JP2017194498A - Focus detector and method thereof, imaging apparatus, program, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detector advantageous in detecting a focusing position of a point light source subject.SOLUTION: A focus detector comprises: acquisition means (15a) for acquiring an image outputted from an image pick-up device receiving light through an imaging optical system; calculation means (14) for calculating an evaluation value representing contrast of the image; and control means (15) for detecting a focusing position of the imaging optical system using the evaluation value when the evaluation value is determined to be reliable based on acceptance criterion for determining reliability of the evaluation value. The control means changes the acceptance criterion of the reliability according to imaging conditions.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a focus detection device, and more particularly to a focus detection device capable of detecting a focus position of a point light source subject.

  Japanese Patent Application Laid-Open No. 2004-133620 discloses a technique that enables focus adjustment to a point light source subject even when a point light source subject and a normal subject are mixed in the screen in an automatic focus adjustment operation (AF). In Cited Document 1, the determination as to whether or not a point light source subject is present in the screen differs depending on the brightness of light incident from the photographing optical system.

JP 2014-35437 A

  However, in the above-mentioned patent document 1, even if the point light source subject can be determined, the focus position of the point light source subject may not be appropriately determined. For example, when shooting a point light source subject such as a celestial object at night, there is a possibility of focusing on a subject other than the celestial object such as a night view or an obstacle existing in the screen.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a focus detection apparatus and method, an imaging apparatus, a program, and a storage medium that are advantageous for detecting a focus position of a point light source subject.

  A focus detection apparatus according to one aspect of the present invention includes an acquisition unit that acquires an image output from an image sensor that receives light via an imaging optical system, and a calculation unit that calculates an evaluation value indicating the contrast of the image. Control means for detecting the in-focus position of the imaging optical system using the evaluation value when it is determined to be reliable by a determination criterion for determining the reliability of the evaluation value, and The control means changes the reliability criterion according to the photographing condition.

  According to the present invention, it is possible to provide a focus detection device and method, an imaging device, a program, and a storage medium that are advantageous for detecting a focus position of a point light source subject.

It is a block diagram of the imaging device concerning the Example of this invention. It is a flowchart figure of imaging | photography operation | movement concerning the Example of this invention. It is a figure which shows an example of the program diagram at the time of celestial body AF concerning the Example of this invention. It is a figure explaining the scan AF operation | movement concerning the Example of this invention. It is a flowchart figure of the scan AF operation | movement concerning the Example of this invention. It is a figure explaining the concept of reliability evaluation of AF evaluation value. It is a flowchart figure of the reliability determination method of AF evaluation value signal concerning the Example of this invention. It is a flowchart figure of the operation | movement which calculates | requires the monotone decrease of the infinity direction concerning the Example of this invention. It is a flowchart figure of the operation | movement which calculates | requires the monotone decrease of the near end direction concerning the Example of this invention. It is a figure explaining arrangement | positioning of the AF area | region provided in the screen concerning the Example of this invention, and the division area which divided | segmented this AF frame. It is a flowchart figure of the reference | standard position update operation | movement concerning the Example of this invention. It is a flowchart figure of the parameter setting operation | movement concerning 2nd Example of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. In addition, the same reference number is attached | subjected about the same member in each figure, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus 1 according to an embodiment of the present invention.

  The taking lens barrel 31 has an imaging optical system for forming an optical image of an object (subject). The image sensor 5 photoelectrically converts light (subject image) via the imaging optical system and outputs an electrical signal (pixel signal). The imaging optical system includes optical members such as a zoom lens group (hereinafter referred to as zoom lens) 2, a focus lens group (hereinafter referred to as focus lens) 3, and a diaphragm 4. The zoom lens 2 is a scaling unit that changes the focal length of the imaging optical system. The focus lens 3 is a focus adjustment unit that adjusts the focus state of the imaging optical system. The diaphragm 4 is a light amount adjusting means (exposure means) for adjusting the amount of light passing through the imaging optical system. The image sensor 5 (hereinafter referred to as an image sensor) is a light receiving unit that is configured by a solid-state image sensor such as a CMOS and receives light via the imaging optical system.

  The imaging circuit 6 receives the electrical signal output from the imaging sensor 5 and performs various image processing to generate a predetermined image signal. The A / D conversion circuit 7 converts the analog image signal generated by the imaging circuit 6 into a digital image signal. A memory (VRAM) 8 is a buffer memory or the like that receives an output from the A / D conversion circuit 7 and temporarily stores an image signal. The D / A conversion circuit 9 reads out the image signal stored in the VRAM 8, converts it into an analog signal, and converts it into an image signal in a form suitable for reproduction output. The image display device 10 (hereinafter referred to as LCD) is a liquid crystal display device or the like that displays an image signal output from the D / A conversion circuit 9. The storage memory 12 is composed of a fixed type semiconductor memory such as a flash memory, and stores image data. The compression / decompression circuit 11 includes a compression circuit that performs compression processing and encoding processing of image data in order to read out the image signal temporarily stored in the VRAM 8 and make it suitable for storage in the storage memory 12. The compression / decompression circuit 11 has a decompression circuit that performs a decoding process, a decompression process, and the like for making the image data stored in the storage memory 12 optimal for reproduction and display.

  The AE processing circuit 13 receives the output from the A / D conversion circuit 7 and performs automatic exposure (AE) processing. The scan AF processing circuit 14 receives the output from the A / D conversion circuit 7, generates an AF evaluation value, and performs an automatic focus adjustment (AF) process. The CPU 15 is a control unit that incorporates a calculation memory that controls the entire imaging apparatus. An acquisition unit 15a (acquisition means) in the CPU 15 acquires an image generated by the image sensor and various information necessary for processing executed by the CPU 15. Further, the CPU 15 incorporates a memory for calculation (not shown). The CPU 15, the acquisition unit 15a, and the scan AF processing circuit 14 constitute a focus detection device that detects the focus position of the optical system. In the present embodiment, the acquisition unit 15a and the CPU 15 are separate members, but may be configured integrally. A timing generator (hereinafter referred to as TG) 16 receives a signal from the CPU 15 and generates a predetermined timing signal. The image sensor driver 17 receives the signal from the TG 16 and drives the image sensor 5. The aperture drive motor 21 is a first drive unit that drives the aperture 4. The first motor drive circuit 18 drives and controls the diaphragm drive motor 21. The focus drive motor 22 is a second drive unit that drives the focus lens 3. The second motor drive circuit 19 drives and controls the focus drive motor 22. The zoom drive motor 23 is a third drive unit that drives the zoom lens 2. The third motor drive circuit 20 controls the zoom drive motor 23.

  The operation switch 24 includes various switch groups. The EEPROM 25 is an electrically rewritable read-only memory in which programs for performing various controls and the like and data used for performing various operations are stored in advance. The battery 26 is a power source that supplies power to the imaging apparatus 1. The strobe light emitting unit 28 emits strobe light for illuminating the subject. The switching circuit 27 controls the flash emission of the strobe light emitting unit 28. The display element 29 is composed of an LED or the like and displays a warning. The speaker 30 performs voice guidance and warning. The AF auxiliary light 33 is composed of a light source such as an LED, which is an illuminating unit that illuminates all or part of the subject when acquiring the AF evaluation value. The AF auxiliary light driving circuit 32 drives the AF auxiliary light 33. The shake detection sensor 35 (detection means) detects the tilt (elevation angle) and shake (that is, camera shake, etc.) of the imaging device 1. The shake detection circuit 34 processes the signal of the shake detection sensor 35. The face detection circuit 36 receives the output from the A / D conversion circuit 7 and detects the face position on the screen, the size of the face, and the like. The thermometer 37 (measuring means) measures the temperature of the surrounding environment (internal temperature) and sends the measurement data to the CPU 15.

  The storage memory 12 may be a semiconductor memory such as a card-type flash memory that has a card shape or a stick shape and is detachable from the apparatus. In addition, the present invention can be applied to various forms such as a magnetic storage medium such as a hard disk or a floppy disk.

  Further, as the operation switch 24, a main power switch for starting the imaging apparatus 1 to supply power, a release switch for starting a photographing operation (storage operation), a reproduction switch for starting a reproduction operation, and a zoom lens 2 are moved. There is a zoom switch for zooming.

  Here, the release switch has a first stroke (hereinafter referred to as SW1) for generating an instruction signal for starting an AE process and an AF process to be performed prior to a photographing operation, and a second stroke for generating an instruction signal for starting an actual exposure operation. (Hereinafter referred to as SW2) and a two-stage switch.

  The operation of the imaging apparatus according to the present embodiment configured as described above will be described below.

  First, the light flux of the subject that has passed through the photographing lens barrel 31 of the image pickup apparatus 1 is adjusted in its light amount by the diaphragm 4 and then imaged on the light receiving surface of the image sensor 5. This subject image is converted into an electrical signal by photoelectric conversion processing by the image sensor 5 and is output to the imaging circuit 6. In the imaging circuit 6, various signal processing is performed on the input signal, and a predetermined image signal is generated. The image signal is output to the A / D conversion circuit 7 and converted into a digital signal (image data), and then temporarily stored in the VRAM 8. The image data stored in the VRAM 8 is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed on the LCD 10 as an image. On the other hand, the image data stored in the VRAM 8 is also output to the compression / decompression circuit 11. After compression processing is performed by the compression circuit in the compression / decompression circuit 11, it is converted into image data in a form suitable for storage and stored in the storage memory 12.

  Also. For example, when a reproduction switch (not shown) of the operation switches 24 is operated and turned on, the reproduction operation is started. Then, the image data stored in a compressed form in the storage memory 12 is output to the compression / expansion circuit 11, subjected to decoding processing, expansion processing, etc. in the expansion circuit, and then output to the VRAM 8 and temporarily stored. The Further, the image data is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed on the LCD 10 as an image.

  On the other hand, the image data digitized by the A / D conversion circuit 7 is output to the AE processing circuit 13, the scan AF processing circuit 14, and the face detection circuit 36 in addition to the VRAM 8 described above. First, the AE processing circuit 13 receives the input digital image signal and performs arithmetic processing such as cumulative addition on the luminance value of the image data for one screen. Thereby, the AE evaluation value corresponding to the brightness of the subject is calculated. This AE evaluation value is output to the CPU 15.

  The scan AF processing circuit 14 receives the input digital image signal, extracts high-frequency components of the image data through a high-pass filter (HPF) or the like, and performs arithmetic processing such as cumulative addition, AF evaluation value signals corresponding to the contour component amounts and the like are calculated. Specifically, in the scan AF process, a high-frequency component of image data corresponding to a partial area of the screen designated as an AF area is extracted through a high-pass filter (HPF) or the like, and an arithmetic process such as cumulative addition is performed. Thereby, an AF evaluation value signal corresponding to the contour component amount on the high frequency side and the like is calculated. As described above, the scan AF processing circuit 14 has a function as calculation means for calculating an evaluation value indicating the contrast of an image. When this AF area is a central part or one part of an arbitrary part on the screen, the central part or an arbitrary part on the screen and a plurality of adjacent points, or a plurality of points distributed discretely and so on.

  As described above, the scan AF processing circuit 14 serves as a high-frequency component detection unit that detects a predetermined high-frequency component from the image signal generated by the imaging sensor 5 in the process of performing the AF processing.

  The face detection circuit 36 receives the input digital image signal, searches the image for a part characterizing the face such as eyes and eyebrows, and obtains the position of the person's face on the image. Further, the size and inclination of the face are obtained from the positional relationship such as the interval between the parts characterizing the face.

  On the other hand, a predetermined timing signal is output from the TG 16 to the CPU 15, the imaging circuit 6, and the imaging sensor driver 17, and the CPU 15 performs various controls in synchronization with this timing signal. The imaging circuit 6 receives the timing signal from the TG 16 and performs various image processing such as separation of color signals in synchronization with the timing signal. Further, the image sensor driver 17 receives the timing signal of the TG 16 and drives the image sensor 5 in synchronization with the timing signal.

  The CPU 15 controls the first motor drive circuit 18, the second motor drive circuit 19, and the third motor drive circuit 20, respectively. By doing so, the diaphragm 4, the focus lens 3, and the zoom lens 2 are driven and controlled via the diaphragm drive motor 21, the focus drive motor 22, and the zoom drive motor 23. That is, the CPU 15 controls the first motor drive circuit 18 based on the AE evaluation value calculated in the AE processing circuit 13 to drive the aperture drive motor 21 and adjust the aperture amount of the aperture 4 so as to be appropriate. I do. Further, the CPU 15 controls the second motor drive circuit 19 based on the AF evaluation value signal calculated by the scan AF processing circuit 14 to drive the focus drive motor 22 and performs AF control to move the focus lens 3 to the in-focus position. . Although details will be described later, the CPU 15 determines whether or not the AF evaluation value signal (evaluation value) is reliable before moving the focus lens 3 to the calculated in-focus position. Therefore, the CPU 15 detects the in-focus position of the imaging optical system using the AF evaluation value signal when it is determined that the reliability is determined by the parameter (determination criterion) for determining the reliability of the AF evaluation value signal. Control as follows. When a zoom switch (not shown) of the operation switches 24 is operated, the CPU 15 controls the third motor drive circuit 20 to drive the zoom motor 23 to move the zoom lens 2 to move the zoom optical system. Performs zooming operation.

  Next, the actual shooting operation of the imaging apparatus will be described with reference to the flowchart shown in FIG. The flowchart shown in FIG. 2 is executed by the CPU 15.

  In the description of the present invention, the operation of acquiring the AF evaluation value while driving the focus lens 3 to a predetermined position is called scanning, and the interval of the position of the focus lens that acquires the AF evaluation value is called the scanning interval. Also, the number of AF evaluation values to be acquired is referred to as the number of scan points, the range from which the AF evaluation values are acquired is referred to as the scan range, and the area from which the image signal for detecting the focus position is acquired is referred to as the AF frame. The scan range is determined by the product of the scan interval and (number of scan points-1).

  When the main power switch of the imaging apparatus 1 is in the on state and the operation mode of the imaging apparatus is in the shooting (recording) mode, a shooting process sequence is executed, and power is supplied to the imaging sensor 5 and the like to enable imaging To.

  First, in step S201, an image formed on the image sensor 5 through the photographing lens barrel 31 is displayed as an image on the LCD.

  Next, in step S202, it is confirmed whether or not a shooting mode is set in a shooting mode for shooting a celestial object excluding the sun and the moon (hereinafter simply referred to as a celestial object). In step S202, it is determined whether or not the shooting mode is an astronomical shooting mode for shooting a celestial object. If the shooting mode is the astronomical shooting mode, the process proceeds to step S203. If the astronomical shooting mode is not set, the process proceeds to step S230 and normal shooting processing is performed. In this step, AE processing, AF processing, and the like are performed according to the operation of the release switch by the photographer. The specific contents thereof are well known in Japanese Patent No. 04235422 and the description thereof is omitted.

  If the astrophotography mode is set by the photographer, the process proceeds to step S203.

  In step S203, it is determined whether or not a button for starting an AF process for a celestial object (hereinafter referred to as an celestial AF start button) has been operated and an instruction to start an AF process for the celestial object has been issued. If the celestial AF start button has not been operated, the process proceeds to step S210.

  When the celestial AF start button is operated, the process proceeds to step S204, and a photometric value is acquired. This is obtained from the output value of the AE processing circuit 13, the accumulation time of the image sensor 5 when the value is acquired, the signal amplification factor, and the aperture value of the aperture 4.

  Next, in step S205, it is determined whether or not the illuminance at the time of shooting is lower than the predetermined illuminance from the obtained photometric value. If not, the process proceeds to step S220, and processing for driving the focus lens 3 to a fixed point is performed. As described above, when the photometric value of the photographed image is larger than the predetermined value (first photometric value), the focus position detection operation using the AF evaluation value in the astronomical photographing mode is not performed. Here, the fixed point is the position of the focus lens 3 (infinity adjustment position) obtained by measuring the position of the focus lens 3 that is in focus at the infinity position at each focal length during manufacturing. Hereinafter, this position is referred to as a reference position during celestial AF. The reference position is updated if a predetermined condition is satisfied in step S214.

  In this case, the celestial AF failure may be displayed to notify the photographer that the environment is not a desired environment including the moon or ground illumination.

  If the illuminance is lower than the predetermined illuminance, the process proceeds to step S206, and the aperture value of the aperture 4, the accumulation time of the image sensor, and the amplification factor are determined during scan AF.

  This is done by selecting a combination in which a predetermined amount of output signal amount is reduced from a combination of aperture value / accumulation time / amplification factor at which an appropriate signal amount is output from the photometric value acquired in step S204, and further selecting that combination as a predetermined amount Limit within range.

  For example, a combination of aperture value / accumulation time / amplification factor may be selected so as to reduce the 7-stage output signal amount.

  The predetermined amount of output signal is reduced by combining the aperture value / accumulation time / amplification factor for outputting an appropriate signal amount as a captured image and the aperture value / accumulation time for outputting an appropriate signal amount during scan AF. This is because the combination of amplification factors is different. In the photographed image, it does not matter if the signal of a bright star image of 1st to 2nd stars is saturated, but rather a dark star such as 3rd to 6th stars is recognized on the image. It may be preferable for the photographed image to be saturated.

  On the other hand, in the scan AF, when the signal of the bright star image is saturated, the AF evaluation value is generated by the scan AF processing circuit 14 due to the characteristics of the AF evaluation value creation. However, the AF evaluation value becomes larger, and the correct in-focus position cannot be obtained. Details of this phenomenon are described in Japanese Patent Application Laid-Open No. 2012-141457 and the like, and thus description thereof is omitted here.

  Therefore, the output signal is reduced by a predetermined amount so that the bright star image signal is not saturated.

  Specifically, a combination of aperture value / accumulation time / amplification factor is selected according to the program diagram of FIG.

  The upper and lower limits of the program diagram are determined assuming a typical astronomical scene. The upper limit value in the program of FIG. 3 is that the aperture value is F2.8 (Av value = 3), the accumulation time is 1 second (Tv value = 0), and the amplification factor is equivalent to ISO 100 (Sv = 5). This value assumes that AF is performed on a scene in which many first-class stars, second-class stars, and planets exist in the AF frame.

  The upper limit value on the program of FIG. 3 is that the aperture value is F2.8 (Av value = 3), the accumulation time is 4 seconds (Tv value = −2), and the amplification factor is equivalent to ISO 800 (Sv = 8). This value assumes the case where AF is performed on a dark star in which many first-class stars, second-class stars, and planets do not exist or are small in the AF frame, and the number of 3-6 star stars is not large.

  The combination of aperture value / accumulation time / amplification factor determined by the program diagram of FIG. 3 from the value obtained by subtracting the predetermined amount of signal amount from the value obtained from the photometric value obtained in step S204 is shown in the program diagram of FIG. If it is not within the range, clip at the upper or lower limit.

  If the aperture value of the aperture 4, the accumulation time of the image sensor, and the amplification factor are determined in this way during scan AF, the process proceeds to step S207. In step S207, the drive mode of the image sensor 5 is changed to a drive mode for horizontal and vertical non-addition for celestial AF, and the display on the LCD 10 is changed from the live image display so far to the display in celestial AF.

  As shown in the program diagram illustrated in FIG. 3, the display of the LCD 10 is changed because the accumulation time of the image sensor 5 at the time of celestial AF is at least 1 second, and the scan AF requires a plurality of scan points. Therefore, the AF time becomes longer. Further, the update rate of the LCD display is 1 second or more in the example of FIG.

  Therefore, the display on the LCD 10 is changed to notify the photographer that the celestial AF is being executed. This prevents misunderstanding of the photographer such as a camera failure.

  In addition to displaying that the AF is in progress, it is desirable to calculate the time required for the scan AF and display the remaining time or display the elapsed time.

  If the drive mode of the image sensor 5 and the display of the LCD 10 are changed, the process proceeds to step S208 and scan AF is executed. As a result, the focus lens 3 is driven to the in-focus position if the celestial AF is successful, and to the reference position if it fails.

  Details of the scan AF will be described later.

  In step S209, the driving mode of the image sensor 5 is returned from the driving mode for celestial AF to the driving for displaying live images, and the display on the LCD 10 is also returned to displaying live images.

  At the same time, a display for notifying the photographer of the success or failure of the astronomical AF performed in step S208 is performed.

  When the celestial AF is successful, the display element 29 is turned on and at the same time, a green frame is displayed on the LCD. On the other hand, if not successful, the display element 29 is displayed blinking and at the same time, a yellow frame is displayed on the LCD.

  In step S210, the CPU 15 checks SW1 (first stroke of the release switch). If SW1 is on, the process proceeds to step S211 to execute the astronomical object AE.

  This is to determine the aperture value of the diaphragm 4, the accumulation time of the imaging sensor, and the amplification factor from which an appropriate signal amount at the time of photographing is output from the photometric value acquired in step S204.

  In a photographed image, it does not matter if the signal of an image of a bright star of 1st to 2nd stars is saturated, but it is preferable that dark stars such as 3rd to 6th stars are recognized on the image. Select the aperture value, accumulation time, and amplification factor.

  Note that the photometric value may be obtained again from the AE processing circuit 13 at the beginning of the processing.

  If SW1 is not on, the process returns to step S201 to display a live image on the LCD 10.

  Thereafter, in step S212, the CPU 15 confirms SW2 (second stroke of the release switch). If SW2 is turned on, the CPU 15 proceeds to step S212 and executes actual exposure processing.

  If SW2 is not on, the process returns to step S201 to display a live image on the LCD 10.

  After the exposure process is performed, in step S214, it is determined whether or not the reference position is updated, and an actual update operation is performed.

  Here, the operation of the scan AF in step S208 will be described with reference to FIGS.

  As shown in FIG. 4, the scan AF in step S208 scans a relatively narrow range around the reference position during celestial AF.

  First, the reference position is read and determined in step S501 in FIG.

  Next, the scan interval is determined (step S502). The scan interval is set as wide as possible so that the in-focus position can be searched. For example, the value is about 3 to 5 times the depth of the open F value.

  Then, the environment at which the reference position is obtained and the environment at the time of photographing (brightness, elevation angle, internal temperature, etc.) are read (step S503), and the number of scan points is determined by the probability of the reference position being at infinity (step S504).

  When the celestial body AF is not executed at the time of product shipment, the environment in which the infinity adjustment position is measured at the time of manufacture is compared with the environment at the time of photographing (during scan AF).

  Measurement during production is performed with the camera level. Further, since the internal temperature of the lens barrel 31 at the time of measurement is measured at the same time, the number of scan points may be determined by comparing the internal temperature at the time of scan AF and the manufacturing and the posture of the camera.

  For example, a case where the elevation angle is about 30 ° ± 15 ° C. and the internal temperature is normal temperature is taken as a standard case, and the number of scan points at that time is 7 points.

  Further, when the elevation angle is almost horizontal (for example, less than about ± 15 degrees) and the internal temperature at the time of manufacture and the internal temperature at the time of photographing the lens barrel 31 are substantially equal (for example, the difference is within 2 degrees), it is standard. Reduce the number of scan points from the case.

  Conversely, if you are shooting near the zenith, or if the internal temperature at the time of shooting is very high or low, such as when the environment is different from the manufacturing environment, increase the number of scan points to 9 or more to increase the scan range. I have to.

  When the celestial AF is executed and the reference position is updated, the environment in which the celestial AF is executed (focal length, internal temperature, elevation angle) and the environment at the time of photographing (during scan AF) are compared and determined.

  There are cases where the celestial AF has already been executed and only the result has been recorded, and there are cases where there is a reference position where the result of the celestial AF necessary for interpolation is acquired, interpolated and updated. The updated reference position may not be updated under all conditions. For example, it may be updated only for a specific internal temperature and a specific elevation angle.

  Therefore, first, it is checked whether or not the celestial AF is already executed in the environment substantially equal to the environment at the time of shooting and only the result is recorded. If it is executed, the focus position is set as the reference position.

  If it is not executed, it is checked whether there is a reference position updated by interpolation that has substantially the same environment or a small difference, and if there is one, adopts it.

  If there is no updated reference position, it is handled that the celestial AF is not executed.

  Regarding the focal length, the value at the same focal length is referred to. That is, it is determined that the reference position has been updated only when the reference position is updated at the same focal length as that at the time of shooting, and the number of scan points is determined with reference to the internal temperature and elevation angle.

  When the internal temperature and elevation angle are approximately equal, the number of scan points is 5 points, the internal temperature is approximately equal, and when the difference in elevation angle is small, the number of scan points is 7 points, the internal temperature is approximately equal, and the difference in elevation angle is large The number of scan points is 9 or more according to the difference in elevation angle.

  When the difference in internal temperature is small and the elevation angle is substantially equal, the number of scan points is 7 points, and when the difference in internal temperature is small and the elevation angle is not substantially equal, the number of scan points is 9 or more according to the difference in elevation angle.

  The number of scan points when the difference in internal temperature is large is 9 or more according to the difference in elevation angle.

  For example, if the difference between the internal temperature when the celestial AF is executed and the reference position is updated and the internal temperature at the time of photographing is 5 ° C. or less, the internal temperature is substantially the same. If the difference is small or larger, it is determined that the internal temperature difference is large.

  Further, if the difference between the elevation angle when the celestial AF is executed and the reference position is updated and the elevation angle at the time of photographing is 10 ° or less, the elevation angle is substantially equal. If it is more than that, it is determined that the difference in elevation angle is large.

  Actually, the reference positions at a plurality of internal temperatures and elevation angles are recorded. The above determination is made in comparison with the closest environment. This determination is made by first comparing the internal temperature and then comparing the elevation angle.

  The reason for determining the number of scan points in this way is to make it possible to avoid the lengthy time of the celestial AF and to reliably capture the in-focus position.

  Then, a process for determining a parameter for determining the reliability of the AF evaluation value obtained as a result of the scan AF in steps S505 to S513, and an in-focus position within a predetermined range from the reference position are validated in step S524. The process of determining the predetermined range is started.

  First, parameters for determining the reliability of the AF evaluation value will be described.

  Except for the special case of near-far competition, the AF evaluation value signal takes the focus lens position on the horizontal axis and the AF evaluation value on the vertical axis. Therefore, whether or not the AF evaluation value signal is mountain-shaped is determined by the difference between the maximum value and the minimum value of the AF evaluation value signal, the length of the inclined portion with a certain inclination or more, By judging from the gradient, the reliability of the AF evaluation value signal is judged. In other words, the reliability of the AF evaluation value is based on the length of the section where the AF evaluation value monotonously decreases, the average value of the inclination of the section, and the difference between the maximum value and the minimum value of the AF evaluation value. Is judged.

  As shown in FIG. 6, the points P2 and P3 that are recognized as being inclined from the top of the mountain (point P1) are obtained, the width between the points P2 and P3 is defined as the mountain width L, and the points P1 and P2 are obtained. The difference between the AF evaluation values is SL1, and the difference between the AF evaluation values at points P1 and P3 is SL2. Further, the sum SL1 + SL2 of the difference between the AF evaluation values at the points P1 and P2 and the difference between the AF evaluation values at the points P1 and P3 is defined as the height difference SL of the mountain.

  A specific operation for determining the reliability of the AF evaluation value signal will be described below with reference to the flowcharts of FIGS. 7 to 9 with reference to FIG.

  First, in step S701, the maximum value max and the minimum value min of the AF evaluation value output from the scan AF processing circuit 14 and the scan point io that gives the maximum value are obtained. Thereafter, in step S702, a variable L representing the peak width of the AF evaluation value and a variable SL representing the peak height difference are both initialized to zero.

  Next, it is checked whether or not the scan point io giving the maximum value is a position corresponding to ultra-infinity, that is, whether or not io = 0, and if it is a position corresponding to ultra-infinity (YES in step S703). Step S704 is skipped and the process proceeds to step S705. On the other hand, if it is not a position corresponding to super-infinity (NO in step S703), the process proceeds to step S704, and a monotonic decrease in the focus lens position direction corresponding to super-infinity is checked.

  Here, the processing for checking the monotonic decrease in the focus lens position direction corresponding to ultra-infinity in step S704 will be described with reference to the flowchart of FIG.

First, in step S801, a counter variable i is initialized to io. Then, the AF evaluation value d [i] at i is compared with the AF evaluation value d [i-1] at scan point i-1 that is closer to infinity by one scan point (predetermined step) than i. If d [i] −d [i−1] ≧ SlopeThr (YES in step S202), it is determined that a monotonous decrease in the ultra-infinity direction has occurred, and the process proceeds to step S803, where the peak of the AF evaluation value is The variable L representing the width and the variable SL representing the mountain height difference are updated according to the following formula.
L = L + 1
SL = SL + (d [i] -d [i-1])
In the determination of S802, d [i] is determined to be larger than d [i-1] when there is a difference greater than a predetermined value (SlopeThr) in consideration of the influence of noise.

  In step S802, if d [i] −d [i−1] ≧ SlopeThr is not satisfied, it is determined that the monotonic decrease in the ultra-infinity direction has not occurred, and the monotonic decrease in the super-infinity direction is checked. And the process proceeds to step S705.

  After the processing in step S803, the process proceeds to step S804, where i = i-1 and the point to be detected is moved to the one scan point ultra-infinity side.

  Then, in steps S805 and S806, comparison is made with threshold values Lo and SLo relating to the width of the mountain and the difference in height of the mountain so that L and SL are peaks, and it is determined whether or not both are equal to or greater than the threshold value. If both are equal to or greater than the threshold value, the conditions for determining the reliability of the AF evaluation value performed in steps S708 and S709 in FIG. 5 to be described later have already been satisfied. The process of checking the monotonic decrease is not performed, and the process proceeds to step S705.

  If NO in step S805 or S806, the process proceeds to step S807, and it is checked whether or not the counter i has reached a value corresponding to ultra-infinity (= 0). If the value of counter i is not 0, the process returns to step S802 and the above processing is repeated. If it is 0, that is, if the scan point has reached a position corresponding to ultra-infinity, a monotonic decrease in the super-infinity direction is checked. The process ends, and the process proceeds to step S705.

  In this way, a monotonic decrease from i = io to the super-infinity direction is checked.

  If the process of checking the monotonic decrease in the ultra-infinity direction is completed in step S704, next, whether or not the scan point io giving the maximum value max is a position corresponding to the closest end (N) for performing the scan AF. Check out. If it is the position corresponding to the closest end (YES in step S705), step S706 is skipped and the process proceeds to step S707. On the other hand, if the position is not the position corresponding to the close end (NO in step S706), the process proceeds to step S706, and the monotonic decrease in the focus lens position direction corresponding to the close end is checked.

  Here, the processing for checking the monotonic decrease in the focus lens position direction corresponding to the closest end in step S706 will be described with reference to the flowchart of FIG.

First, in step S901, the counter variable i is initialized to io. Then, the AF evaluation value d [i] at i is compared with the AF evaluation value d [i + 1] at the scan point i + 1 from the nearest end by one scan point from i. If d [i] −d [i + 1] ≧ SlopeThr (YES in step S902), it is determined that there is a monotonous decrease in the near-end direction, and the process proceeds to step S903, where the peak width of the AF evaluation value is set. The variable L representing the variable and the variable SL representing the height difference of the mountain are updated according to the following formula.
L = L + 1
SL = SL + (d [i] -d [i + 1])
In step S902, if d [i] −d [i + 1] ≧ SlopeThr, it is determined that no monotonic decrease in the closest end direction has occurred, and the process for checking the monotonic decrease in the close end direction is terminated. Then, the process proceeds to step S707.

  After the processing in step S903, the process proceeds to step S904, where i = i + 1 is set, and the point to be detected is moved to the one scan point closest side.

  Then, in steps S905 and S906, comparison is made with threshold values Lo and SLo regarding the width of the mountain and the height difference of the mountain for regarding L and SL as peaks, and it is determined whether or not both are equal to or greater than the threshold value. If both are equal to or greater than the threshold value, the conditions in the process for determining the reliability of the AF evaluation value performed in steps S708 and S709 in FIG. 5 to be described later have already been satisfied. The process for checking the monotonic decrease is not performed, and the process proceeds to step S707.

  If NO in step S905 or S906, the process proceeds to step S907, and it is checked whether the counter i has reached a value (= N) corresponding to the closest end. If the counter value is not N, the process returns to step S302 and the above processing is repeated. If N, that is, if the scan point has reached a position corresponding to the near end, a process for checking a monotonic decrease in the near end direction. And the process proceeds to step S707.

  In this way, a monotonic decrease from i = io toward the closest end is checked.

  When the monotonic decrease check in the ultra-infinity direction and the near-end direction is completed, the coefficients for determining the reliability of the AF evaluation value are compared with the respective threshold values, and all conditions are satisfied. If so, it is determined that the AF evaluation value is reliable.

  First, in step S707, the difference between the maximum value max and the minimum value min of the AF evaluation value is compared with a threshold value. If the difference is smaller than the threshold value, it is determined that there is no reliability, and the process proceeds to step S711. If YES in step S707, in step S708, the length L of the portion inclined at a certain slope or more is compared with the threshold value Lo, and if smaller than the threshold value Lo, it is determined that there is no reliability. The process proceeds to step S711. If YES in step S708, the height difference SL and SLo are further compared in step S709, and if smaller than the predetermined value, it is determined that there is no reliability, and the process proceeds to step S711.

  If all the above three conditions are satisfied, it is determined that the AF evaluation value is reliable, and the process advances to step S710 to determine that the AF evaluation value is reliable.

  In step S711, it is determined that the AF evaluation value is not reliable.

It is a parameter in the reliability evaluation of the AF evaluation value performed in this way,
Difference between maximum and minimum AF evaluation values max and min max-min
Length Lo of the part inclined at a certain value or more
Height difference SLo of a portion inclined at a certain inclination or more
Threshold value SlopeThr for determining that the AF evaluation value is decreasing
Will be determined.

  First, in step S505, it is determined from the photometric value acquired in step S204 whether or not the illuminance at the time of shooting is an illuminance equivalent to twilight such as before and after sunset or before and after sunrise. If the illuminance is equivalent to twilight, a determination parameter for twilight is set in step S506, and if not, the normal determination parameter is set in step S507. As described above, when the photographing mode is the astronomical photographing mode, the determination criterion (determination parameter) for determining the reliability of the evaluation value is changed according to the photometric value of the image. As described above, when the photometric value is larger than the first photometric value, the focus position is not detected using the AF evaluation value. Further, when the photometric value is smaller than the first photometric value and larger than the second photometric value (illuminance corresponding to twilight), the photometric value is smaller than the second photometric value (illuminance equivalent to normal nighttime). ) Change the criterion so that it is determined that there is no reliability.

  In twilight, there is a possibility that the entire sky is bright and the amount of exposure to stars is insufficient, and subjects other than the stars are illuminated to some extent and affected. Therefore, a parameter is set so as to determine that the AF evaluation value is reliable when there is higher reliability than normal celestial AF performed at night.

  For example, normal determination parameters (standard) are set as shown in Table 1 below.

  Also, the determination parameter (standard) for twilight is set as shown in Table 2 below.

  As shown in Table 1 and Table 2, Lo and SLo are changed by the number of scan points.

  In the case of twilight, the monotonous decrease check flag is turned on in S508. When this flag is on, it is determined that the AF evaluation value is not reliable when the AF evaluation value monotonously decreases toward the far side or the near side and the AF evaluation value at the end position is maximized. Yes. This is because, in twilight, a subject other than the star may be illuminated to some extent and focus on a nearby subject that is affected by the subject. Therefore, in order to always make this determination, a monotonic decrease check flag is set in step S508. Turn on. Although not shown, this flag is turned off at the beginning of the process.

  Next, the focal length set in step S509 is checked, and if the focal length converted to 35 mm film is equal to or larger than the predetermined focal length, the process proceeds to step S513. This is because, when an AF frame is arranged as shown in FIG. 10, if a celestial object having a predetermined focal length or longer is photographed, only the celestial object is considered to enter the screen regardless of the elevation angle. This is because it is not necessary to change the parameter depending on the position of the AF frame, and therefore it is only necessary to set the predetermined range used in step S524 in step S513.

  As shown in FIG. 10, the range for setting the AF frame (detection frame capable of detecting the AF evaluation value) is different between short focus and long focus, and the size of the AF frame is changed according to the focal length of the imaging optical system. To do. Specifically, the size of the AF frame is changed so that the AF frame becomes larger as the focal length is longer. As described above, in this embodiment, the range in which the AF frame is set is increased as the focal length is increased. However, an upper limit and a lower limit are set in the setting range, and the same setting range is set below or above a predetermined focal length. For example, when the focal length is less than 35 mm (35 mm film equivalent), an AF frame of 50% horizontal × 50% vertical is set at the center of the screen. If it is 35 mm or more and less than 50 mm, an AF frame of 60% horizontal × 60% vertical is set at the center of the screen. Further, when it is equal to or greater than 50 mm and less than 80 mm, an AF frame of horizontal 70% × vertical 70% is provided at the center of the screen, and when equal to or greater than 80 mm, an AF frame of horizontal 80% × vertical 80% is provided at the center of the screen. Set.

  This is because the amount of movement of the star per unit time on the screen increases as the focal length increases.

  Although the drawing is complicated, only the short focus is shown in the drawing, but the AF frame is divided into 25 regions of 5 horizontal and vertical divisions at all focal lengths. This excludes the AF frame in which the foreground exists, the AF frame in which a saturated subject such as the moon and illumination exists, and the AF frame affected by the AF frame, and selects the AF frame in which only the star exists and selects the AF frame. This is because astronomical AF is performed using only the focusing position of the frame.

  In step S513, the predetermined range includes a thermometer error, posture detection error, scan AF error, time-dependent change, and in-focus position deviation in the same environment that cause a difference between the reference position and the true in-focus position of the celestial object. It is determined in consideration of reproducibility. Considering the effects of obstacles such as fences and windows on the near side or when the photographer places a subject such as a tree or a building as the foreground, a predetermined range is set on the near side and the far side. Change the near side to a narrower range than the far side. Thus, the predetermined range is changed according to errors such as temperature and inclination.

  For example, the thermometer error is 2.5 ° C., the posture detection error is 5 °, the scan AF error is equivalent to 0.5 depth of the open F value, and the change with time is equivalent to 1.5 depth of the open F value. It is assumed that the reproducibility of the in-focus position shift is equivalent to 1.5 depth of the open F value. Here, it is assumed that the focus position changes by an equivalent of 1.5 depth of the open F value due to an error of 2.5 ° C. of the thermometer, and the focus position changes by an equivalent of 2.5 depth of the open F value by an attitude detection error of 5 °. In this case, the RMS of these values is taken, and the coefficient for viewing safety is taken into consideration, and the far side is set to a value corresponding to 6 to 7 depths of the open F value. If it is assumed that the blur of the celestial body is conspicuous when the focus position shifts more than 3 depths of the open F value, the near side is set to a value of 3 depths of the open F value.

  If it is less than the predetermined focal length, the process proceeds to step S510 to check the elevation angle. If the elevation angle is near the zenith (for example, 90 ° ± 10 °), the process proceeds to step S511. If the elevation angle is near the horizontal (for example, 15 ° or less), the process proceeds to step S512. Otherwise, the process proceeds to step S513.

  In step S511, the AF reliability determination parameters of the surrounding AF frames (00 frame to 04 frame, 10 frames, 14 frames, 20 frames, 24 frames, 30 frames, 34 frames, 40 frames to 44 frames in the example of FIG. 10) and The predetermined range to be compared with the reference position is changed. Here, the CPU 15 can detect the in-focus position of the imaging optical system when the in-focus position detected based on the AF evaluation value is within a predetermined range with respect to the reference position, as will be described later. It is determined that In this step, the predetermined range to be compared with the reference position is changed according to the inclination of the imaging device.

  This is because when the vicinity of the zenith is photographed on the short focus side, the roof ridge or antenna pole of the building of the photographer may enter the surrounding AF frame. The AF reliability determination parameter of the surrounding AF frame is changed so that the AF frame including these subjects is not used. As described above, when the focal length of the imaging optical system is shorter than the predetermined focal length and the inclination (elevation angle) is near the zenith, it is determined that there is no reliability compared to the case where the focal length is longer than the predetermined focal length. Change the criteria as follows. Here, the criterion for the surrounding AF frame is changed according to the position of the AF frame, that is, the surrounding AF frame. Specifically, when the inclination with respect to the horizontal direction is, for example, greater than 80 ° (first angle) and 90 ° or less, detection is performed from a detection region (AF frame) in a peripheral region outside the central region including the center of the image. The criterion for determining the reliability of the AF evaluation value to be changed is changed.

  For example, normal determination parameters (peripheral AF frame) are set as shown in Table 3 below.

  In addition, the determination parameter (peripheral AF frame) for twilight is set as shown in Table 4 below.

  Next, a predetermined range used in step S524 is set. The central AF frame (11 frame to 13 frame, 21 frame to 23 frame, 31 frame to 33 frame in the example of FIG. 10) is set to the same setting as step S513.

  For the peripheral AF frame, the predetermined range on the far side is set to the same setting as in step S513, but on the near side, the predetermined range from the reference position is narrower than the setting in step S513. This is to avoid a situation in which an obstacle or the like is in focus because there is a possibility that a nearby subject exists in the peripheral AF frame. For example, it is a value of 2 depths of the open F value from the reference position.

  In step S512, the AF reliability determination parameter of the lower AF frame (40 frames to 44 frames or 30 frames to 44 frames in the example of FIG. 10) and a predetermined range to be compared with the reference position are changed.

  This is because when the near-horizontal side where the elevation angle is 15 ° or less is photographed on the short focus side, the lighting or illumination of the building in the photographer may enter the lower AF frame. The AF reliability determination parameter of the lower AF frame is changed so that the AF frame including these subjects is not used. As described above, when the focal length of the imaging optical system is shorter than the predetermined focal length and the inclination (elevation angle) is near horizontal, it is determined that there is no reliability compared to the case where the focal length is longer than the predetermined focal length. Change the criteria as follows. Here, the determination criterion of the lower AF frame is changed according to the position of the AF frame. Specifically, when the inclination with respect to the horizontal direction is not less than 0 ° and less than 15 ° (second angle), a part of the peripheral region outside the central region including the center of the image (region below the image) ) To change the determination criterion for determining the reliability of the AF evaluation value detected from the detection area (AF frame) in ().

  For example, normal determination parameters (lower AF frame) are set as shown in Table 5 below.

  Also, the twilight determination parameter (lower AF frame) is set as shown in Table 6 below.

  Next, a predetermined range used in step S524 is set. The upper AF frame (00 frame to 24 frame, or 00 frame to 34 frame in the example of FIG. 10) is set to the same setting as step S513.

  In the lower AF frame, the predetermined range on the far side is set to be the same as that in step S513, but on the near side, the predetermined range from the reference position is narrower than the setting in step S513. This is to avoid a situation in which an obstacle or the like is in focus because there is a possibility that a near subject exists in the lower AF frame. For example, it is a value of 2 depths of the open F value from the reference position. As described above, when the focal length of the imaging optical system is shorter than the predetermined focal length, the predetermined range to be compared with the reference position is changed according to the inclination of the imaging device. Specifically, when the inclination of the imaging device with respect to the horizontal direction is, for example, greater than 80 ° (first angle) and 90 ° or less, or the inclination is, for example, not less than 0 ° and less than 15 ° (second smaller than the first angle). If the angle is less than the angle, the predetermined range to be compared with the reference position is narrowed.

  Here, the peripheral AF frame and the lower AF frame have been described as an example where the camera posture is the normal position, but when the camera is held in the vertical position, the corresponding AF frame corresponding to the posture is change.

  In step S514, an AF evaluation value at each scan point is acquired.

  The CPU 15 controls the focus drive motor 22 via the second motor drive circuit 19 that controls the drive of the focus drive motor 22 and moves the focus lens 3 to the scan start position (“A” in FIG. 4). After the movement, driving is performed from that position to the scan end position ("B" in FIG. 4). The output (AF evaluation value signal) of the scan AF processing circuit 14 is acquired while driving.

  If the AF evaluation values of all the scan points have been acquired, the process proceeds to step S515 to initialize the divided AF frame positions for determining the reliability of the AF evaluation values, and start the processing from the 00 frame shown in FIG. To.

  After the initialization, in step S516, it is checked whether or not there is a saturated subject such as a moon or illumination, and processing for removing the affected AF frame is performed. Therefore, the total luminance value (YI) and the maximum luminance value (YP) in the divided AF frame are used.

  YI can know the theoretical maximum value if the size of the AF frame is known from the characteristics of the AF processing circuit 14. The theoretical maximum value of YP is determined by the characteristics of the AF processing circuit 14.

  Therefore, in the divided AF frames, it is possible to know the existence of the AF frame having the moon / illumination and the AF frame affected by the detection by examining the values for the YI / YP scan points.

  If YP is always the theoretical maximum value at all scan points, it can be determined that the image signal for obtaining the AF evaluation value is saturated even in a blurred state. Therefore, the AF evaluation value is adversely affected by the saturation. It seems that there is. If YI is large at all scan points and the amount of change is small, it is likely that the subject at a short distance, such as greatly blurred illumination, has been adversely affected. For example, if YI is more than half of the theoretical maximum value at all scan points, and the difference between the maximum and minimum values of YI obtained at each scan point is within 10%, the short distance Seems to have been adversely affected by the subject.

  Therefore, if any of the above conditions is met, the AF evaluation value reliability determination described with reference to FIGS. 6 to 9 is not performed, but the AF frame is determined to be unreliable (S517 → S519), and then the step is performed. Proceed to S520.

  If it is determined that there is no adverse influence, in step S518, the determination of the AF evaluation value described with reference to FIGS. 6 to 9 is performed using the determination parameters determined in steps S505 to S513.

Since the processing of 00 frames is initially performed, if the focal length is not equal to or greater than 100 mm,
・ If you are shooting around the zenith in twilight, the judgment parameter for twilight (peripheral AF frame)
・ If you are shooting at dusk and other elevation angles, the judgment parameters for twilight (standard)
・ Normal shooting parameters (peripheral AF frame) if shooting near the zenith other than twilight
・ Normal shooting parameters (standard) if shooting at an elevation angle other than twilight
And the reliability evaluation of the AF evaluation value is performed.

  The presence or absence of reliability is recorded for each AF frame.

The same processing is continued while updating the AF frame to be processed up to all divided AF frames. (NO in step S520 → Return to S521 → S516)
The determination parameter to be selected differs depending on the position of the AF frame to be processed and whether or not it is twilight. A normal determination parameter (standard) or a twilight determination parameter (standard) is selected for the AF frame near the center, but the lower AF frame has a focal length that is not equivalent to 100 mm or more. You will choose the one that suits your situation.

  When the focal length is equal to or greater than 100 mm, the normal determination parameter (standard) or the twilight determination parameter (standard) is selected for any AF frame.

  In addition, in the case of twilight separately from the determination described with reference to FIGS. 6 to 9, since the monotonic decrease check flag is on, the AF evaluation value monotonously decreases to the far side or the near side, and the AF evaluation value at the end position It is determined whether the AF evaluation value is not reliable.

  Specifically, the scan point io giving the maximum AF evaluation value is the scan start point (A in FIG. 4) or the scan end point (B in FIG. 4), and the peak width L is the number of scan points −1. In this case, it is determined that the AF evaluation value is not reliable.

  Thereafter, in step S520, it is checked whether reliability determination has been performed for all the divided AF frames. If not, the AF frame for which reliability determination is performed is updated (step S521).

  If the reliability determination of the AF evaluation value has been completed for all the divided AF frames, it is checked in step S522 whether there is a frame with the reliability of the AF evaluation value, and if not, the process proceeds to step S220. . This process is the same as step S220 in FIG.

  If there is a reliable frame, the position (“C” in FIG. 4) at which the AF evaluation value signal of the reliable AF frame is maximized is obtained in step S523. Acquisition of the output of the AF processing circuit is not performed for all the stop positions of the focus lens 3 in order to increase the speed of scan AF, and the output is acquired at every predetermined scan interval. In this case, the AF evaluation value signal may be acquired at points a1, a2, and a3 shown in FIG. In such a case, the AF evaluation value maximum position C is obtained by calculation from the point where the AF evaluation value signal becomes the maximum value and the points before and after that point.

  When the position of the focus lens 3 is X1, the AF evaluation value becomes maximum and the value is Y1 (FIG. 4a1), and when the AF evaluation values acquired at the front and rear positions X2 and X3 are Y2 and Y3 (FIG. 4a2). , A3), the position X0 of the focus lens 3 at the AF evaluation value maximum position C is

Is required. However, Y1> Y3 and Y1 ≧ Y2.

  Once the AF evaluation value maximum positions of all the reliable AF frames have been obtained, the positions of the focus lens 3 that focuses on the infinity position at each focal length updated according to the result of the celestial AF are used as the positions. Position) (step S524).

  As a result, if there is an object within the predetermined range with respect to the reference position, the process proceeds from step S525 to step S526, an average value of the AF evaluation value maximum positions within the predetermined range from the reference position is obtained, and this is determined as the in-focus position. And

  If the in-focus position has been obtained, the focus lens 3 is driven to the in-focus position which is determined to have been determined that the celestial AF has succeeded (step S526).

  If there is no object within the predetermined range with respect to the reference position, the process proceeds to step 220.

  The predetermined range is determined as follows. Taking into account the error of the thermometer that causes the difference between the reference position and the true in-focus position of the celestial object, attitude detection error, scan AF error, change over time, reproducibility of in-focus position deviation in the same environment, etc. It is decided. Considering the effects of obstacles such as fences and windows on the near side or when the photographer places a subject such as a tree or a building as the foreground, a predetermined range is set on the near side and the far side. Change the near side to a narrower range than the far side.

  For example, the thermometer error is 2.5 ° C., the posture detection error is 5 °, the scan AF error is equivalent to 0.5 depth of the open F value, and the change with time is equivalent to 1.5 depth of the open F value. It is assumed that the reproducibility of the in-focus position shift is equivalent to 1.5 depth of the open F value. Here, it is assumed that the focus position changes by an equivalent of 1.5 depth of the open F value due to an error of 2.5 ° C. of the thermometer, and the focus position changes by an equivalent of 2.5 depth of the open F value by an attitude detection error of 5 °. In this case, the RMS of these values is taken, and the coefficient for viewing safety is taken into consideration, and the far side is set to a value corresponding to 6 to 7 depths of the open F value. If it is assumed that the blur of the celestial body is conspicuous when the focus position shifts more than 3 depths of the open F value, the near side is set to a value of 3 depths of the open F value.

  Here, the update of the reference position in S214 will be described. The operation procedure is shown in FIG.

  The reference position is obtained by measuring the infinity adjustment position at a part of the focal length at the time of manufacture, and the other focal length is obtained by performing interpolation calculation from the measured focal length. As a result, as shown in Tables 7 to 9 below, at the time of manufacturing, the reference position is recorded in the format described as “reference position at the time of manufacturing”. Tables 7 to 9 show the configuration of the reference position at the time of manufacture, the updated focus position, and the recorded contents of the updated reference position. Regarding the focal length, for all settable focal lengths, for the internal temperature and the elevation angle, the reference position at the value in the environment at the time of manufacture is measured and recorded. Assuming that the internal temperature is measured at 20 ° C., the reference position at 20 ° C. is calculated from the measured temperature and the measurement result at the time of manufacture, and the value is recorded.

  Although the focal length is described in 6 positions for simplification, it is not limited to this.

  In FIG. 11, the environment (focal length, internal temperature, elevation angle) at the time of shooting in which the celestial AF is performed in step S1101, and the in-focus position obtained as a result of the celestial AF are read in step S1102.

  In step S1103, it is checked whether or not the celestial AF has been performed in an environment substantially equal to the past by referring to the recording area of “recorded / updated focus position” shown in Table 8.

  If it has been performed, the value recorded in step S1104 is updated. This may simply replace the environment and the focus position, or may record the average value of the recorded value and the newly obtained value. In this case, average the environmental values and record the values.

  If not, the process advances to step S1105 to newly record the in-focus position as the focus position together with the environment in the format shown in Table 8.

  Since this new record has a limit in the capacity of the recording area, if the limit value is reached, the recorded time is deleted from the oldest one, and a new value is recorded in that area. This is done because the old ones are less reliable than the latest ones due to changes over time and are used less frequently.

  Whether or not the celestial AF has been performed in an environment substantially equal to the past is determined based on the focal length, the internal temperature, and the elevation angle. For example, when the reference position is updated and the focal length at the time of shooting is the same, the difference in internal temperature between when the reference position is updated and when shooting is 5 ° C. or less, and when the reference position is updated and at the time of shooting If the difference in elevation angle is 10 ° or less, it is determined that the environments are substantially equal.

  In step S <b> 1106, it is determined whether interpolation is possible regarding the focal length of the reference position.

  If the result of the celestial AF (focus position) is obtained at the focal length (for example, Wide end, intermediate focal length, Tele end) necessary for interpolation at substantially the same internal temperature and elevation angle, It is determined that interpolation is possible.

  If interpolation is possible, interpolation is performed for the focal length of the reference position in S1107, and a table of reference positions at the internal temperature / elevation angle as shown in Index 1 to 6 of Table 7 is created.

  In the interpolation calculation, a quadratic function is obtained from three focus positions at a focal length (Wide end / intermediate focal length / Tele end) necessary for interpolation, and a reference value at the corresponding focal length is obtained using the quadratic function. This quadratic function can be obtained if it has a quadratic Lagrange interpolation polynomial.

  In step S1108, it is determined whether an interpolation regarding the internal temperature of the reference position is possible.

  If a table of updated reference positions necessary for interpolation is created, it is determined that interpolation in the internal temperature direction is possible. For example, if the table of the reference position of the elevation angle 45 ° shown in Index 1 to 6 in Table 9 and the internal temperature 20 ° C. and the elevation angle 45 ° shown in Index 7 to 12 and the internal temperature 10 ° C. is prepared, the elevation angle 45 ° It is determined that a reference position table with an internal temperature of 15 ° C. can be created. Then, in S609, by taking the average of the reference positions of the internal temperature 20 ° C. and the internal temperature 10 ° C., a table of the reference positions of the internal temperature 15 ° C. shown in Index 13 to 17 of Table 9 is created.

  In step S1110, it is determined whether interpolation is possible with respect to the elevation angle of the reference position. If a table of updated reference positions necessary for interpolation is created, it is determined that interpolation in the elevation angle direction is possible. For example, if the table of the reference position of the elevation angle 45 ° shown in Tables 1 to 6 and the internal temperature 20 ° C. shown in Table 9 and the elevation angle 75 ° and the internal temperature 20 ° C. shown in Index 19 to 24 is created, the elevation angle 60 ° It is determined that a reference position table with an internal temperature of 20 ° C. can be created. Then, in S611, by taking the average of the reference positions of elevation angle 45 ° and elevation angle 75 °, a table of reference positions with an elevation angle of 60 ° shown in Index 25 to 30 in Table 9 is created.

  Depending on the focal length at the time of shooting and the elevation angle of the camera, there is a possibility that a foreground may enter the lower side of the AF frame or the periphery. In addition, the exposure amount to the celestial object may become inappropriate in the so-called dusk time zone.

  In the present invention, when focusing (hereinafter also referred to as celestial AF) in a shooting mode mainly for shooting a celestial body or the like, a criterion for determining the reliability of the AF evaluation value according to the shooting conditions. (Parameter) has been changed. Here, the imaging conditions in the present invention refer to various conditions such as the conditions (states) of the imaging apparatus and the conditions (states) of the subject at the time of shooting. For example, the photometric value of the image, the focal length of the imaging optical system And the inclination (elevation angle) of the imaging device. More specifically, a region for acquiring an image signal for performing celestial AF is divided into a plurality of regions. The reliability of the evaluation value obtained from the acquired image signal according to the relative position of the divided area, the output (brightness) of the measuring means, the focal length of the photographing optical system, and the elevation angle of the automatic focus adjustment device The numerical value for judging sex is changed.

  As a result, the reliability of the evaluation value is properly determined, and the sky is bright, such as before dusk and before dawn. It is possible to prevent focusing on a subject other than the celestial body due to entering.

  Therefore, even when automatic focus adjustment is performed on a subject existing at infinity, such as a celestial body, regardless of the brightness of incident light and other conditions, focus adjustment can be reliably performed.

  Also, the program diagram of FIG. 3 is merely an example, and different program diagrams are prepared if various conditions are different, such as the open F value of the taking lens barrel is different.

  The difference between the second embodiment of the present invention and the first embodiment is that the YI / YP AF frame performed in step S516 in FIG. 5 includes the YI determination threshold value in the reliability evaluation and the predetermined range to be compared with the reference position in step S524 in FIG. It is a point that varies depending on the focal length and the elevation angle.

  The operation is performed according to FIG. 5 as in the first embodiment.

  In step S516, it is checked whether or not there is a saturated subject such as a moon or illumination, and when performing the process of removing the affected AF frame, the total luminance value (in the divided AF frame ( The determination using YI) and the maximum luminance value (YP) was performed. On the other hand, in this embodiment, the determination threshold for YI is changed according to the procedure shown in FIG. 12 according to the focal length and the camera elevation angle during celestial AF.

  Similarly, the predetermined range to be compared with the reference position is made different depending on the focal length and the elevation angle by the procedure shown in FIG.

  First, in step S1201, a determination threshold for YI is initialized. This is the same value as in Example 1, and YP is always the theoretical maximum value. Further, YI is, for example, at least half of the theoretical maximum value, and the change is within 10% of the difference between the maximum value and the minimum value of YI obtained at each scan point.

  Next, in step S1202, the focal length at the time of celestial AF is checked. If the focal length is equal to or longer than the first focal length (for example, equivalent to 100 mm in terms of 35 mm film), the process proceeds to step S1207, and no parameter change is performed.

  If it is less than the second focal length (for example, equivalent to 35 mm), the process proceeds to step S1203 and is compared with the first elevation angle (for example, 30 °), and if it is less than that, that is, close to horizontal, the process proceeds to step S1204. .

  When shooting at an angle of elevation close to the horizontal with a short focal length, it is easy for illumination on the ground and the like to occur, and the celestial AF has a high probability of erroneous distance measurement. For this reason, the YI-related parameters are, for example, illumination that is greatly blurred if the difference between the maximum and minimum YI values obtained at each scan point is not less than one-third of the theoretical maximum value and within 20%. Make it easier to determine that a subject at a short distance has been adversely affected. That is, the frequency with which the information of the divided AF frame is used is lowered.

  If the angle is larger than the first elevation angle (for example, 30 °), the process proceeds to step S1207, and the parameter is not changed. This is because, when performing celestial AF at a certain high elevation angle, it is considered that illumination on the ground or the like is unlikely to enter the lower part of the screen.

  If the second focal length (e.g., equivalent to 35 mm) is less than the first focal length, the process proceeds to step S1205. In step S1205, a comparison is made with a second elevation angle (for example, 15 °) smaller than the first elevation angle, and if it is less than that, i.e., close to horizontal, the process proceeds to step S1206, and the parameter relating to YI is changed. As described above, the criterion (parameter) for determining the reliability of the detection area (AF frame) is changed based on the focal length of the imaging optical system and the tilt of the imaging device. For example, when the focal length is shorter than 100 mm, the AF frame reliability determination criterion is changed according to the inclination of the imaging apparatus. Specifically, when the focal length is shorter than, for example, 35 mm (first focal length) and the inclination with respect to the horizontal direction is, for example, 0 ° or more and less than 30 ° (0 ° or more and less than the third angle), The criterion for determining the reliability of the AF frame is changed. The focal length is, for example, 35 mm or more and less than 100 mm (longer than the first focal length and shorter than the second focal length), and the inclination is, for example, 0 ° or more and less than 15 ° (0 ° or more and smaller than the third angle). If the angle is less than the angle, the criterion for determining the reliability of the AF frame is changed.

  When shooting at an elevation angle that is relatively short in focal length and close to horizontal, illumination on the ground is likely to enter, so that the astronomical AF has a high probability of erroneous distance measurement. For this reason, the YI-related parameters are, for example, illumination that is greatly blurred if the difference between the maximum and minimum YI values obtained at each scan point is more than two-fifths of the theoretical maximum value and within 15%. Make it easier to determine that a subject at a short distance has been adversely affected. That is, the frequency with which the information of the divided AF frame is used is lowered.

  If the angle is larger than the second elevation angle (for example, 15 °), the process proceeds to step S1207, and the parameter is not changed.

  Next, in step S1207, it is compared with a third focal length (for example, equivalent to 100 mm), and if it is equal to or greater than the third focal length, is the elevation angle within a predetermined range (for example, 20 ° to 70 °) in step S1208? Check. If it is within the predetermined range, a predetermined range to be compared with the first reference position is set in step S1209.

  This predetermined range is a thermometer error, posture detection error, scan AF error, change over time, reproducibility of in-focus position deviation in the same environment, etc. that cause a difference between the reference position and the true in-focus position of the celestial object Determined in consideration of When the celestial AF is performed in a predetermined elevation range with a focal length longer than a predetermined value, the predetermined range is not changed between the near side and the far side because the probability of an obstacle or foreground entering the near side is low. For example, the thermometer error is 2.5 ° C., the posture detection error is 5 °, the scan AF error is equivalent to 0.5 depth of the open F value, and the change with time is equivalent to 1.5 depth of the open F value. It is assumed that the reproducibility of the in-focus position shift is equivalent to 1.5 depth of the open F value. Here, it is assumed that the focus position changes corresponding to 1.5 depth of the open F value due to an error of 2.5 ° C. of the thermometer, and the focus position changes equivalent to 2.5 depth of the open F value due to an attitude detection error of 5 °. In this case, the RMS of these values is taken, and a value corresponding to 6 to 7 depths of the open F value is set in consideration of a coefficient for viewing safety.

  If the elevation angle is outside the predetermined range in step S1208, the process proceeds to step S1211.

  If the focal length is shorter than the third focal length in step S1207, it is compared with a fourth predetermined focal length (for example, equivalent to 50 mm) in step S1210. If the focal length is longer than this, the flow proceeds to step S1211.

  In step S1211, a predetermined range to be compared with the second reference position is set.

  For the predetermined range on the far side, the same value as the predetermined range to be compared with the first reference position is set.

  For the near side, considering the effects of obstacles such as fences and windows existing on the near side, or when the photographer places a subject such as a tree or building as the foreground, Set a narrow range.

  For example, if it is assumed that the blur of the celestial body is conspicuous when the focus position shifts by 5 depths or more of the open F value, the value of 5 depths of the open F value is set.

  In step S1210, it is compared with a fourth predetermined focal length (e.g., equivalent to 50 mm). If the focal length is shorter than this, the process proceeds to step S1212 to set a predetermined range to be compared with the third reference position.

  For the predetermined range on the far side, the same value as the predetermined range to be compared with the first reference position is set.

  For the near side, considering the effects of obstacles such as fences and windows existing on the near side, or when the photographer places a subject such as a tree or building as the foreground, Set a narrow range. Further, since the focal length is short compared to the predetermined range compared with the second reference position, obstacles such as fences and windows existing on the near side and trees and buildings are likely to enter as the foreground, so a narrower range is set.

  For example, if it is assumed that the blur of the celestial body is conspicuous when the focus position is shifted by 3 depths or more of the open F value, the value of 3 depths of the open F value is set. Thus, in this embodiment, the shorter the focal length, the narrower the predetermined range compared with the reference position.

  In this embodiment, a region for acquiring an image signal for performing celestial AF is divided into a plurality of regions. The reliability of the evaluation value obtained from the acquired image signal according to the relative position of the divided area, the output (brightness) of the measuring means, the focal length of the photographing optical system, and the elevation angle of the automatic focus adjustment device The numerical value for judging sex is changed.

  As a result, the reliability of the evaluation value is judged appropriately, and because the sky is bright, such as at dusk and before dawn, false in-focus due to insufficient signal from the celestial body, and front subjects such as night views and obstacles enter the area below. Therefore, it is possible to prevent focusing on a subject other than the celestial body.

  As described above, according to the present invention, when performing the celestial AF, the determination criterion (parameter) for determining the reliability of the evaluation value is changed according to the imaging condition. Here, the imaging conditions in the present invention refer to various conditions such as the conditions (states) of the imaging apparatus and the conditions (states) of the subject at the time of shooting. For example, the photometric value of the image, the focal length of the imaging optical system And tilt of the imaging device. More specifically, the evaluation value obtained from the acquired image signal according to the relative position of the divided image signal acquisition region, the brightness, the focal length of the imaging optical system, and the elevation angle of the automatic focus adjustment device. The numerical value for judging reliability is changed. By doing so, the reliability of the evaluation value is appropriately judged, and the sky is bright at dusk, before dawn, etc. It is possible to prevent focusing on a subject other than a celestial body due to the entry of the subject.

  As described in the above embodiments, the focus detection apparatus of the present invention is applied to a lens-integrated imaging apparatus in which an imaging optical system (imaging lens) and an imaging apparatus body are integrated. However, the present embodiment is not limited to this, and is applied to an imaging system (optical apparatus) including an imaging device body and an interchangeable lens having an imaging optical system that can be attached to and detached from the imaging device body. You can also

  That is, in the first and second embodiments, the compact type digital camera has been described as an example. However, the present invention can be applied to AF during live view of a digital video camera or a digital single-lens reflex camera.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

  When a software program that realizes the functions of the above-described embodiment is supplied from a recording medium directly to a system or apparatus having a computer that can execute the program using wired / wireless communication, and the program is executed. Are also included in the present invention.

  Accordingly, the program code itself supplied and installed in the computer in order to implement the functional processing of the present invention by the computer also realizes the present invention. That is, the present invention includes a computer program itself in which a procedure for realizing the functional processing of the present invention is described.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS. As a recording medium for supplying the program, for example, a magnetic recording medium such as a hard disk or a magnetic tape, an optical / magneto-optical storage medium, or a nonvolatile semiconductor memory may be used.

  As a program supply method, a computer program that forms the present invention is stored in a server on a computer network, and a connected client computer downloads and programs the computer program.

  The present invention can be suitably used for an imaging apparatus such as a compact digital camera, a single-lens reflex camera, and a video camera.

14 Scan AF processing circuit 15 CPU
15a acquisition unit

Claims (22)

Acquisition means for acquiring an image output from an image sensor that receives light via the imaging optical system;
Calculating means for calculating an evaluation value indicating the contrast of the image;
Control means for detecting the in-focus position of the imaging optical system using the evaluation value when it is determined that the evaluation value is reliable according to a determination criterion for determining the reliability of the evaluation value;
Have
The focus detection apparatus characterized in that the control means changes the determination criterion of the reliability in accordance with an imaging condition. Having a detecting means for detecting inclination;
2. The focus according to claim 1, wherein the control unit changes the reliability criterion based on a photometric value of the image, a focal length of the imaging optical system, and the inclination. Detection device. The control means determines whether or not the shooting mode is an astronomical shooting mode for shooting a celestial body as a subject,
3. The focus detection apparatus according to claim 1, wherein, in the astrophotography mode, the reliability criterion is changed according to a photometric value of the image. 4.   When the photometric value is larger than the first photometric value, the control means does not detect the in-focus position using the evaluation value, and the second photometric value is smaller than the first photometric value. 4. The reliability criterion is changed so that the reliability is determined to be determined to be less reliable than the case where the photometric value is smaller than the second photometric value when the value is larger than the second photometric value. The focus detection apparatus described.   The reliability of the control unit is determined so that the reliability is determined when the focal length of the imaging optical system is shorter than the predetermined focal length than when the focal length is longer than the predetermined focal length. The focus detection apparatus according to claim 1, wherein the determination criterion is changed.   6. The focus detection according to claim 1, wherein the control unit changes a size of a detection frame in which the evaluation value can be detected in accordance with a focal length of the imaging optical system. apparatus.   The focus detection apparatus according to claim 6, wherein the control unit changes a size of the detection frame so that the detection frame becomes larger as the focal distance is longer. Having a detecting means for detecting inclination;
The control means determines that the in-focus position of the imaging optical system has been detected when the in-focus position detected based on the evaluation value is within a predetermined range with respect to a reference position;
The focus detection apparatus according to claim 1, wherein the control unit changes the predetermined range according to the inclination.   The control means is configured such that the inclination with respect to the horizontal direction is greater than the first angle and not more than 90 °, or the inclination with respect to the horizontal direction is not less than 0 ° and less than the second angle that is less than the first angle. The focus detection apparatus according to claim 8, wherein the predetermined range is narrowed.   The focus detection apparatus according to claim 8, wherein the control unit narrows the predetermined range as a focal length of the imaging optical system is shorter. Having measuring means for measuring the ambient temperature,
The control means determines that the in-focus position of the imaging optical system has been detected when the in-focus position detected based on the evaluation value is within a predetermined range with respect to a reference position;
The focus detection apparatus according to claim 1, wherein the control unit changes the predetermined range according to the temperature. Having a detecting means for detecting inclination;
The said control means changes the determination criteria of the said reliability according to the said inclination and the position of the detection area which detects the said evaluation value, The any one of Claim 1 thru | or 11 characterized by the above-mentioned. The focus detection apparatus described. The control means includes
When the inclination with respect to the horizontal direction is larger than the first angle and not more than 90 °, the reliability of the evaluation value detected from the detection area in the peripheral area outside the central area including the center of the image is determined. Change the criteria,
When the inclination is 0 ° or more and less than a second angle smaller than the first angle, the detection is performed from the detection region in a part of the peripheral region outside the central region including the center of the image. The focus detection apparatus according to claim 12, wherein a determination criterion for determining reliability of the evaluation value is changed.   The focus detection apparatus according to claim 13, wherein the partial area is a lower area of the image in the peripheral area. Having a detecting means for detecting inclination;
The control means sets a detection frame capable of detecting the evaluation value in the image, and calculates the evaluation value in each of a plurality of detection areas obtained by dividing the detection frame,
The determination criterion for determining the reliability of the detection region is changed based on the focal length of the imaging optical system and the inclination. Focus detection device.   The control means changes the criterion for determining the reliability of the detection area when the focal length is shorter than the first focal length and the inclination with respect to the horizontal direction is not less than 0 ° and less than the third angle. The focus detection apparatus according to claim 15, wherein:   In the case where the focal length is longer than the first focal length and shorter than the second focal length, and the inclination with respect to the horizontal direction is not less than 0 ° and smaller than the third angle. The focus detection apparatus according to claim 15, wherein the reliability criterion is changed.   The control means, based on the length of the interval in which the evaluation value monotonously decreases, the average value of the slope of the interval, and the difference between the maximum value and the minimum value of the evaluation value, The focus detection apparatus according to claim 1, wherein the focus detection apparatus determines the nature of the focus detection apparatus. An image sensor;
An imaging apparatus comprising: the focus detection apparatus according to claim 1. An acquisition step of acquiring an image output from an image sensor that receives light via the imaging optical system;
A calculation step of calculating an evaluation value indicating the contrast of the image;
A control step of detecting a focus position of the imaging optical system using the evaluation value when it is determined that the evaluation value is reliable according to a determination criterion for determining the reliability of the evaluation value;
Have
The focus detection method according to claim 1, wherein the control step changes the reliability determination standard according to a photographing condition.   A computer-executable program in which each step of the focus detection method according to claim 20 is described.   A computer-readable storage medium storing a program for causing a computer to execute each step of the focus detection method according to claim 20.