JP4785698B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus that performs noise suppression processing to suppress a noise signal included in a video signal.

  In general, in an imaging apparatus such as a digital video camera or a digital still camera, an operation of moving a focus lens within a predetermined range (hereinafter referred to as a search) in order to detect a focus position based on an AF evaluation value signal indicating the sharpness of an image. Operation). During the search operation, the subject image obtained through the imaging optical system is one in which high frequency components are lost except when the focus lens is at the best focus position.

  On the other hand, in the image sensor, random noise is generated according to the amount of incident light. Since this noise is not affected by the focus lens, high frequency components included in the noise are not lost even during the search operation. For this reason, noise that is inconspicuous due to being mixed with the high-frequency component of the subject image in the in-focus state is superimposed on the subject image in which the high-frequency component has deteriorated during the search operation, and thus is easily noticeable. When such noise becomes conspicuous each time the search operation is shifted, the S / N ratio of the entire video signal is reduced, that is, the image quality is deteriorated.

  Here, as an imaging device in which focus determination and noise suppression processing are linked, the screen is divided into a plurality of regions, and noise suppression processing is performed between regions determined to be in focus and regions determined to be out of focus. A technique for varying the strength is disclosed in Patent Document 1.

  In addition, in an imaging apparatus, in order to efficiently record a video signal on a recording medium, encoding and compression processing is performed on the video signal using the correlation between adjacent frame images and subject motion information.

In such an encoding compression process, the smaller the difference between adjacent frame images, the higher the encoding efficiency. Therefore, the code amount control and the noise suppression process are linked, and the noise suppression process is strengthened according to the encoding efficiency. Japanese Patent Application Laid-Open No. 2004-228688 discloses a technique for making the thicknesses different.
JP 2002-176650 A (paragraph 0098 etc.) JP 2005-168053 A (paragraph 0037, etc.)

  However, in the technique disclosed in Patent Document 1, the strength of the noise suppression processing is not changed depending on whether or not the search operation is being performed. Therefore, noise superimposed on the subject image in which the high frequency component has deteriorated during the search operation is not generated. Conspicuously, S / N becomes small.

  Further, in the technique disclosed in Patent Document 2, by increasing the strength of the noise suppression processing, the resolution of the subject image decreases with noise, or an afterimage occurs when the subject moves. , Reduce the image quality.

  It is an object of the present invention to provide an imaging apparatus that can obtain a good S / N image without causing noise to stand out until focusing is achieved.

Imaging apparatus according to one aspect of the present invention includes a focus processing means for performing focus processing based on the signal indicating the sharpness of the image, and a noise suppression means for performing noise reduction processing for the video signal, a focus processing means The first focus processing for searching the focus position by moving the focus lens and the second focus processing for reciprocating the focus lens within the specific range with respect to the searched focus position are performed, and noise suppression means Is characterized in that the noise suppression strength during the first focus processing is made stronger than the noise suppression strength during the second focus processing .
An imaging apparatus according to another aspect of the present invention includes a focus processing unit that performs a focus process based on a signal indicating the sharpness of a video, and a noise suppression unit that performs a noise suppression process on the video signal. The suppression means changes the noise suppression strength in the noise suppression process during the focus process according to the value of the signal indicating the sharpness.

A control method of an imaging apparatus as another aspect of the present invention is used, the number and focus processing step of performing focus processing based on the signal indicating the sharpness of the image, and a noise suppression step of performing noise reduction processing for the video signal In the focus processing step, a first focus process for moving the focus lens to search for a focus position, and a second focus process for reciprocating the focus lens in a specific range with respect to the searched focus position; In the noise suppression step, the noise suppression strength during the first focus processing is made stronger than the noise suppression strength during the second focus processing .

Further, a control method of an imaging apparatus as another aspect of the present invention is used, the number and focus processing step of performing focus processing based on the signal indicating the sharpness of the image, and a noise suppression step of performing noise reduction processing for the video signal and, in the noise suppressing step, according to the value of the signal indicating the該鮮sharpness, and wherein the benzalkonium change the noise suppression strength in the noise suppression processing in the focusing process.

  According to the present invention, it is possible to set an optimum noise suppression strength in accordance with a signal indicating a focus processing state or sharpness. Thereby, for example, noise is not conspicuous even in the out-of-focus state until the in-focus state is obtained, and an image with good image quality can be obtained.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows the configuration of an image pickup apparatus that is Embodiment 1 of the present invention. Reference numeral 1 denotes an image pickup optical system including a lens (such as a focus lens 1a) and a diaphragm 1b, and 2 denotes an image pickup element including a CCD sensor or a CMOS sensor.

  Reference numeral 3 denotes an analog front end unit (noted as AFE in the drawing) including a CDS circuit and an A / D converter (not shown), and 4 denotes a drive circuit that performs zoom driving, focus driving, and aperture driving of the imaging optical system 1.

  An AF evaluation value generation circuit 5 generates an AF evaluation value used for focus processing (hereinafter referred to as AF processing). Reference numeral 6 denotes a focus determination circuit that performs focus determination processing (focus processing) using the AF evaluation value signal output from the AF evaluation value generation circuit 5.

  A camera signal processing circuit 7 generates a luminance signal and a color difference signal from image data obtained from the AFE 3. A noise suppression processing circuit 8 performs noise suppression processing on the luminance and color difference signals output from the camera signal processing circuit 7.

  A system control unit 9 controls the entire imaging apparatus. Reference numeral 10 denotes an operation switch for the user to instruct the operation of the imaging apparatus. Reference numeral 11 denotes a RAM for holding data generated by the circuits (blocks), and reference numeral 16 denotes a video signal output terminal for outputting luminance and color difference signals.

  Hereinafter, an imaging operation in the imaging apparatus configured as described above will be described. First, when an instruction to start imaging is given by the user through the operation switch 10, the drive circuit 4 drives the lens and the diaphragm 1b in the imaging optical system 1 according to a control signal from the system control unit 9 to set an appropriate brightness. The subject image thus formed is formed on the image sensor 2.

  The image sensor 2 converts the subject image into an electrical signal by photoelectric conversion and outputs it as an analog image signal. The analog image pickup signal output from the image pickup device 2 is subjected to removal of clock synchronization noise by the CDS circuit in the AFE 3 and converted to a digital image pickup signal by the A / D converter.

  The digital image signal output from the AFE 3 is subjected to RGB separation processing, white balance processing, luminance / color difference conversion matrix processing, aperture correction processing, gamma processing, and the like in the camera signal processing circuit 7. Thereby, the luminance signal Y1 and the color difference signals CR1 and CB1 as the video signal are generated.

  The digital imaging signal output from the AFE 3 is also input to the AF evaluation value generation circuit 5. The AF evaluation value generation circuit 5 performs band pass filter processing for extracting a high-frequency component of the subject image on the digital imaging signal output from the AFE 3. The high-frequency component of the subject image obtained by the bandpass filter process is integrated in a specific area in the video screen. Thereby, an AF evaluation value signal indicating the sharpness (contrast) of the video is generated. The AF evaluation value (signal) is stored in the RAM 11 under the control of the system control unit 9.

  Further, the system control unit 9 is driven to move the focus lens 1a within a predetermined range (a range from the infinite end to the closest end or a part thereof) in order to detect a focus position based on the AF evaluation value. The circuit 4 is controlled. The focus determination circuit 6 reads an AF evaluation value from the RAM 11 every time the focus lens 1a moves by a predetermined amount. This process of searching for the in-focus position is called a search operation in the focus process.

  The focus determination circuit 6 detects the maximum AF evaluation value corresponding to each focus lens position read from the RAM 11, and determines the focus lens position when the AF evaluation value is maximum as the focus position. . The system control unit 9 transmits a control signal for driving the focus lens 1 a to the drive circuit 4 using the focus determination result of the focus determination circuit 6.

  Further, the system control unit 9 transmits a control signal AF_MODE indicating the state of the focus determination process (focus process) obtained from the focus determination circuit 6 to the noise suppression processing circuit 8. The noise suppression processing circuit 8 is based on the control signal AF_MODE indicating the focus determination processing state output from the system control unit 9 for the luminance signal Y1 and the color difference signals CR1 and CB1 output from the camera signal processing circuit 7. Perform noise suppression processing.

  The luminance signal Y2 and the color difference signals CR2 and CB2 after the noise suppression processing are output from the video signal output terminal 16 as final output video signals. For example, an external device such as an encoding / compression device, a recording device, and a display device (not shown) is connected to the video signal output terminal 16.

  Next, the flow of processing in the system control unit 9 and the focus determination circuit 6 will be described using the flowchart of FIG. This operation is executed according to a computer program stored in the system control unit 9 and the focus determination circuit 6.

  When the in-focus determination process is started, “0” is set to the control signal AF_MODE indicating the in-focus determination process state in step (hereinafter abbreviated as S) 00 and transmitted to the system control unit 9. AF_MODE = 0 indicates a state in which the system controller 9 and the focus determination circuit 6 are performing a search operation (first focus processing) for focus position detection.

In S01, the moving direction of the focus lens 1a is determined. In this embodiment, since so-called hill-climbing AF control is performed, when the movement direction (search direction) of the focus lens 1a is determined, the focus lens 1a is finely reciprocated (reciprocated) . Then, an AF evaluation value is acquired during the minute reciprocating drive, and the direction in which the AF evaluation value increases is regarded as the direction in which the in-focus position exists, and is determined as the search direction.

  In S02, the focus lens 1a is moved by a unit step in the direction determined in S01.

  In S03, the AF evaluation value generation processing circuit 5 acquires the AF evaluation value at the focus lens position moved in S02. The acquired AF evaluation value is written in the RAM 11.

  In S04, the current AF evaluation value acquired in S03 and the AF evaluation value acquired in the focus lens position before (previous) the movement in S02 are read from the RAM 11.

  In S05, the two AF evaluation values read in S04 are compared in magnitude. If the AF evaluation value at the previous focus lens position is larger than the AF evaluation value at the current focus lens position, the process proceeds to S06. Otherwise, the process returns to S02.

  In S06, the AF evaluation value obtained at the previous focus lens position is regarded as the peak (maximum) AF evaluation value in the search operation range, and the previous focus lens position is determined as the in-focus position.

  In S07, the focus lens 1a is moved to the focus lens position determined as the focus position in S06.

  In S08, “1” is set to the control signal AF_MODE indicating the in-focus determination processing state, and is transmitted to the system control unit 9. When AF_MODE = 1, the system controller 9 and the focus determination circuit 6 perform a wobbling operation (second focus process) for reciprocatingly driving the focus lens 1a within a minute specific range centered on the determined focus position. Indicates a broken state.

  In S09, an AF evaluation value is acquired while performing wobbling.

  In S10, the AF evaluation value obtained in S09 is compared with the AF evaluation value of the peak determined in S06. If the difference between the two is larger than the predetermined value TH1, it is considered that the subject has moved or the framing has been changed during the wobbling operation, and the process returns to S00. If the difference between the two is smaller than the predetermined value TH1, it is considered that the camera is in focus, and the process returns to S09 to continue the wobbling operation.

  The above-described focus determination processing operation is regularly performed until a signal instructing to stop imaging is transmitted from the operation switch 10 to the system control unit 9. Thereby, the focus lens position is controlled so as to continuously focus on the subject.

  Next, the configuration of the noise suppression processing circuit 8 will be described with reference to FIG. In the present embodiment, as an example of the noise suppression process, a case where a frame cyclic noise suppression process is performed will be described. However, the noise suppression processing of the present invention is not limited to this, and other noise suppression methods may be employed.

  In FIG. 2, 800, 801, 802, 806, 807 and 808 are subtracters, and 803, 804 and 805 are multipliers. Reference numerals 809, 810, and 811 denote frame memories, and reference numerals 812, 813, and 814 denote cyclic coefficient control units. Reference numeral 816 denotes an NR control coefficient generation processing unit, and 815 denotes a ROM.

  Here, the ROM 815 cycles according to the initial values α, β, γ of cyclic coefficients when performing the frame cyclic noise suppression processing on the luminance signal Y1 and the color difference signals CR1, CB1, and the noise level, respectively. A control value C for controlling the coefficient is stored.

  Hereinafter, the operation of the noise suppression processing circuit 8 will be described with reference to the flowchart of FIG. The noise suppression processing circuit 8 of the present embodiment performs the same noise suppression processing on the luminance signal Y1 and the color difference signals CR1 and CB1. For this reason, in the following, processing for the luminance signal Y1 will be described as an example. This operation is executed by the system control unit 9 controlling the noise suppression processing circuit 8 according to a computer program stored therein.

  When the process is started, in S100, the NR control coefficient generation processing unit 816 acquires a control signal AF_MODE indicating the focus determination processing state in the focus determination circuit 6 from the system control unit 9.

  In S101, the NR control coefficient generation processing unit 816 determines whether AF_MODE is 0 through the system control unit 9. When AF_MODE is 0, that is, when the focus determination processing state is the search operation, the process proceeds to S102. When AF_MODE is 1, that is, when the focus determination processing state is the wobbling operation, the process proceeds to S103.

  In S <b> 102, the NR control coefficient generation processing unit 816 reads the AF evaluation value for the current focus lens position from the RAM 11 through the system control unit 9. Then, the control value C corresponding to the AF evaluation value is read from the ROM 815, and C is set as the control gain k for amplifying the cyclic coefficient (where C> 1).

  In S103, the NR control coefficient generation processing unit 816 sets 1 to the control gain k for amplifying the cyclic coefficient.

  In S104, the cyclic coefficient control unit 812 multiplies the initial value α of the cyclic coefficient for the luminance signal Y1 stored in the ROM 815 by the control gain k (= C or 1) set in S102 or S103. Thereby, the controlled cyclic coefficient ky is generated.

  In S105, the noise suppression processing circuit 8 performs frame cyclic noise suppression processing using the cyclic coefficient ky generated in S104 on the luminance signal Y1 as follows. Thereby, the luminance signal Y2 in which noise is suppressed is generated.

  Here, an example of a frame recursive noise suppression process will be described. In the frame recursive noise suppression processing, first, the subtracter 800 subtracts the luminance signal Y1_p of the previous frame stored in the frame memory 809 from the luminance signal Y1 obtained from the camera signal processing circuit 7. The luminance signal difference value Y1-Y1_p obtained here can be regarded as a noise component. The multiplier 803 multiplies the difference value Y1-Y1_p of the luminance signal by a cyclic coefficient ky.

  Finally, the subtracter 806 subtracts the luminance signal difference value Y1-Y1_p after multiplication by the cyclic coefficient ky from the luminance signal Y1. Thereby, the luminance signal Y2 in which noise is suppressed is output.

In the frame cyclic noise suppression processing, the noise suppression effect increases as the cyclic coefficient ky increases. For this reason, in the present embodiment, the magnitude of the cyclic coefficient ky is changed in accordance with the operation state of the focus determination circuit 6, thereby performing the wobbling operation ( during the second focus process) and the search operation (first operation ) . The intensity of noise suppression during the focusing process is controlled.

  Further, the control value C for setting the cyclic coefficient ky to a value larger than the initial value α is set so as to increase as the noise level increases. In order to determine the control value C, it is necessary to detect the noise level. In this embodiment, the AF evaluation value during the search operation is regarded as the noise level. That is, as the AF evaluation value increases, the control value C (that is, the cyclic coefficient ky) increases, and the noise suppression strength increases. This is because when the focus determination circuit 6 is performing a search operation (when AF_MODE = 0), the high frequency component of the subject image is lost, and noise is dominant in the high frequency component included in the AF evaluation value. It is possible.

  The series of noise suppression processing as described above is also performed on the color difference signals CR1 and CB1 output from the camera signal processing circuit 7, and the color difference signals CR2 and CB2 in which noise is suppressed are generated.

  As described above, in this embodiment, the noise suppression strength is controlled according to the focus determination processing state (focus processing state). As a result, when the in-focus determination processing state is during the wobbling operation, an appropriate noise suppression process is performed to such an extent that the resolution of the subject image is not impaired and no afterimage is generated. On the other hand, when the in-focus determination processing state is the search operation, stronger noise suppression processing is performed so that noise is not noticeable in the subject image in which the high frequency component is degraded. Therefore, the S / N of the entire output video signal can be kept good in the imaging apparatus that acquires the subject video while always performing the focus determination processing.

  The imaging apparatus according to the second embodiment of the present invention is different from the first embodiment in that the noise suppression processing in the noise suppression processing circuit 8 is multi-value controlled using the AF evaluation value. In the present embodiment, the configuration of the imaging device and the noise suppression processing circuit 8 is the same as that shown in FIGS. Here, only the operation of the noise suppression processing circuit 8 of this embodiment will be described.

  FIG. 5 is a flowchart showing the flow of noise suppression processing in the noise suppression processing circuit 8 of this embodiment.

  Also in this embodiment, the noise suppression processing circuit 8 performs the same noise suppression processing on the luminance signal Y1 and the color difference signals CR1 and CB1. Therefore, in the following, processing for the luminance signal Y1 will be described as an example.

  In S <b> 200, the NR control coefficient generation processing unit 816 reads the AF evaluation value for the current focus lens position from the RAM 11 through the system control unit 9.

  In S201 to S205, the NR control coefficient generation processing unit 816 generates the control gain k of the cyclic coefficient using the AF evaluation value AF_Y, the predetermined values TH1 and TH2 for the AF evaluation value, and the control value C corresponding to the noise level. .

  Here, as shown in FIG. 6, each of TH1 and TH2 is a threshold value for determining whether in the hill-climbing AF control, the in-focus state or a state greatly deviated from the in-focus state (denoted as large blur in the drawing). It is. Further, TH1, TH2, and C are read from the ROM 815 as necessary.

  In S201, the NR control coefficient generation processing unit 816 determines whether or not the AF evaluation value AF_Y is larger than a predetermined value TH1. If AF_Y is greater than TH1, the process proceeds to S202, and if not, the process proceeds to S203.

  In S202, the NR control coefficient generation processing unit 816 sets 1 to the control gain k of the cyclic coefficient.

  In S203, the NR control coefficient generation processing unit 816 determines whether the AF evaluation value AF_Y is smaller than a predetermined value TH2. If AF_Y is smaller than TH2, the process proceeds to S204. Otherwise, the process proceeds to S205.

  In S204, the NR control coefficient generation processing unit 816 sets a control value C corresponding to the noise level in the control gain k of the cyclic coefficient. (However, C> 1).

In S205, the NR control coefficient generation processing unit 816 sets the cyclic coefficient control gain k to
k = (AF_Y-TH2) * (C-1) / (TH1-TH2) +1
Set.

  In S206, the NR control coefficient generation processing unit 816 reads the initial value α of the cyclic coefficient for the luminance signal Y1 from the ROM 815 and inputs it to the cyclic coefficient control unit 812.

  In S207, the cyclic coefficient control unit 812 multiplies the initial value α by the control gain k set in S201 to S205 to generate a controlled cyclic coefficient ky.

  In S208, the noise suppression processing circuit 8 performs frame cyclic noise suppression processing using the cyclic coefficient ky generated in S207 on the luminance signal Y1. The frame recursive noise suppression processing is the same as that described in the first embodiment.

  Through the series of processes described above, the luminance signal Y2 in which noise is suppressed is generated. The color difference signals CR1 and CB1 output from the camera signal processing circuit 7 are also subjected to the same noise suppression processing as that of the luminance signal Y1, and the color difference signals CR2 and CB2 in which noise is suppressed are generated.

  Here, the present embodiment is characterized in that the strength of the noise suppression processing is controlled according to the AF evaluation value AF_Y. FIG. 7 shows the relationship between the AF evaluation value AF_Y and the control gain k of the cyclic coefficient.

  In FIG. 7, when the AF evaluation value is equal to or less than TH2, it is a “large blur” state greatly deviating from the in-focus state, so the control gain k of the cyclic coefficient is a control greater than 1 corresponding to the noise level. A value (amplification coefficient) C is set. Further, when the AF evaluation value is equal to or greater than TH1, since it is in focus, 1 is set to the control gain k of the cyclic coefficient. When the AF evaluation value is larger than TH2 and smaller than TH1, a value k ′ satisfying 1 <k ′ <C is set as the cyclic coefficient control gain k according to the value of the AF evaluation value AF_Y.

  In the present embodiment as well, noise is dominant in the high-frequency component included in the AF evaluation value during out-of-focus (during the search operation), so that it depends on the AF evaluation value AF_Y (that is, the noise level). A control value C larger than 1 is read from the ROM 815. However, a means for detecting the noise level may be provided separately.

  As described above, in this embodiment, the noise suppression strength is controlled according to the AF evaluation value used for the focus determination. As a result, a stronger noise suppression process can be performed as the AF evaluation value is smaller and the deviation from the in-focus state is larger. Therefore, even when the high-frequency component of the subject image is small or disappears, it is possible to prevent the noise from being noticeable. On the other hand, as the AF evaluation value is larger and closer to the in-focus state, noise suppression processing is performed with an intensity that takes into account the S / N specific to the image sensor. As a result, it is possible to obtain a video signal with good image quality in consideration of not only the noise suppression effect but also the resolution and afterimage.

  FIG. 8 shows the configuration of an image pickup apparatus that is Embodiment 3 of the present invention. In FIG. 8, components common to the imaging apparatus (FIG. 1) of the first embodiment are denoted by the same reference numerals as those in FIG.

  The image pickup apparatus according to the present embodiment includes an encoding / compression processing circuit 12 that encodes and compresses a video signal output from the noise suppression processing circuit 15 into a format compliant with a video signal standard such as MPEG. In addition, a recording circuit 13 for recording the video signal output from the encoding / compression processing circuit 12 on a detachable recording medium 14 such as an optical disk or a magnetic tape is provided.

  Hereinafter, an imaging operation in the imaging apparatus of the present embodiment will be described. First, when an instruction to start imaging is given by the user through the operation switch 10, the drive circuit 4 drives the lens and the diaphragm 1b in the imaging optical system 1 according to a control signal from the system control unit 9 to set an appropriate brightness. The subject image thus formed is formed on the image sensor 2.

  The image sensor 2 converts the subject image into an electrical signal by photoelectric conversion and outputs it as an analog image signal. The analog image pickup signal output from the image pickup device 2 is subjected to removal of clock synchronization noise by the CDS circuit in the AFE 3 and converted to a digital image pickup signal by the A / D converter.

  The digital image signal output from the AFE 3 is subjected to RGB separation processing, white balance processing, luminance / color difference conversion matrix processing, aperture correction processing, gamma processing, and the like in the camera signal processing circuit 7. Thereby, the luminance signal Y1 and the color difference signals CR1 and CB1 as the video signal are generated.

  The digital imaging signal output from the AFE 3 is also input to the AF evaluation value generation circuit 5. The AF evaluation value generation circuit 5 performs band pass filter processing for extracting a high-frequency component of the subject image on the digital imaging signal output from the AFE 3. The high-frequency component of the subject image obtained by the bandpass filter process is integrated in a specific area in the video screen. Thereby, an AF evaluation value signal indicating the sharpness (contrast) of the video is generated. The AF evaluation value (signal) is stored in the RAM 11 under the control of the system control unit 9.

  Further, the system control unit 9 is driven to move the focus lens 1a within a predetermined range (a range from the infinite end to the closest end or a part thereof) in order to detect a focus position based on the AF evaluation value. The circuit 4 is controlled. The focus determination circuit 6 reads an AF evaluation value from the RAM 11 every time the focus lens 1a moves by a predetermined amount. This process of searching for the in-focus position is called a search operation in the focus process.

  The focus determination circuit 6 detects the maximum AF evaluation value corresponding to each focus lens position read from the RAM 11, and determines the focus lens position when the AF evaluation value is maximum as the focus position. . The system control unit 9 transmits a control signal for driving the focus lens 1 a to the drive circuit 4 using the focus determination result of the focus determination circuit 6.

  Further, the system control unit 9 transmits a control signal AF_MODE indicating the state of the focus determination process (focus process) obtained from the focus determination circuit 6 to the noise suppression processing circuit 15.

  The noise suppression processing circuit 15 is controlled based on the control signal AF_MODE, information output from the encoding / compression processing circuit 12 (code amount F), and information output from the recording circuit 13 (free capacity D). . The noise suppression processing circuit 15 suppresses noise with respect to the luminance signal Y1 and the color difference signals CR1 and CB1 output from the camera signal processing circuit 7, and outputs the luminance signal Y2 and the color difference signals CR2 and CB2.

  The luminance signal Y2 and the color difference signals CR2 and CB2 output from the noise suppression processing circuit 15 are converted into a signal suitable for display (for example, an NTSC analog signal) and displayed on a display (not shown) in the display circuit 17. Is displayed.

  The encoding / compression processing circuit 12 encodes and compresses the luminance signal Y2 and the color difference signals CR2 and CB2 into a format based on a video signal standard such as MPEG. Here, during the encoding and compression process, the code amount F of the video signal is detected. The system control unit 9 controls the encoding / compression processing circuit 12 in accordance with the code amount F so that the code amount F falls within a predetermined range defined by the video signal standard.

  Further, the user can set the image quality in the encoding / compression processing circuit 12 by operating the operation switch 10 as the mode specifying means. For example, when the “high-quality recording mode” is set as the imaging recording mode M via the operation switch 10, the encoding / compression process is performed with a setting that minimizes image quality degradation due to encoding / compression.

  The video signal output from the encoding / compression processing circuit 12 is recorded on the recording medium 14 in the recording circuit 13. Prior to the recording process, the free space D of the recording medium 14 is detected. The system control unit 9 calculates information on the remaining capacity of the recording medium 14 such as the remaining time that can be recorded on the recording medium 14 according to the free capacity D, and displays the information on the display through the display circuit 17.

  It is also possible to specify the recording time by operating the operation switch 10 by the user. For example, when “long-time recording mode” is selected as the imaging recording mode M via the operation switch 10, the recording circuit 13 changes the file format to a low-capacity format so that recording on the recording medium 14 is possible. Change to

  Further, the information of the code amount F output from the encoding compression processing circuit 12 and the information of the free capacity D output from the recording circuit 13 are also transmitted to the noise suppression processing circuit 15 via the system control unit 9. . The code amount F and the free space D are used for controlling the noise suppression processing circuit 15 together with the control signal AF_MODE indicating the focus determination processing state.

  The configuration of the noise suppression processing circuit 15 of the present embodiment is the same as the configuration of the noise suppression processing circuit 8 described in the first embodiment. However, in this embodiment, the NR control coefficient generation processing unit 816 includes the control signal AF_MODE indicating the focus determination processing state, the code amount F, the free space D, and the imaging / recording mode M specified by the operation switch 10. Based on the above, the control gain k for controlling the cyclic coefficient is determined.

  Hereinafter, the operation of the noise suppression processing circuit 15 will be described with reference to the flowchart of FIG. Also in this embodiment, the noise suppression processing circuit 15 performs the same noise suppression processing on the luminance signal Y1 and the color difference signals CR1 and CB1. Therefore, in the following, processing for the luminance signal Y1 will be described as an example.

  When the process is started, in S300, the NR control coefficient generation processing unit 816 reads the code amount F from the encoding / compression processing circuit 12 and the free capacity D from the recording circuit 13 through the system control unit 9.

  In S <b> 301, the NR control coefficient generation processing unit 816 reads the imaging recording mode M instructed by the operation switch 10 through the system control unit 9.

  In S302, the NR control coefficient generation processing unit 816 determines whether or not the imaging recording mode M read in S301 is the “high quality recording mode”. If it is the “high quality recording mode”, the process proceeds to S303, and if not, the process proceeds to S304.

  In S303, the NR control coefficient generation processing unit 816 sets “1” in the control flag S of the noise suppression process.

  In S304, the NR control coefficient generation processing unit 816 determines whether or not the imaging recording mode M read in S301 is the “long-time recording mode”. If it is the “long-time recording mode”, the process proceeds to S303, and if not, the process proceeds to S305.

In S305, the NR control coefficient generation processing unit 816 determines whether or not the code amount F from the encoding / compression processing circuit 12 may exceed a value (specified amount) specified for the video signal. . If the code amount F is likely to exceed the specified value, the process proceeds to S303, and if not, the process proceeds to S306.

  In S306, the NR control coefficient generation processing unit 816 determines whether there is a possibility that the recording capacity in the recording medium 14 is insufficient based on the free capacity D from the recording circuit 13, that is, the free capacity is less than the scheduled recording capacity. It is determined whether or not it is small. If it is likely to be insufficient, the process proceeds to S303, and if not, the process proceeds to S307.

  In S307, the NR control coefficient generation processing unit 816 sets S = 0 to the control flag S for the noise suppression process.

  In S308, the NR control coefficient generation processing unit 816 determines whether or not S = 1. When S = 1, the process proceeds to S100 illustrated in FIG. 3, and when S = 0, the process proceeds to S103 illustrated in FIG.

  The processes after S100 and S103 are the same as those described in the first embodiment. When the process proceeds to S100, as described in the first embodiment, the control gain k of the cyclic coefficient is determined according to the control signal AF_MODE indicating the focus determination processing state.

  Through the series of processes described above, the luminance signal Y2 in which noise is suppressed is generated. The color difference signals CR1 and CB1 output from the camera signal processing circuit 7 are also subjected to the same processing as the luminance signal Y1, and the color difference signals CR2 and CB2 in which noise is suppressed are generated.

In this embodiment, when the code amount in the encoding / compression process is larger than a specified value (specified amount), when the recording medium has insufficient free space, and when the imaging / recording mode designated by the operation switch 10 is the specific mode. In addition, the noise suppression strength is controlled according to the focus determination processing state. When the in-focus determination processing state is the wobbling operation, an appropriate noise suppression process is performed to such an extent that the resolution of the subject is not impaired and an afterimage is not generated. On the other hand, when the in-focus determination processing state is the search operation, stronger noise suppression processing is performed so that noise is not noticeable in the subject image in which the high frequency component is degraded. Therefore, the S / N of the entire output video signal can be kept good in the imaging device that acquires the video while always performing the focus determination process.

  In addition, during the search operation, the temporal and spatial correlation of the subject image is low, so that afterimages and degradation in resolution are not noticeable even if noise suppression processing is applied strongly. For this reason, when the code amount of the encoding and compression process is too large, the code amount of the entire video signal can be reduced by increasing the strength of the noise suppression process for the video signal during the search operation.

  Similarly, even when the free space of the recording medium 14 is small, it is possible to reduce the scheduled recording amount of the entire video signal by increasing the strength of noise suppression processing for the video signal being searched.

  The imaging apparatus that is Embodiment 4 of the present invention differs from the imaging apparatus of Embodiment 3 only in the operation of the noise suppression processing circuit 15. For this reason, the description of the configuration of the imaging apparatus and the imaging operation is omitted here, and only the operation in the noise suppression processing circuit 15 will be described using the flowchart of FIG.

  Also in this embodiment, the noise suppression processing circuit 15 performs the same noise suppression processing on the luminance signal Y1 and the color difference signals CR1 and CB1. Therefore, in the following, processing for the luminance signal Y1 will be described as an example.

  In FIG. 10, the processes in S300 to S307 are the same as those in the third embodiment.

  In S308, the NR control coefficient generation processing unit 816 determines whether the control flag S for noise suppression processing is 1. When S = 1, the process proceeds to S200 illustrated in FIG. 5, and when S = 0, the process proceeds to S203 illustrated in FIG.

  The processes after S200 and S203 are the same as those described in the second embodiment. When the process proceeds to S200, as described in the second embodiment, the control gain k of the cyclic coefficient is determined according to the AF evaluation value.

  Through the series of processes described above, the luminance signal Y2 in which noise is suppressed is generated. The color difference signals CR1 and CB1 output from the camera signal processing circuit 7 are also subjected to the same processing as the luminance signal Y1, and the color difference signals CR2 and CB2 in which noise is suppressed are generated.

  In this embodiment, the AF evaluation is performed when the code amount in the encoding / compression process is larger than the specified value, when the recording medium has insufficient free space, and when the imaging / recording mode specified by the operation switch 10 is the specific mode. The noise suppression strength is controlled according to the value. As a result, the smaller the AF evaluation value is and the greater the deviation from the in-focus state is, the stronger noise suppression processing can be performed. Therefore, even if the high-frequency component of the subject image is small or disappears, the noise does not stand out. Can be. On the other hand, as the AF evaluation value is larger and closer to the in-focus state, noise suppression processing is performed with an intensity that considers the S / N specific to the image sensor. As a result, it is possible to obtain a video signal with good image quality in consideration of not only the noise suppression effect but also the resolution and afterimage.

  Therefore, in the imaging device that acquires the video signal while always performing the focus determination process, the S / N of the entire output video signal can be kept good.

  In addition, during the search operation, the temporal and spatial correlation of the subject image is low, so that afterimages and degradation in resolution are not noticeable even if noise suppression processing is applied strongly. For this reason, when the code amount of the encoding and compression process is too large, the code amount of the entire video signal can be reduced by increasing the strength of the noise suppression process for the video signal during the search operation.

  Similarly, even when the free space of the recording medium 14 is small, it is possible to reduce the scheduled recording amount of the entire video signal by increasing the strength of noise suppression processing for the video signal being searched.

1 is a block diagram illustrating a configuration of an imaging apparatus that is Embodiment 1 of the present invention. FIG. 2 is a block diagram illustrating a configuration of a noise suppression processing circuit according to the first embodiment. 3 is a flowchart illustrating the operation of the noise suppression processing circuit according to the first embodiment. 3 is a flowchart illustrating an operation of a focus determination circuit according to the first exemplary embodiment. 9 is a flowchart illustrating an operation of a noise suppression processing circuit in an imaging apparatus that is Embodiment 2 of the present invention. The graph which shows the relationship between AF evaluation value and a focus lens position in AF control of a hill-climbing method. 10 is a graph showing a relationship between an AF evaluation value and a cyclic coefficient control gain in the noise suppression processing circuit according to the second embodiment (and the fourth embodiment). FIG. 6 is a block diagram illustrating a configuration of an imaging apparatus that is Embodiment 3 of the present invention. 10 is a flowchart illustrating the operation of the noise suppression processing circuit according to the third embodiment. 9 is a flowchart showing the operation of a noise suppression processing circuit in an imaging apparatus that is Embodiment 4 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging optical system 1a Focus lens 2 Imaging element 3 AFE
DESCRIPTION OF SYMBOLS 4 Drive circuit 5 AF evaluation value generation circuit 6 Focus determination circuit 7 Camera signal processing circuit 8,15 Noise suppression processing circuit 9 System control part 10 Operation switch 12 Encoding compression processing circuit 13 Recording circuit 14 Recording medium

Claims (11)

Focus processing means for performing focus processing based on a signal indicating the sharpness of the image;
Noise suppression means for performing noise suppression processing on the video signal,
The focus processing means moves a focus lens to search for a focus position, and second focus processing to reciprocate the focus lens in a specific range with respect to the searched focus position. And
The image pickup apparatus, wherein the noise suppression unit makes a noise suppression strength during the first focus processing stronger than a noise suppression strength during the second focus processing . An encoding / compression unit that performs encoding / compression processing on the video signal;
When the code amount output from the encoding / compression unit is larger than a predetermined amount , the noise suppression unit converts the noise suppression strength during the first focus processing into the noise suppression strength during the second focus processing. The imaging apparatus according to claim 1, wherein the imaging apparatus is stronger than the height. Having a recording means for performing processing for recording a video signal on a recording medium;
The noise suppression means makes the noise suppression strength during the first focus processing stronger than the noise suppression strength during the second focus processing when the free space in the previous recording medium is less than the scheduled recording amount. The imaging apparatus according to claim 1 . Having a mode designation means for designating an imaging recording mode;
The noise suppression means makes the noise suppression strength during the first focus processing stronger than the noise suppression strength during the second focus processing when the designated imaging recording mode is the specific mode. The imaging apparatus according to claim 1 . Focus processing means for performing focus processing based on a signal indicating the sharpness of the image;
Noise suppression means for performing noise suppression processing on the video signal,
The image pickup apparatus , wherein the noise suppression unit changes a noise suppression strength in the noise suppression process during the focus process in accordance with a signal value indicating the sharpness. The imaging apparatus according to claim 5 , wherein the noise suppression unit decreases the noise suppression strength as the value of the signal indicating the sharpness is higher. An encoding / compression unit that performs encoding / compression processing on the video signal;
The noise suppression unit changes the noise suppression strength according to a value of a signal indicating the sharpness when a code amount output from the encoding / compression unit is larger than a specified amount. Item 7. The imaging device according to Item 5 or 6 . Having a recording means for performing processing for recording a video signal on a recording medium;
Said noise suppressing means, prior to when the free space in the recording medium is less than the recording schedule amount, according to claim 5 or 6, characterized in that to change the noise suppression strength in accordance with the state of the focus treatment Imaging device. Having a mode designation means for designating an imaging recording mode;
Said noise suppressing means, when the specified image pickup recording mode is a specific mode, and changes the noise suppression strength according to the value of the signal indicative of the sharpness claim 5 or 6 The imaging device described in 1. A focus processing step for performing focus processing based on a signal indicating the sharpness of the image;
And a noise suppression step of performing noise reduction processing for the video signal,
In the focus processing step, a first focus process for searching a focus position by moving a focus lens, and a second focus process for reciprocating the focus lens in a specific range with respect to the searched focus position And
In the noise suppression step, the noise suppression strength during the first focus processing is made stronger than the noise suppression strength during the second focus processing . A focus processing step for performing focus processing based on a signal indicating the sharpness of the image;
And a noise suppression step of performing noise reduction processing for the video signal,
In the noise suppression step, a noise suppression strength in the noise suppression process is changed during the focus process according to a value of the signal indicating the sharpness.

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