JP2006287666A - Image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pickup device capable of improving the brightness of an image while noise components are suppressed even when being used at a place where the illuminance of an object is low. <P>SOLUTION: At the time of through display, a light quantity sensor 15 measures the illumination of an object image and sends measurement result information to a control part 8. The control part 8 can brighten display contents because the control part 8 reads accumulated electric charge from the entire pixels of an image pickup element 3 and converts the electric charge into image information for display and displays the image information when the illumination of the object image is lower than a predetermined value even though the control part 8 usually reads accumulated electric charge from pixels other than pixels predetermined from the image pickup element 3, converts the electric charge into image information for display and displays the image information on a display part 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus that captures a subject image formed on an imaging element.

  Conventionally, in a digital camera using an image pickup device such as a CCD, the number of pixels of the image pickup device itself is increased to obtain a high-quality image. In this case, for example, in the case of so-called through display in which the subject image captured on the image sensor is displayed in real time on a display device provided in the camera itself, the resolution (number of pixels) of the display device itself is low. Do not read out signals from all pixels of the image sensor, thin out some of them, read out signals from only the number of pixels required for display, and display them, and still images of the subject image captured on the image sensor Only when the signal is stored in the storage device, signals are read from all the pixels of the image sensor, signal processed, and stored in the storage device (see Patent Document 1).

Also, during continuous shooting that captures images continuously or when storing moving image shooting, the number of pixels in each frame image is not as large as that of still images, so some of the pixels of the image sensor are also thinned out. Thus, a signal is read out only from a pixel necessary for moving image storage and is recorded and stored (see Patent Documents 2 and 3).
JP 09-247543 A JP 05-191700 A Japanese Patent Laid-Open No. 05-167976

  However, when a signal is read out by thinning out pixels of an image sensor such as a CCD at the time of through display or moving image shooting, the accumulated charge amount of the read signal is reduced compared to reading from all pixels. When the image is processed and displayed, the illuminance (luminance) decreases. In particular, when shooting in places where the illuminance of the subject is low, a conventional camera is provided with a button key for adjusting the brightness, etc., and this button key is operated to increase the signal gain for display. Although the luminance is increased, if the signal gain is increased, the level of the noise component included in the signal is also increased at the same time, so that there is a disadvantage that the noise is displayed conspicuously.

  Accordingly, an object of the present invention is to provide an imaging apparatus capable of improving the brightness of an image while suppressing a noise component even when used in a place where the illuminance of a subject is low.

  In order to solve the above-described problems, an imaging apparatus according to a first aspect of the present invention includes an imaging device including a plurality of pixels that convert a subject image into an electrical signal, and a predetermined one of the plurality of pixels of the imaging device. First electrical signal readout means for thinning out the obtained pixels and reading out electrical signals from the remaining pixels; and second electrical signal readout means for reading out electrical signals from the plurality of pixels without thinning out the predetermined pixels. The electric signal reading means for reading the electric signal from the image pickup element by the second electric signal reading means when the illuminance of the subject image is low, usually reading the electric signal from the image pickup element by the first electric signal reading means. Processing the electrical signal read by the selection means and the first or second electrical signal readout means selected by the selection means Signal processing means for obtaining image information for display Te, characterized in that it comprises a display means for displaying the image information for the display that has been processed by the signal processing means.

  According to a second aspect of the present invention, still image storage means for storing still image information and a shutter key are provided, and when the shutter key is operated, the second electric signal readout is performed regardless of the illuminance of the subject image. An electrical signal is read out from the imaging device by means, and the electrical signal is processed by the signal processing means to obtain a still image, which is stored in the still image storage means.

  According to another aspect of the present invention, an imaging device having a plurality of pixels for converting a subject image into an electrical signal, and a predetermined pixel among the plurality of pixels of the imaging device are thinned out to generate an electrical signal from the remaining pixels. By a first electric signal reading means for reading out electric signals, a second electric signal reading means for reading out electric signals from the plurality of pixels without thinning out the predetermined pixels, and usually by the first electric signal reading means. The electrical signal is read from the image sensor, and when the illuminance of the subject image is low, the second electrical signal read means reads the electrical signal from the image sensor and the selection means selected by the selection means. Signal processing means for obtaining moving image information by processing the electric signal read by the first or second electric signal reading means; Characterized by comprising a video information storage means for storing the video information processed by the No. processor.

  According to a fourth aspect of the present invention, there is further provided resolution conversion means for obtaining display image information by lowering the resolution of the image information obtained by the signal processing means, and display image information obtained by the resolution conversion means. Display means.

  According to a fifth aspect of the present invention, there is further provided a setting key for invalidating the selection by the selection means and always setting the second electric signal reading means to be selected.

  According to the present invention, at the time of through display or when capturing a moving image, the signal is read out from the normal image sensor, but when the illuminance of the subject is low, the signal is read out from the image sensor without being thinned out. This has the effect of improving the brightness of the image while suppressing the noise component.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.

  FIG. 1 is a block diagram of an image pickup apparatus of the present invention, for example, a digital camera 1 capable of shooting and storing both still images and moving images.

  In FIG. 1, the taking lens 2 is composed of a plurality of lens groups and forms an external subject image on the image sensor 3. The optical drive unit 4 drives the photographic lens 2, and the photographic lens 2 is moved by the optical drive unit 4 to adjust the focus position. The shutter 5 is a shutter whose opening / closing operation and traveling speed are controlled based on a control signal from the shutter driving unit 6.

  The image sensor 3 is a CCD solid-state image sensor in which R (red), G (green), and B (blue) color filters are arranged in front of a plurality of pixels formed in a matrix. The read drive unit 7 supplies a read pulse to the image sensor 3 in response to a read control signal from the control unit 8, and the image sensor 3 captures the subject image captured by the read drive unit 7 receiving the read pulse. Are photoelectrically converted, and the charge accumulated in each pixel is read out as an electric signal.

  Note that the read control signal supplied from the control unit 8 to the read drive unit 7 includes a control signal for instructing to read out an electric signal from all the pixels of the image sensor 3 and a predetermined pixel from the remaining pixels after thinning out the predetermined pixels. A control signal for instructing to read out the electrical signal is selectively sent. The electrical signals photoelectrically converted and read out for each pixel in the image sensor 3 are sequentially output to the CDS / AGC circuit 9.

  The CDS / AGC circuit 9 samples and holds the signal output from the image sensor 3 and amplifies the gain of the signal. The A / D conversion circuit 10 converts the signal input from the CDS / AGC circuit 9 into a digital signal having a predetermined bit, and outputs the digital signal to the control unit 8.

  The control unit 8 is composed of a CPU and the like, and executes various programs in accordance with programs stored in the ROM 11 to control the operation of the entire digital camera 1.

  The control unit 8 supplies a driving signal to the distance sensor driving unit 12, and the distance sensor driving unit 12 supplies an operation command signal to the distance sensor 13 when the driving signal is supplied from the control unit 8. The distance sensor 13 receives the operation command signal, measures the distance to the external subject image, and supplies measurement result information corresponding to the measured distance to the control unit 8 via the distance sensor driving unit 12. . Thereby, the control unit 8 outputs a control signal for focusing to the optical drive unit 4 described above.

  In addition, the control unit 8 supplies a drive signal to the light amount sensor drive unit 14 in order to measure the brightness of the subject, and the light amount sensor drive unit 14 operates on the light amount sensor 15 when the drive signal is supplied from the control unit 8. Supply command signal. The light quantity sensor 13 receives the operation command signal, measures the brightness (illuminance) of the external subject image, and supplies measurement result information corresponding to the illuminance to the control section 8 via the light quantity sensor driving section 14. Yes. As a result, the control unit 8 outputs a control signal for exposure control to the shutter drive unit 6 described above.

  Further, the control unit 8 supplies a drive signal to the color temperature sensor drive unit 16 in order to measure the color temperature of the subject, and the color temperature sensor drive unit 16 receives the drive signal from the control unit 8 and the color temperature sensor. An operation command signal is supplied to 17. The color temperature sensor 17 receives the operation command signal, measures the color temperature of the external subject image, and supplies measurement result information corresponding to the color temperature to the control unit 8 via the color temperature sensor driving unit 16. Yes. Accordingly, the control unit 8 determines a white balance correction value based on the color temperature measurement result information described above, and performs white balance correction described later.

  The RAM 18 stores data for various processes performed by the control unit 8. FIG. 2 shows the storage area of the RAM 18, and the mode value M indicating the operation mode of the digital camera 1 is stored in the mode storage area 18A. That is, the digital camera 1 is configured such that a still image shooting mode, a moving image shooting mode, a captured image playback mode, a captured image deletion mode, and the like are set by key operations described later. When the mode value M is “0” (hereinafter referred to as M = 1), the still image shooting mode, when M = 1, the moving image shooting mode, M = 2 is the playback mode, and M = 3 is erased. It is in mode.

  The moving image shooting flag storage area 18B stores a flag value D that is “0” when moving image shooting is not performed and “1” during moving image shooting. The shooting condition storage area 18C stores shooting conditions during shooting, such as shutter speed, exposure conditions, and white balance values.

  The work area 18D includes, for example, image information for one frame that is transferred from the A / D conversion circuit 10 to the image sensor 3, image information for one frame that has been processed into luminance and color difference signals, which will be described later, This is an area for temporarily storing image information for display whose resolution has been converted.

  Returning to FIG. 1, when the signal from the image sensor 3 is supplied from the A / D conversion circuit 10, the control unit 8 temporarily stores the signal in the work area 18 </ b> D of the RAM 18, and stores an image for one frame in the RAM 18. When the signal is stored, it is read from the RAM and sent to the signal processing circuit 20.

  The signal processing circuit 20 performs signal processing such as white balance correction, processing to convert to luminance signal and color difference signal image information, processing to convert the resolution and generate an image signal for display, and the like. The obtained image signal is stored in the work area 18D of the RAM 18.

  Of the image information stored in the work area 18D, an image signal for display is sent to the display unit 22 including a color matrix liquid crystal display device via the display driving unit 21 and displayed.

  Further, when a shutter key described later is operated, image information including luminance and color difference signal signals stored in the work area 18D is sent to the compression / decompression circuit 23 for compression encoding and R / W (read / write) control. The image data is stored in the image storage unit 25 formed of a non-volatile memory such as a flash memory that can be attached to and detached from the digital camera 1 via the unit 24.

  In this case, when the shutter key is operated in the still image shooting mode, the image information is compressed by the compression conversion circuit 23 in accordance with a standard such as JPEG, and further stored as a file. When a moving image is stored by operating the shutter key, it is compressed according to a standard such as motion JPEG or MPEG, and is stored as a file.

  The key input unit 26 is composed of various operation keys (not shown) such as a power key, a mode switching key for switching each mode described above, or a shutter key.

  Next, the operation of the digital camera 1 will be described with reference to the flowcharts of FIGS.

  FIG. 3 is a flowchart of contents processed by the control unit 8 in the still image shooting mode of M = 0. First, in step S1, the illuminance (brightness) of the external subject is measured by the light quantity sensor 15, and it is determined whether or not the illuminance is greater than or equal to a predetermined value. If the illuminance of the subject is equal to or greater than a predetermined value (step S1, Yes), the process proceeds to step S2, and the read drive unit 7 leaves the remaining pixels excluding the predetermined pixels among the pixels of the image sensor 3. A control signal for reading out electrical signals of the pixels is supplied. That is, the thinned electric signal is output from the image sensor 3.

  As a result, when the digital signal of the thinned electrical signal for one frame is stored in the work area 18D of the RAM 18, in the next step S3, the stored digital signal is sent to the signal processing circuit 20 to perform signal processing to perform luminance and Convert to color difference signal. In the next step S4, the converted luminance and color difference signals are sent to the display unit 22 for through display.

  In the next step S7, it is determined whether or not the shutter key of the key input unit 26 has been operated. If it has not been operated, the process returns to step S1 and the processes in and after step S2 are repeated. Through the above processing, the subject image captured on the image sensor 3 is displayed through on the display unit 22.

  On the other hand, when it is detected in step S1 that the illuminance of the subject is low (No in step S1), the process proceeds to step S5, and a control signal for reading out an electrical signal from all pixels of the image sensor 3 is read out. 7 is supplied. As a result, the electrical signals from all the pixels of the image sensor 3 are sent to the CDS / AGC circuit 9 and further converted into digital signals by the A / D conversion circuit 10 and then stored in the work area 18D of the RAM 18 for further steps. In S6, the signal is sent to the signal processing circuit 20 and converted into luminance and color difference signals.

  In this case, since luminance and color difference conversion is performed using signals from all pixels of the image sensor 3, a signal having a larger luminance amount than the luminance and color difference conversion by the signal thinned out in step S3 is obtained. The luminance and color difference signals obtained in this way are converted into display signals and displayed on the display unit 22 in step S4.

  If it is detected in step S7 that the shutter key has been operated, the process proceeds to step S8. In step S8, the distance sensor 13, the light quantity sensor 15, and the color temperature sensor 17 are driven by operating the shutter key, and the photographing lens 2 and the shutter 5 are driven based on the measurement result information to perform focusing and exposure control, and color. Pre-processing for storing temperature information in the work area 18D of the RAM 18 is performed.

  In the next step S9, electrical signals are read from all the pixels of the image sensor 3 on which the subject is imaged and stored in the work area 18D via the CDS / AGC circuit 9 and the A / D conversion circuit 10, and all pixels ( When the storage of the image information consisting of one frame is completed, the process proceeds to step S10.

  In step S10, the image information and color temperature information stored in the work area 18C are sent to the signal processing circuit 20 to convert them into luminance and color difference signals. In the next step S11, the converted image information is converted according to the JPEG standard. The image data is compressed and stored in the image storage unit 25, and the process returns to step S1.

  FIG. 4 is an operation flowchart in the moving image shooting mode of M = 1. In this flowchart, steps S1 to S4 are the same as the processes of steps S1 to S4 in FIG. 3, and thus the same step numbers are given and detailed description thereof is omitted.

  Accordingly, in step S12, it is determined whether or not the shutter key has been operated. If not, the process proceeds to step S13, and whether or not the flag value D stored in the moving image shooting flag storage area 18B of the RAM 18 is D = 1. Is determined.

  In the moving image shooting mode, as described later, the moving image shooting is started by the first operation of the shutter key and becomes D = 1, and the moving image shooting is stopped by the re-operation of the shutter key and D = 0. When D = 1 is not satisfied, it is determined that no moving image shooting is performed, and the process returns to step S1.

  If the operation of the shutter key is detected in step S12, the process proceeds to step S14, and it is determined whether D = 0. If D = 0, it is determined that the shutter key has been operated for moving image shooting without moving image shooting, and the process proceeds to step S15, where D is converted to “1” and the next step is performed. Proceed to step S16. Step S16 is the same processing as step S8 in FIG. 3, and after performing focusing and exposure control from the measurement results of each distance sensor 13, light quantity 15 and color temperature 17, the process proceeds to step 17.

  Step S17 performs the same processing as step S1 in FIG. 3 to measure the illuminance of the subject. If the illuminance of the subject is equal to or greater than a certain level, the process proceeds to step S18. Step S <b> 18 is a process of reading an electrical signal from a pixel necessary for shooting and storing a moving image among the pixels of the image sensor 3. That is, in moving image shooting, since the image information per frame does not require as much information as a still image, the pixels are thinned out to read out electrical signals only from the necessary pixels. The read image information of the electrical signal is stored in the work area 18D and sent to the signal processing circuit 20 in the next step S19 to be converted into a luminance and color difference signal.

  In the next step S20, the resolution is converted so that the converted luminance and color difference signals become display image information, and the converted display image information is sent to the display unit 22 for display. That is, the moving image storage image information read out after being thinned out from the image sensor 3 does not match the display resolution, so that the resolution is converted and displayed in step S20.

  In the next step S21, the luminance and color difference signals converted in step S19 are compressed and stored in the image storage unit 25.

  On the other hand, if the illuminance of the subject is below a certain value in step S17, the process proceeds to step S22. In step S22, electrical signals from all the pixels of the image sensor 3 are read and the image information is stored in the work area 18D. In the next step S23, the stored image information is sent to the signal processing circuit 20 and converted into luminance and color difference signals.

  In this case, since luminance and color difference conversion is performed using signals from all the pixels of the image sensor 3, a signal having a larger luminance amount than the luminance and color difference conversion by the signal thinned out in step S19 is obtained. The luminance and color difference signals thus obtained are converted into display signals in the next step S24 and displayed on the display unit 22. In the next step S25, the luminance and color difference signals converted in step S23 are compressed and stored in the image storage unit 25.

  When the process of step S21 or S25 is completed, the process returns to step S12, where it is determined whether or not the shutter key has been operated. If the operation has not been performed, the process proceeds to step S13. In step S14, it is determined whether or not D = 1. Since D = 1 during shooting storage, the process proceeds to step S16, and thereafter, the above-described steps S17 to S21 or steps S17 to S25 are repeated. As a result, the moving image information is stored in the image storage unit 25.

  5 shows the vertical registers 31A, 31B,... And the vertical registers 31A, 30B, 30C,..., And the electrical registers 30A, 30B, 30C,. This shows an arrangement configuration of the horizontal register 32 to which electric signals are transferred from the registers 31A, 31B,.

  FIG. 6 shows that among the pixels 30A, 30B, 30C,..., Charges accumulated in the pixels 30A to 30E are read by the charge readout waveforms V1 to V6, respectively. The output states of the pixels 30A, 30C, and 30E in (R) are shown.

  FIGS. 7 and 8 show specific examples of the charge readout waveforms of the charge readout pulses V1 to V6, respectively. Waveforms when the charges are read out by thinning out the pixels of the red (R) pixels 30A, 30C, and 30E (FIG. 7). 7) is a diagram for explaining a waveform (FIG. 8) when reading out charges without thinning out pixels.

  That is, in the waveform of FIG. 7, the pixel 30A reads out charges at the timing of the pulse P2 of the charge readout waveform V1, and the pixel 30E is read out by the pulse P1 of the charge readout waveform V5. On the other hand, no charge reading pulse is supplied to the charge reading waveform V3 of the pixel 30C, and no charge reading is performed.

  In the waveform of FIG. 8, in addition to the pulses P1 and P2, the charge of the pixel 30C is read by the pulse P3 of the charge reading waveform V3. The output of the pulse P3 of the charge readout waveform V3 is read at a timing that does not mix colors with other pixels, and since it is not mixed, it can be output by increasing the signal amount of the electric signal from the image pickup device 3, and the image The signal brightness can be increased.

  As described above in detail, in the present embodiment, in the case of through display and moving image shooting and storage, the signals are read out with the pixels of the normal image sensor 3 being thinned out, but the illuminance around the subject or the like is insufficient. In the case of low illuminance, the signal amount is increased by stopping the thinning and reading the signal, and the luminance (brightness) of the image information can be improved.

  In the above embodiment, signals of all the pixels of the image sensor 3 are read out when the illuminance of the subject is insufficient. However, it is not always necessary to read out all the pixels, and the number of thinned pixels is reduced. You may make it read. Further, the range of illuminance may be divided into a plurality, and the number of thinnings may be changed in each range.

  Further, whether or not the illuminance is greater than or equal to a predetermined value is not determined by the light amount sensor 15, but whether or not the luminance information in the image information read from the image sensor 3 is greater than or equal to a predetermined value. You may make it judge by. In addition, even when the signal is read out when the illuminance is more than a predetermined value, a setting key for forcibly reading the signal from all pixels may be provided. In this case, it is only necessary to proceed from step S1 to step S5 regardless of the value of the illuminance when set by this setting key.

  In addition, the arrangement of the pixels of the image sensor 3 and the readout waveform when the thinning is not performed are not limited to the present embodiment, and various modifications can be made.

  In the above embodiments, examples in which the present invention is applied to a digital camera have been described. However, the present invention can be applied to various electronic devices including an imaging device such as a mobile phone with a camera function and a wristwatch.

1 is a block diagram of a digital camera 1 according to the present embodiment. 2 is a schematic diagram showing a storage area of a RAM 18. FIG. 5 is a flowchart showing a flow of processing in a still image shooting mode. It is the flowchart which showed the flow of the process in imaging | photography mode of a moving image. 2 is a diagram illustrating a partial configuration of an image sensor 3. FIG. 3 is a diagram illustrating a relationship between a pixel of the image sensor 3 and a charge readout waveform. FIG. It is a time chart of a charge read waveform. It is a time chart of a charge readout waveform similarly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital camera 3 Image pick-up element 7 Reading drive part 13 Distance sensor 15 Light quantity sensor 18 RAM
20 Signal Processing Circuit 22 Display Unit 23 Compression / Expansion Circuit 25 Image Storage Unit

Claims (5)

  An image sensor having a plurality of pixels for converting a subject image into an electric signal, and a first electric signal readout for reading out an electric signal from the remaining pixels by thinning out predetermined pixels among the plurality of pixels of the image sensor Means, a second electric signal reading means for reading out an electric signal from the plurality of pixels without thinning out the predetermined pixel, and an electric signal is read out from the image sensor by the first electric signal reading means. When the illuminance of the subject image is low, a selection unit of an electric signal reading unit that reads out an electric signal from the imaging device by the second electric signal reading unit, and the first or second electric signal selected by the selection unit Signal processing means for processing the electrical signal read by the reading means to obtain image information for display, and the signal processing means Imaging apparatus characterized by comprising a display means for displaying the image information for display that has been processed me.   The image sensor further comprises a still image storage means for storing still image information and a shutter key, and when the shutter key is operated, the second electrical signal reading means performs the imaging element regardless of the illuminance of the subject image. The imaging apparatus according to claim 1, wherein an electrical signal is read out from the camera, the electrical signal is processed by the signal processing unit, a still image is obtained and stored in the still image storage unit.   An image sensor having a plurality of pixels for converting a subject image into an electric signal, and a first electric signal readout for reading out an electric signal from the remaining pixels by thinning out predetermined pixels among the plurality of pixels of the image sensor Means, a second electric signal reading means for reading out an electric signal from the plurality of pixels without thinning out the predetermined pixel, and an electric signal is read out from the image sensor by the first electric signal reading means. When the illuminance of the subject image is low, a selection unit of an electric signal reading unit that reads out an electric signal from the imaging device by the second electric signal reading unit, and the first or second electric signal selected by the selection unit Signal processing means for obtaining moving picture information by processing the electrical signal read by the reading means, and processing by the signal processing means. Imaging apparatus characterized by comprising a video information storage means for storing the video information.   Furthermore, a resolution conversion unit that obtains display image information by lowering the resolution of the image information obtained by the signal processing unit, and a display unit that displays the display image information obtained by the resolution conversion unit. The imaging apparatus according to claim 3, further comprising:   5. The imaging according to claim 1, further comprising a setting key for invalidating selection by the selection unit and setting so that the second electric signal reading unit is always selected. apparatus.

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