JP4542126B2 - Focus detection device - Google Patents

Description

The present invention relates to an improvement of a focus detection apparatus having a plurality of focus detection areas.

  Conventionally, as an automatic focus detection device for a camera, a pair of image signals obtained by photoelectrically converting a subject image by combining light beams from a subject passing through different exit pupil regions of a photographing lens onto a pair of line sensors. 2. Description of the Related Art An automatic focus adjustment method for detecting a defocus amount of a subject by obtaining a relative position displacement amount and driving a photographing lens based on the detected defocus amount is widely known.

  Many recent single-lens reflex cameras, as shown in FIG. 2, arrange a plurality of focus detection areas in a shooting screen and automatically select a focus detection area according to various subjects and situations. When an arbitrary focus detection area is selected, the focus detection operation is performed in the selected focus detection area.

Further, due to recent improvements in semiconductor manufacturing technology, the number of focus detection areas tends to increase as shown in FIG.
Japanese Patent Laid-Open No. 5-45576

  When there are a plurality of focus detection areas, the defocus amount is obtained for each focus detection area. As a method of automatically selecting a plurality of focus detection areas so far, the defocus amounts of all focus detection areas are obtained, the detection results are compared, and it is determined that the position corresponds to the main subject position in the screen. The focus detection area most suitable for the above is determined as the final focus detection area, and the defocus amount obtained in that area is set as the defocus amount used for focus adjustment.

  However, as described above, the defocus amount is to obtain the relative position displacement amount of the pair of image signals, and this is obtained by the arithmetic processing of the MPU (microprocessing unit).

  As is well known, the focus detection operation in a plurality of focus detection areas rarely ends at the same time in all focus detection areas because the sensor accumulation time varies depending on the brightness of the subject and the direction of light rays. In general, the calculation processing of the MPU is sequential processing, and the super-multipoint automatic focus detection camera having 45 focus detection areas as shown in FIG. 3 requires a large amount of calculation to obtain all defocus amounts. It took a long time and was not practical.

  With respect to this problem, in Japanese Patent Laid-Open No. 5-45576 (Cited document 1), among the defocus amounts detected in each focus detection region, the first defocus amount obtained satisfies a predetermined standard. It is determined that the main subject is located in the focus detection area where the defocus amount is obtained, regardless of the defocus amount in the other focus detection areas. A method is disclosed that enables a rapid focus detection operation by selecting a defocus amount for focus adjustment.

  Although this concept certainly enables high-speed focus detection, even if the defocus amount of a certain focus detection area satisfies a predetermined standard during focus detection, the remaining focus detection areas are mainly used. There is always a possibility that an appropriate focus detection area is left by determining that it corresponds to the subject position. This is more conspicuous as the number of focus detection areas increases as shown in FIG.

(Object of invention)
An object of the present invention is to provide a focus detection apparatus capable of detecting focus information at high speed and accurately even in a case having a large number of focus detection areas.

In order to achieve the above object, the present invention includes a calculation unit capable of detecting a phase difference in a plurality of focus detection areas and performing a focus detection operation based on outputs obtained in the plurality of focus detection areas. In the focus detection apparatus, when the calculation unit determines that any one of the reliability of at least one focus detection area set as the first priority area among the plurality of focus detection areas exceeds a reference. From among the focus detection areas determined to exceed the reference, the focus detection area contributing to the lens control is determined, the calculation of the focus detection is terminated, and any of the reliability of the focus detection areas belonging to the first priority area If even is determined to not exceed the reference does not belong to the first priority area of the plurality of focus detection areas, focus detection regions near the first priority area as the second priority area Constant, and the second if any of the reliability of the focus detection area belonging to the priority region is determined to exceed the reference contributes focus detection to the lens control from the focus detection area determined to exceed the reference The focus detection apparatus determines the area.

According to the present invention, it is possible to provide a focus detection apparatus capable of detecting focus information at high speed and accurately even in a case having a large number of focus detection areas .

  The best mode for carrying out the present invention is as described in Examples described later.

  Hereinafter, the present invention will be described in detail based on the illustrated embodiments.

  FIG. 1 is a block diagram showing an electrical configuration of a single-lens reflex camera with an automatic focus detection apparatus according to an embodiment of the present invention.

  In FIG. 1, 1 is an MPU (microprocessing unit), 2 is a memory, and 3 is a focus detection unit for performing AF (autofocus). The MPU 1, the memory 2, and the focus detection unit 3 constitute a focus detection device.

  Reference numeral 4 denotes a lens driving unit for driving the photographing optical system based on the detection result of the focus detection unit 3, reference numeral 5 denotes an aperture driving unit, reference numeral 6 denotes a shutter driving unit, and reference numeral 7 denotes a film feeding unit. 8 shows camera settings (aperture value, shutter speed, etc.) on a liquid crystal display (not shown), or when a specific focus detection area in the screen is selected by focus detection control in ONE SHOT-AF mode. In addition, the focus detection area is a display unit for displaying red highlights by LEDs.

  9 is an AF switching switch for switching one of AF modes of ONE SHOT-AF and AI SERVO-AF, 10 is a CF switch for setting a CF (custom function) described later, 11 is a shutter speed, an aperture value, and the like. SW1 is a switch that is turned on by a first stroke operation (half press) of the release button, and SW2 is a switch that is turned on by a second stroke operation (full press) of the release button.

  Next, the main operation of the camera according to the embodiment of the present invention will be described with reference to the flowchart of FIG.

  Normally, the camera is turned on, and if the operator does not perform any operation (switch SW1 on, shutter speed, aperture value, etc.) for a certain period of time or more, the camera enters the power saving standby mode (# 001 → # 002 → # 003 → # 004), the MPU 1 is stopped. When the operator performs any operation (YES in step # 005), the MPU 1 is interrupted and various operations and settings corresponding to the operation are performed. Of the various operations and settings, the AF operation related to the present invention will be described in detail.

  If it is determined in step # 002 that the switch SW1 is turned on, the process proceeds to step # 006, and the MPU 1 selects the focus detection area automatically (MPU 1 automatically selects the focus detection point) or arbitrarily selects (as desired by the photographer). It is determined whether one focus detection area is selected from 45 points). As a result, if it is automatic selection, the process proceeds to step # 007, and a routine of “focus detection area automatic selection photographing” is executed. If it is an arbitrary selection, the process proceeds to step # 008, and a routine of “focus detection area arbitrary selection photographing” is executed. Since this “focus detection area arbitrary selection shooting” is not related to the present invention, a description thereof will be omitted.

  The “focus detection area automatic selection” routine is a routine for performing a series of operations for photographing, and will be described with reference to the flowchart of FIG.

  First, in step # 102, photometry is performed, and in the subsequent step # 103, a routine for performing “focus detection control” is executed. Details of this routine will be described later with reference to the flowcharts of FIGS. When the focus detection control routine is completed and focus detection is performed, the process proceeds to step # 104 to determine whether the ONE SHOT-AF mode or the AI SERVO-AF mode.

  Here, ONE SHOT-AF is a mode that performs focus detection and holds the lens position until the switch SW1 is turned off once the lens drive is completed. Suitable for shooting subjects. AI SERVO-AF is a mode in which focus detection control and lens driving are repeated while the switch SW1 is turned on and immediately before the switch SW2 is turned on and the release operation is started. In this case, lens driving (predictive AF) is performed in consideration of the AF time lag and the release time lag. Suitable for shooting moving subjects such as motor sports and soccer games.

  If the result of the determination is ONE SHOT-AF mode, the process proceeds to step # 105, where it is determined whether or not the subject is in focus. If not in focus, the process proceeds to step # 107, and lens driving is performed. Then, photometry, focus detection control and lens driving are repeated until in-focus (# 107 → # 102 → # 103 → # 104 → # 105 → # 107). ......)

  If it is in focus, the process proceeds to step # 106 to display the focus detection area on which the focus is detected on the focus plate, and in the next step # 110, the state of the switch SW2 is checked. And only when it is ON, it progresses to step # 111 and performs imaging | photography operation | movement. Thereafter, in step # 112, the state of the switch SW1 is checked. If it is on, the process proceeds to step # 113. Since the current mode is the ONE SHOT-AF mode, the process returns from step # 113 to step # 110. The state of the switch SW2 and the switch SW1 is checked until is turned off. Thereafter, when the switch SW1 is turned off, the routine proceeds to step # 114, where this routine is terminated and the routine returns to the main routine of FIG.

  On the other hand, if it is the AI SERVO-AF mode, the process proceeds from step # 104 to step # 108 to determine whether or not it is in focus. Only when the in-focus state is not achieved, the process proceeds to step # 109 to drive the lens.

  Subsequently, as in the ONE SHOT-AF mode, in step # 110, the state of the switch SW2 is checked. And only when it is ON, it progresses to step # 111 and performs imaging | photography operation | movement. Thereafter, in step # 112, the state of the switch SW1 is checked. If the switch SW1 is on, the process proceeds to step # 113. Since the AI SERVO-AF mode is currently set, the process returns from step # 113 to step # 102. Metering, focus detection control and lens drive are repeated until is turned off. Thereafter, when the switch SW1 is turned off, the routine proceeds to step # 114, where this routine is terminated and the routine returns to the main routine of FIG.

  Next, the “focus detection control” executed in step # 103 of FIG. 5 will be described using the flowcharts of FIGS.

  In step # 202, it is checked whether the CF switch (custom function switch that changes focus detection control according to the subject photographed by the operator) 10 is turned on. If it is turned on, the process proceeds to step # 207. The routine “focus detection control when the CF switch is on” is called back to the routine of FIG. Details of this routine will be described later with reference to the flowcharts of FIGS. In the next step # 203, it is checked whether the ONE SHOT-AF mode or the AI SERVO-AF mode. If the AI SERVO-AF mode is selected, the process proceeds to step # 206, and the routine of “focus detection control in AI SERVO-AF” is executed. Call and return to the routine of FIG. Details of this routine will be described later with reference to the flowcharts of FIGS. On the other hand, if the CF switch is off and the ONE SHOT-AF mode is selected, the process proceeds to step # 204, and the “first priority area setting” routine is called. This routine is commonly called from the routine of “focus detection control in AI SERVO-AF” in FIGS. 8 and 9 and from the routine of “focus detection control in CF switch-on” in FIGS. First, this routine will be described with reference to the flowchart of FIG.

  First, in step # 402, it is determined whether the ONE SHOT-AF mode or AI SERVO-AF mode. If the ONE SHOT-AF mode, the process proceeds to step # 403. If AI SERVO-AF mode, the process proceeds to step # 404. Determine if it is turned on. As a result, if the ONE SHOT-AF mode and the CF switch are turned off, the process proceeds from step # 403 to step # 405, where the first priority area is set in ONE SHOT-AF, and the CF switch is turned on. The process proceeds from step # 403 to step # 406, where the first priority area is set when the ONE SHOT-AF, CF switch is turned on. On the other hand, if the AI SERVO-AF mode and the CF switch are off, the process proceeds from step # 404 to step # 407. Here, the first priority area in AI SERVO-AF is set, and if the CF switch is on, The process proceeds from step # 404 to step # 408, where the first priority area is set when the AI SERVO-AF, CF switch is turned on.

  When the “first priority area setting” routine of FIG. 10 is called from step # 204 of FIG. 6, the first priority area is set in ONE SHOT-AF of step # 405 of FIG. 10 described above. become. Specifically, as shown in FIG. 12 (a), this setting is performed by using 1, 4, 7, 18, 20, 23, 26, 28, 39, A total of 11 focus detection areas 42 and 45 are set as the first priority areas.

  Returning to FIG. 6, after the first priority area is set, the process proceeds to step # 205, where 0 is substituted into the variable FLAG1 to start accumulation of the focus detection sensor, and in the next step # 208, the maximum accumulation time is checked. . If sensor accumulation does not end even after a preset time (maximum accumulation time) has elapsed, the process proceeds to step # 210 to forcibly terminate sensor accumulation and read out all image signals. In the next step # 211, the focus detection area (hereinafter referred to as this effective focus detection area) that is most suitable for evaluating the focus detection area, that is, determining that it corresponds to the main subject position from among the 45 focus detection areas. The final focus detection area (area where the defocus amount used for focus adjustment can be obtained) is searched for as a detection area). A specific method for determining the final focus detection area will be described in the evaluation of the first priority area described later. Then, the process proceeds to step # 221, where the found focus detection area is set as a final focus detection area from which a defocus amount for lens driving can be obtained.

  On the other hand, if it is determined in step # 208 that the maximum accumulation time has not elapsed, the process proceeds to step # 209 to perform sensor reading check and reading. As this operation, first, it is determined whether or not the accumulation of each sensor has been completed. If there is a sensor that has completed accumulation among the sensors, if the readout of the image signal of that sensor has not yet been completed, The image signal is read out. Then, in the next step # 212, it is determined whether or not a new image signal has been read out. If reading has not been performed, the image signal reading check and reading are repeated unless the maximum accumulation time has elapsed (# 212). → # 208 ……).

  If it is determined that a new image signal has been read, the process proceeds to step # 213 to perform the correlation calculation. After the correlation calculation is completed, the process proceeds to step # 214 in FIG. Determine if. FLAG1 is a flag variable that becomes 1 when the correlation calculation is completed in all focus detection areas of the first priority area, and 0 otherwise. If it is determined that FLAG1 is 0, the process proceeds to step # 215. Whether or not the correlation calculation has been completed in all focus detection areas of the first priority area by reading a new image signal in step # 209. Determine. If it is determined that the processing has not been completed, the image signal readout check, readout, and correlation calculation are repeated unless the maximum accumulation time has elapsed (# 215 → # 208 → # 209...).

  On the other hand, if it is determined that the process has ended, the process proceeds to step # 216, FLAG1 is set to 1, and in step # 217, the first priority area is evaluated, and an effective focus detection area is selected from the first priority areas. The final focus detection area candidate is determined.

  Specifically, as shown in the flowchart of FIG. 16, first, in step # 602, all focus detection areas of the first priority area are set as focus detection area candidates. In the next step # 604, the focus detection reliability is determined for each focus detection area of the first priority area. As shown in steps # 702 to # 707 of FIG. 17, the focus detection reliability is obtained by considering the degree of coincidence of two image signals to be paired when obtaining the contrast and the relative displacement amount, and taking these two factors into consideration. ing. Since this operation is general, further explanation is omitted.

  When the reliability of all the areas has been determined as described above, the process proceeds to step # 606, and the most effective focus detection area candidate is determined from among the focus detection areas satisfying a certain reference value. The focus detection area candidates are comprehensively obtained based on weights preset for each focus detection area in the screen, a defocus amount calculated by correlation calculation, and the like. This method for determining a focus detection area candidate is a well-known technique for which various methods have been proposed, and will not be described because it is not related to the present invention.

  Returning to FIG. 7, in step 218, it is determined whether the reliability of the selected focus detection region candidate exceeds a predetermined reference value. If it is determined that the reliability exceeds the reference value, the process proceeds to step # 221. Then, this area is set as a final focus detection area for obtaining a defocus amount for lens driving.

  If the reference value is not exceeded, there is a possibility that a more effective focus detection area may exist in the focus detection area shown in FIG. 12B other than the first priority area, so go to step # 208 in FIG. Return and investigate the remaining focus detection area.

  Specifically, since FLAG1 is set to 1 in step # 216, the process proceeds to step # 219 in step # 214, and image signal readout check and readout and correlation calculation are performed unless the maximum accumulation time has elapsed. repeat. If it is determined in step # 219 that all the remaining focus detection correlation operations have been completed, the process proceeds to step # 220, and the remaining focus detection areas are evaluated. Here, the focus detection area with the highest evaluation is selected from the evaluation of the first priority area and the evaluation of the other focus detection areas. After the selection is completed, the process proceeds to step # 221, where the selected area is set as a final focus detection area for obtaining a defocus amount used for lens driving.

  In the above ONE SHOT-AF, the 45-point focus detection area in the screen is divided into two groups as shown in FIGS. 12A and 12B, and one of the divided groups (FIG. 12A). 11 points) is set as the first priority area, and the calculation in this group and its reliability evaluation are performed. If the evaluation result satisfies a predetermined determination value, the calculation is terminated in the group at that time. Yes. In other words, no calculation or evaluation is performed on other groups (the group in FIG. 12B).

  In the above configuration, the movement of the subject is not taken into account. In ONE SHOT-AF, focus detection is not necessarily performed in all focus detection areas, so high-speed and accurate focus detection can be performed particularly on subjects such as landscapes. It becomes possible to do.

  Next, the routine of “focus detection control in AI SERVO-AF” executed in step # 206 of FIG. 6 will be described using the flowcharts of FIGS. The basic flow of the processing is almost the same as the focus detection control in FIGS. 6 and 7 and the “focus detection control in CF switch-on” in FIGS. 18 and 19 described later.

  First, in step # 302, the "first priority area setting" routine of FIG. 10 is called. As described above, this routine is also commonly called from the “focus detection control” in FIG. 6 and the “focus detection control in CF switch-on” in FIGS. 18 and 19 to be described later. In step # 407 of FIG. 10, the first priority area is set in AI SERVO-AF.

  Specifically, as shown in FIG. 14A, this setting uses only 23 focus detection areas indicated by a black frame at the center of the 45 focus detection areas as the first priority areas. However, this is the initial state, and as described above, AI SERVO-AF is a shooting mode that follows lens movement following the movement of the subject, and when the subject moves and the focus detection area moves while repeating focus detection, The focus detection area is set as the first priority area.

  Returning to FIG. 8, after the first priority area is set, the process proceeds to step # 303, where 0 is substituted into variables FLAG1 and FLAG2, and accumulation of the focus detection sensor is started.

  When the process proceeds to step # 304 due to the start of accumulation, the maximum accumulation time is checked here. If the sensor accumulation does not end even after a preset time (maximum accumulation time) has elapsed, the process proceeds to step # 308 to forcibly terminate the sensor accumulation and read out all image signals. In the next step # 309, the focus detection area is evaluated, that is, the most effective focus detection area is selected from the read focus detection areas. Then, the process proceeds to step # 324, where the area selected here is set as a final focus detection area for obtaining a defocus amount used for lens driving.

  On the other hand, if it is determined in step # 304 that the maximum accumulation time has not elapsed, the process proceeds to step # 305 to perform sensor reading check and reading. As this operation, it is first determined whether or not the accumulation of each sensor has been completed. If there is a sensor for which accumulation has been completed among the sensors, the reading of the image signal of that sensor has not yet been completed. The image signal is read out. In step # 306, it is determined whether or not a new image signal has been read out. If reading has not been performed, the image signal reading check and reading are repeated unless the maximum accumulation time has elapsed (# 306 → #). 304 → # 305 → # 306...

  If it is determined that a new image signal has been read, the process proceeds to step # 307, the correlation calculation is performed, and after the correlation calculation is completed, the process proceeds to step # 310. Here, it is determined whether FLAG2 is 0 or not. To do. FLAG2 is a flag variable that is 1 when the correlation calculation is completed in all focus detection areas of the second priority area described later, and 0 otherwise. If FLAG2 is determined to be 0, the process proceeds to step # 311 of FIG. 9; if it is determined to be 1, the process proceeds to step # 317.

  When the process proceeds to step # 311 in FIG. 9, it is determined whether or not FLAG1 is zero. As described above, FLAG1 is a flag variable that is 1 when the correlation calculation is completed in all focus detection areas of the first priority area, and is 0 otherwise. If it is determined that FLAG1 is 0, the process proceeds to step # 312, and by reading a new image signal in step # 305, it is determined whether the correlation calculation has been completed in all focus detection areas of the first priority area. To do. If it is determined that the processing has not been completed, the image signal readout check, readout, and correlation calculation are repeated unless the maximum accumulation time has elapsed (# 312 → # 304 → # 305...).

  On the other hand, if it is determined that the processing has ended, the process proceeds to step # 313, FLAG1 is set to 1, and in the next step # 314, the above-described first priority area is evaluated, and the most promising among the first priority areas. The focus detection area is determined as a final focus detection area candidate.

  In step # 319, it is determined whether or not the reliability of the determined focus detection area candidate exceeds a predetermined reference value. If it is determined that the reliability exceeds the reference value, the process proceeds to step # 324 in FIG. This area is set as a final focus detection area for obtaining a defocus amount for lens driving.

  If the reference value is not exceeded, there is a possibility that a more effective focus detection area exists in the second priority area shown in FIG. 14B other than the first priority area. FLAG2 is set to 1, and in the next step # 321, a "second priority area setting" routine is executed. Since this routine is commonly called from the routine of “focus detection control when the CF switch is turned on” in FIGS. 18 and 19, this routine will be described with reference to the flowchart of FIG.

  First, in step # 502, it is determined whether the ONE SHOT-AF mode or the AI SERVO-AF mode. If the ONE SHOT-AF mode, the process proceeds to step # 503, and the second priority area is set when the ONE SHOT-AF, CF switch is turned on. I do. If the AI SERVO-AF mode is selected, the process proceeds to step # 504 to determine whether the CF switch is turned on. As a result, if the CF switch is turned off in AI SERVO-AF mode, the process proceeds to step # 505 to set the second priority area in AI SERVO-AF. If the CF switch is turned on in AI SERVO-AF, step # 505 is executed. Proceed to 506 to set the second priority area when the AI SERVO-AF, CF switch is turned on.

  Returning to FIG. 9, when the "second priority area setting" routine is called from step # 321, the second priority area is set in the AI SERVO-AF mode in step # 505 of FIG. 11 described above. become. Specifically, in the case where the 23 focus detection areas in FIG. 14A are set as the first priority areas, as shown in FIG. 14B, 12, 13 and 13 around the 23 focus detection areas are set. , 22, 24, 33 and 34 are set as the second priority areas.

  As described above, when FLAG2 is set to 1 in step # 320 and the second priority area is set in step # 321, the process proceeds to step # 317 in step # 310 of FIG. 8, and the maximum accumulation time has elapsed. Unless otherwise, image signal readout check, readout, and correlation calculation are repeated (# 321 → # 304 → # 305 → # 306 → # 307 → # 310 → # 317...). If it is determined in step # 317 that the correlation calculation has been completed in all focus detection areas of the second priority area, the process proceeds to step # 318, where the second priority area is evaluated, and the second priority area is most effective. A focus detection area candidate is selected. In the next step # 322, it is determined whether or not the reliability of the determined focus detection area candidate exceeds a predetermined reference value. If it is determined that the reliability exceeds the reference value, the process proceeds to step 324 to select This area is set as a final focus detection area for obtaining a defocus amount to be used for lens driving.

  If the reference value is not exceeded, the process proceeds to step # 323, FLAG2 is returned to 0 (FLAG1 is 1 at this time), and the focus detection area other than the first priority area and the second priority area (FIG. 14C). ), There is a possibility that a more effective focus detection area exists, so the process returns to step # 304 in FIG. 8 to investigate the remaining focus detection areas.

  Specifically, when FLAG2 is set to 0 and FLAG1 is set to 1, the process proceeds to step # 311 in step # 310, and to step # 315 in step # 311. As long as the maximum accumulation time does not elapse, the image signal The reading check, reading, and correlation calculation are repeated (# 323 → # 304 → # 305 → # 306 → # 307 → # 310 → # 311 → # 315...). If it is determined in step # 315 that all the remaining focus detection correlation calculations have been completed, the process proceeds to step # 316, where the remaining focus detection areas are evaluated. Here, the focus detection area with the highest evaluation is selected from the first priority area, the second priority area, and the other focus detection areas. After the selection is completed, the process proceeds to step # 324 in FIG. 8, and the selected area is set as a final focus detection area for obtaining a defocus amount to be used for lens driving.

  In the above AI SERVO-AF, the 45 focus detection areas in the screen are used as the final focus detection area selected in the past (usually the final defocus amount used for the previous lens drive is obtained). Is divided into a first priority area of the group shown in FIG. 14 (a) and a second priority area of the group shown in FIG. 14 (b) according to the focus detection area). (Groups will change dynamically according to the final focus detection area selected in the past), and priorities of calculation processing are set for these groups, and calculation and evaluation of each group are performed according to these priorities. If the evaluation result of each group satisfies a predetermined determination value, the calculation is finished at that time.

  In the above configuration, in AI SERVO-AF considering the movement of the subject, when the photographer follows the moving subject on the screen, pay attention to the fact that the focus detection area selected once is easily selected again. In the focus detection area, the evaluation is performed by dividing the focus detection area once selected into a plurality of groups, and the focus detection is not necessarily performed in all focus detection areas. Because the focus detection results satisfying the photographer can be obtained, it is accurate even for moving subjects such as motor sports, especially when faster focus detection is required depending on the shooting conditions. Focus detection can be performed.

  Next, the routine of “focus detection control when the CF switch is turned on” executed in step # 207 of FIG. 6 will be described with reference to the flowcharts of FIGS.

  First, in step # 802, the “first priority area setting” routine of FIG. 10 is called. As described above, this routine is also commonly called from the focus detection control routine of FIG. 6, but when this routine is called from step # 802, in FIG. 10, the CF switch is on and the ONE SHOT-AF mode is selected. In step # 406, the first priority area is set when the ONE SHOT-AF, CF switch is ON. When the CF switch is ON and the AI SERVO-AF mode is set, the AI SERVO-AF, The first priority area is set when the CF switch is turned on.

  Specifically, in this setting, in the setting of the first priority area when the ONE SHOT-AF, CF switch is turned on in step # 406, as shown in FIG. A total of seven focus detection areas 4, 18, 20, 23, 26, 28, and 42 shown in FIG.

  Further, in the setting of the first priority area in the AI SERVO-AF, CF switch on in step # 408, in addition to the setting of the first priority area described above, the combination of the final focus detection area selected in the past is set. Do. As described above, AI SERVO-AF is a shooting mode in which the lens drive follows the movement of the subject. For example, the subject moves while the focus detection is repeated, and the main focus detection area is focused on 6 in FIG. If the detection point is moved, the focus detection areas of 4, 18, 20, 23, 26, 28 and 42 are set as the first priority areas in addition to the focus detection area.

  Returning to FIG. 18, after setting the first priority area in accordance with each photographing mode, the process proceeds to step # 803, 0 is substituted into variables FLAG 1 and FLAG 2, and accumulation of the focus detection sensor is started.

  When the process proceeds to step # 804 due to the start of accumulation, the maximum accumulation time is checked here. If sensor accumulation does not end even after a preset time (maximum accumulation time) has elapsed, the process proceeds to step # 808 to forcibly terminate sensor accumulation and read out all image signals. In the next step # 809, the focus detection area is evaluated, that is, the most effective focus detection area is selected from the read focus detection areas. Then, the process proceeds to step # 824, where the area selected here is set as a final focus detection area for obtaining a defocus amount for lens driving.

  On the other hand, if it is determined in step # 804 that the maximum accumulation time has not elapsed, the process proceeds to step # 805 to perform sensor reading check and reading. As this operation, it is first determined whether or not the accumulation of each sensor has been completed. If there is a sensor for which accumulation has been completed among the sensors, the reading of the image signal of that sensor has not yet been completed. The image signal is read out. In step # 806, it is determined whether or not a new image signal has been read out. If reading has not been performed, the image signal reading check and reading are repeated as long as the maximum accumulation time has not elapsed (# 806 → #). 804 → # 805 → # 806 ...).

  If it is determined that a new image signal has been read, the process proceeds to step # 807, where the correlation calculation is performed. After the correlation calculation, the process proceeds to step # 810, where it is determined whether FLAG2 is 0 or not. To do. FLAG2 is a flag variable that is 1 when the correlation calculation is completed in all focus detection areas of the second priority area described later, and 0 otherwise. If FLAG2 is determined to be 0, the process proceeds to step # 811 in FIG. 19; if it is determined to be 1, the process proceeds to step # 817.

  When the process proceeds to step # 811 in FIG. 19, it is determined whether or not FLAG1 is zero. As described above, FLAG1 is a flag variable that is 1 when the correlation calculation is completed in all focus detection areas of the first priority area, and is 0 otherwise. If it is determined that FLAG1 is 0, the process proceeds to step # 812, and it is determined whether or not the correlation calculation has been completed in all focus detection areas of the first priority area by reading a new image signal in step # 805. To do. If it is determined that the processing has not ended, the image signal readout check and readout and the correlation calculation are repeated unless the maximum accumulation time has elapsed (# 821 → # 804 → # 805...).

  On the other hand, if it is determined that the process has been completed, the process proceeds to step # 813, FLAG1 is set to 1, and in the next step # 814, the above-described first priority area is evaluated. Then, the most promising focus detection area candidate is determined from the first priority areas. In the next step # 819, it is determined whether or not the reliability of the determined focus detection area candidate exceeds a predetermined reference value. If it is determined that the reliability exceeds the reference value, the process proceeds to step # 820, and FLAG2 is set to 1. In the next step # 821, a "second priority area setting" routine is executed. As described above, this routine is commonly called from the routine of “focus detection control in AI SERVO-AF” in FIG. 8, but when this routine is called from step # 821, in FIG. 11, the CF switch is turned on and the ONE SHOT is turned on. -In AF mode, in step # 503, the second priority area is set when ONE SHOT-AF, CF switch is ON. In CF #ON and AI SERVO-AF mode, AI SERVO is set in step # 506. -Set the second priority area when the AF and CF switches are on.

  Specifically, in the setting of the second priority area when the ONE SHOT-AF, CF switch is turned on in step # 503, for example, 26 focus detections are performed out of the seven focus detection areas in FIG. When it is determined that the area is promising, a total of eight focus detection areas, ie, 7, 15, 16, 25, 27, 36, 37, and 45 around the 26 focus detection areas are set as the second as shown in FIG. It is set as a priority area.

  Further, in the setting of the second priority area in the AI SERVO-AF, CF switch on in step # 506, when it is determined that 6 focus detection areas are promising among the 8 focus detection areas in FIG. As shown in FIG. 15B, a total of four focus detection areas 5, 7, 14, and 15 around the six focus detection areas are set as the second priority areas.

  Returning to FIG. 19, in step # 819, if the reliability of the focus detection area candidate determined in step # 814 does not exceed a predetermined reference value, promising focus detection in the first priority area. Although there is no area, there is a possibility that an effective focus detection area may exist depending on other focus detection areas. Therefore, the process returns to step # 804 in FIG. 18 to investigate the remaining focus detection areas.

  Specifically, since FLAG1 is set to 1 in step # 813 of FIG. 19, the process proceeds to step # 815 in step # 811, and the image signal readout check and readout are performed unless the maximum accumulation time has elapsed. Repeat the correlation operation. If it is determined in step # 815 that all correlation calculations for the remaining focus detections have been completed, the process proceeds to step # 816 to evaluate the remaining focus detection areas. Here, the focus detection area with the highest evaluation is selected from all the focus detection areas. After the selection is completed, the process proceeds to step # 824 in FIG. 18, and the selected area is set as a final focus detection area for obtaining a defocus amount to be used for lens driving.

  On the other hand, when FLAG2 is set to 1 in step # 820 of FIG. 19 and the second priority area is set in step # 821, the process proceeds to step # 817 in step # 810 of FIG. As long as the time has not elapsed, the image signal readout check and readout and the correlation calculation are repeated. If it is determined in step # 817 that the correlation calculation has been completed in all the focus detection areas of the second priority area, the process proceeds to step # 818, where the second priority area is evaluated, and the second priority area is most effective. A focus detection area is determined as a focus detection area candidate. Then, in the next step # 822, it is determined whether or not the reliability of the determined focus detection area candidate exceeds a predetermined reference value. If it is determined that the reliability exceeds the reference value, the process proceeds to step # 824. The selected area is set as a final focus detection area for obtaining a defocus amount to be used for lens driving.

If the reference value is not exceeded, the process proceeds to step # 823, FLAG2 is returned to 0 (FLAG1 is 1 at this time), and the focus detection area other than the first priority area and the second priority area (FIG. 13C). , FIG. 15 (c)), there is a possibility that a more effective focus detection area exists, so the process returns to step # 804 in FIG. 8 to investigate the remaining focus detection areas.

  In the above ONE SHOT-AF, CF switch-on, the 45-point focus detection area in the screen is first set to the group shown in FIG. 13 (a) as the first priority area. The reliability is evaluated, and the results are further grouped into a plurality of focus detection areas including a focus detection area belonging to the first priority area group according to the evaluation result of the first priority area (see FIG. 13B). The calculation and its reliability evaluation are carried out, and if the evaluation result satisfies a predetermined judgment value, the calculation is finished in the group at that time.

  In the above configuration, in ONE SHOT-AF that does not consider the movement of the subject, when it is determined that a specific focus detection area is promising as the final focus detection area, it is not always necessary to evaluate the focus detection area in the vicinity thereof. We are focusing on the fact that the focus detection results that satisfy the photographer can be obtained by the evaluation results in the middle without performing focus detection in all focus detection areas. When more delicate focus detection is required, high-speed and more accurate focus detection can be performed.

  In addition, when the AI SERVO-AF and CF switches are turned on, the 45 focus detection areas in the screen are changed to the final focus detection areas selected in the past (usually the final defocus amount obtained for the previous lens drive). The group shown in FIG. 15A is dynamically divided into first priority areas (because during AI SERVO-AF) according to the focus detection area), and this group is processed in the first calculation order. According to this ranking, calculation and evaluation are performed. Depending on the evaluation result of the first priority area, the second priority area of the group shown in FIG. 15B is dynamically set, and a predetermined determination is made in this group. If the value is satisfied, the calculation is finished at that time.

  In the above configuration, in AI SERVO-AF considering the movement of the subject, not only the focus detection area once selected, but also the evaluation by dividing the focus detection area in the screen into multiple areas is performed at the same time. If it is determined that the focus detection area is promising as the final focus detection area, the focus detection area in the vicinity thereof is evaluated, and the focus detection is not necessarily performed in all focus detection areas, and the evaluation result during the evaluation is used. Since the calculation is completed at the time, so that the photographer's satisfactory focus detection result is obtained, the moving subject, especially in the soccer game where the main subject of the photographer changes frequently and the subject is moving frequently. Even in such shooting, high-speed and accurate focus detection can be performed.

(Modification)
In the above embodiment, for example, in FIG. 13, when there is a satisfied area in the first priority area, the second priority area centered on the area is newly grouped, and an appropriate area is included in this group. However, the present invention is not limited to this, and is not limited to this. Further, the third priority area centered on the optimum area in this group, and further the first The four priority areas may be newly grouped, and the calculation may be terminated when there is an appropriate area in these groups.

  Further, in the example of FIG. 14, if the first priority area is satisfied, the calculation is terminated at that time, but if this is satisfied, the surrounding area is further calculated and evaluated. (The state of FIG. 14B) If there is a satisfactory region in this, it is possible to make an embodiment in which the calculation is terminated at this point. The six regions are effective cameras for the subject that is the optimal focus detection target region.

  In this embodiment, a single-lens reflex camera has been described, but the present invention can also be applied to other optical devices such as a video camera and an electronic still camera.

  Although the focus detection device is taken as an example, it goes without saying that the present invention can also be applied to a distance measurement device having a plurality of distance measurement regions used for measuring the distance to the subject.

It is a block diagram which shows the electrical constitution of the single-lens reflex camera with an automatic focus detection function which concerns on the Example of this invention. It is a figure which shows the focus detection area | region set in the finder of the conventional camera. It is a figure which shows the focus detection area | region set in the finder of the camera which concerns on the Example of this invention. It is a flowchart which shows the main operation | movement of the camera which concerns on the Example of this invention. FIG. 5 is a flowchart illustrating an operation of focus detection area automatic selection shooting performed in step # 007 of FIG. 4. FIG. It is a flowchart which shows a part of operation | movement of the focus detection control performed by step # 103 of FIG. 7 is a flowchart showing a continuation of the operation of FIG. 6. It is a flowchart which shows a part of operation | movement of the focus detection control performed by step # 206 of FIG. FIG. 9 is a flowchart showing a continuation of the operation of FIG. 8. FIG. FIG. 9 is a flowchart showing a first priority area setting operation executed in step # 204 of FIG. 6 and step # 302 of FIG. It is a flowchart which shows the operation | movement of the setting of the 2nd priority area | region performed by step # 321 of FIG. It is a figure which shows the state which grouped 45 focus detection area | regions into multiple in the camera which concerns on the Example of this invention. It is a figure which shows the state which grouped the focus detection area | region in ONE SHOT-AF, CF switch-on of 45 focus detection areas into multiple in the camera which concerns on the Example of this invention. It is a figure which shows the state which grouped the focus detection area | region in AI SERVO-AF of 45 focus detection areas into multiple in the camera which concerns on the Example of this invention. It is a figure which shows the state which grouped the focus detection area | region in AI SERVO-AF, CF switch-on of 45 focus detection areas into multiple in the camera which concerns on the Example of this invention. FIG. 10 is a flowchart showing the first priority area evaluation operation executed in step # 216 of FIG. 7 and step # 314 of FIG. 9; 17 is a flowchart showing an operation of focus detection reliability determination executed in step # 604 of FIG. It is a flowchart which shows a part of operation | movement of the focus detection control performed by step # 207 of FIG. It is a flowchart which shows the continuation of the operation | movement of FIG.

Explanation of symbols

1 MPU
2 Memory 3 Focus detection unit 4 Lens drive unit 9 AF switch 10 CF switch

Claims (2)

In the focus detection apparatus having a calculation unit that can detect a phase difference in a plurality of focus detection areas and performs a focus detection operation based on an output obtained in the plurality of focus detection areas.
The computing means is
If it is determined that any of the reliability of at least one focus detection area set as the first priority area among the plurality of focus detection areas exceeds the reference, the focus determined to exceed the reference Decide the focus detection area that contributes to lens control from the detection area and finish the focus detection calculation,
Wherein when the first none of the reliability of the focus detection area belonging to the priority region is determined to not exceed the reference does not belong to the first priority area of the plurality of focus detection areas, the first The focus detection area around the one priority area is set as the second priority area, and if any of the reliability of the focus detection area belonging to the second priority area is determined to exceed the reference, it is determined that the reference is exceeded. focus detection device and determines the focus detection area which contributes to the lens control from the focus detection area. When the calculation means determines that none of the reliability of the focus detection area belonging to the second priority area exceeds the reference, the first priority area of the plurality of focus detection areas , The focus detection area having the highest evaluation among the second priority area and the focus detection areas other than the first priority area and the second priority area is determined as a focus detection area contributing to lens control. Item 4. The focus detection apparatus according to Item 1.

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