This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-193412, filed on Sep. 3, 2012; the entire contents of all of which are incorporated herein by reference.
Embodiments relate generally to an image processing device, an image processing method, and a solid-state imaging device.
High dynamic range (HDR) synthesis is known as a shooting technique for expressing a dynamic range wider than that of a normal shooting technique. As a technique for HDR synthesis, for example, there is a technique for acquiring a long-time exposure image signal and a short-time exposure image signal configured such that charge accumulation times are different from each other and generating a synthesized image. In a solid-state imaging device, when HDR synthesis images are captured and an auto exposure (AE) operation is controlled, a complicated calculation process is required for the long-time exposure image signal and the short-time exposure image signal. Therefore, there is a problem of an increase a circuit size or an increase in a processing time.
In general, according to an embodiment, an image processing device includes a high dynamic range synthesizing unit, an exposure value calculating unit, and a control amount converting unit. The high dynamic range synthesizing unit generates a synthesized image by synthesizing first image signal and second image signal. The first image signal is an image signal in accordance with an amount of light incident on a first pixel during a first charge accumulation period. The second image signal is an image signal in accordance with an amount of light incident on a second pixel during a second charge accumulation period. The second charge accumulation period is shorter than the first charge accumulation period. The exposure value calculating unit calculates an exposure value to which a lightness adjustment amount is reflected. The lightness adjustment amount is an adjustment amount used to adjust the lightness of the synthesized image in accordance with illuminance at the time of shooting. The control amount converting unit converts the exposure value into control amounts for an electronic shutter time, an analog gain, and a digital gain. The exposure value calculating unit includes a main control exposure value calculating unit and a sub-control exposure value calculating unit. The main control exposure value calculating unit calculates a main control exposure value based on a signal designated as a main control signal between the first image signal and second image signal. The main control exposure value is the exposure value for the main control signal. The sub-control exposure value calculating unit calculates a sub-control exposure value. The sub-control exposure value is the exposure value for a sub-control signal. The sub-control signal is one of the first image signal and second image signal other than the main control signal. The sub-control signal causes the main control signal to follow lightness adjustment. The sub-control exposure value calculating unit multiplies the main control exposure value calculated by the main control exposure value calculating unit by a high dynamic range magnification and sets the multiplication result as the sub-control exposure value. The high dynamic range magnification is set in advance as a ratio of the first charge accumulation period to the second charge accumulation period.
Hereinafter, an image processing device, an image processing method, and a solid-state imaging device according to embodiments will be described in detail with reference to the attached drawings. Further, the invention is not limited to the embodiments.
A digital camera 1 includes a camera module 2 and a post stage processing unit 3. The camera module 2 includes an imaging optical system 4 and a solid-state imaging device 5. The post stage processing unit 3 includes an image signal processor (ISP) 6, a storage unit 7, and a display unit 8. The camera module 2 is applied not only to the digital camera 1 but also to, for example, an electronic device such as a camera-attached portable terminal.
The imaging optical system 4 acquires light from a subject and forms a subject image. The solid-state imaging device 5 captures the subject image. The ISP 6 performs signal processing on an image signal obtained through the imaging performed by the solid-state imaging device 5. The storage unit 7 stores an image subjected to the signal processing by the ISP 6. The storage unit 7 outputs the image signal to the display unit 8 in response to a user's operation or the like. The display unit 8 displays the image according to the image signal input from the ISP 6 or the storage unit 7. The display unit 8 is, for example, a liquid crystal display.
The solid-state imaging device 5 is, for example, a complementary metal oxide semiconductor (CMOS) image sensor. The solid-state imaging device 5 may be a charge coupled device (CCD) as well as the CMOS image sensor. The solid-state imaging device 5 includes a pixel array 10, a preprocessing unit 11, an imaging processing circuit 12, an interface (I/F) 14, a timing generator 15, and an auto exposure (AE) control circuit 16.
In the pixel array 10, the light acquired by the imaging optical system 4 is converted into a signal charge by a photodiode to capture a subject image. For example, the pixel array 10 generates an analog image signal by acquiring signal values of respective color components of red (R), green (G), and blue (B) in the order corresponding to a Bayer array.
The preprocessing unit 11 performs correlated double sampling, an analog gain (AG) and a digital gain (DG) amplification, analog-to-digital conversion (AD conversion) on the image signal from the pixel array 10.
The imaging processing circuit 12 performs various kinds of signal processing on the digital image signal input from the preprocessing unit 11. The imaging processing circuit 12 includes a high dynamic range (HDR) synthesizing unit 13. The HDR synthesizing unit 13 performs HDR synthesis on the digital image signal input to the imaging processing circuit 12 to generate a synthesized image. The imaging processing circuit 12 performs not only the HDR synthesis by the HDR synthesizing unit 13 but also signal processing such as defect correction, noise reduction, shading correction, and white balance adjustment.
The I/F 14 outputs the image signal subjected to the signal processing by the imaging processing circuit 12. The I/F 14 performs a process of transmitting the image signal to an external device, for example, appropriately performs conversion from serial data to a parallel output or conversion from an parallel input to serial data.
The AE control circuit 16 controls the AE operation of the digital camera 1 according to lightness at the time of shooting. The AE control circuit 16 transmits data of the AG and the DG to the preprocessing unit 11. The AE control circuit 16 transmits data of an electronic shutter time (ES) to the timing generator 15. The imaging processing circuit 12 and the AE control circuit 16 function as an image processing device. The timing generator 15 outputs a pulse used to drive the pixel array 10.
In the pixel array 10, charge accumulation periods are set to be alternately different for each line area including two horizontal lines of a Gr/R line and a B/Gb line. A first charge accumulation period which is a charge accumulation period of a long-time exposure line area (first line area) 17 is longer than a second charge accumulation period which is a charge accumulation period of a short-time exposure line area (second line area) 18.
The long-time exposure line area 17 includes two horizontal lines formed by long-time exposure pixels which are first pixels. The short-time exposure line area 18 includes two horizontal lines formed by short-time exposure pixels which are second pixels. The long-time exposure line area 17 and the short-time exposure line area 18 are alternately disposed in the vertical direction.
The long-time exposure pixel detects the amount of incident light during the first charge accumulation period. The short-time exposure pixel detects the amount of incident light during the second charge accumulation period. The pixel array 10 outputs a long-time exposure image signal (a first image signal) according to the amount of incident light on the long-time exposure pixels during the first charge accumulation period and a short-time exposure image signal (a second image signal) according to the amount of incident light on the short-time exposure pixels during the second charge accumulation period. The HDR synthesizing circuit 13 synthesizes the long-time exposure image signal and the short-time exposure image signal input to the imaging processing circuit 12.
When the amount of incident light is equal to or less than the saturated light amount I0, the signal level of a long-time exposure image signal S1 increases in proportion to an increase in the amount of incident light. When the amount of incident light is greater than the saturated light amount I0, the signal level of the long-time exposure image signal S1 is constant. Even when the amount of incident light is greater than the saturated light amount I0, the signal level of the short-time exposure image signal S2 increases in proportion to an increase in the amount of incident light.
The HDR synthesizing unit 13 multiplies the short-time exposure image signal S2 by a predetermined HDR magnification to cause the output level of the long-time exposure pixel to coincide with the output level of the short-time exposure pixel. The HDR magnification corresponds to an exposure ratio which is a ratio of the first charge accumulation period of the long-time exposure pixel to the second charge accumulation period of the short-time exposure pixel. The HDR synthesizing unit 13 generates a synthesized image signal S through an interpolation process using the long-time exposure image signal S1 and the short-time exposure image signal S2 multiplied by the HDR magnification.
The horizontal axis of the illustrated graph represents illuminance. The illuminance is assumed to be lowered from the left to the right of the horizontal axis direction. The AE control circuit 16 increases the adjustment amount of the signal level because a signal level increases as the illuminance is lowered at the time of shooting. In the drawing, a portion indicated by a tone represents an adjustment amount of the signal level according to the ES, a portion indicated by a diagonal line represents an adjustment amount of the signal level according to the DG, and a portion indicated by a hatching represents an adjustment amount of the signal level according to the AG.
In the camera module 2, so-called flicker in which lightness and darkness of an image is changed due to a power frequency of a fluorescent lamp supplying illumination light may occur at the time of indoor shooting. The camera module 2 can suppress the flicker by adjusting the ES using a double period of the period of the flicker as a unit. For example, when the power frequency of the fluorescent lamp is 60 Hz, the camera module 2 can suppress the flicker by adjusting the ES by 1/120 seconds.
For example, when a frame rate of a synthesized image is assumed to be 60 fps (frame per second), the camera module 2 sets the ES to one of 2/120 seconds and 1/120 seconds to suppress the flicker with 60 Hz. When the illuminance is high, the camera module 2 adjusts the ES within a range equal to or less than 1/120 seconds in order to prioritize the suppression of saturation of an output charge with respect to the amount of incident light than the suppression of the flicker.
In this example, the AE control circuit 16 divides an illuminance range with which shooting sensitivity is correlated by the camera module 2 into three stages and switches the control (lightness adjustment) of the AE operation according to the ES, the AG, and the DG. The AE control circuit 16 fixes the ES to 2/120 seconds within a low illuminance range b3 and adjusts only the AG. The AE control circuit 16 fixes the ES to 1/120 seconds within an illuminance range b2 which is a higher illuminance range than the illuminance range b3 and adjusts only the DG.
The AE control circuit 16 adjusts the ES to be shorter step by step with an increase in the illuminance within an illuminance range b1 which is a higher illuminance range than the illuminance range b2. The AE control circuit 16 adjusts a change amount of the illuminance corresponding to a unit less than a quantization unit of the ES according to the DG. Further, when the quantization unit of the ES is equal to or less than the resolution of the illuminance, the AE control circuit 16 may not perform the adjustment according to the DG.
The form of the control of the AE operation by the AE control circuit 16 can be appropriately changed. For example, after determining the ES according to the illuminance, the AE control circuit 16 may adjust one of the AG and the DG or may adjust both the AG and the DG.
The AE control circuit 16 may appropriately change the setting of the ES according to the frame rate of a synthesized image or the period of flicker. When the frame rate of a synthesized image is set to 30 fps with respect to the flicker with a frequency of 60 Hz, the AE control circuit 16 can adjust the ES to 4/120 seconds maximally. When the frequency of the flicker is 50 Hz, the AE control circuit 16 adjusts the ES by 1/100 seconds.
For example, it is assumed that the long-time exposure image signal is designated as the main control signal. The AE control circuit 16 calculates proper exposure L1 for the long-time exposure pixel based on the long-time exposure image signal and calculates a control amount according to the proper exposure L1. For example, when the proper exposure L1 falls within the illuminance range b3, the AE control circuit 16 calculates a control amount ES1 (for example, 2/120 seconds) for the ES and a control amount AG1 (for example, six times) for the AG.
The AE control circuit 16 calculates proper exposure L2 for the short-time exposure pixel by multiplying the proper exposure L1 by an HDR magnification M. For example, when the HDR magnification M is set to four times, the AE control circuit 16 multiples the proper exposure L1 by 4 to calculate the proper exposure L2.
The AE control circuit 16 calculates a control amount according to the proper exposure L2. For example, when the proper exposure L2 falls within the illuminance range b3, the AE control circuit 16 calculates a control amount ES2 (for example, 2/120 seconds) for the ES and a control amount AG2 (for example, 1.5 times) for the AG.
In
The long-time exposure image signal S1 and the short-time exposure image signal S2 from the imaging processing circuit 12 (see
For example, the change instruction signal 33 is set as a signal generated in response to a user's setting operation. For example, when the image quality of a dark portion of an image is considered to be important, the camera module 2 may select the long-time exposure image signal S1 from the long-time exposure pixel as the main control signal.
The brightness signal generating unit 21 generates a brightness signal 35 from the main control signal from the main control signal switching unit 20. The brightness signal 35 is, for example, a signal for information corresponding to a brightness component of a YUV color space. For example, the brightness signal generating unit 21 extracts brightness information on a G component from RAW image data which is the main control signal and sets the extracted brightness information as the brightness signal 35. The brightness signal generating unit 21 sets the brightness values of G components detected with a Gr pixel and a Gb pixel as the brightness signal 35.
The brightness signal generating unit 21 uses, as the brightness signal 35, the brightness value of a G component from which the most information on the brightness can be obtained among the R, G, and B components. The embodiment is not limited to the case in which the brightness signal generating unit 21 generates the brightness signal 35 only from the brightness value of the G component. For example, the brightness signal generating unit 21 may generate the brightness signal 35 using the brightness values of the R, G, and B components. The brightness signal 35 may be, for example, a signal obtained by adding the brightness values of the R, G, and B components by a predetermined ratio.
The brightness average value calculating unit 22 integrates and averages the brightness signals 35 of the entire screen and calculates a brightness average value 36. The brightness average value calculating unit 22 may calculate the brightness average value 36 after weighting the brightness signals 35 for each area set in a screen.
The brightness target value comparing unit 23 compares the brightness average value 36 from the brightness average value calculating unit 22 to a preset brightness target value and calculates a difference. The brightness target value comparing unit 23 outputs a difference between the brightness average value 36 and the brightness target value as a lightness adjustment amount 37 used to adjust the lightness of a synthesized image according to illuminance at the time of shooting. For example, an adjustment amount of an exposure value (EV) for exposure correction is set as the lightness adjustment amount 37.
The EV calculating unit 24 includes a main control EV calculating unit 31 and a sub-control EV calculating unit 32. The main control EV calculating unit 31 calculates a main control EV 41. The main control EV 41 is an EV for the main control signal. The main control EV calculating unit 31 calculates the main control EV 41 by performing calculation to reflect the lightness adjustment amount 37 from the brightness target value comparing unit 23 to the lightness of an image by the main control signal. The main control EV 41 corresponds to the proper exposure L1 for the main control signal.
The sub-control EV calculating unit 32 calculates a sub-control EV 42. The sub-control EV 42 is an EV for the sub-control signal. The sub-control EV calculating unit 32 multiplies the main control EV 41 calculated by the main control EV calculating unit 31 by the HDR magnification M and sets the multiplication result as the sub-control EV 42. The sub-control EV 42 corresponds to the proper exposure L2 for the sub-control signal.
The sub-control EV calculating unit 32 determines whether one of the long-time exposure image signal S1 and the short-time exposure image signal S2 is the sub-control signal based on the change instruction signal 33. For example, when the HDR magnification M is set to four times and the long-time exposure image signal S1 is designated as the main control signal, the sub-control EV calculating unit 32 multiplies the main control EV 41 by ΒΌ and sets the multiplication result as the sub-control EV 42. On the other hand, when the HDR magnification M is set to four times and the short-time exposure image signal S2 is designated as the main control signal, the sub-control EV calculating unit 32 multiplies the main control EV 41 by four and sets the multiplication result as the sub-control EV 42. Further, the HDR magnification M is set to, for example, a fixed value set in advance.
The flicker detection integration unit 26 performs integration for the flicker detection on the main control signal from the main control signal switching unit 20 and outputs an integration result 34. The flicker period estimating unit 27 estimates the period of the flicker based on the integration result 34 from the flicker detection integration unit 26, and outputs an estimation result 38.
The flicker period is 1/100 s or 1/120 s with respect to the power frequency of 50 Hz or 60 Hz. For example, when the frame period is 1/30 s with respect to the power frequency of 50 Hz, stripes with of a period of 1/100 s occur in which a line corresponding to a horizontal synchronization period T1 in which the amount of light is the maximum is a bright portion and a line corresponding to a horizontal synchronization period T2 in which the amount of light is the minimum is a dark portion. The horizontal synchronization periods T1 and T2 are set to, for example, two ms.
The flicker detection integration unit 26 performs integration of the main control signal for which a line is used as a unit in several portions in the screen. The flicker period estimating unit 27 estimates the flicker period from a difference between the integration results 34 of respective portions in the screen. For example, the flicker period estimating unit 27 estimates one of the flicker period of 1/100 s and the flicker period of 1/120 s by comparing the difference between the integration results 34 at the intervals of 1/100 s to the difference between the integration results 34 at the intervals of 1/120 s.
When the frame period is an integer multiple of 1/100 s with respect to the power frequency of 50 Hz and the frame period is an integer multiple of 1/120 s with respect to the power frequency of 60 Hz, the amount of exposure becomes constant irrespective of an exposure timing, and thus no flicker occurs. The flicker period estimating unit 27 estimates the period of flicker occurring when the frame period is not an integer multiple of the period of the blinking of the fluorescent lamp.
The control amount converting unit 25 converts the main control EV 41 from the main control EV calculating unit 31 into the control amount ES1 for the ES, the control amount AG1 for the AG, and a control amount DG1 for the DG. The control amount converting unit 25 determines the control amount ES1 according to the main control EV 41 as the proper exposure L1 which falls within a given illuminance range (for example, b1 to b3 illustrated in
In the example illustrated in
When the main control EV 41 falls within the illuminance range b3, the control amount converting unit 25 determines the control amount AG1 according to the main control EV 41 based on a linear relation between the main control EV 41 and the control amount AG1. When the main control EV 41 falls within the illuminance range b2, the control amount converting unit 25 determines the control amount DG1 according to the main control EV 41 based on a linear relation between the main control EV 41 and the control amount DG1.
When the main control EV 41 falls within the illuminance range b1, the control amount converting unit 25 determines the control amount ES1 corresponding to the main control EV 41 from the ES set step by step according to the illuminance. In this case, the control amount converting unit 25 determines the control amount ES1 irrespective of the flicker period which is the estimation result 38. The control amount converting unit 25 determines the control amount DG1 according to the main control EV 41 based on a linear relation between the main control EV 41 and the control amount DG1 in the quantization unit of the ES.
The control amount converting unit 25 converts the sub-control EV 42 from the sub-control EV calculating unit 32 into the control amount ES2 for the ES, the control amount AG2 for the AG, and a control amount DG2 for the DG. The control amount converting unit 25 determines the control amount ES2 according to the sub-control EV 42 as the proper exposure L2 which falls within a given illuminance range (for example, b1 to b3 illustrated in
The control amount converting unit 25 performs the conversion of the main control EV 41 calculated by the main control EV calculating unit 31 into each control amount and the conversion of the sub-control EV 42 calculated by the sub-control EV calculating unit 32 into each control amount in a time division manner. The AE control circuit 16 uses the control amount converting unit 25 common to the generation of each control amount in regard to the main control signal and the sub-control signal, and thus the circuit size can be reduced.
For example, when the long-time exposure image signal S1 is designated as the main control signal, the timing generator 15 illustrated in
Further, when the long-time exposure image signal S1 is designated as the main control signal, the preprocessing unit 11 illustrated in
The EV calculating unit 24 calculates the main control EV 41 and the sub-control EV 42 falling within the illuminance range in which the camera module 2 has shooting sensitivity. The main control EV calculating unit 31 sets a limitation on the main control EV 41 so that not only the main control EV 41 but also the sub-control EV 42 calculated by the sub-control EV calculating unit 32 are included in the illuminance range.
For example, when the long-time exposure image signal S1 is designated as the main control signal, the sub-control EV 42 for the short-time exposure image signal S2 have a value which is larger than the main control EV 41 by the HDR magnification M. The main control EV calculating unit 31 limits the maximum value of the main control EV 41 so that the sub-control EV 42 is included in a range equal to or less than the maximum illuminance in which the camera module 2 has shooting sensitivity. Referring to the graph of
For example, when the short-time exposure image signal S2 is designated as the main control signal, the sub-control EV 42 for the long-time exposure image signal S1 have a value which is smaller than the main control EV 41 by the HDR magnification M. The main control EV calculating unit 31 limits the minimum value of the main control EV 41 so that the sub-control EV 42 is included in a range equal to or greater than the minimum illuminance in which the camera module 2 has shooting sensitivity. Referring to the graph of
The EV calculating unit 24 can acquire the main control EV 41 and the sub-control EV 42 according to the shooting sensitivity of the camera module 2 by providing such limitations on the main control EV 41. The AE control circuit 16 can perform the control of the AE operation according to the shooting sensitivity of the camera module 2 on both the long-time exposure image signal S1 and the short-time exposure image signal S2.
For example, the camera module 2 is assumed to switch between an HDR shooting mode in which the HDR synthesis is performed and a normal shooting mode in which the HDR synthesis is not performed. In the HDR shooting mode, the AE control circuit 16 calculates each control amount for the long-time exposure image signal S1 and the short-time exposure image signal S2.
An image signal SO from the imaging processing circuit 12 is input to the AE control circuit 16. The brightness signal generating unit 21 generates the brightness signal 35 from the image signal S0. The brightness average value calculating unit 22 integrates and averages the brightness signals 35 and calculates the brightness average value 36. The brightness target value comparing unit 23 outputs a difference between the brightness average value 36 and the brightness target value as a lightness adjustment amount 37 used to adjust the lightness of an image according to illuminance at the time of shooting. The EV calculating unit 24 calculates the EV 43 by performing calculation to reflect the lightness adjustment amount 37 from the brightness target value comparing unit 23 to the lightness of an image by the image signal S0.
The flicker detection integration unit 26 performs integration for the flicker detection on the image signal S0 and outputs an integration result 34. The flicker period estimating unit 27 estimates the period of the flicker based on the integration result 34 from the flicker detection integration unit 26, and outputs an estimation result 38. The control amount converting unit 25 converts the EV 43 from the EV calculating unit 24 into a control amount ES0 for the ES, a control amount AG0 for the AG, and a control amount DG0 for the DG. In the normal shooting mode, the control amount converting unit 25 calculates each control amount for the image signal S0 obtained by applying the same charge accumulation period on each pixel.
The timing generator 15 illustrated in
The solid-state imaging device 5 according to the first embodiment performs the AE control through a simple calculation process, compared to a case in which a continuously adjusted HDR magnification M is applied, by calculating the control amounts for the sub-control signal based on the fixed HDR magnification M. The solid-state imaging device 5 can control the AE operation according to the lightness at the time of shooting through the simple calculation process in relation to the long-time exposure image signal and the short-time exposure image signal.
The AE control circuit 16 can reduce the circuit size and shorten the processing time by simplifying the calculation process. The solid-state imaging device 5 can realize the control of the AE operation in the HDR shooting mode by adding a circuit with a relatively small size such as the sub-control EV calculating unit 32 to the circuit configuration in which the HDR synthesis is not performed. The solid-state imaging device 5 can be configured by a small and simple circuit.
Each circuit configuration described in this embodiment may realize the function described in this embodiment and may be appropriately modified.
The AE control circuit 50 includes a first control amount converting unit (control amount converting unit for main control) 51 and a second control amount converting unit (control amount converting unit for sub-control) 52 which are control amount converting units, instead of the control amount converting unit 25 illustrated in
The first control amount converting unit 51 converts a main control EV 41 calculated by a main control EV calculating unit 31 into control amounts ES1, AG1, and DG1. The second control amount converting unit 52 converts a sub-control EV 42 calculated by a sub-control EV calculating unit 32 into control amounts ES2, AG2, and DG2.
The solid-state imaging device 5 according to the second embodiment can be configured by a small and simple circuit, as in the first embodiment. The AE control circuit 50 performs conversion of the main control EV 41 into each control amount by the first control amount converting unit 51 and conversion of the sub-control EV 42 into each control amount by the second control amount converting unit 52 in parallel. The AE control circuit 50 causes the AE operation to be performed faster by acquiring the control amounts in regard to the main control signal and the sub-control signal in parallel.
The first control amount converting unit 51 outputs the control amount ES1 calculated from a main control EV 41 to the second control amount converting unit 52. The first control amount converting unit 51 and the second control amount converting unit 52 which are control amount converting units applies the same control amount ES1 for the ES to the main control signal and the sub-control signal. The second control amount converting unit 52 determines the control amounts AG2 and DG2 according to the control amount ES1 from the first control amount converting unit 51 and the sub-control EV 42 from the sub-control EV calculating unit 32. The first control amount converting unit 51 and the second control amount converting unit 52 set different control amounts for at least one of the AG and the DG in regard to the main control signal and the sub-control signal.
The timing generator 15 illustrated in
The AE control circuit 60 may include a control amount converting unit 25 (see
For example, it is assumed that the long-time exposure image signal S1 is designated as the main control signal. The first control amount converting unit 51 calculates proper exposure L1 for the long-time exposure pixel based on the long-time exposure image signal S1. The first control amount converting unit 51 calculates the control amounts such as the ES1 and the AG1 according to the proper exposure L1.
The AE control circuit 60 calculates proper exposure L2 for the short-time exposure pixel by multiplying the proper exposure L1 by an HDR magnification M. The second control amount converting unit 52 calculates a control amount according to the proper exposure L2. The second control amount converting unit 52 uses the control amount ES1 for the long-time exposure image signal S1 as the control amount for the ES without change. Further, the second control amount converting unit 52 calculates the control amount such as the AG2 other than the ES according to the property exposure L2.
In
For example, when the proper exposure L2 falls within the illuminance range b1, the proper exposure L1 falls within the illuminance range b2 or b3 (see
The AE control circuit 60 according to the third embodiment can prevent the flicker from occurring in the short-time exposure pixel by applying the same control amount for the ES to the long-time exposure pixel and the short-time exposure pixel. The AE control circuit 60 according to this embodiment is appropriate when the prevention of the flicker is desirable.
For example, when the camera module 2 mounted on a drive recorder takes a picture of a traffic light in which an LED is used for display, the LED is not turned on and an image is recorded from a deviation between a frame rate and a period in which the LED is turned on and off. In this case, when the camera module 2 prevents the flicker from occurring by applying the AE control circuit 60 according to this embodiment, signal display of the LED can be accurately recorded.
The solid-state imaging device 5 according to the third embodiment can be configured by a small and simple circuit, as in the first embodiment. Further, when the AE control circuit 60 applies the control amount ES1 determined in regard to the main control signal to the sub-control signal without change, a process of separately calculating the control amount for the ES in regard to the sub-control signal may not be provided. Thus, the solid-state imaging device 5 can cause the AE operation to be performed faster.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2012-193412 | Sep 2012 | JP | national |