JP6094154B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus that prevents noise from appearing in an image signal output from an imaging element.

  There is known an image pickup apparatus in which an autofocus lens and a camera shake correction mechanism are installed around an image pickup device. The imaging device captures a subject image and outputs an image signal. However, noise generated by a noise source such as a motor or a coil included in an autofocus lens or a camera shake correction mechanism may be included in the image signal. In order to prevent noise from appearing in the image signal, the motor of the autofocus lens is driven when a pixel that does not constitute an image among the pixels of the image sensor outputs a charge (Cited document 1).

JP 2008-118378 A

  However, since there are a small number of pixels that do not form an image among the pixels included in the image sensor, the period during which the motor can be driven is limited, and there is a possibility that the period necessary for focusing cannot be secured. That is, if the motor is driven in accordance with the timing of the image sensor, the autofocus lens and the camera shake correction mechanism may not function sufficiently.

  The present invention has been made in view of these problems, and provides an image pickup apparatus that prevents noise from appearing on an image signal output from an image pickup element while exhibiting the function of a mechanism that constitutes a noise source. Objective.

  An imaging apparatus according to the present invention includes a signal generation unit that transmits a readout signal at a predetermined cycle, an imaging element that includes a plurality of pixels and outputs charges accumulated in the pixels as an image signal when the readout signal is received, and an operation And a noise source that adds noise to the image signal output from the image sensor, and the signal generator transmits a readout signal when the noise source is not operating, and the noise source is operating Sometimes the readout signal is not transmitted.

  The signal generation unit preferably transmits a read signal when the noise source has been operating for a predetermined period or longer.

  The signal generation unit transmits a horizontal signal to the image sensor, and the image sensor outputs an image signal during a period in which the level of the horizontal signal is Hi, and the level of the horizontal signal has changed from Hi to Lo for a predetermined period. It is preferable to be a period from time to time when it falls again from Hi to Lo.

  It is preferable to further include a warning unit that issues a warning when the signal generation unit transmits a read signal when the noise source is operating for a predetermined period or longer.

  It is preferable to further include a correction unit that moves the image pickup element so as to cancel vibration applied to the image pickup element, and the correction unit preferably includes a noise source.

  The noise source is preferably a voice coil motor.

  According to the present invention, it is possible to obtain an image pickup apparatus that prevents noise from appearing on an image signal output from an image pickup element while exhibiting the function of a mechanism constituting a noise source.

It is the block diagram which showed the imaging device roughly. 3 is a timing chart showing a relationship between a charge reading timing and a coil driving timing in the image sensor. It is the flowchart which showed the imaging process. 5 is a flowchart showing charge reading processing.

  Hereinafter, an imaging apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a digital camera 100 that is an embodiment of an imaging apparatus. The configuration of the digital camera 100 will be described with reference to FIG.

  The digital camera 100 includes a DSP 110 having a signal generation unit, a CMOS 121 that forms an imaging device (CIS), an SR (Shake Reduction) block 122 that forms a noise source and correction unit, a gyro sensor 123, a memory 124, a recording medium 125, and an operation member. 126, a monitor 127 constituting a warning unit, and a photographing lens 130 as a noise source.

  The photographing lens 130 includes a lens 131 and a lens driving motor 132, and is attached to the digital camera 100 so as to be detachable. The taking lens 130 forms a subject image on the CMOS 121. The lens drive motor 132 includes a coil or a magnetic material, and generates electrical noise during operation.

  The CMOS 121 includes a plurality of pixels. Pixels convert the subject image formed by the photographing lens 130 into electric charges and accumulate them. The accumulated charge is output to the DSP 110 as an image signal.

  The DSP 110 includes an SR control unit 111 that controls the SR block 122, a CIS control unit 112 that controls the image sensor, a motor control unit 113 that controls the lens driving motor 132, and an image processing unit 114. The CIS control unit 112 constitutes a signal generation unit.

  The image processing unit 114 receives an image signal from the CMOS 121, performs image processing while using the memory 124 as a temporary storage area, and generates an image or an image file. The image is displayed on the monitor 127 and the image file is stored in the recording medium 125. The storage medium is an SD card, for example, provided so as to be detachable from the digital camera 100.

  The motor control unit 113 receives the image from the image processing unit 114 and determines the in-focus state of the subject image based on the contrast of the image. Then, a drive signal is transmitted to the lens drive motor 132 according to the in-focus state to drive. When driving the lens drive motor 132, the motor control unit 113 also transmits a drive signal to the CIS control unit 112.

  The gyro sensor 123 detects vibration applied to the digital camera 100, that is, angular velocity, and transmits the detected vibration to the SR control unit 111. The SR control unit 111 determines whether or not the angular velocity is greater than or equal to a threshold value when the CMOS 121 is performing exposure. And when it is more than a threshold value, the drive amount required in order to cancel the vibration applied to the digital camera 100 is calculated. Then, the drive amount is transmitted as a drive signal to the SR block 122 and the CIS control unit 112. When the CMOS 121 is outputting an image signal, the SR control unit 111 transmits a fixed signal for fixing the position of the CMOS 121 to the SR block 122 and the CIS control unit 112.

  The SR block 122 includes a voice coil motor 122a. The SR block 122 that has received the drive amount from the SR control unit 111 energizes the voice coil motor 122a in accordance with the drive amount, and moves the CMOS 121 using the force generated by the voice coil motor 122a. As a result, the CMOS 121 moves so as to cancel the vibration applied to the digital camera 100. The voice coil motor 122a includes a magnetic body and a coil, and generates a force by changing the magnitude of a current flowing through the coil. The voice coil motor 122a fixes the position of the CMOS 121 by keeping the magnitude of the current flowing through the coil constant. When the current flowing in the coil is constant, the electrical noise generated by the voice coil motor 122a is extremely small and has a constant value. On the other hand, when the current flowing through the coil changes, the voice coil motor 122a generates electrical noise.

  The CIS control unit 112 transmits a read signal to the CMOS 121. The charges accumulated in the pixels of the CMOS 121 are output in response to the read signal.

  Next, the timing at which the pixel outputs charges will be described with reference to FIG.

  When the level of the vertical signal (VD) transmitted from the CIS control unit 112 to the CMOS 121 is temporarily lowered from Hi to Lo, the pixels included in the CMOS 121 start to accumulate electric charges. A period from when a pixel starts to accumulate electric charge to when all the pixels have accumulated electric charge is called an exposure period. At this time, the SR control unit 111 transmits a drive amount necessary for canceling the vibration applied to the digital camera 100 to the SR block 122 and the CIS control unit 112 as a drive signal. The SR block 122 that has received the drive signal drives the CMOS 121 according to the drive amount.

  When the CIS controller 112 lowers the level of the vertical signal (VD) from Hi to Lo again, the pixel starts to output charges. A period from when a pixel starts outputting charges to when all pixels finish outputting charges is called a reading period. During the reading period, the SR control unit 111 transmits a fixing signal for fixing the position of the CMOS 121 to the SR block 122 and the CIS control unit 112. The SR block 122 that has received the fixed signal fixes the CMOS 121 at the current position. That is, the position of the CMOS 121 is fixed during the reading period, and the electrical noise generated by the voice coil motor 122a is extremely small and constant. The CIS control unit 112 that has received the fixed signal transmits a read signal at a normal cycle. The transmission of the read signal means to temporarily lower the level of the horizontal signal (HD) from Hi to Lo. The CMOS 121 that has received the readout signal starts to output charges accumulated in a predetermined pixel. That is, every time the level of the horizontal signal (HD) falls from Hi to Lo during the readout period, a predetermined pixel outputs an electric charge. Since the noise is generated by the voice coil motor 122a during a period in which the noise is extremely small and constant, the pixel outputs charge, so that the image signal does not have noise.

  On the other hand, when the gyro sensor 123 detects an angular velocity equal to or higher than the threshold during the reading period, the SR control unit 111 calculates a drive amount, and the SR block 122 energizes the voice coil motor 122a accordingly. The period during which the voice coil motor 122a is energized is represented as period A in FIG. As a result, the amount of current to the voice coil motor 122a changes, the CMOS 121 is moved so as to cancel the vibration applied to the digital camera 100, and the voice coil motor 122a generates noise. As described above, at this time, the SR control unit 111 adds the drive signal to the SR block 122 and transmits it to the CIS control unit 112. The CIS control unit 112 that has received the drive signal temporarily stops the transmission of the read signal, that is, maintains the level of the horizontal signal (HD) as Hi. Since the CMOS 121 does not receive the readout signal, it does not output the charges accumulated in the pixels. That is, during the readout period, the pixel temporarily suspends charge output. During operation, the voice coil motor 122a may add noise to the image signal in accordance with the positional relationship with the imaging device. In this embodiment, the pixel is charged during the period in which the voice coil motor 122a generates noise. Is not output, noise does not occur in the image signal.

  When the external force is no longer applied to the digital camera 100 and the angular velocity detected by the gyro sensor 123 becomes less than the threshold value, the SR control unit 111 transmits a fixed signal to the SR block 122 and the CIS control unit 112. Thereby, the amount of current to the voice coil motor 122a becomes constant, the position of the CMOS 121 is fixed, and the voice coil motor 122a does not generate noise. The CIS control unit 112 that has received the fixed signal starts to transmit the read signal again in a normal cycle. The CMOS 121 that has received the readout signal starts to output the charges accumulated in the pixels. That is, since the pixel outputs electric charges during a period when the voice coil motor 122a does not generate noise, noise does not occur in the image signal.

  In addition, when the period during which the gyro sensor 123 detects the angular velocity equal to or greater than the threshold during the reading period is equal to or longer than the predetermined period, that is, when the period A during which the voice coil motor 122a is energized is equal to or longer than the predetermined period, the CIS control unit 112 The read signal is transmitted again at a normal cycle. The predetermined period is, for example, a period from when the level of the horizontal signal changes from Hi to Lo to when it again decreases from Hi to Lo, that is, 1 HD period which is one unit of the horizontal signal. At the same time, the DSP 110 displays a warning on the monitor 127 that there is a risk of noise on the image signal. The CMOS 121 that has received the readout signal starts to output the charges accumulated in the pixels. When an external force is continuously applied to the digital camera 100 for a predetermined period or longer, reading of the image signal from the CMOS 121 is not completed and the next process cannot be executed. Therefore, reading is resumed after a warning is issued to the user. By restarting the reading, the digital camera 100 can smoothly shift to the next process, and the user can be prevented from recognizing that the function of the digital camera 100 has stopped. In addition, the user who has recognized the warning can take measures such as suppressing external force applied to the digital camera 100.

  When receiving the drive signal from the motor control unit 113, the CIS control unit 112 performs the same operation as that received from the SR control unit 111. Therefore, the description is omitted.

  Next, imaging processing will be described with reference to FIG. The imaging process is executed when a shutter release button included in the operation member 126 is operated.

  In the first step S31, a return mirror (not shown) is raised and a shutter (not shown) is opened. In the next step S32, the CMOS 121 starts exposure, that is, enters an exposure period. In step S33, the shutter is closed and the return mirror is lowered. This ends the exposure period.

  In the next step S <b> 34, charge reading processing described later is executed to acquire an image signal from the CMOS 121. Then, the process ends.

  Next, the charge reading process will be described with reference to FIG. The charge reading process is executed in step S34 of the imaging process.

  In the first step S41, it is determined whether or not the gyro sensor 123 has detected an angular velocity equal to or greater than a threshold value. If it is not greater than or equal to the threshold value, the process proceeds to step S42. If it is greater than or equal to the threshold value, the process proceeds to step S44.

  In step S42, an image signal is read from the CMOS 121. That is, the CIS control unit 112 transmits a read signal at a normal cycle. As a result, every time the level of the horizontal signal (HD) falls from Hi to Lo, a predetermined pixel outputs an electric charge.

  In step S43, it is determined whether reading of the image signal is completed, that is, whether all the pixels have output charges. If the reading is complete, the process ends. If the reading is not complete, the process returns to step S41.

  In step S41, when the gyro sensor 123 detects an angular velocity equal to or higher than the threshold, the process proceeds to step S44, and reading of the image signal is interrupted. That is, the CIS control unit 112 temporarily stops reading signal transmission, that is, maintains the level of the horizontal signal (HD) as Hi.

  In the next step S45, it is determined whether or not a predetermined period has elapsed since the reading of the image signal was interrupted. If the predetermined period or more has elapsed, the process proceeds to step S46, and if not, the process returns to step S41.

  In step S46, the monitor 127 displays a warning that there is a risk of noise on the image signal.

  In the next step S47, an image signal is read from the CMOS 121. That is, the CIS control unit 112 transmits a read signal at a normal cycle. As a result, every time the level of the horizontal signal (HD) falls from Hi to Lo, a predetermined pixel outputs an electric charge. Then, the process returns to step S41, and the processes from step S41 to S47 are repeated until all the pixels have finished outputting charges.

  Although the case where the CIS control unit 112 receives a drive signal from the SR control unit 111 has been described, the CIS control unit 112 performs the same operation when the drive signal is received from the motor control unit 113.

  According to the present embodiment, since the pixel does not output charge during a period when the noise source generates noise, and the pixel outputs charge during a period when noise is not generated, noise occurs in the image signal. There is no.

  Since the reading is resumed even when vibration is continuously applied to the digital camera 100, the digital camera 100 can smoothly move to the next processing, and the digital camera 100 has stopped functioning. It is possible to prevent the user from recognizing.

  In addition, since reading is resumed after issuing a warning to the user, it is possible to take measures such as suppressing the external force applied to the digital camera 100 by the user who has recognized the warning.

  The photographing lens 130 is not detachable from the digital camera 100 and may be fixed so as not to be detachable.

  Further, a solid-state imaging device such as a CCD may be used instead of the CMOS 121.

  The CIS control unit 112 may receive an output from the gyro sensor 123 and control the image sensor in accordance with the output.

100 digital camera 110 DSP
111 SR Control Unit 112 CIS Control Unit 113 Motor Control Unit 114 Image Processing Unit 121 CMOS
122 SR block 122a Voice coil motor 123 Gyro sensor 124 Memory 125 Recording medium 126 Operation member 127 Monitor 130 Shooting lens 131 Lens 132 Lens drive motor

Claims (6)

A signal generator for transmitting a read signal at a predetermined cycle;
An image sensor comprising a plurality of pixels and outputting the charge accumulated in the pixels as an image signal when the readout signal is received;
A noise source that adds noise to the image signal output by the image sensor when operating;
The signal generation unit receives the drive signal output to the noise source during an image signal readout period, interrupts transmission of the readout signal, and resumes transmission of the readout signal when the noise source stops operating apparatus.   The imaging apparatus according to claim 1, wherein the signal generation unit transmits the readout signal when the noise source is operating for a predetermined period or longer. The signal generation unit transmits a horizontal signal to the image sensor,
The image sensor outputs the image signal during a period in which the level of the horizontal signal is Hi,
The imaging apparatus according to claim 2, wherein the predetermined period is a period from a time when the level of the horizontal signal changes from Hi to Lo to a time when the level decreases from Hi to Lo again.   The imaging apparatus according to claim 2, further comprising a warning unit that issues a warning when the signal generation unit transmits the readout signal when the noise source is operating for a predetermined period or longer.   5. The imaging apparatus according to claim 1, further comprising a correction unit that moves the image sensor so as to cancel vibration applied to the image sensor, and the correction unit includes the noise source.   The imaging apparatus according to claim 5, wherein the noise source is a voice coil motor.

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