JP4847352B2 - Imaging apparatus and control method thereof - Google Patents

Description

  The present invention relates to an imaging apparatus that performs focus control using a detection result of a light source.

  The performance of autofocus (phase difference AF) based on the phase difference detection method often used in imaging devices such as single-lens reflex cameras varies depending on the type of light source that illuminates the subject (sun, fluorescent light, incandescent light, or other light source). To do. This is because the interval (phase difference) between the two images formed on the focus detection sensor changes depending on the type of light source.

In the imaging device disclosed in Patent Document 1, the type of the light source is detected from the output ratio (luminance ratio) from the visible light sensor and the infrared light sensor included in the light source, and the type of the light source is determined according to the detection result. Correction data for correcting the focus shift due to the difference is read from the memory. Then, correction data is added to the defocus amount detected by the focus detection sensor to obtain a focus lens drive amount for focusing.
Japanese Patent Laying-Open No. 2005-208300 (paragraphs 0144 to 0158, 0160 to 171, FIGS. 14 and 15, etc.)

  Here, not only when performing single imaging (single shooting), but also when performing continuous imaging (continuous shooting), it is preferable to perform the AF operation before each imaging so as to follow the movement of the subject. In this case, if the defocus amount detected by the focus detection sensor before each imaging is corrected based on the light source detection result, it is possible to obtain a continuous shot image with little focus shift due to the influence of the light source.

  However, in order to detect the light source, it is necessary to perform processing such as accumulation and reading of charges in the visible light sensor and the infrared light sensor, calculation of the luminance ratio, and comparison / determination. It takes a certain amount of time. For this reason, if an imaging preparation period of such a length that the focus control can be performed after reliably completing the light source detection before each imaging in the continuous imaging is provided, the continuous shooting speed is limited. On the other hand, if the detection of the light source is not completed before imaging, an error state occurs, and the usability deteriorates, for example, continuous imaging is interrupted.

  An object of the present invention is to provide an imaging apparatus capable of avoiding the occurrence of an error state due to a decrease in continuous shooting speed due to a light source detection operation or a failure of the light source detection operation.

An imaging apparatus according to one aspect of the present invention is based on a first focus detection unit that performs focus detection based on an imaging signal obtained by photoelectrically converting a subject image by an imaging unit, and a signal different from the imaging signal. Second focus detection means for performing focus detection, light source detection means for detecting first information relating to the light source, detection results by the second focus detection means , and focus control based on the first information. generates second information, and control means for performing before every image the focus control of the imaging optical system based on the second information storage for storing one of said first information and said second information And when the focus detection operation is instructed, the first focus is detected during detection of the first information by the light source detection means after the second focus detection means performs focus detection. Detection means performs focus detection When the difference between the in-focus position obtained by the second focus detection means and the in-focus position obtained by the first focus detection means is smaller than a predetermined value, the control means performs focus control on the basis of, in the focus control, if the detection operation of the first information by the light source detecting means before the imaging has not been completed, the control unit, imaging earlier than this dose Focus control is performed on the basis of information previously generated and stored in the storage means.

According to another aspect of the present invention, there is provided a method for controlling an imaging apparatus , comprising: a first focus detection unit that performs focus detection based on an imaging signal obtained by photoelectrically converting a subject image by an imaging unit; A method of controlling an image pickup apparatus having a second focus detection unit that performs focus detection based on a signal different from that and a light source detection unit that detects first information about the light source, the second focus detection unit based on the detection result and the first information to generate the second information on focus control, a control step performed before every image the focus control of the imaging optical system based on the second information, the first Storage step of storing one of the information and the second information in the storage means, and when the focus detection operation is instructed, the second focus detection means performs the focus detection, and then the light source Detection hand During the detection of the first information by the first focus detection means, the first focus detection means performs focus detection, and the in-focus position obtained by the second focus detection means and the first focus detection means When the difference from the in-focus position is smaller than a predetermined value, in the control step, focus control is performed based on the second information, and the detection operation of the first information is completed before imaging in the focus control. never been cases in the control step, and performing a full Okasu control using the information stored in the storage unit be generated before the imaging of the previous times than this.

  According to the present invention, even if the light source detection operation is not completed before the current imaging, the light source detection result detected before the previous imaging (the previous time or the previous time) or the generated focus control is related. Focus control is performed using information. For this reason, it is possible to avoid the occurrence of an error state due to a decrease in the continuous shooting speed due to the light source detection operation or the completion of the light source detection operation.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an optical and electronic configuration of a single-lens reflex digital camera system as an imaging system that is Embodiment 1 of the present invention. An interchangeable lens 100 is detachably attached to a single-lens reflex digital camera (hereinafter simply referred to as a camera) 200 that is an imaging device via a mount unit (not shown). The mount portion is provided with an electrical contact group 107, and communication is performed between the camera 200 and the interchangeable lens 100 via the electrical contact group 107.

  A light beam from a subject (not shown) is guided into the camera 200 through the lenses 101 a and 101 b and the diaphragm 102 in the interchangeable lens 100. The lenses 101a and 101b and the diaphragm 102 constitute an imaging optical system. The lens 101b is a focus lens, and performs focus adjustment by moving in the optical axis direction.

  Reference numeral 202 denotes a quick return mirror. The quick return mirror 202 has a half mirror portion at the center thereof. As shown in the figure, in a state where the quick return mirror 202 is disposed obliquely in the imaging optical path (mirror down state), a part of the light beam from the imaging optical system is reflected by the half mirror part and guided to the finder optical system. It is burned. The viewfinder optical system is an optical system that includes a focus plate (not shown), a pentaprism 201, and an eyepiece lens 206, and allows an object image formed on the focusplate to be observed through the eyepiece lens 206 and the pentaprism 201.

  The light beam that has passed through the half mirror is reflected by the sub mirror 203 disposed behind the quick return mirror 202 and guided to the AF sensor 204 that performs focus detection by the phase difference detection method.

  In the camera 200 of the present embodiment, as shown in FIG. 6, a plurality of (three in this embodiment) focus detection areas 1 to 3 are provided within the range of the imaging screen. For this reason, the AF sensor 204 is provided with three pairs of CCD line sensors corresponding to the three focus detection areas 1 to 3. A signal from the AF sensor 204 (each pair of CCD line sensors) is input to the focus detection circuit 205. The focus detection circuit 205 calculates a focus state (defocus amount) of the imaging optical system with respect to a subject existing in each focus detection area according to the input signal. A focus detection method using the AF sensor 204 will be described later.

  In a state where the quick return mirror 202 and the sub mirror 203 are retracted out of the imaging optical path (mirror up state), the light flux from the imaging optical system passes through the filter 209 having an infrared cut and low-pass function and the shutter 208 to the imaging element 210. To reach. The image sensor 210 is a photoelectric conversion element configured by a photoelectric conversion element such as a CCD sensor or a CMOS sensor. A shutter 208 is a focal plane shutter, and controls exposure of the image sensor 210 by running the front curtain and the rear curtain.

  Reference numeral 223 denotes a system controller that controls the camera 200 and the interchangeable lens 100, and includes a CPU. Specifically, the system controller 223 controls the following circuits and mechanisms provided in the camera 200 and the interchangeable lens 100.

  First, the following circuit and mechanism are provided in the interchangeable lens 100. A lens control circuit 104 controls a lens driving mechanism 103 that moves the focus lens 101b in the optical axis direction. Although not shown, the lens control circuit 104 stores information unique to the interchangeable lens, such as focal length, wide aperture, lens ID information allocated to each interchangeable lens, and various information received from the system controller 223. A memory unit is provided.

  Reference numeral 106 denotes an aperture control circuit that controls an aperture drive mechanism 105 that drives the aperture 102.

  The following circuit and mechanism are provided in the camera 200. Reference numeral 211 denotes a shutter charge / mirror drive mechanism. The shutter charge / mirror drive mechanism 211 performs charge drive of the shutter 208 and up / down drive of the quick return mirror 202.

  A shutter control mechanism 212 controls the travel of the front curtain and rear curtain of the shutter 208.

  Reference numeral 207 denotes a photometric circuit, which detects subject luminance in three photometric areas 1 to 3 including focus detection areas 1 to 3, respectively, as shown in FIG. Information on the detected subject brightness is sent to the system controller 223.

  The photometric circuit 207 is provided with a light receiving sensor 207a mainly sensitive to visible light and a light receiving sensor 207b mainly sensitive to infrared light as light source detection means.

  Reference numeral 222 denotes an EEPROM as a memory (storage means). The EEPROM 222 stores parameters necessary for controlling the camera 200 and ID information that enables individual identification of the camera 200. Further, the EEPROM 222 stores AF correction data adjusted using the adjustment reference lens, correction data for performing automatic exposure, and AF correction amount data corresponding to the type of light source.

  Reference numeral 220 denotes an image data controller. The image data controller 220 includes a DSP (digital signal processor), and controls the image sensor 210 and corrects or processes image data input from the image sensor 210 via the A / D converter 216. Perform according to the command. Auto white balance is also included in the correction and processing of image data. The auto white balance is a function for correcting the maximum luminance portion in the captured image to white. The image data controller 220 changes the auto white balance correction amount according to a command from the system controller 223.

  A timing pulse generation circuit 217, an A / D converter 216, a DRAM 221, a D / A converter 215, and an image compression circuit 219 are connected to the image data controller 220. The timing pulse generation circuit 217 outputs a pulse signal necessary for driving the image sensor 210. The A / D converter 216 receives the timing pulse generated by the timing pulse generation circuit 217 and converts an analog imaging signal corresponding to the subject image output from the imaging element 210 into digital image data. The DRAM 221 temporarily stores image data (digital data) before processing or data conversion into a predetermined format.

  An image display circuit 213 is connected to the D / A converter 215 via an encoder circuit 214. The D / A converter 215 converts the digital image data from the image data controller 220 into analog image data. The encoder circuit 214 converts the analog image data into a video signal (for example, NTSC signal) suitable for display on the image display circuit 213 as a display unit. The image display circuit 213 is configured by a color liquid crystal display element or the like.

  The image compression circuit 219 performs compression and conversion (for example, conversion to JPEG) of image data stored in the DRAM 221. The image data converted by the image compression circuit 219 is recorded on the recording medium 218. As the recording medium 218, a hard disk, a semiconductor memory, an optical disk, or the like is used.

  In addition, the system controller 223 controls multiple imaging (bracket imaging) performed by changing parameters in stages to perform AF, AE, and white balance calibration. Further, the system controller 223 can perform contrast AF in addition to the phase difference AF using the AF sensor 204. In contrast AF, the focus lens 101b is moved to a position where the contrast evaluation value generated from the high-frequency component of the video acquired using the image sensor 210 reaches a peak.

  The system controller 223 is connected to an information display circuit 225, a first release switch (SW1) 231, a second release switch (SW2) 230, a mode setting switch 229, a focus detection area selection switch 228, and a determination switch 227. Yes. Furthermore, a bracket amount setting switch 232, a photometric area selection switch 235, an electronic dial switch 226, a counter 233 and a buzzer 234 are connected to the system controller 223.

  The information display circuit 225 displays the operation mode of the camera 200 and exposure information (shutter time, aperture value, etc.). The information display circuit 225 is configured by a liquid crystal display element or the like. The first release switch 231 is a switch for starting imaging preparation operations such as photometry and AF, and is turned on by a half-press operation of a release button (not shown). The second release switch 230 is a switch for starting a still image capturing operation, and is turned on by fully pressing the release button.

  The mode setting switch 229 is a switch provided to select an operation mode (such as an imaging mode or an AF mode) of the camera 200. The focus detection area selection switch 228 is a switch for allowing a photographer to arbitrarily select a focus detection area corresponding to a subject to be focused out of the three focus detection areas 1 to 3 shown in FIG. .

  The decision switch 227 is a switch for the photographer to select (determine) the most preferable image among a plurality of images obtained by bracket imaging. The bracket amount setting switch 232 is a switch for the photographer to arbitrarily set the bracket step amount in the bracket imaging. The photometry area selection switch 235 is a switch for the photographer to arbitrarily select an area for photometry among the three photometry areas 1 to 3 shown in FIG. The electronic dial switch 226 is a dial type switch for changing various parameters by the rotation operation (number of clicks).

  The counter 233 counts the number of imaging (number of images) when performing bracket imaging. The buzzer 234 outputs various warning sounds based on signals from the system controller 223.

  Note that an external device 300 typified by a personal computer (PC) can be connected to the camera 200. The system controller 223 can communicate with the external device 300 via the communication interface circuit 224.

  Here, a method of detecting the defocus amount using the AF sensor 204 will be described with reference to FIGS.

  A light beam incident on the AF sensor 204 from the subject OBJ via the imaging optical system (focus lens 101b) and mirrors 202 and 203 (see FIG. 1) passes through the condenser lens 501, and then is divided into two by the separator lens 503. The The two split light beams form two images on the pair of line sensors 504. A pair of line sensors 504 outputs signals (image signals) corresponding to the two images. The condenser lens 501 and the separator lens 503 constitute an AF optical system.

  When the image sensor 210 (image sensor equivalent surface 210 ′) is in focus, the distance between the two images formed on the pair of line sensors 504 (the distance between the two image signals) Lo is a specific value. Become. Although this specific value can be obtained by design, in practice, it is not completely the same as the design value due to manufacturing errors such as variations in component dimensions and assembly errors. Therefore, in practice, it is difficult to obtain the reference two-image interval Lo as the specific value unless actual measurement is performed. As shown in FIG. 7, if the two-image interval is narrower than the reference two-image interval Lo, the front pin state is established. If the two-image interval is wider than the reference two-image interval Lo, the rear-pin state is established.

  FIG. 8 shows the principal ray PR from the imaging optical system that reaches the pair of line sensors 504 via the imaging element equivalent surface 210 ′ and the AF optical system (where the condenser lens 501 is not shown).

  Assume that the angle of the principal ray PR with respect to the optical axis of the AF optical system is θ, the magnification of the separator lens 503 is β, and the amounts of image movement on the image sensor equivalent surface 210 ′ and the line sensor 504 are ΔL and ΔL ′, respectively. The defocus amount d is obtained by the following equation.

d = ΔL / tan θ = ΔL ′ / (β · tan θ)
Here, β · tan θ is a parameter determined in the design of the AF optical system. ΔL ′ can be obtained from the reference two-image interval Lo and the actual two-image interval (phase difference) Lx on the line sensor 504.

  In this embodiment, a reference lens that has been adjusted in advance to focus on the light receiving surface of the image sensor 210 with respect to a subject at a predetermined distance is attached to the camera 200. . Then, the two-image interval obtained from the AF sensor 204 at that time is stored in the EEPROM 222 as the reference two-image interval Lo.

  However, when the interchangeable lens 100 different from the reference lens is attached to the camera 200, the two-image interval when the subject is focused on the predetermined distance is shifted from the reference two-image interval Lo due to manufacturing errors. In particular, the above-described deviation increases depending on the type of light source that illuminates the subject, and even when the focus lens 101b is driven using the defocus amount calculated based on the interval between the two images, high-precision focusing cannot be obtained. For this reason, in this embodiment, information on the light source is obtained, and a light source whose two image intervals at the time of focusing are not negligible compared to the reference two-image interval Lo is used as an AF correction amount in AF calibration described later. The focus position shift amount DF is corrected.

  FIG. 2 shows a flowchart of a focus detection area selection sequence in the camera 200 of the present embodiment. Each operation shown in this flowchart and a flowchart described later is executed by the system controller 223 in accordance with a computer program stored in the controller 223.

  In step (abbreviated as S in the drawing) 001, the system controller 223 determines whether or not the focus detection area selection switch 228 is turned on. If it is turned on, the process proceeds to step 002.

  In step 002, the system controller 223 determines whether the electronic dial switch 226 has been operated. Further, if operated, the operation direction and the operation amount are detected.

  In step 003, the system controller 223 changes the focus detection area according to the operation direction and operation amount of the electronic dial switch 226 in step 002. The focus detection areas are all cyclically switched in the order of ← → focus detection area 1 ← → focus detection area 2 ← → focus detection area 3 ← → all.

  In step 004, the system controller 223 determines whether or not the focus detection area selection switch 228 is turned on. If it is on, the process returns to step 002, and if it is off, this sequence is terminated.

  FIG. 3 shows a flowchart of a mode setting sequence in the camera 200 of the present embodiment.

  In step 101, the system controller 223 determines whether or not the mode setting switch 229 is turned on. If it is on, it is determined that the mode setting operation has been started by the photographer, and the process proceeds to step 102.

  In step 102, the system controller 223 detects the number of operation clicks of the electronic dial switch 226. When the electronic dial switch 226 is rotated, the imaging mode is changed to “TV mode” ← → “AV mode” ← → “P (program) mode” ← → “AF calibration mode” ← → “TV mode” for each operation click. ← → ・ ・ ・ and can be changed to a circulation type. The “AF calibration mode” is set so that it cannot be selected unless only one of the focus detection areas 1 to 3 is selected in the focus detection area selection sequence.

  In step 103, the system controller 223 determines whether or not the mode setting switch 229 is turned off. If it is off, in step 104, the imaging mode selected at that time is set.

  In step 105, the system controller 223 determines whether or not the set imaging mode is the AF calibration mode. When the mode is not the AF calibration mode, the process proceeds to step 111, and the process proceeds to an imaging sequence (not illustrated) corresponding to each imaging mode. In the case of the AF calibration mode, the process proceeds to step 106.

  In step 106, the system controller 223 determines whether or not the bracket amount setting switch 232 is turned on. If it is on, the process proceeds to step 107. If not turned on, the AF bracket step amount for AF calibration imaging (bracket imaging) is set to the reference value a, and the process proceeds to step 110.

  In step 107, the system controller 223 detects the number of operation clicks of the electronic dial switch 226. When the electronic dial switch 226 is rotated, the AF bracket step amount is set to “reference value a × 0.25” ← → “reference value a × 0.5” ← → “reference value a” ← → “ Reference value a × 2 ”← →“ reference value a × 4 ”can be changed. However, “reference value × 0.25” and “reference value × 4” are set as a lower limit value and an upper limit value, respectively, and even if the electronic dial switch 226 is operated to change the AF bracket step amount beyond these values, the operation is performed. Is ignored.

  The reference value a of the AF bracket step amount is determined by the following equation when the system controller 223 receives open aperture value information (FNO) from the aperture control circuit 106.

  Reference value a = FNO × ε (ε represents an allowable circle of confusion diameter).

  The reference value a in this embodiment is set to the same value as the depth of focus δ = FNO × ε. In this embodiment, ε = 0.03 mm.

  Making the AF bracket step amount variable as described above has the following advantages. Even when large focus correction is required, the focus correction amount can be narrowed down to an appropriate value by performing AF calibration multiple times by changing the AF calibration step amount from a large step amount to a small step amount in stages. Can do.

  In step 108, the system controller 223 determines whether or not the bracket amount setting switch 232 is turned off. If it is off, the process proceeds to step 109, and the bracket step amount selected at that time is set as the bracket step amount “A”.

  In step 110, the system controller 223 proceeds to the AF calibration imaging sequence.

  FIG. 4 shows a flowchart of an AF calibration imaging sequence in the camera 200 of the present embodiment. In this AF calibration imaging sequence, the AF bracket step amount is changed stepwise and imaging is performed a plurality of times.

  In step 201, the system controller 223 resets the count value N of the counter 233.

  In step 202, the system controller 223 determines whether or not the first release switch (SW1) 231 is turned on. If it is on, the process proceeds to step 203 and step 205. If it is off, step 202 is repeated.

  In step 203, the system controller 223 measures the luminance of the subject from the light flux that has entered the photometry circuit 207 from the imaging optical system via the quick return mirror 202 and the pentaprism 201.

  In step 204, the system controller 223 determines the exposure conditions such as the shutter speed and the aperture value according to the output from the photometry circuit 207. Then, the process proceeds to Step 211.

  In step 205, the system controller 223 uses the AF sensor 204 and the focus detection circuit 205 to detect the focus of the imaging optical system. Specifically, the focus detection circuit 205 obtains a phase difference between the two images from the two image signals obtained from the AF sensor 204, and calculates a defocus amount from the phase difference. Then, the system controller 223 calculates the drive amount and drive direction of the focus lens 101b based on the defocus amount.

  In step 206, the system controller 223 determines whether focus detection has been performed. Since focus detection may not be performed when the subject is low contrast or dark, in this case, the process proceeds to step 210 to perform a warning operation. As a warning operation, a warning is displayed on the image display circuit 213 or a warning sound is output from the buzzer 234.

  At this time, after storing the exposure condition data for resuming AF calibration, the AF calibration imaging sequence is terminated. Information on whether or not the AF calibration can be resumed is stored at the time of the interruption, and when the resume is instructed, it is determined whether or not the calibration can be resumed.

  In step 207, the system controller 223 transmits the drive amount and drive direction information obtained in step 205 to the lens control circuit 104. The lens control circuit 104 controls the lens driving mechanism 103 according to the information on the driving amount and the driving direction, and moves the focus lens 101b. Thereby, the focus lens 101b can be moved to the in-focus position by the phase difference AF.

  In step 208, the system controller 223 obtains a focus lens position (focus position) where the contrast evaluation value of the image reaches a peak while moving the focus lens 101b by contrast AF.

  At this time, if the focus lens position at which the contrast evaluation value reaches the peak is not obtained by contrast AF, that is, if an abnormality is detected, the data related to contrast AF is saved for AF calibration restart, and this sequence is executed. finish. Further, contrast AF may be performed again, or the operation may be held and a warning operation may be performed.

  In step 209, the system controller 223 obtains a difference between the in-focus position obtained by the phase difference AF obtained in step 205 and the in-focus position obtained by the contrast AF obtained in step 208. Then, the reliability of the difference is determined. The reliability is determined by whether or not the difference is smaller than a specific threshold value. If the reliability is high (the difference is larger than the threshold value), the process proceeds to step 211. If the reliability is low (the difference is larger than the threshold value), although not shown, AF calibration is stopped or contrast AF is performed again.

  In step 211, the system controller 223 determines whether or not the second release switch (SW2) 230 is turned on. If it is on, the process proceeds to step 212, and if it is off, step 211 is repeated.

  In step 212, the system controller 223 calculates the focus position shift amount “DF”. Specifically, using the current count value N of the counter 233, the focus position shift amount DF is calculated by the following equation.

DF = A × (N-4)
Here, A is the bracket step amount set in step 109 described above. In the present embodiment, the bracket imaging is performed seven times around the focus position shift amount DF = 0 (that is, N = 4).

  In step 213, the system controller 223 increments the count value N of the counter 233 by one.

  In step 214, the system controller 223 transmits the focus position shift amount DF calculated in step 212 to the lens control circuit 104. The lens control circuit 104 controls the lens driving mechanism 103 to move the focus lens 101b to a position shifted from the focus position by the phase difference AF described above by the focus position shift amount DF.

  In step 215, the system controller 223 controls the shutter charge / mirror drive mechanism 211 to perform the up operation of the quick return mirror 202 and the sub mirror 203.

  In step 216, the system controller 223 transmits the aperture value information set in step 204 to the aperture control circuit 106. The aperture control circuit 106 controls the aperture drive mechanism 105 to narrow the aperture 102 to the set aperture value.

  In step 217, the system controller 223 opens the shutter 208 via the shutter control mechanism 212.

  In step 218, the system controller 223 causes the image sensor 210 to perform a charge accumulation operation via the image data controller 220.

  In step 219, the system controller 223 waits for a predetermined charge accumulation time to elapse and proceeds to step 220.

  In step 220, the system controller 223 closes the shutter 208 via the shutter control mechanism 212.

  In step 221, the system controller 223 controls the shutter charge / mirror drive mechanism 211 in preparation for the next imaging, and performs the charge operation and mirror down drive of the shutter 208.

  In step 222, the system controller 223 causes the aperture control circuit 106 and the aperture control mechanism 105 to drive the aperture 102 to open.

  In step 223, the system controller 223 instructs the image data controller 220 to take in the analog image signal from the image sensor 210 as digital image data via the A / D converter 216. At this time, the captured image data may be limited area data including the focus detection area where the phase difference AF is performed.

  In step 224, the system controller 223 transmits the current focus position shift amount DF to the image data controller 220. The image data controller 220 records the lens ID information, the image data, and the focus position shift amount DF on the recording medium 218 via the image compression circuit 219 in association with each other. Thus, one bracket imaging is completed.

  In step 225, the system controller 223 confirms the value of the count value N of the counter 233. It is determined whether or not the counter value N has reached a predetermined value (7 in this embodiment). When the predetermined value is reached, that is, when all bracket imaging is completed, the AF calibration imaging sequence is terminated, and the process proceeds to an AF calibration image selection sequence described later. If it has not yet reached the predetermined value, that is, if all bracket imaging has not yet been completed, the processing returns to step 211 and the processing of step 211 to step 224 is repeated.

  FIG. 5 shows a flowchart of an AF calibration image selection sequence in the camera 200 of the present embodiment. In this sequence, the one in the best focus state is selected from the seven images (hereinafter referred to as bracket images) acquired by bracket imaging in the AF calibration imaging sequence described above.

  In step 3000, the system controller 223 determines an image selection method. In the case of manual selection, the process proceeds to step 301. In the case of automatic selection, the process proceeds to step 3001. Whether the selection is manual or automatic is determined by the photographer operating the determination switch 227 on the selection screen displayed on the image display circuit 213.

  In step 3001, the system controller 223 takes in the contrast evaluation values of the seven bracket images.

  In step 3002, the system controller 223 compares the contrast evaluation values of the seven bracket images with each other, and selects an image having the maximum contrast evaluation value among them as the best image. Then, the process proceeds to Step 313.

  In step 313, the system controller 223 determines the focus position shift amount DF stored in association with the selected best image as the AF correction amount (CAL data).

  In step 314, the AF correction amount determined in step 313, the focus detection area where the phase difference AF has been performed, and information on the focal length (zoom position) of the imaging optical system at that time are associated with each other, and It is stored in the EEPROM 222 together with the lens ID information. The above processing is performed by changing the focus detection area and the zoom position, and the AF correction amount corresponding to them is stored in the EEPROM 222.

  On the other hand, in step 301, the system controller 223 causes the image display circuit 213 to display the bracket image of the count value “1” captured in the AF calibration imaging sequence through the image data controller 220.

  Here, when displaying the bracket image, the bracket image is displayed by performing image processing different from that in the case of displaying an image captured in a normal imaging sequence described later. Specifically, when displaying an image captured in the normal imaging sequence, edge enhancement is performed to improve the appearance.

  In step 302, the system controller 223 determines whether or not the determination switch 227 is turned on. If it is turned on, the bracket image displayed at that time is determined as the best image by the photographer. When the decision switch 227 is turned on, the process proceeds to step 313. If it is not turned on, the routine proceeds to step 303.

  In step 303, the system controller 223 detects the operation state of the electronic dial switch 226. If it is rotated counterclockwise, the routine proceeds to step 304. If it is rotated clockwise, the routine proceeds to step 308.

  In step 304, the system controller 223 decrements 1 from the count value N.

  In step 305, the system controller 223 determines whether the count value N is “0”. If the count value N is greater than “0”, the process proceeds to step 312. If the count value N is “0”, the process proceeds to step 306 to perform a warning operation indicating that there is no bracket image that can be selected. The warning operation is performed at least one of warning display on the image display circuit 213 and warning sound output from the buzzer 234. Then, the process proceeds to Step 307.

  In step 307, the system controller 223 increments the count value N by one. Then, the process returns to step 303.

  In step 308, the system controller 223 increments the count value N by one.

  In step 309, the system controller 223 determines whether or not the count value N is “7”. If the count value N is smaller than “7”, the process proceeds to step 312. When the count value N is “7”, the process proceeds to step 310 to perform a warning operation indicating that there is no bracket image that can be selected. The warning operation is performed at least one of warning display on the image display circuit 213 and warning sound output from the buzzer 234. Then, the process proceeds to Step 311.

  In step 311, the system controller 223 increments the count value N by 1. Then, the process returns to step 303.

  In step 312, the system controller 223 calls up a bracket image corresponding to the count value N switched according to the operation of the electronic dial switch 226 from the recording medium 218 and displays it on the image display circuit 213.

  In step 313, the system controller 223 determines the focus position shift amount DF recorded on the recording medium 218 in association with the bracket image selected by turning on the determination switch 227 in step 302 as the AF correction amount (CAL data). .

  In step 314, the focus position shift amount DF determined in step 313 is written in the EEPROM 222 together with the lens ID of the interchangeable lens 100 as the AF correction amount of the focus detection area where the phase difference AF is performed.

  In step 315, the system controller 223 deletes all bracket image data from the recording medium 218.

  FIG. 9 shows a flowchart of a first normal imaging sequence in the camera 200 of the present embodiment.

  In step 401, the system controller 223 determines whether or not the first release switch (SW1) 231 is turned on. If it is turned on, the process proceeds to step 402 and step 404. If it is off, step 401 is repeated.

  In step 402, the system controller 223 measures the luminance of the subject from the light flux that has entered the photometry circuit 207 from the imaging optical system via the quick return mirror 202 and the pentaprism 201.

  In step 403, the system controller 223 determines the exposure conditions such as the shutter speed and the aperture value according to the output from the photometry circuit 207. Then, the process proceeds to step 410.

  In step 404, the system controller 223 performs focus detection of the imaging optical system using the AF sensor 204 and the focus detection circuit 205. Specifically, the focus detection circuit 205 obtains a phase difference between the two images from the two image signals obtained from the AF sensor 204, and calculates a defocus amount from the phase difference. Then, the system controller 223 calculates a drive amount (hereinafter referred to as a detection drive amount) and a drive direction of the focus lens 101b based on the defocus amount.

  In step 405, the system controller 223 determines whether focus detection has been performed. If the subject is low contrast or dark, focus detection may not be performed. In this case, the process proceeds to step 409 to perform a warning operation. As a warning operation, a warning is displayed on the image display circuit 213 or a warning sound is output from the buzzer 234.

  In step 406, the system controller 223 receives lens ID information from the interchangeable lens 100 attached to the camera 200. Then, it is confirmed whether or not the lens 222 and the AF correction amount (CAL data) corresponding to the focus detection area where the focus is detected in step 404 are stored in the EEPROM 222. If not stored, the process proceeds directly to step 408, and if stored, the process proceeds to step 407.

In step 407, the AF correction amount (CAL data) checked and read in step 406 is added to the detected drive amount calculated in step 404. Thus, the corrected drive amount of the focus lens 101b is
Detection drive amount + AF correction value (CAL data)
It becomes.

At this time, if there is an AF correction value (adjustment data) measured during assembly adjustment of the camera 200 or the interchangeable lens 100, the corrected driving amount of the focus lens 101b is
Detection drive amount + AF correction value (CAL data) + AF correction value (adjustment data)
It becomes.

  In step 408, the system controller 223 transmits the corrected drive amount information to the lens control circuit 104. The lens control circuit 104 controls the lens driving mechanism 103 according to the received corrected driving amount to drive the focus lens 101b. As a result, the focus lens 101b moves to the in-focus position corresponding to the corrected driving amount.

  In step 410, the system controller 223 determines whether or not the second release switch (SW2) 230 is turned on. If it is on, the process proceeds to step 411. If it is off, step 410 is repeated.

  In step 411, the system controller 223 controls the shutter charge / mirror drive mechanism 211 to perform the up operation of the quick return mirror 202 and the sub mirror 203.

  In step 412, the system controller 223 transmits the aperture value information set in step 403 to the aperture control circuit 106. The aperture control circuit 106 controls the aperture drive mechanism 105 to narrow the aperture 102 to the set aperture value.

  In step 413, the system controller 223 opens the shutter 208 via the shutter control mechanism 212.

  In step 414, the system controller 223 causes the image sensor 210 to perform a charge accumulation operation via the image data controller 220.

  In step 415, the system controller 223 waits for a predetermined charge accumulation time to elapse and proceeds to step 416.

  In step 416, the system controller 223 closes the shutter 208 via the shutter control mechanism 212.

  In step 417, the system controller 223 controls the shutter charge / mirror drive mechanism 211 in preparation for the next imaging, and performs the charge operation and mirror down drive of the shutter 208.

  In step 418, the system controller 223 causes the aperture control circuit 106 and the aperture control mechanism 105 to drive the aperture 102 to the open position.

  In step 419, the system controller 223 instructs the image data controller 220 to capture the analog image signal from the image sensor 210 as digital image data via the A / D converter 216.

  In step 420, the system controller 223 records the captured image data on the recording medium 218 through the image compression circuit 219.

  FIG. 10 shows a flowchart of a normal imaging sequence in the camera 200 as Embodiment 2 of the present invention.

  First, in step 1000, the system controller 223 detects that the interchangeable lens 100 is attached, and acquires lens ID information of the interchangeable lens 100 in step 1010.

  Next, in step 1020, the system controller 223 detects whether or not the first release switch (SW1) 231 is turned on (pressed). If it is off, the process returns to step 1000. If it is on, the process proceeds to Step 1030.

  In step 1030, the system controller 223 performs phase difference AF, and calculates a defocus amount and a focus position (hereinafter referred to as phase difference focus position).

  In step 1040, the system controller 223 starts live view display. The live view display is an operation in which the image display circuit 213 is continuously displayed with the real time video acquired using the image sensor 210 while the shutter 208 is held in an open state.

  In Step 1045, detection of light source information (first information) (light source detection operation) is started. Specifically, an output from the light receiving sensor 207a provided mainly in the photometric circuit 207 and mainly sensitive to visible light, and an output from the light receiving sensor 207b mainly sensitive to infrared light. The ratio (luminance ratio) is obtained. The light source detection operation is an operation for finally determining whether the light source is the sun, a fluorescent lamp, or another light source from this luminance ratio.

  Further, along with the start of the light source detection operation, the timer count of the light source detection time (specific time) is started as a time necessary for completing the light source detection operation or a time allowing a slight margin.

  Next, in step 1050, the system controller 223 obtains a focus lens position (hereinafter referred to as a contrast focus position) where the contrast evaluation value of the image reaches a peak while moving the focus lens 101b by contrast AF.

  In step 1060, if the focus lens position where the contrast evaluation value reaches a peak is not obtained by contrast AF, that is, if an abnormality is detected, the process proceeds to step 1200, and data indicating the state up to that point is stored. finish. If no abnormality is detected, the process proceeds to step 1070.

  In step 1070, the system controller 223 obtains the difference between the phase difference focus position obtained in step 1030 and the contrast focus position obtained in step 1050. When the difference is larger than a predetermined value, processing such as phase difference AF is performed again, although not shown.

  In step 1080, the system controller 223 detects whether or not the second release switch (SW2) 230 is turned on (pressed). If it is off, the process returns to step 1020. If it is on, the process proceeds to Step 1090.

  In step 1090, the system controller 223 ends the live view display.

  In step 1095, the system controller 223 determines whether or not the light source detection operation started in step 1045 has been completed within the light source detection time counted by the timer (that is, whether or not the type of the light source has been completed). ). If the light source detection operation is completed within the light source detection time, the process proceeds to step 1100.

  In step 1100, an AF correction amount (second information regarding focus control) corresponding to the type of light source is calculated (generated) based on the light source detection result. The calculation here may be calculation using a calculation formula or reading of data stored in the EEPROM 222. Also, the calculated AF correction amount is stored in the EEPROM 222.

  Thereafter, in step 1110, an AF correction amount corresponding to the current light source detection result calculated in step 1100 (or an AF correction amount calculated before the previous time read in step 1130 described later) is calculated in step 1030. Is added to the defocus amount. Thereby, the defocus amount corrected according to the type of the light source is obtained.

  The system controller 223 obtains the final focus position (drive amount from the current position) of the focus lens 101b based on the defocus amount after light source correction, and sets the focus position via the lens drive mechanism 103 to the focus position. The focus lens 101b is moved.

  Next, in step 1120, an image capturing operation (including image recording) of the subject image by the image sensor 210 is performed. The specific contents of the imaging operation are the same as those described with reference to FIG.

  When the imaging operation is completed, the system controller 223 determines in step 1121 whether or not the second release switch (SW2) 230 is kept on. If it is off, this flow ends. On the other hand, if ON is continued, the process returns to step 1030 to perform continuous imaging.

  When the processing of steps 1030 to 1090 is performed as the second pre-imaging operation in the continuous imaging and the process proceeds to step 1095, the light source detection operation before the current imaging is not completed within the light source detection time. Advances to step 1130.

  In step 1130, the AF correction amount (however, the latest AF correction amount) corresponding to the result of the light source detection operation performed before the previous imaging is read from the EEPROM 222. The previous time includes the previous and previous times.

  Thereby, even if the light source detection operation before the current imaging is not completed and the type of the light source cannot be determined, the defocus amount after light source correction can be obtained in step 1110. Therefore, the focus lens 101b can be moved to the in-focus position based on the defocus amount after the light source correction, and in the next step 1120, a good image with little focus deviation by the light source (second and subsequent images) ) Can be obtained.

  According to the embodiment described above, when the light source detection operation before the current imaging is not completed within the light source detection time, the AF correction amount corresponding to the light source detection result obtained before the previous imaging is obtained from the EEPROM 222. Read out and perform focus control before the current imaging. For this reason, if the light source detection result is obtained before the previous imaging, the camera does not go into an error state before the current imaging or wait for a long time to complete the light source detection operation before the current imaging. . Therefore, it is possible to repeat the imaging smoothly, and when performing continuous imaging, the continuous shooting speed can be increased while reducing the influence of the light source on the focus.

  In FIG. 10, the AF correction amount corresponding to the type of light source is stored in the EEPROM 222, and if the light source detection operation is not completed within the light source detection time before the current imaging, it is obtained before the previous imaging. The case where the AF correction amount read out from the EEPROM 222 has been described. However, information on the light source is stored in the EEPROM 222, and if the light source detection operation is not completed within the light source detection time before the current imaging, the information on the light source obtained before the previous imaging is read from the EEPROM 222. You may do it. In this case, it is only necessary to obtain the current AF correction amount using the read information on the light source before the previous time, and further obtain the defocus amount after light source correction.

  FIG. 10 illustrates the case where focus control is performed using the previous AF correction amount or the light source detection result when the light source detection operation is not completed within the light source detection time before the current imaging. However, not only when the light source detection operation is not completed within the light source detection time, but also when the normal detection result is not obtained, focus control is similarly performed using the previous AF correction amount or the light source detection result. May be performed.

  Furthermore, when performing continuous imaging, if the movement of the subject is small (that is, focusing can be maintained without performing focus control), the light source detection result before the first imaging is used for the second and subsequent imaging. It may be used for previous focus control. Thereby, the continuous shooting speed can be increased as compared with the case where the light source detection operation is performed before every imaging.

1 is a block diagram showing a configuration of a single-lens reflex digital camera system that is an embodiment of the present invention. 6 is a flowchart illustrating a focus detection area selection sequence in the camera of the embodiment. 6 is a flowchart illustrating a mode setting sequence in the camera of the embodiment. 6 is a flowchart illustrating an AF calibration imaging sequence in the camera of the embodiment. 6 is a flowchart showing an AF calibration image selection sequence in the camera of the embodiment. The figure which shows the relationship between the imaging screen, focus detection area, and photometry area in the camera of an Example. Explanatory drawing of the detection principle of a defocus amount. Explanatory drawing of the detection principle of a defocus amount. 6 is a flowchart illustrating a first normal imaging sequence in the camera of the embodiment. 6 is a flowchart showing a second normal imaging sequence in the camera of the embodiment.

Explanation of symbols

101b Focus lens 200 Camera 204 AF sensor 207 Photometric circuit 207a, 207b Light receiving sensor 222 EEPROM
223 system controller

Claims (4)

First focus detection means for performing focus detection based on an imaging signal obtained by photoelectrically converting a subject image by an imaging means;
Second focus detection means for performing focus detection based on a signal different from the imaging signal;
Light source detection means for detecting first information about the light source;
Generating a second information relating to focus control based upon the detection results and the first information by the second focus detection unit, before every image the focus control of the imaging optical system based on the second information Control means to perform;
Storage means for storing one of the first information and the second information,
When a focus detection operation is instructed, the first focus detection means performs focus detection during the detection of the first information by the light source detection means after the second focus detection means performs focus detection. If the difference between the in-focus position obtained by the second focus detection means and the in-focus position obtained by the first focus detection means is smaller than a predetermined value, the control means Focus control based on information,
In the focus control, if the detection operation is not completed in the first information by the light source detecting means prior imaging, wherein the control means is generated before imaging before the time times in the storage means An image pickup apparatus that performs focus control based on information stored in the camera. Wherein, when the detection operation of the by the light source detecting means prior IMAGING first information is not completed within a predetermined time, the storage means than this is generated before the imaging of the previous round the imaging apparatus according to claim 1, characterized in that the full Okasu control using the information stored in the. Before Stories second information imaging apparatus according to claim 1 or 2, characterized in that the information for correcting the detection result of the second focus detection unit. First focus detection means for performing focus detection based on an imaging signal obtained by photoelectrically converting a subject image by the imaging means, and second focus detection means for performing focus detection based on a signal different from the imaging signal And a control method of an imaging apparatus having a light source detection means for detecting first information about the light source,
Generating a second information relating to focus control based on the detection results and the first information by the second focus detection unit, before every image the focus control of the imaging optical system based on the second information Control steps to perform;
Storing one of the first information and the second information in a storage means;
When a focus detection operation is instructed, the first focus detection means performs focus detection during the detection of the first information by the light source detection means after the second focus detection means performs focus detection. If the difference between the in-focus position obtained by the second focus detection means and the in-focus position obtained by the first focus detection means is smaller than a predetermined value, Focus control based on information,
Information when the focus control, the prior imaging the first detection operation is not completed if the information in the control step, stored in the storage unit be generated before the imaging of the previous times than this control method of an imaging device and performing full Okasu control using.