JP3704256B2 - Multi-point automatic focus detection device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multipoint automatic focus detection apparatus for a camera that performs focus detection processing by emitting auxiliary light when a subject has low brightness or the like.
[0002]
[Prior art and its problems]
A so-called phase difference type autofocus detection (AF) device, which is one of the autofocus (AF) devices of a camera, cannot perform normal focus detection when the subject brightness is low or the subject has no contrast. Therefore, a contrast pattern is projected onto a subject from an AF auxiliary light source built in the camera body, and a contrast is generated in the subject image received by the AF sensor, and focus detection is performed based on the subject image. It is costly to provide an auxiliary light source for use separately from the flash device for photographing, and there are some which emit light intermittently using the flash device as an auxiliary light source as disclosed in Japanese Patent Laid-Open No. 5-34577.
However, in a multipoint autofocus device having a plurality of distance measuring areas, it is also possible that a bright distance measuring area and a dark distance measuring area are mixed. For example, if focus detection is possible for all areas, focus detection processing is performed without emitting auxiliary light if focus detection is possible even if the focus detection area where the main subject exists is dark. The focus detection accuracy of the main subject is reduced because the brightness of the distance measurement area is low. On the other hand, if the distance measurement area where the main subject is located is bright, the focus detection of the main subject is possible and the detection accuracy is high without emitting the auxiliary light, but the auxiliary light is used when the brightness of the other distance measurement areas is low. Since the focus detection process is performed by emitting light, the battery is wasted.
[0003]
OBJECT OF THE INVENTION
The present invention has been made in view of the problems of the conventional multipoint autofocus device, and has a low power consumption that performs focus detection processing by controlling the emission of auxiliary light in accordance with the subject luminance in the selected distance measuring area. An object is to provide a point automatic focus detection device.
[0004]
SUMMARY OF THE INVENTION
According to the present invention for achieving this object, light emitting means for emitting auxiliary light toward a subject and images of subjects in a plurality of distance measuring areas corresponding to different positions in a photographing screen are formed, and the subject images are charged. A light receiving means for integrating the light receiving means, a focus detecting means for detecting a focus state with respect to a subject in each distance measuring area based on an integrated value of each light receiving means, and a focus detection process for the focus detecting means without causing the light emitting means to emit light. When the focus detection is possible in any of the ranging areas, one area is selected from the ranging areas in which the focus detection was possible, and the light reception corresponding to the selected ranging area is performed. And a focus detection control unit that causes the light emitting unit to emit light and re-execute the focus detection processing by the focus detection unit when the integration time of the unit is longer than a predetermined time.
According to the present invention, the integration time of the light receiving unit corresponding to the selected ranging area is longer than a predetermined time, and the photographing distance at the time of the focus detection processing can be effectively detected by the light emitted from the light emitting unit. When it falls within the range, the light emitting means can be caused to emit light via the focus detection control means, and the focus detection means can be re-executed, and the light reception corresponding to the selected distance measurement area can be achieved. When the integration time of the means is shorter than the predetermined time, even if there are other ranging areas whose integration time is longer than the predetermined time, the focus detection processing means performs the focus detection processing by the focus detection means via the focus detection control means. It can be configured to prohibit the light emission of the light emitting means.
Furthermore, the present invention allows the focus detection unit to execute focus detection processing without causing the light emitting unit to emit light, and when focus detection is impossible in all the distance measurement areas, When the integration time of the light receiving means is longer than a predetermined time, the light emitting means can emit light via the focus detection control means, and the focus detection means can be re-executed.
According to said structure, according to the photographic subject brightness | luminance of the selected ranging area, the light emission of the said light emission means can be controlled, and consumption of a battery can be reduced.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main configuration of an automatic focus (AF) single-lens reflex camera to which the present invention is applied. This AF single-lens reflex camera includes a camera body 11 and an AF-compatible photographic lens 51 that can be attached to and detached from the camera body 11.
[0006]
Most of the subject luminous flux that has entered the camera body 11 from the photographic lens 51 is reflected by the main mirror 13 toward the pentaprism 17 constituting the finder optical system, is reflected by the pentaprism 17 and exits from the eyepiece. Part of the subject light beam emitted from the pentaprism 17 is incident on the light receiving element of the photometry IC 18. On the other hand, a part of the light beam incident on the half mirror portion 14 of the main mirror 13 is transmitted therethrough, reflected downward by the sub mirror 15, and incident on the multi-focus detection unit 21.
[0007]
The photometry IC 18 inputs an electrical signal photoelectrically converted according to the amount of received light as a photometry signal to the main CPU 35 via the peripheral control circuit 23. The main CPU 35 performs a predetermined exposure calculation based on the photometric signal, film sensitivity information, and the like, and calculates an appropriate shutter speed and aperture value for exposure. Based on these shutter speed and aperture value, the exposure mechanism and aperture mechanism 25 are driven to expose the film. Further, the peripheral control circuit 23 drives the mirror motor 31 through the motor drive circuit 27 to perform the up / down process of the main mirror 13 during the photographing process, and drives the film winding motor 33 after the exposure is completed. To wind up the film by one frame.
[0008]
The multi-focus detection unit 21 is a so-called phase difference type distance measuring sensor, a splitting optical system that divides a subject light beam forming a subject image included in a plurality of distance measuring areas in a photographing screen (not shown), A CCD line sensor 211 is provided as a light receiving means for receiving and integrating each of the subject light beams divided into two, and a monitor sensor 213 for checking the integrated value of the sensor. The integrated signal charge is converted into a voltage for each pixel, amplified by the amplifier 215, and output to the main CPU 35 as a video signal for each pixel. The main CPU 35 ends the integration of the CCD line sensor 211 when the integration value of the monitor sensor 213 reaches the integration end value.
[0009]
The main CPU 35 calculates the defocus amount by a predetermined calculation based on the video signal corresponding to each ranging area input from the multi-focus detection unit 21. Next, based on the defocus amount, the rotation direction and the number of rotations of the AF motor 39 (number of pulses output by the encoder 41) are calculated. The main CPU 35 drives the AF motor 39 via the AF motor driver 37 based on the rotation direction and the number of pulses. During this driving, the main CPU 35 detects and counts the pulses output from the encoder 41 in conjunction with the rotation of the AF motor 39, and stops the AF motor 39 when the count value reaches the number of pulses.
[0010]
The AF motor 39 transmits the rotation to the photographing lens 51 side through a connection between a joint 47 provided on the mount portion of the camera body 11 and a joint 57 provided on the mount portion of the photographing lens 51. Then, the focus adjustment lens 53 is moved forward and backward through the gear block 55.
[0011]
Further, the main CPU 35 is input from a ROM 35a storing a control program, a RAM 35b temporarily storing predetermined data for calculation and control, a reference timer 35c for timing, a hard counter 35d, and the multi-focus detection unit 21. An A / D converter 35e for A / D converting the video signal is built in, and an EEPROM 43 as external memory means is connected. In the EEPROM 43, various constants unique to the camera body 11 are stored.
[0012]
The camera body 11 has a built-in flash device 71 that can be controlled by the main CPU 35 via the peripheral control circuit 23. Although the details of the built-in flash device 71 are not shown, the light emitting unit is mounted on the upper part of the pentaprism 17 and moves to the pop-up position and the storage position, and the light emitting unit is equipped with a xenon tube. The built-in flash device 71 is a flash used as normal photographing auxiliary illumination. However, when focus detection cannot be performed because the subject has low brightness or low contrast, an auxiliary light source for focus detection is obtained by intermittent light emission. Used as
[0013]
The built-in flash device 71 emits flash light when an FT signal (trigger signal) is input from the main CPU 35 via the peripheral control circuit 23, and performs charging when a charge signal (charge start signal) is input. The charging voltage is detected and a RIF signal (charging voltage detection signal) is output to the main CPU 35 via the peripheral control circuit 23.
[0014]
Further, the main CPU 35 includes a pop-up detection switch SWP that detects that the built-in flash device 71 is popping up, a photometric switch SWS that is turned on when the release button (not shown) is half-pressed, and a release switch SWR that is turned on when the built-in flash device is fully pushed An automatic focus switch SWAF for switching between focus control and manual focus control, and a main switch SWM for turning on / off the power to the peripheral control circuit 23 and the like are connected. The main CPU 35 displays the set AF, exposure, shooting mode, shutter speed, aperture value, and the like on the display 45. The display unit 45 usually includes displays provided at two locations within the outer surface of the camera body 11 and the viewfinder field of view.
[0015]
The main CPU 35 functions as a control unit that comprehensively controls the camera body 11 and the photographing lens 51, and constitutes a communication unit with the lens CPU 61 and the like, and constitutes a focus detection unit with the multi-focus detection unit 21. The multi-focus detection unit 21, the built-in flash device 71, the peripheral control circuit 23, and the like constitute a focus detection control means.
[0016]
On the other hand, the photographing lens 51 is provided with a gear block 55 for driving the focus adjustment lens 53 in the optical axis direction and a mount portion of the photographing lens 51, and is connected to the joint 47 of the camera body 11 to rotate the AF motor 39. Is provided with a lens-side joint 57, a lens CPU 61, and a distance switch 63.
[0017]
The lens CPU 61 changes the position of the focus adjustment lens 53 from the state of the distance switch 63 to the distance code D._VDetect as' and get distance information. The lens CPU 61 is connected to the peripheral portion control circuit 23 of the camera body 11 through the connection of the electrical contact groups 59 and 49, and the lens position between the lens CPU 61 and the main CPU 35 through the peripheral portion control circuit 23. Predetermined data communication such as distance information, focal length information, aperture information, and the like is performed.
[0018]
With reference to FIG. 2, the configuration of the multi-focus detection unit 21 including the CCD line sensor 211 in the present embodiment will be described in more detail.
[0019]
The multi-focus detection unit 21 includes a CCD line sensor 211 as a light receiving means for integrating the received subject light as electric charges, a monitor sensor 213 for monitoring the integrated value of the CCD line sensor 211, and an integrated value of the CCD line sensor 211 after completion of integration. An amplifier 215 that amplifies with a predetermined gain and outputs the amplified signal to the main CPU 35 is provided. The CCD line sensor 211 includes three sensors 211A, 211B, and 211C arranged in a straight line. The sensors 211A, 211B, and 211C are not shown in detail, but are photodiodes that photoelectrically convert the received subject light. A photoelectric conversion element array, an integration unit that independently integrates the signal charge converted by each photoelectric conversion element for each photoelectric conversion element, and a charge holding that transfers and temporarily holds the charge integrated by the integration unit Department. The charges held in each charge holding unit are transferred to the CCD transfer unit 212 and output in order from the CCD transfer unit 212. The monitor sensors 213A, 213B, and 213C are arranged in parallel with the sensors 211A, 211B, and 211C, and detect the integrated values of the sensors 211A, 211B, and 211C.
[0020]
When the main CPU 35 outputs an integration start signal, each of the sensors 211A, 211B, and 211C integrates charges obtained by photoelectric conversion of the subject light received by the photoelectric conversion element by the integration unit, and the integration value is integrated into each of the monitor sensors 213A and 213B. 213C monitors. When the integration values of the monitor sensors 213A, 213B, and 213C reach a predetermined integration end value (VAGC), the charges that the sensors 211A, 211B, and 211C corresponding to the monitor sensors 213A, 213B, and 213C have integrated in the integration unit are obtained. At the same time, the integration is completed by transferring the data to the charge holding unit, and the monitor sensors 213A, 213B, and 213C are cleared.
The main CPU 35 determines the time from when the integration start signal is output until the integrated value of each of the monitor sensors 213A, 213B, and 213C reaches a predetermined integration end value, or the time until the sensors 211A, 211B, and 211C end the integration. Measure and write to internal RAM 35b.
When integration of all the sensors 211A, 211B, and 211C is completed, or when a preset maximum integration time has elapsed, whichever is earlier, the CPU 35 outputs an integration completion signal. Then, the charges held in the charge holding units are transferred to the CCD transfer unit 212 all at once, and are sequentially converted from the CCD transfer unit 212 to a voltage when output from the CCD transfer unit 212. The output voltage signal is the main CPU 35. Is amplified by the amplifier 215 based on the gain signal (GAIN) output from the video signal and taken into the main CPU 35 as a video signal in pixel units. The captured video signal is converted into a digital signal by the A / D converter 35e and stored in the RAM 35b, and the main CPU 35 executes a defocus calculation based on the stored signal.
The sensors 211A, 211B, and 211C that have not finished integration when the integration end signal is output transfer the charges integrated by the integration unit to the charge holding unit and forcibly end the integration.
[0021]
When performing normal integration processing, the process waits until the integration of all the sensors 211A to 211C is completed, but when the integration of all the sensors 211A to 211C is not completed within the preset maximum integration time, that is, If the integration value of any of the monitor sensors 213A, 213B, and 213C does not reach the integration end value within the preset maximum integration time, an integration end signal is output when the maximum integration time has elapsed, and the integration ends. Let The sensors 211A, 211B, and 211C that have not finished integration transfer the charges integrated by the integration unit to the charge holding unit in response to the integration end signal, end the integration, and clear the corresponding monitor sensors 213A, 213B, and 213C.
[0022]
When performing integration processing by emitting flash light as auxiliary light, the integration processing is performed by repeatedly emitting auxiliary light until the integration values of all the monitor sensors 213A to 213C reach the integration end value. When the auxiliary light emission count reaches the preset maximum light emission count, the CPU 35 outputs an integration end signal even if any of the integral values of the monitor sensors 213A to 213C has not reached the integration end value. All the sensors 211A to 211C are forcibly terminated to clear the corresponding monitor sensors 213A to 213C.
[0023]
Next, main operations of the single-lens reflex camera to which the present invention is applied will be described with reference to FIGS. FIG. 3 is a flowchart regarding the main process of the single-lens reflex camera. In this main processing, the system waits for the photometric switch SWS to be turned on. When the photometric switch SWS is turned on, the photometry and exposure calculation processing (AE calculation processing) is executed to obtain the optimum aperture value and shutter speed, and the focus detection processing and A lens driving process (AF process) is executed for focusing, and when the release switch SWR is turned on, an exposure process is executed with the aperture value and shutter speed obtained in the AE process.
[0024]
This main process is entered when a battery is loaded. When entering this process, first, the system port and the like are initialized (S101). Then, power supply to circuits and components other than the main CPU 35 is cut off (S103), and the photometry switch SWS is awaited to be turned on (S105). When the photometric switch SWS is turned on (S105; Y), power supply to the peripheral device is started and VDD loop processing is executed (S107).
[0025]
When the VDD loop process is started, the VDD loop time timer is started (S109), the state of each switch is checked (S111), and predetermined lens communication is executed between the main CPU 35 and the lens CPU 61 to open the aperture stop. Lens data such as a value, minimum aperture value, and focal length data are input (S113).
[0026]
Then, an AE calculation process is executed (S115), and a display relating to shooting such as a shutter speed obtained by the calculation is performed (S117). The AE calculation process is a process in which subject brightness is measured by the photometry IC 18, and an appropriate shutter speed and aperture value are obtained by calculation in a predetermined exposure mode, for example, a program exposure mode, based on subject brightness data and film sensitivity data.
[0027]
When the shutter speed and aperture value are obtained, AF processing is performed in which the focus adjustment lens 53 is moved so as to focus on the subject whose focus is detected via the multi-focus detection unit 21 (S119). The AF process is repeated until the VDD loop time elapses (S121; N, S119).
[0028]
When the loop time elapses (S121; Y), the state of the photometry switch SWS is checked (S123), and when it is on, the process returns to the VDD loop process (S123; Y, S119). If the metering switch SWS is off (S123; N), it is checked whether the power hold flag is set (S125). If it is set, the VDD loop process is repeated until the power hold time elapses (S125; Y, S131; N). If not set, the power hold timer is started (S125; N, S127), and the VDD loop process is repeated until the power hold timer expires after the power hold flag is set (S129, S131; N, S109). ). When the power hold time has elapsed, the power hold flag is cleared and the process returns to the power down process (S131; Y, S133, S103).
[0029]
The AF process executed in “AF process” S121 will be described in more detail with reference to FIG. This AF process is a process of moving the focus adjustment lens 53 so as to focus on the subject in the distance measurement area selected by executing the focus detection process. If a predetermined condition described later is satisfied, an auxiliary process is performed. In this process, light is emitted, focus detection is performed again, and the focus adjustment lens 53 is moved so that the focus-detected subject is focused.
[0030]
When the AF process is started, it is first checked whether or not the built-in flash device 71 is popped up by the pop-up detection switch SWP (S201). If not popped up, the auxiliary light permission flag is cleared (S201; N, S203), and the emission of auxiliary light is prohibited. In the present embodiment, the built-in flash device 71 is configured to use the intermittent light emission as auxiliary light.
[0031]
The auxiliary light permission flag is a flag that permits the emission of auxiliary light when focus detection is impossible due to low brightness of the subject, and is cleared when AF processing starts.
[0032]
If the built-in flash device 71 is popped up, the auxiliary light mode flag is checked (S201; Y, S205). If the auxiliary light mode flag is cleared, the auxiliary light permission flag is set (S205; N, S207). ). The auxiliary light mode flag is cleared in the first AF process, and thereafter, the main CPU 35 sets it based on various conditions. If the auxiliary light mode flag is set (S205; Y), the process proceeds directly to S209.
[0033]
Next, it is checked whether or not the photometric switch SWS is on (S209). If the photometry switch SWS is off, the auxiliary light mode flag, the auxiliary light second time flag, and the in-focus flag are cleared and the process returns (S209; N, S211).
[0034]
If the metering switch SWS is in the on state (S209; Y), the focus flag is checked to see if the subject is in focus (S213), and if it is in focus, the process returns (S213; Y). If not in focus, the integration process is started (S213; N, S215).
[0035]
Although details will be described later, in the first integration process, the multi-focus detection unit 21 performs integration without emitting auxiliary light, and when the integration of the multi-focus detection unit 21 is completed, the main CPU 35 moves to each distance measurement area. The corresponding video signal is input, converted into a digital signal by the A / D converter 35e, stored in the RAM 35b, and defocus calculation is executed to determine the defocus amount for each distance measurement area.
[0036]
Next, an auxiliary light mode check process is executed (S217). Although the details will be described later in the auxiliary light mode check processing, when focus detection processing is executed without emitting auxiliary light and focus detection is possible in any distance measurement area, integration of the distance measurement area is performed. When a predetermined condition such as when the time is longer than the predetermined time is satisfied, an auxiliary light mode flag is set, auxiliary light is emitted, integration processing is performed again, and focus detection processing is performed.
[0037]
Then, whether or not the calculation result of each ranging area calculated in S215 or S217 is valid is checked by a ranging area selection OK flag (S219). The distance measurement area selection OK flag is a flag that is set when a defocus calculation is performed for each distance measurement area and a distance measurement area in which the calculated defocus amount is valid is selected.
[0038]
If the ranging area selection OK flag is set (S219; Y), it is checked whether or not the calculated defocus amount is included in the range of the focus width that can be regarded as in-focus (S221). Is within the in-focus width range, the in-focus flag is set and the process returns (S221; Y, S227).
[0039]
If the defocus amount is outside the range of the focus width (S221; N), since the in-focus state is not achieved, the AF pulse number is calculated from the defocus amount (S223), and AF is performed based on the calculated AF pulse number. The motor 39 is driven to move the focus adjustment lens 53 of the photographic lens 51 and return (S225).
[0040]
If the ranging area selection OK flag is not set (S219; N), the auxiliary light mode flag is checked (S229). If the auxiliary light mode flag is not set, the process returns as it is (S229; N). If the auxiliary light mode is set (S229; Y), the auxiliary light second flag is checked (S231).
[0041]
If the auxiliary light second-time flag is cleared (S231; N), the focus adjustment lens 53 is moved to a predetermined position (S233), the auxiliary light second-time flag is set, and the process returns (S235). The focus adjustment lens 53 is moved, for example, to a shooting distance of 3 m.
[0042]
If the auxiliary light second flag is set (S231; Y), the auxiliary light permission flag is cleared, that is, emission of auxiliary light is prohibited and the process returns (S237). That is, in S229 to S237, when focus detection is performed by emitting auxiliary light in the first AF process, but it is impossible, the focus adjustment lens 53 is moved to a predetermined position, and the second AF process is performed. In the processing, auxiliary light is emitted at the moved position and focus detection is performed again. If focus detection is still impossible, the auxiliary light is not emitted in the subsequent AF processing.
[0043]
The integration process executed in the “integration process” S215 will be described in more detail with reference to FIG. When the integration process is started, the auxiliary light permission flag is first checked (S301). If the auxiliary light permission flag is set (S301; Y), the auxiliary light mode is checked (S303).
[0044]
If the auxiliary light permission flag and the auxiliary light mode flag are not set (S301; N, S303; N), integration is started without emitting auxiliary light (S305). The main CPU 35 outputs an integration start signal to cause the sensors 211A, 211B, and 211C to start integration, and waits until the integration of all the sensors 211A to 211C is completed or until the maximum integration time has elapsed (S307).
[0045]
When integration of all sensors is completed, or when the maximum integration time has elapsed, an integration end signal is output and the integration of the sensor that has not completed integration is completed before video signals are input (S307; Y , S309), defocus calculation is executed for each distance measurement area to determine the defocus amount and return (S311). At the time of the first integration process, since the auxiliary light mode flag is not set, the focus detection process is executed without emitting auxiliary light.
[0046]
When the auxiliary light mode flag is set (S303; Y), the charging voltage of the built-in flash device 71 is checked (S317), and the charging voltage has reached the auxiliary light level necessary for flash light emission. At this time, the process proceeds to S321 as it is (S317; N, S321), and if not reached, a charge signal is output to charge to the auxiliary light level and then the process proceeds to S321 (317; Y, S319, S321).
[0047]
When the charging voltage is equal to or higher than the auxiliary light level (S317; N or S319), the emission counter of the built-in flash unit 71 is cleared (S321), and the multi-focus detection unit 21 starts integration (S323). .
[0048]
After starting the integration, the main CPU 35 outputs a trigger signal (S325), starts light emission of the built-in flash device 71, waits for a predetermined light emission time (S327), and outputs a trigger signal when the light emission time has elapsed. The light emission is stopped, the light emission of the built-in flash device 71 is stopped (S329), and the light emission count is incremented by 1 (S331).
[0049]
Then, it is checked whether or not the flash light emission count has reached a preset maximum light emission count (S333). If the flash light emission count has not reached the maximum light emission count (S333; N), it is checked whether integration of all the sensors 211A to 211C has been completed (S335). When integration of all the sensors 211A to 211C is not completed, the flash light emission is repeated after waiting for the light emission interval time (S335; N, S337, S325). This series of light emission is intermittent light emission.
[0050]
When integration of all the sensors 211A to 211C is completed (S335; Y), the process proceeds to S339. Also, when the flash light emission count reaches the maximum light emission count (S333; Y), the process proceeds to S339.
[0051]
In step S339, an integration end signal is output, the sensors 211A to 211C that have not completed integration are forcibly terminated, and then a video signal is input (S339), and each focus detection area is defocused. The calculation is performed to obtain the defocus amount (S341), the built-in flash device 71 is charged to the auxiliary light level, and the process returns (S343).
[0052]
Defocus calculation processing executed in steps S311 and S341 will be described in more detail with reference to FIG. Upon entering this process, the defocus calculation of each distance measuring area is performed based on each input video signal (S501). Next, it is checked whether or not there is a distance measuring area where the calculation result is valid (S503). In step S501, predetermined calculation processing is executed based on the video signal of each ranging area to obtain the contrast value and defocus amount of the subject image in each ranging area. In step S503, the contrast value is determined in advance. If the contrast value is equal to or greater than the contrast value, it is determined that the distance measurement area and the obtained defocus amount are effective, that is, focus detection is possible.
If there is a distance measurement area where the calculation result is valid, the distance measurement area where the subject is located at the shortest distance is selected, the distance measurement area selection OK flag is set, and the process returns (S503; Y, S505, S507). If there is no distance measurement area where the calculation result is valid, that is, if focus detection is impossible in all the distance measurement areas, the distance measurement area selection OK flag is cleared and the process returns (S503; N, S509). .
[0053]
The auxiliary light mode check process executed in “auxiliary light mode check” S217 will be described in detail with reference to FIG. In the auxiliary light mode check process, the focus detection process is executed without emitting auxiliary light, focus detection is impossible in all the distance measurement areas, and the integration time of one of the distance measurement areas is longer than the predetermined time. When the focus detection is possible in any distance measurement area and the predetermined condition is satisfied such as when the integration time of the distance measurement area is longer than the predetermined time, the auxiliary light is emitted. Re-execute the focus detection process.
[0054]
When entering this process, first, the state of the auxiliary light permission flag is checked (S401). When the auxiliary light permission flag is set (S401; Y), the auxiliary light mode flag is checked (S403). When the auxiliary light mode flag is cleared, the ranging area selection OK flag is checked (S403; N, S405). When the auxiliary light permission flag is cleared or when the auxiliary light mode flag is set, the process returns as it is (S401; N or S403; Y).
[0055]
When the ranging area selection OK flag is cleared (S405; N), that is, when focus detection is impossible in all the ranging areas, the integration time and the predetermined time of each ranging area are next. (S407). Here, the integration time is a period from when the sensors 211A, 211B, and 211C of the multi-focus detection unit 21 start integration, until the integration values of the monitor sensors 213A, 213B, and 213C reach the integration end value and the integration ends. The time it took.
[0056]
If the integration time exceeds a predetermined time in any distance measurement area (S407; Y), that is, if there is a dark area even in one distance measurement area in the shooting screen, the auxiliary light mode flag is set. In step S409, auxiliary light is emitted to perform integration processing again. Since the integration process of S411 is performed by emitting auxiliary light, the integration of the sensors 211A, 211B, and 211C is started in step S323. When the integration time in any distance measurement area does not exceed the predetermined time (S407; N), that is, when it is determined that the subject brightness in all the distance measurement areas is sufficiently bright, focus detection is performed even if auxiliary light is emitted. Since there is a high possibility that this is impossible, the process returns as it is, and the auxiliary light is not emitted.
[0057]
When the distance measurement area selection OK flag is set (S405; N), that is, when there is a distance measurement area in which focus detection is possible without emitting auxiliary light, the integration time of the selected distance measurement area Is compared with a predetermined time (S413).
In the present embodiment, focusing processing is performed by selecting a distance measurement area where the subject is located at the closest distance based on the calculated defocus amount, but the present invention is not limited to this, and for example, the subject is at the farthest distance. May be selected, or a range-finding area selection switch may be provided to allow the photographer to select a range-finding area.
[0058]
When the integration time of the selected ranging area is shorter than the predetermined time (S413; N), the process returns as it is, and the focusing process is executed based on the defocus amount of the selected ranging area. In other words, when the subject brightness of the selected distance measurement area is greater than or equal to the predetermined value, the selected distance measurement area is bright enough for focus detection, so the auxiliary light will not be emitted even if there is a dark distance measurement area other than the selected distance measurement area. It does not emit light. However, when the integration time of the selected distance measurement area is longer than the predetermined time, that is, when the subject brightness in the selected distance measurement area is less than the predetermined value, focus detection can be performed without emitting auxiliary light. Although it was possible, since the selected ranging area was dark, its detection accuracy was poor.
[0059]
Therefore, when the integration time of the selected ranging area is longer than the predetermined time (S413; Y), the defocus amount obtained in S311 of the selected ranging area is compared with the predetermined amount (S415). Here, the defocus amount is compared with the predetermined amount because the photographing distance D corresponding to the position of the focus adjustment lens 53 at the time of focus detection is within the auxiliary light effective range, and the effective focus is obtained by the emission of the auxiliary light. This is to determine whether or not the detection can be performed. The auxiliary light effective range is an imaging distance range in which it is predicted that a subject luminance that enables focus detection by emission of auxiliary light will be obtained.
[0060]
When the defocus amount of the selected ranging area is larger than the predetermined amount (S415; N), the photographing distance D corresponding to the position of the focus adjustment lens 53 at the time of focus detection is not included in the auxiliary light effective range. Since there is a high possibility that the amount of auxiliary light is insufficient or excessive and focus detection becomes impossible, the process returns as it is, and a focusing process is performed based on the defocus amount of the selected distance measuring area.
[0061]
When the defocus amount of the selected distance measuring area is smaller than the predetermined value (S415; Y), the main CPU 35 performs lens communication with the lens CPU 61 and performs focus detection performed without emitting auxiliary light. The focal length information and distance information of the taking lens 51 are input (S417). The distance information includes the shortest shooting distance of the shooting lens 51 and the lens position (shooting distance) of the focus adjustment lens 53. The lens CPU 61 sets the position of the focus adjustment lens 53 to the distance switch 63 (SW₁, SW₂, SW_Three) As ON / OFF information, and distance code D_VConvert to 'Distance code D_V'Is communicated to the camera body 11. Distance code D_VAs shown below, “0” to “7” are set in order by dividing the area up to infinity into eight areas based on the shortest shooting distance of the shooting lens 51 as shown below.
Distance code Distance SW
D_V'SW_Three    SW₂      SW₁
0 (near) 1 1 1
1 1 1 0
2 1 0 0
3 1 0 1
4 0 0 1
5 0 0 0
6 0 1 0
7 (∞) 0 1 1
[0062]
In the present embodiment, the photographing distance area is divided so that the following apex system formula is satisfied.
D_V= D_{Vmin +}D_V'
However, D_VIs the distance apex value, an integer, D_VminIs an apex value of the shortest shooting distance of the taking lens 51. For example, D_Vmin= Apex value D when -1_VIs D_V= -1 to 6. Apex value D_VAnd shooting distance D between D = 2^{( (Dv / 2)}Thus, the corresponding shooting distance D is D = 0.7 to 8 (m). Distance code D received by lens communication_V', The apex value D at the position of the focus adjustment lens 53 during the focus detection process performed without intermittent flash light emission._VIs calculated (S419).
[0063]
Next, the calculated apex value D_VIs in the range of 0 to less than 5 (S421). That is, it is determined whether or not the photographing distance D at the time of focus detection performed without emitting auxiliary light is included within 1 m or more and less than 5.6 m of the auxiliary light effective range. In this embodiment, the effective range of auxiliary light is set to 1 to 5.6 m. This is because the amount of auxiliary light reaching is too much on the near side from 1 m, and on the far side from 5.6 m. This is because there are many cases where the focus cannot be detected outside the range of 1 to 5.6 m due to the small amount of light reaching. The auxiliary light effective range is an imaging distance range in which it is predicted that sufficient subject luminance for focus detection will be obtained by the emission of auxiliary light. Value) and the like.
[0064]
Calculated apex value D_VIs less than 0 or greater than or equal to 5 (S421; N), the flash light is not emitted and the process returns as it is, and focusing processing is performed based on the defocus amount of the selected distance measuring area. Apex value D_VIs within the range of 0 or more and less than 5 (S421; Y), that is, when the shooting distance D is included in the effective range of auxiliary light, the auxiliary light is emitted to improve detection accuracy. The flag is set (S409), auxiliary light is emitted, and the integration process is executed again (S411).
[0065]
In the present embodiment, the built-in flash device 71 emits light intermittently to provide auxiliary light for focus detection. However, the present invention is not limited to this, and the auxiliary light is emitted from a light-emitting unit that emits illumination light such as a lamp built in the camera body 11. The same configuration can be adopted when using auxiliary light by light or light emitting means for emitting illumination light such as a lamp provided in an external flash device.
[0066]
【The invention's effect】
As is apparent from the above description, the present invention executes focus detection processing without emitting auxiliary light, and can detect the focus when focus detection is possible in any distance measurement area. The integration time of the light receiving means in one ranging area selected from the area was compared with the predetermined time, the integration time was longer than the predetermined time, and the shooting distance at the time of the focus detection processing was within the effective light range Since the auxiliary light is emitted and the focus detection process is re-executed, the emission of the auxiliary light can be controlled in accordance with the subject brightness in the selected distance measuring area. Therefore, when the subject brightness in the selected distance measurement area is lower than the predetermined value, even if focus detection is possible, the auxiliary light can be emitted to improve the detection accuracy, and the subject in the selected distance measurement area can be improved. When the brightness is higher than a predetermined value, focus detection is possible and detection accuracy is high, so that auxiliary light is not emitted even in the presence of other dark ranging areas, so battery consumption can be suppressed. .
Further, the present invention executes focus detection processing without emitting auxiliary light, and when focus detection is impossible in all ranging areas, the integration time of each light receiving means in each ranging area When the integration time in any distance measurement area is longer than the predetermined time, the focus detection processing is performed by emitting auxiliary light, and the integration time of the light receiving means is the predetermined time in any distance measurement area. Since the auxiliary light is not emitted in the following cases, the auxiliary light is emitted and the focus detection process is executed only when there is a subject that would be able to detect the focus by emitting the auxiliary light. can do.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the main configuration of an embodiment of a multipoint autofocus single-lens reflex camera to which the present invention is applied.
FIG. 2 is a diagram illustrating a configuration of a multi-focus detection unit of a single-lens reflex camera.
FIG. 3 is a diagram showing a main flowchart regarding the main operation of the single-lens reflex camera.
FIG. 4 is a flowchart related to AF processing of a single-lens reflex camera.
FIG. 5 is a diagram illustrating a flowchart regarding integration processing of the single-lens reflex camera.
FIG. 6 is a flowchart related to a defocus calculation process of the single-lens reflex camera.
FIG. 7 is a flowchart related to an auxiliary light mode check process of the single-lens reflex camera.
[Explanation of symbols]
11 Camera body
13 Main mirror
14 Half mirror
15 Submirror
21 Multi-focus detection unit
35 Main CPU
51 Photo lens
53 Lens for focus adjustment
61 Lens CPU
63 Distance switch
71 Built-in flash device

Claims (4)

A light emitting means for emitting illumination light toward the subject;
A light receiving means for forming images of subjects in a plurality of ranging areas corresponding to different positions in a shooting screen, and integrating the subject images as charges;
A focus detection means for detecting a focus state with respect to a subject in each ranging area based on an integral value of each light receiving means;
When the focus detection process is executed by the focus detection means without causing the light emission means to emit light, and focus detection is possible in any distance measurement area, one focus detection area can be Focus detection that selects an area, and causes the light emitting means to emit light and causes the focus detection means to re-execute focus detection processing when the integration time of the light receiving means corresponding to the selected ranging area is longer than a predetermined time Control means;
A multipoint automatic focus detection apparatus characterized by comprising: The focus detection control unit is configured to assist the effective detection of the focus by the light emission of the light emitting unit when the integration time of the light receiving unit corresponding to the selected ranging area is longer than a predetermined time and the shooting distance at the time of the focus detection process is 2. The multipoint automatic focus detection apparatus according to claim 1, wherein when the light is within an effective light range, the light emitting unit is caused to emit light and the focus detection unit is caused to re-execute focus detection processing. When the integration time of the light receiving means corresponding to the selected distance measurement area is shorter than a predetermined time, the focus detection control means may detect the focus even if there is another distance measurement area with an integration time longer than the predetermined time. 2. The multipoint automatic focus detection apparatus according to claim 1, wherein light emission of the light emission means is prohibited during focus detection processing by the detection means. The focus detection control means causes the focus detection means to execute focus detection processing without causing the light emission means to emit light, and when focus detection is impossible in all distance measurement areas, any of the distance measurement areas 3. The multipoint according to claim 1, wherein when the integration time of the light receiving means is longer than a predetermined time, the light emitting means is caused to emit light and the focus detection means is caused to re-execute focus detection processing. Automatic focus detection device.

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