JP2017173615A - Focus adjustment device and image capturing device - Google Patents

Abstract

A focus adjustment device and an imaging device that are resistant to changes in the amount of light of a subject are provided. A photoelectric conversion unit that photoelectrically converts light incident through an optical system to store charges, and the photoelectric conversion unit stores charges in a first time and a second time longer than the first time. And a controller that adjusts the focal position of the optical system based on a second output from the photoelectric converter that has accumulated charges in the second time by the controller. [Selection] Figure 4

Description

  The present invention relates to a focus adjustment device and an imaging device.

  A technique for improving the S / N ratio of a focus detection signal by adding a plurality of pixel outputs is known (for example, Patent Document 1). In such a technique, it is necessary to provide an additional focus detection pixel for use in addition.

JP 2009-3122 A

According to the first aspect of the present invention, the focus adjustment device includes a photoelectric conversion unit that photoelectrically converts light incident through the optical system to accumulate charges, a first time period in the photoelectric conversion unit, and the first The focus position of the optical system is adjusted based on a control unit that accumulates charges in a second time longer than the time, and a second output from the photoelectric conversion unit that accumulates charges in the second time by the control unit. And an adjustment unit.
According to the second aspect of the present invention, the focus adjustment device includes a photoelectric conversion unit that photoelectrically converts light incident through the optical system to store charges, a first time period in the photoelectric conversion unit, and the first A control unit that accumulates charges in a second time shorter than the second time and a third time that is different from the second time, and a first output from the photoelectric conversion unit that accumulates charges in the first time, or in the third time An adjustment unit that adjusts a focal position of the optical system based on a third output from the photoelectric conversion unit that has accumulated electric charge.
According to the third aspect of the present invention, the imaging apparatus includes: an imaging element that captures an image by an optical system; a photoelectric conversion unit that photoelectrically converts light incident through the optical system to store charges; and the imaging A control unit that causes the photoelectric conversion unit to accumulate charges in a first time and a second time between a first imaging and a second imaging by the element, and the photoelectric that has accumulated charges in the first time by the control unit. An adjustment unit that adjusts a focal position of the optical system based on a first output from the conversion unit and a second output from the photoelectric conversion unit that has accumulated charges in the second time period.

Sectional drawing which shows the structure of an imaging device typically Explanatory drawing of focus detection device Timing chart for automatic focus adjustment when the release switch is half-pressed Timing chart for automatic focus adjustment when the release switch is fully pressed Timing chart for automatic focus adjustment when the release switch is fully pressed Explanatory drawing of the first focus detection result Explanatory drawing of the second focus detection result

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing the configuration of the imaging apparatus according to the first embodiment. The imaging device 1 is a so-called single-lens reflex digital camera. The imaging device 1 includes a camera body 100 and an interchangeable lens 200. The interchangeable lens 200 is provided with an imaging optical system 205 that includes a plurality of lenses 202, 203, and 204. In FIG. 1, the imaging optical system 205 is illustrated as if it is configured by three lenses, but any number of lenses may be configured.

  A lens 203 included in the imaging optical system 205 is a focus lens that adjusts the focal position of the imaging optical system 205. The focus lens 203 is driven in a direction X along the optical axis O of the imaging optical system 205 by an actuator (not shown).

  The camera body 100 includes an imaging element 102 such as a CCD or a CMOS that captures a subject image formed by the imaging optical system 205. The image sensor 102 is arranged so that the imaging surface coincides with the planned focal plane of the imaging optical system 205. A quick return mirror 103 is installed between the imaging optical system 205 and the imaging surface of the imaging element 102 in the camera body 100. At the time of non-photographing, the quick return mirror 103 exists on the optical path of the imaging optical system 205 and reflects subject light in the direction of the focusing screen 104 and the pentaprism 105. The photographer can view the subject image from the viewfinder unit 107 through the eyepiece 106.

  A sub mirror 108 is installed on the back surface of the quick return mirror 103. The surface (reflecting surface) of the quick return mirror 103 is half-mirror processed, and subject light incident thereon passes through the quick return mirror 103 and enters the sub mirror 108. The sub mirror 108 reflects this light beam below the camera body 100. Below the camera body 100, a focus detection device 109 that performs focus detection by a so-called pupil division phase difference detection method is provided.

  The camera body 100 includes a control unit 101 including a microprocessor and its peripheral circuits. The control unit 101 controls each unit of the imaging apparatus 1 by reading and executing a predetermined control program stored in advance in a memory (not shown). Note that the control unit 101 may be configured by an electronic circuit that performs an operation corresponding to the control program.

  When a predetermined automatic focus adjustment operation (for example, a half-press operation of a release switch (not shown)) is performed, the control unit 101 executes an automatic focus adjustment (AF) process described later. With this AF process, the focus lens 203 is driven and the subject is focused.

  When a predetermined still image shooting operation (for example, full pressing operation of a release switch (not shown)) is performed, the control unit 101 performs imaging control. At this time, the control unit 101 moves the quick return mirror 103 and the sub mirror 108 from the light shielding position shown in FIG. Take an image. The control unit 101 performs various image processing on the imaging signal output from the imaging element 102, generates still image data, and stores it in a storage medium (not shown) (for example, a memory card).

  On the back surface of the camera body 100, for example, a monitor 110 composed of a display element such as a liquid crystal is provided. The control unit 101 uses the monitor 110 to display, for example, reproduction of captured still image data and moving image data, display of a setting menu for shooting parameters (F value, shutter speed, etc.), display of a through image during moving image shooting, and the like. Do.

  FIG. 2 is an explanatory diagram of the focus detection device 109. FIG. 2A is a plan view showing a focus detection area arranged on the imaging screen, and FIG. 2B is a plan view schematically showing a photoelectric conversion unit corresponding to one focus detection area. .

  A total of 13 focus detection areas 11 are arranged on the imaging screen 10 shown in FIG. The focus detection device 109 is configured to be able to calculate a focus evaluation value (perform focus detection) for each focus detection region 11. Note that the number and positions of the focus detection areas 11 illustrated in FIG. 2A are merely examples, and a larger number of focus detection areas 11 may be provided, or may be different from the positions illustrated in FIG. The focus detection area 11 may be provided at the position. Hereinafter, processing such as focus detection will be described by focusing on one focus detection region 11, but naturally the contents to be described can be applied to a plurality of focus detection regions 11.

  FIG. 2B shows the photoelectric conversion unit 20 corresponding to one focus detection region 11. The focus detection device 109 includes a plurality of photoelectric conversion units 20 illustrated in FIG. 2B for each focus detection region 11. The photoelectric conversion unit 20 includes a first photoelectric conversion element array 20A and a second photoelectric conversion element array 20B. The first photoelectric conversion element array 20A and the second photoelectric conversion element array 20B have a plurality of photoelectric conversion elements 21 arranged in a line.

  The focus detection device 109 divides the reflected light from the sub mirror 108 into a pair of light beams by a pair of re-imaging lenses (not shown). One of the pair of light beams is incident on the first photoelectric conversion element array 20A. The other of the pair of light beams enters the second photoelectric conversion element array 20B. The focus detection device 109 calculates the phase difference between the photoelectric conversion signal by the first photoelectric conversion element array 20A and the photoelectric conversion signal by the second photoelectric conversion element array 20B by a known method, and uses the known method from the phase difference. The focus evaluation value is calculated.

(Explanation of automatic focus adjustment processing when not shooting)
FIG. 3 is a timing chart relating to automatic focus adjustment processing when the release switch is half-pressed. The horizontal axis in FIG. 3 indicates the passage of time, and the time advances from the left to the right of the page. When the user performs a half-press operation of a release switch (not shown) (when the release switch is half-pressed), the control unit 101 executes an automatic focus adjustment process. While the release switch is in the half-pressed state, the control unit 101 repeatedly executes the automatic focus adjustment process to try to maintain a state where the subject is in focus.

  In FIG. 3, various processes other than the focus adjustment executed by the control unit 101 (for example, updating the display contents of the monitor 110) are referred to as “other processes”. At time t0 in FIG. 3, the control unit 101 performs such processing.

  The focus detection device 109 according to the present embodiment performs focus detection in two stages. The process from time t1 to t4 is the first stage process of focus detection, and the process from time t5 to t8 is the second stage process of focus detection.

  In the first stage, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges for the purpose of measuring the amount of light of the subject (time t1 to t2). The focus detection device 109 reads out the photoelectric conversion signal by this charge accumulation from the photoelectric conversion unit 20 (time t2 to t3). The control unit 101 determines the charge accumulation time (accumulation time) in the second stage based on the output from the photoelectric conversion unit 20 by this charge accumulation (time t3 to t4). In FIG. 3, this process is described as a time determination process.

  In the time determination process, the control unit 101 calculates the accumulation time in the second stage from the charge accumulation result in the first stage. For example, the charge accumulation result in the first stage (that is, the magnitude of the photoelectric conversion signal from the photoelectric conversion unit 20) is given to an expression showing the relationship between the magnitude of the photoelectric conversion signal from the photoelectric conversion unit 20 and the amount of light of the subject, and the subject Find the amount of light. Thereafter, a sufficiently long accumulation time is calculated without being saturated with the subject light amount.

  In the second stage, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges for the time determined by the time determination process (time t5 to t6). The focus detection device 109 reads out the photoelectric conversion signal by the charge accumulation from the photoelectric conversion unit 20 (time t6 to t7). The focus detection device 109 calculates a focus evaluation value based on the output from the photoelectric conversion unit 20 due to this charge accumulation (time t7 to t8). The control unit 101 drives the focus lens 203 based on the calculated focus evaluation value (time t8 to t9).

  As described above, while the release switch is half-pressed, the process shown in FIG. 3 is repeatedly executed. That is, after the period illustrated in FIG. 3, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges for the purpose of measuring the amount of light of the subject (second first stage). Based on the output from the conversion unit 20, the accumulation time in the second stage of the second time is determined. Thereafter, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges for the time determined by the time determination process in the second first stage (second second stage), and the photoelectric conversion unit 20 based on this charge accumulation. Based on the output from, the focus evaluation value is calculated. The control unit 101 drives the focus lens 203 based on the calculated focus evaluation value.

  In the second and subsequent time determination processes, the control unit 101 uses not only the result of the charge accumulation in the first stage of this time but also the result of the charge accumulation in the second stage of the previous time, and uses the result of the current second stage. Determine the accumulation time. For example, the control unit 101 compares the subject light amount obtained from the charge accumulation result in the previous second stage and the subject light amount obtained from the current charge accumulation result in the first stage. If the difference between the two is less than a predetermined amount, it means that the subject light amount has hardly changed since the previous focus detection, so the previously determined accumulation time (the time calculated from the result of the charge accumulation in the previous first stage) Is used as it is. On the other hand, if the difference between the two is equal to or greater than the predetermined amount, it means that the subject light amount has changed from the previous focus detection, and therefore the accumulation time is calculated from the result of the charge accumulation in the first stage this time.

  The charge accumulation in the first stage is charge accumulation for determining the accumulation time in the second stage. Therefore, the accumulation time of the first stage may be a time that can measure the amount of light of the subject, and is shorter than the accumulation time of the second stage as illustrated in FIG. When the amount of light of the subject is extremely large, the first stage accumulation time may be longer than the second stage accumulation time. Further, not only the accumulation time but also the sensitivity (gain) of the photoelectric conversion unit 20 is adjusted, the first stage accumulation time may be longer than the second stage accumulation time.

  When the focus detection is not divided into two stages and the automatic focus adjustment is performed only by the process of the second stage, the accumulation time is determined by the result of the charge accumulation performed in the previous automatic focus adjustment. For example, when the amount of light of the subject changes greatly after the previous automatic focus adjustment, there is a possibility that the current accumulation time does not match the amount of light of the subject and the output of the photoelectric conversion unit 20 is saturated. In this case, since focus detection cannot be performed correctly, the current automatic focus adjustment is skipped, and the lens cannot be driven until the next automatic focus adjustment. In the present embodiment, since charge accumulation for determining the accumulation time is performed in the first stage processing, focus detection can always be performed correctly.

  It should be noted that the first stage process is preferably executed as close as possible to the second stage process. In other words, this is to follow the light amount change of the subject as quickly as possible. For example, it is conceivable to execute the first stage process and the second stage process continuously. However, in such a case, the period during which the control unit 101 is continuously occupied for automatic focus adjustment becomes long. That is, the period during which other processing cannot be performed becomes long. Therefore, in the present embodiment, a time interval is provided between the first stage process and the second stage process. It is not necessary to provide a time interval between the first stage process and the second stage process.

(Explanation of automatic focus adjustment process during shooting)
FIG. 4 is a timing chart relating to automatic focus adjustment processing when the release switch is fully pressed. The horizontal axis of FIG. 4 shows the passage of time, and the time progresses from the left to the right of the page. When the user fully presses a release switch (not shown) (when the release switch is fully pressed), the control unit 101 performs a photographing process.

  In the photographing process, the control unit 101 moves the quick return mirror 103 and the sub mirror 108 to the retracted position (time t11 to t12). Thereafter, the control unit 101 causes the image sensor 102 to capture a subject image (time t13 to t14). The control unit 101 executes various image processing on the imaging signal output from the imaging element 102 to generate still image data (time t14 to t15), and stores the still image data in a storage medium (not shown). (Time t15 to t16). The control unit 101 moves the quick return mirror 103 and the sub mirror 108 from the light shielding position to the retracted position (time t17 to t20), and ends the photographing process.

  In the present embodiment, there is some time between the completion of the movement of the quick return mirror 103 and the sub mirror 108 to the retracted position and the start of imaging of the subject image by the image sensor 102 (time t12 to t13). . This is because the quick return mirror 103 and the sub mirror 108 vibrate immediately after the quick return mirror 103 and the sub mirror 108 move to the retracted position, and the subject image may not be stabilized.

  While the release switch is fully pressed, the control unit 101 repeatedly performs shooting processing to continuously capture subject images (so-called continuous shooting function). The control unit 101 executes an automatic focus adjustment process between the shooting process so that an in-focus image can be obtained even when the subject moves between the continuous shooting frames. Hereinafter, the automatic focus adjustment process executed at the time of photographing will be described.

  The focus detection apparatus 109 according to the present embodiment performs focus detection in two stages in the automatic focus adjustment process executed at the time of shooting, as in the above-described automatic focus adjustment process at the time of non-shooting. The process from time t18 to t21 is the first stage process of focus detection, and the process from time t22 to t25 is the second stage process of focus detection.

  In the first stage, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges for the purpose of measuring the amount of light of the subject (time t18 to t19). The focus detection device 109 reads out the photoelectric conversion signal by this charge accumulation from the photoelectric conversion unit 20 (time t19 to t20). The focus detection device 109 determines the charge accumulation time (accumulation time) in the second stage based on the output from the photoelectric conversion unit 20 by the charge accumulation (time t20 to t21).

  In the second stage, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges for the time determined by the time determination process in the first stage (time t22 to t23). The focus detection device 109 reads out the photoelectric conversion signal by this charge accumulation from the photoelectric conversion unit 20 (time t23 to t24). The focus detection device 109 calculates a focus evaluation value based on the output from the photoelectric conversion unit 20 due to the charge accumulation (time t24 to t25). The control unit 101 drives the focus lens 203 based on the calculated focus evaluation value (time t25 to t26).

  Unlike the automatic focus adjustment process at the time of non-photographing described above, the focus detection device 109 is configured so that the quick return mirror 103 and the sub mirror 108 move from the retracted position to the light shielding position (transition from the mirror up state to the mirror down state). The first stage processing is executed. In other words, the movement period from the retracted position of the quick return mirror 103 and the sub mirror 108 to the light shielding position and the processing period of the first stage at least partially overlap. As described above, some time is required until the vibration is settled and stabilized after the quick return mirror 103 and the sub mirror 108 are moved to the light shielding position. This time can also be considered as a part of the moving period from the retracted position of the quick return mirror 103 and the sub mirror 108 to the light shielding position.

  Since the photoelectric conversion unit 20 performs charge accumulation while the quick return mirror 103 and the sub mirror 108 are moving, the result of charge accumulation in the first stage is not suitable for focus detection calculation. However, the charge accumulation in the first stage is charge accumulation for determining the accumulation time in the second stage as described above. Therefore, it does not matter that the quick return mirror 103 and the sub mirror 108 are moving.

  The focus detection device 109 calculates the amount of light of the subject in consideration that the quick return mirror 103 and the sub mirror 108 are moving. For example, if the result of charge accumulation in the first stage is acquired with a light beam from a subject whose amount of light is known, the output of the photoelectric conversion unit 20 corresponding to a certain amount of light can be determined. By repeating this procedure for subjects with various light amounts, it is possible to know the correspondence between the light amount of the subject and the charge accumulation result in the first stage. Such a measurement is performed in advance, and the above processing is implemented in the focus detection apparatus 109 by creating a table of correspondences and creating an arithmetic expression indicating the correspondences.

  When focus detection is not divided into two stages and the next accumulation time is determined and automatic focus adjustment is performed only by the second stage process, the accumulation time is determined by the result of the charge accumulation performed during the previous automatic focus adjustment. Will be. For example, when the amount of light of the subject changes greatly after the previous automatic focus adjustment, there is a possibility that the current accumulation time does not match the amount of light of the subject and the output of the photoelectric conversion unit 20 is saturated. In this case, since focus detection cannot be performed correctly, the current automatic focus adjustment is skipped, and the lens cannot be driven until the next automatic focus adjustment. In the present embodiment, since charge accumulation for determining the accumulation time is performed in the first stage processing, focus detection can always be performed correctly.

  It should be noted that the first stage process is preferably executed as close as possible to the second stage process. This is to follow the change in the amount of light of the subject as quickly as possible. In this embodiment, since the first stage processing is performed while the mirror is down, the first stage processing and the second stage processing can be executed at very close timings, and quickly follow the change in the amount of light of the subject. can do.

  As described above, while the release switch is fully pressed, the process shown in FIG. 4 is repeatedly executed. That is, after the period illustrated in FIG. 4, the quick return mirror 103 and the sub mirror 108 are moved again to the retracted position, and the image sensor 102 captures the subject image. Thereafter, the quick return mirror 103 and the sub mirror 108 are moved again to the light shielding position. During the movement, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges for the purpose of measuring the amount of light of the subject (2 Based on the output from the photoelectric conversion unit 20 due to this charge accumulation, the accumulation time in the second stage is determined. After the quick return mirror 103 and the sub mirror 108 move to the light shielding position, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges for the time determined by the time determination process in the second first stage (second time). Second stage), a focus evaluation value is calculated based on the output from the photoelectric conversion unit 20 by this charge accumulation. The control unit 101 drives the focus lens 203 based on the calculated focus evaluation value.

According to the embodiment described above, the following operational effects can be obtained.
(1) The photoelectric conversion unit 20 photoelectrically converts the light incident via the imaging optical system 205 to perform charge accumulation. The control unit 101 causes the photoelectric conversion unit 20 to accumulate charges for a first time and a second time longer than the first time. The control unit 101 adjusts the focal position of the imaging optical system 205 based on the output from the photoelectric conversion unit 20 that has accumulated charges in the second time. Since this is done, it is possible to provide a focus adjustment function that is resistant to changes in the amount of light of the subject.

(2) The control unit 101 causes the photoelectric conversion unit 20 to accumulate charges in the second time determined based on the output from the photoelectric conversion unit 20 that accumulated charges in the first time. Since it did in this way, suitable charge storage time when the output from the photoelectric conversion part 20 is not saturated can be determined.

(3) The control unit 101 calculates the second time based on the output from the photoelectric conversion unit 20 that has accumulated charges in the first time. Since it did in this way, the optimal charge accumulation time according to the present light quantity of a to-be-photographed object can be applied.

(4) The control unit 101 causes the photoelectric conversion unit 20 to accumulate charges in the second time, and then causes the photoelectric conversion unit 20 to accumulate charges in the third time and a fourth time longer than the third time, and performs the third time. The charge is accumulated in the photoelectric conversion unit 20 in the fourth time determined based on the third output from the photoelectric conversion unit 20. Since it did in this way, focus adjustment can be repeatedly performed over a long period of time.

(5) The control unit 101 accumulates the charge in the fourth time determined based on the output from the photoelectric conversion unit 20 that accumulated the charge in the second time and the output from the photoelectric conversion unit 20 that accumulated the charge in the third time. Let Since this is done, the charge accumulation time can be determined more precisely in consideration of the past charge accumulation results.

(6) The control unit 101 adjusts the focal position of the imaging optical system 205 based on the output from the photoelectric conversion unit 20 that has accumulated charges in the second time or the output from the photoelectric conversion unit 20 that has accumulated charges in the fourth time. To do. Since it did in this way, focus adjustment can be performed more flexibly.

(7) Based on the output from the photoelectric conversion unit 20 that has accumulated charges in the second time and the output from the photoelectric conversion unit 20 that has accumulated charges in the third time, the control unit 101 can store the photoelectric charges that have accumulated in the second time. From the output from the converter 20, the output from the photoelectric converter 20 that has accumulated charges in the third time, or the output from the photoelectric converter 20 that has accumulated charges in the second time and the photoelectric converter 20 that has accumulated charges in the third time Whether to calculate the fourth time from the output of. Since it did in this way, when there is no light quantity change, an additional process can be abbreviate | omitted.

(8) When the difference between the output from the photoelectric conversion unit 20 that has accumulated charge in the second time and the output from the photoelectric conversion unit 20 that has accumulated charge in the third time is less than a predetermined amount, The fourth time is calculated from the output from the photoelectric conversion unit 20 in which charge is accumulated in the second time, and the output from the photoelectric conversion unit 20 in which charge is accumulated in the second time and the output from the photoelectric conversion unit 20 in which charge is accumulated in the third time. If the difference from the output is greater than or equal to a predetermined amount, the fourth time is calculated from the output from the photoelectric conversion unit 20 that has accumulated charge in the third time. Since this is done, the charge accumulation time can be determined more precisely in consideration of the past charge accumulation results.

(9) The quick return mirror 103 and the sub mirror 108 have a first state in which the light beam that has passed through the imaging optical system 205 travels to the image sensor 102 and a second state in which the light beam that has passed through the imaging optical system 205 travels toward the photoelectric conversion unit 20. Are configured to be switchable. During continuous shooting, the control unit 101 causes the photoelectric conversion unit 20 to perform charge accumulation in the first time while the quick return mirror 103 and the sub mirror 108 are switched from the first state to the second state, and the quick return mirror 103 and the sub mirror While 108 is in the second state, the photoelectric conversion unit 20 is caused to accumulate charges in the second time. Since this is done, it is possible to provide a focus adjustment function that is resistant to changes in the amount of light of the subject without reducing the continuous shooting speed for the first stage charge accumulation.

(10) The quick return mirror 103 and the sub mirror 108 have a first state in which the light beam that has passed through the imaging optical system 205 travels toward the image sensor 102 and a second state in which the light beam that has passed through the imaging optical system 205 travels toward the photoelectric conversion unit 20. Are configured to be switchable. During non-photographing, the control unit 101 causes the photoelectric conversion unit 20 to perform charge accumulation in the first time and the second time while the quick return mirror 103 and the sub mirror 108 are in the second state. Since it did in this way, the focus adjustment function strong against the light quantity change of a to-be-photographed object can be provided, keeping the period when another process cannot be performed for a focus adjustment process to the minimum.

(11) The quick return mirror 103 and the sub mirror 108 have a first state in which the light beam that has passed through the imaging optical system 205 travels toward the image sensor 102 and a second state in which the light beam that has passed through the imaging optical system 205 travels toward the photoelectric conversion unit 20. Are configured to be switchable. At the time of continuous shooting, the control unit 101 causes the photoelectric conversion unit 20 to accumulate charges in the first time or the third time while the quick return mirror 103 and the sub mirror 108 are switched from the first state to the second state. While the mirror 103 and the sub-mirror 108 are in the second state, the photoelectric conversion unit 20 accumulates charges in the second time or the fourth time. Since this is done, it is possible to provide a focus adjustment function that is resistant to changes in the amount of light of the subject without reducing the continuous shooting speed for the first stage charge accumulation.

(Second Embodiment)
The imaging apparatus according to the second embodiment has the same configuration as the imaging apparatus 1 (FIG. 1) according to the first embodiment, and is different from the first embodiment in automatic focus adjustment processing. Is executed during continuous shooting. The automatic focus adjustment process during continuous shooting according to the second embodiment will be described below.

  FIG. 5 is a timing chart relating to automatic focus adjustment processing when the release switch is fully pressed. The horizontal axis in FIG. 5 indicates the passage of time, and the time progresses from the left to the right of the page. When the user fully presses a release switch (not shown) (when the release switch is fully pressed), the control unit 101 performs a photographing process. Since the contents of the photographing process are the same as those in the first embodiment, description thereof is omitted.

  While the release switch is fully pressed, the control unit 101 repeatedly performs shooting processing to continuously capture subject images (so-called continuous shooting function). The control unit 101 executes an automatic focus adjustment process between the shooting process so that an in-focus image can be obtained even when the subject moves between the continuous shooting frames. Hereinafter, the automatic focus adjustment process executed at the time of photographing will be described.

  The focus detection apparatus 109 according to the present embodiment performs focus detection twice in the automatic focus adjustment process executed at the time of shooting. The process from time t32 to t35 is the first focus detection process, and the process from time t36 to t39 is the second focus detection process. Both of these focus detections are performed when the quick return mirror 103 and the sub mirror 108 are in the light shielding position.

  In the first focus detection process, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges (time t32 to t33). This charge accumulation is performed for the purpose of focus detection, unlike the first stage processing in the first embodiment. The charge accumulation time is appropriately determined from, for example, the amount of subject light detected in the past. The focus detection device 109 reads out the photoelectric conversion signal by this charge accumulation from the photoelectric conversion unit 20 (time t33 to t34). The focus detection device 109 calculates a focus evaluation value based on the output from the photoelectric conversion unit 20 due to the charge accumulation (time t34 to t35).

  In the first focus detection process, for example, when a part of the photoelectric conversion signal is too low (so-called blackened state), the focus evaluation value in that part cannot be calculated. Such a case may occur when the light amount of the subject has changed significantly since the previous focus detection. If the focus evaluation value cannot be calculated for a part of the photoelectric conversion signal due to, for example, a part of the photoelectric conversion signal being blacked out, the part is set to an appropriate output level. Is calculated (time t35 to t36). In FIG. 5, the processing for calculating the accumulation time is expressed as time determination processing.

  Note that not the accumulation time but the sensitivity (gain) of the photoelectric conversion unit 20 may be determined so that the output signal does not become a blackout state. Further, both accumulation time and sensitivity may be determined.

  The focus detection device 109 performs a second focus detection process based on the calculated accumulation time. In the second focus detection process, the focus detection device 109 causes the photoelectric conversion unit 20 to accumulate charges (time t36 to t37). The accumulation time here is the accumulation time calculated by the time determination process described above. The focus detection device 109 reads out the photoelectric conversion signal by this charge accumulation from the photoelectric conversion unit 20 (time t37 to t38). The focus detection device 109 calculates a focus evaluation value based on the output from the photoelectric conversion unit 20 due to the charge accumulation (time t38 to t39).

  The control unit 101 applies the focus evaluation value of the same part calculated in the second focus detection process as the focus evaluation value of the part that could not be calculated in the first focus detection process. In the second focus detection process, since the photoelectric conversion signal of the portion has an appropriate signal level, the focus evaluation value can be correctly calculated. The control unit 101 ignores the calculation result in the second focus detection process for the part for which the focus evaluation value can be calculated in the first focus detection process. Thereby, the focus evaluation value is correctly calculated for the entire area of one focus detection area 11. The control unit 101 drives the focus lens 203 based on the calculated focus evaluation value (time t39 to t40).

  FIG. 6 is an explanatory diagram of the first focus detection result. FIG. 6A shows an example of a photoelectric conversion signal obtained as a result of charge accumulation in the first focus detection. In addition, what is illustrated here is a photoelectric conversion output from the first photoelectric conversion element array 20 </ b> A constituting the photoelectric conversion unit 20. The photoelectric conversion output from the other second photoelectric conversion element array 20B is not shown.

  In FIG. 6A, the horizontal axis indicates the element position in the photoelectric conversion element array, and the vertical axis indicates the signal output. In FIG. 6A, the range (element position) of the photoelectric conversion elements 21 included in the first photoelectric conversion element array 20A is expressed as x0 to x3. The output signal S1 is above the threshold th1 in the range of x1 to x2, but is below the threshold th1 in the range of x0 to x1 and the range of x2 to x3. Here, the threshold value th1 indicates a minimum signal level necessary for correctly obtaining the focus evaluation value. That is, when the signal level is lower than the threshold value th1, that portion is in a so-called blackened state.

  In the following description, a photoelectric conversion signal in the range of x0 to x1 is referred to as an output signal S11, a photoelectric conversion signal in the range of x1 to x2 is referred to as an output signal S12, and a photoelectric conversion signal in the range of x2 to x3 is referred to as an output signal S13.

  FIG. 6B schematically shows the result of the focus detection calculation based on the output signal S1 illustrated in FIG. The focus evaluation value can be calculated correctly in the range of x1 to x2, but the focus evaluation value cannot be calculated in the range of x0 to x1 and x2 to x3.

  FIG. 7 is an explanatory diagram of the second focus detection result. FIG. 7A shows an example of a photoelectric conversion signal obtained as a result of charge accumulation in the second focus detection. In addition, what is illustrated here is a photoelectric conversion output from the first photoelectric conversion element array 20 </ b> A constituting the photoelectric conversion unit 20. The photoelectric conversion output from the other second photoelectric conversion element array 20B is not shown.

  In FIG. 7A, the horizontal axis indicates the element position in the photoelectric conversion element array, and the vertical axis indicates the signal output. By making the accumulation time longer than that in the first focus detection, the signal level of the output signal S2 generally exceeds the output signal S1 illustrated in FIG. However, in the range of x1 to x2, a part of the output signal exceeds the threshold th2. Here, the threshold value th2 indicates a saturation level.

  In the following description, the photoelectric conversion signal in the range of x0 to x1 is referred to as output signal S21, the photoelectric conversion signal in the range of x1 to x2 is referred to as output signal S22, and the photoelectric conversion signal in the range of x2 to x3 is referred to as output signal S23.

  When performing focus detection calculation in the second focus detection process, the focus detection device 109 outputs an output signal S22 in a range in which focus detection has been successfully performed in the first focus detection process, in the first focus detection process. Replace with signal S12. By doing in this way, the saturated location can be removed (replaced) from the output signal used for the focus detection calculation.

  FIG. 7B shows the output signal S3 after replacement. The output signal S3 includes the output signal S21 and the output signal S23 in the second focus detection process, and the output signal S12 in the first focus detection process. Note that the output signal S21, the output signal S23, and the output signal S12 have different overall signal levels, and thus are discontinuous signals as they are. The focus detection device 109 smoothly connects these signals having different output levels by performing known level correction processing and smoothing processing.

  FIG. 7C schematically shows the result of the focus detection calculation based on the output signal S3 illustrated in FIG. 7B. Since the signal level of the output signal S3 is the threshold value th1 or more and less than the threshold value th2 in the entire region (range of x0 to x3), the focus evaluation value can be correctly calculated in the entire region. The control unit 101 obtains a final focus detection result by replacing the portion of the first focus detection result in which focus detection has failed with the second focus detection result thus obtained.

  FIG. 7D schematically shows the final focus detection result. The focus evaluation value in the range of x1 to x2 adopts the first focus detection result as it is. The second focus detection result is adopted and applied to the range of x0 to x1 and the range of x2 to x3 (the range in which the calculation has failed in the first focus detection process).

  Note that the final focus detection result may be obtained by a process different from the simple replacement process. For example, the final focus detection result may be obtained by performing a correction calculation for correcting the first focus detection result with the second focus detection result.

According to the embodiment described above, the following operational effects can be obtained.
(1) The control unit 101 causes the photoelectric conversion unit 20 to accumulate charges during the first time and the second time between the first image pickup and the second image pickup by the image pickup device 102. The control unit 101 focuses the imaging optical system 205 based on the first output from the photoelectric conversion unit 20 that accumulates charges in the first time and the second output from the photoelectric conversion unit 20 that accumulates charges in the second time. Adjust the position. Since this is done, it is possible to provide a focus adjustment function that is resistant to changes in the amount of light of the subject.

(2) The control unit 101 determines the second time based on the first output. Since it did in this way, suitable charge storage time when the output from the photoelectric conversion part 20 is not saturated can be determined.

(3) The control unit 101 performs the first calculation based on the first output and the second calculation based on the second output, and when the focus evaluation value is not obtained by the first calculation, the focus obtained by the second calculation. The focus position of the imaging optical system 205 is adjusted by correcting with the evaluation value. Since it did in this way, the reliable focus adjustment function which can calculate a focus evaluation value reliably can be provided.

(4) The control unit 101 adjusts the focus position of the imaging optical system 205 by performing correction for applying the focus evaluation value obtained by the second calculation to the portion where the focus evaluation value has not been obtained by the first calculation. . Since it did in this way, a focus evaluation value can be corrected appropriately with a small amount of processing.

(5) The quick return mirror 103 and the sub mirror 108 have a first state in which the light beam that has passed through the imaging optical system 205 travels toward the image sensor 102 and a second state in which the light beam that has passed through the imaging optical system 205 travels toward the photoelectric conversion unit 20. Are configured to be switchable. During the continuous shooting, the control unit 101 causes the photoelectric conversion unit 20 to accumulate charges in the first time and the second time while the quick return mirror 103 and the sub mirror 108 are in the second state. Since this is done, it is possible to provide a focus adjustment function that is resistant to changes in the amount of light of the subject without reducing accuracy even during continuous shooting.

The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.
(Modification 1)
In the first embodiment, the method by which the control unit 101 determines the accumulation time in the second stage in the second and subsequent time determination processing is not limited to the method described above. For example, an appropriate accumulation time is determined by substituting the result of charge accumulation in the previous second stage and the result of charge accumulation in the first stage this time into an equation for determining the accumulation time. May be. That is, in the above-described embodiment, the result of charge accumulation in the second stage of the previous time is compared with the result of charge accumulation in the first stage of this time, and the accumulation time previously determined according to the comparison result is adopted. Whether to use the accumulation time calculated from the result of charge accumulation in the first stage has been switched. On the other hand, in the above modification, the accumulation time in the second stage of this time is calculated from the result of charge accumulation in the second stage of the previous time and the result of charge accumulation in the first stage of this time. The same applies to the time determination process in the second embodiment.

(Modification 2)
In each of the above-described embodiments, a so-called single-lens reflex camera type digital camera has been described. However, other embodiments may be considered. For example, the automatic focus detection process at the time of non-photographing in the first embodiment and the automatic focus detection process at the time of continuous shooting in the second embodiment are performed using a quick return mirror such as a so-called compact camera or a built-in camera of a mobile phone. It can also be applied to cameras that do not have

  Further, a so-called image plane phase difference focus detection method in which the photoelectric conversion unit 20 is provided in the image sensor 102 can be applied to each embodiment.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Imaging device, 20 ... Photoelectric conversion part, 100 ... Camera body, 101 ... Control part, 102 ... Imaging element, 103 ... Quick return mirror, 108 ... Submirror, 109 ... Focus detection apparatus, 200 ... Interchangeable lens, 205 ... Imaging Optical system

Claims (18)

A photoelectric conversion unit that photoelectrically converts light incident through the optical system and accumulates charges; and
A control unit that causes the photoelectric conversion unit to accumulate charges in a first time and a second time longer than the first time;
An adjustment unit that adjusts a focal position of the optical system based on a second output from the photoelectric conversion unit that has accumulated charges in the second time by the control unit;
A focus adjustment device. The focus adjustment apparatus according to claim 1,
The control unit is configured to cause the photoelectric conversion unit to store electric charges in the second time determined based on a first output from the photoelectric conversion unit that has accumulated electric charges in the first time. The focusing apparatus according to claim 2, wherein
The control unit is a focus adjustment device that calculates the second time based on the first output. The focus adjustment apparatus according to any one of claims 1 to 3,
An image sensor that captures an image of a light beam that has passed through the optical system;
A mirror unit capable of switching between a first state in which the light beam that has passed through the optical system is directed to the image sensor and a second state in which the light beam that has passed through the optical system is directed to the photoelectric conversion unit;
The control unit causes the photoelectric conversion unit to perform charge accumulation in the first time while the mirror unit switches from the first state to the second state, and while the mirror unit is in the second state. An image pickup apparatus that causes the photoelectric conversion unit to perform charge accumulation in the second time. The focus adjustment apparatus according to any one of claims 1 to 3,
An image sensor that captures an image of a light beam that has passed through the optical system;
A mirror unit capable of switching between a first state in which the light beam that has passed through the optical system is directed to the image sensor and a second state in which the light beam that has passed through the optical system is directed to the photoelectric conversion unit;
The control unit is an imaging apparatus that causes the photoelectric conversion unit to perform charge accumulation in the first time and the second time while the mirror unit is in the second state. A photoelectric conversion unit that photoelectrically converts light incident through the optical system and accumulates charges; and
A control unit that causes the photoelectric conversion unit to accumulate charges in a first time, a second time shorter than the first time, and a third time different from the second time;
Adjustment for adjusting the focal position of the optical system based on the first output from the photoelectric conversion unit that has accumulated charge in the first time or the third output from the photoelectric conversion unit that has accumulated charge in the third time And
A focus adjustment device. The focusing apparatus according to claim 6, wherein
The control unit charges the photoelectric conversion unit in the third time determined based on the second output from the photoelectric conversion unit that has accumulated the charge in the second time, or the first output and the second output. Focus adjustment device to accumulate. The focus adjustment device according to claim 7.
The control unit is a focus adjustment device that calculates the third time based on the first output, the second output, or the first output and the second output. In the focus adjustment apparatus according to any one of claims 6 to 8,
The control unit is configured to control the first output, the second output, or the first output and the first output based on the first output and the second output from the photoelectric conversion unit that has accumulated charges in the second time. A focus adjustment device that determines whether to calculate the third time from two outputs. The focus adjustment device according to claim 9.
When the difference between the first output and the second output is less than a predetermined amount, the control unit calculates the third time from the first output, and the first output and the second output When the difference is equal to or greater than a predetermined amount, the focus adjustment device calculates the third time from the second output, or from the first output and the second output. The focus adjustment device according to any one of claims 6 to 10,
An image sensor that captures an image of a light beam that has passed through the optical system;
A mirror unit capable of switching between a first state in which the light beam that has passed through the optical system is directed to the image sensor and a second state in which the light beam that has passed through the optical system is directed to the photoelectric conversion unit;
The control unit causes the photoelectric conversion unit to perform charge accumulation in the second time while the mirror unit switches from the first state to the second state, and while the mirror unit is in the second state. In addition, an image pickup apparatus that causes the photoelectric conversion unit to perform charge accumulation in the first time or the third time. The focus adjustment device according to any one of claims 6 to 10,
An image sensor that captures an image of a light beam that has passed through the optical system;
A mirror unit capable of switching between a first state in which the light beam that has passed through the optical system is directed to the image sensor and a second state in which the light beam that has passed through the optical system is directed to the photoelectric conversion unit;
The control unit is an imaging apparatus that causes the photoelectric conversion unit to perform charge accumulation in the first time, the second time, and the third time while the mirror unit is in the second state. The focus adjustment device according to any one of claims 1 to 10,
An image sensor that has a plurality of photoelectric conversion units including the photoelectric conversion unit and captures an image of a light beam that has passed through the optical system;
An imaging apparatus comprising: An image sensor for capturing an image by an optical system;
A photoelectric conversion unit that photoelectrically converts light incident through the optical system and accumulates charges;
A control unit that causes the photoelectric conversion unit to accumulate charges in a first time and a second time between the first imaging and the second imaging by the imaging element;
The focus of the optical system is based on the first output from the photoelectric conversion unit that has accumulated charges in the first time by the control unit and the second output from the photoelectric conversion unit that has accumulated charges in the second time. An imaging apparatus comprising: an adjustment unit that adjusts a position. The imaging device according to claim 14, wherein
The image pickup apparatus, wherein the control unit determines at least one of the second time and an amplification value of the second output based on the first output. The imaging device according to claim 15, wherein
The adjusting unit performs a first calculation based on the first output and a second calculation based on the second output. When a focus evaluation value is not obtained by the first calculation, the adjustment unit is obtained by the second calculation. An imaging apparatus that adjusts a focal position of the optical system by correcting with a focus evaluation value. The imaging device according to claim 16, wherein
The adjusting unit performs correction for applying the focus evaluation value obtained by the second calculation to a portion where the focus evaluation value is not obtained by the first calculation, and adjusts the focus position of the optical system. . In the imaging device according to any one of claims 14 to 17,
A mirror unit capable of switching between a first state in which the light beam that has passed through the optical system is directed to the imaging element and a second state in which the light beam that has passed through the optical system is directed to the photoelectric conversion unit;
The photoelectric conversion unit causes the photoelectric conversion unit to perform charge accumulation in the first time and the second time while the mirror unit is in the second state.

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