JP2009206801A - Imaging system and adjustment method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging system and an adjustment method thereof which reduce image quality deterioration while accurately extracting a face region by varying the image adjustment level of exposure/analog gain to suppress underexposure/overexposure of a signal in the face region when exposure varies. <P>SOLUTION: A digital camera 10 controls an optical system 12, a preprocessing part 16, a signal processing part 18, and a timing signal generator 24 through a system control part 20, varies adjustment levels in acquiring images to detect faces in the image of an abnormal scene including either state of backlighting or excessive front lighting by an operation control function part 64, controls at least the operation of either the optical system 12, the preprocessing part 16, or the timing signal generator 24, permits or prohibits display according to whether to perform face detection and controls the display according to whether faces are detected or not by the display control function part 66 of the system control part 20 in the continuous display mode of the images, and varies the adjustment levels using only non-display images to detect the faces. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging system and an adjustment method thereof, and in particular, the imaging system of the present invention relates to an image input apparatus capable of displaying a moving image such as a digital camera or a video camera. The present invention relates to display control in a scene such as an over-order light state, and imaging adjustment and signal processing technology that enable face detection in this scene.

  In an environment where there is a large difference in brightness between the subject and the background, such as in backlighting or over-order lighting conditions, the brightness of the subject is determined by performing an average brightness etc. on the screen and determining the exposure. There is a problem that the image of In such a situation, even if the subject includes a face, the solid-state imaging device is difficult to extract a face if the signal of the face area itself is blacked out or whitened out.

In order to avoid this problem, Patent Documents 1 and 2 disclose exposure and analog gain, face extraction by obtaining an image in which the face area is not blacked out or whiteout, and based on this result, face detection is performed. A technique of correcting so that an area is appropriately exposed is disclosed.
JP 2004-201228 JP JP 2005-347873 A

  When the above-described technique is implemented in an apparatus that continuously reads and displays images, such as moving images and through-images, the image is moved forward by changing the signal adjustment level such as exposure and gain for face extraction. It changes darker than the frame or changes brighter. For this reason, a user who uses an apparatus such as a camera is uncomfortable.

  In addition, when the solid-state imaging device increases the adjustment level and attempts to acquire an optical signal excessively, blooming may occur in the obtained image. As a result, this image may be broken. Therefore, the solid-state imaging device has a concern that not only the image quality of the image deteriorates but also face detection from the image becomes difficult.

  In view of such a problem, the present invention controls the image adjustment level of exposure / analog gain at the time of exposure fluctuation such as backlight condition or over-order light condition to suppress blackout / whiteout of the face area signal, and accuracy. An object of the present invention is to provide an imaging system and an adjustment method thereof that can reduce image quality degradation while well extracting a facial region.

  In order to solve the above-described problems, the present invention converts an optical adjustment unit including a mechanism for adjusting the amount of incident light from an object field, an imaging unit that converts the adjusted incident light into an analog electric signal, and Analog processing is performed on the analog electrical signal, the analog processed signal is converted into a digital signal and output as image data, and a face detection function for detecting a face included in the supplied image data is provided. A signal processing unit; a timing signal generating unit that generates a timing signal for operating the imaging unit and the preprocessing unit; a driving unit that generates a driving signal according to the supplied timing signal; an optical adjustment unit; a preprocessing unit; System control means for controlling the signal processing means and the timing signal generating means, and the system control means includes either back light or over-order light. For an image of an abnormal scene including such a state, an adjustment level in image acquisition is changed so as to enable detection of a face, and at least one of an optical adjustment unit, a preprocessing unit, and a timing signal generation unit In the operation control function block that controls the operation and the continuous display mode of the image processed by the signal processing means, display prohibition / display is controlled depending on whether the image is a face detection image, and the face detected image is displayed And a display control function block for controlling display prohibition of images with no face detected.

  In order to solve the above-described problems, the present invention adjusts the amount of incident light from the object field, converts the adjusted incident light into an analog electric signal, and performs analog processing on the converted analog electric signal. In the method of converting an analog processed signal into a digital signal, supplying the image data, and performing signal processing on the image data in a continuous display mode of the supplied image data to adjust imaging conditions and imaging signals The method includes a first step of setting an imaging condition and an adjustment of the imaging signal, a second step of acquiring an image according to the setting, a third step of detecting a face from the acquired image, Obtained based on the fourth step for determining whether or not the face detection is successful, the fifth step for determining whether or not the acquired image is an image obtained based on normal control, and normal control Displayed images A sixth step, a seventh step of prohibiting display of an image obtained based on abnormal control, and temporarily storing setting data of the obtained image, and determining whether or not a face is detected An eighth step of turning on face detection control in an abnormal scene according to the undetected face, and a tenth step of setting new setting data in response to the control being turned on. And returning to the second step according to each of face detection and setting of new setting data.

  According to the imaging system and the adjustment method thereof according to the present invention, the system control unit controls the optical adjustment unit, the preprocessing unit, the signal processing unit, and the timing signal generation unit, and the operation control function block selects either backlight or over-order light. For an image of an abnormal scene including such a state, an adjustment level in image acquisition is changed so as to enable detection of a face, and at least one of an optical adjustment unit, a preprocessing unit, and a timing signal generation unit Control the operation, adjust the amount of incident light from the object field by the optical adjustment means, generate a timing signal for operating the imaging means and the preprocessing means from the timing signal generation means, and supply it by the drive means Drive signal is generated according to the timing signal, and the incident light adjusted according to the drive signal supplied by the imaging means is converted into an analog electrical signal. The analog electrical signal converted by the preprocessing means is subjected to analog processing, the analog processed signal is converted into a digital signal, output as image data, and included in the image data supplied by the face detection function of the signal processing means In the continuous display mode of images processed by the signal processing means, display prohibition / display is controlled according to whether or not the face is detected by the display control function block of the system control means, The display is controlled according to the presence or absence, the image used for face detection is controlled to be non-displayed, and the brightness of the display image is varied by detecting the face by varying the adjustment level using only the non-displayed image. Therefore, it is possible to detect the face without giving the user an unpleasant feeling by controlling so that an abnormal scene where the face cannot be detected is not displayed.

  Next, an embodiment of an imaging system according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIG. 1, in the embodiment of the imaging system according to the present invention, the system control unit 20 controls the optical system 12, the preprocessing unit 16, the signal processing unit 18, and the timing signal generator 24, and the operation control function unit 64 For an image of an abnormal scene including any one of backlight and over-order light, the adjustment level in image acquisition is changed so as to enable face detection, and at least the optical system 12 and the preprocessing unit 16 and the timing signal generator 24 are controlled, the optical system 12 adjusts the amount of incident light from the object scene, and the timing signal generator 24 operates the imaging unit 14 and the preprocessing unit 16. A timing signal to be generated, a driving signal 36 is generated according to the timing signal 80 supplied by the driver 26, and the incident light 35 adjusted according to the driving signal 36 supplied by the imaging unit 14 is converted into an analog electric signal 38. In the pre-processing unit 16 The converted analog electrical signal 38 is subjected to analog processing, the analog processed signal 46 is converted into a digital signal 48, output as image data, and image data 48 supplied by the face detection function unit 54 of the signal processing unit 18 In the continuous display mode of images processed by the signal processing unit 18 and detected by the signal processing unit 18, the display control function unit 66 of the system control unit 20 controls display prohibition / display depending on whether the image is face detection. By controlling the display according to the presence or absence of face detection, in particular, controlling the image used for face detection to be non-displayed, and using only the non-displayed image to vary the adjustment level to detect the face, It is possible to perform face detection without causing discomfort to the user by controlling not to display an abnormal scene in which face detection is not possible without changing the brightness of the display image.

  In this embodiment, the imaging system of the present invention is applied to a digital camera 10. The illustration and description of parts not directly related to the present invention are omitted. In the following description, the signal is indicated by the reference number of the connecting line in which it appears.

  As shown in FIG. 1, the digital camera 10 includes an optical system 12, an imaging unit 14, a preprocessing unit 16, a signal processing unit 18, a system control unit 20, an operation unit 22, a timing signal generator 24, a driver 26, and a monitor 28. A memory card interface (IF: InterFace) unit 30 and a storage 32.

  Although not shown, the optical system 12 has a lens and a lens diaphragm, moves the position of the lens, adjusts the field angle of the field of view to a wide angle and zoom, and the incident light 34 from the field of view is adjusted by the lens diaphragm. The light beam is set to a predetermined light amount, and the converged incident light 35 is supplied to the imaging unit 14. The imaging unit 14 includes a plurality of light receiving elements that convert incident light into electrical signals, and each of the light receiving elements is formed with a microlens and a color filter segment on the incident light side. The plurality of light receiving elements are two-dimensionally arranged. The imaging unit 14 may be a CCD (Charge Coupled Device) type or a C-MOS (Complementary-Metal-Oxide Semiconductor) type. In this embodiment, the imaging unit 14 uses a CCD type imaging device. The imaging unit 14 reads out an electrical signal obtained by photoelectric conversion in accordance with a drive signal 36 supplied from a driver 26 described later. The imaging unit 14 supplies the obtained analog voltage signal 38 to the preprocessing unit 16.

  The preprocessing unit 16 includes an analog processing unit 40 and an ADC (Analog-to-Digital Converter) 42. Although not shown, the analog processing unit 38 includes a clamp circuit having a function of clamping a black level of a supplied signal, a correlated double sampling circuit having a function of removing noise, and an AGC (Automatic function having an amplification function for the signal from which noise is removed. Gain Controller). The clamp circuit, the correlated double sampling circuit, and the AGC operate according to the timing signals 44a and 44b supplied from the timing signal generator 24, and supply the clamped and noise-removed signal 46 to the ADC 42. The ADC 42 digitally converts the signal 46 and outputs image data 48. The clamp circuit turns on / off the clamp for the input signal 38 in accordance with the supplied control signal 84. The preprocessing unit 16 performs signal processing on the supplied analog voltage signal 38 and outputs image data 48 to the signal processing unit 18.

  The signal processing unit 18 has digital signal processing functions such as gamma correction, white balance processing, face detection, and parameter calculation for the supplied image data 48. The gamma correction function unit 50 is a correction process for adjusting the relative relationship of signals when the color data of the supplied image data 48 is actually output to obtain a more natural display. The gamma value in this correction is the ratio of the change in the voltage conversion value to the change in the brightness of the image, and ideally this ratio approaches 1. The gamma correction is a process for correcting these errors when it is desired to reproduce a display faithful to the original data because each device has different values depending on the characteristics of the element.

  The white balance function unit 52 is a function that corrects white to white in order to correspond to the color of the subject that changes depending on the type of light source such as sunlight or fluorescent light. The face detection function unit 54 is a processing function that extracts a human face area from a subject. In the present embodiment, the face detection function unit 54 has a function of determining whether it is in the backlight or over-order light state. The parameter calculation function unit 56 is a function for calculating how much the lens aperture and shutter speed are set based on the supplied image data 48.

  The signal processing unit 18 includes a compression / decompression processing function unit (not shown). The compression / decompression processing function unit performs compression processing on the image data that has undergone signal processing in accordance with a compression instruction, and records the image data in the storage 32. In addition, the compression / decompression processing function unit reads the compressed image data from the storage 32 in accordance with a reproduction instruction and performs decompression processing.

  The signal processing unit 18 supplies the system control unit 20 with data 60 indicating parameters, gains, and backlight or over-order light obtained by calculation via the bus 58. Further, the signal processing unit 18 uses the image data 60 signal-processed in the moving image display mode according to the control signal supplied from the system control unit 20 as a through image, and the frame selected by the monitor 28 via the bus 58. Output an image.

  The system control unit 20 has a function of controlling the optical system 12, the signal processing unit 18, the timing signal generator 24, the monitor 28, and the memory card IF unit 30 based on the data 62 supplied via the bus 58. In particular, in this embodiment, an adjustment level in image acquisition is changed so as to enable detection of a face with respect to an image of an abnormal scene including any one of backlight and excessively forward light, and the optical system. In the continuous display mode of the images processed by the operation control function unit 64 and the signal processing unit 18 for the aperture adjustment mechanism (not shown), the preprocessing unit 16 and the timing signal generator 24, monitoring is performed according to whether or not the image is a face detection image The display control function unit 66 controls display prohibition / display for 28, displays an image with a face detected, and controls display prohibition for an image with no face detected. The system control unit 20 generates a control signal based on the supplied data 62, supplies control signals 68, 70, and 72 to the optical system 12, the signal processing unit 18, and the timing signal generator 24, respectively, A control signal 70 is supplied to the processing unit 18, the monitor 28, and the memory card IF unit 30 via the bus 58 and the signal lines 60, 74, and 76, respectively.

  The system control unit 20 controls the pre-processing unit 16 to vary the analog gain, varies the speed of the electronic shutter in the timing signal generator 24, varies the exposure time per frame, and varies the drive frequency. Either the pixel addition number or the pixel thinning number of the imaging means is variably controlled according to the timing signal to be controlled and generated. Further, the system control unit 20 variably controls the aperture value set in an aperture adjustment mechanism (not shown). Further, the system control unit 20 performs control so as to cancel the control of the OB clamp for the image used for face detection. Regarding these controls, the control of the operation will be described in detail later in accordance with the signal processing.

  The operation unit 22 is set for operations such as a still image shooting mode, a moving image shooting mode, a playback mode, and a through image display in the still image shooting mode, and an instruction signal 78 is set according to the set and selected timing. To supply.

  The timing signal generator 24 has a function of generating timing signals 44a, 44b and 80 in accordance with the control signal 72. The timing signal generator 24 has a function of generating a clock to be used in accordance with the control signal 72 at a predetermined frequency. The timing signal generator 24 supplies the generated timing signals 44a, 44b, and 80 to the analog processing unit 40, the ADC 42, and the driver 26, respectively. The timing signals 44a and 44b are a sampling timing signal in correlated double sampling and a sampling timing signal in digital conversion. The timing signal 80 is a signal indicating the driving timing of the imaging unit 14.

  The driver 26 has a function of generating a drive signal corresponding to the supplied timing signal 80. The driver 26 supplies the generated drive signal 36 to the imaging unit 14.

  The monitor 28 has a function of displaying image data supplied from the signal processing unit 18 via the bus 58 and the signal line 74. As the monitor 28, a liquid crystal monitor including a monitor interface (IF) unit (not shown) is used. The monitor 28 is controlled to display or not as a frame image in accordance with the supplied control signal 70. The monitor interface (IF) unit has a function of converting image data into a format in which the liquid crystal monitor can be driven.

  The memory card IF unit 30 converts the image data supplied from the signal processing unit 18 via the bus 58 and the signal line 76 into a predetermined format and writes it, or stores the image data stored in the predetermined format from the storage 32. Data is read out via the bus 58 and the signal line 76. Therefore, the memory card IF unit 30 is interposed in the exchange of image data between the bus 58 and the storage 32.

  The storage 32 has a function of writing the image data 60 according to the supplied control signal 70 and reading the data stored in the storage 32. The storage 32 exchanges data with the memory card IF unit 30 via the signal line 82. The storage 32 includes a micro drive and a memory card.

  Next, the operation of the digital camera 10 to which the present invention is applied will be described. The shooting scene may be backlit or over-ordered. In general, in such a case, a digital camera adjusts parameters such as exposure based on the luminance of the entire image, and captures an image at an image level after gain adjustment, thereby obtaining an image. In the signal of the face area of the photographed image, so-called blackout or whiteout occurs. Therefore, the digital camera adjusts the above-described parameters within a predetermined range to adjust the signal to an appropriate signal that can detect the face in the face area.

  The conventional digital camera adjusts the signal in the face area from the state where the face cannot be detected such as a backlight scene by adjusting in this way. However, in the case of continuous shooting such as a moving image / through image in which an image obtained by this adjustment is displayed on a liquid crystal monitor, an abrupt change in image luminance causes discomfort to the user.

  With reference to FIG. 4, a procedure will be described for the operation of continuous shooting such as moving images and through images in the digital camera 10. Turn on the digital camera 10. Set to still image mode. With this setting, the digital camera 10 sets parameters and gains for shooting an image when displaying a moving image / through image (step S10). In addition, a flag is set. That is, the face detection flag A = 0, the abnormal image control flag B = 0, and the predetermined cycle flag C = 0.

  Next, incident light from the object scene is photoelectrically converted by the imaging unit 14 in accordance with the setting to obtain image data (step S12). Next, a face is detected from the acquired image data (step S14). A face in the image is detected by the face detection function unit 54 of the signal processing unit 18. The face detection function unit 54 supplies the detection result to the system control unit 20.

  Next, it is determined whether face detection is successful (step S16). The determination is performed by the system control unit 20. If the face detection is successful (YES), the process proceeds to the setting of the face detection flag A (to step S18). If face detection fails (NO), the process proceeds to a determination process of whether or not the image is a control image for face detection in backlight, that is, a backlight image (to step S20).

  Next, the system control unit 20 sets the face detection flag A to “1” in response to successful face detection (step S18).

  Next, the system control unit 20 determines whether the acquired image is a normal image according to the face detection failure (step S20). If it is determined that the image is normal (YES), the process proceeds to monitor display control (to step S22). If it is determined that the image is a backlight image among the abnormal images, the control proceeds to the abnormality handling control (to step S24).

  The display control function unit 66 performs control so that the acquired image corresponding to the signal processing unit 18 is supplied to the monitor 28, and performs control so that the acquired image supplied to the monitor 28 is normally displayed (step S22).

  Further, the display control function unit 66 performs non-display control on the monitor 28 as abnormality response control, and temporarily stores the parameters for image acquisition, that is, setting data, in a memory (not shown) (step S24).

  After each of the normal display and temporary storage processing, the process proceeds to face detection determination processing (to step S26). The face detection determination process is performed based on whether flag A = 1 or not (step S26). When the flag A = 1 (YES), it is determined that a face has been detected, it is determined that there is no problem with the set parameters, and the process proceeds to image acquisition (to step S12). When flag A = 0 (NO), the process proceeds to start of face detection control for an abnormal scene (backlight) via connectors A and B (to step S28).

  To start the abnormal face detection control, the value of the abnormal image control flag B is set to “1” (step S28). The system control unit 20 starts abnormal image control. Next, the system control unit 20 sets, as new setting data, a setting value that is changed more greatly than the setting data stored in the memory via the connector C (step S30). After this setting, the process proceeds to the acquisition of an image via the connector D (to step S12). Thereafter, the series of processes described above is repeated, and the image is displayed on the monitor 28.

  By operating in this way, when the control is performed with varying the adjustment level, the corresponding frame image is not displayed, and the frame image acquired immediately before is displayed. In the present embodiment, the procedure in the backlight state is disclosed, but the present invention is not limited to this. The image is controlled so as not to be displayed, and an image capable of detecting the face is obtained. As a result, the display image does not undergo a sudden change in luminance, so that it is possible to avoid discomfort to the user.

  Further, the digital camera 10 may perform display control so that image display and image non-display are performed periodically. This case is shown in FIG. In the case of performing display control with a predetermined cycle, as shown in FIG. 3, a determination process for determining whether or not display is set with a predetermined cycle is provided via the connector A of FIG. 2, and the process proceeds to this process (step S32). What).

  In this determination process, for example, it is determined whether or not the user setting is set to display an image on the monitor 28 at a predetermined cycle (step S32). When the flag C = 0 (NO), the process proceeds to a determination process for determining whether or not to set display at a predetermined cycle (to step S34). When the flag C = 1 (YES), it is determined that the display control has been set for a predetermined cycle, and the process proceeds to the face detection control process via the connector B (to step S28).

  In the display control setting determination, as a user setting, for example, when a predetermined button is pressed, the interrupt process is activated and it is determined whether or not the control is set to display in a predetermined cycle (step S34). When the user selects to set display control at a predetermined cycle, the digital camera 10 sets the value of the flag C to “1” (step S36). In addition, although the interrupt process is functional, if it is selected not to set the display control at a predetermined cycle, the digital camera 10 sets the value of the flag C to “0” (step S38). .

  The digital camera 10 receives the setting of the flag C = 1, and sets display control at a predetermined cycle in the display control function unit 66 (step S40). Display control may display 1 sheet or display M sheets during a cycle of N sheets. Specifically, control may be performed so that the level is variably adjusted in succession, not one at a time. After this setting, the digital camera 10 proceeds to the level adjustment setting via the connector E (to step S10). Further, the digital camera 10 receives the setting of the flag C = 0, and proceeds to the face detection control process via the connector B (to step S28).

  In this way, a step-by-step image frame is periodically displayed, a step-by-step image frame whose adjustment level is variably controlled is hidden, and a previous image frame is displayed in the non-display image frame. As a result, not only does the user feel uncomfortable due to the image display of a sudden change in brightness, but the user can also reduce the discomfort of the user because the period during which the continuous image such as a moving image stops like a frame advance can be shortened. Can do.

  Moreover, although the procedure mentioned above illustrated the case of backlight as an abnormal scene, it respond | corresponds in the case of excessive order light. After the abnormal image control is started by the system control unit 20, as shown in FIG. 4, the system control unit 20 controls the analog gain to be smaller than the setting data stored in the memory via the connector C. The set value is set as new setting data (step S30a). In this case, the system control unit 20 outputs a control signal 84 for reducing the analog gain to the analog processing unit 40 as shown in FIG. After this setting, the process proceeds to acquisition of an image via the connector D (to step S12), and the series of processes described above is repeated to display the image on the monitor 28.

  With this control, the digital camera 10 can detect the face of the face area signal by increasing the analog gain for the black face area signal and decreasing the analog gain for the white face area signal. It can be set to an appropriate level.

  Similarly, in the case of excessive forward light, after the abnormal image control is started by the system control unit 20 in the above-described procedure, the system control unit 20 stores in the memory via the connector C as shown in FIG. The set value controlled to increase the electronic shutter speed faster than the set data is set as new set data (step S30b). As shown in FIG. 1, the system control unit 20 controls the timing signal generator 24 with a control signal 72, and outputs a timing signal 80 having a higher electronic shutter speed than the setting data stored in the memory to the driver 26. Thereby, the imaging unit 14 decreases the exposure amount. As shown in FIG. 1, the system control unit 20 controls the timing signal generator 24 with a control signal 72 and outputs a timing signal 80 whose electronic shutter speed is slower than the setting data stored in the memory to the driver 26 when backlit. . Thereby, the imaging unit 14 increases the exposure amount. After this setting, the process proceeds to acquisition of an image via the connector D (to step S12), and the series of processes described above is repeated to display the image on the monitor 28.

  By this control, the digital camera 10 can set the face area signal to a level at which face detection is possible during over-forward light and backlight.

  Next, an embodiment of another procedure for dealing with back light and excessive forward light in the digital camera 10 will be described. The display and non-display procedures are basically the same as the procedure in FIG. The difference here is handled in the case of backlight as an abnormal scene. After the abnormal image control is started by the system control unit 20, the system control unit 20 makes the electronic shutter speed slower than the setting data stored in the memory via the connector C as shown in FIG. A setting value controlled so as to arbitrarily set the exposure time per frame to one frame time or more is set as new setting data (subroutine SUB1). After this setting, the process proceeds to acquisition of an image via the connector D (to step S12), and the series of processes described above is repeated to display the image on the monitor 28.

  Next, the setting of the exposure time will be described with reference to FIG. 7 (subroutine SUB1). In order to make the electronic shutter speed slower than the setting data stored in the memory, the Tv (Time value) value represented by the electronic shutter is decreased by ΔTv (substep SS10). This reduction slows down the shutter speed, meaning that the exposure time becomes longer.

  Next, the exposure time is determined (substep SS12). If the Tv value represented by the electronic shutter is smaller than the predetermined value X (YES), it is determined that the exposure time has become longer than the exposure time of one frame, and the process proceeds to setting the exposure time (go to sub-step SS14). The predetermined value X is, for example, an exposure time in the number of frames that the digital camera 10 generates in advance for one second in a moving image. If the Tv value represented by the electronic shutter is equal to or greater than the predetermined value X (NO), the operation is continued with this set value, and the process proceeds to return.

  Next, the exposure time is set by the system control unit 20 controlling the timing signal generator 24 with the control signal 72 as shown in FIG. 1, and the timing signal 80 having an electronic shutter speed slower than the setting data stored in the memory. Is generated by the timing signal generator 24. The timing signal generator 24 outputs the generated timing signal 80 to the driver 26. Thereby, the imaging unit 14 increases the exposure amount. After this setting, proceed to return.

  As described above, after setting the exposure time, the process proceeds to the acquisition of an image via the connector D (to step S12). FIG. 8 shows the relationship between the exposure time setting (SUB1) and the read transfer period. FIG. 8 (a) shows that the exposure period does not straddle the frames as indicated by the arrows, that is, each exposure time is within the exposure time scheduled for one frame. Therefore, it can be seen that the readout of the signal charge generated by exposure is transferred within the next frame period.

  On the other hand, FIG. 8B shows that the exposure period indicated by the arrow may extend over a plurality of frames, that is, each exposure time may be longer than the exposure time scheduled for one frame. This is the case for frame B and frame D. As described above, when the exposure time is set to be long, even if the reading of the frame A is completed as an example, the frame B is still under exposure, so the reading of the signal charge waits until the exposure of the frame B is completed. Even if the time per frame is increased, the read transfer time is the same, so that the read transfer time of the previous frame is increased by the length. Therefore, smear sweeping may be performed during the remaining waiting period, the time from the completion of reading frame A to the completion of exposure of frame B. As a result, the digital camera 10 can prevent deterioration due to smearing on the next read image.

  The exposure time may be set freely as 1.5 times, 2 times, 3 times, 4 times, and so on.

  By operating in this way, the exposure time can be increased by further increasing the exposure time when the face area is very dark, and the image can be output as an image more suitable for face detection.

  Moreover, a present Example is a case of over-order light as an abnormal thorn. After the abnormal image control is started by the system control unit 20, the system control unit 20 increases the electronic shutter speed faster than the setting data stored in the memory via the connector C as shown in FIG. A setting value controlled so as to arbitrarily set the exposure time per frame to less than half of one frame time is set as new setting data (subroutine SUB2). After this setting, the process proceeds to acquisition of an image via the connector D (to step S12), and the series of processes described above is repeated to display the image on the monitor 28.

  Next, the setting of the exposure time will be described with reference to FIG. 10 (subroutine SUB2). In order to make the electronic shutter speed faster than the setting data stored in the memory, the Tv (Time value) value represented by the electronic shutter is increased by ΔTv (substep SS20). This increase increases the shutter speed, which means that the exposure time is shortened.

  Next, the exposure time is determined (substep SS22). If the Tv value represented by the electronic shutter is greater than the predetermined value Y (YES), it is determined that the exposure time has become shorter than half of the exposure time in one frame, and the process proceeds to the setting of the exposure time (to sub-step SS24). The predetermined value Y is, for example, a 1/2 exposure time in the number of frames that the digital camera 10 generates in advance for one second in a moving image. If the Tv value represented by the electronic shutter is equal to or greater than the predetermined value Y (NO), the operation is continued with this set value, and the process proceeds to return.

  Next, in setting the exposure time, the system control unit 20 controls the timing signal generator 24 with a control signal 72 as shown in FIG. 1, and a timing signal 80 having an electronic shutter speed faster than the setting data stored in the memory. Is generated by the timing signal generator 24. The timing signal generator 24 selects a driving frequency used for generating the timing signal, for example, a driving frequency that is twice as fast as a normal driving frequency, and generates a timing signal. The timing signal generator 24 outputs the generated timing signal 80 to the driver 26. Thereby, the imaging unit 14 decreases the exposure amount. After this setting, proceed to return.

  As described above, after setting the exposure time, the process proceeds to the acquisition of an image via the connector D (to step S12). FIG. 11 shows the relationship between the drive frequency, exposure time setting (SUB2), and readout transfer period. In FIG. 11 (a), the exposure time is indicated by an arrow. The digital camera 10 sets the drive frequency to 20 MHz and exposes the incident light from the object scene to the imaging unit 14 regardless of the length of the exposure time. Therefore, it can be seen that the readout of the signal charge generated by exposure is transferred within the next frame period.

  On the other hand, FIG. 11 (b) shows that the exposure period indicated by the arrow may be less than the planned half exposure time in one frame. The system controller 20 in this embodiment uses a timing signal generator so that a double frequency is used as the driving frequency in the exposure of the frames B, C, E, F, H, and I shown in FIG. 24 is controlled by a control signal 72. The signal charges of the frames A, B, D, E, G, and H require half the read transfer time because the drive frequency used at the time of exposure is applied. Frames A, D and G are displayed on the monitor 28.

  In this way, not only can the time per frame of the image with the changed image adjustment level be shortened to increase the number of image frames to be acquired, but the image frame with a short readout transfer period can be compared with normal driving. Since the amount of smear can be reduced and image quality deterioration can be reduced, the digital camera 10 can output an image more suitable for face detection.

  Further, the digital camera 10 may control the aperture to the small aperture side in the case of excessive forward light, and control the aperture to the open side in the case of backlight. That is, after starting abnormal image control in the system control unit 20, as shown in FIG. 12, the system control unit 20 is connected to the setting data stored in the memory in the determination of overorder light via the connector C. A set value that is controlled to increase the aperture value and reduce the amount of incident light is set as new set data (step S30c). In this case, although not shown, the system control unit 20 outputs a control signal that causes the aperture adjustment driver of the optical system 12 to operate in the direction of narrowing the aperture. After this setting, the process proceeds to acquisition of an image via the connector D (to step S12), and the series of processes described above is repeated to display the image on the monitor 28.

  In the case of backlight, after starting abnormal image control in the system controller 20, via the connector C, the system controller 20 uses the setting data stored in the memory for determination of backlight as shown in FIG. A setting value that is controlled to increase the amount of incident light by decreasing the aperture value is set as new setting data (step S30d). In this case, although not shown, the system control unit 20 outputs a control signal that causes the aperture adjustment driver of the optical system 12 to operate the aperture in the open side direction. After this setting, the process proceeds to acquisition of an image via the connector D (to step S12), and the series of processes described above is repeated to display the image on the monitor 28.

  In this way, the amount of signal in the face area can be adjusted by controlling the aperture to the open side during backlighting, and to the small aperture side during excessive light, so that it can be output as an image more suitable for face detection. it can.

  Further, as another procedure, in the case of backlighting, after starting abnormal image control in the system control unit 20, the system control unit 20 determines the backlighting via the connector C as shown in FIG. The set value controlled to increase the signal charge amount obtained by increasing the pixel addition by S times than the setting data stored in the memory is set as new setting data (step S30e). In this case, the system control unit 20 outputs a control signal 72 that causes the timing signal generator 24 to perform pixel addition. The timing signal generator 24 generates a timing signal so as to add pixels in accordance with the control signal 72. The timing signal generator 24 outputs the generated timing signal 80 to the driver 26. Thereby, the imaging unit 14 increases the signal charge amount by addition while reducing the number of pixels. The imaging unit 14 reads out pixels by the reciprocal of the ratio reduced by the addition in accordance with the increase in the number of pixel additions by the drive signal 36 from the driver 26 so that the final number of pixel signals becomes constant. .

As a specific example, when the total number of pixels is 8 million and the pixel addition number 3 is increased to 2 ³ = 8, the number of pixels to be read is set to 1 million pixels. For example, the digital camera 10 sets the image to a fixed number of pixels so that the final number of pixel signals is set to 1 million pixels.

  For example, the imaging unit 14 increases the signal charge amount by S times by pixel addition. After this setting, the process proceeds to acquisition of an image via the connector D (to step S12), and the series of processes described above is repeated to display the image on the monitor 28. In the case of excessive forward light, the number of pixel additions should be reduced.

  In the case of over-order light, after starting abnormal image control in the system control unit 20, the system control unit 20 stores in the memory in the determination of over-order light via the connector C as shown in FIG. A setting value that is controlled so as to reduce the amount of signal charge obtained by thinning out pixels from the setting data is set as new setting data (step S30f). In this case, the system control unit 20 outputs a control signal 72 for thinning out pixels. The timing signal generator 24 generates a timing signal so as to thin out pixels in accordance with the control signal 72. The timing signal generator 24 outputs the generated timing signal 80 to the driver 26. Thereby, in this case, the imaging unit 14 increases the pixel thinning number and decreases the signal charge amount.

  Here, the pixel thinning-out number is a pixel thinning-out number that is performed by the imaging device for reading speed. After this setting, the process proceeds to image acquisition via the connector D (to step S12), that is, the system control unit 20 sends a control signal 72 for increasing the signal charge amount to 1 / S times, for example, to the timing signal generator 24. Output. The timing signal generator 24 supplies the generated timing signal 80 to the driver 26. The driver 26 supplies the generated drive signal 36 to the imaging unit 14. The imaging unit 14 outputs an image signal 38 captured according to the supplied drive signal 36 to the preprocessing unit 16. Thus, the digital camera 10 repeats the series of processes described above and displays an image on the monitor 28.

  Note that pixel addition and thinning are not limited to the imaging unit 14, and may be performed by the signal processing unit 18 as long as the real-time property of the through image display is not impaired. In this case, since processing can be performed by calculation for each pixel data, face detection can be performed without impairing the resolution of the face area.

  In this way, the amount of signal charge per pixel can be adjusted by increasing the number of pixel additions during backlighting and decreasing the number of pixel additions during excessive forward lighting, and output as an image more suitable for face detection. Can do. When the number of pixel additions increases, pixels are read out by the reciprocal number accordingly, and driving is performed so that the final number of pixel signals is constant, so that there is no fluctuation in resolution due to pixel addition, and the number of pixel additions It is not necessary to prepare for each face detection control.

  By the way, if the exposure is varied in the backlight state and the signal charge amount is increased, a blooming phenomenon may occur. In a high-luminance part such as a backlit background, if the amount of signal charge increases excessively and exceeds a saturation level that can be stored in the light receiving element, the signal charge may leak into the OB (Optical Black) pixel region. When this charge leakage occurs, the black level to be clamped in the digital camera 10 changes.

  Here, since the pixel signal obtained from the floating OB area caused by charge leakage is set as the black level, the read signal line should normally be obtained by the amount of the floating signal using this black level. As a result, an image in a broken state is acquired.

  Next, a procedure will be described with reference to FIG. 16 on how to adjust the black level to be clamped for an image having such a backlight or over-order light state. In this case, the control of the OB clamp is freely switched through the connector A (step S42). Actually, at the same time when the control for changing the image adjustment level is entered, the control is switched to the control without OB clamping. That is, the system control unit 20 supplies the analog processing unit 40 with a control signal 84 for switching to control without OB clamping.

  Further, the system control unit 20 supplies a control signal 72 for switching to the control not to perform OB clamping to the timing signal generator 24, and the timing signal generator 24 transmits an OB clamp ON / OFF control signal to the analog signal processing unit 40. And may be controlled.

  Thereafter, the process proceeds to a determination of whether or not to set the display with a predetermined cycle (to step S32).

  In this way, not only the adjustment of the image level is changed so that the face can be detected even in the backlit state or the excessively forward lighted state, but by switching to the control without OB clamping at the time of control, from the high luminance region exceeding the saturation level Image blooming due to blooming or signal charge leakage can be avoided, and an image suitable for face detection can be output.

  Further, the OB clamp off control is not limited to the above-described procedure. As shown in FIG. 17, after the setting of new setting data (step S30), the OB clamp control is freed (step S42). ). As a result, control is performed so that only the person who does not display an image does not perform OB clamping, and when displaying an image, control is performed so that OB clamping is performed for each image frame as usual.

  Without OB clamping, as shown in FIG.18A, the digital camera 10 has a tendency that the device accuracy of the analog signal processing unit fluctuates due to the heat generation of the device itself and the change of the environmental temperature, and the clamp level tends to shift with time, Clamp level varies. If the clamp level is deviated, the black level is also deviated, leading to image quality degradation.

  On the other hand, as shown in FIG. 18B, the digital camera 10 controls the operation according to the presence or absence of display by the system control unit 20, and performs OB clamping at the positions of arrows 86, 88, and 90. This periodic OB clamp control can reduce this clamp level fluctuation.

  In this way, when controlling to change the image adjustment level so that the face can be detected even in the backlight / over-order light state, by switching to the control that does not clamp only the image that is not displayed, the fluctuation of the clamp level can be reduced, When combined with the previous procedure, it is possible to avoid black level fluctuation due to blooming for an image not to be displayed, and to output an image more suitable for face detection.

It is a block diagram which shows the schematic structure of the Example in the digital camera to which the imaging system which concerns on this invention is applied. 2 is a flowchart of an operation procedure in the digital camera shown in FIG. 1. 3 is a flowchart showing display setting and control setting procedures in a predetermined cycle in the operation procedure in the digital camera shown in FIG. 2. 3 is a flowchart of a main part showing a specific setting procedure in new setting data in the digital camera shown in FIG. 2. 3 is a flowchart of a main part showing a specific setting procedure in new setting data in the digital camera shown in FIG. 2. FIG. 3 is a flowchart of a main part showing a specific setting procedure (subroutine SUB1) in new setting data in the digital camera shown in FIG. 2; FIG. It is a flowchart showing the specific setting procedure in the new setting data with the digital camera shown in FIG. 2 is a timing chart showing a relationship between an exposure time and a read transfer period in the digital camera shown in FIG. FIG. 3 is a flowchart of a main part showing a specific setting procedure (subroutine SUB2) in new setting data in the digital camera shown in FIG. 2; FIG. 10 is a flowchart showing a specific setting procedure in new setting data in the digital camera shown in FIG. 9. 2 is a timing chart showing a relationship among a drive frequency, an exposure time, and a read transfer period in the digital camera shown in FIG. 3 is a flowchart of a main part showing a specific setting procedure in new setting data in the digital camera shown in FIG. 2. 3 is a flowchart of a main part showing a specific setting procedure in new setting data in the digital camera shown in FIG. 2. 3 is a flowchart of a main part showing a specific setting procedure in new setting data in the digital camera shown in FIG. 2. 3 is a flowchart of a main part showing a specific setting procedure in new setting data in the digital camera shown in FIG. 2. It is a flowchart of the principal part showing the position of the free control of the OB clamp added to the digital camera shown in FIG. It is a flowchart of the principal part showing the position of the free control of the OB clamp added to the digital camera shown in FIG. It is a figure showing the fluctuation | variation of the clamp level by the free control of a clamp in the digital camera shown in FIG. It is a figure showing the fluctuation | variation of the clamp level at the time of clamp control being turned on regularly in the digital camera shown in FIG.

Explanation of symbols

10 Digital camera
12 Optical system
14 Imaging unit
16 Preprocessing section
18 Signal processor
20 System controller
22 Operation unit
24 Timing signal generator
26 Drivers
28 Monitor
64 Operation control function section
66 Display control function

Claims (19)

Optical adjustment means including a mechanism for adjusting the amount of incident light from the object scene;
Imaging means for converting the adjusted incident light into an analog electrical signal;
Preprocessing means for performing analog processing on the converted analog electrical signal, converting the analog processed signal into a digital signal, and outputting the image data;
Signal processing means having a face detection function for detecting a face included in the supplied image data;
Timing signal generating means for generating a timing signal for operating the imaging means and the preprocessing means;
Driving means for generating a driving signal in accordance with a supplied timing signal;
System control means for controlling the optical adjustment means, the preprocessing means, the signal processing means and the timing signal generating means,
The system control means changes an adjustment level in the acquisition of the image so as to enable detection of the face with respect to an image of an abnormal scene including any one of backlight and over-order light, and at least An operation control function block for controlling the operation of any of the optical adjustment means, the preprocessing means, and the timing signal generation means;
In the continuous display mode of the image processed by the signal processing means, display prohibition / display is controlled according to whether or not the image is a face detection image, the face detected image is displayed, and a face undetected image is displayed. An imaging system comprising: a display control function block for prohibition control.   The imaging system according to claim 1, wherein the system control unit varies an analog gain of the preprocessing unit.   2. The imaging system according to claim 1, wherein the system control unit varies the exposure time per frame by varying the speed of the electronic shutter in the timing signal generating unit.   The imaging system according to claim 1, wherein the system control unit varies a driving frequency in the timing signal generation unit.   The imaging system according to claim 1, wherein the system control unit varies an aperture value set in the optical adjustment unit.   2. The system according to claim 1, wherein the system control unit varies one of a pixel addition number and a pixel thinning number of the imaging unit in accordance with a timing signal generated by the timing signal generation unit. Imaging system.   The imaging system according to claim 1, wherein the system control unit cancels the control of the optical black clamp on the image used for the face detection. Adjust the amount of incident light from the object field, convert the adjusted incident light into an analog electrical signal, apply analog processing to the converted analog electrical signal, convert the analog processed signal into a digital signal, In a method of supplying signal processing as image data and performing signal processing on the image data in a continuous display mode of the supplied image data and adjusting imaging conditions and imaging signals, the method includes:
A first step of setting the imaging condition and the adjustment of the imaging signal;
A second step of acquiring an image according to the setting;
A third step of detecting a face from the acquired image;
A fourth step of determining whether the detection of the face is successful;
A fifth step of determining whether the acquired image is an image obtained based on normal control;
A sixth step of displaying an image obtained based on normal control;
A seventh step of prohibiting display of an image obtained based on abnormal control and temporarily storing setting data of the obtained image;
An eighth step of determining whether or not the face is detected;
A ninth step of turning on face detection control in an abnormal scene according to the undetected face;
A tenth step of setting new setting data in response to turning on of the control,
An imaging adjustment method, wherein the process returns to the second step in accordance with each of the detection of the face and the setting of the new setting data. The method according to claim 8, wherein the method includes an eleventh step of determining whether or not the display is performed in a predetermined cycle before the ninth step;
In the case of prohibiting setting the display at the predetermined cycle, a twelfth step of determining whether or not to set the display at the predetermined cycle;
A thirteenth step of setting and controlling display at the predetermined cycle;
A 14th step of setting to prohibit display in the predetermined cycle,
In this method, when the display at the predetermined cycle is set and after the 14th step, the process proceeds to the 9th step, and after the 13th step, the process proceeds to the first step. Method.   9. The imaging adjustment method according to claim 8, wherein the tenth step sets setting data for decreasing the analog gain.   9. The imaging adjustment method according to claim 8, wherein the tenth step sets the electronic shutter faster than the stored value.   9. The imaging adjustment method according to claim 8, wherein the tenth step sets the exposure time to one frame or more.   9. The imaging adjustment method according to claim 8, wherein in the tenth step, the driving frequency is made faster than the stored value and the exposure time is set to be shortened.   9. The imaging adjustment method according to claim 8, wherein the tenth step sets the aperture value to be larger than the stored value.   9. The imaging adjustment method according to claim 8, wherein the tenth step sets the aperture value to be smaller than the stored value.   9. The imaging adjustment method according to claim 8, wherein the tenth step sets the number of pixel additions to be larger than the stored value.   9. The imaging adjustment method according to claim 8, wherein in the tenth step, the number of pixel thinning is set to increase from the stored value.   9. The imaging adjustment method according to claim 8, wherein the optical black clamping control is made free before the eleventh step.   19. The imaging adjustment method according to claim 8, wherein the optical black clamping control is made free after the tenth step.

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