JP6254780B2 - Focus detection apparatus and method, and imaging apparatus - Google Patents

Description

  The present invention relates to a focus detection apparatus and method for performing focus detection by a phase difference detection method, and an imaging apparatus equipped with the focus detection apparatus.

  Conventionally, a so-called phase difference detection type focus detection device is known as a focus detection device for a camera that provides an AF function. In such a focus detection apparatus, a light beam from a subject that has passed through different exit pupil regions of the photographing lens is imaged on a pair of focus detection sensors, and correlation calculation is performed while relatively shifting a pair of pixel signal sequences. Do. Then, the relative phase difference between the pair of pixel signal sequences is detected, and the defocus amount of the photographing lens is obtained based on the phase difference.

  Patent Document 1 proposes a focus detection device that detects an abnormal signal in an image signal of a focus detection sensor and excludes the abnormal signal to perform a correlation calculation.

JP 2012-042597 A

  However, in the conventional technique disclosed in Patent Document 1 described above, since the calculation is performed from the correlation amounts of a plurality of shift waveforms, pixels that are excluded by the shift amount of the pixel signal sequence when performing the correlation calculation by excluding abnormal pixels. The number is different. Although details will be described later, since the correlation amount is a value obtained by summing up the differences between the image signals paired with each pixel, if the number of operation pixels is different, the correlation amount in each shift amount cannot be accurately compared, The focus detection accuracy may be deteriorated.

  The present invention has been made in view of the above problems, and an object of the present invention is to avoid deterioration in focus detection accuracy due to a phase difference detection method when an abnormal pixel occurs.

Focus detecting device of the present invention in order to achieve the above object, is outputted light beams passing through different pupil areas of projection optical system Taking photoelectrically converting, from the imaging means capable of outputting a pair of pixel signal sequence Detecting means for detecting an abnormal signal included in the pair of pixel signal sequences , and when the abnormal signal is present in one pixel signal sequence of the pair of pixel signal sequences for each of a plurality of different shift amounts , wherein the abnormal signal of one pixel signal string, excluding the images signals corresponding to the position of the abnormality signal included in the other pixel signal string, different with previous SL relatively shifting the pair of pixel signal string and a calculating means for calculating the correlation of a plurality of shift amounts, respectively, said computing means, the position in the pair of pixel signal string of an image signal that excludes the case of shifting the first shift amount first The place where To, in the pair of pixel signal sequence shifted by the second shift amount different from the first shift amount, by excluding an image signal corresponding to the first position, in the first shift amount and shifted the pair of pixel signal string, the said respective second pair of pixel signal sequence shifted by the shift amount, and calculates a correlation amount by excluding equal number of images signals.

  According to the present invention, when an abnormal pixel occurs, it is possible to avoid deterioration in focus detection accuracy due to the phase difference detection method.

1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to a first embodiment. The block diagram which shows schematic structure of the focus detection apparatus containing the focus detection unit of FIG. 6 is a flowchart illustrating a basic operation of the imaging apparatus according to the embodiment. The flowchart which shows the focus detection process in embodiment. The figure which shows an example of the image signal which has not reached the saturation level. The figure which shows the shift waveform in a 1st correlation calculation. The figure which shows the correlation amount for every shift amount in a 1st correlation calculation. The figure which shows an example of the image signal containing the pixel which has reached the saturation level. The figure which shows the correlation amount in the image signal without a saturation pixel, and the image signal with a saturation pixel. The flowchart which shows a 2nd correlation calculation process. The figure which shows the shift waveform in a 2nd correlation calculation. The figure explaining the saturation pixel and exclusion pixel of a shift waveform in 2nd correlation calculation. The circuit diagram which shows an example of a structure of the image sensor in 2nd Embodiment. Sectional drawing of the wiring part concerning two pixels of the image sensor in 2nd Embodiment. The drive timing chart of the image sensor in 2nd Embodiment. FIG. 6 is a diagram illustrating a structure of an imaging pixel according to a second embodiment. The top view and sectional drawing explaining the structure of the pixel for a focus detection which divides a pupil in the horizontal direction of the imaging lens in 2nd Embodiment. FIG. 10 is a plan view and a cross-sectional view illustrating the structure of a focus detection pixel that performs pupil division in the vertical direction of the photographing lens according to the second embodiment. Explanatory drawing of the pixel arrangement | sequence of the minimum unit of the image pick-up element in 2nd Embodiment. Explanatory drawing of the pixel arrangement | sequence of the upper unit of the image pick-up element in 2nd Embodiment. Explanatory drawing of the pixel arrangement | sequence in the whole area | region of the image pick-up element in 2nd Embodiment. Explanatory drawing of the pixel grouping method at the time of the focus detection of the horizontal direction in 2nd Embodiment. Explanatory drawing of the pixel grouping method at the time of the focus detection of the orthogonal | vertical direction in 2nd Embodiment. 9 is a flowchart illustrating a shooting operation of the imaging apparatus according to the second embodiment. The flowchart of the focus detection process performed by S44 of FIG. The flowchart of the imaging | photography process performed by S46 of FIG.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a block diagram illustrating a schematic configuration of an imaging apparatus including a focus detection apparatus according to the first embodiment of the present invention. The imaging apparatus according to the first embodiment is an interchangeable lens single-lens reflex camera (hereinafter simply referred to as “camera”) 100. The camera 100 includes a camera body 30 and a photographing lens unit 20 configured to be detachable from the camera body 30. The taking lens unit 20 and the camera body 30 are connected via a mount indicated by a dotted line in FIG. Note that the present embodiment is not limited to a lens interchangeable camera, and can also be applied to a camera in which a lens unit and a camera body are integrally configured.

  The photographing lens unit 20 includes a photographing lens 21, a diaphragm 22, a lens side microprocessing unit (MPU) 1, a lens driving unit 2, a diaphragm driving unit 3, a repeat position detection unit 4, and a memory 5. . The photographing lens 21 and the aperture 22 constitute a photographing optical system.

  The lens side MPU 1 performs all calculations and controls related to the operation of the photographic lens unit 20. The lens driving unit 2 is a driving unit that drives the photographing lens 21 in accordance with control by the lens side MPU 1. The aperture drive unit 3 is a drive unit that drives the aperture 22 according to control by the lens side MPU 1. The repeat position detection unit 4 is a detection unit that detects the repeat position of the lens barrel. The memory 5 stores an optical information table that is optical information necessary for automatic focus adjustment.

  The camera body 30 includes a camera-side MPU 6, a focus detection unit 7, a shutter drive unit 8, a dial unit 10, and a photometry unit 11. The camera body 30 includes a main mirror 12, a sub mirror 13, a focus plate 14, a penta mirror 15, a finder 16, a display 17, an image sensor (image sensor) 101, a switch SW1_18, and a switch SW2_19. Is provided.

  The camera side MPU 6 performs all calculations and controls related to the operation of the camera body 30. The camera-side MPU 6 is connected to the lens-side MPU 1 via a mount signal line, and acquires lens position information from the lens-side MPU 1 or acquires unique optical information for each lens driving and interchangeable lens.

  The camera-side MPU 6 includes a ROM (not shown) that stores a program for controlling the operation of the camera body 30, a RAM (not shown) that stores variables, and an EEPROM (electrical erasure, A writable memory (not shown) is incorporated. A focus detection process to be described later is executed by a program stored in the ROM.

  The focus detection unit 7 includes a focus detection sensor described later, and performs focus detection by a phase difference detection method. The focus detection unit 7 notifies the camera-side MPU 6 of the completion of signal readout from the focus detection sensor. The shutter drive unit 8 is a drive unit for driving a shutter (not shown). The dial unit 10 is an operation unit for changing various settings of the camera 100 and is operated by the user to switch, for example, continuous shooting speed (continuous shooting speed), shutter speed, aperture value, shooting mode, and the like. It can be carried out.

  The photometric unit 11 includes a photometric sensor, and performs photometric processing via a photometric sensor (not shown) based on the light flux from the pentamirror 15 in response to a half-press operation on a release button (not shown). The photometric sensor comprises a photoelectric conversion element such as a photodiode and its signal processing circuit, and outputs a signal related to the luminance level of the subject. The output signal is input to the camera-side MPU 6.

  The main mirror 12 has a function of folding most of the light beam incident through the photographing lens unit 20 upward and forming a subject image on the focus plate 14. The subject image on the focus plate 14 is converted and reflected into an erect image by the pentamirror 15 and guided to the viewfinder 16. Thereby, it functions as an optical viewfinder. A part of the light transmitted through the pentamirror 15 is guided to the photometry unit 11. The main mirror 12 transmits a part of the incident light beam, and the transmitted light is guided to the focus detection unit 7 through the sub mirror 13. When the camera 100 is in the shooting state, the main mirror 12 and the sub mirror 13 are retracted from the optical path, and the light flux from the subject incident through the photographing lens unit 20 is imaged on the image sensor 101, and the subject image is displayed. The signal is photoelectrically converted and output.

  The display unit 17 is composed of an LCD or the like, and displays information related to the shooting mode of the camera, a preview image before shooting, a confirmation image after shooting, and the like.

  The switch SW1_18 is a switch that is turned on by a first stroke operation (for example, half pressing) of a release button (not shown), and the switch SW2_19 is a switch that is turned on by a second stroke operation (for example, full pressing) of a release button (not shown).

  Next, a schematic configuration of the focus detection apparatus including the focus detection unit 7 will be described with reference to FIG. As described above, part of the incident light from the photographic lens unit 20 passes through the main mirror 12, is bent downward by the rear sub-mirror 13, and is guided to the focus detection unit 7. The focus detection unit 7 includes a field mask 102, an infrared cut filter 103, a field lens 104, a diaphragm 105, a secondary imaging lens 106, a focus detection sensor 107, and a plurality of reflection mirrors 108a to 108c.

  The focus detection sensor 107 for focus detection is a pair of lines composed of photoelectric conversion elements such as photodiodes that photoelectrically convert a pair of subject images formed by light beams that have passed through different exit pupil regions of the photographic lens unit 20. It consists of a sensor and its signal processing circuit. The focus detection sensor 107 outputs a pixel signal (image signal), and the output image signal is input to the camera side MPU 6. Hereinafter, a pair of image signals output from the pair of line sensors are referred to as an A image (one image signal) and a B image (the other image signal). In addition, the camera side MPU 6 includes an abnormal pixel detection unit 111 and a correlation calculation unit 112.

  Next, the basic operation of the camera 100 of FIG. 1 will be described using the flowchart shown in FIG. When the power of the camera 100 is turned on, the memory contents and the initialization state of the execution program are detected, and the shooting preparation operation is executed. In S11, the camera side MPU 6 recognizes that the user has performed various settings of the camera by operating various buttons (not shown). In S12, the camera side MPU 6 determines whether or not the switch SW1_18 is turned on.

  When the switch SW1_18 is turned on, the process proceeds to S14. On the other hand, if it is not turned on, the process proceeds to S13 to determine whether the power is on or off. When the power is off, a series of shooting operations are terminated. If the power is on, the process returns to S11. In S14, the camera side MPU 6 performs a focus detection process described later in response to the switch SW1_18 being turned on.

  After focus detection processing described later, in S15, the camera-side MPU 6 determines whether or not the switch SW2_19 is turned on. If it is determined that the switch SW2_19 is turned on, the camera-side MPU 6 performs shooting processing in S16. On the other hand, if it is determined that the switch SW2_19 is not turned on, the process returns to S11.

  FIG. 4 is a flowchart showing the focus detection process performed in S14 of FIG. 3 in the first embodiment. In S <b> 20, the camera side MPU 6 outputs a signal accumulation instruction to the focus detection sensor 107. Based on the instruction, the focus detection sensor 107 starts a signal accumulation operation. When the accumulation operation ends, the focus detection sensor 107 outputs the image signals obtained by the pair of line sensors to the camera side MPU 6 as an A image and a B image, respectively.

  An example of the A image and the B image output in S20 of FIG. 4 is shown in FIG. The A image and the B image have a phase difference of −2 to −3 bits. Here, the case where the A image exists on the right side of the B image is defined as a negative phase difference. The signal levels of the A and B images shown in FIG. 5 do not exceed the saturation level. If a pixel exceeding the saturation level exists in the A and B images, the pixel signal exceeding the saturation level is clipped to the saturation level and output.

  Next, in S21, the camera side MPU 6 performs a first correlation calculation (pre-processing) in the correlation calculation unit 112 based on the A image and the B image. Here, the first correlation calculation will be described in detail. In the following description, a waveform obtained by relatively shifting the image signal acquired from the focus detection sensor is referred to as a shift waveform. First, the calculation method of the shift waveforms and correlation amounts of the A and B images in the first correlation calculation will be described with reference to FIG.

  6A shows a shift waveform with a shift amount of 0, FIG. 6B shows a shift waveform with a shift amount of −1 bit, and FIG. 6C shows a shift waveform with a shift amount of −2 bits. Here, the shift amount is controlled by fixing the B image and shifting the A image left and right. The correlation amount C (k) at the shift amount kbit can be calculated using the correlation calculation formula (1).

この例では、最大シフト量は±４bitとし、９つのシフト波形をＲＡＭに保存する。また、演算範囲はシフト可能な最大シフト量を考慮し、出力されたＡ像、Ｂ像の総画素数ｍのうち、最初と最後の４bit分を演算から除外した範囲を演算範囲として設定する。そこで、各シフト波形のＡ像、Ｂ像の差分面積（図６（ａ）〜（ｃ）の斜線部の面積）を相関量Ｃとし、各シフト波形の相関量Ｃが最も小さくなるシフト量がＡ像、Ｂ像の位相差に対応する。

In this example, the maximum shift amount is ± 4 bits, and nine shift waveforms are stored in the RAM. Further, the calculation range is set as a calculation range in consideration of the maximum shift amount that can be shifted, and out of the total number of pixels m of the output A image and B image, the first and last 4 bits are excluded from the calculation. Therefore, the difference area between the A and B images of each shift waveform (the area of the shaded area in FIGS. 6A to 6C) is the correlation amount C, and the shift amount that minimizes the correlation amount C of each shift waveform is the same. This corresponds to the phase difference between the A and B images.

  FIG. 7 shows the correlation amount C obtained by shifting the pixel signal of FIG. 6A by ± 4 bits. The correlation amount C (−2) with the shift amount k = −2 bits is the smallest value, but the minimum value is between k = −2 and −3 bits as indicated by the dotted line. Therefore, the phase difference detection resolution is increased by performing an interpolation calculation from the shift amount k = -2 bits and the correlation amount information in the vicinity thereof. Here, the interpolation calculation is performed by using four correlation amounts C of shift amounts k = −1 to −4 bits.

  In S22, the camera-side MPU 6 uses the abnormal pixel detection unit 111 provided with a unit for detecting the abnormal signal illustrated in FIG. 2 to detect abnormal pixels (saturated pixels, in the pair of image signals, A image, and B image acquired in S20. Detect defective pixels). In the following description, the abnormal pixel is assumed to be a saturated pixel.

  In S23, it is determined whether a saturated pixel exists based on the information detected in S22. If there is no saturated pixel, the process proceeds to S25. On the other hand, if there is a saturated pixel, the process proceeds to S24, and a second correlation calculation is performed to exclude the saturated pixel signal. Details of the second correlation calculation will be described later.

  In S25, the lens driving amount is calculated based on the phase difference information calculated in S21 or S24 and transmitted to the lens side MPU1. The lens side MPU 1 performs lens drive control based on the transmitted lens drive amount, and ends a series of focus detection processes.

  Next, the second correlation calculation performed in S24 will be described. Prior to the description of the second correlation calculation, the saturation level of the image signal shown in FIG. 5 is lowered for the correlation calculation error when there is a saturated pixel. I will explain. FIG. 8 shows a case where some pixels of the A and B images, which are the image signals shown in FIG. 5, exceed the saturation level by lowering the saturation level. Of course, the same phenomenon occurs even if the signal level is raised by applying gain, for example, without changing the saturation level.

  FIG. 9 shows a comparison result of calculating the correlation amount C using the above equation (1) for the image signal without saturated pixels (FIG. 5) and the image signal with saturated pixels (FIG. 8). In the example illustrated in FIG. 9, the correlation amount C is the minimum with the shift amount k = −2 bits regardless of the presence / absence of the saturated pixel. However, the result of the interpolation calculation produces a difference with and without saturated pixels. This difference occurs because the saturated pixel signal is clipped to the saturation level, and becomes an error when calculating the phase difference. Therefore, in order to reduce this error, the second correlation calculation is performed by excluding the saturated pixel signal.

  Hereinafter, the second correlation calculation will be described in detail with reference to the flowchart of FIG. In the first correlation calculation, the shift amount k = −4 to +4 bits, that is, the correlation amount of nine shift waveforms is calculated, whereas in the second correlation calculation, the minimum correlation amount is obtained as a result of the first correlation calculation. The saturated pixel signal is excluded from the four shift waveforms corresponding to the vicinity of C, and the correlation amount is calculated.

  In S30, the range of the shift amount used in the second correlation calculation is determined based on the phase difference P detected in the first correlation calculation. First, the shift amount k = F−1 of the shift waveform to be processed first is set. F is a value rounded to an integer smaller than the detected phase difference P. Taking FIG. 7 as an example, since the phase difference P is between −2 bits and −3 bits, F = −3.

  In S31, the shift waveform (k) of the shift amount k acquired by the first correlation calculation is read from the RAM. In S32, it is determined whether one of the A image and the B image is a saturated pixel from the shift waveform (k) read in S31, and the position of the saturated pixel is detected. Here, saturation is determined by comparing the pixel signal with a saturation level value stored in advance in the RAM.

In S33, the pixel position determined as the saturated pixel in S32 is stored in the RAM. In S34, it is determined whether or not k is F + 2 or more . If it is F + 2 or more , the process proceeds to S36. That is, here, when the saturation pixel detection process is performed for the shift waveforms of the four shift amounts, the process proceeds to the next S36. On the other hand, if it is smaller than F + 2, there remains a shift waveform for detecting a saturated pixel, so in S35, the shift amount k = k + 1 is set, and the detection processing is performed for the shift waveform of the next shift amount.

  In S36, the pixel position stored as the saturated pixel position in S33 is read from the RAM, and the pixel signal at the pixel position stored as the saturated pixel position in any one of the four shift waveforms is set to zero. Thereby, pixel signals at those pixel positions are excluded in the correlation calculation performed later.

  Here, the exclusion pixel determination process performed in S36 will be described in detail with reference to FIGS. FIG. 11 shows four shift waveforms used in the second correlation calculation. The horizontal axis indicates the pixel position, and the vertical axis indicates the image signal.

  The shift waveforms in FIG. 11 are the shift amounts of F−1, F, F + 1, and F + 2 stored in the RAM as the result of the first correlation calculation in S21 of FIG. This is a shift waveform of an amount k = −4, −3, −2, −1 bit (first shift amount). FIG. 11A shows a shift waveform with a shift amount k = −1 bit, and a saturated pixel exists in either the A image or the B image at pixel positions 9 to 12. In this case, the camera-side MPU 6 stores four pixels at pixel positions 9, 10, 11, and 12 in the RAM as saturated pixel positions.

  FIG. 11B shows a shift waveform with a shift amount k = −2 bits (second shift amount), and three pixels at pixel positions 9, 10 and 11 are stored in the RAM by the same determination as in FIG. . FIG. 11C shows a shift waveform with a shift amount k = −3 bits, and three pixels at pixel positions 9, 10, and 11 are stored in the RAM by the same determination as described above. FIG. 11D shows a shift waveform with a shift amount k = −4 bits, and four pixels at pixel positions 8, 9, 10, and 11 are stored in the RAM by the same determination as described above.

  FIG. 12 summarizes the saturated pixel positions in the shift waveforms of FIGS. 11 (a) to 11 (d) in a table. In FIG. 12, pixel positions corresponding to saturated pixels and excluded pixels to be described later are represented by “x”. Thus, the number of pixels in which either the A image or the B image is saturated differs depending on the shift waveform.

Further, the correlation amount C in the second correlation calculation is a value obtained by summing up the differences between the image signals paired with each pixel, as shown in the correlation calculation expression (1). If only saturated pixels or only pixels that are paired with saturated pixels and saturated pixels are excluded, the number of operation pixels differs for each shift waveform, and the total number of pixels differs. It is different, and a correct calculation result cannot be obtained.

  Therefore, when the pixel position (i) (first position) is stored as the saturated pixel position in any one of the shift waveforms in FIGS. 11A to 11D, the pixel position (i ) Is an excluded pixel. In this case, the excluded pixel may be a normal pixel. That is, in the four shift waveforms used for the second correlation calculation, as shown in FIG. 12, five pixels 8, 9, 10, 11, and 12 are excluded pixels. Therefore, for example, in the shift waveform of FIG. 11A, the pixel positions 9, 10, 11, and 12 are saturated pixels, but the pixel position 8 that is a normal pixel is also handled in the same manner as the saturated pixels.

  In S37, the correlation amount C is obtained using the above equation (1) for the four shift waveforms in which the pixel signal at the position determined as the saturated pixel in S36 is 0, similarly to the first correlation calculation. The shift amount that is the minimum value is obtained from C and is set as the second correlation calculation result. Then, the intersection of the straight line connecting the correlation amounts C (F-1) and C (F) and the straight line connecting the correlation amounts C (F + 1) and C (F + 2) is set as the minimum value of the correlation amount. Calculate the phase difference.

  As described above, when a saturated pixel exists in either the A image or the B image in S36, the pixel signal of that pixel is set to zero. As a result, when the correlation amount C is calculated in S37, the pixel signal of the first term and the second term paired in the above equation (1) becomes 0, so that the pixel signal saturated from the correlation amount C is obtained. Can be removed.

  Further, since the pixel at the saturated pixel position in any shift waveform is removed from the four shift waveforms in S36, the calculation range and the number of calculation pixels are calculated when calculating the correlation amount C of the four shift waveforms in S37. And the phase difference can be detected with high accuracy.

  Further, by narrowing the shift range used in the second correlation calculation based on the first correlation calculation result, the number of pixels excluded as the saturated pixel number in S36 can be reduced. Therefore, it is possible to avoid a deterioration in focus detection accuracy caused by a decrease in the number of pixels used for correlation calculation.

  Further, in the first embodiment, as illustrated in FIG. 12, a case has been described in which a pixel position determined as a saturated pixel in at least one of the four shift waveforms is an excluded pixel. That is, the number of excluded pixels including normal pixels may be determined to be minimized so that the number of excluded pixels in all shift waveforms is the same.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. In the second embodiment, focus detection processing in a case where focus detection pixels are discretely arranged in the image sensor will be described.

FIG. 13 is a circuit diagram showing a schematic configuration of the image sensor 101 in the second embodiment. Although FIG. 13 shows a range of 2 columns × 4 rows of pixels of a two-dimensional CMOS area sensor, in practice, a large number of pixels shown in FIG. 13 are arranged to enable acquisition of a high resolution image. Here, the description will be made as an image sensor for a digital still camera having a pixel pitch of 2 μm, an effective pixel number of 3000 columns × 2000 rows = 6 million pixels, and an imaging screen size of 6 mm × 4 mm.

In FIG. 13, 201 is a photoelectric conversion portion of a photoelectric conversion element comprising a MOS transistor gate and a depletion layer under the gate, 202 is a photogate, 203 is a transfer switch MOS transistor, and 204 is a reset MOS transistor. 205 is a source follower amplifier MOS transistor, 206 is a horizontal selection switch MOS transistor, and 207 is a load MOS transistor of the source follower. 208 is a dark output transfer MOS transistor, 209 is a light output transfer MOS transistor, 210 is a dark output storage capacitor C _TN , and 211 is a light output storage capacitor C _TS . 212 is a horizontal transfer MOS transistor, 213 is a horizontal output line reset MOS transistor, 214 is a differential output amplifier, 215 is a horizontal scanning circuit, and 216 is a vertical scanning circuit.

  FIG. 14 is a cross-sectional view of a wiring portion relating to two pixels in the Y direction of FIG. In the figure, 217 is a P-type well, 218 is a gate oxide film, 219 is a first-layer poly-Si, 220 is a second-layer poly-Si, and 221 is an n + floating diffusion (FD) portion. The FD unit 221 is connected to two photoelectric conversion units via two transfer MOS transistors. In the figure, the drain of two transfer MOS transistors 203 and the FD portion 221 are shared to improve the sensitivity by miniaturization and the capacity reduction of the FD portion 221, but the FD portion 221 is connected by an aluminum (Al) wiring. May be.

  Next, the operation in the case of the all-pixel independent output in the image sensor 101 shown in FIGS. 13 and 14 will be described using the timing chart of FIG.

First, the timing output from the vertical scanning circuit 216 sets the control pulse φL to high to reset the vertical output line. Further, the control pulses φR ₀ , φPG ₀₀ and φPG _e0 are set high, the reset MOS transistor 204 is turned on, and the first-layer polysilicon 219 of the photogate 202 is set high. At time T ₀ , the control pulse φS ₀ is set high, the selection switch MOS transistor 206 is turned on, and the pixels on the first and second lines are selected. Next, the control pulse φR _{0 is set} to low, the reset of the FD unit 221 is stopped, the FD unit 221 is brought into a floating state, and the source-follower amplifier MOS transistor 205 is set to the through state. Thereafter, the control pulse .phi.T _N and high at time T _1, to output a dark voltage of the FD section 221 to the storage capacitor C _TN 210 by the source follower operation.

Next, in order to perform photoelectric conversion output from the pixels of the first line, first, conducts the transfer switch MOS transistor 203 to control pulse .phi.TX ₀₀ of the first line as a high. Then, lowering the control pulse FaiPG ₀₀ as a low at time T _2. At this time, a voltage relationship is preferable in which the potential well that has spread under the photogate 2 is raised so that the photogenerated carriers are completely transferred to the FD portion 221. Therefore, if complete transfer is possible, the control pulse φTX may be a fixed potential instead of a pulse.

At time T ₂ , charges from the pixels on the first line of the photodiode are transferred to the FD portion 221, whereby the potential of the FD portion 221 changes according to light. At this time, since the source follower amplifier MOS transistor 205 is in a floating state, the potential of the FD portion 221 is output to the storage capacitor C _TS 211 with the control pulse φT _s being high at time T ₃ . At this time, the dark output and the bright output of the pixels on the first line are stored in the storage capacitors C _TN 210 and C _TS 211, respectively. At time T ₄ , the control pulse φHC is temporarily set to high to turn on the horizontal output line reset MOS transistor 213 to reset the horizontal output line, and in the horizontal transfer period, the dark output of the pixel to the horizontal output line is performed by the scanning timing signal of the horizontal scanning circuit 215. And bright output. At this time, if the differential output V _OUT is obtained by the differential amplifier 214 of the storage capacitors C _TN 210 and C _TS 211, a signal with good S / N from which random noise and fixed pattern noise of the pixel are removed can be obtained.

Further, the dark output and the bright output of the pixels on the first line are simultaneously stored in the storage capacitors C _TN 210 and C _TS 211 connected to the respective vertical output lines. Accordingly, by sequentially turning on the horizontal transfer MOS transistor 212, the charges accumulated in the respective storage capacitors C _TN 210 and C _TS 211 are sequentially read out to the horizontal output line and output from the differential amplifier 214. .

In the second embodiment, a configuration in which the differential output V _OUT is performed in the chip is shown. However, the same effect can be obtained even if a conventional CDS (Correlated Double Sampling) circuit is used outside without being included in the chip.

On the other hand, after a bright output is output from the pixels on the first line to the storage capacitor C _TS 211, the control pulse φR _{0 is set} to high to turn on the reset MOS transistor 4, and the FD unit 221 is reset to the power supply V _DD . After the horizontal transfer of the charge on the first line is completed, reading from the pixels on the second line is performed. In reading the second line, the control pulse φTX _e0 and the control pulse φPG _e0 are first driven as in the first line. Next, high pulses are supplied to the control pulses φT _N and φT _S , respectively, and dark output and bright output are stored in the storage capacitors C _TN 210 and C _TS 211, respectively, and dark output and bright output are taken out.

With the above driving, the first and second lines can be read independently. Thereafter, by scanning the vertical scanning circuit 216 and reading out 2n + 1 and 2n + 2 (n = 1, 2,...) In the same manner, independent output from all pixels can be performed. That is, when n = 1, first, the control pulse φS ₁ is set high, then φR ₁ is set low, and then the control pulses φT _N and φTX ₀₁ are set high. The low control pulses FaiPG _01, high control pulse .phi.T _S, reads the dark output and bright output from each pixel of the third line control pulse φHC as a temporary high. Subsequently, the control pulses φTX _e1 and φPG _e1 and the control pulse are applied in the same manner as described above, and the dark output and the bright output are read from each pixel of the fourth line.

  16 to 18 are diagrams for explaining the structures of the imaging pixels and the focus detection pixels. In the second embodiment, out of 4 pixels of 2 rows × 2 columns, pixels having a spectral sensitivity of G (green) are arranged on 2 diagonal pixels, and R (red) and B are placed on the other 2 pixels. A Bayer arrangement in which one pixel each having (blue) spectral sensitivity is arranged is employed. A focus detection pixel having a structure to be described later is arranged between the Bayer arrays.

  FIG. 16 shows the arrangement and structure of the imaging pixels. FIG. 16A is a plan view of 2 × 2 imaging pixels. As is well known, in the Bayer array, G pixels are arranged diagonally, and R and B pixels are arranged in the other two pixels. The 2 rows × 2 columns structure is repeatedly arranged.

FIG. 16B is a cross-sectional view taken along the line AA in FIG. ML denotes an on-chip microlens arranged in front of each pixel, CF _R is a color filter, CF _G of R (red), a G (green) color filter. PD (Photo Diode) schematically shows a photoelectric conversion element of the image sensor 101. CL (Contact Layer) is a wiring layer for forming signal lines for transmitting various signals in the image sensor 101. TL (Taking Lens) schematically shows the photographing lens 21.

  Here, the on-chip microlens ML and the photoelectric conversion element PD of the imaging pixel are configured to capture the light beam that has passed through the photographing lens TL as effectively as possible. In other words, the exit pupil EP (Exit Pupil) of the photographic lens TL and the photoelectric conversion element PD are in a conjugate relationship by the microlens ML, and the effective area of the photoelectric conversion element is designed to be large. In FIG. 16B, the incident light beam of the R pixel has been described, but the G pixel and the B (blue) pixel have the same structure. As described above, the exit pupil EP corresponding to each of the RGB pixels for imaging has a large diameter, and the S / N of the image signal is improved by efficiently capturing the light flux from the subject.

FIG. 17 shows a plan view and a cross-sectional view of a focus detection pixel for performing pupil division in the x direction in the drawing of the photographing lens TL. FIG. 17A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. When obtaining an image signal for recording or viewing, the main component of luminance information is acquired by G pixels. This is because human image recognition characteristics are sensitive to luminance information, and if G pixels are lost, image quality degradation is easily recognized. On the other hand, the R pixel or the B pixel is a pixel that acquires color information (color difference information). However, since human visual characteristics are insensitive to color information, the pixel that acquires color information has some defects. However, image quality degradation is difficult to recognize. Therefore, in the second embodiment, among the pixels of 2 rows × 2 columns, the G pixel is left as an imaging pixel, and the R pixel and the B pixel are replaced with a focus detection pixel at a certain ratio. This focus detection pixel pair is denoted as S _HA and S _HB in FIG.

FIG. 17B is a cross-sectional view taken along the line BB in FIG. The microlens ML and the photoelectric conversion element PD have the same structure as the imaging pixel shown in FIG. In the second embodiment, since the signal of the focus detection pixel is not used for image generation, a transparent film CF _W (white) is disposed instead of the color separation color filter. Further, since pupil division is performed by the image sensor 101, the opening of the wiring layer CL is biased in the x direction with respect to the center line of the microlens ML. Specifically, since the opening OP _HA of the pixel S _HA is deviated in the −x direction with respect to the center line of the microlens ML, the light flux that has passed through the exit pupil region EP _HA in the + x direction of the photographing lens TL is reflected. Receive light. Similarly, since the opening OP _HB of the pixel S _HB is deviated in the + x direction with respect to the center line of the microlens ML, the light beam that has passed through the exit pupil region EP _HB in the −x direction of the photographing lens TL is received. .

The pixels _SHA having the above configuration are regularly arranged in the x direction, and an A image (one image signal) is formed from the outputs of these pixel groups as will be described later. Further, the pixels _SHB are also regularly arranged in the x direction, and a B image (the other image signal) is formed from the outputs of these pixel groups as described later. Then, by detecting the relative positions of the acquired A and B images, it is possible to detect the amount of defocus (defocus amount) of the subject image having a luminance distribution in the x direction.

In the pixels S _HA and S _HB , focus detection is possible for an object having a luminance distribution in the x direction on the photographing screen, for example, a line (vertical line) in the y direction, but x having a luminance distribution in the y direction. The direction line (horizontal line) cannot detect the focus. Therefore, in the second embodiment, pixels that perform pupil division are also provided in the y direction of the photographic lens so that the latter can be focus-detected.

FIG. 18 shows a plan view and a cross-sectional view of a focus detection pixel for performing pupil division in the y direction in the drawing of the photographing lens TL. FIG. 18A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. Like FIG. 17A, the G pixel is left as an imaging pixel, and there are an R pixel and a B pixel. Replace with focus detection pixels at a rate. This focus detection pixel pair is denoted as S _VC and S _VD in FIG.

FIG. 18B shows a cross-section C-C in FIG. 18A. The pixel shown in FIG. 17B has a structure in which pupil separation is performed in the x direction, whereas FIG. The pixel has only the pupil separation direction in the y direction, and the pixel structure does not change. That is, the opening _{OP VC} of the pixel _{S VC} is because it is biased to -y direction with respect to the center line of the microlens ML, it receives a light flux passing through the exit pupil region _{EP VC} of + y direction of the photographing lens TL. Similarly, since the opening OP _VC of the pixel S _VD is deviated in the + y direction with respect to the center line of the microlens ML, the light beam that has passed through the exit pupil region EP _VD in the −y direction of the photographing lens TL is received. .

The pixels _SVC having the above configuration are regularly arranged in the y direction, and a C image (one image signal) is formed from the outputs of these pixel groups as will be described later. Also, the pixels _SVD are regularly arranged in the y direction, and a D image (the other image signal) is formed from the outputs of these pixel groups as will be described later. Then, by detecting the relative position of the acquired C image and D image, it is possible to detect the amount of defocus (defocus amount) of the subject image having a luminance distribution in the y direction.

FIGS. 19 23 is a diagram for explaining the arrangement rule of an image sensing pixel and focus detection pixels described in FIGS. 16 to 18. FIG. 19 is a diagram for explaining a minimum unit arrangement rule when focus detection pixels are discretely arranged between imaging pixels. In FIG. 19, 10 rows × 10 columns = 100 pixels are defined as one block. The upper left block BLK (i, j) = BLK (1,1) is set, and the downward direction and the right direction are positive. In the block BLK (1, 1), the lower left R pixel and B pixel are replaced with a set of focus detection pixels S _HA and S _HB that perform pupil division in the horizontal direction.

In the block BLK (1, 2) on the right side, the lower left R pixel and B pixel are similarly replaced with a set of focus detection pixels S _VC and S _VD that perform pupil division in the vertical direction. The pixel arrangement of the block BLK (1, 1) adjacent below the first block BLK (1, 1) is the same as that of the block BLK (1, 2). The pixel arrangement of the block BLK (2, 2) on the right side is the same as that of the block BLK (1, 1).

  In this case, when the arrangement rule shown in FIG. 19 is expressed universally, in block BLK (i, j), if i + j is an even number, a focus detection pixel in which the pupil division direction is horizontal is arranged, and i + j is If the number is odd, focus detection pixels whose pupil division direction is vertical are arranged. Then, 2 × 2 = 4 blocks in FIG. 19, that is, an area of 20 rows × 20 columns = 400 pixels is defined as a cluster as an upper array unit of the blocks.

FIG. 20 is a diagram for explaining an arrangement rule in units of clusters. In FIG. 20, the upper left cluster composed of 20 rows × 20 columns = 400 pixels is CST (u, w) = CST (1,1), and the downward direction and the right direction are positive. In the cluster CST (1, 1), the lower left R pixel and B pixel of each block are replaced with focus detection pixels S _HA and S _HB or S _VC and S _VD .

  In the cluster CST (1, 2) on the right side, the focus detection pixels in the block are arranged at positions shifted upward by two pixels with respect to the cluster CST (1, 1). Further, in the cluster CST (2, 1) adjacent below the first cluster CST (1, 1), the focus detection pixels are arranged in the block in the right direction with respect to the cluster CST (1, 1). Arranged at a position shifted by two pixels. When the above rules are repeatedly applied, the arrangement shown in FIG. 20 is obtained.

  Here, the coordinates of the focus detection pixels are defined by the coordinates of the upper left pixel of the four pixels including the G pixel shown in FIG. 17 or 18 as one unit (pair). In the coordinates in each block, the upper left is (1, 1), and the lower direction and the right direction are positive. In this case, the arrangement rule shown in FIG. 20 is universally expressed as follows. In the cluster CST (u, w), the horizontal coordinate of the focus detection pixel pair in each block is 2 × u−1, and the vertical coordinate is 11-2 × w. Then, 5 × 5 = 25 clusters in FIG. 20, that is, an area of 100 rows × 100 columns = 10,000 pixels is defined as a field as an upper array unit of the clusters.

  FIG. 21 is a diagram for explaining an arrangement rule in units of fields. In FIG. 21, the upper left field composed of 100 rows × 100 columns = 10,000 pixels is FLD (q, r) = FLD (1,1), and the downward direction and the right direction are positive. In the second embodiment, all the fields FLD (q, r) have the same arrangement as the first field FLD (1,1). Therefore, if 30 FLDs (1, 1) are arranged in the horizontal direction and 20 in the vertical direction, the imaging region of 3000 columns × 2000 rows = 6 million pixels is composed of 600 fields. In this way, focus detection pixels can be uniformly distributed over the entire imaging region.

Next, a group of pixels and a signal addition method at the time of focus detection will be described with reference to FIGS. FIG. 22 is a diagram for explaining a pixel grouping method when performing horizontal focus detection of a subject image formed by a photographing optical system. In the horizontal focus detection, the phase difference calculation is performed using the focus detection pixels S _HA and S _HB for dividing the exit pupil of the photographing optical system in the horizontal direction (left and right direction) described in FIG. Refers to that.

The pixel arrangement shown in FIG. 22 is the same as that shown in FIG. 20. However, in focus detection, a total of 10 blocks of 1 block in the horizontal direction and 10 blocks in the vertical direction are grouped into one group. Define (k). In the second embodiment, 30 sections (k = 1 to 30) arranged in the horizontal direction constitute one focus detection area (AF area). That is, an area of 100 rows × 300 columns = 30,000 pixels is one focus detection area. Here, in one section, five focus detection pixels S _HA that perform pupil division in the horizontal direction and five focus detection pixels S _HB that perform pupil division in the vertical direction are included. Therefore, in the second embodiment, the outputs of the five focus detection pixels S _HA are added to form a 1AF pixel of an A image (one image signal) for phase difference calculation. Similarly, the outputs of the five _SHBs are added to form a 1AF pixel of the B image (the other image signal) for phase difference calculation.

FIG. 23 is a diagram for explaining a pixel grouping method in the case where vertical focus detection is performed on a subject image formed by the photographing optical system. The focus detection in the vertical direction is the phase difference type focus detection using the focus detection pixels S _VC and S _VD for dividing the exit pupil of the photographing optical system in the vertical direction (vertical direction) described in FIG. To do. That is, this corresponds to the technique described with reference to FIG. 22 rotated 90 degrees.

The pixel arrangement shown in FIG. 23 is the same as that shown in FIG. 20, but in focus detection, a total of 10 blocks, 10 blocks in the vertical direction and 1 block in the vertical direction, are grouped into a group SCTv. Define (k). In the second embodiment, one focus detection region is configured by 30 sections (k = 1 to 30) arranged in the vertical direction. That is, an area of 300 rows × 100 columns = 30,000 pixels is one focus detection area. This one focus detection area is also defined as an AF area as in FIG. Here, in one section, five pixels _SVC that perform one pupil division in the vertical direction and five pixels _SVD that perform the other pupil division are included. Therefore, in the second embodiment, the outputs of the five _SVCs are added to form a 1AF pixel of a C image (one image signal) for phase difference calculation. Similarly, the outputs of five _SVDs are added to form a 1AF pixel of a D image (the other image signal) for phase difference calculation.

  FIGS. 24 to 26 are flowcharts for explaining the photographing operation and the focus detection process according to the second embodiment. Hereinafter, the shooting operation in the second embodiment will be described along the flowcharts of FIGS. 24 to 26 with reference to FIGS. 13 to 23 described above on the premise of live view shooting.

  FIG. 24 is a flowchart showing the photographing operation of the camera of the second embodiment. When the photographer turns on the power switch of the camera 100, in S40, the memory contents and the execution program are initialized, and the photographing preparation operation is executed. Further, a target exposure value is set. In S41, the imaging operation of the image sensor 101 is started. The exposure time is controlled to achieve the target exposure value set in S40, and a preview low-pixel moving image is output. In S42, the read moving image is displayed on the display device 17 provided on the back of the camera, and the photographer visually determines the composition at the time of photographing by viewing the preview image.

  In S43, it is determined whether or not the switch SW1_18 has been turned on. If the switch SW1_18 has not been turned on, the process returns to S41. Then, the preview image display in S42 is repeatedly executed from the driving of the image sensor 101. When SW1_18 is turned on in S43, the process proceeds to S44, and focus detection processing is executed. The focus detection process performed here will be described with reference to FIG.

  FIG. 25 is a flowchart showing the focus detection process in the second embodiment. In S <b> 50, first, the camera side MPU 6 outputs a signal accumulation instruction to the image sensor 101. Based on the instruction, the image sensor 101 starts a signal accumulation operation. When the accumulation operation ends, the focus detection pixels are read out. In the second embodiment, as described with reference to FIGS. 22 and 23, the AF pixel is configured to add the outputs of a plurality of focus detection pixels. The image sensor 101 outputs an image signal obtained from the AF pixel as an A image, a B image, a C image, or a D image, and outputs a pair of image signals to the camera side MPU 6.

  Next, in S21, the first correlation calculation is performed in the same manner as in the first embodiment. A waveform obtained by shifting the image signal acquired from the AF pixel of the image sensor 101 is referred to as a shift waveform. First, the correlation amount C (k) is calculated from each shift waveform using the above-described correlation calculation expression (1), and the phase difference of the image signal is calculated.

  Next, in S51, the camera-side MPU 6 detects abnormal pixels (saturated pixels, defective pixels) in the pair of image signals acquired in S50. Here, a saturated pixel is detected as an abnormal pixel.

  In the second embodiment, the AF pixel is configured to add the outputs of a plurality of focus detection pixels. Saturated pixels defined here are those of SCTh (k) and SCCTv (k) when at least one of the focus detection pixels included in each section SCTh (k) and SCThv (k) contains a saturated pixel. Focus detection pixels are treated as saturated pixels. The subsequent processing from S23 to S25 is the same as the processing described in the first embodiment with reference to FIG.

  When the focus detection process shown in FIG. 25 is completed, the process returns to the process of FIG. 24. In S45, the camera side MPU 6 determines whether or not the switch SW2_19 is turned on, and if it is determined that the switch SW2_19 is turned on, I do. On the other hand, if it is determined that the switch SW2_19 is not turned on, the process returns to S11.

  FIG. 26 is a flowchart of the photographing process performed in S46. When the switch SW2_19 is turned on, in S60, the aperture 22 is driven so that the target exposure value set in S40 of FIG. 24 is driven, and the aperture control of the mechanical shutter that defines the exposure time of the image sensor 101 is performed. In S61, image reading for high-pixel still image shooting, that is, reading of all pixels is performed. In S62, defective pixel interpolation of the read image signal is performed. Here, since the output of the focus detection pixel does not have RGB color information for imaging and corresponds to a defective pixel in obtaining an image, an image signal is created by interpolation from information on surrounding imaging pixels. To be born.

  In S63, image processing such as γ correction and edge enhancement of the image is performed, and in S64, the captured image is recorded in a memory (not shown). In S65, the photographed image is displayed on the display device 17, and the process returns to the photographing operation process of FIG.

  As described above, according to the second embodiment, even when the focus detection pixels are discretely arranged on the image sensor, the same effect as that of the first embodiment can be obtained.

  In the second embodiment, the focus detection pixels are described as a plurality of pixel pairs that shield light from areas different from each other. However, each focus detection pixel has a plurality of divided photoelectric elements. A conversion area may be provided, and a signal may be read independently from each photoelectric conversion area.

  In the first and second embodiments, the case where a saturated pixel is detected as an abnormal pixel has been described. However, the abnormal pixel of the present invention is not limited to a saturated pixel, and other defective pixels may be detected. Good.

  Further, in the first and second embodiments, four shift waveforms are used when obtaining the phase difference. However, the present invention is not limited to four, and can be achieved by using a plurality of shift waveforms. Phase difference can be derived.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

Claims (9)

The light beams passing through different pupil areas of projection optical system Taking photoelectrically converting, detection for detecting an abnormality signal included in a pair of pixel signal string outputted from the image pickup means capable of outputting a pair of pixel signal sequence Means,
For each of a plurality of different shift amounts, when the abnormal signal is present in one of the pair of pixel signal columns, the abnormal signal of the one pixel signal column and the other pixel signal column are included. exclude the images signals corresponding to the position of the abnormality signal, before SL and a calculating means for calculating respective correlation of a plurality of shift amounts different from each other while relatively shifting the pair of pixel signal string ,
The arithmetic means, when the position in the pair of pixel signal sequences of the image signal excluded when shifted by the first shift amount is the first position, a second shift different from the first shift amount also in the pair of pixel signal sequence shifted by an amount, the first by excluding the image signal corresponding to the position, and the first of said pair of pixel signal sequence shifted by the shift amount, the second for each shift amount of the pair of pixel signal sequence shifted in, the focus detection device, characterized in that by excluding equal number of images signals for calculating a correlation amount. Detection means for detecting an abnormal signal contained in a pair of pixel signal sequences output from an imaging means capable of photoelectrically converting light beams that have passed through different pupil regions of the imaging optical system and outputting a pair of pixel signal sequences When,
  For each of a plurality of different shift amounts, when the abnormal signal is present in one of the pair of pixel signal columns, the abnormal signal of the one pixel signal column and the other pixel signal column are included. And calculating means for calculating correlation amounts at a plurality of different shift amounts while relatively shifting the pair of pixel signal sequences, excluding image signals corresponding to the positions of the abnormal signals to be detected,
  In a case where there is a position where the abnormal signal exists with at least one shift amount among a plurality of different shift amounts, the calculation means includes the pair of pixel signal sequences of the plurality of different shift amounts, A focus detection apparatus that calculates a correlation amount by excluding an image signal at a position where an abnormal signal exists. Prior to the detection of an abnormal signal by the detection means, the calculation means performs preprocessing for obtaining a shift amount that maximizes the correlation, based on the correlation amount obtained by shifting the pair of pixel signal sequences ,
The detection means detects the position of the abnormal signal at a predetermined number of different shift amounts across the shift amount at which the correlation obtained by the preprocessing is highest,
The said calculating means calculates | requires the correlation amount in the said predetermined number of different shift amounts, when calculating | requiring the said correlation amount using the said pair of pixel signal sequence after the said exclusion. The focus detection apparatus according to 1 or 2 . Said calculating means, characterized in that excluding said abnormal signal of each of the pair of pixel signal string, the images signal corresponding to the abnormal signal included in the other pixel signal string, a normal image signal in the vicinity The focus detection apparatus according to any one of claims 1 to 3 . The focal point according to any one of claims 1 to 4 , wherein the imaging unit includes a pair of line sensors that respectively receive light beams that have passed through different pupil regions of the photographing optical system. Detection device. A focus detection apparatus according to any one of claims 1 to 5 ,
Wherein the light beam incident through the imaging optical system and photoelectrically converted, an imaging apparatus characterized by having an imaging means for outputting a signal. The imaging means has a plurality of pixels arranged two-dimensionally, and a pair of pixels obtained by receiving at least a part of the plurality of pixels, respectively, light beams that have passed through different pupil regions of the photographing optical system configured as capable of focus detection pixels for outputting a signal sequence,
Said detecting means and said calculating means, according to a pair of pixel signal sequence output from the focus detection is possible pixel to claim 6, characterized by using as a pixel signal string output from the imaging unit Imaging device. The light beams passing through different pupil areas of projection optical system Taking photoelectrically converting, detection for detecting an abnormality signal included in a pair of pixel signal string outputted from the image pickup means capable of outputting a pair of pixel signal sequence Process,
For each of a plurality of different shift amounts, when the abnormal signal is present in one of the pair of pixel signal columns, the abnormal signal of the one pixel signal column and the other pixel signal column are included. and images signals and exclude exclusion process corresponding to the position of the abnormality signal,
A calculation step of calculating a correlation amount at a different shift amount while relatively shifting the pair of pixel signal sequences after the exclusion,
In the exclusion step, a second shift different from the first shift amount when the position of the image signal excluded when the shift is performed by the first shift amount is set to the first position. also in the pair of pixel signal sequence shifted by an amount, the first by excluding the image signal corresponding to the position, and the first of said pair of pixel signal sequence shifted by the shift amount, the second for each shift amount of the pair of pixel signal sequence shifted in the focus detection method characterized by excluding equal number of images signals. A detection step of detecting an abnormal signal included in a pair of pixel signal sequences output from an imaging unit capable of photoelectrically converting light beams that have passed through different pupil regions of the imaging optical system and outputting a pair of pixel signal sequences When,
  For each of a plurality of different shift amounts, when the abnormal signal is present in one of the pair of pixel signal columns, the abnormal signal of the one pixel signal column and the other pixel signal column are included. An exclusion step of excluding the image signal corresponding to the position of the abnormal signal
  A calculation step of calculating a correlation amount at a different shift amount while relatively shifting the pair of pixel signal sequences after the exclusion,
  In the exclusion step, when there is a position where the abnormal signal exists with at least one shift amount among a plurality of different shift amounts, the pair of pixel signal sequences of the plurality of different shift amounts, A focus detection method characterized by excluding an image signal at a position where an abnormal signal exists.

Images