JP2018101929A - Imaging device and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device capable of forming a high-quality image. An image pickup device includes an image pickup element in which pixels are arranged in two dimensions, a drive circuit for setting a pulse for driving the image pickup element, and a first power supply for each circuit at a first drive frequency. A power supply circuit having an operation mode of the above and a second operation mode for supplying power to the image pickup element at a second drive frequency higher than the first drive frequency, and driving of the image pickup element and the power supply circuit. It has a system control unit that performs control, and when the system control unit notifies the power supply circuit unit that the image pickup device has entered the image data acquisition sequence, it depends on the settings and drive conditions of the image pickup element. The drive frequency of the power supply circuit is changed from the first drive frequency to the second drive frequency. [Selection diagram] Fig. 5

Description

  The present invention relates to an imaging apparatus and the like that can perform drive control of a power source supplied to an imaging element.

  Power is supplied from a power supply circuit to an image pickup element used in an image pickup unit of the image pickup apparatus. FIG. 2 shows an example of the power supply circuit configuration of the imaging unit. The power supply unit 301 is mainly composed of a DCDC converter used to keep the output voltage constant even if the voltage between terminals of the battery used changes, and between the DCDC converter and the load of the power supply destination as necessary. A regulator may be connected to the The regulator is used to remove a noise component of the output voltage of the DCDC converter and supply a more stable power source to the load side.

  A CMOS image sensor, a CCD image sensor, or the like is used for the image sensor. FIG. 7 is a diagram showing an overall layout of the CMOS image sensor 801. FIG. 8 is a pixel circuit configuration diagram of the CMOS image sensor.

  A CMOS image sensor 801 shown in FIG. 7 includes the following components. A plurality of pixels are arranged in a row direction and a column direction, and have an effective area and a light shielding area. The effective area is an area 804 where pixels that are not shielded from light are arranged. The light shielding area is an area where a light-shielded pixel among a plurality of pixels is arranged, and includes a vertical optical black area (VOB area) 803 and a horizontal optical black area (HOB area) 802.

  Since the signals read from the VOB area 803 and the HOB area 802 include a dark current component or a reference level (black level) shift due to temperature fluctuation and do not include a signal component, dark shading in a signal read from the effective area Used to correct the component. The signal read from the VOB area 803 is used for correcting the dark shading component in the horizontal direction. The signal read from the HOB area 802 is used for correcting the dark shading component in the vertical direction.

  Each pixel 901 in the pixel array shown in FIG. 8 includes a photodiode (hereinafter referred to as PD) 902, a transfer switch (hereinafter referred to as TX) 903, a floating diffusion (hereinafter referred to as FD) 905, an amplifier 906, a selection switch 907, And a reset switch 904.

  The PD 902 generates and accumulates charges corresponding to light. The TX 903 transfers the charge generated in the PD 902 to the FD 905. The FD 905 is equivalently a capacitor and converts the transferred charge into a voltage. The amplifier 906 is composed of MOS transistors, and outputs a signal corresponding to the voltage of the FD 905 to the column signal line 908 by performing a source follower operation together with a constant current source connected to the column signal line 908. The selection switch 907 turns the pixel 901 into a selected state when turned on, and puts the pixel 901 into a non-selected state when turned off. A reset switch 904 resets the FD 905.

  The vertical scanning circuit 808 shown in FIG. 7 selects a row of pixels from which signals are to be read in the pixel array, and drives the pixels in each column of the selected row so that the signals are read to the reading circuit 805. The readout circuit 805 performs CDS processing for obtaining a difference between an optical signal (S signal) and a noise signal (N signal) output from a pixel in each column of the selected row. As a result, the readout circuit 805 obtains an image signal of a pixel in each column from which fixed pattern noise unique to the CMOS image sensor is removed. The readout circuit 805 holds the obtained image signal of the pixel in each column.

  The fixed pattern noise includes noise generated when the reset switch 904 shown in FIG. 8 resets the FD 905, noise due to variation in the threshold voltage of the amplifier (MOS transistor) 906 from pixel to pixel, and the like. This fixed pattern noise is almost eliminated by performing the CDS process.

  The horizontal scanning circuit 807 shown in FIG. 7 sequentially selects the image signals of the pixels in each column held in the readout circuit 805 and transfers them to the output amplifier 806. The output amplifier 806 amplifies and outputs the transferred image signal. Accordingly, in the subsequent stage of the output amplifier 806, the dark shading component in the image signal of the pixel in the effective region is corrected using the image signal of the pixel in the light shielding region.

  The image sensor operates in accordance with an externally supplied clock signal or the like. The clock signal is asynchronous with the power supply clock signal generated by the clock generation circuit included in the DCDC converter. That is, the image sensor and the DCDC converter operate asynchronously. Since the DCDC converter periodically performs a switching operation according to the power supply clock signal, voltage fluctuation occurs.

  Therefore, since the reading operation of the optical signal (S signal) and the noise signal (N signal) described above cannot be performed at the same time, a difference occurs in the power supply voltage when reading each signal, and noise that cannot be removed by CDS processing. There is a possibility that the image quality is deteriorated by the component. Therefore, proposals have been made to synchronize the drive timings of the image sensor and the DCDC converter.

  Japanese Patent Application Laid-Open No. 2004-228561 proposes that an appropriate clock is selected from a plurality of clock signals according to an operation mode to drive a DCDC converter and suppress fluctuations in power supply voltage. Japanese Patent Application Laid-Open No. 2004-228561 proposes controlling the readout timing of each row of the image sensor so as to be an integral multiple of the periodic noise period.

JP 2008-219292 A JP 2010-56795 A

  Due to the recent increase in sensitivity of image sensors, the influence on image quality due to fluctuations in power supply voltage has become more prominent. In the prior art disclosed in Patent Document 1, since the power supply clock is selective, it cannot follow the surrounding environment and component variations, and cannot always be set to the optimum clock. In the prior art disclosed in Patent Document 2, since the readout timing of the image sensor is synchronized with the period of noise, there is a possibility that the readout timing of the image sensor is limited depending on the period of noise.

  Therefore, the present invention provides an imaging apparatus capable of forming a high-quality image by increasing the switching frequency of the DCDC converter to an appropriate frequency for the purpose of reducing power supply noise and reducing the response of the image sensor to power supply noise. The purpose is to provide.

  In order to achieve the above object, an image pickup apparatus according to the present invention includes an image pickup element in which pixels are two-dimensionally arranged, a drive circuit that sets a pulse for driving the image pickup element, and a first drive frequency. A power supply circuit having a first operation mode for supplying power to the circuit and a second operation mode for supplying power to the image sensor at a second drive frequency that is higher than the first drive frequency; An imaging apparatus having an imaging element and a system control unit that performs drive control of the power supply circuit, wherein the power supply circuit unit is notified from the system control unit that the imaging apparatus has entered an image data acquisition sequence The drive frequency of the power supply circuit is changed from the first drive frequency to the second drive frequency in accordance with the setting of the image sensor and the drive conditions.

  In order to achieve the above object, a control method according to the present invention includes an image sensor in which pixels are two-dimensionally arranged, a drive circuit that sets a pulse for driving the image sensor, and a first drive frequency. A power supply circuit having a first operation mode for supplying power to the circuit, a second operation mode for supplying power to the image sensor at a second drive frequency that is higher than the first drive frequency, and the imaging An image pickup apparatus control method including an element and a system control unit that performs drive control of the power supply circuit, wherein the system control unit notifies the power supply circuit unit that the image pickup apparatus has entered an image data acquisition sequence. Then, the drive frequency of the power supply circuit is changed from the first drive frequency to the second drive frequency in accordance with the setting of the image sensor and the drive conditions.

  According to the present invention, image quality degradation caused by the power supply circuit can be reduced by raising the switching frequency of the DCDC converter to a frequency at which the imaging element cannot respond. Furthermore, according to the present invention, a regulator between the DCDC converter and the power supply destination can be eliminated, and power loss in the regulator unit can be eliminated and space saving can be achieved.

1 is a block diagram illustrating a configuration of an imaging apparatus 100 according to Embodiment 1. FIG. Power supply circuit configuration in Embodiment 1 Control flowchart in Embodiment 1 Operation Sequence in Embodiment 1 Power supply circuit configuration in Embodiment 2 Control flowchart in Embodiment 2 Overall layout diagram of CMOS image sensor CMOS image sensor pixel circuit diagram

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.
[Embodiment 1]
Hereinafter, the imaging apparatus 100 according to the first embodiment will be described with reference to FIG.

  The system of the imaging apparatus includes an imaging apparatus 100 and a lens unit 200 that guides incident light to the imaging element 108. The imaging apparatus 100 includes an optical mechanism, various circuits, various operation buttons, a control unit, and the like. Although not shown, in the imaging apparatus 100, the lens unit 200 is detachable via a mount mechanism. The mount mechanism includes a plurality of electrical contacts 210, and the lens unit 200 includes a photographing lens 201, an aperture 202, a lens / aperture drive control circuit 203, and the like. The lens / aperture drive control circuit 203 also includes a storage device that stores information unique to the lens and information received from the imaging device 100.

  Various signal communications between the imaging apparatus 100 and the lens unit 200 are realized by a plurality of electrical contacts 210. For example, the imaging apparatus 100 moves the photographing lens 201 in the optical axis direction according to a control signal from the camera control unit 117 to perform focusing, aperture control, and the like. The camera control unit 117 is configured by a CPU that controls the entire system. The plurality of electrical contacts 210 may have not only electrical communication but also functions such as optical communication and voice communication. In FIG. 1, only one photographic lens is shown for simplification, but in actuality, it is composed of a large number of photographic lenses.

  Incident light from the subject is guided to the quick return mirror 105 that can be driven in the direction of the arrow shown in the drawing through the photographing lens 201 and the diaphragm 202. The central portion of the quick return mirror 105 is configured as a half mirror, and the quick return mirror 105 transmits a part of incident light when it is down. Incident light transmitted through the quick return mirror 105 is reflected toward the AF circuit 110 by the sub mirror 104 provided in the quick return mirror 105.

  The AF circuit 110 includes an AF sensor unit and a focus detection circuit. The focus detection circuit controls the AF sensor unit by a control signal from the camera control unit 117, and performs focus detection by the phase difference detection method.

  The light reflected by the quick return mirror 105 reaches the photographer side via the pentaprism 101 and the eyepiece lens 103. When the quick return mirror 105 is up, the incident light that has passed through the photographing lens 201 and the diaphragm 202 reaches the image sensor 108 via the focal plane shutter 106 and filter 107 that are mechanical shutters. A specific example of the image sensor 108 is a CMOS sensor. The filter 107 has a function of removing infrared rays and a function as an optical low-pass filter.

  The camera control unit 117 has a function of controlling the up / down operation of the quick return mirror 105 and the shutter charge of the focal plane shutter 106, and a driving control function of the front and rear curtains of the focal plane shutter 106. Is connected. Although not shown, a photometric circuit 102, which is an automatic exposure device that outputs a signal from a photometric sensor installed in the vicinity of the eyepiece 103, is connected. The photometric sensor is a sensor that measures the luminance of a subject.

  The camera control unit 117 is connected to the image processing unit 115. The image processing unit 115 is configured by a DSP, and executes control of the image sensor 108, correction and processing of image data from the image sensor 108, and the like based on instructions from the camera control unit 117. Connected to the image processing unit 115 is an ADTG 109 equipped with a timing pulse generation circuit for driving the image sensor 108 and an A / D converter for converting the analog output of the image sensor 108 into a digital output. Note that the ADTG 109 may be built in the image sensor 108. Further, a memory 116 for temporarily storing the obtained image data is connected.

  In order to display image data from the image sensor 108, a DAC 114, an encoder 113, and a monitor 112 are connected to the image processing unit 115. The DAC 114 converts the image data on the memory 116 into an analog signal. The encoder 113 converts the signal from the DAC 114 into a video signal for display on the monitor 112. Since the configuration and operation of the image sensor 108 have been described in the background art with reference to FIGS.

  FIG. 2 shows an example of the configuration of the power supply unit 301 and the image sensor 305 in the first embodiment. Note that the image sensor 305 illustrated in FIG. 2 corresponds to the image sensor 108 illustrated in FIG. 1. It has a power supply unit 301 that supplies power to each functional block, an image sensor 305 that converts optical information into electronic information, and a system control unit 304 that controls the operation of each functional block. The power supply unit 301 and the system control unit 304 are included in the camera control unit 117 in FIG.

  The image sensor 305 has a built-in TG 306 for performing drive timing control in FIG. 2, but may be externally attached. The power supply unit 301 includes a signal processing unit 303 that recognizes imaging information, and a SW frequency control unit 302 that changes the switching frequency of the DCDC converter according to information from the signal processing unit. It is possible to set the switching frequency. In addition, it is good also as a structure which raises the frequency of the clock input into a DCDC converter as a structure which can change a switching frequency.

  The system control unit 304 supplies a timing signal for driving to the imaging apparatus 100, and supplies imaging information for setting a switching frequency to the power supply unit 301.

  FIG. 3 shows a control flowchart of the power supply unit 301 in the first embodiment. When shooting is started (401), it is determined whether the sensitivity set in the imaging apparatus 100 is equal to or greater than an arbitrary sensitivity a (402). When imaging is performed at a sensitivity lower than an arbitrary sensitivity a that does not affect the image quality due to power supply fluctuation due to switching of the DCDC converter, the imaging operation (406) is performed without changing the switching frequency of the DCDC converter, and the imaging ends (405). .

  On the other hand, when shooting at a higher sensitivity than the arbitrary sensitivity a, the switching frequency of the DCDC converter is changed (403). The change of the switching frequency of the DCDC converter may be handled at the time when the sensitivity set in the imaging apparatus 100 is determined. However, since the power efficiency may be reduced, the pixel value reading of the imaging element 305 is performed. It is desirable to implement changes only during the period. When the pixel value reading period of the image sensor 305 ends, the switching frequency of the DCDC converter is returned to the setting before the change (404), and the image capturing is ended (405).

  The operation sequence diagram of FIG. 2 is shown in FIG. VD in FIG. 4 is a timing signal for transitioning the operation of the image sensor 305. Each time VD is input, the image pickup device 305 transitions between standby (standby), Rst (reset), Acc (accumulation), and Readout (readout). Then, the switching frequency of the DCDC converter is changed in synchronization with the readout timing.

  As described above, according to the first embodiment, by increasing the switching frequency of the DCDC converter at a timing that affects the image quality of the acquired image, it is possible to prevent image quality degradation due to power supply fluctuation due to switching of the DCDC converter. Become. Furthermore, a regulator between the DCDC converter and the power supply destination can be eliminated, and power loss in the regulator unit can be eliminated and space can be saved.

  Further, by changing the switching frequency of the DCDC converter in accordance with the imaging conditions set in the imaging apparatus 100 and the operation timing of the imaging element 305, it is possible to reduce a decrease in power efficiency caused by increasing the switching frequency of the DCDC converter. Is possible.

  However, in the first embodiment, whether or not the sensitivity is low is a determination criterion for switching frequency control of the DCDC converter, and is not detailed switching frequency control of the DCDC converter according to photographing conditions. Therefore, it is necessary to further optimize the control and minimize the decrease in power efficiency due to the increase of the switching frequency of the DCDC converter. Therefore, a detailed description will be given of the switching frequency control of the DCDC converter according to the photographing conditions in the second embodiment.

[Embodiment 2]
Next, the imaging device 100 according to the second embodiment will be described. FIG. 5 shows an example of the configuration of the power supply unit 301 and the image sensor 305 in the second embodiment. Note that the image sensor 305 illustrated in FIG. 5 corresponds to the image sensor 108 illustrated in FIG. 1.

  As a difference between the configuration of the power supply unit 301 and the image sensor 305 in the first embodiment illustrated in FIG. 2, in FIG. 5, an AE sensor 307 for acquiring exposure conditions and a temperature sensor 308 for acquiring temperature information of the image sensor 305 are provided. It is connected to the system control unit 304. The system control unit 304 receives the outputs of the AE sensor 307 and the temperature sensor 308 and notifies the power supply unit 301 of exposure information and temperature information, and the power supply unit 301 performs power supply control based on the information. The AE sensor 307 is included in the photometry circuit 102 of FIG. The temperature sensor 308 is not shown in FIG.

  FIG. 6 shows a control flowchart of the power supply unit 301 in the second embodiment. When shooting is started (701), it is determined whether the sensitivity set in the imaging apparatus 100 is an arbitrary sensitivity a or higher (702). When imaging with a sensitivity lower than an arbitrary sensitivity a that does not affect the image quality due to power supply fluctuation due to switching of the DCDC converter, the imaging operation (709) is performed without changing the switching frequency of the DCDC converter, and the imaging ends ( 708).

  On the other hand, when photographing with a sensitivity higher than the arbitrary sensitivity a, the sensitivity set in the imaging apparatus 100 is compared with the arbitrary sensitivity b (703). The arbitrary sensitivity b means a high sensitivity that is easily affected by power supply fluctuations accompanying switching of the DCDC converter. If the sensitivity set in the imaging apparatus 100 is higher than the arbitrary sensitivity b, it is determined to change (706) the switching frequency of the DCDC converter at that time. If the sensitivity set in the imaging apparatus 100 is lower than the arbitrary sensitivity b, the current exposure condition is acquired from the latest exposure information acquired at the time of shooting (704).

  When the acquired exposure condition is brighter than the appropriate exposure, that is, when the amount of light is sufficient, the effect on the image quality due to power supply fluctuation due to switching of the DCDC converter is difficult to visually recognize, so the imaging operation is performed without changing the switching frequency of the DCDC converter. (709) is performed, and imaging is terminated (708). When the acquired exposure condition is darker than the appropriate exposure, the influence on the image quality due to the power supply fluctuation due to the switching of the DCDC converter becomes easy to visually recognize. Next, determination based on the current temperature information of the image sensor 305 is performed (705).

  If the current temperature of the image sensor 305 is higher than the arbitrary temperature c, the imaging operation (709) is performed without changing the switching frequency of the DCDC converter, and the imaging is terminated (708). This is because when the temperature rises in the image sensor 305, the increase in random noise is more dominant than the influence on the image quality due to the power supply fluctuation due to the switching of the DCDC converter due to the influence of dark current or the like.

  On the other hand, when the current temperature of the image sensor 305 is lower than the arbitrary temperature c, the switching frequency of the DCDC converter is changed (706). Then, as in the first embodiment, when the pixel value reading period of the image sensor 305 ends, the switching frequency of the DCDC converter is returned to the setting before the change (707), and the imaging ends (708).

  In addition, this invention is not limited to the above-mentioned embodiment, A various deformation | transformation or change is possible within the range of the summary.

[Embodiment 3]
The various functions, processes, and methods described in the first and second embodiments can also be realized by using a program by a personal computer, a microcomputer, a CPU (Central Processing Unit), or the like. Hereinafter, in the third embodiment, a personal computer, a microcomputer, a CPU, and the like are referred to as “computer X”. In the third embodiment, a program for controlling the computer X and realizing the various functions, processes, and methods described in the first and second embodiments is referred to as “program Y”.

  The various functions, processes, and methods described in the first and second embodiments are realized by the computer X executing the program Y. In this case, the program Y is supplied to the computer X via a computer-readable storage medium. The computer-readable storage medium according to the third embodiment includes at least one of a hard disk device, a magnetic storage device, an optical storage device, a magneto-optical storage device, a memory card, a volatile memory, and a nonvolatile memory. The computer-readable storage medium in the third embodiment is a non-transitory storage medium.

DESCRIPTION OF SYMBOLS 100 Digital camera 101 Penta prism 102 Photometry circuit 103 Eyepiece 104 Sub mirror 105 Quick return mirror 106 Focal plane shutter 107 Filter 108 Image sensor 109 ADTG
110 AF circuit 111 Shutter drive control circuit 112 Monitor 113 Encoder 114 DAC
115 Image Processing Unit 116 Memory 117 Camera Control Unit 200 Lens Unit 201 Shooting Lens 202 Aperture 203 Lens / Aperture Drive Control Circuit 301 Power Supply Unit 302 Switching Frequency Control Unit 303 Signal Processing Unit 304 System Control Unit 305 Image Sensor 306 Timing Generator (TG)
307 AE sensor 308 Temperature sensor 801 CMOS image sensor 802 Horizontal optical black 803 Vertical optical black 804 Effective area 805 Reading circuit 806 Output amplifier 807 Horizontal scanning circuit 808 Vertical scanning circuit 901 Pixel 902 Photo diode 903 Transfer switch 904 Reset switch 905 Floating diffusion 906 amplifier 907 selection switch 908 column signal line

Claims (8)

An image sensor in which pixels are two-dimensionally arranged;
A drive circuit for setting a pulse for driving the image sensor;
A first operation mode in which power is supplied to each circuit at a first drive frequency; and a second operation mode in which power is supplied to the imaging device at a second drive frequency that is higher than the first drive frequency. A power circuit having
An image pickup apparatus having the image pickup element and a system control unit that performs drive control of the power supply circuit,
When the system control unit notifies the power supply circuit unit that the imaging device has entered an image data acquisition sequence, the drive frequency of the power supply circuit is set to the first drive according to the setting of the image sensor and the drive conditions. An imaging apparatus characterized by changing from a frequency to a second drive frequency.   2. The system control unit determines to change the driving frequency of the power supply circuit from a first driving frequency to a second driving frequency according to a photographing sensitivity set by the imaging device. Imaging device. A temperature sensor for detecting the temperature of the image sensor;
The temperature information acquired from the temperature sensor is notified from the system control unit to the power supply circuit, and it is determined that the drive frequency of the power supply circuit is changed from the first drive frequency to the second drive frequency. The imaging device according to claim 1. An AE sensor for detecting an exposure condition at the time of shooting;
The exposure information acquired from the AE sensor is notified from the system control unit to the power supply circuit, and it is determined that the drive frequency of the power supply circuit is changed from the first drive frequency to the second drive frequency. The imaging device according to claim 1. An image sensor in which pixels are two-dimensionally arranged;
A drive circuit for setting a pulse for driving the image sensor;
A first operation mode in which power is supplied to each circuit at a first drive frequency, and a second operation mode in which power is supplied to the image sensor at a second drive frequency that is higher than the first drive frequency. A power circuit having
A control method of an imaging apparatus having the imaging device and a system control unit that performs drive control of the power supply circuit,
When the system control unit notifies the power supply circuit unit that the imaging device has entered an image data acquisition sequence, the drive frequency of the power supply circuit is set to the first drive according to the setting of the image sensor and the drive conditions. A control method characterized by changing from a frequency to a second drive frequency.   6. The system control unit determines to change the driving frequency of the power supply circuit from a first driving frequency to a second driving frequency according to a photographing sensitivity set by the imaging device. Control method. The imaging apparatus further includes a temperature sensor that detects a temperature of the imaging element,
The temperature information acquired from the temperature sensor is notified from the system control unit to the power supply circuit, and it is determined that the drive frequency of the power supply circuit is changed from the first drive frequency to the second drive frequency. The control method according to claim 5. The imaging apparatus further includes an AE sensor that detects an exposure condition during shooting,
The exposure information acquired from the AE sensor is notified from the system control unit to the power supply circuit, and it is determined that the drive frequency of the power supply circuit is changed from the first drive frequency to the second drive frequency. The control method according to claim 5.