JP2016054366A - Imaging apparatus and imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus and an imaging method, capable of performing proper black level correction even when high luminance region occurs in an imaging area due to generation of a smear in an imaging apparatus using a CCD image sensor with a vertical OB (OPTICAL BLACK) area.SOLUTION: An imaging apparatus comprises: a division imaging area obtained by dividing an imaging area into a plurality of areas in a horizontal direction; and a vertical OB area that is an OB area is arranged to each division area in horizontal direction. The vertical OB area has a plurality of detection areas 17 and 18 obtained by dividing the area into a plurality of areas in the horizontal direction, and a smear determination unit part 22 that determines whether or not there is a smear in the detection area based on a signal level of the detection, a black level correction part 26 that the level signal of the detection area determined that the smear not exist in the smear determination part 22 is subtracted from the level signal of division imaging area.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an imaging apparatus and an imaging method.

  As a method for increasing the number of effective pixels in order to improve the image quality of a captured image, there is an imaging device equipped with a CCD (CHARGE COUPLED DEVICE) image sensor that reads an imaging area by dividing it into two or more, left and right or up and down. is there. Multiple imaging areas are output using different output circuits, but the amplifier characteristics are different for each output circuit, so there are differences in characteristics such as offset, linearity, sensitivity, dark noise, etc. Will occur. In addition, in the one-screen captured image obtained by combining these divided images, the division lines are conspicuous in a linear shape, and problems such as differences in color and noise between the left and right of the division lines occur.

  In order to correct such a step, a divided imaging area obtained by dividing the imaging area into a plurality of parts in the horizontal direction and an OB area (hereinafter referred to as a “vertical OB area”) provided in the horizontal direction of the divided imaging area. ), The size of the level signal of OB (OPTICAL BLACK), which is the reference signal of the image sensor, is generally acquired from the left and right OB areas, and is corrected from the difference.

As background art of this technical field, Japanese Patent Application Laid-Open No. 2009-284424 (Patent Document 1) has an imaging area divided into left and right, and an OB area divided into left and right (hereinafter, “vertical OB area”). An imaging device including the above is disclosed. In this publication, “an image pickup device 40 having effective pixel portions 42 and 44 composed of a plurality of regions having different dark current characteristics and VOB portions 43 and 45 arranged around the effective pixel portions 42 and 44, and A storage unit 26 that stores in advance the correlation between the dark current differences of the plurality of regions and the dark currents of the VOB units 43 and 45; a detection unit 14 that detects the dark currents of the VOB units 43 and 45 at the time of shooting; 26, based on the dark current difference obtained by the control unit 22 for obtaining a dark current difference of a plurality of regions at the time of photographing from the dark current of the VOB units 43 and 45 detected at the time of photographing based on the correlation stored in The correction processing unit 14 corrects the video signal obtained from the effective pixel regions 42 and 44. ”.

JP2009-284424

  However, even if an attempt is made to use the difference in level signal at the time of light shielding at the time of shooting, the level signal in the OB area varies depending on the video, and therefore the use of the difference in level signal at the time of light shielding is not necessarily an optimal correction. Therefore, it is desirable to acquire the level signal of the OB area in real time. Furthermore, when a vertical OB area is provided, it is desirable to obtain a level signal near the boundary between the left and right OB areas, that is, near the center of the vertical OB area. By doing so, it is possible to correct the level signal difference at the boundary of the imaging area with an appropriate value.

  By the way, in a camera using a CCD image sensor, when a subject extremely brighter than the surroundings is photographed, a phenomenon (smear) in which an imaging area is blown out may occur. The smear occurs in a straight line having a width substantially the same as that of the light emitting portion of the subject, perpendicular to the imaging area. Therefore, when the OB area is provided vertically, the OB area is also affected, and the level signal of the OB area cannot be accurately captured. As a result, right and left luminance level correction and black level correction cannot be appropriately performed.

  Therefore, the present invention performs an appropriate black level correction even in the case where a high-luminance area is generated in the imaging area due to the occurrence of smear or the like in an imaging apparatus using a CCD image sensor having a vertical OB area. With the goal.

In order to solve the above problems, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above-described problems. If one example is given, the present invention is characterized in that.

According to the present invention, in an imaging apparatus using a CCD image sensor having a vertical OB area, appropriate black level correction can be performed even when a high-luminance area is generated in the imaging area due to the occurrence of smear or the like. .

It is a block diagram which shows the whole structure of the imaging device by this Embodiment. The details of the black level correction circuit 16 and the signal flow in the present embodiment are shown. It is a figure at the time of dividing the level detection part L (19L) and the level detection part R (19R) into five area | regions, respectively. Details of the smear determination unit 22 and a signal flow are shown. The detail about the level | step difference correction | amendment part 25 is shown. Details of the black level correction unit 26 will be described. It is a flowchart which shows the correction method by this Embodiment.

The following examples will be described with reference to the drawings.

  In the present embodiment, an example of a monitoring system for realizing the present invention and an algorithm for correction will be described.

  FIG. 1 is a block diagram showing the overall configuration of the imaging apparatus according to the present embodiment.

  The imaging device includes a lens 1, an OB area L (2L), an OB area R (2R), an imaging area L (3L), an imaging area R (3R), an output amplifier L (4L), an output amplifier R (4R), and a CDS. (Correlated Double Sample) / AD (Analog Digital) conversion unit L (5L), CDS / AD conversion unit R (5R), iris (aperture) 6, iris control unit 7, microcomputer control unit 8, monitor display unit 12, recording The apparatus 13 includes an image LSI 14 and a solid-state image sensor 15. The image LSI 1 includes an image composition unit 9, various image processing units 10, a video output processing unit 11, and a black level correction circuit 16.

  First, the operation and signal flow during shooting and recording will be described. External light taken in from the lens 1 in FIG. The solid-state imaging device 15 includes an OB area L (2L) and an OB area R (2R), an imaging area L (3L), and an imaging area R (3R). Optical images irradiated in the OB area L (2L) and the imaging area L (2L) are output to the output amplifier L (4L). Similarly, the optical images irradiated in the OB area R (2R) and the imaging area R (3R) are output to the output amplifier R (4R). Each optical image is output as an analog signal to the CDS / AD converter L (5L) via the output amplifier L (4L) and to the CDS / AD converter R (5R) via the output amplifier R (4R). Respectively input, correlated double sampling, analog-digital conversion and output. The black level correction circuit 16 corrects the left and right black levels of the video signals output from the CDS / AD conversion unit L (5L) and the CDS / AD conversion unit R (5R). The corrected video signal is output to the image synthesizing unit 9 and converted into one output signal. The various image processing units 10 perform contour correction, white balance adjustment, noise removal, and the like, and the video output processing unit 11 It is converted into a video signal suitable for the output destination. The video signal for display is output to the monitor display unit 12 and the video signal for recording is output to the recording device 13 for display and recording processing. Further, the iris control unit 7 controls the iris 6 by the iris drive signal in accordance with the iris drive command from the microcomputer control unit 8.

  FIG. 2 shows details of the black level correction circuit 16 and the signal flow in this embodiment.

  The black level correction circuit 16 includes a level detection unit L (19L), a level detection unit R (19R), a smear determination unit 22, a black level calculation unit 20, a storage unit 24, a correction value calculation unit 23, a step correction unit 25, black The level correction unit 26 is configured.

  Here, the step correction and the black level correction are performed based on the average value of the level signal of the detection area obtained by dividing the left and right vertical OB areas into an arbitrary number n. The divided vertical OB areas will be described with reference to FIG. .

  In the present embodiment, the level detection unit L (19L) and the level detection unit R (19R) adopt a configuration in which the OB area L (2L) and the OB area R (2R) are each divided into arbitrary equal numbers of regions. To do. When the OB area L (2L) and the OB area R (2R) are each divided into n regions, in the OB area L (2L), the OB area L1 to the OB area Ln are sequentially detected from the detection area near the center of the vertical OB area. It shall be called. The level signals of the respective detection areas are set as level signal XL1 to level signal XLn. The same applies to the OB area R (2R).

  FIG. 3 shows a case where the level detection section L (19L) and the level detection section R (19R) are each divided into five areas, and the five areas on the left and right are detected areas L1 to L5 and detection areas R1 to R5, respectively. And

  Returning to FIG. 2, in the level detection unit L (19L) and the level detection unit R (19R), pixels are detected from the detection area L (52) and the detection area R (51) with the iris 6 closed when the camera is activated. The level signal XL and the level signal XR are acquired for each time. The acquired level signal XL and level signal XR are output to the black level calculation unit 20. The black level calculation unit 20 calculates average values AL0 and AR0 of the level signals in the left and right detection areas 51 and 52 based on the acquired level signal XL and level signal XR. The average values A0L and A0R are stored in the storage unit 24.

  Further, the level detection unit L (19L) and the level detection unit R (19R) acquire level signals XLn and XRn in the respective detection areas obtained by dividing the detection areas 17 and 18 into an arbitrary number n.

  The acquired level signals XLn and XRn are output to the smear determining unit 22 to determine whether smear has occurred. Then, average level signal L (AL) and level signal R (AR) of detection area L (17) and detection area R (18) determined not to have smear are acquired and output to correction value calculation unit 23. .

  Here, in any one of the detection areas L (17) and R (18), if there is smear in all detection areas, the smear determination unit 22 sets the smear detection flag 37 to 1 and sets this flag as a correction value. The result is output to the calculation unit 23 and the black level correction unit 26.

  The correction value calculation unit 23 determines the smear detection flag 37, and when it is 1, the previously used signal levels ZL and ZR are called from the storage unit 24, and the difference value 31 is calculated by (ZL-ZR). At this time, in order to store the level signals AL and AR used in the calculation in the storage unit 24, the values of the respective level signals are converted into ZL and ZR and stored in the storage unit 24. This value is updated every time the difference value 31 is rewritten by the correction value calculation unit 23.

  The step correction unit 25 receives the calculated correction value 31 and corrects the left and right luminance steps. Specifically, the level signal 35 of the left imaging area 3L and the level signal 32 of the right imaging area 3R corrected for the luminance step are output. Details of the correction processing in the step correction unit 25 will be described later with reference to FIG.

  Next, the level signal 35 and the level signal 32 output from the step correction unit 25 are output to the black level correction unit 26. The black level correction unit 26 subtracts the level signal L (AL) determined to have no smear from the level signal 35 of the left imaging area 3L and the level signal 32 of the right imaging area, thereby obtaining a luminance step. Perform the correction. Details will be described later with reference to FIG.

  Hereinafter, the smear determination unit 22, the step correction unit 25, and the black level correction unit 26 will be described with reference to the drawings.

  FIG. 4 shows details of the smear determination unit 22 and a signal flow.

  The smear determination unit 22 includes an average value calculation unit L (40L), an average value calculation unit R (40R), a difference calculation unit L (41L), a difference calculation unit R (41R), a difference determination unit L (42L), and a difference determination It comprises a part R (42R), a state comparison part L (43L), a state comparison part R (43R), and an all area smear determination part (44).

  In the smear determination unit 22, first, level signals of all pixels in the left and right detection areas (XL1 to XLn, XR1 to XRn) are input by the average value calculation unit L (40L) and the average value calculation unit R (40R). Based on XL1 to XLn and XR1 to XRn, average values ALn and ARn of level signals are calculated for each detection area.

  The difference calculation unit L (41L) and the difference calculation unit R (41R) obtain the difference value YLn between ALn and the previously acquired ZL, and the difference value YRn between ARn and the previously acquired ZR, respectively.

  Further, a difference value Y0Ln between ALn and the level signal A0L acquired at the time of activation, and a difference value Y0Rn between ARn and the level signal A0R acquired at the time of activation are calculated. These calculation results are output to the difference determination unit L (42L) and the difference determination unit R (42R), respectively.

  The difference determination unit L (42L) determines whether the difference value YLn is equal to or less than the threshold value D1, and whether the difference value Y0Ln is equal to or less than the threshold value D2. The determination result is output to the state comparison unit L (43L) as SLn. Similarly, the difference determination unit R (42R) determines whether the difference value YRn is equal to or less than the threshold value D1, and whether Y0Rn is equal to or less than D2. The determination result is output as SRn to the state comparison unit L (43L).

  When the difference values YLn and YRn are both equal to or less than the threshold value D1 and both Y0Ln and Y0Rm are equal to or less than the threshold value D2, it is determined that there is no smear. On the other hand, if any of them is greater than or equal to the threshold, it is determined that smear is present. Here, by performing the smear determination based on the difference value YLn and the difference value YRn, the smear determination can be performed in real time as compared with the case of performing the smear determination based on the difference value Y0Ln and the difference value Y0Rn.

  Next, based on the determination results SLn and SRn, the state comparison unit L (43L) and the state comparison unit R (43R) determine whether there is smear in each area. Then, the level signals in the detection area determined to have no smear are output to the correction value calculation unit 23 as AL and AR, respectively. The smear presence / absence information in each area is sent to the all-area smear determination unit (44), and when it is determined that all of the left detection area or the right detection area are smeared, the smear detection flag 37 is set to 1. This is sent to the correction value calculation part 23.

  FIG. 5 shows details of the step correction unit 25.

  The difference value 31, the level signal 35 obtained from the left video area 3L, and the level signal 36 obtained from the right video area 3R are input to the step correction unit 25. The adder provided in the step correction unit 25 adds the difference value 31 and the level signal 36, and outputs a level signal 32 of the right imaging area on which the step correction process has been performed. The level signal 35 from the left image area 3L passes through without being input to the adder. With this configuration, it is possible to obtain the level signal 32 in which the level signal 36 of the right imaging area 3R matches the luminance of the level signal 35 of the left imaging area 3L, and the difference between the left and right signal levels can be suppressed. It should be noted that the level signal can be similarly processed so that the level signal 35 of the left imaging area 3L matches the level signal 36 of the right imaging area 3R.

  FIG. 6 shows details of the black level correction unit 26.

  The black level correction unit 26 includes a black level correction value calculation unit 27, a black level correction unit L (28L), and a black level correction unit R (28R). The black level correction unit 26 receives the level signal 32 of the right imaging area corrected by the step correction unit 25 and the level signal 35 of the left imaging area, and receives the black level correction unit L (28L) and the black level correction, respectively. Input to the part R (28R).

  The smear detection flag 37 is input to the black level correction value calculation unit 27. If the smear detection flag 37 is 0 (no smear), the level signal AL is input and the black level correction unit L (28L). To the black level correction unit R (28R). Then, the black level is corrected by subtracting the level signal L (AL) determined that there is no smear from the level signal 35 of the left imaging area 3L and the level signal 32 of the right imaging area. When the level signal 36 of the right imaging area 3R is matched with the level signal 35 of the left imaging area 3L, the level signal is processed by subtracting AR from each level signal instead of AL. It is also possible to do this.

  On the other hand, when the smear detection flag 37 is 1 (smear is present), it is determined that one of the left and right or both detection areas is all smear, and the current level signal is not an appropriate value. . Therefore, ZL held in the storage unit 24 is output as an average value to the black level correction unit L (28L) and the black level correction unit R (28R). In the black level correction unit L (28L), ZL is subtracted from the level signal 35 output from the level difference correction unit 25. In the black level correction unit R (28R), ZL is subtracted from the level signal 32 output from the step correction unit 25.

  FIG. 7 is a flowchart showing a correction method according to this embodiment.

  Here, a case where the left and right detection areas are each divided into five will be described as an example.

  First, in the level detection unit L (19L) and the level detection unit R (19R), each pixel is detected from the detection area L (52) and the detection area R (51) with the iris 6 closed when the camera is activated. Respectively, the level signal XL and the level signal XR are obtained. The acquired level signal XL and level signal XR are output to the black level calculation unit 20, and the black level calculation unit 20 determines the level in each of the left and right detection areas 51 and 52 based on the level signal XL and the level signal XR. Average values AL0 and AR0 of the signal are calculated and acquired (SP1).

  Next, the level detection unit L acquires average values AL1 to AL5 of the level signal for each of the detection areas L1 to L5 (SP2).

  Similarly, the level detection unit R acquires average values AR1 to AR5 of the level signal for each of the detection areas R1 to R5 (SP2 ′).

  Next, the difference calculation unit L in the smear determination unit acquires YL1 to YL5, which are difference values between the average values AL1 to AL5 and the average value ZL used for the previous correction. (SP3).

  Similarly, the difference calculation unit R in the smear determination unit acquires YR1 to YR5, which are difference values between the average values AR1 to AR5 and the average value ZR used for the previous correction. (SP3 ').

  Further, the difference calculation unit L in the smear determination unit acquires difference values Y0L1 to Y0L5 between AL1 to AL5 and the average value A0L. (SP4).

  Similarly, the difference calculation unit R in the smear determination unit acquires difference values Y0R1 to Y0R5 from AR1 to AR5 and the average value A0R. (SP4 ').

  Next, the difference determination unit L and the difference determination unit R determine whether each detection area L and detection area R has a smear. For example, in the detection area L1, if the difference value YL1 is less than or equal to the threshold value DL1 and the difference value Y0L1 is less than or equal to the threshold value DL2, it is determined that the detection area L1 has no smear. Similarly, it is determined whether the difference values of the detection areas L2 to L5 are equal to or greater than the threshold values DL1 and DL2, respectively, and are stored in the storage unit 24 as state flags SL1 to SL5. Then, in the state comparison unit L (43L), the presence or absence of smear is determined based on the state flags SL1 to SL5, and is set to 0 when there is no smear and 1 when there is smear (SP5).

  Similarly, for each area, it is determined whether smear is present or not, and the presence or absence of smear is used as a flag, and is held as the status flags SR1 to SR5 of the detection areas R1 to R5 (SP5 ').

Next, the state comparison unit L determines whether SL1 = 0. When the detection area L1 is not smeared, it is determined that correction processing is performed using the detection area L1. If the detection area L1 is smeared, it is determined whether SL2 = 0. When the detection area L2 has no smear, it is determined to perform correction processing using the detection area L2. Similarly, when there is a smear, the detection area is sequentially moved from near the center of the vertical OB area to determine the detection area. This is because the detection area near the center is more reliable (SP6).
The detection area is similarly determined for the right detection area (SP6 ′).

  In the above description, after determining the presence or absence of smear in all the detection areas (S5, S5 ′), the detection areas used for correction are determined based on the presence or absence of smear in order from the vicinity of the center of the vertical OB area. (S6, S6 ′). However, the detection area used for correction may be determined every time the presence or absence of smear in the detection area near the center is determined. In other words, if smear is determined from near the center and there is a detection area where it is determined that there is no smear, the detection area is determined as a detection area to be corrected, and the presence or absence of smear in other detection areas is determined. Alternatively, the detection area may not be determined.

  After the left and right detection areas are determined, the all-area smear determination unit 44 determines where there is no smear anywhere in the left and right detection areas (SP7).

  In the all-area smear determining unit 44, when there is no smear in any of the left and right detection areas (YES in SP7), the level signal L (AL) of the determined detection area is stored as ZL and the level signal R (AR) is stored as ZR. Stored in the unit 24 (SP8). When there is no smear in any of the left and right detection areas, it is highly reliable to correct the detection area near the center in the vertical OB area, and therefore the detection areas are preferably the detection areas L1 and R1. .

  Then, using the level signals of the determined detection areas, the level difference correction unit performs level difference correction as described above (SP9), and then the black level correction unit performs black level correction (SP10).

  On the other hand, if either the left or right detection area is smear (SP7 NO), the difference value is calculated using the level signals ZL and ZR used last time, the step correction (SP11), and the black level. Correction is performed (SP12).

As described above, in this embodiment, it is possible to obtain a highly reliable level signal by checking the presence or absence of detection area smear and moving the detection area to a place without smear. Correction can be performed.

1 ... Lens 2L ... OB area L
2R ... OB area R
3L ... Imaging area L
3R: Imaging area R
4L ... Output amplifier L
4R: Output amplifier R
5L ... CDS / AD conversion L
5R ... CDS / AD conversion R
6 ... Iris 7 ... Iris control unit 8 ... Microcomputer control unit 9 ... Image composition unit 10 ... Various image processing units 11 ... Video output processing unit 12 ... Monitor display unit 13 ... Recording device 14 ... Image processing LSI

Claims (6)

In an imaging apparatus having a divided imaging area obtained by dividing an imaging area into a plurality of horizontal directions, and a vertical OB area that is an OB area provided in the horizontal direction for each of the divided imaging areas.
The vertical OB area has a plurality of detection areas obtained by dividing into a plurality of areas in the horizontal direction, and a smear determination unit that determines whether smear exists in the detection areas based on the signal level of each detection area; ,
A black level correction unit that subtracts the level signal of the detection area determined as having no smear in the smear determination unit from the level signal of the divided imaging area;
An imaging device comprising:
The imaging device according to claim 1,
For the plurality of detection areas, a level detection unit that acquires a signal level of each detection area,
The level detection unit sequentially acquires a signal level from a detection area located on a side where the plurality of detection areas are in contact with each other,
The said smear determination part performs a smear determination in an order from the detection area located in the side which the said several detection area touches based on the said acquired signal level.
The imaging device according to claim 2,
The smear determining unit is configured to detect smear in the detection area to be determined based on a difference between the signal level of the detection area in which it is determined that there is no smear acquired in the past and the signal level of the detection area to be determined. It is determined whether or not there is an image pickup apparatus.
The imaging device according to claim 3.
The smear determination unit is configured to determine a signal level of a detection area to be determined,
It is determined whether smear exists in the detection area to be determined based on a difference from the signal level of the divided imaging area in which the detection area is provided in a state where the iris of the imaging apparatus is closed. An imaging apparatus characterized by that.
The imaging device according to claim 1,
An image pickup apparatus comprising: a step correction unit that corrects luminance by subtracting a level signal of a detection area determined as having no smear in the smear determination unit from the signal level of the divided imaging area. .
For each divided imaging area obtained by dividing the imaging area into a plurality of parts in the horizontal direction, the vertical OB area, which is an OB area provided in the horizontal direction, has a plurality of detection areas obtained by dividing the imaging area into parts in the horizontal direction. And determining whether smear exists in the detection area based on the signal level of each detection area,
An imaging method comprising: subtracting a level signal of a detection area determined to have no smear from a level signal of the divided imaging area.