JP3762573B2 - Automatic focus adjustment device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an automatic focusing apparatus for a camera that uses a flash device as an auxiliary light source when a subject has low brightness or low contrast.
[0002]
[Prior art and its problems]
In general, so-called passive AF (automatic focus adjustment) cameras have a contrast pattern applied to the subject using the light emitted from the AF auxiliary light source built in the camera body as auxiliary light when the subject has low brightness or low contrast. Contrast is generated in the subject image projected and received by the AF sensor, and focus detection is performed from the subject image. However, it is costly to provide an auxiliary light source for focus detection separately from the flash device for photographing. Therefore, as disclosed in Japanese Patent Laid-Open No. 5-34577, the flash device intermittently emits light as auxiliary light. Some are used.
[0003]
At the time of focus detection, an AF sensor equipped with a light receiving element receives subject light, photoelectrically converts and integrates the charge, ends the integration when the integration value of the AF sensor reaches the integration end value, and ends the integration. Focus detection is performed based on an integration value obtained by amplifying the time integration value with a predetermined gain (amplification factor). If focus detection is impossible, integration is performed again while intermittently emitting flash light. At this time, when the subject distance is long, the flash light emission amount necessary for focus detection is large. Therefore, the number of times of auxiliary light emission must be increased in order for the integrated value of the AF sensor to reach the integration end value. However, if the amount of light emission increases, the charging voltage of the flash device decreases, and if the number of times of light emission increases, the integration time becomes longer. To reduce the amount of light emitted, the gain of the integral value should be set high in advance, but if the subject distance is short, the amplified integral value range exceeds the focus detection processing range and an error occurs, resulting in detection accuracy. Will fall.
[0004]
OBJECT OF THE INVENTION
In order to solve the above problems, the present invention provides an automatic focus adjustment device that can shorten the integration time by changing the integration end value and the gain of the amplification means in accordance with the light emission amount of auxiliary light necessary for focus detection. The purpose is to provide.
[0005]
SUMMARY OF THE INVENTION
  The present invention provides a light emitting means for emitting a flash to photograph a subject, a light receiving means for receiving the subject light, integrating the subject image as an electric charge, and terminating the integration when the integration value reaches an integration end value. Amplifying means for amplifying the integrated value at the end of integration of the light receiving means with a predetermined gain, focus detecting means for detecting focus based on the integrated value amplified by the amplifying means, and focus detection of the focus detecting means is not possible. When possible, the integration of the light receiving means is performed while causing the light emitting means to intermittently emit light, and each time the light emitting means is intermittently emitted a predetermined number of times until the integral value of the light receiving means reaches an integration end value,The integration end value is increased by one step so that the time until the integration value of the light receiving means reaches the integration end value is shortened.An automatic focus adjustment device characterized in that an integration control means for repeatedly executing the processing is provided.
The present invention also provides a light emitting means for emitting a flash to photograph a subject, a light receiving unit that receives the subject light, integrates the subject image as a charge, and ends the integration when the integration value reaches an integration end value. Means, amplifying means for amplifying the integrated value at the end of integration of the light receiving means with a predetermined gain, focus detecting means for detecting focus based on the integrated value amplified by the amplifying means, and focus detection of the focus detecting means When it is impossible, the integration of the light receiving means is executed while intermittently emitting the light emitting means, and the light emitting means is allowed to intermittently emit light a predetermined number of times until the integrated value of the light receiving means reaches the integration end value. When the integral value of the light receiving means has not reached the integration end value, the integration control means for repeatedly executing the process of raising the integration end value by one step so that the time until the integration end value is reached is shortened An automatic focusing device, characterized in that provided.
  The integration control means preferably changes the integration end value and the gain of the amplification means so that the time until the integration value of the light receiving means reaches the integration end value is shortened,When the integration end value is increased by one stepWhen the integral value of the light receiving means does not reach the integration end value increased by one step, it is preferable to increase the gain of the amplifying means by one step, and the integral value of the light receiving means is the predetermined value. When the integration end value after the step change is not reached, the light emitting means is caused to intermittently emit light until reaching a preset maximum light emission number, and when the light emission number of the light emission means reaches the maximum light emission number, It is preferable that the integration of the light receiving means is terminated even if the integration value of the means does not reach the integration end value changed by the predetermined step. Furthermore, it is preferable that the integration control means does not change the integration end value and the gain after the gain of the amplification means reaches the maximum.
  According to said structure, according to the frequency | count of light emission of the said light emission means, the integration end value and the gain of an amplification means can be changed, and the integration time of the said light reception means can be shortened.
[0006]
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. The camera body 11 includes an automatic focus adjusting means and a built-in flash device 71.
[0007]
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 AF sensor unit 21.
[0008]
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.
[0009]
The AF sensor unit 21 is a so-called phase difference type distance measuring sensor, and is divided into two, a splitting optical system that splits a subject light beam that forms a subject image included in a focus detection area in a shooting screen (not shown), and a split optical system. A CCD line sensor 211 that receives and integrates each of the subject luminous fluxes, and a monitor sensor 213 that checks the integrated value of the CCD line sensor 211. The signal charge integrated by the CCD line sensor 211 is converted into a voltage for each pixel, amplified by an 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.
[0010]
The main CPU 35 calculates the defocus amount by a predetermined calculation based on the video signal input from the AF sensor 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.
[0011]
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.
[0012]
The main CPU 35 also includes a ROM 35a storing control programs and the like, a RAM 35b temporarily storing predetermined data for calculation and control, a reference timer 35c for timing, a hard counter 35d, and a video input from the AF sensor unit 21. An A / D converter 35e for A / D converting the signal is built in, and an EEPROM 43 as an external memory means is connected. In the EEPROM 43, various constants unique to the camera body 11 are stored.
[0013]
The camera body 11 includes a 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, but is used as an auxiliary light source for focus detection when focus detection cannot be performed because the subject has low brightness or low contrast. 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 pressed. 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. In addition, the main CPU 35 constitutes a light emission control unit with the built-in flash device 71, the peripheral control circuit 23, and the like. The control circuit 23 and the like constitute integration control means for controlling the integration process of the AF sensor unit 21.
[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 obtains distance information by detecting the position of the focus adjustment lens 53 as a distance code from the state of the distance switch 63. The lens CPU 61 is connected to the peripheral control circuit 23 of the camera body 11 through the connection of the electrical contact groups 59 and 49, and performs lens communication with the main CPU 35 through the peripheral control circuit 23. Execute and input lens data such as distance information, focal length information, aperture information.
[0018]
With reference to FIG. 2, the configuration of the AF sensor unit 21 including the CCD line sensor 211 in this embodiment will be described in more detail.
[0019]
The AF sensor unit 21 receives subject light and integrates it as a charge, a CCD line sensor 211 as a light receiving means, a monitor sensor 213 that monitors the integrated value of the CCD line sensor 211, and integration of the CCD line sensor 211 after completion of integration. An amplifier 215 is provided as amplification means for amplifying the value with a predetermined gain and outputting the amplified value to the main CPU 35. Although not shown in detail, the CCD line sensor 211 integrates a photoelectric conversion element such as a photodiode that receives subject light and performs photoelectric conversion, and a signal charge converted by each photoelectric conversion element independently for each photoelectric conversion element. And a charge holding unit for transferring and temporarily holding the charge integrated by the integrating unit. 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 sensor 213 is arranged in parallel with the CCD line sensor 211 and detects an integrated value of the CCD line sensor 211.
[0020]
The CCD line sensor 211 starts integration processing in response to an integration start signal from the main CPU 35. The photoelectric conversion element of the CCD line sensor 211 that has received the subject light performs photoelectric conversion of the subject light, and the monitor sensor 213 monitors the integration value integrated by the integration unit. When the integration value of the monitor sensor 213 reaches the integration end value (VAGC), the charge integrated by the integration unit of the CCD line sensor 211 is transferred to the charge holding unit, the integration ends, and the monitor sensor 213 is cleared. When the main CPU 35 outputs an integration end signal, the charge held in the charge holding unit is transferred to the CCD transfer unit 212 and output from the CCD transfer unit 212. The electric charge is converted into a voltage in units of pixels when output from the CCD transfer unit 212, and the output voltage signal is amplified with a predetermined gain by the amplifier 215 and taken into the main CPU 35 as a video signal in units of pixels. 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 operation based on the stored signal.
[0021]
When integration processing is performed without emitting flash light, when the integration value of the monitor sensor 213 reaches the integration end value, an integration end signal is output to the CCD line sensor 211 to end the integration. When the integration of the CCD line sensor 211 does not end within the preset maximum integration time, that is, when the integration value of the monitor sensor 213 does not reach the integration end value within the preset maximum integration time. When the maximum integration time has elapsed, an integration end signal is output to cause the CCD line sensor 211 to end the integration. In response to the integration end signal, the CCD line sensor 211 transfers the charge integrated by the integration unit to the charge holding unit, ends the integration, the monitor sensor 213 is cleared, and the initial state is restored.
[0022]
When integration processing is performed while intermittently emitting flash light as auxiliary light for focus detection, if the integral value of the monitor sensor 213 does not reach the integration end value (VAGC) even if the flash light is intermittently emitted a predetermined number of times, The integration end value is increased by one step so that the time until the integration value reaches the integration end value is shortened, and the integration value of the monitor sensor 213 is compared with the integration end value increased by one step. When the value does not reach the integration end value increased by one step, the process of increasing the gain of the amplifier 215 by one step is repeatedly executed. In this processing, when the flash light emission count reaches the preset maximum light emission count, the monitor sensor 213 is cleared by forcibly terminating the integration even if the integration of the CCD line sensor 211 is not completed. Also, after the gain reaches the maximum, the integration end value and gain are not changed.
[0023]
FIG. 3 shows a timing chart relating to integral control of the CCD line sensor 211 executed while intermittently emitting flash light in the present embodiment. This integration control process is started on condition that the photometry switch SWS is turned on. When the photometric switch SWS is turned on, the main CPU 35 outputs an integration start signal, causes the CCD line sensor 211 to start integration, and causes the built-in flash device 71 to emit light intermittently. When integration is started, the monitor sensor 213 monitors the integration value of the CCD line sensor 211. The integration value of the monitor sensor 213 changes in a direction that becomes lower than the initial value as the integration of the CCD line sensor 211 progresses, and the main CPU 35 indicates that the integration value of the monitor sensor 213 has reached the integration end value (VAGC). When detected, an integration end signal is output, and the integration of the CCD line sensor 211 is ended. After the integration is completed, the monitor sensor 213 is cleared and returns to the initial state.
[0024]
If the integrated value of the monitor sensor 213 has not reached the integration end value even if the flash light is emitted twice, the main CPU 35 increases the integration end value by one step. If the integration value of the monitor sensor 213 does not reach the integration end value increased by one step even if the integration end value is increased by one step, the gain of the amplifier 215 is increased by one step. Here, increasing the integration end value by one level means increasing the output of VAGC so that the difference (AGC level) between the monitor level before integration start and the integration end value (VAGC) becomes 1/2. .
[0025]
Since the integral value of the monitor sensor 213 has not reached the integral end value even after the fourth light emission, the AGC level is halved, that is, ¼ times the AGC level at the start of integration. Then, since the integral value of the monitor sensor 213 reaches the integral end value, the main CPU 35 detects that the integral value of the monitor sensor 213 has reached the integral end value at this time and outputs an integral end signal to output the CCD line. The integration of the sensor 211 is terminated and the monitor sensor 213 is cleared. The integral value is converted into a voltage signal, amplified by a gain at the end of integration by the amplifier 215, and input as a video signal in pixel units.
[0026]
In the illustrated embodiment, if the integrated value of the monitor sensor 213 does not reach the integration end value even after flash light is emitted twice, the AGC level is increased by a factor of 1/2, and the integrated value of the monitor sensor 213 is still However, the gain of the amplifier 215 is increased by a factor of two, but the present invention is not limited to this.
[0027]
Next, main operations of the single-lens reflex camera to which the present invention is applied will be described with reference to FIGS. FIG. 4 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.
[0028]
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).
[0029]
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).
[0030]
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.
[0031]
When the shutter speed and aperture value are obtained, AF processing is performed in which the focus adjustment lens 53 is moved to focus on the subject whose focus is detected via the AF sensor unit 21 (S119). The AF process is repeated until the VDD loop time elapses (S121; N, S119).
[0032]
When the loop time elapses (S121; Y), the state of the photometry switch SWS is checked (S123), and when it is turned on, the process returns to the VDD loop processing (S123; Y, S109). 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).
[0033]
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 whose focus is detected by executing the focus detection process. However, the focus detection process is executed without emitting flash light. If it is determined that focus detection is impossible due to low brightness or the like, focus detection is performed again while intermittently emitting flash light, and the focus adjustment lens 53 is adjusted so that the focus is detected. It is a process to move.
[0034]
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 use of auxiliary light is prohibited.
[0035]
The auxiliary light permission flag is a flag that permits intermittent light emission of the built-in flash device 71 as auxiliary light for focus detection when focus detection is impossible because the subject has low brightness or low contrast. It is cleared during the AF process.
[0036]
If it is popped up, the auxiliary light mode flag is checked (S201; Y, S205), and if the auxiliary light mode flag is in the clear state, the auxiliary light permission flag is set (S205; N, S207).
[0037]
The auxiliary light mode flag is cleared in the first AF process, and thereafter, the main CPU 35 sets it based on various conditions.
[0038]
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).
[0039]
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).
[0040]
Although details will be described later, in the first integration process, the AF sensor unit 21 performs integration without causing the built-in flash device 71 to emit light. When the integration of the AF sensor unit 21 is completed, the main CPU 35 inputs a CCD video signal. The A / D converter 35e converts the signal into a digital signal, stores it in the RAM 35b, and executes the defocus calculation to obtain the defocus amount.
[0041]
Then, an auxiliary light mode check process is executed (S217). Although the details will be described later in the auxiliary light mode check processing, the built-in flash is activated when conditions such as when the effective calculation result is not obtained in the integration processing of S215 or when the integration time is longer than the predetermined time are satisfied. The integration process is performed again by causing the device 71 to intermittently emit light.
[0042]
Then, it is checked by the operation OK flag whether a valid operation result is obtained in S215 or S217 (S219). The calculation OK flag is a flag that is set when the calculated defocus amount is valid after completion of the defocus calculation. When the calculation OK flag is set (S219; Y), it is checked whether or not the calculated defocus amount is within the range of the focus width that can be regarded as in-focus (S221), and the defocus amount is in focus. If it is within the range of the width, the focus flag is set and the process returns (S221; Y, S227).
[0043]
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 and return (S225).
[0044]
If the calculation OK flag is not set (S219; N), it is next checked whether the auxiliary light mode flag is set (S229). If the auxiliary light mode flag is not set, the process returns as it is (S229; N). If the auxiliary light mode flag is set (S229; Y), the auxiliary light second time flag is checked (S231).
[0045]
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.
[0046]
If the auxiliary light second flag is set (S231; Y), the auxiliary light permission flag is cleared, that is, the flash light emission is prohibited and the process returns (S237). That is, if focus detection is not possible in the first AF process using flash light according to S229 to S237, the focus adjustment lens 53 is moved to a predetermined position, and flash light is intermittently emitted at the moved position. Then, focus detection is performed again, and if focus detection is still impossible, flash light as auxiliary light for focus detection is not emitted thereafter.
[0047]
The integration process executed in the “integration process” S215 will be described in more detail with reference to FIG. In this process, if focus detection is not possible by performing focus detection without emitting flash light, the CCD line sensor 211 performs integration while intermittently emitting flash light to perform focus detection. Do. At that time, if the integral value of the monitor sensor 213 does not reach the integral end value even if the flash light is intermittently emitted for a predetermined number of times, the integral end value is increased by one step, and the integral value is increased by one step. When the integration value has not reached the integration end value increased by one step, the process of increasing the gain of the amplifier 215 by one step is performed until the flash light emission count reaches a predetermined maximum light emission count or the gain is maximized. It is repeatedly executed until it reaches.
[0048]
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). The auxiliary light mode is cleared at the time of the first integration process, and when the effective calculation result is not obtained in the integration process of S215 during the auxiliary light mode check process, the integration time is longer than the predetermined time, etc. Set in S409 when the above condition is satisfied.
[0049]
When the auxiliary light mode is not set (S303; N), integration is started without emitting flash light (S305), CCD video signal is input after the integration is completed (S307; Y, S309), and defocus calculation To determine the defocus amount (S311), determine whether the calculation result is valid (S313), and if the calculation result is valid, set the calculation OK flag and return (S313; Y , S315), focusing processing is executed based on the calculated defocus amount. If the calculation result is not valid, the calculation OK flag is cleared and the process returns (S313; N, S314). Since the auxiliary light mode flag is not set during the first integration process, focus detection is performed without emitting flash light.
[0050]
When the auxiliary light mode is set (S303; Y), the charging voltage of the built-in flash device 71 is checked (S317), and if the charging voltage has not reached the auxiliary light level, it is charged to the auxiliary light level ( S317; Y, S319).
[0051]
When the completion of charging of the built-in flash device 71 is detected (S317; N, S319), the integration end value (VAGC) of the CCD line sensor 211 is set via the peripheral control circuit 23 (S321). The light emission number counter is cleared (S323), and the comparison number is initialized (S325).
[0052]
The number of comparisons is a value for setting the number of times of light emission for changing the integration end value, and the integration end value is changed when the set number of comparisons equals the number of times of auxiliary light emission.
[0053]
Next, an integration start signal is output to cause the CCD line sensor 211 to start integration (S327), a light emission trigger signal is output (S329), the built-in flash device 71 is caused to emit light, and the set light emission time has elapsed. Wait (S331).
[0054]
When the light emission time has elapsed, the trigger signal is turned off, the internal flash unit 71 stops light emission (S333), and the light emission number counter is incremented by 1 (S335). Then, it is checked whether or not a predetermined maximum number of times of light emission has been reached (S337). If the maximum number of times of light emission has not been reached (S337; N), it is checked whether the integral value of the monitor sensor 213 has reached the integral end value (S339).
[0055]
When the maximum number of flashes has been reached (S337; Y) or when the integral value of the monitor sensor 213 has reached the integration end value (S339; Y), a CCD video signal is input (S355), and defocus calculation is performed. To obtain the defocus amount (S357). If the calculation result is valid, the calculation OK flag is set (S359; Y, S361). If the calculation result is not valid, the calculation OK flag is set. Is cleared (S359; N, S362), the built-in flash device 71 is charged to the charge level for auxiliary light, and the process returns (S363).
[0056]
If the integration value of the monitor sensor 213 has not reached the integration end value, it is checked whether or not the gain (amplification degree) of the amplifier 215 is maximum (S339; N, S341), and if the gain is not maximum (S341). N), the number of times of light emission is compared with the number of comparisons (S343).
[0057]
The number of comparisons is set in S325 for the first time, and in S345 for the second and subsequent times. When the number of times of light emission is equal to the number of times of comparison (S343; N), the number of times of comparison is reset to the sum of the number of times of light emission and the initial value of the number of times of comparison (S345), and the AGC level is halved (S347). ). Through S343 to S347, the integration end value can be changed according to the number of flash light emissions. For example, when the initial value of the comparison number is set to 2 in S325, every two intermittent flash light emissions, If the integral value of the monitor sensor 213 has not reached the integral end value, the integral end value is changed.
[0058]
Then, it is checked whether or not the integrated value of the monitor sensor 213 has reached the AGC level multiplied by 1/2 (S349). If not, the gain of the amplifier 215 is doubled (S349; N, S351). . After changing the gain to double, it waits for the set interval time until the next intermittent light emission (S353).
[0059]
When the gain of the amplifier 215 is maximum (S341; Y) and when the number of times of light emission is not equal to the number of comparisons (S343; N), the set interval time is waited until the next intermittent light emission (S353).
[0060]
If the integration value of the monitor sensor 213 has reached the integration end value (S349; Y), the CCD video signal is input (S355), the defocus calculation is performed to determine the defocus amount (S357), It is determined whether the calculation result is valid (S359). If the calculation result is valid, the calculation OK flag is set (S359; Y, S361). If the calculation result is not valid, the calculation OK flag is cleared. (S359; N, S362), the built-in flash unit 71 is charged to the auxiliary light charge level (S363).
[0061]
The auxiliary light mode check process executed in “auxiliary light mode check” S217 will be described in detail with reference to FIG. This auxiliary light mode check process sets the auxiliary light mode flag when the focus detection is not possible by executing the focus detection process without emitting the flash light, and the flash light is emitted intermittently. This is a process for executing detection.
[0062]
When entering this process, first, the state of the auxiliary light permission flag is checked (S401). If the auxiliary light permission flag is set (S401; Y), the auxiliary light mode flag is checked (S403). If the auxiliary light mode flag is not set (S403; N), the calculation OK flag is checked. (S405).
[0063]
If the operation OK flag is cleared (S405; N), the integration time is compared with a predetermined time (S407). Here, the integration time refers to the time taken from the start of integration by the CCD line sensor 211 until the integration value of the monitor sensor 213 reaches the integration end value. If the integration time exceeds the predetermined time (S407; Y), that is, if the subject is dark, an auxiliary light mode flag is set (S409), and the integration process is performed again while intermittently emitting auxiliary light (S411). .
[0064]
The auxiliary light permission flag is cleared at the start of AF processing, and is set in S207 at the first AF processing on the condition that the built-in flash device 71 is popped up, and moves the focus adjustment lens 53 to a predetermined position. Then, when focus detection cannot be performed even if focus detection processing is performed while intermittently emitting flash light, the process is cleared in S237. The auxiliary light mode flag is set in step S409 when the detection result is not valid because the subject is dark in the focus detection process performed without emitting the flash light. That is, in this auxiliary light mode check process, the integration process (S411) is executed while the built-in flash unit 71 emits light only once, and the auxiliary light mode flag is already set for the second and subsequent times. The auxiliary light is intermittently emitted in the process, and the integration process is not executed in this auxiliary light mode check. Furthermore, after clearing the auxiliary light permission flag in S237 and prohibiting flash light emission, the auxiliary light permission flag in S207 is not set unless the photometry SW is turned off once and the auxiliary light mode flag is cleared in S211. .
[0065]
In the present embodiment, the light emitting means has been described as the built-in flash device 71, but the present invention is not limited to this, and can be applied to an external flash device that is connected to the camera body 101 and can be controlled by the main CPU 35.
[0066]
【The invention's effect】
As is apparent from the above description, in the present invention, when the light receiving means performs integration while causing the light emitting means to emit light intermittently, the light emitting means is intermittently emitted a predetermined number of times until the integrated value of the light receiving means reaches the integration end value. Each time the integration end value or the gain of the amplifying means is changed stepwise, the integration time of the light receiving means can be shortened by suppressing the number of light emission of the light emitting means. Further, in the present invention, the integration end value is increased by one step and the integration end value of the light receiving unit is increased by one step every time the light emitting unit is caused to intermittently emit light a predetermined number of times until the integral value of the light receiving unit reaches the integration end value. When the value does not reach the value, if the process of increasing the gain of the amplification means by one step is repeated, the gain is low when the integration value of the light receiving means reaches the integration end value at an early stage of the integration process. The focus detection accuracy can be improved with little error.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the main configuration of an embodiment of an autofocus single-lens reflex camera to which the present invention is applied.
FIG. 2 is a diagram illustrating a configuration of an AF sensor unit of a single-lens reflex camera.
FIG. 3 is a diagram illustrating a timing chart in integral control processing of the single-lens reflex camera.
FIG. 4 is a diagram illustrating a main flowchart regarding the main operation of the single-lens reflex camera.
FIG. 5 is a flowchart related to AF processing of a single-lens reflex camera.
FIG. 6 is a flowchart related to integration processing 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 AF sensor unit
211 CCD line sensor
213 Monitor sensor
215 amplifier
35 Main CPU
51 Photo lens
53 Lens for focus adjustment
71 Built-in flash device

Claims (5)

A light emitting means for emitting a flash to photograph a subject;
Light receiving means for receiving subject light, integrating the subject image as a charge, and terminating the integration when the integration value reaches an integration end value;
Amplifying means for amplifying the integrated value at the end of integration of the light receiving means by a predetermined gain;
A focus detection means for detecting a focus based on the integrated value amplified by the amplification means;
When the focus detection of the focus detection means is impossible, the light emission means is integrated while causing the light emission means to emit light intermittently until the integration value of the light reception means reaches an integration end value. An integral control means for repeatedly executing a process of increasing the integral end value by one step so that the time until the integral value of the light receiving means reaches the integral end value is shortened every time the light is intermittently emitted a predetermined number of times,
An automatic focusing apparatus characterized by comprising:   A light emitting means for emitting a flash to photograph a subject;
  Light receiving means for receiving subject light, integrating the subject image as a charge, and terminating the integration when the integration value reaches an integration end value;
  Amplifying means for amplifying the integral value at the end of integration of the light receiving means by a predetermined gain;
  A focus detection means for detecting a focus based on the integrated value amplified by the amplification means;
  When the focus detection of the focus detection unit is impossible, the light-emission unit is caused to perform integration while causing the light-emission unit to emit light intermittently, and the light-emission unit until the integration value of the light-receiving unit reaches an integration end value. If the integral value of the light receiving means does not reach the integration end value even after intermittent light emission for a predetermined number of times, a process of increasing the integration end value by one step so that the time until the integration end value is reached is shortened. Integration control means to be executed repeatedly;
An automatic focusing device characterized by comprising: 3. The automatic focusing apparatus according to claim 1 , wherein when the integration control unit increases the integration end value by one step, the integration value of the light receiving unit does not reach the integration end value increased by one step. In some cases, the automatic focusing apparatus increases the gain of the amplification means by one step. An automatic focusing device according to any one of claims 1 to 3, wherein the integration control means, when the integral value of the light receiving means has not reached the predetermined phase changed integration completion value is set in advance When the light emitting means intermittently emits light until the maximum number of times of light emission is reached and the number of times of light emission of the light emitting means reaches the maximum number of times of light emission, the integrated value of the light receiving means does not reach the integration end value changed by the predetermined step. However, the automatic focusing device is characterized in that the integration of the light receiving means is terminated. An automatic focusing device according to any one of claims 1 to 4, wherein the integration control means, after the gain of said amplifying means reaches a maximum, not change the predetermined integration completion value and the gain Automatic focusing device characterized by not having.

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