronic shutter pulses are applied (S107).

  FIG. 8 is a timing chart showing the relationship between the registers together with the synchronization signal (horizontal synchronization, vertical mobile device), readout pulse, electronic shutter pulse, and charge accumulation of the photodiode shown in FIG. As shown in FIG. 8, HD_Cnt 52 counts the number of horizontal syncs from the previous vertical sync to the present, and SUB_Cnt 55 counts the number of horizontal syncs from the previous read pulse to the present.

  The timing generator 125 is connected to the control microcomputer (CPU 111) of the image processor 110 through serial communication, and has a configuration in which a register can be rewritten from a control program operating on the control microcomputer. For example, the exposure time can be adjusted by rewriting the value of the nSUB register 56.

  The above is a basic control example that is a premise of controlling the timing signal by the imaging apparatus according to the present invention. In such a control method, horizontal readout from the readout of the photodiode to the start of the exposure period of the next frame is performed. Since the electronic shutter pulse is continuously applied every blanking period, there arises a problem that power consumption increases.

  Therefore, the imaging apparatus according to the present embodiment includes an imaging unit (CCD image sensor 121), a timing signal generation unit (timing generator 125) that outputs a horizontal synchronization signal and an electronic shutter pulse to the imaging unit, and a timing signal generation unit. Control means (image processor 110) for controlling, and in an imaging apparatus that adjusts the exposure period of the imaging means by outputting an electronic shutter pulse to the imaging means. The electronic shutter pulse is controlled to be output at intervals of an integer multiple of 2 or more of the period in which the synchronization signal is output, and the electronic shutter interval is changed to an integral multiple of the horizontal scanning period during the period when the electronic shutter pulse is applied. To do. Hereinafter, timing signal control of the imaging apparatus according to the present embodiment will be described. Note that a description of the same points as in the above control example will be omitted.

  FIG. 9 is a schematic diagram showing the configuration of the register 50 in the timing generator 125. In this embodiment, in addition to VD_Cnt51, HD_Cnt52, nHD53, SUB_Start54, SUB_Cnt55, and nSUB56 shown in FIG. 4, registers nSUB_Interval57 and SUB_Interval_Cnt58 are provided.

  Here, nSUB_Interval 57 holds the output interval of the electronic shutter in units of the vertical synchronization number. SUB_Interval_Cnt58 is an electronic shutter output interval counter.

  FIG. 10 is a flowchart showing counter control and electronic shutter pulse output performed in the timing generator 125 during horizontal synchronization.

  First, processing related to a register that is updated every horizontal synchronization is performed. Specifically, HD_Cnt52, SUB_Cnt55, and SUB_Interval_Cnt58 are counted up (S201), and then HD_Cnt52 is reset. That is, when HD_Cnt52 is counted up to nHD-1 (S202: y), it is reset to 0 (S203).

  Next, a reset process of SUB_Cnt55 is performed. That is, when the HD_Cnt 52 is counted up to the Sub_Start 54 (S204: y), the SUB_Cnt 55 and the SUB_Interval_Cnt 58 are reset to 0 (S205).

  Further, the SUB_Interval_Cnt 58 is reset. That is, when SUB_Interval_Cnt58 is counted up to nSub_Interval 57 (S206: y), SUB_Interval_Cnt58 is reset to 0 (S207).

  Finally, an electronic shutter application process is performed. That is, since SUB_Cnt55 = SUB_Start54 (S208: y) and SUB_Interval_Cnt58 = 0 or SUB_Cnt55 = nSUB56 (S209: y), an electronic shutter pulse is applied (S210).

  As described above, in the present embodiment, when the electronic shutter pulse becomes SUB_Interval_Cnt = 0, that is, once every nSUB_Interval times, and when SUB_Cnt55 = nSUB56, that is, the same timing as S107 in FIG. The timing at which the electronic shutter pulse is finally output).

  FIG. 11 is a timing chart showing the synchronization signal (vertical synchronization, horizontal synchronization), readout pulse, electronic shutter pulse, and photodiode charge accumulation. Note that the vertical axis represents signal output, the amount of accumulated charge (charge accumulation in the photodiode), and the horizontal axis represents time.

  According to the present embodiment, compared with the case shown in FIG. 4, the number of electronic shutter pulses can be set to about “1 / nSUB_Interval”, and power consumption by the electronic shutter can be reduced. Note that the value of nSUB_Interval 57 can be changed via a serial communication from a control program operating on the control microcomputer.

  The image processing apparatus further includes a counting unit (saturated pixel counting unit 114) that counts the number of pixels having a luminance equal to or higher than a threshold based on image data output from the imaging unit (CCD image sensor 121). 110) preferably sets an interval for outputting the electronic shutter pulse based on the number of pixels counted by the counting means and the exposure time. FIG. 12 shows a functional block diagram of an imaging apparatus provided with the saturated pixel count means 114.

  The saturated pixel counting means 114 counts the number of pixels whose luminance in a frame is equal to or higher than a certain threshold from the information of video pixels input from the digital signal line of the analog front end 120. Note that the luminance threshold may be set according to the saturation signal amount of the photodiode.

  FIG. 13 shows an example of a setting value table of nSUB_Interval. As shown in FIG. 13, for each combination of the saturated pixel output from the saturated pixel counting means 114 and the exposure time (= nHD−nSub), an nSUB_Interval value is set so that the photodiode is not saturated during the output of the electronic shutter pulse. By measuring in advance and setting nSUB_Interval from the program on the control microcomputer according to the set value table, it is possible to control so that blooming due to photodiode saturation is not given to the image.

  According to the imaging apparatus according to the present embodiment described above, the application of excessive electronic shutter pulses can be suppressed by adding a function to the timing generator to specify the interval between electronic shutter pulses as an integer multiple of the horizontal synchronization period. , Power consumption can be reduced. Further, by adding a function for estimating the degree of saturation of the photodiode to the image processor, it is possible to further suppress application of an excessive electronic shutter pulse and reduce power consumption.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

1 Sub LCD
2 Release shutter (SW1)
3 Flash unit 4 Mode dial (SW2)
5 Distance measuring unit 6 Remote control light receiving unit 7 Lens unit 8 AFLED
9 Strobe LED
10 LCD Monitor 11 Optical Finder 12 Zoom Button TELE (SW4)
13 Power switch (SW13)
14 Zoom button WIDE (SW3)
15 Self-timer / deletion switch (SW5)
16 Menu switch (SW6)
17 OK switch (SW12)
18 Left / image confirmation switch (SW11)
19 Lower / Macro switch (SW10)
20 Up / Strobe switch (SW7)
21 Right switch (SW8)
22 Display switch (SW9)
23 Memory card throttle 30 ROM
31 Operation unit 32 Motor driver 33 SDRAM
34 Memory card 41 P-well layer 42 N-type substrate 43 Vsub terminal 50 Register 51 VD_Cnt
52 HD_Cnt
53 nHD
54 SUB_Start
55 SUB_Cnt
56 nSUB
57 nSUB_Interval
58 SUB_Interval_Cnt
110 Image processor (signal processing IC)
111 CPU (control microcomputer)
112 CCD I / F
113 Resize processing unit 114 Saturated pixel counting means (counting means)
115 Memory Controller 116 Display Output Control Unit 117 Compression / Extension Unit 118 Media I / F
119 YUV converter 120 F / E (analog front end)
121 CCD image sensor (CCD)
122 CDS
123 AGC
124 A / D converter 125 TG (timing generator)

Japanese Patent Laid-Open No. 9-130682

Claims (4)

Imaging means, timing signal generating means for outputting a horizontal synchronization signal and an electronic shutter pulse to the imaging means, and control means for controlling the timing signal generating means,
In an imaging apparatus that adjusts a period of exposure of the imaging unit by outputting the electronic shutter pulse to the imaging unit,
The image pickup apparatus, wherein the control means controls the timing signal generating means to output the electronic shutter pulse at an interval that is an integer multiple of 2 or more of a period in which the horizontal synchronizing signal is output. Based on image data output from the imaging means, further comprising a counting means for counting the number of pixels having a luminance equal to or higher than a threshold;
2. The imaging apparatus according to claim 1, wherein the control unit sets an interval for outputting the electronic shutter pulse based on the number of pixels counted by the counting unit and an exposure time.   The control means controls the timing signal generating means to output the electronic shutter pulse in synchronization with the horizontal synchronizing signal outputted immediately before the imaging means starts exposure. The imaging apparatus according to 1 or 2. A timing signal control method for outputting a horizontal synchronization signal and an electronic shutter pulse to an imaging means that converts light incident from an optical system into an electrical signal and outputs it as an imaging signal,
Timing in which the electronic shutter pulse is output to the imaging unit at intervals of an integer multiple of 2 or more of the period in which the horizontal synchronization signal is output to adjust the exposure period of the imaging unit. Signal control method.